Continuous synthesis method of 2, 6-dihalo-4-nitroaniline and equipment for implementing synthesis method

Abstract

The invention provides a continuous synthesis method of 2, 6-dihalogenated-4-nitroaniline and equipment for implementing the synthesis method. The continuous synthesis method of 2, 6-dihalo-4-nitroaniline comprises the following steps: obtaining an acidic solution of paranitroaniline; mixing the acid solution of the paranitroaniline with a halogen simple substance to obtain a mixed product, continuously conveying the mixed product to a primary ultrasonic stirrer group for pre-reaction, and dividing the mixed product into a first pre-reaction product and a second pre-reaction product; the first pre-reaction product is internally circulated in the primary ultrasonic stirrer group; mixing the second pre-reaction product with an oxidizing substance, and conveying the mixture to a secondary ultrasonic stirrer group; and carrying out a halogenation reaction in the secondary ultrasonic stirrer group to obtain a halogenated product containing the 2, 6-dihalogenated-4-nitroaniline. According to the synthesis method, the reaction time is greatly shortened, the safety is high, and the obtained product is high in purity and high in yield.

Description

Technical Field

[0001] The invention relates to a continuous synthesis method of 2,6-dihalogenated-4-nitroaniline and equipment for implementing the synthesis method, and belongs to the field of dye intermediate synthesis. Background Art

[0002] 2,6-Dihalogenated-4-nitroaniline is an important dye intermediate. Among them, 2,6-dibromo-4-nitroaniline is generally a yellow crystalline powder. 2,6-Dibromo-4-nitroaniline is soluble in organic solvents such as ethanol, dimethylformamide and dichloromethane, but insoluble in water. 2,6-Dibromo-4-nitroaniline is often used in organic synthesis and can be used as an intermediate or coupling reagent for the preparation of other organic syntheses. It is an important disperse dye intermediate.

[0003] At present, the commonly used process for preparing 2,6-dibromo-4-nitroaniline is to brominate p-nitroaniline with bromine in a hydrochloric acid medium, then use chlorine or sodium chlorate and other oxidants to replace the bromine in the reaction system and further brominate, and then filter, wash and dry to obtain solid 2,6-dibromo-4-nitroaniline. However, this method has the disadvantages of complicated process, not simple operation, large floor space required for production, more equipment, high energy consumption and more waste.

[0004] Furthermore, the preparation of 2,6-dibromo-4-nitroaniline can also be obtained by nitration and bromination reactions. p-Nitroaniline reacts with concentrated nitric acid to obtain p-nitrophenol. Then, p-nitrophenol reacts with bromine or cuprous bromide to generate 2,6-dibromo-4-nitroaniline. However, this method is less safe and needs to be kept away from high temperature and open flame environments. Appropriate personal protective equipment, such as gloves, protective glasses and protective clothing, should be worn during the operation to avoid inhalation of dust or contact with the skin.

[0005] Therefore, researching a continuous synthesis device and method for 2,6-dibromo-4-nitroaniline has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In view of the technical problems existing in the prior art, the present invention first provides a continuous synthesis method of 2,6-dibromo-4-nitroaniline. The synthesis method of the present invention has simple process, simple operation, small production site, equipment, energy consumption and three wastes.

[0008] Furthermore, the present invention also provides a device for implementing the above-mentioned synthesis method of the present invention. The device of the present invention can achieve rapid mixing of liquids and intensification of chemical reactions, significantly improve production efficiency, and achieve continuous production.

[0009] Solutions for solving problems

[0010] The present invention provides a continuous synthesis method of 2,6-dihalogenated-4-nitroaniline, which comprises the following steps:

[0011] Obtain an acidic solution of p-nitroaniline;

[0012] The acidic solution of p-nitroaniline and the halogen element are mixed to obtain a mixed product, and the mixed product is continuously transported to a primary ultrasonic stirrer group for pre-reaction and is divided into a first pre-reaction product and a second pre-reaction product;

[0013] The first pre-reaction product is internally circulated in the first-stage ultrasonic agitator group; the second pre-reaction product is mixed with an oxidizing substance and then transported to the second-stage ultrasonic agitator group;

[0014] A halogenation reaction is carried out in the secondary ultrasonic agitator group to obtain a halogenated product containing 2,6-dihalogenated-4-nitroaniline.

[0015] According to the continuous synthesis method of the present invention, the acidic solution of p-nitroaniline comprises the steps of mixing and slurrying p-nitroaniline in an acidic medium;

[0016] Preferably, the acidic medium comprises an aqueous solution of an acidic substance;

[0017] Preferably, in the aqueous solution of the acidic substance, the mass percentage of the acidic substance is 20 to 98%;

[0018] Preferably, the temperature of the mixing and beating is 30 to 90° C., and the time of the mixing and beating is 0.5 to 3.0 hours;

[0019] Preferably, the molar ratio of the p-nitroaniline to the acidic substance is 1:2.0-8.0.

