Cobalt Loading Effects on the Structure and Activity for Fischer-Tropsch and Water-Gas Shift Reactions of Co/Al2O3 Catalysts

An extensive study of Fischer-Tropsch synthesis (FTS) on alumina-supported cobalt catalysts with different amounts of cobalt is reported. Up to 40 wt % of cobalt, is added to the catalysts by impregnation method. The effect of the cobalt loading on the reducibility of the cobalt oxide species, dispersion of the cobalt, average clusters size, water-gas shift (WGS) activity and activity and selectivity of FTSis investigated. Increasing the cobalt loading resulted in increasing the average cobalt cluster size, improvements in the reducibility of Co3O4, decreasing the cobalt surface interaction with the support and decreasing the dispersion of cobalt. The maximum concentration of active surface Coo sites and FTS activity are achieved for the 34 wt% cobalt loading. While the maximum WGS activity is achieved for the 40 wt % cobalt loading.  The methane selectivity in the catalyst with 40 wt % of cobalt loading was about 43.7 % less compared to that of the less reducible 8 wt % cobalt catalyst. The C5+ selectivity for the 40 wt % cobalt catalyst was 60.8% higher than that of the 8 wt % Cobalt catalyst.