The rationale of this work is to study the effect of using Pt containing catalysts supported on NH(4)-MOR zeolite, before or after steaming, to show how steam treatments affect the activities of catalysts used primarily for the hydroconversion of light naphtha to improve its octane rating. Hence, the reactions of the hydroisomerization and hydrocracking of n-pentane, were investigated at temperatures between 250 and 500 degrees C in a pulsed microcatalytic reactor using catalysts containing 0.25, 0.35 and 0.60 wt.% Pt supported on NH(4)-MOR. The effect of steaming on the dispersion of Pt, acid sites strength distribution, intraparticle diffusion resistance and the catalytic activities were investigated. Steaming was found to enhance catalytic activity deterioration. This effect was significantly increased with increasing Pt content in the catalysts. The calculated activation energy and entropy values using the current catalysts were correlated with the activity levels for hydroisomerization and hydrocracking of n-pentane. (C) 2007 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.