Co-production recovery process of 5-ethyl hydantoin and hydrochloride

Abstract

The co-production and recovery process comprises the following steps: dissolving alpha-aminobutyric acid and potassium cyanate in water, and carrying out heating reaction to obtain an intermediate water solution; directly dropwise adding hydrochloric acid into the intermediate water solution, heating for reaction, cooling and filtering to obtain a main product filter cake and mother liquor; and drying the obtained main product filter cake to obtain the 5-ethyl hydantoin. Adding potassium hydroxide into the mother liquor to adjust the pH value, carrying out reduced pressure distillation until no distillate exists, adding ethanol, heating and filtering to obtain a potassium chloride filter cake and ethanol filtrate; concentrating and drying the ethanol filtrate, and recovering to obtain 5-ethyl hydantoin; washing the potassium chloride filter cake with ice water; drying the washed potassium chloride filter cake to obtain potassium chloride; and concentrating and drying the washing water after washing the potassium chloride filter cake to obtain the potassium chloride / ammonium chloride composite salt. According to the method, the product yield is increased, the waste liquid amount is reduced, and the production cost is further reduced, so that the method is very suitable for industrial large-scale environment-friendly production.

Description

Technical Field

[0001] The invention relates to a combined production process of a silver plating complexing agent and hydrochloride. Background Art

[0002] Both cyanide and hydantoin compounds can be used as coordination agents for silver ions in silver plating solutions. 5-Ethylhydantoin is a typical hydantoin compound with a ring-shaped carbonyl structure. The carbonyl group is connected to two NH bonds, so the lone pair of electrons of the N atom can form coordination bonds with the empty orbital of the metal ion.

[0003] However, the traditional synthesis route of 5-ethylhydantoin has problems such as low yield, large amount of waste liquid and high production cost, which is particularly inconsistent with the current trend of energy conservation and environmental protection. Summary of the invention

[0004] The object of the present invention is to provide an improved production process for 5-ethylhydantoin which is particularly suitable for industrial-scale production.

[0005] The present invention provides a co-production and recovery process of 5-ethylhydantoin and hydrochloride, comprising:

[0006] Dissolve α-aminobutyric acid and potassium cyanate represented by formula III in water, stir and heat to 75°C to 85°C for reaction for 1 to 3 hours, cool to 10°C to 20°C after the reaction to obtain an aqueous solution of the intermediate represented by formula II, wherein the molar ratio of α-aminobutyric acid to potassium cyanate is 1:(1.10 to 1.40);

[0007] Directly add hydrochloric acid to the obtained intermediate aqueous solution, raise the temperature to 90°C to 93°C for reaction for 1 to 3 hours, cool to 5°C to 10°C after the reaction, and then filter to obtain the main product filter cake and mother liquor, wherein the mass fraction of hydrochloric acid is 26% to 36%;

[0008] The main product filter cake is dried at 65°C to 75°C to obtain the compound 5-ethylhydantoin represented by formula I;

[0009] Potassium hydroxide is added to the obtained mother liquor to adjust the pH value to 6.5-7.5, and the mixture is distilled under reduced pressure at 40°C-50°C in a water bath until no distillation occurs, and then ethanol is added and the mixture is heated to 40°C-50°C and filtered to obtain a potassium chloride filter cake and an ethanol filtrate;

[0010] The ethanol filtrate is concentrated and dried, and then recovered again to obtain the compound 5-ethylhydantoin represented by formula I;

[0011] Wash the potassium chloride filter cake with ice water;

[0012] The washed potassium chloride filter cake is dried at 55°C to 65°C to obtain potassium chloride; and the washing water after washing the potassium chloride filter cake is concentrated and dried at 40°C to 50°C to obtain a potassium chloride / ammonium chloride composite salt.

[0013] According to the co-production and recovery process of the present invention, solid potassium hydroxide is preferably added to the obtained mother liquor to adjust the pH value to about 7.

[0014] According to the co-production recovery process of the present invention, the drying and / or concentration drying process is preferably carried out under reduced pressure conditions, for example, a vacuum degree of -0.096 MPa to -0.080 MPa.

[0015] According to the co-production and recovery process of the present invention, the volume concentration of ethanol is preferably above 90%, for example 95%. In addition, the weight of ethanol can be 6 to 10 times the weight of α-aminobutyric acid.

