(653a) Physical Property Characterization of Ionic Liquids in HFC-32 and HFC-125 Using a High-Pressure View Cell
The current hydrofluorocarbon (HFC) refrigerants used in automobile air conditioning, home appliances and air-conditioners, and retail refrigerant systems are being phased out due to high global warming potentials, resulting in millions of kilograms of refrigerant needing to be recycled and repurposed. Many of these refrigerants are HFC mixtures, and if separated, the components may be repurposed or reused to prevent release of greenhouse gases into the atmosphere. Since most HFC mixtures are azeotropic, separation is difficult and energy intensive and thus no reasonable technologies exist today. Ionic liquids (ILs) offer a sustainable way to separate HFC refrigerants if an IL can be found with a large solubility difference between the components of an HFC mixture. This research is part of Project EARTH (Environmentally Applied Research Toward Hydrofluorocarbons) that is working to create an efficient and sustainable process for the separation of HFC refrigerants. The group has measured the solubility of HFC-125 (CHF2CF3) and HFC-32 (CH2F2), which make up the refrigerant R-410A (50-50 wt%), in selected ILs using a microbalance. The microbalance does not allow for visually observing what phase the IL might exist in when pressurized with the refrigerant, therefore this project utilizes a high-pressure view cell with quartz windows to visually study the solid-liquid phase change of imidazolium halide based ILs. In some cases, the ILs are solid at room temperature, but in the presence of HFC-125 and HFC-32 as a function of pressure melt and undergo a phase change. Understanding the phase behavior of an IL during HFC sorption allows for the management of heat in separation processes as heat of fusion can help reduce the heat of sorption. Other property measurements based on visual data, including melting point, the presence of metastable states, and occurrence of foaming, are taken in addition to phase change data. This presentation will be discussing how the physical properties of imidazolium halide based ILs change with the sorption of HFC-32 and HFC-125 to indicate the viability of the ILs for separation of the refrigerant R-410A.