In situ trapping of enol intermediates with alcohol during acid-catalysed de-polymerisation of lignin in a nonpolar solvent

Kaiho, Atsushi; Kogo, Makiko; Sakai, Ryo; Saito, Kaori; Watanabe, Takashi

doi:10.1039/c5gc00130g

Cited by 58 publications

(42 citation statements)

References 15 publications

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“…Barta and co‐workers reported another approach that circumvented the repolymerization of lignin by stabilizing the reactive aldehydes by their transformation into acetals upon the addition of ethyleneglycol (Figure B) . Acetal formation with methanol has also been reported . The Rh‐catalyzed in situ decarbonylation of reactive aldehydes formed during the triflate‐catalyzed cleavage of lignin was recently reported by Bruijnincx and co‐workers (Figure B) .…”

Section: Introductionmentioning

confidence: 58%

Zeolite‐Assisted Lignin‐First Fractionation of Lignocellulose: Overcoming Lignin Recondensation through Shape‐Selective Catalysis

et al. 2020

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Organosolv pulping releases reactive monomers from both lignin and hemicellulose by the cleavage of weak C−O bonds. These monomers recombine to form undesired polymers through the formation of recalcitrant C−C bonds. Different strategies have been developed to prevent this process by stabilizing the reactive monomers (i.e., lignin‐first approaches). To date, all reported approaches rely on the addition of capping agents or metal‐catalyzed stabilization reactions, which usually require high pressures of hydrogen gas. Herein, a metal‐ and additive‐free approach is reported that uses zeolites as acid catalysts to convert the reactive monomers into more stable derivatives under organosolv pulping conditions. Experiments with model lignin compounds showed that the recondensation of aldehydes and allylic alcohols produced by the cleavage of β‐O‐4′ bonds was efficiently inhibited by the use of protonic β zeolite. By applying a zeolite with a preferred pore size, the bimolecular reactions of reactive monomers were effectively inhibited, resulting in stable and valuable monophenolics. The developed methodology was further extended to birch wood to yield monophenolic compounds and value‐added products from carbohydrates.

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Section: Introductionmentioning

confidence: 58%

Zeolite‐Assisted Lignin‐First Fractionation of Lignocellulose: Overcoming Lignin Recondensation through Shape‐Selective Catalysis

et al. 2020

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“…Watanabe and co-workers 192 ( Table 1 , entry 12) treated two types of wood species, namely eucalyptus globulus and cedar, with a catalytic amount (<1%) of sulfuric acid in a mixture of hydrophobic solvent (e.g., toluene) and alcohol (e.g., methanol) to result in homovanillyl aldehyde dimethyl acetal ( M31G ) and homosyringaldehyde dimethyl acetal ( M31S ) at 140 °C. Owing to the presence of methanol, the aromatic C2 enol ether intermediate obtained upon acid catalysis underwent acetal formation in situ.…”

Section: Catalytic Strategies Aiming At High Yield and Selective Prodmentioning

confidence: 99%

Bright Side of Lignin Depolymerization: Toward New Platform Chemicals

et al. 2018

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Lignin, a major component of lignocellulose, is the largest source of aromatic building blocks on the planet and harbors great potential to serve as starting material for the production of biobased products. Despite the initial challenges associated with the robust and irregular structure of lignin, the valorization of this intriguing aromatic biopolymer has come a long way: recently, many creative strategies emerged that deliver defined products via catalytic or biocatalytic depolymerization in good yields. The purpose of this review is to provide insight into these novel approaches and the potential application of such emerging new structures for the synthesis of biobased polymers or pharmacologically active molecules. Existing strategies for functionalization or defunctionalization of lignin-based compounds are also summarized. Following the whole value chain from raw lignocellulose through depolymerization to application whenever possible, specific lignin-based compounds emerge that could be in the future considered as potential lignin-derived platform chemicals.

