Selective Alkene Production by the Hydrogenation of Carbon Dioxide over Fe-Cu Catalyst

The hydrogenation of carbon dioxide over the catalyst comprised of Fe and Cu (Fe-Cu catalyst) was studied at 523-673 K under 5 MPa using a flow-type fixed-bed reactor. The main products were carbon monoxide, hydrocarbons, and alcohols. The hydrocarbon products were followed by the Schulz-Flory-Anderson distribution law. The effect of the metal additives (Li, Na, K, Cs, Ca, and La) to the Fe-Cu catalyst was also examined. The additives significantly affected the ratio of light alkenes. The cesium-promoted Fe-Cu catalyst gave high alkene ratios in the C2 and C3 products compared with other alkali metal-promoted Fe-Cu catalysts. According to the XPS analysis, the binding energy of Fe(2p3/2) for the catalysts after the reaction was rather close to that for FeO although Fe3O4 was found in the XRD analysis. The carbonate species were found on the catalyst surface, suggesting the presence of the basic sites. The clear relationship was revealed between the basicity of the additives and the alkene content in the product.