Bessala Lionnel Frederique Bidzanga, Gao Jingjing, He Zhengbin, Wang Zhenyu, Yi Songlin
State Key Laboratory of Efficient Production of Forest Resources, Beijing Key Laboratory of Wood Science and Engineering, MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University Beijing 100083 China
RSC Adv. 2024 Mar 1;14(11):7414-7429. doi: 10.1039/d3ra07779a. eCollection 2024 Feb 29.
With China's increasing dependence on foreign wood, African wood has gradually become a potential imported species, but its use is seriously affected by problems such as unpleasant odors. In this study, we investigate the effect of heat treatment medium on odor-causing VOCs, decomposition of structural polymers, Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) of hardwood. Samples of "" and "" wood were heated under air and palm oil for two hours at 160 °C, 180 °C, and 200 °C, respectively. Then, the nature of the odor of each VOC emitted by the wood before and after heat treatment was identified using the GCMS method. The decomposition of hemicelluloses, cellulose and lignin in wood samples was examined using a ThermoGravimetric Analyzer coupled to Fourier Transform InfraRed spectrometry (TGA-FTIR). The 3-point bending test was used to evaluate MOR and MOE. The results indicate that the main VOCs responsible for unpleasant smells are acetic acid and hexanal; the reduction in hexanal emissions after heat treatment is mainly due to the treatment temperature, while the reduction in acetic acid emissions depends on the heat treatment medium and is due to the chemical interactions between palm oil and acetic acid; thus, the heat treatment under palm oil reduces the percentage area of VOCs with unpleasant odors in and wood better than the heat treatment under air. Based on TGA-3D FTIR analysis and mechanical results, the reduction in MOR is greater in heat treatment under air because the said treatment induces a greater loss of woody matter, which was characterized by higher HO and CO emissions during heat treatment of wood under palm oil than during heat treatment of wood under air. On the other hand, palm oil more than air, promotes lignin deacetylation, which is characterized by the fact that the 1050 cm wavelength peak was far higher in samples treated with palm oil than in those treated under air; and this might explain why heat treatment under palm oil reduces MOE more than heat treatment under air.
随着中国对国外木材的依赖度不断增加，非洲木材逐渐成为一种潜在的进口木材品种，但其使用受到诸如气味难闻等问题的严重影响。在本研究中，我们探究了热处理介质对阔叶材中产生气味的挥发性有机化合物（VOCs）、结构聚合物的分解、抗弯强度（MOR）和弹性模量（MOE）的影响。分别将“”和“”木材样本在空气和棕榈油中于160℃、180℃和200℃下加热两小时。然后，使用气相色谱 - 质谱联用（GCMS）方法鉴定木材热处理前后释放的每种VOC的气味性质。使用与傅里叶变换红外光谱仪联用的热重分析仪（TGA - FTIR）检测木材样本中半纤维素、纤维素和木质素的分解情况。采用三点弯曲试验评估MOR和MOE。结果表明，导致难闻气味的主要VOC是乙酸和己醛；热处理后己醛排放量的减少主要归因于处理温度，而乙酸排放量的减少取决于热处理介质，这是由于棕榈油与乙酸之间的化学相互作用；因此，在棕榈油中进行热处理比在空气中进行热处理能更好地降低“”和“”木材中带有难闻气味的VOC的百分比面积。基于TGA - 3D FTIR分析和力学结果，在空气中进行热处理时MOR的降低幅度更大，因为该处理导致木质物质损失更大，这表现为在棕榈油中对木材进行热处理时的HO和CO排放量高于在空气中对木材进行热处理时的排放量。另一方面，棕榈油比空气更能促进木质素脱乙酰化，其特征在于在棕榈油中处理的样本中1050 cm波长处的峰远比在空气中处理的样本中的高；这可能解释了为什么在棕榈油中进行热处理比在空气中进行热处理使MOE降低得更多。
