CO2 conversion to light hydrocarbons over K/Fe2O3-Al2O3 synthesized via the reverse microemulsion method

Abstract

The increasing concentration of atmospheric carbon dioxide (CO2), primarily driven by human activity, has intensified global concerns over climate change. One promising strategy to address this issue is the catalytic conversion of CO2 into valuable hydrocarbons, offering a sustainable route for emission reduction and fuel production. Potassium-promoted iron-based catalysts were investigated for CO2 hydrogenation via a modified Fischer–Tropsch (FT) process. High specific surface area catalysts were synthesized using the reverse microemulsion method, enabling controlled particle size and dispersion. The effects of potassium (K) loading (0-11.3 wt%), active phase, support, H2:CO2 feed ratio (1-4), reaction temperature (300-500 °C), pressure (4-12 bar), and GHSV (750-4000 mL/(gcat∙h)) were examined. Catalytic performance was evaluated by CO2 conversion, C2+ hydrocarbon selectivity, and space time yield (STY). Fresh and spent catalysts were characterized using XRD, TPR, BET, TEM, TGA-FTIR, and ICP techniques. The 7.8%K/Fe2O3-Al2O3 catalyst exhibited the highest activity, achieving 50% CO2 conversion, 53% C2+ selectivity, and a STY of 7.72 mmol/(gcat∙h) at 11 bar, 1000 mL/(gcat∙h), and 400 °C. In contrast, the catalyst without potassium showed significantly lower performance, with 24% conversion, 12% selectivity, and a STY of 0.87 mmol/(gcat∙h). The enhanced activity is attributed to the formation of active χ-Fe5C2 and Fe3O4 phases under reaction conditions, facilitated by the uniform nanoscale morphology of the catalysts synthesized via the reverse microemulsion method.