Solubility and diffusivity of six volatile compounds in ionic liquids [BMIM][Tf2N], [BMPy][Tf2N], [BMIM][TfO] and [BMPy][TfO]

Diffusivity and solubility of water, methanol, ethanol, 1-butanol, acetone and p-xylene in four ionic liquids (ILs) were determined microgravimetrically by studying the absorption of the vapors (without air) in the ILs at 40 degrees C. The studied ILs comprised of all four possible combinations of two cations [1-butyl-3-methylimidazolium, BMIM, and 1-butyl-1-mehtylpyrrolidinium, BMPy] and two anions [bis(trifluoromethylsulfonyl)imide, Tf2N, and trifluoromethanesulfonate, TfO]; data for 24 systems are reported. Higher solubility of the vapors of protic compounds (water, methanol, ethanol and 1-butanol) was observed for the ILs containing the TfO anion while higher solubility of aprotic compounds (acetone and p-xylene) was observed for ILs containing the Tf2N anion. While ILs containing BMPy cation showed discernibly higher solubilities than those containing BMIM in for 1-butanol in TfO based ILs and p-xylene in Tf2N based ILs, limited solubility changes due to the cation exchange were observed for the remaining systems. The equilibrium dissolution was parameterized using the Margules and Guggenheim, Anderson, de Boer (GAB) models. For all compounds except water, mutual diffusivity followed the relations BMIM > BMPy and Tf2N > TfO, while for water it followed BMIM > BMPy and TfO > Tf2N. Diffusion was anomalously fast with respect to the Einstein-Stokes-Sutherland equation in all studied systems presumably due to the cage and jump mechanism. Despite the observed non-ideality of the liquid phase, mutual diffusivities were practically constant over the tested ranges of vapor activity (and concentration) for most systems while thermodynamic (self) diffusivities varied with the experimental conditions. Overall, structure-property relationships were assessed for four combinations of practically relevant constituting ions and six volatile solutes at 40 degrees C. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The diffusivity and solubility of various compounds in ionic liquids were studied. The results showed that different ionic liquids had different effects on the solubility of different compounds. The diffusion was anomalously fast, and there was a relationship between the structure and properties.