A preparation device and preparation method for high-purity granular 2,5-dichloroaniline

Abstract

The present invention relates to a preparation device and a preparation method of high-purity granular 2,5-dichloroaniline. The preparation method uses spray drying to quickly and effectively separate 2,5-dichloroaniline from components such as a solvent, aniline, o-chloroaniline and m-chloroaniline in a 2,5-dichloroaniline hydrogenation reaction liquid, and uses an antioxidant to protect the color stability of the product. The high-purity granular 2,5-dichloroaniline prepared by the present invention has a purity of more than 99.8%, and after long-term storage, it still has a white appearance and has good product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis and relates to a method for preparing dichloroaniline, in particular to a device and a method for preparing high-purity granular 2,5-dichloroaniline. Background Art

[0002] 2,5-Dichloroaniline is an important fine chemical intermediate that can be used in the preparation of a variety of pesticides, dyes and pigments. In the pesticide industry, it is a nitrogen fertilizer synergist and can also be used to prepare the herbicide dicamba. In the dye and pigment industry, 2,5-Dichloroaniline is often used to synthesize ice dye scarlet base G, printing and dyeing scarlet cloth color developer and organic pigments.

[0003] At present, the mainstream method for industrial preparation of 2,5-dichloroaniline is catalytic hydrogenation. For example, CN112479900A discloses a method for synthesizing 2,5-dichloroaniline by continuous hydrogenation in a kettle, comprising a feed pump, a preheater, a reactor, a gas-liquid separator and a production pump, wherein the feed pump, the preheater, the reactor, the gas-liquid separator and the production pump are connected in series in sequence, a plurality of hydrogen distribution pipes are arranged in the reactor, a plurality of through holes are opened on the side of the hydrogen distribution pipe, and a catalyst is arranged therein; a 2,5-dichloronitrobenzene solution is input into the reactor by the feed pump, and hydrogen is input into the reactor, and the hydrogen reacts with the 2,5-dichloronitrobenzene solution to generate 2,5-dichloroaniline after being adsorbed by the catalyst. The method uses 2,5-dichloronitrobenzene as a raw material, hydrogen as a reducing agent, and alcohols / water as a solvent, and a hydrogenation reaction is carried out in the presence of a catalyst, and the reaction material is separated and refined to obtain 2,5-dichloroaniline.

[0004] During the reaction process of preparing 2,5-dichloroaniline by catalytic hydrogenation, a small amount of hydrogenation dechlorination byproducts such as o-chloroaniline, m-chloroaniline and aniline are generated. Conventional hydrogenation reactants need to go through steps such as desolventizing, drying and dehydrating, light-removing, decoking and deheavy-removing, and distillation to obtain products with higher purity. The post-processing process is long and the equipment investment is large.

[0005] In addition, the substituents of 2,5-dichloroaniline are relatively active and are easily affected by external factors such as light, heat, and air during the post-processing and refining process, causing some products to have a darker color, which in turn affects the downstream use of the product.

[0006] US4409386A discloses an acid extraction process for separating 3,4-dichloroaniline from 2,3-dichloroaniline and 2,5-dichloroaniline, wherein 3,4-dichloroaniline hydrochloride is selectively formed in a multi-stage extraction device, and an immiscible mixture is formed with 3,4-dichloroaniline, and different types of dichloroaniline are obtained after separation. However, the process introduces additional acid and base reagents, resulting in a large amount of by-product salts, and the multi-stage extraction device occupies a large area, has a high investment cost, and is difficult to implement industrially.

[0007] CN108033885A discloses a method for purifying 2,5-dichloroaniline by vacuum continuous distillation. The method improves the automation level and production efficiency of the post-treatment of 2,5-dichloroaniline, but the continuous distillation equipment is large and the investment is large. At the same time, the purity of the product extracted from the process embodiment is only 99.69%, which cannot meet the product quality requirements of international high-quality products.

[0008] In summary, the existing technology cannot obtain high-purity 2,5-dichloroaniline with stable chromaticity and regular morphology. If a preparation method of high-purity granular 2,5-dichloroaniline can be provided, it will have important industrial significance for obtaining 2,5-dichloroaniline with stable product performance. Summary of the invention

[0009] In view of the shortcomings of the prior art, the object of the present invention is to provide a preparation device and a preparation method for high-purity granular 2,5-dichloroaniline. The preparation device has a simple structure and can separate the substances in the 2,5-dichloroaniline hydrogenation reaction liquid to obtain 2,5-dichloroaniline with a purity of ≥99.8wt%; and its sphericity is ≥0.96 and the appearance is good; the "high purity" in the present invention refers to a purity of ≥99.8wt%.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a device for preparing high-purity granular 2,5-dichloroaniline, the device comprising a mixing unit, a protective gas supply unit, a drying unit, a granulation unit and a separation unit;

[0012] The mixing unit comprises a 2,5-dichloroaniline hydrogenation reaction liquid supply device, an antioxidant solution supply device and a mixing device; the 2,5-dichloroaniline hydrogenation reaction liquid supply device and the antioxidant solution supply device are independently connected to the mixing device;

