Polyoxometalate (POM) oxidation of lignin model compounds

Holzforschung ◽  
2008 ◽  
Vol 62 (1) ◽  
pp. 38-49 ◽  
Author(s):  
Yong Sik Kim ◽  
Hou-min Chang ◽  
John F. Kadla
Keyword(s):  
Reaction Rate ◽  
Model Compound ◽  
Reaction Rates ◽  
Hydroxyl Group ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
First Order ◽  
Resonance Stabilization ◽  
Lignin Model

Abstract Various lignin model compounds were oxidized with polyoxometalate (POM), K5[SiVW11O40]·12 H2O, in sodium acetate buffer (I=0.2 M, pH 5.0) and the reaction kinetics were investigated. The reactions were found to have second order reaction rates, first order with regards to both lignin model compound and POM. A dramatic increase in reactivity was observed upon addition of methoxyl groups in ortho-positions to the phenolic hydroxyl group. Syringyl units reacted faster than guaiacyl units. Reaction rates of para-substituted guaiacyl and syringyl model compounds showed a strong dependency on the nature of the substituents. The reaction rate of a 5-5′ dimer lignin model compound was extremely fast. The addition of the ortho-phenol substituent not only increased the electron density of the aromatic ring, but also helped stabilize the intermediate phenoxy radical through resonance stabilization and delocalization.

scholarly journals Effect of lignin structure on adsorbable organic halogens formation in chlorine dioxide bleaching

2019 ◽  
Vol 6 (2) ◽  
pp. 182024 ◽  
Author(s):  
Lisheng Shi ◽  
Jiayan Ge ◽  
Shuangxi Nie ◽  
Chengrong Qin ◽  
Shuangquan Yao
Keyword(s):  
Chlorine Dioxide ◽  
Model Compound ◽  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Organic Halogens ◽  
Adsorbable Organic Halogens ◽  
Lignin Structure

Adsorbable organic halogens (AOX) are formed in pulp bleaching as a result of the reaction of residual lignin with chlorine dioxide. The natural structure of lignin is very complex and it tends to be damaged by various extraction methods. All the factors can affect the study about the mechanism of AOX formation in the reaction of lignin with chlorine dioxide. Lignin model compounds, with certain structures, can be used to study the role of different lignin structures on AOX formation. The effect of lignin structure on AOX formation was determined by reacting phenolic and non-phenolic lignin model compound with a chlorine dioxide solution. Vanillyl alcohol (VA) and veratryl alcohol (VE) were selected for the phenolic and non-phenolic lignin model compound, respectively. The pattern consumption of lignin model compounds suggests that both VA and VE began reacting with chlorine dioxide within 10 min and then gradually steadied. The volume of AOX produced by VE was significantly higher than that produced by VA for a given initial lignin model compound concentration. In a solution containing a combination of VA and VE in chlorine dioxide, VE was the dominant producer of AOX. This result indicates that the non-phenolic lignin structure was more easily chlorinated, while the phenolic lignin structure was mainly oxidized. In addition, AOX content produced in the combined experiments exceeded the total content of the two separate experiments. It suggested that the combination of phenolic and non-phenolic lignin structure can promote AOX formation.

Thermal stability of lignin in ground pulp (GP) and the effect of lignin modification on GP’s thermal stability: TGA experiments with dimeric lignin model compounds and milled wood lignins

Holzforschung ◽  
2019 ◽  
Vol 73 (5) ◽  
pp. 493-499 ◽  
Author(s):  
Daisuke Ando ◽  
Fumiaki Nakatsubo ◽  
Hiroyuki Yano
Keyword(s):  
Thermal Stability ◽  
Model Compound ◽  
Pinus Densiflora ◽  
Wood Fiber ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Oh Groups ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Thermal Stability Of

Abstract For ground pulp (GP) utilization in wood fiber composites as reinforced material, its thermal behavior is relevant. The contribution of lignin to thermal performance of GP from Pinus densiflora was the focus of the present study. Dimeric lignin model compounds and isolated milled wood lignins (MWLs) from three sources were submitted for thermogravimetric analysis (TGA). The temperatures leading to 1% weight loss (T per 1% WL) for the material were determined. The thermal stability of β-O-4 models was the lowest. Among the MWLs, the abaca MWL with its high β-O-4 content was the least thermostable. An acetylated nonphenolic β-O-4 lignin model compound showed that acetylation improves the thermal stability of this type of dimeric models. The acetylation of benzylic OH groups in β-O-4 linkages is especially relevant for the thermal resistance, which was also shown based on pre-acetylated benzylic OH groups in the GP before the total acetylation.

