Method for removing cyclohexane in low-molecular brominated polystyrene recovery solvent
The cyclohexane in the brominated polystyrene recovery solvent was removed by sulfonation of fumed sulfuric acid and water washing and distillation, which solved the problem of low removal efficiency in the prior art, achieved efficient and low-cost solvent purification, and improved product performance.
Patent Information
- Application Number
- CN202510563328.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-30
- Publication Date
- 2025-07-25
AI Technical Summary
The prior art is difficult to efficiently remove trace concentrations of cyclohexane in the brominated polystyrene recovery solvent, affecting product performance.
The sulfonated cyclohexane of sulfonated cyclohexane is used to form sulfonate cyclohexane, and then removed by water washing and distillation. The specific steps include adding pyrogen sulfuric acid, stirring reaction, quenching with water, leaving the standstill delamination and organic layer water washing, and finally distillation.
It achieves efficient and low-cost removal of cyclohexane, which is suitable for industrial production, and improves the color and thermal stability of brominated polystyrene products.
Abstract
Description
Technical Field
[0001] The present invention relates to a method for removing cyclohexane from the recovered solvent of low-molecular-weight brominated polystyrene, belonging to the technical field of chemical purification. Background Art
[0002] In the process of chemical production, brominated polystyrene (BPS) is usually directly brominated using polystyrene (PS) as raw material and halogenated hydrocarbon as solvent, and its molecular weight is determined by that of polystyrene. The synthesis methods of polystyrene include free radical polymerization and anionic polymerization. In the vast majority of cases, low-molecular-weight polystyrene is synthesized by anionic polymerization in cyclohexane, which will cause hundreds to thousands of parts per million of cyclohexane to remain in the polystyrene product. Further, when low-molecular-weight polystyrene is brominated, the cyclohexane therein will enter the recovered solvent system, and with continuous reuse of the solvent, the cyclohexane content will continuously increase. After reaching a certain concentration, it is easy to react with bromine to form bromocyclohexane during reuse, and in the post-treatment process, the bromocyclohexane with a relatively high boiling point cannot be removed, ultimately having a greater impact on the properties such as the color and thermal stability of the brominated polystyrene product.
[0003] For different components with boiling point differences in a solution, distillation is a simple and efficient separation method. During the recovery process of the brominated polystyrene solvent in the workshop, distillation is also used for purification. When the reflux ratio is 0.66, by continuously monitoring the cyclohexane content in the feed and product of the distillation column, it is found that the cyclohexane content in the solvent hardly changes. In the laboratory, a small-scale distillation test of the recovered solvent was carried out with a reflux ratio of 9, and only 20%-30% of cyclohexane can be removed. Therefore, distillation cannot efficiently remove trace amounts of cyclohexane in the recovered solvent of brominated polystyrene. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to efficiently remove trace amounts of cyclohexane in the recovered solvent of brominated polystyrene, and provide a method for removing cyclohexane from the recovered solvent of low-molecular-weight brominated polystyrene, with high purification efficiency and low energy consumption.
[0005] The technical solution adopted by the present invention to solve the above problems is as follows: A method for removing cyclohexane from the recovered solvent of low-molecular-weight brominated polystyrene, characterized by comprising the following steps: S1, adding the recovered dichloromethane solvent containing cyclohexane into a reaction flask, and then adding a certain amount of fuming sulfuric acid; S2, reacting under stirring at a certain reaction temperature for a period of time; S3, quenching with water, standing for stratification, washing the organic layer until neutral, and standing for stratification; S4, distilling the organic layer and collecting the corresponding fractions.
[0006] Further, the amount of fuming sulfuric acid added in S1 is 2 - 10 times the mass of cyclohexane, and the cyclohexane content is detected by gas chromatography.
[0007] Further, the reaction temperature in S2 is 30 - 80°C, and the reaction time is 0.5 - 10 h.
[0008] Further, the amount of water used for quenching with water and washing in S3 is 0.5 - 2 times the volume of the recovered solvent in S1, and the washing time is 15 min.
