A Review on Catalytic Ethanol Synthesis via Hydrogenation of Carbon Dioxide

Abstract

The catalytic hydrogenation of carbon dioxide (CO2) is a promising strategy for mitigating greenhouse gas emissions while generating sustainable fuels and valuable chemicals. Among potential products, ethanol stands out as a renewable energy carrier due to its compatibility with existing fuel infrastructure and ability to reduce CO2 emissions when integrated into energy systems. Despite the success in converting CO2 into C1-Chemicals with high yields, the selective conversion of C2+ products, including ethanol, remains a challenge due to the synthetic complexity. This review explores recent advances in CO2 hydrogenation to ethanol, emphasizing the catalytic performance of noble metals (e.g., Rh, Pd, Au, Ir, and Pt) and non-noble metals (e.g., Co, Cu, and Fe) catalysts. Mechanistic insights into CO2 conversion and the role of metal active sites in governing selectivity and by product formation are addressed. A critical balance between reductive and C–C coupling steps for achieving high ethanol yields is highlighted, supported by thermodynamic analyses. Experimental results from batch and continuous-flow reactor systems are discussed. Challenges such as low selectivity and byproduct formation are analyzed alongside strategies to address them, including advanced catalyst designs. This review outlines future research directions for catalyst development and the potential industrial application of CO2 hydrogenation to ethanol.