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  • 1.
    Azhar, Shoaib
    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.
    Henriksson, Gunnar
    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.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Lindström, Mikael
    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.
    Extraction of hemicelluloses from fiberized spruce wood2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 117, p. 19-24Article in journal (Refereed)
    Abstract [en]

    A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses. 

  • 2. Bylin, Susanne
    et al.
    Olsson, Carina
    Westman, Gunnar
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Solvation behavior of cellulose and xylan in the MIM/EMIMAc ionic liquid solvent system: Parameters for small-scale solvation2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 1, p. 1038-1054Article in journal (Refereed)
    Abstract [en]

    Ionic liquid treatment has been reported by several researchers as a possible step in the process of fractionating lignocellulosic biomass within the biorefinery concept. However, understanding how solvation can be achieved and how the feedstock biopolymers are affected is needed prior to a viable implementation. An effective two-component solvent system for the wood components cellulose and xylan has been developed. Furthermore, the solvation of these components in the system consisting of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EMIMAc) in a novel combination with the co-solvent 1-methylimidazole (MIM) is investigated. Focused beam reflectance measurement (FBRM) particle characterization in combination with microscopic analysis and molecular weight determinations (xylan) shows that cellulose and xylan can be most efficiently solvated using only 3 to 4% IL (n/n anhydro-glucose units and n/n anhydro-xylose units) and 9% IL, respectively, while still avoiding any significant polymer degradation. A model for a two-step process of cellulose solvation in the present system is proposed.

  • 3.
    Bylin, Susanne
    et al.
    Chalmers University of Technology, Sweden.
    Wells, Tyrone
    Sun, Qining
    Ragauskas, Art
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lignin Structure and Aggregation Behavior in a Two-Component Ionic Liquid Solvent System2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, p. 6002-6018Article in journal (Refereed)
    Abstract [en]

    Ionic liquids are of potential interest in the processing of lignocellulosic biomass. In this study, the ionic liquid co-solvent system of 1-methylimidazole (MIM) and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc) was used to solvate LignoBoost lignin fractionated from black liquor obtained from a kraft paper mill. Lignin ethanol-precipitated (LEP) and ethanol-soluble (LES) fractions were characterized via gel permeation chromatography (GPC) and C-13- and P-31-nuclear magnetic resonance spectroscopy (NMR) to determine structural characteristics and their relationship to polymer solubility in the system. Polymer integrity and solubility were optimal at -20% lignin loading (w/w). Results showed that LEPs were generally of higher apparent molecular weight (Mw) and enriched with condensed/aliphatic ether linkages and aliphatic hydroxyls. The LESs had a lower apparent Mw and were enriched with carboxylic and phenolic groups. This newly gained knowledge on lignin fractionation and aggregation in the present solvent system provides future opportunities for tuning fractionation/extraction to suit a specific biomass-derived product, e.g., carbon fibers.

  • 4. Dang, Binh T. T.
    et al.
    Brelid, Harald
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 6, p. 495-501Article in journal (Refereed)
    Abstract [en]

    The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (M-w) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to M-w decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].

  • 5. Durruty, J.
    et al.
    Mattsson, T.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Local filtration properties of Kraft lignin: The influence of residual xylan2017In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 179, p. 455-466Article in journal (Refereed)
    Abstract [en]

    The influence of lignin and xylan interactions on the filtration properties of precipitated LignoBoost lignin was investigated. LignoBoost lignin was (i) suspended in acid water with xylan added and (ii) dissolved together with xylan and then re-precipitated. The resulting lignin-xylan mixtures were more difficult to filter than the original LignoBoost lignin, although the formed filter cake was also found more porous in the case of re-precipitated solids. Furthermore, the pressure dependency of the filtration properties was shown to increase after the addition of xylan. One possible explanation based on the findings presented in this paper is that xylan is sorbed at the surface of the lignin agglomerates: it increases the contact area between solid and liquid, thus making the particle structure more porous. The influence of ionic strength was also investigated through the addition of sodium sulphate: it was found that increasing the ionic strength of the slurries made the solids easier to separate, possibly due to a decrease in electrostatic repulsive interactions between the solids and the formation of a denser solid structure.

