Density prediction of pyridinium, imidazolium, pyrrolidinium, ammonium, and phosphonium-based ionic liquids using an equation of state

A group contribution equation of state (EOS) has already been developed to calculate the density of imidazolium-based ionic liquids (ILs) with good accuracy. IL was divided into several groups, i.e. cation head, anion, and alkyls. In order to further prove the widely applicability of the model and the group segmentation method for IL, the densities of 1-alkyl-3-methylimidazolium salts containing metal of group III and a large number of pyridinium, pyrrolidinium, ammonium, and phosphonium-based pure ILs were correlated/predicted in this work. First, a total of 222 data points of density for 27 pure ILs, were regressed to obtain the new soft-core diameter and dispersive energy parameters. Then, 908 density data points of 42 pure ILs from 278.15 to 393.15 K and up to 65.01 MPa were predicted on the basis of the obtained parameters. The results indicated that the EOS could well capture the effects of temperature, pressure and alkyl types on density. Finally, the EOS was further evaluated to predict the density data for binary IL mixtures without introducing any new parameters, and testified the extensive applicability of the EOS with average relative deviation of 0.70%.