聚合酸性离子液体的制备及其催化合成丁二酸二甲酯

Preparation of poly acidic ionic liquids and their catalytic application in dimethyl succinate

以1-乙烯基咪唑和1-丙烯咪唑为单体,首先和溴乙酸、3-溴丙酸、5-溴戊酸和三氟甲磺酸一步反应合成酸性离子液体,然后与苯乙烯共聚,合成8种聚合酸性离子液体催化剂。采用红外光谱、热重分析和扫描电镜对其进行表征。首次研究聚合酸性离子液体对丁二酸二甲酯的合成反应的催化活性,并优化了工艺条件。结果表明,聚乙烯咪唑三氟甲磺酸(P[Vim]CF_3SO_3)为最佳催化剂,催化效果和机械强度优于市售大孔酸性树脂,且易于分离,最佳工艺条件为:反应温度87℃,酸醇比为1∶5,催化剂用量为5%(质量分数),反应4 h,丁二酸二甲酯的收率为96.5%,丁二酸二甲酯的选择性100%。重复使用5次,效果没有明显下降。

Eight acidic ionic liquids were prepared by 1-vinylimidazole（ 1-allylimidazole） reacted with bromoacetic acid,3-bromopropionic acid and 5-bromovaleric acid. Then,acidic ionic liquids were copolymerized with styrene. Their structures and morphology were characterized by IR spectra,scanning electron microscope and thermogravimetric analyzer. The synthesis of dimethyl succinate catalyzed by poly-ionic liquids was studied for the first time. It was shown that poly-vinylimidazole trifluoromethane sulfonic acid（ P[Vim]CF3SO3） had the best catalytic performance,and optimal conditions for the synthesis of dimethyl succinate were obtained,reaction temperature 87 ℃,succinic acid ∶ methanol = 1 ∶ 5（ molar ratio）,amount of catalyst 5%（ mass fraction）,reaction time 4 h,yield of dimethyl succinate 96. 5% and selectivity of dimethyl succinate 100%. The catalyst was recycled 5 times without substantial decrease in activity.