Properties of the Nano-Particle Fe-based catalyst for the hydrogenation of carbon dioxide to hydrocarbons

Combining co-precipitation-gelation, mechanical mixing and impregnation methods, a series of catalysts of FeK-M/γ-Al₂O₃(M=Cd or Cu) have been attained. The catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ physisorption, X-ray diffraction (XRD) and temperature-programmed reduction of hydrogen (H₂-TPR). The hydrogenation of carbon dioxide over these catalysts was also investigated in a fixed bed. Given a reaction time of 100 h, CO₂ conversion over a 15%Fe/10%K/γ-Al₂O₃ catalyst reached 51.3%, with a selectivity towards C₂₊ of 62.6% at 3 MPa, 673 K, a space velocity of 3600 h^-1 and at a molar ratio of H₂/CO₂ of 3. At the lower Fe content of 2.5%, the selectivity towards C₂₊ was still greater than 60.0%. Increasing the potassium content from 0% to 10%, increased the selectivity towards C₂-C⁼ ₄ and the molar ratio of C₂-C⁼ ₄/C₂-C⁰ ₄ increased to 3.6. The addition of Cd and Cu improved the reduction and catalytic activities. Specifically, Cu improved the molar ratio of C₂-C⁼ ₄/C₂-C⁰ ₄ from 3.6 to 5.4, and the Cd increased the selectivity of C₅₊ by 12%.