Predominant formation of aromatic aldehyde and acid from a dimeric β-O-4-type lignin model compound under hydrogen peroxide bleaching conditions with high pH levels

Summary The kinetics of delignification of a kraft-AQ southern pine pulp with hydrogen peroxide catalyzed by [LMn(IV)(μ-O)3Mn(IV)](ClO4)2 (1), where L = 1,2-bis(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)ethane was studied. The degree of delignification was significantly improved by using the catalyst. The pulp was bleached for 2 hours at 80°C, in 10% consistency with 2% NaOH, 4% H2O2 and 60 ppm catalyst charges on pulp (O.D.). Kappa number of the pulp was reduced from 31.6 to 16.8 corresponding to a degree of delignification of approximately 4%, while GE brightness was increased from 24.2 to 44.7. At the same time, viscosity of the resulting pulp was reduced from 31.1 mPa•s to 20.1 mPa•s compared to the reduction from 31.1 mPa•s to 20.1 mPa•s in the uncatalyzed bleaching under the same reaction condition. This indicates that the degradation of the carbohydrates was moderate in the catalyzed bleaching compared to the uncatalyzed bleaching. The delignification was found to follow pseudo first order kinetics with respect to kappa number, i.e., residual lignin, in the initial phase and quickly slowed down after 30 minutes (residual phase) under all the reaction temperatures investigated. The delignification rate constants in the initial phase were 0.17, 0.18, and 0.21 min−1 at 50, 60, and 80°C, respectively. Degree of delignification at the delignification time of 30 minutes is approximately 40% at 80°C. The possible delignification mechanism was discussed on the basis of the kinetic studies and lignin model compound experiments.

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Revisiting the mechanism of β-O-4 bond cleavage during acidolysis of lignin VII: acidolyses of non-phenolic C6-C2-type model compounds using HBr, HCl and H2SO4, and a proposal on the characteristic action of Br− and Cl−

Journal of Wood Science ◽

10.1186/s10086-020-01928-6 ◽

2020 ◽

Vol 66 (1) ◽

Author(s):

Qiaoqiao Ye ◽

Tomoya Yokoyama

Keyword(s):

Model Compound ◽

Bond Cleavage ◽

Type Model ◽

Enol Ether ◽

Lignin Model Compound ◽

Benzyl Cation ◽

Acid Type ◽

Unstable Compound ◽

Lignin Model ◽

Acidolysis Reaction

AbstractA non-phenolic C6-C2-type lignin model compound with the β-O-4 bond, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (I), was acidolyzed in aqueous 82% 1,4-dioxane containing HBr, HCl, or H2SO4 with a concentration of 0.2 mol/L at 85 ℃ to examine the differences between these acidolyses. Compound I primarily converted to an enol ether compound, 1-(2-methoxyphenoxy)-2-(3,4-dimethoxyphenyl)ethene (II), via the benzyl cation followed by acidolytic β-O-4 bond cleavage regardless of the acid-type, although the disappearance rates of compound I were remarkably different (HBr > HCl >> H2SO4). Acidolyses of compound II using these acids under the same conditions showed a similar tendency, but the rate differences were much smaller than in the acidolyses of compound I. Acidolyses of the α-methyl-etherified derivative of compound I (I-α-OMe) using these acids under the same conditions suggested that the formation rates of the benzyl cation from compound I-α-OMe (also from compound I) are not largely different between the acidolyses using these acids, but those of compound II from the benzyl cation are remarkably different. Acidolysis of the α-bromo-substituting derivative of compound I (I-α-Br) using HBr under the same conditions showed a characteristic action of Br¯ in the acidolysis. Br¯ adds to the benzyl cation generated from compound I or I-α-OMe to afford unstable compound I-α-Br, resulting in acceleration of the formation of compound II and of the whole acidolysis reaction.

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Model compounds-based study on adsorption and dispersion properties of lignin-based superplasticizer

Science Progress ◽

10.1177/0036850420980624 ◽

2021 ◽

Vol 104 (1) ◽

pp. 003685042098062

Author(s):

Shuangping Ma ◽

Qingjun Ding ◽

Fen Zhou ◽

Huaxiong Zhu

Keyword(s):

