Study Of The Synthesis,Characterization And Propane Dehydrogenation Properties Of PtFe/silicalite-1 Catalyst

Propylene is one of the most important feedstocks in the global economy and is essential for the production of a wide range of valuable chemicals and fuels.Due to the scarcity of fossil fuels and the discovery of shale gas,we can obtain a large amount of propane from shale gas as raw materials,through propane dehydrogenation（PDH）way to produce the target product propylene,PDH can also be seen as a potential way to produce large amounts of propylene.Among them,Pt-based catalysts stand out in PDH reaction because of their high activity and stability.In this paper,silicalite-1（S-1）was used as the catalyst carrier,through changing the loading of trivalent and divalent iron on S-1,and the doping amount of trivalent iron in S-1,the effect of transition metal iron content and the synergistic effect between metal and carrier on propane dehydrogenation was studied.The catalysts were characterized by XRD,XPS,Raman,N₂-adsorption,H₂-TPR,SEM,TG and TEM,and the propane dehydrogenation performance was tested.The following conclusions were reached:（1）A series of xFe-S-1 support with doping amounts of Fe（III）were prepared by hydrothermal method,and Pt/x Fe-S-1 catalyst was synthesized by incipient wetness impregnation method,the catalysts were characterized and the catalytic performances of PDH were tested.The results showed that the propane conversion of Pt/1.0Fe-S-1 catalyst was the highest,the initial conversion was 56.2%,and the conversion was maintained at 48.3%after 6 h dehydrogenation,the results show that the prepared catalyst is stable.（2）In order to avoid the formation of acid center caused by Fe doping into S-1skeleton during in situ synthesis S-1 support,Ptx Fe Cl₃/S-1 catalysts were prepared by co-impregnation method using S-1 as support and H₂Pt Cl₆·6H₂O and Fe Cl₃·6H₂O as precursors.The iron contents of these catalysts were 0.1wt%,0.5wt%,0.7wt%,1.0wt%,1.5wt%and 2.0wt%,respectively.The test results show that the moderate amount of iron can strengthen the interaction between metals,support and metal,and improve the dispersion of Pt.Among these catalysts,the propane conversion of Pt2.0Fe Cl₃/S-1 catalyst was the highest with the initial conversion of propane 58.9%,and the conversion maintained at 56.2%after 6 h reaction,indicating that the catalyst prepared by co-impregnation method was stable.（3）In order to further study the effect of Fe valence in Fe precursor on catalyst,Ptx Fe Cl₂/S-1 catalysts were prepared by co-impregnation method using H₂Pt Cl₆·6H₂O and Fe Cl₂·4H₂O as precursors and S-1 as support.The iron contents of these catalysts were 0.1wt%,0.5wt%,0.7wt%,1.0wt%,1.5wt%and 2.0wt%,respectively.The test results show that the proper amount of iron can strengthen the interaction between metals,support and metal,and improve the dispersion of Pt.The results of PDH tests showed that the propane conversion of Pt0.7Fe Cl₂/S-1 catalyst was the highest with the initial conversion of propane 61.2%,and the conversion maintained at 57.0%after 6 h reaction.It was found that Fe²⁺was converted to Fe³⁺during the preparation process according to characterizations.The propane activation ability was enhanced compared with Fe³⁺as the precursor catalyst.