Abstract
The addition of potassium to a Pt/Sn/SiO2 catalyst enhances the rates for both isobutylene hydrogenation and isobutane dehydrogenation, and a Pt/Sn/K L-zeolite catalyst exhibits considerably higher reaction rates than Pt/Sn/SiO2 and Pt/Sn/K/SiO2. The results of microcalorimetric measurements for hydrogen and isobutylene adsorption, steady-state kinetics investigations for isobutane dehydrogenation and isobutylene hydrogenation, and deuterium tracing investigations for the dehydrogenation and hydrogenation reactions were combined to develop a quantitative kinetic model based on a four step Horiuti-Polanyi mechanism. The dissociative adsorption/desorption of isobutane appears to be the rate determining step for isobutane dehydrogenation and isobutylene hydrogenation. The higher reaction rates observed over Pt/Sn/K-L suggest that the zeolite pore structure and/or the presence of potassium may promote the hydrogenation and dehydrogenation reactions by stabilization of activated complexes for elementary steps involving hydrocarbon species.
Published Version
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