摘要
以咪唑、氢氧化钾和1-乙基-3-甲基咪唑溴盐([Emim]Br)为原料,制得1-乙基-3-甲基咪唑咪唑盐([Emim]IM)。并考察了一系列咪唑类离子液体对催化碳酸乙烯酯(EC)与甲醇(MeOH)酯交换合成碳酸二甲酯(DMC)的影响。根据GC-MS分析,推测了反应机理及路径。结果表明:提高碱强度、增加阴离子半径或缩短咪唑阳离子烷基取代基碳链长度均有利于促进酯交换反应的进行。离子液体[Emim]IM具有阴、阳离子作用相对较弱、阴离子电负性较强的特性,将其用于催化EC与MeOH酯交换合成DMC。结果显示,[Emim]IM活性与甲醇钠相当。在反应温度为68℃,n(EC)∶n(MeOH)=1∶10,催化剂用量为反应原料总质量的0.3%时,1 min即达到反应平衡,DMC选择性为100%,收率为88.70%。随着温度升高、MeOH含量增加,DMC收率逐渐升高。即使在0℃下反应,[Emim]IM仍具有较好的催化活性,与商业化的最优1,3-二甲基咪唑碘盐([Mmim]I)离子液体催化效率相当。催化剂重复使用20次,DMC收率一直维持在88%~90%,展现出极佳的稳定性。
1-Ethyl-3-methylimidazole salt([Emim]IM)was prepared from imidazole,potassium hydroxide and 1-ethyl-3-methylimidazole bromide([Emim]Br).The effects of a series of imidazole ionic liquids on the transesterification of ethylene carbonate(EC)with methanol to synthesize dimethyl carbonate(DMC)were investigated.The reaction mechanism and route were proposed according to GC-MS analysis results.The results showed that increasing the base strength,increasing the anion radius or shortening the length of imidazole cationic alkyl substituent carbon chain were all beneficial to promote the transesterification.[Emim]IM had the characteristics of relatively weak anion and cation action and strong electronegativity of anions.It was used to catalyze synthesis of DMC.It was found that the catalytic activity of[Emim]IM was consistent with that of sodium methoxide.The reaction equilibrium was reached in 1 min,the selectivity and yield of DMC were 100%and 88.70%under the conditions of reaction temperature 68℃,catalyst amount 0.3%of the total mass of reaction raw material,n(EC)∶n(MeOH)=1∶10.With the increasing of reaction temperature and MeOH content,the yield of DMC increased gradually.[Emim]IM still exhibited better activity even if the reaction was carried out at 0℃,which was equivalent to that of commercial optimal ionic liquid 1,3-dimethylimidazole iodized salt([Mmim]I).After reused for 20 times,the yield of DMC was maintained at 88%~90%,showing that[Emim]IM had excellent stability.
作者
刘菊
石磊
陈飞
邓文杰
范家麒
许光文
LIU Ju;SHI Lei;CHEN Fei;DENG Wenjie;FAN Jiaqi;XU Guangwen(Key Laboratory on Resources Chemicals and Materials of Ministry of Education,Shenyang University of Chemical Technology,Shenyang 110142,Liaoning,China;Institute of Industrial Chemistry and Energy Technology,Shenyang University of Chemical Technology,Shenyang 110142,Liaoning,China)
出处
《精细化工》
EI
CAS
CSCD
北大核心
2020年第7期1438-1446,共9页
Fine Chemicals
基金
国家重点研发计划(2018YFB0604500)
国家自然科学基金(21303106)
辽宁省高等学校创新人才(LR2016015)。
关键词
碳酸二甲酯
碳酸乙烯酯
酯交换反应
离子液体
强碱性
催化技术
dimethyl carbonate
ethylene carbonate
transesterification
ionic liquids
strong alkalinity
catalysis technology
