Study of CO conversion to liquid fuel over ZSM -۵ Supported Fe catalysts

Fischer-Tropsch synthesis (FTS) is a catalytic process to produce clean liquid fuels and chemicals from syngas. Syngas is a mixture of hydrogen and carbon monoxide derived from coal, natural gas or biomass. Although several metals are active for FTS, only iron and cobalt catalysts are economically feasible in industrial applications. Except low cost and availability, the high water-gas shift (WGS) activity makes Fe-based catalysts more suitable for the conversion of low H۲/CO ratio syngas. To stabilized iron active phases from sintering, γ-Al۲O۳, SiO۲, and TiO۲ are often used as supports to disperse Fe particles. Generally, chemical promoters such as Cu, K, Ru and Zn are added to Fe to facilitate reduction of hematite or improve the activity of catalysts. ZSM-۵ zeolite was synthesized by hydrothermal crystallization of reactants NaOH, H۲SO۴, aluminum sulfate and water glass. The mixture was crystallized in an autoclave at ۱۸۰°C for ۲۴ h, then the obtained solid was centrifuged, washed to neutrality, dried at ۱۱۰°C overnight, and calcined at ۵۰۰°C for ۴ h to obtain Na-ZSM-۵. ZSM-۵ Supported Fe catalysts were prepared by the impregnation method. The catalysts are characterized by BET, XRD, H۲-TPR and ICP techniques. The catalysts were pressed and sieved to give ۲۰–۳۰ mesh particles. The catalysts tested in a fixed-bed reactor under pressure of ۲۰ atm, temperature of ۲۸۰-۳۲۰°C, H۲ to CO ratio of ۱, and GHSV of ۳ l.h-۱.gcat-۱. The results of the best catalyst indicated that C۵+ selectivity and CO conversion are ۵۶.۳۱% and ۷۱.۲۳%, respectively.

کلیدواژه ها:

CO ، ZSM-۵ ، Fe catalysts ، C۵+ hydrocarbons