O hidrogênio é visto como um importante combustível alternativo aos combustíveis convencionais, como a gasolina e o óleo diesel, devido a sua alta eficiência energética e não geração de poluentes. Porém, a maior parte do hidrogênio produzido é proveniente de fontes não renováveis, como o gás natural e o petróleo. Novas tecnologias para a geração de hidrogênio vem sendo estudadas e dentre elas se destaca a reação de reforma a vapor de compostos oxigenados. Os ácidos graxos voláteis gerados durante o tratamento anaeróbio de águas residuárias constitui uma matéria-prima interessante para a produção de hidrogênio a partir de biomassa. Os principais produtos gerados no tratamento de águas residuárias são o etanol, o ácido acético e o ácido butírico, este, chega a representar 35 % em massa podendo ser utilizado como molécula modelo na reação de reforma a vapor. Neste trabalho, foram desenvolvidos catalisadores a base de níquel (Ni) modificados com vanádio (V), zinco (Zn) e nióbio (Nb) suportados em alumina (γ-Al2O3), visando minimizar os depósitos carbonáceos, assim como aumentar a atividade e seletividade para o hidrogênio na reação de reforma a vapor do ácido butírico. Os catalisadores foram modificados com diferentes teores de V, Zn e Nb (2,5, 5 e 10 % em massa). Nas reações feitas a 600 ºC utilizando razão estequiométrica ácido butírico:vapor, dentre os catalisadores modificados com V, o com 5 % (10Ni2,5VAl2O3) apresentou o melhor desempenho, chegando a uma conversão de 86 % para o ácido butírico, além de aumentar a estabilidade do catalisador quando comparado ao catalisador contendo apenas Ni (10NiAl2O3). Para o grupo de catalisadores modificados com Zn, o catalisador com 10 % em massa de Zn (10Ni10ZnAl2O3) apresentou uma conversão de 83 %, sendo este grupo o com menor taxa de formação de carbono. Dentre os catalisadores modificados com Nb, o com menor teor (10Ni2,5NbAl2O3) foi o que apresentou o melhor desempenho, alcançado uma conversão de 82 %. Testes catalíticos utilizando excesso de água mostraram alta conversão, superiores a 90 %, e alta seletividade para H2. Dessa forma, a adição de metais com diferentes propriedades pode contribuir para uma maior seletividade para hidrogênio, seja pela redução dos depósitos de carbono ou pela melhora na estabilidade catalítica.  / Hydrogen is an important alternative fuel to conventional fuels, such as gasoline and diesel, due to its high energy efficiency and non-generation of pollutants. However, most of the hydrogen produced comes from non-renewable sources such as natural gas and diesel oil. New technologies for the generation of hydrogen have been studied, among them the reaction of steam reforming of oxygenated compounds. Volatile fatty acids generated during the anaerobic treatment of wastewater are an interesting raw material for the production of hydrogen from biomass. The main products generated in the treatment of wastewater are ethanol, acetic acid and butyric acid, which represents 35% by mass and can be used as a model molecule in the steam reforming reaction. In this work, nickel-based (Ni) catalysts modified with vanadium (V), zinc (Zn) and niobium (Nb) supported on alumina (γ-Al2O3) were developed, aiming at minimizing carbonaceous deposits, as well as increasing activity and selectivity for the hydrogen in the steam reforming reaction of butyric acid. The catalysts were modified with different levels of V, Zn and Nb (2.5, 5 and 10 % by mass). In the reactions made at 600 ºC using stoichiometric butyric acid: steam ratio, among the catalysts modified with V, the 5 % (10Ni2,5VAl2O3) showed the best performance, reaching a conversion of 86 % to butyric acid, besides increasing The stability of the catalyst when compared to the catalyst containing only Ni (10NiAl2O3). For the group of catalysts modified with Zn, the catalyst with 10 % by mass of Zn (10Ni10ZnAl2O3) showed a conversion of 83 %, this group being the one with the lowest rate of carbon formation. Among the catalysts modified with Nb, the one with the lowest content (10Ni2,5NbAl2O3) was the one that presented the best performance, achieving a conversion of 82 %. Catalytic tests using excess water showed high conversion, higher than 90%, and high selectivity for H2. Thus, the addition of metals with different properties may contribute to a higher selectivity for hydrogen, either by reducing carbon deposits or by improving catalytic stability.

