Low-temperature oxidation of diethyl ether: Reactions of hot radicals across coupled potential energy surfaces

Danilack, Aaron D.; Klippenstein, Stephen J.; Georgievskii, Yuri; Goldsmith, C. Franklin

doi:10.1016/j.proci.2020.07.111

Cited by 19 publications

(41 citation statements)

References 48 publications

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“…A low-temperature DEE oxidation mechanism from a prior study was used as the starting point for this work . This mechanism contained a single DEE chain-branching pathway, which is shown as pathway A at the top of Figure .…”

Section: Theory and Mechanism Developmentmentioning

confidence: 99%

“…Although DEE is large enough to form a pair of diastereomers in this process, their presence has not been accounted for in published mechanisms. In fact, over the past 5 years, at least seven studies have examined the low-temperature oxidation of DEE, but none of these mechanisms accounted for diastereomers. ,− The present theoretical work uses simulations of ignition delay time, a global combustion observable, to test the effect of including diastereomers in a low-temperature oxidation mechanism for DEE.…”

Section: Introductionmentioning

confidence: 99%

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Diastereomers and Low-Temperature Oxidation

et al. 2021

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Diastereomers have historically been ignored when building kinetic mechanisms for combustion. Low-temperature oxidation kinetics, which continues to gain interest in both combustion and atmospheric communities, may be affected by the inclusion of diastereomers in radical chain-branching pathways. In this work, key intermediates and transition states lacking stereochemical specification in an existing diethyl ether lowtemperature oxidation mechanism were replaced with their diastereomeric counterparts. Rate coefficients for reactions involving diastereomers were computed with ab initio transition state theory master equation calculations. The presence of diastereomers increased rate coefficients by factors of 1.2−1.6 across various temperatures and pressures. Ignition delay simulations incorporating these revised rate coefficients indicate that the diastereomers enhanced the overall reactivity of the mechanism by almost 15% and increased the peak ketohydroperoxide concentration by 30% in the negative temperature coefficient region at combustion-relevant pressures. These results provide an illustrative indication of the important role of stereomeric effects in oxidation kinetics.

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Section: Theory and Mechanism Developmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diastereomers and Low-Temperature Oxidation

et al. 2021

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“…To rationally design (bioderived) ethers with improved properties, there have been experimental and computational studies on the combustion kinetics of C2-C8 linear [11][12][13][14][15][16][17][18][19] and branched ethers [20][21][22][23]. These studies give insights into the oxidation chemistry and provide kinetic models for combustion simulations.…”

Section: Main Textmentioning

confidence: 99%

Bioderived ether design for low emission and high reactivity transport fuels

Cho

Kim

Etz

et al. 2021

Preprint

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Bioderived ethers have recently drawn attention as a response to increasing demands on clean alternative fuels. A theory-experiment combined approach was introduced for the five ether molecules representing linear, branched, and cyclic ethers to derive rational design principles for low-emission and high-reactivity ethers. Flow reactor experiments and quantum-mechanical calculations were performed at high (750–1100K) and low temperature (400–700K) regimes to investigate the structural effects on their sooting tendency and reactivity, respectively. At a high-temperature regime, ethers’ high sooting tendency is related to increased C3 and C4 hydrocarbon formation compared to C1 and C2 products from oxidation reactions. On the other hand, the reactivity at the low-temperature regime is determined by the activation energies of reaction steps until ketohydroperoxide formation. These studies found that ethers’ sooting tendency and reactivity are relevant to two structural factors: the carbon type (primary to quaternary) and the relative position of ether oxygen atoms to carbon atoms. These factors were utilized to build a multivariate model to predict the cetane number (CN) and yield sooting index (YSI) of 50 different ethers. The model suggests building blocks with specific carbon types that maximize CN and minimize YSI, leading to the design principles of ethers toward low emissions and high reactivity fuels for transport applications. Ethers with a high CN and low YSI were then proposed using the developed model, and through experimental measurements, it was proved that they are promising biodiesel candidates.

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“…However the chemistry of larger ethers is much less understood. Several studies have looked specifically at ethyl methyl ether, methyl tertiary butyl ether, ethyl tertiary butyl ether, and diethyl ether 11–14 . However, these studies focused primarily on high‐temperature ranges.…”

Section: Introductionmentioning

confidence: 99%

Oxidation and pyrolysis of methyl propyl ether

Johnson

Nimlos

Ninnemann

et al. 2021

Int J of Chemical Kinetics

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The ignition, oxidation, and pyrolysis chemistry of methyl propyl ether (MPE) was probed experimentally at several different conditions, and a comprehensive chemical kinetic model was constructed to help understand the observations, with many of the key parameters computed using quantum chemistry and transition state theory. Experiments were carried out in a shock tube measuring time variation of CO concentrations, in a flow tube measuring product concentrations, and in a rapid compression machine (RCM) measuring ignition delay times. The detailed reaction mechanism was constructed using the Reaction Mechanism Generator software. Sensitivity and flux analyses were used to identify key rate and thermochemical parameters, which were then computed using quantum chemistry to improve the mechanism. Validation of the final model against the 1–20 bar 600–1500 K experimental data is presented with a discussion of the kinetics. The model is in excellent agreement with most of the shock tube and RCM data. Strong non‐monotonic variation in conversion and product distribution is observed in the flow‐tube experiments as the temperature is increased, and unusually strong pressure dependence and significant heat release during the compression stroke is observed in the RCM experiments. These observations are largely explained by a close competition between radical decomposition and addition to O2 at different sites in MPE; this causes small shifts in conditions to lead to big shifts in the dominant reaction pathways. The validated mechanism was used to study the chemistry occurring during ignition in a diesel engine, simulated using Ignition Quality Test (IQT) conditions. At the IQT conditions, where the MPE concentration is higher, bimolecular reactions of peroxy radicals are much more important than in the RCM.

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Low-temperature oxidation of diethyl ether: Reactions of hot radicals across coupled potential energy surfaces

Cited by 19 publications

References 48 publications

Diastereomers and Low-Temperature Oxidation

Diastereomers and Low-Temperature Oxidation

Bioderived ether design for low emission and high reactivity transport fuels

Oxidation and pyrolysis of methyl propyl ether

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