Molecular Structure ◽

Zeta Potential ◽

Model Compound ◽

Research Work ◽

Structure Activity Relationship ◽

Activity Relationship ◽

Lignin Model Compound ◽

Structure Activity ◽

Lignin Model ◽

Relationship Of

The chemical modifications of lignin-based superplasticizers have attracted extensive attentions during recent years. The comprehending of the structure-activity relationship of lignin-based superplasticizer is important to promote the modification and application research of lignin resources. However, lignin features complex and variable molecular structure, which is not conducive to study on structure-activity relationship of lignin-based superplasticizer as well as development and application of new lignin-based superplasticizer. However, the related research work can be simplified by selecting small molecular compound with appropriate molecular structure as the lignin model compound. This article intends to study the structure-activity relationship of lignin-based superplasticizer by using dihydroeugenol as the lignin model compound. Through the substitution of lignin by dihydroeugenol during the synthesis process, a model compound lignin-based superplasticizer (DAFS) was synthesized. The adsorption and dispersion properties of this superplasticizer and reference sample (LAFS) were investigated by fluidity test, Zeta-potential measurement, Total organic carbon analysis and others. The results suggest that the adsorption behavior of both DAFS and LAFS conformed to the Langmuir isotherms and Pseudo-second order kinetic. In cement paste, added with 1 g/L of LAFS and DAFS, Zeta potential were reduced from +3.5 to −15.2 mV and −18.7 mV, respectively. The substitution of lignin by dihydroeugenol has no significantly influence on the dispersive property, but differences on rheological properties which need to be optimized in the future. All the tests confirmed that dihydroeugenol is suitable to replace lignin on exploring the structure-activity relationship of lignin-based superplasticizer. This research work provides new insight on model study of lignin-based superplasticizer.

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Evidence for superoxide-radical anion, singlet oxygen and OH-radical intervention during the degradation of the lignin model compound (3-methoxy-4-hydroxyphenylmethylcarbinol)

Journal of Photochemistry and Photobiology A Chemistry ◽

10.1016/j.jphotochem.2004.07.009 ◽

2005 ◽

Vol 169 (3) ◽

pp. 271-278 ◽

Cited By ~ 72

Author(s):

P. Raja ◽

A. Bozzi ◽

H. Mansilla ◽

J. Kiwi

Keyword(s):

Singlet Oxygen ◽

Radical Anion ◽

Model Compound ◽

Superoxide Radical ◽

Oh Radical ◽

Superoxide Radical Anion ◽

Lignin Model Compound ◽

Lignin Model ◽

Radical Intervention

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Cleavage of the β–O–4 bond in a lignin model compound using the acidic ionic liquid 1-H-3-methylimidazolium chloride as catalyst: a DFT mechanistic study

Journal of Molecular Modeling ◽

10.1007/s00894-018-3854-x ◽

2018 ◽

Vol 24 (11) ◽

Cited By ~ 5

Author(s):

Youtao Zhu ◽

Zhe Han ◽

Lijun Fu ◽

Chengbu Liu ◽

Dongju Zhang

Keyword(s):

Ionic Liquid ◽

Model Compound ◽

Mechanistic Study ◽

Lignin Model Compound ◽

Acidic Ionic Liquid ◽

Lignin Model

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Inside Cover: CC or CO Bond Cleavage in a Phenolic Lignin Model Compound: Selectivity Depends on Vanadium Catalyst (Angew. Chem. Int. Ed. 14/2012)

Angewandte Chemie International Edition ◽

10.1002/anie.201200720 ◽

2012 ◽

Vol 51 (14) ◽

pp. 3278-3278 ◽

Cited By ~ 1

Author(s):

Susan K. Hanson ◽

Ruilian Wu ◽

Louis A. “Pete” Silks

Keyword(s):

Model Compound ◽

Bond Cleavage ◽

Vanadium Catalyst ◽

Lignin Model Compound ◽

Lignin Model

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Synthesis and application of Co(salen) complexes containing proximal imidazolium ionic liquid cores

Canadian Journal of Chemistry ◽

10.1139/v11-106 ◽

2012 ◽

Vol 90 (1) ◽

pp. 60-70 ◽

Cited By ~ 15

Author(s):

Swapnil Sonar ◽

Kenson Ambrose ◽

Arthur D. Hendsbee ◽

Jason D. Masuda ◽

Robert D. Singer

Keyword(s):

Ionic Liquid ◽

Ionic Liquids ◽

Model Compound ◽

Veratryl Alcohol ◽

Oxidation Catalysts ◽

Imidazolium Ionic Liquid ◽

Lignin Model Compound ◽

Salen Complexes ◽

Lignin Model ◽

Salen Ligand

Ionic ligands derived from a salen ligand containing two proximal 1,3-disubstituted imidazolium ionic liquid cores form cobalt(III) complexes capable of selectively oxidizing veratryl alcohol, a lignin model compound, to veratraldehyde using air as the source of oxygen. These complexes are easy to prepare, inexpensive, water stable, and soluble in ionic liquids, making them viable candidates for use as oxidation catalysts.

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Exhaustive laccase-catalysed oxidation of a lignin model compound (vanillyl glycol) produces methanol and polymeric quinoid products

Biochemical Journal ◽

10.1042/bj2290277 ◽

1985 ◽

Vol 229 (1) ◽

pp. 277-279 ◽

Cited By ~ 41

Author(s):

K Lundquist ◽

P Kristersson

Keyword(s):

Model Compound ◽

Polymerization Process ◽

Lignin Biodegradation ◽

Simultaneous Formation ◽

Initial Formation ◽

Lignin Model Compound ◽

Catalysed Oxidation ◽

Visible Spectra ◽

Lignin Model

Laccase-catalysed oxidation of the lignin-related phenol vanillyl glycol results in the initial formation of dimers and subsequent polymerization. The polymerization is accompanied by a liberation of methanol corresponding to 15-20% demethylation. Visible spectra together with reduction experiments suggest the simultaneous formation of o-quinones. The participation of quinone formation in the polymerization process and the possible role of such intermediates in lignin biodegradation is discussed.

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