The role of non-phenolic lignin in chlorate-forming reactions during chlorine dioxide bleaching of softwood kraft pulp

Holzforschung ◽  
2005 ◽  
Vol 59 (2) ◽  
pp. 110-115 ◽  
Author(s):  
Doug R. Svenson ◽  
Hou-min Chang ◽  
Hasan Jameel ◽  
John F. Kadla
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Hypochlorous Acid ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Kraft Pulps ◽  
Kinetic Rates ◽  
Softwood Kraft Pulp ◽  
Phenolic Hydroxyl Groups ◽  
Inorganic Reactions

Abstract The affect of phenolic hydroxyl groups on the reaction efficiency during chlorine dioxide pre-bleaching of a softwood kraft pulp was investigated. The removal of phenolic hydroxyl groups via pulp methylation did not adversely affect the chlorine dioxide bleaching efficiency or the amount of chlorate formed during exposure to chlorine dioxide. Ion analysis of the reaction systems revealed that the formation of chloride and chlorite ions during the bleaching process were very similar between the kraft and methylated kraft pulps. These results indicate that the kinetic rates of lignin oxidation by chlorine dioxide and its reduction products, chlorite and hypochlorous acid, are much faster than the rate of inorganic reactions leading to chlorate formation.

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.

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.

Inorganic Reactions in Chlorine Dioxide Bleaching of Softwood Kraft Pulp

2006 ◽  
Vol 26 (3) ◽  
pp. 201-213 ◽  
Author(s):  
Douglas R. Svenson ◽  
Hasan Jameel ◽  
Hou‐min Chang ◽  
John F. Kadla
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Softwood Kraft Pulp ◽  
Inorganic Reactions

Methylation of Phenolic Hydroxyl Group and Demethylation of Anisoles

2009 ◽  
Vol 2009 (4) ◽  
pp. 229-230 ◽  
Author(s):  
Nobuhiro Sato ◽  
Hiroyuki Endo
Keyword(s):  
Microwave Heating ◽  
Room Temperature ◽  
Reverse Reaction ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups ◽  
Phenyl Ethers ◽  
Methyl Phenyl

A mild methylation of phenolic hydroxyl groups with iodomethane was enabled in the presence of sodium bis(trimethylsilyl)amide at room temperature. The reverse reaction, namely demethylation of methyl phenyl ethers, was easily achieved by microwave heating with neat iodotrimethylsilane.

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