Abstract:

The main problems in the synthesis of vitamin E are large dosage and much loss of the catalyst, as well as difficulty to recycle the catalyst. There also exist serious environmental problems caused by contamination of water with the catalysts in the washing process. Several ionic liquids were synthesized to catalyze the synthesis of vitamin E. [(C₂H₅)₃NH]Cl/ZnCl₂ ionic liquid had the best catalytic performance. The inorganic anion in the ionic liquid played the major catalytic role, and the quaternary ammonium cation could form hydrogen bonds with isophytol easily, which enabled directed condensation reaction between isophytol and trimethylhydroquinone. The structure and acidity of [(C₂H₅)₃NH]Cl/ZnCl₂ ionic liquid were characterized by FT-IR, and its effect on production of vitamin E was investigated. With the increase of mole fraction of ZnCl₂, the ionic liquid showed stronger acidity. When the mole fraction of ZnCl₂ in ionic liquid was 0.66, yield of vitamin E could reach 87.4% under catalysis of [(C₂H₅)₃NH]Cl/ZnCl₂. The ionic liquid could be reused 5 times without significant decrease in catalytic performance.

Key words: Lewis acid, ionic liquid, vitamin E, synthesis, catalyst

摘要：

维生素E合成过程中催化剂用量大、损失严重且不能循环使用, 后处理过程产生大量废液导致严重的环境问题。实验合成了几种Lewis酸性离子液体, 并应用于维生素E合成。研究发现, [(C₂H₅)₃NH]Cl/ZnCl₂离子液体催化合成维生素E效果最好, 该离子液体中无机阴离子起主要催化作用, 季铵阳离子易与异植物醇的羟基形成氢键, 能使异植物醇与主环发生定向缩合反应。采用FT-IR研究了[(C₂H₅)₃NH]Cl/ZnCl₂离子液体结构和酸性, 并系统考察了其对维生素E合成的影响。随着ZnCl₂摩尔分数增加, 离子液体的Lewis酸性增强。在ZnCl₂摩尔分数为0.66的[(C₂H₅)₃NH]Cl/ZnCl₂离子液体催化作用下, 维生素E的产率可达到87.4%, 该离子液体重复使用5次, 催化性能没有明显下降。

关键词: Lewis酸, 离子液体, 维生素E, 合成, 催化剂