A wastewater treatment process for 4,6-dichloropyrimidine synthesis

Abstract

The present application relates to a kind of wastewater treatment processes for 4,6-dichloropyrimidine synthesis, acidic waste liquid generated by substitution reaction, after first static stratification, distillation, second static stratification, then adding 1-naphthylamine diazonium salt wastewater treatment, while recovering normal organic amine odor compound fertilizer raw material, N,N-dimethyl aniline difficult to remove in wastewater can be removed, reduce the consumption of decoloring agent in subsequent decoloring treatment, solve the problem that wastewater generated in the preparation of 4,6-dichloropyrimidine is difficult to handle and utilize.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to a wastewater treatment process for 4,6-dichloropyrimidine synthesis. BACKGROUND

[0002] 4,6-dichloropyrimidine, English name 4,6-dichloropyrimidine, for short DCP, is a very important pesticide and pharmaceutical intermediate, which is mainly used for synthesizing the strobilurin fungicide azoxystrobin.

[0003] At present, the synthesis process of 4,6-dichloropyrimidine mainly uses 4,6-dihydroxypyrimidine and phosphorus oxychloride. Although this process has large production capacity and less equipment investment, it has more wastewater and large treatment difficulty. Since the organic amine acid-binding agent can form small particles with other organic matters in the salt-containing wastewater, it is difficult to completely remove from the water phase; after using a large amount of activated carbon for adsorption, the ammonia nitrogen content and chemical oxygen demand in the water phase are still high. According to experimental calculation, the amount of activated carbon consumed per ton of wastewater reaches 500 Kg, and about 800 Kg of activated carbon waste residue is produced.

[0004] Therefore, the wastewater treatment process for 4,6-dichloropyrimidine synthesis needs to be improved. SUMMARY

[0005] The purpose of the present application is to overcome the above technical deficiencies, and to provide a wastewater treatment process for 4,6-dichloropyrimidine synthesis, which solves the technical problems of high activated carbon consumption and poor treatment effect in the wastewater treatment of 4,6-dichloropyrimidine synthesis in the prior art.

[0006] To achieve the above technical purpose, the technical solution provided by the present application is as follows:

[0007] In a first aspect, the present application provides a wastewater treatment process for 4,6-dichloropyrimidine synthesis, comprising the following steps: using 4,6-dihydroxypyrimidine and phosphorus oxychloride as raw materials, performing a synthesis reaction in the presence of an acid-binding agent and a solvent, obtaining a substitution mixture after the synthesis reaction is completed, adding water to the substitution mixture to obtain a mixture solution; after standing and layering, obtaining a first upper layer liquid and a first lower layer liquid; separating 4,6-dichloropyrimidine from the first lower layer liquid; the first upper layer liquid is wastewater to be treated; the first upper layer liquid is subjected to distillation to obtain a distillation residue and a hydrochloric acid solution;

[0008] After the distillation residue is adjusted to alkaline and then is subjected to standing and layering, a second upper layer liquid and a second lower layer liquid are obtained; the second upper layer liquid is subjected to deamination and dehydration treatment to recover the acid-binding agent;

[0009] The 1-naphthylamine diazonium salt wastewater is added to the second lower layer liquid to remove N,N-dimethyl aniline, and the azo compound solid and filtrate are separated.

[0010] Preferably, the mass ratio of 4,6-dihydroxypyrimidine, phosphorus oxychloride and acid binding agent is (7-8):(9-10):(7-8).

[0011] Preferably, the acid binding agent is N,N-dimethyl aniline.

[0012] Preferably, the solvent is dichloroethane; and the mass ratio of 4,6-dihydroxypyrimidine and dichloroethane is (7-8):(32-40).

[0013] Preferably, before the synthesis reaction, the 4,6-dihydroxypyrimidine and phosphorus oxychloride are stirred and mixed according to the ratio at 30-50℃, then dissolved in the solvent, and then the acid binding agent is added drop by drop, the temperature is controlled to be not more than 50℃, after the dropwise addition is completed, 10-30min is maintained, and then the synthesis reaction is carried out by increasing the temperature.

