Chemistry of inorganic compounds – Nitrogen or compound thereof – Binary compound
Reexamination Certificate
2001-01-25
2003-05-13
Langel, Wayne A. (Department: 1754)
Chemistry of inorganic compounds
Nitrogen or compound thereof
Binary compound
C564S249000, C568S403000
Reexamination Certificate
active
06562311
ABSTRACT:
The present invention relates to a process for the preparation of hydrazine hydrate. The present invention relates more specifically to an improved process for the manufacture of hydrazine hydrate from methyl ethyl ketone azine obtained by oxidation of ammonia with hydrogen peroxide in the presence of a coreactant or of a catalyst.
The industrial production of hydrazine hydrate is carried out according to the Raschig, Bayer or hydrogen peroxide processes.
In the Raschig process, ammonia is oxidized with a hypochlorite in order to obtain a dilute hydrazine hydrate solution, which solution subsequently has to be concentrated by distillation. This process is not very selective, has a low yield and is highly polluting, and is virtually no longer used.
The Bayer process is an alternative form of the Raschig process which consists in shifting a chemical equilibrium by trapping, using acetone, the hydrazine formed in the azine form (CH
3
)
2
C═N—N═C—(CH
3
)
2
. The azine is subsequently isolated and then hydrolysed to hydrazine hydrate. The yields are improved but there is no improvement with respect to the discharges to the environment.
The process with hydrogen peroxide consists in oxidizing a mixture of ammonia and a ketone with hydrogen peroxide in the presence of a means for activating the hydrogen peroxide in order to directly form the azine, which it is sufficient subsequently to hydrolyse to hydrazine hydrate. The yields are high and the process is not polluting. This process with hydrogen peroxide is used by the Applicant Company and is disclosed in numerous patents, for example U.S. Pat. No. 3,972,878, U.S. Pat. No. 3,972,876, U.S. Pat. No. 3,948,902 and U.S. Pat. No. 4,093,656.
The hydrolysis of an azine to hydrazine hydrate is disclosed in U.S. Pat. No. 4,724,133 (Schirmann et al.), U.S. Pat. No. 4,725,421 (Schirmann et al.) and GB 1,164,460. This hydrolysis is carried out in a distillation column which is fed with water and azine. The ketone is recovered at the top and the hydrazine hydrate at the bottom.
EP 70,155 also discloses another hydrogen peroxide process.
These processes are also described in Ullmann's Encyclopaedia of Industrial Chemistry (1989), vol. A 13, pages 182-183 and the references included.
In hydrogen peroxide processes, ammonia is oxidized with hydrogen peroxide in the presence of a ketone and of a means for activating the hydrogen peroxide according to the following overall reaction, an azine being formed:
The activation means can be a nitrile, an amide, a carboxylic acid or a selenium, antimony or arsenic derivative. The azine is then hydrolysed to hydrazine and the regenerated ketone is recycled according to the following reaction:
This hydrolysis is carried out in a distillation column. The ketone is recovered at the top and the hydrazine hydrate at the bottom.
The formation is observed, in all processes using MEK (methyl ethyl ketone) and hydrogen peroxide, of impurities derived from MEK and resulting from side reactions. In particular, the formation of 2-butanol is observed, which product originates from a reduction of methyl ethyl ketone by a hydrazine derivative, which can be according to a process of the diimine type
This formation of 2-butanol has already been disclosed in European Patent Application EP 758,642 A2 and it is indicated that the azine yield is sizeably reduced if the 2-butanol is allowed to accumulate and if its ratio with respect to the methyl ethyl ketone exceeds 0.05 mol per mole of MEK and that it was necessary to separate the 2-butanol by distillation and then to bleed it off.
The Applicant Company has discovered that it is possible to dehydrogenate 2-butanol to MEK and to reintroduce it into the process.
A first advantage is that there is a saving of MEK. Another advantage is that it is not necessary to bleed off a stream which is rich in 2-butanol or composed essentially of 2-butanol. Patent EP 758,642 discloses that the 2-butanol is bled off after it has been separated from the MEK and the water. In this prior art, it is necessary to obtain a stream which is fairly rich in 2-butanol in order to avoid also bleeding off MEK. To obtain a stream which is rich in 2-butanol, a separation operation, such as a distillation, is necessary. This concentrating of 2-butanol is no longer necessary in the present invention or does not need to be pushed as far as in the prior art. This is because the stream comprising the 2-butanol can comprise MEK; this mixture of MEK and of 2-butanol is converted, using a dehydrogenating catalyst, to a stream of MEK, which is recycled in the process.
According to a first form, the present invention is a process for the preparation of methyl ethyl ketone azine, in which:
(a) ammonia, hydrogen peroxide and methyl ethyl ketone are reacted in the presence of a working solution, in order to form an azine;
(b) the working solution and the azine, optionally comprising unreacted methyl ethyl ketone and 2-butanol, are separated;
(c) the working solution is recycled to the stage (a) after an optional treatment;
(d) the methyl ethyl ketone and the 2-butanol are separated from the azine;
(e) all or part of the stream from the stage (d) comprising methyl ethyl ketone and 2-butanol is treated in order to dehydrogenate all or part of the 2-butanol to methyl ethyl ketone and the whole (treated and untreated) is recycled to the stage (a).
In a preferred embodiment of this first form of the invention, the azine collected in the stage (d) is hydrolysed in a stage (f) in order to obtain hydrazine hydrate and the regenerated methyl ethyl ketone is recycled to the stage (a).
Use is made, in Application EP 758,642, of a means for activating hydrogen peroxide composed of a mixture of cacodylic acid (dimethylarsinic acid) and of ammonium acetate or of ammonium propionate. If the amount of 2-butanol is 0.05 mol per mole of MEK, the azine yield with respect to the hydrogen peroxide is 84%. If the amount of 2-butanol is 0.1 mol per mole of MEK, the azine yield with respect to the hydrogen peroxide falls to 60%. The Applicant Company has just discovered that this effect of the butanol is not general and is related to the nature of the system for activating the hydrogen peroxide.
Thus, the Applicant Company has just discovered that, in contrast to what is disclosed in Patent Application EP 758,642, the 2-butanol does not have an effect on the yield if the system for activating the hydrogen peroxide is composed of a mixture of a carboxylic acid amide and of the corresponding ammonium salt (for example, acetamide and ammonium acetate) in aqueous solution and if there is no derivative comprising arsenic. It is therefore necessary to distinguish activation systems for which the butanol has an effect on the azine yield, that is to say that the azine yield with respect to the hydrogen peroxide falls when the 2-butanol/MEK ratio increases or is greater than a certain threshold, and activation systems for which the butanol has no effect on the azine yield.
The Applicant Company has also discovered that, in processes using an activation system for which the butanol is without effect on the yield, it is useful to bleed off this butanol because, although it does not cause the reaction yield to fall as described above, it takes the place of the MEK and the production falls due to lack of reactant. The 2-butanol is therefore bled off so that its molar proportion with respect to the MEK is, for example, from 5 to 15 mol per 100 mol of MEK. This purification of the MEK is therefore easy because this content is not excessively low and is easy to achieve and fluctuations with regard to the level of 2-butanol in the MEK can be accepted without there being variations with regard to the yield of the reaction for the synthesis of azines.
According to a second form, the present invention is therefore a process for the preparation of methyl ethyl ketone azine, in which:
(a) ammonia, hydrogen peroxide and methyl ethyl ketone are reacted in the presence of a working solution, in order to form an azine;
(b) the working solution and the
Bourdauducq Paul
Schirmann Jean-Pierre
Atofina
Langel Wayne A.
Pennie & Edmonds LLP
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