A method for treating sodium bromide wastewater during photoinitiator production.

Abstract

This invention relates to a method for treating sodium bromide wastewater during the production of photoinitiators. The method includes vacuum distilling the sodium bromide wastewater in the presence of an adsorbent until sodium bromide precipitates, adding sulfuric acid and mixing, filtering, and adding hydrogen peroxide to the filtrate to react and obtain bromine. The bromine is then collected by distillation and separation. The method described in this invention can recover bromine from the wastewater during the preparation of photoinitiators and convert it into bromine, thereby achieving the recycling of bromine, reducing process costs and the pressure of treating waste gas, wastewater, and solid waste.

Description

Technical Field

[0001] This invention belongs to the field of photoinitiators and relates to a method for treating sodium bromide wastewater during the production of photoinitiators. Background Technology

[0002] Photoinitiators are compounds that can absorb energy of a certain wavelength in the ultraviolet or visible light region, generate free radicals, cations, etc., and thus initiate monomer polymerization, cross-linking and curing.

[0003] α-Aminoacetophenone photoinitiators possess advantages such as good thermal stability, long shelf life, good solubility, light color, good anti-yellowing properties, fast photocuring speed, and good deep curing performance. They are particularly suitable for colored systems and have been widely used in the UV curing field, including in photocurable coatings, inks, and photoresists. Commercially available products include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone and 2-(4-methylbenzyl)-2-dimethylamino-1-(4-morpholinophenyl)butanone, etc.

[0004] CN105384707A discloses a method for preparing α-aminoacetophenone-based photoinitiators. The preparation process includes bromination, dimethylamine substitution, benzyl chloride or methylbenzyl chloride substitution, and morpholine substitution reactions. In the above preparation process, the dimethylamine substitution reaction uses dimethylamine to replace bromine, which generates a large amount of sodium bromide wastewater. The salinity of this wastewater is extremely high (>100,000 mg / L), making it extremely difficult to treat. Existing technologies generally recover a mixture of sodium bromide and organic impurities from the wastewater to reduce the salinity before it enters the wastewater treatment process. However, due to the complex composition of the distilled solids (mainly sodium bromide), it can only be treated as hazardous waste, resulting in high treatment costs. Taking the production of 2-benzyl-2-dimethylamino-1-(4-morpholinephenyl)butanone as an example, the treatment cost of sodium bromide wastewater accounts for about 5% of the total cost.

[0005] Therefore, it is still of great significance to develop a resource-based treatment method for sodium bromide wastewater that can effectively recover bromine from wastewater and has a low cost. Summary of the Invention

[0006] The purpose of this invention is to provide a method for treating sodium bromide wastewater during the production of photoinitiators. The method includes vacuum distilling the sodium bromide wastewater in the presence of an adsorbent until sodium bromide precipitates, adding sulfuric acid and mixing, filtering, and adding hydrogen peroxide to the filtrate to react and obtain bromine. The bromine is then collected by distillation and separation. The method described in this invention can recover bromine from the wastewater during the preparation of photoinitiators and convert it into bromine, thereby achieving the recycling of bromine, reducing process costs and the pressure of treating waste gas, wastewater, and solid waste.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for treating sodium bromide wastewater during the production of photoinitiators, the method comprising the following steps:

[0009] (1) Add an adsorbent to sodium bromide wastewater and perform vacuum distillation until sodium bromide precipitates out. Then add sulfuric acid and mix to obtain a mixed solution.

[0010] (2) Filter the mixture in step (1), add hydrogen peroxide to the filtrate, react, distill, condense, and obtain a mixture of bromine and water. Separate the liquid to obtain bromine.

[0011] α-Aminoacetophenone photoinitiators, taking photoinitiator 369 and photoinitiator 379 as examples, generally involve bromination and dimethylamine substitution reactions during their preparation. After the dimethylamine substitution reaction is completed, the substituted bromine is converted into sodium bromide and dissolved in the aqueous phase, forming sodium bromide wastewater. The salinity of this sodium bromide wastewater is extremely high (>100,000 mg / L), making it extremely difficult to treat. Existing technologies generally use distillation to remove a mixture of sodium bromide and organic impurities. The mixture has a complex composition, mainly sodium bromide, and is treated as hazardous waste, resulting in high treatment costs. To address these issues, this invention provides a resource-based treatment method for sodium bromide wastewater that can effectively recover bromine from the wastewater and has a lower cost.

