JPS61176553A - Method for extracting fatty acid - Google Patents

Abstract

PURPOSE:To extract efficiently a lower fatty acid from a dilute aqueous solution of the lower fatty acid, by using a specific mixed solvent, having a low viscosity, scarcely forming an emulsion, capable of reducing the separation time, and exhibiting a high partition coefficient at a low concentration of the lower fatty acid. CONSTITUTION:A mixed solvent of a straight chain primary alcohol having a higher boiling point than a lower fatty acid, e.g. n-hexanol, and 10-80wt%, based on the straight chain primary alcohol, tertiary amine having a higher boiling point than the lower fatty acid, e.g. trioctylamine, is brought into contact with an aqueous solution containing the 1-3C lower fatty acid, e.g. formic acid, acetic acid or propionic acid, in a low concentration to extract the aimed compound at a high partition coefficient. EFFECT:The solubility in the aqueous phase and the solubility of water in the mixed solvent are low, and the method is advantageous to the energy cost in purification and further to continuous extraction of an aqueous solution of the lower fatty acid in a low concentration such as a fermentation liquor, etc. the number of theoretical plates in extraction can be reduced when an extractor, e.g. mixer-settler type, is used. The construction cost can be saved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for extracting lower fatty acids from an aqueous solution containing lower fatty acids. In particular, the present invention relates to a method for extracting lower fatty acids from a dilute aqueous solution of lower fatty acids obtained through the fermentation industry.

(Prior Art) Currently, in the fermentation industry, research on producing lower fatty acids using microorganisms and the like is widely conducted. Lower fatty acids produced in the fermentation industry are dilute aqueous solutions with a concentration of several percent, and have a high water content, creating considerable difficulties in the distillation purification process in order to obtain pure lower fatty acids. Efficient extraction of lower fatty acids from such aqueous solutions containing small amounts of lower fatty acids can cause drawbacks in the fermentation industry and is an important factor in terms of energy costs.

As a method for extracting lower fatty acids from an aqueous solution, the acid fraction coefficient, which has a large effect on the effectiveness, is lower for lower fatty acids.
In general, since it is small in size, in order to increase extraction efficiency, a large amount of solvent is used, and the partition coefficient for acids, especially acetic acid, is relatively large in the separation process.It is a commonly used extraction solvent because it is easy to obtain. Since the boiling point is low, the solvent used in Oma must be evaporated for a long time, and since a large amount of water is dissolved in the extract, the loss of dissolution in water is large, so the mutual solubility with water is also unsatisfactory. . On the other hand, when a solvent with a boiling point higher than that of a lower fatty acid is used, if a distribution coefficient similar to that of a low-point solvent is obtained, it is not necessary to evaporate the solvent all the time, which is advantageous in terms of energy consumption. For example, trioctylamine is a solvent with a high boiling point, and attempts have been made to extract acetic acid using diisobutylcarbinol as a diluent for trioctylamine.As the concentration of acetic acid decreases, the partition coefficient increases. It is known (Japanese Unexamined Patent Publication No. 56-10131).

(Problem to be solved by the invention) However, the partition coefficient of trioctylamine/DIBC is 1
．． In an extreme case where the viscosity of DISC is not sufficiently high (4.27 in a 77% acetic acid aqueous solution) and the viscosity of DISC is high, the present invention was arrived at as a result of studying combinations of methods to form an emulsion during extraction.

That is, the present invention uses a mixed solvent of a tertiary amine having a higher boiling point than the lower fatty acid and a linear primary alcohol having a higher boiling point than the lower fatty acid in a method for extracting lower fatty acids from an aqueous solution containing lower fatty acids using a mixed solvent. This is a method for extracting lower fatty acids characterized by the following.

The tertiary amine used in the present invention is one that has a higher boiling point than lower fatty acids and forms a non-aqueous phase. In consideration of low solubility in the aqueous phase and separability from lower fatty acids by distillation, those having about 12 to 40 carbon atoms are preferred. Furthermore, in order to obtain a large apparent distribution coefficient, it is desirable to use a tertiary amine that does not have a large branch near the nitrogen atom. Having a substituent larger than the ethyl group not only adjacent to the nitrogen atom but also on the carbon atom separated from the nitrogen atom by CH2 has an adverse effect, and there are cyclic structures close to the nitrogen atom such as the benzyl group. It's not good either.

That is, the partial structure of the tertiary amine is >N-CH2-CR
When represented by R-, R1 should be a hydrogen atom and R2 should be a hydrogen atom or a methyl group. C6 or higher alkyl such as dimethyllaurylamine, dimethylhexadecylamine, methyldi(tridecylamine), dimethyldecylamine trialkylamine with groups, dimethyloleylamine, butylbis(5,5,7.7-tetramethyl-oct-2-en-1-yl)amine (XE-20
Examples include tertiary amines having an alkenyl group such as 4), tertiary amine mixtures such as dimethyl cocoa amine, dimethyl C8-12 alkyl amine, and dimethyl hydrogenated beef tallow amine.

