DE1128859B - Process for the continuous neutralization of cleavage mixtures which have been obtained by cleaving alkyl aromatic hydroperoxides in the presence of acids - Google Patents

Description

Process for the continuous neutralization of fission mixtures, obtained by cleaving alkyl aromatic hydroperoxides in the presence of acids It is known that aralkyl hydroperoxides are combined with mineral acids such as sulfuric acid, Phosphoric acid, or with organic acids such as acetic acid, to phenols and ketones split. This process has become particularly important for the cleavage of Cumene hydroperoxide to phenol and acetone. From the mixture obtained in the cleavage must be carried out before the separation of the individual, for example by distillation Components the acid is removed. This can be done in a number of ways, for example by neutralizing with ion exchangers. You have the split mixture already neutralized with solid or dilute aqueous alkali. Partly has been an aqueous alkali phenolate liquor is also used for neutralization.

As a so-called »weighting agent«, these alkalis are used to make things easier a saturated sodium sulfate solution to settling. One can use this procedure although they achieve a complete removal of the acid, they have the disadvantage, however, that they are too little in their implementation, especially in the large-scale process are operationally safe. For the rest, it is when neutralizing with ion exchangers It is very difficult to achieve a uniform p 1 value for the neutralized mixture to obtain.

On the other hand, the neutralization with lye with the addition of sodium sulfate associated with the disadvantage that you have a cleavage product with a salt content of over Receives 50 mg per kilogram. There are therefore still special and cumbersome procedural measures required to remove this salt content.

To avoid these disadvantages, it has already been proposed that Wash out acid from the cleavage mixture with water. However, this is a special one and difficult work-up of the wash water containing phenol and acetone is required.

The split mixture must also be washed for a long time without that you can completely remove the acid. Also by washing the split mixture for a long time The mineral acid can be eliminated with very dilute, aqueous solutions of carboxylic acids do not remove completely.

It has now been found that the cleavage mixtures obtained by cleaving alkylaromatic hydroperoxides of the general formula in which R1 and R2 are alkyl groups and Ar is an aryl or substituted aryl group, especially obtained from cumene hydroperoxide in the presence of acids, by treatment with 1 to 50% of the above aqueous alkali and / or alkali phenolate liquor at a temperature of 10 to 400 C can be neutralized very easily and reliably in a continuous process by the cleavage mixture, which still contains considerable amounts of hydrocarbons, only very briefly, preferably only 0.5 to 20 seconds, with the dilute aqueous alkali and / or alkali phenolate in one Treated centrifugal or turbulence pump, the liquor being added to the cleavage mixture in a ratio of 1:20 to 1:80, and then separating the neutralized mixture in a separating vessel from the aqueous layer. A so-called "orifixer" can be connected downstream of the centrifugal pump. The "Orifixer" consists of a pipe with internal fittings through which the liquid is passed, which creates further turbulent mixing.

The separation of the organic layer from the aqueous layer can can be carried out both batchwise and continuously.

In the continuous process, the separator is set up in such a way that that the neutralized cleavage mixture introduced below and the separated from the liquor Fissure mixture is discharged at the top. The respective size of the separation vessel then depends on the throughput away. This is expediently set up so that the neutralized mixture a Reached residence time of 24 to 72 hours. In this way, salt levels can be determined of the organic layer of less than 20 mg per kilogram, usually between 5 and Achieve 10 mg per kilogram without difficulty in continuous operation. In the separation vessel Other unknown compounds contained in the mixture in traces also settle, which would affect the purity of the phenol.

The method of the invention also has the advantage that undesirable Condensation, which can occur due to the alkali in the cleavage mixture, to a minimum be reduced. The desired pll value, which is between 4 and 7, preferably is between 5 and 6 can be set much more reliably than at the previously known method. This is important because of fluctuations in the p-value in the subsequent separation of the mixture by distillation to form undesirable By-products can lead. An addition of so-called »weighting agents« is not allowed necessary.

It is already known that in the splitting of organic hydroperoxides, for intensive mixing of the reactants by turbulent flow a To use centrifugal pump (see. Belgian patent 526 682). With this one The splitting process is carried out in a centrifugal pump that only uses one Fraction of their normal filling is charged and the acid is in a lot brought to use, which is sufficient to dissipate the majority of the heat of reaction. In the method of the invention, however, the pump is filled with its full volume loaded. The basting process is one with strong heat tint ongoing cleavage reaction, while in the process of the invention primarily the acid contained in the cleavage mixture is neutralized. But besides that a number of other conversions take place, which are necessary for the special effect of the process are of the utmost importance. The fission mixture was found to contain in addition to the well-known impurities such as acetophenone and a-methylstyrene, in a great deal small amount of various not yet identified compounds. These Compounds can be removed in the subsequent work-up of the phenol by distillation can only be eliminated incompletely and with difficulty and thus reduce the quality of the end product.

