An investigation was undertaken to determine the feasibility of increasing the hydrogen production rate by coupling the water gas shift (WGS) process to the hybrid sulphur process (HyS). This investigation also involved the technical and economical analysis of the water gas shift and the H2 separation by means of Pressure swing adsorption (PSA) process. A technical analysis of the water gas shift reaction was determined under the operating conditions selected on the basis of some information available in the literature. The high temperature system (HTS) and low temperature system (LTS) reactors were assumed to be operated at temperatures of 350°C and 200°C, respectively. The operating pressure for both reactors was assumed to be 30 atmospheres. The H2 production rate of the partial oxidation (POX) and the WGS processes was 242T/D, which is approximately two times the amount produced by the HyS process alone. The PSA was used for the purification process leading to a hydrogen product with a purity of 99.99%. From the total H2 produced by the POX and the WGS processes only 90 percent of H2 is recovered in the PSA. The unrecovered H2 leaves the PSA as a purge gas together with C02 and traces of CH4, CO, and saturated H20. The estimated capital cost of the WGS plant with PSA is about US$50 million. The production cost is highly dependent on the cost of all of the required raw materials and utilities involved. The production cost obtained was US $1.41/kg H2 based on the input cost of synthesis gas as produced by the POX process. In this case the production cost of synthesis gas based on US $6/GJ for natural gas and US $0/Ton for oxygen was estimated to be US $0.154/kg. By increasing the oxygen and natural gas cost, the corresponding increase in synthesis gas has resulted in an increase in H2 production cost of US $1.84/kg. / Thesis (M.Sc. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2009.

Esta dissertação mostra um estudo preliminar da preparação de precursores catalíticos a base de níquel (II) e de sua conversão em catalisadores de xerogéis contendo níquel (NS), bem como o estudo da sua atividade catalítica na reação de deslocamento gás-água. Esta reação foi escolhida como reação modelo para avaliar a atividade catalítica, em especial frente a adição do ácido fosfotungstico (HPW) como promotor catalítico e de organosilanos como agentes promotores da dispersão do Ni. Foram preparados catalisadores NS e NS-x (x = 0,5; 1; 2; 3; 5 e 10% em massa de HPW) via processo sol-gel. A caracterização estrutural foi realizada utilizando-se as técnicas de Energia Dispersiva de Raios X, Difratometria de Raios X, Redução a Temperatura Programada, Fisissorção de Nitrogênio, Espectroscopia de Absorção de Raios X e Espectroscopia de Absorção na Região do Infravermelho. Os testes catalíticos foram realizados no Laboratório de Catálise Heterogênea do IQSC/USP numa temperatura de 250-425 °C, em uma lin ha de reação acoplada a um cromatógrafo a gás para análises in situ dos produtos reacionais gasosos. Os resultados obtidos da primeira parte mostraram que a adição do HPW até 2% em massa de precursor catalítico leva a uma melhora gradual na atividade catalítica de 10 a 31 % medido pela taxa de conversão do CO. Contudo acima de 2% ocorre uma queda de atividade catalítica resultando num comportamento global da conversão de CO do tipo gaussiano com o máximo em 2%. Para explicar este comportamento um modelo qualitativo é proposto baseado na formação de fosfotungstato de níquel amorfo acima de 2%. Na segunda parte do trabalho, a concentração de HPW foi fixada em 2% e a temperatura de reação em 425 °C e foram adicionados organosilanos nitrogenados (amino e nitrila) para avaliar a sua capacidade de funcionar como agentes de dispersão do cátion metálico no precursor híbrido (Ormosil) e do metal no catalisador. O catalisador proveniente do precursor contendo grupo amina possui maior atividade catalítica que aquele contendo nitrila, porém ambos possuem menor atividade que o xerogel catalítico obtido de precursores sem grupos nitrogenados. Contudo, os catalisadores preparados a partir de Ormosils mostravam-se estáveis ao longo do tempo da reação estudada quando comparados com os xerogeis NS-x. / This dissertation describes the preparation of Ni (II)-based catalyst precursor