Effects of 1-nitropropane on pyrolysis of n-hexane at atmospheric pressure

Abstract

In order to investigate the effects of 1-nitropropane (1-NP) on the pyrolysis of n-hexane, the pyrolysis processes of pure n-hexane and n-hexane/1-NP mixture in a jet-stirred reactor (JSR) were experimentally studied at atmospheric pressure with the technique of synchrotron ultraviolet photoionization mass spectrometry (SVUV-PIMS). The pyrolysis experiments of pure n-hexane and n-hexane/1-NP mixture were performed in the temperature ranges of 673–1143 K and 598–1128 K, respectively. The species pools for the pyrolysis of pure n-hexane and n-hexane/1-NP mixture were comprehensively determined and 25 species for pyrolysis of pure n-hexane versus 18 species for pyrolysis of n-hexane/1-NP mixture were identified. Based on the photoionization mass spectra scanned at different photon energies, the mole fraction profiles of all the pyrolysis species were evaluated. The experimental results showed that the initial pyrolysis temperature of n-hexane was observably reduced by 75 K with the addition of 1-NP, and the initial formation temperatures (IFTs) of some major pyrolysis products and important intermediates were correspondingly reduced. A high degree of conformity in the species pools of the pyrolysis of pure n-hexane and n-hexane/1-NP mixture (at both low and atmospheric pressures) was observed. On the basis of the experimental observations, modeling simulations and mechanisms proposed in previous studies, the low-temperature mechanisms for the 1-NP-initiated pyrolysis of n-hexane were discussed. A mechanism, including unimolecular dissociation reactions of 1-NP, radical reactions to produce highly active radicals, H-abstraction reactions of n-hexane and subsequent C-C bond dissociation reactions of hexyl radicals, was proposed.