Chlorination bromine removal process of decabromodiphenyl ethane bromine distillation process

Abstract

The invention belongs to the technical field of brominated flame retardant synthesis, and particularly provides a decabromodiphenyl ethane bromine distillation process chlorination bromine removal process, which comprises the following steps: S1, adding bromine into a reaction kettle, adding a catalyst, and mixing; cooling and dropwise adding molten diphenylethane; then heating, carrying out a heat preservation reaction, and cooling to obtain a brominated crude product; s2, S201, adding the brominated crude product obtained in S1 into a bromine steaming kettle, and heating; s202, chlorine is introduced, and the total amount of bromine and chlorine is detected; carrying out segmented control on the introduced chlorine according to the total amount of bromine and chlorine; s203, when the total amount of bromine and chlorine is reduced to a threshold value, stopping introducing chlorine, standing, cooling, and introducing nitrogen; s3, filtering the feed liquid in the bromine steaming kettle, washing and purifying for three times, and finally, centrifugally dewatering to obtain a faint yellow solid; and S4, adding the faint yellow solid into a high-temperature jet mill, performing high-temperature aging to obtain white powder, and then performing jet milling on the white powder to obtain a finished product. Physical distillation is replaced by chemical replacement, so that bromine is highly separated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bromine flame retardant synthesis, in particular to a chlorination debromination process for a decabromodiphenyl ethane steam bromination process. BACKGROUND

[0002] Decabromodiphenyl ethane is a new, efficient, environmentally friendly additive flame retardant developed in recent years, which has better heat resistance, light resistance and less dialysis than decabromodiphenyl ether. Although the flame retardancy of the two is basically the same, it will not produce the problem of polybrominated dibenzo-p-dioxin that people are worried about, and the toxicity is lower than that of decabromodiphenyl ether. Decabromodiphenyl ethane is suitable for polystyrene, high styrene, ABS, epoxy resin, elastomer and other adhesives and sealants.

[0003] The preparation process of decabromodiphenyl ethane mainly includes diphenyl ethane synthesis, bromination reaction, post-treatment, aging treatment and other processes. The steam bromination process is one of the post-treatment steps, which aims to separate and recover unreacted bromine. After the completion of the bromination reaction, the reaction mixture contains a large amount of unreacted liquid bromine, which needs to be treated immediately to avoid the influence of residual bromine on product purity and subsequent operation safety.

[0004] The conventional steam bromination adopts physical distillation method, that is, water is added to the reaction mixture, and then heated and distilled to recover bromine vapor, which is recycled after condensation. This reaction requires high temperature and has high energy consumption, and the recovery rate is low, so that the residual bromine may cause the product to turn yellow or the impurities to increase. SUMMARY

[0005] In view of the above defects, the present application provides a chlorination debromination process for a decabromodiphenyl ethane steam bromination process, which replaces physical distillation with chemical displacement to achieve high separation of bromine in the steam bromination process.

[0006] To achieve the above purpose, the present application provides the following technical scheme: a chlorination debromination process for a decabromodiphenyl ethane steam bromination process, comprising: S1: bromination process: bromine is added to the reaction kettle, and a catalyst is added and mixed uniformly; after cooling, molten diphenyl ethane is slowly added dropwise; after the dropwise addition is completed, the temperature is raised for a holding reaction, and then cooled to room temperature to obtain a bromination crude product; S2: steam bromination and chlorination debromination process: S201: the bromination crude product obtained in S1 is added to a steam bromination kettle and heated; S202: chlorine gas is introduced, and the total amount of bromine and chlorine in the steam bromination kettle is detected; according to the total amount of bromine and chlorine, the introduced chlorine gas is controlled in sections; S203: when the total amount of bromine and chlorine decreases to a threshold value, stop introducing chlorine gas, maintain the original temperature and stand still, then cool down and introduce nitrogen gas; S3: washing and purification: filtering the liquid in the bromine distillation kettle to obtain wet material, and carrying out three times of washing and purification, and finally carrying out centrifugal dehydration to obtain a light yellow solid; S4: aging treatment: adding the light yellow solid into a high-temperature jet mill for high-temperature aging, converting the light yellow solid into a white powder, and then carrying out jet milling on the white powder to obtain a finished product.

