Pretreatment methods for detoxification of wastewater containing 2-methylpyridine, triethylamine, and organic solvents

Abstract

This invention relates to wastewater pretreatment technology and discloses a method for detoxifying high-concentration wastewater containing 2-methylpyridine, triethylamine, and organic solvents. The method includes the following steps: adding high-concentration wastewater I (containing 2-methylpyridine, triethylamine, and organic solvents) to liquid alkali for alkali adjustment and release; subjecting the resulting alkali-adjusted and released high-concentration wastewater II to distillation to obtain organic phase I (containing 2-methylpyridine, triethylamine, and organic solvents); the bottom of the distillation column contains detoxified high-concentration wastewater III. High-concentration wastewater III is suitable for anaerobic / aerobic biological treatment, i.e., it meets the requirement that 2-methylpyridine concentration is less than 30 mg / L. Therefore, the detoxified high-concentration wastewater III can be fed into the biological treatment tank of a wastewater treatment plant for anaerobic / aerobic biological treatment, resulting in wastewater that meets discharge standards.

Description

Technical Field

[0001] This invention relates to wastewater pretreatment technology, and in particular to a method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine and organic solvents. Background Technology

[0002] Aminopropionate hydrochloride is a commonly used anticoccidial drug. Due to its special structure, it is not easy to develop drug resistance. Since its application in the 1960s, no drug resistance or tolerance has been reported, so it is widely used.

[0003] The current mainstream production route for amprolium hydrochloride mainly uses butamidinium, hemiacetal, and 2-methylpyridine as raw materials, and obtains the amprolium hydrochloride active pharmaceutical ingredient through processes such as freeing, cyclization, extraction, acidification, condensation, and recrystallization. This production process generates a significant amount of wastewater containing 2-methylpyridine, triethylamine, and organic solvents. Specifically, this wastewater, containing 2-methylpyridine, triethylamine, and organic solvents, originates from the amprolium hydrochloride production process, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, containing approximately 5–20 kg / m³ of 2-methylpyridine. 3 Triethylamine 0.5–2.0 kg / m 3 It also contains organic solvents such as methanol, isopropanol, toluene, and xylene, with a pH of 2-4 and a total organic carbon content of 35,000-50,000 mg / L. It is a brown liquid with a strong odor and has very high biotoxicity to nitrifying bacteria in wastewater treatment plants (the lethality rate is as high as 50-80% when diluted 1000 times).

[0004] The nitrifying bacteria inhibition test uses the half-maximal effect concentration (N-ECso) method. Using commercially available nitrifying bacteria as the test species, the lowest water sample concentration at which the ammonia oxidation inhibition rate reaches 50% after 24 hours is defined as N-ECso, compared to a blank control group. A higher N-ECso value indicates lower toxicity. Example: If the N-ECso value of a wastewater is 1%, it means that the wastewater achieves a 50% inhibition rate of nitrifying bacteria when diluted 100 times. Therefore, the wastewater needs to be diluted >100 times to minimize inhibition of the nitrification reaction.

[0005] Conventional methods such as phenolton oxidation, iron-carbon micro-electrolysis, catalytic oxidation, and high-temperature anaerobic treatment are often insufficient to remove or degrade highly toxic substances in wastewater. This can lead to fluctuations in the operation of wastewater treatment plants and, in severe cases, cause the death of large numbers of nitrifying and denitrifying bacteria, thereby affecting the wastewater treatment effect.

[0006] To avoid the death of a large number of nitrifying and denitrifying bacteria, the wastewater entering the wastewater treatment plant needs to meet the following conditions: 2-methylpyridine less than 30 mg / L.

[0007] Therefore, there is an urgent need for a pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents, so that the pretreated wastewater can meet the requirement of 2-methylpyridine being less than 30 mg / L, and thus enter the wastewater treatment plant for corresponding anaerobic / aerobic biochemical treatment. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a pretreatment method for detoxification of wastewater containing 2-methylpyridine, triethylamine and organic solvents.

[0009] To address the aforementioned technical problems, this invention provides a pretreatment method for detoxifying highly polluted wastewater containing 2-methylpyridine, triethylamine, and organic solvents, comprising the following steps:

[0010] 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I;

[0011] High-quality wastewater I is put into an alkali-adjusting and freeing vessel, and liquid alkali is added for alkali-adjusting and freeing to obtain high-quality wastewater II with a pH of 11.5-13.5 (preferably 11.5-12.5);

[0012] 2) The high-temperature wastewater II obtained in step 1) after alkali adjustment and detoxification is fed into the distillation and detoxification tower for distillation and detoxification to obtain organic phase I (organic phase I containing 2-methylpyridine, triethylamine and organic solvents). The bottom of the tower is the high-temperature wastewater III after distillation and detoxification.

[0013] The high-grade wastewater III after detoxification and treatment is wastewater that can be treated by anaerobic / aerobic biochemical processes, that is, it meets the requirement that 2-methylpyridine is less than 30 mg / L. Therefore, the high-grade wastewater III after detoxification and treatment can enter the biological treatment tank of the wastewater treatment plant and be discharged in compliance with the standards through anaerobic / aerobic biochemical treatment.

[0014] As an improvement to the method of the present invention, the following steps are also included:

[0015] 3) The organic phase I obtained from the extraction in step 2) is put into the acidification kettle (acid-adjusting and salt-forming kettle), and acid is added to form salt, so as to obtain organic phase II after acid-adjusting and salting with a pH of 2-3 (preferably 2.2-2.8) (organic phase II after salting contains 2-methylpyridine, triethylamine and organic solvent).

[0016] 4) Transfer the acidified and salted organic phase II obtained in step 3) into a distillation kettle (distillation desolvation kettle), and obtain an organic solvent by distillation (the organic solvent is methanol, isopropanol, toluene and xylene contained in wastewater I, so it is a mixed organic solvent, which can be purified by distillation). The resulting bottom liquid I is an aqueous solution containing 2-methylpyridinium salt (e.g. 2-methylpyridinium sulfate) and triethylamine salt (e.g. triethylamine sulfate).

[0017] 5) Transfer the bottom liquid I obtained in step 4) into the alkali-free liquid vessel, add liquid alkali for freeing, until the pH of the system is 12±0.5 (preferably 12.0~12.25), then heat up to perform azeotropic distillation (thereby azeotropically distilling out 2-methylpyridine, triethylamine and water) to obtain a mixture of 2-methylpyridine, triethylamine and water. The resulting bottom liquid II is returned to step 1) and combined with high-quality wastewater I for recycling treatment.

[0018] 6) Add xylene to the mixture of 2-methylpyridine, triethylamine and water obtained by azeotropic distillation in step 5) for extraction to obtain a mixed organic phase of 2-methylpyridine, triethylamine and xylene. The raffinate is returned to step 1) and combined with high-quality wastewater I for recycling.

[0019] 7) The mixed organic phase of 2-methylpyridine, triethylamine and xylene obtained from the extraction in step 6) is put into a distillation vessel to remove low-boiling substances, thereby removing the fore fraction (containing methanol, isopropanol, triethylamine and water, etc.). The resulting bottom liquid III is a mixture of 2-methylpyridine and xylene (purified 2-methylpyridine and xylene mixture).

[0020] Note: The purified mixture of 2-methylpyridine and xylene meets the raw material quality requirements of the aminopropyl hydrochloride condensation process, thus realizing resource utilization.

[0021] The raw material quality requirements for the condensation process of aminopropyl hydrochloride are as follows: the mixture of 2-methylpyridine and xylene contains 12-20% 2-methylpyridine, ≤0.1% triethylamine, and ≤0.05% moisture.

[0022] As a further improvement to the method of the present invention: the liquid alkali mentioned in step 1) is an aqueous solution of sodium hydroxide with a mass concentration of 28-32% (preferably 30%).

