Purification method of chlorobenzene

Abstract

The invention relates to the technical field of 2-ethyl anthraquinone production, in particular to a chlorobenzene purification method, which specifically comprises the following steps: adding chlorobenzene needing to be purified into a reaction kettle, starting stirring, adding anhydrous aluminum trichloride at normal temperature until ethylbenzene is completely reacted, adding benzyl chloride to carry out next-step reaction, generating diphenylmethane from benzene and benzyl chloride, hydrolyzing after the reaction is completed, and purifying to obtain 2-ethyl anthraquinone. The organic phase components after hydrolysis are chlorobenzene, diphenylmethane and some high-boiling-point substances, the upper-layer organic phase is subjected to steam distillation or azeotropic distillation with water, the distilled chlorobenzene enters a chlorobenzene drying system to be dried and recycled, and the content of the recycled chlorobenzene is 99.5% or above.

Description

Technical Field

[0001] The invention relates to the technical field of 2-ethylanthraquinone production, and in particular to a method for purifying chlorobenzene. Background Art

[0002] In the production of 2-ethylanthraquinone, chlorobenzene is used as solvent, ethylbenzene and phthalic anhydride are used as raw materials, and an acylation reaction occurs under the catalysis of anhydrous aluminum chloride to generate an intermediate. The acylated liquid is then hydrolyzed in hydrochloric acid, the aluminum chloride water is separated, and chlorobenzene is recovered by distillation. In the recovered solvent chlorobenzene, the content of chlorobenzene is 91.5%; benzene is about 3.5%; ethylbenzene is about 3%; diethylbenzene is about 2%, and it directly enters the distillation tower for distillation. The boiling point of benzene is 80.1℃, the boiling point of chlorobenzene is 131.7℃, the boiling point of ethylbenzene is 136℃, and the boiling point of diethylbenzene is 180℃. The temperature difference between the boiling points of chlorobenzene and ethylbenzene is too small, making it difficult to separate, resulting in residual ethylbenzene in the recovered chlorobenzene. If you want to increase the content of chlorobenzene, you need to increase the height of the distillation tower, which not only consumes financial resources, but also requires more manpower and energy to debug again and again. Summary of the invention

[0003] In order to solve the defects in the prior art, the present invention provides a method for purifying chlorobenzene, which is specifically achieved by the following technical scheme: A method for purifying chlorobenzene comprises the following steps: Step 1: inject chlorobenzene to be purified into the first reaction kettle and start stirring; Step 2, adding anhydrous aluminum chloride into the first reaction kettle, and stirring thoroughly until the ethylbenzene reacts completely; Step 3, after the ethylbenzene reacts completely, benzyl chloride is added dropwise, and after the addition is completed, the mixture is kept warm and stirred until the benzene reacts completely to obtain a reaction solution; Step 4, adding dilute hydrochloric acid to the second reaction kettle, starting stirring, then adding the reaction solution in step 3 to the second reaction kettle, and controlling the temperature in the second reaction kettle to be below 50° C. until the hydrolysis is completed; Step 5: After the hydrolysis is completed, continue to keep warm and stir for 30 minutes, let it stand to separate the layers, and remove the lower layer of aluminum chloride water; Step 6, adding water to the second reaction kettle for washing, standing and stratifying after washing, and removing the lower aqueous phase; Step 7, adding water to the second reaction kettle, starting stirring, starting steam heating and azeotropic distillation, and collecting chlorobenzene; Step 8, the evaporated chlorobenzene is tested after removing the upper layer of water, and the chlorobenzene content is tested. If it is qualified, it enters the chlorobenzene drying system for reuse.

[0004] In the steps 1 and 2, the temperature in the first reaction kettle is maintained at 30° C. to 35° C.

[0005] The amount of anhydrous aluminum chloride added is 0.75% to 0.94% by weight of the chlorobenzene to be purified.

[0006] In the step 3, the amount of benzyl chloride used is 3.44% to 3.88% of the weight of the chlorobenzene to be purified, and the dripping time is less than or equal to 1 hour.

