Highly active Fe-Co-Zn/K-Al2O3 catalysts for CO2 hydrogenation to light olefins

Abstract

Abstract CO2 hydrogenation to light olefins over Fe-Co-Zn/K-Al2O3 catalysts with different Zn loading contents (0–1.74\xa0wt%) is studied. The addition of Zn improves the dispersion and the reducibility of iron oxides. The amount of CO adsorbed of the catalysts showed a volcanic trend as a function of Zn content with its maximum of 2.42\xa0μmol\xa0g−1 at 0.58\xa0wt% Zn, suggesting an increase of number of active sites. The 0.58\xa0wt% Zn-promoted Fe-Co/K-Al2O3 catalyst shows superior activity for light olefins yield (19.9%) under the optimum operating conditions of 340\xa0°C, 25\xa0bar, 9,000\xa0mL gcat−1 h−1 and H2 to CO2 ratio\xa0=\xa04. A gradual decrease in olefin to paraffin ratio with an almost constant CO2 conversion as a function of time-on-stream is observed, which is related to a continuous increase of iron carbide content, indicating that the iron carbide can be acted as the active site for paraffins production.