Application of CP-PC-SAFT and PC-SAFT for Simultaneous Prediction of LLE and High-Pressure VLE with Universal k12 Values: II. Systems of Gases and Aliphatic Hydrocarbons with O-, S-, and N-Heterocyclic Compounds

Abstract

This work continues a series of studies examining the reliability of critical point-based perturbed-chain statistical association fluid theory (CP-PC-SAFT) and PC-SAFT EoS models with universal k₁₂ values (0.023 and 0.017, respectively) for predicting vapor–liquid equilibrium (VLE) and liquid–liquid equilibrium (LLE) in systems of gases and aliphatic hydrocarbons with substituted aromatics and heterocyclic compounds. This time, systems of pyrrole, furan, tetrahydrofuran, thiophene, 1,4-dioxane, tetrahydrothiophene, γ-valerolactone, 2,3-benzofuran, and sulfolane are considered. It is found that PC-SAFT is usually more accurate than CP-PC-SAFT in modeling vapor pressures but inferior in estimating densities and sound velocities. The relation of the latter result to the additional fictitious critical point predicted by PC-SAFT is discussed. PC-SAFT is typically less accurate than CP-PC-SAFT in predicting the high-pressure VLE in the systems of gases. Due to rigorous obedience of pure compounds' T_c and P_c, CP-PC-SAFT has an obvious advantage in predicting the critical VL data. At the same time, PC-SAFT is somewhat more accurate in estimating VLE in butane and butene isomer systems. The CP-PC-SAFT predictions for LLE in systems of n-alkanes with pyrrole and γ-valerolactone continue the patterns found in the previously discussed cases. In particular, it accurately estimates upper critical solution temperatures (UCSTs) and compositions of heterocyclic compound-rich phases but deviates from the data of n-alkane-rich ones. PC-SAFT underestimates UCSTs and yields poorer results for both LLE phases. The considered models comparably predict binary LLE in n-alkane–sulfolane systems. CP-PC-SAFT is generally superior to PC-SAFT in evaluating LLE in the considered aliphatic–aromatic–heterocyclic ternary systems. Based on the findings of this study, it can be concluded that both models with the universal k₁₂ values can be used for preliminary evaluation of inaccessible data on phase equilibria in a large number of systems including gases and aliphatic hydrocarbons with heterocyclic compounds. CP-PC-SAFT may be more reliable in estimating LLE and high-pressure VLE, while PC-SAFT may be more accurate in predicting low-pressure VLE data.