马尾松磨木木素在硫酸盐法蒸煮过程中的降解及缩合

Degradation and Condensation of MWL from Pinus massoniana Lamb during Kraft Cooking

中文关键词:  马尾松  磨木木素  聚葡萄糖甘露糖  硫酸盐法蒸煮  苯甲醚键型  木素-碳水化合物复合体

Key Words:Pinus massoniana Lamb  MWL  glucomannan  kraft cooking  benzyl ether linkage  LCC

中文摘要:

      在聚葡萄糖甘露糖存在的条件下，利用硫酸盐法蒸煮马尾松磨木木素（MWL），并采用离心分离、酸析沉淀木素等方法将蒸煮后的产物分级，然后用傅里叶变换红外光谱（FT-IR）分析仪和13C-核磁共振波谱（13C-NMR）对分级后的组分进行分析。结果表明，硫酸盐法蒸煮过程中，在亲核试剂OH-、HS-的进攻下，木素大分子结构单元之间的α-烷基芳基醚键、β-O-4型连接键很容易发生断裂而生成许多小分子木素；另外，酸不溶物中有新的木素-碳水化合物复合体（LCC）结构单元形成，这种新形成的LCC结构单元主要是由β-O-4型木素结构单元与聚葡萄糖甘露糖形成的以苯甲醚键连接的LCC结构单元以及由5-5缩合型木素结构单元与木糖形成的以苯甲醚键连接的LCC结构单元，并且这种新形成的LCC结构单元对碱非常稳定。而缩合型木素结构单元（β-β、β-5、β-1、5-5木素结构单元）在硫酸盐法蒸煮过程中非常稳定，很难发生降解。

Abstract:

      In order to research the changes of LCC structures, MWL from Pinus massoniana Lamb was cooked with kraft method in existence of glucomannan. The products from kraft cooking were classified into two fractions by centrifugal separation and acidfying precipitation. Techniques of FT-IR and 13C-NMR were applied to determine the fractions and to identify the newly formed LCC structures. The results showed that the lignin linkages, especially α-aryl ether linkages and β-aryl ether linkages were easy to be cleaved under the attack of OH- and HS- in kraft cooking. New LCC structure was found in acid insoluble residue which was formed during the cleaving of lignin linkages, the newly formed LCC was stable in alkali solution and existed with the type of benzyl ether linkage. When MWL from Pinus massoniana Lamb was cooked with kraft method in existence of glucomannan, the newly formed LCC came from β-O-4 lignin structure and glucomannan or 5-5 lignin structure and xylose. The condensed type lignin structures such as β-β, β-5, β-1, 5-5, were stable and difficult to be degraded by kraft cooking.