A method for removing impurities in an epoxy cyclododecene separation process

Abstract

The application discloses a method for removing acid and ester impurities in an epoxy cyclododecadiene continuous separation process, wherein the raw material is derived from an epoxy cyclododecadiene device. The reaction liquid first enters a tert-butyl alcohol recovery tower, the top of which obtains a TBA crude product, and the bottom of which obtains a material containing TBA of less than or equal to 2%; the bottom liquid enters an impurity separation tower, the top material is mixed with an ethylene glycol solution of alkali, and is separated into two phases, the upper material is refluxed into the tower, and the lower material is continuously discharged, and the acid and ester impurities in the material are removed through washing and phase separation; the bottom liquid enters a subsequent rectification system, and the product is separated. The above method can effectively remove the acid and ester impurities in the material, reduces the occurrence of side reactions, improves the product quality, prevents the corrosion of the system caused by the accumulation of acid impurities, and improves the running stability of the device.

Description

TECHNICAL FIELD

[0001] The application discloses a method for removing impurities in a continuous separation process of epoxy cyclododecadiene and belongs to the field of chemical processes. BACKGROUND

[0002] Epoxy cyclododecadiene (ECDD for short) is an important intermediate for producing nylon 12 resin and a synthetic precursor of many macrocyclic compounds, is widely applied to epoxy systems such as composite materials, electronic potting, stone glue and the like, can be used as an environment-friendly plasticizer to improve the performance of polymer materials and improve production efficiency, and can be used as a solvent oil, a cleaning agent and the like.

[0003] Generally, epoxy cyclododecadiene is prepared by epoxidizing 1,5,9-cyclododecatriene (CDT), and a reaction equation is as shown in the following formula:

[0004]

[0005] Generally, an epoxy compound is obtained by epoxidizing an olefin under the catalysis of a catalyst and the oxidation of an oxidizing agent, and the epoxidation activity and the selectivity of an epoxidation product are different due to different catalysts and oxidizing agents. Currently, epoxy cyclododecadiene is produced by adopting a method of epoxidizing organic peroxide tert-butyl hydroperoxide (TBHP), and the method is simple in process and high in safety. The TBHP solution generally contains some acid and ester impurities, including but not limited to formic acid, acetic acid, isobutyric acid, tert-butyl formate, isobutyl formate and the like. If the impurities are not removed in time, the impurities will be accumulated in the system, which not only causes corrosion of the system but also catalyzes a side reaction to affect the product quality, and if the impurities are returned to the reaction with the raw materials, the reaction will be affected to cause production fluctuation. Therefore, removal of the impurities is an important consideration in the production process of epoxy cyclododecadiene.

[0006] Generally, the impurities are removed by distillation in engineering, but due to the large number of impurities, the impurities need to be removed by a multi-stage distillation tower, which not only is complicated in process but also is high in energy consumption, and cannot guarantee the removal effect of the impurities and the damage of the system caused by the accumulation of the acid impurities. Therefore, a reasonable and efficient impurity removal method is urgently needed to reduce the production cost of the epoxy cyclododecadiene device, improve the product quality and the stability of production operation. SUMMARY

[0007] In view of the above problems in the prior art, the application aims to provide a method for removing impurities in a continuous separation process of epoxy cyclododecadiene, and solves the problems of incomplete removal of impurities, high energy consumption, poor product quality and strong corrosion.

[0008] In order to achieve the above application purpose, the technical scheme adopted by the application is as follows:

[0009] A method for removing impurities during the continuous separation of epoxy cyclododecadiene, comprising:

[0010] (1) The epoxy dodecadiene reaction liquid stream ① obtained from the epoxy dodecadiene unit first enters the TBA recovery tower A, the top of the tower is the crude TBA product stream ②, and the bottom of the tower is the material stream ③ after TBA removal.

[0011] (2) The above-mentioned bottom liquid stream ③ enters the impurity removal tower B. After condensation at the top of the tower, a cyclododecanetriene solution stream ④ containing impurities is obtained. This stream of material is mixed with the ethylene glycol solution stream ⑤ of the alkali through the static mixer C to obtain a mixed liquid stream ⑥. Then, it enters the phase separator D for phase separation. The upper layer is the cyclododecanetriene solution stream ⑦, which flows back into tower B. The lower layer is the ethylene glycol solution stream ⑧, which contains the washed impurities and is continuously discharged to the waste liquid system.