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“…For example, the application of acids between 80 °C to 180°C is very effective in cleaving the β-O-4 linkage forming aldehyde and ketone fragments 7,8 . Our groups and others have recently demonstrated that acidolysis combined with the methodologies to stabilize and trap reactive fragments is extremely potent to obtain phenolic monomers with specific chemical motifs 9,10,11,12 . Of these, in particular acetal trapping of reactive aldehydes with alcohols to obtain phenolic 2-arylmethyl-1,3dioxolanes (acetals) proved powerful due to its relative simple application and the retention of the highly functionalized nature of the lignin monomers (Figure 1b) 13,14…”

Section: Introductionmentioning

confidence: 99%

Extraction of Lignin with High β-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield

Zijlstra¹,

Santi²,

Oldenburger³

et al. 2019

JoVE

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Lignin valorization strategies are a key factor for achieving more economically competitive biorefineries based on lignocellulosic biomass. Most of the emerging elegant procedures to obtain specific aromatic products rely on the lignin substrate having a high content of the readily cleavable β-O-4 linkage as present in the native lignin structure. This provides a miss-match with typical technical lignins that are highly degraded and therefore are low in β-O-4 linkages. Therefore, the extraction yields, and the quality of the obtained lignin are of utmost importance to access new lignin valorization pathways. In this manuscript, a simple protocol is presented to obtain lignins with high β-O-4 content by relatively mild ethanol extraction that can be applied to different lignocellulose sources. Furthermore, analysis procedures to determine the quality of the lignins are presented together with a depolymerization protocol that yields specific phenolic 2-arylmethyl-1,3-dioxolanes, which can be used to evaluate the obtained lignins. The presented results demonstrate the link between lignin quality and potential for the lignins to be depolymerized into specific monomeric aromatic chemicals. Overall, the extraction and depolymerization demonstrates a trade-off between the lignin extraction yield and the retention of the native aryl-ether structure and thus the potential of the lignin to be used as the substrate for the production of chemicals for higher-value applications. Video Link The video component of this article can be found at https://www.jove.com/video/58575/ 17. This also has precedence in organosolv extraction of lignin, which is a popular method to fractionate lignin. Many variations of this process exist, with the methods employing different temperatures, acid content, extraction times and solvents. Here, the extraction severity has a direct impact on the obtained lignin structure and thus its suitability for further valorization 19,20,21. For example, organosolv lignin produced by the ethanol based Alcell process, operated for 5 years at demonstration scale, had relatively low amount of β-O-4 linkages left as it was operated at relatively high

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In situ trapping of enol intermediates with alcohol during acid-catalysed de-polymerisation of lignin in a nonpolar solvent

Abstract: Acid-catalysed degradation of wood in toluene–MeOH yields the lignin monomers homovanillyl aldehyde dimethyl acetal and homosyringaldehyde dimethyl acetal selectively.

Cited by 58 publications

References 15 publications

Zeolite‐Assisted Lignin‐First Fractionation of Lignocellulose: Overcoming Lignin Recondensation through Shape‐Selective Catalysis

Zeolite‐Assisted Lignin‐First Fractionation of Lignocellulose: Overcoming Lignin Recondensation through Shape‐Selective Catalysis

Bright Side of Lignin Depolymerization: Toward New Platform Chemicals

Extraction of Lignin with High β-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield

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In situ trapping of enol intermediates with alcohol during acid-catalysed de-polymerisation of lignin in a nonpolar solvent

Abstract: Acid-catalysed degradation of wood in toluene–MeOH yields the lignin monomers homovanillyl aldehyde dimethyl acetal and homosyringaldehyde dimethyl acetal selectively.

Cited by 58 publications

References 15 publications

Zeolite‐Assisted Lignin‐First Fractionation of Lignocellulose: Overcoming Lignin Recondensation through Shape‐Selective Catalysis

Zeolite‐Assisted Lignin‐First Fractionation of Lignocellulose: Overcoming Lignin Recondensation through Shape‐Selective Catalysis

Bright Side of Lignin Depolymerization: Toward New Platform Chemicals

Extraction of Lignin with High &#946;-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield

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Extraction of Lignin with High β-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield