Method for preparing 2, 6-dichloro-4-nitrophenol or 2, 4-dichloro-6-nitrophenol with zero discharge of wastewater

Abstract

The invention provides a method for preparing 2, 6-dichloro-4-nitrophenol or 2, 4-dichloro-6-nitrophenol with zero discharge of wastewater, and the method comprises the following steps: dropwise adding an organic solvent solution of 2, 6-dichlorophenol or 2, 4-dichlorophenol into a nitric acid solution, and carrying out heat preservation reaction to obtain a 2, 6-dichlorophenol nitride or a 2, 4-dichlorophenol nitride reaction solution; cooling, carrying out solid-liquid separation on the reaction liquid obtained in the nitration reaction step, washing with water, and drying to obtain a 2, 6-dichloro-4-nitrophenol or 2, 4-dichloro-6-nitrophenol product; the organic layer sleeve obtained through solid-liquid separation is used for preparing a 2, 6-dichlorophenol or 2, 4-dichlorophenol solution, and the water layer sleeve is used for preparing a nitric acid solution; neutralizing water washing liquid with alkali, and performing reduced pressure distillation and recycling for water washing. According to the application, not only is efficient preparation of 2, 6-dichloro-4-nitrophenol or 2, 4-dichloro-6-nitrophenol realized, but also resources are comprehensively utilized, and no wastewater is discharged.

Description

Technical Field

[0001] The present application relates to the technical field of synthesis of chemical intermediates, and in particular to a method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge. Background Art

[0002] 2,6-Dichloro-4-nitrophenol is off-white to light brown crystals, mp127℃, soluble in ether, chloroform and hot ethanol, hardly soluble in water and benzene. It is an organic synthesis intermediate. It is used in pesticides to synthesize the intermediate 2,6-dichloro-4-aminophenol of hexaflumuron, and in anticoccidial drugs to synthesize the intermediate 2,6-dichloro-4-nitroanisole of diclazuril.

[0003] At present, the industrial production of 2,6-dichlorophenol mainly adopts:

[0004] A. Chlorination method (as shown in Formula 1). Dissolve p-nitrophenol in ethanol, then pour it into concentrated hydrochloric acid, cool to below 5°C, add potassium chlorate aqueous solution under constant stirring, control the temperature below 10°C, filter out the crystals and wash with water to obtain a crude product. Recrystallize once with ethanol, then heat and dissolve with a mixed solvent of chloroform and ethanol, decolorize and filter, add petroleum ether to the filtrate, cool, and crystallize to obtain the finished product.

[0005]

[0006] However, this process has the following problems:

[0007] 1) There are many process steps and the operation is complicated.

[0008] 2) Large amount of acidic wastewater.

[0009] 3) Large amounts of solvents are used, making recycling and reuse difficult.

[0010] 4) High energy consumption.

[0011] B. Nitration method (as shown in Formula 2). Dissolve 2,6-dichlorophenol in toluene and prepare concentrated nitric acid into 15-30% dilute nitric acid. Add the toluene solution of 2,6-dichlorophenol dropwise into the nitric acid at 15-30°C and keep warm until the reaction is completed. Centrifuge, wash with water, and dry to obtain 2,6-dichloro-4-nitrophenol.

[0012]

[0013] This process has the following problems:

[0014] 1) Large amount of nitric acid is used.

[0015] 2) After production is completed, toluene processing becomes difficult.

[0016] 2,4-Dichloro-6-nitrophenol can be used as an intermediate in medicine, pesticides, and organic synthesis. For example, it can be used to prepare oxyclozanide, also known as hydroxychlorosalicylic acid anilide, hydroxychlorosalicylic acid anilide, and hydroxyclozanide. It belongs to the halogenated salicylanilide class of compounds and is a salicylanilide anthelmintic. It is currently mainly used to treat and control trematodes in animals such as cattle and sheep. Similar to other salicylanilide anthelmintics, oxyclozanide is an oxidative phosphorylation uncoupler. Its mechanism of action is to inhibit the phosphorylation process of the mitochondria of the insect body, prevent the production of adenosine triphosphate (ATP), i.e., energy, in the insect body, thereby causing the insect body to die due to energy metabolism disorders.

[0017] This product is off-white to yellow crystalline powder with a melting point of 118-120℃.

[0018] At present, the industrial production of 2,4-dichlorophenol mainly adopts the nitration method (as shown in Formula 3). 2,4-dichlorophenol (0.3 mol) is dissolved in methanol, and the methanol solution of 2,4-dichlorophenol is slowly added dropwise to 15% dilute nitric acid (1.0 mol) at below 25°C. After the nitration is completed, the methanol is distilled off, the temperature is lowered, centrifuged, washed with water, and dried to obtain 2,4-dichloro-6-nitrophenol.

[0019]

[0020] However, this process has the following problems:

[0021] 1) Large amount of nitric acid is used.

