Influence of noble metals (Rh, Pd, Pt) on Co-saponite catalysts for HDS and HC of heavy oil

The promotional effects of trace amount of noble metal (Rh, Pd, Pt) on Co-saponite (high surface area) catalysts were studied by different characterization and evaluation techniques. BET experiments showed that the specific surface area and the pore volume of the noble metal promoted catalysts remained almost unchanged. The reduction/adsorption characteristics of the catalysts were significantly influenced by the presence of the noble metals as revealed by the temperature programmed studies. The main reduction peak was shifted remarkably to the lower temperature due to the noble metal effects. It also increased the amount of cobalt oxide phase reduction. Pulse chemisorptions and H₂-TPD kinetics studies revealed that the improved metal dispersion and the lower desorption activation energy have combined effects on the enhanced reducibility of the modified Co-saponite catalysts. The reactivity experiments showed that all of the noble metal promoted catalysts exhibited higher hydrodesulfurization (HDS) and hydrocracking (HC) activities as compared to the unpromoted Co-saponite and among those the Rh promoted catalyst provides superior performances. The coke deposition on the catalyst was also considerably decreased due to the noble metals. These superior activities were attributed to enhanced reducibility and metal dispersion of cobalt due to the influence of the noble metals.