Role of sulfur in catalytic reforming of hydrocarbons on platinum-rhenium/alumina

Abstract

Cyclohexane reforming and n-heptane reforming were studied on 0.3-0.3% Pt-Re/AlO-0.95% Cl catalyst in the presence of sulfur. The combined effect of Re-S and Pt-S(Sis the irreversible form of platinum) that modified the platinum ensemble size and the electronic interactions caused the hydrogenolysis and dehydrocyclization activities to decrease. The presence of reversible sulfur (S) is explained in terms of the equilibrium between hydrogen sulfide and adsorbed S. Due to the added effect of Re-S decreasing the ensemble size, the fewer “available” free Pt crystallites on Pt-Re/AlOcompared to Pt/AlOmeans the toxicity of Swas greater for the bimetallic catalysts. The model previously proposed for sulfided Pt/AlOcan be extended to Pt-Re/AlOafter taking into consideration the additional effect of ensembling due to Re-S. Spillover of adsorbed hydrocarbon species to alumina during periods of high Slevels has been proposed for Pt-Re/AlO.