Catalytic conversion of a lignin model compound to value-added products using Cu/TEMPO-catalyzed aerobic oxidation

AbstractDevelopment of catalysts for efficient conversion of lignin polymer to value-added materials requires appropriately-functionalized lignin model compounds. The predominant structural feature of lignin biopolymer is an extensive network of β-O-4 linkages. Access to large amounts of a model compound containing the β-O-4 linkage is crucial for the valorisation of lignin biopolymer to aromatic raw materials. Starting from commercially available vanillin, synthesis of dilignol model compound, containing a β-O-4 linkage, is accomplished in good overall yield.

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Ru-Catalyzed Oxidative Cleavage of Guaiacyl Glycerol--Guaiacyl Ether-a Representative -O-4 Lignin Model Compound

Catalysts ◽

10.3390/catal9100832 ◽

2019 ◽

Vol 9 (10) ◽

pp. 832 ◽

Cited By ~ 2

Author(s):

Melián-Rodríguez ◽

Saravanamurugan ◽

Meier ◽

Kegnæs ◽

Riisager

Keyword(s):

Model Compound ◽

Supported Catalysts ◽

Batch Reactor ◽

Aerobic Oxidation ◽

Catalytic Performance ◽

Ruthenium Catalysts ◽

Consecutive Reaction ◽

Lignin Model Compound ◽

Lignin Model ◽

A Minor

The introduction of efficient and selective catalytic methods for aerobic oxidation of lignin and lignin model compounds to aromatics can extend the role of lignin applications in biorefineries. The current study focussed on the catalytic oxidative transformation of guaiacyl glycerol--guaiacyl ether (GGGE)–a -O-4 lignin model compound to produce basic aromatic compounds (guaiacol, vanillin and vanillic acid) using metal-supported catalysts. Ru/Al2O3, prepared with ruthenium(IV) oxide hydrate, showed the highest yields of the desired products (60%) in acetonitrile in a batch reactor at 160 C and 5-bar of 20% oxygen in argon. Alternative catalysts containing other transition metals (Ag, Fe, Mn, Co and Cu) supported on alumina, and ruthenium catalysts based on alternative supports (silica, spinel, HY zeolite and zirconia) gave significantly lower activities compared to Ru/Al2O3 at identical reaction conditions. Moreover, the Ru/Al2O3 catalyst was successfully reused in five consecutive reaction runs with only a minor decrease in catalytic performance.

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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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