(214a) Ionic Liquids As Entrainers for Azeotropic Distillation Systems

Nowadays, the great energy consumptions are one of the main workhorses that the process industries are addressing in the XXI century. It is well known that the most important consumptions are due to separation processes. Besides, it is common that the more complex operation, the greater energy consumption, which is especially true for the separations of azeotropic mixtures. Azeotropes are quite usual in chemical industries appearing in solvent, gasoline or monomer industries, making impossible the separation of individual components of the mixtures by conventional distillation. This is overcome by using, on one hand, material separation agents in operations such as adsorption or liquid-liquid extraction, or by adding an entrainer to a distillation column (azeotropic or extractive distillation). This work is focussed on the application of recently developed solvents, called ionic liquids, as entrainers for the separation of azeotropic mixtures. Ionic liquids are molten salts with a fusion point below (or near) ambient conditions. They are composed by an anion and an organic cation, so they can be chosen in order to tune their physical properties (tailor made solvents).

The application of ionic liquids for azeotropic separations is being under research, mainly by experimental measurements of liquid-liquid equilibria compositions. On the other hand it is also under research the development of accurate models for the correlation and prediction of their properties. In this way, new prediction methods, such as COSMO-RS and COSMO-SAC, have emerged in the last years, being successfully applied to model ionic liquid mixtures. They are not based in traditional group contribution approach, but they are based in the Conductor-like Screening Model (COSMO) (a solvation model) where molecule geometry and energies are computed by means of quantum chemistry software (i.e. GAMESS).  In addition, some current commercial process simulation tools offer COSMO based thermodynamic models as property packages to be used in flowsheet simulations. It means that the design of ionic liquids can be carried out with quantum chemistry software and then translated to commercial software, such as Aspen Plus, to perform technical and economic evaluations of azeotropic separations using ionic liquids as entrainers. So this work is structured as follows: First a short introduction to ionic liquids and COSMO based model is shown, then the methodology employed to couple quantum calculations with Aspen Plus is described. Third, a comparative evaluation of ionic liquids with a conventional entrainer is done, and finally the main conclusion of the work are infered