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This work takes a closer look at ceria catalyst synthesis through micelle self-assembly. We compare surfactants, precursors, solvent systems, and doping. The surfactants are the building blocks upon which the ceria can crystallize. The samples are calcinated to test their thermal stability. Characterization is performed using pXRD as well as physisorption. The samples that exhibited a higher thermal stability were characterized to have a high surface area as well as low fluctuations in crystallite size, pore volume, and pore size. Ceria synthesized with cerium (III) nitrate hexahydrate and CTAB in a water:ethanol mixture using sodium hydroxide showed to be the most effective at providing a thermally stable product. Doping the catalyst with titanium increased the thermal stability significantly. Select samples were run in a variety of fuel to oxygen ratios to determine the best conditions in which we could perform partial methane oxidation to recuperate hydrogen gas. Most of the experiments show oxygen depletion with minor changes in other gas levels indicating that there is no oxidation occurring. Curiously the oxygen levels do decrease. There is a possibility that there is a reaction occurring initially at room temperature and being exacerbated with further temperature increase.

This work takes a closer look at ceria catalyst synthesis through micelle self-assembly. We compare surfactants, precursors, solvent systems, and doping. The surfactants are the building blocks upon which the ceria can crystallize. The samples are calcinated to test their thermal stability. Characterization is performed using pXRD as well as physisorption. The samples that exhibited a higher thermal stability were characterized to have a high surface area as well as low fluctuations in crystallite size, pore volume, and pore size. Ceria synthesized with cerium (III) nitrate hexahydrate and CTAB in a water:ethanol mixture using sodium hydroxide showed to be the most effective at providing a thermally stable product. Doping the catalyst with titanium increased the thermal stability significantly. Select samples were run in a variety of fuel to oxygen ratios to determine the best conditions in which we could perform partial methane oxidation to recuperate hydrogen gas. Most of the experiments show oxygen depletion with minor changes in other gas levels indicating that there is no oxidation occurring. Curiously the oxygen levels do decrease. There is a possibility that there is a reaction occurring initially at room temperature and being exacerbated with further temperature increase.

This work takes a closer look at ceria catalyst synthesis through micelle self-assembly. We compare surfactants, precursors, solvent systems, and doping. The surfactants are the building blocks upon which the ceria can crystallize. The samples are calcinated to test their thermal stability. Characterization is performed using pXRD as well as physisorption. The samples that exhibited a higher thermal stability were characterized to have a high surface area as well as low fluctuations in crystallite size, pore volume, and pore size. Ceria synthesized with cerium (III) nitrate hexahydrate and CTAB in a water:ethanol mixture using sodium hydroxide showed to be the most effective at providing a thermally stable product. Doping the catalyst with titanium increased the thermal stability significantly. Select samples were run in a variety of fuel to oxygen ratios to determine the best conditions in which we could perform partial methane oxidation to recuperate hydrogen gas. Most of the experiments show oxygen depletion with minor changes in other gas levels indicating that there is no oxidation occurring. Curiously the oxygen levels do decrease. There is a possibility that there is a reaction occurring initially at room temperature and being exacerbated with further temperature increase.

There have been many applications of cerium oxide in oxidation catalysis but the understanding of its role in catalysis is rather limited. This research is concerned with the use of nano-size cerium oxide in methane steam reforming reaction. It is found that addition of cerium oxide to the commercial supported Ni catalysts can dramatically reduce the undesirable carbon deposition (through surface oxidation), which is thermodynamically favorable under low steam conditions. In order to understanding the fundamental role of oxidation activity of the cerium oxide, different sizes of nano-crystallined cerium oxides have been carefully prepared by micro-emulsion technique. Their reactivity is clearly shown to be size dependent. We found that ceria particle sizes of lower than 5.1 nm are able to activate molecular oxygen, which accounts for the unprecedentedly reported critical size effect on oxidation. Characterizations by EPR, XPS, TPR suggest that a substantially large quantity of adsorbed oxygen species (O₂ ^-) is preferentially formed in the small size ceria from air. Also, it is found that the oxygen vacancies are formed in the interface of metal and oxide, and the strength of the metal oxide interaction may influence the formation of the efficient oxygen vacancies, which are responsible for the adsorbed surface oxygen.