Free radical reaction promoted by ionic liquid: a route for metal-free oxidation depolymerization of lignin model compound and lignin

2015 ◽  
Vol 51 (19) ◽  
pp. 4028-4031 ◽  
Author(s):  
Yingying Yang ◽  
Honglei Fan ◽  
Jinliang Song ◽  
Qinglei Meng ◽  
Huacong Zhou ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Model Compound ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Organosolv Lignin ◽  
Lignin Model ◽  
Free Oxidation

Ionic liquid can efficiently promote the transformation of lignin model compounds and organosolv lignin.

Synthesis of lignin model compound containing a β-O-4 linkage

2017 ◽  
Vol 72 (2) ◽  
pp. 119-124 ◽  
Author(s):  
Asma Mukhtar ◽  
Muhammad Zaheer ◽  
Muhammad Saeed ◽  
Wolfgang Voelter
Keyword(s):  
Structural Feature ◽  
Model Compound ◽  
Raw Materials ◽  
Value Added ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Efficient Conversion ◽  
Lignin Model

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.

Recyclable ionic liquid tagged Co(salen) catalysts for the oxidation of lignin model compounds

2013 ◽  
Vol 91 (12) ◽  
pp. 1258-1261 ◽  
Author(s):  
Kenson Ambrose ◽  
Bitu B. Hurisso ◽  
Robert D. Singer
Keyword(s):  
Ionic Liquid ◽  
Liquid Phase ◽  
Model Compound ◽  
Veratryl Alcohol ◽  
Pure Oxygen ◽  
Model Compounds ◽  
Imidazolium Ionic Liquid ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model

Ionic liquid tagged salen ligands 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 or pure oxygen as the source of oxygen. Entrainment of these catalysts in either 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], or 1-butyl-3-methylimidazolium bistriflimide, [bmim][NTf2], hydrophobic ionic liquid solvents, results in biphasic reactions when water is used as the second solvent allowing the catalyst/ionic liquid phase to be recycled.

Oxidative conversion of lignin and lignin model compounds catalyzed by CeO2-supported Pd nanoparticles

2015 ◽  
Vol 17 (11) ◽  
pp. 5009-5018 ◽  
Author(s):  
Weiping Deng ◽  
Hongxi Zhang ◽  
Xuejiao Wu ◽  
Rongsheng Li ◽  
Qinghong Zhang ◽  
...  
Keyword(s):  
Model Compound ◽  
Pd Nanoparticles ◽  
Oxidative Conversion ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Supported Pd

Pd/CeO2 efficiently catalyzes the oxidative conversion of 2-phenoxy-1-phenylethanol, a lignin model compound with a β-O-4 linkage, in methanol, producing monomeric aromatics.

scholarly journals Study of the Reactivity of Lignin Model Compounds to Fluorobenzylation Using 13C and 19F NMR: Application to Lignin Phenolic Hydroxyl Group Quantification by 19F NMR

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3211
Author(s):  
Esakkiammal Sudha Esakkimuthu ◽  
Nathalie Marlin ◽  
Marie-Christine Brochier-Salon ◽  
Gérard Mortha
Keyword(s):  
Reaction Medium ◽  
19F Nmr ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Nmr Analysis ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Wide Range ◽  
Lignin Model ◽  
13C And 19F Nmr

Lignin is an aromatic biopolymer derived from lignocellulosic biomass. Providing a comprehensive structural analysis of lignin is the primary motivation for the quantification of various functional groups, with a view to valorizing lignin in a wide range of applications. This study investigated the lignin fluorobenzylation reaction and performed a subsequent 19F-NMR analysis to quantify hydroxyl groups, based on a work developed two decades ago by Barrelle et al. The objectives were to check the assignments proposed in this previous study and to examine the reactivity of various types of lignin hydroxyls with the derivatization agent. Selected lignin model compounds containing phenolic and aliphatic hydroxyls were subjected to the fluorobenzylation reaction, and the obtained reaction medium was analyzed by 13C and 19F NMR spectroscopy. The model compound results showed that phenolic hydroxyls were totally derivatized, whereas aliphatic hydroxyls underwent minimal conversion. They also confirmed that 19F NMR chemical shifts from −115 ppm to −117.3 ppm corresponded to phenolic groups. Then, a 19F NMR analysis was successfully applied to Organosolv commercial lignin after fluorobenzylation in order to quantify its phenolic group content; the values were found to be in the range of the reported values using other analytical techniques after lignin acetylation.

