Bayer Ketazine process

Hydrazine is thermally stable and storable for years without adverse effects either to the product or the storage container. However the recommended materials must be used all systems must be clean and an inert gas (such as nitrogen) must be maintained over the system at all times. Suitable materials of construction for handling hydrazine are given in Table 18.2253. 

TABLE 18.2. Materials of Construction for Aqueous Hydrazine Solutions8 

S = generally satisfactory NR = not recommended NS = not suitable owing either to decomposition or to adverse effects ofthe solution on the material of construction. b Onlyupto650C c PTFE=poly(tetrafluoroethylene) 

For solutions that contain less than 10% hydrazine, cold-rolled steel is satisfactory. PVC is not recommended. Ethylene-propylene-diene monomer (EPDM) rubber, polyketones and polyphenylene sulfides are suitable for use with anhydrous hydrazine253. 

In some cases testing may be needed to identify a suitable material. For example, low concentrations of CO2 (250 ppm) in anhydrous hydrazine accelerate the decomposition of hydrazine in stainless steel. Long-term storage tests of hydrazine propellants in 17-7 PH stainless steel and AM350 precipitation-hardened stainless steel at 50°C for about three years showed no pressure rise or hydrazine decomposition253. 

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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. 

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. 

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). 

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. 

The Bergbau or Bayer Process is somewhat similar to the Ugine Kuhlmann technology where a ketazine intermediate is formed. The... 

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