A treatment method for k acid synthesis oxidation section wastewater

Abstract

The application provides a treatment method of K acid synthesis oxidation section wastewater, comprising the following steps: S1, adding ammonium thiosulfate to mother liquor wastewater generated in the oxidation section at normal temperature, continuously stirring for 30-60 min, and passing in ammonia gas until no precipitate is separated out; S2, centrifuging the solid-liquid mixture, separating out ammonium sulfate crystals and mother liquor, recycling the ammonium sulfate, and separating out ammonia gas, water and DMF from the mother liquor through rectification. The ammonium sulfate produced by the application can be directly sold for the chemical fertilizer industry, the rectification-purified DMF can be reused in the oxidation section, and the water can be reused to clean the oxidation section products, so that the wastewater in the oxidation section is maximally recycled and recovered. The application has the advantages of simple process operation, low labor intensity, no environmental pollution and the like, meets the clean production standard, and is suitable for large-scale wastewater treatment. Meanwhile, the application can not only save the cost of treating wastewater in a wastewater treatment station, but also bring additional sales benefits, so that the economic benefits of enterprises are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical wastewater treatment, and particularly relates to a treatment method of K acid synthesis oxidation section wastewater. BACKGROUND

[0002] 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid (also known as K acid) is an important intermediate for synthesizing chlorantraniliprole, cyantraniliprole and other o-formamidobenzoic acid amide insecticides. In recent years, the use of chlorantraniliprole and cyantraniliprole is increasing because they are new pesticides with high efficiency, low residue, less environmental pollution and less impact on ecological balance. In order to produce chlorantraniliprole and cyantraniliprole, the demand for K acid as a raw material in industrial synthesis is also increasing.

[0003] There are mainly three routes for the synthesis of K acid: route 1 is to condense 3-bromopyrazole and 2,3-dichloropyridine to obtain 3-bromo-1-(5-chloro-2-pyrazolyl)pyrazole, then treat with diisopropyl lithium to obtain a lithium salt, and then quench the lithium salt with carbon dioxide to prepare; route 2 is to use 2,3-dichloropyridine and diethyl maleate as starting materials; and route 3 is to use maleic acid monomethyl ester and 2,3-dichloropyridine as starting materials.

[0004] Among the three synthesis methods of K acid, the synthesis process of route 2 is more commonly used, and the detailed process and reaction formula are as follows Figure 1 2,3-dichloropyridine and diethyl maleate as raw materials, through hydrazinolysis, cyclization, bromination, oxidation and hydrolysis to synthesize K acid. After the product oxidate in the oxidation section is extracted, the oxidation mother liquor wastewater can only be treated in the sewage treatment station. However, the composition of the oxidation section mother liquor wastewater includes ammonium persulfate, ammonium sulfate, sulfuric acid and DMF, among which ammonium sulfate can be used as a chemical fertilizer raw material, sulfuric acid and ammonium persulfate are also one of industrial raw materials, and the residual DMF is one of the raw materials in the oxidation section. Directly discharging the mother liquor wastewater into the sewage treatment station not only needs additional treatment cost, but also wastes a large amount of chemical raw materials that can be recycled. Therefore, a better treatment method is needed to realize the recycling of the oxidation section wastewater. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a treatment method of K acid synthesis oxidation section wastewater, which solves the problems of waste of resources and additional water treatment cost in the prior art.

[0006] According to an embodiment of the present application, a treatment method of K acid synthesis oxidation section wastewater comprises the following steps:

[0007] S1, the mother liquor wastewater generated in the oxidation section is introduced into a reaction kettle, ammonium thiosulfate is added at room temperature, stirring is continued for 30-60 min, then ammonia gas is introduced until no precipitate is precipitated;

[0008] S2, the solid-liquid mixture in the reaction kettle is centrifuged to separate ammonium sulfate crystals and mother liquor, ammonium sulfate is recovered, and the separated mother liquor is separated into ammonia gas, water and DMF by rectification, wherein the ammonia gas continues to be introduced into the mother liquor wastewater, and only DMF is left in the remaining kettle liquid, which is directly used as an oxidation section raw material.

[0009] Further, after the centrifugation in step S2, the ammonium sulfate is first washed and then recovered and stored.

[0010] Further, the washing process uses one of methanol, ethanol or acetone as a washing agent.

[0011] Further, the washing agent is recovered during the rectification stage of step S2 and then reused.

[0012] Further, the introduction of ammonia gas can be replaced by the addition of concentrated ammonia water.

[0013] Further, the ammonium thiosulfate added in step S1 is 4-6% of the mass of the mother liquor wastewater.

