A method for improving the yield and purity of insecticide products

Abstract

The invention discloses a method for improving the yield and purity of a single insecticide product. The mother liquor of insecticide double is mixed with an azeotropic agent, and azeotropic dehydration is performed at normal pressure to obtain a concentrated mother liquor and a primary steam; the concentrated mother liquor is subjected to acid adjustment, cooling and crystallization to obtain a primary insecticide single crystal and a primary mother liquor with a mass purity higher than 95 wt%, and the primary mother liquor is mixed with the azeotropic agent and then heat-exchanged with the primary steam to obtain a primary steam condensate and a vapor-liquid mixture. The vapor-liquid mixture is subjected to reduced pressure azeotropic dehydration to obtain a secondary steam and a primary concentrated mother liquor. The secondary steam and the primary steam condensate are subjected to condensation and phase separation to separate an organic phase from an aqueous phase. The primary concentrated mother liquor is subjected to acid adjustment, cooling and crystallization to obtain a secondary insecticide single crystal and a secondary mother liquor, and the secondary mother liquor enters a preparation section of an insecticide double aqueous solution. The invention adopts a secondary atmospheric and reduced pressure double-effect azeotropic dehydration to achieve the concentration of the mother liquor of insecticide double and the primary mother liquor, significantly improves the yield and purity of the primary insecticide single and the secondary insecticide single products, and improves the utilization efficiency of resources and energy.

Description

Technical Field

[0001] The invention relates to the field of pesticide production, and in particular to a method for improving the yield and purity of a single insecticide product. Background Art

[0002] Insecticide is a synthetic analogue of nereis toxin, which has strong contact, stomach poison and systemic transmission effects. It is mainly used to control the larvae of lepidopteran pests. It has the advantages of little impact on the environment, not easy to develop resistance, and no residual toxicity. At present, the industrial synthesis methods of insecticide are mainly water method and solvent method. The content of insecticide produced by water method is low (usually less than 90%). The solvent method introduces methanol or ethanol as a production solvent, and the purity of insecticide product can be increased to about 95% in one crystallization. Although the solvent method effectively improves the purity of insecticide, the yield of insecticide product is still low, and the total yield of insecticide is only 50% - 60%. In order to further improve the yield and quality of insecticide products, many researchers have carried out relevant research. For example, Chinese invention patent application CN202110298375.0 discloses a water-saving high-purity insecticide synthesis process. This method mainly improves the reaction system of the amination reaction in the insecticide synthesis process, replaces water with pyridine as the reaction system, and replaces dimethylamine with pyridine as the acid-binding agent. The purity and conversion rate of N,N-dimethylpropyleneamine can reach more than 99%, thereby improving the production efficiency of the subsequent process and reducing wastewater discharge. Chinese invention patent ZL200910183580.1 provides a membrane concentration process for insecticide mother liquor. This method treats the insecticide mother liquor through a first-stage ultrafiltration and a two-stage nanofiltration treatment, and then treats the concentrated liquid through acid adjustment crystallization and solid-liquid separation to obtain an insecticide product. The total powder yield of insecticide can reach about 78%. Chinese invention patent ZL201511017072.8 discloses a method for improving the powder yield of insecticide monochloride centrifugal mother liquor. In this method, stabilizers such as tert-butylhydroquinone are added to the insecticide monochloride centrifugal mother liquor to prevent the decomposition of the insecticide monochloride isomer; and the pH value of the centrifugal mother liquor is adjusted to 6.8-7.2 with liquid alkali, and the temperature is raised to 40-70°C. After the reaction is kept warm, vacuum concentration and dehydration are performed to further concentrate the centrifugal mother liquor and improve the crystallization yield of insecticide monochloride acid.