[0014] Preferably, the temperature of the synthesis reaction is 70-85℃, and the time is 2-4h.

[0015] Preferably, the mass ratio of the substitution mixture and water is (55-66):(40-50).

[0016] Preferably, the first lower layer liquid is added to water and adjusted to neutral pH, and then the 4,6-dichloropyrimidine is obtained by sequentially undergoing standing, separation, distillation and crystallization.

[0017] Preferably, the first upper layer liquid is distilled at 100-110℃; and the concentration of the obtained hydrochloric acid solution is 15-25%.

[0018] Preferably, the pH value adjustment of the distillation residue is to add ammonia water to a pH value of 8-10.

[0019] Preferably, the deamination and dehydration treatment is to add a deamination agent to the second upper layer liquid for deamination treatment, and then vacuum dehydration is carried out to recover the acid binding agent.

[0020] Preferably, the deamination agent is potassium hydroxide or sodium hydroxide; and the recovered acid binding agent is reused in the synthesis reaction.

[0021] Preferably, the mass concentration of the 1-naphthylamine diazonium salt wastewater is 3-10%; and the volume ratio of the second lower layer liquid and the 1-naphthylamine diazonium salt wastewater is 1000:(3-10).

[0022] Preferably, the decolorization treatment is to add activated carbon to the filtrate; and the mass ratio of the filtrate and activated carbon is 1000:(10-60).

[0023] Compared with the prior art, the present application has the following advantages:

[0024] The present application provides a treatment process for wastewater generated in the post-treatment process of 4,6-dichloropyrimidine preparation. The acidic waste liquid generated by substitution reaction is subjected to first static layering, distillation, second static layering, and then 1-naphthylamine diazonium salt wastewater treatment. In this way, the N,N-dimethylaniline that is difficult to remove in the wastewater can be removed, the consumption of decolorizing agent in the subsequent decolorization treatment is reduced, and the problem of difficult treatment and utilization of wastewater generated in the preparation process of 4,6-dichloropyrimidine is solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the process flow diagram of the treatment process for wastewater generated in the post-treatment process of 4,6-dichloropyrimidine preparation in the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0027] Please refer to Figure 1 , Figure 1 is the wastewater treatment process flow diagram for the synthesis of 4,6-dichloropyrimidine in the present application, and the steps include:

[0028] (1) N,N-dimethylaniline is gradually added to the mixed solution of 4,6-dihydroxypyrimidine and phosphorus oxychloride to obtain a substitution mixture after substitution reaction.

[0029] Preferably, in this step, 4,6-dihydroxypyrimidine and phosphorus oxychloride are mixed and dissolved in dichloroethane solvent at 30-50°C after stirring according to the ratio, N,N-dimethylaniline is added dropwise, and the temperature is controlled to be not more than 50°C, wherein the mass ratio of 4,6-dihydroxypyrimidine, phosphorus oxychloride, dichloroethane and N,N-dimethylaniline is preferably (7-8):(9-10):(32-40):(7-8); after the addition is completed, it is maintained for 10-30 min, then slowly heated to 70-85°C and maintained for 2-4 h, and then cooled to below 35°C to obtain the substitution mixture.

[0030] (2) The substitution mixture is slowly added to water to perform first static layering, and the first upper layer liquid and the first lower layer liquid are separated.

[0031] Preferably, in this step, the substituted mixture is slowly added to water to undergo a hydrolysis reaction, preferably the mass ratio of the substituted mixture to water is (55-66):(40-50), the hydrolysis reaction temperature is controlled to be no more than 30°C, after the mixture is completely added, stirring is continued for 30 min, after standing and layering, a first upper layer liquid and a first lower layer liquid are separated. At this time, the first upper layer liquid mainly contains PO4 - , Cl - , and N,N-dimethylaniline, and the first lower layer liquid mainly contains 4,6-dichloropyrimidine and dichloroethane, and the wastewater treatment process of the present application is mainly performed on the first upper layer liquid.

