JP2907582B2 - Glycine purification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying glycine and, more particularly, to a method for obtaining practically colorless glycine from an aqueous glycine solution. Glycine is a useful compound widely used as a food additive for processed foods, a raw material for agricultural chemicals and pharmaceuticals.

[0002]

2. Description of the Related Art Hitherto, as a method for producing glycine, (1) amination method of monochloroacetic acid, (2) Strecker method, (3) hydantoin method and the like have been known.

(1) In the amination method of monochloroacetic acid, the raw materials are expensive, and ammonium mineral salts such as ammonium chloride, iminodiacetic acid, and nitrilotriacetic acid are formed, and the separation of these from glycine is complicated. .

(2) The Strecker method is a method in which glycolonitrile, which can be synthesized from hydrocyanic acid and formalin, is reacted with ammonia and then hydrolyzed with an alkali such as sodium hydroxide to produce a metal salt of glycine. Cannot be directly produced.

As a method for producing free glycine from the glycine metal salt, (a) a method of ion-exchanging a glycine metal salt with an acidic cation exchange resin or (b)
Although a method of neutralizing and desalting with a mineral acid such as sulfuric acid is known, the use of an ion exchange resin requires a huge amount of resin,
On the other hand, when, for example, sulfuric acid is used as the mineral acid, separation of glycine from sodium sulfate as a neutralizing salt, iminodiacetic acid as a by-product, and the like becomes complicated, and treatment of these neutralizing salts becomes a problem. .

(3) The hydantoin method comprises glycolonitrile and ammonia which can be synthesized from hydrocyanic acid and formaldehyde.
This is a method for producing hydantoin by reacting carbon dioxide gas in the presence of water and producing glycine by hydrolysis. When sodium cyanide or potassium cyanide is used instead of hydrocyanic acid as a raw material, or when an alkali such as sodium hydroxide is used in hydrolysis, free glycine cannot be directly produced as in the case of the Strecker method, As a result, there are also problems such as treatment of neutralized salts.

In this hydantoin method, a method for directly obtaining glycine without using an alkali such as sodium hydroxide (hereinafter referred to as a direct hydantoin method) does not involve by-products such as sodium sulfate and the like, and has no pollution and economical glycine. It is a manufacturing method.

As such a direct hydantoin method, for example, a method of heating hydrogen cyanide, aldehyde, ammonia and carbon dioxide in an aqueous solvent at 100 ° C. or more (USP 3,5)
36,726).

For the decolorization of crude glycine obtained by the above-mentioned various methods, a method of treating an aqueous solution of crude glycine with an ion exchange resin or activated carbon is generally known. Crystallization using methanol and washing with methanol are also effective for decolorization.

In the Strecker method, in order to obtain free glycine, a metal salt of glycine is usually neutralized with sulfuric acid or the like to about 6 to 7 which is convenient for crystallization of glycine, and desalting is carried out. In the state of glycine aqueous solution containing salt,
Alternatively, decolorization is performed using activated carbon, an anion exchange resin, or the like in the state of an aqueous glycine solution from which most of the neutralized salt has been separated.

In Japanese Patent Publication No. 54-1686, glycine obtained by the Strecker method, the monochloroacetic acid method, etc. is treated with a weakly basic anion exchange resin or a medium basic ion exchange resin at 50 ° C. or lower at a pH of 7 or less. A method for purifying glycine is disclosed. Furthermore, when activated carbon is used for decolorization, the crude glycine is decolorized at first glance, but recolors when heated for concentration.Therefore, when activated carbon is used, it is necessary not only to repeat recrystallization, but also to use the amount of activated carbon. It is also described that this will be enormous.

On the other hand, US Pat. No. 3,536,726 discloses a method for decolorizing a colored glycine obtained directly by a hydantoin method, in which a glycine is obtained by treating a reaction solution as it is with activated carbon and performing crystallization with methanol. No. 127915 discloses a method in which glycine crystals are precipitated by concentrating the reaction solution under reduced pressure, decolorized with activated carbon, and recrystallized with water-methanol to obtain white glycine.

