| 1. |
- Azhar, Shoaib, et al.
(författare)
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Chemoenzymatic separation of softwood polymers
- 2011
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Ingår i: Proceedings of the 16th international symposium of wood, fiber and pulp chemistry. - 9787501982066 ; , s. 932-936
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Konferensbidrag (refereegranskat)abstract
- Spruce wood chips were chemically pre-treated with sodium hydroxide to open up the compact structure of wood. The wood was then treated with enzymes (xylanase, gamanase and mannanase) and subjected to extraction with a mixture of methanol and alkali to efficiently isolate lignin and hemicelluloses. Chemical pre-treatment improved enzyme efficiency which consequently enhanced the extraction of lignocelluloses with higher average molar mass than the references.
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| 2. |
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| 3. |
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| 4. |
- Helander, Mikaela, et al.
(författare)
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Fractionation of Technical Lignin: Molecular Mass and pH Effects
- 2013
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 8:2, s. 2270-2282
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Tidskriftsartikel (refereegranskat)abstract
- Today, lignin from kraft pulping is used mainly as fuel, with only very small amounts being used as raw material for chemicals and materials. This work focuses on using a convenient method for separating large amounts of low molecular weight lignin from the kraft process. Low molecular weight lignin contains larger amounts of phenolic structural units, which are possible modification sites and can be used as antioxidants. Moreover, a product that has reduced polydispersity, low molecular weight, and purified lignin could be a potential material for new applications. The studied process for separating lignin from weak black liquor used a membrane with a cut-off of 1000 Da. During precipitation of the 1000 Da permeate, it is necessary to prevent formation of fairly large, rigid particles/agglomerates of lignin by keeping the temperature low. To improve the dead-end filtration, higher ionic strength is needed for the weak black liquor. Additionally, reducing the end pH will cause more material to precipitate. More sulfur was found in the low molecular weight lignin and at lower precipitation pH, indicating that most sulfur left in the lignin samples might be bound to low molecular weight lignin.
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| 5. |
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| 6. |
- Mattsson, Tuve, et al.
(författare)
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The Development of a Wood-based Materials-biorefinery
- 2017
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 12:4, s. 9152-9182
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Tidskriftsartikel (refereegranskat)abstract
- Several different methods for the extraction, separation, and purification of wood constituents were combined in this work as a unified process with the purpose of achieving a high overall efficiency of material extraction and utilization. This study aimed to present a laboratory-scale demonstrator biorefinery that illustrated how the different wood constituents could be separated from the wood matrix for later use in the production of new bio-based materials and chemicals by combining several approaches. This study builds on several publications and ongoing activities within the Wallenberg Wood Science Center (WWSC) in Sweden on the theme "From wood to material components." Combining the approaches developed in these WWSC projects - including mild steam explosion, membrane and chromatographic separation, enzymatic treatment and leaching, ionic liquid extraction, and fractionation together with Kraft pulping - formed an outline for a complete materials-biorefinery. The process steps involved were tested as integral steps in a linked process. The scale of operations ranged from the kilogram-scale to the gram-scale. The feasibility and efficiency of these process steps in a biorefinery system were assessed, based on the data, beginning with whole wood.
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| 7. |
- Mattsson, Tuve, 1979, et al.
(författare)
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The Development of a Wood-based Materials-biorefinery
- 2017
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 12:4, s. 9152-9182
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Tidskriftsartikel (refereegranskat)abstract
- Several different methods for the extraction, separation, and purification of wood constituents were combined in this work as a unified process with the purpose of achieving a high overall efficiency of material extraction and utilization. This study aimed to present a laboratory-scale demonstrator biorefinery that illustrated how the different wood constituents could be separated from the wood matrix for later use in the production of new bio-based materials and chemicals by combining several approaches. This study builds on several publications and ongoing activities within the Wallenberg Wood Science Center (WWSC) in Sweden on the theme "From wood to material components." Combining the approaches developed in these WWSC projects - including mild steam explosion, membrane and chromatographic separation, enzymatic treatment and leaching, ionic liquid extraction, and fractionation together with Kraft pulping - formed an outline for a complete materials-biorefinery. The process steps involved were tested as integral steps in a linked process. The scale of operations ranged from the kilogram-scale to the gram-scale. The feasibility and efficiency of these process steps in a biorefinery system were assessed, based on the data, beginning with whole wood.
