Kinetics and intraparticle diffusion modelling of a complex multistep reaction: Hydrogenation of acetophenone over a rhodium catalyst

In a first step the intrinsic kinetics of acetophenone hydrogenation on a Rh/C catalyst was studied in a semi-batch reactor. Tiny catalyst grains of 17 mu m in average diameter were used in order to avoid any intraparticle diffusion limitation. Experiments were performed over a wide range of operating conditions and various Langmuir-Hinshelwood kinetic equations were discriminated over the complete conversion range. The model based on nondissociative adsorption of hydrogen and noncompetitive adsorption of the organic species with the gas molecules was found to fit better all the experimental data. The relevance of its optimized parameters was then discussed. In a second step the intraparticle diffusion limitations were also studied in a semi-batch reactor by varying the particle size. Two models based on the complex kinetics previously established were developed, taking into account the catalyst grain size and shape. After an additional adjustment of one of the adsorption constants ratios, they were found to provide a good representation of the data in terms of activity and selectivity. (C) 1998 Academic Press.