Obtención de hidrógeno a partir de biogás mediante catalizadores derivados de hidrotalcita

270 páginas, 78 tablas y 135 figurasEl objetivo de este trabajo ha sido el desarrollo de catalizadores derivados de la estructura hidrotalcita, que permitan la obtención de hidrógeno a partir de biogás mediante la reacción de reformado de metano con dióxido de carbono. Se han considerado tres variables a estudiar en el diseño de catalizadores: el contenido en lantano, la temperatura de calcinación y la relación molar Mg/Al. Tanto los precursores, como los catalizadores sintetizados a partir de ellos, fueron caracterizados por diversas técnicas físico-químicas para determinar la influencia que cada una de esas variables ejerce sus propiedades composicionales, texturales y estructurales. Los catalizadores fueron evaluados en la reacción de reformado de metano con dióxido de carbono en diversas condiciones de reacción, estudiando el comportamiento de cada uno de ellos en función de sus propiedades físico-químicas. Con el catalizador que presentó mejores prestaciones en cuanto a actividad, selectividad y estabilidad (LaHT3), se llevó a cabo un estudio de la influencia de diversas variables de operación (velocidad espacial, temperatura de reacción, composición de la alimentación) con objeto de optimizar las condiciones de reacción. Finalmente, se llevaron a cabo ensayos de larga duración y posterior caracterización para evaluar la estabilidad y resistencia a la desactivación.Peer reviewe

Формирование модели системы воспитания в школе на основе интеграции общего и дополнительного образования (из опыта работы)

Trabajo presentado en la European Hydrogen Energy Conference - EHEC, celebrada en Sevilla (España) del 12 al 14 de mayo de 2014.There is a growing interest in the development of power sources that use renewable fuels and reduce emission of pollutants. This interest is justified by the heightening concern about environmental degradation, energy security as well as the possible exhaustion of the fossil fuel resources. One example is the use of biogas (mainly composed by CH4 and CO2) which is generated from anaerobic digestion of sewage or wastewater [1]. In order to produce hydrogen from this renewable gas, it is necessary a reforming step. There are two alternatives: 1) carbon dioxide reforming (DR: CH4 + CO2 2H2 + 2CO) and 2) steam reforming (SR: CH4 + H2O 3H2 + CO). The first reaction has two drawbacks: the deactivation of the catalyst due to carbon deposition [2] and the participation of reverse water-gas-shift (RWGS: H2 + CO2 H2O + CO) which decreases the amount of the produced hydrogen. On the other hand, steam reforming is the most extended way to produce hydrogen from CH4, but it is necessary to eliminate the CO2 from the feed. Since previous studies [3] had reported good results when La-promoted catalysts, obtained from hydrotalcite-like precursor calcination, were used in dry reforming of methane, this catalyst will be used for these tests. The aim of this work is to study the influence of H2O addition over dry reforming and the addition of CO2 over steam reforming using a La-promoted catalyst obtained from hydrotalcite-like precursor.Financial support from Comunidad de Madrid (DIVERCELCM, S2009/ENE-1475) is gratefully acknowledged.Peer Reviewe

Photoactive nano-confined Pt in titania nanotubes (Pt-TiNT) via microwave-assisted flow synthesis

