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

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

Holzforschung ◽

10.1515/hf.2006.020 ◽

2006 ◽

Vol 60 (2) ◽

pp. 123-129 ◽

Cited By ~ 8

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.

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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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Effects of Manganese Peroxidase on Residual Lignin of Softwood Kraft Pulp

Applied and Environmental Microbiology ◽

10.1128/aem.64.6.2273-2274.1998 ◽

1998 ◽

Vol 64 (6) ◽

pp. 2273-2274 ◽

Cited By ~ 21

Author(s):

Ian D. Reid ◽

Michael G. Paice

Keyword(s):

Manganese Peroxidase ◽

Kraft Pulp ◽

Kappa Number ◽

Residual Lignin ◽

Softwood Kraft Pulp

ABSTRACT Manganese peroxidase treatment lowered the kappa number of kraft pulp and increased the alkali extractability of the residual lignin but did not directly solubilize it. This indicates that MnP partially oxidizes the lignin in the pulp but does not degrade it to soluble fragments.

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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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An improved procedure for isolation of residual lignins from hardwood kraft pulps

Holzforschung ◽

10.1515/hf.2004.070 ◽

2004 ◽

Vol 58 (5) ◽

pp. 464-472 ◽

Cited By ~ 10

Author(s):

Ewellyn Augsten Capanema ◽

Mikhail Yurievich Balakshin ◽

Chen-Loung Chen

Keyword(s):

Molecular Mass ◽

Nitrogen Content ◽

Mass Distribution ◽

Kraft Pulp ◽

Molecular Mass Distribution ◽

Eucalyptus Grandis ◽

Kraft Pulps ◽

Carbohydrate Composition ◽

Residual Lignin ◽

Hydrolysis Of

Abstract Residual lignin preparations were isolated from birch, aspen and Eucalyptus grandis kraft pulp by enzymatic hydrolysis of the pulps with cellulase:hemicellulase mixture. Residual lignin preparations were characterized by investigation of nitrogen content, carbohydrate composition and molecular mass distribution. The use of enzyme with high activity and optimization of enzyme charge resulted in significant decrease in protein contaminants in residual lignin preparations as compared to previously published results. A second order law correlation between enzyme mass charge and nitrogen content in birch residual lignin preparations indicates a strong effect of enzyme charge on the amount of protein contaminants. However, the enzyme charge in the range studied does not appreciably affect either the yields of the residual lignin preparations or percentage and composition of carbohydrates in these preparations. The optimal enzyme charge was highest for Eucalyptus grandis pulp and lowest for birch pulp. It has been suggested that a significant part of the hardwood residual lignin in pulps, especially in E. grandis pulp, consists of low molecular mass lignin fragments bonded to pulp carbohydrates. Higher amount of glucose in E. grandis residual lignin preparation compared to those from birch and aspen implied a higher frequency of lignin-cellulose bonds in eucalypt pulp. Different fractions of birch residual lignin have rather similar molecular mass distribution, which was not affected by the charge of the enzyme. Eucalypt residual lignin preparation had higher molecular mass than birch residual lignin.

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Bleached kraft pulp production from Pinus tecunumanii (Eguiluz e Perry)

Revista Árvore ◽

10.1590/s0100-67622005000300017 ◽

2005 ◽

Vol 29 (3) ◽

pp. 489-494 ◽

Cited By ~ 2

Author(s):

Leonel F. Torres ◽

Roberto Melo ◽

Jorge Luiz Colodette

Keyword(s):

Kraft Pulp ◽

Strength Properties ◽

Kappa Number ◽

Raw Material ◽

Kraft Pulps ◽

Optimum Conditions ◽

Oxygen Delignification ◽

Bleached Kraft Pulp ◽

Pinus Tecunumanii ◽

Pulp Production

The use of 12-year-old Pinus tecunumanii (Eguiluz e Perry) grown in Colombia was evaluated for bleached kraft pulp production. Kraft pulps of kappa number 30 ± 1 were produced, and oxygen delignified and bleached to 90% ISO with ECF processes. The bleached pulps produced under optimum conditions were evaluated with regard to their strength properties. Pinus tecunumanii wood required low effective alkali charge to reach the desired kappa number and the unbleached pulp showed high oxygen delignification efficiency and bleachability when a OD(EO)DED sequence was used. The bleached pulps presented good physical-mechanical properties, which are comparable to those obtained with more traditional pines such as Pinus taeda and Pinus radiata. The results demonstrate that this tropical pine species is a suitable raw material for bleached kraft pulp production

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Assessment of Q(OP)D(PO) bleachability of softwood kraft pulp

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2021-0022 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Sara Starrsjö ◽

Maria Boman ◽

Olena Sevastyanova ◽

Mikael E. Lindström ◽

Juha Fiskari

Keyword(s):

Kraft Pulp ◽

Kappa Number ◽

Carbohydrate Content ◽

Residual Lignin ◽

Three Samples ◽

Softwood Kraft Pulp ◽

Pulp Sample ◽

Yield Gain ◽

Hexenuronic Acid

Abstract Bleachability is evaluated as how easily a pulp sample is bleached and it depends on the structure of residual lignin and carbohydrates. Also, the bleachability varies depending on the bleaching sequence. ECF light sequences have been improved significantly in the recent years. However, we still don’t fully understand how ECF light bleach plants are optimally run. This work studies the bleachability of softwood kraft pulp in an ECF light bleaching sequence, (OO)Q(OP)D(PO). Three pulp samples with brown stock kappa number 27, 32 and 35 were bleached and studied for residual lignin, hexenuronic acid and carbohydrate content. It was found that in the bleaching stages that are highly delignifying, it is beneficial with a higher kappa number for the delignifying bleachability. However, in the bleaching stages where the objective is brightness increase, the brightness gain bleachability is improved by a lower kappa number. We also intended to determine which of the three samples had the best suited kappa number for this particular bleaching sequence. According to our results, the bleaching was most effective with kappa number around 32. Although an even higher kappa number resulted in higher yield after cooking, it seemed that this bleaching sequence cannot preserve the yield gain.

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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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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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