The influence of metal-support interactions on the reaction of n-hexane over supported Pt catalysts

Abstract

The hydrogenolysis and skeletal rearrangement reactions of n-hexane have been investigated on Pt catalysts supported on silica and titania. The results show that the product distribution is dependent on the choice of support but that Pt/titania catalysts in the “normal” state are similar to Pt/titania catalysts in the “strong metal-support interaction” (SMSI) state. It is observed that in the SMSI state, when more than 99% of the Pt is inaccessible to hydrogen, the activity is only slightly reduced. Surprisingly, the selectivity for hydrogenolysis versus skeletal isomerisation is almost the same in normal and in SMSI catalysts. The results provide evidence that the same active centre is involved in both the hydrogenolysis and the skeletal rearrangement reactions, and do not support the contention that hydrogenolysis requires a larger ensemble of Pt atoms than skeletal rearrangement. The results are interpreted in terms of an active centre consisting of a single Pt atom located in the planes of the small Pt crystallites. The precise selectivity observed may depend on the local environment of the Pt atom during the sojourn of the n-hexane molecule on the active Centre.