Hydrazine Bayer process

In the modified Raschlg process , used by Bayer A.G. and by Mobay Chem. Co. for large scale production of hydrazine, the intermediacy of an oxaziridine could be clearly evidenced (81MI50800). In this process ammonia and hypochlorite are reacted in the presence of acetone to form ketazine (302). Nitrogen-nitrogen bond formation is faster by a factor of about 1000 in the presence of acetone than in its absence. Thus acetone does not merely trap hydrazine after formation, but participates in the N —N bond forming reaction. Very fast formation of oxaziridine (301), which is isolable, is followed by its likewise fast reaction with ammonia. 

Bayer ketazine A process for making hydrazine by the reaction of sodium hypochlorite with ammonia in the presence of acetone. Acetone azine is an intermediate. Never commercialized. See also Raschig (1). 

Hydrazine hydrate is prepared by treating hydrazine sulfate, N2H4 H2SO4 with sodium hydroxide. The product is collected by distillation under nitrogen. It also is obtained as a by-product in the Bayer Ketazine process for producing hydrazine in which hydrazine solution is hydrolysed under pressure in a ketazine column. 

Commercial production of hydrazine from its elements has not been successful. However three processes are available for the commercial production of hydrazine 1) The Raschig Process, 2) The Raschig/Olin Process, 3) The Hoffmann (urea) Process, 4) Bayer Ketazine Process, and 5) the Peroxide process from Produits Chimiques Ugine Kuhlmann (of France). 

The Bayer Ketazine process is based on the reaction of chloramine with ammonia in the presence of acetone at pH 12 to 14. NaOCl, acetone and a 20% aqueous solution of ammonia (at a mole ratio of 1 2 20, respectively) are fed to a reactor at 35°C and 200 kPa to make the aqueous dimethyl ketazine solution. Excess ammonia and acetone are removed in a series of columns and recycled to the reactor. The ketazine solution is distilled to make a hydrazine hydrate containing 64% hydrazine. A sketch of this process is shown in Figure 18.4132. Use of NaOCl is estimated to be 3.5 pounds per pound of hydrazine. 

Figure 18.4. Bayer Hydrazine Process. (Reproduced by permission of Wiley-VCH)...

Hydrazine is currently prepared via a plethora of methods, the most popular of which is the Raschig process, which involves controlled hypochlorite oxidation leading to hydrazine formation. The Raschig process suffers from the formation of a stoichiometric quantity of sodium chloride by-product. The Bayer Ketazine process employs acetone to trap the hydrazine as dimethyl-ketazine. The acetone is re-cycled but sodium chloride is again formed. 

Hydrazine is formed in a multitude of chemical reactions. Only a few processes have acquired commercial importance. These all oxidize ammonia or urea, an ammonia derivative, to hydrazine. Sodium hypochlorite or hydrogen peroxide is used as the oxidizing agent. Certain processes (Bayer-, H202-processes) operate in the presence of ketones. 

Of a number of hydrazine syntheses based on the oxidation of ammonia with sodium hypochlorite in the presence of ketones (acetone, methyl ethyl ketone) (see Fig. 1.4-4), only that of Bayer A.G. appears to have graduated to a commercial process. 

According to the process of Bayer et al. (1969), the compound can also be obtained by the single-step reaction of orthoformic acid triethyl ester (68), formic acid hydrazine (69) and butylamine ... 

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