咪唑类酸性离子液体催化正戊醛自缩合反应性能及机理

制备了一系列咪唑类酸性功能化离子液体，用于催化正戊醛自缩合反应。考察了酸性基团种类、与酸性基团相连碳链长度、阴离子种类对离子液体酸性及其催化性能的影响。在此基础上，考察了反应条件对酸性功能化离子液体1 (4 磺酸丁基) 3 甲基咪唑对甲苯磺酸盐(［HSO3 bmim］p TSA)催化性能的影响和离子液体的催化稳定性；采用密度泛函理论模拟了离子液体［HSO3 bmim］p TSA与正戊醛的相互作用情况，探讨了其催化正戊醛自缩合反应机理。结果表明：酸性较强的磺酸功能化离子液体催化活性明显高于羧酸功能化离子液体；对于磺酸功能化离子液体，正戊醛的转化率与离子液体酸强度正相关；［HSO3 bmim］p TSA具有最好的催化性能。［HSO3 bmim］p TSA催化正戊醛自缩合反应适宜的反应条件为：反应温度120 ℃，反应时间6 h，催化剂质量分数8%。在此条件下，正戊醛的转化率为886%；2 丙基 2 庚烯醛的收率和选择性分别为808%和912%。［HSO3 bmim］p TSA至少可循环使用6次，其催化性能基本保持不变。在理论模拟的基础上提出了［HSO3 bmim］p TSA催化正戊醛自缩合反应的机理。

Catalytic Performance and Mechanism of Imidazolium Acidic Ionic Liquids for n-Valeraldehyde Aldol Self-Condensation Reaction

Several acid functionalized ionic liquids were synthesized and studied for catalyzing n valeraldehyde self condensation. Effects of acidic group type, carbon chain length and anion type on their acidities and catalytic performances were investigated. Based on the above results, effect of reaction conditions, catalytic stability of the ionic liquid and reaction mechanism of n valeraldehyde self condensation were studied. Experimental results show that sulfonic acid functionalized ionic liquids (SFILs) exhibited a better catalytic performance than that of carboxylic acid functionalized ionic liquids, and the conversion of n valeraldehyde was correlated well with the acid strength of the SFILs. For all acid functionalized ionic liquids prepared in this work, ［HSO3 bmim］p TSA demonstrated the best catalytic performance. Under the optimal reaction conditions, ie, reaction temperature 120 ℃, reaction time 6 h, and mass ratio of ［HSO3 bmim］p TSA/n valeraldehyde〖JP〗 008∶1, 886% n valeraldehyde conversion can be achieved. Under the above conditions, the yield and selectivity of 2 propyl 2 heptenal were 808% and 912%, respectively. ［HSO3 bmim〖DK〗］p TSA could be reused at least six times without a significant loss in its catalytic performance. In addition, density functional theory (DFT) calculation was performed to simulate the interaction between n valeraldehyde and ［HSO3 bmimp TSA. A possible reaction mechanism for n valeraldehyde self condensation catalyzed by ［HSO3 bmim］p TSA was proposed.