Excess properties, spectral analyses, and CO2 capture performance of N-methyldiethanolamine plus polyethylene glycol 300 binary system

Density (p) and viscosity (q) data of polyethylene glycol 300 (PEG300) + N-methyldiethanolamine (MDEA) binary system at T = (298.15-318.15) K with a step of 5 K were measured at P = 1005 hPa. After that, the experimental p and q values were correlated and predicted by several semi-empirical models. Meanwhile, the Jouyban-Acree model presented a better fitting for the density, and the McAllister four-body equation presented a better fitting for the kinematic viscosity. Based on the p and q values, excess molar volume (VEm), partial molar volume (V1 and V2), viscosity deviation (Aq), and excess Gibbs energy of activation of viscous flow (Delta G*E) of PEG300 (1) + MDEA (2) binary system were systematically calculated and analyzed. These excess properties showed the predominance of intermolecular self-conjugation in PEG300 (1) + MDEA (2) binary system, and it was further demonstrated by various spectral characterizations. Importantly, the PEG300 + MDEA aqueous system was used for 5 CO2 absorption (room temperature)-desorption (371.15 K) cycles at a CO2 flow rate of 200 mL/min, with the average CO2 capture performance of 0.65 mol CO2/mol MDEA of per cycle, demonstrating excellent absorption capability, and remained stable throughout the entire cycle.

Automated summary

In this study, the density and viscosity characteristics of the PEG300 + MDEA binary system were systematically studied through experiments and model calculations, and correlated models for the two properties were obtained. The results showed the presence of intermolecular self-conjugation in the binary system, which was further confirmed by various spectral characterizations. Additionally, the PEG300 + MDEA aqueous system exhibited excellent absorption capability in the CO2 absorption-desorption cycle and remained stable.