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The decomposition of nitrous oxide at 1.5 ⩽ P ⩽ 10.5 atm and 1103 ⩽ T ⩽ 1173 K
Author(s) -
Allen Mark T.,
Yetter Richard A.,
Dryer Frederick L.
Publication year - 1995
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550270906
Subject(s) - chemistry , nitrous oxide , decomposition , organic chemistry
Reaction experiments on mixtures of N 2 O/H 2 O/N 2 were performed in a variable pressure flow reactor over temperature, pressure, and residence time ranges of 1103–1173 K, 1.5–10.5 atm, and 0.2–0.8 s, respectively. Mixtures of approximately 1% N 2 O in N 2 were studied with the addition of varying amounts of water vapor, from background to 3580 ppm. Experimentally measured profiles of N 2 O, O 2 , NO, NO 2 , H 2 O, and temperature were compared with predictions from detailed kinetic modeling calculations to assess the validity of a reaction mechanism developed from currently available literature thermochemical and rate constant parameters. Sensitivity and reaction flux analyses were performed to determine key elementary reaction path processes and rates. Reaction rate constants for the uni‐molecular reaction, N 2 O → N 2 + O, were determined at various pressures in order to match overall experimental and numerical decomposition rates of N 2 O. The numerical model included a newly determined rate constant for N 2 O + OH → HO 2 + N 2 with an upper limit of 5.66 × 10 8 cm 3 mol −1 sec −1 at 1123 K. This is considerably smaller than presently reported in the literature. The experimentally observed rate of N 2 O decomposition was found to be slightly dependent on added water concentration. The rate constant determined for the elementary decomposition is strongly dependent on the choice of rate constants for the N 2 O + O ⇔ N 2 + O 2 and N 2 O + O ⇔ NO + NO reactions. In the absence of accurate data at the temperatures of this work, and based on these and other experiments in this laboratory, we presently recommend rate constants from the review of Baulch et al. The basis for this recommendation is discussed, including the impact on the rate constants derived for elementary nitrous oxide decomposition. The uncertainties in the rate constants as reported here are ±30%. The present mechanism was applied to previously reported high‐pressure shock tube data and yields a high‐pressure limit rate constant a factor of three larger than previously reported at these temperatures. The following expressions for the elementary decomposition reaction are recommended: k 0, N 2= 9.13 × 10 14 exp (−57, 690/ RT ) cm 3 mol −1 s −1 and k ∞ = 7.91 × 10 10 exp(−56020/ RT ) s −1 . Simple Lindemann fits utilizing these parameters reproduce the pressure dependent rate constants measured here within ±25%. © 1995 John Wiley & Sons, Inc.