Treatment of dewaxed rice straw with 60% methanol, 60% ethanol, 60% propanol, 60% butanol, 60% ethanol containing 0.01 M HCl, and 60% ethanol containing 0.25 M NaOH at 75 �C for 3 h resulted in solubilization of 14.6%, 13.0%, 16.3%, 12.2%, 13.0%, and 75.6% of the original lignin, respectively. The yield and purity of acid-insoluble lignin extracted with 60% ethanol containing 0.25 M NaOH was much higher than those prepared with other alcohols. The order of the lignin purity of different alcohol treatments was methanol > propanol > butanol > ethanol. Furthermore, the treatment with 60% ethanol under alkali catalyst produced purer lignin than 60% ethanol treatments with or without acid catalyst. The six alcohol-soluble lignin fractions were comparatively characterized by UV, FTIR, 13C and 2D-HSQC NMR, and GPC. 2D-HSQC NMR spectrum showed that the prominent linkage of the lignin fraction obtained by 60% ethanol containing 0.25 M NaOH was �-O-4 ether substructure, and the other linkages observed were �-5' and �-�' ones.

Isolation and characterization of different alcohol-soluble lignins from rice straw

243rd National Meeting (2012)

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