A method for recovering aniline tar

Abstract

The present application relates to a kind of high-efficiency recovery aniline tar method, aniline and catalyst in tar are recovered by azeotropic distillation and filtration, specific operation as follows: a certain amount of aniline tar and azeotropic solvent are added to distilling flask, the gaseous component of distillation is condensed and separated into water phase and aniline, after distillation, the liquid in flask is filtered while hot, filter cake is aniline catalyst crude product, and recovered catalyst is obtained by using mixed solvent elution and drying.The present application realizes the separation of aniline from tar at lower temperature, and efficiently recovers catalyst by filtration and mixed solvent elution method, realizes the comprehensive utilization of aniline tar, and has good economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic chemical separation, and introduces a method for efficiently recovering aniline tar, which recovers aniline and catalyst in the tar by azeotropic distillation and filtration, and the specific operation is as follows: a certain amount of aniline tar and water (as an azeotropic solvent) are added to a distillation flask, heated to boiling, and the gaseous components distilled out are cooled and separated into an aqueous phase and aniline, and the water is returned to the dropping funnel for recycling, heating is stopped when distillation is completed without aniline fraction, and the liquid in the flask is filtered while hot, the filter cake is a crude aniline catalyst, and the recovered catalyst is obtained after elution with a mixed solvent and drying. The present application can separate effective components such as aniline and catalyst particles in the tar, realize efficient recovery and utilization of the tar, and reduce the outsourcing treatment amount of the tar, thereby having good economic benefits. BACKGROUND

[0002] The production process of aniline in the company is mainly gas-phase catalytic hydrogenation of nitrobenzene in a fluidized bed, and a part of small particles of catalyst escapes from the top of the fluidized bed into the rectification system with the gas phase, and forms aniline tar with other aniline by-products. The tar is a black viscous liquid with a pungent odor, and the light components are mainly aniline, and a small amount of cyclohexanone, methyl aniline, phenol, diphenylamine, etc., and the heavy components are long-chain oligomers of aniline, etc. Most manufacturers treat it as dangerous waste for outsourcing. Analysis shows that the aniline content in the tar is more than 50%, the by-product is about 40%-45%, and the particle catalyst is about 5%.

[0003] In recent years, the reported aniline tar separation and utilization technology mainly hydrogenates the tar, and under the conditions of high temperature, high pressure and high hydrogen to oil ratio, the aniline tar is cracked, and the cracking products are hydrogenated to realize comprehensive recovery and treatment of the aniline tar. However, this method has defects such as high energy consumption, treatment cost greater than the value of recovered materials, and difficulty in recovering the particle catalyst. At present, the treatment method for aniline tar is mainly to extract a small amount of residual aniline by secondary rectification and then bury or burn it. And there is no effective recovery process for the lost catalyst, which not only wastes the catalyst, but also pollutes the environment.

[0004] Therefore, it is of great environmental protection significance and economic value to choose a suitable method to treat the tar, on the one hand to recover the effective components therein, and on the other hand to reduce the treatment amount of the tar as dangerous waste. SUMMARY

[0005] The purpose of the present application is to provide an efficient treatment method for aniline tar, which can not only recover the main component aniline in the tar, but also realize the recovery and reuse of the catalyst.

[0006] The application is characterized in that according to the principle that various organic matters in tar have different volatility when being distilled with azeotropic solvent, the main component aniline is separated from the tar at a lower temperature, and the catalyst is efficiently recovered by using the method of solid-liquid separation and mixed solvent elution, so that the comprehensive utilization of aniline tar is realized.

[0007] The main technical scheme of the application is that the aniline tar and the azeotropic solvent water are distilled by azeotropic distillation, the gaseous phase component is separated into water phase and organic phase by cooling, the water phase is recycled, and the distillation residue is filtered while hot, the filter cake is eluted with mixed solvent, and the catalyst is dried and recovered.

[0008] A typical method of the application comprises the following steps: (1) building an azeotropic distillation device, adding aniline tar and azeotropic solvent (water) with a certain mass ratio in a distillation flask, and heating the material to make it boil under normal pressure; (2) collecting the gaseous phase component at a certain temperature, and flowing into a liquid separator after being condensed, and separating into water phase and organic phase; (3) recycling the water to the distillation flask, and discharging the oil phase at the bottom of the liquid separator; (4) while discharging the oil phase at the bottom of the liquid separator, adding a certain amount of tar to the distillation flask; (5) when the temperature of the gaseous phase changes obviously, stopping heating, filtering the material in the distillation flask while hot, and eluting the catalyst from the filter cake with mixed solvent.

[0009] Further, the mass ratio of aniline tar to azeotropic solvent in step (1) is 1-8:1, and preferably 1.5-6.5:1.

