State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
Bioresour Technol. 2013 Sep;143:378-83. doi: 10.1016/j.biortech.2013.06.026. Epub 2013 Jun 18.
Xylan and three monosaccharides (mannose, galactose, and arabinose) were selected as model compounds to investigate the mechanism of hemicellulose pyrolysis. The evolution of several typical pyrolysis products were observed by thermogravimetric analysis coupled to Fourier transform infrared spectroscopy. Monosaccharides underwent similar pyrolysis routes involving ring opening and secondary decomposition. Breakage of the O-acetyl groups and 4-O-methylglucuronic acid units in xylan branches resulted in its different pyrolysis behavior for the formation of acetic acid, CO2, and CO. The detailed reaction pathways of the monosaccharides were studied using density functional theory calculations. Furfural formation was more favorable than the formation of 1-hydroxy-2-propanone and 4-hydroxydihydrofuran-2(3H)-one during xylose degradation. However, in the pyrolysis of mannose and galactose, formation of 5-hydroxymethyl-2-furaldehyde was preferred because of the high energy barrier of the dissociation of the hydroxymethyl group. Meanwhile, the breakage of O-acetyl groups leading to acetic acid formation easily occurred because of its lower energy barrier.
木聚糖和三种单糖（甘露糖、半乳糖和阿拉伯糖）被选为模型化合物，以研究半纤维素热解的机理。通过热重分析与傅里叶变换红外光谱联用，观察了几种典型热解产物的演变。单糖经历了类似的热解途径，包括开环和二次分解。木聚糖支链上的 O-乙酰基和 4-O-甲基葡萄糖醛酸单元的断裂导致其热解行为不同，形成了乙酸、CO2 和 CO。通过密度泛函理论计算研究了单糖的详细反应途径。在木糖降解过程中，糠醛的形成比 1-羟基-2-丙酮和 4-羟二氢呋喃-2(3H)-酮的形成更有利。然而，在甘露糖和半乳糖的热解中，由于羟甲基的离解能垒较高，5-羟甲基-2-糠醛的形成更有利。同时，由于其较低的能量障碍，导致乙酸形成的 O-乙酰基的断裂很容易发生。
