The Investigation On The Oxidative Dehydrogenation Of Propane To Propene

The Oxidative Dehydrogenation of Propane to propene is currently the subject of intense investigation in the field of catalysis because of its great economic potentials. In the reaction, propene is more active than propane, high temperature not only easily makes catalyst coke but also makes overoxidation of propene heavily. So, effective realization of propane to propene at low temperatures is an alterative to make high yield of propene.The first part of my dissertation (chapter 3, chapter 4) focuses on the preparation and investigation of catalysts that are effective for the Oxidative Dehydrogenation of Propane at low temperatures. Although catalyst VaOs/T^ can activate propane at quite low temperature (-250癈), overoxidation products, such as CO, CO2, are the main products. There are two main reasons. First, vanadium is ready to aggregate and form tower-like structure on the surface of TiO2. These aggregates not only cover the active sites for the Oxidative Dehydrogenation of Propane, but also cause the overoxidation of propane and propene because of its vast reservoir of oxygen. Second, there is synergistic effect between ?05 and TiO2. It makes lattice oxygen very active. So, catalyst V2OsfTi02 can activate propane at very low temperatures but overoxidation products are the main products. In order to overcome these drawbacks, ZrO2 was introduced into TiO2, which was expected to improve the reactivity of prepared catalyst. In addition, TiO2 support was prepared by sol-gel method in order to increase the surface area. The reaction result shows that catalyst V2Oj/TiO2-ZrO2 is active at low temperatures, especially, selectivity to propene is almost twice as high as that of catalyst V2Os/TiO2. At steady state, a yield of 6.4% is obtained at 350 癈 for catalyst 10V/TZ-48, which is slightly better than that of reported in the literature before at the same temperature. It is mainly because the addition of ZrO2 improves the dispersion of vanadium on the support, reduces the synergistic effect between ?05 and TiO2 and, as a result, increases the CsHs selectivity of the prepared catalyst.Because of the restriction of temperature, the oxidative dehydrogenation of propane to propene at low temperatures has low conversion of propane and low yield of propene. Rising temperature can greatly increase the conversion of propane and then the yield of propene. But there are still many difficulties, such as catalyst coke,overoxidation of propene heavily. However ODHP at high temperatures is still a very promising direction.The second part of my dissertation (chapter 5) is dealing with this direction. The structure-activity relationship of catalyst V2O5/BaAlO for Oxidative Dehydrogenation of Propane was investigated. Catalyst V2Os/BasAlO is very stable even at high temperatures. Applying catalyst V2O5/BaAlO, the higher selectivity to propene was obtained. The selectivity is above 50% even when reaction temperature is higher than 500 癈. It is mainly because the layered structure of BaAl2C>4 effectively partitions vanadium layer on the surface, reduces its aggregate state and improves the C3H6 selectivity of the catalyst.