JPH0412265B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing hydantoin, and more particularly to a method for producing hydantoin in a high yield, with extremely few impurities, and in the form of white crystals. It has long been known that hydantoin provides α-amino acids through condensation reactions with various aldehydes, and is used industrially as a raw material for producing α-amino acids by the so-called hydantoin method. Substituted hydantoins into which hydantoins have been introduced are useful compounds as agricultural chemicals, pharmaceuticals, or intermediate raw materials for their production. (Prior Art) It is known that the production of unsubstituted hydantoin by the so-called Bucherer-Bergs reaction, which has been systematized as a method for synthesizing 5-substituted hydantoin, is insufficient in terms of yield and product quality ( HR
Henry et al., JACS; 64522 (1942)). However, various improved methods have been proposed since then, but all of them focus on improving the yield, and no method has been proposed for producing white crystals with high commercial value in good yield. For example, the method in JP-A-138557 proposes a reaction using a mixed solvent of water and water-soluble alkoxyethanol, but in order to obtain a white crystal product, reconsolidation and activated carbon treatment are required. is required, and the operation for recovering the solvent after the reaction is complicated. (Problems to be Solved by the Invention) The present inventors have developed a method for producing hydantoin with high yield, high selectivity, and significantly improved coloring by the cyanohydrin method, by improving the drawbacks seen in the prior art. That is, various studies were conducted to find a method for economically producing high-quality hydantoin.
As a result, they discovered that the objective could be achieved by limiting the molar ratio of ammonia to carbon dioxide gas in the reaction system and the glycolonitrile concentration in the reaction system, and arrived at the present invention. (Means for Solving the Problems) That is, the present invention provides a method for producing hydantoin by reacting glycolonitrile with carbon dioxide and ammonia using water as a reaction solvent, including: (a) carbon dioxide and ammonia in the reaction system; The molar ratio of both is carbon dioxide/ammonia ≧
(b) supplying glycolonitrile so that the concentration of glycolonitrile in the reaction system does not exceed 1.1%. In the method of the present invention, the relationship in the amounts of the raw materials glycolonitrile, carbon dioxide, and ammonia in the reaction system is important. That is, the molar ratio of carbon dioxide gas/ammonia in the reaction system is 0.7 or more,
From the economic point of view, it is preferably supplied in a range of 0.75 to 1.5. If this molar ratio is less than 0.7, the coloring of the reaction product liquid will be significant, and the hydantoin crystals of the reaction product will become pale yellow, which is not preferable, and the yield will also decrease. On the other hand, if the molar ratio exceeds 1.5, the effect on hue and yield is small, but the reaction pressure becomes abnormally high, which is economically disadvantageous and undesirable. In the method of the present invention, ammonium carbonate or ammonium bicarbonate can also be used instead of carbon dioxide gas and ammonia. The molar ratio of ammonia and carbon dioxide to glycolonitrile is as follows. Carbon dioxide/Glycolonitrile≧1.0 Ammonia/Glycolonitrile≧1.2 Carbon dioxide, ammonia and glycolonitrile are used so as to satisfy this relationship. In the method of the present invention, the concentration of glycolonitrile in the reaction system is 1.1% or less. When the glycolonitrile concentration exceeds 1.1%, the coloring of the liquid becomes significant and the yield also decreases. This is presumed to be because glycolonitrile reacts with aminoacetonitrile, which is an intermediate. In other words, in order to improve the hue and yield, it is necessary to keep the carbon dioxide/ammonia molar ratio at least 0.7 in order to shorten the existence time of aminoacetonitrile produced as an intermediate as much as possible. In order to suppress side reactions of the aminoacetonitrile produced, it is necessary to keep the glycolonitrile concentration in the reaction system to 1.1% or less. Further, the reaction may be carried out either batchwise or continuously, but it is preferable to carry out the reaction in a semi-batch manner because it is easier to control the glycolonitrile concentration in the reaction system to 1.1% or less. The reaction is preferably carried out under sealed pressure, and the reaction temperature is usually 60 to 150°C, preferably
It is in the range of 80-120℃. The reaction time varies depending on the reaction temperature, but usually
It ranges from 0.25 to 5 hours. After the reaction, the obtained crude product is subjected to acid treatment by adding an acid such as sulfuric acid or hydrochloric acid to an acid concentration of 10 to 30% by weight, and stirring at a temperature of 70 to 100°C for 2 to 3 hours. Hydantoic acid and hydantoic acid amide can be cyclized to hydantoin. (Operations and Effects of the Invention) The advantages brought about by the present invention are as follows. (1) Since the reaction has high selectivity and most of the by-products are hydantoic acid amide, by-products can be easily removed by acid treatment using mineral acid at 70-100℃ for 2-3 hours after the reaction. It becomes hydantoin, and the yield reaches over 90%. (2) Since the process is carried out under conditions of excessive carbon dioxide gas, there are few by-products of amines and colored components are reduced, and white crystalline hydantoin can be easily obtained by methods such as activated carbon treatment. (3) Since the reaction is possible even at high temperatures of 80 to 120°C or higher, the reaction time can be shorter than conventional methods. That is, by the method of the present invention, hydantoin with extremely high yield and excellent hue can be obtained. (Example) Hereinafter, the present invention will be specifically explained with reference to Examples. Note that the chromaticity in the Examples was measured by the following method. Add and dissolve 2.49 g of potassium chloroplatinate (K ₂ PtCl ₆ ), 2.0 g of crystalline cobalt chloride (CoCl ₂ .6H ₂ O) and 200 ml of concentrated hydrochloric acid, and then dilute to 1 with water. The absorbance of this liquid at a wavelength of 370 mμ was measured using a colorimeter, and this was defined as a chromaticity of 1000 degrees.
The chromaticity of 10 times dilution was defined as 100 degrees. Example 1 150.9 g of ammonium bicarbonate, 38.5 g of 28.10% ammonia aqueous solution, and 510.6 g of pure water were charged into a glass pressure-resistant reaction vessel with an internal volume of 1000 ml and equipped with a pressure sampling device and a stirring device, and the mixture was heated to 100°C. Warm up. ( _CO2 / _NH3 =0.75 molar ratio). When the temperature reached 100°C, 72.6 g of 50% by weight glycolonitrile was charged over 1 hour (NH ₃ /
glycolonitrile = 4.0 molar ratio). Charging speed is 1.21
g/min. After charging, the mixture was reacted for 1 hour and concentrated under reduced pressure to obtain 28.6 g (yield: 45%) of hydantoin and 34.5 g (yield: 46%) of hydantoic acid amide. Sampling was performed 30 minutes after the start of glycolonitrile charging, and total cyanide was analyzed by the method described in JISKO102. When converted to unreacted glycolonitrile, the glycolonitrile concentration was 0.6%. Furthermore, after charging glycolonitrile, sampling was immediately performed, analyzed in the same way, and converted to 0.8.
It was %. Aminoacetonitrile (NH ₂ CH ₂ CN), which is considered as an intermediate, was not detected as a cyanide compound by the JISKO102 method. After concentration, acid treatment is performed by refluxing with 20% sulfuric acid for 3 hours, and the resulting solution is passed through an activated carbon layer packed in a 150 mm x 15 φ column to neutralize it, and further concentrated to produce white hydantoin.
55.4g (87% yield) was obtained. The chromaticity of the liquid after passing through activated carbon was 250. Examples 2 to 4, Comparative Example 1 Using the same reactor as in Example 1, the amounts of ammonium bicarbonate and ammonia aqueous solution were varied to examine the influence of the molar ratio. Table 1 shows the results. The crude reaction liquid represents the reaction liquid in Example 1, which was reacted for 1 hour after charging glycolonitrile. Fixed NH ₃ / glycolonitrile = 4.0 molar ratio,
Other conditions were the same as in Example 1.

