scholarly journals Demethylation and other modifications of industrial softwood kraft lignin by laccase-mediators

Holzforschung ◽  
2018 ◽  
Vol 72 (5) ◽  
pp. 357-365 ◽  
Author(s):  
Miao Wang ◽  
Yadong Zhao ◽  
Jiebing Li
Keyword(s):  
Phenol Formaldehyde ◽  
Kraft Lignin ◽  
Aromatic Rings ◽  
Reaction Solution ◽  
Lower Reactivity ◽  
Diammonium Salt ◽  
Mass Increment ◽  
Modified Lignin ◽  
Softwood Kraft Lignin ◽  
Technical Lignins

Abstract Substitution of phenol in phenol-formaldehyde (PF) resin preparations by technical lignins is hindered by the inherently lower reactivity of lignin compared to phenol. Demethylation of an industrial softwood kraft lignin (SKL) to improve its reactivity is the focus of this paper. To this purpose, kraft lignin (KL) was treated with two commercial laccases, NS51002 (L1) and NS51003 (L2), for 24 h in combination with three mediators, 2,2′-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 1-hydroxybenzotriazole (HBT) and 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO). The characterizations of the reaction solution and the resultant KL showed that methanol was released as a result of the methoxy group splitting from the aromatic rings, while such demethylation was dependent on the laccase-mediator system (LMS). The catechol structures formed, which were further oxidized to a quinone structures prone to polymerization, led to molecular mass increment. Also this reaction was LMS dependent. The same is true to the cleavage of β-O-4′ linkages, which resulted in depolymerization. The L1-ABTS, L1-TEMPO and L2-HBT combinations are the most efficient and the resulting modified lignin would be suitable to phenol substitution. Challenging is the lignin polymerization following the demethylation, especially in case of L1-ABTS, which might inhibit the reactivity of the treated lignin.

scholarly journals Lignin Phenol Formaldehyde Resoles Using Base-Catalysed Depolymerized Kraft Lignin

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1162 ◽  
Author(s):  
Pia Solt ◽  
Björn Rößiger ◽  
Johannes Konnerth ◽  
Hendrikus van Herwijnen
Keyword(s):  
Phenol Formaldehyde ◽  
Lignin Content ◽  
Building Blocks ◽  
Kraft Lignin ◽  
Phenol Content ◽  
Adhesive Properties ◽  
Phenolic Resins ◽  
Adhesive Bonds ◽  
Phenolic Components ◽  
Softwood Kraft Lignin

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building blocks were further used to substitute phenol in the synthesis of phenolic resins and were characterized in detail (such as viscosity, free formaldehyde and phenol content, chemical composition, curing and bonding behaviour). The adhesive properties were compared to a phenol formaldehyde (PF) reference resin and a LPF with untreated kraft lignin. The resins synthesized with the two depolymerized lignin types differ significantly from each other with increasing phenol substitution. While with LPF-BCD-oligomers the viscosity increases and the bonding strength is not effected by increasing lignin content in the resin, a reduction of these properties could be observed with LPF-BCD-oil. Furthermore, LPF-BCD-oil showed similar curing behaviour and ultimate strength as the reference LPF. Adhesive bonds made using LPF-BCD-oligomers exhibited similar strength to those made using PF. Compared to the reference resins, it has been demonstrated that modified renewable lignin based phenolic components can be an equally performing alternative to phenol even for high degrees of substitution of 70%.

scholarly journals Improved Procedure for Electro-Spinning and Carbonisation of Neat Solvent-Fractionated Softwood Kraft Lignin

2021 ◽  
Author(s):  
Inam Khan ◽  
Bongkot Hararak ◽  
Gerard Franklyn Fernando
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Kraft Lignin ◽  
Binary Solvent ◽  
Natural Polymers ◽  
Solvent Fractionation ◽  
Custom Made ◽  
Treatment Procedures ◽  
Softwood Kraft Lignin ◽  
Soluble Lignin

Abstract In general, the electro-spinning of lignin requires it to be functionalised and/or blended with synthetic or natural polymers. This paper reports on the use of solvent fractionated lignin-lignin blend to electro-spin BioChoice® softwood Kraft lignin. The blend consisted of acetone-soluble and ethanol-soluble lignin in a binary solvent of acetone and DMSO. Solvent fractionation was used to purify lignin where the ash content was reduced in the soluble lignin fractions from 1.24% to ~0.1%. The corresponding value for conventional acid-washing in sulphuric acid was 0.34%. A custom-made electro-spinning apparatus was used to produce the nano-fibres. Heat treatment procedures were developed for drying the electro-spun fibres prior to oxidation and carbonisation; this was done to prevent fibre fusion. The lignin fibres were oxidised at 250⁰C, carbonised at 1000⁰C and 1500⁰C. The cross-section of the fibres was circular and they were observed to be void-free. The longitudinal sections showed that the fibres were not fused. Thus, this procedure demonstrated that solvent fractionated lignin can be electro-spun without using plasticisers or polymer blends using common laboratory solvents and subsequently carbonised to produce carbon fibres with a circular cross-section.