Magister Philosophiae - MPhil / Due to an increasing demand for energy, alternative renewable energy sources are investigated globally. However fossil fuels are still one of the main energy sources. The combustion of these fuels produces by-products such as SOx, NOx and CO2, which have detrimental effects on the environment and human health. Therefore, effective methods are needed to minimize the pollution and affects that these by-products cause. Catalysts are commonly employed to convert these by-products to less harmful and/or resalable products. Ceria and ceria based materials are good candidates for the removal and conversion of SOx and NOx. Ceria and ceria related materials are most effective as catalysts when they are in the nano-form with good crystallinity and nanoparticles that are uniform. The growth of nanoparticles is preceded by a nucleation process which can occur by solid-state restructuring of a gel or precipitation from a saturated solution. The precipitation method was selected to synthesize Ceria nanoparticles. Synthesis conditions such as temperature, solution type and ageing time and their effect on the physical and chemical forms of the Ceria particles were investigated. The morphology and structural properties were investigated using Scanning Electron Microscopy, X-ray diffraction and Transmission Electron Microscopy. X-ray Photoelectron Spectroscopy was used to investigate the chemical properties. It was found that low temperatures, low base volume and a solvent with a small dielectric constant favor the formation of small crystallites with a relatively large concentration of defects. These defects are desirable since they enhance the catalytic activity of ceria.

This work aimed to evaluate the subsystems of a novel mediated oxycombustion system and determine the expected final conditions of the integrated subsystems. The subsystems included a cerium based oxygen transport membrane, transport membrane coatings to assist in the pickup and release of oxygen, and a molten intermediary oxygen carrier. Various doping levels of yttrium and zirconium were investigated, both as singular dopants and in a co-doped scheme. Regression analysis was performed to quantitatively evaluate how each dopant affected the material properties. Zirconium was not found to have statistically significant effects, although an effect was clearly noted on pure ceria. Functions of the doping level of yttrium were found for relative density, hardness, and the contributing factors of electrical conductivity. Chemical looping combustion experiments were performed to determine viable candidates for oxygen pickup and release coatings. It was discovered that a release coating was not necessary due to the use of a reactive fluid, and iron showed promise as a pickup coating but short of showing statistical significance. The ability of antimony oxide to react with hydrocarbon fuels and be regenerated by oxygen was investigated to determine the reaction rates. It was discovered that a co-doping scheme of yttrium and zirconium at a level of 8.33% (1/12th) each achieved the highest oxygen flux with a value of 3.671x10-7 mol O/s/cm2. All of the subsystems were we analyzed and a complete, theoretical system was described. It is recommended that the shape of the oxygen transport membrane be of a single-closed-end cylinder. This allows the increase of oxygen permeation with a smaller device footprint. It was found that the system would be capable of combusting 6.699 grams of carbon based fuel per minute per square meter of footprint. This equates to a heat rate of 3.6 kilowatts per square meter when utilizing a medium volatile bituminous coal. This value will continue to be improved as further research is conducted into the components of the system.

Cerium and zirconium oxides are materials that have unique catalytic properties and are finding many applications in industrial catalysis. Particularly, the great advances attained in the past 30 years in curbing the amount of gaseous pollutants released can be attributed to the development of catalysts employing such materials. However, oxides of sulfur are known poisons of many catalytic systems and are encountered in many commercial applications. In this investigation, polycrystalline ceria-zirconia solid solutions of various molar ratios were synthesized. High resolution x-ray photoemission spectra were obtained and examined to reveal the surface species that form on these metal oxides after exposure to sulfur dioxide under various conditions. The model catalysts are exposed to sulfur dioxide using an in-situ high-pressure reaction cell. A reliable sample platen heater was designed to allow the observation of any temperature dependency up to 673 K. The results of this study demonstrate the formation of sulfate and sulfite adsorbed sulfur species. Temperature and compositional dependencies are also displayed, with higher temperatures and ceria mole fractions displaying a larger propensity for the formation of surface sulfur species.

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