[0020] According to the continuous synthesis method of the present invention, the molar ratio of the p-nitroaniline to the halogen element is 1:1.0-2.5;

[0021] Preferably, the temperature of the mixture of the acidic solution of p-nitroaniline and the halogen element is 30 to 90° C., and the temperature of the internal circulation is 30 to 90° C.;

[0022] Preferably, the mass ratio of the first pre-reaction product to the second pre-reaction product is 5 to 12:1.

[0023] According to the continuous synthesis method of the present invention, the molar ratio of the p-nitroaniline to the oxidizing substance is 1:0.5-2.5;

[0024] Preferably, the oxidizing material is mixed with the second pre-reaction product in the form of an aqueous solution of the oxidizing material;

[0025] Preferably, in the aqueous solution of the oxidizing substance, the mass percentage of the oxidizing substance is 15% to 35%;

[0026] Preferably, the temperature at which the second pre-reaction product is mixed with the oxidizing substance is 30-60°C, and the temperature at which the halogenation reaction is performed is 30-60°C.

[0027] According to the continuous synthesis method of the present invention, the synthesis method further comprises dividing the halogenated product into a first halogenated product and a second halogenated product;

[0028] The first halogenated product is internally circulated in the secondary ultrasonic agitator group, and after being mixed with the second pre-reaction product of the next batch and the oxidizing substance, the halogenation reaction is continued; the second halogenated product is separated after cooling to obtain 2,6-dihalogenated-4-nitroaniline;

[0029] Preferably, the mass ratio of the first halogenated product to the second halogenated product is 5 to 12:1.

[0030] The present invention also provides a device for implementing the continuous synthesis method according to the present invention, wherein the device comprises a primary ultrasonic agitator group and a secondary ultrasonic agitator group connected to each other; wherein,

[0031] The first-stage ultrasonic agitator group has more than two groups of ultrasonic agitators, and the second-stage ultrasonic agitator group has more than two groups of ultrasonic agitators.

[0032] According to the device of the present invention, the inlet of the first-stage ultrasonic agitator group is connected to the first-stage mixer, the inlet of the second-stage ultrasonic agitator group is connected to the second-stage mixer; and the outlet of the first-stage ultrasonic agitator group is connected to the second-stage mixer;

[0033] Preferably, the outlet of the first-stage ultrasonic agitator group is connected to the first-stage mixer, and the outlet of the second-stage ultrasonic agitator group is connected to the second-stage mixer.

[0034] According to the device of the present invention, the outlet of the secondary ultrasonic agitator group is also connected to a cooling kettle and / or a separation device;

[0035] Preferably, the outlet of the secondary ultrasonic agitator group is connected to the inlet of the cooling kettle, and the outlet of the cooling kettle is connected to the inlet of the separation device;

[0036] More preferably, the cooling kettle comprises a first cooling kettle and a second cooling kettle connected in parallel.

[0037] According to the equipment of the present invention, the separation device is further connected to a distillation kettle;

[0038] Preferably, the outlet of the separation device is connected to the inlet of the distillation kettle;

[0039] More preferably, the distillation pot comprises a first distillation pot and a second distillation pot connected in parallel.

[0040] According to the device of the present invention, the device further comprises a batching kettle;

[0041] Preferably, the outlet of the batching kettle is connected to the inlet of the primary mixer;

[0042] Preferably, the inlet of the batching kettle is connected to the outlet of the distillation kettle.

[0043] Effects of the Invention

[0044] The synthesis method of the invention greatly shortens the reaction time, has high safety, and obtains products with high purity and high yield.

[0045] The equipment for implementing the above-mentioned synthesis method of the present invention can realize rapid mixing of liquids and intensification of chemical reactions, significantly improve production efficiency, and realize continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The equipment flow chart of the continuous synthesis method of 2,6-dibromo-4-nitroaniline according to the present invention is shown.

[0047] Figure 2 The schematic diagram of the structure of the two-stage series ultrasonic agitator group of the present invention is shown.

[0048] Figure 3 The schematic diagram of the structure of the three-stage series ultrasonic agitator group of the present invention is shown.

[0049] Figure 4 The schematic diagram of the structure of the four-stage series ultrasonic agitator group of the present invention is shown.

