Chapter 1. A Brief Introduction to Lignin Structure

Kathahira, Rui; Elder, Thomas; Beckham, Gregg T.

doi:10.1039/9781788010351-00001

Cited by 102 publications

(80 citation statements)

References 117 publications

(157 reference statements)

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“…Lignin is a complex aromatic renewable heteropolymer and is considered to be the most recalcitrant among lignocellulosic-based biomass. [1] Advantageously, lignin contains nearly 30% of organic carbon resource in nature, [2] that endows an exceptional advantage in producing aromatic chemicals and transportation fuels. [3] In general lignin is produced by biomass in various processes.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Functional Chemicals from Lignin‐derived Monomers by Selective Organic Transformations

et al. 2020

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The valorization of lignin and its model compounds represents a key technology applied for the production of lignin-monomers, which constitute as renewable feedstocks and intermediates for the synthesis of value-added chemicals and fuels as well as molecules related to life science applications. Hence, in addition to lignin-depolymerization, the effective utilization of lignin-derived feedstocks such as phenols, ethers, alcohols, ketones and aldehydes is also gaining significant importance. In this regard, number of methodologies has been developed on the utility of these feedstocks for the production of various functional chemicals. In this review, we summarize the valorization of lignin-derived feedstocks by amination, hydrogenation, dehydrogenation oxidation, carbonylation, and trifluoromethylation, hydrolysis reactions for the synthesis of amines, cyclohexanes, cyclohexanols, cyclohexanones, esters, ketones, cyclic ethers, trifluoromethylated compounds and heterocycles as well as pharmaceuticals and biomolecules.

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Section: Introductionmentioning

confidence: 99%

Synthesis of Functional Chemicals from Lignin‐derived Monomers by Selective Organic Transformations

et al. 2020

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“…To date, most lignin that is separated from wood fibers by chemical pulping is used for its fuel value; less than 2% of the approximately 70 million tons of lignin produced by the paper industry is used for alternative applications (e.g., concrete additives, surfactants) [1]. Regarding the conversion of lignocellulosic biomass to fuels and chemicals in a biorefinery, efforts to improve the economics of such operations have emphasized the development of higher value uses for the residual lignins; however, the chemical heterogeneity and relatively low reactivity of these lignins also lends them to be used as fuel [2]. Therefore, the development of modified lignins with improved properties (e.g., physical, thermal) and/or reactivity seems to be a rational start to increase the use of this sustainable biopolymer [3,4].…”

Section: Introductionmentioning

confidence: 99%

Demethylation of Alkali Lignin with Halogen Acids and Its Application to Phenolic Resins

et al. 2019

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Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to increase its hydroxyl content and thereby enhance its reactivity for the preparation of phenolic resins. Analyses by FT-IR, 1H-NMR and 2D-NMR(HSQC) demonstrated both a decrease in methoxyl groups and an increase in hydroxyl groups for each demethylated lignin (DL). In addition, the molar amounts of phenolic hydroxyls, determined by 1H-NMR, increased to 0.67 mmol/g for the HI-DL, and 0.64 mmol/g for the HBr-DL, from 0.52 mmol/g for the AL. These results showed that HI, a stronger nucleophilic reagent than HBr, provided a higher degree of AL demethylation. Lignin-containing resins, prepared by copolymerization, met the bonding strength standard for exterior plywood with DL used to replace as much as 50 wt.% of phenol. The increased hydroxyl contents resulting from the lignin demethylations also imparted faster cure times for the lignin-containing resins and lower formaldehyde emissions. Altogether, the stronger nucleophilicity of HI, compared to HBr, impacted the degree of lignin demethylation, and carried through to measurable differences the thermal properties and performance of the lignin-containing PF resins.

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“…The particular structure of lignin depends on its natural source (type of wood) as well as the pulping procedure . It is characterized by a highly branched, semiaromatic structure with high molar mass and dispersity, as well as a huge number of terminal functional groups . It is chemically rather heterogeneous and consists of infusible parts with high molar mass ( M n > 5000 g/mol) mixed with lower molar mass components that soften above the glass transition temperature ( T g ) .…”

Section: Introductionmentioning

confidence: 99%

Fiber formation and properties of polyester/lignin blends

Pospiech

Korwitz

Eckstein

et al. 2019

J of Applied Polymer Sci

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Thermotropic liquid crystalline polyesters with varied chemical structure are synthesized by melt transesterification polycondensation. They are employed as matrix for blends with lignin materials to obtain melt-spinnable precursors for carbon fibers. The lignin samples are carefully purified by fractionation, enzymatic removal of reducing sugars, and subsequent modification of the terminal OH groups. Effective melt blending is achieved with liquid-crystalline aromatic-aliphatic polyesters having melting ranges that match the softening temperature of the lignin fractions, which is necessary to prevent thermal decomposition of the lignin. Polyester/lignin blends are partially compatibilized, phase-separated materials. The polyester/lignin materials are melt-spun successfully. The fiber properties depend on the lignin purification process. X-ray scattering reveals that orientation in lignin-containing fibers is maintained. First experiments show that the fibers can be converted successfully to carbon fibers by thermal annealing procedures.In the past, many efforts were undertaken to improve the spinnability of lignin either from the melt or from solution, in particular including: (1) chemical modification of the lignin, and (2) mixing lignin with synthetic polymers to ease processability. The chemical modification of the terminal aliphatic and aromatic OH groups interrupts the hydrogen bonds and reduces T g which Additional Supporting Information may be found in the online version of this article.

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Chapter 1. A Brief Introduction to Lignin Structure

Cited by 102 publications

References 117 publications

Synthesis of Functional Chemicals from Lignin‐derived Monomers by Selective Organic Transformations

Synthesis of Functional Chemicals from Lignin‐derived Monomers by Selective Organic Transformations

Demethylation of Alkali Lignin with Halogen Acids and Its Application to Phenolic Resins

Fiber formation and properties of polyester/lignin blends

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