JPH04193861A - Production of methionine - Google Patents

Abstract

PURPOSE:To easily obtain methionine in colorless state by hydrolyzing 5-(beta- methylmercaptoethyl)-hydantoin, neutralizing with carbon dioxide gas, separating crystallized methionine, decoloring the separated filtrate with a specific adsorbent and recycling the decolored liquid to the hydrolysis process. CONSTITUTION:Methionine is produced by heating 5-(beta-methylmercaptoethyl)- hydantoin in the presence of an alkali metal (bi)carbonate and/or an alkali metal hydroxide and separating the precipitated crystal by filtration. The filtrate left after the separation of methionine is decolored with a styrene-divinylbenzene adsorbent resin having a macroporous structure and free from functional group at 5-40 deg.C and pH7-9, and the decolored liquid is recycled to the hydrolysis process. The adsorbent resin has e.g. a pore diameter of 140-1,500nm, a specific surface area of 400-700m<2>/g and a pore-volume of 0.4-1.5ml/g.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an industrial method for producing methionine useful as animal feed.

[Conventional technology]

Methionine is obtained by hydrolyzing 5-(β-methylmercaptoethyl)-hydantoin (hereinafter simply referred to as hydantoin) in the presence of an alkali, neutralizing the solution with acid to precipitate crystals, and separating the crystals. It will be done. A mixture of an alkali metal carbonate and an alkali metal hydroxide as the alkali, carbon dioxide gas as the acid (Japanese Patent Publication No. 19530/1983),
In addition, alkali metal carbonates and/or alkali metal bicarbonates are used as alkalis, and carbon dioxide gas is used as acids (Special Publications No. 5).
4-9174) is known. After crystallizing methionine and separating it, some of the methionine is dissolved in the filtrate, and in order to recover it, a part of the filtrate is concentrated and further crystallized and separated, or the filtrate is recycled to the hydantoin hydrolysis process. It is also known to use (Japanese Patent Publication No. 54-9174).

On the other hand, in a method for producing methionine that includes a hydantoin reaction, the methionine is colored because coloring impurities are produced as by-products. As a method for obtaining uncolored methionine, there is a method in which an organic solvent such as acetone is present when crystallizing methionine (1-TE Publication No. 1986-86819);
A bleaching method in which a chemical reducing agent such as sulfite is present during hydrolysis of hydantoin (Japanese Unexamined Patent Publication No. 15837/1983), a method in which the hydrolyzed hydantoin solution is decolorized and purified with activated carbon in advance and then crystallized ( Japanese Unexamined Patent Publication 1973-1991
No. 74) is known.

[Invention or problem to be solved]

However, the method of crystallizing in the coexistence of an organic solvent not only requires a step of separating and recovering the solvent, but also undesirably introduces an unavoidable amount of solvent into the recovered recycle system, increasing the number of impurities. Although the method of coexisting a reducing agent has a large decolorizing effect, sulfates and the like generated after reductive decolorization with sulfite etc. accumulate in the system and are difficult to remove, causing problems in product quality. Furthermore, when activated carbon is used, complicated post-treatments such as its separation, regeneration, and disposal are required, and this is not necessarily a preferable method for industrially producing methionine.

In view of these circumstances, as a result of intensive studies on a method for producing methionine that is efficient and free of coloration, we found that the filtrate after crystallization and separation after the hydantoin hydrolysis process was used in styrene-divinylbenzene rather than the hydantoin hydrolysis solution. The method of decolorizing using a non-functional adsorption resin with a macroporous structure of the system increases the amount of adsorption per unit weight of adsorption resin, even though the concentration of colored components is low, and it is possible to obtain uncolored methionine. discovered that it could be easily manufactured,
The present invention has now been completed.

[Means to solve the problem]

That is, the present invention provides a method for producing methionine by hydrolyzing 5-(β-methylmercaptoethyl)-hydantoin in the presence of an alkali, neutralizing the hydrolysis solution with carbon dioxide gas, and crystallizing and separating methionine. In this method, the filtrate after crystallizing and separating methionine is decolorized using a non-functional adsorption resin having a styrene-divinylbenzene-based macroporous structure, and then recovered in the hydrolysis step of the hydantoin. This is a distinctive method for producing methionine.

The hydantoins of the present invention are obtained by known methods, namely by reaction of β-methylmercap)propionaldehyde with hydrogen cyanide and ammonium carbonate. Hydrolysis of hydantoins is also carried out using known methods, namely alkali metal carbonates, alkali metal bicarbonates and/or alkaline metals.
It is carried out by heating in the presence of a metal hydroxide. The hydrolyzed solution is an alkaline solution exceeding PHII, and carbon dioxide gas is usually blown into this solution under pressure to neutralize it, and the precipitated crystals are filtered off to obtain methionine. The filtrate usually has a pH of about 7 to 9, contains about 2 to 5% by weight of methionine salt, and is light yellowish brown to yellowish brown in color.

The adsorption resin used to decolorize this filtrate is granular;
It is a non-functional resin having a styrene-divinylbenzene macroporous structure.

This adsorption resin has, for example, a pore size of 140 to 500 nm,
Specific surface area 400-700M/g, pore volume 0.4-1.
5 ml/g, it is a resin with high adsorption capacity. A commercially available product is 5-861 manufactured by Sumima Kagaku Kogyo Co., Ltd. S-
876, HP series manufactured by Mitsubishi Kasei Corporation, etc.

