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Solubility and Diffusivity of Chlorodifluoromethane in Imidazolium Ionic Liquids: [emim][Tf₂N], [bmim][BF₄], [bmim][PF₆], and [emim][TFES]

Minnick, David L., Shiflett, Mark B.
Industrial & engineering chemistry process design and development 2019 v.58 no.25 pp. 11072-11081
absorption, data collection, diffusivity, enthalpy, entropy, hydrodynamics, imidazoles, ionic liquids, perfluorocarbons, solubility, solutes, temperature
Solubility and diffusivity measurements of chlorodifluoromethane (HCFC-22) in four ionic liquids (ILs)—[emim][Tf₂N], [bmim][BF₄], [bmim][PF₆], and [emim][TFES]—were conducted using an IGA gravimetric microbalance at temperatures between 283.2 and 348.2 K. The solubility results were modeled using the NRTL activity coefficient method and were also used to calculate Henry’s law constants (kH) at infinite dilution. van’t Hoff relationships were used to calculate the enthalpy (ΔH̅ₛₒₗ) and entropy (ΔS̅ₛₒₗ) of absorption for HCFC-22 in each IL. Time-dependent absorption data collected by the IGA microbalance was used to calculate the diffusion coefficient of HCFC-22 in each IL. The diffusion coefficient results were used to calculate the hydrodynamic radius of the solute molecule using the Stokes–Einstein relationship. The experimental results for chlorodifluoromethane and [emim][Tf₂N] are compared with previous studies on trifluoromethane and other fluorocarbons to understand the impact of atom substitution (e.g., CHF₂-F vs CHF₂-Cl) on fluorocarbon solubility in an ionic liquid.