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Le syngas est un mélange gazeux de CO et H2 qui constitue un intermédiaire important dans l’industrie pétrochimique. Plusieurs approches sont utilisées pour le produire. L’oxydation partielle non catalytique (POX) et le reformage à la vapeur (SMR) en font partie. Le reformage auto thermique du méthane (ATR) combine quant à lui ces deux procédés au sein d’un même réacteur. L’amélioration du rendement global du procédé ATR requiert une meilleure caractérisation du comportement des gaz au sein de la chambre. La simulation numérique apparaît comme un outil efficace pour y parvenir. Pour réduire le coût CPU, c'est généralement l'approche RANS (Reynolds Average Numerical Simulation) qui est privilégiée pour la simulation complète de la chambre. Cette approche repose sur l'utilisation de modèles, parmi lesquels le modèle de combustion turbulente, qui a pour objectif de représenter les interactions entre la turbulence et la réaction chimique au sein du mélange. Plusieurs stratégies ont été proposées pour le calculer, qui bénéficient globalement d'une large expérience pour les systèmes classiques mettant en jeu la combustion. Cependant, les flammes observées dans les réacteurs ATR présentent des propriétés assez différentes de ces configurations classiques. La validité des modèles de combustion turbulente classiques doit donc y être vérifiée. L'objectif de cette thèse est de répondre à ce besoin, en testant la validité de différents modèles de combustion turbulente. La première partie du travail a consisté à analyser les propriétés des flammes CH4/O2 enrichies en vapeur d'eau à haute pression, et a notamment permis le développement d’une méthode d’évaluation des temps caractéristiques d’un système chimique. Dans un deuxième temps, une expérience numérique à l’aide d’un code DNS a été réalisée, afin de servir de référence pour tester a priori sur des configurations ATR plusieurs modèles RANS de combustion turbulente couramment utilisés dans le milieu industriel. / Syngas is a gaseous mixture mainly composed of CO and H2, which constitutes a major feedstock in petrochemical industry. Several industrial approaches are commonly used to produce it. Non catalytic Partial Oxidation (POX) and Steam Methane Reforming (SMR) are two of them. Autothermal Reforming (ATR) is a third process that combines both POX and SMR in the same reactor. A better knowledge of the reactive flow properties inside the chamber is required in order to improve the ATR process efficiency. Numerical simulation appears as an efficient tool to reach this goal. Because of the high CPU cost required for these simulations, RANS (Reynolds Average Numerical Simulation) formulation is usually preferred for the simulation of the whole chamber. This approach relies on the use of models, like the turbulent combustion model that aims at describing the interactions between turbulence and chemical reactions. Several approaches have been proposed to compute it, which benefit from a relatively wide experience for the simulation of classical combustion systems. However, ATR flames have some specific properties that make them quite different from these classical configurations, especially because of high pressure, reactants dilution with water and high global equivalence ratio. The validity of classical turbulent combustion models therefore requires to be assessed in ATR configurations. The objective of this thesis is to meet this need by testing the validity of several turbulent combustion models. The first part of this work has been to analyze water-enriched CH4/O2 flames properties at high pressure. In particular, a strategy for evaluating characteristic chemical time scales of a reactive system has been proposed within this context. In a second part, a DNS numerical experiment has been performed. Its results are then used as a benchmark for a priori testing several turbulent combustion models in the context of ATR reactor RANS simulations.

