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| Titel |
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
| VerfasserIn |
Y. J. Liu, I. Herdlinger-Blatt, K. A. McKinney, S. T. Martin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 11 ; Nr. 13, no. 11 (2013-06-14), S.5715-5730 |
| Datensatznummer |
250018700
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| Publikation (Nr.) |
 copernicus.org/acp-13-5715-2013.pdf |
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| Zusammenfassung |
| The photo-oxidation chemistry of isoprene (ISOP; C5H8) was studied
in a continuous-flow chamber under conditions such that the reactions of the
isoprene-derived peroxyl radicals (RO2) were dominated by the
hydroperoxyl (HO2) pathway. A proton-transfer-reaction time-of-flight
mass spectrometer (PTR-TOF-MS) with switchable H3O+ and NO+
reagent ions was used for product analysis. The products methyl vinyl ketone
(MVK; C4H6O) and methacrolein (MACR; C4H6O) were
differentiated using NO+ reagent ions. The MVK and MACR yields via the
HO2 pathway were (3.8 ± 1.3)% and (2.5 ± 0.9)%,
respectively, at +25 °C and < 2% relative humidity. The
respective yields were (41.4 ± 5.5)% and (29.6 ± 4.2)%
via the NO pathway. Production of MVK and MACR via the HO2 pathway
implies concomitant production of hydroxyl ((6.3 ± 2.1)%) and
hydroperoxyl ((6.3 ± 2.1)%) radicals, meaning a HOx
recycling of (12.6 ± 4.2)% given that HO2 was both a reactant
and product. Other isoprene oxidation products, believed to be mostly organic
hydroperoxides, also contributed to the ion intensity at the same
mass-to-charge (m/z) ratios as the MVK and MACR product ions for
HO2-dominant conditions. These products were selectively removed from
the gas phase by placement of a cold trap (−40 °C) inline prior to
the PTR-TOF-MS. When incorporated into regional and global chemical transport
models, the yields of MVK and MACR and the concomitant HOx
recycling reported in this study can improve the accuracy of the simulation
of the HO2 reaction pathway of isoprene, which is believed to be the
fate of approximately half of atmospherically produced isoprene-derived
peroxy radicals on a global scale. |
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