固载离子液体[HSO_(3)-BMIM][HSO_(4)]/SiO_(2)的制备及其催化乙酸乙醇酯化反应的研究

Preparation of supported ionic liquid[HSO3-BMIM][HSO4]/SiO2 and its catalytic property in the esterification of acetic acid and ethanol

为使离子液体(ILs)在保持催化活性的前提下更易分离回收,减轻ILs的腐蚀,制备了固载ILs,并用于催化酯化反应合成乙酸乙酯(EtAc)。通过红外光谱、热失重、N_(2)吸附-脱附、扫描电镜等对固载ILs进行表征分析,发现溶胶-凝胶(Sol-Gel)法比浸渍法能更有效地固载ILs于二氧化硅(SiO_(2))载体上,在催化乙酸乙醇酯化合成EtAc时催化效果较好。反应条件为酸醇比R_(A∶E)^(0)=1,反应温度T在323.15~338.15 K范围内,催化剂与乙酸质量比x_(cat∶HAc)在5%~15%范围内时,Sol-Gel法制备的[HSO_(3)-BMIM][HSO_(4)]/SiO_(2)初始反应速率较快,反应30 min时乙酸转化率(X_(HAc))超过50%,达到平衡转化率(68%)的约70%。使用LHHW模型拟合[HSO_(3)-BMIM][HSO_(4)]/SiO_(2)催化酯化反应的速率,结果表明该模型预测准确。重复性考察发现,[HSO_(3)-BMIM][HSO_(4)]/SiO_(2)在前三次使用时的X_(HAc)(t=4 h)超过60%,经六次使用后有所下降。使用Sol-Gel法制备的固载ILs的催化活性和稳定性优于浸渍法,表明Sol-Gel法更适合用于制备固载ILs。

In order to make the ionic liquids(ILs)easier to separate and recycle while maintaining the catalytic activity,and to reduce the corrosion,a variety of supported ILs were prepared to catalyze the esterification for the synthesis of ethyl acetate(EtAc).The supported ILs are analyzed and characterization by infrared spectroscopy,thermogravimetric,nitrogen adsorption-desorption and scanning electron microscopy.It is found that sol-gel method can immobilize ILs on SiO_(2) more effectively than impregnation.In the conditions of R_(A∶E)^(2)=1,T in the range of 323.15—338.15 K,and x_(cat∶HAc) in the range of 5%—15%,the supported IL[HSO_(3)-BMIM][HSO_(4)]/SiO_(2) which prepare by sol-gel method shows fast reaction rate,the conversion of acetic acid(X_(HAc))exceeds 50%at the first 30 min,which achieves 70% of the equilibrium conversion(X_(HAc)=68%).The LHHW model was used to fit the rate of[HSO_(3)-BMIM][HSO_(4)]/SiO_(2)-catalyzed esterification reaction,and the results showed that the model predicted accurately.The repeatability experimental result showed that X_(HAc)(t=4 h)of[HSO_(3)-BMIM][HSO_(4)]/SiO_(2) in the third run exceeded 60%,which decreased at the 6th run.The catalytic activity and stability of supported IL prepared by sol-gel method are better than that of impregnation.These results show that sol-gel method is more suitable for the preparation of supported ILs.