Polyoxometalate Oxidation of Phenolic Lignin Models Chapter 18
نویسندگان
چکیده
A new environmentally friendly technology for wood pulp delignification, based on the use of polyoxometalates (POMs) and oxygen, is being developed. Polyoxometalate solutions that selectively oxidize lignin under anaerobic conditions can be reoxidized by oxygen and also catalyze the aerobic mineralization ofthe lignin fragments to CO2 and H2O, making possible the closed-mill manufacture of paper. Model studies on the oxidation of various lignin-like soluble compounds with POMs suggest that single-electron oxidation of phenolic substructures occurs first, followed by the hydrolysis of cationicintermediates. Detailed physico-chemical studies of the solutions of the alkali-metal salts of POMs show a correlation between the reduction potentials of POMs and the rate of oxidation of a phenolic lignin model that is ascribed to ion pairing between alkali-metal cations and POM anions.
منابع مشابه
Oxidation of a non-phenolic lignin model compound by two Irpex lacteus manganese peroxidases: evidence for implication of carboxylate and radicals
BACKGROUND Manganese peroxidase is one of the Class II fungal peroxidases that are able to oxidize the low redox potential phenolic lignin compounds. For high redox potential non-phenolic lignin degradation, mediators such as GSH and unsaturated fatty acids are required in the reaction. However, it is not known whether carboxylic acids are a mediator for non-phenolic lignin degradation. RESUL...
متن کاملPii: S0968-0896(98)00173-4
ÐA number of model compounds resembling the fundamental bonding patterns of residual kraft lignin, including a series of stilbenes, were incubated with laccase from Trametes versicolor in the presence and absence of deligni®cation `mediators' ABTS and HBT. The condensed kraft lignin model compounds seem to undergo initial degradation by laccase mainly via benzylic oxidation, demethylation and h...
متن کاملOxidation of non-phenolic substrates. An expanded role for laccase in lignin biodegradation.
In the presence of substrates such as Remazol Blue and 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate) (ABTS), laccases Coriolus (Trametes) versicolor can also oxidize non-phenolic lignin model compounds. Veratryl alcohol (I) and 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-propane-1,3-diol (III) were oxidized by laccase and mediator to give the alpha-carbonyl derivatives. The beta-1 lignin m...
متن کاملLaccase/Mediator Systems: Their Reactivity toward Phenolic Lignin Structures
Laccase-mediator systems (LMS) have been widely studied for their capacity to oxidize the nonphenolic subunits of lignin (70-90% of the polymer). The phenolic subunits (10-30% of the polymer), which can also be oxidized without mediators, have received considerably less attention. Consequently, it remains unclear to what extent the presence of a mediator influences the reactions of the phenolic...
متن کاملUltra‐high performance supercritical fluid chromatography of lignin‐derived phenols from alkaline cupric oxide oxidation
Traditional chromatographic methods for the analysis of lignin-derived phenolic compounds in environmental samples are generally time consuming. In this work, an ultra-high performance supercritical fluid chromatography method with a diode array detector for the analysis of major lignin-derived phenolic compounds produced by alkaline cupric oxide oxidation was developed. In an analysis of a col...
متن کامل