[0016] According to the co-production and recovery process of the present invention, the nucleophilic addition reaction and the ring-closing reaction can be directly carried out in one reactor ("one-pot method"), without the need for the recrystallization process of the intermediate, which significantly improves the reaction yield and reduces the amount of reaction wastewater. In addition, the present invention further uses solid potassium hydroxide to neutralize the acidic mother liquor, and recovers the main product through the ethanol filtrate to further improve its yield; the by-product filter cake or potassium chloride filter cake is processed step by step to obtain high-purity potassium chloride and potassium chloride / ammonium chloride composite salt (which can be used as agricultural fertilizer); this further reduces the amount of waste liquid, thereby reducing the production cost and is very suitable for industrial-scale environmentally friendly production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The HPLC detection spectrum of the compound (Formula I) prepared according to the example.

[0018] Figure 2 This is the HPLC detection spectrum of the compound (Formula I) prepared according to Comparative Example 1.

[0019] Figure 3 This is the HPLC detection spectrum of the compound (Formula I) prepared according to Comparative Example 2. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below through specific embodiments, comparative examples and drawings, but they are not intended to limit the present invention.

[0021] Example

[0022] 1) Nucleophilic addition reaction: The reaction is shown in the following formula (I). Dissolve 20.0g of α-aminobutyric acid (Formula III) and 19.7g of potassium cyanate in 75g of drinking water, stir and heat to 80°C, and continue to keep warm for 2 hours; then cool to 15°C to obtain an aqueous solution of the intermediate (Formula II).

[0023]

[0024] 2) Ring-closing reaction: The reaction is shown in the following formula (II). 50.2 g of concentrated hydrochloric acid (industrial grade; concentration of about 31%) was dropped into the aqueous solution of the intermediate (Formula II), and the temperature was raised to 92°C for 2 hours of heat preservation; after the reaction was completed, the temperature was cooled to 8°C and filtered, and the filter cake was washed with a small amount of ice water, and dried at 70°C under reduced pressure (vacuum degree ≤-0.080 MPa) to obtain 18.0 g of a white compound (Formula I), with a purity of 99.9% (HPLC area normalization method) and a yield of 72.4%.

[0025]

[0026] 3) Recovery and treatment of mother liquor to prepare hydrochloride: solid potassium hydroxide was added to the acidic mother liquor of the ring-closure reaction under stirring to adjust the pH to 7, and the mixture was distilled under reduced pressure at 45°C in a water bath until no distillation occurred. 160 g of 95% ethanol was added, the temperature was raised to 45°C, and the mixture was filtered while hot. The ethanol filtrate was concentrated until no distillation occurred and then recovered to obtain 1.5 g of compound (Formula I); the filter cake (mainly composed of potassium chloride and a small amount of ammonium chloride) was washed with a small amount of ice water, and dried under reduced pressure at 60°C to obtain 24.6 g of potassium chloride; the filter cake washing water was concentrated and dried under reduced pressure at 45°C, and scraped to obtain 5.8 g of potassium chloride / ammonium chloride composite salt.

[0027] Comparative Example 1

[0028] 10.0 g of α-aminobutyric acid and 8.0 g of potassium cyanate were added to 25 ml of water, heated on a boiling water bath for 1.5 hours, cooled to room temperature, and then 1 N hydrochloric acid was added to neutralize to pH = 2, and the intermediate 2-ureide butyric acid was recrystallized in a boiling water bath. The intermediate 2-ureide butyric acid was added to 35.4 g of 10% hydrochloric acid, and the boiling water bath was continued to heat for 1 hour, cooled to 8°C, and dried under reduced pressure at 70°C to obtain 4.6 g of white crystals with a yield of 37% and a purity of 99.69% (HPLC area normalization method).

[0029] Comparative Example 2

[0030] 20.0 g of α-aminobutyric acid and 18.9 g of potassium cyanate were added to 80.0 ml of water, heated on a boiling water bath for 1.5 hours, and then cooled to 15° C. to obtain an aqueous solution of the intermediate (Formula II).

