Direct Synthesis of Oxygenates over Fe-Based Composite Catalysts: Effect of Feed Gas Composition

This study investigates the effects of feed gas composition (CO/H2, CO2/H2, or CO/CO2/H2) on the activity and selectivity of an Fe-based composite catalyst (20Fe/2K–2V/PVA) for the synthesis of oxygenates, specifically higher alcohols. Physicochemical characterization using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis revealed that feed gas composition governs the final phase composition of the active catalyst (χ-Fe5C2, Fe, Fe3O4). The highest yield of higher (C5+) alcohols (up to 3.4 g/m3), with carbon conversion of approximately 46% and higher alcohols accounting for up to 19% of hydrocarbon products (C4–C7 to C8+ ratio ≈ 3), was achieved at a CO : CO2 : H2 ratio of 1 : 1 : 6. The distribution of higher alcohols follows the Anderson–Schulz–Flory model, confirming a polymerization mechanism for chain growth.