Catalytic transformation of oxygen containing compounds into valuables : effect of ceria redox properties
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The focus of this thesis is the investigation of sustainable routes for the production of commercially valuable oxygen containing compounds through the application of ceria-based catalysts. The catalytic transformation of levulinic acid (to γ-valerolactone), CO2, methanol and nitrobenzene (to methyl-N-phenyl carbamate), 1butanol (to 1-butene) and 1,3-butanediol (to 3-buten-2-ol) have been examined. Taking the conversion of levulinic acid as a model system, it was established that the surface oxygen vacancies, formed during temperature programmed reduction of reducible oxides, activate levulinic acid for reaction. Process sustainability has been examined in terms of full hydrogen utilisation with 100% yield of the target γ-valerolactone under stoichiometric conditions over supported Au catalysts. The production of the carbamate directly from CO2 was initially optimised towards dimethyl carbonate formation as a reaction intermediate, where the highest reported rate has been achieved. It was shown that total surface area of CeO2 is not a determining parameter for catalytic performance, while a decrease in Ce3+ content upon calcination improves CO2 activation. Dehydration of 1-butanol/1,3-butanediol revealed the requirement for the strong Lewis acid sites on the surface of the catalyst to form an alkene. The results presented in this thesis demonstrate direct participation of the ceria in the catalytic dehydration and carboxylation reactions.