Selective Conversion of Biomass Model Compounds Using Promoted Metal Catalysts

Extensive research and development have gone into modern biomass upgrading in order to mitigate the environmental concerns and other impending challenges associated with conventional fuels and chemicals. The phenolic and furanic compounds produced by primary upgrading processes represent a collection of biomass intermediates that still preserve the valuable chemical structures, but they require further upgrading due to unfavorable oxygen contents and unstable functional groups. This dissertation seeks to demonstrate the viability of utilizing bimetallic and metal-oxide-promoted metal catalysts to further upgrade biomass-derived oxygenates by selective C-O bond scissions. Useful fuels and chemicals are produced from model compounds (2-hydroxymethylfurfural, furfural, tetrahydrofurfuryl alcohol and m-cresol) which represent the main fractions of lignocellulosic biomass. In all studies featured in this thesis, promoted metal catalysts exhibit special activity, selectivity and stability to produce desired products, even though the individual components are not active, selective or stable. In order to bridge the gap between these enhanced catalytic performances and their mechanistic fundamentals, well-defined catalysts synthesized by either solvothermal method (for bimetallic nanocrystals) or atomic layer deposition (for metal-oxide-promoted metal catalysts) were also used to characterize the structure-activity relationships. Notably, I will demonstrate in this dissertation that the active form of the Pt-WOx catalyst exists as a thin, submonolayer film of the oxide on the Pt surface. Direct bonding between the Pt and supported WOx complexes both stabilizes the oxide and lowers the barrier to oxygen vacancy formation. The latter plays a pivotal role in the formation of redox sites on the WOx which are active for direct C-O bond hydrogenolysis. These contributions from the fundamentals should help developing catalysts that are suitable for practical applications