Abstract
Conformational effect is an important feature of the low-temperature (low-T) oxidation chemistry of cycloalkanes. In this work, both theoretical calculation and conformational analysis were performed for the first oxygen addition in methylcyclohexane (MCH) oxidation to better understand the influence of the spatial orientation and the steric hindrance of substituted functional groups. Based on synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) measurements and adiabatic ionization energy calculations, reactive hydroperoxides, highly oxygenated molecules and stable products were identified in the jet-stirred reactor (JSR) oxidation of 1.0% and 0.5% MCH at 1.04 bar, 500–900 K and the equivalence ratio of 0.25. The abundant formation of 1-methylcyclohexene and the observation of alkenylhydroperoxides and their decomposition products verify the existence of conformation-dependent pathways in first and second oxygen addition in low-T MCH oxidation, respectively. A MCH oxidation model incorporated with conformation-dependent pathways was constructed to consider the conformational effects of cyclohexane ring and sidechain, and was validated against experimental data over a wide range of conditions in this work and literature. The consideration of conformational effects of cyclohexane ring and sidechain can generally better predict the measured species profiles and ignition delay time under low-T conditions. Based on modeling analysis, conformational effects of cyclohexane ring were found to play important roles in first oxygen addition and chain-branching in low-T MCH oxidation. Compared with the situation in low-T cyclohexane oxidation, the methyl substitution on cyclohexane ring reduces its conformational effects on chain-branching process.
| Original language | English (US) |
|---|---|
| Article number | 111963 |
| Journal | Combustion and Flame |
| Volume | 243 |
| DOIs | |
| State | Published - Sep 2022 |
Bibliographical note
Funding Information:This work was supported by the National Key R&D Program of China (2017YFE0123100) and National Natural Science Foundation of China (91841301, U1832171). The quantum chemistry calculation was performed on the High Performance Computing Cluster of Shanghai Jiao Tong University. The authors appreciate Dr. Lili Ye at Dalian University of Technology for constructive suggestions on theoretical calculations and Mr. Weiye Chen and Mr. Huaijiang Su at University of Science and Technology of China for the technician assistance of SVUV-MBMS experiments.
Funding Information:
This work was supported by the National Key R&D Program of China ( 2017YFE0123100 ) and National Natural Science Foundation of China ( 91841301 , U1832171 ). The quantum chemistry calculation was performed on the High Performance Computing Cluster of Shanghai Jiao Tong University. The authors appreciate Dr. Lili Ye at Dalian University of Technology for constructive suggestions on theoretical calculations and Mr. Weiye Chen and Mr. Huaijiang Su at University of Science and Technology of China for the technician assistance of SVUV-MBMS experiments.
Publisher Copyright:
© 2021 The Combustion Institute
Keywords
- Conformational analysis
- Kinetic model
- Low-T oxidation
- Methylcyclohexane
- SVUV-PIMS
ASJC Scopus subject areas
- General Chemistry
- General Chemical Engineering
- Fuel Technology
- Energy Engineering and Power Technology
- General Physics and Astronomy