EP0000532A1 - Process for the preparation of vinyl oxirane - Google Patents

Abstract

1. Process for the preparation of vinyloxirane from hydrogen peroxide and butadiene, characterised in that a) an aqueous solution containing 10 to 45% by weight of a watersoluble, acid catalyst and 20 to 50% by weight of hydrogen peroxide is reacted with a carboxylic acid containing 2 to 5 carbon atoms in a molar ratio of hydrogen peroxide to carboxylic acid of 0.5-30:1 at temperatures of 10 to 70 degrees C, b) the resulting reaction mixture is extracted with an inert, organic solvent, in counter-current, c) all or some of the aqueous raffinate from the extraction, which essentially contains hydrogen peroxide and acid catalyst, is concentrated by removing the water by distillation, d) the concentrated raffinate, and the portion of the raffinate which is optionally not concentrated, are recycled into the reaction stage (a), the concentrations of hydrogen peroxide and water - soluble acid catalyst required for the reaction with the carboxylic acid being re-established, and the hydrogen peroxide necessary for re-establishing the hydrogen peroxide concentration required for the reaction with the carboxylic acid being added, before or after the removal of water by distillation according to (c), to the portion of the raffinate to be concentrated or to the portion of the raffinate which is optionally not concentrated, e) the organic extract, which essentially contains percarboxylic acid and carboxylic acid, is treated with water or an aqueous solution, f) the water-containing organic extract, which is now virtually free from hydrogen peroxide, is subjected to azeotropic distillation in a manner such that the residual content of water in the bottom product of the azeotropic column is less than 0.5% by weight, g) the organic solution now obtained, which contains percarboxylic acid and carboxylic acid, is reacted with butadiene in excess at a molar ratio of butadiene to percarboxylic acid of 1.5 to 6:1 at temperatures of 0 degrees C to 80 degrees C and under a pressure of 0.8 to 20 bars, and h) the vinyloxirane-containing reaction mixture is worked up by a distillative route, pure vinyloxirane being isolated and the excess butadiene, the carboxylic acid and the inert organic solvent being recovered and wholly or partly recycled into the process.

Description

The present invention relates to an improved process for the continuous production of vinyl oxirane.

Vinyloxirane, the monoepoxide of butadiene, is an important technical intermediate product which, due to its bifunctional character, is widely used in the field of polymers (FC Frostick, B. Phillips and PS Starcher, Journal of Am. Chem. Society, Vol 81, p 3351 (1959)). Vinyloxirane belongs to the class of compounds of epoxy vinyl monomers, which are distinguished by the fact that they can be converted into polyethers by reaction of the epoxy ring. These polyethers then contain free vinyl groups suitable for crosslinking or copolymerization with other olefinic compounds. However, it is also possible to polymerize vinyloxirane first on the olefinic double bond of the molecule, so that polymers are then obtained which have epoxide groups which can be used for the further reaction in the hydrocarbon chain.

In accordance with the potential technical importance of vinyloxirane, there has been no lack of attempts in the past to find simple and economical processes for producing vinyloxirane. So far, however, this has not been possible. The difficulties in the production of vinyloxirane consist on the one hand in the reaction of the reaction of butadiene with the epoxidation reagent, and on the other hand in the separation of the reaction mixtures obtained during the reaction and containing vinyloxirane.

Pummerer and Reindel (Chem .berichte 66, 335-339 (1933)) already proposed the use of perbenzoic acid in 1933 for the production of vinyl oxirane from butadiene. However, the yields achieved were only 40-60%.

The production of vinyloxirane using an ethereal solution of this percarboxylic acid containing 3% peracetic acid is also unsatisfactory since the yield is only 50% (Pudovik, Ivanow, Journal of Gen. Chem. Of USSR Vol 26, 3087 (1956) in Engl . translation).

F.C. Frostick et.al., (Journal of Am.Chem.Soc. 81, 3354 (1959)) cannot be achieved. When butadiene was reacted with peracetic acid obtained by oxidation of acetaldehyde in organic solvents, the yield was only 56%.

Peracetic acid obtained by oxidation of acetaldehyde is also described in Japanese Patent No. J 7-4046-284 as a suitable reagent for the production of vinyl oxirane. However, no yields are given.

Processes for the production of vinyloxirane, which use peracetic acid prepared from acetaldehyde for the epoxidation of butadiene, have the fundamental disadvantage that they require acetaldehyde as an auxiliary and that this auxiliary does not leave the process unchanged, so that recycling into the process is practically impossible. In addition, such processes are complex to carry out industrially, since an additional oxidation stage is required. In addition, the oxidation of acetaldehyde or other aldehydes to peracetic acid or percarboxylic acids is a reaction which is difficult to carry out, the safety risks of which are not insignificant in industrial use due to the highly explosive aldehyde peracrylates which occur as intermediates (D.Swern, "Organic Peroxides", Vol 1, pp. 353, 354; wiley-Interscience (1971)).

British Patent 735,974 (Union Carbide Corp.) proposes using acetaldehyde or propionaldehyde monoperacylate for the epoxidation of butadiene to vinyloxirane, likewise obtained by oxidation of the corresponding aldehydes.

The conversion of acetaldehyde monoperacetate in the reaction with butadiene is only 33%. The subsequent distillative processing of such a reaction mixture to obtain vinyloxirane takes place in the presence of the per compound, which precludes industrial use because of the existing risk of explosion.

The application of special procedural measures, such as those proposed in German patent specification 1 216 306 for carrying out epoxidations, is also an advantage of butadiene does not have the desired success, as can be seen from Example 3 of this patent, where the epoxidation of butadiene by this process with peracetic acid only gives a 68% selectivity for vinyloxirane.

In US Patent 3,053,856 the reaction of acetonitrile and hydrogen peroxide is described, in the presence of butadiene _', where according to Example XII arises this patent vinyloxirane as the main product. However, since in this process d .. = carboxylic acid amide corresponding to the nitrile used in each case is obtained, which is to be regarded as a co-product and either has to be put to a suitable use or has to be converted back into the nitrile by dehydration, a technically satisfactory solution to the problem of vinyloxirane production not given.

umgewandelt. Das Kohlenwasserstoffperoxid R-OOH wirkt also als Sauerstoffüberträger, so daß nach Abgabe des Peroxid-Sauerstoffs der entsprechende Alkohol als Koppe-produkt anfällt und häufig als unerwünschtes Nebenprodukt entfernt werden muß. Die technischen Einsatzmöglichkeiten eines solchen Verfahrens sind dementsprechend begrenzt, da nicht in jedem Falle das Nebenprodukt Alkohol verwertet werden kann.The use of alkyl hydroperoxides, such as cumene and tert-butyl hydroperoxide, for the epoxidation of dienes under the cat.lytic influence of molybdenum or vanadium compounds has been described by Sheng and Zajacek (Journal of Organic Chemistry Vol 35, 6, 1839- 1843 (1970)). Butadiene can be converted into vinyl oxirane using this process with 85% selectivity. The alkyl hydroperoxide R-OOH is in this reaction, as can be seen from equation (1), in the corresponding alcohol R-OH

transformed. The hydrocarbon peroxide R-OOH thus acts as an oxygen carrier, so that after the peroxide oxygen has been released, the corresponding alcohol is obtained as a coproduct and often has to be removed as an undesirable by-product. The technical application possibilities of such a process are accordingly limited, since the by-product alcohol cannot be used in every case.

