Estimation of the Densities of Ionic Liquids Using a Group Contribution Method

A simple and general atomic group contribution method is developed for the prediction of liquid densities of ionic liquids as a function of temperature and pressure. Available literature data are used as a comprehensive database, consisting of 25 850 data points for a vast variety of ionic liquid families, and within wide ranges of pressures (0.10–300 MPa) and temperatures (217.58–473.15 K). In developing the group contribution model, the idea was to propose a simple equational form, with straightforward groups which will be easy to use, yet be general and predictive for a vast range of ionic liquids at the same time. To do this, as functional groups, we have chosen atoms and a few small and simple groups. This feature makes the model rather capable and global for a wide range of ionic liquids. Despite the generality and simplicity of the model, and by considering that the only necessary information required to use this method is the chemical structure of the ionic liquid, a good accuracy (AARD% of 0.95%) was achieved. This makes the proposed model a reliable method for prediction of the densities of ionic liquids whenever experimental data are not available.