[0050] Description of Reference Numerals

[0051] A: batching kettle, B: first-stage mixer, C: first-stage ultrasonic agitator group,

[0052] D: Secondary mixer, E: Secondary ultrasonic agitator group, F: First cooling kettle,

[0053] G: second cooling kettle, H: first distillation kettle, I: first distillation kettle. DETAILED DESCRIPTION

[0054] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0055] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0056] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0057] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0058] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0059] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0060] <First aspect>

[0061] The first aspect of the present invention provides a continuous synthesis method of 2,6-dihalogenated-4-nitroaniline, which comprises the following steps:

[0062] Obtain an acidic solution of p-nitroaniline;

[0063] The acidic solution of p-nitroaniline and the halogen element are mixed to obtain a mixed product, and the mixed product is continuously transported to a primary ultrasonic stirrer group for pre-reaction and is divided into a first pre-reaction product and a second pre-reaction product;

[0064] The first pre-reaction product is internally circulated in the first-stage ultrasonic agitator group; the second pre-reaction product is mixed with an oxidizing substance and then transported to the second-stage ultrasonic agitator group;

[0065] A halogenation reaction is carried out in the secondary ultrasonic agitator group to obtain a halogenated product containing 2,6-dihalogenated-4-nitroaniline.

[0066] The synthesis method of the invention greatly shortens the reaction time, has high safety, and obtains products with high purity and high yield.

[0067] Specifically, the 2,6-dihalogenated-4-nitroaniline of the present invention may be 2,6-dichloro-4-nitroaniline or 2,6-dibromo-4-nitroaniline.

[0068] In the present invention, the acidic solution of p-nitroaniline includes the step of mixing and slurrying p-nitroaniline in an acidic medium. Specifically, the acidic medium includes an aqueous solution of an acidic substance; preferably, in the aqueous solution of the acidic substance, the mass percentage of the acidic substance is 20-98%, preferably 30-90%, for example: 25%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc. Preferably, the molar ratio of the p-nitroaniline to the acidic substance is 1:2.0-8.0, preferably 1:3.0-7.0, for example: 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, etc. Furthermore, in the present invention, the temperature of the mixing and beating is 30-90° C., and the time of the mixing and beating is 0.5-3.0 hours, for example: 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, etc.

[0069] In the present invention, the acidic substance is not particularly limited, and can be any feasible acidic substance in the art, such as sulfuric acid and / or phosphoric acid, etc. Considering the convenience of recycling operation, sulfuric acid is preferably used in the present invention. When sulfuric acid is used as the acidic substance, there are no other excessive impurities in the distillation process, and the sulfuric acid solution after distillation and concentration is directly reused, and the distilled water can also meet the industrial water needs.

[0070] Further, the acidic solution of p-nitroaniline and the halogen element are mixed to obtain a mixed product. Specifically, the molar ratio of p-nitroaniline to the halogen element is 1:1.0-2.5, preferably 1:1.1-1.5, for example: 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, etc. When the molar ratio of p-nitroaniline to the halogen element is 1:1.0-2.5, using an equal amount or an excess of the halogen element can effectively carry out the reaction. In the present invention, the halogen element can be F2, Cl2, Br2, I2, preferably Br2 (bromine). Preferably, the temperature of mixing the acidic solution of p-nitroaniline and the halogen element is 30-90°C; for example: 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, etc.

[0071] Further, the mixed product is continuously transported to a primary ultrasonic agitator group for pre-reaction and is divided into a first pre-reaction product and a second pre-reaction product. Preferably, the mass ratio of the first pre-reaction product to the second pre-reaction product is 5 to 12:1, preferably 7 to 10:1, for example: 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, etc.

[0072] The first pre-reaction product is internally circulated in the first-stage ultrasonic agitator group. The second pre-reaction product and the oxidizing material are transported to the second-stage ultrasonic agitator group. The inventors of the present invention have found that by allowing the first pre-reaction product to be internally circulated in the first-stage ultrasonic agitator group, the reaction can be ensured to be more fully carried out. Specifically, the temperature of the internal circulation is 30 to 90°C, preferably 40 to 70°C; for example: 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, etc.

[0073] Specifically, in the present invention, the oxidizing substance may be hydrogen peroxide. By using hydrogen peroxide as the oxidizing substance, no other excessive impurities are introduced during the reaction.

[0074] In some specific embodiments, the molar ratio of the p-nitroaniline to the oxidizing substance is 1:0.5-2.5, preferably 1:0.8-1.5, for example: 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, etc.

[0075] Specifically, the oxidizing substance is mixed with the second pre-reaction product in the form of an aqueous solution of the oxidizing substance; preferably, the mass percentage of the oxidizing substance in the aqueous solution of the oxidizing substance is 15% to 35%, for example: 18%, 20%, 22%, 25%, 28%, 30%, 32%, etc.; preferably, the temperature at which the second pre-reaction product and the oxidizing substance are mixed is 30 to 60°C; for example: 35°C, 40°C, 45°C, 50°C, 55°C, etc.

