Tertiary amine-catalyzed generation of chlorine dioxide from hypochlorous acid and chlorite ions

Ferro, Estefania Isaza; Perrin, Jordan; Dawson, Owain George John; Vuorinen, Tapani

doi:10.1007/s00226-020-01247-5

Cited by 7 publications

(1 citation statement)

References 32 publications

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“…Practical applications and exotic kinetic phenomena have generated considerable interest in the chemistry of chlorite ion that has been utilized as oxidizing agent in very diverse areas. − Chlorite ion is also the precursor in the generation of chlorine dioxide, − which has extensively been used in water and wastewater treatment technologies, cellulose bleaching, disinfection processes, deactivation of Bacillus anthracis spores, food industry, etc. ,− In these systems, chlorine(I) always forms as an intermediate and, in turn, is involved in complex reactions with chlorite ion yielding Cl – , ClO 2 , and ClO 3 – in variable concentration ratios depending on the actual conditions. − According to earlier studies, the stoichiometry of this reaction is very sensitive to the pH, the concentrations as well as the concentration ratios of the reactants, and the presence of additional components that may act as promoters or inhibitors in the overall process. In general, the stoichiometry can be defined as the linear combination of eqs and . ClO 2 − + HOCl = ClO 3 − + Cl − + normalH + 2 ClO 2 − + HOCl + normalH +…”

Section: Introductionmentioning

confidence: 99%

Kinetic Role of Reactive Intermediates in Controlling the Formation of Chlorine Dioxide in the Hypochlorous Acid–Chlorite Ion Reaction

2023

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An advanced experimental protocol is reported for studying the kinetics and mechanism of the complex redox reaction between chlorite ion and hypochlorous acid under acidic condition. The formation of ClO2 is followed directly by the classical two-component stopped-flow method. In sequential stopped-flow experiments, the target reaction is chemically quenched using NaI solution and the concentration of each reactant and product is monitored as a function of time by utilizing the principles of kinetic discrimination. Thus, in contrast to earlier studies, not only the formation of one of the products but the decay of the reactants was also directly followed. This approach provides a firm basis for postulating a detailed mechanism for the interpretation of the experimental results under a variety of conditions. The intimate details of the reaction are explored by simultaneously fitting 78 kinetic traces, i.e., the concentration vs. time profiles of ClO2 –, HOCl, and ClO2, to an 11-step kinetic model. The most important reaction steps were identified, and it was shown that two reactive intermediates have a pivotal role in the mechanism. While chlorate ion predominantly forms via the reaction of Cl2O, chlorine dioxide is exclusively produced in reaction steps involving Cl2O2. This study leads to clear conclusions on how to control the stoichiometry of the reaction and achieve optimum conditions to produce chlorine dioxide and to reduce the formation of the toxic chlorate ion in practical applications.

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Section: Introductionmentioning

confidence: 99%

Kinetic Role of Reactive Intermediates in Controlling the Formation of Chlorine Dioxide in the Hypochlorous Acid–Chlorite Ion Reaction

2023

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Stoichiometry of reactions of ozone and hypochlorous acid with lignin and hexenuronic acid and its chlorination

et al. 2022

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The stoichiometry of ozone and hypochlorous acid reactions with lignin and hexenuronic acid (HexA) was measured in bleaching experiments of Eucalyptus sp. kraft pulp. The progress of the reactions was followed by UV Resonance Raman spectroscopy that can quantify lignin and HexA based on the Raman scattering intensities of the carbon–carbon double bond in HexA and the aromatic ring in lignin. Here, one mol of ozone converted 0.16 mol of lignin (C9 monomer units) and 0.28 mol of HexA, whereas 1 mol of hypochlorous acid converted 0.09 mol of lignin and 0.23 mol of HexA. The use of a tertiary amine catalyst with the hypochlorous acid treatments did not affect these stoichiometries. The stoichiometric ratios showed that ozone was more efficient in oxidizing lignin than hypochlorous acid, while both electrophiles reacted with HexA to a similar extent. HexA reaction by hypochlorous acid was concluded to involve initial electrophilic chlorination of the carbon–carbon double bond, contributing to significant organochlorine (OX) formation in the pulp. Evidence on this was the linear correlation between the initial HexA content and OX (0.59 mol OX per mol HexA) and the high OX content in the xylan extracted from the bleached pulp. The 2D NMR HSQC and TOCSY spectra of the isolated xylans showed the disappearance of HexA signals after the treatment with hypochlorous acid and the appearance of a new spin system, yet to be fully identified.

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A note on the chemical fate of the DABCO catalyst in amine-catalyzed hypochlorite bleaching of cellulosic pulps

Lehrhofer,

Isaza Ferro,

Hosoya

et al. 2024

Cellulose

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Hypochlorous acid bleaching under amine catalysis (Hcat bleaching stage) is an optimized bleaching stage variant that is characterized by working at weakly acidic, near-neutral pH, having high bleaching efficiency, and discharging only very small amounts of chloro-organics. This study addressed the chemical fate of the used 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyst. While literature proposed either homolytic or heterolytic breakage of one ethylene bridge and subsequent release of the resulting fragments as two molecules of formaldehyde, we demonstrated the degradation to proceed by ionic elimination of one ethylene bridge starting from mono-N-chlorinated DABCO. The resulting N-vinyl (enamine) derivative adds water under the release of acetaldehyde and formation of piperazine. The generation of acetaldehyde was experimentally confirmed by 2,4-dinitrophenylhydrazine trapping, directly from the processing liquid. The experimental findings agreed superbly with computations which showed the “acetaldehyde mechanism” to be much favored over the previously proposed pathways under C–C bond cleavage and release of formaldehyde. The results of this study add to a better understanding of the novel Hcat bleaching system. Graphical abstract

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Tertiary amine-catalyzed generation of chlorine dioxide from hypochlorous acid and chlorite ions

Cited by 7 publications

References 32 publications

Kinetic Role of Reactive Intermediates in Controlling the Formation of Chlorine Dioxide in the Hypochlorous Acid–Chlorite Ion Reaction

Kinetic Role of Reactive Intermediates in Controlling the Formation of Chlorine Dioxide in the Hypochlorous Acid–Chlorite Ion Reaction

Stoichiometry of reactions of ozone and hypochlorous acid with lignin and hexenuronic acid and its chlorination

A note on the chemical fate of the DABCO catalyst in amine-catalyzed hypochlorite bleaching of cellulosic pulps

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