Methylation of softwood kraft lignin with dimethyl carbonate

Sen, Sanghamitra; Patil, Shradha; Argyropoulos, Dimitris S.

doi:10.1039/c4gc01759e

Cited by 84 publications

(110 citation statements)

References 53 publications

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“…While lignin is increasingly used for production of thermoplastics, 47 crosslinkers 48 and carbon materials; 49 its use as an aromatic commodity chemical feedstock is minimal with the exception of vanillin production. The present study represents a clear example of how DMC as a reactive co-solvent can be used to intercept reactive intermediates generated during the reductive disassembly of lignin to give aromatic monomers.…”

Section: Discussionmentioning

confidence: 99%

Enhancing Aromatic Production from Reductive Lignin Disassembly: in Situ O-Methylation of Phenolic Intermediates

Barrett

Gao

Bernt

et al. 2016

ACS Sustainable Chem. Eng.

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ABSTRACT:The selective conversion of lignin into aromatic compounds has the potential to serve as a "green" alternative to the production of petrochemical aromatics. Herein, we evaluate the addition of dimethyl carbonate (DMC) to a biomass conversion system that uses a Cu-doped porous metal oxide (Cu 20 PMO) catalyst in supercritical methanol (sc-MeOH) to disassemble lignin with little to no char formation. While Cu 20 PMO catalyzes C-O hydrogenolysis of aryl-ether bonds linking lignin monomers, it also catalyzes arene methylation and hydrogenation, leading to product proliferation. The MeOH/DMC co-solvent system significantly suppresses arene hydrogenation of the phenolic intermediates responsible for much of the undesirable product diversity via Omethylation of phenolic -OH groups to form more stable aryl-OCH 3 species. Consequently, product proliferation was greatly reduced and aromatic yields greatly enhanced with lignin models, 2-methoxy-4-propylphenol, benzyl phenyl ether, and 2-phenoxy-1-phenylethan-1-ol. In addition, organosolv poplar lignin (OPL) was examined as a substrate in the MeOH/DMC co-solvent system. The products were characterized by nuclear magnetic resonance spectroscopy ( 31 P, 13 C, and 2D 1 H-13 C NMR) and gas chromatography-mass spectrometry techniques. The co-solvent system demonstrated enhanced yields of aromatic products. INTRODUCTION.

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Section: Discussionmentioning

confidence: 99%

Enhancing Aromatic Production from Reductive Lignin Disassembly: in Situ O-Methylation of Phenolic Intermediates

Barrett

Gao

Bernt

et al. 2016

ACS Sustainable Chem. Eng.

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“…1 With a content of [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] wt%, lignin is a main component of biomass such as wood and annual plants. The total lignin resources on earth are estimated to be 300 billion tons, with a natural production of 20 billion tons per year.…”

Section: Introductionmentioning

confidence: 99%

Sustainable allylation of organosolv lignin with diallyl carbonate and detailed structural characterization of modified lignin

Over

Meier

2016

Green Chem.

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The allylation of European beech wood organosolv lignin (OL) with diallyl carbonate (DAC) in the presence of base catalysts is shown to be an efficient, non-toxic, and sustainable modification technique. Comparative studies of different bases and temperatures were performed to optimize the solvent-free allylation of OL. Up to 90% of the aromatic and aliphatic hydroxyl groups in OL were converted to the respective allyl ethers or allyl carbonates using tetrabutylammonium bromide (TBAB) as recyclable base. The demonstrated strategy allows the introduction of functional groups into the structure of lignin, which will enable further modification. Detailed structural analytics by 31 P, 1 H, and 13 C NMR, as well as IR spectroscopy and detailed mass analysis using SEC-ESI-MS verified the functionalization and delivered insights into the structure of lignin.

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“…A number of studies have shown that one of the main constraint on lignin from readily becoming a versatile feedstock for a variety of applications is its heterogeneity which leads to unpredictable and uncontrollable reactions 4,27,28,33 . Consequently, we have examined this issue here by making sure that the PDI of our samples is actually narrow so that we minimize this variable before proceeding to a more complex polydisperse system.…”

Section: Resultsmentioning

confidence: 99%

“…This is a novel approach for the simultaneous systematic modulation of the functionality and the reactivity of lignin developed in earlier parts of our work 7,27 .…”

Section: Methodsmentioning

confidence: 99%

“…The original kraft lignin was fractionated into two high and low molecular weight fractions based on its solubility in acetone (1g/15 mL) 4,27 .The lignin was mixed with pure acetone (1g/10 mL) at room temperature for 10h. The dissolved acetone soluble fraction (ASKL) was separated from the residue by filtration and recovered by evaporating the solvent in a rotary evaporator followed by drying in a vacuum oven at room temperature for 12 hrs.…”

Section: Acetone Soluble Fraction Of Kraft Ligninmentioning

confidence: 99%

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Toward Carbon Fibers from Single Component Kraft Lignin Systems: Optimization of Chain Extension Chemistry

Sadeghifar

Sen

Patil

et al. 2016

ACS Sustainable Chem. Eng.

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Single component softwood kraft lignins have been sought after as precursors to carbon fibers.This noble goal can be achieved by adding carbon onto lignin via propargylation. The reactivity of propargylated lignins may then be modulated via methylation thus eliminating the onset of gelation via phenoxyl radical initiated random polymerization. This paper demonstrates that properly installed, propargyl groups of an acetone soluble kraft lignin (ASKL) fraction can be thermally polymerized to high molecular weights in a controlled manner. In order to create single component chain extended softwood kraft lignin systems for carbon fiber applications, one needs toregulate the amount and the positioning of the propargyl groups on the lignin. This became possible and it is now demonstrated that the propargylation of lignin needs to occur first, followed by methylation and not the other way around. Such a sequence offers substantial benefits for the onset of a Claisen rearrangement to occur between the propargyl groups and the free C5 positions of the softwood lignin. Furthermore, once in position, the created benzopyrans can effectively further polymerize in a controlled manner offering chain extended kraft lignin products of sufficient molecular weight so as to apply subsequent stabilization and carbonization steps to it.

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Methylation of softwood kraft lignin with dimethyl carbonate

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

Cited by 84 publications

References 53 publications

Enhancing Aromatic Production from Reductive Lignin Disassembly: in Situ O-Methylation of Phenolic Intermediates

Enhancing Aromatic Production from Reductive Lignin Disassembly: in Situ O-Methylation of Phenolic Intermediates

Sustainable allylation of organosolv lignin with diallyl carbonate and detailed structural characterization of modified lignin

Toward Carbon Fibers from Single Component Kraft Lignin Systems: Optimization of Chain Extension Chemistry

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