Bio-oil obtained from fast pyrolysis of biomass contains a large number of oxygenates that adversely affect its properties. Catalytic hydrotreating is one possibility to reduce the oxygen content of bio-oil and Ru/TiO2 catalysts have been found active for this reaction. We chose acetaldehyde as a model oxygenate and use density functional theory combined with kinetic Monte Carlo simulations to investigate the preferred reaction pathways and the nature of the active site on Ru/TiO2. Acetaldehyde can undergo three main reaction channels during hydrodeoxygenation (HDO): (i) the hydrogenation/dehydration pathway (HYD), (ii) direct deoxygenation (DDO), and (iii) decarbonylation (DCN). Pathway (ii) is most desirable, because it eliminates oxygen without breaking C-C bonds and consumes the least amount of hydrogen. Our results show that the selectivity depends on the catalytic site of Ru/TiO2. Metalic Ru clearly favors C-C bond scission and DCN, while oxygen vacancy sites on TiO2 or Ru-modified TiO2 preferentially break the C-O bond in the HYD and DDO pathway. A computational model comprised of a 10-atom Ru cluster on TiO2(110) was used to investigate the interplay between Ru and the TiO2 support for HDO. Ru facilitates the formation of oxygen vacancy sites on TiO2, which in turn are active for the selective HDO of acetaldehyde.

Mechanism and nature of the active site of Ru/TiO<sub>2</sub> for hydrodeoxygenation of acetaldehyde

248th National Meeting (2014)

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Mechanism and nature of the active site of Ru/TiO2 for hydrodeoxygenation of acetaldehyde

Mechanism and nature of the active site of Ru/TiO₂ for hydrodeoxygenation of acetaldehyde