[0012] This invention, through compositional analysis of sodium bromide wastewater, reveals that the main component is sodium bromide, along with some organic impurities. Existing processes struggle to separate sodium bromide from the mixture. However, this invention utilizes a specific method to convert sodium bromide in the wastewater into valuable bromine, thus turning waste into treasure and increasing added value. This solves the wastewater treatment problem, saves on the treatment costs of the wastewater and the mixture of sodium bromide and organic impurities, reduces production costs, and allows the bromine obtained from the wastewater to be recycled for photoinitiator preparation, forming a circular economy. This also saves on raw material procurement costs and enhances the competitiveness of the company's products.

[0013] The treatment method of this invention includes adding a specific adsorbent to sodium bromide wastewater and distilling until sodium bromide solid precipitates out. Then, sulfuric acid is added, the mixture is stirred, and hydrogen peroxide is added for an oxidation reaction. Through these steps, sodium bromide in the wastewater is converted into bromine. The bromine and water are then distilled off, condensed, and separated to obtain bromine. This method enables the effective recovery of bromine from sodium bromide wastewater, and the obtained bromine can be reused in the bromination reaction of α-aminoacetophenone photoinitiators, achieving bromine recycling and reducing raw material procurement costs, while also reducing the treatment cost of high-salinity wastewater.

[0014] The treatment method described in this invention achieves the separation of bromine from organic impurities through adsorption, oxidation reaction (converting sodium bromide into bromine) combined with distillation, thereby realizing the resource recovery of bromine. The obtained bromine can be used in the photoinitiator preparation process, forming a circular economy of sodium bromide-bromine-sodium bromide. Moreover, the above process consumes only a small amount of hydrogen peroxide and sulfuric acid. Compared with the traditional treatment method of evaporating and desalinating sodium bromide wastewater to obtain a mixture of sodium bromide and organic impurities and then treating the mixture as hazardous waste, this method significantly reduces production costs.

[0015] The treatment method described in this invention solves the problems of difficult and costly treatment of high-salt sodium bromide wastewater and the resulting hazardous waste. The treatment process consumes only a small amount of inexpensive hydrogen peroxide and sulfuric acid, which not only reduces treatment costs but also reduces the amount of bromine to be purchased, thereby significantly reducing production costs.

[0016] The adsorbent in this invention has two functions: first, to adsorb impurities, including organic and mechanical impurities; and second, to aid filtration and improve the filtration effect.

[0017] Preferably, the sodium bromide wastewater is sodium bromide wastewater generated during the preparation of α-aminoacetophenone photoinitiators.

[0018] The α-aminoacetophenone photoinitiators mentioned here include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (photoinitiator 369) and 2-(4-methylbenzyl)-2-dimethylamino-1-(4-morpholinophenyl)butanone (photoinitiator 379), etc.

[0019] Preferably, the adsorbent in step (1) is selected from any one or a combination of at least two of diatomaceous earth, activated carbon powder or resin.

[0020] The treatment method described in this invention uses the specific adsorbent mentioned above, which has the advantages of strong adsorption, high CODcr removal efficiency, and easy filtration.

[0021] Preferably, in step (1), the mass ratio of sodium bromide wastewater to adsorbent is 150 to 250:1, for example, 160:1, 170:1, 180:1, 190:1, 200:1, 210:1, 220:1, 230:1 or 240:1.

[0022] Preferably, the temperature of vacuum distillation in step (1) is 80℃~90℃, for example 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃ or 89℃.

[0023] Preferably, the mass of the remaining solution at the end of the vacuum distillation in step (1) is 0.4 to 0.6 times the mass of the sodium bromide wastewater, for example, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55 or 0.58.

[0024] Preferably, sulfuric acid is added dropwise in step (1).

[0025] In this invention, the reaction vessel is kept at atmospheric pressure during the addition of sulfuric acid, and the sulfuric acid is slowly added. At the same time, the liquid condition in the vessel needs to be observed through a sight glass during the addition process. If foaming is violent or the temperature rises violently, the addition rate can be reduced. If the problem cannot be alleviated, the addition should be stopped until there is no more foam and then the addition can continue.

[0026] Preferably, the temperature is controlled to ≤80°C during the addition of sulfuric acid in step (1), for example, 40°C, 50°C, 60°C or 70°C.

