Post-treatment method of benzotriazole synthesis liquid

Abstract

The present invention provides a post-treatment method for a benzotriazole synthetic liquid. The method comprises the following steps: washing the benzotriazole synthetic liquid with water to obtain a water layer and an oil layer; adding water to the oil layer to crystallize the solution, filtering to obtain a filter cake; melting and crystallizing the filter cake to obtain a crystal layer, sweating and melting the crystal layer to obtain a molten liquid; vibrating and molding the molten liquid to obtain benzotriazole. The present invention obtains a high-purity benzotriazole molten liquid with a purity of ≥99.5% by subjecting the benzotriazole synthetic liquid to a two-step crystallization process of solution crystallization and melt crystallization, and then vibrating and molding to prepare spherical particles with a large bulk density. Not only is the overall processing temperature low, inherently safe, low in energy consumption, and green and environmentally friendly, but the molding process is simple to operate and the particle quality is high, and the purity, strength and particle bulk density of the benzotriazole product are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemical industry, in particular to a post-treatment method of benzotriazole synthesis liquid. Background Art

[0002] Benzotriazole (BTA) is mostly used as a vapor phase corrosion inhibitor, circulating water treatment agent, automotive antifreeze, photographic antifogging agent, polymer stabilizer, plant growth regulator, lubricating oil additive, ultraviolet absorber, etc. for copper and copper alloys. It is an important fine chemical product. The main methods for synthesizing benzotriazole are o-phenylenediamine method, o-nitrophenylhydrazine method, benzimidazolone method, etc., among which the o-phenylenediamine method is a more commonly used method. The o-phenylenediamine method is further divided into the o-phenylenediamine normal pressure method and the o-phenylenediamine high pressure method. Since the o-phenylenediamine high pressure method has a higher yield, it is more widely used. The o-phenylenediamine high pressure method uses o-phenylenediamine and sodium nitrite as raw materials, reacts at 220-300°C and pressure of 3-6MPa to generate benzotriazole sodium salt, and then adjusts the pH to 6 with acid, and then undergoes a series of post-treatments to obtain high-purity benzotriazole. The post-processing and refining process after acid adjustment is critical and directly affects the quality of the finished product. At the same time, the molding process of benzotriazole has always been a difficult problem.

[0003] Patent CN201910461699.4 discloses a solution for continuously synthesizing BTA sodium salt using a tubular reactor, and then using a distillation method for post-processing and purification to obtain a qualified BTA product. However, the post-processing and purification method using distillation has the defects of high reaction temperature, poor safety, and high energy consumption. Patent CN 202020043500.4 uses relatively rotating rollers to roll and granulate BTA powder particles. This method not only produces dust pollution, but also the prepared particles are weak and easy to break. In addition, most of the products on the market use a rotary drum slicing process to slice and granulate BTA. Although this granulation process is a relatively mature process, it also has the defects of large dust pollution and low particle bulk density. Therefore, it is of great practical significance to explore a low-energy, green and safe BTA refining process and a high-quality molding process. Summary of the invention

[0004] The main purpose of the present invention is to provide a post-treatment method for benzotriazole synthesis liquid to solve the problem that the benzotriazole refining process in the prior art cannot take into account the cost, environmental protection and quality.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a post-treatment method for a benzotriazole synthetic liquid, comprising the following steps: step S1, washing the benzotriazole synthetic liquid with water to obtain a water layer and an oil layer; step S2, adding water to the oil layer to crystallize the solution, and obtaining a filter cake after filtering; step S3, melting and crystallizing the filter cake to obtain a crystal layer, and sweating and melting the crystal layer to obtain a molten liquid; step S4, vibrating and molding the molten liquid to obtain benzotriazole.

[0006] Further, step S2 comprises: adding water to the oil layer to form a mixture, heating the mixture for the first time to a first crystallization starting temperature, then cooling the mixture for the first time to a first crystallization endpoint temperature to crystallize the solution, and filtering to obtain a filtrate and a filter cake; preferably, the first crystallization starting temperature is 65-75°C, the first crystallization endpoint temperature is 0-25°C, and the temperature is kept constant for 30-90 minutes after reaching the first crystallization endpoint temperature; the heating rate of the first heating is 1-100°C / h, and the cooling rate of the first cooling is 1-50°C / h; more preferably, the mass ratio of water to the oil layer is (9-20):1; further preferably, after obtaining the filtrate, it is returned to the water washing step.

