posted on 2024-01-04, 18:06authored byYuwen Deng, Jijun Guo, Zaili Xiong, Wang Li, Changyang Wang, Meirong Zeng, Zhongyue Zhou, Long Zhao, Jiuzhong Yang, Wenhao Yuan, Fei Qi
The oxidation of pure n-butanal and the n-butanal/NO mixture was investigated
in an atmospheric
jet-stirred reactor at stoichiometric conditions and over the temperature
range of 425–925 K. Mole fraction profiles of characteristic
intermediates, like nitrogenous, carbonyl, and hydrocarbon intermediates
were obtained using synchrotron vacuum ultraviolet photoionization
mass spectrometry (SVUV–PIMS) via molecular beam sampling.
A previous reported kinetic model of n-butanal oxidation
was improved and a submechanism interpreting n-butanal/NOx interaction kinetics was developed and validated
against experimental measurements. Results show that NO addition results
in a featured temperature dependence of n-butanal
reactivity similar to that of hydrocarbon fuels, i.e., inhibiting
reactivity at low temperatures while promoting at intermediate temperatures.
However, the presence of the n-butanal carbonyl group
introduces distinct kinetic effects on this system compared to previously
reported hydrocarbon/NO systems. Model analysis suggests a pronounced
interaction between NO and the n-butanal carbonyl
group, particularly at low temperatures where NO notably accelerates
the removal of the carbonyl group, yielding large amounts of propyl
radicals. This interaction results in the suppression of peroxy radical
chemistry on the alkyl chain and chain-branching reactions of the
propyl radical, thus decreasing the low-temperature reactivity of n-butanal. At intermediate temperatures, the influence of
the carbonyl group on reactivity is not as pronounced and the increased
reactivity primarily depends upon the impact of NOx on the active radical pool. For example, NOx-related chemistry accelerated the formation of OH radicals,
thus facilitating fuel decomposition and the further conversion of
CO to CO2. Besides, NO addition significantly affects the
speciation of several products, such as methane, ethane, and formaldehyde,
which was correlated to the additional competitive pathways introduced
by NOx.