Ce travail vise à étudier la transestérification de l'huile de tournesol pour la production de biodiesel et le vaporeformage du glycérol pour la production d'hydrogène renouvelable. Les oxydes mixtes Mg-Al prépares par voie hydrotalcite ont été choisis comme supports catalytiques. Pour la production de biodiesel, les effets du traitement thermique et de la méthode de préparation pour l'incorporation de calcium ont été étudiés. Le catalyseur Ca600/Mg₄Al₂HT calciné à 600°C, préparé par imprégnation de 40 wt% de Ca sur le support Mg₄Al₂ non calciné, a montré les meilleures performances catalytiques en raison de ses propriétés basiques améliorées. Pour le vaporeformage catalytique du glycérol, l'activité des oxydes de métaux purs imprégnés par le Ni a d'abord été étudiée, puisque les oxydes de métaux purs sont souvent utilisés comme supports catalytiques. Le catalyseur Ni/ZrO₂ s'est révélé le plus efficace pour la production d'hydrogène. Pour le vaporeformage du glycérol en présence d'oxydes mixtes obtenus par voie hydrotalcite, les catalyseurs au Ru-Mg-Al ont été étudiés. L'effet de la méthode de préparation (imprégnation ou greffage) sur l'activité catalytique a été étudié. Le catalyseur préparé par imprégnation permettait une plus grande accessibilité à la phase active. Pour des catalyseurs Ni-Mg-Al, les supports ont été modifiés par du lanthane. Le catalyseur Ni/Mg₆Al₁.₆La₀.₄ était le plus performant en raison de sa basicité accrue et de son interaction métal-support. Les activités des catalyseurs Ni/ZrO₂ et Ni/Mg₆Al₁.₆La₀.₄ ont été comparées. Les deux catalyseurs ont produit des rendements en hydrogène similaires. Moins de coke a été produit sur le catalyseur préparé par voie hydrotalcite, en raison de sa basicité supérieure. Un test de stabilité à 600°C a montré la désactivation du catalyseur Ni/Mg₆Al₁.₆La₀.₄ après 6 heures. Lors de l'optimisation des conditions de réaction sur le catalyseur Ni/Mg₆Al₁.₆La₀.₄, une amélioration significative de la stabilité a été observée, étendant ainsi sa durée de vie à 24 heures. / This work aims to study the transesterification of sunflower oil for biodesel production and the steam reforming of glycerol for renewable hydrogen production. Mg-Al hydrotalcite derived mixed oxides were chosen as catalytic support materials given their known basicity, thermal stability and low cost. Only one active phase was studied for biodiesel production (Ca) and two different active phases (Ru and Ni) for glycerol steam reforming. The various prepared catalysts were characterized by different techniques such as X-Ray Diffraction (XRD), specific surface area determination by BET method, Fourier Transform Infrared Spectroscopy (FTIR), H₂-Temperature Programmed Reduction (H₂-TPR), CO₂-Temperature Programmed Desorption (CO₂-TPD) and Simultaneous Thermogravimetric-Differential Scanning Calorimetry (TG-DSC). For biodiesel production, the effects of thermal treatment and the preparation method for Ca incorporation were both studied. The catalyst that showed the best catalytic performance was an uncalcined Mg₄Al₂ support impregnated with 40 wt% Ca followed by a calcination at 600°C (Ca/600Mg₄Al₂HT) due to its enhanced basic properties. After several optimization steps over this catalyst, the optimum conditions for biodiesel synthesis were: a methanol to oil molar ratio of 15:1, a catalyst to oil ratio of 2.5 wt% and a reaction time of 6 hours which gave a FAME yield of 95%. The properties of the produced biodiesel were studied and found to be in good agreement with ASTM (American Society for Testing and Materials) requirements. For the catalytic steam reforming of glycerol, the activity of NI-based pure metal oxides (Ni/CeO₂, Ni/Y₂O₃, Ni/ZrO₂) was first studied as pure metal oxides are commonly used as support