JPH0665168A - Method for purifying glycine - Google Patents

Abstract

PURPOSE:To obtain glycine useful as a food additive, an agrichemical and a medicine raw material by a simple operation by reacting glyconitrile with carbon dioxide and ammonia organic water to give crystal of glycine, redissolving the crystal in water and adding a water-soluble organic solvent. CONSTITUTION:In the presence of water, 0.01-0.5 pt.wt. glyconitrile based on 1 pt.wt. water is reacted with 1-50 pts.wt. ammonia based on 1 pt.wt. glyconitrile and 0.9-1.1mol carbon dioxide based on 1mol ammonia at 100-200 deg.C to give a reaction solution, which is cooled to 5-50 deg.C and crystallized. The prepared crude crystal of glycine is redissolved in water, the solution is mixed with a water-soluble organic solvent (preferably methanol or acetone) and glycine is recrystallized to purify glycine.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying glycine. Specifically, it relates to a method for purifying glycine obtained by reacting glycolonitrile, ammonia and carbon dioxide.

[0002]

2. Description of the Related Art Conventionally, as a method for producing glycine, in addition to an amination method of monochloroacetic acid, a Strecker method, etc.,
A hydantoin method via hydantoin obtained from hydrogen cyanide and formaldehyde as raw materials is known. Since this hydantoin method has many by-products, it is necessary to efficiently purify glycine from the product. The most general method for purifying glycine in this case is
It is a crystallization method. As the crystallization method, usually, a method of concentrating and cooling a reaction solution containing glycine to precipitate glycine crystals is adopted.

Furthermore, since by-products or coloring substances are still attached to the crystals, there is a method of washing the crystals with water or methanol or acetone containing water as a washing liquid. Proposed (JP-A-2
-250854).

[0004]

However, in the method for washing glycine crystals with the above-mentioned washing solution, the composition and amount of the washing solution are adjusted, so that separation from impurities and decolorization are not sufficient, or glycine is dissolved. Problems such as loss and reduction of crystal recovery rate tend to occur. Therefore, the crystal washing operation should be performed as carefully as possible.

[0005]

Therefore, in view of the above problems, the present inventor diligently studied a more efficient method for purifying glycine, and once obtained a crude crystal of glycine obtained by crystallization. It was found that high purity glycine can be obtained by a relatively simple operation by re-dissolving in water and then recrystallizing by adding a specific organic solvent to the solution, and thus reached the present invention.

That is, the gist of the present invention is that in the presence of water,
Glycine crystals obtained by crystallizing a reaction solution obtained by reacting glycolonitrile, carbon dioxide and ammonia are redissolved in water, and then an organic solvent soluble in water is added to the solution. A method for purifying glycine is characterized by recrystallizing glycine. Hereinafter, the present invention will be described in detail.

The glycine targeted by the present invention is obtained by reacting glycolonitrile, carbon dioxide and ammonia in the presence of water. Glycolonitrile is
Usually, a reaction system in which glycolonitrile itself is charged is used, but a compound capable of producing glycolonitrile under reaction conditions can also be used. Examples of the compound include a mixture of hydrogen cyanide and formaldehyde, a mixture of sodium cyanide and paraformaldehyde, and the like.

Regarding carbon dioxide and ammonia, it is usually possible to use them as they are, but it is also possible to use compounds which form these compounds under the reaction conditions, such as ammonium carbonate and ammonium bicarbonate. . The above glycine production reaction is carried out in an aqueous solvent. The amount of glycolonitrile used is usually 0.01 to 0.5 times by weight the amount of water. The amount of ammonia used is usually 1 to 50 mole times the amount of glycolonitrile used. The amount of carbon dioxide used is usually 0.5 to 2.0 mol times, preferably 0.9 to 1.1 mol times the amount of ammonia. The reaction temperature is not particularly limited, but the lower the temperature, the higher the yield and the less the coloration, but the slower the reaction rate.
Set in the range of 200 ° C. Also, the reaction pressure is not particularly limited, and it is possible to appropriately purge the gas generated in the system during the reaction in consideration of the pressure resistance of the reactor. The reaction system is not particularly limited and may be a batch system, a flow system, or a semi-flow system.

