A detailed kinetic model for the thermal decomposition of hydroxylamine

Hydroxylamine may decompose explosively if processed and stored in certain conditions, posing critical safety issues that need to be carefully addressed. A key aspect is related to the characterization of chemical aspects involved in the explosive decomposition of hydroxylamine (HA), requiring accurate and detailed kinetic mechanisms. This work was devoted to the experimental and numerical characterization of the thermal decomposition of aqueous solutions of HA included in the range of 10%_w to 50%_w. The onset temperatures of thermal decomposition were determined in the range of 143-198 °C under heating rates of 2 and 5 °C min^-1, respectively. A reduced mechanism listing 13 species and 11 reactions involving nitrogen-containing species was produced and validated against experimental measurements. Reaction pathways ruling the decomposition of HA were identified. The hydrogen abstraction toward HNOH and H₂NO dominates the primary steps of NH₂OH decomposition. The generated mechanism was adopted for the definition of a dimensionless stability diagram for the safe use of HA. Finally, results show a self-accelerating behaviour for any temperature larger than 186 °C, defining a monitoring criterion for safe storage of hydroxylamine-solutions.