On the reaction mechanism of the thermal yellowing of bleached chemical pulps
2006 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 21, no 2, 188-192 p.Article in journal (Refereed) Published
The mechanism of moist thermal yellowing of fully bleached chemical pulps was studied using dissolving pulp impregnated with different types of degradation products from hexenuronic acid, viz. 2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid and 2,3-dihydroxy-2-cyclopenten-l-one (reductic acid) either alone or in combination with Fe2+ or Fe3+ ions. It was found that the two latter acids take part in reactions leading to colour formation whereas 2-furancarboxylic acid does not. The effect of iron ions on the colour formation appears to depend on their oxidation state. The brightness loss caused by either 5-formyl-2-furancarboxylic acid or reductic acid, present in an amount similar to the content of hexenuronic acid in industrial pulps, was of the same order of magnitude as that observed for industrial pulps aged under the same conditions. Based on these findings, the overall mechanism of thermal yellowing is suggested to involve several stages, including the degradation of hexenuronic acid and the formation of reactive precursors, such as 5-formyl-2-furancarboxylic acid or reductic acid, which subsequently take part in the yellowing reactions. The presence of ferrous ions further enhances the discoloration.
Place, publisher, year, edition, pages
2006. Vol. 21, no 2, 188-192 p.
2, 3-dihydroxy-2-cyclopenten-1-one (reductic acid), 2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, Chemical pulps, Hexenuronic acid, Reaction mechanism, Thermal yellowing
Paper, Pulp and Fiber Technology
IdentifiersURN: urn:nbn:se:kth:diva-8867DOI: 10.3183/NPPRJ-2006-21-02-p188-192ISI: 000238726200004ScopusID: 2-s2.0-33745615826OAI: oai:DiVA.org:kth-8867DiVA: diva2:14335
QC 20100924. Uppdaterad från Submitted till Published (20100924).2005-12-022005-12-022010-09-24Bibliographically approved