HBr-MgBr_(2)催化己糖二酸脱水环合制备2,5-呋喃二甲酸的研究

Study on cyclodehydration of hexaric acids to 2,5-furandicarboxylic acid catalyzed with HBr-MgBr_(2)

2,5-呋喃二甲酸(2,5-FDCA)是生物可降解塑料聚呋喃二甲酸乙二醇酯的聚合单体,未来需求量巨大。针对己糖二酸脱水环合制备2,5-呋喃二甲酸存在的收率低问题,开展了更高选择性催化体系的构建研究,成功筛选到了两个优良的催化体系:HBr-MgBr_(2)、HBr-LiBr。3%(质量)HBr-6%(质量)MgBr_(2)催化、120℃下反应2 h,D-葡萄糖二酸单钾盐脱水环合制备2,5-FDCA收率达到84.2%。当反应底物浓度低于5%(质量)以及水含量从3.3%富集到16.5%时,2,5-FDCA的摩尔收率未见明显下降,且都可维持在80%以上。测定了100-130℃温度范围内3%(质量)HBr-6%(质量)MgBr_(2)催化D-葡萄糖二酸单钾盐脱水环合制备2,5-FDCA动力学数据,采用一级反应动力学拟合得到2,5-FDCA的生成反应活化能为108.9 kJ/mol、副产物生成活化能为136.6 kJ/mol。研究工作对己糖二酸脱水环合制备2,5-FDCA路线的工业化具有积极推动作用。

2,5-Furandicarboxylic acid(2,5-FDCA)is a monomer of biodegradable plastic polyethylene furanoate and will be in huge demand in the near future.In order to solve the problem of lower yield in the preparation of 2,5-furandicarboxylic acid during cyclodehydration of hexaric acid,higher selective catalytic systems were explored in this paper.HBr-MgBr_(2) and HBr-LiBr were found to have excellent catalytic ability for cyclodehydration of hexaric acid.2,5-FDCA yield of 84.2%was achieved for potassium bisaccharate cyclodehydration catalyzed with 3%(mass)HBr-6%(mass)MgBr_(2) at 120℃and 2 h reaction time.The molar yield of 2,5-FDCA remained above 80%when substrate concentration was up to 5%(mass)and actual water concentration was enriched from 3.3%to 16.5%.The kinetics of cyclodehydration of potassium bisaccharate to 2,5-FDCA at temperatures from 100℃to 130℃were measured with 3%(mass)HBr-6%(mass)MgBr_(2).The activation energy of 2,5-FDCA formation was 108.9 kJ/mol and that of by-product formation was 136.6 kJ/mol by first-order kinetic fitting.The research work has played a positive role in promoting the industrialization of 2,5-FDCA route by dehydration and cyclization of hexadecanoic acid.