Protic ethanolamine hydrochloride-based deep eutectic solvents for highly efficient and reversible absorption of NH3

Abstract

Ammonia (NH3) is essential for nitrogen fertilizer and is also considered as a promising energy carrier recently. In considering the role of NH3 for energy storage, the health and environmental risks from NH3 emission must be minimized and efficiently eliminated. To this end, a wide range of materials such as metal halides, ionic liquids and porous materials have been examined for NH3 absorption. Deep eutectic solvents (DESs) with unique properties and low cost are considered as potential solvents for absorbing NH3. Herein, we report a DES composed of protic ethanolamine hydrochloride (EACl), weakly acidic resorcinol (Res) and neutral glycerol (Gly) can absorb 0.240 g NH3/g DES for EACl/Res/Gly (1:4:5) at 293 K and 0.1 MPa, which is much higher than most of reported DESs. The absorption mechanism of NH3 is hydrogen-bonding interaction from the results of NMR and FT-IR spectra. The ternary DESs EACl/Res/Gly have abundant hydrogen-bonding sites to absorb NH3 without structural damage, in which EACl and Res play a major role in the interaction with NH3, while Gly is helpful for structural stability during NH3 absorption. Besides, DES EACl/Res/Gly (1:4:5) has good reversibility, excellent NH3/CO2 selectivity, is a potential NH3 absorption and storage material for industrial application.