Phase equilibrium thermodynamic modeling for the methanol+fatty acid methyl ester systems at high temperatures and pressures

Phase equilibrium plays an important role in studying biodiesel production. This work aimed to find a general model to calculate and predict the phase equilibrium compositions of methanol+fatty acid methyl ester (FAME) systems which are the product system of biodiesel production with supercritical methanol. Three systems including methanol+methyl laurate (C12), methanol+methyl myristate (C14) and methanol+methyl oleate (C18) were investigated in the temperature range from 493-573 K and pressure range from 2.16-11.45 MPa and the experimental data in literature were correlated with three kinds of equations of state (EOS, i.e., PR, SRK and CPA) combining with two kinds of mixing rules (i.e., AS mixing rule and quadratic mixing rule). The correlation result shows that PR-AS and SRK-AS models can accurately describe the phase equilibria of methanol+FAMEs with the least correlation deviations compared with other models. In addition, the two models can lead to high accuracy in predicting the phase equilibria compositions of methanol+FAMEs at high temperatures and pressures.