A method for recovering tribromophenol, tetrabromobisphenol a, and dibromophenol from a bromine-containing solid waste by melt crystallization

Abstract

The application provides a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melting crystallization, and relates to the field of solid waste recovery. The method comprises the following steps: mixing bromine-containing solid waste, a solvent and a catalyst to perform a reaction, then performing liquid-liquid separation to obtain a bromine-containing organic phase and salt-containing wastewater; recovering the solvent in the bromine-containing organic phase to obtain a bromine-containing organic mixture; preheating the bromine-containing organic mixture, then performing melting, cooling, sweating and melting treatment to obtain crude tribromophenol and crude tetrabromobisphenol A; performing vacuum rectification on the crude tribromophenol to obtain dibromophenol and a column still product; performing recrystallization, solid-liquid separation, water washing and drying on the column still product to obtain tribromophenol; and performing recrystallization, solid-liquid separation, alkali washing and drying on the crude tetrabromobisphenol A to obtain tetrabromobisphenol A. The method provided in the application adopts reaction impurity removal and melting crystallization and is coupled with a recrystallization process, so that tribromophenol, tetrabromobisphenol A and dibromophenol products can be obtained at the same time, the process is simple, and the energy consumption is significantly reduced compared with the traditional method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste recycling, and particularly relates to a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melting crystallization. BACKGROUND

[0002] Bromine-based flame retardants play an important role in various fields, but the recycling of solid waste has not made breakthrough progress.

[0003] The existing treatment of bromine-containing solid waste is mainly through incineration. However, on the one hand, the incineration tail gas treatment is difficult and easy to cause secondary pollution, and on the other hand, special equipment needs to be used for solid waste with high bromine content, and the corrosion prevention requirement is also high, so the treatment cost is high. In addition, the existing technology also uses distillation and other methods to recover tribromophenol and tetrabromobisphenol A, but it cannot solve the problem of difficult recovery of tetrabromobisphenol A caused by the decomposition of tribromophenol and the deterioration of the components of the pot residue.

[0004] Therefore, the present application is proposed. SUMMARY

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

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0007] A method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melting crystallization, comprising:

[0008] Mixing bromine-containing solid waste, solvent and catalyst for first reaction, and then performing liquid-liquid separation to obtain bromine-containing organic phase and salt-containing wastewater;

[0009] The bromine-containing organic phase is subjected to solvent recovery to obtain recovered solvent and bromine-containing organic mixture;

[0010] The solvent recovery device is an evaporation device with a scraper, which can operate under normal pressure or vacuum. The principle of the solvent recovery device is that the significant difference in boiling point between the solvent and the bromine-containing organic matter can facilitate the complete removal of the solvent; the function of the scraper is to form a film of liquid to promote solvent evaporation, and to improve the recovery rate of the bromine-containing organic matter.

[0011] The bromine-containing organic mixture is preheated, and then subjected to melting, cooling, sweating and melting treatment to obtain tribromophenol crude product and tetrabromobisphenol A crude product;

[0012] The tribromophenol crude product is subjected to vacuum rectification to obtain dibromophenol product and tower kettle product, and the tower kettle product is subjected to first recrystallization, first solid-liquid separation, water washing and first drying to obtain tribromophenol product;

[0013] The second recrystallization, the second solid-liquid separation, the alkali washing and the second drying are performed on the crude tetrabromobisphenol A to obtain the tetrabromobisphenol A product.

[0014] Preferably, the solvent is a mixture of an organic substance and water, the organic substance including one or more of methanol, acetone, chloroform, chlorobenzene, ethyl acetate, isopropyl alcohol, benzene, toluene, methyl tert-butyl ether; the mass ratio of the solvent to the bromine-containing solid waste is 0.5-2:1.

[0015] The water content of the solvent is 5-30wt%.

[0016] 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 0.5-2:1; the water content of the solvent can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt% or any value between 5-30wt%.

[0017] Preferably, the catalyst is a reducing catalyst, including one or more of formaldehyde, acetaldehyde, benzaldehyde, hydrazine hydrate, sodium borohydride; the mass ratio of the catalyst to the bromine-containing solid waste is 0.05-0.3:1.

[0018] 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 0.05-0.3:1.

[0019] Preferably, the temperature of the first reaction is 40-90℃ and the time is 0.5-2h.

