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Carbon Fibres from Kraft Lignin
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Kolfiber från sulfatlignin (Swedish)
Abstract [en]

Kraft lignin has a high potential for use in more valuable applications than its current use as fuel in pulp mills and integrated pulp and paper mills. The possibility of using kraft lignin, a green material with a carbon content of more than 60 %, for the manufacturing of carbon fibres was investigated in this thesis. The strong and lightweight carbon fibre material has many potential application areas, e.g. in cars; the main obstacle limiting its demand is the high production cost, with the raw material (petroleum pitch and polyactrylonitrile) and fibre spinning constituting approximately 50 % of the cost.

Industrial kraft lignins originating from both softwood (spruce/pine) and hardwood (birch/aspen) were isolated with the LignoBoost technique and then purified and characterized to determine the best suitable lignin for the production of carbon fibre. Using ultrafiltration of the black liquor before isolation using the LignoBoost technique, a kraft lignin with satisfactory high purity was obtained. The fractionated kraft lignin can be used either as such or as a softening agent during melt spinning to obtain continuously spun kraft lignin fibres.

The behaviour during thermal treatment was found to differ depending on the type of kraft lignin used. After oxidative stabilisation, the studied lignins became more stable, and thus, the final yield after carbonisation was increased by 10-20 % in comparison to stabilisation in absence of oxygen. The identified products indicate that the main reactions during oxidative stabilisation are radical, oxidation, condensation and rearrangement reactions.

The structural differences between softwood and hardwood kraft lignins facilitated the stabilisation of the softwood lignin fibre as compared with the hardwood lignin fibres. Thermal stabilisation in an inert atmosphere using only heat was successfully achieved for the softwood kraft lignin fibres. Stabilisation and carbonisation was successfully performed in a one-step operation on softwood kraft lignin fibres. Thus, it seems possible that the separate stabilisation step can be omitted, which may reduce the processing costs of softwood kraft lignin-based carbon fibres.

Abstract [sv]

Sulfatlignin har hög potential för att kunna användas i mer värdefulla applikationer jämfört med idag då det främst används som bränsle i massabruk och integrerade massa/pappersbruk. I egenskap av ett grönt material med en kolhalt på mer än 60 %, har möjligheterna att använda kraftlignin vid kolfibertillverkning undersöks i den här avhandlingen. Kolfiber är lätt och starkt med många olika potentiella användningsområden. Det som idag huvudsakligen begränsar efterfrågan är den höga produktionskostnaden, där råmaterialet (petroleum pitch och polyakrylonitril) och fiberspinningen står för ca 50 % av kostnaden.

Industriella sulfatligniner från både barrved (gran/tall) och lövved (björk/asp) har framställts enligt LignoBoost-processen och har därefter renats och karaktäriserats med syfte att hitta det mest lämpliga råmaterialet för tillverkning av kolfiber. Genom att använda ultrafiltrering av svartlut innan isolering med LignoBoost-tekniken, kan man få ett kraftlignin som är tillräckligt rent. Det fraktionerade kraftligninet kan användas antingen rent eller som mjukgörare under smältspinning, för att få fram kontinuerligt spunna sulfatligninfibrer.

Sulfatligniner från olika vedslag beter sig olika under termisk behandling. Efter oxidativ stabilisering blir ligninerna mer stabila jämfört med stabilisering i frånvaro av syre, vilket medför ett högre utbyte med 10-20 % av den slutgiltiga kolfibern efter karbonisering. De viktigaste reaktionerna som sker under oxidativ stabilisering av fibrer från sulfatlignin är radikal-, oxiderings- och omlagringsreaktioner.

