Lignin reactions in oxygen delignification catalysed by Mn(II)-substituted molybdovanadophosphate polyanion

authors	Gaspar, A; Evtuguin, DV; Neto, CP
nationality	International
journal	HOLZFORSCHUNG
author keywords	delignification; lignin; oxidative catalysis; oxygen; polyoxometalate
keywords	MODEL COMPOUNDS; WOOD LIGNIN; KRAFT PULP; PART II; DEGRADATION; OXIDATION
abstract	The lignin oxidation in the oxygen delignification/bleaching process catalysed by Mn(II) substituted heptamolybdopentavanadophosphate polyanion (HPA-5-Mn-II) 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-Mn-II 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-Mn-II/O-2 than with HPA-5/O-2 was explained by the protective effect of Mn-II in the heteropolyanion towards oxidative degradation of polysaccharides. The study of lignin adsorbed on bleached sulphite pulp, in the HPA-5-Mn-II/O-2 delignification system, showed the cleavage of beta-O-4 linkages as the major contribution to the lignin depolymerisation. The formation of Calpha-O-polysaccharide linkages in beta-O-4 structures of lignin during the delignification was observed.
publisher	WALTER DE GRUYTER & CO
issn	0018-3830
year published	2004
volume	58
issue	6
beginning page	640
ending page	649
digital object identifier (doi)	10.1515/HF.2004.118
web of science category	Forestry; Materials Science, Paper & Wood
subject category	Forestry; Materials Science
unique article identifier	WOS:000224277300009