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.

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.

The Kismet of Residual During LMS Delignification of High-Kappa Kraft Pulps

Holzforschung ◽  
2000 ◽  
Vol 54 (6) ◽  
pp. 647-653 ◽  
Author(s):  
F.S. Chakar ◽  
A.J. Ragauskas
Keyword(s):  
Spectral Analysis ◽  
Carboxylic Acid ◽  
Kraft Pulp ◽  
Structural Changes ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Alkaline Extraction ◽  
Kraft Pulps ◽  
Before And After ◽  
Phenolic Hydroxyl Groups

SummaryA series of laccase-mediator treatments (LMS) with 1-hydroxybenzotriazole (HBT) andN-acetyl-Nphenylhydroxylamine(NHAA) (Fig. 1) as the mediators were performed on a laboratory prepared southern softwood conventional kraft pulp (kappa # 75.4). Subsequent to the LMS treatments, the treated pulps were subjected to various oxidatively reinforced alkaline extraction stages (E*). The kappa results suggested that both LMSHBTand LMSNHAAtreatments delignified this high-kappa pulp. The E* stages were beneficial in countering the darkening effect observed after the LMS treatments. Structural changes in residual lignins isolated before and after laccase-mediator (LMSNHAA(E*) and LMSHBT(E*)) treatments were explored. The spectral analysis of phosphitylated residual lignins revealed an increase in carboxylic acid content and a depletion of phenolic hydroxyl groups in non-condensed at C-5 lignin moieties. Aliphatic hydroxyl groups were substantially decreased when NHAA was used. Overall, it appears that LMSHBTand LMsNHAAtreatments on high-kappa kraft pulps primarily attack phenolic hydroxyl groups in non-condensed at C-5 lignin structures.

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.

Optimization of elemental chlorine-free bleaching for a softwood kraft pulp • part 2: economic analysis of chemical and steam consumption

TAPPI Journal ◽  
2010 ◽  
Vol 9 (9) ◽  
pp. 47-53 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Chlorine Dioxide ◽  
Previous Investigation ◽  
Kraft Pulp ◽  
Energy Costs ◽  
Alkaline Extraction ◽  
Stage Versus ◽  
Kraft Pulps ◽  
Steam Consumption ◽  
Elemental Chlorine ◽  
Softwood Kraft Pulp

Our previous investigation [1] re-analyzed the data from Basta and co-workers (1992 TAPPI Pulping Conference) to demonstrate how oxidative alkaline extraction can be augmented and how these changes affect chlorine dioxide consumption with elemental chlorine-free (ECF) sequences. The current study manipulates extraction delignification variables to curtail bleaching costs with a conventional U.S. Southern softwood kraft pulp. The economic advantages of ~0.35% to 0.65% H2O2 peroxide reinforcement in a 70°C (EOP)-stage versus 90°C (EO)-stage are predisposed to the brightness targets, to short or long bleach sequences, and to mill energy costs. Minimized bleaching costs are generally realized when a 90°C (EO) is employed in D0(EO)D1 bleaching, whereas a 70°C (EOP) is economically advantageous for D0(EOP)D1E2D2 bleaching. The findings we disclose here help to clarify previous ECF optimization studies of conventional softwood kraft pulps.

Investigations into Laccase-Mediator Delignification of Kraft Pulps

Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 498-502 ◽  
Author(s):  
J. Sealey ◽  
A.J. Ragauskas ◽  
T.J. Elder
Keyword(s):  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Kraft Pulp ◽  
Substituent Effects ◽  
Computational Results ◽  
Kraft Pulps ◽  
Bond Dissociation ◽  
Structure Activity ◽  
Softwood Kraft Pulp

SummaryThe structure activity effects of 1-hydroxy benzotriazole and phthalimide derivatives as mediators for laccase were studied. Using a softwood kraft pulp it was shown that the N-hydroxy unit is a key component of 1-hydroxybenzotriazole for efficient laccase mediator delignification to occur. It was also found that the 1-hydroxybenzotriazole structure was very sensitive to substituent effects with respect to laccase-mediator delignification. Computational results from PM3 indicate that the bond dissociation energy, and electronic factors of the radical may contribute to the efficiency of the mediator for LMS delignification.

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.

Oxygen Delignification of High-Yield Kraft Pulp. Part I: Structural Properties of Residual Lignins

Holzforschung ◽  
1999 ◽  
Vol 53 (4) ◽  
pp. 416-422 ◽  
Author(s):  
Størker T. Moe ◽  
Arthur J. Ragauskas
Keyword(s):  
Carboxylic Acid ◽  
Acid Hydrolysis ◽  
Extraction Method ◽  
Kraft Pulp ◽  
Kraft Pulping ◽  
High Yield ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Oxygen Delignification ◽  
Carboxylic Acid Groups

Summary The chemistry of oxygen delignification of high-yield kraft pulp was studied by analysis of residual lignin extracted from kraft and kraft-oxygen pulps using the acid hydrolysis/dioxane extraction method. For reference pulps cooked to kappa numbers between 20 and 25, the content of free phenolic groups decreased to about 50% the original value upon oxygen delignification, while the content of carboxylic acid groups increased by 50–100%. For lignins isolated from high-yield kraft pulp and oxygen delignified high-yield kraft pulp, it was shown that high-yield kraft pulping with polysulfide (PS) and anthraquinone (AQ) gives a residual lignin which is chemically different from that of kraft pulps cooked to lower kappa numbers. Lignin extracted from oxygen delignified high-yield PS/AQ kraft pulp was more similar to lignins extracted from kraft pulps cooked to lower kappa numbers.

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