materials. The effect of the support was evaluated and the Ni/ZrO₂ catalyst was found to be the most efficient for hydrogen production. To study the effect of the zirconia phase, a tetragonal Ni/ZrO₂ was also prepared. The tetragonal catalyst was less active for hydrogen production compared to the monoclinic catalyst. A stability test at 600°C also showed the desactivation of the tetragonal Ni/ZrO₂ after 6 hours on stream. For the catalytic steam reforming of glycerol using Mg-Al hydrotalcite derived mixed oxides, Ru-based Mg-Al catalysts were first studied. The effect of the preparation method (impregnation vs grafting) on the catalytic activity of Ru-Mg-Al catalysts was studied. The catalyst prepared by the impregnation method resulted in a better catalytic activity than the catalyst prepared by the grafting method as it allowed a higher accessibility of the active phase. For the Ni-based Mg-Al catalysts, the hydrotalcite supports were modified with La to study the effects of promoter addition on catalytic properties and activity. The bimetallic effect (1%Ru-5%Ni) and effect of a higher Ni loading (15 wt%) were also studied. The 5 wt% Ni impregnated on a La modified Mg-Al support (Ni/Mg₆Al₁.₆La₀.₄) catalyst was the most efficient for hydrogen production due to its enhanced basicity and metal-support interaction. The activities of the most efficient catalysts, Ni/ZrO₂ and Ni/Mg₆Al₁.₆La₀.₄, were compared. Both catalysts produced similar hydrogen yields. Differences in glycerol conversion to gaseous products were attributed to a higher formation of liquid by-products over the hydrotalcite support compared to the zirconia support. Nevertheless, less coke was produced over the hydrotalcite catalyst given its higher basicity. A stability test at 600°C showed the desactivation of the Ni/Mg₆Al₁.₆La₀.₄ catalyst after 6 hours on stream. Upon optimization of the reaction conditions on Ni/Mg₆Al₁.₆La₀.₄, a significant improvement in the stability was observed as the catalyst lasted for 24 hours on steam.Therefore, Ni/Mg₆Al₁.₆La₀.₄ could be a promising candidate for industrial application.

"Multitubular packed bed reactors with low tube-to-particle diameter ratios (N) are especially selected for strongly endothermic reactions such as steam reforming and propane dehydrogenation. For low N tubes, the presence of the wall causes changes in bed structure, flow patterns, transport rates and the amount of catalyst per unit volume. In particular, the particles close to the wall will behave differently to those inside the bed. The problem is that, due to the simplifying assumptions, such as uniform catalyst pellet surroundings, that are usual for the current pseudo-continuum reactor models, the effects of catalyst pellet design changes in the near-wall environment are lost. The challenge is to develop a better understanding of the interactions between flow patterns, species pellet diffusion, and the changes in catalyst activity due to the temperature fields in the near wall region for the modeling and design of these systems. To contribute to this improved understanding, Computational Fluid Dynamics (CFD) was used to obtain detailed flow, temperature, and species fields for near-wall catalyst particles under steam reformer and propane dehydrogenation reactor inlet conditions. As a first step, a reduced size model was generated by only considering a 120 degree segment of an N = 4 tube, and validated with a larger size complete bed model. In terms of the flow and temperature contours and profiles, the complete tubes can be represented well by the reduced size models, especially focusing on the center particles positioned in the middle of the near wall region. The methane steam reforming heat effects were implemented by a user-defined code with the