OXIDATIVE-DEGRADATION OF IN-SITU AND ISOLATED SPRUCE LIGNINS BY WATER-SOLUBLE HYDROGEN-PEROXIDE RESISTANT PENTAFLUOROPHENYLPORPHYRIN

The catalytic activity of a new oxidation-resistant Fe(III) is(pentafl uorophenyl)-beta-tetrasulfonatoporphyrin [Fe(TF5PS4P)] on spruce mille d wood lignin (MWL) and lignin in extractive free spruce wood (EFW) wa s investigated in the presence of H2O2. Size exclusion chromatography analysis shows that MWL was rapidly repolymerized by Fe(TF5PS4P)/H2O2 before undergoing further degradation. IR and H-1-NMR spectroscopy of oxidized lignins suggested that ring-opening reactions and demeth(ox)y lations occurred. Analysis by thioacidolysis of MWL revealed an 80-90% decrease in guaiacyl units involved in beta-O-4 bonds after catalysis . The formation of some vanillin and vanillic acid structures in ligni ns was evidenced, confirming that C alpha-C beta cleavages are promote d by the metalloporphyrin. Lignin in EFW was also degraded by Fe(TF5PS 4P)/H2O2 in the same manner as MWL, but to a lesser extent. In conclus ion, Fe(TF5PS4P)/H2O2 mimics the action of fungal ligninolytic peroxid ases but is also able to penetrate within the compact structure of woo d and degrade lignin to a significant extent.