CH635574A5 - Process for separating Laurent's acid from a mixture of Laurent's acid and peri acid - Google Patents

Description

The present invention thus relates to a process for separating lauric acid from a mixture of lauric and peric acid, which is characterized in that a slurry of the mixture of lauric and peric acid is mixed with ammonia or an organic amine, warmed and filtered warm.

The process according to the invention is expediently carried out by adding the mixture of lauric and peracid in 5 to 20 times the amount, preferably in 10 to 15 times the amount of a solvent, preferably water or a process mother liquor, which is water, ammonia or contains an organic amine as well as lauric and peric acid, slurried and simultaneously or subsequently mixed with ammonia or an amine.

Suitable organic amines which can be used in the process according to the invention are primary, secondary or tertiary amines, for example methylamine, diethylamine, triethylamine, ethanolamine or benzylamine. However, ammonia is preferably used. These compounds are preferably used as aqueous solutions, but can, if desired, also be used in the liquid or gaseous state.

The amount of ammonia or amine must be sufficient to convert the entire proportion of peracid into the ammonium salt. However, it is preferred to use 2-20 times, in particular 5-15 times, the molar amount. An excess of ammonia or amine beyond this is unsuitable since the purity of the undissolved lauric acid is only slightly improved as a result, but on the other hand the yield is significantly reduced.

However, one should not add so much ammonia or amine that the whole acid mixture goes into solution. Preferably at most 0.8, in particular at most 0.6 moles of ammonia or amine per mole of lauric and peracid are used.

After the addition of ammonia or amine, the slurry is heated to 50 to 150 ° C, preferably 90 to 125 ° C with stirring for 15 minutes to 10 hours, preferably for 30 minutes to 5 hours. As soon as the undissolved portion is readily filterable, the mixture is filtered without cooling, the residue is washed with warm water and dried. If necessary, these operations are carried out in pressure-resistant apparatus.

The filter residue consists of Laurent acid, which, depending on the reaction conditions, is still contaminated with approx. 0.5 to 4% peracid. The process is then preferably repeated with the laurent acid obtained, as a result of which the proportion of peracid is further reduced. If the process is carried out twice, it is less than 1%, but can be further reduced by repeated repetition in order to achieve an even higher product purity.

In this case, it is expedient to reuse the mother liquor obtained in the second separation for slurrying the mixture of peri- and lauric acid in one of the preceding stages, whereby ammonia or amine can be saved.

The method according to the invention can also be carried out continuously in conventional apparatus, for example as shown in FIG. 1.

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The mixture of lauric and peracid to be separated is continuously fed into a kettle together with ammonia or an organic amine and water or a mother liquor containing water, lauric and peri acid as well as ammonia or an organic amine (1 ) passed, which is provided with a heating, a stirring device and a reflux condenser (2). From this kettle, the reaction mixture is continuously passed to a heatable filter (3) and the filter residue is fed together with water and ammonia or an organic amine into another similar kettle (4), from where the suspension obtained is transferred to another heatable filter (5) transferred, the filter residue continuously discharged and dried. The mother liquor is returned to the process and used to slurry the mixture of lauric and peric acid to be separated.

The present invention further relates to the laurent acid obtained by the process according to the invention, in particular one having a peracid content of less than 1%.

The following examples serve to illustrate the invention. Percentages by weight mean parts by weight, and the temperatures are given in degrees Celsius.

example 1

15 parts of a mixture which contains 85.3% Laurent acid, 7.2% Peri acid, 1.8% Cleve acids (l-naphthylamine-6- or -7-sulfonic acid) (rest: water and others Impurities) are placed together with 180 parts of water and 1.7 g of 25% ammonia (40 mol%, based on the sum of the acids used) in a boiler with a double jacket, heated to 100 ° and under reflux for 4 hours touched. The resulting suspension is filtered at 100 ° and washed with water at 100 ° until the filtrate is colorless.

6.4 parts of lauric acid are obtained, which have 1.5-2% peracid and less than 0.5% of other impurities. The mother liquor, which contains about 50% of the laurent acid used as the ammonium salt, can be reused in a further analogous approach instead of water for slurrying the mixture of lauric and peracid.

Example 2

150 g of the mixture of lauric and peracid used in Example 1 are in 18% mother liquor from an analogous previous batch (containing about 77.5 g lauric and 2.0 g peracid - both dissolved as ammonium salt - 18 g 25% ammonia and approx. 1715 g water) slurried, heated to 98-100 ° with stirring and heated under reflux for 4 hours. The resulting suspension is filtered off and washed with 150 g of water at 98 °.

The moist filter residue, which contains 141.2 g Laurent acid and 2.3 g Peri acid (1.6% based on Laurent acid), becomes 1800 g with the addition of 18 g 25% ammonia

635 574

Slurried water, heated to 98-100 ° and heated under reflux for 4 hours. The resulting suspension is filtered off and washed with 150 g of water at 98 °. The filter residue is dried. It consists of 68.55 g Laurent acid and 0.45 g Peri acid (0.66%, based on Laurent acid). The mother liquor can be reused in an analogous approach as described above for slurrying the mixture of lauric and peracid.