[0032] (3) The first lower layer liquid in step (2) is added to water and the pH is adjusted to 7, and after standing, separation, distillation, and crystallization in turn, a 4,6-dichloropyrimidine product is obtained.

[0033] Preferably, in this step, the first lower layer liquid in step (2) is added to water, and sodium hydroxide is added to adjust the pH to 7, after standing for 20-30 min, the lower layer material is removed, heating to 40-45°C, and distillation under reduced pressure to separate the dichloroethane solvent, distillation under reduced pressure at 100-110°C, and then cooling crystallization at 5-10°C, centrifugation, and drying in turn, a 4,6-dichloropyrimidine product is obtained.

[0034] (4) The first upper layer liquid in step (2) is distilled at 100-110°C to obtain a hydrochloric acid solution with a concentration of about 15-25%.

[0035] (5) Ammonia water is gradually added to the residue from step (4) until the pH is about 8-10, and a second standing and layering is performed, and after separation, a second upper layer liquid and a second lower layer liquid are obtained; the second upper layer liquid is treated by deamination and dehydration to recover the acid-binding agent.

[0036] Preferably, in this step, first, a deamination agent (potassium hydroxide or sodium hydroxide) is added to the second upper layer liquid until the pH is 12-14, deamination treatment is performed, and then vacuum dehydration is performed, N,N-dimethylaniline can be recovered, the recovery rate is more than 95%, and the purity is 99.0%. The main components of the second lower layer liquid are ammonium dihydrogen phosphate and ammonium chloride.

[0037] (6) The second lower layer liquid is added with 1-naphthylamine diazonium salt wastewater to remove the difficult-to-remove N,N-dimethyl aniline in the wastewater by filtration. Since the acid-binding agent N,N-dimethyl aniline can form dispersed small particles with other organic matters in the salt-containing wastewater, it is difficult to be completely removed from the water phase; adsorption is performed using activated carbon, the consumption of activated carbon is large, and the ammonia nitrogen content and chemical oxygen demand in the water phase are still high. Therefore, the second lower layer liquid in step (5) is first treated with 1-naphthylamine diazonium salt wastewater (from another mature process) with a mass concentration of 3-10% (volume ratio of the second lower layer liquid:diazonium salt wastewater / 1000:(3-10)) in the present application, and is stirred at room temperature for 20-40 min to make N,N-dimethyl aniline react with diazonium salt to form azo compound solids, which are removed by filtration, effectively solving the problem that N,N-dimethyl aniline forms dispersed small particles in the wastewater and is difficult to remove.

[0038] Preferably, the reaction temperature of the wastewater and the 1-naphthylamine diazonium salt wastewater is 0-40°C, and further preferably 0-20°C.

[0039] (7) The filtrate in step (6) is decolorized by activated carbon, and then distilled and frozen to salt out, to obtain a compound fertilizer raw material without an organic amine odor and which can be recycled. In this step, the main components of the obtained compound fertilizer raw material are ammonium dihydrogen phosphate and ammonium chloride, and the above-mentioned mixed salt can be sold as a commodity to compound fertilizer production enterprises. In actual production, if the difficult-to-remove N,N-dimethyl aniline in the wastewater is not removed, the amount of activated carbon consumed per ton of wastewater reaches 450-550 Kg, and about 750-850 Kg of activated carbon waste residue is produced, resulting in a large amount of waste of activated carbon; the obtained compound fertilizer raw material has a pungent odor, which does not meet the use standard of compound fertilizer raw materials. Therefore, in step (6) of the present application, the N,N-dimethyl aniline is completely removed by adding 1-naphthylamine diazonium salt wastewater, and then decolorized by activated carbon, and the consumption of activated carbon is 10-60 Kg per ton of wastewater. The obtained compound fertilizer raw material after treatment has no organic amine odor and can be recycled; the wastewater changes from a thick purple color with a pungent odor to colorless and odorless, and the COD value decreases significantly, reaching the discharge standard. The present application can not only recycle the compound fertilizer raw material without an organic amine odor, but also reduce the use of activated carbon, solving the problem of difficult treatment and utilization of wastewater generated in the preparation process of 4,6-dichloropyrimidine.

