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Fiskari, J., Henriksson, G., Swerin, A., Carlsson-Kvarnlöf, G., Sjöstrand, B. & Germgård, U. (2025). After Decades of Extensive Research, Is Kraft Lignin Valorization Still Up In The Air? – Obstacles, Opportunities, and Myths. BioResources, 20(3), 5218-5221
Open this publication in new window or tab >>After Decades of Extensive Research, Is Kraft Lignin Valorization Still Up In The Air? – Obstacles, Opportunities, and Myths
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2025 (English)In: BioResources, E-ISSN 1930-2126, Vol. 20, no 3, p. 5218-5221Article in journal, Editorial material (Other academic) Published
Abstract [en]

In the past decades, substantial research efforts have been directed towards increasing the availability of renewable and recycled raw materials. Lignin, one of the most abundant natural polymers, constitutes a vast, renewable, and largely untapped source of aromatic structures. In addition, it is one of the most abundant renewable sources of carbon. Despite the countless research projects aimed at valorizing kraft lignin, the largest source of industrial lignin, relatively few commercial kraft lignin products have emerged. Simultaneously, lignosulfonates represent a commercially successful range of products with a steady and growing global market. This paper reviews the current outlook of technical lignin research, including common misunderstandings, and discusses various factors that have hampered the use of lignin as a renewable source of materials and chemicals.

Place, publisher, year, edition, pages
BioResources, 2025
Keywords
Kraft lignin, Lignin research, Lignocellulose, Myths, Valorization
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-363985 (URN)10.15376/biores.20.3.5218-5221 (DOI)001485164600002 ()2-s2.0-105005428771 (Scopus ID)
Note

QC 20250603

Available from: 2025-06-02 Created: 2025-06-02 Last updated: 2025-06-03Bibliographically approved
Senthilkumar, E. R., Henriksson, G., Lindström, M., Vikström, T. & Sevastyanova, O. (2025). Effects of chemical environment on softwood kraft pulp: Exploring beyond conventional washing methods. Nordic Pulp & Paper Research Journal, 40(1), 83-93
Open this publication in new window or tab >>Effects of chemical environment on softwood kraft pulp: Exploring beyond conventional washing methods
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2025 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 40, no 1, p. 83-93Article in journal (Refereed) Published
Abstract [en]

Brownstock washing, a critical process in cleansing kraft pulp, removes dissolved lignin residues from the pulp after it has passed through the cooking digester. It plays a significant role in kraft pulp mills by enhancing economic efficiency and environmental sustainability. Improved washing efficiency leads to better pulp quality and more effective recovery of cooking chemicals. Our study aimed to better understand the impact of different chemical compositions in washing liquors on washing performance. We tested a range of washing liquors, including neutral solutions (deionized water, 1M NaCl, 3M NaCl, 1M Na2SO4) and alkaline solutions (tap water, washing liquor composed of 0.35M NaOH and 1M Na2SO4, and white liquor with 50 g[OH]/l and 8.77 g[HS]/l). These liquors were evaluated for their efficacy in maximizing lignin extraction. Our findings suggest that salt solutions generally reduce washing efficiency. Deionized water and white liquor proved to be the most efficient washing agents, while high-concentration salts and those with high ionic strength negatively impacted washing efficiency. This suggests that brownstock washing may not be operating at its full potential.

Place, publisher, year, edition, pages
Walter de Gruyter GmbH, 2025
Keywords
brownstock washing, ionic strength, kraft pulping, leaching, lignin
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-363111 (URN)10.1515/npprj-2023-0061 (DOI)001379468800001 ()2-s2.0-105003160184 (Scopus ID)
Note