[0013]

As shown in JP-B-54-1686, when activated carbon is used for decolorizing glycine,
The amounts used are high and the known methods are not efficient and uneconomical.

The reaction solution obtained by the direct hydantoin method is also colored yellow to brown as in the other methods, and the reaction solution is described by the present inventors in the above-mentioned US Pat.
As a result of using the method described in Example of -127915, it was found that the amount of activated carbon used was enormous and was not industrially feasible at all. Further, in the method described in JP-B-54-1686, that is, a method in which a crude glycine aqueous solution adjusted to pH 7 or less with hydrochloric acid is used and treated with a weakly basic anion exchange resin, the decolorization rate is about 60 to 70%. In addition, it was found that the service life of the weakly basic anion exchange resin was short, and it was not applicable to the decolorization of glycine by the direct hydantoin method.

[0015] As described above, even if the known method is industrially implemented, the economic efficiency is not yet sufficient. Especially,
At present, there is no known effective method for decolorizing a reaction solution obtained by the direct hydantoin method.

An object of the present invention is to provide a method for producing a colored glycine,
It is to provide an industrially economical decolorization method.

[0017]

Means for Solving the Problems As a result of intensive studies on the method for decolorizing glycine, the present inventors have found that the decolorizing ability of an aqueous glycine solution with activated carbon is extremely small at pH 6 to 7,
In addition, it was found that at pH 7 or more, the adsorbed colored impurities were rather eliminated. Further, the inventors have found that the activated carbon used for decolorization can be easily regenerated with an aqueous alkali solution, and completed the present invention. That is, the present invention is the presence of water
Reacts glycolonitrile, carbon dioxide and ammonia
And then remove carbon dioxide and ammonia from the resulting reaction solution.
The glycine-containing aqueous solution from which most of the
Less selected from mechanical acid or acidic cation exchange resin
A method for purifying glycine, characterized in that at least one of them is adjusted to pH 3.5 to 6, and then treated with activated carbon.
Further, the present invention provides the glycine-containing aqueous solution by crystallization.
Once separated into glycine and mother liquor, and the mother liquor is transferred to the reactor.
Glycine that has been recycled and the glycine has been converted to an aqueous solution again
Use aqueous solution with mineral acid, organic acid or acidic cation exchange resin
PH 3.5 to 6 with at least one selected from
A method for purifying glycine, characterized in that the glycine is treated with activated carbon after conditioning .

According to the method of the present invention, it is possible to treat only activated carbon, which was conventionally considered to be inapplicable industrially,
Almost completely decolorization can be achieved, the amount of activated carbon used can be greatly reduced, and regeneration is easy.

The aqueous solution applied to the present invention is directly
The present invention can be applied to an aqueous solution of crude glycine obtained by the Toin method and further to a case where glycine is present as a solution in the production process. The concentration of glycine in the aqueous solution is 2 to 45% by weight, preferably 5 to 35% by weight at the time of the activated carbon treatment. If this concentration is less than 5 wt%, the utility cost of concentrating the aqueous solution of glycine after decolorization increases, and if it exceeds 35 wt%, glycine precipitates, so the activated carbon treatment equipment needs to keep the temperature at 80 ° C or higher, On the contrary, when an ion exchange resin is used for adjusting the pH of the aqueous solution to be treated, deterioration of the resin is promoted, which is not preferable.

[0020]

The pH of the aqueous glycine solution is adjusted to 3.5 to 6 by using at least one selected from mineral acids, organic acids and acidic cation exchange resins, alone or as a mixture or in combination. Can be. For example, it can be carried out by adding a mineral acid such as sulfuric acid, phosphoric acid or hydrochloric acid, or an organic acid such as formic acid, acetic acid or oxalic acid alone or as a mixture, or treating an aqueous solution with an acidic cation exchange resin. Furthermore, when treating with an acidic cation exchange resin, it is also possible to use the above mineral acids and organic acids in combination.

