Delignification and cellulose degradation kinetics models for high lignin content softwood Kraft pulp during flow-through oxygen delignification

Cellulose ◽  
2015 ◽  
Vol 22 (3) ◽  
pp. 2055-2066 ◽  
Author(s):  
Vahid Jafari ◽  
Kaarlo Nieminen ◽  
Herbert Sixta ◽  
Adriaan van Heiningen
Keyword(s):  
Kraft Pulp ◽  
Lignin Content ◽  
Degradation Kinetics ◽  
Cellulose Degradation ◽  
Oxygen Delignification ◽  
Kinetics Models ◽  
Softwood Kraft Pulp ◽  
Flow Through ◽  
Cellulose Degradation Kinetics ◽  
High Lignin Content

Effect of lignin content and magnesium-to-manganese ratio on the selectivity of oxygen delignification in softwood kraft pulp

2001 ◽  
Vol 73 (12) ◽  
pp. 2059-2065
Author(s):  
Lucian A. Lucia ◽  
Rachel S. Smereck
Keyword(s):  
Chemical Process ◽  
Kraft Pulp ◽  
Lignin Content ◽  
Dry Mass ◽  
The Other ◽  
Kraft Pulps ◽  
Oxygen Delignification ◽  
Pulp Viscosity ◽  
Softwood Kraft Pulp ◽  
Temperature Time

A series of oxygen delignification experiments were performed on two softwood kraft pulps that had differing starting lignin contents. One had an initial kappa of 40 and the other 25, corresponding to lignin contents of 6% and 3.75% by dry mass, respectively. Several chemical process modifications were examined to determine their influence over the delignification selectivity and final pulp viscosity. A 2k factorial format was used to assess the significance of varying the temperature, time, and Mg/Mn ratio during the oxygen delignification of the pulps. It was found that the lower lignin content pulp displayed greater delignification selectivity than the higher lignin content pulp. Kappa numbers, viscosity values, and ICP metals contents were determined and are the basis of discussion for the results obtained.

Elucidating carboxylic acid profiles for extended oxygen delignification of high-kappa softwood kraft pulps

Holzforschung ◽  
2006 ◽  
Vol 60 (2) ◽  
pp. 123-129 ◽  
Author(s):  
Dongcheng Zhang ◽  
Yunqiao Pu ◽  
Xing-Sheng Chai ◽  
Ved Naithani ◽  
Hasan Jameel ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Acid Content ◽  
Kraft Pulp ◽  
Lignin Content ◽  
Acid Group ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Oxygen Delignification ◽  
Acid Ratio ◽  
Softwood Kraft Pulp

Abstract Two laboratory high-lignin-content softwood (SW) kraft pulps with kappa values of 48.0 and 49.5, prepared by cooking at high and low active alkali (AA), were used for the study of fiber charge development during two-stage oxygen delignification with inter-stage washing (OwO). It was established that the first oxygen delignification (O) stage increased total fiber charge by 2–4%, and further O-delignification via a second O-stage led to a 3–18% decrease in total fiber charge. Carboxylic acid content in pulp holocelluloses decreased by 12–26% with respect to a 35–70% kappa number reduction due to an O and OwO stage of delignification for high and low AA cooked SW kraft pulps. After an OwO-stage delignification, the residual lignin was found to exhibit a 50–100% increase in carboxylic acid content. 13C NMR spectral data for the residual lignin samples indicated that the unconjugated/conjugated acid ratio was approximately (3–4):1. Generally, the carboxylic acid content in low AA cooked softwood kraft pulp and the corresponding oxygen-delignified pulps was systematically higher (13–23%) than that in high AA cooked SW kraft pulp and the corresponding oxygen-delignified pulps. The experimental results also demonstrated that maximum acid-group content in total fiber occurred after 45–50% oxygen delignification of the SW kraft pulps studied.