[0027] Preferably, the mass ratio of H2SO4 in sulfuric acid to sodium bromide wastewater added in step (1) is 0.35 to 0.55:1, for example, 0.36:1, 0.38:1, 0.4:1, 0.42:1, 0.45:1, 0.48:1, 0.5:1 or 0.52:1, and more preferably 0.4 to 0.45:1.

[0028] Preferably, the concentration of sulfuric acid in step (1) is 20% to 40%, such as 22%, 25%, 28%, 30%, 32%, 35%, or 38%, and more preferably 25% to 30%.

[0029] Preferably, the temperature is controlled at 40°C to 60°C during the mixing process in step (1), for example, 45°C, 50°C or 55°C.

[0030] Preferably, the sulfuric acid in step (1) is selected from waste sulfuric acid generated during the production of α-aminoacetophenone photoinitiators.

[0031] In the production process of α-aminoacetophenone photoinitiators, concentrated sulfuric acid is used to oxidize bromine in the bromination reaction to increase the utilization rate of bromine. The sulfuric acid is in excess. After the bromination reaction is completed, the aqueous phase obtained by separation contains sulfuric acid. The waste sulfuric acid can be used to acidify sodium bromide wastewater, thereby realizing the resource utilization of waste sulfuric acid and further reducing process costs.

[0032] Preferably, hydrogen peroxide is added dropwise in step (2).

[0033] Preferably, the mass ratio of H2O2 added to hydrogen peroxide in step (2) to the mass of sodium bromide wastewater in step (1) is 15% to 30%, for example, 18%, 20%, 22%, 25% or 28%.

[0034] Preferably, the concentration of H2O2 in the hydrogen peroxide in step (2) is 20% to 60%, such as 25%, 30%, 35%, 40%, 45%, 50% or 55%, and more preferably 30% to 50%.

[0035] Preferably, the temperature is controlled to ≤80℃ during the addition of hydrogen peroxide in step (2), such as 60℃, 65℃, 70℃ or 75℃, preferably 60℃~80℃, and more preferably 75℃~80℃.

[0036] Preferably, distillation is carried out during the addition of hydrogen peroxide in step (2).

[0037] Preferably, after hydrogen peroxide is added in step (2), the distillation temperature is controlled to 95℃~105℃, such as 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃ or 104℃.

[0038] Preferably, stirring is performed during the distillation process in step (2).

[0039] Preferably, step (2) further includes adding liquid alkali to the remaining liquid phase after distillation to neutralize it, thereby obtaining a neutralized solution.

[0040] Preferably, the temperature is controlled to ≤80℃ during the neutralization process of adding liquid alkali, such as 50℃, 55℃, 60℃, 65℃, 70℃ or 75℃.

[0041] Preferably, the endpoint of neutralization by adding liquid alkali is reached when the pH of the solution is 7 to 8, such as 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8 or 7.9.

[0042] This invention, based on the concept of turning waste into treasure, transforms high-salinity wastewater into reaction raw materials through resource utilization, achieving a circular economy of sodium bromide → bromine → sodium bromide. Traditional wastewater treatment methods, through distillation and desalination, yield a mixture of sodium bromide and organic impurities. This mixture is complex in composition, and the sodium bromide and organic impurities are difficult to separate, making it unsuitable for sale as a byproduct and requiring disposal as hazardous waste. This invention converts sodium bromide into bromine through a reaction, while the organic impurities do not react with hydrogen peroxide. Even if a small amount of impurities reacts with hydrogen peroxide, the organic impurities cannot be vaporized and distilled off during distillation like bromine. This not only solves the problem of separating organic impurities and sodium bromide but also utilizes waste sulfuric acid generated during the preparation of photoinitiators in the bromine production process, further reducing waste generation. Moreover, the treatment method described in this invention consumes only a small amount of inexpensive hydrogen peroxide and sulfuric acid, eliminating the treatment costs of high-salinity wastewater and hazardous waste, reducing the procurement of bromine raw materials, and thus significantly lowering production costs.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The treatment method of the present invention includes vacuum distilling sodium bromide wastewater in the presence of an adsorbent until sodium bromide precipitates, adding sulfuric acid to mix, filtering, and adding hydrogen peroxide to the filtrate to react and obtain bromine, and then collecting the bromine by distillation and separation. The above method can separate bromine from organic impurities in high-salt wastewater and recover bromine by resource recovery, avoiding the problem that the traditional process requires distilling out a mixture of sodium bromide and organic impurities and treating it as hazardous waste with high treatment costs, thus realizing the transformation of waste into treasure.