  • 6. Durruty, Julie
    et al.
    Sewring, Tor
    Schneider, Helen
    Schneider, Lynn
    Mattsson, Tuve
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Filtration properties of kraft lignin: The influence of xylan and precipitation conditions2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 4, p. 508-526Article in journal (Refereed)
    Abstract [en]

    LignoBoost lignin powder was dissolved together with xylan and re-precipitated. The influence of the (i) precipitation temperature, (ii) rate of acidification and (iii) final pH of the slurries on the resulting material and its filtration properties was investigated. In the case of slow acidification, larger agglomerates were obtained for slurries with higher precipitation temperatures as well as with higher ionic strengths. Fast acidification led to a more heterogeneous formation of particles, having a broader particle size distribution, compared to slow acidification. Chemical analysis of different layers of the filter cakes formed revealed that xylan was distributed evenly on the solid lignin, reinforcing the hypothesis that xylan is sorbed onto the lignin agglomerates when precipitated together with lignin. Furthermore, the resulting lignin-xylan mixtures were found to be more difficult to filter in the case of a higher final pH of the slurry (pH 4), close to the pKa values of the carboxylic acid groups of xylan, compared to lower pH values (pH 1-3). This is likely the result of an increase in electrostatic repulsive interactions between the particles/agglomerates at higher pH: a locally more porous solid structure is formed, leading to a larger solid/liquid surface area during filtration.

  • 7. Gunnarsson, Maria
    et al.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system2017In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 6, p. 2427-2436Article in journal (Refereed)
    Abstract [en]

    A natural abundance of the air CO2 in NaOH(aq) at low temperature was investigated in terms of cellulose-CO2 interactions upon cellulose dissolution in this system. An organic superbase, namely 1,8-diazabicyclo[5.4.0]undec-7-ene, DBU, known for its ability to incorporate CO2 in carbohydrates, was employed in order to shed light on this previously overlooked feature of NaOH(aq) at low temperature. The chemisorption of CO2 onto cellulose was investigated using spectroscopic methods in combination with suitable regeneration procedures. ATR-IR and NMR characterisation of regenerated celluloses showed that chemisorption of CO2 onto cellulose during its dissolution in NaOH(aq) takes place both with and without employment of the CO2-capturing superbase. The chemisorption was also observed to be reversible upon addition of water: CO2 desorbed when water was used as regenerating agent but could be preserved when instead ethanol was used. This finding could be an important parameter to take into consideration when developing processes for dissolution of cellulose based on this system.

  • 8.
    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.

  • 9.
    Helander, Mikaela
    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.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lawoko, Martin
    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.
    Henriksson, Gunnar
    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.
    Zhang, Liming
    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.
    Lindström, Mikael E.
    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.
    Fractionation of Technical Lignin: Molecular Mass and pH Effects2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, p. 2270-2282Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Helander, Mikaela
    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.
    Theliander, Hans
    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.
    Zhang, Liming
    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.
    Henriksson, Gunnar
    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.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    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.
    Lignin for new materials - molar mass and pH effects2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Article in journal (Other academic)
  • 11.
    Jedvert, Kerstin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wells, Tyrone, Jr.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Analyses of wood components in mild steam explosion liquors from spruce2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 4, p. 557-566Article in journal (Refereed)
    Abstract [en]

    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.

  • 12. Jedvert, Kerstin
    et al.
    Saltberg, Anna
    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.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Mild steam explosion and chemical pre-treatment of Norway spruce2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 2, p. 2051-2074Article in journal (Refereed)
    Abstract [en]

    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.

  • 13. Jedvert, Kerstin
    et al.
    Saltberg, Anna
    Lindström, Mikael
    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.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology.
    Extraction of hemicelluloses after chemical pretreatment combined with mild steam explosion2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, 2011, p. 867-871Conference paper (Refereed)
    Abstract [en]

