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Detection and Identification of the Keto-Hydroperoxide (HOOCH 2 OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether

Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

Moshammer, Kai F.; Jasper, Ahren W.; Popolan-Vaida, D P.; Lucassen, A L.; Dievart, P D.; Selim, H S.; Eskola, Arkke J.; Taatjes, Craig A.; Leone, S L.; Sarathy, S.M.; Ju, Y J.; Dagaut, P D.; Kohse-Hoinghaus, K K.; Hansen, Nils H.

Abstract not provided.

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TYPE Journal Article YEAR 2015
OSTIDOI

Direct observation and kinetics of a hydroperoxyalkyl radical (QOOH)

Science

Savee, John D.; Papajak, Ewa P.; Rotavera, Brandon R.; Huang, Haifeng; Eskola, Arkke J.; Welz, Oliver; Sheps, Leonid S.; Taatjes, Craig A.; Zador, Judit Z.; Osborn, David L.

Oxidation of organic compounds in combustion and in Earth's troposphere is mediated by reactive species formed by the addition of molecular oxygen (O2) to organic radicals. Among the most crucial and elusive of these intermediates are hydroperoxyalkyl radicals, often denoted "QOOH." These species and their reactions with O2 are responsible for the radical chain branching that sustains autoignition and are implicated in tropospheric autoxidation that can form low-volatility, highly oxygenated organic aerosol precursors. We report direct observation and kinetics measurements of a QOOH intermediate in the oxidation of 1,3-cycloheptadiene, a molecule that offers insight into both resonance-stabilized and nonstabilized radical intermediates. The results establish that resonance stabilization dramatically changes QOOH reactivity and, hence, that oxidation of unsaturated organics can produce exceptionally long-lived QOOH intermediates.

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TYPE Conference Poster YEAR 2015
ScopusOSTI

Note: Absolute photoionization cross-section of the vinyl radical

Journal of Chemical Physics

Savee, John D.; Lockyear, Jessica F.; Borkar, Sampada; Eskola, Arkke J.; Welz, Oliver W.; Taatjes, Craig A.; Osborn, David L.

This work measures the absolute photoionization cross-section of the vinyl radical (σvinyl(E)) between 8.1 and 11.0 eV. Two different methods were used to obtain absolute cross-section measurements: 193 nm photodissociation of methyl vinyl ketone (MVK) and 248 nm photodissociation of vinyl iodide (VI). The values of the photoionization cross-section for the vinyl radical using MVK, σvinyl(10.224 eV) = (6.1 ± 1.4) Mb and σvinyl(10.424 eV) = (8.3 ± 1.9) Mb, and using VI, σvinyl(10.013 eV) = (4.7 ± 1.1) Mb, σ vinyl(10.513 eV) = (9.0 ± 2.1) Mb, and σ vinyl(10.813 eV) = (12.1 ± 2.9) Mb, define a photoionization cross-section that is ∼1.7 times smaller than a previous determination of this value. © 2013 AIP Publishing LLC.

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TYPE Journal Article YEAR 2013
ScopusOSTIDOI

Low-temperature combustion chemistry of biofuels: Pathways in the low-temperature (550-700 K) oxidation chemistry of isobutanol and tert-butanol

Proceedings of the Combustion Institute

Welz, Oliver W.; Savee, John D.; Eskola, Arkke J.; Sheps, Leonid S.; Osborn, David L.; Taatjes, Craig A.

Butanol isomers are promising next-generation biofuels. Their use in internal combustion applications, especially those relying on low-temperature autoignition, requires an understanding of their low-temperature combustion chemistry. Whereas the high-temperature oxidation chemistry of all four butanol isomers has been the subject of substantial experimental and theoretical efforts, their low-temperature oxidation chemistry remains underexplored. In this work we report an experimental study on the fundamental low-temperature oxidation chemistry of two butanol isomers, tert-butanol and isobutanol, in low-pressure (4-5.1 Torr) experiments at 550 and 700 K. We use pulsed-photolytic chlorine atom initiation to generate hydroxyalkyl radicals derived from tert-butanol and isobutanol, and probe the chemistry of these radicals in the presence of an excess of O2 by multiplexed time-resolved tunable synchrotron photoionization mass spectrometry. Isomer-resolved yields of stable products are determined, providing insight into the chemistry of the different hydroxyalkyl radicals. In isobutanol oxidation, we find that the reaction of the a-hydroxyalkyl radical with O2 is predominantly linked to chain-terminating formation of HO2. The Waddington mechanism, associated with chain-propagating formation of OH, is the main product channel in the reactions of O2 with b-hydroxyalkyl radicals derived from both tert-butanol and isobutanol. In the tert-butanol case, direct HO2 elimination is not possible in the b-hydroxyalkyl + O2 reaction because of the absence of a beta C-H bond; this channel is available in the b-hydroxyalkyl + O2 reaction for isobutanol, but we find that it is strongly suppressed. Observed evolution of the main products from 550 to 700 K can be qualitatively explained by an increasing role of hydroxyalkyl radical decomposition at 700 K. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

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TYPE Journal Article YEAR 2013
ScopusOSTI
Results 1–25 of 30
Results 1–25 of 30