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Catálisis para el Medioambiente y la Energía

Grupos de Investigación:

  • Fotocatálisis Heterogénea: Aplicaciones (web)
  • Materiales y Procesos Catalíticos de Interés Ambiental y Energético (web)
  • Química de Superficies y Catálisis (web)


Catedráticos

Caballero Martínez, Alfonso

Catedrático

Universidad de Sevilla


✉ caballero@us.es
☎ 954 48 95 38 ✆ 446138
ORCID 0000-0003-1704-3261

Ivanova, Svetlana

Catedrática

Universidad de Sevilla


✉ svetlana@icmse.csic.es
☎ 954 13 92 39 ✆ 446174
ORCID 0000-0003-4552-3289

Odriozola Gordón, José Antonio

Catedrático

Universidad de Sevilla


✉ odrio@us.es
☎ 954 48 95 44 ✆ 446144
ORCID 0000-0002-8283-0459


Investigadores Científicos

Centeno Gallego, Miguel Angel

Investigador Científico

CSIC


✉ centeno@icmse.csic.es
☎ 954 48 95 43 ✆ 446143
ORCID 0000-0002-8349-3044

Colón Ibáñez, Gerardo

Investigador Científico

CSIC


✉ gcolon@icmse.csic.es
☎ 954 48 96 26 ✆ 446126
ORCID 0000-0002-4086-0270


Científicos Titulares

Hidalgo López, María del Carmen

Científica Titular

CSIC


✉ mchidalgo@icmse.csic.es
☎ 954 48 96 30 ✆ 446160
ORCID 0000-0001-9862-6578

Holgado Vázquez, Juan Pedro

Científico Titular

CSIC


✉ holgado@icmse.csic.es
☎ 954 48 95 36 ✆ 446136
ORCID 0000-0003-4551-5094


Profesores Titulares

Bobadilla Baladrón, Luis Francisco

Profesor Titular

Universidad de Sevilla


✉ bobadilla@icmse.csic.es
☎ 955 608 736 ✆ 446124
ORCID 0000-0003-0085-9811

Córdoba Gallego, José Manuel

Profesor Titular

Universidad de Sevilla


✉ jmcordob@us.es
☎ 954 55 01 22
ORCID 0000-0003-1699-7928

Domínguez Leal, María Isabel

Profesora Titular

Universidad de Sevilla


✉ mleal@icmse.csic.es
☎ 954 13 92 30 ✆ 446164
ORCID 0000-0002-4118-7313

Martínez Tejada, Leidy Marcela

Profesora Titular

Universidad de Sevilla


✉ leidy@icmse.csic.es
☎ 954 13 92 30 ✆ 446164
ORCID 0000-0002-0471-5033

Penkova, Anna Dimitrova

Profesora Titular

Universidad de Sevilla


✉ anna@icmse.csic.es
☎ 954 13 92 40 ✆ 446175
ORCID 0000-0001-5792-2362

Pereñiguez Rodríguez, Rosa María

Profesora Titular

Universidad de Sevilla


✉ rosa@icmse.csic.es
☎ 954 48 95 48 ✆ 446148
ORCID 0000-0002-4022-5082

Ramírez Reina, Tomás

Profesor Titular

Universidad de Sevilla


✉ tramirez@us.es
☎ 955 60 80 21 ✆ 446127
ORCID 0000-0001-9693-5107

Romero Sarria, Francisca

Profesora Titular

Universidad de Sevilla


✉ francisca@icmse.csic.es
☎ 954 55 97 64
ORCID 0000-0002-6547-2151


Investigadores Honorarios

Navío Santos, José Antonio

Investigador Honorario

Universidad de Sevilla


✉ navio@us.es
☎ 954 48 95 50 ✆ 446150
ORCID 0000-0002-7884-1067


Doctores Contratados

González Arias, Judith

Doctora Contratada

Universidad de Sevilla


✉ jgonzalez15@us.es

ORCID 0000-0001-5470-6939

González Castaño, Miriam

Doctora Contratada

Universidad de Sevilla


✉ miriam.gonzalez@icmse.csic.es

ORCID 0000-0003-2575-8398

Jurado Fuentes, Dolores

Doctora Contratada

CSIC


✉ dolores.jurado@icmse.csic.es

ORCID 0000-0003-1908-899X

Nawaz, Muhammad Asif

Doctor Contratado

Universidad de Sevilla


✉ muhammad.asif@icmse.csic.es

ORCID 0000-0003-3234-031X

Pastor Pérez, Laura

Doctora Contratada

Universidad de Sevilla


✉ lpperez@us.es
☎ 954 48 95 76 ✆ 446176
ORCID 0000-0003-4943-0282

Platero Moreno, Francisco Jesús

Doctor Contratado

Universidad de Sevilla


✉ fplatero@us.es

ORCID 0000-0003-4067-5902

Ruiz López, Estela

Doctora Contratada

Universidad de Sevilla


✉ eruizl@us.es
☎ 954 48 95 76 ✆ 446176
ORCID 0000-0001-9198-3919


Personal Investigador en Formación

Alvarenga Salinas, Gerardo Andrés

Invesigador en Formación

Universidad de Sevilla




ORCID 0000-0002-2858-1017

Alvarez Hernández, Débora

Investigadora en Formación

CSIC


✉ debora.alvarez@icmse.csic.es
☎ 954 13 92 13 ✆ 446117
ORCID 0000-0002-1873-1341

Blay Roger, José Rubén

Investigador en Formación

Universidad de Sevilla


✉ ruben.blay@icmse.csic.es

ORCID 0000-0002-3085-8134

Carrasco Ruiz, Sergio

Investigador en Formación

Universidad de Sevilla


✉ sergio.carrasco@icmse.csic.es
☎ 954 13 92 37 ✆ 446172
ORCID 0000-0003-3057-303X

Delgado Martín, Gabriel

Investigador en Formación

CSIC


✉ gabriel.delgado@icmse.csic.es
☎ 954 13 92 37 ✆ 446172

Luque Alvarez, Ligia Amelia

Investigadora en Formación

Universidad de Sevilla


✉ ligia.luque@icmse.csic.es
☎ 954 13 92 37 ✆ 446172
ORCID 0000-0002-3998-580X

Oreggioni Gadea, Daniela Aielen

Investigadora en Formación

Universidad de Sevilla





Ribota Peláez, María

Investigadora en Formación

Universidad de Sevilla


✉ maria.ribota@icmse.csic.es
☎ 954 13 92 13 ✆ 446117

Saif, Maria

Investigadora en Formación

Universidad de Sevilla


✉ maria.saif@icmse.csic.es

ORCID 0000-0002-2369-7846

Torres Sempere, Guillermo

Investigador en Formación

Universidad de Sevilla


✉ guillermo.torres@icmse.csic.es
☎ 954 13 92 37 ✆ 446172
ORCID 0000-0001-6343-0698


Personal Técnico Contratado

Escamilla Rebollo, María

Técnico en Formación

Universidad de Sevilla


✉ maria.escamilla@icmse.csic.es


Fernández Sánchez, Ana María

Técnico

CSIC





Ibáñez Rodríguez, Juan Carlos

Técnico en Formación

Universidad de Sevilla


✉ juancarlos.ibanez@icmse.csic.es


Serrano Cruz, Melania

Técnico en Formación

Universidad de Sevilla



☎ 954 13 92 13 ✆ 446117

Aplicaciones de Procesos Avanzados de desinfección de aguas con nanomateriales, para la reducción del impacto procedente de presiones urbanas, en el marco de la economía circular




Investigador Principal: Rosa Mosteo Abad (UNIZAR) / Mª Peña Ormad Melero (UNIZAR)
Periodo: 01-12-2022 / 30-11-2024
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: TED2021-129267B-I00
Componentes: María Carmen Hidalgo López (ICMS), Francisca Romero Sarria (ICMS), MªPilar Goñi Cepero (UNIZAR) y Encarnación Rubio Aranda (UNIZAR)
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

El agua es uno de los recursos naturales que, por su carácter limitado y variable, tanto en cantidad como en calidad, debe ser protegido con especial intensidad, en consonancia con los Objetivos Medioambientales que apoyan la transición ecológica: el uso sostenible y la protección de los recursos hídricos y marinos, la economía circular, la prevención y control de la contaminación y la protección y recuperación de la biodiversidad y los ecosistemas. Estudios realizados en colaboración con la Confederación Hidrográfica del Ebro indican que las fuentes puntuales urbanas son las presiones que en la mayoría de los casos son la causa del incumplimiento de los objetivos de calidad ambiental establecidos por la DMA. Estos incumplimientos están relacionados principalmente con la contaminación microbiológica en las aguas receptoras de estos vertidos. Generalmente, al no existir una exigencia legal, las instalaciones de tratamiento de aguas residuales no incluyen procesos de desinfección que reduzcan la carga microbiológica de los efluentes y, en consecuencia, estos agentes se incorporan a las aguas naturales, limitando el uso que se hace de ellas, especialmente en el abastecimiento de poblaciones y en el uso recreativo (baño y otros). Asimismo, dicha contaminación en las aguas residuales limita la posibilidad de su posterior reutilización, reduciendo la capacidad de aumentar la disponibilidad de recursos hídricos. Es importante destacar que, la reutilización del agua para el riego agrícola también puede contribuir a la economía circular al recuperar los nutrientes del agua regenerada y aplicarlos a los cultivos y reduciendo la necesidad de uso suplementarias de fertilizantes minerales. Por lo tanto, es necesario intensificar la eficiencia del tratamiento de las aguas residuales mediante procesos no convencionales que mejoren la calidad del agua tratada con el objetivo final de permitir una reutilización segura de los efluentes (reglamento (UE) 2020/741). Por otro lado, el control de más parámetros microbiológicos es esencial para un correcto análisis de aplicación de las tecnologías. Consciente de esta necesidad, el grupo AySA lleva años desarrollando proyectos centrados en procesos convencionales y no convencionales, basados en procesos fotocatalíticos, aplicados a desinfección de aguas y control microbiológico en EDARs. El objetivo principal de este proyecto es seleccionar la mejor tecnología de desinfección de aguas residuales urbanas tratadas para su aplicación a gran escala mediante la mejora de los procesos de oxidación avanzada previamente estudiados en desinfección de este tipo de aguas. Además, el control microbiológico, no sólo de los indicadores bacterianos utilizados convencionalmente, sino también de los protozoos y de las bacterias endosimbióticas que se encuentran en el interior de las amebas, se considera muy relevante en este proyecto ya que, hasta donde sabemos, no existen estudios con una variedad tan amplia de microorganismos potencialmente patógenos. Se espera que este enfoque realista minimice el impacto en aguas receptoras y aumente la reutilización reduciendo el riesgo sanitario y ambiental.


Hacia la transición digital en Química Solar (SolarChem5.0): Fotorreactores




Investigador Principal: Sixto Malato Rodríguez (PSA-CIEMAT) / Diego C. Alarcón Padilla (PSA-CIEMAT)
Periodo: 01-12-2022 / 30-11-2024
Organismo Financiador: Ministerio de Ciencia e Innovación "Transición Ecológica y Transición Digital"
Código: TED2021-130173B-C43
Componentes: Gerardo Colón Ibáñez, Alba Ruiz Aguirre (PSA-CIEMAT)
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

El reto de la energía solar. A lo largo de la historia, las mejoras más significativas de la humanidad han estado ligadas a la revolución industrial (RI). Hoy en día, estamos inmersos en la 4ª RI "La era digitalmente disruptiva" donde Europa se encuentra en una transición hacia la neutralidad climática y el liderazgo digital.1 La Industria 5.0 pretende posicionar la investigación y la innovación al servicio de la transición hacia una industria europea sostenible, centrada en el ser humano y resiliente.2 Las tecnologías químicas solares alterarán radicalmente los modelos actuales de producción industrial y de transformación y almacenamiento de energía. Sin embargo, la escala necesaria está a la vista pero aún no se ha alcanzado debido a la falta de tecnologías disponibles de alto rendimiento y bajo coste. SolarChem 5.0 pretende contribuir a la 5ª RI, sentando las bases de la sinergia entre la transición ecológica y digital en el marco de la Química Solar a través de:

"El desarrollo de una tecnología innovadora de Química Solar Digital, para convertir los recursos y contaminantes abundantes en la Tierra en combustibles y productos químicos, llenando el vacío existente entre las tecnologías sostenibles y escalables impulsadas por la energía solar"

Para alcanzar este ambicioso objetivo y teniendo en cuenta la complejidad y la duración del proyecto nuestra estrategia se basa en el diseño de un consorcio interdisciplinar formado por cuatro subproyectos (SP) que incluyen grupos de investigación punteros en disciplinas complementarias como: Química, Ciencia de Materiales, Biocatálisis, Fotoelectroquímica, Inteligencia Artificial (IA), Tecnologías Solares y Caracterización Avanzada. Cada SP incorpora un equipo multidisciplinar compuesto por más de un equipo de investigación de diferentes instituciones de investigación, universidades y/o instalaciones singulares.

Este subproyecto dedicado a fotorreactores (SP3) se concentrará en el diseño conceptual y desarrollo de un reactor solar fotoelectroquímico (PEC) para la selección de la configuración más adecuada para la reacción y el funcionamiento del colector solar. Las actividades de investigación de este SP3 se desarrollarán en el WP5 y serán gestionadas por investigadores de dos instituciones diferentes: PSA-CIEMAT (líder del SP3) e ICMSE-CSIC. La Plataforma Solar de Almería (PSA) es una Gran Instalación Científica Europea y una Infraestructura Científica y Técnica Singular de España (ICTS) con un amplio historial en el diseño, construcción e implementación de reactores solares para reacciones fotoquímicas, junto con instalaciones destacadas. El equipo de la PSA-CIEMAT cuenta también con una amplia experiencia en el uso de programas de trazado de rayos como TONATIUH y SOLTRACE para la caracterización optoenergética de sistemas de concentración solar. Asimismo, dispone de un conjunto de herramientas de simulación solar térmica de desarrollo propio validadas en las diferentes plantas piloto solares de baja y media temperatura disponibles en la PSA. Además, el equipo ICMSE-CSIC participará en el desarrollo de la célula PEC y en la integración de los electrodos.


Desarrollo de materiales heteroestructurados basados en biocarbones con propiedades fotofuncionales para aplicaciones en procesos de descontaminación de aguas y desinfección




Investigador Principal: María Carmen Hidalgo López / Francisca Romero Sarria
Periodo: 01-09-2022 / 31-08-2025
Organismo Financiador: Ministerio de Ciencia e Innovación "Generación de Conocimiento"
Código: PID2021-122413NB-I00
Componentes: José Manuel Córdoba Gallego, Concepción Real Pérez, María Dolores Alcalá Gonzalez, José Antonio Navío Santos y Rosa Mosteo Abad (UNIZAR)
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

En el presente proyecto de investigación se propone el desarrollo de sistemas fotocatalíticos heteroestructurados (ZnWO4/ZnO, WO3/AgBr, WO3/TiO2, Bi2WO6/TiO2, ZnBi2O4/ZnO, BixTiyOz) acoplados o soportados sobre biocarbones (procedentes de la pirólisis de restos de poda de olivo, cascarilla de arroz y hueso de aceituna y que permiten una vía de revalorización de estos residuos), el estudio de las diferentes variables y métodos de síntesis, su optimización, y su comportamiento fotocatalítico evaluado en la desinfección de aguas y eliminación de contaminantes emergentes. En los últimos años se han estudiado nuevos fotocatalizadores basados en materiales heteroestructurados, donde se desarrollan heterouniones de semiconductores para conseguir una mejor separación espacial de electrones y huecos fotogenerados, obteniendo mayores tiempos de vida de estos portadores, aumentando así la eficiencia de los sistemas. Aunque estos materiales han mostrado buena actividad fotocatalítica en diferentes sustratos estudiados, generalmente presentan valores de superficie específica moderados o bajos, y algunos tienen problemas de estabilidad tras pocos ciclos de reacción.
El proyecto propone el acoplamiento o soporte de estos fotocatalizadores heteroestructurados con biocarbones de diferentes características, con el objetivo de dotarlos de mayor área superficial y aumentar su eficacia y estabilidad para sus aplicaciones como fotocatalizadores; mejorando la capacidad de absorción, estrechando el bad-gap donde el biocarbón puede actuar como fotosensibilizador, mejorando el transporte de electrones, permitiendo una mejor separación de los portadores fotogenerados prolongando su vida útil y proporcionando estabilización y fotoestabilización a los sistemas.
Los biocarbones son materiales ricos en carbono que se obtienen mediante la calcinación de la biomasa en ausencia de oxígeno (pirólisis) y presentan interesantes propiedades, como gran área superficial y alta porosidad, y pueden ser modulados, mediante el control de las condiciones de operación, para obtener la cantidad y el tipo de grupos funcionales deseados en la superficie, hidrofobicidad o hidrofilicidad o diferentes pH superficial.
Los objetivos del proyecto incluyen la caracterización físico-química completa y la optimización de los fotocatalizadores
heteroestructurados/biocarbón para las aplicaciones propuestas bajo diferentes condiciones de operación, como iluminación solar o visible. Se evaluará la eficacia de cada sistema en la eliminación de contaminantes emergentes (antibióticos) y en la inactivación de microorganismos potencialmente patógenos habitualmente presentes en aguas.
La presencia de microorganismos patógenos en las aguas es un tema de especial preocupación debido al riesgo potencial de transmisión de enfermedades y, en consecuencia, es necesario el control microbiano en las aguas. Asimismo, los productos farmacéuticos y de higiene son ampliamente usados hoy en día, llegando hasta las aguas. Sus potenciales efectos adversos sobre la salud humana han llevado a catalogarlos como contaminantes ambientales relevantes de la clase de contaminantes emergentes El proyecto se aborda desde un punto de vista interdisciplinar y en el contexto de la economía circular, revalorizando un residuo (biomasa) para desarrollar fotocatalizadores que den solución a un problema (descontaminación y desinfección de aguas) mediante procesos respetuosos con el medio ambiente (fotocatálisis heterogénea).


DiSeño de catalizadores Multifuncionales para la conversión de gAs de síntesis Rico en CO2 en combusTibles líquidos sostenibles, en una única etapa, vía síntesis de FTS y HCR: SMART-FTS




Investigador Principal: José Antonio Odriozola Gordón / Tomás Ramírez Reina
Periodo: 01-09-2022 / 31-08-2025
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: PID2021-126876OB-I00
Componentes: Luis Francisco Bobadilla Baladrón, Anna Dimitrova Penkova, Francisco Manuel Baena Moreno, José Rubén Blay Roger, Nuria García Moncada, Miriam González Castaño, Ligia Amelia Luque Álvarez
Grupo de Investigación: Química de Superficies y Catálisis

Siguiendo las indicaciones de los Objetivos de Desarrollo Sostenible de las Naciones Unidas (UNSDG), es obligatorio tomar acción al respecto buscando alternativas de energía limpia y asequible (objetivo 7) para favorecer ciudades y comunidades sostenibles (objetivo 11) mientras se mitiga el cambio climático. cambio (objetivo 13). De hecho, Horizon Europe da prioridad a las tecnologías bajas y cero emisiones de carbono como objetivos clave para la próxima generación de Europa. Sobre la base de estas premisas, la biomasa, y en particular los residuos de biomasa, representan un prometedor sustituto de los combustibles fósiles y una excelente materia prima para la fabricación de combustibles bajos en carbono. Durante su breve ciclo de vida, todo el carbono de la biomasa proviene de la atmósfera y el suelo y se libera al medio ambiente cuando se quema. Por lo tanto, la biomasa se considera un combustible neutro en carbono. Además, los combustibles derivados de biomasa son hidrocarburos de alta densidad energética que son ideales para vehículos de aviación, marítimos y pesados, a diferencia de las baterías y los dispositivos electroquímicos, que son adecuados para aplicaciones más ligeras y, por lo tanto, complementarios de los biocombustibles. En pocas palabras, no podemos hacer volar un avión con baterías durante largas distancias, pero podemos alimentarlo con biocombustibles sostenibles. Por lo tanto, los biocombustibles de biomasa están destinados a desempeñar un papel clave en la descarbonización del sector del transporte. Además, ofrecer una segunda vida a los biorresiduos es crucial para algunas comunidades (es decir, la agricultura y el sector agrícola) cuyos horizontes de mercado pueden expandirse convirtiendo un "residuo" problemático en "precursores de biocombustibles" rentables. En este sentido, SMART-FTS trae conceptos disruptivos sobre la producción de biocombustibles a partir de bio-syngas para impulsar la descarbonización del transporte en armonía con la estrategia de economía circular.


Reactores estructurados no convencionales para el craqueo catalítico de metano libre de CO2




Investigador Principal: Miguel Angel Centeno Gallego
Periodo: 01-09-2022 / 31-08-2025
Organismo Financiador: Unión Europea
Código: EU240226_01
Componentes: Maria Isabel Domínguez Leal, Leidy Marcela Martínez Tejada, Svetlana Ivanova
Grupo de Investigación: Química de Superficies y Catálisis

STORMING desarrollará reactores estructurados innovadores calentados con electricidad renovable, para convertir CH4 fósil en H2 libre de CO2 y en nanomateriales de carbono de alto valor para aplicaciones de baterías. Más específicamente, se desarrollarán catalizadores innovadores basados en Fe, altamente activos y fácilmente regenerables mediante procesos que no generen residuos, a través de un protocolo de diseño racional de catalizadores, que combina estudios teóricos (Teoría del Funcional de la Densidad y Cálculos de Dinámica Molecular) y experimentales (cluster), todos de ellos asistidos por caracterización in situ y operando y herramientas de Machine Learning. La electrificación (con calentamiento por microondas o por efecto joule) de reactores estructurados, diseñados por fluidodinámica computacional y preparados mediante impresión 3D, permitirá un control térmico preciso que dará como resultado una alta eficiencia energética. El proyecto validará, en un nivel 5 de TRL, la tecnología catalítica más prometedora (elegida con criterios tecnológicos, económicos y ambientales) para producir H2 con eficiencia energética (> 60 %), cero emisiones netas y con un coste hasta un 10 % menor al del proceso convencional. La difusión y comunicación de los resultados impulsará la aceptación social de las tecnologías relacionadas con el H2 y la participación de las partes interesadas en la explotación y el despliegue de procesos a corto plazo. La clave para alcanzar los desafiantes objetivos de STORMING es el muy alto grado de complementariedad e interdisciplinaridad de los grupos que forman el consorcio, donde las ciencias básicas y aplicadas se fusionan con la ingeniería, la informática y las ciencias sociales. El Grupo del ICMS implicado llevará a cabo el desarrollo del catalizador desde la preparación de los catalizadores en polvo hasta su washcoating sobre soportes estructurados. CSIC participa como miembro del consorcio, participando la Universidad de Sevilla como entidad asociada.

https://cordis.europa.eu/project/id/101069690

Storming - Unión Europea

Storming - ICMS


Diseño de Catalizadores Avanzados para procesos de HDO: un apuesta revolucionaria para la conversión de biomasa: CLEVER-BIO




Investigador Principal: Tomás Ramírez Reina
Periodo: 05-10-2021 / 31-12-2022
Organismo Financiador: Junta de Andalucía
Código: P20_00667
Componentes: Luis Francisco Bobadilla Baladrón, José Antonio Odriozola Gordón, Laura Pastor Pérez, Anna Dimitrova Penkova
Grupo de Investigación: Química de Superficies y Catálisis

CLEVER-BIO propone un concepto revolucionario para la producción de biocombustibles limitando la emisión de gases de efecto invernadero sembrando las bases de una tecnología verde: conversión de residuos a combustibles y productos de alto valor. La idea central de CLEVER-BIO es el Desarrollo de catalizadores avanzados para llevar a cabo la reacción de HDO de bio-aceites derivados de lignina. El proyecto se llevara a cabo en 24 meses y comprende un programa intenso de investigación multidisciplinar con fuerte participación de instituciones internacionales.


Diseño de fotocatalizadores altamente eficientes mediante control de la nanoescala para la producción de H2 NanoLight2H2




Investigador Principal: Gerardo Colón Ibañez
Periodo: 05-10-2021 / 30-06-2023
Organismo Financiador: Junta de Andalucía
Código: P20-00156 - PAIDI 2020
Componentes: Alfonso Caballero Martínez, Rosa Pereñiguez Rodríguez, Juan Pedro Holgado Vázquez
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

El objetivo principal de este proyecto es el desarrollo de catalizadores heteroestructurados basados en óxidos semiconductores altamente eficientes (Nb2O5, WO3, TiO2 y Fe2O3) y g-C3N4, con control a nivel de la nanoescala, y potencial aplicación en la reacción de fotoreformado de alcoholes para la producción de H2.  Así mismo, se pretende estudiar la optimización del proceso catalítico mediante una aproximación multi-catalítica, mediante la combinación de termocatálisis y fotocatálisis. La producción fotocatalítica de H2 una reacción de gran interés desde el punto de vista energético mediante el uso de una tecnología limpia y sostenible como la fotocatálisis. En este proyecto se pretende el desarrollo de sistemas altamente eficientes para la producción de hidrógeno. Se prestará especial atención al diseño de heteroestructuras que permitan la optimización del proceso fotoinducido. De igual modo se incidirá en el uso de co-catalizadores alternativos a los tradicionales metales nobles; sistemas basados en metales de transición (Cu, Co, Ni), así como estructuras bimetálicas con metales nobles formado aleaciones o core-shell. Junto al proceso fotocatalítico en fase líquida, se estudiará la viabilidad de un proceso de fotoreformado en fase gas, basándonos en recientes estudios que ponen de manifiesto el efecto sinérgico de una aproximación foto-termo catalítica en estos procesos. De esta forma esta propuesta pretende abordar de forma ambiciosa el aumento de la eficiencia del proceso fotocatalítico a fin de poder plantear esta tecnología a mayor escala. En este sentido, además de los estudios de optimización de los catalizadores y del proceso fotocatalítico, se afrontará como algo primordial su escalado a planta solar piloto. 


Integración de Energía y Gasificación para procesos sostenibles (GENIUS)




Investigador Principal: José Antonio Odriozola Gordón
Periodo: 05-10-2021 / 31-12-2022
Organismo Financiador: Junta de Andalucía
Código: P20_00594
Componentes: Luis Francisco Bobadilla Baladrón, Laura Pastor Pérez, Anna Dimitrova Penkova, Tomás Ramírez Reina
Grupo de Investigación: Química de Superficies y Catálisis

GENIUS representa una propuesta innovadora para la conversion de bio-residuos en vectores energeticos sostenibles. El proyecto propone la combinacion de tecnologias maduras como la gasificacion y reformado acuaso para aportar soluciones cataliticas al proceso de conversion de bioresiduos. GENIUS desarrollara reactores de micronales que permiten el diseño de plantas compactas para el procesado de residuos lo que facilita su implementacion en aplicaciones deslocalizadas como por ejemplo explotaciones agricolas donde los residuos pueden convertirse en productos de valor añadido


Acido fórmico como vector de energía: de la biomasa al hidrógeno verde




Investigador Principal: Miguel Angel Centeno Gallego / Svetlana Ivanova
Periodo: 01-09-2021 / 31-08-2025
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: PID2020-113809RB-C32 - Proyectos I+D+i "Retos Investigación"
Componentes: Leidy Marcela Martínez Tejada, María Isabel Domínguez Leal
Grupo de Investigación: Química de Superficies y Catálisis

El presente proyecto forma parte del proyecto coordinado ENERCATH2 que pretende integrar una estrategia que involucra múltiples reacciones para la producción y uso de hidrogeno verde a partir de la biomasa. El objetivo último es contribuir al desarrollo de tecnologías energéticas sostenibles que sustituyan a las actuales, derivadas de las fuentes fósiles. Específicamente, el proyecto del ICMS se centra en el uso del ácido fórmico como vector energético de hidrógeno, dado que es un compuesto químico líquido con una alta densidad gravimétrica de energía, que puede ser almacenado, transportado y manipulado de manera segura usando la infraestructura existente de distribución de hidrocarburos.

El objetivo principal del proyecto es la generación de ácido fórmico a partir de biomasa lignocelulósica y la posterior obtención de corrientes de hidrógeno a partir de éste. Para este fin, se pretende desarrollar catalizadores novedosos, preferiblemente basados en carbones derivados de la biomasa y/o en metales de transición, no nobles, (V, Ni, Cu, Co, etc.), activos, selectivos y estables, para: i) la oxidación directa y selectiva de la biomasa lignocelulósica, e.g. glucosa, bien hacia la producción masiva de ácido fórmico, bien hacia la producción de una mezcla de ácido fórmico con otros co-productos, tales como el ácido levulínico, que pueden servir como punto de partida para la generación de productos plataforma de interés industrial, intermedios en la producción de combustibles y ii) la deshidrogenación de ácido fórmico, tanto en fase líquida como gaseosa, para la producción de corrientes de hidrógeno libres de CO.

Los catalizadores preparados serán caracterizados estructural y químicamente por una gran variedad de técnicas (DRX, XPS, SEM, HRTEM, Raman, DRIFTS, TPR/TPD, UV-Vis, Análisis textural), tanto pre- como post-reacción, para evaluar las posibles modificaciones ocurridas en el transcurso de la misma. Igualmente, se realizarán estudios en condiciones de reacción (in-situ y operando) por espectroscopias DRIFTS y ATR, lo que, junto con los resultados de actividad y de caracterización, permitirá analizar el mecanismo de las reacciones y así poder establecer la relación estructura-actividad en cada caso. El conocimiento de esta relación permitirá optimizar el catalizador diseñado y, en última instancia, cada proceso catalítico de producción de vectores sostenibles de energía propuesto en el proyecto


Avanzando hacia la economía circular: Biocombustibles para el transporte pesado, a partir del reciclado de residuos (NICER BIOFUELS)




Investigador Principal: José Antonio Odriozola Gordón / Tomás Ramírez Reina
Periodo: 01-09-2021 / 31-08-2024
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: PLEC2021-008086
Componentes: María Isabel Domínguez Leal, Laura Pastor Pérez
Grupo de Investigación: Química de Superficies y Catálisis

Financiado por el programa RETOS-COLABORACION PUBLICO-PRIVADA del Ministerio de Ciencia e Innovacion con fondos EU bajo el marco Next Generation Europe, NICER BIOFUELS es fruto de la colaboracion entre las Universidades de Zaragoza y Sevilla y la multinacional URBASER. En el contexto de la economia circular y el desarollo de combustibles sostenibles que permitan descarbonizar el transporte y avanzar hacia una sociedad libre de emisiones, NICER-BIOFUELS representa un paso adelante para combatir el cambio climitaco combinando ciencia fundamental e ingenieria aplicada.


Valorización de CO2 mediante procesos catalíticos y termofotocatalíticos: reducción de emisiones y obtención de metano y otros hidrocarburos ligeros




Investigador Principal: Alfonso Caballero Martínez / Gerardo Colón Ibáñez
Periodo: 01-09-2021 / 31-08-2024
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: PID2020-119946RB-I00
Componentes: Juan Pedro Holgado Vázquez y Rosa María Pereñiguez Rodríguez
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

En este proyecto se llevarán a cabo diversos estudios y desarrollos relacionados con la reacción de hidrogenación de CO2 para la producción de Gas Natural Sintético (GNS) e hidrocarburos ligeros. Así, la metanación y las denominadas reacciones modificadas de Fischer-Tropsch a olefinas (FTO) se están convirtiendo en procesos muy interesantes desde el punto de vista económico, energético y medioambiental. Por otra parte, el uso de hidrógeno verde como agente reductor, obtenido a su vez a partir de fuentes renovables, representa, además de la reducción de las emisiones de gases de efecto invernadero, una forma de almacenar la energía procedente de fuentes renovables, muchas de las cuales son intermitentes y, por tanto, difíciles de ajustar a las necesidades de consumo.
Con todo ello, este proyecto persigue un enfoque multicatalítico que comprende la termocatálisis y la fotocatálisis térmica con el fin de conseguir altos rendimientos, alta sostenibilidad y con los menores costes de producción, orientados en todo caso a una aplicación industrial final. Por otro lado, el desarrollo y optimización de los materiales catalíticos, considerando nuevos sistemas catalíticos heterogéneos basados en Ni, Fe, Co, Ru, Au, Pd entre otros metales, que han mostrado un gran potencial para estas reacciones de hidrogenación en los últimos años. En cuanto a los materiales catalíticos, se seleccionarán soportes micro y mesoporosos de composición variable (zeolitas, SBA-15, etc.), así como otros basados en óxidos y perovskitas ABO3. Para ello se utilizarán una serie de técnicas de preparación recientemente descritas (cristalización por microondas, proceso de autocombustión, mesoestructuración por nanocasting y porosidad jerárquica) que permiten obtener sistemas de alta superficie específica y nanoestructura controlada. La combinación de diferentes elementos en las posiciones A y B de la estructura de la perovskita, que actúan tanto como promotores de sistemas catalíticos como precursores de aleaciones metálicas en sistemas catalíticos reducidos, permitirá obtener materiales con propiedades catalíticas sintonizables, muy variadas y versátiles.


Conversión Avanzada de Biogas a Ácido Acético: Soluciones Catalíticas para una Sociedad con Bajas Emisiones de Carbono




Investigador Principal: Laura Pastor Pérez
Periodo: 01-10-2020 / 30-09-2023
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: PID2019-108502RJ-I00
Componentes:
Grupo de Investigación: Química de Superficies y Catálisis

En ADVENTURE se presenta un nuevo concepto para convertir biogás, procedente de desechos orgánicos, en productos químicos de alto valor industrial, como es el ácido acético (AA), de una manera tanto amigable con el medio ambiente como viable económicamente. El AA se emplea como precursor de muchos productos procedentes de la química fina, con numerosas aplicaciones, como son la fabricación de pinturas y recubrimientos, la producción de plásticos y adhesivos basados en agua, entre muchos otros, siendo una molécula plataforma muy versátil para la industria química. Tradicionalmente el AA se produce a escala comercial a través de una ruta indirecta produciendo una considerable huella global de CO2. Por ello, el objetivo principal de ADVENTURE es re-diseñar el proceso de producción de AA introduciendo biogás como principal materia prima - un enfoque completamente nuevo que provoca una sinergia entre la utilización de CO2 y la síntesis de química fina.

En este contexto AVENTURE abordará tres desafíos principales: (i) un desafío global: las preocupaciones ambientales asociadas con la emisión de gases de efecto invernadero; (ii) una oportunidad industrial: abordará el problema de la sostenibilidad económica de la industria del biogás ofreciendo alternativas viables para la conversión de materia prima de bajo valor en bio-químicos de alto valor añadido a escala industrial; y (iii) un desafío a escala científica fundamental: se presentan dos propuestas, la intensificación de una ruta indirecta usando reactores de microcanales y una ruta directa llevada a cabo con catálisis por plasma. Para lograr estos ambiciosos objetivos, se diseñará una nueva generación de catalizadores avanzados multifuncionales capaces de proporcionar los productos específicos deseados con alta actividad, selectividad y durabilidad a largo plazo para garantizar el éxito de AVENTURE.


Valorización de CO2: obtención de hidrocarburos mediante procesos catalíticos de hidrogenación




Investigador Principal: Alfonso Caballero Martínez / Juan Pedro Holgado Vázquez
Periodo: 01-02-2020 / 31-01-2022
Organismo Financiador: Junta de Andalucía
Código: US-1263455
Componentes: Gerardo Colón Ibáñez, Rosa Pereñíguez Rodríguez, Andrew M. Beale (UCL), Angeles M. López Martín, Francisco Jesús Platero Moreno
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

En el presente proyecto se llevarán a cabo diversos estudios y desarrollos relacionados con la reducción de CO2 a productos de alto valor añadido, como metano, olefinas ligeras, gasolinas y otros hidrocarburos funcionalizados, de gran interés económico, energético y medioambiental. El uso de hidrógeno como agente reductor, obtenido este a su vez de fuentes renovables supone, además de la reducción de las emisiones de gases de efecto invernadero, una vía para el almacenamiento de la energía procedente de fuentes renovables, muchas de ellas de carácter intermitente y por tanto difícilmente acoplable a las necesidades de consumo.

Con todo ello en este proyecto se propone el desarrollo de nuevos sistemas catalíticos heterogéneos basados en Ni, Fe, Co, Ru e In, entre otros metales, los cuales han mostrado en los últimos años un gran potencial para esta reacción de hidrogenación. Dado el carácter bifuncional de los mecanismos de reacción involucrados en estas reacciones, se seleccionarán soportes micro y mesoporosos de composición variable (zeolitas, SBA-15, etc.), así como otros basados en estructura perovskita ABO3. Para ello se emplearán una serie de técnicas de preparación recientemente descritas (Cristalización por Microondas, Proceso de Autocombustión, Mesoestructuración por Nanocasting y Porosidad Jerarquizada) que permiten obtener sistemas de alta superficie específica y nanoestructura controlada. La combinación de diferentes elementos en las posiciones A y B de la estructura perovskita, que actúen tanto como agentes promotores de los sistemas catalíticos como de precursores de aleaciones metálicas en los sistemas catalíticos reducidos, permitirá obtener materiales con propiedades catalíticas modulables, muy variadas y versátiles.

http://matproner.icms.us-csic.es/projects/


Ácido fórmico como vector energético: viabilidad de los ciclos de carga y descarga de hidrógeno




Investigador Principal: Svetlana Ivanova / Miguel Angel Centeno
Periodo: 01-01-2020 / 31-12-2022
Organismo Financiador: Junta de Andalucía
Código: P18-RT-3405
Componentes: María Isabel Domínguez Leal, Leidy Marcela Martínez Tejada
Grupo de Investigación: Química de Superficies y Catálisis

El presente proyecto se encuadra en la actual tendencia a nivel mundial de búsqueda de tecnologías para la captura y uso del dióxido de carbono (Carbon dioxide Capture and Utilization CCU). Su interés radica en la utilización directa del CO2 atmosférico para almacenar hidrógeno verde, esto es, producido con la ayuda de energías renovables, en forma de ácido fórmico, usado como vector energético. Desde el punto de vista medioambiental, el desarrollo de esta tecnología permitiría preservar la huella de CO2 durante el ciclo completo de generación, almacenamiento y liberación de energía, sin generar más gases de efecto invernadero. La posibilidad de almacenar hidrógeno de esta forma facilitaría su transporte y su uso en aplicaciones deslocalizadas diversas, tanto móviles como estacionarias. Indirectamente, esta tecnología racionalizaría el almacenamiento de las energías renovables, haciéndolas independientes de las condiciones climáticas. Este proyecto pretende estudiar la viabilidad de la tecnología basándose en el desarrollo de un único catalizador, estable y selectivo para los ciclos de carga y descarga de hidrógeno (CO2/HCOOH).


CO2 como fuente de carbono para la producción de compuestos químicos de alto valor añadido




Investigador Principal: José Antonio Odriozola Gordón / Svetlana Ivanova
Periodo: 01-02-2020 / 31-01-2022
Organismo Financiador: Junta de Andalucía
Código: US-1263288
Componentes: Anna Dimitrova Penkova, Ligia Amelia Luque Alvarez, Débora Álvarez Hernández
Grupo de Investigación: Química de Superficies y Catálisis

El principal reto científico de este proyecto es el diseño de un dispositivo catalítico activo y selectivo en la reducción catalítica de CO2 a CO. El proyecto pretende resolver dos problemas interrelacionados, el diseño del catalizador, que pasa por una comprensión a nivel molecular de la reacción estudiada, y el diseño de un reactor de microcanales que permita realizar la reacción en régimen isotermo y tiempos de residencia muy cortos. Para ello se propone la síntesis de catalizadores constituidos por metales nobles o de transición soportados en óxidos reducibles para llevar a cabo el proceso catalítico analizando los factores determinantes de la reacción: tamaño de partícula de la fase metálica, reducibilidad del soporte, interacciones metal-soporte y resistencia de la desactivación. Las características de la reacción exigen el desarrollo de reactores de microcanales que permitan disminuir las pérdidas de carga y los tiempos de residencia manteniendose isotermos. El estudio, por tanto, busca diseñar un dispositivo catalítico activo, selectivo y estable que trabaje en régimen isotermo y permita tiempos de residencia inferiores a 100 ms.


Procesos Power-to-X para la Valorización de Co2 en Reactores Catalíticos Estructurados (Co2-Ptx)




Investigador Principal: José Antonio Odriozola Gordón / Francisca Romero Sarria
Periodo: 1-1-2019 / 31-12-2021
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: RTI2018-096294-B-C33 "Retos Investigación"
Componentes: Luis F. Bobadilla Baladron, Maria Isabel Dominguez Leal, Anna Dimitrova Penkova, Lola de las Aguas Azancot Luque, Marta Romero Espinosa, Juan Carlos Navarro de Miguel
Grupo de Investigación: Química de Superficies y Catálisis

La tecnología Power-to-X (PTX) tiene como objetivo el almacenamiento de energía (preferentemente renovable) en productos químicos. Dichos productos pueden usarse luego como combustibles o como moléculas plataforma para otras síntesis químicas. Por tanto, esta tecnología juega un papel fundamental incrementando la fracción renovable del mix energético en línea con los objetivos de la UE para la reducción de emisiones de gases con efecto invernadero.

La producción de H2 por electrólisis de agua para PTX es una tecnología madura disponible comercialmente que puede ser usada durante los periodos valle de consumo de energía renovables.

Por otro lado, el CO2 es una fuente de carbono desaprovechada por lo que el uso combinado de H2 renovable y CO2 añade un importante plus al proceso PTX ya que el CO2 asociado a las emisiones de gases de efecto invernadero es reintegrado contribuyendo a la economía circular y la descarbonización. Esta es la idea central que guía la presente propuesta. En particular, se trata de llevar a cabo las siguientes reacciones: hidrogenación de CO2 a metano (también llamada metanación de CO2 o reacción de Sabatier), la reacción reversa Water-Gas-Shift (activación del CO2 y ajuste de la relación H2/CO), síntesis de biocombustibles (dimetil éter y SFT) y producción de ácido acético. Estas reacciones ofrecen notables retos químico-ingenieriles en aspectos como: i) desarrollo de catalizadores multifuncionales adecuados; ii) gestión térmica de reacciones fuertemente exotérmicas; iii) control de la selectividad en reacciones múltiples en serie por acción conjunta de la temperatura, el tiempo de residencia, la formulación del catalizador y el diseño del reactor. El conocimiento adquirido por el consorcio en los proyectos previos (MAT2006-12386, ENE2009-14522, ENE2012-37431 y ENE2015-66975) nos permite proponer de una manera sólida y fundamentada el uso de catalizadores y reactores estructurados para superar estos retos.

Por tanto, el objetivo fundamental de esta propuesta es el estudio de sistemas catalíticos estructurados para reacciones relevantes del proceso Power-To-X con CO2 (CO2-PTX). Por otro lado, esperamos que la intensificación que aportan los sistemas estructurados sobre metales y los patrones de flujo desarrollados en sistemas como espumas de poro abierto jueguen papeles determinantes en el control de la temperatura y la selectividad de la reacción. En este sentido se estudiarán diferentes arquitecturas de sustrato junto a las variables principales como la densidad de celda o poro, el espesor de película catalítica o la aleación metálica del sustrato. Finalmente, para aproximarnos a la aplicación industrial de estos sistemas CO2-PtX se considerará la valorización de CO2 presente en corrientes diluidas como los gases de combustión. Esto supone nuevos retos debido a la baja concentración de CO2, altos caudales volumétricos y efectos negativos de otros componentes (H2O, SOx, etc.) en la actividad y estabilidad de los catalizadores. Se investigarán nuevas formulaciones de catalizadores junto con estrategias avanzadas de adsorción-desorción-reacción de CO2 sobre los sustratos estructurados estudiados.

Globalmente, el proyecto se estructurará en forma matricial con tareas transversales de cada grupo basadas en sus líneas de especialización (modelado, estructuración y caracterización avanzada) junto a reacciones concretas de cada laboratorio que conformarán las tareas longitudinales del proyecto


Aprovechamiento de biomasa y producción sostenible de energía mediante (foto)catalizadores y reactores estructurados basados en materiales carbonosos




Investigador Principal: Miguel Angel Centeno Gallego / Svetlana Ivanova
Periodo: 01-01-2018 / 30-09-2021
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: ENE2017-82451-C3-3-R "Retos de la Sociedad"
Componentes: Carlos López Cartes, Leidy Marcela Martínez Tejada, María Isabel Domínguez Leal, Regla Ayala Espinar
Grupo de Investigación: Química de Superficies y Catálisis

El objetivo principal del presente proyecto coordinado entre la U. de Zaragoza, el ICMS y la U. de Cádiz, es el desarrollo de catalizadores multifuncionales y estructurados basados en materiales catalíticos carbonosos, tanto de carácter biomórfico, como grafénico-grafítico. Estos materiales catalíticos han de ser activos, selectivos y estables en reacciones directamente relacionadas con el aprovechamiento de la biomasa lignocelulósica (producción de 5-HMF, ácido levulínico, FDCA, o γ-valerolactona) y la producción sostenible de energía (producción de H2), así como la valorización química y fotoquímica de CO2 (hidrogenación de CO2, descomposición de biogás, foto-reformado de bio-alcoholes), usando H2 de origen renovable ("water splitting"). Este proyecto trata de mejorar procesos actualmente implementados que están relacionados con la producción de energía, y otros más novedosos, como el aprovechamiento de la luz solar, que sin lugar a dudas están llamados a tener un papel importante en este campo. De hecho, la utilización de la energía solar haría más viable energéticamente, por ejemplo, la reacción de metanación de CO2 al usar H2 de origen (foto)renovable producido por “water splitting”. Se busca también la generación de productos de alto valor añadido por procesos de biorefinería, que sustituyan los obtenidos actualmente a partir de fuentes fósiles. Se pretende conseguir un conjunto de sólidos carbonosos con propiedades estructurales (porosidad jerárquica meso/micro), hidrofilicidad-hidrofobicidad, funcionalidades químicas, composición superficial etc. diseñados ad hoc para cada una de las reacciones consideradas por los distintos subproyectos, incluyendo la implementación de procesos en continuo mediante la utilización de reactores estructurados a partir de los catalizadores más eficientes. El desarrollo y utilización de sistemas catalíticos estructurados aumenta la viabilidad e intensificación de los procesos y por tanto la eficiencia energética y medioambiental. La complementariedad de los tres grupos proponentes abre la posibilidad de abordar en un solo proyecto todos estos objetivos, permitiendo aplicar distintas metodologías emergentes para la síntesis de nuevos materiales carbonosos, como son la mineralización biomórfica, la expansión/funcionalización de compuestos intercalados de grafito, grafitos especiales (e.g. “graphite nanolayers” o "nanoflakes”), uso de plantillas inorgánicas para generación de carbones mesoporosos, su funcionalización avanzada y su aplicación en procesos de alto impacto en el área de la energía, tecnología química y tecnologías ambientales.


Desarrollo de nuevos materiales nanoestructurados para la valorización de metano a hidrógeno y olefinas C2-C4




Investigador Principal: Alfonso Caballero Martínez / Gerardo Colón Ibáñez
Periodo: 1-1-2018 / 31-12-2020
Organismo Financiador: Ministerio de Ciencia, Innovación y Universidades
Código: ENE2017-88818-C2-1-R "Retos de la Sociedad"
Componentes: Rosa Pereñiguez Rodríguez, Francisco Jesús Platero Moreno, Angeles Maria López Martín, Juan Pedro Holgado Vázquez
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

El desarrollo de nuevos materiales con propiedades singulares en distintos campos de aplicación se ha convertido en las últimas décadas en una prioridad en multitud de áreas de la ciencia y la tecnología. Entre ellas, además de materiales micro y mesoporosos de composición variable, pueden destacarse los sólidos basados en estructura perovskita ABO3. La versatilidad que presentan estos últimos mediante la sustitución parcial en las posiciones A y B por distintos metales alcalinos, alcalino-terreos y de transición los convierte en una alternativa interesante, y de hecho tienen aplicaciones en campos relacionados con sus propiedades electricas, ópticas, térmicas, catalíticas y como adsorbentes. En el presente proyecto coordinado se plantea la preparación de un conjunto de materiales, entre ellos algunos con estructura perovskita (Fe, Co, Mn, Cu y Bi en posiciones B; Ca, Mg, Ce y La en posiciones A), y estudiar su aplicación en distintos procesos de catálisis heterogénea y de adsorción de contaminantes. Para ello se emplearán una serie de técnicas de preparación recientemente descritas (Cristalización por Microondas, Proceso de Autocombustión, Mesoestructuración por Nanocasting y Porosidad Jerarquizada) que permiten obtener sistemas de alta superficie específica y nanoestructura controlada. De esta forma, y combinando los metales en posiciones A y B para que actuen tanto como agentes promotores como precursores de aleaciones metálicas en los sistemas reducidos, se obtendrán sistemas con propiedades muy variadas y versatiles. Asi, en el subproyecto 1 se estudiarán sus propiedades catalíticas en procesos de enorme interés para la valorización de metano, principal componente del gas natural y una de las fuentes de energía más abundantes en la actualidad. En concreto, y junto con sistemas soportados en materiales mesoporosos y otros, se estudiará en primer lugar la actividad de perovskitas de niquel para la reacción de reformado seco de metano con el fin de obtener gas de síntesis. El objetivo será obtener sistemas activos y sobre estables frente a los fenómenos de desactivación habituales por deposición de coque. En segundo lugar, se estudiarán sistemas basados principalmente en Fe y Co para la reacción de Fisher-Tropsch a olefinas C2-C4, productos de gran interés económico por ser precursores de una gran cantidad de otros productos de alto valor añadido. Por otro lado, los trabajos propuestos en el subproyecto 2 están relacionados con la aplicación de estos sólidos de estructura perovskita para el desarrollo de procesos de eliminación de contaminantes emergentes, un nuevo tipo de desechos que suelen ser resistentes a los procesos de degradación biológico convencionales, constituyendo por tanto un problema medioambiental de primer orden. En concreto, el proyecto pretende desarrollar tratamientos integrados de depuración (adsorción-POA), utilizando perovskitas para la eliminación de contaminantes emergentes (Ibuprofeno, Salicílico, Ciprofloxacina, Cafeína, Gemfibrozil y  Benzafibrato), optimizando parámetros como el rendimiento, la reciclabilidad de los catalizadores, la aplicabilidad y la sostenibilidad. De especial relevancia en este tipo de procesos es la utilización de procesos de fotocatálisis heterogénea, por lo que el desarrollo de nuevos óxidos semiconductores como las perovskitas, con características fisicoquímicas y estructurales superiores a las del TiO2, es un objetivo de primer orden del presente subproyecto.


Diseño racional de fotocatalizadores altamente eficientes mediante control a nivel atómico




Investigador Principal: Gerardo Colón Ibañez
Periodo: 02-10-2017 / 31-12-2020
Organismo Financiador: Ministerio de Economía y Competitividad
Código: PCIN-2017-056
Componentes: Alfonso Caballero Martínez, Angeles Martín
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

El uso de la energía solar para la generación de hidrógeno a partir de agua es probablemente uno de procesos más limpios y sostenibles para la obtención de energía. Sin embargo, los catalizadores que dan mejores rendimientos son demasiado caros para ser económicamente viables. El proyecto RATOCAT tiene como objetivo el desarrollo de materiales fotocatalíticos optimizados.    De esta forma las prestaciones fotocatalíticas de sistemas basados en TiO2 y gC3N4 podrían optimizarse mediante el diseño de su superficie con nanoestructuras de composición, nanoarquitectura, tamaño y estado químico altamente controladas. Se empleará para ello estudios de simulación teórica para proponer la nanoestructuras óptimas que serán depositadas de forma controlada y precisa mediante atomic layer deposition (ALD). Los test de actividad fotocatalítica tanto a escala de laboratorio como en planta piloto (Plataforma Solar de Almería).


Desarrollo de Materiales Foto-Funcionales para Aplicaciones Medioambientales




Investigador Principal: José Antonio Navío Santos
Periodo: 01-01-2016 / 31-12-2018
Organismo Financiador: Ministerio de Economía y Competitividad
Código: CTQ2015-64664-C2-2-P
Componentes: María del Carmen Hidalgo López, Manuel Macías Azaña
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

La fotocatálisis heterogénea es un proceso avanzado de oxidación que ha sido objeto de una enorme cantidad de estudios relacionados con la purificación de gases y del agua. La mayoría de estos estudios se han realizado para el tratamiento de aguas y utilizando el TiO2 o materiales basados en este óxido y más recientemente, aunque en una clara minoría, se han estudiado otros óxidos inorgánicos binarios, ternarios y cuaternarios, predominando en todo caso los estudios de estos últimos materiales para el tratamiento de aguas. En cuanto al catalizador (base del proceso fotocatalítico) que es el responsable de la eficacia o fracaso del proceso, en la última década se han desarrollado numerosos y variados métodos de síntesis que han sido principalmente probados en procesos de degradación fotocatalítica en fase acuosa. Sin embargo, pocos estudios se han realizado con óxidos mixtos ( binarios, binarios-acoplados, ternarios y cuaternarios) y menos en fase gasesosa.

En base a estas consideraciones y a la dilatada y reconocida experiencia que el grupo de este Subproyecto#2 tiene el campo de la síntesis y caracterización de materiales foto-funcionales (en el UV y UV/Vis), y debido al reducido número de estudios fotocatalíticos en fase gas, en su mayoría estudiando un sólo componente, se plantea en este Subproyecto#2, el desarrollo de materiales foto-funcionales que conduzcan a materiales basados no sólo en TiO2 con propiedades mejoradas sino a otros materiales basados en este óxido y a otros óxidos inorgánicos binarios, los obtenidos por acoplamientos de óxidos binarios y ternarios, que se obtengan por procedimientos de síntesis distintos (o modificados) a los ya recogidos en la bibliografía, y cuya fotoactividad sea evaluada por el grupo del Subproyecto#1, sin que se descarte ensayos previos de actividad fotocatalítica en agua por el grupo del Subproyecto#2.

Entre los materiales que se pretenden sintetizar en el Subproyecto#2 (empleando métodos no-hidrotermales, hidrotermales y sol-gel) se contemplan: óxidos binarios (TiO2, ZnO, ZnO2, Fe2O3, WO3, Bi2O3, Ta2O5 , La2O3), óxidos binarios acoplados (TiO2-WO3, TiO2-ZnO, TiO2-ZnO2; TiO2-Ta2O5, TiO2-La2O3, ZnO-Fe2O3 y ZnO2-Fe2O3), óxidos ternarios (Bi2WO6, Bi2WO6-ZnO, Bi2WO6-ZnO2, Bi2WO6-Fe2O3, Bi2Ti2O7, ZnWO4, La2Ti2O7), contemplando la foto-deposición de metales (Pt, Ag, Au) en los sistemas que muestren una actividad fotocatalítica considerable (Semiconductores/Metal).

Los mejores sistemas evaluados se remitirán al grupo del Subproyecto#1 para el estudio de la viabilidad fotocatalítica en la eliminación de NOx,COVs, CO, CO2 y SO2 presentes en emisiones gaseosas.


Sistemas Catalíticos Estructurados para la Producción de Biocombustible




Investigador Principal: José Antonio Odriozola Gordón
Periodo: 01-01-2016 / 31-12-2018
Organismo Financiador: Ministerio de Economía y Competitividad
Código: ENE2015-66975-C3-2-R
Componentes: María Isabel Domínguez Leal, Anna Dimitrova Penkova, Francisca Romero Sarria
Grupo de Investigación: Química de Superficies y Catálisis

La dependencia de nuestro actual sistema energético de las fuentes de combustibles fósiles y sus adversos efectos medioambientales están potenciando el desarrollo de fuentes de energía de origen renovable. Este es el caso de los biocombustibles de segunda generación. Los procesos de producción de combustibles a partir de biomasa lignocelulósica y residuos orgánicos son habitualmente catalíticos y se caracterizan por la necesidad de un intenso intercambio de calor asociado al elevado efecto térmico de las reacciones químicas implicadas, dificultad para minimizar simultáneamente las limitaciones difusionales y la caída de presión en los reactores convencionales de lecho fijo y, en ocasiones, por necesitar tiempos de contacto extremadamente cortos. Todo ello hace que las tecnologías catalíticas convencionales trabajen en condiciones no óptimas.

Los sistemas catalíticos estructurados, catalizadores estructurados y reactores de microcanales ofrecen excelentes oportunidades para superar estas limitaciones ya que permiten minimizar simultáneamente las limitaciones difusionales y la caída de presión, mejorar los flujos radiales de calor y materia y permitir tiempos de contacto muy cortos con elevadas eficiencias. Los monolitos de canales paralelos longitudinales, las espumas de porosidad abierta y las mallas metálicas son sustratos que pueden fabricarse a partir de numerosas aleaciones metálicas y con diferentes densidades de celda o poro. También pueden ser recubiertas de cualquier catalizador de interés, adaptándose así a los diferentes requerimientos de cada proceso. Por otro lado, los reactores de microcanales pueden proporcionar una intensificación del proceso sin igual que va acompañada de un excelente control de la temperatura, de la calidad de producto y con mejoras sustanciales en la seguridad del proceso.

El objetivo del proyecto es estudiar sistemas catalíticos estructurados para la producción de energía de origen renovable. En concreto, se estudiarán la síntesis de Fischer-Tropsch, la síntesis directa de dimetiléter y la producción del gas de síntesis que alimentará estos procesos mediante reformado de biogás y "producer gas".Además se estudiará la reacción de desplazamiento del gas de agua que resulta clave para el ajuste de la relación H2/CO en el gas de síntesis.

Se hará especial hincapié en la influencia de las características térmicas de los sistemas estructurados en su comportamiento catalítico. Para ello se estudiará el efecto de la densidad de celdas en monolitos, densidad de poros en espumas, luz de malla en mallas apiladas, tipo de aleación metálica, espesor del recubrimiento catalítico y geometría del sustrato (incluyendo en algunos casos reactores de microcanales).Se considerarán como fases activas catalizadores muy próximos al estado del arte.

El desarrollo de estos estudios se hará con el apoyo de tres tareas transversales lideradas por cada uno de los tres grupos participantes, pero en las que participarán todos ellos: la preparación de los sistemas catalíticos estructurados, la caracterización mediante técnicas avanzadas y los estudios de modelado y simulación. Mediante este proyecto se pretende generar un conocimiento que contribuya a expandir el actual campo de aplicación de los sistemas catalíticos estructurados hacia aplicaciones energéticas sostenibles que se verían beneficiadas por las ventajas que ofrecen estos sistemas en línea con el reto Energía segura, eficiente y limpia.


Desarrollo de procesos catalíticos y fotocatalíticos para la valorización del gas natural: activación y transformación de metano e hidrocarburos ligeros




Investigador Principal: Alfonso Caballero Martínez
Periodo: 1-01-2015 / 31-12-2018
Organismo Financiador: Ministerio de Economía y Competitividad
Código: CTQ2014-60524-R
Componentes: Juan Pedro Holgado Vázquez, Gerardo Colon Ibáñez, Rosa María Pereñiguez Rodríguez, Alberto Rodríguez Gómez
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

  En el presente proyecto se pretenden realizar diversos estudios y desarrollos relacionados con distintos procesos de activación y transformación de metano en moléculas de más valor añadido. Con este fin se estudiarán tanto procesos bien establecidos de conversión indirecta, a través de reacciones de reformado (RM) para la obtención de gas de síntesis, como distintos procesos de conversión directa, en concreto la oxidación directa a metanol (DOM) y la aromatización de metano (DAM).

    En lo que respecta a la reacción de reformado, se plantea el desarrollo de sistemas catalíticos con resistencia mejorada a los procesos de desactivación. Para ello se prepararán y caracterizarán nuevos catalizadores bimetálicos nanoestructurados de niquel depositados en soportes como ceria, alumina y alumina/ceria, así como soportes mesoporosos de tipo SBA-15, dopados con ceria y alumina. Como segundo metal se utlizarán cobalto o hierro. Paralelamente, se realizará un estudio de la reacción de reformado por vía fotocatalítica utilizando sistemas de Cu, Pt y Ni depositados en soportes activos clásicos como titania o ceria, así como otros de más reciente desarrollo, como son Ga2O3, nitruro de carbono o grafeno. En este caso, se pretende igualmente explorar las posibilidades de la activación fotoquímica para la reacción de oxidación preferencial de CO (foto-PROX) en presencia de hidrógeno, de utilidad en los procesos de purificación de hidrógeno procedente del gas de síntesis. Se incidirá en la preparación de sistemas con una estructura de de bandas apropiada para el control de esta oxidación selectiva de CO.

     En cuanto a los procesos de conversion directa, se estudiará la reacción de DOM usando O2, H2O2 o N2O como activadores de la reacción, en combinación con sistemas basados en Au/Pd, Fe, Cu y/o Ni depositados en soportes como zeolitas ZSM-5, grafeno y TiO2. En este último caso, utilizando Au/Pd como fase metálica activa en presencia de H2O2 como especie oxidante se planteará la posibilidad de combinar la síntesis in situ de agua oxigenada con la posterior oxidación directa de metano. Igualmente, se explorará el proceso de oxidación fotocatalítica de metano a metanol como una alternativa novedosa y altamente atractiva. En este caso, el uso de nuevos fotocatalizadores de oxidación como el BiVO4 así como la presencia de mediadores redox permitirán controlar la oxidación selectiva a metanol.

    Algunos sistemas estrechamente relacionados con los anteriores, y en particular los basados en Mo soportados en zeolitas ZSM-5 y MCM-22, se utilizarán para el estudio de la reacción de aromatización de metano. La proporción de aluminio, el porcentaje de molibdeno y su activación en la estructura microporosa del soporte, así como la adición de promotores como Ga, Tl o Pb serán algunas de las variables a optimizar para esta reacción. De forma paralela se podrá estudiar el proceso de aromatización fotoinducido, recientemente descrito por algunos autores.


Desarrollo de catalizadores biomórficos obtenidos a partir de biomasa residual para producción de hidrógeno y refino de bio-oil




Investigador Principal: Miguel Angel Centeno Gallego
Periodo: 1-01-2014 / 31-12-2018
Organismo Financiador: Ministerio de Economía y Competitividad
Código: ENE2013-47880-C3-2-R
Componentes: María Isabel Dominguez Leal, Carlos López Cartes, Leidy Marcela Martínez Tejada, Svetlana Ivanova
Grupo de Investigación: Química de Superficies y Catálisis

El objetivo principal del presente proyecto coordinado entre las universidades de Zaragoza y el Instituto de Ciencias de Materiales de Sevilla es el desarrollo de catalizadores metálicos soportados en carbones biomórficos (CB), para su posterior aplicación a procesos de producción de hidrógeno y de refino de bio-oil. La técnica de Mineralización Biomórfica es una innovadora herramienta capaz de sintetizar materiales inorgánicos funcionales utilizando como plantilla diversas estructuras formadas en procesos biológicos. Así, a partir de materiales lignocelulósicos (biomasa) se puede preparar una gran variedad de materiales cerámicos microestructurados. No obstante, la replicación de los distintos niveles jerárquicos existentes en los tejidos biológicos sigue siendo un gran reto a día de hoy. Para avanzar en esta línea, en este proyecto se va a abordar el estudio de la síntesis, caracterización y aplicación de catalizadores metálicos soportados en carbón biomórfico (Me/CB), con distribuciones de tamaño homogénea y porosidad jerarquizada.
La preparación de estos materiales se realiza mediante descomposición térmica en atmósfera reductora (o inerte) a alta temperatura, y elevadas velocidades de calentamiento, de un material lignocelulósico (e.g. celulosa, lignina, papel) impregnado con los precursores metálicos catalíticos. De esta manera, en una sola etapa, se obtiene un soporte carbonoso biomórfico con nanopartículas de metal dispersas en su superficie. Este método de síntesis presenta una extraordinaria versatilidad, puesto que además de poder utilizar diferentes materias primas de partida, se pueden obtener catalizadores de muy distintas composiciones y contenidos metálicos, así como su estructuración en dispositivos monolíticos y espumas. Como materias primas, además de celulosa, lignina o papel, se van estudiar biomasas agrícolas residuales.
Los catalizadores tipo Me/CB se pretenden aplicar en procesos de producción de hidrógeno (descomposición de hidrocarburos ligeros, de amoniaco y deshidrogenación de ácido fórmico), en la reacción de Water-Gas-Shift (WGS), y en distintas reacciones test de refino de bio-oil (conversión de acético a acetona, hidrogenación de vainillina y ciclohexeno y conversión de m-cresol a fenol).
 


Aprovechamiento de CO2 para la obtención de gas de síntesis en catalizadores




Investigador Principal: Miguel Angel Centeno Gallego
Periodo: 01-02-2013 / 31-01-2017
Organismo Financiador: Junta de Andalucía
Código: P11-TEP-8196 (Proyecto de Excelencia)
Componentes: Svetlana Ivanova, Maria Isabel Domínguez Leal, José Antonio Odriozola Gordón, Tomás Ramírez Reina, Francisca Romero Sarria
Grupo de Investigación: Química de Superficies y Catálisis

Hoy en día no existen dudas acerca de que la concentración de gases de efecto invernadero, en particular la de CO2, está aumentando de manera considerable en la atmósfera terrestre. Para evitar este aumento continuado se debe aumentar la eficiencia en la producción de energía, disminuir la intensidad del uso de las fuentes fósiles y, finalmente, potenciar la captura y secuestro del CO2. Todo esto debe conseguirse manteniendo el crecimiento económico y la calidad de vida. En consecuencia, si tenemos en cuenta el desarrollo de las naciones menos industrializadas y el intensivo consumo energético necesario para aumentar su nivel de vida, la captura y secuestro de CO2 parece la alternativa más favorable.
En el presente proyecto se propone la utilización del CO2 como materia prima para el reformado de gas natural como paso previo a la obtención de combustibles líquidos sintéticos. Usando tecnologías convencionales, esta propuesta sólo es económicamente viable asociada a grandes reservas de gas natural. Sin embargo, la tecnología de microcanales permite abordar la síntesis de combustibles sintéticos de forma discontinua y con capacidad de producción flexible de modo económicamente viable. Para ello, es necesario el diseño, caracterización y ensayo de catalizadores activos, selectivos y estables en la reacción de reformado de metano con vapor y CO2:

CO2 + 3CH4 + 2H2O  → 4CO + 8H2

La selección de estos catalizadores culminará con la estructuración de los mismos utilizando soportes metálicos con microcanales paralelos (micromonolitos) a fin de establecer las condiciones necesarias para, en un futuro, la construcción de reactores de microcanales.


Aprovechamiento de gas no convencional: Reactores de microcanales en GTL




Investigador Principal: José Antonio Odriozola Gordón
Periodo: 01-01-2013 / 31-12-2015
Organismo Financiador: Ministerio de Economía y Competitividad
Código: ENE2012-37431-C03-01
Componentes: Svetlana Ivanova, Anna Dimitrova Penkova, Tomás Ramírez Reina, Sandra Palma del Valle, Ara Muñoz Murillo, María Isabel Domínguez Leal, Francisca Romero Sarria
Grupo de Investigación: Química de Superficies y Catálisis

Existen en la actualidad fuentes de gas que podríamos agrupar bajo el calificativo de no-convencional que incluyen el que se encuentra confinado en formaciones geológicas de baja permeabilidad, el gas asociado al crudo, los pequeños yaciemientos en lugares remotos, el biogas producido en la digestión anaerobia de residuos y los denominados product gas generados en la gasificación de biomasa y en la combustión de alquitran. La composición de todas estas fuentes de gas es similar estando constituidas por una mezcla de metano y dióxido de carbono con cantidades inferiores de otros gases permanentes. La concentración de CO2 puede llegar a ser de hasta el 40% en volumen como ocurre con el gas asociado de algunos campos off-shore y el biogas producido por fermentación de residuos agrícolas. La valorización de este gas mediante el proceso GTL (Gas to Liquid) es una alternativa cuando su localización remota o distante de los gaseoductos no permite ser agregado a las fuentes convencionales o no puede ser consumido in situ, ya que los combustibles líquidos son más fáciles de almacenar y transportar y tienen aplicación directa en el transporte.
La tecnología GTL convencional no es aplicable ya que su viabilidad económica exige instalaciones y suministros a una escala elevadísima. Por ello, se está desarrollando esa misma tecnología en reactores de microcanales de pared catalítica que consiguen incrementar de forma notable el rendimiento de las unidades de producción de gas de síntesis y síntesis de Fischer-Tropsch (SFT), al poder trabajar con elevadas velocidades espaciales, mejorando el control de la temperatura y con ello de la selectividad y la seguridad del proceso; además, la naturaleza modular basada en la replicación de unidades simplifica de forma considerable el escalado del proceso, adaptándose bien a unidades de producción de gas no convencional que, por lo general, no son grandes.
En el presente proyecto se pretende desarrollar la tecnología de microcanales para el proceso GTL utilizando mezclas metano-dióxido de carbono para simular las fuentes de gas no convencional. Los estudios que hemos venido realizando sobre reactores de microcanales deberán ampliarse a condiciones de presión y temperatura más drásticas, lo que debe permitir validar y mejorar la selección de materiales para la construcción y las técnicas de unión.
La aplicación de esta tecnología requiere el desarrollo de nuevos catalizadores activos, selectivos y estables que se adapten a los procesos GTL en reactores de microcanales. Se diseñarán catalizadores para el reformado al vapor, el reformado seco y la oxidación parcial de metano para la producción de gas de síntesis, así como catalizadores SFT. Se construirán reactores de microcanales para el ensayo de dichos catalizadores, se obtendrán las ecuaciones cinéticas de los catalizadores seleccionados y se modelarán y simularán los reactores construidos.
 


Desarrollo de sistemas catalíticos nanoestructurados preparados mediante métodos sol-gel y de deposición fotoquímica para aplicaciones energéticas y medioambientales (NanoFotoCat)




Investigador Principal: Alfonso Caballero Martínez
Periodo: 01-01-2012 / 31-12-2014
Organismo Financiador: Ministerio de Ciencie e Innovación
Código: ENE2011-24412
Componentes: Gerardo Colón Ibáñez, Juan Pedro Holgado Vázquez, Sergio Obregón Alfaro, Rosa María Pereñiguez Rodríguez, Fátima Ternero Fernández
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

En el presente proyecto se plantea el desarrollo de una serie de catalizadores nanoestructurados basados en metales de transición tales como Ni, Cu, Au o Pd, y depositados en soportes activos (TiO2, CeO2, WO3, Fe2O3 y soportes mesoporosos como SBA-15 dopado con titania y ceria). Se utilizarán métodos de preparación convencionales (impregnación, deposición-precipitación, etc.), junto con procedimientos de síntesis de desarrollo más reciente, como métodos sol-gel y, muy especialmente, el denominado Fotodeposición Asistida Fotoquímicamente (Photochemical Assisted Deposition, PAD). De esta forma, esperamos controlar de manera rigurosa a la escala nanométrica tanto el tamaño de la partícula metálica y/o bimetálica, como la interacción metal-soporte. En el caso concreto del método PAD, uno de los objetivos principales del proyecto es el estudio y la optimización de las variables del proceso de deposición de manera que, además de controlar el tamaño de la partícula metálica desde diámetros en torno a 15nm hasta sistemas atómicamente dispersos sobre soportes activos como ceria o titania, nos permita diseñar la distribución de los metales en la partícula metálica, haciendo uso de procesos controlados de fotodeposición consecutivos y/o simultáneos de los metales. Esta metodología debe permitir la obtención de distribuciones metálicas de tipo core-shell o aleadas, lo que como es conocido, puede llegar a afectar de manera fundamental a las prestaciones catalíticas. Estas prestaciones serán comprobadas en diferentes reacciones de interés energético y/o medioambiental, tanto en fase gas como en fase líquida. Así, los sistemas basados en niquel y oro se utilizarán en las reacciones de reformado húmedo y seco de metano (Steam and Dry Methane Reforming, SRM/DRM) y la oxidación selectiva de CO (Preferential Oxidation of CO, PROX), respectivamente. Los sistemas mono y bimetálicos basados en paladio y paladio-oro serán utilizados para la optimización de la reacción de síntesis directa de agua oxigenada a partir de hidrógeno y oxígeno, realizada en fase líquida a alta presión. La correlación entre el estado físico-químico y la reactividad de los sistemas catalíticos nos permitirá aclarar aspectos fundamentales de los mecanismos de las reacciones heterogéneas propuestas.


Materiales Foto-Activos para el desarrollo de la Energía Solar en Procesos Fotocatalíticos de Interés Medioambiental




Investigador Principal: José Antonio Navío Santos
Periodo: 1-01-2012 / 31-12-2012
Organismo Financiador: Ministerio de Ciencia e Innovación
Código: CTQ2011-26617-C03-02
Componentes: Mª del Carmen Hidalgo López, Manuel Macías Azaña, Julie J. Murcia Mesa; Sebastián Murcia López
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

La fotocatálisis heterogenea ha mostrado sobradamente su potencial para destoxificación y desinfección de medios acuosos y gaseosos. Sin embargo, su desarrollo tecnológico ha sido muy limitado debido a una serie de dificultades que pueden agruparse en dos grupos principales:

1. Dificultades para separar el catalizador del medio al finalizar el proceso, para su reactivación y reutilización.

2. Bajo rendimiento del proceso, que sólo aprovecha un porcentaje muy pequeño de los fotones útiles, siendo estos además una pequeña parte del espectro natural.

En nuestra propuesta se coordinan tres subproyectos liderados por tres grupos que aunan amplia experiencia en: Síntesis, modificación y caracterización de materiales fotocatalíticos (principalmente el grupo de la Universidad de Sevilla), Preparación y caracterización de óxidos metálicos en lámina delgada sobre diferentes substratos(principalmente el grupo del CIEMAT) y Modificación, caracterización espectroscópica de centros activos y estudios de fotorreactividad en fase acuosa y gaseosa (principalmente el grupo de la ULPGC).

 

Sobre la base de esta experiencia acumulada y de las principales tendencias en el desarrollo de la fotocatálisisheterogénea, nuestro consorcio se plantea como objetivo central de este proyecto: Sintetizar materiales basados en TiO2, SnO2, ZnO y materiales ternarios tipo titanato de bismuto (BITs),  en forma de polvo con tamaño manométrico con alta actividad fotocatalítica y su fijación sobre sustratos adecuados (vidrio, membranas, láminas metálicas, etc.) recubiertos con películas delgadas de diferentes óxidos metálicos que faciliten el anclaje de estas partículas y/o actúen como semilla para la formación o cristalización de estas partículas, para poder utilizar estos sistemas de forma eficiente en procesos de descontaminación fotocatalítica en fase acuosa y gaseosa.