    The aim of this research is to separate different wood components from softwood as a first step towards development of novel materials made from Scandinavian wood. The approach is pre-treatment with a reducing agent in combination with mild steam explosion (T< 160°C, t < 15 min); followed by extraction with different liquors. The aim is to retain an increased amount of hemicelluloses in general, and glucomannans in particular, during chemical treatments, preferably of high molecular weight. Experiments were performed on wood chips from spruce in small scale steam explosion equipment. A pre-treatment method with sodium borohydride (NaBH 4) as a reducing agent model substance was chosen. Wood chips pre-treated with NaBH 4 were compared to untreated chips, and the chips were treated with steam explosion followed by extraction in alkali. Results showed that a higher amount of glucomannan was retained in chips treated with NaBH 4 than in untreated chips. An increase in the extraction rate as an effect of steam explosion indicates a possible combination of chemical reactions that breaks up the lignin-polysaccharide network and a more porous wood structure. An experimental series with wood powder as raw material were also performed in order to study the chemical reactions during steam explosion, e. g. autohydrolysis. Water impregnated wood powder as well as wood powder treated with NaBH 4 was subjected to mild steam explosion for different retention times. It was shown that a decrease in hemicelluloses content occurred after only 5 min, and the degradation was more severe at longer residence times. However, the degradation of hemicelluloses was not as severe as in the chemical treatments at conditions corresponding to chemical pulping, and consequently might be a more prudent method to access the wood structure. Extractions after steam explosion were investigated at different pH levels, and the results showed that most of the glucomannan was still in the wood residue at the tested conditions. The stabilization of glucomannans by pre-treatment with NaBH 4 was clearly seen also in these experiments.

  • 14. Jedvert, Kerstin
    et al.
    Saltberg, Anna
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mild steam explosion followed by kraft cooking and oxygen delignification of spruce (Picea abies)2013In: Appita journal, ISSN 1038-6807, Vol. 66, no 4, p. 322-330Article in journal (Refereed)
    Abstract [en]

    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.

  • 15. Mattsson, Cecilia
    et al.
    Andersson, Sven-Ingvar
    Belkheiri, Tallal
    Amand, Lars-Erik
    Olausson, Lars
    Vamling, Lennart
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Using 2D NMR to characterize the structure of the low and high molecular weight fractions of bio-oil obtained from LignoBoost (TM) kraft lignin depolymerized in subcritical water2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 95, p. 364-377Article in journal (Refereed)
    Abstract [en]

    In this work a multilevel analysis approach have been used for characterization of LignoBoostTM kraft lignin and bio-oil produced from LignoBoostTM kraft lignin using a process based on subcritical water (350 degrees C, 25 MPa). LignoBoostTM kraft lignin and the different fractions of the bio-oil (light oil, heavy oil and suspended solids) was characterized with high field NMR (18.8 T, 2D(13)C, H-1-HSQC NMR and C-13-NMR), GPC, GC-MS and elemental composition to improve understanding of the subcritical process. By using high resolution 2D HSQC NMR it was possible determine the chemical structures both on low and high molecular weight fractions of the bio-oil. It was confirmed that the signals from the aliphatic lignin inter-unit linkages, i.e. beta-O-4', beta-beta', beta-1' and beta-5', had disappeared from all of the bio-oil fractions studied. This means that both the aliphatic carbon-oxygen (C-O) and to some extent carbon-carbon (C-C) bonds in LignoBoostTM kraft lignin have been cleaved and an effective depolymerization has occurred. However, re-polymerization into higher molecular weight (Mw) fractions takes place simultaneously. These higher Mw fractions (heavy oil and suspended solids) were found to be re-polymerized macromolecules, with new structural networks based on guaiacol/disubstituted aromatic ethers and polyaromatic hydrocarbon structures bound tightly together.

  • 16. Mattsson, Tuve
    et al.
    Martinez, Eduard Laguarda
    Sedin, Maria
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Local solidosity of microcrystalline cellulose during dead-end filtration and sedimentation2013In: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 91, no 6, p. 1155-1162Article in journal (Refereed)
    Abstract [en]

    Solid-liquid separation by filtration and sedimentation are important operations used in a wide range of industries. One important characteristic of both the filtration and sedimentation processes is the solidosity of the filter cake/sediment that is formed, affecting the efficiency and design of the separation. In this study local solidosity was investigated using a gamma-attenuation method during both filtration and sedimentation experiments for microcrystalline cellulose, a highly crystalline cellulose with particles of about 2-80 mu m in diameter. Constitutive relationships for the solidosity were investigated using both filtration (i.e. cake build-up and expression) and sedimentation data for experiments at different pH and suspension concentrations. The sedimentation behaviour under these different conditions was also investigated. It was found that a three parameter empirical model could be used to describe the constitutive relationship between local solidosity and local solid compressible pressure for the sediment formed and the filter cake after both cake build-up and expression. This correlation worked well for the material investigated even at low solid compressible pressures.

