| 1. |
- Deshpande, Raghu, 1979-
(author)
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The initial phase of sodium sulfite pulping of softwood : A comparison of different pulping options
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Single stage and two-stage sodium sulfite cooking were carried out on either spruce, pine or pure pine heartwood chips to investigate the influence of several process parameters on the initial phase of such a cook down to about 60 % pulp yield. The cooking experiments were carried out in the laboratory with either a lab-prepared or a mill-prepared cooking acid and the temperature and time were varied. The influences of dissolved organic and inorganic components in the cooking liquor on the final pulp composition and on the extent of side reactions were investigated. Kinetic equations were developed and the activation energies for delignification and carbohydrate dissolution were calculated using the Arrhenius equation. A better understanding of the delignification mechanisms during bisulfite and acid sulfite cooking was obtained by analyzing the lignin carbohydrate complexes (LCC) present in the pulp when different cooking conditions were used. It was found that using a mill-prepared cooking acid beneficial effect with respect to side reactions, extractives removal and higher stability in pH during the cook were observed compared to a lab-prepared cooking acid. However, no significant difference in degrees of delignification or carbohydrate degradation was seen. The cellulose yield was not affected in the initial phase of the cook however; temperature had an influence on the rates of both delignification and hemicellulose removal. It was also found that the corresponding activation energies increased in the order: xylan, glucomannan, lignin and cellulose. The cooking temperature could thus be used to control the cook to a given carbohydrate composition in the final pulp. Lignin condensation reactions were observed during acid sulfite cooking, especially at higher temperatures. The LCC studies indicated the existence of covalent bonds between lignin and hemicellulose components with respect to xylan and glucomannan. LCC in native wood showed the presence of phenyl glycosides, ϒ-esters and α-ethers; whereas the α-ethers were affected during sulfite pulping. The existence of covalent bonds between lignin and wood polysaccharides might be the rate-limiting factor in sulfite pulping.
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| 2. |
- Ek, Monica, et al.
(author)
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New cellulose derivatives from wood for high value products
- 2008
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In: TAPPSA: Technical Association of the Pulp and Paper Industry of Southern Africa. - 1029-0109. ; :September 2008
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Journal article (peer-reviewed)abstract
- Various pre-treatment methods to increase the accessibility of cellulose materials to swelling and reactive agents at different hierarchical levels, has been developed. It was demonstrated that enzymes are very efficient at increasing the cellulose reactivity. A new method to measure the reactivity and accessibility of the hydroxyl groups on cellulose was developed. Reversible addition-fragmentation chain transfer (RAFT) agents were synthesized and used further in esterification reactions with cellulose samples to prepare cellulose based graft-copolymers. MALDI-TOFMS was evaluated for characterization of cellulose derivatives. Methods to prepare electrospun fibres, casings, sponges and beads, were developed with target applications in pharmaceuticals and foods.
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| 3. |
- Gericke, Martin, et al.
(author)
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The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040: Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources
- 2024
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In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 326
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Journal article (peer-reviewed)abstract
- Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve.
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| 4. |
- Grénman, Henrik, et al.
(author)
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Modeling the influence of wood anisotropy and internal diffusion on delignification kinetics
- 2010
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9703-11
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Journal article (peer-reviewed)abstract
- A general mathematical model for the chemical pulping of wood including coupled chemical reactions and diffusion limitations in anisotropic wood chips was developed. The model, which consists of coupled parabolic partial differential equations (PDEs) and ordinary differential equations (ODEs), describes the time-dependent behavior of wood chips as they are exposed to chemicals in the liquid phase. In addition to the reaction−diffusion phenomena, the model describes the change of the wood chip porosity during the process. A numerical algorithm that combines spatial discretization by finite differences with a stiff ODE solver based on the backward difference method was used as an efficient strategy to solve the mass balances of wood chips in batch reactors. Numerical simulations with the software can be used to predict the progress of industrial delignification, that is, production of primarily cellulose through chemical pulping. The effect of the reaction parameters, such as the temperature and the concentrations of the alkaline delignification chemicals, as well as the sizes of the wood chips, can be evaluated with the model, the final goal being the intensification of the chemical pulping process. The model can be used to describe both the current kraft pulping (sulfate pulping) technique, as well as other processes, such as sulfite pulping and pulping in nonaqueous solvents.
