Phase behavior of CO2 in room-temperature ionic liquid 1-ethyl-3-ethylimidazolium acetate.

Carbon dioxide solubility (vapor-liquid equilibria: VLE) in an ionic liquid, 1-ethyl-3-ethylimidazolium acetate ([eeim][Ac]) was measured using a gravimetric microbalance at four isotherms (about 283, 298, 323, and 348 K) up to about 2 MPa. An equation-of-state (EOS) model was used to analyze the VLE data and has predicted vapor-liquid-liquid equilibria (VLLE: or liquid-liquid separations) in CO(2)-rich solutions. The VLLE prediction was confirmed experimentally using a volumetric method and likely the liquid-liquid equilibria will intersect with the solid-liquid equilibria such that no lower critical solution temperature can exist and the binary system may be classified as Type III phase behavior.