[0013] The drying unit comprises a drying tower; a first atomizing device is arranged at the top of the drying tower; the bottom of the drying tower is a discharge area; a gas distribution device is arranged between the discharge area and the atomizing device; the discharge port of the mixing device is connected to the first atomizing device;

[0014] The granulation unit comprises an air-cooled granulation tower and a gas-solid separation device; a second atomization device is arranged on the top of the air-cooled granulation tower, and the second atomization device is connected to the discharge area; the bottom discharge port of the air-cooled granulation tower is connected to the gas-solid separation device;

[0015] The separation unit comprises at least two-stage separation devices and a solvent capture device, the top gas outlet of the drying tower is connected to the at least two-stage separation device; the gas outlet of the at least two-stage separation device is connected to the solvent capture device;

[0016] The protective gas supply unit provides protective gas for the mixing device, the drying tower and the air-cooled granulation tower.

[0017] The separation device of the present invention includes at least 2 stages, for example, 2 stages, 3 stages, 4 stages or 5 stages, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. The increase in the number of stages of the separation device is conducive to the recovery of the crude 2,5-dichloroaniline entrained by the gas in the drying tower, but it will greatly increase the cost of the device; therefore, from the perspective of both the cost of the device and the recovery rate of 2,5-dichloroaniline, the number of stages of the separation device is preferably 2-3 stages.

[0018] The separation device of the present invention is a conventional separation device in the art, as long as it can achieve gas-solid separation. Exemplarily, the separation device includes a cyclone separator.

[0019] When the separation device of the present invention is used, the temperature of the separation device is 25-45°C, for example, it can be 25°C, 30°C, 35°C, 40°C or 45°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] The present application controls the temperature of the separation device to be 25-45°C, so that part of the 2,5-dichloroaniline entrained by the gas can be separated from the gas in the separator and then mixed with the bulk product obtained from the drying tower, thereby reducing the drying loss of the drying tower and improving the product yield.

[0021] The solvent capture device of the present invention recovers the solvent in the gas-liquid mixture flowing out of the separation device through the capture liquid. Exemplarily, the capture liquid includes water and / or an alcohol solvent; the temperature of the capture liquid is 15-30°C, for example, it can be 15°C, 18°C, 20°C, 21°C, 24°C, 25°C, 27°C, 28°C or 30°C, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0022] In the present invention, the captured liquid in the solvent capture device is the same as the solvent in the 2,5-dichloroaniline hydrogenation reaction liquid.

[0023] The protective gas supply unit of the present invention further comprises necessary auxiliary devices. Exemplarily, when the protective gas output by the protective gas supply unit needs to be heated, the auxiliary devices comprise heating devices.

[0024] Preferably, the solvent capturing device is connected to an antioxidant solution supply device.

[0025] The present invention connects the solvent capturing device with the antioxidant solution supply device, and reuses the solvent captured by the solvent capturing device to the antioxidant solution supply device, thereby facilitating reduction of solvent consumption.

[0026] Preferably, the bottom outlet of the at least two-stage separation device is connected to the second atomization device.

[0027] The present invention connects the bottom outlet of at least two-stage separation devices with the second atomization device, and transports the 2,5-dichloroaniline crude material recovered by the separation device to the granulation unit, which is beneficial to improving the recovery rate of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid.

[0028] Preferably, the gas outlets of the solvent capture device and the gas-solid separation device are independently connected to the air-cooled granulation tower.

[0029] The present invention enables the gas outlets of the solvent capture device and the gas-solid separation device to be independently connected to the air-cooled granulation tower, and the protective gas separated by the solvent capture device and the protective gas obtained by the gas-solid separation device are reused in the air-cooled granulation tower, thereby reducing the consumption of the protective gas. Exemplarily, the gas-solid separation device includes a cyclone separator.

[0030] In a second aspect, the present invention provides a method for preparing high-purity granular 2,5-dichloroaniline, the preparation method comprising the following steps:

[0031] (1) under a protective atmosphere, uniformly mixing a 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution to obtain a hydrogenation mixed liquid;

[0032] (2) spray drying the mixed solution obtained in step (1) under a protective atmosphere to obtain a crude 2,5-dichloroaniline material;

[0033] (3) The crude 2,5-dichloroaniline obtained in step (2) is cooled and granulated to obtain the high-purity granular 2,5-dichloroaniline.

[0034] The preparation method provided by the present invention can quickly and effectively separate components such as 2,5-dichloroaniline, solvent, aniline, o-chloroaniline and m-chloroaniline in a 2,5-dichloroaniline hydrogenation reaction liquid by spray drying, thereby reducing the heating time of post-processing materials and effectively reducing the generation of tar and high-boiling substances; at the same time, the use of an antioxidant solution can ensure that the color of the high-purity granular 2,5-dichloroaniline finally obtained is stable; and the 2,5-dichloroaniline obtained by cooling and granulating has a uniform morphology, which is conducive to its subsequent use.

[0035] As a preferred technical solution of the preparation method described in the second aspect of the present invention, the preparation method is carried out in the preparation device described in the first aspect.