Biobleaching chemistry of laccase-mediator systems on high-lignin-content kraft pulps

2004 ◽  
Vol 82 (2) ◽  
pp. 344-352 ◽  
Author(s):  
Fadi S Chakar ◽  
Arthur J Ragauskas
Keyword(s):  
Kraft Pulp ◽  
Structural Changes ◽  
Lignin Content ◽  
Kraft Pulps ◽  
Carboxylic Acid Groups ◽  
Violuric Acid ◽  
Mediator Systems ◽  
Before And After ◽  
Softwood Kraft Pulp ◽  
High Lignin Content

A high-lignin-content softwood kraft pulp was reacted with laccase in the presence of 1-hydroxybenzotriazole (HBT), N-acetyl-N-phenylhydroxylamine (NHA), and violuric acid (VA). The biodelignification response with violuric acid was superior to both 1-hydroxybenzotriazole and N-acetyl-N-phenylhydroxylamine. NMR analysis of residual lignins isolated before and after the biobleaching treatments revealed that the latter material was highly oxidized and that the magnitude of structural changes was most pronounced with the laccase – violuric acid biobleaching system. An increase in the content of carboxylic acid groups and a decrease in methoxyl groups were noted with all three laccase-mediator systems. The oxidation biobleaching pathway is directed primarily towards noncondensed C5 phenolic lignin functional structures for all three laccase-mediated systems. The laccase – violuric acid system was also reactive towards C5-condensed phenolic lignin structures.Key words: laccase, mediator, lignin, pulp, biobleaching, phenolics.

Lignin modification in the initial phase of softwood kraft pulp delignification with polyoxometalates (POMs)

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 492-498 ◽  
Author(s):  
Biljana Bujanovic ◽  
Sally A. Ralph ◽  
Richard S. Reiner ◽  
Rajai H. Atalla
Keyword(s):  
Kraft Pulp ◽  
Lignin Content ◽  
Kappa Number ◽  
Ring Cleavage ◽  
Residual Lignin ◽  
Glucose Content ◽  
Lower Glucose ◽  
Softwood Kraft Pulp ◽  
Alkaline Conditions ◽  
Extraneous Material

Abstract Commercial softwood kraft pulp with kappa number 30.5 (KP30.5) was delignified with polyoxometalates (POM, Na5(+2)[SiV1(-0.1)MoW10(+0.1)O40]), and POM-treated kraft pulp of kappa number 23.6 was obtained (KPPOM,23.6). Residual lignin from pulps was isolated by mild acid hydrolysis and characterized by analytical and spectral methods to gain insight into lignin reactions taking place during the initial delignification phase. Lignin from POM-delignified pulp was isolated in lower yield. Comparative analysis of residual lignins (RL-KP30.5, RL-KPPOM,23.6) showed that POM leads to products enriched in carbonyl/carboxyl groups and carbohydrates. POM lignins have a lower molecular mass and a lower content of phenolic hydroxyl and methoxyl groups. Based on these results and FTIR spectra, we suggest that aromatic ring cleavage and quinone formation occur during POM delignification. The degree of lignin-cellulose association increases after POM delignification. Lignin-cellulose association was found to be partially unstable under mild alkaline conditions, as residual lignin isolated after alkaline extraction of KPPOM,23.6 pulp (RL-KPPOM/NaOH) exhibited lower glucose content, higher Klason lignin content, and less extraneous material.

Changes in the lignin-carbohydrate complex in softwood kraft pulp during kraft and oxygen delignification

Holzforschung ◽  
2004 ◽  
Vol 58 (6) ◽  
pp. 603-610 ◽  
Author(s):  
Martin Lawoko ◽  
Rickard Berggren ◽  
Fredrik Berthold ◽  
Gunnar Henriksson ◽  
Göran Gellerstedt
Keyword(s):  
Kraft Pulp ◽  
Kappa Number ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Oxygen Delignification ◽  
Number Range ◽  
Morphological Aspects ◽  
Carbohydrate Complex ◽  
Softwood Kraft Pulp ◽  
Hydrolysis Of

Abstract Three kraft pulps in the kappa number range between 50 and 20 and the same pulps oxygen-delignified to similar lignin contents (kappa approximately 6) were analyzed for lignin-carbohydrate complexes (LCC) by a method based on selective enzymatic hydrolysis of the cellulose, and quantitative fractionation of the LCC. Between 85 and 90% of residual lignin in the unbleached kraft pulp and all residual lignin in the oxygen-delignified pulps were isolated as LCC. Three types of complexes were found; viz., xylan-lignin, glucomannan-lignin-xylan and glucanlignin complexes. After pulping to a high kappa number, most of the residual lignin was linked to xylan. Different delignification rates were observed so that most of the residual lignin was linked to glucomannan when the pulping was extended to a low kappa number. With increasing degree of oxygen delignification, a similar trend in the delignification rates of LCC was observed so that the residual lignin was increasingly linked to glucomannan. Complex LCC network structures seemed to be degraded into simpler structures during delignification. The differences in delignification rates are discussed with reference to the solubility properties and structural differences of LCC, and to morphological aspects of the pulp.

