Process for purifying 5-chlorobenzotriazole and purification apparatus

Abstract

The application discloses a refining method and a refining device for 5-chlorobenzotriazole. The refining method comprises the following steps: dissolving 5-chlorobenzotriazole crude powder in an organic solvent at a temperature of 50-60 DEG C, heating and dissolving for 3-4 hours to form a mixed solution, wherein the weight ratio of 5-chlorobenzotriazole crude powder to the organic solvent is 1:4-1:5; filtering the mixed solution by using a precision filter membrane with a pore size of 40 nm to remove impurities and metal particles; ion exchanging the mixed solution after the filtering treatment by using a cation exchange resin at a temperature of 25+ / -1 DEG C for at least 6 hours, taking out part of the cation exchange resin to obtain a refined solution; heating the refined solution at a temperature of 135-145 DEG C for at least 12 hours to distill the organic solvent, leaving blocky refined 5-chlorobenzotriazole; and crushing the blocky refined 5-chlorobenzotriazole to obtain refined 5-chlorobenzotriazole powder with a fineness of 2 mm.

Description

Technical Field

[0001] This invention relates to a method and apparatus for purifying organic compounds, and particularly to a method and apparatus for purifying 5-chlorobenzotriazole. Background Technology

[0002] 5-Chlorobenzotriazole is a widely used organic compound. It is frequently used in organic synthesis with other compounds to create downstream organic compounds, and is also used as an electroplating additive. Furthermore, 5-Chlorobenzotriazole is used as an effective anti-fogging agent and stabilizer in photosensitive materials, thus it is also widely used in the production of photographic paper emulsions and developing solutions.

[0003] The purity of 5-chlorobenzotriazole sold on the market is not low, but it is usually below 99%. Impurities mixed in with 5-chlorobenzotriazole powder are usually metallic impurities, such as iron, sodium, magnesium, calcium, potassium, copper, nickel, chromium, and zinc. To produce a higher-quality product, the purity of 5-chlorobenzotriazole needs to be increased, ideally to between 99.5% and 99.9%. The content of the aforementioned metallic impurities needs to be reduced. For example, the iron content should be around 10 ppm before refining, and below 2 ppm after refining; the calcium content should be around 5 ppm before refining, and also below 2 ppm after refining; the content of other trace metals should also be below 1 ppm after refining.

[0004] However, there is currently no effective method for refining 5-chlorobenzotriazole. Therefore, this invention proposes a method and apparatus for refining 5-chlorobenzotriazole. Summary of the Invention

[0005] The purpose of this invention is to provide a purification method and apparatus for 5-chlorobenzotriazole.

[0006] This invention provides a method for purifying 5-chlorobenzotriazole, comprising the following steps:

[0007] Heating and dissolving step: At a temperature of 50-60℃, the crude 5-chlorobenzotriazole powder is dissolved in an organic solvent and heated for 3-4 hours to form a mixed solution, wherein the weight ratio of the crude 5-chlorobenzotriazole powder to the organic solvent is 1:4 to 1:5.

[0008] Filtration step: The mixed solution is filtered using a precision filter membrane with a pore size of 40 nm to remove impurities and metal particles.

[0009] Ion exchange step: At a temperature of 25±1℃, the filtered mixed solution is subjected to ion exchange with cation exchange resin for at least 6 hours, and a portion of the cation exchanged solution is removed to obtain a refined solution.

[0010] Desolventization step: Heat the refined solution at 135-145°C for at least 12 hours to distill the organic solvent, leaving behind lumpy refined 5-chlorobenzotriazole; and

[0011] Crushing step: Crush the blocky refined 5-chlorobenzotriazole to obtain refined 5-chlorobenzotriazole powder with a fineness grade of 2 mm.

[0012] Preferably, the organic solvent is methanol, ethanol or isopropanol.

[0013] Preferably, the batch processing of this mixed solution does not exceed 800 kg.