In another process, which is described in Belgian Patent 747,316, the reaction for the production of vinyloxirane from butadiene and hydrogen peroxide is carried out in the presence of a catalyst system containing tin. In addition to the disadvantage that a solvent, such as n-propanol, is required to carry out the reaction, which in turn can react with vinyloxirane that has already formed, high losses in product are to be expected, which are due to the fact that the product used Hydrogen peroxide after the reaction with the butadiene-forming water reacts with vinyloxirane with cleavage of the epoxy ring. Furthermore, the separation of the catalyst from the reaction mixture is not an easy task to solve on an industrial scale.

Just as numerous as the proposals that have been made to achieve improvements in the performance of the reaction in the epoxidation of butadiene to vinyloxirane have been the efforts made to overcome the problems encountered in the technical implementation of the separation of vinyloxirane-containing mixtures . These problems when working up mixtures containing vinyloxirane are essentially due to the fact that the epoxy ring in the molecule of vinyloxirane very easily undergoes side reactions, which leads to sometimes considerable losses of vinyloxirane, and that the economic viability of a technical process for the production of vinyloxirane is no longer given. There is a particular risk of product loss if the mixtures from which vinyloxirane is to be separated contain acidic components.

This is always the case if vinyloxirane is prepared from butadiene and a percarboxylic acid, since then the carboxylic acid corresponding to the percarboxylic acid is inevitably contained in the reaction mixture.

In British patent specification 852 097 it is proposed for such a reaction mixture for the separation of vinyloxirane and the carboxylic acid to remove the carboxylic acid, for example acetic acid, by firstly dissolving a solution of vinyloxirane and the carboxylic acid in an organic, water-insoluble solvent, such as chlorinated hydrocarbons, and then extracting the solution with water or an aqueous solution of an inert alkali metal salt at temperatures below 15 ° C. This extraction process is complex since it not only requires an additional solvent, but also requires a subsequent separation of the water from the carboxylic acid if the carboxylic acid is to be recovered. Obtaining carboxylic acids from aqueous solutions by distillation is a task that can only be accomplished with considerable effort because of the formation of azeotropic mixtures.

The scope of for such extraction process for obtaining vinyl oxirane _- technically necessary action is See U.S. Patent 3,019,234. The solution containing vinyloxirane and the carboxylic acid resulting from the largely insoluble solvent must be extracted below 25 ° C with water or an aqueous solution. The extraction effort is considerable. Example 1 of the above-mentioned patent shows that 10 theoretical extraction stages are required. In addition, work must be carried out at 0 ° C. The problem solution for the lossless separation of vinyloxirane and carboxylic acid given by this process for obtaining vinyloxirane is not satisfactory, since there are not insignificant amounts of vinyloxirane in the aqueous phase after extraction.

In French patent specification 1 468 814 it is proposed that the free carboxylic acid obtained in this case after the epoxidation of butanediene - in this case acetic acid - contains reaction mixture which also contains an acetic acid ester as solvent, vinyl oxirane and butadiene, with strong bases such as alkali or alkaline earth metal hydroxides to neutralize free carboxylic acid, which is thus prevented from reacting with vinyl oxirane. After the neutralization step, the aqueous acetate-containing phase is separated off. In any case, the process according to the above patent provides a saline wastewater, even if the acetate-containing aqueous solution obtained after neutralization of the acetic acid would be worked up after the addition of a strong acid in order to recover the free acetic acid.

It can thus be seen from the literature on processes for the preparation of vinyloxirane which has become known that all of these processes only disclose approaches for an economical, technical production of vinyloxirane, but in no case can offer a satisfactory solution to the problems posed by technical requirements and the question of economy.

• a) eine 10 bis 45 Gew.-% eines wasserlöslichen , sauren Katalysators und 20 bis 50 Gew.-% Wasserstoffperoxid enthaltende wäßrige Lösung mit einer 2 bis 5 Kohlenstoffatomen enthaltenden Carbonsäure im Molverhältnis Wasserstoffperoxid zu Carbonsäure wie 0,5 --30 :1 bei Temperaturen von 10 bis 70°C umsetzt,
• b) das erhaltene Reaktionsgemisch mit einem inerten, organischen Lösungsmittel im Gegenstrom extrahiert,
• c) das im wesentlichen Wasserstoffperoxid und sauren Katalysator enthaltende wäßrige Raffinat der Extraktion ganz oder teilweise durch destillative Entfernung von Wasser aufkonzentriert,
• d) das aufkonzentrierte Raffinat, sowie den gegebenenfalls nicht auf konzentrierten Anteil des Raffinats, unter Wiederherstellung der für die Umsetzung mit der Carbonsäure erforderlichen Konzentrationen an Wasserstoffperoxid und wasserlöslichem sauren Katalysator in die Umsetzungsstufe (a) zurückführt, wobei das zur Wiederherstellung der für die Umsetzung mit der Carbonsäure erforderlichen Wasserstoffperoxidkonzentration benötigte Wasserstoffperoxid dem aufzukonzentrierenden Anteil des Raffinats vor oder nach der destillativen Entfernung von Wasser gemäß (c) zugesetzt wird oder zu dem gegebenenfalls nicht aufkonzentrierten Teil des Raffinats zugegeben wird,
• e) den im wesentlichen Percarbonsäure und Carbonsäure enthaltenden organischen Extrakt mit Wasser oder einer wäßriqen Lösung behandelt und
• f) den nunmehr praktisch wasserstoffperoxidfreien, wasserhaltigen, organischen Extrakt einer Azeotropdestillation derart unterwirft, daß der Restgehalt an Wasser im Sumpfprodukt der Azeotropkolonne weniger als 0,5 Gew.-% beträgt,
• g) die nunmehr gewonnene, Percarbonsäure und Carbonsäure enthaitence, organische Lösung mit Butadien im Überschuß bei einem Molverhältnis von Butadien zu Percarbonsäure von 1,5 bis 6 : 1 bei Temperaturen von 0°C bis 80°C und bei einem Druck von 0,8 bis 20 bar umsetzt, und
• h) das vinyloxiranhaltige Reaktionsgemisch auf destillativem Wege aufarbeitet, wobei reines Vinyloxiran isoliert wird und das überschüssige Butadien, die Carbonsäure und das inerte organische Lösungsmittel wiedergewonnen und ganz oder teilweise in das Verfahren zurückgeführt werden.