Real wash loss compounds in oxygen delignification of softwood kraft pulp

2004 ◽  
Vol 19 (2) ◽  
pp. 264-270 ◽  
Author(s):  
Minna Sankari ◽  
Kari Ala-Kaila ◽  
Olli Dahl ◽  
Paavo Perämäki
Keyword(s):  
Kraft Pulp ◽  
Oxygen Delignification ◽  
Softwood Kraft Pulp

scholarly journals Limitations on the protective action of MgSO4 for cellulose during kraft pulp oxygen delignification

BioResources ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. 1438-1452
Author(s):  
Hai Huang ◽  
Yuantao Hu ◽  
Hui Zhang ◽  
Shilin Cao ◽  
Xiaojuan Ma
Keyword(s):  
Adverse Effects ◽  
Trace Metal ◽  
Metal Ions ◽  
Kraft Pulp ◽  
Cellulose Degradation ◽  
Protective Action ◽  
Oxygen Delignification ◽  
Negative Effects ◽  
Trace Metal Ions ◽  
Factors Influencing

Magnesium sulfate (MgSO4) is the most widely used protector for alleviating the effects that metal ions have on cellulose degradation. However, the efficiency of MgSO4 is limited by the oxygen delignification conditions. This work discusses the factors influencing MgSO4 efficiency in terms of cellulose protection and delignification. The type and concentration of metal ions, delignification rate, additions order, and mixing degree of MgSO4 should affect the cellulose degradation during oxygen delignification in the presence of MgSO4. The most adverse effects on cellulose are observed with Mn2+ and Fe2+ ions followed by Cu2+ and Fe3+. MgSO4 addition can diminish such negative effects; however the protection becomes reduced in the presence of higher concentrations of metal ions. In addition, the optimum MgSO4 application level is closely dependent on the delignification rate and metal ions concentration. Adding MgSO4 is optional for pulps with trace metal ions at relatively low delignification levels, but it is essential for pulps with concentrated metal ions or when the oxygen delignification rate is relatively high. More simply, when the added MgSO4 is thoroughly mixed with the pulp before the addition of NaOH, it exhibits a prominent effect on cellulose protection.

Selectivity of oxygen delignification for southern softwood kraft pulps with high lignin content

TAPPI Journal ◽  
2011 ◽  
Vol 10 (8) ◽  
pp. 29-39 ◽  
Author(s):  
LI TAO ◽  
JOSEPH M. GENCO ◽  
BARBARA J.W. COLE ◽  
RAYMOND C. FORT
Keyword(s):  
Hydroxyl Radicals ◽  
Lignin Content ◽  
Degree Of Polymerization ◽  
Kraft Pulping ◽  
Kraft Pulps ◽  
Oxygen Delignification ◽  
Kraft Process ◽  
Carbohydrate Degradation ◽  
Polymeric Chains ◽  
High Lignin Content

The selectivity of kraft pulping versus the oxygen delignification processes over the range of kappa nos. 25–90 was compared. Kraft pulping was found to be more selective than oxygen delignification for removing lignin from southern softwood kraft pulps. The greater selectivity is thought to be related to hydroxyl radicals that form in the oxygen delignification process that are not present in the kraft process. The hydroxyl radicals attack the carbohydrates and randomly cleave the polymeric chains, causing a significant decrease in the degree of carbohydrate polymerization and thus a loss of viscosity. Kraft pulping generates hydrosulfide ions that are highly selective and attack the lignin. Carbohydrate degradation occurs mainly from peeling reactions, which do not appreciably reduce the degree of polymerization of the cellulose and thus there is less viscosity loss. At low lignin content (i.e., low kappa number), the remaining lignin is likely bound covalently to the carbohydrate portion in both processes. Therefore, removal of the lignin results in significant degradation of the carbohydrates.

Alkaline steeping of dissolving pulp. Part I: cellulose degradation kinetics

Cellulose ◽  
2013 ◽  
Vol 20 (3) ◽  
pp. 1437-1451 ◽  
Author(s):  
Danuta Joanna Mozdyniewicz ◽  
Kaarlo Nieminen ◽  
Herbert Sixta
Keyword(s):  
Degradation Kinetics ◽  
Cellulose Degradation ◽  
Dissolving Pulp ◽  
Cellulose Degradation Kinetics
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