Analyzing the Molecular Behavior of Ionic Liquids through Kamlet-Taft Parameters

The American Innovation and Manufacturing Act of 2020 initiated the phase-out of hydrofluorocarbon (HFC) refrigerants for more environmentally friendly hydrofluoroolefin (HFO) refrigerants. In response, Project E.A.R.T.H (Environmentally Applied Research Towards Hydrofluorocarbons) and our collaborators are actively pursuing methods of recycling HFC refrigerants that will no longer be usable. However, widely used mixtures of HFC refrigerants often form azeotropes which are not separable through conventional separation techniques like distillation. Thus, new separation methods are necessary and ionic liquids are proposed as entrainers in extractive distillation for the separation of HFC refrigerant mixtures. To design these complicated new systems, thermophysical data for ionic liquids and ionic liquid mixtures are necessary but uncommon. Our group aims to elucidate the complex behavior of ionic liquid mixtures with respect to their thermophysical properties in hopes to examine potential correlations between thermophysical properties and Kamlet-Taft parameters. Kamlet-Taft parameters π*, α, and β represent polarizability, hydrogen bond donating ability, and hydrogen bond accepting ability respectively. We hypothesize that the molecular characteristics described by Kamlet-Taft parameters are related to viscosity, density, and thermal conductivity. In which case, the necessary thermophysical data needed to design HFC separation systems could be derived from Kamlet-Taft parameters. This correlation would aid the effort to integrate ionic liquids as an entrainer in extractive distillation systems for the separation of hydrofluorocarbon refrigerant mixtures.