The catalytic conversion of CO2 to hydrocarbons over Fe-K supported on Al2O3-MgO mixed oxides

Al2O3–MgO mixed oxides prepared by a co-precipitation method have been used as supports for potassium-promoted iron catalysts for CO2 hydrogenation to hydrocarbons. The catalysts have been characterized by XRD, BET surface area, CO2 chemisorption, TPR and TPDC techniques. The CO2 conversion, the total hydrocarbon selectivity, the selectivities of C2–C4 olefins and C5+ hydrocarbons are found to increase with increase in MgO content upto 20 wt% in Fe–K/Al2O3–MgO catalysts and to decrease above this MgO content. The TPR profiles of the catalysts containing pure Al2O3 and higher (above 20 wt%) MgO content are observed to contain only two peaks, corresponding to the reduction of Fe2O3 to Fe0 through Fe3O4. However, the TPR profile of 20 wt% MgO catalyst exhibits three peaks, which indicate the formation of iron phase through FeO phase. The TPDC profiles show the formation of three types of carbide species on the catalysts during the reaction. These profiles are shifted towards high temperatures with increasing MgO content in the catalyst. The activities of the catalysts are correlated with physico-chemical characteristics of the catalysts.