Ni-WO₃/TiO₂-ZrO₂ Catalysts Preparation And Its Performance Study

In recent years, the study on the isomerization of alkanes has become more and more active, because it not only meets the requirements of environmental protection, but also can improve the quality of the gasoline. For n-heptane isomerization catalyst, the universal study is noble metal supported by SAPO, HZSM-5 and Y, β type molecular sieve and composite metal oxide, in which the composite metal oxides（TiO₂-ZrO₂, SiO₂-ZrO₂, Al₂O₃-ZrO₂） as the catalyst carrier has better performance whose development trend will be more than other molecular sieve catalysts. Ni-WO₃/TiO₂-ZrO₂ catalyst was prepared in this paper, and applyed in n-heptane isomerization reaction.In this paper, TiO₂-ZrO₂ composite oxide prepared by changing the factors of preparation method, titanium zirconium molar ratio and template agent dosage, calcination temperature,calcination time and discussed the influence of the structure on TiO₂-ZrO₂ composite oxide.The results show that compared with homogeneous precipitation method, co-precipitation method, sol-gel method, template-sol-gel method, the TiO₂-ZrO₂ composite oxides prepared by template-sol-gel method was the best which has the strongest acidity, porous surface and larger specific surface area. When the ratio of n（Ti）:n（Zr）=1, n（P123）/n（Zr）=0.03, and calcination temperature, calcination time is 650℃, 5h respectivel, which TiO₂-ZrO₂ composi-te oxide has a good crystallinity.The TiO₂-ZrO₂ composite oxides as the carrier which prepared by template-sol-gel method was supported by WO₃ and Ni to obtain Ni-WO₃/TiO₂-ZrO₂ catalyst. And n-heptane was used as a probe and the preparation method, calcination temperature, the content of WO₃ and Ni, reaction temperature, reduction temperature, weight hourly space velocity and other factors was discussed to study the influence of the structure on the catalyst and catalytic performance on isomerization reaction of n-heptane The results show that, under the condition that when the calcination temperature of the carrier, the calcination temperature of the carrier supported by WO₃, the calcination temperature of the carrier supported by Ni is650℃, 800℃, 500℃ respectively and when the content WO₃ and Ni is 15% and 5%respectively and when the reaction temperature, the reduction temperature, the weight space velocity is 230℃, 450℃, 6.8h-1 respectively,the catalyst has the highest activity in isomerization of n-heptane. The selectivity of isoheptane and the conversion of n-heptane is80.81% and 69.69% respectively. Anyway, Ni-WO₃/TiO₂-ZrO₂ can be prepared by the adjustment of the catalyst preparation conditions and reaction conditions to improve the conversion of n-heptane and the selectivity of isoheptane, so as to achieve the good catalytic effect.