Phase equilibria in ternary mixtures of the ionic liquid bmim[BF₄], (S)-naproxen and CO₂ to determine optimum regions for green processing

In order to optimize reaction and separation processes, knowledge of the phase behaviour of the system is of fundamental importance. In this contribution we present the solid–liquid and liquid–vapour equilibria of the ternary system 1-butyl-3-methylimidazolium tetrafluoroborate + (S)-naproxen + carbon dioxide. Five different samples were studied, with CO₂ concentrations ranging from 10 to 50 mol%, and pressure and temperature conditions of 1 to 14 MPa, and 310 to 370 K, respectively. It is shown that the amount of CO₂ influences not only the location of the homogeneous liquid phase region, but also the extension of the region in which it occurs. Based on the collected experimental data, optimum pressure and temperature conditions can be selected for the precipitation of (S)-naproxen from the ionic liquid in order to improve the efficiency of the separation.