JPH06234695A - Method for purifying fatty acid - Google Patents

Abstract

PURPOSE:To efficiently separate and purify a high-purity specific fatty acid (stearic acid or palmitic acid) from a fatty acid mixture (e.g. a mixture of the stearic acid with the palmitic acid) forming an intermolecular compound under pressurized conditions. CONSTITUTION:This method is to isolate and purify a specific fatty acid from a mixture of fatty acids forming an intermolecular compound. In the method, the mixture of the fatty acids is pressurized to a pressure region below a pressure in which the intermolecular compound is produced to form a crystal of the specific fatty acid. The pressure is then reduced to make a part of the crystal remain as a seed crystal and melt the remainder. The seed crystal is subsequently grown under pressurization and separated from the mother liquor.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for efficiently isolating and purifying a specific fatty acid from a mixture of fatty acids forming an intermolecular compound by utilizing a pressure crystallization method.
And this method can be effectively utilized, for example, as a method for isolating and purifying stearic acid from a mixture of stearic acid and palmitic acid or a method for isolating and purifying stearic acid from a mixture of stearic acid and margaric acid.
In the present specification, a case where stearic acid is isolated and purified from a fatty acid mixture will be representatively described.

[0002]

2. Description of the Related Art Needs for high purification of fatty acids such as stearic acid have been rapidly increasing recently for the development of new applications in the fields of medicine, biochemicals, fragrances, cosmetics and the like. As a refining method of fatty acids such as stearic acid, a cooling crystallization method, an adsorption method, a chromatography method and the like, which utilize a change in solubility with temperature, are used. Among them, the cooling crystallization method has an advantage that a large amount of treatment is possible and the refining cost is low, but on the other hand, it is difficult to obtain a high-purity substance of about 90% or more, and it is possible to satisfy the demand of consumers in terms of purity. Can not. On the other hand, the adsorption method and the chromatographic method can easily achieve high purity of 98 to 99% or more, but on the other hand, in terms of processing capacity, large-scale processing is difficult and the processing cost becomes very expensive. From such a point, the development of refining technology that meets the requirements in terms of purity, processing capacity, and cost is awaited.

[0003]

The present invention has been made in view of the above circumstances, and its object is to obtain a specific fatty acid with high purity from a fatty acid mixture containing two or more fatty acids. It is intended to establish a technique that enables efficient isolation and purification.

[0004]

The method for purifying a fatty acid according to the present invention, which has been able to solve the above-mentioned problems, is a method for isolating and purifying a specific fatty acid from a mixture of fatty acids forming an intermolecular compound. After the fatty acid mixture is pressurized to a pressure region below the pressure at which the intermolecular compound is generated to form crystals of the specific fatty acid, and then the pressure is reduced to leave a part of the crystals as seed crystals and melt the rest. The method is characterized in that the seed crystal is grown under pressure and then separated from the mother liquor, and this method comprises, for example, isolating and purifying stearic acid and / or palmitic acid from a mixture of stearic acid and palmitic acid. Similarly, it can be effectively utilized as a method for isolating and purifying stearic acid and / or palmitic acid from a mixture of stearic acid and margaric acid.

[0005]

The present inventors have been conducting research on a separation and purification method utilizing the pressure crystallization method for some time, and as a part thereof, the possibility of isolating and purifying a specific fatty acid using the pressure crystallization method. I have been pursuing.

However, when the fatty acids are to be purified by a crystallization method, the fatty acids have extremely fine crystals that are difficult to completely separate from the mother liquor. It was found that there was a tendency to form a solid solution and appearance of crystalline polymorphs, which became a major obstacle to achieving high-purity purification.

[0007] Among the above tendencies, if two kinds of fatty acids are crystallized as intermolecular compounds in the crystallization step, isolation and purification as specific fatty acids becomes impossible. For example, FIG. 1 shows a melting curve having a pressure when a mixture of stearic acid and palmitic acid is pressurized at 345 K (72 ° C.) as a parameter, and the lower side of the curve is the liquid phase and the upper side is the solid phase. Represents a phase. As is clear from this figure, curve A,
In the melting curves shown by B and C, peaks (eutectic points) appear at two points of the stearic acid / palmitic acid content ratios of 30/70 and 50/50, and the same content ratio is 30/70 to 50 /.
It can be confirmed that an intermolecular compound is generated in the region of 50. This tendency is in agreement with the tendency of the melting curve of the stearic acid / palmitic acid mixture under normal pressure shown in FIG.

Therefore, for example, when the pressure of the fatty acid mixture (liquid substance) having the content ratio (for example, point X in FIG. 1) for forming the intermolecular compound is increased, crystals are precipitated when the pressure reaches the curve B. First, since the curve B is the intermolecular compound generation region, all the crystallized substances are intermolecular compounds, and the specific fatty acid (for example, stearic acid) cannot be isolated.

