Unraveling the role of metal promoters (Zn, Cu, Co, Mn and Mg) in CO2 hydrogenation to light olefins over Fe-K catalysts

Abstract

Efficient CO₂ utilization is crucial for mitigating environmental concerns. In this study, the promoting effect of transition metal (Zn, Cu, Co and Mn) and alkaline earth metal Mg on Fe-K catalysts for CO₂ hydrogenation to light olefins were investigated. A series of Fe-K catalysts with different metal modified were prepared using the activated carbon template method proposed in this work. This method greatly improves catalyst dispersion, enabling the synthesis of high-performance Fe-K catalysts. The promoter-dependent mechanisms governing catalyst performance and selectivity were revealed. Zn promotion significantly enhances Fe dispersion and electron transfer, resulting in electron-rich Fe₅C₂ and exceptional light olefin selectivity with a value of 35.00 %. Co maximizes CO₂ conversion (46.88 %). However, Co promotes H₂ dissociation, enhancing the formation of n-alkane products and reducing C₂-C₄ olefin-to-paraffin ratio. Adding Cu, while greatly enhancing the reduction and carburization behavior of iron oxides, significantly weakens the adsorption of CO₂. The strong interaction between Mn and iron species leads to a complex reduction and carburization process of Fe-K catalyst and greatly reduces its basicity. The addition of Cu, Mg, and Mn greatly promote C-C coupling towards heavier hydrocarbons. These findings provide a comprehensive understanding of promoter roles and offer a rational strategy for designing advanced Fe-K catalysts for tailed CO₂ hydrogenation product distributions.