In contrast, it has now surprisingly been found that vinyloxirane can be prepared from hydrogen peroxide and butadiene in a technically simple and economically advantageous manner if one

• a) an aqueous solution containing 10 to 45% by weight of a water-soluble acidic catalyst and 20 to 50% by weight of hydrogen peroxide with a carboxylic acid containing 2 to 5 carbon atoms in a molar ratio of hydrogen peroxide to carboxylic acid such as 0.5-30: 1 Converts temperatures from 10 to 70 ° C,
• b) the reaction mixture obtained is extracted with an inert, organic solvent in countercurrent,
• c) the aqueous raffinate of the extraction, which essentially contains hydrogen peroxide and acid catalyst, is wholly or partly concentrated by removing water by distillation,
• d) the concentrated raffinate, as well as the possibly not concentrated portion of the raffinate, restoring the concentrations of hydrogen peroxide and water-soluble acidic catalyst required for the reaction with the carboxylic acid in reaction stage (a), the restoration of the reaction with the hydrogen peroxide concentration required of the carboxylic acid required the hydrogen concentration of the raffinate to be concentrated before or after the distillative removal of water according to (c) is added or to the possibly not concentrated part of the raffinate is added,
• e) the organic extract containing essentially percarboxylic acid and carboxylic acid is treated with water or an aqueous solution and
• f) subjecting the now practically hydrogen peroxide-free, water-containing organic extract to an azeotropic distillation in such a way that the residual water content in the bottom product of the azeotropic column is less than 0.5% by weight,
• g) the now obtained, percarboxylic acid and carboxylic acid enthaitence, organic solution with butadiene in excess at a molar ratio of butadiene to percarboxylic acid from 1.5 to 6: 1 at temperatures from 0 ° C to 80 ° C and at a pressure of 0.8 up to 20 bar, and
• h) the vinyl oxirane-containing reaction mixture is worked up by distillation, pure vinyl oxirane being isolated and the excess butadiene, the carboxylic acid and the inert organic solvent being recovered and being wholly or partly recycled into the process.

Percarboxylic acids suitable for the process according to the invention are those which are derived from aliphatic carboxylic acids having 2 to 5 carbon atoms, such as acetic acid, propionic acid, n-butyric acid, isobutyric acid and valeric acid or trimethylacetic acid and dimethylpropionic acid. Peracetic acid, perpropionic acid and perisobutyric acid are particularly suitable. Perpropionic acid is particularly suitable.

In the reaction according to (a) between hydrogen peroxide and the carboxylic acid in the presence of an acidic catalyst, an equilibrium is formed between the carboxylic acid and the percarboxylic acid, which can be represented according to the following equation:

The carboxylic acid settles depending on the concentration of acid catalyst, e.g. Sulfuric acid, and hydrogen peroxide depending on the molar ratio of hydrogen peroxide to carboxylic acid to about 30 to 70% to percarboxylic acid.

In general, in addition to the 10 to 45% by weight of water-soluble, acidic catalyst, for example sulfuric acid or methanesulfonic acid, and 20 to 50% by weight of aqueous solution containing hydrogen peroxide, the carboxylic acid is used in pure, undiluted form. However, it is also possible to use a carboxylic acid containing water, a hydrogen peroxide-containing or an acidic catalyst, in which case the concentration of the aqueous solution must be changed accordingly in order to maintain the ratio of hydrogen peroxide, acidic catalyst, carboxylic acid and water required for the reaction. For example, instead of pure carboxylic acid, it is also possible to use a mixture of carboxylic acid and hydrogen peroxide, for example a carboxylic acid containing 20% by weight of hydrogen peroxide. Of course, the content of hydrogen peroxide in the must then according to the content of hydrogen peroxide in the carboxylic acid aqueous, acidic catalyst and hydrogen peroxide-containing feed solution are adjusted so that they result from the hydrogen peroxide contained in the carboxylic acid and that of the aqueous solution in a total use of hydrogen peroxide which corresponds to a content of 20 to 50% by weight of hydrogen peroxide in the aqueous solution. For example, in such a case where the carboxylic acid to be converted to percarboxylic acid already contains hydrogen peroxide, the hydrogen peroxide content in the aqueous solution itself may be less than 20% by weight, for example 12 to 19% by weight. All conceivable mixing ratios can be used within the specified concentration ratios of catalyst and hydrogen peroxide.

An aqueous solution comprising 20 to 43, particularly preferably 23 to 38% by weight of acid catalyst and 22 to 35% by weight of hydrogen peroxide is preferably reacted.

Sulfuric acid is advantageously used as the water-soluble acid catalyst. Other water-soluble acids can also be used, for example sulfonic acids such as methane, ethane, propane, butane, isobutanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, trifluoromethane, 1-fluoroethane, perfluoroethane, perfluoropropane or perfluorobutanesulfonic acid; Phosphoric acid, phosphonic acids, such as methane or ethanephosphonic acid, phosphinic acids, or acidic salts, such as sodium hydrogen sulfate or potassium hydrogen sulfate. Mixtures of water-soluble acids can also be used. Commercial hydrogen peroxide, for example 30 to 90% by weight H ₂ O _{2, is} used as the hydrogen peroxide to prepare the aqueous solution. Of course, hydrogen peroxide, which is obtained as a by-product of other chemical processes or as a recycle stream, is also suitable.

The reaction temperature is generally about 10 to 70 ° C. It is advisable to work at 20-60 ° C. Temperatures below 43 ° C, e.g. Temperatures from 25 - 43 ° C.

In general, the reaction is carried out until equilibrium is established between the carboxylic acid and the percarboxylic acid. However, it is also possible to terminate the reaction before equilibrium is reached and to obtain the reaction mixture thus obtained for the next process step, i.e. extraction with the inert organic solvent.

The pressure is not important for the reaction of the carboxylic acid with hydrogen peroxide, so that it is possible to work at normal pressure, elevated pressures or even at reduced pressure. In general, it is expedient to implement at pressures below 1.1 bar, e.g. at pressures of 0.8 - 1.1 bar.

The reaction can be carried out in a wide variety of reaction vessels. It is advisable to ensure a steady-state concentration profile and in particular to avoid so-called dead zones, in which parts of the reaction mixture remain for a disproportionately long time. Suitable are, for example, the usual reaction tubes of different diameters and lengths, which are also used as a closed circuit, e.g. can be arranged as loop reactors, and agitator kettle.

The reaction mixture from reaction stage (a) is now fed to countercurrent extraction with the inert organic solvent according to (b). This countercurrent extraction can be carried out in one or more extraction units.

Suitable solvents for the percarboxylic acids are all water-immiscible organic solvents which are inert to the reaction mixture of reaction (a). For example, aromatic hydrocarbons containing 6 to 10 carbon atoms, aliphatic or cycloaliphatic hydrocarbons each containing up to 12 carbon atoms, chlorinated hydrocarbons containing 1 to 10 carbon atoms and 1 to 4 chlorine atoms, and esters of 1 to 5 C atoms have been found to be suitable containing carboxylic acids with straight-chain or branched alcohols in which there are 1 to 8 carbon atoms in the molecule, and ethers which contain 2 to 10 carbon atoms. Examples of suitable solvents are: benzene, toluene, xylene, n-pentane, isooctane, cyclohexane, methylene chloride, chloroform, 1,2-dichloroethane, 1,2-dichloropropane, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate , Isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, as well as chlorobenzene and ether. However, it is also possible to use mixtures of the solvents mentioned as solvents for the percarboxylic acid, in which case the components of the mixture are then advantageously chosen so that they have a similar boiling point. Chlorinated hydrocarbons, such as methylene chloride, dichloroethane or dichloropropane, aromatic hydrocarbons, such as benzene, or ether, such as diisopropyl ether, or mixtures of these solvents are preferably used. Benzene is very particularly preferably used as the solvent for the process according to the invention.

