(383r) Extractive Distillation Process Design for Recovering and Recycling Components from High-GWP Refrigerant R-410A Using Ionic Liquids

Refrigeration technology is critical in society. However, many current hydrofluorocarbons (HFCs) refrigerants have high global warming potential (GWP). Moreover, many of these refrigerants are azeotropic mixtures. For instance, R-410A (residential and commercial AC) is a mixture of difluoromethane (HFC-32), which has a relatively low GWP, and pentafluoroethane (HFC-125) with a high GWP. Recycled HFC-32 with a low GWP has a future in new refrigerant blends, while the recycled HFC-125 can be reused in new materials. Traditional distillation is incapable of separating azeotropic mixtures. We and others have shown the use of extractive distillation with ionic liquids (ILs) offers an alternative to recover and recycle refrigerants in a circular economy model. The Peng Robinson – Boston Mathias EoS is used to regress experimental VLE data and provides a model for equilibrium extractive distillation simulations. A sensitivity analysis reveals the optimum process design parameters. High-purity products (>99.5 wt%) were obtained with [C₂C₁im][tcm] providing superior results over the other ILs investigated. Robust models based on transport properties (i.e., interfacial tension, viscosity, heat capacity) are needed to have accurate predictions of the extractive distillation process, minimizing energy consumption and total investment cost. Therefore, in this work, the interfacial tension of two refrigerants, difluoromethane HFC-32 (CH₂F₂) and pentafluoroethane HFC-125 (CHF₂CF₃), in a mixture with ionic liquid, [C₁C₂im][Tf₂N] has been measured over a temperature range from 283.15 to 373.15 K and a pressure range from 1 to 9 bar. The pendant drop method is used in a high-pressure, high-temperature (HPHT) interfacial tension (IFT) cell. Outcomes from this effort significantly support the design and scale-up of the extractive distillation process for industrial applications.