The aim of this work is to investigate the skeletal isomerization of n-butane to isobutane over Pt-modified mordenite zeolite catalysts and proton form mordenite with different SiO2/Al2O3 ratios. The 2-wt% Pt-H-MOR-20 and 2-wt% Pt-H-MOR-12.8 catalysts were synthesized by impregnation method. while H-MOR-12.8 and H-MOR-20 were obtained by calcinations of their ammonium-form counterparts. The influence of reaction temperature, carrier gas and dilution of the feed stream on the conversion of n-butane and yield of isobutane during, time-on-stream has been studied. The Pt-modified mordenite catalysts have been characterized using XRD, scanning electron microscopy (SEM), nitrogen adsorption, CO chemisorption and FTIR of adsorbed pyridine. Pt-H-MOR-12.8 exhibited the highest yield and selectivity to isobutane and it was the most stable towards catalyst deactivation. Typically, an excess of propane with respect to pentanes was formed and the selectivity to pentanes remained constant for the different Pt-H-MOR and conditions tested. Selectivity to propane was inversely dependent on the H-2 concentration in the feed and the SiO2/Al2O3 ratio. (c) 2005 Elsevier B.V. All rights reserved.