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Paper Information

Journal:   IRANIAN JOURNAL OF WOOD AND PAPER SCIENCE RESEARCH   FALL 2017 , Volume 32 , Number 3 (60) ; Page(s) 369 To 381.

Qualitative structural characterization of two lignin samples and quantitative determination of hydroxyl and methoxyl functional groups in kraft lignin via acetylation

* Polymer Reaction Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran, I.R. Iran
In this research, two types of lignin, i. e. one extracted from industrial waste water of kraft paper producing factory as black liquor and another provided from Aldrich company, were studied. First, the lignin was precipitated from its black liquor by a dilute acid and was then purified by dissolving in tetrahydrofuran (THF). Lignin samples were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopies. The results revealed that the Aldrich lignin has a structure similar with the lignosulfonate while lignin extracted from black liquor does not have a hydrophilic sulfonate group and has a Kraft lignin structure. Using acetylation of Kraft lignin and complementary characterization with 1HNMR spectroscopy, the ratio of hydroxyl functional groups to methoxy groups was calculated to be 1. 11 to 1, and the amount of the hydroxyl groups was calculated to be 5. 91 mmol/g of acetylated lignin, where 53% of the hydroxyl groups is related to the aromatic hydroxyl groups. Molecular weight of the Kraft lignin which was determined from the gel permeation chromatography (GPC) analysis of the acetylated Kraft lignin was 1260 g/mol, average number of the hydroxyl groups per acetylated lignin chain was calculated to be 7. 44.
Keyword(s): Lignin,acetylation,structural characterization,FTIR,1H-NMR
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