键合接枝法制备固载酸性离子液体及其催化合成醋酸丁酯

Preparation of Supported Acidic Ionic Liquid by Covalent Bond Grafting and Its Catalysis in Synthesis of n-Butyl Acetate

采用键合接枝法,以偶氮二异丁腈为引发剂,利用3-巯丙基三乙氧基硅烷改性的硅胶与乙烯基咪唑(VIm)类酸性离子液体发生自由基聚合反应,制成固载化离子液体催化剂[(CH2)3SO3HVIm]HSO4/硅胶。通过元素分析、傅里叶变换红外光谱、热重-示差扫描量热分析等方法对催化剂进行了表征。表征结果显示,离子液体较好地负载在硅胶表面,负载量(以每克催化剂计)为2.671mmol/g,催化剂具有良好的热稳定性。将该催化剂用于合成醋酸丁酯,较佳的反应条件为:反应温度94℃,n(正丁醇):n(醋酸)=1.2,m(催化剂):m(反应物)=0.06,反应时间3h,酯收率达到99.5%。反应后催化剂易分离,重复使用8次后,酯收率仍可达到90.1%。

Immobilized acidic ionic liquid catalyst [ （CH2 ）3SO3HVIm ] HSO4/silica gel was prepared from 1-vinylimidazole （Vim） acidic ionic liquid and 3-mercaptopropyltrimethoxysilane modified silica gel by radical polymerization with azodiisobutyronitrile as initiator. The method is so called covalent bond grafting. The catalyst was characterized by means of FTIR, TG-DSC and element analysis. Results showed that ionic liquid was well confined on modified silica gel. The catalyst is good in thermal stability. The supported capacity of [ （CH2）3SO3HVIm] HSO4 on modified silica gel is 2.671 mmo1/g （based on 1 g catalyst）. The catalyst was used in synthesis of n-butyl acetate by esterification of acetic acid with n-butyl alcohol. Under optimal esterification conditions： temperature 94°C, mole ratio of n-butanol to acetic acid 1.2, mass ratio of catalyst to reactants 0.06 and reaction time 3 h, the yield of n-butyl acetate can reach 99.5 %. The catalyst can be separated easily and yield of n-butyl acetate can maintain at 90.1% after reuse for 8 times.