Application of Acid Modified Catalysts with Different SiO2 Contents in the Hydrocracking of Light Cycle Oil for Light Aromatics Production

A series of functionalized USY/SiO2 zeolite composite supports were synthesized using the coating coprecipitation method,with tetraethyl orthosilicate(TEOS)as the silicon source and different ratios of USY to TEOS.Active metals nickel(Ni)and molybdenum(Mo)were loaded onto the supports using the impregnation method.Finally,a series of hydrogenation catalysts were synthesized.The characterization results showed that,compared with the USY catalyst,the addition of a certain quantity of SiO2 resulted in the disappearance of the strong acid sites on the catalyst,the number of weak acid and medium strong acid sites decreased,and a certain number of secondary mesoporous structures were formed.The addition of SiO2 reduced the secondary cracking of benzene,toluene,xylene,and ethylbenzene(BTXE)effectively,while excessive amounts of SiO2 reduced the hydrogenation activity of the catalyst,leading to a decline in the final yield of BTXE.At a maximum SiO2 content of 45％,the hydrogenation depth of light cycle oil(LCO)reached an optimum value.The hydrogenation performance of LCO was investigated in a fixed bed reactor at 380℃,4 MPa,and H2/oil volume ratio of 800:1,where the gasoline and diesel fractions reached 80.00％and 16.74％,respectively.NiMo-YS45 had the highest BTXE selectivity,and the final yield of BTXE reached 21.27％.