[0007] As a further improvement of the present application, in S1, the bromine is 1500-1800 parts by weight, the benzhydride is 100-120 parts by weight, and the catalyst is iron powder, and the amount of the catalyst is 15 wt%-20 wt% of the benzhydride.

[0008] As a further improvement of the present application, in S1, the mixing temperature of the bromine and the catalyst is 45°C, the mixing time is 0.5h; the temperature after cooling is 35-30°C, and the dropping speed of the benzhydride is 30-50kg / h; the temperature after heating is 58-60°C, and the holding time is 7.5-8 hours.

[0009] As a further improvement of the present application, in S201, the temperature is raised to 85°C.

[0010] As a further improvement of the present application, in S202, the introduction of chlorine is controlled in stages, and specifically: When the total amount of bromine and chlorine is greater than 800ppm, chlorine is introduced at a rate of 10L / min; When the total amount of bromine and chlorine is less than or equal to 800ppm and greater than 600ppm, chlorine is introduced at a rate of 5L / min.

[0011] As a further improvement of the present application, in S203, the threshold value is 600ppm, the temperature is maintained at 85°C after the threshold value is reached, and the standing time is 10min.

[0012] As a further improvement of the present application, in S203, the nitrogen flow is 8L / min, the time is 5min, and the temperature is lowered before the nitrogen is introduced and maintained at 50°C.

[0013] As a further improvement of the present application, S3 specifically includes: S301: filtering the liquid in the bromine distillation kettle to obtain wet material, and cleaning the wet material with a washing liquid containing 15% NaOH and 0.5% ascorbic acid at 40-45°C for 8-10min; S302: secondary filtration, and cleaning with a washing liquid containing 5% NaOH and 1% Na2SO3 at 40-45°C for 8-10min; S303: three times filtration, washing at 40-45℃ using deionized water, stirring speed of 200-250rpm, washing time of 8-10min, and then centrifugal dewatering.

[0014] As a further improvement of the present application, the centrifugal dewatering speed is 2000rpm and the time is 5-7min.

[0015] As a further improvement of the present application, the high-temperature aging temperature in S4 is 200-220℃ and the time is 6-6.5h.

[0016] The beneficial effects of the present application are: The segmented chlorination debromination mechanism is adopted, the total amount of bromine and chlorine is monitored in real time by infrared, and the chlorine flow is switched to realize high flow in the early stage to promote oxidation, efficient removal of free bromine, low flow in the later stage to avoid excess chlorine side reactions, and complex bromine deep dissociation, thereby reducing the content of free bromine in the product, and combining with nitrogen blowing to prevent internal gas residue reaction and improve the recovery rate of bromine.

[0017] At the same time, the multiple washing and purification method is combined, and the washing liquid is adjusted synchronously according to the number of washing times, so as to further reduce the content of free bromine in the product, and then through the high-temperature aging treatment process, the overall free bromine content of the product is reduced and the whiteness is higher. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0019] The present application provides a chlorination debromination process for decabromodiphenyl ethane steam bromine process, comprising: S1: bromination process.

[0020] S101: bromine is added to the reaction kettle, and catalyst is added, stirred at 45℃ for 0.5h, and mixed uniformly.

[0021] S102: cooling to 35-30℃, then slowly adding molten diphenyl ethane, and the dropping speed is 30-50kg / h.

[0022] S103: after the addition is completed, the temperature is raised to 58-60℃, and the reaction is kept for 7.5-8h, and then cooled to room temperature to obtain the bromination crude product.