[0076] Further, a halogenation reaction is carried out in the secondary ultrasonic agitator group to obtain a halogenated product containing 2,6-dihalogenated-4-nitroaniline. Specifically, the temperature of the halogenation reaction is 30 to 60°C; for example: 35°C, 40°C, 45°C, 50°C, 55°C, etc.

[0077] In some specific embodiments, the synthesis method also includes dividing the halogenated product into a first halogenated product and a second halogenated product; wherein the first halogenated product is internally circulated in the secondary ultrasonic agitator group, and after being mixed with the next batch of the second pre-reaction product and the oxidizing substance, the halogenation reaction continues; the second halogenated product is separated after cooling to obtain 2,6-dihalogenated-4-nitroaniline; preferably, the mass ratio of the first halogenated product to the second halogenated product is 5 to 12:1, preferably 7 to 10:1, for example: 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, etc.

[0078] In the present invention, the first halogenated product is internally circulated in the secondary ultrasonic agitator group, so that the reaction can be carried out more fully.

[0079] The present invention does not specifically limit the cooling separation method, which can be a cooling separation method commonly used in the art. The separated sulfuric acid solution is distilled and then reused in the preparation of 2,6-dihalogenated-4-nitroaniline. The distilled water is tested, which can meet environmental protection requirements. For distillation, it can be specifically distilled at a temperature of 80 to 110°C.

[0080] <Second Aspect>

[0081] like Figure 1 As shown, the second aspect of the present invention provides a device for implementing the continuous synthesis method of 2,6-dihalo-4-nitroaniline according to the first aspect of the present invention, wherein the device includes a first-level ultrasonic agitator group C and a second-level ultrasonic agitator group E connected to each other; wherein the first-level ultrasonic agitator group C has more than two ultrasonic agitators connected in series, and the second-level ultrasonic agitator group E has more than two ultrasonic agitators connected in series.

[0082] In the present invention, since the materials cannot be fully reacted in a single ultrasonic agitator, the purity of the product is low. Figure 2-4 As shown, the first-level ultrasonic agitator group C has more than two ultrasonic agitators connected in series, preferably 2 to 4 ultrasonic agitators. When the second-level ultrasonic agitator group E has more than two ultrasonic agitators connected in series, the material can be fully reacted and the product purity can be improved.

[0083] Specifically, both the primary ultrasonic agitator group C and the secondary ultrasonic agitator group E have external circulating water temperature control. The primary ultrasonic agitator group C preferably has circulating water at 30 to 90° C. to control the bromination reaction temperature, and the secondary ultrasonic agitator group E preferably has circulating water at 30 to 60° C. to control the bromination reaction temperature. By controlling the bromination reaction temperature, the material can be subjected to bromination reaction at a suitable bromination reaction temperature, thereby improving the reaction efficiency and product yield.

[0084] In some specific embodiments, the inlet of the first-level ultrasonic agitator group C is connected to the first-level mixer B, the inlet of the second-level ultrasonic agitator group E is connected to the second-level mixer D; and the outlet of the first-level ultrasonic agitator group C is connected to the second-level mixer D.

[0085] The primary mixer B is used to mix the acidic solution of p-nitroaniline and the halogen element. The secondary mixer E is used to mix the second pre-reaction product and the oxidizing substance.

[0086] In some specific embodiments, the outlet of the primary ultrasonic agitator group C is also connected to the primary mixer B, and the outlet of the secondary ultrasonic agitator group C is also connected to the secondary mixer D. That is, a circulation connection is formed, so that the first pre-reaction product can be internally circulated in the primary ultrasonic agitator group C, and the first halogenated product can be internally circulated in the secondary ultrasonic agitator group C.

[0087] In some specific embodiments, the outlet of the secondary ultrasonic agitator group E is also connected to a cooling kettle and / or a separation device; preferably, the outlet of the secondary ultrasonic agitator group E is connected to the inlet of the cooling kettle, and the outlet of the cooling kettle is connected to the inlet of the separation device. By using the cooling kettle and the separation device, the halogenated product can be cooled and separated into a sulfuric acid solution, thereby obtaining high-purity 2,6-dihalogenated-4-nitroaniline.

[0088] In some specific embodiments, the cooling kettle comprises a first cooling kettle F and a second cooling kettle G connected in parallel. Continuous cooling can be achieved by using the first cooling kettle F and the second cooling kettle G. Specifically, a liquid level setting value can be set in the first cooling kettle F, and when the halogenated product in the first cooling kettle F reaches the liquid level setting value, the second cooling kettle G is switched, and at this time, the halogenated product in the first cooling kettle F is transported to a separation device for separation treatment.

