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Modification of industrial softwood kraft lignin using Mannich reaction with and without phenolation pretreatment
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), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
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.ORCID iD: 0000-0002-2900-4713
2014 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 52, 729-735 p.Article in journal (Refereed) Published
Abstract [en]

The amination of industrial softwood kraft lignin was conducted using the Mannich reaction to modify the lignin structure for value-added applications. To understand the reaction mechanism and to quantify the amount of amine groups that were introduced, different types of NMR analyses were performed. The lignin was also pretreated by phenolation to increase its reactivity and the amount of the amine groups that were introduced. The Mannich reaction was very selective at the C-5 position of the guaiacyl units and complete under acidic conditions with similar to 11-fold amounts of reagents of dimethylamine and formaldehyde over either model lignin (4-hydroxy-3-methoxyacetophenone, HMAP) or industrial spruce kraft lignin (LignoBoost lignin, LBL). For LBL, 28 amine groups were introduced over 100 aromatic rings. By weight, the nitrogen content was 2.5%. The animated lignin was found to possess a higher molecular mass, reaching a Mp of 4.9 x 10(3) Da compared to the original 319 x 10(3) Da, and with a considerably increased dispersibility, especially in a dilute aqueous solution of hydrochloric acid (pH = 3), namely 5.2 mg/ml. With a preceding phenolation treatment, which increased the amount of phenolic aromatic rings available for the Mannich reaction, an introduction of 42 amine groups over 100 aromatic rings, or a nitrogen content of 4.8%, was obtained, which caused a further increase of the molecular mass to 5.1 x 10(3) Da (Mp) and of dispersibility in the aqueous solution of hydrochloric acid up to 32.0 mg/ml. The aminated lignins with or without the phenolation pretreatment formed very stable colloidal suspensions in water, with large particle sizes (391 and 39 nm), high zeta potentials (31.6 and 27.2 mV), and large charge densities (1.6 and 1.2 x 10(-7) equiv./ml, respectively). The potential value-added applications of these modified lignins with high amine contents include use as surfactant chemicals, polycationic materials and slow-release fertilisers, among others.

Place, publisher, year, edition, pages
2014. Vol. 52, 729-735 p.
Keyword [en]
Amination, Colloidal properties, Dispersibility, NMR, Mannich reaction, Phenolation, Softwood kraft lignin
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-126271DOI: 10.1016/j.indcrop.2013.11.035ISI: 000332189200097Scopus ID: 2-s2.0-84890617812OAI: oai:DiVA.org:kth-126271DiVA: diva2:642016
Note

QC 20140404. Updated from manuscript to article in journal.

Available from: 2013-08-20 Created: 2013-08-20 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Deepening the insights of lignin structure: Lignin-carbohydrate complex (LCC) fractionation and characterization and Kraft lignin amination
Open this publication in new window or tab >>Deepening the insights of lignin structure: Lignin-carbohydrate complex (LCC) fractionation and characterization and Kraft lignin amination
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Improvement of kraft pulping delignification efficiency and value-addition of industrial kraft lignin are two attractive topics. The proposal that delignification is deteriorated by the presence of lignin-carbohydrate complex (LCC) is still being debated. Therefore, it is theoretically and practically important to investigate various LCC structures from native wood and their changes during different treatments. Currently, however, there is no effective LCC fractionation method that could quantitatively isolate all LCC fractions and be applicable for all types of lignocellulosic materials. The fractionation should also be followed by comprehensive and reliable structural characterisation. Additionally the Kraft lignin has a heterogeneous structure and poor properties. Structural modification is therefore one possible solution for creating more economical benefits than the presently direct combustion for heat.

In this work, an LCC fractionation method has been developed, which preserves original lignin and lignin-carbohydrate (LC) bonding structures and is nearly quantitative. It is universally applicable for hardwood, softwood or non-wood species. A whole set of subsequent analytical tools for the comprehensive elucidation of the different LCC fractions has also been established and applied. After applying the LCC fractionation and characterisation:

1). spruce wood was found to consist of 49.5% glucan-lignin (GL), 30.9% glucomannan–lignin (GML) and 12.0% xylan–lignin (XL). Although the LC and lignin-lignin (LL) linkage signals could not be directly observed by a 400 MHz NMR instrument, these linkages have been clearly observed by a 600 MHz NMR instrument equipped with a cryogenic probe after enzymatic hydrolysis. The LC bondings include phenyl glycoside, benzyl ether and γ-ester. Based on the LL bond frequencies, GML is less condensed than XL.

2). a general lignin biodegradation mechanism by the laccase-mediator system (LMS) has been proposed, which mainly involves Cα oxidation and Cα-Cβ bond cleavage of the lignin side chain and eventually aromatic ring cleavage. The LMS delignification efficiency depends largely on the species of the applied laccase and mediator. Some LMS has been proven to possess an obvious capacity for hexenuronic acid (HexA) removal. For Kraft pulp bleaching, there are potential benefits of various combinations among biological treatment (by LMS), non-oxidative chemical (by urea treatment, U), and mechanical treatment (by refining, R).

In addition, it has been demonstrated in this work that the structures and properties of industrial softwood Kraft lignin (LignoBoost lignin) could largely be upgraded by amination via the Mannich reaction. With or without a phenolation pretreatment, the aminated lignins obtained are promising polycationic materials, especially in the application as colloidal suspensions. During this investigation of kraft lignin amination, NMR methods have been developed for the quantification of the N content introduced and for the deepened insights of the structural changes of the lignin. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 65 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:30
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-126279 (URN)978-91-7501-818-8 (ISBN)
Public defence
2013-09-10, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130820

Available from: 2013-08-20 Created: 2013-08-20 Last updated: 2013-08-20Bibliographically approved

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Lindström, Mikael

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