Preparation And Aromatization Activity Of Bi-functional WC/HZSM-5 Catalysts

As the global supply of forssil fuels predictably diminishes,there has been overwhelming interest in developing the technology to obtain high-octane,benzene,toluene and xylene(BTX)from the rich and cheap light hydrocarbons.Tungsten carbide(WC)is a non-noble metal catalyst material and has been considered as a promising catalyst due to its Pt-like chemical property,excellent acid and alkali resistance and lower price.However,the catalytic property of WC is less than that of platinum metal.In this study,bi-functional tungsten carbide supported on HZSM-5(WC/HZSM-5)catalysts were prepared and studied in n-hexane aromatization.Two series of catalysts with varying WC loadings were synthesized by in-situ reduction-carbonization(WC/HZSM-5(RC))and impregnation methods(WC/HZSM-5(IP)).The catalysts were characterized by XRD?SEM?EDS?NH3-TPD?FT-IR and TG methods.The results showed that WC/HZSM-5(RC)had the higher catalytic activity than WC/HZSM-5(IP)and enhanced the yield of formation of aromatics comparing with WC/HZSM-5(IP)and HZSM-5.These results are interpreted by the bi-functional mechanism due to the synergistic action between the HZSM-5 and WC.Based on this,the catalyst WC/HZSM-5(RC)were modified by addition of Zn,and then its property was examined in n-hexane aromatization,The results showed that Zn/WC/HZSM-5(RC)had much higher catalytic activity than WC/HZSM-5(RC).It is found that the proper addition of Zn to WC/HZSM-5(RC)markedly improved the conversion of n-hexane and greatly enhanced the yield of aromatics along with effective reduction of coke formation.