Research On The Vapor-liquid Equilibrium Of The Mixture Of Methyl Palmitate And Methyl Stearate At Reduced Pressures

The phase equilibrium data of fatty esters are very important in the design,modeling, simulation and optimization of the production and separation of biodiesel.Although lots of studies in biodiesel production have been reported, there are fewarticles focusing on measuring and predicting the vapor-liquid equilibrium forcomponents made of biodiesel.Based on the principle of vapor and liquid circulation for equilibrium and therequirement for the vacuum system, a modified Othmer still was well connected witha vacuum system. The pressure was ranged from100Pa to10kPa, which belonged tothe high vacuum system in the distillation region. The device for measuring thevapor-liquid equilibrium data at reduced pressures was established and proved to bereliable.Methyl palmitate and methyl stearate, the main components of biodiesel, wereselected as the research objects. Their boiling temperature was high at atmosphericpressure. The vapor-liquid equilibrium of methyl palmitate-methyl stearate systemwas systematically studied at reduced pressures (0.1kPa、1kPa、5kPa and10kPa),which enriched the basic data for biodiesel. The data were satisfied thethermodynamic consistency by Herington method.The thermodynamic properties of methyl palmitate and methyl stearate wereanalyzed. The Wilson model and NRTL model were correlated with the experimentaldata. The model parameters were obtained by the nonlinear least squares method. Thegroup contribution model (UNIFAC model), Wilson model and NRTL model wereused to calculate the VLE data. The calculated data were compared with theexperimental data. The results showed that the UNIFAC model was poor to predict theVLE data, the maximum relative deviations of the vapor composition (y1) and thetemperature (T) were40%and1.86%, respectively. The average relative deviationsof the vapor composition (y1) and the temperature (T) were11.61%and1.07%,respectively. The Wilson model and NRTL model were better than the UNIFACmodel. At1kPa、5kPa and10kPa, the maximum and were6.52%and0.40%, respectively. The () and () were3.73%and0.22%, respectively. Thecalculated data were coincide with the experimental data. At0.1kPa, the results were not good as those at1kPa,5kPa and10kPa. The maximum y1and Twere17.80%�'�0.41%, respectively. The (y1) and (T) were4.98%and0.19%,respectively. In general, the Wilson model and NRTL model were both well correlated withthe experimental VLE data, and the correlated results were getting poorer with the pressuredecreasing.The microwave VLE and batch distillation devices were established. Themicrowave energy effect on the vapor-liquid equilibrium and batch distillation of theethanol-benzene system were studied preliminarily.