JPH059149A - Method for recovering high-purity organic acid - Google Patents

Abstract

PURPOSE:To inexpensively and effectively recover a high-purity organic acid from a crude organic acid in high yield by a simple process. CONSTITUTION:A crude organic acid is extracted by using an organic solvent such as methanol, ethanol or acetone to give an extract of organic solvent containing an organic acid. Then the extract is mixed with a high pressure gas of about 0-80C, preferably having hydrophobic property and low polar property and kept to critical pressure or below, preferably at 1-150kg/cm2. Impurities having solubility lower than that of organic acid, such as proteins, amino acids or saccharides, are deposited and separated to provide an organic acid whose purity is far higher than that of the crude organic acid (e.g. 90% high purity). This method has advantages enabling cost down in producing the high-purity organic acid, because a reagent such as calcium hydroxide or sulfuric acid is not used and capable of reducing waste and miniaturizing equipment and, simultaneously, continuously recovering a large amount of an organic acid in a short time.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for recovering highly pure organic acids.

[0002]

2. Description of the Related Art As a method for separating and purifying an organic acid from a crude organic acid containing citric acid as a main component produced by a fermentation method, there are the following conventional methods. That is, a metal hydroxide (eg, calcium hydroxide) is added to an organic acid aqueous solution obtained by extracting fermented koji with warm water to precipitate a metal salt of an organic acid (eg, calcium salt), and then filtered to remove the organic acid. To obtain a metal salt of. Next, after suspending the metal salt of this organic acid in water, adding sulfuric acid to obtain a precipitate of the free organic acid and the metal sulfate (for example, calcium sulfate), and then filtering to remove the free organic acid. A filtrate containing is obtained. Next, this filtrate is subjected to ion exchange treatment and activated carbon treatment, then concentrated, recrystallized several times, and dried to recover an organic acid. However, this prior art method (a) requires a large amount of reagents such as calcium hydroxide and sulfuric acid, (b) the process is complicated and requires a long time, (c) batch treatment, column treatment However, there is a problem that continuous operation is not possible, and as a result, high cost cannot be avoided when recovering the organic acid, and a large amount of continuous treatment is impossible.

[0003]

OBJECTS OF THE INVENTION It is therefore an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a method capable of efficiently recovering a highly pure organic acid from a crude organic acid at low cost.

[0004]

To achieve the above object, a method for recovering a high-purity organic acid according to the present invention is a method of extracting a crude organic acid with an organic solvent to obtain an organic solvent extract containing the organic acid. It is characterized in that the organic solvent extract is obtained and then mixed with a high-pressure gas to precipitate and separate impurities to obtain a high-purity organic acid-containing solution, and then the organic acid is separated from the solution.

The present invention will be described in detail below. In the method for recovering a high-purity organic acid of the present invention, the crude organic acid used as a starting material means a mixture containing the organic acid to be recovered, and specific examples thereof include starch meal, molasses, etc. Fermented koji (hereinafter referred to as crude organic acid (a)) obtained by solid-culturing in the presence of a microorganism of the genus Mold; an organic acid aqueous solution obtained by subjecting this crude organic acid (a) to hot water extraction (hereinafter referred to as crude organic acid) (B)); a culture solution (hereinafter referred to as a crude organic acid (c)) obtained by liquid-culturing the above starch meal, molasses and the like in the presence of a known microorganism of the genus Mold. These crude organic acids (a), (b) and (c) usually contain 0.5 to 50 wt% of organic acid. The organic acid has 3 to 3 carbon atoms.
There may be mentioned 20 carboxylic acids, especially citric acid, malic acid, lactic acid and the like.

In the crude organic acids (a), (b) and (c), water is about 65 wt% and about 80 wt, respectively, as an example.
%, About 80 wt%, but water has a great influence on the organic solvent extraction process and the high-pressure gas mixing process adopted in the method for recovering a high-purity organic acid according to the present invention.
That is, when the amount of water is small, an extract liquid with a small amount of impurities can be obtained by the organic solvent extraction treatment, and the gas mixture amount during the high pressure gas mixture treatment is small, and the treatment can be performed at a low pressure.
Therefore, it is preferable to reduce the water content in advance.

