A detailed chemical kinetics model for the initial decomposition of gas-phase hydroxylamine

Initial decomposition mechanisms of hydroxylamine in the gas phase were identified and investigated, and a detailed chemical kinetics model based on quantum chemical calculations was developed. The computational studies revealed the following reaction pathways : 2NH(2)OH -> NH3+HNO+H2O; 2NH(2)OH -> t-N2H2+2H(2)O; and NH2OH+NH3O -> NH3+HNO +H2O. Optimized structures of reactants, products, and transition states were obtained at the omega B97XD/6-311++G(d,p) level of theory and the total electron energies of such structures were calculated at the CBS-QB3 level of theory. Detailed chemical reaction calculations revealed ignition of a thermal explosion after an induction period. The bimolecular reaction of NH2OH occurs to yield HNO which attacks another NH2OH to form N-2 and H2O during the induction period. The series of reactions increases temperature and it promotes chain growth reactions, i.e., NH2OH+NH2 -> NH2O+NH3, and another chain initiation reaction, HONO+M -> OH+NO+M, activated radicals accumulate in the system. After sufficient radical accumulation, a thermal explosion is ignited and the temperature rises sharply to approximately 2400 degrees C.