Synthesis,Characterization And Propane Dehydrogenation Performance Of PtMn/Silicalite-1 Catalyst

As an important chemical raw material,propene plays a pivotal role in the development of the national economy.However,the propene produced by the petroleum-based refining process has been far from meeting the growing economic demands.Propane is an important component of natural gas,shale gas,etc,the efficient catalytic conversion of propane not only has important theoretical research significance but also has broad application prospect.At present,propane dehydrogenation to propene has become one of the important means to increase the production of propene.In this thesis,silicalite-1（S-1）with confined Pt nanoparticles property is selected as the support for Pt-based catalysts.The influence of molar ratio of Mn to Si,the loadings of Pt and Mn and the synergistic effect between metal and support on propane dehydrogenation had been studied by changing the molar ratio of transition metal Mn to Si,the loadings of Mn and Pt.The physicochemical properties of the catalysts were characterized by XRD,UV-Vis DRS,N₂-adsorption and desorption,SEM,TEM,CO-DRIFT and Raman,and the propane dehydrogenation performance was also tested.The main conclusions are as follows:（1）A series of xMn-S-1 supports with different Mn:Si molar ratios were prepared by hydrothermal method,and 0.1Pt/xMn-S-1 catalysts were prepared by impregnation method.And a series of characterizations and performance evaluations were carried out.It can be known from the results that an appropriate molar ratio of Mn to Si can enhance the interaction between metals and between support and metal,which is beneficial to improve the dispersion of Pt.And it was found that a small amount of Pt loading in this series of catalysts can also obtain high propane conversion.The initial propane activity of the 0.1Pt/0.1Mn-S-1 catalyst is 52.1%,and the propane conversion decreases to 47.8%after 6 h,propene selectivity is 84.0%.（2）The S-1 support was prepared by the hydrothermal method,and a series of xMn0.1Pt/S-1 catalysts with different Mn:Si molar ratios were prepared by a stepwise impregnation method.And a series of characterizations and performance evaluations were carried out.It can be seen from the results that a moderate Mn loading is beneficial to increase the exposure of active sites,thereby enhancing the interaction between the support and the active components.And at the same time,it is conducive to the migration of coke deposition,which promotes the exposure of more active sites,and improves the propane dehydrogenation.It is found that the active components exist in the form of alloys,and the initial propane conversion of is 47.5%over the 0.3Mn0.1Pt/S-1 catalyst with high propene selectivity and stability.（3）A series of xMn0.5Pt/S-1 catalysts with different Mn:Si molar ratios were prepared by hydrothermal method and stepwise impregnation method,and a series of characterization and performance evaluation of the series of catalysts were carried out.It can be seen from the results that the space-time yield of propene on the xMn0.5Pt/S-1 catalyst is higher than that of the xMn0.1Pt/S-1 catalyst.The active components exist in the form of Pt_xMn_y alloys in these catalysts,indicating that interactions between the metals formed.And the initial propane conversion of the 0.1Mn0.5Pt/S-1 catalyst is 50.5%,and it keeps 47.0% after 6 h reaction.