Process for recovering tribromophenol in production of bromotriazine
By employing steps such as pH adjustment, extraction, and crystallization, dichloromethane and n-hexane are used to recover tribromophenol, solving the problem of recovering tribromophenol from wastewater in the production of bromotriazine and achieving efficient and environmentally friendly resource recycling.
Patent Information
- Application Number
- CN202511243606.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-02
- Publication Date
- 2025-11-28
AI Technical Summary
In the existing technology, the crystallization mother liquor wastewater containing high concentrations of tribromophenol generated during the production of bromotriazine is difficult to recover effectively, leading to environmental pollution and waste of chemical raw materials.
Through steps such as pH adjustment, extraction, static separation, dehydration, desolvation under reduced pressure, and crystallization, dichloromethane and n-hexane are used for extraction and crystallization, and process parameters are precisely controlled to achieve efficient recovery of tribromophenol.
This method achieves efficient recovery of tribromophenol, significantly reduces environmental pollution risks, lowers production costs, and improves the continuity and economy of the process.
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of wastewater treatment, in particular to a recovery process of tribromophenol in the production of brominated triazine. BACKGROUND
[0002] Brominated triazine is an important flame retardant material and is widely used in the field of polymer materials. In its production process, a large amount of crystallization mother liquor wastewater containing high concentration of tribromophenol is generated.
[0003] Tribromophenol itself is toxic and chemically stable, and if directly discharged, it will cause serious harm to the environment, and also cause waste of valuable chemical raw materials. Therefore, effective recovery of tribromophenol from such wastewater is of great significance for reducing environmental pollution, realizing resource recycling and reducing production cost.
[0004] At present, the common methods for the treatment of wastewater containing phenol and the recovery of phenolic substances include solvent extraction method, adsorption method, biological degradation method, etc. The extraction method is commonly used, but the extractant used in extraction is prone to hydrolysis under acidic conditions, which limits the application of the extraction method. SUMMARY
[0005] In order to solve the defects in the prior art, the present application provides a recovery process of tribromophenol in the production of brominated triazine, which is realized by the following technical scheme: A recovery process of tribromophenol in the production of brominated triazine, characterized in that it comprises the following steps: Step 1, adjusting the pH of the wastewater, placing the wastewater in a reaction kettle, and adjusting the pH to 8.0±0.2 under stirring by using hydrochloric acid; Step 2, extraction, adding dichloromethane in a proportion of 1:100-1:50 by volume ratio of dichloromethane:wastewater for extraction, and then standing and separating after extraction is completed; Step 3, two-phase separation, transferring the wastewater phase to a neutralization tank and adjusting to neutral; the organic phase is dehydrated by anhydrous magnesium sulfate column to obtain an enrichment liquid; Step 4, desolventizing, transferring the enrichment liquid into a glass-lined distillation kettle for vacuum desolventizing; Step 5, crystallization, first pre-concentrating the distillation residue, then cooling to 4-6℃, adding n-hexane for crystallization; then centrifuging to obtain white needle-shaped crystals, washing the crystals twice with cold n-hexane at-1-1℃, and then vacuum drying to obtain tribromophenol.
[0006] The specific operation of step 2 is as follows: keeping the temperature at 22-28℃, adding dichloromethane in three times; after the addition of dichloromethane is completed, stirring for 10 minutes, and then standing and separating.
[0007] The specific operation of adding dichloromethane in three times is as follows: first adding 50%, stirring at 250 rpm for 10 minutes; after standing for 5 minutes, adding the remaining 50% of dichloromethane, stirring at 250 rpm for 10 minutes; after standing for 5 minutes again, adding the remaining dichloromethane, stirring at 250 rpm for 10 minutes.
[0008] The industrial-grade hydrochloric acid of 4% used in step 1 is added dropwise at a speed of not more than 5 L / min, and after reaching the end point, the stirring is continued for 15 min.
[0009] The specific operation of step 4 is as follows: the enrichment liquid is transferred into a glass-lined distillation kettle, and first, dichloromethane is recovered at 32-38℃ and -0.095 to -0.080 MPa, and then distilled at 42-47℃ and -0.105 to -0.09 MPa until the solid content of the residual liquid is greater than or equal to 25%.