[0012] (3) The liquid stream from the bottom of the impurity removal tower (⑨) enters the subsequent distillation system, where it is separated into epoxy cyclododecadiene product by the feed recovery tower and the product purification tower. This is a conventional distillation separation operation, which will not be described in detail in this invention.

[0013] In this invention, in step (1), the epoxy cyclododecadiene reaction liquid stream ① originates from the reaction unit of the epoxy cyclododecadiene device and is obtained by epoxidation of cyclododecadiene with a TBA solution of TBHP under the action of a catalyst solution.

[0014] The impurities introduced by the TBA solution from TBHP are mainly acids and esters, including but not limited to formic acid, acetic acid, isobutyric acid, tert-butyl formate, and isobutyl formate, with boiling points between 80-200℃. In the epoxy dodecadiene reaction solution, the total content of impurities is usually >2%, and after distillation and concentration, the content increases to more than 10%. The enrichment of acidic impurities not only causes product isomerization and impurities, but also easily causes equipment corrosion. Therefore, impurities need to be separated in a timely manner in the separation system.

[0015] In the preparation process of the epoxy cyclododecane triene reaction solution of the present invention, the solvent of the catalyst solution is ethylene glycol. Cyclododecane triene has low solubility in ethylene glycol. Due to the large difference in polarity between the two solvents, they are immiscible and can separate phases in the absence of other solvents or in the presence of trace amounts of other solvents.

[0016] In this invention, in step (1), the TBA recovery tower A achieves the effect of separating TBA by adjusting the temperature and pressure. Preferably, the pressure inside the tower is controlled at 30-50 kPaA and the temperature at the bottom of the tower is 80-120°C. The residual TBA content in the bottom material stream ③ is controlled to be ≤2%, preferably, the TBA content in the bottom material is ≤1.5%. If the material with high TBA content in the bottom of the tower enters the impurity removal tower, the ethylene glycol and cyclododecanetriene in the top of the tower will be completely miscible and cannot be separated. The reflux material contains a large amount of impurities and returns to the tower B. Furthermore, the external collection of waste liquid results in a large amount of raw material waste.

[0017] In this invention, in step (2), the impurity removal tower B controls the content of ethylene glycol in the bottom stream ⑨ to be <10ppm by adjusting the temperature and pressure. Preferably, the pressure inside the tower is controlled to be 10-20KPaA and the temperature in the bottom stream is 120-180℃. The content of cyclododecanetriene in the top stream ④ is ≥10%. Preferably, the content of cyclododecanetriene in the top stream is ≥20%.

[0018] Since the boiling points of impurities such as formic acid, acetic acid, isobutyric acid, tert-butyl formate, and isobutyl formate are usually between 80-200℃, and the distillation gradient is between TBA and ethylene glycol, the key material indicators of the bottom and top of the distillation column can be controlled by adjusting the temperature, pressure, reflux ratio, and other parameters of the distillation column so that the impurities are enriched at the top of the impurity removal column.

[0019] After the material at the top of the impurity removal tower is condensed, it is mixed with a fresh alkali ethylene glycol solution and enters the phase separator. The phase separator is designed with a coalescing separator, where the material is separated into two phases. The upper layer is the cyclododecanetriene phase, which is returned to the impurity removal tower as a reflux stream. The lower layer is the ethylene glycol phase. According to the principle of like dissolves like, impurities are more easily dissolved in the ethylene glycol phase and are continuously collected into the waste liquid system.

[0020] The alkali in the ethylene glycol solution can neutralize acidic impurities in the top material of the tower, which is conducive to the formation of salts that enter the ethylene glycol phase and provides an alkaline environment, thus avoiding equipment corrosion caused by the accumulation of acidic impurities.

[0021] The ethylene glycol solution of the alkali can be one or a mixture of sodium hydroxide, potassium hydroxide, calcium hydroxide, etc., preferably sodium hydroxide; the alkali content in the ethylene glycol solution of the alkali is 1%-20%, preferably 2-5%;

[0022] The ethylene glycol solution of the alkali is continuously fed, and the flow rate is 1%-50% of the flow rate of the material at the top of the impurity removal tower (stream ④). Preferably, the flow rate of the ethylene glycol solution of the alkali is 2%-10% of the flow rate of the material at the top of the tower.

[0023] In this invention, an ethylene glycol solution of alkali is selected because the solvent of the catalyst in the reaction unit of this device is ethylene glycol, which needs to be separated during distillation. In order to avoid introducing new solvent, an ethylene glycol solution of alkali is selected.