As the acidic cation exchange resin used in the method of the present invention, commercially available products can be used. Examples of such ion exchange resins include, for example, Amberlite IR-116 by trade name,
IR-252, IRC-84 (Organo Co., Ltd.), Diaion SK1
02, SK110, PK212, WK10, WK20 (Mitsubishi Chemical Corporation),
Levacit S100, SP112, CNP80 (Mitsui Toatsu Fine Co., Ltd.) and the like. The cation exchange resin itself has little decoloring ability, but is preferred as a method for adjusting the pH of the glycine aqueous solution, which is important in the present invention. Among these, the use of a strongly acidic cation exchange resin is preferable because the pH can be adjusted to a low value of 4 to 5, the decoloring ability with the next activated carbon can be improved, and the life of the activated carbon can be prolonged. The ion form of the acidic cation exchange resin may be a salt form, but H form is preferably used.

It is preferable that the pH value after the pH adjustment is low, but if the pH value is 2 or less, an expensive material is required.
If it is less than 3.5, the solubility of glycine in water increases, which adversely affects the subsequent crystallization step, which is not preferable. On the other hand, when the pH exceeds 6, the decolorizing ability by activated carbon is low,
At a pH of 7 or more, the coloring substance adsorbed on the activated carbon is desorbed. Accordingly, the pH to be adjusted is in the range of pH 3.5 to 6, preferably in the range of pH 4 to 5.5, and more preferably in the range of pH 4.5 to 5.3.

The activated carbon used in the method of the present invention may be made of a plant such as coconut shell or a mineral such as coal or pitch. For example, in the case of coconut shell charcoal, trade names are Shirasagi C (Takeda Pharmaceutical), Tsurumikoru HC-30 (Tsurumi), etc.
For coal-based products, trade names include CPG, CAL (Toyo Calgon), and A-BAG (Kureha Chemical). Among them, activated carbon such as CPG which is acid-treated so that trace components of activated carbon are not eluted even when an acidic solution is passed through is particularly preferable.

In the method of the present invention, for the pH adjustment with an acidic cation exchange resin or the decolorization treatment with activated carbon, a method of passing a liquid through a packed column, which is generally performed, is preferred because it is efficient. As in the case of the acidic cation exchange resin and activated carbon, the packing length / diameter is 2 or more and 20 or more.
The processing is performed in the following range, and the processing speed is set to SV (liquid space velocity) of 0.1.
It is in the range of 1-20. The pH adjustment temperature and the decolorization temperature with activated carbon are not limited, but the pretreatment with an acidic cation exchange resin is preferably in the range of 20 to 80 ° C, and the activated carbon is preferably in the range of 20 to 100 ° C.

If necessary, an anion exchange resin may be used after the activated carbon treatment or before the step of performing the acid treatment to remove anions and to remove an extremely small amount of coloring that cannot be completely removed by the activated carbon alone. Substances can also be removed, and further improvement in glycine purity can be expected.

It has been found that the activated carbon used for decolorization in the present invention can be easily regenerated with a general-purpose alkaline aqueous solution such as sodium hydroxide. Furthermore, it has been found that the regeneration efficiency is further improved by adding a mineral salt such as sodium chloride to the alkaline aqueous solution. Activated carbon regeneration is performed by applying an aqueous alkali solution such as 0.1 to 10 equivalents of sodium hydroxide, which is 2 to 30 times the amount of activated carbon to be regenerated, at the liquid space velocity.
It is preferable to remove impurities adsorbed on the activated carbon by passing the solution at 0.05 to 20 (1 / H), and then wash it with 2 to 50 times the amount of activated carbon to be regenerated. Further, an alkaline aqueous solution containing a mineral acid salt such as sodium chloride or sodium sulfate is preferable. The content of these salts is preferably in the range of 1 to 20% by weight, more preferably 5 to 10% by weight in the aqueous alkali solution. As a result, the operation of extracting activated carbon for regeneration as performed in most other production methods becomes unnecessary, and the initial filling amount of activated carbon can be further reduced. The regeneration temperature of activated carbon is not particularly limited,
Usually it is 20-90 ° C.