[0022] 2) There are safety and environmental risks in the methanol distillation process.

[0023] 3) Large amount of acidic wastewater.

[0024] In view of the problem of large amount of waste acid in the above process route, the purpose of the present invention is to provide a method for preparing 2,4-dichloro-6-nitrophenol or 2,6-dichloro-4-nitrophenol which is suitable for production in a green environment with zero wastewater discharge. Summary of the invention

[0025] The present application provides a method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge, so as to solve the above-mentioned problems mentioned in the background technology.

[0026] The present application provides a method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge, comprising the following steps:

[0027] Under stirring, an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol is added dropwise to a nitric acid solution, and after the addition is completed, the reaction is carried out by keeping the temperature to obtain a nitration reaction step of a 2,6-dichlorophenol nitrate reaction solution or a 2,4-dichlorophenol nitrate reaction solution; after the reaction is completed, the temperature is lowered to 5-9° C., and the 2,6-dichlorophenol nitrate reaction solution or the 2,4-dichlorophenol nitrate reaction solution is subjected to solid-liquid separation, water washing and drying to obtain a 2,6-dichloro-4-nitrophenol product or a purification step of a 2,4-dichloro-6-nitrophenol product; the mother liquor obtained by solid-liquid separation is allowed to stand for stratification, and the obtained organic layer is used as an organic solvent jacket to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and the obtained water layer jacket is used to prepare a nitric acid solution; the washing liquid obtained by water washing is neutralized with an alkali, and the water jacket is recovered by reduced pressure distillation for waste water reuse for water washing;

[0028] The organic solvent used is 1,2-dichloroethane or toluene.

[0029] Optionally, the molar ratio of nitric acid to 2,6-dichlorophenol or 2,4-dichlorophenol in the nitric acid solution is 1.0-4.6:1.

[0030] Optionally, the mass concentration of the nitric acid solution is 15-30%.

[0031] Optionally, the mass concentration of the nitric acid solution is 22-25%.

[0032] Optionally, the weight volume ratio of 2,6-dichlorophenol or 2,4-dichlorophenol to the organic solvent is 1:2 g / mL.

[0033] Optionally, the method further includes: preparing an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol: adding 2,6-dichlorophenol or 2,4-dichlorophenol to a reactor containing an organic solvent in a weight-to-volume ratio, heating to 45-55° C. under stirring to dissolve, thereby obtaining an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol.

[0034] Optionally, in the nitration reaction step, the temperature of adding the organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol dropwise into the nitric acid solution is 0-30° C., and the dropping rate is 0.75-1.25 mL / min.

[0035] Optionally, in the nitration reaction step, the reaction temperature is kept at 0-30°C for 1 hour.

[0036] Optionally, the purification step also includes solid-liquid separation of the 2,6-dichlorophenol nitrate reaction solution or the 2,4-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separation mother liquor, washing the solid nitrate with water to pH = 6, and then vacuum drying to constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain a 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol product.

[0037] Optionally, the washing liquid obtained after washing the solid nitrate with water is neutralized to pH=7-8 by adding alkali, and the water is recovered by vacuum distillation and used for subsequent washing of the solid nitrated material;

[0038] The alkali is one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate, calcium carbonate, and sodium carbonate.

[0039] The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge provided in the present application realizes the preparation of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol, and has the following beneficial effects compared with the prior art:

[0040] (1) Dissolving 2,6-dichlorophenol or 2,4-dichlorophenol in an organic solvent to form an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and dropping the organic solvent solution into a nitric acid solution under stirring to perform a nitration reaction, using nitric acid as a nitrating agent, to obtain a 2,6-dichlorophenol nitrate reaction solution or a 2,4-dichlorophenol nitrate reaction solution. The reaction solution is cooled to precipitate a solid, and solid-liquid separation, water washing and drying are performed to obtain a 2,6-dichloro-4-nitrophenol product or a 2,4-dichloro-6-nitrophenol product. The obtained separated mother liquor is allowed to stand for stratification, and the obtained organic layer is used as an organic solvent jacket to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and the obtained water layer jacket is used to prepare a nitric acid solution; after the water washing liquid is neutralized with an alkali, the water jacket is recovered by vacuum distillation for water washing. It avoids the treatment of large-load acidic wastewater, reduces production costs, and achieves comprehensive resource utilization and zero wastewater discharge.

[0041] (2) The 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol product prepared by the technical solution provided in the present application has good quality, with a GC purity of ≥99.7% and a high yield of ≥88.0%.

