Method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol in bromine-containing solid waste through melt crystallization

Abstract

The invention provides a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol in bromine-containing solid waste through melt crystallization, and relates to the field of solid waste recovery. The method comprises the following steps: mixing the bromine-containing solid waste, a solvent and a catalyst for reaction, and then carrying out liquid-liquid separation to obtain a bromine-containing organic phase and salt-containing wastewater; recovering the bromine-containing organic phase solvent to obtain a bromine-containing organic mixture; preheating the bromine-containing organic mixture, melting, cooling, sweating and melting to obtain a tribromophenol crude product and a tetrabromobisphenol A crude product; carrying out reduced pressure rectification on the tribromophenol crude product to obtain a dibromophenol product and a tower kettle product, and carrying out recrystallization, solid-liquid separation, washing and drying on the tower kettle product to obtain a tribromophenol product; and carrying out recrystallization, solid-liquid separation, alkali washing and drying on the crude tetrabromobisphenol A product to obtain the tetrabromobisphenol A product. According to the method, reaction impurity removal, melt crystallization and recrystallization are coupled, tribromophenol, tetrabromobisphenol A and dibromophenol products are obtained at the same time, the process is simple, and energy consumption is remarkably reduced compared with traditional methods.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste recovery, and in particular relates to a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization. Background Art

[0002] Brominated flame retardants play an important role in various fields, but there has been no breakthrough in the recycling of their solid waste.

[0003] Existing treatment methods for bromine-containing solid waste primarily rely on incineration. However, incineration exhaust is difficult to treat and can easily generate secondary pollution. Furthermore, waste with high bromine content requires specialized equipment and high corrosion protection requirements, resulting in high treatment costs. Furthermore, existing technologies also utilize distillation and other methods to recover tribromophenol and tetrabromobisphenol A, but these methods fail to address the difficulty in recovering tetrabromobisphenol A due to the decomposition of tribromophenol, which leads to the deterioration of the still residue.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization, so as to solve the above problems.

[0006] In order to achieve the above objectives, the present invention adopts the following technical solutions: A method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization, comprising: The bromine-containing solid waste, solvent and catalyst are mixed to perform a first reaction, and then liquid-liquid separation is performed to obtain a bromine-containing organic phase and saline wastewater; The bromine-containing organic phase is subjected to solvent recovery to obtain a recovered solvent and a bromine-containing organic mixture; The solvent recovery unit is an evaporation device equipped with a scraper, which can operate under atmospheric pressure or vacuum. The principle of the solvent recovery unit is to utilize the significant difference in boiling points between the solvent and bromine-containing organic matter to facilitate the complete removal of the solvent. The scraper's function is to form a film of liquid to promote solvent evaporation and improve the recovery rate of bromine-containing organic matter.

[0007] The bromine-containing organic mixture is preheated, then melted, cooled, sweated, and dissolved to obtain crude tribromophenol and crude tetrabromobisphenol A; The crude tribromophenol product is subjected to vacuum distillation to obtain a dibromophenol product and a bottom product, and the bottom product is subjected to a first recrystallization, a first solid-liquid separation, water washing, and a first drying to obtain a tribromophenol product; The crude tetrabromobisphenol A product is obtained by subjecting the crude tetrabromobisphenol A to a second recrystallization, a second solid-liquid separation, an alkali washing, and a second drying.

[0008] Preferably, the solvent is a mixture of an organic matter and water, and the organic matter includes one or more of methanol, acetone, chloroform, chlorobenzene, ethyl acetate, isopropanol, benzene, toluene, and methyl tert-butyl ether; the mass ratio of the solvent to the bromine-containing solid waste is 0.5-2:1; The water content of the solvent is 5-30 wt %.

[0009] Optionally, the mass ratio of the solvent to the bromine-containing solid waste can be 0.5:1, 1:1, 1.5:1, 2:1 or any value between 0.5 and 2:1; the water content of the solvent can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt% or any value between 5-30wt%.

[0010] Preferably, the catalyst is a reducing catalyst, including one or more of formaldehyde, acetaldehyde, benzaldehyde, hydrazine hydrate, and sodium borohydride; the mass ratio of the catalyst to the bromine-containing solid waste is 0.05~0.3:1.

