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In this manuscript, the application of different nanocatalysts derived from metal oxides impregnated on the surface of the magnetite in different reaction of general interest in Organic Chemistry is described. In the First Chapter, a cobalt derived catalyst was used to study the hydroacylation reaction of azodicarboxylates with aldehydes. In the Second Chapter, a catalyst derived from copper was used to perform different reactions, including homocoupling of terminal alkynes and the subsequent hydration reaction to obtain the corresponding 2,5-disubstituted benzofurans, the reaction of alcohols and amines (or nitroarenes) to obtain the corresponding aromatic imines, the cross-dehydrogenative coupling reaction of N-substituted tetrahydroisoquinolines using deep eutectic solvents and air as final oxidant. Finally, the formation of benzofurans from aldehydes and alkynes through a tandem coupling-allenylation-cyclization process has been performed. In the Third Chapter, a bimetallic catalyst derived from nickel and copper was used to study the multicomponent reaction between benzyl bromides, sodium azide and alkynes to obtain the corresponding triazoles. In the Fourth Chapter, a catalyst derived from palladium was used in the direct arylation of heterocycles using iodonium salts. Also the synthesis of 4-aryl coumarins through the Heck arylation reaction and subsequent cyclization using the same catalyst is described. In the last Chapter, the use of different eutectic mixtures were studied as alternative media to perform in a single vessel the cyclation reaction of N-hydroxy imidoyl chlorides and alkynes, without any type of catalyst under oxidizing conditions.

Fundamental studies of heterogeneous catalysis were performed and presented in this dissertation to gain a better understanding of heterogeneous catalytic reactions at a molecular level. Surface science techniques were employed in achieving the goal. Low energy ion scattering spectroscopy (LEISS) is the main surface science technique which will be used in all the studies discussed throughout this dissertation. The main objectives of LEISS measurements are to: 1) obtain the information of surface composition of heterogeneous catalysts from the topmost layer; 2) observe the effects of reaction conditions on the surface composition of heterogeneous catalysts. The surface composition and morphology of Au-Pd clusters bimetallic model catalysts supported on SiO2 were characterized using LEISS, infrared reflection absorption spectroscopy (IRAS), and temperature programmed desorption (TPD). It is observed that relative to the bulk, the surface of the clusters is enriched in Au. Ethylene adsorption and dehydrogenation show a clear structure-reactivity correlation with respect to the structure/composition of these Au-Pd model catalysts. Fundamental studies of heterogeneous catalysis were performed and presented in this dissertation to gain a better understanding of heterogeneous catalytic reactions at a molecular level. Surface science techniques were employed in achieving the goal. Low energy ion scattering spectroscopy (LEISS) is the main surface science technique which will be used in all the studies discussed throughout this dissertation. The main objectives of LEISS measurements are to: 1) obtain the information of surface composition of heterogeneous catalysts from the topmost layer; 2) observe the effects of reaction conditions on the surface composition of heterogeneous catalysts. The surface composition and morphology of Au-Pd clusters bimetallic model catalysts supported on SiO2 were characterized using LEISS, infrared reflection absorption spectroscopy (IRAS), and temperature programmed desorption (TPD). It is observed that relative to the bulk, the surface of the clusters is enriched in Au. Ethylene adsorption and dehydrogenation show a clear structure-reactivity correlation with respect to the structure/composition of these Au-Pd model catalysts.

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In this study, a new arranged catalyst support with distinct open pore morphology has been fabricated via thermal oxidation of an FeCrAl alloy with an aim to address mass transfer limitations that conventional supports have due to their internal porosity. Subsequent characterization tests including, drop shape analysis, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy revealed that the support formed upon thermal oxidation for 1 hour at 930C, 1 hour at 960C and 2 hours at 990C embodies advantageous support characteristics. Preliminary tests were performed using palladium (active component) deposited on the new support in representative three phase hydrogenation reactions of 2-methyl-3-butyn-2-ol or 2-methyl-3-buten-2-ol. Absence of mass transfer limitations was verified for 2-methyl-3-buten-2-ol hydrogenation at 35-50C, 1200 rpm stirring speed and 0.46 MPa pressure of hydrogen in a 300 ml semi-batch reactor using ethanol as solvent. The study paves the way to the development of arranged catalysts based on FeCrAl alloy fibers for structured reactors. / Chemical Engineering