[0023] In terms of weight ratio, bromine is 1500-1800 parts by weight, diphenyl ethane is 100-120 parts by weight, and the catalyst is iron powder, and the amount is 15 wt%-20 wt% of diphenyl ethane.

[0024] As a further explanation of this embodiment, liquid bromine used is in excess to ensure complete bromination.

[0025] S2: Bromine removal by evaporation and chlorination.

[0026] S201: The bromination crude obtained in S1 is added to the bromine evaporation kettle, which is heated and stabilized at 85°C.

[0027] S202: Chlorine is introduced, and the infrared online monitoring system is started at the same time to detect the total amount of bromine and chlorine in the bromine evaporation kettle. Subsection flow control is adopted: Early stage: Introduce chlorine into the bromine evaporation kettle at a high flow rate of 10 L / min. The reaction is mainly oxidation of free bromine (fast rate, high flow rate of chlorine is required to push it).

[0028] Late stage: When the total amount of bromine and chlorine reaches 800 ppm, introduce chlorine into the bromine evaporation kettle at a low flow rate of 5 L / min. The reaction shifts to deep removal of bromide complexes (slow rate, low flow rate is required to avoid excess chlorine).

[0029] As a further explanation of this embodiment, the introduced chlorine reacts with free bromine in the system to convert free bromine into bromine gas, which is discharged.

[0030] S203: When the total amount of bromine and chlorine is less than or equal to 600 ppm, stop introducing chlorine into the interior; maintain 85°C for 10 min to allow the remaining chlorine to naturally overflow; then cool to 50°C, and introduce high-purity nitrogen into the kettle (flow rate is 8 L / min, duration is 5 min).

[0031] As a further explanation of this embodiment, the purpose of introducing nitrogen into the kettle is to drive out residual chlorine, prevent the generation of hypochlorite during subsequent alkali washing, and avoid product oxidation and yellowing.

[0032] S3: Purification by washing.

[0033] S301: Filter the liquid in the bromine evaporation kettle to obtain wet material. Then, at 40-45°C, use a washing solution of 15% NaOH and 0.5% ascorbic acid to clean for 8-10 min to remove residual acidic impurities and residual bromine.

[0034] As a further explanation of this embodiment, NaOH reacts with free Br2 to generate sodium bromide NaBr and sodium hypobromite NaOBr, and NaOBr is decomposed into sodium bromide NaBr by ascorbic acid C6H8O6.

[0035] S302: Perform secondary filtration to obtain wet material. Then, at 40-45°C, use a washing solution of 5% NaOH and 1% Na2SO3 to clean for 8-10 min.

[0036] As a further explanation of the present embodiment, the secondary addition of NaOH continues to react Br2 to generate sodium bromide NaBr and sodium hypobromite NaOBr, and the unstable NaOBr is converted to NaBr by Na2SO3, and Na2SO3 is converted to Na2SO4, and Na2SO3 is more reducing than NaOBr, so it is used for secondary cleaning to remove less NaOBr.

[0037] S303: Three times of filtration are performed to obtain wet material. Then, at 40-45°C, deionized water is used for cleaning, the stirring speed is 200-250 rpm, and the cleaning time is 8-10 min. Then, centrifugal dewatering is performed (at a speed of 2000 rpm for 5-7 min) to obtain a light yellow solid.

[0038] S4: Aging treatment.

[0039] The light yellow solid is added to a ball mill tank, and after entering the ball mill, it is aged at a high temperature of 200-220°C for 6-6.5 hours to convert it into a stable white powder, and then the white powder is subjected to airflow crushing to obtain a finished product.

[0040] Example 1 S1: Bromination process.

[0041] S101: 1500 parts by weight of bromine is added to a reaction kettle, and 15 parts by weight of a catalyst is added, and stirred at 45°C for 0.5 hours to mix uniformly.

[0042] S102: The temperature is lowered to 35°C, and 100 parts by weight of molten diphenylmethane is slowly added at a speed of 30 kg / h.

