真空热处理粗皮桉木材化学性质的变化

以粗皮桉木材为研究对象,在不同的处理温度下(160、200和240℃)对其真空热处理4 h。为探究热处理前后木材化学性质的变化,对热处理前后木材的高位热值进行了测定与分析;利用紫外-可见光谱、傅里叶变换拉曼光谱和电子自旋共振波谱分析了热处理前后木材化学结构和表面自由基的变化。结果表明:随着热处理温度的升高,木材的高位热值呈逐渐增大的趋势,木材热值的改变与化学组分含量的变化具有一定相关性。紫外-可见光谱显示,热处理材的紫外与可见吸收增强,说明热处理使得木材的共轭和芳香结构以及发色基团增多。拉曼光谱分析表明,热处理材多糖发生降解,木质素部分化学键断裂,木质素化学结构发生改变,热处理过程中木质素发生解聚再缩合反应。电子自旋共振波谱显示,热处理前后木材表面自由基的类型未发生改变,木材表面自由基的数量随热处理温度的升高而增多。

Changes in the Chemical Properties of Vacuum Heat-Treated Eucalyptus pellita Wood

Eucalyptus pellita wood specimens were heat treated in vacuum at 160, 200, and 240℃ for 4h.In order to understand the changes in chemical properties of wood before and after heat treatment, higher calorific value was measured.The changes of chemical structures and surface free radical were studied by UV-Vis spectroscopy, FT-Raman and ESR.The higher calorific value was increased with the increase of heat treatment temperature, and the changes in wood calorific value were related to the changes of chemical composition.The increase in the intensities of UV-Vis spectroscopy after heat treatment indicated that the heat treatment increased the number of conjugated and aromatic structure and auxochrome groups of wood.By FT-Raman, the degradation of polysaccharide occurred and lignin was depolymerized followed by re-condensation reactions during heat treatment.By ESR, radical type was not changed before and after the heat treatment.With the increase of heat treatment temperature, the number of free radicals was increased.