Influence of the source of sulfur on the hydroconversion of 1-methylnaphthalene over a Pt–Pd/USY catalyst

Abstract

Hydroconversion of 1-methylnaphthalene was performed over a Pt–Pd/USY catalyst in a batch reactor at 310 °C and 5 MPa of hydrogen pressure in cyclohexane as the solvent and in the presence of 800 ppm of sulfur resulting from different sources, hydrogen sulfide, thiophene and dibenzothiophene. In a general manner, hydrogenation of 1-methylnaphthalene into the corresponding mixture of methyltetralines is not significantly affected by the nature of the sulfur species present in the starting feed. On the contrary, going from hydrogen sulfide to thiophene and finally to dibenzothiophene, hydrogenation of methyltetralines into methyldecalines is lowered and ring-opening of methyltetralines to alkylbenzenes is enhanced. This would agree with the expected sequence of appearance of hydrogen sulfide in the feed. These results are in agreement with dissociation of hydrogen into protonic and hydride species, as already proposed in the presence of sulfided catalysts, i.e., protonic species would be involved for the hydrogenation steps and hydride species for the ring-opening steps. Hydrogen sulfide present as such or resulting from the transformation of thiophene or dibenzothiophene would then reduce the hydrogenation route, and, as a consequence, increase the hydrogenolysis route.