Kinetics and modeling of the H₂O₂NO_x system

Abstract

The addition of NO (0 to 400ppm) to mixtures of Hz (ca. 1%) and 0 2 (0.7 to 22%) has been studied over the temperature range 700 to 825 K, in a flow reactor at atmospheric pressure. The overall effect of NO is to promote the oxidation of Hz but high concentrations of 0 2 actually inhibit the NO-promoted oxidation of Hz.A detailed kinetic mechanism has been constructed and found to describe the experimental observations. The promotion of the oxidation of HZ arises through the catalytic cycleThe ability of R.34 to reactivate chains normally terminated by the formation of HO2 is a key feature of this system. The predictions are highly sensitive to the rate of the reaction R.5 and the rate constants for this reaction is the only adjustable parameter required in the model. The value of h 5 ,~2 found to describe all the results K 5 ,~2 = 2.60 X lOI5 exp(+1350 cal.mol-l/RT) cm6.mol -'.s-l has an absolute uncertainty 135%. The uncertainty relative to other important rate constants in the Ha-02 system is less than 10%. 0 1995 John Wiley & Sons, Inc.

Flow reactor studies and kinetic modeling of the H2/O2 reaction

“…Since that publication, new rate constant data have been published for several important reactions including H ϩ O 2 (ϩM) ϭ HO 2 (ϩM) [6,7] and HO 2 ϩ OH ϭ H 2 O ϩ O 2 [8]. In particular, the studies of Bromly et al [6] and Davidson et al [7] recommended rate expressions for H ϩ O 2 ϩ N 2 ϭ HO 2 ϩ N 2 which, when incorporated into our H 2 /O 2 submechanism, adversely affected the predictive ability of the CO/H 2 O/O 2 mechanism at conditions where HO 2 /H 2 O 2 chemistry is important. To resolve this discrepancy, we recently derived new rate constant data for the low-pressure limit H ϩ O 2 ϩ M ϭ HO 2 ϩ M (M ϭ N 2 ,Ar) [9].…”

“…In a previous paper [4], we presented a moist CO oxidation reaction mechanism incorporating a detailed H 2 /O 2 submechanism developed and validated using high-pressure (2.5 -15.7 atm) flow reactor data which placed significant emphasis on reactions involving HO 2 and H 2 O 2 [5]. Since that publication, new rate constant data have been published for several important reactions including H ϩ O 2 (ϩM) ϭ HO 2 (ϩM) [6,7] and HO 2 ϩ OH ϭ H 2 O ϩ O 2 [8]. In particular, the studies of Bromly et al [6] and Davidson et al [7] recommended rate expressions for H ϩ O 2 ϩ N 2 ϭ HO 2 ϩ N 2 which, when incorporated into our H 2 /O 2 submechanism, adversely affected the predictive ability of the CO/H 2 O/O 2 mechanism at conditions where HO 2 /H 2 O 2 chemistry is important.…”

Experimental study and detailed kinetic modeling of the effect of exhaust gas on fuel combustion: mutual sensitization of the oxidation of nitric oxide and methane over extended temperature and pressure ranges

“…This can be viewed as a mutual sensitization: the oxidation of the fuel is promoted by NO x and the oxidation of NO into NO 2 is promoted by hydrocarbons. Kinetic studies have mainly been performed in tubular flow reactors (FR), investigating the promoting effect of NO on the oxidation of hydrogen [3], methane to n-pentane [4][5][6][7][8][9][10][11][12][13], while other studies concentrated on the promotion of the NO to NO 2 conversion by simple hydrocarbons [11,[14][15][16]. Kinetic modeling was previously presented [4,5,11,13,17].…”

Thermochemical properties for n‐propyl, iso‐propyl, and tert‐butyl nitroalkanes, alkyl nitrites, and their carbon‐centered radicals

“…61 and 40 kcal mol −1 , respectively [4][5][6][7][8]. The nitro alkanes and alkyl nitrites can release NO and NO 2 and can serve as catalysts in oxidation of hydrocarbons [9][10][11]. In this regard, nitro compounds have been widely studied by both experimental and theoretical methods [4][5][6][7][8]; nevertheless, the thermochemical data are surprisingly limited.…”