| dc.description.abstract | Growing environmental concerns has necessitated the development of cleaner and renewable sources of energy such as biomass. Bio-oil derived from lignocellulosic biomass is a promising source for producing renewable chemicals and fuels, however due to the instability of this complex mixture, with its high oxygen content contributing mainly to this, catalytic upgrading is required to improve on undesirable properties. Therefore not only is it necessary to decrease the oxygen content of bio-oil, a good upgrading strategy should preserve valuable carbon in the liquid. Metals supported on reducible oxides hold considerable promise for upgrading pyrolysis vapors, as they are capable of converting corrosive light compounds such as acetic acid to the chemical building block acetone as well as catalyzing the deoxygenation and transalkylation of larger phenolic compounds to produce alkyl-aromatics. The combination of reducible oxides such as TiO2 coupled with metals such as Ru can result in a complex catalyst. Potential active sites include the sites on the metal surface, the highly reducible sites at the Ru/TiO2 interface, traditional acid sites on the TiO2 surface, and defects on the TiO2 support. While the roles of the various types of active sites for Ru/TiO2 catalysts have been studied in detail for reactions such as Fischer Tropsch synthesis, little is known regarding the role of these active sites for the conversion of lignin-derived phenolic compounds. In this dissertation, the author will use a combination of model compound studies coupled with catalyst modifications to better understand the reactivity of the various phenolic functional groups and also furfural, an important compound derived from the sugar fraction of biomass feed stocks, over the active sites present on Ru/TiO2 .
In the first section of this dissertation, the role of TiO2 crystal morphology phase – anatase and rutile- on resistance to Ru agglomeration during different catalyst pre-treatment conditions and the impact on the conversion of guaiacol, a phenolic compound with both methoxy and hydroxyl functions is investigated. The superior ability of the rutile TiO2 phase in stabilizing ruthenium particles compared to anatase was investigated. This is essential to designing Ru catalysts that have enhanced stability during high temperature oxidation treatments. These chapters will also give insights into the nature of active sites on the Ru/TiO2 catalyst responsible for guaiacol deoxygenation. Differentiation between Ru/TiO2 interfacial sites and oxygen vacancies on the TiO2 support for the conversion of guaiacol was achieved. In other chapters, the conversion of important phenolic compounds such as anisole, catechol and m-cresol was addressed. By utilizing a series of Ru catalysts with varying support types (SiO2, C, TiO2); TiO2 support phase (anatase, rutile and a mixture of both phases) and Ru particle sizes, the role of the various sites on the Ru/TiO2 catalyst for the conversion of these compounds was elucidated. These chapters demonstrate that while initial guaiacol deoxygenation to monooxygenates occur preferentially over defect sites on the TiO2 support, Ru/TiO2 interfacial sites are the important sites for complete deoxygenation to aromatic hydrocarbons. Finally, the last chapter will show that furfural can be converted to compounds which are valuable intermediates for fuels and chemicals over this catalyst. For example, high yields of 2-methylfuran can be achieved over this catalyst. Perhaps more importantly, the Piancatelli rearrangement to produce cyclopentanone which is a building block for molecules in the jet fuel range was observed to occur over this catalyst. The role of water in enhancing the formation of this product at the expense of 2-methylfuran will be discussed.
Keywords: Catalysis, Biofuels, Ruthenium, Titania | en_US |