[0010] In step 5, the addition of n-hexane is in a ratio of n-hexane: residual liquid = 2.8:1 to 3.3:1 by volume.
[0011] In step 5, the n-hexane is added in the following manner: first, 50% of n-hexane is added, and stirred at 100 rpm for 10 min; then the remaining 50% is added dropwise at a rate of 0.8-1.2 mL / min, and stirring is maintained at 100 rpm; after the addition of n-hexane is completed, the stirring is continued for 2 min.
[0012] After the stirring in step 5 is completed, it is necessary to stand at -1 to 1℃ for 1.8 to 2.2 h.
[0013] The centrifugal separation conditions are 2800-3200 rpm for 9-11 min.
[0014] The technical scheme of the present application has the following advantages: High efficiency recovery and environmental protection, through precise pH control-extraction-desolventization-crystallization process chain, high efficiency recovery of tribromophenol in wastewater is realized, and the COD of wastewater is reduced to below 1500 mg / L, significantly reducing the risk of environmental pollution.
[0015] Process continuity and economic efficiency are improved, the whole process uses step-by-step operation and parameter optimization, avoiding the disturbance of solid phase precipitation to continuous production, the purity of recovered tribromophenol is high, which can be directly reused as raw material, reducing production cost.
[0016] In the crystallization stage, pre-concentration, cold n-hexane gradient addition, and cold n-hexane gradient addition are used to reduce impurity wrapping. DETAILED DESCRIPTION
[0017] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.
[0018] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0019] Example 1 The wastewater is taken from the crystallization mother liquor of the TBC flame retardant production line and is alkaline. Main components: tribromophenol 320±25 mg / L, soluble dichloromethane 0.12% w / w, sodium bromide 1.5% w / w and trace amount of cyanuric acid derivatives. The wastewater needs to be screened through a 100-mesh screen before use to remove suspended particles.
[0020] First, the pH of the wastewater is adjusted.
[0021] 500 L of wastewater is pumped into a glass-lined reaction kettle, and stirring is started with a rotation speed of 200 rpm. Industrial-grade hydrochloric acid with a mass concentration of 4% is slowly added at a speed not exceeding 5 L / min, and the end point pH=8.0 is controlled by an online pH monitor. After reaching the end point, stirring is continued for 15 min.
[0022] At pH=8, tribromophenol is completely dissolved in the form of phenolate, avoiding the precipitation of free phenol under acidic conditions; at the same time, the hydrolysis reaction of dichloromethane under strong acid is inhibited.
[0023] Extraction.
[0024] Dichloromethane (DCM) is used for extraction.
[0025] The temperature is maintained at 25°C Dichloromethane is accurately measured at a volume ratio of dichloromethane:wastewater=1:100, and is added in three times: 50% is added first, stirring at 250 rpm for 10 minutes; after standing for 5 minutes, the remaining 50% of dichloromethane is added, stirring at 250 rpm for 10 minutes; after standing for another 5 minutes, the remaining dichloromethane is added, stirring at 250 rpm for 10 minutes.
[0026] Then, standing for layering for 60 minutes.
[0027] Then, two-phase separation is performed.
[0028] The wastewater phase is transferred to a neutralization tank and adjusted to neutral. At this time, the COD is reduced to below 1500 mg / L, and sent to the plant area sewage station for biochemical treatment.
[0029] The organic phase was dehydrated by an anhydrous magnesium sulfate column to obtain a concentrated solution.
[0030] Then, desolventization is performed.
[0031] The enriched solution was transferred to a glass-lined distillation vessel. First, DCM was recovered at 35℃ and -0.09MPa, and then the solution was distilled at 45℃ and -0.10MPa until the solid content of the residual liquid was ≥25%.
[0032] The recovered DCM is dehydrated and recycled using a molecular sieve column.
[0033] Then crystallization occurs.
[0034] First, the distillation residue is pre-concentrated and then rotary evaporated at 60°C until the solid content reaches 40%.
[0035] The distillation residue was cooled to 5°C, and hexane was added in a gradient of 3:1 (volume ratio of hexane to residue): first, 50% hexane was added and stirred at 100 rpm for 10 min; then the remaining 50% was added dropwise at a rate of 1 mL / min while maintaining stirring at 100 rpm. After the hexane was completely added, stirring was continued for 2 min. The mixture was then allowed to stand at 0°C for 2 h to improve crystal purity and morphology.
