Method and system for synthesizing bromo-carbene by using tetrabromobisphenol A production wastewater

Abstract

The invention provides a method and a system for synthesizing bromo-carbene by using tetrabromobisphenol A production wastewater, and belongs to the technical field of flame retardants. After the tetrabromobisphenol A production wastewater is subjected to evaporation concentration and pH adjustment, a mixed salt solution with high organic concentration is obtained, and the mixed salt solution with high organic concentration reacts with bromo-carbene in the presence of a catalyst, so that bromo-carbene is synthesized. According to the method, a plurality of complex organic mixtures in the wastewater are subjected to a series of chain scission recombination step by step through three times of oxidation in sequence and accurate condition control, and finally, a large number of various brominated organic compounds contained in the tetrabromobisphenol A production wastewater are converted into single-chain bromine-containing organic substances. And high-activity organic matter bromo-carbene and inorganic sodium bromide salt are generated through a synthesis reaction, so that the resource utilization of the bromine element in the wastewater is realized, the utilization value of the wastewater is improved, and a new treatment path is provided for difficult wastewater treatment generally existing in tetrabromobisphenol A production.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardants, and in particular relates to a method and system for synthesizing bromocarbene by using the production wastewater of tetrabromobisphenol A. Background Art

[0002] Dibromocarbene is often used as a carbene intermediate in synthetic reactions. This substance is a neutral and polar carbene with two bromine atoms in its structure. Due to the high unevenness of the electron cloud density in the carbene molecule, it exhibits high reactivity and has become an important reagent in organic synthesis reactions, having important value in the synthesis of drugs and cycloaddition reactions.

[0003] A large amount of wastewater is generated during the production of tetrabromobisphenol A. This wastewater contains a large amount of organic substances, which are doped with various organic substances such as tetrabromobisphenol A, benzaldehyde, bisphenol A, and tribromobisphenol A, existing in the form of a mixture. The physical and chemical properties of various substances are not very different, making it difficult to achieve effective separation. In daily production, the above substances are mostly stored or treated as hazardous waste along with inorganic salts, and it is very difficult to achieve further utilization. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a method and system for synthesizing bromocarbene by using the production wastewater of tetrabromobisphenol A.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: A method for synthesizing bromocarbene by using the production wastewater of tetrabromobisphenol A, comprising the following steps: S1. Evaporate and concentrate the production wastewater of tetrabromobisphenol A and adjust the pH, ensuring that no obvious solid precipitates during the evaporation process. The outlet temperature of the wastewater is 80 - 95°C, the total salt content of the wastewater outlet is 35 - 45%, and the pH of the wastewater outlet is adjusted to 4.5 - 5.5.

[0006] When the pH of the wastewater outlet drops to 4.5 - 5.5, some solid flocculent substances will precipitate from the wastewater. This solid substance is mostly tribromophenol and can directly participate in the next reaction without filtration.

[0007] Step S1 uses the wastewater obtained during the production of tetrabromobisphenol A as the raw material. The main components of the salts contained in this raw material are sodium sulfate and sodium bromide, and the main components of the organic substances contained are various substances such as tetrabromobisphenol A, benzaldehyde, tribromophenol, dibromophenol, bisphenol A, acetophenone, and macromolecular phenolic polymers, and its total chemical oxygen demand is about 10000.

[0008] S2. Introduce the wastewater obtained in step S1 into a high-temperature and high-pressure reaction tower. After the high-temperature and high-pressure reaction tower is evacuated, fill it with oxygen to 2.5 - 3.2 MPa, heat the wastewater to 300 - 350 °C for an oxidation reaction for 10 - 30 min, and after the reaction, cool the wastewater to below 90 °C.

[0009] In the reaction of step S2, macromolecular phenolic polymers and condensates in the wastewater undergo chain-breaking reactions under the action of high-pressure oxygen, and are gradually decomposed into p-isopropenylphenol substances under the addition of an acidic environment, and further undergo chain-breaking to generate benzaldehyde substances and other alcohol substances. By-products such as phenolic substances can combine with free bromide ions to form derivatives such as dibromophenol and tribromophenol. After this stage of the reaction, the main components of the organic components in the wastewater are dibromobenzaldehyde, dibromo- and tribromophenol substances, etc.

[0010] At this time, the chemical oxygen demand in the wastewater decreases by about 3000 - 4500.

