Study On The Catalyst For Dehydrogenation Of Propane To Propene In The Presence Of CO₂

Propylene is an important intermediate in chemical industry.The route of producting olefins by dehydrogenation of alkanes is the research emphasis at present.The direct dehydrogenation of propane has been put into industrial production for a long time,but there are still some defects in this process,which need to be reacted at high temperature,and lead to rapid deactivation of the catalyst,side reaction and high energy consumption.The oxidative dehydrogenation of propane in oxygen atmosphere has low selectivity,and propylene may be deeply oxidized during the reaction.The thermodynamic equilibrium conversion of propane is higher when CO2 is used as weak oxidant instead of O2.The combination of dehydrogenation and reverse water gas shift reaction(RWGS)can reduce the probability of side reaction and increase the selectivity of propylene.At the same time,CO2 can react with carbon deposit on the surface of catalyst,which can eliminate carbon deposit and improve the stability of catalyst.In this thesis,the dehydrogenation of propane in CO2 atmosphere was studied by using non-noble metal Fe and Ni catalysts,noble metal Pt catalysts and Pt catalysts prepared by sputtering method.the activity,stability and selectivity of the reaction products were investigated,and the interaction of the catalysts was studied through detailed characterization.The reaction mechanism and catalytic essence were discussed.The specific research results were as follows:1.Dehydrogenation of propane over non-noble metal catalysts.By preparing Fe-based catalysts supported on CeO2 with different Fe contents,it was found that the catalyst supported on 5%Fe has the highest propylene selectivity(96%)and the best activity with the increase of Fe loading,the results show that with the increase of Fe loading,the carbon deposition increases and the selectivity of propylene decreases,and the oxygen vacancy in cerium oxide may participate in the selective dehydrogenation,it was found that the selectivity of propylene decreased(82%),but the conversion of propane(5%)and the conversion of CO2(97%)increased significantly with Ni doping,CeO2 can eliminate carbon deposition and promote propylene formation.2.Dehydrogenation of propane over Pt-based catalysts.In this chapter,a series of PtxCe/Al2O3 catalysts with different CeO2 contents were prepared by impregnation method.The addition of appropriate amount of CeO2 can decrease the reduction temperature of Pt oxide,promote the reduction of Pt oxide,decrease the absence of structure on alumina carrier,decrease the amount of strong acid and strong acid sites,and strengthen the interaction between Pt and carrier,the conversion of propane was increased to more than 40%,and the selectivity of propylene remained 80%and the conversion of CO2 remained 90%.3.Properties of Pt/HZSM-5 catalysts prepared by magnetron sputtering.Pt/HZSM-5 catalysts were prepared by adjusting sputtering deposition conditions.The results show that the sputtering conditions have great influence on the samples,the longer the sputtering time,the more the metal loading,the higher the sputtering power and the larger the metal particle size.The propane conversion of the sputtered catalyst was increased to 13%under certain olefin selectivity and CO2 conversion,and the sputtered catalyst had obvious effect on inhibiting carbon deposition.