Study On The Phase Equilibria Of Methyl Ester Related Biodiesel Systems

Faced with the energy crisis and environmental pollution, biodiesel with its excellent reproducibility has attracted more and more attention. The phase equilibrium data related to biodiesel are very important to the design of reactors and separation devices and the blend of the mixed fuel.In this study, the isobaric vapor-liquid equilibrium(VLE) data for seven binary systems n-undecane + methyl dodecanoate, n-dodecane + methyl dodecanoate, ntridecane + methyl dodecanoate, n-tetradecane + methyl dodecanoate, n-tetradecane + methyl laurate, n-pentadecane + methyl myristate and n-hexadecane + methyl myristate were measured at 5.00 kPa by an Rose still. All the experimental data were checked by Herington area method and were found to be thermodynamiclly consistent. The measured data were correlated by NRTL equation, UNIQUAC equation and Wilson equation, respectively. The corresponding interactional parameters for the three models were obtained.The liquid-liquid equilibrium data of eleven ternary systems fatty acid methyl ester(methyl laurate / methyl myristate / methyl palmitate / methyl stearate) + ethanol + glycerol, alkane(n-undecane / n-dodecane / n-tridecane / n-tetradecane) + methyl laurate + methanol, alkane(n-tetradecane / n-pentadecane / n-hexedecane) + methyl laurate + methanol and quaternary system n-dodecane + n-tetradecane + methyl laurate + methanol at(303.15, 318.15 and 333.15) K and atmospheric pressure were measured. The eleven ternary liquid-liquid equilibrium data were correlated by NRTL model. The obtained binary interactional parameters were used to calculate the liquid-liquid equilibrium data for the quaternary system n-dodecane + n-tetradecane + methyl laurate + methanol. The calculated results agree well with the experimental data.The experimental ternary liquid-liquid equilibrium data were fitted to UNIFACDortmund model and the binary parameters for the pair of UNIFAC groups(CH2COOCH3OH and CH3OH-CH2) were obtained. Then UNIFAC-Dortmund model with these group interactional parameters were used to estimate the liquid-liquid equilibrium data of five ternary systems n-pentadecane + methyl laurate + methanol, n-hexadecane + methyl laurate + methanol, n-undecane + methyl myristate + methanol, n-dodecane + methyl myristate + methanol and n-tridecane + methyl myristate + methanol, which have not been determined. These estimated data were correlated by NRTL model and the binary parameters were obtained.The liquild-liquid equilibrium data of three systems alkane mixtures + methyl laurate + methanol, alkane mixtures + methyl myristate + methanol and alkane mixtures + fatty acid methyl ester mixtures + methanol at 303.15 K were calculated by NRTL and UNIFAC-Dortmund model. The calculated data by the two models agree very well. The data are useful for the mixing use of biodiesel, diesel and methanol.