JPH05286926A - Production of methionine - Google Patents

Abstract

PURPOSE:To provide a process for producing methionine while forming little impurities and suppressing the amounts of waste methionine and potassium bicarbonate to prevent the accumulation of the compounds. CONSTITUTION:5-(beta-Methylmercaptoethyl)-hydantoin is hydrolyzed in the presence of an alkali metal carbonate and/or bicarbonate, the obtained solution is neutralized with carbon dioxide gas to crystallize methionine and the remaining filtrate is recovered and reused for the hydrolysis of 5-(beta- methylmercaptoethyl)-hydantoin. The 5-(beta-methylmercaptoethyl)-hydantoin to be used in the above process for the production of methionine is produced by converting 3-methylmercaptopropionaldehyde to cyanhydrin with hydrocyanic acid in the presence of potassium carbonate, potassium bicarbonate and/or potassium hydroxide as a catalyst and converting the obtained 3- methylmercaptopropionaldehyde cyanhydrin to hydantoin with carbon dioxide gas and ammonia.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing methionine which is useful as a feed additive. More specifically, the present invention relates to a method for producing methionine that produces less impurities.

[0002]

Methionine hydrolyzes 5- (β-methylmercaptoethyl) -hydantoin (hereinafter abbreviated as MH) in the presence of alkali, neutralizes the hydrolyzed solution with an acid, and precipitates crystals. Obtained separately. In this case, a method using a mixture of an alkali metal carbonate and an alkali metal hydroxide as the alkali and carbon dioxide as the acid (Japanese Patent Publication No.
9530), or a method using an alkali metal carbonate or an alkali metal bicarbonate as an alkali and carbon dioxide as an acid (Japanese Patent Publication No. 54-9174).

Since part of methionine is dissolved in the filtrate after methionine has been crystallized and separated, the filtrate is recovered in the MH hydrolysis step (Japanese Patent Publication No. 54-9174). At this time, the filtrate may be optionally concentrated, and then collected by crystallization and then recovered.

On the other hand, for the production of MH, an aqueous solution (raw material aqueous solution) containing carbon dioxide and ammonia, ammonium bicarbonate or ammonium carbonate and hydrocyanic acid or a salt thereof, and 3-methylmercaptopropionaldehyde (hereinafter referred to as M) are used.
A method of reacting (abbreviated as AD) is known. At that time, in order to accelerate the reaction, the reaction may be carried out at a high temperature (100 to 200 ° C.) under pressure (Japanese Patent Publication No. 39-14688), or a solution prepared by previously dissolving MAD in the raw material aqueous solution or the MH-forming reaction solution may be mixed with the raw material aqueous solution. It is known to be done by (Japanese Patent Publication Sho 42-3495
issue).

[0005]

When recovering the filtrate after separation of methionine, impurities such as homoserine and coloring components are accumulated, so that the filtrate must be discarded at a certain ratio. It is also possible to add an organic solvent such as acetone to the discarded filtrate to crystallize and separate methionine and the like, but if the amount of impurities generated is large, the amount accumulated will also increase, and the amount of filtrate processed and the solvent used will increase. It also increases the loss of valuable components such as methionine, which is not always a satisfactory method.

The generation of impurities is remarkable when the conversion rate of MAD during MH conversion is low. In order to solve this, the above-mentioned measures have been taken, but under high temperature and pressure, coloring tends to occur, and industrially there is a problem in terms of equipment safety. In addition, the method of dissolving MAD in a raw material aqueous solution or the like and then reacting is complicated in operation, and there is a problem that unreacted MAD is likely to occur.

Recently, in converting benzaldehyde cyanohydrin (hereinafter abbreviated as BCH) into hydantoin,
A method of adding an excess of prussic acid or a salt thereof to the unreacted aldehyde in BCH has been reported (Japanese Patent Laid-Open No. 2-1695).
No. 77), this method is also effective for MH conversion, but it is difficult to adopt it in the process of recycling the filtrate, since excess hydrocyanic acid added is hydrolyzed to formic acid, which becomes a problem as an impurity.