Methylation of softwood kraft lignin with dimethyl carbonate

2015 ◽  
Vol 17 (2) ◽  
pp. 1077-1087 ◽  
Author(s):  
Sanghamitra Sen ◽  
Shradha Patil ◽  
Dimitris S. Argyropoulos
Keyword(s):  
Thermal Stability ◽  
Dimethyl Carbonate ◽  
Kraft Lignin ◽  
Softwood Kraft Lignin

Methylation of lignin is essential for inducing thermal stability when a multitude of thermoplastic applications are envisaged.

Rigid polyurethane foams from unrefined crude glycerol and technical lignins

2018 ◽  
Vol 9 (3-4) ◽  
pp. 111-132 ◽  
Author(s):  
Louis Christiaan Muller ◽  
Sanette Marx ◽  
Hermanus CM Vosloo ◽  
Elvis Fosso-Kankeu ◽  
Idan Chiyanzu
Keyword(s):  
Crude Glycerol ◽  
Thermal Characteristics ◽  
Kraft Lignin ◽  
Polyurethane Foams ◽  
Pulp And Paper ◽  
Rigid Polyurethane Foam ◽  
Organosolv Lignin ◽  
Green Materials ◽  
By Products ◽  
Technical Lignins

The need for green materials has driven interest in the preparation of rigid polyurethane foam (PUF) from various biomass types. The present study aims at increasing bio-based content by utilizing by-products from both the pulp and paper and biodiesel industries. Bio-based polyols from respective liquefaction of kraft lignin, organosolv lignin and lignosulphonate in crude glycerol were employed to prepare rigid PUFs. The highest foam compressive strength was 345 kPa with density 79 kg m−3; thermal conductivity was 0.039 W m−1 K−1 and the corresponding material had 44 wt% renewable content. Thermal characteristics and biodegradability were also evaluated. Technical lignin type was found to determine product properties to a large extent. Based on the use of existing industrial scale by-products in this study, the findings can be beneficial for present and future biorefineries in the valorization of lower value by-product streams.

Carbohydrate-free and highly soluble softwood kraft lignin fractions by aqueous acetone evaporation fractionation

2017 ◽  
Vol 32 (4) ◽  
pp. 485-492 ◽  
Author(s):  
Anna-Stiina Jääskeläinen ◽  
Pia Willberg Keyriläinen ◽  
Tiina Liitiä ◽  
Tarja Tamminen
Keyword(s):  
Kraft Lignin ◽  
Aqueous Acetone ◽  
Softwood Kraft Lignin

scholarly journals Insights into the Potential of Hardwood Kraft Lignin to Be a Green Platform Material for Emergence of the Biorefinery

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1795
Author(s):  
Juliana M. Jardim ◽  
Peter W. Hart ◽  
Lucian Lucia ◽  
Hasan Jameel
Keyword(s):  
Research And Development ◽  
Polymer Blends ◽  
Carbon Fibers ◽  
Aromatic Compounds ◽  
Critical Review ◽  
Black Liquor ◽  
Kraft Lignin ◽  
Softwood Kraft Lignin ◽  
Structure Properties

Lignin is an abundant, renewable, and relatively cheap biobased feedstock that has potential in energy, chemicals, and materials. Kraft lignin, more specifically, has been used for more than 100 years as a self-sustaining energy feedstock for industry after which it has finally reached more widespread commercial appeal. Unfortunately, hardwood kraft lignin (HWKL) has been neglected over these years when compared to softwood kraft lignin (SWKL). Therefore, the present work summarizes and critically reviews the research and development (R&D) dealing specifically with HWKL. It will also cover methods for HWKL extraction from black liquor, as well as its structure, properties, fractionation, and modification. Finally, it will reveal several interesting opportunities for HWKL that include dispersants, adsorbents, antioxidants, aromatic compounds (chemicals), and additives in briquettes, pellets, hydrogels, carbon fibers and polymer blends and composites. HWKL shows great potential for all these applications, however more R&D is needed to make its utilization economically feasible and reach the levels in the commercial lignin market commensurate with SWKL. The motivation for this critical review is to galvanize further studies, especially increased understandings in the field of HWKL, and hence amplify much greater utilization.

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