[0042] (3) The technical solution provided in this application has simple process and convenient operation, and is suitable for large-scale promotion in the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1-Figure 3 The gas chromatogram of 2,4-dichloro-6-nitrophenol provided in Examples 1 to 3 of the present application;

[0045] Figure 4-Figure 8 The gas chromatogram of 2,6-dichloro-4-nitrophenol provided in Examples 4 to 8 of the present application. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0047] The present application provides a method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge, comprising the following steps:

[0048] Under stirring, an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol is added dropwise to a nitric acid solution, and after the addition is completed, the reaction is carried out by keeping the temperature to obtain a nitration reaction step of a 2,6-dichlorophenol nitrate reaction solution or a 2,4-dichlorophenol nitrate reaction solution; after the reaction is completed, the temperature is lowered to 5-9° C., and the 2,6-dichlorophenol nitrate reaction solution or the 2,4-dichlorophenol nitrate reaction solution is subjected to solid-liquid separation, water washing and drying to obtain a 2,6-dichloro-4-nitrophenol product or a 2,4-dichloro-6-nitrophenol product purification step; the mother liquor obtained by solid-liquid separation is allowed to stand for stratification, and the obtained organic layer is used as an organic solvent jacket to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and the obtained water layer jacket is used to prepare dilute nitric acid; the washing liquid obtained by water washing is neutralized with an alkali, and the water jacket is recovered by reduced pressure distillation for waste water reuse step for water washing;

[0049] The organic solvent used is 1,2-dichloroethane or toluene.

[0050] Specifically, the nitration reaction step is: dissolving 2,6-dichlorophenol or 2,4-dichlorophenol in an organic solvent to form an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and adding it dropwise to a nitric acid solution under stirring for nitration reaction, using nitric acid as a nitrating agent, and reacting to obtain a 2,6-dichlorophenol nitrate reaction liquid or a 2,4-dichlorophenol nitrate reaction liquid. Dissolving 2,6-dichlorophenol or 2,4-dichlorophenol in an organic solvent helps to increase the contact area between the reaction raw materials, improve the efficiency of the nitration reaction, and thus facilitate the generation efficiency of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol. Among them, the nitric acid solution is prepared by mixing concentrated nitric acid or fuming nitric acid with water.

[0051] Among them, the synthesis process of 2,4-dichloro-6-nitrophenol is shown in Formula 4:

[0052]

[0053] The synthesis process of 2,6-dichloro-4-nitrophenol is shown in Formula 5:

[0054]

[0055] Purification step: After the reaction is completed, the reaction liquid of 2,6-dichlorophenol nitrate or 2,4-dichlorophenol nitrate is obtained, and the temperature is lowered to 5-9°C to reduce the solubility of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol, so that the solid of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol is precipitated, and the solid and the mother liquor are separated by solid-liquid separation. The solid is washed with water to remove nitric acid and a small amount of reaction raw materials, and finally dried to obtain a 2,6-dichloro-4-nitrophenol product or a 2,4-dichloro-6-nitrophenol product.

[0056] Wastewater reuse step: the mother liquor obtained by solid-liquid separation is allowed to stand for stratification, and the obtained organic layer is used as an organic solvent to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol. The obtained water layer contains nitric acid. The nitric acid content in the water layer is detected, and concentrated nitric acid / fuming nitric acid is added at the same time according to the detected nitric acid content, and the water layer is used in the process of preparing nitric acid solution; alkali is added to the water washing liquid to neutralize the acid in the water washing liquid, and then water is recovered by reduced pressure distillation and used in the solid water washing process. In this way, resources are comprehensively utilized in the production process, wastewater is discharged zero, and production efficiency is reduced.

[0057] The present application realizes the preparation of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol through the above scheme, by dissolving 2,6-dichlorophenol or 2,4-dichlorophenol in an organic solvent to form an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and adding it dropwise to a nitric acid solution under stirring for nitration reaction, using nitric acid as a nitrating agent, and reacting to obtain a 2,6-dichlorophenol nitrate reaction liquid or a 2,4-dichlorophenol nitrate reaction liquid. The reaction liquid is cooled to precipitate a solid, and a 2,6-dichloro-4-nitrophenol product or a 2,4-dichloro-6-nitrophenol product is obtained by solid-liquid separation, water washing and drying. The obtained mother liquor is allowed to stand for stratification, and the obtained organic layer is used as an organic solvent jacket to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and the obtained water layer jacket is used to prepare a nitric acid solution; after the water washing liquid is neutralized with an alkali, the water jacket is recovered by vacuum distillation for water washing. This avoids the treatment of heavy-load acidic wastewater, reduces production costs, and achieves comprehensive resource utilization and zero wastewater discharge.

[0058] Optionally, the molar ratio of nitric acid to 2,6-dichlorophenol or 2,4-dichlorophenol in the nitric acid solution is 1.0-4.6:1.

[0059] Specifically, nitric acid is used as a nitrating agent to react with 2,6-dichlorophenol or 2,4-dichlorophenol. If the amount of nitric acid is too much, it will cause waste and will not promote the reaction efficiency and product yield. If the amount of nitric acid is too little, the nitration reaction effect cannot be achieved, affecting the production efficiency of 2,6-dichlorophenol or 2,4-dichlorophenol.

