新型环己亚胺类离子液体的合成及其催化酯化反应性能

利用环己亚胺与1，3-丙烷磺酸内酯生成的1-(3-磺丙基)环己亚胺盐，合成了2种新型Br?nsted酸性离子液体1-(3-丙磺基) 环己亚胺硫酸氢盐（HMIPS]HSO4）和1-(3-丙磺基) 环己亚胺对甲苯磺酸盐（HMIPS]OTs）。采用1H NMR、FT-IR、LC-ESI-MS及DSC-TG等方法对其进行了表征。结果表明，所合成的HMIPS]HSO4和HMIPS]OTs是一类新型的Br?nsted酸性离子液体。该类型离子液体含有环己亚胺7元环，分解温度高于260℃，其水溶液的pH值与相同浓度的硫酸水溶液的相近，具有较强的Br?nsted酸性。最后考察了所合成的新型离子液体对柠檬酸和正丁醇酯化反应的催化性能，并与传统咪唑类离子液体进行了对比。结果显示，所合成的新型离子液体具有良好的催化活性，HMIPS]HSO4为催化剂时，在n(柠檬酸):n(正丁醇):n(HMIPS]HSO4)＝5:1:0.02，110-130℃和回流反应2 h的条件下，柠檬酸的转化率为98.3%，柠檬酸三丁酯的收率可达97.5%。而传统的咪唑离子液体MIMPS]HSO4为催化剂时，柠檬酸的转化率和柠檬酸三丁酯的收率分别为95.8%和94.7%。HMIPS]HSO4催化剂在重复使用10次后催化活性未见明显下降。

Synthesis and catalysis performance in esterification of novel hexamethyleneiminium-based ionic liquid

Two novel Br?nsted acidic ionic liquids,1-(3-sulfopropyl)hexamethyleneiminium hydrogen sulfate(HSO4)and 1-(3-sulfopropyl)hexamethyleneiminium tosilate(OTs)were prepared using hexamethyleneimine and 1,3-propane sultone,etc.They were characterized by 1H NMR,FT-IR,LC-ESI-MS and DSC-TG.The results proved that the ionic liquids synthesized contain a hexamethyleneimine with seven member ring and possess stronger Br?nsted acidity,decomposition temperayure are over 260 ℃ and the acidity of aqueous solution of HSO4 is similar to that of aqueous solution with the same concentration of sulfuric acid.Their catalytic activities for the esterification of citric acid with n-butanol were examined and compared with the imidazolium-based ionic liquids.The results showed that HSO4 exhibits excellent catalytic activity,the conversion of citric acid was 98.3% and the yield of tributyl citrate reached 97.5% under the conditions of n(citric acid)∶n(n-butyl alcohol)∶n(HSO4)=5∶1∶0.02,110—130 ℃ and reflux 2 h.Furthermore,The activity of HSO4 catalyst reused at least 10 times was not significantly decreased.