Study On M_xFe_1-xVO₄Catalysts For Oxidative Dehydrogenation Of Propane To Propene

In recent years, the catalytic dehydrogenation of propane to propene is ofincreasing importance due to the growing demand for propene, which is animportant resource in the production of polypropene, polyacrylonitrile,acrolein, and acrylic acid. The dehydrogenation provides a promisingalternative route for the propene from the propane, which are abundant andlow cost raw materials. The oxidative dehydrogenation （ODH） of propane topropene is attractive because it is an exothermic and nonthermo dynamicallylimited reaction; hence propane can converts on the catalysts at lowtemperature. However, the propene selectivity of the catalytic reactionremains an unsolved problem owing to the over oxidation of propane andpropene. Researchers aim to prepare catalysts with high conversion ofpropane and high selectivity to propene. For these reasons, our main work isdivided into the following sections:1、FeVO₄catalysts were respectively prepared by solid grinding method,a liquid phase precipitation method, hydro-thermal method and citric acidsol-gel method. The catalysts were characterized by X-ray diffraction （XRD）,N₂-sorption, hydrogen-temperature programmed reduction （H₂-TPR） andammonia-temperature-programmed desorption （NH₃-TPD）. The influences ofthe preparation methods on physical and chemical properties of FeVO₄catalysts and their catalytic behavior were studied. The best result of propaneoxidative dehydrogenation was obtained on FeVO₄catalyst prepared withcitric acid sol-gel method （ncitric acid：n（Fe+V）=1:1）, calcined at600℃.2、M_xFe_1-xVO₄（M=Ni, Co） catalysts were prepared by citric acid sol-gelmethod. The catalysts were characterized by X-ray diffraction （XRD）,hydrogen-temperature programmed reduction （H₂-TPR）, ammonia-temperature programmed desorption （NH₃-TPD） and oxygen-temperature programmed desorption （O₂-TPD）. Their catalytic performances for oxidativedehydrogenation of propane to propene were studied. The results show thatthe Ni_0.1Fe_0.9VO₄catalyst has better catalytic property for the oxidativedehydrogenation of propane. Co_0.1Fe_0.9VO₄and Co_0.2Fe_0.8VO₄catalysts havebetter selectivity to propene at low temperature （300-400℃）.3、RExFe1-xVO₄（RE=La, Ce, Pr, Nd, Sm） catalysts were prepared bycitric acid sol-gel method. The catalysts were characterized by X-raydiffraction （XRD）, hydrogen-temperature programmed reduction （H₂-TPR）,ammonia-temperature programmed desorption （NH₃-TPD） and carbondioxide-temperature programmed desorption （CO₂-TPD）. Their catalyticperformances for oxidative dehydrogenation of propane to propene werestudied. The results show that Pr_0.1Fe_0.9VO₄and Sm_0.2Fe_0.8VO₄catalystsexhibit stable catalytic performance in the oxidative dehydrogenation ofpropane at high temperature.4、Sm_0.2Fe_0.8VO₄/Al₂O₃catalyst was prepared by impregnation method.The catalyst was characterized by X-ray diffraction （XRD）, TGA-DTA,N₂-sorption and hydrogen-temperature programmed reduction （H₂-TPR）. Inconclusion, the catalyst Sm_0.2Fe_0.8VO₄/Al₂O₃（SABET=226m2·g-1） exhibited thehighest catalytic property for the oxidative dehydrogenation of propane at lowtemperature.