Use of isoperibolic calorimetry for the study of the effect of water concentration, temperature and reactor venting on the rate of hydroxylamine thermal decomposition

Hydroxylamine, NH2OH, thermal decomposition has been responsible for two serious accidents. However, its reactive behavior and the synergy of factors affecting the rate of its decomposition are not understood. In this work, isoperibolic calorimetric measurements were performed in a metal reactor, in the temperature range 130–150 °C, employing 30–80 ml solutions containing 1.4–20 g of pure hydroxylamine (2.8–40 g of the supplied reagent). The calorimetric measurements were performed in order to assess the effects that NH2OH concentration, temperature and reactor venting has on NH2OH rate of decomposition. The measurements showed that increased concentration or temperature, results in faster reactions and probably higher pressure generation per mass of reactant, with concentration having a more pronounced effect. However, when both factors work synergistically the result is dramatically worse in terms of reaction rate. The pressure generation is also different, thus indicating that different reaction pathways predominate each time. Venting the produced gases in stages resulted in the highest mass loss of the solution.

► Larger quantities of samples were employed in a systematic isoperibolic study.
► Indication that different decomposition paths are followed at higher NH2OH concentrations.
► Indication that different decomposition paths are followed at higher temperatures.
► Strong synergistic effects of temperature and NH2OH concentration causing disproportionally steep temperature rise.
► The higher mass loss was in staged measurements with inter-stage venting.