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制备了具有咪唑、吗啡啉、吡咯烷酮和吡啶等氮杂环的8种硫酸氢盐离子液体,并考察了这些离子液体应用于大豆油和甲醇的酯交换制备生物柴油的催化活性。其中4种离子液体为1-甲基咪唑硫酸氢盐、吗啡啉硫酸氢盐、2-吡咯烷酮硫酸氢盐、吡啶硫酸氢盐,其余为基于该4种氮杂环引入丙烷磺酸基的磺酸型离子液体。离子液体的酸性测定结果表明,氮杂环相同时,引入磺酸基的离子液体酸性得以增强,催化活性均高于非磺酸型离子液体。磺酸型离子液体的催化活性可与浓硫酸相比拟,反应结束后均可与生物柴油产物自动分层。以活性较佳的1-(3-磺丙基)-2-吡咯烷酮硫酸氢盐和4-(3-磺丙基)吗啡啉硫酸氢盐作催化剂时,n(甲醇)∶n(大豆油)∶n(IL)=12∶1∶0.114,油浴120℃下反应6 h,生物柴油收率分别可达95.0%和94.6%。磺酸型吗啡啉离子液体重复使用5次后,催化活性没有明显下降。
Eight kinds of bisulfate ionic liquids with imidazole, morpholine, pyrrolidone and pyridine and other nitrogen heterocycles were prepared. The catalytic activity of these ionic liquids for the transesterification of soybean oil and methanol to prepare biodiesel was also investigated. The four ionic liquids were 1-methylimidazolium hydrogensulfate, morpholine hydrogensulfate, 2-pyrrolidone hydrogensulfate and pyridine bisulfate, and the rest were sulfonic acids based on the 4 kinds of nitrogen heterocycles for propane sulfonate Ionic liquid. The results of acid determination of ionic liquids showed that the acidity of the ionic liquid with sulfonic acid groups was enhanced and the catalytic activity was higher than that of non-sulfonic acid ionic liquids when the nitrogen heterocycles were the same. The catalytic activity of sulfonic ionic liquids can be compared with that of concentrated sulfuric acid. After the reaction is over, the biodiesel products can be stratified automatically. When n (methanol): n (soybean oil) is used as a catalyst with the more active 1- (3-sulfopropyl) -2-pyrrolidone hydrogensulfate and 4- (3- sulfopropyl) : N (IL) = 12:1:1.114, and the reaction was carried out in an oil bath at 120 ℃ for 6 h. The yield of biodiesel reached 95.0% and 94.6%, respectively. After repeated use of sulfonic acid morphine ionic liquid for 5 times, the catalytic activity did not decrease obviously.