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Composition of the organic components in polyxometalate (POM) liquors from kraft pulp bleachingAuthor(s): Biljana Bujanovic; Kolby C. Hirth; Sally A. Ralph; Richard S. Reiner; Rajai H. Atalla
Source: Proceedings of the 14th International Symposium on Wood Fibre and Pulping Chemistry : 2007 June 25-28, Durban, South Africa. Kloof, South Africa : TAPPSA, 2007:  pages.
Publication Series: Miscellaneous Publication
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DescriptionPromising results from the selective oxidative delignification of kraft pulp with polyoxometalates (POMs) prompted interest in elucidating the lignin oxidation mechanism. The degradation of lignin model compounds and residual lignin in kraft pulps, upon treatment with POMs was studied and differences in the reaction mechanisms between guaiacyl (G-) and syringyl (S-) units were found. Our studies are aimed at comparing soluble lignin products resulting from POM treatment of softwood and hardwood kraft pulps to further explore the behavior of G/GS units of lignin incorporated in the pulp matrix. Oxidative treatment of unbleached kraft pulps, commercial mixed softwood and laboratory birch, was performed using POM solutions containing the active [SiVW11O40]5anion. The solutions obtained after POM bleaching were extracted with organic solvents of different polarity, after acidification to pH2 and centrifugation/filtration. Only low-molecular weight lignin fragments were dissolved during POM treatment since acidification did not induce lignin precipitation. The extracts were analyzed by NMR spectroscopy and GC-MS. The majority of degradation compounds were carbonyl and carboxyl aromatic compounds indicating extensive oxidation reactions on lignin. These reactions included C[alpha]-C[beta] and alkyl-aryl cleavage.
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CitationBujanovic, Biljana; Hirth, Kolby C.; Ralph, Sally A.; Reiner, Richard S.; Atalla, Rajai H. 2007. Composition of the organic components in polyxometalate (POM) liquors from kraft pulp bleaching. Proceedings of the 14th International Symposium on Wood Fibre and Pulping Chemistry : 2007 June 25-28, Durban, South Africa. Kloof, South Africa : TAPPSA, 2007:  pages.
KeywordsCarbonyl compounds, acidification, oxidation, chemical reactions, sulphate pulping process, bleaching, pulping, polyoxometalates, lignin, carboxyl groups, syringyl, guaiacyl, lignin, analysis, chemistry, pulp, pulp and paper processes, sulfate pulping, delignification
- Structural changes of residual lignin of softwood and hardwood kraft pulp upon oxidative treatment with polyoxometalates
- Studies of lignin transformation in polyoxometalate (POM) bleaching of kraft pulp
- Polyoxometalate delignification of birch kraft pulp and effect on residual lignin
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