Study On The Nitride Isodewaxing Catalysts Of Lubricating Oil

The isomerization dewaxing catalyst developed at present is mainly supported by precious metal Pt/Pd catalyst.Although the type of precious metal catalyst has high activity,but it can't tolerate sulfur and nitrogen compounds,so it's very strict to hydrotreatment of raw materials.The study of catalysts loaded with transition metal nitrides on SAPO molecular sieves has not been completed.Therefore,it is of great theoretical and practical significance to carry out this work.In this paper,the initial gel composition was determined for SAPO-11 preparation as the carrier.The performance of transition metals isomerization catalysts with different loadings and loading ratioes,and the effects of different nitriding conditions on the nitride catalysts were studied.The isomerization dewaxing performance and suitable process conditions of the catalyst were investigated by using the mixture of hydrocracking tail oil and vacuum second-line wax oil as raw material in high pressure hydrogenation reactor.First,SAPO-11 molecular sieves were prepared by static hydrothermal synthesis.The initial gel composition?molar ratio?was 0.6SiO₂:1.0Al₂O₃:1.0P₂O₅:1.2DPA:55H₂O,and the crystallization time was 48h.Nitrided catalysts with different loadings and proportions were prepared by loading Ni-Mo active component on the SAPO-11 molecular sieve with equal volume impregnation method.The results show that the nitride catalyst has good pore structure and acidity.The metal center of the catalyst is mainly Ni₂Mo₃N.When the metal loading is 10%and the molecular proportion is 1.0,the catalyst has good catalytic activity.Secondly,the effects of nitridation conditions on the formation of metal nitrides and their isomerization dewaxing performance were also investigated.The results show that both nitridation temperature and nitridation time affect the formation of active components on the catalyst surface.When the nitridation temperature is lower than 600°C,the metal is mainly mono-metal nitride and Ni₂Mo₃N appears only above 600?.The excessive nitridation time will cause transition metal alloy on the surface of the catalyst.Therefore,the nitridation conditions with nitridation temperature of 600-700?and nitridation time of 60-90min are favorable for the preparation of nitride catalyst.In the investigation of hydrogenation conditions,when the reaction pressure was 15MPa,the reaction temperature was 390?,the space velocity was 0.6h^-1,and the hydrogen/oil volume ratio was 1000:1,the isomerization dewaxing effect of the catalyst is best.Under these conditions,the pour point of the base oil was-8?,and the base oil yield was 61.9%,and the viscosity index was 92.