[0014] Further, the rectification process in step S2 is carried out at 50-65 DEG C under reduced pressure for 2-3 h.

[0015] Further, the water distilled in step S2 is used to wash ammonium sulfate or directly discharged.

[0016] Further, the solid-liquid mixture in step S2 is first added with ethanol until no precipitate is precipitated, and then centrifuged.

[0017] The technical principle of the present application is that ammonium thiosulfate is added to the mother liquor wastewater in the oxidation section to convert ammonium persulfate into ammonium sulfate, and then ammonia gas is introduced, which not only converts sulfuric acid into ammonium sulfate, but also precipitates ammonium sulfate in the wastewater due to the excess ammonium ion in the saturated ammonia water, and centrifugation can obtain ammonium sulfate crystal product for the chemical fertilizer industry. The mother liquor after centrifugation can obtain DMF, reusable ammonia gas and water after rectification, and the method realizes the maximum resource recovery of the wastewater in the K acid preparation process oxidation section.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The ammonium sulfate product produced by the present invention can be directly sold for use in the fertilizer industry. The distilled and purified DMF can be reused as raw material in the oxidation process, and the treated water can be reused to clean the oxidation products, thereby achieving maximum resource recovery of oxidation wastewater. The process has the advantages of simple operation, low labor intensity, and no environmental pollution. It meets clean production standards and is suitable for large-scale wastewater treatment. Furthermore, the present invention not only saves the cost of treating wastewater at sewage treatment plants but also generates additional sales revenue, thereby improving the economic benefits of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic diagram of the chemical reaction principle of the process flow of Route 2 used in the prior art.

[0021] Figure 2 1 is a process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention are further described below with reference to the accompanying drawings and embodiments.

[0023] like Figure 2 As shown, the working principle of the present invention is as follows: ammonium thiosulfate is added to the mother liquor wastewater from the oxidation section to convert ammonium persulfate into ammonium sulfate. Ammonia gas is then introduced to convert sulfuric acid into ammonium sulfate. The excess ammonium ions in the saturated ammonia water also cause the ammonium sulfate in the wastewater to precipitate. Centrifugation then yields ammonium sulfate crystals for use in the fertilizer industry. The mother liquor after centrifugation is then distilled to yield DMF, reusable ammonia gas, and water.

[0024] Example 1:

[0025] In this embodiment, 1000 g of the mother liquor wastewater generated in the oxidation section is first added to the reactor, 40 g of ammonium thiosulfate is added at room temperature, stirred for 30 min, ammonia is introduced until no precipitate is precipitated, and then centrifuged. The ammonium sulfate obtained by centrifugation is washed with methanol in batches and the content is analyzed. The mother liquor after centrifugation is subjected to reduced pressure distillation at 65 ° C for 2 h. The distilled ammonia can continue to be introduced into the oxidation mother liquor wastewater. The distilled water can be used to clean the product or directly discharged, and the remaining kettle liquid DMF can be directly reused in the oxidation section.

[0026] In this embodiment, 360 g of crude wet ammonium sulfate salt was obtained, with an ammonium sulfate content of 70% and a water content of 21%. After drying in a vacuum drying oven at 70° C. for 12 h, 242 g of crude dry ammonium sulfate salt was obtained, and the ammonium sulfate content was analyzed to be 96.2%. 228 g of the distillate (water) was received, and 480 g of the kettle liquid remained after rectification, and the DMF content was analyzed to be 99.9%.

[0027] Example 2:

[0028] Oxidation mother liquor wastewater 1000g, at room temperature, add 45g of ammonium thiosulfate, stirring for 40min, pass in ammonia gas until no precipitate is precipitated, then centrifuge, the ammonium sulfate centrifuged out, add acetone in batches to wash, analyze the content, the mother liquor after centrifugation is distilled at 65℃ under reduced pressure for 2h, the ammonia gas distilled out can continue to be passed into the oxidation mother liquor wastewater, the water distilled out can be used for cleaning products or directly discharged, the remaining DMF in the kettle can be directly reused to the oxidation section.

[0029] This example obtains 336g of crude wet ammonium sulfate salt, the ammonium sulfate content is 75%, directly dried in a vacuum drying oven at 70℃ for 12h, to obtain 234g of crude dry ammonium sulfate salt, the ammonium sulfate content is 99.8%; the distillate (water) receives 229g, the kettle liquid remaining after rectification is 480g, and the DMF content is 99.9%.

