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  • 1. Christiernin, Maria
    et al.
    Notley, Shannon M.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Thomas
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Comparison between 10 000 year old and contemporary spruce lignin2009In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 43, no 1-2, p. 23-41Article in journal (Refereed)
    Abstract [en]

     Wood from white spruce Picea glauca that had been preserved by rapid burial in lake sediments 10,000 years ago, was investigated and compared to a contemporary reference white spruce wood. The 10,000-year old sample appeared to have an intact primary cell wall and middle lamella, whereas the carbohydrate monomer distribution, and microscopic images showed that the secondary wall was at least partially removed, indicating that this structure had been selectively attacked by bacteria. The Klason lignin amount in the aged spruce was found to be 60%. The relative lignin monomer content in the aged spruce was 9% lower than that of the reference wood, showing that there were fewer beta-O-4' linkages in the aged sample. This finding was supported by SEC analysis of the thioacidolysed samples as a larger proportion of lignin oligomers were observed in the aged spruce than in the reference material. This indicates a somewhat greater number of condensed bonds in the aged spruce than in the reference spruce sample. Quantitative C-13 NMR analysis and HSQC techniques applied on milled wood lignins (MWL) revealed no significant structural differences between the aged spruce and the reference.

  • 2.
    Christiernin, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Nilsson, Thomas
    Virkeslära, Sveriges Lantrbruksuniversitet, Uppsala.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Analysis of lignin isolated from spruce with secondary cell wall removed2005In: 59th Appita Annual Conference and Exhibition, incorporating the 13th ISWFPC: International Symposium on Wood, Fibre and Pulping Chemistry, 2005, p. 73-79Conference paper (Refereed)
    Abstract [en]

    Wood from white spruce, Picea glauca, that has been preserved by rapid burial in lake sediments 10 000 years ago was investigated and compared to fresh white spruce wood. The old sample has an intact outer cell wall and middle lamella but most of the secondary cell wall has been selectively removed by bacteria. Klason lignin content was found to be 60% in the old sample, more than twice as high as that found in normal wood. This was rather expected since the middle lamella and primary wall has a higher content of lignin than the secondary wall. After thioacidolysis of the samples the lignin monomer content in the old spruce was 9% lower than that of the reference wood, possibly due to more condensed lignin. This finding was supported by SEC analysis of the thioacidolysed samples. A small amount of coumaryl monomers, 3%, was found in the old spruce and none in the reference wood. The carbohydrate monomer distribution showed that galactose and arabinose and xylose content is higher in old spruce than in white spruce reference, and glucose content is 20% lower in old spruce as compared to reference white spruce. This confirms microscopical evidence that secondary wall was at least partially removed. No new oligomeric lignin structures could be identified with GC-MS analysis of the thioacidolysis products. Millwood lignin from samples were subjected to quantitative NMR analysis by combining 13 C and HSQC techniques, which showed that the lignin structures in mill wood lignin from the old spruce sample was almost identical to those of the reference wood.

  • 3. del Rio, Jose C.
    et al.
    Rencoret, Jorge
    Marques, Gisela
    Gutierrez, Ana
    Ibarra, David
    Santos, J. Ignacio
    Jimenez-Barbero, Jesus
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Martinez, Angel T.
    Highly Acylated (Acetylated and/or p-Coumaroylated) Native Lignins from Diverse Herbaceous Plants2008In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 56, no 20, p. 9525-9534Article in journal (Refereed)
    Abstract [en]

    The structure of lignins isolated from the herbaceous plants sisal (Agave sisalana), kenaf (Hibiscus cannabinus), abaca (Musa textilis) and curaua (Ananas erectifolius) has been studied upon spectroscopic (2D-NMR) and chemical degradative (derivatization followed by reductive cleavage) methods. The analyses demonstrate that the structure of the lignins from these plants is highly remarkable, being extensively acylated at the gamma-carbon of the lignin side chain (up to 80% acylation) with acetate and/or p-coumarate groups and preferentially over syringyl units. Whereas the lignins from sisal and kenaf are gamma-acylated exclusively with acetate groups, the lignins from abaca and curaua are esterified with acetate and p-coumnarate groups. The structures of all these highly acylated lignins are characterized by a very high syringyl/guaiacyl ratio, a large predominance of beta-O-4' linkages (up to 94% of all linkages), and a strikingly low proportion of traditional beta-beta' linkages, which indeed are completely absent in the lignins from abaca and curaua. The occurrence of beta-beta' homocoupling and cross-coupling products of sinapyl acetate in the lignins from sisal and kenaf indicates that sinapyl alcohol is acetylated at the monomer stage and that, therefore, sinapyl acetate should be considered as a real monolignol involved in the lignification reactions.