[0023] As a further improvement to the method of the present invention: Step 2) distillation and extraction is as follows: the bottom temperature of the extraction and detoxification tower (reboiler) is controlled at 102-103℃, the top temperature is controlled at 65-68℃, and the reflux ratio is 1:3-5 (v / v).

[0024] illustrate:

[0025] To ensure effective distillation and detoxification, the moisture content of the resulting organic phase I (containing 2-methylpyridine, triethylamine, and organic solvents) must be controlled between 30% and 40%, and the concentration of 2-methylpyridine in the detoxified wastewater III must be less than 30 mg / L. The distillation and distillation parameters set in this invention ensure the achievement of the aforementioned distillation and detoxification effects.

[0026] If the moisture content of organic phase I is too low, it will be impossible to completely remove toxic substances from the wastewater; if the moisture content is too high, it will affect the subsequent comprehensive utilization.

[0027] Organic phase I is drawn from the top of the tower, while high-quality wastewater III, after detoxification and purification, is drawn from the bottom of the tower.

[0028] As a further improvement to the method of the present invention: the acid mentioned in step 3) is hydrochloric acid, sulfuric acid, or nitric acid (preferably sulfuric acid).

[0029] As a further improvement to the method of the present invention, step 5) azeotropic distillation is performed as follows: depending on the content of 2-methylpyridine in the high-temperature wastewater I of step 1) of that batch, the following methods are selected for operation:

[0030] Method 1: When the content of 2-methylpyridine is <150Kg / batch, start collecting the distillate when the temperature of the kettle is raised to 80-90℃, continue to raise the temperature to collect the distillate, and stop collecting the distillate when the temperature of the kettle is raised to 98-100℃.

[0031] That is, Method 1 does not require water replenishment before or during distillation, and the azeotropic distillation volume is approximately 600-800 liters;

[0032] Method 2: When the batch contains 150 to less than 200 kg of 2-methylpyridine, first add 400 ± 20 liters of water, raise the temperature of the kettle to 80 to 90°C and start collecting the distillate. Continue to raise the temperature and collect the distillate until the temperature of the kettle reaches 98 to 100°C and then stop collecting the distillate.

[0033] That is, in Method 2, water is added before distillation, but no water is added during the distillation process, and the azeotropic distillation volume is approximately 800 to 1000 liters.

[0034] Method 3: When the batch contains 200-250 kg of 2-methylpyridine, first add 400±20 liters of water, raise the temperature of the distillation vessel to 80-90°C and start collecting the fraction. Continue to raise the temperature and collect the fraction until the temperature of the distillation vessel reaches 98-100°C. Then add 200±10 liters of water and continue azeotropic distillation to collect the fraction (raise the temperature to 80-90°C and start collecting the fraction) until the temperature of the distillation vessel reaches 98-100°C again and stop collecting the fraction.

[0035] That is, Method 3 requires water replenishment before and during distillation (the amount of water replenishment is 400±20 liters and 200±10 liters respectively), and the azeotropic distillation volume is approximately 1000 to 1400 liters.

[0036] Method 4: When the batch contains 250-300 kg / batch of 2-methylpyridine, first add 400±20 liters of water, raise the temperature of the distillation vessel to 80-90°C and start collecting the distillate. Continue to raise the temperature and collect the distillate until the temperature of the distillation vessel rises to 98-100°C, then add 400±20 liters of water and continue azeotropic distillation to collect the distillate (raise the temperature to 80-90°C and start collecting the distillate) until the temperature of the distillation vessel rises to 98-100°C again and stop collecting the distillate.

[0037] That is, Method 4 requires 400±20 liters of water to be added before and during distillation, and the azeotropic distillation volume is approximately 1400 to 1600 liters.

[0038] The content of 2-methylpyridine in the bottom liquid II obtained by azeotropic distillation is about 0.1 g / L.

[0039] In summary, the amount of material collected in this invention is adjusted based on the 2-methylpyridine data in the reactor. During feeding, the amount of material can be controlled to ensure that the 2-methylpyridine content in each batch of high-quality wastewater I is ≤300 kg.

[0040] As a further improvement to the method of the present invention: the distillation temperature in step 4) is 60-105℃.

[0041] As a further improvement to the method of the present invention: In step 6), during the extraction operation, the volume ratio of the mixture of 2-methylpyridine, triethylamine and water to xylene is 1:(1±0.1), V / V, and the extraction is performed twice. The mixed organic phase of 2-methylpyridine, triethylamine and xylene obtained from the first extraction is fed into the distillation vessel in step 7). The mixed organic phase containing 2-methylpyridine, triethylamine and xylene obtained from the second extraction can replace the xylene used in the first extraction to achieve recycling and reduce the energy consumption of subsequent distillation and purification.

[0042] As a further improvement to the method of the present invention: In step 7), when removing low-boiling substances from the mixed organic phase of 2-methylpyridine, triethylamine and xylene, atmospheric distillation is used, and the bottom temperature is controlled to not exceed 132°C (generally 128-132°C). The fore-distillate is collected when the top temperature is 60°C and the collection of the fore-distillate is stopped when the top temperature reaches 88°C, thus ending the distillation and purification process.

[0043] The resulting purified mixture of 2-methylpyridine and xylene contains ≤0.1% triethylamine and ≤0.05% moisture.

[0044] As a further improvement to the method of the present invention: the wastewater containing 2-methylpyridine, triethylamine, and organic solvents originates from the production process of amprolium hydrochloride, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, wherein the wastewater contains approximately 5–20 kg / m³ of 2-methylpyridine.3 Triethylamine 0.5–2.0 kg / m 3 It also contains organic solvents such as methanol, isopropanol, toluene, and xylene, with a pH of 2-4 and a total organic carbon content of 35,000-50,000 mg / L. It is a brown liquid with a strong odor and has very high biotoxicity to nitrifying bacteria in sewage treatment plants (the lethality rate is as high as 50-80% when diluted 500-1000 times).

[0045] For wastewater containing 2-methylpyridine, triethylamine, and organic solvents, this invention has demonstrated through extensive experiments that 2-methylpyridine and triethylamine in this wastewater are highly toxic to nitrifying bacteria (30 mg / L can cause a 50% mortality rate). Without detoxification pretreatment, subsequent biological treatment is difficult to sustain. Therefore, through long-term research, this invention proposes a detoxification technology using alkali addition for ionization and distillation. The organic phase obtained from distillation and detoxification, containing 2-methylpyridine, triethylamine, and organic solvents, is purified through processes such as acid addition for salt formation, distillation for solvent removal, alkali addition for ionization, azeotropic distillation, and extraction. This process allows for the resource utilization of 2-methylpyridine in the wastewater, achieving a low-carbon and high-efficiency goal and changing the traditional harmless treatment mode for wastewater containing 2-methylpyridine. Attached Figure Description

[0046] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] Figure 1 This is a process flow diagram of a high-temperature wastewater detoxification pretreatment method containing 2-methylpyridine, triethylamine, and organic solvents according to the present invention. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0049] In this invention, all percentages not explicitly stated refer to mass%.

[0050] Example 1: A pretreatment method for detoxifying wastewater containing 2-methylpyridine, triethylamine, and organic solvents, the main steps of which are as follows:

[0051] 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I;

[0052] Wastewater I originates from the production process of amprolium hydrochloride, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, containing approximately 15 kg / m³ of 2-methylpyridine. 3 Triethylamine 1.5 kg / m 3It also contains organic solvents such as methanol, isopropanol, toluene, and xylene. The pH is 3.2, and the total organic carbon content is 49,600 mg / L. It is a brown liquid with a strong odor and has very high biotoxicity to nitrifying bacteria in sewage treatment plants (the lethality rate is as high as 80% when diluted 1,000 times).

[0053] 15m 3 High-quality wastewater I was fed into an alkali-adjusting and separating reactor, and approximately 240 liters of a 30% sodium hydroxide aqueous solution were added for alkali adjustment and separation, yielding approximately 15.2 m³. 3 After alkali treatment and release, the pH value of wastewater II was 12.48.

