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A series of Fe-based catalysts with accurately controlled amounts of Na are synthesized to investigate the relationship between the promoter and the catalytic performance for CO2 hydrogenation to alkenes. With the increasing amount of Na, both CO2 conversion and alkenes selectivity increase at low and moderate amounts and then plateau (with the highest to be 36.8% and 64.3%, respectively), while the corresponding methane production decreases to 7.2%. It is found that the addition of Na enhances the adsorption of CO2, facilitates the formation and stability of active species Fe5C2, and inhibits the secondary hydrogenation of alkenes. All these effects lead to the desirable catalytic performance. Besides, it is observed that the content of Fe5C2 is related to the amount of Na. This study can provide scientific guidance to the design and the synthesis of high-efficiency catalysts for CO2 hydrogenation to high-value chemicals.
Liang et al. (Mon,) studied this question.