[0040] Preferably, the mass ratio of the wastewater to activated carbon is 1000:30.

[0041] The main mechanism and advantages of the wastewater treatment process provided by the application are: (1) the 1-naphthylamine diazonium salt wastewater is used to treat the wastewater containing N,N-dimethyl aniline after the synthesis of 4,6-dichloropyrimidine, which is environmentally friendly, safe and simple to operate; (2) the key raw material 1-naphthylamine diazonium salt wastewater is obtained from the recovery wastewater with stable diazonium salt content in another mature process, without any cost; (3) in addition to recovering the compound fertilizer raw material without the smell of organic amine, the use of activated carbon is also reduced. The application reduces the wastewater treatment cost, improves the product competitiveness, and solves the problem of difficult treatment and utilization of wastewater generated in the preparation process of 4,6-dichloropyrimidine.

[0042] The application will be further described in detail through specific examples.

[0043] Example 1

[0044] (1) 4,6-dihydroxypyrimidine and phosphorus oxychloride were mixed at a ratio of 7:9:35:7 at 40℃, and then N,N-dimethyl aniline was added dropwise, and the temperature was controlled to be not more than 50℃. After the addition was completed, 20 min was maintained, then the temperature was slowly increased to 75℃ and maintained for 3h, and then the temperature was decreased to below 35℃, to obtain a substitution mixture.

[0045] (2) The substitution mixture was slowly added to water to generate a hydrolysis reaction, and the mass ratio of the substitution mixture to water was 60:45. The hydrolysis reaction temperature was controlled to be not more than 30℃. After standing and layering, the first upper layer liquid and the first lower layer liquid were separated.

[0046] (3) The first lower layer liquid in step (2) was added to water, and sodium hydroxide was added to adjust the pH to 7. After standing for 25 min, the lower layer material was taken out, heated to 40-45℃, and then distilled under reduced pressure to separate the dichloroethane solvent. Distillation was carried out at 100-110℃ under reduced pressure, and then 5-10℃ crystallization, centrifugation and drying were carried out in sequence to obtain 4,6-dichloropyrimidine product.

[0047] (4) The first upper layer liquid in step (2) was distilled at 100-110℃ to obtain a hydrochloric acid solution with a concentration of about 20%.

[0048] (5) Ammonia water was gradually added to the distillation residue in step (4) until the pH was about 9.0, and the second standing and layering were carried out, and then the second upper layer liquid and the second lower layer liquid were separated.

[0049] N,N-dimethyl aniline was recovered by adding sodium hydroxide as a deamination agent to the second upper layer liquid for deamination treatment, and then vacuum dehydration was carried out. The recovery rate was more than 95%, and the purity was 99.0%.

[0050] (6) The main components of the second lower layer liquid are ammonium dihydrogen phosphate and ammonium chloride. The 1-naphthylamine diazonium salt wastewater is added to the second lower layer liquid in a mass fraction of 5%, and the volume ratio of the second lower layer liquid to the 1-naphthylamine diazonium salt wastewater is 1000:7. After stirring at room temperature for 30 min, N,N-dimethylaniline reacts with diazonium salt to generate azo compound solids, which are removed by suction filtration.

[0051] (7) The filtrate obtained by suction filtration in step (6) is decolorized by activated carbon, distilled, and frozen and salted out to obtain a composite fertilizer raw material without the odor of organic amine and which can be recycled. In this step, the main components of the obtained composite fertilizer raw material are ammonium dihydrogen phosphate and ammonium chloride, and the mixed salt can be sold as a commodity to a composite fertilizer production enterprise. In actual production, if N,N-dimethylaniline in the wastewater cannot be removed and activated carbon is directly used for decolorization, the amount of activated carbon consumed per ton of wastewater reaches 500 kg, and about 800 kg of activated carbon waste residue is generated, resulting in a large amount of waste of activated carbon; the obtained composite fertilizer raw material has a pungent odor and does not meet the use standard of composite fertilizer raw material. Therefore, in step (6), the 1-naphthylamine diazonium salt wastewater is added for treatment to completely remove N,N-dimethylaniline, and then activated carbon is used for decolorization, and the amount of activated carbon consumed per ton of filtrate is 30 kg. The composite fertilizer raw material obtained after treatment has no odor of organic amine and can be recycled; the wastewater changes from thick purple and pungent odor to colorless and odorless, and the COD value changes from 10,000 mg / L to 260 mg / L, which can be discharged in accordance with the standard.