  • 4.
    Gellerstedt, Göran
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Majtnerová, Andrea
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Zhang, Liming
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Towards a new concept of lignin condensation in kraft pulping. Initial results2004In: Comptes rendus. Biologies, ISSN 1631-0691, E-ISSN 1768-3238, Vol. 327, no 9-10, p. 817-826Article in journal (Refereed)
    Abstract [en]

    In kraft pulping, a comparatively large amount of lignin remains in the fibres after the cook. Based on various analytical techniques for lignin, such as thioacidolysis, GPC and NMR, it is suggested that lignin condensation reactions take place during the cook. The reaction seems, however, not to involve ionic intermediates as has been suggested previously but rather a one-electron mechanism with elemental sulphur as the initiator. Support for such a reaction has been found through kraft cooks in the presence of an added phenol, 2,6-xylenol, as well as through NMR analysis of kraft lignin. It was found that the added phenol is incorporated in the pulp lignin with linkages indicative of radical coupling. Furthermore, kraft lignin was found to contain substantial amounts of chemically linked fatty acids. By complementary analyses of sulphur and polysulphide in an industrial black liquor, the presence of these compounds throughout a kraft cook was demonstrated.

  • 5.
    Geng, Xiumei
    et al.
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Zhang, Yelong
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Jiao, Li
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Yang, Lei
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Hamel, Jonathan
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Giummarella, Nicola
    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.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhu, Hongli
    Bioinspired Ultrastable Lignin Cathode via Graphene Reconfiguration for Energy Storage2017In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 5, no 4, p. 3553-3561Article in journal (Refereed)
    Abstract [en]

    Lignin extracted from trees is one of the most abundant biopolymers on Earth. Quinone, a sub-structure in lignin, can be used for energy storage via reversible redox reactions through absorbing and releasing electrons and protons. However, these efforts have encountered hindrances, such as short life cycle, low cycling efficiency, and a high self-discharge rate. All of these issues are related to electrode dissolution by electrolyte solvents and the insulating nature of lignin. Addressing these critical challenges, for the first time we use a reconfigurable and hierarchical graphene cage to capture the lignin by mimicking the prey-trapping of venus flytraps. The reconfigurable graphene confines the lignin within the electrode to prevent its dissolution, while acting as a three-dimensional current collector to provide efficient electron transport pathways during the electrochemical reactions. This bioinspired design enables the best cycling performance of lignin reported so far at 88% capacitance retention for 15000 cycles and 211 F g-1 capacitance at a current density of 1.0 A g-1. This study demonstrates a feasible and effective strategy for solving the long-term cycling difficulties of lignin-based electrochemically active species, and makes it possible to utilize lignin as an efficient, cheap, and renewable energy storage material.

  • 6.
    Giummarella, Nicola
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, Royal Inst Technol, Wallenberg Wood Sci Ctr, Stockholm, Sweden..
    Zhang, Liming
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, Fibre & Polymer Technol, Stockholm, Sweden..
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, Royal Inst Technol, Wallenberg Wood Sci Ctr, Stockholm, Sweden.;KTH, Fibre & Polymer Technol, Stockholm, Sweden..
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, Royal Inst Technol, Wallenberg Wood Sci Ctr, Stockholm, Sweden..
    Global protocol for the mild quantitative fractionation of lignin carbohydrate complexes (LCC)2016In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Article in journal (Other academic)
  • 7.
    Giummarella, Nicola
    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. Wallenberg Wood Science Center.
    Zhang, Liming
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Wallenberg Wood Science Center.
    Lawoko, Martin
    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. Wallenberg Wood Science Center.
    Structural features of mildly fractionated lignin carbohydrate complexes (LCC) from spruce2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 48, p. 42120-42131Article in journal (Refereed)
    Abstract [en]

    A protocol for the quantitative fractionation of lignin carbohydrate complexes (LCC) from wood under mild conditions has been developed. All operations occur at near-neutral pH conditions and low temperatures, in order to preserve the native structure. The protocol also achieved the fractionation of hemicelluloses of relatively high purity enabling for the first time estimates of hemicelluloses fractions not chemically bound to lignin in wood. 2D HSQC NMR was applied to decipher the structure of LCCs and was complemented by thioacidolysis-GC MS techniques. The carbohydrates linked to lignin in LCC are hemicelluloses, mainly arabinoglucuronoxylan (AGX) and galactoglucomannan (GGM). Benzylether (BE) and phenyl glycosidic (PG) linkages were detected. Significant structural differences in the lignin part of LCCs are also reported. The novelty of this work is that we report the first quantitative pH neutral protocol for LCC fractionation and detailed chemical analyses unveil important structural differences of relevance to fundamental knowledge in lignin polymerization and wood-based biorefineries.

