Measurement and calculation of vapor-liquid equilibria for methanol + glycerol and ethanol + glycerol systems at 493-573 K

The vapor-liquid equilibria for methanol + glycerol and ethanol + glycerol systems were measured by a flow method at 493-573 K. The pressure conditions focused in this work were 3.03-11.02 MPa for methanol + glycerol system and 2.27-8.78 MPa for ethanol + glycerol system. The mole fractions of alcohol in vapor phase are close to unity at the pressures below 7.0 MPa for both systems. The pressures of liquid saturated lines of the liquid phase for methanol + glycerol and ethanol + glycerol systems are higher than that for the mixtures containing alcohol and biodiesel compound, methyl laurate or ethyl laurate. The experimental data in this work were modelled with Peng-Robinson equation of state. A conventional mixing rule and PRASOG model were adopted for the energy and size parameters in the equation of state. In the conventional mixing rule, two binary parameters were determined from the fitting to the vapor-liquid equilibrium data for each binary system. No fitting parameters were required for the PRASOG model. The calculated results by the conventional mixing rule are better than those by PRASOG in liquid phase. In vapor phase, the calculated results by PRASOG model are more accurate than those by the conventional mixing rule.