[0020] Optionally, the temperature of the first reaction can be 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or any value between 40-90℃, and the time can be 0.5h, 1h, 1.5h, 2h or any value between 0.5-2h.

[0021] Preferably, the temperature of the melting is 100-200℃, the end point temperature of the cooling is 0-40℃, the temperature of the sweating is 90-130℃, and the temperature of the melting is 100-200℃.

[0022] Optionally, the temperature of the melting can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any value between 100-200℃, the end temperature of the cooling can be 0℃, 10℃, 20℃, 30℃, 40℃, or any value between 0-40℃, the temperature of the sweating can be 90℃, 100℃, 110℃, 120℃, 130℃, or any value between 90-130℃, the temperature of the melting can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any value between 100-200℃;

[0023] The rate of the cooling is 0.02-0.5℃ / min, and the rate of the sweating is 0.02-0.5℃ / min.

[0024] Optionally, the rate of the cooling 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 rate of the sweating 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.

[0025] Preferably, the temperature of the melting is 150-180℃, the end temperature of the cooling is 10-25℃, the temperature of the sweating is 95-105℃, and the temperature of the melting is 150-180℃.

[0026] The rate of the cooling is 0.05-0.1℃ / min, and the rate of the sweating is 0.05-0.1℃ / min.

[0027] Preferably, the number of theoretical plates of the vacuum rectification is 60-80, the operating pressure is 1-5kPa, and the operating temperature is 130-230℃.

[0028] Optionally, the number of theoretical plates of the vacuum rectification can be 60, 70, 80, or any value between 60-80, the operating pressure can be 1kPa, 2kPa, 3kPa, 4kPa, 5kPa, or any value between 1-5kPa, and the operating temperature can be 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, or any value between 130-230℃.

[0029] Preferably, the first recrystallization has an initial temperature of 50-60℃ and a final temperature of -5 to 5℃, and the recrystallization solvent is chlorobenzene;

[0030] The water washing has a temperature of 80-100℃;

[0031] The first drying has a pressure of 10-50kPa and a temperature of 50-70℃.

[0032] Optionally, the first recrystallization has an initial temperature of 50℃, 55℃, 60℃, or any value between 50-60℃, and a final temperature of -5℃, 0℃, 5℃, or any value between -5 to 5℃, and the recrystallization solvent is chlorobenzene;

[0033] The water washing has a temperature of 80℃, 90℃, 100℃, or any value between 80-100℃;

[0034] The first drying has a pressure of 10kPa, 20kPa, 30kPa, 40kPa, 50kPa, or any value between 10-50kPa, and a temperature of 50℃, 60℃, 70℃, or any value between 50-70℃.

[0035] Preferably, the second recrystallization has an initial temperature of 60-85℃ and a final temperature of 5-25℃, and the recrystallization solvent is chlorobenzene;

[0036] The alkali washing has a temperature of 80-100℃ and is performed using one or more of caustic soda, soda ash, sodium sulfite, and sulfurous acid dihydrate;

[0037] The second drying has a pressure of 10-50kPa and a temperature of 60-160℃.

[0038] Optionally, the second recrystallization has an initial temperature of 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, or any value between 60-85℃, and a final temperature of 5℃, 10℃, 15℃, 20℃, 25℃, or any value between 5-25℃, and the recrystallization solvent is chlorobenzene;

[0039] The alkali washing has a temperature of 80℃, 90℃, 100℃, or any value between 80-100℃;

[0040] The second drying has a pressure of 10kPa, 20kPa, 30kPa, 40kPa, 50kPa, or any value between 10-50kPa, and a temperature of 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, or any value between 60-160℃.

[0041] Preferably, the bromine-containing solid waste comprises, calculated based on the total mass of the bromine-containing solid waste as 100%:

[0042] tribromophenol 35-70%, tetrabromobisphenol A 20-50%, inorganic salt 1-5%, and other organic matter 5-10%;

[0043] The inorganic salt comprises sodium bromide and sodium sulfate, and the other organic matter comprises one or more of bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,4,6-tetrabromo-2,5-cyclohexadienone.

