WO2003040033A1

WO2003040033A1 - Improved method for making hydrazine hydrate

Info

Publication number: WO2003040033A1
Application number: PCT/EP2002/012063
Authority: WO
Inventors: Jean-Pierre Schirmann
Original assignee: Fluorotech, Llc
Priority date: 2001-11-09
Filing date: 2002-10-29
Publication date: 2003-05-15
Also published as: FR2832142A1

Abstract

The invention concerns an improved method for making hydrazine hydrate, characterized by the following steps: a) in a reaction medium, oxidizing ammonia in aqueous solution in the presence of pivalone with sodium hypochlorite or with hydrogen peroxide associated with an activating agent to obtain pivalone hydrazone; b) when the reaction is completed, separating an organic phase consisting essentially of pivalone hydrazone from aqueous phase containing sodium chloride or the hydrogen peroxide activating agent, c) hydrolyzing the organic phase consisting essentially of pivalone hydrazone to obtain hydrazine hydrate in aqueous solution and pivalone and recycling to step a) the pivalone obtained at step c).

Description

Improved process for the manufacture of hydrazine hydrate

The present invention relates to a significant improvement in current industrial manufacturing processes for hydrazine hydrate.

Hydrazine hydrate is only produced by processes involving the oxidation processes of ammonia either by sodium hypochlorite or by hydrogen peroxide.

It has been known since the work of Raschig (1907) that hydrazine hydrate can be obtained by reaction of an aqueous solution of sodium hypochlorite with an aqueous solution of ammonia. We also know that it is necessary to operate in two stages and that considerable amounts of ammonia must be used if an acceptable yield is to be obtained.

In fact, initially, chloramine NH2CI is formed at low temperature:

NaCIO + NH3 NH ₂ C1 + NaOH (1) then this reacts with excess ammonia to form hydrazine at around 120 ° C: NH ₂ C1 + NH3 + NaOH + N ₂ H ₄ , H ₂ O + NaCl (2)

In this process, the reaction (1) is instantaneous and is not dependent on the temperature while the reaction (2) takes place at a sufficient speed only at high temperature. Under these conditions a third reaction also develops and has the effect of simultaneously destroying the chloramine and hydrazine: 2 NH ₂ C1 + N ₂ H * 2 NH4CI + N ₂ (3)

A significant improvement has been made to this process when it has been proposed to operate in a single step by working in the presence of a carbonyl compound and more particularly of a ketone. This is called the Bayer process which traps hydrazine in the form of an azine:

N ₂ H ₄ + 2 Ri-CO-R ₂ RχR ₂ C = NN = C RιR ₂ + 2 H ₂ O

This technique, described for example in US Patents 2,993,758 and US 3,077,383, has made it possible to significantly reduce the excess of ammonia involved, to improve yields and to significantly reduce energy consumption.

It has also been proposed to use either chlorine (GB 893388) or chloramine (GB 1150743) in place of sodium hypochlorite but these techniques do not provide any significant advantage. They can lead to the formation of azine but also of a another cyclic derivative of hydrazine called isohydrazone or also diaza-cyclopropane or to mixtures of azine and isohydrazone:

It has also been described in numerous patents, in particular US 3972878, US 3919256, FR 2323635, US 3972878 obtaining ketone magazines by the action of hydrogen peroxide on ammonia in the presence of ketone and of means A activation of hydrogen peroxide:

2 NH3 + 2 R! R ₂ C = 0 + H ₂ O ₂ Δ ^ RiR ₂ C = NN = C RιR ₂ + 4 H ₂ O

This type of process has the advantage of not coproducing sodium chloride which constitutes an expensive effluent to treat. In these two types of process, the azine obtained is then hydrolyzed to hydrazine hydrate and a ketone which can be recycled to the oxidation reaction:

Detailed descriptions of the industrial processes operating in these two ways can be found in encyclopedias such as Kirk-Othmer Encyclopedia, 1997 edition, vol.13, pages 575 to 582 or even Ullmann's Encyclopedia of Industrial Chemistry, 1989 edition, vol.13, pages 179 to 183.

