A Study on the Structure of Wheat Straw Lignin by Nuclear Exchange Method

摘要

Nuclear exchange reaction was employed to study the lignin structures in the wheat straw meal, SFP-AQ (Na_2SO_3-HCHO-AQ) pulp, ASP-AQ (NaOH-Na_2SO_3-AQ) pulp, and AP-AQ (NaOH-AQ) pulp. The types of phenyl nuclei of G and S units in the original and the residual lignins of wheat straw were quantitatively analyzed through nuclear exchange reaction and alkaline nitrobenzene oxidation. Results showed that the G and S units of wheat straw lignin were composed of 25.35 mol% non-condensed G unit, 17.60 mol% non-condensed S unit and 57.05 mol% condensed G unit. The dissolving rate of S unit was found to be faster than that of G unit in SFP-AQ and ASP-AQ pulps. Compared with AP-AQ pulp, the residual lignin in SFP pulp was found to have less DPM structural units.