[0036] White needle-like crystals were obtained by centrifugation at 3000 rpm for 10 min. The crystals were washed twice with cold n-hexane at 0 °C and dried under vacuum at 50 °C and -0.1 MPa for 4 hours to obtain tribromophenol. Gradient cooling crystallization combined with cold n-hexane rinsing significantly improved crystal purity and reduced impurity encapsulation.
[0037] Example 2 The wastewater is taken from the crystallization mother liquor of the TBC flame retardant production line and is alkaline. Its main components are: tribromophenol 280±25 mg / L, soluble dichloromethane 0.08% w / w, sodium bromide 1.2% w / w, and trace amounts of cyanuric acid derivatives. The wastewater needs to be sieved through a 100-mesh screen before use to remove suspended particles.
[0038] First, the pH of the wastewater is adjusted.
[0039] Pump 500L of wastewater into a glass-lined reactor, start the stirrer, and maintain a stirring speed of 200 rpm. Slowly add 4% (w / w) industrial-grade hydrochloric acid, with a dropping rate not exceeding 5L / min, and control the final pH to 7.8 using an online pH monitor. After reaching the endpoint, continue stirring for 15 minutes.
[0040] Under pH=7.8 conditions, tribromophenol completely dissolves in the form of phenol salts, avoiding the precipitation of free phenol under acidic conditions; at the same time, it inhibits the hydrolysis reaction of dichloromethane under strong acid.
[0041] extraction.
[0042] Dichloromethane was used for extraction.
[0043] Maintain the temperature at 22℃.
[0044] The dichloromethane (DCM) and wastewater were precisely measured at a volume ratio of 1:80, and the dichloromethane was added in three parts: 50% was added first and stirred at 250 rpm for 10 minutes; after standing for 5 minutes, the remaining 50% of the dichloromethane was added and stirred at 250 rpm for 10 minutes; after standing for another 5 minutes, the remaining dichloromethane was added and stirred at 250 rpm for 10 minutes.
[0045] Then let it stand for 55 minutes to separate into layers.
[0046] Then, two-phase separation is performed.
[0047] The wastewater phase is transferred to a neutralization tank and adjusted to neutral. At this point, the COD drops below 1400 mg / L and is then sent to the plant's wastewater treatment plant for biological treatment.
[0048] The organic phase was dehydrated by an anhydrous magnesium sulfate column to obtain a concentrated solution.
[0049] Then, desolventization is performed.
[0050] The enriched solution was transferred to a glass-lined distillation vessel. First, DCM was recovered at 32℃ and -0.08MPa, and then the solution was distilled at 42℃ and -0.09MPa until the solid content of the residual liquid was ≥25%.
[0051] The recovered DCM is dehydrated and recycled using a molecular sieve column.
[0052] Then crystallization occurs.
[0053] First, the distillation residue is pre-concentrated and then rotary evaporated at 58°C until the solid content reaches 38%.
[0054] The distillation residue was cooled to 4°C, and hexane was added in a gradient of 2.8:1 (volume ratio of hexane to residue): first, 50% hexane was added and stirred at 100 rpm for 10 min; then the remaining 50% was added dropwise at a rate of 0.8 mL / min while maintaining stirring at 100 rpm. After the hexane addition was complete, stirring was continued for 2 min. The mixture was then allowed to stand at -1°C for 1.8 h to improve crystal purity and morphology.
[0055] The white needle-like crystals were obtained by centrifugation at 2800 rpm for 9 min. The crystals were washed twice with cold n-hexane at -1℃ and dried under vacuum at 48℃ and -0.09 MPa for 3.8 hours to obtain tribromophenol.
[0056] Example 3 The wastewater is taken from the crystallization mother liquor of the TBC flame retardant production line and is alkaline. Its main components are: tribromophenol 350±25 mg / L, dissolved dichloromethane 0.15% w / w, sodium bromide 1.8% w / w, and trace amounts of cyanuric acid derivatives. The wastewater needs to be sieved through a 100-mesh screen before use to remove suspended particles.
[0057] First, the pH of the wastewater is adjusted.