[0011] S3. Introduce the wastewater obtained in step S2 into the first reaction tower, adjust the pH of the wastewater in the first reaction tower to 2 - 3, start the second oxidation reaction. In this reaction, hydrogen peroxide is added to the wastewater, and the addition ratio of hydrogen peroxide is 4 - 10% of the total mass of the wastewater. Heat it to 150 - 180 °C, and maintain the pressure in the first reaction tower at 0.5 - 0.9 Mpa, and the reaction time is 60 - 80 min.

[0012] In the above process, the upper limit of hydrogen peroxide addition is 10%. Excessive addition of hydrogen peroxide not only has no obvious benefit to this reaction, but on the contrary, it causes the reaction rate to be too fast and generates extra organic substances, hindering the synthesis of the final product bromocarbene.

[0013] Unit volume of hydrogen peroxide can greatly increase the generation rate and production concentration of hydroxyl radicals, and increase the initial decomposition rate of benzene ring long-chain substances. That is, for high-concentration initial organic substances, under the action of a catalyst, the higher the initial organic concentration, the faster the degradation rate.

[0014] In the main oxidation reaction of step S3, benzaldehyde substances are converted into tribromophenol substances and aldehyde substances, and bromocarbene begins to be gradually generated. Some aldehyde substances are further converted into ketone substances and carboxylic acid substances, including tribromoacetone, tetrabromoacetone and acetic acid, etc.

[0015] In the reaction of step S3, the chemical oxygen demand in the wastewater decreases by about 2000 - 3000.

[0016] S4. Feed the wastewater obtained from the second oxidation reaction in step S3 into the second reaction tower, adjust the pH of the wastewater to 2 - 3, and start the third oxidation reaction. During this reaction, hydrogen peroxide is continuously added to the wastewater, and the addition ratio of hydrogen peroxide is 2 - 5% of the total mass of the wastewater. Heat up to 120 - 150 °C, the pressure in the second reaction tower is 0.4 - 0.6 Mpa, and the reaction time is 100 - 120 min.

[0017] The reaction time of step S4 is relatively long, and the reaction conditions are milder than the above reactions. During the reaction process, phenols and their derivatives are further decomposed, and the proportion of single-chain bromoalkanes increases significantly (about 60 - 80% of the total organic matter), and the proportion of organic by-products in the water is relatively low, mainly composed of dibromoacrylic acid, dibromoacetaldehyde, etc.

[0018] In this reaction, hydrogen peroxide oxidation is used again, and the reaction time is extended, which can greatly increase the final main content of bromocarbene. It is an indispensable repeated step.

[0019] At this time, the chemical oxygen demand of the wastewater drops to less than 2000.

[0020] S5. Cool the wastewater obtained from the third oxidation reaction in step S4 to 8 - 12 °C to precipitate the solid salts in the wastewater. The remaining wastewater is fed into a fractionating tower to collect and condense the obtained single-chain bromohaloalkane components, with a purity of over 80 - 90%.

[0021] Among them, the cooling is completed by the cooling water of the cooling heat exchanger.

[0022] Among them, the remaining organic components in the wastewater after fractionation are absorbed by sodium hydroxide solution, and the remaining bottom liquid can participate in biochemical treatment and be discharged.

[0023] S6. Feed the single-chain bromohaloalkane components obtained by condensation in step S5 into a reaction kettle, add octadecyltrimethylammonium bromide, and then feed sodium hydroxide solution for reaction to obtain the final product dibromocarbene, and the by-product is sodium bromide solution.

[0024] After the treatment of steps S1 - S6, the chemical oxygen demand of the wastewater from the production of tetrabromobisphenol A drops significantly to less than 2000, the benzene ring-containing compounds are basically all broken, and the B / C ratio (B / C is the abbreviation of the ratio of BOD to COD, and this ratio can represent the biodegradable characteristics of the wastewater) increases significantly, and it can directly participate in the biochemical process for further degradation, thereby converting the difficult-to-degrade organic wastewater into easily degradable wastewater, and converting most of the organic matter in the water into dibromocarbene, realizing resource utilization.

[0025] The present invention also provides a system for synthesizing bromocarbenes using the wastewater from the production of tetrabromobisphenol A, which includes a high-temperature and high-pressure reaction tower, a first reaction tower, a second reaction tower, a fractionating tower, and a reaction kettle connected in sequence. The feed inlet of the high-temperature and high-pressure reaction tower is connected to the discharge outlet of the evaporator. A cooling heat exchanger is arranged between the second reaction tower and the fractionating tower. The feed inlet of the cooling heat exchanger is connected to the discharge outlet of the second reaction tower, and the discharge outlet of the cooling heat exchanger is connected to the discharge outlet of the fractionating tower.

