NO
x mitigation is a central focus of combustion technologies with increasingly stringent emission regulations. NO
x can also enhance the autoignition of hydrocarbon fuels and can promote soot oxidation. The reaction between allyl radical (C
3H
5) and NO
x plays an important role in the oxidation kinetics of propene. In this work, we measured the absolute rate coefficients for the redox reaction between C
3H
5 and NO
x over the temperature range of 1000–1252 K and pressure range of 1.5–5.0 bar using a shock tube and UV laser absorption technique. We produced C
3H
5 by shock heating of C
3H
5I behind reflected shock waves. Using a Ti:Sapphire laser system with frequency quadrupling, we monitored the kinetics of C
3H
5 at 220 nm. Unlike low-temperature chemistry, the two target reactions, C
3H
5 + NO → products (R1) and C
3H
5 + NO
2 → products (R2), exhibited a strong positive temperature dependence for this radical-radical type reaction. However, these reactions did not show any pressure dependence over the pressure range of 1.5–5.0 bar, indicating that the measured rate coefficients are close to the high-pressure limit. The measured values of the rate coefficients resulted in the following Arrhenius expressions (in unit of cm
3/molecule/s):
To our knowledge, these are the first high-temperature measurements of allyl + NO
x reactions. The reported data will be highly useful in understanding the interaction of NO
x with resonantly stabilized radicals as well as the mutual sensitization effect of NO
x on hydrocarbon fuels.
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