Method and device for extracting butyl glycolate from organic wastewater

Abstract

The present invention relates to a method and device for extracting butyl glycolate from wastewater. After removing phenol from the wastewater produced by producing phenoxycarboxylic acid pesticides, butyl glycolate is obtained after esterification, concentration and desalination with butanol under acidic conditions. Compared with the existing production technology, it does not directly extract low-concentration glycolic acid, but extracts more valuable butyl glycolate, and does not use any solid heterogeneous catalyst. It not only reduces the recovery cost, does not generate new "three wastes", and improves the recovery rate of butyl glycolate, but also avoids the waste of high-value compounds in wastewater, realizes waste into treasure, and meets the needs of green development.

Description

Technical Field

[0001] The invention belongs to the field of pesticide wastewater recycling, and in particular relates to a method for recovering glycolic acid ester from phenoxyacetic acid pesticide wastewater. Background Art

[0002] The synthetic process route of phenoxyacetic acid pesticides is through the condensation process of chloroacetic acid and phenol, in which redundant chloroacetic acid can be hydrolyzed to produce glycolic acid. At present, the domestic manufacturers of phenoxyacetic acid pesticides will produce a large amount of waste water with high COD (mainly glycolic acid produced by the hydrolysis of sodium chloroacetate and unreacted 2,4-dichlorophenol). Processing these waste waters will produce a large amount of high COD solid wastes, which not only greatly increases the three wastes treatment cost, but also pollutes the environment. However, glycolic acid esterification is an important fine chemical intermediate, which is widely used in adhesive, dyeing, textile, daily chemical industry. Therefore, the recovery of glycolic acid in phenoxyacetic acid pesticide wastewater is of great significance for phenoxyacetic acid pesticide enterprises, and can avoid the generation of a large amount of solid wastes, and can recycle valuable glycolic acid or glycolic acid butyl ester, realizing turning waste into treasure.

[0003] There are two main methods for synthesizing glycolic acid esters: one is to generate esters by reacting glycolic acid and alcohol under acid catalysis; the other is to react glycolic acid with halogenated hydrocarbons under alkaline conditions to generate esters, and separate and purify the generated esters by distillation. The disadvantage of the first method is that the conversion rate is low, resulting in low raw material utilization; the disadvantage of the second method is that the halogenated hydrocarbons used are generally more expensive than the corresponding alcohols, and at least an equivalent amount of base is consumed to promote the reaction, generating new solid waste, which makes industrial production very uneconomical.

[0004] Patents CN104910017A and CN104744254A disclose the use of acidic cation exchange resins instead of other acids as catalysts to recover glycolic acid esters in phenoxyacetic acid pesticide wastewater. This method has two disadvantages: first, it is necessary to use solvents such as dioxane, benzene, toluene, xylene, trimethylbenzene, dichloromethane, chloroform, ethyl acetate, acetonitrile or N,N-dimethylformamide to dissolve the concentrated mother liquor of the wastewater containing glycolic acid; second, the activity of the acidic cation exchange resin used is gradually reduced during long-term use, and eventually becomes solid waste.

[0005] Patent CN104744238A discloses that the wastewater produced by phenoxyacetic acid pesticides is concentrated and desalted under the condition of reduced pressure heating to obtain a wastewater concentrated mother liquor containing glycolic acid; the wastewater concentrated mother liquor is dissolved in a solvent, a desiccant is added and dried, and then cooled and crystallized after centrifugation to obtain glycolic acid, and finally high-purity glycolic acid is obtained by recrystallization. This method has two disadvantages: first, it is necessary to use solvents such as methanol, ethanol, n-butanol, isopropanol n-pentanol, tert-butanol, tert-amyl alcohol, toluene, xylene, trimethylbenzene, chlorobenzene, dichloromethane, chloroform, ethylene dichloride, acetone, ethyl acetate, butyl acetate, methyl formate, ethyl formate, butyl formate, petroleum ether or n-hexane; second, the wastewater concentrated mother liquor is dehydrated using a desiccant such as anhydrous magnesium sulfate, anhydrous sodium sulfate, anhydrous calcium chloride, calcium oxide, anhydrous calcium sulfate, phosphorus pentoxide or color-changing silica gel, and this method cannot achieve continuous industrial production.

