Evaluation of COSMO-RS for the prediction of LLE and VLE of alcohols + ionic liquids

The huge number of possible combinations of binary mixtures of alcohols and ionic liquids (ILs) make the exhaustive measurement of all these ystems impracticable requiring the use of a predictive model for their study. In this work, the predictive capability of COSMO-RS, a model based n unimolecular quantum chemistry calculations, was evaluated for the description of the liquid–liquid equilibria and the vapour–liquid equilibria f binary mixtures of alcohols and several imidazolium and pyridinium-based ILs. The effect of the ions and alcohols conformers on the quality of he predictions was assessed and the quantum chemical COSMO calculation at the BP/TZVP level derived from the lower energy conformations as adopted. Although a degradation in the liquid–liquid equilibria predictions with increasing size length of the alkyl chain of the alcohol or f the ionic liquid and with the short chain alcohol methanol in the vapour–liquid equilibria predictions were observed, in general a reasonable ualitative agreement between the model predictions and experimental data for a large combination of structural variations of both alcohols and Ls was obtained. COSMO-RS can thus be very useful in the scanning of the growing number of known ILs to find suitable candidates, or help esigning new ILs, for specific applications before extensive experimental measurements. 2007 Elsevier B.V. All rights reserved.