temperature-dependent sinks in the catalyst particles, near to the pellet surfaces for different activity levels. For the sinks terms, bulk phase species concentrations were used in the reaction rates, and with the reaction heat effects inclusion, significant pellet sensitivity was observed with different activity levels. Furthermore, non-symmetric temperature fields in and around the near wall particles were noticed as contrary to the conventional approach. In order to focus on the 3D intra-pellet distributions of temperature and species, diffusion and reaction were coupled to the external flow and temperature fields by user-defined code. Strong deviations from uniformity and symmetry on the temperature and species distributions existed as a result of the strong wall heat-flux into the particles Additionally, the pseudo-continuum type of packed bed model was created, which considers the simplified environment for the reacting particles. The results obtained by the diffusion reaction application in the 3D discrete packing model could not be re-produced by the conventional simplified pseudo-continuum approach, no matter which parameter values were chosen for the latter. The significance of these observations is that, under the conventional assumption of symmetric particle surroundings, the tube wall temperature and reaction rates for catalyst particles can be incorrectly evaluated and important design considerations may not be well predicted, thus, negative consequences on the plant safety and efficiency may be observed. "

Neste trabalho foram preparados catalisadores Co/Al2O3 e Co/SiO2 por impregnação com concentração metálica entre 4,0% e 20,0% e avaliados frente às reações de reforma a vapor e reforma oxidativa de etanol, com o objetivo de avaliar a estabilidade catalítica e o rendimento em hidrogênio. Os catalisadores foram caracterizados por espectrofotometria de absorção atômica, difração de raios-X, espectroscopia Raman, redução a temperatura programada, fisissorção de nitrogênio e análise elementar de carbono. A caracterização das amostras mostrou a formação da fase Co3O4 e interações de espécies de cobalto com o suporte. Evidenciou-se que apenas os sítios de Co0 são ativos para as reações de reforma a vapor e oxidativa de etanol. A produção de hidrogênio variou de 50-70% e a de CO de 0-10%. Alta concentração metálica sobre a superfície do suporte acarretou uma baixa produção de monóxido de carbono. As reações tiveram deposições de carbono nos catalisadores variando de 2,7 a 12,7 (mg. h-1), indicando que a desativação dos materiais é devido a deposição de coque. O uso de oxigênio diminuiu a produção de coque sobre os catalisadores Co/Al2O3 e Co/SiO2. / In this work Co/Al2O3 and Co/SiO2 catalysts were prepared by impregnation with metal load between 4,0% and 20,0% and were evaluated in the reactions of ethanol steam reforming and ethanol oxidative reforming to study the catalytic stability and the hydrogen yield. Atomic absorption, X-ray powder diffraction, Raman spectroscopy, temperature programmed reduction, nitrogen fisisorption and elemental analysis of carbon were applied to describe the physical and chemical characteristics of these catalysts. The characterization of the catalysts showed the Co3O4 phase and interactions of cobalt species with the support. It was evidenced that only Co0 sites are active for the steam reforming and oxidative reforming of ethanol. The production of hydrogen was about 50-70% and CO was 0- 10%. A high metallic load gave less carbon monoxide production. In the reactions, 2,7-12,7(mg.h-1) of carbon was deposited on all catalysts, indicating that the deactivation of the materials is due to coke deposition. The use of oxygen decreases the production of carbon on the catalysts Co/Al2O3 and Co/SiO2.

