CONICET | Buscador de Institutos y Recursos Humanos

Systems that formazeotropes or have relative volatilities close to 1.0 represent very energy andcapital intensive separations. Ionic liquids (ILs) can serve as nonvolatile entrainersto break azeotropes and enable a more energy efficient and environmentallyfriendly process. Here, six ILs have been investigated for their ability tobreak the ethanol + ethyl acetate azeotrope at 313.15 K. Three of the ILsinvestigated, 1-ethyl-3-methyl-imidazolium methanesulfonate [emim][MeSO3],1-ethyl-3-methyl-imidazolium methylsulfate [emim][MeSO4], and1-butyl-3-methyl-imidazolium trifluoromethanesulfonate [bmim][CF3SO3]are excellent entrainer candidates. In fact, the ethanol + ethyl acetate azeotropecan be broken over the entire composition range by adding as little as 2.5 molepercent of either [emim][MeSO3] or [emim][MeSO4] tothe binary organic mixture, which is less IL than what is needed to break any azeotropic system discussed in literature to date. Theother three ILs, 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide[emim][Tf2N], 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide[hmim][Tf2N], and 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [bmpyrr][Tf2N]are limited in their ability to break this azeotrope. The difference betweenthese two groups correlates with the infinite dilution activity coefficients ofthe ethyl acetate and ethanol in each of the ILs. Both polarity and hydrogen bondingare important in determining the preferential affinity of the ethanol for theILs, which raises the ethyl acetate/ethanol relative volatility. In addition, the experimental binary andternary vapor-liquid equilibrium data have been fit to the Non Random TwoLiquid (NRTL) activity coefficientmodel, which is able to predict and correlate the amount of IL needed to breakthe azeotrope in these ternary vapor-liquid equilibrium systems.

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