QC 20250506

Available from: 2025-05-06 Created: 2025-05-06 Last updated: 2025-05-06Bibliographically approved
Sjöström, J., Lindström, M., Vikström, T., Esteves, C. V., Henriksson, G. & Sevastyanova, O. (2025). On the nature of the selectivity of oxygen delignification. Nordic Pulp & Paper Research Journal, 40(1), 61-69
Open this publication in new window or tab >>On the nature of the selectivity of oxygen delignification
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2025 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 40, no 1, p. 61-69Article in journal (Refereed) Published
Abstract [en]

This work has focused on oxygen's role in the delignification process within the context of pulp production. We have investigated the role of oxygen in a complex set of chemical reactions taking place during this process, including both oxidative and non-oxidative reactions. This study explores the impact of pH changes during the oxygen delignification process and the characteristics of the resulting pulps. Additionally, this research examines the effect of oxygen, by comparing conventional oxygen delignification with trials using air and nitrogen. Industrial softwood kraft pulps with a kappa number of 35 were subjected to delignification for 20-120 min under alkaline conditions. The resulting pulps were assessed for kappa number, intrinsic viscosity, fiber charge, and ISO brightness. An important observation from this research is the reduction in lignin molecular weight upon exposure to oxygen and air, suggesting depolymerization reactions facilitated by oxygen species, whereas nitrogen exposure results in less pronounced changes. This finding underscores the impact of oxygen in altering lignin structure, thus informing the selectivity and effectiveness of the delignification process.

Place, publisher, year, edition, pages
Walter de Gruyter GmbH, 2025
Keywords
alkaline extraction, alkaline leaching, kraft pulp, oxygen delignification, selectivity, viscosity
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-363103 (URN)10.1515/npprj-2024-0026 (DOI)001359220200001 ()2-s2.0-105003286446 (Scopus ID)
Note

QC 20250506

Available from: 2025-05-06 Created: 2025-05-06 Last updated: 2025-05-06Bibliographically approved
Heinonen, E., Sivan, P., Jiménez-Quero, A., Lindström, M., Wohlert, J., Henriksson, G. & Vilaplana, F. (2025). Pattern of substitution affects the extractability and enzymatic deconstruction of xylan from Eucalyptus wood. Carbohydrate Polymers, 353, Article ID 123246.
Open this publication in new window or tab >>Pattern of substitution affects the extractability and enzymatic deconstruction of xylan from Eucalyptus wood
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2025 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 353, article id 123246Article in journal (Refereed) Published
Abstract [en]

Glucuronoxylan is the main hemicellulose in the secondary cell wall of angiosperms. Elucidating its molecular structure provides a basis for more accurate plant cell wall models and the utilization of xylan in biorefinery processes. Here, we investigated the spacing of acetyl, glucuronopyranosyl and galactopyranosyl substitutions on Eucalyptus glucuronoxylan using sequential extraction combined with enzymatic hydrolysis and mass spectrometry. We found that the acetyl groups are preferentially spaced with an even pattern and that consecutive acetylation is present as a minor motif. Distinct odd and even patterns of glucuronidation with tight and sparse spacing were observed. Furthermore, the occurrence of consecutive glucuronidation is reported, which adds to the growing body of evidence that this motif is not only present in gymnosperms but also in angiosperms. In addition, the presence of terminal galactopyranosyl units, which can be released by β-galactosidase, altered the digestibility of the glucuronoxylan by GH30 and GH10 xylanase and appeared to be clustered within the polymeric backbone. These findings increase our understanding of the complex structure of glucuronoxylans and its effect on the extractability and biological degradation of Eucalyptus wood.

