Study On Preparation Of Oil-Soluble NiMo Bimetallic Catalyst For Hydroconversion Of Heavy Oil

With the rapid development of the world economy,the global demand for petroleum products continues to increase,but the quality of crude oil continues to develop in the direction of heavy quality and inferior quality.How to utilize heavy crude oil resources more efficiently has become a research hotspot in the world.Slurry bed hydrogenation technology is a very ideal technology for heavy oil hydrogenation because of its simple process and high feedstock adaptability.The development of efficient and cheap catalyst is the key to the application of this technology.In this paper,a preparation method of self-curing oil-soluble nickel-based catalyst was developed,and a nickel-molybdenum bimetallic catalytic system was constructed.The slurry bed hydrogenation process conditions were optimized and the mechanism of hydrogenation coking inhibition of oil-soluble catalyst was preliminarily explored.In this paper,the preparation method of a sulfur-containing organic ligand was studied,and the self-sulfurized oil-soluble nickel based catalyst was successfully prepared with it as the catalyst precursor.The low-cost preparation scheme of the catalyst was initially formed,and the processing conditions of the slurry bed hydrogenation of the residual oil were optimized.The results show that the prepared oil-soluble nickel-based catalyst can achieve excellent dispersion effect in the processed oil,and can be completely decomposed before 250℃.Moreover,it has the function of self-vulcanization,and can be decomposed in situ into metal sulfides with hydrogenation activity.Taking Qingdao refinery vacuum residue as raw material,the optimal reaction conditions were obtained as follows:reaction temperature 420℃,hydrogen initial pressure 11 MPa,catalyst concentration 1000 μg·g^-1,reaction time 1 h.The slag reduction conversion rate of Qingdao refinery reached 48.18%,and the total amount of coke was only 0.51%.The oil-soluble nickel-based catalyst and molybdenum based catalyst were combined to construct a nickelmolybdenum bimetallic catalyst system.The results show that the catalyst can be completely decomposed into MoS₂ and NiS at 350℃,in which the length of MoS₂ layer is concentrated in the range of 2～5 nm,and the number of stacked layers is mostly 1～2.The results show that the bimetallic catalyst has obvious synergistic effect,which can increase the yield of light oil while maintaining good coking inhibition performance.The optimal reaction conditions are as follows:reaction temperature is 420℃,initial pressure of hydrogen is 11 MPa,reaction time is 1 h,the composite ratio of Ni/Mo is 1:2,the slag reduction conversion of Qingdao refinery is 54.01%,and the coke production is only 0.3%.The mechanism of hydrogenation and coke suppression of oil-soluble catalyst was investigated and the change of asphaltene with temperature and reaction time during the heating process was investigated.The results showed that the prepared oil-soluble catalyst exhibited better activity of hydrogenation and coke suppression in the early stage of reaction.It can inhibit the polymerization of macromolecular aromatic lamellae at low temperature stage,and can form enough hydrogen free radicals to saturate macromolecular free radicals at the early stage of the reaction,thus avoiding the carbonization process at the source at the later stage of the reaction.In the asphaltene reaction system,the side chain breaking reaction of aromatic ring and ring opening reaction of naphthenic ring are mainly occurred.