[0026] Further, in step S1, the organic insoluble substances precipitated during the evaporation and concentration process are fully dispersed by stirring to avoid agglomeration.

[0027] Further, in step S1, the wastewater from the production of tetrabromobisphenol A is subjected to evaporation and concentration through an evaporator to obtain wastewater effluent and evaporation condensate. Steam is introduced into the evaporator, and steam condensate is discharged.

[0028] Further, in step S2, the catalyst used in the oxidation reaction is Nb 2 O 5 .NH 2 O, Ta 2 O 5 , octadecyltrimethylammonium chloride, CR 2 O 3 , SNO 2 , Er 2 O 3 / TiO 2 .

[0029] Further, in steps S3 and S4, the catalysts used in the second oxidation reaction and the third oxidation reaction both include an iron-based component and chromium-aluminum-cobalt-aluminum (also known as layered-structured iron-cobalt-aluminum), that is, the catalysts used are based on an iron-based component and have chromium-aluminum-cobalt-aluminum as the main component.

[0030] Further, in steps S3 and S4, the hydrogen peroxide used is hydrogen peroxide with a mass fraction of 27.5%.

[0031] Further, in step S5, the bottom temperature of the fractionating tower is 105 °C, and the feed temperature is 145 °C.

[0032] Further, in step S6, the addition ratio of octadecyltrimethylammonium bromide is 1.2% of the single-chain brominated hydrocarbon component, and then a sodium hydroxide solution with a concentration of 50% (mass fraction) is introduced, and the reaction is carried out at 65 °C for 2 h.

[0033] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects: After the production wastewater of tetrabromobisphenol A is evaporated and concentrated, the pH of the concentrated solution is adjusted to obtain a mixed salt solution with a high organic concentration. In the presence of a catalyst, the mixed salt solution with a high organic concentration undergoes three oxidation processes in sequence. Through precise control, a series of chain-breaking and recombination reactions are carried out on various complex organic mixtures in the wastewater. Eventually, a large number of various brominated organic compounds contained in the production wastewater of tetrabromobisphenol A are transformed into intermediate substances mainly composed of single-chain bromoalkanes, and further through a synthesis reaction, highly active organic bromocarbenes and inorganic sodium bromide salts are generated (i.e., the generation of dibromocarbene and sodium bromide), realizing the resource utilization of bromine elements in the wastewater and thus enhancing the utilization value of the wastewater.

[0034] The solid catalyst is adopted in the present invention, without the need for light source irradiation, and the pressure reaction and temperature increase are adopted in this application, which can realize continuous inlet and outlet of liquid and shorten the reaction time.

[0035] While significantly degrading the COD of the production wastewater of tetrabromobisphenol A, the present invention basically breaks all the benzene ring-containing compounds, greatly increases the B / C ratio, which can directly participate in the biochemical process for further degradation, and finally synthesizes a bromocarben finished product from a series of organic substances in the wastewater. In addition, the form of the catalyst adopted in this treatment process helps to realize various organic conversions in a low-cost and orderly manner, promotes the clean production of salts in the wastewater, and provides a new treatment path for the difficult treatment of wastewater commonly existing in tetrabromobisphenol A production enterprises. Brief Description of the Drawings

[0036] The present invention will be specifically described below with reference to the drawings and in combination with examples. The advantages and implementation manners of the present invention will become more obvious. The content shown in the drawings is only used for the explanation of the present invention and does not constitute any limitation to the present invention in any sense. In the drawings: Figure 1 is the flow chart of the present invention.

[0037] In the figure: 1. High-temperature and high-pressure reaction tower; 2. First reaction tower; 3. Second reaction tower; 4. Fractionating tower; 5. Reaction kettle; 6. Evaporator; 7. Cooling heat exchanger. Detailed Embodiments

[0038] As Figure 1 shown, a method for synthesizing bromocarben using the production wastewater of tetrabromobisphenol A according to the present invention includes the following steps: S1. Evaporate and concentrate the production wastewater of tetrabromobisphenol A and adjust the pH, ensure that no obvious solid precipitates during the evaporation process, maintain the outlet temperature of the wastewater at 80 - 95 °C, maintain the total salt content of the wastewater outlet at 35 - 45%, and adjust the pH of the wastewater outlet to 4.5 - 5.5.

