JP3206103B2 - Method for producing methionine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing methionine useful as an animal feed additive. More specifically,
The present invention relates to a method for recovering methionine and potassium bicarbonate when producing methionine from 5- (β-methylmercaptoethyl) hydantoin.

[0002]

2. Description of the Related Art A method for producing methionine is disclosed in
No. 9174 has 5- (β-methylmercaptoethyl)
After hydrolyzing hydantoin with an alkali metal carbonate and / or alkali metal bicarbonate, neutralize and crystallize under the pressure of carbon dioxide, separate and obtain methionine, and circulate the filtrate to hydrolyze hydantoin. A method for re-use is disclosed.

In this method, the filtrate containing impurities is reused repeatedly, but it is necessary to remove the filtrate from the system at a fixed rate (so-called partial purging) in order to avoid an increase in impurities and coloring components. is there. Since valuable substances such as methionine and potassium still exist in this partial purge solution, it is not economically advantageous to discard it without treatment from the viewpoint of environmental protection and environmental protection. For this reason, it is disclosed that after adding methanol or acetone to this partial purge solution, carbon dioxide gas is saturated under cooling at normal pressure, and methionine and potassium bicarbonate precipitated are collected by filtration.

On the other hand, Japanese Patent Publication No. 55-42985 discloses that the partial purging solution has a potassium content of 120 g / liter.
, and carbon dioxide saturation under cooling at a pressure of 0.5 to
It has been proposed to carry out the reaction at 20 kg / cm ² G and recover the precipitated methionine and potassium bicarbonate by filtration.

[0005]

However, the method of adding methanol or acetone and saturating carbon dioxide gas at normal pressure does not provide a sufficient recovery rate, and the recovery of acetone by distillation from a basic aqueous solution at the time of recovery. As a result, a part of the polymer is multiplied and foaming occurs, thereby deteriorating the recovery rate and the quality of valuable resources, and the multimer remains undesirably in the wastewater.

A method of concentrating a partial purge solution and performing carbon dioxide gas saturation at a pressure of 0.5 to 20 gauge under cooling is as follows.
Although the recovery of methionine and potassium bicarbonate can be improved by an amount corresponding to the reduced amount of water, the viscosity of the mother liquor when these are separated by filtration increases significantly, and the filterability deteriorates.
Therefore, impurities and coloring remain in the recovered methionine and potassium bicarbonate, and the purpose of the partial purge operation is reduced by half.

In view of such circumstances, as a result of diligent studies on a method for producing methionine from 5- (β-methylmercaptoethyl) hydantoin, isopropyl alcohol was added to a part of the filtrate from which methionine was separated, ie, a partial purge solution. By saturating the carbon dioxide gas under cooling, it was found that methionine and potassium bicarbonate could be easily recovered without concentration, avoiding contamination of other impurities and coloring matter, and completed the present invention.

[0008]

That is, the present invention provides a 5-
After hydrolyzing (β-methylmercaptoethyl) hydantoin using potassium carbonate and / or potassium bicarbonate, neutralized and crystallized under pressure of carbon dioxide gas to separate and obtain methionine, and the filtrate was subjected to hydrolysis of hydantoin. Circulation,
In the method for producing methionine for reuse, methionine
A part of the filtrate after the separation was added without concentration, by adding 0.5 to 2 parts by weight of isopropyl alcohol to 1 part by weight of the filtrate, and carbon dioxide gas was added under cooling to a pressure of 0 %. .5-
A method for producing methionine, comprising saturating with 20 kg / cm ² G, crystallizing methionine and potassium bicarbonate, and separating and collecting the methionine and potassium bicarbonate.

The amount of the filtrate to which isopropyl alcohol is added varies depending on the amount of impurities and coloring matter, but usually about 10 to 10 parts of the filtrate circulated and reused for the hydrolysis of hydantoin.
20%. The filtrate usually contains about 90 to 110 g.
/ L titratable potassium and about 40-60 g / l methionine. In the present invention, the filtration is performed without concentrating the filtrate, that is, using a liquid having a titratable potassium concentration of less than about 120 g / l.

