Entropy-Based Solubility Parameter-Translated Peng–Robinson Equation of State (eSPT-PR EoS)

Peng–Robinson equation of state (PR EoS) has good prediction accuracy for phase diagrams of pure substances or mixtures, but liquid density, especially for high polar substances, is known to be ~20% lower value compared with experimental data at standard atmospheric temperature and pressure (SATP) conditions. To overcome this issue, translation via entropy-based solubility parameter (eSP) Peng–Robinson EoS (eSPT-PR EoS) is proposed in this work. The technique uses eSP for the liquid phase at SATP conditions and correlates the ideal value and a constant C for each substance as a correction. As a result, the C value can be linearly correlated with critical compressibility factor (ZC). Finally, the liquid density was improved and gave an average relative deviation (ARD) value of 4.2% for the generally used 27 chemicals selected at SATP condition. Furthermore, critical density was also improved and gave ARD values of 3.9% compared with the original PR EoS of 21.8%. Thus, a universal calculation method based on PR EoS was developed for improving liquid density representation with the eSPT-PR EoS.