[0089] The present invention does not impose any particular limitation on the liquid level setting value, and it can be set according to equipment requirements, for example, 10-90% of the cooling kettle volume.

[0090] In some specific embodiments, the separation device is further connected to a distillation kettle; preferably, the outlet of the separation device is connected to the inlet of the distillation kettle;

[0091] In some specific embodiments, the still includes a first still H and a second still I connected in parallel. Continuous distillation can be achieved by using the first still H and the second still I. Specifically, a liquid level setting value can be set in the first still H, and when the amount of the halogenated product in the first still H reaches the liquid level setting value, the still is switched to the second still I, and at this time, the acidic medium in the first still H is reused for the continuous synthesis of 2,6-dihalogenated-4-nitroaniline.

[0092] The present invention does not specifically limit the liquid level setting value, and it can be set according to equipment requirements, for example, 10-90% of the volume of the distillation kettle.

[0093] In some specific embodiments, the equipment further comprises a batching kettle A; preferably, the outlet of the batching kettle A is connected to the inlet of the primary mixer B; preferably, the inlet of the batching kettle A is connected to the outlet of the distillation kettle. By using the batching kettle A, an acidic solution of p-nitroaniline can be obtained.

[0094] In some specific embodiments, 2,6-dihalogenated-4-nitroaniline can be continuously prepared by using the device of the present invention, and the specific process flow is as follows:

[0095] Para-nitroaniline and sulfuric acid solution are continuously added to the batching kettle A at the same time to obtain a sulfuric acid solution of para-nitroaniline. The sulfuric acid solution of para-nitroaniline is transported to the primary mixer B. At the same time, the halogenated element is also added to the primary mixer B, and the mixed product obtained after the sulfuric acid solution of para-nitroaniline is mixed with bromine enters the primary ultrasonic agitator group C from the primary mixer B for pre-reaction and is divided into a first pre-reaction product and a second pre-reaction product. The first pre-reaction product is circulated back to the primary ultrasonic agitator group C through the circulation pump through the primary mixer B, and the second pre-reaction product is mixed with the oxidizing material through the secondary mixer D and enters the secondary ultrasonic agitator group E.

[0096] After the bromination reaction is carried out in the secondary ultrasonic agitator group E, the reaction is judged to be complete when there is no color change using potassium iodide test paper, and a halogenated product is obtained, and the halogenated product is divided into a first halogenated product and a second halogenated product using a secondary mixer D. The first halogenated product is circulated back to the secondary ultrasonic agitator group E through a circulation pump and the secondary mixer D, and the second halogenated product enters the first cooling kettle F.

[0097] After the liquid level in the first cooling kettle F reaches the set value, switch to the second cooling kettle G. At the same time, the brominated product after cooling is released from the first cooling kettle F for standby use; when the liquid level in the second cooling kettle G reaches the set value, switch to the first cooling kettle F, and at the same time release the brominated product after cooling from the second cooling kettle G for standby use, and repeat this cycle.

[0098] After centrifuging the bromination product using a centrifuge, a sulfuric acid solution and 2,6-dihalogenated-4-nitroaniline are obtained. The sulfuric acid solution first enters the first distillation kettle H for heating and concentration, and when the liquid level reaches a set value, it is switched to the second distillation kettle I, and the heated and concentrated sulfuric acid solution is released from the first distillation kettle H for standby use; when the liquid level of the second distillation kettle I reaches a set value, it is switched to the first distillation kettle H, and the heated and concentrated sulfuric acid solution is released from the second distillation kettle I for standby use, and this cycle is repeated.

[0099] Example

[0100] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0101] Example 1

[0102] like Figure 1As shown, the equipment includes a first-level ultrasonic agitator group C and a second-level ultrasonic agitator group E, both of which use three-stage series ultrasonic agitators, two parallel first cooling kettles F and second cooling kettles G, and two parallel first distillation kettles H and first distillation kettles I. Among them, the volume of the first-level ultrasonic agitator C and the second-level ultrasonic agitator E is 50L, and the volume of the first cooling kettle F and the second cooling kettle G is 1000L. The volume of the first distillation kettle H and the second distillation kettle I is 1500L. The liquid level setting value of the first cooling kettle F and the second cooling kettle G is 65% of its volume, and the liquid level setting value of the first distillation kettle H and the second distillation kettle I is 60% of its volume. The volume of the first mixer B and the second mixer D is 500ml.

[0103] Into batching kettle A (volume 1000L), p-nitroaniline and 50% by mass sulfuric acid solution were continuously added simultaneously, and the feeding rates of the two were 38.4kg / h and 288.6kg / h respectively. After mixing and beating, a sulfuric acid solution containing p-nitroaniline was obtained. The beating temperature was 40°C and the beating time was 1 hour.

