Fischer-tropsch synthesis on charcoal-supported molybdenum: The effect of preparation conditions and potassium promotion on activity and selectivity

Abstract

High dispersion and high activity charcoal-supported molybdenum catalysts were prepared using incipient wetness and equilibrium adsorption methods. Activities and selectivities of these catalysts were tested after reducing the catalysts at 773 K in flowing hydrogen. It was found that all the catalysts, particularly those prepared by the equilibrium adsorption method, showed high activities in Fischer-Tropsch synthesis of C1 to C3 hydrocarbons. Potassium promotion increased the selectivity towards C2 and C3 hydrocarbons while reducing moderately the activity. Without potassium promotion, C2+ selectivities of all the catalysts with metal loading of three weight percent or higher were about 50 +/- 5% under differential reactor conditions. Promotion by potassium increased the C2+ selectivity to as much as 70%. It was found that there was a critical potassium loading at which point the activity decrease levelled off. The method of potassium addition to the catalyst also plays a major role in determining the final activity.