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Auxiliary power units, which operate independently of the main engine, are promising alternatives for supplying trucks with electricity. Fuel cell-based auxiliary power units could offer high efficiencies and low noise. The hydrogen required for the fuel cell could be generated in an onboard fuel reformer using the existing truck fuel. The work presented in this thesis concerns hydrogen generation from transportation fuels by autothermal reforming focusing on the application of fuel cell auxiliary power units. Diesel and dimethyl ether have been the fuels of main focus. The work includes reactor design aspects, preparation and testing of reforming catalysts including characterization studies and evaluation of operating conditions. The thesis is a summary of five scientific papers. Major issues for succeeding with diesel reforming are fuel injection, reactant mixing and achieving fuel cell quality reformate. The results obtained in this work contribute to the continued research and development of diesel reforming catalysts and processes. A diesel reformer, designed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell has been evaluated for autothermal reforming of commercial diesel fuel. The operational results show the feasibility of the design to generate hydrogen-rich gases from complex diesel fuel mixtures and have, together with CFD calculations, been supportive in the development of a new improved reformer design. In addition to diesel, the reforming reactor design was shown to run satisfactorily with other hydrocarbon mixtures, such as gasoline and E85. Rh-based catalysts were used in the studies and exhibit high performance during diesel reforming without coke formation on the catalyst surface. An interesting finding is that the addition of Mn to Rh catalysts appears to improve activity during diesel reforming. Therefore, Mn could be considered to be used to decrease the noble metal loading, and thereby the cost, of diesel reforming catalysts. Dimethyl ether is a potential diesel fuel alternative and has lately been considered as hydrogen carrier for fuel cells in truck auxiliary power units. The studies related to dimethyl ether have been focused on the evaluation of Pd-based catalysts and the influence of operating parameters for autothermal reforming. PdZn-based catalysts were found to be very promising for DME reforming, generating product gases with high selectivity to hydrogen and carbon dioxide. The high product selectivity is correlated to PdZn interactions, leading to decreased activity of decomposition reactions. Auxiliary power systems fueled with DME could, therefore, make possible fuel processors with very low complexity compared to diesel-fueled systems. The work presented in this thesis has enhanced our understanding of diesel and DME reforming and will serve as basis for future studies. / QC 20100804

<p>Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute.</p><p>The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations.</p><p>In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kW_e polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I.</p><p>In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature.</p>

Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transport sector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed. In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration. In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning. / <p>QC 20150213</p>

Die vorliegende Arbeit beschäftigt sich mit der Entwicklung eines dieselbetriebenen autothermen Reformierungssystems (ATR-Einheit) zur Bereitstellung von wasserstoff- und kohlenmonoxidreichem Synthesegas für den maritimen Betrieb einer MCFC-Brennstoffzelle. Aufgrund der niedrigen Schadstoffemissionen sowie des hohen Wirkungsgrades hat dieses System das Potential eine mögliche Alternative zu den bisherigen Schiffsdieselmotoren aufzuzeigen, welche die zukünftigen Emissionsgrenzwerte einhält und zudem noch zu Kosteneinsparungen durch einen geringeren Brennstoffverbrauch beiträgt. Die Hauptkomponenten des Reformierungssystems umfassen im Wesentlichen einen autothermen Reformierungsreaktor sowie einen nachgeschalteten Entschwefelungsreaktor. Für den optimalen Betrieb der beiden Reaktoren wurde ein Verschaltungskonzept entwickelt und umgesetzt, welches durch zusätzliche Peripheriekomponenten wie Strömungsverteiler, Mischer und Wärmeübertrager ergänzt wurde. Diese haben die Aufgabe einen stabilen Reformierungs- und Entschwefelungsprozess zwischen 50 % bis 100 % Betriebslast zu gewährleisten, wofür diverse experimentelle und numerische Methoden zur Optimierung herangezogen wurden. Darüber hinaus wurde die Konzeptionierung der Gesamtverschaltung im Hinblick auf eine gute Regelbarkeit untersucht. Hierfür wurden mehrere Bypassschaltungen vorgesehen, welche bei Teillastbetrieb konstante Betriebstemperaturen am Eintritt des Entschwefelungsreaktors und der Brennstoffzellen ermöglichen. Für die Bestimmung der optimalen Betriebskenngrößen wurden umfangreiche Prozesssimulationen durchgeführt mit Hilfe deren die Auslegung der einzelnen Baugruppen erfolgte. Darüber hinaus wurden insbesondere die optimalen O/C- und S/C-Verhältnisse bestimmt, welche sowohl einen hohen Wirkungsgrad als auch die Einhaltung der Systemrandbedingungen gewährleisten. Mit Hilfe der ermittelten Betriebskenngrößen wurde ein Gesamtkonzept entwickelt, womit neben der konstruktiven Umsetzung insbesondere die Werkstoffauswahl für das druckbeaufschlagte System definiert werden konnte. Im Hinblick auf die Erzielung eines möglichst hohen Reformerwirkungsgrades unter stabilen Betriebsbedingungen wurde das Reformierungssystem als Kernkomponente eines Fuel Processing Moduls realisiert und charakterisiert. Hierbei konnte gezeigt werden, dass sich mit Hilfe des in dieser Arbeit entwickelten Systems ein stabiler Betrieb über mehrere Tage ohne Katalysatordeaktivierung realisieren lässt. Ebenfalls konnte ein modulierender Betrieb zwischen 50 % bis 100 % Betriebslast dargestellt werden, wobei alle Temperaturrestriktionen eingehalten wurden. Zusammenfassend kann festgehalten werden, dass mittels des entwickelten Reformierungssystems eine mögliche Alternative zu den bisherigen Schiffsdieselmotoren aufgezeigt wurde, welche in Kombination mit MCFC-Brennstoffzellen die zukünftig geforderten Schadstoffrestriktionen erfüllt.

