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 diffe rent 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 hydrogenat ion 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 increa ses in the reaction rates are caused by increased reducibility and inc reased number of surface exposed Go-atoms. Steady-state isotopic trans ient kinetic analysis (SSITKA) with carbon tracing was used to decoupl e the effects of the concentration of active surface intermediates and the average site reactivity of intermediates during steady-state CO h ydrogenation. The SSITKA results show that the concentration of active surface intermediates leading to CH4 increased as a result of the add ition of a noble metal promoter. However, the average site activity wa s not significantly affected upon Re or Pt addition.