Group Contribution Prediction of Vapor Pressure with Statistical Associating Fluid Theory, Perturbed-Chain Statistical Associating Fluid Theory, and Elliott-Suresh-Donohue Equations of State

The group contribution methodology developed by Elliott and Natarajan has been extended to the statistical associating fluid theory (SAFT) and perturbed-chain statistical associating fluid theory (PC-SAFF) equations of state (EOS). Thermodynamic properties were correlated and predicted for a database of 878 compounds, including associating compounds. Association contributions were treated with Wertheim's theory. The database covers 19 chemical families including hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, amines, nitriles, thiols, sulfides, aldehydes, ketones, esters, ethers, halocarbons, and silicones. The present group contribution (GC) method was developed in two stages. Initially, pure component parameters of each EOS were obtained by matching their boiling temperatures at 10 or 760 mmHg and available GC estimates of solubility parameter and liquid density, while applying standard hydrogen-bonding parameters. Then, group contributions were regressed for the shape factor parameters of each EOS. Group contributions are presented for 84 first-order functional groups (FOG). Given the GC shape factors, the same GC estimates of solubility parameter and liquid density can be applied to estimate all EOS parameters on a GC basis. The resulting correlation enables three-parameter corresponding states, predictions without any experimental data. A byproduct of the correlation for equation of state parameters is the capability to predict vapor pressure only on the basis of chemical structure. This capability was evaluated by computing the vapor pressures at 10, 100, and 760 mmHg. On the basis of the present work, vapor pressure average absolute percent deviations (P AAD%) were 36% for Elliott-Suresh-Donohue (ESD) EOS, 65% for SAFT, 32% PC-SAFT. For comparison, the first- and second-order groups (FOG and SOG) provided by Tihic et al. (for simplified PC-SAFT) have been applied to similar to 650 nonassociating compounds. The resulting P AAD% were 53% for Tihic FOG and 42% for Tihic SOG. An alternative characterization of accuracy is the average absolute deviation (I Delta T|) between experimental and calculated saturated temperature. These were 8, 12, 8, 10, and 9 K for ESD, SAFT, PCSAFT, Tihic FOG, and Tihic SOG equations, respectively.