吗啡啉离子液体磷钨酸盐的合成及其催化制备生物柴油

Synthesis of Morpholine Ionic Liquid Heteropolyacid Salt and its Catalytic Activity for Biodiesel Production

摘要:

通过两步法合成了阴离子为磷钨酸根离子的两种离子液体杂多酸盐：1-(3-磺丙基)吗啡啉磷钨酸盐([C3SO3Hnhm]3PW12O40)和N-甲基-N-丁基吗啡啉磷钨酸盐([Nbmm]3PW12O40)。分别采用1H-NMR、FT-IR、元素分析和TG对两种离子液体磷钨酸盐的结构、组成和热稳定性进行表征；同时对溶解性进行了测定。此外，以大豆油和甲醇进行酯交换反应过程为模型反应，考察了[C3SO3Hnhm]3PW12O40的催化活性。结果表明，当n(甲醇):n(大豆油)=14:1，离子液体磷钨酸盐用量为大豆油和甲醇总质量的4%，反应时间6h，反应温度100℃时，脂肪酸甲酯（生物柴油）的收率为 94.90%（质量分数），且该离子液体经回收、真空干燥，重复使用6次后催化活性没有明显降低。另外，在酯交换反应过程中，[C3SO3Hnhm]3PW12O40是反应诱导的自分离催化剂，具有“高温均相反应、低温多相分离”的特性，有利于提高催化活性，同时方便催化剂回收和循环使用。

Abstract:

Two new morpholine ionic liquid heteropolyacid salts were synthesized by a two-step proceeding. They were [C3SO3Hnhm]3PW12O40 and [Nbmm]3PW12O40. The structure of IL was characterized by FT-IR and 1H NMR spectra. The thermal stability was characterized by TG. At the same times, the solubility of ionic liquid heteropolyacid salt was also studied. In addition, the catalytic activity of [C3SO3Hnhm]3PW12O40 for the transesterification of soybean with methanol was investigated. The results show that under the optimized conditions of n(methanol):n(soybean)=14:1, catalyst dosage was 4%, reaction temperature was 100 oC and reaction time was 6 h, the yield of biodiesel up to 94.90%. The IL could reuse more than 6 times, and it will without a significant decrease in activity after regeneration by drying under vacuum. During the transesterification process, [C3SO3Hnhm]3PW12O40 was self separation catalyst induced by the reaction. The catalytic activity was increased and the catalyst was easy to be recycled and used repeatedly, which was due to [C3SO3Hnhm]3PW12O40 has the characteristic of homogeneous reaction in the high temperature and heterogeneous separation in the low temperature.