[0104] The sulfuric acid solution containing p-nitroaniline is then injected into the primary mixer B at a rate of 327 kg / h. At the same time, bromine is added to the primary mixer B at a feed rate of 53 kg / h. The sulfuric acid solution containing p-nitroaniline is mixed with bromine and then enters the primary ultrasonic agitator group C from the primary mixer B. A part of the material in the primary ultrasonic agitator group C is circulated back to the primary ultrasonic agitator group C through the circulation pump (not shown) through the primary mixer B, and the other part is mixed with a 27.5% hydrogen peroxide solution with a flow rate of 37 kg / h through the secondary mixer D and enters the secondary ultrasonic agitator group E. The mass ratio between the material circulating in the primary ultrasonic agitator group C and the material entering the secondary ultrasonic agitator group E is 8:1. Among them, the jacket heating of the primary ultrasonic agitator group C is about 58°C; the jacket heating of the secondary ultrasonic agitator group E is about 38°C. The temperature of the primary mixer B is about 58°C, and the temperature of the secondary mixer D is about 38°C.

[0105] After bromination reaction in secondary ultrasonic agitator group E, potassium iodide test paper is used to detect that there is no color change and then it is judged that the reaction is complete to obtain a bromo product. A part of the material in secondary ultrasonic agitator group E is returned to secondary ultrasonic agitator group E through the internal circulation of secondary mixer D after a circulating pump (not shown), and another part of the material enters the first cooling kettle F with a flow rate of 417kg / h. The mass ratio of the material circulated in the secondary ultrasonic agitator group E to the first cooling kettle F is 8:1.

[0106] After the liquid level in the first cooling kettle F reaches the set value, switch to the second cooling kettle G. At the same time, the brominated product after cooling is released from the first cooling kettle F for standby use; when the liquid level in the second cooling kettle G reaches the set value, switch to the cooling kettle F, and at the same time release the brominated product after cooling from the second cooling kettle G for standby use, and repeat this cycle.

[0107] After the brominated product is centrifuged by a centrifuge, the sulfuric acid solution in the brominated product is released. The sulfuric acid solution first enters the first distillation kettle H and is heated and concentrated at 95°C. When the liquid level reaches the set value, it is switched to the second distillation kettle I to continue heating and concentrating at 95°C, and the heated and concentrated sulfuric acid solution is released from the first distillation kettle H for standby use; when the liquid level of the second distillation kettle I reaches the set value, it is switched to the first distillation kettle H, and the heated and concentrated sulfuric acid solution is released from the second distillation kettle I for standby use, and this cycle is repeated, and the distilled water is used for the detection of environmental protection indicators.

[0108] The centrifugal product obtained after the above centrifugation is 2,6-dibromo-4-nitroaniline. The purity of 2,6-dibromo-4-nitroaniline measured by high performance liquid chromatography (HPLC) is 99.0%, and the yield is calculated to be 96.7%.

[0109] Example 2

[0110] The sulfuric acid solution from the first distillation kettle H and the second distillation kettle I in Example 1 was used for the continuous synthesis of the second batch of 2,6-dibromo-4-nitroaniline, and the remaining steps were exactly the same as in Example 1, and the distilled water was used for the detection of environmental protection indicators. The purity of 2,6-dibromo-4-nitroaniline was measured by high performance liquid chromatography (HPLC) to be 98.8%, and the yield was calculated to be 97.2%.

[0111] Example 3

[0112] like Figure 1 As shown, the equipment includes a primary ultrasonic agitator group C and a secondary ultrasonic agitator group E, both of which use three-stage series-connected ultrasonic agitators, and the volume of the primary ultrasonic agitator C and the secondary ultrasonic agitator E are both 50 L. The rest of the equipment is exactly the same as in Example 1.

[0113] Para-nitroaniline and a 65% sulfuric acid solution were added to a batching kettle A (volume 1000L) at the same time and continuously, and the feeding rates of the two were 64kg / h and 480kg / h, respectively, and a sulfuric acid solution containing para-nitroaniline was obtained after mixing and beating. The beating temperature was 40°C and the beating time was 1 hour.

[0114] The sulfuric acid solution containing p-nitroaniline is then injected into the primary mixer B at a rate of 544 kg / h. At the same time, bromine is added to the primary mixer B at a feed rate of 85 kg / h, and the sulfuric acid solution containing p-nitroaniline is mixed with bromine and enters the primary ultrasonic agitator group C from the primary mixer B. A part of the material in the primary ultrasonic agitator group C is circulated back to the primary ultrasonic agitator group C through the circulation pump (not shown) through the primary mixer B, and the other part is mixed with a 35% hydrogen peroxide solution with a flow rate of 48.5 kg / h through the secondary mixer D and enters the secondary ultrasonic agitator group E. The mass ratio between the material circulating in the primary ultrasonic agitator group C and the material entering the secondary ultrasonic agitator group E is 10:1. Among them, the jacket heating of the primary ultrasonic agitator group C is about 68°C. The jacket heating of the secondary ultrasonic agitator group E is about 48°C.

