Reactivity of concentrated ammonium nitrate solutions in the presence of organic impurities

Abstract

Assessment of mixtures reactivity under certain conditions is essential for safe and conscious designing and improving manufacturing processes. One commonly used compound, the reactivity of which is very important, is ammonium nitrate and its solutions. The biggest influence on the reactivity of ammonium nitrate has the temperature and presence of other compounds, including impurities, that catalyze reactions leading to degradation. One of such impurities are organic compounds which impact on the ammonium nitrate has not yet been clearly described. The aim of the research was to investigate the influence of selected organic impurities on the reactivity of aqueous solutions containing up to 50 wt % ammonium nitrate, buffered with 15 wt % diammonium phosphate. The measurements were carried out using differential scanning calorimetry. Solution without organic compounds showed no reactivity up to 240 C. The addition of 8 wt % ammonium oxalate did not increase the reactivity of ammonium nitrate. It was observed an endothermic decomposition reaction of oxalic acid, beginning at 185 C. During the measurement of a solution containing 6 wt % phenidone, it was registered an exothermic complex reaction, beginning at 189 C and showing relatively small thermal effect. Addition of 6 wt % pyrogallol caused a significant increase in reactivity of ammonium nitrate solution. Strongly exothermic reaction beginning at 192 C was observed. Spectrophotometric measurement showed a clear nitrate concentration loss in the sample after calorimetric measurement. The results show that the nitrate ion selectively oxidizes certain functional groups in organic compounds.