The quantitative ratio of organic solvent to the reaction mixture containing the percarboxylic acid to be extracted is generally 10 to 0.1: 1. Larger amounts of inert, organic solvent can also be used. The most favorable range in each case of the ratio of the reaction mixture obtained according to (a) to the organic solvent to be used for the extraction according to (t) depends on the particular percarboxylic acid chosen and the extraction properties of the organic solvent and can easily be determined by a person skilled in the art. For the perpropionic acid / benzene system, for example, it is advantageous to choose a quantitative ratio of the reaction mixture to be extracted, which was obtained in step (a), to benzene, of from 4 to 0.3: 1. If the extraction according to (b) is carried out in several extraction units, the amount of the organic solvent can vary from unit to unit within the specified limits.

The content of percarboxylic acid in the extract can be varied within wide limits by the amount of extractant and by the number of extraction stages. In general, the procedure is such that an approximately 3 to 40% by weight percarboxylic acid is obtained in the organic solvent. An organic extract containing 5-30% by weight of percarboxylic acid is preferably obtained. Accordingly, the number of extraction stages should be as high as possible. In general, however, an extraction unit with 3 to 10 theoretical extraction stages is sufficient to prepare the solutions with the desired concentration of percarboxylic acids. Of course. it is desirable to obtain the raffinate of extraction stage (b) as free as possible from percarboxylic acid and carboxylic acid. In general, however, it is sufficient if no more than 0.5% by weight of carboxylic acid and percarboxylic acid remain in the raffinate.

For the process according to the invention, a percarboxylic acid is used whose corresponding carboxylic acid has a higher boiling point than the vinyloxirane and an organic solvent which has a boiling point which is either higher than the boiling point of the carboxylic acid corresponding to the percarboxylic acid or between the boiling point of vinyloxirane and that Carboxylic acid is. However, it is also possible to choose the solvent so that its boiling point is below the boiling point of vinyloxirane. Of the compounds already listed, the inert organic solvent for the percarboxylic acid is preferably a solvent which boils at normal pressure at least 5 ° C. above the boiling point of vinyloxirane and at least 20 ° _C. below the boiling point of the perearbonic acid corresponding carboxylic acid. In addition, the percarboxylic acid or the corresponding carboxylic acid and the solvent for the process according to the invention are advantageously selected such that no pronounced azeotropes of binary or ternary nature occur within the combination of carboxylic acid / solvent / vinyloxirane.

The temperature during the extraction can be varied within wide limits. In general, temperatures from 10 to 70 ° C. It is expedient to choose the same temperature as in the production of the percarboxylic acid according to (a), so that the other temperatures mentioned for the reaction step (a) are also suitable for the extraction (b). As far as pressure is concerned, you can work at normal pressure, reduced pressure or even at elevated pressures.

The known extraction systems, which enable a multi-stage countercurrent extraction, come into consideration as extraction units. Mixer-separators, sieve plate extractors, pulsed sieve plate columns or spray columns are suitable. However, one-stage or multi-stage centrifugal extractors can also be used.

In addition to the percarboxylic acid and the carboxylic acid, the organic extract also contains small amounts of free hydrogen peroxide, water and traces of the acid used as catalyst, e.g. Sulfuric acid. The raffinate essentially contains the unreacted hydrogen peroxide and the acid catalyst.

The raffinate of the extraction, which essentially contains water, hydrogen peroxide and, for example, sulfuric acid as the acid catalyst, is then again processed in process step (c) for the reaction of the carboxylic acid and hydrogen peroxide by concentrating it wholly or partly by removing water in a distillation. The amount of water to be distilled off from the raffinate stream supplied to this concentration essentially corresponds to both the amount of water which is formed in the reaction of hydrogen peroxide with the carboxylic acid according to (a) and the amount of water which is used with the fresh hydrogen peroxide which is used to supplement the consumed Amounts are required in the process. The top product of the distillation is water, which can contain small amounts of hydrogen peroxide, percarboxylic acid and carboxylic acid. In general, the distillation is carried out under reduced pressure, for example at bridges of 10 to 250 torr, preferably 40 to 150 torr, and at temperatures in the bottom from 40 to 120 ° C., preferably from 60 to 85 ° C. In general, the entire raffinate stream leaving the extraction is also suitable for the concentration if the extraction is carried out in a single extraction unit. However, it is also possible to extract the reaction mixture obtained in (a) in, for example, two extraction units feed both the raffinate from the first and the raffinate from the second extraction stage to the concentration. If the raffinate of the first unit is divided into a larger and a smaller partial stream in an extraction that takes place in two extraction units, each of these portions is in principle suitable for the concentration. In the case of an extraction consisting of two extraction units, in which the raffinate leaving the first unit is divided into a small and a larger partial stream and the smaller portion is introduced into the second unit, the raffinate from the second extraction unit is advantageously subjected to the distillation for concentration.

The fresh hydrogen peroxide to supplement the consumed amounts can be added in any concentration. Commercially available, e.g. 30 to 90% by weight aqueous hydrogen peroxide, which can be mixed with the usual stabilizers. For example, stabilizers come into consideration, such as those listed in Gmelins "Handbuch der inorganic chemie", 8th edition, oxygen volume, delivery 7, 1966, on page 2274 and page 2275.

The fresh hydrogen peroxide can be mixed with the raffinate to be concentrated from the extraction according to process step (b) before entering the distillation unit; the two streams can also be fed separately into the distillation unit. It is also possible to add the fresh hydrogen peroxide to the raffinate after concentration. A portion of the fresh hydrogen peroxide can also be mixed into the raffinate before concentration and the remaining amount of the fresh hydrogen peroxide can be added to the raffinate after concentration.
However, the fresh hydrogen peroxide can also be introduced directly into the reaction according to (a), or else the raffinate portion of the extraction which is not concentrated can be added to the extraction. A distillation unit is advantageously a column provided with a condenser and an evaporator unit.

The known tray columns or packed columns infrdge are used for the distillation. The number of deatillation stages is chosen so that the top product contains as little hydrogen peroxide as possible. It is desirable to obtain less than 0.1% by weight of water peroxide in condensate. The known evaporators are basically used as the evaporator unit. For example, suitable evaporator units are those in which the residence time of the product is less than 20 minutes, preferably less than 10 minutes. Downflow or thin film evaporators are particularly suitable. High-alloy materials are suitable as materials for the distillation unit. te, rustproof stainless steels, which essentially contain chromium and nickel in addition to iron, such as a material with the DIN designation 1.4571, which in addition to iron contains 17.5% by weight chromium, 11.5% by weight nickel, 2, 25% by weight of molybdenum, as well as up to 2% by weight of manganese, up to 1% by weight of silicon, up to 0.1% by weight of carbon and small amounts of titanium, or a material which, in addition to iron 25 % By weight chromium, 25% by weight nickel, 2.25% by weight molybdenum and up to 2% by weight manganese, up to 1% by weight silicon, up to 0.06% by weight carbon as well as small amounts of titanium and is designated according to DIN with the number 1.4577. Particularly suitable as a material for the distillation unit, in particular for the evaporator, zircon, zircon-containing materials and zirconium alloys.

