TY - JOUR

T1 - Thermophysical and thermodynamic properties of 1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate over an extended pressure range

AU - de Azevedo, RG

AU - Esperanca, JMSS

AU - Najdanovic-Visak, Vesna

AU - Visak, ZP

AU - Guedes, HJR

AU - da Ponte, MN

AU - Rebelo, LPN

PY - 2005

Y1 - 2005

N2 - The current study focuses on 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim] [BF4], and 1-butyl3-methylimidazolium hexafluorophosphate, [bmim] [PF6]. The objective is to study the influence of pressure as well as that of the anion on several properties of this type of ionic liquid. The speed of sound and densities in pure ionic liquids (ILs) as a function of temperature and pressure have been determined. Several other thermodynamic properties such as compressibilities, expansivities, and heat capacities have been obtained. To the best of our knowledge, this research comprises both the first speed of sound data and the first evaluation of heat capacities at high pressures for ILs. Speed of sound measurements have been carried out in broad ranges of temperature (283 < T/K < 323) and pressure (0.1 < p/MPa < 150), sometimes inside the metastable liquid region using a nonintrusive microcell. The T-P melting line of [bmim] [PF6] has also been determined by an acoustic method. Density measurements have been performed for broad ranges of temperature (298 < T/K < 333) and pressure (0.1 < p/MPa < 60) using a vibrating tube densimeter. The pressure dependence of the heat capacities, which is generally mild, is found to be highly dependent on the curvature of the temperature dependence of the density.

AB - The current study focuses on 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim] [BF4], and 1-butyl3-methylimidazolium hexafluorophosphate, [bmim] [PF6]. The objective is to study the influence of pressure as well as that of the anion on several properties of this type of ionic liquid. The speed of sound and densities in pure ionic liquids (ILs) as a function of temperature and pressure have been determined. Several other thermodynamic properties such as compressibilities, expansivities, and heat capacities have been obtained. To the best of our knowledge, this research comprises both the first speed of sound data and the first evaluation of heat capacities at high pressures for ILs. Speed of sound measurements have been carried out in broad ranges of temperature (283 < T/K < 323) and pressure (0.1 < p/MPa < 150), sometimes inside the metastable liquid region using a nonintrusive microcell. The T-P melting line of [bmim] [PF6] has also been determined by an acoustic method. Density measurements have been performed for broad ranges of temperature (298 < T/K < 333) and pressure (0.1 < p/MPa < 60) using a vibrating tube densimeter. The pressure dependence of the heat capacities, which is generally mild, is found to be highly dependent on the curvature of the temperature dependence of the density.

KW - WATER

KW - SOUND

KW - MIXTURES

KW - TEMPERATURE IONIC LIQUIDS

KW - IMIDAZOLIUM

KW - MPA

KW - COMPRESSIBILITIES

KW - SPEED

KW - SALTS

U2 - 10.1021/je049534w

DO - 10.1021/je049534w

M3 - Journal article

VL - 50

SP - 997

EP - 1008

JO - Journal of Chemical and Engineering Data

JF - Journal of Chemical and Engineering Data

SN - 0021-9568

IS - 3

ER -