[0007] Furthermore, in step S3, the filter cake is dried and then heated for a second time to a second crystallization starting temperature, and then cooled for a second time to a second crystallization end temperature to perform melt crystallization to obtain an uncrystallized mother liquor and a crystal layer; preferably, vacuum drying is used for drying, and the drying temperature is ≤90°C; more preferably, after obtaining the uncrystallized mother liquor, it is returned to the solution crystallization step.

[0008] Furthermore, the second crystallization starting point temperature is 98-105°C, the second crystallization endpoint temperature is 90-95°C, and the temperature is kept constant for 30-90 minutes after reaching the second crystallization endpoint temperature; the second heating rate is 0.5-30°C / h, and the second cooling rate is 0.5-4°C / h.

[0009] Further, in step S3, the sweating and melting process includes: heating the crystal layer for a third time to the sweating temperature to sweat, obtaining a sweating liquid and a remaining crystal layer, melting the remaining crystal layer to obtain a molten liquid; preferably, after obtaining the sweating liquid, returning it to the melting crystallization step.

[0010] Furthermore, the sweating temperature is 94-98°C, and the temperature is kept constant for 30-90 minutes after reaching the sweating temperature; the heating rate of the third heating is 1.5-10°C / h.

[0011] Further, in step S4, the vibration molding process is carried out in a vibration molding device, which includes an exciter, a connecting rod, a nozzle, a jet, a transmission pump and a layer crystallizer. The vibration molding process includes: the molten liquid in the layer crystallizer is ejected from the nozzle through the transmission pump to form a jet, the nozzle and the exciter are connected by a connecting rod to make the jet vibrate, and then cooled and molded to obtain benzotriazole.

[0012] Furthermore, the aperture of the nozzle is 0.1-3 mm, the velocity of the jet is 0.71-4 m / s, and the vibration frequency of the exciter is 100-400 Hz; preferably, the transmission pump is a screw pump, a gear pump or a centrifugal pump.

[0013] Furthermore, in step S1, the water washing temperature is 55-70°C; preferably, the mass ratio of water to benzotriazole synthesis liquid is (0.5-2):1.

[0014] Furthermore, after obtaining the water layer, step S1 also includes: sequentially performing water layer crystallization and water layer filtering on the water layer to obtain a water layer filter cake, and returning the water layer filter cake to the water washing step; preferably, the crystallization starting temperature of the water layer crystallization is 55-70°C, and the crystallization end temperature is 0-20°C.

[0015] The present invention provides a benzotriazole post-processing method with low energy consumption, green safety and excellent product quality. The benzotriazole synthetic liquid is subjected to a two-step crystallization process of solution crystallization and melt crystallization to obtain a high-purity benzotriazole melt with a purity of ≥99.5%, and then vibrated to form spherical particles with a large bulk density. The above-mentioned crystallization treatment temperature can be controlled below 100°C, eliminating the risk of thermal decomposition and explosion of benzotriazole in traditional methods; the vibration molding method can not only eliminate the dust pollution caused by traditional processes, but also make the benzotriazole product particles have better strength. In summary, the post-processing method of the present invention not only has a low overall processing temperature, is inherently safe, has low energy consumption, and is green and environmentally friendly, but also has a simple molding process and high particle quality, and the purity, strength and particle bulk density of the benzotriazole product are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 A flow chart of post-treatment of benzotriazole synthesis liquid according to Example 1 of the present invention is shown;

[0018] Figure 2 A diagram showing a vibration forming device for post-treatment of a benzotriazole synthesis liquid according to an embodiment of the present invention; and

[0019] Figure 3 An enlarged view of the nozzle of a vibration molding device for post-treatment of a benzotriazole synthetic liquid according to an embodiment of the present invention is shown.