  • 8. Gordobil, O.
    et al.
    Moriana, Rosana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Labidi, J.
    Sevastyanova, Olena
    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.
    Assesment of technical lignins for uses in biofuels and biomaterials: Structure-related properties, proximate analysis and chemical modification2016In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 83, p. 155-165Article in journal (Refereed)
    Abstract [en]

    The potential of organosolv and kraft eucalyptus and spruce lignin as feedstock for polymeric materials and biofuel applications was assessed. Proximate analysis was used to predict the heating values and char formation. Chemical modification, based on the esterification reaction with methacryloyl chloride, was applied to introduce vinyl groups into the lignin macromolecules for enhanced reactivity. Kraft eucalyptus and spruce lignins had a more condensed structure than organosolv lignins, which resulted in greater thermal stability for these lignins. For different species within the same process, the thermal parameters showed a correlation with certain structural and compositional parameters (ash and sugars content, molecular weight and degree of condensation). Organosolv spruce lignin produced the highest heating value of 24. MJ/Kg, which is suitable for biofuel applications. The content of phenolic OH groups was higher for kraft lignins and especially higher for softwood lignins, both organosolv and kraft. The degree of methacrylation, estimated from the content of vinyl groups per C9 lignin unit, was significantly greater for organosolv lignins than for kraft lignins despite the higher OH-groups content in the latter.

  • 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.
    Henriksson, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lignin Utilization2010In: Thermochemical conversion of biomass to liquid fuels and chemicals / [ed] M. Crocker, RSC Publishing, 2010, p. 222-262Chapter in book (Refereed)
    Abstract [en]

    Lignin is one of the most abundant biopolymers on Earth, carrying out important biological roles in vascular plants. It has somewhat higher energy content than polysaccharides, but has a complex and heterogeneous structure including covalent bonds to polysaccharides. The partly random structure of lignin is explained by the fact that it is created by an uncatalyzed radical polymerization. Lignin is obtained as a by-product of various types of technical processes based on biomass, of which chemical pulping of wood is the most important. These technical lignins have structures that differ from native lignin. Sulphite pulping of wood generates a water soluble lignin derivate, which among other things, is used as a dispersing agent and dust binder. Kraft pulping generates a lignin that is insoluble at neutral pH, which today is mainly burned for heat generation in the chemical recovery system of the kraft pulp mill. Recently, efficient methods have been developed for the preparation of lignin from the process liquids, for use in energy generation or other applications. Conversion of technical lignin to liquid fuels for use in combustion engines is an interesting possibility that represents a technical challenge. This chapter reviews the structure and biopolymerisation of lignin, reactions of lignin during technical processes, and different applications of technical lignins.

  • 12.
    Henriksson, Gunnar
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Zhang, Liming
    KTH, Superseded Departments, Pulp and Paper Technology.
    Li, Jiebing
    KTH, Superseded Departments, Pulp and Paper Technology.
    Ljungquist, P.
    Reitberger, T.
    Pettersson, G.
    Johansson, G.
    Is cellobiose dehydrogenase from Phanerochaete chrysosporium a lignin degrading enzyme?2000In: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology, ISSN 0167-4838, E-ISSN 1879-2588, Vol. 1480, no 02-jan, p. 83-91Article in journal (Refereed)
    Abstract [en]

    Cellobiose dehydrogenase (CDH) is an extracellular redox enzyme of ping-pong type, i.e. it has separate oxidative and reductive half reactions. Several wood degrading fungi produce CDH, but the biological function of the enzyme is not known with certainty. It can, however, indirectly generate hydroxyl radicals by reducing Fe3+ to Fe2+ and O-2 to H2O2. Hydroxyl radicals are then generated by a Fenton type reaction and they can react with various wood compounds, including lignin. In this work we study the effect of CDH on a non-phenolic lignin model compound (3,4-dimethoxyphenyl glycol). The results indicate that CDH can affect lignins in three important ways. (1) It breaks beta-ethers; (2) it demethoxylates aromatic structures in lignins; (3) it introduces hydroxyl groups in non-phenolic lignins. The gamma-irradiated model compound gave a similar pattern of products as the CDH treated model compound? when the samples were analyzed by HPLC, suggesting that hydroxyl radicals are the active component of the CDH system.

