PROCESS FOR PREPARING HYDRAZINE HYDRATE WITH OXIME RECYCLING

Abstract

The present invention relates to an improved process for preparing hydrazine hydrate from the azine of methyl ethyl ketone obtained from methyl ethyl ketone by oxidizing ammonia with hydrogen peroxide in the presence of an activator, characterized in that it comprises a step of recycling the methyl ethyl ketone oxime purge.

Claims

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; and hydrolyzing the resulting azine of methyl ethyl ketone to give hydrazine hydrate, with the oxime of methyl ethyl ketone being purged during said hydrolysis step, wherein said methyl ethyl ketone oxime purge is recycled upstream of the hydrolysis step.

2. The process for preparing hydrazine hydrate as claimed in claim 1, 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; (b) treating the reaction mixture from step (a) to isolate: the aqueous phase comprising the activator(s); and the organic phase comprising the resulting azine and oxime of methyl ethyl ketone and optionally the unreacted methyl ethyl ketone; (c) optionally recycling the aqueous phase to step (a) after optional treatment; (d) washing the organic phase, preferably in countercurrent; (e) optionally distilling the washed organic phase to recover the azine; (f) hydrolyzing the azine to give hydrazine hydrate and regenerate 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).

3. The process as claimed in claim 2, wherein the methyl ethyl ketone oxime purge obtained in step (f) is recycled to one at least of steps (c), (d) or (g).

4. The process as claimed in claim 2, wherein the methyl ethyl ketone oxime purge obtained in step (f) is recycled to the organic phase washing step (d).

5. The process as claimed in claim 4, wherein the methyl ethyl ketone oxime purge is sufficient to perform said organic phase washing, without addition of water.

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

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

8. 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.

9. The process as claimed in claim 8, 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.

10. The process as claimed in claim 1, in which said activator is acetamide.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0113] The FIGURE represents an example of industrial implementation of the process for preparing hydrazine hydrate according to the invention.

[0114] A shows the mekazine synthesis step (a); stream 1 comprises ammonia, hydrogen peroxide and supplementary required amounts of acetic acid, ammonium acetate or acetamide or else of methyl ethyl ketone, and also the various additives used during the synthesis step, such as the peroxide stabilizers, for example. Stream 13 corresponds to the recycling of the aqueous phase as per step (c), after it has been thermally regenerated and concentrated to remove excess water. Stream 8 corresponds to the recycling of the methyl ethyl ketone regenerated during the hydrolysis step and recovered at the exit from the hydrolysis column E as per step (g).

[0115] B shows a settler at the exit from azine synthesis step (a), which receives the reaction mixture 2. It allows the organic phase containing the crude mekazine corresponding to stream 3 and the aqueous phase containing the activator, acetamide for example, and corresponding to stream 4 as per step (b).

[0116] C shows a countercurrent washing column as per step (d). The organic phase, stream 3, is introduced at the foot of column C and is washed in countercurrent with stream 10, corresponding to the methyl ethyl ketone oxime purge extracted from the trays of the azine hydrolysis column E as per step (h). Stream 12, corresponding to the aqueous phase at the exit from the washing column C is then sent to section G, corresponding to the step of thermal regeneration and concentration of the aqueous phase with stream 4.

[0117] The washed organic phase, stream 5, is sent for purification on a distillation column D as per step (e). With this column it is possible to recover a little methyl ethyl ketone recycled at A at the top and to remove in the bottoms the heavy impurities present in the azine (not shown).

[0118] The organic phase comprising the distilled azine, stream 6, is then sent to the hydrolysis column E. The hydrolysis column E is a distillation column operating under pressure. The distilled azine, 6, is introduced into column E, as is the water, stream 7, needed for the hydrolysis.

[0119] After the hydrolysis step (f), at the top, after condensation of the vapors and decanting in F, stream 8 is obtained, comprising principally methyl ethyl ketone, water and a little azine. This phase is recycled to the azine synthesis step A.