The bottom product of this distillation unit is returned to the reaction stage (a), if necessary with the hydrogen peroxide and catalyst concentrations required for the reaction with the carboxylic acid being restored. As a result of this measure of returning the raffinate of the extraction to the reaction stage according to (a), having previously passed all or part of the concentration according to (c), one essentially obtains process stages (a), (b), (c) and (d) comprehensive cycle of hydrogen peroxide and catalyst. It can be expedient here, or even a part, for example 0.1 to 6% by weight, of the circulation flow from time to time continuously removed as a side stream from the process. This side stream is advantageously removed at a point in the process where the circulating stream has the lowest possible concentration of hydrogen peroxide and acid catalyst and, if appropriate, of percarboxylic acid and carboxylic acid. The raffinate of the extraction before addition of fresh hydrogen peroxide and before concentration according to (c) is particularly suitable for this side stream withdrawal. This side stream, which is part of the recycle stream an aqueous solution essentially containing hydrogen peroxide and acid catalyst, can either be discarded or be worked up in a regeneration stage. A regeneration of this portion of the circulating stream can be carried out, for example, by distilling off the hydrogen peroxide contained therein in vacuo with steam, an aqueous solution of the acid catalyst being obtained as the distillation residue. The aqueous solution containing hydrogen peroxide obtained as a distillate can, if appropriate after concentration, be returned to the process. After purification, for example by distillation, the aqueous solution of the acidic catalyst can likewise be returned to the process. This cycle exchange removes a corresponding part of the catalyst, for example sulfuric acid, from the process, which must therefore be supplemented in the process.

The organic extract which essentially contains the percarboxylic acid and the carboxylic acid and is obtained in process step (b) is treated in process step (e) with water or an aqueous solution. In general, the procedure is such that the organic percarboxylic acid extract is washed with water in one of the customary devices.

It is advisable to use this laundry as an extraction, for example as a multi-stage countercurrent extraction, with water, for example in a three-stage extraction unit. Instead of countercurrent extraction, extraction in cocurrent or crosscurrent can of course also be used. When working with several extraction stages, the extraction can also be carried out partly in cocurrent and partly in countercurrent.

It is expedient to use 0.1 to 10% by volume of water or aqueous solution, based on the organic extract. Preferably 0.5 to 7% by volume of water is used. Instead of pure water, it is also possible to use an aqueous solution which is essentially free of hydrogen peroxide and of mineral acid. It is expedient to use an aqueous phase which is obtained in the process. For example, the distillate obtained in carrying out process step (d) is suitable. The aqueous phase of the water treatment can be returned to the extraction according to (b) in order to obtain the proportions of percarboxylic acid, carboxylic acid and hydrogen peroxide therein for the process.

The known extraction systems are suitable as devices for the water treatment according to process stage (e), e.g. Mixer-separators, sieve plate extractors, pulsed sieve plate columns or extraction centrifuges.

After the organic solution of the percarboxylic acid has been treated with water or an aqueous solution according to (e), an organic solution of the percarboxylic acid which is essentially free of hydrogen peroxide and sulfuric acid is obtained, which is now the azeotropic distillation according to process step (f) is subjected, whereby water contained in the organic solution is removed. The water content of the organic solution which is dried is generally 0.5 to 7% by weight. This water content is essentially dependent both on the nature of the organic solvent used in each case and on the selected concentration of fercarboxylic acid in the extract obtained in (b).

The entrainer used to remove water from the percarboxylic acid organic solution by azeotropic distillation is generally the inert organic solvent. However, it is also possible to add another suitable entrainer to the organic solution of the percarboxylic acid before entering process step (f) or directly into the distillation unit according to (f) and to carry out the azeotropic distillation with it.

In process stage (f), the amount of distillate is generally chosen so that the residual water content in the bottom product of the azeotrope column is less than 0.5% by weight, preferably less than 0.2% by weight, for example 0.05-0 , 2% by weight. However, it is also possible to reduce the water content to a negligible value. After the condensation of the top vapors of the azeotropic column, the entraining agent which separates out as the organic phase is fed to the column as reflux. The aqueous phase obtained after condensation of the top vapors, which generally contains small amounts of percarboxylic acid, carboxylic acid and hydrogen peroxide, is fed back to the process at a suitable point, for example the extraction according to (e) or (b); however, it can also be removed from the process.

The azeotropic distillation (f) can be carried out under normal or reduced pressure, for example at 200 to 400 torr. The bottom temperature is, for example, 30 to 80 ° C. In general, a bottom temperature of below 70 ° C is sufficient.

The usual columns, for example the known tray or packed columns, are suitable for azeotropic distillation. The usual devices can be used as evaporators. Downflow or thin-film evaporators are particularly suitable.

The organic solution of a percarboxylic acid which is essentially free of water and hydrogen peroxide and which is now obtained as the bottom of the azeotropic distillation is treated with an excess of butandiene in a molar ratio of butadiene to percarboxylic acid of 1.5 to 6: 1 at temperatures of 0 ° in process step (g) C to 80 ° C and implemented at a pressure of 0.8 to 20 bar.

But you can also work at a pressure of 1 to 10 bar. A suitable pressure range is, for example, pressures from 1.2 to 8 bar. It is preferred to work at a pressure of 1.5 to 5 bar.

The reaction temperature is preferably kept at 10 to 70 ° C. The reaction of butadiene with the organic solution of percarboxylic acid is very particularly preferably carried out at from 20 to 60.degree. In addition to working under isothermal conditions, i.e. Maintaining a uniform temperature in the entire reaction mixture, the reaction can also be carried out with the formation of a so-called temperature gradient, which generally increases with the progress of the reaction. However, the reaction can also be carried out in such a way that a gradient of falling temperature is formed as the reaction proceeds.

The pressure when carrying out process step (g) is expediently chosen so that the reaction mixture is essentially in the liquid phase. With a molar ratio of butadiene to percarboxylic acid of, for example, 2.5: 1 and at a reaction temperature of 40 to 50 ° C., the pressure is, for example, 2 to 3.5 bar.

The molar ratio of butadiene to percarboxylic acid is preferably 1.5 to 4: 1. It is very particularly advantageous to use a molar ratio of 2.0 to 3.0 mol of butadiene per mol of percarboxylic acid.

The devices which are customary for reactions of this type, such as stirred tanks, tubular reactors, loop reactors or loop reactors, can be used to carry out the reaction. In general, a device is used that behaves like a cascade of at least two ideally mixed kettles. It is particularly advantageous to use a reaction system which behaves like a cascade of 4 to 50, preferably 10 to 30, ideally mixed vessels. In the practical implementation of the implementation, e.g. a sequence of several agitator tanks, for example a cascade of 3 to 6 tank reactors.

Technical butadiene is generally used for the reaction in process step (g). It can contain the usual admixtures in technical use, especially n-butenes.

The butadiene can be introduced into the reaction unit in various ways. You can use the butadiene in liquid or in gaseous form. The butadiene can also be passed into the reactor unit together with the fercarboxylic acid solution. Both feed materials can also be introduced into the reactor separately from one another. It is also possible to pass the butadiene and the percarboxylic acid solution into the reactor unit at various points. When using several reactors connected in cascade, it may be expedient to introduce all of the butadiene into the first reactor. Butadiene can also be divided between the various reactors.

