Direct formation of isobutene from n-butane was investigated over zeolite TON and gamma -Al2O3 supported platinum and platinum-copper catalysts. Addition of Cu decreases Pt dispersion, irrespective of preparation methods and nature of catalyst supports. The presence of potassium was found to reduce acidity and Pt dispersion. The experiments were performed in a fixed-bed microreactor system operating at 673 K and atmospheric pressure. Changing the support from gamma -Al2O3 to TON, shows that n-butane conversion is almost independent of acidity. However, significant changes in products selectivities are observed. The selectivities to isobutene, C-1-C-3 fractions, and aromatics increases drastically from 3.5 to 32.6%, 20.3 to 27.2%, and 3.0 to 20.6%, respectively, for the TON-supported catalyst whereas dehydrogenation is largely predominant when gamma -Al2O3 is used as support. Addition of Cu, as expected, has an adverse effect on n-butane conversion as less active sites are available due to the reduction in Pt dispersion. Though Cu addition has marginal effect on isobutene selectivity, it certainly suppresses hydrogenolysis which evidences a reduction in size of the Pt ensembles at the surface of the Pt particles. (C) 2000 Published by Elsevier Science B.V.