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Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. To obtain products of high quality, these so-called "special" pulps must fulfill certain requirements, such as high cellulose content, low hemicellulose content, a uniform molecular weight distribution and high cellulose reactivity. Most, if not all, of the commercial dissolving pulps accomplish these demands to a certain extent. Nevertheless, achieving high cellulose accessibility as well as solvent and reagent reactivity is not an easy task due to the compact and complex structure presented by the cellulose.

In the first part of this work, three commercial monocomponent endoglucanases were investigated with the purpose of enhancing the cellulose accessibility and reactivity of a hardwood dissolving pulp. A monocomponent endoglucanase with a cellulose-binding domain (CBD) was shown to significantly improve the cellulose reactivity. The positive effect of this enzyme on dissolving-grade pulps was also observed on paper-grade pulps.

The main focus of the forest industry is the production of paper-grade pulps. Paper-grade pulps are mostly produced by the kraft process. In contrast, dissolving-grade pulps are produced by the sulfite and prehydrolysis kraft processes due to the high purity required for these pulps. The kraft process is known for being the most efficient process in terms of energy and chemical recovery, which makes the production costs of paper-grade pulps lower than those of sulfite dissolving-grade pulps. Besides, the production of dissolving pulps present, among others, higher capital and chemical costs than paper-grade pulps.

Therefore, the viability of converting paper-grade pulps into dissolving pulps is brought into a question. However, this task is not simple because paper-grade pulps contain a lower cellulose content and a higher hemicellulose content than dissolving pulps. They also present lower cellulose reactivity and an inhomogeneous molecular weight distribution. As a consequence, the second part of this work focused on the study of the feasibility of converting kraft pulps into dissolving pulps. Several sequences of treatments of hardwoods and non-wood pulps were investigated. The best sequence for each suitable pulp was developed, and the parameters involved were optimized. After several attempts, it was demonstrated that pulps from birch, eucalypt and sisal fulfill the requirements of a commercial dissolving pulp for the viscose process after being subjected to a sequence of treatments that included two commercial enzymes, a xylanase and a monocomponent endoglucanase, and alkali extraction steps.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , p. 57
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:46
National Category
Wood Science
Identifiers
URN: urn:nbn:se:kth:diva-26967ISBN: 978-91-7415-777-2 (print)OAI: oai:DiVA.org:kth-26967DiVA, id: diva2:373492
Public defence
2010-12-03, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20101201Available from: 2010-12-01 Created: 2010-11-30 Last updated: 2010-12-01Bibliographically approved
List of papers
1. Increasing accessibility and reactivity of paper grade pulp by enzymatic treatment for use as dissolving pulp
Open this publication in new window or tab >>Increasing accessibility and reactivity of paper grade pulp by enzymatic treatment for use as dissolving pulp
2008 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 4, p. 363-368Article in journal (Refereed) Published
Abstract [en]

 In this study, the feasibility of using different kraft pulps as dissolving pulps for the viscose process was investigated. Two different bleached hardwood kraft pulps from eucalypt (Eucalyptus globulus) and birch (Betula pendula) were subjected to several enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of the pulps and to reduce the hemicellulose content. Enzymatic treatments were carried out using a commercial monocomponent endoglucanase and a commercial xylanase. Chemical treatment consisted of an alkali extraction. The effects of these pretreatments on reactivity and viscosity were assayed. In both pulps, the endoglucanase enhanced the cellulose reactivity and reduced the viscosity. The sequential combination of xylanase and endoglucanase enhanced the positive effect of endoglucanase treatment alone for eucalypt but showed no major effect for birch. The addition of an alkali extraction step after the xylanase followed by endoglucanase treatment as a final step significantly reduced the hemicellulose content to 24% while the reactivity reached the value of a commercial dissolving pulp (65-70%). The viscosity, on the other hand, showed a considerably decrease.

