Process for preparing hydrazine hydrate with oxime recycling

1. A process for preparing hydrazine hydrate, comprising the following steps:

reacting ammonia, hydrogen peroxide and methyl ethyl ketone in the presence of a solution comprising at least one activator to form an azine of methyl ethyl ketone; and

hydrolyzing the azine of methyl ethyl ketone to give hydrazine hydrate, with an oxime of methyl ethyl ketone being purged during the hydrolyzing step,

wherein the methyl ethyl ketone oxime purge is recycled upstream of the hydrolyzing step.

2. The process as claimed in claim 1 , wherein the methyl ethyl ketone oxime purge is carried out by withdrawal.

3. The process as claimed in claim 1 , in which the recycling step (h) is carried out continuously.

4. The process as claimed in claim 1 , in which the azine hydrolysis and methyl ethyl ketone regeneration step (f) is performed in a packed or tray distillation column.

5. The process as claimed in claim 4 , wherein the amount of methyl ethyl ketone oxime is not more than 20% by weight relative to the total weight of the liquid phase on the trays or in the parts of the column at which its concentration is at its maximum.

6. The process as claimed in claim 1 , in which the activator is acetamide.

7. The A process for preparing hydrazine hydrate, comprising the following steps:

(a) reacting ammonia, hydrogen peroxide and methyl ethyl ketone in the presence of a solution comprising at least one activator to form an azine of methyl ethyl ketone;

(b) treating the reaction mixture from step (a) to isolate:

an aqueous phase comprising the at least one activator; and

an organic phase comprising the azine of methyl ethyl ketone, an oxime of methyl ethyl ketone, and optionally unreacted methyl ethyl ketone;

(c) optionally recycling the aqueous phase to step (a) after optional treatment;

(d) washing the organic phase;

(e) optionally distilling the washed organic phase from step (d) to recover the azine of methyl ethyl ketone;

(f) hydrolyzing the azine of methyl ethyl ketone to give hydrazine hydrate and regenerated methyl ethyl ketone, with the oxime of methyl ethyl ketone being purged;

(g) optionally recycling the methyl ethyl ketone obtained in step (f) to step (a); and

(h) recycling the methyl ethyl ketone oxime purge obtained in step (f) to one at least of steps (a), (b), (c), (d) or (g).

8. The process as claimed in claim 7 , wherein the methyl ethyl ketone oxime purge obtained in step (f) is recycled to one at least of steps (c), (d) or (g).

9. The process as claimed in claim 7 , wherein the methyl ethyl ketone oxime purge obtained in step (f) is recycled to the organic phase washing step (d).

10. The process as claimed in claim 9 , wherein the methyl ethyl ketone oxime purge is sufficient to perform the organic phase washing without addition of water.