High-Pressure and High-Temperature Density Data, DerivativeProperties, and Group Contribution Models Applied for 1-Methyl-3-octylimidazolium Trifluoromethanesulfonate, 1-Butyl-1-methylpyrrolidinium Dicyanamide, and 1-Ethyl-3-methylimidazolium Acetate Ionic Liquids

In this work, high-pressure and high-temperaturedensity data for 1-methyl-3-octylimidazolium trifluoromethanesul-fonate [C8C1Im][OTf], 1-butyl-1-methylpyrrolidinium dicyana-mide [C4C1Pyr][DCA], and 1-ethyl-3-methylimidazolium acetate[C2C1Im][C1COO] ionic liquids (ILs) were determined atP=(0.2 to 100.0) MPa andT= (298.15 to 398.15) K with steps of 25K, by using a tube vibration method. It was observed that densityincreases in the following sequence: [C4C1Pyr][DCA] <[C2C1Im][C1COO] < [C8C1Im][OTf], according to theirintermolecular interactions. These experimental density datawere correlated by using the Tammann-Tait equation, with theaverage absolute relative deviation less than 0.0090% for[C8C1Im][OTf] and [C2C1Im][C1COO] and less than 0.0220% for [C4C1Pyr][DCA]. From these data, the following derivativethermodynamic properties were calculated: isothermal compressibility (Kappa T), isobaric expansivity (alpha p), thermal pressure coefficient(gamma v), and internal pressure (Pi). Furthermore, the densities of the studied ILs were predicted using six different group contributionmodels. The best agreement between experimental and calculated data was obtained when the model proposed by Paduszynski andDomanska was applied