This work investigates the effects of potassium addition on light olefin production from CO2 hydrogenation over the Al2O3-supported Fe-Co bimetallic catalysts. The addition of small amount of K on the Fe-Co catalyst significantly enhanced C2-C4 olefin formation. The C2-C4 olefins predominated among C2+ hydrocarbons at K/Fe atomic ratio of 1. Temperature-programmed desorption experiments demonstrated that K addition diminished the weakly adsorbed hydrogen but enhanced CO2 adsorption on the catalyst surface, which led to significantly enhanced production of light olefins. For C2-C4 olefin synthesis at 573 K and 1.0 MPa, the K-promoted Fe-Co/Al2O3 catalyst also showed better performance than the K-promoted Fe-Mn/Al2O3 catalyst which is known as a good catalyst for olefin production, under the present conditions employed. The pathway of olefin formation from CO2 hydrogenation was analyzed. Light olefins were formed via two-step reactions over K-promoted Fe-Co catalysts with the formation of CO or CO-like intermediate as the first step. Some of these olefins could be further hydrogenated to paraffins, depending on the type and concentration of chemisorbed hydrogen on the catalyst surface.
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