Study Of Catalysts For Dehydrogenation Of Propane For Propene

Pt/β、Pt-Sn/β、Pt/γ-Al₂O₃、Pt-Sn/γ-Al₂O₃were prepared on βzeolite and γ-Al₂O₃for thepropane dehydrogenation and the catalysts were anlysed by several characterization methods, thecatalyst owning the best reaction performace and stability were analyzed and optimized with theresponse surface analysis methodology（RSM） to study the best process conditions for thenon-oxidative dehydrogenation of propane.1. Catalysts supported on β zeolite were studied for the non-oxidative dehydrogenation ofpropane for propene. The experimental results showed that β zeolite has no catalytic activityfor dehydrogenation of propane,and after the loading of Pt to the βzeolite,the catalyst becameactive,but the catalysts deactived fastly and the propene selectivity was poor. At the same time，the preparation method of the catalysts and reaction conditions were explored,determined thebest preparation method was a two step impregnation（Sn was firstly deposited then Pt）,and thepreliminary study of the reaction conditons were that the catalyst was previously reduced underflowing H2（20mL/min） at773K for2.5h,Then the reaction mixture composed of H2andC3H8（H2/C3H8molar ratio=1:4）was fed to the microreactor,then the influence of the contents of Ptand Sn was researched,the results showed that a suitable addition of Sn could improve thecatalytic performance and the best content of Pt and Sn were0.5wt%and0.7wt%,then thecharacterization of BET、XRD、NH₃-TPD and TG were used to analysis the physicalstructure,the nature and quantity of the acid sites and coking of the catalyst.2. Catalysts using γ-Al₂O₃as the carrier were researched for the dehydrogenation ofpropane for propene. The results showed that the initial activity of the Pt/γ-Al₂O₃catalyst ispretty high,but it deactived fastly and the propene selectivity is not very high.Suitable quantity ofSn could improve the catalytic behavior of the Pt/γ-Al₂O₃catalyst for the dehydrogenation ofpropane obviously,for the addition of Sn could increase the dispersion of Sn on the surface of the catalyst and made the matching between acid functions and metal functions stand at the bestbalance.The experimental result showed that the best appropriate content of Sn was0.9wt%,atthis Sn content,the highest and most stable conversion levels were obtained,then a stability testof the Sn（0.9）Pt（0.5）/γ-Al₂O₃was carried out,the results showed that the catalyst has a highreaction stability and coversion level in11h,and after11h its deactivation became faster,then thecharacterization of BET、XRD、NH₃-TPD、Py-IR and TG were conducted to analysis thephysical structure，the nature and quantity of the acid sites,interactions between metal andcarrier and coking of the catalysts.3.The catalytic acvtivity and stability depended not only on the carrier and activecomponents,but also the operating conditions.This article carried out a more detailed study of theSn（0.9）Pt（0.5）/γ-Al₂O₃catalyst by the response surface methodology and determined theoptimum operating conditions parameters,the reaction temperature was600℃,WHSV is6.45h-1and the molar ratio of H2-Propane was0.25,Under this condition, an activity and stability test ofthe Sn（0.9）Pt（0.5）/γ-Al₂O₃catalyst was conducted, the results showed that the catalyst has ahigher conversion level compared with the previous reaction conditions and the propeneselectivity and the catalytic stability were also pretty good.