Experimental and kinetic modeling study of low-temperature oxidation of n -pentane

Attractiveness in advanced low-temperature combustion engines drives a constantly updated understanding of low-temperature oxidation chemistry. In this work, the low-temperature oxidation chemistry of n -pentane in two jet-stirred reactors at atmospheric pressure and in the temperature range of 500- 825 K was investigated using combined analysis methods of synchrotron vacuum ultraviolet photoionization mass spectrometry, gas chromatography, and Fourier transform infrared spectroscopy. Furthermore, the gaseous mixture from JSR was collected in acetonitrile for subsequent product characterization using flow injection analysis, high-pressure and ultra-high-pressure liquid chromatography coupled to a Thermo Scientific TM Orbitrap (R) Q-Exactive high-resolution mass spectrometry. Numerous intermediate species were identified by these analytical methods, which contributed to unraveling the low-temperature oxidation reaction network of n -pentane. A detailed n -pentane model was tentatively developed to reduce deviations between experimental measurements and model predictions by updating the rate constants of C 5 keto-hydroperoxide decomposition, C 5 hydroperoxy cyclic ether decomposition, and Korcek reactions of C 5 keto-hydroperoxide, and by introducing pressure-dependent rate constants for the reaction classes of Q OOH + O 2 , Q OOH decompositions, concerted H O 2 -elimination of R O 2 , C 5 keto-hydroperoxide decomposition, C 5 hydroperoxy cyclic ether decomposition, and Korcek reactions of C 5 keto-hydroperoxide, and by adding more detailed sub-mechanisms for C 5 cyclic ethers and C 5 keto-hydroperoxides. This updated model was validated against a set of available experimental data, including jet-stirred reactor species data and ignition delay times. These exploratory updates of the kinetic model reveal the considerable influence of the rate constants of hydroperoxide decomposition and the pressure-dependent rate constants of key reaction classes on the kinetic model predictions, highlighting the future demands for high-precision quantum chemistry calculations of the pressure-dependent rate constants of the aforementioned reaction classes to reduce mechanism uncertainties and to develop accurate and robust chemical kinetic models.(c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

In this study, the low-temperature oxidation chemistry of n-pentane was investigated using various analysis methods. Intermediate species were identified, contributing to the understanding of the reaction network of n-pentane. A detailed model was developed and validated against experimental data, showing the importance of rate constants and pressure-dependent reactions in kinetic model predictions. This highlights the need for accurate quantum chemistry calculations and robust chemical kinetic models.