The research presented in this dissertation involved characterization of the Cu/ZnO solid catalyst system as applied to methanol/steam reformation. Thermogravimetry was used to investigate in-lab synthesized samples and a commercial product G66B (Cu/ZnO 33/67 wt. %). The 33% Cu sample contained Cu ions in the ZnO matrix. This phase required the highest temperatures (400°C) for H₂ reduction. The 50% Cu sample reduced at a lower temperature (220°C) but its complete reduction required the same maximum temperature. The higher temperature process was similar to the 33% case, while the lower one was due to the reduction of a amorphous CuO phase. The 66% Cu sample reduced in a fairly narrow low temperature (270°C) range. Therefore, its CuO phase has a amorphous structure. G55B reduced at lower temperatures than the in-lab samples. This difference is possibly due to different synthetic procedures used in the production of G66B and the in-lab samples. The CuO phase of G66B appears to be amorphous and well dispersed. Raman spectroscopy was used to identify the crystal phases of these solids. The complexity of the initial precipitate was monitored versus the Cu/Zn ratio of the system. The nature of the phases present under reduction conditions was determined. This information has provided insight into the active phases involved in methanol reformation. The role of the solids lattice oxygen was determined. The reaction was carried out on labelled ¹⁸O-containing Cu/ZnO. Incorporation of ¹⁸O into both CO₂ and H₂O clearly indicates the involvement of these oxygens in the reaction. Observation of C¹⁸O¹⁸O indicates that the C-O bond in methanol does not remain intact. XPS was used to determine the effects of oxidation, reduction, and reaction on the Cu component of G66B. Upon oxidation all Cu exists as Cu⁺². The catalyst always contains Cu⁺¹ and Cuᵒ after H₂ reduction. After methanol/steam reformation with a 50/50 vol% mxiture, all Cu is reduced to Cuᵒ. Changes in the Cu/Zn ratio of the surface are interpreted in terms of changes in surface morphology.

Uma das principais aplicações do metano é a produção de gás de síntese, mistura de hidrogênio e monóxido de carbono. Três processos podem levar à formação de gás de síntese a partir do metano: reforma a vapor, reforma com CO2 e oxidação parcial. Vários catalisadores de metais não-preciosos foram estudados para os processos de reforma, embora a deposição de carbono ou a sinterização do metal sempre esteja presente. Catalisadores obtidos de precursores do tipo hidrotalcita têm se mostrado resistentes à coqueificação nas reações de reforma a vapor do metano, podendo ser aplicados ao processo combinado de reforma e oxidação parcial de metano para obtenção de gás de síntese, com potencial para minimizar as dificuldades inerentes aos processos: altas temperaturas e desativação do catalisador. Catalisadores de níquel e de cobalto, obtidos a partir de precursores do tipo hidrotalcita, com a adição de cério e de lantânio como promotores, foram preparados, caracterizados e aplicados em testes catalíticos nas reações de reforma a vapor, oxidação parcial e reforma oxidativa do metano, com o intuito de avaliar a atividade e estabilidade destes catalisadores e o efeito dos promotores. Os catalisadores não-promovidos foram obtidos por três métodos: método tradicional, método da co-precipitação com quelato, e troca-ânionica. A adição de promotores foi feita por troca-aniônica. Os compostos foram caracterizados por Energia dispersiva de Raios-X , Área Superficial Específica Total, Análise Termogravimétrica, Difração de Raios-X, Espectroscopia de Absorção na região do Infravermelho, Redução a Temperatura Programada, Espectroscopia Fotoeletrônica de Raios-X, Espectroscopia de Absorção de Raios-X e testes catalíticos com as reações de Reforma a vapor do metano, com razões molares de alimentação H2O:CH4= 4:1; 2:1 e 0,5:1, Oxidação Parcial do metano com razões molares de alimentação CH4:O2=2:1 e 4:1 e Reforma oxidativa do metano com razão molar de alimentação CH4:H2O:O2= 