[0020] The above drawings include the following reference numerals:

[0021] 1. Vibrator; 2. Connecting rod; 3. Nozzle; 4. Jet; 5. Transmission pump; 6. Layer crystallizer. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] It should be noted that the benzotriazole synthetic liquid of the present invention refers to the benzotriazole oil phase obtained by reacting benzotriazole sodium salt using a high-pressure o-phenylenediamine method and adjusting the pH to 5-7 with an acid and then separating the layers. The acid for adjusting the pH can be sulfuric acid, hydrochloric acid or nitric acid.

[0024] As described in the background of the present invention, there is a problem in the prior art that the benzotriazole refining process cannot take into account cost, environmental protection and quality. In order to solve the above problems, in a typical embodiment of the present invention, a post-processing method of a benzotriazole synthetic liquid is provided, comprising the following steps: step S1, washing the benzotriazole synthetic liquid with water to obtain a water layer and an oil layer; step S2, adding water to the oil layer to crystallize the solution, and filtering to obtain a filter cake; step S3, melting and crystallizing the filter cake to obtain a crystal layer, sweating and melting the crystal layer to obtain a molten liquid; step S4, vibrating and molding the molten liquid to obtain benzotriazole.

[0025] The method firstly washes the benzotriazole synthetic liquid with water, and then stands for stratification. Due to the density difference, the water phase is in the upper layer and the oil phase is in the lower layer, so as to obtain a water layer and an oil layer. Secondly, water is added to the oil layer for solution crystallization (water crystallization), and pure water is used as a single solvent to cool and crystallize the washed benzotriazole oil layer to obtain a solid-liquid suspension, and a filter cake is obtained after filtering. Then, the filter cake is melted and crystallized (layer crystallization) to obtain a crystal layer, and the crystal layer is sweated and melted. A high-purity benzotriazole melt with a purity of ≥99.5% is obtained through a two-step crystallization process. The crystallization treatment temperature can be controlled below 100°C, thereby eliminating the risk of thermal decomposition and explosion of benzotriazole in a traditional distillation method.

[0026] Finally, the molten liquid is subjected to vibration molding. Vibration molding granulation is to disturb the benzotriazole jet by longitudinal vibration of a certain vibration frequency, so that the jet is broken into uniform droplets, and then solidified into spherical solid particles with large bulk density in a low-temperature nitrogen atmosphere to obtain benzotriazole. The vibration molding method can not only eliminate the dust pollution caused by the traditional drum slicing process and the tableting process, but also make the benzotriazole product particles have better strength. The post-processing method of the present invention not only has low overall processing temperature, intrinsic safety, low energy consumption, and green environmental protection, but also has simple molding process operation and high particle quality, and the purity and particle bulk density of the benzotriazole product are greatly improved.

[0027] Specifically, in a preferred embodiment, step S2 includes: adding water to the oil layer to form a mixture, heating the mixture for a first time to a first crystallization starting temperature, then cooling the mixture for a first time to a first crystallization end temperature, stirring for a certain time after reaching the first crystallization end temperature to crystallize the solution, and filtering to obtain a filtrate and a filter cake; the first crystallization starting temperature refers to the temperature at which the water and the oil layer are heated to completely dissolve after mixing, also called the water crystallization starting temperature, the first crystallization end temperature refers to the temperature at which a large amount of needle-shaped solids of benzotriazole are precipitated in water, also called the water crystallization end temperature, which is related to the content of the solute in the solution to be crystallized. In this application, the BTA content in the BTA synthetic solution is combined with the BTA content in the BTA synthetic solution. Preferably, the first crystallization starting point temperature is 65-75°C, the first crystallization endpoint temperature is 0-25°C, and after reaching the first crystallization endpoint temperature, the temperature is kept constant for 30-90 minutes to fully crystallize; the first heating rate is 1-100°C / h, and the first cooling rate is 1-50°C / h. More preferably, the mass ratio of water to oil layer is (9-20):1; under the above crystallization conditions, the water crystallization process can be made more sufficient, thereby purifying most of the BTA in the oil layer for subsequent treatment and improving the product purity; further preferably, after the filtrate is obtained, it is returned to the water washing step for further purification, while reducing the amount of water used for post-treatment, further saving costs.

