Hydrazine

• Diamide
• Diazane

• 302-01-2 (anhydrous)
• 7803-57-8 ( 64 % hydrazine, hydrazine hydrate )
• 10217-52-4 ( hydrazine 55%)

Colorless, clear liquid

1.01 g · cm -3 ( 20 ° C)

1.5 ° C

113.5 ° C

21 hPa ( 20 ° C)

• 8.0 ( N2H4/N2H5 , in water)
• -1.0 ( N2H5 / N2H62 , in water)

Miscible with water

1.47 (20 ° C)

Risk

Not classified as carcinogenic in animal experiments

Hydrazine is an inorganic chemical compound consisting of nitrogen and hydrogen with the formula N2H4. It is a colorless, oily, like ammonia smelling fumes in air liquid. Hydrazine burns with an almost invisible flame. In the trade it is usually as an aqueous solution or as hydrazine ( H2N - NH2 · H2O).

• 2.1 Säure-/Baseverhalten

• 3.1 fuel
• 3.2 reducing agent / corrosion inhibitor

Representation

Technically

• Raschig synthesis: oxidation of ammonia ( NH3) with sodium hypochlorite.

• Bayer process: oxidation of ammonia with sodium hypochlorite in the presence of acetone.

• Pechiney Ugine Kuhlmann - process: The process technically strengthened applied consists in the oxidation of ammonia with hydrogen peroxide ( H2O2) in the presence of methyl ethyl ketone as Ketazinbildner and acetamide and sodium dihydrogen phosphate as activators.

In the laboratory

• By introducing chlorine into a 20 - % urea solution and subsequent addition of 20 - % sodium hydroxide solution. The yield is about 50%.

• To 99.5 % of anhydrous hydrazine is produced by fractional distillation of the monohydrate with sodium hydroxide in a nitrogen stream.
• A further possibility for producing dry hydrazine is the cleavage of hydrazinium salts with ammonia:

Properties

Hydrazine has a dynamic viscosity of 0.9 x 10-3 Pa · s. Pure hydrazine can explosively disproportionate to ammonia and nitrogen when heated.

Concentrated solutions are highly explosive in combination with oxidizing agents, partially hypergol. Hydrazine can also be decomposed catalytically.

The compound forms an azeotrope with water with a hydrazine content of 58.5%, which boils at 120.5 ° C.

Hydrazine is a divalent base ( pKb1 = 6.07; PKB2 = 15 ), but weaker than ammonia pKb = 4.75). It reacts as divalent base with acids to form two rows of hydrazinium (name analogous to ammonium ) with the general composition [ H2N -NH3 ] X and [ H3N -NH3 ] 2 2 X. With hydrochloric acid to form Hydraziniummonochlorid ( [ H2N -NH3 ] Cl) and Hydraziniumdichlorid ( [ H3N -NH3 ] Cl2). With sulfuric acid to hydrazinium sulfate ( [ H3N -NH3 ] SO4 ) and dihydrazinium opposite forms ( [ H2N -NH3 ] 2SO4. Strong bases ( pK b << 0) hydrazine acts as acid. Thus, by reaction of sodium hydride or sodium amide with hydrazine extremely oxidation- sensitive sodium hydrazide is obtained, in which the anions are present hydrazide ( N2H3 ). Conversely hydrazide ions react with water almost completely to hydroxide ions and hydrazine.

Use

Fuel

Due to its highly reactive properties is used mainly as rocket fuel hydrazine, which forms a hypergolic propellant combination with oxidizers dinitrogen tetroxide or nitric acid. Hydrazine is not only pure but also mixed together with 1,1- dimethylhydrazine used with the oxidants mentioned above. Known mixtures with different concentrations of the two components are mutually Aerozin 50 and 25 UH Even alone hydrazine is used in thrusters, where it is catalytically decomposed, for example, even when the Voyager probes.

Hydrazine is used as a storable fuel in many rockets, satellites and space probes. This can lead to a significant environmental hazard if a rocket launch fails. If a satellite has already reached an orbit, it is due to the high speed of at least eight kilometers per second and the unfavorable aerodynamic conditions at the spherical tanks virtually ruled out that these hit the ground, as they burn up in the atmosphere due to the high kinetic energy. The hydrazine decomposes it.

When the Challenger disaster no hydrazine contamination was detected. After a successful shuttle landing one of the first security measures, the standing Orbiter was always to investigate on leaking hydrazine. Only when this test was negative, to other auxiliary vehicles were allowed, such as for cooling, approaching the shuttle.

In the Columbia disaster in 2003 was warned of a possible hydrazine contamination by NASA in the media, and in fact a largely intact hydrazine tank from Columbia in 2011 was found.

The shooting down of the American USA 193 satellite was founded in the media with the risks arising from the on-board hydrazine.

Hydrazine is carried in aircraft such as the F -16 as a fuel for a Notenergieaggregat.

Hydrazine is used for electrochemical power generation in secondary cells and alkaline fuel cells, which ( it is here also used as an integral component of a rescue system ), primarily in the aerospace, submarines and other military equipment are used.

Reducing agent / corrosion inhibitor

Diluted hydrazine solutions are used as reagents in the laboratory and for deoxygenation ( deoxygenation ) of boiler feed water in steam power plants. The use is carried out both for the removal of residual oxygen after Speisewasserentgasung, to protect against possible low oxygen dips in the area of the capacitor as well as for the catalytic removal of oxygen from the additional water. The advantage of hydrazine is that only nitrogen and water formed in this reaction. In addition to the deoxygenation and an increase in the pH is achieved in the water - steam circuit.

In the chemical synthesis of hydrazine is used primarily as a strong nucleophile ( so-called alpha- effect), and as the reducing agent of the carbonyl groups (Wolff -Kishner reaction ) or as hydrogen source in the catalytic hydrogenation.

Safety

Hydrazine is toxic, carcinogenic in animal studies and has a highly toxic to aquatic organisms. Hydrazine can be absorbed through the skin. Hydrazine has a technical reference concentration of 0.13 mg · m- third

The use of hydrazine in water-steam systems (Steam boilers and district heating systems ) subject since 1991, strict regulations that are defined in the Technical Rule 608. For example, is the instantaneous domestic hot water in district heating systems, which have been conditioned with hydrazine, is not permitted, but it must be installed a dual-circuit system.

Hydrazine is added since June 2011 on suspicion of carcinogenic effect in the SVHC Candidate List ( List of SVHC ). This has initially affect only specific information requirements in the supply chain.