[0036] Preferably, the content of the solvent in the 2,5-dichloroaniline hydrogenation reaction liquid in step (1) is 50-95wt%, for example, it can be 50wt%, 60wt%, 70wt%, 80wt%, 90wt% or 95wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable, and the remainder is the hydrogenation reaction product.

[0037] The hydrogenation reaction products include aniline, o-chloroaniline, m-chloroaniline, 2,5-dichloroaniline and high boiling substances.

[0038] The high boiling substances mentioned in the present invention refer to substances with a boiling point ≥ 251°C.

[0039] Preferably, the solvent includes water and / or an alcohol solvent.

[0040] The alcohol solvent of the present invention includes anhydrous ethanol and / or anhydrous methanol.

[0041] Preferably, based on the total mass of the hydrogenation reaction product as 100wt%, the mass fraction of the aniline is 0.01-0.2wt%, for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.15wt% or 0.2wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, based on the total mass of the hydrogenation reaction product as 100wt%, the mass fraction of o-chloroaniline is 0.1-0.6wt%, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% or 0.6wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, based on the total mass of the hydrogenation reaction product as 100wt%, the mass fraction of the m-chloroaniline is 0.05-0.5wt%, for example, it can be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, based on the total mass of the hydrogenation reaction product as 100wt%, the mass fraction of the 2,5-dichloroaniline is 98-99.3wt%, for example, 98wt%, 98.2wt%, 98.5wt%, 98.8wt%, 99wt% or 99.3wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, based on 100 wt% of the total mass of the hydrogenation reaction product, the mass fraction of the high boiling point is ≤0.01 wt%.

[0046] Preferably, the antioxidant used in the antioxidant solution in step (1) includes any one of antioxidant 1010, antioxidant 264, antioxidant BHT or triphenylphosphine, or a combination of at least two of them. Typical but non-limiting combinations include a combination of antioxidant 1010 and antioxidant 264, a combination of antioxidant BHT and triphenylphosphine, a combination of antioxidant 1010, antioxidant 264 and antioxidant BHT, a combination of antioxidant 264, antioxidant BHT and triphenylphosphine, or a combination of antioxidant 1010, antioxidant 264, antioxidant BHT and triphenylphosphine.

[0047] Preferably, the concentration of the antioxidant solution in step (1) is 5-15wt%, for example, 5wt%, 8wt%, 10wt%, 12wt% or 15wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] The present invention adopts an antioxidant solution to carry out the reaction, which can ensure homogeneous feeding of the antioxidant and enable the antioxidant to be uniformly mixed with the 2,5-dichloroaniline hydrogenation reaction liquid.

[0049] Preferably, the amount of the antioxidant is 100-1000 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid, for example, it can be 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm or 1000 ppm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, the temperature of the uniform mixing in step (1) is 55-60°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the spray drying method in step (2) comprises: the atomized hydrogenated mixed liquid is brought into countercurrent contact with a hot protective gas to obtain a crude 2,5-dichloroaniline material.

[0052] The method of convective contact described in the present invention includes but is not limited to fluidized convection, spray convection or centrifugal convection, and the present invention does not make any specific limitation here, as long as the hydrogenation mixture can be fully contacted with the thermal protection gas.

[0053] Preferably, the temperature of the thermal protection gas is 100-240°C, for example, it can be 100°C, 120°C, 150°C, 160°C, 180°C, 200°C, 210°C or 240°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] Preferably, the temperature of the obtained crude 2,5-dichloroaniline is 55-125°C, for example, 55°C, 65°C, 75°C, 85°C, 95°C, 105°C, 115°C or 125°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, in the present invention, the temperature of the discharge zone is controlled so that the temperature of the crude 2,5-dichloroaniline is 55-125°C.

[0056] Preferably, based on the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%.

[0057] Preferably, the present invention further comprises the steps of recovering the crude 2,5-dichloroaniline obtained from the separation device and then cooling and granulating the recovered 2,5-dichloroaniline.

[0058] Taking the total mass of the crude 2,5-dichloroaniline obtained from the separation device as 100wt%, the mass fraction of aniline is ≤0.05wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%.

[0059] Preferably, the cooling rate of the cooling granulation in step (3) is 20-50°C / min, for example, it can be 20°C / min, 25°C / min, 30°C / min, 35°C / min, 40°C / min, 45°C / min or 50°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] Preferably, the cooling granulation method in step (3) comprises: a protective gas is brought into countercurrent contact with the 2,5-dichloroaniline crude material obtained in step (2) to perform heat exchange.

[0061] The temperature of the protective gas in the present invention is room temperature. The present invention does not further limit the flow rate of the protective gas, as long as the cooling rate of the cooling granulation is 20-50°C / min.

[0062] The protective gas described in the present invention includes nitrogen and / or an inert gas, and the inert gas includes any one of helium, neon or argon or a combination of at least two of them. Typical but non-limiting combinations include a combination of helium and neon, a combination of neon and argon, a combination of helium and argon, or a combination of helium, neon and argon.

