Refrigerant solubility in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide and upper-bound for R-410A separation with ionic liquids

Ionic liquids (ILs) are promising entrainers for the separation of azeotropic refrigerant mixtures, particularly within the ongoing transition toward low-global-warming-potential (GWP) alternatives. The development of extractive distillation processes requires reliable vapor–liquid equilibrium (VLE) data and accurate thermodynamic models. In this work, the solubility of several hydrofluorocarbons (R-32, R-125 and R-134a), hydrofluoroolefins (R-1234yf and R-1234ze(E)) and CO₂ in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([C₂C₁im][FSI]) was experimentally determined over temperatures from 283.15 to 323.15 K and pressures up to 1.1 MPa applying the isochoric saturation method. All refrigerant/IL systems were satisfactorily described using both the Peng–Robinson equation of state coupled with the Boston–Mathias mixing rule and the Non-Random Two-Liquid (NRTL) activity coefficient model, yielding average absolute deviations below 1% and 6%, respectively. The relative absorption performance was assessed through the Henry’s law constants and mixing thermodynamic properties, showing that the IL selected exhibited high ideal selectivity towards different refrigerant blends. In the case of R-410A, a near-azeotropic mixture of R-32 and R-125, the [C 2 C 1 im][FSI] selectivity was higher than previously reported for any other IL with a fluorinated anion, yet lower than for nitrile-based ILs. Furthermore, an upper-bound relationship between the ideal R-32/R-125 selectivity and R-32 absorption capacity was reported for the first time, establishing a quantitative benchmark for future IL screening and design. The presented data and its subsequent analysis expand the available thermodynamic knowledge for refrigerant/IL systems and provide a basis for future development an IL-based separation process for R-410A.