Kinetics and Mechanism of Thermal and Catalytic Decomposition of Hydroxylammonium Nitrate (HAN) Monopropellant

Abstract

Hydroxylammonium nitrate (HAN) monopropellant with its low sensitivity, volatility and toxicity, not only promises a safer substitute to hydrazine but also offers a higher specific impulse and a positive oxygen balance. This study primarily explores the decomposition mechanism and underlying kinetics for a newly developed cerium oxide‐based catalyst. The chemical kinetics involved in the thermal and catalytic decomposition was examined through an isoconversional method using thermogravimetric analysis (TG) data. The activation energy (Ea) was evaluated using differential isoconversional method (Friedman's method) and advanced integral isoconversional method (Popescu‐Ortega's method). To find frequency factor, compensation effect method (ACE) and intercept method (A0) were used. Advanced integral method could not provide realistic kinetic parameters while differential method predicted values similar to reported values for thermal decomposition. The values obtained for thermal decomposition were found matching with reported values obtained by other techniques which validated the methodology adopted. The reaction mechanism for both thermal and catalytic decomposition were proposed based on evolved gas analysis. The mechanism proposed was able to describe the variable kinetic parameters extracted from isoconversional method. Overall Ea of thermal decomposition of HAN was ∼95 kJ/mol. The decomposition over ceria‐based catalyst was distributed over three stages namely inception, peak and decay with Ea of ∼33 kJ/mol, ∼170 kJ/mol and ∼130 kJ/mol, respectively. Under identical conditions, iridium‐based catalyst show two decomposition stages with Ea of ∼65 kJ/mol and ∼120 kJ/mol while final stage being evaporation of HNO3. The ceria catalyst favoured N2 formation, increased decomposition of HNO3 and enhanced decomposition enthalpy.

Experimental Studies on Parametric Effects and Reaction Mechanisms in Electrolytic Decomposition and Ignition of HAN Solutions

“…Figure 9 shows the FTIR spectra of the gaseous products at different stages in different modes of HAN electrolytic decomposition. It is determined that, at different stages, the gas products contain mainly nitrogen dioxide (NO 2 ) and nitrous oxide (N 2 O), with their characteristic IR absorption peaks at 1630 and 2237 cm –1 , respectively 27 (the two peaks around 1300 cm –1 also correspond to the vibration frequencies of N 2 O in these cases).…”

On-Line Thermally Induced Evolved Gas Analysis: An Update—Part 1: EGA-MS

“…Agnihotri and Oommen primarily explored the decomposition mechanism and underlined kinetics for a newly developed cerium oxide-based catalyst. The reaction mechanism for both thermal and catalytic decomposition was proposed based on evolved gas analysis and the mechanism proposed was able to describe variable kinetic parameters extracted from the isoconversional method [ 288 ].…”

Catalytic decomposition of hydroxylamine nitrate and hydrazine nitrate using Ru/ZSM-5 catalyst under mild reaction conditions

“…[6][7][8][9][10][11] Recently, a new high temperature tolerant catalyst based on cobalt doped cerium oxide that was found to be both thermally and chemically stable under monopropellant decomposition conditions was developed by Ruchika and the kinetics and mechanism of the thermal decomposition and catalytic decomposition of hydroxylamine nitrate were studied. 12,13 Heterogeneous catalytic decomposition of hydroxylamine nitrate has not been reported in the HNO 3 system. Among various metal catalysts proposed for hydrazine decomposition, noble metals, such as Ru and Pt, exhibited good catalytic activity and stability in acid solutions.…”