Method and device for automatic washing of violuric acid

Abstract

The invention provides a method for automatic washing of murexuric acid, wherein materials are washed in a classified manner according to the content of murexuric acid or the pH value of a filtrate after the murexuric acid is dissolved; the invention also provides a device for realizing automatic washing of murexuric acid; the invention solves the problem that conventional water washing of murexuric acid can only remove water-soluble impurities in murexuric acid, and reduces the influence of impurities carried by murexuric acid on subsequent hydrogenation reduction; the classification and graded washing of murexuric acid is realized, and the consumption of organic solvent and washing water is reduced.

Description

Technical Field

[0001] The invention belongs to the field of chemical pharmacy, and in particular relates to a method and a device for automatic washing of violuric acid. Background Art

[0002] The caffeine synthesis process using cyanoacetic acid and dimethylurea as starting materials has become the mainstream production process for caffeine products due to its simple process, high yield, and good stability of intermediates. Murexuric acid is produced by ring closure and nitrosation of dimethylurea and cyanoacetic acid. It is an important intermediate in the production of caffeine products. The content and impurity level of murexuric acid directly affect the subsequent hydrogenation reduction reaction, and thus affect the yield and quality of caffeine products. How to reduce the impurity level in the reaction system before hydrogenation reduction has become the top priority for improving the quality and yield of caffeine products.

[0003] At present, in order to reduce the impact of murexuric acid on the nickel catalyst in the hydrogenation reduction system, the water-soluble impurities in murexuric acid are mainly washed away by washing with clean water, but the organic impurities in murexuric acid cannot be effectively removed. Studies have shown that some organic impurities in murexuric acid will hydrolyze under alkaline conditions, and the hydrolysis products will condense with the subsequent intermediate dimethyl-FAU to form a ring. In the presence of light and oxygen, under the catalysis of residual nickel, they are heated for dehydrogenation aromatization, and are hydrolyzed in the presence of alkali and acid to form a carboxylic acid compound, which seriously affects the quality of the finished caffeine product.

[0004] Patent (CN101812024B) discloses a purification method of dimethyl murexuric acid, which specifically uses alcohol, ether or ketone organic solvents mixed with water and adds soluble zinc salts to achieve washing of murexuric acid, which can increase the content of murexuric acid from 60% to more than 90%. However, the disclosed method remains in the laboratory research stage, and the organic solvents such as methanol, tert-butyl alcohol and acetone used in the disclosed method will remain in caffeine, thereby causing the organic impurities in the finished caffeine to exceed the standard, and the introduction of halogen elements such as zinc chloride and zinc bromide will also affect the impurity system, which is obviously a greater risk for caffeine with dual properties of medicine and food. After washing, murexuric acid still has 10% impurities, and the residual impurities will still affect the subsequent hydrogenation reduction reaction. Summary of the invention

[0005] The present invention provides a method for automatic washing of murexuric acid, wherein materials are washed in a classified manner according to the murexuric acid content or the pH of the filtrate after the murexuric acid is dissolved in the material:

[0006] (1) When the content of murexuric acid is greater than 95% (w / w) or the pH of the filtrate obtained by dispersing murexuric acid in purified water is greater than 4, the first method of washing is adopted;

[0007] (2) When the content of murexuric acid is ≤95% (w / w) and the pH of the filtrate obtained by dispersing murexuric acid in purified water is ≤4, the second washing method is adopted.

[0008] The first method washing step is:

[0009] (1) Disperse the violaceous acid and water in a dissolving tank V1 at a mass ratio of 1:3, stir for 10-15 minutes until the material is evenly dispersed, and then press the material into a washing tank V2-1 with compressed air. After stirring for 10 minutes, open the washing tank V2-1 to compress the air and squeeze out 2 / 3 of the washing water;

[0010] (2) After pressing, add water to the washing tank V2-1 to the original volume, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the filtrate collection tank V4-1;

[0011] (3) After pressing, add water to the washing tank V2-1 to the original volume, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the filtrate washing tank V4-1;

[0012] (4) Monitor the pH of the third washing water. If the pH is greater than 6.5, the washing is completed. After adding water to the material in the washing tank V2-1 to make up to the original volume, the material is transferred to the pulping tank V3-1 for pulping and standby use.