Desarrollo de nuevos procesos industriales basados en sistemas catalíticos para la obtención sostenible de ingredientes base en fragancias y aromas




Investigador Principal: Juan Pedro Holgado Vázquez
Periodo: 04-05-2011 / 31-12-2014
Organismo Financiador: Ministerio de Economía y Competitividad
Código: IPT-2011-1553-420000
Componentes: Alfonso Caballero Martínez, Víctor Manuel González de la Cruz, Rosa Pereñíguez Rodríguez, Gerardo Colón Ibáñez
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

En la actualidad, los procesos industriales utilizados para la transformación de muchos compuestos utilizados en el campo de las fragancias y los aromas ofrecen bajos rendimientos y generan una enorme cantidad de residuos peligrosos, que requieren varias etapas de segregación y tratamiento de los mismos durante el proceso. La mayor parte de estos procesos se basan en reacciones de oxidación/reducción de compuestos estequiometricos, o están basados en sistemas de catálisis homogénea, los cuales presentan inconvenientes asociados con la corrosión, la recuperación del catalizador de la mezcla de reacción y su regeneración para su posible reutilización. En este contexto “eco-amigable”, existe un interés creciente para el uso de oxidantes menos contaminantes, tales como el peróxido de hidrógeno o el oxígeno molecular, y la integración de dichos oxidantes en sistemas de catálisis heterogénea. Obviamente uno de los mayores retos que presentan las reacciones basadas en sistemas catalíticos es lograr el máximo rendimiento (producto de conversión por selectividad) con objeto de reducir el consumo de reactivos (materias primas), y minimizar los procesos de separación y eliminación de subproductos no deseados fruto de la ineficacia del proceso. En este tipo de reacciones (con compuestos principalmente orgánicos, muchos de origen natural), no es, en general, difícil obtener una alta conversión, pero dado que estos compuestos presentan multiples funcionalidades y/o puntos susceptibles de ser oxidados , el reto se centra en la obtención de una alta selectividad, generalmente incluso a nivel enantiomérico.

En el marco del proyecto, se han seleccionado procesos de interés en la industria cosmética y alimentaria, con objeto de conseguir el desarrollo a escala industrial de procesos basados en sistemas de catálisis heterogénea para la obtención de compuestos intermedios de gran valor añadido en el mercado de los perfumes y aromas, como son, entre otros, el proceso de obtención de la l-carvona a partir de la oxidación catalítica del d-limoneno.


Nuevos fotocatalizadores basados en compuestos de Bi3+ altamente fotoactivos en el visible




Investigador Principal: Gerardo Colon Ibáñez
Periodo: 11-03-2011 / 31-03- 2015
Organismo Financiador: Junta de Andalucía
Código: P09-FQM-4570
Componentes: M. Carmen Hidalgo López, José Antonio Navío Santos, Manuel Macías Azaña, Sebastián Murcia López
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

El objetivo principal de este proyecto es el desarrollo de una nueva generación de materiales nanoestructurados alternativos al TiO2 que presenten una alta fotoactividad en la región del visible y que puedan ser utilizados de forma competitiva y eficiente en procesos de tratamiento de efluentes líquidos y gaseosos mediante el aprovechamiento de la luz solar. El presente proyecto pretende desarrollar nuevos sistemas de nanocatalizadores heterogéneos basados en Bi3+ (Bi2WO4, Bi2MoO6, BiVO4, Bi3O4Cl, CaBi2O4, PbBi2Nb2O9,…) que presenten unas propiedades optoelectrónicas adecuadas para el aprovechamiento de la energía solar en el rango del visible (Fotocatálisis Solar) y que al mismo tiempo exhiban unas propiedades fisicoquímicas mejoradas que optimicen el proceso fotocatalítico desde el punto de vista de difusión y transferencia de portadores de carga fotogenerados.


Catalizadores nanoestructurados basados en Au para reacciones de oxidación selectiva




Investigador Principal: Juan Pedro Holgado Vázquez
Periodo: 1-01-2011 / 31-12-2011
Organismo Financiador: Ministerio de Ciencia y Tecnología
Código: CTQ2010-21348-C02-01
Componentes: Alfonso Caballero Martínez, Víctor Manuel González de la Cruz, Fátima Ternero Fernán-dez, Richard M. Lambert
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

El objetivo del proyecto es el desarrollo de catalizadores con base oro, con alta reactividad en los procesos de oxidación selectiva. En este contexto, se abordan reacciones tales como la oxidación selectiva del alcohol bencílico (y derivados) o la oxidación selectiva de CO.  esta última conectada con su aplicación en Catálisis Ambiental como es el control de la calidad del aire y en aplicaciones energéticas como la purificación de corriente de H2 procedente de procesos de reformado (PROX).

Las propiedades del oro, metal biocompatible y no tóxico, puede ser explotadas en catálisis cuando se usa en forma soportada y muy dispersa. Se pretende optimizar el rendimiento de los catalizadores mediante el control del tamaño, forma de las nanopartículas y su interacción con el soporte, en base a la “dependencia de la estructura” de estas reacciones.  Así, se preparan catalizadores basados en Au, doblemente nanoestructurados (tanto a nivel de la fase activa como del soporte) soportados sobre CeO2 y TiO2 (Al2O3 y SiO2 como referencia) mediante distintas estrategias de síntesis; evaluando sus propiedades mediante técnicas de caracterización avanzadas y evaluando su comportamiento en reactividad (en régimen estacionario y transitorio) en procesos de oxidación. En el mismo contexto, y considerando la reciente aparición de catalizadores bimetálicos (AuCu, AuPd) para estas reacciones con elevados rendimientos, se prepararan sistemas AuPt, AuCu y Au Ni con control del tamaño y la composición de la fase activa.


Integración de reactores catalíticos de microcanales para la producción de hidrógeno a partir de alcoholes




Investigador Principal: José Antonio Odriozola Gordón
Periodo: 1-01-2010 / 31-12-2012
Organismo Financiador: Ministerio de Ciencia y Tecnología
Código: ENE2009-14522-C05-01
Componentes: Miguel Angel Centeno, Svetlana Ivanova, Francisca Romero Sarria, M.Isabel Domínguez, Sandra Palma, Oscar Laguna, Ana Penkova, Sylvia Cruz, W.Yesid Hernández, Luis Bobadilla
Grupo de Investigación: Química de Superficies y Catálisis

El uso masivo y generalizado de dispositivos eléctricos y electrónicos portátiles aumenta la necesidad de fuentes de potencia autónomas y eficientes, de hasta unos 50 We, capaces de reemplazar la tecnología actual basada en el uso de baterias. El uso de combustibles o productos químicos convencionales, hidrocarburos o alcoholes por ejemplo, es una alternativa prometedora cuando se combina con los recientes desarrollos en intensificación de procesos basados en la tecnología de reactores de microcanales. El desarrollo de la tecnología de microcanales para la producción de hidrógeno, in situ y a de-manda, a partir de alcoholes, se comenzó a estudiar en el proyecto anterior (MAT2006-12386-C05). Este estudio permitió la construcción de reactores de microcanales para las reacciones de reformado catalítico de metanol y oxidación preferente de CO (PROX) . En el presente proyecto se pretenden aplicar los conocimientos adquiridos para acoplar los microrreactores entre sí integrando flujos térmicos y materiales, escalarlos, y unirlos a una celda de combustible comercial de 50 We (PEMFC). En paralelo, se desarrollarán reactores de microcanales para el reformado catalítico de etanol y la reacción de desplazamiento del gas de agua (WGS) lo que permite aumentar la versatilidad el dispositivo diseñado. La viabilidad de estas fuentes de potencia autónomas requiere el estudio no sólo de la fabricación, escalado de los microreactores e integración de los flujos térmicos y materiales sino también explorar el uso de materiales de mayor disponibilidad (aceros ferríticos adaptados al uso), su durabilidad (aceros, catalizadores, soldaduras, juntas, …) y el desarrollo de un algoritmo de control para el conjunto formado por el procesador de combustible (reformado + eliminación de CO) y la pila de combustible.


Reformado Catalítico de Glicerina




Investigador Principal: José Antonio Odriozola Gordón
Periodo: 01-01-2010 / 31-12-2012
Organismo Financiador: Junta de Andalucía
Código: P09-TEP-5454 (Proyecto de Excelencia)
Componentes: Luis F. Bobadilla Baladrón, Sylvia A. Cruz Torres, M. Isabel Domínguez Leal, Anna Dimitrova Penkova, Francisca Romero Sarria, Andrea Alvarez Moreno
Grupo de Investigación: Química de Superficies y Catálisis

Este proyecto pretende la producción de hidrógeno a partir del reformado de glicerina. La glicerina es el producto secundario principal en la producción de bio-diesel a través de la transesterificatión de ácidos grasos. Si tenemos en cuenta el desarrollo actual, la producción de bio-combustibles se estima en 9.9 Mtoe para 2010, lo que representa el 50% de los objetivos de la Unión Europea. Los sistemas de energía actuales necesita el desarrollo de modelos energéticos alter-nativos. El empleo de hidrógeno como vector energético representa una de esas alternativas, aunque para asegurar la sostenibilidad se requiere que el hidrógeno se produzca a partir de fuentes renovables. La principal ventaja del planteamiento que proponemos, aprovechamiento de la glicerina, reside en que además de sostenible el balance de carbono es prácticamente neutro. Además, su valorización debe conducir a aumentar la rentabilidad de las bio-refinerías que de otro modo se verían afectadas por el incremento de costes asociados a la eliminación de este producto.


Desarrollo de estrategias para la preparación y optimización de materiales altamente fotoactivos




Investigador Principal: José Antonio Navío Santos
Periodo: 01-01-2009 / 31-12-2011
Organismo Financiador: Ministerio de Ciencia y Tecnología
Código: CTQ2008-05961-C02-01
Componentes: Gerardo Colón Ibáñez, M. Carmen Hidalgo López, Manuel Macías Azaña, Marina Maicu
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

El objetivo general de este proyecto coordinado es “diseñar una nueva generación de materiales en forma de polvo con tamaño manométrico basados en TiO2, SnO2 y ZnO simples, mixtos y/o dopados con otros iones, con alta actividad fotocatalítica en el visible y su fijación en otros materiales (membranas, vidrios, arcillas y láminas metálicas) que permitan emplear-los, de manera eficiente y competitiva en procesos de descontaminación fotocatalítica de efluentes líquidos y gases contaminados”. La hipótesis fundamental de la que se parte es que existen pigmentos inorgánicos (tales como el TiO2, SnO2, ZnO, etc.) con actividad fotocatalítica en UV capaces de degradar de forma no selectiva a especies tóxicas presentes en nuestro medio ambiente. El reto es superar los problemas derivados de la utilización sólo de la parte UV del espectro solar y extender la respuesta hacia el visible, implementando al mismo tiempo, las propiedades fisicoquímicas de los fotocatalizadores. Para realizar este estudio se proponen dos bloques principales de actividad que serán el diseño y desarrollo de catalizadores heterogéneos de tamaño nanométricos altamente fotoactivos, basados en TiO2, SnO2 y ZnO que puedan hacer las transformaciones de degradación de contaminantes mediante el concurso de luz solar visible (Química Solar Medioambiental) y la inmovilización de nanopartículas de estos semiconductores, simples, mixtos y/o dopados, en soportes adecuados (membranas, vidrios, láminas metálicas, fibras, placas cerámicas, etc,) con el fin de desarrollar dispositivos fotocatalíticos con alta actividad para el tratamiento de contaminantes en gases y aguas, para la generación de superficies autolimpiables.


Producción de gas de síntesis e hidrógeno mediante reformado de hidrocarburo con catalizadores nanoestructurados de niquel




Investigador Principal: Alfonso Caballero Martínez
Periodo: 1-12-2007 / 30-11-2011
Organismo Financiador: Ministerio de Educación y Ciencia
Código: ENE2007-67926-C02-01
Componentes: Juan Pedro Holgado Vázquez, Agustín R. Gon-zález-Elipe, Victor Manuel González de la Cruz, Rosa Pereñiguez Rodríguez
Grupo de Investigación: Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Este proyecto coordinado de investigación, que puede considerarse como extensión de los anteriores ENE2004-01660 y ENE2004-06176, pretende la preparación de nuevos sistemas catalíticos,con tamaños de partícula discretos y con alta resistencia a la desactivación. El objetivo ultimo es la mejora de la reacción de reformado de hidrocarburos para producción de H2(+CO), principalmente metano y propano, al ser esta una reacción dependiente de la estructura, y por tanto sensible al tamaño de partícula.

Para ello, se prepararán diferentes series de nanopartículas de níquel de tamaño y morfología bien definidos, utilizando métodos ex-situ como la irradiación mediante plasma de microondas, líquidos iónicos, microemulsión inversa o la impregnación con modificación externa del soporte por sililación.

Estos métodos nos permitirán obtener partículas con un rango de tamaños muy amplio, desde menos de 10nm hasta valores entorno a los 100nm y con una estrecha distribución de tamaños de partícula.

La actividad catalítica de estas nanopartículas, una vez depositadas en soportes como ZrO2 or Al2O3, será evaluada en las reacciones de reformado de metano y propano; estableciendo una correlación estructura-reactividad. Se estudiarán con una especial atención los procesos de deposición de carbón sobre los catalizadores en condiciones de reacción, ya que son los principales responsables de la disminución en la eficiencia de estos sistemas catalíticos. El control estricto de la morfología de las nanopartículas metálicas nos permitirá, por tanto, correlacionar la cinética de estos procesos de desactivación con sus características estructurales. Por otro lado, estudiaremos el efecto en la mejora de las prestaciones catalíticas globales de la adición de promotores como Pt, Au, Sr, K, etc.

Alternativamente, se realizará un estudio de la reacción de reformado inducida por un plasma de microondas, con el fin último de desarrollar un sistema integrado térmico-plasma, que esperamos mejore las condiciones de reacción, reduciendo la temperatura necesaria y/o disminuyendo los procesos de deposición de coque sobre los catalizadores.


Diseño de sistemas fotocatalíticos con alta actividad en el visible para aplicaciones ambientales




Investigador Principal: Gerardo Colón Ibáñez
Periodo: 01-01-2007 / 31-12-2010
Organismo Financiador: Junta de Andalucía
Código: FQM-1406
Componentes: José Antonio Navío Santos, Manuel Macías Azaña, Carmen Hidalgo López, Marina Maicu
Grupo de Investigación: Fotocatálisis Heterogénea: Aplicaciones

La Fotocatálisis ha demostrado ser una técnica muy eficiente en la oxidación de una gran variedad de sustratos en cortos tiempos de reacción. Es conocido que los catalizadores más utilizados, solo pueden ser activados por radiaciones menores de 390 nm, constituyéndose en una limitación para su empleo a mayor escala por el impedimento de usar luz solar. El objetivo principal de este proyecto se basa en el desarrollo en nuestro laboratorio de sistemas basados en TiO2 de alta eficiencia fotocatalítica en UV, capaz de degradar de forma no selectiva a especies tóxicas presentes en nuestro medio ambiente. El reto es superar los problemas derivados de la utilización sólo de la parte UV del espectro solar. El bloque central de la actividad de este proyecto consistirá en el desarrollo de sistemas de óxidos de Ti y Zn dopados, de forma que podamos obtener sistemas cuyo umbral de absorción esté en la región del visible. 

Así, desde el punto de vista de la mejora en las eficiencias de los procesos fotocatalíticos, es evidente que el diseño y desarrollo de fotocatalizadores alternativos al TiO2 es de un interés considerable. Se pretende la obtención de materiales altamente eficientes en procesos fotocatalíticos heterogéneos (en fase líquida y gaseosa) mediante la incorporación de distintos dopantes y la inmovilización de estos sistemas en distintos soportes. Para ello se abordarán distintas rutas de síntesis de polvo, y métodos de deposición. La evaluación la actividad fotocatalítica de los catalizadores se abordará estudiando procesos de fotooxidación de distintos compuestos orgánicos tóxicos (fenol y pigmentos orgánicos).




2024


Química de Superficies y Catálisis

Biomass gasification, catalytic technologies and energy integration for production of circular methanol: New horizons for industry decarbonisation

Bobadilla, Luis F; Azancot, Lola; González-Castaño, Miriam; Ruíz-López, Estela; Pastor-Pérez, Laura; Durán-Olivencia, Francisco J.; Ye, Runping; Chong, Katie; Blanco-Sánchez, Paula H; Wu, Zenthao; Reina, TR; Odriozola, JA
Journal of Environmental Sciences, 140 (2024) 306-318

Show abstract ▽

The Intergovernmental Panel on Climate Change (IPCC) recognises the pivotal role of renewable energies in the future energy system and the achievement of the zero-emission target. The implementation of renewables should provide major opportunities and enable a more secure and decentralised energy supply system. Renewable fuels provide long-term solutions for the transport sector, particularly for applications where fuels with high energy density are required. In addition, it helps reducing the carbon footprint of these sectors in the long-term. Information on biomass characteristics feedstock is essential for scaling-up gasification from the laboratory to industrial-scale. This review deals with the transformation biogenic residues into a valuable bioenergy carrier like biomethanol as the liquid sunshine based on the combination of modified mature technologies such as gasification with other innovative solutions such as membranes and microchannel reactors. Tar abatement is a critical process in product gas upgrading since tars compromise downstream processes and equipment, for this, membrane technology for upgrading syngas quality is discussed in this paper. Microchannel reactor technology with the design of state-of-the-art multifunctional catalysts provides a path to develop decentralised biomethanol synthesis from biogenic residues. Finally, the development of a process chain for the production of (i) methanol as an intermediate energy carrier, (ii) electricity and (iii) heat for decentralised applications based on biomass feedstock flexible gasification, gas upgrading and methanol synthesis is analysed.


Junio, 2024 | DOI: 10.1016/j.jes.2023.09.020

6.90
Química de Superficies y Catálisis

Nickel-based cerium zirconate inorganic complex structures for CO2 valorisation via dry reforming of methane

Martín-Espejo, Juan Luis; Merkouri, Loukia-Pantzechroula; Gándara-Loe, Jesús; Odriozola, José Antonio
Journal of Environmental Sciences

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The increasing anthropogenic emissions of greenhouse gases (GHG) is encouraging extensive research in CO2 utilisation. Dry reforming of methane (DRM) depicts a viable strategy to convert both CO2 and CH4 into syngas, a worthwhile chemical intermediate. Among the different active phases for DRM, the use of nickel as catalyst is economically favourable, but typically deactivates due to sintering and carbon deposition. The stabilisation of Ni at different loadings in cerium zirconate inorganic complex structures is investigated in this work as strategy to develop robust Ni-based DRM catalysts. XRD and TPR-H2 analyses confirmed the existence of different phases according to the Ni loading in these materials. Besides, superficial Ni is observed as well as the existence of a CeNiO3 perovskite structure. The catalytic activity was tested, proving that 10 wt.% Ni loading is the optimum which maximises conversion. This catalyst was also tested in long-term stability experiments at 600 and 800°C in order to study the potential deactivation issues at two different temperatures. At 600°C, carbon formation is the main cause of catalytic deactivation, whereas a robust stability is shown at 800°C, observing no sintering of the active phase evidencing the success of this strategy rendering a new family of economically appealing CO2 and biogas mixtures upgrading catalysts.


Junio, 2024 | DOI: 10.1016/j.jes.2023.01.022

6.90
Química de Superficies y Catálisis

Hydrochar and synthetic natural gas co-production for a full circular economy implementation via hydrothermal carbonization and methanation: An economic approach

Judith González-Arias, Guillermo Torres-Sempere, Miriam González-Castaño, Francisco M. Baena-Moreno, Tomás R. Reina
Journal of Environmental Sciences

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Herein we study the economic performance of hydrochar and synthetic natural gas co-production from olive tree pruning. The process entails a combination of hydrothermal carbonization and methanation. In a previous work, we evidenced that standalone hydrochar production via HTC results unprofitable. Hence, we propose a step forward on the process design by implementing a methanation, adding value to the gas effluent in an attempt to boost the overall process techno-economic aspects. Three different plant capacities were analyzed (312.5, 625 and 1250 kg/hr). The baseline scenarios showed that, under the current circumstances, our circular economy strategy in unprofitable. An analysis of the revenues shows that hydrochar selling price have a high impact on NPV and subsidies for renewable coal production could help to boost the profitability of the process. On the contrary, the analysis for natural gas prices reveals that prices 8 times higher than the current ones in Spain must be achieved to reach profitability. This seems unlikely even under the presence of a strong subsidy scheme. The costs analysis suggests that a remarkable electricity cost reduction or electricity consumption of the HTC stage could be a potential strategy to reach profitability scenarios. Furthermore, significant reduction of green hydrogen production costs is deemed instrumental to improve the economic performance of the process. These results show the formidable techno-economic challenge that our society faces in the path towards circular economy societies.


Junio, 2024 | DOI: 10.1016/j.jes.2023.04.019

6.90
Fotocatálisis Heterogénea: Aplicaciones

Evaluation of Pt/TiO2-Nb2O5 systems in the photocatalytic reforming of glucose for the generation of H2 from industrial effluents

Lara Sandoval, AE; Serafin, J; Murcia Mesa, JJ; Rojas Sarmiento, HA; Hernandez Niño, JS; Llorca, J; Navío Santos, JA; Hidalgo Lõpez; MC
Fuel, 363 (2024) 130932

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Different Pt-TiO2-Nb2O5 systems were synthesized and studied in the photocatalytic reforming of glucose for the generation of H2. The physicochemical properties of the synthesized photocatalysts were analyzed using different characterization techniques from which it was found that fluoridation and sulphation have different effects on the oxides under study such as a protective effect on the crystalline phase in anatase, and greater response in the visible region of the electromagnetic spectrum. The addition of fluorine or sulfates favors the reduction of platinum species on the surface of the semiconductor oxides and a better homogeneity of size and distribution of the particles of this metal. Studies were carried out in the gas phase that allowed the monitoring and quantification of the hydrogen produced from aqueous glucose solutions and it was determined that Pt-F-Nb2O5 and Pt-F-TiO2 are the most efficient materials for the production of hydrogen from this substrate. Similarly, liquid phase studies were carried out with a real sample from a confectionery industry where it was determined that with the material Pt-F-Nb2O5 the highest transformation of glucose is obtained, without the formation of any other sugar or intermediate compound, indicating the preferential production of hydrogen during the photocatalytic reaction. The foregoing demonstrates the potential of the evaluated process in obtaining this gas from the recovery of polluting residues derived from the samples under study.


Mayo, 2024 | DOI: 10.1016/j.fuel.2024.130932

7.40
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic activity enhancement by noble metal deposition on faceted F-TiO2 synthesised by microwave assisted method. A study of selective oxidation of gas-phase ethanol in a FBPR reactor

Hernández-Laverde, M; Murcia, JJ; Morante, N; Sannino, D; Vaiano, V; Navío, JA; Hidalgo, MC
Catalysis Today, 433 (2024) 114645

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In the present work, fluorinated titanium dioxide (TiO2-F) with high exposition of facet {001} was prepared by following a facile and high yield hydrothermal method assisted by microwave. This faceted TiO2 was then modified by Au or Ag deposition at two different metal loadings (0.125 and 0.25 wt%). A wide physicochemical characterisation of the materials was performed. X-ray difractograms showed high {001} facet exposition in all materials. By X-ray fluorescence it was found that the different samples contained about 5% of fluor. All samples presented high surface area and high uniformity and homogeneity of particles, which highlights the good properties that can be achieved by the microwave synthesis method compared to conventional hydrothermal methods. Oxidation state of the noble metals was studied by XPS. On the other side, TiO2-F and the metallised titania powders were immobilised on polystyrene pellets (PS) for evaluating their gas photocatalytic activity in volatile organic compounds (VOCs) decontamination by following the reaction of photoxidation of ethanol in gas phase. It was found that activity was considerably improved by the addition of noble metals, obtaining high conversion and selectivity to CO2. It is remarkable that the selectivity to CO is almost zero. The highest efficiency was found for the faceted TiO2-F sample with the lowest Au loading (0.125 wt%) immobilised on PS where 91% ethanol conversion and 100% CO2 selectivity were achieved. Different reaction variables were also studied.


Mayo, 2024 | DOI: 10.1016/j.cattod.2024.114645

5.30
Química de Superficies y Catálisis

Reforming of biomass-derived producer gas using toluene as model tar: Deactivation and regeneration studies in Ni and K-Ni catalysts

Azancot, L; González-Castaño, M; Bobadilla, LF; Centeno, MA; Odriozola, JA
Environmental Research, 247 (2024) 118210

Show abstract ▽

Within the syngas production from biomass gasification, tar removal constitutes a chief issue to overcome for advanced catalytic systems. This work investigates the performance of Ni and Ni-K catalysts for reforming of derived-biomass producer gas using toluene as model tar. At 750 degrees C and 60Lg(-1)h(-1), the stability test (70 h) revealed stable performances (CO2, CH4 and C7H8 conversions of 60, 95 and 100%, correspondingly) uniquely for the Ni-K catalyst. Although the efficient protection towards coking let by K was demonstrated, TPO studies over the post-reacted systems still evidenced the presence of carbon deposits for both samples. Conducting three successive reaction/regeneration cycles with different gasifying agents (air, steam and CO2) at 800 C for 1h, the capability towards regeneration of both catalytic systems was assessed and the spent catalysts were characterized by XRD, SEM and TEM. While none of the regeneration treatments recovered the performance of the unpromoted catalyst, the Ni-K catalysts demonstrated the capability of being fully regenerated by air and CO2 and exhibited analogous catalytic performances after a series of reaction/regeneration cycles. Hence, it is proved that the addition of K into Ni catalysts not only enhances the resistance against deactivation but enables rather facile regenerative procedures under certain atmospheres (air and CO2).


Abril, 2024 | DOI: 10.1016/j.envres.2024.118210

8.30
Química de Superficies y Catálisis

A profitability study for catalytic ammonia production from renewable landfill biogas: Charting a route for the next generation of green ammonia

González-Arias, J; Nawaz, MA; Vidal-Barrero, F; Reina, TR
Fuel, 360 (2024) 130584

Show abstract ▽

This study introduces a novel techno-economic approach to renewable ammonia production using landfill biogas. The proposed process involves bio-hydrogen generation from landfill biogas, nitrogen production via air separation, and the Haber-Bosch process. Building on our prior research, which demonstrated the economic competitiveness of renewable hydrogen production from landfill gas, we extend our investigation to analyze the feasibility of producing renewable ammonia from biogas-derived bio-hydrogen. However, the economic analysis for the baseline scenario reveals the current lack of profitability (net present value of −18.3 M€), with ammonia prices needing to quadruple to achieve profitability. Major costs, including investment, maintenance, overhead expenses, and electricity, collectively account for over 70%, suggesting the potential efficacy of investment subsidies as a political tool. Only cases with subsidies exceeding 50% of total investment costs, under current ammonia market prices, would render the green ammonia route profitable. Our findings underscore the significant techno-economic challenges in realizing renewable ammonia production, emphasizing the need for innovation in process engineering and catalytic technologies to enable competitive and scalable green ammonia production.


Marzo, 2024 | DOI: 10.1016/j.fuel.2023.130584

7.10
Química de Superficies y Catálisis

Optimizing biogas methanation over nickel supported on ceria-alumina catalyst: Towards CO2-rich biomass utilization for a negative emissions society

González-Arias, J; Torres-Sempere, G; Arroyo-Torralvo, F; Reina, TR; Odriozola, JA
Enrironmental Research, 242 (2024) 117735

Show abstract ▽

Biogas methanation emerges as a prominent technology for converting biogas into biomethane in a single step. Furthermore, this technology can be implemented at biogas plant locations, supporting local economies and reducing dependence on large energy producers. However, there is a lack of comprehensive studies on biogas methanation, particularly regarding the technical optimization of operational parameters and the profitability analysis of the overall process. To address this gap, our study represents a seminal work on the technical optimization of biogas methanation obtaining an empirical model to predict the performance of biogas methanation. We investigate the influence of operational parameters, such as reaction temperature, H2/CO2 ratio, space velocity, and CO2 share in the biogas stream through an experimental design. Based on previous research we selected a nickel supported on ceria-alumina catalyst; being nickel a benchmark system for methanation process such selection permits a reliable data extrapolation to commercial units. We showcase the remarkable impact of studied key operation parameters, being the temperature, the most critical factor affecting the reaction performance (ca. 2 to 5 times higher than the second most influencing parameter). The impact of the H2/CO2 ratio is also noticeable. The response surfaces and contour maps suggest that a temperature between 350 and 450 degrees C and an H2/CO2 ratio between 2.5 and 3.2 optimize the reaction performance. Further experimental tests were performed for model validation and optimization leading to a reliable predictive model. Overall, this study provides validated equations for technology scaling-up and techno-economic analysis, thus representing a step ahead towards real-world applications for bio-methane production.


Febrero, 2024 | DOI: 10.1016/j.envres.2023.117735

8.30
Química de Superficies y Catálisis

Renewable Carbonaceous Materials from Biomass in Catalytic Processes: A Review

Villora-Picó, JJ; González-Arias, J; Baena-Moreno, FM; Reina, TR
Materials, 17 (2024) 565

Show abstract ▽

This review paper delves into the diverse ways in which carbonaceous resources, sourced from renewable and sustainable origins, can be used in catalytic processes. Renewable carbonaceous materials that come from biomass-derived and waste feedstocks are key to developing more sustainable processes by replacing traditional carbon-based materials. By examining the potential of these renewable carbonaceous materials, this review aims to shed light on their significance in fostering environmentally conscious and sustainable practices within the realm of catalysis. The more important applications identified are biofuel production, tar removal, chemical production, photocatalytic systems, microbial fuel cell electrodes, and oxidation applications. Regarding biofuel production, biochar-supported catalysts have proved to be able to achieve biodiesel production with yields exceeding 70%. Furthermore, hydrochars and activated carbons derived from diverse biomass sources have demonstrated significant tar removal efficiency. For instance, rice husk char exhibited an increased BET surface area from 2.2 m2/g to 141 m2/g after pyrolysis at 600 °C, showcasing its effectiveness in adsorbing phenol and light aromatic hydrocarbons. Concerning chemical production and the oxidation of alcohols, the influence of biochar quantity and pre-calcination temperature on catalytic performance has been proven, achieving selectivity toward benzaldehyde exceeding 70%.


Febrero, 2024 | DOI: 10.3390/ma17030565

3.40
Química de Superficies y Catálisis

A review on high-pressure heterogeneous catalytic processes for gas-phase CO2 valorization

Villora-Picó, J.J; González-Arias, J; Pastor-Pérez, L; Odriozola, JA; Reina, TR
Environmental Research, 240 (2024) 117520

Show abstract ▽

 

This review discusses the importance of mitigating CO2 emissions by valorizing CO2 through high-pressure catalytic processes. It focuses on various key processes, including CO2 methanation, reverse water-gas shift, methane dry reforming, methanol, and dimethyl ether synthesis, emphasizing pros and cons of high-pressure operation. CO2 methanation, methanol synthesis, and dimethyl ether synthesis reactions are thermodynami-cally favored under high-pressure conditions. However, in the case of methane dry reforming and reverse water -gas shift, applying high pressure, results in decreased selectivity toward desired products and an increase in coke production, which can be detrimental to both the catalyst and the reaction system. Nevertheless, high-pressure utilization proves industrially advantageous for cost reduction when these processes are integrated with Fischer-Tropsch or methanol synthesis units. This review also compiles recent advances in heterogeneous catalysts design for high-pressure applications. By examining the impact of pressure on CO2 valorization and the state of the art, this work contributes to improving scientific understanding and optimizing these processes for sustainable CO2 management, as well as addressing challenges in high-pressure CO2 valorization that are crucial for industrial scaling-up. This includes the development of cost-effective and robust reactor materials and the development of low-cost catalysts that yield improved selectivity and long-term stability under realistic working environments.


Enero, 2024 | DOI: 10.1016/j.envres.2023.117520

8.30
Fotocatálisis Heterogénea: Aplicaciones

Ba3(PO4)2 Photocatalyst for Efficient Photocatalytic Application

Naciri, Y; Ahdour, A; Benhsina, E; Hamza, MA; Bouziani, A; Hsini, A; Bakiz, B; Navio, JA; Ghazzal, MN
Global Challenges

Show abstract ▽

 

Barium phosphate (Ba-3(PO4)(2)) is a class of material that has attracted significant attention thanks to its chemical stability and versatility. However, the use of Ba-3(PO4)(2) as a photocatalyst is scarcely reported, and its use as a photocatalyst has yet to be reported. Herein, Ba-3(PO4)(2) nanoflakes synthesis is optimized using sol-gel and hydrothermal methods. The as-prepared Ba-3(PO4)(2) powders are investigated using physicochemical characterizations, including XRD, SEM, EDX, FTIR, DRS, J-t, LSV, Mott-Schottky, and EIS. In addition, DFT calculations are performed to investigate the band structure. The oxidation capability of the photocatalysts is investigated depending on the synthesis method using rhodamine B (RhB) as a pollutant model. Both Ba-3(PO4)(2) samples prepared by the sol-gel and hydrothermal methods display high RhB photodegradation of 79% and 68%, respectively. The Ba-3(PO4)(2) obtained using the sol-gel process exhibits much higher stability under light excitation after four regeneration cycles. The photocatalytic oxidation mechanism is proposed based on the active species trapping experiments where O-2(center dot-) is the most reactive species. The finding shows the promising potential of Ba-3(PO4)(2) photocatalysts and opens the door for further investigation and application in various photocatalytic applications.


Enero, 2024 | DOI: 10.1002/gch2.202300257

4.90
Química de Superficies y Catálisis

Subnanometric Pt clusters dispersed over Cs-doped TiO2 for CO2 upgrading via low-temperature RWGS: operando mechanistic insights to guide an optimal catalyst design

Torres-Sempere, G; Blay-Roger, R; Luque-Alvarez, LA; Santos, JL; Bobadilla, LF; Pastor-Pérez, L; Centeno, MA; Hernández, WY; Yousef, I; Odriozola, JA; Reina, TR
Journal of Matertials Chemistry A, 12 (2024) 1779-1792

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The RWGS reaction is gathering momentum as an effective route for CO2 valorisation and given its endothermic nature the challenge lies in the design of active low-temperature catalysts. Herein we have designed two catalysts based on subnanometric Pt clusters providing effective CO2 conversion and, more importantly, high CO selectivity in the low-temperature range. The impact of Cs as a dopant in the catalyst's formulation is crucial leading to full selectivity at 300 °C. The reaction mechanisms for the studied systems namely Pt/TiO2 and PtCs/TiO2 are significantly different due to the presence of the alkali promoter. The presence of Cs neutralises the hydroxide groups of the TiO2 surface, changing the reaction pathway. The Pt/TiO2 catalyst follows a redox mechanism where CO2 dissociates to CO in the oxygen vacancies, and then these vacancies are recovered by the migration of H2 by spill over phenomena. On the other hand, the Cs doped catalyst has two possible mechanism pathways: the (ii) formyl/acyl pathway, where –CHO species are formed and, depending on the reaction conditions, evolve to CO gas or oxygenated compounds, and (ii) frustrated Lewis pair (FLP) assisted CO2 reduction route, in which the FLP induces the heterolytic dissociation of H2 and the subsequent hydrogenation of CO2 to CO. The latter route enabled by Cs-doping combined with the subnanometric Pt domains seems to be responsible for the excellent catalytic behaviour leading to fully selective low-temperature RWGS systems and thus unlocking new possibilities for less energy demanding CO2 valorisation units based on RWGS.


Enero, 2024 | DOI: 10.1039/D3TA05482A

11.90
Química de Superficies y Catálisis

Natural hydrogen in the energy transition: Fundamentals, promise, and enigmas

Blay-Roger, R; Bach, W; Bobadilla, LF; Reina, TR; Odriozola, JA; Amils, R; Blay, V
Renewable & Sustainable Energy Reviews, 189 (2024) 113888

Show abstract ▽

Beyond its role as an energy vector, a growing number of natural hydrogen sources and reservoirs are being discovered all over the globe, which could represent a clean energy source. Although the hydrogen amounts in reservoirs are uncertain, they could be vast, and they could help decarbonize energy-intensive economic sectors and facilitate the energy transition. Natural hydrogen is mainly produced through a geochemical process known as serpentinization, which involves the reaction of water with low-silica, ferrous minerals. In favorable locations, the hydrogen produced can become trapped by impermeable rocks on its way to the atmosphere, forming a reservoir. The safe exploitation of numerous natural hydrogen reservoirs seems feasible with current technology, and several demonstration plants are being commissioned. Natural hydrogen may show variable composition and require custom separation, purification, storage, and distribution facilities, depending on the location and intended use. By investing in research, in the mid-term, more hydrogen sources could become exploitable and geochemical processes could be artificially stimulated in new locations. In the long term, it may be possible to leverage or engineer the interplay between microorganisms and geological substrates to obtain hydrogen and other chemicals in a sustainable manner.


Enero, 2024 | DOI: 10.1016/j.rser.2023.113888

15.90
Química de Superficies y Catálisis

Synthetic natural gas production using CO2-rich waste stream from hydrothermal carbonization of biomass: Effect of impurities on the catalytic activity

González-Arias, J; Torres-Sempere, G; Villora-Picó, JJ; Reina, TR; Odriozola, JA
Journal of CO2 Utilization, 79 (2024) 102653

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The utilization of biomass and bio-waste, particularly through hydrothermal processes, has shown promise as a technology for converting these materials into valuable products. While most research has traditionally focused on the solid and liquid byproducts of these hydrothermal treatments, the gaseous phase has often been over-looked. This study specifically investigates the conversion of off-gases produced during hydrothermal carbonation (HTC) into synthetic natural gas, offering a readily marketable product with economic potential. Although the methanation of conventional flue gases has been extensively studied, dealing with non-standard off-gases from processes like HTC presents challenges due to the presence of minor impurities like CO and CH4. This novel research seeks to experimentally evaluate the methanation of HTC off-gases using nickel-based catalysts and analyze how these impurities affect the catalytic performance. The studied catalysts include nickel supported by ceria and alumina, as well as alumina supported nickel-cobalt systems. The results demonstrate that these catalysts exhibit high CO2 conversion and CH4 selectivity under ideal gas conditions. However, when real gas compositions with impurities are considered, CO2 conversion decreases at lower temperatures (ca. 20% lower conversion for real gas vs. ideal), probably due to side reactions such as CH4 cracking. This difference becomes less pronounced at higher temperatures. Nevertheless, the catalysts perform satisfactorily, especially at temperatures exceeding 350 degrees C. In conclusion, this study sheds light on the methanation of HTC off-gases and underscores the significance of understanding how impurities in real gases impact the process, providing potential directions for future research.


Enero, 2024 | DOI: 10.1016/j.jcou.2023.102653

7.70
Química de Superficies y Catálisis

Optimized electrocatalytic degradation of ciprofloxacin using Co3O4 coated stainless steel electrodes

Saleem, MU; Jawad, M; Azad, F; Nawaz, MA; Zaman, WQ; Miran, W
Colloids and Surfaces A-Physicochemical and Engineering Aspects, 681 (2024) 132738

Show abstract ▽

Ciprofloxacin (CIP) is a fluoroquinolone antibiotic that is widely used across the globe and its release is a serious concern due to its persistent nature, partial degradation, and simple transport through different environmental matrices. Pharmaceuticals have been degraded effectively by electrochemical oxidation. Exploring ways to in-crease the mineralization of these compounds while maintaining low power consumption is important. In this study, the treatability and degradation of CIP were investigated by using cobalt oxide-coated stainless steel (SS) electrodes in a lab-scale electrochemical (EC) reactor. The performance of the electrochemical reactor was determined under various operational conditions. The feed wastewater was synthetically prepared in the laboratory with varying concentrations of CIP ranging from 8 to 41 mg/L and the EC reactor was operated with an applied voltage and airflow rate of 2.6-9.3 volts and 1.6-3.5 L/min, respectively. A 3-factor central composite experimental design (CCD) was developed by using response surface methodology (RSM) in Design-Expert software. At a residence time of 27 min, initial concentration of 25 mg/L, airflow rate of 2.5 L/min, and applied voltage of 6 volts, the EC reactor achieved a removal efficiency of 70.8% for CIP with SS electrodes. On the contrary, the removal efficiency was increased to 91.5% at a reduced residence time of 21 min with cobalt oxide (Co3O4) coated over SS plates. The results indicated that Co3O4@SS electrodes resulted in better removal efficiency of CIP at a lower residence time. This system can be used as a robust benchmark for a single or consortium of antibiotics present in domestic and hospital wastewater.


Enero, 2024 | DOI: 10.1016/j.colsurfa.2023.132738

5.20
Química de Superficies y Catálisis

Switchable catalysis for methanol and synthetic natural gas synthesis from CO2: A techno-economic investigation

Merkouri, LP; Mathew, J; Jacob, J; Reina, TR; Duyar, MS
Journal of CO2 Utilization, 79 (2024) 102652

Show abstract ▽

The oil and gas sector produces a considerable volume of greenhouse gas emissions, mainly generated from flaring and venting natural gas. Herein, a techno-economic analysis has been performed of a switchable catalytic process to convert the CH4 and CO2 in flared/vented natural gas into syngas or methanol. Specifically, it was shown that depending on greenhouse gas composition, dry methane reforming (DRM), reverse water-gas shift (RWGS), and CO2 methanation could be chosen to valorise emissions in an overall profitable and flexible operation scenario. The switchable process produced methanol and synthetic natural gas as its products, resulting in an annual income of €687m and annual operating expenses of €452m. The pre-tax profit was calculated at €234m, and at the end of the project, the net present value was calculated as €1.9b with a profitability index of 4.7€/€. The expected payback time of this process was ca. 4 years, and with a 35% internal rate of return (IRR). Most importantly, this process consumed 42.8m tonnes of CO2 annually. The sensitivity analysis revealed that variations in operation time, green hydrogen price, and products' prices significantly impacted the profitability of the process. Overall, this techno-economic analysis demonstrated that switchable catalysis in greenhouse gas utilisation processes is profitable, and thus it could play an important role in achieving net zero emissions.


Enero, 2024 | DOI: 10.1016/j.jcou.2023.102652

7.70
Química de Superficies y Catálisis

Mechanistic insights into methanol carbonylation to methyl acetate over an efficient organic template-free Cu-exchanged mordenite

Luque-Alvarez, LA; Gonzalez-Arias, J; Romero-Sarria, F; Reina, TR; Bobadilla, LF; Odriozola, JA
Catalysis Science & Technology, 14 (2024) 128-136

Show abstract ▽

Currently, acetic acid is produced via the carbonylation reaction of methanol with the main route entailing the use of homogeneous noble metal-based catalysts, which has certain limitations, including the use of polluting alkyl halide promoters and difficulty in catalyst recovery. To overcome these challenges, the exploration of alternative methods utilizing heterogeneous catalysts, particularly zeolites with copper as a redox center, has gained attention. Nonetheless, the conversion and selectivity obtained are sought after to compete against the homogeneous route. Therefore, a deeper understanding of the reaction and mechanism is needed to determine the weak points and overcome them. In this study, we propose the use of time-resolved operando DRIFTS-MS to study the methanol carbonylation reaction over a Cu–H-MOR catalyst. The study aimed to propose a reaction mechanism through an investigation of the behavior of the catalyst, including potential identification of the location of the copper redox center in the zeolite. The catalytic performance of the Cu–H-MOR catalyst was also evaluated, demonstrating its activity and stability in the methanol carbonylation reaction. The operando DRIFTS-MS results provide insights into the reaction mechanism and the involvement of the acid and redox centers in the process. Based on the findings, we propose a reaction mechanism for methanol carbonylation on Cu–H-MOR zeolite: (i) methanol dehydration, (ii) CO insertion into methoxide groups, (iii) reaction between dimethyl ether and acetyl groups, and (iv) hydrolysis of methyl acetate. Overall, we believe that this work contributes to a deeper understanding of the heterogeneous route for acetic acid production and offers potential avenues for optimizing the process.


Enero, 2024 | DOI: 10.1039/d3cy01271a

5.00
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

CuO-TiO2 pilot-plant system performance for solar photocatalytic hydrogen production

Villachica-Llamosas, JG; Ruiz-Aguirre, A; Colón, G; Peral, J; Malato, S
International Journal of Hydrogen Energy, 51 (2024) 1069-1077

Show abstract ▽

 

The main goal of the present study was to explore photocatalytic performance of the TiO2 -CuO mixture, for solar to hydrogen conversion at pilot plant scale under two different irradiation conditions (sunny and partly cloudy), focusing on high-temperature pretreat-ment of the catalyst mixture to try to improve TiO2 doping with copper. P25-TiO2 and commercial CuO were used with different amounts of Cu (2 wt% or 7 wt% Cu) calcined at 200-400 degrees C during several hours. Catalysts were tested at pilot plant scale using solar compound parabolic collectors, with glycerol as the sacrificial agent. The photocatalyst prepared after heating at 200 degrees C for 3 h and with 7 wt% Cu, resulted in higher hydrogen production than under the other heating conditions, and results were slightly better (5 -10%) than the reference values with the untreated catalysts. Photocatalytic efficiency was slightly lower at the higher calcination temperature (400 degrees C). CO2 production and formation of formate and glycolate clearly demonstrated glycerol photoreforming. The Cu from the calcined catalyst remaining on the solid was significantly less (2.5%) than on the non -calcined catalyst (4.2%), with an important fraction of lixiviated copper and copper deposition on the reactor walls. This is a critical drawback that must be considered for large-scale applications.


Enero, 2024 | DOI: 10.1016/j.ijhydene.2023.07.149

7.20
Química de Superficies y Catálisis

Boosting Low-Temperature CO2 Hydrogenation over Ni-based Catalysts by Tuning Strong Metal-Support Interactions

Ye, RP; Ma, LX; Hong, XL; Reina, TR; Luo, WH; Kang, LQ; Feng, G; Zhang, RB; Fan, MH, Zhang, RG
Angewandte Chemie-International Edition,

Show abstract ▽

Rational design of low-cost and efficient transition-metal catalysts for low-temperature CO2 activation is significant and poses great challenges. Herein, a strategy via regulating the local electron density of active sites is developed to boost CO2 methanation that normally requires >350 °C for commercial Ni catalysts. An optimal Ni/ZrO2 catalyst affords an excellent low-temperature performance hitherto, with a CO2 conversion of 84.0 %, CH4 selectivity of 98.6 % even at 230 °C and GHSV of 12,000 mL g−1 h−1 for 106 h, reflecting one of the best CO2 methanation performance to date on Ni-based catalysts. Combined a series of in situ spectroscopic characterization studies reveal that re-constructing monoclinic-ZrO2 supported Ni species with abundant oxygen vacancies can facilitate CO2 activation, owing to the enhanced local electron density of Ni induced by the strong metal-support interactions. These findings might be of great aid for construction of robust catalysts with an enhanced performance for CO2 emission abatement and beyond.


Enero, 2024 | DOI: 10.1002/anie.202317669

16.60



2023


Química de Superficies y Catálisis

Alkane metathesis over immobilized pincer-ligated iridium complexes: Effect of support nature

Megías-Sayago, C; Centeno-Vega, I; Bobadilla, LF; Ivanova, S; Rendon, N; Suarez, A
Applied Catalysis B-Environmental, 338 (2023) 123002

Show abstract ▽

In this work, catalytic alkane metathesis has been evaluated as a suitable approach to upcycle hydrocarbons (polyolefins) at moderate temperatures. To this end, a pincer-ligated iridium complex (dehydrogenation catalyst) has been combined with a rhenium-based (metathesis) catalyst, being the effect of immobilizing the Ir complex over different supports deeply investigated. FTIR spectroscopy has been used to confirm the complex grafting and to elucidate the anchoring site to the support. Additionally, the supports have been dehydroxylated at different conditions to evaluate its possible impact in both the complex grafting and the catalytic activity. The influence of the support nature and its participation in the catalytic reaction have been clearly evidenced.


Diciembre, 2023 | DOI: 10.1016/j.apcatb.2023.123002

22.10
Química de Superficies y Catálisis

Effect of zeolite topological structure in bifunctional catalyst on direct conversion of syngas to light olefins

Meng, FH; Gong, ZY; Yang, LL; Wang, Q; Xing, MQ; Nawaz, MA; Li, Z
Microporous and Mesoporous Materials, 362 (2023) 112792

Show abstract ▽

Bifunctional catalyst composed of metal oxide and zeolite (OX-ZEO) is a promising strategy for the direct conversion of syngas to light olefins (STO), where the structure of zeolite plays a vital role in determining the selectivity of product. Herein, three kinds of silicoaluminophosphate zeolites with different topological structures, i.e., the ERI(SP17), AEI(SP18) and CHA(SP34), were hydrothermally synthesized, after the combination with Mn-Ga oxide, the prepared OX-ZEO was applied for STO reaction. The variation in the crystallization time for SP17 synthesis has a great impact on the generation of impurity phase of SAPO-5, where a crystallization time of 48-96 h is found to be beneficial in synthesizing SP17 zeolite with pure phase. SP17 zeolite with a crystallization time of 96 h, possesses the micropores and columnar morphology, where the small cage-defining 8-ring size of SP17 shows the olefins selectivity of 87.0% at a low CO conversion of 19.4%, significantly deviating towards the major fraction of ethylene (45.6%) than that of butene (8.2%). In a contrast, SP18 and SP34 zeolites with the same and large cage-defining 8-ring size, are richer in propylene and butene fractions than that of ethylene in overall similar olefins selectivity of 87.0% and 87.1% at CO conversion of 28.7% and 28.5%, respectively. Interestingly, it is further interpreted that the SP17 sample generated more carbon species during the reaction due to the small 8-ring size, while those amounts of carbon species were restricted in the hierarchical pore structure and plate-like morphology in SP18 and SP34 samples.


Diciembre, 2023 | DOI: 10.1016/j.micromeso.2023.112792

5.20
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Photoreforming of glycerol to produce hydrogen from natural water in a compound parabolic collector solar photoreactor

Villachica-Llamosas, JG; Sowik, J; Ruiz-Aguirre, A; Colón, G; Peral, J; Malato, S
Journal of Environmental Chemical Engineering, 11 (2023) 111216

Show abstract ▽

To improve TiO2 for H2 generation, one strategy for the separation of photogenerated charges is the formation of heterostructures with other materials. In particular, NiO is a photocatalyst known for its good stability and low cost. However, no studies at pilot scale using solar energy have been described. Consequently, an evaluation of a physical NiO:TiO2 mixture at pilot scale (25 L) with natural irradiation (2.10 m2 of sun-exposed surface) and with simultaneous glycerol photoreforming was explored. NiO:TiO2 50 mg & sdot;L- 1 resulted in the highest hydrogen production, showing an STH = 1.44%, considering only the UV fraction of the solar irradiation. H2 and CO2 production were analysed by on-line GC; Glycerol, dissolved organic carbon, carboxylic acids and nickel leaching were also evaluated. The NiO:TiO2 mixtures rendered a systematically lower H2 production in natural water than in high-purity water. The increase of ionic strength increased the mean size of particle clusters, promoting rapid sedimentation. All this indicates the importance of testing under real field conditions for attaining reliable solar to hydrogen (STH) efficiency.


Diciembre, 2023 | DOI: 10.1016/j.jece.2023.111216

7.70
Fotocatálisis Heterogénea: Aplicaciones

Bismuth ferrite as innovative and efficient photocatalyst for the oxidation of As(III) to As(V) under visible light

Chianese, L; Murcia, JJ; Hidalgo, MC; Vaiano, V; Iervolino, G
Materials Science in Semiconductor Processing, 167 (2023) 107801

Show abstract ▽

The presence of As in drinking water is a problem felt all over the world. In particular, arsenic is present in +3 (As(III)) and +5 (As(V)) oxidation states. However, As(III) is the most toxic and difficult to remove with conventional adsorption processes. A pre-oxidation process is therefore necessary. In this work, we report, for the first time, the use of BiFeO3 as a visible-light active photocatalyst for the complete and fast oxidation of As(III) to As(V) in water. In particular, the influence of annealing temperature for BiFeO3 preparation was studied and the prepared photocatalysts were characterized through XRD, N2 adsorption at −196°C, TEM, XPS, Raman and UV–Vis DRS spectroscopy. The best photocatalytic activity was achieved with BiFeO3 calcined at 550°C. The influence of catalyst dosage and the role of the main oxidizing species was evaluated, evidencing the key role of h+ in the photooxidation reaction of As(III) to As(V). Moreover, the efficiency of the photocatalyst was also evaluated in the case of drinking water contaminated by arsenic. The results demonstrated that, despite the presence of dissolved salts in the drinking water, the photocatalyst maintained its activity. The results obtained in this work prove that BiFeO3 calcined at 550°C evidenced photocatalytic performances better than different photocatalyst formulations studied for the photooxidation of As(III) to As(V) under visible light.


Noviembre, 2023 | DOI: 10.1016/j.mssp.2023.107801

4.10
Química de Superficies y Catálisis

Coal Chemistry Industry: From Production of Liquid Fuels to Fine Chemicals to Carbon Materials

Zhang, YY; Li, HT; Reina, TR; Liu, J
Energy & Fuels, (2023)

Show abstract ▽

Coal resources are one of the key energy sources and essential for modern economic development. Despite the traditional coal industries having made considerable contributions to chemical production and energy storage, the accompanying environmental pollution and high energy consumption have also arisen that cause significant influence of the ecological balance. Hence, there is an urgent need to exploit feasible approaches to the sustainable utilization of coal resources. This review begins with a comprehensive summary of the representative coal chemistry technologies with critical discussions. Subsequently, a novel strategy coupled with green hydrogen is discussed for sustainable conversion of coal and highly efficient manufacture of downstream products. Moreover, the unique role of coal in terms of high-value-added carbon material production is highlighted as a low-cost resource for distinct applications. Finally, we propose several future directions for advanced coal chemistry development.


Noviembre, 2023 | DOI: 10.1021/acs.energyfuels.3c02661

5.30
Química de Superficies y Catálisis

Experimental optimization of Ni/P atomic ratio for nickel phosphide catalysts in reverse water-gas shift

Gul Hameed, Ali Goksu, Loukia-Pantzechroula Merkouri, Anna Penkova, Tomas Ramirez Reina, Sergio Carrasco Ruiz, Melis Seher Duyar
Journal of CO2 Utilization, 77 (2023) 102606

Show abstract ▽

Nickel phosphide catalysts show a high level of selectivity for the reverse water-gas shift (RWGS) reaction, inhibiting the competing methanation reaction. This work investigates the extent to which suppression of methanation can be controlled by phosphidation and tests the stability of phosphide phases over 24-hour time on stream. Herein the synthesis of different phosphide crystal structures by varying Ni/P atomic ratios (from 0.5 to 2.4) is shown to affect the selectivity to CO over CH4 in a significant way. We also show that the activity of these catalysts can be fine-tuned by the synthesis Ni/P ratio and identify suitable catalysts for low temperature RWGS process. Ni12P5-SiO2 showed 80–100% selectivity over the full temperature range (i.e., 300–800 °C) tested, reaching 73% CO2 conversion at 800 °C. Ni2P-SiO2 exhibited CO selectivity of 93–100% over a full temperature range, and 70% CO2 conversion at 800 °C. The highest CO2 conversions for Ni12P5-SiO2 at all temperatures among all catalysts showed its promising nature for CO2 capture and utilisation. The methanation reaction was suppressed in addition to RWGS activity improvement through the formation of nickel phosphide phases, and the crystal structure was found to determine CO selectivity, with the following order Ni12P5 >Ni2P > Ni3P. Based on the activity of the studied catalysts, the catalysts were ranked in order of suitability for the RWGS reaction as follows: Ni12P5-SiO2 (Ni/P = 2.4) > Ni2P-SiO2 (Ni/P = 2) > NiP-SiO2 (Ni/P = 1) > NiP2-SiO2 (Ni/P = 0.5). Two catalysts with Ni/P atomic ratios; 2.4 and 2, were selected for stability testing. The catalyst with Ni/P ratio = 2.4 (i.e., Ni12P5-SiO2) was found to be more stable in terms of CO2 conversion and CO yield over the 24-hour duration at 550 °C. Using the phosphidation strategy to tune both selectivity and activity of Ni catalysts for RWGS, methanation as a competing reaction is shown to be no longer a critical issue in the RWGS process for catalysts with high Ni/P atomic ratios (2.4 and 2) even at lower temperatures (300–500 °C). This opens up potential low temperature RWGS opportunities, especially coupled to downstream or tandem lower temperature processes to produce liquid fuels.


Noviembre, 2023 | DOI: 10.1016/j.jcou.2023.102606

7.70
Química de Superficies y Catálisis

Glucose dehydration reaction over metal halides supported on activated charcoal catalysts

Martin, Gabriel Delgado; Lara, Beatriz; Bounoukta, Charf Eddine; Domínguez, María Isabel; Ammari, Fatima; Ivanova, Svetlana; Centeno, Miguel Ángel
Catalysis Today, 423 (2023) 114012

Show abstract ▽

Different metal halide catalysts supported on a commercial active charcoal have been synthesized, activated, characterized and tested in glucose dehydration to 5-hydroxymethylfurfural using a biphasic water/methyl isobutyl ketone media. The influence of the cation nature (K+, Ca2+, Sr2+, Mg2+) and anion nature (F-, Cl-, Br-) on the catalytic performance of the solid is discussed in terms of glucose conversion, HMF yield and products selectivity. The activation of the impregnated catalysts results in a great diversity of active sites, such as Bronsted sites (carboxylic groups), basic sites (metal oxide), and Lewis acid site (Mn+). Their distribution within the samples determinates the resulting products and the final HMF yield. 


Noviembre, 2023 | DOI: 10.1016/j.cattod.2023.01.019

5.30
Química de Superficies y Catálisis

Multicomponent graphene based catalysts for guaiacol upgrading in hydrothermal conditions: Exploring "H2-free" alternatives for bio-compounds hydrodeoxygenation

Parrilla-Lahoz, S; Jin, W; Pastor-Perez, L; Duyar, MS; Martinez-Quintana, L; Dongil, AB; Reina, TR
Catalysis Today, 422 (2023) 114235

Show abstract ▽

 

Catalytic hydrodeoxygenation (HDO) is a critical technique for upgrading biomass derivatives to deoxygenated fuels or other high-value compounds. Phenol, guaiacol, anisole, p-cresol, m-cresol and vanillin are all monomeric phenolics produced from lignin. Guaiacol is often utilised as a model lignin compound to deduce mechanistic information about the bio-oil upgrading process. Typically, a source of H2 is supplied as reactant for the HDO reaction. However, the H2 supply, due to the high cost of production and additional safety precautions needed for storage and transportation, imposes significant economic infeasibilities on the HDO process's scaling up. We investigated a novel H2-free hydrodeoxygenation (HDO) reaction of guaiacol at low temperatures and pressures, using water as both a reaction medium and hydrogen source. A variety of Ni catalysts supported on zirconia/ graphene/with/without nitrogen doping were synthesised and evaluated at 250 degrees C and 300 degrees C in a batch reactor, with the goal of performing a multi-step tandem reaction including water splitting followed by HDO. The catalysts were characterised using H2-TPR, XRD, TEM and XPS to better understand the physicochemical properties and their correlation with catalytic performance of the samples in the HDO process. Indeed, our NiZr2O/Gr-n present the best activity/selectivity balance and it is deemed as a promising catalyst to conduct the H2-free HDO reaction. The catalyst reached commendable conversion levels and selectivity to mono-oxygenated compounds considering the very challenging reaction conditions. This innovative HDO approach provides a new avenue for cost-effective biomass upgrading.


Noviembre, 2023 | DOI: 10.1016/j.cattod.2023.01.027

5.30
Química de Superficies y Catálisis

Guaiacol hydrotreatment in an integrated APR-HDO process: Exploring the promoting effect of platinum on Ni-Pt catalysts and assessing methanol and glycerol as hydrogen sources

Jin, W; Gandara-Loe, J; Pastor-Perez, L; Villora-Pico, JJ; Sepulveda-Escribano, A; Rinaldi, R; Reina, TR
Renewable Energy, 215 (2023) 118907

Show abstract ▽

This study presents an integrated approach combining aqueous phase reforming (APR) and hydrodeoxygenation (HDO) for the hydrotreatment of guaiacol, a model compound representing lignin-derived phenols in pyrolysis bio-oils. The APR process enables in-situ H2 generation, eliminating the need for an external hydrogen source. We examine the interplay between metal species, the Pt-promoting effect on Ni-Pt catalyst supported on activated carbon (AC), and the choice of hydrogen source (methanol or glycerol). Amongst the monometallic catalysts, a 1% Pt/AC catalyst notably achieved over 96% guaiacol conversion at 300 degrees C with either hydrogen source. Interestingly, when 0.5-1% of the Ni loading is replaced with Pt, the resulting bimetallic Ni-Pt/AC catalysts demonstrate a significant improvement in guaiacol conversion, reaching 70% when methanol is employed as the hydrogen source. Surprisingly, no comparable enhancement in guaiacol conversion is observed when employing glycerol as the hydrogen source. This observation underlines one of the pivotal effects of the hydrogen source on catalyst performance. X-ray photoemission spectroscopy (XPS) pinpointed strong Ni-Pt interactions in the catalyst. It also revealed distinctive electronic features of Ni-Pt/AC, which are favourable for steering selectivity towards cyclohexanol rather than phenol when Pt loading is increased from 0.5 to 1%. Moreover, Pt enhanced catalyst stability by inhibiting the oxidation of Ni sites and mitigating Ni-Pt phase sintering. Overall, our findings offer important insights into integrating APR and HDO processes, the promotion effect of Pt, and the importance of hydrogen source selection in terms of guaiacol conversion and catalyst stability.


Octubre, 2023 | DOI: 10.1016/j.renene.2023.118907

8.70
Química de Superficies y Catálisis

Catalytic conversion of syngas to light hydrocarbons via simulated intermediates CO/CO2/DME/N2/H2 over the regulated acidity of SAPO-34

Meng, FH; Wang, LA; Nawaz, MA; Wang, Q; Gong, ZY; Li, Z
Chemical Engineering Journal,

Show abstract ▽

 

Direct conversion of syngas to light hydrocarbons has been intensively studied in recent years; however, the high selectivity of light hydrocarbons is still a challenging task to achieve a high CO conversion. Here, a bifunctional catalyst consisting of a methanol synthesis catalyst (CZA) and a methanol to dimethyl ether (DME) catalyst (Al2O3) was employed with a hydrocarbon synthesis catalyst (SAPO-34), for syngas conversion to light hydrocarbons in a dual fixed-bed reactor. The conversion of simulated intermediates CO/CO2/DME/N2/H2 with a molar ratio of 9/6/4/5/76, obtained from syngas conversion to DME over CZA and Al2O3, was studied over SAPO-34 zeolites. It was found that SP34-0.1 with Si/Al ratio of 0.1, exhibited low amount of strong acid (0.60 mmol/g) and high selectivity to light olefins (74.1%), while SP34-0.4 with Si/Al ratio of 0.4 exhibited high amount of strong acid (1.00 mmol/g) leading to high selectivity of light paraffins (88.4%). The in-situ DRIFTS analysis illustrated that DME can be rapidly adsorbed on the hydroxyl site of SAPO-34 and decomposed into the surface methyl species, where SP34-0.4 could produce more dimethylcyclopentenyl cationic species than SP340.1. It was suggested that the overall reaction route led to a high selectivity to light olefins (84.2%) with a CO conversion of 61.2% on (CZA + Al2O3) catalyst combined with SP34-0.1, while a high selectivity to light paraffins (76.3%) could be achieved by combining with SP34-0.4 at 70.3% CO conversion. Since, the current study interprets that the selectivity of hydrocarbons can be adjusted by regulating the acidity of SAPO-34 to achieve a high CO conversion in the dual fixed-bed reactor scheme.


Octubre, 2023 | DOI: 10.1016/j.cej.2023.145895

15.10
Fotocatálisis Heterogénea: Aplicaciones - Nanotecnología en Superficies y Plasma

Mechanistic aspects of the reduction of rutile titanium dioxide and its Re-oxidation. Development and destruction of crystallographic shear structures

Bickley, RI; Garside, GR; González-Carreño, T; González-Elipe, AR; Navío, JA
Journal of Solid State Chemistry, 326 (2023) 124174

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A model is presented giving the mean dimensions of acicular octadecahedral microcrystallites of a rutile titanium dioxide powder. Reduction at 823 K, in conjunction with ESR, electrical conductivity and controlled re-oxidation has enabled the model to be applied to reduced microcrystallites. At 300 K they contain <0.1% of paramagnetic [Ti3+↑ VO: Ti3+] reduced edge sites and >99.9% of reduced spin-paired [Ti3+↑↓ Ti3+ VO:] sites. These sites are situated on the external crystal faces and on polygonal bulk crystallographic shear (CS) structures inclined to the microcrystal four-fold symmetry axis. CS structures are quantum-sized [Ti4O7VO:] environments which broaden the paramagnetic signals at 78 K. Temperature programmed reduction in H2(g) reveals atomic hydrogen as a precursor to CS structure formation via a lattice template formed on microcrystallite faces. Shear structures are oxidised on their polygonal perimeters at differing rates on the respective microcrystallite faces by anionic vacancy transfer from sub-surface regions.


Octubre, 2023 | DOI: 10.1016/j.jssc.2023.124174

3.30
Química de Superficies y Catálisis

Enroute to the Carbon-Neutrality Goals via the Targeted Development of Ammonia as a Potential Nitrogen-Based Energy Carrier

Nawaz, MA; Blay-Roger, R; Saif, M; Meng, FH; González-Arias, J; Miao, BJ; Bobadilla, LF; Ramírez-Reina, T; Odriozola, J.A.
ACS Catalysis, 13 (2023) 14415-14453

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The reliance of a future carbon-free horizon is strongly aligned with the long-term energy storage avenues which are completely derived from renewable energy resources. Ammonia with its high energy content and density can perform as a decent candidate for buffering the short-term storage options. However, the current NH3 production majorly feeding the current huge desire for ammonia is dominated by the conventional nonrenewable Haber–Bosch (H–B) process route, thus continuously damaging the target of carbon neutrality goals. High-purity hydrogen (H2) gas is an essential precursor for the H–B process; however, it is a significant energy consumer (about 2% of the global energy supply) and contributes over 420 million tons of CO2/annum. Therefore, the research on the renewable synthesis of nitrogen-based energy carriers (such as ammonia) from the direct electrochemical, photocatalytic, or plasma catalytic processes; its conversion; and utilization to the potential derivatives has been a hot topic in the past few decades. A prospective analysis of the highly appealing processes has been summarized in this study, which could facilitate the adaption of renewable alternatives as an effective approach for zero carbon emission, paving the excellent pathways along the road to the development of nitrogen-based energy technologies, especially the targeted development of ammonia. Further, this Review covers the current and future impacts of the H–B process, the development of aspiring ammonia synthesis routes (via electro, photo, bio, chemical loop, or plasma catalysis), and its conversion and utilization to the renewable derivatives in terms of fabrication of model catalysts, advanced characterization technology, and efficient device design.


Octubre, 2023 | DOI: 10.1021/acscatal.3c02410

12.90
Química de Superficies y Catálisis

Impact of topology framework of microporous solids on methanol carbonylation: An operando DRIFTS-MS study

Luque-Alvarez, LA; Serrano-Cruz, M; Gonzalez-Castano, M; Bobadilla, LF; Odriozola, JA
Microporous and mesoporous materials, 360 (2023) 112725

Show abstract ▽

Methanol carbonylation was evaluated over heterogeneous catalysts based on Cu-exchanged zeolitic materials with different topology: Cu@MOR, Cu@FER, and Cu@ZSM-5. Despite the similar Si/Al ratios, it is crucial to acknowledge that the acid strength is influenced by the framework topology, as supported by the NH3-TPD results. This, along with other characterization techniques allowed us to estimate the impact of pore size and pore distribution in these microporous materials on catalytic performance. The channel structure influenced catalytic parameters such as conversion and selectivity. The higher methanol conversion achieved on Cu@FER shows the importance of Bronsted acid sites and redox centres location regarding the topology of the material. Concerning the selectivity, the production of acetic acid was endorsed by the 12-MR (MOR) channels, methyl acetate's production by the 10-MR (FER) channels. Finally, the presence of 6-MR (ZSM-5) channels led to a complete selectivity towards DME production. The reaction mechanism was elucidated via operando DRIFTS-MS and results revealed a bifunctional mechanism in which methanol adsorbs and dehydrates on acidic Bronsted sites and CO is activated over Cu+ species.


Octubre, 2023 | DOI: 10.1016/j.micromeso.2023.112725

5.20
Química de Superficies y Catálisis

Water-assisted HDO of biomass model compounds enabled by Ru-based catalysts

Carrasco-Ruiz, S; Parrilla-Lahoz, S; Santos, JL; Penkova, A; Odriozola, JA; Reina, TR; Pastor-Pérez, L
Fuel Processing Technology, 249 (2023) 107860

Show abstract ▽

Biofuels upgrading gathering momentum in view of the gradual depletion of fossil fuels and the pursuit of renewable energy sources to mitigate global warming. Hydrodeoxygenation (HDO) is a key reaction in the upgrading of bio-oil to produce hydrocarbon fuels or high-value chemicals. Oxygen removal in bio-oil increases its calorific value, improve thermal and chemical stability, reduce corrosiveness, etc., making the upgraded biooil suitable as a fuel or blending fuel. However, the dependence on high-pressure hydrogen is a serious disadvantage, as it is an expensive resource whose use also poses safety concerns. In this scenario, we propose a pioneering route for model biomass compounds upgrading via H2-free HDO. Herein we have developed multifunctional catalysts based on Ru and ceria supported on carbon able conduct the hydrodeoxygenation reaction using water as hydrogen source. We found that cerium oxide improves ruthenium metallic dispersion and the overall redox properties of the multicomponent system leading to enhanced catalytic performance. Along with the successful catalytic formulation we identify 300 degrees C as an optimal temperature validating the H2-free HDO route for bio-compounds upgrading.


Octubre, 2023 | DOI: 10.1016/j.fuproc.2023.107860

7.50
Química de Superficies y Catálisis

Low-temperature reverse water gas-shift reaction over highly efficient Cu-hydrotalcites: Mechanistic insights on the role of malachite phase

Alvarez-Hernandez, D; Marin-Sanchez, M; Lobo-Andrades, L; Azancot, L; Bobadilla, LF; Ivanova, S; Centeno, MA
Catalysis Today, 422 (2023) 114235

Show abstract ▽

Carbon dioxide (CO2) transformation into valuable fuels and chemicals is in most cases a challenge far from readiness nowadays. One possible route for its conversion is the reverse water gas shift reaction (rWGS), crucial for syngas generation and required for the chemical conversion of CO2 to fuels and platform chemicals. In this paper, well organized Cu/Zn/Al structures were proposed as efficient catalysts for rWGS reaction at low tem-peratures. The results of in situ XRD revealed the formation of layered structures such malachite and hydro-talcite. The operando DRIFTS-MS studies of those structure suggests a participation of Cu2+/Cu+ pair in the reaction, promoting the redox mechanism and enhancing the activity at lower temperature. This work also provides a new strategy to design Cu-based rWGS catalysts able to prevent the sintering of active phase.


Octubre, 2023 | DOI: 10.1016/j.cattod.2023.114235

5.30
Química de Superficies y Catálisis

Process design and utilisation strategy for CO2 capture in flue gases. Technical assessment and preliminary economic approach for steel mills

Navarro, JC; Baena-Moreno, FM; Centeno, MA; Laguna, OH; Almagro, JF; Odriozola, JA
Renewable & Sustainable Energy Reviews, 184 (2023) 113537

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The steel industry is the most relevant sector in emerging economies due to its application in numerous fields. However, steel manufacturing involves large energy investment and produces significant greenhouse gas emissions. The current world economic and environmental scenario therefore necessitates that improvements in the footprint of the steel industry be made without affecting its viability. Considering the present challenge, we report two possible processes for Carbon Capture and Utilization (CCU). The first process is the competitive capture of CO2-SO2, followed by CO2 valorisation to methane. However, the CO2 capture capacity and lifetime for the adsorbent after multiple cycles could be improved through preliminary desulphurization of the gas current. The improved system demonstrates net profitability in a typical stainless steel plant. Therefore, it can be implemented in an industrial setting without profitability loss to steelmaking operations, fulfilling bot the goal of reducing CO2 emissions while protecting the mainstay of the plant.


Septiembre, 2023 | DOI: 10.1016/j.rser.2023.113537

15.90
Fotocatálisis Heterogénea: Aplicaciones - Reactividad de Sólidos

Effect of Alkaline Salts on Pyrolyzed Solid Wastes in Used Edible Oils: An Attenuated Total Reflectance Analysis of Surface Compounds as a Function of the Temperature

Romero-Sarria, F; Real, C; Córdoba, JM; Hidalgo, C; Alcalá, MD
Spectroscopy Journal, 1 (2023) 98-110

Show abstract ▽

Biochars obtained via the pyrolysis of biomass are very attractive materials from the point of view of their applications and play key roles in the current energy context. The characterization of these carbonaceous materials is crucial to determine their field of application. In this work, the pyrolysis of a non-conventional biomass (solid wastes in used edible oils) was investigated. The obtained biochars were characterized using conventional techniques (TG, XRD, and SEM-EDX), and a deep analysis via ATR-FTIR was performed. This spectroscopic technique, which is a rapid and powerful tool that is well adapted to study carbon-based materials, was employed to determine the effect of temperature on the nature of functional groups on the surface. Moreover, the water washing of the raw sample (containing important quantities of inorganic salts) before pyrolysis evidenced that the inorganic salts act as catalysts in the biomass degradation and influence the degree of condensation (DOC) of PAH. Moreover, it was observed that these salts contribute to the retention of oxygenated compounds on the surface of the solid.


Septiembre, 2023 | DOI: 10.3390/spectroscj1020009

0.00
Química de Superficies y Catálisis

Charting a path to catalytic upcycling of plastic micro/nano fiber pollution from textiles to produce carbon nanomaterials and turquoise hydrogen

Silvia Parrilla-Lahoz; Marielis C. Zambrano; Vlad Stolojan; Rachida Bance-Soualhi; Joel J. Pawlak; Richard A. Venditti; Tomas Ramirez Reina; Melis S. Duyar
RSC Sustainability, 1 (2023) 1177-1183

Show abstract ▽

Washing synthetic textile fibers releases micro/nano plastics, endangering the environment. As new filters and associated regulations are developed to prevent fiber release from washing machines, there emerges a need to manage the collected waste, for which the only current options are combustion or landfill. Herein we show for the first time the application of a catalytic pyrolysis approach to upcycle textile derived fibrous micro/nano plastics waste, with the aim of keeping carbon in the solid phase and preventing its release as a greenhouse gas. Herein, we demonstrate the co-production of hydrogen and carbon nanomaterials from the two most prevalent global textile microfiber wastes: cotton and polyester. Our results pave a way forward to a realistic process design for upcycling mixed micro/nano fiber waste collected from laundering, drying, vacuuming, and environmental cleanup.


