半纤维素稀酸循环喷淋冲滤水解动力学

采用稀酸循环喷淋冲滤（dilute acid cycle spray flow-through，DCF）反应器在温和的条件下水解玉米秸秆半纤维素，分析了半纤维素稀酸水解产物组分，研究不同温度、硫酸浓度和时间对主要产物木糖浓度的影响。探讨了其水解反应机理并以酸催化反应机理为基础，把玉米秸秆半纤维素及其水解产物按化学组成和性质进行集总划分，并对反应网络进行合理简化，提出了一种半纤维素稀酸水解反应的简化集总动力学模型。通过参数估计求取动力学参数，建立集总动力学模型以预测半纤维素主要水解产物。结果表明，喷淋作用加快了半纤维素的连续解聚过程，从而使得木糖得率超过90%，而其降解产物糠醛等较少。得到的模型能较好预测不同条件下主要产物含量。通过改进的Arrhenius方程确定木糖生成和降解的活化能分别为107.1 kJ·mol^-1和102.2 kJ·mol^-1。

Kinetics of hemicellulose hydrolysis by dilute acid with cycle spray flow-through

Hemicellulose hydrolysis of corn stover catalyzed dilute acid was conducted at mild conditions in a reactor with cycle spray flow-through (DCF). The hydrolysate was analyzed and the effect of temperature, sulfuric acid concentration and reaction time on the concentration of main product xylose was studied.The results show that cycle spray can speed effectively up the process for continuos depolymerization of hemicellulose, and make the yield of xylose over 90% and less degradation products such as furaldehyde.Based on the acid catalyzed reaction mechanism of hemicellulose hydrolysis, hemicellulose and their hydrolysates were classified and lumped by their chemical composition and property, and a lumped kinetic model was proposed on reasonable simplification of reaction network.The kinetic rate constants were obtained by parameters estimation.The lumped kinetic model established can be used to predict the major hydrolysates and their contents at various hydrolysis conditions.The activation energy of xylose formation and degradation, calculated from a modified Arrhenius equation, was 107.1 kJ·mol^-1 and 102.2 kJ·mol^-1 respectively.