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 FeCx to FeOx 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 FeCx by H2O and CO2. This study revealed the deactivation mechanism and stabilization effects of Zn on the active phase of FeCx during CO2 hydrogenation.