TY - JOUR

T1 - Pressure, isotope, and water co-solvent effects in liquid-liquid equilibria of (ionic liquid plus alcohol) systems

AU - Najdanovic-Visak, Vesna

AU - Esperanca, JMSS

AU - Rebelo, LPN

AU - da Ponte, MN

AU - Guedes, HJR

AU - Seddon, Kenneth R.

AU - de Sousa, HC

AU - Szydlowski, J

PY - 2003/11/20

Y1 - 2003/11/20

N2 - 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.

AB - 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.

KW - BUTAN-1-OL

KW - POLYSTYRENE

KW - SOLVENTS

KW - ETHANOL

KW - PHASE-EQUILIBRIA

KW - BEHAVIOR

KW - THERMODYNAMIC PROPERTIES

KW - 1-N-BUTYL-3-METHYLIMIDAZOLIUM HEXAFLUOROPHOSPHATE

KW - VAPOR-PRESSURE

KW - DEPENDENCE

U2 - 10.1021/jp034576x

DO - 10.1021/jp034576x

M3 - Journal article

VL - 107

SP - 12797

EP - 12807

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 46

ER -