[0009] Further, the rectification reflux ratio in S4 is 0.66 - 3, and the rectification draw temperature is 39 - 41°C.
[0010] Further, the rectification draw temperature is 39.5 - 40.5°C.
[0011] The fuming sulfuric acid used in the present invention contains excessive sulfur trioxide and has stronger sulfonation ability. It sulfonates cyclohexane to generate cyclohexane sulfonic acid group, and then removes it by water washing. The removal rate is high, the operation is convenient, the cost is low, and it is suitable for industrial production. Specific Embodiments
[0012] The present invention will be further described below in conjunction with embodiments. The embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.
[0013] Example 1: Add 200 g of dichloromethane solution containing cyclohexane (the cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid, start stirring, reflux at 60°C for 5 h, add 100 g of water for quenching, cool to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, then rectify the organic layer at a reflux ratio of 0.66, start collecting fractions at 39.5°C, it takes 91 min to collect 150 g of fractions, and detect that the cyclohexane content therein is 3.7 ppm.
[0014] Example 2: Add 200 g of dichloromethane solution containing cyclohexane (the cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of concentrated sulfuric acid (98%), start stirring, reflux at 60°C for 5 h, add 100 g of water for quenching, cool to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, then rectify the organic layer at a reflux ratio of 0.66, start collecting fractions at 39.5°C, it takes 92 min to collect 150 g of fractions, and detect that the cyclohexane content therein is 984.9 ppm.
[0015] Implementation: 3: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 0.4 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 5 h, add 100 g of water for quenching, cool to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, then rectify the organic layer at a reflux ratio of 0.66, start collecting fractions at 39.5 °C, it takes 92 min to collect 150 g of fractions, and the detected cyclohexane content is 589.3 ppm.
[0016] Implementation: 4: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid, start stirring, stir at 30 °C for 5 h, add 100 g of water for quenching, cool to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, then rectify the organic layer at a reflux ratio of 0.66, start collecting fractions at 39.5 °C, it takes 89 min to collect 150 g of fractions, and the detected cyclohexane content is 943.8 ppm.
[0017] Implementation: 5: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 0.5 h, add 100 g of water for quenching, cool to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, then rectify the organic layer at a reflux ratio of 0.66, start collecting fractions at 39.5 °C, it takes 90 min to collect 150 g of fractions, and the detected cyclohexane content is 784.6 ppm.
[0018] Implementation: 6: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1.5 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 8 h, add 100 g of water for quenching, cool to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, then rectify the organic layer at a reflux ratio of 0.66, start collecting fractions at 39.5 °C, it takes 91 min to collect 150 g of fractions, and the detected cyclohexane content is 1.4 ppm.
[0019] Implementation: 7: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 2 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 8 h, add 100 g of water for quenching, cool down to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, and then rectify the organic layer at a reflux ratio of 0.66. Start collecting fractions at 39.5 °C. It takes 88 min to collect 150 g of fractions, and the detected cyclohexane content is 1.8 ppm.
[0020] Implementation: 8: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 5 h, add 100 g of water for quenching, cool down to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, and then rectify the organic layer at a reflux ratio of 1. Start collecting fractions at 39.5 °C. It takes 110 min to collect 150 g of fractions, and the detected cyclohexane content is 4.4 ppm.
[0021] Example 9: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 5 h, add 100 g of water for quenching, cool down to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, and then rectify the organic layer at a reflux ratio of 3. Start collecting fractions at 39.5 °C. It takes 216 min to collect 150 g of fractions, and the detected cyclohexane content is 3.6 ppm.
[0022] Example 10:: Add 200 g of dichloromethane solution containing cyclohexane (cyclohexane content is 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid, start stirring, reflux at 60 °C for 5 h, add 100 g of water for quenching, cool down to about room temperature, let it stand for liquid separation, wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, and then rectify the organic layer at a reflux ratio of 5. Start collecting fractions at 39.5 °C. It takes 323 min to collect 150 g of fractions, and the detected cyclohexane content is 3.2 ppm.