[0115] After bromination reaction in secondary ultrasonic agitator group E, potassium iodide test paper is used to detect that there is no color change and then the reaction is judged to be complete to obtain a bromo product. A part of the material in secondary ultrasonic agitator group E is returned to secondary ultrasonic agitator group E through the internal circulation of secondary mixer D after a circulating pump (not shown), and another part of the material enters the first cooling kettle F with a flow rate of 677.5kg / h. The mass ratio between the material of internal circulation in secondary ultrasonic agitator group E and the first cooling kettle F entering is 10:1.

[0116] After the liquid level in the first cooling kettle F reaches the set value, switch to the second cooling kettle G. At the same time, the brominated product after cooling is released from the first cooling kettle F for standby use; when the liquid level in the second cooling kettle G reaches the set value, switch to the cooling kettle F, and at the same time release the brominated product after cooling from the second cooling kettle G for standby use, and repeat this cycle.

[0117] After the brominated product is centrifuged by a centrifuge, the sulfuric acid solution in the brominated product is released. The sulfuric acid solution first enters the first distillation kettle H and is heated and concentrated at 95°C. When the liquid level reaches the set value, it is switched to the second distillation kettle I to continue heating and concentrating at 95°C, and the heated and concentrated sulfuric acid solution is released from the first distillation kettle H for standby use; when the liquid level of the second distillation kettle I reaches the set value, it is switched to the first distillation kettle H, and the heated and concentrated sulfuric acid solution is released from the second distillation kettle I for standby use, and this cycle is repeated, and the distilled water is used for the detection of environmental protection indicators.

[0118] Comparative Example

[0119] In a 1500L jacketed enamel reactor, add 1000Kg of hydrochloric acid with a mass concentration of 24%, start stirring, add 5Kg of dispersant MF and 192kg of p-nitroaniline, and after the feeding is completed, close the feeding hole. Control the temperature in the reactor at about 55°C, slowly add 240Kg of bromine, take 1 hour, and continue to react at about 55°C for 3.0 hours. Then slowly add 163kg of 30% sodium chlorate solution at about 60°C, take 1 hour, and continue to react at about 55°C for 4.0 hours. After the reaction is completed, open the bottom valve to discharge and filter to obtain 400kg of the target product 2,6-dibromo-4-nitroaniline, the purity of which is 97.9% measured by high performance liquid chromatography (HPLC), and the yield is calculated to be 94.4%. The filtered mother liquor water is used for the detection of environmental protection indicators.

[0120] In the production process of comparative example 1, it takes 9 hours from the beginning of adding bromine to the end of the reaction. In contrast, the continuous bromination reaction in Examples 1 and 3 is significantly better than the comparative example, and its production efficiency is also significantly improved, and the generation of three wastes is reduced.

[0121] Performance Testing

[0122] 1. The COD values ​​of the distilled water of Examples 1-3 and the filtered mother liquor water of Comparative Example 1 were determined by potassium dichromate method. The results are shown in Table 1 below.

[0123] 2. The ammonia nitrogen content of the distilled water of Examples 1-3 and the filtered mother liquor water of Comparative Example 1 was measured according to HJ535-2009. The results are shown in Table 1 below.

[0124] 3. GB11889-89 was used to measure the content of aniline compounds in the distilled water of Examples 1-3 and the filtered mother liquor water of Comparative Example 1. The results are shown in Table 1 below.

[0125] 4. The salt content of the distilled water of Examples 1-3 and the filtered mother liquor water of Comparative Example 1 was measured using a salinity meter. The results are shown in Table 1 below.

[0126] Table 1

[0127] Example COD(mg / L) <![CDATA[NH3-N(mg / L)]]> Aniline(mg / L) Salt content (%) Distilled water of Example 1 42 0.6 0.1 Not detected Distilled water of Example 2 48 0.8 0.1 Not detected Distilled water of Example 3 44 0.6 0.1 Not detected Comparative Example Filtered Mother Liquor Water 17009 398 124 2.1

[0128] As can be seen from Table 1, the continuous synthesis method of 2,6-dihalogenated-4-nitroaniline of the present invention greatly reduces the generation of waste, especially substantially does not contain aniline and salt, COD and ammonia nitrogen content is extremely low, it can be seen that the continuous synthesis method of 2,6-dihalogenated-4-nitroaniline of the present invention is more environmentally friendly.

