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 hazardous unless handled in solution as, for example, hydraz ...

. 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 viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

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 "Electron acceptor, accepts"/"receives" an electron from a (called the , , or ''electr ...

instead of sodium hypochlorite, which is traditionally used to generate hydrazine. The main advantage of the peroxide process to hydrazine relative to the traditional Olin Raschig process is that it does not coproduce salt. In this respect, the peroxide process is an example of

green chemistry Green chemistry, similar to sustainable chemistry or circular 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. Wh ...

. 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. This mixture does not react with

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

directly but does so in the presence of

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

to give the oxaziridine. : Pechiney-Ugine-Kuhlmann process

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: :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 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 An endothermic process is a chemical or physical process that absorbs heat from its surroundings. In terms of thermodynamics, it is a thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, ...

, 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 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 ketazine is immiscible in the reaction mixture and can be separated by decantation... The world's largest hydrazine hydrate plant is in Lannemezan 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 Hydrazines Hydrazones {{chem-process-stub