The adjustment of the pH of the reaction solution obtained by the direct hydantoin method of the present invention will be described below.

As described above, the direct hydantoin method refers to a method in which carbon dioxide and ammonia are removed from a reaction solution obtained by reacting glycolonitrile, carbon dioxide and ammonia in the presence of water to obtain a glycine-containing aqueous solution. it can.

The glycolonitrile used here is most commonly and economically manufactured using hydrocyanic acid and formalin as raw materials. Even if paraformaldehyde is dissolved in water as a formalin source, it can be used. it can.
The reaction for producing glycolonitrile is fast, for example,
Injecting prussic acid in gaseous form into an aqueous solution of holymarin,
Glycolonitrile is easily formed simply by mixing hydrocyanic acid in a liquid form with an aqueous formalin solution. The reaction temperature here is
It is sufficient that the reaction is carried out at 0 to 80 ° C. for 2 minutes to 5 hours. Further, glycolonitrile can be used even if it contains sulfuric acid, phosphoric acid or the like used as a stabilizer.

Ammonia and carbon dioxide may be used as they are, but compounds known to those skilled in the art for producing these compounds (ammonia or carbon dioxide) under the reaction conditions, such as ammonium carbonate and ammonium bicarbonate May be used. Further, even when these are mixed and used, preferable results are obtained.

The molar ratio of the starting materials in the reaction is such that the amount of ammonia used is 1 to 12 moles per mole of glycolonitrile, and the amounts of carbon dioxide and water are determined by the amount of ammonia used. Therefore, the amount of carbon dioxide gas and water used per mole of ammonia is 1/3 to 3 moles, respectively.
~ 15 moles.

The lower the reaction temperature, the higher the glycine yield, but the lower the reaction rate. However, when the reaction temperature is high, the reaction rate is high, but the coloration of the reaction solution is remarkable, so that the reaction temperature is usually 100 to 200 ° C, preferably 140 to 180 ° C, more preferably 150 to 170 ° C. The reaction time is usually
It is 30 minutes to 20 hours, preferably 1 to 10 hours.

The reaction pressure is not particularly limited, and the reaction may be performed at a pressure higher than the pressure generated during the reaction, or the reaction may be performed by appropriately extracting ammonia, carbon dioxide, water vapor or the like generated during the reaction. be able to.

After the completion of the reaction performed under these conditions, the raw material glycolonitrile does not substantially remain in the reaction solution containing glycine, but in addition to glycine, hydantoic acid, glycylglycine, hydantoin, etc. It contains by-products such as acid amide, triglycine, hydantoin, and 2,5-diketopiperazine. Concentrate these reactions,
Glycine is separated by a crystallization method described later or the like. Specifically, the reaction solution is flashed and / or heated at about 50 to 200 ° C. and about 10 mmHg to 30 kg / cm ² to evaporate water and concentrate the reaction solution. At this time, usually, ammonia and carbon dioxide are also vaporized and separated from the reaction solution. Incidentally, an inert gas such as air or nitrogen may be blown at about 50 to 200 ° C. and about 10 mmHg to 30 kg / cm ² , and separated from the reaction solution by stripping carbon dioxide gas and ammonia. Concentration of the reaction solution
It is carried out for 10 seconds to 20 hours, preferably for about 1 minute to 10 hours.

What is important in this step is to sufficiently separate carbon dioxide gas and ammonia from the reaction solution. If the separation of carbon dioxide and ammonia is insufficient, in the step of crystallizing the concentrated solution to separate glycine, these precipitate as ammonium carbonate and adhere to the glycine crystals. As a result, the amount of the colored mother liquor adhered to the glycine crystals is larger than that of the high-purity glycine crystals. As a result, not only a large amount of rinsing water is required, but also when a mineral acid is used for pH adjustment, the ammonium salt of the mineral acid increases, and when an acidic cation exchange resin is used for the acid treatment, Is unfavorable because its life is shortened. Therefore, it is preferable that the residual concentrations of carbon dioxide gas and ammonia in the concentrated liquid be 10 wt% or less in terms of ammonium carbonate. This concentrated liquid may be subjected to activated carbon treatment by adjusting the pH as it is, but it is preferable to use an aqueous glycine solution in which glycine is separated and dissolved in water as shown below.

