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

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.

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.

scholarly journals Effects of Manganese Peroxidase on Residual Lignin of Softwood Kraft Pulp

1998 ◽  
Vol 64 (6) ◽  
pp. 2273-2274 ◽  
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.

High-consistency ozonation of hardwood kraft pulp

Holzforschung ◽  
2006 ◽  
Vol 60 (6) ◽  
pp. 685-690 ◽  
Author(s):  
Ai Van Tran
Keyword(s):  
Kraft Pulp ◽  
Kappa Number ◽  
Second Phase ◽  
Residual Lignin ◽  
Two Phase ◽  
Elemental Chlorine ◽  
Ozonation Time ◽  
Shrinking Core ◽  
High Consistency ◽  
Hexenuronic Acid

Abstract At present, ozone is one of the main chemicals in elemental chlorine-free (ECF) and totally chlorine-free (TCF) bleaching sequences. High consistency (HC) and medium consistency (MC) technologies are in use. This study shows that HC ozonation of hardwood kraft pulp, as expressed by the overall kappa number encompassing both hexenuronic acid groups and residual lignin, is a two-phase path. The reaction rate of the first phase is two- to three-fold higher than that of the second phase. We propose that the first phase is due to ozonation of both hexenuronic acid groups and residual lignin, whereas the second phase involves only residual lignin. The fiber width and wall thickness were relatively unchanged during ozonation. These results are in contrast to the “shrinking core kinetic model” frequently discussed in the context of HC ozonation. The development of pulp brightness and the decrease in pulp viscosity with the ozonation time are well correlated with the overall kappa number or the kappa number due to residual lignin alone.

Isolation of residual lignin from softwood kraft pulp. Advantages of the acetic acid acidolysis method

2004 ◽  
Vol 327 (9-10) ◽  
pp. 911-916 ◽  
Author(s):  
Dominique Lachenal ◽  
Gérard Mortha ◽  
Rose-Marie Sevillano ◽  
Michail Zaroubine
Keyword(s):  
Acetic Acid ◽  
Kraft Pulp ◽  
Residual Lignin ◽  
Softwood Kraft Pulp

Voltammetric analysis of the bleachability of softwood kraft pulps

Holzforschung ◽  
2004 ◽  
Vol 58 (6) ◽  
pp. 581-587 ◽  
Author(s):  
Robert Bourbonnais ◽  
Loredana Valeanu ◽  
Michael G. Paice
Keyword(s):  
Chlorine Dioxide ◽  
Acid Content ◽  
Black Spruce ◽  
Kappa Number ◽  
Western Hemlock ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Redox Mediators ◽  
Voltammetric Analysis ◽  
Hexenuronic Acid

Abstract Kraft and oxygen delignified pulps with various kappa numbers were prepared from black spruce and western hemlock chips. The bleachability (ratio of kappa number decrease to chlorine dioxide applied) of the different pulps at the same kappa number varied with both wood furnish and delignification process. Thus, unbleached kappa number alone is not a reliable indicator of bleachability for these pulps. This may be due in part to the variable hexenuronic acid content of the pulps; those with higher ratio of hexenuronic acid content to kappa number (HexA/kappa) are harder to bleach. Voltammetric analysis of the same kraft pulps in the presence of redox mediators was found to measure both the content and reactivity of residual lignin. Peak current ratios of redox mediators correlated with pulp bleachability for all pulps. These ratios may therefore provide a more accurate prediction of bleachability than unbleached kappa number.

Hydrogen peroxide and supercritical carbon dioxide: a new bleaching stage for Eucalyptus kraft-O2 pulps

Holzforschung ◽  
2011 ◽  
Vol 65 (3) ◽  
Author(s):  
Roberta Pacheco Francisco ◽  
Jorge Luiz Colodette ◽  
Antonio Aprigio da Silva Curvelo
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Peroxide ◽  
Supercritical Carbon Dioxide ◽  
Kraft Pulp ◽  
Poor Performance ◽  
Kappa Number ◽  
Elemental Chlorine ◽  
Chlorine Gas ◽  
Hexenuronic Acid ◽  
Supercritical Carbon

Abstract Kraft pulp is currently bleached largely by the elemental chlorine free (ECF) technology with oxygen, chlorine dioxide, and hydrogen as active agents. This technology brought about significant environmental improvements in relation to standard processes based on chlorine gas and hypochlorite, but there is still need for further improvements. This study presents a novel environmentally friendly bleaching stage – the so-called ‘hydrogen peroxide in supercritical carbon dioxide’, P(SC-CO2) – that can be adapted to current ECF bleaching processes, with preference in cases where hydrogen peroxide is already used. In this study, the P(SC-CO2) stage was evaluated as a replacement to the last peroxide stage of the D(EP)DP bleaching sequence and to the first peroxide stage of the D(EP)DP sequence, for an oxygen delignified eucalypt kraft-O2 pulp. The P(SC-CO2) stage was run with 0.5% hydrogen peroxide, at 15% consistency, 70°C, and 73 bar. The reaction time was 30 min. The performances of regular P stages and the new P(SC-CO2) stage were compared. Promising results were observed with the DEP(SC-CO2)DP sequence; the P(SC-CO2) decreased kappa number from 2.7 to 2.1, and the hexenuronic acid groups from 17.0 to 12.4 mmol kg-1. The P(SC-CO2) stage showed poor performance when applied in the D(EP)DP(SC-CO2) sequence. It is concluded that the process presents potential but requires further optimization to improve selectivity and efficiency.

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