The amount of isopropyl alcohol used is determined based on the amount of the filtrate. About 0.1 parts by weight of the filtrate.
Used in an amount of 5 to 2 parts by weight. If the amount is less than about 0.5 part by weight, the recovery of methionine and potassium bicarbonate decreases. If the amount is more than about 2 parts by weight, the effect corresponding thereto cannot be obtained.

The pressure of the carbon dioxide used is about 0.5-20.
a kg / cm ² G, preferably 2~6kg / cm ² G. Below about 0.5 kg / cm ² G, an unsatisfactory recovery rate can be obtained regardless of the amount of isopropyl alcohol.
A recovery rate of more than about 20 kg / cm ² G cannot be obtained. Further, the treatment temperature is desirably low, particularly at about 20 to 0 ° C., preferably around 10 ° C. at the end of crystal precipitation. The operation can be performed batchwise or continuously.

[0012]

According to the method of the present invention, methionine and potassium bicarbonate can be easily and efficiently recovered from a partial purge solution in a method for producing methionine without concentration, without contaminating impurities and coloring matters. .

[0013]

EXAMPLE 1 A filtrate containing 100 g / l of titratable potassium and 50 g / l of methionine, and an equal weight of isopropyl alcohol were placed in a pressurized reaction vessel, and the system was maintained at 10 ° C. Until the pressure reached a saturated state of 3 kg / cm ² G. The pH value of the content was 8.0, and the precipitated crystals were mostly methionine and potassium bicarbonate. Potassium and methionine, which can be titrated in the filtrate after filtration of these crystals, were 6 g / l and 7 g / l, respectively. there were.

The removal ratio of the coloring components was 89%. The removal rate indicates the ratio of the coloring components in the raw material filtrate remaining in the filtrate after the solvent crystallization, and was determined from the absorbance at 434 nm and the volume of each filtrate. Further, isopropyl alcohol in the filtrate after the solvent crystallization could be recovered by distillation without deterioration.

Comparative Example 1 The procedure of Example 1 was repeated except that methanol and acetone were used instead of isopropyl alcohol. The concentrations of potassium and methionine in the filtrate after crystallization of the solvent when methanol was used were 15 g / l and 9 g / l, respectively, and those when acetone was used were 6 g / l and 6 g / l. When acetone was used, the recovery rate was good, but when acetone was recovered, acetone deteriorated by 3.1% due to condensation or the like.

Comparative Example 2 The neutralized crystallization filtrate was concentrated twice to obtain a solution containing 200 g / l and 100 g / l of titratable potassium and methionine, respectively. This solution was supplied with carbon dioxide gas at 10 ° C. until the pressure in the system became saturated at 3 kg / cm ² G. The titratable potassium and methionine concentrations in the filtrate after crystallization were 75 g / l and 24 g / l, respectively, and the removal rate of the coloring components was 74%.

Example 2 The procedure of Example 1 was repeated except that the amount of isopropyl alcohol was changed. Table 1 shows the results.

[0018]

[Table 1]

Example 3 Example 3 was carried out in the same manner as in Example 1 except that the pressure inside the system was changed with carbon dioxide gas. Table 2 shows the results.

[0020]

[Table 2]

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Haruki Okamura 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Industries, Ltd. (56) References JP-A-48-86819 (JP, A) JP-A Sho 48-19517 (JP, A) JP-B 55-42985 (JP, B2) JP-B 46-19610 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 323/58 C07C 319/20 C07C 319/28

Claims (1)

(57) [Claims] 1. Hydrolysis of 5- (β-methylmercaptoethyl) hydantoin with potassium carbonate and / or potassium bicarbonate, followed by neutralization and crystallization under pressure of carbon dioxide gas to separate and obtain methionine. In the methionine production method, in which the filtrate is circulated and reused for the hydrolysis of hydantoin, part of the filtrate after methionine separation is concentrated.
Without filtration, 0.5 to 2 parts by weight of isopropyl alcohol was added to 1 part by weight of the filtrate, and carbon dioxide was saturated with cooling at a pressure of 0.5 to 20 kg / cm ² G under cooling to give methionine and bicarbonate. A method for producing methionine, comprising crystallizing potassium and separating and recovering it.