[0011] Optionally, the mass ratio of the catalyst to the bromine-containing solid waste can be 0.05:1, 0.1:1, 0.2:1, 0.3:1 or any value between 0.05 and 0.3:1.

[0012] Preferably, the temperature of the first reaction is 40-90° C., and the time is 0.5-2 h.

[0013] Optionally, the temperature of the first reaction can be 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or any value between 40-90°C, and the time can be 0.5h, 1h, 1.5h, 2h or any value between 0.5-2h.

[0014] Preferably, the melting temperature is 100-200°C, the cooling end temperature is 0-40°C, the sweating temperature is 90-130°C, and the melting temperature is 100-200°C; Optionally, the melting temperature may be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or any value between 100-200°C, the cooling endpoint temperature may be 0°C, 10°C, 20°C, 30°C, 40°C or any value between 0-40°C, the sweating temperature may be 90°C, 100°C, 110°C, 120°C, 130°C or any value between 90-130°C, and the melting temperature may be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or any value between 100-200°C; The cooling rate is 0.02-0.5°C / min, and the sweating rate is 0.02-0.5°C / min.

[0015] Optionally, the cooling rate can be 0.02℃ / min, 0.05℃ / min, 0.1℃ / min, 0.2℃ / min, 0.3℃ / min, 0.4℃ / min, 0.5℃ / min or any value between 0.02-0.5℃ / min, and the sweating rate can be 0.02℃ / min, 0.05℃ / min, 0.1℃ / min, 0.2℃ / min, 0.3℃ / min, 0.4℃ / min, 0.5℃ / min or any value between 0.02-0.5℃ / min.

[0016] Preferably, the melting temperature is 150-180°C, the cooling end point temperature is 10-25°C, the sweating temperature is 95-105°C, and the melting temperature is 150-180°C; The cooling rate is 0.05-0.1°C / min, and the sweating rate is 0.05-0.1°C / min.

[0017] Preferably, the number of theoretical plates of the vacuum distillation is 60-80, the operating pressure is 1-5 kPa, and the operating temperature is 130-230°C.

[0018] Optionally, the number of theoretical plates of the vacuum distillation can be 60, 70, 80 or any value between 60 and 80, the operating pressure can be 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa or any value between 1 and 5 kPa, and the operating temperature can be 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C or any value between 130 and 230°C.

[0019] Preferably, the initial temperature of the first recrystallization is 50-60°C, the final temperature is -5 to 5°C, and the recrystallization solvent is chlorobenzene; The water washing temperature is 80-100°C; The first drying process is performed at a pressure of 10-50 kPa and a temperature of 50-70°C.

[0020] Optionally, the initial temperature of the first recrystallization can be 50°C, 55°C, 60°C or any value between 50-60°C, the final temperature can be -5°C, 0°C, 5°C or any value between -5 and 5°C, and the recrystallization solvent is chlorobenzene; The water washing temperature can be 80°C, 90°C, 100°C or any value between 80-100°C; The pressure of the first drying may be 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa or any value between 10 and 50 kPa, and the temperature may be 50°C, 60°C, 70°C or any value between 50 and 70°C.

[0021] Preferably, the initial temperature of the second recrystallization is 60-85°C, the final temperature is 5-25°C, and the recrystallization solvent is chlorobenzene; The alkaline washing is carried out at a temperature of 80-100° C. using one or more of caustic soda, soda ash, sodium sulfite and thiourea dioxide; The second drying process is performed at a pressure of 10-50 kPa and a temperature of 60-160°C.

[0022] Optionally, the initial temperature of the second recrystallization can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or any value between 60-85°C, the final temperature can be 5°C, 10°C, 15°C, 20°C, 25°C or any value between 5-25°C, and the recrystallization solvent is chlorobenzene; The temperature of the alkali washing can be 80°C, 90°C, 100°C or any value between 80-100°C; The pressure of the second drying can be 10kPa, 20kPa, 30kPa, 40kPa, 50kPa or any value between 10-50kPa, and the temperature can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or any value between 60-160°C.

