JPH0132880B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for refining fatty acids, and more specifically, to refining crude fatty acids obtained by hydrolyzing fats and oils, or solid acids or liquid acids obtained by fractionating these fatty acids. This invention relates to a method for obtaining highly purified fatty acids with good hue.

The main impurities contained in crude fatty acids are:
They are undecomposed glycerides (mainly di- and monoglycerides), oxygenated compounds (oxidation products containing hydroxyl and carbonyl groups), nitrogen and sulfur compounds derived from proteins, and phosphorus compounds derived from phospholipids.

The distillation method that has been commonly used to purify such crude fatty acids removes impurities based on the difference in boiling point with the fatty acids, and this method produces products with good color and relatively high purity. Fatty acids can be obtained. However, as the energy costs required for distillation operations have increased in recent years, improvements in terms of cost have been desired, and since there has been a problem of deterioration of fatty acids due to thermal denaturation during distillation, a solution to this problem is also desired.

For a long time, methods for refining fatty acids as an alternative to distillation have been studied and many proposals have been made. However, no method has so far been found that achieves the same purification effect as the distillation method using a single method, and most of the methods lack industrial practicality. For example, there is a method in which crude fatty acids are brought into contact with a solid adsorbent such as silicic acid gel or activated clay, and impurities are adsorbed and removed by this adsorbent. This method utilizes the difference in polarity between fatty acids and impurities to adsorb and remove highly polar impurities with a solid adsorbent, but a large amount of organic solvent is required for the adsorption process, and the However, it consumes a large amount of thermal energy and is dangerous in handling the solvent, so it is extremely impractical for industrial use.

In other words, in general, when removing impurities using solid adsorbents such as silicic acid gel, activated clay, molecular sieves, and ion exchange resins, the removal effect greatly depends on the movement speed of the adsorbed molecules. If it is not large, a sufficient removal effect cannot be obtained. The rate of migration is related to the viscosity of the system; for example, a fairly low viscosity of less than about 1-2 centipoise at the adsorption treatment temperature will provide sufficient migration rate to enhance the removal effect.

On the other hand, crude fatty acids are usually solid or liquid at around 10 to 30 centipoise at room temperature (25°C), so
In order to increase the transfer rate of the impurities contained in this and increase the adsorption removal effect, it is necessary to reduce the viscosity of the system to the above-mentioned level by heating it to 100°C or higher or by dissolving or diluting it with an organic solvent. It won't happen. However, the former heating method tends to cause desorption of impurities, which are adsorbed substances, from the solid adsorbent, and also causes problems such as deterioration of fatty acids due to catalytic reactions of the adsorbent.
It is not appropriate to adopt this method. In the end, the latter method of diluting the organic solvent has to be adopted, and in this case a considerably large amount of organic solvent is required, giving rise to the above-mentioned problem.

Moreover, according to the findings of the inventors, it was difficult to obtain highly pure fatty acids even if such an organic solvent dilution method was used. For example, when crude fatty acids are diluted 10 times with n-hexane and passed through a silicic acid gel column, highly polar impurities are adsorbed and removed, but less polar impurities such as undecomposed glycerides remain. Although the color of the purified fatty acids obtained is relatively good, the purity of the fatty acids expressed as (neutralization value / saponification value) × 100 (%) is less than 99.0%, and the purification process is comparable to that of distillation. It was not possible to obtain fatty acids.

From the above point of view, the present invention aims to obtain a purification effect equivalent to or better than that of a distillation method using another single method, without using any organic solvents, which are indispensable for purification methods using solid adsorbents. The object of the present invention is to provide an industrially useful method for refining fatty acids that does not cause the problems of thermal energy and thermal deterioration that occur in distillation methods.

That is, the present invention provides (a) adding a crude fatty acid to an aqueous solution of urea or thiourea containing an anionic surfactant or a nonionic surfactant with an HLB of 10 or more to form a urea adduct or thiourea adduct of a fatty acid. (b) After separating the adduct, washing with a saturated aqueous solution of urea or thiourea containing an anionic surfactant or a nonionic surfactant with an HLB of 10 or more; and (c) a step of decomposing the washed adduct to regenerate the fatty acid.

In this way, the present invention takes advantage of the property of fatty acids and urea or thiourea to form adducts, generates adducts from crude fatty acids, and then separates them to remove impurities that do not participate in adduct formation. This method uses a method of decomposing separated adducts to regenerate fatty acids. This method avoids the problems of thermal energy and thermal deterioration that occur in distillation methods, and allows highly advanced production by a single method of adduct generation. It becomes possible to obtain the purification effect of Furthermore, since the adduct is produced in an aqueous solution of urea or thiourea, problems caused by organic solvents, which are considered inevitable in purification using the solid adsorbent, do not occur.

