Development and Performance Evaluation of Polyether-Induced Biphasic Solvents for Energy-Efficient CO2 Capture

Conventional aqueous amine solvents used for post-combustion CO2 capture offer excellent absorption performance but require high regeneration energy. To reduce the energy demand, this study developed water-lean biphasic solvents by partially replacing water with polyether-based organic solvents. These biphasic solvents remain monophasic before CO2 absorption but undergo liquid-liquid phase separation into CO2-rich and CO2-lean phases upon CO2 absorption. Monoethanolamine (MEA) was used as the primary absorbent, and several polyethers with varying polarities were screened. Among them, diethylene glycol monobutyl ether (DEGMBE) demonstrated the highest CO2 concentration effect via phase separation. With increasing DEGMBE content, the CO2 loading in the rich phase increased, reaching 235 gCO2/Lsolvent at 50 wt% DEGMBE. Phase separation enhances the cyclic capacity due to selective regeneration of the CO2-rich phase. The mechanism was confirmed using 13C NMR, revealing that MEA carbamate and bicarbonate species preferentially migrate to the aqueous phase due to their poor solubility in DEGMBE. These findings suggest that polyether-induced biphasic solvents offer a promising pathway for improving the energy efficiency of amine-based CO2 capture systems.