A new instrument for time-resolved measurement of HO<sub>2</sub> radicals
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Published:2020-02-20
Issue:2
Volume:13
Page:839-852
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Speak Thomas H.ORCID, Blitz Mark A.ORCID, Stone DanielORCID, Seakins Paul W.ORCID
Abstract
Abstract. OH and HO2 radicals are closely coupled in the
atmospheric oxidation and combustion of volatile organic compounds (VOCs).
Simultaneous measurement of HO2 yields and OH kinetics can provide the ability to assign site-specific rate coefficients that are important for understanding the oxidation mechanisms of VOCs. By coupling a fluorescence
assay by gaseous expansion (FAGE) laser-induced fluorescence (LIF) detection system for OH and HO2 with a high-pressure laser flash
photolysis system, it is possible to accurately measure OH pseudo-1st-order loss processes up to ∼100 000 s−1 and to determine
HO2 yields via time-resolved measurements. This time resolution allows discrimination between primary HO2 from the target reaction and secondary production from side reactions. The apparatus was characterized by measuring yields from the reactions of OH with H2O2 (1:1 link between OH and HO2), with C2H4∕O2 (where secondary chemistry can generate HO2), with C2H6∕O2 (where there should be zero HO2 yield), and with CH3OH∕O2 (where there is a well-defined HO2 yield). As an application of the new instrument, the reaction of OH with n-butanol has been studied at 293 and 616 K. The bimolecular rate coefficient at 293 K, (9.24±0.21)×10-12 cm3 molec.−1 s−1, is in good agreement with recent literature, verifying that this instrument can measure accurate OH kinetics. At 616 K the regeneration of OH in the absence of O2, from the decomposition of the β-hydroxy radical, was observed, which allowed the determination of the fraction of OH reacting at the β site (0.23±0.04). Direct observation of the HO2 product in the presence of oxygen has allowed the assignment of the α-branching fractions (0.57±0.06) at 293 K and (0.54±0.04) at 616 K, again in good agreement with recent literature; branching ratios are key to modelling the ignition delay times of this potential “drop-in” biofuel.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
Reference40 articles.
1. Agbro, E., Tomlin, A. S., Lawes, M., Park, S., and Sarathy, S. M.: The
influence of n-butanol blending on the ignition delay times of gasoline and
its surrogates at high pressures, Fuel, 187, 211–219, https://doi.org/10.1016/j.fuel.201609.052, 2017. 2. Assaf, E. and Fittschen, C.: Cross Section of OH Radical Overtone Transition near 7028 cm−1 and Measurement of the Rate Constant of the
Reaction of OH with HO2 Radicals, J. Phys. Chem. A, 120, 7051–7059, https://doi.org/10.1021/acs.jpca.6b06477, 2016. 3. Assaf, E., Liu, L., Schoemaecker, C., and Fittschen, C.: Absorption spectrum
and absorption cross sections of the 2v1 band of HO2 between 20
and 760 Torr air in the range 6636 and 6639 cm−1, J. Quant. Spectrosc. Ra., 211, 107–114, https://doi.org/10.1016/j.jqsrt.2018.02.035, 2018. 4. Atkinson, R., Aschmann, S. M., Winer, A. M., and Pitts, J. N.: Rate constants for the reaction of OH radicals with a series of alkanes and alkenes at 299 ±2 K, Int. J. Chem. Kinet., 14, 507–516, https://doi.org/10.1002/kin.550140508, 1982. 5. Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., Troe, J., and IUPAC Subcommittee: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625–4055, https://doi.org/10.5194/acp-6-3625-2006, 2006.
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