In the reaction solution obtained by the above method, in addition to glycine, hydantoic acid, glycylglycine, 2,5
-By-products such as diketopiperazine, hydantoinamide and the like are contained. Therefore, by crystallization from the reaction solution,
Glycine is isolated as crystals. As the crystallization operation,
Generally, the reaction solution is usually concentrated in a temperature range of 50 to 150 ° C. to separate and remove most of the water in the reaction solution, as well as ammonia and carbon dioxide. Next, the concentrated reaction liquid is usually cooled to 5 to 50 ° C. to separate the precipitated crude crystals of glycine by filtration.

In the method for purifying glycine of the present invention, next,
The crude crystal thus obtained is redissolved in water. The glycine concentration in the solution is usually 20 to 70% by weight, preferably 30 to 50% by weight. If the concentration is too low, the recovery rate when recrystallizing glycine is lowered, and if the concentration is too high, the separation efficiency from impurities is lowered, which is not preferable.

Furthermore, the glycine recrystallized by adding an organic solvent soluble in water to the above-mentioned glycine solution in an amount of usually 1 to 20 times by weight, preferably 5 to 15 times by weight, of glycine. Analyze. The recrystallization temperature is usually 5 to 80.
C., preferably 20-60.degree. The water-soluble organic solvent of the present invention is a solvent that is uniformly mixed with water in the glycine solution under the above condition range. Such water-soluble organic solvents include methanol, alcohols such as ethanol, acetone, ketones such as mesityl oxide, tetrahydrofuran, alicyclic ethers such as dioxane, keto alcohols such as diacetone alcohol,
Examples thereof include lactones such as 2-pyrrolidone and N-methylpyrrolidone, acetonitrile and the like, and usually methanol and acetone are preferable. The purified crystals of glycine obtained by recrystallization are separated by filtration and dried to give the final product according to a conventional method.

[0012]

EXAMPLES The method of the present invention will be further described by way of Examples. The purity of glycine was analyzed by liquid chromatography.

Example 1 Using a Ti autoclave, glycolonitrile / N
A mixture of H ₃ / carbon dioxide / water = 1: 2: 2: 50 (molar ratio) was reacted at 165 ° C. for 3 hours. The obtained reaction solution was decompressed and concentrated at 80 ° C., further cooled to room temperature,
The precipitated crude glycine crystals (I) were filtered off. At this time, the purity of crude glycine crystals was 88.0%. Next, 100 parts by weight of this crude crystal was dissolved in 200 parts by weight in water. To this aqueous solution of glycine, 825 parts by weight of methanol was added, recrystallized at room temperature for 15 minutes, filtered, and then dried at 100 ° C. for 3 hours in a vacuum dryer. The purity of the obtained crystal was 99.5%. The recovery rate of glycine was 90.5%.

Example 2 A glycine recrystallization experiment was conducted in the same manner as in Example 1 except that the solvent was changed from methanol to acetone. The obtained glycine crystals had a purity of 99.2% and a recovery rate of 9
It was 2.3%.

Example 3 The solvent was changed from methanol to diacetone alcohol, and 40
A glycine crystallization experiment was carried out in the same manner as in Example 1 except that recrystallization was carried out at 0 ° C. The purity of the obtained glycine crystals is 9
The recovery rate was 9.3% and the recovery rate was 92.0%.

Comparative Example 1 The crude crystal (I) used in Example 1 was dissolved in 2.0 times by weight of water, stirred at 110 ° C. for 3 hours and then cooled to 20 ° C. for recrystallization. Crystals are separated by filtration and further dried under reduced pressure to 1
It was dried at 00 ° C. for 3 hours. The purity of the obtained glycine crystals was 90.0%, and the recovery rate was 37.2%.

[0017]

Industrial Applicability According to the method of the present invention, highly pure glycine can be efficiently obtained by a simple procedure without carefully washing the glycine crystal with a solvent. Glycine is an effective compound widely used as a raw material for food additives, agricultural chemicals, and pharmaceuticals, and the industrial utility value of the present invention is great.

Claims (1)

[Claims] 1. A glycine crystal obtained by crystallization of a reaction solution obtained by reacting glycolonitrile, carbon dioxide and ammonia in the presence of water, is redissolved in water, and then water is added to the solution. A method for purifying glycine, which comprises recrystallizing glycine by adding a soluble organic solvent to the glycine.