Selective synthesis of C2–C4 olefins via CO2 hydrogenation over spinel-structured Fe–Co bimetal catalysts

Catalytic hydrogenation of CO 2 into light olefins has gained increasing attention, nevertheless the design of an efficient catalyst with high selectivity towards light olefins is still challenging. Herein, aiming at improving the selectivity of targeted light olefins, we successfully synthesized a series of Na/MFe 2 O 4 (M = Co, Zn and Cu) spinel catalysts via hydrothermal synthesis, and tried to establish their activity-structure relationship. Among the Na/MFe 2 O 4 spinel catalysts, the Na/CoFe 2 O 4 catalyst shows superior catalytic performance, thanks to the well-crystallized CoFe 2 O 4 nanoparticle which has the good dispersibility, reducibility and carburizing ability. Moreover, compared with the traditional Na/Fe–Co catalyst obtained via co-precipitation, the formation of CoFe 2 O 4 with uniform crystal phase and smaller crystal size for Na/CoFe 2 O 4 spinel catalyst is more conducive to the formation of active and stable χ-(Co x Fe 1 − x ) 5 C 2 alloy carbide, thereby resulting in excellent catalytic activity and stability. On this basis, to further improve the C 2-4 = selectivity, we coupled the Na/CoFe 2 O 4 component with acidic zeolites (e.g., SAPO-34, MOR and Hβ), and the Na/CoFe 2 O 4 @SAPO-34 catalyst is found to possess a superior C 2-4 = selectivity of 42 % with a CO 2 conversion of 39 %. This work can provide a useful understanding of designing efficient spinel-structured bimetal catalysts for selective conversion of CO 2 into value-added light olefins.