Microkinetic Modeling of Benzyl Alcohol Oxidation on Carbon-Supported Palladium Nanoparticles

Six products are formed from benzyl alcohol oxidation over Pd nanoparticles using O2 as the oxidant: benzaldehyde, toluene, benzyl ether, benzene, benzoic acid, and benzyl benzoate. Three experimental parameters were varied here: alcohol concentration, oxygen concentration, and temperature. Microkinetic modeling using a mechanism published recently with surface intermediates was able to produce all 18 trends observed experimentally with mostly quantitative agreement. Approximate analytical equations derived from the microkinetic model for isothermal conditions reproduced the isothermal trends and provided insight. The most important activation energies are Ea2=57.9 kJ mol−1, Ea5=129 kJ mol−1, and Ea6=175 kJ mol−1, which correspond to alcohol dissociation, alkyl hydrogenation, and the reaction of alkyl species with alkoxy species. Upper limits for other activation energies were identified. The concepts of a sticking coefficient and steric factor in solution were applied.