Catalysis for environment and energy

Broad objectives:
Synthesis procedures of supported and structured catalysts for pollution control and hydrogen production
Application of microchannel reactor technology for pollution abatement and hydrogen production

Specific objectives:
Development of new synthesis procedures, e.g. SIL (Supported Ionic Liquids) catalysts
Development of surface Chemical Functionalization procedures, e.g. superhydrophilic and self-cleaning surfaces under day-light illumination
Development of microreactor welding procedures, e.g. SPW (Spark Plasma Welding) of component

Specific advantages
The line is able of addressing answers to the catalytic problems from the very basic aspects (ab initio calculations; study of model catalysts) to the manufacturing of state-of-the-art devices (microreactors) due to the acquired knowledge in other fields of Materials Science, e.g. metallurgy, and the network of collaborating scientific groups


Professors


Caballero Martínez, Alfonso
954 48 95 38 (lab. ext. 909225)
caballero@us.es
web: sisius
Navío Santos, José Antonio
954 48 95 50 (ext.lab. 909220)
navio@us.es
web: sisius
Odriozola Gordón, José Antonio
954 48 95 44 (ext.lab. 909222)
odrio@us.es
web: sisius


Scientific Researchers


Centeno Gallego, Miguel Angel
954 48 95 43 (ext.lab. 909222)
centeno@icmse.csic.es
Colón Ibáñez, Gerardo
954 48 95 36 (ext.lab. 909225)
gcolon@icmse.csic.es


Tenured Scientists


Hidalgo López, María del Carmen
954 48 95 50 (lab. ext. 909220)
mchidalgo@icmse.csic.es
web: mchidalgo
Holgado Vázquez, Juan Pedro
954 48 95 36 (lab. ext. 909624)
holgado@icmse.csic.es


Assistant Professors


Macías Azaña, Manuel
954 48 95 41
mmacias@icmse.csic.es
web: sisius
Romero Sarria, Francisca
954 48 95 43
francisca@icmse.csic.es
web: sisius


Posdoctoral Researchers


Domínguez Leal, María Isabel
954 48 95 00 (ext. 909218)
mleal@icmse.csic.es
Ivanova Lyuvimirova, Svetlana
954 48 95 00 (ext. 909218)
svetlana@icmse.csic.es
Laguna Espitia, Oscar
954 48 95 43
oscarh@icmse.csic.es
Martínez Tejada, Leidy Marcela
954 48 95 76
leidy@icmse.csic.es
Penkova, Anna Dimitrova
954 48 95 00 (ext. 909218)
anna@icmse.csic.es
Pereñiguez Rodríguez, Rosa
954 48 95 76
rosa@icmse.csic.es
web: sisius
Ternero Fernández, Fátima
954 48 95 00 ext. 909218
fatimater@icmse.csic.es


PhD Students


Alvarez Moreno, Andrea
954 48 95 00 (ext- 909209)
andrea.alvarez@icmse.csic.es
Garcilaso de la Vega González, Victoria
954 48 95 00 (ext. 909222)
victoriagarcilaso@icmse.csic.es
González Castaño, Miriam
954 48 95 00 ext. 909221
miriam.gonzalez@icmse.csic.es
Jiménez Barrera, Elena
954 48 95 00 (ext. 909222)

Obregón Alfaro, Sergio Alberto
954 48 95 00 (ext. 909225)
sergio.obregon@icmse.csic.es
Palma del Valle, Sandra
954 48 95 00 (ext. 909222)
sandra.palma@icmse.csic.es
Ramírez Reina, Tomás
954 48 95 00 ext. 909221
tomas.ramirez@icmse.csic.es
Rodríguez Gómez, Alberto
954 48 95 00 ext. 909225
albrodgom@icmse.csic.es


Personal Contratado


González de la Cruz, Victor Manuel
954 48 95 00 (ext. 909235)
vmanuel@icmse.csic.es

Ministerio


Development of nanostructured catalytic systems prepared by sol-gel and fotoassisted deposition (PAD) methods for energy and environmental applications
Research head: Alfonso Caballero Martínez
Period: 01-01-2012 / 31-12-2014
Financial source: Ministerio de Ciencie e Innovación
Code: ENE2011-24412
Research group: Gerardo Colón Ibáñez, Juan Pedro Holgado Vázquez, Sergio Obregón Alfaro, Rosa María Pereñiguez Rodríguez, Fátima Ternero Fernández

Abstract [+]


In the present project we propose the development of a series of nanostructured catalysts based on transition metals such as Ni, Cu, Au or Pd deposited in active supports (TiO2, CeO2, WO3, Fe2O3 and mesoporous supportslike SBA-15 doped with titania and ceria). Conventional methods of preparation will be used (impregnation, deposition-precipitation, etc.), along with procedures of synthesis of more recent development, like sol-gel and, very specially, the denominated Photochemical Assisted Deposition (PAD). In this way, we expect to control at the nanometric scale the size of the metallic and/or bimetallic particle, along with the interaction between the metal and support surface. In the case of the PAD method, one of the primary targets of the project is the study and optimization of the different parameters affecting the deposition process. So that, besides the control of the metallic particle size from diameters around 15nm to atomic dispersed systems on active supports like ceria or titania, it would allow us to design the distribution of metals in bimetallic particles, making use of consecutive and/or simultaneous controlled processes of fotodeposition of metals. Using this methodology, we will try to obtain metallic distributions of different kinds: core-shell, alloys, etc., which as it is well-known, can strongly affect the catalytic performances. These benefits will be verified in different catalytic reactions of energetic and/or environmental interest, both in gas and liquid phase. Thus, the systems based on nickel and gold will be used in the steam and dry reforming reactions of methane and the selective oxidation of CO (Preferential Oxidation of CO, PROX), respectively. The bimetallic catalytic systems based on palladium and palladium-gold will be used for the optimization of the reaction of direct synthesis of hydrogen peroxide from hydrogen and oxygen, made in liquid phase at high pressure. The correlation between the physical-chemistry state and the reactivity of the catalytic systems will allow us to clarify fundamental aspects of the mechanisms of the proposed heterogeneous reactions


Development of new industrial processes based on catalytic systems for Sustainable production of base compounds of fragrances and aromas
Research head: Juan Pedro Holgado Vázquez
Period: 04-05-2011 / 31-12-2014
Financial source: Ministerio de Economía y Competitividad
Code: IPT-2011-1553-420000
Research group: Alfonso Caballero Martínez, Víctor Manuel González de la Cruz, Rosa Pereñíguez Rodrí-guez, Gerardo Colón Ibáñez

Abstract [+]


Nowadays, most of the industrial processes used for transformations of many com-pounds used in the field of fragrances and aromas have low yields, and generate a lot of environmentally noxious products, being necessary to accomplish several stages of segregation and treatment during the process of production of these chemicals. Most of these processes are done by reduction or oxidation reactions using stoichiometric compounds, or are based in homogeneous catalysis, that present associated hitches associated with corrosion, recovery of the catalysts from reaction media and its regeneration for its possible recycle. In this “environmentally friendly” context, there is a growing interest in the use of oxidants less contaminants, such as molecular oxygen or hydrogen peroxide, and the integration of these oxidants into heterogeneous catalysis processes. Obviously, one of the big challenges for catalytic systems is to maximize the yield (conversion times selectivity), in order to reduce the consumption of reactants (raw material), and minimize the separation and elimination of undesired sub-products obtained as consequence of process inefficacy. In these type of reactions (with mainly organic products, many from natural sources), it is not, as a general rule, difficult to obtain a high conversion, but as the starting materials present many functionalities and/or points susceptible to be oxidized, the main challenge is to obtain a (very) high selectivity, in many cases even at enantiomer level.
In this project, we have selected processes and reactions with a direct interest in the food and cosmetic industry, with the scope to develop processes, at industrial scale, based on heterogeneous catalysts to obtain compounds with high added value in the aromas and fragrances fields, such as the production of l-carvone from catalytic oxidation of d-limonene.


Development of photocatalytic-materials highly activ in the visible for environmental applications
Research head: José Antonio Navío Santos
Period: 01-01-2009 / 31-12-2011
Financial source: Ministerio de Ciencia y Tecnología
Code: CTQ2008-05961-C02-01
Research group: Gerardo Colón Ibáñez, M. Carmen Hidalgo López, Manuel Macías Azaña, Marina Maicu

Abstract [+]


The main goal of this coordinated project is “the tailoring of a new generation of pow-dered materials having nanometer size based on TiO2, SnO2 and ZnO single, mixed an/or doped showing high photoactivity in the visible region (nanophotocatalysts), eventually immobilized on other selected materials (membranes, glass, ceramic tiles, clays and metal films) in order to be used in a competitive and efficiently way to the treatment of pollutants in water and air by using the solar energy”. The principal hypothesis is the existence of inorganic pigments such as TiO2, SnO2 ZnO having high oxidizing power in the UV region that are capable of degrading toxic species present in our environment. The project intends to develop new heterogeneous TiO2, SnO2 and ZnO nanocatalysts exhibiting good optoelectronic properties in the visible region at the same time that the physicochemical properties are being implemented. Two main research activities will be proposed to cover the development of heterogeneous nanosized TiO2, SnO2 and ZnO powders (nanocatalysts) capable to design and develop the photodegradation of pollutants in water and air, by the use of Solar Light (Environmental Solar Chemistry). The project also will address the immobilization of different semiconductor nanoparticles (single, mixed and/or doped) on selected supports (membranes, glass and metal films) with the intention of developing heterogeneous systems exhibiting high photocatalytic activity for their applicability to the treatment of pollutants that would represent an improvement in the catalyst filtration and at the same time, with the generation of self-cleaning surfaces.


Gold based nanostructured catalysts for selective oxidation reactions
Research head: Juan Pedro Holgado Vázquez
Period: 1-01-2011 / 31-12-2011
Financial source: Ministerio de Ciencia y Tecnología
Code: CTQ2010-21348-C02-01
Research group: Alfonso Caballero Martínez, Víctor Manuel González de la Cruz, Fátima Ternero Fernán-dez, Richard M. Lambert

Abstract [+]


The aim of the proposed project is the development of highly active gold-based catalysts for selective oxidation processes. In these context, benzyl alcohol oxidation (and derivatives) under mild conditions and low temperature CO oxidation in connection with applications in Environment Catalysis as the air control (CO-removal from air) and applications in Catalysis for Energy as the purification of H2 produced by reforming (CO removal from H2) will be considered.

The outstanding properties of gold, a biocompatible non-toxic metal, can be exploited in catalysis when used in highly dispersed form. In order to get elevated yields and selectivities, doubly nanostructured (considering both the active phase and support) gold-based catalysts deposited onto CeO2 and TiO2 (Al2O3 and SiO2 as references) will be prepared. Monometallic gold catalysts will be prepared with control of size and shape of the Au particles, taking advantage of the observed “structure sensitivity” of the proposed reactions.  In the same context, it has been recently reported that bimetallic composition based on Gold (AuPd, AuCu, etc) may enhance the performance of these catalysts. Therefore bimetallic catalysts such as AuPt, AuCu and AuNi, will be explored and tested.


Integration of microchannel catalytic reactors for hydrogen production from alcohols
Research head: José Antonio Odriozola Gordón
Period: 1-08-2009 / 31-07-2012
Financial source: Ministerio de Ciencia y Tecnología
Code: ENE2009-14522-C05-01
Research group: Miguel Angel Centeno, Svetlana Ivanova, Francisca Romero Sarria, M.Isabel Domínguez, Sandra Palma, Oscar Laguna, Ana Penkova, Sylvia Cruz, W.Yesid Hernández, Luis Bobadilla

Abstract [+]


The widespread use of portable electric and electronic devices increases the need for efficient autonomous power supplies (up to 50 We) that replace the currently predominant battery technology. The use of common fuels/chemicals, such as hydrocarbons or alcohols, as an energy source is a promising alternative when combined with the recent developments in microchannel reactor technology. In the previous project (MAT2006-12386-C05) we began to explore the use of micro-channel reactor technology to generate hydrogen on site and on demand by processing alco-hols which has allowed the manufacturing of microreactors for the catalytic steam reforming of methanol and CO preferential oxidation (PROX) reactions. In the present project, the main focus is set on the scaling up of the already designed microreactors which will allow the fueling of a 50 We commercial fuel cell (PEMFC) and the integration of both, the material and thermal flows generated in the fuel processor and the fuel cell, including the production and cleaning steps required by the PEMFC. In addition to this, the development of microreactors for the catalytic steam reforming of ethanol and the water-gas-shift (WGS) reactions is considered in this project for increasing the versatility of the designed device. The feasibility of this kind of autonomous power supplies would require the study of the manufacturing, scaling up of the microreactors and material and thermal flows integration, but also to explore the use of easily available materials (new steels adapted to use), the ageing behaviour of devices (steel, catalysts, sealings, …) and the development of a control algorithm of the fuel processor/fuel cell system.


Photo-active materials to exploit solar energy for photocatalytic processes of environmental interest
Research head: José Antonio Navío Santos
Period: 1-01-2012 / 31-12-2012
Financial source: Ministerio de Ciencia e Innovación
Code: CTQ2011-26617-C03-02
Research group: Mª del Carmen Hidalgo López, Manuel Macías Azaña, Julie J. Murcia Mesa; Sebastián Murcia López

Abstract [+]


The heterogeneous photocatalysis has extensively shown its potential for detoxification and disinfection of aqueous and gaseous media. However, technological development has been very limited due to a number of difficulties that can be grouped into two main groups:

1. Difficulties inseparating the catalyst from the reacting medium for recovery and reuse once completed the process.

2. Poor performance of the process, which uses only a very small percentage of photons useful, and these are only a small part of the natural spectrum.

Our proposal is composed by three sub-projects led by three groups which combine extensive experience in: Synthesis, modification and characterization of photocatalytic materials (mainly the group at the University of Seville), Preparation and characterization of metal oxide thin films on different substrates (mainly the group from CIEMAT) and Modification, spectroscopic characterization of active centers and photoreactivity studies in aqueous and gaseous phase (mainly the group from the ULPGC).

Based onthe experience gained and the main trends in the development of heterogeneous photocatalysis, our consortium proposal has a central objective: Synthesize materials based on TiO2, SnO2, ZnO and ternary materials such as bismuth titanate (BITs), in powder form with nanometric size, with high photocatalytic activity and its support on suitable substrates (glass, membrane, metal sheets, etc.) coated with thin films of different metal oxides to facilitate the fixation of powder particles and/or acting as seed for the formation or crystallization of these particles in order to use these systems efficiently in photocatalytic detoxification processes in aqueous phase and gas phase.


Syngas and Hydrogen Production by Hydrocarbon Reforming on Nickel Nanostructured Catalysts (SYNANOCAT)
Research head: Alfonso Caballero Martínez
Period: 1-12-2007/30-11-2011
Financial source: Ministerio de Educación y Ciencia
Code: ENE2007-67926-C02-01
Research group: Juan Pedro Holgado Vázquez, Agustín R. Gon-zález-Elipe, Victor Manuel González de la Cruz, Rosa Pereñiguez Rodríguez

Abstract [+]


The coordinated proposed research project, that seek to be an extension of the references ENE2004- 01660 and ENE2004-06176,pretends to prepare new catalytic systems, with a discrete crystallite size and a higher resistance to deactivation. The aim is to obtain catalysts for an optimum performance in the reforming reaction of hydrocarbons to yield H2(+CO), principally from methane and propane. These reactions being structure-sensitive, are affected by the size of metallic particles.

Nanoparticles of nickel with well controlled size and morphology will be prepared by ex-situ methods as microwave plasma irradiation, ionic liquid, reverse microemulsion or impregnation with external surface modification by silylation. These methods will allow us to obtain metal particles of a very different range of size: from less than 10nm to sizes about 100nm and a narrow particle size distribution. The catalytic activity of these nanoparticles, supported on different oxides as ZrO2 or Al2O3, will be evaluated in the reforming reactions of methane and propane to establish a structure-reactivity relationship. Special attention will be devoted to the carbon deposition over the catalyst in reaction conditions, the more important process hindering the performances of these kind of catalysts. The strict control of the morphology of the particles must allow us to correlate the kinetic of the deactivation process to the different type of nanoparticles. Also, we will evaluate the effect of different kind of additives, as Pt, Au, Sr, K, etc., reported in the literature as beneficial for the overall activity of these materials.

The reforming reactions of hydrocarbon will be alternatively studied in the presence of a microwave generated plasma. We expect finally to develop an integrated thermal-plasma reactor that could permit the reaction at a lower temperature and/or with less deposition of coke over the catalyst.


Junta de Andalucía


Catalytic reforming of glycerol
Research head: José Antonio Odriozola Gordón
Period: 01-01-2010 / 31-12-2012
Financial source: Junta de Andalucía
Code: P09-TEP-5454 (Proyecto de Excelencia)
Research group: Luis F. Bobadilla Baladrón, Sylvia A. Cruz Torres, M. Isabel Domínguez Leal, Anna Dimitrova Penkova, Francisca Romero Sarria, Andrea Alvarez Moreno

Abstract [+]


The main objective of this Project is the production of Hydrogen from glicerol steam reforming. Glycerol is the most important by-product of the biodiesel production from the transterification of fatty acids. In the year 2010, the estimated production of biofuels was about 9.9 millions of tonnes, which represents 50% of the aims of the European Union objec-tives. The current energy system needs the development of alternative energetic models. The use of hydrogen as energetic vector is one of these alternatives, but, to assure the sustainability, its production must be from renewable sources. Among the possible renewable sources of hydrogen, the main advantage of the use of glycerol is the almost neutral carbon balance. In addition, the glycerol valorisation must lead to increase the profitability of the bio-refineries that, differently, would meet affected by the increase of costs associated with the elimination of this product.


Design of photocatalytic systems highly active in the visible for environmental applications
Research head: Gerardo Colón Ibáñez
Period: 01-01-2007 / 31-12-2010
Financial source: Junta de Andalucía
Code: FQM-1406
Research group: José Antonio Navío Santos, Manuel Macías Azaña, Carmen Hidalgo López, Marina Maicu

Abstract [+]


The heterogeneous photocatalysis has demonstrated to be a promising and efficient technology for the oxidation of a large variety of toxic substrates in relatively short reaction times. It is widely known that the most used photocatalysts can be only activated by means of photons with wavelengths lower than 390 nm, being an important limitation for large scale use. The main objective of this project is based on previous development in our group of highly UV photoactive TiO2 powders able to completely remove different toxic species for the environment. Our challenge is to overcome the problems and limitations of the UV range in the solar spectrum. The core of our activity will be the development of new oxidic photoactive doped systems based on Ti and Zn, which could provide a shift in the absorption edge toward the visible range.

 Thus, under the point of view of the enhancement in the photon efficiencies of the photocatalytic processes, it is evident that the designing and development of alternative photocatalysts is of great interest.  We intend the obtention of highly efficient materials that can be used for the degradation of contaminants in water and gas effluents by the incorporation of cationic/anionic dopants and the immobilization in different adequate supports.The evaluation of the photocatalytic activity will be performed for the photooxidation of a great variety of toxic organic compounds and using solar simulation lamps.


New Bi3+ based photocatalysts highly active in the visible
Research head: Gerardo Colon Ibáñez
Period: 11-03-2011 / 31-03- 2015
Financial source: Junta de Andalucía
Code: P09-FQM-4570
Research group: M. Carmen Hidalgo López, José Antonio Navío Santos, Manuel Macías Azaña, Sebastián Murcia López

Abstract [+]


The main objective of this project is the development of a new generation of nanostructured materials alternative to TiO2 with high photoactivity in the visible region that could be efficiently used in liquid or gaseous effluent treatment. The present project intent to develop new heterogeneous nanocatalytic systems based on Bi3+ (Bi2WO4, Bi2MoO6, BiVO4, Bi3O4Cl, CaBi2O4, PbBi2Nb2O9,…) exhibiting appropriated optoelectronic properties for the solar light use in the visible range (Solar Photocatalysis). Moreover, from the point of view of the photoinduced charge carriers diffusion and transfer, the improved physicochemical properties would optimize the photocatalytic process.


2014


Title: Production of hydrogen by water photo-splitting over commercial and synthesised Au/TiO2 catalysts
Author(s): Mendez, JAO; Lopez, CR; Melian, EP; Diaz, OG; Rodriguez, JMD; Hevia, DF; Macias, M
Source: Applied Catalysis B: Environmental, 147 (2014) 439-452

abstract | fulltext

H2 production from methanol/water photo-splitting was compared using various commercial photocatalysts (Evonik P25 (P25), Hombikat UV-100 (HB) and Kronos vlp7000 (KR)) and others synthesised with a sol–gel-hydrothermal (HT) process and a sol–gel method followed by calcination (SG400 and SG750). All photocatalysts had been surface modified with Au at different concentrations, from 0.2 to 6.0 wt.%, using the photodeposition method. A complete characterisation study of the different photocatalysts was performed (BET, XRD, TEM, SEM-EDX, FTIR, UV–vis Reflectance Diffuse Spectra and aggregate size). The experiments were conducted for 3.5 h using 1 g L−1 of photocatalyst with methanol (25 vol.%) as sacrificial agent. In addition to H2 generation, production of the main intermediates, formaldehyde and formic acid, and of CO2 was also evaluated. The commercial photocatalyst KR at 0.8 wt.% Au had the highest H2 production of all the photocatalysts studied with 1542.9 μmol h−1. Of the photocatalysts synthesised by our group, SG750 at Au loading of 2.0 wt.% gave the highest H2 production of 723.1 μmol h−1. The SG750 photocatalyst at Au loading of 2.0 wt.% also had the highest H2 production yield per unit of surface area at 45.5 μmol g h−1 m−2.

April, 2014 | DOI: 10.1016/j.apcatb.2013.09.029

Title: Improved H2 production of Pt-TiO2/g-C3N4-MnOx composites by an efficient handling of photogenerated charge pairs
Author(s): Obregon, S; Colon, G
Source: Applied Catalysis B: Environmental, 144 (2014) 775-782

abstract | fulltext

Pt-TiO2/g-C3N4-MnOx hybrid structures are synthesized by means of a simple impregnation method of Pt-TiO2 and g-C3N4-MnOx. From the wide structural and surface characterization we have stated that TiO2/g-C3N4 composites are formed by an effective covering of g-C3N4 by TiO2. The modification of composite by Pt and/or MnOx leads to improved photoactivities for phenol degradation reaction. Moreover, enhanced photoactivities have been obtained for composites systems for H2 evolution reaction. The notably photocatalytic performance obtained was related with the efficient separation of charge pairs in this hybrid heterostructure.

January, 2014 | DOI: 10.1016/j.apcatb.2013.07.034

Title: Effect of gold on a NiLaO3 perovskite catalyst for methane steam reforming
Author(s): Palma, S; Bobadilla, LF; Corrales, A; Ivanova, S; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: Applied Catalysis B: Environmental, 144 (2014) 846-854

abstract | fulltext

The effect of gold addition to a supported Ni SRM catalyst has been studied in this work in order to determine the influence of gold on both the amount and type of carbon species formed during the reaction. The structure of the support, a mixed La–Al perovskite, determines the catalyst reducibility and Ni particle size. Gold addition affects the metal particle size increasing metal dispersion on increasing the gold content. Therefore, although gold blocks step Ni sites, the more active sites for Csingle bondH activation, and increases electron density on nickel, the higher dispersion results in an apparently higher activity upon gold addition. Moreover, gold addition increases the catalyst stability by decreasing the rate of growth of carbon nanotubes.

January, 2014 | DOI: 10.1016/j.apcatb.2013.07.055

Title: Exalted photocatalytic activity of tetragonal BiVO4 by Er3+ doping through a luminescence cooperative mechanism
Author(s): Obregon, S; Lee, SW; Colon, G
Source: Dalton Transactions, 43 (2014) 311-316

abstract | fulltext

Er-doped BiVO4 are synthesized by means of a surfactant free microwave assisted hydrothermal method having good photoactivities under sun-like excitation for the degradation of methylene blue. From the structural and morphological characterization, it has been stated that the presence of Er3+ induces a slight stabilization of the tetragonal phase, probably due to its incorporation in the BiVO4 lattice. The best photocatalytic performances were attained for the samples with Er3+ content higher than 3 at%. The occurrence of the Er3+ doped tetragonal BiVO4 clearly induces higher photocatalytic activities. The existence of a luminescence process has been related with the enhanced photoactivity observed.

January, 2014 | DOI: 10.1039/C3DT51923F

Title: Gold supported on CuOx/CeO2 catalyst for the purification of hydrogen by the CO preferential oxidation reaction (PROX)
Author(s): Laguna, OH; Hernandez, WY; Arzamendi, G; Gandia, LM; Centeno, MA; Odriozola, JA
Source: Fuel, 134 (2014) 9-20

abstract | fulltext

We design a fully stable numerical solution of the Maxwell's equations with the transfer matrix method (TMM) to understand the interaction between an electromagnetic field and a finite, one-dimensional, non-periodic structure. Such an exact solution can be tailored from a conventional solution by choosing an adequate transformation between its reference systems, which induces a mapping between its associated TMMs. The paper demonstrates theoretically the numerical stability of the TMM for the exact solution within the framework of Maxwell's equations, but the same formalism can efficiently be applied to resolve other classical or quantum linear wave-propagation interaction in one, two, and three dimensions. This is because the formalism is exclusively built up for an in depth analysis of the TMM's symmetries.

