Thermal stability of systems containing ammonium nitrate and sulfate salts: an experimental study

The overall effect of reactants in the form of sulfates of ammonium, calcium, copper(II), iron(III), manganese(II) and zinc on the thermal behavior of ammonium nitrate has been reported. Thermal stability assessment was performed with the use of thermogravimetric analysis and differential thermal analysis coupled with mass spectroscopy. Interestingly, sulfate anions present in the system were often not sufficient to properly inhibit the decomposition of ammonium nitrate. Sulfate ion and cation supplied with the selected compound significantly influence the studied process. Studied mixtures with ammonium sulfate and calcium sulfate were concluded to show the highest stability. Manganese and iron sulfate salts caused a significant acceleration of the initial thermal decomposition. The addition of these compounds led to visible changes in the process mechanism, which allowed them to be classified as catalysts of the decomposition of ammonium nitrate. Furthermore, small amounts of substances in the system, even those that are generally considered to be inhibitors, worsened the thermal stability of AN. Zinc and copper sulfates, under studied conditions, created double salts that were characterized by a higher thermal stability than pure ammonium nitrate. This property indicates the possibility of obtaining systems containing ammonium nitrate with significantly higher thermal stability, what could potentially have multiple useful applications.