| 1. |
- Argyropoulos, Dimitris D. S., et al.
(author)
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Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges
- 2023
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In: ChemSusChem. - : John Wiley and Sons Inc. - 1864-5631 .- 1864-564X. ; 16:23
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Research review (peer-reviewed)abstract
- Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.
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| 2. |
- Cailotto, Simone, et al.
(author)
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N-Doped Carbon Dot Hydrogels from Brewing Waste for Photocatalytic Wastewater Treatment
- 2022
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:5, s. 4052-4061
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Journal article (peer-reviewed)abstract
- The brewery industry annually produces huge amounts of byproducts that represent an underutilized, yet valuable, source of biobased compounds. In this contribution, the two major beer wastes, that is, spent grains and spent yeasts, have been transformed into carbon dots (CDs) by a simple, scalable, and ecofriendly hydrothermal approach. The prepared CDs have been characterized from the chemical, morphological, and optical points of view, highlighting a high level of N-doping, because of the chemical composition of the starting material rich in proteins, photoluminescence emission centered at 420 nm, and lifetime in the range of 5.5–7.5 ns. With the aim of producing a reusable catalytic system for wastewater treatment, CDs have been entrapped into a polyvinyl alcohol matrix and tested for their dye removal ability. The results demonstrate that methylene blue can be efficiently adsorbed from water solutions into the composite hydrogel and subsequently fully degraded by UV irradiation.
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| 3. |
- Duval, Antoine, et al.
(author)
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Modification of Kraft Lignin to Expose Diazobenzene Groups : Toward pH- and Light-Responsive Biobased Polymers
- 2015
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 16:9, s. 2979-2989
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Journal article (peer-reviewed)abstract
- A pH- and light-responsive polymer has been synthesized from softwood kraft lignin by a two-step strategy that aimed to incorporate diazobenzene groups. Initially, styrene oxide was reacted with the phenolic hydroxyl groups in lignin, to offer the attachment of benzene rings, thus creating unhindered reactive sites for further modifications. The use of advanced spectroscopic techniques H-1 and P-31 NMR, UV and FTIR) demonstrated that the reaction was quantitative and selective toward the phenolic hydroxyl groups. In a second step, the newly incorporated benzene rings were reacted with a diazonium cation to form the target diazobenzene motif, whose formation was again thoroughly verified. As anticipated, the diazobenzene-containing kraft lignin derivatives showed a pH-dependent color change in solution and light-responsive properties resulting from the cis-trans photoisomerization of the diazobenzene group.
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| 4. |
- Duval, Antoine, et al.
(author)
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Reversible crosslinking of lignin via the furan-maleimide Diels-Alder reaction
- 2015
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In: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 17:11, s. 4991-5000
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Journal article (peer-reviewed)abstract
- Two distinct functionalization schemes for Kraft lignin (KL) were developed to selectively incorporate furan and/or maleimide motifs as chain ends. The incorporation of furan functionalities was carried out by the selective and quantitative reaction of the lignin's phenolic OH groups with furfuryl glycidyl ether (FGE). Maleimide groups were introduced by esterifying the lignin's aliphatic and phenolic OH groups with 6 maleimidohexanoic acid (6-MHA), offering a high loading despite a somewhat incomplete conversion. Furan-and maleimide-functionalized lignins were subsequently combined to generate crosslinking via the Diels-Alder (DA) [4 + 2] cycloaddition reaction. The formation of the DA adduct was confirmed by H-1 NMR. Under appropriate conditions, the formation of a gel was apparent, which turned back into the liquid state after performing the corresponding retro-DA reaction upon heating to 120 degrees C. This study reveals the significant versatility and potential of the developed strategy for the utilization of lignin-based recyclable networks.
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| 5. |
- Duval, Antoine, et al.
(author)
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Solvent screening for the fractionation of industrial kraft lignin
- 2016
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In: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:1, s. 11-20
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Journal article (peer-reviewed)abstract
- The polydispersity of commercially available kraft lignins (KLs) is one of the factors limiting their applications in polymer-based materials. A prerequisite is thus to develop lignin fractionation strategies compatible with industrial requirements and restrictions. For this purpose, a solvent-based lignin fractionation technique has been addressed. The partial solubility of KL in common industrial solvents compliant with the requirements of sustainable chemistry was studied, and the results were discussed in relation to Hansen solubility parameters. Based on this screening, a solvent sequence is proposed, which is able to separate well-defined KL fractions with low polydispersity.
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| 6. |
- Karnaouri, Anthi C, et al.
(author)
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Chemoenzymatic Fractionation and Characterization of Pretreated Birch Outer Bark
- 2016
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 4:10, s. 5289-5302
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Journal article (peer-reviewed)abstract
- In this study, the application of different chemical and enzymatic treatment methods for the fractionation of the birch outer bark components was evaluated. More specifically, untreated and steam exploded, hydrothermally and organosolv treated bark samples were incubated with enzyme mixtures that consisted of cellulases, hemicellulases and esterases, and the effect of enzymes was analyzed with 31P NMR and {13C-1H} HSQC. The biocatalysts performed the cleavage of ester bonds resulting in reduction of methoxy and aliphatic groups in the remaining solid fraction, whereas the aromatic fraction remained intact. Moreover, the suberin and lignin fraction were isolated chemically and their properties were characterized by gas chromatography (GC-MS), 31P NMR, {13C-1H} HSQC and gel permeation chromatography (GPC). It was demonstrated that the lignin fraction was enriched in guaiacyl phenolics but still contained some associated aliphatic acids and carbohydrates, whereas the suberin fraction presented a polymodal pattern of structures with different molecular weight distributions. This work will help in getting a deeper fundamental knowledge of the bark structure, the intermolecular connection between lignin and suberin fractions, as well as the potential use of enzymes in order to degrade the recalcitrant bark structure toward its valorization.