Agosto, 2023 | DOI: 10.1039/D3SU00095H

0.00
Química de Superficies y Catálisis

Hydrogen production by catalytic aqueous-phase reforming of waste biomass: a review

González-Arias, J; Zhang, Z; Reina, TR; Odriozola, JA
Environmental Chemistry Letters, 21 (2023) 3089-3104

Show abstract ▽

The rising adverse effects of climate change call for a rapid shift to low-carbon energy and reducing our dependence on fossil fuels. For that, biorefineries appear as promising alternatives to produce energy, chemicals, and fuels using biomass and waste as raw materials. Here, we review catalytic aqueous-phase reforming to convert biomass and organic waste carbohydrates into renewable hydrogen, with focus on reforming basics; catalyst design; reforming of model compounds, wastewater and biomass; economics and life cycle assessment. We found that platinum and palladium are technically highly effective, yet their high price may limit upscaling. Alternatively, addition of tin to nickel gives acceptable results and improves hydrogen selectivity from 35 to 90%. We observed that hydrogen production decreases from 14% for crude glycerol to 2% for pure glycerol, thus highlighting the need to do experiments with real wastewater. The rare experiments on real wastewater from brewery, juice, tuna, and cheese industries have given hydrogen production rates of up to 149.7 mg/L. Aqueous-phase reforming could be shortly competitive with prices around 3-6 USD per kg of hydrogen, which are nearing the current market prices of 2-3 USD per kg.


Agosto, 2023 | DOI: 10.1007/s10311-023-01643-w

15.70
Química de Superficies y Catálisis

H2-rich syngas production from biogas reforming: Overcoming coking and sintering using bimetallic Ni-based catalysts

Carrasco-Ruiz, S; Zhang, Q; Gándara-Loe, J; Pastor-Pérez, L; Odriozola, JA; Reina, TR; Bobadilla, LF
International Journal of Hydrogen Energy, 48 (2023) 72

Show abstract ▽

Dry reforming of methane is a very appealing catalytic route biogas (mainly composed by greenhouse gases: carbon dioxide and methane) conversion into added value syngas, which could be further upgraded to produce liquid fuels and added value chemicals. However, the major culprits of this reaction are coking and active phase sintering that result in catalysts deactivation. Herein we have developed a highly stable bimetallic Ni–Rh catalyst supported on mixed CeO2–Al2O3 oxide using low-noble metal loadings. The addition of small amounts of rhodium to nickel catalysts prevents coke formation and improves sintering resistance, achieving high conversions over extended reaction times hence resulting in promising catalysts for biogas upgrading.


Agosto, 2023 | DOI: 10.1016/j.ijhydene.2023.03.301

7.20
Fotocatálisis Heterogénea: Aplicaciones

ZnO/TiO2 and ZnO/Nb2O5 as effective systems for the treatment of enteric bacteria and commercial dyes

Hernandez, JS; Murcia, JJ; Rojas, H; Hidalgo, MC; Navio, JA
Revista Facultad de Ingeniería-Universidad de Antioquia, 108 (2023) 9-17

Show abstract ▽

In this study, ZnO/TiO2 and ZnO/Nb2O5 photocatalysts were evaluated in the river pollution remediation and wastewater treatment from textile factories, thus, the target pollutants selected for this study were enteropathogenic bacteria and commercial dyes. The mixed oxide systems were extensively analyzed in order to explore their physicochemical properties. From this analysis, it was found that the coupling of two oxides did not modify the crystallinity of the pristine semiconductors. As a result, XRD Wurtzite phase, hexagonal phase, and anatase phases were identified for ZnO, Nb2O5, and TiO2 photocatalyst, respectively. Using UV-Vis DRS, a higher absorption for mixed oxides in the visible region of the electromagnetic spectrum was observed, along with a decrease in the band gap value in these materials. The results of the photocatalytic activity evaluation showed that the coupling of ZnO with Nb2O5 and TiO2 increased the effectiveness of the total organic carbon (TOC) and E. Coli elimination. 83% of TOC and elimination of 64% of E. coli were achieved using ZnO/Nb2O5 photocatalyst for the treatment of water samples from the polluted river.


Julio, 2023 | DOI: 10.17533/udea.redin.20220785

0.32
Química de Superficies y Catálisis

Biochar production from cellulose under reductant atmosphere: influence of the total pyrolysis time

Santos, JL; Centeno, MA; Odriozola, JA
RSC Advances, 13 (2023) 21071-21079

Show abstract ▽

Today's rising energy costs, coupled with increasing energy demand, make it necessary to search for more efficient energy processes. In recent years, there have been increasing efforts to develop efficient catalysts based on waste-derived char, by a single step where the carbon precursor and the metallic active phase one undergo a single common thermal process under a reductant atmosphere at high temperature. The use of a reductant atmosphere drives the formation of carbonaceous materials with different characteristics than those obtained under the standard nitrogen-inert one. Our work evaluates the influence of the residence time and the heating rate on the physicochemical properties of the biochar obtained. Relatively long residence times and slow heating rates, improve the yield to the resulting biochar, without increasing production cost, making the subsequent char-based metallic catalyst synthesis more efficient. The heating rate was shown to be key in improving the properties of the char in a smoother and more controlled way, unlocking a new working pathway for the efficient design and production of char-based catalysts in a one-pot synthesis.


Julio, 2023 | DOI: 10.1039/d3ra03093h

3.90
Química de Superficies y Catálisis

Effect of noble metal addition over active Ru/TiO2 catalyst for CO selective methanation from H2 rich- streams

Bobadilla, LF; Muñoz-Murillo, A; Gandara-Loe, J; Perez, A; Laguna, OH; Martinez, TLM; Penkova, A; Centeno, MA; Odriozola, JA
International Journal of Hydrogen Energy, 48 (2023) 25065-25074

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Selective CO methanation from H2-rich stream has been regarded as a promising route for deep removal of low CO concentration and catalytic hydrogen purification processes. This work is focused on the development of more efficient catalysts applied in practical conditions. For this purpose, we prepared a series of catalysts based on Ru supported over titania and promoted with small amounts of Rh and Pt. Characterization details revealed that Rh and Pt modify the electronic properties of Ru. The results of catalytic activity showed that Pt has a negative effect since it promotes the reverse water gas shift reaction decreasing the selectivity of methanation but Rh increases remarkably the activity and selectivity of CO methanation. The obtained results suggest that RuRh-based catalyst could become important for the treatment of industrial-volume streams.


Julio, 2023 | DOI: 10.1016/j.ijhydene.2022.07.072

7.20
Química de Superficies y Catálisis

New 3D Printing Strategy for Structured Carbon Devices Fabrication

Delgado-Martin, G; Rodriguez, N; Dominguez, MI; Agamez-Pertuz, YY; Tejada, MM; Ruiz-Lopez, E; Ivanova, S; Centeno, MA
Catalysts, 13 (2023) 1039

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This work shows a new method for the preparation of 100% carbon-structured devices. The method is based on resorcinol-formaldehyde polymerization, using starch as a binder with the addition of a certain amount of external carbon source before polymerization. Molds obtained by 3D printing are used to shape the structured devices in the desired shape, and the ultimate pyrolysis step consolidates and produces the carbonaceous devices. The proposed method allows obtaining supports with different textural and surface properties varying the carbonaceous source, the solvent, or the pyrolysis conditions, among other factors. The as-obtained devices have demonstrated their usefulness as palladium supports for the gas-phase formic acid dehydrogenation reaction. The monolith shows a high conversion of formic acid (81% according to H-2 production) and a high selectivity towards hydrogen production at mild temperatures (80% at 423 K).


Julio, 2023 | DOI: 10.3390/catal13071039

3.90
Química de Superficies y Catálisis

Formic Acid Dehydrogenation over a Monometallic Pd and Bimetallic Pd:Co Catalyst Supported on Activated Carbon

Pelaez, MR; Ruiz-Lopez, E; Dominguez, MI; Ivanova, S; Centeno, MA
Catalysts, 13 (2023) 977

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In this study, palladium is proposed as an active site for formic acid dehydrogenation reaction. Pd activity was modulated with Co metal with the final aim of finding a synergistic effect that makes possible efficient hydrogen production for a low noble metal content. For the monometallic catalysts, the metal loadings were optimized, and the increase in the reaction temperature and presence of additives were carefully considered. The present study aimed, to a great extent, to enlighten the possible routes for decreasing noble metal loading in view of the better sustainability of hydrogen production from liquid organic carrier molecules, such as formic acid.


Junio, 2023 | DOI: 10.3390/catal13060977

3.90
Química de Superficies y Catálisis

Are Ni/ and Ni5Fe1/biochar catalysts suitable for synthetic natural gas production? A comparison with g-Al2O3 supported catalysts

González-Castaño, M; Morales, C; de Miguel, JCN; Boelte, JH; Klepel, O; Flege, JI; Arellano-Garcia, H
Green Energy & Environment, 8 (2023) 744-756

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Among challenges implicit in the transition to the post-fossil fuel energetic model, the finite amount of resources available for the technological implementation of CO2 revalorizing processes arises as a central issue. The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes. Taking Ni and NiFe catalysts supported over g-Al2O3 oxide as reference materials, this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO2 methanation. The development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst surface. Displaying lower Turn Over Frequencies than Ni/Al catalyst, the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst performances. For NiFe catalysts, analogous Ni5Fe1 alloys were constituted over both alumina and biochar supports. The highest specific activity of the catalyst series, exhibited by the NiFe/C catalyst, was related to the development of surface basic sites along with weaker NiFe-C interactions, which resulted in increased Ni0:NiO surface populations under reaction conditions. In summary, the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.


Junio, 2023 | DOI: 10.1016/j.gee.2021.05.007

13.30
Química de Superficies y Catálisis

Toluene combustion on MnOx, CeO2, and Mn-Ce-O solids prepared via citrate complexation, and citrate and urea combustion methods

Rahou, S; Benadda-Kordjani, A; Ivanova, S; Odriozola, JA; Chebout, R; Mahzoul, H; Zouaoui, N
Journal of Nanoparticle Research, 25 (2023) 114

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MnOx, CeO2, and MnCe-O (Mn/Ce = 1) solids have been prepared via the citrate complexation and combustion method using citrate and urea precursors. The solids have been characterized by XRD, SEM-EDX, N-2-adsorption-desorption, UV-Vis spectroscopy, TPR, O-2-TPD, and XPS techniques. The catalytic reactivity of the manganese oxides was not affected by the preparation protocol. In the case of ceria and mixed oxides, the synthesis method greatly affected the structural and chemical properties, ultimately altering their reactivity. The citrate complexation method produced the most homogeneous and active mixed oxide, whereas the urea combustion method resulted in less active solids. The mixed oxide prepared via urea combustion was less active than the manganese single oxide; the decrease in activity was attributed to phase separation and the formation of Mn3O4 domains on the surface of ceria. In contrast, citrate complexation resulted in solids with the lowest particle size (similar to 3 nm), the highest oxidation state for manganese, and the highest proportion of oxygen vacancies, which promote the oxidation reaction.


Junio, 2023 | DOI: 10.1007/s11051-023-05759-6

2.50
Química de Superficies y Catálisis

Hydrothermal carbonization vs. anaerobic digestion to valorize fruit and vegetable waste: A comparative technical and energy assessment

Metyouy, K; Gonzalez, R; Gomez, X; Gonzalez-Arias, J; Martinez, EJ; Chafik, T; Sanchez, ME; Cara-Jiménez, J
Journal of Environmental Chemical Engineering, 11 (2023) 109925

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Herein, the valorization of vegetable and fruit waste was assessed via hydrothermal carbonization (HTC) and anaerobic digestion (AD) in terms of product characterization and energy requirements. HTC was conducted at reaction temperatures between 150 & DEG;C and 190 & DEG;C, and residence times between 20 min and 40 min. The increase in the process severity resulted in hydrochars with higher carbon contents and higher energy densification ratios. AD was performed in two different ways. i.e., batch and semi-continuous reactions. From the batch experiments a methane yield of 300 L CH4/kg VS was obtained, while for the semi-continuous, the average specific methane production estimated (for HRTs from 75 to 50 days) was 213 & PLUSMN; 32 L CH4/kg VS. To estimate the energy re-quirements, mass and energy balances were performed considering the basic stages of each process to obtain a suitable biofuel material. In this sense, it was concluded that for this specific waste, AD was a more suitable process with a positive energy net balance. On the contrary, HTC presented a negative energy net balance being required 1.29 MJ/kg of fresh food waste. A combined HTC-AD treatment may be an efficient method to take advantage of both technologies leading to higher energy efficiencies and other valuable products.


Junio, 2023 | DOI: 10.1016/j.jece.2023.109925

7.70
Química de Superficies y Catálisis

Review and Perspectives of CO2 Absorption by Water- and Amine-Based Nanofluids

Yuan, CT; Wang, Y; Baena-Moreno, FM; Pan, Z; Zhang, R; Zhou, H; Zhang, Z
Energy & Fuels, 37 (2023) 8883-8901

Show abstract ▽

The emission of greenhouse gases, especially CO2, hasbecome a major cause of environmental degradation, and carbon capture,utilization, and storage (CCUS) is a proposed solution to mitigateits impact. Nanofluids, a relatively new method for CO2 absorption, have gained attention in recent years. This review focuseson conventional methods for preparing nanofluids along with techniquesto improve their stability and enhance the CO2 absorptionand desorption mechanisms. Additionally, the influences of factors,i.e., nanoparticle and base solution types as well as nanoparticleconcentration, on the CO2 absorption process are summarized.Furthermore, models that can predict the absorption of CO2 accurately are outlined. It is found that the types of both baseliquids and nanoparticles have an important impact on the absorptionby nanofluids. In-depth studies on the predictive capabilities ofartificial intelligence (AI) models hold immense potential in thisregard. This review also puts forth effective strategies to addressprevailing challenges. This will provide a solid theoretical basisfor this field and underscore the promising potential of nanofluidsas CO2 solvents. There are still many unexplored aspectsto be considered, such as the economic viability and energy consumptionof this technology.


Junio, 2023 | DOI: 10.1021/acs.energyfuels.3c00874

5.30
Química de Superficies y Catálisis

Unravelling the CO2 capture and conversion mechanism of a NiRu-Na2O switchable dual-function material in various CO2 utilisation reactions

Merkouri, LP; Martin-Espejo, JL; Bobadilla, LF; Odriozola, JA; Penkova, A; Reina, T; Duyar, MS
Journal of Materials Chemistry C

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Time-resolved operando DRIFTS-MS was performed to elucidate the CO2 capture and conversion mechanisms of a NiRuNa/CeAl DFM in CO2 methanation, reverse water-gas shift, and dry reforming of methane. CO2 was captured mainly in the form of carbonyls and bidentate carbonates, and a spillover mechanism occurred to obtain the desired products.


Mayo, 2023 | DOI: 10.1039/d3ta01892j

11.90
Química de Superficies y Catálisis

The Need for Flexible Chemical Synthesis and How Dual-Function Materials Can Pave the Way

Merkouri, LP; Paksoy, AI; Reina, TR; Duyar, MS
ACS Catalysis, 13 (2023) 7230-7242

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Since climate change keeps escalating, it is imperativethat theincreasing CO2 emissions be combated. Over recent years,research efforts have been aiming for the design and optimizationof materials for CO2 capture and conversion to enable acircular economy. The uncertainties in the energy sector and the variationsin supply and demand place an additional burden on the commercializationand implementation of these carbon capture and utilization technologies.Therefore, the scientific community needs to think out of the boxif it is to find solutions to mitigate the effects of climate change.Flexible chemical synthesis can pave the way for tackling market uncertainties.The materials for flexible chemical synthesis function under a dynamicoperation, and thus, they need to be studied as such. Dual-functionmaterials are an emerging group of dynamic catalytic materials thatintegrate the CO2 capture and conversion steps. Hence,they can be used to allow some flexibility in the production of chemicalsas a response to the changing energy sector. This Perspective highlightsthe necessity of flexible chemical synthesis by focusing on understandingthe catalytic characteristics under a dynamic operation and by discussingthe requirements for the optimization of materials at the nanoscale.


Mayo, 2023 | DOI: 10.1021/acscatal.3c00880

12.90
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Catalytic performance of cobalt supported onto APTES functionalized TiO2 for Fischer-Tropsch reaction

Platero, F; Caballero, A; Colon, G
Fuel, 340 (2023) 127528

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Cobalt supported TiO2 catalysts have been prepared by wet-impregnation and by immobilization over APTES (3-aminopropyl triethoxysilane) grafted TiO2. Impregnated system showed better catalytic performance after reduction at 260 degrees C but significant deactivation is observed. On the contrary, functionalized catalyst showed better catalytic performance after reduction at 400 degrees C with notable stability. We have stated from CO-DRIFT operando analysis that impregnated system is strongly affected by negative SMSI (strong metal-support inter-action) upon reduction at higher temperature. While immobilization on APTES hinders the loss of metal active sites. The study of spent catalysts denotes that Co is redispersed in the impregnated catalyst while functionalized trends to form agglomerates.


Mayo, 2023 | DOI: 10.1016/j.fuel.2023.127528

7.40
Química de Superficies y Catálisis

MIL-100(Fe)-derived catalysts for CO2 conversion via low- and high-temperature reverse water-gas shift reaction

Loe, JG; Pena, AP; Espejo, JLM; Bobadilla, LF; Reina, TR; Pastor-Perez, L
Heliyon, 9 (2023) e16070

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Fe-derived catalysts were synthesized by the pyrolysis of MIL-100 (Fe) metal-organic framework (MOF) and evaluated in the reverse water-gas shift (RWGS) reaction. The addition of Rh as a dopant by in-situ incorporation during the synthesis and wet impregnation was also considered. Our characterization data showed that the main active phase was a mixture of & alpha;-Fe, Fe3C, and Fe3O4 in all the catalysts evaluated. Additionally, small Rh loading leads to a decrease in the particle size in the active phase. Despite all three catalysts showing commendable CO selectivity levels, the C@Fe* catalyst showed the most promising performance at a temperature below 500 degrees C, attributed to the in-situ incorporation of Rh during the synthesis. Overall, this work showcases a strategy for designing novel Fe MOF-derived catalysts for RWGS reaction, opening new research opportunities for CO2 utilization schemes.


Mayo, 2023 | DOI: 10.1016/j.heliyon.2023.e16070

4.00
Química de Superficies y Catálisis

Carbon Capture Enhancement by Water-Based Nanofluids in a Hollow Fiber Membrane Contactor

Yuan, CT; Pan, Z; Wang, Y; Baena-Moreno, FM; Constantinou, A; Zhang, Z
Energy Technology, 11 (2023) 2300254

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Nanoparticles are being used in the CO2 solvents to improve the capture performance. Herein, a 2D model is proposed to study the CO2 capture performance from a gaseous mixture using a hollow fiber membrane contactor (HFMC). Both water-based nanofluids of carbon nanotubes (CNT) and SiO2 are deployed as the carbon absorbents. It is verified that Brownian motion and grazing effect are the major reasons to enhance the mass transfer of nanofluids. The simulation findings show that the modeling data conform well with the experimental studies. The root-mean-square errors for SiO2 nanofluid and CNT nanofluid are 2.37% and 2.56%, respectively. When the amounts of nanoparticles increase between 0.02 and 0.06 wt%, CO2 capture efficiencies of SiO2 and CNT nanofluids increase by 7.92% and 13.17%, respectively. Also, the CNT nanofluid has a better capture performance than the SiO2 nanofluid. Furthermore, research is conducted into how membrane characteristics affect HFMC performance. It is indicated that increasing the membrane porosity and decreasing the membrane tortuosity have a positive impact on the capture efficiency. This work demonstrates the potentials in the use of nanoparticles in CO2 solvents and provides a solid theoretical basis for nanofluids to significantly enhance gas absorption.


Mayo, 2023 | DOI: 10.1002/ente.202300254

3.80
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

High-Performance Photocatalytic H2 Production Using a Binary Cu/ TiO2/SrTiO3 Heterojunction

Gonzalez-Tejero, M; Villachica-Llamosas, JG; Ruiz-Aguirre, A; Colon, G
ACS Applied Energy Materials, 6 (2023) 4007-4015

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Cu/TiO2/SrTiO3 hybrid structures have been synthesized by the simple impregnation method from Cu/TiO2 and SrTiO3 systems. The structural and surface characterization stated that Cu/TiO2/SrTiO3 composites form an effective covering of SrTiO3 by Cu/TiO2. The heterostructured catalysts lead to an outstanding improved photoactivity for hydrogen production from methanol photoreforming that would be related with the efficient separation of charge pairs favored by the Cu/ TiO2/SrTiO3 heterojunction. The best photoproduction is attained for the 30 wt % SrTiO3 heterojunction showing 81.7 mmol/g H2 after 6 h (leading to an apparent quantum yield of ca 1%), 1.7 times higher than that of bare Cu/TiO2.


Abril, 2023 | DOI: 10.1021/acsaem.3c00219

6.40
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic treatment based on TiO2 for a coal mining drainage

Murcia-Mesa, JJ; Patino-Castillo, CG; Rojas-Sarmiento, HA; Navio-Santos, A; Hidalgo-Lopez, MD; Angel-Botero, A
Revista Facultad de Ingeniería-Universidad de Antioquia, 107 (2023) 88-101

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The aim of the present work was to evaluate the effectiveness of a heterogeneous photocatalyst based on TiO2 in the treatment of coal mining drainage which contains a variety of heavy metals and high concentration sulfates and sulfides. The photocatalytic behavior of the commercial reference Sigma Aldrich and the different materials synthesized using the Sol-gel methodology with surface modifications using sulfation and fluorination processes were analyzed. To find a possible correlation between the physicochemical properties of photocatalysts and their behavior, a characterization was carried out using X-Ray Diffraction (XRD), X-Ray Fluorescence spectrometry (XRF), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance Spectra (UV-Vis DRS), N2 physisorption, X-ray photoelectron spectroscopy (XPS), and particle size analysis. Results indicated that the modification of the TiO2 prepared in the laboratory using sulfation and fluorination allowed the successful control of the physicochemical properties of this oxide. However, commercial TiO2 showed the greatest effectiveness in removing metals such as: Fe, Cu, Cr, and As after a photocatalytic reaction for a maximum of 1 hour under continuous nitrogen flow and a light intensity of 120 W/m2.


Abril, 2023 | DOI: 10.17533/udea.redin.20211063

0.32
Química de Superficies y Catálisis

Scalable synthesis of 2D Ti2CTx MXene and molybdenum disulfide composites with excellent microwave absorbing performance

Miao, BJ; Cao, YE; Zhu, QS; Nawaz, MA; Ordiozola, JA; Reina, TR; Bai, ZM; Ren, JN; Wei, FC
Advanced Composites and Hybrid Materials, 6 (2023) 61

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The signal crosstalk and electromagnetic interference (EMI) problems direly need to be resolved in the rapid development of modern microwave communication technology for a better working frequency and transmission power of electronic systems. Where the new absorbing materials such as molybdenum disulfide (MoS2)/titania (TiO2)/Ti2CTx and MoS2/Ti2CTx composites could meet the requirement of "thin, strong, light weight, and wide band" for excellent absorbing performance. In this work, a lighter Ti2CTx material was selected as the matrix, and MoS2 was in-situ grown on Ti2CTx matrix by traditional hydrothermal method and microwave solvothermal method. The fabricated composite exhibited synergic effect of two-dimensional heterostructural interface and double dielectric elements, where a small amount of TiO2 and a certain proportion of MoS2 jointly improve the impedance matching of the composite material. In here, the extreme reflection loss (RLmin) can reach - 54.70 dB (with a frequency of 7.59 GHz, 3.39 mm thickness), and the maximum effective absorption bandwidth (EAB(max)) can reach 4 GHz. Polyethylene glycol 200 was used as the solvent instead of water to make Ti2CTx less oxidized during the composite process, where the microwave heating would attain fast speed, short time, high efficiency, and uniform product. Since, the MoS2/Ti2CTx composite without oxidizing possessed a wider effective absorption bandwidth (EAB) at a thinner thickness, thus resulting in the excellent microwave absorption performance and confirming the validity and rationality of new microwave absorption materials.


Abril, 2023 | DOI: 10.1007/s42114-023-00643-2

20.10
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Facile Synthesis of Heterogeneous Indium Nanoparticles for Formate Production via CO2 Electroreduction

Perez-Sequera, AC; Diaz-Perez, MA; Angulo, MAL; Holgado, JP; Serrano-Ruiz, JC
Nanomaterials, 13 (2023) 3052

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In this study, a simple and scalable method to obtain heterogeneous indium nanoparticles and carbon-supported indium nanoparticles under mild conditions is described. Physicochemical characterization by X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed heterogeneous morphologies for the In nanoparticles in all cases. Apart from In-0, XPS revealed the presence of oxidized In species on the carbon-supported samples, whereas these species were not observed for the unsupported samples. The best-in-class catalyst (In-50/C-50) exhibited a high formate Faradaic efficiency (FE) near the unit (above 97%) at -1.6 V vs. Ag/AgCl, achieving a stable current density around -10 mA center dot cm(geo)(-2), in a common H-cell. While In-0 sites are the main active sites for the reaction, the presence of oxidized In species could play a role in the improved performance of the supported samples.


Abril, 2023 | DOI: 10.3390/nano13081304

5.30
Química de Superficies y Catálisis

In-situ DRIFTS steady-state study of CO2 and CO methanation over Ni-promoted catalysts

González-Castaño, M; González-Arias, J; Bobadilla, LF; Ruíz-López, E; Odriozola, JA; Arellano-García, H
Fuel, 338 (2023) 127241

Show abstract ▽

Promoting the performance of catalytic systems by incorporating small amount of alkali has been proved effective for several reactions whilst controversial outcomes are reported for the synthetic natural gas production. This work studies a series of Ni catalysts for CO2 and CO methanation reactions. In-situ DRIFTS spectroscopy evidenced similar reaction intermediates for all evaluated systems and it is proposed a reaction mechanism based on: i) formate decomposition and ii) hydrogenation of lineal carbonyl species to methane. Compared to bare Ni, the enhanced CO2 methanation rates attained by NiFe/Al and NiFeK/Al systems are associated to promoted formates decomposition into lineal carbonyl species. Also for CO methanation, the differences in the catalysts' performances were associated to the relative concentration of lineal carbonyl species. Under CO methanation conditions and opposing the CO2 methanation results where the incorporation of K delivered promoted catalytic behaviours, worsened CO methanation rates were discerned for the NiFeK/Al system.


Abril, 2023 | DOI: 10.1016/j.fuel.2022.127241

7.40
Química de Superficies y Catálisis

Engineering exsolved catalysts for CO2 conversion

Ali, SA; Safi, M; Merkouri, LP; Soodi, S; Iakovidis, A; Duyar, MS; Neagu, D; Reina, TR; Kousi, K
Frontiers in Energy Research, 11 (2023) 1150000

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Introduction: Innovating technologies to efficiently reduce carbon dioxide (CO2) emission or covert it into useful products has never been more crucial in light of the urgent need to transition to a net-zero economy by 2050. The design of efficient catalysts that can make the above a viable solution is of essence. Many noble metal catalysts already display high activity, but are usually expensive. Thus, alternative methods for their production are necessary to ensure more efficient use of noble metals.Methods: Exsolution has been shown to be an approach to produce strained nanoparticles, stable against agglomeration while displaying enhanced activity. Here we explore the effect of a low level of substitution of Ni into a Rh based A-site deficienttitanate aiming to investigate the formation of more efficient, low loading noblemetal catalysts.Results: We find that with the addition of Ni in a Rh based titanate exsolution is increased by up to similar to 4 times in terms of particle population which in turn results in up to 50% increase in its catalytic activity for CO2 conversion.Discussion: We show that this design principle not only fulfills a major research need in the conversion of CO2 but also provides a step-change advancement in the design and synthesis of tandem catalysts by the formation of distinct catalytically active sites.


Marzo, 2023 | DOI: 10.3389/fenrg.2023.1150000

3.40
Fotocatálisis Heterogénea: Aplicaciones

Boosting the photocatalytic properties of NaTaO3 by coupling with AgBr

Puga, F; Navío, JA; Hidalgo, MC
Photochemical & Photobiological Sciences, 22 (2023) 549-566

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AgBr/NaTaO3 composites, with different molar % of NaTaO3 (Br/NTO(X%)), have been synthesized by simple precipitation methods; bare NaTaO3 was synthesized by hydrothermal procedure, while AgBr was synthesized by a precipitation procedure using cetyl-tri-methyl-ammonium bromide (CTAB) and AgNO3. Samples have been characterized by X-ray diffraction (XRD), N2 adsorption, UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photo-catalysts was evaluated through photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and caffeic acid (CAFA) under UV and visible illumination. Single AgBr material and Br/NTO(X%) composites displayed the ability to absorb light in the visible region, while NaTaO3 is only photoactive under UV irradiation. Based on the position of conduction and valence bands of AgBr and NaTaO3, the heterojunction between these two photo-catalysts corresponds to a type II junction. In the case of photocatalytic degradation of RhB and CAFA, Br/NTO(x%) composites have highest photocatalytic activity than that obtained by both parental materials under the same operational conditions. AgBr and Br/NTO(x%) composites achieve a fast degradation of MO, together with a considerable adsorption capacity, attributed to the presence of a remaining amount of residual CTAB on the AgBr surface. In summary, coupling AgBr with NaTaO3 improves the photocatalytic activity under both UV and visible illumination with respect to the parental components, but the performance of the composites is highly dependent on the type of substrate to be degraded and the illumination conditions.


Marzo, 2023 | DOI: 10.1007/s43630-022-00334-9

3.10
Química de Superficies y Catálisis

Functionalized Biochars as Supports for Ru/C Catalysts: Tunable and Efficient Materials for γ-Valerolactone Production

Bounoukta, CE; Megias-Sayago, C; Navarro, JC; Ammari, F; Ivanova, S; Centeno, MA
Nanomaterials, 13 (2023) 1129

Show abstract ▽

Cotton stalks-based biochars were prepared and used to synthetize Ru-supported catalysts for selective production of gamma-valerolactone from levulinic acid in aqueous media. Different biochars' pre-treatments (HNO3, ZnCl2, CO2 or a combination of them) were carried out to activate the final carbonaceous support. Nitric acid treatment resulted in microporous biochars with high surface area, whereas the chemical activation with ZnCl2 substantially increases the mesoporous surface. The combination of both treatments led to a support with exceptional textural properties allowing the preparation of Ru/C catalyst with 1422 m(2)/g surface area, 1210 m(2)/g of it being a mesoporous surface. The impact of the biochars' pre-treatments on the catalytic performance of Ru-based catalysts is fully discussed.


Marzo, 2023 | DOI: 10.3390/nano13061129

5.30
Fotocatálisis Heterogénea: Aplicaciones

CO2 Methanation over Nickel Catalysts: Support Effects Investigated through Specific Activity and Operando IR Spectroscopy Measurements

Gonzalez-Rangulan, VV; Reyero, I; Bimbela, F; Romero-Sarria, F; Daturi, M; Gandia, LM
Catalysts, 13 (2023) 448

Show abstract ▽

Renewed interest in CO2 methanation is due to its role within the framework of the Power-to-Methane processes. While the use of nickel-based catalysts for CO2 methanation is well stablished, the support is being subjected to thorough research due to its complex effects. The objective of this work was the study of the influence of the support with a series of catalysts supported on alumina, ceria, ceria-zirconia, and titania. Catalysts' performance has been kinetically and spectroscopically evaluated over a wide range of temperatures (150-500 degrees C). The main results have shown remarkable differences among the catalysts as concerns Ni dispersion, metallic precursor reducibility, basic properties, and catalytic activity. Operando infrared spectroscopy measurements have evidenced the presence of almost the same type of adsorbed species during the course of the reaction, but with different relative intensities. The results indicate that using as support of Ni a reducible metal oxide that is capable of developing the basicity associated with medium-strength basic sites and a suitable balance between metallic sites and centers linked to the support leads to high CO2 methanation activity. In addition, the results obtained by operando FTIR spectroscopy suggest that CO2 methanation follows the formate pathway over the catalysts under consideration.


Febrero, 2023 | DOI: 10.3390/catal13020448

3.90
Química de Superficies y Catálisis

Spinel ferrite catalysts for CO2 reduction via reverse water gas shift reaction

Navarro, JC; Hurtado, C; Gonzalez-Castano, M; Bobadilla, LF; Ivanova, S; Cumbrera, FL; Centeno, MA; Odriozola, JA
Journal of CO2 Utilization, 68 (2023) 102356

Show abstract ▽

The production of CO via Reverse Water Gas Shift (RWGS) reaction is a suitable route for CO2 valorization. In this study a series of modified spinels AB2O4 (A site symbolscript Ni, Zn and Cu and B symbolscript are investigated as RWGS catalysts and their structure-to-function relationships derived from the changes on the A-site cation are ratio-nalized. For all ferrite systems, the RWGS reaction the process main activity and selectivity is governed by the B -site cation, but the variations on the A-site metals determines catalysts' structural features and stability in the reaction. Among the catalyst series, superior RWGS performance displayed the ferrites modified with Cu and Ni associated to the greater oxygen vacancy population for those spinels enabled by the partial allocation on symbolscript cations into the tetrahedral sites.


Febrero, 2023 | DOI: 10.1016/j.jcou.2022.102356

7.70
Fotocatálisis Heterogénea: Aplicaciones

Effect of phenol concentration on the photocatalytic performance of ZnO nanoparticles

Gonzalez, RL; De la Fuente, O; Garcia, RL; Lopez, MDU; Owen, PQ; Lopez, MCH; Lemus, MAA
Journal of Chemical Technology and Biotechnology (2023)

Show abstract ▽

BACKGROUND: Phenol and its derivatives are considered toxic compounds, even at low concentrations. Their accumulation in water effluents has become a serious problem that could be resolved by using zinc oxide (ZnO)-based photocatalysts.RESULTS: ZnO nanoparticles were synthesized through the precipitation method, using zinc nitrate and sodium carbonate as reagents. The as-synthesized powder was calcined for 4 h at 500 degrees C (2 degrees C min(-1)). X-Ray diffraction analysis confirmed a hexag-onal crystalline phase (wurtzite) with an average crystallite size of 38 nm. The Kubelka-Munk method was used to determine a band gap of 3.27 eV through UV-Vis diffuse reflectance spectrum and a Brunauer-Emmett-Teller (BET) specific area of 12 m(2) g(-1) was obtained from N2 adsorption analysis. The photocatalytic activity of ZnO was evaluated under visible light (300 W) lamp, with 1 mg mL(-1) of photocatalyst and using phenol solutions at different concentrations of 5,10, 25, and 50 ppm; the obtained degradation percentages were 98%, 97%, 94%, and 71%, respectively. Three cycles were performed with the ZnO used in the reactions with phenol at 5 and 50 ppm, decreasing the degraded percentages to 87% and 65%, respectively. The generation of hydroxyl radicals was estimated for the ZnO and ZnO samples after three cycles by means of fluorescence spectroscopy analy-sis. It was observed that the first-used ZnO material generated a significant amount of hydroxyl radicals.CONCLUSION: When compared to ZnO after three cycles of reaction, the amount of generated hydroxyl radicals decreased. It was observed that the higher the amount of phenol, the lower the generation of hydroxyl radicals after reuse; this was probably due to the presence of some adsorbed by-products of the photocatalytic reaction on the surface of ZnO, as the FTIR spectrum of the post-reaction sample showed.


Febrero, 2023 | DOI: 10.1002/jctb.7334

3.40
Química de Superficies y Catálisis

Flexible NiRu Systems for CO2 Methanation: From Efficient Catalysts to Advanced Dual-Function Materials

Merkouri, LP; Martin-Espejo, JL; Bobadilla, LF; Odriozola, JA; Duyar, MS; Reina, TR
Nanomaterials, 13 (2023) 506

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CO2 emissions in the atmosphere have been increasing rapidly in recent years, causing global warming. CO2 methanation reaction is deemed to be a way to combat these emissions by converting CO2 into synthetic natural gas, i.e., CH4. NiRu/CeAl and NiRu/CeZr both demonstrated favourable activity for CO2 methanation, with NiRu/CeAl approaching equilibrium conversion at 350 degrees C with 100% CH4 selectivity. Its stability under high space velocity (400 L center dot g(-1)center dot h(-1)) was also commendable. By adding an adsorbent, potassium, the CO2 adsorption capability of NiRu/CeAl was boosted, allowing it to function as a dual-function material (DFM) for integrated CO2 capture and utilisation, producing 0.264 mol of CH4/kg of sample from captured CO2. Furthermore, time-resolved operando DRIFTS-MS measurements were performed to gain insights into the process mechanism. The obtained results demonstrate that CO2 was captured on basic sites and was also dissociated on metallic sites in such a way that during the reduction step, methane was produced by two different pathways. This study reveals that by adding an adsorbent to the formulation of an effective NiRu methanation catalyst, advanced dual-function materials can be designed.


Febrero, 2023 | DOI: 10.3390/nano13030506

5.30
Química de Superficies y Catálisis

Low CO2 hydrogen streams production from formic acid through control of the reaction pH

Santos, JL; Lopez, ER; Ivanova, S; Monzon, A; Centeno, MA; Odriozola, JA
Chemical Engineering Journal, 455 (2023) 140645

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There are multiple factors that influence the catalyst performance in the reaction of formic acid dehydrogena-tion: the nature of catalyst and/or support, the used solvent and reaction variables such as temperature, time, formic acid concentration, presence/absence of formates and pH of the solution. This work evaluates a series of important parameters like the influence of the pH by itself, the influence of the nature of used alkali agents and the effect of direct formate addition as reactive on hydrogen production via formic acid dehydrogenation over a commercially available catalyst. The catalytic performance appears to depend on the ionic radius of the cations of the used base which reflects consequently on the hydrogen selectivity. The best base to be used must have lower hydrated cationic radii and a starting pH around 4 to achieve important hydrogen selectivity for medium term formic acid conversion.


Febrero, 2023 | DOI: 10.1016/j.cej.2022.140645

15.10
Química de Superficies y Catálisis

Engineering morphologies of yttrium oxide supported nickel catalysts for hydrogen production

Zhang, RB; Tu, ZA; Meng, S; Feng, G; Lu, ZH; Yu, YZ; Reina, TR; Hu, FY; Chen, XH; Ye, RP
Rare Metals, 42 (2023) 176-188

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The catalytic performance is highly related to the catalyst structure. Herein, a series of Ni nanoparticles supported on Y2O3 with different morphologies were successfully synthesized via hydrothermal process screening different pH environments. These Ni/Y2O3 catalysts were applied to efficiently produce COx-free H-2 through ammonia decomposition. We identify a significant impact of Y2O3 supports on nickel nanoclusters sizes and dispersion. The experimental results show that Ni/Y11 catalyst achieves 100% ammonia decomposition conversion under a gas hour space velocity (GHSV) of 12,000 ml.h(-1).g(cat)(-1) and temperature of 650 degrees C. Such a high level of activity over Ni/Y11 catalyst was attributed to a large specific surface area, appropriate alkalinity, and small Ni nanoparticles diameter with high dispersion.


Enero, 2023 | DOI: 10.1007/s12598-022-02136-5

8.80
Química de Superficies y Catálisis

Is the RWGS a viable route for CO2 conversion to added value products? A techno-economic study to understand the optimal RWGS conditions

Portillo, E; Gandara-Loe, J; Reina, TR; Pastor-Perez, L
Science of the Total Environment, 857 (2023) 159394

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Understanding the viability of the RWGS from a thermodynamic and techno-economic angle opens new horizons within CO2 conversion technologies. Unfortunately, profitability studies of this technology are scarce in literature and mainly focused on overall conversion and selectivity trends with tangential remarks on energy demands and pro-cess costs. To address this research gap, herein we present a comprehensive techno-economic study of the RWGS reac-tion when coupling with Fischer-Tropsch synthesis is envisaged to produced fuels and chemicals using CO2 as building block. We showcase a remarkable impact of operating conditions in the final syngas product and both CAPEX and OPEX. From a capital investment perspective, optimal situations involve RWGS unit running at low temperatures and high pressures as evidenced by our results. However, from the running cost angle, operating at 4 bar is the most favorable alternative within the studied scenarios. Our findings showcase that, no matter the selected temperature the RWGS unit should be preferentially run at intermediate pressures. Ultimately, our work maps out multiple operat-ing scenarios in terms of energy demand and process cost serving as guideline to set optimal reaction conditions to un-lock the potential of the RWGS for chemical CO2 recycling.


Enero, 2023 | DOI: 10.1016/j.scitotenv.2022.159394

9.80
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Methanation of CO2 over High Surface Nickel/Aluminates Compounds Prepared by a Self-Generated Carbon Template

Roudane, S; Bettahar, N; Caballero, A; Holgado, JP
Catalysts, 13 (2023) 142

Show abstract ▽

Catalytic gas-phase hydrogenation of CO2 into CH4 was tested under three different nickel/aluminate catalysts obtained from precursors of hexaaluminate composition (MAl16O19, M = Mg, Ca, Ba). These catalysts were prepared using a carbon template method, where carbon is self-generated from a sol-gel that contains an excess of citric acid and the Al and M salts (Ba2+, Ca2+, Mg2+) by two-step calcination in an inert/oxidizing atmosphere. This procedure yielded Ni particles decorating the surface of a porous high surface area matrix, which presents a typical XRD pattern of aluminate structure. Ni particles are obtained with a homogeneous distribution over the surface and an average diameter of ca 25-30 nm. Obtained materials exhibit a high conversion of CO2 below 500 degrees C, yielding CH4 as a final product with selectivity >95%. The observed trend with the alkaline earth cation follows the order NiBaAlO-PRx > NiCaAlO-PRx > NiMgAlO-PRx. We propose that the high performance of the NiBaAlO sample is derived from both an appropriate distribution of Ni particle size and the presence of BaCO3, acting as a CO2 buffer in the process.


Enero, 2023 | DOI: 10.3390/catal13010142

3.90
Química de Superficies y Catálisis

Selective hydrodeoxygenation of levulinic acid to gamma-valerolactone over Ru supported on functionalized carbon nanofibers

Bounoukta, CE; Megias-Sayago, C; Rendon, N; Ammari, F; Penkova, A; Ivanova, S; Centeno, MA; Odriozola, JA
Sustainable Energy & Fuels, 7 (2023) 857-867

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In this work, carbon nanofibers (CNFs) have been successfully functionalized by using different approaches and finally used for the preparation of Ru based catalysts. The organometallic approach has been demonstrated to be suitable for CNF functionalization, leading to well-defined Ru NPs (by adding organosilane, amino or mercapto functionalities, among others) in comparison with mineral acid treatments conventionally used to activate and/or functionalize carbonaceous solids. All catalysts have been tested in levulinic acid hydrodeoxygenation to γ-valerolactone under mild conditions, with the impact of CNF functionalization on the catalysts' performance fully discussed in comparison with unmodified commercial CNFs.


Enero, 2023 | DOI: 10.1039/d2se01503j

5.60
Química de Superficies y Catálisis

Highly dispersed Rh single atoms over graphitic carbon nitride as a robust catalyst for the hydroformylation reaction

Jurado, L; Esvan, J; Luque-Alvarez, LA; Bobadilla, LF; Odriozola, JA; Posada-Perez, S; Poater, A; Comas-Vives, A; Axet, MR
Catalysis Science & Tecnology, 13 (2022) 1425-1436

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Rhodium-catalysed hydroformylation, effective tool in bulk and fine-chemical synthesis, predominantly uses soluble metal complexes. For that reason, the metal leaching and the catalyst recycling are still the major drawbacks of this process. Single-atom catalysts have emerged as a powerful tool to combine the advantages of both homogeneous and heterogeneous catalysts. Since using an appropriate support material is key to create stable, finely dispersed, single-atom catalysts, here we show that Rh atoms anchored on graphitic carbon nitride are robust catalysts for the hydroformylation reaction of styrene.


Enero, 2023 | DOI: 10.1039/d2cy02094g

5.00
Química de Superficies y Catálisis

Formic Acid Dehydrogenation over Ru- and Pd-Based Catalysts: Gas- vs. Liquid-Phase Reactions

Ruiz-Lopez, E; Pelaez, MR; Ruz, MB; Leal, MID; Tejada, MM; Ivanova, S; Centeno, MA
Materials, 16 (2023) 472

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Formic acid has recently been revealed to be an excellent hydrogen carrier, and interest in the development of efficient and selective catalysts towards its dehydrogenation has grown. This reaction has been widely explored using homogeneous catalysts; however, from a practical and scalable point of view, heterogeneous catalysts are usually preferred in industry. In this work, formic acid dehydrogenation reactions in both liquid- and vapor-phase conditions have been investigated using heterogeneous catalysts based on mono- or bimetallic Pd/Ru. In all of the explored conditions, the catalysts showed good catalytic activity and selectivity towards the dehydrogenation reaction, avoiding the formation of undesired CO.


Enero, 2023 | DOI: 10.3390/ma16020472

3.40



2022


Química de Superficies y Catálisis

Development of Power-to-X Catalytic Processes for CO2 Valorisation: From the Molecular Level to the Reactor Architecture

Bobadilla, LF; Azancot, L; Luque-Alvarez, LA; Torres-Sempere, G; Gonzalez-Castano, M; Pastor-Perez, L; Ramírez-Reina, T; Ivanova, S; Centeno, MA; Odriozola, JA
Chemistry, 4 (2022) 1250-1280

Show abstract ▽

Nowadays, global climate change is likely the most compelling problem mankind is facing. In this scenario, decarbonisation of the chemical industry is one of the global challenges that the scientific community needs to address in the immediate future. Catalysis and catalytic processes are called to play a decisive role in the transition to a more sustainable and low-carbon future. This critical review analyses the unique advantages of structured reactors (isothermicity, a wide range of residence times availability, complex geometries) with the multifunctional design of efficient catalysts to synthesise chemicals using CO2 and renewable H-2 in a Power-to-X (PTX) strategy. Fine-chemistry synthetic methods and advanced in situ/operando techniques are essential to elucidate the changes of the catalysts during the studied reaction, thus gathering fundamental information about the active species and reaction mechanisms. Such information becomes crucial to refine the catalyst's formulation and boost the reaction's performance. On the other hand, reactors architecture allows flow pattern and temperature control, the management of strong thermal effects and the incorporation of specifically designed materials as catalytically active phases are expected to significantly contribute to the advance in the valorisation of CO2 in the form of high added-value products. From a general perspective, this paper aims to update the state of the art in Carbon Capture and Utilisation (CCU) and PTX concepts with emphasis on processes involving the transformation of CO2 into targeted fuels and platform chemicals, combining innovation from the point of view of both structured reactor design and multifunctional catalysts development.


Diciembre, 2022 | DOI: 10.3390/chemistry4040083

2.10
Química de Superficies y Catálisis

CO2 methanation on Ni/YMn1-xAlxO3 perovskite catalysts

Safdar, M; Gonzalez-Castano, M; Penkova, A; Centeno, MA; Odriozola, JA; Arellano-Garcia, H
Applied Materials Today, 29 (2022) 101577

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Seeking for advanced catalytic systems for the CO2 methanation reaction, the use of Ni supported catalysts over redox materials is often proposed. Profiting the superior redox properties described for layered perovskite systems, this work has investigated a series Ni supported YMn1-xAlxO3 (x = 0, 0.2, 0.5, 0.8, 1) perovskite catalysts. The obtained results evidenced the impact of the support nature on the systems redox properties and Ni-support interactions. Within the catalysts series, the greater methanation rates displayed by Ni/YMn0.5Al0.5O3 catalyst (0.748 mmol(CO2,conv.)s(-1) g(Ni)(-1) at 400 ? and 60 L/gh) were associated to the interplay between the support redox properties and superior Ni dispersion. The improved redox behavior attained through the Al-incorporation (up to x = 0.5) was associated to the layered perovskite structures which, being distorted and constituted by smaller crystal sizes, facilitated the behavior of Mn redox couples as surface species readily interconverted. Exhibiting catalytic performances comparable to precious metals based catalysts, this work proposes the Ni/YMn0.5Al0.5O3 catalyst as an effective system for the CO2 methanation reaction.


Diciembre, 2022 | DOI: 10.1016/j.apmt.2022.101577

8.30
Química de Superficies y Catálisis

Materials challenges and opportunities to address growing micro/ nanoplastics pollution: a review of thermochemical upcycling

Parrilla-Lahoz, S; Mahebadevan, S; Kauta, M; Zambrano, MC; Pawlak, JJ; Venditti, RA; Reina, TR; Duyar, MS
Materials Today Sustainability, 20 (2022) 100200

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Micro/nanoplastics have sparked attention in recent years due to their widespread presence in the environment. Currently, several waste valorization approaches are under development in order to upcycle micro/nanoplastics. Thermal conversion technologies such as pyrolysis, gasification, liquefaction, or hydrothermal carbonization can yield high-value solid products, oil, and gases from plastics waste. The common thermal conversion technologies investigated focus on maximizing the production of oil and gases (such as H2 and CH4) for use as fuel. Except for hydrogen, when these products are used to generate energy, the carbon emissions generated are comparable to those produced by traditional fossil fuels. Herein, we present a review of the current efforts to capture and convert plastic waste into valuable products with an emphasis on identifying the need to develop processes specifically for micro/nano-plastics while also preventing the release of CO2 emissions. We identify the development of efficient catalytic materials as a critical research need for achieving economically viable thermochemical con-version of micro/nanoplastics.


Diciembre, 2022 | DOI: 10.1016/j.mtsust.2022.100200

7.80
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Assessment of pilot-plant scale solar photocatalytic hydrogen generation with multiple approaches: Valorization, water decontamination and disinfection

Ruiz-Aguirre, A; Villachica-Llamosas, JG; Polo-Lopez, MI; Cabrera-Reina, A; Colon, G; Peral, J; Malato, S
Energy, 260 (2022) e10272

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The main goal of the present study was to explore pilot-scale combination of H-2 generation with simultaneous water disinfection or decontamination. Performance of a TiO2-CuO mixture for solar-to-hydrogen (STH) con-version was studied, focusing on treatment optimization (catalyst dose, proportion of semiconductors in the mixture and concentration of the sacrificial agent). Experiments were performed in a 25-L compound parabolic collector (2 m(2)) solar pilot plant specifically designed for photocatalytic hydrogen generation. The best operating conditions were 100 mg L-1 TiO2-CuO (10:1) with 0.075 M glycerol as the sacrificial agent. The best STH conversion attained was 0.9%. 25 mg L-1 imidacloprid was completely degraded (over 99%). The synergetic effect of anoxic conditions, TiO2:CuO and solar radiation caused a significant reduction (> 5 Log) in concen-tration of E. coli, used as a model waterborne pathogen, in less than 10 min.


Diciembre, 2022 | DOI: 10.1016/j.energy.2022.125199

9.00
Fotocatálisis Heterogénea: Aplicaciones

Effective photocatalytic conversion of formic acid using iron, copper and sulphate doped TiO2

Zouheir, M; Tanji, K; Navío, JA; Hidalgo, MC; Jaramillo-Paez, CA; Kherbeche, A
Journal of Central South University, 29 (2022) 3592-3607

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In this paper, the combined addition of copper or iron and sulphate ions onto TiO2 prepared by a simple sol-gel method is studied for formic acid photocatalytic conversion. A wide structural and morphological characterization of the different photocatalysts was performed by X-ray diffraction (XRD), N2-physisorption for BET surface area measurements, scanning and transmission electronic microscopies (SEM and TEM), UV-Vis diffuse spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS), in order to correlate the physico-chemical properties of the materials to their photocatalytic efficiencies for formic acid oxidation. Results have shown important differences among the catalysts depending on the metal added. Sulphated TiO2/Cu (1%Cu) was the best photocatalyst obtaining about 100% formic acid conversion in only 5 min. The appropriate physico-chemical features of this photocatalyst, given by the addition of combined copper and sulphate ions, explain its excellence in photocatalytic reaction.


Noviembre, 2022 | DOI: 10.1007/s11771-022-5172-9

4.40
Química de Superficies y Catálisis

Ni-Phosphide catalysts as versatile systems for gas-phase CO2 conversion: Impact of the support and evidences of structure-sensitivity

Zhang, Q; Pastor-Perez, L; Villora-Pico, JJ; Joyce, M; Sepulveda-Escribano, A; Duyar, MS; Reina, TR
Fuel, 323 (2022) 124301

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We report for the first time the support dependent activity and selectivity of Ni-rich nickel phosphide catalysts for CO2 hydrogenation. New catalysts for CO2 hydrogenation are needed to commercialise the reverse water-gas shift reaction (RWGS) which can feed captured carbon as feedstock for traditionally fossil fuel-based processes, as well as to develop flexible power-to-gas schemes that can synthesise chemicals on demand using surplus renewable energy and captured CO2. Here we show that Ni2P/SiO2 is a highly selective catalyst for RWGS, producing over 80% CO in the full temperature range of 350-750 degrees C. This indicates a high degree of suppression of the methanation reaction by phosphide formation, as Ni catalysts are known for their high methanation activity. This is shown to not simply be a site blocking effect, but to arise from the formation of a new more active site for RWGS. When supported on Al2O3 or CeAl, the dominant phase of as synthesized catalysts is Ni12P5. These Ni12P5 catalysts behave very differently compared to Ni2P/SiO2, and show activity for methanation at low temperatures with a switchover to RWGS at higher temperatures (reaching or approaching thermodynamic equilibrium behaviour). This switchable activity is interesting for applications where flexibility in distributed chemicals production from captured CO2 can be desirable. Both Ni12P5/Al2O3 and Ni12P5/CeAl show excellent stability over 100 h on stream, where they switch between methanation and RWGS reactions at 50-70% conversion. Catalysts are characterized before and after reactions via X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), temperature-programmed reduction and oxidation (TPR, TPO), Transmission Electron Microscopy (TEM), and BET surface area measurement. After reaction, Ni2P/SiO(2 )shows the emergence of a crystalline Ni12P5 phase while Ni12P5/Al2O3 and Ni12P5/CeAl both show the crystalline Ni3P phase. While stable activity of the latter catalysts is demonstrated via extended testing, this Ni enrichment in all phosphide catalysts shows the dynamic nature of the catalysts during operation. Moreover, it demonstrates that both the support and the phosphide phase play a key role in determining selectivity towards CO or CH4.


Septiembre, 2022 | DOI: 10.1016/j.fuel.2022.124301

7.40
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Unraveling the Mo/HZSM-5 reduction pre-treatment effect on methane dehydroaromatization reaction

Lopez-Martin, A; Caballero, A; Colon, G
Applied Catalysis B-Environmental, 312 (2022) 121382

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Reduction pre-treatment at different temperatures were performed over Mo/HZSM-5 system before methane dehydroaromatiztion reaction. We have shown the crucial effect of reduction temperature on the final catalytic performance. Outstanding improvement in the aromatics conversion has been attained. Thus, H-2 formation form methane cracking reaction seems to be hindered for pre-treated catalysts. As a consequence, the deposition of coke in these samples appeared also notably suppressed. The optimum performance has been achieved for reduction pre-treatment at 550 degrees C. For this temperature, we have observed that the fraction of reduced Mo species is higher.


Septiembre, 2022 | DOI: 10.1016/j.apcatb.2022.121382

22.10
Química de Superficies y Catálisis

Hydrogen production from landfill biogas: Profitability analysis of a real case study

Vidal-Barrero, F; Baena-Moreno, FM; Preciado-Cardenas, C; Villanueva-Perales, A; Reina, TR
Fuel, 324 (2022) 124438

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Hydrogen is not only considered as a cornerstone within renewable energy portfolio but it is also a key enabler for CO2 valorisation being a central resource for industrial decarbonization. This work evaluates the profitability of hydrogen production via combined biogas reforming and water-gas shift reaction, based on a real case scenario for landfill biogas plant in Seville (Spain). A techno-economic model was developed based on a process model and the discounted cash-flow method. A biogas flow of 700 m(3)/h (input given by the landfill biogas plant) was used as plant size and the analysis was carried out for two different cases: (1) use of already available energy sources at the industrial plant, and (2) solar energy generation to power the process. The economic outputs obtained showed that under the current circumstances, this hydrogen production route is not profitable. The main reason is the relatively low current hydrogen prices which comes from fossil fuels. A revenues analysis indicates that hydrogen from biogas selling prices between 2.9 and 5.7 euro/kg would be needed to reach profitability, which are considerably higher than the current hydrogen cost (1.7 euro/kg). A subsidy scheme is suggested to improve the competitiveness of this hydrogen production process in the short-medium term. A cost analysis is also performed, revealing that electricity prices and investment costs have a high impact on the total share (23-40% and 8-22%, respectively). Other potential costs reduction such as catalyst, labour and manteinance & overhead are also evaluated, showing that cutting-down production costs is mandatory to unlock the potential of hydrogen generation from biogas. Our work showcases the techno-economic challenge that green energy policies face in the path toward sustainable societies.


Septiembre, 2022 | DOI: 10.1016/j.fuel.2022.124438

7.40
Química de Superficies y Catálisis

Sustainable routes for acetic acid production: Traditional processes vs a low-carbon, biogas-based strategy

Martin-Espejo, JL; Gandara-Loe, J; Odriozola, JA; Reima, TR; Pastor-Pérez, L
Science of the Total Environment, 840 (2022) 156663

Show abstract ▽

The conversion of biogas, mainly formed of CO2 and CH4, into high-value platform chemicals is increasing attention in a context of low-carbon societies. In this new paradigm, acetic acid (AA) is deemed as an interesting product for the chemical industry. Herein we present a fresh overview of the current manufacturing approaches, compared to potential low-carbon alternatives. The use of biogas as primary feedstock to produce acetic acid is an auspicious alternative, representing a step-ahead on carbon-neutral industrial processes. Within the spirit of a circular economy, we propose and analyse a new BIO-strategy with two noteworthy pathways to potentially lower the environmental impact. The generation of syngas via dry reforming (DRM) combined with CO2 utilisation offers a way to produce acetic acid in a two-step approach (BIO-Indirect route), replacing the conventional, petroleum-derived steam reforming process. The most recent advances on catalyst design and technology are discussed. On the other hand, the BIO-Direct route offers a ground-breaking, atom-efficient way to directly generate acetic acid from biogas. Nevertheless, due to thermodynamic restrictions, the use of plasma technology is needed to directly produce acetic acid. This very promising approach is still in an early stage. Particularly, progress in catalyst design is mandatory to enable low-carbon routes for acetic acid production.


Septiembre, 2022 | DOI: 10.1016/j.scitotenv.2022.156663

9.80
Química de Superficies y Catálisis

Feasibility of switchable dual function materials as a flexible technology for CO2 capture and utilisation and evidence of passive direct air capture

Merkouri, LP; Reina, TR; Duyar, MS
Nanoscale, 14 (2022) 12620-12637

Show abstract ▽

The feasibility of a Dual Function Material (DFM) with a versatile catalyst offering switchable chemical synthesis from carbon dioxide (CO2) was demonstrated for the first time, showing evidence of the ability of these DFMs to passively capture CO2 directly from the air as well. These DFMs open up possibilities in flexible chemical production from dilute sources of CO2, through a combination of CO2 adsorption and subsequent chemical transformation (methanation, reverse water gas shift or dry reforming of methane). Combinations of Ni Ru bimetallic catalyst with Na2O, K2O or CaO adsorbent were supported on CeO2-Al2O3 to develop flexible DFMs. The designed multicomponent materials were shown to reversibly adsorb CO2 between the 350 and 650 degrees C temperature range and were easily regenerated by an inert gas purge stream. The components of the flexible DFMs showed a high degree of interaction with each other, which evidently enhanced their CO2 capture performance ranging from 0.14 to 0.49 mol kg(-1). It was shown that captured CO2 could be converted into useful products through either CO2 methanation, reverse water-gas shift (RWGS) or dry reforming of methane (DRM), which provides flexibility in terms of co-reactant (hydrogen vs. methane) and end product (synthetic natural gas, syngas or CO) by adjusting reaction conditions. The best DFM was the one containing CaO, producing 104 mu mol of CH4 per kg(DFM) in CO2 methanation, 58 mu mol of CO per kg(DFM) in RWGS and 338 mu mol of CO per kg(DFM) in DRM.


Agosto, 2022 | DOI: 10.1039/d2nr02688k

6.70
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Shepherding reaction intermediates to optimize H-2 yield using composite-doped TiO2-based photocatalysts

Barba-Nieto, I.; Colon, G; Fernández-García, M; Kubacka, A
Chemical Engineering Journal, 442 (2022) 136333

Show abstract ▽

Optimization of Pt-promoted TiO2-based is key to promote the photocatalytic production of hydrogen using sacrificial alcohol molecules. Combination of doping and surface decoration of the mentioned base photoactive material is here exploited to maximize hydrogen yield. Using the quantum efficiency parameter, it is shown that the resulting composite system can boost activity up to 7.3 times within the whole methanol:water mixture ratio, yielding quantum efficiencies in the ca. 13-16 % range. The key role of the different components in generating charge carrier species and their use to trigger the sacrificial molecule evolution and control reaction kinetics are examined through an in-situ spectroscopic study. The study unveils the complex reaction mechanism, with generation of C1 to C3 molecules from different carbon-containing radicals, and interprets the physical origin of the huge H2 production enhancement occurring in doped-composite titania-based catalysts.


Agosto, 2022 | DOI: 10.1016/j.cej.2022.136333

15.10
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Tuning the co-catalyst loading for the optimization of thermo-photocatalytic hydrogen production over Cu/TiO2

Platero, F; Caballero, A; Colon, G
Applied Catalysis A-General, 643 (2022) 118804

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We have optimized the H-2 production by methanol thermo-photocatalytic reforming in the gas phase using Cu/TiO2 catalyst by tuning metal loading. Metal co-catalyst has been deposited by means of chemical reduction deposition. We have stated that thermo- and thermo-photocatalytic process leads to a notable H-2 production at 200 C. By in-situ FTIR studies we evidenced that formate formation follows a different evolution depending on the reforming experiment. These surface formate would lead to CO formation through dehydration reaction. At higher Cu content the low CO selectivity denote that water-gas-shift reaction would predominate and exalt H-2 yield. Thus, different optimum Cu content is found for each reforming experiment. While for the photocatalytic reforming Cu/TiO2 (2 wt%) is the best catalyst of the series, we should increase the Cu content to Cu/TiO2 (5 wt%) to achieve the optimum performance for thermo-photocatalytic reforming of methanol.


Agosto, 2022 | DOI: 10.1016/j.apcata.2022.118804

5.50
Química de Superficies y Catálisis

Catalytic Upgrading of Biomass-Gasification Mixtures Using Ni-Fe/ MgAl2O4 as a Bifunctional Catalyst

Tarifa, P; Reina, TR; González-Castaño, M; Arellano-Garcia, H
Energy & Fuels, 36 (2022) 8267-8273

Show abstract ▽

Biomass gasification streams typically contain a mixture of CO, H-2, CH4, and CO(2 )as the majority components and frequently require conditioning for downstream processes. Herein, we investigate the catalytic upgrading of surrogate biomass gasifiers through the generation of syngas. Seeking a bifunctional system capable of converting CO2 and CH4 to CO, a reverse water gas shift (RWGS) catalyst based on Fe/MgAl(2)O(4 )was decorated with an increasing content of Ni metal and evaluated for producing syngas using different feedstock compositions. This approach proved efficient for gas upgrading, and the incorporation of adequate Ni content increased the CO content by promoting the RWGS and dry reforming of methane (DRM) reactions. The larger CO productivity attained at high temperatures was intimately associated with the generation of FeNi3 alloys. Among the catalysts' series, Ni-rich catalysts favored the CO productivity in the presence of CH4, but important carbon deposition processes were noticed. On the contrary, 2Ni-Fe/MgAl2O4 resulted in a competitive and cost-effective system delivering large amounts of CO with almost no coke deposits. Overall, the incorporation of a suitable realistic application for valorization of variable composition of biomass-gasification derived mixtures obtaining a syngas-rich stream thus opens new routes for biosyngas production and upgrading.


Agosto, 2022 | DOI: 10.1021/acs.energyfuels.2c01452

5.30
Química de Superficies y Catálisis

Recent advances on gas-phase CO2 conversion: Catalysis design and chemical processes to close the carbon cycle

Torres-Sempere, G; Pastor-Perez, L; Odriozola, JA; Yu, J; Duran-Olivencia, FJ; Bobadilla, LF; Reina, TR
Current Opinion in Green andd Sustainable Chemistry, 36 (2022) 100647

Show abstract ▽

Chemical CO2 recycling in the gas phase constitutes a straightforward approach for effective CO2 conversion to added-value products like syngas or synthetic methane. In this scenario, some traditional processes such as the dry and bi-reforming of methane, the CO2 methanation and the reverse water-gas shift have gained a renewed interest from the CO2 utilisation perspective. Indeed, these reactions represent flexible routes to upgrade CO2 and their application at an industrial scale could substantially reduce CO2 emissions. The bottleneck for the implementation of these processes at the commercial level is the development of highly active and robust heterogeneous catalysts able to overcome CO2 activation and deliver sufficient amounts of the upgrading products (i.e. syngas or synthetic natural gas) at the desired operating conditions. This review paper gathers the most recent advances in the design of new catalytic formulations for chemical CO2 recycling in the gas phase and constitutes an overview for experts and newcomers in the field to get fundamental insights into this emerging branch of low-carbon technologies.


Agosto, 2022 | DOI: 10.1016/j.cogsc.2022.100647

9.30
Química de Superficies y Catálisis

Emerging natural and tailored perovskite-type mixed oxides-based catalysts for CO2 conversions

Wu, J; Ye, RP; Xu, DJ; Wan, LZ; Reina, TR; Sun, H; Ni, Y; Zhou, ZF; Deng, XA
Frontiers in Chemistry, 10 (2022) 961355

Show abstract ▽

The rapid economic and societal development have led to unprecedented energy demand and consumption resulting in the harmful emission of pollutants. Hence, the conversion of greenhouse gases into valuable chemicals and fuels has become an urgent challenge for the scientific community. In recent decades, perovskite-type mixed oxide-based catalysts have attracted significant attention as efficient CO2 conversion catalysts due to the characteristics of both reversible oxygen storage capacity and stable structure compared to traditional oxide-supported catalysts. In this review, we hand over a comprehensive overview of the research for CO2 conversion by these emerging perovskite-type mixed oxide-based catalysts. Three main CO2 conversions, namely reverse water gas shift reaction, CO2 methanation, and CO2 reforming of methane have been introduced over perovskite-type mixed oxide-based catalysts and their reaction mechanisms. Different approaches for promoting activity and resisting carbon deposition have also been discussed, involving increased oxygen vacancies, enhanced dispersion of active metal, and fine-tuning strong metal-support interactions. Finally, the current challenges are mooted, and we have proposed future research prospects in this field to inspire more sensational breakthroughs in the material and environment fields.


Agosto, 2022 | DOI: 10.3389/fchem.2022.961355

5.50
Química de Superficies y Catálisis

Structure effect of modified biochar in Ru/C catalysts for sugar mixture hydrogenation

Santos, JL; Sanz-Moral, LM; Aho, A; Ivanova, S; Murzin, DY; Centeno, MA
Biomass & Bioenergy, 163 (2022) 106504

Show abstract ▽

This study deals with the production and activation of biochars and their use as supports for a series of ruthenium catalysts for hydrogenation of L-arabinose/D-galactose sugar mixture. The synthesized biochars differ in physicochemical properties and surface chemistry influencing ruthenium metal uptake and dispersion and as a consequence its catalytic behaviour. Selectivity exceeding 95% was observed for both hexitols. The catalytic performance of the prepared Ru supported catalysts is also compared to the already known Ru/activated carbon commercial catalyst.


Agosto, 2022 | DOI: 10.1016/j.biombioe.2022.106504

6.00
Química de Superficies y Catálisis

The effect of support surface hydroxyls on selective CO methanation with Ru based catalysts

Martínez, LMT; Muñoza, A; Pérez, A; Laguna, OH; Bobadilla, LF; Centeno, MA; Odriozola, JA
Applied Catalysis A: General, 641 (2022) 118678

Show abstract ▽

The aim of this work was to clarify the effect of the support on CO selective methanation with Ru/TiO2 catalysts. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity should be ascribed to anatase:rutile ratio, RuO2 +TiO2 solid solution formation, as well as the metal content and the thermal treatment used. All these characteristics result in active and selective catalysts in which the suppression of the reverse water gas shift reaction was observed. The catalytic performance must be explained by both the formation of more active Ru species as a result of support influence and the higher Ru dispersion. The study allows to conclude that for CO activation the role of support surface hydroxyls seems to be determinant for both the activity and selectivity of Ru/TiO2 catalysts.


Julio, 2022 | DOI: 10.1016/j.apcata.2022.118678

5.50
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic oxidation of pollutants in gas-phase via Ag3PO4-based semiconductor photocatalysts: Recent progress, new trends, and future perspectives

Y. Naciri; A. Hsini; A. Bouziani; R. Djellabi; Z. Ajmal; M. Laabd; J.A. Navío; A. Mills; C.L. Bianchi; H.Li; B. Bakiz; A. Albourine
Critical Reviews in Environmental Science and Technology, 52 (2022) 2339-2382

Show abstract ▽

Air pollution has become a significant challenge for both developing and developed nations. due to its close association with numerous fatal diseases such as cancer, respiratory, heart attack, and brain stroke. Over recent years, heterogeneous semiconductor photocatalysis has emerged as an effective approach to air remediation due to the ease of scale-up, ready application in the field, use of solar light and ready availability of a number of different effective photocatalysts. To date, most work in this area has been conducted using UV-absorbing photocatalysts, such as TiO2 and ZnO; However, recent studies have revealed Ag3PO4 as an attractive, visible-light-absorbing alternative, with a bandgap of 2.43 eV. In particular, this material has been shown to be an excellent photocatalyst for the removal of many types of pollutants in the gas phase. However, the widespread application of Ag3PO4 is restricted due to its tendency to undergo photoanodic corrosion and the poor reducing power of its photogenerated conductance band electrons, which are unable to reduce O2 to superoxide •O2 −. These limitations are critically evaluated in this review. In addition, recent studies on the modification of Ag3PO4 via combination with the conventional heterojunctions or Z-scheme junctions, as well as the photocatalytic mechanistic pathways for enhanced gas-pollutants removal, are summarized and discussed. Finally, an overview is given on the future developments that are required in order to overcome these challenges and so stimulate further research into this promising field.


Julio, 2022 | DOI: 10.1080/10643389.2021.1877977

12.60
Química de Superficies y Catálisis

Catalytic reforming of model biomass-derived producer gas

Azancot, L; Bobadilla, LF; Centeno, MA; Odriozola, JA
Fuel, 320 (2022) 123843

Show abstract ▽

This work includes a complete study of the reaction of reforming a simulated producer gas stream comparing a Ni-based catalyst with another one promoted with potassium to enhance the resistance to coke formation. Although coke deposition is unavoidable in the presence of tars in the stream, the analysis of different reaction parameters revealed that operating at 750 degrees C, weight hourly space velocity (WHSV) of 60 L-1 g(-1) h(-1) and 10-20 vol% of steam is possible to minimize the accumulation of carbon deposits. Moreover, it was demonstrated that the addition of potassium helps to mitigate carbon formation, but a high concentration of steam leads to nickel sintering and/or partial oxidation of metallic nickel. On this basis, it was successfully evidenced that the Ni-K catalyst is an excellent candidate for obtaining clean syngas from producer gas reforming.


Julio, 2022 | DOI: 10.1016/j.fuel.2022.123843

7.40
Química de Superficies y Catálisis

Insights on Guerbet Reaction: Production of Biobutanol From Bioethanol Over a Mg-Al Spinel Catalyst

Crespo, MAP; Vidal-Barrero, F; Azancot, L; Reina, TR; Campoy, M
Frontiers in Chemistry, 10 (2022) 945596

Show abstract ▽

The production of biobutanol from bioethanol by the Guerbet reaction is an alternative pathway to renewable sources. The commercial viability of this green route requires improvements in the process development. This study experimentally examines the influence of operating conditions on the performance of a Mg-Al spinel catalyst prepared from hydrotalcite precursors. This catalyst demonstrates an exceptional performance in the Guerbet reaction with a promising activity/butanol selectivity balance, excellent long-term stability, and very-low-carbon footprint (CO2 generation as by-products is minimal). This study showcases a systematic strategy to optimize the reaction parameters in the Guerbet reaction for biobutanol production using an advanced spinel catalyst. Upon carefully adjusting temperature, pressure, space velocity, and reactants co-feeding, very promising conversion (35%) and butanol selectivity values (48%) were obtained.


Julio, 2022 | DOI: 10.3389/fchem.2022.945596

5.50
Química de Superficies y Catálisis

Evidence of new Ni-O-K catalytic sites with superior stability for methane dry reforming

Azancot, L; Blay, V; Blay-Roger, R; Bobadilla, LF; Penkova, A; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 307 (2022) 121148

Show abstract ▽

Liquid fuels produced via Fischer-Tropsch synthesis from biomass-derived syngas constitute an attractive and sustainable energy vector for the transportation sector. This study focuses on the role of potassium as a promoter in Ni-based catalysts for reducing coke deposition during catalytic dry reforming. The study provides a new structural link between catalytic performance and physicochemical properties. We identify new Ni-O-K chemical states associated with high stability in the reforming process, evidenced by different characterization techniques. The nickel particles form a core surrounded by a Ni-O-K phase layer (Ni@Ni-O-K) during the reduction of the catalyst. This phase likely presents an alkali-nickelate-type structure, in which nickel is stabilized in oxidation state + 3. The Ni-O-K formation induces essential changes in the electronic, physical, structural, and morphological properties of the catalysts, notably enhancing their long-term stability in dry reforming. This work thus provides new directions for designing more efficient catalysts for sustainable gas-to-liquids processes.


