Formation of gas-phase bromine compounds by reaction of solid sodium bromide with gaseous nitryl hypochlorite, chlorine and chlorine bromide at 298 K

Berko, H.; McCaslin, P. C.; Finlayson-Pitts, Barbara J.

doi:10.1021/j100171a041

Cited by 23 publications

(32 citation statements)

References 8 publications

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“…J. W. Adams et al: Uptake and reaction of HOBr 3.7.2 BrCl, Cl 2 and Br 2 uptake to frozen and dry surfaces There have been a number of studies of the interactions of the di-halogens BrCl, Cl 2 and Br 2 with both dry and frozen salt surfaces. Berko et al (1991) examined qualitative aspects of the uptake and reaction of Cl 2 and BrCl with dry NaBr crystals. They found that whilst BrCl reacted with NaBr to form Br 2 directly, the uptake of Cl 2 resulted in initial formation and release of Br 2 , followed by BrCl.…”

Section: Hobr Uptake Onto Frozen Salt Surfaces: Uptake Coefficientsmentioning

confidence: 99%

Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

2002

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Abstract. The uptake and reaction of HOBr with frozen salt surfaces of variable NaCl / NaBr composition and temperature were investigated with a coated wall flow tube reactor coupled to a mass spectrometer for gas-phase analysis. HOBr is efficiently taken up onto the frozen surfaces at temperatures between 253 and 233 K where it reacts to form the di-halogens BrCl and Br 2 , which are subsequently released into the gas-phase. The uptake coefficient for HOBr reacting with a frozen, mixed salt surface of similar composition to sea-spray was ≈ 10 −2 . The relative concentration of BrCl and Br 2 released to the gas-phase was found to be strongly dependent on the ratio of Cl − to Br − in the solution prior to freezing / drying. For a mixed salt surface of similar composition to sea-spray the major product at low conversion of surface reactants (i.e. Br − and Cl − ) was Br 2 .Variation of the pH of the NaCl / NaBr solution used to prepare the frozen surfaces was found to have no significant influence on the results. The observations are explained in terms of initial formation of BrCl in a surface reaction of HOBr with Cl − , and conversion of BrCl to Br 2 via reaction of surface Br − . Experiments on the uptake and reaction of BrCl with frozen NaCl / NaBr solutions served to confirm this hypothesis. The kinetics and products of the interactions of BrCl, Br 2 and Cl 2 with frozen salt surfaces were also investigated, and lower limits to the uptake coefficients of > 0.034, > 0.025 and > 0.028 respectively, were obtained. The uptake and reaction of HOBr on dry salt surfaces was also investigated and the results closely resemble those obtained for frozen surfaces. During the course of this study the gas diffusion coefficients of HOBr in He and H 2 O were also measured as (273 ± 1) Torr cm 2 s −1 and (51 ± 1) Torr cm 2 s −1 , respectively, at 255 K. The implications of these results for modelling the chemistry of the Correspondence to: J. N. Crowley (Crowley@mpch-mainz.mpg.de) Arctic boundary layer in springtime are discussed.

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Section: Hobr Uptake Onto Frozen Salt Surfaces: Uptake Coefficientsmentioning

confidence: 99%

Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

2002

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“…The mass balance expressed per chlorine atom is established including the products of desorption listed in Table 5 for Cl 2 O uptake according to equation (20) where the brackets correspond to molar yields: 2! (Cl 2 O taken up ) = HOCl produced + HOCl desorbed + 2!…”

Section: Mass Balance For Pure CL 2 O Uptakementioning

confidence: 99%

“…(Cl 2 O taken up ) = HOCl produced + HOCl desorbed + 2! (Cl 2 O desorbed ) + (Cl 2 ) produced (20) In equation (20), we assume that for each Cl 2 produced, one Cl • came from the Cl 2 O source while the second Cl…”

Section: Mass Balance For Pure CL 2 O Uptakementioning

confidence: 99%

“…Only when the heterogeneous reactions (4) and (5) of HOBr on ice and snow are included does the simulation of tropospheric ozone destruction agree with field measurements through halogen activation [15]. However, only few data are available for HOCl heterogeneous reactions on marine aerosol and sea ice in comparison to uptake experiments of HOBr or HOCl performed on solid substrates [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Heterogeneous Chemistry of Cl₂O and HOCl on Frozen Natural Sea Salt, Recrystallized Sea Salt, KCl and NaCl Solutions at 200 and 215 K

