(204a) Prediction of Vapor Pressure and Critical Properties for Non-Electrolyte Organic Compounds from PR+Cosmosac Eos

Thermodynamic properties, such as vapor pressures, are important information for both process design and optimization in chemical industry and estimation of gas/particle partitioning of organic compounds in environmental applications. The PR+COSMOSAC EOS has been developed to estimate the energy and volume parameters of the PR EOS from quantum mechanical and COSMO solvation calculations with the only input of the molecular structure. This method has been shown to provide reasonable prediction for vapor pressures of pure substances and fluid phase equilibrium of mixtures without the issue of missing parameters. In this study, the temperature-dependence of the dispersion contribution was revised to improve the accuracy in predicting vapor pressure of pure substances, especially at temperatures lower than the normal boiling temperature of the substance. Furthermore, a hydrogen-bonding correction term was newly introduced for amines, accompanying with two new dispersion parameters. The revised model has a total of 16 global parameters and three parameters for each element (one atomic radius and two dispersion parameters). All the dispersion parameters involved in the dispersion contribution were re-optimized by regressing vapor pressures of a few selected pure substances. A total of 1125 pure substances are included to investigate the accuracy of the revised model. The overall average logarithmic deviation in pressure (ALD-P) is 0.195 from the revised model which is better than that from the original model (ALD-P = 0.241). The accuracy of the revised PR+COSMOSAC EOS in predicting critical properties is underway. In general, the PR+COSMOSAC EOS could be useful when no experimental data is available.