[0043] S103: After the addition is completed, the temperature is raised to 58°C, and the reaction is maintained for 7.5 hours, and then cooled to room temperature to obtain a bromination crude product.

[0044] S2: Bromine evaporation and debromination by chlorination process.

[0045] S201: The bromination crude product obtained in S1 is added to a bromine evaporation kettle, and the temperature is raised and stabilized at 85°C.

[0046] S202: An infrared online monitoring system is started, and chlorine gas is introduced into the bromine evaporation kettle at a high flow rate of 10 L / min. When the total amount of bromine and chlorine reaches 800 ppm, chlorine gas is introduced into the bromine evaporation kettle at a low flow rate of 5 L / min.

[0047] S203: When the total amount of bromine and chlorine is less than or equal to 600 ppm, the introduction of chlorine gas into the interior is stopped; 85°C is maintained for 10 min; then the temperature is lowered to 50°C, and high-purity nitrogen gas is introduced into the kettle at a flow rate of 8 L / min for 5 min.

[0048] S3: Washing and purification.

[0049] S301: The material liquid in the bromine evaporation kettle was filtered to obtain a wet material. Then, at 40°C, the wet material was washed with a washing solution of 15% NaOH and 0.5% ascorbic acid for 8 min to remove residual acidic impurities and residual bromine.

[0050] S302: Secondary filtration was performed to obtain a wet material. Then, at 40°C, the wet material was washed with a washing solution of 5% NaOH and 1% Na2SO3 for 8 min.

[0051] S303: Tertiary filtration was performed to obtain a wet material. Then, at 40°C, the wet material was washed with deionized water at a stirring speed of 200 rpm for 8 min. Then, centrifugal dewatering was performed at a speed of 2000 rpm for 5 min to obtain a light yellow solid.

[0052] S4: Aging treatment.

[0053] The light yellow solid was added to a high-temperature jet mill, and after entering the ball mill, it was aged at a high temperature of 200°C for 6 hours to convert into a stable white powder. Then, the white powder was subjected to jet milling to obtain a finished product.

[0054] Example 2 S1: Bromination process.

[0055] S101: 1650 parts by weight of bromine was added to a reaction kettle, and 19.25 parts by weight of a catalyst was added. The mixture was stirred at 45°C for 0.5 hours to mix uniformly.

[0056] S102: The temperature was lowered to 32°C, and 110 parts by weight of molten diphenylethane was slowly added at a speed of 40 kg / h.

[0057] S103: After the addition was completed, the temperature was raised to 59°C, and the reaction was maintained for 7.75 hours. Then, the temperature was cooled to room temperature to obtain a bromination crude product.

[0058] S2: Bromine evaporation and bromine removal by chlorination process.

[0059] Steps S201, S202, and S203 are consistent with Example 1.

[0060] S3: Washing and purification.

[0061] S301: The material liquid in the bromine evaporation kettle was filtered to obtain a wet material. Then, at 40°C, the wet material was washed with a washing solution of 15% NaOH and 0.5% ascorbic acid for 8 min to remove residual acidic impurities and residual bromine.

[0062] S302: Secondary filtration was performed to obtain wet material. Then, at 43°C, the wet material was washed with a washing solution of 5% NaOH and 1% Na2SO3for 9 min.

[0063] S303: Tertiary filtration was performed to obtain wet material. Then, at 43°C, the wet material was washed with deionized water at a stirring speed of 225 rpm for 9 min. Then, the wet material was centrifugally dewatered at a speed of 2000 rpm for 6 min to obtain a light yellow solid.

[0064] S4: Aging treatment.

[0065] The light yellow solid was added into a high-temperature jet mill, and was converted into a stable white powder after being aged at a high temperature of 210°C for 6.25 hours in a ball mill. Then, the white powder was jet-milled to obtain a finished product.

[0066] Example 3 S1: Bromination process.

[0067] S101: 1800 parts by weight of bromine was added into a reaction kettle, and 24 parts by weight of a catalyst was added and uniformly mixed at 45°C for 0.5 hours.

