| 1. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Analyses of wood components in mild steam explosion liquors from spruce
- 2014
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 29:4, s. 557-566
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Tidskriftsartikel (refereegranskat)abstract
- Steam explosion at mild conditions is an intriguing pre-treatment method for future biorefineries. Here, mild steam explosion liquors, i.e. the condensed steam generated from water-impregnated and NaBH4-impregnated spruce at various steam explosion conditions, are comprehensively characterized. The characterization includes several chromatographic techniques along with nuclear magnetic resonance (NMR), in order to determine relative abundances of solubilized lignin, carbohydrates, and acetate content. The findings show that the main components in the liquors originated from hemicelluloses and, to some extent, wood extractives. Arabinose side substituents of arabinoglucuronoxylan were cleaved early during the steam treatment. The amount of (galacto) glucomannan in the liquors increased from 16% for the sample from the 4 bar (0.4 MPa) treatment, to 23% for the sample from the 7 bar treatment. The effects of different conditions on wood during NaBH4-treatment were also investigated. For this treatment, it was found that the degree of deacetylation increased at harsher conditions.
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| 2. |
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| 3. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Mild steam explosion: A way to activate wood for enzymatic treatment, chemical pulping and biorefinery processes
- 2012
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 27:5, s. 828-835
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Tidskriftsartikel (refereegranskat)abstract
- Industrially chipped wood chips of Norway spruce (Picea abies) were subjected to mild steam explosion (115 - 160 degrees C) in a small-scale steam explosion reactor. This was followed by kraft cooking or extraction in alkali at 130 degrees C for two hours, or by an enzymatic treatment with a culture filtrate in order to investigate the efficiency of the process in opening wood structure. The results demonstrated that mild explosion has an effect on opening wood structure, shown by increased release of glucomannans during alkaline extraction and faster delignification in kraft cooks for steam-exploded samples. The effect was also shown by analysis of the released reducing sugars of enzymatic treated wood chips, which showed that the wood structure became accessible for enzymes even at very modest mild steam explosion conditions. This was not observed in untreated wood chips, used as reference. The enzyme activity increased with increased temperature during mild steam explosion, and the effect did not seem to be linear. The mechanical effect of steam explosion seems to be of great importance at lower temperatures, and both chemical and mechanical effects are important at higher steam explosion temperatures. Samples for enzymatic treatment were taken both from the edges of wood chips as well as from the middle part of the chips, and the effect of steam explosion was somewhat greater in samples from the middle parts.
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| 4. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Mild Steam Explosion and Chemical Pre-Treatment of Norway Spruce
- 2012
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 7:2, s. 2051-2074
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to open up the structure of wood while retaining a large amount of hemicelluloses, in particular (galacto)glucomannans. The effects of pre-treatments on wood meal from spruce (Picea abies) with a reducing agent (NaBH4) combined with steam explosion at very mild conditions were investigated. The effects of steam explosion at 160 degrees C were studied for various residence times (5 to 35 min) on both water-impregnated wood meal and samples pre-treated with NaBH4. The findings showed that pre-treatment with sodium borohydride stabilized the reducing end-groups of glucomannans and that the treatment was effective both during mild steam explosion, for both long and short residence times, as well as during subsequent treatment in alkali. Extraction experiments at different pH and temperatures showed that the main part of the hemicelluloses still remained in the wood residue after treatment. The molecular weight distributions of the extracted material from the liquors indicated that there were broad molecular distributions and that the molecular weight averages were between 3 and 6 kDa.
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| 5. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Mild steam explosion followed by kraft cooking and oxygen delignification of spruce (Picea abies)
- 2013
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Ingår i: Appita Journal. - 1038-6807. ; 66:4, s. 322-330
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Tidskriftsartikel (refereegranskat)abstract
- The paper considers mild steam explosion as an initial biorefinery process step to make wood more accessible for chemicals and enzymes in subsequent extraction and isolation procedures. Wood chips were exploded at four and seven bars and the effects of the treatments were followed during both kraft cooking and oxygen delignification. The properties of the unbleached and bleached pulps, including kappa number, pulp yield, fibre length, intrinsic viscosity, chemical composition and ISO brightness, were analysed using standard methods. The findings showed a difference between treatment at four and seven bars, as the higher pressure leads to more significant visual changes as well as somewhat increased degradation of hemicelluloses. These changes however, have no apparent significant negative effect on the final pulp properties. To the contrary, a benefit of steam treatment seems that the time to reach a certain kappa number was slightly reduced with steam-exploded wood chips.