The considerable heat of reaction is dissipated by internal and external coolers. To remove the heat of reaction, the reaction can also be carried out under reflux, ie in boiling reactors. The reaction is expediently carried out with the most complete possible conversion of the percarboxylic acid. In general, more than 98% of the percarboxylic acid is converted. It is advisable to convert more than 99% percarboxylic acid. The reaction can be carried out with a particularly high selectivity if it is partially carried out in a reaction tube through which turbulent flow flows and which is connected, for example, to the sequence of agitator vessels. It is particularly expedient to use a reaction tube which is equipped with internals which largely prevent backmixing, for example perforated transverse bottoms. For example, the reaction is first carried out in a few, for example 1 to 3, stirred reaction units connected in series and the reaction mixture is then passed to a reaction tube to complete the reaction. 'The reaction tube can be operated under adiabatic conditions; however, it is also possible to cool , for example by external cooling, or you can attach coolers between individual pipe sections. The dimensioning of a suitable reaction tube depends on the intended throughput. It is essential that the flow rate in the reaction tube is so high that backmixing of the reaction components is essentially excluded. The diameter of the reaction tube can be 0.01 to 10 meters with a length of 1 to 200 meters. You can also operate several pipes in parallel. For example, you can also use tube bundles. If a reaction tube with perforated transverse plates is used, the transverse plates are generally at a distance of 0.1 to 5 m from one another.

When carrying out the reaction between butadiene and the percarboxylic acid (step g) according to the invention, it is possible to achieve vinyloxirane yields of over 95%, based on the percarboxylic acid used. The amount of by-products, e.g. the butene (1) diol (3,4) and its mono- and diester mi1 of the carboxylic acid corresponding to the percarboxylic acid is less than 2%, based on the vinyl oxirane formed. The amount of polymerized butadiene, based on the total amount of butadiene used in the reaction stage according to (g), is less than 1% by weight.

The reaction mixture is worked up by distillation, pure vinyloxirane being obtained and excess butadiene, the carboxylic acid and the organic solvent being isolated to such a degree of purity that recycling, which can also be carried out only partially, is possible in the process. It is advisable to separate vinyloxirane and the carboxylic acid very quickly. A distillation column, for example, is used for this purpose, in which viynloxirane and butadiene are first taken off, if appropriate together with lower-boiling constituents and part of the solvent, and the remaining solvent and the carboxylic acid are obtained as bottom product. The top product becomes one if the butadiene is separated off by distillation, worked up in a further distillation column to obtain pure vinyl oxirane. The organic solvent and the carboxylic acid are recovered from the bottoms of these two distillation columns. The distillation residue of carboxylic acid distillation is the small amount of higher-boiling by-products already mentioned. The organic solvent can basically be recovered quantitatively.

In many cases it may be advantageous to add a stabilizer or a solution of a stabilizer to the reaction mixture leaving process step (g) before entering the first distillation column. However, the reaction mixture can also be worked up by distillation without using a stabilizer. All compounds which are capable of binding oxygen or traces of peroxidic compounds are suitable as stabilizers. These compounds can also contain nitrogen and / or sulfur. Examples include hydroquinone, 4-tert-butyl catechol, 2,6-di-tert-butyl-4-methylphenol, phenothiazine, N, N-dimethylaniline, tetramethylhydroquinone, N-kitrosodiphenylamine, pyrogallol, 2 -Hethyl-benzothiazole, 6-methoxy-2-amino-benzothiazole, 2,3-dihydroxyquinoxaline and the addition compound from diisobutylene and nitrogen oxide.

An embodiment of the method according to the invention will be explained with reference to Figure 1.

In the first reaction stage (1), an aqueous solution containing 30 to 40% by weight of sulfuric acid and 25 to 35% by weight of hydrogen peroxide and (3) propionic acid in a molar ratio of hydrogen peroxide to propionic acid such as 0.9 up to 1.2: 1 at a temperature of 25 to 45 ° C given. The residence time in the reaction system (1) is ₁₀ to 30 minutes. The reaction mixture that leaves the reaction system (1) via (4) contains about 26 to 32% by weight of perpropionic acid, 12 to 17% by weight of propionic acid, 17 to 21% by weight of sulfuric acid, 5 to 8% by weight. -% hydrogen peroxide and 2 to 5% by weight Caro's acid. It arrives in an extraction system (5) which consists of a pulsed sieve plate column with 60 bJ; 90 sieve trays exist and which is loaded with benzene with a propionic acid content of less than 0.5% via (6). The raffinate of this extraction, which is removed from the extraction system (5) via (7), contains the hydrogen peroxide which has not been converted in the reaction system (1) and the sulfuric acid. It is passed together with about 50% commercially available aqueous hydrogen peroxide, which is fed in via (9), into the distillation unit (8) consisting of evaporator and column, in which at 40-120 torr and a bottom temperature of 60 to 80 ° C. so much water is taken off at the top that an aqueous solution containing 30 to 40% by weight of sulfuric acid and 25 to 35% by weight of hydrogen peroxide is obtained as the bottom product and is returned to the reaction system (1) via (2). The water taken overhead in the distillation unit (8) is removed from the process via (10). The amount of water obtained as distillate essentially corresponds to the amount of water contained in the hydrogen peroxide used and formed in the process step according to (a), that is to say in the reaction system (1). A downflow evaporator is used as the evaporator unit of the distillation column (8). The benzene perpropionic acid extract from the extraction system (5) is passed via (11) into the extraction system (12) consisting of 3 mixer separators, where the extract is extracted in countercurrent with water which is fed in via (13). The amount of water is 3 to 6 percent by volume of the benzene solution. The aqueous phase of this extraction unit (12) is returned to the extraction unit (5) via (14).

The water-treated benzene perpropionic acid solution passes through (15) into the distillation unit (16) where an azeotropic dewatering is carried out. The pressure within the distillation system (16) is 100 to 300 torr. The bottom temperature is 50 to 75 ° C. The water content of the benzene perproionic acid flowing out of the bottom of this column is less than 0.3% by weight. The essentially water- and hydrogen peroxide-free benzene perpropionic acid obtained as the bottom of the azeotropic distillation is passed via (17) into the reaction system (18), where the reaction with butadiene takes place in a molar ratio of butadiene to perpropionic acid such as 2 to 4: 1. The butadiene reaches the reaction system (18) via (19), (20) and (22). The pressure in (18) is 3 - 5 bar. The reaction system (18) consists of 2 loop reactors connected in series with a downstream retention tube of 10 to 80 m in length. The temperature in the two loop reactors, in which the reactants are mixed by means of a circulation pump, is 20 to 50 ° C. Perpropionic acid is converted to 80 to 95%. The further reaction of the perpropionic acid up to a conversion of 99.8% takes place in the downstream retention tube, which is operated without cooling. The reaction mixture obtained is passed via (23) into an expansion vessel (21) and expanded there. The gas phase obtainable essentially contains butadiene, which is returned to the reaction with perpropionic acid via (22). Vinyloxirane, together with butadiene and part of the benzene, is first separated by distillation from the liquid phase, which passes into the distillation unit (25) via (24). The stream containing butadiene, vinyloxirane and benzene is fed via (26) to the distillation unit (27), where the further separation of the components takes place and vinyl vinylirane is obtained which leaves the process via (28). Butadiene is returned to the reaction system (18) via (20). The bottoms of the columns (25) and (27) are fed via (29) and (30) to a further distillation unit (31), where benzene is recovered as the top product and returned to the extraction system (5) via (6). Of the Bottom of the benzene recovery column (31) consisting essentially of propionic acid is fed via (32) to the distillation unit (33), in which propionic acid is distilled off as top product, which is returned to the reaction system (1) via (3). The products boiling higher than fropionic acid are obtained as the bottom product of distillation (33) and discharged via (34).

According to the process of the invention, vinyloxirane can be produced in yields of at least 90%, based on the hydrogen peroxide used, and at least 95%, based on the butadiene used.

