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Behavior of chromophoric structures in softwood TMP during H 2O2 bleaching
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2005 (English)In: Appita Annual Conference, Vol 2, Australia: Appita, Inc. , 2005, 299-302 p.Conference paper, Published paper (Refereed)
Abstract [en]

A commercial TMP and an isolated lignin from the TMP (milled pulp lignin, or MPL) were treated with alkaline H2O2 bleaching as well as with several other specially designed chemical reactions. Analyses with NMR indicated that coniferaldehyde structures were eliminated completely from the lignin polymer by H2O2 bleaching. Phenolic content was found to have little impact on the final brightness of the TMP sample. Significant amounts of vanillin units (∼4%) were stable towards alkaline H2O2 bleaching and they remained in the TMP lignin after H2O2 bleaching. Even though the lignin sample was completely dissolved during the bleaching treatment, full brightness could not be achieved with the alkaline H2O2 bleaching treatment alone irrespective of the H2O2 charges being used, indicating that physical hindrance was less likely to be an important factor causing the brightness ceiling. It was probably the presence of certain H 2O2-resistant chromophores in the unbleached TMP that limited the further brightness improvement of the TMP at a certain brightness level. The bulk of the polymeric lignin structure seemed to be stable towards alkaline H2O2. The total coniferaldehyde and vanillin units present in the lignin polymer can only account for part of the H 2O2 consumed (not more than 10 kg/ton) during the bleaching process. The predominant reaction responsible for the consumption of H2O2 during the bleaching process was found to be the formation of carboxylic acid groups.

Place, publisher, year, edition, pages
Australia: Appita, Inc. , 2005. 299-302 p.
Series
Appita. Annual Conference Proceedings, ISSN 1443-5454 ; 2
Keyword [en]
Bleaching, Chemical reactions, Chromophores, Hydrogen peroxide, Lignin, Nuclear magnetic resonance, Carboxylic acid groups, Coniferaldehydde structures, Softwoods
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-156560Scopus ID: 2-s2.0-29344434910OAI: oai:DiVA.org:kth-156560DiVA: diva2:767419
Conference
59th Appita Annual Conference and Exhibition, incorporating the 13th ISWFPC: International Symposium on Wood, Fibre and Pulping Chemistry, 16 May 2005 through 19 May 2005, Auckland
Note

QC 20141201

Available from: 2014-12-01 Created: 2014-12-01 Last updated: 2014-12-01Bibliographically approved

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