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Aspects of the chemistry of cellulose degradation and the effect of ethylene glycol during ozone delignification of kraft pulps
KTH, Superseded Departments, Chemistry.
2000 (English)In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 26, no 7, 239-244 p.Article in journal (Refereed) Published
Abstract [en]

The viscosities of oxygen-predelignified kraft pulps were measured as they were ozonated at high consistency. The degree of degradation of thc cellulose was calculated from the viscosities as direct (ds) and indirect, alkali-induced, scissions (als) in the polymer: Als was derived using the decrease in the observed degradation when a borohydride reduction preceded the alkaline extraction of the ozonated pulps. The mechanism of these Scissions is discussed in terms of free-radical reactions and their relative significance. A given charge of ozone to a lignin-containing or lignin-free pulp produced similar degrees of carbohydrate degradation, indicating that the degradation does not depend greatly on the presence of the lignin in the pulp. Ethylene glycol (EG) increases the selectivity during ozone delignification much more than methanol. This effect is optimal at pH3 and 25 wt% EG in the reaction system. The increased selectivity may have several possible reasons. one is the limited extent of free-radical reactions (e.g. hydroxyl radicals) occurring in the carbohydrate chain.

Place, publisher, year, edition, pages
2000. Vol. 26, no 7, 239-244 p.
Keyword [en]
kraft pulps, ozone bleaching, delignification, oxygen, viscosity, high consistency, cellulose degradation, mechanism, hydroxyl
URN: urn:nbn:se:kth:diva-19914ISI: 000088289600001OAI: diva2:338606
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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