[0054] Therefore, the batch corresponding to this case contains approximately 225 kg of 2-methylpyridine.

[0055] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3 The flow rate is fed into a 1250mm diameter high gravity distillation and detoxification tower for distillation and detoxification. The distillation and detoxification parameters are as follows: the temperature of the reboiler in the high gravity distillation and detoxification tower is controlled at 102-103℃, the temperature of the top of the tower is controlled at 65-68℃, and the reflux ratio is 1:3 (v / v).

[0056] The top of the tower is about 1.5m high. 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, yields approximately 13.7 m at the bottom of the column. 3 High-quality wastewater III after detoxification and treatment.

[0057] The organic phase I obtained by distillation contained 32.16% water, 148.67 g / L of 2-methylpyridine, 14.23 g / L of triethylamine, and the remainder was organic solvents (including methanol, isopropanol, and xylene).

[0058] The high-toxicity wastewater III, after detoxification, contains 6600 mg / L of total organic carbon, 12 mg / L of 2-methylpyridine, and a pH of 10.96. When diluted 2 times, it has a 30% lethality rate for nitrifying bacteria in the wastewater treatment plant (a reduction in toxicity of nearly 1000 times compared to high-toxicity wastewater I). Therefore, it can enter the biological treatment tank of the wastewater treatment plant and undergo anaerobic / aerobic biological treatment to achieve the required discharge standards.

[0059] 3) The approximately 1.5m obtained from the extraction in step 2) 3 Organic phase I, containing 2-methylpyridine, triethylamine, and organic solvent, is added to an acidification reactor, and approximately 165 liters of 98% concentrated sulfuric acid is added to form a salt, resulting in organic phase II after acid adjustment and salt formation (i.e., organic phase II containing 2-methylpyridine, triethylamine, and organic solvent after salt formation).

[0060] Organic phase II, after acidification and salt formation, has a pH of 2.8.

[0061] 4) Transfer the acidified and salted organic phase II obtained in step 3) into a distillation kettle and distill it (distillation temperature is 60-105℃, the fraction is collected at 60℃ and distillation ends at 105℃) to obtain a mixed organic solvent of about 850 liters of methanol, isopropanol, toluene and xylene (of which methanol content is 72%, isopropanol 12.3%, toluene and xylene 2.2%, water 10.21%, and the remainder are other impurities, which can be purified by distillation).

[0062] The resulting bottom liquid is named Bottom Liquid I, which is approximately 800 liters of aqueous solution containing 2-methylpyridine sulfate and triethylamine sulfate.

[0063] 5) Transfer approximately 800 liters of bottom liquid I obtained in step 4) to the alkali-free liquid vessel, and add approximately 375 liters of 30% sodium hydroxide aqueous solution for freeing (pH value 12.25). Since this batch of high-temperature wastewater I contains approximately 225 kg of 2-methylpyridine, 400 liters of water are added before azeotropic distillation. The vessel temperature is raised to 82°C to start collecting the distillate. The temperature is continued to rise and the distillate is collected until the vessel temperature rises to 98°C. Then, 200 liters of water are added, and azeotropic distillation is continued to collect the distillate until the vessel temperature rises again to 98-100°C and the collection of the distillate is stopped.

[0064] A mixture of approximately 1200 liters of 2-methylpyridine, triethylamine, and water was obtained.

[0065] The resulting bottom liquid is named Bottom Liquid II (azeotropic distillation bottom liquid). Bottom Liquid II contains 0.042 g / L of 2-methylpyridine and has a pH of 12.16. Bottom Liquid II can be returned to step 1) and combined with wastewater I for recycling.

[0066] 6) Add 1200 liters of xylene to the mixture of 2-methylpyridine, triethylamine and water obtained by azeotropic distillation in step 5) for the first extraction. After standing and separating the layers, the first extraction yields 1420 liters of mixed organic phase I of 2-methylpyridine, triethylamine and xylene. The raffinate is then subjected to a second extraction, again with the addition of 1200 liters of xylene. After standing and separating the layers, the second extraction yields 1200 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene.

[0067] The 1200 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene obtained from the second extraction are used as a substitute for step 6) in the next batch of xylene extraction to reduce the energy consumption of xylene distillation.

[0068] The secondary raffinate (with a 2-methylpyridine concentration of 3.26 g / L and a pH of 10.74) can be returned to step 1) and combined with high-quality wastewater I for further treatment.

[0069] In the mixed organic phase I of 2-methylpyridine, triethylamine and xylene, 2-methylpyridine accounts for 15.84%, triethylamine 1.58%, water 0.87%, and the remainder is xylene.

[0070] 7) The 1420 L mixed organic phase I of 2-methylpyridine, triethylamine and xylene obtained from the first extraction in step 6) is added to a distillation vessel to remove low-boiling substances:

[0071] Atmospheric distillation is employed, with the bottom temperature controlled to not exceed 132℃ (generally 128-132℃). The fore-fraction is collected starting at a top temperature of 60℃ and stopping at 88℃ (end of distillation and purification). 180 liters of fore-fraction are obtained (containing 24.42% methanol, 35.51% isopropanol, 11.36% triethylamine, 16.2% toluene and xylene, 0.75% 2-methylpyridine, and the remainder being impurities and water).

[0072] The resulting bottom liquid was named Bottom Liquid III. Bottom Liquid III is a mixture of 2-methylpyridine and xylene (a purified mixture of 2-methylpyridine and xylene), wherein the content of 2-methylpyridine is 18.14%, triethylamine is 0.042%, water content is ≤0.05%, and the balance is mainly xylene. This meets the quality requirements for raw materials used in the condensation of aminopropyl hydrochloride, thus achieving resource utilization.

[0073] Note: The quality requirements for the raw materials used in the condensation of aminopropyl hydrochloride are as follows: a mixture of 2-methylpyridine and xylene, wherein the content of 2-methylpyridine is 12-20%, triethylamine is ≤0.1%, and moisture is ≤0.05%.

[0074] Example 2: A pretreatment method for detoxifying wastewater containing 2-methylpyridine, triethylamine, and organic solvents, the main steps of which are as follows:

[0075] 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I;

[0076] High-quality wastewater I is the same as high-quality wastewater I in Example 1.

[0077] 15m 3 Wastewater I, containing 2-methylpyridine, triethylamine, and organic solvents, was fed into an alkali-adjusting and separating reactor. Approximately 220 liters of a 30% sodium hydroxide aqueous solution were added for alkali adjustment and separation, yielding approximately 15.2 m³. 3 After alkali treatment and release, the pH value of the high-alkali wastewater II was 11.52.

[0078] Therefore, the batch corresponding to this case contains approximately 225 kg of 2-methylpyridine.

[0079] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3The flow rate is fed into a 1250mm diameter high gravity distillation and detoxification tower for distillation and detoxification. The temperature of the reboiler in the high gravity distillation and detoxification tower is controlled at 102-103℃, the temperature of the top of the tower is controlled at 65-68℃, and the reflux ratio is 1:3 (v / v).

[0080] The top of the tower is about 1.5m high. 3 Organic phase I, containing 2-methylpyridine, triethylamine, and organic solvents, and the bottom of the column yield approximately 13.7 m. 3 High-quality wastewater (III grade) after detoxification and purification;

[0081] The organic phase I obtained by distillation contained 32.48% water, 148.54 g / L of 2-methylpyridine, 14.01 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0082] The high-toxicity wastewater III, after detoxification, contains 6690 mg / L of total organic carbon, 26 mg / L of 2-methylpyridine, and a pH of 10.53. When diluted twice, it reduces the mortality rate of nitrifying bacteria in the wastewater treatment plant to 50% (compared to high-toxicity wastewater I, the toxicity is reduced by nearly 1000 times). Therefore, it can enter the biological treatment tank of the wastewater treatment plant and undergo anaerobic / aerobic biological treatment to achieve the required discharge standards.