As the drying or concentrating method for reducing the water content, any conventionally known drying or concentrating method can be used, but it is preferable to use the drying or concentrating method under reduced pressure or vacuum. Drying or concentration at a temperature of higher than 100 ° C. is not desirable because the organic acid may cause side reactions with impurities, and a temperature of about 40 to 80 ° C. is preferable. By this drying or concentration treatment, the crude organic acid (a) (fermented koji) has a water content of about 3 to 30 wt%, the crude organic acid (b) (organic acid aqueous solution) and the crude organic acid (c) (culture solution). Then, it is preferable to dehydrate to a water content of about 3 to 40 wt%.

An organic acid mixture obtained by a synthetic method may be used as the crude organic acid. The high-purity organic acid recovery method of the present invention uses the above-mentioned crude organic acid as a starting material,
This crude organic acid is subjected to extraction treatment using an organic solvent to obtain an organic solvent extract containing the organic acid, and then the organic solvent extract is mixed with a high pressure gas to precipitate and separate impurities to obtain a high purity organic acid. It is characterized in that an acid-containing solution is obtained and then the organic acid is separated from this solution.

Therefore, first, the extraction process using an organic solvent will be described. In this extraction treatment, an organic solvent is added to the crude organic acid, and the organic acid is extracted at, for example, 20 to 40 ° C. As the organic solvent, methanol, ethanol,
One or more of alcohols such as propanol, isopropanol and butanol, ketones such as acetone and methyl ethyl ketone, and ethers such as diethyl ether and petroleum ether can be used. Methanol, ethanol, and acetone are suitable because they are easy to use. The amount used is preferably 2 to 20 times the amount of the crude organic acid after dehydration (drying or concentration). The amount of the organic solvent used varies depending on the water content of the crude organic acid after drying or concentration. That is, the water content in the organic solvent extract is adjusted to 0.5 to 20%, preferably about 3 to 15%.

In this extraction operation, an organic solvent is added and mixed, and impurities (sugars, proteins) are separated as a precipitate, so that a residence time or a standing time of about 0.5 to 3.0 hours is required. Is. After the extraction process using this organic solvent,
Impurity precipitation is filtered by a conventional method to obtain an organic solvent extract containing an organic acid.

An example of the composition of the resulting organic solvent extract is about 2% to about 35% solids containing an organic acid as a main component.
%, Water content is about 0.5% to about 20%, and the balance is mainly an organic solvent, and the above solid content is dissolved and present in the extract. However, since the extract contains a large amount of saccharides mainly composed of monosaccharides, disaccharides and trisaccharides as impurities, the purity (content) of the organic acid in the solid content is about 60% to about 90%. It is only%.

Therefore, a purification step is required to increase the purity of the organic acid. According to the present invention, impurities are precipitated by mixing the organic solvent extract with a high pressure gas as the purification step. Separation to obtain a high-purity organic acid-containing solution, and then the step of separating the organic acid from this solution is carried out.

The high-pressure gas mixed with the organic solvent extract is preferably a high-pressure gas that is hydrophobic and has a low polarity and has a critical pressure or less, such as CO ₂ , ethylene, propylene and N _2.
High pressure gases such as O (laughing gas) and fluoromethane (CFC) can be used. Alternatively, a high pressure gas near the critical point may be used. When the above-mentioned hydrophobic and low-polarity organic solvent extract is mixed with high-pressure gas at a critical pressure or lower, the organic solvent in the extract becomes a poor solvent due to dissolution of the high-pressure gas in the extract, and as a result, the organic solvent becomes On the other hand, impurities such as proteins, amino acids, and sugars, which have lower solubility than organic acids, are deposited. This mixing is preferably carried out, for example, in a mixing tank, and suitable mixing conditions are a temperature of about 0 to 80 ° C.
The pressure is about 1 to 150 kg / cm ² G, which is lower than the critical pressure. That is, the pressure used in the present invention does not require a pressure of 150 kg / cm ² G or more, which is usually used in supercritical fluid extraction, and the gas necessary for causing the precipitation of impurities is dissolved in the organic solvent extraction liquid. The pressure required for is sufficient. For example, in the case of CO _2, a pressure sufficient to dissolve 0.1 to 50 wt% CO ₂ gas in the organic solvent extract,
That is, it is sufficient to apply 5 to 70 kg / cm ² G. The weight ratio of the high-pressure gas to the organic solvent extract liquid is preferably about 0.1 to 5 for the former one. The precipitation of impurities is also affected by the concentration of impurities in the extract and the content of water in the extract, and the higher the concentration of impurities and the lower the content of water, the lower the precipitation of impurities at low pressure. Be started.

