Calorimetric studies on thermal decomposition of tri isoamyl phosphate–nitric acid systems

The thermal decomposition of tri isoamyl phosphate (TiAP), nitric acid-solvates namely, TiAP·1.1HNO3 and TiAP·2.2HNO3, solutions of TiAP in n-dodecane (n-DD) and in pentamethylheptane (PMH) with nitric acid were studied using an adiabatic calorimeter in air under closed and opened conditions employing heat-wait-search mode. Neat TiAP was found to be stable up to 535 K and decompose above this temperature. The acid-solvates were found to decompose exothermically at 384 and 365 K, respectively and caused high rise in temperature and pressure, producing non-condensable gasses such as N2O, CO2 and CO and a blackish residue. Decomposition enthalpies for TiAP·1.1HNO3 and TiAP·2.2HNO3 were derived and found to be −465.1 ± 2.4 and −937.0 ± 6.2 kJ mol−1, respectively. Kinetic parameters have been derived wherever possible. Heat capacities of acid-solvates have been measured at constant pressure in the temperature range 305–340 K using heat flux type differential scanning calorimeter and are reported in this paper.