(Liquid + liquid) equilibria of methanol + isooctane + methylcyclohexane + ethylbenzene quaternary system at T = 303.15 K

Abstract

Tie line data of {methanol + isooctane + methylcyclohexane}, {methanol + ethylbenzene + methylcyclohexane}, and {methanol + ethylbenzene + isooctane} ternary systems were obtained at T = 303.15 K. A quaternary system {methanol + isooctane + methylcyclohexane + ethylbenzene} was also studied at the same temperature. In order to obtain the binodal surface of the quaternary system, four quaternary sectional planes with several methylcyclohexane/isooctane ratios were studied. Experimental results show that the binodal surface in the solid diagram is small and that the highest ethylbenzene mass fraction values beyond which only one phase is present for the methanol-rich phase and hydrocarbon-rich one, respectively, are: 0.0783 and 0.0864 for P1, 0.0791 and 0.0906 for P2, 0.0798 and 0.0805 for P3, 0.0812 and 0.0935 for P4. So, if this quaternary system contains the correct methanol and hydrocarbons concentrations, this blend can be used as a reformulated gasoline because no phase separation should be observed. The distribution of ethylbenzene between both phases was also analysed. Ternary experimental results were correlated with the UNIQUAC and NRTL equation, and predicted with the original UNIFAC group contribution method. The equilibrium data of the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. The UNIQUAC and NRTL equations are more accurate than the UNIFAC method for the ternary systems studied here, because this last model predicts an immiscibility region larger than the experimentally observed in the methanol-rich phase. The UNIQUAC equation fitted to the experimental data is more accurate than the UNIFAC method for this quaternary system.