Alternatives for lignocellulosic pulp delignification using polyoxometalates and oxygen: a review

Gaspar, Armindo R.; Gamelas, José A. F.; Evtuguin, Dmitry V.; Neto, Carlos Pascoal

doi:10.1039/b607824a

Cited by 127 publications

(121 citation statements)

References 37 publications

(85 reference statements)

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“…In principle, every POM having a redox potential higher than lignin units and lower than O 2 might be used as a redox catalyst. Possible candidates are vanadium containing mixed-addenda anions wPMo 12-x V x O 40 x (3qx)-which were previously successfully employed in POM delignification (Gaspar et al 2007). …”

Section: Resultsmentioning

confidence: 99%

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

2010

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One kraft lignin and two lignosulfonates were oxidized in aqueous acidic solutions containing a polyoxometalate (POM). The degradations were carried out in H 2 O or MeOH/ H 2 O mixtures in the presence of oxygen. The treatment with aqueous H 3 PMo 12 O 40 led to the dissolution of the studied lignins in the acidic medium (pH 1-2) and to the formation of up to 6.5 wt% vanillin and 6.2 wt% methyl vanillate based on the weight of dry lignin. The lignin oxidation products were analyzed by size-exclusion chromatography (SEC). For this purpose, a SEC method was developed, which allows the analysis of kraft lignin, lignosulfonates, and reaction products thereof without the need to remove the homogeneous catalyst. This method allows the direct observation of depolymerization and repolymerization reactions and hence the provision of a tool for studying the underlying chemistry. It has been demonstrated that the depolymerization of kraft lignin in water is accompanied by counterproductive condensation reactions. These repolymerization reactions were effectively prevented by addition of methanol, which couples competitively with lignin intermediates.

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Section: Resultsmentioning

confidence: 99%

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

2010

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“…Polyoxometalates are robust redox catalysts, and effective for oxidative degradation; when performed in the presence of molecular oxygen, a two-step process occurs, in which the polyoxoanion is first reduced and, subsequently, reoxidised without any net structural change [76]. Polyoxometalates applied for the decomposition of lignin residues under molecular oxygen often yields CO 2 and H 2 O by-products [77]. Dimethyl succinate and aromatics have also been produced from pyrolytic lignin using a vanadium/molybdenum polyoxometalate in a methanol/ water solvent mixture under oxygen [72].…”

Section: Oxidative Transformationsmentioning

confidence: 99%

Heterogeneously catalyzed lignin depolymerization

Pineda

Lee

2016

Appl Petrochem Res

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Biomass offers a unique resource for the sustainable production of bio-derived chemical and fuels as drop-in replacements for the current fossil fuel products. Lignin represents a major component of lignocellulosic biomass, but is particularly recalcitrant for valorization by existing chemical technologies due to its complex crosslinking polymeric network. Here, we highlight a range of catalytic approaches to lignin depolymerisation for the production of aromatic bio-oil and monomeric oxygenates.

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“…[19][20][21][22] These reactions usually cause oxidative damage to the aromatic structures of lignin, leading to deep oxidation to CO x and H 2 O. [23][24][25] Besides, the oxidation product, e.g. vanillin, would repolymerize into oligomers leading to lower recovered lignin depolymerization products.…”

Section: Introductionmentioning

confidence: 99%

Lignin depolymerization (LDP) in alcohol over nickel-based catalysts via a fragmentation–hydrogenolysis process

Song

Wang

Cai

et al. 2013

Energy Environ. Sci.

790

651

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Valorization of native birch wood lignin into monomeric phenols over nickel-based catalysts has been studied. High chemoselectivity to aromatic products was achieved by using Ni-based catalysts and common alcohols as solvents. The results show that lignin can be selectively cleaved into propylguaiacol and propylsyringol with total selectivity >90% at a lignin conversion of about 50%. Alcohols, such as methanol, ethanol and ethylene glycol, are suitable solvents for lignin conversion. Analyses with MALDI-TOF and NMR show that birch lignin is first fragmented into smaller lignin species consisting of several benzene rings with a molecular weight of m/z ca. 1100 to ca. 1600 via alcoholysis reaction. The second step involves the hydrogenolysis of the fragments into phenols. The presence of gaseous H 2 has no effect on lignin conversion, indicating that alcohols provide active hydrogen species, which is further confirmed by isotopic tracing experiments. Catalysts are recycled by magnetic separation and can be reused four times without losing activity. The mechanistic insights from this work could be helpful in understanding native lignin conversion and the formation of monomeric phenolics via reductive depolymerization. Broader contextNature efficiently synthesizes aromatic structures and deposits them as lignin in plants. Incorporation of catalytic technologies into lignin conversion is a possible option for valorizing the feedstock as a renewable raw material for aromatic chemical production. Use of heterogeneous catalysts facilitates separation and recycling, and has attracted great attention. However, the detailed chemistry between solid catalysts and solid feedstocks still remains unknown because of mass transfer limitations. Herein we report the valorization of native birch wood lignin into monomeric phenols over nickel-based catalysts. High chemoselectivity to aromatic products was achieved by using Ni-based catalysts and common alcohols as solvents. The results show that lignin can be selectively cleaved into propylguaiacol and propylsyringol with total selectivity >90% at a lignin conversion of about 50%. Analysis results show that birch lignin is rst fragmented into smaller lignin species consisting of several benzene rings with a molecular weight of m/z ca. 1100 to ca. 1600 via alcoholysis reaction. The second step involves the hydrogenolysis of the fragments into phenols. This study will greatly contribute to the understanding of the lignin depolymerization reaction and will be interesting for other biomass conversion.

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Alternatives for lignocellulosic pulp delignification using polyoxometalates and oxygen: a review

Cited by 127 publications

References 37 publications

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Heterogeneously catalyzed lignin depolymerization

Lignin depolymerization (LDP) in alcohol over nickel-based catalysts via a fragmentation–hydrogenolysis process

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