Preparation And Characterization Of Ni₂Cr_xV_2-xO₇ 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 (ODH) of propane to propylene. Ni-V-O catalysts have good catalytic performance for propane oxidative dehydrogenation to propylene at low-temperature. In order to obtain a good catalytic performance for propane oxidative dehydrogenation to propylene by the optimization of preparation method and conditions as well as by the substitution of a certain amount of chromium for vanadium, in this thesis, we did the following research work.At first, Ni2V2O7 catalysts were respectively prepared by solid grinding method, solvent evaporating method, oxalate co-precipitation and citric acid sol-gel method. The catalysts were characterized by BET nitrogen physisorption, X-ray diffraction, inductively-coupled plasma (ICP) atomic emission spectroscopy, hydrogen temperature-programmed reduction (H2-TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and TG-DTA. The influences of the preparation methods on physical and chemical properties of Ni2V2O7 catalyst and its catalytic behavior were studied. The best result of propane oxidative dehydrogenation was obtained on Ni2V2O7 catalyst prepared with citric acid sol-gel method. In the catalyst preparation process, nitrogen oxides were not released. It is a green environment-friendly preparation method.Secondly, Ni2V2O7 catalyst was prepared by citric acid sol-gel method. The influence of calcining temperatures on the structure, morphology, specific area of Ni2V2O7 and its catalytic performance were investigated. Besides, the effects of citric acid dosage in precursors on gel formation and catalytic performance were further investigated. The results show that the Ni2V2O7 catalyst prepared by n citric acid /(nNi+nV)= 3 and calcined at 600℃has a good catalytic performance for propane oxidative dehydrogenation to propylene.Finally, the catalytic performance of Ni2V2O7 catalyst was improved with substitution of chromium for Vanadium. The best result of propane oxidative dehydrogenation to propylene was obtained over Ni2Cr0.1V1.9O7.