[0024] In this invention, the residence time of the material in the phase separator is 0.2-2 hours, preferably 0.5-1 hour.

[0025] Compared with conventional technologies, the present invention has the following advantages:

[0026] 1) This invention provides a method for removing acid and ester impurities during the continuous separation of epoxy cyclododecadiene. By replenishing the alkaline solution with fresh solvent, an alkaline environment is provided, which avoids the equipment corrosion conditions that exist in the distillation separation and improves the operational stability of the production unit.

[0027] 2) The process of this invention is simple, easy to operate, and yields high-quality products with high yield. Attached Figure Description

[0028] Appendix Figure 1 This is a schematic diagram of the continuous separation and impurity removal process of epoxy cyclododecadiene, where ① epoxy cyclododecadiene reaction solution; ② crude TBA product; ③ bottom liquid after TBA removal; ④ cyclododecadiene solution containing impurities; ⑤ ethylene glycol solution containing alkali; ⑥ mixed solution; ⑦ cyclododecadiene solution; ⑧ ethylene glycol solution; ⑨ bottom liquid of impurity removal tower; A: TBA recovery tower; B: impurity removal tower; C: static mixer; D: phase separator (including coalescence separator). Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. It should be noted that these specific embodiments are merely illustrative and should not be construed as limiting the scope of protection of the present invention.

[0030] The analytical testing methods used in the following embodiments of the present invention are as follows:

[0031] Gas chromatography: Shimadzu 2010Plus; Injector temperature: 280℃; Split ratio: 30:1; Column: DB-5 (30m×0.25mm×0.25μm); Temperature program: 50℃ for 2 minutes, increase to 80℃ at 5℃ / min, hold for 10 minutes, increase to 300℃ at 15℃ / min, hold for 10 minutes; FID detector temperature: 300℃.

[0032] The following embodiments of the present invention use information on the main sources of raw materials. Unless otherwise specified, all other raw materials are common commercially available materials:

[0033] Epoxy-cyclododecadiene reaction solution, produced in-house by Wanhua Chemical Group Co., Ltd. Epoxy-cyclododecadiene unit;

[0034] Ethylene glycol, 99%, CAS: 107-21-1, purchased from Beijing Innocare Technology Co., Ltd.;

[0035] Sodium hydroxide, 99%, CAS: 1310-73-2, purchased from Beijing Innocare Technology Co., Ltd.

[0036] Potassium hydroxide, 99%, CAS: 1310-58-3, purchased from Beijing Innocare Technology Co., Ltd.

[0037] Acetonitrile, 99.9% (GC), CAS: 75-05-8, purchased from Beijing Innocare Technology Co., Ltd.

[0038] Methanol, 99.9% (GC), CAS: 67-56-1, purchased from Beijing Innocare Technology Co., Ltd.

[0039] Example 1

[0040] The epoxy cyclododecadiene reaction liquid stream ① is continuously fed with a feed rate of 1000 kg / h. Its composition and content test results are shown in Table 1 below.

[0041] After passing through TBA recovery tower A, the TBA content in the bottom stream ③ is 0.548 wt%. The operating pressure of tower A is 30 kPaA, and the bottom temperature is 80℃. Stream ③ enters impurity removal tower B, which operates at 15 kPaA and has a bottom temperature of 150℃. The flow rate of the overhead stream ④ is 220 kg / h. The overhead stream ⑤ is a continuous feed of sodium hydroxide in ethylene glycol solution with a sodium hydroxide content of 5 wt% and a flow rate of 4.4 kg / h. The residence time of the mixed stream ⑥ in the phase separator is 0.5 h. Stream ⑧ is continuously collected into the waste liquid tank with a discharge flow rate of 140 kg / h. The ethylene glycol content and acid and ester impurity content in the bottom stream ⑨ of the impurity removal tower are all below the gas chromatography detection limit. After subsequent distillation separation, the purity of the epoxy cyclododecadiene product is 99.874% (product standard ≥99.5%).

[0042] Example 2

[0043] The difference from Example 1 is that the overhead stream ⑤ is a continuous feed of potassium hydroxide in ethylene glycol solution, that is, the sodium hydroxide in ethylene glycol solution is replaced with potassium hydroxide in ethylene glycol solution. The operating pressure of column A is 50 kPaA and the bottom temperature is 120°C. The operating pressure of column B is 20 kPaA and the bottom temperature is controlled at 180°C. The residence time of the mixed stream ⑥ in the phase separator is 1 hour. All other operating conditions are the same. Finally, the epoxy cyclododecadiene product obtained has a purity of 99.814%.