material and its subsequent conversion to Ni-based xerogels catalyst as well as the catalytic activity of the resultant catalyst in water-gas shift reaction. The water-gas shift reaction was selected as a model reaction for the evaluation of catalytic activity of the prepared catalysts. The effect of addition of phosphotungstic acid (HPW) as an activity promoting agent and organosilane as dispersing agents of Ni was also studied. For this purpose, Ni-based catalyst (NS-x) containing various amounts (x) of HPW (x= 0, 0.5, 1, 2, 3, 5, 10 wt. %) were prepared using the sol-gel process. These catalysts were characterized by x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), temperature-programmed reduction (TPR), nitrogen adsorption measurements (BET method) and Fourier transform infrared spectroscopy (FTIR). The catalytic tests were performed at a temperature of 250-425 °C in a reactor coupled with gas chromatograph (GC) for direct in situ analysis of the reaction products. The results obtained showed that addition of HPW up to 2 wt % leads to an increase in the efficiency of the catalyst from 10% to 31%, as measured by the rate of conversion of CO. However, further increase in the amount of HPW above 2 wt. % leads to a decrease in activity of the catalyst. A qualitative model based on the formation of amorphous Ni-phosphotungstate salt is proposed to explain this behaviour of the catalyst. In a second part of this study, the amount of HPW (2 wt. %) and temperature (425 °C) were fixed and nitrogenate d silanes with amine and nitrile functional groups were added to the catalyst to evaluate the role of these ormosils as dispersing agents for metallic cations in the hybrid precursor material as well as metallic nickel in the final catalyst. The catalyst derived from precursor containing ormosils with ammine functional groups (3-Aminopropyltriethoxysilane) showed better catalytic activity than those containing nitrile functional groups (4-(Triethoxysilyl)butyronitrile). However, the catalytic activity of the catalysts obtained using ormosils bearing nitrogenated silanes was lower than xerogels catalyst prepared without addition of these silanes. Although, the catalysts prepared using the ormosils bearing nitrogenated silanes showed higher stability than NS-x catalyst.

Orientador: Daniela Zanchet / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T07:36:24Z (GMT). No. of bitstreams: 1 Kokumai_TathianaMidori_M.pdf: 2185484 bytes, checksum: f809cfde78398806bc98554749cf01c8 (MD5) Previous issue date: 2014 / Resumo: Nanobastões de céria (CeO2) funcionalizados com grupos amino foram utilizados como suporte em catalisadores de cobre para a reação de deslocamento gás-água (WGS). A funcionalização da superfície do óxido foi realizada visando uma melhor dispersão da fase metálica no suporte, através da interação entre o grupo amino e o precursor Cu2+, com a posterior correlação entre esta modificação e a atividade do catalisador. Utilizou-se o método hidrotérmico para a síntese dos nanobastões, que foram posteriormente funcionalizados com 3-(aminopropil)trimetoxisilano. A adição do precursor Cu2+ ao suporte foi feita via impregnação, seguida de calcinação e redução (ativação do catalisador), etapa na qual se formaram as nanopartículas metálicas (Cu0) suportadas. Comparando os catalisadores com suporte de céria pura e de céria funcionalizada, observou-se que de fato a funcionalização resultou na maior dispersão do Cu2+ na superfície. No entanto, ela causou a menor dispersão do metal (Cu0) após a redução, a diminuição da redutibilidade da céria superficial, a fragmentação dos bastões e o menor desempenho catalítico frente à reação de WGS. Visando a compreensão destes sistemas, verificou-se que a calcinação após a adição de Cu2+ na amostra funcionalizada formou uma camada de SiO2 na superfície da céria, o que diminui a atividade por reduzir as interações Cu-CeO2 (formação de Cu-O-Si), corroborando a grande influência desta interface no desempenho destes catalisadores. Além disso, a menor dispersão de Cu0 na superfície funcionalizada após a redução demonstrou a importância da céria também na estabilização da fase metálica. Desta maneira, a funcionalização da superfície se mostrou uma abordagem interessante no que se refere à dispersão do precursor metálico no