February, 2014 | DOI: 10.1016/j.jqsrt.2013.10.007

Title: A ternary Er3+-BiVO4/TiO2 complex heterostructure with excellent photocatalytic performance
Author(s): Obregon, S; Colon, G
Source: RSC Advances, 43 (2014) 20765-20771

abstract | fulltext

Ternary erbium doped BiVO4/TiO2 complexes are synthesized by means of a simple impregnation method with good photoactivities under sun-like excitation for the degradation of phenol. From the structural and morphological characterization it has been stated that the presence of Er3+ induces a slight stabilization of the tetragonal phase probably due to its incorporation in the BiVO4 lattice. Therefore a ternary heterostructured material has been obtained. The best photocatalytic performance was attained for the samples with 1 wt% of Er3+-doped BiVO4 content with respect to TiO2. The occurrence of a complex structural mixture with the adequate band position leads to effective charge pair separation which induces higher photocatalytic activities.

January, 2014 | DOI: 10.1039/C3RA46603E

Title: Surface Oxygen Vacancies in Gold Based Catalysts for CO Oxidation
Author(s): Romero-Sarria, F; Plata, JJ; Laguna, OH; Marquez, AM; Centeno, MA; Sanz, JF; Odriozola, JA
Source: RSC Advances, 4 (2014) 13145-13152

abstract | fulltext

Experimental catalytic activity measurements, Diffuse Reflectance Infrared Fourier Spectroscopy, and Density Functional Theory calculations are used to investigate the role and dynamics of surface oxygen vacancies in the CO oxidation with O2 catalyzed by Au nanoparticles supported on a Y-doped TiO2 catalyst. Catalytic activity measurements show that the CO conversion is improved in a second cycle of reaction if the reactive flow is composed by CO and O2 (and inert) while if water is present in the flow, the catalyst shows a similar behaviour in two successive cycles. DRIFTS-MS studies indicate the occurrence of two simultaneous phenomena during the first cycle in dry conditions: the surface is dehydroxylated and a band at 2194 cm-1 increases (proportionally to the number of surface oxygen vacancies). Theoretical calculations were conducted in order to explain these observations. On one hand, the calculations show that there is a competition between gold nanoparticles and OH to occupy the surface oxygen vacancies and that the adsorption energy of gold on these sites increases as the surface is being dehydroxylated. On another hand, these results evidence that a strong electronic transfer from the surface to the O2 molecule is produced after its adsorption on the Au/TiO2 perimeter interface (activation step), leaving the gold particle in a high oxidation state. This explains the appearance of a band at a wavenumber unusually high for the CO adsorbed on oxidized gold particles (2194 cm-1) when O2 is present in the reactive flow. These simultaneous phenomena indicate that a gold redispersion on the surface occurs under reactive flow in dry conditions generating small gold particles very actives at low temperature. This fact is notably favoured by the presence of surface oxygen vacancies that improve the surface dynamics. The obtained results suggest that the reaction mechanism proceeds through the formation of a peroxo-like complex formed after the electronic transfer from the surface to the gas molecule.

April, 2014 | DOI: 10.1039/c3ra46662k

Title: Spinodal decomposition and precipitation in Cu–Cr nanocomposite
Author(s): Sheibani, S; Heshmati-Manesh, S; Ataie, A; Caballero, A; Criado, JM
Source: Journal of Alloys and Compounds, 587 (2014) 670-676

abstract | fulltext

In this study, spinodal decomposition and precipitation mechanism of mechanically alloyed supersaturated Cu–3wt.%Cr and Cu–5wt.%Cr solid solutions was investigated under nonisothermal aging. Decomposition mechanism and kinetics were studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. Also, the microstructure was characterized by transmission electron microscopy (TEM). Effect of Al2O3 reinforcement on the aging kinetics was also evaluated. It was found that Cu–3wt.%Cr and Cu–5wt.%Cr solid solutions undergo spinodal decomposition at initial stages of ageing. However, decomposition mechanism was changed to nucleation and growth by the aging progress. The aging kinetics for the Cu–Cr/Al2O3 composition appeared to be slightly faster than that for Cu–Cr, since the ageing activation energy is decreased in presence of Al2O3 nano-particles. This behavior is probably due to the higher dislocation density and other structural defects previously produced during ball milling. A detailed comparison of the DSC results with those obtained by TEM, showing good consistency, has been presented. The average size of Cr-rich precipitates was about 10 nm in the copper matrix.

February, 2014 | DOI: 10.1016/j.jallcom.2013.11.019

Title: Promoting effect of Ce and Mg cations in Ni/Al catalysts prepared from hydrotalcites for the dry reforming of methane
Author(s): Djebarri, B; Gonzalez-Delacruz, VM; Halliche, D; Bachari, K; Saadi, A; Caballero, A; Holgado, JP; Cherifi, O
Source: Reaction Kinetics, Mechanisms and Catalysis, 111 (2014) 259-275

abstract | fulltext

Several catalytic systems containing Ni/Mg/Al/Ce were synthesized from nitrates of Ni2+, Mg2+, Al3+ and Ce3+ cations with M2+/M3+ = 2 ratios by means of the carbonate co-precipitation method and subsequent calcination at 800 A degrees C. Atomic absorption spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy, BET, temperature programmed reduction and scanning electron microscopy were used in order to describe the structural, morphological and surface characteristics of the solids completely. The effect of substitution/incorporation of Al by Ce and/or Mg on NiAl sample was studied. XRD analyses confirm that on Al-containing samples (NiAl, NiMgAl), the formation of the precursors layered double hydroxide structure. On the other hand, on cerium containing samples (NiCe, NiMgCe), poorly resolved diffractograms were observed what can be explained by the large radius of cerium. The catalysts were evaluated in the reaction of CO2 reforming of methane at 750 A degrees C. NiCe and NiMgAl catalysts exhibit higher activity and a H-2/CO ratio of almost 1. NiAl and NiMgCe samples showed lower conversions and a CH4/CO2 ratio < 1, indicating the occurrence of reverse water gas shift reaction.

February, 2014 | DOI: 10.1007/s11144-013-0646-2

2013


Title: A single-source route to bulk samples of C3N and the co-evolution of graphitic carbon microspheres
Author(s): King, TC; Matthews, PD; Holgado, JP; Jefferson, DA; Lambert, RM; Alavi, A; Wright, DS
Source: Carbon, 64 (2013) 6-10

abstract | fulltext

The thermolysis of commercially available m-phenylenediamine (1,3-(NH2)2C6H4) at 800 °C under a static vacuum in a sealed quartz tube provides the first bulk synthesis of C3N, whose properties have only been predicted theoretically previously. Hollow carbon microspheres (CMSs) which do not contain significant nitrogen doping (1–3 μm diameter) are co-produced in the reaction and readily separated from the C3N flakes. The separate C3N flakes and CMSs have been characterized by electron microscopy, X-ray spectroscopy and X-ray diffraction. These studies show that the samples of C3N and CMSs both possess multi-layered turbostratic graphitic structures. A new mechanism for the template-free assembly of CMSs is proposed on the basis of electron microscopy that involves bubble evolution from a static carbonized layer.

November, 2013 | DOI: 10.1016/j.carbon.2013.04.043

Title: Multiple Zeolite Structures from One Ionic Liquid Template
Author(s): Blanes, JMM; Szyja, BM; Romero-Sarria, F; Centeno, MA; Hensen, EJM; Odriozola, JA; Ivanova, S
Source: Chemistry-A European Journal, 19 (2013) 2122-2130

abstract | fulltext

This study reports the use of 1-butyl-3-methyl imidazolium methanesulfonate ionic liquid as a template in the synthesis of zeolites. It is found that the silicon source determines the formation of beta (BEA), mordenite framework inverted (MFI), or analcime (ANA) zeolites. Depending on this source, different preorganized complexes are obtained that drive the formation of the different zeolite structures. In the presence of ethanol, the ionic liquid form preorganized complexes that drive the formation of MFI. In its absence, BEA is obtained. Whereas, the large amount of sodium present when using sodium metasilicate leads to ANA formation. A molecular simulation study of the relative stability of the template-framework system and location of the template provides further insight into the mechanism of synthesis.

February, 2013 | DOI: 10.1002/chem.201202556

Title: Preferential oxidation of CO in excess H2 over CuO/CeO2 catalysts: Characterization and performance as a function of the exposed face present in the CeO2 support
Author(s): Gamarra, D; Camara, AL; Monte, M; Rasmussen, SB; Chinchilla, LE; Hungria, AB; Munuera, G; Gyorffy, N; Schay, Z; Corberan, VC; Conesa, JC; Martinez-Arias, A
Source: Applied Catalysis B: Environmental, 130-131 (2013) 224-238

abstract | fulltext

A series of oxidised copper-cerium nanostructured catalysts prepared by impregnation of copper over ceria supports synthesized by different methods (hydrothermal with varying preparation parameters, microemulsion/precipitation), in order to achieve different specific morphologies (nanocubes, nanorods and nanospheres), have been examined with respect to their catalytic properties for preferential oxidation of CO in excess H2 (CO-PROX). The catalysts have been characterized in detail by XRD, Raman, SBET measurement, HREM, XPS, TPR and EPR, which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of CO-PROX catalytic properties by means of catalytic activity measurements complemented by operando-DRIFTS. Structural dependence of the CO oxidation reaction on the dispersed copper oxide entities as a function of the exposed face present at the surface of the different ceria supports is revealed. An important overall enhancement of the CO-PROX performance is detected for the sample supported on ceria nanocubes which is proposed to be a consequence of the interaction between copper oxide and (1 0 0) faces of the ceria support.

February, 2013 | DOI: 10.1016/j.apcatb.2012.11.008

Title: Erbium doped TiO2–Bi2WO6 heterostructure with improved photocatalytic activity under sun-like irradiation
Author(s): Obregon, S; Colon, G
Source: Applied Catalysis B: Environmental, 140-141 (2013) 299-305

abstract | fulltext

Erbium doped TiO2–Bi2WO6 have been synthesized by means of a surfactant free hydrothermal method having good photoactivities under sun-like excitation for the degradation of Rhodamine B. From the structural and morphological characterization it has been stated that the presence of Er3+ induces a progressive russelite cell contraction due to its incorporation in the Bi2WO6 lattice in substitutional sites. The best photocatalytic performance was attained for the samples with 1 at% of Er. From the study of the photocatalytic activity under different irradiation conditions it can be inferred that Er3+ presence induces a significant improvement of the photoactivity in the UV range. The evolution of band-gap values seems to be similarly related with the reaction rate progression. Thus, the higher band-gap values in lower Er doped systems would be the cause of a better electron hole separation under UV irradiation.

August, 2013 | DOI: 10.1016/j.apcatb.2013.04.014

Title: In situ FT-IR study of the adsorption and photocatalytic oxidation of ethanol over sulfated and metallized TiO2
Author(s): Murcia, JJ; Hidalgo, MC; Navio, JA; Arana, J; Dona-Rodriguez, JM
Source: Applied Catalysis B: Environmental, 142-143 (2013) 205-213

abstract | fulltext

TiO2 Degussa P25, TiO2 prepared by sol–gel submitted to sulfation pre-treatment and some metallized catalysts obtained by photodeposition of Au or Pt over the sulfated TiO2, were evaluated in the reaction of ethanol photo-oxidation. FT-IR spectroscopy was used to investigate the surface features of the photocatalysts, identifying adsorbed species and following the evolution of intermediate products in the ethanol photo-oxidation reaction. Nature of surface acidity in terms of Brönsted and Lewis centers was also studied.

Results showed that sulfation pre-treatment and metallization were important factors influencing the selectivity. Acetaldehyde was the main oxidation product on sulfated TiO2; in the case of P25 also acetates production was observed. The photodeposition of metals had a detrimental effect on the selectivity to acetaldehyde; on metallized catalysts the formation of stable secondary intermediates was detected.

Based on these findings, a reaction pathway for the ethanol photo-oxidation over the different photocatalysts, via acetaldehyde or via acetate formation is proposed.

October, 2013 | DOI: 10.1016/j.apcatb.2013.05.022

Title: High-performance Er3+–TiO2 system: Dual up-conversion and electronic role of the lanthanide
Author(s): Obregon, S; Kubacka, A; Fernandez-Garcia, M; Colon, G
Source: Journal of Catalysis, 299 (2013) 298-306

abstract | fulltext

Erbium-doped TiO2 materials are synthesized by means of a surfactant-free hydrothermal method having good photoactivities for the liquid-phase degradation of phenol and MB and the gas phase of toluene. From the structural and morphological characterization, it has been stated that the presence of Er3+ induces a progressive anatase cell expansion due to its incorporation in the TiO2 lattice. The best photocatalytic performance was attained for the samples with 2 at% of Er3+ irrespective of the chemical degradation reaction essayed. From activity and optical studies under different irradiation excitation conditions, a dual-type mechanism is proposed to be at the origin of the photocatalytic activity enhancement. On one hand, the improvement observed under UV irradiation occurs by the effective charge separation promoted by Er3+ species which would act as electron scavenger. Besides, the up-conversion luminescence process of Er3+ allows profiting the NIR range of the lamp and transferring energy in the UV range to the TiO2. The dual action of Er ions located at anatase networks will open up a wide roadway for the developing of an integral solar active photocatalyst.

March, 2013 | DOI: 10.1016/j.jcat.2012.12.021

Title: Promotional effect of the base metal on bimetallic Au-Ni/CeO2 catalysts prepared from core-shell nanoparticles
Author(s): Holgado, JP; Ternero, F; Gonzalez-delaCruz, VM; Caballero, A
Source: ACS Catalysis, 3 (2013) 2169-2180

abstract | fulltext

A set of three catalysts (a Au–Ni bimetallic and their corresponding Au and Ni monometallics) has been prepared by impregnation of previously prepared suspensions of monodisperse metallic particles to ensure the precise control of their physicochemical characteristics (size and composition). The Au–Ni/CeO2 bimetallic catalysts present better reactivity toward CO oxidation than monometallic Au/CeO2 and Ni/CeO2 prepared under identical conditions. “operando-like” characterization of Ni and Au atoms into the bimetallic particles using, among other techniques, ambient-pressure photoelectron spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy has allowed us to determine that under oxidative conditions the samples present a Au@NiO core–shell distribution, where Ni surface atoms are affected by an electronic effect from inner Au atoms.

September, 2013 | DOI: 10.1021/cs400293b

Title: Gold(III) stabilized over ionic liquids grafted on MCM-41 for highly efficient three-component coupling reactions
Author(s): Bobadilla, LF; Blasco, T; Odriozola, JA
Source: Physical Chemistry Chemical Physics, 39 (2013) 16927-16934

abstract | fulltext

Two alkoxysilyl-modified ionic liquids (ILs) have been synthesized and further grafted onto mesoporous silica, MCM-41; these ionic liquids were used for dispersing AuCl3 catalysts that activate C–H bonds as required for the synthesis of propargylamines by coupling alkyne, aldehyde and amine (A3 coupling) species. 29Si NMR experiments demonstrate the formation of covalent bonds between alkoxysilyl-modified Bmim IL and the MCM-41 surface through silanol groups. The catalytic activities of Au(III)-supported MCM-41 and Au(III) homogeneous catalysts are lower than those obtained for the IL functionalized Au–MCM-41 solids when the same gold loading is considered. An interaction between Au(III) species and the IL is proposed for explaining the stabilization of gold(III) species. However, successive reaction cycles result in a decrease in the catalytic activity that has been explained on the basis of gold leaching.

October, 2013 | DOI: 10.1039/C3CP52924J

Title: Impact of Ce–Fe synergism on the catalytic behaviour of Au/CeO2–FeOx/Al2O3 for pure H2 production
Author(s): Reina, TR; Ivanova, S; Idakiev, V; Delgado, JJ; Ivanov, I; Tabakova, T; Centeno, MA; Odriozola, JA
Source: Catalysis Science & Technology, 3 (2013) 779-787

abstract | fulltext

In this work the development of a series of gold catalysts, essentially based on γ-alumina promoted with a small superficial fraction of Ce–Fe mixed oxides, is reported. The catalytic behaviour is evaluated in the water gas shift reaction. The formation of a Ce–Fe solid solution is evidenced by XRD and related to the catalytic activity where the importance of the Ce–Fe interaction is demonstrated. The best catalyst reached CO conversions very close to the equilibrium limit. A long-term stability test is performed and the loss of activity is observed and attributed to reaction intermediates. Almost complete recovery of the initial conversion is achieved after oxidation treatment, suggesting that the problem of stability could be overcome by a suitable change in the reaction parameters thus leading to a highly efficient catalyst for future applications in H2 production and clean-up.

March, 2013 | DOI: 10.1039/C2CY20537H

Title: Steam reforming of methanol over supported Ni and Ni–Sn nanoparticles
Author(s): Bobadilla, LF; Palma, S; Ivanova, S; Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: International Journal of Hydrogen Energy, 38 (2013) 6646-6656

abstract | fulltext

The influence of the synthesis method and Sn addition on Ni/CeO2–MgO–Al2O3 catalyst is correlated to its catalytic behavior in the reaction of methanol steam reforming. The catalysts prepared by impregnation method are compared to samples obtained by deposition of previously obtained nanoparticles by the polyol method. X-ray diffraction (XRD), specific surface area measurements and H2-temperature programmed reduction (TPR) were used to characterize the catalysts. The differences of the structure, phase transformation and reduction behavior are discussed and related to the catalytic performance of the samples as well as the nature of the carbonaceous deposits formed during the reaction.

May, 2013 | DOI: 10.1016/j.ijhydene.2013.03.143

Title: Hydrogen production using Pt-loaded TiO2 photocatalysts
Author(s): Melian, EP; Lopez, CR; Mendez, AO; Diaz, OG; Suarez, MN; Rodriguez, JMD; Navio, JA; Hevia, DF
Source: International Journal of Hydrogen Energy, 38 (2013) 11737-11748

abstract | fulltext

A series of synthesised TiO2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using sol–gel and sol–gel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance, Brunauer–Emmett–Teller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 μmol h−1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.

September, 2013 | DOI: 10.1016/j.ijhydene.2013.07.006

Title: Role of activated carbon on the increased photocatalytic activity of AC/Bi2WO6 coupled materials
Author(s): Murcia-López, S; Navío, J.A.; Hidalgo, M.C.
Source: Applied Catalysis A: General, 466 (2013) 51-59

abstract | fulltext

The photocatalytic activities of several Bi2WO6 and TiO2/Bi2WO6 materials with different activated carbon (AC) contents were studied for Rhodamine B (RhB) (and Phenol) photodegradation under UV–vis and vis illumination. A wide characterization of the materials was carried out. The addition of AC strongly affected the Bi2WO6 morphology although not the crystalline phase. Even in the material with the lowest AC content (2 wt% nominal content) a structure with hierarchical porosity was formed. AC presence increased the initial reaction rates in the degradation of RhB. An important improvement in the photoactivity under both UV–vis and vis illumination conditions was obtained with the lowest AC content (2 wt%) when compared to the pristine material Bi2WO6 or to the systems with higher AC additions. AC/TiO2/Bi2WO6 materials were also improved in comparison to the TiO2/Bi2WO6 heterostructure without carbon. The improvement cannot be only ascribed to adsorption capability and surface area effects. A mechanism explaining the role of AC on the photocatalytic activity improvement is proposed.

September, 2013 | DOI: 10.1016/j.apcata.2013.06.022

Title: On the different photocatalytic performance of BiVO4 catalysts for Methylene Blue and Rhodamine B degradation
Author(s): Obregon, S; Colon, G
Source: Journal of Molecular Catalysis A: Chemical, 376 (2013) 40-47

abstract | fulltext

BiVO4 hierarchical structures were synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of Methylene Blue and Rhodamine B under UV–vis irradiation. From the structural and morphological characterization it has been stated that BiVO4 present the monoclinic crystalline phase with different morphologies depending on the pH value. For Methylene Blue the photodegradation rate is strongly affected by the crystallite size and higher (0 0 4) facet exposition. On the contrary, for Rhodamine B, the ζ-potential of the surface clearly determines the photocatalytic performance of BiVO4 catalyst.

September, 2013 | DOI: 10.1016/j.molcata.2013.04.012

Title: Influence of the O2/CO ratio and the presence of H2O and CO2 in the feed-stream during the preferential oxidation of CO (PROX) over a CuOx/CeO2-coated microchannel reactor
Author(s): Laguna, OH; Dominguez, MI; Oraa, S; Navajas, A; Arzamendi, G; Gandia, LM; Centeno, MA; Montes, M; Odriozola, JA
Source: Catalysis Today, 203 (2013) 182-187

abstract | fulltext

The catalytic performance of a CuOx/CeO2 powder catalyst and that of a microchannel reactor or microreactor (MR) coated with the same solid was determined and compared. The catalytic activity measurements were carried out with varying O2/CO molar ratios in the feed-stream. In addition, the influence of the presence of CO2 and H2O in the reaction mixture was studied. Some discrepancies were observed between the performances of the powder catalyst and the MR depending on the O2/CO ratio. The MR presented a very good performance with a superior selectivity for CO conversion. This behaviour was due to a more efficient heat removal in the case of the MR that inhibited the H2 oxidation reaction and the r-WGS. The isothermicity of the microreactor during the process was demonstrated through the monitoring of the MR inlet and outlet temperatures.

Concerning the presence of CO2 or H2O in the feed-stream, both compounds gave rise to a decrease of the CO conversion. The negative effect on the catalytic performance was more marked when both compounds were fed together, although the principal inhibitor effect was associated to the CO2. This seems to be related with the formation of stable carbonates at the catalyst surface.

March, 2013 | DOI: 10.1016/j.cattod.2012.04.021

Title: In situ characterization of iron-promoted ceria–alumina gold catalysts during the water-gas shift reaction
Author(s): Reina, TR; Xu, WQ; Ivanova, S; Centeno, MA; Hanson, J; Rodriguez, JA; Odriozola, JA
Source: Catalysis Today, 205 (2013) 41-48

abstract | fulltext

In this work an in situ XRD and XANES study of two gold catalysts supported on iron-promoted ceria–alumina carriers was carried out during the water-gas shift reaction (WGS). The first catalyst, Au/CeO2–FeOx/Al2O3, was prepared using a commercial alumina support in order to obtain a Ce–Fe oxide solid solution and in the second one, Au/FeOx/CeO2–Al2O3, an iron oxide monolayer was deposited onto a ceria–alumina commercial support to promote its redox properties. Catalytic activities in the WGS were remarkably different for both systems. The catalytic activity of the Au/CeO2–FeOx/Al2O3 catalyst was higher than the one shown by the Au/FeOx/CeO2–Al2O3 catalyst that resulted active at much higher temperatures. In situ XRD demonstrates the formation of magnetite (Fe3O4) during the WGS reaction and the presence of big gold particles, ca. 21 nm in diameter, in the low-activity system. This in contrast to the high-activity system that shows undetectable gold nanoparticles and the absence of diffraction peaks corresponding to magnetite during the WGS. The data obtained using in situ XANES states that Ce4+ species undergo reduction to Ce3+during the WGS for both catalysts, and also confirms that in the high-activity catalyst iron is just present as Fe3+ species while in the low-activity catalyst Fe3+ and Fe2+ coexist, resulting in iron spinel observed by XRD. These results allow us conclude that the Au/CeO2–Fe2O3/Al2O3 catalyst is a suitable catalyst for WGS when avoiding the formation of magnetite, in such a case Fe3+ species favors reduction and water splitting increasing the catalytic activity in the WGS reaction.

April, 2013 | DOI: 10.1016/j.cattod.2012.08.004

Title: Effect of the alloy on micro-structured reactors for methanol steam reforming
Author(s): Echave, FJ; Sanz, O; Velasco, I; Odriozola, JA; Montes, M
Source: Catalysis Today, 213 (2013) 145-154

abstract | fulltext

Micro-monoliths and foams made of aluminium, Fecralloy® and brass were studied as substrates for structured systems for methanol steam reforming (MSR). All the alloys exhibited very adherent oxide layer produced by pre-treatment to improve the adhesion between substrate and catalyst. 2.5% Pd/ZnO catalyst was prepared and deposited on structured substrates. Both, good catalyst adhesion and stable catalytic performance were achieved in the case of brass micro-monoliths. The Fecralloy® and aluminium substrates reacted with the catalytic active components resulting in catalyst modification. The aluminium based substrates promoted dimethyl ether (DME) formation. Aluminium foam produced better performance than aluminium micro-monoliths that could be related to improved mass and heat transfer properties in foams.

September, 2013 | DOI: 10.1016/j.cattod.2013.02.027

Title: Cyclohexane photocatalytic oxidation on Pt/TiO2 catalysts
Author(s): Murcia, JJ; Hidalgo, MC; Navio, JA; Vaiano, V; Sannino, D; Ciambelli, P
Source: Catalysis Today, 209 (2013) 164-169

abstract | fulltext

Gas-solid heterogeneous photocatalytic oxidation (PCO) of cyclohexane in humidified air over TiO2 and Pt/TiO2 catalyst was studied.

Pt/TiO2 photocatalysts were synthesized by photodeposition method at different Pt loadings (0.5–2 wt.%). The addition of 0.5 wt.% Pt does not significantly modify the TiO2 properties. The increase in Pt loading induces to an aggregation of metallic particles on TiO2 surface.

