| 1. |
- Andersson, Sofia, et al.
(author)
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The impact of inorganic elements on lignin‐based carbon fibre quality
- 2018
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In: 15th European workshop on lignocelllulosics and pulp. ; , s. 119-122
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Conference paper (other academic/artistic)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.
(author)
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Carbon Fibers from Lignin-Cellulose Precursors : Effect of Stabilization Conditions
- 2019
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 7:9, s. 8440-8448
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Journal article (peer-reviewed)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.
(author)
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Carbon Fibers from Lignin-Cellulose Precursors : Effect of Carbonization Conditions
- 2020
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 8:17, s. 6826-6833
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Journal article (peer-reviewed)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.
(author)
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Conditions for the stabilisation of lignin-cellulose prefibres for carbon fibre production
- 2018
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In: 15th European workshop on lignocellulosics and pulp. ; , s. 111-114
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Conference paper (other academic/artistic)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.
(author)
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Improved yield of carbon fibres from cellulose and kraft lignin
- 2018
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In: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:12, s. 1007-1016
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Journal article (peer-reviewed)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.
(author)
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Kraft lignin as feedstock for chemical products : The effects of membrane filtration
- 2009
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In: Holzforschung. - 0018-3830 .- 1437-434X. ; 63:3, s. 290-297
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Journal article (peer-reviewed)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.
(author)
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Oxidative stabilisation of kraft lignin for carbon fibre production
- 2012
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In: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 66:2, s. 141-147
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Journal article (peer-reviewed)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.
(author)
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The behavior of kraft lignin during thermal treatment
- 2010
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In: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 87:1, s. 70-77
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Journal article (peer-reviewed)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.
(author)
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Activated carbon from kraft lignin : A sorbent for in situ remediation of contaminated sediments
- 2017
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In: Environmental technology and innovation. - : Elsevier BV. - 2352-1864. ; 7, s. 160-168
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Journal article (peer-reviewed)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.
(author)
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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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In: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 115, s. 410-418
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Journal article (peer-reviewed)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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| 11. |
- Norberg, Ida, 1982-, et al.
(author)
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A new method for stabilizing softwood kraft lignin fibers for carbon fiber production
- 2013
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In: Journal of Applied Polymer Science. - : Wiley-Blackwell. - 0021-8995 .- 1097-4628. ; 128:6, s. 3824-3830
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Journal article (peer-reviewed)abstract
- 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.
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| 12. |
- Nordström, Ylva, et al.
(author)
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A new softening agent for melt spinning of softwood kraft lignin
- 2013
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In: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 129:3, s. 1274-1279
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Journal article (peer-reviewed)abstract
- Kraft lignin obtained from the pulping of wood is an interesting new precursor material for carbon fiber production because of its high carbon content and ready availability. However, continuous spinning of softwood kraft lignin (SKL) has been impossible because of its insufficient softening characteristics and neat hardwood kraft lignin (HKL) has required extensive pretreatments to enable fiber formation. Softwood kraft lignin permeate (SKLP) and hardwood kraft lignin permeate (HKLP), fractionated by membrane filtration, were continuously melt spun into fibers. To improve the spinnability of SKL and HKL, HKLP was added as a softening agent. SKL- and HKL-based fibers were obtained by adding 3-98 wt % HKLP. A suitable temperature range for spinning was 20-85°C above the Tg of the lignin samples, and this range gave a flawless appearance according to the SEM analysis. Smooth, homogeneous fibers of SKLP, HKLP, and SKL with HKLP were successfully processed into solid carbon fibers.
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| 13. |
- Nordström, Ylva, et al.
(author)
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Mechanical characterization and application of Weibull statistics to the strength of softwood lignin-based carbon fibers
- 2013
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In: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 130:5, s. 3689-3697
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Journal article (peer-reviewed)abstract
- Mechanical characterization of the first generation of softwood kraft lignin-based carbon fibers (CF) was carried out. The single fiber tensile tests of filaments with different diameters and length were performed to evaluate stiffness and strength of carbon fibers. The average mechanical properties were measured as follows: tensile strength of approximately 300 MPa, the elastic modulus of 30 GPa and a strain at failure within interval of 0.7-1.2%. The fiber strength data was evaluated by the two-parameter Weibull statistics and parameters of this distribution were obtained. Although strength of the produced fibers is still significantly lower than that of commercially available, the experimental results and predictions based on Weibull statistics show a fairly good fit.
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| 14. |
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| 15. |
- Olsson, Carina, et al.
(author)
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Carbon fibres from lignin-cellulose precursor
- 2015
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In: 18th International Symposium on Wood, Fiber and Pulping Chemistry, September 9-11, 2015, Vienna. ; , s. 126-129
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Conference paper (other academic/artistic)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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| 16. |
- Olsson, Carina, et al.
(author)
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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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In: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:4, s. 275-283
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Journal article (peer-reviewed)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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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Sjöholm, Elisabeth, Associiate Professor, et al.
(author)
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Microwave assisted etherification of lignin
- 2017
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In: International symposium on green chemistry (ISGC 2017), May 16-19, 2017, La Rochelle, France.
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Conference paper (other academic/artistic)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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| 23. |
- Tomani, Per, et al.
(author)
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Lignin separation from pulp mills and potential use in different applications
- 2015
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Conference paper (other academic/artistic)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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| 24. |
- Wang, Miao, et al.
(author)
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Fast and reliable quantification of lignin reactivity via reaction with dimethylamine and formaldehyde (Mannich reaction)
- 2017
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In: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:1, s. 27-34
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Journal article (peer-reviewed)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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| 25. |
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