Study On The Ni-Mo Catalysts For Lubricating Oils Hydrotreating

At present, hydrotreating technology is widely used in order to improve the production of high viscosity index base oil, of which the research, development and application is key to the development of the whole hydrogenation process. A series of Ni-Mo/γ-Al₂O₃ catalysts with the same metal loading have been prepared by different methods. These methods include dry mixing, step impregnation and co-impregnation. Then the catalysts were analyzed by BET, XRD, SEM. The results indicated that, dispersion of active metals in the catalyst by dry mixing was very low and the crystalline phase particles were inhomogenous. In co-impregnated catalysts, Mo was easy to reunite and Ni was easy to form NiAl2O4. Comparatively, the decentralized state of Ni and Mo in catalysts prepared by step impregnation was the best of all.A series of Ni-Mo/γ-Al₂O₃ catalysts with different Ni and Mo loading were prepared by step impregnation to investigate influences of Ni and Mo loading on catalytic performance. The optimal loading was determined taking into account the HDS and HDN performance of catalysts. Meanwhile the hydrogenation process of M20N4 catalyst was optimized using the high-pressure fixed-bed hydrotreating device, with wax oil as reactants. The studies indicated that:（1）With the increase of Ni and Mo, specific surface area, pore volume and pore size decreased, and active phases of the catalysts increased.（2）If Ni or Mo loading was low, active phases of catalysts would reduce, limiting hydrotreating activity of the catalysts. While high content of Ni or Mo would exacerbate the interaction between metal atoms and carriers, forming a large number of NiAl2O4, NiMoO4 and Al2（MoO4）3, which would reduce the hydrogenation activity.（3）With the increase of Ni or Mo, HDS and HDN activity would first increase and then decrease. HDS and HDN achieved the best activity when w（NiO）=4wt%, w（MoO3）=20wt%.（4）The hydrogenation process improved with reaction temperature rising, velocity decreasing and H/O increasing. HDS and HDN boomed under the condition of reaction temperature of 400oC,space velocity at 0.25h-1, and H/O 2000:1.The influence of Si, P, and USY zeolite as promoters on carriers and catalysts was also investigated, meanwhie comparing different catalysts. The results showed that, with SiO2, P, and USY zeolite, specific surface area of catalysts and carriers enlarged and the distribution of catalytic pore changed. At the same time, with the dispersion of active components enhanced and the surface acidity of the catalysts improved, HDN activity was greatly improved.