[0010] The liquid phase temperature of the hot azeotropic distillation in steps (1) and (2) is 97-102℃, and the gaseous phase temperature is 88-90℃.

[0011] The volume ratio of oil phase to water phase in the liquid separator in steps (2) and (3) is 0.5-10:1, and further preferably 2-5:1.

[0012] G1-G5 type sand core funnels are used in step (5) for hot filtering, and the hot filtering temperature is 85-100℃.

[0013] One or more of methanol, ethanol, isopropyl alcohol, dichloromethane, chloroform, acetone, ethyl acetate and water is used as the solvent for eluting the impurities attached to the catalyst.

[0014] G2-G3 type sand core funnels are preferably used, and one or more of methanol, ethanol, chloroform, acetone and water is used as the solvent.

[0015] Compared with the prior art, the application has the following beneficial effects:

[0016] (1) The present application can efficiently recover aniline and catalyst components in tar, and the components are azeotropically distilled at normal pressure and at a relatively low temperature, compared with the method of rectification or hydrogenation cracking, the process conditions are mild, and the energy consumption is low;

[0017] (2) The loss of organic components under vacuum conditions is avoided, the cost of reprocessing of vacuum tail gas is reduced, and the amount of three wastes is small;

[0018] (3) The method of mixed solvent elution is adopted, and the catalyst reuse effect is good. DETAILED DESCRIPTION

[0019] The present application will be further described below in combination with specific examples, all examples are operated according to the operation conditions of the above technical solution, and the purpose is to better understand the content of the present application. Therefore, the examples do not limit the protection scope of the present application.

[0020] Example 1

[0021] A 1000 mL four-necked flask is used as a distillation flask, connected with a speed-regulating stirrer, a thermometer, a dropping funnel, a condenser tube, a heating system, a liquid separator, a filter and an elution device. 320 g of aniline tar is added to the four-necked flask, and then 320 g of azeotropic solvent (water) is added. The stirring and heating are started, and the solution is heated to 102 DEG C. The gas phase is collected at a temperature of 90 DEG C. According to the amount of gas phase collected, the azeotropic solvent is continuously added. The gas phase components are separated into organic phase and water by a liquid separator. When the temperature of the gas phase reaches 95 DEG C, the distillation is completed, and 152 g of organic phase is obtained. The aniline content is 95.6%, and the aniline recovery rate is about 90.8% (calculated based on the aniline content of 50% in the tar). The residue in the flask is filtered at 100 DEG C using a G1 sand core funnel. The filter cake is eluted with a mixed solvent of ethanol: acetone: water = 3:4.5:1 by volume ratio, and 12.5 g of catalyst is obtained after drying. The recovery rate is about 78% (calculated based on the catalyst content of 5% in the tar), and the catalyst is reused for the gas phase hydrogenation of nitrobenzene with good catalytic effect.

[0022] Example 2

[0023] The device in Example 1 is built. 500 g of aniline tar and 63 g of water are added to the four-necked flask, heated to a liquid phase temperature of about 100 DEG C, and the gas phase is collected at a temperature of 91 DEG C. The azeotropic solvent is continuously added to the dropping funnel. After the distillation is completed, 226 g of organic phase is obtained, the aniline content is 96.2%, and the aniline recovery rate is about 87%. The filter cake is eluted with a mixed solvent of methanol: ethanol: water = 4:6:1 by volume ratio using a G3 sand core funnel at 85 DEG C. After drying, 21.8 g of catalyst is obtained, the recovery rate is about 87.3%, and the catalyst reuse effect is good.

[0024] Example 3

[0025] The apparatus is the same as above, 500 g of aniline tar and 77 g of water are added into a four-necked flask, heated to a liquid phase temperature of 97°C, and the fraction with a gas phase temperature of 88°C is collected, and an appropriate amount of water is added into the flask. After distillation, 243 g of organic phase is obtained, with an aniline content of 97.7%, and an aniline recovery rate of about 94.9%. Filtration is performed at 90°C using a G2 sand core funnel, the filter cake is eluted with a mixed solvent of methanol: ethanol: acetone: water = 4:4:2:1 by volume ratio, and after drying, 20.1 g of catalyst is obtained, with a recovery rate of about 80.4%, and the catalyst has good reusability.

[0026] Example 4

[0027] The apparatus is the same as above, 600 g of aniline tar and 100 g of water are added into a four-necked flask, heated to a liquid phase temperature of 99°C, and the fraction with a gas phase temperature of 90°C is collected, and an appropriate amount of water is added into the flask. After distillation, 290 g of organic phase is obtained, with an aniline content of 96%, and an aniline recovery rate of about 92.8%. Filtration is performed at 96°C using a G3 sand core funnel, the filter cake is eluted with a mixed solvent of methanol: ethanol: acetone: water = 4:4:2:1 by volume ratio, and after drying, 27.6 g of catalyst is obtained, with a recovery rate of about 92%, and the catalyst has good reusability.

