Selective Transition-Metal Catalysis of Oxygen Delignification. Using Water-Soluble Salts of Polyoxometalate (POM) Anions. Part II. Reactions of α-[SiVW11O40]5-with Phenolic Lignin-Model Compounds

Weinstock, Ira A.; Hammel, Kenneth E.; Moen, Mark A.; Landucci, Lawrence L.; Ralph, Sally A.; Sullivan, C. E.; Reiner, Richard

doi:10.1515/hfsg.1998.52.3.311

Cited by 42 publications

(43 citation statements)

References 22 publications

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“…3). This intermediate was suggested earlier in the oxidation of different dimeric model compounds with tungstovanadosilicate polyanion [SiW 11 VO 40 ] 6-(one-electron oxidant) under anaerobic conditions (Weinstock et al 1998) and in aerobic lignin oxidation with HPA-n (Evtuguin et al 1998). Indirectly, the formation of cyclohexadienyl cations is confirmed by the appearance of product 7 after oxidation at 20°C (Table 1) as a predictable solvolysis product (Fig.…”

Section: Oxidation Of Vanillyl Alcoholsupporting

confidence: 66%

Lignin Degradation in Oxygen Delignification Catalysed by [PMo7V5O40]8- Polyanion. Part II. Study on Lignin Monomeric Model Compounds

Evtuguin¹,

Neto²,

Carapuça³

et al. 2000

Holzforschung

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Vanillyl and veratryl alcohols were used as monomeric lignin model compounds in experiments aiming to enhance the understanding of the lignin oxidation mechanisms involved in the oxygen delignification in acidic media catalysed by [PMo 7 V 5 O 40 ] 8-(HPA-5) heteropolyanion. Based on the model compound experiments, the first step of lignin oxidation is suggested to be a one-electron oxidation by the catalyst. This step is followed by coupling reactions and/or by further oxidation by the catalyst. The ratio of coupling/oxidation reaction products depends on the oxidation conditions and decreases with temperature raise. The higher oxidation rate of vanillyl alcohol as compared to the veratryl alcohol in the reaction system O 2 /HPA-5 was explained by the redox properties of the catalyst. The insufficiently high redox potential of HPA-5 did not allow the efficient oxidation of veratryl alcohol. The former was oxidised by VO 2 + ions dissociated from the HPA-5 under the acidic conditions. The reactivity of different lignin structural units in the reaction system O 2 /HPA-5 was estimated by electrochemical methods using various lignin model compounds.

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Section: Oxidation Of Vanillyl Alcoholsupporting

confidence: 66%

Lignin Degradation in Oxygen Delignification Catalysed by [PMo7V5O40]8- Polyanion. Part II. Study on Lignin Monomeric Model Compounds

Evtuguin¹,

Neto²,

Carapuça³

et al. 2000

Holzforschung

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“…The latter cationic intermediates would degrade by lateral chain cleavage. 236 The catalytic cycle is closed upon reoxidation of the reduced polyoxometalate form by oxygen.…”

Section: Heteropolyacids As Oxidation Catalystsmentioning

confidence: 99%

Lewis Acids as Catalysts in Oxidation Reactions: From Homogeneous to Heterogeneous Systems

2002

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I. Introduction and Scope 3837 II. Oxidation Strategies 3838 III. Lewis Acids as Oxidation Catalysts 3839 A. Oxidations by Single Electron Abstraction 3839 B. Oxidations by an Assembly of Lewis Acid, Lewis Basic and Redox Centers 3841 1. Vanadium-Based Systems 3842 2. Metal Oxides Other than Vanadium 3844 C. Oxidations via Lewis Acid−Base Adducts 3847 1. Oxidations in Homogeneous Phase 3848 2. Oxidations in Biphasic Fluorous Systems 3854 3. Heteropolyacids as Oxidation Catalysts 3855 4.

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“…A review of the oxygen delignification literature [18][19][20][21][22][23][24][25] indicates that the use of a co-oxidant and/or catalyst in an O-stage is most frequently applied to extend delignification but not fiber charge. Nonetheless, several studies have reported the use of noble metal catalysts to selectively oxidize the hydroxyl groups of carbohydrates into the corresponding acid groups under reaction conditions similar to oxygen delignification [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Lignocellulosic fiber charge enhancement by catalytic oxidation during oxygen delignification

Zhang¹,

Chai²,

Pu³

et al. 2007

Journal of Colloid and Interface Science

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Selective Transition-Metal Catalysis of Oxygen Delignification. Using Water-Soluble Salts of Polyoxometalate (POM) Anions. Part II. Reactions of α-[SiVW₁₁O₄₀]^5-with Phenolic Lignin-Model Compounds

Cited by 42 publications

References 22 publications

Lignin Degradation in Oxygen Delignification Catalysed by [PMo7V5O40]8- Polyanion. Part II. Study on Lignin Monomeric Model Compounds

Lignin Degradation in Oxygen Delignification Catalysed by [PMo7V5O40]8- Polyanion. Part II. Study on Lignin Monomeric Model Compounds

Lewis Acids as Catalysts in Oxidation Reactions: From Homogeneous to Heterogeneous Systems

Lignocellulosic fiber charge enhancement by catalytic oxidation during oxygen delignification

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