4:4:1. Os catalisadores mostraram-se ativos nas reações de reforma a vapor do metano, com exceção dos catalisadores de cobalto que não foram ativos para a razão de alimentação H2O:CH4= 4:1. A adição de promotores favoreceu a reação de deslocamento gás-água. Nas reações de oxidação parcial do metano, os catalisadores foram ativos para a razão de alimentação CH4:O2=4:1, com considerável redução na velocidade de formação de carbono para os catalisadores promovidos. Na reforma oxidativa do metano, o acoplamento levou a um favorecimento na seletividade para formação de CO2 e a uma maior velocidade de formação de carbono. / One of the most important applications of methane is the syngas production, a mixture of H2 and CO. Three processes can lead to syngas formation from methane: steam reforming, CO2 reforming and partial oxidation. Various non-noble metal catalysts were studied in these processes, although the carbon deposition or the metal sinterization is always observed. Catalysts prepared from hydrotalcite precursors have presented resistance to carbon deposition, and considering this aspect they could be applied to the combined process of methane reforming with partial oxidation to produce syngas, with potential to minimize the difficulties of the process: high temperatures and catalyst deactivation. In this work, nickel and cobalt catalysts, prepared from hydrotalcites and promoted with lanthanum and cerium, were prepared, characterized and tested in the reactions of steam reforming, partial oxidation and oxidative reforming of methane, with the goal of evaluating the activity and stability of these catalysts and the effect of promoter addition. The un-promoted catalysts were prepared through three methods: the traditional method, the method of co-precipitation with chelate and the anion-exchange method. The promoter addition was made through the anion-exchange method. The compounds were characterized by Energy Dispersive X-Ray Spectroscopy (EDX), Specific Surface Area, Thermo gravimetric Analysis, X-Ray Diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Temperature Programend Reduction (TPR), X-Ray Photoelectron Spectroscopy (XPS), X-Ray Absortion Spectroscopy (XAS) and catalytic tests using the folowing reactions of methane: steam reforming with molar ratio in feed of H2O:CH4= 4:1; 2:1 and 0,5:1, partial oxidation with molar ratio in feed of CH4:O2=2:1 e 4:1 and oxidative reforming with molar ratio in feed of CH4:H2O:O2= 4:4:1. All catalysts showed activity for methane steam reforming, except the cobalt catalysts, which did not present activity for the reaction with molar in feed of H2O:CH4= 4:1. The promoters addition favored the shift reaction. For the partial oxidation reactions, the catalysts presented activity for molar ratio in feed of CH4:O2=4:1, with pronounced reduction in the velocity of carbon formation for promoted catalysts. In the oxidative reforming, the coupling of the reactions lead to a favoring in the selectivity for CO2 but a higher velocity of carbon formation.\"

<p>Biomass derived oil (BDO) reforming with CO2 was carried out at 800oC under atmospheric pressure in a tubular fixed bed vertical reactor packed with quartz particles. The feed gas was a mixture of CO2 and N2 at various compositions with a flow rate of 30 to 60 cm3/min. The BDO flow rate was 5 g/h. The product gas consisted mostly of H2, CO, CO2, CH4 and C2H4.</p><p>The maximum production of synthesis gas (~76 mol%) was observed at a total carrier gas flow rate of 60 cm3/min and a mole fraction of CO2 in carrier gas of 0.1. Maximum hydrogen (42 mol%) and H2 to CO molar ratio (1.44) were obtained while using only N2 as the carrier gas at a flow rate of 50 cm3/min. In the range of residence time considered, CO2 was not consumed in BDO gasification at 800oC but helped to increase gas production at the expense of the char.