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

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.

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

Holzforschung ◽

10.1515/hf.2004.114 ◽

2004 ◽

Vol 58 (6) ◽

pp. 603-610 ◽

Cited By ~ 48

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.

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

Holzforschung ◽

10.1515/hf.1999.069 ◽

1999 ◽

Vol 53 (4) ◽

pp. 416-422 ◽

Cited By ~ 12

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

Pure and Applied Chemistry ◽

10.1351/pac200173122059 ◽

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.

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

Holzforschung ◽

10.1515/hf.2007.102 ◽

2007 ◽

Vol 61 (5) ◽

pp. 492-498 ◽

Cited By ~ 2

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.

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Factors limiting oxygen delignification of kraft pulp

Canadian Journal of Chemistry ◽

10.1139/v01-007 ◽

2001 ◽

Vol 79 (2) ◽

pp. 201-210 ◽

Cited By ~ 9

Author(s):

Leonid G Akim ◽

Jorge Luiz Colodette ◽

Dimitris S Argyropoulos

Keyword(s):

Kraft Pulp ◽

Oxidation Mechanism ◽

Quantitative Information ◽

Total Phenolic ◽

Residual Lignin ◽

Analytical Pyrolysis ◽

Oxygen Delignification ◽

Softwood Kraft Pulp ◽

Major Factors ◽

C Nmr

Softwood kraft pulp was subjected to a laboratory one- and three-stage oxygen delignification process. Pulp and liquor samples were collected at different stages of the process with particular attention being paid to the early and late stages. A novel residual lignin isolation method extracted about 65% of the oxidized residual lignins at a purity exceeding 90%. Using this methodology coupled to quantitative 31P NMR, 13C NMR, 2D heteronuclear (HMQC) NMR spectroscopic and analytical pyrolysis techniques allowed a thorough characterization of the residual and solubilized lignin fractions at the various stages of the process. Our conclusions do not point to a single factor as being responsible for the limits confronting oxygen delignification. Amongst the major factors impeding the effectiveness of oxygen delignification are: (i) the accumulation of relatively inert 5,5' biphenyl structures originally present in kraft lignin from dibenzodioxocin ring opening reactions; and (ii) the accumulation of considerably less reactive p-hydroxyphenyl structures. Detailed quantitative information was obtained and discussed in relation to the presence and role of these unreactive phenolic fractions on the residual oxidized lignins. As such we arrived at important conclusions as to why and how these structures remain and accumulate on the fiber. In addition, issues related to the profiles of the total phenolic hydroxyl content of the residual lignins and the remaining arylglycerol β-O-4 structures are discussed.Key words: analytical pyrolysis, biphenyl structures, HMQC, NMR, oxidation mechanism, oxygen delignification, p-hydroxyphenyl moieties, quantitative 13C NMR, quantitative 31P NMR, residual lignin, solubilized lignin, total phenolic hydroxyls.

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

Cellulose ◽

10.1007/s10570-015-0593-3 ◽

2015 ◽

Vol 22 (3) ◽

pp. 2055-2066 ◽

Cited By ~ 5

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

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

Canadian Journal of Chemistry ◽

10.1139/v03-195 ◽

2004 ◽

Vol 82 (2) ◽

pp. 344-352 ◽

Cited By ~ 24

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.

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

TAPPI Journal ◽

10.32964/tj9.9.47 ◽

2010 ◽

Vol 9 (9) ◽

pp. 47-53 ◽

Cited By ~ 2

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.

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Deep eutectic solvent delignification: Impact of initial lignin

BioResources ◽

10.15376/biores.12.4.7301-7310 ◽

2017 ◽

Vol 12 (4) ◽

pp. 7301-7310

Author(s):

Veronika Majová ◽

Silvia Horanová ◽

Andrea Škulcová ◽

Jozef Šima ◽

Michal Jablonský

Keyword(s):

Lactic Acid ◽

Oxalic Acid ◽

Lignin Content ◽

Choline Chloride ◽

Deep Eutectic Solvent ◽

Deep Eutectic Solvents ◽

Kappa Number ◽

Kraft Pulps ◽

Oxygen Delignification ◽

Detailed Understanding

This study aimed to resolve the issue of the lack of detailed understanding of the effect of initial lignin content in hardwood kraft pulps on pulp delignification by deep eutectic solvents. The authors used Kappa number of the concerned pulp, intrinsic viscosity, and selectivity and efficiency of delignification as the parameters of the effect. The pulp (50 g oven dry pulp) was treated with four different DESs systems based on choline chloride with lactic acid (1:9), oxalic acid (1:1), malic acid (1:1), and system alanine:lactic acid (1:9); the results were compared to those reached by oxygen delignification. The results showed that the pulp with a higher initial lignin content had a greater fraction of easily removed lignin fragments.

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