Preparation Technology And Hydrodesulfurization Performance Of NiFeMo Catalyst

Environmental pollution is one of the most serious problems during recent years,the whole world emphasizes a strict legislation on the sulfur content of diesel.Hydrodesulfurization?HDS?process plays a vital role in removing sulfur for most refineries,and the researchs of more economical HDS catalysts with better performance are penetrating deeply and have got some new progressions for the past decades.Effect of iron promoter on the physicochemical and catalytic properties of unsupported nickel-molybdenum catalysts were studied.A series of NiFeMo precursors with various iron contents were synthesized by chemical precipitation method.Results revealed that with increasing iron content,the surface area and pore volume of NiFeMo precursors decreased.MoS₂ nanoperticles were observed in the sulfided catalysts by XRD and HRTEM characterizations due to the XRD peaks and specific spacings,respectively.The stacking degree and slab length of MoS₂ slabs was decreased with increasing iron content,which was accordance with the XRD result.Sodium dodecyl benzene sulfonate was selected for prevent blocking,which improved the surface area and pore volume of modified precursors.The HDS activities of the catalysts towards dibenzothiophene?DBT?were evaluated.The results showed that iron was not an efficient promoter,while for the modified NiFeMo catalysts,direct desulfurization?DDS?pathway was predominant.Compared to NiMo catalyst,the modified NiFeMo catalyst had higher HDS activity towards DBT,and the low-temperature activity of the catalyst was enhanced.The?-Fe₂O₃ nanoparticles were synthesized by homogeneous precipitation method,using iron nitrate and urea as raw material,using sodium dodecyl sulfate and cetyl trimethyl ammonium bromide as dispersants,respectively.The effect of two surfactants in the preparation of?-Fe₂O₃ nanoparticle was studied.The results showed that the properly sized?-Fe₂O₃ nanoparticles could be obtained when using cetyl trimethyl ammonium bromide as dispersant.A series of spherical shaped nickel and molybdenum composite oxides coated?-Fe₂O₃ catalyst percursors have been prepared,by traditional homogeneous precipitation method.The particle size of the coating structure catalyst precursors is about 100 nm.The MoS₂ and Ni₃S₂ nanoparticles were detected on the sulfided catalysts.With increasing amount of?-Fe₂O₃,the bending and stacking degree of the MoS₂ nanoparticles decreased.The coating structure catalysts had higher low-temperature activity than unsupported catalysts towards DBT,and DDS pathway was predominant.