Incidentally, a method for purifying fatty acids that utilizes the production of adducts between fatty acids and urea or thiourea is already known. In this method, crude fatty acids and urea or thiourea are heated and dissolved in an organic solvent and then cooled, and the adducts that precipitate out during this cooling are separated from the organic solvent solution and decomposed and regenerated. As is clear, such methods involve the use of large amounts of organic solvents and therefore suffer from the same problems as when using solid adsorbents.

On the other hand, in this invention, an adduct of fatty acid and urea or thiourea is produced in water, and in this point, there is an essential difference from the above-mentioned known method. On the other hand, such production in water has difficulties in separating the produced adduct and impurities. That is, in an organic solvent system, since impurities are dissolved in the organic solvent, it is easy to separate the precipitated adduct from the impurities. However, in aqueous systems, fatty acids and impurities are both dispersed in water, and adducts are formed under such conditions. Therefore, it is not easy to separate these adducts from impurities; Impurities cannot be avoided.

The inventors have discovered that the above problem can be solved by adding a surfactant to an aqueous solution of urea or thiourea. That is, if an adduct is produced with the crude fatty acid sufficiently emulsified and dispersed by a surfactant, entanglement between the adduct and impurities can be prevented as much as possible. In addition, by washing the adduct separated from water with impurities inhibited in this way with a saturated solution of urea or thiourea containing the same surfactant as above, impurities adhering to the surface of the adduct can be removed. It has been found that substantially all of the impurities can be removed, thereby making it possible to substantially separate the impurities.

In other words, the fatty acids separated and regenerated from the adducts from which impurities have been removed by the above method are completely comparable in properties to those obtained by distillation, have good color, and are highly pure products with a purity of 99.0% by weight or more. , can be advantageously used industrially as a purified fatty acid.

In step a in this invention, first, an aqueous solution of urea or thiourea containing a surfactant is prepared. This aqueous solution is heated to a predetermined temperature, for example, about 50 to 80°C, and as much urea or thiourea as can be dissolved at this temperature is added. Generally 30~
It is about 80% by weight. In addition, the surfactant to be included may be one that does not have reactivity with crude fatty acids, and is usually a nonionic surfactant with an HLB of 10 or higher, or an anionic surfactant of the sulfate or sulfonate type. Activators are preferably used. The content of surfactant is usually 0.2 to 5% by weight,
It is preferably 0.5 to 2.0% by weight.

The crude fatty acid, preferably heated to the same temperature or close to it, is added to the above-mentioned heated aqueous solution and mixed with stirring. The amount of crude fatty acid added is usually 5 to 20% by weight, preferably 8 to 10% by weight based on the aqueous solution. After the addition, when the mixture is gradually cooled to a predetermined temperature while stirring, urea or thiourea reaches a saturated solubility and precipitates, at the same time forming an adduct with the fatty acid dispersed in water to form a slurry. At this time, the surfactant contained in the water effectively prevents impurities from being mixed into the adduct.

In step b of the present invention, the adduct produced above is separated and then washed with a saturated aqueous solution of urea or thiourea containing a surfactant. This washing is repeated several times as necessary to remove impurities adhering to the surface of the adduct. The use of a surfactant is essential for removing the above-mentioned impurities, and without its use no cleaning effect can be obtained. The type and content of the surfactant are the same as in step a above.
Note that the reason why the washing liquid used in step b is a saturated aqueous solution of urea or thiourea is to prevent destruction of the adduct.

Next, in step c, the adduct washed as described above is decomposed by heating to an appropriate temperature, for example, about 60°C, to regenerate fatty acids and separate urea or thiourea. By washing the regenerated and separated fatty acids with hot water at about 60 to 80°C and dehydrating them, a purified fatty acid product with the desired color and high purity can be obtained.

Next, examples of the present invention will be described in more detail. In the following, parts and % mean parts by weight and % by weight. In addition, the hues described below are based on standard oil and fat analysis test methods 4.3.1.1 (Gardner method) and 4.3.1.2 (APHA method) established by the Japan Oil Chemists' Association.
method).

Example 1 Neutralization value 196.4, saponification value 201.2, fatty acid purity 97.6
%, Hue Gardner 11 Beef Tallow Hydrolyzed Crude Fatty Acid
100 parts were heated to 60°C and added with stirring to 1000 parts of an aqueous urea solution (containing 61% urea) containing 1% sodium dodecyl sulfate, which had also been heated to 60°C. After the addition was completed, the mixture was cooled to 25° C. over 1.5 hours while stirring was continued. At this point, the inside of the system became a slurry containing urea adducts of fatty acids.

After the urea adduct was separated, it was poured into 250 parts of a saturated aqueous solution of urea at 25°C containing 1% sodium dodecyl sulfate, stirred at 25°C for 30 minutes, and then separated. This operation was repeated again to thoroughly wash. Next, the adduct was heated to 60°C to regenerate fatty acids, separated from urea, and then washed with hot water at 70°C. The dehydration treatment yielded 93.6 parts of purified fatty acids. This fatty acid had a neutralization value of 201.8, a saponification value of 202.3, a fatty acid purity of 99.8%, and a hue of APHA 140 (Gardner 1).