117 f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-05-20T13:36:45Z No. of bitstreams: 1 TESE DOUTORADO - GUILLERMO P BERROCAL.pdf: 2123714 bytes, checksum: dbd07cf34792ac2cac402476f9c17a8a (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-06-06T15:58:28Z (GMT) No. of bitstreams: 1 TESE DOUTORADO - GUILLERMO P BERROCAL.pdf: 2123714 bytes, checksum: dbd07cf34792ac2cac402476f9c17a8a (MD5) / Made available in DSpace on 2013-06-06T15:58:28Z (GMT). No. of bitstreams: 1 TESE DOUTORADO - GUILLERMO P BERROCAL.pdf: 2123714 bytes, checksum: dbd07cf34792ac2cac402476f9c17a8a (MD5) Previous issue date: 2009 / FAPESB / Níquel suportado em alumina tem sido reconhecido como um catalisador efetivo das reações de reforma de metano. No entanto, ele apresenta desativação por coque e problemas de estabilidade térmica, em altas temperaturas, principalmente devido à transição de fase do suporte e sinterização do metal. Uma opção atrativa, para obter suportes mais adequados para esses catalisadores, é a combinação da alumina com a zircônia que possui elevada estabilidade térmica, dureza e propriedades anfotéricas. Por outro lado, a adição de metais nobres ao catalisador de níquel usado na reforma de metano poderia evitar a desativação por formação de coque, assim como conduzir a atividades mais elevadas. Desta forma, neste trabalho, foram estudados catalisadores de níquel associados, ou não, ao rutênio suportados em óxidos de alumínio e zircônio, destinados à reforma a vapor e reforma autotérmica de metano. . Foram sintetizados catalisadores monometálicos de níquel (15 %) e bimetálicos de níquel (15 %) e rutênio (razão molar Ru/Ni = 0,1), por impregnação em óxidos de alumínio e/ou zircônio. Estes sólidos foram preparados por métodos de precipitação à temperatura ambiente, a partir de soluções de oxicloreto de zircônio e nitrato de alumínio, obtendo-se materiais com razões molares Al/Zr = 1, 2, 5 e 10 além do óxido de zircônio e de alumínio puros. As amostras foram caracterizadas por espectroscopia no infravermelho com transformadas de Fourier, termogravimetria, análise térmica diferencial, difração de raios X, redução a temperatura programada e medidas de área superficial específica e porosidade. Os catalisadores foram testados na reação de reforma a vapor e autotérmica de metano na faixa de 450 a 750 ºC. . Observou-se a formação da fase γ-Al2O3 na alumina pura e a fases tetragonal e monoclínica na zircônia pura. Com a adição de alumínio à zircônia houve a estabilização da fase tetragonal em todos os casos, em detrimento da monoclínica. A adição de pequenas quantidades de zircônio ao óxido de alumínio produziu um aumento na área superficial especifica da alumina, associado à ação textural do zircônio como espaçador entre as partículas de óxido de alumínio ou à geração de tensões no sólido, causando o deslocamento do equilíbrio para a formação de partículas menores. A adição dos metais (níquel e rutênio) ao suporte causou diminuição da área superficial específica, o que pode estar associado ao bloqueio de alguns poros por esse metal e/ou à sinterização da amostra após a impregnação e calcinação ou a uma combinação desses efeitos. A redução do níquel foi facilitada pela presença do zircônio e/ou do rutênio. Todos os catalisadores foram ativos na reação de reforma a vapor e na reforma autotérmica de metano, observando-se aumento na conversão de metano com a temperatura. Na reação de reforma a vapor e na reforma autotérmica, observouse, que em temperaturas típicas dessas reações, o catalisador de níquel impregnado no suporte com razão molar Al/Zr =10 levou às conversões mais elevadas. O rutênio produz um efeito similar, em catalisadores de níquel isentos de zircônio. Dessa forma, as amostras mais promissórias são aquelas contendo níquel suportado em alumina contendo zircônio ou rutênio. / Salvador

