Bisimidazolium Tungstate Ionic Liquids: Highly Efficient Catalysts for the Synthesis of Linear Organic Carbonates by the Reaction of Ethylene Carbonate with Alcohols

• Published in: Catalysis letters 2023, Vol.153 (1), p.62-73
• Main Authors: Wu, Shi, Huang, Jie, Wang, Yingting, Tao, Huilin, Yu, Zhongliang, Zhang, Yongfan
• Format: Article
• Language: English
• Subjects: Alcohols; Carbonates; Catalysis; Catalysts; Catalytic activity; Chemical synthesis; Chemistry; Chemistry and Materials Science; Ethanol; Ethylene; Industrial Chemistry/Chemical Engineering; Ionic liquids; Ions; NMR spectroscopy; Nuclear magnetic resonance spectroscopy; Organometallic Chemistry; Physical Chemistry; Synergistic effect
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-022-03969-6

A series of bisimidazolium tungstate ionic liquids were synthesized and applied to catalyze the reaction of ethylene carbonate (EC) with alcohols. A detailed investigation was carried out on the relationship between catalyst structures and catalytic activities. The result showed that 1-butyl-3-methyl-bisimidazolium tungstate ([Bmim] 2 WO 4 ) containing double C 2 –H in bisimidazolium and WO 4 2− had more effectively catalytic performance than other bisimidazolium tungstate and conventional imidazolium salt (OAc − , Cl − , Br − ). Under the optimized conditions of 1:15 molar ratio of EC and ethanol, 5 mol% [Bmim] 2 WO 4 , 85 °C and 0.5 h, the yield of diethyl carbonate (DEC) was nearly 100%. The detailed DFT calculations and NMR spectroscopy indicated that the high catalytic activity of [Bmim] 2 WO 4 was not only because the strong nucleophilic ability of WO 4 2− could activate ethanol, but also the special structure of double C 2 –H in bisimidazolium could cooperatively activate EC. The reaction was catalyzed by synergistic effect in double C 2 –H and WO 4 2− of [Bmim] 2 WO 4 . In addition, [Bmim] 2 WO 4 could be used seven times without significant loss of catalytic activity. Graphical Abstract