Progress in the solvent depolymerization of lignin

Patil, Vivek; Adhikari, Sushil; Cross, Phillip; Jahromi, Hossein

doi:10.1016/j.rser.2020.110359

Cited by 97 publications

(52 citation statements)

References 188 publications

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“…Additionally, Figure S5 also indicates that a small peak is present in the Solvo‐N 2 sample at the 1 t R and 2 t R of EV , indicating the incorporation of the hydrogen donating solvent (ethanol) into the products ( V in this case) during solvolysis as reported in literature. [ 33 , 34 , 35 , 36 , 37 ] Finally, while Solvo‐N 2 and Cata‐N 2 display no pronounced selectivity towards a singular peak within the region of low peak density, as expected due to the aforementioned decreased selectivity of solvolysis and catalytic liquid phase reforming,[ 33 , 34 , 35 , 36 , 37 ] Cata‐H 2 and Cata‐O 2 do display a strong selectivity towards singular peaks within this region (see Figures S2 and S3 in the Supporting Information). More specifically, Figure S5 in the Supporting Information indicates that V is abundantly present in the Solvo‐N 2 , Cata‐N 2 and Cata‐O 2 samples, especially within the latter as expected for the mild oxidative depolymerization conditions.…”

Section: Resultsmentioning

confidence: 99%

“…[ 15 , 30 , 31 , 32 ] Moreover, if a protic solvent, e. g., alcohols, is used as the only hydrogen source, i. e., solvolysis or catalytic liquid phase reforming under inert atmosphere, a relatively lower product selectivity is reached due to the increased complexity of the reaction pathways and incorporation of the solvent into the final products. [ 33 , 34 , 35 , 36 , 37 ]…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, products obtained after mild reductive depolymerization under hydrogen atmosphere contain a higher number of hydroxyl functional groups (OH) and, comparatively, display the highest selectivity towards functionalized aromatics [15,30–32] . Moreover, if a protic solvent, e. g., alcohols, is used as the only hydrogen source, i. e., solvolysis or catalytic liquid phase reforming under inert atmosphere, a relatively lower product selectivity is reached due to the increased complexity of the reaction pathways and incorporation of the solvent into the final products [33–37] …”

Section: Introductionmentioning

confidence: 99%

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Fast screening of Depolymerized Lignin Samples Through 2D‐Liquid Chromatography Mapping

et al. 2021

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Lignin valorization and particularly its depolymerization into bio‐aromatics, has emerged as an important research topic within green chemistry. However, screening of catalysts and reaction conditions within this field is strongly constrained by the lack of analytical techniques that allow for fast and detailed mapping of the product pools. This analytical gap results from the inherent product pool complexity and the focus of the state‐of‐the‐art on monomers and dimers, overlooking the larger oligomers. In this work, this gap is bridged through the development of a quasi‐orthogonal GPC‐HPLC‐UV/VIS method that is able to separate the bio‐aromatics according to molecular weight (hydrodynamic volume) and polarity. The method is evaluated using model compounds and real lignin depolymerization samples. The resulting color plots provide a powerful graphical tool to rapidly assess differences in reaction selectivity towards monomers and dimers as well as to identify differences in the oligomers.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fast screening of Depolymerized Lignin Samples Through 2D‐Liquid Chromatography Mapping

et al. 2021

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“…Various thermal- and chemical-based lignin depolymerization processes have been proposed and applied in the literature [ 1 , 22 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. Pyrolysis (thermolysis), gasification, hydrogenolysis, hydrolysis under supercritical conditions, and oxidation reactions are the major depolymerization methods studied ( Figure 4 ).…”

Section: Oxidative Depolymerization Of Ligninmentioning

confidence: 99%

Added-Value Chemicals from Lignin Oxidation

2021

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Lignin is the second most abundant component, next to cellulose, in lignocellulosic biomass. Large amounts of this polymer are produced annually in the pulp and paper industries as a coproduct from the cooking process—most of it burned as fuel for energy. Strategies regarding lignin valorization have attracted significant attention over the recent decades due to lignin’s aromatic structure. Oxidative depolymerization allows converting lignin into added-value compounds, as phenolic monomers and/or dicarboxylic acids, which could be an excellent alternative to aromatic petrochemicals. However, the major challenge is to enhance the reactivity and selectivity of the lignin structure towards depolymerization and prevent condensation reactions. This review includes a comprehensive overview of the main contributions of lignin valorization through oxidative depolymerization to produce added-value compounds (vanillin and syringaldehyde) that have been developed over the recent decades in the LSRE group. An evaluation of the valuable products obtained from oxidation in an alkaline medium with oxygen of lignins and liquors from different sources and delignification processes is also provided. A review of C4 dicarboxylic acids obtained from lignin oxidation is also included, emphasizing catalytic conversion by O2 or H2O2 oxidation.

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“…Numerous heterogeneous catalysts have been reported for the DPE cleavage, [4c, 6c] among them, supported metal catalysts appear the most active and selective for this reaction [8] . However, cleavage of aryl ethers over metal catalysts at elevated temperature and high H 2 pressure always causes hydrogenation of aromatic rings in the valuable mono‐aromatic products with high consumption of expensive hydrogen [8a, 9] …”

Section: Introductionmentioning

confidence: 99%

Lignin Compounds to Monoaromatics: Selective Cleavage of C−O Bonds over a Brominated Ruthenium Catalyst

Wang

Safonova

et al. 2021

Angewandte Chemie

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The cleavage of C−O linkages in aryl ethers in biomass‐derived lignin compounds without hydrogenation of the aromatic rings is a major challenge for the production of sustainable mono‐aromatics. Conventional strategies over the heterogeneous metal catalysts require the addition of homogeneous base additives causing environmental problems. Herein, we propose a heterogeneous Ru/C catalyst modified by Br atoms for the selective direct cleavage of C−O bonds in diphenyl ether without hydrogenation of aromatic rings reaching the yield of benzene and phenol as high as 90.3 % and increased selectivity to mono‐aromatics (97.3 vs. 46.2 % for initial Ru) during depolymerization of lignin. Characterization of the catalyst indicates selective poisoning by Br of terrace sites over Ru nanoparticles, which are active in the hydrogenation of aromatic rings, while the defect sites on the edges and corners remain available and provide higher intrinsic activity in the C−O bond cleavage.

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Progress in the solvent depolymerization of lignin

Cited by 97 publications

References 188 publications

Fast screening of Depolymerized Lignin Samples Through 2D‐Liquid Chromatography Mapping

Fast screening of Depolymerized Lignin Samples Through 2D‐Liquid Chromatography Mapping

Added-Value Chemicals from Lignin Oxidation

Lignin Compounds to Monoaromatics: Selective Cleavage of C−O Bonds over a Brominated Ruthenium Catalyst

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