Thermal and Catalytic Decomposition of AN, ADN andHNF-Based Ionic Monopropellants

摘要

A procedure is described to determine the mass balance corresponding to the thermal or catalytic decomposition of several nitrogen-based ionic liquid monopropellants. A dynamic flow reactor with online mass spectroscopy product analysis has been used to establish the gas phase composition after the injection of the propellant. The analytical results have been supplemented by Raman scattering spectroscopy and acid-base titration of the aqueous solutions trapped at 0 °C after the reactor. The decomposition of ammonium dinitramide (ADN), ammonium nitrate (AN) and hydrazinium nitroformate are investigated. The thermal decomposition results of ADN-water mixture containing 50 wt.-% gave sole major nitrogen N_2 (thermodynamic product) as primary products; secondary kinetic products are medium N_2O, minor nitric oxide NO and traces NO_2. The second expected primary product O_2 was not observed. Moreover, the trapped solution contains a mixture of nitric acid and ammonium nitrate. The decomposition in the presence of the platinum-based catalyst gave the same decomposition products except the emergence of NO as primary product and less ammonium nitrate in trapped solution. The thermal behavior of AN(50 wt.-%)-water mixture is much different, as major vaporization takes part without catalyst. Only small amounts of primary N_2 and secondary N_2O are detected beside the presence of ammonium nitrate in the cold trap. On the other hand, an important gas release occurs in the presence of the catalyst, containing major nitrogen N_2 (thermodynamic product) and minor nitric oxide NO (kinetic product) as primary products; secondary product is medium N_2O, whereas NO_2 and O_2 were not observed. The trapped solution analysis reveals the formation of nitric acid. The thermal decomposition of HNF(50 wt.-%)-water solution reveals the formation of major N_2, medium NO and N_2O, and minor CO_2. However, in the presence of the catalyst, the amounts of CO_2 increases and minor CO is present; the trapped solution contains mainly nitrate and nitroformate ions, in agreement with the primary decomposition of the hydrazinium cation.