[0014] The present invention also provides a purification apparatus for 5-chlorobenzotriazole, comprising:

[0015] A heating and dissolving tank assembly is used to provide a temperature of 50-60°C to dissolve crude 5-chlorobenzotriazole powder in an organic solvent and heat and dissolve for 3-4 hours to form a mixed solution, wherein the weight ratio of crude 5-chlorobenzotriazole powder to the organic solvent is 1:4 to 1:5.

[0016] A precision membrane filter, connected to the heated dissolving tank assembly to circulate and return the mixed solution, includes a 40 nm pore size precision filter membrane for circulating and filtering the mixed solution for at least 90 minutes each time.

[0017] An ion exchanger, connected to the precision membrane filter and having a cation exchange resin, exchanges and removes a portion of the cations in the cyclically filtered mixed solution at a temperature of 25±1℃ to obtain a refined solution.

[0018] In a solvent removal process, the refined solution is heated at 135-145°C for at least 12 hours to distill the organic solvent, leaving behind lumpy refined 5-chlorobenzotriazole; and

[0019] A pulverizing mechanism is used to pulverize the blocky refined 5-chlorobenzotriazole to obtain refined 5-chlorobenzotriazole powder with a fineness grade of 2 mm.

[0020] Preferably, the organic solvent is methanol, ethanol or isopropanol.

[0021] Preferably, the precision membrane filter further comprises:

[0022] A 450nm pore size precision filter membrane is used to perform circulating filtration of the mixed solution for at least 45 minutes each time; and

[0023] A 200 nm pore size precision filter membrane was used to perform circulating filtration of the mixed solution for at least 45 minutes each time.

[0024] The execution order is as follows: the 450nm pore size precision filter membrane, the 200nm pore size precision filter membrane, and the 40nm pore size precision filter membrane.

[0025] Preferably, the cation exchange resin is a strongly acidic cation exchange resin or a weakly acidic cation exchange resin.

[0026] Preferably, the solvent removal mechanism further includes a recovery tank for recovering the organic solvent and reusing it in the heating and dissolving tank assembly.

[0027] Preferably, the solvent removal mechanism further comprises:

[0028] A condenser;

[0029] A distillation vessel includes a top cover and a barrel body that can be opened and closed with the cover. The barrel body is sealed to a condenser. The refined solution is heated in the sealed distillation vessel. The distilled organic solvent is discharged from the distillation vessel through the condenser. Lumpy refined 5-chlorobenzotriazole remains in the distillation vessel.

[0030] An electric heater receives electricity to generate heat and conducts the heat to the distillation tank, maintaining the temperature inside the distillation tank between 135-145°C.

[0031] Preferably, the crushing mechanism further comprises:

[0032] An input tank is used to receive the block-shaped refined 5-chlorobenzotriazole and release the block-shaped refined 5-chlorobenzotriazole from a height;

[0033] Two rollers, with an adjustable spacing between them, rotate relative to each other. A block of refined 5-chlorobenzotriazole, falling from the input end above the rollers by gravity, is ground by the rollers into refined 5-chlorobenzotriazole powder with a fineness of 2mm, which then falls downwards.

[0034] A receiving tank is used to receive the dropped refined 5-chlorobenzotriazole powder.

[0035] According to the purification method and apparatus disclosed in this invention, the purity of 5-chlorobenzotriazole can be ensured to be higher than 99.5%, which is superior to existing products sold on the market. Attached Figure Description

[0036] Figure 1This is a schematic diagram of the components of a purification apparatus for 5-chlorobenzotriazole according to the present invention.

[0037] Figure 2 This is a flowchart of a purification method for 5-chlorobenzotriazole according to the present invention.

[0038] Explanation of icon numbers:

[0039] 1-5-Chlorobenzotriazole refining apparatus; 10-Heating and dissolving tank assembly;

[0040] 11-Organic solvent supply source; 111-First switch valve; 112-Second switch valve;

[0041] 12-Dissolving tank; 121-Opening; 13-Heating tank; 131-Recovery pipeline; 132-Injection pipeline;

[0042] 14-5-Chlorobenzotriazole crude powder supply source; 20-Precision membrane filter;

[0043] 201 - Liquid inlet line; 202 - Liquid outlet line; 203 - First control valve; 204 - Second control valve;