  • 17. Mattsson, Tuve
    et al.
    Sedin, Maria
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Filtration properties and skin formation of micro-crystalline cellulose2012In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 96, p. 139-146Article in journal (Refereed)
    Abstract [en]

    Solid-liquid filtration is an important unit operation used in several applications in the pulp and paper industry. It can be challenging especially for materials that forms filter cakes that has a tendency to be highly compressible. The formation of a skin, i.e. an initial cake with a considerably higher filtration resistance, can further increase the filtration resistance for these filter cakes. The separation process in these cases requires considerably larger filter areas. This study investigates skin formation during the filtration of micro-crystalline cellulose, examining the effect of the filter medium, filtration pressure and pH. Depending on the choice of filter medium, the average specific filtration resistance was found to vary by more than one order of magnitude. A decrease in the suspension pH from 6.3 to 2.9 lowered both the filtration resistance and the differences between the filtration media. Using local pressure profiles, a region of high filtration resistance for some of the filter media and pH values was identified close to the bottom of the filter cell. Characterisation of the media and micro-crystalline cellulose indicated that internal clogging of the filter medium was unlikely. This suggests that the filter cake closest to the filter medium had a considerably higher filtration resistance compared to the cake formed immediately after, i.e. a skin had been formed under certain conditions.

  • 18.
    Mattsson, Tuve
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Sedin, Maria
    Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Investigating skin formation during the filtration of micro-crystalline cellulose2013In: FILTRATION, ISSN 1479-0602, Vol. 13, no 2, p. 114-121Article in journal (Refereed)
    Abstract [en]

    Separating solids from liquids through filtration is an important unit operation employed in a wide range of industrial sectors. It is vital that accurate and applicable models are employed when designing industrial sized filters. Comprehensive models are readily available for materials that form incompressible cakes, whereas those for compressible cakes are lacking. Materials that form compressible filter cakes may also form a dense initial cake close to the filter medium, i.e. a 'skin'. In this study the local filtration properties of a model material, TiO<inf>2</inf>, and micro-crystalline cellulose (MCC), are measured to investigate skin formation in a compressible filter cake. Indications of the formation of a skin in the filtration experiments using MCC could be observed; local pressure measurements were found to be useful in the investigation of its formation. Both the choice of the filter medium and the electrostatic interactions affected the skin formation. The tendency for skin to form was reduced at a lower pH, this lower pH corresponding to less charged particles and filter media.

  • 19. Mattsson, Tuve
    et al.
    Sedin, Maria
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zeta-potential and local filtration properties: Constitutive relationships for TiO(2) from experimental filtration measurements2011In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 66, no 20, p. 4573-4581Article in journal (Refereed)
    Abstract [en]

    The use of filtration to separate solid from liquids is a commonly-used unit operation employed in a range of different applications. The development of accurate models is therefore important in facilitating e.g. design, scale-up and troubleshooting. Accurate constitutive relationships between local filtration properties need to be formulated in order to form precise models of the filtration process. One important parameter that is seldom considered explicitly in filtration models is the inter particle forces, e. g. electrostatic forces. The aim of this study is to investigate local filtration properties, under controlled conditions, for the model material TiO(2) where the zeta-potential, and thereby one important parameter affecting the inter-particle interactions, is altered. In this study the local solidosity is measured during filtration by gamma-attenuation, the local pressure is measured using capillary tubes. These data are used to calculate the local specific filtration resistance. The compressibility of the filtration cake was changed substantially by altering the zeta-potential. Several published constitutive relationships between local data and specific filtration resistance were applied; they yielded very similar parameters that were in good accordance with the characterization of the material.

  • 20. Muzamal, Muhammad
    et al.
    Jedvert, Kerstin
    Theliander, Hans
    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. Chalmers, Sweden..
    Rasmuson, Anders
    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. Chalmers, Sweden..
    Structural changes in spruce wood during different steps of steam explosion pretreatment2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 1, p. 61-66Article in journal (Refereed)
    Abstract [en]

    Steam explosion (SE) is a promising hydrothermal pretreatment technology for future biorefineries. In this study, the three steps of the steam explosion process, (1) the steam treatment (2) the explosion, and (3) the impact step were separately considered and their effects on structural changes of wood were studied. The SE experiments were performed on single wood pieces in different experimental set-ups at 7 and 14 bar pressure with 5 and 10 min treatment times. Mercury porosimetry and environmental scanning electron microscopy analyses were conducted to characterise both internal and external changes in the wood. It was found that the explosion step is not responsible for the disintegration of the wood material into small pieces; instead, the disintegration occurs due to impact of softened wood chips. However, the porosity profiles of the tracheids change during the explosion step. Altogether, all three steps of the SE process contribute in a synergistic way to an increase in pore size and total intrusion volume.

