The Particle Sizeand Crystalsurface Effect Of Supported Feand Cofe Alloy Catalysts In Co Hydrogenation

CO hydrogenation （Fischer-Tropsch synthesis） is of great significancein industrial catalysis. It can produce low-carbon hydrocarbons, gasoline,diesel, alcohol and some other clean energy. The source of the feed gas ofFischer-Tropsch synthesis is very extensive. It can be obtained both throughthe coal gasification and biomass degradation. Fischer-Tropsch synthesis isone important method to replace the traditional oil energy industry. But, howto improve the activity and the selectivity of high value-added products ofFischer-Tropsch synthesis is a key problem that we face together.As we know, the metal atoms disperse on atomic level on the plate oflayered double hydrotalcites （LDHs）, and we can easily change the types ofmetal atoms. In this paper, we use the LDHs to synthesis the MgO and ZnOsupported Fe and CoFe alloy catalysts with high degree of dispersion. Thedispersion of the Fe/MgO, Fe/ZnO, CoFe/MgO and CoFe/ZnO catalystsare as high as90.32%,52.95%,77.71%and19.08%respectively. Here aresome conclusions when we use the catalysts in CO hydrogenation:1When the particle size of the active site is similar, the dispersions of Fe/MgO and CoFe/MgO are both higher than Fe/MgO and CoFe/MgOseparately. We use MgO as the support, the activity and the yield of C₅₊ andoxygenated chemicals are both higher than ZnO support.;2Through the H₂TPD test, we find the alloy of Co and Fe is moreconducive to H₂desorption, that contributes to the active center exposure. Theactivity and the yield of C₅₊ and oxygenated chemicals of CoFe/MgO is higherthan Fe/MgO, as the same as the CoFe/ZnO and Fe/ZnO catalysts. That meansthe CoFe alloy has more advantages compared with Fe catalyst.1When weuse MgO as the support, the activity and the yield of C₅₊ and oxygenatedchemicals are both higher than ZnO support.3For different particle sizes of Fe/MgO catalysts, the influence ofparticle size effect on the catalytic activity and the yield of C₅₊ and oxygenatedchemicals are not significant. While for CoFe/MgO catalyst, it is positive sizeeffect. When the particle size is14.22nm, the CO conversion can reach to94.71%, the TOF is12.33×10^-3 s^-1, and the yield of C₅₊ and the oxygenatedchemicals is24.56%.