Reforming of n-hexane over Pt-tin silicalite-1

Abstract

The catalytic behavior of Pt supported on non-acidic silicalite-1 (MFI structure) and on the stannosilicate, Sn-sil-1 molecular sieves in the aromatization of n-hexane is investigated. The influence of Pt content, temperature, space velocity, H₂/n-hexane ratio and time on stream (TOS) on the n-hexane conversion, aromatic selectivity and aromatic yield are presented. Aromatics are the main products and this suggests that the aromatization proceeds via dehydrocyclization and/or hydrogenolysis, dehydrogenation to C₂-C₄ olefins followed by oligomerization inside the pores of the molecular sieve into cyclic intermediates in presence of hydrogen. The incorporation of Pt during the synthesis of the stannosilicate (Sn-sil-1) yields a more active catalyst (42 wt% aromatic selectivity) without any deactivation than when Pt is loaded by impregnation on Sn-sil-1 because catalyst deactivation associate with platinum outside the zeolite pores. A formation mechanism is proposed.