Abstract: In order to improve the activity of lignin and promote the efficient utilization of lignin, the refined lignin (PL) obtained by fermenting corn stover to produce ethanol residue and alkali-soluble acid precipitation is used as the raw material, and reacted with isopropanol-water cosolvent. The degradation of lignin (DL) was obtained by catalytic degradation under the condition of medium, liquid-solid ratio of 10:1 (mL:g) and aluminum-oxygen monosodium solid superbase as catalyst. The orthogonal conditions were used to optimize the degradation conditions before and after degradation, followed by the analyzed and characterized of lignin. The results showed that the optimized degradation condition was 20% lignin mass, 200℃ reaction temperature and 150 min reaction time. The yield and formaldehyde value of lignin degradation were 77.5% and 0.365, respectively. The aromatic structure of lignin was well retained in the process of the solid superbase catalyzed degradation of lignin, which was confirmed by Fourier transform infrared spectroscopy (FT-IR), two-dimensional nuclear magnetic resonance (2D HSQC), gel permeation chromatography (GPC), thermogravimetric (TG) analysis. The content of β-O-4, β-β and β-5/α-O-4 in the DL side chain region was significantly reduced after degradation, and Ar-O-C ether bond was partially cleavage through the degradation of lignin. The content of phenolic hydroxyl group and alcohol hydroxyl group increased, whereas the molecular mass and polydispersity decreased significantly. Compared with PL, the main pyrolysis temperature range of DL became narrower and the maximum pyrolysis rate decreased.

Key words: solid superbase, aluminum oxide monosodium, lignin, catalytic degradation