[0003] Although the above method can achieve an increase in the yield of a single insecticide product, it still has shortcomings such as expensive production equipment, high operating costs and material loss under high vacuum conditions, which directly leads to difficulties in industrial application and promotion. Summary of the invention

[0004] In view of the technical deficiencies in the above methods, the present invention provides a method for improving the yield and purity of insecticide monohydrate, which adopts secondary atmospheric and vacuum double-effect azeotropic dehydration to achieve the concentration of insecticide monohydrate mother liquor and primary mother liquor, significantly improve the yield and purity of primary insecticide monohydrate and secondary insecticide monohydrate products, and improve the efficiency of resource and energy utilization.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for improving the yield and purity of insecticides comprises the following steps:

[0007] S1. The mother liquor of dimethoate is mixed with the entrainer from the entrainer storage tank, and then pumped into a normal pressure azeotropic dehydration device, and the mother liquor of dimethoate is further concentrated by azeotropic dehydration to obtain primary steam, concentrated mother liquor and sodium chloride crystals; the concentrated mother liquor and sodium chloride crystals are separated by a centrifuge to achieve a solid-liquid separation, and the mass concentration of dimethoate in the concentrated mother liquor reaches 50 wt% - 80 wt%;

[0008] S2. After the concentrated mother liquor is cooled to 30°C - 50°C by circulating cooling water, a hydrochloric acid solution is added to adjust the pH of the concentrated mother liquor to 4.0 - 6.0; the concentrated mother liquor is then subjected to step cooling and temperature reduction crystallization using frozen brine as a cooling medium to obtain a single insecticide product and a primary mother liquor having a mass concentration of 95wt% - 98wt%;

[0009] S3. The primary mother liquor obtained in S2 is mixed with an azeotropic agent to form a mixed solution, and the mixed solution is heat exchanged with the primary steam obtained in S1 in a heat exchanger, and the primary steam heat exchange obtains a primary steam condensate, and the heated part of the mixed solution is vaporized and enters a vacuum azeotropic dehydration device, the device pressure is 0.4-1.0 atm, and the device temperature is 30 ℃-60 ℃; a primary concentrated mother liquor, secondary steam and sodium chloride crystals are obtained by vacuum azeotropic dehydration, and the primary concentrated mother liquor and the sodium chloride crystals are separated into solid and liquid by a centrifuge, and the mass concentration of dichlorvos in the primary concentrated mother liquor is 35 wt%-50 wt%, and the mass concentration of dichlorvos is 15wt%-30wt%;

[0010] S4. The primary steam condensate obtained in S3 is mixed with the secondary steam obtained in S3 or the secondary steam obtained in S3 enters the cooling system alone, and is cooled and condensed by circulating cooling water and then pumped into a phase separator to separate the organic phase and the aqueous phase; the obtained organic phase is pumped into the azeotropic agent storage tank for recycling, and the aqueous phase enters the preparation section of the insecticide double aqueous solution;

[0011] S5. After cooling the concentrated mother liquor obtained in S3, hydrochloric acid solution is added to adjust the acidity and crystallize it, and the temperature is gradually cooled by using frozen brine to obtain a secondary insecticide product and a secondary mother liquor with a mass concentration of 90 wt% - 96 wt%. The secondary mother liquor enters the preparation section of the insecticide double aqueous solution.

[0012] Furthermore, in S1, the insecticide double mother liquor is the insecticide double mother liquor obtained by removing the methanol solvent from the reaction liquid obtained by the sulfonation reaction under normal pressure, and its mass concentration is 30 wt% - 45 wt%, the mass ratio of the insecticide double mother liquor and the entrainer is 1:1-10, and the feed temperatures of the insecticide double mother liquor and the entrainer are both 30 ℃ - 85 ℃; the heating medium of the atmospheric pressure azeotropic dehydration device is 100 ℃ - 150 ℃ saturated steam.

[0013] Furthermore, the entrainer in S1 and S3 is independently selected from one or a mixed solvent of two or more of diethyl ether, diisopropyl ether, cyclohexane, n-hexane, benzene, toluene, dichloromethane, monochloroethane, dichloroethane, trichloroethane and carbon tetrachloride, and the atmospheric azeotropic temperature of the azeotrope formed by these entrainers and water is lower than 85°C, and the entrainer is insoluble or slightly soluble in water; the pressure of the atmospheric azeotropic dehydration device is 1.0-2.0 atm (i.e., atmospheric pressure or slightly positive pressure), and the temperature is not higher than 85°C, preferably 40°C-85°C.