Pt-TiNT with PtO nanoparticles dispersed within the lumen and interlayer spaces of titania nanotubes (TiNT) were prepared by a new process involving titanate nanosheets (TiNS) synthesis in an optimized microwave-assisted flow reactor, followed by ion-exchange with a Pt precursor, before triggering the titanate layer rolling to trap the Pt precursor clusters inside the titania nanotubes, followed by a thermal treatment. TEM, XRD, and Raman analyses confirm the total conversion of TiO2 into TiNS in 15 min at 120 °C and 4 bar, and the TiNS transformation into 181 nm-long TiNT with 10 and 6 nm outer and inner diameter, respectively. The 2% Pt-TiNT comprises 0.7 nm PtO clusters (according to XPS), causing slight distortions of the interlayer spaces, while a few larger 2–3 nm Pt clusters reside within the lumen. As a result, Pt-TiNT is 14-fold more active than TiNT for visible light (400–780 nm) photocatalytic oxidation of diclofenac under 2136 μW·cm−2 irradiation, and>1000-fold better than the uncatalyzed photoconversion reaction under 100 mW·cm−2 artificial solar lighting. In addition, nano-confinement of PtO clusters narrowed the bandgap of the TiNT, which, combined with its excellent absorptivity to harvest light, allowed a broader spectral range of photon energies to activate the photocatalyst. © 2023 Elsevier B.V.This work is supported by the Horizon 2020 BIORIMA project and the Hong Kong Research Grant Council E-HKUST601/17 and in part by the Project of Hetao Shenzhen-Hong Kong University of Science and Technology Innovation Cooperation Zone (HZQB-KCZYB-2020083). Dr. Y.J. Luo stay at the Instituto de Cat´alisis y Petroleoquímica is supported by the HKUST Overseas Research Award. Finally, the authors acknowledge the support of the Central Facilities of the Hong Kong University of Science and Technology including the Material Characterization and Preparation Facility (MCPF) and the Environmental Central Facility (ENVF).Supplementary data to this article can be found online at https://doi. org/10.1016/j.cej.2023.143254Peer reviewe

Lifestyle Evolution And Peroxidase Diversity In Agaricales As Revealed By Comparative Genomics

Descripción de 1 páginas de la comunicación oral presentada en Oxizymes2022 10th edition of the international “Oxizymes” meeting. Siena, Italy, July 5-8, 2022Basidiomycetes of the class Agaricomycetes have developed complex enzymatic machineries that allow them to decompose plant polymers, including lignin. Within this group, saprotrophic Agaricales are characterized by an unparalleled diversity of habitats and lifestyles in comparison with fungi from other orders. With the aim of shedding light on the evolution of lignocellulose-decaying lifestyles in Agaricales we conducted a comparative analysis of 52 Agaricomycetes genomes [1]. This study revealed that Agaricales possess a large diversity of hydrolytic and oxidative enzymes. Surprisingly, computer-assisted gene-family evolution analysis of these enzymes revealed that a few oxidoreductase families showed significantly higher evolutionary rates. Based on these gene families we reconstructed the lifestyles of the ancestors that led to the extant lignocellulose-decomposing Agaricomycetes. According to this, we determined that changes in the oxidative enzymatic toolkit of ancestral Agaricales correlate with the evolution of their ability to grow not only on wood, but also on leaf and grass litter and decayed wood. In this context, the aboye families were analyzed and special attention was paid to peroxidases as a central component of the enzymatic toolkit of saprotrophic Agaricomycetes responsible for lignin degradation. We identified a widespread presence of new ligninolytic peroxidase types in Agaricales, some of them not previously identified in this order, and others also not found in woodrottingPolyporales and other orders of Agaricomycetes. Peroxidase evolution was analyzed in Agaricomycetes by ancestral sequence reconstruction and several major evolutionary pathways were unveiled. The study of the newly identified peroxidases will provide insight into their role in the lignin degradation process. In fact, these studies have already been initiated with the expression and characterization of the first lignin peroxidase identified in Agaricales. [1] Ruiz-Dueñas FJ, Barrasa JM, Sánchez-García M, Camarero S, Miyauchi S, Serrano A, et al., 2021, Mol Biol Evol, 38, 1428-1446.Projects/contracts BI02017-86559-R, BI02015-7369-JIN, AGL2014-55971-R, NSFgrant-1457721 , CEFOX-031 B0831 S, PIE-201620E081 , ANR-11-LABX-0002-01 , US-DOE-DE-AC02-05CH11231N