[0028] Melt crystallization can separate high-purity compounds, and low-temperature operation can minimize the impact on the compound itself, avoid the risk of thermal decomposition and explosion of benzotriazole, make the post-processing process safer and more environmentally friendly, and reduce energy consumption and cost. Specifically, in a preferred embodiment, in step S3, the filter cake is dried and then heated for a second time to a second crystallization starting temperature, and then cooled for a second time to a second crystallization end temperature, and the temperature is kept constant for a period of time to perform melt crystallization to obtain an uncrystallized mother liquor and a crystal layer; wherein the second crystallization starting temperature refers to the temperature at which the filter cake is heated to completely melt, also called the layer crystallization starting temperature, and the second crystallization end temperature refers to the temperature at which the benzotriazole melt is converted into crystals and a small amount of mother liquor, also called the layer crystallization end temperature. Preferably, vacuum drying is used for drying to isolate the air, and the filter cake is dried at a constant temperature until the weight is constant, and the drying temperature is ≤90°C; more preferably, after the uncrystallized mother liquor is obtained, it is returned to the solution crystallization step for further purification to save costs.

[0029] In a preferred embodiment, the second crystallization starting point temperature is 98-105°C, the second crystallization endpoint temperature is 90-95°C, and the temperature is kept constant for 30-90 minutes after reaching the second crystallization endpoint temperature; the second heating rate is 0.5-30°C / h, and the second cooling rate is 0.5-4°C / h. Within the above-mentioned melt crystallization temperature and time range, the layer crystallization process can be more complete, the impurities contained in the crystals are less, and the impurities in the sweating process can be better discharged.

[0030] Sweating treatment can further purify the high-purity compound after melting treatment. In a preferred embodiment, in step S3, the sweating melting process includes: heating the crystal layer for a third time, keeping the temperature constant for a period of time to sweat, obtaining a sweating liquid and a remaining crystal layer, melting the remaining crystal layer, and obtaining a molten liquid; preferably, after obtaining the sweating liquid, returning it to the melting crystallization step.

[0031] In a preferred embodiment, the sweating temperature is 94-98°C, and the temperature is kept constant for 30-90 minutes after reaching the sweating temperature; the heating rate of the third heating is 1.5-10°C / h, and the sweating time is 30-90 minutes. Under the above temperature and time conditions, when the BTA crystal is slightly higher than the melting crystallization end temperature (90-95°C), the low melting point impurities inside it continue to melt and seep out, so that the BTA crystal is further purified.

[0032] During the vibration forming process, applying vibration or periodic disturbance to the jet can produce uniform droplets. This principle can be used in granulation to greatly improve the particle size distribution, improve product quality, and reduce environmental pollution and losses caused by fine particles being entrained by air. In a preferred embodiment, in step S4, the vibration forming process is carried out in a vibration forming device, such as Figure 2As shown, the nozzle enlargement diagram is as follows Figure 3 As shown, the vibration forming device includes a vibrator 1, a connecting rod 2, a nozzle 3, a jet 4, a transmission pump 5 and a layer crystallizer 6. The vibration forming process includes: the molten liquid in the layer crystallizer 6 is ejected from the nozzle 3 through the transmission pump 5 to form a jet 4, the nozzle 3 is connected to the vibrator 1 through the connecting rod 2 to make the jet 4 vibrate, and then cooled and formed to obtain benzotriazole. Specifically, the molten liquid in the layer crystallizer 6 is provided with pressure by the transmission pump 5, and is ejected from the nozzle 3 to form a jet 4. The nozzle is connected to the vibrator 1 through the connecting rod 2. The vibrator 1 transmits a longitudinal vibration of a certain frequency to the nozzle 3 through the connecting rod 2. The jet 4 will break into uniform beads under the disturbance of vibration, and cool to form a benzotriazole granular product. The cooling atmosphere can be cold nitrogen.

[0033] In order to further improve the strength and bulk density of the vibration-formed particles, in a preferred embodiment, the aperture of the nozzle 3 is 0.1-3 mm, the speed of the jet 4 is 0.71-4 m / s, the vibration frequency of the exciter 1 is 100-400 Hz, and the quality of the BTA particles is higher; preferably, the transmission pump 5 is a screw pump, a gear pump or a centrifugal pump.

