Vapor Liquid Equilibria of Binary Mixtures of 1-Butyl-3-methylimidazolium Triflate (C₄mimTfO) and Molecular Solvents: n-Alkyl Alcohols and Water

Abstract

Isobaric vapor liquid equilibria (VLE) of binary mixtures of the ionic liquid (IL) 1-butyl-3-methylimidazolium trifluoromethanesulfonate (CmimTfO) with either water or short chained n-alkyl alcohols (methanol, ethanol, propan-1-ol, and butan-1-ol) are described in this study. Two different microebulliometers and a classical VLE apparatus were compared and the VLEs were determined in the composition range 0.4 ≤ x(solvent) ≤ 1 at three different pressure levels ( p = 500 mbar, 700 mbar, and 1000 mbar). The experimental data were modeled using the soft-SAFT equation of state, which was able to accurately describe the nonideal behavior of these mixtures. The combined experimental-modeling results obtained contribute to establish the structure-property relationship between the CmimTfO and n-alkyl alcohol molecules and to infer about its influence on the phase behavior of these solvents.

Interplay of Different Moieties in the Binary System 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate/Water Studied by Raman Spectroscopy and Density Functional Theory Calculations

“…A change of the structure from IL-like to water-rich solutions upon complexation was reported; however, a theoretical interpretation of the molecular interactions was not presented. Most recently, the vapor–liquid equilibria of binary mixtures of 1-butyl-3-methylimidazolium triflate (C 4 mimTfO) with various solvents such as methanol, ethanol, propan-1-ol, and butan-1-ol were reported . The structure–property relationship between the C 4 mimTfO and n -alkyl alcohol was obtained by a combination of experiments and theoretical modeling, which provided a better understanding of the phase behavior of these solvents.…”

Ion Pairs of 1-Butyl-3-Methylimidazolium Triflate Do Not Dissociate in Propan-1-ol: A Vibrational Spectroscopic Viewpoint

“…The resulting maxima and minima of these polynomials are all located around x(PrOH) = 0.66, hence pointing to the 2:1 stoichiometry again. Interestingly, this molar ratio also stood out in a previous study, in which the vapor-liquid equilibrium (VLE) of the binary mixtures was studied [11]. In that work, the VLE data were fitted using a modified Raoult's law, and the activity coefficients were derived.…”

“…Hence, conclusions about the general behavior of imidazolium ILs in alcohols can hardly be drawn at this point. For completeness, the macroscopic properties and thermodynamics of alcohol-IL solutions have already been studied for longer chain lengths, and interesting correlations could be identified there [10][11][12][13]. Deducing information about the molecular scale solely from the measurement of macroscopic parameters, however, bears the danger of over-interpreting the data.…”

“…We have recently shown that TfO ILs represent interesting model systems for spectroscopic studies as the TfO − anion exhibits a single configuration, hence reducing the complexity of the spectra [14], e.g., in contrast to the common NTf 2 − ILs [15]. Moreover, we have chosen this combination of an IL and an alcohol as the thermodynamic behavior of their binary mixtures is well understood [11].…”

“…For this purpose, the band areas over characteristic spectral windows in the excess spectra were calculated. Panel (d) shows the profile of the activity coefficient derived from vapor-liquid equilibrium (VLE) data[11] for comparison.…”