Acetophenone hydrogenation on Rh/Al2O3 catalyst: Intrinsic reaction kinetics and effects of internal diffusion

Abstract

Acetophenone hydrogenation on 1% Rh/Al2O3 catalyst was conducted using various support sizes to study intrinsic kinetics and internal diffusion effects. In the first part of this work, results from different noble metals and supports were compared, and the 1% Rh/Al2O3 was selected. From experiments at 60–100°C, 1.1–4.1MPa PH2 and 0.04–0.4M CAP.o using powder catalysts, intrinsic reaction kinetic modeling with the Langmuir–Hinshelwood mechanism was conducted. The selected kinetic model included dissociative and non-competitive hydrogen adsorption, along with saturated active sites for organic species, and surface reaction as the rate determining step. With the obtained intrinsic reaction kinetics, internal diffusion effects were investigated using two catalyst particle sizes and diffusion–reaction models. The properties of the egg-shell type catalyst particles, including metal dispersion, were characterized and utilized in the models. The concentration–time profiles calculated from models developed in this work correspond well with the experimental results, explaining the effects of internal diffusion inside catalyst particles on reaction rates and selectivity, and are suitable for future use in trickle-bed reactor modeling studies.