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| 7. |
- Kumaniaev, Ivan, 1995-
(author)
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Fractionation of woody biomass : lignin and suberin in focus
- 2020
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Doctoral thesis (other academic/artistic)abstract
- This thesis is dedicated to the research of fractionation and valorization of different types of woody biomass. In the first part, oak (Quercus suber) and birch (Betula pendula) barks are considered. Bark is the outer layer of wood and is treated as waste in the current wood processing technologies. The main polymers which form bark are lignin (aromatic polyether) and suberin (aliphatic polyester). In the present study, these compounds have been transformed into monomeric phenols which may serve as a precursors for bio-based polyesters, and hydrocarbon bio-oil of gasoline, diesel, and heavy gas oil ranges. The bio-oil has been studied with GC-MS, 2D GC, and simulated distillation techniques. The second part concerns birch heartwood. In contrast with bark, wood does not contain suberin but has a higher content of lignin. A variety of fractionation processes are known for wood. The major disadvantages are contamination of pulp with catalyst and irreversible recondensation of lignin which takes place in harsh pulping conditions. For the purpose of solving these problems, a flow process has been developed in which the biomass and the catalyst are separated in time and space and the lignin is stabilized and cleaved into monomers immediately after its extraction. The process has been optimized to obtain monophenolic lignin-derived compounds, while the remaining cellulose pulp was enzymatically converted into glucose. Hemicellulose serves as a hydrogen donor for the lignin reduction, and therefore no external hydrogen source is required. The experimental work was complemented with a theoretical study of the process of lignin cleavage on the Pd surface. Computations under on the ReaxFF approach were used to model the successive steps of the adsorption of the molecules on the catalyst, their fragmentation, reactions, and desorption. The products obtained in the experiment have been also observed in this simulation.
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| 8. |
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| 9. |
- Nitsos, Christos, et al.
(author)
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Isolation and Characterization of Organosolv and Alkaline Lignins from Hardwood and Softwood Biomass
- 2016
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 4:10, s. 5181-5193
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Journal article (peer-reviewed)abstract
- Isolation of lignins from hardwood and softwood biomass samples, containing 26.1% and 28.1% lignin, respectively, has been performed with the use of alkaline and organosolv pretreatment methods. The effect of catalyst loading, ethanol content, particle size, and pretreatment time on the yields and properties of the isolated lignins were investigated. Alkaline lignins had higher carbohydrate content - up to 30% - and exhibited higher molecular weights in the range of 3000 Da, with a maximum phenolic hydroxyl content of 1 mmol g-1 for birch and 2 mmol g-1 for spruce. Organosolv lignins, on the other hand, showed high purity - 93% or higher - despite the more extensive biomass dissolution into the pretreatment medium; they also exhibited a lower range of molecular weights between 600 and 1600 Da depending on the source and pretreatment conditions. Due to the lower molecular weight, phenolic hydroxyl content was also increased, reaching as high as 4 mmol g-1 with a simultaneous decrease in aliphatic hydroxyl content as low as 0.6 mmol g-1. Efficient lignin dissolution of 62% for spruce and 69% for birch, achieved at optimal pretreatment conditions, was combined with extensive hemicellulose removal
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| 10. |
- Paulsen Thoresen, Petter, et al.
(author)
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Characterization of Organosolv Birch Lignins : Toward Application-Specific Lignin Production
- 2021
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:6, s. 4374-4385
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Journal article (peer-reviewed)abstract
- Organosolv pretreatment represents one of the most promising biomass valorization strategies for renewable carbon-based products; meanwhile, there is an overall lack of holistic approach to how extraction conditions affect the suitable end-usages. In this context, lignin extracted from silver birch (Betula pendula L.) by a novel hybrid organosolv/steam-explosion treatment at varying process conditions (EtOH %; time; catalyst %) was analyzed by quantitative NMR (1H–13C HSQC; 13C NMR; 31P NMR), gel permeation chromatography, Fourier transform infrared (FT-IR), Pyr-gas chromatography–mass spectroscopy (GC/MS), and thermogravimetric analysis, and the physicochemical characteristics of the lignins were discussed regarding their potential usages. Characteristic lignin interunit bonding motifs, such as β-O-4′, β-β′, and β-5′, were found to dominate in the extracted lignins, with their abundance varying with treatment conditions. Low-molecular-weight lignins with fairly unaltered characteristics were generated via extraction with the highest ethanol content potentially suitable for subsequent production of free phenolics. Furthermore, β-β′ and β-5′ structures were predominant at higher acid catalyst contents and prolonged treatment times. Higher acid catalyst content led to oxidation and ethoxylation of side-chains, with the concomitant gradual disappearance of p-hydroxycinnamyl alcohol and cinnamaldehyde. This said, the increasing application of acid generated a broad set of lignin characteristics with potential applications such as antioxidants, carbon fiber, nanoparticles, and water remediation purposes.
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