Prediction, fine tuning, and temperature extrapolation of a vapor liquid equilibrium using COSMOtherm

As our entry for the third industrial fluid property simulation challenge, the COSMO-RS method in its COSMOtherm implementation has been used to predict the vapor liquid equilibrium (VLE) of ethanol and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) at 343.13 K. The absolute prediction of the VLE without any system specific adjustments already yields a reasonable agreement with the experimental data provided for the binary mixture at 283.17 K. Because the special emphasis of the this challenge is state conditions transferability, we also considered two special ways of fine tuning to the experimental data provided for this VLE at 283.17 K. The first way of fine tuning was by fitting of correction charges, the second was by adjustment of a single van der Waals (vdW) interaction parameter. Since vdW parameters used in COSMOtherm are the weakest part of the COSMO-RS parameterization, the fine tuning of the vdW parameters is considered as physically most plausible. Therefore our final prediction of the VLE ethanol and HFC-227ea at 343.13 K is based on the vdW fine tuning.