[0006] Patent CN103193622A discloses a method for recovering glycolic acid in phenoxyacetic acid pesticide wastewater. According to this method, most of the inorganic salts, phenol and phenoxyacetic acid organic impurities can be removed. However, due to the strong water solubility of such phenol and phenoxyacetic acid organic impurities, the amount of phenol and phenoxyacetic acid organic impurities contained in the glycolic acid with a content of more than 70wt% obtained by the extraction and concentration method in the patent cannot be ignored; when acetone or acetic acid is used to extract and prepare glycolic acid crystals, the solubility of phenol and phenoxyacetic acid organic impurities in these two organic solvents is good, and most of them will enter the organic phase, and it is not easy to remove when the solvent is concentrated, so that they are more present in the glycolic acid crystals. Phenol and phenoxyacetic acid organic impurities are more present in the recycled 70wt% or glycolic acid crystals, which will seriously affect their quality and scope of use. Summary of the invention

[0007] The purpose of the invention is to overcome the defects of the above-mentioned prior art and provide a method for recovering high-quality butyl glycolate from phenoxyacetic acid pesticide wastewater with low recovery cost and high recovery efficiency, so as to realize industrialized continuous and stable production.

[0008] A device for extracting butyl glycolate from wastewater, wherein a glycolate solution storage tank, an acid storage tank, a n-butanol storage tank, and a liquid alkali storage tank are respectively connected to an esterification kettle;

[0009] The liquid phase pipeline of the esterification kettle is connected to the filter press via the esterification kettle transfer pump;

[0010] The filter press is connected with the butyl glycolate transfer tank and the dilute brine transfer tank in sequence through the filter press material transfer pump.

[0011] The esterification kettle is connected to the esterification condenser through a gas phase pipeline; the esterification condenser is connected to the esterification oil-water separator, and the esterification oil-water separator is connected to the oil phase receiving tank and the water phase receiving tank respectively;

[0012] The water phase receiving tank is connected to the water phase transfer pump, and then connected to the material inlet of the filter press; the oil phase receiving tank is connected to the oil phase transfer pump, and then connected to the n-butanol storage tank.

[0013] The dilute brine transfer tank is connected to the dilute n-butanol intermediate storage transfer tank via a dilute n-butanol transfer pump;

[0014] The dilute n-butanol intermediate storage transfer tank is connected to the distillation kettle oil-water separator via the dilute n-butanol distillation kettle condenser;

[0015] The distillation kettle oil-water separator is respectively connected to the dilute n-butanol water phase receiving tank and the dilute n-butanol oil phase receiving tank.

[0016] The receiving tank for the diluted n-butanol aqueous phase is connected to the filter press;

[0017] The dilute n-butanol oil phase receiving tank is connected to the n-butanol storage tank via the distillation kettle oil phase transfer pump.

[0018] A method for extracting butyl glycolate from organic wastewater comprises the following steps:

[0019] (1) Hydroxyacetic acid solution and n-butanol are pumped into an esterification kettle for heating and reflux reaction;

[0020] (2) Adding a catalyst to react during the temperature rise reflux reaction;

[0021] (3) After the reaction is completed, the liquid phase is cooled to room temperature and a base is added to adjust the pH;

[0022] (4) The reaction solution in step (3) is filtered to obtain an esterified solution, which is butyl glycolate.

[0023] The glycolic acid solution is 2,4-D wastewater containing 35-50% by mass of glycolic acid, 0.5-5% by mass of glycolic acid polymer, 1-20% by mass of sodium chloride and 0.1-2% by mass of other organic impurities.

[0024] The volume ratio of the n-butanol feed amount to the glycolic acid feed amount is controlled between 1.5 and 1.9; the acid catalyst is one or more of 30% hydrochloric acid, ferric chloride, aluminum chloride, zinc chloride, and tin chloride aqueous solutions, and the added amount of the catalyst is 0.1-10% of the mass of the glycolic acid solution.

[0025] During the esterification reaction, the pH value is controlled at 0.5-1.5; the temperature of the reflux reaction is 90-135° C.; and the reflux insulation time is 1-2 hours.

