Activation and Hydrodesulfurization Activity of MoO3/Al2O3 Catalyst Presulfided by Ammonium Thiosulfate

MoO3/γ-Al2O3 catalyst has been presulfided by ammonium thiosulfate. The effects of the presulfidation methods and the activation conditions on the hydrodesulfurization of thiophene were investigated. The results showed that the catalyst presulfided by ammonium thiosulfate (designated as Mo-ATS) exhibited higher activity than the one presulfided by dimethyldisulfide (denoted as Mo-DMDS). The former method gave a conversion of more than 99% in contrast to 92% obtained by the latter one under the same reaction conditions. The optimum temperature for the catalyst activation was in the range of 200–300 °C. An increase in the pressure was favorable for the activation and the enhancement in the HDS activity. In comparison to Mo-DMDS, the higher activity of Mo-ATS than that of Mo-DMDS was mainly attributed to the formation of an active type II MoS2 phase as a result of suppressing the interaction of Mo with γ-Al2O3 by modifying its surface with sulfate species. In addition, an increase in sulfidation degree (S2−/Mo molar ratio) was observed after activation and supplemental sulfidation. This is also favorable for hydrodesulfurization.