Structural Characterization of Lignin Extracted with Alkaline Hydrogen Peroxide from Furfural Residue

Lignin from furfural residue was extracted with alkaline hydrogen peroxide at different temperatures and times. The structural features of lignins were characterized by elemental analysis, GPC, FT-IR, H NMR, C NMR and Py-GC/MS. Results showed that the yield of lignin increased with the increase of reaction time and temperature. The maximum lignin yield of 41.4% (corresponding to the original lignin) was achieved by extraction at 80 oC for 3 h. The average-molecular weight (Mw) of the extracted lignins (780-850) was about 1/4 of that of the MWL (milled wood lignin) of furfural residue (2890), which indicated a severe degradation of furfural residue lignin under the treatment. Py-GC/MS analysis indicated that the major unit in lignins was p-hydroxycinnamyl (H), together with lower amounts of syringyl (S) and guaiacyl (G) units. The relative molar content of the H unit in the extracted lignins increased, as compared to MWL.