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| 5. |
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| 6. |
- Johansson, Dan, 1980-
(author)
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Carbohydrate degradation and dissolution during Kraft cooking : Modelling of kinetic results
- 2008
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Licentiate thesis (other academic/artistic)abstract
- Chemical pulp fibres from wood are commonly used in products associated with packaging as well as with printing and writing. The prevalent way of liberating fibres is by subjecting wood chips to Kraft cooking. This process has a history of almost 130 years and should be both well described and well established. However, new products and new applications that use fibres as an important renewable resource make it all the more important that the properties of fibres be controllable. The properties of wood fibres are influenced by their carbohydrate composition which, in turn, is dependent on the cooking conditions used. This thesis studies the degradation and dissolution of the different carbohydrates during Kraft cooking and summarizes the results in kinetic expressions. Industrial wood chips from Norway spruce (Picea abies) were cooked at a high liquor-to-wood ratio in an autoclave digester at varying concentrations of hydroxide ions, hydrogen sulphide ions and sodium ions as well as varying temperatures. The pulps were analysed for carbohydrate composition, kappa number, content of hexenuronic acid and the pure cellulose viscosity, i.e. only the cellulose content in the pulp sample was used for calculating the viscosity. Kraft cooking of Eucalyptus urophylla and Eucalyptus grandis was also studied, using industrial liquor-to-wood ratios, to examine the relationship between hexenuronic acids and the amount of xylan in the pulp samples. For Kraft cooking of Norway spruce it was found that an increase in the concentration of hydroxide ions increased the rate of dissolution of the carbohydrates and the degradation of the cellulose degree of polymerization (DP). However, measured at a kappa number of 30, it is seen that a low hydroxide ion concentration can lower the carbohydrate yield and the pure cellulose viscosity dramatically. The hydroxide ion concentration not only affects the rate of dissolution but also the amount of xylan that reacts in the slower, final phase. Both cellulose and hemicelluloses were found to be affected by the hydrogen sulphide ion concentration. The dissolution of cellulose and hemicelluloses at varying sodium ion concentrations was found to be affected in different directions. The effect of sodium ion concentration on the DP was found to be dependent on the method of evaluation. The pulp viscosity was found to be affected twice as much by the sodium ion concentration than the pure cellulose viscosity was. For Kraft cooking of hardwood it was found that a high xylan yield not always is synonymous with a high hexenuronic acids content.
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| 7. |
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| 8. |
- Pykönen, Maiju, et al.
(author)
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Influence of surface chemical composition on UV-varnish absorption into permeable pigment-coated paper
- 2010
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 49:5, s. 2169-2175
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Journal article (peer-reviewed)abstract
- Fluorocarbon, organosilicon, and hydrocarbon plasma coatings were used to modify the surface permeable pigment-coated paper, and their impact on UV-varnish absorption was investigated. According to mercury porosimetry results, the plasma coatings had no influence on the porous structure of the paper. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) results showed characteristic surface chemical compositions for each plasma coating. The fluorocarbon plasma coating increased the UV-varnish contact angles significantly, whereas the hydrocarbon plasma coating had no clear influence. When the UV varnish was applied with a flexography unit including nip pressure, the role of surface chemical composition seemed to become minimal. The viscosity of the UV varnish was shown to impact the absorption rate with and without external pressure.
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| 9. |
- Wäne, Gerd, 1956-
(author)
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Fibre surface properties of kraft pulp : The influence of wood raw material, bleaching and storage
- 2009
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Licentiate thesis (other academic/artistic)abstract
- The aim of this thesis was to study the fibre surface properties of Birch (Betula ssp.), Eucalyptus (E. urograndis and E. globulus) and Spruce (Picea Abies) pulps bleached using two different methods: ECF (Elementary Chlorine Free) and TCF (Totally Chlorine Free). The hardwood pulps were subjected to a hot acidic stage prior to ECF bleaching in order to remove hexenuronic acid. The effect of prolonged storage (ageing) on the fibre surface properties was studied for all of the pulps. The characteristics of the fibre surfaces were determined by measuring the dynamic contact angle of single fibres (DCA) and by using Electron Spectroscopy for Chemical Analysis (ESCA) and Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The correlation between the fibre surface properties and the sizing efficiency of the hardwood pulps were evaluated by measuring the amount of alkyl ketene dimer (AKD) needed to reach a certain water absorption level(measured as Cobb60). The birch pulp was more hydrophilic than the eucalyptus pulps, thus requiring more AKD to reach a certain water absorption value, and also had a lower DCA. The introduction of a hot acidic stage (A stage) in the ECF bleaching sequence applied to the hardwood pulps (i.e. A/D(EP)DD versus D(EP)DD) lowered, as expected, the total fibre charge due to the removal of hexenuronic acids groups (HexA). According to the DCA measurements all of the pulps became more hydrophilic after the A/D(EP)DD bleaching than after the D(EP)DD bleaching sequence. The sizing ability of the pulps, measured as the AKD demand to a certain Cobb60 value, showed that the AKD demand was more or less the same for the eucalyptus pulps regardless of the bleaching sequence used. The birch pulp, on the other hand, required somewhat less AKD in the A/D(EP)DD sequence than in the D(EP)DD. The AKD demand to a certain Cobb60 value decreased further for the bleached birch and E. globulus pulps after ageing due to an increase in the fibre surface hydrophobicity. ESCA analysis revealed an increase of surface extractives on the pulps after ageing, which was also supported by ToF-SIMS analysis. It was concluded that there was an increase in fatty acids, fatty acid salts and possibly even sterols and glycerides on the fibre surfaces due to ageing. A migration of these components from the interior of the fibre wall to the fibre surface during ageing was verified in this study. The TCF and ECF bleached softwood pulps also showed differences in their fibre surface properties that were tangible and thereby measurable. The dynamic contact angle was highest for the TCF bleached softwood fibres, i.e. these were more hydrophobic. Although changes caused by ageing were much more pronounced for the ECF fibres, all pulps became more hydrophobic upon ageing. The hydrophobicity of pulp fibres can be determined using DCA, which is a rather rapid and economically viable analysis. Using this information, a paper/board mill can base its sizing strategy on scientific findings. The ageing effects seen on the fibre surfaces in the form of the migration of extractives might be an important parameter from an industrial point of view, especially when pulps are stored and/or transported for a long time period. Nowadays it is quite common for pulps to be shipped around the world and subjected to warm and humid conditions. It is therefore probable that the properties of the pulp change in such a way that the papermaking process requires adjustment.