[0014] Furthermore, in S2, the gradient cooling process is to cool down to 10 ℃ - 20 ℃ at a uniform rate of 2 ℃ / h - 4 ℃ / h, and maintain it for 2 h - 6 h, and then cool down to -10 ℃ - 5 ℃ at a uniform rate of 2 ℃ / h - 4 ℃ / h, and maintain it for 2 h - 6 h. This operation can prevent the co-precipitation of sodium chloride and insecticide.

[0015] Furthermore, in S2, the mass concentration of dimehypo in the primary mother liquor is 20 wt% - 30 wt%, and the mass concentration of dimehypo is 10 wt% - 15 wt%.

[0016] Further, in S3, the mass ratio of the primary mother liquor to the entrainer is 1:1 - 1:10, the mixed solution feed temperature is 0°C - 40°C, and the feed pressure is 0.4 atm - 1.0 atm; the primary steam feed temperature is 40°C-85°C; the mixed solution heat exchanger discharge temperature is 30°C - 60°C, and the absolute pressure is 0.4 atm - 1.0 atm; the azeotropic dehydration device temperature is 30°C - 60°C, and the absolute pressure is 0.4 atm - 1.0 atm.

[0017] Furthermore, in S4, when the azeotropic agents of S1 and S3 are the same, the secondary steam obtained from S3 is mixed with the primary steam condensate obtained from S3 and then enters the cooling system; when the azeotropic agents of S1 and S3 are different, the secondary steam obtained from S3 enters the cooling system alone.

[0018] Furthermore, in S2 and S5, the mass concentration of the hydrochloric acid solution is not less than 30 wt %.

[0019] Further, in S5, the main components of the secondary mother liquor are 25 wt% - 35 wt% of dimexico and 10 wt% -20 wt% of chlorpyrifos. The pH value of the secondary mother liquor is adjusted to 5.0-7.5 using a sodium hydroxide solution with a concentration of more than 30 wt%, and then mixed with the water phase of the separator to produce 18 wt% / 29 wt% / 36 wt% of dimexico soluble solution.

[0020] The beneficial effects of the present invention are:

[0021] The present invention adopts secondary atmospheric and vacuum double-effect azeotropic dehydration to achieve the concentration of the insecticide double mother liquor and the primary mother liquor, significantly improve the yield and purity of the high value-added primary insecticide single and secondary insecticide single products, and improve the efficiency of resource and energy utilization. At the same time, the present invention improves the total concentration of insecticide double and insecticide single in the secondary mother liquor, and the agent-salt ratio (i.e., the ratio of the total mass concentration of insecticide double and insecticide single to the mass concentration of sodium salt), which is conducive to the production of high-specification insecticide single aqueous solution. The present invention mixes the aqueous phase in the phase separator with the secondary mother liquor to produce an insecticide double soluble solution, reduces wastewater discharge, meets green production, and significantly increases economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The process flow diagram of the method of the present invention is shown in FIG. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to specific embodiments, but the present invention is not limited thereto. Example 1

[0024] S1. Mix the insecticidal mother liquor with the entrainer n-hexane from the entrainer storage tank, the feeding temperature of the insecticidal mother liquor is 40°C, the feeding flow rate is 10 kg / h, the feed composition is 50 wt% water, 35.2 wt% insecticidal, and 14.8 wt% sodium chloride, the feeding temperature of the entrainer n-hexane is 40°C, and the feeding flow rate is 20 kg / h; the insecticidal mother liquor and the entrainer are mixed and the temperature is raised to 85°C and pumped into the atmospheric pressure azeotropic dehydration device, the pressure is 1.0atm, and the mass flow rate of the top is 16.55 kg / h, which is composed of primary steam composed of 11.2wt% water and 88.8 wt% n-hexane. The concentrated mother liquor at the bottom and the sodium chloride crystals are separated by solid-liquid separation by a centrifuge, and the insecticidal concentration in the concentrated mother liquor reaches 80wt%;

[0025] S2. After the concentrated mother liquor is cooled to 30°C - 50°C by circulating cooling water, a hydrochloric acid solution with a mass concentration of more than 30 wt% is added to adjust the pH of the concentrated mother liquor to about 5.0; the concentrated mother liquor is then subjected to step cooling and temperature reduction crystallization using frozen brine as a cooling medium to obtain a single insecticide product and a primary mother liquor with a mass purity of 97.8 wt%;