Continuing his research in the field of hydrazine, the applicant has just discovered that these processes could be considerably improved by using 2,2,4,4-tetramethyl-3-pentanone as the ketone used to trap the hydrazine. , also called pivalone. In fact, the oxidation reaction does not lead to the corresponding azine, as is the case for the other ketones such as acetone or methyl ethyl ketone for example, but only to the hydrazone of pivalone which moreover is very slightly soluble in water and forms with water an azeotrope with a boiling point below 100 ° C but higher than that of the water / pivalone azeotrope. All of these properties not known to date, added to the fact that, given its structure, pivalone cannot undergo degradations linked to aldolization, crotonization or even oxidation reactions under mild conditions of hydrazine synthesis, make this molecule a unique means to improve existing industrial processes.

The process according to the invention therefore only involves a single ketone molecule:

NaCIO NaCl +2 H ₂ O 2 NH ₃ + ((CH) ₃ C) ₂ C = O + or ((CH ₃ ) ₃ C) ₂ C = N-NH ₂ + or

H ₂ O ₂ 3 H ₂ O

This has the effect of considerably limiting the amount of organic product to be treated for oxidation, but especially during hydrolysis and consequently greatly limiting energy expenditure:

((CH ₃ ) ₃ C) ₂ C = N-NH ₂ + 2 H ₂ O »N ₂ H ₄ , H ₂ O + ((CH ₃ ) ₃ C) ₂ C = O

The released pivalone is recycled to the ammonia oxidation reaction by hydrogen peroxide or by sodium hypochlorite.

The hydrazone of pivalone is known and can also be obtained, as described in the article DHBarton et al., J. Chem. Soc. (Perkin) 1794 (1974), by reaction of hydrazine hydrate with the imine of pivalone itself obtained from pivalonitrile as described in US patent 2742503. The process for the manufacture of hydrazine hydrate in aqueous solution according to the invention, is characterized by the following stages: a) in a reaction medium, ammonia is oxidized in aqueous solution in the presence of pivalone, either by an aqueous solution of sodium hypochlorite, or by hydrogen peroxide associated with an activating agent, to give the hydrazone of pivalone, b) when the reaction is complete, an organic phase is essentially separated, consisting of hydrazone of pivalone, from an aqueous phase containing sodium chloride in case the oxidant is sodium hypochlorite or the activating agent of hydrogen peroxide in the case where the oxidant is H ₂ O ₂ , c) the organic phase is hydrolyzed essentially containing prazone hydrazone to obtain l hydrazine hydrate in aqueous solution on the one hand and pivalone on the other hand and the pivalone obtained in step c) is recycled in step a).

Step a), whatever the oxidant, is advantageously carried out at atmospheric pressure at a temperature between 30 ° C and 60 ° C and preferably between 35 ° C and 50 ° C. The reagents are mixed according to known methods and the reaction is advantageously carried out over a period of three to six hours. The reaction medium is heterogeneous and consists of an organic phase and an aqueous phase. Preferably, an excess of ammonia is used relative to the pivalone used with an ammonia / pivalone molar ratio ranging from 3 to 10 and preferably close to 5. The amount of oxidant used is at most equal to that of pivalone in terms molar ratio but it is preferred to use a slight excess of pivalone, that is to say that the pivalone / oxidant molar ratio ranges from 1 to 1.2.

