Improvement to PR+COSMOSAC EOS for Predicting the Vapor Pressure of Nonelectrolyte Organic Solids and Liquids

Abstract

The PR+COSMOSAC EOS has been shown to be able to utilize quantum mechanical calculation results to predict the thermodynamic properties and fluid phase equilibrium with the only input of molecular structure. In this study, two modifications are introduced to further improve its accuracy in predicting vapor pressures of pure fluids. The average logarithmic deviation in vapor pressure (ALD-P) from the triple-point temperature to the normal boiling temperature for 1124 substances is reduced from 0.321 to 0.256 (or from 109.4% to 80.2%) (a reduction of 20% in ALD-P), while ALD-P from the normal boiling temperature to the critical temperature remains similar. The average absolute deviation (AAD) in the normal boiling temperature for 1405 substances is reduced from 16.32 to 14.25 K. Furthermore, its accuracy in predicting the critical properties and sublimation pressures (1140 substances) of pure fluids and vapor–liquid equilibrium of binary mixtures (1118 systems) is investigated and compared with the previous versions of PR+COSMOSAC. The accuracy of the revised PR+COSMOSAC EOS is generally improved, and the effect of each modification on the accuracy is discussed. This model is particularly useful when no experimental data are available.