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Lignin modification in the initial phase of softwood kraft pulp delignification with polyoxometalates (POMs)Author(s): Biljana Bujanovic; Sally A. Ralph; Richard S. Reiner; Rajai H. Atalla
Source: Holzforschung. Vol. 61 (2007): Pages 492-498.
Publication Series: Miscellaneous Publication
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DescriptionCommercial softwood kraft pulp with kappa number 30.5 (KP30.5) was delignified with polyoxometalates (POM, Na5(+2)[SiV1(-0.1)MoW10(+0.1)O40]), and POM-treated kraft pulp of kappa number 23.6 was obtained (KPPOM,23.6). Residual lignin from pulps was isolated by mild acid hydrolysis and characterized by analytical and spectral methods to gain insight into lignin reactions taking place during the initial delignification phase. Lignin from POM-delignified pulp was isolated in lower yield. Comparative analysis of residual lignins (RL-KP30.5, RL-KPPOM,23.6) showed that POM leads to products enriched in carbonyl/carboxyl groups and carbohydrates. POM lignins have a lower molecular mass and a lower content of phenolic hydroxyl and methoxyl groups. Based on these results and FTIR spectra, we suggest that aromatic ring cleavage and quinine formation occur during POM delignification. The degree of lignin-cellulose association increases after POM delignification. Lignin-cellulose association was found to be partially unstable under mild alkaline conditions, as residual lignin isolated after alkaline extraction of KPPOM,23.6 pulp (RL-KPPOM/NaOH) exhibited lower glucose content, higher Klason lignin content, and less extraneous material.
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CitationBujanovic, Biljana; Ralph, Sally A.; Reiner, Richard S.; Atalla, Rajai H. 2007. Lignin modification in the initial phase of softwood kraft pulp delignification with polyoxometalates (POMs). Holzforschung. Vol. 61 (2007): Pages 492-498.
KeywordsHydrolysis, chemical reactions, bleaching, pulping, sulphate pulping process, polyoxometalates, spectrum analysis, carbonyl compounds, lignin, pulp, pulp and paper processes, delignification, softwoods
- Studies of lignin transformation in polyoxometalate (POM) bleaching of kraft pulp
- Structural changes of residual lignin of softwood and hardwood kraft pulp upon oxidative treatment with polyoxometalates
- Polyoxometalate delignification of birch kraft pulp and effect on residual lignin
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