[0120] The decanted aqueous phase, stream 9, is sent to the top of the hydrolysis column.

[0121] Stream 11 corresponds to the hydrazine hydrate solution obtained and recovered at the column bottom.

[0122] The examples are given solely for illustrative purposes and do not limit the invention.

EXAMPLES

Example 1: Preparation Process According to the Invention

[0123] The process as described for the FIGURE is employed.

[0124] Column E operates under the conditions described below:

TABLE-US-00001 Bottom temperature 178-190° C. Overhead condenser 160° C. temperature Overhead pressure 7.5 to 9.7 bar absolute Reboiling temperature 200° C., pressure 16 bar Feed of distilled azine 6 5000 kg/hour Feed of water 7 10000 kg/hour Bottom hydrazine takeoff 12 t/h of a 22.2% aqueous solution as
expressed in terms of hydrazine hydrate (or 14.2% as expressed in terms of hydrazine N.sub.2H.sub.4)

[0125] After hydrolysis step (f), at the top, after condensation of the vapors and decanting, approximately 6 500 kg/hour of organic phase, stream 8, is withdrawn, comprising principally methyl ethyl ketone, water and a little azine. This phase is recycled to the step of synthesis of the azine A.

[0126] The decanted aqueous phase, stream 9, is returned to the hydrolysis column, at the top.

[0127] A purge, stream 10, is performed on the trays of the hydrolysis column at a rate of 1477 kg/h, at the location where the methyl ethyl ketone oxime accumulates. This purge is sent to the washing column C to wash the organic phase from the separator B.

[0128] The flow rates and analyses performed around the washing column C are reported in table 1:

TABLE-US-00002 TABLE 1 Washing column c for crude azine organic phase aqueous phase inlet outlet gain inlet outlet gain 3 5 5 − 3 10 12 12 − 10 stream n° kg/h kg/h kg/h kg/h kg/h kg/h MEC 315 370 0.3 18 MEC-azine 5416 5565 150 75 38 −37 MEC-hydrazone 0 0 89 2 −88 MEC-Oxime 154 318 164 171 3 −168 acetamide 46 0 0 49 WATER 49 318 1137 777 stream total 7006 7401 1477 892

[0129] It is seen that 150 kg/h of azine are thus recovered in organic phase (stream 5) when stream 3 is washed with the oxime purge 10. Subject to analytical uncertainties, this corresponds to the recovery of 37 and 88 kg of azine and of hydrazone contained in this purge 10. The oxime contained in the purge 10 is transferred near-quantitatively also into the stream of azine 5 at the exit from the washing column.

[0130] The audit is also performed around the hydrolysis column E, and is reported in table 2:

TABLE-US-00003 hydrolysis column E distilled washed washed oxime recycled hydrazine azine azine purge MEC WATER hydrate 5 6 10 8 7 11 stream n° kg/h kg/h kg/h kg/h kg/h kg/h MEC 370 21 0.3 5206 0 MEC-azine 5565 5523 75 404 0 MEC-hydrazone 0 0 89 0 6 MEC-Oxime 318 283 171 0 0 0 acetamide 0 0 0 0 0 WATER 318 21 1137 849 11000 7768 N2H4 hydrazine 0 0 0 0 0 1305 impurities div QSP 829 139 4 330 0 106 stream total 7401 5987 1477 6789 11000 9186

[0131] It is seen that the oxime is consumed principally during hydrolysis of the azine in column E when the process is operated according to the invention with recycling of the purge 10.

[0132] Stream 3 (table 1) represents 154 kg/h of oxime produced upstream of the hydrolysis by the step of synthesis of the azine A and of thermal regeneration of the aqueous phase G. This production is well compensated by the loss of oxime observed between washing step C and hydrolysis E, and thus between stream 5 (318 kg/h of oxime) and stream 10 recycling the oxime at 171 kg/h, corresponding to consumption of 318-171=147 kg/h of oxime.

[0133] The oxime is observed not to increase in the process, remaining at a concentration of 11% on the trays of the hydrolysis column E.