[0063] As a preferred technical solution of the preparation method described in the second aspect of the present invention, the preparation method comprises the following steps:

[0064] (1) under a protective atmosphere, uniformly mixing a 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution at 55-60° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution comprises any one of antioxidant 1010, antioxidant 264, antioxidant BHT or triphenylphosphine, or a combination of at least two thereof; the concentration of the antioxidant solution is 5-15 wt %; the amount of the antioxidant used is 100-1000 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid;

[0065] (2) under a protective atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with a hot protective gas at a temperature of 100-240° C. by convection, to obtain a crude 2,5-dichloroaniline material at a temperature of 55-125° C.;

[0066] Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0067] (3) The protective gas is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and a cooling rate of 20-50° C. / min is used for granulation to obtain the high-purity granular 2,5-dichloroaniline.

[0068] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) The preparation method provided by the present invention can quickly and effectively separate 2,5-dichloroaniline, solvent, aniline, o-chloroaniline and m-chloroaniline components in the 2,5-dichloroaniline hydrogenation reaction liquid by spray drying, so that the purity of the obtained high-purity granular 2,5-dichloroaniline is ≥99.9wt%; at the same time, the use of the antioxidant solution can ensure the color stability of the finally obtained high-purity granular 2,5-dichloroaniline; the 2,5-dichloroaniline obtained by cooling and granulation has a uniform morphology, which is conducive to its subsequent utilization;

[0071] (2) The preparation method provided by the present invention uses spray drying and cooling granulation to make the residence time of the material in the drying tower ≤300s and the residence time in the air-cooled granulation tower ≤180s, thereby effectively controlling the time of post-processing of the material, effectively reducing the generation of tar and high-boiling substances, and further ensuring that the purity of the obtained high-purity granular 2,5-dichloroaniline is ≥99.9wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 The present invention provides a schematic structural diagram of a device for preparing high-purity granular 2,5-dichloroaniline.

[0073] Wherein: 1-1, 2,5-dichloroaniline hydrogenation reaction liquid supply device; 1-2, antioxidant solution supply device; 1-3, mixing device; 2-1, drying tower; 2-2, first atomizing device; 2-3, discharge area; 2-4, gas distribution device; 3-1, air-cooled granulation tower; 3-2, second atomizing device; 3-3, gas-solid separation device; 4-1, separation device; 4-2, solvent capture device; 5-1, protective gas supply unit; 5-2, heating device. DETAILED DESCRIPTION

[0074] The present invention provides a Figure 1The preparation device of high-purity granular 2,5-dichloroaniline shown in the figure includes a mixing unit, a protective gas supply unit 5-1, a drying unit, a granulation unit and a separation unit; the necessary valves and connecting pipes in the preparation device of the present invention are no longer specifically limited, and technicians in this field can make reasonable choices according to needs.

[0075] The mixing unit comprises a 2,5-dichloroaniline hydrogenation reaction liquid supply device 1-1, an antioxidant solution supply device 1-2 and a mixing device 1-3; the 2,5-dichloroaniline hydrogenation reaction liquid supply device 1-1 and the antioxidant solution supply device 1-2 are independently connected to the mixing device 1-3;

[0076] The drying unit comprises a drying tower 2-1; a first atomizing device 2-2 is arranged at the top of the drying tower 2-1; a discharge area 2-3 is arranged at the bottom of the drying tower 2-1; a gas distribution device 2-4 is arranged between the discharge area 2-3 and the atomizing device; and a discharge port of the mixing device 1-3 is connected to the first atomizing device 2-2;

[0077] The granulation unit includes an air-cooled granulation tower 3-1 and a gas-solid separation device 3-3; a second atomization device 3-2 is provided on the top of the air-cooled granulation tower 3-1, and the second atomization device 3-2 is connected to the discharge area 2-3; the bottom discharge port of the air-cooled granulation tower 3-1 is connected to the gas-solid separation device 3-3;

[0078] The separation unit comprises at least a two-stage separation device 4-1 and a solvent capture device 4-2, the top gas outlet of the drying tower 2-1 is connected to the at least two-stage separation device 4-1; the gas outlet of the at least two-stage separation device 4-1 is connected to the solvent capture device 4-2;

[0079] The protective gas supply unit 5 - 1 provides protective gas for the mixing device 1 - 3 , the drying tower 2 - 1 and the air-cooled granulation tower 3 - 1 .

[0080] When the preparation device provided by the present invention is used, the 2,5-dichloroaniline hydrogenation reaction liquid is added to the mixing device 1-3 by the 2,5-dichloroaniline hydrogenation reaction liquid supply device 1-1, and the antioxidant solution is added to the mixing device 1-3 by the antioxidant solution supply device 1-2, so that the 2,5-dichloroaniline hydrogenation reaction liquid and the antioxidant solution are uniformly mixed in the mixing device 1-3.

