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Radical coupling - A major obstacle to delignification in kraft pulping
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2006 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 1, 129-134 p.Article in journal (Refereed) Published
Abstract [en]

Lignin dissolution is very slow in the final delignification phase of kraft pulping whereas carbohydrate degradation and dissolution proceeds at a rate that is about the same as that in the bulk phase. The reason for the change in lignin reactivity has been studied by the addition of selected phenols to laboratory kraft cooks of spruce. A substantial formation of new biphenyl bonds between the added phenol and lignin was found both in the residual fiber lignin and in the dissolved kraft lignin, as revealed by GC-MS of thioacidolysis products and complementary NMR analysis of isolated lignins. The formation of biphenyl structures can be explained by a radical coupling mechanism between the added phenol and free aromatic C-5 positions in phenolic lignin units, possibly involving sulfur/polysulfide as radical initiator. The possibility that similar radical coupling reactions may take place between dissolved low molecular mass phenols of lignin origin and polymeric lignin is discussed and it is suggested that this may be the reason for the slow delignification in the final phase.

Place, publisher, year, edition, pages
2006. Vol. 21, no 1, 129-134 p.
Keyword [en]
Biphenyl structures, Kappa number, Kraft pulping, Lignin, Phenols, Picea abies, Radical coupling
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-5373DOI: 10.3183/NPPRJ-2006-21-01-p129-134ISI: 000236358800020Scopus ID: 2-s2.0-33645666410OAI: oai:DiVA.org:kth-5373DiVA: diva2:9722
Note
QC 20100928. Uppdaterad från Submitted till Published (20100928).Available from: 2006-02-14 Created: 2006-02-14 Last updated: 2017-11-21Bibliographically approved
In thesis
1. On the structure of residual lignin in kraft pulping
Open this publication in new window or tab >>On the structure of residual lignin in kraft pulping
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 41 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:43
Keyword
biphenyl structures, kappa number, kraft pulping, phenols, radical coupling, residual delignificaiton, residual lignin, softwood
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-3855 (URN)
Presentation
2006-02-09, E2, KTH, Lindstedtsvägen 3, Stockholm, 10:00
Note
QC 20101213Available from: 2006-02-14 Created: 2006-02-14 Last updated: 2010-12-13Bibliographically approved

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