[0039] Among them, concentrated sulfuric acid is used to adjust the pH of the wastewater effluent.

[0040] Among them, the organic insoluble substances precipitated during the evaporation and concentration process are fully dispersed by stirring to avoid agglomeration.

[0041] Among them, the wastewater from the production of tetrabromobisphenol A is evaporated and concentrated by an evaporator 6 to obtain wastewater effluent and evaporation condensate. Steam is introduced into the evaporator 6, and steam condensate is discharged.

[0042] When the pH of the wastewater effluent decreases to 4.5 - 5.5, some solid flocculant substances will precipitate from the wastewater. This solid substance is mainly tribromophenol and can directly participate in the next reaction without filtration.

[0043] Step S1 uses the wastewater obtained during the production of tetrabromobisphenol A as the raw material. The main components of the salts contained in this raw material are sodium sulfate and sodium bromide, and the main components of the organic substances contained are tetrabromobisphenol A, benzaldehyde, tribromophenol, dibromophenol, bisphenol A, acetophenone, macromolecular phenolic polymers and other substances. Its total chemical oxygen demand is about 10000.

[0044] S2. The wastewater obtained in step S1 is introduced into a high-temperature and high-pressure reaction tower 1. After the high-temperature and high-pressure reaction tower 1 is evacuated, oxygen is filled to 2.5 - 3.2 MPa, and the wastewater is heated to 300 - 350 °C for an oxidation reaction for 10 - 30 minutes. After the reaction ends, the wastewater is cooled to below 90 °C.

[0045] Among them, the catalysts used in the oxidation reaction include Nb 2 O 5 .NH 2 O, Ta 2 O 5 , octadecyltrimethylammonium chloride, CR 2 O 3 , SNO 2 , Er 2 O 3 / TiO 2 .

[0046] At this time, the decrease in the chemical oxygen demand of the wastewater is about 3000 - 4500.

[0047] In the reaction of step S2, the macromolecular phenolic polymers and condensates in the wastewater undergo chain-breaking reactions under the action of high-pressure oxygen, and are gradually decomposed into p-isopropenylphenol substances under the addition of an acidic environment, and further chain-breaking generates benzaldehyde substances and other alcohol substances. The by-products such as phenolic substances can combine with free bromide ions to form derivatives such as dibromophenol and tribromophenol. After this stage of the reaction, the main components of the organic components in the wastewater are dibromobenzaldehyde, dibromo- and tribromophenol substances, etc.

[0048] S3. Feed the wastewater obtained in step S2 into the first reaction tower 2, adjust the pH of the wastewater in the first reaction tower 2 to 2 - 3, and start the second oxidation reaction. In this reaction, hydrogen peroxide is added to the wastewater, and the addition ratio of hydrogen peroxide is 4 - 10% of the total mass of the wastewater. Heat up to 150 - 180 °C, maintain the pressure in the first reaction tower 2 at 0.5 - 0.9 Mpa, and the reaction time is 60 - 80 min.

[0049] Among them, the catalyst used in the second oxidation reaction includes iron-based and chromium-aluminum-cobalt-aluminum (also known as layered iron-cobalt-aluminum), that is, the catalyst used is based on iron-based and mainly composed of chromium-aluminum-cobalt-aluminum.

[0050] Among them, the hydrogen peroxide is hydrogen peroxide with a mass fraction of 27.5%.

[0051] In the reaction of step S3, the decline range of the chemical oxygen demand of the wastewater is about 2000 - 3000.

[0052] In the main oxidation reaction of step S3, benzaldehyde substances are converted into tribromophenol substances and aldehyde substances, bromocarbene begins to be gradually produced, and some aldehyde substances are further converted into ketone substances and carboxylic acid substances, including tribromoacetone, tetrabromoacetone and acetic acid, etc.

[0053] In the above process, the upper limit of hydrogen peroxide addition is 10%. Excessive addition of hydrogen peroxide not only has no obvious benefit to this reaction, but also leads to too fast reaction rate and generates extra organic substances, hindering the synthesis of the final product bromocarbene.

[0054] Unit volume of hydrogen peroxide can greatly increase the generation rate and production concentration of hydroxyl radicals, and increase the initial decomposition rate of benzene ring long-chain substances. That is, for high-concentration initial organic substances, under the action of the catalyst, the higher the initial organic concentration, the faster the degradation rate.

