Tailoring the product polarity to facilitate the controllable phase transition of a 2-(ethylamino)ethanol-based nonaqueous absorbent for energy-efficient CO2 capture: An integrated experimental and quantum simulation study

Secondary amines are highly suitable candidates for constructing non-aqueous phase change absorbents (PCAs) that boast low viscosity and regeneration heat. However, the secondary amine-based PCAs often encounter the challenge of inadequate phase separation. This study proposed an innovative strategy of tailoring the polarity of absorption products to facilitate the controllable phase transition of the secondary amine-based PCA. Specifically, using aminoethylethanolamine (AEEA) as a regulator of product polarity to endow the 2-(ethylamino)ethanol (EAE)/pentamethyldiethylenetriamine (PMDETA)/dimethyl sulfoxide (DMSO) non-aqueous absorbent with tunable liquid–liquid phase transition behavior. The AEEA/EAE/PMDETA/DMSO (A/E/P/D) PCA realized a high CO 2 loading of 0.77 mol·mol −1 , with over 92% of the absorbed CO 2 being enriched in the CO 2 -rich phase, which exhibited a low viscosity of 13.83 mPa·s. The A/E/P/D PCA also possessed good reusability, maintaining a cyclic loading of 0.65 mol·mol −1 even after five absorption–desorption cycles. Analysis of the phase change mechanism indicated that AEEA reacted with CO 2 to form highly polar AEEA-derived products, which played a pivotal role in driving the phase transition of the A/E/P/D system. In brief, the AEEA-derived product easily combined with polar DMSO , creating a “polar sink” that continually attracted the medium-polar EAE-derived products. Consequently, these products clustered together to form the CO 2 -rich phase with less polar PMDETA being isolated to form the CO 2 -lean phase. Moreover, estimation of the regeneration heat demonstrated that the combined sensible heat and latent heat of A/E/P/D amounted to 0.32 GJ·ton −1 CO 2 , representing a significant reduction of 84% compared to 30 wt% MEA. This study provided a novel idea to manipulate the phase behavior of PCAs and offered a promising A/E/P/D PCA for energy-efficient CO 2 capture.