Preparation Optimization Of PtGaCe/Al 2 O 3 And Pt/Al 2 O 3 Catalysts And Their Properties In The Dehydrogenation Of Propane

As an important petrochemical raw material,the downstream products of propylene are very rich,so the demand of propylene is increasing.Propylene can be prepared by propane dehydrogenation.The research on catalytic dehydrogenation is mainly focused on the preparation of efficient catalysts.Among all the catalysts,the Pt base catalyst has the most extensive application,and the catalytic activity of the catalyst increased significantly after adding the auxiliaries of Ga and Ce.The catalysts of PtGaCe supported on alumina were prepared by sol-gel method,then the catalysts were studied for exploring the influence of calcination temperature on the structure and catalytic performance.The results show that the catalytic activity increases with the increasing of calcination temperature of the catalysts,just as the PtGaCe/Al2O3-800(the calcination temperature of catalyst is 800°C)catalytic exhibited the highest propane conversion and propylene selectivity.Although PtGaCe/Al2O3-400 catalyst has the smallest average pt particle size and the largest specific surface area,these two factors have no significant effect on the final catalytic performance.Besides,NH3-TPD and XPS reveal that with the increasing of calcination temperature,the catalyst has more percentage of weak acid sites and Ga3+ions.The both factors play a crucial role in the catalytic reaction.In summary,PtGaCe/Al2O3-800 catalytic presents the initial propane conversion and propylene selectivity above 68.0%and 97.0%respectively.The best catalytic performance benefits from lowest coke amount and the highest percentage of weak acid sites and Ga3+ ions.In the process of preparing PtGaCe/Al2O3 catalyst,when the contents of Ga and Ce were changed,we can investigated the influence of metal loads on the structure and performance of catalytic through various characterization and catalytic performance evaluation.It can be seen that the catalyst has the highest catalytic activity when the load of Ga is 3wt%and the load of Ce is 1wt%.In this case,both Ga and Ce species have the lowest H2-TPR reduction temperature and the best metal interaction.In the process of preparation of Pt/Al2O3 catalyst,CTAB,P123 and F127 template were added respectively,and then the catalysts were calcinated in the atmosphere of nitrogen.It can be seen that the method has a significant effect on the decrease of Pt particle size and the improvement of catalytic performance.After adding CTAB template,the catalyst has the smallest Pt particle size,the largest Pt dispersion,the lowest percentage of strong acid,and the best catalytic performance is obtained.This indicates that the smaller Pt particle size and lower percentage of strong acid are beneficial to improve the catalytic activity,and there is no necessary relationship between carbon content and catalytic activity.