Place, publisher, year, edition, pages
Elsevier BV, 2025
Keywords
Acetylation, Eucalyptus, Galactosylation, Glucuronidation, Recalcitrance, Xylan
National Category
Organic Chemistry Structural Biology
Identifiers
urn:nbn:se:kth:diva-358894 (URN)10.1016/j.carbpol.2025.123246 (DOI)39914950 (PubMedID)2-s2.0-85214689958 (Scopus ID)
Note

Not duplicate with DiVA 1892598

QC 20250124

Available from: 2025-01-23 Created: 2025-01-23 Last updated: 2025-05-27Bibliographically approved
Svagan, A. J., Vilaplana, F., Pettersson, T., Anusuyadevi, P. R., Henriksson, G. & Hedenqvist, M. S. (2024). Centrifuge fractionation during purification of cellulose nanocrystals after acid hydrolysis and consequences on their chiral self-assembly. Carbohydrate Polymers, 328, Article ID 121723.
Open this publication in new window or tab >>Centrifuge fractionation during purification of cellulose nanocrystals after acid hydrolysis and consequences on their chiral self-assembly
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2024 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 328, article id 121723Article in journal (Refereed) Published
Abstract [en]

The inherent colloidal dispersity (due to length, aspect ratio, surface charge heterogeneity) of CNCs, when produced using the typical traditional sulfuric acid hydrolysis route, presents a great challenge when interpreting colloidal properties and linking the CNC film nanostructure to the helicoidal self-assembly mechanism during drying. Indeed, further improvement of this CNC preparation route is required to yield films with better control over the CNC pitch and optical properties. Here we present a modified CNC-preparation protocol, by fractionating and harvesting CNCs with different average surface charges, rod lengths, aspect ratios, already during the centrifugation steps after hydrolysis. This enables faster CNC fractionation, because it is performed in a high ionic strength aqueous medium. By comparing dry films from the three CNC fractions, discrepancies in the CNC self-assembly and structural colors were clearly observed. Conclusively, we demonstrate a fast protocol to harvest different populations of CNCs, that enable tailored refinement of structural colors in CNC films.

Place, publisher, year, edition, pages
Elsevier Ltd, 2024
Keywords
Cellulose nanocrystals, Fractionation, Structural colors, Sulfuric acid hydrolysis
National Category
Polymer Technologies Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-342832 (URN)10.1016/j.carbpol.2023.121723 (DOI)2-s2.0-85182892792 (Scopus ID)
Note

QC 20240201

Available from: 2024-01-31 Created: 2024-01-31 Last updated: 2024-02-01Bibliographically approved
Chakraborty, M., Battestini Vives, M., Abdelaziz, O. Y., Henriksson, G., Wreland Lindström, R., Hulteberg, C. P. & Khataee, A. (2024). Lignin-Based Electrolytes for Aqueous Redox Flow Batteries. ACS Sustainable Chemistry and Engineering, 12(42), 15409-15417
Open this publication in new window or tab >>Lignin-Based Electrolytes for Aqueous Redox Flow Batteries
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2024 (English)In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 12, no 42, p. 15409-15417Article in journal (Refereed) Published
Abstract [en]

Lignin is one of the most naturally occurring biopolymers on Earth and exists in a relatively large portion of the residual stream of the pulp and paper industry. Technical lignin is water-soluble, nontoxic, and rich in quinone-type groups; therefore, it could be a potential redox species for next-generation aqueous redox flow batteries (RFBs). Despite having attractive features, lignin does not show a reversible electrochemical behavior. Herein, we implemented a straightforward approach to modify the structure of soda-based lignin by oxidative depolymerization. The modified lignin showed good electrochemical activity through cyclic voltammetry with distinct redox peaks, which match lignin monomers, such as vanillin and acetovanillone. The modified lignin was used as the negolyte of the RFB setup with potassium ferrocyanide as the counterpart. The RFB was cycled for over 200 cycles with an average Coulombic efficiency of 91%. In addition, the modified lignin electrolyte maintained the (electro)chemical properties even after four months of storage, as proven by RFB tests.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
Keywords
lignin, oxidative depolymerization, redox flow battery, sustainability, energy storage
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-355344 (URN)10.1021/acssuschemeng.4c04227 (DOI)001336911800001 ()2-s2.0-85206454971 (Scopus ID)
Funder
Swedish Energy Agency, P2021-00137KTH Royal Institute of Technology, C6899
Note