The cyclohexane PCO was performed in a fluidized bed photoreactor at 60 and 100 °C. Pure TiO2 was more active than 1 and 2 wt.% Pt/TiO2 samples at 60 °C. Nevertheless, the conversion level increases with temperature on Pt/TiO2 photocatalysts. The cyclohexane was mineralized into CO2, water and low amount of CO. A beneficial effect of Pt addition was found, since total CO2 selectivity was obtained. The Pt/TiO2 photocatalysts prepared by photodeposition provide the total cyclohexane PCO without CO production. Photocatalysts deactivation was not observed in any performed test. Evidence of an opportune tuning of temperature is highlighted.

June, 2013 | DOI: 10.1016/j.cattod.2012.11.018

Title: Preferential oxidation of CO over Au/CuOx–CeO2 catalyst in microstructured reactors studied through CFD simulations
Author(s): Uriz, I; Arzamendi, G; Dieguez, PM; Laguna, OH; Centeno, MA; Odriozola, JA; Gandia, LM
Source: Catalysis Today, 216 (2013) 283-291

abstract | fulltext

A computational fluid dynamics (CFD) simulation study of the preferential oxidation of CO (CO-PROX) in microstructured reactors consisting in square and semicircular microchannels coated with an Au/CuOx–CeO2 catalyst is presented. The CO content of the feed stream was set at 1 vol.%. A parametric sensitivity analysis has been performed under isothermal conditions revealing that an optimal reaction temperature exists that leads to a minimum CO content at the microreactor exit. The influence of the space velocity, CO2 concentration and oxygen-to-CO molar ratio in the feed stream (λ), catalyst loading, and microchannel characteristic dimension (d) on the microreactor performance has been investigated. Under suitable conditions, the CO concentration can be reduced below 10 ppm at relatively low temperatures within the 155–175 °C range. A negative effect of the increase of d from 0.35 mm to 2.8 mm on the CO removal efficiency has been found and attributed to a more detrimental effect of the mass transport limitations on the oxidation of CO than that of H2. Non-isothermal CFD simulations have been performed to investigate the cooling of the CO-PROX reactor with air or a fuel cell anode off gas surrogate in parallel microchannels. Due to the very rapid heat transfer allowed by the microreactor and the strong influence of the reaction temperature on the exit CO concentration, a careful control of the coolant flow rate and inlet temperature is required for proper reactor operation. The microreactor behavior is virtually isothermal.

November, 2013 | DOI: 10.1016/j.cattod.2013.04.023

Title: A low-temperature single-source route to an efficient broad-band cerium(III) photocatalyst using a bimetallic polyoxotitanium cage
Author(s): Lv, YK; Yao, MM; Holgado, JP; Roth, T; Steiner, A; Gan, LH; Lambert, RM; Wright, DS
Source: RSC Advances, 3 (2013) 13659-13662

abstract | fulltext

Aqueous hydrolysis of a series of cerium-containing polyoxotitanium cages gives Ce(III)-doped TiO2 [TiO2(Ce)] or TiO2-supported Ce(III)2Ti2O7, depending on the starting Ti : Ce ratio of the precursor. TiO2-supported Ce2Ti2O7 exhibits superior photocatalytic activity to the Ce-doped TiO2 materials and unusual broad-band absorption behaviour across the visible and near-infrared regions.

September, 2013 | DOI: 10.1039/C3RA41524D

Title: Au/CeO2 metallic monolith catalysts: influence of the metallic substrate
Author(s): Tejada, LMM; Dominguez, MI; Sanz, O; Centeno, MA; Odriozola, JA
Source: Gold Bulletin, 46 (2013) 221-231

abstract | fulltext

Ceria-based gold catalysts were successfully deposited on ferritic stainless steel (Fecralloy) and aluminium monoliths. The prepared monolithic and reference powder catalysts were characterized by means of S-BET, X-ray diffraction, glow discharge optical emission spectroscopy and scanning electron microscopy-energy dispersive X-ray analysis techniques and tested in the CO oxidation reaction. Characterization results put in evidence the diffusion of cations from the catalytic layer on the surface of the monoliths to the metallic oxide scale and inversely, from the oxide scale to the catalysts, thus altering the catalytic formulation and affecting the CO oxidation properties of the catalytic device. The extension and nature of the modifications produced depend on the nature of the catalysts and the metallic substrate, as well as the reaction conditions applied. These facts must be considered when gold catalysts are supported on metallic-structured devices.

December, 2013 | DOI: 10.1007/s13404-013-0102-0

Title: Improved photocatalytic activity of g-C3N4/TiO2 composites prepared by a simple impregnation method
Author(s): Miranda, C; Mansilla, H; Yanez, J; Obregon, S; Colon, G
Source: Journal of Photochemistry and Photobiology A: Chemistry, 253 (2013) 16-21

abstract | fulltext

g-C3N4 and TiO2 hybrid structures are synthesized by means of a simple impregnation method having good photoactivities for the degradation of phenol under UV irradiation. From the wide structural and surface characterization we have stated that the presence of g-C3N4 notably affect the surface feature of TiO2 (surface area and pore size distribution). Enhanced photoactivities have been obtained for composites systems. The best result was obtained for 2 wt% loading of g-C3N4 leading to a 70% of improvement with respect to bare TiO2 in the reaction rate. The effective charge carrier separation was proposed as the responsible of such improved photoactivity.

February, 2013 | DOI: 10.1016/j.jphotochem.2012.12.014

Title: Degradation of Rhodamine B/Phenol Mixtures in Water by Sun-Like Excitation of a Bi2WO6–TiO2 Photocatalyst
Author(s): Murcia-López, S; Navío, J.A.; Hidalgo, M.C.
Source: Photochemistry and Photobiology, 89 (2013) 832-840

abstract | fulltext

Bi2WO6 and Bi2WO6–TiO2 (5% molar Ti) nano-heterostructures were synthesized by a hydrothermal method. The properties of the synthesized catalysts were characterized, having high photoactivity for Rhodamine B degradation under sun-like illumination, explained by a synergetic mechanism previously proposed through UV and visible induced processes, in which the photosensitization effect of Rhodamine B is considered. We now report that using Phenol, a molecule which does not lead the photosensitization process, the photoactivity decreased considerably, thus emphasizing how important is the model molecule selected as degradation substrate for evaluating the photoactivity. The photocatalytic properties of the synthesized catalysts have been evaluated by exposing a mixture of Rhodamine B and Phenol in water, to different illumination conditions. It can be confirmed that the photoinduced mechanism via the photosensitization of Rhodamine B is a key factor responsible for the increase on the photocatalytic activity showed by the Bi2WO6–TiO2 compound and that the degradation mechanism of Rhodamine B is not changed by the simultaneous presence of other transparent substrate as Phenol.

July, 2013 | DOI: 10.1111/php.12054

Title: Strong quantum confinement effects in SnS nanocrystals produced by ultrasound-assisted method
Author(s): Azizian-Kalandaragh, Y; Khodayari, A; Zeng, ZP; Garoufalis, CS; Baskoutas, S; Gontard, LC
Source: Journal of Nanoparticle Research, 15 (2013) 1388

abstract | fulltext

Nanocrystalline SnS powder has been prepared using tin chloride (SnCl2) as a tin ion source and sodium sulfide (Na2S) as a sulfur ion source with the help of ultrasound irradiation at room temperature. The as-synthesized SnS nanoparticles were quantitatively analyzed and characterized in terms of their morphological, structural, and optical properties. The detailed structural and optical properties confirmed the orthorhombic SnS structure and a strongly blue shifted direct band gap (1.74 eV), for synthesized nanoparticles. The measured band gap energy of SnS nanoparticles is in a fairly good agreement with the results of theoretical calculations of exciton energy based on the potential morphing method in the Hartree–Fock approximation.

January, 2013 | DOI: 10.1007/s11051-012-1388-1

Title: Au/TiO2 supported on ferritic stainless steel monoliths as CO oxidation catalysts
Author(s): Milt, VG; Ivanova, S; Sanz, O; Dominguez, MI; Corrales, A; Odriozola, JA; Centeno, MA
Source: Applied Surface Science, 270 (2013) 169-177

abstract | fulltext

Metallic supported structured catalysts were obtained by washcoating AluchromYHf monoliths with an Au/TiO2 catalyst. The powder catalyst was synthesized by DAE (direct anionic exchange) method. Using this catalyst, a stable slurry was prepared and used to washcoat the monoliths. TEM and SEM studies revealed that gold nanoparticles in the Au/TiO2 powder catalyst had an average diameter of 3–4 nm, but during the preparation of the structured catalyst, aggregate Au particles of the slurry reached diameters of 9 nm. Before coating, Aluchrom YHf monoliths were thermally treated to generate a homogeneous and well-adhered oxide rough surface layer, mainly composed of α-Al2O3 whiskers, which favored the anchoring of the catalyst. The catalytic layer deposited was well attached and contained not only the Au/TiO2 catalyst but also metallic oxides formed from stainless steel components that diffused through the oxide scale. The structural characterization was performed by XRD, XRF, TEM, SEM, GD-OES and SBET.

The catalytic activity of the powder and structured catalysts was tested in the oxidation of the CO reaction. Catalysts demonstrated to be active at room temperature. After a first activation run, and in spite of their larger gold particle size, the catalytic activities of the structured catalysts overcame those of the powder catalyst. This improvement is probably due to the segregation of the transition metal oxides toward the surface oxide scale.

April, 2013 | DOI: 10.1016/j.apsusc.2012.12.159

Title: Gas-phase Photocatalytic Partial Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone on Au/TiO2 Photocatalysts
Author(s): Sannino, D; Vaiano, V; Ciambelli, P; Murcia, JJ; Hidalgo, MC; Navio, JA
Source: Journal of Advanced Oxidation Technologies, 16 (2013) 71-82

abstract | fulltext

The heterogeneous photocatalytic partial oxidation of cyclohexane in gas-phase as an alternative green process for fine chemicals synthesis was successfully achieved on Au/TiO2 photocatalysts prepared by photodeposition technique. Different gold loadings ranging between 0.5 and 2 wt.% of photodeposited Au on TiO2 synthesized by sol-gel method were obtained by changing the concentration of gold precursor at fixed illumination intensity and time. The cyclohexane partial photoxidation was conducted in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. Main observed reaction products were cyclohexanol, cyclohexanone and CO2. The resulting selectivity was dramatically influenced by the gold content. The reaction temperature was a critical parameter to reach the photocatalysts stability, avoiding deactivation phenomena while the tuning of Au content of the photocatalysts, resulted in the promotion of the formation of cyclohexanol or cyclohexanone with high selectivity. In particular, by increasing Au content, the process selectivity is completely reversed, passing from high cyclohexanol selectivity (75%) to high selectivity to cyclohexanone (80%). These promising results evidenced that Au/TiO2 catalysts in the selected operating conditions, are effective materials for the synthesis of cyclohexanone and cyclohexanol in gas-phase by photocatalysis, at very low reaction temperatures and without the additional step of catalyst recovering needed in the liquid partial oxidation of cyclohexane.

January, 2013 | DOI: ---

Title: Preparation of Titanium Oxide/Silicon Oxide (TiO2/SiO2) systems through the solvothermal method for applications in photocatalysis
Author(s): Galeano, L.; Navío, J.A.; Restrepo, G.M.; Marín, J.M.
Source: Información Tecnológica, 24 (2013) 81-92

abstract | fulltext

Sistemas Óxido de Titanio/Óxido de Silicio (TiO2/SiO2) fueron obtenidos por anclaje de TiO2 en SiO2. El fotocatalizador TiO2 se obtuvo por alcohólisis del TiCl4 con 2-propanol y posterior cristalización a presión autógena a 200 °C, excluyendo etapas de calcinación a altas temperaturas. Se emplearon diferentes relaciones SiO2/TiCl4 para determinar su influencia en la estabilidad, propiedades y fotoactividad de los sistemas TiO2/SiO2. La actividad fotocatalítica fue evaluada por la fotodegradación de metanol en fase gaseosa. El TiO2 cristalizó como fase anatasa o como una mezcla rutilo/anatasa, dependiendo por la relación SiO2/TiCl4 inicial. Los resultados muestran que se producen materiales compuestos con alta cristalinidad del TiO2. Se encontró también que hay una fuerte relación entre la actividad fotocatalítica con las propiedades fisicoquímicas y de estas con las composiciones iniciales de síntesis.

December, 2013 | DOI: 10.4067/S0718-07642013000500010

2012


Title: Advanced nanoarchitectures for solar photocatalytic applications
Author(s): Kubacka, A; Fernandez-Garcia, M; Colon, G
Source: Chemical Reviews, 112 (2012) 1555-1614

abstract | fulltext

Advanced nanostructured materials that demonstrate useful activity under solar excitation in fields concerned with the elimination of pollutants, partial oxidation and the valorization of chemical compounds, water splitting and CO 2 reduction processes, are discussed. Point defects present in nanoparticulated anatase present both 5-fold- and 6-fold-coordinated titanium atoms, as well as 2-fold- and 3-fold-coordinated oxygens. The requirement of using sunlight as the excitation source for the degradation reaction demands, as a principal requirement, the modification of the electronic characteristics of a UV absorber system such as anatase-TiO 2. Some reports also indicate the need for large doping concentrations for N-doping in specific cases where notable changes in the valence band onset are subsequently observed. The effect of cetyltrimethylammonium bromide (CTAB) on the crystallization is reported by Yin et al. They showed that the presence of CTAB induces the appearance of BiOBr during the synthesis at 80°C using an aqueous method.

March, 2012 | DOI: 10.1021/cr100454n

Title: Evidence of upconversion luminescence contribution to the improved photoactivity of erbium doped TiO2 systems
Author(s): Obregon, S; Colon, G
Source: Chemical Communications, 48 (2012) 7865-7867

abstract | fulltext

Er3+–TiO2 synthesized by a surfactant free hydrothermal method exhibits good photoactivities under sun-like excitation for the degradation of phenol. The presence of Er3+ does not affect the structural and morphological features of the TiO2 significantly. The best photocatalytic performance was attained for the samples with 2 wt% of Er. Different photocatalytic runs indicated that the incorporation of the Er3+ cation would be responsible for the enhanced photocatalytic activity, which participates in different mechanisms under UV and NIR excitation.

August, 2012 | DOI: 10.1039/C2CC33391K

Title: Hydrothermal synthesis of BiVO4: Structural and morphological influence on the photocatalytic activity
Author(s): Obregon, S; Caballero, A; Colon, G
Source: Applied Catalysis B-Environmental, 117 (2012) 59-66

abstract | fulltext

BiVO 4 hierarchical heterostructures are synthesized by means of a surfactant free hydrothermal method having good photoactivities for the degradation of methylene blue under UV-vis irradiation. From the structural and morphological characterization it has been stated that BiVO 4 present the monoclinic crystalline phase with different morphologies depending on the pH value, type of precipitating agent and hydrothermal temperature and treatment time. The best photocatalytic performance was attained for the samples with needle-like morphology.

May, 2012 | DOI: 10.1016/j.apcatb.2011.12.037

Title: Effect of the active metals on the selective H-2 production in glycerol steam reforming
Author(s): Araque, M; Martinez, LM; Vargas, JC; Centeno, MA; Roger, AC
Source: Applied Catalysis B-Environmental, 125 (2012) 556-566

abstract | fulltext

The production of hydrogen by glycerol steam reforming was studied using CeZr(Co, CoRh) catalysts. The effect of Co and Rh presence on the properties of the mixed oxides and the effect on the catalytic behavior were considered. The catalysts were characterized before and after testing by XRD, Raman, TPR, H 2-TPD, TPD-TPO and HRTEM. It was observed that the presence of Co allowed the selective H 2 production related with the presence of a metallic phase at the beginning of the reaction. The presence of Rh favored even more the H 2 production and also increased the stability of the catalyst. For CeZrCoRh, the presence of both metals enhanced the catalyst reduction capacity, a characteristic that significantly improved the catalytic behavior for glycerol steam reforming. The selective H 2 production was related to the capacity of the catalyst to activate H 2O under the reaction conditions. The progressive loss of this capacity decreases the production of H 2, and glycerol decomposition is actually favored over glycerol steam reforming. According to the initial distribution of products, and its evolution with time on stream, two main reaction pathways were proposed.

August, 2012 | DOI: 10.1016/j.apcatb.2012.06.028

Title: Effect of deposition of silver on structural characteristics and photoactivity of TiO2-based photocatalysts
Author(s): Melian, EP; Diaz, OG; Rodriguez, JMD; Colon, G; Navio, JA; Macias, M; Pena, JP
Source: Applied Catalysis B-Environmental, 127 (2012) 112-120

abstract | fulltext

The homemade bare TiO2 photocatalyst obtained in a previous work was modified with nanosized silver particles by liquid impregnation and photodeposition methods to obtain different noble metal loadings (0.3–1 at.%). Characterization of the synthesized photocatalysts was carried out by the BET method, XPS, TEM, SEM-EDX, XRD and diffuse reflectance measurements. Photocatalytic activity of these silver-deposited TiO2 nanoparticles was tested by photocatalytic degradation of phenol as a reference model representing phenolic pollutants. The noble metal content on the TiO2 surface affected the efficiency of the photocatalytic process, and the photocatalytic activity of noble metal-modified TiO2 was considerably better than that of bare TiO2. Phenol decomposition rate was higher with TiO2 modified by the liquid impregnation method than with TiO2 modified by the photodeposition method.

October, 2012 | DOI: 10.1016/j.apcatb.2012.08.007

Title: Insights towards the influence of Pt features on the photocatalytic activity improvement of TiO2 by platinisation
Author(s): Murcia, JJ; Navio, JA; Hidalgo, MC
Source: Applied Catalysis B-Environmental, 126 (2012) 76-85

abstract | fulltext

The influence of Pt features, such as particle size, dispersion, oxidation state and amount of metal, on the improvement of the photoactivity of TiO2 for phenol and methyl orange degradation was studied.

The size of Pt deposits was precisely controlled by changing deposition time under medium light intensity during the photodeposition, with sizes ranging from 3 to 6 nm. Pt oxidation state was also strongly dependent on the photodeposition time.

Photocatalytic activity results showed that the fraction of metallic platinum (Pt0) was the crucial factor for the improvement of the activity. When the fraction of Pt0 was similar, metal deposit size became the dominant parameter influencing the activity.

The influence of the substrate to be degraded (phenol or methyl orange) was also studied.

September, 2012 | DOI: 10.1016/j.apcatb.2012.07.013

Title: Selective photooxidation of alcohols as test reaction for photocatalytic activity
Author(s): Lopez-Tenllado, F. J.; Marinas, A.; Urbano, F. J.; Colmenares, J. C.; Hidalgo, M. C.; Marinas, J. M.; Moreno, J. M.
Source: Applied Catalysis B-Environmental, 128 (2012) 150-158

abstract | fulltext

Twenty-four different titania-based systems synthesized through the sol–gel process varying the precursor (titanium isopropoxide or tetrachloride) and/or the ageing conditions (magnetic stirring, ultrasounds, microwave or reflux) were tested for liquid-phase selective photooxidation of 2-butenol (crotyl alcohol) to 2-butenal (crotonaldehyde) and gas-phase selective photooxidation of 2-propanol to acetone. To the best of our knowledge, the former process is suggested for the first time as test reaction for photocatalytic activity. Interestingly, both test reactions (despite having very different reactant/catalyst ratio and contact times) showed quite similar results in terms of influence of the precursor (titanium isopropoxide leading to better results than titanium tetrachloride) and the metals (the presence of iron, palladium or zinc being detrimental to activity whereas zirconium and especially gold improved the results as compared to pure titania). To our mind, these results give validity to both processes as test reactions for a fast screening of catalysts for photocatalytic tranformations. Finally, some gold-containing solids even improved photocatalytic activity of Degussa P25.

November, 2012 | DOI: 10.1016/j.apcatb.2012.02.015

Title: Cu-modified cryptomelane oxide as active catalyst for CO oxidation reactions
Author(s): Hernandez, Willinton Y.; Centeno, Miguel A.; Ivanova, Svetlana; Eloy, Pierre; Gaigneaux, Eric M.; Odriozola, Jose A.
Source: Applied Catalysis B-Environmental, 123-124 (2012) 27-35

abstract | fulltext

Manganese oxide octahedral molecular sieves (cryptomelane structure) were synthesized by a solvent-free method and tested in the total oxidation of CO (TOX), and preferential oxidation of CO in presence of hydrogen (PROX). The influence of Cu in the cryptomelane structure was evaluated by several characterization techniques such as: X-ray fluorescence (XRF), thermogravimetric analysis (TGA), hydrogen temperature programmed reduction (TPR-H2) and X-ray photoelectron spectroscopy (XPS). The Cu-modified manganese oxide material (OMS-Cu) showed very high catalytic activity for CO oxidation in comparison to the bare manganese oxide octahedral molecular sieve (OMS). The improved catalytic activity observed in OMS-Cu catalyst was associated to a high lattice oxygen mobility and availability due to the formation of Cusingle bondMnsingle bondO bridges. In addition, under PROX reaction conditions the catalytic activity considerably decreases in the presence of 10% (v/v) CO2 in the feed while the same amount of water provokes an improvement in the CO conversion and O2 selectivity.

July, 2012 | DOI: 10.1016/j.apcatb.2012.04.024

Title: Influence of the shape of Ni catalysts in the glycerol steam reforming
Author(s): Bobadilla, L. F.; Alvarez, A.; Dominguez, M. I.; Romero-Sarria, F.; Centeno, M. A.; Montes, M.; Odriozola, J. A.
Source: Applied Catalysis B-Environmental, 123-124 (2012) 379-390

abstract | fulltext

Biomass is an alternative to replace the use of fossil fuels. Glycerol, a byproduct in the biodiesel production, can be used for obtaining hydrogen. The most efficient method for obtaining hydrogen from glycerol is the steam reforming (SR). So far all the published papers report the use of conventional catalyst. In this paper, a structured catalyst has been prepared and compared with the conventional ones (powder and spherical pellets). Results show that the structured catalyst (monolith) is more stable as formation of coke was not observed.

July, 2012 | DOI: 10.1016/j.apcatb.2012.05.004

Title: LaNiO3 as a precursor of Ni/La2O3 for CO2 reforming of CH4: Effect of the presence of an amorphous NiO phase
Author(s): Rosa Pereñiguez , Victor M. Gonzalez-delaCruz, Alfonso Caballero, Juan P. Holgado,
Source: Applied Catalysis B-Environmental, 123-124 (2012) 324-32

abstract | fulltext

The objective of the present work has been the study of the physico-chemical and catalytic properties of Ni/La2O3 catalysts obtained by reduction of four LaNiO3 samples prepared by different methods. The LaNiO3 precursors as well as the resulting Ni/La2O3 catalysts, were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), temperature programmed reduction and oxidation (TPR, TPO). The catalytic performances of these systems for dry reforming of methane (DRM) were also tested. These samples show different physico-chemical properties resulting from the synthesis method used. The XAS and TPR measurements show that in all four LaNiO3 samples there is, in addition of the crystalline LaNiO3 rhombohedrical phase, a significant amount of an amorphous NiO phase, not detectable by XRD but evidenced by XAS. The amount of this NiO amorphous phase seems to play, together with some other microstructural parameters, an important role in the performance of the Ni/La2O3 samples for the DRM reaction.

July, 2012 | DOI: 10.1016/j.apcatb.2012.04.044

Title: CO-Induced Morphology Changes in Zn-Modified Ceria: A FTIR Spectroscopic Study
Author(s): Penkova, A; Laguna, OH; Centeno, MA; Odriozola, JA
Source: Journal of Physical Chemistry C, 116 (2012) 5747-5756

abstract | fulltext

A FTIR study of the CO adsorption on a Zn-modified ceria is presented. The results indicate that at lower activation temperatures only Ce 4+ carbonyls were detected, which were reduced with the increase of the activation temperature. At higher activation temperatures, up to three Zn 2+ carbonyls were also identified according to the arrangement of the Zn 2+ cations. The consecutive CO adsorptions demonstrated an irreversible modification of the surface, resulting in an agglomeration of the zinc cations. A stepwise conversion of the isolated Zn 2+ carbonyls into carbonyls of the closely situated zinc cations followed by formation of bigger zinc oxide clusters was observed. The carbon monoxide coordinated on the isolated Zn 2+ cations at the interface with ceria reacts with the lattice oxygen leading to formation of oxygen vacancies. An insight into the origin of the activation during the CO oxidation process is proposed.

March, 2012 | DOI: 10.1021/jp210996b

Title: In Situ XAS Study of Synergic Effects on Ni-Co/ZrO2 Methane Reforming Catalysts
Author(s): Gonzalez-delaCruz, VM; Pereniguez, R; Ternero, F; Holgado, JP; Caballero, A
Source: Journal of Physical Chemistry C, 116 (2012) 2919-2926

abstract | fulltext

Four different mono and bimetallic Ni–Co/ZrO2 catalysts have been studied by means of in situ XAS, X-ray diffraction, TPR, and measurements of the catalytic activity in the dry reforming reaction of methane (DRM). Even though the cobalt monometallic system has no activity for the methane reforming reaction, both bimetallic catalysts (with 1:1 and 1:2 Ni/Co ratio, respectively), showed a better activity and stability than the nickel monometallic system. The XRD data indicate that a mixed cobalt–nickel spinel is formed by calcination of the precursor solids, leading to the formation of an alloy of both metals after reduction in hydrogen. In situ XAS experiments showed a much better resistance of metals in the bimetallic systems to be oxidized under reaction conditions at temperatures until 750 °C. After these results, we proposed the formation in the bimetallic systems of a more reducible nickel–cobalt alloy phase, which remains completely metallic in contact with the CO2/CH4 reaction mixture at any temperature. The presence of adjacent nickel and cobalt sites seems to avoid the deactivation of cobalt in the DRM reaction. In the case of cobalt sites, the presence of adjacent nickel atoms seems to prevent the deposition of carbon over the cobalt sites, now showing its higher activity in the dry reforming reaction. Simultaneously, this higher activity of the cobalt sites in the bimetallic system produces more hydrogen as a product, maintaining the nickel atoms completely reduced under reaction conditions. This synergic effect accounts for the better performance of the bimetallic systems and points at both, the oxidation state of nickel particles under reaction conditions and the carbon deposition processes, as important factors responsible for differences in catalytic activities and stabilities in this hydrocarbon reaction.

