Hydrodesulfurization and hydrodenitrogenaton of dibenzothiophene mixed with pyridine in diesel oil over CoMo catalysts supported on Al₂O₃-TiO₂

Abstract

This research studied the hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of dibenzothiophene (DBT) mixed with pyridine in diesel oil over CoMo catalysts supported on Al₂O₃-TiO2 mixed oxides were prepared by sol-gel methods. The amount of TiO₂ that was incorporated into Al₂O₃ was in the range of 10-50 wt. %. Then cobalt and molybdenum were co-deposited on these mixed oxide supports. The catalysts were characterized by ICP-OES, XRD, N₂ physisorption, H₂-TPR, NH₃-TPD, and CO-Chemisorption techniques. HDS and HDN reactions were carried out in a packed bed microreactor at 350oC and 80 bars of H₂ pressure. Five different nitrogen concentrations from pyridine were employed to investigate its effect on the catalytic activity. Prior to each run, the catalyst was sulfided using dimethyldisulfide (DMDS) under hydrogen atmosphere to activate the catalysts. From this study, the addition of TiO2 to Al₂O₃ increased the surface acidity and led to move reduction of Mo to the lower state by lowering the metal-support interaction of catalysts. The CoMo catalyst on Al₂O₃-TiO₂ supports containing 50 wt. % of Al₂O₃ exhibited the highest activities for both HDS and HDN. Addition of pyridine to the feed lowered the HDS activity of the catalysts. An increase in the concentration of nitrogen compound in the feed led to further reduction in HDS activity of the catalyst.