</p><p>Pyrolysis of lard was performed to produce a diesel-like liquid and a high heating value gaseous fuel. Lard was fed into the reactor at 5 g/h using N2 (10-70 cm3/min) as carrier gas. Two particle size ranges of quartz particles (0.7-1.4 and 1.7-2.4 mm) were used as reactor packing material. The liquid product essentially consisted of linear and cyclic alkanes and alkenes, aromatics, ketones, aldehydes and carboxylic acids. The maximum yield for diesel-like liquid product (37g/100g lard) was obtained at 600oC, residence time of 1.5 s and packing particle size of 1.7- 2.4 mm. The liquid product obtained at 600oC, carrier gas flow rate of 50 cm3/min and quartz packing particle size of 0.7-1.4 mm has a cetane index of 46, specific gravity of 0.86, a heating value of 40 MJ/kg and cloud and pour points of 10 and -18 respectively. The heating value of the product gas ranged between 68 and 165 MJ/m3. This study shows that there is a potential for producing diesel-like liquid from pyrolysis of lard. It also identifies the pyrolysis of animal fats as a source of high heating value gaseous fuel.</p><p>Steam reforming of lard was performed at 500, 550, 600 and 800oC and at steam to lard mass ratios of 0.5 to 2.0. The maximum diesel-like liquid yield from the steam reforming process (39 g/100g of lard) was obtained at a steam to lard ratio of 1.5 and a temperature of 600oC. Higher cetane index (52) and lower viscosity (4.0 mPa.s at 40oC) were obtained by addition of steam. The net energy recovered from pyrolysis and steam reforming processes were 21.7and 21.9 kJ/g of lard respectively. Thus, the processes are energy efficient.</p><p>In comparison, lard is a better feedstock for the production of hydrogen, char, high heating value gas and high H2/CO ratio than BDO. On the other hand, BDO is the preferred feedstock for the production of synthesis gas with H2/CO in the vicinity of 1.</p>

Consuming two major greenhouse gases, carbon dioxide (CO2) and methane (CH4), to produce synthesis gas, which is a mixture of carbon monoxide (CO) and hydrogen (H2), CO2 reforming of CH4 shows significant environmental and economic benefits. However, the process has not found wide industrial application due to severe catalyst deactivation, basically caused by carbon formation. Therefore, it is of great interest to develop stable catalysts without severe deactivation. This work is primarily focused on the development of novel nickel-based catalysts to achieve stable operation for CO2 reforming of CH4.<p> Following Dowdens strategy of catalyst design, a series of nickel-based catalysts are designed with a general formula: Ni-Me/AlMgOx (Me = Co, Cu, Fe, or Mn). The designed catalysts are prepared using co-precipitation method and tested for CO2 reforming of CH4. Catalyst screening showed that the Ni-Co/AlMgOx catalyst has superior performance in terms of activity and stability to other Ni-Me/AlMgOx (Me = Cu, Fe, or Mn) catalysts. A 2000 h long-term deactivation test has shown that the Ni-Co/AlMgOx has high activity and excellent stability for CO2 reforming of CH4.<p> Further investigation on the Ni-Co/AlMgOx catalysts shows that adjusting Ni/Co ratio and Ni-Co loading can significantly affect the catalyst performance. Carbon free operation for CO2 reforming of CH4 can be achieved on the catalysts with a Ni/Co close to 1 and Ni-Co overall loading between 4-10 %. In addition, calcination temperature shows important impacts on the performance of Ni-Co/AlMgOx catalysts. A calcination temperature range of 700-900 oC is recommended.<p> The Ni-Co/AlMgOx catalysts are characterized using various techniques such as ICP-MS, BET, CO-chemiosorption, XRD, TPR, TG/DTA, TEM, and XPS. It has been found that the high activity and excellent stability of Ni-Co/AlMgOx catalysts can be ascribed to its high surface area, high metal disperation, small particle size, strong metal-support interaction, and synergy between Ni and Co.<p> Kinetic studies have shown that the CH4 decomposition and CO2 activation could be the rate-determining steps. Both Power-Law and Langmuir-Hinshelwood kinetic models can fit the experiment data with satisfactory results.

<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).