[0044] Advantages of the present application:

[0045] The method provided by the present application for recovering tribromophenol, tetrabromobisphenol A, and dibromophenol from bromine-containing solid waste by melt crystallization utilizes the strong reducing property of the catalyst to reduce ketone substances such as 2,4,4,6-tetrabromo-2,5-cyclohexadienone in the bromine-containing solid waste into products such as tribromophenol, thereby improving the product yield and purity; melt crystallization separates organic matter without the need for additional solvents, thereby improving the product purity (the product purity is greater than or equal to 99 wt%), and the principle is to utilize the different melting points of organic matter, gradually reduce the temperature to achieve partial crystallization, thereby forming a concentration difference between the crystalline solid and the components in the mother liquor, and achieving the purpose of separating organic matter. Through the melt crystallization process, tribromophenol and tetrabromobisphenol A crude products can be obtained with low energy consumption and in a simple manner, thereby improving the product quality.

[0046] The method adopts reaction impurity removal and melt crystallization and couples a recrystallization process, simultaneously obtaining tribromophenol, tetrabromobisphenol A, and dibromophenol products; the process is simple, significantly reduces the energy consumption compared with the traditional method, efficiently recovers high-value chemicals in the bromine-containing solid waste, and achieves ecological and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0048] Figure 1 The process flow diagram of the method for recovering tribromophenol, tetrabromobisphenol A, and dibromophenol from bromine-containing solid waste by melt crystallization is provided for the embodiments. DETAILED DESCRIPTION

[0049] 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.

[0050] Example 1

[0051] 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:

[0052] 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.

[0053] 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.

[0054] 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.

[0055] S4, the crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as recrystallization solvent, the initial temperature of crystallization is 85℃, the final temperature is 5℃, the solid after recrystallization is washed with sodium sulfite aqueous solution for 30 minutes (95℃), the crystalline product is vacuum dried (pressure is 10 kPa(A), temperature is 60℃) to obtain tetrabromobisphenol A product.

[0056] Finally, the purity of the obtained tribromophenol product is 99.9wt%; the purity of the tetrabromobisphenol A product is 99.3wt%; the purity of the dibromophenol product is 99.2%. The total recovery rate of tribromophenol, tetrabromobisphenol A and dibromophenol is 86%.

[0057] Example 2

[0058] The embodiment provides a method for recovering tribromophenol, tetrabromobisphenol A and dibromophenol from bromine-containing solid waste by melt crystallization, comprising the following steps:

[0059] S1, the bromine-containing solid waste, which is composed of 35wt% tribromophenol, about 50wt% tetrabromobisphenol A, about 10% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,4,6-tetrabromo-2,5-cyclohexadienone and the like, and about 5% inorganic salt (NaBr / Na2SO4), is mixed with chlorobenzene and water mixed solvent (the mass content of chlorobenzene is 70%, the mass ratio of the mixed solvent to the bromine-containing solid waste is 0.5:1) and sodium borohydride aqueous solution (the mass ratio of the sodium borohydride solution to the bromine-containing solid waste is 0.05:1) in a reaction kettle, and after reacting at 90℃ for 0.5 hours, it is placed in a liquid-liquid separator for desalination. The lower salt-containing wastewater is discharged after wastewater treatment; the upper bromine-containing organic phase enters a scraper evaporator, the scraper evaporator is operated at normal pressure, the recovered solvent is recycled, and the remaining residue is a desalted bromine-containing organic mixture.

[0060] S2, the desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device, and after melt crystallization, cooling, sweating and melting treatment, tribromophenol crude and tetrabromobisphenol A crude are obtained. The melt temperature is 150℃, the cooling temperature is 25℃, the sweating temperature is 95℃, the melting temperature is 150℃, the cooling rate is 0.1℃ / min, and the sweating rate is 0.1℃ / min.

[0061] S3, the tribromophenol crude enters a vacuum rectification column, the theoretical plate number of the vacuum rectification is 80, the operating pressure is 1kPa(A), and the top temperature is 130℃. The dibromophenol mixture product is obtained at the top, and the material at the bottom enters 1# recrystallization. Chlorobenzene is used as the recrystallization solvent, the initial temperature of crystallization is 50℃, the final temperature is 5℃, the solid after recrystallization is washed with water for 30 minutes (80℃), and the crystalline product is vacuum dried (pressure is 50 kPa(A), temperature is 60℃) to obtain tribromophenol product.

[0062] 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.

[0063] 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%.

[0064] Example 3

[0065] This embodiment provides a method for recovering tribromophenol, tetrabromobisphenol A, and dibromophenol from bromine-containing solid waste by melt crystallization, comprising the following steps:

[0066] 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.

