Biomimetic Fenton-Catalyzed Lignin Depolymerization to High-Value Aromatics and Dicarboxylic Acids

By mimicking natural lignin degradation systems, the Fenton catalyst (Fe3+, H2O2) can effectively facilitate lignin depolymerization in supercritical ethanol (7MPa, 250 degrees C) to give organic oils that consist of mono- and oligomeric aromatics, phenols, dicarboxylic acids, and their derivatives in yields up to (66.0 +/- 8.5)%. The thermal properties, functional groups, and surface chemistry of lignin before and after Fenton treatment were examined by thermogravimetric analysis, pyrolysis-gas chromatography-mass spectrometry, (PNMR)-P-31 spectroscopy, and X-ray photoelectron spectroscopy. The results suggest that the Fenton catalyst facilitates lignin depolymerization through cleavage of -ether bonds between lignin residues. The formation of a lignin-iron chelating complex effectively depresses lignin recondensation; thus minimizing charcoal formation and enhancing the yield of liquid products.