[0013] The second method washing step is:

[0014] (1) Disperse violaceous acid and water in a mass ratio of 1:2 in a dissolving tank V1, stir for 10-15 minutes until the material is evenly dispersed, and then use compressed air to press the material into a washing tank V2-2. After stirring for 10 minutes, open the compressed air in the washing tank V2-2 to press out 1 / 2 of the washing water into the filtrate collection tank V4-1;

[0015] (2) Add the solvent in the auxiliary solvent tank V5-1 and the saline solution in the auxiliary solvent tank V5-2 into the washing tank V2-2 to make up the volume of the original solvent. After stirring for 15 minutes, turn on the compressed air to squeeze out 3 / 4 of the washing liquid to the filtrate collection tank V4-2;

[0016] (3) After pressing, add water to the washing tank V2-2 to 1.5 times the volume of the original solution, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the filtrate washing tank V4-2;

[0017] (4) After pressing, add water to the washing tank V2-2 to 1.5 times the volume of the original molten material, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the filtrate washing tank V4-1;

[0018] (5) Monitor the pH of the fifth washing water. If the pH is greater than 6.5, the washing is completed. After adding water to the material in the washing tank V2-2 to 1.5 times the volume of the original dissolved material, the material is transferred to the pulping tank V3-2 for pulping and standby use.

[0019] The present invention also provides a device for automatically washing violuric acid, which includes a dissolving tank V1, two washing tanks V2-1 and V2-2, two beating tanks V3-1 and V3-2, two filtrate collecting tanks V4-1 and V4-2, and two auxiliary solvent tanks V5-1 and V5-2; the dissolving tank V1 is connected to the washing tank V2-1 and the washing tank V2-2, the washing tank V2-1 is connected to the beating tank V3-1, the washing tank V2-1 is connected to the filtrate collecting tank V4-1, the washing tank V2-2 is connected to the beating tank V3-2, the beating tank V3-2 is connected to the filtrate collecting tanks V4-1 and V4-2, wherein the auxiliary solvent tanks V5-1 and V5-2 are respectively connected to the washing tank V2-2.

[0020] All tanks of the described violuric acid automatic washing device are equipped with liquid level gauges, and the dissolving tank, washing tank and beating tank are respectively provided with double-layer stirring, wherein the washing tank is equipped with a pressure gauge, and the pipeline connecting the washing tank and the filtrate collecting tank is equipped with a pH monitor, and the pH monitor, pressure gauge and liquid level counter value can be automatically controlled by PLC control.

[0021] The solvent in the auxiliary solvent tank V5-1 is ethanol with a volume fraction greater than 99%;

[0022] The salt solution in the auxiliary solvent tank V5-2 is a saturated aqueous solution of zinc sulfate.

[0023] The invention solves the problem that the conventional water washing of murexuric acid can only remove water-soluble impurities in murexuric acid, reduces the influence of impurities in murexuric acid on subsequent hydrogenation reduction, realizes the classification and graded washing of murexuric acid, reduces the amount of organic solvent and washing water, and also determines salt and organic solvent suitable for washing murexuric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the automatic washing process flow of violaceous acid, wherein: V1 is a dissolving tank, V2-1 and V2-2 are washing tanks, V3-1 and V3-2 are pulping tanks, V4-1 and V4-2 are filtrate collecting tanks, V5-1 and V5-2 are auxiliary solvent tanks, liquid level gauges (L1, L2-1, L2-2, L3-1, L3-2, L4-1, L4-2), double-layer stirring (M1, M2-1, M2-2, M3-1, M3-2), pH monitors (pH-1, pH-2), and pressure gauges (P2-1 and P2-2). DETAILED DESCRIPTION

[0025] The following is further described in conjunction with the accompanying drawings, but does not limit the scope of the present invention. Specific embodiments are as follows:

[0026] Embodiment 1:

[0027] After testing, the absolute content of violaceous acid is 96.21%. The first floor washing method is used for washing. 500kg of violaceous acid is put into the dissolving tank V1, and 1500L of water is added to disperse the dissolving material. After stirring for 13 minutes, the material is pressed to the washing tank V2-1 with compressed air for washing. After stirring for 10 minutes, the compressed air in the washing tank V2-1 is opened to squeeze out 1000L of water. Then, 1000L of water is added to the washing tank V2-1. After stirring for 10 minutes, the compressed air is opened to squeeze out 1000L of washing water to the filtrate collecting tank V4-1. Then, 1000L of water is added to the washing tank V2-1 again. After stirring for 10 minutes, the compressed air is opened to squeeze out 1000L of washing water to the filtrate collecting tank V4-1. The pH value of the washing water for the third time is detected to be 6.75. After washing, 1000L of water is added to the washing tank V2-1, and the material is transferred to the pulping tank V3-1 for pulping and standby. The murexuric acid in the pulping tank V3-1 was filtered and dried, and then the absolute content was detected. The detection result was 99.85%. The washed murexuric acid was used for hydrogenation reduction reaction, and the yield was 97.82%.