suporte / Abstract: Amino functionalized ceria nanorods were explored as support on copper catalysts for the water-gas shift (WGS) reaction. The purpose of the design of a functionalized oxide surface was to obtain a better metal phase dispersion on the support provided by amino-Cu2+ interaction, in addition to further correlation between this modification and the catalyst activity. The hydrothermal method was used to synthetize the nanorods, which were subsequently functionalized with 3-(aminopropyl)trimethoxysilane. The Cu2+ precursor was added to the support by impregnation, followed by calcination and reduction (catalyst activation), when the supported metallic (Cu0) nanoparticles were formed. By comparison of the catalysts obtained with pure ceria and functionalized ceria supports it was observed that the functionalization indeed caused a greater Cu2+ dispersion on the oxide surface. However, it gave rise to a lower metal dispersion (Cu0) after reduction step, along with the decrease of surface ceria reducibility, nanorods fragmentation and inferior catalytic performance towards WGS reaction. In order to understand these systems, it was confirmed that the calcination step (after Cu2+ addition) on functionalized sample created a SiO2 layer above ceria surface, therefore lowering the activity due to the decrease of Cu-CeO2 interactions (formation of Cu-O-Si), which corroborated the great influence of Cu-CeO2 interface on the activity. Also, the lower Cu0 dispersion on the functionalized surface after reduction showed the importance of ceria on the metallic phase stabilization. Hence, the surface functionalization demonstrated to be an interesting approach to the dispersion of metal precursor on the catalyst support / Mestrado / Quimica Inorganica / Mestra em Química

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京都大学 / 新制・論文博士 / 博士(理学) / 乙第13460号 / 論理博第1577号 / 新制||理||1683(附属図書館) / (主査)教授 北川 宏, 教授 吉村 一良, 教授 竹腰 清乃理 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM

A comprehensive process intensification analysis was performed for the integration of the Pd-based membrane reactor technology into IGCC power plants by designing effective process control strategies as well as identifying and optimally characterizing inherently safe operational conditions to achieve the most favorable economic outcomes. Experimental results indicated that Pd-based composite membranes supported on porous stainless steel tubes, fabricated with H2 permeance values as high as ~50 m3/[m2.h.atm0.5] at 450°C were capable of extra purity H2 production (≥99.99%). Two illustrative process control and performance monitoring cases namely, process regulation and servo mechanism, were considered and quite satisfactory process control was attained by maintaining CO conversion at levels higher than 95% so that the retentate stream could become suitable for high pressure CO2 sequestration. From a process safety standpoint, process parameters and operating conditions were identified and optimized to achieve the target performance level of 98% CO conversion and 95% H2 recovery and at the same time to prevent conditions which could potentially induce hazards and thus compromise process system safety. Furthermore, the average total product cost of a water-gas shift membrane reactor module including manufacturing costs and general expenses was carefully estimated by taking into account the full cost structure and found to be 1464 $/ft2. Moreover, a comprehensive economic assessment was performed for composite Pd/Alloy membrane reactor technology options integrated into IGCC power plants in the presence of market and regulatory uncertainty (possible regulatory action on CO2 emissions) as well as technology risks with the aid of Monte-Carlo simulation techniques. Within such a context, it was demonstrated that an IGCC plant with embedded Pd-based membrane reactors and a stream of revenues coming from electricity and H2 selling (IGCC co-production mode), represented an economically attractive and advantageous option when comparatively assessed against its main competitors namely, an IGCC plant with shift reactors and double stage Selexol units as well as the more traditional supercritical pulverized coal power plant option with an Econamine unit installed for CO2 capture purposes.