[0067] 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.

[0068] 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.

[0069] S4, the crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as recrystallization solvent, the initial temperature of crystallization is 70℃, the final temperature is 10℃, the solid after recrystallization is washed with 10% lye solution for 30 minutes (90℃), the crystalline product is vacuum dried (pressure is 50 kPa(A), temperature is 120℃) to obtain tetrabromobisphenol A product.

[0070] Finally, the purity of the obtained tribromophenol product is 99.4wt%; the purity of the tetrabromobisphenol A product is 99.1wt%; the purity of the dibromophenol product is 99.1%. The total recovery rate of tribromophenol, tetrabromobisphenol A and dibromophenol is 83%.

[0071] Comparative Example 1

[0072] S1, the bromine-containing solid waste, which is composed of 70wt% tribromophenol, about 24wt% tetrabromobisphenol A, about 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,4,6-tetrabromo-2,5-cyclohexadienone and the like, and about 1% inorganic salt (NaBr / Na2SO4), is mixed with toluene solvent (the mass ratio of toluene to bromine-containing solid waste is 2:1) and formaldehyde solution (the mass ratio of formaldehyde solution to bromine-containing solid waste is 0.3:1) in a reaction kettle, and after reacting at 60℃ for 2 hours, it enters a liquid-liquid separator for static desalination. The lower salt-containing wastewater is discharged after wastewater treatment; the upper bromine-containing organic phase enters a wiped film evaporator, which is operated at normal pressure, and the recovered solvent is recycled, and the remaining residue is a desalted bromine-containing organic mixture.

[0073] S2, the desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device, and after melt, cooling, sweating and melting treatment, respectively, tribromophenol crude and tetrabromobisphenol A crude are obtained. The melt temperature is 180℃, the cooling temperature is 10℃, the sweating temperature is 105℃, the melting temperature is 180℃, the cooling rate is 0.05℃ / min, and the sweating rate is 0.05℃ / min.

[0074] S3, the tribromophenol crude enters a vacuum rectification column, the theoretical plate number of the vacuum rectification is 80, the operating pressure is 5kPa(A), and the top temperature is 165℃. The top of the column obtains a dibromophenol mixture product, and the column bottom material enters 1# recrystallization. Chlorobenzene is used as the recrystallization solvent, the initial temperature of crystallization is 60℃, the final temperature is -5℃, the solid after recrystallization is washed with water for 30 minutes (95℃), and the crystalline product is vacuum dried (pressure is 50 kPa(A), temperature is 60℃) to obtain tribromophenol product.

[0075] S4, the crude tetrabromobisphenol A enters 2# recrystallization, using chlorobenzene as recrystallization solvent, the initial temperature of crystallization is 85℃, the final temperature is 5℃, the solid after recrystallization is washed with sodium sulfite aqueous solution for 30 minutes (95℃), the crystalline product is vacuum dried (pressure is 10 kPa(A), temperature is 60℃) to obtain tetrabromobisphenol A product.

[0076] Finally, the purity of the obtained tribromophenol product is 99.5wt%; the purity of the tetrabromobisphenol A product is 99.1wt%; the purity of the dibromophenol product is 99.1%. The total recovery rate of tribromophenol, tetrabromobisphenol A and dibromophenol is 72%. It can be found from Comparative Example 1 and Comparative Example 1 that the solvent of the present application can improve the purity and yield of tribromophenol, tetrabromobisphenol A and dibromophenol. In addition, the solvent of the present application can improve the removal rate of raw material salt.

[0077] Comparative Example 2

[0078] S1, the bromine-containing solid waste, which is composed of 70wt% tribromophenol, about 24wt% tetrabromobisphenol A, about 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,4,6-tetrabromo-2,5-cyclohexadienone and the like, and about 1% inorganic salt (NaBr / Na2SO4), is mixed with methanol and water mixed solvent (the mass content of methanol is 85%, the mass ratio of mixed solvent to bromine-containing solid waste is 2:1) in a reaction kettle at 60℃ for 2 hours, and then enters a liquid-liquid separator for static desalination. The lower salt-containing wastewater is discharged after wastewater treatment; the upper bromine-containing organic phase enters a scraper evaporator, which is operated at normal pressure, and the recovered solvent is recycled, and the remaining residue is a desalted bromine-containing organic mixture.