The concentrated liquid in this case is cooled to, for example, about 0 to 80 ° C. to precipitate glycine crystals. The method of precipitating glycine from this concentrated solution is performed by a method known to those skilled in the art. For example, a crystallization method such as a cooling crystallization method, an evaporation crystallization method, or a vacuum crystallization method is preferably used industrially. . It is also possible to add a crude solvent such as methanol to the concentrated solution for crystallization.

The slurry obtained by such a crystallization method is then subjected to solid-liquid separation into glycine crystals and a mother liquor using a general-purpose separator, and the mother liquor is returned to the reactor. By circulating the mother liquor, not only the ammonium carbonate in the mother liquor can be effectively reused, but also the glycine yield can be greatly improved. The crystallization ratio at this time is preferably 40% by weight or more. If the crystallization rate is less than 40% by weight, not only is the reactor bulky, but also the crystallization cost is increased, which is not economical. However, even if the crystallization rate is 40 wt% or more, the purity is 95 wt%.
% Glycine is obtained.

PH when the glycine crystal is converted to an aqueous solution
Can be controlled to some extent by adjusting the concentration ratio of the reaction solution, but pH can be controlled by ordinary concentration operation alone.
It can only be obtained in the range of 8-9.

When glycine is separated by a centrifugal separator or the like, washing the glycine crystal with water of 15 to 35% by weight or washing with glycine-containing water improves the glycine purity and increases the ammonia attached to the glycine crystal. Is further removed. However, the pH of the solution obtained by dissolving the obtained glycine crystals in water is still about 6.5 to 7.5.

If this glycine aqueous solution is directly treated with activated carbon, it cannot be completely decolorized, and the life of the activated carbon is shortened, so that it cannot be used industrially. These aqueous solutions have a pH of 6 or less , that is , a pH of 3.5 to 6 by the operation described above .
Adjust to a range . The aqueous glycine solution adjusted to the pH of 3.5 to 6 is almost completely decolorized in the subsequent activated carbon treatment, the color return is hardly recognized, and the life of the activated carbon is greatly extended.

Glycine is separated and separated from the above-mentioned concentrated solution,
When the mother liquor is circulated through the reactor and the glycine thus precipitated is dissolved in water and decolorized, pH adjustment should be made in consideration of accumulation in the mother liquor or contamination of the glycine crystals with acidic cation exchange resin. It is desirable to use The acidic cation exchange resin has almost no decoloring ability, but its pH can be adjusted to 4-5.5, which is optimal for glycine crystallization after activated carbon treatment.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

Example 1 An 2202 g aqueous solution containing 115 g (2.01 mol) of glycolonitrile, 206 g (12.1 mol) of ammonia, and 267 g (6.1 mol) of carbon dioxide gas per hour was placed in a 10 liter tubular reactor. The reaction was carried out at a reaction temperature of 150 ° C. and a reaction pressure of 32 kg / cm ² -G.

The raw material composition was H ₂ O / NH ₃ / CO ₂ / glyconitrile = 45/6/3/1 molar ratio, and the average residence time was 5 hours. When it becomes steady, the reaction solution is continuously kept at normal pressure at 100 ℃
, Water, ammonia and carbon dioxide gas totaling 1830g
After removal, crystallization was performed at 5 ° C. 5 ° C pure water per hour
While rinsing with 16 g, glycine 0.89 mol (purity
98.2 wt%). As a result of analysis of the remaining mother liquor, a total of 0.97 mol of hydantoic acid, glycylglycine, hydantoic acid amide, 2,5-
Diketopiperazine, hydantoin, triglycine and glycine were detected. Thus, a mother liquor for initial supply was prepared.

