Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation
The photo-oxidation chemistry of isoprene (ISOP; C<sub>5</sub>H<sub>8</sub>) was studied in a continuous-flow chamber under conditions such that the reactions of the isoprene-derived peroxyl radicals (RO<sub>2</sub>) were dominated by the hydroperoxyl (HO<sub&g...
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doaj-beb279dd4e72456499220130e03f52542020-11-24T22:15:54ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242013-06-0113115715573010.5194/acp-13-5715-2013Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidationY. J. LiuI. Herdlinger-BlattK. A. McKinneyS. T. MartinThe photo-oxidation chemistry of isoprene (ISOP; C<sub>5</sub>H<sub>8</sub>) was studied in a continuous-flow chamber under conditions such that the reactions of the isoprene-derived peroxyl radicals (RO<sub>2</sub>) were dominated by the hydroperoxyl (HO<sub>2</sub>) pathway. A proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) with switchable H<sub>3</sub>O<sup>+</sup> and NO<sup>+</sup> reagent ions was used for product analysis. The products methyl vinyl ketone (MVK; C<sub>4</sub>H<sub>6</sub>O) and methacrolein (MACR; C<sub>4</sub>H<sub>6</sub>O) were differentiated using NO<sup>+</sup> reagent ions. The MVK and MACR yields via the HO<sub>2</sub> 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 HO<sub>2</sub> pathway implies concomitant production of hydroxyl ((6.3 ± 2.1)%) and hydroperoxyl ((6.3 ± 2.1)%) radicals, meaning a HO<sub>x</sub> recycling of (12.6 ± 4.2)% given that HO<sub>2</sub> 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 (<i>m/z</i>) ratios as the MVK and MACR product ions for HO<sub>2</sub>-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 HO<sub>x</sub> recycling reported in this study can improve the accuracy of the simulation of the HO<sub>2</sub> 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.http://www.atmos-chem-phys.net/13/5715/2013/acp-13-5715-2013.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Y. J. Liu I. Herdlinger-Blatt K. A. McKinney S. T. Martin |
spellingShingle |
Y. J. Liu I. Herdlinger-Blatt K. A. McKinney S. T. Martin Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation Atmospheric Chemistry and Physics |
author_facet |
Y. J. Liu I. Herdlinger-Blatt K. A. McKinney S. T. Martin |
author_sort |
Y. J. Liu |
title |
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
title_short |
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
title_full |
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
title_fullStr |
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
title_full_unstemmed |
Production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
title_sort |
production of methyl vinyl ketone and methacrolein via the hydroperoxyl pathway of isoprene oxidation |
publisher |
Copernicus Publications |
series |
Atmospheric Chemistry and Physics |
issn |
1680-7316 1680-7324 |
publishDate |
2013-06-01 |
description |
The photo-oxidation chemistry of isoprene (ISOP; C<sub>5</sub>H<sub>8</sub>) was studied in a continuous-flow chamber under conditions such that the reactions of the isoprene-derived peroxyl radicals (RO<sub>2</sub>) were dominated by the hydroperoxyl (HO<sub>2</sub>) pathway. A proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) with switchable H<sub>3</sub>O<sup>+</sup> and NO<sup>+</sup> reagent ions was used for product analysis. The products methyl vinyl ketone (MVK; C<sub>4</sub>H<sub>6</sub>O) and methacrolein (MACR; C<sub>4</sub>H<sub>6</sub>O) were differentiated using NO<sup>+</sup> reagent ions. The MVK and MACR yields via the HO<sub>2</sub> 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 HO<sub>2</sub> pathway implies concomitant production of hydroxyl ((6.3 ± 2.1)%) and hydroperoxyl ((6.3 ± 2.1)%) radicals, meaning a HO<sub>x</sub> recycling of (12.6 ± 4.2)% given that HO<sub>2</sub> 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 (<i>m/z</i>) ratios as the MVK and MACR product ions for HO<sub>2</sub>-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 HO<sub>x</sub> recycling reported in this study can improve the accuracy of the simulation of the HO<sub>2</sub> 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. |
url |
http://www.atmos-chem-phys.net/13/5715/2013/acp-13-5715-2013.pdf |
work_keys_str_mv |
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