Influence of the operating parameters over dry reforming of methane to syngas

The influence of operating parameters over dry reforming of methane reaction was evaluated using a Ni-based catalyst obtained after calcination of a hydrotalcite-like precursor. The studied variables were mass to flow ratio (W/F), reaction temperature and CO2/CH4 ratio. Maximum methane and carbon dioxide conversions were achieved at W/F ratios above 0.21 g h L−1. The higher the W/F ratio was, the lower amount of water was formed, which led to a higher H2/CO ratio. The increase in reaction temperature produced an increase in conversions. Water concentration in the outlet stream showed a maximum at 600 °C. At this temperature, reverse water–gas-shift reaction (RWGS) was favoured because it is endothermic. However, steam reforming and carbon gasification were also favoured and they consumed great part of the water produced. CO2/CH4 ratios above 1 led to a higher CH4 conversion but selectivity to hydrogen decreased because RWGS reaction was favoured. When CO2/CH4 was below unity, CH4 conversion decreased but less amount of water was produced so a higher H2 selectivity was achieved. The catalyst exhibited good stability over dry reforming of methane under all the tested conditions, which may be ascribed to its high basicity. This property improved CO2 adsorption and then RWGS reaction and carbon gasification.Financial support from Comunidad de Madrid (DIVERCEL-CM Program, S-2009/ENE-1475) and Ministerio de Economía y Competitividad (MAT2010-20846) is gratefully acknowledged.Peer Reviewe

Long-term stability test of Ni-based catalyst in carbon dioxide reforming of methane

A La-NiMgAlO catalyst, obtained after calcination of a hydrotalcite precursor, was evaluated in dry reforming of methane at 650 and 700 °C and compared with a previous test performed at 750 °C. At 700 °C the catalyst showed no sign of deactivation during 200 h, while it deactivated slowly afterwards. However, at 650 °C conversion decay was detected from the beginning of the test. In both tests, CH4 and CO2 conversion were higher than thermodynamic equilibrium estimation which suggests the participation of other reactions such as methane decomposition or steam reforming of methane. The occurrence of reverse water-gas-shift reaction (RWGS) was responsible for the H2/CO ratios below unity and for the higher CO2 conversion compared with CH4. Used catalysts were characterized by several techniques (TEM, 27Al MAS NMR, XRD, TPO and Raman spectroscopy) in order to study catalyst structure and to establish whether carbon was deposited and its nature. Ni particle diameter increased when reaction temperature decreased but no differences in 27Al MAS NMR or XRD results were observed. A higher coke deposition rate was detected when the temperature was increased. At 700 and 650 °C carbon species were mainly graphite ribbons, coating carbon and graphite nanoencapsulates, while at 750 °C there were multi-walled carbon nanotubes (MWCNT), fibres and graphite ribbons. The deactivation of the catalysts tested at 650 and 700 °C can be related to: (i) the presence of coating carbon, graphite nanoencapsulates and Ni particles embedded inside the carbon nanotubes (CNT); (ii) partial sintering and (iii) a lower hydrogen production what makes that carbon transportation away the surface was less favoured.Financial support from Comunidad de Madrid (DIVERCEL-CM Programme, S-2009/ENE-1475) is gratefully acknowledged.Peer Reviewe

Síntesis de catalizadores activos a la reacción de reformado seco de CH4: Influencia del pH

Trabajo presentado en el Congreso de la Sociedad Española de Catálisis SECAT 13, celebrado en Sevilla (España) del 26 al 28 de junio de 2013.Los catalizadores más empleados en la reacción de reformado seco de metano son los que emplean Ni como fase activa pero presentan el inconveniente de desactivarse por formación de carbono [1]. Catalizadores derivados del precursor tipo hidrotalcita han mostrado mejoras significativas en la estabilidad en esta reacción puesto que presentan alta dispersión de las partículas metálicas, alta área superficial y son básicos lo que favorece la quimisorción de CO2 [2]. Para mejorar la resistencia a la formación de carbono, se adicionó La que aumenta la dispersión de níquel, mejora la adsorción de CO2 y retrasa la sinterización de la fase activa [3]. Existen diversos métodos de preparación de hidrotalcitas, siendo la coprecipitación el método más empleado [4]. Las condiciones de síntesis más comúnmente utilizadas son pH entre 7 y 10 y temperaturas entre 60 y 80 ºC [3]. El objetivo de este trabajo es estudiar la influencia del pH de síntesis sobre la actividad y estabilidad de un catalizador derivado de la estructura hidrotalcita en la reacción de reformado seco de metano.Este trabajo ha sido financiado por la Comunidad de Madrid (Programa DIVERCEL-CM, S2009/ENE-1475).Peer Reviewe