Keywords
Hardwood, Kraft pulp, Dissolving pulp, Reactivity, Xylanase, Monocomponent endoglucanase, Alkali extraction
National Category
Wood Science
Identifiers
urn:nbn:se:kth:diva-8614 (URN)10.3183/NPPRJ-2008-23-04-p363-368 (DOI)000262102700002 ()2-s2.0-58149242427 (Scopus ID)
Note
QC 20100917. Uppdaterad från Manuskript till Artikel (20100917).Available from: 2008-06-03 Created: 2008-06-03 Last updated: 2017-12-14Bibliographically approved
2. Exploring enzymatic treatments for the production of dissolving grade pulp from different wood and non-wood paper grade pulps
Open this publication in new window or tab >>Exploring enzymatic treatments for the production of dissolving grade pulp from different wood and non-wood paper grade pulps
2009 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 6, p. 721-730Article in journal (Refereed) Published
Abstract [en]

The feasibility of producing dissolving grade pulps for viscose production from different fiber raw materials, such as paper grade pulps from wood and non-woody plants, was investigated. Commercial dried bleached hardwood kraft pulps from eucalypt, and bleached non-wood soda/AQ pulps from flax, hemp, sisal, abaca, and jute, were subjected to enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of cellulose and to reduce their hemicellulose content. A commercial monocomponent endoglucanase and a commercial xylanase were employed for biochemical treatment. The chemical treatment consisted of cold alkaline extraction. The effects of these pre-treatments on pulps were studied by reactivity, according to Fock's method, and viscosity measurements, determination of hemicellulose content, and recording of molecular weight distributions. The results were compared to those of commercial bleached eucalypt dissolving pulp. Eucalypt and sisal pulps showed high improvement in reactivity, reaching levels near or even higher than that of the eucalypt dissolving pulp (65%-70%), and a low hemicellulose content (2%-4%), when both were submitted to a sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction, and a final endoglucanase treatment. However, the viscosity decreased considerably. A uniform and narrow molecular weight distribution was observed in both eucalypt and sisal pulps after this sequential pre-treatment.

Keywords
dissolving grade pulp, endoglucanase, non-woody plants, paper grade, pulp, reactivity, regenerated cellulose, size exclusion chromatography, (SEC), viscose, wood, xylanase, kraft pulp, monocomponent endoglucanase, trichoderma cellulases, nitren, extraction, reactivity, enzymes, xylan, accessibility, cellulose, removal
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-18944 (URN)10.1515/hf.2009.102 (DOI)000271661600012 ()2-s2.0-73449134861 (Scopus ID)
Note
QC 20100525 10th European Workshop on Lignocellulosics and Pulp, Stockholm, SWEDEN, AUG 25-28, 2008Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Optimization of treatment sequences for the production of dissolving pulp from birch kraft pulp
Open this publication in new window or tab >>Optimization of treatment sequences for the production of dissolving pulp from birch kraft pulp
2010 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 1, p. 31-38Article in journal (Refereed) Published
Abstract [en]

As a continuation of our work, the viability of converting paper-grade kraft pulps into dissolving-grade pulps, for several raw materials, has been presented. It has been demonstrated that a combination of an enzymatic treatment using a commercial xylanase followed by alkali extraction resulted in an efficient hemicellulose removal. Furthermore, the cellulose reactivity could be enhanced by an additional enzymatic treatment using a commercial monocomponent endoglucanase. As a result, pulps with the characteristics of those of a commercial dissolving pulp, in terms of hemicellulose content and cellulose reactivity, were obtained. The viscosity of the treated pulps, however, was significantly affected by the treatments; they present lower values than those suitable for the production of cellulose derivatives and regenerated cellulose. The pulps, on the other hand, contained mostly cellulose II, which may also affect the process. Therefore, as a continuation of this work, an optimization of the sequences of treatments as well as a study of the parameters involved was performed in order to overcome the low viscosity values and the presence of cellulose II. After the optimization, it was observed that the xylanase treatment could be replaced by an alkali extraction step, the reaction time for the alkali treatment could be shortened, the viscosity could be increased and pulps containing cellulose I could be obtained. ;  In addition, the hemicellulose content and cellulose reactivity values remained in the range of those of a commercial dissolving-grade pulp.

