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<p>The purpose of this work was to design and to develop a high performance catalyst for the production of hydrogen from reforming of crude ethanol and also, to develop the kinetics and reactor model of crude ethanol reforming process. Crude ethanol reforming is an endothermic reaction of ethanol and other oxygenated hydrocarbons such as (lactic acid, glycerol and maltose) with water present in fermentation broth to produce hydrogen (H2) and carbon dioxide (CO2). Ni/Al2O3 catalysts were prepared using different preparation methods such as coprecipitation, precipitation and impregnation methods with different Ni loadings of 10 25 wt.%, 10-20 wt.%, and 10-20 wt.% respectively.</p><p>All catalysts were characterised by thermogravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), (including X-ray line broadening), temperature programmed reduction (TPR), BET surface area measurements, pore volume and pore size distribution analysis. TG/DSC analyses for the uncalcined catalysts showed the catalyst were stable up from 600oC. XRD analyses showed the presence of NiO, NiAl2O4 and Al2O3 species on the calcined catalysts whereas Ni, NiAl2O4, and Al2O3 were present on reduced catalysts. BET surface area decreased and average pore diameter reached a maximum and then decreased as the Ni loading increased. The temperature programmed reduction profiles showed peaks corresponding to the reduction of NiO between 400-600oC and reduction of NiAl2O4 between 700-800oC. Catalyst screening was performed in a micro reactor with calcination temperature, reaction temperature and the ratio of catalyst weight to crude ethanol flow rate (W/Fcrude-C2H5OH) of 600 oC, 400oC and 0.59 h respectively. Maximum crude-ethanol conversion of 85 mol% was observed for catalyst with 15wt% Ni loading prepared by precipitation method (PT15), while maximum hydrogen yield (= 4.33 moles H2 / mol crude-ethanol feed) was observed for catalyst with 15wt% Ni loading prepared by coprecipitation (CP15). </p><p>Performance tests were carried out on (CP15) in which variables such as space velocity (WHSV) 1.68h-1to 4.68h-1, reduction temperature 400 to 600oC and reaction temperature 320 to 520 oC, were changed for optimum performance evaluation of the selected catalyst. The catalyst deactivated over first three hours of 11 hours time-on-stream (TOS) before it stabilized, the reaction conditions resulted in a drop of ethanol conversion from 80 to 70mol%.</p><p>The compounds identified in the liqiud products in all cases were ethanoic acid, butanoic acid, butanal, propanone, propanoic acid, propylene glycol and butanedioic acid. The kinetic analysis was carried out for the rate data obtained for the reforming of crude ethanol reaction that produced only hydrogen and carbon dioxide. These data were fitted to the power law model and Eldey Rideal models for the entire temperature range of 320-520 oC. The activation energy found were 4405 and 4428 kJ/kmol respectively. Also the simulation of reactor model showed that irrespective of the operating temperature, the benefit of an increase in reactor length is limited. It also showed that by neglecting the axial dispersion term in the model the crude ethanol conversion is under predicted. In addition the beneficial effects of W/FAO start to diminish as its value increases (i.e. at lower flow rates).