[0052] Therefore, the present application can not only recycle a composite fertilizer raw material without the odor of organic amine, but also reduce the use of activated carbon, and solve the problems of difficult treatment and utilization of wastewater generated in the preparation process of 4,6-dichloropyrimidine.

[0053] Example 2

[0054] The difference from example 1 is only that the volume ratio of the second lower layer liquid to the 1-naphthylamine diazonium salt wastewater is adjusted to 1000:3, and the other steps and conditions are the same as those in example 1.

[0055] Example 3

[0056] The difference from example 1 is only that the volume ratio of the second lower layer liquid to the 1-naphthylamine diazonium salt wastewater is adjusted to 1000:10, and the other steps and conditions are the same as those in example 1.

[0057] Comparative Example 1

[0058] The difference from example 1 is only that the volume ratio of the second lower layer liquid to the 1-naphthylamine diazonium salt wastewater is adjusted to 1000:1, and the other steps and conditions are the same as those in example 1.

[0059] Comparative Example 2

[0060] The difference from Example 1 is only that the volume ratio of the second underlayer liquid and 1-naphthylamine diazonium salt wastewater is adjusted to 1000:12, and other steps and conditions are the same as those in Example 1.

[0061] The specific proportions and test results of Examples 1-3 and Comparative Examples 1-2 are statistically analyzed as shown in Table 1 below.

[0062] Table 1 Specific proportions and test results of Examples 1-3 and Comparative Examples 1-2

[0063] Experimental group Volume ratio Activated carbon dosage kg / ton of wastewater Effluent COD value mg / L Example 1 1000：7 30 260 Example 2 1000：3 40 290 Example 3 1000：10 36 268 Comparative example 1 1000：1 80 375 Comparative example 2 1000：12 37 270

[0064] As shown in Table 1, when the volume ratio is decreased from 1000:7 to 1000:3, the activated carbon dosage and COD value are increased in Comparative Example 1, Example 2 and Comparative Example 1, and when the volume ratio is further decreased to 1000:1, the activated carbon dosage and COD value change greatly; when the volume ratio is increased from 1000:7 to 1000:10 and 1000:12 respectively in Comparative Example 1, Example 3 and Comparative Example 2, the activated carbon dosage and COD value change little. Therefore, the volume ratio of the second underlayer liquid and 1-naphthylamine diazonium salt wastewater is preferably 1000:(3-10) in the present application.

[0065] Compared with the prior art, the present application provides a wastewater treatment process for the synthesis of 4,6-dichloropyrimidine, and the specific steps are as follows: 4,6-dichloropyrimidine is prepared from 4,6-dihydroxypyrimidine and phosphorus oxychloride, the obtained substitution mixture is added with water, and then subjected to first static separation, distillation, second static separation, and then added with 1-naphthylamine diazonium salt wastewater for treatment to remove N,N-dimethyl aniline which is difficult to remove in the wastewater, and to normally recover the compound fertilizer raw material without the odor of organic amine; then added with activated carbon for treatment, and the use amount of activated carbon is decreased from about 500 Kg to 30 Kg, and the generated activated carbon waste residue is decreased from about 800 Kg to 70 Kg. The treated water is changed from the original purple liquid with irritating odor to colorless and odorless liquid, and the COD value is decreased from 10000 mg / L before treatment to 260 mg / L. The developed wastewater treatment process in the present application uses 1-naphthylamine diazonium salt wastewater in another mature process to treat N,N-dimethyl aniline which is difficult to remove in the wastewater, and in addition to recovering the compound fertilizer raw material without the odor of organic amine, the use of activated carbon is also reduced, the wastewater treatment cost is reduced, the product competitiveness is improved, and the problem of difficult treatment and utilization of wastewater generated in the preparation process of 4,6-dichloropyrimidine is solved.