[0034] The purpose of water washing is mainly to remove water-soluble impurities in the BTA synthesis solution and reduce the burden of subsequent crystallization and purification. In a preferred embodiment, in step S1, the water washing temperature is 55-70°C; preferably, the mass ratio of water to benzotriazole synthesis solution is (0.5-2):1, and the impurity removal effect is better.

[0035] In a preferred embodiment, after the water layer is obtained, step S1 also includes: sequentially performing water layer crystallization and water layer filtration on the water layer to obtain a water layer filter cake, and returning the water layer filter cake to the water washing step for further purification, while reducing the amount of water used for post-treatment, thereby further saving costs; in order to further improve the crystallization effect, preferably, the crystallization starting temperature of the water layer crystallization is 55-70°C, and the crystallization end temperature is 0-20°C.

[0036] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0037] Example 1

[0038] The post-treatment flow chart of the benzotriazole synthesis solution of Example 1 is as follows Figure 1 shown.

[0039] (1) Water washing: At 70°C, add 500g of BTA synthetic liquid and 750g of water into the water washing equipment and stir at constant temperature for 30 minutes. Let it stand for a period of time to separate the layers. Cool the separated water layer to 20°C for crystallization, and recover the BTA dissolved in it. After the crystallization is completed, filter it, and use the filter cake to wash with water. The salt-containing filtrate leaves the system. The separated oil layer enters the solution crystallization process.

[0040] (2) Solution crystallization: 480 g of the oil layer obtained in step (1) was dissolved in 4800 g of pure water at 70°C, the BTA aqueous solution was cooled to 25°C under stirring, and stirred at this temperature for 30 min, the solid-liquid suspension was filtered, and part of the filtrate was used in the water washing process. The filter cake entered the drying process.

[0041] (3) Drying: Dry the filter cake in a vacuum drying oven at 60°C to constant weight.

[0042] (4) Melt crystallization: Add the dried filter cake to the layer crystallizer and heat it to 100°C to melt it completely. Then cool it down to 92°C at a cooling rate of 3°C / h and keep it constant for 60 minutes. Release the uncrystallized mother liquor and apply it to the solution crystallization process. The crystallization layer enters the sweating melting process.

[0043] (5) Sweating and melting: The crystal layer in the layer crystallizer is heated to 96°C at a heating rate of 2°C / h, kept at a constant temperature for 30 minutes, and the sweating liquid is discharged to be applied to the melting crystallization process. The remaining crystal layer is heated until it is completely melted and enters the vibration granulation process.

[0044] (6) Vibration molding granulation: A screw pump is used to provide pressure to the melt, and a jet is ejected from a 1 mm aperture nozzle with a flow rate of 0.9 m / s. The vibration frequency provided by the vibrator to the nozzle is 200 Hz, and the jet breaks into uniform beads, which are cooled by cold nitrogen to form a benzotriazole granular product.

[0045] Example 2

[0046] The difference between Example 2 and Example 1 is that in step (2), in the solution crystallization process, 480 g of the oil layer is dissolved in 7200 g of pure water.

[0047] Example 3

[0048] The difference between Example 3 and Example 2 is that in step (2), the solution crystallization process, the BTA aqueous solution is cooled to 20°C.

[0049] Example 4

[0050] The difference between Example 4 and Example 2 is that in step (4) the melt crystallization process, the final temperature of the cooling is 93°C.

[0051] Example 5

[0052] The difference between Example 5 and Example 2 is that in the sweating and melting process of step (5), the final sweating temperature is 97°C.

[0053] The product results of Examples 1 to 5 are shown in Table 1.

[0054] Test method:

[0055] BTA content: 1. The oil layer adopts high performance liquid chromatography and external standard method to obtain the content of benzotriazole and o-phenylenediamine. 2. After crystallization, the pure product uses chemical analysis method, dissolves the sample and adds excess silver nitrate solution to generate white precipitate, which is dried to constant weight, and the content of benzotriazole is calculated based on the mass of the precipitate.

