(335r) High-Efficiency Synthesis of Cyclic Carbonates From Epoxides and CO2 Over Immoblized Hydroxyl Ionic Liquid Catalyst

High-Efficiency Synthesis of Cyclic Carbonates from Epoxides and CO₂ over Immoblized Hydroxyl Ionic Liquid Catalyst

Wei-Li Dai¹, Chak-Tong Au², Shuang-Feng Yin^1,*

(¹ College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China; ²Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China)

*Corresponding author. Shuang-Feng Yin, Tel/ Fax: 86-731-88821171, E-mail: sf_yin@hnu.edu.cn(S.F. Yin).

The fixation of CO₂ into valuable compounds has attracted much attention. Of the most interesting is to synthesize five-membered cyclic carbonates by the coupling of CO₂ with terminal epoxide. Many catalysts have been reported for the coupling reaction, including quaternary ammonium salts, metal oxide, molecular sieve, and so on. Due to the disadvantages related to product separation using homogeneous catalysts, heterogeneous catalysts have attracted much attention. In the past ten years, ionic liquid attracted much interest in their uses as catalysts for synthesizing cyclic carbonates. As a strategy for the fabrication of stable and reusable heterogeneous catalysts, ionic liquids were immobilized on solid materials such as MgO, SiO₂, and MCM-41. However, catalyst reusability is far from satisfaction.

Herein, we report the fabrication and characterization of hydroxyl ionic liquid grafted onto cross-linked divinylbenzene polymer (PDVB-HEIMBr). It was evaluated as a catalyst for the synthesis of cyclic carbonates from CO₂ and epoxides without the use of any co-catalyst and organic solvent. The catalyst shows good performance across a wide range of epoxides, giving almost quantitative yield of carbonates. The effects of reaction temperature, time and initial CO₂pressure on product yield were investigated. It is suggested that the synergetic effect between the bromide ions and the hydroxyl groups facilitates the coupling reaction. Furthermore, the PDVB-HEIMBr catalyst shows excellent stability and reusability. From the viewpoint of industrial application, the catalystis very attractive because of its simplicity, activity, stability, and reusability.

Scheme 1