[0044] Precision filter membranes with pore sizes of 21-450nm; Precision filter membranes with pore sizes of 22-200nm;

[0045] 23-40nm pore size precision filter membrane; 24-Third control valve; 25-Discharge line; 26-Purification tank

[0046] 30 - Ion exchanger; 31 - Cation exchange resin; 32 - Auxiliary filter; 33 - Flow control valve;

[0047] 341 - Refining solution tank 1; 342 - Refining solution tank 2; 35 - Circulation pipe; 40 - Solvent removal mechanism;

[0048] 41-Condenser; 42-Distillation barrel; 421-Lid; 422-Barrel body; 43-Electric heater;

[0049] 44-Recycling tank; 50-Crushing mechanism; 51-Input tank; 52-Roller; 53-Receiving tank;

[0050] B - Refined 5-chlorobenzotriazole in bulk form; F - Refined 5-chlorobenzotriazole powder;

[0051] H - Mixed solution; P1 - First pump; P2 - Second pump; P3 - Third pump; R - Refined solution Detailed Implementation

[0052] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0053] Please see Figure 1 The figure is a schematic diagram of the components of a 5-chlorobenzotriazole refining apparatus 1 according to the present invention. The 5-chlorobenzotriazole refining apparatus 1 includes a heating and dissolving tank assembly 10, a precision membrane filter 20, an ion exchanger 30, a solvent removal mechanism 40, and a pulverizing mechanism 50. The appearance, function, and operation of the aforementioned components will be described in detail below.

[0054] The function of the heating and dissolving tank assembly 10 is to provide a temperature of 50-60°C to dissolve the crude 5-chlorobenzotriazole powder in an organic solvent for 3-4 hours to form a mixed solution H. The purity of the crude 5-chlorobenzotriazole powder is less than 99%, generally around 98%. Too many impurities and impurities cause considerable trouble for subsequent processing operations and need to be further reduced. The detailed device of the heating and dissolving tank assembly 10 includes an organic solvent supply source 11, a dissolving tank 12, a heating tank 13, and a crude 5-chlorobenzotriazole powder supply source 14. According to the present invention, the organic solvent can be an alcohol, such as methanol, ethanol, or isopropanol. In the following embodiments, ethanol is used as an example, with a purity greater than 99.5%. Since alcohols are liquids, the organic solvent supply source 11 can be a storage tank or a pipeline connected to an external recyclable source of alcohol, such as a storage tank. The organic solvent can be injected into the dissolving tank 12 in various ways. For example, it can be injected directly into the dissolving tank 12 by controlling a first switch valve 111; or it can be injected into the circulating filtered mixed solution H by controlling a second switch valve 112.

[0055] The dissolving tank 12 is the main location for forming the mixed solution H. The dissolving tank 12 has several openings 121 through which the mixed solution H flows for heating and recovery. The heating tank 13 uses a first pump P1 to draw the cooled mixed solution H from one opening 121 through a recovery line 131, heats it, and then reinjects the heated mixed solution H back into another opening 121 through a injection line 132. The circulation direction of the mixed solution H is as follows: Figure 1The solid line segment is indicated by an arrow. The heating tank 13 can heat the mixed solution H to a temperature range of 50-60°C. The heat carried by the mixed solution H may be lost in the pipeline; it is sufficient to ensure that the temperature inside the dissolving tank 12 is maintained at 30-40°C. The crude 5-chlorobenzotriazole powder supply source 14 can add the crude 5-chlorobenzotriazole powder to the dissolving tank 12 and mix it with the organic solvent according to a specific weight. It should be noted that, according to the present invention, the weight ratio of crude 5-chlorobenzotriazole powder to organic solvent is limited to 1:4 to 1:5. Taking a weight concentration of 20% as an example, 120 kg of crude 5-chlorobenzotriazole powder can be mixed with 480 kg of ethanol to prepare a mixed solution H of 600 kg.

