Neopentane conversion over zeolite-supported platinum and palladium catalysts

Neopentane conversion has been studied over platinum supported on L- and Y-zeolites, and palladium supported on KL-zeolite. The Pd/KL-zeolite catalysts exhibit the enhanced activation energies previously reported in the literature. The preexponential factors and activation energies show a compensation effect for both the palladium and the platinum catalysts. The trend in activation energies is compared with hydrogen TPD studies. Pressure dependence studies (in excess hydrogen) show reaction orders of approximately -2 and 0.8 for hydrogen and neopentane, respectively, except for hydrogenolysis over Pd/KL which exhibits reaction orders of similar to -4 and 0.64, respectively. At lower hydrogen pressures (< 70 Torr) the reaction order in hydrogen becomes less negative, which may signify a change in the rate-limiting step of the reaction. The nature of the adsorbed intermediates, probable reaction pathways, and the compensation effect are discussed. (C) 1997 Academic Press.