Experimental and modeling investigation of the oxidation of n-hexylbenzene: Insight into the formation of low-temperature intermediates

Abstract

As vital components in transportation fuels, an in-depth understanding of the oxidation mechanism of n-alkylbenzenes is pivotal for minimizing pollutant emissions during combustion processes. However, previous research was mostly focused on high-temperature oxidation, while investigations on low-temperature oxidation of long-chain n-alkylbenzenes remains scarce. In this work, n-hexylbenzene (C12H18) was selected to conduct low-temperature oxidation experiments in a jet-stirred reactor. A series of crucial intermediates and products were detected and then quantified by the synchrotron vacuum ultraviolet radiation photoionization mass spectrometry (SVUV-PIMS). In particular, characteristic aromatic oxygenated intermediates with compositions of C12H18Oy, C12H16Oy, C12H14Oy and C12H12Oy (0 ≤ y ≤ 3) were measured, which reveal the occurrence of first O2 addition, second O2 addition, and sequential oxidation reactions. To disclose the crucial reactions that control the fuel decomposition and formation of oxygenated intermediates, a detailed kinetic model of n-hexylbenzene was developed. This model was further utilized to explore the oxidation behaviors of C6 to C12n-alkylbenzenes. It was revealed that n-hexylbenzene exhibits the strongest low-temperature oxidation reactivity, while C6C10n-alkylbenzenes display little reactivity under present conditions. In conclusion, the reasonable performance of this model in predicting the oxidation behaviors of n-alkylbenzenes indicates its potential application in elucidating the low-temperature oxidation chemistry of heavier n-alkylbenzenes.