| Summary: | 碩士 === 長庚大學 === 化工與材料工程學系 === 98 === Distillative crystallization (DC), also called distillative freezing (DF), is a new separation technique which combines distillation and crystallization to produce pure crystals. In principle, DC is operated at a triple-point condition, in which the liquid mixture is simultaneously vaporized and crystallized due to the three-phase equilibrium.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 no impurities are adhered on the crystal surfaces at the end of DC.
Due to the close-boiling points, it is very difficult to separate enantiomers by distillation. DC is applied in this study to separate the enantiomers, including lactic acid, mandelic acid and ibuprofen. The experimental results show that it is very difficult to purify S-(+)-lactic acid by DC as the mixture contains water, leading to the non-ideal solution behavior. As the polymerization occurs between hydroxyl group and carboxyl group among mandelic acid, it is also difficult to separate R-(-)-mandelic acid by DC. However, DC can be applied to separate and purify S-(+)-ibuprofen by seeding the S-(+)-ibuprofen crystals.
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