[0045] (2) The processing method described in this invention consumes only a small amount of inexpensive hydrogen peroxide and sulfuric acid, and the obtained bromine can be recycled for the preparation process of photoinitiator, which reduces the amount of bromine raw material purchased, thereby reducing production costs and enhancing the competitiveness of the product. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0047] Example 1

[0048] This embodiment provides a method for treating sodium bromide wastewater during the production of photoinitiator 369, specifically including the following steps:

[0049] (1) Add 500 kg of sodium bromide wastewater to a distillation kettle, add 2.5 kg of diatomaceous earth, start stirring, heat to 85°C for vacuum distillation. When the amount distilled out in the kettle reaches 250 kg, observe the situation in the kettle. When sodium bromide can be clearly seen precipitating in the kettle, stop distillation. Let the pressure in the kettle return to normal pressure and cool down to 70°C. Slowly drip 840 kg of 25% sulfuric acid into the kettle. During the dripping process, keep the temperature below 80°C. Observe the sight glass during dripping. If foaming is violent or the temperature rises violently, reduce the dripping rate. If it cannot be reduced, stop dripping until there is no foam and continue adding material. After the sulfuric acid is dripped, control the temperature at 50°C and stir for 30 min to obtain a mixed liquid.

[0050] (2) Filter the mixture in step (1) to obtain filtrate. Heat the filtrate to 60°C and add 200 kg of 50% hydrogen peroxide dropwise to the filtrate. The temperature is controlled at 75°C during the dropwise addition process. The mixture of bromine and water is distilled off. After the hydrogen peroxide is added, the temperature is raised to 100°C and stirred for 30 min. Bromine is further distilled off and condensed to obtain a mixture of bromine and water. When no dark red liquid condenses out, the reaction is over. The mixture is separated to obtain the lower bromine layer and the upper aqueous phase.

[0051] (3) Transfer the remaining liquid phase from distillation in step (2) to a neutralization reactor. When the temperature is controlled to below 60°C, add liquid alkali to the reactor for neutralization. During neutralization, control the temperature inside the reactor to not exceed 80°C. During the neutralization process, pay attention to the liquid level inside the reactor to prevent overflow. Neutralize to pH 7.5 to obtain a neutralized liquid.

[0052] In this embodiment, the purity of the bromine obtained in step (2) is 94.1%, and the yield is 70%.

[0053] In this embodiment, the sodium bromide wastewater mentioned above is the sodium bromide wastewater obtained from the dimethylamine substitution reaction during the preparation of photoinitiator 369.

[0054] Example 2

[0055] The only difference between this embodiment and Embodiment 1 is that the diatomaceous earth in step (1) of Embodiment 1 is replaced with activated carbon powder, while the other parameters and conditions are exactly the same as in Embodiment 1.

[0056] In this embodiment, the purity of the bromine obtained in step (2) is 93.7%, and the yield is 70%.

[0057] Example 3

[0058] The only difference between this embodiment and Embodiment 1 is that the amount of diatomaceous earth added is replaced with 2 kg, while the other parameters and conditions are exactly the same as in Embodiment 1.

[0059] In this embodiment, the purity of the bromine obtained in step (2) is 92%, and the yield is 67%.

[0060] Example 4

[0061] The only difference between this embodiment and Embodiment 1 is that the amount of diatomaceous earth added is replaced with 3 kg, while the other parameters and conditions are exactly the same as in Embodiment 1.

[0062] In this embodiment, the purity of the bromine obtained in step (2) is 94%, and the yield is 70%.

[0063] Example 5

[0064] The only difference between this embodiment and Example 1 is that 840 kg of 25% sulfuric acid is replaced with 530 kg of 40% sulfuric acid; all other parameters and conditions are exactly the same as in Example 1.

[0065] In this embodiment, the purity of the bromine obtained in step (2) is 94%, and the yield is 70%.

[0066] Example 6

[0067] The only difference between this embodiment and Example 1 is that the sulfuric acid is replaced with waste sulfuric acid produced by the photoinitiator 369 bromination process. The concentration of the waste sulfuric acid is 28%, and the amount added is 750 kg. All other parameters and conditions are exactly the same as in Example 1.

[0068] In this embodiment, the purity of the bromine obtained in step (2) is 94%, and the yield is 75%.

[0069] The bromine prepared in the above embodiments of the present invention meets the requirements for raw material bromine in the production process of photoinitiator 369 and can be recycled.