[0058] Pump 500L of wastewater into a glass-lined reactor, start the stirrer, and maintain a stirring speed of 200 rpm. Slowly add 4% (w / w) industrial-grade hydrochloric acid, with a dropping rate not exceeding 5L / min, and control the final pH to 8.2 using an online pH monitor. After reaching the endpoint, continue stirring for 15 minutes.
[0059] At pH 8.2, tribromophenol completely dissolves as a phenolate salt, preventing the precipitation of free phenol under acidic conditions; at the same time, it inhibits the hydrolysis of dichloromethane under strong acid.
[0060] extraction.
[0061] Dichloromethane was used for extraction.
[0062] Maintain the temperature at 28℃.
[0063] The dichloromethane (DCM) and wastewater were precisely measured at a volume ratio of 1:60, and the dichloromethane was added in three parts: 50% was added first and stirred at 250 rpm for 10 minutes; after standing for 5 minutes, the remaining 50% of the dichloromethane was added and stirred at 250 rpm for 10 minutes; after standing for another 5 minutes, the remaining dichloromethane was added and stirred at 250 rpm for 10 minutes.
[0064] Then let it stand for 65 minutes to separate into layers.
[0065] Then, two-phase separation is performed.
[0066] The wastewater phase is transferred to a neutralization tank and adjusted to neutral. At this point, the COD drops below 1600 mg / L and is then sent to the plant's wastewater treatment plant for biological treatment.
[0067] The organic phase was dehydrated by an anhydrous magnesium sulfate column to obtain a concentrated solution.
[0068] Then, desolventization is performed.
[0069] The enriched solution was transferred to a glass-lined distillation vessel. First, DCM was recovered at 38℃ and -0.095MPa, and then the solution was distilled at 47℃ and -0.105MPa until the solid content of the residual liquid was ≥25%.
[0070] The recovered DCM is dehydrated and recycled using a molecular sieve column.
[0071] Then crystallization occurs.
[0072] First, the distillation residue is pre-concentrated and then rotary evaporated at 62°C until the solid content reaches 42%.
[0073] The distillation residue was cooled to 6°C, and hexane was added in a gradient of 3.2:1 (volume ratio of hexane to residue): first, 50% hexane was added and stirred at 100 rpm for 10 min; then the remaining 50% was added dropwise at a rate of 1.2 mL / min while maintaining stirring at 100 rpm. After the hexane addition was complete, stirring was continued for 2 min. The mixture was then allowed to stand at 1°C for 2.2 h to improve crystal purity and morphology.
[0074] The white needle-like crystals were obtained by centrifugation at 3200 rpm for 11 min. The crystals were washed twice with cold n-hexane at 1 °C and dried under vacuum at 52 °C and -0.11 MPa for 4.2 h to obtain tribromophenol.
[0075] Example 4 The wastewater is taken from the crystallization mother liquor of the TBC flame retardant production line and is alkaline. Its main components are: tribromophenol 300±25 mg / L, dissolved dichloromethane 0.10% w / w, sodium bromide 1.3% w / w, and trace amounts of cyanuric acid derivatives. The wastewater needs to be sieved through a 100-mesh screen before use to remove suspended particles.
[0076] First, the pH of the wastewater is adjusted.
[0077] Pump 500L of wastewater into a glass-lined reactor, start the stirrer, and maintain a stirring speed of 200 rpm. Slowly add 4% (w / w) industrial-grade hydrochloric acid, with a dropping rate not exceeding 5L / min, and control the final pH to 7.9 using an online pH monitor. After reaching the endpoint, continue stirring for 15 minutes.
[0078] At pH 7.9, tribromophenol completely dissolves as a phenolate salt, preventing the precipitation of free phenol under acidic conditions; it also inhibits the hydrolysis of dichloromethane under strong acid.
[0079] extraction.
[0080] Dichloromethane was used for extraction.
[0081] Maintain the temperature at 24℃.
[0082] The dichloromethane (DCM) and wastewater were precisely measured at a volume ratio of 1:50, and the DCM was added in three parts: 50% was added first and stirred at 250 rpm for 10 minutes; after standing for 5 minutes, the remaining 50% of the DCM was added and stirred at 250 rpm for 10 minutes; after standing for another 5 minutes, the remaining DCM was added and stirred at 250 rpm for 10 minutes.