[0026] S3. The primary mother liquor with a mass flow rate of 7.0 kg / h is mixed with the azeotropic agent n-hexane in a ratio of 1:1, and then heat-exchanged with the primary steam in a heat exchanger to raise the temperature to 50°C, and then enters the vacuum azeotropic dehydration device with a pressure of 0.4 atm and a temperature of 40°C. A secondary steam with a mass flow rate of 7.8 kg / h is obtained at the top, and 6.2 kg / h of primary concentrated mother liquor and sodium chloride crystals are obtained at the bottom. The primary concentrated mother liquor and the sodium chloride crystals are separated into solid and liquid by a centrifuge;

[0027] S4. The condensate obtained after the primary steam is heat exchanged in S3 is mixed with the secondary steam obtained in S3 and then enters the cooling system. After cooling and condensing by circulating cooling water, it is pumped into the phase separator to separate the organic phase and the aqueous phase. The obtained organic phase is pumped into the azeotropic agent storage tank for recycling, and the aqueous phase enters the preparation section of the insecticide double aqueous solution;

[0028] S5. After cooling the concentrated mother liquor obtained in S3, add 30wt% hydrochloric acid solution to adjust the acidity and crystallize it, and use frozen brine to cool it step by step to obtain a secondary insecticide product and a secondary mother liquor with a mass purity of 93.4 wt%. The secondary mother liquor enters the preparation section of insecticide aqueous solution; the total powder yield of insecticide is 63.5 wt%, and the energy consumption of concentration and dehydration is 2.03 t low-pressure steam / t water. Example 2

[0029] In the process of decompressing and dehydrating the primary mother liquor in S3, low-pressure steam is used as the heat source instead of the primary steam, and the other conditions are the same as those in Example 1. Example 3

[0030] The mass ratio of the primary mother liquor to the entrainer in S3 is 1:2, and the other conditions are consistent with those in Example 1. Example 4

[0031] Diisopropyl ether was used as the azeotropic agent, and the other feed conditions were the same as those in Example 3. Example 5

[0032] Dichloromethane was used as the azeotropic agent, and the other feed conditions were consistent with those in Example 3. Example 6

[0033] Normal pressure azeotropic dehydration uses n-hexane as the azeotropic agent, and reduced pressure azeotropic dehydration uses dichloromethane as the azeotropic agent. The other feed conditions are the same as those in Example 3. Example 7

[0034] No azeotropic agent was used, and the other feed conditions were consistent with those in Example 3.

[0035]

[0036] It can be seen from the above table that the method of the present invention can significantly improve the powder yield and purity of insecticide, and significantly reduce the energy consumption of mother liquor concentration through the atmospheric and vacuum double-effect azeotropic distillation technology.

