Gomez Martin, JC orcid.org/0000-0001-7972-085X, Seaton, C, De Miranda, MP et al. (1 more author) (2017) The Reaction between Sodium Hydroxide and Atomic Hydrogen in Atmospheric and Flame Chemistry. Journal of Physical Chemistry A, 121 (40). pp. 7667-7674. ISSN 1089-5639
Abstract
We report the first direct kinetic study of the gas-phase reaction NaOH + H → Na + H₂O, which is central to the chemistry of sodium in the upper atmosphere and in flames. The reaction was studied in a fast flow tube, where NaOH was observed by multiphoton ionization and time-of-flight mass spectrometry, yielding k(NaOH + H, 230–298 K) = (3.8 ± 0.8) × 10⁻¹¹ cm³ molecule ⁻¹ s⁻¹ (at 2σ confidence level), showing no significant temperature dependence over the indicated temperature range and essentially in agreement with previous estimates of the rate constant in hydrogen-rich flames. We show, using theoretical trajectory calculations, that the unexpectedly slow, yet T-independent, rate coefficient for NaOH + H is explained by severe constraints in the angle of attack that H can make on NaOH to produce H₂O. This reaction is also central to explaining Na-catalyzed flame inhibition, which has been proposed to occur via the sequence Na + OH (+ M) → NaOH followed by NaOH + H → Na + H₂O, thereby effectively recombinating H and OH to H₂O. RRKM calculations for the recombination of Na and OH yield k(Na + OH + N₂, 300–2400 K) = 2.7 × 10⁻²⁹ (300/T)¹·² cm⁶ molecule⁻² s⁻¹, in agreement with a previous flash photolysis measurement at 653 K and Na-seeded flame studies in the 1800–2200 K range. These results therefore provide strong evidence to support the mechanism of flame inhibition by Na.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry A, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpca.7b07808. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Funding Information: | Funder Grant number EU - European Union 291332 |
Depositing User: | Symplectic Publications |
Date Deposited: | 18 Sep 2017 14:16 |
Last Modified: | 13 Sep 2018 00:38 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.jpca.7b07808 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:121264 |