JPH0629214B2 - Method for producing sorbic acid - Google Patents

Description

The present invention relates to a method for purifying crude sorbic acid separated from a reaction solution by decomposing a polyester obtained by a reaction of crotonaldehyde and ketene with hydrochloric acid.

(Prior art and its problems) There are hydrochloric acid decomposition method, alkali decomposition method, thermal decomposition method and the like for decomposing the polyester obtained by the reaction of crotonaldehyde and ketene to synthesize sorbic acid.
It is known that the hydrochloric acid decomposition method is most advantageous in terms of decomposition results in terms of yield and quality without generation of isomers. However, in any case, since the tar component by-produced during the reaction exists as an impurity together with the polyester residue, there is a problem that a special refining step is required.
Further, even in the comparatively superior hydrochloric acid decomposition method, this problem remains, and the crude sorbic acid obtained by decomposing the polyester and then cooling and passing it contains tar. At this time,
It is also necessary to perform dehydrochlorination.

Conventionally, the purification of the sorbic acid includes an activated carbon treatment method, a recrystallization method using water or water + organic solvent, etc., but in any case, sorbic acid is adsorbed or remains in the liquid, and the economical disadvantage is large. Also, there is a disadvantage that it becomes complicated as an industrial device.

(Means for Solving Problems) The inventors of the present invention have conducted extensive studies on the purification of the sorbic acid in consideration of the drawbacks of the conventional method, and as a result, it is very simple compared with this. By adopting the treatment means, we succeeded in obtaining sorbic acid of good quality economically in terms of equipment and yield. That is, in the present invention, in the method for producing sorbic acid in which the polyester obtained by the reaction of crotonaldehyde and ketene is decomposed with hydrochloric acid and the crude sorbic acid separated from the reaction solution is purified, 1) in the temperature range of 100 to 140 ° C., Essentially, so that the operating point is maintained within the two-liquid phase separation region (B) in the sorbic acid-petroleum-tar component ternary liquid-liquid equilibrium diagram shown in FIG. 1, 2) crude sorbic acid Is continuously dissolved in petroleum, and the residual water and hydrochloric acid content in the petroleum solution of sorbic acid are evaporated and continued to be separated from the tar content.

Is.

By the way, the basis of the technical idea in the present invention is to clarify the behavior of the tar component contained in the crude sorbic acid in the liquid separation operation by interposing a specific petroleum in the system. When the crude sorbic acid obtained by decomposing the polyester with hydrochloric acid was dissolved in petroleum, not only sorbic acid but also the tar content was dissolved, and troubles frequently occurred because they were carried over to the next step.

The inventors of the present invention can appropriately separate the petroleum solution of sorbic acid into a petroleum layer and a tar layer by appropriately selecting the temperature and the sorbic acid concentration, and in particular, considerably suppress the dissolution of the tar component in the former. Found that is possible. Hereinafter, specific experimental data supporting these facts will be shown.

FIG. 1 is a ternary liquid-liquid equilibrium diagram for sorbic acid, petroleum, and tar. The solid line is the equilibrium diagram at 100 ° C. and the broken line is the equilibrium diagram at 130 ° C. The region A is a region where undissolved sorbic acid is precipitated, and the lower limit represents the solubility curve. Area B is for use in liquid separation into oil and tar layers, and the tie line showed a slight downward trend. Here, the upper limit represents a liquid separation curve, the left side shows the composition of the petroleum layer, and the right side shows the composition of the tar layer. The area of C is
The area where the tar layer and the petroleum layer are mixed and becomes uniform is shown.

Further, from the same figure, it can be seen from the difference between the equilibrium diagrams at 100 ° C. and 130 ° C. that the liquid separation of the tar layer and the petroleum layer greatly depends on the temperature condition as well as the sorbic acid concentration.

(Effect of the Invention) According to the method of the present invention, most of the tar content in the crude sorbic acid can be removed by a very simple operation of dissolving in petroleum and separating. Further, as can be seen from FIG. 1, sorbic acid and petroleum contained in the tar layer to be liquid-separated can be suppressed as much as possible under the same conditions, which is very advantageous in terms of yield.

(Structure of the Invention) Next, the method of the present invention will be described.