[0026] The gas phase obtained during the temperature reflux reaction is condensed and then separated into oil and water, the oil phase n-butanol solvent is refluxed, and the water phase enters the filter press; until there is no water phase in the obtained gas phase, the heat preservation reaction is carried out for 1-2 hours.

[0027] After the reaction is completed, alkali is added to the esterification kettle to adjust the pH value to 7.5-10.5; the esterified liquid obtained after filter pressing is butyl glycolate, and the solid after filter pressing is separated by an oil-water separator. The water phase is dissolved in the sodium chloride in the filter press and then pressed into a dilute n-butanol storage tank with nitrogen. The n-butanol is recovered by distillation and reused as a raw material. At the same time, the water phase is recovered and separated by a filter press to obtain sodium chloride. The separated water phase is pumped into a dilute brine transfer tank for continued use.

[0028] The invention has the following advantages after implementation:

[0029] (1) Instead of directly extracting glycolic acid, it is converted into an ester. Glycolic acid decomposes at 100°C and is miscible with water. Therefore, glycolic acid cannot be purified or concentrated by evaporation, thereby avoiding excessive energy consumption for water evaporation. In addition, glycolic acid is quickly converted into butyl glycolate under a homogeneous catalyst system, thereby achieving efficient separation of the impurity sodium chloride in the material and the aqueous phase material, and recovering a high-quality butyl glycolate product.

[0030] (2) Butyl glycolate is separated from wastewater with high purity, which solves the problem of treating wastewater from phenoxyacetic acid products, complies with the requirements of national industrial policies, and realizes the resource utilization of organic matter in wastewater, achieves good economic benefits, reduces environmental protection treatment costs, and meets the requirements of clean production.

[0031] (3) This process does not require the use of a large amount of organically dissolved hydroxyacetic acid-containing wastewater to concentrate the mother liquor, thus avoiding secondary pollution.

[0032] (4) This process does not require drying to remove moisture and does not generate new waste, so it is a clean production process.

[0033] (5) Hydrochloric acid is used to control the pH value. It can also be used as the acid for the entire reaction system. No new solid superacid or superbase is introduced as a catalyst. This ensures that the finishing system is a chloride ion system. It is best to discharge it out of the system in the form of sodium chloride, which is suitable for industrial large-scale production.

[0034] (6) The 50-70% water brought into the hydroxyacetic acid solution raw material is evaporated and separated into oil and water, and then applied to the filter press to dissolve sodium chloride. Finally, the sodium chloride is evaporated and extracted through an environmental protection device and then reused in the form of condensed water for the synthesis of phenoxyacetic acid pesticides, thus recycling the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1This is a schematic diagram of a device for extracting butyl glycolate from organic wastewater. Among them, 1. Hydroxyacetic acid solution storage tank, 2. 30% hydrochloric acid storage tank, 3. n-butanol storage tank, 4. 32% liquid alkali storage tank, 5. Hydroxyacetic acid solution transfer pump, 6. Hydrochloric acid transfer pump, 7. n-butanol transfer pump, 8. Liquid alkali transfer pump, 9. Esterification kettle, 10. Esterification kettle transfer pump, 11. Filter press, 12. Esterification condenser, 13. Esterification oil-water separator, 14. Water phase receiving tank, 15. Oil phase receiving tank, 16. Water phase transfer pump, 17. Oil phase transfer pump , 18. Butyl glycolate transfer tank, 19. Dilute brine transfer tank, 20 filter press material transfer pump, 21. Butyl glycolate transfer pump, 22. Dilute n-butanol transfer pump, 23. Dilute n-butanol distillation kettle, 24. n-butanol distillation kettle transfer pump, 25. Dilute n-butanol distillation kettle condenser, 26. Distillation kettle oil-water separator, 27. Dilute n-butanol water phase receiving tank, 28 Dilute n-butanol oil phase receiving tank, 29. Distillation kettle water phase transfer pump, 30 distillation kettle oil phase transfer pump. DETAILED DESCRIPTION

[0036] Example 1

[0037] A device for extracting butyl glycolate from wastewater, wherein a glycolate solution storage tank 1, an acid storage tank 2, an n-butanol storage tank 3, and a liquid alkali storage tank 4 are respectively connected to an esterification kettle 9; and transfer pumps are provided at the connection points of the glycolate solution storage tank 1, the acid storage tank 2, the n-butanol storage tank 3, the liquid alkali storage tank 4 and the esterification kettle 9, and the specific embodiments are a glycolate solution transfer pump 5, a hydrochloric acid transfer pump 6, an n-butanol transfer pump 7, and a liquid alkali transfer pump 8.