[0068] S102: The temperature was lowered to 30°C, and 120 parts by weight of molten diphenylethane was slowly added at a speed of 40 kg / h.

[0069] S103: After the addition was completed, the temperature was raised to 60°C, and the reaction was maintained for 8 hours. Then, the temperature was lowered to room temperature to obtain a bromination crude product.

[0070] S2: Bromine evaporation and debromination by chlorination process.

[0071] Steps S201, S202 and S203 were consistent with Example 1.

[0072] S3: Washing and purification.

[0073] S301: The liquid in the bromine evaporation kettle was filtered to obtain wet material. Then, at 45°C, the wet material was washed with a washing solution of 15% NaOH and 0.5% ascorbic acid for 10 min to remove residual acidic impurities and residual bromine.

[0074] S302: Secondary filtration was performed to obtain wet material. Then, at 45°C, the wet material was washed with a washing solution of 5% NaOH and 1% Na2SO3for 10 min.

[0075] S303: The wet material was obtained by filtering three times. Then, the wet material was washed with deionized water at 45℃, the stirring speed was 250 rpm, and the washing time was 10 min. Then, the wet material was centrifuged at a speed of 2000 rpm for 7 min to obtain a light yellow solid.

[0076] S4: Aging treatment.

[0077] The light yellow solid was put into a high-temperature jet mill, and after entering the ball mill, it was aged at a high temperature of 220℃ for 6.5 hours to convert into a stable white powder. Then, the white powder was subjected to jet milling to obtain a finished product.

[0078] Comparative Example 1 This comparative example is based on Example 1, except that in step S2, a traditional conventional physical bromine distillation method was used. The bromination crude product of S1 was transferred into a distillation kettle, deionized water was added, and bromine vapor was recovered by high-temperature normal-pressure distillation.

[0079] Comparative Example 2 This comparative example is based on Example 1, except that in step S2, chlorine was passed at a rate of 10 L / min throughout the process to a total amount of bromine and chlorine of 600 ppm.

[0080] Comparative Example 3 This comparative example is based on Example 1, except that in step S2, the nitrogen purging step was omitted.

[0081] Comparative Example 4 This comparative example is based on Example 1, except that in step S3, only 15% NaOH washing solution was used for washing once.

[0082] Comparative Example 5 This comparative example is based on Example 1, except that in step S4, the aging condition was changed to 180℃ for 8 hours.

[0083] The decabromodiphenyl ethane obtained in Examples 1-3 and Comparative Examples 1-5 was subjected to experimental determination: Free bromine residue determination: according to HG / T 5342-2018 “Flame Retardant Chemicals Decabromodiphenyl Ethane”, ion chromatography method was used.

[0084] Whiteness determination: according to GB / T 5950-2008 (or enterprise standard), the whiteness meter reflection method was used.

[0085] The determination results of each example and comparative example are shown in the following comparison table:

[0086] From the data in the above table, it can be seen that, compared with Comparative Example 1, the removal of free bromine by the traditional physical distillation method is lower, and the reaction removal of bromine by passing chlorine can effectively reduce the residual free chlorine.

[0087] Compared with Comparative Example 2, the high flow rate continuous chlorine passing can affect the whiteness of the product, and the reason is that the excessive chlorine passing leads to an increase in by-products.

[0088] Compared with Comparative Example 3, the whiteness of the product in Comparative Example 3 is lower, and the reason is that the residual bromine and chlorine due to no nitrogen purging can react again, resulting in an increase in free bromine and a decrease in whiteness.

[0089] Compared with Comparative Example 4, the residual free bromine in Comparative Example 4 is increased, and the reason is that the free bromine cannot be completely decomposed, and NaOBr cannot be completely decomposed, thereby affecting the residual free bromine and whiteness.

[0090] Compared with Comparative Example 5, the whiteness of the product in Comparative Example 5 is lower, and the reason is that the uneven whiteness caused by the too low aging temperature.