La energía se ha convertido en una necesidad vital para garantizar el desarrollo de las sociedades modernas. Entre las diferentes posibles alternativas para producir energía, el hidrogeno presenta varias características que lo convierten en un atractivo vector energético: primero, se trata de una tecnología más eficiente para transformar la energía química en electricidad -por ejemplo, utilizando pilas de-combustible, las cuales también reducen de manera significativa los niveles de emisión de CO2 -; en segundo lugar, el hidrogeno puede ser producido a partir de una amplia variedad de materias primas, incluyendo recursos renovables y no renovables. Sin embargo, las tecnologías para producir hidrogeno para applicaciones con pilas de combustible aun requieren de un esfuerzo en investigación y desarrollo.El objetivo principal de esta tesis fue de evaluar técnicamente las opciones para preparar y utilizar catalizadores en placas insertados en un reactor de pared catalítica para producir hidrogeno mediante el reformado por vapor de etanol bajo condiciones de alta eficiencia térmica. Para completar el objetivo general y los objetivos específicos, se diseño un plan experimental sistemático, compuesto de tres partes: documentación, experimentación y simulación numérica. La información utilizada se puede clasificar en tres ramas: primero, una revisión detallada de las características generales que presentan las técnicas de reformado, seguido por una revisión descriptiva del reformado por vapor de etanol, enfocado en los principales aspectos de la preparación de catalizadores y la realización de la reacción química. A continuación en segundo lugar, se presenta una descripción acerca de reactores estructurados y los métodos para preparar catalizadores. Por último, en tercer lugar, se expone una explicación centrada en los materiales, equipos y métodos empleados para explorar el rendimiento de los catalizadores. Esta parte incluye la descripción de: algunas de las técnicas analíticas más comunes para caracterizar y evaluar tanto catalizadores como compuestos químicos y la descripción de las herramientas utilizadas en la simulación numérica.El primer bloque de simulación numérica tiene como fin evaluar las posibles restricciones termodinámicas por medio de análisis específicos basados en el equilibrio termodinámico, tanto del reactor como del proceso integrado. Luego, se ejecuta un mapeo del conjunto de condiciones operacionales, compuesto por cuatro variables principales: (temperatura, relación vapor carbón, presión y factor de recobro de hidrogeno en el separador de membrana). Ello con el fin de garantizar una operación auto-térmica del procesador de combustible. Se compara la habilidad y la ventaja entre los diferentes tipos de catalizadores publicados en trabajos previos en base a las condiciones termodinámicas ideales determinadas en el análisis termodinámico.Para los catalizadores en polvo, se realizo experimentos de caracterización y reacción mediante el empleo de un reactor de lecho fijo. Se ha efectuado un estudio sistematico para comparar la actividad y la selectividad de dos tipos de catalizadores, bajo condiciones moderadas de temperatura y relación vapor carbón. Los catalizadores basados en níquel (Ni/La2O3-Al2O3) y cobalto (Co-Fe/ZnO y Co-Mn/ZnO) han sido preparados y probados a las siguientes condiciones: temperatura en el rango de 400-500°C, relación vapor carbono entre 2 y 4, tiempo de contacto desde 4.3 hasta 1100 min·gcat molEtOH-1, cubriendo un rango de conversión de etanol desde 20 hasta 100%. Se ha efectuado un diseño de análisis multifactorial para establecer la influencia de las variables (temperatura, relación vapor carbón, tiempo de contacto y formulación del catalizador) en términos de la conversión de etanol y la selectividad hacia los diferentes productos.Por último, se ha efectuado la caracterización, simulación y experimentación utilizando una configuración de reactor de pared catalítica. Primero, se emplea un modelo en 2D para analizar las características principales del reactor de pared catalítica diseñado y construido para realizar la reacción sobre las placas con catalizador previamente preparadas. En segundo lugar, se expone de manera detallada el método seguido para preparar dos tipos diferentes de placas catalíticas. Estas placas con catalizador son caracterizadas de manera similar al método empleado con los catalizadores en polvo. Luego, se ha realizado un estudio sistemático para comparar la actividad y la selectividad de los dos tipos de placas catalíticas. Por último, mediante un modelo 1D se revelan aspectos fundamentales de la configuración del reactor de pared catalítica utilizando una configuración con dos canales paralelos, en los cuales se ejecutan una reacción endotérmica y otra exotérmica respectivamente.La principal conclusión de este trabajo