O + NNH: A possible new route for NOX formation in flames

International Journal of Chemical Kinetics - Tập 27 Số 11 - Trang 1097-1109 - 1995
Joseph W. Bozzelli1, Anthony M. Dean1
1Corporate Research Laboratories , Exxon Research and Engineering Co. , Annandale, New Jersey, 08801

Tóm tắt

AbstractWe propose a new high temperature pathway for NO formation that involves the reaction of NNH with oxygen atoms. This reaction forms the HNNO* energized adduct via a rapid combination reaction; HNNO* then rapidly dissociates to NH + NO. The rate constant for O + NNH  NH + NO is calculated via a QRRK chemical activation analysis to be 3.3 × 1014 T−0.23exp(+510/T) cm3 mol−1 s−1. This reaction sequence can be an important or even major route to NO formation under certain combustion conditions. The presence of significant quantities of NNH results from the reaction of H with N2. The H + N2  NNH reaction is only ca. 6 kcal/mol endothermic with a relatively low barrier. The reverse reaction, NNH dissociation, has been reported in the literature to be enhanced by tunneling. Our analysis of NNH dissociation indicates that tunneling dominates. We report a two‐term rate constant for NNH dissociation: 3.0 × 108 + [M] {1.0 × 1013T0.5exp(−1540/T)} s−1. The first term accounts for pressure‐independent tunneling from the ground vibrational state, while the second term accounts for collisional activation to higher vibration states from which tunneling can also occur. ([M] is the total concentration in units of mol cm−3.) Use of this dissociation rate constant and microscopic reversibility results in a large rate constant for the H + N2 reaction. As a result, we find that NNH  H + N2 can be partially equilibrated under typical combustion conditions, resulting in NNH concentrations large enough for it to be important in bimolecular reactions. Our analysis of such reactions suggests that the reaction with oxygen atoms is especially important. © 1995 John Wiley & Sons, Inc.

Từ khóa


Tài liệu tham khảo

Bowman C. T., 1992, Twenty‐fourth Symposium (International) on Combustion, 859

Zeldovich Y. B., 1946, Acta Physicochim. URSS, 21, 577

Fenimore C. P., 1970, Thirteenth Symposium (International) on Combustion, 373

10.1002/cite.330441004

10.1080/00102207408960360

10.1016/0010-2180(76)90075-4

10.1016/0010-2180(81)90008-0

Melius C. F., 1984, Twentieth Symposium (International) on Combustion, 575

10.1002/kin.550180702

10.1016/0009-2614(87)85154-0

10.1063/1.455875

10.1063/1.460768

10.1063/1.465972

10.1016/0009-2614(94)01471-7

10.1002/aic.690321206

10.1002/kin.550190305

10.1021/j100340a009

10.1021/j100371a021

10.1021/j100119a030

10.1080/00102209108951777

10.1016/0360-1285(89)90017-8

10.1002/kin.550260405

10.1002/kin.550240509

10.1021/j100002a039

10.1021/j100368a026

10.1063/1.555759

J. W.BozzelliandA. M.Dean Combustion Chemistry of Nitrogen inCombustion Chemistry 2nd ed. W. C. Gardiner Jr. Ed. in press.

Bozzelli J. W., 1994, Twenty‐fifth Symposium (International) on Combustion, 965

10.1002/kin.550230208

Miller J. A., 1992, Twenty‐fourth Symposium (International) on Combustion, 719

10.1016/0010-2180(94)90198-8

C. F.Melius BAC‐MP4 Heats of Formation and Free Energies 1993.

Thông tin
Thông tin xuất bản

International Journal of Chemical Kinetics

Tập 27 Số 11

1097-1109

Thông tin tác giả