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  • 1.
    Brännvall, Elisabet
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tormund, Disa
    Bakkstrom, Marie
    Bergstrom, Jonas
    Tubek-Lindblom, Anna
    Separate bleaching of pulp fractions enriched in earlywood and latewood fibers2007In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 27, no 2, p. 99-112Article in journal (Refereed)
    Abstract [en]

    Unbleached softwood kraft pulp was fractionated in hydrocyclones into a fine fraction, enriched in earlywood fibers, and a coarse fraction, enriched in latewood fibers. The response to individual bleaching chemicals and the bleachability in bleaching sequences of the pulp fractions was studied. The light absorption coefficient, light scattering coeffient, and brightness were higher in the unbleached fine fraction than in the coarse fraction. Hydrogen peroxide managed to reduce the light absorption coefficient of the earlywood enriched fine fraction more efficiently than that of the latewood enriched fraction. In the TCF-sequence the light absorption coefficient of the fine fraction was reduced to the level of the coarse fraction at a given consumption of bleaching chemicals. In the ECF-sequence the difference in light absorption coefficient remained between the fractions. At a given consumption of bleaching chemicals, the fine fraction had higher brightness than the coarse fraction, 2%- and 1%-units on the ISO-scale in the TCF and ECF bleaching sequence, respectively.

  • 2.
    Gonzalo Epelde, I.
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Lindgren, C. T.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Lindström, Mikael E.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Kinetics of wheat straw delignification in soda and kraft pulping1998In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 18, no 1, p. 69-82Article in journal (Refereed)
    Abstract [en]

    Kraft and soda delignification kinetics of wheat straw, Triticum aestivum, have been studied as a function of OH- concentration, HS- concentration, and temperature. It was found that about 90% of the lignin is dissolved in the rapid initial phase. The rates of delignification in the bulk and residual phases were found to be similar to those of birch wood, Betula pubescens, The amount of residual phase lignin was found to be considerably less than in birch or spruce, Picea abies, and it was affected by the same factors, A model that accurately describes the delignification of wheat straw was derived.

  • 3.
    Helander, Mikael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mattsson, Tuve
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Parameters Affecting the Cross-flow Filtration of Dissolved LignoBoost Kraft Lignin2015In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 36, no 1, p. 1-8Article in journal (Other academic)
    Abstract [en]

    In the kraft pulping process, the lignin-containing by-product kraft black liquor is currently combusted as an energy source. LignoBoost is a technique that extracts lignin from kraft black liquor, resulting in a lignin-lean black liquor, which is returned to the process, and an extracted kraft lignin. To facilitate the use of the extracted kraft lignin in high-value applications, it can be refined via fractionation to produce a more homogeneous starting raw material. Hence, the aim of this study is to investigate the behavior of dissolved softwood kraft lignin during cross-flow filtration. The effects of the lignin concentration, pH, and ionic strength on the fractionation of the dissolved lignin during cross-flow filtration are investigated. The results indicate that large amounts of low-molecular-weight kraft lignin can be produced from solutions having a low lignin concentration. Furthermore, the effects of pH and ionic strength on the fractionation of low-molecular-weight lignin are identified within the studied ranges.

  • 4. Johansson, E. E.
    et al.
    Lind, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Free radical mediated cellulose degradation during high consistency ozonation2005In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 25, no 3, p. 171-186Article in journal (Refereed)
    Abstract [en]

    A study was performed on the ozonation of cotton linters at high consistency, 40%, and pH3, in order to shed some light on the mechanism of degradation of cellulose during pulp bleaching. Ferryl ions (FeO2+), produced in the reaction of O-3 with Fe(H), was used to initiate free radical chain reactions to investigate the relation between chain reactions and degradation. The degradation was evaluated by viscometry. The degradation of cellulose responded more strongly to the propagation than to the initiation of the chain reactions. Also, the results suggest that the reactions responsible for initiation do not in themselves contribute to the observed degradation. Complementary experiments were made on cellulose beads (<5% crystalline). In contrast to the results from the cotton linters, the degradation of cellulose beads appears to correspond directly to ferry] ion formation. In non-structured cellulose (cellulose beads), cellulose is highly accessible. The degradation is thus directly linked to the total amount of radical attack. In naturally structured cellulose (cotton linters) only cellulose at fibril surfaces is accessible and will react. A chemical attack of fast-reacting agents on surfaces in structured cellulose should thus not be highly efficient in lowering the average chain length. What distinguishes radical chain reaction degradation in this context is that the spreading chain reaction is governed by the time of each step in the reaction cycle. The explanation that best fits our results is that of a free radical chain reaction, where the propagation step is rapid, which also implies that degradation is concentrated to zones along fibrils or fibers.

