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The solubility behavior of HCl gas in four 1-ethyl-3-methylimidazolium chloride([Emim]Cl)-based deep eutectic solvents (DESs), i.e., an [Emim]Cl mixture with 4-methylimidazole (DES1), 2-methylimidazole (DES2), malonic acid (DES3), and poly(ethylene glycol) 400 (DES4), was studied at 301.15−348.15 K and a 0−101.325 kPa partial pressure of HCl. The H-bonding interaction and the dissolution mechanism were studied via Fourier-transform infrared spectroscopy (FTIR), 1 H NMR, and 13 C NMR. The HCl solubility increases with the alkalinity of the DESs and its H-bonding interaction with the solvent and follows the order DES1 > DES2 > DES4 > DES3. The HCl solubility in DES1 is 0.584 g-HCl/g-DES with partially irreversible desorption due to its chemical interaction with HCl. In contrast, HCl is physically dissolved in DES3 and DES4 with facile and reversible desorption. The solution viscosity decreases sharply and the density increases slightly as the absorption proceeds. Considering its higher solubility, thermal stability, and facile desorption, DES4 is more viable for HCl absorption. The result is instructive for the development of a greener recovery process for HCl gas and the selection of efficient DESs.

The design of efficient absorbent is the premise for the recovery and resource utilization of hydrogen chloride (HCl) from its industrial tail gases. Herein, a series of 1-butyl-3-methylimidazolium chloride (BmimCl)...