The structure of acidified ionic liquid [emim]BF₄ and its catalytic performance in the reaction for 4,4′-MDC synthesis

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• 作者：Xinqiang Zhao ; Liyan Hu ; Yanlou Geng ; Yanji Wang
• 关键词：[emim]BF₄ ionic liquid ; Structure ; Methyl N-phenyl carbamate ; Formaldehyde ; Methylene diphenyl dimethylcarbamate
• 刊名：Journal of Molecular Catalysis A ; Chemical
• 出版年：2007
• 期刊代码：57_13811169
• 类别：ch
• 出版时间：17 October 2007
• 卷：276
• 期：1-2
• 页码：168-173
• 文件大小：582 K

摘要

Acidified ionic liquid [emim]BF₄ (H⁺[emim]BF₄) was prepared and its structure was ascertained using ¹H NMR analysis and experimental verification. It was found that the cation of H⁺[emim]BF₄ is composed of a central immidazole molecule surrounded by a water layer in which excessive HBF₄ molecules are dissolved. H⁺[emim]BF₄ showed high catalytic performance in the condensation of methyl N-phenyl carbamate (MPC) and formaldehyde (HCHO) to methylene diphenyl dimethylcarbamate (4,4′-MDC). Under the suitable reaction conditions of 70 °C, molar ratio of MPC to HCHO = 4, weight ratio of H⁺[emim]BF₄ to MPC = 4, and reaction time 1.5 h, the yield and selectivity of 4,4′-MDC attained 71.7%and 71.9%, respectively. Besides, H⁺[emim]BF₄ could be reused for 4 runs after being treated by ultrasonic extraction with CHCl₃ and no significant catalytic activity loss was observed after the second run.