[0056] The function of the precision membrane filter 20 is to circulate and filter the mixed solution H to remove impurities and impurities (such as metal particles) from the crude 5-chlorobenzotriazole powder. The precision membrane filter 20 can be connected to the heating and dissolving tank assembly 10 to circulate and return the mixed solution H. To achieve the aforementioned purpose, the precision membrane filter 20 can use a second pump P2 to draw in the mixed solution H via an inlet line 201 (as indicated by the slashed arrow), and after circulation filtration, discharge it through an outlet line 202 back to the dissolving tank 12 (as indicated by the hollow arrow), thus repeating the cycle. Furthermore, a first control valve 203 can be installed on the inlet line 201 to discharge residual waste (as indicated by the solid arrow) when emptying the dissolving tank 12, preventing it from entering the circulation filtration. A second control valve 204 can also be installed on the outlet line 202 to switch the circulated mixed solution H to the next processing unit after circulation filtration is completed. The precision membrane filter 20 contains multiple precision filter membranes: a 450nm pore size precision filter membrane 21, a 200nm pore size precision filter membrane 22, and a 40nm pore size precision filter membrane. The mixed solution H can be selectively directed to one of the third control valves 24 via the switching of multiple third control valves 24. The 450nm pore size precision filter membrane 21 can be used for circulating filtration of the mixed solution H for at least 45 minutes (e.g., 60 minutes) each time, the 200nm pore size precision filter membrane 22 can be used for circulating filtration of the mixed solution H for at least 45 minutes (e.g., 60 minutes) each time, and the 40nm pore size precision filter membrane 23 can be used for circulating filtration of the mixed solution H for at least 90 minutes (e.g., 120 minutes) each time. Precision filter membranes with different pore sizes can physically remove impurities larger than that pore size. Although smaller pore size precision filter membranes can remove almost all impurities, their flow and filtration speeds are slow, resulting in low filtration efficiency. Therefore, each precision filter membrane is used sequentially, in the following order: 450nm pore size precision filter membrane 21, 200nm pore size precision filter membrane 22, and 40nm pore size precision filter membrane 23. Each precision filter membrane can be cycled several times. In subsequent embodiments, the precision filter membranes used are MEP-0.45, MEP-0.2, and MES-0.04 manufactured by Xuran International Co., Ltd., made of polypropylene (PP) and polyethersulfone (PES). The mixed solution H after cycle filtration can flow out through a discharge line 25 and be temporarily stored in a purification tank 26. Before deciding to discharge the purification tank 26, the concentration of metal components in the mixed solution H can be measured at the outlet of the 40nm pore size precision filter membrane 23 using inductively coupled plasma mass spectrometry (ICP-MS) to ensure that the amount of impurities such as metals can be effectively reduced by the precision membrane filter 20.

[0057] The ion exchanger 30 is connected to the precision membrane filter 20 (via the purification tank 26, or in practice, directly) and contains cation exchange resin. It can exchange and remove some of the cations (metal ions) in the circulated filtered mixed solution H at a temperature of 25±1℃ (room temperature) to obtain a refined solution R. The ion exchanger 30 contains several cation exchange resins 31 (… Figure 1 The following is an example using two cation exchange resins 31: a third pump P3, an auxiliary filter 32, four flow control valves 33, two refining solution tanks 341 and 342, and a circulation pipe 35. According to the present invention, the cation exchange resin 31 can be a strongly acidic cation exchange resin or a weakly acidic cation exchange resin. The strongly acidic cation exchange resin is a styrene polymer containing a strongly acidic sulfonic acid exchange group (-SO3H), while the weakly acidic cation exchange resin is a resin containing a weakly acidic functional group, such as a carboxyl group (-COOH), as the exchange group. In the subsequent embodiments, the cation exchange resin 31 used is a strongly acidic cation exchange resin manufactured by Mitsubishi Chemical Corporation, brand name DIAION SK1BH, with a single use of approximately 100L (approximately 80kg). The third pump P3 draws the mixed solution H from the purification tank 26 through the pipeline, and through the cation exchange resin 31 and the auxiliary filter 32, prepares the refined solution R. Figure 1 The solution (marked in light gray) flows into the refining solution tank 341 for temporary storage at a rate of up to 3.3 kg / min. The auxiliary filter 32 is used to filter out strongly acidic cation exchange resin debris carried away by the mixed solution H flowing through the cation exchange resin 31, preventing contamination of the refining solution R. The auxiliary filter 32 is manufactured by Xuran International Co., Ltd., and is made of a precision filter membrane of polyethersulfone (PES). Four flow control valves 33 control the flow direction of the mixed solution H, allowing it to undergo repeated ion exchange through the circulation pipe 35. The refining solution R can be moved to the solvent removal unit 40 for processing by moving the refining solution tank 342. To determine whether a solution becomes refining solution R, the concentration of metal components in the mixed solution H can be measured at the outlet of the auxiliary filter 32 using an inductively coupled plasma mass spectrometer to confirm a significant reduction in metal components in the refining solution R. Once a solution becomes refining solution R, the repeated ion exchange cycle ends. The ion exchanger operates for approximately 6 hours for 30 pairs of 600kg mixed solution H.

