Thermodynamic properties of some ionic liquids using a simple equation of state

In this work, we have used a simple equation of state (EoS) to predict the density and other thermodynamic properties such as isobaric expansion coefficient, α_P , isothermal compressibility, κ_T, and internal pressure, P_i, for nine ionic liquids including trihexyl (tetradecyl) phosphonium chloride ((C₆H₁₃)₃P(C₁₄H₂₉)]Cl]), trihexyl (tetradecyl) phosphonium acetate ((C₆H₁₃)₃P(C₁₄H₂₉)]Ac]), trihexyl (tetradecyl) phosphonium bis {(trifluoromethyl) sulfonyl} amide ((C₆H₁₃)₃P(C₁₄H₂₉)]NTf₂]), 1-butyl-3-methylimidazolium bis {(trifluoromethyl) sulfonyl} amide (bmim]NTf₂]), 1-hexyl-3-methylimidazolium bis {(trifluoromethyl) sulfonyl} amide (hmim]NTf₂]), 1-butyl-3-methylimidazolium tetrafluoroborate (bmim]BF₄]), 1-butyl-3-octylimidazolium tetrafluoroborate (omim]BF₄]), 1-butyl-3-octylimidazolium hexafluorophosphate (omim]PF₆]), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmim]PF₆]) at different temperatures and pressures. A wide comparison with experimental and literature data has been made. The results show that this EoS can be used to reproduce and predict different thermodynamic properties of ionic liquids within experimental errors.