Potassium-Promoted Iron Carbide Interfaces for Direct CO2 Conversion to Light Olefins

Abstract

Direct CO2 hydrogenation to light olefins provides a promising route for producing carbon-based chemicals from non-fossil carbon sources. In this work, potassium-promoted Fe-based catalysts were prepared by co-precipitation and evaluated for CO2 hydrogenation under Fischer–Tropsch conditions. XRD, Mössbauer spectroscopy, CO2-TPD, H2-TPR, and in situ XPS were used to identify the evolution of iron carbide phases and surface basicity. The catalyst with 1.5 wt% K showed a CO2 conversion of 34.8%, C2–C4 olefin selectivity of 42.6%, and an olefin/paraffin ratio of 5.3 at 320 °C and 2.5 MPa. Potassium addition increased medium-strength CO2 adsorption sites by 68.2% and promoted the formation of χ-Fe5C2, which was identified as the main active phase for chain growth. Excessive potassium loading suppressed hydrogen activation and reduced hydrocarbon productivity