Fixation of Amine Copper Preservatives. Part 1. Reaction of Vanillin, a Lignin Model Compound with Monoethanolamine Copper Sulphate Solution

Holzforschung ◽  
2001 ◽  
Vol 55 (6) ◽  
pp. 585-589 ◽  
Author(s):  
J.N.R. Ruddick ◽  
C. Xie ◽  
F.G. Herring
Keyword(s):  
Copper Sulphate ◽  
Model Compound ◽  
Axial Direction ◽  
Sulphate Solution ◽  
Hydroxyl Group ◽  
Copper Sulphate Solution ◽  
Lignin Model Compound ◽  
Binuclear Molecule ◽  
Lignin Model ◽  
Fixation Reaction

Summary The fixation reaction of copper-ethanolamine preservatives in wood was studied using the reaction between vanillin, a lignin model compound, and ethanolamine-copper sulphate solution. The green compound precipitated after the reaction has been characterized spectroscopically as di(ethanolamine)-bis (vanillinato)dicopper(II); [Cu(vanillin) (ethanolamine)]2. Single crystal X-ray crystallographic studies showed that the crystals of [Cu(vanillin)(ethanolamine)]2 are triclinic with the space group P1 with a = 9.1271(7), b = 10.8723(9), c = 6.360(1) Å, α = 97.08(1), β = 100.63(1), and γ = 110.024(7)°. Z = 1. The binuclear molecule has crystallographic inversion symmetry. The ligand arrangement around the Cu(II) is a distorted square based pyramid, with a base plane made up of two oxygen atoms from the ethanolamine ligands, one oxygen atom from a hydroxyl group in vanillin and one nitrogen atom from ethanolamine. Two Cu-O [1.916(2) and 1.950(5) Å], one Cu-O (hydroxyl) [1.926(4) Å] and one Cu-N [1.999(3) Å] bonds form a plane with Cu-O (methoxyl) [2.303(2) Å] bond in an axial direction at an angle 77 ° to the plane. The result suggests that after treatment with copper-ethanolamine wood preservatives, stable copper-nitrogen-lignin complexes can be formed through reaction with guaiacyl units in lignin.

The Reactions of Lignin Model Compounds with Hydrogen Peroxide at Low pH

Holzforschung ◽  
2003 ◽  
Vol 57 (1) ◽  
pp. 52-88 ◽  
Author(s):  
T. Kishimoto ◽  
J. F. Kadla ◽  
H.-m. Chang ◽  
H. Jameel
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction System ◽  
Model Compounds ◽  
Reaction Conditions ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Decreasing Ph ◽  
Hydroxyl Compounds ◽  
Acidic Hydrogen

Summary In peroxymonosulfuric acid bleaching, the presence of hydrogen peroxide is dependent on the reaction conditions and the conversion ratios used to generate the peroxy acid. Substantial amounts of hydrogen peroxide may be present in the reaction system under certain conditions. An understanding of the reactions of hydrogen peroxide under these conditions would be beneficial. Therefore, several simple lignin model compounds were reacted with acidic hydrogen peroxide, pH 1-3, at 70°C. In all cases the phenolic lignin model compounds reacted much faster than their non-phenolic counterparts. In fact, the extent of reaction was very much dependent on the structure of the lignin model compound. The α-hydroxyl compounds, 4-(1-Hydroxy-ethyl)-2-methoxy-phenol and 1-(3,4-Dimethoxy-phenyl)-ethanol, reacted faster than the corresponding α-carbonyl compounds with both reacting much faster than the aromatic compounds, with simple alkyl substituents. A new reaction mechanism for α-hydroxyl compounds is proposed, in which benzyl carbocation formation is followed by nucleophilic addition of hydrogen peroxide. Unlike the mechanisms proposed in the past, no evidence of aromatic hydroxylation via perhydronium ion was observed. The reactivities were very pH dependent, in that higher reactivity was associated with lower pH. Decreasing pH further increased the amount of condensation products identified, such that condensation was competitive with degradation. These condensation reactions were also present under the Caro's acid bleaching conditions at pH below 2. However, under all conditions the reactivity of acidic peroxide was found to be much less than that of peroxymonosulfuric acid.

Sign in / Sign up

Export Citation Format

Share Document