LLE of Methanol-Methylcyclohexane-Isooctane-Benzene Quaternary System

A quaternary system {methanol + methylcyclohexane + isooctane + benzene} was studied at T = 303.15 K. Only after all ternary equilibria data were determined experimentally, the quaternary binodal surface could be characterized fully. For this purpose, tie line data of {methanol + methylcyclohexane + benzene} ternary systems were obtained at the same temperature, while data for {methanol + isooctane+ benzene}, and {methanol + + isooctane + methylcyclohexane} were taken from literature. Experimental results show that the binodal surface with four quaternary sectional planes P1,P2,P3,P4 with several methylcyclohexane/isooctane in the solid diagram is small and that the highest benzene mass fraction values beyond which only one phase is present for the methanol-rich phase and hydrocarbon-rich one, respectively, are: 0.046 and 0.053 for P1, 0.053 and 0.057 for P2, 0.055 and 0.049 for P3, 0.034 and 0.041 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 benzene between both phases was also analysed. Ternary experimental results were correlated with the UNIQUAC and NRTL equation.The UNIQUAC equation is more accurate than the NRTL equation for the ternary systems studied here. The equilibria data of the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. The UNIQUAC equation fitted to the experimental data is more accurate than the UNIFAC method for this quaternary system. The main reason for this is that F is fit in the size of the quaternary binodal surface.