Research on FTIR Analysis of Populus nigra L. Lignin Structure Changes in Different Bleaching Processes

摘要

To study the bleaching mechanisms of H_2O_2 bleaching, H_2O_2 displacement bleaching and H_2O_2/TAED bleaching, three kinds of lignin bleached with above processes were obtained. Three types of treated Populus nigra L lignins structure were identified and the functional groups were quantitied by FTIR. In contrast, the deacetylation and the breakage of ester bonds in H_2O_2/TAED bleaching system was much more significant. The total carbonyl group of H_2O_2 bleached lignin decreased 6.6% while displacement bleached lignin and H_2O_2/TAED bleached lignin decreased 9.2% and 15.8% respectively. The PT bleaching process had stronger oxidability to destroy the syringyl units in lignin. The breakage of ether bonds and alcoholic hydroxyl dehydration in side chain increased after bleaching. In contrast, the stronger destroyed effection on guaiacyl dialkyl ether bond with PT bleaching processes. The conclusions obtained may interpret H_2O_2 displacement bleaching and H_2O_2/TAED bleaching systems have better bleaching efficiency than H_2O_2 bleaching system.