Reversible Carbon Dioxide Capture at High Temperatures by Tetraethylenepentamine Acetic Acid and Polyethylene Glycol Mixtures with High Capacity and Low Viscosity

Ionic liquids (ILs) are investigated in many studies to capture CO₂ in recent years. However, almost all of these studies carried out the absorption of CO₂ by ILs at relatively low temperatures (lower than 333.15 K or even around room temperature). Besides, the viscosity of ILs increases dramatically after absorbing CO₂, which could reduce the absorption efficiency significantly. Reversible and efficient absorption of CO₂ at high temperatures was investigated by IL of tetraethylenepentamine acetic acid ([TEPA]Ac) and polyethylene glycol 200 (PEG-200) mixtures with low viscosity. The results showed that the absorption capacity of [TEPA]Ac/PEG-200 mixtures achieved 1.24 mol of CO₂/mol of [TEPA]Ac at 353.15 K at ambient pressure (1.01 bar). The mixtures could be easily regenerated by bubbling dried N₂ through them. The addition of PEG-200 in [TEPA]Ac could increase the efficiency of absorption and desorption significantly. Furthermore, the solubility data of CO₂ in the [TEPA]Ac/PEG-200 mixtures at T = 353.15, 368.15, 383.15, and 398.15 K under different pressures were measured, and the solution enthalpy (ΔH_sol) and solution entropy (ΔS_sol) were calculated. Under all of the conditions, the negative value of ΔH_sol indicated that the capture process is exothermic. The process of CO₂ capture described that using [TEPA]Ac/PEG-200 mixtures is a promising approach for CO₂ absorption with high reversibility and excellent absorption property at a relatively high temperature.