Thermoanalytical Studies on the Decomposition of Energetic Ionic Liquids
Hydrazine has been extensively used as a propellant for space applications for more than half a century. However, its hazardous characteristics cause high storage and handling costs. For this reason, the search for alternatives, the so-called “green monopropellants,” is of great interest. Most green monopropellants are mixtures of an oxidizer and a fuel, and several ionic liquids (ILs) have been proposed for this application. Among them, hydroxylammonium nitrate (HAN) and 2-hydroxylethylhydrazinium nitrate (HEHN) are promising oxidizer and fuel, respectively. The objective of the present work was to clarify the decomposition kinetics of both HAN and HEHN, using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), mass spectrometry (MS), and Fourier-transform infrared (FTIR) spectroscopy. For HAN decomposition at atmospheric pressure, the TGA and DSC methods revealed similar values of the apparent activation energy: 62.2 ± 3.7 kJ/mol and 57.5 ± 3.5 kJ/mol, respectively, with H2O, HNO3, N2, NO, N2O, and NO2 being identified as products. An iridium/rhodium foam catalyst decreased the temperature of HAN decomposition at atmospheric pressure by over 60 °C. The temperature of thermal decomposition of HAN decreases by ca. 50 °C with increasing pressure from atmospheric to 2 MPa and remains virtually constant with further increase to 15 MPa. The experiments revealed two stages of HEHN decomposition. The analysis of TGA and DSC has shown autocatalytic behavior and produced apparent activation energies of 113.7 ± 1.7 kJ/mol at the first stage and 123.6 ± 2.5 kJ/mol at the second stage. The evolved gas analysis has shown that the first stage generates H2O, N2, NH3, NO, N2O, and NO2, while the second stage also generates HNO3 and CO2.
Aerospace engineering|Chemical engineering
Esparza Hernandez, Alan Alberto, "Thermoanalytical Studies on the Decomposition of Energetic Ionic Liquids" (2020). ETD Collection for University of Texas, El Paso. AAI27996023.