Enhanced CO₂ Hydrogenation to C₂₊ Hydrocarbons\nover Mesoporous <i>x</i>�₂O₃–Al₂O₃ Catalysts

Abstract

This work describes the preparation\nof mesoporous binary <i>x</i>�₂O₃–Al₂O₃ mixed oxides with varying Fe₂O₃ nominal\nloading (<i>x</i> = 5, 10, and 20 wt %) by a one-step soft\ntemplate sol–gel process. The binary oxides were used as catalysts\nin CO₂ hydrogenation to produce C₂₊ hydrocarbons.\nThe catalytic test was conducted at 280, 300, and 320 °C at a\npressure of 20 bar, under a gas mixture of H₂ and CO₂ with a molar ratio H₂/CO₂ = 3. The\nmain reaction products were methane, CO, C₂- C₄ olefins, and traces of C₅₊ compounds depending on the\nFe₂O₃ nominal content. The catalyst modified\nwith 20 wt % Fe₂O₃ displayed the best catalytic\nperformance in terms of C₂₊ hydrocarbons production. An\nincrease in the Fe₂O₃ nominal content from 5\nto 20% induces a significant decrease in the reverse water gas shift\n(RWGS) reaction because of a 5-fold higher surface exposure of the\nFe⁰ species. The TPR and FTIR results of adsorbed CO confirmed\nan easier reduction of Fe₂O₃ species and a decrease\nin the metallic-support interaction, as Fe₂O₃ content of the composite catalyst increased. A linear correlation\nwas found between the surface exposure of the Fe⁰ species\nand the yield of C₂₊ hydrocarbons. Minimal coke deposition\nwas detected after reaction tests.