FISCHER-TROPSCH SYNTHESIS ON SUPPORTED COBALT CATALYSTS PROMOTED BY PLATINUM AND RHENIUM

An investigation of the CO hydrogenation of Pt- or Re-promoted 8.7 wt% Co/Al2O3 (1.0 wt% Pt or 1.0 wt% Re) has been carried out at two different conditions: 473 K, 5 bar, H-2/CO = 2 and 493 K, 1 bar, H-2/CO = 7.3. The addition of Pt or Re significantly increases the CO hydrogenation rate (based on weight of Co), but the selectivity was not changed by the presence of Pt or Re. The results show that the observed increases in the reaction rates are caused by increased reducibility and increased number of surface exposed Go-atoms. Steady-state isotopic transient kinetic analysis (SSITKA) with carbon tracing was used to decouple the effects of the concentration of active surface intermediates and the average site reactivity of intermediates during steady-state CO hydrogenation. The SSITKA results show that the concentration of active surface intermediates leading to CH4 increased as a result of the addition of a noble metal promoter. However, the average site activity was not significantly affected upon Re or Pt addition.