A shock tube study of the pyrolysis of NO2

Abstract

NO 2 concentration profiles in shock-heated NO 2 /Ar mixtures were measured in the temperature range of 1350 -2100 K and pressures up to 380 atm using Ar ϩ laser absorption at 472.7 nm, IR emission at , and visible emission at 300 -600 nm. In the course of this study, the absorption coefficient of NO 2 at 472.7 nm was measured at temperatures from 300 K to 2100 K and pressures up to 75 atm. Rate coefficients for the reactions and were derived by comparing the measured and calculated NO 2 profiles. For reaction (1), the following low-and high-pressure limiting rate coefficients were inferred which describe the measured fall-off curves in Lindemann form within 15%:The inferred rate coefficient at the low-pressure limit, k 1o , is in good agreement with previous work at higher temperatures, but the energy of activation is lower by 20 kJ/mol than reported previously. The pressure dependence of k 1 observed in the earlier work of Troe [1] was confirmed. The rate coefficient inferred for the high pressure limit, k 1ϱ , is higher by a factor of two than Troe's value, but in agreement with data obtained by measuring specific energydependent rate coefficients.For the reactions (2a) and (2b), least-squares fits of the present data lead to the following Arrhenius expressions:For reaction (2), the new data agree with previously recommended values of k 2a and k 2b , although the present study suggests a slightly higher preexponential factor for k 2a . © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 483 -493, 1997. k 2b ϭ 10 13.0Ϯ0.3 exp(Ϫ(108 Ϯ 8) kJ mol Ϫ1 / RT) cm 3 mol Ϫ1 s Ϫ1 k 2a ϭ 10 12.3Ϯ0.2 exp(Ϫ(105 Ϯ 7) kJ mol Ϫ1 / RT) cm 3 mol Ϫ1 s Ϫ1 k 1ϱ ϭ 10 (14.6Ϯ0.3) exp(Ϫ300 kJ mol Ϫ1 / RT) s Ϫ1 k 1o ϭ 10 (15.6Ϯ0.2) exp(Ϫ(251 Ϯ 5) kJ mol Ϫ1 /RT) cm 3 mol Ϫ1 s Ϫ1 (2b) NO 2 ϩ NO 2 : NO 3 ϩ NO NO 2 ϩ M : NO ϩ O ϩ M (1), NO 2 ϩ NO 2 : 2NO ϩ O 2 (2a), 6.25 Ϯ 0.25 m

Computational study of collisions between O(3P) and NO(2Π) at temperatures relevant to the hypersonic flight regime

“…At 2700 K, the computed rate coefficient compares favourably with experimental data. 53,54 No correction was made for zero-point energy (ZPE) and other quantum effects, such as tunneling through the centrifugal barrier which can be still significant at low temperatures. The centrifugal barrier originates from the conservation of the total angular momentum and consists of the rotational energy associated with the orbital angular momentum of the colliding partner with respect to the center of mass of the whole system.…”

Experimental measurements and kinetic modeling of CO/H2/O2/NOx conversion at high pressure

“…The recombination reaction between NO and O to form NO 2 (R31) is well‐characterized across wide temperature and pressure intervals, i.e. 117–120, and old 121 and recent 41 reviews are generally in good agreement. The present mechanism uses high‐ and low‐pressure limits from Tsang and Herron including falloff parameters.…”

“…through NO+NO+O 2 ⇋ NO 2 +NO 2 ⇋ N 2 O 4 , whereas increasing temperatures promote the reverse decomposition reactions. A shock tube study of the thermal decay of NO 2 by Röhrig et al 119 has recently provided experimental data for (R42) and (R43) at high temperatures (1350–2100 K). Park et al 145 combined these data for (R42) with pyrolysis measurements for NO x at intermediate temperatures (602–954 K) to obtain an expression of k 42 across the temperature range 600–1450 K. Data of (–R42) are also available at intermediate temperatures: Olbregts 147 conducted static reactor experiments with NO/O 2 mixtures at temperatures from 226 to 758 K to yield an expression of k −42 that agrees within 15% of the expression of Park et al at temperatures from 600 to 1450 K, when using thermodynamic data from Table I to calculate k 42 .…”

Nonideal effects behind reflected shock waves in a high-pressure shock tube

“…Unfortunately, when performing chemistry measurements in a shock tube, errors in the reaction temperature can lead to large uncertainties in the rate coefficient or ignition delay time [1]. For example, the high-pressure rate coefficient of N0 2 has an activation energy of 300 kJ/mol (i.e., k^T) = 4xl0 14 exp(300/RT) ) [2]. For an average temperature of 1500 K, a 15-K error in temperature (i.e., only 1%) can lead to a 25% uncertainty in the measured rate coefficient.…”