An experimental and modelling study of n-pentane oxidation in two jet-stirred reactors: The importance of pressure-dependent kinetics and new reaction pathways

Abstract

Two jet-stirred reactors (JSRs) coupled to gas chromatographic and spectroscopic techniques have been utilised to detect chemical species evolved during n -pentane oxidation at 1 and 10 atm, in the temperature range 500-1100 K, and at equivalence ratios of 0.3-2.0. To the authors' knowledge, this is the first study of a fuel's oxidation in two JSRs. In addition, the choice of experimental conditions results in there being the same concentration of n -pentane in all investigated mixtures; 1% at 1 atm, and 0.1% at 10 atm. This permits the additional assessment of the importance of pressure-dependent kinetics in predicting species concentration profiles. A recently published literature model served as the starting point in simulating these experiments, with only minor additions and modifications necessary to achieve good overall agreement. The main adjustments were made to account for multi-oxygenated species (C 5 aldehydes, ketones, diones, etc .) detected mainly at low temperatures ( < 800 K) in both JSRs. In this paper we present new experiments, the most important of which are very well predicted using the aforementioned literature model. The effect of adding chemical pathways, which have been postulated to contribute to the generation of multi-oxygenated species, has been investigated. Finally, a brief account on the importance of pressure-dependent kinetics in the modelling of these experiments is provided.

Measuring hydroperoxide chain-branching agents during n-pentane low-temperature oxidation

“…Also, while some m/zpeaks can be seen for larger alkenes or oxygenated compounds in the MS spectra, it is difficult to compare with chromatographic analysis due to the large number of isomers. The Galway model displayed excellent performance in reproducing the JSR data, as already shown by [9] (Figures S4 and S5) Figure 1: Mass spectrum obtained during stoichiometric n-pentane oxidation at 600 K using SPI-MS (zoomed in the ketene and propene m/z = 42 region). Numbers are m/z discussed in the text.…”

“…The three apparatuses described above were used to study the oxidation of n-pentane between 500 K and 1100 K, under quasi-atmospheric pressure (1.05 atm), at a mean residence time of 2.00 ± 0.01 s, and for a fuel initial mole fraction of 0.010 (complete gas-chromatographic analysis of the gases leaving the JSR can be found in [9]). All the experimental data presented here are detailed in an SM spreadsheet.…”

“…All the experimental data presented here are detailed in an SM spreadsheet. The model used for simulations is that newly proposed by the Galway group [9] with formation reactions of diones adapted from [14]. A few changes have been tested in this mechanism and are listed in SM.…”

“…While ketene is frequently detected in flame experiments [16] and it is also a possible decomposition product of ketohydroperoxides, its detection was only reported recently in a jet-stirred reactor oxidation study of an alkane [9]. Figure 1 shows SPI-MS peaks at m/z 42 that correspond to ketene (m/z = 42.0367) and propene (m/z = 42.0797).…”

“…These three objectives are achieved for the oxidation of n-pentane for a large range of equivalence ratios (0.5-2); n-pentane is a fuel representative of gasoline components for which several recent investigations, including new model development, have been performed [8][9].…”