[0038] The liquid phase pipeline of the esterification kettle 9 is connected to the filter press 11 via the esterification kettle transfer pump 10;

[0039] The filter press 11 is connected to the butyl glycolate transfer tank 18 and the dilute brine transfer tank 19 in sequence via the filter press material transfer pump 20 .

[0040] The esterification kettle 9 is connected to the esterification condenser 12 via a gas phase pipeline; the esterification condenser 12 is connected to the esterification oil-water separator 13, and the esterification oil-water separator 13 is connected to the oil phase receiving tank 15 and the water phase receiving tank 14 respectively;

[0041] The water phase receiving tank 14 is connected to the water phase transfer pump 16, and then connected to the filter press 11 and the material inlet of the esterification kettle 9 respectively; the oil phase receiving tank 15 is connected to the oil phase transfer pump 17, and then connected to the n-butanol storage tank 3.

[0042] The dilute brine transfer tank 19 is connected to the dilute n-butanol intermediate storage transfer tank 23 via the dilute n-butanol transfer pump 22;

[0043] The dilute n-butanol intermediate storage and transfer tank 23 is connected to the distillation kettle oil-water separator 26 via the dilute n-butanol distillation kettle condenser 25;

[0044] The distillation kettle oil-water separator 26 is connected to the diluted n-butanol water phase receiving tank 27 and the diluted n-butanol oil phase receiving tank 28 respectively.

[0045] The dilute n-butanol water phase receiving tank 27 is connected to the filter press 11 via the distillation kettle water phase transfer pump 29;

[0046] The dilute n-butanol oil phase receiving tank 28 is connected to the n-butanol storage tank 3 via the distillation kettle oil phase transfer pump 30.

[0047] Example 2 (Lewis acid catalyst: 30% hydrochloric acid, esterification reaction pH 1.23)

[0048] Add 7.8m3 of glycolic acid solution into the tank 3 The glycolic acid aqueous solution is pumped into the esterification kettle, and then the 12.5m3 of the n-butanol storage tank is pumped into the n-butanol transfer pump. 3 n-Butanol is pumped into the esterification kettle, the steam valve of the esterification kettle is opened, the temperature is raised, the esterification oil-water separator is separated, and the n-butanol is refluxed. During the heating and reflux process, the temperature in the kettle reaches 100°C, and 30% hydrochloric acid is added to control the pH value in the kettle to 1.23. When the esterification oil-water separator separates little or no water, n-butanol is evaporated until the kettle temperature is greater than 125°C, and n-butanol reflux is started again. After reflux and heat preservation for 2 hours, the temperature is lowered to 50°C, the pH value is adjusted to 1.22, and the material is discharged into the filter press. The esterification liquid enters the butyl glycolate transfer tank, the esterification water in the water phase receiving tank is added to the esterification kettle, and the pH value is adjusted to 8.05 with liquid alkali, and added to the filter press to dissolve all the sodium chloride. The dissolved sodium chloride solution is pressed into the dilute n-butanol storage tank with nitrogen. The sodium chloride solution in the diluted n-butanol storage tank is pumped into the diluted n-butanol distillation kettle through the diluted n-butanol transfer pump. The distillation temperature is 105°C. When the oil-water separator of the diluted n-butanol distillation kettle separates little or no water, the evaporation stops. The oil phase enters the diluted n-butanol oil phase receiving tank, and the water phase enters the diluted n-butanol water phase receiving tank. The water in the diluted n-butanol water phase receiving tank is continuously used to dissolve the sodium chloride in the filter press, and the n-butanol in the diluted n-butanol oil phase receiving tank is continuously pumped into the n-butanol storage tank. The butyl glycolate content is 99.2%, the water content is 0.03%, the butanol content is 0.5%, the acid value is 0.05mg / g, and the other impurities are 0.06%.

