Optimization of Fe content of Cu-FeOX/MgAl2O4 catalyst in low-temperature reverse water-gas shift reaction for superior CO formation

초록

E-fuels offer a viable alternative to fossil fuels for achieving carbon neutrality in the transportation sector. In the E-fuel production process, which relies on the reverse water-gas shift (RWGS) followed by the Fischer-Tropsch reaction, the RWGS step requires high CO generation and stability. In this research, 25 wt% Cu-FeOX/MgAl2O4 catalysts are synthesized via an ultrasonic method by adjusting the Fe content (x = 0, 5, 15, and 25 wt%). The addition of Fe to Cu enhances the catalytic activity by promoting particle dispersion. However, adding more than 15 wt% of Fe leads to Cu aggregation, as evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, while also reducing CO2 adsorption owing to fewer oxygen vacancies. Carbon deposition is not observed on the Cu-FeOX catalysts during the RWGS reaction. Analysis of the spent catalysts confirms that carbon deposition occurs around the Fe species. The optimal catalyst is confirmed to be 25C5F, which contains 5 wt% Fe. It exhibits the smallest Cu particle size, enhanced dispersion, and suppressed coke formation during the reaction. In addition, it achieves the highest CO formation rate (266 mu mol/gcat & sdot;s) at 400 degrees C under under a gas hourly space velocity (GHSV) of 360,000 mL/gcat & sdot;h and an H2/CO2 ratio = 4. These findings underscore the significance of the Fe content in Cu-FeOX catalysts for enhancing Cu dispersion and ensuring reaction stability in low-temperature RWGS reactions, highlighting the importance of Fe optimization for producing CO and syngas required for Fischer-Tropsch reactions in E-fuel production.

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