Theoretical investigation of the catalytic effect of microingredients on ammonium perchlorate (AP) thermal decomposition

This study employed quantum chemical modeling to explore the low‐temperature (i.e., below 300 °C) decomposition of ammonium perchlorate (AP) in terms of the reaction mechanisms, analyzing the kinetics of decomposition in gaseous noncatalyzed and catalyzed systems. Based upon transition‐state theory, the calculated rate constant together with the initial partial pressure of the reaction species were included in the integrated form into the rate law of the elementary reaction to compute the half‐life of AP decomposition and further evaluate the corresponding lifetime of the stored material. The results of this study revealed that upon increasing the reaction temperature, the stepwise decrease in the activation barrier and the stepwise increase in the rate constant of AP decomposition exhibited expected trends. In addition, via proton transfer and bond‐cleavage mechanisms, ammonium chlorate exerted a positive catalytic effect that showed decomposition is unfavorable. However, ammonium dihydrogen phosphate and ammonium halide exhibited negative catalytic effects that slowed decomposition, and both of them may be incorporated into AP composite propellants to prolong their shelf life. The use of these stabilizing catalysts is estimated to increase the relative lifetime of materials under storage by two orders of magnitude, potentially benefiting ammunition storage. Desired half‐life and lifetime are estimated according to the rate law of elementary reaction, and corresponding relative storage duration are compared for non‐catalyzed/catalyzed proton transfer during gaseous AP decomposition. The apparent inhibition capacity is in ammonium dihydrogen phosphate>ammonium bromide>ammonium chloride sequence, in accordance with literature results.