[0055] S4. Feed the wastewater obtained from the second oxidation reaction in step S3 into the second reaction tower 3, adjust the pH of the wastewater to 2 - 3, and start the third oxidation reaction. In this reaction, hydrogen peroxide is continuously added to the wastewater, and the addition ratio of hydrogen peroxide is 2 - 5% of the total mass of the wastewater. Heat up to 120 - 150 °C, maintain the pressure in the second reaction tower 3 at 0.4 - 0.6 Mpa, and the reaction time is 100 - 120 min.

[0056] Among them, the catalyst used in the third oxidation reaction includes iron-based and chromium-aluminum-cobalt-aluminum (also known as layered iron-cobalt-aluminum), that is, the catalyst used is based on iron-based and mainly composed of chromium-aluminum-cobalt-aluminum.

[0057] Among them, the hydrogen peroxide is hydrogen peroxide with a mass fraction of 27.5%.

[0058] At this time, the chemical oxygen demand of the wastewater drops to less than 2000.

[0059] The reaction time of step S4 is relatively long, and the reaction conditions are milder than the above reactions. During the reaction process, phenols and derivatives are further decomposed, and the proportion of single-chain bromoalkanes increases significantly (about 60 - 80% of the total organic matter), while the proportion of organic by-products in water is relatively low, mainly composed of dibromoacrylic acid, dibromoacetaldehyde, etc.

[0060] In this reaction, hydrogen peroxide oxidation is used again and the reaction time is extended, which can greatly increase the final main content of bromocarbene and is an indispensable repeated step.

[0061] S5. Cool the wastewater obtained from the third oxidation reaction in step S4 to 8 - 12 °C to precipitate the solid salts in the wastewater. The remaining wastewater is fed into fractionating column 4. The bottom temperature of fractionating column 4 is 105 °C and the feed temperature is 145 °C. The single-chain bromohaloalkane components obtained are collected and condensed, and the purity can reach over 80 - 90%.

[0062] Among them, the cooling is completed by the cooling water of the cooling heat exchanger 7.

[0063] Among them, the remaining organic components in the wastewater after fractionation are absorbed by sodium hydroxide solution, and the remaining bottom liquid can participate in biochemical treatment and be discharged.

[0064] S6. Feed the single-chain bromohaloalkane components obtained by condensation in step S5 into reaction kettle 5, add octadecyltrimethylammonium bromide, and the addition ratio of octadecyltrimethylammonium bromide is 1.2% of the single-chain bromohaloalkane components. Then feed a 50% (mass fraction) sodium hydroxide solution, and react at 65 °C for 2 h to obtain the final product dibromocarbene, and the by-product is sodium bromide solution.

[0065] After the treatment of steps S1 - S6, the chemical oxygen demand of the wastewater from tetrabromobisphenol A production is greatly reduced to less than 2000, the benzene ring-containing compounds are basically all broken, and the B / C ratio (the ratio of BOD to COD, which can represent the biodegradability characteristics of the wastewater) increases significantly, and it can directly participate in the biochemical process for further degradation, thereby converting the difficult-to-degrade organic wastewater into easily degradable wastewater, and converting most of the organic matter in the water into dibromocarbene, realizing resource utilization.

[0066] Example 1: S1. Evaporate and concentrate the wastewater from tetrabromobisphenol A production and adjust the pH to ensure that no obvious solids precipitate during the evaporation process. The outlet temperature of the obtained wastewater is maintained at 80 °C, and the total salt content of the wastewater outlet is maintained at 35%. Adjust the pH of the wastewater outlet with concentrated sulfuric acid to 4.5.

[0067] Among them, the wastewater from tetrabromobisphenol A production is evaporated and concentrated by an evaporator 6 to obtain wastewater effluent and evaporation condensate. Steam is introduced into the evaporator 6, and steam condensate is discharged.

[0068] When the pH of the wastewater effluent drops to 4.5, some solid flocculent substances will precipitate from the wastewater. This solid substance is mainly tribromophenol and can directly participate in the next reaction without filtration.

[0069] S2. The wastewater obtained in step S1 is introduced into a high-temperature and high-pressure reaction tower 1. After the high-temperature and high-pressure reaction tower 1 is evacuated, oxygen is filled to 2.5 MPa, and the wastewater is heated to 320 °C for an oxidation reaction for 15 min. After the reaction ends, the wastewater is cooled to below 90 °C.