The liquid temperature when carrying out the liquid contact treatment using the adsorption resin of the present invention is selected from the allowable heat resistance range of the adsorption resin, or is usually 5.
~40°C, and the pH at that time is the P of the filtrate.
It is in the range of H7-9.

In addition, the adsorption resin may be used in the treatment of the present invention, either by suspending it in the target liquid and stirring it, or by filling it in a column and passing it through the column.The latter is preferable from the standpoint of efficiency and operation. The liquid passing rate when filling the column and passing it through is usually 5V = 1 to 15
The ratio of the amount of treatment liquid to the weight of the adsorption resin is usually 1 to 500 times, preferably 250 to 350 times.

In addition, the adsorption resin after the treatment of the present invention is
Organic solvents such as methanol, ethanol, isopropanol, butanol, or acetone/water-5015
It can be easily regenerated by bringing it into contact with a water mixture such as water, hot water, a heated organic solvent, or a water mixture of organic solvents, making it possible to use it repeatedly.

The filtrate from which the adsorption resin has been separated is recycled to the hydantoin hydrolysis step and recovered. In addition, the filtrate is concentrated,
If necessary, it is also possible to further crystallize and separate methionine and then recover it.

It is not necessarily necessary to decolorize the entire amount of the filtrate after methionine has been filtered off, and the amount to be treated is determined by the degree of coloring of the product methionine.

Compared to the method of crystallizing the methionine of the present invention and decolorizing the separated filtrate with an adsorption resin, or decolorizing the solution before crystallizing methionine with an adsorption resin, although it contains fewer colored components, First, the amount of coloring component adsorbed per unit weight of adsorbed resin is increased.

〔Effect of the invention〕

Compared to conventional methods, the method of the present invention can easily produce decolorized methionine with less adsorption resin,
In addition, it is easy to regenerate the used adsorption resin, and its industrial value is high.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

The adsorption treatment was evaluated by determining the decolorization rate and unit adsorption amount based on the absorbance of the solution before and after treatment.

Unit adsorption amount = (absorbance difference before and after decolorization) x absorbance was measured at a wavelength of 434 nm using a JEOL spectrometer (Ubest-30) with a 10 mm cell using distilled water as a control solution. (However, the absorbance is a value measured at room temperature, and it is assumed that there is no change in liquid volume before and after decolorization.) Example 1 16°3 kg of potassium carbonate after crystallizing and separating methionine
and 26A of filtrate containing 3.7 kg of methionine.
was added to an aqueous solution 1131 in which 15°I kg of 5-(β-memethymercaptoethyl)-hydantoin was dissolved. Add 0.7 kg of potassium carbonate and heat to 180°C.
hydrolyzed.

The carbon dioxide gas and ammonia generated at this time are recovered as ammonium carbonate water and used in the production of hydantoin.

The hydrolyzed solution was heated to a pressure of 2 ki</i>G using carbon dioxide gas,
The mixture was neutralized at 20°C and methionine was crystallized. By introducing carbon dioxide gas into the solution, the pH changes from 11.3 to 8.
It dropped to 5. As a result of crystal separation, methionine 3.
2 kg was obtained. The yield was 99% based on the hydantoin used.

The filtrate was concentrated to 32% and collected for the hydantoin hydrolysis step.

This cycle of hydrolysis-crystallization, separation, and recovery of the filtrate to the hydrolysis step was repeated nine times. A part of the filtrate after neutralization crystallization in the 10th cycle was heated at room temperature (23°C) using 0.93g of adsorption resin S-861 manufactured by Sumitomo Chemical Co., Ltd. (Kiku).
°C) and decolorized by flowing under the conditions of 5V = 7 to 9. In addition, after regenerating the used S-861 with hot water and heated methanol,
The filtrate was decolorized under the same conditions. The regeneration-filtrate decolorization operation of S-861 was performed three times, and no deterioration of the adsorption resin was observed after the regeneration treatment, indicating that there was a sufficient decolorization effect. The results are shown in Table 1.

Table 1 - The absorbance of the filtrate before decolorization is 0.57.

- The filtrate passing through the resin was stopped when the decolorization rate reached 30% or less.

Decolorized filtrate to 32%? It was agriculturally reduced and reused for hydrolysis of hydantoin to produce the 11th cycle of methionine.

The absorbance of the obtained methionine is 0.034.

Methionine absorbance was measured by dissolving 4 g of methionine crystals in 100 g of water.

Comparative Example 1 After repeating the cycle operation 10 times in the same manner as in Example 1,
After hydrolyzing hydantoin, a portion of the hydrolyzed solution was decolorized using 0.93 g of the same adsorption resin as in Example 1 under the same conditions as in Example 1, but the effect was small. The results are shown in Table 2.

Table 2 - The absorbance of the hydrolyzed solution before decolorization is 0.745.

- The filtrate passing through the resin was stopped when the decolorization rate reached 30% or less.

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Claims (1)

[Claims] In a method for producing methionine by hydrolyzing 1,5-(β-methylmercaptoethyl)-hydantoin in the presence of an alkali, neutralizing the hydrolyzed solution with carbon dioxide gas, and crystallizing and separating methionine, methionine is The filtrate after crystallization and separation is decolorized using a non-functional adsorption resin having a styrene-divinylbenzene macroporous structure, and then recovered in the hydrolysis step of the hydantoin. Method for producing methionine.