Transesterification reactions are common in the production of some important chemicals, such as biodiesel and mono- and diglycerides. Knowledge of the phase equilibrium conditions of the reactive mixture is essential to explore possible operating conditions for the reactor and the downstream separation process. In this work, liquidliquid and vaporliquidliquid equilibrium data have been measured for the ternary system methyl oleatemethanolglycerol, at temperatures between 313 and 393 K. The group contribution with association equation of state (GCA-EOS) and the A-UNIFAC model were applied to represent the phase equilibria of this ternary system. Self-association in glycerol and methanol and cross-association with methyl esters were taken into account.

Recent experimental studies on noncatalytic transesterification have shown that high reaction rates, which justify the commercial application of this process, can be obtained if the operating conditions are above the critical pressure and temperature of methanol. Although it is generally agreed that temperatures of >550 K and high methanol/oil ratios are required to obtain high conversions and high reaction rates, there is disagreement in the literature regarding the operating pressure, the assumed phase conditions, the use of co-solvents, and the justification of the sudden increase of rate of reaction with temperature. In the present work, the reactor phase transitions are directly observed in a double-windowed cylindrical reactor and the conversion to methyl esters is measured. From direct observations and the modeling of the phase behavior, a better understanding of the supercritical methanol transesterification process is obtained.