Anti-degradation Biphasic Absorbent for Efficient and Stable CO₂ Capture

Biphasic absorbents are promising candidates for the separation of CO₂ from industrial flue gas; however, amine degradation can alter absorbent properties and reduce process efficiency, thereby limiting the industrial scalability of chemical absorption methods. To address this, amine compounds with high chemical stability were screened on the basis of their molecular structural properties, leading to the preparation of a 3-amino-1-propanol (MPA)-2-amino-2-methyl-1-propanol (AMP)-N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA)-polyethylene glycol dimethyl ether (NHD) biphasic absorbent for CO₂ capture. Comprehensive evaluations revealed that this absorbent exhibits effective phase separation, low regeneration energy consumption, and high stability. The CO₂-rich phase loading and volume fraction reached 4.13 mol/L and 53.1%, respectively, whereas the regeneration energy consumption was as low as 1.99 GJ/t-CO₂, marking a 48.3% reduction compared with that of the benchmark solvent monoethanolamine (MEA). After 14 days of degradation testing, the alkalinity loss of thermal degradation was only 0.29 mol/kg, with the oxidative degradation solution exhibiting an alkalinity loss rate of approximately 10%. Additionally, NH₃ emissions and acid ion concentration were significantly lower than those observed in the MEA-NHD biphasic absorbent. Furthermore, the degradation mechanisms of both the absorbents were thoroughly examined using various characterization methods. This study provides a theoretical foundation and an effective solution for developing low-energy, highly stable CO₂ capture technologies for industrial applications.