Preparation Of Highly Active Ni-mo Hydrogenation Catalyst For Diesel By In Situ Crystallization On Support

In this dissertation, a new method for catalyst preparation by in situ crystallization on support was described, conquering the problems that large particles and low dispertion of the activity components which catalyst prepared by traditional impregnation method essentially caused. The active components precursor was produced by means of crystallization reaction under hydrothermal conditions and was simultaneously dispersed evenly on the support attributed to the high reactivity and strong penetration of the water under the mild critical stateA serial of NiO/Al₂O₃ composite supports containing different NiO was prepared by the method of mixing kneading and impregnation respectively. And the influences of the aluminum type, calcining temperature and petizater type on the pore structure of composite support were investigated. The results shows that NiO/Al₂O₃ composite support prepared by type WL pseudo-boehmite(PB) as the binder and acetic acid as petizater possessed large specific surface area and specific volume while MoO₃/Al₂O₃ composite support prepared in the same way had small specific surface area. Specific surface area of NiO/Al₂O₃ composite support prepared by impregnation method relativily decreased and the pore size distribution had a decrease as well.XRD and IR characterization results indicated that (NH₄)HNi₂(OH)₂(MoO₄)₂ can be produced by NiO/Al₂O₃ composite support and in situ crystallization reaction. The influence of reaction temperature, molybdenum concentration, reaction time , MoNi atomic ratio and reaction additives on the crystallization reaction were examined systematically. NiMo catalyst prepared by in situ crystallization method were evaluated. It was found that compared with industrial NiMo catalyst, in situ NiMo catalyst exhibited superior naphthalene hydrogenation activity and DBT hydrodesulfurization activity, and had a higher HYD path selectivity with a hydrogenation depth duing the HDS. XRD and BET characterization of the sulfided catalysts proved that the in situ catalyst possessed higher MoS₂ stack layers, thus more active sites of type II can be formed, and superior hydrogenation activity can be gained. The in situ Ni-Mo catalyst and industrial catalyst as a reference were both evaluated employing mixed model compound consisted of the naphthalene, DBT and quinoline. It was shown that HDAr, HDS and HDN activity of the in situ catalyst was superior to industrial catalyst; nitrogen-containing organic compunds in the mixed system evidently suppressed HDS and HDAr process, and mainly affected the HYD route. The in situ NiMo catalyst and industrial catalyst as a reference were both evaluated as well employing coker gasoline and diesel, and the in situ-NiMo catalyst performed a higher HDS and HDN activity than the industrial catalyst.The in situ crystallization was scaled-up to kilogram class and the catalysts prepared were successively evaluated employing diesel in the 100ml industrial small scale device. The results showed that in situ catalyst performed higher HDS and HDN activity, and it could decrease the sulfur content of diesel from 103160μg·g^-1 to 50μg·g^-1 when temperature was 360℃, pressure was 6.4 MPa and space velocity was 2.0 h^-1 while the traditional catalyst could only decrease the sulfur content to 121μg·g^-1 under the same conditions.