A shock tube study of the thermal decompositions of acetaldehyde and ethylene oxide

Kern, R. D.; Singh, Hari Ji; Xie, Keyu

doi:10.1063/1.39379

Cited by 9 publications

(27 citation statements)

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“…These observations bring to question whether the use of sensitive diagnostics and/or a unique set of reaction conditions in this recent study 15 permitted the detection of these previously undetected intermediates. On the other hand, CH 2 CO and C 2 H 2 have been observed in prior studies, 8,9,12 and the formation of these intermediates was attributed to bimolecular and secondary reactions in these studies.…”

Section: Introductionmentioning

confidence: 80%

“…Higher temperature (> 1000 K) shock tube studies [6][7][8]10,11 have relied on a subset of these reactions (R1), and (R3) -(R19) as proposed by Laidler and co-workers 3,20 to reconcile experimental…”

Section: Mechanismmentioning

confidence: 98%

“…[5][6][7][8][9][10][11][12] However, this well characterized decomposition has merited renewed scrutiny in the combustion and gas phase chemical physics community for two main reasons:…”

Section: Introductionmentioning

confidence: 99%

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Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

et al. 2015

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The mechanism for the thermal decomposition of acetaldehyde has been revisited with an analysis of literature kinetics experiments using theoretical kinetics. The present modeling study was motivated by recent observations, with very sensitive diagnostics, of some unexpected products in high temperature microtubular reactor experiments on the thermal decomposition of CH3CHO and its deuterated analogs, CH3CDO, CD3CHO, and CD3CDO. The observations of these products prompted the authors of these studies to suggest that the enol tautomer, CH2CHOH (vinyl alcohol), is a primary intermediate in the thermal decomposition of acetaldehyde. The present modeling efforts on acetaldehyde decomposition incorporate a master equation reanalysis of the CH3CHO potential energy surface (PES). The lowest-energy process on this PES is an isomerization of CH3CHO to CH2CHOH. However, the subsequent product channels for CH2CHOH are substantially higher in energy, and the only unimolecular process that can be thermally accessed is a reisomerization to CH3CHO. The incorporation of these new theoretical kinetics predictions into models for selected literature experiments on CH3CHO thermal decomposition confirms our earlier experiment and theory-based conclusions that the dominant decomposition process in CH3CHO at high temperatures is C-C bond fission with a minor contribution (∼10-20%) from the roaming mechanism to form CH4 and CO. The present modeling efforts also incorporate a master-equation analysis of the H + CH2CHOH potential energy surface. This bimolecular reaction is the primary mechanism for removal of CH2CHOH, which can accumulate to minor amounts at high temperatures, T > 1000 K, in most lab-scale experiments that use large initial concentrations of CH3CHO. Our modeling efforts indicate that the observation of ketene, water, and acetylene in the recent microtubular experiments are primarily due to bimolecular reactions of CH3CHO and CH2CHOH with H-atoms and have no bearing on the unimolecular decomposition mechanism of CH3CHO. The present simulations also indicate that experiments using these microtubular reactors when interpreted with the aid of high-level theoretical calculations and kinetics modeling can offer insights into the chemistry of elusive intermediates in the high-temperature pyrolysis of organic molecules.

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Section: Introductionmentioning

confidence: 80%

Section: Mechanismmentioning

confidence: 98%

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Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

et al. 2015

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“…The detection of some oxygenated intermediates shed light on chemistry details which were ignored in previous studies. CH 3 oxidation and radical recombination in CH 3 CHO combustion might be ignored in previous studies. The species mole fraction profiles provide valuable information that should guide the development of future acetaldehyde sub-mechanisms for the C 0 -C 4 core mechanisms.…”

Section: Discussionmentioning

confidence: 96%

“…Kern et al [3] and Gupte et al [4] studied the thermal decomposition of acetaldehyde in a shock tube (ST) and developed their mechanisms. Also, using a shock tube, Won et al [5] measured the ignition delay of acetaldehyde and proposed a mechanism consisting of 34 species and 110 reactions.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the chemical structures of laminar premixed flames fueled by acetaldehyde

Tao

Sun

Yang

et al. 2017

Proceedings of the Combustion Institute

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Acetaldehyde is a key intermediate formed during the combustion of hydrocarbon and oxygenated fuels, and its role as an air pollution is concern-arousing. A better understanding of its combustion characteristics is of significance in developing core mechanisms and reducing the associated emissions. In this work, chemical structures of low-pressure laminar premixed acetaldehyde flames with equivalence ratios of 1.7 and 1.0 were measured by employing molecular-beam mass spectrometry with synchrotron vacuum ultraviolet light for ionization. Totally, about 40 species were identified and their mole fraction profiles are reported with well estimated uncertainty. To our knowledge, some oxygenated species, such as ethenol and butanal, were measured for the first time in acetaldehyde flames. Experimental species mole fraction profiles were compared with modeling results using several available kinetic mechanisms. These mechanisms well reproduce the mole fraction profiles of the major species and the C 1 /C 2 hydrocarbon intermediates, however, their unsatisfactory predictive capability for some fuel-related oxygenated intermediates, such as C 2 H 3 O isomers, suggests that the acetaldehyde sub-mechanism needs further investigation. Our experimental results provide valuable information for future mechanism development.

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