Thermophysical and thermodynamic properties of ionic liquids over an extended pressure range: [bmim][NTf 2] and [hmim][NTf 2]

• Published in: The Journal of chemical thermodynamics Vol. 37; no. 9; pp. 888 - 899
• Main Authors: Gomes de Azevedo, R., Esperança, J.M.S.S., Szydlowski, J., Visak, Z.P., Pires, P.F., Guedes, H.J.R., Rebelo, L.P.N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2005; Elsevier
• Subjects: [bmim][NTf 2]; [hmim][NTf 2]; Chemical thermodynamics; Chemistry; Density; Elements, mineral and organic compounds; Exact sciences and technology; General and physical chemistry; Heat capacity; Ionic liquids; Pressure; Solutions; Solvation. Solvent properties; Speed of sound; Thermodynamic properties; [hmim][NTf 2]; Speed of sound; [bmim][NTf 2]; Heat capacity; Ionic liquids; Density; Pressure; [bmim][NTf2]; Physical properties; [hmim][NTf2]; Operating conditions; Sound velocity; Ionic liquid; Thermal properties; Pressure effect; Acoustic properties; Thermodynamic properties; Thermophysical properties
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2005.04.018

The current study focuses on 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [bmim][NTf 2], and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [hmim][NTf 2]. The objective is to study the influence of pressure as well as that of the cation’s alkyl chain length on several properties of this type of ionic liquids. Speed of propagation of ultrasound waves 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. Speed of sound measurements have been carried out in broad ranges of temperature (283 < T/K < 323) and pressure (0.1 < p/MPa < 150), using a non-intrusive microcell. Density measurements have been performed at broad ranges of temperature (298 < T/K < 333) and pressure (0.1 < p/MPa < 60) using a vibrating tube densimeter. The pressure dependence of heat capacities, which is generally mild, is highly dependent on the curvature of the temperature dependence of density.