Analytical study of platinum group catalysts deactivation in catalytic propellant in space industry

Catalytic decomposition of hydrazine and ammonia has an important role in many industrial catalytic processes including gas generators, catalytic monopropellant systems and pure hydrogen production for electric fuel cells. Iridium on gamma-alumina is the ordinary industrial-commercial catalyst in catalytic monopropellant systems and gas generators, chosen because it combines reasonable activity and high thermal stability. But this catalyst has some problems such as deactivation during subject to hydrazine in long time. It is possible that reaction conditions in high temperature causes sintering of small metal particles. Also remaining of nitrogen atoms on catalyst surface can poison the catalyst. Cold start is another problem in applied space programs. This work is to study platinum group catalysts deactivation in catalytic monopropellant systems in space industry. In this study industrial catalyst used in real monopropellant systems was reviewed first. Then iridium on gamma-alumina as the usual catalyst in this filed was studied in details. Also deactivation of this catalyst was investigated. The results of this work indicated that the best catalyst in monopropellant systems must had several specification such as: activity in low temperatures and stability in high temperatures.

Keywords:

Iridium on gamma-alumina catalyst , deactivation of catalyst , space industry , propulsion