| 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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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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
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| 8. |
- Olsson, Carina, et al.
(författare)
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Carbon fibres from lignin-cellulose precursor
- 2015
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Ingår i: 18th International Symposium on Wood, Fiber and Pulping Chemistry, September 9-11, 2015, Vienna. ; , s. 126-129
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A series of two-component precursor fibres for carbon fibre production has been produced by air-gap spinning of kraft lignin with cellulose as the fibreforming polymer, the latter from paper grade or dissolving grade pulps. The spun precursor fibres,containing 70% lignin and 30% cellulose, demonstrate mechanical properties equivalent to commercial textile fibres. Precursor fibres based on softwood kraft lignin were treated thermally in twosteps to carbon fibres, which had mechanical properties equal to or greater than those reported for neat lignin-based carbon fibres produced by melt spinning. An advantage of the wet-spun precursor fibres developed in this project is that they are more flexible and easier to handle with a decreased risk ofbrittle fracture. The potential for further improvement for the new type of carbon fibre is very high.
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| 9. |
- Olsson, Carina, et al.
(författare)
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Carbon fibres from precursors produced by dry-jet wet-spinning of kraft lignin blended with kraft pulps
- 2017
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:4, s. 275-283
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Tidskriftsartikel (refereegranskat)abstract
- A part of kraft lignin (KL) can be used as a value-added product without detracting the chemical recovery and the energy balance of the kraft mill. The focus of this study is the production of light-weight carbon fibres (CFS) from KL obtained by the LignoBoost process. For this purpose, crude KL and various cellulose products from kraft pulping of hardwood (HW) and softwood (SW) were dissolved in 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) and submitted to dry-jet wet-spun to obtain precursor fibres containing 70% KL and 30% cellulose, which were thermally stabilised and further converted by thermal treatments into CF. The initial and final products were characterised with respect to, e.g. mole mass distribution, thermal properties, tensile strength and tensile modulus determination. The optimised precursor fibres are smooth and flexible with similar mechanical properties as commercial textile fibres. The best CFS made had a tensile strength of 780 MPa and a tensile modulus of 68 GPa and are thus stronger and stiffer than those produced by melt-spinning of SW-based lignins alone. The new CFS based on dry-jet wet-spun precursors still have a high potential for further improvements.
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| 10. |
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| 11. |
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| 12. |
- Sjöholm, Elisabeth, Associiate Professor, et al.
(författare)
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Microwave assisted etherification of lignin
- 2017
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Ingår i: International symposium on green chemistry (ISGC 2017), May 16-19, 2017, La Rochelle, France.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The content of phenol and aliphatic groups of softwood kraft lignin has been altered to control the reactivity and the physical properties of the lignin. The influence of microwave assisted alkylation was evaluated using dimethyl carbonate (DMC) or diethyl carbonate (DEC) together with different bases. The influence of reaction conditions on the final lignin products were compared by NMR.
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| 13. |
- Tomani, Per, et al.
(författare)
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Lignin separation from pulp mills and potential use in different applications
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Pulp mill biorefining is still a relatively young area in modern pulping R&D driven by megatrends such as big variations in cost for fossil oil and increased cost for wood, but also increased competition on the pulp market. The need for new revenues is obvious if the pulp and paper industry is to maintain its strong position. Biorefining can simplified be defined as the efforts to reach as complete utilization of wood raw material as possible in a pulp mill to reach as high revenues as possible. A pulp mill producing chemical pulp is for several reasons an excellent an industrial platform for biorefining. The chemical pulp mill is able to produce relatively pure cellulose, hemicelluloseand lignin.Lignin removal from kraft black liquors has been developed to a commercial process (the LignoBoost process) in cooperation between Innventia and Chalmers University of Technology. The technology was sold to Valmet 2008 and there are now two full-scale installations in operation. One installation in USA by Domtar (25000 t/y) and one in Finland by Stora Enso (50000 t/y). Lignin separation, purification, modification and applications have since many years back in time a high priority in R&D work at Innventia. The focus for this poster is on separation of lignin from kraft pulp black liquors and the potential to use this ligninin different applications. Promising results have been obtained with for example industrial dispersing applications, activated carbon and carbon fibres.
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| 14. |
- Wang, Miao, et al.
(författare)
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Fast and reliable quantification of lignin reactivity via reaction with dimethylamine and formaldehyde (Mannich reaction)
- 2017
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- The influence of pH on the Mannich reaction (amino alkylation in the presence of formaldehyde) has been analyzed by liquid chromatography-mass spectrometry (LC-MS) with vanillin (VA) as a model compound and a purified softwood kraft lignin (SKL) as a substrate. The reaction products of VA were studied at pH 5, 7, and 9 at 60°C for 4 h. The Mannich adduct and side reaction products with methylene bridge were found at both pH 7 and 9, while only di-substituted by-products were observed at pH 5. Nitrogen contents determined from blank runs were substantial at pH 5 and negligible at pH 7. In VA or SKL, the resulting N-contents at pH 7 corresponded to a 76 or 62 mol% of the theory, respectively, i.e. based on the available C5 positions in phenolic guaiacyl units (G-units). In the case of SKL, 31P-NMR analysis confirmed a 77% conversion of all phenolic G-units into their C5 substituted derivatives. The Mannich reaction should be performed on lignin at pH 7 for 1 h to suppress unwanted side reactions, which could be observed by LC-MS under other pH conditions. The reaction is suitable for fast and reliable determination of reactive C5-positions in lignin by multiplication of the N-content of the reaction products with a factor of 1.6.
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