es que el reformado por vapor de etanol puede ser realizado bajo condiciones de alta eficiencia térmica si se emplea un diseño basado en un reactor de pared catalítica con recobro de calor integrado a una unidad de separación para la purificación del hidrogeno. Las placas catalíticas han demostrado ser un elemento fundamental en este tipo de reactor porque incrementan de manera significativa el transporte de calor que se requiere para sostener las reacciones endotérmicas. / Energy has become a fundamental necessity to guarantee modern society development. Among different alternatives possible to produce energy, hydrogen presents several characteristics which make it an attractive energy vector: first, more efficient processes to transform chemical energy into electricity -such as Fuel Cells that, in addition, will help to reduce significantly CO2 emission levels-; and second, hydrogen can be produced from a large variety of feed stocks, including fossil and renewable resources. However, as hydrogen production technologies for Fuel Cell applications are not available commercially yet, it still requires additional R&D efforts.The principal objective of this thesis was to evaluate technical feasibility for preparing and using catalytic plates in a Catalytic Wall Reactor configuration to produce hydrogen by Steam Reforming of Ethanol under conditions of high thermal efficiency. To fulfill the overall and specific objectives, a systematic experimental plan was designed and executed. It was composed of three main parts: documentation, experimentation and numerical simulation. Background information is divided into three branches, first a detailed overview of technical features for reforming technology, followed by a descriptive review of Steam Reforming of Ethanol key aspects for catalysts preparation and reaction performance. Third is presented a comprehensive examination on structured reactor and catalyst preparation methods. In this part is exposed a detailed explanation of materials, equipments, and methods employed for screening catalyst and evaluating catalytic reactor performance. Also, is presented employed techniques for catalyst characterization and fluid analysis. Finally are described tools for numerical simulation.First component of numerical simulations evaluates possible thermodynamic constrains through specific analyses based on thermodynamic equilibrium of reactor and integrated fuel processor. Then, is performed a mapping for the set of four operational variables (temperature, steam to carbon ratio, pressure, and hydrogen recovery in the membrane separator), that allow an auto-thermal operation of the fuel processor. The suitability and advantages of the different catalysts preparations that are known from recent publications are discussed on the basis of the operation conditions determined on the thermodynamic analysis.Experimental work is performed for powder catalyst characterization and catalytic experimentation using a Packed Bed Reactor (PBR). It has conducted a systematic study to compare the activity and selectivity of two types of catalyst at moderate temperature and steam to carbon (SC) ratios. Nickel-based catalysts (Ni/La2O3-Al2O3) and novel Co-based catalysts (Co-Fe/ZnO and Co-Mn/ZnO) have been prepared and tested at temperatures of 400 and 500 °C, Steam to Carbon (SC) molar ratios of 2 and 4, and contact times from 4.3 to 1100 min·gcat molEtOH-1, covering a range of ethanol conversion from 20 to 100%. A multifactorial design analysis has been conducted to establish the significance of temperature, SC ratio, contact time and catalyst formulation on ethanol conversion and selectivity towards the different reaction products.At last, it is carried out the catalytic plate characterization, simulation and experimentation using a Catalytic Wall Reactor configuration. First, is used a 2D modeling to analyze main characteristics of the Catalytic Wall Reactor designed and constructed to perform reactions on the prepared catalytic plates. Prepared catalytic plates are characterize in a similar way to that employed for the powder catalysts. After that, it was conducted a systematic study to compare the activity and selectivity of two types of catalytic plates. 1D model reveals main aspects on thermal performance for a theoretical Catalytic Wall Reactor using two co-current channels with endothermic and exothermic reactions respectively.Main conclusion from this work is that Steam Reforming of Ethanol can be performed at high thermal efficiency if the design of the fuel processor is based on structured catalytic wall reactors with integrated heat recovery coupled to a separation unit for hydrogen purification. Catalytic plates have proven to be a key component on CWR because improves significantly the heat transfer which is required to sustain endothermic reactions.

