Catalytic upgrade of bio-oil to fuels and chemicals requires the selective reduction of its 10 – 40 wt% oxygen content. Ruthenium supported on titanium dioxide (Ru/TiO2) has evolved as one of the better performing catalysts for such hydrodeoxygenation (HDO) processes.1,2 Commonly proposed HDO mechanisms on oxide containing materials invoke oxygen vacancy sites as catalytically active sites, but the mechanism of their formation and detailed description of active sites at the interface of Ru/TiO2 is still lacking. We previously reported a positive linear relation between the toluene formation rate from m-cresol and the Ru perimeter length for Ru/TiO2 catalyst, supporting the placement of active sites at the metal-support interface.3 We also reported that water partial pressure plays a significant role in increasing the toluene formation rate for low loading Ru/TiO2 catalysts, which may be attributed to a proton-assisted HDO mechanism.2,3 By combining density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations we investigate the reduction and hydroxylation properties of rutile TiO2(110) in the presence and absence of Ru nanoparticles, as well as m-cresol HDO reactions, with particular focus on the Ru/TiO2 interface. Our kMC results show that the presence of Ru nanoparticles substantially increases the reduction rate of the TiO2(110) surface and HDO rate. We attribute this rate enhancement to a facile, heterolytic H2 cleavage pathway across the Ru/TiO2 interface and to a lesser extent H spillover. Under HDO reaction conditions over Ru/TiO2 with water in the gas phase, coverage transitions occur. Consequently, the Arrhenius plot exhibits two or three kinetic regimes corresponding to different reaction mechanisms at low and high temperature, respectively. To our knowledge, there exists no comparable model with the ability to discriminate between metal, oxide and interfacial activity, and assign a dominant catalytic role to each component. The ability to generate such detailed fundamental insight can be leveraged for the future design of multifunctional catalysts with unprecedented selectivity advantages.

First-principles kinetic Monte Carlo study of water-mediated C-O bond cleavage in phenolic compounds at the Ru/TiO2 interface

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.