Kinetics and Mechanism of Ketonization of Acetic Acid on Ru/TiO2 Catalyst

Ru/TiO2 shows great promise as a catalyst in ketonization of carboxylic acids, an effective reaction for upgrading pyrolysis vapors that contain significant amounts of acetic acid. In this study, we have investigated the kinetics of acetic acid ketonization over Ru/TiO2 catalysts from different pre-treatments. The observed reaction order (> 1.5) with respect to acetic acid lends support to a bimolecular pathway of adsorbed carboxylates that produces a beta-ketoacid intermediate. The negative reaction orders with respect to CO2, water, and acetone reflect the inhibition by competitive adsorption on the active sites. The observed rate enhancement by reduction in H-2 and inhibition by the presence of O-2 indicate that the active sites for this reaction include coordinatively unsaturated cation sites.