In addition, when the above crude fatty acid is distilled by the usual method,
93.9 parts of purified fatty acid was obtained, and its characteristics were a neutralization value of 202.2, a saponification value of 203.0, a fatty acid purity of 99.6%, and a hue of APHA 160.

Reference Example 1 A fatty acid was obtained in the same manner as in Example 1, except that sodium dodecyl sulfate was not contained in the urea aqueous solution used for adduct production. The hue of this fatty acid was Gardner 6. This shows that the use of a surfactant in the adduct formation step is essential in this invention.

Example 2 Neutralization value 191.2, saponification value 200.8, fatty acid purity 95.2
%, Hue: 100 parts of crude liquid acid obtained by solid-liquid separation of beef tallow hydrolyzed crude fatty acid of Gardner 18 was heated to 55℃,
1.5% polyoxyethylene (20
molar addition) octyl phenyl ether (HLB=
16) Aqueous urea solution (containing 65% urea) 850
was added to the solution while stirring. Thereafter, in the same manner as in Example 1, 90.6 parts of purified liquid acid was obtained. However, the surfactant included in the urea saturated aqueous solution for cleaning is 1.5% polyoxyethylene (20 moles added).
It is octyl phenyl ether (HLB=16).
This liquid acid has a neutralization value of 202.0, a saponification value of 202.3, a fatty acid purity of 99.9%, and a hue of APHA 200 (Gardner 1 to
2) It was.

In addition, when the above crude liquid acid is distilled by the usual method,
90.8 parts of purified liquid acid was obtained, and its properties were a neutralization value of 202.4, a saponification value of 203.5, a fatty acid purity of 99.5%, and a hue of APHA 250.

Reference example Except for not washing with a urea saturated aqueous solution containing a surfactant after separating the adduct,
97.4 parts of fatty acid were obtained in the same manner as in Example 2. This fatty acid had a neutralization value of 193.3, a saponification value of 201.2, a fatty acid purity of 96.1%, and a hue of Gardner 12. This shows that washing with a saturated aqueous urea solution containing a surfactant after producing the adduct is essential in the present invention.

Example 3 Neutralization value 192.5, saponification value 196.7, fatty acid purity 97.9
%, Hue Gardner 8, 100 parts of hydrolyzed crude fatty acids in high oleic horsetail flower oil were heated to 60°C, and a urea aqueous solution containing 0.5% sodium dodecylbenzenesulfonate (urea 61% (containing 61%) was added with stirring.
Thereafter, in the same manner as in Example 1, 92.6 parts of purified fatty acid was obtained. However, the surfactant included in the urea saturated aqueous solution for cleaning is 0.5% sodium dodecylbenzenesulfonate. The obtained purified fatty acid had a neutralization value of 193.1, a saponification value of 194.9, a fatty acid purity of 99.1%, and a hue of APHA 180 (Gardner 1).

In addition, when the above crude fatty acid is distilled by the usual method,
92.9 parts of purified fatty acid was obtained, and its characteristics were a neutralization value of 193.9, a saponification value of 195.3, a fatty acid purity of 99.3%, and a hue of APHA 200.

Example 4 Neutralization value 197.0, saponification value 200.2, fatty acid purity 98.4
%, Hue Gardner 10 pork fat hydrolyzed crude fatty acids
100 parts were heated to 60°C and added with stirring to 1000 parts of a thiourea aqueous solution (containing 35% thiourea) containing 1% sodium dodecyl sulfate, which had also been heated to 60°C. Thereafter, in the same manner as in Example 1, 93.2 parts of purified fatty acid was obtained. However, as a washing solution for the separated adduct, a saturated aqueous solution of thiourea containing 1% sodium dodecyl sulfate at 25° C. was used. The obtained purified fatty acids have a neutralization value
201.1, saponification value 201.9, fatty acid purity 99.6%, hue
It was APHA130 (Gardner 1).

In addition, when the above crude fatty acid is distilled by the usual method,
93.8 parts of purified fatty acid was obtained, and its characteristics were a neutralization value of 200.7, a saponification value of 201.5, a fatty acid purity of 99.6%, and a hue of APHA 130.

Claims (1)

[Scope of Claims] 1 (a) A crude fatty acid is added to an aqueous solution of urea or thiourea containing an anionic surfactant or a nonionic surfactant with an HLB of 10 or more to produce a urea adduct of fatty acid or thiourea. (b) a step of separating the adduct and washing it with a saturated aqueous solution of urea or thiourea containing an anionic surfactant or a nonionic surfactant with an HLB of 10 or more; and (c) a step of decomposing the washed adduct to regenerate the fatty acid.