[0028] Example 5

[0029] The apparatus is the same as above, 400 g of aniline tar and 267 g of water are added into a four-necked flask, heated to a liquid phase temperature of 100°C, and the fraction with a gas phase temperature of 88°C is collected, and an appropriate amount of water is added into the flask. After distillation, 185 g of organic phase is obtained, with an aniline content of 98.2%, and an aniline recovery rate of about 90.8%. Filtration is performed at 100°C using a G5 sand core funnel, the filter cake is eluted with a mixed solvent of ethanol: acetone: water = 4:4:1 by volume ratio, and after drying, 17.8 g of catalyst is obtained, with a recovery rate of about 89%, and the catalyst has good reusability.

[0030] Example 6

[0031] The apparatus is the same as above, 500 g of aniline tar and 100 g of water are added into a four-necked flask, heated to a liquid phase temperature of 102°C, and the fraction with a gas phase temperature of 90°C is collected, and an appropriate amount of water is added into the flask. After distillation, 226 g of organic phase is obtained, with an aniline content of 96.6%, and an aniline recovery rate of about 87.3%. Filtration is performed at 100°C using a G3 sand core funnel, the filter cake is eluted with a mixed solvent of methanol: acetone: ethyl acetate: water = 4:4:2:1 by volume ratio, and after drying, 19.9 g of catalyst is obtained, with a recovery rate of about 79.6%, and the catalyst has good reusability.

[0032] Example 7

[0033] The apparatus is the same as above, 500 g of aniline tar and 125 g of water are added into a four-necked flask, heated to 100 ℃, the distillate is collected at 88 ℃, and an appropriate amount of water is added into the flask. The distillation ends with 230 g of organic phase, the aniline content is 97.7%, and the aniline recovery rate is about 90%. Filtration is performed at 98 ℃ using a G2 sand core funnel, the filter cake is eluted with a mixed solvent of ethanol: acetone: water = 4:4:3 by volume, and 19.6 g of catalyst is obtained after drying, with a recovery rate of about 78.4%, and the catalyst has good reuse effect.

[0034] Comparative Example 1

[0035] 500 g of aniline tar is subjected to vacuum distillation at a vacuum degree of -0.093 MPa, and the distillate is collected at 92-94 ℃. After cooling, 215 g of distillate is obtained, with an aniline content of 78.8% and a recovery rate of about 67.7%. The distillation residue is filtered at 98 ℃ using a G3 sand core funnel, and the material has poor flowability and poor filtration effect.

[0036] Comparative Example 2

[0037] 500 g of aniline tar is subjected to rectification at a vacuum degree of -0.09 MPa, a reflux ratio of 5:1, and a distillate collection temperature of 95-96 ℃. 182 g of distillate is obtained, with an aniline content of 85.8% and a recovery rate of about 62.4%. The distillation residue is filtered at 90 ℃ using a G5 sand core funnel, and the material has poor flowability and cannot be separated by solid-liquid separation.

Claims

1. A method of recovering aniline tar, characterized by The aniline and catalyst in the tar are recovered by azeotropic distillation and filtration, and the specific process is as follows: the aniline tar and the azeotropic solvent water are azeotropically distilled, the mass ratio of the aniline tar to the azeotropic solvent water is 1-8:1, the liquid phase temperature of the azeotropic distillation is 97-102℃, the gas phase temperature of the azeotropic distillation is 88-90℃, the gas phase component distilled out is divided into water phase and organic phase by cooling, the water phase is returned for recycling, the distillation residue after the distillation is filtered while hot, the filter cake is washed and eluted by the mixed solvent, and the catalyst is recovered by drying. The aniline tar is the material intermittently collected from the aniline rectification tower, and contains more than 50% of aniline and about 5% of catalyst particles.

2. The method of claim 1, wherein The mass ratio of the aniline tar to the azeotropic solvent water is 1.5-6.5:

1.

3. The method of claim 1, wherein The volume ratio of the organic phase to the water phase is 0.5-10:

1.

4. The method of claim 3, wherein The volume ratio of the organic phase to the water phase is 2-5:

1.

5. The method of claim 1, wherein The G1-G5 type sand core funnel is used for filtration, and the filtration temperature while hot is 85-100℃.

6. The method of claim 5, wherein The G2-G3 type sand core funnel is used.

7. The method of claim 1, wherein Methanol, ethanol, isopropyl alcohol, dichloromethane, chloroform, acetone, ethyl acetate and water are used as the solvent.

8. The method of claim 7, wherein Methanol, ethanol, chloroform, acetone and water are used as the solvent.