[0066] The specific embodiments of the present application described above do not constitute a limitation on the protection scope of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A wastewater treatment process for the synthesis of 4,6-dichloropyrimidine, characterized in that: The following steps are involved: Using 4,6-dihydroxypyrimidine and phosphorus oxychloride as raw materials, a synthesis reaction is carried out in the presence of an acid binder and a solvent, and after completion of the synthesis reaction, a substitution mixture is obtained, water is added to the substitution mixture to obtain a mixture solution; after standing and stratifying, a first upper layer liquid and a first lower layer liquid are obtained; and 4,6-dichloropyrimidine is separated from the first lower layer liquid; The first upper layer liquid is wastewater to be treated; the first upper layer liquid is distilled to obtain a distillation residue and a hydrochloric acid solution; Ammonia water is added to the distillation residue until the pH value is 8 to 10, and the mixture is allowed to stand for separation to obtain a second upper layer liquid and a second lower layer liquid; the second upper layer liquid is subjected to deamination and dehydration treatment to recover the acid binding agent; Adding 1-naphthylamine diazonium salt wastewater to the second lower liquid to remove N,N-dimethylaniline, stirring at room temperature for 20 to 40 minutes, and separating to obtain azo compound solid and filtrate; the obtained filtrate is decolorized, distilled, and frozen for salting out to obtain a compound fertilizer raw material; The mass concentration of the 1-naphthylamine diazonium salt wastewater is 3-10%; the volume ratio of the second lower layer liquid to the 1-naphthylamine diazonium salt wastewater is 1000:(3-10); The decolorization treatment is to add activated carbon to the filtrate; the mass ratio of the filtrate to the activated carbon is 1000:(10-60).

2. The wastewater treatment process for 4,6-dichloropyrimidine synthesis according to claim 1, characterized in that: The mass ratio of the 4,6-dihydroxypyrimidine, phosphorus oxychloride and acid binding agent is (7-8): (9-10): (7-8).

3. The wastewater treatment process for 4,6-dichloropyrimidine synthesis according to claim 1, characterized in that: The acid-binding agent is N,N-dimethylaniline; the solvent is dichloroethane; and the mass ratio of 4,6-dihydroxypyrimidine to dichloroethane is (7-8):(32-40).

4. The wastewater treatment process for 4,6-dichloropyrimidine synthesis according to claim 1, characterized in that: Before the synthesis reaction, 4,6-dihydroxypyrimidine and phosphorus oxychloride are stirred and mixed according to the ratio at 30-50°C and then dissolved in a solvent. Then, an acid-binding agent is added dropwise, and the temperature is controlled not to exceed 50°C. After the addition is completed, the temperature is maintained for 10-30 minutes, and then the temperature is raised to 70-85°C for the synthesis reaction for 2-4 hours.

5. The wastewater treatment process for 4,6-dichloropyrimidine synthesis according to claim 1, characterized in that: The mass ratio of the substitution mixture to water is (55-66): (40-50); The first lower layer liquid is added to water and the pH is adjusted to neutral. After standing, separation, distillation and crystallization, 4,6-dichloropyrimidine is obtained.

6. The wastewater treatment process for 4,6-dichloropyrimidine synthesis according to claim 1, characterized in that: The first upper layer liquid is distilled at 100-110° C.; the concentration of the obtained hydrochloric acid solution is 15-25%.

7. The wastewater treatment process for 4,6-dichloropyrimidine synthesis according to claim 1, characterized in that: The deamination and dehydration treatment is to add a deamination agent to the second upper liquid for deamination treatment, then perform vacuum dehydration and recover the acid binding agent; the deamination agent is potassium hydroxide or sodium hydroxide; the recovered acid binding agent is reused in the synthesis reaction.

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