February, 2012 | DOI: 10.1021/jp2092048

Title: Making Photo-selective TiO2 Materials by Cation–Anion Codoping: From Structure and Electronic Properties to Photoactivity
Author(s): Marquez, AM; Plata, JJ; Ortega, Y; Sanz, JF; Colon, G; Kubacka, A; Fernandez-Garcia, M
Source: Journal of Physical Chemistry C, 116 (2012) 18759-18767

abstract | fulltext

Photoselective oxidation yielding high-added value chemicals appears as a green novel process with potential to be explored. In this study we combine spectroscopic XPS (N 1s and O 1s) and multiwavelength Raman data with density functional theory calculations to explore the structural and electronic properties of W,N-codoped TiO2 anatase surfaces and interpret the outstanding photocatalytic properties of such a system in partial oxidation reactions. Theoretical calculations allow us to examine several substitutional and N-interstitial configurations at different concentrations of the W,N dopants (similar to those experimentally found), as well as their interaction with structural point defects: Ti cation vacant sites and surface wolframyl species that are required to compensate the extra charge of the W6+ and N-containing anions. The joint use of theoretical and experimental XPS and Raman tools renders key structural information of W,N-codoped microcrystalline TiO2 solids. The incorporation of N at substitutional positions of anatase with the concomitant presence of W═O species introduces localized states in the band gap, a result that is critical in interpreting the chemical behavior of the solids. The combination of the electronic and geometric structural information leads to a simple mechanism that rationalizes the experimentally observed photoactivity and selectivity in partial oxidation reactions.

September, 2012 | DOI: 10.1021/jp3045143

Title: Operando DRIFTS study of the redox and catalytic properties of CuO/Ce1−xTbxO2−δ (x = 0–0.5) catalysts: evidence of an induction step during CO oxidation
Author(s): Martinez-Arias, A.; Hungria, A. B.; Fernandez-Garcia, M.; Iglesias-Juez, A.; Soria, J.; Conesa, J. C.; Anderson, J. A.; Munuera, G.
Source: Physical Chemistry Chemical Physics, 14 (2012) 2144-2151

abstract | fulltext

Catalysts of 1 wt% copper oxide supported on cerium oxide or cerium–terbium mixed oxides are comparatively examined with respect to their redox and catalytic properties for CO oxidation. Characterization of the catalysts had shown that they contain highly dispersed CuO-type entities on the corresponding nanostructured fluorite supports with copper dispersion increasing with increasing amounts of terbium in the support. In contrast, the CO oxidation catalytic activity decreases with increasing amounts of terbium in the support. On the basis of operando-DRIFTS experiments, one of the factors that could explain such behaviour is related to the greater difficulty in generating reduced copper sites active for the reaction in the presence of terbium, which in turn is evidenced to constitute an induction stage. Analysis of the redox properties is complemented by XPS which confirms the greater resistance to copper reduction in the presence of terbium.

February, 2012 | DOI: 10.1039/C1CP23298C

Title: Sub-ambient CO oxidation over mesoporous Co3O4: Effect of morphology on its reduction behavior and catalytic performance
Author(s): Alvarez, A; Ivanova, S; Centeno, MA; Odriozola, JA
Source: Applied Catalysis A-General, 431 (2012) 9-17

abstract | fulltext

The influence of the Co 3O 4 morphology on its redox behavior and catalytic performance in the CO oxidation reaction is studied. Three different Co 3O 4 morphologies were synthesized by precipitation and hydrothermal methods. TEM and SEM observations clearly show the different obtained morphologies: rods, wires and a mixture of plates and cubes. The textural properties depend on the morphology and the redox ones on the particle size. XRD analysis reveals a spinel structure in all solids with a preferential exposition of the [1 1 0] plane in the Co 3O 4 rods sample. This preferential exposition, along with its higher specific surface area provides the rods with more efficient oxygen storage capacity resulting in an excellent catalytic performance compared to the other two morphologies.

July, 2012 | DOI: 10.1016/j.apcata.2012.04.006

Title: Photocatalytic activity of single and mixed nanosheet-like Bi2WO6 and TiO2 for Rhodamine B degradation under sunlike and visible illumination
Author(s): Murcia-Lopez, S; Hidalgo, MC; Navio, JA
Source: Applied Catalysis A-General, 423-424 (2012) 34-41

abstract | fulltext

The photocatalytic activity, under sunlike illumination, for Rhodamine B (RhB) degradation using Bi2WO6-TiO2 samples, is reported. Two different kinds of Bi2WO6-TiO2 samples were studied, obtained by distinct methods: first, a mechanical mixing, by adding to synthesized nanosheet-like Bi2WO6 powder the corresponding amount of TiO2 nanoparticles (P25) in order to obtain physical mixtures of both catalysts with different percentages of TiO2 (5, 10 and 50 wt%); second, a single Bi2WO6-TiO2 heterostructure was prepared by adding commercial TiO2-P25 to the Bi2WO6 precursors (50 wt%) prior to the hydrothermal treatment, thus obtaining a sample with "in situ" TiO2 incorporation. Comparisons between the photocatalytic behaviour of these samples and those exhibited by the single materials Bi2WO6 and TiO2 (P25) were carried out, in order to establish the effect not only of the TiO2 addition but also of the way in which TiO2 (P25) is incorporated. The role of each single photocatalyst in the mixtures in the RhB degradation and mineralization under sunlike and just visible illumination was also studied.

May, 2012 | DOI: 10.1016/j.apcata.2012.02.016

Title: Gold supported cryptomelane-type manganese dioxide OMS-2 nanomaterials deposited on AISI 304 stainless steels monoliths for CO oxidation
Author(s): Martinez, LM; Romero-Sarria, F; Hernandez, WY; Centeno, MA; Odriozola, JA
Source: Applied Catalysis A-General, 423 (2012) 137-145

abstract | fulltext

Gold supported on cryptomelane-type OMS-2 catalysts deposited on AISI 304 stainless steels monoliths have been prepared for the first time, characterised and tested in the CO oxidation reaction. An easy and non-conventional method of incorporation of gold to the cryptomelane solid is used. This method allows the preparation of the monolithic catalysts without altering the structural and textural characteristics of the parent OMS-2 material. Although these catalysts do not show an optimal performance for the oxidation of CO, the presence of small gold particles enhances the catalytic performances of the cryptomelane producing promissory CO oxidation catalysts. The non-conventional gold deposition favours a partial loss of K + into the channels, resulting in an increment of the average oxidation state of manganese which favours the catalytic behaviour of these kinds of materials. This study can be taken as a starting point to obtain very active gold catalysts supported on OMS-2 materials through the optimisation of the gold-support interaction and the decrease in the gold particle size.

May, 2012 | DOI: 10.1016/j.apcata.2012.02.026

Title: Sub-ambient CO oxidation over Au/MOx/CeO2-Al2O3 (M = Zn or Fe)
Author(s): Reina, TR; Ivanova, S; Dominguez, MI; Centeno, MA; Odriozola, JA
Source: Applied Catalysis A-General, 419-420 (2012) 58-66

abstract | fulltext

A series of ZnO and Fe 2O 3 modified ceria/alumina supports and their corresponding gold catalyst were prepared and studied in the CO oxidation reaction. ZnO-doped solids show a superior catalytic activity compared to the bare CeO 2-Al 2O 3, which is attributed to the intimate contact of the ZnO and CeO 2 phases, since an exchange of the lattice oxygen occurs at the interface. In a similar way, Fe 2O 3-modified supports increase the ability of the CeO 2-Al 2O 3 solids to eliminate CO caused by both the existence of Ce-Fe contact surface and the Fe 2O 3 intrinsic activity. All of the gold catalysts were very efficient in oxidising CO irrespective of the doping metal oxide or loading, with the ZnO containing systems better than the others. The majority of the systems reached total CO conversion below room temperature with the ZnO and Fe 2O 3 monolayer loaded systems the most efficient within the series.

March, 2012 | DOI: 10.1016/j.apcata.2012.01.012

Title: Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts
Author(s): Todorova, S; Naydenov, A; Kolev, H; Holgado, JP; Ivanov, G; Kadinov, G; Caballero, A
Source: Applied Catalysis A-General, 413-414 (2012) 43-51

abstract | fulltext

Mono- and bi-component cobalt and manganese samples were prepared by impregnation of silica with aqueous solutions of Co(NO3)2·6H2O and/or Mn(NO3)2·6H2O. The bi-component samples were obtained by a common solution of Co- and Mn nitrates (CoMn-MS) or by deposition of cobalt on calcined Mn sample (Co + Mn). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction (TPR), Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis and tested in reaction of complete n-hexane oxidation. It was observed that the well crystalline cobalt oxide partially covers poorly crystalline manganese oxide in the Co + Mn catalysts, while finely divided oxides (MnO2 and Mn2O3, Co3O4) are present on the surface of the (CoMn-MS) sample. Four Langmuir–Hinshelwood and two Mars–van Krevelen models were fitted with the experimental data from the catalytic tests. According to the model calculations and results from instrumental methods, the reaction pathway over single component manganese and bi-component Co-Mn catalysts proceeds through Mars–van Krevelen mechanism (the oxidation of the catalyst surface being the rate determining step), while Langmuir–Hinshelwood mechanism is more probable for the Co sample. A considerable increase in activity for the sample obtained from a mixed solution is explained by low crystallinity, simultaneous presence of Mn4+–Mn3+ and enrichment of the surface in oxygen species.

January, 2012 | DOI: 10.1016/j.apcata.2011.10.041

Title: Effect of hydrothermal treatment on structural and photocatalytic properties of TiO2 synthesized by sol-gel method
Author(s): Melian, EP; Diaz, OG; Rodriguez, JMD; Colon, G; Navio, JA; Pena, JP
Source: Applied Catalysis A-General, 411 (2012) 153-159

abstract | fulltext

TiO 2 nanoparticles have been prepared by sol-gel precipitation and further hydrothermal treatment. In this way, the effect of the hydrothermal treatment on the structural properties and photocatalytic activity of sol-gel synthesized catalysts has been investigated. These catalysts have been produced by hydrolysis of a mixture of isopropanol-titanium tetraisopropoxide (iPrOH-TiiP). The prepared photocatalysts were characterized by means of X-ray diffraction (XRD), surface area analysis (BET), transmission microscopy (TEM), thermogravimetric analysis (TG), scanning electron microscopy (SEM) analysis, diffuse reflectance, sedimentability analysis and aggregate size study. Besides, the structural evolution with the temperature of the photocatalysts treated or not hydrothermally was studied. It was observed that the calcination produces approaching between the characteristics of both sets of photocatalysts. The photocatalytic activity of the obtained photocatalysts was investigated, using phenol as a model pollutant. The calcination temperature is the most remarkable factor that can affect the ultimate photocatalytic activity of the prepared photocatalysts. However, the hydrothermal treatment previous to calcination led to obtain photocatalysts which exhibit larger photocatalytic activity than their homologous photocatalysts without hydrothermal treatment. The obtained photocatalyst TiO 2ht600 exhibits the same photocatalytic activity per surface area than the commercial TiO 2 Degussa P25 but with much faster sedimentability.

January, 2012 | DOI: 10.1016/j.apcata.2011.10.033

Title: Rapid microwave-assisted synthesis of one-dimensional silver–H2Ti3O7 nanotubes
Author(s): Rodriguez-Gonzalez, V; Obregon-Alfaro, S; Lozano-Sanchez, LM; Lee, SW
Source: Journal of Molecular Catalysis A-Chemical, 353 (2012) 163-170

abstract | fulltext

The formation of silver hydrogen trititanate nanotubes, based on the controllable microwave-assisted hydrothermal nanocrystalline TiO2 transition, was investigated by means of XRD, UV–vis–DRS, Raman, FESEM and HRTEM. The results show that the rapid formation of H-trititanate nanotubes is achieved by self-assemblage of silver nanoparticles in which the lamellar intermediates react with NaOH in hydrothermal conditions. The presence of Ag° nanoparticles in the precursor promotes rapid and more complete formation of layered H2Ti3O7 nanotubes. After reacting for 4 h without subsequent thermal treatment, the inner diameters of the cylinder-like nanotubes are in the range of 3.6–4.0 nm, while their outer diameters are in the range of 7.6–8 nm. In addition, some straight nanotubes form bundles which are hundreds of nanometers in length. As-synthesized ultrathin nanotubes and crystalline precursors were evaluated by methyl orange dye (MOD) UV photo-oxidation. The complete degradation of MOD is achieved after 3.5 h of UV irradiation in the presence of silver–TiO2 nanocomposites, resulting in 50% of dye mineralization.

February, 2012 | DOI: 10.1016/j.molcata.2011.11.020

Title: Hydrogenation of 2,2,2-trifluoroacetophenone: Molecular insight into the role of solvent in enantioselection
Author(s): Rosa Pereñiguez; Gianluca Santarossa; Tamas Mallat; Alfons Baiker
Source: Journal of Molecular Catalysis A: Chemical, 365 (2012) 39-49

abstract | fulltext

The unique solvent effect in the enantioselective hydrogenation of α-fluorinated ketones has been investigated in ten different solvents using the  hydrogenation of 2,2,2-trifluoroacetophenone (1) on cinchonine (CN)-modified Pt/Al2O3 as a model reaction. Application of strongly basic solvents – but also increasing hydrogen pressure or conversion – inverted the sense of enantiodifferentiation from (S)-alcohol (expected enantiomer based on the stereochemistry of CN) to (R)-alcohol. The known formation of hemiketals was the origin of the inversion in alcohols. Considering only the non-reacting solvents and low conversions at low pressures, the best correlation was established between the enantiomeric excess and the solvent basicity represented by the H-bond acceptor ability (β). In contrast to former proposals, solvent acidity (α) did not play a significant role. The experimental results are validated by theoretical calculations. The docking of 1 to CN has been investigated in the absence of solvent and also in the presence of toluene and dimethyl formamide. Several competing docking complexes have been isolated that can coexist on the metal surface. Detailed analyses of these complexes show that their stabilities depend on the formation of enantiospecific local interactions between 1, CN, and the platinum surface. The presence of solvent interferes with these interactions, affecting the relative stability of the docking complexes. A correlation between the solvent-induced interactions at molecular level and changes in enantioselectivity is suggested.

December, 2012 | DOI: 10.1016/j.molcata.2012.08.006

Title: Preferential oxidation of CO (CO-PROX) over CuOx/CeO2 coated microchannel reactor
Author(s): Laguna, OH; Ngassa, EM; Oraa, S; Alvarez, A; Dominguez, MI; Romero-Sarria, F; Arzamendi, G; Gandia, LM; Centeno, MA; Odriozola, JA
Source: Catalysis Today, 180 (2012) 105-110

abstract | fulltext

The general aspects of the synthesis and characterization results of a CuO x/CeO 2 catalyst were presented. In addition the principal steps for manufacturing a microchannel reactor and for the coating of the CuO x/CeO 2 catalyst onto the microchannels walls, were also summarized. The catalytic activity of this microchannel reactor during the preferential oxidation of CO (CO-PROX) was evaluated employing a feed-stream that simulates a reformate off-gas after the WGS unit. Two activation atmospheres were studied (H 2/N 2 and O 2/N 2). The reducing pretreatment improved the resistance to deactivation by formation of carbonaceous species over the catalyst surface at high temperatures. The presence of H 2O and CO 2 in the feed-stream was also analyzed indicating that the adsorption of CO 2 inhibited the conversion of CO at lower temperatures because these compounds modified the active sites through the formation of carbonaceous species on the catalyst surface. Finally, the experimental results of the microreactor performance were compared with CFD simulations that were carried out using a kinetic for the CuO x/CeO 2 powder catalyst. The experimental results were reasonably well described by the model, thus confirming its validity.

January, 2012 | DOI: 10.1016/j.cattod.2011.03.024

Title: Ethanol partial photoxidation on Pt/TiO2 catalysts as green route for acetaldehyde synthesis
Author(s): Murcia, JJ; Hidalgo, MC; Navio, JA; Vaiano, V; Ciambelli, P; Sannino, D
Source: Catalysis Today, 196 (2012) 101-109

abstract | fulltext

Heterogeneous photocatalytic partial oxidation of ethanol was studied over different Pt/TiO2 as an alternative green process for acetaldehyde production.

The catalysts were synthesized through the photodeposition of Pt over sol–gel TiO2 with platinum loads of 0.5 and 1 wt.%. The effect of some experimental conditions during photodeposition, such as deposition time and Pt loading, was investigated. A short deposition time at 0.5 wt.% Pt nominal loading led to small average particle size of platinum (2–3 nm) homogeneously distributed all over the TiO2 surface.

Ethanol partial oxidation was tested in a gas–solid photocatalytic fluidized bed reactor at high illumination efficiency, using different reaction temperatures. Activity results have been correlated with characterization results of the different samples. Platinized samples prepared with short deposition times showed high conversion levels and high selectivity to acetaldehyde. Materials prepared at longer times, 120 min, showed selectivities >98%, although with lower ethanol conversion.

Sample with 1 wt.% Pt loading prepared with 15 min deposition time combined a good compromise between a relevant ethanol conversion and a very high selectivity to acetaldehyde at a selected reaction temperature of 80 °C, with an acetaldehyde yield higher than 80%, which make of this catalyst a good candidate for acetaldehyde production by photocatalysis.

November, 2012 | DOI: 10.1016/j.cattod.2012.02.033

Title: Redox and catalytic properties of CuO/CeO2 under CO + O2 + NO: Promoting effect of NO on CO oxidation
Author(s): Martinez-Arias, A.; Hungria, A. B.; Iglesias-Juez, A.; Fernandez-Garcia, M.; Anderson, J. A.; Conesa, J. C.; Munuera, G.; Soria, J.
Source: Catalysis Today, 180 (2012) 81-87

abstract | fulltext

A CuO/CeO2 catalyst has been studied with respect to its catalytic activity for CO oxidation under stoichiometric conditions employing either O2 or O2–NO mixture as oxidants. The obtained results are rationalised on the basis of analysis of redox properties upon interaction with CO and O2–NO by EPR as well as by redox/catalytic analysis by operando-DRIFTS. These provide useful insight into the processes involved during NO reduction, for which two well differentiated steps associated to a change in the type of active centres during the course of the reaction are evidenced. Nevertheless, the most interesting result is related to observation of a novel promoting effect of NO on CO oxidation. This is explained mainly on the basis of DRIFTS results and appears to be associated with phenomena of adsorption/desorption of NOx species at interfacial positions which apparently activate such interfacial region allowing formation of greater amounts of active reduced copper centres in the presence of NO.

January, 2012 | DOI: 10.1016/j.cattod.2011.02.014

Title: DRIFTS study of methanol adsorption on Mg-Al hydrotalcite catalysts for the transesterification of vegetable oils
Author(s): Navajas, A; Arzamendi, G; Romero-Sarria, F; Centeno, MA; Odriozola, JA; Gandia, LM
Source: Catalysis Communications, 7 (2012) 189-193

abstract | fulltext

Mg-Al hydrotalcites rehydrated after calcination are promising catalysts for the methanolysis of vegetable oils. To gain insight into the basis of their catalytic action, the adsorption of methanol over some commercial Mg-Al hydrotalcites was studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Different species formed after methanol adsorption were identified, being the total quantity of methoxy species related to the basic character of the sample. A linear correlation between the amount of adsorbed monodentate methoxy species and the catalytic activity in the biodiesel production was found. Therefore, it is proposed that these species are the mainly involved in the transesterification reaction.

January, 2012 | DOI: 10.1016/j.catcom.2011.11.005

Title: Photocatalytic Ethanol Oxidative Dehydrogenation over Pt/TiO2: Effect of the Addition of Blue Phosphors
Author(s): Murcia, JJ; Hidalgo, MC; Navio, JA; Vaiano, V; Ciambelli, P; Sannino, D
Source: International Journal of Photoenergy, 2012 (2012) 687262

abstract | fulltext

Ethanol oxidative dehydrogenation over Pt/TiO2 photocatalyst, in the presence and absence of blue phosphors, was performed. The catalyst was prepared by photodeposition of Pt on sulphated TiO2. This material was tested in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. The effect of the addition of blue phosphors into the fluidized bed has been evaluated. The synthesized catalysts were extensively characterized by different techniques. Pt/TiO2 with a loading of 0.5 wt% of Pt appeared to be an active photocatalyst in the selective partial oxidation of ethanol to acetaldehyde improving its activity and selectivity compared to pure TiO2. In the same way, a notable enhancement of ethanol conversion in the presence of the blue phosphors has been obtained. The blue phosphors produced an increase in the level of ethanol conversion over the Pt/TiO2 catalyst, keeping at the same time the high selectivity to acetaldehyde.

January, 2012 | DOI: 10.1155/2012/687262

Title: A CFD study on the effect of the characteristic dimension of catalytic wall microreactors
Author(s): Arzamendi, G; Uriz, I; Navajas, A; Dieguez, PM; Gandia, LM; Montes, M; Centeno, MA; Odriozola, JA
Source: AlChE Journal, 58 (2012) 2785-2797

abstract | fulltext

A three-dimensional computational fluid dynamics study of the steam methane reforming (SMR) in microreactors is presented. Emphasis has been made on investigating the effects of the characteristic dimension (d: 0.35, 0.70, 1.40, and 2.80 mm) on the performance of two microreactor geometries: square microchannels and microslits. Results have shown that for both geometries the SMR conversion decreases markedly as d increases. Conversely, the microchannels provide a methane conversion slightly higher than that of the microslits. The different performance of the microreactors is only partially due to the different surface-to-volume ratio. Pronounced transverse temperature and concentration gradients develop as the characteristic dimension increases especially for microslits in the first half of the reactor. Therefore, external transport limitations can affect the performance of microreactors for SMR, although the characteristic dimensions are of the order of very few millimeters.

September, 2012 | DOI: 10.1002/aic.12790

Title: Gold supported on pillared clays for CO oxidation reaction: Effect of the clay aggregate size
Author(s): Alvarez, A; Moreno, S; Molina, R; Ivanova, S; Centeno, MA; Odriozola, JA
Source: Applied Clay Science, 69 (2012) 22-29

abstract | fulltext

A series of 1% m/m gold particles supported on Fe, Ce and Al pillared bentonite (from Valle del Cauca, Colombia) and clay “M64” (from Tolima, Colombia) using three different fractions of aggregate sizes (≤ 2 μm, ≤ 50 μm, and ≤ 150 μm) were characterized by particle size measurements, X-ray diffraction, transmission electronic microscopy (TEM), SBET and X-ray fluorescence spectrometry (XRF) techniques. The materials tested with CO oxidation. The separation yield for each fraction depended on the type of clay. Whatever the clay or the aggregate size, the pillaring process was successfully carried out, introducing Fe, Ce and Al pillars and increasing the microporosity and the specific surface area of the material. Gold particles presented a homogenous distribution of 2–3 nm on the pillared bentonite, and of about 10 nm on the pillared clay M64. The aggregate size slightly influenced the amount of deposited gold particles and their size. All gold catalysts were active in CO oxidation, the activity depending on the nature of the clay as well as the gold loading and average gold particle size but not on the aggregate size.

November, 2012 | DOI: 10.1016/j.clay.2012.07.008

Title: Study of Oxygen Reactivity in La1-x Sr (x) CoO3-delta Perovskites for Total Oxidation of Toluene
Author(s): Pereniguez, R; Hueso, JL; Gaillard, F; Holgado, JP; Caballero, A
Source: Catalysis Letters, 142 (2012) 408-416

abstract | fulltext

The total oxidation of toluene is studied over catalytic systems based on perovskite with general formula AA′CoO 3-δ (A = La, A′ = Sr). The systematic and progressive substitution of La 3+ by Sr 2+ cations in the series (La 1-xSr xCoO 3-δ system) of the perovskites have been studied to determine their influence in the final properties of these mixed oxides and their corresponding reactivity performance for the total oxidation of toluene as a model volatile organic compound with detrimental effects for health and environment. The structure and morphology of the samples before and after reaction have been characterized by XRD, BET and FE-SEM techniques. Additional experiments of temperature programmed desorption of O 2 in vacuum and reduction in H 2 were also performed to identify the main surface oxygen species and the reducibility of the different perovskites. It is remarkable that the La 1-xSr xCoO 3-δ series presents better catalytic performance for the oxidation of toluene, with lower values for the T 50 (temperature of 50 % toluene conversion) than the previously studied LaNi 1-yCoyO 3 series.