[0023] Preferably, the bromine-containing solid waste, calculated with its total mass as 100%, includes: Tribromophenol 35-70%, tetrabromobisphenol A 20-50%, inorganic salts 1-5% and other organic matter 5-10%; The inorganic salts include sodium bromide and sodium sulfate, and the other organic substances include one or more of bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienone.

[0024] Beneficial effects of the present invention: The present application provides a method for recovering tribromophenol, tetrabromobisphenol A, and dibromophenol from bromine-containing solid waste by melt crystallization. The method utilizes the strong reducing properties of a catalyst to reduce ketones such as 2,4,4,6-tetrabromo-2,5-cyclohexadienone in the bromine-containing solid waste to products such as tribromophenol, thereby improving product yield and purity. The melt crystallization process separates organic matter without the need for additional solvent, improving product purity (product purity is greater than or equal to 99 wt%). The principle is to utilize the different melting points of organic matter to achieve partial crystallization by gradually lowering the temperature, thereby creating a concentration difference between the crystalline solid and the mother liquor components, achieving the purpose of separating the organic matter. Through the melt crystallization process, crude tribromophenol and tetrabromobisphenol A can be obtained simply and with low energy consumption, improving product quality.

[0025] This method uses reaction impurity removal and melt crystallization coupled with recrystallization process to simultaneously obtain tribromophenol, tetrabromobisphenol A and dibromophenol products; the process is simple, significantly reduces energy consumption compared to traditional methods, and efficiently recovers high-value chemicals from bromine-containing solid waste, while achieving both ecological and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The present invention provides a process flow diagram of a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0029] Example 1 like Figure 1 As shown, this embodiment provides a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization, comprising the following steps: Bromine-containing solid waste S1, composed of 70% tribromophenol (TBP), approximately 24% tetrabromobisphenol A (TBBPA), approximately 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone (2,4,4,6-tetrabromo-2,5-cyclohexadienone), and approximately 1% inorganic salt (NaBr / Na2SO4), was mixed with a methanol-water mixed solvent (85% methanol by weight, with a 2:1 mass ratio of the mixed solvent to the bromine-containing solid waste) and a formaldehyde solution (0.3:1 mass ratio of the formaldehyde solution to the bromine-containing solid waste) in a reactor. After reacting at 60°C for 2 hours, the mixture was placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged. The bromine-containing organic phase in the upper layer was placed in a scraped-surface evaporator, which operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0030] S2. The desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A are obtained, respectively. The melting temperature is 180°C, the cooling temperature is 10°C, the sweating temperature is 105°C, the melting temperature is 180°C, the cooling rate is 0.05°C / min, and the sweating rate is 0.05°C / min.

[0031] S3, the crude tribromophenol product, enters a vacuum distillation tower with 80 theoretical plates, an operating pressure of 5 kPa(A), and a tower top temperature of 165°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters the recrystallization unit #1. Chlorobenzene is used as the recrystallization solvent, with an initial crystallization temperature of 60°C and a final crystallization temperature of -5°C. The recrystallized solid is washed with water for 30 minutes at 95°C. The crystals are then vacuum dried (pressure of 50 kPa(A), temperature of 60°C) to obtain the tribromophenol product.

[0032] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as the recrystallization solvent. The initial crystallization temperature is 85°C and the final crystallization temperature is 5°C. The solid after recrystallization is washed with a sodium sulfite aqueous solution for 30 minutes (95°C). The crystallized product is vacuum dried (pressure of 10 kPa(A), temperature of 60°C) to obtain tetrabromobisphenol A product.

[0033] The final product obtained had a purity of 99.9% by weight for tribromophenol, 99.3% by weight for tetrabromobisphenol A, and 99.2% for dibromophenol. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 86%.

[0034] Example 2 This embodiment provides a method for recovering tribromophenol, tetrabromobisphenol A, and dibromophenol from bromine-containing solid waste by melt crystallization, comprising the following steps: Bromine-containing solid waste S1, composed of 35% by weight tribromophenol; approximately 50% by weight tetrabromobisphenol A; approximately 10% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone; and approximately 5% inorganic salt (NaBr / Na2SO4), was mixed with a chlorobenzene and water mixture (70% by weight chlorobenzene, with a 0.5:1 mass ratio of the mixed solvent to the bromine-containing solid waste) and a sodium borohydride aqueous solution (0.05:1 mass ratio of the sodium borohydride solution to the bromine-containing solid waste) in a reactor. After reacting at 90°C for 0.5 hours, the mixture was placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged. The bromine-containing organic phase in the upper layer was placed in a scraped-surface evaporator, which operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0035] S2. The desalted bromine-containing organic mixture is preheated and then introduced into a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A are obtained, respectively. The melting temperature is 150°C, the cooling temperature is 25°C, the sweating temperature is 95°C, the melting temperature is 150°C, the cooling rate is 0.1°C / min, and the sweating rate is 0.1°C / min.

