Ketazine process

KetaZine Processes. The oxidation of ammonia by chlorine or chloramine in the presence of ahphatic ketones yields hydrazones (36), ketazines (37), or diaziddines (38), depending on the pH, ketone ratios, and reaction conditions (101). 

Peroxide-Ketazine Process. Elf Atochem in France operates a process patented by Produits Chimiques Ugine Kuhhnaim (PCUK). Hydrogen peroxide (qv), rather than chlorine or hypochlorite, is used to oxidize ammonia. The reaction is carried out in the presence of methyl ethyl ketone (MEK) at atmospheric pressure and 50°C. The ratio of H202 MEK NH2 used is 1 2 4. Hydrogen peroxide is activated by acetamide and disodium hydrogen phosphate (117). Eigure 6 is a simplified flow sheet of this process. The overall reaction results in the formation of methyl ethyl ketazine [5921-54-0] (39) and water ... 

Fig. 6. Peroxide—ketazine process flow sheet. MEK = ethyl ketone.

Comparison to the Raschig Process. The economics of this peroxide process in comparison to the Raschig or hypochlorite—ketazine processes depend on the relative costs of chlorine, caustic, and hydrogen peroxide. An inexpensive source of peroxide would make this process attractive. Its energy consumption could be somewhat less, because the ketazine in the peroxide process is recovered by decantation rather than by distillation as in the hypcochlorite process. A big advantage of the peroxide process is the elimination of sodium chloride as a by-product this is important where salt discharge is an environmental concern. In addition to Elf Atochem, Mitsubishi Gas (Japan) uses a peroxide process. 

The estimated world production capacity for hydrazine solutions is 44,100 t on a N2H4 basis (Table 6). About 60% is made by the hypochlorite—ketazine process, 25% by the peroxide—ketazine route, and the remainder by the Raschig and urea processes. In addition there is anhydrous hydrazine capacity for propellant appHcations. In the United States, one plant dedicated to fuels production (Olin Corp., Raschig process), has a nominal capacity of 3200 t. This facihty also produces the two other hydrazine fuels, monomethyUiydrazine and unsymmetrical dimethyUiydrazine. Other hydrazine fuels capacity includes AH in the PRC, Japan, and Russia MMH in France and Japan and UDMH in France, Russia, and the PRC. 

Keshan disease, selenium and, 22 101 Kessener brush aerators, 26 162 Kestner-Johnson dissolver, 22 672 Kestner process, 2 723 Ketals, aroma chemicals, 3 253 Ketazine processes, 13 576, 579—581 disadvantages of, 13 581 Ketene(s), 10 484... 

Peroxide cure systems, in rubber compounding, 22 793-794 Peroxide decomposers, 3 111-114 Peroxide decomposition, 24 279-280 Peroxide formation, by VDC, 25 694. See also Hydrogen peroxide Peroxide initiators, 23 379-380 worldwide producers of, 24 303 Peroxide-ketazine process, 23 582-583 flow sheet for, 23 582 versus Raschig process, 23 583 Peroxide linkages, in VDC polymer degradation, 25 713... 

Rare-metal thermocouples, 24 461 RAR receptors, 25 787-789 Raschig process, 13 571, 576, 577-579 flow sheet for, 13 578 versus hypochlorite-ketazine processes, 13 581... 

In Ketazine processes, hydrazine derivatives are obtained first. Ammonia is oxidized by chlorine or chloramines in the presence of aliphatic ketones. The products are hydrazones and isohydrazones. These are converted to ketazines with excess ketone. The ketazines or the intermediate hydrazine derivatives may be hydrolyzed to hydrazine after all the oxidizing reactants, such as CI2, NaOCl, or NH2CI are consumed. Unlike hydrazine, ketazines do not readily oxidize, and, therefore, the product yield is higher in these processes. 

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. 

In the PCUK process (introduced by Produits Chimiques Ugine Kuhlmann), ammonia is oxidized with hydrogen peroxide in the presence of a ketone. A ketazine is formed as in the ketazine process, which is then processed similarly. Ketones with many different substituents, even aldehydes,... 

For most uses, hydrazine is produced as hydrazine hydrate in a formulation with water. The hydrate may be produced commercially by three methods the Raschig process, the ketazine process, and the peroxide process. The Raschig process, the original commercial production process for hydrazine, involves oxidation of ammonia to chloramine with sodium hypochlorite, then further reaction of the chloramine with excess ammonia and sodium hydroxide to produce an aqueous solution of hydrazine with sodium chloride as a by-product. Fractional distillation of the product yields hydrazine hydrate solutions. Currently, most hydrazine is produced by the ketazine process, which is a variation of the Raschig process. Ammonia is oxidized by chlorine or chloramine in the presence of an aliphatic ketone, usually acetone. The resulting ketazine is then hydrolyzed to hydrazine. In the peroxide process, hydrogen peroxide is used to oxidize ammonia in the presence of a ketone. Anhydrous hydrazine is the formulation used in rocket fuels and is produced by dehydration of the hydrate by azeotropic distillation with aniline as an auxiliary fluid (Budavari et al. 1989 lARC 1974 Schmidt 1988 WHO 1987). 

One of the most interesting waterborne systems is polyurethane (93). Polyurethane dispersions can be made by the following processes (94) acetone, prepolymer mixing, melt-dispersion (95), self-dispersion of solids, ketimine process (96), and ketazine process (97). The acetone... 

In the ketazine process (97), the NCO prepolymer is mixed with a ketazine, aldazine, or hydrazone before dispersing. Upon the addition of water, hydrazine is liberated to promote chain extension ... 

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