(377a) Prediction of Critical Properties and Vapor Pressure from PR+Cosmosac Eos Based on Different Quantum Mechanical Calculations

Authors: 
Hsieh, C. M., National Central University
Liang, H. H., National Central University
Thermodynamic properties are important information for chemical engineering process design and optimization. The PR+COSMOSAC EOS has been developed to estimate the energy and volume parameters of the Peng-Robinson 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 performance of the PR+COSMOSAC EOS is examined based on three sets of quantum mechanical calculations from three different software packages (VWN-BP/DNP/DMol3, b3lyp/6-31G(d,p)-cosmo/Gaussian09, GGA-BP/TZP/ADF) and one set of semi-empirical calculations (PM6/Gaussian09). All model parameters are re-optimized for each quantum chemical calculation method and the prediction accuracy is evaluated using the vapor pressure, sublimation pressure, normal boiling temperature, and critical properties for 1085 non-electrolyte organic compounds. It is found that the prediction results based on ADF are slightly accurate compared to those based on other quantum chemical calculations in most of thermodynamic properties investigated. Although prediction results based on semi-empirical PM6 are the least accurate, it still has great potential for large molecules because the other DFT calculation methods require more computational effort.