The Study Of Oxidative Dehydrogenation Of Propane On Supported Metal Oxide Catalysts And In A Dense Membrane Reactor

The oxidative dehydrogenation of propane (ODP) to propylene is currently the subject of intense investigation in the field of catalysis. which aims to activate less expensive propane and air to produce more valuable olefin. Due to the formation of water in the reaction, it is an exothermal process favored by dynamic and thermodynamic. Compared with the traditional cracking dehydrogenation reaction, ODP process has advantages of low energy consumption, low temperature, less coke deposition, and no equilibrium limitation. So it is a promising alternative process to produce propylene. However, due to the high reactivity of product propylene, the selectivity to propylene is usually low. Therefore, how to improve the selectivity to propylene is one of key issues in ODP. In this dissertation, we work out the kinetic equation, and proved that the formation rate of propylene is first order in propane and zero order in oxygen. Based on the kinetic study. we proposed a Mar-Van Krevelen kinetic scheme for the catalytic oxidative dehydrogenation of propane. Combined the calculated active energy and the competitive reaction of propane and propylene on the same active site, we proved that there are an optimum yield of propylene whatever the catalytic systems are used. From the calculation of the relative rate constants of propane and propylene in the oxidative reaction, we concluded that low temperature favors complete oxidation of propylene while high temperature favors selective oxidation of propane. From the study of heterogeneous and homogeneous reaction of propane, we found that a high propylene yield could be obtained by optimizing the oxygen/propane ratio and the size of reactor even in the absence of catalysts. In this dissertation, supported vanadium catalysts were explored in detail by changing the loading and supports. Among the supported vanadium catalysts, vanadium-magnesium oxide is one of the best catalysts. We also studied the molybdenum-containing catalysts. In spite of its high selectivity to propylene, the low catalytic activity of molybdenum-containing catalyst limits its further -3 2 Dissertation of Master Fang Xiaomin application. To design active catalysts used at low temperature is one of our goals. We concluded that the chromium and manganese containing catalysts are among the potential target catalysts, which show high activity at very low temperature. Finally, we tried ODP reaction in mixed conducting dense membrane reactor Ba0 5Sr0.5Coo8Fe0.2O3~, which has high permeability for oxygen. Reaction results showed that the lattice oxygen has potential catalytic ability to improve the propylene selectivity.