[Table] With the chromaticity of Comparative Example 1, no white crystals were obtained even if decolorized by the method of Example 1. In Examples 3 to 5, white crystals were obtained. The carbon dioxide/ammonia molar ratio is preferably 0.7 or more. Comparative Example 2 In the pressure-resistant reaction vessel of Example 1, 150.9 g of ammonium bicarbonate, 38.5 g of 28.10% ammonia aqueous solution,
Pure water 510.6 g, 50% by weight glycolonitrile 72.6
Charge g and seal (CO ₂ /NH ₃ = 0.75 molar ratio, NH ₃ / glycolonitrile = 4.0 molar ratio), 1.25
The temperature was raised to 100°C over time, and when the temperature reached 100°C, sampling was performed and the glycolonitrile concentration was determined to be 1.2%. Thereafter, the reaction was carried out at 100°C for 2 hours. The yields of hydantoin and hydantoic acid amide were 39% and 36%, respectively. Purification with acid treatment and activated carbon was carried out in the same manner as in Example 1. The yield of hydantoin was 71%, and the color of the crystals was pale yellow. The chromaticity of the liquid after passing through activated carbon was 510. Examples 5 to 7, Comparative Example 3 150.9 g of ammonium bicarbonate, 38.5 g of 28.10% ammonia aqueous solution, and 510.6 g of pure water were placed in the same glass pressure-resistant reaction vessel as in Example 1, and heated to 100°C. When the temperature reached 100°C, 72.6 g of 50% by weight glycolonitrile was charged intermittently and in portions over 1 hour (CO ₂ /NH ₃ = 0.75 molar ratio, NH ₃ / glycolonitrile = 4.0 molar ratio). . Table 2 shows the number of divisions and the results obtained by analyzing, concentrating, and acid-treating glycolonitrile in the same manner as in Example 1.

[Table] Example 8 In the same glass pressure-resistant reaction vessel as in Example 1.
154.0 g of a 28.10% ammonia aqueous solution and 427.6 g of pure water were charged, the container was sealed, and 84.0 g of carbon dioxide was further supplied from a cylinder (CO ₂ /NH ₃ =0.75 molar ratio). After heating to 100°C, the same method as in Example 1 was carried out, and white crystals were finally obtained with a hydantoin reaction yield of 81%. The chromaticity of the liquid at that time was 230.

Claims (1)

[Claims] 1. A method for producing hydantoin by reacting glycolonitrile with carbon dioxide and ammonia, in which (a) the molar ratio of carbon dioxide and ammonia in the reaction system is carbon dioxide/ammonia ≧0.7;
(b) The concentration of glycolonitrile in the reaction system is
A method for producing hydantoin, characterized in that glycolonitrile is supplied in an amount not exceeding 1.1%.