Catalytic conversion of methane into alkanes and oxygenates and deactivation of hydrodeoxygenation catalysts
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In this thesis, a catalyst comprising of NiO/Ce0.83Zr0.17O2 (NiO/CZ) that is capable of activating methane to form surface methyl groups was developed. Some of these species couple to higher alkyl chains. These alkyl groups can be removed as ethane and ethylene at temperatures below 500 oC in a non-oxidative environment. Bi-functional activity on the catalyst also leads to the production of aromatics. However, due to thermodynamic constraints, only very low yields of higher hydrocarbons is achievable in this reaction. To facilitate the production of oxygenates, steam was used to hydrolyze the surface groups from methane activation into methanol and ethanol. Oxygen is co-fed to convert surface hydrogen to water providing a thermodynamic driving force. In addition to alcohols, carbon dioxide and hydrogen and small amounts of aromatics are formed as by-products. Importantly, the formation of alcohols occurs at 450 °C in steady state with a turnover frequency of at least 50 h-1. This is a significant improvement from previous studies, in which a high-temperature calcination step was required for every turnover. The performance of NiO/CZ towards alcohol production was optimized by using several synthesis techniques. Strong electrostatic adsorption (SEA) of Ni on ceria zirconia was found to be the best catalysts showing improved dispersion of Ni and subsequently, improved reactivity towards alcohol production. In this thesis, the effect of strongly adsorbed “roadblocks” on zeolitic catalysts during hydrodeoxygenation of bio-oils was illustrated. This was done by deliberately introducing “roadblocks” from catechol. Physicochemical characterization and reactivity studies were performed on certain HDO catalysts (Pt/HBEA, Ni/ZSM-5 and Ga/ZSM-5). These provided insight on the effect of “roadblocks” on the catalysts as a pathway for deactivation during hydrodeoxygenation.