Title of Invention

A PROCESS FOR THE PREPARATION OF METHVL ETHVL KETONE AZINE

Abstract

This invention relates to a process for the preparation of methyl ethyl ketone azine by reacting ammonia, hydrogen peroxide, and methyl ethyl ketone in the presence of a working solution consisting of a mixture of carboxylic acid amide and the corresponding ammonium salt. After separation of the azine produced the working solution is recycled. Part of methyl ethyl ketone and 2-butanol are separated from the azine and the separated 2-butanol is bled off from the stream to maintain a ratio of 2-butanol/methyl ethyl ketone of 0.05 and 0.15 at the inlet.

Full Text

The present invention relates to a process for the preparation of methyl ethyl ketone azine. 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 (CHj)2C=N-N=C-(CH3)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 5 the process is not polluting. This process with hydrogen peroxide is used by the Applicant Company and is disclosed in numerous patents, for example US 3,972,878, US 3,972,876, US 3,948,902 and US 4,093,656. 10 The hydrolysis of an azine to hydrazine hydrate is disclosed in Patents US 4,724,133 (Schirmann et al.), US 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, 15 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 20 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 25 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 This hydrolysis is carried out in a distillation column. The ketone is recovered at the top and the hydrazine hydrate at the bottom. 10 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 15 methyl ethyl ketone by a hydrazine derivative, [lacuna] This formation of 2-butanol has already been disclosed in European Patent Application EP 758,642 A2 20 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. Use is made, in Application EP 758,642, of a means for activating hydrogen peroxide composed of a mixture of cacodylic acid (dimethylarsenic 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 invented 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 invented 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 that 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 found 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 rnol 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 the present invention, there is therefore provided 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 wording solution comprising an activation system composed of a carboxylic acid amide and of the corresponding ammonium salt, 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 wording 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) part of the 2-butanol is bled off from the stream from the stage (d), so as to maintain the2-butano!/MEKmolarratiobetween0.05andO.I5at the inlet of the stage (a). In a preferred embodiment, 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). Stage fa) The hydrogen peroxide can be used in the usual commercial form, for example as an aqueous solution of between 30 and 90% by weight of H202. One or more conventional stabilizers for peroxide solutions can advantageously be added, for example phosphoric acid, pyrophosphonc 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 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 to 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-pentanedio 1. The reactants can be used in stoichiometric amounts. However, use is made, per mole of hydrogen peroxide, of 0.2 to 5 mol and preferably of 1.5 to 4 mol of methyl ethyl ketone and of 0.1 to 10 mol and preferably of 1.5 to 4 mol of ammonia. The amount of working solution is between 0.1 and 1 kg per mole of hydrogen peroxide. This amount depends on its quality, that is to say on its catalytic strength or its activity which makes it possible to convert the reactants to azine. The proportions of the reactants laid down above make it possible to obtain complete conversation of the hydrogen peroxide and a production of azine corresponding to more that 50%, and which can reach 90%, of the hydrogen peroxide charged. The hydrogen peroxide, ammonia and methyl ethyl ketone can be brought into contact with the working solution in any way. The reaction is advantageously carried out in a homogeneous medium or in a medium which provides at least sufficient solubilization of the reactants for it to be possible to obtain the azine. The reaction can be carried out in a very wide temperature range, for example between 0 and 100DC, and is advantageously carried out between 30 and 70°C. Although it is possible to carry out the reaction at any pressure, it is simpler to be at atmospheric pressure, however, the pressure can rise up to approximately 10 bar if this is necessary in order to preferably maintain the reaction of the stage a in the liquid phase. The reactants can be introduced simultaneously or separately and in any order into the working solution. It is possible to use all kinds of reactors, stirred or nonstirred, or even simple tanks, which can be arranged in parallel or in series, cocurrentwise or countercurrentwise, or any combination of these possibilities. Stage (b) Known means, such as liquid-liquid extraction, distillation, separation by settling or any combination of these possibilities, are used to separate (i) the azine, the excess methyl ethyl ketone and the 2-butanol from (ii) the working solution. Methyl ethyl ketone is advantageous because its azine is insoluble in the working solution. The working solution can be treated in the stage (c). The stages (a), (b) and (c) are disclosed, for example, in Patents EP 399866 and EP 518,728, the contents of which are incorporated in the present application. Stage (d) The methyl ethyl ketone and the 2-butanol are separated from the azine. The operation can be carried out by distillation at atmospheric pressure or under reduced pressure. The methyl ethyl ketone azine (also denoted by mekazine) is collected at the bottom of the distillation column. The stage (f) is carried out, for example, in a plate or packed column of distillation column type which is fed with the azine originating from the stage (b) and water. The following are obtained: (i) at the top, methyl ethyl ketone in the form of an azeotrope with water, and (ii) at the bottom, an aqueous hydrazine hydrate solution. The hydrolysis of azines is known. For example, E. C. Gilbert, in an article in the Journal of the American Chemical Society, vol. 51, pp. 3397-3409 (1929), describes equilibrium reactions for the formation of azine and the