Catalytic Performance and Reaction Mechanism of Co and Zn-Codoped Fe Catalysts on Different Supports for CO2 Hydrogenation

Abstract

Metal oxides are commonly used as supports for catalysts for CO2 hydrogenation. However, systematic studies on the influence of different metal oxide supports on the catalytic performance of catalysts for light olefin production remain limited. Therefore, a series of cobalt- and zinc-co-doped Fe-based catalysts supported on various metal oxides were synthesized via a wet impregnation method, and the CO2 hydrogenation performance of different catalysts was compared to understand the influence of the support materials. The Al2O3-supported catalyst exhibited the best catalytic performance, which may be associated with a relatively higher Co3+/Co2+ ratio. The KFeCoZn/Al2O3 catalyst demonstrated superior activity and selectivity toward light olefins, achieving a CO2 conversion of 32% and a light olefin yield of 14.1% under optimized conditions. The higher temperature promoted the reverse water–gas shift reaction to increase CO selectivity, while the elevated pressure and lower gas hourly space velocity favored light olefin production. In situ DRIFTS analysis suggested a reaction pathway in which CO2 is first converted to CO via the reverse water–gas shift reaction with carbonate, bicarbonate, and formate as intermediates and then rapidly hydrogenated to CHx species and subsequently underwent chain growth to form hydrocarbons. Theoretical calculations found that *CO formation is activated by 1.99 eV. Orbital hybridization and electron transfer are responsible for CO2 adsorption and activation. This work highlights the crucial role of supports in modulating the hydrogenation of CO2 to light olefins.