Kinetics of homogeneous nitrous oxide decomposition

The major uncertainties in the consumption mechanism for N[sub 2]O are related to the efficiency of various components as collision partners in N[sub 2] dissociation and to the rate constant for the N[sub 2]O + OH reaction. In this work thermal dissociation of N[sub 2]O in different carrier gases has been measured at atmospheric pressure in the temperature range 1,000--1,400 K. Based on these, as well as earlier data from this laboratory, collision efficiencies were determined for O[sub 2], CO[sub 2], N[sub 2] and H[sub 2]O. The relative efficiencies compared to Ar were found to be 1.4[+-]0.3, 3.0[+-]0.6, 1.7[+-]0.3, and 12[+-]3.5, respectively. The fast rate measured for N[sub 2]O + H[sub 2]O indicates that the commonly accepted rate constant for N[sub 2]O dissociation at the high-pressure limit may be too low around 1300 K. The reaction between N[sub 2]O and OH was investigated by addition of N[sub 2]O to moist CO oxidization experiments. The N[sub 2]O + OH reaction was found to be very slow under the present conditions, with an upper limit of 3[times]10[sup 9] cm[sup 3]/mole-s for the rate constant at 1,250 K. In agreement with recent theoretical studies, this makes the reaction more than one order ofmore » magnitude slower than estimates currently used in modeling. The implications of the present results for modeling N[sub 2]O chemistry in fluidized bed and other combustion systems are discussed.« less

[1]  K. P. Lim,et al.  Rate constants for the N2O reaction system: Thermal decomposition of N2O; N+NO→N2+O; and implications for O+N2→NO+N , 1992 .

[2]  James A. Miller,et al.  Mechanism and modeling of nitrogen chemistry in combustion , 1989 .

[3]  C. M. Faust,et al.  Detailed structure study of a low pressure, stoichiometric H2/N2O/Ar flame , 1993 .

[4]  B. Leckner,et al.  Reduction of N2O by gas injection in CFB boilers , 1991 .

[5]  James A. Miller,et al.  Kinetic modeling of the reduction of nitric oxide in combustion products by isocyanic acid , 1991 .

[6]  J. Troe,et al.  Shock wave study of collisional energy transfer in the dissociation of nitrogen dioxide, nitrosyl chloride, ozone, and nitrous oxide , 1979 .

[7]  Peter Glarborg,et al.  Modeling the thermal DENOx process in flow reactors. Surface effects and Nitrous Oxide formation , 1994 .

[8]  Mikko Hupa,et al.  Homogeneous N2O chemistry at fluidized bed combustion conditions: A kinetic modeling study , 1991 .

[9]  Wing Tsang,et al.  Chemical Kinetic Data Base for Propellant Combustion I. Reactions Involving NO, NO2, HNO, HNO2, HCN and N2O , 1991 .

[10]  P. Marshall,et al.  High‐temperature photochemistry and BAC‐MP4 studies of the reaction between ground‐state H atoms and N2O , 1987 .

[11]  F. Kaufman,et al.  Upper limits of the rate constants for the reactions of CFCl3(F-11), CF2Cl2(F-12), and N2O with OH. Estimates of corresponding lower limits to their tropospheric lifetimes , 1977 .

[12]  Richard A. Yetter,et al.  A Comprehensive Reaction Mechanism For Carbon Monoxide/Hydrogen/Oxygen Kinetics , 1991 .

[13]  W. Cooper,et al.  Product channel dynamics of the cyanato radical + nitric oxide reaction , 1993 .

[14]  R. A. Perry,et al.  Kinetics of the reactions of OH radicals with CO and N2O , 1976 .

[15]  F. Stuhl,et al.  Rate Constant for the Reaction of OH with N2O at 298 K , 1976 .

[16]  James A. Miller,et al.  A theoretical analysis of the reaction between hydrogen atoms and isocyanic acid , 1992 .

[17]  T. Hulgaard,et al.  Homogeneous nitrous oxide formation and destruction under combustion conditions , 1993 .

[18]  A. Hayhurst,et al.  Emissions of nitrous oxide from combustion sources , 1992 .