Junio, 2022 | DOI: 10.1016/j.apcatb.2022.121148

22.10
Fotocatálisis Heterogénea: Aplicaciones

Pursuing efficient systems for glucose transformation to levulinic acid: Homogeneous vs. heterogeneous catalysts and the effect of their co-action

Bounoukta, CE; Megias-Sayago, C; Ivanova, S; Ammari, F; Centeno, MA; Odriozola, JA
FUEL, 318 (2022) 123712

Show abstract ▽

Exploring available catalytic systems to understand their behavior is a must to properly design efficient catalysts aiming to definitively drive biomass from laboratory to industrial scale. Glucose transformation to levulinic acid involves cascade reactions with specific requirements, different active sites in each case and secondary reactions hard to avoid which are intrinsically linked to the catalyst's nature and reaction conditions. In the present work, homogeneous, heterogeneous and heterogeneous/homogeneous catalysts are considered with the unique goal of improving levulinic acid yield while understanding the catalytic behaviour of cost-effective catalysts. The choice of the catalytic systems and the effect of the main reaction parameters on activity and selectivity is studied and discussed.


Junio, 2022 | DOI: 10.1016/j.fuel.2022.123712

7.40
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Enhanced photocatalytic activity of TiO2/WO3 nanocomposite from sonochemical-microwave assisted synthesis for the photodegradation of ciprofloxacin and oxytetracycline antibiotics under UV and sunlight

Moghni, N; Boutoumi, H; Khalaf, H; Makaoui, N; Colon, G
Journal of Photochemistry and Photobiology A-Chemistry, 428 (2022) 113848

Show abstract ▽

The TiO2/WO3 photocatalysts were prepared by a simple assisted sonochemical -microwave combination. The wide surface and structural characterization of synthesized material confirmed that the adopted preparation method resulted in nanoparticulated crystallite anatase phase of TiO2 with a large surface area (> 200 m(2)/g), and the dispersion of WO3 on the surface of TiO2. The photoactivity was assessed for the photodegradation of ciprofloxacin (CIP) and oxytetracycline (OTC) antibiotics under UV and sunlight irradiation. The mineralization rate, toxicity assessment, pollutant concentration effect on photodegradation efficiency, and reusability potential under sunlight were all investigated. Results showed that TiO2 doped with 5 wt% of WO3 exhibited the best photocatalytic activity under UV (100% degradation) and solar light. Rate constants for CIP and OTC degradation showed that TiO2/WO3 significantly improved with respect to bare TiO2. The antibacterial study revealed that the photodegraded solutions became less toxic than the initial CIP and OTC solutions showing a significant decrease in the inhibition zone diameter and mineralization rates. The prepared TiO2/WO3 maintained high performances in the presence of high concentrations of pollutants as well as good stability after four consecutive uses. The increased photocatalytic activity is attributed to the incorporation of WO3, which extends the light absorption range and decreases the rate of electron -hole recombination.


Junio, 2022 | DOI: 10.1016/j.jphotochem.2022.113848

4.30
Química de Superficies y Catálisis

Design of Full-Temperature-Range RWGS Catalysts: Impact of Alkali Promoters on Ni/CeO2

Gandara-Loe, J; Zhang, Q; Villora-Pico, JJ; Sepulveda-Escribano, A; Pastor-Perez, L; Reina, TR
Energy & Fuels, 36 (2022) 6362-6373

Show abstract ▽

Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.


Junio, 2022 | DOI: 10.1021/acs.energyfuels.2c00784

5.30
Química de Superficies y Catálisis

Electrocatalytic CO2 conversion to C-2 products: Catalysts design, market perspectives and techno-economic aspects

Ruiz-López, E; Gandara-Loe, J; Baena-Moreno, F; Reina, TR; Odriozola, JA
Renewable & Sustainable Energy Reviews, 161 (2022) 112329

Show abstract ▽

The energy crisis caused by the incessant growth in global energy demand joint to its associated greenhouse emissions motivates the urgent need to control and mitigate atmospheric CO2 levels. Leveraging CO2 as carbon pool to produce value-added products represents a cornerstone of the circular economy. Among the CO2 utilization strategies, electrochemical reduction of CO2 conversion to produce fuels and chemicals is booming due to its versatility and end-product flexibility. Herein most of the studies focused on C-1 products although C-2 and C2+ compounds are chemically and economically more appealing targets requiring advanced catalytic materials. Still, despite the complex pathways for C2+ products formation, their multiple and assorted applications have motivated the search of suitable electrocatalysts. In this review, we gather and analyse in a comprehensive manner the progress made regarding C2+ products considering not only the catalyst design and the electrochemistry features but also techno-economic aspects in order to envisage the most profitable scenarios. This state-of-the-art analysis showcases that electrochemical reduction of CO2 to C-2 products will play a key role in the decarbonisation of the chemical industry paving the way towards a low-carbon future.


Junio, 2022 | DOI: 10.1016/j.rser.2022.112329

15.90
Química de Superficies y Catálisis

Versatile Ni-Ru catalysts for gas phase CO2 conversion: Bringing closer dry reforming, reverse water gas shift and methanation to enable end-products flexibility

Merkouri, LP; le Sache, E; Pastor-Perez, L; Duyar, MS; Reina, TR
Fuel, 315 (2022) 123097

Show abstract ▽

Advanced catalytic materials able to catalyse more than one reaction efficiently are needed within the CO2 utilisation schemes to benefit from end-products flexibility. In this study, the combination of Ni and Ru (15 and 1 wt%, respectively) was tested in three reactions, i.e. dry reforming of methane (DRM), reverse water-gas shift (RWGS) and CO2 methanation. A stability experiment with one cycle of CO2 methanation-RWGS-DRM was carried out. Outstanding stability was revealed for the CO2 hydrogenation reactions and as regards the DRM, coke formation started after 10 h on stream. Overall, this research showcases that a multicomponent Ni-Ru/CeO2 -Al2O3 catalyst is an unprecedent versatile system for gas phase CO2 recycling. Beyond its excellent performance, our switchable catalyst allows a fine control of end-products selectivity.


Mayo, 2022 | DOI: 10.1016/j.fuel.2021.123097

7.40
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Characterization of Re-Mo/ZSM-5 catalysts: How Re improves the performance of Mo in the methane dehydroaromatization reaction

Lopez-Martin, A; Sini, MF; Cutrufello, MG; Caballero, A; Colon, G
Applied Catalysis B-Environmental, 304 (2022) 120960

Show abstract ▽

In this study, the promoting effect of rhenium addition as a co-dopant on Mo/ZSM-5 catalysts system has been analysed. Hence, bimetallic (Re-Mo/ZSM-5) catalysts have been synthesized using a sequential impregnation methodology. The catalytic performance for direct aromatization of methane reaction has been determined and correlated with their physical and chemical state combining multiple characterization techniques. An important synergy between Mo and Re, affected by the sequential impregnation, has been observed. Thus, Re1-Mo4/ZSM-5 in which Re has been incorporated first shows notably higher aromatic yields and stability against deactivation. Characterization results suggest that catalytic enhancement is due to the important effect of Re presence in close interaction with Mo. Improved evolution of ethane through C-C coupling would be correlated to this catalytic performance. As we discuss, Mo nature and location in the bimetallic systems are strongly conditioned by Re and the impregnation sequence and favours such intermediate step.


Mayo, 2022 | DOI: 10.1016/j.apcatb.2021.120960

22.10
Fotocatálisis Heterogénea: Aplicaciones

Insights into the structural and physicochemical properties of Zn-Bi-O composites for efficient photodegradation of caffeic acid, rhodamine B and methyl orange

F.Puga; J.A.Navío; J.M.Córdoba; F.Romero-Sarria; M.C.Hidalgo
Applied Surface Science, 581 (2022) 152351

Show abstract ▽

Different Zn-Bi-O composites were synthesized following the starting chemical molar composition of ZnBi2O4 spinels by a sol–gel method, (ZnBiO)-SG, and its subsequent hydrothermal treatment, (ZnBiO)-HT. The acquired X-ray diffractograms after sequential thermal treatments at a programmed rate indicate that both precursors evolved, after calcination at 500 °C, to materials (ZnBiO) with different stoichiometry. The use of different characterization techniques (both FT-IR and TEM), allowed us to establish that, with the sol–gel process a mixed ZnO/Bi2O3 oxide is generated, while after hydrothermal process a ternary Zn-Bi-O oxide is formed, with small amounts of residual ZnO. The photocatalytic properties of the synthesized samples were evaluated using Caffeic acid, Rhodamine B and Methyl Orange as model substrates. It can be concluded that both catalysts showed excellent photocatalytic activity for the degradation of trans-caffeic acid under both UV and visible illumination. The leaching process (in particular of zinc), which is produced with the illumination time (in particular under UV illumination) in the presence of oxygen, raises the hypothesis of a foreseeable formation of complexes (photochemically stable or unstable) of caffeic acid with Zn2+ and Bi3+ ions. The plausible donor/acceptor interactions between the toxic molecules studied and the Zn2+ and Bi3+ ions, could condition the degradation processes, by means of a photoassisted process that would take place both, in the heterogeneous (photocatalytic) and homogeneous (photoassisted) phases. For the degradation processes of Rhodamine B and Methyl Orange, additional experimental conditions are studied that significantly improved their photocatalytic degradation.


Abril, 2022 | DOI: 10.1016/j.apsusc.2021.152351

6.70
Química de Superficies y Catálisis

3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries

Gonzalez-Castano, M; Baena-Moreno, F; De Miguel, JCN; Miah, KUM; Arroyo-Torralvo, F; Ossenbrink, R; Odriozola, JA; Benzinger, W; Hensel, A; Wenka, A; Arellano-García, H
Energy Conversion and Management, 258 (2022) 115464

Show abstract ▽

This work investigates the CO2 methanation rate of structured catalysts by tuning the geometr y of 3D-printed metal Fluid Guiding Elements (FGEs) structures based on periodically variable pseudo-gyroid geometries. The enhanced performance showed by the structured catalytic systems is mostly associated with the capability of the FGEs substrate geometries for efficient heat usages. Thus, variations on the channels diameter resulted in ca. 25% greater CO2 conversions values at intermediate temperature ranges. The highest void fraction evidenced in the best performing catalyst (3D-1) favored the radial heat transfer and resulted in significantly enhanced catalytic activity, achieving close to equilibrium (75%) conversions at 400 ? and 120 mL/min. For the 3D-1 catalyst, a mathematical model based on an experimental design was developed thus enabling the estimation of its behavior as a function of temperature, spatial velocity, hydrogen to carbon dioxide (H-2/CO2) ratio, and inlet CO2 concentration. Its optimal operating conditions were established under 3 different scenarios: 1) no restrictions, 2) minimum H-2:CO2 ratios, and 3) minimum temperatures and H-2/CO2 ratio. For instance, for the lattest scenario, the best CO2 methanation conditions require operating at 431 ?, 200 mL/min, H-2/CO2 = 3 M ratio, and inlet CO2 concentration = 10 %.


Abril, 2022 | DOI: 10.1016/j.enconman.2022.115464

10.40
Fotocatálisis Heterogénea: Aplicaciones

Fast photodegradation of rhodamine B and caffeine using ZnO-hydroxyapatite composites under UV-light illumination

KarimTanji, J.A.Navio, Abdellah Chaqroune, Jamal Naja, F.Puga, M.C.Hidalgo, AbdelhakKherbeche
Catalysis Today, 388 (2022) 176-186

Show abstract ▽

Zinc oxide-hydroxyapatite composites were prepared using wet impregnation method. Firstly, a natural phosphate ore rich in silica and calcium phosphate was sieved to separate silica phase from phosphate phase. Then, through a chemical precipitation method, a pure hydroxyapatite (HAP) was obtained, which was used as a support for ZnO immobilization and applied for the photodegradation of two toxic contaminants: a transparent molecule (caffeine) and dye molecule (rhodamine B). During the present work two weight ratio percentages of zinc oxide were used: 25 wt.% and 50 wt.% of ZnO relative to HAP. The samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), X-ray Fluorescence (XRF), BET surface area (SBET), Scanning Electron Microscopy (SEM-EDS) and by Transmission Electron Microscopy (TEM-STEM). The immobilization of ZnO on HAP surface followed by thermal treatment at 400 °C for 2 h to get a homogenous dispersion of ZnO on the hydroxyapatite support. At high ZnO impregnation percentage, photodegradation performances of ZnO-HAP under UV illumination were fast and superior than the ZnO photocatalyst alone. The results showed that due to the presence of HAP, the conversion of both molecules became faster and greater, since it promotes the synergic phenomena of adsorption and photocatalysis. The toxicity of the treated substrate solutions obtained in the corn kernels germination test indicated a low toxicity after the photodegradation processes, probably due to a high mineralization degree.


Abril, 2022 | DOI: 10.1016/j.cattod.2020.07.044

5.30
Fotocatálisis Heterogénea: Aplicaciones

Insights into the physicochemical properties of Sugar Scum as a sustainable biosorbent derived from sugar refinery waste for efficient cationic dye removal

F. Atmani, M.M. Kaci, N. Yeddou-Mezenner, A. Soukeur, I. Akkari, J.A. Navío
Biomass Conversion and Biorefinery (2022)

Show abstract ▽

The objective of this study was to determine the ability of sugar scum (SS), an industrial waste, as a novel biosorbent for the removal of Basic Blue 41 (BB 41) from aqueous solutions. The biosorbent was characterized by SEM/EDS, BET, FTIR, and pHpzc measurements, respectively. To reach a maximum adsorption capacity of 26.45 mg.g–1, impacting operational factors such as pH, biosorbent dose, contact duration, starting dye concentration, and temperature were adjusted, when the removal efficiency reached 84% during 60 min at pH 10, 1.5 g.L–1 of biosorbent and Co = 10 mg.L–1. The experimental data were modeled by various isotherm models, whereas the best fit was found for Freundlich with a high correlation coefficient (R2 = 0.991). Other kinetic models including pseudo-first, pseudo-second order, and intra-particle diffusion models were tested to fit the kinetic data. The biosorption of BB 41 onto SS was spontaneous (∆G° < 0) and exothermic (∆H° < 0), while the biosoprtion mechanism of BB41 over SS was proposed with repeated reuse showing that SS could be regenerated after four successive runs. Furthermore, this study revealed that sugar scum is an underutilized bioresource in Algeria, with the potential to provide low-cost environmental removal of additional contaminants in the wastewater treatment domain.


Abril, 2022 | DOI: 10.1007/s13399-022-02646-3

4.00
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

H2 Photoproduction Efficiency: Implications of the Reaction Mechanism as a Function of the Methanol/Water Mixture

Barba-Nieto, I; Colon, G; Kubacka, A; Fernandez-Garcia, M
Catalysts, 12 (2022) 402

Show abstract ▽

The influence of the reaction pathway of the sacrificial molecule oxidation to generate hydrogen is here investigated for lean and rich methanol reaction mixtures. Pt-TiO2 powders promoted or not with tin sulfide were used as catalysts. With the help of in situ infrared experiments under reaction conditions, methanol evolution was shown to take place by hole-related oxidation steps, with alkoxy and carbon-centered species as key radical species. The study analyzed quantitatively the fate and chemical use of the photons absorbed by the solids with the help of the quantum efficiency and the useful fraction of photons observables. Within this framework, the role of the sulfide component to promote photoactivity is interpreted, braiding chemical and photonic information.


Abril, 2022 | DOI: 10.3390/catal12040402

3.90
Fotocatálisis Heterogénea: Aplicaciones

Z-scheme WO3/PANI heterojunctions with enhanced photocatalytic activity under visible light: A depth experimental and DFT studies

Y. Naciri; A.Hsini; A.Bouziani; K.Tanji; B.El Ibrahimi; M.N.Ghazza; B. Bakiz; A.Albourine; A.Benlhachemi; J.A. Navío
Chemosphere, 292 (2022) 133468

Show abstract ▽

A WO3@PANI heterojunction photocatalyst with a various mass ratio of polyaniline to WO3 was obtained via the in situ oxidative deposition polymerization of aniline monomer in the presence of WO3 powder. The characterization of WO3@PANI composites was carried via X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The photocatalytic efficiency of WO3@PANI photocatalysts was assessed by following the decomposition of the Rhodamine B (RhB) dye under visible light irradiation (λ >420 nm). The results evidenced the high efficiency of the WO3@PANI (0.5 wt %) nanocomposite in the photocatalytic degradation of RhB (90% within 120 min) under visible light irradiation 3.6 times compared to pure WO3. The synergistic effect between PANI and WO3 is the reason for the increased photogenerated carrier separation. The superior photocatalytic performance of the WO3@PANI catalyst was ascribed to the increased visible light in the visible range and the efficient charge carrier separation. Furthermore, the Density Functional Theory study (DFT) of WO3@PANI was performed at the molecular level, to find its internal nature for the tuning of photocatalytic efficiency. The DFT results indicated that the chemical bonds connected the solid-solid contact interfaces between WO3 and PANI. Finally, a plausible photocatalytic mechanism of WO3@PANI (0.5 wt %) performance under visible light illumination is suggested to guide additional photocatalytic activity development.


Abril, 2022 | DOI: 10.1016/j.chemosphere.2021.133468

8.80
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Research on properties and catalytic behaviour in CO hydrogenation at atmospheric and high pressure of bimetallic systems (10%Co+0.5%Pd)/TiO2 (Al2O3)

Shopska, M; Caballero, A; Platero, F; Todorova, S; Tenchev, K; Fabian, M; Aleksieva, K;Kolev, H; Kadinov, G
Reaction Kinetics Mechanisms and Catalysis, 135 (2022) 589-618

Show abstract ▽

The properties of prereduced (10%Co + 0.5%Pd)/Al2O3 (TiO2) systems in the CO hydrogenation reaction at atmospheric and high pressure were studied. At atmospheric pressure, alumina-supported catalysts were more selective toward methane but those using titania were more active. Alumina containing samples demonstrated high temperature H-2 desorption, firmly held surface carbonate species, high tendency to agglomeration. During the reaction metal surface reconstruction and increased formation of CH2 groups occurred being more pronounced with titania-supported catalysts. Stability tests at 250 degrees C showed opposite behaviour of both systems. Monodentate carbonate intermediates adsorbed on sites of moderate strength prevailed on titania samples, while formate species predominated on high strength sites of alumina-supported catalysts. High pressure catalytic tests revealed dependence of activity on T-red, synthesis of C2+ hydrocarbons, decreased CO2 production, a higher CH4/CO2 ratio for alumina containing system. Due to SMSI, increased CO2 production on titania samples was preserved. Titania-supported catalysts revealed a stronger decrease of CO conversion rising T-red while alumina catalysts had almost unchanged activity. CO conversion decreased with time due to difficulties in surface diffusion of reagents/intermediates/products and metal particle agglomeration. Concerning T-red comparison of product distribution showed a steady trend. Because of stable CO and CHx surface species, titania containing catalysts produced lower content of C5+ compounds. Alumina-supported samples showed a higher selectivity to C5+ compounds at the expense of methane. A higher selectivity ratio for CH4 and CO2 determined in catalytic CO hydrogenation over a certain catalyst at atmospheric pressure could indicate that a given sample is predisposed to form C2+ hydrocarbons at a higher pressure.


Marzo, 2022 | DOI: 10.1007/s11144-022-02194-x

1.80
Química de Superficies y Catálisis

Understanding the promotional effect of Pt/CeO2 in cobalt-catalyzed Fischer-Tropsch synthesis using operando infrared spectroscopy at moderated pressures

Bobadilla, LF; Egana, A; Castillo, R.; Romero-Sarria, F.; Centeno, M.A.; Sanz, O.; Montes, M.; Odriozola, J.A.
FUEL, 312 (2022) 122964

Show abstract ▽

Fischer-Tropsch (FTS) reaction is a well-known catalytic process for the conversion of synthesis gas into liquid fuels. The addition of a water gas shift (WGS) catalyst to the FTS one has been postulate to notably increase the efficiency of the process. In order to investigate this issue, we conducted the FTS reaction over a Co-Re/Al2O3 catalyst combined with an optimal WGS Pt/CeO2 catalyst. We observed a notable increase of CO conversion in presence of the Pt/CeO2 catalyst that a priori could be attributed to the WGS reaction. However, the WGS reaction is unfavourable at pressures higher than 1 bar and CO/CO2 hydrogenation over Pt/CeO2 could be more favoured under FTS reaction conditions. In order to gain insights on this fact and elucidate the role of Pt/CeO2 in the FTS reaction we have performed an operando DRIFTS-MS study under close FTS reaction conditions at 4 bar over the Pt/CeO2 catalyst.


Marzo, 2022 | DOI: 10.1016/j.fuel.2021.122964

7.40
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Preferential CO oxidation in hydrogen-rich gases over Ag catalysts supported on different supports

Todorova, S; Kolev, H; Karakirova, Y; Filkova, D; Grahovski, B; Aleksieva, K; Holgado, JP; Kadinov, G; Caballero, A
Reaction Kinetics Mechanisms and Catalysis, 135 (2022) 1405-1422

Show abstract ▽

The monometallic silver supported on SiO2, Al2O3, ZSM-5 (Si:Al = 100) and bi-metallic AgCe/SiO2 samples were studied in the reaction of the preferential CO oxidation. It was established that the supported silver catalysts are promising systems for selective oxidation of CO at low temperatures and the addition of cerium oxide increases the catalytic activity and selectivity most probably because of the increase in the silver dispersion; the homogeneous distribution of Ag and ceria on the silica support; formation of Ag-n(delta+) clusters; increase in bulk and subsurface oxygen.


Marzo, 2022 | DOI: 10.1007/s11144-022-02158-1

1.80
Química de Superficies y Catálisis

Analysis of Dry Reforming as direct route for gas phase CO2 conversion. The past, the present and future of catalytic DRM technologies

le Sache, E; Reina, TR
Progress in Energy and Combustion Science, 89 (2022) 100970

Show abstract ▽

Transition to low carbon societies requires advanced catalysis and reaction engineering to pursue green routes for fuels and chemicals production as well as CO2 conversion. This comprehensive review provides a fresh perspective on the dry reforming of methane reaction (DRM) which constitutes a straightforward approach for effective CO2 conversion to added value syngas. The bottleneck for the implementation of this process at industrial scale is the development of highly active and robust heterogeneous catalysts able to overcome the CO2 activation barrier and deliver sufficient amount of the upgrading products at the desired operation conditions. Also, its high energy demand due to the endothermic nature of the reaction imposes extra difficulties. This review critically discusses the recent progresses on catalysts design ranging from traditional metal-supported catalysts to advanced structured and nanostructured systems with promising performance. The main advantages and culprits of the different catalytic systems are introduced aiming to inspire the catalysis community to further refine these formulations towards the development of "supercatalysts" for DRM. Besides the design of increasingly complex catalyst morphologies as well as other promising alternatives aiming at reducing the energy consumption of the process or tackle deactivation through reactor design are introduced.


Marzo, 2022 | DOI: 10.1016/j.pecs.2021.100970

29.50
Fotocatálisis Heterogénea: Aplicaciones

Exploring the photocatalytic activities of a highly {0 0 1} faceted TiO2 sensitized by coupling with AgBr or Ag3PO4

F.Puga; J.A.Navío; M.A.Paulete-Romero; J.M.Córdoba; M.C.Hidalgo
Materials Science and Engineering: B, 276 (2022) 115555

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TiO2 with high {0 0 1} facet exposure was coupled with AgBr or Ag3PO4. Catalysts were widely characterized and tested with rhodamine B (RhB) or caffeic acid under UV and visible light. Combination of the used sensitizer (AgBr or Ag3PO4) with TiO2, not only enhances the high photocatalytic activity shown in the UV for TiO2, but it also largely increases the degradation activity under visible illumination. A synergistic effect toward photocatalytic degradation in the visible light was observed when coupling AgBr and TiO2, with the photocatalytic degradation profiles being strongly related to the molar percentages of the coupled materials and to the nature of the contaminant. The recycling of the coupled materials allows us to conclude that the AgBr(50%)/TiO2 sample presents better results in the consecutive reuse cycles and percentages of RhB dye mineralization, in contrast to those observed for the Ag3PO4(50%)/TiO2 composite.


Febrero, 2022 | DOI: 10.1016/j.mseb.2021.115555

3.60
Fotocatálisis Heterogénea: Aplicaciones

Visible light photodegradation of blue basic 41 using cobalt doped ZnO: Box–Behnken optimization and DFT calculation

K. Tanji; M. Zouheir; Y. Naciri; H. Ahmoum; A. Hsini; O. Mertah; A. El Gaidoumi; J.A. Navio; M.C. Hidalgo; A Kherbeche
Journal of the Iranian Chemical Society, 19 (2022) 2779-2794

Show abstract ▽

CoxZn1−xO system (0 ≤ x ≤ 0.2) was synthesized using the solution combustion method with urea as a fuel source. Photocatalytic tests were performed under visible light to assess the Basic Blue 41 (BB41) conversion. Various characterization techniques, including XRD, FT-IR analysis, SEM, EDS, XRF, BET-surface area, and DRS were used to investigate the composition, structure, and morphology of the synthesized catalysts. In addition, the density functional theory calculation was used in order to study the electronic properties of the ZnO structure. The Box–Behnken model was valid for describing the degradation of BB41 dye according to the analysis of variances results. A maximum conversion of 100% for BB41 dye has been reached with high mineralization and important removal of chemical oxygen demand. The optimum conditions for BB41 conversion are reported. On the other hand, the reuse tests of the best catalyst showed high-performance stability after five cycles. Furthermore, the activity of superoxide ions (O2·−) and hydroxyl radicals (OH.) as the spices responsible for BB41 dye conversion was well confirmed by the free radicals scavenging tests. The use of Box–Behnken optimization and DFT calculation applied to the synthesized catalysts proves to be a very suitable procedure to establish the operating conditions under which the synthesis strategy of the CoxZn1−xO catalyst in its activity in the visible region performs an excellent efficiency for the degradation of organic dyes and makes contributions to the current literature related to the field of environmental technology.


Enero, 2022 | DOI: 10.1007/s13738-022-02496-w

2.40
Química de Superficies y Catálisis

Enhanced catalytic activity and stability of nanoshaped Ni/CeO2 for CO2 methanation in micro-monoliths

Garcia-Moncada, N; Navarro, JC; Odriozola, JA; Lefferts, L; Faria, JA
Catalysis Today, 383 (2022) 205-215

Show abstract ▽

Coupling inherently fluctuating renewable feedstocks to highly exothermic catalytic processes, such as CO2 methanation, is a major challenge as large thermal swings occurring during ON- and OFF- cycles can irreversible deactivate the catalyst via metal sintering and pore collapsing. Here, we report a highly stable and active Ni catalyst supported on CeO2 nanorods that can outperform the commercial CeO2 (octahedral) counterpart during CO2 methanation at variable reaction conditions in both powdered and mu-monolith configurations. The long-term stability tests were carried out in the kinetic regime, at the temperature of maximal rate (300 degrees C) using fluctuating gas hourly space velocities that varied between 6 and 30 L h- 1.gcat- 1. Detailed catalyst characterization by mu-XRF revealed that similar Ni loadings were achieved on nanorods and octahedral CeO2 (c.a. 2.7 and 3.3 wt. %, respectively). Notably, XRD, SEM, and HR-TEM-EDX analysis indicated that on CeO2 nanorods smaller NiClusters with a narrow particle size distribution were obtained (- 7 +/- 4 nm) when compared to octahedral CeO2 (- 16 +/- 13 nm). The fast deactivation observed on Ni loaded on commercial CeO2 (octahedral) was prevented by structuring the reactor bed on mu-monoliths and supporting the Ni catalyst on CeO2 nanorods. FeCrAlloy (R) sheets were used to manufacture a multichannel mu-monolith of 2 cm in length and 1.58 cm in diameter, with a cell density of 2004 cpsi. Detailed catalyst testing revealed that powdered and structured Ni/ CeO2 nanorods achieved the highest reaction rates, c.a. 5.5 and 6.2 mmol CO2 min- 1.gNi - 1 at 30 L h- 1.gcat- 1 and 300 degrees C, respectively, with negligible deactivation even after 90 h of fluctuating operation.


Enero, 2022 | DOI: 10.1016/j.cattod.2021.02.014

5.30
Química de Superficies y Catálisis

Au and Pt Remain Unoxidized on a CeO2-Based Catalyst during the Water-Gas Shift Reaction

Reina, TR; Gonzalez-Castano, M; Lopez-Flores, V; Martinez, LMT; Zitolo, A; Ivanova, S; Xu, WQ; Centeno, MA; Rodriguez, JA; Odriozola, JA
Journal of the American Chemical Society, 144 (2022) 446-453

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The active forms of Au and Pt in CeO2-based catalysts for the water-gas shift (WGS) reaction are an issue that remains unclear, although it has been widely studied. On one hand, ionic species might be responsible for weakening the Ce-O bonds, thus increasing the oxygen mobility and WGS activity. On the other hand, the close contact of Au or Pt atoms with CeO2 oxygen vacancies at the metal-CeO2 interface might provide the active sites for an efficient reaction. In this work, using in situ X-ray absorption spectroscopy, we demonstrate that both Au and Pt remain unoxidized during the reaction. Remarkable differences involving the dynamics established by both species under WGS atmospheres were recognized. For the prereduced Pt catalyst, the increase of the conversion coincided with a restructuration of the Pt atoms into cuboctahedrical metallic particles without significant variations on the overall particle size. Contrary to the relatively static behavior of Pt-0, Au-0 nanoparticles exhibited a sequence of particle splitting and agglomeration while maintaining a zero oxidation state despite not being located in a metallic environment during the process. High WGS activity was obtained when Au atoms were surrounded by oxygen. The fact that Au preserves its unoxidized state indicates that the chemical interaction between Au and oxygen must be necessarily electrostatic and that such an electrostatic interaction is fundamental for a top performance in the WGS process.


Enero, 2022 | DOI: 10.1021/jacs.1c10481

15.00
Química de Superficies y Catálisis

Structured and micro-structured catalysts: A fascinating future for a sustainable world – A special issue in tribute to the careers of Professors Mario Montes and José Antonio Odriozola

M.A.Centeno; L.M.Gandía; F.Romero-Sarria; O.Sanz
Catalysis Today, 383 (2022) 1-4

Show abstract ▽

5.30
Química de Superficies y Catálisis

Performance of AISI 316L-stainless steel foams towards the formation of graphene related nanomaterials by catalytic decomposition of methane at high temperature

Cazana, F; Latorre, N; Tarifa, P; Royo, CJ; Sebastian, V; Romeo, E; Centeno, MA; Monzon, A
Catalysis Today, 383 (2022) 236-246

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This work explores the preparation of graphene-related materials (GRMs) grown on stainless steel foams via catalytic decomposition of methane (CDM). The main active phases for the reaction are the Fe nanoparticles segregated from the stainless-steel after the activation stage of the foam. The effect of the feed composition and reaction temperature has been studied in order to maximize the productivity, stability and selectivity to GRMs. The maximum productivity attained was 0.116 g(C)/g(foam) h operating at 950 degrees C with a feed ratio of CH4/H-2 = 3 (42.9 %CH4:14.3 %H-2). The carbonaceous nanomaterials (CNMs) obtained were characterized by X-Ray diffraction, Raman spectroscopy and by transmission and scanning electron microscopy. The parameters of the kinetic model developed are directly related to the relevant stages of the process, including carburization, diffusion-precipitation and deactivation-regeneration. The balance among these sequential stages determines the overall performance of the activated foam. In conditions of rapid carburization of the Fe NPs (p(CH4) > 14 %), the productivity to CNMs is favoured, avoiding an initial deactivation of the active sites by fouling with amorphous carbon. After a rapid carburization, the selectivity to the different CNMs is governed by the ratio CH4/H-2, and mainly by the temperature. Thus, the formation of GRMs, mainly Few Layer Graphene (FLG) and even graphene, is favoured at temperatures above 900 degrees C. At lower temperatures, carbon nanotubes are formed.


Enero, 2022 | DOI: 10.1016/j.cattod.2020.12.003

5.30
Química de Superficies y Catálisis

Boosting water activation determining-step in WGS reaction on structured catalyst by Mo-doping

Garcia-Moncada, N; Jurado, L; Martinez-Tejada, LM; Romero-Sarria, F; Odriozola, JA
Catalysis Today, 383 (2022) 193-204

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Proton conductors Mo-Eu-Zr mixed oxide systems were synthesized and further mixed with a conventional Pt/CeO2/Al2O3 catalyst to develop a highly efficient water-gas-shift (WGS) catalyst. The designed catalyst, once structured, allows reach the equilibrium conversion at medium temperatures (similar to 350 degrees C) at 80 L.g(-1) h(-1) space velocity. The ability of the proton conductor to maintain an elevated water concentration at the metal-support interface by Grotthuss' mechanism boosts the catalytic activity in WGS reaction.

The Mo-containing proton conductor is extensively characterized allowing to establish the formation of molybdenum oxide phases nucleating on top of the Eu sites in Eu-Zr oxide solid solution. [MoO4](2-) to [Mo7O24](6-) clusters nucleates at low Mo contents resulting in a alpha-MoO3 layer on increasing its content. In presence of H-2, Mobronzes are formed from similar to 200 degrees C enhancing water concentration at the surfaces and boosting the catalytic activity in the WGS reaction. These results pave the way for developing lower volume WGS reactors.


Enero, 2022 | DOI: 10.1016/j.cattod.2020.06.003

5.30
Química de Superficies y Catálisis

Unravelling the role of Fe in trimetallic Fe-Cu-Pt/Al2O3 catalysts for CO-PROX reaction

Palma, S; Gonzalez-Castano, M; Romero-Sarria, F; Odriozola, JA
Molecular Catalysis, 517 (2022) 112015

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This work proposes a trimetallic Fe-Cu/Pt/Al2O3 catalyst as an appealing system for preferential oxidation of CO (CO-PROX) reaction. The excellent conversion rates achieved by the Fe-Cu/Pt/Al2O3 catalysts under realistic reforming-surrogated feed streams along with the catalyst stability, reproducibility, and scalability showcase a very competitive system for CO-PROX reaction units. Furthermore, the systematic analysis conducted for Pt/Al2O3, Cu/Pt Al2O3, and Fe-Cu/Pt/Al2O3 catalysts enabled establishing meaningful relationships between catalytic behaviour and the catalyst surface to reactants interactions. Thus, the enhanced CO oxidation performances attained by the incorporation of Fe species into bimetallic Cu/Pt/Al2O3 catalysts were associated to superior surface electron densities and inhibited CO adsorption process over Pt surfaces. Remarkably, operando-DRIFTS spectroscopy evidenced significantly larger H-containing surface species developed over the trimetallic system. The enhanced abilities for developing thermally instable intermediates favoured by small amounts of Fe should indeed determine the enhanced catalysts behaviours displayed by the trimetallic Fe-Cu/Pt/Al2O3 catalyst.


Enero, 2022 | DOI: 10.1016/j.mcat.2021.112015

4.60
Química de Superficies y Catálisis

Metal micromonoliths for the cleaning of H-2 by means of methanation reactions

Laguna, OH; Munoz-Murillo, A; Bobadilla, LF; Martinez, LM; Montes, M; Centeno, MA; Odriozola, JA
Catalysis Today, 383 (2022) 216-225

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The present manuscript presents for the first time the structuring of a Ru/TiO2 catalyst that was achieved by means of the washcoating procedure using homemade metal micromonoliths (Fecralloy (R)) of 1330 cpsi. For this, an optimized formulation of the slurried catalyst as well as a reproducible protocol for the coating of the micromonoliths were successfully achieved. The obtained structured systems were tested in the selective CO methanation reaction and the effect of different variables over the catalytic performance were analyzed such as the amount of loaded catalyst in the micromonoliths, the temperature of reaction, the space velocity, and the amount of CO and H-2 within the feed-stream. The study of all of these parameters allowed to establish optimal conditions to maximize the performance of the structured Ru/TiO2 catalyst and subsequently, this was tested under those cited conditions in long-term tests (similar to 375 h), including shut-down/start-up cycles, aiming to evaluate its catalytic stability. The system presented a considerable stability along the different test without loss of catalytic activity, being specially remarkable its resistance to the inclusion of shut-down/start-up cycles. Therefore, this study lays the foundations for future development of more sophisticated structured systems for the selective CO methanation based on the structuring strategy proposed.


Enero, 2022 | DOI: 10.1016/j.cattod.2021.04.026

5.30



2021


Química de Superficies y Catálisis

In Situ DRIFTS-MS Methanol Adsorption Study onto Supported NiSn Nanoparticles: Mechanistic Implications in Methanol Steam Reforming

Bobadilla, LF; Azancot, L; Ivanova, S; Delgado, JJ; Romero-Sarria, F; Centeno, MA; Roger, AC
Nanomaterials, 11 (2021) 3234

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Methanol adsorption over both supported NiSn Nps and analogous NiSn catalyst prepared by impregnation was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to gain insights into the basis of hydrogen production from methanol steam reforming. Different intermediate species such as methoxides with different geometry (bridge and monodentate) and formate species were identified after methanol adsorption and thermal desorption. It is proposed that these species are the most involved in the methanol steam reforming reaction and the major presence of metal-support interface sites in supported NiSn Nps leads to higher production of hydrogen. On the basis of these results, a plausible reaction mechanism was elucidated through the correlation between the thermal stability of these species and the evolution of the effluent gas released. In addition, it was demonstrated that DME is a secondary product generated by condensation of methoxides over the acid sites of alumina support in an acid-catalyzed reaction.


Diciembre, 2021 | DOI: 10.3390/nano11123234

5.72
Fotocatálisis Heterogénea: Aplicaciones

LaFeO3 Modified with Ni for Hydrogen Evolution Via Photocatalytic Glucose Reforming in Liquid Phase

G. Iervolino; V. Vaiano; D. Sannino; F. Puga; J.A. Navío; M.C. Hidalgo
Catalysts, 11 (2021) 1558

Show abstract ▽

In this work, the optimization of Ni amount on LaFeO3 photocatalyst was studied in the photocatalytic molecular hydrogen production from glucose aqueous solution under UV light irradiation. LaFeO3 was synthesized via solution combustion synthesis and different amount of Ni were dispersed on LaFeO3 surface through deposition method in aqueous solution and using NaBH4 as reducing agent. The prepared samples were characterized with different techniques: Raman spectroscopy, UltraViolet-Visible Diffuse Reflectance Spettroscopy (UV–Vis-DRS), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), X-ray Fluorescence (XRF), Transmission Electron microscopy (TEM), and Scanning Electron microscopy (SEM) analyses. For all the investigated photocatalysts, the presence of Ni on perovskite surface resulted in a better activity compared to pure LaFeO3. In particular, it is possible to identify an optimal amount of Ni for which it is possible to obtain the best hydrogen production. Specifically, the results showed that the optimal Ni amount was equal to nominal 0.12 wt% (0.12Ni/LaFeO3), for which the photocatalytic H2 production was equal to 2574 μmol/L after 4 h of UV irradiation. The influence of different of photocatalyst dosage and initial glucose concentration was also evaluated. The results of the optimization of operating parameters indicated that the highest molecular hydrogen production was achieved on 0.12Ni/LaFeO3 sample with 1.5 g/L of catalyst dosage and 1000 ppm initial glucose concentration. To determine the reactive species that play the most significant role in the photocatalytic hydrogen production, photocatalytic tests in the presence of different radical scavengers were performed. The results showed that •OH radical plays a significant role in the photocatalytic conversion of glucose in H2. Moreover, photocatalytic tests carried out with D2O instead of H2O evidenced the role of water molecules in the photocatalytic production of molecular hydrogen in glucose aqueous solution.


Diciembre, 2021 | DOI: 10.3390/catal11121558

4.50
Química de Superficies y Catálisis

K-Promoted Ni-Based Catalysts for Gas-Phase CO2 Conversion: Catalysts Design and Process Modelling Validation

Gandara-Loe, J; Portillo, E; Odriozola, JA; Reina, TR; Pastor-Perez, L
Frontiers in Chemistry, 9 (2021) 785571

Show abstract ▽

The exponential growth of greenhouse gas emissions and their associated climate change problems have motivated the development of strategies to reduce CO2 levels via CO2 capture and conversion. Reverse water gas shift (RWGS) reaction has been targeted as a promising pathway to convert CO2 into syngas which is the primary reactive in several reactions to obtain high-value chemicals. Among the different catalysts reported for RWGS, the nickel-based catalyst has been proposed as an alternative to the expensive noble metal catalyst. However, Ni-based catalysts tend to be less active in RWGS reaction conditions due to preference to CO2 methanation reaction and to the sintering and coke formation. Due to this, the aim of this work is to study the effect of the potassium (K) in Ni/CeO2 catalyst seeking the optimal catalyst for low-temperature RWGS reaction. We synthesised Ni-based catalyst with different amounts of K:Ni ratio (0.5:10, 1:10, and 2:10) and fully characterised using different physicochemical techniques where was observed the modification on the surface characteristics as a function of the amount of K. Furthermore, it was observed an improvement in the CO selectivity at a lower temperature as a result of the K-Ni-support interactions but also a decrease on the CO2 conversion. The 1K catalyst presented the best compromise between CO2 conversion, suppression of CO2 methanation and enhancing CO selectivity. Finally, the experimental results were contrasted with the trends obtained from the thermodynamics process modelling observing that the result follows in good agreement with the modelling trends giving evidence of the promising behaviour of the designed catalysts in CO2 high-scale units.


Noviembre, 2021 | DOI: 10.3389/fchem.2021.785571

5.55
Química de Superficies y Catálisis

Assessing the impact of textural properties in Ni-Fe catalysts for CO2 methanation performance

Gonzalez-Castano, M; de Miguel, JCN; Boelte, JH; Centeno, MA; Klepel, O; Arellano-Garcia, H
Microporous and Mesoporous Materials, 327 (2021) 111405

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In heterogeneous catalysis, the benefits of employing adequate textural properties on the catalytic performances are usually stated. Nevertheless, the quantification of the extent of improvement is not an easy task since variations on the catalysts' specific areas and pore structures might involve modifications on a number of other surface catalytic features. This study establishes the impact of the catalyst textural properties on the CO2 methanation performance by investigating bimetallic Ni–Fe catalysts supported over carbon supports with different textural properties regarding surface area and pore structure. The comparable metal loading and dispersions attained for all systems enabled establishing forthright relationships between the catalyst textural properties and CO2 methanation rate. Once the influence of the external mass diffusions on the catalysts’ performance was experimentally discarded, the estimated Thiele modulus and internal effectiveness (φ and ηEff) values showed that the catalyst performance was majorly governed by the surface reaction rate whilst the pore size affected in no significant manner within the examined range (Dpore = 10.2 to 5.8 nm). Therefore, the rapport between the catalyst performance and surface area was quantified for the CO2 methanation reaction over Ni–Fe catalysts: increasing the surface area from 572 to 802 m2/g permit obtaining ca. 10% higher CO2 conversions.


Noviembre, 2021 | DOI: 10.1016/j.micromeso.2021.111405

5.88
Fotocatálisis Heterogénea: Aplicaciones

Polyaniline coated tungsten trioxide as an effective adsorbent for the removal of orange G dye from aqueous media

Hsini, A.; Naciri, Y.; Bouziani, A.; Aarab, N.; Essekri, A; Imgharn, A.; Laabd. M.; Navío, J.A.;Puga, F.; Lakhmirid, R.; Albourine, A.
RSC Advances, 11 (2021) 31272-31283

Show abstract ▽

In this work, the core–shell PANI@WO3 composite was obtained from the reaction of aniline monomer polymerization with WO3 particles; sodium persulfate was used as an oxidant. Various analytical techniques such as scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-prepared PANI@WO3 adsorbent, which well confirmed that the WO3 particles were coated by polyaniline polymer. The PANI@WO3 composite was tested as an adsorbent to remove reactive orange G (OG) for the first time. pH, adsorbent dose, contact time, initial dye concentration, and temperature were systematically investigated in order to study their effect on the adsorption process. The experimental findings showed that the PANI@WO3 composite has considerable potential to remove an aqueous OG dye. Langmuir and Freundlich's models were used to analyze the equilibrium isotherms of OG dye adsorption on the PANI@WO3 composite. As a result, the best correlation of the experimental data was provided by the Langmuir model, and the maximum capacity of adsorption was 226.50 mg g−1. From a thermodynamic point of view, the OG dye adsorption process occurred spontaneously and endothermically. Importantly, PANI@WO3 still exhibited an excellent adsorption capability after four regeneration cycles, indicating the potential reusability of the PANI@WO3 composite. These results indicate that the as prepared PANI@WO3 composite could be employed as an efficient adsorbent and was much better than the parent material adsorption of OG dye.


Noviembre, 2021 | DOI: 10.1039/D1RA04135E

4.04
Química de Superficies y Catálisis

Recent Advances in the Bronsted/Lewis Acid Catalyzed Conversion of Glucose to HMF and Lactic Acid: Pathways toward Bio-Based Plastics

Megias-Sayago, C; Navarro-Jaen, S; Drault, F; Ivanova, S
Catalysts, 11 (2021) 1395

Show abstract ▽

One of the most trending topics in catalysis recently is the use of renewable sources and/or non-waste technologies to generate products with high added value. That is why, the present review resumes the advances in catalyst design for biomass chemical valorization. The variety of involved reactions and functionality of obtained molecules requires the use of multifunctional catalyst able to increase the efficiency and selectivity of the selected process. The use of glucose as platform molecule is proposed here and its use as starting point for biobased plastics production is revised with special attention paid to the proposed tandem Bronsted/Lewis acid catalysts.


Noviembre, 2021 | DOI: 10.3390/catal11111395

4.50
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic Treatment of Stained Wastewater Coming from Handicraft Factories. A Case Study at the Pilot Plant Level

Murcia Mesa, JJ; Hernández Niño, JS; González, W; Rojas, H; Hidalgo, MC; Navío, JA
Water, 13 (2021) 2705

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UV/H2O2 process and TiO2-based photocatalysis were studied in the present work. The effectiveness of these methods was tested in the treatment of effluents taken from handicraft factories. Microorganisms, dyes, and different organic pollutants were detected in the industrial effluents. The experimental procedure for the wastewater treatment was carried out in a patented sunlight reactor on a pilot plant scale. From this study, UV/H2O2 was found to be the best treatment for dye elimination. The optimal peroxide dosage for the degradation of dyes and the elimination of bacteria was 0.07 M. In this case, 70.80% of discoloration was achieved after 7 h of sunlight exposure, under an average sunlight intensity of 3.42 W/m2. The photocatalytic treatment based on TiO2 achieved the highest elimination of coliform bacteria and the lowest TOC value; however, the presence of this material in the reactor had a detrimental effect on the overall elimination of dyes. A combination of both UV/H2O2 and TiO2 treatments significantly improves the dyes discoloration, the elimination of bacteria, and the organic compounds degradation. Some of the results of this study were presented at the 4th Congreso Colombiano de Procesos Avanzados de Oxidación, 4CCPAOx. 


Octubre, 2021 | DOI: 10.3390/w13192705

3.53
Fotocatálisis Heterogénea: Aplicaciones

Development of a novel PANI@WO3 hybrid composite and its application as a promising adsorbent for Cr(VI) ions removal

Abdelghani Hsinia, Yassine Naciri, Mohamed Laabd, Asmae Bouziani, J.A.Navío, F.Puga, Rabah Boukherroub, Rajae Lakhmiri, Abdallah Albourine
Journal of Environmental Chemical Engineering, 9 (2021) 105885

Show abstract ▽

In the current study, an in-situ oxidative polymerization method was used to synthesize polyaniline-coated tungsten trioxide biphasic composite (PANI@WO3). The as-developed composite material properties were elucidated using different characterization tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), N2 sorption-desorption isotherm, and X-ray photoelectron spectroscopy (XPS). The PANI@WO3 was further applied to remove hexavalent chromium (Cr(VI)) from aqueous solutions. The results demonstrated that the optimal removal efficacy was achieved at pH 2. Meanwhile, the pseudo-second-order kinetic and isotherm of the Langmuir model were fitted for Cr(VI) adsorption. Cr(VI) amount of 549.37 mg·g−1 was the maximum capacity of adsorption attained for PANI@WO3, which is significantly higher than that of existing adsorbents. From a thermodynamic point of view, the Cr(VI) adsorption process occurred spontaneously and endothermically. Importantly, PANI@WO3 still exhibited an excellent adsorption capability after five regeneration cycles, indicating the potential reusability of the PANI@WO3 composite. XPS analysis of PANI@WO3 surface after adsorption of Cr(VI) confirmed its adsorption and concomitant reduction into Cr(III) ions. The transfer of mass phenomenon, electrostatic attraction, and reduction reaction were the primary processes for Cr(VI) ions elimination. These findings revealed that the synthesized PANI@WO3 exhibited a high potential for wastewater treatment containing Cr(VI).


Octubre, 2021 | DOI: 10.1016/j.jece.2021.105885

7.97
Química de Superficies y Catálisis

Effect of potassium loading on basic properties of Ni/MgAl2O4 catalyst for CO2 reforming of methane

Azancot, L; Bobadilla, LF; Centeno, MA; Odriozola, JA
Journal of CO2 Utilization, 52 (2021) 101681

Show abstract ▽

Coke deposition is one of the key issues in the dry reforming of methane on Ni catalysts. In the present work, we investigate the effect of potassium addition for suppressing carbon deposition in the Dry Reforming of Methane. The results obtained demonstrated that potassium contents above 3 wt% promote carbon gasification, favouring both Reverse Water Gas Shift and Boudouard reaction. Strong basic Mg-O-K sites are responsible for these reactions allowing the suppression of carbon deposits and allowing the stability of the catalyst.


Octubre, 2021 | DOI: 10.1016/j.jcou.2021.101681

8.32
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic production of hydrogen and methane from glycerol reforming over Pt/TiO2–Nb2O5

Iervolino, G; Vaiano, V; Murcia, JJ; Lara, AE; Hernández, JS; Rojas, H; Navío, JA; Hidalgo, MC
International Journal of Hydrogen Energy

Show abstract ▽

In this study, platinized mixed oxides (TiO2–Nb2O5) were tested on photocatalytic hydrogen production from a glycerol solution under UV light. Different samples with different Ti:Nb ratios were prepared by using a simple method that simultaneously combined a physical mixture and a platinum photochemical reduction. This method led to improved physicochemical properties such as low band gap, better Pt nanoparticle distribution on the surface, and the formation of different Pt species. Niobia content was also found to be an important factor in determining the overall efficiency of the Pt–TiO2–Nb2O5 photocatalyst in the glycerol reforming reaction. The photocatalytic results showed that Pt on TiO2–Nb2O5 enhanced hydrogen production from the aqueous glycerol solution at a 5 wt% initial glycerol concentration. The influence of different operating conditions such as the catalyst dosage and initial glycerol concentration was also evaluated. The results indicated that the best hydrogen and methane production was equal to 6657 μmol/L and 194 μmol/L, respectively after 4 h of UV radiation using Pt/Ti:Nb (1:2) sample and with 3 g/L of catalyst dosage. Moreover, the role of water in photocatalytic hydrogen production was studied through photocatalytic activity tests in the presence of D2O. The obtained results confirmed the role of water molecules on the photocatalytic production of hydrogen in an aqueous glycerol solution.


Septiembre, 2021 | DOI: 10.1016/j.ijhydene.2021.09.111

7.14
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Examination of the Deactivation Cycle of NiAl- and NiMgAl-Hydrotalcite Derived Catalysts in the Dry Reforming of Methane

Abdelsadek, Z.; Holgado, J.P.; Halliche, D.; Caballero, A.; Cherifi, O.; Gonzalez-Cortes, S.; Masset, P.J.
Catalysis Letters, 151 (2021) 2696-2715

Show abstract ▽

The importance of the dry reforming of methane (DRM) lies in its capability to upgrade two greenhouse gases (CH4 and CO2) into synthesis gas (CO and H-2), which is one of the main building block for synthesizing hydrocarbons. However, the Ni-based catalysts for DRM reaction usually have a major catalytic stability drawback. This works aims to assess the catalytic activity and stability of two Ni-based catalysts obtained from hydrotalcite (HT) precursors (i.e., NiAl-HT and NiMgAl-HT). The precursors, calcined (-c), reduced (-R) and spent samples were characterized by a series of techniques to gain insight into the influence of MgO over Ni-based catalyst in the drying reforming of methane. An in-situ ageing cycle process to speed up the deactivation of hydrotalcite-derived catalysts showed that the NiMgAl-HTc-R catalyst displayed a higher activity and resistance to coke formation (stability) than NiAl-HTc-R because of the introduction of Mg into hydrotalcite structure in the catalyst precursor. The presence of this element enhances several factors involved in the stability of Ni-based catalysts for the DRM process such as the reducibility and textural features of the catalysts, size and dispersion of Ni-0 nanoparticles and also maintains a good compromise between the acid and base properties of the solid catalysts.


Septiembre, 2021 | DOI: 10.1007/s10562-020-03513-4

2.94
Química de Superficies y Catálisis

Mesoporous Carbon Production by Nanocasting Technique Using Boehmite as a Template

Ortega-Franqueza, M; Ivanova, S; Dominguez, MI; Centeno, MA
Catalysts, 11 (2021) 1132

Show abstract ▽

A series of mesoporous carbonaceous materials were synthesized by the nanocasting technique using boehmite as a template and glucose as a carbon precursor. After pyrolysis and template removal, the resulting material is a mesoporous carbon that can be additionally doped with N, B and K during prepyrolysis impregnation. In addition, the influence of doping on the morphology, crystallinity and stability of the synthesized carbons was studied using X-ray diffraction, nitrogen physisorption, thermogravimetry, Raman and IR spectroscopy and transmission electron microscopy. While the nanocasting process is effective for the formation of mesopores, KOH and urea do not modify the textural properties of carbon. The use of H3PO4 as a dopant, however, led to the formation of an AlPO4 compound and resulted in a solid with a lower specific surface area and higher microporosity. All doped solids present higher thermal stability as a positive effect of the introduction of heteroatoms to the carbon skeleton. The phosphorus-doped sample has better oxidation resistance, with a combustion temperature 120-150 degrees C higher than those observed for the other materials.


Septiembre, 2021 | DOI: 10.3390/catal11091132

4.50
Química de Superficies y Catálisis

Structure-sensitivity of formic acid dehydrogenation reaction over additive-free Pd NPs supported on activated carbon

Santos, J.L.; Megías-Sayago, C.; Ivanova, S.; Centeno, M.A.; Odriozola, J.A.
Chemical Engineering Journal, 420 (2021) 127641

Show abstract ▽

In this study the size-activity dependence of palladium based catalysts in formic acid dehydrogenation reaction was investigated and evaluated. A wide range of particle sizes was considered and the catalyst series were prepared upon variation of some synthetic parameters, precursor and solvent nature in particular. Synthesis method variations affect significantly Pd particle size and results in diverse activity toward hydrogen production. An optimal size was observed and explained by the diverse proportion of low and high coordinated Pd states available for different samples within the series. The evaluation of particles much bigger than 6 nm changes importantly the fraction of high and low coordination atoms and allows the clear confirmation of the importance of the presence of low coordination atoms on the surface of catalyst.


Septiembre, 2021 | DOI: 10.1016/j.cej.2020.127641

16.74
Fotocatálisis Heterogénea: Aplicaciones

ZnO/Ag3PO4 and ZnO–Malachite as Effective Photocatalysts for the Removal of Enteropathogenic Bacteria, Dyestuffs, and Heavy Metals from Municipal and Industrial Wastewater

Murcia, JJ; Hernández Miño, JS; Rojas, H; Brijaldo, MH; Martin-Gómez, AN; Sánchez-Cid, P; Navío, JA; Hidalgo, MC; Jaramillo-Pérez, C
Water, 13 (2021) 2264

Show abstract ▽

Different composites based on ZnO/Ag3PO4 and ZnO–malachite (Cu2(OH)2CO3) were synthesized in order to determine their effectiveness in the treatment of municipal and industrial wastewaters (mainly polluted by enteropathogenic bacteria, dyes, and heavy metals). The addition of Ag3PO4 and malachite did not significantly modify the physicochemical properties of ZnO; however, the optical properties of this oxide were modified as a result of its coupling with the modifiers. The modification of ZnO led to an improvement in its effectiveness in the treatment of municipal and industrial wastewater. In general, the amount of malachite or silver phosphate and the effluent to be treated were the determining factors in the effectiveness of the wastewater treatment. The highest degree of elimination of bacteria from municipal wastewater and discoloration of textile staining wastewater were achieved by using ZnO/Ag3PO4 (5%), but an increase in the phosphate content had a detrimental effect on the treatment. Likewise, the highest Fe and Cu photoreduction from coal mining wastewater was observed by using ZnO–malachite (2.5%) and ZnO/Ag3PO4 (10%), respectively. Some of the results of this work were presented at the fourth Congreso Colombiano de Procesos Avanzados de Oxidación (4CCPAOx).


Agosto, 2021 | DOI: 10.3390/w13162264

3.53
Química de Superficies y Catálisis

Bimetallic Ni-Ru and Ni-Re Catalysts for Dry Reforming of Methane: Understanding the Synergies of the Selected Promoters

Moreno, AA; Ramirez-Reina, T; Ivanova, S; Roger, AC; Centeno, MA; Odriozola, JA
Frontiers in Chemistry, 9 (2021) 694976

Show abstract ▽

Designing an economically viable catalyst that maintains high catalytic activity and stability is the key to unlock dry reforming of methane (DRM) as a primary strategy for biogas valorization. Ni/Al2O3 catalysts have been widely used for this purpose; however, several modifications have been reported in the last years in order to prevent coke deposition and deactivation of the samples. Modification of the acidity of the support and the addition of noble metal promoters are between the most reported strategies. Nevertheless, in the task of designing an active and stable catalyst for DRM, the selection of an appropriate noble metal promoter is turning more challenging owing to the lack of homogeneity of the different studies. Therefore, this research aims to compare Ru (0.50 and 2.0%) and Re (0.50 and 2.0%) as noble metal promoters for a Ni/MgAl2O4 catalyst under the same synthesis and reaction conditions. Catalysts were characterized by XRF, BET, XRD, TPR, hydrogen chemisorption (H2-TPD), and dry reforming reaction tests. Results show that both promoters increase Ni reducibility and dispersion. However, Ru seems a better promoter for DRM since 0.50% of Ru increases the catalytic activity in 10% and leads to less coke deposition.


Julio, 2021 | DOI: 10.3389/fchem.2021.694976

5.55
Química de Superficies y Catálisis

How a small modification in the imidazolium-based SDA can determine the zeolite structure? MFI vs. TON

Megias-Sayago, C; Blanes, JMM; Szyja, BM; Odriozola, JA; Ivanova, S
Microporous and Mesoporous Materials, 322 (2021) 111160

Show abstract ▽

The present study proposes an important contribution to the understanding of ionic liquid role as structure directing agent for zeolite synthesis. A series of imidazolium based ionic liquids are used for this purpose. While the anionic counterpart influences the micellar organization during the synthesis, the imidazolium cation clearly directs the structure to one or another zeolite family as a function of its substituents and their interaction with the zeolite framework. The experimental observations are contrasted with molecular modeling explaining the distinct zeolite families obtained on the basis of different preferential orientation of the ionic liquids to the Si33 precursor.


Julio, 2021 | DOI: 10.1016/j.micromeso.2021.111160

5.88
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Mechanistic Considerations on the H-2 Production by Methanol Thermal-assisted Photocatalytic Reforming over Cu/TiO2 Catalyst

Platero, F; Lopez-Martin, A; Caballero, A; Colon, G
CHEMCATCHEM, 13 (2021) 3878-3888

Show abstract ▽

We have studied the gas phase H-2 production by methanol thermo-photoreforming using Cu-modified TiO2. Metal co-catalyst has been deposited by means of photodeposition method. The concentration of methanol in the steam was also considered. It appears that H-2 production is notably higher as temperature increases. Moreover, the optimum H-2 yield is achieved using methanol concentration of 10 % v/v. CO and CO2 were monitored as side products of the overall reaction. It has been stated that CO evolution is significant at lower temperatures. As temperature increases, CO evolution is hindered and H-2 appeared boosted. We have demonstrated that other reactions such water-gas-shift or formate dehydration would participate in the overall process. On this basis, optimal operational condition for H-2 production is attained for thermo-photocatalytic reforming of methanol solution 10 % v/v at 200 degrees C.


Julio, 2021 | DOI: 10.1002/cctc.202100680

5.50
Química de Superficies y Catálisis

Current scenario and prospects in manufacture strategies for glass, quartz, polymers and metallic microreactors: A comprehensive review

Dominguez, MI; Centeno, MA; Martinez, TM; Bobadilla, LF; Laguna, OH; Odriozola, JA
Chemical Engineering Research & Design, 171 (2021) 13-35

Show abstract ▽

One of the most remarkable benefits of the microreactors is the achievement of more efficient processes by enhancing the heat and mass transfer phenomena, which is the key factor for processes intensification in chemical reactions, resulting in higher conversion, selectivity and yield towards desired products. Currently, the entire scenario of microreaction approach is an emergent technology and further advances are ongoing. Several strategies have been successfully applied for structuring processes that imply the fixation of the catalysts on the microreactors. However, there are features such as the physicochemical stability of the coatings under reaction conditions that must be improved, motivating the search for new protocols. This review provides a general overview of the most important methodologies applied for glass, quartz, polymers and metals microreactors manufacture and for their coating, analyzing the advantages and drawbacks of every procedure. Furthermore, an outline of the novel insights based on additive manufacturing techniques are described.


Julio, 2021 | DOI: 10.1016/j.cherd.2021.05.001

4.12
Química de Superficies y Catálisis

In-situ HDO of guaiacol over nitrogen-doped activated carbon supported nickel nanoparticles

Jin, Wei; Pastor-Perez, Laura; Villora-Pico, Juan J.; Mercedes Pastor-Blas, M.; Odriozola, Jose A.; Sepulveda-Escribano, Antonio; Ramirez Reina, Tomas
Applied Catalysis A-General, 620 (2021) 118033

Show abstract ▽

In-situ hydrodeoxygenation of guaiacol over Ni-based nitrogen-doped activated carbon supported catalysts is presented in this paper as an economically viable route for bio-resources upgrading. The overriding concept of this paper is to use water as hydrogen donor for the HDO reaction, suppressing the input of external highpressure hydrogen. The effect of nitrogen sources, including polypyrrole (PPy), polyaniline (PANI) and melamine (Mel) on the structural, electronic and ultimately of catalytic features of the designed materials have been addressed. Nitrogen-doped samples are more active than the undoped counterparts in the "H2-free" HDO process. For instance, the conversion of guaiacol increased by 8 % for Ni/PANI-AC compared to that of Ni/AC catalysts. The superior performance of Ni/NC can be attributed to the acid-base properties and modified electronic properties, which favours the C-O cleavage and water activation as well as enhances dispersion of Ni particles on the catalysts' surface.


Junio, 2021 | DOI: 10.1016/j.apcata.2021.118033

5.72
Fotocatálisis Heterogénea: Aplicaciones

Features of coupled AgBr/WO3 materials as potential photocatalysts

Puga, F.; Navío, J.A.; Hidalgo, M.C.
Journal of Alloys and Compounds, 867 (2021) 159191

Show abstract ▽

AgBr/WO3 composite photocatalysts with different selected molar AgBr/WO3 ratios were prepared and widely characterized by XRD, N2-adsorption, SEM, TEM, UV–visible/DRS and XPS techniques. The samples were tested using rhodamine B (RhB) or caffeine, under two illumination conditions (UV and visible light). Although AgBr and WO3 pristine materials have relatively low band gap values (2.6 eV and 2.8 eV, respectively), they exhibit low or no photocatalytic activity under visible light, at least for caffeine degradation. This fact may be mainly related to a high recombination rate of photogenerated charge carriers in these samples. However, the coupling of both leads to a substantial improvement in the degradation of caffeine and RhB under both UV and visible lighting conditions. The increased photocatalytic activity found in the coupled systems with respect to the pristine materials can be attributed to the formation of a type II heterostructure in the coupled AgBr/WO3 samples. Our results show that for AgBr/WO3 coupled systems, kinetic degradation profiles have clear dependence on the molar percentages of the coupled pristine materials, as well as on the nature (sensitizing or not sensitizing effect) of the substrate. For caffeine photodegradation, the best performance was obtained when AgBr/WO3(10–15%) catalysts were used. The AgBr/WO3(20%) sample showed the best photocatalytic activity for rhodamine B degradation, exhibiting also excellent dark adsorption capacity (40–45%). Additionally, studies of activity in five consecutive tests showed a good RhB degradation during the successive reuses being involving a N-de-ethylation mechanism with the main O2•− radicals participation; relatively low mineralization percentages were observed, both under UV and visible light conditions. In these successive runs, no silver leaching to the medium was observed but a change from AgBr towards Ag2CO3 and/or AgxO was produced at the catalyst surface. These features should be known in the use of these systems as potential photocatalysts for practical applications.


Junio, 2021 | DOI: 10.1016/j.jallcom.2021.159191

6.37
Química de Superficies y Catálisis

Stepping toward Efficient Microreactors for CO2 Methanation: 3D-Printed Gyroid Geometry

Baena-Moreno, FM; Gonzalez-Castano, M; de Miguel, JCN; Miah, KUM; Ossenbrink, R; Odriozola, J.A.
ACS Sustainable Chemistry & Engineering, 9 (2021) 8198-8206

Show abstract ▽

This work presents a comparative study toward the development of efficient microreactors based on three-dimensional (3D)-printed structures. Thus, the study evaluates the influence of the metal substrate geometry on the performance of structured catalysts for the CO2 methanation reaction. For this purpose, the 0.5%Ru-15%Ni/MgAl2O4 catalyst is washcoated over two different micromonolithic metal substrates: a conventional parallel channel honeycomb structure and a novel 3D-printed structure with a complex gyroid geometry. The effect of metal substrate geometry is analyzed for several CO2 sources including ideal flue gas atmospheres and the presence of residual CH4 and CO in the flue gas, as well as simulated biogas sources. The advantages of the gyroid 3D complex geometries over the honeycomb structures are shown for all evaluated conditions, providing in the best-case scenario a 14% improvement in CO2 conversion. Moreover, this contribution shows that systematically tailoring geometrical features of structured catalysts becomes an effective strategy to achieve improved catalyst performances independent of the flue gas composition. By enhancing the transport processes and the gas-catalyst interactions, the employed gyroid 3D metal substrates enable boosted CO2 conversions and greater CH4 selectivity within diffusion-controlled regimes.


Junio, 2021 | DOI: 10.1021/acssuschemeng.1c01980

9.22
Química de Superficies y Catálisis

Ni/YMnO3 perovskite catalyst for CO2 methanation

Gonzalez-Castano, M; de Miguel, JCN; Penkova, A; Centeno, MA; Odriozola, JA; Arellano-Garcia, H
Applied Materials Today, 23 (2021) 101055

Show abstract ▽

This work proposes an innovative Ni catalyst supported over YMnO3 perovskite as a promising catalytic system for CO2 methanation reaction. Under reductive conditions, the attendance of Mn redox couples within the layered perovskite structure promotes the constitution of sub-stoichiometric YMnO3-x units which, by means of the flexible YMnO3-x reorganization capacity, results in boosted anionic mobility's. The competitive turnover frequencies (20.1 and 17.0 s(-1) at 400 degrees C under dry- and steamed- CO2 methanation conditions) displayed by Ni/YMnO3 system were related to the synergism between strongly interacting Ni particles with partially reduced YMnO3-x perovskites. The optimal Ni dispersions, for which no relevant signs of sintering issues were discerned, combined to effective role of oxygen vacancies towards the dissociative activation of CO2 molecules enabled highly active and stable catalytic behaviours with no evidence of cooking phenomena. On evaluating the water presence within CO2 methanation feedstock's, the deprived catalytic behaviour was fundamentally associated to depleted oxygen vacancies concentrations and promoted WGS side reactions.


Junio, 2021 | DOI: 10.1016/j.apmt.2021.101055

8.66
Química de Superficies y Catálisis

Dehydration of glucose to 5-Hydroxymethlyfurfural on bifunctional carbon catalysts

Bounoukta, CE; Megias-Sayago, C; Ammari, F; Ivanova, S; Monzon, A; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 286 (2021) 119938

Show abstract ▽

The proposed study tries to reply on one important question concerning glucose dehydration: What is the role of bare or tandem Lewis/Bronsted acid sites in the reaction and which are better? A series of mono and bifunctional catalyst are designed and screened for the glucose dehydration reaction. The results clearly reveal that catalyst activity is a function of catalyst composition. The presence of Lewis sites the reaction toward first step isomerization, while the Brunsted acid dehydrate directly glucose to HMF via levoglucosane intermediate. This study proposed also a kinetic modelling of the included reactions and their contrast with the empirical observations.


Junio, 2021 | DOI: 10.1016/j.apcatb.2021.119938

24.32
Química de Superficies y Catálisis

IR spectroscopic insights into the coking-resistance effect of potassium on nickel-based catalyst during dry reforming of methane

Azancot, L; Bobadilla, LF; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 285 (2021) 119822

Show abstract ▽

Dry reforming of methane (DRM) is an effective catalytic route for transforming CO2 and CH4 into valuable syngas and thus potentially attractive for mitigating the emission of environmental harmful gases. Therefore, it is crucial to develop rationally Ni-based catalysts highly resistant to coking and sintering. In this scenario, the addition of small amounts of potassium to nickel catalyst increases their resistance to coking during dry reforming of methane. Nonetheless, the specific role of potassium in these catalysts not have been fully understood and there are still important discrepancies between the different reported studies. This work provides a new approach on the anticoking nature of a K-promoted Ni catalyst by means of a combined IR spectroscopic study of in situ characterization by CO adsorption under static conditions and operando DRIFTS measurements under dynamic conditions of DRM reaction. The involved surface species formed during the reaction were elucidated by transient and steady-state operando DRIFTS studies. It was revealed that the existence of Ni-K interfacial sites favours the gasification of carbonaceous deposits towards reverse Boudouard reaction and reduces the sticking probability of CO2 dissociative adsorption. Moreover, the presence of strongly Mg-O-K basic sites leads to the formation of carbonate intermediates that are subsequently reduced into CO gaseous towards the associative mechanism by RWGS reaction. These results provide a fundamental understanding of the relevant anticoking effect of potassium on Ni-based catalysts.


Mayo, 2021 | DOI: 10.1016/j.apcatb.2020.119822

24.32
Química de Superficies y Catálisis

Understanding the opportunities of metal-organic frameworks (MOFs) for CO2 capture and gas-phase CO2 conversion processes: a comprehensive overview

Gandara-Loe, J; Pastor-Perez, L; Bobadilla, LF; Odriozola, JA; Reina, TR
Reaction Chemistry & Engineering, 6 (2021) 787-814

Show abstract ▽

The rapid increase in the concentration of atmospheric carbon dioxide is one of the most pressing problems facing our planet. This challenge has motivated the development of different strategies not only in the reduction of CO2 concentrations via green energy alternatives but also in the capture and conversion of CO2 into value-added products. Metal-organic frameworks (MOFs) are a relatively new class of porous materials with unique structural characteristics such as high surface areas, chemical tunability and stability, and have been extensively studied as promising materials to address this challenge. This comprehensive review identifies the specific structural and chemical properties of MOFs that result in advanced CO2 capture capacities and fairly encouraging catalytic CO2 conversion behaviour. More importantly, we describe an interconnection among the unique properties of MOFs and the engineering aspects of these intriguing materials towards CO2 capture and conversion processes.


Mayo, 2021 | DOI: 10.1039/d1re00034a

5.20
Química de Superficies y Catálisis

Effect of the sulphonating agent on the catalytic behavior of activated carbons in the dehydration reaction of fructose in DMSO

Bounoukta, CE; Megias-Sayago, C; Ivanova, S; Penkova, A; Ammari, F; Centeno, MA; Odriozola, JA
Applied Catalysis A-General, 617 (2021) 118108

Show abstract ▽

A series of -SO3R functionalized activated carbons (R=H, O, aryl) were prepared and applied in fructose dehydration reaction to 5-hydroxymethylfurfural. Different sulphonating methods introduce groups on catalyst surface with distinct donor-acceptor and hydrophilic properties. Their nature influences significantly not only activated carbon?s textural and chemical properties but also the product yields and selectivity in fructose dehydration reaction. The viability of the solvent free reaction was also investigated and compared to the performance of the catalyst series in presence of DMSO, where the best catalytic results were obtained.


Mayo, 2021 | DOI: 10.1016/j.apcata.2021.118108

5.72
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Elucidating the nature of Mo species on ZSM-5 and its role in the methane aromatization reaction

Lopez-Martin, A.; Platero, F; Colon, G.; Caballero, A.
Reaction Chemistry & Engineering

Show abstract ▽

The valorization of methane is one of the most important goals during the transition period to the general use of renewable energies. Its transformation into a valuable chemical like benzene by direct aromatization of methane (DAM) reaction has been extensively studied in the past years, mainly using Mo/ZSM-5 catalytic systems. Although viable, this DAM reaction poses a number of issues mainly derived from poor conversion and deactivation processes. Therefore, a deeper knowledge of these systems is needed. Herein, by combining chemical (TPR), spectroscopic (XPS), HAADF and other techniques, we have identified the different Mo precursors stabilized in the calcined ZSM-5 support, their nature (monomers, dimers and bulk Mo oxides), location in the zeolite framework (external surface or micropores), and the partial segregation of aluminum during the preparation of catalysts. The role of each Mo phase promoting or hindering the transformation of methane in aromatics has been also clarified.


Abril, 2021 | DOI: 10.1039/d1re00044f

5.20
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

LED-driven controlled deposition of Ni onto TiO2 for visible-light expanded conversion of carbon dioxide into C-1-C-2 alkanes

Sanz-Marco, A; Hueso, JL; Sebastian, V; Nielsen, D; Mossin, S; Holgado, JP; Bueno-Alejo, CJ; Balas, F; Santamaria, J
Nanoscale Advances

Show abstract ▽

Photocatalytic gas-phase hydrogenation of CO2 into alkanes was achieved over TiO2-supported Ni nanoparticles under LED irradiation at 365 nm, 460 nm and white light. The photocatalysts were prepared using photo-assisted deposition of Ni salts under LED irradiation at 365 nm onto TiO2 P25 nanoparticles in methanol as a hole scavenger. This procedure yielded 2 nm Ni particles decorating the surface of TiO2 with a nickel mass content of about 2%. Before the photocatalytic runs, Ni/TiO2 was submitted to thermal reduction at 400 °C in a 10% H2 atmosphere which induced O-defective TiO2−x substrates. The formation of oxygen vacancies, Ti3+ centers and metallic Ni sites upon photocatalytic CO2 hydrogenation was confirmed by operando EPR analysis. In situ XPS under reaction conditions suggested a strong metal–support interaction and the co-existence of zero and divalent Ni states. These photoactive species enhanced the photo-assisted reduction of CO2 below 300 °C to yield CO, CH4 and C2H6 as final products.