Example 3

In Fig. 1 a plant for the continuous implementation of the method is shown.

A mixture of lauric and peric acid together with the mother liquor II mentioned below is fed continuously into the kettle I, a ratio of 15 parts of lauric and peric acid: 180 parts of mother liquor containing 1.84 parts of 25% ammonia ( 40 mol%, based on Laurent and Peri acid) is observed.

The suspension is stirred at 100-130 ° under appropriate pressure and an average residence time of 4 hours. At the overflow, continuous filtration takes place on a rotary pressure filter.

The moist filter cake is fed continuously into the boiler II together with water and ammonia, a ratio of 15 parts of lauric and peracid: 180 parts of water: 1.84 parts of 25% ammonia (40 mol%, based on Laurent and Peri acid) is observed. The suspension is stirred and filtered under the conditions mentioned above. The mother liquor II is used to slurry the feed mixture.

The filter cake is continuously removed and dried. It consists of lauric acid with less than 1% peracid.

The peric acid can be isolated from the mother liquor I by acidification and the filtrate can be used again to slurry the mixture of lauric and peric acid to be separated.

Example 4

15 parts of a mixture containing 85.3% Laurent acid, 7.2% Peri acid and 1.8% Cleve acids (rest: water and other impurities) together with 180 parts water 0.85 parts methylamine (40 mol%, based on the total of the acids used) placed in a sulfonation flask with a double jacket, heated to 100 ° and stirred under reflux for 4 hours. The resulting suspension is filtered at 100 °, washed with water at 100 ° until the filtrate is colorless and sucked dry.

5.1 g of lauric acid are obtained, which has 1.5-2% peracid and less than 0.5% of other impurities.

The peracid content can be reduced to less than 1% by repeating the operation.

Example 5

If the procedure is exactly as described in Example 4, but instead of 40 mol% of methylamine, the same amounts of di- or triethylamine, ethanolamine or benzylamine are used, then lauric acid is obtained which has a similar purity.

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1 sheet of drawings

Claims (10)

635 574 1. A process for separating lauric acid from a mixture of lauric and peri acid, characterized in that a slurry of the mixture of lauric and peri acid is mixed with ammonia or an organic amine, heated and filtered warm. 2. The method according to claim 1, characterized in that one uses an aqueous slurry. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that a slurry of lauric and peracid is used in a process mother liquor, which contains water, ammonia or an organic amine, and Laurent * and peracid. 4. The method according to claims 1-3, characterized in that the slurry of the mixture contains 5-20 times, preferably 10 to 15 times the amount of water and / or process mother liquor, based on the amount of lauric and peracid used. 5. The method according to claims 1-4, characterized in that a slurry of the mixture of lauric and peracid is mixed with ammonia. 6. The method according to claim 1, characterized in that ammonia or an amine in 2-20 times, preferably 5-15 times the molar amount, based on the content of the mixture of peracid, but at most 0.8, preferably 0 , 6 moles per mole of lauric and periacid. 7. The method according to claim 1, characterized in that the slurry is heated to 50 to 150 ° C, preferably 90 to 125 ° C for 15 minutes to 10 hours, preferably for 30 minutes to 5 hours. 8. The method according to claim 1, characterized in that the entire method is repeated one or more times. 9. The method according to claims 1 and 8, characterized in that the mother liquor obtained in the repetition is used for slurrying the mixture of lauric and peracid in one of the preceding stages. 10. Laurent acid obtained by the process according to claim 1. Laurent acid (l-naphthylamine-5-sulfonic acid) and peric acid (l-naphthylamine-8-sulfonic acid) are produced industrially according to a process described in Ullmanns Encyklopadie der Technische Chemie, 3rd edition (1953), volume 12, pages 625 and 626 prepared by first nitriding the sulfonation mixture formed in the production of a -naphthalenesulfonic acid and then reducing it. From the solution obtained, practically pure peracid precipitates at 90-95 ° C. and a pH of 4.3. Laurent acid is precipitated by acidifying the filtrate more strongly, but this is still mixed with approx. 5-10% peracid. After stirring in water and adding magnesite, the lauric acid can be hotly dissolved from this mixture, filtered and, after cooling, separated out in pure form as the Mg salt, while the Mg salt of the peracid remains in solution. This process is unsatisfactory because, for ecological reasons, it is desirable to avoid the deposition of the Laurent acid as the Mg salt. In addition, the Mg salt must be converted back into the free acid before further use. It has now been found that when ammonia or organic amines are added to an aqueous slurry of a mixture of lauric and peracid at elevated temperature, the peracid is surprisingly dissolved first. The Laurent acid remains undissolved in the form of the free acid. This was unpredictable. Since the Laurent acid is the stronger acid, it was to be expected that this would go into solution first when the base was added. Compared to the known process, the new separation process has the advantages that the use of the ecologically questionable Mg salts can be dispensed with and that one operation is also saved.