April, 2012 | DOI: 10.1007/s10562-012-0799-z

Title: Nanostructured Spark Plasma Sintered Ce-TZP Ceramics
Author(s): Cruz, SA; Poyato, R; Cumbrera, FL; Odriozola, JA
Source: Journal of the American Ceramic Society, 95 (2012) 901-906

abstract | fulltext

In this work, spark plasma sintering (SPS) of 10 mol% CeO 2-doped ZrO 2 nanocrystalline powders, obtained by a two-step synthesis procedure, allows the preparation of fully densified nanostructured ceramics. The CeO 2-ZrO 2 powders with particle size below 100 nm are obtained after CeO 2 deposition on hydrothermally synthesized ZrO 2 particles by the impregnation method. Tetragonal CeO 2-ZrO 2 ceramics are obtained when sintering at 1200°C without holding time. A graded material containing tetragonal, monoclinic, and pyrochlore phases are obtained when sintering at 1200°C and for 5 min holding time. This is explained in terms of the gradual reduction of Ce 4+ to Ce 3+ species by carbon in the graphite environment during SPS. With the successful combination of the stabilizer coating technique and SPS, we achieve not only the stabilization of the tetragonal phase in the ceramics, but also good control of the grain size, by producing nanostructured ceramics with 40-70 nm grain sizes.

March, 2012 | DOI: 10.1111/j.1551-2916.2011.04978.x

Title: Influence of PVP in magnetic properties of NiSn nanoparticles prepared by polyol method
Author(s): Bobadilla, LF; Garcia, C; Delgado, JJ; Sanz, O; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: Journal of Magnetism and Magnetic Materials, 324 (2012) 4011-4018

abstract | fulltext

The influence of PVP on the magnetic properties of NiSn nanoparticles prepared by polyol method has been studied. NiSn nanoparticles exhibit superparamagnetic behavior although there is a ferromagnetic contribution due to particles agglomerated below the blocking temperature. The particle size is controlled by the addiction of PVP in varying amounts. The addition of PVP also favours the particles isolation, narrow the particle size distribution and decrease the interparticle interaction strength increasing the superparamagnetic contribution.

November, 2012 | DOI: 10.1016/j.jmmm.2012.07.005

Title: Preparation of nanostructured nickel aluminate spinel powder from spent NiO/Al2O3 catalyst by mechano-chemical synthesis
Author(s): Nazemi, M. K.; Sheibani, S.; Rashchi, F.; Gonzalez-DelaCruz, V. M.; Caballero, A.
Source: Advanced Powder Technology, 23 (2012) 833-838

abstract | fulltext

In this paper, the possibility of mechano-chemical synthesis, as a single step process for preparation of nanostructured nickel aluminate spinel powder from NiO/Al2O3 spent catalyst was investigated. Powder samples were characterized in terms of composition, morphology, structure, particle size and surface area using complementary techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA) and volumetric adsorption of nitrogen. It was found that formation of spinel was possible after 60 h of milling with no heat treatment. Additionally, influence of mechanical activation on the heat treatment temperature was discussed. It was observed that heat treatment of 15 h milled sample at 1100 °C is enough to produce nickel aluminate spinel. A product of direct mechanical milling showed higher value of surface area (42.3 m2/g) and smaller crystallite size (12 nm) as compared to the heat treated product.

November, 2012 | DOI: 10.1016/j.apt.2011.11.004

Title: Oxidative Dehydrogenation of Ethanol over Au/TiO2 Photocatalysts
Author(s): Sannino, Diana; Vaiano, Vincenzo; Ciambelli, Paolo; Carmen Hidalgo, M.; Murcia, Julie J.; Antonio Navio, J.
Source: Journal of Advanced Oxidation Technologies, 15 (2012) 284-293

abstract | fulltext

Au/TiO2 photocatalysts were used in ethanol oxidative dehydrogenation. Catalysts at gold loading ranging between 0.5-2 wt.% were synthesized by photodeposition (using different deposition times: 15 and 120 min) over an own-prepared TiO2 by sol-gel method. For reference purposes, a commercial 1 wt.% Au/TiO2 catalyst (AUROlite (TM), Strem Chemicals) was also tested. Photocatalytic reactions were carried out in a gas-solid photocatalytic fluidized bed reactor. Catalytic activity depends strongly both on Au loading and on the material properties, such as particle size and distribution of metal on titania surface. Acetaldehyde was the main reaction product, with ethylene, crotonaldehyde and CO2 as by-products. An important improvement of TiO2 photoactivity was achieved for the catalyst with 0.5 wt.% gold prepared with 120 min deposition time. For an ethanol inlet concentration of 0.2 vol% at 60 degrees C, the maximum conversion and acetaldehyde selectivity were 82% and 95%, respectively. These values are considerably higher than those obtained over pristine TiO2 and over the commercial catalyst.

July, 2012 | DOI: ---

2011


Title: Effect of thermal treatments on the catalytic behaviour in the CO preferential oxidation of a CuO-CeO2-ZrO2 catalyst with a flower-like morphology
Author(s): Moretti, E; Storaro, L; Talon, A; Lenarda, M; Riello, P; Frattini, R; de Yuso, MDM; Jimenez-Lopez, A; Rodriguez-Castellon, E; Ternero, F; Caballero, A; Holgado, JP
Source: Applied Catalysis B-Environmental, 102 (2011) 627-637

abstract | fulltext

A Ce–Zr–Cu oxide system with a flower-like morphology was prepared by a slow co-precipitation method in the absence of any structure directing agent. Four portions of the oxide were thermally treated at four different temperatures (350 °C, 450 °C, 550 °C, 650 °C). The resulting materials samples were characterized by quantitative XRD, adsorption–desorption of N2 at-196 °C, SEM and TEM microscopy, –H2-TPR, XPS and Operando-XANES. All samples were tested in the preferential CO oxidation (CO-PROX) in the 40–190 °C temperature range. Thermal treatments were found to induce slight structural changes without altering the starting morphology of the samples. The samples treated at higher temperature 550–650 °C showed a quite interesting CO-PROX activity and selectivity in a temperature range suitable for a practical use within the FEMFC technology.

February, 2011 | DOI: 10.1016/j.apcatb.2011.01.004

Title: CO oxidation at low temperature on Au/CePO4: Mechanistic aspects
Author(s): Romero-Sarria, F., Domínguez, M.I., Centeno, M.A., Odriozola, J.A.
Source: Applied Catalysis B: Environmental, 107 (2011), 268-273

abstract | fulltext

This work reports the synthesis and characterization of a cerium phosphate supported gold catalyst as well as its catalytic activity for the oxidation of CO. A precipitation method in the presence of an organic modifier followed by a hydrothermal treatment was used for the support synthesis, resulting in high surface area nanometric particles. Gold/cerium phosphate catalyst with a 1% (w/w) nominal gold content was characterized using XRF, XRD, N2 adsorption-desorption measurements, TEM and DRIFTS-MS. The catalyst shows good catalytic activity at low temperature. The activity is related to the generation of oxygen vacancies in the support caused by the elimination of structural oxygen. In situ studies revealed that the reaction of the oxygen vacancies with gaseous oxygen resulted in the formation of peroxo species. These species are responsible for the activity detected at room temperature in both the catalyst and the support. Moreover, the presence of carbonate and hydrogen carbonate acting as reaction intermediates have been observed.

September, 2011 | DOI: 10.1016/j.apcatb.2011.07.022

Title: Fe-doped ceria solids synthesized by the microemulsion method for CO oxidation reactions
Author(s): O.H. Laguna, M.A. Centeno, M. Boutonnet, J.A. Odriozola
Source: Applied Catalysis B: Environmental, 106 (2011) 621-629

abstract | fulltext

A series of Ce-Fe mixed oxides as well as the pure oxides were synthesized by the microemulsions method. The solid solution formation was established for all the Fe-doped systems and only a hardly noticeable segregation of &#945;-Fe2O3 was appreciated for the solid with the maximum iron content (50at.% Fe). The oxygen exchange is improved for all the Fe-doped systems; however the 10at.% Fe appears as the optimal iron content for achieving the maximum oxygen vacancies concentration and the higher reducibility efficiency. The CO oxidation (TOX, PROX) is especially achieved for the solids with the lower iron contents but with a superior oxygen vacancies proportion. These Ce-Fe systems prepared from microemulsions are very attractive to be considered as supports for depositing active phases capable of enhancing oxygen exchange ability of the whole system, allowing higher CO oxidation abilities.

August, 2011 | DOI: 10.1016/j.apcatb.2011.06.025

Title: Modifying the Size of Nickel Metallic Particles by H2/CO Treatment in Ni/ZrO2 Methane Dry Reforming Catalysts
Author(s): Gonzalez-Delacruz, VM; Pereñiguez, R; Ternero, F; Holgado, JP; Caballero, A
Source: ACS Catalysis, 1 (2011) 82-88

abstract | fulltext

The effect of a reduction process with CO or H-2 on the Size of nickel particles in Ni/ZrO2 dry methane reforming catalysts have been studied by means of in situ X-ray Spectroscopy (XAS) and Diffuse Reflectance FTIR Spectroscopy (DRIFTS). Our results clearly indicate that a high temperature treatment with CO increases the dispersion of the nickel metallic phase. XAS results have shown a lower coordination number of Ni in the sample treated with CO than that reduced with H-2. From the DRIFTS results, it can he established that, under the CO treatment, the formation of Ni(CO)(4) complexes corrodes the nickel particles, decreasing their size. The formation of these gas molecules occurs without measurable losses of nickel from the catalyst which maintains the same nickel content after the hydrogen or the CO treatment at high temperature:Therefore, this airborne nickel compound, by colliding with the zirconia surface, must deposit the nickel metal metal atoms around onto the support. This behavior is evidence of an important interaction b etween nickel and zirconia surface as unlike other supports there is no losses of nickel during the dispersion process on zirconia. Although different effects of CO on nickel catalysts have been previously described, we have found for the first time several experimental evidences demonstrating the whole redispersion phenomenon.

February, 2011 | DOI: 10.1021/cs100116m

Title: Well-defined negatively charged gold carbonyls on Au/SiO2
Author(s): Chakarova, K., Mihaylov, M., Ivanova, S., Centeno, M.A., Hadjiivanov, K.
Source: Journal of Physical Chemistry C, 115 (2011) 21273-21282

abstract | fulltext

A Au/SiO2 sample was prepared by ammonia-assisted grafting using HAuCl4 as a gold precursor. Gold on the sample evacuated at 673 K is essentially in metallic form: adsorption of CO at 100 K results in formation of Au0-CO species (IR band at 2122 cm-1 shifting to 2103 cm-1 at high coverage). Coadsorption of CO and O2 even at ambient temperature leads to creation of Auδ+ sites and oxidation of CO. On the contrary, increase of the contact time between CO and the sample leads to a gradual reduction of Au0 to Au δ- species. The process is slightly favored by the presence of water and strongly enhanced in the presence of hydrogen. Back oxidation of Auδ- to Au0 and to Auδ+ occurs in the presence of oxygen. The Auδ- sites strongly adsorb CO and form different interconverting carbonyls observed in the 2080-2050 cm -1 region. On the basis of adsorption of CO-13CO and CO-13C18O isotopic mixtures, it is concluded that all Auδ--CO species are linear, and probably ordered structures are formed. Intensity transfer phenomena are nicely monitored during adsorption of CO isotopic mixtures. The eventual role of negatively charged gold in catalysis is discussed.

November, 2011 | DOI: 10.1021/jp2070562

Title: Novel Bi2WO6-TiO2 heterostructures for Rhodamine B degradation under sunlike irradiation
Author(s): Lopez, SM; Hidalgo, MC; Navio, JA; Colon, G
Source: Journal of Hazardous Materials, 185 (2011) 1425-1434

abstract | fulltext

Highly efficient Bi2WO6-TiO2 heterostructure is synthesized by means of a hydrothermal method having highly photoactivity for the degradation of Rhodamine B under sunlike irradiation. From the structural characterization it has been demonstrated that TiO2 is incorporated on the Aurivillius structure. Interesting synergetic effect between TiO2 and Bi2WO6 leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance under sunlike irradiation. The photocatalytic performance of Bi2WO6 and Bi2WO6-TiO2 was compared under different irradiation conditions and using increasing Rhodamine B concentration up to 25ppm. After the photocatalytic analysis of both systems, the mineralization efficiency of the heterostructure appears significantly higher with respect to Bi2WO6.

January, 2011 | DOI: 10.1016/j.jhazmat.2010.10.065

Title: Hydrogen production by methanol steam reforming on NiSn/MgO-Al2O3 catalysts: The role of MgO addition
Author(s): Penkova, A; Bobadilla, L; Ivanova, S; Dominguez, MI; Romero-Sarria, F; Roger, AC; Centeno, MA; Odriozola, JA
Source: Applied Catalysis A-General,392 (2011) 184-191

abstract | fulltext

The effect of the magnesia loading on the surface structure and catalytic properties of NiSn/MgO-Al2O3 catalysts for hydrogen production by methanol steam reforming has been investigated. The catalysts have been obtained by impregnation of γ-Al2O3 by the incipient wetness method, with variation of the MgO content. X-ray diffraction (XRD), BET surface area and H2-temperature programmed reduction (TPR) have been used to characterise the prepared catalysts. From this, it has been concluded that the incorporation of MgO results in the formation of MgAl2O4 spinel, which modifies the acid-base properties of the catalysts. The formation of Ni-Sn alloys after the reductive pre-treatment has also been evidenced. The influence of the temperature of reaction and of the MgO loading on the hydrogen production by reforming of methanol has been established. Moreover, tests of catalytic stability have been carried out for more than 20 h. The carbonaceous deposits have been examined by temperature-programmed oxidation (TPO). The analysis of the catalysts after reaction has confirmed the low level of carbon formation on these catalysts. In no case, carbon nanotubes have been detected on the solids.

January, 2011 | DOI: 10.1016/j.apcata.2010.11.016

Title: Photodeposition of gold on titanium dioxide for photocatalytic phenol oxidation
Author(s): Hidalgo, MC; Murcia, JJ; Navio, JA; Colon, G
Source: Applied Catalysis A-General, 397 (2011) 112-120

abstract | fulltext

The influence of experimental conditions during the photodeposition in the preparation of supported Au on TiO2 has been studied. Besides preparation pH, light intensity and deposition time showed to have a high influence on the final properties of gold deposits. Photodeposition using illumination with a high light intensity UV-vis lamp (140 W/m2 UVA range) resulted to be an ineffective method for obtaining nanoparticles of gold on the titania, producing very large and poorly distributed gold deposits. Thus obtained materials did not show any important improvement of their photocatalytic activity tested for phenol oxidation. By contrast, photodeposition using a low light intensity of illumination (0.15 W/m 2 UVA range), produced materials with notably improved photocatalytic activity. The illumination with such a low light intensity allowed the control of the amount, aggregation and oxidation state of gold by changing deposition time, enabling a feasible method of tailoring Au-TiO2 with the appropriate properties for a high photocatalytic activity. Best photocatalytic behaviour for phenol photodegradation was obtained for Au-TiO2 samples prepared by photodeposition at low light intensity with 120 min photodeposition time for catalysts with a 0.5% and 1% nominal content of gold and with 60 min photodeposition time for catalyst with a 2% nominal content of gold.

April, 2011 | DOI: 10.1016/j.apcata.2011.02.030

Title: Synthesis, characterization and photocatalytic activity of Bi-doped TiO2 photocatalysts under simulated solar irradiation
Author(s): Murcia-López, S., Hidalgo, M.C., Navío, J.A.
Source: Applied Catalysis A: General, 404 (2011) 59-67

abstract | fulltext

A series of Bi3+-doped TiO2 catalysts with a doping concentration up to 2 wt% were prepared by a sol-gel hydrothermal method. The prepared photocatalysts were characterized by different techniques to determine their structure, morphology and light absorption properties. The activities were evaluated in the photocatalytic oxidation of phenol in aqueous solution under UV-vis illumination. The experimental results indicate that the presence of Bi3+ in TiO2 catalysts enhances the photocatalytic reaction of phenol degradation, although the efficiency of the process markedly depends on the nominal content of the Bi3+ and on the calcination temperature. It was found that the optimal dosage of 0.5 wt% Bi3+ in TiO2 and calcinations at 600 °C 4 h achieved the fastest reaction of phenol degradation under the experimental conditions. From the comparison of the initial rates of the photocatalytic degradation of phenol between home prepared undoped and Bi3+-doped TiO2 with commercial TiO2 Degussa P25, it can be inferred that home prepared TiO 2 calcined at temperatures above 500 °C clearly exceed the photocatalytic performance of P25. When bismuth is incorporated, the reaction rate values are even higher, especially at 600 °C. Even when Bi 3+-doped TiO2 (0.5 wt% Bi3+) calcined at 600 °C has almost the same BET surface than P25, its activity is better. In particular, the reaction rate for the sample with a 0.5% mass content of Bi 3+ calcined at 600 °C not only present higher value with respect to the other series but also a degree of mineralization close to 100%.

September, 2011 | DOI: 10.1016/j.apcata.2011.07.008

Title: Selective CO removal over Au/CeFe and CeCu catalysts in microreactors studied through kinetic analysis and CFD simulations
Author(s): Arzamendi, G; Uriz, I; Dieguez, PM; Laguna, OH; Hernandez, WV; Alvarez, A; Centeno, MA; Odriozola, JA; Montes, M; Gandia, LM
Source: Chemical Engineering Journal, 167 (2011) 588-596

abstract | fulltext

A kinetic study of the preferential oxidation of CO in H2 rich streams (CO-PrOx) over a cerium-copper oxide (CeCu) and a gold catalyst supported on cerium-iron oxide (Au/CeFe) is presented. The gold catalyst is very active but the CeCu oxide is more selective. A kinetic model describing the CO-PrOx system with CO2 and H2O in the feed has been formulated considering the oxidation of CO and H2 and the reverse water-gas shift reaction. The rate equations have been implemented in computational fluid dynamics codes to study the influence of the operating variables on the CO-PrOx in microchannels and microslits. The CeCu catalyst is the only one capable of achieving final CO contents below 10-100ppmv. Due to the opposite effect of temperature on activity and selectivity there is an optimal temperature at which the CO content is minimal over CeCu. This temperature varies between 170 and 200°C as the GHSV increases from 10,000 to 50,000h-1. Simulations have evidenced the very good heat transfer performance of the microdevices showing that the CO-PrOx temperature can be controlled using air as cooling fluid although the inlet temperature and flow rate should be carefully controlled to avoid reaction extinction. Both microchannels and microslits behaved similarly. The fact that the microslits are much easier to fabricate may be an interesting advantage in favour of that geometry in this case. © 2010 Elsevier B.V.

March, 2011 | DOI: 10.1016/j.cej.2010.08.083

Title: Design and testing of a microchannel reactor for the PROX reaction
Author(s): Cruz, S; Sanz, O; Poyato, R; Laguna, OH; Echave, FJ; Almeida, LC; Centeno, MA; Arzamendi, G; Gandia, LM; Souza-Aguiar, EF; Montes, M; Odriozola, JA
Source: Chemical Engineering Journal, 167 (2011) 634-642

abstract | fulltext

The different steps for manufacturing a microchannel reactor for the PROX reaction are discussed. Transient Liquid Phase bonding (TLP) using a Ni-B-Si amorphous melt spun is used for joining micromilled Al-alloyed ferritic stainless steel plates followed by recrystallization at 1200°C for 5h. A CuOx-CeO2 catalyst synthesized by the coprecipitation method was washcoated on the microchannel block resulting in a homogenous 20-30μm thick layer. The catalytic activity for CO-PROX reaction is similar in both the powder catalyst and the microchannel coated reactor but the selectivity is higher in the microchannel reactor. © 2010 Elsevier B.V.

March, 2011 | DOI: 10.1016/j.cej.2010.08.088

Title: Fischer-Tropsch synthesis in microchannels
Author(s): Almeida, LC; Echave, FJ; Sanz, O; Centeno, MA; Arzamendi, G; Gandia, LM; Sousa-Aguiar, EF; Odriozola, JA; Montes, M
Source: Chemical Engineering Journal, 167 (2011) 536-544

abstract | fulltext

Different metallic supports (aluminum foams of 40ppi, honeycomb monolith and micromonolith of 350 and 1180cpsi, respectively) have been loaded with a 20%Co-0.5%Re/γ-Al2O3 catalyst by the washcoating method. Layers of different thicknesses have been deposited onto the metallic supports. The catalytic coatings were characterized measuring their textural properties, adhesion and morphology. These structured catalysts have been tested in the Fischer-Tropsch synthesis (FTS) and compared with a microchannel block presenting perpendicular channels for reaction and cooling. The selectivity depends on the type of support used and mainly on the thickness of the layer deposited. In general, the C5+ selectivity decreased at increasing CO conversion for all of the systems (powder, monoliths, foams and microchannels block). On the other hand, the selectivity to methane increased with the thickness of the catalytic layer due to the higher effective H2/CO ratio over the active sites resulting from the higher diffusivity of H2 compared with CO in the liquid products filling the pores. The C5+ selectivity of the microchannels reactor is higher than that of the structured supports and the powder catalyst. © 2010 Elsevier B.V.

March, 2011 | DOI: 10.1016/j.cej.2010.09.091

Title: Oxidation of CO over gold supported on Zn-modified ceria catalysts
Author(s): Laguna, O.H., Centeno, M.A., Romero-Sarria, F., Odriozola, J.A.
Source: Catalysis Today, 172 (2011) 118-123

abstract | fulltext

A series of Zn-modified ceria solids were prepared by thermal decomposition of the corresponding metal propionates. The formation of segregated ZnO particles on the ceria surface is evidenced for these solids using X-ray diffraction; in addition to this the characterization data may allow discarding the formation of a ZnO-CeO2 solid solution. On modifying with Zn, the reducibility of the ceria support is enhanced, being the highest reducibility the one obtained for the ZnO-CeO2 solid having a 1:9 Zn:Ce atomic ratio (CeZn10). The activity of this solid in the CO oxidation reaction was the highest among the tested Zn-modified ceria solids. Therefore, catalysts containing 1 wt.% gold, supported on pure ceria and CeZn solids, were prepared, characterized and their catalytic activities tested. The Zn-modified gold catalyst is more active than the un-modified Au/CeO2 catalyst in the oxidation of CO; this behavior is related to the higher metallic dispersion of gold on the CeZn support surface. However, the number of oxygen vacancies acting as nucleation sites for gold, is hardly modified in the Zn-modified ceria support and, therefore, the higher gold dispersion must be related to high electron density sites on the catalyst surface as a result of Au-Ce-Zn interaction, this improved gold dispersion results in higher activities for CO oxidation.

August, 2011 | DOI: 10.1016/j.cattod.2011.02.015

Title: Ionic liquid protected heteropoly acids for methanol dehydration
Author(s): Ivanova, S., Nitsch, X., Romero-Sarria, F., Louis, B., Centeno, M.A., Roger, A.C., Odriozola, J.A.
Source: Catalysis Today, 171 (2011) 236-241

abstract | fulltext

We report herein the synthesis of an organic-inorganic hybrid composed by the ionic liquid protected Keggin structure, as a precursor for acid catalyst and its subsequent application in the methanol dehydration reaction. Special attention was paid to the thermal stability of the resulted hybrids as a function of the Keggin anion. The catalytic behaviour of these new materials are also studied and compared to the metal salt Cs2HPW 12O40. The prepared hybrids are less thermally stable than the metal salt, but their partial decomposition results in very active and selective catalysts for the dehydration of methanol to dimethyl ether.

August, 2011 | DOI: 10.1016/j.cattod.2011.03.077

Title: Influence of the strong metal support interaction effect (SMSI) of Pt/TiO(2) and Pd/TiO(2) systems in the photocatalytic biohydrogen production from glucose solution
Author(s): Colmenares, JC; Magdziarz, A; Aramendia, MA; Marinas, A; Marinas, JM; Urbano, FJ; Navio, JA
Source: Catalysis Communications, 16 (2011) 1-6

abstract | fulltext

Two different catalysts consisting of Pt/TiO2 and Pd/TiO 2 were submitted to diverse oxidative and reductive calcination treatments and tested for photocatalytic reforming of glucose water solution (as a model of biomass component) in H2 production. Oxidation and reduction at 850°C resulted in better photocatalysts for hydrogen production than Degussa P-25 and the ones prepared at 500°C, despite the fact that the former consisted in very low surface area (6-8 m2/g) rutile titania specimens. The platinum-containing systems prepared at 850°C give the most effective catalysts. XPS characterization of the systems showed that thermal treatment at 850°C resulted in electron transfer from titania to metal particles through the so-called strong metal-support interaction (SMSI) effect. Furthermore, the greater the SMSI effect, the better the catalytic performance. Improvement in photocatalytic behavior is explained in terms of avoidance of electron-hole recombination through the electron transfer from titania to metal particles.

