Preparation And Characterization Of La-V-O Catalysts And Their Catalytic Performances For Oxidative Dehydrogenation Of Propane

The development and application of high-active and high propylene selectivity catalyst are vital for oxidative dehydrogenation of propane to propene. We prepared the mixed phase of tetragonal phase (t) with zircon structure t-LaVO4and monoclinic phase (m) with monazite structure m-LaVO4by different methods. In order to obtain a good catalytic performance for propane oxidative dehydrogenation to propene, the effect of nickel and cerium promoters on catalyst performance has been evaluated by dopoing with different amount. In this thesis, we did the following research work.At first, tetratronal phased t-LaVO4catalysts were prepared by hydrothermal method. The influence of calcining temperatures on the structure, morphology of t-LaVO4and catalytic performance were investigated. The mixed of tetratronal and monoclinic LaVO4catalysts were prepared by ultrasonic method with different pH values. The catalysts were characterized by X-ray diffraction (XRD), N2adsorption, hydrogen temperature programmed reduction (H2-TPR) and NH3temperature programmed desorption (NH3-TPD). The influences of the preparation methods on physical and chemical properties of mixed phased LaVO4catalysts and catalytic behavior were studied. The result showed that the mixture of tetratronal and monoclinic LaVO4obtained with pH value was7and11. Investigation of relationship between the catalytic performance of propane oxidative dehydrogenation and the structure of catalyst showed that mixed phase LaVO4prepared by ultrasonic method with pH=7had optimum catalytic property. The propane conversion and propene selectivity are24.64%、39.10%at500℃.Secondely, LaVO4catalysts were prepared by the ultrasonic method with pH=7. The influence of calcining temperatures and calcining time on the structure, morphology, specific area and catalytic performance of LaVO4catalysts were investigated. The results showed that the LaVO4catalysts prepared with pH=7and calcind at600℃for2h has a better catalytic performance for propane oxidative dehydrogenation to propene.Finally, the effect of nickel and cerium promoters on catalyst performance has been evaluated by dopoing with different amount. Comparision of the LaVO4catalyst, showed that1%Ce/LaVO4catalyst was a promising catalyst for propane oxidative dehydrogenation to propene due to its high conversion of propane and high selectivity to propene at300℃-400℃. In contrast,3%Ni/LaVO4catalyst only enhanced selectivity to propene for propane oxidative dehydrogenation to propene at300℃-400℃...