[0007] In the step 3, the temperature in the first reaction kettle is maintained at 30°C to 35°C.

[0008] In the step 4, the dilute hydrochloric acid is a dilute hydrochloric acid with a water content of 5% by weight, and the amount added is 12.50% to 18.75% of the weight of the chlorobenzene to be purified.

[0009] In step 6, the amount of water added is 12.5% ​​of the weight of the chlorobenzene to be purified.

[0010] In the step 7, the amount of water added is 31.25% of the weight of the chlorobenzene to be purified.

[0011] In the step 7, the distillation temperature is 90°C and the final distillation temperature is 100°C.

[0012] The technical solution of the present invention has the following advantages: Add chlorobenzene to be purified into the reactor, start stirring, add anhydrous AlCl3 at room temperature, stir until dissolved, keep warm at room temperature for 1 hour, add benzyl chloride for the next reaction, benzene and benzyl chloride generate diphenylmethane, slightly negative pressure absorbs HCl gas to generate hydrochloric acid for hydrolysis, keep warm, hydrolysis, after hydrolysis, the lower layer of aluminum chloride water is transported to the polyaluminum workshop for the next reaction, the organic phase components are chlorobenzene and diphenylmethane and some high boiling point substances, the upper organic phase is steam distilled or azeotropic distilled with water, after distillation, chlorobenzene enters the chlorobenzene drying system for drying and reuse, and the recovered chlorobenzene content is more than 99.5%. DETAILED DESCRIPTION

[0013] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] The present invention provides a method for purifying chlorobenzene, which specifically comprises the following steps: Step 1: inject the chlorobenzene to be purified into the first reaction kettle, start stirring, and control the temperature in the kettle to be 30° C. to 35° C.

[0016] Step 2: Add 0.75% to 0.94% of anhydrous aluminum chloride by weight of the chlorobenzene to be purified into the first reaction kettle, stir thoroughly until the ethylbenzene reacts completely, and keep the temperature in the kettle at 30° C. to 35° C. during the whole process.

[0017] During the stirring process, aluminum chloride is dissolved in the chlorobenzene to be purified and used as a catalyst.

[0018] The reaction principle of step 2 is as follows:

[0019] The reaction temperature itself is room temperature. After adding anhydrous aluminum chloride, the reaction system will heat up by itself, and the temperature needs to be controlled, because when the temperature exceeds 40°C, more side reactions will occur, and when the temperature is below 30°C, the reaction is very slow, affecting production efficiency. Therefore, the present invention adopts 30°C to 35°C, which can not only ensure a faster reaction speed, but also avoid side reactions.

[0020] The sign of judging that the ethylbenzene reaction is complete is to take a sample from the first reactor and analyze the ethylbenzene content by gas chromatography. The result shows that the ethylbenzene content in chlorobenzene is less than 0.1%, which means that the ethylbenzene reaction is complete. When the ethylbenzene reaction is complete, the reaction time of step 2 is not less than 1 hour, so the anhydrous aluminum chloride can be stirred until the anhydrous aluminum chloride is completely dissolved, and then continue to keep warm and stir for 1 hour, and then take a sample for testing.

[0021] Step 3: After the ethylbenzene reacts completely, benzyl chloride is added dropwise. After the addition is completed, the mixture is kept warm and stirred until the benzene reacts completely to obtain a reaction solution. The amount of benzyl chloride used is 3.44% to 3.88% of the weight of the chlorobenzene to be purified. The entire addition process does not exceed 1 hour, and the temperature is kept constant at 30°C to 35°C.

[0022] In this step three, the reaction principle is as follows:

[0023] The hydrogen chloride gas produced by the reaction is recycled to prepare 5% by mass dilute hydrochloric acid for the next step of hydrolysis.

[0024] The method for judging whether the benzene reaction is complete is to take a sample and perform gas chromatography analysis. If the result shows that the benzene content is less than 0.1%, the benzene reaction is complete. The benzene reaction is usually completed about 1 hour after the benzyl chloride is added. Therefore, the mixture can be kept warm and stirred for 1 hour after the benzyl chloride is added, and then sampled for testing.