November, 2011 | DOI: 10.1016/j.catcom.2011.09.003

Title: Gold nanoparticles on yttrium modified titania: Support properties and catalytic activity
Author(s): Plata, JJ; Marquez, AM; Sanz, JF; Avellaneda, RS; Romero-Sarria, F; Dominguez, MI; Centeno, MA; Odriozola, JA
Source: Topics in Catalysis, 54 (2011) 219-228

abstract | fulltext

A series of titanium oxide catalysts modified with yttrium has been prepared by sol-gel method and their structural properties have been studied. The incorporation of yttrium in the titania lattice favors the formation of oxygen vacancies while at low Y loadings the anatase structure is preserved. The catalytic activity of these solids for CO oxidation is found to be significantly dependent on their physical properties. In particular the amount of dopant controls the number of surface oxygen vacancies created as well as the gold particle size, which directly affects the catalytic activity. Also, a linear relationship between the catalytic activity and the band gap values, which depend on the Y loading, is observed. Density functional theory based calculations show that Y atoms are incorporated at the TiO2 surface at substitutional positions only, while the preferred oxygen vacancies arise by removing the bridge surface oxygen atoms. These O-vacancies are the preferential adsorption sites for Au atoms and nanoparticles, acting as nucleation centers that favor the dispersion of the catalyst active phase over the support surface. In agreement with experiment, Y doping is found to decrease the band gap of the support due to a destabilization of the valence band of the oxide. © 2011 Springer Science+Business Media, LLC 2011.

March, 2011 | DOI: 10.1007/s11244-011-9639-4

Title: Comparative study of the photodeposition of Pt, Au and Pd on pre-sulphated TiO2 for the photocatalytic decomposition of phenol
Author(s): Maicu, M; Hidalgo, MC; Colon, G; Navio, JA
Source: Journal of Photochemistry and Photobiology A: Chemistry, 217 (2011) 275-283

abstract | fulltext

A comparative study of the photodeposition of Pt, Au and Pd under the same experimental conditions onto pre-sulphated and non-sulphated TiO2 was performed. Morphological and surface characterisation of the samples as well as photocatalytic activity for phenol photooxidation was studied. The influence of sulphate pre-treatment on the deposits size and dispersion onto the TiO2 surface, and photodeposition yields with the different metals were also analysed. The photocatalytic activity of the doped materials was then investigated, observing that catalytic behaviour can be correlated to physical characteristics of the samples determined by (XRD) X-ray diffraction, (XPS) X-ray photoelectron spectroscopy, (XRF) X-ray fluorescence spectrometry and (TEM) transmission electron microscopy. Sulphate pre-treatment was found to influence both the level of dispersion and the size of metal clusters on the TiO2 surface. Sulphation and metallisation of samples was found to produce a synergistic enhancement in photoactivity for the degradation of phenol. The photoactivity of the catalysts with respect to the doped metal species was ordered Pt > Pd > Au.

January, 2011 | DOI: 10.1016/j.jphotochem.2010.10.020

Title: Photocatalytic coatings of silver–TiO2 nanocomposites on foamed waste-glass prepared by sonochemical process
Author(s): Lee, S.W., Obregón-Alfaro, S., Rodríguez-González, V.
Source: Journal of Photochemistry and Photobiology A: Chemistry, 221 (2011) 71-76

abstract | fulltext

Silver-TiO2 nanocomposite was prepared by photodeposition of silver nanoparticles on the surface of titanium dioxide. The sonochemical method was used for the deposition of silver-TiO2 powder on commercial foamed waste-glass strips (FWGS). The silver-TiO2 and the coated FWGS was characterized by XRD, DRS, SEM, TEM and nitrogen adsorption. In order to enhance silver-TiO2 deposition, different parameters were evaluated such as the solvent effect and use of stabilizing agents. The best deposition was obtained with an aqueous solution of polyvinyl alcohol (PVA) and an ultrasound irradiation source of 23.3 kHz. The photocatalytic activity of the silver-TiO2 coated FWGS was evaluated in the UV photo-assisted destruction of the noxious microalgae, Tetraselmis suecica. It was found that after the photocatalytic irradiation, for 180 min, the algae cells were deformed, fragmented and annihilated, thereby avoiding its regeneration.2

June, 2011 | DOI: 10.1016/j.jphotochem.2011.04.026

Title: High-stable mesoporous Ni-Ce/clay catalysts for syngas production
Author(s): Daza, C.E., Gamba, O.A., Hernández, Y., Centeno, M.A., Mondragón, F., Moreno, S., Molina, R.
Source: Catalysis Letters, 141 (2011) 1037-1046

abstract | fulltext

A mesoporous-type catalytic support was synthesized through the modification of a smectite with polyvinyl alcohol (PVA) and microwaves. Texture and micro-morphology of the support was determined. Several techniques were employed in order to describe the chemical environment of active species on the surface. Ni0 particle sizes were dependent on the structural site of reducible species. High stable Ni-Ce catalysts (calcined at 800 °C) were evaluated in the CO2 reforming of methane reaction at 700 °C (WHSV = 96 L g-1 h-1, without dilution gas and pre-reduction). The catalysts have presented CH4 conversions between 40 and 65%, CO2 conversion between 35 and 65% and H2/CO ratios between 0.2 and 0.4.

July, 2011 | DOI: 10.1007/s10562-011-0579-1

Title: Aluminum anodization in oxalic acid: Controlling the Texture of Al 2O3/Al monoliths for catalytic aplications
Author(s): Sanz, O; Echave, FJ; Odriozola, JA; Montes, M
Source: Industrial and Engineering Chemistry Research, 50 (2011) 2117-2125

abstract | fulltext

The anodization and postanodization processes of aluminum in order to prepare monoliths for catalytic applications have been studied in this work using oxalic acid as electrolyte. The effect of anodization variables (anodization time, current density, temperature, and electrolyte concentration) and postanodization processes on the surface morphology and textural properties of AAO (anodic aluminum oxide) films is analyzed. The anodization variables affect the two main processes taking part in the Al2O3 layer formation: alumina generation and its dissolution that are controlled by temperature, electrolyte concentration and time. The proper combination of both processes, as a result of the anodization variables choice, produces adherent alumina layers with tailored porosity and surface morphology that show excellent properties to be used as catalyst structured support. Larger pore sizes and the complete absence of sulfur that may poison reduced metal-supported active phases are main differences with the classical, most often used, sulfuric acid anodization process. © 2011 American Chemical Society.

February, 2011 | DOI: 10.1021/ie102122x

Title: Structural and catalytic properties of lanthanide (La, Eu, Gd) doped ceria
Author(s): Hernandez, WY; Laguna, OH; Centeno, MA; Odriozola, JA
Source: Journal of Solid State Chemistry, 184 (2011) 3014-3020

abstract | fulltext

Ce0.9M0.1O2-δ mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO2 (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F2g Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce4/Ce3. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO2, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area.

November, 2011 | DOI: 10.1016/j.jssc.2011.09.018

2010


Title: Room-Temperature Reaction of Oxygen with Gold: An In situ Ambient-Pressure X-ray Photoelectron Spectroscopy Investigation
Author(s): Jiang, P; Porsgaard, S; Borondics, F; Kober, M; Caballero, A; Bluhm, H; Besenbacher, F; Salmeron, M
Source: Journal of the American Chemical Society, 132 (2010) 2858-2859

abstract | fulltext

The interaction of O-2 with gold foil and gold nanoparticles grown by thermal deposition on TiO2(110) was studied by in situ ambient pressure X-ray photoelectron spectroscopy at room temperature. No spontaneous dissociation of O-2 was observed either on Au foil or oil Au nanoparticles up to 1 Torr of O-2. X-ray irradiation, however, is very effective in promoting gold oxidation on both surfaces in the presence of O-2. Our results help reconcile recent conflicting experimental observations regarding the activation of molecular oxygen, which is a crucial issue in Au catalyzed oxidation reactions.

March, 2010 | DOI: 10.1021/ja909987j

Title: In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel
Author(s): Caballero, A; Holgado, JP; Gonzalez-delaCruz, VM; Habas, SE; Herranz, T; Salmeron, M
Source: Chemical Communications, 46 (2010) 1097-1099

abstract | fulltext

In situ APPES technique demonstrates that the strong metal support interaction effect (SMSI) in the Ni-ceria system is associated with the decoration and burial of metallic particles by the partially reduced support, a phenomenon reversible by evacuation at high temperature of the previously absorbed hydrogen.

February, 2010 | DOI: 10.1039/b920803h

Title: Sunlight highly photoactive Bi2WO6-TiO2 heterostructures for rhodamine B degradation
Author(s): Colon, G; Lopez, SM; Hidalgo, MC; Navio, JA
Source: Chemical Communications, 46 (2010) 4809-4811

abstract | fulltext

Highly efficient Bi2WO6-TiO2 heterostructures are synthesized by means of a hydrothermal method; they have high photoactivity for the degradation of rhodamine B under sunlike irradiation. An interesting synergetic effect between TiO2 and Bi2WO6 leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance.

July, 2010 | DOI: 10.1039/c0cc00058b

Title: Gold supported on metal-doped ceria catalysts (M = Zr, Zn and Fe) for the preferential oxidation of CO (PROX)
Author(s): Laguna, OH; Sarria, FR; Centeno, MA; Odriozola, JA
Source: Journal of Catalysis, 276 (2010) 360-370

abstract | fulltext

A series of ceria oxides doped with 10 mol % of Zr Zn and Fe have been prepared by a pseudo sol-gel method throughout the thermal decomposition of the corresponding metallic propionates With these supports 1 wt % gold catalysts were prepared by the deposition-precipitation method All the solids were characterized by means of XRF N-2 adsorption XRD Raman spectroscopy and SEM techniques and their catalytic activity toward preferential oxidation of CO (PROX) reaction tested The results showed solid solution when doping with Zr and Fe and ZnO surface segregation in the case of Zn We demonstrate that gold dispersion depends on not only the oxygen vacancy concentration but also the nature of the doping agent Finally the catalytic activity was highly promoted by gold in all cases being the doped gold catalysts more active than Au/CeO2 at low temperature.

December, 2010 | DOI: 10.1016/j.jcat.2010.09.027

Title: Study of the stabilization of zinc phthalocyanine in sol-gel TiO2 for photodynamic therapy applications
Author(s): Lopez, T; Ortiz, E; Alvarez, M; Navarrete, J; Odriozola, JA; Martinez-Ortega, F; Paez-Mozo, EA; Escobar, P; Espinoza, KA; Rivero, IA
Source: Nanomedicine-Nanotechnology Biology and Medicine, 6 (2010) 777-785

abstract | fulltext

Photodynamic therapy (PDT) has emerged as an alternative and promising noninvasive treatment for cancer. It is a two-step procedure that uses a combination of molecular oxygen, visible light, and photosensitizer (PS) agents; phthalocyanine (Pc) was supported over titanium oxide but has not yet been used for cell inactivation. Zinc phthalocyanine (ZnPc) molecules were incorporated into the porous network of titanium dioxide (TiO2) using the sol-gel method. It was prepared from stock solutions of ZnPc and TiO2. ZnPc-TiO2 was tested with four cancer cell lines. The characterization of supported ZnPc showed that phthalocyanine is linked by the N-pyrrole to the support and is stable up to 250 degrees C, leading to testing for PDT. The preferential localization in target organelles such as mitochondria or lysosomes could determine the cell death mechanism after PDT. The results suggest that nanoparticulated TiO2 sensitized with ZnPc is an excellent candidate as sensitizer in PDT against cancer and infectious diseases. From the Clinical Editor: Photodynamic therapy is a two-step procedure that uses a combination of molecular oxygen, visible light and photosensitizer agents as an alternative and promising non-invasive treatment for cancer. The results of this study suggest that nanoparticulated TiO2 sensitized with ZnPc is an excellent photosensitizer candidate against cancer and infectious diseases.

December, 2010 | DOI: 10.1016/j.nano.2010.04.007

Title: Doping level effect on sunlight-driven W,N-co-doped TiO2-anatase photo-catalysts for aromatic hydrocarbon partial oxidation
Author(s): Kubacka, A; Bachiller-Baeza, B; Colon, G; Fernandez-Garcia, M
Source: Applied Catalysis B-Environmental, 93 (2010) 274-281

abstract | fulltext

A series of nanosized W,N-co-doped anatase TiO2 catalysts with different dopant contents has been prepared by a microemulsion method and examined in the sunlight selective photo-oxidation of toluene and styrene. The activity results have been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD-Rietveld, N-2 physisorption and NH3 chemisorption-calorimetry, XPS, Infrared, and UV-visible spectroscopies. Irrespective of the reaction, a consistent reaction rate enhancement with respect to titania (nano-TiO2, P25) references and W-doped TiO2 systems is observed for single-phase anatase W,N-co-doped samples. This is likely linked with the decrease of the band gap energy decrease and results from a combined W-N cooperative effect on structural properties of the anatase network. W,N simultaneous presence also makes a drastic effect on selectivity, maximizing the yield to partial oxidation products. This appears related with surface properties of the materials.

January, 2010 | DOI: 10.1016/j.apcatb.2009.09.039

Title: Synthesis and characterization of a LaNiO3 perovskite as precursor for methane reforming reactions catalysts
Author(s): Pereñiguez, R; Gonzalez-DelaCruz, VM; Holgado, JP; Caballero, A
Source: Applied Catalysis B-Environmental, 93 (2010) 346-353

abstract | fulltext

The objective of the present work has been the study of the physicochemical and catalytic properties of a Ni/La2O3 catalyst obtained by reduction of a lanthanum nickelite, LaNiO3, with perovskite structure. The perovskite, obtained by means of a spray pyrolysis method, provides a Ni/La2O3 system active in different methane reforming reactions. The catalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-Ray photoemission spectroscopy (XPS), temperature-programmed reduction and oxidation (TPR, TPO) and catalytic activity tests. Although not evidenced by XRD data, XAS and TPR measurements show the presence of an amorphous NiO phase in the original sample, together with the crystalline LaNiO3 phase. Upon reoxidation treatment of the reduced Ni/La2O3 catalyst, the LaNiO3 structure is partly recovered which provides a convenient way to regenerate a waste catalyst (reoxidation and new reduction in hydrogen). The catalyst is active in several reactions of methane with oxygen, water and CO2, showing a remarkable stability specially under dry reforming of methane (DRM) reaction conditions. This quite great catalytic performance has been explained by the high resistance of the nickel particles to be oxidized, as detected by in situ XAS. In the presence of water, as in steam reforming of methane (SRM) reaction conditions, these metallic particles are gradually oxidized, which explains the linear decreasing of the catalytic performance observed for the SRM reaction.

January, 2010 | DOI: 10.1016/j.apcatb.2009.09.040

Title: Complete n-hexane oxidation over supported Mn-Co catalysts
Author(s): Todorova, S; Kolev, H; Holgado, JP; Kadinov, G; Bonev, C; Pereniguez, R; Caballero, A
Source: Applied Catalysis B-Environmental, 94 (2010) 46-54

abstract | fulltext

Two series of Co-Mn samples were prepared by impregnation of silica with aqueous solutions or Co(NO3)(2)center dot 6H(2)O and/or Mn(NO3)(2)center dot 6H(2)O. Cobalt oxide was the predominant phase in one of the series and manganese was used as the promoter. The major component in the second series was manganese oxide and Co was the promoter. The prepared samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) and tested in the reaction of complete n-hexane oxidation. The catalytic activity of both single component cobalt and manganese samples was similar, however, a combination between the two elements changed significantly the activity and this depended on the method of preparation. Catalysts prepared by a common solution of Co- and Mn nitrates manifested a considerable increase in activity as a result of very low crystallinity of the supported metal oxide phases, partial enrichment of the surface with cobalt and uniform distribution of oxide agglomerates on the support.

February, 2010 | DOI: 10.1016/j.apcatb.2009.10.019

Title: N- and/or W-(co)doped TiO2-anatase catalysts: Effect of the calcination treatment on photoactivity
Author(s): Kubacka, A; Colon, G; Fernandez-Garcia, M
Source: Applied Catalysis B-Environmental, 95 (2010) 238-244

abstract | fulltext

A series of nanosized W,N-codoped and single-doped N- and W-anatase-TiO2 catalysts have been prepared by a microemulsion method and calcined at different temperatures. The activity in the sunlight selective photo-oxidation of toluene and styrene has been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD-Rietveld, N-2 physisorption, X-ray photoelectron, infrared, electron paramagnetic resonance (EPR) and UV-vis spectroscopies. Irrespective of the reaction, W,N-codoped nanocatalysts showed an enhanced photoactivity with respect to bare anatase and single-doped N-TiO2 and W-TiO2 materials. A strong W-N synergistic interaction appears to play a decisive role in driving the excellent photoactivity performance of W,N-codoped materials by affecting (i) electronic properties, particularly maximizing the anatase band gap decrease and enhancing the subsequent visible light photon absorption, and (ii) surface properties, in turn related to the formation of OH radicals upon light excitation. The maximum photoactivity is reached by calcination at 450 degrees C and is concomitantly observed with a near complete selectivity to partial oxidation products. Higher calcination temperatures yielded solids with significantly inferior photocatalytic performance. The properties of the W-N interaction are discussed as a function of the calcination temperature.

April, 2010 | DOI: 10.1016/j.apcatb.2009.12.028

Title: Photocatalytic degradation of phenolic compounds with new TiO2 catalysts
Author(s): Araña, J; Dona-Rodriguez, JM; Portillo-Carrizo, D; Fernandez-Rodriguez, C; Perez-Pena, J; Diaz, OG; Navio, JA; Macias, M
Source: Applied Catalysis B-Environmental, 100 (2010) 346-354

abstract | fulltext

New TiO2 catalysts have been synthesised by means of a sol-gel method in which aggregates have been selected before thermal treatment. Sieving and calcination temperature have been proved to be key factors in obtaining catalysts with greater photoactivity than that of Degussa P-25. These new catalysts have been characterized by means of transmission electron microscopy (TEM), BET surface area, diffuse reflectance spectroscopy (DRS). UV-vis spectroscopy, Fourier transformed infrared (FTIR) and X-ray diffraction (XRD). The different parameters studied were compared to those obtained from two commercial catalysts (Degussa P-25 and Hombikat-UV100). The photocatalytic efficiency of the new catalysts was evaluated by the degradation of various phenolic compounds using UV light (maximum around 365 nm, 9 mW). The catalyst sieved and calcinated at 1023 K, ECT-1023t, showed phenol degradation rates 2.7 times higher than those of Degussa P-25. Also in the degradation of different phenolic compounds, this catalyst showed a higher activity than that of the commercial one. The high photoactivity of this new catalyst has been attributed to the different distribution of surface defects (determined from FTIR studies) and its increased capacity to yield H2O2.

October, 2010 | DOI: 10.1016/j.apcatb.2010.08.011

Title: Synthesis of biodiesel from the methanolysis of sunflower oil using PURAL (R) Mg-Al hydrotalcites as catalyst precursors
Author(s): Navajas, A; Campo, I; Arzamendi, G; Hernandez, WY; Bobadilla, LF; Centeno, MA; Odriozola, JA; Gandia, LM
Source: Applied Catalysis B-Environmental, 100 (2010) 299-309

abstract | fulltext

A series of commercial Mg-Al hydrotalcites have been used as catalyst precursors for the methanolysis of sunflower oil.The solids were characterized by low Mg/Al molar ratios in the 0.5-2.3 range. Additionally, a solid consisting mainly of Mg(OH)(2) but containing some Al (4.2 wt.%) was also employed. The as-received materials were inactive for biodiesel synthesis so calcination and rehydration in boiling water were considered as activation treatments. Among the calcined solids, only the material consisting of MgO was significantly active, achieving about 50% oil conversion after 24h at 60 degrees C, methanol/oil molar ratio of 12 and 2 wt.% of catalyst. The effects of the calcination temperature in the 350-700 degrees C range have been investigated; calcination at 500 degrees C led to the best catalytic performance. In the case of the rehydrated materials, only the solids with the highest Mg/Al molar ratios recovered a well-ordered layered double hydroxide structure. These samples showed an improved catalytic activity compared with their calcined counterparts. A good correlation between catalytic activity and the basic properties determined using Hammett indicators and benzoic acid titration has been found. Rehydrated hydrotalcites were slightly more selective to biodiesel (75%) at intermediate levels of oil conversion than the calcined counterparts (66%). It has been verified that no Mg or Al leaching in the reaction mixture took place; however, the rehydrated samples deactivated significantly. In the case of MgO, after washing and calcination. the recycled catalyst gave 68% of the original oil conversion.

October, 2010 | DOI: 10.1016/j.apcatb.2010.08.006

Title: In Situ Characterization of the Dynamic Gold-Support Interaction over Ceria Modified Eu3+. Influence of the Oxygen Vacancies on the CO Oxidation Reaction
Author(s): Hernandez, WY; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: Journal of Physical Chemistry C, 114 (2010) 10857-10865

abstract | fulltext

Gold-supported ceria and europium-doped ceria catalysts were prepared by the deposition-precipitation method. The influence of the pretreatment atmosphere and temperature on the concentration of oxygen vacancies and gold dispersion on the Au/CeEti(10) catalyst under actual reaction conditions was investigated by "in situ" X-ray diffraction and Raman analysis. By Raman spectroscopy, a preferential interaction of the gold with the support across the oxygen vacancies was established and correlated with the gold dispersion. The increase in the concentration of oxygen vacancies in the presence of hydrogen induces changes in the gold crystallite size by breaking-off and migration of gold nanoparticles toward the oxygen vacancies on the CeEu(10) support. The activity of the Au/CeEu(10) solid in the CO oxidation reaction was significantly improved when the catalyst was preactivated in a reducing atmosphere. This trend could be associated with the redispersion of gold together with the increase in the concentration of oxygen vacancies in the support.

June, 2010 | DOI: 10.1021/jp1013225

Title: Study of nanostructured Ni/CeO2 catalysts prepared by combustion synthesis in dry reforming of methane
Author(s): Gonzalez-Delacruz, VM; Ternero, F; Pereniguez, R; Caballero, A; Holgado, JP
Source: Applied Catalysis A-General, 384 (2010) 1-9

abstract | fulltext

This work reports the study of several catalysts of Ni-CeO2 active for dry methane reforming process (CH4 + CO2 -> 2CO + 2H(2)). The use of Ni as active phase is highly preferred, due to its availability, high activity and low cost, although its main lack is the coke formation on the surface of Ni metal particles, resulting in a severe deactivation. Here we report a new synthesis method that allows a simple, effective and fast way to prepare Ni-CeO2 catalysts, in a wide range of metallic loadings, resulting in all the cases in well-formed NiO crystallites with sizes in the range of 12-18 nm. The use of CeO2 as a support has been based on its massive use in TWC catalysts formulations, where it is recognized to activate CH4 and lower hydrocarbon dissociation. Moreover, CeO2 has been reported to have an intrinsic activity in the CH4 reforming reaction. Besides the metallic loading, several factors that control the preparation method of the catalyst have been varied, in order to optimize their performance. Most of the catalysts prepared show activity and selectivity values close to thermodynamic ones, maintaining a good stability on long periods of time and severe conditions. Nevertheless, formation of some carbon nano-fibers has been observed, which could result in a drawback for their application at large scale.

August, 2010 | DOI: 10.1016/j.apcata.2010.05.027

Title: Characterisation and photocatalytic properties of titania-silica mixed oxides doped with Ag and Pt
Author(s): Llano, B; Restrepo, G; Marin, JM; Navio, JA; Hidalgo, MC
Source: Applied Catalysis A-General, 387 (2010) 135-140

abstract | fulltext

TiO2-SiO2 mixed oxides have been synthesised and modified by Ag and Pt deposition. Due to the effect of the silica on the mixed oxide, the prepared materials presented high surface areas and stabilised anatase as the only crystalline phase after calcination at 700 degrees C. Even using the same photodeposition experimental conditions, the yield for metal deposition depended highly on the metal considered, being much lower for Ag deposition. XPS studies permitted to estimate metal dispersion and oxidation state of the different samples, being both factors of high importance regarding photocatalytic improvement by metal deposition.

October, 2010 | DOI: 10.1016/j.apcata.2010.08.021

Title: Computational fluid dynamics study of heat transfer in a microchannel reactor for low-temperature Fischer-Tropsch synthesis
Author(s): Arzamendi, G; Dieguez, PM; Montes, M; Odriozola, JA; Sousa-Aguiar, EF; Gandia, LM
Source: Chemical Engineering Journal, 160 (2010) 915-922

abstract | fulltext

A three-dimensional computational fluid dynamics (CFD) study of heat transfer in a microchannel reactor for the low-temperature Fischer-Tropsch synthesis (FTS) is presented. The microreactor studied is a steel block with 80 square microchannels of 1 mm of side arranged in cross-flow configuration for the transport of syngas and cooling water. Syngas space velocities in the 5000-30,000 h(-1) (SIP) range have been considered. The microreactor exhibited good isothermicity under most simulated conditions. The FTS can be conducted with very low-temperature change between 483 and 523 K within a wide range of CO conversions using boiling water as coolant. To this end the pressure has to be set at the appropriate value between about Sand 35 atm. The pressure would have to be reduced as the CO conversion increases which might have a negative effect on the FTS selectivity to middle distillates. However, adjusting the cooling water flow rate in the range 0.25-250 g min(-1) allows maintaining the FTS temperature at suitable values while avoiding the use of low pressures. Relatively high values of the overall heat transfer coefficient in the 20-320 W m(-2) K-1 range have been obtained. A significant effect of the buoyancy forces on the thermal performance of the microreactor has been found.