  • 21.
    Wetterling, John
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Chemistry and Chemical Engineering, Chalmers University of Technology.
    Jonsson, S.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology.
    Mattsson, Tuve
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Chemistry and Chemical Engineering, Chalmers University of Technology.
    Theliander, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Chemistry and Chemical Engineering, Chalmers University of Technology.
    The Influence of Ionic Strength on the Electroassisted Filtration of Microcrystalline Cellulose2017In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 56, no 44, p. 12789-12798Article in journal (Refereed)
    Abstract [en]

    The production of materials such as microfibrillated cellulose and cellulose nanocrystals is gathering significant research interest by combining mechanical strength and toughness with a low density, biodegradability and renewability. However, one of the challenges with production on an industrial scale is to obtain an energy-efficient solid-liquid separation which is difficult because of the high specific filtration resistance of these materials. This study investigates electroassisted filtration as a method to facilitate the dewatering of cellulosic materials and the influence of ionic strength on the electrofiltration behavior. Electroassisted filtration is found to improve the dewatering rate of the studied cellulosic material, and the potential improvement compared to pressure filtration increased with the specific surface area of the solid material. Increasing the ionic strength of the system increased the power demand of the electroassisted filtration, and the major potential for industrial application is thus for systems with a limited ionic strength.

  • 22.
    Wetterling, John
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Mattsson, Tuve
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Modelling filtration processes from local filtration properties: The effect of surface properties on microcrystalline cellulose2017In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 165, p. 14-24Article in journal (Refereed)
    Abstract [en]

    The influence of structure and charge of particles surfaces on the cake filtration behaviour of microcrystalline cellulose was investigated. The local filtration properties were evaluated experimentally and used to model the overall filtration behaviour. At suspension conditions where the microcrystalline cellulose particles are charged, a large pressure drop was observed close to the filter medium, thereby indicating that a rate-limiting skin layer was formed. Measurements of the local solidosity of the filter cake indicated that a secondary filter cake, with a negligible filtration resistance, formed above the rate-limiting skin layer. This behaviour was not observed when the surface roughness of the particles was increased or when the surface charge of the particles was neutralised by making a change to the pH of the suspension. The filtration behaviour of particles with these surface properties was instead dominated by the formation of a compressible filter cake. Local filtration properties of compressible filter cakes determined experimentally were used to successfully model the overall filtration behaviour. The filtration model used an empirical relationship to describe the pressure dependence of the local solidosity of the filter cake along with a cell model to describe the relationship between the solidosity and the permeability of the filter cake.

  • 23.
    Wetterling, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mattsson, Tuve
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Effects of surface structure on the filtration properties of microcrystalline cellulose2014In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 136, p. 1-9Article in journal (Refereed)
    Abstract [en]

    The filtration of biomaterials is often a challenge due to high filtration resistances and the formation of compressible filter cakes. This study investigates how the local filtration properties of microcrystalline cellulose, a biomaterial forming compressible filter cakes, are affected by the surface structure of its particles. The surface structure was modified through mechanical shearing and the treatment resulted in an increased surface ruggedness along with a small decrease in particle size distribution. The mechanical treatment was found to increase the local specific filtration resistance to a large extent whereas no significant change to the local filter cake solidosity was observed. The relationship between the local solidosity of the filter cake and the local specific filtration resistance could be described by a cell model as flow around porous spheres with negligible permeability. The effect of an increased surface ruggedness was represented in this model as an increased specific surface area subjected to drag as well as a decrease in particle solidosity.

  • 24.
    Wetterling, Jonas
    et al.
    KTH. Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Royal Inst Technol, Wallenberg Wood Sci Ctr, S-10044 Stockholm, Sweden..
    Sahlin, Karin
    KTH. Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Royal Inst Technol, Wallenberg Wood Sci Ctr, S-10044 Stockholm, Sweden..
    Mattsson, Tuve
    KTH. Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Royal Inst Technol, Wallenberg Wood Sci Ctr, S-10044 Stockholm, Sweden..
    Westman, Gunnar
    KTH. Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Royal Inst Technol, Wallenberg Wood Sci Ctr, S-10044 Stockholm, Sweden..
    Theliander, Hans
    KTH. Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Royal Inst Technol, Wallenberg Wood Sci Ctr, S-10044 Stockholm, Sweden..
    Electroosmotic dewatering of cellulose nanocrystals2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 4, p. 2321-2329Article in journal (Refereed)
    Abstract [en]