[0083] 3) The approximately 1.5m obtained from the extraction in step 2) 3 Organic phase I, containing 2-methylpyridine, triethylamine, and organic solvent, is added to an acidification reactor, and approximately 165 liters of 98% concentrated sulfuric acid is added to form a salt, resulting in organic phase II after acidification and salt formation (organic phase II containing 2-methylpyridine, triethylamine, and organic solvent after salt formation).

[0084] Organic phase II, after acidification and salt formation, has a pH of 2.42.

[0085] 4) Transfer the acidified and salted organic phase II obtained in step 3) into a distillation kettle and distill it (distillation temperature is 60-105℃) to obtain 850 liters of methanol, isopropanol and toluene and xylene mixed organic solvent (of which methanol content is 72.4%, isopropanol 12.1%, toluene and xylene 2.3%, water 10.72%, and the remainder is other impurities).

[0086] The resulting bottom liquid I was an aqueous solution of approximately 800 liters containing 2-methylpyridine sulfate and triethylamine sulfate.

[0087] 5) Transfer the 800 liters of bottom liquid I obtained in step 4) to the alkali-free liquid treatment vessel, and add about 375 liters of 30% sodium hydroxide aqueous solution for freeing (pH value 12.01). Since this batch of high-temperature wastewater I contains about 225 kg of 2-methylpyridine, 400 liters are added before azeotropic distillation. The vessel temperature is raised to 82°C to start collecting the distillate. The temperature is continued to rise and the distillate is collected until the vessel temperature rises to 98°C. Then, 200 liters of water are added and azeotropic distillation is continued to collect the distillate until the vessel temperature rises again to 98-100°C and the collection of the distillate is stopped.

[0088] A mixture of approximately 1200 liters of 2-methylpyridine, triethylamine, and water was obtained; the bottom liquid II (azeotropic distillation bottom liquid) contained 0.031 g / L of 2-methylpyridine and had a pH of 11.88; the bottom liquid II could be returned to step 1) and combined with the high-quality wastewater I for recycling.

[0089] 6) Add 1200 L of mixed organic phase II of 2-methylpyridine, triethylamine and xylene obtained from the second extraction in step 6) of Example 1 to the mixture of 2-methylpyridine, triethylamine and water obtained from the azeotropic distillation in step 5) for the first extraction. After standing and separating the layers, the first extraction yields 1460 L of mixed organic phase I of 2-methylpyridine, triethylamine and xylene. The raffinate is then subjected to a second extraction. 1200 L of fresh xylene is added for extraction. After standing and separating the layers, the second extraction yields 1200 L of mixed organic phase II of 2-methylpyridine, triethylamine and xylene.

[0090] The 1200 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene obtained from the second extraction is used as a substitute for the xylene used in the first extraction in the next batch, thereby reducing the energy consumption of xylene distillation.

[0091] The secondary raffinate (with a 2-methylpyridine concentration of 2.96 g / L and a pH of 10.93) can be returned to step 1) and combined with high-quality wastewater I for further treatment.

[0092] 7) The 1460 L mixed organic phase I of 2-methylpyridine, triethylamine and xylene obtained from the first extraction in step 6) is added to a distillation vessel to remove low-boiling substances:

[0093] Atmospheric distillation was used, with the bottom temperature controlled to not exceed 132℃. The fore-fraction was collected starting at a top temperature of 60℃ and stopping at a top temperature of 88℃, yielding 200 liters of fore-fraction (containing 22.19% methanol, 35.51% isopropanol, 11.14% triethylamine, 16.8% toluene and xylene, 0.54% 2-methylpyridine, with the remainder being impurities and water).

[0094] The bottom liquid III is a mixture of 2-methylpyridine and xylene, wherein the content of 2-methylpyridine is 18.03%, triethylamine is 0.038%, moisture is ≤0.05%, and the balance is mainly xylene. This meets the quality requirements for raw materials used in the condensation of aminopropyl hydrochloride, thus achieving resource utilization.

[0095] Example 3: A pretreatment method for detoxifying wastewater containing 2-methylpyridine, triethylamine, and organic solvents, the main steps of which are as follows:

[0096] 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I;

[0097] Wastewater I originates from the production process of amprolium hydrochloride, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, containing approximately 5.22 kg / m³ of 2-methylpyridine. 3 Triethylamine 0.76 kg / m 3 It also contains organic solvents such as methanol, isopropanol, toluene, and xylene, has a pH of 2.2, and a total organic carbon content of 34,600 mg / L. It is a brown liquid with a strong odor and has very high biotoxicity to nitrifying bacteria in wastewater treatment plants (the lethality rate is as high as 50% when diluted 500 times).

[0098] 15m 3 Wastewater I, containing 2-methylpyridine, triethylamine, and organic solvents, was fed into an alkali-adjusting and separating reactor. Approximately 120 liters of a 30% sodium hydroxide aqueous solution was added for alkali adjustment and separation, yielding approximately 15.1 m³. 3 After alkali treatment and release, the pH value of wastewater II was 12.03.

[0099] Therefore, the batch corresponding to this case contains approximately 78.3 kg of 2-methylpyridine.

[0100] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3 The flow rate is fed into a 1250mm diameter high gravity distillation and detoxification column for distillation and detoxification. The temperature of the reboiler in the high gravity distillation and detoxification column is controlled at 102-103℃, the temperature of the top of the column is controlled at 65-68℃, and the reflux ratio is 1:5 (v / v).

[0101] The top of the tower is about 1.0m. 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, yields approximately 14.1 m³ at the bottom of the column. 3 High-quality wastewater (III grade) after detoxification and purification;

[0102] The organic phase I obtained by distillation contained 38.76% water, 77.82 g / L of 2-methylpyridine, 11.37 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0103] The high-toxicity wastewater III, after detoxification, contains 5730 mg / L of total organic carbon, 24 mg / L of 2-methylpyridine, and a pH of 11.23. When diluted 2 times, it has a 50% lethality rate for nitrifying bacteria in the wastewater treatment plant (compared to high-toxicity wastewater I, the toxicity is reduced by nearly 500 times). Therefore, it can enter the biological treatment tank of the wastewater treatment plant and undergo anaerobic / aerobic biological treatment to ensure that the wastewater meets the discharge standards.

[0104] 3) The approximately 1.0 mg obtained from step 2) extraction 3 Organic phase I, containing 2-methylpyridine, triethylamine, and organic solvent, is added to an acidification reactor, and approximately 75 liters of 98% concentrated sulfuric acid is added to form a salt, resulting in organic phase II after acidification and salt formation (i.e., organic phase II containing 2-methylpyridine, triethylamine, and organic solvent after salt formation).

[0105] Organic phase II, after acidification and salt formation, has a pH of 2.2.

[0106] 4) Transfer the acidified and salted organic phase II obtained in step 3) into a distillation vessel and distill it (distillation temperature is 60-105℃) to obtain about 510 liters of methanol, isopropanol and toluene and xylene mixed organic solvent (of which methanol content is 74.1%, isopropanol 14.6%, toluene and xylene 2.6%, water 7.6%, and the remainder is other impurities). The bottom liquid I is about 500 liters of aqueous solution containing 2-methylpyridine sulfate and triethylamine sulfate.

[0107] 5) Transfer approximately 500 liters of bottom liquid I obtained in step 4) to the alkali-adjusting and freeing vessel, and add approximately 240 liters of 30% sodium hydroxide aqueous solution for freeing (pH value 12.14). Since this batch of high-temperature wastewater I contains approximately 78.3 kg of 2-methylpyridine, there is no need to add water. Directly raise the temperature for azeotropic distillation. Start collecting the distillate when the vessel temperature reaches 82°C, and continue to raise the temperature to collect the distillate until the vessel temperature reaches 98°C and then stop collecting the distillate. Azeotropic distillation yields a mixture of 540 liters of 2-methylpyridine, triethylamine, and water. Bottom liquid II (azeotropic distillation bottom liquid) contains 0.013 g / L of 2-methylpyridine and has a pH of 12.08. Bottom liquid II can be returned to step 1) and combined with high-temperature wastewater I for recycling.