June, 2010 | DOI: 10.1016/j.cej.2009.12.028

Title: AISI 304 austenitic stainless steel monoliths: Modification of the oxidation layer and catalytic coatings after deposition and its catalytic implications
Author(s): Martinez, LMT; Sanz, O; Centeno, MA; Odriozola, JA
Source: Chemical Engineering Journal, 162 (2010) 1082-1090

abstract | fulltext

Monolithic CeO2 and Au/CeO2 catalysts were prepared using austenitic stainless steel (AISI 304) as metallic substrate. Both monolithic and powdered catalysts were characterized before and after CO oxidation reaction by N-2 adsorption desorption, XRD, SEM, TEM and GD-OES. Catalyst deposition on the stainless steel surface results in modifications of the catalyst, the oxide scale and the oxide scale/alloy interface through the interaction between the coating and the steel oxidation layer. Besides this, oxidation of the alloy is also detected. The extension and nature of these modifications depends on the catalyst nature, and on the reaction conditions. As a result of these modifications CO oxidation on Au/CeO2 catalysts is enhanced and gold surface dynamics is modified.

September, 2010 | DOI: 10.1016/j.cej.2010.07.005

Title: Supported nickel catalysts with a controlled molecular architecture for the catalytic reformation of methane
Author(s): Hufschmidt, D; Bobadilla, LF; Romero-Sarria, F; Centeno, MA; Odriozola, JA; Montes, M; Falabella, E
Source: Catalysis Today, 149 (2010) 394-400

abstract | fulltext

In this work a lanthanum and nickel catalyst having perovskite structure, grown on a gamma-alumina carrier, is being presented. The structure of the catalyst was confirmed by XRD. The behaviour of this material under the conditions of steam reforming has been studied and the influence of the temperature, the space velocity and the steam/carbon ratio on the conversion of methane and the product distribution in the process was determined. In all cases at higher temperatures conversions of more than 90% and high selectivities were achieved. The experiments to determine the stability of the catalyst demonstrated that no deactivation in experimental runs of more than 17h occurred. Additionally a study of the catalyst after the reaction showed that only lowly structured carbonaceous species were formed on the catalyst surface, which is not expected to inhibit strongly the initial catalytic activity.

January, 2010 | DOI: 10.1016/j.cattod.2009.06.002

Title: Operando XAS and Raman study on the structure of a supported vanadium oxide catalyst during the oxidation of H2S to sulphur
Author(s): Holgado, JP; Soriano, MD; Jimenez-Jimenez, J; Concepcion, P; Jimenez-Lopez, A; Caballero, A; Rodriguez-Castellon, E; Nieto, JML
Source: Catalysis Today, 155 (2010) 296-301

abstract | fulltext

The modification of crystalline phases of a vanadium oxide supported on mesoporous zirconium phosphate during the partial oxidation of H2S to sulphur has been studied by using an operando Raman-GC approach and XAS in reaction conditions. The catalyst, mainly presenting crystalline V2O5, is transformed during the oxidation of H2S at 200 degrees C, presenting crystals of V4O9, which is identified by the presence of a band at ca. 900 cm(-1) in the Raman spectra (using a 785 nm line of an Argon ion laser) and by the presence of a pre-edge at 5469.8 eV (and a main-edge at 5482.2 eV) in XANES spectra. At the same time, it is observed a high conversion of H2S to sulphur (the main reaction product) and SO2 (as minority). Both activity and selectivity depend on the time on stream. In this way, the selectivity to SO2 decreases from ca. 5 to 1% with the time on stream. This change could be explained on the basis of the nature of V-species: the initial presence of V5+-O-V5+ pairs and the appearance of V5+-O-V4+ pairs at high time on stream.

October, 2010 | DOI: 10.1016/j.cattod.2010.02.050

Title: Modified cryptomelane-type manganese dioxide nanomaterials for preferential oxidation of CO in the presence of hydrogen
Author(s): Hernandez, WY; Centeno, MA; Romero-Sarria, F; Ivanova, S; Montes, M; Odriozola, JA
Source: Catalysis Today, 157 (2010) 160-165

abstract | fulltext

Transition metal (Cu Co Ni and Zn)-modified cryptomelane-type manganese dioxide nanomaterials were synthesized by the milling method The obtained solids have been characterized by means of Xray diffraction (XRD) scanning electron microscopy and transmission electron microscopy (SEM and TEM) N-2 adsorption-desorption measurements at 77 K Raman spectroscopy and temperature programmed reduction (TPR-H-2) showing similar structural and textural properties All the solids were active in the preferential oxidation of CO in the presence of hydrogen (PROX) being the modified with copper the most active The catalytic activity correlates fairly well with the TPR results finding higher CO conversion for the material with higher reducibility (OMS-Cu) The O-2 selectivity measured as ([CO](in)-[CO](out)/2[O-2](in)-[O-2](out)) x 100 is very similar for all synthesized materials.

November, 2010 | DOI: 10.1016/j.cattod.2010.03.010

Title: Iron-modified ceria and Au/ceria catalysts for Total and Preferential Oxidation of CO (TOX and PROX)
Author(s): Laguna, OH; Centeno, MA; Arzamendi, G; Gandia, LM; Romero-Sarria, F; Odriozola, JA
Source: Catalysis Today, 157 (2010) 155-159

abstract | fulltext

Iron-modified ceria supports containing different molar percentages of Fe (0% 10% 25% and 50%) were synthesized by thermal decomposition of the metal propionates The formation of a Ce-Fe oxide solid solution is evidenced through XRF XRD BET and Raman spectroscopy For Iron contents above 25% the formation of alpha-Fe2O3 was detected pointing out the formation of the isolated oxides The catalytic activity of the Fe-modified catalysts in the Total Oxidation of CO reaction (TOX) is higher than for the bare CeO2 material The synergy between Ce and Fe shows a maximum for 10% Fe content (CeFe10) catalyst that shows the highest CO conversion per atom of Fe incorporated Gold catalyst was also prepared on CeFe10 and its catalytic activity compared with Au/CeO2 catalyst The addition of iron to the gold catalyst resulted in an enhancement of the catalytic activity for CO oxidation especially at low temperature This Au/CeFe10 catalyst was also active and selective with excellent stability in the Preferential Oxidation of CO (PROX) showing a higher CO conversion than the Au/CeO2 catalyst at temperatures below 150 C being hardly affected by the presence of CO2 and H2O in the gas stream.

November, 2010 | DOI: 10.1016/j.cattod.2010.04.011

Title: Study of nanoporous catalysts in the selective catalytic reduction of NOx
Author(s): Rico, MJO; Moreno-Tost, R; Jimenez-Lopez, A; Rodriguez-Castellon, E; Pereniguez, R; Caballero, A; Holgado, JP
Source: Catalysis Today, 158 (2010) 78-88

abstract | fulltext

Two SBA-15 type materials were synthesized using a low-cost route, a pure silica SBA-15 and an Al containing SBA-15 (with a Si/Al ratio of 10), where Al was added by a post-synthesis modification. The later solid was achieved without any significant loss in the textural properties of SBA-15, besides improving its properties as support of catalysts. Copper impregnated catalysts were prepared through the incipient wetness impregnation of the two supports. With both supports, the copper weight loading were 1, 3 and 6 wt%. The copper incorporation kept the support mesoporous structures, obtaining a better dispersion of the active phase in the containing aluminium support. All the catalysts showed a moderated catalytic activity in the SCR of NO with propane in presence of an excess of oxygen in the whole studied interval of temperatures and a much better performance was observed when using NH3 instead of propane. The changes of the active phases were studied by operando XAS spectroscopy. Factor analysis of in operando XANES results with sample SiAl_6 indicate that no Cu-0 was detected, but only Cu1+ and Cu2+. The temperature where the Cu1+/Cu2+ ratio is maximum occurs at the reaction temperature where the observed catalytic NO conversion is also maximum.

December, 2010 | DOI: 10.1016/j.cattod.2010.04.016

Title: Gas phase photocatalytic oxidation of toluene using highly active Pt doped TiO2
Author(s): Colon, G; Maicu, M; Hidalgo, MC; Navio, JA; Kubacka, A; Fernandez-Garcia, M
Source: Journal of Molecular Catalysis A-Chemical, 320 (2010) 14-18

abstract | fulltext

Platinum doped TiO2 materials were studied for the gas phase photocatalytic degradation of toluene. Platinum deposition was achieved by photodeposition method over TiO2 prepared by means of a sol-gel route. The effect of sulphuric acid pretreatment on the further platinisation process has been extensively studied. From the wide structural and surface analysis of the catalysts an interesting synergetic effect has been demonstrated. The previous sulphate treatment over TiO2 leads to improved dispersion of the Pt which presents a lower aggregation and homogeneous cluster size. This fact, together with the adequate control of anatase structural and surface parameter due to the sulphate treatment, renders a good photocatalytic performance for toluene oxidation reaction. The highest reaction rates and CO2 selectivities have been obtained for Pt-S-TiO2 samples.

April, 2010 | DOI: 10.1016/j.molcata.2009.12.009

Title: Catalytic nanomedicine: Functionalisation of nanostructured cryptomelane
Author(s): Lopez, T; Ortiz, E; Alvarez, M; Manjarrez, J; Montes, M; Navarro, P; Odriozola, JA
Source: Materials Chemistry and Physics, 120 (2010) 518-525

abstract | fulltext

Nanostructured cryptomelanes (KMn8O16) were synthesized from manganese sulphate and manganese acetate precursors by the reflux method. The respectively obtained samples, CRYSO4 and CRYAc, were functionalised with hydroxyl, ammonium, sulphate and phosphate groups in order to modify the biocompatibility and surface properties of cryptomelane. Characterization by FTIR and XRD confirmed bond formation of CRY-NH, CRY=S=O, CRY-NH, and CRY=PO4. In both functionalise samples (CRYSO4-F and CRYAc-F), IR bands occurred at 1399 cm(-1), corresponding to the sulphate species, and 1106 cm(-1), related to phosphate vibrations; along with the OH and NH characteristic vibration bands in the high energy region. Biocompatibility of functionalised samples was tested by implantation of cryptomelane reservoir in the basolateral amygdala and caudal nucleus of Wistar rats using stereotactic surgery. The brains of the rats were processed in order to evaluate any damage associated with the implant. The results showed that functionalised cryptomelanes did not cause tissue damage or inflammation while not functionalised cryptomelanes caused cell death.

April, 2010 | DOI: 10.1016/j.matchemphys.2009.11.049

Title: Chemical and electronic characterization of cobalt in a lanthanum perovskite. Effects of strontium substitution
Author(s): Hueso, JL; Holgado, JP; Pereniguez, R; Mun, S; Salmeron, M; Caballero, A
Source: Journal of Solid State Chemistry, 183 (2010) 27-32

abstract | fulltext

Two different cobaltites, LaCoO3 and La0.5Sr0.5CoO3-delta, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). Even though half of the La(III) is substituted by Sr(II), little or no changes call be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic state of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which explains the well-known increase in the reactivity of this Substituted perovskite. O K-edge XAS experiments show that the Sr(II) species induce the transitions of d electrons of cobalt cations from low to high Spill Configuration. We propose that this change in Spill Multiplicity is induced by two cooperative effects: the oxygen vacancies. creating five coordinated cobalt atoms, and the bigger size of Sr(II) cations, aligning the Co-O-Co atoms, and favoring the overlapping of pi-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e(g) and t(2g) levels.

January, 2010 | DOI: 10.1016/j.jssc.2009.10.008

Title: The Effect of Water on Particle Size, Porosity and the Rate of Drug Release From Implanted Titania Reservoirs
Author(s): Lopez, T; Ortiz, E; Alexander-Katz, R; Odriozola, JA; Quintana, P; Gonzalez, RD; Lottici, PP; Marino, LG
Source: Journal of Biomedical Materials Research Part-B Applied Biomaterials, 93B (2010) 401-406

abstract | fulltext

The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders Sol-gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats The kinetics of the drug release depend on. (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir The titanium n-butoxide/water ratio was systematically varied during the sol-gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements The particle agglomerate size and porosity were found to depend on the amount of water used in the sol-gel reactio.

May, 2010 | DOI: 10.1002/jbm.b.31595

Title: Structure and microstructure of EB-PVD yttria thin films grown on Si (111) substrate
Author(s): Hartmanova, M; Jergel, M; Holgado, JP; Espinos, JP
Source: Vacuum, 85 (2010) 535-540

abstract | fulltext

Structure and microstructure of yttria thin films grown by electron beam physical vapour deposition on a stationary Si (111) substrate at room temperature (RT), 500 degrees and 700 degrees C, were investigated by the grazing-incidence X-ray diffraction and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy provided information on the surface contamination from the atmosphere and the oxidation state. A strong effect of the deposition temperature and the vapour flux incidence angle was found. The film deposited at RT is polycrystalline with very fine grains of the body-centered cubic (bcc) crystallographic symmetry. An increase of deposition temperature results in a rapid growth of bcc grains with an improved crystalline structure. Moreover, the based-centered monoclinic phase appears for the deposition temperature of 700 degrees C. Preferred grain orientation (texture) with two main components, (400) and (622), was observed in the films deposited at 500 degrees C whereas no texture was found for 700 degrees C. The microstructure exhibits the columnar feather-like structure of different degrees of perfection which can be explained by the shadowing effects caused by an oblique vapour flux incidence angle. Surface morphology of the films is governed by a combination of the triangular and four-sided (square) columns. All films were found to be dense with a little porosity between the columns.

October, 2010 | DOI: 10.1016/j.vacuum.2010.09.003

Title: Physicochemical Characterization and Use of Wastes from Stainless Steel Mill
Author(s): Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: Environmental Progress & Sustainable Energy, 29 (2010) 471-480

abstract | fulltext

Several types of wastes are produced during the manufacture of stainless steel (slags, refractory bricks, and dust). Most of these wastes are not recycled but stored in security deposits or landfills depending on their environmental danger This article reports the study of the physicochemical and mineralogical properties of stainless steel wastes. Their possible uses are also discussed.

December, 2010 | DOI: 10.1002/ep.10435

Title: Determination of the local structure of a highly dispersed Pd-Nanosystem located on a titanium dioxide carrier
Author(s): Kriventsov, VV; Novgorodov, BN; Yakimchuk, EP; Kochubey, DI; Zyuzin, DA; Simakova, IL; Chistyakov, AV; Zhmakin, VV; Bukhtenko, OV; Tsodikov, MV; Kozitsyna, NY; Vargaftik, MN; Moiseev, II; Maksimovskii, EA; Nechepurenko, SF; Navio, JA; Nikitenko, SG
Source: Journal of Surface Investigation-X-Ray Synchrotron and Neutron Techniques, 4 (2010) 636-639

abstract | fulltext

This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO2 matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(mu-OOCMe)(4)(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.

August, 2010 | DOI: 10.1134/S1027451010040166

2009


Title: Self-Assembling of Er2O3-TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal Route
Author(s): Julian-Lopez, B; Martos, M; Ulldemolins, N; Odriozola, JA; Cordoncillo, E; Escribano, P
Source: Chemistry-A European Journal, 15 (2009) 12426-12434

abstract | fulltext

An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3-TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O 3-TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313 m 2g-1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol-gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers.

November, 2009 | DOI: 10.1002/chem.200901423

Title: CO-TPR-DRIFTS-MS in situ study of CuO/Ce 1-xTbxO 2-y (x = 0, 0.2 and 0.5) catalysts: Support effects on redox properties and CO oxidation catalysis
Author(s): Hornes, A; Bera, P; Camara, AL; Gamarra, D; Munuera, G; Martinez-Arias, A
Source: Journal of Catalysis, 268 (2009) 367-375

abstract | fulltext

Catalysts of copper oxide supported on CeO2 and Ce1−xTbxO2−y have been studied by temperature-programmed reduction employing CO as a reductant (CO-TPR) using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) cell as well as conventional tubular reactors in order to get insights into redox changes occurring in the course of interaction of the systems with CO. CO-TPR results collected in the classical way, i.e. starting the temperature ramp after reactant gas equilibration at room temperature, suggest that the reduction of the copper species occurs at temperatures which decrease with the terbium content of the support. However, such result contrasts with CO oxidation activity of the systems under CO-PROX condition which follows just the opposite trend. DRIFTS results and analysis of low temperature redox processes, typically disregarded during recording of classical TPR tests, show that catalytic activity can be correlated to the magnitude of reduction achieved already at room temperature, which is related to reduction of interfacial copper oxide species.

December, 2009 | DOI: 10.1016/j.jcat.2009.10.007

Title: FTIR study of photocatalytic degradation of 2-propanol in gas phase with different TiO2 catalysts
Author(s): Arana, J; Alonso, AP; Rodriguez, JMD; Colon, G; Navio, JA; Pena, JP
Source: Applied Catalysis B-Environmental, 89 (2009) 204-213

abstract | fulltext

The photocatalytic efficiency of different TiO 2 catalysts in the degradation of 2-propanol in gas phase has been studied. The obtained efficiencies have been compared considering the distribution of rutile-anatase phases, surface area, particle size, distribution of surface hydroxyl groups and Brönsted or Lewis acid centres. The catalysts used were Degussa-P25 (TiO 2-P25), Hombikat, Millennium, Kemira and s/g-TiO 2, a catalyst prepared by a sol-gel method. The best photocatalytic behaviours have been obtained with those catalysts with higher surface area and the presence of only anatase phase (Hombikat and Millennium). A progressive deactivation of TiO 2-P25 and s/g-TiO 2 has been observed during the photocatalytic process. FTIR studies indicated that degradation mechanisms depended on the catalyst employed. Deactivation processes observed in TiO 2-P25 have been correlated with the formation of carboxylates.

July, 2009 | DOI: 10.1016/j.apcatb.2008.11.027

Title: Ionic liquid templated TiO2 nanoparticles as a support in gold environmental catalysis
Author(s): Avellaneda, RS; Ivanova, S; Sanz, O; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: Applied Catalysis B-Environmental, 93 (2009) 140-148

abstract | fulltext

This work presents the synthesis of a nanostructured titania support and its subsequent utilization for the gold particles deposition and application in the reaction of the CO oxidation. A functionalized ionic liquid has been used as a templating agent for the titanium oxide synthesis resulting in a high specific surface nanostructured titania anatase. The as prepared support was then used for gold nanoparticles deposition without ionic liquid removal in order to study the possible role of the latter in the stabilization of the gold particles. The presence of ionic liquid in the catalysts results in an unusual catalytic behaviour—strong dependence on the presence of CO and changed kinetics and rate of oxidation.

November, 2009 | DOI: 10.1016/j.apcatb.2009.09.023

Title: Influence of sulfur on the structural, surface properties and photocatalytic activity of sulfated TiO2
Author(s): Colon, G; Hidalgo, MC; Navio, JA; Kubacka, A; Fernandez-Garcia, M
Source: Applied Catalysis B-Environmental, 90 (2009) 633-641

abstract | fulltext

TiO2 materials were prepared by sol–gel method and then impregnated with sulfuric acid and calcined using different temperatures and atmosphere (air and nitrogen). Systematic variation of these two experimental parameters makes possible to modulate the amount of surface sulfur from the impregnation procedure. The best photocatalyst for liquid phenol degradation was obtained after calcination at 700 °C in air, while gas toluene degradation optimum performance is obtained by calcination at 700 °C in nitrogen from 500 °C. Structural analysis of these materials by XRD, micro-Raman spectroscopy and FE-SEM shows that once calcined at 700 °C the material was a well-crystallized, high surface area anatase structure in all cases. The surface characterization by FTIR and XPS confirms the presence of a higher amount of sulfur species and acidic OH groups in samples partially calcined in nitrogen, and a low XPS O/Ti-atomic ratio with the O 1s peak shifted to higher binding energies (1.8 vs. 2 ± 0.1 and 530.4 eV vs. 529.8 eV, respectively, against the reference materials) for samples calcined at 700 °C, temperature at which most of sulfate species have been evolved. The paper presents an attempt to correlate the contribution of the observed structural defects within the anatase sub-surface layers and surface acidity to the different photoactivity behaviour exhibited for phenol liquid phase and toluene gas phase photodegradation.

August, 2009 | DOI: 10.1016/j.apcatb.2009.04.026

Title: Gold/hydroxyapatite catalysts: Synthesis, characterization and catalytic activity to CO oxidation
Author(s): Dominguez, MI; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: Applied Catalysis B-Environmental, 87 (2009) 245-251

abstract | fulltext

This work reports the synthesis, characterization and catalytic activity for CO oxidation of gold catalysts supported on calcium hydroxyapatite. On both, the hydroxyapatite support and the gold-supported hydroxyapatite catalyst, the CO conversion shows a peak near 100% of conversion at room temperature. The generation of structural vacancies by interaction of CO with the solid provokes the formation of peroxide species in the presence of gaseous oxygen, which seems to be responsible of this high conversion of CO at room temperature. Moreover, the influence of the pre-treatment temperature on the activity has been observed and related with the elimination of carbonate species and the generation of structural defects in the apatite structure, which are able to modify the gold oxidation state.

April, 2009 | DOI: 10.1016/j.apcatb.2008.09.016

Title: Manganese and iron oxides as combustion catalysts of volatile organic compounds
Author(s): Duran, FG; Barbero, BP; Cadus, LE; Rojas, C; Centeno, MA; Odriozola, JA
Source: Applied Catalysis B-Environmental, 92 (2009) 194-201

abstract | fulltext

FeMn mixed oxides were prepared by the citrate method with Fe:Mn atomic ratio equal to 1:1, 1:3 and 3:1. The sample was characterized by means of specific surface area measurements, X-ray diffractometry (XRD), temperature programmed desorption of oxygen (O2-DTP), temperature programmed reduction (TPR), X-ray fluorescence (XRF), transmission electron microscopy (TEM and SAED) and high resolution TEM (HREM). The characterization results demonstrated the formation of a Mn2O3–Fe2O3 solid solution. The catalytic performance in ethanol, ethyl acetate and toluene total oxidation on these samples was better than on Fe2O3 and Mn2O3 pure oxides.

October, 2009 | DOI: 10.1016/j.apcatb.2009.07.010

Title: Synthesis and Characterization of Ce1−xEuxO2−x/2 Mixed Oxides and Their Catalytic Activities for CO Oxidation
Author(s): Hernandez, WY; Centeno, MA; Romero-Sarria, F; Odriozola, JA
Source: Journal of Physical Chemistry C, 113 (2012) 5629-5635

abstract | fulltext

A series of Ce1−xEuxO2−x/2 mixed oxides was synthesized by coprecipitation. The solids were characterized by means of XRF, SBET, XRD, UV−vis, and Raman techniques, and their catalytic activities toward CO oxidation were tested. A solid solution, with CeO2 F-type structure, is formed for europium contents (measured as Eu2O3 by XRF) ≤20% wt. For higher contents, the solid solution is not formed, but a physical mixture is detected. The existence of oxygen vacancies in the solids with Eu2O3 contents between 3 and 17% wt was demonstrated by the presence of bands at 532 and 1275 cm−1 in their Raman spectra. The catalytic performances of the solids correlate with the amount of these punctual defects in the solid solution.

April, 2009 | DOI: 10.1021/jp8092989

Title: Effect of Sulfate Pretreatment on Gold-Modified TiO2 for Photocatalytic Applications
Author(s): Hidalgo, MC; Maicu, M; Navio, JA; Colon, G
Source: Journal of Physical Chemistry C, 113 (2009) 12840-12847

abstract | fulltext

The influence of sulfated pretreatment of TiO2 on the structure, morphology, and dispersion of gold and photocatalytic properties of Au/TiO2 were studied. Notable enhancements in the photocatalytic activity of TiO2 were achieved by deposition of gold onto samples that had previously undergone sulfate treatment followed by high temperature calcination. The enhancement in activity can be attributed to the stronger bonding and improved electronic communication between gold particles and TiO2 on defect rich surfaces as are found on sulfated samples after calcination at 700 °C. Two different methods for gold deposition were evaluated: chemical reduction by citrate and photodeposition. The citrate method produced more homogeneous and smaller gold particles with a better dispersion than photodeposition, which lead to greater increases in activity in the photocatalytic degradation of phenol when the former method was used for deposition on both sulfated and nonsulfated TiO2. The combination of sulfate pretreatment and gold deposition by chemical reduction was shown to be a good strategy to obtain gold/titania catalysts possessing homogeneous particle size and dispersion of the metal and a strong bonding between the Au and the TiO2 surface.

July, 2009 | DOI: 10.1021/jp903432p

Title: W,N-Codoped TiO2-Anatase: A Sunlight-Operated Catalyst for Efficient and Selective Aromatic Hydrocarbons Photo-Oxidation
Author(s): Kubacka, A; Bachiller-Baeza, B; Colon, G; Fernandez-Garcia, M
Source: Journal of Physical Chemistry C, 113 (2009) 8553-8555

abstract | fulltext

New W,N-doped TiO2 anatase-based materials are synthesized having both unprecedent high activity and selectivity in the gas-phase partial oxidation of aromatic hydrocarbons using sunlight as excitation energy and molecular oxygen as oxidant.

May, 2009 | DOI: 10.1021/jp902618g

Title: Deposition of Al-Fe pillared bentonites and gold supported Al-Fe pillared bentonites on metallic monoliths for catalytic oxidation reactions
Author(s): Martinez, LM; Dominguez, MI; Sanabria, N; Hernandez, WY; Moreno, S; Molina, R; Odriozola, JA; Centeno, MA
Source: Applied Catalysis A-General, 364 (2009) 166-173

abstract | fulltext

Al-Fe pillared bentonite and gold supported on Al-Fe pillared bentonite catalysts deposed on Fecralloy monoliths have been prepared, characterized and tested in two oxidation reactions: gaseous oxidation of CO and phenol oxidation in aqueous medium. The deposition of the solid on the metallic substrate does not alter its structural characteristics. The use of monoliths improves the activity in both reactions and offers the additional advantage to facilitate the separation of the catalyst from the reaction medium.