[0036] S3, the crude tribromophenol product, enters a vacuum distillation tower with 80 theoretical plates, an operating pressure of 1 kPa(A), and a tower top temperature of 130°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters the recrystallization unit #1. Chlorobenzene is used as the recrystallization solvent, with an initial crystallization temperature of 50°C and a final crystallization temperature of 5°C. The recrystallized solid is washed with water at 80°C for 30 minutes. The crystals are then vacuum dried at 50 kPa(A) and 60°C to obtain the tribromophenol product.

[0037] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as the recrystallization solvent. The initial crystallization temperature is 60°C and the final crystallization temperature is 25°C. The solid after recrystallization is washed with thiourea dioxide solution for 30 minutes (80°C). The crystallized product is vacuum dried (pressure of 50 kPa(A), temperature of 120°C) to obtain tetrabromobisphenol A product.

[0038] The final product obtained had a purity of 99.1% for tribromophenol, 99.0% for tetrabromobisphenol A, and 99.1% for dibromophenol. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 81%.

[0039] Example 3 This embodiment provides a method for recovering tribromophenol, tetrabromobisphenol A, and dibromophenol from bromine-containing solid waste by melt crystallization, comprising the following steps: Bromine-containing solid waste S1, composed of 50% tribromophenol; approximately 35% tetrabromobisphenol A; approximately 10% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone; and approximately 5% inorganic salt (NaBr / Na2SO4), was mixed with a mixed solvent of ethyl acetate and water (95% ethyl acetate by weight, with a 1:1 mass ratio of the mixed solvent to the bromine-containing solid waste) and an aqueous hydrazine hydrate solution (0.15:1 mass ratio of the aqueous hydrazine hydrate solution to the bromine-containing solid waste) in a reactor. After reacting at 90°C for 1 hour, the mixture was placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged. The bromine-containing organic phase in the upper layer was transferred to a scraped-surface evaporator operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0040] S2. The desalted bromine-containing organic mixture was preheated and then entered into a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A were obtained, respectively. The melting temperature was 170°C, the cooling temperature was 15°C, the sweating temperature was 100°C, the melting temperature was 170°C, the cooling rate was 0.07°C / min, and the sweating rate was 0.07°C / min.

[0041] S3, the crude tribromophenol product, enters a vacuum distillation tower with 60 theoretical plates, an operating pressure of 3 kPa(A), and a tower top temperature of 148°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters the recrystallization unit #1. Chlorobenzene is used as the recrystallization solvent, with an initial crystallization temperature of 55°C and a final crystallization temperature of 0°C. The recrystallized solid is washed with water for 30 minutes at 90°C. The crystals are then vacuum dried (pressure of 50 kPa(A), temperature of 60°C) to obtain the tribromophenol product.

[0042] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as the recrystallization solvent. The initial crystallization temperature is 70°C and the final crystallization temperature is 10°C. The solid after recrystallization is washed with 10% caustic soda solution for 30 minutes (90°C). The crystallized product is vacuum dried (pressure of 50 kPa(A), temperature of 120°C) to obtain tetrabromobisphenol A product.

[0043] The final product obtained had a purity of 99.4% by weight for tribromophenol, 99.1% by weight for tetrabromobisphenol A, and 99.1% for dibromophenol. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 83%.

