Effect of SiO2-coating of FeK/Al2O3 catalysts on their activity and selectivity for CO2 hydrogenation to hydrocarbons

Abstract

SiO₂-coated FeK/Al₂O₃ catalysts with different silica content were prepared and examined for the synthesis of hydrocarbons from CO₂ hydrogenation. It was found that SiO₂ coating affects both the activity for CO₂ conversion and the selectivity to higher hydrocarbons, depending on the loading level. The catalyst with 9 wt% SiO₂ coating showed both high CO₂ conversion (63%) and high selectivity toward C₂+ hydrocarbons (74%), while further higher coating led to suppression of catalyst activity. The analytical characterization of SiO₂-coated catalysts confirmed the interactions of SiO₂–Fe and SiO₂–Al₂O₃, which largely reduced the metal–support interaction and decreased the reduction temperature of iron oxide. In addition, an increase of adsorption capacity for CO was observed with desired SiO₂ coating. It is likely that SiO₂-coating improved the catalyst hydrophobic property, thereby reducing the negative impact of water by-product and facilitating the reverse water gas shift reaction and subsequent hydrogenation towards higher CO₂ conversion to higher hydrocarbons.