Decomposition of Monopropellant Blends of Hydroxylammonium Nitrate and Imidazole-Based Ionic Liquid Fuels

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Decomposition of Monopropellant Blends of Hydroxylammonium Nitrate and Imidazole-Based Ionic Liquid Fuels

Berg, Steven P. / Rovey, Joshua L.

Potential dual-mode monopropellant/electrospray-capable mixtures of hydroxylammonium nitrate with ionic liquid fuels [Bmim][ ${NO}_{3}$ ] and [Emim][ ${EtSO}_{4}$ ] are synthesized and tested for catalytic decomposition in a microreactor setup. The setup is benchmarked using a 30% hydrogen peroxide solution decomposed via silver catalyst. Results show similar trends but with variance in the quantitative data obtained in the literature. This was found to be a direct result of the sample-holder geometry. Hydrazine decomposition was conducted on an unsupported iridium catalyst. The same trends in terms of pressure-rise rate during decomposition ( $\sim 160 mbar / s$ ) are obtained with unsupported catalyst but at 100 °C instead of room temperature for tests conducted on supported catalysts in the literature. For the [Bmim][ ${NO}_{3}$ ]/hydroxylammonium nitrate propellant, rhenium catalyst preheated to 160 °C yielded a pressure-rise rate of $26 mbar / s$ , compared to $14 mbar / s$ for iridium catalyst and $12 mbar / s$ for no catalyst at the same temperature. [Emim][ ${EtSO}_{4}$ ]/hydroxylammonium nitrate propellant shows slightly less activity at 160 °C preheat temperature, yielding a pressure-rise rate of 20, 4, and $2.5 mbar / s$ for injection onto rhenium, iridium, and the thermal plate, respectively. Final results indicate that desirable ignition performance may potentially be obtained by using a supported rhenium catalyst.