(57c) Purification of S-1-Phenylethanol from the Enantiomer Mixture By Three-Phase Crystallization

1-Phenylethanol is one of the most commonly available chiral alcohols. As each enantiomer has its distinct odor, it is essential to obtain the enantiopure 1-phenylethanol from the racemic mixture for application in food ingredients and in the cosmetics. The enantiopure 1-phenylethanol is also an important precursor in the synthesis of other flavors, fragrances, and pharmaceuticals. Three-phase crystallization (TPC) is a new separation technique which combines melt crystallization and vaporization. Basically, TPC is operated at a triple-point condition, in which the liquid is simultaneously vaporized and crystallized due to the three-phase transformation. In essence, the process is continued until the liquid phase is completely eliminated and only the pure solid crystals remain in the feed. Thus, crystal washing is not required since only pure solid crystals remain in the feed and no impurities are adhered on the crystal surfaces at the end of TPC. In the previous research, TPC has been successfully applied to separate p-xylene from the mixed xylenes by Shiau et al. (2008, 2018). TPC is introduced in this work for chiral purification of S-1-phenylethanol from the enantiomer mixture. The operating pressure for the three-phase transformation during the TPC cooling process is determined based on the thermodynamic calculations. A model based on the mass and energy balances is proposed to determine the product yield and enantiomeric purity of S-1-phenylethanol for TPC. The experimental yield and purity of the final product are compared with those predicted by the model.

References;

1. Shiau, L. D. “Purification of styrene from a styrene/ethylbenzene mixture by stripping crystallization”, Eng. Chem. Res, 2018, 57, p6759-6765.
2. Shiau, L. D., Wen, C. C. and Lin, B. S. “Separation of p-xylene from the multicomponent xylene system by stripping crystallization”, AIChE Journal, 2008, 54(1), p337-342.