Abril, 2021 | DOI: 10.1039/d1na00021g

5.60
Química de Superficies y Catálisis

Cu supported Fe-SiO2 nanocomposites for reverse water gas shift reaction

Gonzalez-Castano, M; de Miguel, JCN; Sinha, F; Wabo, SG; Klepel, O; Arellano-Garcia, H
Journal of CO2 Utilization, 46 (2021) 101493

Show abstract ▽

This work analyses the catalytic activity displayed by Cu/SiO2, Cu-Fe/SiO2 and Cu/FSN (Fe-SiO2 nanocomposite) catalysts for the Reverse Water Gas Shift reaction. Compared to Cu/SiO2 catalyst, the presence of Fe resulted on higher CO?s selectivity and boosted resistances against the constitution of the deactivation carbonaceous species. Regarding the catalytic performance however, the extent of improvement attained through incorporation Fe species strongly relied on the catalysts' configuration. At 30 L/gh and H-2:CO2 ratios = 3, the performance of the catalysts? series increased according to the sequence: Cu/SiO2 < Cu-Fe/SiO2 << Cu/FSN. The remarkable catalytic enhancements provided by Fe-SiO2 nanocomposites under different RWGS reaction atmospheres were associated to enhanced catalyst surface basicity's and stronger Cu-support interactions. The catalytic promotion achieved by Fe-SiO2 nanocomposites argue an optimistic prospective for nanocomposite catalysts within future CO2-valorising technologies.


Abril, 2021 | DOI: 10.1016/j.jcou.2021.101493

8.32
Química de Superficies y Catálisis

Fructose dehydration reaction over functionalized nanographitic catalysts in MIBK/H2O biphasic system

Martin, GD; Bounoukta, CE; Ammari, F; Dominguez, MI; Monzon, A; Ivanova, S; Centeno, MA
Catalysis Today, 366 (2021) 68-76

Show abstract ▽

A series of functionalized nanographitic carbons is prepared, characterized and tested in fructose dehydration reaction to 5-hydroxymethylfurfural. The functionalization treatment was selected to introduce various Bro?nsted acid sites and to modify the textural and catalytic properties of the initial carbon material. Within the series, the sulfonated carbons present the most interesting catalytic behavior resulting in important selectivity to the desired product once the reaction variables were properly adjusted.


Abril, 2021 | DOI: 10.1016/j.cattod.2020.03.016

6.56
Fotocatálisis Heterogénea: Aplicaciones

Fluorinated and platinized Titania for Glycerol oxidation

Murcia, J.J.; Bautista, E; Ávila Martínez, E.G.; Rangel R.N.; Romero, R.; Cubillos Lobo, J.A.; Rojas Sarmiento, H.A.; Hernández, J.S.; Cárdenas, O.; Hidalgo, M.C.; Navío, J.A.; Baeza, R.
Materials Proceedings, 4 (2021) 37

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In this research, photocatalysts based on TiO2 modified by fluorination and platinum addition were evaluated in the glycerol oxidation. These materials were characterized by different instrumental analysis techniques to determine the physicochemical properties. It was found that the surface modification lead to improve the materials absorption in the Visible region of the electromagnetic spectra and to increase the surface area of TiO2. By HPLC analysis was possible to observed that the photocatalysts 0.5% Pt-F-TiO2 showed the highest yield and selectivity towards glyceraldehyde (GAL). It was also observed that the increase in the platinum content until values of 2% had a negative effect in the effectiveness of fluorinated Titania in the glycerol photo-oxidation. The fluorination and platinum addition modify some physicochemical properties of TiO2, leading also to modify the reaction mechanism and selectivity during glycerol partial photo-oxidation and the dose of photocatalysts is an important reaction condition to obtain GAL and Dyhidroxyacetone (DHA) with yields above to 70%.


Abril, 2021 | DOI: 10.3390/IOCN2020-07792

0.00
Química de Superficies y Catálisis

Biogas Conversion to Syngas Using Advanced Ni-Promoted Pyrochlore Catalysts: Effect of the CH4/CO2 Ratio

le Sache, E; Moreno, AA; Reina, TR
Frontiers in Chemistry, 9 (2021) 672419

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Biogas is defined as the mixture of CH4 and CO2 produced by the anaerobic digestion of biomass. This particular mixture can be transformed in high valuable intermediates such as syngas through a process known as dry reforming (DRM). The reaction involved is highly endothermic, and catalysts capable to endure carbon deposition and metal particle sintering are required. Ni-pyrochlore catalysts have shown outstanding results in the DRM. However, most reported data deals with CH4/CO2 stoichiometric ratios resulting is a very narrow picture of the overall biogas upgrading via DRM. Therefore, this study explores the performance of an optimized Ni-doped pyrochlore, and Ni-impregnated pyrochlore catalysts in the dry reforming of methane, under different CH4/CO2 ratios, in order to simulate various representatives waste biomass feedstocks. Long-term stability tests showed that the ratio CH4/CO2 in the feed gas stream has an important influence in the catalysts' deactivation. Ni doped pyrochlore catalyst, presents less deactivation than the Ni-impregnated pyrochlore. However, biogas mixtures with a CH4 content higher than 60%, lead to a stronger deactivation in both Ni-catalysts. These results were in agreement with the thermogravimetric analysis (TGA) of the post reacted samples that showed a very limited carbon formation when using biogas mixtures with CH4 content <60%, but CH4/CO2 ratios higher than 1.25 lead to an evident carbon deposition. TGA analysis of the post reacted Ni impregnated pyrochlore, showed the highest amount of carbon deposited, even with lower stoichiometric CH4/CO2 ratios. The later result indicates that stabilization of Ni in the pyrochlore structure is vital, in order to enhance the coke resistance of this type of catalysts.


Abril, 2021 | DOI: 10.3389/fchem.2021.672419

5.55
Química de Superficies y Catálisis

Zr and Fe on Pt/CeO2-MOx/Al2O3 catalysts for WGS reaction

Gonzalez-Castano, M; Ivanova, S; Centeno, MA; Ioanides, T; Arellano-Garcia, H; Odriozola, JA
International Journal of Hydrogen Energy, (2021)

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By evaluating the functional modifications induced by Zr and Fe as dopants in Pt/CeO2‐MOx/Al2O3 catalysts (M = Fe and Zr), the key features for improving water gas shift (WGS) performance for these systems have been addressed. Pt/ceria intrinsic WGS activity is often related to improved H2 surface dynamics, H2O absorption, retentions and dissociation capacities which are influenced greatly by the support nature. Two metals, iron and zirconia, were chosen as ceria dopants in this work, either in separate manner or combined. Iron incorporation resulted in CO‐redox properties and oxygen storage capacities (OSC) improvement but the formation of Ce‐Fe solid solutions did not offer any catalytic benefit, while the Zr incorporation influenced in a great manner surface electron densities and shows higher catalytic activity. When combined both metals showed an important synergy evidenced by 30% higher CO conversions and attributed to greater surface electron densities population and therefore absorption and activity. This work demonstrates that for Pt/ceria catalysts OSC enhancement does not necessarily imply a catalytic promotion.


Marzo, 2021 | DOI: 10.1002/er.6646

4.67
Química de Superficies y Catálisis

Functionalized biochars as supports for Pd/C catalysts for efficient hydrogen production from formic acid

Santos, JL; Megias-Sayago, C; Ivanova, S; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 282 (2021) 119615

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Biomass waste product was used to generate biochars as catalytic supports for selective hydrogen production from formic acid. The supports were obtained after pyrolysis in CO2 atmosphere of non-pretreated and che-mically ZnCl2 activated raw materials (vine shoot and crystalline cellulose). The support series includes materials with different textural properties and surface chemistry. The support nature and especially textural properties firstly affects significantly Pd size and dispersion and its interaction with the support and secondly influence in a great extent the catalytic behavior of the final material. The presence of prevailing mesoporous character appeared to be the most important parameter influencing formic acid dehydrogenation and overall hydrogen production.


Marzo, 2021 | DOI: 10.1016/j.apcatb.2020.119615

24.32
Química de Superficies y Catálisis

Synergizing carbon capture and utilization in a biogas upgrading plant based on calcium chloride: Scaling-up and profitability analysis

Baena-Moreno, FM; Reina, TR; Rodriguez-Galan, M; Navarrete, B; Vilches, LF
Science of The Total Environment, 758 (2021) 143645

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Herein we analyze the profitability of a novel regenerative process to synergize biogas upgrading and carbon dioxide utilization. Our proposal is a promising alternative which allows to obtain calcium carbonate as added value product while going beyond traditional biogas upgrading methods with high thermal energy consumption. Recently we have demonstrated the experimental viability of this route. In this work, both the scale-up and the profitability of the process are presented. Furthermore, we analyze three representative scenarios to undertake a techno-economic study of the proposed circular economy process. The scale-up results demonstrate the technical viability of our proposal. The precipitation efficiency and the product quality are still remarkable with the increase of the reactor size. The techno-economic analysis reveals that the implementation of this circular economy strategy is unprofitable without subsidies. Nonetheless, the results are somehow encouraging as the subsides needed to reach profitability are lower than in other biogas upgrading and carbon dioxide utilization proposals. Indeed, for the best-case scenario, a feed-in tariff incentive of 4.3 (sic)/MWh makes the approach profitable. A sensitivity study through tornado analysis is also presented, revealing the importance of reducing bipolar membrane electrodialysis energy consumption. Overall our study envisages the big challenge that the EU faces during the forthcoming years. The evolution towards bio-based and circular economies requires the availability of economic resources and progress on engineering technologies.


Marzo, 2021 | DOI: 10.1016/j.scitotenv.2020.143645

10.75
Fotocatálisis Heterogénea: Aplicaciones

Facile synthesis and characterization of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate nanocomposite for highly efficient removal of hazardous hexavalent chromium ions from water

Abdelghani Hsini, Yassine Naciri, Mohamed Benafqir, Zeeshan Ajmal, Nouh Aarab, Mohamed Laabd, J.A. Navío, F. Puga, Rabah Boukherroub, Bahcine Bakiz, Abdallah Albourine
Journal of Colloid and Interface Science, 585 (2021) 560-573

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The present study describes the preparation of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate (BTCA-PANI@ZnP) nanocomposite via a facile two-step procedure. Thereafter, the as-prepared composite material adsorption characteristics for Cr(VI) ions removal were evaluated under batch adsorption. Kinetic approach studies for Cr(VI) removal, clearly demonstrated that the results of the adsorption process followed the pseudo second order and Langmuir models. The thermodynamic study indicated a spontaneous and endothermic process. Furthermore, higher monolayer adsorption was determined to be 933.88 mg g1 . In addition, the capability study regarding Cr(VI) ions adsorption over BTCA-PANI@ZnP nanocomposite clearly revealed that our method is suitable for large scale application. X-ray photoelectron spectroscopy (XPS) analysis confirmed Cr(VI) adsorption on the BTCA-PANI@ZnP surface, followed by its subsequent reduction to Cr(III). Thus, the occurrence of external mass transfer, electrostatic attraction and reduction phenomenon were considered as main mechanistic pathways of Cr(VI) ions removal. The superior adsorption performance of the material, the multidimensional characteristics of the surface and the involvement of multiple removal mechanisms clearly demonstrated the potential applicability of the BTCA-PANI@ZnP material as an effective alternative for the removal of Cr(VI) ions from wastewater.


Marzo, 2021 | DOI: 10.1016/j.jcis.2020.10.036

9.97
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Overcoming Pd-TiO2 Deactivation during H-2 Production from Photoreforming Using Cu@Pd Nanoparticles Supported on TiO2

Platero, F; Lopez-Martin, A; Caballero, A; Rojas, TC; Nolan, M; Colon, G
ACS Applied Nano Materials, 4 (2021) 3204-3219

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Different Cu@Pd-TiO2 systems have been prepared by a two-step synthesis to obtain a bimetallic co-catalyst for the H-2 photoreforming reaction. We find that the tailored deposition of Pd covering the Cu nanoclusters by a galvanic replacement process results in the formation of a core@shell structure. The photocatalytic H-2 production after 18 h is 350 mmol/g on the Cu@Pd-1.0-TiO2 bimetallic system, which is higher than that on the monometallic ones with a H-2 production of 250 mmol/g on Pd-supported TiO2. Surface characterization by highangle annular dark-field scanning transmission electron microscopy, H-2-temperatureprogramed reduction, CO-FTIR spectroscopy, and XPS gives clear evidence of the formation of a core@shell structure. With a Pd loading of 0.2-0.3 at. %, we propose a full coverage of the Cu nanoparticles with Pd. Long-time photoreforming runs show the enhanced performance of supported Cu@Pd with respect to bare palladium leading to a more stable catalyst and ultimately higher H-2 production.


Marzo, 2021 | DOI: 10.1021/acsanm.1c00345

6.14
Fotocatálisis Heterogénea: Aplicaciones

Enhanced UV and visible light photocatalytic properties of synthesized AgBr/SnO2 composites

Puga, F.; Navío, J.A.; Hidalgo, M.C.
Separation and Purification Tecnology, 257 (2021) 117948

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Composites (AgBr/SnO2) comprised of AgBr and SnO2 with different molar % of bare SnO2, have been synthesized by simple precipitation methods; the bare SnO2 used, was synthesized by hydrothermal procedure. Samples have been characterized by X-ray diffraction (XRD), N2-adsorption, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photocatalysts was evaluated through photocatalytic degradation of rhodamine B (RhB) and caffeic acid (CAFA) under UV and Visible illumination. In photocatalytic degradation studies, for both substrates, conversion rates of around 95% were found in 45 min of both UV-illumination and 85% under visible lighting. These conversion rates were superior than the conversion rates of pure parental components, AgBr and SnO2 under the same experimental conditions. At least, for RhB no loss of photocatalytic activity has been observed after five recycles although the mineralization degree progressively diminished along the recycles. The enhanced photocatalytic degradation of AgBr/SnO2 compounds was attributed, in part, to a synergistic increase in adsorption viability, as well as to the effective separation of photoinduced load carriers that resulted from the formation of a heterojunction according to the type II junction. Radical scavengers’ experiments indicated that active oxidant species as O2.−, ·OH and h+ all are involved in this photocatalytic system, although it seems that O2.− played the major role in the photocatalytic degrading of RhB by AgBr/SnO2 composites. In summary, coupling AgBr with SnO2 remarkably improves the photocatalytic activity under both UV and visible-illumination with respect to the parental components. These features open the route to future applications of this material in the field of environmental remediation.


Febrero, 2021 | DOI: 10.1016/j.seppur.2020.117948

9.14
Química de Superficies y Catálisis

Guaiacol hydrodeoxygenation in hydrothermal conditions using N-doped reduced graphene oxide (RGO) supported Pt and Ni catalysts: Seeking for economically viable biomass upgrading alternatives

Parrilla-Lahoz, S; Jin, W; Pastor-Perez, L; Carrales-Alvarado, D; Odriozola, JA; Dongil, AB; Reina, TR
Applied Catalysis A-General, 611 (2021) 117977

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Herein we present an innovative route for model biomass compounds upgrading via “H2-free” hydrodeoxygenation (HDO) reactions. The underlaying idea is to implement a multifunctional catalyst able to activate water and subsequently use in-situ generated hydrogen for the HDO process. In this sense we have developed a series of effective Ni and Pt based catalysts supported on N-promoted graphene decorated with ceria. The catalyst reached commendable conversion levels and selectivity to mono-oxygenated compounds considering the very challenging reaction conditions. Pt outperforms Ni when the samples are tested as-prepared. However, Ni performance is remarkably boosted upon applying a pre-conditioning reductive treatment. Indeed, our NiCeO2/GOr-N present the best activity/selectivity balance and it is deemed as a promising catalyst to conduct the H2-free HDO reaction. Overall, this “proof-concept” showcases an economically appealing route for bio-compounds upgrading evidencing the key role of advanced catalysts for a low carbon future.


Febrero, 2021 | DOI: 10.1016/j.apcata.2020.117977

5.72
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic activity of ZnO nanoparticles and the role of the synthesis method on their physical and chemical properties

Uribe-Lopez, MC; Hidalgo-Lopez, MC; Lopez-Gonzalez, R; Frias-Marquez, DM; Nunez-Nogueira, G; Hernandez-Castillo, D; Alvarez-Lemus, MA
Journal of Photochemistry & Photobiology, A: Chemistry, 404 (2021) 112866

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In the present study, we report on the effect of the synthesis method in the photoactivity of ZnO-NPs. The nanoparticles were prepared by precipitation and sol-gel procedures using zinc nitrate and zinc (II) acetylacetonate as ZnO precursors, respectively. The obtained samples were named as ZnO-PP (precipitation method) and ZnO-SG (sol-gel method). The powders were calcined at 500 degrees C and further characterized by Fourier Transform Infrared spectroscopy, X-ray Powder Diffraction, N-2 adsorption, thermal analysis, Diffuse Reflectance UV-Vis spectroscopy, and Electron Microscopy. Both methods of synthesis lead to formation of pure ZnO with hexagonal-wurtzite crystalline structures with average crystallite sizes similar to 30 nm. The specific surface area was affected by the synthesis method, since SBET values were 5 m(2)/g and 13 m(2)/g for sol-gel and precipitation method, respectively. The electron microscopy revealed significant changes in morphology for the obtained nanoparticles, as sol-gel directed the hexagonal rod-like geometries (similar to 50 nm in diameter) while quasi-spherical nanoparticles (similar to 100 nm in diameter) were formed using precipitation method. Photocatalytic activity was estimated by degrading phenol (50 ppm) as probe molecule under UVA irradiation (lambda = 356 nm), the results demonstrated that ZnO-PP reached 100 % of degradation after 120 min and 90 % of the pollutant was mineralized, whereas for ZnO-SG the results were 80 % and 48 % respectively. Fluorescence test using terephthalic acid (TA) demonstrated higher formation of OH center dot radicals for ZnO synthesized by precipitation method, which could explain the higher photodegradation and mineralization observed. These results support that even slight differences in physical and chemical properties of ZnO, have a significant impact on the photocatalytic performance of such nanoparticles.


Enero, 2021 | DOI: 10.1016/j.jphotochem.2020.112866

5.14
Fotocatálisis Heterogénea: Aplicaciones

Sol-gel synthesis of ZnWO4-(ZnO) composite materials. Characterization and photocatalytic properties

Jaramillo-Páez, C., Navío, J.A., Puga, F., Hidalgo, M.C.
Journal of Photochemistry & Photobiology, A: Chemistry, 404 (2021) 112962

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ZnWO4 based powder photocatalyst have been successfully prepared by calcining a co-precipitated precursor (ZnWO) obtained from aqueous Zn2+ and WO4 2− solutions at pH = 7, without surfactants addition. The as-formed sample was characterized by XRD, N2-absorption, SEM, TEM, DRS and XPS. Both techniques, XRD and XPS results showed that prepared sample corresponds to a crystalline, Zn-enriched composition, ZnWO4 indicating the formation of a ZnWO4-(ZnO) composite, whit ca. 10 wt.-% of ZnO confirmed by XRF analysis. Photocatalytic activities towards degradation of Rhodamine B (RhB), Methyl Orange (MO) and Phenol, under UV-illumination, was investigated not only by monitoring the percentages of conversion of substrates, but also by estimating the corresponding percentages of mineralization that accompany the photocatalytic process. Comparative substrateconversion rates estimated per surface area unit of catalyst, showed that the activity for ZnWO4-(ZnO) composite is similar to that for TiO2(P25), at least for MO and RhB, and even higher that for TiO2(P25) in respect to phenol conversion. By adding TEA to the synthesis procedure, a composite named as ZnWO4-ZnO-(pH = 10)-600 is generated, which has a higher proportion of ZnO (ca. 39 %) and superior specific surface area than the so-called ZnWO4-(ZnO) sample. Furthermore, the photocatalytic degradation of MO using the former material indicates that it is superior to ZnWO4-(ZnO) and even that TiO2(P25) itself under the same operational conditions. 


Enero, 2021 | DOI: 10.1016/j.jphotochem.2020.112962

5.14
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Elucidating the Promotional Effect of Cerium in the Dry Reforming of Methane

Rodriguez-Gomez, A; Lopez-Martin, A; Ramirez, A; Gascon, J; Caballero, A
Chemcatchem, 13 (2021) 553-563

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A series of Ni-Ce catalysts supported on SBA-15 has been prepared by co-impregnation, extensively characterized and evaluated in the carbon dioxide reforming of methane (DRM). The characterization by TEM, XRD and TPR has allowed us to determine the effect of metal loading on metal dispersion. Cerium was found to improve nickel location inside the mesopores of SBA-15 and to suppress coke formation during the DRM reaction. The analysis by XPS allowed us to associate the high cerium dispersion with the presence of low-coordinated Ce3+ sites, being main responsible for its promotional effect. A combination of XAS and XPS has permitted us to determine the physicochemical properties of metals under reduction conditions. The low nickel coordination number determined by XAS in N-Ce doped systems after reduction suggests the generation of very small nickel particles which showed greater catalytic activity and stability in the reaction, and a remarkable resistance to coke formation.


Enero, 2021 | DOI: 10.1002/cctc.202001527

5.50



2020


Fotocatálisis Heterogénea: Aplicaciones

Influence of Water on the Oxidation of NO on Pd/TiO2 Photocatalysts

M.J. Hernández Rodríguez; E. Pulido Melián; J. Araña; J.A. Navío; O.M. González Díaz; Dunia E. Santiago; J.M. Doña Rodríguez
Nanomaterials, 10 (2020) 2354

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Two series of new photocatalysts were synthesized based on modification with Pd of the commercial P25 photocatalyst (EVONIK®). Two techniques were employed to incorporate Pd nanoparticles on the P25 surface: photodeposition (series Pd-P) and impregnation (series Pd-I). Both series were characterized in depth using a variety of instrumental techniques: BET, DRS, XRD, XPS, TEM, FTIR and FESEM. The modified series exhibited a significant change in pore size distribution, but no differences compared to the original P25 with respect to crystalline phase ratio or particle size were observed. The Pd0 oxidation state was predominant in the Pd-P series, while the presence of the Pd2+ oxidation state was additionally observed in the Pd-I series. The photoactivity tests were performed in a continuous photoreactor with the photocatalysts deposited, by dip-coating, on borosilicate glass plates. A total of 500 ppb of NO was used as input flow at a volumetric flow rate of 1.2 L·min−1, and different relative humidities from 0 to 65% were tested. The results obtained show that under UV-vis or Vis radiation, the presence of Pd nanoparticles favors NO removal independently of the Pd incorporation method employed and independently of the tested relative humidity conditions. This improvement seems to be related to the different interaction of the water with the surface of the photocatalysts in the presence or absence of Pd. It was found in the catalyst without Pd that disproportionation of NO2 is favored through its reaction with water, with faster surface saturation. In contrast, in the catalysts with Pd, disproportionation took place through nitro-chelates and adsorbed NO2 formed from the photocatalytic oxidation of the NO. This different mechanism explains the greater efficiency in NOx removal in the catalysts with Pd. Comparing the two series of catalysts with Pd, Pd-P and Pd-I, greater activity of the Pd-P series was observed under both UV-vis and Vis radiation. It was shown that the Pd0 oxidation state is responsible for this greater activity as the Pd-I series improves its activity in successive cycles due to a reduction in Pd2+ species during the photoactivity tests.


Diciembre, 2020 | DOI: 10.3390/nano10122354

5.08
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

(NH4)4[NiMo6O24H6].5H2O / g-C3N4 materials for selective photo-oxidation of Csingle bondO and Cdouble bondC bonds

Caudillo-Flores, U; Ansari, F; Bachiller-Baeza, B; Colon, G; Fernandez-Garcia, M; Kubacka, A
Applied Catalysis B-Environmental, 278 (2020) 119299

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Novel composite photo-catalysts having (NH4)(4)[NiMo6O24H6]center dot 5H(2)O Polyoxometalate (POM) species deposited over g-C3N4 are synthesized. Materials were characterized through a multitechnique approach showing the stability of the carbon nitride component both through the synthesis process and under reaction. Contrarily, the POM component evolves under reaction conditions to maximize the interaction with the support. Such a behavior renders, as measured by the quantum efficiency, highly active photo-catalysts in the photo-oxidation of 2-propanol and styrene both under UV and sunlight illumination, setting up the basis for a green catalytic process. The material having a 4 wt. % POM showed improved activity with respect to both parent constituents but also higher selectivity to the partial oxidation of the alcohol and the aromatic hydrocarbon to generate added value chemical compounds. A multitechnique approach investigating charge carrier fate demonstrates the key role played by the interaction between components to promote activity and selectivity in selective oxidation reactions.


Diciembre, 2020 | DOI: 10.1016/j.apcatb.2020.119299

19.50
Química de Superficies y Catálisis

Ru-Ni/MgAl2O4 structured catalyst for CO2 methanation

Navarro, Juan C.; Centeno, Miguel A.; Laguna, Oscar H.; Odriozola, Jose A.
Renewabel Energy, 161 (2020) 120-132

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Novel catalytic systems should be tested for the valorization of CO2 through the Sabatier reaction, since this process is gaining great importance within strategic sectors of the chemical industry. Therefore, this work explores the feasibility of structuring a catalyst (0.5%Ru-15%Ni/MgAl2O4) for CO2 methanation using metal micromonoliths. The coating of the catalyst over the surface of the micromonoliths is carried out by means of the washcoating procedure and different characterization techniques are applied to establish possible changes in the catalyst during structuring.
Regarding the performance in the Sabatier reaction, the structured systems are tested as well as the powder catalyst in order to establish the possible effects of the structuring processes. For this, variables such as catalyst loading, space velocity, inclusion of water in the feed-stream and the pressurization of the process were studied.
In general, the structuring of the proposed catalyst by the reported procedure is absolutely feasible. There are no substantial changes in the main features of the catalyst and this means that its catalytic performance is not altered after the structuring process either. Furthermore, the structured system exhibits high stability in a long-term test and is comparable with other CO2 methanation catalysts reported in research to date. 


Diciembre, 2020 | DOI: 10.1016/j.renene.2020.07.055

8.00
Química de Superficies y Catálisis

Flexible syngas production using a La2Zr2-xNixO7-delta pyrochlore-double perovskite catalyst: Towards a direct route for gas phase CO2 recycling

le Sache, E; Pastor-Perez, L; Garcilaso, V; Watson, DJ; Centeno, MA; Odriozola, JA; Reina, TR
Catalysis Today, 357 (2020) 583-589

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The bi-reforming of methane (BRM) has the advantage of utilising greenhouse gases and producing H2 rich syngas. In this work Ni stabilised in a pyrochlore-double perovskite structure is reported as a viable catalyst for both Dry Reforming of Methane (DRM) and BRM. A 10 wt.% Ni-doped La2Zr2O7 pyrochlore catalyst was synthesised, characterised and tested under both reaction conditions and its performance was compared to a supported Ni/La2Zr2O7. In particular the effect of steam addition is investigated revealing that steam increases the H2 content in the syngas but limits reactants conversions. The effect of temperature, space velocity and time on stream was studied under BRM conditions and brought out the performance of the material in terms of activity and stability. No deactivation was observed, in fact the addition of steam helped to mitigate carbon deposition. Small and well dispersed Ni clusters, possibly resulting from the progressive exsolution of Ni from the mixed oxide structure could explain the enhanced performance of the catalyst.


Noviembre, 2020 | DOI: 10.1016/j.cattod.2019.05.039

6.77
Química de Superficies y Catálisis

Upgrading the PtCu intermetallic compounds: The role of Pt and Cu in the alloy

Castillo, R; Garcia, ED; Santos, JL; Centeno, MA; Sarria, FR; Daturi, M; Odriozola, JA
Catalysis Today, 356 (2020) 390-398

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This work is devoted to the study of the role of both metals in the intermetallic PtxCuy/ γ Al2O3 catalysts commonly employed in CO-PROX reaction. Therefore, monometallic Pt and Cu based catalysts and PtCu intermetallic compound with different molar ratios (Pt3Cu1 and Pt1Cu3) supported catalysts were carefully synthesized and deeply characterized. Room temperature CO adsorptions by FTIR spectroscopy were carried out on the mono- and intermetallic catalysts being the monometallic catalyst determinant for the study. From the analysis of the nature of the platinum surface in Pt/ γ Al2O3, we have demonstrated that the role of Pt sites is based in the CO dissociation for the CO2 formation and also how the platinum surface is partially blocked by leftovers from the synthesis. Moreover, the study of the Cu/ γ Al2O3 and the bimetallic catalysts PtxCuy/ γ Al2O3 allowed elucidating the effect of the copper in the metallic site and support interphase as well as the role of copper in the hydrocarbon oxidation.


Octubre, 2020 | DOI: 10.1016/j.cattod.2019.11.026

6.77
Química de Superficies y Catálisis

Bimetallic PdAu catalysts for formic acid dehydrogenation

Santos, JL; Leon, C; Monnier, G; Ivanova, S; Centeno, MA; Odriozola, JA
International Journal of Hydrogen Energy, 45 (2020) 23056-23068

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A series of monometallic and bimetallic palladium gold catalyst were prepared and studied for the formic acid dehydrogenation reaction. Different Pd/Au compositions were employed (PdxAu100-x, where x = 25; 50 and 75) and their impact on alloy structure, particle size and dispersion was evaluated. Active phase composition and reaction parameters such as temperature, formic acid concentration or formate/formic acid ratio were adjusted to obtain active and selective catalyst for hydrogen production. An important particle size effect was observed and related to Pd/Au composition for all bimetallic catalysts. 


Septiembre, 2020 | DOI: 10.1016/j.ijhydene.2020.06.076

5.82
Química de Superficies y Catálisis

Free-Carbon Surface for PtCu Nanoparticles: An In Situ Near Ambient Pressure X-ray Photoelectron Spectroscopy Study

Castillo, R; Navarro-Jaen, S; Romero-Sarria, F; Perez-Dieste, V; Escudero, C; Centeno, MA; Daturi, M; Odriozola, JA
Journal of Physical Chemistry C, 124 (2020) 19046-19056

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Usually, nanoparticle synthesis methodologies require the use of organic molecules (capping agent, solvent molecules, etc.), which results in carbon deposits on the nanoparticle surface. These residues modify the surface properties mainly affecting the catalytic behavior. In this work, unsupported poly(vinylpyrrolidone) (PVP)-stabilized PtCu (1:3 molar ratio) bimetallic alloy nanoparticles were synthetized and characterized. An alternative surface cleaning method has been designed, which successfully removes the presence of organic fragments. To address this key issue, we have combined a first nanoparticle washing step with a near ambient pressure X-ray photoelectron spectroscopy (NAPXPS) study in order to obtain a clean active site and the total understanding of the carbon elimination mechanism. The dynamic evolution of the surface organic species composition under different gas mixtures at 750 mTorr and 350 degrees C has been studied, and only under CO2 exposure, NAPXPS analysis revealed a total availability of the active site by the removal of the organic nanoparticle coating.


Septiembre, 2020 | DOI: 10.1021/acs.jpcc.0c04713

4.13
Química de Superficies y Catálisis

Experimental evidence of HCO species as intermediate in the fischer tropsch reaction using operando techniques

Diaz-Sanchez, RM; de-Paz-Carrion, A; Serrera-Figallo, MA; Torres-Lagares, D; Barranco, A; Leon-Ramos, JR; Gutierrez-Perez, JL
Applied Catalysis B-Environmental, 272 (2020) 119032

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Fischer Tropsch's reaction, known from 1925, receives special attention nowadays due to its key role in the CO2 or biomass valorization to liquid fuels and chemicals. Several aspects on the exact mechanism or the role of water in this reaction are not yet completely clear. Formyl species, HCO, have been proposed as the most probable reaction intermediate, but they have never been observed under operation conditions closed to the real ones. In this work, using DRIFTS-MS operando techniques, HCO intermediates are detected under a H2/CO flow and 200 °C. IR bands at 2900 cm−1 and 1440 cm−1 attributed to ν(C–H) and δ(HCO) vibrations modes characterize these species. Evolution of these bands with the reaction time evidences its high reactivity with OH groups, which explains the positive effect of water on the CO conversion previously observed.


Septiembre, 2020 | DOI: 10.1016/j.apcatb.2020.119032

19.50
Química de Superficies y Catálisis

Elucidation of Water Promoter Effect of Proton Conductor in WGS Reaction over Pt-Based Catalyst: An Operando DRIFTS Study

Jurado, L; Garcia-Moncada, N; Bobadilla, LF; Romero-Sarria, F; Odriozola, JA
Catalysts, 10 (2020) 841

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A conventional Pt/CeO2/Al(2)O(3)catalyst physically mixed with an ionic conductor (Mo- or Eu-doped ZrO2) was tested at high space velocity (20,000 h(-1)and 80 L h(-1)g(cat)(-1)) under model conditions (only with CO and H2O) and industrial conditions, with a realistic feed. The promoted system with the ionic conductor physically mixed showed better catalytic activity associated with better water dissociation and mobility, considered as a rate-determining step. The water activation was assessed by operando diffuse reflectance infrared fourier transformed spectroscopy (DRIFTS) studies under reaction conditions and the Mo-containing ionic conductor exhibited the presence of both dissociated (3724 cm(-1)) and physisorbed (5239 cm(-1)) water on the Eu-doped ZrO(2)solid solution, which supports the appearance of proton conductivity by Grotthuss mechanism. Moreover, the band at 3633 cm(-1)ascribed to hydrated Mo oxide, which increases with the temperature, explains the increase of catalytic activity when the physical mixture was used in a water gas shift (WGS) reaction.


Agosto, 2020 | DOI: 10.3390/catal10080841

4.15
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Thermo-Photocatalytic Methanol Reforming for Hydrogen Production over a CuPd-TiO2 Catalyst

Lopez-Martin, A; Platero, F; Caballero, A; Colon, G
ChemPhotoChem, 4 (2020) 630-637

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A bimetallic CuPd/TiO2 system has been prepared by a two-step synthesis and was used for a methanol steam photoreforming reaction. By sequential deposition, palladium is deposited over copper nanoclusters through a galvanic replacement process. Hydrogen production by steam reforming from methanol was achieved by both thermo-photocatalytic and photocatalytic processes. It appears that H-2 production on the bimetallic system is notably higher than the Pd monometallic reference. Moreover this difference in the catalytic performance could be related to the higher CO evolution observed for the monometallic Pd-1.0 TiO2 system which is partially inhibited in the bimetallic catalyst. In addition, an important thermal effect can be envisaged in all cases. Nevertheless, this improved effect in the thermo-photocatalytic process is accompanied by a remarkable CO evolution and SMSI effect (important strong metal-support interactions) that hindered the efficiency as temperature increases. On this basis, optimal operational conditions for H-2 production are obtained for thermo-photocatalytic reforming at 100 degrees C, for which the synergetic effect is higher with lower CO production (H-2/CO=4)


Agosto, 2020 | DOI: 10.1002/cptc.202000010

3.85
Química de Superficies y Catálisis

Metal catalysts supported on biochars: Part I synthesis and characterization

Santos, JL; Maki-Arvela, P; Monzon, A; Murzin, DY; Centeno, MA
Applied Catalysis B-Environmental, 268 (2020) 118423

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In the current study, synthesis and detailed characterization of cellulose biochars as a waste biomass model component and vine shoot biochars as a real waste biomass catalyst was performed. Although initially biochars exhibit poor textural properties, a simple activation process can make them much more suitable as a catalyst supports. A combination of physical (CO2) and chemical activation (ZnCl2) was evaluated. The characterization results indicated that the surface area and pore volume of the biochars have increased significantly by chemical activation treatment with ZnCl2. A series of metal catalysts (Pd, Au and Ru) supported on biochars was prepared and characterized. The prepared materials represent a set of noble metal catalysts supported on biochars with different textural and surface properties, which can be used to evaluate the catalytic role of the active phase and carbon support nature in catalytic reactions of interest, such as hydrodeoxygenation, described in the part II.


Julio, 2020 | DOI: 10.1016/j.apcatb.2019.118423

19.50
Química de Superficies y Catálisis

Hydrodeoxygenation of vanillin over noble metal catalyst supported on biochars: Part II: Catalytic behaviour

Santos, JL; Maki-Arvela, P; Warna, J; Monzon, A; Centeno, MA; Murzin, DY
Applied Catalysis B-Environmental, 268 (2020) 118425

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Vanillin hydrodeoxygenation was investigated using noble metal (Pd, Au, Ru) supported on active carbon prepared from waste derived biochars, which were produced via pyrolysis in CO2 atmosphere. Chemical activation with ZnCl2 and HNO3 was also used in the preparation of active carbon to enhance the specific surface area and demineralize material, respectively. Both fresh and spent catalysts were characterized with X-ray diffraction, DRIFTS, zeta potential measurement and HR-TEM. The highest selectivity to p-creosol, 92 % selectivity at complete vanillin conversion after 3 h was obtained in vanillin hydrodeoxygenation at 100 degrees C under 30 bar in hydrogen in water with Pd/C catalyst prepared via pyrolysis under CO2 from wine waste and using ZnCl2 as a chemical activation agent. Hydrodeoxygenation activity increased with increasing metal dispersion. A kinetic model including adsorption of vanillin described well the experimental data.


Julio, 2020 | DOI: 10.1016/j.apcatb.2019.118425

19.50
Química de Superficies y Catálisis

Evaluation of the Oxygen Mobility in CePO4-Supported Catalysts: Mechanistic Implications on the Water-Gas Shift Reaction

Navarro-Jaen, S; Bobadilla, LF; Romero-Sarria, F; Laguna, OH; Bion, N; Odriozola, JA
Journal of Physical Chemistry C, 124 (2020) 16391-16401

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The hexagonal and monoclinic phases of CePO4 have been demonstrated to be excellent catalytic supports for Pt-based water-gas shift (WGS) catalysts. Consequently, the elucidation of the WGS reaction mechanism in these materials constitutes a fundamental aspect in order to explain their catalytic behavior. Because the observed WGS reaction path is closely related to the absence or presence of oxygen vacancies in the support, the study of the oxygen mobility in these solids constitutes a key factor for the understanding of the structure of the materials and its influence on the reaction mechanism. In this study, the oxygen mobility in CePO4 supports and the corresponding Pt catalysts has been evaluated by means of isotopic exchange experiments using O-18(2) and (CO2)-O-18 as probe molecules. Results demonstrate that the evaluated solids present a low exchange activity when O-18(2) is used, indicating the absence of oxygen vacancies in these solids, thus suggesting a poor influence of the WGS redox mechanism. On the contrary, a high oxygen exchange activity is observed using (CO2)-O-18, demonstrating that the exchange in these materials takes place through the formation of carbonate-like intermediates, thus suggesting the associative mechanism of the WGS reaction as the preferred path in these solids. Operando diffuse reflectance infrared spectroscopy experiments under WGS reaction conditions confirm these results, proving that the WGS reaction in the studied materials takes place through a formate-mediated associative mechanism.


Julio, 2020 | DOI: 10.1021/acs.jpcc.0c03649

4.13
Fotocatálisis Heterogénea: Aplicaciones

Influence of Sr-doping on structural, optical and photocatalytic properties of synthesized Ca3(PO4)2

Y.Naciri; A.Hsini; Z.Ajmal; A.Bouddouch; B.Bakiz; J.A.Navío; A.Albourine; J-C.Valmalette; M.Ezahri; A.Benlhachemi
Journal of Colloid and Interface Science, 572 (2020) 269-280

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Well-crystallized Ca3(PO4)2 doped and un-doped nano-particles with the maximum strontium content (40 wt% Sr) followed by calcination at 800 °C for 3 h were synthesized via facile co-precipitation method. DTA/TGA, X-ray diffraction (XRD), energy dispersive scanning electron microscopy (SEM/EDX), UV–vis diffuse reflectance spectrum (UV–vis DRS), Raman spectroscopy and photoluminescence (PL) techniques were used for material characterization. The (XRD) patterns of as-synthesized Sr-doped Ca3(PO4)2 solid solution samples exhibited a systematic shift toward lower angles by possessing a single rhombohedral crystal structure without any secondary phases. The UV light driven photocatalytic activity was assessed for rhodamine B (RhB) degradation. As a result, ultrafast photodegradation activity was observed after Sr doping. Moreover, the 30 wt% Sr-Ca3(PO4)2 sample showed the highest photocatalytic degradation among the Sr-doped Ca3(PO4)2 samples toward RhB. It was further suggested that as-synthesized 30 wt% Sr-Ca3(PO4)2 superior photocatalytic performance is ascribed to the more proficient partition of photogenerated electron-hole pairs. Furthermore, the involved mechanism of superior photocatalytic performance of the 30 wt% Sr-Ca3(PO4)2 solid solution was also investigated. In addition, regeneration cycles indicated the higher stability of the photocatalyst to be effectively recycled up to four times without any considerable reduction in photocatalytic performance. Thus, these informations further provides us a scalable pathway to fabricate Sr doped Ca3(PO4)2 and its consequent use as an efficient photocatalyst for rhodamine B (RhB) contaminated wastewater treatment.


Julio, 2020 | DOI: 10.1016/j.jcis.2020.03.105

8.13
Química de Superficies y Catálisis

5-Hydroxymethyl-2-Furfural Oxidation Over Au/Ce(x)Zr(1-x)O(2)Catalysts

Megias-Sayago, C; Bonincontro, D; Lolli, A; Ivanova, S; Albonetti, S; Cavani, F; Odriozola, JA
Frontiers in Chemistry, 8 (2020) 461

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A series of gold catalysts supported on pure CeO2, ZrO2, and two different Ce-Zr mixed oxides have been prepared and tested in the 5-hydroxymethyl-2-furfural oxidation reaction. All catalysts show high catalytic activity (100% conversion) and important selectivity (27-41%) to the desired product i.e., 2,5-furandicarboxylic acid at low base concentration. Products selectivity changes with the support nature as expected, however, the observed trend cannot be related neither to gold particle size, nor to catalyst reducibility and oxygen mobility. An important relation between the FDCA selectivity and the support textural properties is observed, conducing to the general requirement for optimal pore size for this reaction.


Junio, 2020 | DOI: 10.3389/fchem.2020.00461

5.22
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Surface Modification of Rutile TiO2 with Alkaline-Earth Oxide Nanoclusters for Enhanced Oxygen Evolution

Rhatigan, S; Sukola, E; Nolan, M; Colon, G
ACS Applied Nano Materials, 3 (2020) 6017-6033

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The oxygen (O-2) evolution reaction (OER) is accepted as the bottleneck in the overall water splitting and has seen intense interest. In this work, we prepared rutile TiO2 modified with nanoclusters of alkaline-earth metal oxides for the OER. Photocatalytic OER was performed over rutile TiO2 surface-modified with alkaline-earth oxide nanoclusters, namely, CaO and MgO. The O-2 evolution activity is notably enhanced for MgO-modified systems at low loadings and a combination of characterization and first-principles simulations allows interpretation of the role of the nanocluster modification in improving the photocatalytic performance of alkaline-earth-modified rutile TiO2. At such low loadings, the nanocluster modifiers would be small, and this facilitates a close correlation with theoretical models. Structural and surface characterizations of the modified systems indicate that the integrity of the rutile phase is maintained after modification. However, charge-carrier separation is strongly affected by the presence of surface nanoclusters. This improved performance is related to surface features such as higher ion dispersion and surface hydroxylation, which are also discussed with first-principles simulations. The modified systems are reducible so that Ti3+ ions will be present. Water dissociation is favorable at cluster and interfacial sites of the stoichiometric and reduced modified surfaces. Pathways to water oxidation at interfacial sites of reduced MgO-modified rutile TiO2 are identified, requiring an overpotential of 0.68 V. In contrast, CaO-modified systems required overpotentials in excess of 0.85 V for the reaction to proceed.


Junio, 2020 | DOI: 10.1021/acsanm.0c01237

5.10
Fotocatálisis Heterogénea: Aplicaciones

Recent progress on the enhancement of photocatalytic properties of BiPO4 using π–conjugated materials

Naciri, Y., Hsini, A., Ajmal, Z., Navio, J.A., Bakiz, B., Albourine, A., Ezahri, M., Benlhachemi, A.
Advances in Colloid and Interface Science, 280 (2020) 102160

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Semiconductor photocatalysis is regarded as most privileged solution for energy conversion and environmental application. Recently, photocatalysis methods using bismuth-based photocatalysts, such as BiPO4, have been extensively investigated owing to their superior efficacy regarding organic pollutant degradation and their further mineralization into CO2 and H2O. It is well known that BiPO4 monoclinic phase exhibited better photocatalytic performance compared to Degussa (Evonik) P25 TiO2 in term of ultraviolet light driven organic pollutants degradation. However, its wide band gap, poor adsorptive performance and large size make BiPO4 less active under visible light irradiation. However, extensive research works have been conducted in the past with the aim of improving visible light driven BiPO4 activity by constructing a series of heterostructures, mainly coupled with π-conjugated architecture (e.g., conductive polymer, dye sensitization and carbonaceous materials). However, a critical review of modified BiPO4 systems using π-conjugated materials has not been published to date. Therefore, this current review article was designed with the aim of presenting a brief current state-of-the-art towards synthesis methods of BiPO4 in the first section, with an especial focuses onto its crystal-microstructure, optical and photocatalytic properties. Moreover, the most relevant strategies that have been employed to improve its photocatalytic activities are then addressed as the main part of this review. Finally, the last section presents ongoing challenges and perspectives for modified BiPO4 systems using π–conjugated materials


Junio, 2020 | DOI: 10.1016/j.cis.2020.102160

12.98
Química de Superficies y Catálisis

Cost-effective routes for catalytic biomass upgrading

Jin, W; Pastor-Perez, L; Yu, J; Odriozola, JA; Gu, S; Reina, TR
Current Opinion in Green and Sustainable Chemistry, 23 (2020) 1-9

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Catalytic hydrodeoxygenation (HDO) is a fundamental and promising route for bio-oil upgrading to produce petroleum-like hydrocarbon fuels or chemical building blocks. One of the main challenges of this technology is the demand of high-pressure H-2, which poses high costs and safety concerns. Accordingly, developing cost-effective routes for biomass or bio-oil upgrading without the supply of commercial H-2 is essential to implement the HDO at commercial scale. This article critically reviewed the very recent studies relating to the novel strategies for upgrading the biofeedstocks with 'green' H-2 generated from renewable sources. More precisely, catalytic transfer hydro-genation/hydrogenolysis, combined reforming and HDO, combined metal hydrolysis and HDO, water-assisted in-situ HDO and nonthermal plasma technology and self-supported hydrogenolysis are reviewed herein. Current challenges and research trends of each strategy are also proposed aiming to motivate further improvement of these novel routes to become competitive alternatives to conventional HDO technology.


Junio, 2020 | DOI: 10.1016/j.cogsc.2019.12.008

6.46
Química de Superficies y Catálisis

Reductant atmospheres during slow pyrolysis of cellulose: First approach to obtaining efficient char -based catalysts in one pot

Santos, JL; Centeno, MA; Odriozola, JA
Journal of Analytical and Applied Pyrolysis, 148 (2020) 104821

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Char based metallic (Pd-Au-Ru-Pt/C) catalysts have drawn increasing research interest due to their versatility in biomass related industrial reactions. Recent studies dealing with the synthesis of char-based catalysts in one single step (one-pot) use reductant atmospheres for biomass pyrolysis. In this work, the influence of the use of a reductant N2/H2 atmosphere on the physicochemical properties of the resulting chars was evaluated in comparison with the use of an inert N2 atmosphere. Specifically, the fundamental parameter of the pyrolysis process, the temperature, was evaluated in the 500−900 °C range. Produced chars were fully characterized by N2 isotherms, ultimate CHNS analysis, X-ray Diffraction, Raman spectroscopy, Diffuse Reflectance Infrared spectroscopy, X-ray Photoelectron spectroscopy, helium Temperature Programmed Decomposition and Isoelectric Point analysis. Slow pyrolysis under reductant atmosphere favours deoxygenation reaction against dehydrogenation ones, reduces the carbon yield and results in chars with a more hydrophobic and graphitic character, higher thermal stability and weak surface functionalization. The use of intermediates temperatures (700 °C) favours the obtaining of chars with suitable physicochemical properties and good surface functionalization, which will facilitate the anchoring of the active phase on the surface, improving the metallic dispersion of the resulting one pot catalyst. This leads us to affirm that the use of reducing atmospheres at intermediate temperatures, is superior to the use of inert atmospheres for this purpose. This analysis on the impact of the use of a reductant atmosphere during slow pyrolysis of microcrystalline cellulose opens a new working path for the optimization of char-based catalysts obtained in a single stage.


Junio, 2020 | DOI: 10.1016/j.jaap.2020.104821

5.54
Química de Superficies y Catálisis

Time-resolved operando DRIFTS-MS study of the moisture tolerance of small-pore SAPO-34 molecular sieves during CH4/CO2 separation

Romero, M; Navarro, JC; Bobadilla, LF; Dominguez, MI; Ivanova, S; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Microporous and Mesoporous Materials, 298 (2020) 110071

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This study pretends to evaluate and understand the effect of moisture presence during CO2/CH4 separation on small-pore SAPO-34 molecular sieves. Two SAPO-34 samples with different physicochemical properties (composition, crystal size and texture) were prepared by hydrothermal synthesis using either one or a mixture of two templates. Transient operando DRIFTS-MS measurements revealed that the sample's hydrophobic character is associated to the presence of Si islands, which enhanced sample's moisture tolerance during repetitive adsorption/desorption cycles. This knowledge is fundamental to achieve the rational design of efficient SAPO-34 membranes under realistic conditions.


Mayo, 2020 | DOI: 10.1016/j.micromeso.2020.110071

5.46
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Structural and surface considerations on Mo/ZSM-5 systems for methane dehydroaromatization reaction

Lopez-Martin, A; Caballero, A; Colon, G
Molecular Catalysis, 486 (2020) 110787

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We have prepared a series of Mo/ZSM-5 systems by impregnation method with different metal loading. The optimum performance has been attained for 4% metal loading, yielding to ca. 2 mmol(benzene)/g(ca)(t) at the end of the reaction. The obtained catalysts were widely structural and surface characterized. As Mo content increases, the surface feature of the support is affected specially its mesoporosity. It has been stated the enormous complexity of Mo species present in the studied system. In situ characterization by XPS reveals different reduction and carburization behaviour depending on the Mo content.


Mayo, 2020 | DOI: 10.1016/j.mcat.2020.110787

5.06
Fotocatálisis Heterogénea: Aplicaciones

Microwave-assisted sol-gel synthesis of TiO2 in the presence of halogenhydric acids. Characterization and photocatalytic activity

Puga,F.;Navío,J.A.;Jaramillo-Páez,C.;Sánchez-Cid,P.;Hidalgo,M.C.
Journal of Photochemistry and Photobiology A: Chemistry, 394 (2020) 112457

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The synthesis of mesoporous TiO2 nanosheets is reported using Ti(IV) Isopropoxide as Ti(IV) precursor. A sol-gel process combined with microwave activation is used. Three different halogenhydric acids (HX), were used to peptise the sol: HF(ac), HCl (ac) and HBr (ac). The three obtained TiO2-I(HX) samples were characterized by XRD, XRF, N2-adsorption, SEM, TEM, DRS and XPS. The three synthesized samples have high values of specific surfaces (between 100 m2/g and 200 m2/g) and similar band gap values (3.2–3.3 eV). The analysis of the surface composition by XPS confirms the presence of the halogenated species (F, Cl or Br) on the surface of each ones of the samples. The nanometric size (ca 5 nm) of the particles for each of the three samples was confirmed by XRD and by TEM. On the other hand, the nature of the halogenated acid used plays a role in the composition of the phases. While the TiO2-I (HF) sample was 100 % anatase, the other samples turned out to be biphasic, showing anatase/rutile in the TiO2-I(HCl) sample and anatase/brookite in the TiO2-I(HBr) sample. The samples were tested under two illumination conditions (UV and visible light) using rhodamine B and caffeine. The indirect role of the halide agent on the photocatalytic activities thereof is discussed.


Mayo, 2020 | DOI: 10.1016/j.jphotochem.2020.112457

4.29
Química de Superficies y Catálisis

Potentialization of bentonite properties as support in acid catalysts

Amaya, J; Bobadilla, L; Azancot, L; Centeno, M; Moreno, S; Molina, R
Materials Research Bulletin, 123 (2020) 110728

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Enhancement of the main physicochemical properties of a natural bentonite was carried out by means of modifications using surfactant, reflux, microwave treatment and, subsequently, the incorporation of AlZr and AlCe species. The evolution of the main changes in each modification stage was evaluated by means of X-ray diffraction, N-2 sortometry, scanning microscopy (SEM), NH3-TPD, NH3-DRIFTS and CO adsorption at low temperature. For the evaluation of the catalytic behavior, the dehydration-dehydrogenation reactions of 2-propanol and hydro-conversion of decane were used; both of which generate, in addition, information regarding the acidic properties of the materials. The correlation of the number, type and acid strength with the catalytic behavior, allowed establishing the effect produced by both the delamination method and the nature of the incorporated cation. This generated tools that allow controlling the physicochemical properties, and more specifically, the enhancement of the acidity of new supports based on this type of natural clay mineral.


Marzo, 2020 | DOI: 10.1016/j.materresbull.2019.110728

4.64
Fotocatálisis Heterogénea: Aplicaciones

Pt–TiO2–Nb2O5 heterojunction as effective photocatalyst for the degradation of diclofenac and ketoprofen

Sacco, O.l; Murcia, J.J.; Lara, A.E.; Hernández-Laverde, M.; Rojas, H.; Navío, J.A.; Hidalgo, M.C.; Vaiano, V.
Materials Science in Semiconductor Processing, 107 (2020) 104839

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Pt–TiO2–Nb2O5 heterojunction was synthetized and studied for the photocatalytic removal of diclofenac (DCF) and ketoprofen (KTF) under UV light irradiation. The physical-chemical properties of the prepared catalysts were analysed by different characterization techniques revealing that the lowest platinum nanoparticle size and the better metal distribution was observed in Pt–TiO2–Nb2O5 sample. The Pt–TiO2–Nb2O5 heterojunction possessed the best photocatalytic activity toward both the photodegradation and mineralization of the two selected pollutants. The optimal photocatalyst showed a DCF and KTF mineralization rate of 0.0555 and 0.0746 min−1, respectively, which were higher than those of Pt–TiO2 (0.0321 min−1 for DCF and 0.0597 min−1 for KTF). The experiments driven to analyse the effects of free radical capture showed that ·OH, ·O2− and h+ have a primary role in reactive during the photocatalytic reaction. The improved photocatalytic performances of the Pt–TiO2–Nb2O5 heterojunction could be argue by a direct Z-scheme mechanism in which the Pt0 nanoparticles could act as a bridge between TiO2 and Nb2O5, improving the electron-hole separation and, ultimately, enhancing the photocatalytic removal rate of both DCF and KTF.


Marzo, 2020 | DOI: 10.1016/j.mssp.2019.104839

3.93
Fotocatálisis Heterogénea: Aplicaciones

Preparation of ZnFe2O4/ZnO composite: Effect of operational parameters for photocatalytic degradation of dyes under UV and visible illumination

Zouhier, M.; Tanji, K.; Navio, J.A.; Hidalgo, M.C.; Jaramillo-Páez, C.; Kherbeche, A.
Journal of Photochemistry and Photobiology A: Chemistry, 390 (2020) 112305

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An ZnFe2O4/ZnO composite catalyst was prepared by solution combustion method. In this study, one nominal molar percentage of iron was used in the synthesis, corresponding to 20 % molar relative to ZnO. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray Fluorescence (XRF), Scanning Electronic Microscopy (SEM), Transmission Electronic Microscopy (TEM) and Ultraviolet-visible (UV–vis) diffuse spectroscopy (DRS). The photocatalytic activities of the catalysts were investigated based on the degradation of two dyes, methylene blue (MB) and remazol brilliant blue (RBB), in aqueous solution under both UV and visible light illumination respectively. It was found that the composite had a good photocatalytic activity at basic pH by using 1 g/L of catalyst under UV illumination for both MB and RBB. Under visible illumination, while pristine ZnO showed no activity, the composite exhibited an excellent visible efficiency, reaching up to an 80 % conversion of the initial dye concentrations in 2 h. The enhancement of the visible photocatalytic activity of Fe/ZnO sample with respect to pristine ZnO is attributed to the formation of ZnFe2O4 coupled with ZnO, having a narrow band gap value that contributes to the absorption of visible photons with an improved separation path for the photo-generated carriers.


Marzo, 2020 | DOI: 10.1016/j.jphotochem.2019.112305

4.29
Química de Superficies y Catálisis

Effect of Gold Particles Size over Au/C Catalyst Selectivity in HMF Oxidation Reaction

Megias-Sayago, C; Lolli, A; Bonincontro, D; Penkova, A; Albonetti, S; Cavani, F; Odriozola, JA; Ivanova, S
Chemcatchem, 12 (2020) 1177-1183

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A series of gold nanoparticles in the 4-40 nm range were prepared, immobilized on activated carbon and further tested, at low base concentration, in the catalytic oxidation of 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Gold particles size variation has no influence on HMF conversion but significantly affects product selectivity and carbon balance. This behavior is ascribed to the thermodynamically favorable oxygen reduction reaction on Au(100) faces. As the gold particle size decreases the Au(100)/Au(111) exposure ratio, estimated by using the van Hardeveld-Hartog model, increases as well as the FDCA selectivity. The smaller the gold particle size the smaller the 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) to FDCA ratio pointing to the gold size dependent behavior of the oxidation of the alcohol function of the HMF molecule.


Febrero, 2020 | DOI: 10.1002/cctc.201901742

5.69
Fotocatálisis Heterogénea: Aplicaciones

Role of Fe(III) in aqueous solution or deposited on ZnO surface in the photoassisted degradation of rhodamine B and caffeine

Tanji, Karim; Navio, J A; Martin-Gomez, A N; Hidalgo, M C; Jaramillo-Paez, C; Naja, Jamal; Hassoune, Hicham; Kherbeche, Abdelhak
Chemosphere, 241 (2020) 125009

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Iron (III) was incorporated, to the surface of a synthesized ZnO, using two nominal molar percentages of Fe (III): 1% and 5% Fe relative to ZnO. Samples dried and calcined at 200 °C and 400 °C for 2 h, were characterized by XRD, XPS, XRF, N2-adsorption-BET and (UV–vis)-DRS. Photocatalytic activities of the catalysts were assessed based on the degradation of rhodamine B (RhB) and caffeine (CAF) in aqueous solution under two irradiation conditions: UV and visible light illumination. Prior to the photocatalytic tests, the interaction of each one of the substrates with either Fe(III) or Fe(II) was studied in homogeneous medium under UV-illumination and oxygenated environment. It was found that Fe (III) can play an important role in homogeneous media in the photoassisted degradation, both of rhodamine B and caffeine, while Fe (II) does not exert a relevant role in the photoassisted degradation of the referred substrates. Fe–ZnO samples display similar or poorer performance than pure ZnO in the presence of UV light for both studied substrates. The phenomenon can be attributed to the formation of either goethite or ZnFe2O4 at the ZnO surface where the coupled Fe3+/Fe2+ can act as recombination centers for the photogenerated charges. On the contrary, all Fe–ZnO samples showed enhanced photocatalytic activity under visible illumination which seems to be independent of the iron content. In this context, the mechanisms for photoassisted degradation of both the substrates in homogeneous medium and photocatalytic degradation are discussed, as well as the role of Fe in the photodegradation processes.


Febrero, 2020 | DOI: 10.1016/j.chemosphere.2019.125009

7.09
Química de Superficies y Catálisis

Recent advances in selective oxidation of biomass-derived platform chemicals over gold catalysts

Megias-Sayago, C; Navarro-Jaen, S; Castillo, R; Ivanova, S
Current Opinion in Green and Sustainable Chemistry, 21 (2020) 50-55

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Gold is without a doubt the best known metal for chemical oxidation. The noblest of the noble metals gained its place because of its resistance to overoxidation, low temperature of operation, especially in gas-phase oxidation, and fairly good selectivity when required. The aim for sustainable development and the need for new technologies open the possibility to introduce new raw materials and new catalyst formulation. That is why new horizons appear in the otherwise uncertain future of gold catalysis. The old glory becomes now a glorious alternative, and this mini-review gives only a small example of it.


Febrero, 2020 | DOI: 10.1016/j.cogsc.2019.12.001

6.46
Fotocatálisis Heterogénea: Aplicaciones

Evaluation of Au–ZnO, ZnO/Ag2CO3 and Ag–TiO2 as Photocatalyst for Wastewater Treatment

Murcia, J.J.; Hernández, J.S.;Rojas, H.; Moreno-Cascante, J.; Sánchez-Cid, P.; Hidalgo, M.C.; Navío, J.A.; Jaramillo-Páez, C.
Topics in Catalysis, (2020)

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In this work series of photocatalysts based on ZnO modified by Au and Ag2CO3 addition and Ag–TiO2 materials were synthesized and evaluated in the treatment of handicrafts factories wastewater and water samples taken from a highly polluted river. In general, it was found that ZnO series were more effective in the bacteria elimination than the commonly used TiO2 semiconductor. It was also observed that the metal (Au, Ag) or silver carbonate addition significantly increases the photocatalytic activity of ZnO and TiO2. It was determined that the content of the metal or carbonate added is an important factor to take into account in order to obtain suitable efficiency in the photocatalytic process, so, for example in the case of the river water samples the increase of Ag2CO3 content from 1 to 5%, had a detrimental effect over the bacteria elimination. The optimal conditions for dyes photodegradation and bacteria elimination were found by using a response surface study and the Au–ZnO (1%) photocatalyst. From this study it was determined that even after recycling this material leads to obtain a removal percentage of these pollutants over than 94%.


Febrero, 2020 | DOI: 10.1007/s11244-020-01232-z

2.91
Química de Superficies y Catálisis

Modulation of the acidity of a vermiculite and its potential use as a catalytic support

Amaya, J; Bobadilla, L; Azancot, L; Centeno, M; Moreno, S; Molina, R
Journal of Materials Science, 55 (2020) 6482-6501

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The modulation and characterization of the acidity of a vermiculite were carried out, which was modified by delamination by means of hydrothermal and acid treatments with the subsequent incorporation of AlZr and AlCe species to modulate the acidity. The effect of these species was evaluated regarding the structural (XRD, XPS and IR), textural (N-2 sortometry) and acidity properties (NH3-TPD, NH3-DRIFTS and CO adsorption at low temperature). The catalytic performance was studied in the dehydration-dehydrogenation reactions of 2-propanol and the hydroconversion of decane, which generate important information about the acidity properties such as the type, number and strength of acidic sites. The correlation between the number, type and acid strength with the catalytic behavior allowed to establish the important effect regarding the nature of the mineral, its method of delamination and the nature of the incorporated cation, thus generating tools for controlled processes for the potentiation of the acidity of new supports from raw vermiculite.


Febrero, 2020 | DOI: 10.1007/s10853-020-04445-5

4.22
Química de Superficies y Catálisis

Monolithic stirrer reactor: The selective lactose oxidation in liquid phase over Au/Al2O3 nanostructured catalysts

Regenhardt, SA; Meyer, CI; Sanz, O; Sebastian, V; Ivanova, S; Centeno, MA; Odriozola, JA; Montes, M; Marchi, AJ; Garetto, TF
Molecular Catalysis, 481 (2020) 110219

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The performance of rotating metallic monolith stirrer reactor was studied for selective lactose oxidation in liquid phase at 65 degrees C, atmospheric pressure and with air as oxidant agent. The Au/Al(2)O(3)deposition on metallic substrates was performed by wash-coating, producing catalyst coating thicknesses between 5 and 20 mu m. Monoliths with different configuration (channel size between 0.36 and 1.06 mm) were used as stirrer blades in a batch reactor. Internal and external mass transfer limitations were observed during liquid phase lactose oxidation. For stirring rates equal or higher than 600 rpm there were no important external diffusional restrictions and this was also independent of the monolith configuration. Coating with thickness higher than 15 mu m presents loss of catalyst effectiveness due to internal diffusional restrictions. Excellent stability in the catalytic tests was obtained after three regeneration-reaction cycles. Regeneration was carried out at 400 degrees C in air flow. Gold particle size distribution in the monolith washcoat, determined by TEM before and after reaction, was homogeneous with a medium size of around 5 nm. This is in agreement with the very good reproducibility and stability obtained in the catalytic tests. After calcination at 500 degrees C, some sintering and a heterogeneous distribution of metal particle size was observed, accompanied by a slight loss in catalyst activity. It is concluded that metallic monolith stirrer reactors are a promising application for selective lactose oxidation in liquid phase.


Febrero, 2020 | DOI: 10.1016/j.mcat.2018.10.014

5.06
Fotocatálisis Heterogénea: Aplicaciones

Hybrid ZnO/Ag3PO4 photocatalysts, with low and high phosphate molar percentages

Martín-Gómez, A.N.;Navío, J.A.;Jaramillo-Páeza, C.;Sánchez-Cid, P.;Hidalgo, M.C.
Journal of Photochemistry and Photobiology A: Chemistry, (2020) 112196

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In this work, a previously optimized synthesized ZnO photocatalyst was modified with different molar percentages of Ag3PO4 through a facile in situ precipitation–deposition method and then characterized by different techniques (XRD, XRF, BET, UV–vis DRS, SEM, TEM and XPS). The incorporation of Ag3PO4 produces important changes in the light absorption properties with a significant absorbance in the visible region observed for ZnO modified with different amounts of Ag3PO4; the optical absorption intensity in the visible region of the coupled ZnO/Ag3PO4 increases as the molar percentages of Ag3PO4 increases, evidencing a clear dependence on the content of Ag3PO4. However, this work shows that the incorporation of Ag3PO4 in almost all cases reduces the photocatalytic capacity of ZnO, except when it is used in a specific percentage of 10 % and only being more active against rhodamine B and not on the Caffeine. SEM images and elemental mapping indicate that Ag3PO4 disperses very well in the ZnO particles, exhibiting an almost homogeneous distribution, showing zones with cumulus of Ag3PO4 (rich in P-Ag) in contact with ZnO-zones (rich in Zn). All the prepared photocatalysts were tested in the photocatalytic degradation of rhodamine B as a dye, and caffeine as a toxic and persistent emerging compound under UV and visible light illumination. It is reported that not only the ZnO:Ag3PO4 ratio is an important factor that influences the photocatalytic process of substrate degradation, but also the nature of the substrate has an important influence on the photocatalytic behavior of the materials under both UV and visible illumination. Thus, pristine Ag3PO4 showed high photocatalytic degradation for rhodamine B, while for caffeine negligible photocatalytic degradation was found in both the UV and visible regions. The thermal- and photo-stability of the coupled system was also studied. At least, for rhodamine B no loss of photocatalytic activity has been observed after five recycles although the mineralization degree progressively diminished along the recycles.


Febrero, 2020 | DOI: 10.1016/j.jphotochem.2019.112196

4.29
Química de Superficies y Catálisis

Catalytic Performance of Bulk and Al2O3-Supported Molybdenum Oxide for the Production of Biodiesel from Oil with High Free Fatty Acids Content

Navajas, A; Reyero, I; Jimenez-Barrera, E; Romero-Sarria, F; Llorca, J; Gandia, LM
Catalysts, 10 (2020) 158

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Non-edible vegetable oils are characterized by high contents of free fatty acids (FFAs) that prevent from using the conventional basic catalysts for the production of biodiesel. In this work, solid acid catalysts are used for the simultaneous esterification and transesterification with methanol of the FFAs and triglycerides contained in sunflower oil acidified with oleic acid. Molybdenum oxide (MoO3), which has been seldom considered as a catalyst for the production of biodiesel, was used in bulk and alumina-supported forms. Results showed that bulk MoO3 is very active for both transesterification and esterification reactions, but it suffered from severe molybdenum leaching in the reaction medium. When supported on Al2O3, the MoO3 performance improved in terms of active phase utilization and stability though molybdenum leaching remained significant. The improvement of catalytic performance was ascribed to the establishment of MoO3-Al2O3 interactions that favored the anchorage of molybdenum to the support and the formation of new strong acidic centers, although this effect was offset by a decrease of specific surface area. It is concluded that the development of stable catalysts based on MoO3 offers an attractive route for the valorization of oils with high FFAs content.


Febrero, 2020 | DOI: 10.3390/catal10020158

4.15
Fotocatálisis Heterogénea: Aplicaciones

Effect of synthesis pH on the physicochemical properties of a synthesized Bi2WO6 and the type of substrate chosen, in assessing its photo-catalytic activities

Jaramillo-Páez, C.; Navío, J.A.; Hidalgo, M.C.
Arabian Journal of Chemistry, 13 (2020) 431-443

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Crystalline orthorhombic Bi2WO6 powders were synthesized by a hydrothermal method from aqueous solutions of Bi(NO3)35H2O and Na2WO42H2O over a range of three selected pH values (2.0, 5.0 and 7.0), using NaOH as precipitating agent. The as-prepared catalysts were characterized by XRD, BET, FE-SEM, TEM, XPS and UV-vis spectroscopy. The effect of pH-synthesis on crystallinity,  morphologies, surface area and optical absorption properties, were investigated.
Although the pH has a marked influence on morphology, the nature of the precipitating agent (NaOH or TEA) also influences the morphology and surface structure composition, as it is observed in the present work. Three different probe molecules were used to evaluate the photocatalytic properties under two illumination conditions (UV and Visible): Methyl Orange and Rhodamine B were chosen as dye substrates and Phenol as a transparent substrate. The photo-catalytic activities are strongly dependent not only on the pH used in the synthesis but also on the nature of the chosen substrate in assessing the photo-catalytic activities. Results were compared with those obtained when using TiO2(P25, Evonik) in the same experimental conditions. The photocatalytic activity of one of the synthesised samples has been evaluated by exposing a mixture of Rhodamine B and Phenol in water, to different illumination conditions. Our results provide new evidences about the issue of whether dyes are suitable substrates to assess the activity of a photo-catalyst.


Enero, 2020 | DOI: 10.1016/j.arabjc.2017.05.014

5.17



2019


Química de Superficies y Catálisis

Dry Reforming of Ethanol and Glycerol: Mini-Review

Yu, J; Odriozola, JA; Reina, TR
Catalysts, 9 (2019) art. 1015

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Dry reforming of ethanol and glycerol using CO2 are promising technologies for H-2 production while mitigating CO2 emission. Current studies mainly focused on steam reforming technology, while dry reforming has been typically less studied. Nevertheless, the urgent problem of CO2 emissions directly linked to global warming has sparked a renewed interest on the catalysis community to pursue dry reforming routes. Indeed, dry reforming represents a straightforward route to utilize CO2 while producing added value products such as syngas or hydrogen. In the absence of catalysts, the direct decomposition for H-2 production is less efficient. In this mini-review, ethanol and glycerol dry reforming processes have been discussed including their mechanistic aspects and strategies for catalysts successful design. The effect of support and promoters is addressed for better elucidating the catalytic mechanism of dry reforming of ethanol and glycerol. Activity and stability of state-of-the-art catalysts are comprehensively discussed in this review along with challenges and future opportunities to further develop the dry reforming routes as viable CO2 utilization alternatives.


Diciembre, 2019 | DOI: 10.3390/catal9121015

3.52
Química de Superficies y Catálisis

Colombian metallurgical coke as catalysts support of the direct coal liquefaction

Rico, D; Agamez, Y; Romero, E; Centeno, MA; Odriozola, JA; Diaz, JD
Fuel, 255 (2019) 115748

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A Colombian metallurgical coke was modified in its surface chemistry and was used as support of iron sulfide catalysts for direct coal liquefaction. The modification was made by treatments with diluted oxygen and HNO3 at different conditions. Changes in surface chemistry were studied by determining the point of zero charge (PZC), the isoelectric point (IEP), thermogravimetric analysis (TGA), temperature programmed decomposition-mass spectrometry (TPD-MS), Diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) and nitrogen adsorption at 77 K. The results show that the materials obtained have a wide range of functional groups incorporated in a different proportion and quantity. The textural parameters indicate that treatment with diluted oxygen increases the surface area and incorporates micropores while the samples treated with HNO3 maintain the textural properties of the original material. The catalysts were also characterized by Raman spectroscopy. It was found that impregnation with the iron sulfide precursor does not significantly affect the Raman characteristics of the support. Additionally, XRD analysis shows smaller pyrite crystallites in the coke enriched with oxygenated groups of phenol and lactone indicating better dispersion of the active phase. The amount of oxygen chemisorbed per gram of catalyst shows that both, oxygen and nitric acid treatments, improve the relative dispersion of the active phase. It was found that the presence of the catalysts increases the conversion and yields towards oils and gases with respect to those of the tests without catalysts. Cokes modified by dilute oxygen gaseous treatment contain surface phenol and lactone groups and present the highest yield to oils.


Noviembre, 2019 | DOI: 10.1016/j.fuel.2019.115748

5.58
Química de Superficies y Catálisis

Effect of starch as binder in carbon aerogel and carbon xerogel preparation

Rodriguez, N; Agamez-Pertuz, YY; Romero, E; Diaz-Velasquez, JD; Odriozola, JA; Centeno, MA
Journal of Non-Crystalline Solids, 522 (2019) UNSP 119554

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Carbon aerogels and carbon xerogels were synthesized through resorcinol - formaldehyde polycondensation using Na2CO3 as catalyst. The effect of soluble starch introduction in the organic gel preparation on the porous surface properties of these materials was studied. The role of the drying process of the organic gels on the changes in the surface and structural properties of these materials after the addition of soluble starch is discussed. The presence of starch in the prepared carbon xerogels results in the development of microporosity while maintaining the characteristic mesoporosity of carbon xerogels. The Brunauer - Emmett -Teller (BET) surface area increases from 309 m(2)/g in carbon xerogel without soluble starch until 685 m(2)/g when 10% of soluble starch is added. The R- value and average crystallite lattice parameters, inter-layer spacing, crystallite height, crystallite diameter and the average number of aromatic layers per carbon crystallite are discussed in function of drying step and presence of soluble starch. The surface properties were also studied by Raman and DRIFT spectroscopies.


