(285b) Extractive Distillation Process Design and Techno-Economic Analysis for Separating High-GWP Refrigerant R-410A with Imidazolium-Cyano-Based Ionic Liquids

Refrigeration technology is critical in society, especially in data center air conditioning, food chain preservation, and medical applications. However, hydrofluorocarbons (HFCs), the current replacement for ozone-layer-depleting (hydro)chlorofluorocarbons (CFCs and HCFCs) refrigerants, generally have global warming potentials (GWP) thousands of times more potent than carbon dioxide. Hydrofluoroolefins (HFOs) and low GWP HFCs will represent the next-generation refrigerants. Most of the HFC refrigerants in current use are azeotropic mixtures of HFCs. 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. HFC-32 has a future in refrigerant HFO blends, while HFC-125 can be reused in new materials. As azeotropes, traditional distillation is incapable of separating the components. We and others have shown the use of extractive distillation with ionic liquids (ILs) as an alternative to recover and recycle refrigerants in a circular economy model. n-1-Alkyl-3-methylimidazolium tetracyanomethanide ([R-MIm][TCM])-cyano-based, e.g. [C₂C₁im][tcm], [C₄C₁im][tcm], [C₆C₁im][tcm], and [C₈C₁im][tcm] can be used as entrainers in an extractive distillation system. The Peng Robinson – Boston Mathias EoS is used to regress experimental VLE data and provide a model for equilibrium extractive distillation simulations. A sensitivity analysis reveals the optimum techno-economic parameters. High-purity products (>99.5 wt%) were obtained with [C₂C₁im][tcm], providing superior results over the other ILs investigated. Outcomes from this effort significantly support the design of state-of-the-art industrial applications to reduce global warming emissions from the refrigeration sector.