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Polymers 2018, 10(9), 967; https://doi.org/10.3390/polym10090967

Lignin Structure and Solvent Effects on the Selective Removal of Condensed Units and Enrichment of S-Type Lignin

1
Liaoning Key Laboratory of Pulp and Papermaking Engineering, Dalian Polytechnic University, Dalian 116034, China
2
Jining Ming Sheng New Material Co., Ltd., Jinan 272100, China
3
State Key Laboratory of Pulp and Papermaking Engineering, South China University of Technology, Guangzhou 510640, China
*
Authors to whom correspondence should be addressed.
Received: 30 July 2018 / Revised: 27 August 2018 / Accepted: 27 August 2018 / Published: 1 September 2018
(This article belongs to the Special Issue Lignin Polymers: Structures, Reactions and Applications)
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Abstract

This study focused on the structural differences of lignin after pyridine–acetic acid–water (PAW) and dioxane–acidic water (DAW) purification processes. These structural differences included the S/G ratio, condensed structure, weight-average (MW) molecular weights, β-O-4 linkages and sugar content. The chemical structure of the isolated crude lignin (CL), PAW purified lignin (PPL) and DAW purified lignin (DPL) was elucidated using quantitative 13C NMR, 2D-HSQC NMR spectra, thermogravimetric analysis (TGA), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). The results showed that the PPL fractions contain fewer condensed structures, higher S/G ratios, more β-O-4 linkages, higher average MW and lower thermal degradation properties compared to the CL and DPL fractions. Furthermore, the PAW process was more selective in removing condensed units and enriching S-type lignin from CL compared to the DAW process. These results provide valuable information for understanding which purification process is more suitable to be applied for lignin. View Full-Text
Keywords: lignin purification; structural recognition; condensed lignin; S/G ratio lignin purification; structural recognition; condensed lignin; S/G ratio
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Gao, S.; Zhao, J.; Wang, X.; Guo, Y.; Han, Y.; Zhou, J. Lignin Structure and Solvent Effects on the Selective Removal of Condensed Units and Enrichment of S-Type Lignin. Polymers 2018, 10, 967.

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