Branching ratio of the reaction amidogen + nitric oxide at elevated temperatures

Abstract

The branching ratios into the O H and H 2 0 producing channels in the reaction of NH2 with N O have been measured at four temperatures ranging from room temperature to 900 O C . The reaction was initiated by production of NH2 by excimer laser photolysis of ammonia at 193 nm in the presence of nitric oxide and was probed using a color center laser in conjunction with fast IR detectors. Upon photolysis, the NH3 infrared absorption decreases with consequent appearance of NH2 infrared absorption lines. The magnitude of the decrease in the NH3 infrared absorption is compared with infrared absorbance of O H and H 2 0 produced by the reaction. Measurement of room temperature peak absorption cross sections for NH3, NH2, and H 2 0 combined with the literature value of the OH cross section permits the determination of the branching ratios.For elevated temperatures, the appropriate Boltzmann factors and partition functions were used to calculate the required cross sections from the room temperature values. The branching ratio into the O H channel was observed to increase from 10% a t room temperature to 17% at 900 OC. However, the total contribution of the two channels decreased from -94% a t 26 OC to -70% at 900 OC, possibly indicating the onset of an additional reaction channel. The possibility that the O H signal might arise from an artifact source was investigated.

The role of NNH in NO formation and control

“…For the overall process to be self-sustainable, it is required that the branching fraction of the NH 2 + NO reaction, defined as α = k 15 / (k 14 + k 15 ) must be at least 25% [1]. While early experiments [4,6] indicated a smaller branching fraction, it is now well established that α in the 1100-1400 K range attains values of 0.3 to 0.4 [12,16,22].…”

“…Subsequent work, e.g. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], has confirmed that NNH (or N 2 + H) is indeed formed in the NH 2 + NO reaction, and modeling studies have identified it as a key intermediate in Thermal DeNO x [9,[19][20][21][22][23], where NH 3 is used as a reducing agent for selective non-catalytic reduction of NO.…”

Theoretical investigation of the potential energy surface for the NH2+NO reaction via density functional theory and ab initio molecular electronic structure theory

“…[1][2][3][4][5] Numerous investigations for the reaction system have been carried out via direct kinetic measurements, [6][7][8][9][10][11][12] high temperature kinetic modeling, 4,[13][14][15][16][17] ab initio/molecular orbital ͑MO͒ theory, [18][19][20][21][22][23] and Rice-Ramsperger-Kassel-Marcus ͑RRKM͒ calculations. 11,19,24,25 In view of the thermochemistry for the system, three exit channels may be involved in the reaction mechanism according to their reaction enthalpies,…”

“…[3][4][5] For this reason, it has been the focus of much attention experimentally [7][8][9]12,[14][15][16][17] in recent years. However, the comparison between the temperature dependence of ␣ measured from direct laser kinetic studies and that measured indirectly from high temperature flame modeling still remains controversial.…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…Elimination to form OH + HN 2 can occur at any point along the surface. While results from early studies on the branching ratio for OH formation differ significantly, the most recent studies (Hall et al,Dolson [405], Silver and Kolb [1188], Atakan et al, Stephens et al [1236], Park and Lin [1036]) agree on a value around 0.1 at 300 K, with N 2 +H 2 O making up the balance. (Table: 97-4, Note: 97-4) Back to Table C28.…”