Densities and viscosities of, and solubilities of acidic gases (SO2 and H2S) in natural deep eutectic solvents

Abstract

Natural deep eutectic solvents (NADESs) are a subcategory of deep eutectic solvents (DESs) consisting solely of natural compounds. They can replace existing DESs that contain toxic compounds and are difficult to dispose of in many applications. However, the detailed physical properties data of NADESs are still very scarce in the literature. In this work, a series of NADESs with choline chloride (ChCl) as the shared hydrogen-bond acceptor (HBA), and five dicarboxylic acids (oxalic, malonic, maleic, malic and tartaric) as the varied hydrogen-bond donors (HBDs) were prepared. The densities and viscosities of prepared NADESs were determined from 293.2 to 353.2 K at 1.013 bar. The densities and viscosities data were fitted using empirical equations. An important application of DESs is gas separation, which requires knowing the solubilities of gases in DESs. Therefore, a NADES with relatively good fluidity was selected out as a representative to determine the solubilities of two typical acidic gases (SO2 and H2S) in it. The solubilities of SO2 and H2S were determined from 298.2 to 333.2 K and from 0 to 1 bar. The SO2 and H2S solubilities data were fitted using the Krichevsky − Kasarnovsky equation.