Thermal decomposition of gaseous ammonium dinitramide at low pressure: Kinetic modeling of product formation with ab initio MO/cVRRKM calculations

Abstract

The thermal decomposition of ammonium dinitramide, NH4N(NO2)2) (ADN), in the gas phase has been studied at 373–920 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor. The reaction of the sublimed mixture of NH3 and HN(NO2)2 (dinitraminic acid, DN) was found to be initiated by the unimolecular decomposition of DN, HN(NO2)2→HNNO2+NO2, followed by the rapid decomposition reaction, HNNO2+M→N2O+OH+M. The measured absolute yields of NH3, H2O, N2, and N2O, calibrated with standard mixtures, could be satisfactorily modeled at 10 Toor He carrier gas pressure by employing the theoretically computed values of k2=6.79×1049 T−11.0 exp(−21780/T) s−1 and k3=7.53×1024 T−29 exp(−12958/T) cm3/(mol s) by high-level ab initio molecular orbital and canonical variational Rice-Ramsperger-Kassel-Marcus (MO/cVRRKM) calculations. The key reactions with recommended rate constants are presented.