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Absorption of Carbon Dioxide Using Ethanolamine-Based Deep Eutectic Solvents

Li, Zhuo, Wang, Lili, Li, Changping, Cui, Yingna, Li, Shenmin, Yang, Guang, Shen, Yongming
ACS sustainable chemistry & engineering 2019 v.7 no.12 pp. 10403-10414
absorbents, absorption, carbon dioxide, electrostatic interactions, energy, ethanolamine, hydrogen bonding, lithium chloride, nuclear magnetic resonance spectroscopy, solvents, temperature, tetraethylammonium compounds, tetramethylammonium compounds, water content
The development of a new, green CO₂ absorbent with high energy utilization and low solvent loss can replace CO₂ capture by ethanolamine solution, which is currently a necessary and important issue. This work is devoted to the design and synthesis of DESs based on ethanolamine and the absorption of CO₂, focusing on the systematic study of the effects of CO₂ absorption and the effect of water on the deep eutectic solvents (DESs) of ChCl/MEA, TMAC/MEA, and TEAC/MEA (MEA = ethanolamine, TMAC = tetramethylammonium chloride, and TEAC = tetraethylammonium chloride). A series of DESs comprise various hydrogen-bonding donor–acceptor pairs as CO₂-capturing solvents. The main factors that influence the absorption process, such as rotational speed, flow rate, temperature, absorption time, molar ratio, and water content on the absorption of CO₂, are examined. Simultaneously, the influence on the DESs after absorption was analyzed, and the absorption mechanism was systematically studied. Furthermore, the use of three-component alkaline DESs (TMAC/MEA/MDEA) (MDEA = methyl diethanolamine) and the three components of TMAC/MEA/LiCl, TMAC/MEA/ZnCl₂, and TMAC/MEA/NH₄Cl were investigated by adding pure water to remove CO₂ performance. The TMAC/MEA/LiCl solvent reaches a maximum absorption of 36.81 wt % at 50 °C, and for TMAC/MEA/LiCl + 10% H₂O system, the absorption of CO₂ decreases with increasing temperature. The TMAC/MEA/LiCl + 10% H₂O system has the highest absorption at 30 °C and reaches 37.31 wt %. NMR was applied to investigate the absorption mechanisms. The hydrogen-bonding and electrostatic interactions were the main driving force for this specifically high CO₂ absorption process.