The conversion of ethanol to hydrogen or syngas can be achieved by reacting ethanol with water via steam reforming, CH3CH2OH + (1-x)H2O = (4-x)H2 + (2-x)CO + xCO2 (R.1) CH3CH2OH + H2O = 4H2 + 2CO (R.2) CO + H2O = H2 + CO2 (R.3) Ideally, the ethanol steam reforming reaction can achieve a hydrogen yield of 6 moles of hydrogen per mole of ethanol when the value of x in (R.1) equals 2. High theoretical H2 yield makes ethanol steam reforming a very attractive route for H2 production. Thermodynamic equilibrium studies have shown that ethanol steam reforming produces mixtures of H2, CO, CO2, and CH4 below 950 K, while above 950 K the ethanol steam reforming reaction (R.1) adequately describes the product composition In this study a series of 10wt% Ni loaded Mg-Al mixed oxide supported catalysts were evaluated for the production of hydrogen via the steam reforming of ethanol. Mg-Al mixed oxide supported nickel catalysts were found to give superior activity, steam reforming product selectivity (H2 and COx), and improved catalyst stability than the pure oxide supported nickel catalyst at both temperatures investigated. Activity, product selectivity, and catalyst stability were dependent upon the Al and Mg content of the support. At 923 K, the Mg-Al mixed oxide supported nickel catalysts were the best performing catalysts exhibiting the highest steam reforming product yield and were highly stable, showing no signs of deactivation after 20 h of operation. The improved performance of the Mg-Al mixed oxide supported catalysts was related to the incorporation of the pure oxides, MgO and Al2O3, into MgAl2O4. The formation of MgAl2O4 reduced nickel incorporation with the support material since MgAl2O4 does not react with Ni; therefore, nickel was retained in its active form. In addition, incorporation of Mg and Al in to MgAl2O4, a slight basic material, modified the acid-base properties resulting in a catalyst that exhibited moderate acidic and basic site strength and density compared to the pure oxide supported catalysts. Moderation of the acid-base properties improved the activity, selectivity, and stability of the catalysts by reducing activity for by-product reactions producing ethylene and acetaldehyde. At lower reaction temperatures, below 823 K, Mg-Al mixed oxide supported nickel catalysts experienced substantial deactivation resulting in reduced ethanol conversion but interestingly, the H2 and CO2 yields increased, exceeding equilibrium expectations with time on stream while CH4 yield decreased far below equilibrium expectations, suggesting a direct ethanol steam reforming reaction pathway. Over stabilized Mg-Al mixed oxide supported nickel catalysts, direct ethanol steam reforming was activated by a reduction in the catalyst’s activity for the production and desorption of CH4 from the surface. The effect of pressure on the direct ethanol steam reforming reaction pathway over stabilized Mg-Al mixed oxide supported nickel catalysts was investigated at 673 and 823 K. At 823 K, increasing the total pressure resulted in a product distribution that closely matched the thermodynamic expectations. However, at 673 K, the product distribution deviated from thermodynamic expectations, giving substantially greater yields for the steam reforming products, H2, CO, and CO2, while CH4 yield was consistently less than equilibrium expectations. The identification of an alternative direct ethanol steam reforming reaction pathway at relatively low temperatures (below 823 K) that could be operated at elevated pressures will result in an energy efficient process for the production of hydrogen from bio-ethanol.

The conversion of ethanol to hydrogen or syngas can be achieved by reacting ethanol with water via steam reforming, CH3CH2OH + (1-x)H2O = (4-x)H2 + (2-x)CO + xCO2 (R.1) CH3CH2OH + H2O = 4H2 + 2CO (R.2) CO + H2O = H2 + CO2 (R.3) Ideally, the ethanol steam reforming reaction can achieve a hydrogen yield of 6 moles of hydrogen per mole of ethanol when the value of x in (R.1) equals 2. High theoretical H2 yield makes ethanol steam reforming a very attractive route for H2 production. Thermodynamic equilibrium studies have shown that ethanol steam reforming produces mixtures of H2, CO, CO2, and CH4 below 950 K, while above 950 K the ethanol steam reforming reaction (R.1) adequately describes the product composition In this study a series of 10wt% Ni loaded Mg-Al mixed oxide supported catalysts were evaluated for the production of hydrogen via the steam reforming of ethanol. Mg-Al mixed oxide supported nickel catalysts were found to give superior activity, steam reforming product selectivity (H2 and COx), and improved catalyst stability than the pure oxide supported nickel catalyst at both temperatures investigated. Activity, product selectivity, and catalyst stability were dependent upon the Al and Mg content of the support. At 923 K, the Mg-Al mixed oxide supported nickel catalysts were the best performing catalysts exhibiting the highest steam reforming product yield and were highly