Pt-ZnO(CeO₂)/SiO₂ Catalyzed CO₂ Oxidative Dehydrogenation Of Propane

The oxidative dehydrogenation of propane to propylene with CO2(CO2-ODP)is a green process,which has the advantages of alleviated thermodynamics limitation and the effective utilization of the greenhouse gas of CO2.However,the catalysts for CO2-ODP suffer from the rapid deactivation and poor activity,thus,the rational design of an efficient catalyst is still challenged.In view of the analyses of the open literature,this paper prepared a series of Pt/ZnOCeO2,Pt-ZnO/SiO2,Pt-ZnO-CeO2/SiO2 catalysts for CO2-ODP by adding different amount of ZnO and using the support of SiO2 on the basis of Pt/CeO2 catalyst.BET,XRD,TEM,XPS,H2-TPR,C3H6/CO2/C3H8-TPD etc.were used to characterize these catalysts,and correlated with the reaction results.The main research contents and conclusions are as follows:(1)A series of Pt/ZnO-CeO2 catalysts were prepared by impregnating 1 wt.%Pt on the ZnO-CeO2 complex oxides with different composition.The results of XPS,C3H6TPD etc.demonstrate that the addition of ZnO on the CeO2 enhances the Pt electron density over the ZnO-CeO2 complex oxides.The reaction results indicate that the C3H6 selectivity over Pt/ZnO-CeO2 for CO2-ODP is significantly enhanced after adding the ZnO,while it still maintains the high C3H8 conversion.Among,the optimal catalyst is Pt/50ZnO-CeO2,with the best C3H6 yield(29.2%),high conversions of C3H8(46.0%)and CO2(14.7%),as well as excellent C3H6 selectivity(63.5%)at a time on stream of 5 min.(2)A series of Pt-ZnO/SiO2 catalysts were prepared by co-impregnating different amounts of ZnO and 1 wt.%Pt over SiO2.The results of XRD,TEM etc.demonstrate that the addition of ZnO can enhance the dispersion of Pt over Pt-ZnO/SiO2.The optimal catalyst of Pt-10ZnO/SiO2 displays the conversions of C3H8(25.9%)and CO2(5.1%),C3H6 selectivity(84.8%),and C3H6 yield(22.0%)at a time on stream of 5 min.(3)On the basis of the Pt-10ZnO/SiO2 catalyst,Pt-10(50ZnO-CeO2)/SiO2 catalyst was prepared by the impregnation method.The results of H2-TPR etc.reveal that the redox ability is strengthened by adding the CeO2.The initial catalytic activity and C3H6 selectivity is still kept at a high value(?93%).