Selective hydrogenation of CO2 and CO into olefins over Sodium- and Zinc-Promoted iron carbide catalysts

Abstract

The hydrogenation of CO2 and CO to chemicals are highly attractive but very challenging. Here, we report that a Na- and Zn-promoted iron catalyst composed of Na+, ZnO and χ-Fe5C2 is efficient for the hydrogenation of CO2 and CO into C2+ olefins. The selectivity of C2−C12 olefins reached 78%, and the space–time yield of olefins attained as high as 3.4 g gcat−1h−1 in CO2 hydrogenation. The intrinsic formation rate of C2−C12 olefins in CO hydrogenation was about twice higher as compared to that in CO2 hydrogenation. The hydrogenation of CO2 to olefins proceeds via CO intermediate over our catalyst. We unravel that ZnO functions for the reverse water–gas shift reaction of CO2 to CO, while χ-Fe5C2 catalyzes CO hydrogenation to olefins and the presence of Na+ suppresses the hydrogenation of olefins. The close proximity between ZnO and χ-Fe5C2 plays a key role in conversion of CO2 to olefins.