Elsevier

Thermochimica Acta

Volume 6, Issue 4, June 1973, Pages 353-360
Thermochimica Acta

Isothermal decomposition of urea nitrate

https://doi.org/10.1016/0040-6031(73)87002-9Get rights and content

Abstract

The kinetics of isothermal decomposition of urea nitrate, an organic secondary explosive with monoclinic structure and chemical formula CO(NH2)2 · HNO3, which melts with decomposition at 152°C, was studied in open air in the temperature range 106-150°C, using a gravimetric method. Gas chromatographic analysis of product gases indicate CO2, N2O and traces of water vapor as product gases. A pasty amorphous product on the basis of wet chemical and infrared analysis was found to be cyanourea. The weight loss-time curve exhibited an acceleratory region extending almost to the end of the main reaction (35% decomposition) and followed a three-dimensional nucleation model obeying the relation x1/3 = K(t—t0 where α = fraction of sample reacted at time t, K = reaction rate constant, and t0 = induction time. On the basis of this model, an enthalpy of activation of 27.6 ± 1.2 kcal/mole was calculated at 95% confidence range. The rate of decomposition was slightly accelerated in He atmosphere and slightly retarded in N2O and CO2 atmospheres, while water vapor drastically reduced the rate. The reaction 3CO(NH2)2 · HNO3 → CNNHCONH2 (cyanourea) + 6H2O+3N2O+CO2 is presented as the most likely one for decomposition of urea nitrate in open air.

References (17)

  • G.C. Anderson
    (1965)
  • G.M. Thornley
    (1965)
  • M.A. Cook et al.

    Ind. Eng. Chem.

    (1956)
  • R.D. Farmer

    J. Chem. Soc.

    (1930)
  • A.D. Yoffe

    Proc. Roy. Soc.

    (1951)
  • M. Mori et al.

    Bull. Chem. Soc. Jap.

    (1959)
  • C.N. Hinshelwood

    J. Chem. Soc.

    (1921)
  • R. Robertson

    J. Chem. Soc.

    (1921)
There are more references available in the full text version of this article.

Cited by (12)

  • Analyses of the thermal decomposition of urea nitrate at high temperature

    2011, Thermochimica Acta
    Citation Excerpt :

    The use of UN as a civilian or military explosive is not advantageous partly because of its corrosive and acidic properties, and possibly due to its degradation property producing nitric acid. The decomposition of UN at much higher temperatures was studied in the literature describing important parts of the decomposition mechanism [7–11]. Our study has found that, at 100 °C over a period of 48 h, urea nitrate degraded into a mixture of solids; ammonium nitrate, urea and biuret [6].

  • Degradation mechanism and thermal stability of urea nitrate below the melting point

    2011, Thermochimica Acta
    Citation Excerpt :

    The use of urea nitrate as a civilian or military explosive is not acceptable because of its corrosive acidic properties that may cause instability in some cases and possibly due to its degradation properties. Decomposition processes of urea nitrate were studied by quantum chemistry calculations [3,6] and evaluated by thermal analysis as reported in a few papers [7–10]. We have recently shown the complexity of the decomposition mechanism at high temperature up to 360 °C and determined the associated kinetic parameters [11].

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