Example 1 (see also Fig. 2)

Through the reaction system (1) consisting of a heatable residence tube of 55 cm in length and a diameter of 5 cm, filled with fillers, 1034 g of a mixture of 415 g (= 5.6 mol) of propionic acid and 619 g are produced per hour during continuous operation an aqueous solution containing 37.8% by weight sulfuric acid and 30.8 g% by weight hydrogen peroxide (= 5.6 mol H ₂ O ₂ ).

• 32,8 Gew.-% freie Schwerefelsäure, 29,1 Gew.-% freies Wasserstoffperoxid und 5,8 Gew.-% Carosche Säure. Das Molverhältnis von Wasserstoffperoxid zu Propionsäure beträgt in dem in das Reaktionssystem (1) gelangenden Gemisch 1 :1 , wobei das in der Caroschen Säure gebundene Wasserstoffperoxid als freies H₂O₂ gerechnet wird.

In the aqueous solution containing hydrogen peroxide and sulfuric acid, some of these components are present as Caro's acid. This part is 5.3% by weight, based on the total amount of the aqueous solution, for which the following composition thus results:

• 32.8% by weight of free heavy sulfuric acid, 29.1% by weight of free hydrogen peroxide and 5.8% by weight of Caro's acid. The molar ratio of hydrogen peroxide to propionic acid in the mixture entering reaction system (1) is 1: 1, the hydrogen peroxide bound in Caro's acid being calculated as free H ₂ O ₂ .

Within the reaction system (1), the mixture now consisting of propionic acid, sulfuric acid, hydrogen peroxide, water and Carosic acid is heated to 40 ° C. for about 18 minutes, 59% of the propionic acid being converted to perpropionic acid. After passing through the residence time tube, an average of 28.8% by weight rergropieric acid, 16.5% by weight propionic acid, 19.6% by weight sulfuric acid, 3.47% by weight Caro's acid, 6.54% by weight. -% hydrogen peroxide and 25.1 water containing product stream (1034 g per hour) cooled to room temperature and passed into a gas separator, where 166 ml of a gas consisting of 87% oxygen and 13% carbon dioxide escape per hour. Then the degassed mixture, after having been combined with the mixture of the two aqueous phases running out of the extraction unit (12), the. Extraction system
(5) fed. The extraction process is carried out at a temperature of 32 ° C. A pulsed sieve plate column, which is provided with 80 sieve plates, has a length of 4 m and a diameter of 25 mm, as well as a separation vessel at the upper and lower end, in which the phase separation takes place, is used as the extraction column. At the upper end of the column (5), the product stream obtained after the degassing and with the mixture of the aqueous phases of the extraction system (12) fed in via line (14) is added, which flows through the column from top to bottom as the heavy phase, while on lower end, the benzene serving as extractant, which contains 0.09% by weight of propionic acid and traces of water, is introduced into the column at a rate of 1092 ml per hour (= 961 g / h). From the upper separating vessel, 1585 ml of a benzene solution of perpropionic acid (= 1490 g / h) is drawn off per hour, which in addition to 21.4% by weight of perpropionic acid and 12.6% by weight of propionic acid, 0.97% by weight. -% water, 0.51 wt .-% hydrogen peroxide and traces of sulfuric acid.

The raffinate from the extraction collects as a heavy phase in the lower separating vessel and is continuously removed from there via line (7). This raffinate, which is obtained in an amount of about 587 g per hour, contains on average 34.58% by weight of sulfuric acid, 11.16% by weight of hydrogen peroxide, 6.12% by weight of Caro's acid, and 0.1 % By weight propionic acid and 0.06% by weight perpropionic acid. This raffinate is prepared again for the reaction with propionic acid by adding 195.6 ml of a 50% strength aqueous solution of hydrogen peroxide (= 117 g = 3.44 mol of H ₂ O ₂ ) per hour (9) and the mixture thus obtained is concentrated again by distilling off 202 g of water. This process of concentration takes place in the distillation unit (8), which consists of a column provided with bubble-cap trays (length = 1 m, diameter = 50 mm), a condenser, a device which allows the reflux ratio to be varied, and a falling film evaporator which can be heated with the vapors of a boiling liquid exists and is betrayed at a pressure of 50 tons. The mixture consisting of the raffinate of the extraction (5) and the aqueous solution of hydrogen peroxide is introduced into the lower part of the column (8). At a suction temperature of 68 - 70 ° C, a temperature at the top of the column of 32 ° C, and a reflux ratio of 0.7 (return flow / withdrawal), 202 ml of water distill over per hour. This distillate contains traces of hydrogen peroxide as well as 0.2% by weight of perpropionic acid and 0.3% by weight of propionic acid. 619 g of an aqueous solution, which in turn contains 32.8% by weight of sulfuric acid, 29.1% by weight of hydrogen peroxide and 5.8% by weight of Caro's acid, are drawn off from the bottom of the column via line (2) per hour. After cooling to room temperature, this mixture is returned to the reaction system (1).

About 4.5 g per hour are discharged as raffinate of the extraction (5) from the circulating stream of hydrogen peroxide and sulfuric acid which forms in this way and which comprises the reaction and extraction system (1) or (5) and the distillation unit (8). The loss of sulfuric acid thus generated in the circuit is supplemented by continuously adding the same amount of a mixture having the composition of the raffinate of the extraction (5) to the circuit before the distillation unit (8).

The loss of hydrogen peroxide resulting from this cycle exchange is 0.5%, based on the fresh hydrogen peroxide used before the distillation unit (a).

The benzene solution of perpropionic acid removed from the extraction system (5) as a light phase is formed via line (11) to the extraction system (12), which is a three-stage mixer-separator battery, each consisting of a mixing pump with a subsequent separating vessel of about 2 liters is fed and runs through the system from the bottom to cben.

The mixing pump in the lower stage is fed, in addition to aerobolic solution of perpropionic acid, 67 ml per hour of an aqueous solution which is obtained if the water phase of the top product of the subsequent azeotropic distillation (distillation unit (16)). which is produced in an amount of 60 ml per hour and contains 1.48% by weight H202, 2.43% by weight perpropionic acid and 0.27% propionic acid, mixed with 7 ml deionized water. After passing through the middle mixer-separator arrangement, the benzene solution, which is taken from the lower separating vessel as a light phase, is fed together with 17 ml / h fresh water to the mixing pump belonging to the upper mixer-separator unit. The resulting aqueous phase after phase separation is passed into the middle extraction stage. The aqueous solutions collecting as a heavy phase in the middle and lower separating vessels are combined and re-introduced into the extraction unit (5) via (14), so that this stream consisting of an aqueous solution containing 25.23% by weight Perpropionic acid, 6.8% by weight hydrogen peroxide and 22.35% by weight propionic acid, with a quantity of d1 ml / h immediately before entering the pulsed sieve tray column (extraction system (5)), with that coming from the reaction system (1) Product stream (4) mixes.

From the separating vessel of the extraction system (12) belonging to the upper mixer-separator unit, 1493 g (- 1570 ml) of a benzene solution of perpropionic acid with the composition 20.04% by weight of perpropionic acid are converted into the light phase per line (15) , 11.41,% by weight of propionic acid, 3.95% by weight of water and 0.2% by weight of hydrogen peroxide are drawn off and introduced into the distillation unit (16), where the solution is dried azeotropically. Before entering the distillation unit (16), 5 ml of an approximately 3% by weight solution of a stabilizer of the ^type of the commercially available Na salts of partially esterified polypnosphoric acids in propionic acid are added to the benzene solution of perpropionic acid per hour.

