二氧化氯氧化云杉木质素的光谱研究

Study on the Spectra of Spruce Lignin with Chlorine Dioxide Oxidation

采用傅里叶变换红外光谱(FTIR)、紫外-可见光谱(UV-visible)、傅里叶变换拉曼光谱(FT-Raman)以及核磁共振(1H NMR)分析技术对云杉木质素被二氧化氯氧化前后的结构变化进行了研究。当木质素被二氧化氯氧化时,其骨架结构中的芳香环基团被有效地氧化开环。红外光谱显示木质素中的愈疮木基特征峰强度显著降低,紫丁香基苯基以及对羟基苯基特征吸收峰完全消失,在被氧化后的木质素中出现C O共轭羰基伸缩振动特征峰。紫外光谱显示木质素在被氧化后位于280 nm处的紫外吸收显著降低。1H核磁共振波谱显示,木质素中连接在芳香环侧链的甲氧基数量被氧化后出现显著的降低,同时与苯环相连的脂肪族侧链在后也相应地减少。研究结果说明二氧化氯能有效地氧化木质素中的芳香环,并将其氧化为带有C O基因的粘康酸及其酯类物质或带有醌型基团的物质。

The Fourier transform infrared spectroscopy （FTIR）, ultraviolet-Visible spectroscopy （UV-visible）, Fourier trans- form Raman spectroscopy （FT-Raman）, and nuclear magnetic resonance spectroscopy （1 H NMR） were used to study the oxida- tion of spruce lignin by chloride dioxide. The results are as following： The selective oxidation of lignin by chlorine dioxide was obtained by spectroscopy study. FTIR showed that the characteristic absorbance peak of guaiacyl unit in the lignin structure was decreased after chloride dioxide oxidation, while the peaks of syringyl and para-hydroxyphenol disappeared after oxidation. The largely increased absorbance for the band around 1 720 cm^-1 corresponding to carbonyl stretching was achieved in the oxidized lignin. The ultraviolet-visible spectroscopy showed that the absorbance around 280 nm was largely reduced after the lignin had been oxidized. The 1 H NMR spectroscopy also showed the decrease of aromatic units and methoxyl group in the oxidized lignin. These indicated the formation of ester, or quinone derivatives when the lignin was selectively oxidized by chloride dioxide.