Thermal and catalytic decomposition of HNF and HAN liquid ionic as propellants

Binary aqueous hydroxylammonium nitrate (HAN: [NH3OH]+[NO3]−) and hydrazinium nitroformate (HNF: [N2H5]+[C(NO2)3]−) have been prepared, then thermally and catalytically decomposed. The HAN solutions were prepared with different concentrations (20, 40, 79 wt.%), whereas HNF solution contains is 40 wt.% due to its lower solubility limit (about 50 wt.%). The catalyst was prepared by impregnation of modified support (Si-modified alumina) with monometallic active phase precursor (platinum) and characterized by transmission electron microscopy, X-ray diffraction and chemisorption. The reactions were followed by thermal analysis and by using a constant volume batch reactor. This work shows the essential effect of the monopropellant concentration to determine the best formulation for an industrial application. Moreover, HAN laboratory made solutions are more efficient for catalytic decomposition due to the absence of stabilizer to inhibit the catalyst. The Pt(10%)/Al2O3Si + HAN79% lab association shows lower decomposition temperatures (down to room temperature), larger reaction rates and leads to higher amount of gaseous products, giving the most efficient system. With the same catalyst, HNF solution gave lower performances than HAN solutions, suggesting that the catalyst needs to be improved for this oxidizer.