El Capítulo I trata la actual crisis energética y hace una breve introducción sobre el uso del hidrógeno como vector energético, mencionando los diferentes métodos que pueden utilizarse para la producción/purificación de hidrógeno a partir de recursos renovables. También incluye una breve descripción del papel que puede jugar la biomasa como alternativa a los combustibles fósiles, y su conversión a biocombustibles y productos químicos de valor añadido. El reformado catalítico de glicerol para la producción de gas de síntesis o corrientes ricas en hidrógeno se presenta como una ruta potencial, alternativa y prometedora que ha llamado la atención en los últimos años. Esta reacción se suele llevar a cabo sobre catalizadores basados en metales soportados en materiales estables. En el Capítulo II se estudia el efecto de la adición de Sn sobre las propiedades y la estabilidad de catalizadores de Pt soportado en carbón en la reacción de reformado glicerol en fase gas. Para ello, se preparó y caracterizó una serie de catalizadores con diferentes relaciones atómicas Pt/Sn. El alto precio de los metales nobles motiva la búsqueda y empleo de metales más baratos y abundantes que también tengan un buen comportamiento catalítico en esta reacción. Por ello, en el Capítulo III se emplearon catalizadores basados en Ni promovidos por óxido de cerio para el reformado de glicerol. Por otro lado, se hace necesario optimizar el uso del CeO2 debido a su limitada disponibilidad y sus extensas aplicaciones. Así, en este trabajo se dispersó CeO2 sobre carbón activado de alta área superficial, obteniendo gran superficie de óxido de cerio expuesta al mismo tiempo que se redujo su consumo. También se estudió el efecto de la presencia de estaño en estos catalizadores. Se obtienen diversas ventajas al realizar el reformado de glicerol en fase líquida. Así, se obtienen corrientes más ricas en H2 con menor cantidad de CO. Esto se debe a las moderadas temperaturas y altas presiones empleadas, que favorecen la reacción de desplazamiento del gas de agua. También se suprime la necesidad de evaporar la disolución acuosa de glicerol, por lo que el requerimiento energético es menor y se evitan reacciones indeseadas de descomposición térmica. De este modo, en el Capítulo IV se hace un estudio comparativo sobre las propiedades catalíticas de tres muestras, Pt/CeO2, Ni/CeO2 y Pt-Ni/CeO2, en la reacción de reformado de glicerol en fase líquida. Además, se empleó espectroscopía de reflectancia total atenuada in situ para obtener información relevante sobre los intermedios de reacción y la evolución de los catalizadores durante la reacción, permitiendo así proponer los caminos de reacción más probables. Para obtener corrientes de hidrógeno suficientemente puro para su uso es las pilas de combustible, la corriente obtenida después del reformado debe ser procesada en varias etapas, entre las que se incluyen la eliminación del CO por medio de la reacción de desplazamiento del gas de agua (water-gas shift, WGS). En el Capítulo V se estudia la serie de catalizadores de Ni promovidos por CeO2 soportados en carbón en la reacción de desplazamiento del gas de agua a bajas temperaturas. Para este estudio se emplearon diferentes corrientes de entrada, tanto ideales (sólo CO y H2O) como reales (CO, CO2, H2 y H2O). Por último, en el Capítulo VI, el catalizador que presentó mejor comportamiento catalítico en el apartado anterior fue estudiado en mayor profundidad, relacionando sus propiedades con la actividad catalítica, sometiéndolo finalmente a ensayos de estabilidad en condiciones más demandantes.

No description available.

No description available.

Para que o processo de produção de biodiesel se torne auto-sustentado, ou seja, socialmente, ecologicamente e economicamente viáveis, alguns aspectos químicos ainda precisam ser estudados e aprimorados. Dentre estes, dois são relevantes: alta eficiência no rendimento da reação e o uso de catalisadores de maneira ecologicamente responsável. Para atendê-los é necessário o uso de catalisadores eficientes, robustos, e facilmente manipuláveis com baixo impacto ao meio ambiente. Para atingir tais objetivos, foi estudado o uso de diferentes catalisadores heterogêneos e métodos analíticos para a determinação do rendimento e caracterização dos produtos formados pela reação de esterificação do ácido oléico, principal componente do óleo de soja, utilizando-se o Etanol e um catalisador heterogêneo à base de sílica, o ormosil. A reação de transesterificação do óleo de soja também foi estudada utilizando-se o Etanol e catalisadores ácidos homogêneos e heterogêneos. / For the biodiesel production process to become self-sustaining, namely, sociably, environmentally and economically viable some chemical aspects have to be studied and improved. Among all of its aspects, two of them are relevant: high efficiency on the reaction yield and the use of catalysts in an environmentally responsible way. To attend to these, the use of, robust and easily manipulated with low environmental impact efficient catalysts is necessary. In order to attain to these objectives, the use of different heterogeneous catalysts and analytical methods for the determination of the yield and characterization of the products formed by the esterification reaction of oleic acid, the main component of soy bean oil, using ethanol and a silica based heterogeneous catalyst, the ormosil, was be studied. The transesterification reaction of the soy oil was also studied, making use of ethanol and homogeneous and heterogeneous acid catalysts.

It is proposed that an integrated ammonia-PEM fuel cell could unlock the potential of ammonia to act as a high capacity chemical hydrogen storage vector and enable renewable energy to be delivered eectively to road transport applications. Catalysts are developed for low temperature ammonia decomposition with activity from 450 K (ruthenium and cesium on graphitised carbon nanotubes). Results strongly suggest that the cesium is present on the surface and close proximity to ruthenium nanoparticles and that it produces activity in ruthenium by donation of electrons. The activity of sustainable cobalt for ammonia decomposition is shown to be a function of particle size and is more active on microporous carbon supports compared to mesoporous ones. Unlike ruthenium, activity for cobalt was not inuenced by the degree of surface graphitic nature and cobalt supported on microporous carbon approached the activity of ruthenium on the same support. In accordance with the sustainable objectives of this thesis, a case-study on the sustainability of ammonia as a sustainable hydrogen storage vector was undertaken. In this scheme, hydrogen produced from renewable electricity by electrolysis is con- verted to ammonia by the Haber-Bosch process and then converted back to deliver pure hydrogen at the point of use. The energy eciency and carbon footprint fell short of targets set by the US Department of Energy and the UK Department for Transport, the biggest impact was the production of hydrogen by electrolysis and not the Haber-Bosch process which accounts for only 9 % of total energy losses. To assess the feasibility of the ammonia-PEM fuel cell, a conceptual design was un- dertaken to quantify the palladium membrane size and catalyst quantity required for a typical road transport vehicle. The predicted quantity of palladium was excessive and future work must consider improvements to membrane technology.