Next, this mother liquor, a 50 wt% aqueous solution of glycolonitrile and an aqueous solution of ammonium carbonate were supplied to a reactor so that the supply composition in terms of glycolonitrile was the same. That is, per hour, the mother liquor, 22 g of an aqueous solution containing 59 g (1.04 mol) of glycolonitrile and 6.1 mol of ammonium carbonate are supplied to a reactor, and the obtained reaction solution is continuously used at 100 ° C. using a concentrator. Concentrate,
Remove water, ammonia and carbon dioxide gas in total of 1916 g
Crystallize at ℃ and rinse with glycine 68g per hour
(98.6% purity). This amount corresponds to a glycine yield of 86%. In this concentration step, ammonia and carbon dioxide gas are substantially removed.

The glycine crystals (purity 98.6%) were dissolved in water at 70 ° C. to prepare a 20 wt% glycine aqueous solution (pH 7.3), which was used for decolorization. The chromaticity of this glycine aqueous solution was 162 when expressed in Hazen color (APHA).

[0048] 300 ml of H-type weakly acidic cation exchange resin (Levatit CNP80) and 100 ml of activated carbon (CPG) pretreated in a usual manner were charged into tubular columns having diameters of 3.5 cm and 2.5 cm, respectively. 50 ℃ at 25 ℃, 200ml / H
kg, the pH at the outlet of the acidic cation exchange resin tower is
5.5, APHA is 148, APHA at the outlet of activated carbon tower is 2-2.
It was five. At this time, the glycine recovery rate was 99.8%. Table 1 shows the results. Further, even if the obtained decolorized solution was concentrated, the coloration hardly increased, and 1 g of glycine crystals (purity: 99.3 wt%) obtained by cooling was dissolved in 10 g of water, and the absorbance (10 mm cell) was examined. Result, 370nm, 430nm
The absorbance at both wavelengths is 0.000 to 0.005, which corresponds to 0 to 3 for APHA. In addition, as a result of measuring commercially available glycine by the same method, APHA was in the range of 3 to 6.

Example 2 A decolorization test was carried out in the same manner as in Example 1 except that a strongly acidic cation exchange resin (Levatit SP112) was used instead of the weakly acidic cation exchange resin, and that the activated carbon was changed to Shirasagi C. went. As a result, the pH at the outlet of the acidic cation exchange resin tower was 4.
5, APHA was 139, and APHA at the outlet of the activated carbon tower was 1.8 up to a value of 50 kg. The glycine recovery rate at this time is
99.2%. Table 1 shows the results.

Example 3 A decolorization test was carried out in the same manner as in Example 1 except that the aqueous glycine solution was adjusted to pH 5.0 with phosphoric acid without using a weakly acidic cation exchange resin. As a result, the APHA at the outlet of the activated carbon tower at the time of passing 10 kg of the liquid was 0.6. The glycine recovery at this time was 99.4%.

Comparative Example 1 The 20 wt% glycine aqueous solution obtained in Example 1 (pH
7.3, APHA162) was subjected to a decolorization test in the same manner as in Example 1 except that it was treated with activated carbon (CPG) without pretreatment with an acidic cation exchange resin. When 10 kg of the glycine aqueous solution was passed, the APHA at the outlet of the activated carbon tower was 14. The glycine crystals obtained by crystallization from the decolorized aqueous glycine solution had an APHA of 6 to 10. In addition, 50kg in total
After passing the liquid, the chromaticity at the outlet of the activated carbon further increased. Table 1 shows the results.

Comparative Example 2 In Example 1, glycine crystals were obtained without rinsing, and dissolved in water at 60 ° C. to prepare a 20 wt% glycine aqueous solution (pH 8.1, APHA193). An aqueous solution was used. Activated carbon (CPG) using this raw material without pretreatment with acidic cation exchange resin
Except having performed the process, it carried out by the method similar to Example 1. When 10 kg of glycine aqueous solution is passed, APHA at the outlet of the activated carbon tower is
It was 20. Table 1 shows the results.

