Synthesis Of Benzo-15-crown-5 Derivatives For Extractive Separation Of Lithium Isotopes

Effective separation of lithium isotopes ⁶Li and ⁷Li is of strategic value for the development of nuclear industry,which is attracting widespread attention in recent years.The lithium-amalgam method was once established for efficient separation of lithium isotopes to an industrial scale.However,the employment of a large amount of highly toxic mercury seriously threatened environmental safety and the human health.The lithium-amalgam method has thus been abandoned.Due to the selective coordination ability of crown ether compounds to the alkali and alkaline earth metals,combined with advantages of liquid-liquid extraction,such as good selectivity,mature process and equipments,easy to scale up and automatically control,it is promising to use crown ether as extractants for lithium isotopes separation in liquid-liquid system.In this study,a series of crown ether compounds including benzo-15-crown-5,4-nitrobenzo-15-crown-5,4-aminobenzo-15-crown-5,and 4-tert-butylbenzo-15-crown-5were designed and synthesized.Gas chromatograph,infrared spectroscopy,nuclear magnetic resonance and other analytical methods were used for confirming the structures of the obtained products.The performance for the separation of lithium isotopes in liquid-liquid extraction system was investigated,highlighting the effects of substituent,anion,solvent,temperature,phase ratio,etc.The result showed that the crown ether compounds with electron-donating amino group had stronger ability for lithium isotopes separation.Finally,an optimal system for lithium isotopes separation in liquid-liquid extraction was established,and the highest separation factor 1.041±0.001could be achieved when using 4-aminobenzo-15-crown-5 as extractant,dissolved in dichloroform?organic phase?,for contact with pH=1 CF₃COOLi aqueous solution at0?for 60 min.The research of this thesis can provide theoretical and experimental supports for the development of lithium isotopes separation techniques.