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™ Orbitrap® 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 HȮ 2 -elimination of RȮ 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.