[0056] Chroma: The color of the sample dissolved in ethanol is compared visually with the color of the standard platinum-cobalt colorimetric solution, and the result is expressed in Hazen (platinum-cobalt) color units. Hazen (platinum-cobalt) color units are the color of a solution containing 1 mg of platinum (in the form of chloroplatinic acid) and 2 mg of cobalt chloride hexahydrate per liter of solution.

[0057] Compressive strength: Use a computer servo peeling tensile testing machine to compress and destroy the benzotriazole particles to obtain the required compressive strength value.

[0058] Table 1

[0059]

[0060]

[0061] Example 6

[0062] The difference between Example 6 and Example 4 is that in the vibration molding granulation process of step (6), the nozzle aperture is 0.3 mm.

[0063] Example 7

[0064] The difference between Example 7 and Example 4 is that in the vibration molding granulation process of step (6), the jet velocity is 3 m / s.

[0065] Example 8

[0066] The difference between Example 8 and Example 4 is that in the vibration molding granulation process of step (6), the vibration frequency is 300 Hz.

[0067] Example 9

[0068] The difference between Example 9 and Example 4 is that in the vibration molding granulation process of step (6), the vibration frequency is 400 Hz.

[0069] Examples 10 to 11

[0070] The difference between Examples 10 to 11 and Example 4 is that in the vibration molding granulation process of step (6), the nozzle aperture, jet velocity and vibration frequency are different.

[0071] The vibration forming parameters and product results of Examples 6 to 11 are shown in Table 2.

[0072] Table 2

[0073]

[0074] Examples 12 to 13

[0075] The only difference between Examples 12 to 13 and Example 2 is that the temperature parameters of step (2) solution crystallization process, step (4) melt crystallization process, and step (5) sweating melting process are different. The parameters and product results are shown in Table 3.

[0076] Table 3

[0077]

[0078] Embodiment 14

[0079] The difference between Example 14 and Example 2 is that in step (1) of the water washing process: at 55°C, 500g of BTA synthetic liquid and 1000g of water are added to the water washing equipment and stirred at a constant temperature for 30min. After standing for a period of time to separate the layers, the separated water layer is cooled to 0°C for crystallization, and the BTA dissolved therein is recovered. After the crystallization is completed, the filter cake is reused in the water washing process, and the salt-containing filtrate is discharged from the system. The separated oil layer enters the solution crystallization process. In step (2) of the solution crystallization process: at 70°C, 480g of the oil layer obtained in step (1) is dissolved in 4320g of pure water, the BTA aqueous solution is cooled to 25°C under stirring, and stirred at this temperature for 30min, the solid-liquid suspension is filtered, and part of the filtrate is reused in the water washing process. The filter cake enters the drying process.

[0080] Embodiment 15

[0081] The difference between Example 15 and Example 2 is that in step (1) of the water washing process: at 70°C, 500g of BTA synthetic liquid and 250g of water are added to the water washing equipment and stirred at a constant temperature for 30min. After standing for a period of time to separate the layers, the separated water layer is cooled to 20°C for crystallization, and the BTA dissolved therein is recovered. After the crystallization is completed, the filter cake is reused in the water washing process, and the salt-containing filtrate is discharged from the system. The separated oil layer enters the solution crystallization process. In step (2) of the solution crystallization process: at 70°C, 480g of the oil layer obtained in step (1) is dissolved in 9600g of pure water, the BTA aqueous solution is cooled to 25°C under stirring, and stirred at this temperature for 30min, the solid-liquid suspension is filtered, and part of the filtrate is reused in the water washing process. The filter cake enters the drying process.

[0082] The parameters and product results of Examples 12 to 15 are shown in Table 4.

[0083] Table 4

[0084] Example 12 Example 13 Embodiment 14 Embodiment 15 BTA content / % 99.4 99.5 99.7 99.7 Hazen 35 35 30 30 Compressive strength / MPa 6 6 6 6 <![CDATA[Bulk density g / cm 3 > 0.55 0.55 0.55 0.55

[0085] Comparative Example 1

[0086] (1) Water washing: At 70°C, add 500g of BTA synthetic liquid and 750g of water into the water washing equipment and stir at constant temperature for 30 minutes. Let it stand for a period of time to separate the layers. Cool the separated water layer to 20°C for crystallization, and recover the BTA dissolved in it. After the crystallization is completed, filter it, and use the filter cake to wash with water. The salt-containing filtrate leaves the system. The separated oil layer enters the solution crystallization process.

