Effect of Mn loading onto MnFeO nanocomposites for the CO2 hydrogenation reaction

• Synthesis of mesoporous xMnFe oxide (x = 0–0.5 molar ratios) has been achieved.
• Fischer–Tropsch reactions for the production of high hydrocarbons were studied.
• 0.05MnFe catalyst was the only one showing mesoporous structure.
• 0.05MnFe catalyst showed much higher CO2 conversion to hydrocarbons.
• Mesoporous 0.05MnFe oxide catalyst displayed the best performance.

This work describes the preparation of mesoporous xMnFe oxide (x = 0, 0.05, 0.1, 0.2, 0.3 and 0.5 molar ratios) nanocomposites through a one-step sol–gel process in the presence of a triblock copolymer as a structure-directing agent. The prepared oxides were used as catalysts in the CO2 hydrogenation via Fischer–Tropsch reactions for the production of valuable hydrocarbons. Among the catalysts, the 0.05MnFe catalyst performed best under the selected reaction conditions: a reaction temperature of 340 °C, overall pressure of 20 bar, reactant mixture of 23% CO2/69% H2/8% N2 and flow rate of 20 mL min−1. This catalyst provided a much higher conversion of CO2 to hydrocarbons (63.2% C2–C5, 3.9% to C6+ and 3.6% to oxygenates) and the lowest levels of CO and methane formation among the xMnFe series. Moreover, 0.05MnFe was the only catalyst with a mesoporous structure, and it had a substantially lower reduction temperature than did the other members of the series. The enhanced catalytic activity of the 0.05MnFe catalyst, which contains only a small amount of Mn, appears to result primarily from its high specific area and relatively easy reduction.

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