Sulfur-tolerant Pt-supported zeolite catalysts for benzene hydrogenation I. Influence of the support

Benzene hydrogenation was investigated over a series of Pt-supported MOR an d LTL zeolites in the presence of varying thiophene concentrations. Higher activity and a higher sulfur resistance were observed for Pt supported on p artially alkali-exchanged zeolites compared to completely alkali-exchanged and purely acidic zeolites. This is attributed to the contribution of catal ytically active sites on the metal and on Bronsted acid sites in the vicini ty or at the perimeter of the metal particles. Increasing temperature and h ydrogen partial pressure increased the sulfur tolerance of the catalysts. A lthough the deactivation of Pt by thiophene during benzene hydrogenation wa s higher for Pt/KH-LTL compared to Pt/NaH-MOR, the higher overall hydrogena tion activity for benzene in the presence of thiophene was observed for Pt/ KH-LTL. This is attributed to the high Pt dispersion and the closer vicinit y of Pt and Si(OH)Al groups in LTL. As a consequence, the benzene hydrogena tion route on Bronsted acid sites with spillover of hydrogen from Pt is mor e effective on Pt/KH-LTL than on Pt/NaH-MOR. (C) 2001 Academic Press.