    One of the main challenges for industrial production of cellulose nanocrystals is the high energy demand during the dewatering of dilute aqueous suspensions. It is addressed in this study by utilising electroosmotic dewatering to increase the solid content of suspensions of cellulose nanocrystals. The solid content was increased from 2.3 up to 15.3 wt%, i.e. removal of more than 85% of all the water present in the system, at a much lower energy demand than that of thermal drying. Increasing the strength of the electric field increased not only the dewatering rate but also the specific energy demand of the dewatering operation: the electric field strength used in potential industrial applications is thus a trade-off between the rate of dewatering and the energy demand. Additionally, it was found that high local current intensity had the potential of degrading cellulose nanocrystals in contact with the anode. The maximum strength of the electric field applied should therefore be limited depending on the equipment design and the suspension conditions.

  • 25. Wojtasz-Mucha, J.
    et al.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hydrothermal pretreatment of wood by mild steam explosion and hot water extraction2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 241, p. 120-126Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step.

  • 26. Zhu, Weizhen
    et al.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Precipitation of Lignin from Softwood Black Liquor: An Investigation of the Equilibrium and Molecular Properties of Lignin2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 1, p. 1696-1714Article, review/survey (Refereed)
    Abstract [en]

    Extracting lignin from black liquor is an attractive option in modern pulp mills as a unit process for a combined biorefinery. The lignin obtained can be utilized as solid fuel or other high-value added products. The precipitation equilibrium of kraft lignin from softwood black liquor was studied in this work. It was found that with decreasing pH and temperature, or increasing ion strength, the solid yield increases. Moreover, precipitated softwood kraft lignin has a higher molecular weight and contains lower amounts of carbohydrates and phenolic groups than lignin precipitated from mixed hardwood/softwood black liquor. The content of methoxyl groups in softwood kraft lignin was found to decrease with increasing precipitation yield. An empirical model for estimating the precipitation yield of lignin was proposed and evaluated.

  • 27.
    Zhu, Weizhen
    et al.
    Chalmers, Sweden.
    Westman, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers, Sweden.
    Lignin separation from kraft black liquor by combined ultrafiltration and precipitation: a study of solubility of lignin with different molecular properties2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 2, p. 270-278Article in journal (Refereed)
    Abstract [en]

    Lignin from wood is by far the largest source of bio-based aromatic raw material. Today a vast amount of lignin is processes and incinerated in kraft pulp mills around the world. One possible option to utilize the energy surplus in a modern kraft pulp mill is to extract lignin from black liquor. Precipitation of lignin is one important step in an extraction process. This study investigates how the molecular size and functional groups of lignin influenced the precipitation yield. Cross-flow filtration was applied to fractionate lignin with different molecular weights from a black liquor, precipitation studies was made on the different fractions. The precipitated lignin was characterized by GPC, HPAEC-PAD and NMR analysis. The results show that it was possible to obtain a more homogenous lignin by fractionation using cross-flow filtration. It was found that the molecular properties of kraft lignin, i.e. molecular weight and functional groups, influenced the yield of lignin precipitation: at the same precipitation condition, lignin fraction with higher molecular weight has higher precipitation yield. Lignin fraction with lower molecular weight contains less amount of carbohydrates and methoxyl groups but higher amount of phenolic groups.

  • 28. Zhu, Weizhen
    et al.
    Westman, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    The molecular properties and carbohydrate content of lignins precipitated from black liquor2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 2, p. 143-152Article in journal (Refereed)
    Abstract [en]

    Precipitation and utilization of lignin from black liquor (BL) offers many promising advantages to modern kraft pulp mills. A novel process, known as "LignoBoost", has recently been introduced as a process for separating lignin from BL; it results in lignins with a low ash and high dry solid content. There is a lack of knowledge regarding the influences of process parameters on the behavior of lignin in the precipitation step. In this study, the yield of precipitated lignin and its average molecular weight (MWt) and carbohydrate content were the focus. Nuclear magnetic resonance (NMR) analysis showed that the lignin yield increased at lower pH and temperatures or when the ion strength of BL was elevated. High yield lignins contained more low MWt components and such lignins have more phenolic OH and methoxy groups. Xylan content of the lignins decreased with decreasing pH and increasing temperature, but glucomannan content was virtually unaffected by the conditions of precipitation.

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