Ammonium dinitramide

History

Ammonium dinitramide was invented in 1971 at the Zelinsky Institute of Organic Chemistry in the USSR. Initially all information related to this compound was classified because of its use as a rocket propellant, particularly in Topol-M intercontinental ballistic missiles. In 1989 ammonium dinitramide was independently synthesized at SRI International. SRI obtained US and international patents for ADN in the mid-1990s, at which time scientists from the former Soviet Union revealed that they had discovered ADN earlier.

Propellant mixtures

ADN can be mixed with conventional propellants such as nitrocellulose to improve its oxygen balance. One of the challenges of using ADN is its hygroscopicity. Hu et al. have investigated the possibility of reducing the hygroscopicity of ADN by co-crystallization with 3,4-diaminofurazan.

There is also interest in using ADN to make liquid monopropellants. When ADN is co-crystalized with a crown ether (18C6), the hygroscopicity is greatly reduced, but so is its performance as an explosive. ADN was mixed with amine nitrates in order to lower its melting point for use as a liquid monopropellant. The onset temperature for ADN was essentially unchanged, but some cross-reaction with the amine nitrates was observed. Kim et al. have also examined mixtures of ADN with hydrogen peroxide as a potential liquid monopropellant.

Preparation

There are at least 20 different synthesis routes that produce ammonium dinitramide. In the laboratory ammonium dinitramide can be prepared by nitration of sulfamic acid or its salts (here sodium sulfamate) at low temperatures in the presence of concentrated sulfuric acid, followed by neutralization of the intermediate dinitramidic acid () with ammonia: : :

The process is performed under red light, since the compound is decomposed by higher-energy photons. An improvement of this method instead synthesizes Guanylurea dinitramide (FOX-12) as a starting point, reacts this with potassium hydroxide (KOH) to form a potassium dinitramide (KDN), and finally produces ammonium dinitramide via salt metathesis reaction of KDN with ammonium sulfate.

Other sources report ammonium synthesis from ammonium nitrate, anhydrous nitric acid, and fuming sulfuric acid (oleum) containing 20% free sulfur trioxide. A base other than ammonia must be added before the acid dinitramide decomposes. The final product is obtained by fractional crystallization.

Another synthesis known as the urethane synthesis method requires four synthesis steps and results in a yield of up to 60%. Ethyl carbamate is nitrated with nitric acid: :

and then reacted with ammonia to form the ammonium salt of N-nitrourethane: :

This is nitrated again with nitrogen pentoxide to form ethyl dinitrocarbamate and ammonium nitrate: :

Finally, treatment with ammonia again splits off the desired ammonium dinitramide and regenerates the urethane starting material: :

References

References

1. "Ammonium dinitramide".
2. (1 June 2000). "The properties of ammonium dinitramide (ADN): Part 1, basic properties and spectroscopic data". Journal of Energetic Materials.
3. (2011-02-14). "Advances in Spacecraft Technologies". InTech.
4. "Dinitramide Salts: ADN Plus Other Salts". [[SRI International]].
5. (3 March 2023). "Thermal Behaviors and Interaction Mechanism of Ammonium Dinitramide with Nitrocellulose". Molecules.
6. (September 2023). "Studies on ammonium dinitramide and 3,4-diaminofurazan cocrystal for tuning the hygroscopicity". Chinese Journal of Chemical Engineering.
7. (June 2022). "Decreasing the hygroscopicity of ammonium dinitramide (ADN) through cocrystallization". Energetic Materials Frontiers.
8. (November 2018). "Thermal behavior of ammonium dinitramide and amine nitrate mixtures". Journal of Thermal Analysis and Calorimetry.
9. (February 2, 2022). "Room-temperature catalytically reactive ammonium dinitramide–H2O2 monopropellant for microsatellites". Advances in Space Research.
10. (January 2023). "A review on the high energy oxidizer ammonium dinitramide: Its synthesis, thermal decomposition, hygroscopicity, and application in energetic materials". Defence Technology.
11. "Process for preparing ammonium dinitramide".