[0030] Example three:

[0031] Oxidation mother liquor wastewater 1000g, at room temperature, add 50g of ammonium thiosulfate, stirring for 50min, continuously add saturated ammonia water, add ethanol until no precipitate is precipitated, then centrifuge, the ammonium sulfate centrifuged out, analyze the content, the mother liquor after centrifugation is distilled at 50-65℃ under reduced pressure for 3h, the ammonia gas distilled out can continue to be passed into the oxidation mother liquor wastewater, the ethanol distilled out is reused, the water distilled out can be used for cleaning products or directly discharged, the remaining DMF in the kettle can be directly reused to the oxidation section.

[0032] This example obtains 350g of crude wet ammonium sulfate salt, the ammonium sulfate content is 72%, the water content is 19%, directly dried in a vacuum drying oven at 70℃ for 12h, to obtain 240g of crude dry ammonium sulfate salt, the ammonium sulfate content is 96.8%; the distillate 1 (ethanol) receives 31g, the distillate 2 (water) receives 227g, the kettle liquid remaining after rectification is 480g, and the DMF content is 99.9%.

[0033] Example four:

[0034] Oxidation mother liquor wastewater 1000g, at room temperature, add 60g of ammonium thiosulfate, stirring for 60min, continuously add saturated ammonia water, add ethanol until no precipitate is precipitated, then centrifuge, the ammonium sulfate centrifuged out, add ethanol in batches to wash, analyze the content, the mother liquor after centrifugation (including the washed ethanol) is distilled at 50-65℃ under reduced pressure for 2.5h, the ammonia gas distilled out can continue to be passed into the oxidation mother liquor wastewater, the ethanol distilled out is reused, the water distilled out can be used for cleaning products or directly discharged, the remaining DMF in the kettle can be directly reused to the oxidation section.

[0035] The crude wet ammonium sulfate salt obtained in this example is 328 g, and the ammonium sulfate content is 77%. After drying in a vacuum drying oven at 70°C for 12 h, the crude dry ammonium sulfate salt is 233 g, and the analytical ammonium sulfate content is 99.9%. Fraction 1 (ethanol) is 180 g, fraction 2 (water) is 228 g, and the remaining pot liquid after rectification is 486 g, and the analytical DMF content is 99.6%.

[0036] In the present application, adding ethanol to precipitate ammonium sulfate before centrifugation and mixing the washed ethanol with the mother liquor after centrifugation for rectification can increase the processing capacity and affect the processing effect and purity. In order to reduce the types of raw materials used and avoid too many distillates, in Example 3 and Example 4, ethanol is used to wash the crude ammonium sulfate after centrifugation, and then the washed ethanol is mixed with the mother liquor after centrifugation, and then reused after rectification.

[0037] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for treating wastewater from K acid synthesis oxidation process, characterized in that: The steps include: S1. The mother liquor wastewater produced in the oxidation section is passed into the reactor, ammonium thiosulfate is added at room temperature, and stirring is continued for 30-60 minutes, and then ammonia gas is introduced until no precipitate is precipitated; S2. The solid-liquid mixture in the reactor is centrifuged to separate ammonium sulfate crystals and mother liquor, and the ammonium sulfate is recovered. The separated mother liquor is distilled to separate ammonia, water and DMF, wherein the ammonia is continued to be introduced into the mother liquor wastewater. Only DMF remains in the remaining kettle liquid, which is directly used as a raw material in the oxidation section.

2. The method for treating wastewater from a K acid synthesis oxidation process according to claim 1, wherein: After the centrifugation in step S2 is completed, the ammonium sulfate is first washed and then recovered and stored.

3. The method for treating wastewater from a K acid synthesis oxidation process according to claim 2, wherein: The washing process uses one of methanol, ethanol or acetone as a washing agent.

4. The method for treating wastewater from a K acid synthesis oxidation process according to claim 3, wherein: The detergent is recovered in the distillation stage of step S2 and then reused.

5. The method for treating wastewater from a K acid synthesis oxidation process according to claim 1, wherein: The introduction of ammonia gas can be replaced by the addition of concentrated ammonia water.

6. The method for treating wastewater from the K acid synthesis oxidation process according to claim 1, wherein: The amount of ammonium thiosulfate added in step S1 is 4-6% of the mass of the mother liquor wastewater.

7. The method for treating wastewater from a K acid synthesis oxidation process according to claim 1, wherein: In the distillation process of step S2, the distillation is carried out under reduced pressure at 50-65° C. for 2-3 hours.

8. The method for treating wastewater from a K acid synthesis oxidation process according to claim 1, wherein: The water distilled in step S2 is used to wash ammonium sulfate or is directly discharged.

9. The method for treating wastewater from a K acid synthesis oxidation process according to claim 1, wherein: The solid-liquid mixture in step S2 is first added with ethanol until no precipitate is formed, and then centrifuged.

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