Thermal decomposition behaviour of diglycolamide – Nitric acid system

• Thermal stability of TODGA and TEHDGA, their solutions in n-dodecane and DGA-nitric acid mixtures have been studied for the first time.
• Incompressible gases and viscous residue were formed on decomposition.
• Decomposition of acid solvated diglycolamides was found to be exothermic and follows first order kinetics.
• The thermodynamic and kinetic parameters were derived wherever possible.
• The studies indicate the possibility of “red-oil” type excursions while evaporating nitric acid solutions containing diglycolamides.

The thermal decomposition behaviour of N,N,N′,N′-tetraoctyldiglycolamide (TODGA) and N,N,N′,N′-tetraethylhexyldiglycolamide (TEHDGA) and their solutions with n-dodecane, dihexyloctanamide and isodecanol was studied in the presence and absence of HNO3. Experiments were conducted in air ambience with closed vessel using an adiabatic calorimeter. While neat TODGA and TEHDGA were thermally stable up to ∼600 K, they decomposed in the presence of HNO3 at ∼400 K. The presence of n-dodecane enhanced the onset of decomposition by 20–40 K, while the dihexyloctanamide and isodecanol lowered the onsets by about 20 K. From the results the rise in true adiabatic temperature (ΔTad) and the pressure (ΔP) as well as thermokinetic parameters such as, the enthalpy change, the activation energy and the pre exponential factor for the decomposition reaction were derived. The ΔTad and ΔP were seen to increase exponentially with increasing HNO3 content.