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 : 2NH2OH → NH3+HNO+H2O ; 2NH2OH → t-N2H2+2H2O ; and NH2OH+NH3O → NH3+HNO +H2O. Optimized structures of reactants, products, and transition states were obtained at the ωB97XD/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 N2 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 °C.
hydroxylamine, decomposition, runaway reaction, kinetic model, ab initio calculation