  • 13.
    Henriksson, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Nilsson, Thomas
    Inst för virkeslära Sveriges Lantbruksuniversitet, Uppsala.
    Ohlsson, Anna
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Torkil
    KTH, School of Biotechnology (BIO), Glycoscience.
    Inhomogenity inlignin structure between different cell wall layers i  conifers and hardwood2006In: Fifth Plant Biomechanics Conference, 2006, p. 145-150Conference paper (Refereed)
  • 14.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Brunow, Gösta
    Department of Chemistry, University of Helsinki.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ralph, John
    US Dairy Forage Research Center, USDA-Agricultural Research Service.
    Non-enzymatic reduction of quinone methides during oxidative coupling of monolignols: implications for the origin of benzyl structures in lignins2006In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 4, no 18, p. 3456-3461Article in journal (Refereed)
    Abstract [en]

    Lignin is believed to be synthesized by oxidative coupling of 4-hydroxyphenylpropanoids. In native lignin there are some types of reduced structures that cannot be explained solely by oxidative coupling. In the present work we showed via biomimetic model experiments that nicotinamide adenine dinucleotide ( NADH), in an uncatalyzed process, reduced a beta-aryl ether quinone methide to its benzyl derivative. A number of other biologically significant reductants, including the enzyme cellobiose dehydrogenase, failed to produce the reduced structures. Synthetic dehydrogenation polymers of coniferyl alcohol synthesized ( under oxidative conditions) in the presence of the reductant NADH produced the same kind of reduced structures as in the model experiment, demonstrating that oxidative and reductive processes can occur in the same environment, and that reduction of the in situ-generated quinone methides was sufficiently competitive with water addition. In situ reduction of beta - beta-quinone methides was not achieved in this study. The origin of racemic benzyl structures in lignins therefore remains unknown, but the potential for simple chemical reduction is demonstrated here.

  • 15.
    Holmgren, Anders
    et al.
    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.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Effects of a Biologically Relevant Antioxidant on the Dehydrogenative Polymerization of Coniferyl Alcohol2008In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 9, no 12, p. 3378-3382Article in journal (Refereed)
    Abstract [en]

    Dehydrogenation polymers (DHPs or synthetic lignins) were synthesized from coniferyl alcohol by enzymatic oxidation in the presence of ascorbic acid to study the potential effects of an antioxidant upon their structure. Specific interunit substructures (beta-O-4', beta-beta', and beta-5') were quantified by C-13 NMR, which showed how ascorbic acid altered their amounts compared with control syntheses without this antioxidant, especially by increasing the amount of beta-O-4' substructures. The effect of ascorbic acid increased with its concentration. Surprisingly, no influence on the sizes of the synthetic lignins, as determined by size exclusion chromatography, was observed. The chemistry of this antioxidant effect during dehydrogenative polymerization and the potential biological significance (cell wall lignification) of these observations are discussed.

  • 16.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Norgren, Magnus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Zhang, Liming
    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.
    On the role of the monolignol gamma-carbon functionality in lignin biopolymerization2009In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 70, no 1, p. 147-155Article in journal (Refereed)
    Abstract [en]

    In order to investigate the importance of the monomeric gamma-carbon chemistry in lignin biopolymerization and structure, synthetic lignins (dehydrogenation polymers; DHP) were made from monomers with different degrees of oxidation at the gamma-carbon, i.e., carboxylic acid, aldehyde and alcohol. All monomers formed a polymeric material through enzymatic oxidation. The polymers displayed similar sizes by size exclusion chromatography analyses, but also exhibited some physical and chemical differences. The DHP made of coniferaldehyde had poorer solubility properties than the other DHPs, and through contact angle of water measurement on spin-coated surfaces of the polymeric materials, the DHPs made of coniferaldehyde and carboxylic ferulic acid exhibited higher hydrophobicity than the coniferyl alcohol DHP. A structural characterization with C-13 NMR revealed major differences between the coniferyl alcohol-based polymer and the coniferaldehyde/ferulic acid polymers, such as the predominance of aliphatic double bonds and the lack of certain benzylic structures in the latter cases. The biological role of the reduction at the gamma-carbon during monolignol biosynthesis with regard to lignin polymerization is discussed.