[0070] In step S2, the catalyst used in the oxidation reaction is Nb 2 O 5 .NH 2 O, Ta 2 O 5 , octadecyltrimethylammonium chloride. It can also be CR 2 O 3 , SNO 2 , Er 2 O 3 / TiO 2 .

[0071] At this time, the chemical oxygen demand in the wastewater drops by about 3000 - 4000.

[0072] S3. The wastewater obtained in step S2 is introduced into a first reaction tower 2. The pH of the wastewater in the first reaction tower 2 is adjusted to 3, and the second oxidation reaction starts. In this reaction, hydrogen peroxide with a mass fraction of 27.5% is added to the wastewater. The addition ratio of hydrogen peroxide is 5% of the total mass of the wastewater. The temperature is raised to 150 °C, and the pressure in the first reaction tower 2 is maintained at 0.6 Mpa. The reaction time is 60 min.

[0073] Among them, the catalyst used in the second oxidation reaction includes iron-based and chromium-aluminum-cobalt-aluminum (also known as layered iron-cobalt-aluminum), that is, the catalyst used is based on iron-based and mainly composed of chromium-aluminum-cobalt-aluminum.

[0074] Specifically, the catalyst used in the reaction is Fe 3 C, chromium-aluminum-cobalt-aluminum. It can also be ZnSn, MnO 2 .

[0075] In this reaction, the chemical oxygen demand in the wastewater drops by about 2000 - 3000.

[0076] S4. Feed the wastewater obtained from the second oxidation reaction in step S3 into the second reaction tower 3, adjust the pH of the wastewater to 2, and start the third oxidation reaction. In this reaction, hydrogen peroxide with a mass fraction of 27.5% is continuously added to the wastewater, and the addition ratio of hydrogen peroxide is 2% of the total mass of the wastewater. Heat the mixture to 150°C, maintain the pressure in the second reaction tower 3 at 0.6 Mpa, and the reaction time is 120 min.

[0077] Among them, the catalyst used in the third oxidation reaction includes an iron-based catalyst and chromium-aluminum-cobalt-aluminum (also known as layered iron-cobalt-aluminum), that is, the catalyst used is based on an iron-based catalyst and has chromium-aluminum-cobalt-aluminum as the main component.

[0078] Specifically, the catalyst used in step S4 is Fe 3 C, chromium-aluminum-cobalt-aluminum, and can also be ZnSn and MnO 2 .

[0079] At this time, the chemical oxygen demand of the wastewater drops to less than 2000.

[0080] S5. Cool the wastewater obtained from the third oxidation reaction in step S4 to 10°C to precipitate the solid salts in the wastewater. The remaining wastewater is fed into the fractionating tower 4. The bottom temperature of the fractionating tower 4 is 105°C, and the feed temperature is 145°C. Collect and condense the obtained single-chain brominated halohydrocarbon components, and the purity can reach more than 85%.

[0081] Among them, the cooling is completed by the cooling water of the cooling heat exchanger 7.

[0082] The remaining organic components in the fractionated wastewater are absorbed by sodium hydroxide solution, the tail gas is treated, and the remaining bottom liquid can participate in biochemical treatment and be discharged.

[0083] S6. Feed the single-chain brominated halohydrocarbon components obtained by condensation in step S5 into the reaction kettle 5, add octadecyltrimethylammonium bromide, and the addition ratio of octadecyltrimethylammonium bromide is 1.2% of the single-chain brominated halohydrocarbon components. Then, feed a 50% sodium hydroxide solution and react at 65°C for 2 h to obtain the final product dibromocarbene, and the yield can reach 65%. The by-product is sodium bromide solution, and at this time, the process is regarded as completed.

[0084] Among them, dibromocarbene has high activity and is mostly a reaction intermediate. Generally, it is directly used for direct production reactions with olefins and aldehydes, and is not used as a finished product for sale alone.

[0085] Example 2: S1. Evaporate and concentrate the wastewater from the production of tetrabromobisphenol A and adjust the pH to ensure that no obvious solids precipitate during the evaporation process. The outlet temperature of the obtained wastewater is maintained at 85°C, and the total salt content in the wastewater outlet is maintained at 40%. Adjust the pH of the wastewater outlet with concentrated sulfuric acid to adjust the pH to 5.

[0086] Among them, the wastewater from the production of tetrabromobisphenol A is evaporated and concentrated by an evaporator 6 to obtain wastewater effluent and evaporation condensate. Steam is introduced into the evaporator 6, and steam condensate is discharged.

