Cerium oxide based active catalyst for hydroxylammonium nitrate (HAN) fueled monopropellant thrusters

Abstract

Hydroxylammonium nitrate (HAN) is an energetic ionic liquid which is fast emerging as a promising environmentally friendly, high performing monopropellant for space propulsion application. The high performance due to the higher adiabatic temperature for HAN based compositions also poses challenges as high temperature tolerant catalysts have to be developed for its decomposition. A novel cobalt doped cerium oxide based catalyst has been prepared by the co-precipitation route and characterized by SEM/EDS, XRD, and XPS. The effectiveness of the catalyst in decomposing HAN has been tested using thermo-analytical techniques. An evolved gas analysis (EGA) to examine decomposition products and the possible reaction mechanism was also performed using the hyphenated DTA-TG-FTIR technique. Formation of an in situ Ce³⁺/Ce⁴⁺ ion couple in ceria during co-precipitation was found to be critical in deciding the reactivity of HAN decomposition over the catalyst. The activity of the catalyst was also examined in a batch reactor for its longevity. The prepared catalyst was found to be more versatile and durable than a hitherto reported alumina supported iridium catalyst in the present studies.