[0108] 6) Add 540 liters of xylene to the mixture of 2-methylpyridine, triethylamine and water obtained from the azeotropic distillation in step 5) for the first extraction. After standing and separating the layers, the first extraction yields 610 liters of mixed organic phase I of 2-methylpyridine, triethylamine and xylene. The raffinate is then subjected to a second extraction, again with the addition of 540 liters of xylene. After standing and separating the layers, the second extraction yields approximately 545 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene.

[0109] The second extraction yielded 545 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene, which was used as a substitute for the xylene in the first extraction in the next batch, thus reducing the energy consumption of xylene distillation.

[0110] The secondary raffinate (with a 2-methylpyridine concentration of 2.67 g / L and a pH of 10.53) can be returned to step 1) and combined with high-quality wastewater I for further treatment.

[0111] 7) The 610 L mixed organic phase I of 2-methylpyridine, triethylamine, and xylene obtained from the first extraction in step 6) is added to a distillation vessel to remove low-boiling substances.

[0112] Atmospheric distillation was used, with the bottom temperature controlled to not exceed 132℃. The fore-fraction was collected starting at a top temperature of 60℃ and stopping at a top temperature of 88℃, yielding 85 liters of fore-fraction (containing 23.12% methanol, 36.27% isopropanol, 12.41% triethylamine, 14.7% toluene and xylene, 0.36% 2-methylpyridine, with the remainder being impurities and water).

[0113] The bottom liquid III is a mixture of 2-methylpyridine and xylene, wherein the content of 2-methylpyridine is 14.72%, triethylamine is 0.033%, moisture is ≤0.05%, and the balance is basically xylene; it meets the quality requirements of the raw materials used in the condensation of aminopropyl hydrochloride; and realizes resource utilization.

[0114] Example 4: A pretreatment method for detoxifying wastewater containing 2-methylpyridine, triethylamine, and organic solvents, the main steps of which are as follows:

[0115] 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I;

[0116] Wastewater I originates from the production process of amprolium hydrochloride, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, containing approximately 12 kg / m³ of 2-methylpyridine. 3 Triethylamine 1.5 kg / m 3 It also contains organic solvents such as methanol, isopropanol, toluene, and xylene, has a pH of 3.2, and a total organic carbon content of 46,300 mg / L. It is a brown liquid with a strong odor and has very high biotoxicity to nitrifying bacteria in wastewater treatment plants (the lethality rate is as high as 60% when diluted 1,000 times).

[0117] 15m 3 Wastewater I, containing 2-methylpyridine, triethylamine, and organic solvents, was fed into an alkali-adjusting and separating reactor. Approximately 210 liters of a 30% sodium hydroxide aqueous solution was added for alkali adjustment and separation, yielding approximately 15.2 m³. 3 After alkali treatment and release, the pH value of the high-alkali wastewater II was 11.86.

[0118] Therefore, the batch corresponding to this case contains approximately 180 kg of 2-methylpyridine.

[0119] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3 The flow rate is fed into a 1250mm diameter high gravity distillation and detoxification tower for distillation and detoxification. The temperature of the reboiler in the high gravity distillation and detoxification tower is controlled at 102-103℃, the temperature of the top of the tower is controlled at 65-68℃, and the reflux ratio is 1:3 (v / v).

[0120] The top of the tower is about 1.5m high. 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, yields approximately 13.7 m at the bottom of the column. 3 High-quality wastewater (III grade) after detoxification and purification;

[0121] The organic phase I obtained by distillation contained 35.48% water, 119.23 g / L of 2-methylpyridine, 13.98 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0122] After detoxification, the high-quality wastewater III contains 6470 mg / L of total organic carbon, 21 mg / L of 2-methylpyridine, and a pH of 10.72. When diluted 2 times, it has a 30% lethality rate for nitrifying bacteria in the wastewater treatment plant (the toxicity is reduced by nearly 1000 times compared to high-quality wastewater I). Therefore, it can enter the biological treatment tank of the wastewater treatment plant and undergo anaerobic / aerobic biological treatment to ensure that the wastewater meets the discharge standards.

[0123] 3) The approximately 1.5m obtained from the extraction in step 2) 3 Organic phase I, containing 2-methylpyridine, triethylamine, and organic solvent, is added to an acidification reactor, and approximately 138 liters of 98% concentrated sulfuric acid is added to form a salt, resulting in organic phase II after acidification and salt formation (organic phase II containing 2-methylpyridine, triethylamine, and organic solvent after salt formation).

[0124] Organic phase II, after acidification and salt formation, has a pH of 2.37.

[0125] 4) Transfer the acidified and salted organic phase II obtained in step 3) into a distillation kettle and distill it (distillation temperature is 60-105℃) to obtain about 840 liters of methanol, isopropanol and a mixed organic solvent of toluene and xylene (of which methanol content is 73.6%, isopropanol 14.1%, toluene and xylene 2.6%, water 12.43%, and the remainder is other impurities).

[0126] The resulting bottom liquid I was an aqueous solution of approximately 800 liters containing 2-methylpyridine sulfate and triethylamine sulfate.

[0127] 5) Transfer the 800 liters of bottom liquid I obtained in step 4) to the alkali-free liquid vessel, and add about 320 liters of 30% sodium hydroxide aqueous solution for freeing (pH value 12.07). Since this batch of high-temperature wastewater I contains about 180 kg of 2-methylpyridine, 400 liters are added before azeotropic distillation. The vessel temperature is raised to 82°C to start collecting the distillate. The temperature is continued to rise to collect the distillate until the vessel temperature rises to 98°C. Azeotropic distillation is then continued to collect the distillate until the vessel temperature rises again to 98-100°C and then the collection of the distillate is stopped.

[0128] A total of 900 liters of a mixture of 2-methylpyridine, triethylamine and water was obtained; the bottom liquid II (azeotropic distillation bottom liquid) contained 0.031 g / L of 2-methylpyridine and had a pH of 11.96; the bottom liquid II can be returned to step 1) and combined with the high-quality wastewater I for recycling treatment.

[0129] 6) Add 545 liters of the mixed organic phase II of 2-methylpyridine, triethylamine and xylene obtained from the second extraction in step 6) of Example 3 and 355 liters of fresh xylene to the mixture of 2-methylpyridine, triethylamine and water obtained from the azeotropic distillation in step 5) for the first extraction. After standing and separating the layers, the first extraction yields 1120 liters of mixed organic phase I of 2-methylpyridine, triethylamine and xylene. The raffinate is then subjected to a second extraction, with 900 liters of fresh xylene added for extraction. After standing and separating the layers, the second extraction yields 900 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene.

[0130] The secondary extraction yields 900 liters of a mixed organic phase II of 2-methylpyridine, triethylamine, and xylene, which can be used as a substitute for the xylene used in the first extraction in the next batch, thereby reducing the energy consumption of xylene distillation.

[0131] The secondary raffinate (with a 2-methylpyridine concentration of 2.87 g / L and a pH of 10.52) can be returned to step 1) and combined with high-quality wastewater I for further treatment.

[0132] 7) The 1120 L mixed organic phase I of 2-methylpyridine, triethylamine and xylene obtained from the first extraction in step 6) is added to a distillation vessel to remove low-boiling substances:

[0133] Atmospheric distillation was used, with the bottom temperature controlled to not exceed 132℃. The fore-fraction was collected starting at a top temperature of 60℃ and stopping at a top temperature of 88℃, yielding 180 liters of fore-fraction (containing 24.33% methanol, 33.42% isopropanol, 12.06% triethylamine, 14.8% toluene and xylene, 0.31% 2-methylpyridine, and the remainder being impurities and water).

