| 1. |
- Nosach, L.V, et al.
(author)
-
Gas-phase crosslinking of the lignin on the nanoscale fumed silica surface
- 2021
-
In: PHYSICS AND CHEMISTRY OF SOLID STATE. - : Vasyl Stefanyk Precarpathian National University. - 1729-4428 .- 2309-8589. ; 22:4, s. 724-728
-
Journal article (peer-reviewed)abstract
- A method for the polymerization modification of nanoscale fumed silica by crosslinking a lignin layer adsorbed on a nanosilica surface under a gas dispersion medium is described. A mixture of phenol and formaldehyde in the presence of HCl proved to be the most effective crosslinking agent. It has been suggested that the crosslinking of lignin molecules occurs by a mechanism similar to the production of phenol formaldehyde resins.
|
|
| 2. |
|
|
| 3. |
- Berglund, Jennie, et al.
(author)
-
Wood hemicelluloses exert distinct biomechanical contributions to cellulose fibrillar networks
- 2020
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 11:1
-
Journal article (peer-reviewed)abstract
- Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interactions with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of wood xylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties.
|
|
| 4. |
- Galysh, V., et al.
(author)
-
Impact of ferrocyanide salts on the thermo-oxidative degradation of lignocellulosic sorbents
- 2017
-
In: Journal of thermal analysis and calorimetry (Print). - : Springer. - 1388-6150 .- 1588-2926. ; 128:2, s. 1019-1025
-
Journal article (peer-reviewed)abstract
- The catalytic effect of ferrocyanide salts of d-metals on the thermo-oxidative degradation of lignocellulose-inorganic sorbents derived from apricot seed shells was investigated by differential thermal analysis. A comparative analysis of the thermal characteristics of the apricot seed shells and the lignocellulose matrix obtained from the shells by alkali-acid pretreatment was performed. It was shown that acid-alkali pretreatment of the apricot seed shells increases the thermal stability of the lignocellulosic material, due to the removal of low molecular weight carbohydrates and other components. The thermal degradation process of the lignocellulose-inorganic samples containing different ferrocyanides occurred at lower temperatures than the initial lignocellulose matrix, indicating the catalytic activity of modifiers. It was demonstrated that for the sorbents containing mixed salts of potassium cobalt and potassium nickel ferrocyanide, thermal destruction ends at temperatures that are 60 A degrees C lower than those for the initial lignocellulose matrix. The obtained results also show that the thermal destruction of composite lignocellulose-inorganic sorbents can be a suitable method for their disposal.
|
|
| 5. |
- Henriksson, Gunnar, 1965-, et al.
(author)
-
Lignin Utilization
- 2010
-
In: Thermochemical conversion of biomass to liquid fuels and chemicals. - : RSC Publishing. - 9781849732260 ; , s. 222-262
-
Book chapter (peer-reviewed)abstract
- Lignin is one of the most abundant biopolymers on Earth, carrying out important biological roles in vascular plants. It has somewhat higher energy content than polysaccharides, but has a complex and heterogeneous structure including covalent bonds to polysaccharides. The partly random structure of lignin is explained by the fact that it is created by an uncatalyzed radical polymerization. Lignin is obtained as a by-product of various types of technical processes based on biomass, of which chemical pulping of wood is the most important. These technical lignins have structures that differ from native lignin. Sulphite pulping of wood generates a water soluble lignin derivate, which among other things, is used as a dispersing agent and dust binder. Kraft pulping generates a lignin that is insoluble at neutral pH, which today is mainly burned for heat generation in the chemical recovery system of the kraft pulp mill. Recently, efficient methods have been developed for the preparation of lignin from the process liquids, for use in energy generation or other applications. Conversion of technical lignin to liquid fuels for use in combustion engines is an interesting possibility that represents a technical challenge. This chapter reviews the structure and biopolymerisation of lignin, reactions of lignin during technical processes, and different applications of technical lignins.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Zhao, Yadong, 1985-, et al.
(author)
-
The Impact of Lignin Structural Diversity on Performance of Cellulose Nanofiber (CNF)-Starch Composite Films
- 2019
-
In: Polymers. - : MDPI. - 2073-4360. ; 11:3
-
Journal article (peer-reviewed)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.
|
|