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, it was studied the kinetics of sugarcane straw pyrolysis and the required heat for the biomass degradation using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) under oxidative and inert atmosphere.The biomass characterization was performed using ultimate and elemental analyses, infrared spectroscopy (FTIR), lignine, holocellulose and cellulose quantification. The activation energy (Ea), required heat for biomass pyrolysis and percentage of remnant residues after biomass degradation were evaluated in base of a preliminary study using different oxygen percentages at increasing temperature using three heating rate 5, 10 and 20 ºC/min (50 mL/min). Moreover, in the base of the obtained results, it was performed an experiment planning (Central Compound Planning CCP) in order to optimize the biomass pyrolysis process (sugarcane straw). The biomass decomposition process occurred between 250 and 515ºC using 3% O2 (95% weight loss after pyrolysis process), between 250 and 501ºC using 20% O2 (93% weight loss) and between 250 and 600ºC under inert atmosphere (92% weight loss). The Ea values for the sugarcane straw pyrolysis were obtained in the base of Flynn-Ozawa-Wall (FOW) model. In this context, the lowest Ea value for sugarcane straw pyrolysis was 101-130 kJ/mol when 3% O2 was used. On the other hand, using 20% O2 in a heating rate of 20ºC/min (50 ml/min) for the sugarcane straw pyrolysis, the required heat was the lowest, 161 kJ/kg. In this case, the pyrolysis process needed less energy for the entire process. So, according with the adjusted surface analyses showed that, under the evaluated conditions, the lowest required heat occurred when the percentage of O2 was around 10% and the heating rate increased independently of the used total gas flow. Nevertheless, in the case of remnant residues percentage, this value was the lowest when the heating rate decreased and the oxygen percentage increased. In the analysis of two results showed that the variables in the central level (X1, X2 and X3 equal 0) resulted in optimizing the pyrolysis process to heat required and % remaining residue from about 181.74 kJ/kg and 9, 89%, respectively. It was concluded then that, within the ranges studied, the oxidative pyrolysis was presented as one of the best practicable means for the production of bio-oil through lignocellulosic biomass, as currently investigated conditions showed that the best values for achieving the process bench scale are: oxygen concentrations and rates of heat around the central 10% and 25°C/min, respectively, regardless of the total flow of gas to the technology of pyrolysis, generating a system autothermal, optimizing and enabling the process. / Neste trabalho estudou-se a cinética da pirólise da palha de cana-de-açúcar e o calor requerido para a decomposição térmica da biomassa através de Análise Termogravimétrica (TGA) e Calorimetria Exploratória Diferencial (DSC) em atmosfera inerte e oxidante. Foi realizada a caracterização da biomassa (análise imediata, elementar, espectroscopia de infravermelho por transformada de Fourier - FTIR, quantificação da lignina, obtenção da holocelulose e celulose. O cálculo da energia de ativação (Ea), calor requerido para o processo de pirólise da biomassa e porcentagem de resíduo remanescente após a degradação da palha de cana foram estudados com base em um estudo preliminiar da influência de porcentagem de oxigênio utilizando uma taxa de aquecimento de 5, 10 e 20 ºC/min (50 mL/min) no processo de termoconversão. Em vista dos resultados preliminares obtidos, foi elaborado um planejamento de experimentos (Planejamento Composto Central - PCC) com o objetivo de otimizar o processo de pirólise da biomassa (palha de cana-de-açúcar). O processo de decomposição da biomassa ocorreu entre 250 e 515°C para a atmosfera 3% O2 (95% de perda de massa após o processo de pirólise), 250 e 501ºC para atmosfera 20% O2 (93% de perda de massa) e entre 250 e 600ºC para atmosfera inerte (92% de perda de massa). Através do modelo de Flynn-Ozawa-Wall (FOW) foram obtidos os valores da Ea para pirólise da palha, onde a atmosfera 3% O2 apresentou a menor faixa (101-130 kJ/mol) em comparação com atmosfera de inerte e 20% O2. Entretanto, para o calor requerido, a atmosfera 20% O2 e taxa de aquecimento de 20ºC/min (50 ml/min) apresentou um menor valor de calor requerido, 161 kJ/kg, indicando que maiores taxas de aquecimento e % de oxigênio resultam em menor exigência energética para o processo. Com as faixas estudadas não foi possível obter um ponto ótimo para as respostas calor requerido e porcentagem de resíduo remanescente após a termoconversão. Portanto, de acordo com a análise das superfícies ajustadas, a menor exigência de fornecimento de energia para o processo de pirólise (calor requerido) sucedeu-se quando a porcentagem de oxigênio na mistura dos gases encontrou-se bem próximo do nível central (10% O2) e a taxa de aquecimento aumentou dentro das faixas estudadas, independentemente dos valores de fluxo total de gás. Em relação à porcentagem de resíduo remanescente, esta diminui conforme a taxa de aquecimento diminui e a porcentagem de oxigênio na mistura dos gases aumenta. Na análise conjunta das duas respostas observou-se que as variáveis nos níveis centrais (X1, X2 e X3 iguais a 0) resultou na otimização do processo de pirólise, com calor requerido e % resíduo remanescente de aproximadamente 181,74 kJ/kg e 9,89% respectivamente. Concluiu-se então que, dentro das faixas estudadas, a pirólise oxidativa apresentou-se como um dos meios mais viáveis para a produção de bio-óleo através de biomassas lignocelulósicas, visto que, atualmente, as condições investigadas demonstraram que os melhores valores para realização do processo em escala de bancada são: concentrações de oxigênio e taxas de aquecimento em torno do nível central, 10% e 25ºC/min, respectivamente, independente do fluxo total de gás, para a tecnologia de pirólise, gerando um regime autotérmico, otimizando e viabilizando todo o processo. / Mestre em Engenharia Química

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute. The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations. In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I. In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature. / QC 20101115

Heavy-duty diesel truck engines are routinely idled at standstill to provide cab heating or air conditioning, and in addition to supply electricity to comfort units such as radio and TV. Idling is an inefficient and unfavorable process resulting in increased fuel consumption, increased emissions, shortened engine life, impaired driver rest and health, and elevated noise. Hydrogen-fueled, polymer-electrolyte fuel-cell auxiliary power unit (PEFC-APU) as a silent external power supply, working independently of the main engine, is proposed as viable solution for better fuel economy and abatement of idling emissions. In a diesel PEFC-APU, the hydrogen storage problem is circumvented as hydrogen can be generated onboard from diesel by using a catalytic reformer. In order to make catalytic diesel PEFC-APU systems viable for commercialization research is still needed. Two key areas are the development of reforming catalyst and reformer design, which both are the scope of this thesis. For diesel-reforming catalysts, low loadings of Rh and RhPt alloys have proven to exhibit excellent reforming and hydrogen selectivity properties. For the development of a stable reforming catalyst, more studies have to be conducted in order to find suitable promoters and support materials to optimize and sustain the long-term performance of the Rh catalyst. The next step will be full-scale tests carried out at realistic operating conditions in order to fully comprehend the overall reforming process and to validate promising Rh catalysts. This thesis can be divided into two parts; the first part addresses the development of catalysts in the form of washcoated cordierite monoliths for autothermal reforming (ATR) of diesel. A variety of catalyst compositions were developed containing Rh or RhPt as active metals, CeO2, La2O3, MgO, Y2O3 as promoters and Al2O3, CeO2-ZrO2, SiO2 and TiO2 as support materials. The catalysts were tested in a bench-scale reactor and characterized by using N2-BET, XRD, H2 chemisorption, H2-TPR, O2-TPO, XPS and TEM analyses. The second part addresses the development and testing of full-scale reformers at various realistic operating conditions using promising Rh catalysts. The thesis shows that a variety of Rh on alumina catalysts was successfully tested for ATR of diesel (Papers I-IV). Also, zone-coating, meaning adding two washcoats on specific parts of the monolith, was found to have beneficial effects on the ATR catalyst performance (Paper II). In addition, RhPt supported on CeO2-ZrO2 was found to be one of the most active and promising catalyst candidates for ATR of diesel. The superior performance may be attributed to higher reducibility of RhiOx species and greater dispersion of Rh and Pt on the support (Paper IV). Finally, two full-scale diesel reformers were successfully developed and proven capable of providing high fuel conversion and hydrogen production from commercial diesel over selected Rh catalysts (Papers II-III, V-VI). / QC 20110418