Oxidized Derivatives of Lipophilic Extractives Formed during Hardwood Kraft Pulp Bleaching

Summary The structural changes of E. globulus wood extractives during bleaching with chlorine dioxide (D), oxygen (O), ozone (Z) and hydrogen peroxide (P) were studied. The detailed characterisation of the extractive derivatives detected in the partially bleached D, O, P and Z pulps was achieved by performing reactions of pure reference compounds with the different bleaching agents. The results show that the unsaturated sterols and fatty acids are extensively degraded during chlorine dioxide and ozone bleaching and only partially degraded during oxygen and hydrogen peroxide bleaching. The corresponding saturated extractives as well as the long chain aliphatic alcohols and ω-hydroxyfatty acids were stable during bleaching. The main oxidation products of β-sitosterol and oleic and linoleic acids, including one chlorinated derivative of linoleic acid, were identified here for the first time in E. globulus bleached pulps and bleaching filtrates.

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Application of a Catalyst in Peroxide Bleaching of Eucalyptus Kraft Pulp

Holzforschung ◽

10.1515/hf.2000.068 ◽

2000 ◽

Vol 54 (4) ◽

pp. 407-412 ◽

Cited By ~ 8

Author(s):

L. Kühne ◽

J. Odermatt ◽

T. Wachter

Keyword(s):

Hydrogen Peroxide ◽

Kraft Pulp ◽

Pulp Bleaching ◽

Selective Catalyst ◽

Peroxide Bleaching ◽

Softwood Pulp ◽

Kraft Pulp Bleaching ◽

Eucalyptus Kraft Pulp ◽

Softwood Kraft Pulp

Summary A binuclear [Mn(III)Mn(IV)(μ-O)2(μ-CH3COO)L](ClO4−)2 complex with L = 1,2 Bis-(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)-ethane, described as a selective catalyst in hydrogen peroxide bleaching of softwood pulps, was tested in hardwood kraft pulp bleaching. The catalyst application gave rise to a higher consumption of peroxide which resulted in higher pulp brightness. The delignification improvement caused by the catalyst was shown to be much lower compared to catalysed peroxide bleaching of softwood kraft pulp. In contrast to the results of softwood pulp bleaching no selectivity improvements could be found when using the catalyst in bleaching of eucalyptus kraft pulp.

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Kraft pulp bleaching with a P-stage catalyzed by both bicarbonate and TAED

TAPPI Journal ◽

10.32964/tj18.7.409 ◽

2019 ◽

Vol 18 (7) ◽

pp. 409-414

Author(s):

N. DAS ◽

S.K. BOSE ◽

R.C. FRANCIS

Keyword(s):

Hydrogen Peroxide ◽

Sodium Bicarbonate ◽

Sodium Hydroxide ◽

Sodium Carbonate ◽

Kraft Pulp ◽

Kraft Pulps ◽

Pulp Bleaching ◽

Peroxide Bleaching ◽

Kraft Pulp Bleaching ◽

Peroxide Activation

Peroxide bleaching of softwood and hardwood (eucalypt) kraft pulps was performed in solutions of sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH). The conventional P stage (hydrogen peroxide + sodium hydroxide; H2O2 + NaOH) was the most effective brightening system without an additional activator. However, peroxide activation by bicarbonate anion (HCO3–) was obvious in all cases where NaHCO3 or Na2CO3 was used. When N,N,N’,N’-tetraacetylethylenediamine (TAED) was added to the bleaching system, Na2CO3 as the alkali source afforded equal or slightly higher bleached brightness compared to NaOH usage for both the softwood and hardwood pulps. This outcome is attributed to simultaneous peroxide activation by HCO3 and TAED. When applied to the eucalypt pulp, the H2O2/Na2CO3/TAED bleaching system also decreased the brightness loss due to thermal reversion.