[0058] The solvent removal mechanism 40 is an apparatus for recovering organic solvents from the refined solution R. The solvent removal mechanism 40 heats the refined solution R at a temperature of 135-145°C (e.g., about 140°C) for at least 12 hours to distill the organic solvents, leaving behind lumpy refined 5-chlorobenzotriazole B. The solvent removal mechanism 40 includes a condenser 41, a distillation tank 42, an electric heater 43, and a recovery tank 44. The condenser 41 cools the vaporized organic solvent to form a liquid organic solvent and transfers it to the recovery tank 44. The recovery tank 44 is used to recover the organic solvent for reuse in the heating and dissolving tank assembly 10. The distillation tank 42 includes a top cover 421 and a barrel 422 that is closable with the cover 421. The barrel 422 is sealed to the condenser 41, and the refined solution R is heated within the sealed distillation tank 42. The distilled organic solvent is discharged from the condenser 41 into the distillation tank 42, while the refined 5-chlorobenzotriazole B remains in the distillation tank 42. The electric heater 43 receives electricity to generate heat and conducts the heat to the distillation tank 42, maintaining the temperature inside the distillation tank 42 between 135-145°C for the distillation of the organic solvent.

[0059] Since the distilled, blocky refined 5-chlorobenzotriazole B is not in powder form and is difficult to use industrially, it must be pulverized. The pulverizing mechanism 50 is the tool for performing this operation. The pulverizing mechanism 50 can pulverize the blocky refined 5-chlorobenzotriazole B to obtain refined 5-chlorobenzotriazole powder F with a fineness grade of 2 mm. The pulverizing mechanism 50 includes an input trough 51, two rollers 52, and a receiving trough 53. The input trough 51 is used to collect the blocky refined 5-chlorobenzotriazole B and release it from a height. The two rollers 52 are located below the input trough 51, and the distance between the rollers 52 is adjustable and they rotate relative to each other (along the direction of rotation). Figure 1 (The arrow in the middle arc curve indicates the direction of the material grinding). The grinding effect is achieved through friction generated between the two rollers 52 at the same rotational speed. The blocky refined 5-chlorobenzotriazole B, falling from the input end 51 under gravity onto the two rollers 52, is ground by the rollers 52, forming refined 5-chlorobenzotriazole powder F with a fineness of 2mm, which then falls downwards. The receiving tank 53, located below the rollers 52, is used to collect the falling refined 5-chlorobenzotriazole powder F. The refined 5-chlorobenzotriazole powder F is a refined finished product suitable for industrial use, with a purity of over 99.5%.

