Predict Thermodynamic Models Of The Ionic Liquids System And Their Applications In The Chemical Separation Science

Due to the special thermodynamic properties, ionic liquids have beenwidely used as "green solvents" and are playing an increasingly important rolein separation science including extractions, gas separations. It's possible totailor the suitable ionic liquids for a specific separation task. But it is no senseto choose the best one for a given system through massive experiments, whichare time-consuming and very expensive. The predictive thermodynamicmodels can predict the thermodynamic properties of the unknown system. Ifthe predictive ability and accuracy of models are reliable, these models areeasy to obtain the thermodynamic data. These data have important theoreticalsignificance for the practical application.In this work, COSMO-RS model and UNIFAC model were used topredict the selectivity and capacity of the different ionic liquids for thehexane/benzene, heptanes/benzene, cyclohexane/benzene and ethanol/watersystem. The consistency between the predicted results from the COSMO-RSand UNIFAC models and experimental data reported in the literature waschecked. The results showed that UNIFAC model was more accurate and COSMO-RS model was qualitatively consistent with the experimental data.By fitting the literature data, the most complete UNIFAC parameter wasestablished and the model application was extended. This work obtained therelationship between molecular structure of ionic liquids and separationperformance, to help guide the selection of suitable separating agents for polarand non-polar systems in separation science. Meanwhile, this paper carried outthe liquid-liquid extraction experiments for ionic liquids at finite dilution. Theresults proved that the calculation results of the COSMO-RS model can beextended to the finite dilution case, and the predicted result was accurate.The COSMO-RS model, UNIFAC model and UNIFAC-FV model wereused to predict the solubility of CO₂in different ionic liquids. Combined withthe experimental data reported in the literature, the accuracy of the models waschecked and the law of the ionic liquids absorbing CO₂was summarized.Meanwhile, this work carried out the experimental measuring the solubility ofCO₂and the CO/CO₂mixed gas in the ionic liquid at the low temperature. Theexperimental results were fitted to prove that the model at low temperaturesstill had a good predictability, while the experimental results showed that thelower temperature could improve the solubility and selectivity of CO₂.