  • 17.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Brunow, G.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Origin of reduced lignin structures: Quinone methides2005In: Appita Annu. Conf., 2005, p. 147-150Conference paper (Refereed)
    Abstract [en]

    Recent discoveries have shown the presence of reduced lignin structures in softwood lignin, such as dihydroconiferyl alcohol and secoisolariciresinol. During lignin polymerization, the oxidative radical coupling of monolignols generates quinone methides as intermediates. Several reduction agents were tested on a quinone methide model. The products were analyzed by GC-MS and 1H, 13C, DEPT and HSQC NMR techniques were used to confirm the structure of the reduced quinone methide. An uncatalyzed reduction of this quinone methide model was achieved with β-NADH, a biologically significant reducing agent, demonstrating that the formation of reduced lignin structures is not necessarily biologically controlled.

  • 18.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Brunow, Gösta
    Helsingfors Universitet.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Origin of reduced structures: Quinomethids2005In: 13th ISWFPC V3, 2005, p. 147-150Conference paper (Other (popular science, discussion, etc.))
  • 19.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    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.
    In vitro monolignol dehydrogenative polymerization in the presence of a candidate dimer template modelManuscript (Other academic)
  • 20.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    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.
    Monolignol dehydrogenative polymerization in vitro in the presence of dioxane and a methylated beta-beta ' dimer model compound2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 5, p. 508-513Article in journal (Refereed)
    Abstract [en]

    Lignin formation is believed to occur by polymerization of resonance-stabilized monolignol radicals formed by enzymatic oxidation. Recently, different hypotheses suggested that lignin polymerization is influenced by surfaces in the cell wall which can be polysaccharides or proteins. The latter is called the proteinaceous dirigent sites/template polymerization hypothesis. According to another hypothesis, lignin itself is believed to act as a template and replicate its primary structure. In this work, dehydrogenative polymerization (DHP) of the lignin precursor coniferyl alcohol was performed in vitro in the presence and absence of pinoresinol dimethyl ether (a beta-beta ' dimer model). Another peculiarity of the experiments was the presence of dioxane which afforded a high solubility of the reactants. The question was whether the presence of beta-beta ' dimer model would change the structure of the DHP formed. The DHPs were analyzed by quantitative C-13 NMR, GC-FID, and GC-MS. The dimer model as a template in the homogeneous polymerization state (in solution) did not influence the DHP structure.

  • 21. Johansson, M.
    et al.
    Zhang, Liming
    KTH, Superseded Departments, Pulp and Paper Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Pulp and Paper Technology.
    On chromophores and leucochromophores formed during the refining of wood2002In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, no 1, p. 5-+Article in journal (Refereed)
    Abstract [en]

    The discoloration reactions taking place when wood is converted to thermomechanical pulp (TMP) were studied using milled wood lignin (MWL), from spruce wood chips and from first-stage refined pulp respectively. As analytical tools, advanced NMR techniques and UV-VIS spectroscopy were used, to detect differences in the chemical composition. It was found that the most probable reason for the discoloration reactions is an oxidation of lignin, giving rise to small amounts of aryl-alpha-carbonyl structures, together with the formation of coloured metal ion complexes. Despite the results from earlier works, on beta-1 and beta-5 lignin model compounds, no stilbenes seemed to be formed during refining.

  • 22.
    Majtnerová, Andrea
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran L. F.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    On the delignification mechanism in kraft pulping2005Conference paper (Refereed)
    Abstract [en]

    The successive retardation of lignin dissolution towards the end of a kraft pulping process can be explained by the predominance of biphenyl and biphenyl ether structures being present in the lignin. As a possible mode of formation of such structures during the cook, a one-electron transfer reaction involving elemental sulfur/polysulfide has been suggested. Consequently, reactions between dissolved phenolic lignin fragments and pulp lignin might give rise to the formation of stable biphenyl (or biphenyl ether/thioether) structures. In order to find further support for such reactions, kraft pulps (isolated lignins) and the corresponding black liquor lignins were subjected to analysis using thioacidolysis in combination with GC-MS as well as quantitative 1D and 2D NMR techniques. The results obtained so far support the hypothesis that radical coupling reactions may play an essential role for the presence of residual lignin in kraft pulps.