[0060] Based on the operation of the above-described purification apparatus 1 for 5-chlorobenzotriazole, this invention also proposes a purification method for 5-chlorobenzotriazole (hereinafter referred to as the purification method). Please see... Figure 2The diagram shows a flowchart of the refining method. The refining method includes the following steps: heating and dissolving (S01), filtration (S02), ion exchange (S03), solvent removal (S04), and pulverization (S05). The heating and dissolving step involves dissolving crude 5-chlorobenzotriazole powder in an organic solvent (methanol, ethanol, or isopropanol) at 50-60°C for 3-4 hours to form a mixed solution, wherein the weight ratio of crude 5-chlorobenzotriazole powder to the organic solvent is 1:4 to 1:5. The filtration step involves filtering the mixed solution through a 40nm precision filter membrane to remove impurities and metal particles. Although the precision membrane filter 20 includes a 450nm pore size precision filter membrane 21, a 200nm pore size precision filter membrane 22, and a 40nm pore size precision filter membrane 23, the 40nm pore size precision filter membrane 23 is primarily used to filter out impurities and impurities larger than 40nm. The 450nm pore size precision filter membrane 21 and the 200nm pore size precision filter membrane 22 are only used to accelerate the filtration speed. The ion exchange step involves subjecting the filtered mixed solution to ion exchange with a cation exchange resin at a temperature of 25±1℃ for at least 6 hours, and then removing a portion of the cation exchanged solution to obtain a refined solution. The solvent removal step involves heating the refined solution at a temperature of 135-145℃ for at least 12 hours to distill the organic solvent, leaving lumpy refined 5-chlorobenzotriazole. The pulverization step involves pulverizing the lumpy refined 5-chlorobenzotriazole to obtain refined 5-chlorobenzotriazole powder with a fineness grade of 2mm. Due to equipment limitations, in order to achieve better quality, it is best to process no more than 800 kg of mixed solution in a single batch.

[0061] The following methods are used to prepare several types of crude 5-chlorobenzotriazole powder, each containing 120 kg of different metallic impurities (including particulate and ionic forms), by mixing each powder with 480 kg of ethanol to produce several types of crude 5-chlorobenzotriazole powder, each weighing 600 kg. The compositional changes of the refined 5-chlorobenzotriazole powder are then observed using the above-mentioned 5-chlorobenzotriazole refining apparatus 1.

[0062] Example 1

[0063] Please see Table 1, which lists the various metal concentrations of the crude 5-chlorobenzotriazole powder, the various metal concentrations in the mixed solution at the outlet of the 40nm pore size precision filter membrane, the various metal concentrations in the refining solution at the outlet of the auxiliary filter, and the various metal concentrations of the refined 5-chlorobenzotriazole powder.

[0064] Table 1

[0065] Metal types aluminum iron sodium magnesium calcium Potassium copper nickel chromium Zinc 5-Chlorobenzotriazole Crude Powder 0.36 1.96 0.58 1.03 2.62 0.21 <0.1 0.21 0.16 0.13 40nm pore size precision filter membrane outlet 0.15 0.63 0.58 0.94 1.91 0.21 <0.1 0.17 <0.1 0.13 Auxiliary filter outlet <0.1 0.40 <0.1 <0.1 0.58 <0.1 <0.1 <0.1 <0.1 <0.1 Refined 5-chlorobenzotriazole powder <0.1 0.44 <0.1 <0.1 0.53 <0.1 <0.1 <0.1 <0.1 <0.1

[0066] Unit: ppm

[0067] The results showed that after the solution passed through a 40nm pore size precision filter membrane, the concentrations of metals such as aluminum, iron, and calcium were significantly reduced. Sodium and magnesium, which had not been removed, were removed in the ion exchange resin (at the outlet of the auxiliary filter). Regarding sodium and magnesium, their concentrations were reduced to below the upper limit of analysis (<0.1ppm), confirming removal by the ion exchanger. The purified 5-chlorobenzotriazole powder had metal concentrations of less than 1ppm for iron and calcium, and less than 0.1ppm for other metals. The purity of the purified product was >99.9%, meeting the requirements.

[0068] Example 2

[0069] Please see Table 2, which lists the various metal concentrations of the crude 5-chlorobenzotriazole powder, the various metal concentrations in the mixed solution at the outlet of the 40nm pore size precision filter membrane, the various metal concentrations in the refining solution at the outlet of the auxiliary filter, and the various metal concentrations of the refined 5-chlorobenzotriazole powder.