[0134] The bottom liquid III is a mixture of 2-methylpyridine and xylene, wherein the content of 2-methylpyridine is 18.87%, triethylamine is 0.042%, water content is ≤0.03%, and the balance is mainly xylene. This meets the quality requirements for raw materials used in the condensation of aminopropyl hydrochloride, thus achieving resource utilization.

[0135] Example 5: A pretreatment method for detoxifying wastewater containing 2-methylpyridine, triethylamine, and organic solvents, the main steps of which are as follows:

[0136] 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I;

[0137] Wastewater I originates from the production process of amprolium hydrochloride, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, containing approximately 20 kg / m³ of 2-methylpyridine. 3 Triethylamine 2.0 kg / m 3 It also contains organic solvents such as methanol, isopropanol, toluene, and xylene. The pH is 3.1, and the total organic carbon content is 49,600 mg / L. It is a brown liquid with a strong odor and has very high biotoxicity to nitrifying bacteria in sewage treatment plants (the lethality rate is as high as 80% when diluted 1,000 times).

[0138] 15m 3 Wastewater I, containing 2-methylpyridine, triethylamine, and organic solvents, was fed into an alkali-adjusting and separating reactor. Approximately 310 liters of a 30% sodium hydroxide aqueous solution were added for alkali adjustment and separation, yielding approximately 15.3 m³. 3 After alkali treatment and release, the pH value of the high-alkali wastewater II was 12.13.

[0139] Therefore, the batch corresponding to this case contains approximately 300 kg of 2-methylpyridine.

[0140] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3 The flow rate is fed into a 1250mm diameter high gravity distillation and detoxification tower for distillation and detoxification. The temperature of the reboiler in the high gravity distillation and detoxification tower is controlled at 102-103℃, the temperature of the top of the tower is controlled at 65-68℃, and the reflux ratio is 1:3 (v / v).

[0141] The top of the tower is about 1.5m high. 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, yields approximately 13.8 m³ at the bottom of the column. 3 High-quality wastewater (III grade) after detoxification and purification;

[0142] The organic phase I obtained by distillation contained 31.11% water, 199.06 g / L of 2-methylpyridine, 18.87 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0143] The high-toxicity wastewater III, after detoxification, contains 5180 mg / L of total organic carbon, 26 mg / L of 2-methylpyridine, and a pH of 10.94. When diluted 2 times, it has a 50% lethality rate for nitrifying bacteria in the wastewater treatment plant (the toxicity is reduced by nearly 1000 times compared to high-toxicity wastewater I). Therefore, it can enter the biological treatment tank of the wastewater treatment plant and undergo anaerobic / aerobic biological treatment to ensure that the wastewater meets the discharge standards.

[0144] 3) The approximately 1.5m obtained from the extraction in step 2) 3 Organic phase I, containing 2-methylpyridine, triethylamine, and organic solvent, is added to an acidification reactor, and approximately 220 liters of 98% concentrated sulfuric acid is added to form a salt, resulting in an acid-adjusted and salted organic phase II (organic phase II containing 2-methylpyridine, triethylamine, and organic solvent after salt formation).

[0145] Organic phase II, after acidification and salt formation, has a pH of 2.23.

[0146] 4) Transfer the acidified and salted organic phase II obtained in step 3) into a distillation kettle and distill it (distillation temperature is 60-105℃) to obtain 850 liters of methanol, isopropanol and toluene and xylene mixed organic solvent (of which methanol content is 70.6%, isopropanol 16.1%, toluene and xylene 3.7%, water 10.43%, and the remainder is other impurities).

[0147] The resulting bottom liquid I was an aqueous solution of approximately 850 liters containing 2-methylpyridine sulfate and triethylamine sulfate.

[0148] 5) Transfer approximately 850 liters of bottom liquid I obtained in step 4) to the alkali-free liquid treatment vessel, and add approximately 500 liters of 30% sodium hydroxide aqueous solution for freeing (pH value 12.23). Since this batch of high-temperature wastewater I contains approximately 300 kg of 2-methylpyridine, 400 liters of water are added before azeotropic distillation. The vessel temperature is raised to 82°C to start collecting the distillate. The temperature is continued to rise and the distillate is collected until the vessel temperature rises to 98°C. Then, another 400 liters of water are added, and azeotropic distillation is continued to collect the distillate until the vessel temperature rises again to 98-100°C and the collection of the distillate is stopped.

[0149] A mixture of approximately 1600 liters of 2-methylpyridine, triethylamine, and water was obtained; the bottom liquid II (azeotropic distillation bottom liquid) contained 0.026 g / L of 2-methylpyridine and had a pH of 12.06; the bottom liquid II could be returned to step 1) and combined with the high-quality wastewater I for recycling.

[0150] 6) Add 900 liters of the mixed organic phase II of 2-methylpyridine, triethylamine and water obtained from the azeotropic distillation in step 5) and 700 liters of fresh xylene to the mixture obtained from the second extraction in step 6) of Example 4. Perform a first extraction, allow the layers to stand, and the first extraction yields 1900 liters of mixed organic phase I of 2-methylpyridine, triethylamine and xylene. Perform a second extraction on the raffinate, add 1600 liters of fresh xylene, allow the layers to stand, and the second extraction yields 1600 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene.

[0151] The 1600 liters of mixed organic phase II of 2-methylpyridine, triethylamine and xylene obtained from the second extraction is used as a substitute for the xylene used in the first extraction in the next batch, thereby reducing the energy consumption of xylene distillation.

[0152] The secondary raffinate (with a 2-methylpyridine concentration of 3.44 g / L and a pH of 10.83) can be returned to step 1) and combined with high-quality wastewater I for further treatment.

[0153] 7) The 1900 liters of mixed organic phase I of 2-methylpyridine, triethylamine, and xylene obtained from the first extraction in step 6) is added to a distillation vessel to remove low-boiling substances:

[0154] Atmospheric distillation was used, with the bottom temperature controlled to not exceed 132℃. The fore-fraction was collected starting at a top temperature of 60℃ and stopping at a top temperature of 88℃, yielding 210 liters of fore-fraction (containing 25.77% methanol, 31.22% isopropanol, 14.28% triethylamine, 14.1% toluene and xylene, 0.28% 2-methylpyridine, with the remainder being impurities and water).

[0155] The bottom liquid III is a mixture of 2-methylpyridine and xylene, wherein the content of 2-methylpyridine is 17.65%, triethylamine is 0.021%, moisture is ≤0.03%, and the balance is mainly xylene. This meets the quality requirements for raw materials used in the condensation of aminopropyl hydrochloride, thus achieving resource utilization.

[0156] Experiment 1: The bottom liquid III obtained in Example 1 was used as the raw material for the condensation of amprolium hydrochloride to prepare amprolium hydrochloride. The weight ratio of 2-methylpyridine to the key intermediate (cyclic pyrimidine) of amprolium hydrochloride was controlled to be 1.1 to 1.3:1.

[0157] Specifically as follows:

[0158] 1200 liters of bottom liquid III (containing 18.14% 2-methylpyridine, 0.042% triethylamine, ≤0.05% water, and the remainder being mainly xylene) was added to the condensation reactor of amprolium hydrochloride, followed by 170 kg of the key intermediate of amprolium hydrochloride (cyclic pyrimidine compound). Hydrogen chloride gas was introduced until the pH reached 1.5, and then the temperature was raised (reacted at 135-138℃ for 20 hours) to prepare amprolium hydrochloride, yielding the reaction product.

[0159] The product obtained from the reaction was analyzed by liquid chromatography, and the content of amprolium hydrochloride was 99.23%, the highest single impurity was 0.16%, and the total impurities were 0.67%, which meets the quality requirements of amprolium hydrochloride in USP43 and CP2020.