  • 23.
    Oinonen, Petri
    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.
    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.
    Lawoko, Martin
    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.
    On the formation of lignin polysaccharide networks in Norway spruce2015In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 111, p. 177-184Article in journal (Refereed)
    Abstract [en]

    In this study we were mirroring suggested in vivo phenomena of lignin-hemicellulose complex formation in vitro, by cross-linking Norway spruce (Picea abies) galactoglucomannans, xylans and lignin moieties to high molecular weight complexes by laccase treatment. We were able to observe the oxidation and cross-linking of non-condensed guaiacyl-type phenolic moieties attached to both of the hemicelluloses by P-31 NMR and size-exclusion chromatography. We suggest that hemicelluloses-lignin complexes form covalently linked structural units during the early stages of lignification via radical enzymatic cross-linking catalyzed by laccase. This work shows that the hemicellulose molecules in wood are covalently linked to two or more lignin units thereby making them suited for forming network structures.

  • 24.
    Oinonen, Petri
    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.
    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.
    Lawoko, Martin
    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.
    Structural studies of an enzymatically produced Norway spruce lignin-carbohydrate complexManuscript (preprint) (Other academic)
  • 25. Onnerud, H.
    et al.
    Zhang, Liming
    KTH, Superseded Departments, Pulp and Paper Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Pulp and Paper Technology.
    Henriksson, Gunnar
    KTH, Superseded Departments, Pulp and Paper Technology.
    Polymerization of monolignols by redox shuttle-mediated enzymatic oxidation: A new model in lignin biosynthesis I2002In: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 14, no 8, p. 1953-1962Article in journal (Refereed)
    Abstract [en]

    Lignin is one of the most abundant biopolymers, and it has a complex racemic structure. It may be formed by a radical polymerization initiated by redox enzymes, but much remains unknown about the process, such as how molecules as large as enzymes can generate the compact structure of the lignified plant cell wall. We have synthesized lignin oligomers according to a new concept, in which peroxidase is never in direct contact with the lignin monomers coniferaldehyde and coniferyl alcohol. Instead, manganese oxalate worked as a diffusible redox shuttle, first being oxidized from Mn(II) to Mn(III) by a peroxidase and then being reduced to Mn(II) by a simultaneous oxidation of the lignin monomers to radicals that formed covalent linkages of the lignin type. Furthermore, a high molecular mass polymer was generated by oxidation of coniferyl alcohol by Mn(III) acetate in a dioxane and water mixture. This polymer was very similar to natural spruce wood lignin, according to its NMR spectrum. The possible involvement of a redox shuttle/peroxidase system in lignin biosynthesis is discussed.

  • 26. Rundlof, Eva Svensson
    et al.
    Zhang, Liming
    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.
    The. behavior of chromophoric structures in softwood mechanical pulp on bleaching with alkaline hydrogen peroxide2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 3, p. 359-364Article in journal (Refereed)
    Abstract [en]

    A commercial TMP as well as the corresponding isolated milled wood lignin were bleached/oxidized with alkaline hydrogen peroxide in order to explore the reasons for the limited brightness increase and the large consumption of hydrogen peroxide in the bleaching of mechanical pulp. Experiments with pulp showed that the elimination of phenolic hydroxyl groups in the lignin gave only a marginal increase in the bleaching response. It was, however, also observed that the bleaching reactions in the pulp could be accompanied by a color-forming reaction. This was further explored by peroxide oxidation of isolated lignin and subjecting the resulting product to different types of NMR analysis. It was found that the oxidative breakdown of coniferaldehyde and vanillin structures in lignin can give rise to a comprehensive consumption of hydrogen peroxide with the formation of new colored structures. This finding may well explain the brightness ceiling in mechanical pulp bleaching.

  • 27.
    Sevasyanova, Olena
    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.
    Helander, Mikaela
    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.
    Chowdhury, Sudip
    Lange, Heiko
    Wedin, Helena
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Kadla, John F.
    Crestini, Claudia
    Lindström, Mikael F.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Tailoring the Molecular and Thermo-Mechanical Properties of Kraft Lignin by Ultrafiltration2014In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 18, p. 9505-9515Article in journal (Refereed)
    Abstract [en]

    This study has shown that ultrafiltration allows the selective extraction from industrial black liquors of lignin fraction with specific thermo-mechanical properties, which can be matched to the intended end uses. Ultrafiltration resulted in the efficient fractionation of kraft lignin according to its molecular weight, with an accumulation of sulfur-containing compounds in the low-molecular weight fractions. The obtained lignin samples had a varying quantities of functional groups, which correlated with their molecular weight with decreased molecular size, the lignin fractions had a higher amount of phenolic hydroxyl groups and fewer aliphatic hydroxyl groups. Depending on the molecular weight, glass-transition temperatures (T-g) between 70 and 170 degrees C were obtained for lignin samples isolated from the same batch of black liquor, a tendency confirmed by two independent methods, DSC, and dynamic rheology (DMA). The Fox-Flory equation adequately described the relationship between the number average molecular masses (M-n) and T-g's-irrespective of the method applied. DMA showed that low-molecular-weight lignin exhibits a good flow behavior as well as high-temperature crosslinking capability. Unfractionated and high molecular weight lignin (M-w > 5 kDa), on the other hand, do not soften sufficiently and may require additional modifications for use in thermal processings where melt-flow is required as the first step.