[0070] Table 2

[0071]

[0072]

[0073] Unit: ppm

[0074] The concentrations of aluminum, iron, sodium, magnesium, calcium, and zinc in the second crude 5-chlorobenzotriazole powder were 3.08 times, 2.06 times, 2.09 times, 0.43 times, 1.46 times, and 1.38 times, respectively, of the same components in the first crude 5-chlorobenzotriazole powder in Example 1. The nickel concentration was low, while the concentrations of the other metals did not change significantly. The results showed that the concentrations of aluminum, iron, and calcium decreased significantly after the liquid passed through a 40nm pore size precision filter membrane. Sodium and magnesium, which had not been removed, were removed by the ion exchange resin. The concentrations of sodium and magnesium were reduced to below the upper limit of analysis, confirming removal by the ion exchanger. The purified 5-chlorobenzotriazole powder had metal concentrations of less than 1 ppm for iron, calcium, and chromium, and less than 0.1 ppm for other metals. The purity of the purified product was >99.9%, meeting the requirements.

[0075] Example 3

[0076] Please see Table 3, which lists the various metal concentrations of crude 5-chlorobenzotriazole powder, the various metal concentrations in the mixed solution at the outlet of a 40nm pore size precision filter membrane, the various metal concentrations in the refining solution at the outlet of an auxiliary filter, and the various metal concentrations of refined 5-chlorobenzotriazole powder.

[0077] Table 3

[0078] Metal types aluminum iron sodium magnesium calcium Potassium copper nickel chromium Zinc 5-Chlorobenzotriazole Crude Powder 1.14 8.24 1.82 1.05 3.97 0.16 0.47 0.11 0.18 0.25 40nm pore size precision filter membrane outlet 0.45 1.94 1.80 1.00 2.84 0.14 0.41 <0.1 0.14 0.24 Auxiliary filter outlet 0.20 1.23 <0.1 <0.1 0.39 <0.1 0.15 <0.1 0.13 <0.1 Refined 5-chlorobenzotriazole powder 0.22 1.26 <0.1 <0.1 0.32 <0.1 0.16 <0.1 0.14 <0.1

[0079] Unit: ppm

[0080] The third and second crude 5-chlorobenzotriazole powders are similar in that the concentrations of metals such as aluminum, iron, sodium, calcium, copper, and zinc are significantly higher than those in the first crude 5-chlorobenzotriazole powder, and the nickel concentration is similarly lower, while the concentrations of other metals show little change. The results show that after the liquid passes through a 40nm precision filter membrane, the concentrations of metals such as aluminum, iron, and calcium are significantly reduced. Sodium and magnesium, which were not removed, are removed by the ion exchange resin. Regarding sodium and magnesium, their concentrations have dropped below the upper limit of analysis, confirming removal by the ion exchanger. The purified 5-chlorobenzotriazole powder has metal concentrations of less than 1 ppm for aluminum, calcium, copper, and chromium, less than 2 ppm for iron, and less than 0.1 ppm for other metals. The purity of the purified product is >99.9%, which meets the requirements.

Claims

1. A method for purifying 5-chlorobenzotriazole, characterized in that, It includes the following steps: Heating and dissolving step: At a temperature of 50-60℃, the crude 5-chlorobenzotriazole powder is dissolved in an alcohol solvent and heated for 3-4 hours to form a mixed solution, wherein the weight ratio of the crude 5-chlorobenzotriazole powder to the alcohol solvent is 1:4~1:

5. Filtration step: The mixed solution is filtered using a precision filter membrane with a pore size of 40 nm to remove impurities and metal particles. Ion exchange step: At a temperature of 25±1℃, the filtered mixed solution is subjected to ion exchange with cation exchange resin for at least 6 hours, and a portion of the cation exchanged solution is removed to obtain a refined solution. Desolventization step: Heat the refined solution at 135-145°C for at least 12 hours to distill the alcohol solvent, leaving lumpy refined 5-chlorobenzotriazole; and Crushing step: Crush the blocky refined 5-chlorobenzotriazole to obtain refined 5-chlorobenzotriazole powder with a fineness grade of 2 mm.

2. The purification method of 5-chlorobenzotriazole as described in claim 1, characterized in that: The alcohol solvent is methanol, ethanol, or isopropanol.

3. The purification method for 5-chlorobenzotriazole as described in claim 1, characterized in that: The batch processing of this mixed solution shall not exceed 800 kg.

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