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Chemical Properties and Thermal Behaviour of Kraft Lignins
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Research concerning lignin has increased during the last years due to its renewability and ready availability in black liquor at pulp mills. Today, the kraft lignin found in black liquor is used as a fuel to gain energy in the recovery boiler at the mill. However, a new isolation concept, LignoBoost®, has enabled isolation of part of the lignin while allowing the use of black liquor as a fuel. This isolated lignin can be utilised as a fuel in, for example, thermal power stations or further upgraded to more value-added products. In this context, the most interesting value-added product is carbon fibre. The demand for carbon fibre has increased, but the biggest obstacle for a more extended use is the high production cost. About half of the production cost is related to the raw material.

In this work, the possibility of using kraft lignin as a precursor for carbon fibre production has been investigated through fundamental studies. Kraft lignins originating from birch, Eucalyptus globulus, softwoods and softwoods from liner production have been studied. By separating the lignin while still in solution in the black liquor, unwanted large particles such as carbohydrates can easily be removed. After isolation according to the LignoBoost process and purification with the use of an ion-exchanger, the lignins have been both chemically and thermally characterised. Identification of the released compounds at different temperatures has been performed because only 40% of carbon relative to original lignin remains, down from theoretical 60% after thermal treatment up to 1000°C. The main released compounds were phenols, as revealed by pyrolysis-GC/MS. Additionally, a pre-oxidation was done in order to try to stabilise the lignins. It was shown that an oxidation prior to the thermal treatment increases the yield by more than 10% and that the main release of compounds takes place between 400°C and 600°C. Fractionated lignin is better qualified as raw material for carbon fibre production because it is purer and its softening temperature can be detected. Fractionated kraft lignins from all investigated wood sources have high possibilities to act as precursors for the manufacture of carbon fibre.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , ix, 47 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:47
National Category
Analytical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-11010ISBN: 978-91-7415-406-1 (print)OAI: oai:DiVA.org:kth-11010DiVA: diva2:234300
Presentation
STFI-salen, Innventia, Drottning Kristinas väg 61, 114 86 Stockholm (Swedish)
Opponent
Supervisors
Available from: 2009-09-10 Created: 2009-09-07 Last updated: 2010-11-03Bibliographically 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

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