| 1. |
- Andersson, Sofia, et al.
(författare)
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The impact of inorganic elements on lignin‐based carbon fibre quality
- 2018
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Ingår i: 15th European workshop on lignocelllulosics and pulp. ; , s. 119-122
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The influence of inorganic elements on lignin ‐based carbon fibre (CF) quality was studied using sulphates of Na +, K+, Mg2+, Fe2+, Al3+. The metal sulphates were added to wet spun prefibres made from softwood kraft lignin (SKL):cellulose (70:30) and melt spun prefibres made from low molecular mass SKL. An increase in concentration from 0.1 w% to about 0.4 w% did neither affect the mechanical properties nor the morphology as observed by SEM. In contrast, metal sulphates added to the initial 0.45 w% to a total range 1.5 to 5.0 w%, was found detrimental to the melt spinning and to the final CF quality. Thus, the recommendation of <0.1 w% ash in kraft lignin may be exceeded, but more research is needed to establish the upper concentration limit.
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| 2. |
- Bengtsson, Andreas, et al.
(författare)
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Carbon Fibers from Lignin-Cellulose Precursors : Effect of Stabilization Conditions
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 7:9, s. 8440-8448
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for lightweight composites reinforced with carbon fibers (CFs). Due to its high availability and carbon content, kraft lignin has gained attention as a potential low-cost CF precursor. CFs with promising properties can be made from flexible dry-jet wet spun precursor fibers (PFs) from blends (70:30) of softwood kraft lignin and fully bleached softwood kraft pulp. This study focused on reducing the stabilization time, which is critical in CF manufacturing. The impact of stabilization conditions on chemical structure, yield, and mechanical properties was investigated. It was possible to reduce the oxidative stabilization time of the PFs from about 16 h to less than 2 h, or even omitting the stabilization step, without fusion of fibers. The main reactions involved in the stabilization stage were dehydration and oxidation. The results suggest that the isothermal stabilization at 250 °C override the importance of having a slow heating rate. For CFs with a commercial diameter, stabilization of less than 2 h rendered in tensile modulus 76 GPa and tensile strength 1070 MPa. Impregnation with ammonium dihydrogen phosphate significantly increased the CF yield, from 31-38 to 46-50 wt %, but at the expense of the mechanical properties.
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| 3. |
- Bengtsson, Andreas, et al.
(författare)
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Carbon Fibers from Lignin-Cellulose Precursors : Effect of Carbonization Conditions
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 8:17, s. 6826-6833
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Tidskriftsartikel (refereegranskat)abstract
- Carbon fibers (CFs) are gaining increasing importance in lightweight composites, but their high price and reliance on fossil-based raw materials stress the need for renewable and cost-efficient alternatives. Kraft lignin and cellulose are renewable macromolecules available in high quantities, making them interesting candidates for CF production. Dry-jet wet spun precursor fibers (PFs) from a 70/30 w/w blend of softwood kraft lignin (SKL) and fully bleached softwood kraft pulp (KP) were converted into CFs under fixation. The focus was to investigate the effect of carbonization temperature and time on the CF structure and properties. Reducing the carbonization time from 708 to 24 min had no significant impact on the tensile properties. Increasing the carbonization temperature from 600 to 800 °C resulted in a large increase in the carbon content and tensile properties, suggesting that this is a critical region during carbonization of SKL:KP PFs. The highest Young's modulus (77 GPa) was obtained after carbonization at 1600 °C, explained by the gradual transition from amorphous to nanocrystalline graphite observed by Raman spectroscopy. On the other hand, the highest tensile strength (1050 MPa) was achieved at 1000 °C, a decrease being observed thereafter, which may be explained by an increase in radial heterogeneity.
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| 4. |
- Bengtsson, Andreas, et al.
(författare)
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Conditions for the stabilisation of lignin-cellulose prefibres for carbon fibre production
- 2018
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Ingår i: 15th European workshop on lignocellulosics and pulp. ; , s. 111-114
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Stabilisation of the prefibre is a time-consuming step in carbon fibre (CF) production. In this paper the stabilisation condition of dry-jet wet-spun lignin-cellulose (LC) prefibres (70:30 t%) are reported. The impact of prefibre-impregnation by ammonium dihydrogen phosphate (ADHP) and various thermal conditions were evaluated by measuring the yield and mechanical properties of the final CFs. The addition of ADHP improved the CF yields from 32-40 wt% to 45-47 wt% but had a slight negative impact on the tensile modulus (TM) whereas no significant difference in tensile strength (TS) was observed. The absence of fibre fusion and glass transition temperature (Tg) indicate successful stabilisation of all prefibres. This implies possibilities of using short stabilisation times of LC prefibres in CF production.
