(180v) Prediction of Vapor-Liquid and Liquid-Liquid Equilibria of Mixtures From Peng-Robinson+COSMOSAC Equation of State

In this work we demonstrate successful vapor-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE) predictions for mixture fluids from a novel approach which combines cubic equations of state and first principle calculations. In particular, the energy parameter a(T,x) and volume parameter b(x) in Peng-Robinson equation of state (PR EOS) are respectively obtained from the result of first principle solvation calculations. As a consequence, the phase equilibrium of mixtures can be determined without using any experimental data. In our previous work, we have used this method to predict the critical properties, vapor pressure (as a function of temperature), the liquid phase density, and the complete phase diagram for pure substances. The same method has also been tested for vapor-liquid equilibrium of mixture fluids without using any binary interaction parameters.

In this work, we examined this method in describing LLE. In particular, the same set of parameters is used in describing VLE and LLE of pure and mixture fluids. Therefore, this method is capable to describe the phase diagram over a large temperature/pressure range, and the vapor-liquid-liquid equilibrium. The overall average deviation in LLE composition for 57 binary systems is found to be 6.16 %, similar to those from the modified UNIFAC and UNIFAC-LLE models.