Tertiary amine based-biphasic solvent using ionic liquids as an activator to advance the energy-efficient CO2 capture

• Published in: Separation and purification technology 2025-03, Vol.355, p.129671, Article 129671
• Main Authors: Zhao, Huajun, Zhang, Ningtao, Hong, Yuxing, Wang, Rujie, Li, Qiangwei, Li, Ming, Wang, Lidong
• Format: Article
• Language: English
• Subjects: Biphasic solvents; CO2 absorption; Ionic Liquids; Reaction mechanism; Regeneration energy; Tertiary amine
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2024.129671

[Display omitted] •A tertiary amine-based biphasic solvent using ionic liquid as an activator was proposed.•It still had good absorption performance at lower CO2 partial pressures.•It showed greater desorption capacity than those of MEA at 393.15 K.•Extremely low Qrxn (1.21 GJ/t CO2) led to reduced regeneration energy (1.78 GJ/t CO2).•With the addition of ionic liquids, CO2 was mainly enriched in the CO2-lower phase. The newly developed tertiary amine-based biphasic solvents have low reaction heat, and good desorption performance, but no CO2 reactivity under low CO2 pressure. A novel tertiary amine-based biphasic solvent (DMEA/[DETAH]Lys/n-BuOH/H2O, abbreviated as D-DL-B-H) using ionic liquids (ILs) as the activator was proposed. With the assistance of [DETAH]Lys, the CO2-rich phase exhibited enhanced CO2 loading (from 3.69 to 4.09 mol/L) and CO2 distribution (from 88.5 % to 96.8 %). In addition, at 5 kPa, D-DL-B-H achieved an absorption capacity up to 1.58 mol/L, which was 79 times that of the DMEA/n-BuOH/H2O, suggesting the D-DL-B-H had good CO2 capture property at low CO2 pressure. At 393.15 K, the desorption efficiency of D-DL-B-H was as high as 80.9 %. In addition, the Qreg of D-DL-B-H was reduced to 1.78 GJ/t CO2, accounting for 44.61 % of the 30 wt% MEA. At 323.15 K, the viscosity of the CO2-rich phase was only 4.63 mPa·s, and the corrosion rate was 46.88 % of 30 wt% MEA. The reaction mechanism obtained from 13C NMR and DFT analysis indicated that [DETAH]Lys was more inclined to react with CO2 than DMEA. The main reason for the occurrence of phase splitting was the formation of hydrogen bonds between the CO2 product and the water.