[0060] Preferably, the molar ratio of nitric acid to 2,6-dichlorophenol or 2,4-dichlorophenol is 1.3:1.

[0061] Optionally, the mass concentration of the nitric acid solution is 15-30%.

[0062] Optionally, the mass concentration of the nitric acid solution is 22-25%.

[0063] Specifically, nitric acid is a volatile acid. The higher the concentration, the stronger the volatility. Therefore, the concentration of nitric acid needs to be controlled to ensure the stable progress of the reaction.

[0064] Optionally, the weight volume ratio of 2,6-dichlorophenol or 2,4-dichlorophenol to the organic solvent is 1:2 g / mL.

[0065] Optionally, the method further includes: preparing an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol: adding 2,6-dichlorophenol or 2,4-dichlorophenol to a reactor containing an organic solvent by weight-volume ratio, heating to 45-55° C. under stirring to dissolve, thereby obtaining an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol. Dissolving 2,6-dichlorophenol or 2,4-dichlorophenol in an organic solvent under heating is beneficial to improving reaction efficiency.

[0066] Optionally, in the nitration reaction step, the temperature of adding the organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol dropwise into the nitric acid solution is 0-30° C., and the dropping rate is 0.75-1.25 mL / min.

[0067] Specifically, the nitration reaction process is an exothermic reaction, therefore, the organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol is added to the nitric acid solution by dropwise addition to carry out the reaction, and the dropwise addition speed is controlled to control the temperature of the reaction system and prevent the reaction system from being locally overheated. The dropwise addition speed is controlled to be 0.75-1.25 mL / min to maintain the dropwise addition temperature at 0-30°C, which is conducive to the efficient and stable progress of the reaction.

[0068] Optionally, in the nitration reaction step, the reaction temperature is kept at 0-30°C for 1 hour.

[0069] Optionally, the purification step also includes: performing solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution or the 2,4-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separation mother liquor, washing the solid nitrate with water to a pH of 6, and then vacuum drying to a constant weight at a temperature of 70-80° C. and a vacuum degree of -0.06 MPa to -0.03 MPa to obtain a 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol product.

[0070] Specifically, the 2,6-dichlorophenol nitrate reaction liquid or the 2,4-dichlorophenol nitrate reaction liquid contains solid products 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol. In the purification step, solid-liquid separation is first performed to obtain solid nitrate and separation mother liquor. The solid nitrate is washed with water to pH = 6 to remove a small amount of nitric acid in the solid nitrate to achieve a purification effect. And vacuum drying to constant weight under the conditions of a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol products. The nitric acid in the solid nitrate is washed away during the water washing process, and the residual nitric acid can be prevented from being decomposed into nitrogen oxides during the vacuum drying process, causing air pollution, thereby realizing the environmentally friendly production of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol.

[0071] Optionally, the washing liquid obtained after washing the solid nitrate with water is neutralized to pH=7-8 by adding alkali, and the water is recovered by vacuum distillation and used for subsequent washing of the solid nitrated material;

[0072] The alkali is one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate, calcium carbonate, and sodium carbonate.

[0073] Specifically, the acid in the water washing liquid is neutralized with alkali to generate nitrate, the water therein is evaporated by reduced pressure distillation, and used in the preparation process of nitric acid solution, thereby realizing the recycling of water resources, avoiding the large-load acid wastewater treatment, and reducing production costs. Among them, the sodium hydroxide can be flake alkali or liquid alkali.

[0074] Preferably, the nitrate remaining after the reduced pressure distillation is recovered and sold or used to achieve comprehensive utilization of resources.

[0075] The technical solution of the present application is described in detail below with reference to specific embodiments.

[0076] Example 1

[0077] A method for preparing 2,4-dichloro-6-nitrophenol with zero wastewater discharge comprises the following steps:

[0078] (1) Nitration reaction step: Add 50 g of 2,4-dichlorophenol and 100 mL of 1,2-dichloroethane to a 250 mL reaction bottle under stirring, and heat to 45°C to dissolve to form an organic solvent solution of 2,4-dichlorophenol, which is set aside. Add 75 mL of water to the 250 mL reaction bottle, and dropwise add 25 g of fuming nitric acid to form a nitric acid solution, which is set aside.

[0079] The organic solvent solution of 2,4-dichlorophenol was added dropwise to the nitric acid solution at 18°C ​​for 3 hours. After the addition was completed, the mixture was kept at 18°C ​​for 1 hour to obtain a 2,4-dichlorophenol nitrate reaction solution.

[0080] (2) Purification step: After the reaction is completed, cool to 5°C, filter, and perform solid-liquid separation on the 2,4-dichlorophenol nitrate reaction solution to obtain solid nitrate and separation mother liquor. The solid nitrate is washed with 300 mL of water until the pH is 6, and vacuum dried to constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 57.4 g of 2,4-dichloro-6-nitrophenol product. MP.118.5-119.5°C (literature value 118-120°C), GC purity 99.80%, yield 89.97%. The GC spectrum is as follows Figure 1 shown.