Pratte

Rossi²

2010

Zeitschrift Für Physikalische Chemie

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The HOCl heterogeneous reaction on frozen natural (NSS) and recrystallized (RSS) sea salt, KCl and NaCl solutions was studied using a low pressure flow reactor in order to measure the uptake coefficient γ and products of reaction. The HOCl sample used in these experiments always contained up to 25% Cl2O which was also studied separately as a pure gas in order to understand the heterogeneous chemistry of both gases. By performing HOCl uptake on frozen NSS solution at 200 K and a gas-phase residence time of (1.6±0.6) s we obtained a steady state uptake coefficient γHOCl on NSS = (2.5±0.7)×10-3 and γCl2O on NSS = (2.8±0.8)×10-3. On frozen KCl solution at 200 K we obtain γHOCl on KCl = (2.8±1.3)×10-3, identical to NSS, and γCl2O on KCl = (4.6±0.8)×10-4. The main product formed during the uptake on frozen NSS solution is Cl2 which is sustained for at least one hour. In contrast, only a transient Cl2 flow (pulse) decreasing on the time scale of 100 s was observed on frozen KCl (NaCl) solution. 25±10 % of the HOCl taken up on all chloride-containing frozen substrates at 200 K react to produce Cl2 at high HOCl concentration (4.5×1011 molecule cm-3) and at a residence time of 1.6 s in comparison with twice that for Cl2O. For smaller concentrations such as [HOCl] = 3.7×1010 molecule cm-3 and/or a shorter residence time (0.137±0.004s), HOCl uptake did not generate Cl2 in contrast to Cl2O. A single Br2 burst event was monitored when a Cl2O or HOCl/Cl2O mixture is taken up on fresh frozen NSS solution during the first uptake at 200 K. Further Cl2O or HOCl/Cl2O uptake on the same sample, even after annealing at 240 K does not show an additional Br2 pulse. This Br2 release may be significant in the autocatalytic ozone destruction mechanism in the troposphere during polar sunrise. Some of the atmospheric implications of the present results are highlighted with emphasis on the preequilibrium Cl2O(ads) + H2O(ice) ↔ 2 HOCl(ads) between adsorbed HOCl and Cl2O, with the latter being the gateway to reactive uptake of HOCl at low temperatures.

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“…Several mechanisms that involve heterogeneous processing on Arctic aerosols have been proposed to account for this observation [14][15][16][17]. For example, incorporation of bromine from airborne seawater onto ice pack surfaces, and subsequent release as Br2 at polar sunrise, has been proposed as the first step in a series of chemical reactions that result in ozone depletion in the Arctic boundary layer 133.…”

Section: Background and Research Objectivesmentioning

confidence: 99%

Heterogeneous processing of bromine compounds by atmospheric aerosols: Relation to the ozone budget

Robinson¹,

Henson²,

Dubey³

et al. 1998

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Formation of gas-phase bromine compounds by reaction of solid sodium bromide with gaseous nitryl hypochlorite, chlorine and chlorine bromide at 298 K

Cited by 23 publications

References 8 publications

Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

Heterogeneous Chemistry of Cl₂O and HOCl on Frozen Natural Sea Salt, Recrystallized Sea Salt, KCl and NaCl Solutions at 200 and 215 K

Heterogeneous processing of bromine compounds by atmospheric aerosols: Relation to the ozone budget

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Formation of gas-phase bromine compounds by reaction of solid sodium bromide with gaseous nitryl hypochlorite, chlorine and chlorine bromide at 298 K

Cited by 23 publications

References 8 publications

Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

Uptake and reaction of HOBr on frozen and dry NaCl/NaBr surfaces between 253 and 233 K

Heterogeneous Chemistry of Cl2O and HOCl on Frozen Natural Sea Salt, Recrystallized Sea Salt, KCl and NaCl Solutions at 200 and 215 K

Heterogeneous processing of bromine compounds by atmospheric aerosols: Relation to the ozone budget

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Heterogeneous Chemistry of Cl₂O and HOCl on Frozen Natural Sea Salt, Recrystallized Sea Salt, KCl and NaCl Solutions at 200 and 215 K