[0087] When the pH of the wastewater effluent drops to 5, some solid flocculent substances will precipitate from the wastewater. The solid substances are mostly tribromophenol and can directly participate in the next reaction without filtration.

[0088] S2. The wastewater obtained in step S1 is introduced into a high-temperature and high-pressure reaction tower 1. After the high-temperature and high-pressure reaction tower 1 is evacuated, oxygen is filled to 3.2 MPa, and the wastewater is heated to 320 °C for an oxidation reaction for 30 min. After the reaction ends, the wastewater is cooled to below 90 °C.

[0089] In step S2, the catalyst used in the oxidation reaction is Nb 2 O 5 .NH 2 O, Ta 2 O 5 , octadecyltrimethylammonium chloride. It can also be CR 2 O 3 , SNO 2 , Er 2 O 3 / TiO 2 .

[0090] At this time, the decline in the chemical oxygen demand of the wastewater is about 3000.

[0091] S3. The wastewater obtained in step S2 is introduced into a first reaction tower 2. The pH of the wastewater in the first reaction tower 2 is adjusted to 3, and the second oxidation reaction starts. In this reaction, hydrogen peroxide with a mass fraction of 27.5% is added to the wastewater. The addition ratio of hydrogen peroxide is 8% of the total mass of the wastewater. The temperature is raised to 170 °C, and the pressure in the first reaction tower 2 is maintained at 0.7 Mpa. The reaction time is 80 min.

[0092] The catalysts used in the reaction include iron-based and chromium-aluminum-cobalt-aluminum, that is, the reagents used are based on iron-based and mainly composed of chromium-aluminum-cobalt-aluminum.

[0093] Specifically, the catalysts used in the reaction include Fe 3 C, chromium-aluminum-cobalt-aluminum, ZnSn and MnO 2 .

[0094] In this reaction, the decline in the chemical oxygen demand of the wastewater is about 2000 - 3000.

[0095] S4. Feed the wastewater obtained from the second oxidation reaction in step S3 into the second reaction tower 3, adjust the pH of the wastewater to 3, and start the third oxidation reaction. In this reaction, hydrogen peroxide with a mass fraction of 27.5% is continuously added to the wastewater, and the addition ratio of hydrogen peroxide is 2% of the total mass of the wastewater. Heat up to 150 °C, maintain the pressure in the second reaction tower 3 at 0.6 Mpa, and the reaction time is 120 min.

[0096] The catalyst used in step S4 includes Fe 3 C, chromium-aluminum-cobalt-aluminum, ZnSn, and MnO 2 .

[0097] At this time, the chemical oxygen demand of the wastewater drops to less than 2000.

[0098] S5. Cool the wastewater obtained from the third oxidation reaction in step S4 to 8 °C to precipitate the solid salts in the wastewater. The remaining wastewater is fed into the fractionating tower 4. The bottom temperature of the fractionating tower 4 is 105 °C, and the feed temperature is 145 °C. Collect and condense the obtained single-chain bromo-halohydrocarbon components, and the purity can reach more than 87%.

[0099] Among them, the cooling is completed by the cooling water of the cooling heat exchanger 7.

[0100] The remaining organic components in the fractionated wastewater are absorbed by sodium hydroxide solution, the tail gas is treated, and the remaining bottom liquid can participate in biochemical treatment and be discharged.

[0101] S6. Feed the single-chain bromo-halohydrocarbon components obtained by condensation in step S5 into the reaction kettle 5, add octadecyltrimethylammonium bromide, and the addition ratio of octadecyltrimethylammonium bromide is 1.2% of the single-chain bromo-halohydrocarbon components. Then, feed a 50% concentration of sodium hydroxide solution, and react at 65 °C for 2 h to obtain the final product dibromocarbene, and its yield can reach 65%. The by-product is sodium bromide solution. At this time, the process is regarded as completed.

[0102] Among them, dibromocarbene has high activity and is mostly a reaction intermediate. Generally, it is directly used for direct production reactions with olefins and aldehydes, and is not used as a finished product for sale alone.

[0103] The present invention also provides a system for synthesizing bromocarbene using the wastewater from the production of tetrabromobisphenol A, including a high-temperature and high-pressure reaction tower 1, a first reaction tower 2, a second reaction tower 3, a fractionating tower 4, and a reaction kettle 5 connected in sequence. The feed inlet of the high-temperature and high-pressure reaction tower 1 is connected to the discharge outlet of the evaporator 6. A cooling heat exchanger 7 is arranged between the second reaction tower 3 and the fractionating tower 4. The feed inlet of the cooling heat exchanger 7 is connected to the discharge outlet of the second reaction tower 3, and the discharge outlet of the cooling heat exchanger 7 is connected to the discharge outlet of the fractionating tower 4.

