In situ analysis of chemical changes of thermally compressed wood by 2D NMR

IF 3.1 2区农林科学 Q1 FORESTRY

Wood Science and Technology Pub Date : 2025-02-07 DOI:10.1007/s00226-025-01632-y

Lili Li, Xiaofei Shan, Yali Shao, Jianfang Yu, Wenwen Liu, Zhiying Luo, Ximing Wang

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Abstract

Scots pine was subjected to radial compression at 160 °C and heat treatment at 180–220 °C using hot pressing to produce compressed wood and thermally compressed wood (heartwood and sapwood). Then, the macromolecular structure changes of modified wood without destruction were analyzed using high-resolution 2D HSQC NMR. After heat treatment, the contour signals in NMR spectra evidently reduced. Its reduction mainly came from side-chain cleavage of O-acetylated galactoglucomannans (GGMs) and 4-O-methyl-gluconoxylans (MGXs) in hemicellulose. Moreover, the thermal stability of GGMs was lower than that of MGXs. Specifically, the thermal stability order of monosaccharides in heartwood and sapwood should be as follows: glucose > xylose > mannose > 2-O- and 3-O-Ac- Manp > galactose > 4-O-methyl-α-D-glucuronic acid ≥ arabinose. At 220 °C, hemicellulose only left minor xylan and mannan. Conversely, the change of cellulose structure was not obvious. NMR spectra indicated high temperature caused the breaking of β-O-4, β-5, and α-O-4 bonds, leading to the mass loss of lignin.

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二维核磁共振热压缩木材化学变化的原位分析

苏格兰松在160°C进行径向压缩，在180-220°C进行热压热处理，生产压缩木材和热压木材（心材和边材）。然后，利用高分辨率二维HSQC核磁共振分析了改性木材在不破坏的情况下大分子结构的变化。热处理后，核磁共振谱中的轮廓线信号明显减少。它的还原主要来自半纤维素中o -乙酰化半乳糖甘露聚糖（GGMs）和4- o -甲基葡萄糖氧基聚糖（MGXs）的侧链裂解。此外，GGMs的热稳定性低于MGXs。具体来说，单糖在心材和边材中的热稳定性顺序应为：葡萄糖>；木糖>；甘露糖>； 2-O-和3-O-Ac- Manp >；半乳糖>； 4- o -甲基-α- d -葡萄糖醛酸≥阿拉伯糖。在220°C时，半纤维素只剩下少量木聚糖和甘露聚糖。相反，纤维素结构变化不明显。核磁共振表明，高温导致木质素β-O-4、β-5和α-O-4键断裂，导致木质素质量损失。

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来源期刊

Wood Science and Technology 工程技术-材料科学：纸与木材

CiteScore

5.90

自引率

5.90%

发文量

审稿时长

3 months

期刊介绍： Wood Science and Technology publishes original scientific research results and review papers covering the entire field of wood material science, wood components and wood based products. Subjects are wood biology and wood quality, wood physics and physical technologies, wood chemistry and chemical technologies. Latest advances in areas such as cell wall and wood formation; structural and chemical composition of wood and wood composites and their property relations; physical, mechanical and chemical characterization and relevant methodological developments, and microbiological degradation of wood and wood based products are reported. Topics related to wood technology include machining, gluing, and finishing, composite technology, wood modification, wood mechanics, creep and rheology, and the conversion of wood into pulp and biorefinery products.