[0079] S2, the desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device to obtain tribromophenol crude and tetrabromobisphenol A crude after melt, cooling, sweating and melting treatment, respectively. The melt temperature is 180℃, the cooling temperature is 10℃, the sweating temperature is 105℃, the melting temperature is 180℃, the cooling rate is 0.05℃ / min, and the sweating rate is 0.05℃ / min.

[0080] S3, the tribromophenol crude enters a vacuum rectification column, the theoretical plate number of vacuum rectification is 80, the operating pressure is 5kPa(A), and the top temperature is 165℃. The dibromophenol mixture product is obtained at the top, and the material at the bottom enters 1# recrystallization. Chlorobenzene is used as recrystallization solvent, the initial temperature of crystallization is 60℃, the final temperature is -5℃, the solid after recrystallization is washed with water for 30 minutes (95℃), and the crystalline product is vacuum dried (pressure is 50 kPa(A), temperature is 60℃) to obtain tribromophenol product.

[0081] S4, the crude tetrabromobisphenol A enters 2# recrystallization, chlorobenzene is used as recrystallization solvent, the initial temperature of crystallization is 85 DEG C, the final temperature is 5 DEG C, the solid after recrystallization is washed with sodium sulfite aqueous solution for 30 minutes (95 DEG C), the crystalline product is vacuum dried (pressure is 10 kPa (A), temperature is 60 DEG C) to obtain tetrabromobisphenol A product.

[0082] Finally, the purity of the obtained tribromophenol product is 99.6wt%; the purity of the tetrabromobisphenol A product is 98.2wt%; the purity of the dibromophenol product is 98.5%. The total recovery rate of tribromophenol, tetrabromobisphenol A and dibromophenol is 76%. It can be found from Comparative Example 1 and Comparative Example 2 that the catalyst of the application can improve the purity and yield of tribromophenol, tetrabromobisphenol A and dibromophenol.

[0083] Comparative Example 3

[0084] S1, the bromine-containing solid waste, which is composed of 70wt% tribromophenol, about 24wt% tetrabromobisphenol A, about 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,4,6-tetrabromo-2,5-cyclohexadienone and the like, and about 1% inorganic salt (NaBr / Na2SO4), is mixed with methanol and water mixed solvent (the mass content of methanol is 85%, the mass ratio of mixed solvent to bromine-containing solid waste is 2:1) and formaldehyde solution (the mass ratio of formaldehyde solution to bromine-containing solid waste is 0.3:1) in a reaction kettle, and after reacting at 60 DEG C for 2 hours, it enters a liquid-liquid separator for static desalination. The lower salt-containing wastewater is discharged after wastewater treatment; the upper bromine-containing organic phase enters a wiped film evaporator, which is operated at normal pressure, and the recovered solvent is recycled, and the remaining residue is a desalted bromine-containing organic mixture.

[0085] S2, the desalted bromine-containing organic mixture is preheated and then enters a melt crystallization device, and after melt crystallization, cooling, sweating and melting treatment, tribromophenol crude and tetrabromobisphenol A crude are obtained respectively. The melt temperature is 200 DEG C, the cooling temperature is 60 DEG C, the sweating temperature is 150 DEG C, the melting temperature is 200 DEG C, the cooling rate is 1 DEG C / min, and the sweating rate is 1 DEG C / min.

[0086] S3, the tribromophenol crude enters a vacuum rectification column, the theoretical plate number of vacuum rectification is 80, the operating pressure is 5 kPa (A), and the top temperature is 165 DEG C. The dibromophenol mixture product is obtained at the top, and the material at the bottom enters 1# recrystallization. Chlorobenzene is used as recrystallization solvent, the initial temperature of crystallization is 60 DEG C, the final temperature is -5 DEG C, the solid after recrystallization is washed with water for 30 minutes (95 DEG C), and the crystalline product is vacuum dried (pressure is 50 kPa (A), temperature is 60 DEG C) to obtain tribromophenol product.

[0087] S4, the crude tetrabromobisphenol A enters 2# recrystallization, chlorobenzene is used as recrystallization solvent, the initial temperature of crystallization is 85 DEG C, the final temperature is 5 DEG C, the solid after recrystallization is washed with sodium sulfite aqueous solution for 30 minutes (95 DEG C), the crystalline product is vacuum dried (pressure is 10 kPa (A), temperature is 60 DEG C) to obtain tetrabromobisphenol A product.

