Examinando por Autor "Coronado, J.M."

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Catalytic hydrodeoxygenation of m-cresol over Ni2P/hierarchical ZSM-5
(Elsevier B.V., 2018) Berenguer, A.; Bennett, J.A.; Hunns, J.; Moreno, I.; Coronado, J.M.; Lee, A.F.; Pizarro, P.; Wilson, K.; Serrano, D.P.
Bifunctional catalysts comprising Ni2P supported over a hierarchical ZSM-5 zeolite (h-ZSM-5) were synthesized and applied to the hydrodeoxygenation (HDO) of m-cresol, a model pyrolysis bio-oil compound. Surface and bulk characterization of Ni2P/h-ZSM-5 catalysts by XRD, TEM, DRIFTS, TPR, porosimetry and propylamine temperature-programmed desorption reveal that Ni2P incorporation modifies the zeolite textural properties through pore blockage of the mesopores by phosphide nanoparticles, but has negligible impact of the micropore network. Ni2P nanoparticles introduce new, strong Lewis acid sites, whose density is proportional to the Ni2P loading, accompanied by new Brönsted acid sites attributed to the presence of P–OH moieties. Ni2P/h-ZSM-5 is ultraselective (97%) for m-cresol HDO to methylcyclohexane, significantly outperforming a reference Ni2P/SiO2 catalyst and highlighting the synergy between metal phosphide and solid acid support. m-Cresol conversion was proportional to Ni2P loading reaching 80 and 91% for 5 and 10 wt% Ni respectively. Turnover frequencies for m-cresol HDO are a strong function of Ni2P dispersion, evidencing structure sensitivity, with optimum activity observed for 4 nm particles.
Engineering the acidity and accessibility of the zeolite ZSM-5 for efficient bio-oil upgrading in catalytic pyrolysis of lignocellulose
(Royal Society of Chemistry, 2018) Hernando, H.; Hernández-Gimenez, A.M.; Ochoa-Hernández, C.; Bruijnincx, P.C.A.; Houben, K.; Baldus, M.; Pizarro, P.; Coronado, J.M.; Fermoso, J.; Cejka, J.; Weckhuysen, B.M.; Serrano, D.P.
The properties of the zeolite ZSM-5 have been optimised for the production and deoxygenation of the bio-oil∗ (bio-oil on water-free basis) fraction by lignocellulose catalytic pyrolysis. Two ZSM-5 supports possessing high mesopore/external surface area, and therefore enhanced accessibility, have been employed to promote the conversion of the bulky compounds formed in the primary cracking of lignocellulose. These supports are a nanocrystalline material (n-ZSM-5) and a hierarchical sample (h-ZSM-5) of different Si/Al ratios and acid site concentrations. Acidic features of both zeolites have been modified and adjusted by incorporation of ZrO2, which has a significant effect on the concentration and distribution of both Brønsted and Lewis acid sites. These materials have been tested in the catalytic pyrolysis of acid-washed wheat straw (WS-ac) using a two-step (thermal/catalytic) reaction system at different catalyst/biomass ratios. The results obtained have been assessed in terms of oxygen content, energy yield and composition of the produced bio-oil∗, taking also into account the selectivity towards the different deoxygenation pathways. The ZrO2/n-ZSM-5 sample showed remarkable performance in the biomass catalytic pyrolysis, as a result of the appropriate combination of accessibility and acidic properties. In particular, modification of the zeolitic support acidity by incorporation of highly dispersed ZrO2 effectively decreased the extent of secondary reactions, such as severe cracking and coke formation, as well as promoted the conversion of the oligomers formed initially by lignocellulose pyrolysis, thus sharply decreasing the proportion of the components not detected by GC-MS in the upgraded bio-oil∗
The role of the surface acidic/basic centers and redox sites on TiO2 in the photocatalytic CO2 reduction
(Elsevier B.V., 2022) Collado, L.; Reñones, P.; Fermoso, J.; Fresno, F.; Garrido, L.; Pérez-Dieste, V.; Escudero, C.; Hernández-Alonso, M.; Coronado, J.M.; Serrano, D.P.; de la Peña O´Shea, V.A.
The development of sustainable processes for CO2 reduction to fuels and chemicals is one of the most important challenges to provide clean energy solutions. The use of sunlight as renewable energy source is an interesting alternative to power the electron transfer required for artificial photosynthesis. Even if redox sites are mainly responsible for this process, other reactive acidic/basic centers also contribute to the overall reaction pathway. However, a full understanding of the CO2 photoreduction mechanism is still a scientific challenge. In fact, the lack of agreement on standardized comparison criteria leads to a wide distribution of reported productions, even using the same catalyst, which hinders a reliable interpretation. An additional difficulty is ascertaining the origin of carbon-containing products and effect of surface carbon residues, as well as the reaction intermediates and products under real dynamic conditions. To determine the elusive reaction mechanism, we report an interconnected strategy combining in-situ spectroscopies, theoretical studies and catalytic experiments. These studies show that CO2 photoreduction productions are influenced by the presence of carbon deposits (i.e. organic molecules, carbonates and bicarbonates) over the TiO2 surface. Most importantly, the acid/base character of the surface and the reaction medium play a key role in the selectivity and deactivation pathways. This TiO2 deactivation is mainly initiated by the formation of carbonates and peroxo- species, while activity can be partially recovered by a mild acid washing treatment. We anticipate that these findings and methodology enlighten the main shadows still covering the CO2 reduction mechanism, and, most importantly, provide essential clues for the design of emergent materials and reactions for photo(electro)catalytic energy conversion.
Unravelling the effect of charge dynamics at the plasmonic metal/semiconductor interface for CO2 photoreduction
(Nature Publishing Group, 2018) Collado, L.; Reynal, A.; Fresno, F.; Barawi, M.; Escudero, C.; Pérez-Dieste, V.; Coronado, J.M.; Serrano, D.P.; Durrant, J.R.; de la Peña O´Shea, V.A.
Sunlight plays a critical role in the development of emerging sustainable energy conversion and storage technologies. Lightinduced CO2 reduction by artificial photosynthesis is one of the cornerstones to produce renewable fuels and environmentally friendly chemicals. Interface interactions between plasmonic metal nanoparticles and semiconductors exhibit improved photoactivities under a wide range of the solar spectrum. However, the photo-induced charge transfer processes and their influence on photocatalysis with these materials are still under debate, mainly due to the complexity of the involved routes occurring at different timescales. Here, we use a combination of advanced in situ and time-resolved spectroscopies covering different timescales, combined with theoretical calculations, to unravel the overall mechanism of photocatalytic CO2 reduction by Ag/TiO2 catalysts. Our findings provide evidence of the key factors determining the enhancement of photoactivity under ultraviolet and visible irradiation, which have important implications for the design of solar energy conversion materials.