Study On Supported Ni-W Catalysts For Diesel Deep Hydrodesulfurization

With the rapid development of the national economy,more and more people pay more attention to environmental protection.One fundamental source of acid rain is the use of diesel with high sulful content,in order to control the content of the pollutants in the atmosphere,the environmental protection department is more stringent on the requirements of the sulfur content of vehicle diesel oil.With the enforcement of increasingly stringent environment laws,it is very important to develop a highly active desulfurization catalysts.The influence of catalyst carrier,metal loading and metal promoter on Ni-W supported catalyst was studied in this paper,aiming at developing a catalyst for deep hydrodesulfurization of diesel.A series of NiW/Support catalysts were prepared by equal volume impregnation method usingγ-Al₂O₃,ZrO₂-Al₂O₃,SiO₂-Al₂O₃ and TiO₂-Al₂O₃ as the carrier.The effects of different carriers on the hydrodesulfurization activity of catalysts were investigated in a high pressure fixed bed tube reactor,using thiophene and octane as the simulated oil,and comprehensive characterizations including XRD,BET and SEM were conducted on these catalysts.The results show that four kinds of catalyst preparation,thiophene sulfur removal rate of Ni-W/TiO₂-Al₂O₃ catalyst was the highest,which indicates that TiO₂-Al₂O₃ is the surface structure properties of the carrier as compared to the other three kinds of carrier is more conducive to improving the depth of desulfurization catalyst.Through characterization and analysis of four groups of catalysts impregnated with TiO₂-Al₂O₃ composite carrier prepared by different TiO₂ content,the TiO₂ content of 15%is the best carrier ratio.At this time,the desulfurization rate of Ni-W/TiO₂-Al₂O₃ catalyst can reach 93.6%.In order to find out the best active metal load of catalyst,a series of Ni-W/TiO₂-Al₂O₃ catalysts with same metal atom ratio and different loading capacity were prepared on the basis of previous research.The results show that with increasing metal loading,catalyst activity of HDS increased first and then decreased,when the metal loading was 25%,the highest removal rate of thiophene Ni atoms in WS₂,at the edge of the formation of more species of class II Ni-W-S catalytic activity,and the activity of metal ions did not occur a large area of aggregation,conducive to catalyze reaction.To further improve the Ni-W/TiO₂-Al₂O₃ catalyst HDS activity,in this paper,using the rare earth metal oxide(CeO₂,La₂O₃,Pr₆O₁₁)to modificate catalysts,then the high pressure tubular fixed bed reactor is investigated in different content of rare earth metal oxides and the hydrodesulfurization activity of Ni-W/TiO₂-Al₂O₃ catalyst,and by XRD,BET and H₂-TPR means to characterize the structural properties of the catalyst and the activity evaluation.The results show that in the three kinds of rare earth metal modified Ni-W/TiO₂-Al₂O₃ catalyst,CeO₂ catalyst and La₂O₃ modified HDS was significantly higher than that of the unmodified catalysts,the modification effect of La₂O₃ is particularly prominent,hydrodesulfurization activity and Pr₆O₁₁modified catalyst instead of increase to drop.It was found that that optimum dope amount of La₂O₃ was 2%,and the thiophene thiophene removal rate of the catalyst was up to 98.6%.For the right select,which is used to simulate the oil（500ppm）,in the pressure fixed-bed tube reactor,to determine the best reaction conditions.Results show that the optimum process conditions of catalyst to reaction temperature 300℃,pressure of 3MPa,hydrogen oil than in 600,air speed of 2.0h^-1,under the condition of the reaction process,catalyst in continuous 192h of continuous reaction basic remain above 98%,desulfurization efficiency in showed higher HDS activity and stability.