Investigation of Imidazolium-Based Ionic Liquids with the Sorption of HFC-32 and HFC-125 Refrigerant Gases

Refrigerants are used around the world in enormous quantities for a variety of purposes. However, the current generation of refrigerants, hydrofluorocarbons (HFCs), have a detrimental impact on the environment due to their high global warming potentials. Currently, the most common methods of disposing of HFCs are venting them into the atmosphere or incinerating the mixtures. The goal of Project Earth is to develop sustainable processes to separate refrigerant mixtures, with an initial focus on R-410A. R-410A is an azeotropic mixture consisting of 50 wt% pentafluoroethane (HFC-125) and 50 wt% difluoromethane (HFC-32). One approach for separating this azeotropic mixture is using extractive distillation techniques using differences in gas solubility using ionic liquids (ILs). ILs are defined as organic salts with a melting temperature below 100ºC. Their unique properties, particularly their negligible vapor pressure, make them promising entrainers for this process. To assess the feasibility of a specific HFC/IL system, vapor-liquid equilibrium data is collected for HFC and IL systems at various temperatures and pressures using a high-accuracy gravimetric analyzer (IGA). In some cases, the ILs can be solids at room temperature, and during pretreatment in the IGA may undergo a phase transition. To observe these physical changes, a high-pressure view cell is used to record this phenomenon. The data discussed in this presentation will include the phase transitions and solubility data for imidazolium based ILs that have been observed using the view cell and studied with the IGA, as well as observing patterns present in the sorption data gathered.