Separation Science and Technology, Vol.48, No.8, 1272-1279, 2013
Fractionation of Lignocellulosic Materials for the Biorefinery: Separation and Characterization of Lignin from Calamagrostis angustifolia Kom
Dewaxed Calamagrostis angustifolia Kom was pretreated with hot water at 60 and 90 degrees C for 3h, and then the residue obtained was successively treated with 70% ethanol, and 70% ethanol containing 0.2%, 1.0%, 2.0%, 4.0%, and 8.0% NaOH at 80 degrees C for 3h. The dissolved components were subjected to further separation to get eight lignin fractions, which were characterized by gel permeation chromatography, Fourier transform infrared, and sugar analysis. All the lignin fractions had small weight-average molecular weights between 810 and 2580g/mol. Two typical lignins, L-3 (prepared with 70% ethanol) and L-5 (prepared with 70% ethanol containing 1.0% NaOH), were further analyzed using H-1, C-13 NMR and HSQC spectroscopy. Signals from guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H) units observed in aromatic/olefinic region of HSQC spectra indicated that the lignin from Calamagrostis angustifolia Kom could be classified as GSH lignin. In aliphatic-oxygenated region, -O-4 together with small amounts of -5, -, and p-hydroxycinnamyl alcohol end group were the main interunit linkages observed. Aqueous ethanol, which could avoid the cleavage of ether bonds in lignin at neutral condition, was more effective than water on lignin extraction.