Physicochemical Properties, Intermolecular Interactions and CO2 Absorption Performance of N-Methyldiethanolamine + Polyethylene Glycol 300 + Water Solution

The impact of water on the physicochemical properties and CO 2 absorption capability of the N -methyldiethanolamine (MDEA) + polyethylene glycol 300 (PEG300) solution was explored. The molar ratio of PEG300 to MDEA was fixed at 0.3734: 0.6266, and the density and viscosity of the aqueous solutions were measured at P  = 100.5 kPa and T  = (298.15–318.15) K. Based on these measurements, the excess properties of the system were calculated. Meanwhile, spectral analysis confirmed the formation of intermolecular hydrogen bonds among MDEA, PEG300, and H₂O. Building on these findings, the influence of water content on the cyclic CO 2 absorption performance of the H₂O + (PEG300 + MDEA) system was systematically investigated, with particular emphasis on the regeneration behavior at 15 wt% MDEA concentration. Furthermore, the underlying mechanism of the cyclic CO₂ absorption process was elucidated using multiple analytical techniques. These insights provide certain theoretical support for the industrial application of PEG300 + MDEA aqueous systems in CO 2 capture.