[0023] Example 11: Add 200 g of dichloromethane solution containing cyclohexane (with a cyclohexane content of 1000 ppm) into a 500 mL flask, then add 1 g of fuming sulfuric acid. Start stirring and reflux at 60 °C for 5 h. Add 100 g of water for quenching. Cool to around room temperature and let it stand for liquid separation. Wash the organic layer with 100 g of water for 15 min, let it stand for liquid separation, repeat the water washing three times, and then rectify the organic layer at a reflux ratio of 9. Start collecting fractions at 39.5 °C. It takes 543 min to collect 150 g of fractions, and the detected cyclohexane content is 2.5 ppm.
[0024] As can be seen from Examples 1 - 11 above, in Example 6, a rectification reflux ratio of 0.66 is used, the collection time is 91 min, and the detected cyclohexane content is 1.4 ppm, with the best time consumption and removal performance; compared with Example 2, the sulfonation effect using concentrated sulfuric acid is extremely poor, and the final cyclohexane removal amount is very low; compared with Example 3, 0.4 g of fuming sulfuric acid is used, with a low dosage, and the final cyclohexane removal rate is close to 50%; compared with Example 4, 1 g of fuming sulfuric acid is used, the sulfonation temperature is only 30 °C, the reaction is stirring without reflux, and at a rectification reflux ratio of 0.66, the final cyclohexane removal amount is very low; compared with Example 5, 1 g of fuming sulfuric acid is used, the reflux reaction time is only 0.5 h, and the final cyclohexane removal rate is close to 25%; compared with Example 7, 2 g of fuming sulfuric acid is used, with a 25% increase in the dosage of fuming sulfuric acid. Under the same rectification reflux ratio, the collection time is close, and the cyclohexane removal amount is close; compared with Examples 8 and 1, when the rectification reflux ratio increases to 1, the cyclohexane removal amount decreases. Compared with Example 11, when 1 g of fuming sulfuric acid is used and the rectification reflux ratio increases to 9, with the final collection time consumption increasing by more than 496%, the cyclohexane content decreases from 3.7 to 2.5, still lower than 1.4 ppm in Example 6.
Claims
1. A method for removing cyclohexane from the recovered solvent of low-molecular-weight brominated polystyrene, characterized in that, It includes the following steps: S1. Add the recovered solvent containing cyclohexane and dichloromethane into a reaction flask, and then add a certain amount of fuming sulfuric acid; S2. React with stirring at a certain reaction temperature for a period of time; S3. Quench with water, let it stand for layering, wash the organic layer with water until it is neutral, and let it stand for layering; S4. Rectify the organic layer and collect the corresponding fractions.
2. A method for removing cyclohexane from the recovered solvent of low molecular weight brominated polystyrene according to claim 1, characterized in that: The amount of fuming sulfuric acid added in S1 is 2 - 10 times the mass of cyclohexane, and the cyclohexane content is detected by gas chromatography.
3. A method for removing cyclohexane from the recovered solvent of low molecular weight brominated polystyrene according to claim 1, characterized in that: S2 The reaction temperature described in [S2] is 30 - 80 °C, and the reaction time is 0.5 - 10 h.
4. A method for removing cyclohexane from the recovered solvent of low molecular weight brominated polystyrene according to claim 1, characterized in that: S3 The amount of water used for quenching with water and washing in [S3] is 0.5 - 2 times the volume of the recovered solvent in S1, and the washing time is 15 min.
5. A method for removing cyclohexane from the recovered solvent of low molecular weight brominated polystyrene according to claim 1, characterized in that: The rectification reflux ratio in S4 is 0.66 - 3, and the rectification draw-off temperature is 39 - 41 °C.
6. The method for removing cyclohexane from the recovered solvent of low molecular weight brominated polystyrene according to claim 5, characterized in that: The rectification draw-off temperature is 39.5 - 40.5 °C.