Thermodynamic Analysis of Chemical and Phase Equilibria in CO2 Hydrogenation to Methanol, Dimethyl Ether, and Higher Alcohols

CO2 hydrogenation can lead to the formation of various products, of which methanol, dimethyl ether (DME) and ethanol have received great attention. In this study, a comprehensive thermodynamic analysis of CO2 hydrogenation in binary (methanol/CO) and ternary product systems (methanol/CO with DME or ethanol) is conducted in Aspen Plus by the Gibbs free energy minimization method combined with phase equilibrium calculations. It is demonstrated that product condensation can be utilized to circumvent thermodynamic restrictions on product yield. Significant improvements in CO2 conversion can be achieved by operating at conditions favorable for product condensation, whereas the selectivity is mildly affected. The relevance of the results herein is discussed with regards to recent advances in catalysis and process design for CO2 hydrogenation. Our study highlights the importance of obtaining a thorough understanding of the thermodynamics of CO2 hydrogenation processes, which will be critical for developing potential breakthrough technology applicable at the industrial scale.