[0087] (2) Dehydration: Under nitrogen protection, the water-washed oil layer was heated to 90°C and the vacuum was controlled to -0.095 MPa for dehydration until the kettle temperature reached 140°C.

[0088] (3) Melt crystallization: Add the dried filter cake to the layer crystallizer and heat it to 100°C to melt it completely. Then cool it down to 92°C at a cooling rate of 3°C / h and keep it constant for 60 minutes. Release the uncrystallized mother liquor and apply it to the solution crystallization process. The crystallization layer enters the sweating melting process.

[0089] (4) Sweating and melting: The crystal layer in the layer crystallizer is heated to 96°C at a heating rate of 2°C / h, kept at a constant temperature for 30 minutes, and the sweating liquid is discharged to be applied to the melting crystallization process. The remaining crystal layer is heated until it is completely melted and enters the vibration granulation process.

[0090] (5) Vibration molding granulation: A screw pump is used to provide pressure to the melt, and a jet is ejected from a 1 mm aperture nozzle with a flow rate of 0.9 m / s. The vibration frequency provided by the vibrator to the nozzle is 200 Hz, and the jet breaks into uniform beads, which are cooled by cold nitrogen to form a benzotriazole granular product.

[0091] The product has a BTA content of 98.8%, a chromaticity of 60, and a compressive strength of 5 MPa.

[0092] Comparative Example 2

[0093] (1) Water washing: At 70°C, add 500g of BTA synthetic liquid and 750g of water into the water washing equipment and stir at constant temperature for 30 minutes. Let it stand for a period of time to separate the layers. Cool the separated water layer to 20°C for crystallization, and recover the BTA dissolved in it. After the crystallization is completed, filter it, and use the filter cake to wash with water. The salt-containing filtrate leaves the system. The separated oil layer enters the solution crystallization process.

[0094] (2) Solution crystallization: 480 g of the oil layer obtained in step (1) was dissolved in 4800 g of pure water at 70°C, the BTA aqueous solution was cooled to 25°C under stirring, and stirred at this temperature for 30 min, the solid-liquid suspension was filtered, and part of the filtrate was used in the water washing process. The filter cake entered the drying process.

[0095] (3) Drying: Dry the filter cake in a vacuum drying oven at 60°C to constant weight.

[0096] (4) Vibration molding granulation: The dried filter cake is heated until it is completely melted, and a screw pump is used to provide pressure to the molten liquid, which is ejected from a 1mm aperture nozzle to form a jet with a flow rate of 0.9m / s. The vibration frequency provided by the vibrator to the nozzle is 200Hz, and the jet breaks into uniform beads, which are cooled by cold nitrogen to form benzotriazole granular products.

[0097] The product has a BTA content of 98.1%, a chromaticity of 65, and a compressive strength of 6MPa.

[0098] As can be seen from the above, compared with the comparative example, each embodiment of the present invention obtains a high-purity benzotriazole melt with a purity of ≥99.5% by subjecting the benzotriazole synthetic liquid to a two-step crystallization process of solution crystallization and melt crystallization, and then prepares spherical particles with a large bulk density by vibration molding. The above crystallization treatment temperature can be controlled below 100°C, eliminating the risk of benzotriazole decomposition and explosion due to heat in the traditional method; the vibration molding method can not only eliminate the dust pollution caused by the traditional process, but also make the benzotriazole product particles have better strength.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A post-treatment method for a benzotriazole synthesis solution, characterized in that: The following steps are involved: Step S1, washing the benzotriazole synthesis liquid with water to obtain a water layer and an oil layer; Step S2, adding water to the oil layer to form a mixture, heating the mixture to a first crystallization starting temperature, then cooling the mixture to a first crystallization endpoint temperature to crystallize the solution, and filtering to obtain a filtrate and a filter cake; the first crystallization starting temperature is 65-75° C., and the first crystallization endpoint temperature is 0-25° C.; Step S3, after drying the filter cake, heating it for the second time to a second crystallization starting temperature, and then cooling it for the second time to a second crystallization end temperature to perform melt crystallization to obtain an uncrystallized mother liquid and a crystal layer, and sweat melting the crystal layer to obtain a melt; the second crystallization starting temperature is 98-105° C., and the second crystallization end temperature is 90-95° C.; Step S4, vibrating and molding the molten liquid to obtain benzotriazole; The benzotriazole synthetic liquid is a benzotriazole oil phase obtained by reacting benzotriazole sodium salt using a high-pressure o-phenylenediamine method, adjusting the pH to 5-7 with an acid, and then separating the layers; the acid for adjusting the pH is sulfuric acid, hydrochloric acid or nitric acid.

