The peroxide process is a method for the industrial production of

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 ...

. In this process

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

is used as an

oxidant An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

instead of

sodium hypochlorite Sodium hypochlorite (commonly known in a dilute solution as bleach) is an Inorganic chemistry, inorganic chemical compound with the chemical formula, formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may ...

, which is traditionally used to generate hydrazine. The main advantage of the peroxide process to hydrazine relative to the traditional

Olin Raschig process The Olin Raschig process is a chemical process for the production of hydrazine. The main steps in this process, patented by German chemist Friedrich Raschig in 1906 and one of three reactions named after him, are the formation of monochloramine from ...

is that it does not coproduce salt. In this respect, the peroxide process is an example of

green chemistry Green chemistry, also called sustainable chemistry, is an area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances. While environmental che ...

. Since many millions of kilograms of hydrazine are produced annually, this method is of both commercial and environmental significance.Jean-Pierre Schirmann, Paul Bourdauducq "Hydrazine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. .

Production

Ketazine formation

In the usual implementation, hydrogen peroxide is used together with

acetamide Acetamide (systematic name: ethanamide) is an organic compound with the formula CH3CONH2. It is the simplest amide derived from acetic acid. It finds some use as a plasticizer and as an industrial solvent. The related compound ''N'',''N''-dimeth ...

. This mixture does not react 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 ...

directly but does so in the presence of

methyl ethyl ketone Butanone, also known as methyl ethyl ketone (MEK), is an organic compound with the formula CH3C(O)CH2CH3. This colourless liquid ketone has a sharp, sweet odor reminiscent of acetone. It is produced industrially on a large scale, but occurs in nat ...

to give the

oxaziridine An oxaziridine is an organic molecule that features a three-membered heterocycle containing oxygen, nitrogen, and carbon. In their largest application, oxaziridines are intermediates in the industrial production of hydrazine. Oxaziridine deri ...

. :

Balanced equations for the individual steps are as follows. Imine formation through condensation: :Me(Et)C=O + NH₃ → Me(Et)C=NH + H₂O Oxidation of the imine to the oxaziridine: :Me(Et)C=NH + H₂O₂ → Me(Et)CONH + H₂O Condensation of the oxaziridine with a second molecule of ammonia to give the hydrazone: :Me(Et)CONH + NH₃ → Me(Et)C=NNH₂ + H₂O The hydrazone then condenses with a second equivalent of ketone to give the

ketazine Azines are a functional class of organic compounds with the connectivity RR'C=N-N=CRR'. These compounds are the product of the condensation of hydrazine with ketones and aldehydes, although in practice they are often made by alternative routes ...

: :Me(Et)C=O + Me(Et)C=NNH₂ → Me(Et)C=NN=C(Et)Me + H₂O Typical process conditions are 50 °C and atmospheric pressure, with a feed mix of H₂O₂:ketone:NH₃ in a molar ratio of about 1:2:4. Methyl ethyl ketone is advantageous to acetone because the resulting ketazine is

immiscible Miscibility () is the property of two chemical substance, substances to mix in all mixing ratio, proportions (that is, to fully dissolution (chemistry), dissolve in each other at any concentration), forming a homogeneity and heterogeneity, homoge ...

in the reaction mixture and can be separated by decantation. A similar process based on

benzophenone Benzophenone is the organic compound with the formula (C6H5)2CO, generally abbreviated Ph2CO. It is a white solid that is soluble in organic solvents. Benzophenone is a widely used building block in organic chemistry, being the parent diarylket ...

has also been described.

Ketazine to hydrazine

The final stage involves hydrolysis of the purified ketazine: :Me(Et)C=NN=C(Et)Me + 2 H₂O → 2 Me(Et)C=O + N₂H₄ The

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of the azine is acid-catalyzed, hence the need to isolate the azine from the initial ammonia-containing reaction mixture. It is also

endothermic In thermochemistry, an endothermic process () is any thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principle of Modern Chemistry'', Brooks Cole. p. ...

, and so requires an increase in temperature (and pressure) to shift the equilibrium in favour of the desired products: ketone (which is recycled) and hydrazine hydrate. The reaction is carried out by simple

distillation Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...

of the azeotrope: typical conditions are a pressure of 8 bar and temperatures of 130 °C at the top of the column and 179 °C at the bottom of the column. The hydrazine hydrate (30–45% aqueous solution) is run off from the base of the column, while the methyl ethyl ketone is distilled off from the top of the column and recycled.

History

The peroxide process, also called the Pechiney–Ugine–Kuhlmann process, was developed in the early 1970s by Produits Chimiques Ugine Kuhlmann.. .. Originally the process used acetone instead of methyl ethyl ketone. Methyl ethyl ketone is advantageous because the resulting

is immiscible in the reaction mixture and can be separated by decantation... The world's largest

hydrazine hydrate 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 h ...

plant is in

Lannemezan Lannemezan (; Gascon Occitan ''Lanamesa'', "heath of the middle") is a commune in the Hautes-Pyrénées department and the Occitanie region in south-western France. The inhabitants are called Lannemezanais. Lannemezan is the largest city in ...

in France, producing 17,000 tonnes of hydrazine products per year..

Bayer ketazine process

Before invention of the peroxide process, the Bayer ketazine process had been commercialized. In the Bayer process, the oxidation of ammonia by sodium hypochlorite is conducted in the presence of acetone. The process generates the ketazine but also sodium chloride: :2 Me₂CO + 2 NH₃ + NaOCl → Me₂C=NN=CMe₂ + 3 H₂O + NaCl :Me₂C=NN=CMe₂ + 2 H₂O → N₂H₄ + 2 Me₂CO

References

Chemical processes Industrial processes {{reaction-stub