咪唑型室温离子液体介质中甲苯氯甲基化反应的研究

Blanc Reaction of Toluene in 1-Alkyl-3-methylimidazolium Bromide Ionic Liquids

在溴化N,N-二烷基咪唑型室温离子液体反应介质中,尝试了甲苯、多聚甲醛和氯化氢气体的氯甲基化反应。以[C5mim]Br为催化剂,考察了反应温度、反应时间和离子液体用量对反应转化率的影响,获得的较佳反应条件为:反应温度65℃,反应时间10h,离子液体催化剂用量为甲苯物质的量的4%,在此条件下甲苯的转化率为82.6%,单氯甲基化选择性为100%。随着溴化N,N-二烷基咪唑型室温离子液体烷基链的增长,甲苯转化率有所提高;以溴化N-十二烷基-3-甲基咪唑离子液体为催化剂时,甲苯转化率可达90%,单氯甲基化选择性为100%。反应结束后产物与离子液体自动分层,便于分离。离子液体催化剂重复使用6次,甲苯转化率保持恒定。

Blanc reaction of toluene with formaldehyde and hydrogen chloride was carried out in 1- alkyl-3-methylimidazolium bromide ionic liquids. The effects of temperature, reaction time and the amount of ionic liquids were investigated by using [ C5mim] Br ionic liquid （alkyl = pentyl ） as catalyst. The proper reaction conditions were reaction temperature 65 ℃, reaction time 10 h and n （ ionic liquid） ：n （toluene） = 4：100. Under these conditions, the conversion of toluene was 82.6% and the selectivity to mono-chloromethylation was 100%. It was also found that length of alkyl of the cations affects the conversion of toluene. The longer the length of alkyl,the higher the conversion of toluene. With 1-dodecyl-3-methylimidazolium bromide as catalyst,the conversion of toluene was 90% and the selectivity to mono-chloromethylation was 100%. The product was easy to separate from the ionic liquid phase due to their immiscibility. The ionic liquid can be reused in almost constant yield for six times.