对氧碱漂白过程中木质素氧化进行定量分析,分析方法是基于氧化前后高锰酸钾消耗量的变化.该方法对溶出残余木质素的氧化结果分析发现其呈明显3个阶段:第一段木质素氧化的当量电荷数约4～5/木质素单元;木质素总氧化电荷数大约为9/木质素单元.这些数据以及甲氧基的脱除(75%)均表明:木质素的氧化不仅发生在酚型木质素单元,同时也发生在非酚型结构单元上.只有第一阶段氧化反应是木质素与氧气直接反应,而在第二、三阶段主要是协同氧化作用,氧化反应过程中产生的活性氧基团扮演了一定角色.通过对低浓度针叶材硫酸盐浆的氧漂研究发现:当卡伯值下降一半(25.4至13.4)时平均每个木质素单元氧化3当量电子,氧漂后的纸浆中仍然有大量未被氧化的残余木质素.定量地证明了在氧漂过程中木质素氧化是脱木质素反应的实质.%Unbleached softwood kraft pulp was subjected to low consistency oxygen bleaching. Total KMnO4 consumptions bv lignin in both pulp and effluent were measured and the difference of this value from the KMnO4 consumption by lignin in original unbleached kraft pulp was used as the indication of the extent of oxidation that lignin in the pulp experienced during oxygen bleaching. Extent of lignin oxidation thus estimated well correlated to the delignification. One lignin unit was found to be oxidized by about 3 electrons as an average when Kappa number of the pulp became about half (from 25.4 to 13.4). Methoxyl determination of the bleached pulp suggested that the residual lignin still remaining in the oxygen-bleached pulp was not extensively oxidized. These results confirmed quantitatively that lignin oxidation is essential for the delignification during oxygen bleaching.
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