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Ammonium dinitramide (ADN) has attracted significant interest as a potential oxidizer for next-generation rocket propellants, since it is a halogen-free alternative to the widely used oxidizer ammonium perchlorate. Because ADN synthesis requires N-nitration generates a very unstable intermediate to form the N–(NO2)2 group, this study used a reaction calorimeter to assess the heat of decomposition during the nitration of potassium sulfamate with various nitration agents (HNO3/H2SO4 and HNO3) by using the HNO3 density between 1.52 and 1.38 gcm−3. The heat of decomposition of potassium sulfamate in HNO3 was found to decrease with decreasing HNO3 density. In contrast, the heat of decomposition did not decrease with density in HNO3/H2SO4, since a significant temperature rise was generated when combining the lower density HNO3 with H2SO4. The heat of decomposition in high-density HNO3 (1.52 gcm−3) was greater than that in the mixed acid, likely because protonation of the potassium sulfate nitrogen by H2SO4 inhibited the subsequent nitration step.

Ammonium dinitramide (ADN) has attracted great interest as a potential oxidizer for next generation rocket propellants. It is a halogen-free alternative to ammonium perchlorate, which is currently in wide used as a solid propellant oxidizer. However, in ADN synthesis, N-nitration is necessary to form the N-(NO2)2 group. Using a reaction calorimeter, the thermal behavior of nitration of sulfamates (K, Na, and NH4) using a mixture of acids (HNO3/H2SO4 and HNO3/AcOH) as the nitration agent was examined. The heat of decomposition of potassium sulfamate at −10 °C was greater than that at 20 °C. The heat of decomposition decreased in the following order: K salt>Na salt>NH4 salt in HNO3/H2SO4. The dipole moments of the sulfamates were calculated, and the results revealed that the electronic states of nitrogen were different. Thus, the dipole moments of sulfamates affect the decomposition heat of sulfamates. The heat of decomposition in HNO3/AcOH was larger than that in HNO3/H2SO4.