The three-phase catalytic hydrogenation (TPCH) of alpha-methylstyrene using supercritical carbon dioxide (SCCO2) in a slurry reactor is reported. Kinetic data are presented for the reaction at 323 K over the range of pressure from 7.0 to 13.0 MPa using a carbon-supported palladium catalyst. The experimental data are fitted to a first-order power-law model. A detailed explanation of the methodology used to isolate the effect Of CO2 on the rate of reaction is presented. Particular attention is given to the phase behaviour of the reaction system and the volumetric expansion of the liquid phase with CO2. It is shown that scCO(2) significantly enhances the rate of reaction. This effect is attributed to the enhancement of the solubility of hydrogen in the liquid phase. (C) 2002 Elsevier Science B.V. All rights reserved.