(184d) Separation of Azeotropic Refrigerant Mixtures Using Extractive Distillation with Ionic Liquid Entrainers

Hydrofluorocarbons (HFCs) have been used as refrigerants globally since the 1990’s and replaced chlorofluorocarbons (CFCs), which were linked to the depletion of the Earth’s ozone layer. HFCs have zero ozone depletion potential (ODP), but some HFCs have a high Global Warming Potential (GWP). The next-generation of refrigerants, hydrofluoroolefins (HFOs), are being developed to replace HFCs in certain applications as a result of the Kigali Amendment to the Montreal Protocol. The Kigali Amendment became effective in January 2019 and limits the production and application of HFCs over the next two decades; therefore, the refrigerant industry is moving toward the production and marketing of HFOs and HFO/HFC refrigerant blends. This will require the recycling and repurposing of HFC mixtures, but many of the HFC mixtures are azeotropic or near azeotropic (i.e., R-410A, R-404A, R-407C, to name a few) making the separation of the components impossible using current methods.

Project EARTH (Environmentally Applied Research Towards Hydrofluorocarbons) aims to develop environmentally responsible methods to separate azeotropic HFC mixtures and recycle the pure component refrigerants. Extractive distillation is one method used to separate azeotropic mixtures with a similar boiling point. Ionic liquids (ILs) are being developed as novel entrainers for extractive distillation because of their negligible vapor pressure, thermal and chemical stability, and high and differential solubility with HFC refrigerants. Initially, Project EARTH will focus on the separation and recycling of a common commercial refrigerant mixture, R-410a, an azeotropic mixture containing 50 mass % R-32 (difluoromethane, CF₂H₂) and 50 mass % R-125 (pentafluoroethane, CHF₂CF₃). This presentation will provide results from ASPEN modeling and design and construction of the extractive distillation process for separating azeotropic HFC refrigerant mixtures.