[0088] Finally, the purity of the obtained tribromophenol product is 96.5wt%; the purity of the tetrabromobisphenol A product is 97.6wt%; the purity of the dibromophenol product is 98.7%. The total recovery rate of tribromophenol, tetrabromobisphenol A and dibromophenol is 55%. It can be found from Comparative Example 1 and Comparative Example 3 that the melting crystallization process of the present application can greatly improve the purity and yield of tribromophenol, tetrabromobisphenol A and dibromophenol.

[0089] Comparative Example 4

[0090] S1, the bromine-containing solid waste, which is composed of 70wt% tribromophenol, about 24wt% tetrabromobisphenol A, about 5% bisphenol A, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,4,6-tetrabromo-2,5-cyclohexadienone and the like, and about 1% inorganic salt (NaBr / Na2SO4), is mixed with methanol and water mixed solvent (the mass content of methanol is 85%, the mass ratio of mixed solvent to bromine-containing solid waste is 2:1) and formaldehyde solution (the mass ratio of formaldehyde solution to bromine-containing solid waste is 0.3:1) in a reaction kettle, and after reacting at 60 DEG C for 2 hours, it enters a liquid-liquid separator for static desalination. The lower salt-containing wastewater is discharged after wastewater treatment; the upper bromine-containing organic phase enters a wiped film evaporator, which is operated at normal pressure, and the recovered solvent is recycled, and the remaining residue is a desalted bromine-containing organic mixture.

[0091] S2, the desalted bromine-containing organic mixture is preheated and then enters a melting crystallization device, and after melting, cooling, sweating and melting treatment, tribromophenol crude and tetrabromobisphenol A crude are obtained. The melting temperature is 180 DEG C, the cooling temperature is 10 DEG C, the sweating temperature is 105 DEG C, the melting temperature is 180 DEG C, the cooling rate is 0.05 DEG C / min, and the sweating rate is 0.05 DEG C / min.

[0092] S3, the tribromophenol crude enters a vacuum rectification column, the theoretical plate number of vacuum rectification is 80, the operating pressure is 5 kPa (A), and the top temperature is 165 DEG C. The dibromophenol mixture product is obtained at the top, and the material at the bottom enters 1# recrystallization. N-heptane is used as recrystallization solvent, the initial temperature of crystallization is 60 DEG C, the final temperature is -5 DEG C, the solid after recrystallization is washed with water for 30 minutes (95 DEG C), and the crystalline product is vacuum dried (pressure is 50 kPa (A), temperature is 60 DEG C) to obtain tribromophenol product.

[0093] S4, the crude tetrabromobisphenol A enters 2# recrystallization, using n-heptane as recrystallization solvent, the initial temperature of crystallization is 85℃, the final temperature is 5℃, the solid after recrystallization is washed with sodium sulfite aqueous solution for 30 minutes (95℃), the crystalline product is vacuum dried (pressure is 10kPa(A), temperature 60℃) to obtain tetrabromobisphenol A product.

[0094] Finally, the purity of the obtained tribromophenol product is 93.6wt%; the purity of the tetrabromobisphenol A product is 92.1wt%; the purity of the dibromophenol product is 98.5%. The total recovery rate of tribromophenol, tetrabromobisphenol A and dibromophenol is 78%. It can be found from Comparative Example 1 and Comparative Example 4 that the recrystallization solvent of the present application can greatly improve the purity and yield of tribromophenol, tetrabromobisphenol A and dibromophenol.

[0095] Note that the technical features of the above examples can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above examples are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application. The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be interpreted as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended 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 is subjected to a second recrystallization, a second solid-liquid separation, an alkali washing, and a second drying to obtain a tetrabromobisphenol A product; 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 5-30wt%; The catalyst is a reduction catalyst, including one or more of formaldehyde, hydrazine hydrate, and sodium borohydride; the mass ratio of the catalyst to the bromine-containing solid waste is 0.05-0.3:1; The temperature of the first reaction is 40-90°C and the time is 0.5-2h; 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; 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; 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 pressure is 10-50 kPa and the temperature is 50-70° C.; 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 pressure is 10-50 kPa and the temperature is 60-160°C; 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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