A utilização de combustíveis fósseis é um problema a ser contornado visto que sua utilização gera problemas ambientais tais como o aumento do efeito estufa. Como combustível alternativo, ganha destaque o hidrogênio, o qual pode ser utilizado em células à combustível, gerando energia e apenas água como sub-produto. Uma forma de produção de hidrogênio é a partir da reforma a vapor do bio-óleo, proveniente da pirólise da biomassa. Devido à complexidade do bio-óleo, compostos modelo, como o ácido acético e acetol, vêm sendo estudados nos sistemas reacionais. Neste trabalho, estudou-se a reação de reforma a vapor do acetol para obtenção de H2 utilizando-se catalisadores baseados em Ni0 e Co0 derivados de hidróxidos duplos lamelares (HDLs), também chamados de compostos do tipo hidrotalcita. Os HDLs foram sintetizados pelo método de coprecipitação. Análise de difração de raios X (DRX) mostraram a formação dos HDLs e os diferentes teores de Al3+ nas lamelas foram observados através da técnica de espectroscopia na região do infravermelho. Espectroscopia por energia dispersiva de raios X (EDX) indicou que os catalisadores derivados de HDLs calcinados a 750°C possuem quantidades reais de metais ativos próximas aos valores nominais e que possuem diferentes teores de Mg2+. As análises de TPR-H2 mostraram a redução das fases óxidas presentes em altas temperaturas, devido a formação de solução sólida MgNiO2, MgCoO2 e fases espinélios. Nos ensaios catalíticos, catalisadores baseados em Ni0 se mostraram mais seletivos para H2 enquanto que os baseados em Co0 foram mais seletivos para o eteno e compostos líquidos. Ainda, observou-se a tendência de maior seletividade para H2 quanto maior o teor de Mg2+ no catalisador. Para os catalisadores derivados de HDL´s calcinados a 600°C, as caracterizações mostraram resultados semelhantes aos calcinados a 750°C, evidenciando a facilidade de formação das soluções sólida para estes compostos do tipo HDL´s. Para estas amostras também ficou evidenciado que maiores teores de Mg2+ nos catalisadores facilitam a conversão em H2 na reforma a vapor do acetol, o que pode estar associado a propriedade basicidade, que foi quantificada através de termo-dessorção programada de CO2 (TPD-CO2). / The use of fossil fuels is a problem to be circumvented, since its use generates environmental problems such as the increase of the greenhouse effect. As an alternative fuel, hydrogen is highlighted, which can be used in fuel cells, generating energy without the emission of polluting gases. One form of hydrogen production is from the steam reforming of the bio-oil, from the pyrolysis of the biomass. Due to the complexity of the bio-oil, model compounds, present in greater quantity, such as acetic acid and acetol have been studied individually. In this work, the reaction of steam reforming of the acetol to obtain H2 was carried out using catalysts based on Ni0 and Co0 derived from lamellar double hydroxides (HDLs), also called hydrotalcite like compounds. HDLs were synthesized by the coprecipitation method. X-ray diffraction (XRD) analysis showed the formation of HDLs and different Al3+ contents in the lamellae, as well as the Fourier transform infrared spectroscopy technique. X-ray dispersive energy spectroscopy (EDS) has indicated that the catalysts derived from HDLs calcined at 750°C have real amounts of active metals close to the nominal values and that have different levels of Mg2 + and Al3+. The TPR-H2 analysis showed that the reduction of Ni2+ and Co2+ occurs at high temperatures due to the formation of solid solutions MgNiO2, MgCoO2, and spinel phases. In the catalytic tests, Ni2+ based catalysts were more selective for H2, while Co0 based catalysts were more selective for liquid compounds such as acetone. Also, the tendency of greater selectivity for H2 was observed when the Mg2+ content in the catalyst was higher. For the catalysts derived from HDL\'s calcined at 600°C, the characterizations showed results similar to those calcined at 750°C, evidencing the difficult reducibility of oxides derived from HDL\'s. For these catalysts, it was also observed that higher Mg2+ contents facilitate the conversion to H2 in the steam reforming of the acetol, which may be associated with the basicity of the material, which was quantified by means of programmed thermodesorption of CO2 (TPD-CO2).

