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Show 1.6.3 (2): CN03C = k2COH3/ki (4) Reference [123 includes experimental results for [N03c in the temperature range 1150-1500 K. It was found that [N03c strongly increases with temperature. Detailed chemical kinetic models for the NH3/NO/02/H20 system have recently been presented by Miller, Branch and Kee [133, by Silver, Gozewski and Kolb [153, and by Sahmian and Hanson [163. These models incorporate 82, 54 and 49 elementary reactions, respectively. The rate constants of these reactions are not all known. The present reactions (l)-(3) represent principal reaction paths also in the models of [133, [153 and [163, except that the overall products of (1) are taken to be (1 - a)(N2 + H20) • oc(N2 + H + OH). The branching coefficient oc had previously been introduced by Lyon and Benn [103, who noted that reaction (1) is a chain-terminating process if a < 1/2. In the studies of [153 and [163, <x was treated as an adjustable parameter. Satisfactory agreement of the computations of [163 with the expintroduced by Lyon and Benn C103, who noted that reaction (1) is a chain-terminating process if a < 1/2. In the studies of [153 and [163, a was treated as an adjustable parameter. Satisfactory agreement of the computations of [163 with the expucts of reaction (1) are reported in [203. These showed that the principal products are N2H + OH, confirming a hypothesis made earlier in [133 concerning the details of channel 1(A). Also discussed in [133 are various plausible details of reaction (2) ("channel II"), as well as plausible factors contributing to the dominance of (2) over (i) at high temperatures. Figs. 3 and 4 of [13] represent mole fraction time histories for various species of importance in the process. Various spectroscopic studies of chemically reacting NH3-NO mixtures have been reported by Caralp et al. C213-C233, who also discussed the mechanism of reaction. The influence of thiophene on the selective reduction of NO by NH3 has recently been investigated by Lucas and Brown [243. In the first part of the present paper, the consequences of the Seery-Zabielski-Fenimore model represented by reactions (l)-(3) are investigated in detail. The rate equations are solved by a perturbation scheme (Sec. II). If it is assumed that [OH3 is independent of time and exponentially dependent on temperature, and that both k3 and the ratio k2/kj = [N03c/[OH3 are constant, the value of k^k3/k2 can be determined from some of the experimental data of Muzio, Arand and Teixeira [43 (cf. Sec. IID. The procedure followed yields complete numerical results for [N03 as a function of time and temperature. These results are in satisfactory agreement with the remaining data of [43. The corresponding OH-concentration is found to be considerably below its equilibrium value. This lends support |
