Brønsted酸性离子液体中的二甘醇脱水环化反应

首次报道了Brønsted酸性离子液体介质中的二甘醇的脱水环化反应，考察了不同的离子液体、离子液体/二甘醇摩尔比、反应温度和时间对反应的影响。结果表明，Brønsted酸性离子液体作为反应介质能够促进脱水环化反应的有效进行，且在离子液体1-(3-磺酸根丙基)-3-甲基咪唑硫酸氢盐(SPmim]HSO4)中，二甘醇的转化率和1,4-二氧六环的选择性更高。采用Hammett指示剂法测定了离子液体的酸度函数H0，其酸性强弱顺序为SPmim]HSO4 > Bmim]HSO4 > Amim]HSO4 > Hmim]BF4> Bmim]H2PO4 >Amim]H2PO4 > Hmim]Tsa，这与离子液体在脱水环化反应中的催化效果一致。当温度为170 ˚C，离子液体/二甘醇摩尔比为1:1时，二甘醇在SPmim]HSO4中反应2 h，转化率可达到97.0%，1,4-二氧六环的选择性为89.3%。

Brønsted Acidic Ionic Liquids as Efficient Reaction Medium for Cyclodehydration of Diethylene Glycol

Cyclodehydration of diethylene glycol using various Brønsted acidic ionic liquids as dual solvent‐catalysts was studied for the first time. Better results were obtained in the presence of 1‐butyl‐3‐methylimidazolium hydrogen sulfate (SPmim]HSO₄) than other Br?nsted acidic ionic liquids. The effects of reaction conditions such as reaction temperature, reaction time and molar ratio of ionic liquid/diethylene glycol were investigated. Good conversion rate and high selectivity were obtained in ionic liquid SPmim]HSO₄ under the optimum conditions. A Hammett method was used to determine the acidity order of these ionic liquids and the results were consistent with the catalytic activities observed in the cyclodehydration reaction.