[0160] Similarly, when the bottom liquid III obtained in Examples 1 to 5 was operated according to the method described in Experiment 1 above, the products obtained from the reaction all met the quality requirements of USP43 and CP2020 versions of aminopropionate hydrochloride.

[0161] Comparative Example 1: Based on Example 1, step 5) of water replenishment is omitted, while other steps remain the same as in Example 1, as detailed below:

[0162] Steps 1) to 4) are the same as steps 1) to 4) in Example 1.

[0163] 5) Transfer the 800 liters of bottom liquid I obtained in step 4) to the alkali-adjusting and freeing vessel, add approximately 375 liters of 30% sodium hydroxide aqueous solution for freeing, and then directly heat for azeotropic distillation. Begin collecting the distillate when the vessel temperature reaches 82°C, and continue heating until the vessel temperature reaches 98°C, at which point collection stops. A total of approximately 900 liters of a mixture of 2-methylpyridine, triethylamine, and water is obtained. Bottom liquid II (azeotropic distillation bottom liquid) contains 23.78 g / L of 2-methylpyridine and has a pH of 11.78. Bottom liquid II can be returned to step 1) and combined with high-quality wastewater I for recycling.

[0164] Because no water was added before and during the azeotropic distillation in step 5) of Comparative Example 1, 2-methylpyridine in the vessel could not be completely distilled out, resulting in an excessively high residual level of 2-methylpyridine in the bottom liquid (bottom liquid II). Therefore, effective recovery of 2-methylpyridine could not be achieved.

[0165] Comparative Example 2: Based on Example 1, the water added in step 5) was replenished all at once before azeotropic distillation, and the rest was the same as in Example 1, as follows:

[0166] Steps 1) to 4) are the same as steps 1) to 4) in Example 1.

[0167] 5) Transfer the 800 liters of bottom liquid I obtained in step 4) to the alkali-free mixing vessel, add approximately 375 liters of 30% liquid alkali for separation, and add 600 liters of water at once. Raise the vessel temperature to 82°C and begin collecting the distillate. Continue raising the temperature and collecting the distillate until the vessel temperature reaches 98°C, at which point collection is stopped. A total of approximately 1200 liters of a mixture of 2-methylpyridine, triethylamine, and water is obtained. Bottom liquid II (azeotropic distillation bottom liquid) contains 18.43 g / L of 2-methylpyridine and has a pH of 12.13. Bottom liquid II can be returned to step 1) and combined with high-quality wastewater I for recycling.

[0168] In Comparative Example 2, water was added all at once before azeotropic distillation in step 5), but 2-methylpyridine in the vessel could not be completely distilled out, resulting in an excessively high residual amount of 2-methylpyridine in the bottom liquid, thus failing to achieve effective recovery of 2-methylpyridine.

[0169] Comparative Example 3: Based on Example 1, the distillation and purification step in step 7) is omitted. The mixed organic phase I of 2-methylpyridine, triethylamine, and xylene obtained from the first extraction in step 6) is directly used as the raw material for aminopropyl hydrochloride. Other steps are the same as in Example 1, as detailed below:

[0170] Steps 1) to 6) are the same as steps 1) to 6) in Example 1.

[0171] As described in Example 1, in the mixed organic phase I of 2-methylpyridine, triethylamine and xylene obtained from the first extraction in step 6), 2-methylpyridine accounts for 15.84%, triethylamine 1.58%, water 0.87%, and the remainder is xylene; this clearly does not meet the quality requirements of the raw materials used for the condensation of aminopropyl hydrochloride.

[0172] 7) The 1420 L mixed organic phase I of 2-methylpyridine, triethylamine and xylene obtained from the first extraction in step 6) is added to the amprolium hydrochloride condensation reactor, and then 170 kg of the key intermediate of amprolium hydrochloride (cyclic pyrimidine compound) is added. Hydrogen chloride gas is introduced until the pH reaches 1.5, and then the temperature is raised (reacted at 135-138℃ for 20 hours) to prepare amprolium hydrochloride and obtain the reaction product.

[0173] 8) The product obtained from step 7) was detected by liquid chromatography and showed that there were significantly more impurity peaks, with the impurity peak content reaching more than 3%, which did not meet the quality requirements of amprolium hydrochloride.

[0174] As can be seen from Comparative Example 3, by omitting the distillation and purification step 7) of the present invention and directly using the mixed organic phase I of 2-methylpyridine, triethylamine and xylene obtained from the first extraction in step 6) as the raw material for amprolium hydrochloride, it is impossible to produce a qualified amprolium hydrochloride product.

[0175] Comparative Example 4: Based on Example 1, the alkali adjustment and release step in step 1) is omitted, and step 2) is performed directly. Everything else is the same as in Example 1, as follows:

[0176] 1) Place 15m 3 High-grade wastewater I containing 2-methylpyridine, triethylamine, and organic solvents (same as the high-grade wastewater I used in Example 1) was treated at a rate of 1 m 3 The solution was fed into a 1250mm diameter high-gravity distillation and detoxification tower at a flow rate of / h for extraction and detoxification. The distillation parameters were the same as in Example 1; 1.2m³ was obtained. 3 Organic phase I containing 2-methylpyridine, triethylamine, and an organic solvent, and 13.8 m 3 High-quality wastewater II after detoxification and purification;

[0177] The organic phase I obtained by distillation contained 39.16% water, 1.26 g / L of 2-methylpyridine, 0.47 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0178] The high-toxicity wastewater II after extraction and detoxification contained 12800 mg / L total organic carbon, 16.18 g / L 2-methylpyridine, and a pH of 3.36. A 1000-fold dilution resulted in an 80% lethality rate for nitrifying bacteria in the wastewater treatment plant (toxicity was not reduced).

[0179] As can be seen from Comparative Example 4, the alkali-free process in step 1) cannot be eliminated.

[0180] Comparative Example 5-1: Based on Example 1, the amount of free alkali in step 1) is reduced, and the pH is controlled at 10. Everything else remains the same as in Example 1, as detailed below:

[0181] 1) High-quality wastewater I is the same as the high-quality wastewater I used in Example 1;

[0182] 15m 3 Wastewater I, containing 2-methylpyridine, triethylamine, and organic solvents, was fed into an alkali-adjusting and separating reactor. Approximately 180 liters of a 30% sodium hydroxide aqueous solution was added for alkali adjustment and separation, yielding approximately 15.2 m³. 3 After alkali treatment and release, the pH value of the high-alkali wastewater II is 10.02.

[0183] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3 The solution was fed into a 1250mm diameter high-gravity distillation and detoxification tower at a flow rate of / h for extraction and detoxification. The distillation parameters were the same as in Example 1.

[0184] The top of the tower is about 1.5m high. 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, yields approximately 13.6 m at the bottom of the column. 3 High-quality wastewater (III grade) after detoxification and purification;

[0185] The organic phase I obtained by distillation contained 33.52% water, 121.53 g / L of 2-methylpyridine, 14.23 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0186] The high-quality wastewater III after detoxification contained 6600 mg / L of total organic carbon, 3.02 g / L of 2-methylpyridine, and a pH of 10.26. When diluted 100 times, it had a 50% lethality rate on nitrifying bacteria in the wastewater treatment plant and could not enter the biological treatment tank of the wastewater treatment plant.

[0187] As can be seen from Comparative Example 5-1, reducing the amount of free alkali in step 1) (lowering the pH from 12 to 10.02) does not achieve the effect of the present invention.

[0188] Comparative Example 5-2: Based on Example 1, the free alkali in step 1) is added to control the pH at 13.5. Everything else is the same as in Example 1, as detailed below:

[0189] 1) High-quality wastewater I is the same as the high-quality wastewater I used in Example 1;

[0190] 15m 3 Wastewater I, containing 2-methylpyridine, triethylamine, and organic solvents, was fed into an alkali-adjusting and separating reactor. Approximately 280 liters of a 30% sodium hydroxide aqueous solution was added for alkali adjustment and separation, yielding approximately 15.3 m³. 3 After alkali treatment and release, the pH value of wastewater II is 13.5.