QC 20241030

Available from: 2024-10-29 Created: 2024-10-29 Last updated: 2024-10-30Bibliographically approved
Hubbe, M. A., Sjostrand, B., Lestelius, M., Hakansson, H., Swerin, A. & Henriksson, G. (2024). Swelling of cellulosic fibers in aqueous systems: A review of chemical and mechanistic factors. BioResources, 19(3), 6859-6945
Open this publication in new window or tab >>Swelling of cellulosic fibers in aqueous systems: A review of chemical and mechanistic factors
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2024 (English)In: BioResources, E-ISSN 1930-2126, Vol. 19, no 3, p. 6859-6945Article, review/survey (Refereed) Published
Abstract [en]

Factors affecting the swelling of cellulosic fibers are considered in this review. Emphasis is placed on aqueous systems and papermaking fibers, but the review also considers cellulose solvent systems, nanocellulose research, and the behavior of cellulosic hydrogels. The topic of swelling of cellulosic fibers ranges from effects of humid air, continuing through water immersion, and extends to hydrogels and the dissolution of cellulose, as well as some of its derivatives. The degree of swelling of cellulose fibers can be understood as involving a balance between forces of expansion (especially osmotic pressure) vs. various restraining forces, some of which involve the detailed structure of layers within the fibril structure of the fibers. The review also considers hornification and its effects related to swelling. The expansive forces are highly dependent on ionizable groups, pH, and the ionic strength of solution. The restraining forces depend on the nature of lignin, cellulose, and their detailed structural arrangements.

Place, publisher, year, edition, pages
BioResources, 2024
Keywords
Osmotic pressure, Donnan equilibrium, Dissociation, Hydrophilicity, Crystallinity, Water retention value
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-354225 (URN)10.15376/biores.19.3.Hubbe (DOI)001306586000034 ()2-s2.0-85203495607 (Scopus ID)
Note

QC 20241001

Available from: 2024-10-01 Created: 2024-10-01 Last updated: 2025-05-27Bibliographically approved
Lindén, P. A., Lindström, M., Lawoko, M. & Henriksson, G. (2023). Adapting the kraft cooking process in glycerol media. Studies of impregnation kinetics. Nordic Pulp & Paper Research Journal, 38(1), 9-18
Open this publication in new window or tab >>Adapting the kraft cooking process in glycerol media. Studies of impregnation kinetics
2023 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 38, no 1, p. 9-18Article in journal (Refereed) Published
Abstract [en]

Although organosolv processes using high-boiling solvents have been investigated in recent decades for developing novel industrial processes, there are potential benefits of using high-boiling point solvents for traditional sulphate-based cooking processes, both from an industrial perspective and from a laboratory perspective. Using high-boiling solvents, experiments can be done under atmospheric conditions, thus making it easier to continually monitor laboratory experiments and extracting aliquots at desired intervals. Using such a system, alkaline consumption was monitored during impregnation of spruce chips in glycerol media using chemical charges of 1 M NaOH and 0.1 M NaHS, i. e., kraft pulping conditions, and compared to a similar investigation of alkaline consumption in water media using steel autoclaves. The resulting data was fitted to a first order kinetic model, with an apparent activation energy of 22 kJ mol-1 in glycerol media. Finally, a "normal quality pulp"of kappa number 28 and a viscosity of 1113 ml g-1 was successful produced using a cooking process with an impregnation step at 140 °C for 3 h and a cooking step at 160 °C for 4 h. A nuclear magnetic resonance study on the dissolved lignin produced for said experiment showed characteristics typical of other kraft lignins.

