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 and LTL zeolites in the presence of varying thiophene concentrations. Higher activity and a higher sulfur resistance were observed for Pt supported on partially alkali-exchanged zeolites compared to completely alkali-exchanged and purely acidic zeolites. This is attributed to the contribution of catalytically active sites on the metal and on Bronsted acid sites in the vicinity or at the perimeter of the metal particles. Increasing temperature and hydrogen partial pressure increased the sulfur tolerance of the catalysts. Although the deactivation of Pt by thiophene during benzene hydrogenation was higher for Pt/KH-LTL compared to Pt/NaH-MOR, the higher overall hydrogenation 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 vicinity of Pt and Si(OH)Al groups in LTL. As a consequence, the benzene hydrogenation route on Bronsted acid sites with spillover of hydrogen from Pt is more effective on Pt/KH-LTL than on Pt/NaH-MOR. (C) 2001 Academic Press.