[0081] The hot protective gas provided by the protective gas supply unit 5-1 enters the drying tower 2-1 through the gas distribution device 2-4, and adjusts the temperature of the spray drying in the drying tower 2-1 and the temperature of the discharge area 2-3 to stabilize the temperature of the corresponding areas. Then, the hydrogenated mixed liquid in the mixing device 1-3 is introduced into the top of the drying tower 2-1 through the first atomizing device 2-2, and the hydrogenated mixed liquid is fully convectively contacted with the hot protective gas. The obtained 2,5-dichloroaniline crude material enters the air-cooled granulation tower 3-1 through the discharge area 2-3 of the drying tower 2-1, and is atomized by the second atomizing device 3-2.

[0082] In some embodiments, the protective gas supply unit 5 - 1 further includes a heating device 5 - 2 .

[0083] The gas in the air-cooled granulation tower 3-1 contacts the atomized 2,5-dichloroaniline crude material for rapid heat exchange, and is rapidly condensed into regular and uniform particles, which are then separated by spiral sinking in the gas-solid separation device 3-3 to obtain the high-purity granular 2,5-dichloroaniline.

[0084] The top gas outlet of the drying tower 2-1 is connected to at least a second-stage separation device 4-1, wherein the at least second-stage separation device 4-1 is connected to recover the 2,5-dichloroaniline crude material in the top gas outlet of the drying tower 2-1. The tail gas flowing out of the at least second-stage separation device 4-1 enters the solvent capture device 4-2, and the solvent capture device 4-2 is used to collect the solvent entrained in the tail gas.

[0085] In some embodiments, the solvent capture device 4 - 2 is connected to the antioxidant solution supply device 1 - 2 .

[0086] In some embodiments, the bottom outlet of the at least two-stage separation device 4-1 is connected to the second atomization device 3-2.

[0087] By connecting the bottom outlet of at least the second-stage separation device 4-1 to the second atomization device 3-2, the crude 2,5-dichloroaniline recovered by the separation device 4-1 and the crude 2,5-dichloroaniline discharged from the discharge area 2-3 can enter the air-cooled granulation tower 3-1 together.

[0088] In some embodiments, the gas outlets of the solvent capture device 4-2 and the gas-solid separation device 3-3 are independently connected to the air-cooled granulation tower 3-1.

[0089] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0090] Example 1

[0091] This embodiment provides a device for preparing high-purity granular 2,5-dichloroaniline, which includes a mixing unit, a protective gas supply unit 5-1, a drying unit, a granulation unit, and a separation unit.

[0092] The mixing unit comprises a 2,5-dichloroaniline hydrogenation reaction liquid supply device 1-1, an antioxidant solution supply device 1-2 and a mixing device 1-3; the 2,5-dichloroaniline hydrogenation reaction liquid supply device 1-1 and the antioxidant solution supply device 1-2 are independently connected to the mixing device 1-3 respectively; the mixing device 1-3 is a stirred tank.

[0093] The drying unit includes a drying tower 2-1; a first atomizing device 2-2 is arranged at the top of the drying tower 2-1; the bottom of the drying tower 2-1 is a discharge area 2-3; a gas distribution device 2-4 is arranged between the discharge area 2-3 and the atomizing device; and the discharge port of the mixing device 1-3 is connected to the first atomizing device 2-2.

[0094] The granulation unit includes an air-cooled granulation tower 3-1 and a gas-solid separation device 3-3; a second atomization device 3-2 is arranged on the top of the air-cooled granulation tower 3-1, and the second atomization device 3-2 is connected to the discharge area 2-3; the bottom discharge port of the air-cooled granulation tower 3-1 is connected to the gas-solid separation device 3-3; the gas-solid separation device 3-3 is a cyclone separator.

[0095] The separation unit includes a two-stage separation device 4-1 and a solvent capture device 4-2. The top gas outlet of the drying tower 2-1 is connected to the two-stage separation device 4-1; the gas outlet of the two-stage separation device 4-1 is connected to the solvent capture device 4-2. The solvent capture device 4-2 recovers the solvent in the gas-liquid mixture flowing out of the separation device 4-1 through the capture liquid. The two-stage separation device 4-1 is a two-stage cyclone separator.

[0096] The protective gas supply unit 5 - 1 provides protective gas for the mixing device 1 - 3 , the drying tower 2 - 1 and the air-cooled granulation tower 3 - 1 .

[0097] The solvent collection device 4 - 2 is connected to the antioxidant solution supply device 1 - 2 .

[0098] The bottom outlet of the two-stage separation device 4-1 is connected to the second atomization device 3-2.

[0099] The gas outlets of the solvent capture device 4-2 and the gas-solid separation device 3-3 are independently connected to the air-cooled granulation tower 3-1.

[0100] The solvent content in the 2,5-dichloroaniline hydrogenation reaction liquid treated by the present invention is 50-95wt%, and the balance is hydrogenation reaction products; the hydrogenation reaction products include aniline, o-chloroaniline, m-chloroaniline, 2,5-dichloroaniline and high boiling substances; the solvent includes water and / or alcohol solvents; based on the total mass of the hydrogenation reaction products as 100wt%, the mass fraction of the aniline is 0.01-0.2wt%, the mass fraction of o-chloroaniline is 0.1-0.6wt%, the mass fraction of m-chloroaniline is 0.05-0.5wt%, the mass fraction of 2,5-dichloroaniline is 98-99.3wt%, and the mass fraction of the high boiling substances is less than or equal to 0.01wt%.

