Performance and deactivation of Ir-based catalyst during hydroxylammonium nitrate catalytic decomposition

[Display omitted] ► Uniform distribution of nano-size iridium particles into the alumina before test. ► Deactivation of iridium catalyst after HAN decomposition. ► Deactivation phenomena was caused by oxidation of iridium. ► Severe sintering of iridium catalyst after HAN decomposition reaction. The catalytic performance of Ir-based catalyst for the decomposition of high energetic liquid propellant was investigated in a monopropellant thruster. The changes of ignition delay, catalyst bed temperature and chamber pressure with the numbers of pulse-injection were demonstrated to be effective signposts of catalyst bed efficiencies. The catalyst in fresh state and that after its deactivation were characterized by N2-physisorption, XRD, H2-chemisorption, TEM, H2-TPR and XPS. It was noted that the particle distribution and oxidation state of iridium are the major indicators of catalyst deactivation.