[0104] The above has described the embodiments of the present invention in detail, but the above content is only the preferred embodiments of the present invention and cannot be considered as defining the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention shall still fall within the scope covered by the present invention.

Claims

1. A method for synthesizing brominated carbene using wastewater from the production of tetrabromobisphenol A, characterized in that: The steps include: S1. Evaporation and concentration of tetrabromobisphenol A production wastewater and pH adjustment are performed to obtain a wastewater outlet temperature of 80-95°C and a wastewater outlet pH of 4.5-5.5; S2, passing the wastewater obtained in step S1 into a high-temperature and high-pressure reaction tower, evacuating the high-temperature and high-pressure reaction tower and filling it with oxygen to 2.5-3.2 MPa, heating the wastewater to 300-350°C for oxidation reaction for 10-30 minutes, and cooling the wastewater to below 90°C after the reaction; S3, passing the wastewater obtained in step S2 into the first reaction tower, adjusting the pH of the wastewater in the first reaction tower to 2-3, starting the second oxidation reaction, adding hydrogen peroxide to the wastewater, the hydrogen peroxide addition ratio is 4-10% of the total mass of the wastewater, heating to 150-180° C., maintaining the pressure of the first reaction tower at 0.5-0.9 MPa, and the reaction time is 60-80 min; S4, passing the wastewater obtained by the second oxidation reaction in step S3 into the second reaction tower, adjusting the pH of the wastewater to 2-3, starting the third oxidation reaction, continuing to add hydrogen peroxide to the wastewater, the hydrogen peroxide addition ratio is 2-5% of the total mass of the wastewater, heating to 120-150° C., the pressure of the second reaction tower is 0.4-0.6 MPa, and the reaction time is 100-120 min; S5, cooling the wastewater obtained by the third oxidation reaction in step S4 to 8-12°C to precipitate solid salts in the wastewater, and passing the remaining wastewater into a fractionation tower to collect and condense the obtained single-chain brominated halocarbon components; S6, passing the single-chain brominated halocarbon component obtained in step S5 into a reaction kettle, adding octadecyltrimethylammonium bromide, and then passing a sodium hydroxide solution into the reaction kettle to obtain a final product, dibromocarbene, and a by-product, a sodium bromide solution.

2. The method for synthesizing brominated carbene using tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S1, the organic insoluble matter precipitated during the evaporation and concentration process is fully dispersed by stirring.

3. The method for synthesizing brominated carbene using tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S2, the catalysts used in the oxidation reaction are Nb2O5.NH2O, Ta2O5, octadecyltrimethylammonium chloride, CR2O3, SNO2, and Er2O3 / TiO2.

4. The method for synthesizing brominated carbene using tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S3 and step S4, the catalysts used in the second oxidation reaction and the third oxidation reaction both include iron-based and chromium-aluminum-cobalt-aluminum.

5. The method for synthesizing brominated carbene using tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S3 and step S4, the hydrogen peroxide is hydrogen peroxide with a mass fraction of 27.5%.

6. The method for synthesizing brominated carbene using tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S5, the bottom temperature of the fractionation tower is 105°C and the feed temperature is 145°C.

7. The method for synthesizing brominated carbene using tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S6, the octadecyltrimethylammonium bromide is added in a ratio of 1.2% of the single-chain bromohalogenated hydrocarbon component, and then a 50% concentration sodium hydroxide solution is introduced and reacted at 65° C. for 2 hours.

8. A system for synthesizing brominated carbene using wastewater from the production of tetrabromobisphenol A, used to implement the method for synthesizing brominated carbene using wastewater from the production of tetrabromobisphenol A as claimed in any one of claims 1 to 7, characterized in that: It comprises a high-temperature and high-pressure reaction tower, a first reaction tower, a second reaction tower, a fractionation tower and a reaction kettle which are connected in sequence, wherein the feed port of the high-temperature and high-pressure reaction tower is connected with the discharge port of an evaporator, a cooling heat exchanger is arranged between the second reaction tower and the fractionation tower, the feed port of the cooling heat exchanger is connected with the discharge port of the second reaction tower, and the discharge port of the cooling heat exchanger is connected with the discharge port of the fractionation tower.

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