(689b) Elucidating Particle Size Effects on the Hydrodeoxygenation (HDO) of Phenolics By Micro-Pulse Experiments and DFT Calculations

The catalytic hydrodeoxygenation (HDO) of phenolic compounds is very important for the upgrading of bio-oil as transportation fuels. This study investigated mechanistic aspects of HDO of different phenolic compounds such as m-cresol and anisole over different metal catalysts (Pt, Rh, Ru and Fe) using a micro-pulse reaction system, in which the catalyst is flushed with hydrogen all the time and a small amount of feed is passed through the catalyst bed in each pulse. This reactor system thus allows monitoring the deactivation of different sites with great precision and study the activity of very active, but quickly deactivating sites. Here, the effects of the metal particle size on the HDO of phenolic compounds were studied. The TOF for both the ring hydrogenation and the HDO of m-cresol and anisole were calculated over the metal catalysts with different particle size. Density functional theory calculations were also carried out to explore the reaction pathways at both the terrace sites and the steps sites to understand the particle size effects on the HDO reactions at the molecular level. Different mechanisms including the direct deoxygenation (DDO), and the tautomerization-hydrogenation-dehydration paths were examined and analyzed. It was found that the plausible pathway for the HDO of phenolic compounds may be different at the terrace and step sites which leads to the different catalytic activity and product distribution at the metal catalysts with different particle size.