When the oxidizing agent is hydrogen peroxide, the activating agent can be an organic acid, an amide or a nitrile or an arsenic-based catalyst such as for example cacodylic acid or phenylarsonic acid . Preferably when all the oxidant has been consumed, the reaction mixture is subjected during step b) to decantation and the organic phase is separated to be optionally washed and then used in the hydrolysis step c) which is carried out with water in a reactive distillation column so that the pivalone is collected at the top of the column and the hydrazine hydrate at the bottom. Preferably, the hydrazone of the pivalone constituting the major part of the organic phase is then hydrolysed continuously during step c) in a distillation column called the reactive column, comprising trays with bells having a barrier sufficient to allow long residence times and into which water is injected. The hydrolysis is advantageously carried out under a pressure ranging from 5 to 10 bar absolute and preferably between 6 and 8 bar absolute so as to be able to work at temperatures ranging from 160 to 170 ° C at the top of the column and from 180 to 190 ° C at the bottom. The pivalone released during the hydrolysis exits at the top of the column in the form of a hetero azeotropic with water of composition close to 60% by weight in pivalone. After condensation, the pivalone is separated from the water by decantation and then returned to the oxidation stage. The water is returned to the column. The water / hydrazone molar ratio at the inlet of the column is generally between 2 and 100 but it is preferable to inject only 10 to 15 moles of water per mole of hydrazone of the pivalone injected. Most of the platforms are occupied by heterogeneous mixtures comprising water, free pivalone, pivalone hydrazone or hydrazine in variable quantities according to the rate of hydrolysis achieved locally on the considered plateau and the distillation regime. Towards the bottom of the column, the last trays have a homogeneous content essentially comprising hydrazine and water. At the bottom there is an aqueous hydrazine hydrate solution having a titer ranging from 8 to 12% by weight and preferably between 8 and 10%.

The following examples illustrate, without limitation, the scope of the present invention:

Example 1: To 200 ml of an aqueous solution of sodium hypochlorite, containing 152 g of active chlorine per liter, 200 ml of distilled water are added. This solution is gradually added to an emulsion consisting of 600 ml of an aqueous solution of ammonia at 25% by weight and 62.5 g of pivalone while maintaining the temperature at 35 ° C by cooling. At the end of the addition, the system is cooled and an organic phase is separated in which 0.35 mole of hydrazone from the pivalone is assayed.

EXAMPLE 2 20.5 g of acetonitrile (0.5 mole), 71 g of pivalone (0.5 mole) and 180 g of water are placed in a reactor successively, as well as 1 g of disodium salt of ethylenediaminetetracetic acid, then bubbled gaseous ammonia until 34 g of this gas was dissolved in the medium kept stirred. The temperature of the mixture is brought to 50 ° C. and 19.5 g of an aqueous solution of hydrogen peroxide at 70% by weight of H ₂ O ₂ (0.4 mol) are introduced over 10 minutes. This is left to react for 6 hours while maintaining a bubbling of gaseous ammonia at the rate of 1.7 g / hour. After cooling, an organic phase is separated in which 59.5 g of hydrazone from the pivalone are measured, ie a yield of 95% relative to the hydrogen peroxide used.

Example 3: 2 g of phenylarsonic acid, then 30 ml of water and finally 40 ml of pivalone are placed in a 100 ml capacity reactor. This mixture is then saturated with gaseous ammonia while bringing its temperature to 50 ° C. with stirring. 11 g of a 70% by weight aqueous hydrogen peroxide solution are then introduced dropwise over a period of approximately 5 minutes. It is left to react for another 2 hours at 50 ° C. We then dose by iodometry 29.5 g of hydrazone pivalone, which corresponds to a yield of 84% compared to hydrogen peroxide.

EXAMPLE 4 The hydrolysis of the hydrazone of the pivalone is carried out continuously in a column of 316 L stainless steel 4 m high, 70 mm in diameter equipped with 40 trays with a perforated monocoque 30 mm in diameter and spaced apart. others with a height of 80 mm. The holes of each bell are 4 mm high by 2 mm wide and are 12 in number. This column is also equipped with temperature sockets on trays 2, 5, 10, 15, 20, 25, 30 and 35 as well than at the top and bottom of the column. The introduction of the reactants in continuous regime is carried out on plate 26 for hydrazone and on plate 16 for water. It is ensured by means of metering pumps. The reflux flow at the top of the column is measured using a rotameter previously calibrated. Calories are supplied at the bottom of the column and are provided by electric heating. The adiabatism of the barrel of the column is carried out thanks to a sheath of hot air. The condenser at the head of the column is supplied in its external circuit by a circulation of hot oil maintained at a temperature between 130 and 140 ° C.