Ceria (CeO2) containing materials are the subject of numerous investigations recently owing to their broad range of applications in various fields. Ceria is one of the most important components of three-way catalysts (TWC). Two unique features are responsible for making CeO2 a promising material for use either as a support or as an active catalyst: (a) the Ce3+/Ce4+ redox couple, and (b) its ability to shift between CeO2 and CeO2–δ under oxidizing and reducing conditions retaining fluorite structure. Despite widespread applications, pure CeO2 has a serious problem of degradation in performance with time at elevated temperatures. CeO2 undergoes rapid sintering under high operating temperatures, which leads to loss of oxygen buffer capacity and deactivation of the catalyst. In addition, the amount of lattice oxygen taking part in the redox reactions is small (δ ~ 0.05), and therefore unsatisfactory for practical applications. Therefore further improvement of OSC of CeO2 has led to development of new CeO2-based oxygen storage materials. Modifications of CeO2 with isovalent or aliovalent ion (noble metal, rare-earth or transition metal) confer new properties to the catalysts, such as better resistance to sintering and high catalytic activity. The demand for ceria-based oxygen storage materials were accelerated in the 1970s with the introduction of strict automotives exhaust treatment worldwide to combat the obnoxious gases released in the atmosphere causing deterioration of air quality. Significant developments have occurred in this field leading to better understanding of the catalysts synthesis, structure and improved catalytic activity. The introductory chapter 1 is a compendium to provide an overview of the topic, examine the critical lacunae in the field and the proposal for future developments. In chapter 2 we present the studies on synthesis and catalytic properties of Ce1– xSnxO2 (x= 0.1–0.5) solid solution and its Pd substituted analogue. A brief description of the single step solution combustion synthesis, catalysts characterization techniques such as powder X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) are given. Design and fabrication of temperature programmed reduction by hydrogen (H2-TPR) system in this laboratory is given in details. The home-made temperature programmed catalytic reaction system with a quadrupole mass spectrometer and an on-line gas-chromatograph for gas analysis is described. For the synthesis of Ce1–xSnxO2 solid solution by a single-step solution combustion method we have used tin oxalate as precursor for Sn. The compounds were characterized by XRD, XPS and TEM. Oxygen storage capacity of the Ce1–xSnxO2 solid solution was measured by H2-TPR. The cubic fluorite structure remained intact up to 50% of Sn substitution in CeO2, and the compounds were stable up to 700 °C. Oxygen storage capacity of Ce1–xSnxO2 was found to be much higher than that of Ce1–xZrxO2 due to accessible Ce4+/Ce3+ and Sn4+/Sn2+ redox couples at temperatures between 200 to 400 °C. Pd2+ ions in Ce0.78Sn0.2Pd0.02O2-δare highly ionic, and the lattice oxygen of this catalyst is highly labile, leading to low temperature CO to CO2 conversion. The rate of CO oxidation was 2 μmolg–1s–1 at 50 °C. NO reduction by CO with 70% N2 selectivity was observed at ~200 °C and 100% N2 selectivity below 260 °C with 1000-5000 ppm NO. Pd2+ ion substituted Ce1–xSnxO2 catalyst can be used for low temperature exhaust applications due to the involvement of the Sn2+/Sn4+ redox couple along with Pd2+/Pd0 and Ce4+/Ce3+ couples. With the goal to understand the improved OSC for Ce1–xSnxO2 solid solution, we have investigated the structure and its relative stability based on first-principles density functional calculations. In chapter 3, we present our studies on the relative stability of Ce1–xSnxO2 solid solution in fluorite in comparison to rutile structure of the other end-member SnO2. Analysis of relative energies of fluorite and rutile phases of CeO2, SnO2, and Ce1–xSnxO2 indicates that fluorite structure is most stable for Ce1–xSnxO2 solid solution. An analysis of local structural distortions reflected in phonon dispersion show that SnO2 in fluorite structure