Development of novel AMP-based absorbents for efficient CO₂ capture with low energy consumption through modifying the electrostatic potential

The global deployment of aqueous amine absorbents for carbon dioxide (CO₂) capture is hindered by their high energy consumption. A potential solution to this challenge lies in the utilization of non-aqueous amine systems, which offer energy-efficient alternatives. However, they are prone to form precipitation during CO₂ absorption process, which limits their application. Combining experimental and theoretical studies, we found that the electrostatic potential of carbamate, instead of van der Waals force, is a major factor controlling the precipitation, and hydrogen bonds can effectively reduce the electrostatic potential of carbamate and prevent precipitation. Single solvent screening experiments have also demonstrated that the absorption rate is closely related to the viscosity of the organic solvent and the affinity of the functional group for CO₂. The polar solvents (Dimethylformamide (DMF), Dimethyl sulfoxide (DMSO), and N-Methylformamide (NMF)) exhibit higher absorption rates, but suffer from issues of precipitation. Hydroxyl group riched solvents (Ethylene glycol (EG) and Glycerol) exhibit lower absorption rate, but they don't have the issue of precipitation. Based on these findings, several novel 2-Amino-2-methyl-1-propanol (AMP)-based non-aqueous absorbents have been developed aiming at reducing the energy penalty, and improving CO₂ absorption and desorption performance. Among these absorbents, AMP-EG-DMF (4–3) exhibits maximum CO₂ absorption rate and absorption capacity of 9.91 g-CO₂/(kg-soln.·min.) and 122 g-CO₂/(kg-soln.), respectively, which are 64.1% and 28.4% higher than those of 30 wt% AMP aqueous solution, respectively. Additionally, compared to 30 wt% MEA, the energy consumption of AMP-EG-DMF (4–3) shows 46.30% reduction. The addition of EG effectively improves the electrostatic solubility of AMP-carbamate by increasing the number and strength of hydrogen bonds, thus avoiding the generation of precipitation. The final product species and reaction mechanism were analysed by using ¹³C and ¹H NMR, In-situ ATR-FTIR, and quantum chemical calculation. The combination of theoretical and experimental results indicates that bi-solvent AMP-based absorbents can serve as a promising alternative for low-energy CO₂ capture. © 2023 The Authors