Lignin Analysis by Permanganate Oxidation. II. Lignins in Acidic Organosolv Pulps

Bose, Samar K.; Wilson, Kate L.; Hausch, Diane L.; Francis, Raymond C.

doi:10.1515/hf.1999.100

Cited by 12 publications

(7 citation statements)

References 19 publications

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“…If the benzyl cation intermediate II is formed from acidic cleavage of a methoxyl group, the coupling with methanol corresponds to the reverse reaction. The possible prevention of condensation with alcohols has been discussed in a number of publications (Bose et al 1999;Evtuguin et al 2000;Oliet et al 2001), whereas no direct experimental proof has been reported so far.…”

Section: Resultsmentioning

confidence: 99%

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

2010

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One kraft lignin and two lignosulfonates were oxidized in aqueous acidic solutions containing a polyoxometalate (POM). The degradations were carried out in H 2 O or MeOH/ H 2 O mixtures in the presence of oxygen. The treatment with aqueous H 3 PMo 12 O 40 led to the dissolution of the studied lignins in the acidic medium (pH 1-2) and to the formation of up to 6.5 wt% vanillin and 6.2 wt% methyl vanillate based on the weight of dry lignin. The lignin oxidation products were analyzed by size-exclusion chromatography (SEC). For this purpose, a SEC method was developed, which allows the analysis of kraft lignin, lignosulfonates, and reaction products thereof without the need to remove the homogeneous catalyst. This method allows the direct observation of depolymerization and repolymerization reactions and hence the provision of a tool for studying the underlying chemistry. It has been demonstrated that the depolymerization of kraft lignin in water is accompanied by counterproductive condensation reactions. These repolymerization reactions were effectively prevented by addition of methanol, which couples competitively with lignin intermediates.

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Section: Resultsmentioning

confidence: 99%

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

2010

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“…MnO 2 oxidation of lignin has been examined in only a few studies, at least from a pure chemistry viewpoint, , although nonrecyclable permanganate (MnO 4 ¯) oxidation of lignin has been reported fairly widely. − It is generally known that MnO 2 oxidizes allyl and benzyl alcohols selectively among various types of alcohols to afford the corresponding conjugate and aromatic carbonyls, respectively, with the oxidation rates being higher in nonpolar organic solvents than in polar solvents. − MnO 2 oxidation of other alcohols progresses only under severe conditions. , However, if MnO 2 had oxidized only benzyl alcohols in the residual lignin, and consequently the corresponding α-carbonyl groups had just formed in our previous study, in accordance with this general knowledge, sufficient delignification must not have been attained. Just introducing α-carbonyl groups does not contribute to delignification at the employed pH and temperature.…”

Section: Introductionmentioning

confidence: 99%

Differences in the Mechanisms of MnO₂Oxidation between Lignin Model Compounds with thep-Hydroxyphenyl, Guaiacyl, and Syringyl Nuclei

Sun

Akiyama

Yokoyama

et al. 2020

J. Agric. Food Chem.

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The purpose of this study was to examine how the rate and mechanism of MnO 2 oxidation differ between the phydroxyphenyl (H), guaiacyl (G), and syringyl (S) types of simple nonphenolic lignin model compounds as well as the p-ethylphenyl (E) type compounds. The oxidation was conducted using an excess amount of MnO 2 in a sulfate buffer solution at a pH value of 1.5 at room temperature. MnO 2 oxidized at least the G and S nuclei, although it commonly oxidizes alcohols present at the benzyl position. The oxidation rates of the benzyl alcohol derivatives were in the order of G-> S-≫ H-> E-type, which suggests that the rates are determined by the electronic effects of their methoxy and ethyl functional groups on not only their benzyl positions but also their aromatic π-electron systems. The kinetic isotope effect was observed in the MnO 2 oxidations of the same derivatives deuterated at their benzyl hydroxymethyl groups. The observed magnitudes were in the order of E-≫ H-> G-≫ S-type, suggesting that the contribution of oxidation of their aromatic nuclei, which is another reaction mode of the oxidation of their benzyl positions, increases in the reverse order.

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“…A second alkaline selfcondensation of AP was performed, and on this occasion the residual AP after alkaline treatment was 15.5%, and that value decreased to 7.7% after acidolysis (Table 7). The likely cause of AP disappearance during acidolysis is acid-catalyzed condensation of the AP to the C-6 position of other aromatic rings, which occurs at a higher rate in water alone as compared to water/solvent mixtures (Bose et al 1999). Two 8 mL aliquots of the acidified reaction products were then supplemented with 2 mL of n-propanol before being acidolyzed.…”

Section: Alkaline Lmc-xylan Reaction and Subsequent Hydrolysis Of Lccmentioning

confidence: 99%

Inclusion of a pressurized acidolysis stage in chemical pulp bleaching

Bose

Leavitt

Stromberg

et al. 2011

BioRes

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Hardwood soda-AQ pulps are believed to be rich in benzyl sugar ethers (BSE) that can be partially cleaved by aqueous acidic treatments. The aim of this investigation was to evaluate the effect of acidolysis on final bleached brightness for kraft and soda-AQ (SAQ) hardwood pulps. The increase in final brightness due to acidolysis at 110 °C was twice as high for a eucalyptus SAQ pulp as compared to the kraft pulp. An oxygen delignified maple C-SAQ pulp (carbonate pre-treated SAQ) was acidolyzed at 120 °C and pH 2.6 for 30 min. When 1.60% ClO2 + 0.25% H2O2 on pulp was used in DEPD final bleaching of the control sample a brightness of 91.5% was achieved. When only 1.00% ClO2 + 0.25% H2O2 on pulp was used for the acidolyzed sample a brightness of 92.0% was attained. Analyses of the maple pulp after the acidolysis showed no major change in lignin content, brightness, or pulp yield. The minor changes suggest that a facile reaction such as benzyl ether cleavage was responsible for the improved bleachability. Preliminary research involving a lignin model compound and commercial birch xylan showed that lignin-carbohydrate condensation products were generated under SAQ cooking conditions. Furthermore, a fraction of these lignin-carbohydrate moieties were subsequently cleaved by acidolysis at pH 2.5 and 105 °C.

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Lignin Analysis by Permanganate Oxidation. II. Lignins in Acidic Organosolv Pulps

Cited by 12 publications

References 19 publications

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Differences in the Mechanisms of MnO₂Oxidation between Lignin Model Compounds with thep-Hydroxyphenyl, Guaiacyl, and Syringyl Nuclei

Inclusion of a pressurized acidolysis stage in chemical pulp bleaching

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Lignin Analysis by Permanganate Oxidation. II. Lignins in Acidic Organosolv Pulps

Cited by 12 publications

References 19 publications

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Analysis of products from the oxidation of technical lignins by oxygen and H3PMo12O40 in water and aqueous methanol by size-exclusion chromatography

Differences in the Mechanisms of MnO2Oxidation between Lignin Model Compounds with thep-Hydroxyphenyl, Guaiacyl, and Syringyl Nuclei

Inclusion of a pressurized acidolysis stage in chemical pulp bleaching

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Differences in the Mechanisms of MnO₂Oxidation between Lignin Model Compounds with thep-Hydroxyphenyl, Guaiacyl, and Syringyl Nuclei