Commercially available tertiary amines can be used as they are, or primary amines and secondary amines can be obtained as intermediates and used as tertiary amines in known alkylation methods.

Various tertiary amines can be used as mentioned above, but trioctylamine is easy to obtain and has an excellent apparent distribution coefficient when used in combination with a linear primary alcohol as an extractant, so this is the most suitable. The inventors mainly used this.

The linear primary alcohol having a boiling point higher than the lower fatty acid used in the present invention includes the lower fatty acid to be extracted.

Preferred lower fatty acids that can be extracted in the present invention are fatty acids having 1 to 3 carbon atoms, specifically formic acid, acetic acid, and propionic acid.

The mixing ratio of tertiary amine and linear primary alcohol can be changed as appropriate depending on the purpose, but too much tertiary amine is disadvantageous in terms of cost and distribution coefficient; If it is too high, it will not be possible to achieve the high distribution coefficient that characterizes the present invention, so it is common to use the tertiary amine in a range of 10 to B□vo+%.

When extracting lower fatty acids from an aqueous solution, the S/F, that is, the ratio of the amount of extractant to the amount of diluted lower fatty acid (1), can take various values depending on the concentration of diluted lower fatty acids. Reflecting the large distribution coefficient that is characteristic of S/F, it is possible to take an extremely small value such as S/F=0.5 to 2, for example. The use of a small amount of extractant in this way is advantageous because it helps reduce the size of the equipment and the utility costs required for operation.

Continuous extractors in the chemical industry include packed columns, perforated plate columns, ring plates, mixer-settler type extractors, etc., and these can be used. Lower fatty acids can be recovered from the extract by conventional means such as distillation.

(Effects of the Invention) By using the mixed solvent of the present invention, lower fatty acids can be extracted into the solvent phase from a low concentration lower fatty acid aqueous solution with an extremely high distribution coefficient. Therefore, it is advantageous for continuous extraction of low concentration aqueous solutions of lower fatty acids such as fermentation liquors. In addition, when a mixer-settler type extractor is used, the number of theoretical extraction plates can be reduced and construction costs can be saved. All solvents have a low viscosity of 10 cps, making it difficult to form an emulsion and shortening separation time. In addition, the linear primary alcohol, which has a higher boiling point than the lower fatty acid used as the diluent in the present invention, has a low solubility in the aqueous phase and also has a low solubility in the water diluent, which is advantageous in terms of energy costs during purification. It is.

(Example) The present invention will be explained below with reference to Examples.

Example 1 A 0.5 to 9 v/v % acetic acid aqueous solution was prepared. Equal amounts of trioctylamine as an organic extractant and n-hexanol as a diluent (50v/50v)
The mixture was used as an organic extractant. Mix acetic acid aqueous solution and organic extractant at a ratio of 1:1 in a 21 ml screw-cap test tube, shake at 30°C for about 2 hours, and then leave at 30°C to separate acetic acid in the aqueous and organic phases. , was analyzed by gas chromatography, and the distribution coefficient was calculated from the following formula.

As shown in the table below, acetic acid could be extracted with a high distribution coefficient of 24.0 using 0.02% acetic acid in the aqueous phase.

Organic phase acetic acid (X) Aqueous phase acetic acid Cz) Partition coefficient (-) 0
．． 48 0.02 24.0 0.95 0.05 19.0 2.79 0.21 13.3 4.43 0.57 7.8 6.11 0.89 6.9 Example 2゜As lower fatty acid Formic acid, propionic acid 0.5-9v
/v%, and extraction was performed in the same manner as in Example 1 using a mixture of trioctylamine and n-hexanol at equal ff1 (50v150V) as an organic extractant. The results are shown in the figure.

As shown in Figures 1 and 2, formic acid and propionic acid could be extracted with high partition coefficients.

[Brief explanation of the drawing]

Figure 1 shows trioctylamine and n-hexanol (50
FIG. 3 is a diagram showing the apparent partition coefficient in formic acid extraction using a mixed solvent of v150v) as a function of the formic acid concentration in the equilibrium aqueous phase. Figure 2 shows trioctylamine and n-hexanol (5
FIG. 2 is a diagram showing the apparent partition coefficient in propionic acid extraction with a mixed solvent of 0v150v) as a function of propionic acid concentration in the equilibrium aqueous phase.

Claims (1)

[Scope of Claims] 1) A method for extracting lower fatty acids from an aqueous solution containing lower fatty acids using a mixed solvent, in which a tertiary amine having a boiling point higher than that of the lower fatty acids and a linear primary alcohol having a higher boiling point than the lower fatty acids; A method for extracting lower fatty acids, characterized by using a mixed solvent of 2) The method for extracting lower fatty acids according to claim 1, wherein the lower fatty acids are fatty acids having 1 to 3 carbon atoms. 3) The method for extracting lower fatty acids according to claims 1 and 2, wherein the linear primary alcohol is n-hexanol, n-heptanol, n-octanol, or n-nonanol.