Seven kinds of ionic liquids, N-methyl-imidazolium bisulfate ( [ Hmim] HSO4 ), l-butyl-3-methyl imidazole phosphate ( [Bmim]H2PO4 ) , l-butyl-3-methyl imidazole bisulfate ( [Bmim]HSO4) , 1-butyl-3-methyl imidazole tetrafluoroborate ( [Bmim]BF4), JV-butyl-pyridine bisulfate ( [Bpy]HSO4), N-butyl-pyridine phosphate ( [Bpy]HzPO4), N-ethyl-pyridine bisulfate ( [Epy]HSO4), were designed and synthesized. The synthesis of dimethyl succinate catalyzed by ionic liquids was studied for the first time. It was shown that [Epy]HSO4 had the best catalytic performance, and optimal conditions for the synthesis of dimethyl succinate were obtained, succinic acid and methanol molar ratio 1 : 3. 0, amount of catalyst 5% (g/g) of succinic acid, reaction temperature 70"C and reaction time 2 h. Under the optimal conditions, the yield of dimethyl succinate was up to 91. 83% , esterification rate was 96. 32%. The catalyst was recycled 7 times without substantial decrease in activity. Moreover, compared to conventional industrial catalysts, ionic liquid catalyst had the superiority of smaller catalyst dosage, less by-product, mild reaction conditions, high yield, and recycled catalyst usage. Finally, the mechanism of esterification catalyzed by ionic liquids was discussed.%引言rn丁二酸二甲酯也称琥珀酸二甲酯,是一种重要的合成香料和食品添加剂,可作为食用防腐剂,同时,它还是一种重要的化工中间体,广泛应用于多种化学品的制取.目前,它的世界需求量很大,每年约2000 t.传统方法合成丁二酸二甲酯是以丁二酸和甲醇为原料、浓硫酸作催化剂通过酯化反应得到,但这种采用浓硫酸催化酯化的工艺收率低、后处理复杂,设备要求高,有剧毒副产物硫酸二甲酯生成,严重污染环境.近年来随着对催化剂的深入研究,出现了固体超强酸、杂多酸、强酸性阳离子交换树脂、对甲苯磺酸[1-3 ]等多种酯化催化剂,但是这些催化剂普遍存在催化反应温度高、酸强度分布不均、催化剂活性下降快、与产品分离困难等缺陷,使其工业化应用受到限制.因此,研究开发新型催化剂及工艺具有非常重要的现实意义.
展开▼
