Influence of the pressure, temperature, cation and anion on the volumetric properties of ionic liquids: New experimental values for two salts

Experimental densities of two ionic liquids (ILs), 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4C1Pyrr][NTf2]) and 1-(2-methoxyethyl)-1-methyl-pyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([C1OC2C1Pyrr][(C2F5)3PF3]), were measured over a broad temperature and pressure range, i.e. from (278.15 to 398.15) K and up to 120 MPa, respectively. The isobaric thermal expansion coefficient of the two ILs was determined from these measurements finding a non-monotonous behaviour over the entire pressure range. The density values obtained were used to analyse the prediction ability of the methods proposed by Gardas and Coutinho and by Jacquemin et al. Furthermore, the influence of the cation and anion structure on the densities and the isothermal compressibilities was analyzed, also considering literature values.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Experimental densities of 2 ILs from (278.15 to 398.15) K up to 120 MPa are provided. ► The anion κT sequence is [NTf2]− > [C(CN)3]− > [C2SO4]− > [C1SO4]− > [PF6] − ≈ [BF4] −. ► Gardas-Coutinho and Jacquemin et al. predictive methods were analysed for κT and αp. ► Minima in αp (T) curves were found for all the isobars in agreement with recent works.