Three-phase crystallization (TPC) was introduced in this study to purify L-menthol from menthol enantiomer mixtures in consideration of the formation of solid solutions. TPC is a new separation technology, which combines melt crystallization and vaporization to result in the desired crystalline product from a liquid mixture along with the unwanted components vaporized via the three-phase transformation by reducing temperature and pressure. The three-phase transformation conditions for the liquid menthol enantiomer mixtures were determined based on the thermodynamic calculations to direct the TPC experiments. A new model was proposed based on the mass and energy balances in consideration of the formation of the solid solutions to predict the yield and purity of the final L-menthol product during TPC. The yield and purity obtained from the TPC experiments were compared with those predicted by the model.
Keywords: crystallization; menthol; purification; thermodynamics process; vaporization.