摘要
为研究木素在热诱导条件下的颜色变化,对模拟干燥处理前后刺槐Brauns木素(BNL)的UV-Vis、FTIR和13C-NMR等光谱进行了比较分析。结果表明:①木素受热后颜色变深是导致刺槐木材颜色变深的重要原因。刺槐木素紫外光谱具有K带、B带和R带吸收,受热后曲线总体上移,吸光系数增加;木素受热后R带吸收峰加宽,并延伸至可见光区域;②在模拟干燥条件下,木素C5位有缩合反应发生而使木素共轭体系延长,木素受热后α-O-4结构发生断裂使酚羟基增加,共轭芳酮结构(α-羰基)信号仍然很强。这些均为木素受热后吸收光谱发生深色位移导致颜色变深的重要原因。
The structure alteration of Brauns lignin（BNL） from the xylem of Robinia pseudocacia before and after thermal treatment was analyzed by UV-Vis, FTIR and 13 C-NMR techniques. The results showed that the darkening of BNL after thermal treatment played an important role in the darken wood of R. pseudocacia. The UV-Vis spectra of BNL absorbed R, B and K bands. The thermal treatment led to the upward displacement of spectra curve, the increase of extinguishing coefficient in UV-Vis spectra and the broadening of the R band of BNL, which possibly reached the visible vision. Under the simulated drying condition, some condensation reactions at C5 position of the BNL units were found by the analysis of FTIR and 13 C-NMR spectra, which could result in the extension of conjugated lignin structure. The breakage of the α-O-4 after thermal treatment caused the increase of the phenolic hydroxyl group in lignin units. The strong signal of conjugated carbonyl group C=O was detected both before and after thermal treatment. The condensation, the increase of phenolic hydroxyl group in lignin units and the existence of arone structure could be the main reasons of the darkening of BNL from the xylem of R. pseudocacia.
出处
《北京林业大学学报》
EI
CAS
CSCD
北大核心
2008年第6期128-131,共4页
Journal of Beijing Forestry University
基金
国家自然科学基金项目(30671633)
关键词
Brauns木素
热诱导变色
刺槐
Brauns lignin
thermal-induced discoloration
Robinia pseudocacia
