Decompositions of Urea and Guanidine Nitrates

The decompositions of urea nitrate (UN) and guanidine nitrate (GN) are determined with isothermal heating followed by quantification of both remaining nitrate and remaining base. Activation energies determined for UN were 158 and 131 kJ/mol with the preexponential factors being 1.39 × 1012 s−1 and 2.66 × 109 s−1 for nitrate and urea, respectively. These pairs of Arrhenius constants predict decomposition rates less than a factor of two apart. For GN the activation energies were 199 and 191 kJ/mol with the preexponential factors being 1.94 × 1015 s−1 and 3.20 × 1014 s−1 for nitrate and guanidine, respectively. These pairs of Arrhenius constants predict identical decomposition rates. Literature values for ammonium nitrate decomposition indicate that it should decompose somewhat slower than UN and faster than GN. DSC also indicates this ordering but suggested that UN is substantially less stable than was observed in the isothermal experiments. Decomposition products, both gaseous and condensed, are reported for UN and GN, and decomposition routes are suggested. Experimental results indicate that is generated during the decomposition mechanism. This mechanism appears to differ from that of the analogous nitro derivatives.