功能化离子液体萃取分离甘氨酸

Extraction of glycine using functional ionic liquids

以结构和功能可设计的离子液体为萃取剂,通过液–液萃取分离甘氨酸,考察了不同结构的咪唑和季铵离子液体萃取分离甘氨酸的效果,研究了pH值、萃取温度、萃取时间、甘氨酸初始浓度和二环己基-18-冠醚-6(DCH18C6)浓度等工艺参数对甘氨酸分配系数和萃取率的影响,考察了胆碱双三氟甲磺酰亚胺盐([N1112(OH)][NTf2])的循环利用性,通过FT-IR和量子化学计算探究了[N1112(OH)][NTf2]和DCH18C6萃取甘氨酸的机理。结果表明,[N1112(OH)][NTf2]的萃取率高于其它离子液体,加入DCH18C6可提高萃取率,[N1112(OH)][NTf2]–DCH18C6复配体系中,甘氨酸萃取率可达85.4%。在最优条件下,分配系数和萃取率分别为10.9和94.4%。离子液体循环利用5次,甘氨酸萃取率仍保持90%。[N1112(OH)][NTf2],DCH18C6和甘氨酸之间存在的强氢键作用为萃取分离的关键。因此,[N1112(OH)][NTF2]-DCH18C6可有效萃取分离甘氨酸,为甘氨酸的绿色分离新工艺奠定基础。

Glycine, also known as aminoacetic acid, is the amino acid with the simplest structure and is widely used in food, medicine and pesticides. It is an important chemical raw material and intermediate. Chloroacetic acid ammoniation is one of the main approaches to produce glycine. However, it needs a large amount of toxic and volatile methanol to separate glycine from the ammonium chloride byproduct, with low separation efficiency and theformation of a large amount of waste liquor which is environmental non-benign. Ionic liquids, as a novel green media, have shown great potential in the field of extraction and separation owing to their advantages of low vapor pressure, good thermal stability, adjustable structures and properties. In this work, designable ionic liquids(ILs) were proposed as the extractant to separate glycine. The effects of the ILs structure on the extraction efficiency were studied using imidazolium and quaternary ammonium ILs. The effects of pH, extraction temperature, time, and the initial concentrations of glycine and dicyclohexyl-18-crown-6(DCH18 C6) on the partition coefficient and extraction efficiency were investigated. The IL system was recycled and reused for glycine separation. The extraction mechanism was revealed by FT-IR and quantum chemical calculation. The results showed that choline bis(trifluoromethylsulfonyl)imide([N1112(OH)][NTf2]) had best extraction efficiency. The addition of DCH18 C6 to the system could enhance the extraction efficiency, and that of the [N1112(OH)][NTf2]–DCH18 C6 system could reach 85.4%. Under the optimal conditions, the partition coefficient and extraction efficiency reached 10.9 and 94.4%, respectively. The extraction efficiency remained 90% after the IL was recycled 5 times. The strong hydrogen bonds between [N1112(OH)][NTf2], DCH18 C6 and glycine played an important role in the extraction of glycine. Thus, the system of [N1112(OH)][NTf2]–DCH18 C6 was effective in separating glycine from water and could be an alternative extractant in the industrial glycine purification process.