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| 5. |
- Bengtsson, Andreas, et al.
(författare)
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Improved yield of carbon fibres from cellulose and kraft lignin
- 2018
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:12, s. 1007-1016
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Tidskriftsartikel (refereegranskat)abstract
- To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48-51%). No difference in the mechanical properties of the produced CF was observed.
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| 6. |
- Brodin, Ida, et al.
(författare)
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Kraft lignin as feedstock for chemical products : The effects of membrane filtration
- 2009
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 63:3, s. 290-297
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Brodin, Ida, 1982-, et al.
(författare)
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Oxidative stabilisation of kraft lignin for carbon fibre production
- 2012
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 66:2, s. 141-147
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Brodin, Ida, et al.
(författare)
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The behavior of kraft lignin during thermal treatment
- 2010
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 87:1, s. 70-77
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Gustafsson, Åsa, et al.
(författare)
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Activated carbon from kraft lignin : A sorbent for in situ remediation of contaminated sediments
- 2017
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Ingår i: Environmental technology and innovation. - : Elsevier BV. - 2352-1864. ; 7, s. 160-168
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Tidskriftsartikel (refereegranskat)abstract
- A new type of activated carbon derived from Kraft lignin, separated from black liquor in the paper pulp process, was evaluated for its use as an alternative sorbent to commercial powdered activated carbons (AC) from anthracite (ACCOAL) or coconut (ACBIO) for remediation in situ of contaminated sediments. Two types of kraft lignins (KL): (1) softwood (SKL), (2) hardwood (HKL) were first evaluated for their sorption to PAHs using assays in water with passive samplers (POMs). Results showed that without further chemical modifications the two kraft lignins tested had lower sorption coefficients than commercial ACCOAL or ACBIO and are not good sorbents for remediation. Following these initial tests a new type of AC derived from softwood (ACSKL) was produced in the lab using activation with potassium hydroxide (KOH) (lignin:KOH, 1:3 by dry weight) and pyrolysis at 700 °C. Sorption properties of the new ACSKL was compared to the other ACs in water spiked with PAHs and in water with PAH-contaminated sediment. Sorption results were also compared to bioavailability measurements, using digestive fluid extraction (DFE) in vitro, a method that mimics the solubilization of contaminants that occurs in the gut of a sediment-ingesting invertebrate. ACSKL was found to have similar surface area, pore volume and sorption coefficients as ACCOAL and ACBIO and thus offers a new potential sorbent for remediation, based on a more renewable biomass-derived source than AC from coal. Sediment amendment with 1% AC-SKL reduced the bioavailability of larger PAHs on average by 54% (measured by DFE), and reduced pore water concentrations of ΣPAH by 80% (measured with passive samplers). Our results show that a new type of AC based on softwood kraft lignin, a renewable and locally produced biomass material, could be used as an alternative sorbent for sediment and water remediation provided it is produced in sufficient amount and at a competitive price compared to other traditional ACs.
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| 10. |
- Kalogiannis, Konstantinos G., et al.
(författare)
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Pyrolysis of lignin with 2DGC quantification of lignin oil : Effect of lignin type, process temperature and ZSM-5 in situ upgrading
- 2015
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 115, s. 410-418
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Tidskriftsartikel (refereegranskat)abstract
- Thermal and catalytic pyrolysis of various types of lignin and their influence on the yield and the quality of the produced lignin oil were studied. Lignins originated from a mixture of pine and spruce wood (softwood), a mixture of birch and aspen wood (hardwood) and Eucalyptus Urograndis. High degree of deoxygenation of the bio-oil and maximum yield of value-added chemicals were the main targets of this work. 2DGC-ToFMS analysis was used for the qualitative and quantitative characterization of the lignin oils. Softwood lignin was found to be the most attractive feedstock and high yields of a mixture of phenolic compounds were detected in all cases. High char production was also evident for all types of lignins accounting for almost 50% of the original feedstock. The use of a commercial ZSM-5 catalyst was extremely beneficial for the process, enhancing deoxygenation at higher oil yields compared to thermal pyrolysis. Depending on the nature of the lignin, guaiacyl or syringyl groups were dominant in the oils and it was found that process optimization, involving lignin, catalyst selection and temperature could significantly improve the process efficiency.
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