不同己糖二酸脱水环合制备2,5-呋喃二甲酸的对比研究

Comparative studies on the preparation of 2,5-furandicarboxylic acid by cyclodehydration of different hexaric acids

己糖二酸脱水环合制备2,5-呋喃二甲酸(2,5-FDCA)是一条具有工业化应用前景的路线。己糖二酸包括葡萄糖二酸、半乳糖二酸和甘露糖二酸,三者是同分异构体,空间结构有差别。本文研究了己糖二酸原料对脱水环合制备2,5-FDCA动力学的影响。结果表明,不同己糖二酸原料对脱水环合制备2,5-FDCA收率影响较大,收率从大到小的次序为:葡萄糖二酸^(-1),4-内酯>葡萄糖二酸钙>葡萄糖二酸单钾盐>半乳糖二酸。与半乳糖二酸相比,以葡萄糖二酸钙为原料制备2,5-FDCA不仅收率高,而且反应条件温和。拟合得到葡萄糖二酸钙的降解反应活化能、2,5-FDCA生成活化能和其他副反应活化能分别为91.7、87.7和98.2 kJ×mol^(-1),而半乳糖二酸的降解反应活化能、2,5-FDCA生成活化能和其他副反应活化能分别为95.2、92.2和98.3 kJ×mol^(-1),可见葡萄糖二酸钙的降解反应活化能和2,5-FDCA生成活化能均比半乳糖二酸的低,主、副反应的活化能之差大于半乳糖二酸的,在硫酸催化下葡萄糖二酸钙更易生成2,5-FDCA。本研究工作将为己糖二酸路线制备2,5-FDCA提供重要的基础数据。

Cyclodehydration of hexaric acid is a promising route for the industrial scale production of 2,5-furandicarboxylic acid(2,5-FDCA).Hexaric acids including gluconic acid,galactaric acid and mannaric acid are isomers with different spatial structures.The effects of hexaric acid sources on the kinetics of cyclodehydration reaction to prepare 2,5-FDCA were studied.The result shows that hexaric acids have certain effects on cyclodehydration and the yield is in order of:glucaric acid^(-1),4-lactone>calcium saccharate>potassium bisaccharate>galactaric acid.Compared with galactaric acid,calcium saccharate has higher yield and milder reaction condition.The degradation activation energy of calcium saccharate,generation activation energy of 2,5-FDCA and activation energy of side reactions are 91.7,87.7 and 98.2 kJ×mol^(-1),respectively,while those of galactaric acid are 95.2,92.2 and 98.3 kJ×mol^(-1),respectively.Therefore,calcium saccharate has lower degradation activation energy and 2,5-FDCA generation activation energy than these of galactaric acid,and the gap between the activation energy of the main and side reactions is greater.These results suggest that calcium saccharate is more conducive to produce 2,5-FDCA with sulfuric acid,which provide basic data for the cyclodehydration of hexaric acid.