The thermal degradation reactivities of hemicellulose and cellulose in wood cell walls are significantly different from the thermal degradation behavior of the respective isolated components. Furthermore, the degradation of Japanese cedar (Cryptomeria japonica, a softwood) is distinct from that of Japanese beech (Fagus crenata, a hardwood). Lignin and uronic acid are believed to play crucial roles in governing this behavior. In this study, the effects of ball milling for various durations of time on the degradation reactivities of cedar and beech woods were evaluated based on the recovery rates of hydrolyzable sugars from pyrolyzed wood samples. The applied ball-milling treatment cleaved the lignin β-ether bonds and reduced the crystallinity of cellulose, as determined by X-ray diffraction. Both xylan and glucomannan degraded in a similar temperature range, although the isolated components exhibited different reactivities because of the catalytic effect of uronic acid bound to the xylose chains. These observations can be explained by the more homogeneous distribution of uronic acid in the matrix of cell walls as a result of ball milling. As observed for holocelluloses, cellulose in the ball-milled woods degraded in two temperature ranges (below 320 °C and above); a significant amount of cellulose degraded in the lower temperature range, which significantly changed the shapes of the thermogravimetric curves. This report compares the results obtained for cedar and beech woods, and discusses them in terms of the thermal degradation of the matrix and cellulose microfibrils in wood cell walls and role of lignin. Such information is crucial for understanding the pyrolysis and heat treatment of wood.

中文翻译：

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球磨雪松和山毛榉木中半纤维素和纤维素的热降解

木质细胞壁中半纤维素和纤维素的热降解反应性与各个分离组分的热降解行为有很大不同。此外，日本柳杉（柳杉，软木）的降解与日本山毛榉（山毛榉，硬木）的降解是不同的。据信木质素和糖醛酸在控制这种行为中起关键作用。在这项研究中，基于从热解木材样品中可水解糖的回收率，评估了球磨不同时间对雪松和山毛榉木材降解活性的影响。通过X射线衍射测定，所进行的球磨处理使木质素β-醚键断裂并降低了纤维素的结晶度。木聚糖和葡甘露聚糖都在相似的温度范围内降解，尽管分离的组分由于结合在木糖链上的糖醛酸的催化作用而表现出不同的反应性。这些观察结果可以通过球磨的结果将糖醛酸在细胞壁基质中的分布更均匀地解释。如对全纤维素观察到的那样，球磨木材中的纤维素在两个温度范围内（低于320°C或更高）降解。在较低温度范围内，大量纤维素会降解，从而显着改变了热重曲线的形状。该报告比较了从雪松和山毛榉木材获得的结果，并就基质和纤维素微纤维在木材细胞壁中的热降解以及木质素的作用进行了讨论。