(191p) Revision and Extension of the COSMO-SAC Model

In this work two modifications are introduced to the COSMO-SAC model for a better description of non-ideality of liquid phase. First, the electrostatic interactions are made to be temperature dependent. This modification is proven to be crucial for the description of miscible gap of non-hydrogen-bonding system over a wide range of temperatures. Second, the strengths hydrogen-bonding interaction are considered to be dependent on both the screening charge density and the type of atoms involved in the hydrogen bond. This is achieved by introducing two sigma-profiles for hydrogen bonding elements. We demonstrate the accuracy in predictions of vapor-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE) for mixture fluids from the revised COSMO-SAC model is improved significantly. The overall RMS error of liquid phase compositions in LLE predictions of 278 binary mixtures from the new model is 0.1047, which is 30% lower than that from the original COSMO-SAC (0.1446), 10% lower from that of UNIFAC-LLE (0.1161), and comparable to that from the modified UNIFAC model (0.1048). The accuracy in VLE predictions is improved by about 10%. The average absolute relative deviation in total pressure at a fixed liquid composition is 6.54% and the overall average absolute deviation in vapor phase composition is 2.57% for 1338 binary mixtures (which are 7.25% and 2.83% from the original model).