[0101] Due to space limitations and for the convenience of illustrating the technical solution of the present invention, in the following application example, based on the total mass of the hydrogenation reaction product as 100wt%, the mass fraction of aniline is 0.2wt%, the mass fraction of o-chloroaniline is 0.6wt%, the mass fraction of m-chloroaniline is 0.5wt%, the mass fraction of 2,5-dichloroaniline is 98.69wt%, and the mass fraction of high boiling substances is 0.01wt%.

[0102] Application Example 1

[0103] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. The preparation method is carried out in the preparation device described in Example 1 and comprises the following steps:

[0104] (1) under a nitrogen atmosphere, 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution are uniformly mixed at 58° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution is antioxidant 1010; the concentration of the antioxidant solution is 10 wt %; the amount of the antioxidant used is 500 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid;

[0105] (2) under a nitrogen atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with hot nitrogen at a temperature of 100° C. by convection, to obtain a crude 2,5-dichloroaniline at a temperature of 55° C.;

[0106] Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0107] The crude 2,5-dichloroaniline in the atomized tail gas is recovered at a recovery temperature of 35° C. The temperature of the solvent capture device is 25° C.; based on the total mass of the crude 2,5-dichloroaniline obtained from the atomized tail gas being 100wt%, the mass fraction of aniline is ≤0.05wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0108] (3) nitrogen is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and granulation is performed at a cooling rate of 20° C. / min to obtain the high-purity granular 2,5-dichloroaniline.

[0109] The solvent content of the 2,5-dichloroaniline hydrogenation reaction liquid treated in this application example is 70 wt %, and the solvent is water.

[0110] Application Example 2

[0111] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. The preparation method is carried out in the preparation device described in Example 1 and comprises the following steps:

[0112] (1) under a nitrogen atmosphere, uniformly mixing a 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution at 55° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution is antioxidant 264; the concentration of the antioxidant solution is 5 wt %; the amount of the antioxidant used is 200 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid;

[0113] (2) under a nitrogen atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with hot nitrogen at a temperature of 150° C. by convection, to obtain a crude 2,5-dichloroaniline at a temperature of 70° C.;

[0114] Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0115] The crude 2,5-dichloroaniline in the atomized tail gas is recovered at a recovery temperature of 30° C. The temperature of the solvent capture device is 30° C.; based on the total mass of the crude 2,5-dichloroaniline obtained from the atomized tail gas being 100wt%, the mass fraction of aniline is ≤0.05wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0116] (3) nitrogen is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and granulation is performed at a cooling rate of 25° C. / min to obtain the high-purity granular 2,5-dichloroaniline.

[0117] The composition of the 2,5-dichloroaniline hydrogenation reaction liquid treated in this application example is the same as that in application example 1.

[0118] Application Example 3

[0119] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. The preparation method is carried out in the preparation device described in Example 1 and comprises the following steps:

[0120] (1) under a nitrogen atmosphere, 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution are uniformly mixed at 60° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution is an antioxidant 264 and triphenylphosphine in a mass ratio of 1:1; the concentration of the antioxidant solution is 15 wt %; the amount of the antioxidant used is 200 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid;

[0121] (2) under a nitrogen atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with hot nitrogen at a temperature of 200° C. by convection, to obtain a crude 2,5-dichloroaniline at a temperature of 80° C.;

[0122] Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0123] The crude 2,5-dichloroaniline in the atomized tail gas is recovered at a recovery temperature of 45° C. The temperature of the solvent capture device is 20° C. Taking the total mass of the crude 2,5-dichloroaniline obtained from the atomized tail gas as 100wt%, the mass fraction of aniline is ≤0.05wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0124] (3) nitrogen is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and granulation is performed at a cooling rate of 30° C. / min to obtain the high-purity granular 2,5-dichloroaniline.

[0125] The composition of the 2,5-dichloroaniline hydrogenation reaction liquid treated in this application example is the same as that in application example 1.

[0126] Application Example 4

[0127] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. The preparation method is carried out in the preparation device described in Example 1 and comprises the following steps:

[0128] (1) under a nitrogen atmosphere, uniformly mixing a 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution at 58° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution is an antioxidant BHT; the concentration of the antioxidant solution is 10 wt %; the amount of the antioxidant used is 1000 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid;

[0129] (2) under a nitrogen atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with hot nitrogen at a temperature of 240° C. by convection current to obtain a crude 2,5-dichloroaniline at a temperature of 85° C.;

[0130] Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0131] The crude 2,5-dichloroaniline in the atomized tail gas is recovered at a recovery temperature of 25° C. The temperature of the solvent capture device is 25° C.; based on the total mass of the crude 2,5-dichloroaniline obtained from the atomized tail gas being 100wt%, the mass fraction of aniline is ≤0.05wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0132] (3) nitrogen is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and granulation is performed at a cooling rate of 40° C. / min to obtain the high-purity granular 2,5-dichloroaniline.

