TY - JOUR
T1 - Conformation-dependent low-temperature oxidation chemistry of methylcyclohexane
T2 - First oxygen addition and chain-branching
AU - Zou, Jiabiao
AU - Zhang, Jianguo
AU - Lian, Tianyou
AU - Xu, Qiang
AU - Liu, Bingzhi
AU - Wang, Zhandong
AU - Yang, Jiuzhong
AU - Li, Yuyang
N1 - 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
PY - 2022/9
Y1 - 2022/9
N2 - 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.
AB - 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.
KW - Conformational analysis
KW - Kinetic model
KW - Low-T oxidation
KW - Methylcyclohexane
KW - SVUV-PIMS
UR - http://www.scopus.com/inward/record.url?scp=85122992523&partnerID=8YFLogxK
U2 - 10.1016/j.combustflame.2021.111963
DO - 10.1016/j.combustflame.2021.111963
M3 - Article
AN - SCOPUS:85122992523
SN - 0010-2180
VL - 243
JO - Combustion and Flame
JF - Combustion and Flame
M1 - 111963
ER -