(435a) The Conversion of Various Phenolic Compounds over Ru/TiO2: Active Site Requirements

One of the greatest challenges associated with the conversion of lignocellulosic biomass to fuels and chemical lies in the stable and selective conversion of lignin derived phenolics.  Metals supported on reducible oxides such as Ru/TiO₂ have demonstrated the potential to preserve the carbon contained in methoxy groups and avoiding excessive hydrogen consumption of the ring upon deoxygenation of phenolic OH groups. Ru supported on TiO₂ also exhibits activity and stability enhancements for the conversion of phenolics when compared with Ru supported on other non-reducible supports. In this contribution, we have systematically varied the Ru/TiO₂ interfacial area, as well as the TiO₂ phase, and measured the initial rates of conversion of several model compounds containing hydroxyl and methoxy groups including, guaiacol, anisole, catechol and cresol. The implications of these results will be discussed in the context of kinetic models to describe the conversion phenolics such as guaiacol, where one must take into account several factors. These include the rate of conversion of each produced product (for example catechol and cresol) over the reduced sites, the interface, and the various metal sites. In-situ titration is also used to discriminate deoxygenation reactions that occur through the continuous production and healing of defects on the support vs. those facilitated by active sites located at the Ru/TiO₂ interface.