In view of such circumstances, in the method for producing methionine in which the filtrate after the separation of methionine is recovered in the hydrolysis step of MH, as a result of earnest studies on a method of producing less impurities, potassium carbonate and potassium bicarbonate were obtained as MH. MAD using at least one potassium compound selected from the group consisting of
Cyanide hydrolyzed with hydrocyanic acid to obtain 3-methylmercaptopropionaldehyde cyanohydrin (hereinafter referred to as M
By using MH obtained by converting (abbreviated as CH) to hydantoin with carbon dioxide gas and ammonia, it was found that the generation of impurities is suppressed, and the present invention has been completed.

[0009]

SUMMARY OF THE INVENTION That is, the present invention is
(Β-Methylmercaptoethyl) -hydantoin is hydrolyzed in the presence of an alkali metal carbonate and / or an alkali metal bicarbonate, the hydrolyzed solution is neutralized with carbon dioxide to crystallize methionine, and methionine is separated. The latter filtrate is 5
In the method for producing methionine recovered in the hydrolysis step of-(β-methylmercaptoethyl) -hydantoin,
As 5- (β-methylmercaptoethyl) -hydantoin, at least one potassium compound selected from the group consisting of potassium carbonate, potassium bicarbonate and potassium hydroxide is used as a catalyst to give 3-methylmercaptopropionaldehyde with hydrocyanic acid and cyanohydrin. The method for producing methionine is characterized by using 5- (β-methylmercaptoethyl) -hydantoin obtained by converting the obtained 3-methylmercaptopropionaldehyde cyanohydrin to hydantoin with carbon dioxide gas and ammonia.

In the present invention, 3-methylmercaptopropionaldehyde is cyanated with hydrocyanic acid to give 3-
At the time of producing methylmercaptopropion cyanhydrin, at least one potassium compound selected from the group consisting of potassium carbonate, potassium bicarbonate and potassium hydroxide is used as a catalyst. As a result, the MAD conversion rate becomes 99% or more, and MCH becomes almost quantitatively, so that carbon dioxide gas and ammonia are subsequently reacted to cause MH
The yield when manufacturing is increased, and impurities (including coloring components)
The by-product of is also suppressed.

Furthermore, since the reaction rate of MCH formation is very fast, the residence time of MCH is only a few minutes to at most 1 hour, and the reaction rate is the same as that of conventional MH formation as a whole. Further, since the MCH-forming catalyst can be selected from the same alkali that hydrolyzes MH in the next step, there is no problem of impurities accumulated in the system derived from the catalyst and supplementation of loss of alkali such as potassium carbonate to be recovered and reused. Doubles as
It is also possible to consider supplying the MCH-forming catalyst.

The catalyst amount is 0.00 in terms of molar ratio to MAD.
The reaction can be performed in the range of 3 to 0.01 and the pH of the MCH-forming solution in the range of 6 to 9. It is better that the MAD used does not contain impurities, and it is preferable to rectify before the reaction. M
The molar ratio of AD to hydrocyanic acid (HCN / MAD) was required to be 1.1 or more in the conventional method, but was 1.
Since the amount of hydrocyanic acid added in excess can be reduced, the by-product of formic acid generated from hydrocyanic acid can be suppressed.
MCH formation can be carried out at 45 ° C. or lower, especially 10 to 3
0 ° C is preferred.

In the MH conversion step, the carbon dioxide gas and the ammonia source may be those normally used. Carbon dioxide and ammonia, ammonium carbonate or ammonium bicarbonate in excess of the stoichiometric amount, preferably 1 to 4 times the stoichiometric amount relative to MCH are used. General conditions such as a reaction temperature of about 60 to 85 ° C. and a residence time of about 3 to 6 hours may be used.

