Stabilization and spheroidization of ammonium nitrate: Co-crystallization with crown ethers and spherical crystallization by solvent screening

Tu Lee, Jeng Wei Chen, Hung Lin Lee, Tsung Yan Lin, Yee Chen Tsai, Shao Liang Cheng, Sheng Wei Lee, Jung Chih Hu, Lien Tai Chen

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43 Scopus citations


Although ammonium nitrate (AN) is a clean burning (chlorine free), non-corrosive, low-hazard, low-flame temperature, inexpensive, easily available energetic material and gives maximum gas horse power per unit weight, propellants incorporating AN suffer from three significant drawbacks: (1) polymorphic (phase) transition near ambient temperature, (2) caking and smoke generation upon burning, and (3) poor flowability for packing. The first two disadvantages could be minimized by forming non-hygroscopic, smokeless 1:1 co-crystals of ammonium nitrate-benzo-18-crown-6 (1:1 co-crystals of AN-B18C6) with a melting point of 125-129°C, produced from the antisolvent precipitation method based on the systems of: ethanol-methyl-tert-butyl-ether (MTBE), methanol-ethyl acetate and methanol-MTBE. From the smoke test and burning characteristics, 1:1 co-crystals of AN-B18C6 is smokeless upon heating and exhibits a slower burning rate than the one of AN. Therefore, co-crystallization may become a solid-state modification method in the areas of propellants and explosives. The third drawback 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 precipitation method. Spherical agglomerates of 1:1 co-crystals of AN-B18C6 grown from Phase IV AN powders (0.32mmol) and B18C6 crystals (0.32mmol) in 0.64mL methanol+11.6mL MTBE+0.08mL water gave relatively high yield of 87.3%, high population density of 20.6/cm3, high sphericity, of 0.86, high friability of 100 showing a greater strength, and low angle of repose of 25.2° indicating a good flowability.

Original languageEnglish
Pages (from-to)809-817
Number of pages9
JournalChemical Engineering Journal
StatePublished - 1 Jun 2013


  • Ammonium nitrate
  • Co-crystallization
  • Crown ethers
  • Propellants
  • Spheroidization


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