stable, showing no signs of deactivation after 20 h of operation. The improved performance of the Mg-Al mixed oxide supported catalysts was related to the incorporation of the pure oxides, MgO and Al2O3, into MgAl2O4. The formation of MgAl2O4 reduced nickel incorporation with the support material since MgAl2O4 does not react with Ni; therefore, nickel was retained in its active form. In addition, incorporation of Mg and Al in to MgAl2O4, a slight basic material, modified the acid-base properties resulting in a catalyst that exhibited moderate acidic and basic site strength and density compared to the pure oxide supported catalysts. Moderation of the acid-base properties improved the activity, selectivity, and stability of the catalysts by reducing activity for by-product reactions producing ethylene and acetaldehyde. At lower reaction temperatures, below 823 K, Mg-Al mixed oxide supported nickel catalysts experienced substantial deactivation resulting in reduced ethanol conversion but interestingly, the H2 and CO2 yields increased, exceeding equilibrium expectations with time on stream while CH4 yield decreased far below equilibrium expectations, suggesting a direct ethanol steam reforming reaction pathway. Over stabilized Mg-Al mixed oxide supported nickel catalysts, direct ethanol steam reforming was activated by a reduction in the catalyst’s activity for the production and desorption of CH4 from the surface. The effect of pressure on the direct ethanol steam reforming reaction pathway over stabilized Mg-Al mixed oxide supported nickel catalysts was investigated at 673 and 823 K. At 823 K, increasing the total pressure resulted in a product distribution that closely matched the thermodynamic expectations. However, at 673 K, the product distribution deviated from thermodynamic expectations, giving substantially greater yields for the steam reforming products, H2, CO, and CO2, while CH4 yield was consistently less than equilibrium expectations. The identification of an alternative direct ethanol steam reforming reaction pathway at relatively low temperatures (below 823 K) that could be operated at elevated pressures will result in an energy efficient process for the production of hydrogen from bio-ethanol.

<p>Biomass derived oil (BDO) reforming with CO2 was carried out at 800oC under atmospheric pressure in a tubular fixed bed vertical reactor packed with quartz particles. The feed gas was a mixture of CO2 and N2 at various compositions with a flow rate of 30 to 60 cm3/min. The BDO flow rate was 5 g/h. The product gas consisted mostly of H2, CO, CO2, CH4 and C2H4.</p><p>The maximum production of synthesis gas (~76 mol%) was observed at a total carrier gas flow rate of 60 cm3/min and a mole fraction of CO2 in carrier gas of 0.1. Maximum hydrogen (42 mol%) and H2 to CO molar ratio (1.44) were obtained while using only N2 as the carrier gas at a flow rate of 50 cm3/min. In the range of residence time considered, CO2 was not consumed in BDO gasification at 800oC but helped to increase gas production at the expense of the char.</p><p>Pyrolysis of lard was performed to produce a diesel-like liquid and a high heating value gaseous fuel. Lard was fed into the reactor at 5 g/h using N2 (10-70 cm3/min) as carrier gas. Two particle size ranges of quartz particles (0.7-1.4 and 1.7-2.4 mm) were used as reactor packing material. The liquid product essentially consisted of linear and cyclic alkanes and alkenes, aromatics, ketones, aldehydes and carboxylic acids. The maximum yield for diesel-like liquid product (37g/100g lard) was obtained at 600oC, residence time of 1.5 s and packing particle size of 1.7- 2.4 mm. The liquid product obtained at 600oC, carrier gas flow rate of 50 cm3/min and quartz packing particle size of 0.7-1.4 mm has a cetane index of 46, specific gravity of 0.86, a heating value of 40 MJ/kg and cloud and pour points of 10 and -18 respectively. The heating value of the product gas ranged between 68 and 165 MJ/m3. This study shows that there is a potential for producing diesel-like liquid from pyrolysis of lard. It also identifies the pyrolysis of animal fats as a source of high heating value gaseous fuel.</p><p>Steam reforming of lard was performed at 500, 550, 600 and 800oC and at steam to lard mass ratios of 0.5 to 2.0. The maximum diesel-like liquid yield from the steam reforming process (39 g/100g of lard) was obtained at a steam to lard ratio of 1.5 and a temperature of 600oC. Higher cetane index (52) and lower viscosity (4.0 mPa.s at 40oC) were obtained by addition of steam. The net energy recovered from pyrolysis and steam reforming processes were 21.7and 21.9 kJ/g of lard respectively. Thus, the processes are energy efficient.</p><p>In comparison, lard is a better feedstock for the production of hydrogen, char, high heating value gas and high H2/CO ratio than BDO. On the other hand, BDO is the preferred feedstock for the production of synthesis gas with H2/CO in the vicinity of 1.</p>

<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).