Oxidation of n-Nonane: Measurements of Low-Temperature Products in Jet-Stirred Reactors

Abstract

n-Nonane is a medium-chain n-alkane representative of the light-end components found in jet and diesel fuels. In this work, low-temperature (low-T) oxidation of n-nonane was investigated in jet-stirred reactors at near-atmospheric pressure, fuel-lean conditions (ϕ = 0.5), an initial fuel concentration of 5000 ppm, a mean residence time of 2 s, and over a temperature range of 500–770 K. Reactants, intermediates, and products were detected and identified by chromatography and mass spectrometry. Gas-phase samples were analyzed by using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Liquid-phase samples were analyzed by two-dimensional gas chromatography coupled with time-of-flight MS (GC × GC-TOF/MS) through flow injection. Besides stable species, some other low-T oxidation species, which are the main first and second O2 addition products, were observed. Through the combination of theoretical, chromatographic, and mass spectrometric results, clarification was achieved regarding various isomers and their formation mechanisms during the low-T oxidation of n-nonane. In addition, simulations were performed using a literature kinetic model to predict the reactivity of n-nonane and the formation of crucial compounds, indicating that improvements are needed to better describe the low-T oxidation of n-nonane under the present conditions. The results of this study provide deep insight into the low-T oxidation of n-nonane and contribute to the development of kinetic models for n-nonane and larger-chain alkane oxidation.