Thermodynamic and\nProcess Analyses of Extractive Distillation\nfor Separating Refrigerant R‑410A Using Imidazolium-Cyano-Based\nIonic Liquids

R-410A is a near-azeotropic refrigerant mixture of difluoromethane\n(HFC-32) and pentafluoroethane (HFC-125) that is scheduled to be phased\nout internationally due to a high Global Warming Potential (GWP).\nWhile conventional distillation cannot be used, extractive distillation\nusing ionic liquids (ILs) has been proposed to separate and recycle\nHFC-32 (lower GWP) for future refrigerant blends and to repurpose\nHFC-125 (high GWP). Here, we present both a thermodynamic and process\ndesign analyses of various ILs using an equation of state method.\nFrom experimental binary vapor–liquid equilibrium data and\nequation of state modeling, 1-ethyl-3-methylimidazolium tricyanomethanide\n[C<sub>2</sub>C<sub>1</sub>im][tcm] and 1-ethyl-3-methylimidazolium\ndicyanamide [C<sub>2</sub>C<sub>1</sub>im][dca] were identified from\n10 ILs as viable entrainers. Selectivity increases with temperature\nand decreases with pressure, while the solvent-to-feed (S/F) ratio\ndid not have much effect. These effects were more pronounced for [C<sub>2</sub>C<sub>1</sub>im][tcm] than for [C<sub>2</sub>C<sub>1</sub>im][dca]. A sensitivity analysis reveals that the optimum operational\nparameters were solvent-to-feed ratio (<i>S</i>/<i>F</i>), reflux ratio (<i>RR</i>), and total number\nof stages (<i>Nt</i>) with values of 5, 3, and 20, respectively,\nfor the case of [C<sub>2</sub>C<sub>1</sub>im][tcm] and 6, 3, and\n20 for [C<sub>2</sub>C<sub>1</sub>im][dca]. High-purity products HFC-32\nand HFC-125 (>99.5 wt %) were obtained with IL [C<sub>2</sub>C<sub>1</sub>im][tcm], providing the lowest energy consumption, compared\nto [C<sub>2</sub>C<sub>1</sub>im][dca] and other ILs.