[0091] In summary, by using the segmented flow control chlorination bromine removal, nitrogen purging, multiple washing and high temperature aging process, the free bromine in the decabromodiphenyl ethane produced by the present patent is more completely separated, thereby ensuring a higher recovery rate and a higher product whiteness, which is significantly better than the traditional process.

[0092] The above is only a preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned implementation measures. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the technical field, some improvements and refinements without departing from the principles of the present application shall also be considered as the protection scope of the present application.

Claims

1. A chlorination process for removing bromine from decabromodiphenyl ethane during bromine distillation, characterized in that, include: S1: Bromination process: Add bromine to the reaction vessel and add catalyst, mix evenly; after cooling, slowly add molten diphenyl ethane; after the addition is complete, raise the temperature to maintain the temperature for reaction, and then cool to room temperature to obtain crude brominated product; S2: Bromine removal process involving bromine distillation and chlorination. S201: Add the crude brominated product obtained in S1 to the bromine distillation vessel and heat it; S202: Introduce chlorine gas and detect the total amount of bromine and chlorine in the bromine distillation vessel; control the introduced chlorine gas in stages according to the total amount of bromine and chlorine. S203: Once the total amount of bromine and chlorine has decreased to the threshold, stop the chlorine gas flow, maintain the original temperature and let it stand, then cool down and introduce nitrogen gas; S3: Washing and purification: Filter the liquid in the bromine distillation vessel to obtain wet material, and perform three washing and purification processes. Finally, centrifuge and dehydrate to obtain a pale yellow solid. S4: Aging treatment: The pale yellow solid is added to a high-temperature airflow pulverizer for high-temperature aging, which transforms it into a white powder. The white powder is then pulverized by airflow to obtain the finished product.

2. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, In S1, by weight ratio, bromine is 1500-1800 parts, diphenyl ethane is 100-120 parts, and the catalyst is iron powder, the amount of which is 15 wt%-20 wt% of diphenyl ethane.

3. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, The mixing temperature of bromine and catalyst in S1 is 45℃, and the mixing time is 0.5h; the temperature after cooling is 35-30℃, and the diphenyl ethane dropping rate is 30-50kg / h; the temperature after heating is 58-60℃, and the holding time is 7.5-8 hours.

4. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, The temperature in S201 is raised to 85°C.

5. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, The specific steps for segmented control of the chlorine gas introduction in S202 are as follows: When the total bromine and chlorine content is greater than 800 ppm, chlorine gas is introduced at a rate of 10 L / min. When the total bromine and chlorine content is less than or equal to 800 ppm but greater than 600 ppm, chlorine gas is introduced at a rate of 5 L / min.

6. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, The threshold value in S203 is 600 ppm. After reaching the threshold, the temperature is maintained at 85°C and the settling time is 10 min.

7. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 6, characterized in that, The nitrogen gas introduced into S203 is introduced at a flow rate of 8 L / min for 5 min, and the temperature is lowered and maintained at 50°C before introduction.

8. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, S3 specifically includes: S301: Filter the liquid in the bromine distillation vessel to obtain wet material, and wash it at 40-45℃ with a washing solution of 15% NaOH and 0.5% ascorbic acid for 8-10 minutes. S302: Secondary filtration, at 40-45℃, wash with a washing solution of 5% NaOH and 1% Na2SO3 for 8-10 minutes; S303: Three-stage filtration, washing with deionized water at 40-45℃, stirring speed of 200-250rpm, washing time of 8-10min, followed by centrifugation for dehydration.

9. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 8, characterized in that, The centrifugation dehydration process is carried out at a speed of 2000 rpm for 5-7 minutes.

10. The chlorination process for removing bromine in the decabromodiphenyl ethane distillation step according to claim 1, characterized in that, The high-temperature aging temperature in S4 is 200-220℃, and the time is 6-6.5 hours.

Images