Lapis Alexandre A M, de Oliveira Luciane F, Neto Brenno A D, Dupont Jairton
Laboratory of Molecular Catalysis, Institute of Chemistry-UFRGS, Av. Bento Gonçalves, 9500 Porto Alegre 91501-970 RS, Brazil.
ChemSusChem. 2008;1(8-9):759-62. doi: 10.1002/cssc.200800077.
The transesterification (alcoholysis) reaction was successfully applied to synthesize biodiesel from vegetable oils using imidazolium-based ionic liquids under multiphase acidic and basic conditions. Under basic conditions, the combination of the ionic liquid 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMINTf2), alcohols, and K2CO3 (40 mol %) results in the production of biodiesel from soybean oil in high yields (>98%) and purity. H2SO4 immobilized in BMINTf2 efficiently promotes the transesterification reaction of soybean oil and various primary and secondary alcohols. In this multiphase process the acid is almost completely retained in the ionic liquid phase, while the biodiesel forms a separate phase. The recovered ionic liquid containing the acid could be reused at least six times without any significant loss in the biodiesel yield or selectivity. In both catalytic processes (acid and base), the reactions proceed as typical multiphasic systems in which the formed biodiesel accumulates as the upper phase and the glycerol by-product is selectively captured by the alcohol-ionic liquid-acid/base phase. Classical ionic liquids such as 1-n-butyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate are not stable under these acidic or basic conditions and decompose.
酯交换（醇解）反应已成功应用于在多相酸性和碱性条件下使用咪唑基离子液体从植物油合成生物柴油。在碱性条件下，离子液体1-正丁基-3-甲基咪唑双（三氟甲基磺酰）亚胺（BMINTf2）、醇和K2CO3（40摩尔%）的组合可使大豆油高产率（>98%）和高纯度地生产生物柴油。固定在BMINTf2中的H2SO4有效地促进了大豆油与各种伯醇和仲醇的酯交换反应。在这个多相过程中，酸几乎完全保留在离子液相中，而生物柴油形成一个单独的相。回收的含酸离子液体可重复使用至少六次，而生物柴油的产率或选择性没有任何显著损失。在两种催化过程（酸催化和碱催化）中，反应均作为典型的多相体系进行，其中形成的生物柴油作为上层相积累，甘油副产物被醇-离子液体-酸/碱相选择性捕获。经典的离子液体如1-正丁基-3-甲基咪唑四氟硼酸盐和六氟磷酸盐在这些酸性或碱性条件下不稳定并会分解。