Octubre, 2019 | DOI: 10.1016/j.jnoncrysol.2019.119554

2.93
Fotocatálisis Heterogénea: Aplicaciones

Comparison of the effects generated by the dry-soft grinding and the photodeposition of Au and Pt processes on the visible light absorption and photoactivity of TiO2

Galeano, L; Valencia, S; Marin, JM; Restrepo, G; Navio, JA; Hidalgo, MC
Materials Research Express, 6 (2019) 1050d9

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The influence of dry-soft grinding and photodeposition of gold (Au) or platinum (Pt) in the improvement of the photoactivity of TiO2 synthesized by an integrated sol-gel and solvothermal method was studied. TiO2 was modified by a dry-soft grinding process in a planetary ball mill (TiO2(G)). Subsequently, Au or Pt particles were photodeposited in both unmodified TiO2 and TiO2(G) obtaining Au-TiO2, Pt-TiO2, Au-TiO2(G), and Pt-TiO2(G) materials. The photoactivity of the materials was evaluated in the phenol photodegradation under simulated solar radiation. Pt-TiO2 showed the greatest degree of photoactivity improvement in comparison with TiO2 and TiO2-P25. The dry-soft grinding process led to a high photocatalytic activity of TiO2(G) that was similar to Pt-TiO2 activity as consequence of a slight increase in the crystallinity in TiO2(G) due to an additional anatase formation in comparison with TiO2. However, further photocatalytic improvement in TiO2(G) were not achieved with the addition of Au or Pt. Therefore, the dry-soft grinding treatment and noble metal deposition led to similar improvements in the photocatalytic activity of TiO2 for phenol oxidation.


Octubre, 2019 | DOI: 10.1088/2053-1591/ab4316

1.93
Química de Superficies y Catálisis

The Success Story of Gold-Based Catalysts for Gas- and Liquid-Phase Reactions: A Brief Perspective and Beyond

Price, CAH; Pastor-Perez, L; Ivanova, S; Reina, TR; Liu, J
Frontiers in Chemistry, 7 (2019) 691

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Gold has long held the fascination of mankind. For millennia it has found use in art, cosmetic metallurgy and architecture; this element is seen as the ultimate statement of prosperity and beauty. This myriad of uses is made possible by the characteristic inertness of bulk gold; allowing it to appear long lasting and above the tarnishing experienced by other metals, in part providing its status as the most noble metal.


Octubre, 2019 | DOI: 10.3389/fchem.2019.00691

3.69
Fotocatálisis Heterogénea: Aplicaciones

Extraordinary visible photocatalytic activity of a Co0.2Zn0.8O system studied in the Remazol BB oxidation

KarimTanji; J.A.Navio; Jamal Naja; M.C.Hidalgo; Abdellah Chaqroune; C.Jaramillo-Páez; Abdelhak Kherbeche
Journal of Photochemistry and Photobiology A: Chemistry, 382 (2019) 111877

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Nanoparticles of CoxZn1-xO system with a nominal composition of x=0.2 were synthesized by the Solution Combustion Method (SCM). Structural and morphological studies as well as the chemical composition of the material were widely investigated by different techniques. Photocatalytic activity under UV and Visible illumination was studied by means of the Remazol Brilliant Blue dye (RBB) oxidation reaction. The effect of different experimental parameters, such as the initial dye concentration, photocatalyst mass, pH or hydrogen peroxide concentration on the RBB discoloration under UV irradiation was studied. Optimal experimental conditions were found to be a photocatalyst mass of 1 g.L-1, dye concentration of 20 mg.L-1 and solution pH of 11. Hydrogen peroxide addition was found to have no effect in the photocatalytic behavior of the material in the range of concentration studied (0 to 6•10-4 M). The optimal parameters were chosen to investigate the degradation of RBB under UV-illumination and just visible illumination. It was observed that the UV-photocatalytic property of pristine ZnO for the RBB removal was scarcely improved after cobalt-incorporation, whereas the effect of cobalt incorporation into ZnO greatly enhanced the RBB conversion under visible illumination. Even more interesting is that, under same experimental conditions, the visible efficiency of the Co-ZnO system is the same that the one showed under UV illumination, i.e. the system does not loose efficiency when illuminated only with visible light.


Septiembre, 2019 | DOI: 10.1016/j.jphotochem.2019.111877

3.31
Química de Superficies y Catálisis

Montmorillonite-stabilized gold nanoparticles for nitrophenol reduction

Chenouf, M; Megias-Sayago, C; Ammari, F; Ivanova, S; Centeno, MA; Odriozola, JA
Comptes Rendus Chimie, 22 (2019) 621-627

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Two gold-based catalysts were obtained by Au chemical reduction of the HAuCl(4 )precursor. The resulting nanoparticles were stabilized and immobilized on montmorillonite (Mt) and montmorillonite-ceria (Mt/CeO2). All prepared catalysts were active in 4-nitrophenol to aminophenol reduction at room temperature. Synergy between montmorillonite and ceria is postulated in such a way that the montmorillonite phase hinders particle growth either by influencing the nucleation behavior of gold or by increasing the number of nucleation sites and raising the overall dispersion. The role of the ceria support, on the other hand, may be associated with the 4-NP adsorption at the ceria-gold interface, stabilizing the reaction intermediate and hence lowering the activation barrier for the reduction of 4-NP to 4-AP. 


Septiembre, 2019 | DOI: 10.1016/j.crci.2019.07.005

2.22
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Support effects on NiO-based catalysts for the oxidative dehydrogenation (ODH) of ethane

Delgado, D; Sanchis, R; Cecilia, JA; Rodriguez-Castellon, E; Caballero, A; Solsona, B; Nieto, JML
Catalysis Today, 333 (2019) 10-16

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We report on the effect of NiO-support interactions on the chemical nature of Ni species in a series of supported NiO catalysts for the ODH of ethane. SiO2, TiO2-anatase, a high surface area TiO2 and a porous clay hetero-structure (PCH) with TiO2 and SiO2 pillars were used as supports, which led to a selectivity to ethylene in the range 30-90% over supported NiO catalysts. The catalysts were characterized by means of XRD, N-2-Adsorption, H-2-TPR, XPS and in situ (under H-2 reductive atmosphere) and ex situ XAS spectroscopy. The catalytic performance of supported materials is discussed in terms of their reducibility and specific reduction kinetics, but also taking into account the specific chemical nature of Ni species on each catalyst. The influence of the particle size and the presence of Ni and O vacancies on the catalytic performance in the ODH of ethane is inferred.


Agosto, 2019 | DOI: 10.1016/j.cattod.2018.07.010

5.83
Química de Superficies y Catálisis

Carbon Supported Gold Nanoparticles for the Catalytic Reduction of 4-Nitrophenol

Molina, HR; Munoz, JLS; Leal, MID; Reina, TR; Ivanova, S; Gallego, MNC; Odriozola, JA
Frontiers in Chemistry, 7 (2019) 548

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This work is a detailed study on how to optimize gold colloids preparation and their deposition to very different in nature carbon materials. The change of the continuous phase and its dielectric constant is used to assure the good dispersion of the hydrophilic/hydrophobic carbons and the successful transfer of the preformed small size colloids to their surface. The sintering behavior of the particles during the calcination step is also studied and the optimal conditions to reduce to a minimum the particle size increase during the protecting agent removal phase are found. The as prepared catalysts have been tested in a relevant reaction in the field of environmental catalysis such as the reduction of 4-nitrophenol leading to promising results. Overall, this work proposes an important methodology to follow when a carbonaceous material are selected as catalyst supports for green chemistry reactions.


Agosto, 2019 | DOI: 10.3389/fchem.2019.00548

3.69
Química de Superficies y Catálisis

Au/Al2O3 - Efficient catalyst for 5-hydroxymethylfurfural oxidation to 2,5-furandicarboxylic acid

Megias-Sayago, C; Lolli, A; Ivanova, S; Albonetti, S; Cavani, F; Odriozola, JA
Catalysis Today, 333 (2019) 169-175

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The catalytic activity of a simple Au/Al2O3 catalytic system prepared by the direct anionic exchange (DAE) method was evaluated in the selective 5-hydroxymethylfurfural (HMF) oxidation under mild conditions, using molecular oxygen as the oxidant. The influence of the HMF/NaOH ratio and reaction time on product yield and distribution were studied and discussed in detail. Extremely high activity and selectivity were observed in mild conditions, with 99% of 2,5-furandicarboxylic acid (FDCA) production at full HMF conversion after 4 h with the use of only 4 equivalents of NaOH at 70 degrees C. Catalyst viability and stability were verified by repeating the cycle up to five times. Changes in the nature of the support were also contemplated by introducing some ceria fraction, i.e. 20 wt%.


Agosto, 2019 | DOI: 10.1016/j.cattod.2018.04.024

5.83
Química de Superficies y Catálisis

Noble Metal Supported on Activated Carbon for "Hydrogen Free" HDO Reactions: Exploring Economically Advantageous Routes for Biomass Valorisation

Jin, W; Santos, JL; Pastor-Perez, L; Gu, S; Centeno, MA; Reina, TR
Chemcatchem (2019) 4434-4441

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An innovative route for bio‐compounds upgrading via “hydrogen‐free” hydrodeoxygenation (HDO) is proposed and evaluated using guaiacol as a model compound in a high‐pressure batch reactor. Experimental results showed that noble metal supported on activated carbon catalysts are able to conduct tandem multiple steps including water splitting and subsequent HDO. The activity of Ru/C catalyst is superior to other studied catalysts (i. e. Au/C, Pd/C and Rh/C) in our water‐only HDO reaction system. The greater dispersion and smaller metal particle size confirmed by the TEM micrographs accounts for the better performance of Ru/C. This material also presents excellent levels of stability as demonstrated in multiple recyclability runs. Overall, the proposed novel approach confirmed the viability of oxygenated bio‐compounds upgrading in a water‐only reaction system suppressing the need of external H2 supply and can be rendered as a fundamental finding for the economical biomass valorisation to produce added value bio‐fuels.


Agosto, 2019 | DOI: 10.1002/cctc.201900841

4.85
Química de Superficies y Catálisis

Size-tailored Ru nanoparticles deposited over gamma-Al2O3 for the CO2 methanation reaction

Navarro-Jaen, S; Navarro, JC; Bobadilla, LF; Centeno, MA; Laguna, OH; Odriozola, JA
Applied Surface Science, 483 (2019) 750-761

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By means of the polyol method, a series of 5 wt% Ru/Al2O3 catalysts was synthesized controlling the particle size of the ruthenium species. The physico-chemical characterization demonstrated the successful particle size control of the Ru species, in such a way that higher the Ru/PVP ratio, higher the Ru particle size. Moreover, there are evidences that suggest preferential growth of the RuO2 clusters depending on the Ru/PVP ratio. Regarding the catalytic activity during the CO2 methanation, the total conversion and the CH4 yield increased with the particle size of Ru. Nevertheless, a considerable enhancement of the catalytic performance of the most active system was evidenced at 4 bar, demonstrating the improvement of the thermodynamics (superior total conversion) and kinetics (superior reaction rate) of the CO2 methanation at pressures above the atmospheric one. Finally, the in situ DRIFTS study allowed to establish that CO2 was dissociated to CO* and O* species on the metallic Ru particles, followed by the consecutive hydrogenation of CO* towards CHO*, CH2O*, CH3O*, and finally CH4 molecules, which were further desorbed from the catalyst. Thus from the mechanistic point of view, a suitable particle size of the Ru nanoparticles along with the high-pressure effects results in the enhancement of the availability of hydrogen and consequently in the formation of CHxO species that enhance the cleavage of the C-O bond, which is the rate-determining step of the overall CO2 methanation process.


Julio, 2019 | DOI: 10.1016/j.apsusc.2019.03.248

6.18
Química de Superficies y Catálisis

Au/CeO2-ZnO/Al2O3 as Versatile Catalysts for Oxidation Reactions: Application in Gas/Liquid Environmental Processes

Megias-Sayago, C; Reina, TR; Ivanova, S; Odriozola, JA
Frontiers in Chemistry, 7 (2019) art. 504

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The present work showcases the versatility of nanogold systems supported on Zn-doped ceria when applied in two important environmental processes, the total CO oxidation, and the liquid phase oxidation of glucose to gluconic acid. In the CO oxidation the suitability of these materials is clearly demonstrated achieving full conversions even at sub-ambient conditions. Regarding the glucose oxidation our materials display high conversion values (always over 50%) and very importantly full or almost full selectivity toward gluconic acid-an added value platform chemical in the context of biomass upgrading routes. The key factors controlling the successful performance on both reactions are carefully discussed and compared to previous studies in literature. To our knowledge this is one of the very few works in catalysis by gold combining liquid and gas phase reactions and represents a step forward in the flexible behavior of nano gold catalysts.


Julio, 2019 | DOI: 10.3389/fchem.2019.00504

3.69
Química de Superficies y Catálisis - Reactividad de Sólidos

Influence of the preparation method in the metal-support interaction and reducibility of Ni-Mg-Al based catalysts for methane steam reforming

Azancot, L; Bobadilla, LF; Santos, JL; Cordoba, JM; Centeno, MA; Odriozola, JA
International Journal of Hydrogen Energy, 44 (2019) 19827-19840

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Ni-Mg-Al based catalysts were prepared using different preparation methods (impregnation, impregnation-coprecipitation and coprecipitation) and tested in steam reforming of methane. The differences observed in catalytic activity were directly correlated to the physicochemical properties and the different degree of Ni-Mg-Al interaction. The reducibility results showed that the catalyst prepared by the impregnation-coprecipitation method presented the most optimal metal-support interaction to reduce the NiO preserving the Ni-0 particles highly dispersed on the support surface. These results demonstrate that the structure and catalytic performance of Ni-Mg-Al based catalysts can be tuned by controlling the metal-support interaction through of the preparation method.


Julio, 2019 | DOI: 10.1016/j.ijhydene.2019.05.167

4.94
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Comprehensive Experimental and Theoretical Study of the CO plus NO Reaction Catalyzed by Au/Ni Nanoparticles

Kyriakou, G; Marquez, AM; Holgado, JP; Taylor, MJ; Wheatley, AEH; Mehta, JP; Sanz, JF; Beaumont, SK; Lambert, RM
ACS Catalysis, 9 (2019) 4919-4929

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The catalytic and structural properties of five different nanoparticle catalysts with varying Au/Ni composition were studied by six different methods, including in situ X-ray absorption spectroscopy and density functional theory (DFT) calculations. The as-prepared materials contained substantial amounts of residual capping agent arising from the commonly used synthetic procedure. Thorough removal of this material by oxidation was essential for the acquisition of valid catalytic data. All catalysts were highly selective toward N-2 formation, with 50-50 Au:Ni material being best of all. In situ X-ray absorption near edge structure spectroscopy showed that although Au acted to moderate the oxidation state of Ni, there was no clear correlation between catalytic activity and nickel oxidation state. However, in situ extended X-ray absorption fine structure spectroscopy showed a good correlation between Au Ni coordination number (highest for Ni50Au50) and catalytic activity. Importantly, these measurements also demonstrated substantial and reversible Au/Ni intermixing as a function of temperature between 550 degrees C (reaction temperature) and 150 degrees C, underlining the importance of in situ methods to the correct interpretation of reaction data. DFT calculations on smooth, stepped, monometallic and bimetallic surfaces showed that N + N recombination rather than NO dissociation was always rate-determining and that the activation barrier to recombination reaction decreased with increased Au content, thus accounting for the experimental observations. Across the entire composition range, the oxidation state of Ni did not correlate with activity, in disagreement with earlier work, and theory showed that NiO itself should be catalytically inert. Au-Ni interactions were of paramount importance in promoting N + N recombination, the rate-limiting step.


Junio, 2019 | DOI: 10.1021/acscatal.8b05154

12.35
Fotocatálisis Heterogénea: Aplicaciones

Preparation, characterization and photocatalytic degradation of Rhodamine B dye over a novel Zn3(PO4)2/BiPO4 catalyst

Naciri,Y.;Chennah,A.;Jaramillo-Páez,C.;Navío,J.A.;Bakiz, B.;Taoufyq,A.;Ezahri,M.;Villain,S.;Guinneton,F.;Benlhachemi,A.
Journal of Environmental Chemical Engineering, 7 (2019) 103075

Show abstract ▽

In this work, a facile method was used to synthesize the Zn3(PO4)2/BiPO4 composite photocatalysts with different Bi contents followed by heat treatment at 900 °C for 3 h. The as-prepared samples were studied by a variety of characterization techniques including X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) combined with energy dispersive X-ray diffraction (EDX), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). The UV–vis spectroscopy was used to analyze the evolution of Rhodamine B discoloration in presence of the synthesized phosphate photocatalysts. The XRD, SEM-EDX, TEM, DRS and XPS analyses confirmed the formation of heterojunction structure between both materials, during the process of co-precipitation and ulterior heat treatment. The photocatalytic tests showed that photocatalytic ability of the 70% Bi-Zn3(PO4)2 composites was higher than that of pure Zn3(PO4)2 and BiPO4 after 1 h of UV-illumination. The obviously enhanced photocatalytic activity of the 70% Bi-Zn3(PO4)2 sample could be mainly attributed to the formation of the heterojunction, accelerating the separation of photogenerated charge carriers. A plausible mechanism of the photocatalytic degradation of RhB on Zn3(PO4)2/BiPO4 composites is proposed. The reduction in the Chemical Oxygen Demand (COD) revealed the mineralization of dye along with color removal. Thus, it can be suggested that the 70% Bi-Zn3(PO4)2 can serve as a promising photocatalyst in the degradation of organic contaminants under UV light.


Junio, 2019 | DOI: 10.1016/j.jece.2019.103075

4.30
Química de Superficies y Catálisis

Phosphate-type supports for the design of WGS catalysts

Navarro-Jaen, S; Romero-Sarria, F; Centeno, MA; Laguna, OH; Odriozola, JA
Applied Catalysis B-Environmental, 244 (2019) 853-862

Show abstract ▽

The importance of water availability during the WGS reaction has been extensively reported. Thus, the search of new supports able to interact with the water molecule is of great importance. In this work, a series of phosphate type supports containing Ce, Ca and Ti have been studied, demonstrating that water interaction with the support is closely related to the textural properties, surface composition and crystal structure of the solids. Additionally, DRIFTS results showed that different interaction mechanisms with the water molecule occur depending on the support. The system containing Ca dissociates the water molecule and interacts with it via the phosphate and Ca2+ ions. However, the Ce systems retain water in its molecular form, which interacts with the solids via hydrogen bonding with the phosphate groups. On the other hand, the Ti system experiences a loss of phosphorous, presenting a low degree of interaction with the water molecule. Additionally, the behavior of the supports with water has been successfully related to the WGS catalytic activity of the corresponding phosphate supported Pt catalysts.


Mayo, 2019 | DOI: 10.1016/j.apcatb.2018.12.022

16.68
Fotocatálisis Heterogénea: Aplicaciones

Coupling of WO3 with anatase TiO2 sample with high {001} facet exposition: Effect on the photocatalytic properties

Lara, M.A.; Jaramillo-Páez, C.; Navío, J.A.; Sánchez-Cid, P.; Hidalgo, M.C.
Catalysis Today, 328 (2019) 142-148

Show abstract ▽

A highly faceted {001} TiO2 catalyst was hydrothermally synthesized by using Ti(IV)-isopropoxide precursor with aqueous HF addition. WO3 was synthesized by following a reported method. Coupled TiO2-WO3 samples were synthesized by adding the corresponding amount of WO3 to fluorinated TiO2 gel followed by a hydrothermal treatment. Additionally the synthesized systems were characterized by using X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS) and N2-adsorption (BET) for specific surface area determination. The photocatalytic activity of the single and coupled oxides was measured by means of three model reactions: the photo-oxidation of phenol (as a colourless substrate) and methyl orange (as a dye) and the photoreduction of Cr(VI) as K2Cr2O7. The coupling of WO3 with a highly faceted {001} TiO2 makes it possible to optimize the photocatalytic properties of the faceted material. In fact, {001} faceted TiO2 by itself presents a substantial improvement with respect to commercial TiO2(P25), as it can implement its photoactivity after the incorporation of WO3 with promising results, which can reduce the limitations of TiO2 in terms of its photoactivity, taking advantage of a higher percentage of solar radiation.


Mayo, 2019 | DOI: 10.1016/j.cattod.2018.11.012

5.83
Fotocatálisis Heterogénea: Aplicaciones

BixTiyOz-Fe multiphase systems with excellent photocatalytic performance in the visible

Zambrano, P.; Navío, J.A.; Hidalgo, M.C.
Catalysis Today, 328 (2019) 136-141

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New photocatalysts based on bismuth titanates doped with iron with outstanding visible photocatalytic activity were prepared by a facile hydrothermal method followed by incipient wetness impregnation. The starting material was composed by three phases; majority of Bi20TiO32 closely interconnected to Bi4Ti3O12 and amorphous TiO2. Fe doping increased the already very high visible activity of the original material. The high visible activity showed by these materials could be ascribed to a combination of several features; i.e. low band gap energy value (as low as 1.78 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. Fe doping could be acting as bonding paths for the bismuth titanates phases, and the amount of Fe on the surface was found to be a crucial parameter on the photocatalytic activity of the materials. Visible activity of the best photocatalyst was superior to UV-Activity of commercial TiO2 P25 used as reference in same experimental conditions.


Mayo, 2019 | DOI: 10.1016/j.cattod.2018.11.032

5.83
Fotocatálisis Heterogénea: Aplicaciones

UV and visible-light driven photocatalytic removal of caffeine using ZnO modified with different noble metals (Pt, Ag and Au)

Vaiano, V.; Jaramillo-Paez, C.A.; Matarangolo, M.; Navío, J.A.; Hidalgo, M.C.
Materials Research Bulletin, 112 (2019) 251-260

Show abstract ▽

In this work, ZnO photocatalyst was modified with different noble metals (Pt, Ag and Au) through photodeposition method and then characterized by different techniques (XRD, XRF, BET, UV–vis DRS, FESEM, and XPS). The addition of noble metals produces important changes in the light absorption properties with a significant absorbance in the visible region due to the existence of surface plasmon resonance (SPR) observed at about 450 nm and 550 nm for ZnO modified with Ag and Au, respectively. The morphology of the samples was studied by TEM and the size ranges of the different metals were estimated. Noble metal nanoparticles were in every case heterogeneously deposited on the larger ZnO particles. All the prepared photocatalysts were tested in the photocatalytic removal of caffeine (toxic and persistent emerging compound) under UV and visible light irradiation. It was observed an enhancement of photocatalytic caffeine removal from aqueous solutions under UV light irradiation with the increase of metal content (from 0.5 to 1 wt %) for ZnO modified with Ag and Au (Ag/ZnO and Au/ZnO). In particular, Ag/ZnO and Au/ZnO with higher Ag and Au content (1 wt %) allowed to achieve the almost complete caffeine degradation after only 30 min and a TOC removal higher than 90% after 4 h of UV light irradiation. These two photocatalysts were investigated also under visible light irradiation and it was found that their photocatalytic performances were strongly enhanced in presence of visible light compared to unmodified ZnO. In particular, Ag/ZnO photocatalyst was able to reach the complete caffeine degradation and a TOC removal of about 70% after 4 h of visible light irradiation.


Abril, 2019 | DOI: 10.1016/j.materresbull.2018.12.034

4.02
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Effect of support oxygen storage capacity on the catalytic performance of Rh nanoparticles for CO2 reforming of methane

Yentekakis, IV; Goula, G; Hatzisymeon, M; Betsi-Argyropoulou, I; Botzolaki, G; Kousi, K; Kondarides, DI; Taylor, MJ; Parlett, CMA; Osatiashtiani, A; Kyriakou, G; Holgado, JP; Lambert, RM
Applied Catalysis B-Environmental, 243 (2019) 490-501

Show abstract ▽

The effects of the metal oxide support on the activity, selectivity, resistance to carbon deposition and high temperature oxidative aging on the Rh-catalyzed dry reforming of methane (DRM) were investigated. Three Rh catalysts supported on oxides characterized by very different oxygen storage capacities and labilities (gamma-Al2O3, alumina-ceria-zirconia (ACZ) and ceria-zirconia (CZ)) were studied in the temperature interval 400-750 degrees C under both integral and differential reaction conditions. ACZ and CZ promoted CO2 conversion, yielding CO enriched synthesis gas. Detailed characterization of these materials, including state of the art XPS measurements obtained via sample transfer between reaction cell and spectrometer chamber, provided clear insight into the factors that determine catalytic performance. The principal Rh species detected by post reaction XPS was Rh, its relative content decreasing in the order Rh/CZ(100%) > Rh/ACZ(72%) > Fth/gamma Al2O3(55%). The catalytic activity followed the same order, demonstrating unambiguously that Rh is indeed the key active site. Moreover, the presence of CZ in the support served to maintain Rh in the metallic state and minimize carbon deposition under reaction conditions. Carbon deposition, low in all cases, increased in the order Rh/CZ < Rh/ACZ < Rh/gamma-Al2O3 consistent with a bi-functional reaction mechanism whereby backspillover of labile lattice O2- contributes to carbon oxidation, stabilization of Rh and modification of its surface chemistry; the resulting O vacancies in the support providing centers for dissociative adsorption of CO2. The lower apparent activation energy observed with CZ-containing samples suggests that CZ is a promising support component for use in low temperature DRM.


Abril, 2019 | DOI: 10.1016/j.apcatb.2018.10.048

16.68
Fotocatálisis Heterogénea: Aplicaciones

Differences in the Catalytic Behavior of Au-Metalized TiO2 Systems During Phenol Photo-Degradation and CO Oxidation

Oscar H. Laguna; Julie J. Murcia; Hugo Rojas; Cesar Jaramillo-Paez; Jose A. Navío; Maria C. Hidalgo
Catalysts, 9 (2019) 331

Show abstract ▽

For this present work, a series of Au-metallized TiO2 catalysts were synthesized and characterized in order to compare their performance in two different catalytic environments: the phenol degradation that occurs during the liquid phase and in the CO oxidation phase, which proceeds the gas phase. The obtained materials were analyzed by different techniques such as XRF, SBET, XRD, TEM, XPS, and UV-Vis DRS. Although the metallization was not totally efficient in all cases, the amount of noble metal loaded depended strongly on the deposition time. Furthermore, the differences in the amount of loaded gold were important factors influencing the physicochemical properties of the catalysts, and consequently, their performances in the studied reactors. The addition of gold represented a considerable increase in the phenol conversion when compared with that of the TiO2, despite the small amount of noble metal loaded. However, this was not the case in the CO oxidation reaction. Beyond the differences in the phase where the reaction occurred, the loss of catalytic activity during the CO oxidation reaction was directly related to the sintering of the gold nanoparticles.


Abril, 2019 | DOI: 10.3390/catal9040331

3.52
Química de Superficies y Catálisis

Operando Spectroscopic Evidence of the Induced Effect of Residual Species in the Reaction Intermediates during CO2 Hydrogenation over Ruthenium Nanoparticles

Navarro-Jaen, S; Szego, A; Bobadilla, LF; Laguna, OH; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Chemcatchem, 11 (2019) 2063-2068

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In this work, we present a highly active catalyst based on Ru nanoparticles dispersed on alumina, which showed an unexpected activity for CO2 methanation. This exceptional catalytic behavior was attributed to the presence of residual species that remained on the surface after synthesis. Furthermore, through Operando DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) measurements it was demonstrated that these remaining species provoked an induced effect on the nature of the surface intermediates spectroscopically observed, and consequently on their mechanistic role during the pathway of the CO2 hydrogenation to methane.


Abril, 2019 | DOI: 10.1002/cctc.201900101

4.85
Química de Superficies y Catálisis

Powder and Nanotubes Titania Modified by Dye Sensitization as Photocatalysts for the Organic Pollutants Elimination

Murcia, JJ; Avila-Martinez, EG; Rojas, H; Cubillos, J; Ivanova, S; Penkova, A; Laguna, OH
Nanomaterials, 9 (2019) 517

Show abstract ▽

In this study, titanium dioxide powder obtained by the sol-gel method and TiO2 nanotubes, were prepared. In order to increase the TiO2 photoactivity, the powders and nanotubes obtained were modified by dye sensitization treatment during the oxide synthesis. The sensitizers applied were Quinizarin (Q) and Zinc protoporphyrin (P). The materials synthesized were extensively characterized and it was found that the dye sensitization treatment leads to modify the optical and surface properties of Titania. It was also found that the effectiveness of the dye-sensitized catalysts in the phenol and methyl orange (MO) photodegradation strongly depends on the dye sensitizer employed. Thus, the highest degradation rate for MO was obtained over the conventional Q-TiO2 photocatalyst. In the case of the nanotubes series, the most effective photocatalyst in the MO degradation was based on TiO2-nanotubes sensitized with the dye protoporfirin (ZnP). Selected catalysts were also tested in the phenol and MO photodegradation under visible light and it was observed that these samples are also active under this radiation.


Abril, 2019 | DOI: 10.3390/nano9040517

4.32
Fotocatálisis Heterogénea: Aplicaciones

Synthesis of sol-gel pyrophyllite/TiO2 heterostructures: Effect of calcination temperature and methanol washing on photocatalytic activity

El Gaidoumi, A.; Doña Rodríguez, J.M.; Pulido Melián, E.; González-Díaz, O.M.; Navío Santos, J.M.; El Bali, B.; Kherbeche, A.
Surfaces and Interfaces, 14 (2019) 19-25

Show abstract ▽

We successfully synthesized an efficient photoactive pyrophyllite/TiO2 heterostructures using a sol-gel route at ambient temperature. The samples were prepared by exfoliation of a pyrophyllite layered-type clay by TiO2. The prepared samples exhibited strong photocatalytic activity for the degradation of phenol. The heterostructure PTi750 (SBET = 16.58 m2/g) calcined at 750 °C, in which the mixed phases of anatase and rutile exist (52.2% anatase/10.7% rutile), showed the highest photocatalytic activity against commercial TiO2Aeroxide P25. The methanol washed PTi750 was 5 times faster than the corresponding unwashed sample; phenol was totally degraded with a TOC reduction of 89.2%. The materials have been characterized by: X-ray diffraction (XRD), Diffuse reflectance UV–vis spectrophotometry (UV–Vis DRS), scanning electron microscopy (SEM) and BET specific surface area.


Marzo, 2019 | DOI: 10.1016/j.surfin.2018.10.003

3.72
Química de Superficies y Catálisis

Promoting effect of CeO2, ZrO2 and Ce/Zr mixed oxides on Co/gamma-Al2O3 catalyst for Fischer-Tropsch synthesis

Garcilaso, V; Barrientos, J; Bobadilla, LF; Laguna, OH; Boutonnet, M; Centeno, MA; Odriozola, JA
Renewable Energy, 132 (2019) 1141-1150

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A series of cobalt-based catalysts have been synthesized using as support gamma-Al2O3 promoted by ceria/zirconia mixed oxides with a variable Ce/Zr molar ratio. The obtained catalysts demonstrated oxide promotion results in the protection of the major textural properties, especially for Zr-rich solids. Reducibility of cobalt species was enhanced by the presence of mixed oxides. The chemical composition of the oxide promoter influenced not only physicochemical properties of final catalysts but also determined their performance during the reaction. In this sense, Zr-rich systems presented a superior catalytic performance both in total conversion and in selectivity towards long chain hydrocarbons. The observed Zr-promotion effect could be explained by two significant contributions: firstly, the partial inhibition of Co-Al spinel compound formation by the presence of Zr-rich phases which enhances the availability of Co actives site and secondly, Zr-associate acidic sites promote higher hydrocarbons selectivity.


Marzo, 2019 | DOI: 10.1016/j.renene.2018.08.080

6.27
Fotocatálisis Heterogénea: Aplicaciones

Catalytic Efficiency of Cu-Supported Pyrophyllite in Heterogeneous Catalytic Oxidation of Phenol

El Gaidoumi, A.; Doña-Rodríguez, J.M.; Pulido Melián, E.; González-Díaz, O.M.; Navío, J.A.; El Bali, B.; Kherbeche, A.
Arabian Journal for Science and Engineering, (2019) 1-13

Show abstract ▽

The copper-impregnated pyrophyllite (Cu/RC) was prepared and used as catalyst in catalytic wet peroxide oxidation (CWPO) of phenol. The catalyst was prepared by impregnation of copper (2.5 wt%) into pyrophyllite-type clay and characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. The optimum operation conditions for CWPO of phenol over Cu/RC were determined by investigating the effects of pH, temperature, catalyst amount, and hydrogen peroxide concentration. Stability of the Cu/RC catalyst and toxicity of treated solution were studied, by measuring the copper concentration leached out from the catalyst and the inhibition of Vibrio fischeri bacteria bioluminescence, respectively. The probable degradation mechanism of phenol over Cu/RC was considered by HPLC analysis. The obtained results showed that Cu/RC achieved highest activity (total phenol degradation and 80% TOC reduction) and detoxification with remarkable low copper leaching concentration (0.006 mg\,L−1)mg\,L−1) at optimized conditions (pH == 3, T=50∘T=50∘C, 2 g\,L−1g\,L−1 catalyst amount, 50 mg L−1L−1phenol concentration and 7.45 mmol\,L−1mmol\,L−1 hydrogen peroxide concentration during 4 h). Meanwhile, few intermediates with low concentration were observed by the HPLC analysis for the CWPO of phenol. The Cu/RC catalyst showed a good activity after five successive runs (88% of degradation and 73% mineralization) at optimized conditions.


Febrero, 2019 | DOI: 10.1007/s13369-019-03757-2

1.71
Fotocatálisis Heterogénea: Aplicaciones

Photodegradation of 2,4-dichlorophenoxyacetic acid over TiO2(B)/anatase nanobelts and Au-TiO2(B)/anatase nanobelts

Chenchana, A.; Nemamcha, A.; Moumeni, H.; Doña Rodríguez, J.M.; Araña, J.; Navío, J.A.; González Díaz, O.; Pulido Melián, E.
Applied Surface Science, 467-468 (2019) 1076-1087

Show abstract ▽

In this work, novel TiO2-based nanobelts with various phases were synthesized: biphasic TiO2(B)/anatase, pure TiO2(B) and pure anatase. These catalysts were obtained via hydrothermal reaction using two nanoparticulated TiO2 photocatalysts as precursors: Aeroxide TiO2 P25 (P25) and TiO2 synthesized via a sol-gel process (SG). In addition, the surface of the photocatalysts was modified with gold using a photodeposition method. A characterization study of the different photocatalysts was performed with X-ray diffraction analysis (XRD), UV–Vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), X-ray photoelectron spectrum analysis (XPS) and Brunauer-Emmett-Teller measurements (BET). The photocatalytic reaction of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated under UVA irradiation. A toxicity analysis was performed with the marine bioluminescent bacteria Vibrio fischeri. The highest 2,4-D removal efficiency of 99.2% was obtained with the biphasic Au-TiO2(TiO2(B)/anatase) nanobelts with anatase as predominant phase. Toxicity was mainly due to the intermediate 2,4-dichlorophenol (2,4-DCP) which was eliminated in 4 h. The TiO2 nanobelt phase structure is shown to have a significant effect on photocatalytic activity.


Febrero, 2019 | DOI: 10.1016/j.apsusc.2018.10.175

6.18
Fotocatálisis Heterogénea: Aplicaciones

Fluorinated and Platinized Titania as Effective Materials in the Photocatalytic Treatment of Dyestuffs and Stained Wastewater Coming from Handicrafts Factories

Murcia, J.J.; Cely, A.C.; Rojas, H.A.; Hidalgo, M.C.; Navío, J.A.
Catalysts, 9 (2019) 179

Show abstract ▽

In this study, commercial and lab-prepared TiO2 were modified by fluorination and platinum photodeposition; and the effect of these modifications over the physicochemical and photocatalytic properties of TiO2 was evaluated. It was found that F and Pt addition leads to the modification of the optical and textural properties of TiO2. The materials prepared were tested in the photocatalytic degradation of different organic dyestuffs such as methylene blue (MB) and methyl orange (MO); the degradation of commercial anilines employed in the staining of natural fibers was also evaluated. Photocatalysis was also studied in this work as an eco-friendly treatment of wastewater coming from handicrafts factories. In general it was observed that the effectiveness of the photocatalytic treatment strongly depends on the substrate to be degraded, thus, fluorinated and platinized commercial Titania (Pt-F-P25) showed the best photocatalytic performance in the MB and MO photodegradation and in contrast, in the case of the anilines the highest degradation was obtained over commercial TiO2 fluorinated (F-P25). These results can be explained by differences observed in the structure and in the adsorption of these dyestuffs over the photocatalysts surfaces. F-P25 photocatalyst also demonstrated to be the best material for the treatment of real wastewater coming from handicrafts factories.


Febrero, 2019 | DOI: 10.3390/catal9020179

3.52
Química de Superficies y Catálisis

Does shaping catalysts modify active phase sites? A comprehensive in situ FTIR spectroscopic study on the performance of a model Ru/Al2O3 catalyst for the CO methanation

Bobadilla, LF; Munoz-Murillo, A; Laguna, OH; Centeno, MA; Odriozola, JA
Chemical Engineering Journal, 357 (2019) 248-257

Show abstract ▽

Routinely, it seems assumed that the catalytic layer coated on monoliths and microchannel reactors preserve the properties of the initial powder catalyst. However, this assumption should be reasonably demonstrated since the set of chemical and physical manipulations involved in the preparation of these catalytic devices hardly does not alter the surface of the starting catalyst powders. This work aims to evaluate the transformations that takes place in a model Ru/Al2O3 catalyst during a typical slurry preparation procedure and their impact on the catalytic performance for the CO methanation reaction and the selective methanation of CO in CO2-rich reformate gases. For this purpose, we have conducted an in situ comprehensive study by means of Fourier Transform Infrared Spectroscopy (FTIR) in which the nature of the species present on the surface of the catalyst during CO hydrogenation was analyzed. This study reveals that during the preparation of the slurry the starting Ru/Al2O3 catalyst suffers a redispersion of metallic Ru particles and more surface hydroxyls are created by the incorporation of additional alumina. These modifications have a noticeable influence in the catalytic performance and despite their importance, these aspects have been poorly considered in other studies.


Febrero, 2019 | DOI: 10.1016/j.cej.2018.09.166

10.65
Química de Superficies y Catálisis

Immobilization of Stabilized Gold Nanoparticles on Various Ceria-Based Oxides: Influence of the Protecting Agent on the Glucose Oxidation Reaction

Chenouf, M; Megias-Sayago, C; Ammari, F; Ivanova, S; Centeno, MA; Odriozola, JA
Catalysts, 9 (2019) 125

Show abstract ▽

The influence of the protecting agent's nature on gold particle size and dispersion was studied in this work over a series of gold-based catalysts. CO and glucose oxidation were chosen as catalytic reactions to determine the catalyst's structure-activity relationship. The nature of the support appeared to be the predominant factor for the increase in activity, as the oxygen mobility was decisive for the CO oxidation in the same way that the Lewis acidity was decisive for the glucose oxidation. For the same catalyst composition, the use of montmorillonite as the stabilizing agent resulted in better catalytic performance.


Febrero, 2019 | DOI: 10.3390/catal9020125

3.52
Fotocatálisis Heterogénea: Aplicaciones

Urban wastewater treatment by using Ag/ZnO and Pt/TiO2 photocatalysts

J.J. Murcia, L.G. Arias Bolivar, H.A. Rojas Sarmiento, E.G. Ávila Martínez, C. Jaramillo Páez, M.A. Lara, J.A. Navío Santos, M.C. Hidalgo López
Environmental Science and Pollution Research (2018) 1-9

Show abstract ▽

In this study, the treatment of wastewater coming from a river highly polluted with domestic and industrial effluents was evaluated. For this purpose, series of photocatalysts obtained by ZnO and TiO2 modification were evaluated. The effect of metal addition and Ti precursor (in the case of the titania series) over the physicochemical and photocatalytic properties of the materials obtained was also analyzed. The evaluation of the photocatalytic activity showed that semiconductor modification and precursor used in the materials synthesis are important factors influencing the physicochemical and therefore the photocatalytic properties of the materials obtained. The water samples analyzed in the present work were taken from a highly polluted river, and it was found that the effectiveness of the photocatalytic treatment increases when the reaction time increases and for both, wastewater samples and isolated Escherichia coli strain follow the next order Pt/TiO2 << ZnO. It was also observed that biochemical and chemical demand oxygen and turbidity significantly decrease after treatment, thus indicating that photocatalysis is a non-selective technology, which can lead to recover wastewater containing different pollutants.


Febrero, 2019 | DOI: 10.1007/s11356-018-1592-3

3.06
Fotocatálisis Heterogénea: Aplicaciones

Mesoporous pyrophyllite–titania nanocomposites: synthesis and activity in phenol photocatalytic degradation

A. El Gaidoumi; J.M. Doña-Rodríguez; E. Pulido Melián; O.M. González-Díaz; B. El Bali; J.A. Navío; A. Kherbeche
Research on Chemical Intermediates, 45 (2019) 333-353

Show abstract ▽

Pyrophyllite–TiO2 nanocomposite PTi750 was successfully synthesized using a sol–gel method at ambient temperature based on exfoliation of the pyrophyllite layered clay by incorporation of the TiO2 precursor titanium(IV) t-butoxide. PTi750 exhibited higher photocatalytic activity in phenol degradation compared with commercial TiO2 Aeroxide P25. Ag-photodeposited PTi750 was more photoactive than PTi750, exhibiting detoxification, total degradation, and good mineralization of polluted solution and excellent stability after five reuses at optimal conditions in terms of the parameters pH, H2O2 concentration, and photocatalyst amount. The nanocomposites were investigated using several techniques, viz. diffuse-reflectance ultraviolet–visible (UV–Vis) spectrophotometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and Brunauer–Emmett–Teller (BET) specific surface area measurements.


Febrero, 2019 | DOI: 10.1007/s11164-018-3605-8

2.26
Fotocatálisis Heterogénea: Aplicaciones

Coupling of Ag2CO3 to an optimized ZnO photocatalyst: Advantages vs. disadvantages

P. Sánchez-Cid; C. Jaramillo-Páez; J.A. Navío; A.N. Martín-Gómez; M.C. Hidalgo
Journal of Photochemistry and Photobiology A: Chemistry, 369 (2019) 119-132

Show abstract ▽

With the aim of improving the photocatalytic properties of a previously optimized zinc oxide photocatalyst, the effect of the incorporation of different amounts of Ag2CO3 on the aforementioned ZnO has been studied. For this purpose we report the synthesis, by means of simple precipitation procedures, of bare ZnO and Ag2CO3 samples as well as the coupled materials ZnO/Ag2CO3 (X) (where X = 1%, 2%, 4% and 5% in molar percentages). Both, single and coupled materials have been characterized by different techniques (XRD, XRF, N2-absorption, SEM, TEM, UV–vis/DRS and XPS). To assess the advantages or disadvantages that Ag2CO3 addition could have over the optimized ZnO, the photocatalytic properties have been established by following the photo-degradation of selected toxic molecules, both in the UV and in the visible, as well as using complementary techniques of liquid medium analyses (TOC and Atomic Emission Spectrometry with plasma ICP). Three selected substrates were chosen: Rhodamine B (RhB) as a dye, and phenol and caffeine as colourless recalcitrant toxic molecules.
Our results suggest that although the use of Ag2CO3 could be beneficial to implement the optical absorption towards the visible region, however, other effects have to be bore in mind, such as the photo-corrosion of Ag2CO3 and the chemical structure of the chosen substrate, to elucidate whether the addition of Ag2CO3 has beneficial or detrimental effects on the photocatalytic properties of the coupled ZnO/Ag2CO3 materials.


Enero, 2019 | DOI: 10.1016/j.jphotochem.2018.10.024

3.31
Fotocatálisis Heterogénea: Aplicaciones

Synthesis and Characterization of ZnO-ZrO2 Nanocomposites for Photocatalytic Degradation and Mineralization of Phenol

Lopez, MCU; Lemus, MAA; Hidalgo, MC; Gonzalez, RL; Owen, PQ; Oros-Ruiz, S; Lopez, SAU; Acosta, J
Journal of Nanomaterials (2019) art. 1015876, 12 pages

Show abstract ▽

ZnO-ZrO2 nanocomposites using zinc (II) acetylacetonate and different ZnO contents (13, 25, 50, and 75% mol) were synthesized through sol-gel method. The synthesis process was strongly related to nanocomposite properties especially on their structural composition. The obtained ZnO-ZrO2 nanomaterials presented tetragonal crystalline structure for zirconia whereas hexagonal one was formed in ZnO. Raman spectroscopy and XRD patterns confirmed the formation of tetragonal zirconia whereas inhibition of monoclinic structure was observed. Addition of ZnO affected the pore size distribution of the composite, and the measured specific surface areas were from 10 m2/g (for pure ZnO) to 46 m2/g (pristine ZrO2). Eg values of ZrO2 were modified by ZnO addition, since calculated values using Kubelka-Munk’s function varied from 4.73 to 3.76 eV. The morphology and size of the nanomaterials investigated by electron microscopy showed formation of nanorods for ZnO with sizes ranging from 50 nm to 300 nm while zirconia was formed by smaller particles (less than 50 nm). The main advantage of using the nanocomposite for photocatalytic degradation of phenol was the mineralization degree, since 75ZnO-ZrO2 nanocomposite surpassed mineralization reached by pure ZnO and also inhibited formation of undesirable intermediates.


Enero, 2019 | DOI: 10.1155/2019/1015876

1.98



2018


Materiales Coloidales - Materiales Ópticos Multifuncionales - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Revealing the substitution mechanism in Eu3+:CaMoO4 and Eu3+,Na+:CaMoO4 phosphors

Becerro, AI; Allix, M; Laguna, M; Gonzalez-Mancebo, D; Genevois, C; Caballero, A; Lozano, G; Nunez, NO; Ocana, M
Journal of Materials Chemistry C, 6 (2018) 47

Show abstract ▽

Eu3+-Doped calcium molybdate is an excellent phosphor for lighting and display devices due to the very intense pure red emission after UV excitation. It has been reported in the literature that the CaMoO4 unit cell volume expands after Eu3+ doping, in spite of the smaller Eu3+ ionic radius compared with Ca2+. Likewise, several studies found that the emission intensity of the phosphor could be improved by codoping with alkaline ions like Li+, Na+ or K+. None of these studies correlated the apparent volume expansion and luminescence enhancement with the crystal structural details. This paper analyses the aliovalent substitution mechanism and crystal structure of Eu3+:CaMoO4 and Eu3+,Na+:CaMoO4 phosphors using complementary techniques like Raman spectroscopy, EXAFS and SPD. We found that the substitution mechanism was different for both systems, with Ca site vacancies forming in the Eu3+:CaMoO4 phosphors and leading to Ca1-3xEu2xxMoO4 compositions, while the Eu3+,Na+:CaMoO4 phosphors formed Ca1-2xEuxNaxMoO4. SPD showed that the cell volume expansion observed with increasing Eu3+ content is related to the increase of the Mo-O bond distance due to the higher electronegativity of Eu3+ compared with Ca2+. Finally, it was shown that the luminescence properties, i.e. lifetime values and quantum yields (the latter reported here for the first time), do not depend on the presence of monovalent ions in the crystal structure but, exclusively, on the Eu3+ content of the phosphor. The integral and detailed analysis of the materials presented in this paper, ranging from crystal structure to luminescent properties including elemental composition, allows a full picture of the structure-property relationships that had never been addressed before for CaMoO4-based phopshors.


Diciembre, 2018 | DOI: 10.1039/c8tc04595j

6.64
Fotocatálisis Heterogénea: Aplicaciones

A comparative assessment of the UV-photocatalytic activities of ZnO synthesized by different routes

Jaramillo-Paez, C; Sanchez-Cid, P; Navio, JA; Hidalgo, MC
Journal of Environmental Chemical Engineering, 6 (2018) 7161-7171

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ZnO was synthesized by a precipitation procedure, free of template agent, by mixing aqueous solutions of Zn (OAc)(2) and dissolved Na2CO3 at pH ca. 7. This material was calcined at different temperatures (200-600 degrees C for 2 h). In two other alternative procedures, after the precipitation, the suspension was taken to hydrothermal treatments or to microwave treatments, subjecting them to calcination treatments at the same temperatures as the previous material. All materials were characterized using various techniques. The photocatalytic activity was assessed in the degradation of methyl orange and phenol using UV-illumination and evaluating the corresponding percentages of conversion and mineralization. A minimal difference between the relative intensities of the exposed faces (I100I002) related to XRD for the synthesized samples seems to be an important factor in obtaining good photocatalytic properties. This minimum, was achieved with a calcination treatment at 400 degrees C for 2 h. With this calcination treatment, no significant variations were observed in the photocatalytic activities of ZnO obtained by the three procedures, although in all cases the zinc oxides obtained exhibited, for each substrate, higher UV-photocatalytic activities than those obtained with TiO2 (P25) used as a reference catalyst. In all cases, the samples showed no photocatalytic activity in the visible region of the spectrum.


Diciembre, 2018 | DOI: 10.1016/j.jece.2018.11.004

0.00
Química de Superficies y Catálisis

New concept for old reaction: Novel WGS catalyst design

Garcia-Moncada, N; Gonzalez-Castano, M; Ivanova, S; Centeno, MA; Romero-Sarria, F; Odriozola, JA
Applied Catalysis B-Environmental, 238 (2018) 1-5

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The viability of water gas shift catalytic system for mobile application passes through obligatory reactor volume reduction, achieved normally by using less charge of more efficient catalyst. Completely new concept for catalyst design is proposed: a catalytic system including classically reported WGS catalysts of different nature or active phase (Cu, Pt or Au) mechanically mixed with an ionic conductor. The influence of the later on catalyst activity is studied and discussed, more precisely its effect on the rate of the reaction-limiting step and catalysts' efficiency. It is demonstrated with this study, that the presence of an ionic conductor in contact with a WGS catalyst is essential for the water supply (dissociation and transport), thereby potentiating the water activation step, whatever the mechanism and catalyst overall performance.


Diciembre, 2018 | DOI: 10.1016/j.apcatb.2018.06.068

14.23
Química de Superficies y Catálisis

Understanding the Role of the Acid Sites in 5-Hydroxymethylfurfural Oxidation to 2,5-Furandicarboxylic Acid Reaction over Gold Catalysts: Surface Investigation on CexZr1-xO2 Compounds

Megias-Sayago, C; Chakarova, K; Penkova, A; Lolli, A; Ivanova, S; Albonetti, S; Cavani, F; Odriozola, JA
ACS Catalysis, 8 (2018) 11154-11164

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A series of CexZr1-xO2 supports with different Ce/Zr molar ratios were utilized for the preparation of gold catalyst used in the selective oxidation of 5-hydroxymethyl-2-furfural to 2,5-furandicarboxylic acid. The used method of gold deposition allows the preparation of gold particles with homogeneous size and shape distribution, a formulation very useful for studies dedicated to revealing the support participation in the reaction. The supports are characterized by Fourier transform infrared spectroscopy using CO as probe molecule, and the sample catalytic activity is thereafter correlated to the support acid site distribution. The possible participation of its Lewis/Bronsted acidity in the reaction mechanism is also proposed.


Diciembre, 2018 | DOI: 10.1021/acscatal.8b02522 DEC 2018

12.22
Química de Superficies y Catálisis

CO/H-2 adsorption on a Ru/Al2O3 model catalyst for Fischer Trospch: Effect of water concentration on the surface species

Jimenez-Barrera, E; Bazin, P; Lopez-Cartes, C; Romero-Sarria, F; Daturi, M; Odriozola, JA
Applied Catalysis B-Environmental, 237 (2018) 986-995

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Water presence and concentration strongly influence CO conversion and CS+ selectivity in the Fischer Tropsch reaction. In this work, the influence of the water concentration was investigated using a model Ru/Al2O3 (5 wt. %) catalyst. The surface species formed after CO and H-2 adsorption in dry and wet (different water concentrations) conditions were analyzed by FTIR. Firstly, water adsorption was carried out up to complete filling of the pores and then CO was put in contact with the catalyst. The absence of adsorbed CO species in these conditions evidences that CO diffusion in water controls the access of the gas to the active sites and explains the negative effect of high water concentrations reported by some authors. Moreover, the adsorption of a mixture of CO + H-2 + H2O, being the water concentration close to that needed to have a monolayer, and a dry mixture of CO + H-2 were carried out and compared. Results evidence that water in this low concentration, is able to gasify the surface carbon species formed by CO dissociation on the metallic sites. This cleaning effect is related to the positive effect of water on CO conversion detected by some authors.


Diciembre, 2018 | DOI: 10.1016/j.apcatb.2018.06.053

14.23
Química de Superficies y Catálisis

Metal Micro-Monoliths for the Kinetic Study and the Intensification of the Water Gas Shift Reaction

Garcia-Moncada, N; Groppi, G; Beretta, A; Romero-Sarria, F; Odriozola, JA
Catalysts, 8 (2018) art. 594

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A kinetic study of the water gas shift (WGS) reaction has been carried out on a Pt-based catalyst promoted by a Zr-based proton conductor. The investigation was first performed on powders with diluted feed mixtures and then extended to more severe and representative conditions by using a catalyst coated metallic micromonolith. Temperature measurements reveal that isothermal conditions were obtained along the micromonolith during the tested conditions. In addition, the very thin catalytic layer allows for the discarding of intraporous resistances, providing excellent conditions to analyse the kinetics of the WGS reaction under the integral regime. The proposed rate expression accounts for independence on CO concentration, an inhibiting effect of H-2 and a promoting effect of H2O; kinetic orders on CO and H-2 are in line with those reported in the literature for the Pt-based catalyst. Instead, the obtained reaction order of water (0.36) is significantly lower than that reported for unpromoted catalysts (typically 0.77-1.10) in good agreement with the proposed water-enhancer effect of the proton conductor on the rate-limiting step. Metallic micromonoliths turn out to be a powerful tool for the kinetic investigation, due to the absence of mass and heat transport limitations and represent a strategy for the intensification of the WGS unit for future applications of fuel processors in small mobile devices.


Diciembre, 2018 | DOI: 10.3390/catal8120594

3.44
Química de Superficies y Catálisis

Policies and Motivations for the CO2 Valorization through the Sabatier Reaction Using Structured Catalysts. A Review of the Most Recent Advances

Navarro, JC; Centeno, MA; Laguna, OH; Odriozola, JA
Catalysts, 8 (2018) art. 578

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The current scenario where the effects of global warming are more and more evident, has motivated different initiatives for facing this, such as the creation of global policies with a clear environmental guideline. Within these policies, the control of Greenhouse Gase (GHG) emissions has been defined as mandatory, but for carrying out this, a smart strategy is proposed. This is the application of a circular economy model, which seeks to minimize the generation of waste and maximize the efficient use of resources. From this point of view, CO2 recycling is an alternative to reduce emissions to the atmosphere, and we need to look for new business models which valorization this compound which now must be considered as a renewable carbon source. This has renewed the interest in known processes for the chemical transformation of CO2 but that have not been applied at industrial level because they do not offer evident profitability. For example, the methane produced in the Sabatier reaction has a great potential for application, but this depends on the existence of a sustainable supply of hydrogen and a greater efficiency during the process that allows maximizing energy efficiency and thermal control to maximize the methane yield. Regarding energy efficiency and thermal control of the process, the use of structured reactors is an appropriate strategy. The evolution of new technologies, such as 3D printing, and the consolidation of knowledge in the structing of catalysts has enabled the use of these reactors to develop a wide range of possibilities in the field. In this sense, the present review presents a brief description of the main policies that have motivated the transition to a circular economy model and within this, to CO2 recycling. This allows understanding, why efforts are being focused on the development of different reactions for CO2 valorization. Special attention to the case of the Sabatier reaction and in the application of structured reactors for such process is paid.


Diciembre, 2018 | DOI: 10.3390/catal8120578

3.44
Química de Superficies y Catálisis

Selective CO methanation with structured RuO2/Al2O3 catalysts

Munoz-Murillo, A; Martinez, LM; Dominguez, MI; Odriozola, JA; Centeno, MA
Applied Catalysis B-Environmental, 236 (2018) 420-427

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Active and selective structured RuO2/Al2O3 catalysts for CO methanation using a flow simulating CO2-rich reformate gases from WGS and PROX units (H-2 excess, CO2 presence and 300 ppm CO concentration) were prepared. Both, the RuO2/Al2O3 powder and the slurry prepared from it for its structuration by washcoating of the metallic micromonolithic structure, were also active and selective. Both the slurry (S-RuAl) and micro monoliths (M-RuAl) were able to completely and selectively methanate CO at much lower temperatures than the parent RuAI powder. The optimal working temperature in which the CO conversion is maximum and the CO2 conversion is minimized was determined to be from 149 degrees C to 239 degrees C for S-RuAl and from 165 degrees C to 232 degrees C for M-RuAl, whilst it was from 217 degrees C to 226 degrees C for RuAI powder. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity for CO methanation among the considered catalysts can be related with modifications in the surface particle size of ruthenium and its reducibility. These were ascribed to the metallic substrate, the presence of PVA and colloidal alumina in the slurry preparation, the aqueous and acidic media and the thermal treatment used, resulting in a more active and selective catalysts than the parent powder.


Noviembre, 2018 | DOI: 10.1016/j.apcatb.2018.05.020

14.23
Química de Superficies y Catálisis

Analysis of the variables that modify the robustness of Ti-SiO2 catalysts for alkene epoxidation: Role of silylation, deactivation and potential solutions

Plata, JJ; Pacheco, LC; Remesal, ER; Masa, MO; Vega, L; Marquez, AM; Odriozola, JA; Sanz, JF
Molecular Catalysis, 459 (2018) 55-60

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Catalytic epoxidation of alkenes plays an essential role in the transformation and synthesis of many organic chemicals. Ti atoms grafted on mesoporous silica, silylated on the surface, is considered the most active and selective catalyst for these reactions. However, the durability and robustness of the active centers remain as the main drawback in industry. In this paper, the characterization of industrial samples is combined with DFT calculations to rationalize the deactivation process of the catalyst and improve its performance. Silylating agents are characterized by experimental and simulated 29Si-NMR and their role in the catalytic mechanism is analysed. Potential deactivation processes are identified before, during and after the reaction. Modifications of the silylating agents and of the active center are proposed to improve the durability of the catalyst.


Noviembre, 2018 | DOI: 10.1016/j.mcat.2018.08.010

2.94
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic H2 production from glycerol aqueous solutions over fluorinated Pt-TiO2 with high {001} facet exposure

V. Vaiano; M.A. Lara; G. Iervolino; M. Matarangolo; J.A. Navío; M.C. Hidalgo
Journal of Photochemistry and Photobiology A-Chemistry, 365 (2018) 52-59

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An optimized fluorinated TiO2 catalyst with high {001} facet exposure loaded with platinum (TiO2-PtFAC) was tested in the photocatalytic hydrogen production from glycerol solution under UV light irradiation. The samples were synthesized by direct hydrothermal treatment starting from two different types of precursors that are titanium tetraisopropoxide (I) or titanium butoxide (B), while platinisation was performed by photodeposition method. The obtained catalysts were characterised by different techniques (XRD, FESEM, TEM, BET, UV–vis DRS, XRF and XPS) and the results evidenced that anatase is the only crystalline phase present in all TiO2 samples. The morphology of the samples was seen as rectangular platelets particles where Pt particles were was observed all over the surface. The presence of Pt and F in the platinised samples was also confirmed by XRF and XPS analysis. The photocatalytic results have shown that the presence of Pt on TiO2{001}facet surface remarkably enhanced the hydrogen production from aqueous solution at 5 wt % of glycerol. Comparing the results obtained from the photocatalysts prepared by the two different precursors, it was found that the best performances in terms of H2 production was achieved with TiO2-PtFAC(I) (about 13 mmol L−1 after 4 h of irradiation time), while the H2 production was lower for TiO2-PtFAC(B) (about 9 mmol L−1 after 4 h of irradiation time). The effect of the operating conditions using TiO2-PtFAC(I) evidenced that the highest H2 production was obtained with a photocatalyst dosage equal to 1.5 g L−1, initial glycerol concentration at 5 wt% and a pH value equal to 7. Finally, a photocatalytic test was also performed on glycerol solution prepared with a real water matrix. Despite the presence of ions scavengers (chlorides and carbonates) in solution, TiO2-PtFAC(I) was able to reach a photocatalytic H2production of about 6 mmol L−1 after 4 h of UV light irradiation.


Octubre, 2018 | DOI: 10.1016/j.jphotochem.2018.07.032

3.26
Química de Superficies y Catálisis

Improving the activity of gold nanoparticles for the water-gas shift reaction using TiO2-Y2O3: an example of catalyst design

Plata, JJ; Romero-Sarria, F; Suarez, JA; Marquez, AM; Laguna, OH; Odriozola, JA; Sanz, JF
Physical Chemistry Chemical Physics, 20 (2018) 22076-22083

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In the last ten years, there has been an acceleration in the pace at which new catalysts for the water-gas shift reaction are designed and synthesized. Pt-based catalysts remain the best solution when only activity is considered. However, cost, operation temperature, and deactivation phenomena are important variables when these catalysts are scaled in industry. Here, a new catalyst, Au/TiO2-Y2O3, is presented as an alternative to the less selective Pt/oxide systems. Experimental and theoretical techniques are combined to design, synthesize, characterize and analyze the performance of this system. The mixed oxide demonstrates a synergistic effect, improving the activity of the catalyst not only at large-to-medium temperatures but also at low temperatures. This effect is related to the homogeneous dispersion of the vacancies that act both as nucleation centers for smaller and more active gold nanoparticles and as dissociation sites for water molecules. The calculated reaction path points to carboxyl formation as the rate-limiting step with an activation energy of 6.9 kcal mol(-1), which is in quantitative agreement with experimental measurements and, to the best of our knowledge, it is the lowest activation energy reported for the water-gas shift reaction. This discovery demonstrates the importance of combining experimental and theoretical techniques to model and understand catalytic processes and opens the door to new improvements to reduce the operating temperature and the deactivation of the catalyst.


Septiembre, 2018 | DOI: 10.1039/c8cp03706j

3.57
Química de Superficies y Catálisis - Reactividad de Sólidos

A direct in situ observation of water-enhanced proton conductivity of Eu-doped ZrO2: Effect on WGS reaction

Garcia-Moncada, N; Bobadilla, LF; Poyato, R; Lopez-Cartes, C; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 231 (2018) 343-356

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Eu-doped ZrO2 solid solutions have been synthesized in order to prepare proton conductors as water-enhancer additives for the WGS reaction. Elemental characterization has been carried out revealing homogeneous dopant distribution resulting in fluorite-type solid solutions for Eu2O3 contents up to similar to 9 mol.%. Representative samples of the Eu-doped ZrO2 series have been analysed by Impedance Spectroscopy (IS) in inert, oxygen and wet conditions. The solid solution with 5 mol.% of Eu2O3 has presented the highest conductivity values for all tested conditions indicating an optimal amount of dopant. Moreover, the presence of vapour pressure results in an increment of the conductivity at temperatures lower than 300 degrees C, meanwhile at higher temperatures the conductivity is the same than that in inert conditions. To elucidate these results, in situ DRIFTS studies were carried out. These experiments evidenced the existence of water dissociation at oxygen vacancies (band at 3724 cm(-1)) as well as the presence of physisorbed water at temperatures up to similar to 300 degrees C where the band at 5248 cm(-1) characteristic of these species disappeared. These results points to a layer model where the physisorbed water interacts with surface hydroxyls generated by dissociated water that improves the proton conductivity through Grotthuss' mechanism in the RT-300 degrees C temperature range. These samples were successfully tested in WGS reaction as additive to a typical Pt-based catalyst. The presence of the mixed oxide reveals an increase of the catalyst' activity assisted by the proton conductor, since improves the water activation step.


Septiembre, 2018 | DOI: 10.1016/j.apcatb.2018.03.001

14.23
Química de Superficies y Catálisis

Operando DRIFTS-MS Study of WGS and rWGS Reaction on Biochar-Based Pt Catalysts: The Promotional Effect of Na

Santos, JL; Bobadilla, LF; Centeno, MA; Odriozola, JA
C-Journal of Carbon Research, 4 (2018) 47

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0.00
Fotocatálisis Heterogénea: Aplicaciones

ZnO and Pt-ZnO photocatalysts: Characterization and photocatalytic activity assessing by means of three substrates

Jaramillo, C; Navio, J.A.; Hidalgo, M.C.; Macías, M.
Catalysis Today, 313 (2018) 12-19

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ZnO nanoparticles have been previously synthesized by a facile precipitation procedure by mixing aqueous solutions of Zn(II) acetate and dissolved Na2CO3 at pH ca. 7.0 without the addition of a template. The as-prepared ZnO material was anealed at 400 °C in air for 2 h. The Pt-ZnO catalysts (0.5 or 1.0 Pt wt.%) were obtained by photochemical deposition method on the surface of the prepared ZnO sample, using hexachloroplatinic acid (H2PtCl6). It has been shown that Zn2+ is lost from the photocatalyst to the medium and a replacement of the cationic vacancies of Zn2+ by Pt4+ cations occurs during the platinization process of the ZnO samples, regardless of whether the platinum metal photodeposition process. The as-prepared catalysts were characterized by XRD, BET, FE-SEM, TEM, XPS and diffuse reflectance spectroscopy (DRS). Three different probe molecules were used to evaluate the photocatalytic properties under UV-illumination: Methyl Orange and Rhodamine B were chosen as dye substrates and Phenol as a transparent substrate. High conversion values (ca. 100%) and a total organic carbon (TOC) removal of 90–96%, were obtained over these photocatalysts after 160 min of UV illumination. In general, it was observed that the presence of Pt on ZnO affects the lattice parameters and the crystallite size. Although ZnO can completely degrade RhB, MO and Phenol totally in ca. 60 min, the process is more efficient for Pt–ZnO photocatalysts.


Septiembre, 2018 | DOI: 10.1016/j.cattod.2017.12.009

4.89
Química de Superficies y Catálisis

Pt/CePO4 catalysts for the WGS reaction: influence of the water-supplier role of the support on the catalytic performance

Navarro-Jaen, S; Centeno, MA; Laguna, OH; Odriozola, JA
Journal of Materials Chemistry A, 6 (2018) 17001-17010

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For Pt catalysts which have demonstrated great activity for the WGS reaction, the activation of water is described as the rate-limiting step. Such limitation could be overcome through the design of supports able to supply water. In this study, the hexagonal and monoclinic phases of CePO4 have been evaluated as supports for Pt WGS catalysts. The hexagonal structure presents channels containing water, absent in the monoclinic structure. The presence of these channels in the hexagonal phase increases the interaction with the water molecules, leading to an enhancement of the WGS catalytic performance. DRIFTS results showed that dissociation of water does not occur on these supports, while calculated apparent activation energies present values similar to those reported in the literature for the dissociation of water in Pt (111). These results suggest that cerium phosphates act as water suppliers, increasing the number of available species to be dissociated on the Pt surface.


Septiembre, 2018 | DOI: 10.1039/c8ta04603d

10.73
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Structural Reversibility of LaCo1-xCuxO3 Followed by In Situ X-ray Diffraction and Absorption Spectroscopy

Pereniguez, Rosa; Ferri, Davide
Chemphyschem, 19 (2018) 1876-1885

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Combinations of perovskite-type oxides with transition and precious metals exhibit a remarkable self-regenerable property that could be exploited for numerous practical applications. The objective of the present work was to study the reversibility of structural changes of perovskite-type oxides under cyclic reducing/oxidizing atmosphere by taking advantage of the reducibility of LaCoO3. LaCoO3 +/- and LaCo0.8Cu0.2O3 +/- were prepared by ultrasonic spray combustion and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR). XRD and XAS data confirmed that copper adopted the coordination environment of cobalt at the B-site of the rhombohedral LaCoO3 under the selected synthesis conditions. The structural evolution under reducing atmosphere was studied by insitu XRD and XANES supporting the assignment of the observed structural changes to the reduction of the perovskite-type oxide from ABB'O-3 (B'=Cu) to B'(0)/ABO(3) and to B'B-0(0)/A(2)O(3). Successive redox cycles allowed the observation of a nearly complete reversibility of the perovskite phase, i.e. copper was able to revert into LaCoO3 upon oxidation. The reversible reduction/segregation of copper and incorporation at the B-site of the perovskite-type oxides could be used in chemical processes where the material can be functionalized by segregation of Cu and protected against irreversible structural changes upon re-oxidation.


Agosto, 2018 | DOI: 10.1002/cphc.201800069

3.08
Química de Superficies y Catálisis

Unravelling the Role of Oxygen Vacancies in the Mechanism of the Reverse Water-Gas Shift Reaction by Operando DRIFTS and Ultraviolet-Visible Spectroscopy

Bobadilla, LF; Santos, JL; Ivanova, S; Odriozola, JA; Urakawa, A
ACS Catalysis, 8 (2018) 7455-7467

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The reaction mechanism of the reverse water gas shift (RWGS) reaction was investigated using two commercial gold-based catalysts supported on Al2O3 and TiO2. The surface species formed during the reaction and reaction mechanisms were elucidated by transient and steady-state operando DRIFTS studies. It was revealed that RWGS reaction over Au/Al2O3 proceeds through the formation of formate intermediates that are reduced to CO. In the case of the Au/TiO2 catalyst, the reaction goes through a redox mechanism with the suggested formation of hydroxycarbonyl intermediates, which further decompose to CO and water. The Ti-3+ species, the surface hydroxyls, and oxygen vacancies jointly participate. The absence of carbonyl species adsorbed on gold particles during the reaction for both catalysts indicates that the reaction pathway involving dissociative adsorption of CO2 on Au particles can be discarded. To complete the study, operando ultraviolet visible spectroscopy was successfully applied to confirm the presence of Ti3+ and to understand the role of the oxygen vacancies of TiO2 support in activating CO2 and thus the subsequent RWGS reaction.


Agosto, 2018 | DOI: 10.1021/acscatal.8b02121

12.22
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Solar pilot plant scale hydrogen generation by irradiation of Cu/TiO2 composites in presence of sacrificial electron donors

Maldonado, MI; Lopez-Martin, A; Colon, G; Peral, J; Martinez-Costa, JI; Malato, S
Applied Catalysis B-Environmental, 229 (2018) 15-23

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A Cu/TiO2 photocatalyst has been synthesised by reducing a Cu precursor with NaBH4 onto the surface of a sulphate pretreated TiO2 obtained by a sol-gel procedure. The catalyst, that shows a clearly defined anatase phase with high crystallinity and relatively high surface area, and contains Cu2O and CuO deposits on its surface, has been used to produce hydrogen in a solar driven pilot plant scale photocatalytic reactor. Different electron donor aqueous solutions (methanol, glycerol, and a real municipal wastewater treatment plant influent) have been tested showing similar or even higher energy efficiency than those obtained using more expensive noble metal based photocatalytic systems. The glycerol solutions have provided the best reactive environments for hydrogen generation.


Agosto, 2018 | DOI: 10.1016/j.apcatb.2018.02.005

14.23
Química de Superficies y Catálisis

Hydrodeoxygenation of vanillin over carbon supported metal catalysts

Santos, JL; Alda-Onggar, M; Fedorov, V; Peurla, M; Eranen, K; Maki-Arvela, P; Centeno, MA; Murzin, DY
Applied Catalysis A-General, 561 (2018) 137-149

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Different carbon supported metal catalysts were synthesized, and characterized with various physico-chemical methods and tested in vanillin hydrodeoxygenation under 30 bar total pressure in water as a solvent at 100 degrees C. The catalysts exhibited high specific surface area and the metal dispersion decreased in following order: Pt/ C > Pd/C > Au/C > Rh/C > Ru/C. The most active catalyst was Pd/C followed by Ru/C. Vanillin hydrodeoxygenation proceeded via hydrogenation forming vanillyl alcohol further to its hydrogenolysis forming p-creosol. Both hydrogenation and hydrogenolysis were promoted by Pd/C, which exhibited rather high dispersion. The highest selectivity to p-creosol, 95% at complete vanillin conversion, was obtained with Pd/C. Kinetic modelling of vanillyl alcohol selectivity as a function of vanillin conversion was performed.


Julio, 2018 | DOI: 10.1016/j.apcata.2018.05.010

4.63
Fotocatálisis Heterogénea: Aplicaciones

Design of Ag/ and Pt/TiO2-SiO2 nanomaterials for the photocatalyti degradation of phenol under solar irradiation

Matos, J; Llano, B; Montana, R; Poon, PS; Hidalgo, MC
Environmental Science and Pollution Research, 25 (2018) 18894-18913

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The design of hybrid mesoporous TiO2-SiO2(TS1) materials decorated with Ag and Pt nanoparticles was performed. The photocatalytic degradation of phenol under artificial solar irradiation was studied and the activity and selectivity of the intermediate products were verified. TiO2-SiO(2)was prepared by sol-gel method while Ag- and Pt-based photocatalysts (TS1-Ag and TS1-Pt) were prepared by photodeposition of the noble metals on TS1. Two series of photocatalysts were prepared varying Ag and Pt contents (0.5 and 1.0 wt%). An increase in the photocatalytic activity up to two and five times higher than TS1 was found on TS1-Ag-1.0 and TS1-Pt-1.0, respectively. Changes in the intermediate products were detected on Ag- and Pt-based photocatalysts with an increase in the catechol formation up to 3.3 and 6.6 times higher than that observed on TS1, respectively. A two-parallel reaction mechanism for the hydroquinone and catechol formation is proposed. A linear correlation between the photocatalytic activity and the surface concentration of noble metals was found indicating that the electron affinity of noble metals is the driven force for both the increase in the photoactivity and for the remarkable changes in the selectivity of products.


Julio, 2018 | DOI: 10.1007/s11356-018-2102-3

2.91
Fotocatálisis Heterogénea: Aplicaciones

Photo/Electrocatalytic Properties of Nanocrystalline ZnO and La–Doped ZnO: Combined DFT Fundamental Semiconducting Properties and Experimental Study

Ahsaine, A.H.; Slassi, A.; Naciri, Y.; Chennah, A.; Jaramillo‐Páez, C.; Anfar, Z.; Zbair, M.; Benlhachemi, A.; Navío, J.A.
Chemistry Select, 3 (2018) 7778-7791

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This work reports the synthesis of nanocrystalline ZnO and 5% La‐doped ZnO (La/ZnO) materials for photo/electrocatalytic degradation of Rhodamine B. The samples were characterized by X‐Ray diffraction, scanning and transmission electron microscopy, X‐Ray photoelectron spectroscopy and diffuse reflectance spectra. The effect of La doping on electronic structure was investigated using density functional theory calculations (DFT), La‐doped ZnO showed an n‐type metallic nature compared to pristine ZnO and La doping creates occupied states within the band gap edge. Under UV light, La/ZnO showed higher kinetic constant and efficiency than ZnO. A possible mechanism was elaborated on the basis of DFT and active trapping measurements. Different initial Rhodamine B concentration were studied to assess the electro‐oxidation of RhB. The electrochemical degradation of RhB over La/ZnO spindles electrode was pronounced with three time's high kinetic constant. The superior electro/photoactivity of La/ZnO was due to its unique morphology, high charge separation of the charge carriers and higher conductivity induced by La‐doping (intermediary levels). Superoxide ions and holes were the main active species for the photodegradation. Whereas, synergetic effect of hydroxyl radicals and hypochlorite ions were responsible of the high RhB electrocatalytic degradation.


