A New Method for Demethylation of Lignin from Woody Biomass using Biophysical Methods

Ferhan, Muhammad; Yan, Ning; Sain, Mohini

doi:10.4172/2157-7048.1000160

Cited by 12 publications

(6 citation statements)

References 24 publications

(30 reference statements)

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“…It has been reported that the methoxyl groups at the ortho positions to the aromatic hydroxyl in the nine-carbon unit of lignin will hinder the reactivity of its free phenolic hydroxyl groups. If the –OCH 3 groups could be removed and demethylated, the demethylated lignin products would have far more free phenolic groups and its reactivity could be significantly enhanced [ 13 ]. Previous works reported that methoxyl groups in lignin were removed through a nucleophilic substitution reaction when the aryl methyl ethers were attacked by nucleophiles such as S and HS − , resulting in demethylated lignin with lower content of methoxyl groups and higher content of phenolic hydroxyl groups [ 13 , 19 ].…”

Section: Resultsmentioning

confidence: 99%

“…If the –OCH 3 groups could be removed and demethylated, the demethylated lignin products would have far more free phenolic groups and its reactivity could be significantly enhanced [ 13 ]. Previous works reported that methoxyl groups in lignin were removed through a nucleophilic substitution reaction when the aryl methyl ethers were attacked by nucleophiles such as S and HS − , resulting in demethylated lignin with lower content of methoxyl groups and higher content of phenolic hydroxyl groups [ 13 , 19 ]. However, the rigid reaction condition obstructed their industrial applications.…”

Section: Resultsmentioning

confidence: 99%

“…In recent decades, many lignin modification methods such as demethylation [ 12 , 13 , 14 ], methylolation [ 15 , 16 ], and phenolation [ 17 , 18 ] have been explored to increase the reactivity of lignin. Among these modification strategies, lignin demethylation is the most efficient and promising method by converting methoxyl groups into phenolic hydroxyl groups, generating catechol moieties in lignin framework [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

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Fast Curing Bio-Based Phenolic Resins via Lignin Demethylated under Mild Reaction Condition

Zhang

et al. 2017

Polymers

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Abstract:Demethylation technique has been used to enhance lignin reactivity for preparation of phenolic resins. However, the demethylation efficiency and the demethylated lignin (DL) reactivity were still unsatisfactory. To improve the demethylation efficiency, alkali lignin was demethylated under different mild conditions using sodium sulfite as a catalyst. Lignin and DL were characterized by 1 H-NMR (nuclear magnetic resonance) and Fourier transform infrared (FT-IR) spectroscopy to determine the demethylation mechanism. With the demethylation of lignin, the methoxyl group content decreased from 1.93 m mol/g to 1.09 m mol/g, and the phenolic hydroxyl group content increased from 0.56 m mol/g to 0.82 m mol/g. These results revealed that methoxyl groups were attacked by SO 3 2− , and some methoxyl groups were converted to phenolic hydroxyl groups by a nucleophilic substitution reaction, generating DL with high reactivity. The chemical properties of lignin-based phenolic resins were studied by 13 C-NMR and FT-IR spectroscopy, and their physical properties were also investigated. The results indicated that lignin-based phenolic resins exhibited faster curing rate and shorter gel time. In addition, the bonding strength increased from 0.92 MPa to 1.07 MPa, and the formaldehyde emission decreased from 0.58 mg/L to 0.22 mg/L after lignin demethylated at the optimum condition.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fast Curing Bio-Based Phenolic Resins via Lignin Demethylated under Mild Reaction Condition

Zhang

et al. 2017

Polymers

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“…For example, the chemical reactivity of demethylated lignins was enhanced through diminishing methoxyl group content while increasing hydroxyl group content. With the lignins demethylated under optimum reaction conditions, the bonding strength of lignin-based phenolic resins increased while the formaldehyde emissions decreased [64][65][66].…”

Section: Mechanical Properties Of Particleboardsmentioning

confidence: 99%

Properties of Eco-Friendly Particleboards Bonded with Lignosulfonate-Urea-Formaldehyde Adhesives and pMDI as a Crosslinker