[0133] The composition of the 2,5-dichloroaniline hydrogenation reaction liquid treated in this application example is the same as that in application example 1.

[0134] Application Example 5

[0135] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. The preparation method is carried out in the preparation device described in Example 1 and comprises the following steps:

[0136] (1) under a nitrogen atmosphere, 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution are uniformly mixed at 58° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution is an antioxidant 1010 and triphenylphosphine in a mass ratio of 1:1; the concentration of the antioxidant solution is 10 wt %; the amount of the antioxidant used is 100 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid;

[0137] (2) under a nitrogen atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with hot nitrogen at a temperature of 180° C. by convection current to obtain a crude 2,5-dichloroaniline at a temperature of 125° C.;

[0138] Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0139] The crude 2,5-dichloroaniline in the atomized tail gas is recovered at a recovery temperature of 45° C. The temperature of the solvent capture device is 25° C.; based on the total mass of the crude 2,5-dichloroaniline obtained from the atomized tail gas being 100wt%, the mass fraction of aniline is ≤0.05wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%;

[0140] (3) nitrogen is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and granulation is performed at a cooling rate of 50° C. / min to obtain the high-purity granular 2,5-dichloroaniline.

[0141] The composition of the 2,5-dichloroaniline hydrogenation reaction liquid treated in this application example is the same as that in application example 1.

[0142] Application Example 6

[0143] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. Except that the solvent in the 2,5-dichloroaniline hydrogenation reaction liquid and the capture liquid of the solvent capture device are ethanol, the rest are the same as Application Example 1.

[0144] Application Example 7

[0145] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. Except that the amount of antioxidant used is 80 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid, the rest is the same as that of Application Example 1.

[0146] Application Example 8

[0147] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. Except that the amount of antioxidant used is 1200 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid, the rest is the same as that of Application Example 1.

[0148] Application Example 9

[0149] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. Except that the temperature of the crude 2,5-dichloroaniline obtained by atomization is 45°C, the rest is the same as that of Application Example 1.

[0150] Application Example 10

[0151] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline. Except that the temperature of the crude 2,5-dichloroaniline obtained by atomization is 135° C., the rest is the same as that of Application Example 1.

[0152] Application Example 11

[0153] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline, which is the same as application example 1 except that the temperature of the hot nitrogen is 80°C.

[0154] Application Example 12

[0155] This application example provides a method for preparing high-purity granular 2,5-dichloroaniline, which is the same as application example 1 except that the temperature of the hot nitrogen is 250°C.

[0156] Comparative application example 1

[0157] This comparative application example provides a method for preparing 2,5-dichloroaniline, which is the same as Application Example 1 except that the antioxidant solution in step (1) is replaced by an equal volume of solvent water.

[0158] Performance Characterization

[0159] The compositions of the high-purity granular 2,5-dichloroaniline obtained in Examples 1-12 and the 2,5-dichloroaniline obtained in Comparative Application Example 1 were tested by gas chromatography.

[0160] The results are shown in Table 1.

[0161] Table 1

[0162]

[0163]

[0164] The sphericity and color stability of the high-purity granular 2,5-dichloroaniline obtained in the corresponding application examples 1-12 and the 2,5-dichloroaniline obtained in the comparative application example 1 were tested; the color stability test method is: the high-purity granular 2,5-dichloroaniline obtained in the application examples 1-12 and the 2,5-dichloroaniline obtained in the comparative application example 1 were stored for 30 days, and the color changes were observed; the results are shown in Table 2.

[0165] Table 2

[0166]

[0167]

[0168] In summary, the preparation method provided by the present invention can quickly and effectively separate the components such as 2,5-dichloroaniline, solvent, aniline, o-chloroaniline and m-chloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid by spray drying, control the time of material post-treatment within 15 minutes, effectively reduce the generation of tar and high boiling points, and make the purity of the obtained high-purity granular 2,5-dichloroaniline ≥99.9wt%; at the same time, the use of the antioxidant solution can ensure the color stability of the finally obtained high-purity granular 2,5-dichloroaniline; the 2,5-dichloroaniline obtained by cooling and granulation has a uniform morphology, which is conducive to its subsequent use.

[0169] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for preparing high-purity granular 2,5-dichloroaniline with a purity of ≥99.8wt%, characterized in that: The preparation device comprises a mixing unit, a protective gas supply unit, a drying unit, a granulation unit and a separation unit; The mixing unit comprises a 2,5-dichloroaniline hydrogenation reaction liquid supply device, an antioxidant solution supply device and a mixing device; the 2,5-dichloroaniline hydrogenation reaction liquid supply device and the antioxidant solution supply device are independently connected to the mixing device; The drying unit comprises a drying tower; a first atomizing device is arranged at the top of the drying tower; the bottom of the drying tower is a discharge area; a gas distribution device is arranged between the discharge area and the atomizing device; the discharge port of the mixing device is connected to the first atomizing device; The granulation unit comprises an air-cooled granulation tower and a gas-solid separation device; a second atomization device is arranged on the top of the air-cooled granulation tower, and the second atomization device is connected to the discharge area; the bottom discharge port of the air-cooled granulation tower is connected to the gas-solid separation device; The separation unit comprises at least two-stage separation devices and a solvent capture device, the top gas outlet of the drying tower is connected to the at least two-stage separation device; the gas outlet of the at least two-stage separation device is connected to the solvent capture device; The protective gas supply unit provides protective gas for the mixing device, the drying tower and the air-cooled granulation tower.

