Aromatization of hexane over Pt/KL catalyst: Role of intracrystalline diffusion on catalyst performance using isotope labeling

Aromatization of hexane using an equimolar mixture of C6H14 and C6D14 was investigated over 1%Pt/KL at 500 degrees C and 1 atm. There is hardly any kinetic isotope effect indicating that entry of hexane molecules into the wider lobes of the channels of L-zeolite through the narrow apertures leads to single-file hexane access to Pt-0 sites. The catalyst displayed high activity and selectivity to benzene and excellent stability at the tested conditions during hexane dehydrocyclization. It is proposed that controlling the entry of hexane into the lobes of the L-zeolite containing the active sites is the reason for the exceptional Pt/KL catalytic performance for aromatization because the narrow windows of the L-zeolite channels inhibit the occurrence of bimolecular reactions that lead to coke formation and catalyst deactivation. (C) 2010 Elsevier Inc. All rights reserved.