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 ar ea, CO2 chemisorption, TPR and TPDC techniques. The CO2 conversion, the tot al hydrocarbon selectivity, the selectivities of C-2-C-4 olefins and C5+ hy drocarbons are found to increase with increase in MgO content upto 20 wt% i n 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%) M gO content are observed to contain only two peaks, corresponding to the red uction of Fe2O3 to Fe-0 through Fe3O4. However, the TPR profile of 20 wt% M gO catalyst exhibits three peaks, which indicate the formation of iron phas e through FeO phase. The TPDC profiles show the formation of three types of carbide species on the catalysts during the reaction. These profiles are s hifted towards high temperatures with increasing MgO content in the catalys t. The activities of the catalysts are correlated with physico-chemical cha racteristics of the catalysts.