Hydrodesulfurization and Hydrogenation Reactions on Noble Metal Catalysts: I. Elucidation of the Behavior of Sulfur on Alumina-Supported Platinum and Palladium Using the 35S Radioisotope Tracer Method

Abstract

Hydrodesulfurization (HDS) reactions of 35S-radioisotope-labeled dibenzothiophene (DBT) were carried out over a series of γ-Al2O3-supported noble-metal-containing catalysts at 5.00 MPa and at 260 and 280°C. The amount of sulfur (STOTAL) accommodated on the catalyst and the amount of labile sulfur (S0) participating in the reaction were determined using a direct method, the 35S radioisotope pulse tracer method, which has recently been developed by the authors. It was observed that both STOTAL and S0 increased linearly with an increase in active metal loading. At the same time, it was found that the sulfided test noble metal catalysts corresponded to a S/Pt (Pd) ratio of 0.25 and that almost all the labile sulfur on these catalysts was mobile in the HDS reaction. Further, the activities of both HDS and hydrogenation reactions over the bimetallic catalyst (Pt–Pd) were higher than those of the monometallic catalysts tested together, whereas the synergetic effects observed on the Pt–Pd catalyst were not as significant as in typical Co–Mo catalyst cases.