Acetophenone Hydrogenation over Rh/Al2O3 Catalyst: Intrinsic Kinetics, Pore Diffusion and Trickle-Bed Reactor Studies

Acetophenone hydrogenation, with a complex reaction scheme and relatively high (10-25 bar) pressure operating conditions, was studied as a representative example for pharmaceutical applications. Based on preliminary tests, 1wt % Rh/Al₂O₃ was selected as the catalyst. From experiments using a slurry reactor with powder catalyst, a Langmuir-Hinshelwood based intrinsic reaction kinetic model was developed, composed of dissociative and non-competitive hydrogen adsorption with saturated active sites for organics. Considering egg-shell catalyst distributions and active site differences of larger size supports (0.5 and 2.5 mm diameters), the pore diffusion effects on reaction rates and desired intermediate product selectivity were investigated and modeled. In a trickle-bed reactor, the effects of trickle and bubbly flow regimes on reaction rates were studied based on operating conditions derived from hydrodynamic tests for regime boundary. In the reaction tests, enhancement of reaction rate in the bubbly flow regime was confirmed. Reactor modeling, including factor for partial wetting and different flow regimes, was carried out and provided good predictions for both reactant conversion and product yield.