Ammonium dinitramide (ADN) has attracted significant interest as a potential oxidizer for next-generation rocket propellants because it is a halogen-free alternative to the widely used ammonium perchlorate. During the synthesis of ADN, N-nitration is required to form the N-(NO2)2 group, in conjunction with the decomposition of sulfamate. The study reported herein used calorimetry to assess thermal variations during the nitration of both K and NH4 sulfamates, applying a number of different nitration agents (HNO3/H2SO4, HNO3/H2SO4+H2O, HNO3/AcOH and HNO3). It was determined that the heat of decomposition of the sulfamates in HNO3/H2SO4 at 0℃ was greater than at 20℃, although the similar trend was not observed in HNO3/AcOH and HNO3. The heats of decomposition in HNO3/AcOH and in HNO3 were greater than in HNO3/H2SO4 because of how the nitration reagent affects the relative contributions of different pathways to the decomposition process. The heat of decomposition in HNO3/H2SO4+H2O was less than that in HNO3/H2 SO4 because the addition of water inhibits both nitration and decomposition by HNO3. Under such conditions, however, a second exothermic peak is observed, due to the hydrolysis of potassium sulfamate.
ammonium dinitramide, sulfamate, nitration, reaction calorimetry, hydrolysis