  • 5.
    Lawoko, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Van Heiningen, A. R. P.
    University of Maine, USA.
    Fractionation and characterization of completely dissolved ball milled hardwood2011In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 31, no 3, p. 183-203Article in journal (Refereed)
    Abstract [en]

    A simplified method for sequentially dissolving and fractionating ball milled hard wood polymers in high yield is presented. The complete dissolution of the whole ball milled wood, and the fractions recovered from it by applying the sequential fractionation, was accomplished in lithium chloride/ dimethylacetamide solvent system enabling size exclusion chromatography studies. The chromatography applied a four detector system; an Ultraviolet-Visible spectroscopy-, Intrinsic Viscosity-Differential Pressure-, Right Angle Laser Light Scattering- and Refractive Index detectors, a combination hereby proposed to enable interpretation of the complex elution profiles with emphasis on chemical interactions. Indirect evidence of the presence of lignin carbohydrate complexes in hardwoods is provided. It is also proposed that cellulose is severely degraded from a degree of polymerization of 10,000 in wood, down to a value of approximately 400 by either the applied ball milling condition or in subsequent solubilization steps.

  • 6.
    Li Jansson, Zheng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Brännvall, Elisabet
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Effect of Kraft Cooking Conditions on the Chemical Composition of the Surface and Bulk of Spruce Fibers2014In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 34, no 4, p. 291-300Article in journal (Refereed)
    Abstract [en]

    By varying cooking temperature, alkali charge, ionic strength, and cooking time in Kraft pulping of spruce chips, pulps ranging between kappa numbers 20-80 were obtained. The unbleached Kraft pulp fibers were subjected to mechanical peeling in order to separate the surface material from the bulk of the fibers and the carbohydrate composition and lignin content of the two fractions were analyzed. As expected, the lignin and xylan contents were higher on the fiber surface than in the fiber wall. The percentage of xylan on the fiber surface was fairly constant, independent of different pulping conditions or degree of delignification. The lignin proportion on the fiber surface gradually decreased with decreasing kappa number. At a given kappa number, pulping at a higher temperature resulted in less lignin on the fiber surface, probably because of the higher solubility of lignin at higher temperature. Cooking at lower alkali charge also resulted in lower lignin content on the fiber surface at a given kappa number. In this case, there was more time available for degradation of the surface lignin since the lower alkali charge resulted in longer cooking time needed to reach a certain kappa number.

  • 7.
    Sewring, Tor
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, .
    Durruty, Julie
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Schneider, Lynn
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Schneider, Helen
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Mattsson, Tuve
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, .
    Theliander, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, .
    Acid Precipitation of Kraft Lignin from Aqueous Solutions: The Influence of pH, Temperature, and Xylan2019In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 39, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    In this study, the manners in which temperature (45-77 degrees C) and the addition of xylan (5 g/95 g lignin) influence the onset of precipitation and evolution of the particle size distribution during acid precipitation of softwood kraft lignin were investigated in situ. No systematic trend between the onset pH of precipitation and the temperature or the addition of xylan could be observed at these conditions: the average onset pH was found to be 9.3. However, the size of the agglomerates increased as the temperature was increased, but added xylan rendered a decrease in agglomerate size. A higher onset pH was measured at increased Na ion concentration. The results indicate that the ionization degree of the phenolic groups influences the precipitation at 1 M Na ions but it is also probable that the degree of ionization of the carboxylic groups (on kraft lignin and xylan) influences precipitation (particle numbers and sizes).

  • 8.
    Stenman, David
    et al.
    KTH, Superseded Departments, Chemistry.
    Carlsson, Magnus
    KTH, Superseded Departments, Chemistry.
    Jonsson, Mats
    KTH, Superseded Departments, Chemistry.
    Reitberger, Torbjörn
    KTH, Superseded Departments, Chemistry.
    Reactivity of the carbonate radical anion towards carbohydrate and lignin model compounds2003In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 23, no 1, p. 47-69Article in journal (Refereed)
    Abstract [en]

    The kinetic selectivity for the reaction of the carbonate radical anion towards lignin and carbohydrate model compounds was determined by pulse radiolysis in the pH-span 8-13. For the cellulose model compound methyl-β-D-glucopyranoside a pKA-value of 14.4 was estimated.

  • 9.
    Stenman, David
    et al.
    KTH, Superseded Departments, Chemistry.
    Carlsson, Magnus
    KTH, Superseded Departments, Chemistry.
    Reitberger, Torbjörn
    KTH, Superseded Departments, Chemistry.
    Peroxynitrite mediated delignification of pulp: A comparative study on the bleaching properties of the carbonate and hydroxyl radicals2004In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 24, no 2, p. 83-98Article in journal (Refereed)
    Abstract [en]

    Oxygen delignified pulps were bleached with hydroxyl and carbonate radicals produced from peroxynitrite. The carbonate radical treated pulps showed better selectivity and an increase in brightness. For both radicals, good kappa reductions were obtained. This study shows that the carbonate radical anion is a possible green oxidant for future delignification technologies.

