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

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.

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► 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.