Armindo Gaspar, Dmitry V. Evtuguin, Carlos Pascoal Neto
Lignin reactions in oxygen delignification catalysed by Mn(II)-substituted molybdovanadophosphate polyanion
The lignin oxidation in the oxygen delignification/bleaching process catalysed by Mn(II) substituted heptamolybdopentavanadophosphate polyanion (HPA-5-MnII) was studied using monomeric lignin model compounds and Eucalyptus globulus dioxane lignin adsorbed on the bleached sulphite pulp. The analysis of reaction products after lignin models oxidation in the presence HPA-5-MnII and the parent heptamolybdopentavanadophosphate polyanion (HPA-5) showed similar qualitative and quantitative patterns, indicating the identical lignin oxidative delignification mechanisms with both catalysts. The higher delignification selectivity of the pulp in the reaction system HPA-5-MnII/O2 than with HPA-5/O2 was explained by the protective effect of MnII in the heteropolyanion towards oxidative degradation of polysaccharides. The study of lignin adsorbed on bleached sulphite pulp, in the HPA-5-MnII/O2 delignification system, showed the cleavage of ?-O-4 linkages as the major contribution to the lignin depolymerisation. The formation of C?-O-polysaccharide linkages in ?-O-4 structures of lignin during the delignification was observed.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 58, 10/2004
Pages: 640 - 649
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