Preparation And Characterization Of Mesoporous ZrO₂-Supported Metal Oxide Catalysts And Their Catalytic Performance For Oxidative Dehydrogenation Of Propane

Propylene as an importantly basic chemical raw material is mainly used for the production of polypropylene,acrylonitrile,propylene oxide,cumene and so on.In recent years,it has difficulty to satisfy the demand of propylene prepared by conventional methods with the market demand for propylene rapidly growing and petroleum mined easily consuming continually.At present,the oxidative dehydrogenation of propane to propylene is research focus in catalysis.Because the reaction is not controlled by thermodynamics and can be carried out with the condition of low-pressure and low-temperature and the catalyst is not easy to coke deactivation,it has extensive application prospects.However,propane and propylene are easy to be oxidized deeply in the presence of oxygen,resulting in the selectivity to propylene decreasing.Therefore,it is significant to prepare the catalyst with high stability and good propylene selectivity.In this paper,mesoporous ZrO₂ supported metal oxide catalysts were prepared by solvothermal method and the loading amounts of metal oxides in catalysts were varied.The effects of different molar ratios of M/Zr on their physical and chemical properties and catalytic performance of propane oxidative dehydrogenation were explored.1.Mesoporous ZrO₂ support was prepared by solvothermal method,which is composed of monoclinic and tetragonal phase.The specific surface area is 22.2m²·g^-1.The propylene yield can be reached 7.28%at 600°C.The propane conversion on the mesoporous La_xZr_yO₂ was improved because of the variation of the redox ability of ZrO₂.When the reaction temperature is600°C,the propylene yield on La_xZr_yO₂?x:y=2:8?is 10.39%.2.A series of V₂O₅/ZrO₂ catalysts were prepared by solvothermal method.The results show that the maximum specific surface area is57.7m²·g^-11 given by 10%V₂O₅/ZrO₂ catalyst.There is no characteristic diffraction peak of V₂O₅.The tetrahedral coordinated vanadium species exist on the surface of the catalyst.10%V₂O₅/ZrO₂ catalyst has the best catalytic performance.The catalytic performance was optimal at 600°C.The propane conversion is 35.47%,the propylene selectivity is 40.63%and the yield of propylene can be reached 14.41%.3.A series of 10%V₂O₅/La_xZr_yO₂ catalysts were prepared by solvothermal method.The results show that the catalysts are the three-phase coexistence of tetragonal ZrO₂,La₂Zr₂O₇,and V₂O₅.The performance of propane oxidative dehydrogenation of 10%V₂O₅/La_0.2Zr_0.8O₂ catalyst is better than that of other catalysts.The propane conversion is 27.18%,and propylene selectivity is 39.79%at 600°C.4.x%V₂O₅/La_0.2Zr_0.8O₂ catalysts were prepared by solvothermal method.The results show that the catalysts are mixed crystal phase of ZrO₂,V₂O₅,La₂O₃andLa₂Zr₂O₇crystals.Thespecificsurfaceareaof15%V₂O₅/La_0.2Zr_0.8O₂ catalyst is maximal,55.7m²·g^-1.The performance of oxidative dehydrogenation of propane is the best at 600°C.The propane conversion is 34.87%and the propylene selectivity is 45.18%.5.A series of MoO₃/ZrO₂ catalysts were prepared by solvothermal method.The results show that when Mo/Zr molar ratio is 0.2,the catalyst is tetragonal ZrO₂,MoO₃ and ZrMoO₄ and the area of the reduction peak is the largest.Through the experiment of propane oxidative dehydrogenation to propylene,it was found that the catalytic activity is increased after loading MoO₃.The catalytic performance is the best under the condition that the loading amount of MoO₃ is 20%and reaction temperature is 600°C.The yield of propylene is 12.29%.