Preparation And Catalytic Performance Of Highly Loaded NiMoS Hydrotreating Catalysts Of Diesel Oil

To control the concentration of sulfur and nitrogen in the environment, regulations are becoming more and more stringent to sulfur and nitrogen content in oil products. Nowadays, the hydrogenation process is the effective measure to deep desulfurization of distillates, and the key of this way is highly depending on the activity of hydrodesulfurization catalysts. Therefore, it’s urgent to improve the performance of hydrogenation catalyst. The preparation, characterization, evaluation and modification of highly loaded NiMoS catalyst for diesel hydrogenation were studied in this thesis.BET、XRD、Py-IR、TPR methods etc were employed to characterize and analysis the properties of catalysts with different metal loading amount, examining the influence of metal content to the formation mechanism of NiMoS active phase and HDS activity. With a variety of mechanical expanding methods, mesoporous alumina with larger pore size and volume, narrow pore size distribution can be prepared, which will effectively improve metal loading capacity and mass transfer. Then, the NiMoS catalyst was modified by complexing agent, and the impacts of complexing agent type on the catalyst activity were studied. In addition, construction process condition was optimized with the hydrogenation device utilizing mixed diesel from Qingdao Refinery as materials.Catalysts screening in the HDS of DBT showed that maximum activity was obtained at an metal loading of 30wt%, the HDS activity was mainly attributed to the desulfurization route, and the increase of loading amount lead to a larger SHYD/DDS ratio. In order to provide a better atomistic understanding of the catalyts, we perform here a TEM analysis, it was found that, the catalysts with a higher loading amount will have a larger MoS2 stacking layer number and longer slab length, as well as more surface Br?nsted acid center. The increasement of metal loading did make certain changes to the pore structure, surface acidity and reducibleness of catalysts.The pore structure of alumina supports can be adjusted and controlled selectively by adjusting stacking manner of alumina particals. It was investigated that, the support prepared by 20wt% 13 nm carbon black, 5wt% sesbania powder and post-treated with 10wt% ammonia solution has larger pore diameter, larger pore volume, proper specific surface area and mechanical strength.To further enhance the activity of catalyst, the properties and catalytic performance of catalysts modified by citric acid, ethylene glycol and polyethylene glycol were examined. Fixed bed microreactor evaluation of the catalysts show that, hydrodesulfurization activity is increased no matter what kind of complexing agents are adopted, and citric acid has better promoting effect. XRD 、 TEM experiments reveal that active metal dispersion degree increases and more active sites exposes after complexing agents are added.The optimization of construction conditions of Ni MoS-CA hydrogenation catalysts were studied on a high-pressure microreactor. The results indicate that the catalysts have good activity and the ratio of HDS and HDN of mixed diesel from Qingdao Refinery can be 98.9% and 98.5% respectively, when reaction temperature being 350℃, hydogen pressure being 8.0 MPa, space velocity being 1.5-1 and H2/Oil ratio being 500/1.