Effect of Copper on Calcium-Modified Alumina-Supported Cobalt Catalysts towards Fischer-Tropsch Synthesis

The present study reports the possibility of using copper as a low-cost reduction promoter in cobaltbased Fischer-Tropsch (FT) catalysts. Adsorption behaviour of CO and H₂ on alumina-supported Co and Co-Cu catalysts has been examined. Amount of CO and H₂ desorption and temperature of desorption are used to gain insights about the performance of the catalysts. Presence of Cu alters CO and H₂ adsorption on Co-alumina catalyst. Modification of alumina with Ca enhances Co dispersion and the amount of CO adsorbed. However, increase in the amount of CO adsorbed does not translate into increase in CO conversion. The Co-Cu-based catalysts display higher amount of H₂ adsorbed and higher CO desorption temperature. The latter is at the expense of the amount of CO adsorbed for low CO conversion resulting in lower activity for FT synthesis. The catalysts display high selectivity towards oxygenates. The high CO adsorption strength on Co-Cu-based catalysts is rationalized in terms of synergistic interaction of CO with cobalt particles through carbon atom and copper particles through oxygen atom.