(664a) Enhancing the Specific Activity of Metal Oxides Using Transition-Metal Dopants

Carbon-oxygen bond scission is an important step for the conversion of biomass-derived feedstocks to fuels and chemicals. The oxygenated compounds present in such feedstocks require selective hydrodeoxygenation (HDO) catalysts as they contain several functional groups that may undergo undesired reactions, such as hydrogenation, ring opening, and decarbonylation in hydrogen-rich environments. Reducible metal oxides are active for the HDO reaction due to the presence of oxygen vacancies on the surface, but the most active oxides are also the least stable under reaction conditions.

The HDO reaction mechanism on Ru/RuO_x shows a synergistic effect between metallic sites and oxide sites for the conversion of furfuryl alcohol to 2-methylfuran. Although this bifunctional catalyst is initially very active and selective for this reaction, the vacancy formation via OH removal is too facile on RuO₂, causing its rapid reduction that deactivates the catalyst. In this work, we promote the HDO activity and selectivity of less reducible metal oxides using transition metal dopants. We model the metal/metal oxide system using Density Functional Theory (DFT) and Microkinetic Modelling (MKM) and obtain qualitative agreement with experimental reactor data. We find that the dopant has a significant effect on the relative stability and hydroxylation degree of different facets, which in turn influences their reactivity.