[0044] Comparative Example 1 Bromine-containing solid waste S1, composed of 70% tribromophenol; approximately 24% tetrabromobisphenol A; approximately 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone; and approximately 1% inorganic salt (NaBr / Na2SO4), was mixed with toluene solvent (the mass ratio of toluene to bromine-containing solid waste was 2:1) and formaldehyde solution (the mass ratio of formaldehyde solution to bromine-containing solid waste was 0.3:1) in a reactor. After reacting at 60°C for 2 hours, the mixture was placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged. The bromine-containing organic phase in the upper layer was transferred to a scraped-surface evaporator operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0045] S2. The desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A are obtained, respectively. The melting temperature is 180°C, the cooling temperature is 10°C, the sweating temperature is 105°C, the melting temperature is 180°C, the cooling rate is 0.05°C / min, and the sweating rate is 0.05°C / min.

[0046] S3, the crude tribromophenol product, enters a vacuum distillation tower with 80 theoretical plates, an operating pressure of 5 kPa(A), and a tower top temperature of 165°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters the recrystallization unit #1. Chlorobenzene is used as the recrystallization solvent, with an initial crystallization temperature of 60°C and a final crystallization temperature of -5°C. The recrystallized solid is washed with water for 30 minutes at 95°C. The crystals are then vacuum dried (pressure of 50 kPa(A), temperature of 60°C) to obtain the tribromophenol product.

[0047] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as the recrystallization solvent. The initial crystallization temperature is 85°C and the final crystallization temperature is 5°C. The solid after recrystallization is washed with a sodium sulfite aqueous solution for 30 minutes (95°C). The crystallized product is vacuum dried (pressure of 10 kPa(A), temperature of 60°C) to obtain tetrabromobisphenol A product.

[0048] Ultimately, the obtained tribromophenol product had a purity of 99.5% by weight; the tetrabromobisphenol A product had a purity of 99.1% by weight; and the dibromophenol product had a purity of 99.1% by weight. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 72%. Comparing Example 1 with Comparative Example 1 reveals that the solvent of the present invention can improve the purity and yield of tribromophenol, tetrabromobisphenol A, and dibromophenol. Furthermore, the solvent of the present invention can improve the removal rate of raw salts.

[0049] Comparative Example 2 Bromine-containing solid waste S1, composed of 70% tribromophenol; approximately 24% tetrabromobisphenol A; approximately 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone; and approximately 1% inorganic salt (NaBr / Na2SO4), was mixed with a methanol-water mixture (85% methanol by weight, with a 2:1 mass ratio of mixed solvent to bromine-containing solid waste) in a reactor at 60°C for 2 hours before being placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged; the bromine-containing organic phase in the upper layer was placed in a scraped-surface evaporator, which operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0050] S2. The desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A are obtained, respectively. The melting temperature is 180°C, the cooling temperature is 10°C, the sweating temperature is 105°C, the melting temperature is 180°C, the cooling rate is 0.05°C / min, and the sweating rate is 0.05°C / min.

[0051] S3, the crude tribromophenol product, enters a vacuum distillation tower with 80 theoretical plates, an operating pressure of 5 kPa(A), and a tower top temperature of 165°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters the recrystallization unit #1. Chlorobenzene is used as the recrystallization solvent, with an initial crystallization temperature of 60°C and a final crystallization temperature of -5°C. The recrystallized solid is washed with water for 30 minutes at 95°C. The crystals are then vacuum dried (pressure of 50 kPa(A), temperature of 60°C) to obtain the tribromophenol product.

[0052] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as the recrystallization solvent. The initial crystallization temperature is 85°C and the final crystallization temperature is 5°C. The solid after recrystallization is washed with a sodium sulfite aqueous solution for 30 minutes (95°C). The crystallized product is vacuum dried (pressure of 10 kPa(A), temperature of 60°C) to obtain tetrabromobisphenol A product.

[0053] Finally, the obtained tribromophenol product had a purity of 99.6% by weight; the tetrabromobisphenol A product had a purity of 98.2% by weight; and the dibromophenol product had a purity of 98.5%. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 76%. Comparison of Example 1 and Comparative Example 2 reveals that the catalyst of the present invention can improve the purity and yield of tribromophenol, tetrabromobisphenol A, and dibromophenol.