[0049] Example 3 (Lewis acid catalyst: 30% hydrochloric acid, esterification reaction pH 0.62)

[0050] The method and steps are the same as those in Example 2, except that the pH value of the esterification reaction in the autoclave is controlled to be 0.62, so that the butyl glycolate content in the production process is 99.8%, the water content is 0.05%, the butanol content is 0.45%, the acid value is 0.18 mg / g, and other impurities are 0.09%.

[0051] Example 4 (Lewis acid catalyst: 30% hydrochloric acid + ferric chloride aqueous solution (the weight of ferric chloride accounts for 20% of the total weight of 30% hydrochloric acid + ferric chloride aqueous solution), pH value of esterification reaction is 0.82)

[0052] Add 7.8m3 of glycolic acid solution into the tank 3 The glycolic acid aqueous solution is pumped into the esterification kettle, and then the 12.5m3 of the n-butanol storage tank is pumped into the n-butanol transfer pump. 3 n-Butanol is pumped into the esterification kettle, the steam valve of the esterification kettle is opened, the temperature is raised, the esterification oil-water separator is separated, and the n-butanol is refluxed. During the heating and reflux process, the temperature in the kettle reaches 100°C, and 30% hydrochloric acid + ferric chloride aqueous solution (the weight of ferric chloride accounts for 20% of the total weight of 30% hydrochloric acid + ferric chloride aqueous solution) is added to control the pH value in the kettle to 1.16. When the esterification oil-water separator separates little or no water, n-butanol is continued to evaporate until the kettle temperature is greater than 125°C, and n-butanol reflux is started again. After reflux and heat preservation for 2 hours, the temperature is lowered to 50°C, the pH value is adjusted to 1.28, and the material is discharged into the filter press. The esterification liquid enters the butyl glycolate transfer tank, the esterification water in the water phase receiving tank is added to the esterification kettle, and the pH value is adjusted to 8.05 with liquid alkali, and added to the filter press to dissolve all the sodium chloride. The dissolved sodium chloride solution is pressed into the dilute n-butanol storage tank with nitrogen. The sodium chloride solution in the diluted n-butanol storage tank is pumped into the diluted n-butanol distillation kettle through the diluted n-butanol transfer pump. The distillation temperature is 105°C. When the oil-water separator of the diluted n-butanol distillation kettle separates little or no water, the evaporation stops. The oil phase enters the diluted n-butanol oil phase receiving tank, and the water phase enters the diluted n-butanol water phase receiving tank. The water in the diluted n-butanol water phase receiving tank is continuously used to dissolve the sodium chloride in the filter press, and the n-butanol in the diluted n-butanol oil phase receiving tank is continuously pumped into the n-butanol storage tank. The content of butyl glycolate is 99.7% butyl ester, 0.04% water, 0.19% butanol, 0.09mg / g acid value, and 0.08% other impurities.

[0053] Example 5 (Lewis acid catalyst: 30% hydrochloric acid + ferric chloride aqueous solution (the weight of ferric chloride accounts for 90% of the total weight of 30% hydrochloric acid + ferric chloride aqueous solution), pH value of esterification reaction 0.82)