<p>The purpose of this work was to design and to develop a high performance catalyst for the production of hydrogen from reforming of crude ethanol and also, to develop the kinetics and reactor model of crude ethanol reforming process. Crude ethanol reforming is an endothermic reaction of ethanol and other oxygenated hydrocarbons such as (lactic acid, glycerol and maltose) with water present in fermentation broth to produce hydrogen (H2) and carbon dioxide (CO2). Ni/Al2O3 catalysts were prepared using different preparation methods such as coprecipitation, precipitation and impregnation methods with different Ni loadings of 10 25 wt.%, 10-20 wt.%, and 10-20 wt.% respectively.</p><p>All catalysts were characterised by thermogravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), (including X-ray line broadening), temperature programmed reduction (TPR), BET surface area measurements, pore volume and pore size distribution analysis. TG/DSC analyses for the uncalcined catalysts showed the catalyst were stable up from 600oC. XRD analyses showed the presence of NiO, NiAl2O4 and Al2O3 species on the calcined catalysts whereas Ni, NiAl2O4, and Al2O3 were present on reduced catalysts. BET surface area decreased and average pore diameter reached a maximum and then decreased as the Ni loading increased. The temperature programmed reduction profiles showed peaks corresponding to the reduction of NiO between 400-600oC and reduction of NiAl2O4 between 700-800oC. Catalyst screening was performed in a micro reactor with calcination temperature, reaction temperature and the ratio of catalyst weight to crude ethanol flow rate (W/Fcrude-C2H5OH) of 600 oC, 400oC and 0.59 h respectively. Maximum crude-ethanol conversion of 85 mol% was observed for catalyst with 15wt% Ni loading prepared by precipitation method (PT15), while maximum hydrogen yield (= 4.33 moles H2 / mol crude-ethanol feed) was observed for catalyst with 15wt% Ni loading prepared by coprecipitation (CP15). </p><p>Performance tests were carried out on (CP15) in which variables such as space velocity (WHSV) 1.68h-1to 4.68h-1, reduction temperature 400 to 600oC and reaction temperature 320 to 520 oC, were changed for optimum performance evaluation of the selected catalyst. The catalyst deactivated over first three hours of 11 hours time-on-stream (TOS) before it stabilized, the reaction conditions resulted in a drop of ethanol conversion from 80 to 70mol%.</p><p>The compounds identified in the liqiud products in all cases were ethanoic acid, butanoic acid, butanal, propanone, propanoic acid, propylene glycol and butanedioic acid. The kinetic analysis was carried out for the rate data obtained for the reforming of crude ethanol reaction that produced only hydrogen and carbon dioxide. These data were fitted to the power law model and Eldey Rideal models for the entire temperature range of 320-520 oC. The activation energy found were 4405 and 4428 kJ/kmol respectively. Also the simulation of reactor model showed that irrespective of the operating temperature, the benefit of an increase in reactor length is limited. It also showed that by neglecting the axial dispersion term in the model the crude ethanol conversion is under predicted. In addition the beneficial effects of W/FAO start to diminish as its value increases (i.e. at lower flow rates).

Biomass gasification offers the chance to produce carbon neutral, renewable fuels. One of the main problems facing the commercialization of biomass gasification technology is the presence of large quantities of methane and carbon dioxide in the biogas. Catalytic reforming of these wastes allows for effective utilization of biomass derived syngas. In most reforming studies, impregnation methods are the primary synthesis technique. Impregnation methods often lead to poor dispersion and are un-reproducible from batch to batch. In the development of a novel catalyst for reforming applications, another preparation method is implemented, controlled adsorption (CA). Ni/Al2O3 and Co/Al2O3 prepared by CA are compared against catalysts that were prepared by a more traditional method, dry impregnation (DI). It is found that controlling the metal deposition provides catalysts with higher dispersion and consequently higher activity for methane dry reforming. NiAl2O4 catalysts prepared by Pechini synthesis were also studied for catalytic conditioning of biomass derived syngas. Physicochemical characterization revealed unique structural properties, indicated a high degree of mobility of nickel in the aluminate structure, and demonstrated the regeneration properties of nickel aluminates under harsh reaction conditions, which will be important at extended reaction times when catalyst regeneration becomes necessary. Fourfold coordinated nickel species are believed to be responsible for high, stable methane dry reforming activity and metallic nickel is believed to be the active site that allows for high, stable conversion during methane dry reforming.

Découverte en 1902, la méthanation du C02 reçoit un intérêt grandissant pour son application aux procédés de stockage d'énergie électrique nécessaires au développement des énergies renouvelables. Sa mise en œuvre requiert le développement de réacteurs catalytiques innovants répondant au cahier des charges de cette application. Ces travaux sont dédiés à l'étude et l'optimisation de trois types de réacteurs-échangeurs conçus au cours de cette thèse :-un réacteur à lit fixe annulaire, -un réacteur à lit fixe milli-structuré et un réacteur à mousses métalliques supports de catalyseur. Leurs performances globales sont déterminées expérimentalement. La désactivation du catalyseur est étudiée et ses causes identifiées. Une modélisation des trois réacteurs permet la simulation de leur fonctionnement. Les propriétés hydrodynamiques et thermiques de leurs structures internes et les vitesses de réaction sont caractérisées expérimentalement. Les résultats numériques des simulations sont comparés aux expériences et complètent l'étude du comportement des réacteurs. Les modèles identifiés permettent finalement d'étudier les limites et les potentiels de ces réacteurs. / Discovered in 1902, the C02 methanation is getting a growing interest for its application to electricity storage processes needed for the development of renewable anergies. lts implementation requires the development of innovative catalytic reactors compatible with the specifications of this application. The present work focuses on the study of three reactor-exchangers designed during this thesis: - an annular fixed bed reactor, a milli-structured fixed bed reactor and a reactor which uses metallic foams as catalyst carriers. Their global performances are experimentally evaluated. The catalyst deactivation is studied and its causes identified. A modeling of these three reactors allows the simulation of their behavior. The hydrodynamic and thermal properties of their internai structure and the reaction kinetics are experimentally characterized . The numerical results of the simulations are compared to the experimental data and complete the analysis of the reactors behavior.The identified models are finally used to study the limits and the potentialities of the reactors.