[0054] Comparative Example 3 Bromine-containing solid waste S1, composed of 70% tribromophenol (TBP), approximately 24% tetrabromobisphenol A (TBBPA), approximately 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone (2,4,4,6-tetrabromo-2,5-cyclohexadienone), and approximately 1% inorganic salt (NaBr / Na2SO4), was mixed with a methanol-water mixed solvent (85% methanol by weight, with a 2:1 mass ratio of the mixed solvent to the bromine-containing solid waste) and a formaldehyde solution (0.3:1 mass ratio of the formaldehyde solution to the bromine-containing solid waste) in a reactor. After reacting at 60°C for 2 hours, the mixture was placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged. The bromine-containing organic phase in the upper layer was placed in a scraped-surface evaporator, which operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0055] S2. The desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A are obtained, respectively. The melting temperature is 200°C, the cooling temperature is 60°C, the sweating temperature is 150°C, the melting temperature is 200°C, the cooling rate is 1°C / min, and the sweating rate is 1°C / min.

[0056] S3, the crude tribromophenol product, enters a vacuum distillation tower with 80 theoretical plates, an operating pressure of 5 kPa(A), and a tower top temperature of 165°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters the recrystallization unit #1. Chlorobenzene is used as the recrystallization solvent, with an initial crystallization temperature of 60°C and a final crystallization temperature of -5°C. The recrystallized solid is washed with water for 30 minutes at 95°C. The crystals are then vacuum dried (pressure of 50 kPa(A), temperature of 60°C) to obtain the tribromophenol product.

[0057] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as the recrystallization solvent. The initial crystallization temperature is 85°C and the final crystallization temperature is 5°C. The solid after recrystallization is washed with a sodium sulfite aqueous solution for 30 minutes (95°C). The crystallized product is vacuum dried (pressure of 10 kPa(A), temperature of 60°C) to obtain tetrabromobisphenol A product.

[0058] Ultimately, the obtained tribromophenol product had a purity of 96.5% by weight; the tetrabromobisphenol A product had a purity of 97.6% by weight; and the dibromophenol product had a purity of 98.7%. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 55%. Comparing Example 1 with Comparative Example 3, it can be seen that the melt crystallization process of the present invention can greatly improve the purity and yield of tribromophenol, tetrabromobisphenol A, and dibromophenol.

[0059] Comparative Example 4 Bromine-containing solid waste S1, composed of 70% tribromophenol (TBP), approximately 24% tetrabromobisphenol A (TBBPA), approximately 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienonone (2,4,4,6-tetrabromo-2,5-cyclohexadienone), and approximately 1% inorganic salt (NaBr / Na2SO4), was mixed with a methanol-water mixed solvent (85% methanol by weight, with a 2:1 mass ratio of the mixed solvent to the bromine-containing solid waste) and a formaldehyde solution (0.3:1 mass ratio of the formaldehyde solution to the bromine-containing solid waste) in a reactor. After reacting at 60°C for 2 hours, the mixture was placed in a liquid-liquid separator for static desalination. The saline wastewater in the lower layer was treated and discharged. The bromine-containing organic phase in the upper layer was placed in a scraped-surface evaporator, which operated at atmospheric pressure to recover the solvent for recycling. The remaining residue was the desalted bromine-containing organic mixture.

[0060] S2. The desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device. After melting, cooling, sweating, and melting, crude tribromophenol and crude tetrabromobisphenol A are obtained, respectively. The melting temperature is 180°C, the cooling temperature is 10°C, the sweating temperature is 105°C, the melting temperature is 180°C, the cooling rate is 0.05°C / min, and the sweating rate is 0.05°C / min.

[0061] S3, crude tribromophenol, enters a vacuum distillation tower with 80 theoretical plates, an operating pressure of 5 kPa(A), and a tower top temperature of 165°C. A dibromophenol mixture product is obtained at the top of the tower, and the bottom of the tower enters recrystallization in stage 1. n-heptane is used as the recrystallization solvent, with an initial crystallization temperature of 60°C and a final crystallization temperature of -5°C. The recrystallized solid is washed with water for 30 minutes at 95°C. The crystals are then vacuum dried (at a pressure of 50 kPa(A) and a temperature of 60°C) to obtain the tribromophenol product.