[0083] Then let it stand for 58 minutes to separate into layers.
[0084] Then, two-phase separation is performed.
[0085] The wastewater phase is transferred to a neutralization tank and adjusted to neutral. At this point, the COD drops below 1450 mg / L and is then sent to the plant's wastewater treatment plant for biological treatment.
[0086] The organic phase was dehydrated by an anhydrous magnesium sulfate column to obtain a concentrated solution.
[0087] Then, desolventization is performed.
[0088] The enriched solution was transferred to a glass-lined distillation vessel. First, DCM was recovered at 34℃ and -0.085MPa, and then the solution was distilled at 44℃ and -0.095MPa until the solid content of the residual liquid was ≥25%.
[0089] The recovered DCM is dehydrated and recycled using a molecular sieve column.
[0090] Then crystallization occurs.
[0091] First, the distillation residue is pre-concentrated and then rotary evaporated at 59°C until the solid content reaches 39%.
[0092] The distillation residue was cooled to 4.5℃, and hexane was added in a gradient of 3.1:1 (volume ratio of hexane to residue): first, 50% hexane was added and stirred at 100 rpm for 10 min; then the remaining 50% was added dropwise at a rate of 0.9 mL / min while maintaining stirring at 100 rpm. After the hexane addition was complete, stirring was continued for 2 min. The mixture was then allowed to stand at -0.5℃ for 1.9 h to improve crystal purity and morphology.
[0093] The white needle-like crystals were obtained by centrifugation at 2900 rpm for 9.5 min. The crystals were washed twice with cold n-hexane at -0.5℃ and dried under vacuum at 49℃ and -0.095 MPa for 3.9 h to obtain tribromophenol.
[0094] Example 5 The wastewater is taken from the crystallization mother liquor of the TBC flame retardant production line and is alkaline. Its main components are: tribromophenol 340±25 mg / L, dissolved dichloromethane 0.13% w / w, sodium bromide 1.7% w / w, and trace amounts of cyanuric acid derivatives. The wastewater needs to be sieved through a 100-mesh screen before use to remove suspended particles.
[0095] First, the pH of the wastewater is adjusted.
[0096] Pump 500L of wastewater into a glass-lined reactor, start the stirrer, and maintain a stirring speed of 200 rpm. Slowly add 4% (w / w) industrial-grade hydrochloric acid, with a dropping rate not exceeding 5L / min, and control the final pH to 8.1 using an online pH monitor. After reaching the endpoint, continue stirring for 15 minutes.
[0097] At pH 8.1, tribromophenol completely dissolves as a phenolate salt, preventing the precipitation of free phenol under acidic conditions; at the same time, it inhibits the hydrolysis of dichloromethane under strong acid.
[0098] extraction.
[0099] Dichloromethane was used for extraction.
[0100] Maintain the temperature at 26℃.
[0101] The dichloromethane (DCM) to wastewater ratio is precisely measured at 1:70 by volume, and the dichloromethane is added in three parts: first, add 50% and stir at 250 rpm for 10 minutes; after standing for 5 minutes, add the remaining 50% of the dichloromethane and stir at 250 rpm for 10 minutes; after standing for another 5 minutes, add the remaining dichloromethane and stir at 250 rpm for 10 minutes.
[0102] Then let it stand for 62 minutes to separate into layers.
[0103] Then, two-phase separation is performed.
[0104] The wastewater phase is transferred to a neutralization tank and adjusted to neutral. At this point, the COD drops below 1550 mg / L and is then sent to the plant's wastewater treatment plant for biological treatment.
[0105] The organic phase was dehydrated by an anhydrous magnesium sulfate column to obtain a concentrated solution.
[0106] Then, desolventization is performed.
[0107] The enriched solution was transferred to a glass-lined distillation vessel. First, DCM was recovered at 36℃ and -0.092MPa, and then the solution was distilled at 46℃ and -0.102MPa until the solid content of the residual liquid was ≥25%.
[0108] The recovered DCM is dehydrated and recycled using a molecular sieve column.
[0109] Then crystallization occurs.
[0110] First, the distillation residue is pre-concentrated and then rotary evaporated at 61°C until the solid content reaches 41%.