2. The post-processing method according to claim 1, characterized in that: In the step S2, the temperature is kept constant for 30 to 90 minutes after reaching the first crystallization endpoint temperature; the first heating rate is 1 to 100°C / h, and the first cooling rate is 1 to 50°C / h.

3. The post-processing method according to claim 1 or 2, characterized in that: In step S2, the mass ratio of water to the oil layer is (9-20):

1.

4. The post-processing method according to claim 1 or 2, characterized in that: In the step S2, after the filtrate is obtained, it is returned to the water washing step.

5. The post-processing method according to claim 1 or 2, characterized in that: In the step S3, the drying is performed by vacuum drying, and the drying temperature is ≤90°C.

6. The post-processing method according to claim 1 or 2, characterized in that: In the step S3, after the uncrystallized mother liquor is obtained, it is returned to the solution crystallization step.

7. The post-processing method according to claim 1 or 2, characterized in that: After reaching the second crystallization endpoint temperature, the temperature is maintained constant for 30 to 90 minutes; the heating rate of the second heating is 0.5 to 30°C / h, and the cooling rate of the second cooling is 0.5 to 4°C / h.

8. The post-processing method according to claim 1 or 2, characterized in that: In the step S3, the sweating and melting process includes: heating the crystal layer for a third time to a sweating temperature to sweat, obtaining a sweating liquid and a remaining crystal layer, and melting the remaining crystal layer to obtain the molten liquid.

9. The post-processing method according to claim 8, characterized in that: In the step S3, after the sweating liquid is obtained, it is returned to the melt crystallization step.

10. The post-processing method according to claim 8, characterized in that: The sweating temperature is 94-98°C, and the temperature is kept constant for 30-90 minutes after reaching the sweating temperature; the heating rate of the third heating is 1.5-10°C / h.

11. The post-processing method according to claim 1 or 2, characterized in that: In the step S4, the vibration molding process is carried out in a vibration molding device, the vibration molding device comprising an exciter (1), a connecting rod (2), a nozzle (3), a jet (4), a transmission pump (5) and a layer crystallizer (6), the vibration molding process comprising: the molten liquid in the layer crystallizer (6) is ejected from the nozzle (3) through the transmission pump (5) to form a jet (4), the nozzle (3) is connected to the exciter (1) through the connecting rod (2) to make the jet (4) vibrate, and then cooled and molded to obtain the benzotriazole.

12. The post-processing method according to claim 11, characterized in that: The aperture of the nozzle (3) is 0.1-3 mm, the velocity of the jet (4) is 0.71-4 m / s, and the vibration frequency of the exciter (1) is 100-400 Hz.

13. The post-processing method according to claim 11, characterized in that: The transmission pump (5) is a screw pump, a gear pump or a centrifugal pump.

14. The post-processing method according to claim 1 or 2, characterized in that: In the step S1, the water washing temperature is 55-70°C.

15. The post-processing method according to claim 1 or 2, characterized in that: In the step S1, the mass ratio of water to the benzotriazole synthesis liquid is (0.5-2):

1.

16. The post-processing method according to claim 1 or 2, characterized in that: After the water layer is obtained, the step S1 further includes: sequentially performing water layer crystallization and water layer filtration on the water layer to obtain a water layer filter cake, and returning the water layer filter cake to the water washing step.

17. The post-processing method according to claim 16, characterized in that: The crystallization starting point temperature of the water layer crystallization is 55-70°C, and the crystallization ending point temperature is 0-20°C.

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