  • 28.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Chemical structure of condensed tannins from 8 different tree species studied by NMR techniques2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry: Proceedings, ISWFPC, Tianjin, China, 2011, p. 93-97Conference paper (Refereed)
    Abstract [en]

    NMR techniques were applied to study and to compare the chemical structure of tannins from 8 different tree species, i.e., Norway spruce (Picea abies), Scots pine (Pinus sylvestris), larch (Larix gmelini), French maritime pine bark extractive, Quebracho (Schinopsis lorentzii), black wattle (Acacia mearnsii), Mangium (Acacia mangium) and Chinese Bayberry tree (Myrica rubra). The tannins from Norway spruce bark and Scots pine bark were extracted in our laboratory by using fresh bark harvested in Stockholmarea. The other tannins were obtained as commercial samples. It was found in this study that the complicated chemical structures of condensed tannins can be elucidated by applying 13C, DEPT90, and 2D HSQC NMR techniques. The tannins from pines and larch were found to be structurally similar to each other, containing mainly the procyanidins. In the case of Norway spruce tannin, stilbene polymer or stilbene- procyanidin co-polymer were found to comprise about half of the tannin content together with procyanidins. Quebracho tannin was found to contain predominantly the profisetinidins, in agreement with results of other earlier studies. Black wattle tannin was also found to contain profisetinidins as the major components, and proanthocyanidins and probably prorobinetinidins as the minor components. Tannin from Mangium was found to contain the prorobinetinidins as the major components. The Chinese Bayberry (Myrica rubra) tannin, however was found to contain mainly the prorobinetinidins and also small amount of the prodelphinidins.

  • 29.
    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.
    2D Heteronuclear (1H-13C) Single Quantum Correlation (HSQC) NMR Analysis of Norway Spruce Bark Components2009In: Characterization of Lignocellulosic Materials, Blackwell Publishing, 2009, p. 1-16Chapter in book (Refereed)
    Abstract [en]

    Norway spruce (Picea abies) bark, collected during the winter and summer seasons, has been separated into inner- and outer-bark fractions followed by extraction using a fivesolvent extraction procedure. The inner-bark fraction was found to contain a rather high amount of carbohydrates but only minor amounts of tannin. In addition, the glucosides of stilbenes such as astringin and isorhapontin were detected. The outer-bark fraction had a high content of high-molecular-mass tannin but was low in carbohydrates. Lignin-derived components were also detected. Further studies of the tannin fraction using advanced nuclear magnetic resonance (NMR) techniques showed that polyflavanol and polystilbene units together with glucoside units were prevalent.

  • 30.
    Zhang, Liming
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Pulp and Paper Technology.
    NMR observation of a new lignin structure, a spiro-dienone2001In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 24, p. 2744-2745Article in journal (Refereed)
    Abstract [en]

    A spiro-dienone structure (eta -1/alpha -O-alpha) has been observed as one of the important structures present in spruce and aspen lignins, with abundance as high as 3% in spruce lignin.

  • 31.
    Zhang, Liming
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Qualitative and quantitative study of lignin structure by applying highresolution 2D HSQC NMR technique2004In: 2nd International Symposium on Technologies Of Pulping, Papermaking and Biotechnology on Fiber Plants, Proceedings / [ed] Jin, YC; Xie, HF, NANJING: NANJING FORESTRY UNIV , 2004, p. 88-92Conference paper (Refereed)
    Abstract [en]

    High-resolution 2D HSQC NMR technique was found to be a powerful analytical tool for studies on lignin structure. High resolution in the F1 dimension of an HSQC spectrum can be obtained by proper sample purification and optimized shimming as well as by acquiring large enough increments. By combining the results from 2D HSQC, HSQC-TOCSY and HMBC NMR experiments, novel lignin structures, including spiro-dienone, secoisolariciresinol and neo-olivil have been observed and identified. The concept of quantitative structure determination by applying 2D HSQC NMR technique was investigated. The influence of T-2 relaxation decays, coupling constant, off-resonance effect and homonuclear couplings on NMR signal quantification have been discussed. beta-5 Structure in a lignin sample was accurately determined by using the HSQC NMR analysis through a unique way of selecting the proper internal standard reference signal(s).

