Abstract:

Immobilized SO₃H-functionalized ionic liquids were prepared by three different pathways and their catalytic performance was evaluated in the condensation reaction for the synthesis of 4, 4'-methylenedianiline (4, 4'-MDA) from aniline and HCHO, and the reusability of the immobilized ionic liquids were investigated. The result showed that ionic liquid loading in the immobilized ionic liquids was consistent with their catalytic activity. Among the immobilized ionic liquids, SiO₂@[HSO₃-ppim]CF₃SO₃-Ⅰ with the highest loading showed the best catalytic activity. Then the influence of reaction conditions on the synthesis of 4, 4'-MDA was investigated using SiO₂@[HSO₃-ppim]CF₃SO₃-Ⅰcatalyst. The suitable reaction conditions were as follows: mass ratio of catalyst to HCHO was 1.5, molar ratio of aniline to HCHO was 4, reaction time of 7 h, and reaction temperature of 80℃. Under the above conditions, the yield and selectivity of 4, 4'-MDA were 74.9% and 94.5%, respectively. However, the catalytic activity of the recovered catalyst declined dramatically. The results of acid-base titration and FT-IR spectroscopy analyses showed that there was a chemical interaction between the immobilized ionic liquids and aniline. The deactivated immobilized ionic liquids could be regenerated by acidization with CF₃SO₃H, and the acidized immobilized ionic liquids could be reused four times with a tolerable loss of its catalytic activity.

Key words: 4, 4'-methylenedianiline, aniline, formaldehyde, immobilized ionic liquids, condensation

摘要：

采用3种方法成功制备了固载型磺酸功能化离子液体, 对其催化苯胺与甲醛缩合制备4, 4'-二氨基二苯甲烷(4, 4'-MDA)的反应性能进行了评价, 并考察了其重复使用性能。结果表明, 固载型磺酸功能化离子液体的催化效果与其固载量正相关, SiO₂@[HSO₃-ppim]CF₃SO₃-Ⅰ的固载量最高, 催化效果最好。以SiO₂@[HSO₃-ppim]CF₃SO₃-Ⅰ为催化剂, 4, 4'-MDA合成反应适宜的反应条件为:w(cat.)/w(HCHO)=1.5, n(AN)/n(HCHO)=4, 反应时间7 h, 反应温度80℃。在此条件下, 4, 4'-MDA的收率和选择性分别为74.9%和94.5%。通过酸碱滴定法测定酸量和红外谱图分析发现, 苯胺与离子液体的酸中心发生化学作用导致回收催化剂活性下降。利用CF₃SO₃H对回收催化剂进行酸化处理, 其活性得以恢复, 重复使用4次, 催化活性没有明显降低。

关键词: 4, 4'-二氨基二苯甲烷, 苯胺, 甲醛, 固载离子液体, 缩合反应