Amine-based physical solvent phase separation absorbents: Interaction study of 2DMEDA with sulfolane-water systems

Liquid-liquid phase-separation absorbents demonstrate promising potential for enhancing CO 2 capture performance and reducing regeneration energy consumption. This work studied N , N -dimethylethylenediaminebased (2DMEDA)-physical solvents-H 2 O systems to evaluate their phase separation behaviors and absorption-desorption performance and developed a new liquid-liquid phase separation absorbent based on a 2DMEDA-sulfolane (SUL)-H 2 O system. Phase separation absorbent with varying 2DMEDA-SUL-H 2 O ratios were evaluated for phase separation behavior, viscosity and absorption-desorption properties. When the 2DMEDA-SUL-H 2 O system was formulated at 30:35:35 mass ratio, it demonstrated a relatively low dynamic viscosity of 20.14 mPa·s and a CO 2 cyclic capacity of 1.83 mol/L which was 1.44 times that of 30 wt% MEA aqueous solution. 13 C NMR analyses suggest that carbamates, bicarbonates and free amines predominantly concentrate in the CO 2 -rich phase, while SUL is primarily located in the CO 2 -lean phase. Furthermore, the phase separation mechanism was elucidated through density functional theory (DFT) calculations at the B3LYP/6–311++G(d,p) level and molecular dynamics (MD) simulations. It indicated that the formation of highly polar products and hydrogen bonding interactions among components were characterized as key contributing factors, and MD simulations further manifest aggregation propensities between reaction products and water molecules, driving spontaneous separation into CO 2 -rich and CO 2 -lean phases.