2. The preparation device according to claim 1, characterized in that: The solvent collection device is connected to the antioxidant solution supply device.

3. The preparation device according to claim 1, characterized in that: The bottom outlet of the at least two-stage separation device is connected to the second atomization device.

4. The preparation device according to claim 1, characterized in that: The gas outlets of the solvent capture device and the gas-solid separation device are independently connected to the air-cooled granulation tower.

5. A method for preparing high-purity granular 2,5-dichloroaniline with a purity of ≥99.8wt%, characterized in that: The preparation method comprises the following steps: (1) under a protective atmosphere, uniformly mixing a 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution to obtain a hydrogenation mixed liquid; wherein the content of the solvent in the 2,5-dichloroaniline hydrogenation reaction liquid is 50-95 wt %, and the remainder is a hydrogenation reaction product; The hydrogenation reaction products include aniline, o-chloroaniline, m-chloroaniline, 2,5-dichloroaniline and high boiling substances; the high boiling substances refer to substances with a boiling point of ≥251°C; Based on the total mass of the hydrogenation reaction product as 100wt%, the mass fraction of aniline is 0.01-0.2wt%; the mass fraction of o-chloroaniline is 0.1-0.6wt%; the mass fraction of m-chloroaniline is 0.05-0.5wt%; the mass fraction of 2,5-dichloroaniline is 98-99.3wt%; the mass fraction of high boiling substances is ≤0.01wt%; The antioxidant used in the antioxidant solution includes any one of antioxidant 1010, antioxidant 264, antioxidant BHT or triphenylphosphine or a combination of at least two thereof; the concentration of the antioxidant solution is 5-15wt%; the amount of the antioxidant used is 100-1000ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid; (2) spray drying the hydrogenated mixed liquid obtained in step (1) under a protective atmosphere to obtain a crude 2,5-dichloroaniline material; the spray drying method comprises: the atomized hydrogenated mixed liquid is convectively contacted with a hot protective gas to obtain a crude 2,5-dichloroaniline material; the temperature of the hot protective gas is 240° C.; (3) The crude 2,5-dichloroaniline obtained in step (2) is cooled and granulated to obtain the high-purity granular 2,5-dichloroaniline.

6. The preparation method according to claim 5, characterized in that: The solvent includes water and / or alcohol solvent.

7. The preparation method according to claim 5, characterized in that: The temperature of the uniform mixing in step (1) is 55-60°C.

8. The preparation method according to claim 5, characterized in that: The temperature of the obtained 2,5-dichloroaniline crude material is 55-125°C.

9. The preparation method according to claim 5, characterized in that: Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%.

10. The preparation method according to claim 5, characterized in that: The cooling rate of the cooling granulation in step (3) is 20-50°C / min.

11. The preparation method according to claim 5, characterized in that: The cooling granulation method in step (3) comprises: a protective gas is brought into countercurrent contact with the 2,5-dichloroaniline crude material obtained in step (2) to perform heat exchange.

12. The preparation method according to claim 5, characterized in that: The preparation method comprises the following steps: (1) under a protective atmosphere, uniformly mixing a 2,5-dichloroaniline hydrogenation reaction liquid and an antioxidant solution at 55-60° C. to obtain a hydrogenation mixed liquid; the antioxidant used in the antioxidant solution comprises any one of antioxidant 1010, antioxidant 264, antioxidant BHT or triphenylphosphine, or a combination of at least two thereof; the concentration of the antioxidant solution is 5-15 wt %; the amount of the antioxidant used is 100-1000 ppm of the mass of 2,5-dichloroaniline in the 2,5-dichloroaniline hydrogenation reaction liquid; (2) under a protective atmosphere, atomizing the hydrogenated mixed liquid obtained in step (1), and then contacting it with a hot protective gas at a temperature of 240° C. by convection, to obtain a crude 2,5-dichloroaniline material at a temperature of 55-125° C.; Taking the total mass of the obtained crude 2,5-dichloroaniline as 100wt%, the mass fraction of aniline is ≤0.03wt%, the mass fraction of o-chloroaniline is ≤0.05wt%, the mass fraction of m-chloroaniline is ≤0.03wt%, the mass fraction of 2,5-dichloroaniline is ≥99.8wt%, the mass fraction of high boiling substances is ≤0.01wt%, and the mass fraction of the solvent is ≤0.1wt%; (3) The protective gas is brought into countercurrent contact with the crude 2,5-dichloroaniline obtained in step (2) to perform heat exchange, and a cooling rate of 20-50° C. / min is used for granulation to obtain the high-purity granular 2,5-dichloroaniline.

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