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Int. J. Mol. Sci. 2010, 11(8), 2988-3001; doi:10.3390/ijms11082988

Molecular Characteristics of Kraft-AQ Pulping Lignin Fractionated by Sequential Organic Solvent Extraction

1 Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing 100083, China 2 State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China
* Author to whom correspondence should be addressed.
Received: 30 June 2010 / Revised: 8 August 2010 / Accepted: 11 August 2010 / Published: 16 August 2010
(This article belongs to the Section Green Chemistry)
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Kraft-AQ pulping lignin was sequentially fractionated by organic solvent extractions and the molecular properties of each fraction were characterized by chemical degradation, GPC, UV, FT-IR, 13C-NMR and thermal analysis. The average molecular weight and polydispersity of each lignin fraction increased with its hydrogen-bonding capacity (Hildebrand solubility parameter). In addition, the ratio of the non-condensed guaiacyl/syringyl units and the content of β-O-4 linkages increased with the increment of the lignin fractions extracted successively with hexane, diethylether, methylene chloride, methanol, and dioxane. Furthermore, the presence of the condensation reaction products was contributed to the higher thermal stability of the larger molecules.
Keywords: Kraft-AQ pulping lignin; characteristics; GPC; 13C-NMR Kraft-AQ pulping lignin; characteristics; GPC; 13C-NMR
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Wang, K.; Xu, F.; Sun, R. Molecular Characteristics of Kraft-AQ Pulping Lignin Fractionated by Sequential Organic Solvent Extraction. Int. J. Mol. Sci. 2010, 11, 2988-3001.

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