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Enzyme pretreatment of dissolving pulp as a way to improve the following dissolution in NaOH/ZnO
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
Martin Luther University Halle-Wittenberg, Department of Natural Scinence III, Institute of Agriculture and Nutritional Science.
Innventia AB, Fibre and Material Science Business area Biorefining, Stockholm.
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2014 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 4, 385-391 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Walter de Gruyter, 2014. Vol. 68, no 4, 385-391 p.
National Category
Other Natural Sciences
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-26959DOI: 10.1515/hf-2013-0070ISI: 000335650900003OAI: oai:DiVA.org:kau-26959DiVA: diva2:616371
Available from: 2013-04-16 Created: 2013-04-16 Last updated: 2015-12-29Bibliographically approved
In thesis
1. Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps
Open this publication in new window or tab >>Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the preparation of chemically and/or enzymatically modified cellulose. This modification can be either irreversible or reversible. Irreversible modification is used to prepare cellulose derivatives as end products, whereas reversible modification is used to enhance solubility in the preparation of regenerated cellulose.

The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. The parameters evaluated were the degree of substitution, the filterability and the amount of gel obtained when the resulting CMC was dissolved in water. Molecular structures of CMC and its gel fractions were analysed by using NIR FT Raman spectroscopy. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50 were obtained. Such CMC dissolved in water resulted in very thick and semi solid gum-like gels, probably due to an uneven distribution of substituents along the cellulose backbone. FT Raman spectra of CMC samples and their gel fractions mercerized at higher alkaline concentration, i.e. 18.25 and 27.5% in the mercerization stage, indicated on the other hand a complete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Higher average DS values of the CMC, i.e. between 0.88 and 1.05 were therefore obtained. When dissolved in water such CMC caused gel formation especially when prepared from dissolving pulp with a high fraction of cellulose II.

The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that although the crystallinity and the specific surface area of the dissolving pulp sustained minimal change during the enzymatic treatment; the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

Abstract [en]

Baksidetext

Cellulose can be chemically and/or enzymatically modified. Irreversible modification is used to prepare cellulose derivatives as end products, reversible modification to enhance solubility in the preparation of regenerated cellulose.

The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. The content of cellulose II had little effect on degree of substitution (DS) at low NaOH concentration, but tended to decrease DS at higher NaOH concentration in both cases compared with cellulose I. It was also found that the content of cellulose II correlates with the gel formation obtained when the CMC is dissolved in water.

The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2013. 69 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2013:22
Keyword
alkali, carboxymethyl cellulose, cellulose I, cellulose II, cellulose dissolution, degree of substitution, enzymatic treatment, filterability, gel formation, mercerization, multivariate analytical methods, NIR FT Raman spectroscopy, sodium hydroxide, zink oxide
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-26960 (URN)91-7063-499-4 (ISBN)
Public defence
2013-05-31, Nyquistsalen 9C 203, Karlstads universitet, Karlstad, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2013-05-17 Created: 2013-04-16 Last updated: 2013-05-17Bibliographically approved

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