On the other hand, a fatty acid mixture (liquid substance) having a mixing ratio (for example, point Y in FIG. 1) outside the intermolecular compound formation region.
As the pressure is increased, when the pressure reaches the curve C, precipitation starts to occur. The crystals produced at this time were only stearic acid, but when the pressure was further increased, the stearic acid concentration in the mother liquor decreased along the curve C as much as stearic acid crystallized, and the crystallization pressure was increased. When the E ₁ point is reached, intermolecular compounds start to crystallize. Therefore, the crystallized substance is a mixture of intermolecular compounds, and the purity of stearic acid cannot be sufficiently increased.

However, the present inventors confirmed the following facts while advancing the pressure crystallization experiment by changing the operating temperature variously. That is, the intermolecular compound formation region in the pressure melting curve of the stearic acid / palmitic acid mixture tends to vary depending on the operating temperature. For example, as shown in FIG.
At 45 (72 ° C.), as shown in FIG. 1, the stearic acid / palmitic acid ratio is in the intermolecular compound formation region between 30/70 and 50/50, but as the operating temperature is increased, the formation region becomes When the operating temperature becomes 85 ° C or higher, the intermolecular compound formation region (curve B) almost disappears,
It was confirmed that when the stearic acid / palmitic acid ratio was about 40/60, only one eutectic point (pressure: about 1500 kgf / cm ² ) was exhibited.

Therefore, if such a phenomenon is utilized, temperature conditions that do not form an intermolecular compound are adopted, and pressure is raised at a pressure outside the eutectic point, stearic acid and / or palmitic acid can be isolated and purified successfully. Conceivable. In fact, when a fatty acid mixture consisting of stearic acid / palmitic acid is pressure-crystallized under a temperature condition of 85 ° C. or higher, the formation of intermolecular compound is not observed, and therefore, by adopting a raw material composition and a pressure condition that deviate from the eutectic crystal, It becomes possible to isolate and purify stearic acid (or palmitic acid) with high purity.

However, it is necessary to raise the operating temperature to 85 ° C. or higher in order to completely eliminate the intermolecular compound forming region.
Along with this, the crystallization pressure must be increased to about 1500 kgf / cm ² or more, so a high pressure equipment is required. Moreover, the purity of stearic acid (or palmitic acid) was expected because it will crystallize as a eutectic with palmitic acid (or stearic acid) when the pressure exceeds normal pressure and exceeds the eutectic pressure. It does not rise as much. In this case, if you perform decompression / perspiration treatment in the final step of squeezing,
The purity of stearic acid is considerably increased, but a considerable amount of stearic acid (or palmitic acid) is eluted during the perspiration process, and the recovery rate is significantly reduced.

Therefore, it is considered that the crystallized stearic acid (or palmitic acid) can be recovered in high yield as a high-purity product without producing an intermolecular compound even at a relatively low operating pressure. I proceeded with my research.
As a result, a fatty acid mixture having a raw material composition that is out of the intermolecular compound formation region is used under the pressure crystallization temperature conditions adopted,
This is pressurized to a pressure region lower than the pressure generated by the intermolecular compound to generate crystals of stearic acid (or palmitic acid), and then the pressure is reduced to leave a part of the crystals as seed crystals and leave the remaining crystals. It was confirmed that stearic acid (or palmitic acid) can be efficiently recovered with high purity by adopting a method in which after melting, the seed crystal is grown under pressure and then separated from the mother liquor.

The separation and purification method will be described below with reference to FIG. Pressure crystallization at 72 ° C as described above
In the case of using a mixture of stearic acid / palmitic acid in the intermolecular compound formation region (for example, point W in FIG. 3) having a mixed composition of stearic acid / palmitic acid in the range of 30/70 to 50/50, the pressure crystallization step is performed. The stearic acid (or palmitic acid) cannot be isolated because the crystals that initially form themselves crystallize out as intermolecular compounds. Therefore, in carrying out the present invention, it is essential to use a fatty acid mixture having a mixed composition of stearic acid / palmitic acid that falls outside the above-mentioned intermolecular compound formation region as a raw material, depending on the operating temperature to be adopted.

However, this intermolecular compound formation region gradually narrows as the operating temperature is raised as described above, and completely disappears when the operating pressure is raised to 85 ° C. or higher. It suffices to select the operating temperature so as to be out of the inter-compound formation region.

Now, the case where the operating pressure is set to 72 ° C. and the mixture of stearic acid / palmitic acid = 80/20 is pressure-crystallized will be described. When the fatty acid mixture (liquid material) of the raw material composition Z is pressurized, When the pressure reaches the curve C, crystals of stearic acid start to be generated, and when the pressure is further increased, the crystals gradually increase and the concentration of stearic acid in the mother liquor decreases along the curve C. If the pressurization is further continued, the amount of stearic acid deposited will increase and the concentration of stearic acid in the mother liquor will further decrease, gradually approaching the intermolecular compound formation region. When the operating pressure rises to the intersection E ₁ with the curve B (about 600 kgf / cm ² ), the intermolecular compound crystallizes at that point, so in the present invention, the pressure required to reach this pressure (eg P point). ) To stop boosting.