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| 8. |
- Wang, Yan, et al.
(författare)
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Improved yield and pulp properties by adding sodium dithionite in kraft pulping of spruce
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The reductive effect of sodium dithionite (Na2S2O4) on sugar model compounds was investigated. Results revealed that parts of open aldehyde forms in the sugars were reduced to the corresponding alditols by Na2S2O4. The possibilities to improve yield and other properties of spruce kraft pulp by addition of Na2S2O4 were also investigated. The yield, carbohydrate compositions, Klason lignin, intrinsic viscosity, kappa number of pulp, tensile strength and optical properties of resultant paper sheets were analysed. Compare with the normal kraft pulp without Na2S2O4 addition, yield together with viscosity were increased, while Klason lignin and kappa number were decreased. The brightness and tensile strength of paper sheet were also improved. The only drawback for adding sodium dithionite to white liquor was higher reject content. This could be overcome by pre-impregnation with Na2S2O4 before kraft pulping process. The possibility of applying Na2S2O4 in industrial kraft pulp mill was discussed, including how to generate Na2S2O4 from black liquor thereby closing the process.
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| 9. |
- Wang, Yan
(författare)
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Pretreatment and Enzymatic Treatment of Spruce : A functional designed wood components separation for a future biorefinery
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The three main components of wood, namely, cellulose, hemicellulose, and lignin, can be used in various areas. However, since lignin covalently crosslinks with wood polysaccharides creating networks that is an obstacle for extraction, direct extraction of different wood components in high yield is not an easy matter. One potential approach to overcome such obstacles is to treat the wood with specific enzymes that degrade the networks by specific catalysis. However, the structure of wood is so compact that the penetration of the wood fibers by large enzyme molecules is hindered. Thus, the pretreatment of wood prior to the application of enzymes is necessary, for “opening” the structure.One pretreatment method that was performed in this thesis is based on kraft pulping, which is a well-established and industrialized technique. For untreated wood, the wood fibers cannot be attacked by the enzymes. A relatively mild pretreatment was sufficient for wood polysaccharides hydrolyzed by a culture filtrate. A methanol-alkali mixture extraction was subsequently applied to the samples that were pretreated with two types of hemicellulases, Gamanase and Pulpzyme HC, respectively. The extraction yield increased after enzymatic treatment, and the polymers that were extracted from monocomponent enzyme-treated wood had a higher degree of polymerization. Experiments with in vitro prepared lignin polysaccharide networks suggested that the increased extraction was due to the enzymatic untying. However, the relatively large loss of hemicellulose, particularly including (galacto)glucomannan (GGM), represents a problem with this technique. To improve the carbohydrate yield, sodium borohydride (NaBH4), polysulfide and anthraquinone were used, which increased the yields from 76.6% to 89.6%, 81.3% and 80.0%, respectively, after extended impregnation (EI). The additives also increased the extraction yield from approximately 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14% w/w wood.Sodium dithionite (Na2S2O4) is an alternative reducing agent for the preservation of hemicelluloses because it is less expensive than metal hydrides and only contains sodium and sulfur, which will not introduce new elements to the recovery system. Moreover, Na2S2O4has the potential to be generated from black liquor. Na2S2O4 has some preservation effect on hemicelluloses, and the presence of Na2S2O4 also contributed to delignification. The extraction yield increased to approximately 15% w/w wood. Furthermore, Na2S2O4 has been applied in the kraft pulping process of spruce. The yield and viscosity increased, while the Klason lignin content and kappa number decreased, which represents a beneficial characteristic for kraft pulp. The brightness and tensile strength of the resulting sheets also improved. However, the direct addition of Na2S2O4 to white liquor led to greater reject content. This problem was solved by pre-impregnation with Na2S2O4 and/or mild steam explosion (STEX) prior to the kraft pulping process. Following Na2S2O4 pre-impregnation and mild STEX, the obtained kraft pulp had substantially better properties compared with the properties exhibited after direct addition of Na2S2O4 to the white liquor.The wood structure opening efficiency of mild STEX alone was also tested. The accessibility of the wood structure to enzymes was obtained even at very modest STEX conditions, according to a reducing sugar analysis, and was not observed in untreated wood chips, which were used as a reference. The mechanical effect of STEX appears to be of great importance at lower temperatures, and both chemical and mechanical effects occur at higher STEX temperatures.
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