Ammonium dinitramide (ADN) is the
ammonium salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
of
dinitraminic acid. ADN decomposes under heat to leave only nitrogen, oxygen, and water. The ions are the ammonium ion NH
4+ and the dinitramide N(NO
2)
2−.
It makes an excellent
solid rocket oxidizer with a slightly higher specific impulse than
ammonium perchlorate and more importantly, does not leave corrosive
hydrogen chloride
The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...
fumes. This property is also of military interest because halogen-free smoke is harder to detect. It decomposes into low-molecular-mass gases so it contributes to higher performance without creating excessive temperatures if used in gun or rocket propellants. The salt is prone to detonation under high temperatures and shock more so than the
perchlorate
A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...
.
The EURENCO Bofors company produced LMP-103S as a 1-to-1 substitute for
hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
by dissolving 65% ammonium dinitramide, NH
4N(NO
2)
2, in 35% water solution of methanol and ammonia. LMP-103S has 6% higher specific impulse and 30% higher impulse density than hydrazine monopropellant. Additionally, hydrazine is highly toxic and carcinogenic, while LMP-103S is only moderately toxic. LMP-103S is UN Class 1.4S allowing for transport on commercial aircraft, and was demonstrated on the Prisma satellite in 2010. Special handling is not required. LMP-103S could replace hydrazine as the most commonly used
monopropellant
Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with bipro ...
.
The ADN-based monopropellant FLP-106 is reported to have improved properties relative to LMP-103S, including higher performance (ISP of 259 s vs. 252 s) and density (1.362 g/cm
3 vs. 1.240 g/cm
3).
History
Ammonium dinitramide was invented in 1971 in Zelinskiy 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
The RT-2PM2 «Topol-M» (russian: РТ-2ПМ2 «Тополь-М», NATO reporting name: SS-27 "Sickle B", other designations: SS-27 Mod 1, RS-12M1, RS-12M2, formerly incorrectly RT-2UTTKh) is one of the most recent intercontinental ballistic missi ...
intercontinental ballistic missiles. In 1989 ammonium dinitramide was independently synthesized at
SRI International
SRI International (SRI) is an American nonprofit scientific research institute and organization headquartered in Menlo Park, California. The trustees of Stanford University established SRI in 1946 as a center of innovation to support economic ...
.
SRI obtained US and international patents for ADN in the mid-1990s, at which time scientists from the former Soviet Union revealed they had discovered ADN 18 years earlier.
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
Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, sulphamic acid and sulfamidic acid, is a molecular compound with the formula H3NSO3. This colourless, water-soluble compound finds many applications. Sulfami ...
or its salt under low temperatures.
:KSO
3NH
2 + 2HNO
3 → KHSO
4 + NH
4N(NO
2)
2 + H
2O
The process is performed under red light, since the compound is decomposed by higher energy photons. The details of the synthesis remain classified.
Other sources report ammonium synthesis from
ammonium nitrate
Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
, anhydrous
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
, and fuming
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
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
Ethyl carbamate (also called urethane) is an organic compound with the formula CH3CH2OC(O)NH2. It is an ester of carbamic acid and a white solid. Despite its name, it is not a component of polyurethanes. Because it is a carcinogen, it is rarely us ...
is nitrated with
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
, and then reacted with
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
to form the ammonium salt of N-nitrourethane. This is nitrated again with
nitrogen pentoxide
Dinitrogen pentoxide is the chemical compound with the formula , also known as nitrogen pentoxide or nitric anhydride. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourles ...
to form ethyl dinitrocarbamate and
ammonium nitrate
Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
. Finally, treatment with ammonia again splits off the desired ammonium dinitramide and regenerates the urethane starting material.
:CH
3CH
2OC(O)NH
2 + HNO
3 → CH
3CH
2OC(O)NHNO
2 + H
2O
:CH
3CH
2OC(O)NHNO
2 + NH
3 → CH
3CH
2OC(O)NNO
2NH
4
:CH
3CH
2OC(O)NNO
2NH
4 + N
2O
5 → CH
3CH
2OC(O)N(NO
2)
2 + NH
4NO
3
:CH
3CH
2OC(O)N(NO
2)
2 + 2NH
3 → CH
3CH
2OC(O)NH
2 + NH
4N(NO
2)
2
References
Further reading
* Modern rocket fuels> PDF> Hesiserman Online Library
* ''Textbook of Chemistry'' 1999 Prentice Press, New York
*{{cite journal
, journal = Propellants, Explosives, Pyrotechnics
, volume = 29
, issue = 3
, pages = 178–187
, year = 2004
, title = An Overview on the Synthetic Routes and Properties of Ammonium Dinitramide (ADN) and other Dinitramide Salts
, author1=Subbiah Venkatachalam , author2=Gopalakrishnan Santhosh , author3=Kovoor Ninan Ninan , doi = 10.1002/prep.200400043
Explosive chemicals
Rocket oxidizers
Nitroamines
SRI International