International Journal of Molecular Sciences, Vol.14, No.8, 16638-16655, 2013
Physico-Chemical Properties and Phase Behavior of the Ionic Liquid-beta-Cyclodextrin Complexes
The solubility of -cyclodextrin (-CD) in ionic liquids (ILs) and the activity coefficients at infinite dilution of more than 20 solutes (alkanes, aromatic hydrocarbons, alcohols) were measured in four chosen ionic liquids, their mixtures with -CD, and in the -CD at high temperatures from 338 to 398 K using the inverse gas chromatography. The intermolecular interactions, inclusion complexes and the possible increasing of the solubility of -CD in water using the IL are presented. The solubility of -CD in ten chosen hydrophobic ILs at the temperature T = 423 K was detected. The solid-liquid phase diagrams (SLE) of {IL (1) + -CD (2)} binary systems at the high mole fraction of the IL were measured for three systems (1-ethyl-3-methylimidazolium chloride, [EMIM][Cl], 1-ethyl-3-methylimidazolium bromide, [EMIM][Br]; and for 1-butyl-3-methylimidazolium chloride, [BMIM][Cl]). The eutectic points were determined at the high IL concentration for all binary systems. The intermolecular interaction and the possibility of inclusion complexes of the IL and/or solvents with -CD were discussed. The infrared spectroscopy, IR was used for the description of the intermolecular interactions in the (-CD + IL) systems. It was shown via the activity coefficients at infinite dilution results that the inclusion complexes are dependent on the temperature. The addition of -CD to the IL does not improve the selectivity of the separation of the aliphatics from aromatics.
Keywords:beta-cyclodextrin-ionic liquid systems;experimental solid-liquid equilibrium;activity coefficients at infinite dilution;intermolecular interactions