[0014]

INDUSTRIAL APPLICABILITY According to the method of the present invention, residual unreacted MAD and generation of impurities derived from it are significantly reduced, so that both the yield and the color of the MH-ized solution are greatly improved. In the recycling use of the filtrate after separation, it is possible to significantly reduce the amount of the filtrate to be treated for removing impurities and the treatment cost, and to reduce the loss of valuable components such as methionine.

[0015]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A continuous reaction tank consisting of 4 tanks equipped with a cooler in the purge line was used, and 99.3 wt% MAD was 78 g / hr at 32 g for the first tank.
66 g / hr of wt% hydrocyanic acid water (molar ratio to MAD 1.05),
5.6 g / hr of 8.6 wt% potassium carbonate water (0.0045 mol ratio to MAD) was supplied, and the residence time was 1 hour at 15 ° C.
Rotation speed of fan turbine stirring blade (6 blades) is 500rp
The MCH was produced by keeping it at m 2. 2 bath th ammonium carbonate water _{(CO 2: 12.3wt%, NH} 3: 9.5wt%)
542 g / hr (CO ₂ / NH ₃ / MAD molar ratio = 2.0
3 / 4.06 / 1, water amount 600m per 1 mol of MAD
l) was supplied, and the rotation speed of the fan turbine stirring blade (6 blades) was maintained at 500 rpm at 70 ° C. for a residence time of 1 hour.
The 3rd and 4th tanks each had a residence time of 1 hour at 70 ° C, the rotation speed of the flat plate stirring blade was kept at 200 rpm, and the MH liquid (695 g / hr).
A material balance of 99% or more) was obtained. Baffles were used for the first and second tanks. When the continuous reaction reached a steady state, MAD conversion rate 100%, pH 8.48 (first tank), MH conversion yield (relative to MAD) 98.2%, absorbance at 434 nm visible light 0.07
It was 1 (4th tank).

Further, 552.8 g of MH-ized solution (MAD
0.60 mol equivalent to 108 g of potassium carbonate (versus MAD)
A molar ratio of 1.3) and 54 g of water were added, and the mixture was vigorously stirred at 180 ° C. for 1 hour in a 1 liter autoclave to obtain a degassing rate of 1
When hydrolyzed at 9.1%, the yield of methionine (based on MAD) was 95.5%, and the absorbance at 434 nm visible light was 0.12.
A saponification solution (hydrolysis solution) of 6 was obtained. This saponified solution was neutralized by blowing carbon dioxide at a pressure of 2 kg / cm ² G and 20 ° C. to crystallize methionine. Methionine 8 after crystallization separation
8.6 g were obtained, which corresponds to a yield of 99% based on the MAD used. All mother liquors were concentrated to 32% and used again for hydrolysis. At this time, such a hydrolysis-
The crystallization-filtrate recycling operation was repeated 9 times, but the yield of the obtained methionine was the same as that of the first time, the purity was 99% or more, and no coloring was observed.

Comparative Example 1 The procedure of Example 1 was repeated except that aqueous ammonia was supplied instead of aqueous potassium carbonate. In the first tank, 6.6 wt% ammonia water was used as the MCH-forming catalyst in place of potassium carbonate water.
8 g / hr (molar ratio to MAD 0.032) was supplied, and the residence time was kept at 2 hours, and the ammonium carbonate water (C
_{O 2: 7.6wt%, NH 3} : 5.8wt%) 696g / hr
(CO ₂ / NH ₃ / MAD molar ratio = 1.60 / 3.20
/ 1, water amount of 850 ml per mol of MAD) is supplied,
A residence time of 0.5 hours was maintained at 70 ° C. The third and fourth tanks were each kept at 85 ° C for a residence time of 1 hour, and the MH liquid (775 g /
hr, material balance over 99%). When the continuous reaction reached a steady state, MAD conversion rate was 98%, MH conversion yield was 95.2.
%, The absorbance at 434 nm visible light was 0.043. Further, the MH-ized solution was used in an amount corresponding to 0.1 mol of MAD and the degassing rate was 17.
When hydrolyzed at 5%, the yield of methionine was 90.3.
%, A saponification solution having an absorbance of 421 nm visible light of 0.221 was obtained.

