Dihydroxybenzenes: driven Fenton reactions

2001 ◽  
Vol 44 (5) ◽  
pp. 251-256 ◽  
Author(s):  
J. Rodríguez ◽  
C. Parra ◽  
D. Contreras ◽  
J. Freer ◽  
J. Baeza
Keyword(s):  
Fenton Reaction ◽  
Model Compound ◽  
Molecular Mass Distribution ◽  
Veratryl Alcohol ◽  
Oxidation Potential ◽  
Dihydroxybenzoic Acid ◽  
Pulp Bleaching ◽  
Lignin Model Compound ◽  
Cellulose Pulp ◽  
Lignin Model

Different compounds that reduce Fe(III) and that simultaneously increase the oxidation potential of the H2O2/Fe2+ system, have been evaluated. In this work, the improving of Fenton reactions by 2,3-dihydroxybenzoic acid (2,3-DHBA), 3,4-dihydroxybenzoic acid (3,4-DHBA) or 1,2-dihydroxybenzene (CAT) were studied. The three compounds are able to reduce Fe(III) to Fe(II), but the kinetic results depend on the method used to determine the Fe(II) ion. The dihydroxybenzenes (DHBs) degrades veratryl alcohol (VA), a lignin model compound, to a greater extent than observed in a typical Fenton reaction. The rate of VA degradation was associated with the duration of the chemiluminescence (CAT > 2,3-DHBA > 3,4-DHBA) and not with the sum of integrated counts. The treatment of a cellulose pulp bleaching effluent with DHBs/Fe(III)/H2O2 was evaluated by analyzing their depolymerization at pH 4 and 7 through molecular mass distribution determinations.

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

2012 ◽  
Vol 90 (1) ◽  
pp. 60-70 ◽  
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.

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.

scholarly journals Inclusion of a pressurized acidolysis stage in chemical pulp bleaching

BioResources ◽  
2011 ◽  
Vol 6 (1) ◽  
pp. 823-840
Author(s):  
Samar K. Bose ◽  
Aaron Leavitt ◽  
Bertil Stromberg ◽  
Dipankar Kanungo ◽  
Raymond C. Francis
Keyword(s):  
Kraft Pulp ◽  
Model Compound ◽  
Lignin Content ◽  
Control Sample ◽  
Major Change ◽  
Pulp Yield ◽  
Pulp Bleaching ◽  
Lignin Model Compound ◽  
Chemical Pulp ◽  
Lignin Model

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.

scholarly journals Biomimetic Catalysts for Oxidation of Veratryl Alcohol, a Lignin Model Compound

Catalysts ◽  
2013 ◽  
Vol 3 (1) ◽  
pp. 232-246 ◽  
Author(s):  
Gustavo González-Riopedre ◽  
María Fernández-García ◽  
Esther Gómez-Fórneas ◽  
Marcelino Maneiro
Keyword(s):  
Model Compound ◽  
Veratryl Alcohol ◽  
Lignin Model Compound ◽  
Biomimetic Catalysts ◽  
Lignin Model

Keggin Type‐Polyoxometalate Decorated Ruthenium Nanoparticles: Highly Active and Selective Nanocatalyst for the Oxidation of Veratryl Alcohol as a Lignin Model Compound

2017 ◽  
Vol 2 (8) ◽  
pp. 2487-2494 ◽  
Author(s):  
Ismail Burak Baguc ◽  
Serif Saglam ◽  
Ilknur Efecan Ertas ◽  
Muhammed Nuri Keles ◽  
Metin Celebi ◽  
...  
Keyword(s):  
Model Compound ◽  
Veratryl Alcohol ◽  
Ruthenium Nanoparticles ◽  
Lignin Model Compound ◽  
Keggin Type ◽  
Highly Active ◽  
Lignin Model

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.

scholarly journals 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−

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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