Superposition of Liquid-Liquid and Solid-Liquid Equilibria of Linear and Branched Molecules: Ternary systems

Oiling-out is an unwanted phenomenon during crystallization processes since it influences the product properties negatively and should, therefore, be avoided. To reduce the time of process development, thermodynamic modeling is usually applied. In the course of fitting model parameters, thermodynamic data of the present molecules are required. In case of branched molecules these thermodynamic data are often not available. To overcome this limitation, a methodology, which allows for the prediction of liquid-liquid equilibria (LLE) of binary systems containing branched molecules was developed recently. The developed methodology was applied in this contribution in order to predict the superposition of ternary LLE and solid-liquid equilibria (SLE) of the system n-hexadecane + 2,2,4,4,6,8,8-heptamethylnonane + ethanol. To consider the influence of the molecular architecture on phase equilibria, the lattice cluster theory in combination with the chemical association lattice model was applied. The prediction of the ternary phase equilibria was based on the binary subsystems. It could be shown that the ternary LLE and the ternary SLE can be predicted in very good agreement with experimental data using the same set of model parameters. All model parameters were fitted using only binary LLE data of linear alkanes dissolved in ethanol. Neither binary experimental data of the branched alkane nor ternary ones were used for parameter fitting. (Graph Presented).