Next, the mixture in which the impurities are precipitated is sent to a stationary tank and allowed to stay under gas pressure for about 3 to 60 minutes to precipitate the precipitated impurities and obtain a supernatant. This supernatant is a solution of a high-purity organic acid dissolved in an organic solvent.
Also, the used gas is discharged from the upper part of the stationary tank and is recycled for use if necessary.

The supernatant thus obtained, which is composed of the high-purity organic acid-containing solution, is returned to atmospheric pressure and, if necessary, after decolorization using, for example, a column packed with activated carbon,
The organic acid is crystallized by a conventional method, and the obtained organic acid crystal is dried by a conventional method to obtain a high-purity organic acid which is a target substance in the method of the present invention. The purity of the obtained organic acid varies depending on the purity (content) of the organic acid in the crude organic acid used as the starting material, but in any case, it is much higher than the purity (content) of the organic acid in the crude organic acid. Is a high value,
For example, 90% or more of high-purity organic acid can be obtained.

According to the method of the present invention in which the organic solvent extraction process and the high pressure gas mixing process are combined, the following advantages can be obtained. (I) Basically, it consists of two steps of organic solvent extraction and high-pressure gas mixing, and the organic acid can be separated in high yield by a simple process. (Ii) Since reagents such as calcium hydroxide and sulfuric acid used in the conventional method are not used, the cost can be reduced.
There is little waste. (Iii) Since the above two steps can be performed continuously, the equipment can be downsized and a large amount of organic acid can be continuously recovered in a short time as compared with batch processing. (iv) Since the high-pressure gas mixing process is performed at a relatively low temperature in an atmosphere where oxygen does not exist, the organic acid does not cause a side reaction. (V) The gas after the high-pressure gas mixing treatment can be easily separated and can be reused.

[0017]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. In the following examples, "%" means "% by weight".

Example 1 As a crude organic acid, 5 kg of citric acid-fermented koji was used, which was vacuum-dried, and 1.702 kg of dried koji (citric acid 36.3).
%, Water content 7.29%) was obtained. Take 0.5 kg of each in 3 containers, and use 2.5 kg of methanol, ethanol, and acetone as organic solvent respectively for 30 minutes for extraction treatment, and then filter to obtain an organic solvent extract containing citric acid. It was Table 1 shows the properties of the obtained organic solvent extract. The citric acid recovery rate was 97 to 99%.

[0019]

[Table 1]

CO ₂ gas was mixed with the organic solvent extract obtained above at 40 ° C. under a pressure of 40 to 80 kg / cm ² G.
The flow rate of the organic solvent extract was 2.0 g / min and CO ₂ was 1.5 g / min. Then, the mixed solution was allowed to stand for 3 minutes to precipitate and separate impurities, and then a supernatant was obtained. Table 2 shows the pressure at the time of mixing the organic solvent extract and the high-pressure gas, the solid content of the supernatant recovered from the overflow line, the citric acid concentration in the solid, and the citric acid recovery rate.

[0021]

[Table 2]

In Table 2, 50 ml of each of the supernatant liquids showing the solid content, the citric acid concentration in the solid content and the citric acid recovery rate were taken, treated with a column packed with 0.5 g of activated carbon, and recrystallized to 1 This was repeated, and colorless and transparent citric acid crystals were obtained. The citric acid crystals all had a very high purity of 99.1 to 99.9%. The obtained citric acid crystals were all odorless. Moreover, one operation was completed in 2 to 3 hours.
This proved to be a very efficient method, compared to the above-mentioned conventional method which required at least 10 hours.

Example 2 As a crude organic acid, 20 liters of fermented citric acid hot water extraction aqueous solution was used, and this was concentrated by an evaporator at 60 ° C. to obtain citric acid 56.8% and water content 10.8%. The yield was 4.437 kg. Each 1.0 kg of this concentrate was placed in a container and subjected to extraction treatment using 2.5 kg of ethanol and acetone as organic solvents, respectively, to obtain an organic solvent extract containing citric acid as in Example-1. Table 3 shows the specific gravity, the solid content, and the citric acid concentration in the solid of the obtained organic solvent extract.

[0024]

[Table 3]

Table 3 shows the specific gravity, the solid content, and the citric acid concentration in the solid content in an organic solvent extract at 40 ° C., 20 to 1
Under the conditions of 10 kg / cm ² G, N ₂ O (laughing gas), ethylene, propane and fluoromethane (fluorocarbon) were used to carry out the same treatment as in Example 1 to precipitate and separate impurities, and then from the overflow line. The supernatant was collected. Table 4 shows the type of gas mixed with the organic solvent, the pressure at the time of mixing, the solid content of the supernatant, the citric acid concentration in the solid, and the citric acid recovery rate.

