The hydrogenation of alpha-methyl styrene on 0.5 wt% Pd/Al2O3 at 40 degrees C and atmospheric pressure was used to study the performance of monolithic catalyst with different washcoat loadings at low gas and low liquid superficial velocities. The superficial velocities of the gas and liquid were varied in the range of 0.31-1.25 cm/s and 0.075-0.3 cm/s, respectively. The measured rate of reaction together with the power law kinetics determined in an earlier study by Mogalicherla et al. (2009, Ind. Eng. Chem. Res. 48, 1443-1450) was used to determine overall effectiveness factor for the monolithic catalyst. Using the approximation of Gottifredi et al. (1981, Chem. Eng. Sci. 36, 713-719) for non-linear kinetics, the internal effectiveness factor and mass transfer coefficient were estimated. The internal effectiveness factor decreased with washcoat loading whereas the productivity of the reactor, mol/m(reactor)(3) s, showed a maxima at a washcoat loading of 25 wt%. At these superficial velocities, mass transfer coefficient increased with liquid superficial velocities but was not significantly influenced by gas superficial velocity. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.