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| 6. |
- Jedvert, Kerstin, 1984
(författare)
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Mild Steam Explosion of Norway Spruce
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The most common wood species in Sweden, and one of the most important renewable raw materials in Northern Europe, is Norway spruce (Picea abies). Today, it is utilized mainly for sawed timber and the production of pulp and paper. A modern kraft pulp mill that produces bleached pulp has a material efficiency of about 40-45%, and the final product contains mainly cellulose. The other components of the wood, e.g. hemicelluloses and lignin, are heavily degraded during the process and end up in the mill’s recovery boiler, where they are burned to recover the latent energy. The biorefinery concept is an approach where biomass is used for the production of a variety of products, e.g. new materials, chemicals and fuels.The aim of this work is to investigate a process called “mild steam explosion” as a pre-treatment step in a biorefinery. During steam explosion, saturated steam is applied to biomass at elevated pressure, which is followed by a fast pressure release. The treatment leads to both mechanical rupture and chemical reactions, such as acid hydrolysis. The conditions of the steam explosion treatment are kept mild (approx. 140-170°C) to ensure that the degradation of the wood components is kept at a minimum. The idea behind the treatment is to make the structure of wood more accessible and facilitate the extraction and isolation of the wood components, preferably those of high molecular weights. The most abundant hemicellulose component in spruce is (galacto)glucomannan and is of primary concern. This is a challenge since it is also the component that is the most sensitive to chemicals. Treatment with reducing agents, such as sodium borohydride and dithionite, are therefore used to stabilize the (galacto)glucomannan.The findings in this thesis showed that steam explosion, even at modest conditions, made the wood structure accessible for enzymatic reactions. It was also shown that wood components from hemicelluloses and wood extractives were released into the condensed steam. Mild steam explosion was also seen to increase the rates of both extraction and delignification during subsequent treatments. The mechanical effects of the steam explosion treatment originated from steam heating, expansion during pressure release and impact. The properties of pulps after kraft cooking and oxygen delignification of steam-exploded wood chips were comparable to reference pulps. It was also found that treatment with a reducing agent stabilizes the (galacto)glucomannan during both mild steam explosion and various chemical treatments.
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| 7. |
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| 8. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Tailoring the physical characteristics of solution blown cellulosic nonwovens by various post-treatments
- 2021
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 36:4, s. 682-695
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Tidskriftsartikel (refereegranskat)abstract
- Nonwovens are increasing in demand due to their versatility which enables use in a broad range of applications. Most nonwovens are still produced from fossil-based resources and there is thus a need to develop competitive materials from renewable feedstock. In this work, nonwovens are produced from cellulose via a direct solution blowing method. Cellulose was dissolved using the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc) and was regenerated into nonwovens by coagulation in water. The properties of such nonwovens were previously rather stiff and papery-like and the aim of this work was to improve the softness and feel of the materials by simple adjustments of the post-processing steps, i. e. washing and drying. It was shown that by primarily changing the drying method, it was possible to create a much softer and bulkier material using the same solution blowing parameters.
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| 9. |
- 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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| 10. |
- Mattsson, Tuve, et al.
(författare)
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Towards a wood based material biorefinery - A demonstrator
- 2015
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Ingår i: 6th Nordic Wood Biorefinery Conference, NWBC 2015. - : VTT Technical Research Centre of Finland. - 9789513883539 ; , s. 92-101
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Konferensbidrag (refereegranskat)abstract
- Wood, the most abundant ligno-cellulosic raw material available, is a key potential feedstock for production of more sustainable alternatives to fossil-based materials. However advances within the fields of extraction and treatment processes within what is often referred to as the biorefinery concept is essential to allow for such transition. In this study, several different methods for the extraction and separation of wood constituents have been combined in a single process with the purpose of achieving a high overall efficiency of material extraction and utilisation. The work builds on several activities within the Wallenberg Wood Science Center (WWSC). The aim is to present a laboratory-scale demonstrator that illustrates how the different constituents can be separated from the wood matrix for later use in the production of bio-based materials and chemicals. The process steps involved have been tested as integral steps in a linked process for a scale of operations that range from the kilogram-scale down to the gram-scale. Industrially chipped softwood, containing mainly spruce with some pine, was used as raw material.
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