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  • 1.
    Regnell Andersson, Sofia
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Rönnols, Jerk
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Aldaeus, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Jacobs, Anna
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Lignin Bimodality: Fact or Artefact?2018In: 15th European workshop on lignocellulosics and pulp: Proceedings for oral presentations, 2018, p. 97-100Conference paper (Other academic)
    Abstract [en]

    Size Exclusion Chromatography (SEC) of lignin poses many challenges. In numerous studies chromatograms of lignin show a bimodal molar mass distribution. Is this a true characteristic of lignin, is it caused by molecular associations or aggregations, or could it could be an artefact from using column combinations with porosities that do not match properly? To improve resolution and enable separation over a larger molar mass range, multiple columns with different porosities are often connected in series. If the porosities do not match properly, the result appears as a shoulder or bimodality in the chromatogram. To understand whether the bimodal distribution is a sample characteristic or an analyze artefact, we have used different columns, column combination and samples to see when the results is a bimodal distribution and when only one peak is formed. Results show that the bimodality of lignin can be an artifact originating from column mismatch. Using single porosity columns with a low molar mass cut-off should be avoided since it can cause false bimodality.

  • 2.
    Rönnols, Jerk
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy.
    Aldaeus, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy.
    Jacobs, Anna
    RISE - Research Institutes of Sweden, Bioeconomy.
    Freichels, Helene
    Magritek, Germany.
    Danieli, Ernesto
    Magritek, Germany.
    Benchtop NMR measurements on kraft lignin2017In: 19th International symposium on wood, fibre and pulping chemistry, August 28 - September 1, 2017, Porto Seguro, Brazil, 2017, p. 434-438Conference paper (Refereed)
    Abstract [en]

    The use of NMR spectroscopy at high magnetic fields is a common tool in the analysis of lignin samples. In the presented study, NMR measurements on a group of softwood and hardwood kraft lignins at low field (1.0 T) with a benchtop NMR spectrometer, containing a permanent magnet, are investigated and evaluated. NMR based diffusion measurements were performed, for which the results were found to be fast, repeatable, and in good agreement numbers to measurements at high field. Measurements were also performed on a sample in alkaline solution, as a model for black liquor analysis, with promising initial results.

  • 3.
    Rönnols, Jerk
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Danieli, Ernesto
    Magritek GmbH, Germany.
    Freichels, Helene
    Magritek GmbH, Germany.
    Aldaeus, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Lignin analysis with benchtop NMR spectroscopy2019In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed)
    Abstract [en]

    Benchtop nuclear magnetic resonance (NMR) spectroscopy is an emerging field with an appealing profile for industrial applications. The instrumentation offers the possibility to measure NMR spectra in situations where high-field NMR spectroscopy is considered too expensive or complicated. In this study, we investigated the scope and limitations of 1H NMR measurements on kraft lignins and black liquors at low magnetic field strengths (1.0 and 1.5 T). The ability to quantify different classes of compounds was investigated and found to be promising. NMR-based diffusion measurements were performed, with the aim of gaining insight into the molar mass of the lignins at hand. These measurements were fast, repeatable and in good agreement with established methods.

  • 4.
    Rönnols, Jerk
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy.
    Jacobs, Anna
    RISE - Research Institutes of Sweden, Bioeconomy.
    Aldaeus, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy.
    Consecutive determination of softwood kraft lignin structure and molar mass from NMR measurements2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 7-8, p. 563-570Article in journal (Refereed)
    Abstract [en]

    The general molecular properties and in particular, the molar mass of lignin are of central importance for industrial applications, as these data govern important thermal and mechanical characteristics. The focus of the present paper is pulsed field gradient-nuclear magnetic resonance (PFG-NMR), which is suitable for determination of lignins’ weight-Average molar mass, based on diffusion constants. The method is calibrated by lignin fractions characterized by matrix-Assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). It could be demonstrated on a set of softwood kraft lignins that the PFG-NMR approach gives results in very good agreement with those obtained using conventional size exclusion chromatography (SEC).

  • 5.
    Rönnols, Jerk
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Jacobs, Anna
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Aldaeus, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Recent advances in NMR spectroscopy of lignin and black liquor2018In: 15th European workshop on lignocellulosics and pulp: proceedings for oral presentations, 2018, p. 57-60Conference paper (Other academic)
    Abstract [en]

    This paper describes improvements in the methodology for NMR spectroscopic analysis of dissolved kraft lignins and black liquors, for structural analysis as well as for reaction monitoring. The described methodologies are variations and applications of non-uniform sampling (NUS) in 2D spectra and diffusion ordered spectroscopy (DOSY), with reduced experiment time and/or increased resolution and novel ways to track reactions through monitoring of diffusion of a reactant mixture.

