Thermal decomposition of ammonium permanganate

Abstract

The parent material, ammonium permanganate, was carefully decomposed in air at 120 ~ . The product, referred to as the starting material (SM), was then subjected to thermal treatment in air for 5 hr in the temperature range 150-1200 ~ Chemical analysis of SM indicated that the main decomposition product of NH4MnO 4 was Mn203, together with MnO2, NH4NO3, HaO and O z. Mn30 a started to form at 900 ~ The infrared spectra of various calcination products revealed the retention of NH,~ in the lattice structure up to 300 ~ and reflected the presence of excess oxygen as coordinated O~-. The TG, DTA and IRA results on SM supported the chemical analysis data. X-ray analysis was carried out for phase identification and to follow transformations and the formation of a solid solution between MnOz and MnzO3.In the literature, studies devoted to the thermal decomposition of ammonium permanganate are rare. Bircumshaw and TaYler [1] studied the explosion of NH4MnO 4 under vacuum in the temperature range 70-111 ~ in an inert oil. They concluded that the oil prevented contact between the individual crystals and damped self-heating effects, and that the decomposition products were MnO2, Mn203, NH4NO3, H20, N 2, 02, NO 2 and N20. Pavlyuchenko et al. [2] showed that decomposition was slow at ~<90 ~ very fast at/>96 ~ and explosive at 1> 100 ~ They identified MnO2, MnO, 02, H20, NO2,. NO and NHa:as thermal decomposition products.The aim o! the present investigation was to characterize the calcination products of NHgMnO 4 as a precursor for manganese oxide catalysts. This was performed through both chemical analysis and a number of physical tools.