[0025] Step 4: Add dilute hydrochloric acid accounting for 12.50% to 18.75% of the weight of chlorobenzene to be purified into the second reactor, start stirring, and then add the reaction solution in step 3 to the second reactor within 1 to 2 hours, and control the temperature in the second reactor below 50° C. until the hydrolysis is completed.

[0026] The mass fraction of dilute hydrochloric acid is 5%.

[0027] The purpose of hydrolysis is to dissolve aluminum chloride in water; the sign of completion of hydrolysis is that the content of aluminum chloride in the aluminum chloride water layer is detected to remain stable.

[0028] In this step, circulating water is used for cooling, and controlling the temperature not higher than 50°C can reduce the volatilization of chlorobenzene.

[0029] Step 5: After the hydrolysis is completed, continue to stir and keep warm for 30 minutes, let it stand for 10 minutes, and separate the lower layer of aluminum chloride water. The purpose of continuous stirring after the hydrolysis is to allow the aluminum chloride to be more fully dissolved in the water. If the stirring is stopped directly after the hydrolysis is completed, the aluminum chloride has not been fully dissolved, and a part of the aluminum chloride will remain in the organic phase.

[0030] Step 6: Add 12.5% ​​of the weight of chlorobenzene to be purified into the second reactor, stir for 30 minutes, and then stand for 10 minutes to separate the lower aqueous phase. This step is used to wash away the residual aluminum chloride water in the chlorobenzene, making the chlorobenzene close to neutral, in preparation for the subsequent distillation.

[0031] Step 7: add 31.25% of the weight of the chlorobenzene to be purified into the second reaction kettle, start stirring, start steam heating and azeotropic distillation, and collect chlorobenzene. The distillation temperature is 90°C and the final distillation temperature is 100°C.

[0032] Step 8: After the upper layer of water is removed from the distilled chlorobenzene, the product is tested. The product with a chlorobenzene content of 99% or more is qualified and enters the chlorobenzene drying system for reuse. The unqualified product is redistilled with the next batch.

[0033] The purity of the chlorobenzene purified through the above steps is above 99.5%.

[0034] The above method is explained in detail below through specific examples.

[0035] Embodiment 1 Into a 2000L glass-lined reactor, 1600kg of chlorobenzene was pumped using a metering pump. Stirring was started and circulating water was introduced into the jacket until the temperature inside the reactor reached 30°C.

[0036] Then add 12 kg of anhydrous aluminum chloride and stir until the anhydrous aluminum chloride is dissolved. Then keep warm at 30°C and stir until the ethylbenzene reacts completely. The stirring time should not be less than 1 hour.

[0037] The method for judging whether the ethylbenzene reaction is complete is to take a sample and analyze the ethylbenzene content by gas chromatography. If the result shows that the ethylbenzene content in chlorobenzene is less than 0.1%, the ethylbenzene reaction is complete.

[0038] At this time, 60 kg of benzyl chloride was added dropwise at a temperature of 30°C, and the benzyl chloride was added dropwise within one hour, and then the temperature was kept warm until the reaction of benzene was completed, and the warming time was not less than 1 hour.

[0039] The method for judging whether the benzene reaction is complete is to take a sample after keeping warm for 1 hour and analyze it by gas chromatography. The result shows that the benzene content is less than 0.1%, that is, the benzene reaction is complete.

[0040] Then add 240 kg of 5% dilute hydrochloric acid to a 3000L glass-lined reactor, start stirring, open the reactor jacket to circulate water, slowly add the reaction solution into the hydrochloric acid for hydrolysis, and add it for 1 hour. Control the reaction temperature below 50°C until the hydrolysis is complete.

[0041] The purpose of hydrolysis is to dissolve aluminum trichloride in water; the sign of completion of hydrolysis is that the content of aluminum trichloride in the aluminum trichloride water layer remains stable.

[0042] After the hydrolysis is completed, stir for 30 minutes, let stand for 10 minutes, and remove the lower layer of aluminum chloride water.

[0043] Then add 200L of water again, stir for 30 minutes, let stand for 10 minutes, separate the lower layer, and use the lower layer water for tail gas absorption.

