Mechanism for the Chloride-Catalyzed Thermal Decomposition of Ammonium Nitrate

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Abstract
A kinetic study of the thermal decomposition of NH4NO3 in the presence of NaCl has been carried out using the differential kinetic technique previously described. The rate law for N2 evolution is of the form k1(NH4+)+k2(NH4+) (Cl—)½. A radical mechanism is proposed in which the role of chloride is catalytic, being oxidized by NO2+ to Cl atoms which are reduced back by NH4+ and NH3. These hydrogen abstraction reactions leave NH3+ and NH2, respectively, in reaction cages in which subsequent radical recombinations yield nitramide and nitrosamine as precursors for N2O and N2. Parallel Cl atom recombinations give Cl2, part of which escapes by volatilization, the rest reacting with NH3 to provide a second source of N2.