  • 6.
    Rönnols, Jerk
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Jacobs, Anna
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Aldaeus, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Larsson, Tomas
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Digging in the structure and functionality of lignocellulosic raw material: from academic knowledge towards industrial applications2018In: The 8th Nordic Wood Biorefinery Conference: NWBC 2018 : proceedings / [ed] Hytönen Eemeli, Vepsäläinen Jessica, Espoo: VTT , 2018, p. 205-205Conference paper (Other academic)
  • 7.
    Rönnols, Jerk
    et al.
    RISE, Innventia.
    Larsson, Karolina
    RISE, Innventia.
    Jacobs, Anna
    RISE, Innventia.
    Aldaeus, Fredrik
    RISE, Innventia.
    Absolute determination of softwood kraft lignin molar mass using MALDI-TOF mass spectrometry and pulsed field gradient NMR2016In: 14th European Workshop on Lignocellulosics and Pulp: EWLP 2016, 2016, p. 143-146Conference paper (Other academic)
    Abstract [en]

    Knowledge of the molecular properties, e.g. the molar mass, of lignin are of central importance for industrial applications, since thermal and mechanical characteristics are governed by these. Here, a method for absolute determination of weight-average molar mass of kraft lignin, based on diffusion constants gained from PFG-NMR calibrated with lignin fractions characterized by MALDI-TOF-MS, is presented. The NMR method is compared to polystyrene calibration, and size exclusion chromatography with tetrahydrofuran as mobile phase.

  • 8.
    Rönnols, Jerk
    et al.
    RISE, Innventia.
    Schweinebarth, Hannah
    RISE, Innventia.
    Jacobs, Anna
    RISE, Innventia.
    Stevanic Srndovic, Jasna
    RISE, Innventia.
    Olsson, Anne-Mari
    RISE, Innventia.
    Reimann, Anders
    RISE, Innventia.
    Aldaeus, Fredrik
    RISE, Innventia.
    Structural changes in softwood kraft lignin during nonoxidative thermal treatment2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 4, p. 550-561Article in journal (Refereed)
    Abstract [en]

    Heat treatment is a promising pre-processing method in the conversion of kraft lignins to carbon fibers. In this study, a kraft lignin was subjected to heat treatment at different lengths of time and at different temperatures. The molecular structure of the untreated and four heat treated lignins were investigated mainly by a variety of nuclear magnetic resonance spectroscopy (NMR) methods. The results were compared to structural information obtained by pyrolysis-gas chromatography-/mass spectrometry (py-GC/MS) and Fourier transform infrared spectroscopy (FTIR). It was observed that during the thermal treatment, the amount of β-O-4 ether moieties decreased, and an intramolecular conversion of secoisolariciresinol residues to cyclic ethers occurred. The effects on shape and size of the lignins were investigated by size exclusion chromatography (SEC) and NMR-diffusion measurements, by which the hydrodynamic radii were found to increase as a result of thermal treatment. It is discussed whether this depends on reduced flexibility and/or increased molar mass. In addition, the trends from the SEC and NMR analyses were compared to changes in glass transition temperature as determined by differential scanning calorimetry (DSC).

  • 9.
    Rönnols, Jerk
    et al.
    RISE, Innventia.
    Schweinebarth, Hannah
    RISE, Innventia.
    Jacobs, Anna
    RISE, Innventia.
    Stevanic Srndovic, Jasna
    RISE, Innventia.
    Olsson, Anne-Mari
    RISE, Innventia.
    Reimann, Anders
    RISE, Innventia.
    Aldaeus, Fredrik
    RISE, Innventia.
    Structural changes in softwood kraft lignin during thermal treatment2015In: 18th International Symposium on Wood, Fiber and Pulping Chemistry: 18th ISWFPC, 2015, Vol. 2, p. 366-369Conference paper (Other academic)
  • 10.
    Sjöholm, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy.
    Törngren, Per
    RISE - Research Institutes of Sweden, Bioeconomy.
    Rönnols, Jerk
    RISE - Research Institutes of Sweden, Bioeconomy.
    Microwave assisted etherification of lignin2017In: International symposium on green chemistry (ISGC 2017), May 16-19, 2017, La Rochelle, France, 2017, article id 1271Conference paper (Other academic)
    Abstract [en]

    The content of phenol and aliphatic groups of softwood kraft lignin has been altered to control the reactivity and the physical properties of the lignin. The influence of microwave assisted alkylation was evaluated using dimethyl carbonate (DMC) or diethyl carbonate (DEC) together with different bases. The influence of reaction conditions on the final lignin products were compared by NMR.

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