[0081] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 85 mL of 1,2-dichloroethane was recovered from the organic layer, and 82.5 g of the recovered water layer was obtained, and the recovered water layer contained 5% nitric acid. 3.5 g of liquid alkali was added to the water washing liquid, stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0082] Example 2

[0083] A method for preparing 2,4-dichloro-6-nitrophenol with zero wastewater discharge comprises the following steps:

[0084] (1) Nitration reaction step: 50 g of 2,4-dichlorophenol, 85 mL of the recovered 1,2-dichloroethane from Example 1 and 15 mL of new 1,2-dichloroethane were added to a 250 mL reaction flask under stirring, and heated to 50° C. to dissolve to form an organic solvent solution of 2,4-dichlorophenol for later use. 80 g of the recovered water layer containing 5% nitric acid from Example 1 was added to a 250 mL reaction flask, and 21 g of fuming acid was added dropwise to form a nitric acid solution for later use.

[0085] The organic solvent solution of 2,4-dichlorophenol was added dropwise to the nitric acid solution at 22°C for 3 hours and 20 minutes. After the addition was completed, the mixture was kept at 22°C for 1 hour to obtain a nitrated 2,4-dichlorophenol reaction solution.

[0086] (2) Purification step: After the reaction is completed, the temperature is lowered to 8°C, filtered, and the 2,4-dichlorophenol nitrate reaction liquid is subjected to solid-liquid separation to obtain a solid nitrate and a separation mother liquor. The solid nitrate is washed with the recycled water from the above Example 1 to a pH of 6, and vacuum dried to a constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 58.8g of 2,4-dichloro-6-nitrophenol product. MP.119.0-119.5°C (literature value 118-120°C), GC purity 99.81%, yield 92.16%. The GC spectrum is as follows Figure 2 shown.

[0087] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 83 mL of 1,2-dichloroethane was recovered from the organic layer, and 85.0 g of the recovered water layer was obtained, and the recovered water layer contained 5% nitric acid. 3.3 g of liquid alkali was added to the water washing liquid, stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0088] Example 3

[0089] A method for preparing 2,4-dichloro-6-nitrophenol with zero wastewater discharge comprises the following steps:

[0090] (1) Nitration reaction step: 50 g of 2,4-dichlorophenol, 83 mL of the recovered 1,2-dichloroethane from Example 2 and 17 mL of new 1,2-dichloroethane were added to a 250 mL reaction flask under stirring, and heated to 55° C. to dissolve to form an organic solvent solution of 2,4-dichlorophenol for later use. 80 g of the recovered water layer containing 5% nitric acid from Example 2 was added to a 250 mL reaction flask, and 21 g of fuming acid was added dropwise to form a nitric acid solution for later use.

[0091] The organic solvent solution of 2,4-dichlorophenol was added dropwise to the nitric acid solution at 25°C for 3 hours and 10 minutes. After the addition was completed, the mixture was kept at 25°C for 1 hour to obtain a nitrated reaction solution of 2,4-dichlorophenol.

[0092] (2) Purification step: After the reaction is completed, the temperature is lowered to 9°C, filtered, and the 2,4-dichlorophenol nitrate reaction solution is subjected to solid-liquid separation to obtain a solid nitrate and a separation mother liquor. The solid nitrate is washed with 290 mL of recovered water from Example 2 above to a pH of 6, and vacuum dried to a constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 60.6 g of 2,4-dichloro-6-nitrophenol product. MP. 119.0-119.5°C (literature value 118-120°C), GC purity 99.82%, yield 95.0%. The GC spectrum is as follows Figure 3 shown.

[0093] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 80 mL of 1,2-dichloroethane was recovered from the organic layer, and 85.0 g of the recovered water layer was obtained, and the recovered water layer contained 5% nitric acid. 4.0 g of liquid alkali was added to the water washing liquid and stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0094] Example 4

[0095] A method for preparing 2,6-dichloro-4-nitrophenol with zero wastewater discharge comprises the following steps:

[0096] (1) Nitration reaction step: Add 50 g of 2,6-dichlorophenol and 100 mL of 1,2-dichloroethane to a 250 mL reaction bottle under stirring, and heat to 45°C to dissolve to form an organic solvent solution of 2,6-dichlorophenol, which is set aside. Add 75 mL of water to the 250 mL reaction bottle, and add 25 g of fuming nitric acid dropwise to form a nitric acid solution, which is set aside.

[0097] The organic solvent solution of 2,6-dichlorophenol was added dropwise to the nitric acid solution at 18°C ​​for 3 hours and 10 minutes. After the addition was completed, the mixture was kept warm at 18°C ​​for 1 hour to obtain a 2,6-dichlorophenol nitrate reaction solution.