hydrolysis reactions of the — .i J —^-^—^^_^_«^^_^^_^—^_ latter and provides the thermodynamic parameters of the system in the case of water-soluble azines. For example, the hydrolysis of acetone azine is disclosed in US 4,724,133. As regards azines which are insoluble in aqueous solutions (for example, methyl ethyl ketone the hydrolysis has to be carried out in a reactive column, such that, by continuously separating the methyl ethyl ketone at the distillation column top and the hydrazine hydrate at the column bottom, complete hydrolysis can be achieved. Of course, this system works best when the operation is carried out continuously, as disclosed in French Patent 1,315,348, British Patent 1,211,547 or Patent US 4,725,421. In all these patents, the reaction is carried out in a packed distillation column or better still a plate distillation column operating under a pressure of 2 to 25 bar with a bottom temperature of 150°C to 20QDC. When the operation is carried out with pure azine, that is to say obtained from hydrazine hydrate and methyl ethyl ketone, for example, it is actually found, by operating according to these patents, that dilute hydrazine hydrate solutions are obtained with a good yield. In this column, the azine is hydrolysed and the hydrazine hydrate is separated from the methyl ethyl ketone. These conditions are known. A person skilled in the art easily determines the number of plates or the packing height, as well as the points for feeding with azine and with water. Solutions comprising 30 or even up to 45% by weight of hydrazine hydrate are obtained at the bottom. This molar ratio of water to azine in feeding this column is at least greater than stoichiometry and advantageously between 5 and 8. The column bottom is between 150°C and 200°C, preferably 175 to 190°C. The pressure depends on the boiling temperature of the azine, water and the reactant carrying a carbonyl group. Such a hydrolysis is disclosed in US 4,725,721. Bleeding off 2-butanol from the stage (e) serves to prevent its accumulation. Since this 2-butanol is not dehydrogenated in order to recycle it in the stage (a), it is preferable to bleed off a stream of 2-butanol which is as pure as possible in order to avoid losing other products, in particular MEK. Example 1 (not in accordance with the invention) 240 g of water (13.3 mol), 118 g of ammonium propionate {1.3 mol), as well as 40 g of cacodylic acid (0.29 mol) and 2 cm3 of Dequest 2066 stabilizer (sodium salt of diethylenediaminepenta(methylenephosphonic acid) as a 25% aqueous solution), sold by the Company Monsanto, are charged to a reactor. This mixture is brought to 55 °C and then gaseous ammonia is introduced until saturation is reached. 38.9 g of 70% hydrogen peroxide (0.8 mol) are then added over one hour, as well as 144 g of methyl ethyl ketone comprising 2 mol % of 2-butanol (2 mol). The mixture is kept stirred for a further two hours at 55DC while continuing to introduce gaseous ammonia. It is then allowed to cool. The organic and aqueous phases are separated and are analysed. It is found that the conversion of the hydrogen peroxide is 65.4% and that the azine yield is 45.8%. Example 2 (not in accordance with the invention) Example 1 is repeated but the ammonium propionate is replaced with 100 g of ammonium acetate (1.3 mol) and the reaction is allowed to last for 7 hours at 55°C. The conversion of the hydrogen peroxide is 79.3% and the methyl ethyl ketone azine yield is 54%. Example 3 (not in accordance with the invention) Example 2 is repeated using methyl ethyl ketone comprising 10 mol % of 2-butanol. The conversion of the hydrogen peroxide is 79.5%, whereas the azine yield falls to 39.8%. Example 4 (in accordance with the invention) 180 g of water (10 mol), 77 g of ammonium acetate (1 mol), 177 g of acetamide (3 mol), 144 g of methyl ethyl ketone (2 mol) and 2 cm3 of Dequest 2066 stabilizer (sodium salt of diethylenediaminepenta-(methylenephosphonic acid) as a 25% aqueous solution), sold by the Company Monsanto, are charged to a reactor. This mixture is brought to 50°C and is then saturated with ammonia. 48.5 g of 70% hydrogen peroxide (1 mol) are then added over a period of 1 hour. Introduction of gaseous ammonia is continued, so as to keep the medium saturated. Reaction is allowed to take place for 7 hours at 50°C. After cooling to ambient temperature, the aqueous and organic phases are separated. Analysis is carried out and it is found that the H^02 conversion is 98% for an azine yield of 81%. Example 5 (in accordance with the invention) Example 4 is repeated but using methyl ethyl ketone comprising 10 mol % of 2-butanol. The conversion of the hydrogen peroxide is 99% and the azine yield is 81.9%. WE CLAIM: 1. 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, comprising an activation an activation system composed of a mixture of a carboxylic acid amide and of the corresponding ammonium salt in order to form an azine; b) the working solution and the azine containing unreacted methyl ethyl ketone and 2-butanol are separated; c) the working solution is recycled to the stage (a); d) the methyl ethyl ketone and the 2-butanol are separated from the azine; e) part of the 2-butanol is bled off from the stream from the stage (d), so as to maintain the 2-butanol/methylethyIketone molar ratio between 0.05 and 0.15 at the inlet of the stage (a). 2. The process as claimed in claim 1, in which, in stage (b), the working solution and the azine comprising unreacted methyl ethyl ketone and 2-butanol are separated. 3. The process as claimed in claim 1 or 2, in which, in stage (c), the working solution is treated prior to being recycled. 4. The process as claimed in any one of claims 1 to 3, in which the azine collected in the stage (d) is hydrolyzed in a stage (f) in order to obtain hydrazine hydrate and the regenerated methyl ethyl ketone is recycled to the stage (a).

Documents:

in-pct-2001-0246-che abstract-duplicate.pdf

in-pct-2001-0246-che abstract.pdf

in-pct-2001-0246-che claims-duplicate.pdf

in-pct-2001-0246-che claims.pdf

in-pct-2001-0246-che correspondence-others.pdf

in-pct-2001-0246-che correspondence-po.pdf

in-pct-2001-0246-che description (complete)-duplicate.pdf

in-pct-2001-0246-che description (complete).pdf

in-pct-2001-0246-che form-1.pdf

in-pct-2001-0246-che form-19.pdf

in-pct-2001-0246-che form-26.pdf

in-pct-2001-0246-che form-3.pdf

in-pct-2001-0246-che form-4.pdf

in-pct-2001-0246-che form-5.pdf

in-pct-2001-0246-che others.pdf

in-pct-2001-0246-che pct.pdf

in-pct-2001-0246-che petition.pdf