[0111] The distillation residue was cooled to 5.5°C, and hexane was added in a gradient of 3.3:1 (volume ratio of hexane to residue): first, 50% hexane was added and stirred at 100 rpm for 10 min; then the remaining 50% was added dropwise at a rate of 1.1 mL / min while maintaining stirring at 100 rpm. After the hexane addition was complete, stirring was continued for 2 min. The mixture was then allowed to stand at 0.5°C for 2.1 h to improve crystal purity and morphology.
[0112] The white needle-like crystals were obtained by centrifugation at 3100 rpm for 10.5 min. The crystals were washed twice with cold n-hexane at 0.5 °C and dried under vacuum at 51 °C and -0.105 MPa for 4.1 h to obtain tribromophenol.
[0113] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A process for recovering tribromophenol in the production of bromotriazine, characterized in that, Includes the following steps: Step 1: Adjust the pH of the wastewater by placing the wastewater in a reaction vessel and adjusting the pH to 8.0 ± 0.2 with hydrochloric acid while stirring. Step 2, extraction: Dichloromethane is added at a volume ratio of 1:50 to 1:25 for extraction. After extraction, the mixture is allowed to stand and separate into layers. Step 3: Two-phase separation. The wastewater phase is transferred to a neutralization tank and adjusted to neutral. The organic phase is dehydrated by an anhydrous magnesium sulfate column to obtain a concentrated solution. Step 4: Desolventizing; the enriched solution is transferred to a glass-lined distillation vessel for desolventizing under reduced pressure. Step 5, crystallization: First, the distillation residue is pre-concentrated, then cooled to 4-6°C, and hexane is added for crystallization; then, the white needle-like crystals are obtained by centrifugation, and the crystals are washed twice with cold hexane at -1 to 1°C; then, the product is dried under vacuum to obtain tribromophenol.
2. The process for recovering tribromophenol in the production of bromotriazine according to claim 1, characterized in that, The specific operation of step 2 is as follows: maintain 22-28°C and add dichloromethane in three portions; after the dichloromethane is added, stir for 10 minutes and then let it stand to separate into layers.
3. The process for recovering tribromophenol in the production of bromotriazine according to claim 2, characterized in that, The specific procedure for adding dichloromethane in three stages is as follows: first, add 50% and stir at 250 rpm for 10 minutes; after standing for 5 minutes, add the remaining 50% of dichloromethane and stir at 250 rpm for 10 minutes; after standing for another 5 minutes, add the remaining dichloromethane and stir at 250 rpm for 10 minutes.
4. The process for recovering tribromophenol in the production of bromotriazine according to claim 1, characterized in that, In step 1, 4% industrial-grade hydrochloric acid is added dropwise at a rate not exceeding 5 L / min, and stirring is continued for 15 min after reaching the endpoint.
5. The process for recovering tribromophenol in the production of bromotriazine according to claim 1, characterized in that, The specific operation of step 4 is as follows: the enriched liquid is transferred into a glass-lined distillation kettle, and dichloromethane is first recovered at 32-38℃ and -0.095--0.080MPa. Then, it is distilled at 42-47℃ and -0.105--0.09MPa until the solid content of the residual liquid is ≥25%.
6. The process for recovering tribromophenol in the production of bromotriazine according to claim 1, characterized in that, In step 5, n-hexane is added at a volume ratio of n-hexane:residual liquid = 2.8:1 to 3.3:
1.
7. The process for recovering tribromophenol in the production of bromotriazine according to claim 1 or 6, characterized in that, In step 5, the method for adding n-hexane is as follows: first add 50% n-hexane and stir at 100 rpm for 10 min; then add the remaining 50% dropwise at a rate of 0.8 to 1.2 mL / min while maintaining stirring at 100 rpm. After the n-hexane has been added, continue stirring for 2 min.
8. The process for recovering tribromophenol in the production of bromotriazine according to claim 7, characterized in that, After stirring in step 5, the mixture needs to stand at -1 to 1°C for 1.8 to 2.2 hours.
9. The process for recovering tribromophenol in the production of bromotriazine according to claim 1, characterized in that, The centrifugation conditions are 2800–3200 rpm for 9–11 min.