Kinetics of the O(³P) + N₂O Reaction. 2. Interpretation and Recommended Rate Coefficients

Abstract

The reaction O( 3 P) + N 2 O is important to models of NO x pollutant and propellant chemistry and to the understanding of the thermal decomposition of N 2 O, which has historically played a key role in the development of unimolecular reaction theory. The reaction has two important product channels: ). Rate coefficients of these reactions have been the subject of several reviews. However, clear reasons why many of the evaluated, nonretained data differ from recommendations have not previously been known. There has been a great deal of controversy over the rate coefficients, particularly for reaction R2. Here, the relevant data are critically evaluated using detailed chemical modeling as an important tool. The results explain many of the discrepancies. Some of the data of central importance in earlier evaluations are shown to be incorrect. Additionally, some important features of the global behavior of the mixtures studied, which had previously not been understood, are explained, and the possible effects of hypothetical H 2 O contamination on N 2 O shock tube studies was quantitatively investigated. It is shown that the bulk of the rate coefficient results remaining after the evaluations can be combined with the intermediate temperature results for k tot ) k 1 + k 2 from FGFAM (Fontijn, A.; Goumri, A.; Fernandez, A.; Anderson, W. R.; Meagher, N. E. J. Phys. Chem., preceding paper in this issue) to obtain fitted recommendations: k 1 ) 1.52 × 10 -10 exp(-13 930/T) cm 3 molecule -1 s -1 (1370-4080 K); k 2 ) 6.13 × 10 -12 exp(-8,020/T) cm 3 molecule -1 s -1 (1075-3340 K). Until recently, it was believed rate coefficients of the two product channels were approximately equal over a very wide temperature range. In contrast, the present study has led to the conclusion that reaction R2 dominates below, and reaction R1 above, 1840 K.

A study of N2O decomposition rate constant at high temperature: Application to the reduction of nitrous oxide by hydrogen

“…The rate constant of the N 2 O + Ar → N 2 + O + Ar reaction could thus be deduced during all the observation time at temperatures above 1900 K. At temperatures higher than 2500 K, the nitrous oxide decomposition rate was too fast to be accurately evaluated. Then, the upper temperature for this study was limited to 2500 K. At temperatures lower than 1900 K, although the rate constant for the studied reaction has been considered to be in the low-pressure limit for pressures ≤600 kPa [7,8], the present experiments showed that, at pressures above approximately 300 kPa, the unimolecular decomposition of N 2 O had to be taken into account for modeling determined by Meagher and Anderson [9] determined by Davidson et al [5] recommended by Tsang and Herron [12] without N 2 O+O elementary reactions precisely the O atom concentration toward the low temperatures (Fig. 9).…”

“…Temperature and pressure behind the reflected shock wave were computed from the incident shock speed, which was measured by piezoelectric pressure gauges. [3] with k N 2 O+Ar suggested by Dean and Bozzelli [13] with k N 2 O+Ar determined by Röhrig et al [7] [3] with k N 2 O+Ar suggested by Dean and Bozzelli [13] with k N 2 O+Ar determined by Röhrig et al [7] [3] with k N 2 O+Ar suggested by Dean and Bozzelli [13] with k N 2 O+Ar determined by Röhrig et al [7] Meagher and Anderson [9] Baulch et al [14] Davidson et al [5] Dean and Bozzelli [13] Röhrig et al [7], Hanson and Salimian [11], Tsang and Herron [12] Zuev and Starikovskii [4] The optical detection technique for measuring O atom concentration was an emission line absorption method. A microwave-excited discharge lamp that contained a flowing mixture of 1% O 2 in He maintained at a pressure of 1.4 kPa was used as light source.…”

“…The high-pressure limiting rate constant determined by Zuev and Starikovskii [3] was chosen. For the reactions involving O with N 2 O, the rate constant results from the intensive study of Meagher and Anderson [9] (also recommended by Baulch et al [14]) were used. Our choice will be justified later on.…”

“…The thermal decomposition and reactions of N 2 O have been the subject of numerous old [1,2] and recent experimental [3][4][5][6][7][8][9] and theoretical [10] studies, as seen in the reviews by Hanson and Salimian [11], Tsang and Herron [12], and more recently, Dean and Bozzelli [13] and Baulch et al [14]. These early studies established that the thermal N 2 O decomposition reaction proceeds via a spin-forbidden, nonadiabatic pathway to form O( 3 P) atoms in preference to the spin-allowed pathway to form O( 1 D) atoms: Consequently, the experimental activation energy of the decomposition reaction was found very much higher than the N 2 -O( 3 P) bond energy.…”

Theoretical Chemical Study on NO Interaction with Cu

“…The reaction of N2O with an O atom can form NO in both the combustion and the thermal decomposition of N2O. Many experimental 11,12 and theoretical 13,14 studies have focused on this interaction. These works suggested that the activation energy of the reaction is about 115.8 kJ/mol.…”