Jet-Stirred Reactor Study of Low-Temperature Neopentane Oxidation: A Combined Theoretical, Chromatographic, Mass Spectrometric, and PEPICO Analysis

Abstract

The oxidation of neopentane was studied in jet-stirred reactors at atmospheric pressure over a temperature range 500–850 K and ϕ = 0.5. The products were analyzed with chromatographic, mass spectrometric, and photoelectron spectroscopic setups complemented with theoretical calculations. This combination provides a comparison of photo-ionization mass spectrometry and gas chromatography for the quantification of mole fractions and highlights the relevant differences between them, while mass-tagged photoelectron spectroscopy sheds light onto the isomeric distribution. The new data and corresponding analyses are expected to provide valuable guidance for an extension of the kinetic model and the choice of experimental methods. The main first and second O2-addition products were observed in agreement with the literature (e.g., 3,3-dimethyloxetane, acetone, isobutene, and γ-ketohydroperoxide). The simulated mole fractions of the products using a literature kinetic model were compared to the experimental results. Even though the kinetic model has been validated previously, significant discrepancies between the measured and simulated mole fractions of 2-methylpropanal and methacrolein, two fuel-specific low-temperature oxidation products, were found. Furthermore, some experimentally observed species related to γ-ketohydroperoxide decomposition were not predicted indicating that the model is incomplete. The detection of 2-methylpropanal and formic acid highlighted the importance of the Korcek-type pathway.

Experimental and Updated Kinetic Modeling Study of Neopentane Low Temperature Oxidation

“…The pressure dependence of the Q̇OOH + O 2 and Q̇OOH decomposition reaction classes was considered, which is important in improving the model predictions under atmospheric conditions. The identification of isobutyric acid supports the existence of the Korcek mechanism during neopentane oxidation, which is consistent with the findings of Bourgalais et al and Eskola et al The Korcek reactions were added to the updated kinetic model. However, the results show that the Korcek reactions could not fully explain the experimental observations.…”

Accounting for molecular flexibility in photoionization: case of tert-butyl hydroperoxide

“…The results can then be used as future reference for its detection in combustion/oxidation reactions via advanced mass spectrometry techniques. 62 Besides, the signal branching ratio between the parent and fragment ions is also provided for the first time in this work for an accurate quantification of t BuOOH in combustion/oxidation experiments and show that a corrective factor of 3.3 needs to be applied to quantify t BuOOH at 10.6 eV. The current work shows that t BuOOH produces a signal at m / z 90 at 9.8 eV that is only a factor of 2–2.5 weaker than the fragment signal at m / z 57 at 10.6 eV.…”

Product Identification in the Low-Temperature Oxidation of Cyclohexane Using a Jet-Stirred Reactor in Combination with SVUV-PEPICO Analysis and Theoretical Quantum Calculations

“…The experiments were performed on the VUV DESIRS beamline at the SOLEIL synchrotron. The experimental setup is identical to that described in Bourgalais et al , and Battin-Leclerc et al and only a summary with the specificities related to this work is given here.…”

“…The peak at m/z 97 is substantially broader than those for m/z 96 and m/z 98, which is characteristic of a fragment peak (see Figure 1: typical time-of-flight mass spectrum obtained by integration over the photon energy range from 10.0 to 11.0 eV with a step size of 5 meV and an acquisition time of 80 s per step during the LTO of cyclohexane at ϕ = 0.5 and T = 590 K. The vertical scale is reduced to zoom out the low intensity peaks so that cyclohexane (m/z 84) and its 7% 13 C isotopomer (m/z 85) are cut off). Accordingly, the simulated spectrum of γKHP shown in Figure 10 should be compared to the sum of the experimental spectra of m/z 130 and m/z 97.…”