Pressure, isotope, and water co-solvent effects in liquid-liquid equilibria of (ionic liquid plus alcohol) systems

Najdanovic-Visak, Vesna and Esperanca, JMSS and Rebelo, LPN and da Ponte, MN and Guedes, HJR and Seddon, Kenneth R. and de Sousa, HC and Szydlowski, J (2003) Pressure, isotope, and water co-solvent effects in liquid-liquid equilibria of (ionic liquid plus alcohol) systems. Journal of Physical Chemistry B, 107 (46). pp. 12797-12807. ISSN 1520-6106

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Liquid-liquid phase splitting in ternary mixtures that contain a room-temperature ionic liquid and an alcohol aqueous solution-namely, [bmim] [PF6] + ethanol + water and [bmim] [NTf2] + 2-methylpropanol + water-is studied. Experimental cloud-point temperatures were obtained up to pressures of 400 bar, using a He-Ne laser light-scattering technique. Although pressurization favors mutual miscibility in the presence of high concentrations of alcohols, the contrary occurs in water-rich solutions. Both ternary mixtures exhibit a very pronounced water-alcohol co-solvent effect. Solvent isotope effects are also investigated. Phase diagrams are discussed using a phenomenological approach based on a "polymer-like" G(E) model coupled with the statistical-mechanical theory of isotope effects. The combined effect of a red shift of -15 cm(-1) for the O-H deformation mode of ethanol with a blue shift of +35 cm(-1) for the O-H stretching mode, both of which occurring after liquid infinite dilution in the ionic liquid, rationalizes the observed isotope effect in the phase diagram. Predicted excess enthalpy (H-E) values are inferred from the model parameters. Furthermore, using the Prigogine-Defay equation, an estimation of the excess volumes (V-E) is obtained.

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Journal Article
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Journal of Physical Chemistry B
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22 Mar 2013 14:18
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20 Sep 2023 00:28