is highly unstable while CeO2 in rutile structure is only weakly unstable. Thus, Sn in Ce1–xSnxO2-fluorite structure is associated with high local structural distortion whereas Ce in Ce1–xSnxO2-rutile structure, if formed, will show only marginal local distortion. Determination of M–O (M = Ce or Sn) bond lengths and analysis of Born effective charges for the optimized structure of Ce1–xSnxO2 show that local coordination of these cations changes from ideal eight-fold coordination expected of Ce4+ ion in fluorite lattice, leading to generation of long and short Ce–O and Sn–O bonds in the doped structure. Bond valence analyses for all ions show the presence of oxygen with bond valence ~1.84. These weakly bonded oxygen ions are relevant for enhanced oxygen storage/release properties observed in Ce1–xSnxO2 solid solution. In chapter 4, we present detailed structural analysis of Ce1–xSnxO2 and Ce1–x– ySnxPdyO2–δsolid solutions based on our DFT calculations supported with EXAFS studies. Both EXAFS analysis and DFT calculation reveal that in the solid solution Ce exhibits 4 + 4 coordination, Sn exhibits 4 + 2 + 2 coordination and Pd has 4 + 3 coordination. While the oxygen in the first four coordination with short M—O bonds are strongly held in the lattice, the oxygens in the second and higher coordinations with long M—O bonds are weakly bound, and they are the activated oxygen in the lattice. Bond valence analysis shows that oxygen with valencies as low as 1.65 are created by the Sn and Pd ion substitution. Another interesting observation is that H2-TPR experiment of Ce1–xSnxO2 shows a broad peak starting from 200 to 500 oC, while the same reduction is achieved in a single step at ~110 oC in presence Pd2+ ion. Substitution of Pd2+ ion thus facilitates synergistic reduction of the catalyst at lower temperature. We have shown that simultaneous reduction of the Ce4+ and Sn4+ ions by Pd0 is the synergistic interaction leading to high oxygen storage capacity at low temperature. In chapter 5, we present the effect of substituting aliovalent Fe3+ ion on OSC and catalytic activity of ceria. Ce0.9Fe0.1O2–δ and Ce0.89Fe0.1Pd0.01O2–δ solid solutions have been synthesized by solution combustion method, which show higher oxygen storage/release property compared to CeO2 and Ce0.8Zr0.2O2. Temperature programmed reduction and XPS study reveal that the presence of Pd ion in Ce0.9Fe0.1O2–δ facilitates complete reduction of Fe3+ to Fe2+ state and partial reduction of Ce4+ to Ce3+ state at temperatures as low as 105 oC compared to 400 oC for monometal-ionic Ce0.9Fe0.1O2–δ. Fe3+ ion is reduced to Fe2 and not to Fe0 due to favorable redox potential for Ce4 + Fe2൅ → Ce3 + Fe3 reaction. Using first-principles density functional theory calculation we determine M—O (M = Pd, Fe, Ce) bond lengths, and find that bond lengths vary from shorter (2.16 Å) to longer (2.9 Å) bond distances compared to mean Ce—O bond distance of 2.34 Åfor CeO2. Using these results in bond valence analysis, we show that oxygen with bond valences as low as –1.55 are created, leading to activation of lattice oxygen in the bimetal ionic catalyst. Temperatures of CO oxidation and NO reduction by CO/H2 are lower with the bimetal ionic Ce0.89Fe0.1Pd0.01O2–δ catalyst compared to monometal-ionic Ce0.9Fe0.1O2–δ and Ce0.99Pd0.01O2–δ catalysts. From XPS studies of Pd impregnated on CeO2 and Fe2O3 oxides, we show that the synergism leading to low temperature activation of lattice oxygen in bimetal-ionic catalyst Ce0.89Fe0.1Pd0.01O2–δ is due to low-temperature reduction of Pd2 to Pd0, followed by Pd0 + 2Fe3൅ → Pd2 +2Fe2, Pd0 + 2Ce4൅ → Pd2 + 2Ce3redox reaction. In chapter 6, we simulate the structure of Ce1–xMxO2–δ (M = transition metal, noble metal and rare–earth ions) for theoretical understanding of origin of OSC in these oxides and to draw a general criteria required to increase the OSC in ceria. The relationship between the OSC and structural changes induced by the dopant ion was investigated by H2-TPR and first-principles based density functional calculations. Transition metal and noble metal ions substitution in ceria greatly enhances the reducibility of Ce1–xMxO2–δ (M = Mn, Fe, Co, Ni, Cu, Pd, Pt, Ru), whereas