Stabilization and spheroidization of ammonium nitrate:

Co-crystallization with crown ethers and spherical crystallization by solvent screening

Chih-Wei Chen, Jeng Wei Chen, Tsung Yan Lin, Yee Chen Tsai, and Tu Lee?
Department of Chemical and Materials Engineering, National Central University,
300 Jhong-Da Road, Jhong-Li City 320, Taiwan R.O.C.

ABSTRACT

Ammonium nitrate is a material full of advantages, such as clean burning,
non-corrosive, low-hazard, low-flame temperature, inexpensive, easily available energetic material and gives maximum gas horse power per unit weight. However, ammonium nitrate still suffers from three significant drawbacks: (1) low phase transition temperature, (2) caking and smoke generation upon burning, and (3) poor particle size distribution. The first two disadvantages could be minimized by forming co-crystals. The 1:1 co-crystals of ammonium nitrate-benzo-18-crown-6 (1:1 co-crystals of AN-B18C6) produced from the antisolvent method based on the systems of: ethanol-methyl-tert-butyl-ether (MTBE), methanol-ethyl acetate and methanol-MTBE, show non-hydroscopic and smokeless properties. The third drawback of the poor flowability of ammonium nitrate could further be eliminated by forming spherical agglomerates of 1:1 co-crystals of AN-B18C6 through the addition of water as a bridging liquid into the co-crystal slurry resulted at the end of the antisolvent method. The spherical agglomerates of 1:1 co-crystals of AN-B18C6 in methanol-MTBE-water solvent system gave relatively high yield of 87.3%, high
population density of 20.6/cm3, high sphericity of 0.86, high friability of 100 showing

? Corresponding author. Telephone: +886-3-422-7151 ext. 34204. Fax: + 886-3-425-2296. E-mail: tulee@cc.ncu.edu.tw

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a greater strength, and low angle of repose of25.2° indicating a good flowability.

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