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碱催化水解提高硫酸盐木素反应活性
任哲,吴远艳,李楠,樊永明
0
(北京林业大学材料科学与技术学院,北京 100083)
摘要:
为了提高硫酸盐木素的反应活性,采用碱催化的方法对木素进行水解。通过改变时间、温度、NaOH用量,探讨不同反应条件对木素中酚羟基含量的影响。采用紫外差示光谱法、凝胶色谱法和红外光谱法,测定碱催化水解前后木素酚羟基含量、分子量及结构变化情况,探讨碱催化水解在提高木素反应活性的有效性。结果表明,7.5%NaOH、反应温度170℃、反应时间6 h是木素碱催化水解相对更佳的反应条件。在碱催化水解过程中,由于木素芳基醚键以及木素单元结构间醚键联接发生断裂,木素结构中的游离酚羟基含量增加,且伴随着木素大分子降解,分子量及其分散性显著减小。
关键词:  木素  碱催化水解  酚羟基  降解
DOI:10.13610/j.cnki.1672-352x.20140620.017
投稿时间:2014-02-19
基金项目:国家自然科学基金(30671633)资助。
Improving the reactivity of kraft lignin by alkali-catalyzed hydrolysis
REN Zhe,WU Yuanyan,LI Nan,FAN Yongming
(College of Materials Science and Technology, Beijing Forestry University, Beijing 100083)
Abstract:
To improve the reactivity of kraft lignin, an alkaline treatment of kraft lignin was performed in the condition of different time, temperature and concentration of NaOH. Differential ultraviolet spectrophotometry and GPC were used to evaluate the content of phenolic hydroxyl and distribution of the molecular weight. The structure changes of lignin were characterized by FTIR. The results showed that the optimal reaction condition for alkali-catalyzed hydrolysis of kraft lignin was 7.5% NaOH, reaction at 170℃ for 6 hours, and the content of free phenolic hydroxyl increased after alkaline treatment. The molecular weight of lignin was obviously lower than the original. The polydispersity also decreased. It indicated that the range of molecular weight of lignin has a tendency to be narrow. The cleavage of aryl-ether bonds and ether bonds linked with the units of lignin may be responsible for the increase of phenolic hydroxyl and degradation of lignin.
Key words:  lignin  alkali-catalyzed hydrolysis  phenolic hydroxyl  depolymerization

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