| 1. |
- Lauberts, Maris, et al.
(författare)
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Fractionation of technical lignin with ionic liquids as a method for improving purity and antioxidant activity
- 2017
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Ingår i: INDUSTRIAL CROPS AND PRODUCTS. - : Elsevier. - 0926-6690. ; 95, s. 512-520
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Tidskriftsartikel (refereegranskat)abstract
- Alder soda lignin, a by-product of the chemical processing of black alder wood, was fractionated using ionic liquids (ILs) based on the 1-buthyl-3-methylimidazolium [Bmim] cation and the following anions: chloride ([Bmim]Cl), dimethylphosphate ([Bmim]Me2PO4), acetate ([Brhim]OAc) and tosylate ([Bmim]OTs). The aim was to obtain lignin fractions of improved purity for further application as antioxidants. The purity and properties of the IL lignin fractions were compared with those of other lignin fractions obtained using sequential extraction with organic solvents. The original lignin and the lignin fractions were characterized by analytical pyrolysis (Py-GC/MS/FID), size-permeation chromatography (GPC), electron paramagnetic resonance (EPR) spectroscopy and wet chemistry methods. The lignin treatment with [Bmim]DMP, [Bmim]OAc and [Bmim]OTs produced fractions with a lignin content of 98-99%. These fractions along with the n-propanol and methanol fractions obtained using sequential organic solvent extraction were enriched with certain structural features that had a positive impact on lignin antioxidant activity, according to the results from DPPH center dot and ORAC assays.
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| 2. |
- Aminzadeh, Selda, 1984, et al.
(författare)
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Membrane filtration of kraft lignin: Structural charactristics and antioxidant activity of the low-molecular-weight fraction
- 2018
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Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 112, s. 200-209
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, which is the second most abundant biomass component and has carbon-rich phenolic content, is a promising renewable raw material for multiple applications, such as carbon fibers, adhesives, and emulsifiers. To use lignin efficiently, it is important to ensure its purity and homogeneity. As a result, the separation of lignin into fractions with high purity and narrow molecular-weight distributions is likely a prerequisite for several applications. Ultrafiltration using ceramic membranes has many advantages, including enabling direct lignin extraction from Kraft pulp cooking liquors without pH and temperature adjustment. One challenge with membrane filtration using such a system is the potential for reduced membrane performance over time, which is associated with fouling. In this study, LignoBoost Kraft lignin was fractionated using a ceramic membrane with a molecular weight cut-off of 1 kDa. The separation behavior during ultrafiltration fractionation was investigated and the antioxidant properties of the recovered low-molecular-weight (low-MW) lignin samples were evaluated. Using this model system, the permeate fluxes were unstable during the 100 h of membrane operation. However, a decrease in the average MW in the permeate over time was observed. The shift in MW was most pronounced for virgin membranes, while a more stable MW distribution was evident for membranes subjected to multiple cleaning cycles. According to 2D NMR analysis, low-MW lignin that was recovered after 100 h of operation, consisted of smaller lignin fragments, such as dimers and oligomers, with a high content of methoxy-groups. This was confirmed using the size exclusion chromatography method, which indicated an weigh average molecular weight in the range of 450–500 Da. 31P NMR spectroscopy showed that, despite the lower total content of phenolic OH groups, the low-MW sample had a higher proportion of non-condensed phenolic OH groups. The results of the antioxidant tests demonstrated the strong potential of lignin and its low-MW fraction as a natural antioxidant, particularly for lipid-containing systems. The low-MW lignin fraction showed better antioxidant activity than the non-fractionated LignoBoost lignin in the kinetic oxygen radical absorbance capacity (ORAC) test and demonstrated three-fold stronger inhibition of the substrate (fluorescein) than the reference antioxidant Trolox (a water-soluble derivative of vitamin E).
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| 3. |
- Rabinovich, Mikhail L., et al.
(författare)
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Carbon adsorbents from industrial hydrolysis lignin : The USSR/Eastern European experience and its importance for modern biorefineries
- 2016
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 57, s. 1008-1024
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Forskningsöversikt (refereegranskat)abstract
- This paper reviews the origin, distribution and composition of hydrolysis lignin, a large-scale by-product of the hydrolysis industry that operated in the Soviet Union and several eastern European countries from 1930s to the end of 1990s. The fundamental and industrial aspects of the production of various types of powdered and granular carbon adsorbents from hydrolysis lignin are considered through the prism of future large-scale production of biofuels and platform chemicals from renewable lignocellulosic resources. The advantages and drawbacks of hydrolysis lignin as a feedstock for the production of carbon adsorbents are compared with other types of feedstock, and the application of lignin-based carbons is discussed.
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| 4. |
- Svärd, Antonia, et al.
(författare)
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COST Action FP1105 : effect of raw materials and pulping conditions on the characteristics of dissolved kraft lignins
- 2016
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:12, s. 1105-1114
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Tidskriftsartikel (refereegranskat)abstract
- The composition, molecular weight (MW), and chemical structure of technical lignins as byproducts of pulping influence their application in terms of physical and chemical properties, reactivity, and performance. It is important to know how the analytical data of technical lignins are influenced by the wood species and the parameters of pulping. The present study focuses on kraft pulping and how the wood species (eucalyptus, pine, and spruce) and variable cooking times influence the characteristics of dissolved lignins. The black liquor (BL) was recovered after three different cooking times and the precipitated lignin was characterized by total acid hydrolysis including the determination of the acid insoluble part (Klason lignin, KL) and the sugars in the hydrolysate, elemental analysis, 31P NMR spectroscopy, analytical pyrolysis (Py-GC/MS), gel permeation chromatography (GPC), thermogravimetry (TG), and differential scanning calorimetry (DSC). The results indicate that the phenolic OH content, MW and glass transition temperature increased with longer cooking times for the softwood (SW) lignins. These lignins had also a higher MW (M-w 5500-8000 g mol(-1)), than the eucalyptus lignin (M-w 2200-2400 g mol(-1)). Eucalyptus lignin had higher sulfur content compared to SW.
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| 5. |
- Tagami, Ayumu, et al.
(författare)
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Lignin-modified tunicate cellulose nanofiber (CNF)-starch composites: impact of lignin diversity on film performance
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF) - starch mixture to prepare 100% bio-based composite films. The aim was to investigate the correlation between lignin diversity and film performance. It was confirmed that lignin’s distribution in the films was dependent on the solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The -OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to the thermal stability decrease and the Young's modulus increase of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic -OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol contents, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the positive relationship between the antioxidant ability of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin’s applications in bio-based materials based on their specific characteristics.
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| 6. |
- Zhao, Yadong, 1985-, et al.
(författare)
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The Impact of Lignin Structural Diversity on Performance of Cellulose Nanofiber (CNF)-Starch Composite Films
- 2019
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF)-starch mixture to prepare 100% bio-based composite films. The aim was to investigate the impact of lignin structural diversity on film performance. It was confirmed that lignin's distribution in the films was dependent on the polarity of solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The -OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to decrease in thermal stability and increase in Young's modulus of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic -OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol content, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the relationship between the chemical structure of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin's applications in bio-based materials based on their specific characteristics.
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