[0028] Embodiment 2:

[0029] After testing, the absolute content of murexuric acid was 94.85%. 100g of the batch of murexuric acid was dispersed in 300mL of water, and the pH of the filtrate was measured to be 4.23. The first floor washing method was used for washing. 500kg of murexuric acid was put into the dissolving tank V1, and 1500L of water was added to disperse the dissolving material. After stirring for 12 minutes, the material was pressed into the washing tank V2-1 with compressed air for washing. After stirring for 10 minutes, the washing tank V2-1 was opened with compressed air to squeeze out 1000L of water, and then in the washing tank V2-1, the washing tank V2-1 was opened with compressed air to squeeze out 1000L of water. Add 1000L of water to the washing tank V2-1, stir for 10 minutes, turn on the compressed air, squeeze out 1000L of washing water to the filtrate collection tank V4-1, then add 1000L of water to the washing tank V2-1 again, stir for 10 minutes, turn on the compressed air, squeeze out 1000L of washing water to the filtrate collection tank V4-1, detect the pH of the third washing water to be 6.83, wash, add 1000L of water to the washing tank V2-1, and transfer the material to the pulping tank V3-1 for pulping. Take the purpuric acid in the pulping tank V3-1, filter and dry it, and then test the absolute content. The test result is 99.65%. The washed purpuric acid is used for hydrogenation reduction reaction, and the yield is 96.92%.

[0030] Embodiment 3:

[0031] After testing, the absolute content of murexuric acid was 93.68%. 100 g of the batch of murexuric acid was dispersed in 300 mL of water, and the pH of the filtrate was measured to be 4.02. The second floor washing method was used for washing. 500 kg of murexuric acid was put into the dissolving tank V1, and 1000 L of water was added to disperse the dissolving material. After stirring for 15 minutes, the material was pressed into the washing tank V2-2 with compressed air for washing. After stirring for 10 minutes, the washing tank V2-2 was opened with compressed air to press out 500 L of washing water to the filtrate collecting tank V4-1. 300 L of solvent in the auxiliary solvent tank V5-1 and 200 L of saline solution in the auxiliary solvent tank V5-2 were added. L was added to the washing tank V2-2, and compressed air was turned on after stirring for 15 minutes, and 750L of washing liquid was pressed out to the filtrate collection tank V4-2, and then 1250L of water was added to the washing tank V2-2, and compressed air was turned on after stirring for 10 minutes, and 1000L of washing water was pressed out to the filtrate washing tank V4-2, and then 1000L of water was added to the washing tank V2-2, and compressed air was turned on after stirring for 10 minutes, and 1000L of washing water was pressed out to the filtrate washing tank V4-1, and the pH of the fifth washing water was detected to be 6.78, and the washing was completed, 1000L of water was added to the washing tank V2-2, and the material was transferred to the pulping tank V3-2 for pulping. The purpuric acid in the pulping tank V3-2 was taken and filtered and dried for absolute content detection, and the test result was 99.72%. The washed purpuric acid was used for hydrogenation reduction reaction, and the yield was 97.03%.