Julio, 2018 | DOI: 10.1002/slct.201801729

1.72
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Understanding the differences in catalytic performance for hydrogen production of Ni and Co supported on mesoporous SBA-15

Rodriguez-Gomez, A; Pereniguez, R; Caballero, A
Catalysts, 307 (2018) 224-230

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Three mono and bimetallic NixCo1-x/SBA-15 catalysts (x = 1, 0.5 and 0) with a total metallic content of 10 wt% have been prepared by a deposition-precipitation (DP) method. The catalytic performances on the dry reforming of methane reaction (DRM) have been determined and correlated with their physical and chemical state before and after the catalytic reaction. So, while the nickel monometallic system presents a high activity and stability in the DRM reaction, the Co/SBA-15 catalytic system turns out completely inactive. For its part, the Ni0.5Co0.5/SBA-15 has initially a catalytic performance similar to the Ni/SBA-15 monometallic system, but rapidly evolving to an inactive system, therefore resembling the behavior of the cobalt-based catalyst. The characterization by TEM and in situ XPS techniques has allowed us to ascribe these differences to the initial state of metallic particles after reduction and their different evolution under reaction conditions. So, while after reduction both nickel containing NixCo1-x/SBA-15 catalysts (x = 1 and 0.5) present a well dispersed metallic phase, the cobalt monometallic catalyst yields big metallic particles with a heterogeneous distribution of sizes. Additionally, unlike the Ni/SBA-15, the NiCo/SBA-15 system increases during reaction the metallic particle sizes. 

Besides indicating that the particle size is a major reason determining the catalytic performances, these results suggest that in the Ni-Co system both metals form after reduction a bimetallic phase mainly located inside the mesoporous channels of SBA-15 support. Under DRM reaction conditions, the cobalt is segregated to the surface of the bimetallic particles, which seems to determine the interaction with the support surface SBA-15. This feature gives rise to a much less stable metallic phase which suffers an important sintering process under DRM catalytic conditions. 


Junio, 2018 | DOI: 10.1016/j.cattod.2017.02.020

4.89
Química de Superficies y Catálisis

Chemical CO2 recycling via dry and bi reforming of methane using Ni-Sn/Al2O3 and Ni-Sn/CeO2-Al2O3 catalysts

Stroud, T; Smith, TJ; Le Sache, E; Santos, JL; Centeno, MA; Arellano-Garcia, H; Odriozola, JA; Reina, TR
Applied Catalysis B-Environmental, 224 (2018) 125-135

Show abstract ▽

Carbon formation and sintering remain the main culprits regarding catalyst deactivation in the dry and bi-reforming of methane reactions (DRM and BRM, respectively). Nickel based catalysts (10 wt.%) supported on alumina (Al2O3) have shown no exception in this study, but can be improved by the addition of tin and ceria. The effect of two different Sn loadings on this base have been examined for the DRM reaction over 20 h, before selecting the most appropriate Sn/Ni ratio and promoting the alumina base with 20 wt.% of CeO2. This catalyst then underwent activity measurements over a range of temperatures and space velocities, before undergoing experimentation in BRM. It not only showed good levels of conversions for DRM, but exhibited stable conversions towards BRM, reaching an equilibrium H-2/CO product ratio in the process. In fact, this work reveals how multicomponent Ni catalysts can be effectively utilised to produce flexible syngas streams from CO2/CH4 mixtures as an efficient route for CO2 utilisation.


Mayo, 2018 | DOI: 10.1016/j.apcatb.2017.10.047

14.23
Química de Superficies y Catálisis

Multicomponent Ni-CeO2 nanocatalysts for syngas production from CO2/CH4 mixtures

le Sache, E.; Santos, J. L.; Smith, T. J.; Centeno, M. A.; Arellano-Garcia, H.; Odriozola, J. A.; Reina, T. R.
Journal of CO2 utilization, 25 (2018) 68-78

Show abstract ▽

The dry reforming of methane with CO2 is a common route to transform CO2/CH4 mixtures into added value syngas. Ni based catalysts are highly active for this goal but suffer from deactivation, as such promoters need to be introduced to counteract this, and improve performance. In this study, mono- and bi-metallic formulations based on 10 wt.% Ni/CeO2-Al2O3 are explored and compared to a reference 10 wt.% Ni/gamma-Al2O3. The effect of Sn and Pt as promoters of Ni/CeO2-Al2O3 was also investigated. The formulation promoted with Sn looked especially promising, showing CO2 conversions stabilising at 65% after highs of 95%. Its increased performance is attributed to the additional dispersion Sn promotion causes. Changes in the reaction conditions (space velocity and temperature) cement this idea, with the Ni-Sn/CeAl material performing superiorly to the mono-metallic material, showing less deactivation. However, in the long run it is noted that the mono- metallic Ni/CeAl performs better. As such the application is key when deciding which catalyst to employ in the dry reforming process.


Mayo, 2018 | DOI: 10.1016/j.jcou.2018.03.012

5.19
Química de Superficies y Catálisis

Multicomponent Au/Cu-ZnO-Al2O3 catalysts: Robust materials for clean hydrogen production

Santos, JL; Reina, TR; Ivanov, I; Penkova, A; Ivanova, S; Tabakova, T; Centeno, MA; Idakiev, V; Odriozola, JA
Applied Catalysis A-General, 558 (2018) 91-98

Show abstract ▽

Clean hydrogen production via WGS is a key step in the development of hydrogen fuel processors. Herein, we have designed a new family of highly effective catalysts for low-temperature WGS reaction based on gold modified copper-zinc mixed oxides. Their performance was controlled by catalysts' composition and the Au-Cu synergy. The utilization of hydrotalcite precursors leads to an optimal microstructure that ensures excellent Au and Cu dispersion and favors their strong interaction. From the application perspective these materials succeed to overcome the major drawback of the commercial WGS catalysts: resistance towards start/stop operations, a mandatory requisite for H-2-powered mobile devices.


Mayo, 2018 | DOI: 10.1016/j.apcata.2018.04.002

4.63
Fotocatálisis Heterogénea: Aplicaciones

Study of the effectiveness of the flocculation-photocatalysis in the treatment of wastewater coming from dairy industries

Murcia, J.J., Hernández-Laverde, M., Rojas, Muñoz, E., Navío, J.A., Hidalgo, M.C.
Journal of Photochemistry and Photobiology A: Chemistry, 358 (2018) 256-264

Show abstract ▽

The aim of the present work was to evaluate the effectiveness of flocculation-photocatalysis as combined processes in the treatment of dairy industries wastewater. Different commercial and lab prepared flocculants and photocatalysts were evaluated. All the materials prepared were extensively characterized. Commercial materials presented the best physicochemical properties and performance in the treatment of the studied wastewater. On one hand, all the photocatalysts evaluated showed bactericidal activity for E. Coli, total coliforms and other enterobacteriaceae. Total elimination of E. coli was obtained by using commercial TiO2 P25 Evonik, under 120 W/m2 of UV–vis light intensity and 5 h of total illumination time. Other species of bacteria remained after treatment under these conditions. It was also found that the highest light intensity of 120 W/m2 led to increase the Chemical Oxygen Demand and Total Organic Carbon in the samples treated, it can be due to the faster formation of new organic compounds as intermediaries during the photocatalytic reactions at the highest photonic flux. Flocculation pre-treatment of the wastewater samples led to improve the effectiveness of the photocatalytic treatment; thus, the combination of flocculation-photocatalysis treatments at low light intensity of 30 W/m2 leads to achieve the total elimination of E. coli, and under this intensity the elimination of total coliforms and other enterobacteriaceae increased 5.48% compared to the photocatalytic treatment alone. These treatment conditions led to comply the Colombian regulations for dairy wastewater.


Mayo, 2018 | DOI: 10.1016/j.jphotochem.2018.03.034

3.26
Fotocatálisis Heterogénea: Aplicaciones

Photo-induced processes on Nb2O5 synthesized by different procedures

Jaramillo-Páez, C., Sánchez-Fernández, F.J., Navío, J.A., Hidalgo, M.C.
Journal of Photochemistry and Photobiology A: Chemistry, 359 (2018) 40-52

Show abstract ▽

The properties of Nb2O5 strongly depend on its synthesis procedure as well as the conditions of ulterior thermal treatment. We report the synthesis of Nb2O5 powders prepared by sol-gel precipitation method using niobium(V) ethoxide as precursor. Two chemical routes were chosen: the presence of tryethyl amine (TEA) as precipitant/template agent, or the oxidant peroxide method. In addition, microwave-assisted activation was also used. The as-prepared samples by the above procedures were amorphous. Structural changes upon heating from room temperature up to 800 °C were investigated by X-ray powder diffraction technique combined with thermogravimetric analysis. The sequential thermal treatment up to 800 °C promotes the crystallization of hexagonal phase to orthorhombic phase whereas the ulterior cooling to room temperature lead to a mixture of both phases. Samples calcined at selected temperatures of either 600 °C or 800 °C for 2 h, were characterized by XRD, SEM, N2-adsorption and diffuse reflectance spectroscopy (DRS). The synthetic approach routes as well as the combined microwave activation followed by ulterior thermal treatment lead to changes not only on particle size but also on the textural properties of the synthesized catalysts. The catalysts synthesized have been evaluated using Rhodamine B (RhB) as a substrate, under both UV and visible lighting conditions. None of the catalysts synthesized showed activity in the visible. Under UV-illumination conditions, some of the catalysts exhibited a relatively low photoactivity in the degradation of RhB, which is associated with a photo-sensitizing effect. However, the addition of Ag+ ions considerably increased the activity of all the catalysts in the degradation of RhB under UV-illumination conditions. A mechanism is proposed to explain the photo-induced processes obtained, leaving the door open to the possible implications of the observed results in relation to the interaction of RhB dye with noble metal nanoparticles such as silver.


Mayo, 2018 | DOI: 10.1016/j.jphotochem.2018.03.040

3.26
Química de Superficies y Catálisis

Influence of gold particle size in Au/C catalysts for base-free oxidation of glucose

Megias-Sayago, C; Santos, JL; Ammari, F; Chenouf, M; Ivanova, S; Centeno, MA; Odriozola, JA
Catalysis Today, 306 (2018) 183-190

Show abstract ▽

A series of gold colloids were prepared and immobilized on commercial activated carbon. The influence of the colloid preparation and stability were studied and related to the gold particle size in the final catalyst. The catalysts show an important activity in the glucose to gluconic acid oxidation reaction, leading to gluconic acid yield close to 90% in base free mild conditions (0.1 MPa O-2 and 40 degrees C). The size-activity correlation and probable mechanism were also discussed. Finally, the viability of the catalyst was tested by recycling it up to four times. 


Mayo, 2018 | DOI: 10.1016/j.cattod.2017.01.007

4.89
Fotocatálisis Heterogénea: Aplicaciones

Silver-modified ZnO highly UV-photoactive

Jaramillo-Páez, C.; Navío, J.C.; Hidalgo, M.C.
Journal of Photochemistry and Photobiology A: Chemistry, 356 (2018) 112-122

Show abstract ▽

ZnO nanoparticles were successfully synthesized by a controlled precipitation procedure by mixing aqueous solutions of Zn(II) acetate and dissolved Na2CO3 at pH ca. 7.0 without template addition and ulterior calcination at 400 °C for 2 h. The Ag-ZnO catalysts (ranging from 0.5 to 10 Ag wt.-%) were obtained by photochemical deposition method at the surface of the prepared ZnO sample, using AgNO3 as precursor. The as-prepared catalysts (with and without silver) were characterized by XRD, BET, FE-SEM, TEM, and XPS and diffuse reflectance spectroscopy (DRS). The effect of Ag-phodeposition on the photocatalytic properties of ZnO nanoparticles was investigated. Three different probe molecules were used to evaluate the photocatalytic properties under UV-illumination and visible illumination: Methyl Orange and Rhodamine B were chosen as hazardous dyes and Phenol as a transparent substrate. For each of the chosen substrates, it was observed that the UV-photocatalytic properties of ZnO improved with the amount of Ag deposited, up to an optimum percentage around 1–5 wt.-% Ag, being even better than the commercial Evonik-TiO2(P25) in the same conditions. Above this amount, the UV-photocatalytic properties of the Ag-ZnO samples remain unchanged, indicating a maximum for Ag-deposition. While ZnO and Ag-ZnO catalysts can photodegrade Rhodamine B, Methyl Orange and Phenol totally within 60 min under UV-illumination, the process is slightly faster for the case of Ag–ZnO nanoparticles. Under Vis-illumination, the silver-metalized samples did not present photocatalytic activity in the degradation of Methyl Orange. However, a very low photoactivity was present for phenol degradation (10% conversion) and a moderate conversion of ca. 70% for Rhodamine B degradation, after 120 min of Visible-illumination. High conversion values and a total organic carbon (TOC) removal of 86–97% were obtained over the Ag-ZnO photocatalysts after 120 min of UV-illumination, suggesting that these Ag-modified ZnO nanoparticles may have good applications in wastewater treatment, due to its reuse properties.


Abril, 2018 | DOI: 10.1016/j.jphotochem.2017.12.044

3.26
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Bimetallic Ni-Co/SBA-15 catalysts for reforming of ethanol: How cobalt modifies the nickel metal phase and product distribution

Rodriguez-Gomez, A; Caballero, A
Molecular Catalysis, 449 (2018) 122-130

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In this study, five mono and bimetallic xNi-(10-x)Co/SBA-15 catalysts (x = 10, 8, 5, 2 and 0, with a total metallic content of 10 wt%) have been synthesized using a deposition-precipitation (DP) methodology. Catalytic performances on the steam reforming of ethanol reaction (SRE) have been determined and correlated with their physical and chemical state. A nickel content of 5% or higher yields catalytic systems with good activity, high selectivity to hydrogen and a low production of acetaldehyde (less than 5%). However, in the systems where the cobalt is the main component of the metallic phase (8-10%), the selectivity changes, mainly due to the production of an excess of acetaldehyde, which is also reflected in the larger H-2/CO2 ratio. In agreement with previous findings, this important modification in the selectivity comes from the formation of a cobalt carbide phase, where only takes place in the cobalt enriched systems, and is inhibited with nickel content larger than 5%. The formation of this carbide phase seems to be responsible for the decrease of cobalt particle size during the SRE reaction. Even though this cobalt carbide phase is thermodynamically metastable against decomposition to metallic cobalt and graphite carbon, our results have shown that it only reacts and decomposes after a hydrogen treatment at 600 degrees C.


Abril, 2018 | DOI: 10.1016/j.mcat.2018.02.011

2.94
Química de Superficies y Catálisis

Epimerization of glucose over ionic liquid/phosphomolybdate hybrids: structure-activity relationship

Megias-Sayago, C; Alvarez, E; Ivanova, S; Odriozola, JA
Green Chemistry, 20 (2018) 1042-1049

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The influence of the crystal structure and chemical nature of some ionic liquid/phosphomolybdate hybrids on their catalytic activity in the epimerization of glucose was studied. A clear evidence of structure-activity relationship was found. The inorganic part of the hybrid ensured the availability of active sites for the reaction, while the organic cation part organized the structure and controled the diffusion of the reactants. This study can be used as a first approach to predict the symmetry, long range order and availability of active sites in the presented class of imidazolium based polyoxometalate hybrids.


Marzo, 2018 | DOI: 10.1039/c7gc03738d

9.41
Química de Superficies y Catálisis

LaFeO3 ceramics as selective oxygen sensors at mild temperature

Jaouali, I; Hamrouni, H; Moussa, N; Nsib, MF; Centeno, MA; Bonavita, A; Neri, G; Leonardi, SG
Ceramics International, 44 (2018) 4183-4189

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In this study, an investigation about the oxygen sensing properties of lanthanum orthoferrite (LaFeO3) ceramics is reported. LaFeO3 nanoparticles were synthesized by using tartaric sol-gel route and annealed in air at different temperatures (500, 700 and 900 degrees C). The samples have been characterized by using thermal analysis (TA), BET surface area and porosity, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results of sensing tests indicate that LaFeO3 nanoparticles exhibit good response to oxygen at mild temperatures (300-450 degrees C). The effect of annealing temperature on gas sensing performance was investigated, demonstrating that LaFeO3 ceramics obtained after annealing at 500 degrees C display better characteristics with respect to others. The oxygen sensor developed shows also high stability in humid environment and excellent selectivity to oxygen over other interfering gases such as CO, NO2, CO2, H-2 and ethanol.


Marzo, 2018 | DOI: 10.1016/j.ceramint.2017.11.221

3.45
Química de Superficies y Catálisis

Numerical study of the accuracy of temperature measurement by thermocouples in small-scale reactors

Blay, V; Bobadilla, LF
Chemical Engineering Research & Design, 131 (2018) 545-556

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Proper temperature measurement is imperative in any laboratory study if reliable data are to be obtained, particularly in the field of chemical kinetics. In this paper we analyze in silico some typical thermowell configurations used in small-scale reactors by coupling computational fluid dynamics (CFD) with conjugated heat transfer phenomena. This allows us to identify deviations in measurements arising from thermal radiation and self-conductivity in mid and high temperature ranges, in addition to radial temperature gradients. A novel design is proposed and optimized by additional simulation, showing potential for faster and more accurate temperature measurements.


Marzo, 2018 | DOI: 10.1016/j.cherd.2017.06.003

3.07
Química de Superficies y Catálisis

Tailoring structured WGS catalysts: Impact of multilayered concept on the water surface interactions

Gonzalez-Castano, M; Le Sache, E; Ivanova, S; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 222 (2018) 124-132

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A novel multilayer approach for designing structured WGS catalyst is employed in this study as a response to the lack of new strategies in the literature. The approach proposes the use of two successive layers with different functionalities on metallic micromonolith substrate. The WGS catalyst behavior is modulated by the nature of the inner layer which determines the active species surface population by acting on the water activation step. The catalytic promotion attained by introducing inner ceria containing solids with increasing number of oxygen defects is intensely analyzed through FT-IR and H2O-TPD. Several evidences about the participation of the oxygen vacancies, as key sites, for water absorption processes are established. Besides, remarkable relationships between the water absorption strengths and the water splitting processes within their influence on the catalyst performance are also discussed.


Marzo, 2018 | DOI: 10.1016/j.apcatb.2017.10.018

14.23
Química de Superficies y Catálisis

Synthesis of Pd-Al/biomorphic carbon catalysts using cellulose as carbon precursor

Cazana, F; Galetti, A; Meyer, C; Sebastian, V; Centeno, MA; Romeo, E; Monzon, A
Catalysis Today, 301 (2018) 226-238

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This work presents the results obtained with novel Pd and Pd-Al catalysts supported on carbon, which have been prepared using a biomorphic mineralization technique. The catalyst synthesis procedure includes a stage of thermal decomposition under reductive atmosphere of cellulose previously impregnated with the metallic precursors. We have studied the influence of the temperature and time of decomposition, and of the Al precursor addition, on the textural and catalytic properties. The characterisation results indicate that the preparation method used leads to the formation of carbonaceous supports with a high microporosity (up to 97% micropore volume) and values of the BET surface up to 470 m2/g while maintaining the original external structure. The use of low temperatures (ca. 600 °C) during the decomposition step allows the preparation of highly dispersed catalysts with narrow Pd particle size distributions. However, the thermal decomposition at elevated temperatures (ca. 800 °C) increases the Pd particle size due to the sintering of the metallic phase. This phenomenon is augmented with the decomposition time and is not affected by the presence of Al. Consequently, the catalytic activity of these materials in cyclohexene hydrogenation is strongly affected by the operational conditions used during the thermal decomposition step. Unexpectedly, the more sintered catalysts, i.e. those prepared at 800 °C, show the highest activity. According to the characterization results, this fact can be explained considering that the smaller Pd particles obtained after preparation at e.g. 600 °C are quite inactive because they are confined in the internal structure of the micropores of the support and/or embedded inside the carbon matrix. In contrast, after decomposition at 800 °C, the larger Pd particles formed are placed at the external surface of the catalyst, being accessible to the reactants. In addition, for the specific conditions under which the Pd is accessible, the presence of Al favours the cyclohexene conversion due to the enhancement of the adsorption on the Pd surface as a consequence of a charge transfer phenomenon. These results can serve as a guideline for the preparation of these catalysts based on raw lignocellulosic materials in order to maximize their catalytic performance.


Marzo, 2018 | DOI: 10.1016/j.cattod.2017.05.026

4.89
Química de Superficies y Catálisis

Gold catalyst recycling study in base-free glucose oxidation reaction

Megias-Sayago, C.; Bobadilla, L. F.; Ivanova, S.; Penkova, A.; Centeno, M. A.; Odriozola, J. A.
Catalysis Today, 301 (2018) 72-77

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This work is devoted to the study of viability of immobilized gold colloids on carbon as catalysts for the base-free glucose oxidation reaction with a special emphasis made on catalysts' recycling, operational life and possible routes for deactivation/reactivation under batch conditions. The observed catalytic behavior is related to all possible manners of deactivation, like gold metal state changes (particle size agglomeration or leaching), support modifications or active sites blocking by intermediates. In an attempt to recover the initial catalytic activity, the samples are subjected to different treatments such as H2O and NaOH washings and calcination. The failure of the regeneration procedures to recover the initial activity and after detailed catalyst' characterization allows us to find out the main cause of deactivation


Marzo, 2018 | DOI: 10.1016/j.cattod.2017.03.022

4.89
Química de Superficies y Catálisis

CO2 reforming of methane over Ni-Ru supported catalysts: On the nature of active sites by operando DRIFTS study

Alvarez, A; Bobadilla, LF; Garcilaso, V; Centeno, MA; Odriozola, JA
Journal of CO2 utilization, 24 (2018) 509-515

Show abstract ▽

The present paper addresses the nature of the active sites of a bimetallic Ni-Ru supported catalyst on the dry reforming of methane (DRM). The structural characterization by XRD and Raman spectroscopy, along with the reducibility study (TPR-H-2) of the samples, evidenced the existence of a strong Ni-Ru interaction in the bimetallic system. We have assumed that Ru atoms block the most reactive Ni sites (step-edge sites) leaving less reactive centers for methane activation (terraces). In this way, operando DRIFTS measurements revealed that Ru decreases the catalytic activity but favors the carbon gasification and prevents the CO dissociation.


Marzo, 2018 | DOI: 10.1016/j.jcou.2018.01.027

5.19
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Improving the direct synthesis of hydrogen peroxide from hydrogen and oxygen over Au-Pd/SBA-15 catalysts by selective functionalization

Rodriguez-Gomez, A; Platero, F; Caballero, A; Colon, G
Molecular Catalysis, 445 (2018) 142-151

Show abstract ▽

A series of gold-palladium catalysts supported in a mesoporous surface functionalized silica SBA-15 was studied for H2O2 direct synthesis. Support functionalization was performed using different organic groups (namely-SO3H, -NH2 and-SH) while metal was then supported by an ion exchanged method. Different Au-Pd/SBA-15 catalysts were tested in the Direct Synthesis of Hydrogen Peroxide (DSHP). Organic functional groups (-SH, -SO3H and-NH2) with acid-base properties acted as anchoring sites controlling both the dispersion of the metallic active phase and the chemical state of gold and palladium species as Au+ and Pd2+, respectively. Compared to a Au-Pd/SBA-15 system prepared by incipient wetness impregnation over non-functionalized SBA-15, catalytic performance is improved upon functionalization, increasing hydrogen peroxide rate in sulfonic-SBA-15 systems and reducing the hydrogenation/decomposition activity by adding amine groups. The occurrence of amine groups clearly suppresses the support microporosity and probably condition the metal cluster size. The analysis of particle size by TEM showed that sulfonated samples lead to a Pd size compromise which improves the H2O2 production hindering the competitive side reactions, particularly suppressed by the presence of amine groups.


Febrero, 2018 | DOI: 10.1016/j.mcat.2017.10.034

2.94
Reactividad de Sólidos - Fotocatálisis Heterogénea: Aplicaciones

High {0 0 1} faceted TiO2 nanoparticles for the valorization of oxygenated compounds present in aqueous biomass-derived feedstocks

Fernández-Arroyo, A.; Lara, M.A.; Domine, M.E.; Sayagués, M.J.; Navío, J.A.; Hidalgo, M.C.
Journal of Catalysts, 358 (2018) 266-276

Show abstract ▽

{0 0 1} faceted TiO2 catalysts are hydrothermally synthesized by using titanium(IV) isopropoxide and butoxide precursors (ISO and BUT TiO2samples) together with HF addition. Their activity and stability are evaluated in the catalytic condensation of light oxygenated organic compounds present in an aqueous model mixture simulating a real bio-refinery effluent, under moderate operation conditions. High {0 0 1} faceted TiO2 catalysts show organic products yields superior to those attained with other TiO2 samples (anatase, rutile, and P25). This enhanced catalytic activity relates to their physico-chemical and textural properties, such as high surface area (≈100 m2/g), regular morphology (platelets conformed by partially agglomerated TiO2 nanoparticles), and adequate Lewis acidity. XRD and Raman measurements evidence the unique presence of anatase crystalline phase in both ISO and BUT materials, in which the use of HF during synthesis produces the preferential growth of TiO2 crystals mainly exposing the {0 0 1} plane. This effective {0 0 1} facet exposition directly determines catalytic results. Moreover, TiO2 ISO catalyst shows outstanding stability under reaction conditions, maintaining practically unaltered their activity after several re-uses. In particular, Lewis acid sites present in TiO2 faceted materials are more stable in the presence of organic acids under aqueous environments. This opens new possibilities for the application of these materials in the valorization of light oxygenated compounds present in biomass-derived aqueous effluents.


Febrero, 2018 | DOI: 10.1016/j.jcat.2017.12.018

7.72
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Ir-Catalysed Nitrous oxide (N2O) Decomposition: Effect of Ir Particle Size and Metal-Support Interactions

Yentekakis, IV; Goula, G; Kampouri, S; Betsi-Argyropoulou, I; Panagiotopoulou, P; Taylor, MJ; Kyriakou, G; Lambert, RM
Catalysis Letters, 148 (2019) 341-347

Show abstract ▽

The effect of the morphology of Ir particles supported on.-Al2O3, 8 mol% Y2O3-stabilized -ZrO2 (YSZ), 10 mol%Gd2O3-doped CeO2 (GDC) and 80 wt%Al2O3-10 wt%CeO2-10 wt%ZrO2 (ACZ) on their stability on oxidative conditions, the associated metal-support interactions and activity for catalytic decomposition of N2O has been studied. Supports with intermediate or high oxygen ion lability (GDC and ACZ) effectively stabilized Ir nanoparticles against sintering, in striking contrast to supports offering negligible or low oxygen ion lability (gamma-Al2O3 and YSZ). Turnover frequency studies using size-controlled Ir particles showed strong structure sensitivity, de-N2O catalysis being favoured on large catalyst particles. Although metallic Ir showed some de-N2O activity, IrO2 was more active, possibly present as a superficial overlayer on the iridium particles under reaction conditions. Support-induced turnover rate modifications, resulted from an effective double layer [O delta--delta(+)](Ir) on the surface of iridium nanoparticles, via O2- backspillover from the support, were significant in the case of GDC and ACZ.


Enero, 2018 | DOI: 10.1007/s10562-017-2233-z

2.37
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Phase-Contact Engineering in Mono- and Bimetallic Cu-Ni Co-catalysts for Hydrogen Photocatalytic Materials

Munoz-Batista, MJ; Meira, DM; Colon, G; Kubacka, A; Fernandez-Garcia, M
Angewandte Chemie-International Edition, 57 (2018) 1199-1203

Show abstract ▽

Understanding how a photocatalyst modulates its oxidation state, size, and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physicochemical techniques and probes employed to study them. A synchrotron micro-beam X-ray absorption spectroscopy study together with the computational simulation and analysis (at the X-ray cell) of the light-matter interaction occurring in powdered TiO2-based monometallic Cu, Ni and bimetallic CuNi catalysts for hydrogen production from renewables was carried out. The combined information unveils an unexpected key catalytic role involving the phase contact between the reduced and oxidized non-noble metal phases in all catalysts and, additionally, reveals the source of the synergistic Cu-Ni interaction in the bimetallic material. The experimental method is applicable to operando studies of a wide variety of photocatalytic materials.


Enero, 2018 | DOI: 10.1002/anie.201709552

12.26
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Nickel Particles Selectively Confined in the Mesoporous Channels of SBA-15 Yielding a Very Stable Catalyst for DRM Reaction

Rodriguez-Gomez, A; Pereniguez, R; Caballero, A
Journal of Physical Chemistry B, 122 (2018) 500-510

Show abstract ▽

A series of four Ni catalysts supported on SBA-15 and on a high SiO2 surface area have been prepared by modified impregnation (ImU) and deposition-precipitation (DP) methods. The catalysts have been extensively characterized, including in situ XAS (bulk sensitive) and XPS (surface sensitive) techniques, and their catalytic activities evaluated in the dry reforming reaction of methane (DRM). The combined use of XPS and XAS has allowed us to determine the location of nickel particles on each catalyst after reduction at high temperature (750 degrees C). Both Ni/SiO2-DP and Ni/SBA-15-DP catalysts yield well-dispersed and homogeneous metallic phases mainly located in the mesoporosity of both supports. On the contrary, the Ni/SiO2-ImU and Ni/SBA-15-ImU catalysts present a bimodal distribution of the reduced nickel phase, with nickel metallic particles located out and into the mesoporous structure of SiO2 or the SBA-15 channels. The Ni/SBA-15-DP catalyst was found the most stable and performing system, with a very low level of carbon deposition, about an order of magnitude lower than the equivalent ImU catalyst. This outstanding performance comes from the confinement of small and homogeneous nickel particles in the mesoporous channels of SBA-15, which, in strong interaction with the support, are resistant to sintering and coke deposition during the demanding reaction conditions of DRM.


Enero, 2018 | DOI: 10.1021/acs.jpcb.7b03835

2.92
Reactividad de Sólidos - Fotocatálisis Heterogénea: Aplicaciones

A facile shape-controlled synthesis of highly photoactive fluorine containing TiO2 nanosheets with high {001} facet exposure

Lara, M.A.; Sayagués, M.J.; Navío, J.A.; Hidalgo, M.C.
Journal of Materials Science, 53 (2018) 435-446

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Surface-fluorinated TiO2 materials with high {001} facet exposure were prepared by a simple and high-yield preparation procedure. Faceted/fluorinated samples showed a high photocatalytic performance not only in oxidation processes, tested in phenol and methyl orange degradation, but also in a reduction process as Cr(VI) photoreduction. Reaction rates for these materials greatly exceeded the ones obtained for materials prepared without fluorine addition and for commercial TiO2 Degussa (Evonik) P25 used as reference photocatalyst. A broad characterisation of the samples allowed us to estimate the percentages of different facets and the amount and form in which the fluorine is found on the surfaces. Good photocatalytic behaviour can be ascribed to both high {001} facet exposure and adsorbed fluorine on the photocatalysts surfaces.


Enero, 2018 | DOI: 10.1007/s1085

3.44
Química de Superficies y Catálisis

Outstanding performance of rehydrated Mg-Al hydrotalcites as heterogeneous methanolysis catalysts for the synthesis of biodiesel

Navajas, A; Campo, I; Moral, A; Echave, J; Sanz, O; Montes, M; Odriozola, JA; Arzamendi, G; Gandia, LM
Fuel, 211 (2018) 173-181

Show abstract ▽

There is still a need for active, selective and stable heterogeneous catalysts for the synthesis of biodiesel. In this work, magnesium-aluminium hydrotalcites with Mg/Al molar ratios within the 1.5-5 range were synthesized by coprecipitation and used as transesterification catalysts for the synthesis of biodiesel. The mixed oxides obtained after calcination recovered the hydrotalcite structure in the form of meixnerite after rehydration in boiling water. The solids were characterized by XRD, TGA, N-2 adsorption-desorption, and SEM. Basic properties were assessed by means of Hammett indicators and CO2-TPD. Rehydrated materials with the highest Mg/Al ratios showed some distinctive features: low surface area, well defined flake-like crystals, high basicity and strong basic sites with H_ values above 11. They were also the most active catalysts allowing to achieve 51-75% sunflower oil methanolysis conversion after 8 h of reaction under mild conditions (60 degrees C, 1 atm), methanol/oil molar ratio of 12 using between 2 and 6 wt% of catalyst. The conversion increased up to 96% (92% fatty acid methyl esters yield) using 2 wt% catalyst and methanol/oil molar ratio of 48. Catalyst leaching was not a serious problem with these solids that could be reutilized maintaining very good activities. A general accordance between solids basic properties and their catalytic performance has been observed. These results are among the best reported in the literature for heterogeneous methanolysis catalysts and have been attributed to the high basicity of the rehydrated solids and the presence of strong and accessible basic sites probably consisting in interlayer hydroxide anions at the edges of the crystals.


Enero, 2018 | DOI: 10.1016/j.fuel.2017.09.061

5.13
Fotocatálisis Heterogénea: Aplicaciones

Enhanced photocatalytic removal of phenol from aqueous solutions using ZnO modified with Ag

Vaiano, V.; Matarangolo, M.; Murcia, J.J.; Rojas, H.; Navío, J.A.; Hidalgo, M.C.
Applied Catalysis B-Environmental, 225 (2018) 197-206

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Different photocatalysts based on commercial ZnO modified by silver photodeposition were prepared in this work. The samples were characterized by X-ray fluorescence spectrometry (XRF), specific surface area (SSA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance (UV–vis DRS). XRD and XPS showed that Ag/ZnO samples are composed of metallic Ag (Ag0) and ZnO structure was identified. Furthermore, TEM analysis evidenced that the number of silver particles increased with the Ag content. At last, UV–vis DRS results revealed a reflectance band for Ag/ZnO samples, ascribed to the surface plasmon resonance (SPR) absorption of metal silver particles. Commercial ZnO and Ag/ZnO samples were evaluated in the phenol removal under UV light irradiation. It was observed an enhancement of photocatalytic phenol removal from aqueous solutions by silver addition in comparison to commercial ZnO. In particular, the phenol removal increased with the silver content from 0.14 to 0.88 wt%, after this content (i.e 1.28 wt%) the phenol degradation significantly decreased indicating that the optimal Ag content was equal to 0.88 wt%. The influence of the best photocatalyst dosage and the change of the initial phenol concentration in solution were also investigated in this work and the best photocatalytic performance was obtained by using 50 mg L−1 of phenol initial concentration and 0.15 g L−1 of photocatalyst dosage. Finally, the optimized Ag/ZnO photocatalyst was employed for the treatment of a real drinking wastewater containing phenol in which the almost total phenol removal was achieved after 180 min of UV irradiation time.


Enero, 2018 | DOI: 10.1016/j.apcatb.2017.11.075

14.23



2017


Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Photochemical methane partial oxidation to methanol assisted by H2O2

López Martin, A.; Caballero, A.; Colón, G.
Journal of Photochemistry and Photobiology A: Chemistry, 349 (2017) 216-223

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The photochemical conversion of methane into methanol from H2O2 aqueous solution as well as the effect of the addition mode were studied. Direct addition of different amounts H2O2 leads to increasing methanol production at the first stage of the reaction. The excess of H2O2 would lead to the reactive oxygen species scavenging and the subsequent O2 production. It was also corroborated that extra hydroxyl radicals in the aqueous medium do not improve the formation of methanol but a noticeable increase in the formation of HCOOH with respect to methanol was evidenced. In contrast, dosing addition at relatively low rates leads to constant methane consumption towards methanol. Methanol formation would be in this case in equilibrium with further oxidation to HCOOH or CO2. This suggests that only a controlled constant availability of HO’s at low concentration can enhance the performance of methanol generation in the photochemical process.


Diciembre, 2017 | DOI: 10.1016/j.jphotochem.2017.09.039

2.89
Química de Superficies y Catálisis

Fischer-Tropsch Synthesis Over Zr-Promoted Co/gamma-Al2O3 Catalysts

Barrientos, J; Garcilaso, V; Venezia, B; Aho, A; Odriozola, JA; Boutonnet, M; Jaras, S
Topics in Catalysis, 60 (2017) 1285-1298

Show abstract ▽

Two Zr-modified alumina supports were synthetized containing the same amount of Zr but a different distribution of this modifier over the alumina surface. These supports, together with the unmodified alumina carrier, were used to prepare three cobalt-based catalysts which were characterized and tested under relevant Fischer-Tropsch conditions. The three catalysts presented very similar porosity and cobalt dispersion. The addition of Zr nor its distribution enhanced the catalyst reducibility. The catalyst activity was superior when using a carrier consisting of large ZrO2 islands over the alumina surface. The use of a carrier with a homogeneous Zr distribution had however, a detrimental effect. Moreover, a faster initial deactivation rate was observed for the Zr-promoted catalysts, fact that may explain this contradictory effect of Zr on activity. Finally, the addition of Zr showed a clear enhancement of the selectivity to long chain hydrocarbons and ethylene, especially when Zr was well dispersed.


Noviembre, 2017 | DOI: 10.1007/s11244-017-0813-1

2.44
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane

Delgado, D; Solsona, B; Ykrelef, A; Rodriguez-Gomez, A; Caballero, A; Rodriguez-Aguado, E; Rodriguez-Castellon, E; Nieto, JML
Journal of Physical Chemistry C, 121 (2017) 25132-25142

Show abstract ▽

NiO and metal-promoted NiO catalysts (M-NiO, with a M/(M+Ni) atomic ratio of 0.08, with M = Nb, Sn, or La) have been prepared, tested in the oxidative dehydrogenation (ODH) of ethane, and characterized by means of XRD, TPR, HRTEM, Raman, XPS, and in situ XAS (using H-2/He, air or C2H6/He mixtures). The selectivity to ethylene during the ODH of ethane decreases according to the following trend: Nb NiO Sn NiO > La NiO > NiO, whereas the catalyst reducibility (determined by both TPR and XAS using H-2/He mixtures) shows the opposite trend. However, different reducibility and catalytic behavior in the absence of oxygen (ethane/He mixtures) have been observed, especially when comparing Nb- and Sn-promoted NiO samples. These differences can be ascribed mainly to a different phase distribution of the promoter. The results presented here are discussed in terms of the nature of active and selective sites for ODH of ethane in selective and unselective catalysts, but also the role of promoters and the importance of their phase distribution.


Noviembre, 2017 | DOI: 10.1021/acs.jpcc.7b07066

4.48
Materiales Nanoestructurados y Microestructura - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Towards Extending Solar Cell Lifetimes: Addition of a Fluorous Cation to Triple Cation-Based Perovskite Films

Salado, M; Fernandez, MA; Holgado, JP; Kazim, S; Nazeeruddin, MK; Dyson, PJ; Ahmad, S
Chemsuschem, 10 (2017) 3846-3853

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Organohalide perovskites have emerged as highly promising replacements for thin-film solar cells. However, their poor stability under ambient conditions remains problematic, hindering commercial exploitation. The addition of a fluorous-functionalized imidazolium cation during the preparation of a highly stable cesium-based mixed perovskite material Cs-0.05(MA(0.15)FA(0.85))(0.95)Pb(I0.85Br0.15)(3) (MA= methylammonium; FA= formamidinium) has been shown to influence its stability. The resulting materials, which vary according to the amount of the fluorous-functionalized imidazolium cation present during fabrication, display a prolonged tolerance to atmospheric humidity (> 100 days) along with power conversion efficiencies exceeding 16%. This work provides a general route that can be implemented in a variety of perovskites and highlights a promising way to increase perovskite solar cell stability.


Octubre, 2017 | DOI: 10.1002/cssc.201700797

7.41
Química de Superficies y Catálisis

Synthesis and characterization of Rh/MnO2-CeO2/Al2O3 catalysts for CO-PrOx reaction

Martinez, TLM; Laguna, OH; Lopez-Cartes, C; Centeno, MA
Molecular Catalysis, 440 (2017) 9-18

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Rh/MnO2-CeO2/Al2O3 catalysts with different manganese-to-ceria ratios have been synthesized, characterized and tested in CO-PrOx reaction. The physicochemical properties of the solids were studied by XRD, Raman spectroscopy, BET surface area, H-2-TPR, TGA-DTG and TEM. The differences observed in the textural, structural and redox properties were related to the Mn-to-ceria ratio of the samples. The segregation of Mn species was observed at high Mn-to-Ce ratios. In opposite way, MnO2-CeO2 solid solutions were obtained at low Mn to Ce ones. In this last case, the physicochemical properties of the solids were favored by the intimate Rh-Ce-Mn contact. The effect of the Mn-Ce presence on Rh catalysts which promotes the catalytic behavior towards selective CO oxidation was observed to be better at low temperatures. At higher temperatures, Mn species promote the Reverse Water Gas Shift reaction, whilst ceria promotes the H-2 oxidation in the whole range of working temperatures.


Octubre, 2017 | DOI: 10.1016/j.mcat.2017.06.018

0.00
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Cobalt Carbide Identified as Catalytic Site for the Dehydrogenation of Ethanol to Acetaldehyde

A. Rodríguez-Gómez; J.P. Holgado; A. Caballero
ACS Catalysis, 7 (2017) 5243-5247

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Two cobalt catalysts, Co/SBA-15 and Co/SiO2, have been studied in steam reforming of ethanol (SRE). Besides the steam reforming products, ethoxide dehydrogenation to acetaldehyde is observed as one of the main reactions. Although by hydrogen treatment cobalt is reduced to the metallic state, under SRE conditions, a phase appears that has been identified as cobalt carbide and correlates with acetaldehyde production. These findings provide insights about the catalytic sites, for SRE, in cobalt catalysts. Comparison with previous results shows that these conclusions are not translatable to other cobalt catalysts, stressing the importance of the support on the catalytic behavior of cobalt.


Julio, 2017 | DOI: 10.1021/acscatal.7b01348

11.38
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Analysis of Ni species formed on zeolites, mesoporous silica and alumina supports and their catalytic behavior in the dry reforming of methane

Drobna, Helena; Kout, Martin; Soltysek, Agnieszka; Gonzalez-Delacruz, Victor M.; Caballero, Alfonso; Capek, Libor
Reaction Kinetics Mechanisms and Catalysis, 121 (2017) 255-274

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The presented investigation is focused on the analysis of Ni species formed on microporous (zeolites MFI and FAU) and mesoporous materials (Al-MCM- 41 and SBA-15) and alumina supports and their catalytic behavior in the dry reforming of methane. The paper lays emphasis on the relationship between the catalytic behavior of Ni-based catalysts and their textural/structural properties. Ni-based catalysts were prepared by wet impregnation (11 wt% of Ni) followed by calcination in air and reduction in hydrogen. The properties of Ni-based catalysts were also compared prior and after the catalytic tests. The critical role was played by the high value of the specific surface area and the high strength of the interaction between the Ni species and the support, which both determined the high dispersion and stability of metal Ni-0 particles. Ni-Al-MCM-41 and Ni-SBA-15 showed the values of the conversion of CO2 and CH4 above 90% (stable during 12 h). Slightly lower values of the conversion of CO2 and CH4 were observed over Ni-Al2O3 (also stable during 12 h). In contrast to these materials, Ni-MFI and Ni-FAU exhibited the worse metallic Ni-0 particles dispersion and very bad catalytic behavior.


Junio, 2017 | DOI: 10.1007/s11144-017-1149-3

1.52
Fotocatálisis Heterogénea: Aplicaciones

NO photooxidation with TiO2 photocatalysts modified with gold and platinum

Rodriguez, MJH; Melian, EP; Santiago, DG; Diaz, OG; Navio, JA; Rodriguez, JMD
Applied Catalysis B-Environmental, 205 (2017) 148-157

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In this study, a comparative analysis is made of TiO2 modified with Pt or Au in NO photoxidation under different radiation and humidity conditions. The metals were deposited on the TiO2 surface using two methods, photodeposition and chemical reduction. All catalysts were supported on borosilicate 3.3 plates using a dip-coating technique. These modified photocatalysts were characterized by X-ray diffraction analysis (XRD), UV-vis diffuse reflectance spectra (DRS), Brunauer-Emmett-Teller measurements (BET), transmission electron microscopy (TEM) and X-ray photoelectron spectrum analysis (XPS). It was found from the XPS results that Pt and oxidized Pt species coexist on the samples obtained by photodeposition and chemical reduction. In the case of Au, though other oxidation states were also detected the dominant oxidation state for both catalysts is Au. TEM results showed most Au-C particles are below 5 nm, whereas for Au-P the nanoparticles are slightly bigger. With UV irradiation, the Pt modified catalysts do not show any significant improvement in NO photocatalytic oxidation in comparison with the unmodified P25. For Au, both modified photocatalysts (Au-P and Au-C) exceed the photocatalytic efficiency of the unmodified P25, with Au-C giving slightly better results. The incorporation of metals on the TiO2 increases its activity in the visible region. 


Mayo, 2017 | DOI: 10.10161/j.apcatb.2016.12.006

11.70
Nanotecnología en Superficies y Plasma - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Critical Role of Oxygen in Silver-Catalyzed Glaser-Hay Coupling on Ag(100) under Vacuum and in Solution on Ag Particles

Orozco, N; Kyriakou, G; Beaumont, SK; Sanz, JF; Holgado, JP; Taylor, MJ; Espinos, JP; Marquez, AM; Watson, DJ; Gonzalez-Elipe, AR; Lambert, RM
ACS Catalysis, 7 (2017) 3113-3120

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The essential role of oxygen in enabling heterogeneously catalyzed Glaser–Hay coupling of phenylacetylene on Ag(100) was elucidated by STM, laboratory and synchrotron photoemission, and DFT calculations. In the absence of coadsorbed oxygen, phenylacetylene formed well-ordered dense overlayers which, with increasing temperature, desorbed without reaction. In striking contrast, even at 120 K, the presence of oxygen led to immediate and complete disruption of the organic layer due to abstraction of acetylenic hydrogen with formation of a disordered mixed layer containing immobile adsorbed phenylacetylide. At higher temperatures phenylacetylide underwent Glaser–Hay coupling to form highly ordered domains of diphenyldiacetylene that eventually desorbed without decomposition, leaving the bare metal surface. DFT calculations showed that, while acetylenic H abstraction was otherwise an endothermic process, oxygen adatoms triggered a reaction-initiating exothermic pathway leading to OH(a) + phenylacetylide, consistent with the experimental observations. Moreover, it was found that, with a solution of phenylacetylene in nonane and in the presence of O2, Ag particles catalyzed Glaser–Hay coupling with high selectivity. Rigorous exclusion of oxygen from the reactor strongly suppressed the catalytic reaction. Interestingly, too much oxygen lowers the selectivity toward diphenyldiacetylene. Thus, vacuum studies and theoretical calculations revealed the key role of oxygen in the reaction mechanism, subsequently borne out by catalytic studies with Ag particles that confirmed the presence of oxygen as a necessary and sufficient condition for the coupling reaction to occur. The direct relevance of model studies to a mechanistic understanding of coupling reactions under conditions of practical catalysis was reaffirmed.


Mayo, 2017 | DOI: 10.1021/acscatal.7b00431

10.61
Química de Superficies y Catálisis

Structural and catalytic properties of Au/MgO-type catalysts prepared in aqueous or methanol phase: application in the CO oxidation reaction

Hernandez, Willinton Y.; Alic, Funda; Navarro-Jaen, Sara; Centeno, Miguel A.; Vermeir, Pieter; Van der Voort, Pascal; Verberckmoes, An
Journal of Materials Science, 52 (2017) 4727-4741

Show abstract ▽

Au/MgO and Au/Mg(OH)(2)-type catalysts for CO oxidation reaction were prepared by using two different synthesis methods in presence of either an aqueous or methanol phase. The influence of the porous and morphological properties of the starting magnesium oxide supports was analyzed and correlated with the catalytic performances of the final gold-supported catalysts. It was found that the deposition of gold in the presence of methanol as a solvent avoids the total rehydration of the MgO support and maintains the textural and morphological properties of the starting oxides. The support synthesized by a surfactant-assisted hydrothermal route, having a combined meso-macroporous structure (i.e., MgO-P) showed a positive influence on the CO oxidation reaction as it favored the dispersion of gold and the surface-to-gas phase interaction during the catalytic process.


Abril, 2017 | DOI: 10.1007/s10853-016-0715-9

2.99
Química de Superficies y Catálisis

Deep insight into Zr/Fe combination for successful Pt/CeO2/Al2O3 WGS catalyst doping

Gonzalez-Castano, M; Ivanova, S; Ioannides, T; Centeno, MA; Odriozola, JA
Catalysis Science & Technology, 7 (2017) 1556-1564

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Efficient promotion of the Pt/CeO2/Al2O3 catalytic system was achieved by the addition of two different ceria promoters, Zr and Fe. From the exhaustive data analysis, the key features for enhanced catalytic performance and the roles of each doping metal are established. The combination of both doping agents manifests a synergistic effect reflected in noteworthy improvements in H2 reducibility. In addition, the catalyst's doping influences its chemisorptive properties, which is reflected in an increase of the easiness of carbonaceous species desorption, thus leading to superior catalyst resistance toward deactivation.


Abril, 2017 | DOI: 10.1039/c6cy02551j

5.37
Fotocatálisis Heterogénea: Aplicaciones

High UV-photocatalytic activity of ZnO and Ag/ZnO synthesized by a facile method

C. Jaramillo-Páez; J.A. Navío; M.C. Hidalgo; M. Macías
Catalysis Today, 284 (2017) 121-128

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ZnO nanoparticles have been successfully synthesized by a facile precipitation procedure by mixing aqueous solutions of Zn(II) acetate and dissolved Na2CO3 at pH ca. 7.0 without template addition. We have investigated the effect of annealing temperature in the final surface and structural properties. Photocatalytic studies were performed using two selected substrates, Methyl Orange and Phenol, both as single model substrates and in mixtures of them.

It has been stated that calcination treatments lead to a significant improvement in the photocatalytic properties of the studied samples, even better than TiO2(P25). As expected, the addition of Ag+ during the photocatalytic degradation of MO increases the reaction rate of the degradation of MO, giving a resultant Ag/ZnO photocatalyst which, after recovery, can be reused at least 18 times for the MO degradation tests, being even more photoactive than ZnO.


Abril, 2017 | DOI: 10.1016/j.cattod.2016.11.021

4.67
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Preferential oxidation of CO on a La-Co-Ru perovskite-type oxide catalyst

Pereniguez, R; Caballero, A; Ferri, D
Catalysis Communication, 92 (2017) 75-79

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A Ru-containing perovskite-type oxide La(Co,Ru)O3 of nominal composition LaCo0.8Ru0.2O3 was prepared by ultrasonic spray combustion and tested for the preferential oxidation of CO (PROX). EXAFS indicated that Ru adopted the coordination environment of Co in LaCoO3 while Co was present as LaCoO3 and Co3O4. PROX activity was replaced by CO hydrogenation activity above 250 °C. Short oxidation at 500 °C between temperature programmed reaction ramps did not restore the initial La(Co,Ru)O3 structure but generated a catalyst with improved PROX activity compared to the initial La(Co,Ru)O3. Under reductive PROX conditions the material experienced structural changes that improved its overall catalytic activity only if the catalyst was oxidized after each temperature programmed ramp.


Marzo, 2017 | DOI: 10.1016/j.catcom.2016.12.020

3.46
Química de Superficies y Catálisis

Monitoring the Reaction Mechanism in Model Biogas Reforming by InSitu Transient and Steady-State DRIFTS Measurements

Bobadilla, LF; Garcilaso, V; Centeno, MA; Odriozola, JA
Chemsuschem, 10 (2017) 1193-1201

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In this work, the reforming of model biogas was investigated on a Rh/MgAl2O4 catalyst. In situ transient and steady-state diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to gain insight into the reaction mechanism involved in the activation of CH4 and CO2. It was found that the reaction proceeds through of an initial pathway in which methane and CO2 are both dissociated on Rh metallic sites and additionally a bifunctional mechanism in which methane is activated on Rh sites and CO2 is activated on the basic sites of the support surface via a formate intermediate by H-assisted CO2 decomposition. Moreover, this plausible mechanism is able to explain why the observed apparent activation energy of CO2 is much lower than that of CH4. Our results suggest that CO2 dissociation facilitates CH4activation, because the oxygen-adsorbed species formed in the decomposition of CO2 are capable of reacting with the CHx species derived from methane decomposition.


Marzo, 2017 | DOI: 10.1002/cssc.201601379

7.41
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Identification of Outer and Inner Nickel Particles in a Mesoporous Support: How the Channels Modify the Reducibility of Ni/SBA-15 Catalysts

Rodriguez-Gomez, A; Caballero, A
Chemnanomat, 3 (2017) 94-97

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Two different nickel supported on SBA-15 catalytic systems have been prepared by means of impregnation (Ni/SBA-15-ImU) and deposition-precipitation (Ni/SBA-15-DP) methodologies. Upon calcination, Ni/SBA-15DP presents a well-developed nickel phyllosilicate phase, which after reduction gives rise to a dispersed and homogeneous metallic phase, mainly located inside the 5 nm in diameter mesoporous structure of the support. On the contrary, as evidenced by XRD and a double temperature programmed reduction (TPR) peak, the Ni/SBA-15-ImU catalyst presents two different NiO phases, which after reduction in hydrogen generate nickel particles in a wide range of sizes. In situ XAS and XPS have unambiguously showed that the distinct TPR profiles obtained for each system are related with particles located in and out the mesoporous structure of the SBA-15 channels. The particles inside the porous are more difficult to reduce, clearly showing a kind of confinement effect of the SBA-15 mesostructure, modifying the reducibility of the NiO phase.


Febrero, 2017 | DOI: 10.1002/cnma.201600297

3.17
Química de Superficies y Catálisis

Gold promoted Cu/ZnO/Al2O3 catalysts prepared from hydrotalcite precursors: Advanced materials for the WGS reaction

Santos, JL; Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
Applied Catalysis B-Envionmental, 201 (2017) 310-317

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Outstanding catalysts for the water was shift reaction are reported in this work. The combination of gold nanoparticles with Cu/ZnO/Al2O3 prepared from hydrotalcite-like precursors leads to very promising systems for pure hydrogen production. Full CO conversion is reached at temperatures as low as 180 degrees C. The key point seems to be the cooperation of Au and Cu and the optimal metal-oxide contact derived from the synthesis method. The high activity of gold for low temperature CO oxidation and the suitability of copper for the WGS results in a perfect synergy. Moreover the materials developed in this work present good stability and tolerance towards start/stop cycles an indispensable requisite for a realistic application in an integrated hydrogen fuel processor.


Enero, 2017 | DOI: 10.1016/j.apcatb.2016.08.017

11.70
Química de Superficies y Catálisis

Gold catalysts screening in base-free aerobic oxidation of glucose to gluconic acid

Megias-Sayago, C.; Ivanova, S.; Lopez-Cartes, C.; Centeno, M.A.; Odriozola, J.A.
Catalysis Today, 279 (2017) 148-154

Show abstract ▽

Base-free aerobic oxidation of glucose in presence of Au/Al2O3, Au/CeO2, Au/CeO2(20 wt%)/Al2O3, Au/CeO2(25 wt%)/ZrO2 and Au/CeO2(50 wt%)/ZrO2 catalysts using molecular oxygen at atmospheric pressure is studied. Within the whole series high conversion and selectivity to gluconic acid are observed after 18 h of reaction at 120 degrees C. The activity and especially the selectivity changes are related to the support nature in a way that the higher the Lewis acidity of the support the lower the selectivity to gluconic acid and the higher the production of lactic acid. The highest yield to gluconic acid is obtained over Au/Al2O3 for which the influence of the reaction time, temperature and stirring rate are further evaluated and discussed.


Enero, 2017 | DOI: 10.1016/j.cattod.2016.06.046

4.67
Fotocatálisis Heterogénea: Aplicaciones

Mixed alpha-Fe2O3/Bi2WO6 oxides for photoassisted hetero-Fenton degradation of Methyl Orange and Phenol

Jaramillo-Paez, C; Navio, JA; Hidalgo, MC; Bouziani, A; El Azzouzi, M
Journal of Photochemistry and Photobiology A-Chemistry, 332 (2017) 521-533

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Mixed oxides, alpha-Fe2O3/Bi2WO6, were prepared using a mechanical mixing procedure by adding to the Bi2WO6 previously obtained by hydrothermal method the corresponding amount of a prepared alpha-Fe2O3, the latter obtained by thermal decomposition of Fe(NO3)center dot 9H(2)O. The physicochemical surface, structural, morphological characteristics and optical properties of the samples, single and mixed, were determined by BET, XRD, FE-SEM, XPS and UV-vis diffuse reflectance spectroscopy. UV-vis diffuse reflectance spectra showed that incorporating a 5%wt. of alpha-Fe2O3 to the corresponding amount of Bi2WO6 sample broadened the visible light absorption of Bi2WO6 as expected. The photocatalytic activity, of single and mixed catalysts, to degrade a selected dye such as Methyl Orange (MO) as well as the transparent substrate Phenol (Ph) was studied, in aqueous medium (pH 5.5) under UV and sun-like illumination conditions in the absence and presence of H2O2. In the present study the use of a alpha-Fe2O3/Bi2WO6/H2O2 system demonstrate much higher photocatalytic efficiency to degrade both MO and Ph than pristine Bi2WO6 or alpha-Fe2O3, single or mixed. Using the system alpha-Fe2O3/Bi2WO6/H2O2, around 85% of MO was degraded in 60 min under sun-like illumination whereas 100% was degraded in 60 min under UV-illumination. However, just around 30% of Ph was degraded in 120 min in the alpha-Fe2O3/Bi2WO6/H2O2 system under sun-like illumination whereas around a 95% was degraded in 90 min under UV-illumination. Under UV illumination, the generation of hydroxyl radicals is favorable; whereas under sun-like illumination, only the small fraction of the UV can produces the center dot OH. Under illumination, the H2O2 could react with photoinduced electrons from the photocatalysts leading to the production of hydroxyl radicals (center dot OH).


Enero, 2017 | DOI: 10.1016/j.jphotochem.2016.09.031

2.89
Química de Superficies y Catálisis

Structuring Pt/CeO2/Al2O3 WGS catalyst: Introduction of buffer layer

Gonzalez-Castano, M; Ivanova, S; Laguna, OH; Martinez, LM; Centeno, MA; Odriozola, JA
Applied Catalysis B-Envionmental, 200 (2017) 420-427

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This work is devoted to the development of novel structured catalytic system for WGS reaction. The new concept is related to the presence of a pre-catalytic "buffer" layer formed by WGS-inert oxide, i.e. not involved in CO conversion, but able to increase the number of participating sites in water dissociation step during the reaction. The performance of the proposed systems appears to depend strongly on the stream composition, being its effect beneficial in highly reducing atmospheres making it ideal for cleanup application. An increment of the partial kinetic order for water species is observed and reveals the key role of the water activation for superior catalytic behavior. 


Enero, 2017 | DOI: 10.1016/j.apcatb.2016.07.039

11.70
Fotocatálisis Heterogénea: Aplicaciones

Study of the E. coli elimination from urban wastewater over photocatalysts based on metallized TiO2

Murcia, JJ; Avila-Martinez, EG; Rojas, H; Navio, JA; Hidalgo, MC
Applied Catalysis B-Envionmental, 200 (2017) 469-476

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In this study, a series of photocatalysts based on TiO2 was tested in the elimination of Escherichia coli (E. coli) from urban wastewater. Firstly, TiO2 obtained by sol-gel method was modified by sulfation, and then gold or platinum nanoparticles were photodeposited on sulfated titania surface. Platinized samples were also prepared with different Pt content of 0.5 and 2 wt.%. The samples thus obtained were extensively characterized and it was found that sulfation considerably increases the S-BET value of TiO2 and promotes the anatase phase formation; it was also found that 0.5 wt.% Pt-TiO2 sample presents the lowest noble metal particle size and the best particle dispersion. All the photocatalysts synthesized have shown bactericidal effect and the results obtained by using bare and metalized TiO2 were considerably better than the results obtained with the commercial TiO2 P25 Evonic. Different light intensities were also evaluated in the photocatalytic tests and it was found that 120 W/m(2) leads to obtain the highest E. coli elimination from wastewater samples; however no total elimination of E. coli or other species of bacteria was achieved even after 5 h of photocatalytic treatment without catalyst. Total elimination of the E. coli was achieved after 3 h of photocatalytic reaction by using 120 Wim(2) of light intensity and 2 wt.% Pt-TiO2 as photocatalyst; no bacterial regrowth was observed even after 72 h. 


Enero, 2017 | DOI: 10.1016/j.apcatb.2016.07.045

11.70
Reactividad de Sólidos - Fotocatálisis Heterogénea: Aplicaciones

Outstanding visible photocatalytic activity of a new mixed bismuth titanatate material

Zambrano, P; Sayagues, MJ; Navio, JA; Hidalgo, MC
Applied Surface Science, 394 (2017) 16-24

Show abstract ▽

In this work, a new photocatalyst based on bismuth titanates with outstanding visible photocatalytic activity was prepared by a facile hydrothermal method. The synthesised material showed visible activity as high as UV activity of commercial TiO2 P25 under the same experimental conditions for phenol degradation. A wide characterisation of the photocatalyst was performed. The material was composed of three phases; majority of Bi20TiO32 closely interconnected to Bi4Ti3O12 and amorphous TiO2. The high visible activity showed by this material could be ascribed to a combination of several features; i.e. low band gap energy value (2.1 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. This photocatalyst appeared as a promising material for solar and visible applications of photocatalysis.


Enero, 2017 | DOI: 10.1016/j.apsusc.2016.10.042

4.44



2016


Química de Superficies y Catálisis

Intensifying glycerol steam reforming on a monolith catalyst: A reaction kinetic model

Bobadilla, LF; Blay, V; Alvarez, A; Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Chemical Engineering Journal, 306 (2016) 933–941

Show abstract ▽

In this work, a structured monolithic catalyst has been tested under a wide range of conditions (partial pressure, residence time, temperature and time-on-stream), with the aim of modeling its kinetic behavior and assessing its economic and upscaling potential. We have developed a sequential model to help us interpret both main trends and salient features. Unexpected behavior was found for certain parameter values, which led us to consider kinetic parasitic effects such as mass or heat transfer limitations. By independently invoking these effects, a conciliatory view of the results observed could not be reached. A combined explanation may prove successful, although overfitting could not be ruled out at this point. More importantly, however, the observed salient features of this stable and selective monolith catalyst may hold potential for process intensification of glycerol steam reforming, thus contributing to a more sustainable industry.


Diciembre, 2016 | DOI: 10.1016/j.cej.2016.08.021

6.22
Química de Superficies y Catálisis

Influence of the ionic liquid presence on the selective oxidation of glucose over molybdenum based catalysts

Megias-Sayago, C; Carrasco, CJ; Ivanova, S; Montilla, FJ; Galindo, A; Odriozola, JA
Catalysis Today, 278 (2016) 82-90

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Two different approaches are proposed in this work in order to study the influence of the ionic liquid presence in the reaction of glucose oxidation by H2O2 in mild conditions. The ionic liquids are applied either as a solvent by using homogeneous Mo based catalyst, [Mo(O)(O2)2(H2O)n] complex, or by using it as an integral part of a heterogeneous catalyst, organic inorganic hybrids based on Mo Keggin structure. Both catalytic strategies resulted in acceptable glucose transformation degrees but lead to different oxidation products depending on the role of the ionic liquid. The hybrid approach restrains the number of the received products being the most selective one. A detailed study of the effect of the hybrid nature and reaction conditions is proposed in the second part of this study.


Diciembre, 2016 | DOI: 10.1016/j.cattod.2016.06.040

4.64
Química de Superficies y Catálisis

Selectivity control in oxidation of 1-tetradecanol on supported nano Au catalysts

Martinez-Gonzalez, S; Ivanova, S; Dominguez, MI; Corberan, VC
Catalysis Today, 278 (2016) 113-119

Show abstract ▽

Selective oxidation of tetradecanol, a model higher fatty alcohol, on Au/CeO2-Al2O3 catalyst has been investigated to assess the factors that control selectivity. The analysis of the effect of operation conditions (temperature, run time and alcohol/metal (AIM) ratio) on catalytic performance revealed a quite complex reaction network, in which acid formation starts only after a certain level of conversion is reached. This level depends linearly on the total support surface available, indicating that it must be saturated by species generated by the reaction itself to allow acid formation to start. Addition of water to reaction medium did not modify this level, indicating that such species is not adsorbed water, as previously hypothesized, but probably spilled over hydrogen species. The resulting drastic change in the selectivity trends makes the ratio A/M a critical factor to control selectivity to aldehyde and to acid. Selectivity to ester is less sensible to operation parameters. It is noteworthy that aldehyde yields up to 27% with 90% selectivity, and acid yields up to 40% with 81% selectivity can be reached by proper selection of operation parameters.


Diciembre, 2016 | DOI: 10.1016/j.cattod.2016.06.019

4.64
Química de Superficies y Catálisis

WGS and CO-PrOx reactions using gold promoted copper-ceria catalysts: "Bulk CuO-CeO2 vs. CuO-CeO2/Al2O3 with low mixed oxide content"

Reina, TR; Ivanova, S; Laguna, OH; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 197 (2016) 62-72

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A copper-ceria bulk catalyst has been compared to a series of catalysts designed according to the as called "supported approach", corresponding to the dispersion of low content mixed copper-ceria oxide on alumina matrix. The principal characteristics of both types of catalysts are contemplated and the differences in their electronic and redox properties discussed in details. As a plus, the gold metal promotion of the catalysts is also envisaged. The advantages of the systems in the CO clean up reactions, WGS and CO-PrOx are commented. While the WGS activity appears to be ruled especially by the Cu/Ce surface to volume ratio, the CO-PrOx reaction is governed by the CuO loading. Gold addition provides benefits only at the low temperature WGS regime. Very importantly, the supported systems are always superior to the bulk configuration in terms of specific activity, a key factor from the catalyst's design perspective. 


Noviembre, 2016 | DOI: 10.1016/j.apcatb.2016.03.022

9.45
Química de Superficies y Catálisis

Recycling of construction and demolition waste generated by building infrastructure for the production of glassy materials

Dominguez, A; Dominguez, MI; Ivanova, S; Centeno, MA; Odriozola, JA
Ceramics International, 42 (2016) 17217-175223

Show abstract ▽

The use of waste materials generated by construction and demolition industry to yield valuable glassy materials, i.e. enamel for glazed ceramic tiles and cellular glasses is presented in this study. Both types of materials are produced by one-step treatment at moderate temperatures after simple waste chemical composition adjust. The enamels are manufactured directly from the initial waste powder by melting, while the expanded materials result from mixing of the vitreous material obtained after waste vitrification with an adequate foaming agent and posterior thermal treatment. Through the manuscript the feasibility of one step production of second generation profit materials is discussed in order to help achieving sustainable development and environmental protection.


Noviembre, 2016 | DOI: 10.1016/j.ceramint.2016.06.157

2.99
Química de Superficies y Catálisis

Forced deactivation and postmortem characterization of a metallic microchannel reactor employed for the preferential oxidation of CO (PROX)

Laguna, OH; Dominguez, MI; Centeno, MA; Odriozola, JA
Chemical Engineering Journal, 302 (2016) 650-662

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This manuscript is one of the few works presenting evidences of the effect of prolonged use of a microreactor. Our reactor has been designed for the PROX reaction. Near to 550 h of operation under different feed-streams, including CO2 and H2O, in the 100-300 degrees C temperature range, and several regeneration cycles, and a final forced deactivation during similar to 360 h resulted in the permanent loss of activity of the microreactor. This could be attributed to some phenomena whose have compromised the chemical nature of the catalyst and that of the reactor including: displacement of the coating to the mouth of the channels, detachments and cracks of the catalytic layer, migration of some elements of the metallic substrate to the surface (Fe, Cr, Y), and deposition of carbonaceous species from the reaction over the catalytic layer and/or the metallic substrate. Furthermore, sulfur compounds were detected in both inlet and outlet zones of the microreactor, coming probably from a lubricant applied over the screws that sealed the assembling of the microreactor. 

This is a first approach for understanding possible effects of deactivation during long-term applications of a microreactor in the PROX reaction that could be considered as a case study useful for future designs of this kind of devices. The presented information could be extrapolated to similar reactions where thermal treatments along with highly corrosive atmospheres would be applied, in order to carry out a more appropriate design of future generations" of microreactors, with a longer useful life. For that purpose not only the adequate selection of the catalysts must be done, but also the adequate choice of the fabrication material of the reactors is needed. 


Octubre, 2016 | DOI: 10.1016/j.cej.2016.05.104

6.22
Química de Superficies y Catálisis

Liquid-phase oxidation with hydrogen peroxide of benzyl alcohol and xylenes on Ca-10(PO4)(6)(OH)(2) - CaWO4

Dominguez, MI; Cojocaru, B; Tudorache, M; Odriozola, JA; Centeno, MA; Parvulescu, VI
Comptes Rendus Chimie, 19 (2016) 1156-1165

Show abstract ▽

A W-containing apatite (W/HAp) catalyst was prepared following a hydrothermal synthesis route and served as a model catalyst. Crystallographic analysis indicated that the resulting material contained hydroxyapatite, Ca10-3xWx(PO4)(6)(OH)(2), W-hydroxyapatite, calcium tungstate, CaWO4, and tricalcium phosphate, Ca-3(PO4)(2). The catalyst was investigated in liquid phase oxidation of benzyl alcohol and xylenes using hydrogen peroxide as an oxidant. For comparison, commercial calcium phosphate, hydroxyapatite and CaWO4 were tested in the same reaction. Calcium phosphate and hydroxyapatite appeared as inactive and decomposed hydrogen peroxide non-selectively. A moderate activity but low hydrogen peroxide efficiency was observed for the CaWO4 phase. In contrast, the W/HAp catalyst showed a reasonable activity and a better hydrogen peroxide efficiency in the oxidation of benzyl alcohol and xylenes. This new W/HAp catalyst showed, after six cycles, losses of the activity below 15% compared to the fresh catalyst with no effect on the selectivity. It is noteworthy that ICP-OES analyses showed no tungsten leaching that is the main advantage of this catalyst. 


Octubre, 2016 | DOI: 10.1016/j.crci.2015.10.013

1.88
Química de Superficies y Catálisis

Au-supported on Fe-doped ceria solids prepared in water-in-oil microemulsions: Catalysts for CO oxidation

Laguna, OH; Centeno, MA; Boutonnet, M; Odriozola, JA
Catalysis Today, 278 (2016) 140-149

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Gold catalysts were synthesized by deposition-precipitation employing Fe-doped ceria systems, previously obtained by means of the water-in-oil microemulsions methodology with different iron contents (10, 25 and 50 Fe at.%). The final catalysts were tested in the CO oxidation reaction in presence of H2. After gold deposition the crystalline structure of the supports was not altered. Moreover no XRD lines associated to gold were detected, indicating its high dispersion. Solid solution was generated in all samples, although the segregation of iron oxide was detected for the material with the highest iron loading. This phenomenon was then enhanced for the corresponding gold catalyst that also presented sintering of the gold nanoparticles.

Strong interaction between gold and the oxygen vacancies of the supports was demonstrated, as well as the promotion of the reducibility of surface Ce4+ and Fe3+species at low temperatures. A remarkable promotion of the CO conversion at lower temperatures respect to that of the supports was observed for the gold catalysts. Below 120 °C, lower the amount of iron incorporated, higher the catalytic performance of the catalyst. This behaviour is closely related not only to a high gold dispersion but also to the ability for creating additional oxygen vacancies in the support, required for the CO oxidation reaction.


Octubre, 2016 | DOI: 10.1016/j.cattod.2016.05.059

4.64
Química de Superficies y Catálisis

Au/CeO2 Catalysts: Structure and CO Oxidation Activity

Centeno, MA; Reina, TR; Ivanova, S; Laguna, OH; Odriozola, JA
Catalysts, 6 (2016) 158

Show abstract ▽

In this comprehensive review, the main aspects of using Au/CeO2 catalysts in oxidation reactions are considered. The influence of the preparation methods and synthetic parameters, as well as the characteristics of the ceria support (presence of doping cations, oxygen vacancies concentration, surface area, redox properties, etc.) in the dispersion and chemical state of gold are revised. The proposed review provides a detailed analysis of the literature data concerning the state of the art and the applications of gold–ceria systems in oxidation reactions.


Octubre, 2016 | DOI: 10.3390/catal6100158

3.08
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Photocatalytic Escherichia coli inactivation by means of trivalent Er3+, Y3+ doping of BiVO4 system

Adan, C; Marugan, J; Obregon, S; Colon, G
Applied Catalysis A-General, 526 (2015) 126-131

Show abstract ▽

BiVO4 samples doped with different contents of Er3+ and Y3+ were prepared by a simple surfactant free hydrothermal method. X-ray diffraction reveals that the doped materials consist of a heterogeneous structure formed by a mixture of tetragonal and monoclinic phases, being found Er3+ and Y3+ co-doping clearly stabilize the tetragonal structure of BiVO4. The monoclinic BiVO4 samples shows a strong absorption in the visible light region leading to band-gap values of around 2.4eV while the tetragonal BiVO4 displays higher band-gap values of 2.9 eV. The photocatalytic activity of the catalysts was investigated for the oxidation of methanol and inactivation of Escherichia coli showing that all the BiVO4 catalysts are photocatalytically active in the oxidation of methanol and are able to inactivate more than 99.99% of bacteria not only under UV light but also under visible light irradiation. The results revealed that the co-doping of Er3+ and Y3+ into BiVO4 exhibited enhanced photocatalytic activity for methanol oxidation under simulated solar light irradiation. The inactivation of E.coli show similar results for the doped systems although in relative terms of activity the Er3+,Y3+-BiVO4 sample show a better use of the visible light, leading to a higher activity than P25-TiO2.


Septiembre, 2016 | DOI: 10.1016/j.apcata.2016.08.002

4.34
Química de Superficies y Catálisis

Growth of carbonaceous nanomaterials over stainless steel foams. Effect of activation temperature

Latorre, N; Cazana, F; Sebastian, V; Royo, C; Romeo, E; Centeno, MA; Monzon, A
Catalysis Today, 273 (2016) 41-49

Show abstract ▽

Some of the problems that occur during the operation of chemical reactors based of structured catalytic substrates, as monoliths, foams, membranes, cloths, fibres and other systems, are related to the preparation of long term stable coatings. Frequently, the deposition of the catalytic layer is carried out by washcoating, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths. In the case of the deposition of layers of carbonaceous materials (CNMs), an alternative route, avoiding the washcoating, it is their direct growth by catalytic decomposition light hydrocarbons (also called CCVD), over the surface of the metallic substrate. In this case, if the metallic substrate is of stainless steel, it already contains the catalytic active phases like Fe and Ni. 