O hidrogênio é visto como um importante combustível alternativo aos combustíveis convencionais, como a gasolina e o óleo diesel, devido a sua alta eficiência energética e não geração de poluentes. Porém, a maior parte do hidrogênio produzido é proveniente de fontes não renováveis, como o gás natural e o petróleo. Novas tecnologias para a geração de hidrogênio vem sendo estudadas e dentre elas se destaca a reação de reforma a vapor de compostos oxigenados. Os ácidos graxos voláteis gerados durante o tratamento anaeróbio de águas residuárias constitui uma matéria-prima interessante para a produção de hidrogênio a partir de biomassa. Os principais produtos gerados no tratamento de águas residuárias são o etanol, o ácido acético e o ácido butírico, este, chega a representar 35 % em massa podendo ser utilizado como molécula modelo na reação de reforma a vapor. Neste trabalho, foram desenvolvidos catalisadores a base de níquel (Ni) modificados com vanádio (V), zinco (Zn) e nióbio (Nb) suportados em alumina (γ-Al2O3), visando minimizar os depósitos carbonáceos, assim como aumentar a atividade e seletividade para o hidrogênio na reação de reforma a vapor do ácido butírico. Os catalisadores foram modificados com diferentes teores de V, Zn e Nb (2,5, 5 e 10 % em massa). Nas reações feitas a 600 ºC utilizando razão estequiométrica ácido butírico:vapor, dentre os catalisadores modificados com V, o com 5 % (10Ni2,5VAl2O3) apresentou o melhor desempenho, chegando a uma conversão de 86 % para o ácido butírico, além de aumentar a estabilidade do catalisador quando comparado ao catalisador contendo apenas Ni (10NiAl2O3). Para o grupo de catalisadores modificados com Zn, o catalisador com 10 % em massa de Zn (10Ni10ZnAl2O3) apresentou uma conversão de 83 %, sendo este grupo o com menor taxa de formação de carbono. Dentre os catalisadores modificados com Nb, o com menor teor (10Ni2,5NbAl2O3) foi o que apresentou o melhor desempenho, alcançado uma conversão de 82 %. Testes catalíticos utilizando excesso de água mostraram alta conversão, superiores a 90 %, e alta seletividade para H2. Dessa forma, a adição de metais com diferentes propriedades pode contribuir para uma maior seletividade para hidrogênio, seja pela redução dos depósitos de carbono ou pela melhora na estabilidade catalítica.  / Hydrogen is an important alternative fuel to conventional fuels, such as gasoline and diesel, due to its high energy efficiency and non-generation of pollutants. However, most of the hydrogen produced comes from non-renewable sources such as natural gas and diesel oil. New technologies for the generation of hydrogen have been studied, among them the reaction of steam reforming of oxygenated compounds. Volatile fatty acids generated during the anaerobic treatment of wastewater are an interesting raw material for the production of hydrogen from biomass. The main products generated in the treatment of wastewater are ethanol, acetic acid and butyric acid, which represents 35% by mass and can be used as a model molecule in the steam reforming reaction. In this work, nickel-based (Ni) catalysts modified with vanadium (V), zinc (Zn) and niobium (Nb) supported on alumina (γ-Al2O3) were developed, aiming at minimizing carbonaceous deposits, as well as increasing activity and selectivity for the hydrogen in the steam reforming reaction of butyric acid. The catalysts were modified with different levels of V, Zn and Nb (2.5, 5 and 10 % by mass). In the reactions made at 600 ºC using stoichiometric butyric acid: steam ratio, among the catalysts modified with V, the 5 % (10Ni2,5VAl2O3) showed the best performance, reaching a conversion of 86 % to butyric acid, besides increasing The stability of the catalyst when compared to the catalyst containing only Ni (10NiAl2O3). For the group of catalysts modified with Zn, the catalyst with 10 % by mass of Zn (10Ni10ZnAl2O3) showed a conversion of 83 %, this group being the one with the lowest rate of carbon formation. Among the catalysts modified with Nb, the one with the lowest content (10Ni2,5NbAl2O3) was the one that presented the best performance, achieving a conversion of 82 %. Catalytic tests using excess water showed high conversion, higher than 90%, and high selectivity for H2. Thus, the addition of metals with different properties may contribute to a higher selectivity for hydrogen, either by reducing carbon deposits or by improving catalytic stability.