[0070] Comparative Example 1

[0071] The only difference between this comparative example and Example 1 is that diatomaceous earth is not added in step (1), while the other parameters and conditions are exactly the same as in Example 1.

[0072] In this comparative example, the purity of the bromine obtained in step (2) is 90%, and the yield is 65%.

[0073] Comparative Example 2

[0074] The only difference between this comparative example and Example 1 is that the diatomaceous earth in step (1) is replaced with quartz sand, while the other parameters and conditions are exactly the same as in Example 1.

[0075] In this comparative example, the purity of the bromine obtained in step (2) is 90%, and the yield is 65%.

[0076] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for treating sodium bromide wastewater in a photoinitiator production process, characterized by, The processing method comprises the following steps: (1) adding an adsorbent to sodium bromide wastewater, and performing vacuum distillation at a temperature of 80-90 DEG C until sodium bromide is precipitated, then adding sulfuric acid, mixing to obtain a mixed solution; (2) filtering the mixed solution in step (1), adding hydrogen peroxide to the filtrate, and performing reaction, distillation, condensation to obtain a mixed solution of bromine and water, and separating to obtain bromine; In step (1), the mass ratio of the sodium bromide wastewater to the adsorbent is 150-250:1; In step (1), the end point of vacuum distillation to the mass of the remaining solution is 0.4-0.6 of the mass of the sodium bromide wastewater; In step (1), the adsorbent is selected from any one or a combination of at least two of diatomite, activated carbon powder or resin, and the adsorbent is used to adsorb organic impurities to remove the organic impurities; In step (1), the sodium bromide wastewater is sodium bromide wastewater generated in the preparation process of an α-aminoacetophenone photoinitiator.

2. The treatment method according to claim 1, characterized in that, In step (1), the sulfuric acid is added dropwise.

3. The treatment method of claim 1, wherein In the process of adding the sulfuric acid in step (1), the temperature is controlled to be ≤80 DEG C.

4. The treatment method of claim 1, wherein In step (1), the mass ratio of the mass of H2SO4 in the sulfuric acid to the mass of the sodium bromide wastewater is 0.35-0.55:

1.

5. The treatment method according to claim 4, characterized in that, In step (1), the mass ratio of the mass of H2SO4 in the sulfuric acid to the mass of the sodium bromide wastewater is 0.4-0.45:

1.

6. The treatment method of claim 4, wherein In step (1), the concentration of the sulfuric acid is 20%-40%.

7. The treatment method according to claim 6, characterized in that, In step (1), the concentration of the sulfuric acid is 25%-30%.

8. The treatment method of claim 1, wherein In the process of mixing in step (1), the temperature is controlled to be 40-60 DEG C.

9. The treatment method of claim 1, wherein, In step (1), the sulfuric acid is selected from waste sulfuric acid generated in the production process of an α-aminoacetophenone photoinitiator.

10. The treatment method of claim 1, wherein, In step (2), the hydrogen peroxide is added dropwise.

11. The treatment method of claim 1, wherein, In step (2), the mass ratio of the mass of H2O2 in the hydrogen peroxide to the mass of the sodium bromide wastewater in step (1) is 15%-30%.

12. The treatment method of claim 1, wherein, In the process of adding the hydrogen peroxide in step (2), the temperature is controlled to be ≤80 DEG C.

13. The treatment method according to claim 12, characterized in that, In the process of adding the hydrogen peroxide in step (2), the temperature is controlled to be 60-80 DEG C.

14. The processing method according to claim 13, characterized by, In the process of adding the hydrogen peroxide in step (2), the temperature is controlled to be 75-80 DEG C.

15. The treatment method of claim 1, wherein, In the process of adding the hydrogen peroxide in step (2), distillation is accompanied.

16. The treatment method of claim 1, wherein, After the hydrogen peroxide is completely added in step (2), the temperature is controlled to be 95-105 DEG C during distillation.

17. The treatment method of claim 1, wherein, In the process of distillation in step (2), stirring is accompanied.

18. The treatment method of claim 1, wherein, After the distillation in step (2) is completed, liquid alkali is further added to the remaining liquid phase to perform neutralization, and a neutralized solution is obtained.

19. The treatment method of claim 18, wherein, In the process of adding the liquid alkali to perform neutralization, the temperature is controlled to be ≤80 DEG C.

20. The processing method of claim 18, wherein, At the end point of adding the liquid alkali to perform neutralization, the pH of the solution is 7-8.