[0026]

[Table 4]

In Table 4, the solid content, the citric acid concentration in the solid content, and the citric acid recovery rate are shown.
After treatment with a column packed with g of activated carbon, the mixture was concentrated to 3 ml for crystallization. In all cases, colorless and transparent citric acid crystals were obtained. The purity of these crystals is 97.6-99.8.
It was in the range of%.

Example 3 As a crude organic acid, 5 liters of citric acid liquid culture solution was used, and after filtering the cells, citric acid 5 was added in the same manner as in Example-2.
It was concentrated to 6.4% and water content 6.38%. Concentrated liquid 1.
0.5 kg of 07 kg was extracted with 0.8 kg of acetone as an organic solvent and then filtered to obtain an extract containing citric acid. This acetone extract has a specific gravity of 0.822 g / m
l, solid content 30.3%, citric acid concentration in solid content 8
It was 1.6%. In the same manner as in Example 1, CO ₂ gas was mixed with this acetone extract at 35 ° C. at a pressure of 38 kg / cm ² G. After the impurities were separated by precipitation, the supernatant was collected and treated with activated carbon and crystallization to give white citric acid crystals of 0.
1592 kg were recovered. The purity of this citric acid crystal is 9
9.8%, and the citric acid recovery rate was 92.4%.

Example 4 300 g of malic acid, 50 g of glucose, 7 g of ammonium sulfate, 3 g of magnesium sulfate, 5 g of corn steep liquor, and 5 liters of water were mixed to prepare a malic acid model fermentation liquid. The purity of malic acid is 82.2%.
The model fermentation liquor prepared is used at 75 ° C using an evaporator.
The water content was concentrated to 13.4% and cooled to room temperature. To this concentrate, 2000 g of acetone was added in two batches, and malic acid was extracted to prepare a crude acetone solution of malic acid. The composition of this crude acetone malate solution has a solute concentration of 1
2.8%, malic acid 11.4%, glucose 1.4%,
Others were 0.1% and the balance was acetone. With this acetone extraction, the purity of malic acid could be 89.1%.

Using this crude acetone acetone solution as a raw material,
Mix carbon dioxide under the conditions of 25 ° C and 22 kg / cm ² G,
Impurities were precipitated. Then, the precipitated impurities were flocculated for about 10 minutes while utilizing bubbles of carbon dioxide, and then allowed to stand for 20 minutes for separation to collect a supernatant. The recovered supernatant had a solute concentration of 11.5% and malic acid concentration of 11.3%, and the purity of malic acid had increased to 98.3%. At this time, most of the precipitate was glucose.

Example 5 250 g of commercially available 70% lactic acid, 150 g of glucose, and 3 g of a mineral mixture for fermentation were dissolved in 5 liters of water to prepare a lactic acid model fermentation liquid. The prepared model fermentation broth was concentrated at 75 ° C to a water content of 9.6% using an evaporator,
Cooled to room temperature. 10 ethanol for all of this concentrate
00 g was added and lactic acid was extracted to prepare a crude lactic acid ethanol solution. The composition of the crude lactic acid ethanol solution is lactic acid 12.
8%, glucose 6.8%, other 0.1%, and the rest was solvent. The purity of lactic acid is 65.0%.

Using this crude lactic acid ethanol solution as a raw material, 8
Carbon dioxide was mixed under the conditions of 15 ° C., 15 kg / cm ² G and 25 ° C., 26 kg / cm ² G to precipitate impurities. And
The precipitated impurities were aggregated while flocculating for 4 minutes, and allowed to stand for 30 minutes for separation, and then the supernatant was collected. Table 5 shows the composition of the supernatant collected under each condition. In each case, a high degree of purification was obtained. In addition, the precipitate under each condition contained glucose as the main component.

[0033]

[Table 5]

[0034]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, there is provided a method capable of efficiently recovering a highly pure organic acid from a crude organic acid at low cost.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Arai 3-4-6 Tomizawa, Taishiro-ku, Sendai City, Miyagi Prefecture

Claims (1)

Claims: 1. A crude organic acid is subjected to an extraction treatment using an organic solvent to obtain an organic solvent extract containing an organic acid, and then the organic solvent extract is mixed with a high pressure gas. A method for recovering a high-purity organic acid, which comprises depositing and separating impurities to obtain a high-purity organic acid-containing solution, and then separating the organic acid from the solution.