Liquid-Liquid Equilibria of the Methanol plus Hexane plus Methylcyclohexane plus Toluene Quaternary System at T=303.15 K

Tie line data of the {methanol + methylcyclohexane + hexane} and {methanol + toluene + hexane} ternary systems were obtained at T = 303.15 K, while data for {methanol + toluene + methylcyclohexane} were taken from the literature. A quaternary system {methanol + methylcyclohexane + hexane + toluene} was also studied at the same temperature. In order to obtain the binodal surface of the quaternary system, four quaternary sectional planes with several hexane/methylcyclohexane ratios were studied. Experimental results show that the binodal surface in the solid diagram is small and that the highest toluene mass fraction values, beyond which only one phase is present for the methanol-rich phase and hydrocarbon-rich one, respectively, are: 0.052 and 0.064 for P1, 0.068 and 0.052 for P2, 0.047 and 0.107 for P3, 0.029 and 0.030 for P4. So, if this quaternary system contains the correct methanol and hydrocarbon concentrations, this blend can be used as a reformulated gasoline, because no phase separation should be observed. Ternary experimental results were correlated with the UNIQUAC and NRTL equations. The equilibrium data for the three ternary systems were used to determine interaction parameters for the UNIQUAC equation. The NRTL equation is more accurate than the UNIQUAC for the ternary systems studied here. The UNIQUAC equation fitted to the experimental data is more accurate than the UNIFAC method for this quaternary system.