磺酸型离子液体催化制备生物柴油的研究

Preparation of biodiesel catalyzed by sulfonic acid-functionalized ionic liquids

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 hydrosuffate ionic liquid based on imidazolium, morpholinium, pyrrolidonium and pyridiniumcations were synthesized, and the catalytic activities in trans- esterification of soybean oil with methanol were investigated. Four of them are 1-methylimidazolium hydrogen sulfate （ [ Hmim] HSO4 ） , morpholinium hydrogen sulfate （ [ Hnhm] HSO4 ）, 2-pyrrolidonium hydrogensulfate （ [ Hnhp ] HSO4 ） and pyridinium hydrogensulfate （ [ Hpy ] HSO4 ）, the others are sulfonic acid-functionalized ionic liquids. The acidities and catalytic activities of sulfonic acid-functionalized ionic liquids were higher than non sulfonic acid-functionalized ionic liquids. The catalytic activities of sulfonic acid-functionalized ionic liquids can be comparable with concentrated sulphuric acid, and these ionic liquids were phase-separated with biodiesel after the reaction. While 1-（3-sulfonic acid） propyl- 2-pyrrolidonium and 4-（ 3-sulfonic acid ） propylmorpholinium as catalysts,under the optimized conditions of n （methanol） ： n（ soybean oil） ： n（IL） = 12：1 ： 0. 114,120℃, and 6 h, the yields of product were 95.0% and 94.6% ,respectively. Ionic liquid could be reused for 5 times without significant loss of the catalytic activity.