Comprehensive Assessment of COSMO-SAC Models for Predictions of Fluid-Phase Equilibria

Two recent and fully open source COSMO-SAC models are assessed for the first time on the basis of very large experimental data sets. The model performance of COSMO-SAC 2010 and COSMO-SAC-dsp (2013) is studied for vapor-liquid equilibrium (VLE) and infinite dilution activity coefficient (γ_i^∞) predictions, and it is benchmarked with respect to the group contribution models UNIFAC and mod. UNIFAC(DO). For this purpose, binary mixture combinations of 2295 components are investigated. This leads to 10897 γ_i^∞ and 6940 VLE mixtures, which correspond to 29173 γ_i^∞ and 139921 VLE data points. The model performance is analyzed in terms of chemical families. A MATLAB program is provided for the interested reader to study the models in detail. The comprehensive assessment shows that there is a clear improvement from COSMO-SAC 2010 to COSMO-SAC-dsp and from UNIFAC to mod. UNIFAC(DO). The mean absolute deviation of γ_i^∞ predictions is reduced from 95% to 86% (COSMO-SAC 2010 to COSMO-SAC-dsp) and from 73% to 58% (UNIFAC to mod. UNIFAC(DO)). A combined mean absolute deviation is introduced to study the temperature, pressure, and vapor mole fraction errors of VLE predictions, and it is reduced from 4.77% to 4.63% (COSMO-SAC 2010 to COSMO-SAC-dsp) and from 4.47% to 3.51% (UNIFAC to mod. UNIFAC(DO)). Detailed error analyses show that the accuracy of COSMO-SAC models mainly depends on chemical family types, but not on the molecular size asymmetry or polarity. The present results may serve as a reference for the reliability of predictions with COSMO-SAC methods and provide direction for future developments.