I. Dissolution (monohydrochloric acid) step First, in the dissolution of crude sorbic acid in petroleum, especially the hydrochloric acid contained in the crude sorbic acid promotes equipment corrosion and itself and the dissolved metal due to corrosion promotes resinification of sorbic acid. It was considered. However, in the batch dissolution, 200 to 300 ppm
The problem is that the hydrochloric acid content of the above remains.

The inventors of the present invention have studied that crude sorbic acid obtained by decomposing hydrochloric acid in petroleum is continuously dissolved and dehydration and dehydrochlorination are simultaneously performed. The results are shown in Table 1.

When the temperature was 100 ° C. or higher, preferably 110 ° C. or higher, when the crude sorbic acid was dissolved, dehydration / dehydrochlorination was very effectively performed by azeotropic distillation with petroleum. However, sorbic acid easily undergoes a polymerization reaction even in a petroleum-dissolved liquid, and the sorbic acid is lost during dissolution of the sorbic acid in petroleum and static liquid separation of insoluble tar. 140 ℃, especially 130 ℃
By setting below, this polymerization reaction could be suppressed to a considerable extent.

As the specific petroleum used in the method of the present invention, any of various lubricating oils can be used as long as it has a boiling point of 180 to 300 ° C. at atmospheric pressure. The amount used is II, due to the restriction of the liquid separation process, the operating point is essentially the sorbic acid-petroleum-tar component, the ternary liquid-liquid equilibrium diagram, and the two-liquid phase separation region. It is important to control so as to keep it in (B). For example, the concentration of sorbic acid in the system is in the range of 5 to 30%, preferably 10 to 20%.

The dissolution temperature range is 100-140 ° C, preferably 110-
It is performed at 130 ° C., and the purpose is usually achieved in 1 to 4 hours.

II. Separation process As described above, tar is composed of petroleum, sorbic acid, and
The liquid-liquid equilibrium relationship shown in the figure was found, and it was found that the solubility of the tar in the petroleum layer is very closely related to the sorbic acid concentration and the liquid separation temperature.

Liquid separation is performed in a temperature range of 100 to 130 ° C, preferably 100 to 130 ° C.
It is carried out at 120 ° C., and the purpose is usually achieved in 1 to 4 hours.

Thus, the obtained petroleum solution of sorbic acid (petroleum layer)
For example, if necessary, after passing through an activated carbon layer,
A sorbic acid crystal is obtained by cooling, crystallizing, separating and drying.

Further, the obtained sosorbic acid cake or crystals can be recrystallized in water or an organic solvent-water system to obtain a commercial grade sorbic acid.

Further, the petroleum sorbic acid solution can be further purified by the petroleum co-distillation method. In this case, since most of the tar content is removed by separation, the amount of evaporation residue is small, and the loss of sorbic acid contained in the residue (usually, about 20% of sorbic acid is contained in the residue). In addition to the advantage in terms of yield due to the suppression, there is an advantage in operation by removing impurities such as a resin compound of sorbic acid that adheres to equipment and causes clogging.

(Examples) Hereinafter, the method of the present invention will be specifically described with reference to Examples.

Example 1. Crude sorbic acid (water content: 20%, tar content: 6.0%, hydrochloric acid content: 2,000 to 6,000 ppm) was obtained by a hydrochloric acid decomposition method in a GL dissolving tank having a capacity of 100 and equipped with a stirrer 1
Lubricating oil (manufactured by Company A) 60 kg / H having 0 kg / H and a boiling point range of 200 to 250 ° C. was continuously supplied and dissolved, dehydrated and dehydrochlorinated at 120 ° C. The residence time was controlled at 1 Hr. As a result, 2.0 kg / H of distilled water was obtained, the water content in the solution was 0.015%, and the hydrochloric acid content was 20 ppm.
Dehydrochlorination could be carried out effectively.

The above solution was continuously supplied to the liquid separation step at 68 kg / H. The residence time in the liquid separation tank (volume 100) was 1 hr, and the liquid separation temperature was controlled at 100 ° C. As a result, an upper layer (petroleum layer) of 67.6 kg / H and a lower layer (tar layer) of 0.5 kg / H were obtained.

At this time, according to the liquid separation operation line (tie line) shown in FIG. 1 and the liquid-liquid equilibrium diagram, the composition of both is as shown in Table 2.

