Correlation Modelfor Solid Solubility In Supercritical Fluids

Solubility data are essential for the design and optimization of supercritical fluid extraction processes. However, the amount of experimental data currently available is limited; besides, an extensive amount of data is needed due to the strong dependence of solubility on density, temperature, and pressure. By using models to correlate the solid solubility in supercritical fluids, the problems mentioned above can be solved. Also it can save money for industries through models instead of experiments.In this study, a new model with three temperature-independent parameters was developed to provide the correlations of solid solubility in supercritical fluids. This model, based partly on the regular solution theory and the Wilson's local composition concept, correlated the solubility data of 24 solid compounds in supercritical carbon dioxide. The results show that the new model can correlate well the solid solubility in supercritical carbon dioxide.A further simplification for the model parameters was attempted, and a model with two parameters was obtained. This new model with two parameters was then used to correlate well the solid solubility. The results demonstrate that the model with two parameters does well in correlation of solid solubility, and the results are close to the model with three parameters.The new model with three parameters also used in correlation of solubility of 3 solids (naphthalene, phenanthrene and benzoic acid) in supercritical ethane and fluoroform. The model performed well, and it demonstrates that the new model with three parameters is a feasible model in correlation of solid solubility in supercritical fluids.Then, the new model was compared with Chrastil's density-based modeling, Su-Chen's solubility parameter model and Valderrama-Alvarez equation of state approach. The results show that the new model is better than Su-Chen solubility parameter model, close to Chrastil's density-based model and as good as Valderrama-Alvarez equation of state model which is more complicated.