Kinetics of liquid-phase catalytic hydrogenation of benzophenone to benzhydrol

Catalytic hydrogenation of benzophenone to benzhydrol was carried out in 2-propanol using Raney nickel as a catalyst at hydrogen pressures in the range of 800-2200 kPa, reaction temperatures 323-343 K, catalyst loadings 4-20 g dm(-3) and benzophenone concentrations 0.44-1.32 mol dm(-3). Effects on the hydrogenation of benzophenone to benzhydrol of various catalysts (Pd/BaSO4, Pd/C, Pt/C, Raney nickel, Pd/CaCO3) and solvents (methanol, 2-propanol, xylene, toluene, hexane, dimethylformamide) have been reported. Speed of agitation beyond 17 rps had no effect on the progress of reaction. Benzophenone can be selectively hydrogenated to benzhydrol, and the initial rate of hydrogenations showed first-order dependence with respect to the hydrogen partial pressure and catalyst loading and zero-order dependence with respect to benzophenone concentration. The activation energy for the catalytic hydrogenation of benzophenone was found to be 56 kJ mol(-1). A Langmuir-Hinshelwood-type kinetic model with hydrogen from the liquid-phase attacking adsorbed benzophenone has been proposed.