漆酶活化碱木质素的磺甲基化反应活性研究  

SULFOMETHYLATION REACTIVITY OF ALKALI LIGNIN WITH LACCASE MODIFICATION

作　　者：杨东杰[1] 周海峰[1] 谢绍胊 伍晓蕾[1] 邱学青[1] 

机构地区：[1]华南理工大学化学与化工学院制浆造纸国家重点实验室,广州510640

出　　处：《高分子学报》2013年第2期232-240,共9页Acta Polymerica Sinica

基　　金：国家重点基础研究发展计划(973计划,项目号2012CB215302,2010CB732205);国家杰出青年科学基金(基金号20925622);国家自然科学基金(基金号21176096)资助项目

摘　　要：采用漆酶对碱木质素进行活化预处理,并对活化碱木质素进行磺甲基化改性,揭示了漆酶活化对碱木质素磺甲基化反应活性影响的作用机理.采用顶空气相色谱、红外光谱、凝胶渗透色谱、核磁共振等研究了漆酶活化碱木质素的结构特征,结果表明,漆酶对碱木质素既有聚合作用又有解聚作用,分子量变化不大,多分散性增加;漆酶活化使得碱木质素发生脱甲基作用,酚羟基含量增大,紫丁香基含量减低;另外,漆酶可氧化酚羟基变成苯氧自由基使碱木质素聚合.采用分子模拟对漆酶活化碱木质素的电子云密度进行了计算,结果表明脱甲基作用增大了木质素苯环上的电子云密度,有利于磺甲基化反应的进行.采用电位滴定测试磺甲基化产物的磺化度来表征其反应活性的大小,结果表明漆酶活化磺甲基化碱木质素的磺化度提高了35%,且对二氧化钛悬浮体系的分散性能得到明显提高.The alkali lignin was modified by laccase,followed by sulfomethylation. To study the mechanism of laccase modification on the influence of sulfomethylation reactivity, the control and laccase modified alkali lignins were characterized by chemical, spectroscopic and chromatographic methods. The molecular weight of sulfomethylated lignins was measured by gel permeation chromatography （GPC） , and the structural changes in laccase modified lignins were characterized by functional groups measurements,headspace gas chromatography （GC） ,infrared spectroscopy （IR） and nuclear magnetic resonance （NMR）. It is proposed that laccase was able to promote both polymerization and depolymerisation. The molecular weight （Mw） changed a little, but the polydispersity was larger than that of the control. The demethylation by laccase oxidation made the increase of the content of phenolic group,while the content of syringyl decreased. At the same time, laccase could oxidise the phenolic end-groups into stabilized radicals that subsequently undergo radical-radical coupling. The charge density of lignin model compounds was calculated by molecular simulation. It was indicated that why demethylation benefited the sulfomethylation. According to structural changes in lignin, the mechanism of the influence laccase modification on the sulfomethylation reactivity was deduced. The sulfomethylation reactivity, measured by the content of sulfonie groups,was increased by 35% after laccase modification. It was mainly due to the increase of the content of phenolic groups and the decrease of steric hindrance. In addition, the dispersion efficiency of sulfomethlated alkali lignin with laccase modification on the TiO2 slurry improved significantly.

关 键 词：漆酶 碱木质素 磺甲基化反应活性 分散性能 

分 类 号：O636.2[理学—高分子化学]