[0129] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0130] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A continuous synthesis method of 2,6-dihalogenated-4-nitroaniline, characterized in that: The following steps are involved: Obtain an acidic solution of p-nitroaniline; The acidic solution of p-nitroaniline and the halogen element are mixed to obtain a mixed product, and the mixed product is continuously transported to a primary ultrasonic stirrer group for pre-reaction and is divided into a first pre-reaction product and a second pre-reaction product; The first pre-reaction product is internally circulated in the first-stage ultrasonic agitator group; the second pre-reaction product is mixed with an oxidizing substance and then transported to the second-stage ultrasonic agitator group; A halogenation reaction is carried out in the secondary ultrasonic agitator group to obtain a halogenated product containing 2,6-dihalogenated-4-nitroaniline.

2. The continuous synthesis method according to claim 1, characterized in that The acidic solution of p-nitroaniline comprises the steps of mixing and slurrying p-nitroaniline in an acidic medium; Preferably, the acidic medium comprises an aqueous solution of an acidic substance; Preferably, in the aqueous solution of the acidic substance, the mass percentage of the acidic substance is 20 to 98%; Preferably, the temperature of the mixing and beating is 30 to 90° C., and the time of the mixing and beating is 0.5 to 3.0 hours; Preferably, the molar ratio of the p-nitroaniline to the acidic substance is 1:2.0-8.

0.

3. The continuous synthesis method according to claim 1 or 2, characterized in that: The molar ratio of the p-nitroaniline to the halogen element is 1:1.0-2.5; Preferably, the temperature of the mixture of the acidic solution of p-nitroaniline and the halogen element is 30 to 90° C., and the temperature of the internal circulation is 30 to 90° C.; Preferably, the mass ratio of the first pre-reaction product to the second pre-reaction product is 5 to 12:

1.

4. The continuous synthesis method according to any one of claims 1 to 3, characterized in that: The molar ratio of the p-nitroaniline to the oxidizing substance is 1:0.5-2.5; Preferably, the oxidizing material is mixed with the second pre-reaction product in the form of an aqueous solution of the oxidizing material; Preferably, in the aqueous solution of the oxidizing substance, the mass percentage of the oxidizing substance is 15% to 35%; Preferably, the temperature at which the second pre-reaction product is mixed with the oxidizing substance is 30-60°C, and the temperature at which the halogenation reaction is performed is 30-60°C.

5. The continuous synthesis method according to any one of claims 1 to 4, characterized in that: The synthesis method further includes separating the halogenated product into a first halogenated product and a second halogenated product; The first halogenated product is internally circulated in the secondary ultrasonic agitator group, and after being mixed with the second pre-reaction product of the next batch and the oxidizing substance, the halogenation reaction is continued; the second halogenated product is separated after cooling to obtain 2,6-dihalogenated-4-nitroaniline; Preferably, the mass ratio of the first halogenated product to the second halogenated product is 5 to 12:

1.

6. An apparatus for implementing the continuous synthesis method according to any one of claims 1 to 5, characterized in that: The device comprises a first-stage ultrasonic agitator group and a second-stage ultrasonic agitator group connected to each other; wherein, The first-stage ultrasonic agitator group has more than two groups of ultrasonic agitators, and the second-stage ultrasonic agitator group has more than two groups of ultrasonic agitators.

7. The device according to claim 6, characterized in that The inlet of the first-stage ultrasonic agitator group is connected to a first-stage mixer, and the inlet of the second-stage ultrasonic agitator group is connected to a second-stage mixer; and the outlet of the first-stage ultrasonic agitator group is connected to the second-stage mixer; Preferably, the outlet of the first-stage ultrasonic agitator group is connected to the first-stage mixer, and the outlet of the second-stage ultrasonic agitator group is connected to the second-stage mixer.

8. The device according to claim 6 or 7, characterized in that The outlet of the secondary ultrasonic agitator group is also connected to a cooling kettle and / or a separation device; Preferably, the outlet of the secondary ultrasonic agitator group is connected to the inlet of the cooling kettle, and the outlet of the cooling kettle is connected to the inlet of the separation device; More preferably, the cooling kettle comprises a first cooling kettle and a second cooling kettle connected in parallel.

9. The device according to claim 8, characterized in that The separation device is also connected to a distillation kettle; Preferably, the outlet of the separation device is connected to the inlet of the distillation kettle; More preferably, the distillation pot comprises a first distillation pot and a second distillation pot connected in parallel.

10. The device according to claim 7 or 9, characterized in that The equipment also includes a batching kettle; Preferably, the outlet of the batching kettle is connected to the inlet of the primary mixer; Preferably, the inlet of the batching kettle is connected to the outlet of the distillation kettle.

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