Preparation And Catalytic Performance Of Composites Supported Tungsten And Molybdenum Catalysts

As an important mean to improve the octane number of gasoline, the research of alkane isomerization has become increasingly active. Efforts are being made to develop the catalyst for alkane isomerization with both high activity and high stability. It is of significance for raising the quality of gasoline, reducing the environmental pollution and improving the surroundings of human survival.In this paper, the sol-gel and coprecipitation methods were used for the preparation of TiO₂-Al₂O₃ and TiO₂-SiO₂ complex oxides. MoO₃ and WO₃ were introduced to the TiO₂-SiO₂ and TiO₂-Al₂O₃ complex oxides by impregnation method to prepare the bifunctional catalysts of MoO₃-WO₃/TiO₂-SiO₂ and MoO₃-WO₃/TiO₂-Al₂O₃. The performances of these catalysts for n-heptane isomerization were investigated. The influences of different preparation conditions, reduction conditions and reaction conditions on the conversions and isomerization selectivities of n-heptane were discussed. The main contents of the thesis were discussed as follows:For MoO₃-WO₃/TiO₂-SiO₂ catalyst, it is found that the conversion of n-heptane and isomerization selectivity to i-heptane reached 23.12% and 77.32%, respectively, when the reduction temperature was 723 K, the flow rate of H2 was 45mL/min, the reduction time was 6 h, WO₃ content of the catalyst was 15wt%, MoO₃ content was 5 wt%, TiO₂ content of TiO₂-SiO₂ was 80wt%, calcination temperature of MoO₃-WO₃/TiO₂-SiO₂ was 773 K, reaction temperature was 553 K, V(H2)/V(n-Heptane) was 1500 and WHSV was 6.12 h^-1.The isomerizations of n-heptane on MoO₃-WO₃/TiO₂-Al₂O₃ catalysts were investigated. The results showed that the conversion of n-heptane and isomerization selectivity to i-heptane reached 37.72% and 72.88%, respectively, when the reduction temperature was 748 K, the flow rate of H2 was 45 mL/min, the reduction time was 6 h, WO₃ content of the catalyst was 20wt%, MoO₃ content was 5wt%, TiO₂ content of TiO₂-Al₂O₃ was 70wt%, calcination temperature of MoO₃-WO₃/TiO₂-Al₂O₃ was 773 K, reaction temperature was 633 K, V(H2)/V(n-Heptane) was 1500 and WHSV was 6.12 h^-1.