Place, publisher, year, edition, pages
Walter de Gruyter GmbH, 2023
Keywords
alkali consumption, atmospheric pulping, kraft pulping, organosolv pulping, spruce
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-328845 (URN)10.1515/npprj-2022-0023 (DOI)000883823100001 ()2-s2.0-85143266828 (Scopus ID)
Note

QC 20241203

Available from: 2023-06-15 Created: 2023-06-15 Last updated: 2025-02-25Bibliographically approved
Vegunta, V. L., Deshpande, R., Lindén, P., Sevastyanova, O., Garcia, A., Björk, M., . . . Lindström, M. (2023). Addition of Green and Black Liquor in Kraft Pulping of Eucalyptus dunnii wood: Possible Solutions for the Problems with Kraft Pulping Caused by High Calcium Content..
Open this publication in new window or tab >>Addition of Green and Black Liquor in Kraft Pulping of Eucalyptus dunnii wood: Possible Solutions for the Problems with Kraft Pulping Caused by High Calcium Content.
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2023 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Samples of Eucalyptus dunnii with high calcium content have less good pulping properties regarding delignification and polysaccharide degradation, as it was shown by us earlier. In this work, we tested the addition of black liquor and green liquor to the Eucalyptus dunnii chips before kraft pulping, Specific improvements were obtained with both liquors, but the most substantial effect was observed with the green liquor, where even wood with the highest calcium content was pulped with a good result. Delignification was faster, and viscosity losses (degree of polymerization of cellulose) were higher for samples treated with green liquor prior to kraft pulping. Bleaching experiments showed that the bleachability of the green liquor-treated pulp was virtually the same as for a control pulp and that the higher viscosity of the bleached pulp was maintained. Possible chemical explanations for the results obtained are discussed.

National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-323319 (URN)
Note

I listan över avhandlingens delarbeten står detta arbete med titeln "Green and black liquor impregnation:possible solutions for problems with kraft pulping caused by calciumcontent.".

QC 20230919

Available from: 2023-01-25 Created: 2023-01-25 Last updated: 2023-09-19Bibliographically approved
White, J., Peters, L., Martín-Yerga, D., Terekhina, I., Anil, A., Lundberg, H., . . . Cornell, A. (2023). Glycerol Electrooxidation at Industrially Relevant Current Densities Using Electrodeposited PdNi/Nifoam Catalysts in Aerated Alkaline Media. Journal of the Electrochemical Society, 170(8), Article ID 086504.
Open this publication in new window or tab >>Glycerol Electrooxidation at Industrially Relevant Current Densities Using Electrodeposited PdNi/Nifoam Catalysts in Aerated Alkaline Media
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2023 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 170, no 8, article id 086504Article in journal (Refereed) Published
Abstract [en]

Through glycerol electrooxidation, we demonstrate the viability of using a PdNi catalyst electrodeposited on Ni foam to facilitate industrially relevant rates of hydrogen generation while concurrently providing valuable organic chemicals as glycerol oxidation products. This electrocatalyst, in a solution of 2 M NaOH and 1 M glycerol at 80 °C, enabled current densities above 2000 mA cm−2 (in a voltammetric sweep) to be obtained in atmospheres of both air and N2. Repeated potential cycling under an aerated atmosphere to these exceptional current densities indicated a high stability of the catalyst. Through steady state polarisation curves, 1000 mA cm−2 was reached below an anodic potential of 0.8 V vs RHE. Chronoamperometry showed glycerate and lactate being the major oxidation products, with increased selectivity for lactate at the expense of glycerate in aerated systems. Aerated atmospheres were demonstrated to consistently increase the apparent Faradaic efficiency to >100%, as determined by the concentration of oxidation products in solution. The excellent performance of PdNi/Ni in aerated solutions suggests that O2 removal from the electrolyte is not needed for an industrial glycerol electrooxidation process, and that combining electrochemical and chemical glycerol oxidation, in the presence of dissolved O2, presents an important process advantage.

Place, publisher, year, edition, pages
The Electrochemical Society, 2023
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-334940 (URN)10.1149/1945-7111/acee27 (DOI)001049747200001 ()2-s2.0-85168440809 (Scopus ID)
Note

QC 20230830

Available from: 2023-08-30 Created: 2023-08-30 Last updated: 2023-11-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8817-2031

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