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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。
In order to improve the reactivity of kraft lignin, lignin is hydrolyzed by a base-catalyzed method. The effects of different reaction conditions on the content of phenolic hydroxyl groups in lignin were investigated by changing the time, temperature and NaOH dosage. The content, molecular weight and structure of lignin phenolic hydroxyl groups before and after base-catalyzed hydrolysis were measured by ultraviolet differential spectroscopy, gel chromatography and infrared spectroscopy, and the effectiveness of alkali-catalyzed hydrolysis in enhancing lignin reactivity was discussed. The results showed that 7.5% NaOH, reaction temperature 170 ℃ and reaction time 6 h were relatively better reaction conditions for the catalytic hydrolysis of lignin. During the base-catalyzed hydrolysis, the content of free phenolic hydroxyl groups in the lignin structure increases due to the cleavage of the lignin ether linkages and the ether linkages between the lignin unit structures, and along with the degradation of the lignin macromolecules, the molecular weight and its dispersion Sex is significantly reduced.