Unveiling the mechanism of CO2-driven phase change in amine + water + glycol ether ternary mixture

Background: Phase separation solvents have been developed for CO2 capture with the advantage of low regeneration energy. Understanding the mechanism of phase change driven by CO2 capture is critical toward design of phase separation solvents. Methods: In this work, the molecular information of σ-profile and simulated ternary liquid–liquid equilibrium (LLE) phase diagram obtained from a predictive modeling based on COSMO-SAC method is used to investigate the phase behavior of phase separation solvents before and after CO2 absorption. Significant findings: Ternary mixtures of three selected amines [2-aminoethanol (MEA), 2-(ethylamino)ethanol (EAE), 2-(butylamino)ethanol (BAE)] + water + glycol ether, with different strengths of hydrophilicity of amines, exhibit three types of partially miscible behaviors. Upon absorption of CO2, amine reacts to form hydrophilic reaction products (carbamate + protonated amine), resulting in the change of the molecular interactions and immiscible behaviors. Our study shows that amines, such as EAE, having a balanced interaction with water and glycol ether (exhibiting small immiscible region) are potential candidates for amine + water + glycol ether based phase separation solvent for CO2 capture. ? 2021