[0098] (2) Purification step: After the reaction is completed, cool to 5°C, filter, and perform solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separation mother liquor. The solid nitrate is washed with 290 mL of recovered water from Example 3 until pH = 6, and vacuum dried to constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 57.4 g of 2,6-dichloro-4-nitrophenol product. MP. 127.0-129.5°C (literature value 123-126°C), GC purity 99.74%, yield 90.0%. The GC spectrum is as follows Figure 4 shown.

[0099] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 85 mL of 1,2-dichloroethane was recovered from the organic layer, and 85.0 g of the recovered water layer was obtained, and the recovered water layer contained 5% nitric acid. 3.1 g of liquid alkali was added to the water washing liquid and stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0100] Example 5

[0101] A method for preparing 2,6-dichloro-4-nitrophenol with zero wastewater discharge comprises the following steps:

[0102] (1) Nitration reaction step: 50 g of 2,6-dichlorophenol, 85 mL of 1,2-dichloroethane recovered from Example 4 and 15 ml of new 1,2-dichloroethane were added to a 250 mL reaction bottle under stirring, and heated to 50° C. to dissolve to form an organic solvent solution of 2,6-dichlorophenol for later use. 85 g of the recovered water layer containing 5% nitric acid from Example 4 was added to a 250 mL reaction bottle, and 21 g of fuming nitric acid was added dropwise to form a nitric acid solution for later use.

[0103] The organic solvent solution of 2,6-dichlorophenol was added dropwise to the nitric acid solution at 22°C for 3 hours. After the addition was completed, the mixture was kept at 22°C for 1 hour to obtain a nitrated 2,6-dichlorophenol reaction solution.

[0104] (2) Purification step: After the reaction is completed, cool to 5°C, filter, and perform solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separation mother liquor. The solid nitrate is washed with 290 mL of recovered water from Example 4 to a pH of 6, and vacuum dried to a constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 57.7 g of 2,6-dichloro-4-nitrophenol product. MP. 127.5-129.0°C (literature value 123-126°C), GC purity 99.91%, yield 90.5%. The GC spectrum is as follows Figure 5 shown.

[0105] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 80.0 mL of 1,2-dichloroethane was recovered from the organic layer, and 80.0 g of the recovered water layer was recovered, and the recovered water layer contained 5% nitric acid. 4.0 g of liquid alkali was added to the water washing liquid, stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0106] Example 6

[0107] A method for preparing 2,6-dichloro-4-nitrophenol with zero wastewater discharge comprises the following steps:

[0108] (1) Nitration reaction step: 50 g of 2,6-dichlorophenol, 80 mL of the recovered 1,2-dichloroethane from Example 5 and 20 ml of new 1,2-dichloroethane were added to a 250 mL reaction bottle under stirring, and heated to 45-55° C. to dissolve to form an organic solvent solution of 2,6-dichlorophenol for later use. 80 g of the recovered water layer containing 5% nitric acid from Example 5 was added to a 250 mL reaction bottle, and 21 g of fuming nitric acid was added dropwise to form a nitric acid solution for later use.

[0109] The organic solvent solution of 2,6-dichlorophenol was added dropwise to the nitric acid solution at 25°C for 2 hours and 50 minutes. After the addition was completed, the mixture was kept at 25°C for 1 hour to obtain a nitrated 2,6-dichlorophenol reaction solution.

[0110] (2) Purification step: After the reaction is completed, cool to 5°C, filter, and perform solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution to obtain solid nitrate and separation mother liquor. The solid nitrate is washed with 290 mL of recovered water from Example 5 to pH = 6, and vacuum dried to constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 57.1 g of 2,6-dichloro-4-nitrophenol product. MP.127.0-129.0°C (literature value 123-126°C), GC purity 99.73%, yield 89.5%. The GC spectrum is as follows Figure 6 shown.

[0111] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 80.0 mL of 1,2-dichloroethane was recovered from the organic layer, and 80.0 g of the recovered water layer was recovered, and the recovered water layer contained 5% nitric acid. 4.0 g of liquid alkali was added to the water washing liquid, stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0112] Example 7

[0113] A method for preparing 2,6-dichloro-4-nitrophenol with zero wastewater discharge comprises the following steps:

[0114] (1) Nitration reaction step: Add 50 g of 2,6-dichlorophenol and 100 mL of toluene to a 250 mL reaction bottle under stirring, heat to 50°C to dissolve, and form an organic solvent solution of 2,6-dichlorophenol for later use. Add 75 mL of water to a 250 mL reaction bottle, and dropwise add 25 g of fuming nitric acid to form a nitric acid solution for later use.

[0115] The organic solvent solution of 2,6-dichlorophenol was added dropwise to the nitric acid solution at 25°C for 2 hours. After the addition was completed, the mixture was kept warm at 18°C-25°C for 1 hour to obtain a 2,6-dichlorophenol nitrate reaction solution.