De strukturella skillnaderna mellan sulfatlignin från barrved och lövved gör det möjligt att stabilisera barrvedslignin mycket fortare. Termisk stabilisering i inert atmosfär med endast värme har lyckats med sulfatligninfibrer från barrved. Vidare har även stabilisering och karbonisering i ett enda steg lyckats med sulfatligninfibrer från barrved. Detta kan göra det möjligt att utesluta stabiliseringssteget, vilket förhoppningsvis kan reducera processkostnaderna för kolfiber från barrvedssulfatlignin.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xvii, 52 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:13
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-92256ISBN: 978-91-7501-283-4 (print)OAI: oai:DiVA.org:kth-92256DiVA: diva2:513032
Public defence
2012-04-20, STFI-salen, Drottning Kristinas väg 61, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120330Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2012-03-30Bibliographically approved
List of papers
1. Kraft lignin as feedstock for chemical products: The effects of membrane filtration
Open this publication in new window or tab >>Kraft lignin as feedstock for chemical products: The effects of membrane filtration
2009 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 3, 290-297 p.Article in journal (Refereed) Published
Abstract [en]

The use of technical lignins as feedstock for chemical products will require improvements in purity, molecular mass distribution, and thermal behavior. Therefore, industrial black liquors from kraft pulping of softwood (spruce/ pine) and hardwood (birch and Eucalyptus globulus) have been subjected to fractionation according to molecular mass by ceramic membranes. After acidification and isolation of the lignin fractions, a variety of analytical methods have been applied to help understand their structure - property relationships. From all types of lignin, the chemical and polymeric properties of fractions isolated from the membrane permeates were more homogeneous. This demonstrates that technical kraft lignins, irrespective of origin, may constitute an interesting feedstock for products, such as carbon fibers, adhesives, and phenol-based polymers.

Keyword
birch, chemical analysis, differential scanning calorimetry, Eucalyptus, globulus, fractionation, kraft lignin, membrane filtration, size, exclusion chromatography, softwood, thermal gravimetric analysis, size-exclusion chromatography, successive extraction, organic-solvents, carbon-fibers, lithium chloride/n, n-dimethylacetamide, mobile-phase, fractionation, wood, reactivity, cooking
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-18422 (URN)10.1515/hf.2009.049 (DOI)000266016900006 ()2-s2.0-63849150249 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. The behavior of kraft lignin during thermal treatment
Open this publication in new window or tab >>The behavior of kraft lignin during thermal treatment
2010 (English)In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 87, no 1, 70-77 p.Article in journal (Refereed) Published
Abstract [en]

Purified kraft lignin fractions from technical pulping liquors of softwood and hardwood have been subjected to step-wise analytical pyrolysis in the temperature interval 200-900 degrees C. The heterogenic structure of kraft lignin was revealed by the formation of pyrolysis products throughout the entire temperature interval although the majority of products were formed at 500-600 degrees C. Beyond 700 degrees C, no further pyrolysis products could be detected but a substantial portion of the lignin was shown to be converted into thermally stable products (char) not accessible by analytical pyrolysis. With pre-oxidation of the lignin with air at 250 degrees C prior to pyrolysis, a shift towards higher pyrolysis temperature was observed with a concomitant change in product composition. Thermal gravimetric analysis on such lignins also showed an improved stability against degradation. Methylation of the lignin prior to pyrolysis did not induce any significant changes in behavior, except for much lower T-g values.

Keyword
Analytical pyrolysis, Dimethyl carbonate, Kraft lignin, Methylation, Oxidation, Thermal gravimetric analysis
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-19180 (URN)10.1016/j.jaap.2009.10.005 (DOI)000274277200011 ()2-s2.0-77949303526 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Oxidative stabilisation of kraft lignin for carbon fibre production
Open this publication in new window or tab >>Oxidative stabilisation of kraft lignin for carbon fibre production
2012 (English)In: Holzforschung, ISSN 0018-3830, Vol. 66, 141-147 p.Article in journal (Refereed) Published
Abstract [en]