[0044] Example 3

[0045] The difference from Example 1 is that the overhead stream ⑤ is a continuous feed of sodium hydroxide in ethylene glycol solution with a sodium hydroxide content of 2 wt% and a flow rate of 22 kg / h; stream ⑧ is continuously collected into the waste liquid tank with a discharge flow rate of 220 kg / h; the operating pressure of tower A is 35 kPaA and the reboiler temperature is 93°C; the operating pressure of tower B is 10 kPaA and the reboiler temperature is 120°C; the residence time of the mixed stream ⑥ in the phase separator is 0.8 h; and other operating conditions are the same. The final separated epoxy cyclododecadiene product has a purity of 99.799%.

[0046] Comparative Example 1

[0047] The method was followed as described in Example 1, with the only difference being that the operating pressure of tower A was 35 kPaA, the reboiler temperature was 75°C, and after stream ① passed through TBA recovery tower A, the TBA content in the reboiler stream ③ was 2.464 wt%, which then entered the impurity removal tower B. Due to the high TBA content at the top of tower B, the phase separation effect in the phase separator was poor. The ethylene glycol waste liquid contained a large amount of cyclododecadiene, and the reflux liquid ⑦ contained ethylene glycol and acidic impurities, which then entered the reboiler. All other conditions remained the same, and the final separated cyclododecadiene epoxy product had a purity of 99.236%.

[0048] Comparative Example 2

[0049] The method was followed as in Example 1, except that the feed of the sodium hydroxide ethylene glycol solution in the overhead stream (⑤) was omitted. All other operating conditions remained the same, and the final separated product, epoxide cyclododecadiene, was obtained with a purity of 98.905%.

[0050] Table 1

[0051]

[0052] As can be seen from the above embodiments and comparative examples, the impurity removal method in the continuous separation process of epoxy cyclododecadiene of the present invention effectively improves product quality and yield through a simple process, while avoiding the corrosive effect on equipment caused by the enrichment of acidic impurities.

[0053] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for removing impurities in a continuous separation process of epoxy cyclododecene, comprising: (1) the epoxy cyclododecene reaction liquid stream ① obtained from the reaction unit of the epoxy cyclododecene device first enters the TBA recovery tower A, the tower top is the TBA crude product stream ②, and the tower bottom is the tower bottom liquid stream ③ after removing TBA; wherein the epoxy cyclododecene reaction liquid stream ① is obtained by epoxidation of cyclododecatriene with a TBA solution of TBHP in the presence of a catalyst solution, and the solvent of the catalyst is ethylene glycol; (2) the tower bottom liquid stream ③ after removing TBA enters the impurity removal tower B, and the tower top condenses to obtain a cyclododecatriene solution stream ④ containing impurities, which is mixed with an alcohol solution stream ⑤ of a base to obtain a mixed liquid stream ⑥, which then enters a phase separator D and is separated into an upper layer of a cyclododecatriene solution stream ⑦ that is refluxed into the tower B and a lower layer of an ethylene glycol solution stream ⑧ containing eluted impurities that is continuously discharged to a waste liquid system; (3) the impurity removal tower bottom liquid stream ⑨ enters a subsequent rectification system to obtain an epoxy cyclododecene product by separation.

2. The method of claim 1, wherein, In step (1), the TBA recovery tower A controls the residual TBA content in the tower bottom material stream ③ to be ≤2% by adjusting the temperature and pressure.

3. The method of claim 2, wherein, In step (1), the TBA recovery tower A controls the tower internal pressure to be 30-50 KPaA and the tower bottom temperature to be 80-120℃.

4. The method of claim 1 or 2, wherein, In step (2), the impurity removal tower B controls the ethylene glycol content in the tower bottom stream ⑨ to be <10 ppm by adjusting the temperature and pressure.

5. The method of claim 4, wherein, In step (2), the impurity removal tower B controls the tower internal pressure to be 10-20 KPaA and the tower bottom temperature to be 120-180℃.

6. The method of claim 1, wherein, The alcohol solution stream ⑤ of the base is one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide, and the base content is 1%-20%.

7. The method of claim 1 or 6, wherein, The alcohol solution stream ⑤ of the base is ethylene glycol.

8. The method of any one of claims 1 or 6, wherein, The flow rate of the alcohol solution of the base is 1%-50% of the flow rate of the material at the top of the impurity removal tower.

9. The method of claim 1, wherein, The residence time of the material in the phase separator is 0.2-2 h.

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