Study On Performance Of Modified MoP And NiMo Sulfide Catalysts For Thioetherification

It is of great practical significance to research catalysts for the thioetherification accompanying with selective hydrogenation,during which mercaptans and diolefins are simultaneously removed from FCC gasoline.In this paper,the cyclohexane solution of isoprene and n-butylmercaptan was used as a simulation oil.The H₂S/H₂sulfided MoP/SiO₂ and P modified NiMo/?-Al₂O₃ sulfide catalysts were tested for the thioetherification and characterizaed by means of XRD,TEM-EDX,XPS,NH₃-TPD,CO chemical adsorption.The effect of sulfuration temperature on the structure and performance of MoP/SiO₂ catalyst was first investigated.It was found that the MoP bulk structure did not change even at the sulfuration temperature as high as 400 ^oC.However,with the increase of sulfuration temperature,the acid amount of the catalysts increased while the number of surface metal sites decreased,which restrained the C-S bond hydrogenolysis and the over-hydrogenation of isoprenebut promoted the olefin polymerization.The sulfuration at 120 ^oC not only improved the thioetherification performance of MoP/SiO₂ but also the resulting catalyst showed good performance for the selective hydrogenation.Thus,the suitable sulfuration temperature was 120oC.The P-modified Ni-Mo/?-Al₂O₃ sulfide catalysts were prepared,and the effect of the impregenatoin sequence on the catalyst structure and performance was studied.On one hand,P modification increased the acid amount of the catalyst.On the other hand,it reduced the interaction between the metal components and?-Al₂O₃,and so promoted the sulfuration of the metal components and increased the exposed metal sites,especially for the P-NiMo catalyst which was prepared by impregnating the P species onto?-Al₂O₃ prior to the Ni-Mo ones.Ni₃S₂ phase was formed in all the sulfide catalysts?including the one without P modification?,but no MoS₂ phase was detected.The catalysts prepared by the consecutive impregnation method showed better thioetherification performance,especially the P-NiMo catalyst.Compared with the consecutive impregnation the co-impregnation method is more conducive to enhace the catalyst activity for the conversion of isoprene.Among all the catalysts,P-NiMo showed the lowest performanc for the selective hydrogenation of isoprene.Additonally,P modification improved the catalyst activity for the olefin polymerization due to the increase of the acid amount.In all,the sulfide catalyst prepared by impregnating the Ni-Mo components prior to the P one showed better performance for the thioetherification than others.