Lignin degradation in oxygen delignification catalysed by [PMo7V5O40](8-) polyanion. Part II. Study on lignin monomeric model compounds
authors Evtuguin, DV; Neto, CP; Carapuca, H; Soares, J
journal HOLZFORSCHUNG
author keywords lignin oxidation; lignin model compounds; polyoxometalate; vanillyl alcohol; veratryl alcohol
keywords HETEROPOLY ACIDS; OXIDATION; DIOXYGEN
abstract Vanillyl and veratryl alcohols were used as monomeric lignin model compounds in experiments aiming to enhance the understanding of the lignin oxidation mechanisms involved in the oxygen delignification in acidic media catalysed by [PMo7V5O40](8-) (HPA-5) heteropolyanion. Based on the model compound experiments, the first step of lignin oxidation is suggested to be a one-electron oxidation by the catalyst. This step is followed by coupling reactions and/or by further oxidation by the catalyst. The ratio of coupling/oxidation reaction products depends on the oxidation conditions and decreases with temperature raise. The higher oxidation rate of vanillyl alcohol as compared to the veratryl alcohol in the reaction system O-2/HPA-5 was explained by the redox properties of the catalyst. The insufficiently high redox potential of HPA-5 did not allow the efficient oxidation of veratryl alcohol. The former was oxidised by VO2+ ions dissociated from the HPA-5 under the acidic conditions. The reactivity of different lignin structural units in the reaction system O-2/HPA-5 was estimated by electrochemical methods using various lignin model compounds.
publisher WALTER DE GRUYTER & CO
issn 0018-3830
year published 2000
volume 54
issue 5
beginning page 511
ending page 518
digital object identifier (doi) 10.1515/HF.2000.087
web of science category Forestry; Materials Science, Paper & Wood
subject category Forestry; Materials Science
unique article identifier WOS:000089643300013
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journal impact factor 1.826
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