Preparation Of Ni-W/SiO₂-TiO₂-ZrO₂ Catalysts And Its Performance For N-Heptane Isomerization

With the rapid development of China's economy,the demand for gasoline is increasing.In the meantime,the research on the isomerization of alkanes is becoming more and more active.Isomerization of n-heptane which accounts for a large proportion of straight-run gasoline is not only meets the environmental protection requirement,but also can effectively improve the octane number of gasoline.Therefore,it is very important to develop a high activity and stability of catalyst for n-heptane isomerization.In this paper,SiO2-TiO2-ZrO2 ternary composite oxides were prepared by sol-gel method and coprecipitation method respectively.Using Ni and W as the active components,and SiO2-TiO2-ZrO2 as support,the Ni-W/SiO2-TiO2-ZrO2 catalyst was prepared by impregnation.And catalytic performance was studied with n-heptane isomerization as the model reaction.The effects of preparation methods,preparation conditions,reduction conditions and reaction conditions on catalyst performance of Ni-W/SiO2-TiO2-ZrO2 catalyst were studied in great detail.The main research contents are as follows:1.The influence of different preparation methods,silicon content,calcination temperature and calcination time of support on the structure and activity of SiO2-TiO2-ZrO2 ternary composite oxides were investigated.The result showed that SiO2-TiO2-ZrO2 has a better crystal shape,larger surface area,higher temperature stability and stronger acidity by sol-gel method.With the ratio of Si/Ti/Zr being 1:1:1 at 700? for 4 h,the crystal struction of SiO2-TiO2-ZrO2 and the catalytic activity of Ni-W/SiO2-TiO2-ZrO2 catalyst was the best.2.The influence of different calcination temperature,template content,the content of Ni and W,reduction temperature,reaction temperature,weight hourly space velocity,H2 flow rate on catalytic performance of n-heptane hydroisomerization of Ni-W/SiO2-TiO2-ZrO2 catalyst were discussed.The result showed that the conversion and the selectivity reached50.61% and 81.70% respectively at calcination temperature 500?,n(P123)/n(Zr)=0.03,5%Ni,15%W,reduction temperature 450?,reaction temperature 240?,WHSV 6.8 h-1,H2 flow rate 50 m L/min.