In order to optimize the process of CNMs growth over structured metallic substrates, we are studying the effect of the main operational variables of the ethane decomposition reaction on stainless steel foams. In this contribution we present a study of the influence of the temperature of the activation (oxidation and reduction) stage on the type and morphology of the carbonaceous materials formed. The results obtained allow us to determine the optimal operating conditions to maximize the amount and the selectivity of the process to obtain a given type of CNM.


Septiembre, 2016 | DOI: 10.1016/j.cattod.2016.02.063

4.64
Química de Superficies y Catálisis

Impact of structured catalysts in amine oxidation under mild conditions

J.L. Santos; P. Navarro; J.A. Odriozola; M.A. Centeno; O.D. Pavel; B. Jurca; V.I. Pàrvulescu
Catalysis Today, 273 (2016) 266-272

Show abstract ▽

A structured graphene/graphite catalyst grown on a commercial austenitic stainless steel sheet providing a micromonolith was obtained by submitting the nude stainless steel structure to a carbon-rich atmosphere (first 300 mL/min of a reductive H-2/N-2 (1:1) flow, then to 180 mL/min of a CH4/H-2 (1:5)) at high temperature (900 degrees C) for 2 h. The preparation procedure resulted in a homogenous surface coated with a carbon-rich film as observed by EDX and SEM images. Further characterizations by Raman spectroscopy revealed characteristic Raman lines of graphene and crystalline graphite disposed in a hierarchical organization. The disposal of the obtained surface layers was also confirmed by grazing incidence X-ray diffraction. Besides this, XRD indicated the overlapping diffraction lines of graphite, cementite and M7C3 carbides. The graphene nature of the outermost layer was also confirmed by XPS. The catalytic behavior of the structured graphene/graphite catalyst was evaluated in the selective oxidation of heptylamine. At 200 degrees C it afforded a total conversion with a combined selectivity in heptanonitrile and N-heptylidene-heptylamine of 67% (10% heptanonitrile) that corresponds indeed to a very efficient system in the absence of any metal. Kinetic experiments with the scope to calculate the activation energies were also performed. 


Septiembre, 2016 | DOI: 10.1016/j.cattod.2016.05.001

4.31
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic removal of patent blue V dye on Au-TiO2 and Pt-TiO2 catalysts

Vaiano, V; Iervolino, G; Sannino, D; Murcia, JJ; Hidalgo, MC; Ciambelli, P; Navio, JA
Applied Catalysis B: Environmental, 188 (2016) 134-146

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In this work it was studied the efficiency of a photocatalytic process for the removal of patent blue V. This dye is very difficult to remove by conventional treatments such as adsorption or coagulation therefore the photocatalytic process is a very interesting alternative for the removal this dye mainly because it does not require expensive oxidants and it can be carried out at mild temperatures and pressures. In this work it was tested the efficiency of Au-TiO2 and Pt-TiO2 photocatalysts in the Patent blue V removal. The Au-TiO2 catalysts were prepared by two different methods: chemical reduction and photochemical deposition; Pt-TiO2 catalysts were obtained only by photochemical deposition. In the synthesis of the catalysts prepared by photochemical deposition, it was evaluated the influence of some parameters, such as deposition time and the intensity of the light source over the physicochemical properties and photocatalytic activity of the materials obtained. An analysis of the effect of the catalyst dosage and initial patent blue V concentration over the dye degradation efficiency was also attempted. 
In general, it was observed that the presence of Au or Pt on TiO2 enhances the patent blue V photodegradation; it was found that noble metal particle size and distribution on TiO2 surface are important factors influencing the dye removal. The highest dye degradation was obtained over the Au-TiO2 catalyst prepared by photochemical deposition, using high light intensity and 15 min of deposition time during the synthesis. A discoloration and a total organic carbon (TOC) removal of 93 and 67% respectively, were obtained over this material after 180 min of UV irradiation. These values are higher than that the obtained on S-TiO2 (discoloration and TOC removal of about 25% and 3%, respectively).


Julio, 2016 | DOI: 10.1016/j.apcatb.2016.02.001

9.45
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic hydrogen production from degradation of glucose over fluorinated and platinized TiO2 catalysts

Iervolino, G; Vaiano, V; Murcia, JJ; Rizzo, L; Ventre, G; Pepe, G; Campiglia, P; Hidalgo, MC; Navio, JA; Sannino, D
Journal of Catalysis, 339 (2016) 47-56

Show abstract ▽

The present work reports the renewable hydrogen production by photocatalytic degradation of glucose over commercial and home prepared TiO2 modified by the simultaneous presence of fluorine and Pt (Pt-F-TiO2). The obtained materials were widely characterized by different techniques (XRD, SBF, UV-Vis DRS, XRF, SEM and TEM) and it was found that surface area, anatase/rutile ratio and the distribution and size of the platinum particles are important factors influencing the effectiveness of these materials in the H-2 production. The photocatalytic H-2 production from the glucose solution was 97 mu mol of H-2 after 3 h of irradiation on home prepared TiO2 modified by F and Pt addition, while a lower value corresponding to 31 mu mol of H-2 was obtained on commercial TiO2 modified by F and Pt, after 3 h of irradiation. The hydrogen production rate increased by decreasing the initial pH of solution reaching the highest value of about 590 mu mol h(-1) g(-1) after 3 h of irradiation time at pH = 2. Accordingly, sugar containing wastewaters from food industry has the potential for producing hydrogen by photocatalytic process while removing organics before disposal or reuse. 


Julio, 2016 | DOI: 10.1016/j.jcat.2016.03.032

6.84
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Nickel catalyst with outstanding activity in the DRM reaction prepared by high temperature calcination treatment

Smolakova, L; Kout, M; Capek, L; Rodriguez-Gomez, A; Gonzalez-Delacruz, VM; Hromadko, L; Caballero, A
International Journal of Hydrogen Energy, 41 (2016) 8459-8469

Show abstract ▽

The catalytic performance of some Ni-Ce/Al2O3 catalytic systems (11 wt.% Ni and 3 wt.% Ce) were checked after being submitted to different calcination and reduction treatments. It was found that, the reduced Ni-Ce/Al2O3 catalysts were more active and stable in the dry reforming reaction of methane than thecorresponding not-reduced catalysts. This high activity was initially connected with the smaller size of pre-reduced Ni species, which at the same time leads on to the formation of filamentous carbon. The best overall performance was obtained for the reduced catalyst after being calcined at 1000 degrees C. This catalyst presents a very high stability, a low level of carbon formation, maintaining the nickel particle size constant during reaction. Surprisingly, although its reduction degree is only 12% at 750 degrees C, its catalytic activity is similar to the full reduced catalysts. So, the small number of reduced metallic particles of this catalyst shows a very high activity, much higher than the other catalysts.


Junio, 2016 | DOI: 10.1016/j.ijhydene.2016.03.161

3.58
Química de Superficies y Catálisis

Promoting effect of Sn on supported Ni catalyst during steam reforming of glycerol

Bobadilla, LF; Romero-Sarria, F; Centeno, MA; Odriozola, JA
International Journal of Hydrogen Energy, 41 (2016) 9234-9244

Show abstract ▽

The promoting effect of Sn on the catalytic performance of supported Ni catalyst in the reaction of glycerol steam reforming was studied. The physico-chemical properties of the prepared samples were investigated by X-ray fluorescence (XRF), BET surface area, in situ X-ray diffraction (XRD), laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and temperature-programmed oxidation (TPO) techniques. The characterization results of the samples after reduction treatment (in the same conditions than the activation before catalytic activity measurements) revealed the formation of NiSn alloy. The Sn-doped catalyst exhibited a high activity and it was demonstrated that the Sn addition increase the catalyst stability and durability by decreasing the coke deposition.


Junio, 2016 | DOI: 10.1016/j.ijhydene.2016.04.119

3.58
Química de Superficies y Catálisis

The role of Au, Cu & CeO2 and their interactions for an enhanced WGS performance

Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
Applied Catalysis B: Environmental, 187 (2016) 98-107

Show abstract ▽

The WGS reaction over multicomponent Au/Ce1-xCuxO2/Al2O3 catalysts is studied in this work. The systems are carefully designed aiming to take advantage of every active phase included in the formulation: gold, ceria and copper. Special emphasis is given to the CeO2-CuO synergy and its influence on the displayed catalytic performance with and without gold. To this aim a meaningful correlation between the physicochemical properties of the mixed materials and their activity/stability is proposed. In general terms the developed catalysts present high activity under realistic WGS reaction conditions, with fairly good long term stability. In addition, the systems successfully withstand start-up/shut-downs situations, indispensable requisite for real applications in the field of pure hydrogen production for fuel cell goals. 


Junio, 2016 | DOI: 10.1016/j.apcatb.2016.01.031

9.45
Química de Superficies y Catálisis

The role of carbon overlayers on Pt-based catalysts for H-2-cleanup by CO-PROX

Romero-Sarria, F; Garcia-Dali, S; Palma, S; Jimenez-Barrera, EM; Oliviero, L; Bazin, P; Odriozola, JA
Surface Science, 648 (2016) 84-91

Show abstract ▽

In this work, we analyze the effect of the activation method on the catalytic activity of Pt-based catalysts supported on alumina in the PROX reaction. For this, model Pt/Al2O3 catalysts with variable amounts of acetic acid were prepared and their thermal evolution studied by FTIR spectroscopy. From the analysis of the nature of the platinum surface upon acetic acid decomposition and the gas phase evolved products, we have demonstrated the formation of partially hydrogenated carbon overlayers that tailor the activity of Pt-based catalysts in the PROX reaction. 


Junio, 2016 | DOI: 10.1016/j.susc.2015.12.017

2.06
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

In-situ hydrogasification/regeneration of NiAl-hydrotalcite derived catalyst in the reaction of CO2 reforming of methane: A versatile approach to catalyst recycling

Abdelsadek, Z; Sehailia, M; Halliche, D; Gonzalez-Delacruz, VM; Holgado, JP; Bachari, K; Caballero, A; Cherifi, O
Journal of CO2 Utilization, 14 (2016) 98-105

Show abstract ▽

A novel approach describing the in-situ regeneration of NiAl hydroalcite derived catalyst between two cycle reaction systems of CO2 reforming of methane, also known as dry reforming of methane (DRM) is described herein. The catalyst was initially prepared by co-precipitation method at pH = 11 and calcined at 450 degrees C for 6 h. The obtained material was characterized using X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TG/ATD) and temperature programmed reduction (TPR-H-2) techniques. Following treatment of our catalyst under DRM conditions, the catalyst was subjected to in-situ hydrogasification conditions to promote regeneration followed by a second DRM cycle. An increase of 15.7% in the conversion of CH4 and 17.3% in the conversion of CO2 was attained, while the ratio of resulting H-2/CO augmented by 14%. The ratio of H-2 consumed over the course of two hours hydrogasification, to that generated over ten hours of DRM, was 9.6%. The small particle sizes of resulting Ni degrees species as well as their high stability were both key factors contributing to the increase in the amount of H-2/CO produced prior to and after regeneration. 


Junio, 2016 | DOI: 10.1016/j.jcou.2016.03.004

4.29
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Towards the hydrogen production by photocatalysis

Colon, G
Applied Catalysis A-General, 518 (2016) 48-59

Show abstract ▽

Nowadays, problems derived from climate change urgently demand us to focus our attention on new alternatives to fossil fuels. Within this framework, the photocatalytic production of hydrogen as a clean fuel from oxygenates arises as a necessary option that must be considered. Thus, the development of highly efficient photocatalyst is crucial in order to achieve a viable technology under the industrial point of view. For this sake, it is necessary to understand the principles of photoreforming reaction. In this brief review we will revisit the different photocatalytic materials proposed in the literature highlighting on the role of different co-catalysts.


Mayo, 2016 | DOI: 10.1016/j.apcata.2015.11.042

4.34
Química de Superficies y Catálisis

O-2-assisted Water Gas Shift reaction over structured Au and Pt catalysts

Gonzalez-Castano, M; Reina, TR; Ivanova, S; Tejada, LMM; Centeno, MA; Odriozola, JA
Applied Catalysis B: Enviromental, 185 (2016) 337-343

Show abstract ▽

Platinum and gold structured catalysts were compared as active phases in classical and O2-assisted Water Gas Shift (WGS) reaction. Both metals were supported on iron-doped ceria mixed oxide and then, structured on metallic micromonolithic devices. As expected the WGS activity of both micromonoliths is conditioned by the nature of the noble metals being Pt the most active metal in traditional conditions. However, the addition of oxygen to the classical water gas feed turns the balance in favor of the gold based catalysts, being the presence of gold responsible for an excessive improvement of the catalytic activity.


Mayo, 2016 | DOI: 10.1016/j.apcatb.2015.12.032

9.45
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Cascade charge separation mechanism by ternary heterostructured BiPO4/TiO2/g-C3N4 photocatalyst

Obregon, S; Zhang, YF; Colon, G
Applied Catalysis B: Enviromental, 184 (2016) 96-103

Show abstract ▽

A complex ternary BiPO4/TiO2/gC(3)N(4) heterostructure has been obtained from a simple impregnation method having good photoactivities for the degradation of phenol under solar-like irradiation. From the wide structural, surface and electronic characterization, we have stated that the formation of the ternary heterojunction notably affect photoactivity of pristine TiO2. Thus, the best result for the binary system was obtained for 70 wt%TiO2-30 wt% BiPO4 system. The incorporation of gC(3)N(4) leads to a further improvement on the photocatalytic activity when it is specifically done over TiO2. By means of photoluminescence spectroscopy and reactive oxygen species formation test, we propose that the effective charge carrier separation is taking place through a cascade-driven electronic mechanism. Therefore, by choosing the adequate band-engineering tailoring an important improved photoactivity can be achieved. 


Mayo, 2016 | DOI: 10.1016/j.apcatb.2015.11.027

9.45
Química de Superficies y Catálisis

Nanogold mesoporous iron promoted ceria catalysts for total and preferential CO oxidation reactions

Reina, TR; Ivanova, S; Idakiev, V; Tabakova, T; Centeno, MA; Deng, QF; Yuan, ZY; Odriozola, JA
Journal of Molecular Catalysis A-Chemical, 414 (2016) 62-71

Show abstract ▽

Herein, a series of highly efficient gold based catalysts supported on mesoporous CeO2-Fe2O3 mixed oxides for CO elimination reactions have been developed. The materials have been fully characterized by means of XRD, Raman and UV-vis spectroscopies among other techniques. We identify the Ce-Fe synergism as a fundamental factor controlling the catalytic performance. Our data clearly reveal that the CO oxidation activity is maximized when the electronic and structural properties of the support are carefully controlled. In this situation, fairly good catalysts for environmental applications as for example H-2 streams purification for fuel cell goals or CO abatement at room temperature can be designed. 


Abril, 2016 | DOI: 10.1016/j.molcata.2016.01.003

4.21
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

TiO2-clay based nanoarchitectures for enhanced photocatalytic hydrogen production

Perez-Carvajal, J; Aranda, P; Obregon, S; Colon, G; Ruiz-Hitzky, E
Microporous and Mesoporous Materials, 222 (2016) 120-127

Show abstract ▽

New functional TiO2-clay nanoarchitectures based on layered and fibrous silicates and incorporating Pd and Pt noble metal nanoparticles (NPs) have been synthesized by applying a sol–gel methodology that involves the use of commercial organoclays. The incorporation of the noble metal NPs can be done using two different approaches: i) direct addition to the synthesis medium of a noble metal precursor (typically acetylacetonate) during the generation of the nanoarchitecture, and ii) selective photodeposition of the noble metal NPs in a post-treatment of the TiO2-clay nanoarchitecture. The resulting materials have been characterized by means of XRD, FTIR, Raman, 29Si-NMR, FE-SEM, TEM and N2 adsorption–desorption isotherms. The efficiency of these nanoarchitectures in the photocatalytic hydrogen production has been tested in the photoreforming of methanol. The higher rate in the hydrogen production corresponds to the nanoarchitectures containing Pt and TiO2 NPs derived from sepiolite.


Marzo, 2016 | DOI: 10.1016/j.micromeso.2015.10.007

3.62
Reactividad de Sólidos - Química de Superficies y Catálisis

Intensification of hydrogen production by methanol steam reforming

Sanz, O; Velasco, I; Perez-Miqueo, I; Poyato, R; Odriozola, JA; Montes, M
International Journal Hydrogen Energy, 41 (2016) 5250-5259

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This paper studies the methanol steam reforming intensification to enhance the hydrogen production in a multi-channel block type micro-reformer. The effects of operating parameters such as reforming temperature, space velocity and catalyst layer thickness on reforming performance are investigated. For optimized design and operating conditions, the 8 cm(3) reformer unit produced 170 LH2/h containing on dry basis 75.0% H-2, 23.5% CO2, 0.06% CH3OH and 1.44% CO at 648 K allowing the production of 218-255 Win a commercial PEMFC with 80% hydrogen utilization. This study shows that high methanol conversion can be achieved with high Pd/ZnO catalyst loading at 648 K with very low CO content (<1.5%) in the outlet stream. 


Marzo, 2016 | DOI: 10.1016/j.ijhydene.2016.01.084

3.58
Fotocatálisis Heterogénea: Aplicaciones

Comparison of supported TiO2 catalysts in the photocatalytic degradation of NOx

Rodriguez, MJH; Melian, EP; Diaz, OG; Arana, J; Macias, M; Orive, AG; Rodriguez, JMD
Journal of Molecular Catalysis A-Chemical, 413 (2016) 56-66

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A comparison is made in this study of the effectiveness of various commercial catalysts in the oxidation of NOx by heterogeneous photocatalysis. The following catalysts were considered: Aeroxide TiO2 P25, Aeroxide TiO2 P90, Hombikat UV-100, Kronos vlp7000, CristalACTIV PC105, CristalACTIV PC500, Kemira 650 and Anatasa Aldrich. All catalysts were deposited by a dip -coating technique onto borosilicate 3.3 glass plates. Optimization of catalyst load showed no significant enhancement of photoactivity, in general, above a deposited mass of 1.16 mg cm(-2). Differences between photocatalyst activity were more apparent at longer illumination times. Photoactivity decreased in the presence of humidity and differences in the adsorbed products were detected. Photocatalyst activity was strongly influenced by specific surface area, with the best results obtained by the catalysts with the largest surface area, namely the PC500, Hombikat and Kronos. Photocatalyst stability was demonstrated in successive reuse cycles. 


Marzo, 2016 | DOI: 10.1016/j.molcata.2015.12.007

4.21
Química de Superficies y Catálisis

Ru-Ni Catalyst in the Combined Dry-Steam Reforming of Methane: The Importance in the Metal Order Addition

Alvarez, MA; Centeno, MA; Odriozola, JA
Topics in Catalysis, 59 (2016) 303-313

Show abstract ▽

Biogas is one of the main biomass-energy resources. Its use for syngas production with a H-2/CO ratio close to two would have huge environmental, social and economic impact in the actual energetic scenario. However, the use of dry reforming, where the two main components are transformed into syngas, does not allow the desired H-2/CO ratio. For this reason, the addition of water is proposed. The process was performed with two Ru-Ni catalysts where the metal order in the impregnation process was varied. The catalysts were prepared either by simultaneous or consecutive impregnation of the active phases and its catalytic performance in the combined dry-steam reforming of methane was tested. The catalysts were characterized by XRF, XRD, S-BET, TPR-H-2 and Raman spectroscopy. The existence of a strong Ni-Ru interaction is evidenced by Raman spectroscopy and TPR-H-2 in the sample synthesized by the simultaneous impregnation. Concerning the catalytic activity, this sample presents the highest CH4 and CO2 conversion values in the entire composition rate and the lowest amount of carbon deposits after reaction. After pulse, and reactivity tests it was concluded that the higher Ni-Ru interaction displayed by the catalyst synthesized by the simultaneous impregnation, enhances the carbon gasification.


Febrero, 2016 | DOI: 10.1007/s11244-015-0426-5

2.49
Química de Superficies y Catálisis

In-situ Raman spectroscopy study of Ru/TiO2 catalyst in the selective methanation of CO

Martinez Tejada, LM; Munoz, A; Centeno, MA; Odriozola, JA
Journal of Raman Spectroscopy, 47 (2016) 189-197

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Raman spectroscopic technique has been used to characterize a Ru/TiO2 catalyst and to follow in situ their structural changes during the CO selective methanation reaction (S-MET). For a better comprehension of the catalytic mechanism, the in-situ Raman study of the catalysts activation (reduction) process, the isolated CO and CO2 methanation reactions and the effect of the composition of the reactive stream (H2O and CO2 presence) have been carried out. Raman spectroscopy evidences that the catalyst is composed by islands of TiO2-RuO2 solid solutions, constituting Ru-TiO2 interphases in the form of RuxTi1-xO2 rutile type solid solutions. The activation procedure with H-2 at 300 degrees C promotes the reduction of the RuO2-TiO2 islands generating Ru-o-Ti3+ centers. The spectroscopic changes are in agreement with the strong increase in chemical reactivity as increasing the carbonaceous intermediates observed. The selective methanation of CO proceeds after their adsorption on these Ru-o-Ti3+ active centers and subsequent C?O dissociation throughout the formation of CHx/CnHx/CnHxO/CHx?CO species. These intermediates are transformed into CH4 by a combination of hydrogenation reactions. The formation of carbonaceous species during the methanation of CO and CO2 suggests that the CO presence is required to promote the CO2 methanation. Similar carbonaceous species are detected when the selective CO methanation is carried out with water in the stream. However, the activation of the catalysts occurs at much lower temperatures, and the carbon oxidation is favored by the oxidative effect of water.


Febrero, 2016 | DOI: 10.1002/jrs.4774

2.68



2015


Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Cu–TiO2 systems for the photocatalytic H2 production: Influence of structural and surface support features

Obregon, S; Munoz-Batista, MJ; Fernandez-Garcia, M; Kubacka, A; Colon, G
Applied Catalysis B: Environmental, 179 (2015) 468-478

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The influence of different TiO2 supports on the Cu active species has been studied. It was found that the photocatalytic H2 evolution is highly affected by the structural and electronic features of surface Cu species. Thus, metal dispersion and oxidation state appears strongly conditioned by the structural and surface properties of the TiO2 support. We have examined three TiO2 supports prepared by different synthetic methods; sol–gel, hydrothermal and microemulsion. In addition, we have induced structural and surface modifications by sulfate pretreatment over freshly prepared TiO2 precursors and subsequent calcination. Notably different copper dispersion and oxidation state is obtained by using these different TiO2 supports. From the wide structural and surface analysis of the catalysts we are able to propose that the occurrence of highly disperse Cu2+ species, the sample surface area as well as the crystallinity of the TiO2 support are directly related to the photocatalytic activity for H2 production reaction.


Diciembre, 2015 | DOI: 10.1016/j.apcatb.2015.05.043

8.33
Fotocatálisis Heterogénea: Aplicaciones

Study of the phenol photocatalytic degradation over TiO2 modified by sulfation, fluorination, and platinum nanoparticles photodeposition

Murcia, JJ; Hidalgo, MC; Navio, JA; Arana, J; Dona-Rodriguez, JM
Applied Catalysis B: Environmental, 179 (2015) 305-312

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In this work, titanium dioxide has been modified by sulfation, fluorination and simultaneous Pt nanoparticles deposition; the influence of these treatments on the photocatalytic activity of this oxide has been studied. A complete characterization study was carried out and it was observed that sulfation, fluorination and metallization were important factors influencing the TiO2 properties. The photocatalytic activity of the materials prepared was evaluated in the phenol degradation and it was found that TiO2fluorination significantly increased the phenol photodegradation rate, compared with bare TiO2, sulfated TiO2 or the commercial TiO2 Degussa P25. It was also found that Pt photodeposition on sulphated TiO2 notably increased the photocatalytic activity of this oxide, while Pt on fluorinated TiO2 did not modify significantly the phenol photodegradation rate.


Diciembre, 2015 | DOI: 10.1016/j.apcatb.2015.05.040

8.33
Fotocatálisis Heterogénea: Aplicaciones

Enhancement of stability and photoactivity of TiO2 coatings on annular glass reactors to remove emerging pollutants from waters

Espino-Estevez, MR; Fernandez-Rodriguez, C; Gonzalez-Diaz, OM; Navio, JA; Fernandez-Hevia, D; Dona-Rodriguez, JM
Chemical Engineering Journal, 279 (2015) 488-497

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TiO2 coatings of highly photoactive lab-made titania were prepared on the outer wall of the inner tube of a glass tubular reactor by dip-coating method. The effect of decreasing the size of the aggregates to improve adhesion and photoactivity of the coatings to degrade phenol, diclofenac and isoproturon was also investigated. Chemical disaggregation of the TiO2 particles resulted in a lower aggregate size, between 0.1 and 1 μm, than mechanical disaggregation, between 1 and 10 μm. The results of the adhesion tape test showed that either milling of aggregate material with a planetary mill or chemical stabilization of the particles were necessary to obtain TiO2 coatings on glass tube with acceptable quality to be used in water treatment applications. SEM images showed that coatings prepared after milling the TiO2 suspension were more homogeneous without surface aggregates. The degree of adhesion of the coatings after increasing the roughness of the support by abrasive blasting was also evaluated. Adhesion to the substrate was slightly lower when using the modified support. The photoactivity results showed that the coatings prepared after wet milling of catalyst during 30 min and after chemical disaggregation were more efficient in terms of degradation and mineralization when using phenol as model molecule. Subsequent studies with two emerging pollutants, diclofenac and isoproturon, also showed enhanced efficiency of these coatings. The reusability of the TiO2 coatings was also evaluated and a promising photocatalytic performance was observed with a very low variation of the decay rate after five consecutive usages.


Noviembre, 2015 | DOI: 10.1016/j.cej.2015.05.038

5.31
Fotocatálisis Heterogénea: Aplicaciones

Simultaneous Production of CH4 and H-2 from Photocatalytic Reforming of Glucose Aqueous Solution on Sulfated Pd-TiO2 Catalysts

Vaiano, V; Iervolino, G; Sarno, G; Sannino, D; Rizzo, L; Mesa, JJM; Hidalgo, MC; Navio, JA
Oil & Gas Science and Technology-Revue D IFP Energies Nouvelles, 70 (2015) 891-902

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In this work, the simultaneous production of CH4 and H-2 from photocatalytic reforming of glucose aqueous solution on Pd-TiO2 catalysts under UV light irradiation by Light-Emitting Diodes (LED) was investigated. The Pd-TiO2 catalysts were prepared by the photodeposition method. The Pd content was in the range 0.5-2 wt% and a photodeposition time in the range 15-120 min was used. Pd-TiO2 powders were extensively characterized by X-Ray Diffraction (XRD), SBET, X-Ray Fluorescence spectrometry (XRF), UV-Vis Diffuse Reflectance Spectra (UV-Vis DRS), TEM and X-Ray Photoelectron Spectroscopy (XPS). It was found that the lower Pd loading (0.5 wt%) and 120 min of photodeposition time allowed us to obtain homogeneously distributed metal nanoparticles of small size; it was also observed that the increase in the metal loading and deposition time led to increasing the Pd-0 species effectively deposited on the sulfated TiO2 surface. Particle size and the oxidation state of the palladium were the main factors influencing the photocatalytic activity and selectivity. The presence of palladium on the sulfated titania surface enhanced the H-2 and CH4 production. In fact, on the catalyst with 0.5 wt% Pd loading and 120 min of photodeposition time, H-2 production of about 26 lmol was obtained after 3 h of irradiation time, higher than that obtained with titania without Pd (about 8.5 lmol). The same result was obtained for the methane production. The initial pH of the solution strongly affected the selectivity of the system. In more acidic conditions, the production of H-2 was enhanced, while the CH4 formation was higher under alkaline conditions.


Noviembre, 2015 | DOI: 10.2516/ogst/2014062

0.75
Química de Superficies y Catálisis

Synergy between gold and oxygen vacancies in gold supported on Zr-doped ceria catalysts for the CO oxidation

Laguna, OH; Perez, A; Centeno, MA; Odriozola, JA
Applied Catalysis B-Environmental, 176 (2015) 385-395

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The CO oxidation activity of 1 wt.% gold catalysts prepared by deposition-precipitation on a series of ceria doped with Zr supports was studied. The supports (10, 25 and 50 Zr at.%) were synthesized by a pseudo sol-gel method through the thermal decomposition of the corresponding metallic propionates. All the prepared solids were characterized by means of XRF, BET, XRD, Raman spectroscopy, SEM, and H-2-TPR. Solid solution was obtained in all mixed systems, while the segregation of different Ce-Zr oxides was observed for the solid with the 50 Zr at.%. The oxygen vacancies population and the amount of easier reducible Ce4+ species in the solids increase with the Zr content. No major textural or structural modifications were detected after gold deposition, although a strong Au-support interaction was generated. Such interaction is strongly influenced by the nucleation of gold deposits on the oxygen vacancies and consequently the amount of Zr inserted in the ceria network also determines the dispersion of gold. The presence of gold eases the surface reduction at lower temperatures, and as higher the amount of Zr in the gold catalysts, higher the CO conversion at low temperatures, probably due to the enhancement of the electronic transfer at the surface of the catalysts. 


Octubre, 2015 | DOI: 10.1016/j.apcatb.2015.04.019

8.33
Química de Superficies y Catálisis

Oxodiperoxomolybdenum complex immobilized onto ionic liquid modified SBA-15 as an effective catalysis for sulfide oxidation to sulfoxides using hydrogen peroxide

Carrasco, Carlos J.; Montilla, Francisco; Bobadilla, Luis; Ivanova, Svetlana; Antonio Odriozola, Jose; Galindo, Agustin
Catalysis Today, 255 (2015) 102-108

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A supported ionic-liquid-phase (SILP) was prepared by the reaction of 1-methyl-3-(3-(triethoxysilyl) propyl)-1H-imidazol-3-ium chloride with a mesoporous SBA-15 silica and then an oxodiperoxomolybdenum complex was immobilized onto the obtained SILP. The resulting material, identified as SBA-15 + ImCl+ MoO5, was characterized by solid state NMR (H-1, C-13 and Si-29), and their textural and thermogravimetric properties were determined. The SBA-15 + ImCl+ MoO5 material was investigated as catalyst for the oxidation of methylphenylsulfide, as model reaction, with aqueous hydrogen peroxide as oxidant at room temperature. The presence of the molybdenum species was crucial for achieving good conversions and methanol was selected as the best solvent (conversion of 95% and selectivity toward sulfoxide 98%). The optimized reaction conditions were applied for the oxidation of several selected sulfides. In general, good catalytic activity and selectivity to sulfoxide were obtained and, remarkably, the selectivity toward sulfoxide is higher than those observed in the study of the same process carried out in [C(4)min][PF6] (C(4)mim = 1-buty1-3-methylimidazolium) and catalyzed by a molecular molybdenum complex, under the same reaction conditions. The importance of the IL-functionalization in the SBA-15 material was evidenced by recycling experiments. The SBA-15 + ImCl+ MoO5 catalyst was used for the sulfoxidation of the methylphenylsulfide substrate for ten reaction cycles without a significant change in conversion, selectivity to sulfoxide and molybdenum content.


Octubre, 2015 | DOI: 10.1016/j.cattod.2014.10.053

4.31
Fotocatálisis Heterogénea: Aplicaciones

Boosting the visible-light photoactivity of Bi2WO6 using acidic carbon additives

Carmona, RJ; Velasco, LF; Hidalgo, MC; Navio, JA; Ania, CO
Applied Catalysis A-General, 505 (2015) 467-477

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We have explored the role of the physicohemical properties of carbon materials as additives to bismuth tungstate on its structure, optical properties, and photocatalytic activity for the degradation of rhodamine B under visible light. For this purpose, C/Bi2WO6 hybrid composites were prepared following two different routes: (i) physical mixture of the catalyst components, and (ii) one-pot hydrothermal synthesis of the semiconductor in the presence of the carbon additive. Three carbons with different properties were selected as additives: biomass-derived activated carbon, carbon nanotubes and carbon spheres obtained from polysaccharides. Data has shown the outstanding role of the acidic/basic nature of the carbon additive, and of the synthetic method on the photocatalytic performance of the resulting composites. For a given additive, the degradation rate of RhB is greatly improved for the catalysts prepared through a one-step hydrothermal synthesis, where there is low shielding effect of the carbon matrix. Carbon additives of acidic nature boost the surface acidity of the hybrid photocatalyst, thereby enhancing the photodegradation of RhB under visible light via a coupled mechanism (photosensitization, semiconductor photocatalysis and carbon-photon mediated reactions).


Septiembre, 2015 | DOI: 10.1016/j.apcata.2015.05.011

4.01
Fotocatálisis Heterogénea: Aplicaciones

A comparative study of Bi2WO6, CeO2, and TiO2 as catalysts for selective photo-oxidation of alcohols to carbonyl compounds

Lopez-Tenllado, FJ; Murcia-Lopez, S; Gomez, DM; Marinas, A; Marinas, JM; Urbano, FJ; Navio, JA; Hidalgo, MC; Gatica, JM
Applied Catalysis A-General, 505 (2015) 375-381

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Several semiconductors based on ceria or bismuth tungstate were tested for selective oxidation of alcohols to carbonyl compounds in a search for photocatalysts more selective than TiO2. Gas-phase selective photo-oxidation of propan-2-ol to acetone and liquid-phase transformation of 2-buten-1-ol (crotyl alcohol) to 2-butenal (crotonaldehyde) were studied as test reactions. In both processes the highest selectivities were achieved with Bi2WO6-based solids. Further studies on crotyl alcohol transformation evidenced the lower adsorption of the aldehyde on these systems which could minimize the decrease in crotyl alcohol yield observed for TiO2 or CeO2 at high conversions. Incorporation of titania (5% molar) to the Bi2WO6 system increased the reaction rate significantly whereas the aldehyde yield remained high. 


Septiembre, 2015 | DOI: 10.1016/j.apcata.2015.08.013

4.01
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Facile Synthesis of Decahedral Particles of Anatase TiO2 with Exposed {001} Facets

Perales-Martinez, IA; Rodriguez-Gonzalez, V; Obregon-Alfaro, S; Lee, SW
Journal of Nanoscience and Nanotechnology, 15 (2015) 7351-7356

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This paper reports a facile synthesis of decahedral particles of anatase TiO2 dominated by {101} and {001} faces. The decahedral particles has been enhanced by means a microwave-assisted hydrothermal method using TiF4 as a titanium precursor and HF as capping agent to promote oriented growth and formation of {001} faces in only 4 h. The prepared samples were characterized by scanning electron microscopy, high resolution of transmission electron microscopy and X-ray diffraction. The morphology of anatase TiO2 particles is consisted of near-perfect-truncated-bipyramid-shape. Reaction time is a key factor to obtain truncated-bipyramid-shaped particles with sharp and well-defined edges. Reaction times longer than 4 h induce irregular particles. Decahedral anatase TiO2 particles are truncated bypiramid crystals which have eight {101} and two {001} facets at top/bottom surfaces. The average size of decahedral anatase TiO2 particles are similar to 250 nm for the samples obtained without applying the microwave irradiation and similar to 350 nm for reaction 4 h.


Septiembre, 2015 | DOI: 10.1166/jnn.2015.10578

1.56
Química de Superficies y Catálisis

Microreactors technology for hydrogen purification: Effect of the catalytic layer thickness on CuOx/CeO2-coated microchannel reactors for the PROX reaction

Laguna, O. H.; Castano, M. Gonzalez; Centeno, M. A.; Odriozola, J. A.
Chemical Engineering Journal, 271 (2015) 45-52

Show abstract ▽

Two blocks of microreactors composed by 100 microchannels and coated, respectively, with 150 and 300 mg of a CuOx/CeO2 catalyst, were prepared and tested in the preferential oxidation of CO in presence of H2 (PROX). The deposition of different amount of catalyst resulted in different catalytic layer thicknesses thus modifying the catalytic performances of the microreactor. The evaluation of the main reaction variables (the space velocity, the O2-to-CO ratio and the presence of H2O and/or CO2 in the stream) was performed over both microreactors and compared to that of the parent powder catalyst. The least loaded microreactor, with a coating thickness around 10 μm, presented the highest CO conversion and selectivity levels at temperatures below 160 °C. This result evidences (i) the improvement of the catalytic performances got by the structuration of the powder catalyst and (ii) the importance of the selection of the adequate thickness of the catalytic layer on the microreactor, which have not to exceed and optimal value. An adequate coating thickness allows minimizing the mass and heat transport limitations, thus resulting in the enhancement of the catalytic performance during the PROX reaction.


Septiembre, 2015 | DOI: 10.1016/j.cej.2015.04.023

5.31
Química de Superficies y Catálisis

Boosting the activity of a Au/CeO2/Al2O3 catalyst for the WGS reaction

Reina, T. R.; Ivanova, S.; Centeno, M. A.; Odriozola, J. A.
Catalysis Today, 253 (2015) 149-154

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Herein a strategy to design highly efficient Au/CeO2/Al2O3 based WGS catalysts is proposed. The inclusion of transition metals, namely Fe, Cu and Zn as CeO2 dopant is considered. All the promoters successfully increased the WGS performance of the undoped sample. The activity improvement can be correlated to structural and/or redox features induced by the dopants. The comparative characterization of the doped samples by means of XRD, Raman spectroscopy and OSC evaluation permits an accurate understanding of the boosted WGS activity arising from the Ce-promoter interaction. This study establishes distinction among both, structural and redox sources of promotion and provides a useful strategy to develop highly active Au/CeO2 based catalysts for the WGS reaction.


Septiembre, 2015 | DOI: 10.1016/j.cattod.2015.01.041

4.31
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

On the origin of the photocatalytic activity improvement of BIVO4 through rare earth tridoping

Obregon, S; Colon, G
Applied Catalysis A-General, 501 (2015) 56-62

Show abstract ▽

Rare earth (Tm3+/Er3+,Yb3+,Y3+) tri-doped BiVO4 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of methylene blue and O-2 evolution reactions. The improved photocatalytic performance has been attained by multiple approach of the overall photocatalytic mechanism. From the structural and morphological characterization it has been stated that the presence of Y3+ induces the stabilization of the tetragonal phase probably due to its substitutional incorporation in the BiVO4 lattice. Moreover, the extensive doping with rare earth ions such as Yb3+ and Er3+/Tm3+ t-BiVO4 evidenced that important structural, electronic changes as well as the luminescence properties were also exalted. Ternary doping clearly prompts the higher photocatalytic activities. A more packed tetragonal structure in conjunction leading to improved charge carriers mobility, with the observed visible and NIR photoactivities of t-BiVO4 could be the responsible of the improved photocatalytic activity under solar-like irradiation.


Julio, 2015 | DOI: 10.1016/j.apcata.2015.04.032

4.01
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic propylene epoxidation on Bi2WO6-based photocatalysts

Murcia-Lopez, S.; Vaiano, V.; Sannino, D.; Hidalgo, M. C.; Navio, J. A.
Research on Chemical Intermediates, 41 (2015) 4199-4212

Show abstract ▽

The photocatalytic epoxidation of propylene (PR) with molecular oxygen was carried out in a fluidized-bed reactor with several Bi2WO6-based materials under UV-A illumination. Three different photocatalysts were tested: one of single Bi2WO6 and two of coupled Bi2WO6-TiO2 heterostructures, thus showing that a mixed system of Bi2WO6 with commercial TiO2 Degussa-P25 leads to the best combination of conversion and PO selectivity. Then, direct support on glass spheres and silica gel was made, being a good alternative for improving the Bi2WO6 performance. Additionally, several reaction conditions of temperature and PR to O-2 feed ratio were studied.


Julio, 2015 | DOI: 10.1007/s11164-013-1523-3

1.83
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

A novel two-steps solvothermal synthesis of nanosized BiPO4 with enhanced photocatalytic activity

Zhang, YF; Sillanpaa, M; Obregon, S; Colon, G
Journal of Molecular Catalysis A-Chemical, 402 (2015) 92-99

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Nano-sized BiPO4 has been successfully synthesized via a novel designed two-steps solvothermal route using ethylene glycol as solvent. Comparing with traditional hydrothermal method, the novel approach could readily prepare BiPO4 with shorter time. The photocatalytic activity of prepared BiPO4 has been tested via degradation of methylene blue (MB) under light irradiation. The experimental results show that the BiPO4 prepared by novel route had enhanced photocatalytic activity and the synthetic parameters also impact the reaction rate meaningfully. Finally, the obtained samples have been widely characterized by means of powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM), UV–vis diffuse reflectance spectra (DRS) and Fourier transformed infrared (FTIR) spectra. BiPO4 prepared by this novel approach have a particles size below 100 nm, which is a big improvement by comparing with previous works (few micrometer). The effect of EG during the formation of BiPO4 has been discussed and a possible formation mechanism is proposed.
 


Junio, 2015 | DOI: 10.1016/j.molcata.2015.03.011

3.96
Química de Superficies y Catálisis

H-2 oxidation as criterion for PrOx catalyst selection: Examples based on Au-Co-O-x-supported systems

Reina, TR; Megias-Sayago, C; Florez, AP; Ivanova, S; Centeno, MA; Odriozola, JA
Journal of Catalysis, 326 (2015) 161-171

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A new approach for understanding PrOx reaction over gold catalysts is proposed in this work. The competition between H-2 and CO oxidation has been studied over a series of Au/MOx/Al2O3 (M = Ce and Co) catalysts in simulated post-reforming gas stream, containing H2O and CO2 for H-2 cleanup goals. The catalysts' behavior is correlated to their oxygen storage capacity, redox behavior, and oxidation ability. The estimation of the reaction rates reveals that in these solids the H-2 combustion, the selectivity limiting factor in the PrOx process, is mainly controlled by the support and not by the gold presence. The possible use of the hydrogen oxidation reaction as a catalyst selection criterion is discussed. 


Junio, 2015 | DOI: 10.1016/j.jcat.2015.03.015

7.35
Nanotecnología en Superficies y Plasma - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Theory and Practice: Bulk Synthesis of C3B and its H2- and Li-Storage Capacity

King, TC; Matthews, PD; Glass, H; Cormack, JA; Holgado, JP; Leskes, M; Griffin, JM; Scherman, OA; Barker, PD; Grey, CP; Dutton, SE; Lambert, RM; Tustin, G; Alavi, A; Wright, DS
Angewandte Chemie International Edition, 54 (2015) 5919-5923

Show abstract ▽

Previous theoretical studies of C3B have suggested that boron-doped graphite is a promising H2- and Li-storage material, with large maximum capacities. These characteristics could lead to exciting applications as a lightweight H2-storage material for automotive engines and as an anode in a new generation of batteries. However, for these applications to be realized a synthetic route to bulk C3B must be developed. Here we show the thermolysis of a single-source precursor (1,3-(BBr2)2C6H4) to produce graphitic C3B, thus allowing the characteristics of this elusive material to be tested for the first time. C3B was found to be compositionally uniform but turbostratically disordered. Contrary to theoretical expectations, the H2- and Li-storage capacities are lower than anticipated, results that can partially be explained by the disordered nature of the material. This work suggests that to model the properties of graphitic materials more realistically, the possibility of disorder must be considered.


Mayo, 2015 | DOI: 10.1002/anie.201412200

11.71
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

The role of silver nanoparticles functionalized on TiO2 for photocatalytic disinfection of harmful algae

Lee, Soo-Wohn; Obregon, S.; Rodriguez-Gonzalez, V.
RSC Advances, 5 (2015) 44470-44475

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Silver loaded TiO2 samples were prepared by photodeposition of different amounts of Ag+ ions over commercial titanium dioxide (Evonik TiO2 P25) in aqueous media without the presence of sacrificial agents. The obtained photocatalysts were characterized by several techniques such as X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in order to correlate the effect of the silver amount on the photocatalytic properties of the final nanocomposite. The effect of the silver nanoparticles on the photocatalytic behaviour of TiO2 was evaluated by means of the photodegradation of methyl orange dye and the inactivation of noxious algae Tetraselmis suecicaand Amphidium carterae under continuous exposure of low power irradiation UV-light. The sample with 1.5% wt of silver nanoparticles showed the highest photocatalytic elimination of the azo dye and both algae types. According to the results, the cells were deformed during the photocatalytic process by the attack of highly reactive species such as hydroxyl radicals, H2O2 and superoxide ions generated on the TiO2 surface. The algae cells were not regenerated by themselves after the photocatalytic process due the high degree of fragmentation that they suffered during the light irradiation.


Mayo, 2015 | DOI: 10.1039/C5RA08313C

3.29
Química de Superficies y Catálisis

Mono and bimetallic Cu-Ni structured catalysts for the water gas shift reaction

O. Arbeláez, T.R. Reina, S. Ivanova, F. Bustamante, A.L. Villa, M.A. Centeno, J.A. Odriozola
Applied Catalysis A-General, 497 (2015) 1-9

Show abstract ▽

The water-gas shift (WGS) reaction over structured Cu, Ni, and bimetallic Cu-Ni supported on active carbon (AC) catalysts was investigated. The structured catalysts were prepared in pellets form and applied in the medium range WGS reaction. A good activity in the 180–350 °C temperature range was registered being the bimetallic Cu-Ni:2-1/AC catalyst the best catalyst. The presence of Cu mitigates the methanation activity of Ni favoring the shift process. In addition the active carbon gasification reaction was not observed for the Cu-containing catalyst converting the active carbon in a very convenient support for the WGS reaction. The stability of the bimetallic Cu-Ni:2-1/AC catalyst under continuous operation conditions, as well as its tolerance towards start/stop cycles was also evaluated.


Mayo, 2015 | DOI: 10.1016/j.apcata.2015.02.041

4.01
Fotocatálisis Heterogénea: Aplicaciones

Photocatalytic reduction of CO2 over platinised Bi2WO6-based materials

Murcia-Lopez, S; Vaiano, V; Hidalgo, MC; Navio, JA; Sannino, D
Photochemical & Photobiological Sciences, 14 (2015) 678-685

Show abstract ▽

The photocatalytic reduction of CO2 with H2O to produce CH4 in the gas phase was carried out in the presence of two Bi2WO6-based materials. For this purpose, single Bi2WO6 and a coupled Bi2WO6-TiO2 system were synthesised and metallised with Pt, through a Pt photodeposition method. Then, the samples were characterised and the photocatalytic activity was evaluated in a continuous fluidised-bed reactor irradiated with UV light. Single Bi2WO6 presents an interesting behaviour under H2O rich conditions. In particular, the metallisation improves the material's performance for CH4 formation, while the TiO2 addition to Bi2WO6 increases the CH4 yield only at low H2O/CO2 ratio. The Bi2WO6-TiO2 system metallised with a Pt photocatalyst displayed the highest CH4 yield among all the prepared photocatalysts. The stability of the system can be enhanced through the addition of a blue phosphor to the reactant mixture, especially under H2O rich conditions.


Abril, 2015 | DOI: 10.1039/c4pp00407h

2.24
Química de Superficies y Catálisis

Role of ruthenium on the catalytic properties of CeZr and CeZrCo mixed oxides for glycerol steam reforming reaction toward H2 production

Martinez, LM; Araque, M; Centeno, MA; Roger, AC
Catalysis Today, 242 (2015) 80-90

Show abstract ▽

The effect of ruthenium on the physico-chemical properties of CeZr and CeZrCo mixed oxides for H2production by glycerol steam reforming reaction has been studied. The combination of in situ Raman spectroscopy under both reductive and oxidative conditions, H2/O2 pulses and XRD, Raman, BET analysis, H2-TPR and TPD-TPO analyses contributed to the determination of the structural and textural properties, redox behavior, re-oxidation capacity and resistance to carbon deposition of the synthesized catalysts. The results show that the catalytic activity is improved by the (positive) cooperative and complementary effect between cobalt and ruthenium that favors the selectivity toward the steam reforming, selective to H2, with respect to the unselective thermal decomposition of glycerol. Ruthenium stabilizes the cobalt cations inserted in the fluorite structure preventing its rejection as Co3O4; and provides the necessary hydrogen to reduce Ce4+. The combination cobalt–ruthenium modifies positively the redoxproperties of the catalysts, increases the re-oxidation capacity (OSC) and promotes the gasification of the carbon deposits. Under the reaction conditions, the decrease in glycerol conversion came along with a change of selectivity. The formation of H2 and CO2 were strongly decreased, while the formation of CO, C2H4 and condensable products (mainly hydroxyacetone) increase. The differences in the catalytic stability and activity of the catalysts are related to the capability of the catalysts to activate H2O under the reaction conditions, favoring the steam reforming reaction over the thermal decomposition.


Marzo, 2015 | DOI: 10.1016/j.cattod.2014.07.034

4.31
Química de Superficies y Catálisis

Ni-CeO2/C Catalysts with Enhanced OSC for the WGS Reaction

Pastor-Perez, L; Ramirez Reina, T; Ivanova, S; Centeno, MA; Odriozola, JA; Sepulveda-Escribano, A
Catalysts, 5 (2015) 298-309

Show abstract ▽

In this work, the WGS performance of a conventional Ni/CeO2 bulk catalyst is compared to that of a carbon-supported Ni-CeO2 catalyst. The carbon-supported sample resulted to be much more active than the bulk one. The higher activity of the Ni-CeO2/C catalyst is associated to its oxygen storage capacity, a parameter that strongly influences the WGS behavior. The stability of the carbon-supported catalyst under realistic operation conditions is also a subject of this paper. In summary, our study represents an approach towards a new generation of Ni-ceria based catalyst for the pure hydrogen production via WGS. The dispersion of ceria nanoparticles on an activated carbon support drives to improved catalytic skills with a considerable reduction of the amount of ceria in the catalyst formulation.


Marzo, 2015 | DOI: 10.3390/catal5010298

2.96
Química de Superficies y Catálisis

Ionic liquid immobilization on carbon nanofibers and zeolites: Catalyst design for the liquid-phase toluene chlorination

Losch, Pit; Martinez Pascual, Antonio; Boltz, Marilyne; Ivanova, Svetlana; Louis, Benoit; Montilla, Francisco; Antonio Odriozola, Jose
Comptes Rendus Chimie, 18 (2015) 324-329

Show abstract ▽

The environmental-friendly chlorination reaction of toluene by trichloroisocyanuric acid (TCCA, C3N3O3Cl3) was investigated applying immobilized ionic liquids (ILs) on different supports. Ionic liquids were grafted either on carbon nanofibers (CNF) or encapsulated in zeolites. Their influence on the chlorination activity as well as on the selectivity in different chlorinated products was studied. An unusually high selectivity toward meta-chlorotoluene was achieved, up to 36%. Hence, the selectivity could be tuned to produce either expected ortho-/para-chlorotoluene or meta-chlorotoluene with a proper support choice. 


Marzo, 2015 | DOI: 10.1016/j.crci.2014.06.006

1.80
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Photocatalytic activity of bismuth vanadates under UV-A and visible light irradiation: Inactivation of Escherichia coli vs oxidation of methanol

Adan, C; Marugan, J; Obregon, S; Colon, G
Catalysis Today, 240 (2015) 93-99

Show abstract ▽

Four bismuth vanadates have been synthesized by using two different precipitating agents (NH3 and triethylamine) following a hydrothermal treatment at 100 °C for 2 h and at 140 °C for 20 h. Then, solids were characterized by X-ray diffraction, BET surface area, UV–vis spectroscopy and scanning microscopy techniques. The characterization of the synthesized materials showed a well crystallized scheelite monoclinic structure with different morphologies. All materials display optimum light absorption properties for visible light photocatalytic applications. The photocatalytic activity of the catalysts was investigated for the inactivation of Escherichia coli bacteria and the oxidation of methanol under UV–vis and visible light irradiation sources. Main results demonstrate that BiVO4 are photocatalytically active in the oxidation of methanol and are able to inactivate bacteria below the detection level. The activity of the catalyst decreases when using visible light, especially for methanol oxidation, pointing out differences in the reaction mechanism. In contrast with bacteria, whose interaction with the catalyst is limited to the external surface, methanol molecules can access the whole material surface.


Febrero, 2015 | DOI: 10.1016/j.cattod.2014.03.059

4.31
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Evolution of H-2 photoproduction with Cu content on CuOx-TiO2 composite catalysts prepared by a microemulsion method

Kubacka, A; Munoz-Batista, MJ; Fernandez-Garcia, M; Obregon, S; Colon, G
Applied Catalysis B: Environmental, 163 (2015) 214-222

Show abstract ▽

Copper oxides in contact with anatase correspond to promising materials with high activity in the photo-production of hydrogen by aqueous reforming of alcohols. By a single pot microemulsion method we obtained a series of Cu-Ti composite systems with controlled copper content in the 0-25 wt.% range. The scanning of such a wide range of composition led to the discovery of two well differentiated maxima in the photo-reaction performance. These maxima present rather high and relatively similar reaction rates and photonic efficiencies but are ascribed to the presence of different copper species. A multi-technique analysis of the materials indicates that the maxima obtained comes from optimizing different steps of the reaction; while the first would be connected with a positive effect on anatase charge handling performance the second seems exclusively related to electron capture by surface copper species.


Febrero, 2015 | DOI: 10.1016/j.apcatb.2014.08.005

8.33
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Water splitting performance of Er3+-doped YVO4 prepared from a layered K3V5O14 precursor

Obregon, S; Colon, G
Chemical Engineering Journal, 262 (2015) 29-33

Show abstract ▽

Erbium-doped YVO4 have been synthesized by means of a simple solution method having good photo activities under UV-like excitation for the water splitting half reactions. From the structural and morphological characterization it has been stated that the presence of Er3+ induces the promotion of luminescence. Moreover the incorporation of erbium clearly affects to the morphology YVO4 leading to 200 nm size well-defined spindle-like particles. The improved photocatalytic performance might be associated to a better electron–hole separation mechanism, probably due to the slight increase of band-gap value. The obtained photoactivities for H2 and O2 evolution reactions make this material a promising candidate for water splitting reactions.


Febrero, 2015 | DOI: 10.1016/j.cej.2014.09.073

5.31
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Effective photoreduction of a nitroaromatic environmental endocrine disruptor by AgNPs functionalized on nanocrystalline TiO2

Hernandez-Gordillo, A; Obregon, S; Paraguay-Delgado, F; Rodriguez-Gonzalez, V
RSC Advances, 5 (2015) 15194-15197

Show abstract ▽

Unprecedented photoactivity of silver nanoparticles photodeposited on nanocrystalline TiO2 for the efficient reduction of 4-nitrophenol at room temperature is reported. The use of Na2SO3 as a harmless scavenger agent for the reduction of a nitroaromatic endocrine disruptor yields a valuable 4-aminophenol reagent.


Febrero, 2015 | DOI: 10.1039/c5ra00094g

3.84
Química de Superficies y Catálisis - Fotocatálisis Heterogénea: Aplicaciones

Synthesis and application of layered titanates in the photocatalytic degradation of phenol

Ivanova, S; Penkova, A; Hidalgo, MD; Navio, JA; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Applied Catalysis B: Environmental, 163 (2015) 23-29

Show abstract ▽

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the “chimie douce”. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol.


Febrero, 2015 | DOI: 10.1016/j.apcatb.2014.07.048

8.33
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study

Hueso, JL; Holgado, JP; Pereniguez, R; Gonzalez-DelaCruz, VM; Caballero, A
Materials Chemistry and Physics, 151 (2015) 29-33

Show abstract ▽

LaCoO3 and La0.5Sr0.5O3O3-delta perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La0.5Sr0.5CoO3-delta perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. 


Febrero, 2015 | DOI: 10.1016/j.matchemphys.2014.11.015

2.10
Química de Superficies y Catálisis

Glycerol steam reforming on bimetallic NiSn/CeO2-MgO-Al2O3 catalysts: Influence of the support, reaction parameters and deactivation/regeneration processes

Bobadilla, LP; Penkova, A; Alvarez, A; Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Applied Catalysis A: General, 492 (2015) 38-47

Show abstract ▽

NiSn bimetallic catalysts supported over Al2O3 modified with different promoter (Mg and/or Ce) were prepared and characterized by powder X-ray diffraction (XRD), N2 sorptometry, and temperature programmed reduction (TPR). Hydrogen production by glycerol steam reforming over these catalysts was investigated. Among the catalysts, NiSn/AlMgCe catalyst shows the highest hydrogen yield as well as the best stability during the reaction. The effect of reaction temperature, water/glycerol molar ratio and space velocity on the glycerol steam reforming over NiSn/AlMgCe were also investigated. Finally, it was verified that the catalyst can be regenerated by oxidation of carbonaceous deposits.


Febrero, 2015 | DOI: 10.1016/j.apcata.2014.12.029

4.01
Nanotecnología en Superficies y Plasma - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Sonogashira Cross-Coupling and Homocoupling on a Silver Surface: Chlorobenzene and Phenylacetylene on Ag(100)

Sanchez-Sanchez, C; Orozco, N; Holgado, JP; Beaumont, SK; Kyriakou, G; Watson, DJ; Gonzalez-Elipe, AR; Feria, L; Sanz, JF; Lambert, RM
Journal of the American Chemical Society, 137 (2015) 940-947

Show abstract ▽

Scanning tunneling microscopy, temperature-programmed reaction, near-edge X-ray absorption fine structure spectroscopy, and density functional theory calculations were used to study the adsorption and reactions of phenylacetylene and chlorobenzene on Ag(100). In the absence of solvent molecules and additives, these molecules underwent homocoupling and Sonogashira cross-coupling in an unambiguously heterogeneous mode. Of particular interest is the use of silver, previously unexplored, and chlorobenzene—normally regarded as relatively inert in such reactions. Both molecules adopt an essentially flat-lying conformation for which the observed and calculated adsorption energies are in reasonable agreement. Their magnitudes indicate that in both cases adsorption is predominantly due to dispersion forces for which interaction nevertheless leads to chemical activation and reaction. Both adsorbates exhibited pronounced island formation, thought to limit chemical activity under the conditions used and posited to occur at island boundaries, as was indeed observed in the case of phenylacetylene. The implications of these findings for the development of practical catalytic systems are considered.


Enero, 2015 | DOI: 10.1021/ja5115584

13.04
Química de Superficies y Catálisis

Catalytic screening of Au/CeO2-MOx/Al2O3 catalysts (M = La, Ni, Cu, Fe, Cr, Y) in the CO-PrOx reaction

Reina, TR; Ivanova, S; Centeno, MA; Odriozola, JA
International Journal of Hydrogen Energy, 40 (2015) 1782-1788

Show abstract ▽

In this work, a series of Au/CeO2-MOx/Al2O3 catalysts has been prepared and evaluated in the PrOx reaction. Within the series of dopants Fe and Cu containing samples enhanced the catalytic performance of the parent Au/CeO2/Al2O3 catalyst being copper the most efficient promoter. For both samples an enhanced oxygen storage capacity (OSC) is registered and accounts for the high CO oxidation activity. More particularly, the Au/CeO2-CuOx/Al2O3 catalyst successfully withstands the inclusion of water in the PrOx stream and presents good results in terms of CO elimination. However to achieve a good selectivity toward, CO2 formation properly adjusting of the reaction parameters, such as oxygen concentration and space velocity is needed. Within the whole screened series the Cu-containing catalyst can be considered as the most interesting alternative for H-2 clean-up applications.


Enero, 2015 | DOI: 10.1016/j.ijhydene.2014.11.141

3.21



2014


Química de Superficies y Catálisis

Heterogeneous selective oxidation of fatty alcohols: Oxidation of 1-tetradecanol as a model substrate

Corberan, VC; Gomez-Aviles, A; Martinez-Gonzalez, S; Ivanova, S; Dominguez, MI; Gonzalez-Perez, ME
Catalysis Today, 238 (2014) 49-53

Show abstract ▽

Selective oxidation of fatty alcohols, i.e., linear long-chain alkanols, has been scarcely investigated to date, despite its potential application in high value chemical's production. We report for the first time the liquid phase heterogeneous oxidation of 1-tetradecanol, used as a model molecule for fatty alcohols, according to green chemistry principles by using a Au/CeO2-Al2O3 catalyst and O-2 as oxidant at normal pressure. High selectivity to tetradecanal (ca. 80%) or to tetradecanoic acid (60-70%) are reached at medium conversion (up to 38%), depending on the reaction conditions used. Comparison with similar tests of 1-octanol oxidation shows that the increase of the carbon chain length decreases the alcohol conversion and the formation of ester, probably due to a greater steric effect.


Diciembre, 2014 | DOI: 10.1016/j.cattod.2014.03.033

3.89
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Heterostructured Er3+ doped BiVO4 with exceptional photocatalytic performance by cooperative electronic and luminescence sensitization mechanism

Obregon, S; Colon, G
Applied Catalysis B: Environmental, 158-159 (2014) 242-249

Show abstract ▽

Er-BiVO4 has been synthesized by means of mw-assisted hydrothermal method having good photoactivity under sun-like excitation. It is stated that the precursor addition sequence plays a critical role which determine the further structural feature of BiVO4. From the structural and morphological characterization, it can be demonstrated that the presence of Er3+ would induce the stabilization of the tetragonal phase probably due to the formation of tetragonal-ErVO4 seeds previous to BiVO4 formation. The best photocatalytic performance is attained for the sample with 0.75 at% Er3+ content. At this dopant loading a mixture of tetragonal and monoclinic phase (70% tetragonal) is obtained. The dramatic increase in the photocatalytic activity for 0.75 at% Er-BiVO4 is related to the occurrence of such heterostructure. For this system, the MB degradation rate constant appears drastically higher as bare m-BiVO4. Furthermore, activities of photocatalysts for visible-light-driven O2 evolution have been evaluated, demonstrating that the photocatalytic activity of this Er-doped system (O2 evolution rate, 1014 μmol g−1 h−1) is 20 times as that of undoped m-BiVO4 (O2 evolution rate, 54 μmol g−1 h−1). From the obtained results, the cooperative conjunction of electronic and luminescence mechanism involved in the reaction is proposed to be the origin of the enhanced photocatalytic efficiencies of such systems.


Octubre, 2014 | DOI: 10.1016/j.apcatb.2014.04.029

7.44
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Active Site Considerations on the Photocatalytic H-2 Evolution Performance of Cu-Doped TiO2 Obtained by Different Doping Methods

Valero, JM; Obregon, S; Colon, G
ACS Catalysis, 4 (2014) 3320-3329

Show abstract ▽

A photocatalytic H2 evolution reaction was performed over copper doped TiO2. The influence of sulfate pretreatment over fresh TiO2 support and the Cu doping method has been evaluated. Wide structural and surface characterization of catalysts was carried out in order to establish a correlation between the effect of sulfuric acid treatment and the further Cu-TiO2photocatalytic properties. Notably a different copper dispersion and oxidation state is obtained by different metal decoration methods. From the structural and surface analysis of the catalysts we have stated that the occurrence of highly disperse and reducible Cu2+ species is directly related to the photocatalytic activity for the H2 production reaction. Highly active materials have been obtained from a chemical reduction method leading to 18 mmol·h–1·g–1for 3 mol % copper loading.


Octubre, 2014 | DOI: 10.1021/cs500865y

9.31
Química de Superficies y Catálisis

Pyridine adsorption on NiSn/MgO-Al2O3: An FTIR spectroscopic study of surface acidity

Penkova, A; Bobadilla, LF; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Applied Surface Science, 317 (2014) 241-251

Show abstract ▽

The acid-base properties of MgO-Al2O3 supports and NiSn/MgO-Al2O3 catalysts were evaluated by IR spectroscopy using pyridine as a probe molecule. The results indicate that only Lewis acid sites were detected on the surface of the supports as well as on the catalysts. Nevertheless, Bronsted acid sites were not detected. In the support without MgO three kinds of coordinatively unsaturated acid sites were detected: Al3+ cations occupying octahedral, tetrahedral and tetrahedral with cationic vacancy in the neighbourhood. The last sites appear as the strongest. Moreover, they are able to activate the pyridine molecules leading to the formation of an intermediate ce-pyridone complex. When MgO or NiO were added to the alumina, the number and strength of the Lewis acid sites decreased and significant changes were observed in the tetrahedral sites with adjoining cation vacancies. The incorporation of the Mg2+ cations into the alumina's structure takes place on the vacant tetrahedral positions, forming spinel MgAl2O4. As a result, the fraction of tetrahedral sites with adjoining cationic vacancy diminished and the intermediate ce-pyridone complex in the support with the highest MgO loading was hardly detected. The addition of Ni2+ cations leads to the filling of the free octahedral positions, resulting in the formation of a NiAl2O4 spinel structure and the thermal stability of the ce-pyridone species decreases. In the catalysts, the progressive reduction of the number and strength of the Lewis acid sites is due to a competitive formation of the two types of MgAl2O4 and NiAl2O4 spinels. In the catalyst NiSn/30MgO-Al2O3 no cationic vacancies were detected and the surface reaction with ce-pyridone formation did not occur. 


Octubre, 2014 | DOI: 10.1016/j.apsusc.2014.08.093

2.71
Nanotecnología en Superficies y Plasma - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Chromium removal on chitosan-based sorbents - An EXAFS/XANES investigation of mechanism

Vieira, RS; Meneghetti, E; Baroni, P; Guibal, E; de la Cruz, VMG; Caballero, A; Rodriguez-Castellon, E; Beppu, MM
Materials Chemistry and Physics, 146 (2014) 412-417

Show abstract ▽

Chitosan is known to be a good sorbent for metal-containing ions as the presence of amino groups and hydroxyl functions act as effective binding sites. Its crosslinking, employing glutaraldehyde or epichlorohydrin, may change the sorption properties (sorption capacity or diffusion properties) of this biopolymer, since the available functional groups are different in each case. X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES), Fourier-transformed infrared spectroscopy with attenuated total reflectance device (FTIR-ATR) was used along with speciation diagrams, in order to identify the binding groups involved in chromate sorption and its mechanisms. In pristine chitosan and epichlorohydrin-crosslinked chitosan membranes, amino groups are most likely responsible for adsorption, although the contribution of hydroxyl groups cannot be excluded (especially for metal-sorbent stabilization). In this case, when adsorbed about 70% of chromate ions remain in the Cr(VI) oxidation state. In the case of glutaraldehyde-crosslinked membranes, the functional groups involved are different. Carbonyl groups and imino bonds – resulting from the reaction of the crosslinking agent and amino groups – may be involved in the adsorption mechanism. Additionally, a higher fraction of chromate anions, around 44% are reduced to Cr(III) oxidation state in loaded sorbent. The presence of free aldehyde groups may explain this partial reduction.


Agosto, 2014 | DOI: 10.1016/j.matchemphys.2014.03.046

2.26
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Improved O-2 evolution from a water splitting reaction over Er3+ and Y3+ co-doped tetragonal BiVO4

Obregon, S; Colon, G
Catalysis Science & Technology, 4 (2014) 2042-2050

Show abstract ▽

Erbium–yttrium co-doped BiVO4 with a tetragonal structure is synthesized by means of a surfactant free hydrothermal method. The studied photocatalyst shows good photoactivity under sun-like excitation for the degradation of methylene blue (MB) and for O2 evolution. From structural and morphological characterization, it has been stated that the presence of lanthanides induces the stabilization of the tetragonal phase. This is probably due to the substitutional occupation that occurs in the BiVO4 lattice. The photocatalytic performance under visible-NIR radiation clearly evidences the occurrence of an up-conversion process involved in the overall photo-electronic mechanism. The tetragonal phase Er0.0075,Y0.03–Bi0.9625VO4 system gives the highest O2 evolution rate (425 μmol g−1 h−1) under sun-like excitation, being 8 times higher than that attained for m-BiVO4 (53 μmol g−1 h−1).


Julio, 2014 | DOI: 10.1039/C4CY00050A

5.43
Materiales Coloidales - Materiales Nanoestructurados y Microestructura - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Bifunctional, Monodisperse BiPO4-Based Nanostars: Photocatalytic Activity and Luminescent Applications

Becerro, AI; Criado, J; Gontard, LC; Obregon, S; Fernandez, A; Colon, G; Ocana, M
Crystal Growth & Design, 14 (2014) 3319-3326

Show abstract ▽

Monodisperse, monoclinic BiPO4 nanostars have been synthesized by a homogeneous precipitation reaction at 120 °C through controlled release of Bi3+ cations from a Bi–citrate chelate, in a mixture of glycerol and ethylene glycol, using H3PO4 as the phosphate source. The set of experimental conditions necessary to obtain uniform nanoparticles is very restrictive, as the change in either the polyol ratio or the reactant concentrations led to ill-defined and/or aggregated particles. The morphology of the particles consists of a starlike, hierarchical structure formed by the ordered arrangement of nanorod bundles. Transmission electron tomography has revealed that the nanostars are not spherical but flattened particles. Likewise, Fourier transform infrared spectroscopy and thermogravimetry have shown that the synthesized nanostars are functionalized with citrate groups. The mechanism of formation of the nanostars has been analyzed to explain their morphological features. The as-synthesized BiPO4 nanostars exhibit an efficient photocatalytic performance for the degradation of Rhodamine B. Finally, it has been demonstrated that the stars can be Eu3+-doped up to 2 mol % without any change in the particle morphology or symmetry, and the doped samples show emission in the orange-red region of the visible spectrum after ultraviolet excitation. These experimental observations make this material a suitable phosphor for biotechnological applications.


Julio, 2014 | DOI: 10.1021/cg500208h

4.89
Nanotecnología en Superficies y Plasma - Materiales y Procesos Catalíticos de Interés Ambiental y Energético

A study of the optical properties of metal-doped polyoxotitanium cages and the relationship to metal-doped titania

Lv, YK; Cheng, J; Matthews, PD; Holgado, JP; Willkomm, J; Leskes, M; Steiner, A; Fenske, D; King, TC; Wood, PT; Gan, LH; Lambert, RM; Wright, DS
Dalton Transactions, 43 (2014) 8679-8689

Show abstract ▽

To what extent the presence of transition metal ions can affect the optical properties of structurally well-defined, metal-doped polyoxotitanium (POT) cages is a key question in respect to how closely these species model technologically important metal-doped TiO2. This also has direct implications to the potential applications of these organically-soluble inorganic cages as photocatalytic redox systems in chemical transformations. Measurement of the band gaps of the series of closely related polyoxotitanium cages [MnTi14(OEt)28O14(OH)2] (1), [FeTi14(OEt)28O14(OH)2] (2) and [GaTi14(OEt)28O15(OH)] (3), containing interstitial Mn(II), Fe(II) and Ga(III) dopant ions, shows that transition metal doping alone does not lower the band gaps below that of TiO2 or the corresponding metal-doped TiO2. Instead, the band gaps of these cages are within the range of values found previously for transition metal-doped TiO2 nanoparticles. The low band gaps previously reported for 1 and for a recently reported related Mn-doped POT cage appear to be the result of low band gap impurities (most likely amorphous Mn-doped TiO2).


Junio, 2014 | DOI: 10.1039/C4DT00555D

4.20
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Excellent photocatalytic activity of Yb3+, Er3+ co-doped BiVO4 photocatalyst

Obregon, S.; Colon, G.
Applied Catalysis B: Environmental, 152-153 (2014) 328-334

Show abstract ▽

Ytterbium-Erbium co-doped BiVO4 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of Methylene Blue and O2 evolution reactions. From the structural and morphological characterization it has been stated that the presence of Yb3+ and Er3+ induces the stabilization of the tetragonal phase probably due to its substitutional incorporation in the BiVO4 lattice. The occurrence of the Yb3+,Er3+ co-doped monoclinic-tetragonal BiVO4 heterostructure induces the higher photocatalytic activities. The best photocatalytic performance was attained for the sample with 1:4 Er3+:Yb3+ ratio. The observed NIR photoactivity clearly denotes the occurrence of an up-conversion mechanism involved in the overall photocatalytic process.


Junio, 2014 | DOI: 10.1016/j.apcatb.2014.01.054

7.44
Reactividad de Sólidos - Química de Superficies y Catálisis

Phase assembly and electrical conductivity of spark plasma sintered CeO2-ZrO2 ceramics

Poyato, R; Cruz, SA; Cumbrera, FL; Moreno, B; Chinarro, E; Odriozola, JA
Journal of Materials Science, 49 (2014) 6353-6362

Show abstract ▽

Cex Zr1−x O2 (x = 0.10, 0.16 and 0.33) nanocrystalline powders were obtained by a two-step synthesis technique and sintered by spark plasma sintering (SPS). As consequence of the reduction of Ce4+ to Ce3+ species by carbon in the graphite environment in SPS, phase assemblies including tetragonal, monoclinic and pyrochlore phases were generated in the ceramics during the sintering process. The electrical conductivity was highly dependent on phase assembly and atmosphere (N2, H2 and O2). A significant decrease in the activation energy was noticed in the ceramics with high pyrochlore content when measuring the conductivity in H2 atmosphere, consequence of the strong reduction promoted in these ceramics during the measurement. Equal conduction behavior with similar activation energy was observed in all the ceramics when measuring in O2 atmosphere.


Junio, 2014 | DOI: 10.1007/s10853-014-8361-6

2.37
Química de Superficies y Catálisis

Metallic structured catalysts: Influence of the substrate on the catalytic activity

Dominguez, MI; Perez, A; Centeno, MA; Odriozola, JA
Applied Catalysis A-General, 478 (2014) 45-57

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In order to study the influence of the metallic substrate on the catalytic activity of structured micromonolithic catalysts, a CuOx/CeO2 catalyst was deposited on different oxidized or enameled metallic micromonoliths and tested in the PROX reaction under ideal and realistic conditions. The obtained results show as both activity and selectivity depend on the nature of the alloy and the nature of the interphase between the metal substrate and the catalyst layer. In oxidized micromonoliths, diffusion of Cr and Fe has been observed. For enameled micromonoliths, together with that diffusion, the interaction of the glass-ceramic interphase with the reactive gas streams resulted in the partial hydrolysis of this layer leading to diffusion toward the catalyst surface of the hydrolysis products, namely Na, Ca and Si cations. In some cases, the alteration of the surface composition favors the spreading of the copper active phase. As a result, it must be concluded that the metallic substrates are not spectators, at least in the PROX reaction, playing a fundamental role in the performances of the catalytic devices.


Mayo, 2014 | DOI: 10.1016/j.apcata.2014.03.028

3.94
Fotocatálisis Heterogénea: Aplicaciones

Effect of the type of acid used in the synthesis of titania–silica mixed oxides on their photocatalytic properties

Llano, B; Hidalgo, MC; Rios, LA; Navio, JA
Applied Catalysis B: Environmental, 150-151 (2014) 389-395

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TiO2–SiO2 mixed oxides were synthesized by the sol–gel technique using three