Keywords
Birch kraft pulp, Dissolving pulp, Enzymatic treatment, Alkali extraction, Cellulose reactivity, Size exclusion chromatography
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-26978 (URN)10.3183/NPPRJ-2010-25-01-p031-038 (DOI)000278043500004 ()2-s2.0-79952537131 (Scopus ID)
Note

QC 20101201

Available from: 2010-12-01 Created: 2010-12-01 Last updated: 2017-12-12Bibliographically approved
4. Optimization of treatments for the conversion of eucalyptus kraft pulp to dissolving pulp
Open this publication in new window or tab >>Optimization of treatments for the conversion of eucalyptus kraft pulp to dissolving pulp
2010 (English)In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 1, no 1Article in journal (Refereed) Published
Keywords
cellulose, dissolving pulp, eucalyptus kraft pulp
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-26981 (URN)2-s2.0-84874016781 (Scopus ID)
Note

QC 20150624

Available from: 2010-12-01 Created: 2010-12-01 Last updated: 2017-01-10Bibliographically approved
5. Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp
Open this publication in new window or tab >>Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp
Show others...
2010 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 19, p. 7416-7423Article in journal (Refereed) Published
Abstract [en]

A sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction and a final endoglucanase treatment was investigated as a process for upgrading non-wood paper-grade pulps to dissolving-grade pulps for viscose production. Five commercial dried bleached non-wood soda/ AQ paper pulps, from flax, hemp, sisal, abaca, and jute, were studied for this purpose. Commercial dried bleached eucalyptus dissolving pulp was used as reference sample. Sisal pulp showed the highest improvement in Fock's reactivity, reaching levels nearly as high or even higher than that of eucalyptus dissolving pulp (65%), and a low hemicellulose content (3-4%) when was subjected to this sequence of treatments. The viscosity, however, decreased considerably. A uniform and narrow molecular weight distribution was observed by size exclusion chromatography. C-13 nuclear magnetic resonance spectroscopy and Raman microspectroscopy revealed that the cellulose structure consisted of cellulose I.

Keywords
Alkaline extraction, Dissolving-grade pulp, Enzymatic treatment, Paper-grade pulp, Non-wood fibers
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-26983 (URN)10.1016/j.biortech.2010.04.050 (DOI)000279894400032 ()20493684 (PubMedID)2-s2.0-77957728796 (Scopus ID)
Note

QC 20101201

Available from: 2010-12-01 Created: 2010-12-01 Last updated: 2017-12-12Bibliographically approved
6. Behavior of different monocomponent endoglucanases on the accessibility and reactivity of dissolving-grade pulps for viscose process
Open this publication in new window or tab >>Behavior of different monocomponent endoglucanases on the accessibility and reactivity of dissolving-grade pulps for viscose process
2010 (English)In: Enzyme and microbial technology, ISSN 0141-0229, E-ISSN 1879-0909, Vol. 47, p. 355-362Article in journal (Refereed) Published
Abstract [en]

Three different commercial monocomponent endoglucanases, with and without a cellulose-binding domain (CBD) and differences in their glycosidic hydrolysis mechanisms, were compared with respect to their ability to enhance the accessibility and reactivity of dissolving-grade pulps for viscose production. Hardwood (eucalyptus) and softwood (mixture of Norway spruce and Scots pine) commercial dried and never-dried bleached sulfite dissolving pulps were used for this purpose. The effects of the enzymatic treatments on pulps were studied by reactivity, according to Fock's method, and viscosity measurements, and recording of molecular weight distributions. Among the different assayed enzymes, endoglucanase with a CBD and an inverting hydrolysis mechanism was found to be the most effective in increasing the reactivity of both pulps. Simultaneously, the viscosity decreased, being more marked for softwood dissolving pulp. A narrower molecular weight distribution, with a great reduction in the amount of long-chain cellulose molecules was observed in both pulps, being more pronounced for softwood dissolving pulp. By contrast, endoglucanase without a CBD and a retaining hydrolysis mechanism showed a barley enhancement of the studied properties. The effects of the different endoglucanase treatments were more pronounced when never-dried dissolving pulps were used.

Keywords
Hardwood, Softwood, Dissolving-grade pulp, Endoglucanase (EG), Cellulose-binding domain (CBD), Reactivity, Viscosity, Molecular weight distribution (MWD)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-26984 (URN)10.1016/j.enzmictec.2010.07.016 (DOI)000284346000008 ()2-s2.0-77957868876 (Scopus ID)
Note
QC 20101201Available from: 2010-12-01 Created: 2010-12-01 Last updated: 2017-12-12Bibliographically approved

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