  • 32.
    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.
    Quantitative 2D HSQC NMR determination of polymer structures by selecting suitable internal standard references2007In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 45, no 1, p. 37-45Article in journal (Refereed)
    Abstract [en]

    A new analytical method based on the 2D HSQC NMR sequence is presented, which can be applied for quantitative structural determination of complicated polymers. The influence of T-1 and T-2 relaxations, off-resonance effects, coupling constants and homonuclear couplings are discussed. It was found that the T-2 values measured on polymeric samples with the conventional HSQC-CPMG sequence could not be used to correct the errors caused by T-2 relaxations during the polarization transfer delay. A unique way of selecting the proper internal standard reference signal(s) is therefore proposed to eliminate the major errors caused by T-2 relaxations, resonance offsets, coupling constant deviations and homonuclear couplings. Two polymer samples, a cellulose triacetate and an acetylated lignin, have been used to illustrate the principles. The methodology developed in this work is robust to instrument miss-setting and it can find wide-spread applications in areas where a quantitative analysis of structurally complicated polymers is necessary.

  • 33.
    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.

  • 34.
    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.
    Svensson-Rundlöf, E.
    Zhang, E.
    Behavior of chromophoric structures in softwood TMP during H 2O2 bleaching2005In: Appita Annual Conference, Vol 2, Australia: Appita, Inc. , 2005, p. 299-302Conference paper (Refereed)
    Abstract [en]

    A commercial TMP and an isolated lignin from the TMP (milled pulp lignin, or MPL) were treated with alkaline H2O2 bleaching as well as with several other specially designed chemical reactions. Analyses with NMR indicated that coniferaldehyde structures were eliminated completely from the lignin polymer by H2O2 bleaching. Phenolic content was found to have little impact on the final brightness of the TMP sample. Significant amounts of vanillin units (∼4%) were stable towards alkaline H2O2 bleaching and they remained in the TMP lignin after H2O2 bleaching. Even though the lignin sample was completely dissolved during the bleaching treatment, full brightness could not be achieved with the alkaline H2O2 bleaching treatment alone irrespective of the H2O2 charges being used, indicating that physical hindrance was less likely to be an important factor causing the brightness ceiling. It was probably the presence of certain H 2O2-resistant chromophores in the unbleached TMP that limited the further brightness improvement of the TMP at a certain brightness level. The bulk of the polymeric lignin structure seemed to be stable towards alkaline H2O2. The total coniferaldehyde and vanillin units present in the lignin polymer can only account for part of the H 2O2 consumed (not more than 10 kg/ton) during the bleaching process. The predominant reaction responsible for the consumption of H2O2 during the bleaching process was found to be the formation of carboxylic acid groups.

  • 35.
    Zhang, Liming
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, Superseded Departments, Pulp and Paper Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Pulp and Paper Technology.
    The formation of beta-beta structures in lignin biosynthesis - are there two different pathways?2003In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 1, no 20, p. 3621-3624Article in journal (Refereed)
    Abstract [en]

    Based on results from 2D NMR studies, both pinoresinol and secoisolariciresinol structures were found to be present in native lignin from spruce wood as well as in spruce kraft lignin and residual kraft pulp lignin. These two structures constitute the major types of beta-beta inter-unit linkages present in spruce lignin, but their formation in the lignin polymer may follow different pathways leading to their different bonding patterns with the rest of the lignin polymer. The mechanisms involved are discussed.

  • 36.
    Zhu, Hongli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Yuanyuan
    Pettersson, Bert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael
    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.
    Technical soda lignin dissolved in urea as an environmental friendly binder in wood fiberboard2014In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 28, no 5, p. 490-498Article in journal (Refereed)
    Abstract [en]

    The application of lignin as binder in wood composite panel is not only environmentally friendly but also commercially attractive. The dissolving of technical soda lignin is the most premier challenge in its application. In this study, the effect of different key factors on soda lignin solubility in urea was investigated. The maximum solubility of 60.16g/L was obtained under the temperature 70 degrees C, urea concentration 8M, lignin content 7%, and pH 8.8. Then, different kinds of wood fiber material were mixed with the dissolved lignin solution to make fiber board separately. The results showed that the lignin can enhance the tensile strength of particleboard and can be used as a binder in wood material, but the strength will be different with different materials. The optimal tensile strength obtained was 44.63MPa with the sample made from oriented cotton linter sheet.

1 - 36 of 36
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