Patent EA-002915-B1 (EA)
Title: Method for preparing hydrazine
Inventor: BRENGUER GEORGES
IPC: C07C251/88
Filed: 1999-09-17
Abstract: 1. A process for preparation of an azine comprising the stages: (i) successively: (a) reacting ammonia, hydrogen peroxide and a reactant carrying a carbonyl group in a working solution in a reactor to form the azine, (b) separating the obtained azine from the working solution, (c) heating the working solution at a temperature of at least about 130 degree C, so that the CO2 and most of the water are removed in the form of an aqueous stream Cl; (d) regenerated in accordance with stage c) working solution is recycled to the reactor of Stage a); and (ii) successively: (a) treating the stream Cl in a stripping column; (b) condensing separated NH3 stream in a gaseous state which comes from the top of the column; (c) separating a liquid phase of the condensation zone into two phases, that is, an organic phase which is rich in reactant carrying a carbonyl group, and an aqueous phase comprising substantially all the CO2 present in Cl; (d) feeding said aqueous phase into a distillation column, and collecting an aqueous stream devoid of CO2 at the top of the distillation column and an aqueous stream C2 comprising substantially all the CO2 present in C1 at the bottom of the distillation column, wherein - at least a portion of the stream C2 is treated with an amount of acid such that pH of the stream C2 is adjusted to less than 6.4, preferably 6, then - said portion (assignable as C3) treated in this way is recycled to the reactor of Stage (i)(a). 2. The process of Claim 1, wherein the treatment with the acid is carried out at a temperature of between about 20 and about 70 degree C, preferably 40-60 degree C, and at a pressure of between about 0.5 and about 4 bar absolute, preferably 0,5-2 bar absolute. 3. The process of Claim 1 or 2, wherein the aqueous stream C2 contains from about 0.1 to about 20% CO2, preferably 0,5-5%, from about 1 to about 15% NH3, preferably 1-6%, and from about 0.1 to 10%, preferably 0,1-5%, reactant carrying a carbonyl group. 4. The process of any of Claims 1-3, wherein entire amount of the stream C2 is subjected to the treatment with the acid. 5. The process of any of Claims 1-4, wherein the reactant carrying a carbonyl group is methyl ethyl ketone. 6. The process of any of Claims 1-5, wherein the acid employed in the treatment of the stream C2 is an acid with a pKa of less than 6.3, preferably less than 5. 7. The process of any of Claims 1-6, wherein the working solution employed comprises an aqueous solution of acetamide and of acetic acid, and the acid used in the treatment of the stream C2 is acetic acid. 8. The process of any of Claims 1-6, wherein the working solution employed comprises an aqueous solution of cacodylic acid and ammonium cacodylate, and the acid used in the treatment of the stream C2 is cacodylic acid. 9. The process of any of Claims 7 or 8, wherein the treatment of the stream C2 is carried out by using acetic or cacodylic acid, introduced into working solution regeneration cycle. 10. The process for obtaining hydrazine, comprising process for obtaining azine according to any of Claims 1-9, which comprises separating azine from the working solution according stage (i) (b) and is subjected to hydrolyzing to obtain hydrazine, wherein the reactant carrying a carbonyl group is recuperated and recycled to the reactor for the synthesis of the azine.