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

Abstract

A procedure is described to determine the mass balance corresponding to the thermal or catalytic decomposition of several nitrogen-based i onic 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 pr opellant. 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 de composition 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 O2 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 ta kes 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 imp ortant 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 r eveals 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 sol ution contains mainly nitrate and nitroformate ions, in a greement with the primary decomposition of the hydrazinium cation.