[0116] The molar ratio of nitric acid to 2,6-dichlorophenol is 1.0-4.6:1, and the mass concentration of the nitric acid solution is 15-30%.

[0117] (2) Purification step: After the reaction is completed, cool to 8°C, filter, and perform solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separated mother liquor. The solid nitrate is washed with 290 mL of recovered water from Example 5 until the pH is 6, and vacuum dried to constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 56.8 g of 2,6-dichloro-4-nitrophenol product. MP.127.5-129.0°C (literature value 123-126°C), GC purity 99.88%, yield 89.0%. The GC spectrum is as follows Figure 7 shown.

[0118] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 95.0 mL of toluene was recovered from the organic layer, and 76.3 g of water layer was recovered, and the recovered water layer contained 5% nitric acid. 4.5 g of liquid alkali was added to the water washing liquid, stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0119] Example 8

[0120] A method for preparing 2,6-dichloro-4-nitrophenol with zero wastewater discharge comprises the following steps:

[0121] (1) Nitration reaction step: 50 g of 2,6-dichlorophenol, 95 mL of toluene recovered from Example 7 and 5 mL of new toluene were added to a 250 mL reaction bottle under stirring, and heated to 50° C. to dissolve to form an organic solvent solution of 2,6-dichlorophenol for later use. 75 mL of the recovered water layer from Example 7 was added to a 250 mL reaction bottle, and 22 g of fuming nitric acid was added dropwise to form a nitric acid solution for later use.

[0122] The organic solvent solution of 2,6-dichlorophenol was added dropwise to the nitric acid solution at 25°C for 3 hours. After the addition was completed, the mixture was kept at 25°C for 1 hour to obtain a nitrated 2,6-dichlorophenol reaction solution.

[0123] (2) Purification step: After the reaction is completed, cool to 8°C, filter, and perform solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separated mother liquor. The solid nitrate is washed with 290 mL of recovered water from Example 7 until pH = 6, and vacuum dried to constant weight at a temperature of 70-80°C and a vacuum degree of -0.06MPa to -0.03MPa to obtain an off-white powder, i.e., 56.1 g of 2,6-dichloro-4-nitrophenol product. MP. 127.5-128.5°C (literature value 123-126°C), GC purity 99.7%, yield 88.0%. The GC spectrum is as follows Figure 8 shown.

[0124] (3) Wastewater recycling step: The mother liquor obtained by solid-liquid separation was allowed to stand for stratification, and 93.0 mL of toluene was recovered from the organic layer, and 78.0 g of water layer was recovered, and the recovered water layer contained 5% nitric acid. 4.5 g of liquid alkali was added to the water washing liquid, stirred, neutralized to pH = 8, and distilled under reduced pressure to recover 290 mL of water.

[0125] Experimental Example 1

[0126] The 2,4-dichloro-6-nitrophenol obtained in Examples 1 to 3 was subjected to gas chromatography analysis to obtain a GC spectrum as shown in Figures 1 to 3 shown.

[0127] Detection method:

[0128] Chromatographic conditions: GC-2010PLUS gas chromatograph, CP CHIRASIL-DEX CB chromatographic column (25m×0.32mm×0.25μm);

[0129] Column temperature: initial temperature 120°C, holding time 0, heating rate 10.0°C / min, final temperature: 200°C;

[0130] Holding time: 7min; Vaporization chamber temperature: 220℃; Detection chamber temperature: 220℃; Split ratio: 1:50; H 2 :30.0ml / min, Air: 400.0ml / min, N 2 : 30.0ml / min;

[0131] Injection volume: 1.0 μL.

[0132] 2,4-Dichloro-6-nitrophenol sample solution: Accurately weigh 150 mg of the sample into a 10 mL volumetric flask, dissolve it in methanol and dilute to the scale.

[0133] Reference solution: 2,4-dichlorophenol stock solution: Accurately weigh 15 mg of 2,4-dichlorophenol in a 10 mL volumetric flask, dissolve it with methanol and dilute to the scale.

[0134] Accurately weigh 150 mg of 2,4-dichloro-6-nitrophenol reference substance into a 10 mL volumetric flask, transfer 1 ml of 2,4-dichlorophenol stock solution into the volumetric flask, dissolve it with methanol and dilute to the scale.

[0135] Result calculation method: Calculate the content of 2,4-dichloro-6-nitrophenol by area normalization method (as shown in formula 6):

[0136]

[0137] Wherein: Ai is the peak area of ​​2,4-dichloro-6-nitrophenol; A is the area of ​​all peaks.

[0138] Experimental Example 2

[0139] The 2,6-dichloro-4-nitrophenol obtained in Examples 4 to 8 was subjected to gas chromatography analysis to obtain a GC spectrum as shown in Figures 4 to 8 shown.

[0140] Detection method:

[0141] Chromatographic conditions: GC-2010PLUS gas chromatograph;

[0142] Chromatographic column: HP-5, (25m×0.32mm×0.52um).