[0062] S4. The crude tetrabromobisphenol A enters 2# recrystallization, using n-heptane as the recrystallization solvent. The initial crystallization temperature is 85°C and the final crystallization temperature is 5°C. The solid after recrystallization is washed with a sodium sulfite aqueous solution for 30 minutes (95°C). The crystallized product is vacuum dried (pressure of 10 kPa(A), temperature of 60°C) to obtain tetrabromobisphenol A product.

[0063] Ultimately, the obtained tribromophenol product had a purity of 93.6% by weight; the tetrabromobisphenol A product had a purity of 92.1% by weight; and the dibromophenol product had a purity of 98.5%. The total recovery rate of tribromophenol, tetrabromobisphenol A, and dibromophenol was 78%. Comparing Example 1 with Comparative Example 4, it can be seen that the recrystallization solvent of the present invention can significantly improve the purity and yield of tribromophenol, tetrabromobisphenol A, and dibromophenol.

[0064] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of this application, several variations and improvements can be made, which all fall within the scope of protection of this application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization, characterized in that: include: The bromine-containing solid waste, solvent and catalyst are mixed to perform a first reaction, and then liquid-liquid separation is performed to obtain a bromine-containing organic phase and saline wastewater; The bromine-containing organic phase is subjected to solvent recovery to obtain a recovered solvent and a bromine-containing organic mixture; The bromine-containing organic mixture is preheated, then melted, cooled, sweated, and dissolved to obtain crude tribromophenol and crude tetrabromobisphenol A; The crude tribromophenol product is subjected to vacuum distillation to obtain a dibromophenol product and a bottom product, and the bottom product is subjected to a first recrystallization, a first solid-liquid separation, water washing, and a first drying to obtain a tribromophenol product; The crude tetrabromobisphenol A product is obtained by subjecting the crude tetrabromobisphenol A to a second recrystallization, a second solid-liquid separation, an alkali washing, and a second drying.

2. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The solvent is a mixture of organic matter and water, and the organic matter includes one or more of methanol, acetone, chloroform, chlorobenzene, ethyl acetate, isopropanol, benzene, toluene, and methyl tert-butyl ether; the mass ratio of the solvent to the bromine-containing solid waste is 0.5-2:1; The water content of the solvent is 5-30 wt %.

3. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The catalyst is a reduction catalyst, including one or more of formaldehyde, acetaldehyde, benzaldehyde, hydrazine hydrate, and sodium borohydride; the mass ratio of the catalyst to the bromine-containing solid waste is 0.05-0.3:

1.

4. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The temperature of the first reaction is 40-90° C., and the time is 0.5-2 h.

5. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The melting temperature is 100-200°C, the cooling end temperature is 0-40°C, the sweating temperature is 90-130°C, and the melting temperature is 100-200°C; The cooling rate is 0.02-0.5°C / min, and the sweating rate is 0.02-0.5°C / min.

6. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 5, characterized in that: The melting temperature is 150-180°C, the cooling end point temperature is 10-25°C, the sweating temperature is 95-105°C, and the melting temperature is 150-180°C; The cooling rate is 0.05-0.1°C / min, and the sweating rate is 0.05-0.1°C / min.

7. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The number of theoretical plates of the vacuum distillation is 60-80, the operating pressure is 1-5 kPa, and the operating temperature is 130-230°C.

8. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The initial temperature of the first recrystallization is 50-60°C, the final temperature is -5 to 5°C, and the recrystallization solvent is chlorobenzene; The water washing temperature is 80-100°C; The first drying process is performed at a pressure of 10-50 kPa and a temperature of 50-70°C.

9. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to claim 1, characterized in that: The initial temperature of the second recrystallization is 60-85°C, the final temperature is 5-25°C, and the recrystallization solvent is chlorobenzene; The alkaline washing is carried out at a temperature of 80-100° C. using one or more of caustic soda, soda ash, sodium sulfite and thiourea dioxide; The second drying process is performed at a pressure of 10-50 kPa and a temperature of 60-160°C.

10. The method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization according to any one of claims 1 to 9, characterized in that: The bromine-containing solid waste is calculated with its total mass as 100%, including: Tribromophenol 35-70%, tetrabromobisphenol A 20-50%, inorganic salts 1-5% and other organic matter 5-10%; The inorganic salts include sodium bromide and sodium sulfate, and the other organic substances include one or more of bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienone.

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