The Preparation And Performance Evaluation Of Low-grade Coking Diesel Hydrotreating Catalyst

Current crude oil is increasingly heavier and more inferior. Coking diesel oil, as a product of delayed coking, has a very high sulfur, nitrogen and olefins content, while its cetane number is very low at the same time. The CoMo catalysts can remove most of the sulfur compounds in the diesel directly due to its excellent hydrodesulfurization activity. The addition of phosphorus-containing additives can provide the necessary Br?nsted acid sites for denitrification. Therefore the CoMoP catalyst has high desulfurization and denitrogenation activity which is suitable for inferior coking diesel oil that contains high concentration of nitrogen and sulfur.The stable and rapid preparation of impregnating solution is the premise of catalyst preparation. A series of impregnating solution were prepared by controlling Co/（Co+Mo） and P/MoO3, and the influence of charging sequence,temperature and solubility were studied respectively. A rapid method to prepare the impregnating solution and the soluble region of CoMoP impregnating solution were obtained. To prepare the CoMoP/γ-Al₂O₃ catalysts with different ratio of active component, we should make sure that the ratio of active component and P content must locate in the soluble region.This paper analyzed the type of heteropoly acid in the CoMoP impregnating solutions with different Co/Mo ratio and phosphorus content. The influence of Co/Mo ratio and phosphorus content on the type of heteropoly acid was studied. The influence of Co/Mo ratio and phosphorus content on the impregnation process was also researched on this basis.Researches on the hydrofining catalysts for coking diesel oil mainly focus on the activity modulation. This paper studied the influence of pore structure, crystal structure, acid properties, reducibility and sulfidation performance on the catalysts’ hydrogenation activity by a series of characterization techniques. The hydrogenization activity of catalysts with different Co/Mo ratio and phosphorus content were evaluated with 10 mL high pressure micro-reactor and 100 mL fixed bed hydrogenation unit respectively, and the most appropriate Co/Mo ratio and phosphorus content for the catalyst were obtained.The results obtained by the 10 m L high pressure micro-reactor indicate that the catalyst with Co/（Co+Mo） of 0.25 has the best activity in HDS reaction. Hydrodesulfurization reaction are mainly conducted in the hydrogenolysis process. The existence of nitride inhibits the performance of HDS reaction, and the inhibition towards hydrogenolysis process is stronger than hydrogenation process. The hydrogenation performance of catalysts were also analyzed at different temperatures, and the results indicate that high temperature can significantly improve the hydrogenation activity of catalysts in the presence of nitride.The activity and stability of the CoMoP/γ-Al₂O₃ hydrofining catalyst with different phosphorus content were evaluated by 100 mL fixed bed hydrogenation unit, and the results show that the catalysts with P/MoO3 ratio of 0.06 has the highest HDS and HDN activity. The HDN activity of the catalysts with phosphorus-containing additives is significantly higher due to the Br?nsted acid sites provided by the phosphorus-containing additives.