Concentrated aqueous solutions of protic ionic liquids as effective CO2 absorbents with high absorption capacities

Solubilities of CO2 in a series of aqueous 3-(dimethylamino)-1-propylamine (DMAPA) cation-based protic ionic liquids (PILs) with different anions were determined at 308.2 K and pressure up to 3.5 bar. Impressively, the solubility of CO2 in the [DMAPAH][F] aqueous solution reached up to 3.62 mol/kg at 1 bar and 308.2 K, which was much superior to the traditional amine solutions and other ILs reported in the literature. A novel absorption mechanism is proposed and verified by 13C NMR and 19F NMR spectra. Based on this, CO2 absorption behaviors on pressure, temperature and concentrations of [DMAPAH][F] in aqueous solutions were studied. Meanwhile, the relevant parameters, such as the apparent absorption rate constant k, the absorption activation energy Ea, the dissolution enthalpy change ΔHSOL and the entropy change ΔSSOL were also calculated from the dynamic and thermodynamic data. Regeneration under the condition of 353.2 K and 15 kPa for 1 h showed that aqueous [DMAPAH][F] solution had good regeneration efficiency (over 94%). The absorption capacity (3.62 mol/kg), the ΔHSOL (− 35 to − 43 kJ·mol− 1), as well as the good recyclability indicate that the aqueous [DMAPAH][F] is a kind of promising absorbent for the separation of CO2 and believed to have potential use in gas decarburization.