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Influence of graphene-based nanostructures processing routes and aspect ratio in flexural strength and fracture mechanisms of 3Y-TZP-matrix composites

Moriche, R; Guisado-Arenas, E; Muñoz-Ferreiro, C; López-Pernía, C; Morales-Rodríguez, A; Jiménez-Piqué, E; Gallardo-López, A; Poyato, R
Ceramics International, 50(11) (2024) 19217-19227

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In this work, the influence of the aspect ratio of graphene-based nanostructures (GBNs) and content on the mechanical properties of 3 mol% yttria tetragonal zirconia polycrystalline 3Y-TZP matrix composites was analysed. The influence of the dispersion method and sintering parameters on the flexural strength and elastic modulus of the composites was studied, and the fracture surfaces were characterized to determine the fracture mechanisms that occur. The results showed that small amounts of exfoliated graphene nanoplatelets, with reduced lateral size, and few layer graphene, up to 1.0 and 2.5 vol%, respectively, slightly increase the 3Y-TZP flexural strength. This has been attributed to the tortuosity of the crack propagation pathways and strengthening mechanisms. Higher contents cause a decrease in flexural strength and stiffness because of overlapped GBNs, which can promote the crack propagation. The pull-out of GBN was more significant in composites with non-exfoliated graphene nanoplatelets, where no increase on the flexural or biaxial strength was measured.

Junio, 2024 | DOI: 10.1016/j.ceramint.2024.03.021

Química de Superficies y Catálisis

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

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

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

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

Química de Superficies y Catálisis

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

Martín-Espejo, Juan Luis; Merkouri, Loukia-Pantzechroula; Gándara-Loe, Jesús; Odriozola, José Antonio
Journal of Environmental Sciences, 140 (2024) 12-23

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

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

Química de Superficies y Catálisis

Enhanced low-temperature CO2 methanation over La-promoted NiMgAl LDH derived catalyst: Fine-tuning La loading for an optimal performance

Wang, ZL; Zhang, TY; Reina, TR; Huang, L; Xie, WF; Musyoka, NM; Oboirien, B; Wang, Q
Fuel, 366 (2024) 131383

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LDH-derived Ni-based catalysts are gathering momentum due to their excellent thermal stability but their lowtemperature CO2 methanation is limited. In this study, various concentrations of La were introduced into the LDH-derived Ni-based catalysts for CO2 methanation, and the underlying mechanisms were investigated. The optimal Ni/La-0.2-MgAlOx catalyst presented a CO(2)conversion level of 69.0 % at 225 C-degrees, which is over 7 times higher than that of conventional Ni/MgAlOx. The addition of small amounts of La could significantly enhance H spillover to promote the reduction of Ni species, but the oxygen vacancy concentration became the dominant factor causing changes in low -temperature activity as the La contents continue to increase. CO2 was found to be adsorbed at the oxygen vacancies in the form of bidentate carbonates, which are more reactive under an enhanced electron -rich environment. The research offers guidance to design effective and sustainable catalysts for low -temperature CO2 methanation.

Junio, 2024 | DOI: 10.1016/j.fuel.2024.131383

Química de Superficies y Catálisis

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

Judith González-Arias, Guillermo Torres-Sempere, Miriam González-Castaño, Francisco M. Baena-Moreno, Tomás R. Reina
Journal of Environmental Sciences, 140 (2024) 69-78

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

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