| Due to the characteristics of oil and gas reserves in China and the increasing demand for propylene in the market,propane dehydrogenation(PDH)technology has attracted extensive attention in recent years.However,key technologies such as propane dehydrogenation process and catalyst are mainly mastered by foreign companies such as UOP and Lummus.Therefore,it is particularly important to develop PDH technology with independent property rights and realize the localization of related catalysts and processes.In this paper,based on Pt-Sn/Al2O3 catalyst,in addition to investigating the effect of the optimization of active components,the surface modification of the support and the addition of metal promoters on the performance of the catalyst,the effect of reaction conditions on the dehydrogenation performance of propane is further explored,and XRD,NH3-TPD,H2-TPR,BET and other characterization methods are used to analyze the structure-activity relationship of the catalyst.The results show that the optimized Pt-Sn-In/K-Al2O3 catalyst has good dehydrogenation activity and stability,which meets the industrial requirements,and provides an important basis for the subsequent industrial production and application.This paper is summarized as follows:(1)The study on the active component content of Pt-Sn/Al2O3 catalyst shows that with the increase of Pt content,the conversion increases firstly and then decreases,while the selectivity decreases gradually,and the optimal loading is 0.3 wt.%.The H2TPR spectra showes that the increase of Pt content could weaken the interaction between Pt and the support and increase the possibility of Pt agglomeration.With the increase of Sn content,the conversion decreases gradually,while the selectivity increases gradually,the optimum loading is 0.6 wt.%.The H2-TPR pattern showes that Sn could improve the catalytic performance of Pt from both geometric and electronic effects,and reduce the occurrence of side reactions.(2)The study on the surface modification of Pt-Sn/N-Al2O3 catalyst support shows that the best support modification auxiliary is K.The catalyst modified with K shows excellent stability.After 110 h of reaction,the propane conversion and propylene selectivity remain stable at the initial value.With the increase of K loading,the conversion tends to decrease,while the selectivity increases gradually,and its optimal loading is 1.5 wt.%.The NH3-TPD pattern shows that the addition of K significantly regulates the medium-strong acid of the catalyst.(3)The study of adding metal auxiliary to Pt-Sn-M/Al2O3 catalyst shows that the best metal auxiliary is In.After 60 h of reaction,the conversion of the catalyst modified by In only decreases from 36.6%to 34.2%,and the selectivity remains at 97.8%,showing good stability.Further study shows that with the increase of In content,the conversion decreases gradually and the selectivity increases gradually.The optimal loading of In is 1.5 wt.%.(4)The study on the influence of reaction conditions on the dehydrogenation performance of the catalyst shows that the most suitable conditions for the dehydrogenation of propane are as follow:Reduction time is 2h,reduction temperature is 600℃,reaction temperature is 600℃,the ratio of hydrogen to propane is 1:3.7.The propane conversion and propylene selectivity of the optimized Pt-Sn-In/K-Al2O3 catalyst remain 35.0%and 98.0%after 110 h reaction under the above conditions. |
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