Thermal decomposition mechanism of aluminum nitrate octahydrate and characterization of intermediate products by the technique of computerized modeling

Thermal decomposition of aluminum nitrate hydrate was studied by thermogravimetry, differential scanning calorimetry, and infrared spectroscopy, so that all mass losses were related to the exactly coincident endothermic effects and vibrational energy levels of the evolved gases. The process starts with the simultaneous condensation of two moles of the initial monomer Al(NO3)3·8H2O. Soon after that, the resulting product Al2(NO3)6·13H2O gradually loses azeotrope HNO3 + H2O, then N2O3 and O2 and, through the formation of Al2O2(NO3)2, is transformed into aluminum oxide. The molecular mechanics method used for comparison of the potential energies of consecutive products of thermal decomposition permits an evaluation of their structural arrangement. On the basis of the results obtained, a probable mechanism for the overall decomposition of Al(NO3)3·8H2O has been proposed.