The distillation unit (16) was operated at 210 Torr and consists of a thin-film evaporator, a 50 cm long column with 5 bubble-cap trays and a diameter of 50 mm, a condenser, and a separator for phase separation of the distillate ac top of the column Column is 65 ° C. 60 ml of water and about 915 ml of benzene are obtained as the distillate per hour. The benzene is added to the column as reflux, while the water obtained in the separator, as already described, is introduced as mesh water via (35) into the lower stage of the extraction unit (12). As the bottom product of this azeotropic distillation, a quantity of 1438 g per hour gives a 20.71% by weight benzene solution of perpropionic acid, which also contains 12.18% by weight propionic acid, 0.1% by weight water and 0.15 Contains% by weight of hydrogen peroxide.

The yield of perpropionic acid in the benzene extract thus dried is 96.15% based on the hydrogen peroxide used in the process.

The dried benzene solution of perpropionic acid thus obtained is reacted with excess butadiene in a four-stage cascade (reaction system (18)). The reaction is carried out at a pressure of 2 bar. The butadiene is introduced into the first reactor in gaseous form via lines (22), (20) and (19). The excess of butadiene, based on perpropionic acid used in the reaction, is a total of 170 mol% (= 482 g of butadiene). The first reactor of this four-stage cascade, which, like the three subsequent reaction vessels, is equipped with a stirrer and has a content of 1600 ml, is at a temperature of 35 ° C., the second, third and fourth reactor at a temperature of 40 ° each C operated.

The perpropionic acid used is converted to 99.8% under these reaction conditions. Behind the fourth reactor is the reaction mixture, which is produced at a rate of 1920 g per hour and on average the composition of 15.62% by weight of butadiene, 11.67% by weight of vinyloxirane, 21.46% by weight of propionic acid and 50.08 % By weight of benzene and 0.13% by weight of water, after cooling to 30 ° C. in the separator (21), relaxed to normal pressure, with a small part of the butadiene (37 g / h) outgassing, which passes through (22) the reaction system (18) is reintroduced. The mixture obtained after the depressurization is now, after it has been mixed with 2.0 g of 4-tert-butyl catechol, fed to a first distillation column (25), where all of the vinyloxirane is combined with the butadiene and part of the benzene decreases as the distillate. This distillate, which contains an average of 32.6% by weight of butadiene, 27.25% by weight of vinyloxirane, 39.9% by weight of benzene and small amounts of water and is obtained at a rate of 822 g per hour, is passed to the distillation column ( 27) via (26), where 224 g of a 99.9% vinyloxirane (product stream 28) and 268 g of butadiene are obtained per hour and are fed via line (20) into the reaction system (18). The bottom products of columns (25) and (27) are fed via line (29) and (30) to column (31), where the benzene is recovered as top product at a rate of 961 g / h and then via line (6) is conveyed back into the extraction system (5). The bottom of the column (31) reaches the distillation column (33) via line (32). The top product obtained here is 415 g / h of propionic acid per hour, which are returned to the reaction system (1) via line (3). From the bottom of column (33), 15 g of a mixture of higher-boiling compounds are discharged per hour (34), which essentially contains butene (1) diol (3,4) mono- and dipropionate .

The yield of vinyloxirane is therefore 96.7%, based on the perpropionic acid used in the reaction system (18). or based on hydrogen peroxide used in the process at (8) via (9), 93%.

Claims (10)

1. A process for the preparation of vinyloxirane from hydrogen peroxide and butadiene, characterized in that a) an aqueous solution containing 10 to 45% by weight of a water-soluble, acidic catalyst and 20 to 50% by weight of hydrogen peroxide with a carboxylic acid containing 2 to 5 carbon atoms in the molar ratio of hydrogen peroxide to carboxylic acid such as 0.5-30: 1 at temperatures of 10 up to 70 ° C b) the reaction mixture obtained is extracted with an inert organic solvent in a countercurrent, c) the aqueous raffinate of the extraction, containing hydrogen peroxide and acid catalyst, in its entirety or. partially concentrated by removing water by distillation, d) the concentrated raffinate and the possibly not concentrated portion of the raffinate with restoration of the concentrations of hydrogen peroxide and water-soluble acidic cavalyoator required for the reaction with the carboxylic acid in reaction stage (a), the restoration of the reaction for the reaction with the carboxylic acid required hydrogen peroxide concentration required hydrogen peroxide is added to the concentration of the raffinate before or after the distillative removal of water according to (c) or is added to the possibly not concentrated part of the raffinate, e) the organic extract containing essentially peroarboxylic acid and carboxylic acid is treated with water or an aqueous solution and f) subjecting the now practically hydrogen-free peroxide-free, water-containing organic extract to an azeotropic distillation in such a way that the residual water content in the bottom product of the azeotropic column is less than 0.5% by weight, g) the now obtained, percarboxylic acid and carboxylic acid-containing organic solution with butadiene in excess at a molar ratio of butadiene to percarboxylic acid from 1.5 to 6: 1 at temperatures from 0 ° C to 80 ° C and at a pressure of 0.8 converts bar to 20 bar, and h) the vinyl oxirane-containing reaction mixture is worked up by distillation, pure vinyl oxirane being isolated and the excess carboxylic acid and the inert organic solvent being recovered and fully or partially recycled into the process. _2nd Process according to Claim 1, characterized in that an aqueous solution containing 20 to 43% by weight of sulfuric acid and 22 to 35% by weight of hydrogen peroxide is used in step (a). 3. The method according to claim 1 and 2, characterized in that in step (a) hydrogen peroxide and carboxylic acid in a molar ratio of 0.5 to 1.3 or 3.5 to 25: 1 is used. 4. The method according to claim 1 to 3, characterized in that in step (a) acetic acid, propionic acid, n-butyric acid or isobutyric acid is reacted as the carboxylic acid. 5. The method according to claim 1 to ₄ , characterized in that in step (b) 1,2-dichloropropane, chlorobenzene, toluene, benzene, n-butyl acetate or diisopropyl ether is used as an inert organic solvent. ^{6. The} method according to claim 1 to 5, characterized in that in step (b) the ratio of inert, organic solvent to that obtained in step (a), the percarboxylic acid-containing reaction mixture such as 4 to 0.3: 1 is selected. 7. The method according to Arspruch to 6. characterized in that one carries out in step (c) the distillative removal of water at pressures of 40 to 150 torr and at temperatures of 60 to 85 ° C. 8. The method according to claim 1 to 7, characterized in that the hydrogen peroxide and sulfuric acid-containing side stream is fed to a regeneration stage and, if appropriate, the recovered proportions of hydrogen peroxide and sulfuric acid are re-entered into the process. 9. The method according to claim to 8, characterized in that in step (g) the conversion is carried out with a molar ratio of butadiene to percarboxylic acid of 1.5 to 4: 1. 10. The method according to claim 1 to _9, characterized in that the organic solvent obtained in stage (h) in stage (b), the carboxylic acid obtained in stage (h) in stage (a) and the butadiene obtained in stage (h) Step (g) can be returned.

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