Pyrolysis of Ammonium, Potassium, and Sodium Hydrogen Amidophosphates

Abstract

Pyrolysis of amidophosphates was investigated by use of DTA, DSC, and TG. These three samples showed no difference in the pyrolytic behavior and decomposed thermally to liberate ammonia through an intermediate phase. The phase was found to be a determinate factor to control the pyrolysis. The mechanism of the pyrolysis was supported by the results of IR spectrum, X-ray diffraction pattern, and chemical analysis. A DSC operated isothermally indicates that the heat of pyrolysis increases almost linearly with increasing temperature in the ranges 443∼458 K for NH₄ salt, 427∼461 K for K salt, and 483∼517 K for Na salt. The heat and order of the pyrolysis were calculated on the basis of DSC curves. The pyrolysis is apparently the first-order reaction. The activation energies of the pyrolysis reaction in the above temperture ranges were estimated to be 208.6 kJ/mol for NH₄ salt, 157.0 kJ/mol for K salt, and 149.8 kJ/mol for Na salt.