A Comparison of the Reactivity and Efficiency of Ozone, Chlorine Dioxide, Dimethyldioxirane and Hydrogen Peroxide with Residual Kraft Lignin

Sun, Yuxuan; Argyropoulos, Dimitris S.

doi:10.1515/hfsg.1996.50.2.175

Cited by 42 publications

(24 citation statements)

References 10 publications

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“…The presence of carboxylic acid groups on the lignin macromolecule is considered to promote lignin solubilization in alkaline media during oxygen delignification (10,23) or other bleaching stages (25). Lignin oxidation reactions may induce the formation of carboxylic acids via a number of pathways either as monomeric fragments or functional groups attached at the end of side chains of the lignin macromolecules (12,31,32).…”

Section: Formation Of Carboxylic Acids Within Residual Kraft Ligninmentioning

confidence: 99%

Article

Asgari¹,

Argyropoulos²

1998

Can. J. Chem.

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The complex interaction of softwood residual kraft lignin with oxygen at elevated temperatures, pressures, and pH's was investigated by isolating and systematically oxidizing the lignin, as a function of time and temperature. The isolation of the oxidized lignin was carried out using a multistep procedure developed specifically to recover all species. Detailed quantitative 31 P NMR measurements provided, for the first time, three-dimensional plots describing the formation and (or) elimination of the various functional groups. Oxidative demethoxylation reactions were found to induce the formation of catechols, which are, most likely, reactive intermediates of the oxidation. The rate of carboxylic acid formation and guaiacyl phenol elimination was found to follow two distinct phases: a rapid initial phase followed by a slower phase. More specifically, the rate of carboxylic acid group formation was found to dramatically increase as the reaction temperature increased, analogous to the profiles obtained for the elimination of guaiacyl phenolic units. At reaction temperatures typical of conventional commercial oxygen delignification installations (80-100°C), only minor oxidation was found to occur within the lignin. At these temperatures, increasing the reaction time did not significantly aid the formation of carboxylic acid groups on lignin despite the idealized twophase homogeneous conditions. The technological ramifications of these data imply that a three-phase oxygen delignification system, operating at temperatures below 100°C, causes only minor oxidative changes to the structure of the lignin in the fibre. It was also possible to isolate the effect of alkali and temperature on the structure of residual kraft lignin through experiments in which pressurized oxygen was replaced by nitrogen. These data revealed a concealed set of alkali-induced condensation and fragmentation reactions.Résumé : En procédant à son isolement et son oxydation systématique en fonction du temps et de la pression, on a étudié l'interaction complexe de la lignine kraft résiduelle de bois mou avec l'oxygène à des températures, pressions et pH élevés. On a réalisé l'isolation de la lignine oxydée en appliquant une méthode en plusieurs étapes développées spécifiquement pour récupérer toutes les espèces. Des mesures quantitatives détaillées de RMN du 31 P ont permis d'obtenir pour la première fois des courbes tridimensionnelles décrivant la formation et (ou) l'élimination de divers groupes fonctionnels. On a trouvé que les réactions de déméthoxylation oxydante induisent la formation de catéchols qui sont vraisemblablement des intermédiaires réactifs dans l'oxydation. On a trouvé que la vitesse de formation de l'acide carboxylique et d'élimination de guaïacol phénolique suit deux phases distinctes : une phase initiale rapide suivie d'une phase plus lente. D'une façon plus spécifique, on a trouvé que la vitesse de formation d'acide carboxylique augmente d'une façon dramatique lorsqu'on élève la température; on a obtenu des profils analogues pour...

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Section: Formation Of Carboxylic Acids Within Residual Kraft Ligninmentioning

confidence: 99%

Article

Asgari¹,

Argyropoulos²

1998

Can. J. Chem.

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“…(Bailey and Dence 1969;Gellerstedt and Pettersson 1982;Lachenal and Papadopoulos 1988;Sun and Argyropoulos 1995) In all cases, hydrogen peroxide was found to depolymerize the lignin macromolecule in combination with oxidative degradation of phenolic structures through ring opening reactions by hydrogen peroxide decomposition products. It is now possible to examine the reactions of hydrogen peroxide under conditions representative of those used in industrial bleaching without the complication of peroxide decomposition.…”

Section: Introductionmentioning

confidence: 99%

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

Kadla¹,

Chang²,

Jameel³

1999

Holzforschung

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A technical pine kraft lignin was subjected to alkaline hydrogen peroxide oxidation in the presence of DTMPA and molecular oxygen at various temperatures. In the presence of DTMPA the lignin was found to undergo increasing levels of oxidation and degradation with increasing temperature. At 110°C over 80 % of the kraft lignin was degraded. Analyses of the degraded lignins indicated that both phenolic and nonphenolic lignin moieties were degraded. At 90°C the addition of molecular oxygen resulted in further lignin demethoxylation, but did not decrease the amount of phenolic hydroxyl groups or hydrogen peroxide consumed. In the absence of DTMPA the hydrogen peroxide was rapidly degraded, and accompanied by only minimal lignin oxidation.

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“…In earlier work we made extensive attempts to clarify the structural characteristics of residual lignin in kraft pulp (RKL, residual kraft lignin) to better understand the structural alterations that occur during pulping and bleaching processes (Jiang and Argyropoulos 1994;Granata and Argyropoulos 1995;Sun and Argyropoulos 1996;Asgari and Argyropoulos 1998;Argyropoulos and Liu 2000;Tohmura and Argyropoulos 2001;Argyropoulos et al 2002a,b;Jä ä skelä inen et al 2003;Wu and Argyropoulos 2003). The coexistence of lignins and carbohydrates is an opportunity to study the nature of lignin carbohydrate bonds on the one hand, and a challenge when lignin analysis is the focus, on the other hand.…”

Section: Introductionmentioning

confidence: 99%

Molecular weight-functional group relations in softwood residual kraft lignins

Koda¹,

Gaspar²,

Liu³

et al. 2005

Holzforschung

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An integrated picture of the distribution of functional groups should be provided as a function of molecular size within residual kraft lignins. With this goal we developed a reliable and reproducible method for determination of the molecular weight and molecular weight distribution of residual kraft lignins (RKLs) over the whole delignification range. In general, our data indicate that for reliable measurement of the molecular weight and its distribution of residual lignin in pulps, the lignin-carbohydrate bonds have to be cleaved prior to size exclusion chromatography. The recently developed method for isolating residual lignins, which involves cellulolytic treatment followed by a mild acid hydrolysis step, was found to be the most suitable approach to achieve this. The molecular weight and polydispersity of all RKLs decreased as a function of delignification. As anticipated, the observed decrease in molecular weight was clearly reflected in the concomitantly decreasing amount of b-O-4 structural linkages present. Similarly, the total phenolic hydroxyl content increased as the molecular weight of the RKLs decreased during kraft pulping. Despite the smaller size of the lignin remaining on the kraft fiber at the end of delignification, the preponderance of condensed phenolic structures within these lignins offers an explanation for delignification problems during bleaching.

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A Comparison of the Reactivity and Efficiency of Ozone, Chlorine Dioxide, Dimethyldioxirane and Hydrogen Peroxide with Residual Kraft Lignin

Cited by 42 publications

References 10 publications

Article

Article

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

Molecular weight-functional group relations in softwood residual kraft lignins

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