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Optimization of elemental chlorine-free bleaching for a softwood kraft pulp – part 1: impact of oxidative extraction on chlorine dioxide stoichiometry

TAPPI Journal ◽

10.32964/tj9.8.27 ◽

2010 ◽

Vol 9 (8) ◽

pp. 27-35 ◽

Cited By ~ 2

Author(s):

BRIAN N. BROGDON

Keyword(s):

Decision Making ◽

Chlorine Dioxide ◽

Kraft Pulp ◽

Alkaline Extraction ◽

Pulp Bleaching ◽

Elemental Chlorine ◽

Kraft Pulp Bleaching ◽

Softwood Kraft Pulp ◽

Chemical Usage ◽

Minimize Costs

The present investigation meticulously analyzes how oxidative alkaline extraction can be augmented through process changes, and how these augmentations can be leveraged to optimize chlorine dioxide usage with elemental chlorine-free (ECF) sequences for a conventional softwood kraft pulp. Bleaching data from Basta and co-workers (1992 TAPPI Pulping Conference) are re-examined and re-interpreted in this study. We determined that ~60% to 65% of the overall ClO2 charge should be applied in the D0-stage. Peroxide addition to an (EOP) can replace 0.6 to 2.5 Kg. ClO2 per Kg H2O2. Boosting the (EO) temperature to 80°C is equivalent to a 70°C (EOP) with 0.25% to 0.30% H2O2,whereas a 90°C (EO) is equivalent to 0.50% – 0.75% H2O2 in a 70°C (EOP). The stoichiometric bleaching data from this study can guide decision-making for lowering chemical usage and minimize costs to reach target brightness levels with three- and five-stage sequences.

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Spectrophotometric Measurement of Chlorine Dioxide Residual in Kraft Pulp Bleaching

IFAC Proceedings Volumes ◽

10.1016/s1474-6670(17)55563-9 ◽

1987 ◽

Vol 20 (13) ◽

pp. 47-52

Author(s):

A.F. Gilbert

Keyword(s):

Chlorine Dioxide ◽

Kraft Pulp ◽

Pulp Bleaching ◽

Spectrophotometric Measurement ◽

Kraft Pulp Bleaching

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Effects of D0-stage temperature, pH, and kappa factor on chlorine dioxide decomposition and D0-(EP)-D1 bleaching performance for eucalypt pulps

TAPPI Journal ◽

10.32964/tj15.4.285 ◽

2016 ◽

Vol 15 (4) ◽

pp. 285-295 ◽

Cited By ~ 2

Author(s):

UMIT SEZGI ◽

JANAINA RESENDE ◽

LEWIS SHACKFORD ◽

JORGE COLODETTE ◽

MARCELA ANDRADE

Keyword(s):

Chlorine Dioxide ◽

Kraft Pulp ◽

Significant Variable ◽

Optimum Conditions ◽

Pulp Bleaching ◽

Elemental Chlorine ◽

Kraft Pulp Bleaching ◽

Eucalyptus Kraft Pulp ◽

Hexenuronic Acid ◽

Proper Operation

Mills have largely used chlorine dioxide (ClO2) for eucalyptus kraft pulp bleaching. Different mills have observed significant variation in ClO2 demand to reach full brightness (≥90 ISO). These large differences in ClO2 consumption derive from many factors. The most significant include differences in carryover loads and hexenuronic acid (HexA) contents and the level of chlorate formation across bleaching. Handling of pulp with high HexA content and ClO2 losses to chlorate can be minimized by proper operation of the ClO2 stages across the bleach plant. An oxygen delignified eucalyptus kraft pulp with a kappa of 10-12 units contains only 4-6 units actually derived from lignin. This scarce amount of lignin (0.6%-0.9%) is not able to consume high ClO2 doses and, as a consequence, the excess ClO2 applied can end up being converted into chlorate. Hence, proper optimization of ClO2 bleaching stages can save significant amounts of this oxidant. This study focused on optimizing ClO2 bleaching for a typical oxygen delignified eucalyptus kraft pulp of kappa number 11.7. Elemental chlorine free bleaching was carried out with the D0-(EP)-D1 sequence. The following conditions were varied in the D0 stage: temperature, end pH, and kappa factor. The results indicated that maximum ClO2 bleaching efficiency is achieved when minimum chlorate is formed, especially when ClO2 bleaching is adjusted in such a way that residual active chlorine is maintained to a minimum. The most significant variable affecting chlorate formation is pH; however, ClO2 doses (ClO2 concentration) also play a very important role. Chlorate formation is more intense in the D1 stage in relation to the D0 stage. Optimum conditions to run the D0 stage were 90°C, 3.5 pH, and 0.22 kappa factor.

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