Modelling kinetics and deactivation for the selective hydrogenation of an aromatic ketone over Pd/SiO2

The kinetics for the selective hydrogenation of 4-isobutylacetophenone (4-IBAP) to 1-(4-isobutylphenyl) ethanol (4-IBPE) over a Pd/SiO2 catalyst has been studied in a semi-batch reactor over a wide range of operating conditions. The effects of varying temperature, catalyst amount, H2 partial pressure, substrate concentration and the effect of H2O on the activity and selectivity have been studied and an adequate kinetic model with Langmuir–Hinshelwood type rate expressions is proposed based on mechanistic insights. The effect of deactivation due to oligomerization on catalyst activity has also been incorporated in the model. The selected model assumes the competitive adsorption of dissociated hydrogen and reactants and products on the same active site. Further, the addition of the second H atom to 4-IBAP and the hydrogenolysis of 4-IBPE by an SN2 mechanism are considered as the rate-determining steps. Optimized operating conditions for maximizing the yield of 4-IBPE could be obtained using this kinetic model.