Study On Oxidative Dehydrogenation Of Propane In Presence Of CO₂ Over Cr/MSU-1 Mesoporous Catalyst

Oxidative Dehydrogenation of propane is an important technology to increace propylene production; with the CO2 as one mild oxidant, it can not only promote propane transformation, but also inhibit the carbon deposition formation. And mesoporous materials because of its excellent structural characteristics, widely used in catalytic field. The catalyst Cr/MSU-1 was preparaed, taking mesoporous materials MSU as the carrier, loaded Cr, as the active species. And it was used in oxidative dehydrogenation of propane in presence of CO2. The main research contents and the conclusions are as follows:(1) A series of Cr/MSU-1 catalysts were prepared with MSU-1 synthetized in different pH environment, and the catalytic properties in oxidative dehydrogenation of propane with CO2 were examined. It was found that when pH value was at around 3.52, the catalytic performance of Cr/MSU-1 was best. The different preparation methods of Cr/MSU-1 catalyst were also studied. It was shown the catalyst prepared by immersion method had a best catalytic effect.(2) Adding ethane to the feed gas, the adaptability of Cr/MSU-1 for gas material was examined. When the ratio of V(C3H8)/V(C2H6) is 3/2, V(CnH2n+2)/V(CO2) is 1/3, there was a higher yield of propylene and total olefins (37.8%,40.0%). On this ratio, the best temperature and space velocity were 650℃and 8400 mL·h-1·g-1, at this time the propylene and total olefins yield were 46.1% and 45.3%.(3) The intrinsic kinetics of oxidative dehydrogenation of propane with CO2 over Cr/MSU-1 catalyst was studied. On the basis of Langmuir Hinshelwood mechanism, the Presumptive models were proposed. Through estimation of model parameters and modeltesting, the model with surface reaction as the rate-determing step was close to reality best.(4) The enlargement and cyclic regeneration experiments of Cr/MSU-1 were studied. The result showed the amplification effect of 50ml catalyst is not obvious, but the existing quick deactivation; with O2 and CO2 both can regenerated the catalyst, and the effect of O2 was better. The deactivation was not only as carbon deposition, but also with structural damage of carrier. On the catalyst Cr6+ species is the main active ingredient in the process of catalytic reactions.