rare–earth ions substituted Ce1–xAxO2–δ (A = La, Y) have very little effect in improving the OSC. Our simulated optimized structure shows deviation in cation–oxygen bond length from ideal bond length of 2.34 Å (for CeO2). For example, our calculation for Ce28Mn4O62 structure shows that Mn—O bonds are in 4+2 coordination with average bond lengths of 2.0 and 3.06 Å respectively. While the four short Mn–O bond lengths for the calculated structure spans the bond distance region of Mn2O3, and the other two Mn–O bonds are moved to longer distances. The dopant transition and noble metal ions also affects Ce coordination shell and results in the formation of longer Ce—O bonds as well. Thus longer cation-oxygen bond lengths for both dopant and host ions results in enhanced synergistic reduction of the solid solution. With Pd ion substitution in Ce1–xMxO2–δ (M = Mn Fe, Co, Ni, Cu) further enhancement in OSC is observed in H2–TPR. This effect is reflected in our calculations by the presence of still longer bonds compared to the model without Pd ion doping. Synergistic effect is, therefore, due to enhanced reducibility of both dopant and host ion induced due to structural distortion of fluorite lattice in presence of dopant ion. For RE ions (RE = Y, La) our calculations show very little deviation of bonds lengths from ideal fluorite structure. The absence of longer Y— O/La—O and Ce–O bonds make the structure very less susceptible to reduction [8]. Since Pd substituted Ce1–xSnxO2 showed high OSC and catalytic activity towards CO oxidation and NO reduction, we tested this catalyst for water-gas shift (WGS) reaction and the results are presented in chapter 7. Over 99.5 % CO conversion to H2 is observed at 300 ± 25 oC. Based on different characterization techniques we found that the present catalyst is resistant to deactivation due to carbonate formation and sintering of Pt on the surface when subjected to longer duration of reaction conditions. The catalyst does not require any pre-treatment or activation between start-up/shut-down reaction operations. Formation of side products such as methane, methanol, formaldehyde, coke etc. was not observed under the WGS reaction conditions indicating the high selectivity of the catalyst for H2. Temperature programmed reduction of the catalyst in hydrogen (H2–TPR) shows reversible reduction of Ce4+ to Ce3+, Sn4+ to Sn2+ and Pt4+ to Pt0 oxidation state with oxygen storage capacity (OSC) of 3500 μmol g–1 at 80 oC. Such high value of OSC indicates the presence of highly activated lattice oxygen. CO oxidation in presence of stoichiometric O2 shows 100 % conversion to CO2 at room temperature. The catalyst also exhibits 100% selectivity for CO2 at room temperature towards preferential oxidation (PROX) of residual CO in presence of excess hydrogen in the feed. To further validate our DFT results presented in the thesis, DFT calculations on Ce2Zr2O8–Ce2Zr2O7 system were performed and the results are given in the last chapter 8. Ce2Zr2O7 does not show any oxygen storage/release property unlike Ce2Zr2O8 (=Ce0.5Zr0.5O2). Bond lengths obtained from DFT simulation on Ce2Zr2O7 structure showed well-defined Ce—O and Zr—O bonds expected of the pyrochlore structure, unlike distribution of bond lengths as has been observed for Ce1–xMxO2–δ case. Absence of bonds distribution indicates that the oxygen sublattice is not distorted in Ce2Zr2O7 in agreement with its closed packed structure. Filling of the 1/8 of the tetrahedral oxide ion vacancies will result in Ce2Zr2O8 structure, and DFT calculation for this structure show wide distribution of bond lengths. Long Ce—O and Zr—O bonds appear in the bond-distribution plot, suggesting substantial distortion of the oxygen sublattice. Thus absence of longer cation-oxygen bond in pyrochlore structure validates the structural calculations presented in this thesis. Based on the results derived in all the chapters, a critical review of the work is presented and major conclusions are given in the last chapter