[0053]

[Table 1]

Example 4 2220 g of an aqueous solution containing 115 g (2.01 mol) of glycolonitrile, 206 g (12.1 mol) of ammonia, and 267 g (6.1 mol) of carbon dioxide gas per hour was fed into a 10-liter tubular reactor. The reaction was carried out at a reaction temperature of 150 ° C. and a reaction pressure of 32 kg / cm ² -G.

The raw material composition was H ₂ O / NH ₃ / CO ₂ / glyconitrile = 45/6/3/1 molar ratio, and the average residence time was 5 hours. When the reaction became steady, the reaction solution (APHA720, glycine concentration 5 wt%) was pretreated by the usual method in the same manner as in Example 1 to obtain an H-type strongly acidic cation exchange resin (Amberlite 200C).
T) 1000 ml and activated carbon (CPG) 100 ml each with a diameter of 3.
The APHA at the outlet of the activated carbon tower at the time when 10 kg of a reaction solution containing glycine was charged into a 5 cm or 2.5 cm tubular column at 25 ° C. and at a rate of 200 ml / H was 3.6. Further, the resulting decolorized solution is concentrated and crystallized to obtain glycine crystals (purity 9
APH of glycine aqueous solution in which 1 g is dissolved in 10 g of water
A was 3, which was satisfactory quality.

Example 5 A decolorization test was carried out in the same manner as in Example 4 except that the pH was adjusted to 4.7 with acetic acid without using an acidic cation exchange resin. The APHA of the glycine crystals obtained by concentrating and crystallizing the decolorized water at the time when 10 kg of the reaction solution containing glycine was passed was 3, which was satisfactory quality.

Comparative Example 3 A decolorization test was performed in the same manner as in Example 4 except that the pH of the reaction solution was not adjusted with an acidic cation exchange resin. When 5 kg of the reaction solution was passed, the APHA at the outlet of the activated carbon tower was already 52. Furthermore, glycine was precipitated by adding methanol, but the APHA of the glycine crystal was 12, and satisfactory quality was not obtained.

Comparative Example 4 A weakly basic anion exchange resin (Amberlite IRA-93, without using an acidic cation exchange resin and activated carbon)
A decolorization test was performed in the same manner as in Example 1 except that 300 ml) was used. As a result of passing 10 kg of the glycine aqueous solution, APHA at the outlet of the anion exchange resin tower was 23. APHA of an aqueous glycine solution obtained by dissolving 1 g of glycine crystals obtained by concentrating and crystallizing the decolorized solution in 10 g of water was 9, and satisfactory quality was not obtained.

[0059]

EFFECT OF THE INVENTION The aqueous glycine solution is placed in an acidic region,
By adjusting to a range of 3.5 to 6, not only can the color be almost completely decolorized only by the activated carbon treatment, but also the life of the activated carbon itself is dramatically improved. As described above, the method of the present invention improves the production of glycine by the direct hydantoin method to an industrially advantageous method.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Atsuhiko Higashi 1-6-6 Takasago, Takaishi City, Osaka Pref. Inspector, Mitsui Toatsu Chemical Co., Ltd. Examiner, Toshiro Karaki (56) References JP-A-53-31616 A) JP-A-52-118421 (JP, A) JP-A-47-12719 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 229/08 C07C 227/40

Claims (2)

(57) [Claims] 1. Glycolonitrile and carbon dioxide in the presence of water
And ammonia, and then the resulting reaction solution
From which most of the carbon dioxide and ammonia have been removed
Synthesizing aqueous solution with mineral acid, organic acid or acidic cation
At least one selected from exchange resins and a pH of 3.5
A method for purifying glycine, which is adjusted to ~ 6 and then treated with activated carbon. 2. The glycine-containing aqueous solution according to claim 1,
Once separated into glycine and mother liquor by crystallization,
Recycled to the reactor, and the glycine was converted to an aqueous solution again
Glycine aqueous solution with mineral acid, organic acid or acidic cation
At least one selected from exchange resins and a pH of 3.5
A method for purifying glycine, which is adjusted to ~ 6 and then treated with activated carbon.