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The Carbonate Radical as One-Electron Oxidant of Carbohydrates in Alkaline media
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
2005 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 2, 143-146 p.Article in journal (Refereed) Published
Abstract [en]

The mechanism by which the carbonate radical anion reacts with D-glucose in alkaline aqueous solutions has been studied by means of gamma-radiolysis. From the product analysis it is concluded that the reaction sequence is initiated by a one-electron transfer between the carbonate radical anion and deprotonated D-glucose. In the presence of molecular oxygen, the major, if not only products of this reaction sequence are formic acid, arabinose and gluconic acid and reaction schemes are proposed to account for the observed formation of these products.

Place, publisher, year, edition, pages
2005. Vol. 59, no 2, 143-146 p.
Keyword [en]
carbonate radical, deprotonated glucose, one-electron transfer, beta-scission, 1, 2 H-shift
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-5266DOI: 10.1515/HF.2005.021ISI: 000227384700006Scopus ID: 2-s2.0-14844314191OAI: oai:DiVA.org:kth-5266DiVA: diva2:8205
Note
QC 20100812Available from: 2005-06-02 Created: 2005-06-02 Last updated: 2017-12-04Bibliographically approved
In thesis
1. The inter-and intramolecular selectivity of the carbonate radical anion in its reactions with lignin and carbohydrates
Open this publication in new window or tab >>The inter-and intramolecular selectivity of the carbonate radical anion in its reactions with lignin and carbohydrates
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the present thesis, the effects of the carbonate radical anion on lignin and cellulose were investigated.

The carbonate radical has a rather high reactivity towards aromatic lignin constituents. It reacts especially fast with phenolates. All these reactions occur by way of electron transfer. Small carbohydrates react with CO3 •- much slower than aromatics. These reactions are hydrogen transfer reactions. However, in very basic media, where the carbohydrates deprotonate to some extent, their anions react with CO3 •- by way of electron transfer and the rates approach those of non-phenolic aromatics. These findings suggest that in neutral or slightly alkaline media CO3 •- might serve as an excellent delignifying agent of pulp down to very low lignin contents. With small carbohydrates possessing one or two glucosidic bonds, CO3 •- abstracts hydrogen predominantly from C1 – H bonds, which results in rupture of the glucosidic linkage. Interestingly, however, the glucosidic bonds in cotton linters are rather resistent towards CO3 •-. This has probably morphological reasons. These results imply that, even at very low lignin contents, where CO3 •- is bound to react with cellulose, the reactions will not lead to substantial decrease in pulp viscosity.

At present the cheapest and most practical way of producing CO3 •- radicals in the presence of pulp is to mix the latter with peroxynitrite and CO2. We have performed such experiments on pulp with very promising results. The Kappa number decreased substantially, brightness increased, while the viscosity remained high. This confirms the predicted excellent properties of the carbonate radical.

However, before the peroxynitrite method can be implemented in the pulp industry, a number of technical problems has to be solved. Chief among them is a slow and steady dosage of peroxynitrite to minimise side reactions of the radicals with peroxynitrite and the nitrite impurity. The fate of the NO2 radical, the coproduct of CO3 •-, has also to be assessed. NO2 will probably have to be removed by vigorous degassing in order to block the possible nitration of cellulose.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 62 p.
Series
Trita-KKE, ISSN 0349-6465 ; 0501
Keyword
Chemistry, nuclear chemistry, Kemi
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-257 (URN)91-7178-098-X (ISBN)
Public defence
2005-06-15, Sal E3, Lindstedtsvägen 3, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20101001Available from: 2005-06-02 Created: 2005-06-02 Last updated: 2010-10-01Bibliographically approved
2. Advanced oxidation technologies for the pulp industry: An investigation on the delignifying properties of the carbonate radical anion
Open this publication in new window or tab >>Advanced oxidation technologies for the pulp industry: An investigation on the delignifying properties of the carbonate radical anion
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2004. 90 p.
Series
Trita-KKE, ISSN 0349-6465 ; 0402
Keyword
Chemistry, chemistry, radiation, industrial engineering, Kemi
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-69 (URN)91-7283-893-0 (ISBN)
Public defence
2004-12-08, kollegiesalen, Valhallavägen 79, Stockholm, 09:00
Opponent
Supervisors
Note
QC 20100812Available from: 2004-12-20 Created: 2004-12-20 Last updated: 2010-08-12Bibliographically approved

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