Design and Use of a Batch Reactor for Catalytic Decomposition of Propellants

The toxicity of pure hydrazine has prompted research on possible "green propellants" to replace this monopropellant for small thruster use. To fulfill this objective, a constant volume computerized batch reactor has been developed, which permits the study of different monopropellants and their associated catalysts. This reactor can be used as a screening reactor, and its main advantages are easy use, fast change of catalyst or propellant, very limited consumption of propellant or catalyst, and simultaneous recording of reactor pressure, catalyst, and gas-phase temperatures. The catalyst can be preheated, and the working pressure is between vacuum and 2 bars. The main parameters that can be obtained for catalyst evaluation are the catalytic decomposition rate, the ignition delay, and the onset decomposition temperature. Three propellants have been checked: pure hydrazine, hydrogen peroxide, and a hydroxylammonium nitrate-(HAN-)triethanolammonium nitrate-(TEAN-) water mixture; they display similar rates and ignition delays but the HAN-based propellant needs higher initial temperature and leads to the simultaneous formation of condensed products at low temperature. For a specific propellant, the results lead to a classification of different catalytic beds prior to further investigation of dynamic reactors using real working conditions. (Author)