Exploring the interaction kinetics of butene isomers and NOx at low temperatures and diluted conditions

摘要

The oxidation of 1-butene and i -butene with and without addition of 1000 ppm NO was experimentallyand numerically studied primarily at fuel-rich ( φ = 2.0) conditions under high dilution (96% Ar) in a flowreactor operated at atmospheric pressure in the low temperature range of approximately 60 0-120 0 K.Numerous intermediate species were detected and quantified using synchrotron vacuum ultraviolet photoionizationmass spectrometry (SVUV-PIMS). An elementary-step reaction mechanism consisting of 3996reactions among 682 species, based on literature and this work, was established to describe the reactionsand interaction kinetics of the butene isomers with oxygen and nitrogenous components. Model predictionswere compared with the experimental results to gain insight into the low- and high-temperaturefuel consumption without and with NO addition and thus the respective interaction chemistry. This investigationfirstly contributes a consistent set of temperature-dependent concentration profiles for thesetwo butene isomers under conditions relevant for engine exhaust gases. Secondly, the observed oxidationkinetics is significantly altered with the addition of NO. Specifically, NO promotes fuel consumption andintroduces for i -butene a low-temperature behavior featuring a negative temperature coefficient (NTC)region. The present model shows reasonable agreement with the experimental results for major productsand intermediate species, and it is capable to explain the promoting effect of NO that is initiated by itscontribution to the radical pool. Further, it can describe the observed NTC region for the i -butene/NOmixture as a result of the competition of chain propagation and chain terminating reactions that wereidentified by reaction flow and sensitivity analyses.