Thermal decomposition products of butyraldehyde

Hatten, Courtney D.; Kaskey, Kevin R.; Warner, Brian J.; Wright, Emily M.; McCunn, Laura R.

doi:10.1063/1.4832898

Cited by 7 publications

(15 citation statements)

References 46 publications

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“…Mechanistic steps analogous to those proposed here may be operating in the pyrolysis of larger aldehydes such as propionaldehyde 45 and butyraldehyde 46 recently studied using microtubular reactors at high temperatures and low pressures. The present model and simulations explain the observed products distributions from the microtubular reactor purely on the basis of gas-phase chemistry without the need for introducing any surface reactions, a conclusion borne out from recent studies on a variety of organic molecules by Barney Ellison and collaborators in ref 43 and references within.…”

Section: ■ Kinetic Modelingmentioning

confidence: 90%

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: ■ Kinetic Modelingmentioning

confidence: 90%

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

et al. 2015

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“…38 and vinoxy radicals was mentioned in this laboratory's previous study of butyraldehyde. 24 There was weak evidence for the detection of vinoxy in that study, and it was suspected that both vinoxy and ethyl would decompose to products that could also be produced by other reactions in the pyrolysis mechanism, so there was some uncertainty regarding the presence of the reaction for butyraldehyde.…”

Section: Products Of Isomerization/eliminationmentioning

confidence: 96%

“…21,24 Current wisdom holds that the aldehyde tautomerizes to the enol, followed by reaction with an H atom. While the experiments herein cannot effectively test this hypothesized mechanism, the results will be discussed, keeping the mechanism in mind, and examined for consistency.…”

Section: Products Of Isomerization/eliminationmentioning

confidence: 99%

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Products From Pyrolysis of Gas-Phase Propionaldehyde

et al. 2014

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A hyperthermal nozzle was utilized to study the thermal decomposition of propionaldehyde, CH3CH2CHO, over a temperature range of 1073-1600 K. Products were identified with two detection methods: matrix-isolation Fourier transform infrared spectroscopy and photoionization mass spectrometry. Evidence was observed for four reactions during the breakdown of propionaldehyde: α-C-C bond scission yielding CH3CH2, CO, and H, an elimination reaction forming methylketene and H2, an isomerization pathway leading to propyne via the elimination of H2O, and a β-C-C bond scission channel forming methyl radical and (•)CH2CHO. The products identified during this experiment were CO, HCO, CH3CH2, CH3CH═C═O, H2O, CH3C≡CH, CH3, H2C═C═O, CH2CH2, CH3CH═CH2, HC≡CH, CH2CCH, H2CO, C4H2, C4H4, and CH3CHO. The first eight products result from primary or bimolecular reactions involving propionaldehyde while the remaining products occur from reactions including the initial pyrolysis products. While the pyrolysis of propionaldehyde involves reactions similar to those observed for acetaldehyde and butyraldehyde in recent studies, there are a few unique products observed which highlight the need for further study of the pyrolysis mechanism.

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“…Figure shows no signal at m / z 72 characteristic of butyraldehyde, which is analogous to the absence of acetaldehyde from pyrolysis of methyl acetate ( P2 ). The pyrolysis of butyraldehyde was examined, and CH 3 CH 2 CH 2 CHO was stable until 1300 K, when it fragmented by a variety of complex pathways. Because there is no evidence for m / z 72, and the analogous channel P2 is inactive for methyl acetate, P10 is discounted as an active channel.…”

Section: Discussionmentioning

confidence: 99%

Thermal Decomposition of Potential Ester Biofuels. Part I: Methyl Acetate and Methyl Butanoate

Porterfield¹,

Bross

Ruščić

et al. 2017

J. Phys. Chem. A

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Two methyl esters were examined as models for the pyrolysis of biofuels. Dilute samples (0.06-0.13%) of methyl acetate (CHCOOCH) and methyl butanoate (CHCHCHCOOCH) were entrained in (He, Ar) carrier gas and decomposed in a set of flash-pyrolysis microreactors. The pyrolysis products resulting from the methyl esters were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by matrix infrared absorption spectroscopy. Pyrolysis pressures in the pulsed microreactor were about 20 Torr and residence times through the reactors were roughly 25-150 μs. Reactor temperatures of 300-1600 K were explored. Decomposition of CHCOOCH commences at 1000 K, and the initial products are (CH═C═O and CHOH). As the microreactor is heated to 1300 K, a mixture of CH═C═O and CHOH, CH, CH═O, H, CO, and CO appears. The thermal cracking of CHCHCHCOOCH begins at 800 K with the formation of CHCHCH═C═O and CHOH. By 1300 K, the pyrolysis of methyl butanoate yields a complex mixture of CHCHCH═C═O, CHOH, CH, CH═O, CO, CO, CHCH═CH, CHCHCH, CH═C═CH, HCCCH, CH═C═C═O, CH═CH, HC≡CH, and CH═C═O. On the basis of the results from the thermal cracking of methyl acetate and methyl butanoate, we predict several important decomposition channels for the pyrolysis of fatty acid methyl esters, R-CH-COOCH. The lowest-energy fragmentation will be a 4-center elimination of methanol to form the ketene RCH═C═O. At higher temperatures, concerted fragmentation to radicals will ensue to produce a mixture of species: (RCH + CO + CH) and (RCH + CO + CH═O + H). Thermal cracking of the β C-C bond of the methyl ester will generate the radicals (R and H) as well as CH═C═O + CH═O. The thermochemistry of methyl acetate and its fragmentation products were obtained via the Active Thermochemical Tables (ATcT) approach, resulting in ΔH(CHCOOCH) = -98.7 ± 0.2 kcal mol, ΔH(CHCO) = -45.7 ± 0.3 kcal mol, and ΔH(COOCH) = -38.3 ± 0.4 kcal mol.

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Thermal decomposition products of butyraldehyde

Cited by 7 publications

References 46 publications

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

Products From Pyrolysis of Gas-Phase Propionaldehyde

Thermal Decomposition of Potential Ester Biofuels. Part I: Methyl Acetate and Methyl Butanoate

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