Enhanced CO₂ Hydrogenation to C₂₊ Hydrocarbons over Mesoporous x%Fe₂O₃-Al₂O₃ Catalysts

This work describes the preparation of mesoporous binary x%Fe2O3-Al2O3 mixed oxides with varying Fe2O3 nominal loading (x = 5, 10, and 20 wt %) by a one-step soft template sol-gel process. The binary oxides were used as catalysts in CO2 hydrogenation to produce C2+ hydrocarbons. The catalytic test was conducted at 280, 300, and 320 degrees C at a pressure of 20 bar, under a gas mixture of H-2 and CO2 with a molar ratio H-2/CO2 = 3. The main reaction products were methane, CO, C-2- C-4 olefins, and traces of C5+ compounds depending on the Fe2O3 nominal content. The catalyst modified with 20 wt % Fe2O3 displayed the best catalytic performance in terms of C2+ hydrocarbons production. An increase in the Fe2O3 nominal content from 5 to 20% induces a significant decrease in the reverse water gas shift (RWGS) reaction because of a 5-fold higher surface exposure of the Fe-0 species. The TPR and FTIR results of adsorbed CO confirmed an easier reduction of Fe2O3 species and a decrease in the metallic-support interaction, as Fe2O3 content of the composite catalyst increased. A linear correlation was found between the surface exposure of the Fe-0 species and the yield of C2+ hydrocarbons. Minimal coke deposition was detected after reaction tests.