On the prediction of the vapor pressure of ionic liquids based on the principle of corresponding states

Abstract

The complexity, coupled with the high cost of the experimental determination of the vapor pressure of pure ionic liquids (ILs), which at moderate temperatures typically assume values below 0.1(Pa), make the development of predictive models for this important thermophysical property crucial. Employing 309 experimental data points belonging to 20 ILs of different classes and based on the truncated Pitzer expansion, in the current work a simple analytical expression has been developed for the prediction of the vapor pressure of pure ILs. In doing so, all the required critical properties have been estimated using a well-known group contribution method. Subsequently, utilizing the Clausius-Clapeyron equation, a very simple expression has been derived for the prediction of the enthalpy of vaporization of ILs. Total AARDs of 6.97% in the prediction of the available experimental vapor pressure data, and of 5.89% in the prediction of the molar heat of vaporization of 62 ILs demonstrate the satisfactory accuracy and predictive performance of the model developed in the current study. A thorough comparison has also been made with two previously published generalized expressions based on the zero-pressure liquid fugacity approach, through which the superiority of the proposed model has been established.