[0191] 2) The high-alkali wastewater II obtained in step 1) after alkali removal is disposed of at a rate of 1m 3 The solution was fed into a 1250mm diameter high-gravity distillation and detoxification tower at a flow rate of / h for extraction and detoxification. The distillation parameters were the same as in Example 1.

[0192] The top of the tower is approximately 1.5 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, yields approximately 13.8 m³ at the bottom of the column. 3 High-quality wastewater (III grade) after detoxification and purification;

[0193] The organic phase I obtained by distillation contained 32.42% water, 148.71 g / L of 2-methylpyridine, 14.31 g / L of triethylamine, and the remainder consisted of organic solvents such as methanol, isopropanol, and xylene.

[0194] The high-grade wastewater III after detoxification contained 6510 mg / L total organic carbon, 8 mg / L 2-methylpyridine, and a pH of 12.98. A 2-fold dilution resulted in a 30% lethality rate for nitrifying bacteria in the wastewater treatment plant.

[0195] As can be seen from Comparative Example 5-2, increasing the amount of free alkali in step 1) (raising the pH from 12 to 13.5) leads to an increase in the amount of alkali used (slightly increasing the cost), but the treatment effect is not further improved; therefore, it is not recommended.

[0196] Comparative Example 6: Based on Example 1, the acid adjustment operation in step 3) is omitted, while everything else remains the same as in Example 1, as detailed below:

[0197] 1)~2) Same as steps 1)~2) of Example 1.

[0198] 3) The approximately 1.5m obtained from the extraction in step 2) 3 Organic phase I, containing 2-methylpyridine, triethylamine, and an organic solvent, was directly transferred to a distillation vessel for rectification. The distillation temperature was 60–105 °C. The 2-methylpyridine content in the mixed organic solvent obtained from the rectification was as high as 5.43%, thus resulting in a loss of 2-methylpyridine compared to Example 1.

[0199] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A pretreatment method for detoxifying wastewater containing 2-methylpyridine, triethylamine, and organic solvents, characterized in that... Includes the following steps: 1) High-quality wastewater containing 2-methylpyridine, triethylamine, and organic solvents is designated as High-quality wastewater I; High-quality wastewater I was put into an alkalinity adjustment and release vessel, and liquid alkali was added for alkalinity adjustment and release to obtain high-quality wastewater II with a pH of 11.5~13.5 after alkalinity adjustment and release. The organic solvents include methanol, isopropanol, toluene, and xylene; 2) The high-quality wastewater II obtained in step 1) after alkali removal is fed into a high-gravity distillation and detoxification tower for distillation and detoxification to obtain organic phase I. The bottom of the tower is the high-quality wastewater III after detoxification. The distillation and extraction process involves controlling the bottom temperature of the high-gravity distillation and extraction detoxification tower at 102~103℃, the top temperature at 65~68℃, and the reflux ratio at 1:3~5. The high-quality wastewater III after extraction and detoxification is wastewater that can be treated using anaerobic / aerobic biochemical methods.

2. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 1, characterized in that... It also includes the following steps: 3) The organic phase I obtained from the extraction in step 2) is put into the acidification kettle, and acid is added to form a salt, so as to obtain the organic phase II after acidification and salt formation with a pH of 2~3; 4) Transfer the organic phase II obtained in step 3) after acidification and salt formation into a distillation vessel, and obtain an organic solvent by distillation. The resulting bottom liquid I is an aqueous solution containing 2-methylpyridinium salt and triethylamine salt. 5) Transfer the bottom liquid I obtained in step 4) to the alkali-free liquid vessel, add liquid alkali for freeing, until the pH of the system is 12±0.5, then heat up for azeotropic distillation to obtain a mixture of 2-methylpyridine, triethylamine and water. The bottom liquid II obtained is returned to step 1) and combined with high-quality wastewater I for recycling treatment. 6) Add xylene to the mixture of 2-methylpyridine, triethylamine and water obtained by azeotropic distillation in step 5) for extraction to obtain a mixed organic phase of 2-methylpyridine, triethylamine and xylene. The raffinate is returned to step 1) and combined with high-quality wastewater I for recycling treatment. 7) The mixed organic phase of 2-methylpyridine, triethylamine and xylene obtained from the extraction in step 6) is added to a distillation vessel to remove low-boiling substances, thereby removing the fore-fraction. The resulting bottom liquid III is a mixture of 2-methylpyridine and xylene.

3. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 1 or 2, characterized in that: The liquid alkali mentioned in step 1) is an aqueous solution of sodium hydroxide with a mass concentration of 28-32%.

4. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 3, characterized in that: The acid mentioned in step 3) is hydrochloric acid, sulfuric acid, or nitric acid.

5. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 4, characterized in that, Step 5) Azeotropic distillation: Depending on the content of 2-methylpyridine in the high-concentration wastewater I from Step 1) of this batch, select the following methods for operation: Method 1: When the content of 2-methylpyridine is <150Kg / batch, start collecting the distillate when the temperature of the kettle reaches 80~90℃, continue to raise the temperature to collect the distillate until the temperature of the kettle reaches 98~100℃ and then stop collecting the distillate. Method 2: When the batch contains 150-200 kg of 2-methylpyridine, first add 400±20 liters of water, raise the temperature of the vessel to 80-90℃ and start collecting the distillate. Continue to raise the temperature and collect the distillate until the temperature of the vessel reaches 98-100℃ and then stop collecting the distillate. Method 3: When the batch contains 200-250 kg of 2-methylpyridine, first add 400±20 liters of water, raise the temperature of the distillation vessel to 80-90℃ and start collecting the distillate. Continue to raise the temperature and collect the distillate until the temperature of the distillation vessel rises to 98-100℃. Then add 200±10 liters of water and continue azeotropic distillation to collect the distillate until the temperature of the distillation vessel rises to 98-100℃ again and stop collecting the distillate. Method 4: When the batch contains 250~300Kg / batch of 2-methylpyridine, first add 400±20L of water, raise the temperature of the distillation vessel to 80~90℃ and start collecting the distillate. Continue to raise the temperature and collect the distillate until the temperature of the distillation vessel rises to 98~100℃, then add 400±20L of water and continue azeotropic distillation to collect the distillate until the temperature of the distillation vessel rises to 98~100℃ again and stop collecting the distillate.

6. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 5, characterized in that: The distillation temperature in step 4) is 60~105℃.

7. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 6, characterized in that: In step 6), during the extraction operation, the volume ratio of the mixture of 2-methylpyridine, triethylamine, and water to xylene is 1:(1±0.1). The extraction is performed twice. The mixed organic phase of 2-methylpyridine, triethylamine, and xylene obtained from the first extraction is fed into the distillation vessel in step 7). The mixed organic phase containing 2-methylpyridine, triethylamine, and xylene obtained from the second extraction can replace the xylene used in the first extraction, thereby achieving recycling.

8. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 7, characterized in that: In step 7), when removing low-boiling substances from the mixed organic phase of 2-methylpyridine, triethylamine, and xylene, atmospheric distillation is used. The bottom temperature is controlled to not exceed 132°C, and the collection of the fore-distillate begins at a top temperature of 60°C and stops at a top temperature of 88°C, thus ending the distillation and purification process.

9. The pretreatment method for detoxifying high-toxicity wastewater containing 2-methylpyridine, triethylamine, and organic solvents according to claim 8, characterized in that: The wastewater containing 2-methylpyridine, triethylamine, and organic solvents originates from the production process of amprolium hydrochloride, including condensation tail gas absorption wastewater, recrystallization tail gas absorption wastewater, and amprolium hydrochloride purification mother liquor recovery wastewater, containing 5~20 kg / m³ of 2-methylpyridine. 3 Triethylamine 0.5~2.0 kg / m 3 pH 2-4, total organic carbon 35000-50000 mg / L.

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