The viscosity of the separated tar component is about 1000 c. p.
Therefore, it was possible to carry out continuous withdrawal using a separating tank.

Next, the solution in the upper layer was passed through the activated carbon layer and then at 20 ° C.
It was cooled to room temperature and separated using a centrifuge. As a result, the yield of sorbic acid contained in the wet cake and in the liquid was 98% based on the sorbic acid in the crude sorbic acid. Of these, the loss due to resinization of sorbic acid was 1.
6%, loss in the tar content extracted from the separation tank was 0.4%.

Further, using a wet cake of sorbic acid, it was recrystallized in an aqueous methanol system according to a conventional method, dried and dried. The color value of 1 g of sosorbic acid thus obtained dissolved in 10 m of methanol was 95.5% when the transmittance at a wavelength of 350 μm was measured using a spectrophotometer, and 1 g of sorbic acid was 1 N. The color value when dissolved in an aqueous NaOH solution is the transmittance at a wavelength of 400 μm, and is 96.
It was 0%.

Example 2. The upper layer solution obtained in Example 1 was evaporated under a reduced pressure of 50 mmHG using a centrifugal thin film evaporator. The evaporator used a heat transfer area of 0.8 m ² , steam heating (jacket side), and 12 kg / cm ² G. The mixed vapor was purified by a mist separator, cooled, and then separated by a centrifuge. As a result, the yield of sorbic acid contained in the wet cake and the liquid was 97.1 based on the crude sorbic acid.
%Met. The concentration of sorbic acid in the generated evaporation residue was about 20%. Even during continuous operation for one week, there was no trouble such as blockage, and the operation was successful.

Further, the sorbic acid cake was dried to obtain 1 g of crystals.
When dissolved in 10m of methanol, the color value is 350
The transmittance at a wavelength of μm is 95.0%, and the color value when 1 g of sorbic acid is dissolved in an 8.8 m 1N-NaOH aqueous solution is 9 at a wavelength of 400 μm.
It was 7.5%.

Comparative Example 1. In Example 2, the same operation was performed except that the liquid separation step was omitted. Hard tar was deposited around the evaporator, and the problem of clogging continued. When the operation was continued while cleaning was interrupted each time, the yield of sorbic acid was 94.
Only 0% was obtained. The reason for this is
This was due to the polymerization loss of sorbic acid in the solution and the loss of sorbic acid in the concentrated residue whose amount increased due to sorbic acid polymerization.

The quality was similar to that of Example 2 when the operation was smooth, but the quality when the operation was interrupted and restarted was poor.

Comparative example 2. The same treatment as in Example 1 was carried out except that the liquid separation temperature was maintained at 140 ° C or higher. As a result, the separated lower layer (tar layer)
There was a large amount of hard tar, and continuous sampling was impossible.
Therefore, the operation was interrupted and the tank was cleaned.
At this time, about 0.1 kg / H of solid tar was deposited.

Furthermore, the obtained sorbic acid cake had a light yellow color and the purity after drying was 98.9%. The cake
The crystals were recrystallized from methanol-hydrogen, dried and dried. When 1 g of the sorbic acid thus obtained was dissolved in 10 m of methanol, the color value was 8 at the transmittance at a wavelength of 350 μm.
It was 0.0%, and the color value when 1 g of sorbic acid was dissolved in a 1N-NaOH aqueous solution was 75.5% in terms of transmittance at a wavelength of 400 μm.

[Brief description of drawings]

FIG. 1 shows an example of a ternary liquid-liquid equilibrium diagram for sorbic acid-petroleum-tar.

Claims (1)

[Claims] 1. A method for producing sorbic acid in which a polyester obtained by a reaction of crotonaldehyde and ketene is decomposed with hydrochloric acid to purify crude sorbic acid separated from a reaction solution. 1) In a temperature range of 100 to 140 ° C. Essentially, so that the operating point is maintained within the two-liquid phase separation region (B) in the sorbic acid-petroleum-tar component ternary liquid-liquid equilibrium diagram shown in FIG. 1, 2) crude sorbic acid Is continuously dissolved in petroleum, and the residual water and hydrochloric acid content in the petroleum solution of sorbic acid are evaporated and continued to be separated from the tar content.