Selective Catalytic Conversion of Bio-ethanol to Propene by Hydrofluoric Acid Modified Nano-ZSM-5 Zeolites
The modified nano-ZSM-5 zeolites were prepared by post-treatment with different contents of hydrofluoric acid(HF)solution for selective conversion of bio-ethanol to propene at temperature of 500 ℃,pressure of 0.1 MPa and MHSV of 10 h-1.The modified and unmodified catalysts were characterized by XRD,N2 physisorption,ICP-OES,TG and NH3-TPD techniques.The results show that HF modification can not only change the acid properties of ZSM-5 zeolites,but also have a great effect on their pore structure.The decrease of acidity in ZSM-5 zeolites has inhibited the formation of coke during the reaction,and the increase of mesopores has enhanced the diffusion ability of products,thus inhibiting the formation of coke and improving the anti-coke ability of catalysts.Therefore,the propene selectivity and working life of nano-ZSM-5 zeolites have been significantly improved and prolonged by the modification of HF solution with suitable content(mass fraction of 6％).In addition,the characterization results of the deactivated catalysts indicate that carbon deposition and decreased acidity may be the main factors of catalyst deactivation.
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