Solubility Behavior and the Mechanism of HCl Gas in Four [EMIM]Cl-Based Deep Eutectic Solvents

Abstract

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.

Bichloride-based ionic liquids for the merged storage, processing, and electrolysis of hydrogen chloride

“…An attractive complementary approach would be a technique that combines the superior safety profile of hydrochloric acid with the advantageous reactivity and electrochemical properties of gaseous hydrogen chloride. Although ionic liquids ( 23 – 25 ) and metal-organic frameworks ( 26 ) for the reversible absorption of HCl are reported, none of them were used as scalable storages that can directly be used for hydrochlorination reactions and electrolysis. Recently, Geng and coworkers ( 27 ) demonstrated that imidazole-based deep eutectic solvents can be used for the efficient coupling of HCl capture and conversion.…”

The Catalytic Mechanism of [Bmim]Cl-Transition Metal Catalysts for Hydrochlorination of Acetylene

“…The solubility of HCl in various imidazolium-based ILs and deep eutectic solvents (DES) has been studied in our group, and the maximum solubility can reach 0.4 g•g −1 [23][24][25][26]. The as-dissolved HCl can be directly used for the hydrochlorination of acetylene, which not only realizes its in situ utilization but also avoids intensive energy consumption in the desorption process.…”

Efficient Hydrochlorination of Acetylene by the Ag–Ru Bimetallic Catalyst in a Deep Eutectic Solvent

“…28−30 We studied the absorption of HCl in DES [Emim]Cl-PEG, and the HCl solubility can reach 0.437 g•g −1 . 31 In addition, the remarkable gas solubility of [Emim]Cl 32 helps activate substrates and improve the catalytic efficiency. 33 The catalytic performance of the metals is closely related to their electron structure.…”

“…Deep eutectic solvents (DESs), IL analogues, consist of hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD). They have a wide liquid range, negligible volatility, and good solubility for various substances, and are widely used in gas absorption, , extraction, and catalysts. − We studied the absorption of HCl in DES [Emim]­Cl-PEG, and the HCl solubility can reach 0.437 g·g –1 . In addition, the remarkable gas solubility of [Emim]­Cl helps activate substrates and improve the catalytic efficiency .…”