Kinetic studies of isobutane dehydrogenation and isobutene hydrogenation over Pt/Sn-based catalysts

Rates of isobutane dehydrogenation and isobutene hydrogenation were measured over Pt/Sn/ SiO2, Pt/Sn/K/SiO2, and Pt/Sn/K-L-zeolite catalysts at temperatures from 673 to 773 K and at various partial pressures for a total pressure of 1 atm. Addition of potassium to Pt/Sn/SiO2 enhances the rate of isobutene hydrogenation and isobutane dehydrogenation, and the Pt/Sn/ K-L-zeolite catalyst exhibits considerably higher rates than Pt/Sn/SiO2 and Pt/Sn/K/SiO2. The kinetic data for the hydrogenation and dehydrogenation reactions over the Pt/Sn catalysts could be described by a four-step Horiuti-Polanyi mechanism, with rate-limiting, dissociative adsorption of isobutane and quasi-equilibrated adsorption of hydrogen and isobutene. The higher rates observed over Pt/Sn/K/SiO2 and Pt/Sn/K-L-zeolite may be attributed to stabilization of the activated complex involved in the dissociative adsorption/desorption of isobutane on the Pt/Sn clusters within the zeolite pore structure and/or stabilization by the presence of potassium.