Reverse-Phase Ternary Phase Diagram for Commercial Biodiesel - Glycerol - Methanol

In the present work, the liquid-liquid ternary phase diagram for a commercial biodiesel/glycerol/methanol system was experimentally determined at 20 °C. Proper knowledge of the phase equilibrium behavior of these systems is required for the design of efficient separation processes. As is common in biodiesel/glycerol/methanol systems, a given mixture generally separates into two liquid phases. The top phase is generally rich in biodiesel while the bottom phase consists of glycerol. Due to these components respective solubility parameters, most of the methanol is found in the glycerol phase. At certain compositions, however, the orientation of the two liquid phases reverse themselves, resulting in the biodiesel phase on the bottom and the glycerol phase on the top. The validity of the experimental data was checked through an Othmer-Tobias plot. The Othmer-Tobias plot was also used to predict the plait point, which was determined to be 60.2% biodiesel, 39.1% methanol, and 0.7% glycerol (by mass).