Claims

1. A method for automatic washing of violuric acid, characterized in that: The materials are classified and washed according to the murexic acid content or the pH of the filtrate after murexic acid dissolution: (1) When the mass percentage of murexuric acid is greater than 95% or the pH of the filtrate obtained by dispersing murexuric acid in purified water is greater than 4, the first method of washing is adopted; (2) When the mass percentage of murexuric acid is ≤95% and the pH of the filtrate obtained by dispersing murexuric acid in purified water is ≤4, the second washing method is adopted; The first method washing step is: 1) Disperse violaceous acid and water in a dissolving tank (V1) at a mass ratio of 1:3, stir for 10-15 minutes until the material is evenly dispersed, and then use compressed air to press the material into the first washing tank (V2-1). After stirring for 10 minutes, open the first washing tank (V2-1) to compress the air and squeeze out 2 / 3 of the washing water; 2) After pressing, add water to the first washing tank (V2-1) to the original volume, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the first filtrate collection tank (V4-1); 3) After pressing, add water to the first washing tank (V2-1) to the original volume, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the first filtrate collection tank (V4-1); 4) Monitor the pH of the third washing water. If the pH is greater than 6.5, the washing is finished. After adding water to the material in the first washing tank (V2-1) to make up to the original volume, the material is transferred to the first pulping tank (V3-1) for pulping. The second method washing step is: ① Disperse the violaceous acid and water in a dissolving tank (V1) at a mass ratio of 1:2, stir for 10-15 minutes until the material is evenly dispersed, and then use compressed air to press the material into the second washing tank (V2-2). After stirring for 10 minutes, open the second washing tank (V2-2) to press out 1 / 2 of the washing water into the first filtrate collection tank (V4-1); ② Add the solvent in the first auxiliary solvent tank (V5-1) and the saline solution in the second auxiliary solvent tank (V5-2) into the second washing tank (V2-2) to make up the volume of the original solvent, stir for 15 minutes, then turn on the compressed air to squeeze out 3 / 4 of the washing liquid to the second filtrate collection tank (V4-2); ③ After pressing, add water to the second washing tank (V2-2) to 1.5 times the volume of the original solution, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the second filtrate collection tank (V4-2); ④ After pressing, add water to the second washing tank (V2-2) to 1.5 times the volume of the original dissolved material, stir for 10 minutes, then turn on the compressed air to press out 2 / 3 of the washing water to the first filtrate collection tank (V4-1); ⑤ Monitor the pH of the fifth washing water. If the pH is greater than 6.5, the washing is finished. After adding water to the material in the second washing tank (V2-2) to 1.5 times the volume of the original dissolved material, the material is transferred to the second pulping tank (V3-2) for pulping and standby; The automatic washing device comprises a dissolving tank (V1), a first washing tank (V2-1), a second washing tank (V2-2), a first pulping tank (V3-1), a second pulping tank (V3-2), a first filtrate collecting tank (V4-1), a second filtrate collecting tank (V4-2), a first auxiliary solvent tank (V5-1) and a second auxiliary solvent tank (V5-2); the dissolving tank (V1) is connected to the first washing tank (V2-1) and the second washing tank (V2-2); the first washing tank ( V2-1) is connected to the first pulping tank (V3-1), the first washing tank (V2-1) is connected to the first filtrate collecting tank (V4-1), the second washing tank (V2-2) is connected to the second pulping tank (V3-2), the second pulping tank (V3-2) is connected to the first filtrate collecting tank (V4-1) and the second filtrate collecting tank (V4-2), wherein the first auxiliary solvent tank (V5-1) and the second auxiliary solvent tank (V5-2) are respectively connected to the second washing tank (V2-2).

2. The method for automatic washing of murexic acid according to claim 1, characterized in that: All tanks are equipped with liquid level gauges. The dissolving tank (V1), the first washing tank (V2-1), the second washing tank (V2-2), the first pulping tank (V3-1), and the second pulping tank (V3-2) are respectively equipped with the first double-layer stirring (M1), the second double-layer stirring (M2-1), the third double-layer stirring (M2-2), the fourth double-layer stirring (M3-1), and the fifth double-layer stirring (M3-2). The first washing tank (V2-1) and the second washing tank (V2-2) are equipped with the first pressure gauge (P2-1 ) and the second pressure gauge (P2-2), the first washing tank (V2-1), the second washing tank (V2-2) and the first filtrate collecting tank (V4-1) and the second filtrate collecting tank (V4-2) connecting pipelines are installed with the first pH monitor (pH-1), the second pH monitor (pH-2), the first pressure gauge (P2-1) and the second pressure gauge (P2-2), and the liquid level counting value can be automatically controlled by PLC control.

3. The method for automatic washing of murexic acid according to claim 1, characterized in that: The solvent in the first auxiliary solvent tank (V5-1) is ethanol with a volume fraction greater than 99%; the salt solution in the second auxiliary solvent tank (V5-2) is a saturated aqueous solution of zinc sulfate.

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