Chemistry of inorganic compounds – Nitrogen or compound thereof – Binary compound
Reexamination Certificate
2000-10-31
2002-11-19
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Nitrogen or compound thereof
Binary compound
C423S387000
Reexamination Certificate
active
06482383
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 Patents 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 Encylopedia 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 Applicant Company has discovered that, in these hydrogen peroxide processes and using methyl ethyl ketone (MEK), small amounts of a by-product, MEK oxime
were formed and that the presence of this oxime disrupted the operation of the process. In particular, the oxime is difficult to separate from the azine, it is found in the column for hydrolysis of the azine and it leads to decomposition of the hydrazine hydrate. The process of the invention consists in bleeding off this oxime.
The present invention is therefore a process for the preparation of hydrazine hydrate, 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 is separated from. the azine comprising methyl ethyl ketone oxime and optionally methyl ethyl ketone;
(c) the working solution is recycled to the stage (a) after an optional treatment;
(d) the azine is hydrolysed in order to obtain hydrazine hydrate and the methyl ethyl ketone is regenerated;
(e) the methyl ethyl ketone is recycled to the stage (a), this process being characterized in that, in the stage (d), methyl ethyl ketone oxime is bled off.
Stage (a)
The hydrogen peroxide can be used in the usual commercial form, for example as an aqueous solution comprising between 30 and 90% by weight of H
2
O
2
. One or more conventional stabilizers for peroxide solutions can advantageously be added, for example phosphoric acid, pyrophosphoric acid, citric acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid or the ammonium or alkali metal salts of these acids. The amount to be used is advantageously between 10 and 1000 ppm and preferably between 50 and 250 ppm of the combined reactants and working solution at the reactor inlet. The ammonia can be anhydrous or in aqueous solution
The working solution comprises a means for activating the hydrogen peroxide, that is to say a product such that the azine can be produced from ammonia, hydrogen peroxide and methyl ethyl ketone.
This activator can be chosen from organic or inorganic oxyacids, their ammonium salts and generally their derivatives: anhydrides, esters, amides, nitriles, acyl peroxides, or their mixtures. Use is advantageously made of amides, ammonium salts and nitrites.
Mention may be made, by way of examples, of (i) amides of carboxylic acids of formula R
5
OOH, in which R
5
is hydrogen, a linear alkyl radical having from 1 to 20 carbon atoms, a branched or cyclic alkyl radical having from 3 to 12 carbon atoms or a phenyl radical which can be substituted, or (ii) amides of polycarboxylic acids of formula R
6
(COOH)
n
, in which R
6
represents an alkylene radical having from 1 to 10 carbon atoms and n is an integer greater than or equal to 2, or R
6
can be a single bond and then n has the value 2. The R
5
and R
6
radicals can be substituted by halogens or OH, NO
2
or methoxy groups. Mention may also be made of the amides of the organic acids of arsenic. The organic acids of arsenic are, for example, methylarsonic acid, phenylarsonic acid and cacodylic acid.
The preferred amides are formamide, acetamide, monochloroacetamide and propionamide.
Use is advantageously made, among ammonium salts, of the salts of hydracids, of inorganic oxyacids, of arylsulphonic acids, of R
5
COOH acids or of R
6
(COOH)
n
acids, R
5
, R
6
and n being defined above, or of the organic acids of arsenic.
The preferred ammonium salts are the formate, acetate, monochloroacetate, propionate, phenylarsonate and cacodylate. Mention may advantageously be made, among the nitriles, of the products of formula R
7
(CN)
n
, it being possible for n to vary from 1 to 5, depending on the valency of R
7
, and R
7
being a cyclic or non-cyclic alkyl having from 1 to 12 carbon atoms or benzene or pyridine. R
7
can be substituted by groups which are not oxidized in the reactor of the stage a, for example halogens or carboxyl, carboxylic ester, nitro, amine, hydroxyl or sulphonic acid groups.
The preferred nitriles are acetonitrile and propionitrile.
The working solution is formed by dissolving one or more products chosen from organic or inorganic oxyacids, their ammonium salts and generally their derivatives: anhydrides, esters, amides, nitriles, acyl peroxides, or their mixtures. Use is advantageously made of the preceding amides, ammonium salts or nitriles.
This solution can be aqueous or based on an alcohol or on a mixture of alcohol and water. Use is advantageously made, among the alcohols, of saturated aliphatic alcohols having from 1 to 6 carbon atoms and preferably 1 or 2 carbon atoms.
Use is also advantageously made of diols and more particularly of diols having from 2 to 5 carbon atoms. Mention may be made, for example, of glycol, propylene glycol, 1,3-propanediol, 1,3- and 1,4-butane-diol and 1,5-pentanediol.
According to an advantageous form of the invention, the working solution is an alcoholic solution of an organic acid of arsenic and is disclosed in Patent EP 70,155, the contents of which are incorporated in the present application. According to another advantageous form of the invention, the working solution is an aqueous solution of an amide of a weak acid and of the ammonium salt corresponding to th
Atofina
Johnson Edward M.
Pennie & Edmonds LLP
Silverman Stanley S.
LandOfFree
Method for preparing hydrazine hydrate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for preparing hydrazine hydrate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for preparing hydrazine hydrate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2977758