Investigation of the Performance and Mechanism of CO2 Capture Using Novel MEA/Polyamine/Sulfolane Biphasic Absorbents

Mixed amine/sulfolane (TMS) biphasic solutions have gained attention for their adjustable structure–activity relationships and lower regeneration energy. In this study, monoethanolamine (MEA) is employed as the main absorbent and polyamine as the co-absorbent, which are subsequently mixed with the phase separation promoter sulfolane (TMS) to form ternary biphasic solvent systems. Polyamine co-absorbents include 3-Dimethylaminopropylamine (DMAPA), 3-Diethylaminopropylamine (DEAPA), and Diethylenetriamine (DETA). Phase separation, absorption, and desorption performances were systematically studied. Reaction and phase separation mechanisms were elucidated through 13C nuclear magnetic resonance (NMR) spectroscopy. The overall mass transfer coefficients (KG) were measured using a wetted wall column (WWC). Variations in the amine-to-sulfolane concentration ratio showed minimal impact on phase volume, while temperature and solvent composition significantly influenced phase separation behavior. All three solvents exhibited superior CO2 capture performance, with CO2 loadings in the rich phases ranging from 4.09 to 4.71 mol/L and over 96.82% of CO2 concentrated in them, cyclic capacities reached or exceeded 3 mol/L, and regeneration energy consumption was 29.63–55.51% lower than 5 M MEA. 13C NMR analysis indicated that multiple N atoms in polyamines promoted the formation of additional ionic species during CO2 absorption, thereby enhancing phase separation completeness. Furthermore, KG values for the ternary systems exceeded that of conventional MEA, with the MEA/DEAPA/TMS system exhibiting a 1.7-fold increase. These findings demonstrated the industrial potential of MEA/polyamine/TMS biphasic solvents for efficient CO2 capture.