A Shock Tube Study of the Product Branching Ratio for the Reaction NH₂ + NO Using Frequency-Modulation Detection of NH₂

Abstract

The product branching ratio of [NH2 + NO → N2H + OH]:[NH2 + NO → N2 + H2O] has been determined in the temperature range of 1340−1670 K in a shock tube study with laser photolytic generation of the NH2 radicals. Sensitive frequency-modulation detection of the NH2 radical enables experiments with very low initial radical concentrations and, hence, virtually no interference from secondary reactions or dependence on the overall rate coefficient of the reaction. The branching ratio, α, defined as α = k 1a/(k 1a+k 1b), increases from 0.42 at 1340 K to 0.53 at 1670 K. Over this temperature range our results can be expressed as α = 0.5 + (3.36 × 10-4)(T/K − 1600). A detailed error analysis yields an uncertainty in the values of α of ±0.02 near 1500 K, increasing to ±0.05 at the temperature extremes.

Modeling the thermal De-NOx process: Closing in on a final solution

“…3). The more recent results for ␣ 1 (T) of Votsmeier et al [24] also agree well with our description of the reaction.…”

Control of combustion-generated nitrogen oxides by selective non-catalytic reduction

“…The rate coefficient expressions were constructed to be a good representation of Park and Lin's data (Park and Lin, 1996) for a(T) up to temperature 1100 K, to lie within the error bars of all data of Glarborg et al (1997), for a(T) in the thermal DeNO x temperature window [1100-1400 K] and also reasonably consistent with other experimental data (Vandooren et al, 1994;Votsmeier, 1999). The expressions were also constructed to give a good representation of total rate coefficient up to 1400 K.…”

Shock tube determination of the overall rate of NH2 + NO → products in the thermal De‐NOx temperature window

“…In our previous study of the branching ratio, we noted that the branching ratio determination depends slightly on the overall rate of the NH 2 + NO reaction [3]. With the new values of k 1 given by Eq.…”

“…As a result of many experimental and theoretical studies, a consensus exists for the branching ratio, α, in the temperature range 300-2000 K [3,4]. As for the overall rate coefficient, k 1 , the low temperature studies show consistent results, but two issues remain for temperatures above 1400 K. The first issue is uncertainty in the absolute value of k 1 at high temperatures, where there are significant discrepancies among the experimental studies.…”