[0054] Add 7.8m3 of glycolic acid solution into the tank 3 The glycolic acid aqueous solution is pumped into the esterification kettle, and then the 12.5m3 of the n-butanol storage tank is pumped into the n-butanol transfer pump. 3n-Butanol is pumped into the esterification kettle, the steam valve of the esterification kettle is opened, the temperature is raised, the esterification oil-water separator is separated, and the n-butanol is refluxed. During the heating and reflux process, the temperature in the kettle reaches 100°C, and 30% hydrochloric acid + ferric chloride aqueous solution (the weight of ferric chloride accounts for 20% of the total weight of 30% hydrochloric acid + ferric chloride aqueous solution) is added to control the pH value in the kettle to 1.46. When the esterification oil-water separator separates little or no water, n-butanol is continued to evaporate until the kettle temperature is greater than 125°C, and n-butanol reflux is started again. After reflux and heat preservation for 2 hours, the temperature is lowered to 50°C, and the pH value is adjusted to 1.39 to discharge the material, and the discharge enters the filter press. The esterification liquid enters the butyl glycolate transfer tank, and the esterification water in the water phase receiving tank is added to the esterification kettle, and the pH value is adjusted to 8.05 with liquid alkali, and added to the filter press to dissolve all the sodium chloride. The dissolved sodium chloride solution is pressed into the dilute n-butanol storage tank with nitrogen. The sodium chloride solution in the diluted n-butanol storage tank is pumped into the diluted n-butanol distillation kettle through the diluted n-butanol transfer pump. The distillation temperature is 105°C. When the oil-water separator of the diluted n-butanol distillation kettle separates little or no water, the evaporation stops. The oil phase enters the diluted n-butanol oil phase receiving tank, and the water phase enters the diluted n-butanol water phase receiving tank. The water in the diluted n-butanol water phase receiving tank is continuously used to dissolve the sodium chloride in the filter press, and the n-butanol in the diluted n-butanol oil phase receiving tank is continuously pumped into the n-butanol storage tank. The content of butyl glycolate is 96.2% butyl ester, 0.12% water, 0.39% butanol, 0.65mg / g acid value, and 0.12% other impurities.

[0055] Example 6

[0056] The method and steps are the same as those in Example 4, except that the reflux holding time is controlled for 1 hour. Then, the butyl glycolate content in the production process is 99.1%, the water content is 0.36%, the butanol content is 0.66%, the acid value is 0.16 mg / g, and other impurities are 0.08%.

[0057] Example 7

[0058] The method and steps are the same as those in Example 4, except that the volume ratio of the n-butanol feed amount to the hydroxyacetic acid feed amount is controlled to be 2, that is, the n-butanol feed amount is 12 m 3 , the feed rate of glycolic acid is 6 m 3 , the butyl glycolate content in the production process is 98.2% butyl acetate, 0.82% water, 1.23% butanol, 0.56 mg / g acid value, and 0.98% other impurities.

Claims

1. A method for extracting butyl glycolate from organic wastewater, characterized in that: The steps include: (1) The hydroxyacetic acid solution and n-butanol are introduced into an esterification kettle for a temperature-raising reflux reaction, and the volume ratio of the n-butanol feed amount to the hydroxyacetic acid solution feed amount is controlled between 1.5 and 1.9; (2) adding an acid catalyst to react during the heating and reflux reaction; the acid catalyst is one or more of 30% hydrochloric acid, ferric chloride, aluminum chloride, zinc chloride, and tin chloride aqueous solutions, and the amount of the catalyst added is 0.1-10% of the mass of the glycolic acid solution; the pH value during the esterification reaction is controlled at 0.5-1.5; the temperature of the heating and reflux reaction is 90-135°C; and the reflux insulation time is 1-2 hours; (3) After the reaction is completed, the liquid phase is cooled to room temperature and a base is added to adjust the pH; (4) The reaction liquid in step (3) is filtered to obtain an esterified liquid, namely butyl glycolate. The solid after the filtration is separated by an oil-water separator, and the water phase is used to dissolve the sodium chloride in the filter press and then pressed into a dilute n-butanol storage tank by nitrogen. The n-butanol is recovered by distillation and reused as a raw material. At the same time, the water phase is recovered and separated by a filter press to obtain sodium chloride. The separated water phase is pumped into a dilute brine transfer tank for further use.

2. The method for extracting butyl glycolate from organic wastewater according to claim 1, characterized in that: The glycolic acid solution is 2,4-D wastewater containing 35-50% by mass of glycolic acid, 0.5-5% by mass of glycolic acid polymer, 1-20% by mass of sodium chloride and 0.1-2% by mass of other organic impurities.

3. The method for extracting butyl glycolate from organic wastewater according to claim 1, characterized in that: The gas phase obtained during the temperature reflux reaction is condensed and then separated into oil and water, the obtained oil phase n-butanol solvent is refluxed, and the water phase enters the filter press tank; until there is no water phase in the obtained gas phase, the heat preservation reaction is carried out for 1-2 hours.

4. The method for extracting butyl glycolate from organic wastewater according to claim 3, characterized in that: After the reaction is completed, alkali is added to the esterification kettle to adjust the pH value to 7.5-10.5.

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