Kinetic Parameters Governing the Rapid Pyrolysis Of Ammonium Perchlorate

Abstract

Ammonium Perchlorate (AP) has been in use in many solid propellant formulations since decades. However, data regarding the chemical reactions taking place in the condensed phase during combustion of AP and their associated kinetic parameters are sparse. This data is crucial in modelling the combustion of AP. To mimic the behaviour of AP in condensed phase during its combustion, it is necessary to isolate the condensed phase reactions and study pyrolysis of AP at heating rates similar to those observed during combustion (~105K.s-1). In the current study, an electrical fast pyrolyser coupled to a Fourier Transform Infrared (FTIR) spectrometer was used to study the fast pyrolysis of AP. Activation energy (Ea) of the global pyrolysis reaction was extracted from the variation of mole fraction with time of the observed pyrolysis products. An activation energy of 48 kJ.mol-1 was obtained along with a pre-exponential factor (A) of 4039 s-1. The value of activation energy obtained in the current study is significantly different than that obtained from Thermo-Gravimetric Analysis (TGA) studies. This signifies that the mechanism of decomposition during rapid pyrolysis maybe different from that occurring during slow pyrolysis.