[0031] 45.8 g of 40% nitric acid was dropped into the aqueous solution of the intermediate (Formula II), and the temperature was raised to 92°C for reaction for 2 hours; after the reaction was completed, the mixture was cooled to 8°C and filtered, and the filter cake was washed with a small amount of ice water, and dried at 70°C (product) under reduced pressure (vacuum degree ≤-0.080 MPa) to obtain 19.9 g of a white compound (Formula I) with a purity of 40.48% (HPLC area normalization method) and a yield of 80.0%.

[0032] Figure 1 , Figure 2 , Figure 3 The HPLC detection spectra of the compounds (Formula I) prepared according to Example and Comparative Examples 1 and 2, respectively, wherein the detection conditions are shown in Table 1 below.

[0033] Table 1

[0034]

[0035] Reference Figure 1-3 Comparative analysis of the above embodiments and comparative examples shows that:

[0036] In comparative example 1, the amount of potassium cyanate used is relatively small, and the molar ratio of potassium cyanate to the raw material α-aminobutyric acid is 1.01:1. In the heating reaction, potassium cyanate is easily decomposed by heat to produce potassium carbonate, urea and other substances, resulting in incomplete reaction of the raw materials; at the same time, the intermediate has a large solubility in water, and recrystallization is required, which further reduces the yield. In addition, a large amount of ammonia-containing waste acid water is also produced in the process, which is very unfavorable for industrial scale-up production.

[0037] In Comparative Example 2, although the amount of potassium cyanate used is increased and the molar ratio with the raw material α-aminobutyric acid is 1.20:1, the nitric acid decomposes due to heat during the ring-closing reaction, resulting in incomplete ring-closing reaction, more intermediates remain, and the purity of the compound (Formula I) is low, which cannot meet the electroplating industry's requirements for the purity of the compound (Formula I).

[0038] The present invention uses a "one-pot method" to prepare 5-ethylhydantoin, omits the recrystallization process of the intermediate, significantly improves the reaction yield, and also reduces the amount of reaction wastewater. In addition, the present invention also uses potassium hydroxide to neutralize the acidic mother liquor, and after concentrated crystallization, high-purity potassium chloride and potassium chloride / ammonium chloride composite salt (which can be used as agricultural fertilizer) are obtained in steps, which further reduces the amount of waste liquid, thereby reducing the production cost and is very suitable for industrial-scale environmentally friendly production.

Claims

1. A co-production and recovery process of 5-ethylhydantoin and hydrochloride, comprising: Dissolve α-aminobutyric acid and potassium cyanate represented by formula III in water, stir and heat to 75°C to 85°C for reaction for 1 to 3 hours, cool to 10°C to 20°C after the reaction to obtain an aqueous solution of the intermediate represented by formula II, wherein the molar ratio of α-aminobutyric acid to potassium cyanate is 1:(1.10 to 1.40); Directly add hydrochloric acid to the obtained intermediate aqueous solution, raise the temperature to 90°C to 93°C for reaction for 1 to 3 hours, cool to 5°C to 10°C after the reaction, and then filter to obtain the main product filter cake and mother liquor, wherein the mass fraction of hydrochloric acid is 26% to 36%; The main product filter cake is dried at 65°C to 75°C to obtain the compound 5-ethylhydantoin represented by formula I; Potassium hydroxide is added to the obtained mother liquor to adjust the pH value to 6.5-7.5, and the mixture is distilled under reduced pressure at 40°C-50°C in a water bath until no distillation occurs, and then ethanol is added and the mixture is heated to 40°C-50°C and filtered to obtain a potassium chloride filter cake and an ethanol filtrate; The ethanol filtrate is concentrated and dried, and then recovered again to obtain the compound 5-ethylhydantoin represented by formula I; Wash the potassium chloride filter cake with ice water; Dry the washed potassium chloride filter cake at 55°C to 65°C to obtain potassium chloride; as well as The washing water after washing the potassium chloride filter cake is concentrated and dried at 40°C to 50°C to obtain a potassium chloride / ammonium chloride composite salt.

2. The co-production and recovery process according to claim 1, wherein solid potassium hydroxide is added to the obtained mother liquor to adjust the pH value to about 7.

3. The co-production and recovery process according to claim 1, wherein the drying and / or concentration-drying process is carried out under reduced pressure conditions.

4. The co-production and recovery process according to claim 1, wherein the ethanol volume concentration is above 90%.

Images