Preparation And Characterization Of Ni-Mo-O Catalysts And Their Catalytic Performances For Oxidative Dehydrogenation Of Propane

Propene is an important organic chemical intermediate. The required amount of propene increase year by year and supply falls short of demand with the rapid process of downstream products. Synthesis of propene by efficiently, energy-saving, environmental friendly method was attracted wide attention by many people. Preparation of propene from resourceful and cheaper propane with oxidative dehydrogenation of propane is the most important way in many other preparation methods. We prepared α-NiMoO₄、 β-NiMoO₄ catalysts and the mixed phase of α-NiMoO₄ and α-NiMoO₄ by different methods.The influence of catalytic performance of different catalysts by changing Ni/Mo molar ratio in the mixed phase of NiMoO₄ were investigated and the effect of the addition of third elements on the Oxidative dehydrogenation of propane was explored.1. α-NiMo04 and β-NiMoO₄ catalysts were prepared by precipitation method、 hydrothermal method and sol-gel method. The influence of preparation method on the structure, morphology of α-NiMoO₄ and β-NiMoO₄ and catalytic performance were investigated. The mixed phase of α-NiMoO₄ and β-NiMoO₄ catalysts were prepared by ultrasonic method. The catalysts were characterized by X-ray diffraction （XRD）, N2 adsorption, hydrogen temperature programmed reduction （H2-TPR）, Differential thermal analysis-Thermogravimetric analysis（DTA-TG） and in-situ conductivity. The influences of the preparation methods on physical and chemical properties of mixed phased NiMoO₄ catalysts and catalytic behavior were studied.2. NiMoO₄ catalysts were prepared by the ultrasonic method. The influence of catalytic performance of different catalysts by changing Ni/Mo molar ratio in the mixed phase of NiMoO₄ were investigated. The results showed that the NiMoO₄ catalysts calcind at 500℃ for 4 h has a better catalytic performance for propane oxidative dehydrogenation to propene. When the ratio of Ni/Mo was 1.4:1, The yield of propylene can reach a maximum of 12.16%. And the ratio of Ni/Mo was 1:1.2, the yield can reach a maximum of 8.81%.3. The elements of Na, K, Mg, Sr, Bi and other elements were doped into NiMoO₄ according to a certain proportion. The effect of the addition of third elements on the crystal phases and the reduction properties was explored. The research showe that the conversion of propane, the selectivity of propylene and yield of propylene were 12.49%、58.44% and 7.30% respectively at 550℃ when the catalyst is 1% Mg/NiMoO₄. The activity of oxidative dehydrogenation of propane of xSr/NiMoO₄ was similar with xMg/NiMoO₄. The conversion of propane, the selectivity of propylene and yield of propylene were 20.46%、59.04% and 12.08% respectively when the catalyst was 1%Sr/NiMoO₄. At the same temperature and same amount of Sr and Mg doped, xSr/NiMoO₄ catalyst showed better performance of propane oxidative dehydrogenation.