  • 10. Tormund, Disa
    et al.
    Brännvall, Elisabet
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Backstrom, Marie
    Olm, Leelo
    Delignification and bleaching response of earlywood and latewood2006In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 26, no 4, p. 325-337Article in journal (Refereed)
    Abstract [en]

    The delignification response in cooking and the impact of bleaching on earlywood and latewood were studied. Spruce earlywood and latewood chips were pulped by the kraft process and subsequently treated with one bleaching chemical at a time. In cooking, latewood required a higher alkali charge to reach the same kappa number. No difference in the light absorption coefficient between the different fiber types was observed. After oxygen delignification the earlywood fibers had a higher light absorption coefficient at the same kappa number. The difference in light absorbing material was maintained when bleaching was performed with chlorine dioxide, ozone, and peracetic acid. Hydrogen peroxide decreased the light absorbing structures in the earlywood to the same level as for latewood. The earlywood pulp had a higher brightness at a given kappa number than the latewood. The higher brightness remained through all bleaching operations and was primarily due to a higher light scattering ability.

  • 11.
    Wang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Azhar, Shoaib
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Stabilisation of polysaccharides during alkaline pretreatment of wood combined with enzyme-supported extractions in a biorefinery2015In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 35, no 2, p. 91-101Article in journal (Refereed)
    Abstract [en]

    Specific enzymes have been demonstrated to increase the possibilities for extracting wood polymers. Enzymatic treatment requires an open wood structure, which was achieved by extended impregnation of the wood. However, some of the hemicelluloses, primarily glucomannan, and lignin were lost during the impregnation. To improve the carbohydrate yield, three glucomannan modification agents: sodium borohydride, polysulphide and anthraquinone, were used, which increased the yields of the impregnated materials from 76.6% to 89.6%, 81.3% and 80.0%, respectively. Through the use of additives, most of the glucomannan could be retained in the wood while still allowing the enzymes to penetrate the wood and attack the polymers. The additives also increased the extraction yield from 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14%. Of the three stabilising agents, sodium borohydride was the most efficient, providing the highest extraction yields.

  • 12.
    Zanao, Marina
    et al.
    Univ Fed Vicosa, Dept Forestry Engn, Vicosa, MG, Brazil..
    Colodette, Jorge L.
    Univ Fed Vicosa, Dept Forestry Engn, Vicosa, MG, Brazil..
    Oliveira, Rubens C.
    Univ Fed Vicosa, Dept Forestry Engn, Vicosa, MG, Brazil..
    Almeida, Diego P.
    Univ Fed Vicosa, Dept Forestry Engn, Vicosa, MG, Brazil..
    Gomes, Fernando J. B.
    Univ Fed Vicosa, Dept Forestry Engn, Vicosa, MG, Brazil..
    de Carvalho, Danila Morais
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Evaluation of Kraft-PS Cooking for Eucalypt and Pine Wood Chip Mixtures2019In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 39, no 3, p. 149-165Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was evaluating polysulfides (PS) as additives in kraft cooking of wood mixtures eucalypt (E) and pine chips (P) wood mixtures, namely: 50E/50P, 70E/30P, and 90E/10P. Bleaching (O(D/A)(EP)D) and refining of pulps were also investigated. The PS addition (1.5 or 3.0%) to the kraft cooking preserved the hemicelluloses resulting increased pulp yield and reduced H-factor. The oxygen delignification was more efficient for chip mixtures containing higher proportion of pine chips, but was not largely affected by the addition of PS. The bleach chemical consumption was not significantly influenced by PS dosage or by the wood chip mixture. The burst and tear indexes were improved by increasing the proportion of pine chips to the mixture, but an opposite effect was observed for refinability, tensile index, and opacity. The kraft-PS pulps showed increased refinability, tensile, and burst strengths in relation the standard pulps, but lower opacities.

  • 13.
    Zhang, Liming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ralph, J.
    Lu, F. C.
    NMR studies on the occurrence of spirodienone structures in lignins2006In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 26, no 1, p. 65-79Article in journal (Refereed)
    Abstract [en]

    Spirodienone structures have been detected in spruce, birch, and kenaf lignin isolates. NMR signals corresponding to guaiacyl and syringyl spirodienones were fully identified and assigned based on C-13, QUAT, HSQC, HSQC-TOCSY, and HMBC NMR data. Spruce lignin contains spirodienone structures of the guaiacyl type. Syringyl spirodienones dominate in kenaf and birch lignins. Each type of spirodienone was found to be present in two different stereoisomeric forms, with one of the isomers being more prevalent. Signal integrations indicate that about three spirodienones per 100 phenylpropanoid units are present in the spruce and birch lignins and about four in the kenaf lignin.

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