Comparative Example 2 The same procedure as in Example 1 was performed, but the first tank was not used, and MAD,
Supply hydrocyanic acid water to the second tank, and add ammonium carbonate water (C
_{O 2: 11.4wt%, NH 3} : 8.8wt%) and 570 g /
_{hr (CO 2 / NH 3 /} MAD molar ratio = 1.99 / 3.9
7/1, 600 ml of water per mol of MAD). The third and fourth tanks each have a residence time of 1 hour at 75 ° C,
An MH liquid (690 g / hr, mass balance 97%) was obtained. When the continuous reaction reached a steady state, the MH yield was 93.2%,
The absorbance at 434 nm visible light was 0.087. Furthermore M
Degassing rate of H-solution is equivalent to MAD 0.6 mole, degassing rate 17.5%
When hydrolyzed with, methionine yield 91.0%,
A saponification solution with an absorbance of 434 nm visible light of 0.189 was obtained.

Example 2 Example 2 was repeated except that potassium bicarbonate water was used instead of potassium carbonate water. In the first tank, 10 wt% potassium bicarbonate water 7.4 g / hr (0.01 to MAD molar ratio) was supplied instead of potassium carbonate water as the MCH-forming catalyst. When the continuous reaction reaches a steady state, the MAD conversion rate is 99%,
pH 7.8 (1st tank) MH yield (relative to MAD) 98.0
%, The absorbance at 434 nm visible light was 0.083 (4th tank). Further, the MH-ized solution was added in an amount corresponding to MAD 0.60 mol,
When hydrolyzed at a degassing rate of 19.3%, a saponification solution (hydrolysis solution) having a methionine yield (relative to MAD) of 95.3% and an absorbance at 434 nm visible light of 0.115 was obtained. The crystallization-filtrate recycling operation was repeated 9 times,
The yield of methionine obtained is 99% or more, and the purity is 99%.
As a result, no coloring was observed.

Example 3 Example 1 was repeated except that aqueous potassium hydroxide was used instead of aqueous potassium carbonate. In the first tank, 4.2 g / hr of 10 wt% potassium hydroxide water (0.01 molar ratio to MAD) was supplied as the MCH-forming catalyst instead of potassium carbonate water.
(However, the first tank at 25 ° C) When the continuous reaction reached a steady state, MAD conversion rate 100%, pH 6.8 (first tank), M
The H conversion yield (relative to MAD) was 95.9%, and the absorbance at 434 nm visible light was 0.078 (4th tank). Furthermore, when the MH-ized solution was hydrolyzed in an amount corresponding to 0.6 mol of MAD at a degassing rate of 19.0%, a methionine yield (relative to MAD) of 96.
A saponification solution (hydrolysis solution) having an absorbance of 0.068 of 2% 434 nm visible light was obtained, and the hydrolysis-crystallization-filtrate recycling operation was repeated 9 times. The yield of methionine obtained was 99%. As described above, the purity was 99% or more, and no coloring was observed.

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Claims (1)

[Claims] 1. 5- (β-Methylmercaptoethyl)-
Hydantoin is hydrolyzed in the presence of an alkali metal carbonate and / or an alkali metal bicarbonate, the hydrolyzed solution is neutralized with carbon dioxide to crystallize methionine, and the filtrate after separation of methionine is treated with 5- (β -Methylmercaptoethyl)
In the method for producing methionine recovered in the hydrolysis step of hydantoin, at least one potassium compound selected from the group consisting of potassium carbonate, potassium bicarbonate and potassium hydroxide as 5- (β-methylmercaptoethyl) -hydantoin 5- (β-methylmercaptoethyl) -hydantoin obtained by converting 3-methylmercaptopropionaldehyde into cyanohydrin with hydrocyanic acid and using the resulting 3-methylmercaptopropionaldehyde cyanohydrin as hydantoin with carbon dioxide and ammonia. A method for producing methionine, which comprises using