A new insight into pure and water-saturated quaternary phosphonium-based carboxylate ionic liquids: Density, heat capacity, ionic conductivity, thermogravimetric analysis, thermal conductivity and viscosity

K. Oster*, P. Goodrich, J. Jacquemin, C. Hardacre, A. P.C. Ribeiro, A. Elsinawi

*Corresponding author for this work

Research output: Contribution to journalArticle

16 Citations (Scopus)


Ionic Liquids (ILs) are task specific materials with tunable properties which may be applied as heat transfer fluids (HTFs) due to their characteristic properties including low vapour pressure, wide liquid range and high thermal stability. This study provides an evaluation of their potential as HTFs from both their physicochemical properties as well as an economic comparison with commonly used materials. The paper presents the thermophysical properties (density, isobaric heat capacity, ionic conductivity, viscosity, thermal stability by TGA, thermal conductivity) and their thermodynamic derivatives (isobaric thermal expansion coefficient, excess molar volume, excess molar heat capacity), as well as the Walden rule of ionicity for a range of hydrophobic ILs based on the trihexyl(tetradecyl)phosphonium, ([P14,6,6,6]+), cation. The ionic liquids studied are trihexyl(tetradecyl)phosphonium acetate ([AcO]), butanoate ([ButO]), hexanoate ([HexO]), octanoate ([OctO]), and decanoate ([DecO]), as well as their mixtures with water. It was shown that investigated systems are highly promising materials as HTFs, especially ILs + water mixtures, which may be the solution for many engineering issues.

Original languageEnglish
Pages (from-to)97-111
Number of pages15
JournalJournal of Chemical Thermodynamics
Early online date13 Feb 2018
Publication statusPublished - 01 Jun 2018



  • Heat transfer fluids
  • Ionic liquid water mixtures
  • Ionic liquids
  • Physical properties

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