Study On The Preparation Of The Unsupported Ni-Mo-W Catalyst By Co-precipitation Methods And Its Preformance

At present, with the stringent environmental regulations and low-quality crude oil increasing,desulfurization becomes more and more important. The requirements of clean fuel with ultra low sulfide or zero sulfide are urgent. However, the active sites providing by conventional supported catalysts are limited by their components. The activity of supported catalysts exists bottleneck which couldn't exceed. Fortunately, unsupported catalyst is a kind of highly activity catalyst without any support in, which has more active sites than conventional supported catalyst. Unsupported catalyst can get ultra high hydrogenation activity by appropriate new technologies. Therefore, studies on the unsupported catalysts have become a new focus of oil hydrogenation.The Ni-Mo-W unsupported deep hydrodesulphurization (HDS) catalysts for ultra clean diesel fuels were studied in this paper. The main research content and results are as follows: Firstly, the precursors of catalyst were prepared by co-precipitation. The effects of metal source, metal ratio, precipitator species, reaction time and temperature were studies. The results indicated that optimal reaction conditions are that using nickelous nitrate, ammonium molybdate and ammonium metawolframate as raw materials, Ni:Mo:W=2:1:1(mol ratio), NH3·H2O as precipitator, the reaction time of 2h and the temperature of 90℃.Secondly, the shape process of precursor was studied. The effects of agglomerant species and amount, the addition mode of agglomerant and the modification elements were investigated. The results indicated that the catalysts with ultra-high activity and proper physical properties are obtained under the conditions of that the ratio of agglomerant to precursor is of 0.4 to 0.6 and the agglomerant is added one time.Moreover, the precursors and catalysts were characterized by BET, XRD, TG/DTA, FT-IR, IR-Py, SEM-EDXA and XRF. The results indicated that the precursor was of high specific surface area and pore volume, obvious multi-layered structure and even distribution of grains in appearance. The catalysts were of coarse appearance and obviously layered structure. XRD indicated that the morphology of catalyst was crystalline structure assembly analogous with NiO. The physical properties of catalyst such as specific surface area, pore volume, bulk density and bulk density meet the requirements of industrial applications.Finally, the hydrotreatment conditions of catalysts were studied comprehensively. The results indicated that reaction temperature and airspeed have obvious influences on the behavior of desulphurization and denitrification. In contrast, the effects of pressure and oil hydrogen ratio were weak. The prepared unsupported catalyst is of excellent behaviors of desulfurization, denitrification, activity stability and feedstock adaptability, even under the condition of large processing load. Under the conventional conditions, the sulfur content of hydrotreated diesel was lower than 10μg·g^-1.