Separation of olefins from FCC naphtha by propylene carbonate: Influence of critical component structure and correlation of ternary LLE thermodynamic models

The separation of olefin from aromatics and sulfides by using propylene carbonate (PC) solvent was studied by the ternary liquid–liquid equilibrium (LLE) of PC + aromatics/sulfide +olefin. The effects of aromatic, sulfide, and olefin structures were investigated by a combination of experiments and quantum chemical calculations. The aromatics and sulfides without side chains were easier to dissolve in PC. Efficient olefin separation was observed because the side chain did not change the positive charge enrichment region of the molecule, and instead increased the steric space when combined with solvent molecules. The olefin separation factor S in the separation of 1-hexene and thiophene is 12.96, which is 1.64 times higher than that in the separation of 1-hexene and 3-methylthiophene. In addition, the binary parameters between the PC and fluid catalytic cracking (FCC) naphtha components for NRTL and UNIQUAC thermodynamic models were obtained using the ternary LLE data to make up for the blank in Aspen simulation for the separation of FCC naphtha by PC solvent. Then, the correlation of NRTL and UNIQUAC models was compared, which the root-mean square deviation (RMSD) of these two models is lower than 0.0043. The NRTL model shows a better correlation with experimental data.