Treatment of fuel cell feed H2 for the removal of CO is important owing to the poisoning of the catalysts, thereby affecting the performance of the fuel cell. Strong and preferential adsorption of CO over the catalyst takes place resulting in a reduction of the power output of the cell. Therefore, it is important to treat the fuel cell feed H2 to reduce its CO content below the tolerable limit. Development of efficient catalysts for the treatment of synthesis gas for the removal of CO and and H2 enrichment of the gas to make it suitable for fuel cells is one of the two goals of this thesis. One of the various possible strategies for the removal of CO from the synthesis gas can be the use of the water-gas shift reaction. We have developed noble metal substituted ionic catalysts for catalyzing the water-gas shift reaction and have studied in detail the kinetics of the reactions by proposing the relevant reaction mechanisms. Solution combustion, a novel technique for synthesizing nanocrystalline materials, was used for the synthesis of all the catalysts. All the compounds synthesized were solid solutions of the noble metal ion and transition or rare earth metal oxide support. Three different supports were used, viz., CeO2, ZrO2 and TiO2. Substitution of Zr and Ti in CeO2 up to 15 at% was also carried out to obtain the compounds with enhanced oxygen storage capacity. All the compounds were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In some cases, where it was required, the use of FT-Raman spectroscopy was made for structural analysis. The compounds were nanocrystalline with metals substituted in ionic form in the support. The water-gas shift reaction was carried out over the synthesized catalysts with a reactant gas mixture that simulated the actual refinery gas composition. The variation of CO concentration with temperature was traced. The changes in the oxidation state of the metal showed the involvement of the various redox pairs over the reducible oxide like substituted CeO2 and TiO2. The mechanism of the reaction over ZrO2-based compounds was found to take place utilizing the surface hydroxyl groups. Rate expressions for the reactions over all the catalysts following different mechanisms were derived from the proposed elementary processes. Nonlinear regression was used for the estimation of various parameters describing the rate of reaction. Having established the high activity of Pt-ion substituted TiO 2 for the reactions, steam reforming of wood gas obtained from the gasification of Casuarina wood chips was carried out. The enrichment of the gas stream, which initially consisted of nearly 10% H 2 was carried out by steam reforming and H2-rich stream was obtained with H2 as high as 40% by volume in the treated gas. The second motive behind this thesis was to test the activity of the noble-metal substituted ionic catalysts for the treatment of the exhaust gas coming out of a fuel cell. In the fuel cell utilizing H2, the exhaust gases contain certain amount of unreacted H2, which can not be recovered or utilized economically. However, the gases are combustible and H 2 has to be removed in order to make the gas clean. We have shown high activity of the combustion-synthesized ionic compounds for catalytic combustion of H2. All the compounds showed high activity for H2 combustion and complete removal of H2 was possible. The rates were found to increase with an decrease in H2:O2 ratio and complete conversion of H2 was possible within 100 oC with air. A mathematical model was developed for the kinetics of catalytic H2 combustion based on the elementary processes that were proposed using the spectroscopic evidences. CO tolerant capacity of the catalysts was also tested. It was found that the temperature requirement for most of the catalysts increased with the introduction of CO. However, it was still possible to obtain complete conversions within 200 oC. To summarize, fuel cell processing systems utilizing H 2 remained central to the study. Treatment of the gases, both before and after reaction from the fuel cell was carried out over noble metal-substituted ionic catalyst, synthesized by solution combustion technique. Mechanisms of the reactions were proposed on the basis of spectroscopic evidences and the kinetic rate parameters were estimated using non-linear regression.

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