Combustion ammonia, kinetics

Other observations of the reaction of hydrazine and nitrogen tetroxide substantiate the production of non-equilibrium combustion products. Non-equilibrium product concentrations were found in combustion gases extracted from a small rocket combustion chamber through a molecular beam sampling device with direct mass spec-trometric analysis (31) (39). Under oxidizer rich conditions excessive amounts of nitric oxide were found under fuel rich conditions excessive amounts of ammonia were found. A correlation between the experimentally observed characteristic velocity and nitric oxide concentration exists (40). Related kinetic effects are postulated to account for the two stage flame observed in the burning of hydrazine droplets in nitrogen dioxide atmospheres (41) (42). 

In their work on the explosive oxidation of ammonia, which has already been discussed earlier, Husain and Norrish also examined the hydrazine system. Their principal results, obtained by the method of flash photolysis and kinetic spectroscopy, were as follows (a) no induction period was observed (b) NH emission, observable in the photolysis of pure N2H4, was visible at the shortest delay times (c) NO and OH were produced as the NH was decaying d) NO added to the hydrazine-oxygen system did not disappear in the combustion ( ) NO represented only about 5 % of the final products. Since, unlike the oxidation of ammonia, the major nitrogenous product is N2 rather than NO, Husain and Norrish concluded that reaction (15 ) is not a part of the main reaction sequence. They felt that the N-N bond was not split in in the main chain propagation. They proposed a mechanism involving nitrosamine, NH2NO, as a chain carrier viz. 

Kinetic Modeling of the Oxidation of Ammonia in Flames", Western States Section Fall Meeting, The Combustion Institute, 1982, Paper WSS/CI 82-93. 

Additives, inhibition of detonation, 186-90 Air jet surface, I69f Aliphatic flames, formation of aromatic species, 3-16 Allene, rate coefficients for cyclopentadienyl cation reactions, 59t,60t,6lt Ammonia combustion, kinetic mechanism, 93,94f... 

Other factors that can modify the adsorption phenomena will also be considered. Special emphasis will be placed on estimating the competitions for adsorption among the molecules that are present in the real reaction mixtures, such as water vapor, carbon dioxide, and ammonia. Indeed, the addition of biofuel to gasoline or diesel fuel can lead to new reactions or to deactivation [24,28,95]. It is, therefore, important to evaluate their impact on catalyst activity and more particularly the influence of the presence of molecules that are typically observed upon biofuel combustion (namely aldehydes but also trace amounts of K and P) on mechanisms, kinetics, and activation temperatures. 

There are no direct observations of the N2H radical. Indirect evidence for its formation was obtained from experimental studies on the reaction NH2 +NOproducts and on the electron-transfer neutralization of N2H. Theoretical arguments for its existence were once provided by kinetic models of ammonia combustion. 

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