The thermal and catalytic decomposition of water–HAN (80 wt.%, hydroxylammonium nitrate NH3OH+NO3−) mixture gave primary products (major N2, medium NO) and secondary products (medium N2O and traces NO2). From the data, a reaction mass balance could be proposed, based on the combination of two parallel competitive reactions:
6NH3OHNO3(aq) = 3N2(g) + 2NO(g) + 10H2O(g) + 4HNO3(g), ΔrH° = −117.8 kJ HAN mol−1 |
6NH3OHNO3(aq) = 2N2(g) + 2N2O(g) + 10H2O(g) + 4HNO3(g), ΔrH° = −121.0 kJ HAN mol−1 |
The influence of the catalyst shape (powder or spheres) has been followed. The isothermal tests at 50 °C display the best activity for the powder catalyst with a complete decomposition of the HAN solution, due to a good contact between catalyst bed and monopropellant. On the other hand, the sphere-shaped catalyst leads only to a partial HAN decomposition, due to preferential paths through the catalyst bed. The thermal decomposition at 200 °C, leads also to a partial reaction.