Process intensification has been the focus of increasing attention in recent years. A volume reduction of distillation and absorption units by a factor of 100 or more using rotating beds has been claimed. Industrial trickle-bed reactors are bulky because the liquid flow and interphase transport of the reacting species are governed by the earth's gravity, as in the case of distillation columns. To explore the possible process intensification in these reactors, we have measured the reaction rates of hydrogenation of a-methyl styrene with palladium as catalyst in the rotating beds of spherical particles and metal foam, which acted as catalyst support. To quantify the intensification achieved, the reaction rates were compared with those of conventional trickle beds. The enhancement in the reaction rates was in the range of 30-40 times in a centrifugal force field of about 450 times the gravitational force field. An industrial reactor of 60 m(3) could be replaced with a rotating bed < 1.5 m(3) in volume. It appears that there is a possibility of further process intensification. However, the volume reduction is possible only for mass-transfer limited reactions. (c) 2005 American Institute of Chemical Engineers.