Highly stable and active catalyst for hydrogen production from biogas

A La-NiMgAlO catalyst, obtained after calcination of a hydrotalcite precursor, was evaluated in dry reforming of methane. The catalyst showed no sign of deactivation during a 300 h test. CH4 and CO2 conversion were higher than thermodynamic equilibrium estimation which suggests the participation of other reactions. Used catalyst was characterized by several techniques (TPO, XPS and Raman spectroscopy and SEM and TEM microscopy) in order to establish whether carbon was deposited and its nature. Two different types of carbon were present: carbon nanotubes (CNTs) and carbon nanofibres (CNFs). These filamentous carbons were well-crystallize but with many structural defects, which can increase the resistivity to fracture and therefore prevent the encapsulation of active sites. In addition, graphite can act as a CHx collector, limiting the deactivation process. The small Ni particles diameter, together with its broad distribution, seems to have also a beneficial effect on the catalytic performance.Financial support from Comunidad de Madrid (DIVERCEL-CM Program, S-2009/ENE-1475) and Ministerio de Economía y Competitividad (MAT2010-20846) is gratefully acknowledged.Peer Reviewe

Hydrogen production from biogas: Influence of calcination temperatrue over catalytic performance

Trabajo presentado en EuropaCat: 11th European Congress on Catalysis, celebrado en Lyon (Francia) del 1 al 6 de septiembre de 2013.Peer Reviewe

Producción de hidrógenon a partir de reformado combinado de biogás

Trabajo presentado en el Congreso Iberoamericano de Hidrógeno y Pilas de Combustible, celebrado en Barcelona (España) del 15 al 17 de octubre de 2014.[EN] The aim of this work was to study the influence of H20/CH4 ratio over the activity and stability of a La-promoted hydrotalcite-derived catalyst in biogas reforming, as a pathway to transform biogas into hydrogen. Biogas composition was CH4/C02 de 2.33. Catalytic tests were performed at 700 ºC and a W/F ratio of 0.25 mg ·min·cm-3. Four tests were performed in which H20/CH4 ratio were changed from O to 1.6. Water addition led to an increase of activity (measured as the increase of methane conversion). None of the catalysts showed any sign of deactivation. H2/CO ratio increased significantly when water was added. lt may be due to the fact that H20 also contribute to H2 formation . Used catalysts where characterized by TPO-MS and TEM microscopy. When H20/CH4 ¿0,8 no carbon deposits were detected, what suggested that ali the formed carbon was gasified. Ni particle size was 3-4 nm in ali cases which could explain the good stability of the catalysts under these sever conditions.[ES] En este trabajo se ha estudiado la influencia de la relación H20/CH4 sobre la actividad y estabilidad de un catalizador promovido por lantano y derivado del precursor hidrotalcita (La-NiMgAlO ) en la reacción de reformado de biogás, como vía para obtener hidrógeno de una fuente renovable. El biogás testado tiene una composición CH4/C02 de 2,33. Los ensayos se realizaron a 700 ºC y una relación W/F = 0,25 mg ·min·cm-3 y se mantuvieron durante 5h. Se realizaron 4 ensayos en los que se varió la relación H20/CH4 desde O a 1,6. La adición de agua provocó un aumento de la actividad (medida como el aumento en la conversión de metano) y una menor formación de carbono. En ninguno de los experimentos se detectó desactivación . La relación H2/CO aumentó de forma notable al adicionar H20 debido a que en ese caso la fuente de H2 no sería únicamente el CH4 si no también el H20 . Los catalizadores usados se caracterizaron mediante TPO-MS y microscopía TEM. Cuando la relación H20/CH4 ¿0,8 no se detectaron depósitos carbonosos, lo que indica que todo el carbono formado por la descomposición del metano es gasificado . El tamaño de partícula de Ni fue en todos los casos de 3-4 nm lo que podría explicar la buena estabilidad observada.Este trabajo ha sido financiado por la Comunidad de Madrid (Programa DIVERCEL-CM, S2009/ENE-1475).Peer Reviewe