et al. 2021

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The purpose of this study was to evaluate the feasibility of using magnesium and sodium lignosulfonates (LS) in the production of particleboards, used pure and in mixtures with urea-formaldehyde (UF) resin. Polymeric 4,4′-diphenylmethane diisocyanate (pMDI) was used as a crosslinker. In order to evaluate the effect of gradual replacement of UF by magnesium lignosulfonate (MgLS) or sodium lignosulfonate (NaLS) on the physical and mechanical properties, boards were manufactured in the laboratory with LS content varying from 0% to 100%. The effect of LS on the pH of lignosulfonate-urea-formaldehyde (LS-UF) adhesive compositions was also investigated. It was found that LS can be effectively used to adjust the pH of uncured and cured LS-UF formulations. Particleboards bonded with LS-UF adhesive formulations, comprising up to 30% LS, exhibited similar properties when compared to boards bonded with UF adhesive. The replacement of UF by both LS types substantially deteriorated the water absorption and thickness swelling of boards. In general, NaLS-UF-bonded boards had a lower formaldehyde content (FC) than MgLS-UF and UF-bonded boards as control. It was observed that in the process of manufacturing boards using LS adhesives, increasing the proportion of pMDI in the adhesive composition can significantly improve the mechanical properties of the boards. Overall, the boards fabricated using pure UF adhesives exhibited much better mechanical properties than boards bonded with LS adhesives. Markedly, the boards based on LS adhesives were characterised by a much lower FC than the UF-bonded boards. In the LS-bonded boards, the FC is lower by 91.1% and 56.9%, respectively, compared to the UF-bonded boards. The boards bonded with LS and pMDI had a close-to-zero FC and reached the super E0 emission class (≤1.5 mg/100 g) that allows for defining the laboratory-manufactured particleboards as eco-friendly composites.

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“…The best results in terms of an increase in OH content and use for PF resins was the sample demethylated with Na 2 SO 3 . Other authors used Na 2 SO 3 for demethylation performed under high-pressure reactors [39] or under reflux [15,40]. Podschun et al chose a different approach in which organosolv lignin was demethylated under microwave radiation [41].…”

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confidence: 99%

Antimicrobial Activity of Lignin-Derived Polyurethane Coatings Prepared from Unmodified and Demethylated Lignins

et al. 2019

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Due to global ecological and economic challenges that have been correlated to the transition from fossil-based to renewable resources, fundamental studies are being performed worldwide to replace fossil fuel raw materials in plastic production. One aspect of current research is the development of lignin-derived polyols to substitute expensive fossil-based polyol components for polyurethane and polyester production. This article describes the synthesis of bioactive lignin-based polyurethane coatings using unmodified and demethylated Kraft lignins. Demethylation was performed to enhance the reaction selectivity toward polyurethane formation. The antimicrobial activity was tested according to a slightly modified standard test (JIS Z 2801(JIS Z :2010. Besides effects caused by the lignins themselves, triphenylmethane derivatives (brilliant green and crystal violet) were used as additional antimicrobial substances. Results showed increased antimicrobial capacity against Staphylococcus aureus. Furthermore, the coating color could be varied from dark brown to green and blue, respectively.Coatings 2019, 9, 494 2 of 16 and DNA in cells of mice against oxidation damage [19] have been tested. Gao [20] and Bshena [21] studied the antimicrobial activity of various textiles, using lignin incorporated into polyethylene films and applied in the finishing processes. For textiles, there are special requirements such as non-toxicity to the consumer, namely cytotoxicity, allergy or irritation and sensitization. In other recent studies, lignosulfonic acid is reported to exhibit broad-spectrum anti-HIV (human immunodeficiency virus) and anti-HSV (herpes simplex virus) properties [22,23]. Thus, Qiu investigated the anti-HIV-1 activity-potential of lignosulfonates as a microbicide to prevent HIV-1 sexual transmission [23]. Another recently reported study revealed that the antimicrobial capacity of lignin correlates with the phenolic components, specifically the side chain structure and the nature of further functional groups [24]. Typically, the presence of a double bond in α, β positions of the side chain and a methyl group in the γ position grants the phenolic fragments with the most potency against microorganisms. However, none of the hitherto published studies included the investigation of the antibacterial activity of lignin when included in polymeric matrices.Unmodified lignin is widely studied as a component for polymer production with a focus on phenol-formaldehyde resins and polyurethanes (PUs) [25], where lignin is used as polyol substitute due to the high amount of hydroxyl groups resulting in high crosslinking densities and variable mechanical properties [26][27][28]. In previous studies, lignin-derived polyurethane coatings have been prepared using Kraft lignin isolated at room temperature from aqueous media (black liquor) at different pH values [29]. In addition, their antioxidative activity has been investigated using the Folin-Ciocalteu (FC) assay [30]. Although lignin contains many functionalities, they are often diff...

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A New Method for Demethylation of Lignin from Woody Biomass using Biophysical Methods

Cited by 12 publications

References 24 publications

Fast Curing Bio-Based Phenolic Resins via Lignin Demethylated under Mild Reaction Condition

Fast Curing Bio-Based Phenolic Resins via Lignin Demethylated under Mild Reaction Condition

Properties of Eco-Friendly Particleboards Bonded with Lignosulfonate-Urea-Formaldehyde Adhesives and pMDI as a Crosslinker

Antimicrobial Activity of Lignin-Derived Polyurethane Coatings Prepared from Unmodified and Demethylated Lignins

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