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.