[0143] Column flow rate: 1.5mL / min

[0144] Injector: split ratio = 50:1; injector temperature: 280°C; injection volume: 1 μL;

[0145] Detector: FID, temperature 330℃;

[0146] H 2 :40mL / min, oxygen; 400mL / min; N 2 :30mL / min

[0147] Column temperature: primary program temperature rise: initial temperature 50℃, final temperature 150℃, heating rate: 5℃ / min; secondary program temperature rise: initial temperature 150℃, final temperature 280℃, heating rate: 10℃ / min

[0148] 2,6-Dichloro-4-nitrophenol sample preparation: Weigh 150 mg of sample into a 10 ml volumetric flask and dissolve to the mark with dichloromethane.

[0149] Result calculation method: Calculate the content of 2,6-dichloro-4-nitrophenol by area normalization method (as shown in formula 6)

[0150]

[0151] Wherein: Ai is the peak area of ​​2,6-dichloro-4-nitrophenol; A is the area of ​​all peaks.

[0152] like Figures 1 to 8 It can be seen that the present application realizes the preparation of 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol, and in the preparation process, the mother liquor obtained by solid-liquid separation is allowed to stand for stratification, the obtained organic layer is used as an organic solvent jacket to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and the obtained water layer jacket is used to prepare a nitric acid solution; after the water washing liquid is neutralized with alkali, the water jacket is recovered by vacuum distillation for the wastewater reuse step of water washing. This makes comprehensive utilization of resources without wastewater discharge.

[0153] The product quality is good, the GC purity is ≥99.7%, and the yield is high, the yield is ≥88.0%.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge, characterized in that: The steps include: Under stirring, an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol is added dropwise to a nitric acid solution, and after the addition is completed, the reaction is carried out by heat preservation to obtain a nitration reaction step of a 2,6-dichlorophenol nitrate reaction solution or a 2,4-dichlorophenol nitrate reaction solution; after the reaction is completed, the temperature is lowered to 5-9° C., and the 2,6-dichlorophenol nitrate reaction solution or the 2,4-dichlorophenol nitrate reaction solution is subjected to solid-liquid separation, water washing and drying to obtain a 2,6-dichloro-4-nitrophenol product or a 2,4-dichloro-6-nitrophenol product purification step; the mother liquor obtained by the solid-liquid separation is allowed to stand for stratification, and the obtained organic layer is used as an organic solvent jacket to prepare an organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol, and the obtained water layer jacket is used to prepare dilute nitric acid; the washing liquid obtained by the washing is neutralized with an alkali, and the water jacket is recovered by reduced pressure distillation for the waste water reuse step of the washing; The organic solvent is 1,2-dichloroethane or toluene.

2. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: The molar ratio of nitric acid in the nitric acid solution to the 2,6-dichlorophenol or the 2,4-dichlorophenol is 1.0-4.6:

1.

3. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: The mass concentration of the nitric acid solution is 15-30%.

4. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 3, characterized in that: The mass concentration of the nitric acid solution is 22-25%.

5. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: The weight-to-volume ratio of the 2,6-dichlorophenol or the 2,4-dichlorophenol to the organic solvent is 1:2 g / mL.

6. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: The method further comprises: preparing the organic solvent solution of the 2,6-dichlorophenol or the 2,4-dichlorophenol: adding the 2,6-dichlorophenol or the 2,4-dichlorophenol to a reactor containing the organic solvent in a weight-to-volume ratio, heating to 45-55° C. under stirring to dissolve, thereby obtaining the organic solvent solution of the 2,6-dichlorophenol or the 2,4-dichlorophenol.

7. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: In the nitration reaction step, the temperature of dripping the organic solvent solution of 2,6-dichlorophenol or 2,4-dichlorophenol into the nitric acid solution is 0-30° C., and the dripping rate is 0.75-1.25 mL / min.

8. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: In the nitration reaction step, the insulation reaction temperature is 0-30° C. and the time is 1 hour.

9. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 1, characterized in that: The purification step also includes: performing solid-liquid separation on the 2,6-dichlorophenol nitrate reaction solution or the 2,4-dichlorophenol nitrate reaction solution to obtain a solid nitrate and a separation mother liquor, washing the solid nitrate with water until the pH value is 6, and then vacuum drying to a constant weight at a temperature of 70-80° C. and a vacuum degree of -0.06 MPa to -0.03 MPa to obtain a 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol product.

10. The method for preparing 2,6-dichloro-4-nitrophenol or 2,4-dichloro-6-nitrophenol with zero wastewater discharge according to claim 9, characterized in that: The washing liquid obtained after washing the solid nitrate with water is neutralized to pH=7-8 by adding alkali, and water is recovered by vacuum distillation and used for subsequent washing of the solid nitrated material; The alkali is one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate, calcium carbonate, and sodium carbonate.

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