[0044] Then, 500L of water was added to the upper layer again, stirring was started, and steam was turned on to heat up the azeotropic distillation to distill out chlorobenzene. The distillation temperature was 90°C and the final distillation temperature was 100°C.

[0045] The evaporated chlorobenzene is tested after the upper layer of water is removed. If the chlorobenzene content is greater than 99.5%, it is qualified and enters the chlorobenzene drying system for reuse.

[0046] Embodiment 2 Into a 2000L glass-lined reactor, 1600kg of chlorobenzene was pumped with a metering pump, stirring was started, and circulating water was passed through the jacket until the temperature inside the reactor reached 35°C.

[0047] Then add 10 kg of anhydrous aluminum chloride and stir until the anhydrous aluminum chloride is dissolved. Then keep the temperature at 38°C and stir until the ethylbenzene reacts completely. The stirring time should not be less than 1 hour.

[0048] The method for judging whether the ethylbenzene reaction is complete is to take a sample and analyze the ethylbenzene content by gas chromatography. If the result shows that the ethylbenzene content in chlorobenzene is less than 0.1%, the ethylbenzene reaction is complete.

[0049] At this time, 55 kg of benzyl chloride was added dropwise at a temperature of 38° C. The benzyl chloride was added dropwise within one hour, and then the temperature was kept warm until the benzene reaction was complete, and the warming time was not less than 1 hour.

[0050] The method for judging whether the benzene reaction is complete is to take a sample and perform gas chromatography analysis. If the result shows that the benzene content is less than 0.1%, then the benzene reaction is complete.

[0051] Then add 200 kg of 5% dilute hydrochloric acid to a 3000L glass-lined reactor, start stirring, open the reactor jacket to circulate water, slowly add the reaction solution into the hydrochloric acid for hydrolysis, and add it for 1.5 hours. Control the reaction temperature below 50°C until the hydrolysis is complete.

[0052] The purpose of hydrolysis is to dissolve aluminum trichloride in water; the sign of completion of hydrolysis is that the content of aluminum trichloride in the aluminum trichloride water layer remains stable.

[0053] After the hydrolysis is completed, stir for 30 minutes, let stand for 10 minutes, and remove the lower layer of aluminum chloride water.

[0054] Then add 200L of water again, stir for 30 minutes, let stand for 10 minutes, separate the lower layer, and use the lower layer water for tail gas absorption.

[0055] Then, 500L of water was added to the upper layer again, stirring was started, and steam heating and azeotropic distillation were started to separate chlorobenzene. The distillation temperature was 90°C and the final distillation temperature was 100°C.

[0056] The evaporated chlorobenzene is tested after the upper layer of water is removed. If the chlorobenzene content is greater than 99.5%, it is qualified and enters the chlorobenzene drying system for reuse.

[0057] Embodiment 3 Into a 2000L glass-lined reactor, 1600kg of chlorobenzene was pumped with a metering pump, stirring was started, and circulating water was passed through the jacket until the temperature inside the reactor reached 32°C.

[0058] Then add 15 kg of anhydrous aluminum chloride and stir until the anhydrous aluminum chloride is dissolved. Then keep the temperature at 35°C and stir until the ethylbenzene reacts completely. The stirring time should not be less than 1 hour.

[0059] The method for judging whether the ethylbenzene reaction is complete is to take a sample and analyze the ethylbenzene content by gas chromatography. If the result shows that the ethylbenzene content in chlorobenzene is less than 0.1%, the ethylbenzene reaction is complete.

[0060] At this time, 62 kg of benzyl chloride was added dropwise at a temperature of 35° C., and the benzyl chloride was added dropwise within one hour, and then the temperature was kept warm until the benzene reaction was complete, and the warming time was not less than 1 hour.

[0061] The method for judging whether the benzene reaction is complete is to take a sample and perform gas chromatography analysis. If the result shows that the benzene content is less than 0.1%, then the benzene reaction is complete.