The crystals that have crystallized at this point consist of stearic acid only, but the crystals are extremely fine, and complete solid-liquid separation by pressing or the like is difficult. Therefore, in the present invention, the pressure at point P is temporarily reduced (for example, Q
Then, a part of the produced stearic acid crystal is left as a seed crystal to melt the rest, and then the pressure is maintained or an arbitrary pressure lower than the intermolecular compound crystallization pressure. Then, without newly forming fine crystals, stearic acid gradually forms and grows around the small amount of seed crystals remaining at the time of pressurization, and coarse crystals of stearic acid are obtained. Therefore, if this is subjected to solid-liquid separation while maintaining the applied pressure, the amount of mother liquor adhered can be almost eliminated only by melting a very small part of the surface of the coarse crystal by pressing and sweating.
High-purity stearic acid can be obtained in high yield.

In the above description, the case of performing pressure crystallization at 72 ° C. has been explained. However, the intermolecular compound formation region changes depending on the temperature, and at the temperature of 85 ° C. only the eutectic crystal is formed and the intermolecular compound is formed. As described above, it is possible to obtain high-purity stearic acid in a high yield by appropriately selecting the processing temperature and pressure conditions according to the raw material composition. Becomes

In the above description, the case of separating and purifying high-purity stearic acid from the stearic acid / palmitic acid mixture has been described, but the separation and purification of palmitic acid can be carried out in the same manner. Further, the present invention is to obtain a high-purity product by performing pressure crystallization under conditions of temperature and pressure such that intermolecular compound crystals are not produced from a fatty acid mixture capable of producing intermolecular compounds, and by producing coarse crystals. Therefore, the present invention is not limited to the isolation and purification of stearic acid or palmitic acid from a stearic acid / palmitic acid mixture as exemplified above, but is also possible under pressure crystallization conditions such as a stearic acid / margaric acid mixture. A mixture of fatty acids that may form an intermolecular compound can be utilized for isolation and purification of a specific fatty acid from any fatty acid mixture.

When the mixed composition of the fatty acid mixture as a raw material is close to the intermolecular compound formation region or the eutectic composition, the pressure crystallization method of the present invention may not be able to increase the yield. In such a case, the concentration of the specific fatty acid may be increased by other means such as cooling crystallization, extraction, and fractional distillation, and then applied to the purification method of the present invention.

[0021]

EXAMPLES Examples of the present invention will be shown below. However, the present invention is not limited by the following examples, and may be modified within a range that is compatible with the gist of the above and the following. Yes, all of them are included in the technical scope of the present invention.

Example 1 Starting from 20 g of a fatty acid mixture of stearic acid / palmitic acid = 88/12 (mol%), the operating temperature was set to 72 ° C., and the mixture was pressurized to 600 kgf / cm ² and then 30
The pressure was reduced to 0 kgf / cm ² . As a result, most of the fine crystals generated during pressurization were redissolved and a small amount of crystals remained. Next, pressurize to 500 kgf / cm ² at the same temperature and hold for 10 minutes to grow crystals, and 500 kgf / cm ² to 200 kgf / cm ²
98% purity when the mother liquor is squeezed off while depressurizing to ²
Stearic acid was obtained with a yield of 20%.

Example 2 Starting from 20 g of a fatty acid mixture of stearic acid / palmitic acid = 93/17 (mol%), the operating temperature was set to 80 ° C. and the pressure of this mixture was raised to 1000 kgf / cm ² , and then 65
The pressure was reduced to 0 kgf / cm ² . Next, after holding the same temperature and the same pressure for 10 minutes, the mother liquor was removed by squeezing to obtain stearic acid having a purity of 98% with a yield of 22%.

[0024]

EFFECTS OF THE INVENTION The present invention is constituted as described above, and a specific fatty acid can be efficiently recovered with high purity from a fatty acid mixture which has been difficult to isolate and purify with high purity due to the formation of intermolecular compounds. I got it.

[Brief description of drawings]

1 is a diagram showing a melting curve with a pressure as a parameter in a stearic acid / palmitic acid mixture.

FIG. 2 is a diagram showing a melting curve of a stearic acid / palmitic acid mixture under normal pressure.

FIG. 3 is an explanatory diagram illustrating the purification method according to the present invention along a melting curve during pressure crystallization.

Claims (3)

[Claims] 1. A method for isolating and purifying a specific fatty acid from a mixture of fatty acids forming an intermolecular compound, which comprises pressurizing the mixture of fatty acids to a pressure region lower than the pressure at which the intermolecular compound is produced, After forming a crystal, and then lowering the pressure to leave a part of the crystal as a seed crystal and melting the rest, the seed crystal is grown under pressure and then separated from the mother liquor. Purification method. 2. The refining method according to claim 1, wherein a fatty acid mixture having a raw material composition that is out of the intermolecular compound formation region is used under the pressure crystallization operating temperature conditions. 3. The purification method according to claim 1, wherein the fatty acid mixture is a mixture of stearic acid and / or palmitic acid, and stearic acid and / or palmitic acid is isolated and purified from the fatty acid mixture.