Electronic effects and effects of particle morphology in n-hexane conversion over zeolite-supported platinum catalysts

n-Hexane conversion over zeolite-supported platinum catalysts has been studied at 360 degrees C in a packed bed reactor. In the absence of sulfur impurities, the deactivation appears to be due to two types of coke formation. The propensity for terminal hydrogenolysis is primarily determined by the particle morphology, i.e., the type of surface sites exposed. The increase in benzene selectivity correlates with a shift to lower stretching frequencies of the CO absorption bands, indicating that an increase in the electron density at the surface metal atoms results in higher benzene selectivity. The effect of the support in the high activity and aromatization selectivity of a monofunctional platinum catalyst for n-hexane conversion is observed to be twofold, i.e., the stabilization of extremely small metal particles of specific morphology under reaction conditions and metal-support interaction, resulting in an increased electron density over the metal particles. (C) 1998 Academic Press.