O uso do hidrogênio, como vetor energético, representa uma opção promissora a fim de se reduzir a dependência dos combustíveis fósseis e controlar a emissão de poluentes na atmosfera. Atualmente, uma das rotas mais propícias para produção de hidrogênio envolve a reação de reforma a vapor de álcoois utilizando-se catalisadores de níquel suportados em alumina. O níquel é amplamente utilizado em catálise devido ao baixo custo e à elevada atividade para ruptura da ligação C-C. A alumina, por sua vez, promove maior dispersão do metal ativo devido aos valores elevados de área superficial das estruturas cristalinas de transição, sobretudo da fase gama, característica esta diretamente relacionada às condições de síntese. A incorporação de lantânia, como aditivo, tem sido considerada por moderar a acidez da superfície do suporte e minimizar a deposição de carbono no catalisador durante a reação de reforma. Tendo em vista que a atividade dos catalisadores na reação de reforma é função das características físicas e químicas desses materiais, avaliou-se, no presente trabalho, a rota de síntese por coprecipitação de hidróxidos em associação ao uso de surfactante e tratamento solvotérmico. A rota de mistura de pós de óxido de níquel com alumina, ambos preparados por precipitação individual, foi adotada para comparação dos resultados obtidos por coprecipitação. Nas condições otimizadas do processo, estudou-se o efeito da adição de óxido de lantânio nas propriedades dos materiais sintetizados. Verificou-se que o método de coprecipitação permitiu a obtenção de óxidos mistos com elevada área superficial (na faixa de 170 a 260 m2g-1), ao passo que a mistura de óxidos conduziu à formação de pós constituídos por fases distintas de alumina e óxido de níquel, com menor área superficial (na faixa de 60 a 180 m2.g-1). Após avaliação do comportamento de redução do óxido de níquel contido nesses materiais, as propriedades dos pós obtidos foram correlacionadas com o desempenho na produção de hidrogênio pela reforma do etanol. De acordo com os resultados, o catalisador preparado por coprecipitação apresentou menor atividade na produção de hidrogênio, comparativamente aos materiais obtidos por coprecipitação em associação com tratamento solvotérmico e mistura de óxidos. Em contraste, verificou-se uma menor quantidade de carbono acumulado sobre o catalisador preparado por coprecipitação, indicativo da elevada estabilidade catalítica deste material durante a reação de reforma. / Hydrogen use as an energy vector represents a promising option in order to reduce the dependence on fossil fuels and to control the emission of pollutants into the atmosphere. Nowadays, one of the most important routes for hydrogen production includes steam reforming reactions of alcohols over alumina-supported nickel catalysts. Nickel is largely applied in catalysis because of its low cost and high activity for C-C bond rupture. Alumina, in turn, promotes appropriate dispersion of the active metal due to the high surface area values of its transition crystalline structures, especially gamma phase. These characteristics are related to synthesis conditions. Incorporation of lanthana as an additive has been considered to control alumina surface acidity and to inhibit catalyst deactivation by carbon deposition during reforming reaction. Considering that catalyst activity is a function of materials physical and chemical properties, it was evaluated in this work powder synthesis route by coprecipitation in association with surfactant templating method and solvothermal treatment. Mechanical milling of nickel oxide and alumina powders, which were individually prepared by chemical precipitation, was adopted for comparison purposes. Under optimized preparation conditions, the effect of lanthanum oxide addition on the materials properties was studied. It was verified that coprecipitation allowed the production of high surface area mixed oxides (170-260 m2g-1). Mechanical mixture led to the formation of materials constituted by alumina and nickel oxide phases, with low surface area (60-180 m2.g-1). After evaluation of nickel oxide reduction behavior, in hydrogen atmosphere, a correlation between properties and performance in hydrogen production by ethanol steam reforming was established. According to the results, the catalyst prepared by coprecipitation was less active for hydrogen generation compared to the ones obtained by coprecipitation followed by solvothermal treatment and mechanical milling methods. In contrast, the lowest amount of carbon deposits was found on the catalyst prepared by coprecipitation, which is an indicative of the high catalytic stability during reforming reaction.

