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

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

doi:10.1515/hfsg.1998.52.3.311

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

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

Research output: Contribution to journal › Article › peer-review

62 Scopus citations

Abstract

When heated under anaerobic conditions, aqueous solutions of the polyoxometalate anion a-[SiVW₁₁O₄]^5- (POM_ox, 1), supplied as the salt K₅[SiVW₁₁O₄] · 12H₂O, selectively delignify unbleached mixed-pine kraft pulps. During delignification, 1 is reduced by residual lignin to α-[SiVW₁₁O₄₀]^6- (POM_red' 2): α-[SiVW₁₁O₄₀]^5-+ le-→α-[SiVW₁₁O₄₀]^6-, E^o = + 0.69V vs. NHE. Model studies suggest that phenolic (hydroxylated phenyl) groups present in residual lignin are substrates for the reduction of 1. Reactions of 1 with phenolic arylglycerol β-aryl ethers and other phenolic lignin models suggest that anaerobic POM degradation of residual lignin may occur via sequential single-electron oxidation reactions of phenolic substructures, first to cyclohexadienyl radicals and subsequently to cyclohexadienyl cations. Hydrolysis of these cationic intermediates results in alkyl-side-chain cleavage, a likely route to polymer degradation.

Original language	English
Pages (from-to)	311-318
Number of pages	8
Journal	Holzforschung
Volume	52
Issue number	3
DOIs	https://doi.org/10.1515/hfsg.1998.52.3.311
State	Published - 1 Jan 1998
Externally published	Yes

Keywords

Bleaching
Delignification
Kraft pulp
Lignin
Oxidation
Oxygen
Phenol
Polyoxometalate

ASJC Scopus subject areas

Biomaterials

Access to Document

10.1515/hfsg.1998.52.3.311

Cite this

Weinstock, I. A., Hammel, K. E., Moen, M. A., Landucci, L. L., Ralph, S., Sullivan, C. E., & Reiner, R. S. (1998). 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. Holzforschung, 52(3), 311-318. https://doi.org/10.1515/hfsg.1998.52.3.311

@article{d0b1e9314fbf4f1aa502137017a67736,

title = "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",

abstract = "When heated under anaerobic conditions, aqueous solutions of the polyoxometalate anion a-[SiVW11O4]5- (POMox, 1), supplied as the salt K5[SiVW11O4] · 12H2O, selectively delignify unbleached mixed-pine kraft pulps. During delignification, 1 is reduced by residual lignin to α-[SiVW11O40]6- (POMred' 2): α-[SiVW11O40]5-+ le-→α-[SiVW11O40]6-, Eo = + 0.69V vs. NHE. Model studies suggest that phenolic (hydroxylated phenyl) groups present in residual lignin are substrates for the reduction of 1. Reactions of 1 with phenolic arylglycerol β-aryl ethers and other phenolic lignin models suggest that anaerobic POM degradation of residual lignin may occur via sequential single-electron oxidation reactions of phenolic substructures, first to cyclohexadienyl radicals and subsequently to cyclohexadienyl cations. Hydrolysis of these cationic intermediates results in alkyl-side-chain cleavage, a likely route to polymer degradation.",

keywords = "Bleaching, Delignification, Kraft pulp, Lignin, Oxidation, Oxygen, Phenol, Polyoxometalate",

author = "Weinstock, {Ira A.} and Hammel, {Kenneth E.} and Moen, {Mark A.} and Landucci, {Lawrence L.} and Sally Ralph and Sullivan, {Cindy E.} and Reiner, {Richard S.}",

note = "Funding Information: This work was funded by the USDA National Research Initiative Competitive Grants Program (93-37103-9270). We gratefully acknowledge Osram Sylvania, Inc., and Shieldalloy Metallurgical Corporation for contributions of tungsten and vanadium, Dr. J. Ralph of the USDA Dairy Forage Research Center, Madison, Wl, for providing access to a high-resolution NMR spectrometer, and Janel Showalter for editorial assistance.",

year = "1998",

month = jan,

day = "1",

doi = "10.1515/hfsg.1998.52.3.311",

language = "English",

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Weinstock, IA, Hammel, KE, Moen, MA, Landucci, LL, Ralph, S, Sullivan, CE & Reiner, RS 1998, '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', Holzforschung, vol. 52, no. 3, pp. 311-318. https://doi.org/10.1515/hfsg.1998.52.3.311

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. et al.
In: Holzforschung, Vol. 52, No. 3, 01.01.1998, p. 311-318.

Research output: Contribution to journal › Article › peer-review

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T1 - 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

AU - Weinstock, Ira A.

AU - Hammel, Kenneth E.

AU - Moen, Mark A.

AU - Landucci, Lawrence L.

AU - Ralph, Sally

AU - Sullivan, Cindy E.

AU - Reiner, Richard S.

N1 - Funding Information: This work was funded by the USDA National Research Initiative Competitive Grants Program (93-37103-9270). We gratefully acknowledge Osram Sylvania, Inc., and Shieldalloy Metallurgical Corporation for contributions of tungsten and vanadium, Dr. J. Ralph of the USDA Dairy Forage Research Center, Madison, Wl, for providing access to a high-resolution NMR spectrometer, and Janel Showalter for editorial assistance.

PY - 1998/1/1

Y1 - 1998/1/1

N2 - When heated under anaerobic conditions, aqueous solutions of the polyoxometalate anion a-[SiVW11O4]5- (POMox, 1), supplied as the salt K5[SiVW11O4] · 12H2O, selectively delignify unbleached mixed-pine kraft pulps. During delignification, 1 is reduced by residual lignin to α-[SiVW11O40]6- (POMred' 2): α-[SiVW11O40]5-+ le-→α-[SiVW11O40]6-, Eo = + 0.69V vs. NHE. Model studies suggest that phenolic (hydroxylated phenyl) groups present in residual lignin are substrates for the reduction of 1. Reactions of 1 with phenolic arylglycerol β-aryl ethers and other phenolic lignin models suggest that anaerobic POM degradation of residual lignin may occur via sequential single-electron oxidation reactions of phenolic substructures, first to cyclohexadienyl radicals and subsequently to cyclohexadienyl cations. Hydrolysis of these cationic intermediates results in alkyl-side-chain cleavage, a likely route to polymer degradation.

AB - When heated under anaerobic conditions, aqueous solutions of the polyoxometalate anion a-[SiVW11O4]5- (POMox, 1), supplied as the salt K5[SiVW11O4] · 12H2O, selectively delignify unbleached mixed-pine kraft pulps. During delignification, 1 is reduced by residual lignin to α-[SiVW11O40]6- (POMred' 2): α-[SiVW11O40]5-+ le-→α-[SiVW11O40]6-, Eo = + 0.69V vs. NHE. Model studies suggest that phenolic (hydroxylated phenyl) groups present in residual lignin are substrates for the reduction of 1. Reactions of 1 with phenolic arylglycerol β-aryl ethers and other phenolic lignin models suggest that anaerobic POM degradation of residual lignin may occur via sequential single-electron oxidation reactions of phenolic substructures, first to cyclohexadienyl radicals and subsequently to cyclohexadienyl cations. Hydrolysis of these cationic intermediates results in alkyl-side-chain cleavage, a likely route to polymer degradation.

KW - Bleaching

KW - Delignification

KW - Kraft pulp

KW - Lignin

KW - Oxidation

KW - Oxygen

KW - Phenol

KW - Polyoxometalate

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