To start the installation, 800 ml of distilled water are placed in the boiler with a useful volume of 1 liter. The installation previously inerted with nitrogen being closed, heating is started and the pressure in the column is allowed to rise to 8 bars. Then as the water rises in the column, the inerting nitrogen is purged while maintaining the pressure at 8 bars. When the water level in the boiler corresponds to a volume of the order of 250 ml, the injection of water is started on the plate 16 at the rate of 250 ml / hour for 2 hours in order to constitute the ballast of water necessary for the proper functioning of the column and the carrying out of the hydrolysis reaction. When the temperature reaches 160 ° C at the level of the plate 25, the injection of hydrazone of pivalone is started at the rate of 100 g / hour for 2 hours. The inerting nitrogen is continued to be purged as the water, hydrazone, pivalone and hydrazine settle in the column while maintaining the pressure at 8 bars. The injections of water and hydrazone of the pivalone are then stopped and the column is allowed to balance and the reflux is established. When equilibrium is reached and all temperatures are stabilized, the injections of hydrazone and water are restarted and the withdrawals are started at the head and at the bottom of the column, while making sure to maintain the pressure at 8 bars. and keep a constant level in the boiler. Hydrazone is introduced at the rate of 117 g / hour and the water at the rate of 510 g / hour. The temperature at the top of the column stabilizes at 170-172 ° C while that at the bottom is between 185 and 188 ° C. In a steady stationary regime, 470 g / hour of colorless hydrazine hydrate solution titrating 8% by weight are drawn off at the bottom. At the head, the azeotropic water pivalone is collected at the rate of 175 g / hour and titrating 60% by weight of pivalone, ie 105 g / hour of pivalone.

Claims

claims

1. A process for the manufacture of hydrazine hydrate in aqueous solution, characterized by the following steps: a) in a reaction medium, ammonia is oxidized in aqueous solution in the presence of pivalone, either with an aqueous hypochlorite solution sodium, either with hydrogen peroxide combined with an activating agent, to give the hydrazone of pivalone, b) when the reaction is complete, an organic phase is separated essentially consisting of hydrazone of pivalone an aqueous phase containing sodium chloride in the case where the oxidant is sodium hypochlorite or the activating agent of hydrogen peroxide in the case where the oxidant is H ₂ O ₂ , c) the organic phase is hydrolyzed essentially containing prazone hydrazone to obtain hydrazine hydrate in aqueous solution on the one hand and pivalone on the other hand and the pivalone obtained is recycled in step a) in step c).

2. Method according to claim 1, characterized in that the activating agent of hydrogen peroxide is an organic acid, an amide, a nitrile.

3. Method according to claim 1, characterized in that the activating agent of hydrogen peroxide is an organic derivative of arsenic.

4. Method according to claim 3, characterized in that the arsenic derivative is cacodylic acid or phenylarsonic acid.

5. Method according to claims 1 to 4, characterized in that the pivalone / oxidant molar ratio ranges from 1 to 1.2.

6. Method according to claims 1 to 5, characterized in that the hydrolysis of step c) is carried out with water in a reactive distillation column so that the pivalone is collected at the top of the column and l hydrazine hydrate at the bottom.

7. Method according to claim 6, characterized in that the hydrolysis column is carried out under a pressure ranging from 6 to 8 bars absolute and at an internal temperature ranging from 180 to 190 ° C at the bottom and from 160 to 170 ° C at the head.