With the aim of investigating kraft lignin as a raw material for carbon fibre production, different lignins have been stabilised in air at conditions varied according to a full factorial experimental design. The lignins under examination were purified kraft lignin powders originating from birch, spruce/pine and Eucalyptus globules, as well as lignin fibres originating from birch with 5% poly(ethylene oxide) (PEO) added as a plasticiser. The influence of temperature, time and heating rate on yield and glass-transition temperature (Tg) was investigated. The highest yield was achieved after stabilisation at 280C during 2 h with a heating rate of 0.2C min-1. The Tg of all lignin powders was increased when stabilisation occurred under harsher conditions. X-ray photoelectron spectroscopy analysis (XPS) of both the outer surface and the cleaved cross-section of individual lignin/PEO fibres showed a clear gradient in the degree of chemical modification, with the major change occurring on the surface resulting in the appearance of a skin-core structure after stabilisation. The behaviour of the lignin fibres during stabilisation is similar to that of pitch-based fibres, indicating good possibilities for lignin as raw material for carbon fibre production.

Place, publisher, year, edition, pages
Walter de Gruyter, 2012
Keyword
carbon fibre, differential scanning calorimetry, experimental design, kraft lignin, lignin fibre, stabilisation, X-ray photoelectron spectroscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-92252 (URN)10.1515/HF.2011.133 (DOI)000300740500001 ()
Funder
Knut and Alice Wallenberg Foundation
Note
QC 20120330Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2012-03-30Bibliographically approved
4. A new method for stabilizing softwood kraft lignin fibers for carbon fiber production
Open this publication in new window or tab >>A new method for stabilizing softwood kraft lignin fibers for carbon fiber production
Show others...
2013 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 128, no 6, 3824-3830 p.Article in journal (Refereed) Published
Abstract [en]

Renewable resources, such as kraft lignin, have shown great potential as precursors for carbon fiber production. This manuscript reports an investigation into the stabilization of softwood kraft lignin (SKL) fibers and the determination of the difference in stabilization between hardwood- and softwood-based kraft lignin fibers. The stabilization was achieved either thermally by using only heat or oxidatively in the presence of air, at various heating rates. A heating rate of 4 degrees C min1 and a holding time of 30 min at 250 degrees C were successfully used for the thermal stabilization experiments. Faster stabilization was achieved using oxidative conditions at a heating rate of 15 degrees C min1 and 30 min holding time at 250 degrees C. Furthermore, stabilization and carbonization in a one-step process was performed on SKL fibers, which show great potential to reduce both production time and costs. The stabilized and carbonized fibers were evaluated using thermal, spectroscopic, and microscopic methods.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2013
Keyword
crosslinking, thermosets, biopolymers and renewable polymers
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-92255 (URN)10.1002/app.38588 (DOI)000316696000039 ()
Funder
Vinnova
Note

QC 20130429. Updated from manuscript to article in journal.

Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2017-12-07Bibliographically approved
5. The Wood-Based Biorefinery: A Source of Carbon Fiber?
Open this publication in new window or tab >>The Wood-Based Biorefinery: A Source of Carbon Fiber?
2010 (English)In: Open Agriculture Journal, ISSN 1874-3315, Vol. 3, 119-124 p.Article in journal (Refereed) Published
Abstract [en]

In this mini-review, various attempts to make carbon fiber from lignins are discussed. The replacement of construction steel in cars and trucks with a much lighter carbon fiber-based composite will ultimately result in more fuelefficient vehicles. To replace the precursors of carbon fiber, polyacrylonitrile (PAN), or other non-renewable materials such as pitch, by cheap (kraft) lignin, a comprehensive understanding of the physical and chemical characteristics of lignin and the development of methods for its homogeneous large-scale production must be achieved.

Place, publisher, year, edition, pages
Bentham eBooks, 2010
Keyword
Black liquor, carbon fiber, kraft lignins, oxidative stabilization, strength properties, thermal analysis
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-92254 (URN)
Note

QC 20120330

Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2017-12-07Bibliographically approved

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