[0062] Then add 300 kg of 5% dilute hydrochloric acid into a 3000L glass-lined reactor, start stirring, open the reactor jacket to circulate water, slowly add the reaction liquid into the hydrochloric acid for hydrolysis, and add it for 2 hours. Control the reaction temperature below 50°C until the hydrolysis is complete.

[0063] The purpose of hydrolysis is to dissolve aluminum trichloride in water; the sign of completion of hydrolysis is that the content of aluminum trichloride in the aluminum trichloride water layer remains stable.

[0064] After the hydrolysis is completed, stir for 30 minutes, let stand for 10 minutes, and remove the lower layer of aluminum chloride water.

[0065] Then add 200L of water again, stir for 30 minutes, let stand for 10 minutes, separate the lower layer, and use the lower layer water for tail gas absorption.

[0066] Then, 500L of water was added to the upper layer again, stirring was started, and steam was started to heat up and azeotropic distillation was carried out to separate chlorobenzene. Chlorobenzene was distilled out at a temperature of 90°C, wherein the outlet temperature was 90°C and the final distillation temperature was 100°C.

[0067] The evaporated chlorobenzene is tested after the upper layer of water is removed. The chlorobenzene content is greater than 99.5%, which is qualified and enters the chlorobenzene drying system for reuse.

[0068] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for purifying chlorobenzene, characterized in that: The following steps are involved: Step 1: inject chlorobenzene to be purified into the first reaction kettle and start stirring; Step 2, adding anhydrous aluminum chloride into the first reaction kettle, and stirring thoroughly until the ethylbenzene reacts completely; Step 3, after the ethylbenzene reacts completely, benzyl chloride is added dropwise, and after the addition is completed, the mixture is kept warm and stirred until the benzene reacts completely to obtain a reaction solution; Step 4, adding dilute hydrochloric acid to the second reaction kettle, starting stirring, then adding the reaction solution in step 3 to the second reaction kettle, and controlling the temperature in the second reaction kettle to be below 50° C. until the hydrolysis is completed; Step 5: After the hydrolysis is completed, continue to keep warm and stir for 30 minutes, let it stand to separate the layers, and remove the lower layer of aluminum chloride water; Step 6, adding water to the second reaction kettle for washing, standing and stratifying after washing, and removing the lower aqueous phase; Step 7, adding water to the second reaction kettle, starting stirring, starting steam heating and azeotropic distillation, and collecting chlorobenzene; Step 8, the evaporated chlorobenzene is tested after removing the upper layer of water, and the chlorobenzene content is tested. If it is qualified, it enters the chlorobenzene drying system for reuse.

2. The method for purifying chlorobenzene according to claim 1, characterized in that: In the steps 1 and 2, the temperature in the first reaction kettle is maintained at 30° C. to 35° C.

3. The method for purifying chlorobenzene according to claim 1, characterized in that: The amount of anhydrous aluminum chloride added is 0.75% to 0.94% by weight of the chlorobenzene to be purified.

4. The method for purifying chlorobenzene according to claim 1, characterized in that: In the step 3, the amount of benzyl chloride used is 3.44% to 3.88% of the weight of the chlorobenzene to be purified, and the dripping time is less than or equal to 1 hour.

5. The method for purifying chlorobenzene according to claim 1 or 4, characterized in that: In the step 3, the temperature in the first reaction kettle is maintained at 30°C to 35°C.

6. The method for purifying chlorobenzene according to claim 1, characterized in that: In the step 4, the dilute hydrochloric acid is a dilute hydrochloric acid with a water content of 5% by weight, and the amount added is 12.50% to 18.75% of the weight of the chlorobenzene to be purified.

7. The method for purifying chlorobenzene according to claim 1, characterized in that: In step 6, the amount of water added is 12.5% ​​of the weight of the chlorobenzene to be purified.

8. The method for purifying chlorobenzene according to claim 1, characterized in that: In the step 7, the amount of water added is 31.25% of the weight of the chlorobenzene to be purified.

9. The method for purifying chlorobenzene according to claim 1, characterized in that: In the step 7, the distillation temperature is 90°C and the final distillation temperature is 100°C.

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