Methanol micro-channel reformer is an important device for generating hydrogen to supply micro fuel-cell needs. In the fuel reforming process, the catalyst is adopted to reduce the activation energy and speed up the reforming reaction. Hydrogen and other chemical substance are produced in the reformer catalytic reaction. The micro-channel structure provides more opportunity for molecules of methanol and steam mixture to collide with catalyst for high reforming reaction to take place. The reforming process of methanol in a micro-channel reformer with Pd/ZnO catalyst is studied numerically in this thesis. The effects of various channel length, channel height, inlet velocity, inlet temperature, and catalyst usage (ratio of wall area covered by catalyst) on the performance of reformer (methanol conversion percentage) are investigated numerically. The results show that the methanol conversion increases with increased channel length until a channel length of about 3000£gm, the conversion approaches 100%. The conversion percentage decreases with increased inlet velocity, however, the production rate of hydrogen depends on flow rate and conversion percentage. Increasing the channel height results in decreased methonal conversion due to less collision opportunity with the catalyst. The methanol conversion percentage increases with the increase of the inlet temperature. However, the production rate of the hydrogen starts to descend when the inlet temperature is higher than about 523 K owing to more methonal preburned in raising the inlet temperature. Methanol conversion increases with the catalyst usage. However, it is worth noting that the increase is only about 15% for catalyst usage from 50% to 100%. The results in this study provide design data for the fuel cell system designer.

Biomass-fuelled proton exchange membrane fuel cells (PEMFCs) offer asolution for replacing fossil fuel for hydrogen production. Through using thebiomass-derived hydrogen as fuel, PEMFCs may become an efficient andsustainable energy system for small and medium-sized enterprises. The aim ofthis thesis is to evaluate the performance and potential applications of biomassfuelledPEMFC systems which are designed to convert biomass to electricity andheat. Biomass-fuelled PEMFC systems are simulated by Aspen plus based ondata collected from experiments and literature.The impact of the quality of the hydrogen-rich gas, anode stoichiometry, CH4content in the biogas and CH4 conversion rate on the performance of the PEMFCis investigated. Also, pinch technology is used to optimize the heat exchangernetwork to improve the power generation and thermal efficiency.For liquid and solid biomass, anaerobic digestion (AD) and gasification (GF),respectively, are relatively viable and developed conversion technologies. ForAD-PEMFC, a steam reformer is also needed to convert biogas to hydrogen-richgas. For 100 kWe generation, the GF-PEMFC system yields a good technicalperformance with 20 % electrical efficiency and 57 % thermal efficiency,whereas the AD-PEMFC system only has 9 % electrical efficiency and 13 %thermal efficiency. This low efficiency is due to the low efficiency of theanaerobic digester (AD) and the high internal heat consumption of the AD andthe steam reformer (SR). For the environmental aspects, the GF-PEMFC systemhas a high CO2 emissions offset factor and the AD-PEMFC system has anefficient land-use.The applications of the biomass-fuelled PEMFC systems are investigated on adairy farm and an olive oil plant. For the dairy farm, manure is used as feedstockto generate biogas through anaerobic digestion. A PEMFC qualified for 40 %electrical efficiency may generate 360 MWh electricity and 680 MWh heat peryear to make a dairy farm with 300 milked cows self-sufficient in a sustainableway. A PEMFC-CHP system designed for an olive oil plant generating annual 50000 m3 solid olive mill waste (SOMW) and 9 000 m3 olive mill waste water(OMW) is simulated based on experimental data from the Biogas2PEM-FCproject1. After the optimization of the heat exchanger network, the PEMFC-CHP  system can generate 194 kW electricity which corresponds to 62 % of the totalelectricity demand of the olive oil plant.The economic performance of the PEMFC and biogas-fuelled PEMFC areassessed roughly including capital, operation &amp; maintenance (O&amp;M) costs of thebiogas plant and the PEMFC-CHP, the cost of heat and electricity, and the valueof the digestate as fertilizer. / <p>QC 20151109</p>

The objective of the thesis was to analyze the ageing processes and the modifications of an Ir/CeO2catalyst for steam reforming of ethanol. Over a model Ir/CeO2 catalyst, the initial and fast deactivationwas ascribed to ceria surface restructuring and the build-up of intermediates monolayer (acetate,carbonate and hydroxyl groups). In parallel, a progressive and slow deactivation was found to come fromthe structural changes at the ceria/Ir interface linked to Ir sintering and ceria restructuring. Theencapsulating carbon, coming from C2 intermediates polymerization, did not seem too detrimental to theactivity in the investigated operating conditions. By doping ceria with PrOx, the oxygen storage capacityand thermal stability were greatly promoted, resulting in the enhanced activity and stability. The Ir/CeO2catalyst was then modified by changing the shape of ceria. It was found that the shape and therefore thestructure of ceria influenced the activity and stability significantly. A simplified modeling of theseprocesses has contributed to support the new proposals of this work.

Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-17T17:43:35Z No. of bitstreams: 1 DissSCMM.pdf: 2059252 bytes, checksum: cf570b86d963584cf183b9fa7c5f16ea (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-17T17:43:43Z (GMT) No. of bitstreams: 1 DissSCMM.pdf: 2059252 bytes, checksum: cf570b86d963584cf183b9fa7c5f16ea (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-17T17:43:50Z (GMT) No. of bitstreams: 1 DissSCMM.pdf: 2059252 bytes, checksum: cf570b86d963584cf183b9fa7c5f16ea (MD5) / Made available in DSpace on 2017-08-17T17:43:56Z (GMT). No. of bitstreams: 1 DissSCMM.pdf: 2059252 bytes, checksum: cf570b86d963584cf183b9fa7c5f16ea (MD5) Previous issue date: 2016-03-28 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / The steam reforming of acetic acid (SRAcH), a model compound of pyrolysis-oil, was studied over MgAl2O4-supported Co-Ni catalysts with different Co/Ni ratios, prepared by impregnation using the incipient wetness method. The catalysts were characterized by X-ray powder diffraction, temperature programmed reduction, temperature programmed desorption, and thermogravimetry. In the steam reforming reaction of AcH, both Ni and Co catalysts suffered partial oxidation due to contact with the reaction mixture. The ketonization reaction occurred on the MgAl2O4 support and the presence of Co or Ni changed the reaction pathway of species adsorbed on the support, which suppressed the formation of acetone. The cleavage of C-C bonds was favored on the Ni surface, resulting in CHx species, which in the presence of H2 were preferentially hydrogenated to CH4 at low temperatures. On the other hand, on the Co surface the CHx species were decomposed to C* and H* as the temperature increased. The addition of Co to Ni catalysts inhibited CH4 formation and carbon accumulation. / A reforma a vapor do ácido acético (RVAAc), um composto modelo da pirólise do bioóleo, foi estudada sobre catalisadores de Co-Ni suportados em MgAl2O4 com diferentes razões Co/Ni, preparados por impregnação úmida incipiente. Os catalisadores foram caracterizados por difração de raios-X, redução a temperatura programada, dessorção a temperatura programada e termogravimetria. Em reação, os catalisadores de Ni e Co sofreram uma oxidação parcial ao entrar em contato com a mistura reacional. A reação de cetonização ocorreu sobre o suporte de MgAl2O4 e a presença de Co ou Ni alterou a rota de reação das espécies adsorvidas no suporte, o que suprimiu a formação de acetona. A quebra das ligações C-C foi favorecida na superfície Ni, resultando em espécies CHx, as quais preferencialmente foram hidrogenadas a CH4 na presença de H2 em baixas temperaturas. Entretanto, na superfície Co com o aumento da temperatura as espécies CHx foram decompostas em C * e H *. A adição de Co aos catalisadores de Ni inibiu a formação de CH4 e o acúmulo de carbono. / CNPq: 407030/2013-1