Abstract
A new approach to increase the reactivity of lignin by thiol-mediated demethylation was investigated in this study. Demethylated lignin was characterized by the changes in its hydroxyl and methoxyl groups, molecular weight, and other properties using titration and spectroscopy methods including
FT-IR, 1H NMR, UV,and
GPC. The total, phenolic, and aliphatic hydroxyl contents in lignin increased while the methoxyl content decreased after demethylation reaction, which indicated the occurrence of demethylation reaction. The results from
FT-IR and
UV analysis also indicated that the kraft lignin in this study contains mainly guaiacyl moiety and demethylated lignin has a higher guaiacyl content than original lignin. The average molecular weight of lignin decreased after demethylation reaction due to the cleavage of ether linkages in lignin macromolecules. No severe degradation of lignin was observed during the demethylation reaction.
Keywords
Biomaterials,
demethylation,
odorless thiol,
nucleophilic substitution,
lignin reactivity
Citation
Hu, Lihong; Pan, Hui; Zhou, Yonghong; Hse, Chung-Yun; Liu, Chengguo; Zhang, Baofang; Xu, Bin. 2014. Chemical groups and structural characterization of lignin via thiol-mediated demethylation. Journal of Wood Chemistry Technology. 34(2):122-134. 13 p.