Two- and Three-Liquid Phase Equilibria in Industrial Mixed-Solvent Electrolyte Solutions
An accurate representation of demixing in mixed-solvent electrolyte solutions remains one of the challenging research areas in chemical engineering. The simulation and design of industrial extraction processes involving electrolytes depends heavily on the availability of models that can describe the influence of ions on the phase behaviour: The presence of charged species in a mixed-solvent solution dramatically influences the phase distribution of a solute between the liquid phases. Moreover, the unexpected occurrence of three liquid phases can have a detrimental influence on the performance of an extraction process and should be anticipated. Therefore, a good understanding of the relevant phase behaviour is essential.
In the extraction process of caprolactam, the monomer of nylon-6, concentrated mixed-solvent solutions of ammonium sulfate exist. In this project a model had to be developed, that is able to represent and predict the demixing behaviour of water + caprolactam + solvent + ammonium sulfate solutions. Because of the lack of relevant experimental data in literature, experiments were to be carried out to provide the equilibrium data required to test and to adjust the model.