Rapid desorption of CO2 from deep eutectic solvents based on polyamines at lower temperatures: an alternative technology with industrial potential

Abstract

Herein we developed a new family of polyamine-based deep eutectic solvents (DESs) dedicated to reduce energy consumption, avoiding the formation of hazardous molecules, aiming at low solvent losses and robust desorption efficiency for carbon dioxide (CO₂) capture technology. A strategy developed for economical, thermally stable and low viscosity absorbents for CO₂ capture by functionalized neoteric media of azolide anions and secondary amine is presented. The prepared anion functionalized ionic liquids (ILs) and the derived DESs with ethylene glycol (EG) have a low viscosity which promotes high uptake of CO₂ (17–22% w/w) at 298.15 K and 1 atm. The absorption capacity of DESs was determined by a gravimetric technique. ¹³C NMR was used to examine the desorption efficiency (DE) of CO₂. It was found that rapid desorption of CO₂ occurs in TEPA polyamine based DESs compared to monoethanolamine at 80 °C. However, the desorption rate of CO₂ was observed to be higher at higher temperatures and, as a result, under a nitrogen flow, complete desorption of CO₂ took place at 100 and 110 °C after 30 and 20 minutes, respectively. Consequently, comparative regeneration of CO₂ was studied in the absence of a nitrogen flow at different temperatures. Excellent reversible uptake of CO₂ was observed without significant loss of the absorption capacity in four consecutive cycles at 100 °C. The chemisorption of CO₂ was verified by ¹³C NMR, 2D-NMR and FT-IR spectroscopy. The solvent loss study demonstrated the low volatility of polyamine based DESs at 100 °C and 120 °C after 50 h. The proposed DESs are thermally stable, cheap and give rise to negligible amounts of hazardous degradation components. Furthermore, they exhibit low solvent losses, low viscosities and rapid CO₂ desorption capability. Therefore they are promising candidates when aiming at improving amine based conventional CO₂ capture technology.