O uso do hidrogênio, como vetor energético, representa uma opção promissora a fim de se reduzir a dependência dos combustíveis fósseis e controlar a emissão de poluentes na atmosfera. Atualmente, uma das rotas mais propícias para produção de hidrogênio envolve a reação de reforma a vapor de álcoois utilizando-se catalisadores de níquel suportados em alumina. O níquel é amplamente utilizado em catálise devido ao baixo custo e à elevada atividade para ruptura da ligação C-C. A alumina, por sua vez, promove maior dispersão do metal ativo devido aos valores elevados de área superficial das estruturas cristalinas de transição, sobretudo da fase gama, característica esta diretamente relacionada às condições de síntese. A incorporação de lantânia, como aditivo, tem sido considerada por moderar a acidez da superfície do suporte e minimizar a deposição de carbono no catalisador durante a reação de reforma. Tendo em vista que a atividade dos catalisadores na reação de reforma é função das características físicas e químicas desses materiais, avaliou-se, no presente trabalho, a rota de síntese por coprecipitação de hidróxidos em associação ao uso de surfactante e tratamento solvotérmico. A rota de mistura de pós de óxido de níquel com alumina, ambos preparados por precipitação individual, foi adotada para comparação dos resultados obtidos por coprecipitação. Nas condições otimizadas do processo, estudou-se o efeito da adição de óxido de lantânio nas propriedades dos materiais sintetizados. Verificou-se que o método de coprecipitação permitiu a obtenção de óxidos mistos com elevada área superficial (na faixa de 170 a 260 m2g-1), ao passo que a mistura de óxidos conduziu à formação de pós constituídos por fases distintas de alumina e óxido de níquel, com menor área superficial (na faixa de 60 a 180 m2.g-1). Após avaliação do comportamento de redução do óxido de níquel contido nesses materiais, as propriedades dos pós obtidos foram correlacionadas com o desempenho na produção de hidrogênio pela reforma do etanol. De acordo com os resultados, o catalisador preparado por coprecipitação apresentou menor atividade na produção de hidrogênio, comparativamente aos materiais obtidos por coprecipitação em associação com tratamento solvotérmico e mistura de óxidos. Em contraste, verificou-se uma menor quantidade de carbono acumulado sobre o catalisador preparado por coprecipitação, indicativo da elevada estabilidade catalítica deste material durante a reação de reforma. / Hydrogen use as an energy vector represents a promising option in order to reduce the dependence on fossil fuels and to control the emission of pollutants into the atmosphere. Nowadays, one of the most important routes for hydrogen production includes steam reforming reactions of alcohols over alumina-supported nickel catalysts. Nickel is largely applied in catalysis because of its low cost and high activity for C-C bond rupture. Alumina, in turn, promotes appropriate dispersion of the active metal due to the high surface area values of its transition crystalline structures, especially gamma phase. These characteristics are related to synthesis conditions. Incorporation of lanthana as an additive has been considered to control alumina surface acidity and to inhibit catalyst deactivation by carbon deposition during reforming reaction. Considering that catalyst activity is a function of materials physical and chemical properties, it was evaluated in this work powder synthesis route by coprecipitation in association with surfactant templating method and solvothermal treatment. Mechanical milling of nickel oxide and alumina powders, which were individually prepared by chemical precipitation, was adopted for comparison purposes. Under optimized preparation conditions, the effect of lanthanum oxide addition on the materials properties was studied. It was verified that coprecipitation allowed the production of high surface area mixed oxides (170-260 m2g-1). Mechanical mixture led to the formation of materials constituted by alumina and nickel oxide phases, with low surface area (60-180 m2.g-1). After evaluation of nickel oxide reduction behavior, in hydrogen atmosphere, a correlation between properties and performance in hydrogen production by ethanol steam reforming was established. According to the results, the catalyst prepared by coprecipitation was less active for hydrogen generation compared to the ones obtained by coprecipitation followed by solvothermal treatment and mechanical milling methods. In contrast, the lowest amount of carbon deposits was found on the catalyst prepared by coprecipitation, which is an indicative of the high catalytic stability during reforming reaction.