Claims

1. A method for improving the yield and purity of insecticides, characterized in that: The following steps are involved: S1. The mother liquor of dimethoate is mixed with the entrainer from the entrainer storage tank, and then pumped into a normal pressure azeotropic dehydration device, wherein the entrainer is a mixed solvent composed of one or more of ether, diisopropyl ether, cyclohexane, n-hexane, benzene, toluene, dichloromethane, monochloroethane, dichloroethane, trichloroethane and carbon tetrachloride; the mother liquor of dimethoate is further concentrated by azeotropic dehydration to obtain primary steam, concentrated mother liquor and sodium chloride crystals; the concentrated mother liquor and sodium chloride crystals are separated into solid and liquid by a centrifuge, and the mass concentration of dimethoate in the concentrated mother liquor reaches 50 wt% - 80 wt%; S2. After the concentrated mother liquor is cooled to 30°C - 50°C by circulating cooling water, a hydrochloric acid solution is added to adjust the pH of the concentrated mother liquor to 4.0 - 6.0; the concentrated mother liquor is then subjected to step cooling and temperature reduction crystallization using frozen brine as a cooling medium to obtain a primary mother liquor and a primary insecticide product having a mass concentration of 95wt%-98wt%; S3. The primary mother liquor obtained in S2 is mixed with an azeotropic agent to form a mixed solution, and the mixed solution is heat exchanged with the primary steam obtained in S1 in a heat exchanger, and the primary steam heat exchange obtains a primary steam condensate, and the heated part of the mixed solution is vaporized and enters a vacuum azeotropic dehydration device, the device pressure is 0.4-1.0 atm, and the device temperature is 30 ℃-60 ℃; a primary concentrated mother liquor, secondary steam and sodium chloride crystals are obtained by vacuum azeotropic dehydration, and the primary concentrated mother liquor and the sodium chloride crystals are separated into solid and liquid by a centrifuge, and the mass concentration of dichlorvos in the primary concentrated mother liquor is 35 wt%-50 wt%, and the mass concentration of dichlorvos is 15 wt%-30wt%; S4. The primary steam condensate obtained in S3 is mixed with the secondary steam obtained in S3 or the secondary steam obtained in S3 enters the cooling system alone, and is cooled and condensed by circulating cooling water and then pumped into a phase separator to separate the organic phase and the aqueous phase; the obtained organic phase is pumped into the azeotropic agent storage tank for recycling, and the aqueous phase enters the preparation section of the insecticide double aqueous solution; S5. After cooling the concentrated mother liquor obtained in S3, hydrochloric acid solution is added to adjust the acidity and crystallize it, and the temperature is gradually cooled by using frozen brine to obtain a secondary insecticide product and a secondary mother liquor with a mass concentration of 90 wt% - 96 wt%. The secondary mother liquor enters the preparation section of the insecticide double aqueous solution.

2. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S1, the insecticide double mother liquor is the insecticide double mother liquor obtained by removing the methanol solvent from the reaction liquid obtained by the sulfonation reaction under normal pressure, and its mass concentration is 30wt% - 45wt%, the mass ratio of the insecticide double mother liquor and the entrainer is 1:1-10, and the feed temperatures of the insecticide double mother liquor and the entrainer are both 30℃ - 85℃; the heating medium of the atmospheric pressure azeotropic dehydration device is saturated steam at 100℃ - 150℃.

3. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S1, the pressure of the atmospheric pressure azeotropic dehydration unit is 1.0 - 2.0 atm, and the temperature is not higher than 85°C.

4. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S2, the gradient cooling process is to cool down to 10 ℃ - 20 ℃ at a constant rate of 2 ℃ / h - 4 ℃ / h, and keep it for 2 h - 6 h, and then cool down to -10 ℃ - 5 ℃ at a constant rate of 2 ℃ / h - 4 ℃ / h, and keep it for 2 h - 6 h to prevent sodium chloride from coprecipitating with insecticide.

5. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S2, the mass concentration of dimehypo in the primary mother liquor is 20 wt% - 30 wt%, and the mass concentration of dimehypo is 10 wt% - 15 wt%.

6. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S3, the mass ratio of the primary mother liquor to the entrainer is 1:1 - 1:10, the feed temperature of the mixed solution is 0 ℃ - 40 ℃, and the feed pressure is 0.4 atm -1.0 atm; the primary steam feed temperature is 40 ℃ -85 ℃; the discharge temperature of the mixed solution heat exchanger is 30 ℃ - 60 ℃, and the absolute pressure is 0.4 atm - 1.0 atm; the temperature of the azeotropic dehydration device is 30 ℃ - 60 ℃, and the absolute pressure is 0.4 atm -1.0 atm.

7. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S4, when the azeotropic agents of S1 and S3 are the same, the secondary steam obtained from S3 is mixed with the primary steam condensate obtained from S3 and then enters the cooling system; when the azeotropic agents of S1 and S3 are different, the secondary steam obtained from S3 enters the cooling system alone.

8. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S2 and S5, the mass concentration of the hydrochloric acid solution is not less than 30 wt%.

9. The method for improving the yield and purity of insecticide according to claim 1, characterized in that: In S5, the main components of the secondary mother liquor are 25 wt% - 35 wt% of dimehypo and 10 wt% - 20 wt% of chlorpyrifos. The pH value of the secondary mother liquor is adjusted to 5.0-7.5 using a sodium hydroxide solution with a concentration of more than 30 wt%, and then mixed with the water phase of the separator to produce 18 wt% / 29 wt% / 36 wt% of dimehypo soluble solution.

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