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| 10. |
- Yang, Jiayi
(author)
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Utilization of cellulosic biomass towards sustainable chemicals and novel biomaterials
- 2020
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Doctoral thesis (other academic/artistic)abstract
- It is predicted by the United Nations that by year 2030 the world will need at least 50 percent more food, 45 percent more energy and 30 percent more water. The emissions of carbon dioxide from combustion of fossil fuels and waste are also increasing. At the same time, the demand for natural resources has never been higher and the planet is under unprecedented stress. This increasing awareness and concerns also drive and accelerate the research to facilitate switching the fossil-dependent economy to biobased economy. In this premise, forest industry plays a significant role, from leading the sustainable development to providing more materials to meeting the expanding demand. Moreover, the forest industry is a crucial part of the solution to global warming. The utilization of forest product has a long history, and the efforts of converting the biomass into value-added products or innovative applications have never been more stimulated than now. This thesis presents some examples of the exploration of lignocellulosic biomass based on the fractionation of lipophilic extractives and utilization of non-derivatized cellulose in novel materials.In the first part of thesis, the biorefinery of thermo-mechanical pulping (TMP) process water for lipophilic extractives was investigated as a way to extract the dissolved and colloidal substance (DCS). It was found that induced air flotation (IAF) combined with the foaming agent dodecyl trimethylammonium chloride (DoTAC) can efficiently remove the unwanted lipophilic extractives (Paper I) and retain valuable hemicelluloses (Paper II) in the TMP process water. By applying 80 ppm of DoTAC at a pH of 3.5 and 50 °C with induced air flotation, 94% of the lipophilic extractives were refined from the process water. The efficient biorefining of lipophilic extractives not only enabled the purification of TMP process water, but also facilitate the selective harvesting of hemicelluloses with very low impurities.In the second part of the work, non-derivatized cellulose (sulfite pulp) dissolved in LiOH/urea was used as substrate to fabricate spherical nanocomposite particles (Paper III), pH-responsive nanocomposite films (Paper IV) and crosslinked cellulose hydrogel (Paper V), respectively. The cellulose-chitosan nanocomposite particles were prepared in three different ways: instantly by dripping alkaline cellulose solution into dissolved chitosan in diluted acetic acid, and by mixing and emulsifying the biopolymer solutions to a water-in-oil emulsion, with or without addition of a crosslinking agent. Spherical cellulose-chitosan nanocomposite particles in the size from millimeter to micrometers were successfully prepared. It was demonstrated that some properties of the spherical particles, for example, morphology and size distribution, could be tuned by choosing between the different routes of preparation. In a different application of LiOH/urea dissolved cellulose, in the form of cellulose-chitosan nanocomposite films with pH-responsive swelling, were shown in the thesis. The nanocomposite film with 75% chitosan content exhibited maximum swelling ratio of 1500% and weight loss of chitosan of 55 wt% after 12 hours at pH 3. The utilization of the non-derivatized cellulose continued with cross-linking the macromolecules with methylenebisacrylamide (MBA) to form a robust hydrogel with superior water absorption properties. The cellulose hydrogel cured at 60 °C for 30 minutes, with a [MBA]/[glucose] molar ratio of 1.05, exhibited the highest water swelling capacity absorbing ca. 220 g H2O/g dry weight. This innovative procedure based on the direct dissolution of unmodified cellulose in LiOH/urea followed by MBA cross-linking provides a simple and fast approach to prepare chemically cross-linked cellulose hydrogels of high molecular weight with superior water uptake capacity.
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