糠酸分解反应动力学与机理研究

Study on kinetics and mechanism of 2-furoic acid decomposition

己糖二酸脱水环合制备2,5-呋喃二甲酸(2,5-FDCA)是一条有工业发展潜力的工艺。针对该工艺母液循环过程中杂质成分不确定、副产物糠酸分解反应动力学和机理不清楚等问题,在糠酸分解产物明确的基础上,测定了糠酸在4种催化体系中的分解反应动力学和分解产物的生成反应动力学。结果表明,在不同催化体系中糠酸的分解速率由快到慢依次为:10%H_(2)SO_(4)、3%HBr+2%MgBr2、3%HBr、3%HBr+2%LiBr(百分数均为质量分数)。采用1级反应动力学拟合得到糠酸在2%HBr+5%LiBr催化下的分解反应活化能为98.74 kJ·mol^(-1)。提出了糠酸分解的可能路径为糠酸先脱羧生成呋喃,呋喃再通过Diels-Alder反应生成相对稳定的2,3-苯并呋喃,2,3-苯并呋喃可与呋喃通过Diels-Alder反应进一步生成氧芴。

Preparation of 2,5-furandicarboxylic acid(2,5-FDCA)by cyclodehydration of hexaric acids is a promising industrial process,but problems such as unclear impurities,less understanding on decomposition kinetics and mechanism of by-product 2-furoic acid are existed,which cause trouble in the mother liquor circulation step.Based on the confirmation of 2-furoic acid decomposition products,its decomposition kinetics and formation kinetics of furan and 2,3-benzofuran under four different catalytic systems were determined.The results show that catalytic systems have different effects on the decomposition rates of 2-furoic acid with an order of:10%H_(2)SO_(4),3%HBr+2%MgBr2,3%HBr,3%HBr+2%LiBr.The activation energy of 2-furoic acid decomposition catalyzed by 2%HBr+5%LiBr(mass fraction)is 98.74 kJ·mol^(-1) fitted by first-order reaction kinetics.A possible pathway of 2-furoic acid decomposition was proposed as:2-furoic acid decarboxylated into furan,and then relatively stable 2,3-benzofuran furan was produced via Diels-Alder reaction of furan,and finally formed dibenzofuran by further Diels-Alder reaction of 2,3-benzofuran with furan.This research work can promote the industrialization process of 2,5-FDCA preparation from hexaric acids.