The impact of dilute sulfuric acid on the selectivity of xylooligomer depolymerization to monomers
The impact of dilute sulfuric acid on the selectivity of xylooligomer depolymerization to monomers
复制标题
DOI：
10.1016/j.carres.2007.10.022
复制
发表时间：
2008-02-04
影响因子：
3.1
通讯作者：
Wyman, Charles E.
中科院分区：
文献类型：
--
作者：
Kumar, Rajeev;Wyman, Charles E.
在160℃下，加入硫酸，将pH值从接近中性调整为1.45，对聚合度为2 ~ 5的木糖和低聚木糖的消失进行了研究，并对低聚合度木糖低聚物和木糖单体的产率进行了研究。此外，假设木糖降解和低聚木水解的一级反应动力学，对这些低聚木消失的实验数据进行了动力学建模，以评估pH如何影响低聚木形成单体的选择性和低聚木直接降解到未知产物的选择性。在一定的酸浓度下，低聚木糖的产率随酸浓度的增加而明显增加，但随低聚木糖DP的增加而降低，这意味着对于高DP的物种，实现相同的木糖产率需要更多的酸。例如，pH为4.75时，DP值为2、3、4和5时木糖产率分别为49.6%、28.0%、13.2%和3.2%。动力学模型表明，在所有ph值下，所有低聚木糖单体的消失速率都高于木糖单体，并且消失速率常数随DP的增加而增加。低DP的2和3的动力学表明，这些物种在没有酸的情况下直接降解为未知化合物。另一方面，DP 4和5的高低聚物在所有ph下对降解产物的损失都可以忽略不计。因此，只有DP 2和3的木低聚物被发现在没有酸的情况下直接降解为不需要的产物，但需要更多的工作来确定高DP物种的行为。该研究还揭示了水源和反应器材料对木糖降解动力学的影响。(c) 2007 Elsevier Ltd.版权所有。
The disappearance of xylose and xylooligosaccharides with degrees of polymerization (DP) ranging from 2 to 5 was followed at 160 C with sulfuric acid added to adjust the pH from near neutral to 1.45, and the impact on the yields of lower DP xylooligomers and xylose monomer was determined. In addition, the experimental data for the disappearance of these xylooligomers was kinetically modeled assuming first-order reaction kinetics for xylose degradation and xylooligomer hydrolysis to evaluate how the pH affected the selectivity of monomer formation from xylooligomers and direct oligomer degradation to unknown products. The yield of xylose from xylooligomers increased appreciably with increasing acid concentration but decreased with increasing xylooligomer DP at a given acid concentration, resulting in more acid being required to realize the same xylose yields for higher DP species. For example, the maximum xylose yields were 49.6%, 28.0%, 13.2% and 3.2% for DP values of 2, 3, 4, and 5, respectively, at pH 4.75. Kinetic modeling revealed that all the xylooligomers disappeared at a higher rate compared to xylose monomer and the disappearance rate constant increased with DP at all pH. The kinetics for lower DP oligomers of 2 and 3 showed that these species directly degrade to unknown compounds in the absence of acid. On the other hand, higher oligomers of DP 4 and 5 exhibited negligible losses to degradation products at all pH. Therefore, only xylooligomers of DP 2 and 3 were found to directly degrade to undesired products in the absence of acid, but more work is needed to determine how higher DP species behave. This study also revealed that the source of water and the material used for the construction of the reactor impacted xylose degradation kinetics. (c) 2007 Elsevier Ltd. All rights reserved.