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Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
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 [en]
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: urn:nbn:se:kau:diva-26960ISBN: 91-7063-499-4 OAI: oai:DiVA.org:kau-26960DiVA: diva2:616374
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
List of papers
1. The influence of extended mercerization on some properties of carboxymethyl cellulose (CMC)
Open this publication in new window or tab >>The influence of extended mercerization on some properties of carboxymethyl cellulose (CMC)
2012 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, 21-27 p.Article in journal (Refereed) Published
Abstract [en]

Carboxymethyl cellulose (CMC) is produced commercially in a two stage process consisting of a mercerization stage in which the pulp is treated with alkali in a water alcohol solution and a second etherification stage whereby monochloro-acetic acid is added to the pulp slurry. In this study, the influence of the conditions of an extended mercerization stage was evaluated on the etherification stage concerning the degree of substitution (DS) and the filterability of the resulting CMC. The parameters studied were: (1) the ratio of cellulose I and cellulose II in the original pulp, (2) the concentration of alkali, (3) the temperature and (4) the retention time in the mercerization stage. The DS results indicate that the NaOH concentration in the mercerization stage is the most important among the parameters studied. When the NaOH concentration in the mercerization stage was high (27.5%), cellulose II showed a lower reactivity than cellulose I with respect to the DS obtained in the resulting CMC. The results from the filtration ability of CMC water solutions are interpreted that the amount of cellulose II in the original pulp and the temperature has a negative influence, while the NaOH concentration in the mercerization stage has a positive influence on the filtration ability. Retention time between 1 h–48 h in the mercerization stage had no effect on the DS or the filtration value. The filtration ability was assumed to be highly influenced by the presence of poorly reacted cellulose segments. The CMC samples with the lowest filtration ability at a given DS can be assumed to have the highest degree of unevenly substituted segments.

Keyword
alkali, carboxymethyl cellulose, cellulose I, cellulose II, degree of substitution, filterability, mercerization
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-6419 (URN)10.1515/HF.2011.131 (DOI)000298290400003 ()
Available from: 2010-09-28 Created: 2010-09-28 Last updated: 2017-12-12Bibliographically approved
2. Quantitative analysis of the transformation process of cellulose I → cellulose II using NIR FT Raman spectroscopy and chemometric methods
Open this publication in new window or tab >>Quantitative analysis of the transformation process of cellulose I → cellulose II using NIR FT Raman spectroscopy and chemometric methods
2009 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 16, 407-415 p.Article in journal (Refereed) Published
Abstract [en]

This paper reports a new, successful, utilization of NIR FT Raman spectroscopy for determinining the polymorphic transformation of native cellulose I into the allomorph cellulose II quantitatively. A rapid prediction of the transformation order is made possible by applying multivariate linear regression to the FT Raman spectral data of alkali-treated cellulose pulps. Simultaneously, changes in the crystallinity of cellulose I of these pulps were followed with respect to the lattice conversion process. The application of both multivariate quantification methods to the FT Raman spectra of the alkali-treated pulps yields a corrected polymorphic transformation order and enables the quantitative description to be made of the cellulose lattice conversion process as a system consisting of three participating forms of cellulose: crystalline cellulose I, amorphous cellulose and cellulose II.

National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-6418 (URN)10.1007/s10570-009-9286-0 (DOI)
Available from: 2010-09-28 Created: 2010-09-28 Last updated: 2017-12-12Bibliographically approved
3. Carboxymethyl cellulose produced at different mercerization conditions and characterized by NIR FT Raman spectroscopy and chemometric methods
Open this publication in new window or tab >>Carboxymethyl cellulose produced at different mercerization conditions and characterized by NIR FT Raman spectroscopy and chemometric methods
2013 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, 1918-1932 p.Article in journal (Refereed) Published
Keyword
carboxymethyl cellulose, cellulose backbone structure, degree of substitution, extended mercerization, gel formation, multivariate analytical methods, NIR FT Taman spectroscopy
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-6420 (URN)000315386400037 ()
Available from: 2010-09-28 Created: 2010-09-28 Last updated: 2017-12-12Bibliographically approved
4. Two new methods determining the degree of substitution of carboxymethyl cellulose by utilizing NIR FT Raman and FT IR (ATR) spectroscopy
Open this publication in new window or tab >>Two new methods determining the degree of substitution of carboxymethyl cellulose by utilizing NIR FT Raman and FT IR (ATR) spectroscopy
2012 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-14499 (URN)
Conference
23rd International Conference on Raman Spectroscopy (ICORS). Bangalore, India, August 12th-17th, 2012
Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2013-05-17Bibliographically approved
5. Enzyme pretreatment of dissolving pulp as a way to improve the following dissolution in NaOH/ZnO
Open this publication in new window or tab >>Enzyme pretreatment of dissolving pulp as a way to improve the following dissolution in NaOH/ZnO
Show others...
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
National Category
Other Natural Sciences
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-26959 (URN)10.1515/hf-2013-0070 (DOI)000335650900003 ()
Available from: 2013-04-16 Created: 2013-04-16 Last updated: 2017-12-06Bibliographically approved

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