July, 2009 | DOI: 10.1016/j.apcata.2009.05.046

Title: ZnO activation by using activated carbon as a support: Characterisation and photoreactivity
Author(s): Melian, EP; Diaz, OG; Rodriguez, JMD; Colon, G; Arana, J; Melian, JH; Navio, JA; Pena, JP
Source: Applied Catalysis A-General, 364 (2009) 176-181

abstract | fulltext

The effect of the mixing ZnO with different portions of activated carbon (AC) has been studied. The resulting catalysts were characterised and evaluated in the photocatalytic decomposition of aqueous pollutants. Changes in the catalyst colour and in the FTIR vibration bands of the surface hydroxyl groups were recorded. νOH vibrations were shifted to lower wavenumbers as AC loading increased, demonstrating modification of the acid-base character of the catalysts. Laser scattering studies showed that AC loading leads to smaller ZnO particles. BET surface area measurements and scanning electron micrograph (SEM) analysis showed agglomeration of ZnO particle pores in the AC structure.

Results showed that in addition to a synergistic effect of the AC-ZnO combination, AC content modifies the ZnO particle properties and consequently photocatalytic behaviour. This was evident in phenol degradation experiments where changes in the concentration profiles of the catechol and hydroquinone degradation intermediates, were observed. However, the AC-ZnO catalysts were less efficient than pure ZnO in the degradation of 2,4-dichlorophenol (DCP). This seems to be due to the strong adsorption of the DCP molecule on AC, resulting in lower diffusion to the catalytic ZnO and thus a lower rate of photocatalysis.

July, 2009 | DOI: 10.1016/j.apcata.2009.05.042

Title: Pillared clays with Al–Fe and Al–Ce–Fe in concentrated medium: Synthesis and catalytic activity
Author(s): Sanabria, NR; Centeno, MA; Molina, R; Moreno, S
Source: Applied Catalysis A-General, 356 (2009) 243-249

abstract | fulltext

This paper proposes a new methodology for the modification of clays with the mixed Al–Fe and Al–Ce–Fe systems, which involves the synthesis of solid polymeric precursors and their use as pillaring agents in the modification of clays. The process of intercalation of clay with Al13, Al13 + Fe and Al13 + Ce + Fe nitrate was performed using ultrasound. The pillaring agents Al13, Al13 + Fe and Al13 + Ce + Fe were characterized by XRF, XRD, SEM and 27Al NMR techniques, and pillared clays were characterized by XRF, XRD and N2 adsorption to 77 K. The catalytic properties of pillared clays were evaluated using catalytic wet peroxide oxidation of phenol in dilute aqueous medium, demonstrating activity comparable to that of solids modified by the conventional method.

March, 2009 | DOI: 10.1016/j.apcata.2009.01.013

Title: Integration of methanol steam reforming and combustion in a microchannel reactor for H2 production: A CFD simulation study
Author(s): Arzamendi, G; Dieguez, PM; Montes, M; Centeno, MA; Odriozola, JA; Gandia, LM
Source: Catalysis Today, 143 (2009) 25-31

abstract | fulltext

A computational fluid dynamics (CFD) study of the thermal integration of the steam reforming of methanol (SRM) and the combustion of methanol in a catalytic microchannel reactor is presented. This issue is of interest for in situ H2 production for portable power units based on low-temperature PEM fuel cells. Three-dimensional simulations have been carried out under relevant conditions for the SRM reaction that have shown that microreactors allow achieving complete methanol reforming and combustion at space velocities as high as 50,000 h−1, with selectivities for H2 above 99% at relatively low temperatures in the 270–290 °C range.

May, 2009 | DOI: 10.1016/j.cattod.2008.09.034

Title: Cationic (V, Mo, Nb, W) doping of TiO2–anatase: A real alternative for visible light-driven photocatalysts
Author(s): Kubacka, A; Colon, G; Fernandez-Garcia, M
Source: Catalysis Today, 143 (2009) 286-292

abstract | fulltext

In this article we investigate the structure–activity link of anatase-type Ti–M (M = V, Mo, Nb, and W) mixed oxides used for toluene photo-oxidation under sunlight-type excitation. An analysis of the local and long-range structural and electronic characteristics of the mixed oxides show that only structurally highly homogeneous anatase-type oxides with electronic properties exclusively leading to a band gap decrease drive to efficient visible light-driven photocatalysts. Within our microemulsion preparation method, this only occurs for Ti–V and Ti–W series of samples. The isoelectronic (V4+) substitution of Ti4+ ions at the anatase lattice is characterized by a low solubility limit (ca. 2.5 at. %), and drives to a limited modification of the band gap and to a moderate enhancement of the photo-activity with respect to bare titania reference systems. W presence at anatase cation positions occurs with concomitant presence of cation vacancies derived by the charge imbalance between the W6+ and Ti4+ species. A unique W-vacancy local arrangement is detected by the structural characterization, leading to both an important band gap decrease and enhancement of the photo-activity upon sunlight excitation.

May, 2009 | DOI: 10.1016/j.cattod.2008.09.028

Title: Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites
Author(s): Hueso, JL; Martinez-Martinez, D; Caballero, A; Gonzalez-Elipe, AR; Mun, BS; Salmeron, M
Source: Catalysis Communications, 10 (2009) 1898-1902

abstract | fulltext

We have studied the oxidation of carbon monoxide over a lanthanum substituted perovskite (La0.5Sr0.5CoO3−d) catalyst prepared by spray pyrolysis. Under the assumption of a first-order kinetics mechanism for CO, it has been found that the activation energy barrier of the reaction changes from ∼80 to ∼40 kJ mol−1 at a threshold temperature of ca. 320 °C. In situ XPS near-ambient pressure (∼0.2 torr) shows that the gas phase oxygen concentration over the sample decreases sharply at ca. 300 °C. These two observations suggest that the oxidation of CO undergoes a change of mechanism at temperatures higher than 300 °C.

August, 2009 | DOI: 10.1016/j.catcom.2009.06.022

Title: Redox chemistry of gold in a Au/FeOx/CeO2 CO oxidation catalyst
Author(s): Penkova, A; Chakarova, K; Laguna, OH; Hadjiivanov, K; Saria, FR; Centeno, MA; Odriozola, JA
Source: Catalysis Communications, 10 (2009) 1196-1202

abstract | fulltext

Calcination and evacuation of a Au/FeOx/CeO2 catalyst at 573 K leads to reduction of the deposited gold to metal. This metal state is stable under oxygen and only at 573 K some metal atoms are oxidized to Auδ+ sites (Au+ cations situated on metal gold particles). However, even at room temperature, gold is readily oxidized in a CO + O2 mixture producing, in addition to the Auδ+ sites, some isolated Au+ cations.

March, 2009 | DOI: 10.1016/j.catcom.2009.01.014

Title: Methane steam reforming in a microchannel reactor for GTL intensification: A computational fluid dynamics simulation study
Author(s): Arzamendia, G; Dieguez, PM; Montes, M; Odriozola, JA; Sousa-Aguiar, EF; Gandia, LM
Source: Chemical Engineering Journal, 154 (2009) 168-173

abstract | fulltext

The integration of the steam reforming and combustion of methane in a catalytic microchannel reactor has been simulated by computational fluid dynamics (CFD). Two models including 4 or 20 square microchannels of 20 mm of length and 0.7 mm of side have been developed. It has been assumed that a thin and homogeneous layer of an appropriate catalyst has been uniformly deposited onto the channels walls. The kinetics of the steam reforming of methane (SRM), water-gas shift (WGS) and methane combustion in air have been incorporated into the models. This has allowed simulating the effect of the gas streams space velocities, catalyst load, steam-to-carbon (S/C) ratio and flow arrangement on the microreformer performance. The results obtained illustrate the potential of microreactors for process intensification: complete combustion of methane is achieved at gas hourly space velocities (GHSV) as high as 130,000 h−1. As concerns the SRM, methane conversions above 97% can be obtained at high GHSV of 30,000 h−1 and temperatures of 900–950 °C. Under these conditions selectivity for syngas is controlled by the WGS equilibrium.

November, 2009 | DOI: 10.1016/j.cej.2009.01.035

Title: AISI 304 Austenitic stainless steels monoliths for catalytic applications
Author(s): Martinez, LM; Sanz, O; Dominguez, MI; Centeno, MA; Odriozola, JA
Source: Chemical Engineering Journal, 148 (2009) 191-200

abstract | fulltext

The thermal treatments of austenitic stainless steels monoliths were studied in order to generate a highly homogeneous and rough oxide scale strongly attached to the base alloy, which will subsequently ensure the good adherence of the catalysts. In this work it has been shown that the morphology, integrity and homogeneity of the scale are strongly influenced by the temperature and time of treatment. Washcoating method was used to deposit on the monolith surface a Au/CeO2 catalyst. The drying procedure turned out to be the most critical variable for the adherence and homogeneity of the catalytic ceria layer, while the ceria colloid concentrations in the starting aqueous dispersion seems to have only a threshold effect. The monolithic reactors containing Au/CeO2 layers are active in the oxidation of CO.

May, 2009 | DOI: 10.1016/j.cej.2008.12.030

Title: Aluminium anodisation for Au-CeO2/Al2O3-Al monoliths preparation
Author(s): Sanz, O; Martinez, LM; Echave, FJ; Dominguez, MI; Centeno, MA; Odriozola, JA; Montes, M
Source: Chemical Engineering Journal, 151 (2009) 324-332

abstract | fulltext

The anodisation of aluminium monoliths was performed in order to generate an alumina layer that ensures a good adherence of the catalysts. In this study, it is demonstrated that the morphology of the produced alumina layer depends on time, temperature, current density and concentration of the selected electrolyte. When anodisation process with the extreme conditions was applied (30 °C, 50 min, 2 A dm−2 and 2.6 M of sulphuric acid) a significant cracks were obtained and used to fix the subsequent catalytic coatings. The washcoating method was used to cover the monoliths with colloidal solutions of CeO2 and/or Au-CeO2 catalysts. The resulting monolithic catalysts were tested in the CO oxidation reaction being 1%Au-CeO2 containing system the most active. The structured catalyst prepared this way changed neither the textural nor the catalytic properties of the deposited catalytic powders.

August, 2009 | DOI: 10.1016/j.cej.2009.03.062

Title: Gold nanoparticles on silica monospheres modified by amino groups
Author(s): Penkova, A; Blanes, JMM; Cruz, SA; Centeno, MA; Hadjiivanov, K; Odriozola, JA
Source: Microporous and Mesoporous Materials, 117 (2009) 530-534

abstract | fulltext

Silica monospheres with a diameter of 330 nm modified with aminosilane compounds of three different basicities have been prepared. Surface coverage of the silica with an organic compound leads to an increase of the point of zero charge (PZC) of the silica surface from 2.1 to 5.1, 6.5 and 7.2 values, depending on the amine used. From these silicas, gold-containing catalysts have been prepared by a deposition–precipitation method at the same pH as the PZC of the support. The best results have been obtained using 3-(Diethoxymethylsilyl) propylamine as a modifying agent, which has allowed obtaining a good dispersion of the gold particles with an average size of 3.8 nm.

January, 2009 | DOI: 10.1016/j.micromeso.2008.07.041

Title: Reactivity of LaNi1−y Co y O3−δ Perovskite Systems in the Deep Oxidation of Toluene
Author(s): Pereniguez, R; Hueso, JL; Holgado, JP; Gaillard, F; Caballero, A
Source: Catalysis Letters, 131 (2009) 164-169

abstract | fulltext

In the present work we have evaluated the oxidation of toluene over different lanthanum perovskites with a general composition of LaNi1−y Co y O3−δ. These catalysts, prepared by a spray pyrolysis method, have been characterised by XRD, BET and FE-SEM techniques. Additional experiments of temperature programmed desorption of O2, reduction in H2 and X-ray absorption spectroscopy were also performed in order to identify the main surface oxygen species and the reducibility of the different perovskites. The catalytic behaviour toward the oxidation of toluene (as a model for VOCs compounds) was evaluated in the range 100–600 °C, detecting a total conversion for all the samples below 400 °C and higher activities for the cobalt-containing perovskites. The catalytic behaviour of these samples is consistent with a suprafacial mechanism, with the α-type oxygen playing an active role in the oxidation reaction.

August, 2009 | DOI: 10.1007/s10562-009-9968-0

Title: Co3O4 + CeO2/SiO2 Catalysts for n-Hexane and CO Oxidation
Author(s): Todorova, S; Kadinov, G; Tenchev, K; Caballero, A; Holgado, JP; Pereniguez, R
Source: Catalysis Letters, 129 (2009) 149-155

abstract | fulltext

Two-component Co–Ce samples deposited onto SiO2 have been prepared, characterized and tested in the reaction of complete n-hexane and CO oxidation. It was established that cerium enhanced the catalytic activity of cobalt in the reaction of n-hexane oxidation, although this depended on the sequence of cobalt and cerium introduction. Co-impregnation of Co and Ce resulted in a close interaction between Co3O4 and CeO2 leading to more surface oxygen species available and, therefore, a better reactivity.

April, 2009 | DOI: 10.1007/s10562-008-9805-x

Title: Structural characteristics and morphology of SmxCe1−xO2−x/2 thin films
Author(s): Hartmanova, M; Jergel, M; Mansilla, C; Holgado, JP; Zemek, J; Jurek, K; Kundracik, F
Source: Applied Surface Science, 255 (2009) 9085-9091

abstract | fulltext

Effect of the deposition temperature (200 and 500 °C) and composition of SmxCe1−xO2−x/2 (x = 0, 10.9–15.9 mol%) thin films prepared by electron beam physical vapor deposition (EB-PVD) and Ar+ ion beam assisted deposition (IBAD) combined with EB-PVD on structural characteristics and morphology/microstructure was investigated. The X-ray photoelectron spectroscopy (XPS) of the surface and electron probe microanalysis (EPMA) of the bulk of the film revealed the dominant occurrence of Ce4+ oxidation state, suggesting the presence of CeO2 phase, which was confirmed by X-ray diffraction (XRD). The Ce3+ oxidation states corresponding to Ce2O3 phase were in minority. The XRD and scanning electron microscopy (SEM) showed the polycrystalline columnar structure and a rooftop morphology of the surface. Effects of the preparation conditions (temperature, composition, IBAD) on the lattice parameter, grain size, perfection of the columnar growth and its impact on the surface morphology are analyzed and discussed.

August, 2009 | DOI: 10.1016/j.apsusc.2009.06.108

Title: Fibrous MnO2 Nanoparticles with (2 × 2) Tunnel Structures. Catalytic Activity in the Total Oxidation of Volatile Organic Compounds
Author(s): Dominguez, MI; Navarro, P; Romero-Sarria, F; Frias, D; Cruz, SA; Delgado, JJ; Centeno, MA; Montes, M; Odriozola, JA
Source: Journal of Nanoscience and Nanotechnology, 9 (2009) 3837-3842

abstract | fulltext

Manganese oxides having 2 × 2 tunnel structures (cryptomelanes) have been synthesized by a milling method in order to test their efficiency as catalysts for the abatement of volatile organic compounds, using toluene as probe molecule. These materials present excellent textural properties, arising from the nanofiber morphology and were active for toluene total oxidation. DRIFTS of the adsorbed phase allow proposing the role of lattice oxygen in the catalytic reaction.

June, 2009 | DOI: 10.1166/jnn.2009.NS76

Title: Determination of nitrogen partitioning coefficients in superduplex stainless steels by NRA using a nuclear microprobe
Author(s): Munoz, C; Morilla, Y; Lopez, JG; Paul, A; Odriozola, JA
Source: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 267 (2009) 2208-2211

abstract | fulltext

Superduplex stainless steels (SDSSs) combine the good mechanical behavior and the high corrosion resistance of the ferrite (α-Fe) and austenite (γ-Fe) phases. The SDSSs properties depend strongly on the partitioning of the elements that form the alloy. The ferrite is generally enriched in P, Si, Cr and Mo while the content of Ni, Mn, Cu and N in the austenite phase is higher. Nitrogen is known to be a strong austenite stabilizer and its presence increases the strength and the pitting corrosion resistance of the stainless steels. While the global nitrogen content in SDSSs can be readily determined using elemental analyzers, it cannot be measured at a microscopic scale.

In this work, the nuclear microprobe of the Centro Nacional de Aceleradores (Sevilla) was used to obtain the quantitative distribution of nitrogen in SDSSs. A deuteron beam of 1.8 MeV was employed to determine the overall elemental concentration of the matrix by deuteron-induced X-ray emission, whereas the nitrogen partitioning coefficients were obtained by using the 14N(d, α0)12C nuclear reaction. Mappings of this element show that the nitrogen ratio between the ferrite and austenite phases ranges from 0.3 to 0.6 in the analyzed samples.

June, 2009 | DOI: 10.1016/j.nimb.2009.03.093

Title: Degradation of n-Butyl tin Chlorides in Waters. A Comparative Assessment of the Process by Photo-assisted and Chemical- treatment Methods
Author(s): Navio, JA; Cerrillos, C; Macias, M
Source: Journal of Advanced Oxidation Technologies, 12 (2009) 158-163

abstract | fulltext

July, 2009 | DOI: ---


Ara Muñoz Murillo
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Director/s: José Antonio Odriozola Gordón y Miguel Angel Centeno Gallego
Universidad de Sevilla
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Julie Joseane Murcia Mesa
Control de la nanoestructura de sistemas M-TiO2 (M=Pt y Au) preparados por fotodeposición con propiedades fotocatalíticas optimizadas

Director/s: Carmen Hidalgo López y José Antonio Navío Santos
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Friday, 12 July, 2013
 


Sebastián Murcia López
Desarrollo de Materiales basados en Bismuto con Alta Eficiencia Fotocatalítica para Aplicaciones de Química Verde

Director/s: José Antonio Navío Santos y M. Carmen Hidalgo López
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Tuesday, 9 April, 2013
 


Fátima A. Ternero Fernández
Sistemas Catalíticos Basados en Nanopartículas Mono y Bimetálicas Activos en Procesos de Interés Medioambiental

Director/s: Alfonso Caballero Martínez y Juan Pedro Holgado Vázquez
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Oscar Hernando Laguna Espitia
Oxidación preferencial de CO en presencia de H2: diseño de catalizadores basados en CeO2 y aplicación a microrreactores

Director/s: José Antonio Odriozola Gordón y Miguel Angel Centeno Gallego
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Luis F. Bobadilla Baladrón
Obtención de hidrógeno a partir de la biomasa. Reformado catalítico de glicerina

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Willinton Yesid Hernández Enciso
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Universidad de Sevilla
Friday, 26 November, 2010
 


Sylvia Andrea Cruz Torres
Aplicaciones de la Técnica “Spark Plasma Sintering” a la Obtención de Materiales y Dispositivos de Interés en Catálisis

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Rosa Pereñíguez Rodríguez
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Universidad de Sevilla
Friday, 21 May, 2010
 


Marina Maicu
Estudio de la actividad fotocatalítica de sistemas basados en TiO2, sulfatado y no sulfatado, y modificado con Pt, Au y Pd

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Rafael Sánchez Avellaneda
Estudio e influencia de itrio y otros modificadores superficiales en el comportamiento de catalizadores soportados en TiO2

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Friday, 5 February, 2010
 


Leidy Marcela Martínez Tejada
Deposición de catalizadores sobre superficies metálicas para aplicaciones catalíticas

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Friday, 4 April, 2008
 


José Luis Hueso Martos
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Wednesday, 19 September, 2007
 


Catalina Mansilla Sánchez
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Ana María Cordón Rodríguez
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María Isabel Domínguez Leal
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Francisco Gracia Torres
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José Jorge Morales Domingo
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Said El Mrabet
Diseño de aceros inoxidables austeníticos resistentes a la oxidación a alta temperatura. Efectos de la composición de la matriz y de las modificaciones superficiales

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Monday, 3 February, 2003
 

Óscar H. Laguna gana el Premio de Tesis Doctoral del Ayuntamiento de Sevilla 2012


El investigador colombiano Óscar Hernando Laguna Espitia ha obtenido uno de los siete premios que concede el Área de Cultura, Educación, Juventud y Deportes del Ayuntamiento de Sevilla a las mejores tesis doctorales defendidas en la Universidad de Sevilla y en la Universidad Pablo de Olavide durante el curso académico 2010-2011. El galardón le ha sido otorgado por su trabajo “Oxidación preferencial de CO en presencia de H2: diseño de catalizadores basados en CeO2 y aplicación a microrreactores”, presentado en la Universidad de Sevilla y realizado, en su mayor parte, en el Instituto de Ciencia de Materiales de Sevilla (ICMS). Esta tesis ha sido dirigida por el Catedrático de Química Inorgánica de la Universidad de Sevilla José Antonio Odriozola y el Investigador Científico del CSIC Miguel Ángel Centeno.

Óscar Hernando Laguna, que actualmente amplía su formación en la Universidad del País Vasco, fue becario FPI entre septiembre de 2007 y octubre de 2011 en el grupo de investigación dirigido por el Profesor Odriozola (Departamento de Química Inorgánica de la Universidad de Sevilla-ICMS). En este período participó en proyectos encaminados a desarrollar procesadores de combustible para aplicaciones móviles basados en la producción de energía a partir de hidrógeno (H2). Guiado por los profesores Odriozola y Centeno, Óscar Hernando Laguna desarrolló su tesis doctoral sobre la eliminación del monóxido de carbono (CO) remanente en las corrientes de hidrógeno producidas al transformar alcoholes. Estas corrientes son las utilizadas para alimentar las celdas de combustible, que, a su vez, producirán electricidad.

Al premiar esta tesis, el Área de Cultura, Educación, Juventud y Deportes del Ayuntamiento de Sevilla ha valorado la relevancia de las aportaciones teóricas y prácticas del trabajo, que cuenta con una amplia proyección en el sector energético. El estudio de la purificación de las corrientes de hidrógeno contribuye, principalmente, a optimizar la utilización del hidrógeno como fuente de energía alternativa, con menores residuos contaminantes. La aplicación de este tipo de investigaciones repercute en un mejor rendimiento de las celdas de combustible, las baterías eléctricas que funcionan a partir del hidrógeno y que, por su versatilidad, pueden usarse con prometedores resultados en dispositivos móviles o en la industria automovilística, por citar un par de ejemplos.

Como señala el propio autor, desde un principio esta tesis se diseñó desde un enfoque integrador, contemplando desde los principios fundamentales hasta las aplicaciones finales. “En primer lugar, se han diseñado catalizadores para la oxidación de CO. Esto implica concebir los sistemas desde escalas atómicas para entender los principios a partir de los cuales se favorece la reacción de oxidación de CO”, describe Óscar Hernando Laguna. Para ello, se han utilizado sistemas basados en óxido de cerio modificado con diferentes metales de transición. “Posteriormente, se ha llevado a cabo un análisis cinético de los sistemas más prometedores en la reacción de oxidación preferencial de CO en presencia de H2 (PROX), pensando en el futuro escalado del proceso”.

Según el investigador, uno de los aspectos más llamativos del trabajo se produjo al considerar la aplicación final. En esta última fase, se puso en funcionamiento un prototipo de microrreactor (o reactor de microcanales), diseñado y fabricado en los laboratorios del ICMS para la reacción PROX, que se saldó con éxito. En palabras de Óscar Hernando Laguna, “estos dispositivos favorecen lo que se denomina ‘intensificación de procesos’, que conduce a un aumento de la eficiencia energética y la producción de menor cantidad de subproductos. Tanto la industria como la comunidad científica están convencidas de que su desarrollo ofrece un atractivo panorama para este tipo de reacciones a nivel industrial”. No en vano, son tales las posibles aplicaciones de este tipo de estudios relacionados con la purificación de las corrientes de hidrógeno que algunos de los proyectos en los que ha participado este investigador se han desarrollado junto a empresas líderes del sector energético, como la multinacional Petróleos de Brasil (Petrobas).

El enfoque integrador de esta tesis doctoral ha permitido no sólo que destaque por su proyección industrial, sino también en el ámbito académico, donde ha cosechado un notable impacto. Hasta la fecha, se han publicado once artículos en revistas internacionales a raíz de esta investigación. Asimismo, Óscar Hernando Laguna ha tenido la oportunidad de participar en diversos congresos internacionales relacionados con el tema de catálisis o los microrreactores, en los que ha realizado presentaciones exponiendo parte de los resultados obtenidos.

El acto de entrega de los premios a las mejores tesis –dotadas económicamente con 2.000 euros cada una– se celebrará en el Salón Colón del Ayuntamiento de Sevilla el 4 de diciembre de 2012, a las 11:00 h. Dicho acto estará presidido por el Alcalde de Sevilla, Juan Ignacio Zoido, y los rectores de la Universidad de Sevilla y la Universidad Pablo de Olavide.

Gold catalyst support of H2 generation that reaches a 100% CO conversion

Spanish public research organisations have developed a new gold catalyst for the Water Gas Shift Reaction (WGSR) useful for the production and/or purification of H2 for applications in fuel cells. It is a catalyst capable of working at low temperatures in the range in which the reaction is thermodynamically more efficient. It has a high stability
and ease of regeneration.

An offer for Patent Licensing



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