Separation of tetrafluoroethylene and carbon dioxide using ionic liquids

This report describes for the first time that the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide can be used as effective solvents in extractive distillation for the separation of an azeotropic mixture containing tetrafluoroethylene and carbon dioxide. The solubility of tetrafluoroethylene was measured at isothermal conditions (about 283–348 K) over a range in pressure from 0 to 1.4 MPa using a volumetric view cell. The solubility of carbon dioxide was measured at four isothermal conditions (about 283–348) K from 0 to 2.0 MPa using a gravimetric microbalance. The binary data were correlated and the feasibility of the extractive distillation process was modeled using ASPEN Plus® simulator. The tetrafluoroethylene and carbon dioxide were efficiently separated using a single absorption column and flash tank. The purity of the tetrafluoroethylene distillate from the top of the absorption column and the purity of the carbon dioxide from the flash tank exceed 99 mol%.

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► Separation of an azeotropic mixture containing TFE and CO2.
► Solubility of TFE in ionic liquids.
► Solubility of CO2 in ionic liquids.
► Extractive distillation process modeled using ASPEN Plus® simulator.