A shock tube study of the pyrolysis of NO2
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NO2concentration profiles in shock-heated NO2/Ar mixtures were measured in the temperature range of 1350-2100 K and pressures up to 380 atm using Ar+laser absorption at 472 7 nm, IR emission at 6.25 ±025 μm. and visible emission at 300-600 nm. In the course of this study, the absorption coefficient of NO2at 472.7 nm was measured at temperatures from 300 K to 2100 K and pressures up to 75 atm Rate coefficients for the reactions NO2+ M→NO + O + M(1), NO2+ NO2→ 2NO + O2(2a), and NO2+ NO2→ NO3+ NO (2b) were derived by comparing the measured and calculated NO2profiles. 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%: κ10= 10(15.6±0.2|exp(-(251 ±5) kJ mol-1/RT) cm3mol-1s-1k1∞= 10(146±)exp(-300 kJ mol-1/RT) s-1The inferred rate coefficient at the low-pressure limit. κ10. 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 k1, observed in the earlier work of Troe  was confirmed. The rate coefficient inferred for the high pressure limit, k1∞. 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: K2a10123±exp(-(105 ±7) kJ mol-1/RT) cm3mol-1s-1k2b= 1013.0±exp(-(l08 ±8)kJ mol-1/RT)cm3mol-1s-1For reaction (2), the new data agree with previously recommended values of k2aand k.2balthough the present study suggests a slightly higher preexponential factor for k2a©1997 John Wiley & Sons, Inc.
author list (cited authors)
Röhrig, M., Petersen, E. L., Davidson, D. F., & Hanson, R. K.