Unraveling the Role of Zinc on Bimetallic Fe₅C₂–ZnO Catalysts for Highly Selective Carbon Dioxide Hydrogenation to High Carbon α‑Olefins

In this work, Fe–Zn catalysts were prepared, characterized, and examined for the synthesis of linear high carbon α-olefins (LAOs; C ≥ 4) directly from CO₂ hydrogenation. The relationship of performance and structure has been established to unravel the role of ZnO in bimetallic Fe₅C₂–ZnO catalysts. A Fe2Zn1 catalyst showed high selectivity to C₂–C₇ olefins (a selectivity of 57.8% in gas phase) after 200 h of time-on-stream and total C₄₊ olefins selectivity in liquid products of 81.9% with 85.9% LAOs in C₄₊ alkenes at a CO₂ conversion of 35.0%. The dominant mechanism of deactivation was ascribed to phase transformation from FeC_x to FeO_x in comparison with Fe₂O₃ and Fe5Zn1. Zn and Na were proved to migrate onto the surface during the activation process. The interaction between Zn and Na could suppress the oxidation of FeC_x by H₂O and CO₂. This study revealed the deactivation mechanism and stabilization effects of Zn on the active phase of FeC_x during CO₂ hydrogenation.