They are also in that returned to the oxidation stage Contains cumene. When they oxidize to cumene hydroperoxide, they have a noticeable effect Reduction of the reaction rate and lead to increased formation of by-products.

It succeeds under the specific conditions of the new process now, surprisingly, these compounds in one of the organic layers transfer easily separable form, so that the difficulties described above can be switched off reliably.

It is also known that the cleavage mixture in an aqueous and Separate organic layer and this first with water and then in one Mixing vessel with a dilute aqueous alkali solution, e.g. B. with a Solvigen sodium carbonate solution can handle. Treatment of the organic Layer takes place with aqueous alkali in this known process only to remove any organic acids still present remove.

It is also known that the gap mixture together with a 10 to 600 per cent, especially 30 to 500 per cent, of the above aqueous alkali metal phenolate solution a mixing vessel can pump. With this procedure arise as a result of the proportionate high alkali concentration insoluble products that are difficult to filter off permit.

You also have very high-concentration cumene hydroperoxide, So with a low hydrocarbon content, split with sulfuric acid, that Fission mixture with a dilute aqueous, z. B with a 50% sodium phenolate solution neutralized in a mixing vessel and then placed in a sedimentation tank.

In contrast, in the method of the invention, a gap mixture, which still contains considerable amounts of hydrocarbons, only for a very short time with a very dilute aqueous alkali and / or alkali phenolate in a centrifugal or turbulence pump treated.

The shortening of the reaction times initially has the consequence that one gets by with much smaller devices and the space requirements accordingly becomes less. On the other hand, however, this becomes unavoidable in the known processes Formation of alkali phenolate is completely avoided because of the short reaction time the alkali will only react with the reactive components of the mixture can, while the apparently somewhat slower conversion to alkali phenolate can no longer take place.

Another surprising advantage of the method of the invention lies in the fact that in the process stage downstream of the neutralization in contrast to the previously known method a very rapid and complete separation of the two layers is achieved. Presumably this is due to the fact that as a result the very short reaction time during neutralization, the formation of tarry polymerization and condensation products are effectively prevented.

These products deposited on the salt germs prevent a complete Neutralization, on the other hand they make the separation more difficult. Given the substantial Difficulties that previously existed in the deposition are eliminated by this advantage particularly important for an operational procedure.

Example By a turbulence pump with a capacity of 5 1 are 13 m8 per hour of a split mixture of the following in a single pass Composition piped: 1,000 o / o water, 0.012 ovo sulfuric acid, 12.100 ° / o Acetone, 21.200 phenol, 0.840 o / o dimethylphenylcarbinol, 0.900% acetophenone, 2.500e / o a-methylstyrene, 61.448 o / o cumene and unknown compounds in traces.

The cleavage mixture is per hour with 2401 of a 20 / above aqueous Sodium hydroxide solution added; the ratio of cracking mixture to alkali is 54: 1, the Dwell time about 1.4 seconds. After mixing and neutralization In the pump, the mixture is fed to a large storage tank, its inlet and Drain is adjusted so that the mixture has 48 hours to separate. The neutralized cleavage mixture has the following composition: 0.00010 / o sulfuric acid, 12,000 ovo acetone, 21,000% phenol, 0.840e / o dimethylphenylcarbinol, 0.820e / o acetophenone, 2.500% α-methylstyrene, 62.840% cumene and traces of unknown compounds.

The salt content is 7 mg per liter.

In addition to the sulfuric acid, the fission mixture also becomes the unknown compounds present in traces removed from the subsequent Distillation would have adversely affected the purity of the phenol.

In the event of fluctuations in the acid content in the cleavage mixture, the pH value from 5 to 6 by regulating the addition of alkali exactly to adjust. This value corresponds to the pH value of the phenol. A formation of by-products is not observed.

Claims (1)

PATENT CLAIM: Process for the continuous neutralization of cleavage mixtures that result from the cleavage of alkyl-aromatic hydroperoxides of the general formula in which Rj and R2 are alkyl groups and Ar is an aryl or substituted aryl group, have been obtained in particular from cumene hydroperoxide in the presence of acids by treatment with 1 to 50% aqueous alkali and / or alkali phenolate liquor at a temperature of 10 to 400 C, characterized in that the cleavage mixture, which still contains considerable amounts of hydrocarbons, is treated only very briefly, preferably only 0.5 to 20 seconds, with the aqueous alkali and / or alkali phenolate liquor in a centrifugal or turbulence pump, the Lye is added to the cleavage mixture in a ratio of about 1:20 to about 1:80, and then the neutralized mixture is separated from the aqueous layer in a separating vessel. Documents considered: Belgian patent specification no. 526,682; British Patent Nos. 670 445, 743 004; U.S. Patent No. 2744143.