WO2021179638A9 - Purification method for electronic-grade ethylene carbonate, and purification apparatus - Google Patents

Abstract

Disclosed are a purification method for electronic-grade ethylene carbonate, and a purification apparatus thereof. The method comprises the following steps: S1: seeding ethylene carbonate having a purity of 99.90%-99.98%; S2: heating to 36-37℃ after the seeding ends, and then maintaining a constant temperature for 0.5-3 h; S3: carrying out cooling and crystallization after the temperature maintenance ends; S4: carrying out heating and sweating on crystals in a gradual heating manner, and carrying out a next round of crystallization on an obtained sweating liquid; S5: after the sweating ends, heating to melt the crystals subjected to sweating to obtain a first product having a purity of 99.995% or more; and S6: rectifying a non-crystallized mother liquor twice to obtain a second product having a purity of 99.990% or more.

Description

Purification method and purification device of electronic grade ethylene carbonate

METHOD AND DEVICE OF PURIFYING ELECTRONIC GRADE ETHYLENE CARBONATE

This application claims the priority of the Chinese patent application filed on March 11, 2020 with the application number 202010164468.X and the invention titled "Method for purifying electronic grade ethylene carbonate and its purification device", the entire contents of which are Incorporated herein by reference.

technical field

The present application relates to the technical field of preparation of electronic-grade reagents, in particular to a purification method of electronic-grade ethylene carbonate and a purification device thereof.

Background technique

Ethylene carbonate, also known as 1,3-dioxolane-2 ketone, ethylene carbonate, ethylene glycol carbonate, molecular formula C ₃ H ₄ O ₃ , abbreviated as EC. Ethylene carbonate is an excellent organic solvent and organic synthesis intermediate, which can be used in various fields such as spinning, medicine, and plastic processing. In the capacitor battery industry, the mixed solution of ethylene carbonate and propylene carbonate has a high dielectric constant and can be used as an electrolyte for lithium ion batteries.

In recent years, with the vigorous development of the new energy industry and the continuous progress of electronic component technology, high-purity ethylene carbonate has become an important organic solvent in the electronics industry, especially in the production of lithium battery electrolytes. Since the electrolyte is the key material of lithium batteries, the performance of the electrolyte depends on the quality of various solvents in the formulation. The purity, total alcohol content, water content, metal ion content and other single impurity components of high-purity ethylene carbonate will be It directly affects the performance of the electrolyte product, which in turn affects the indicators of the battery. Therefore, the quality requirements for high-purity ethylene carbonate are getting higher and higher.

Chinese patent application CN107629030A provides a method for preparing electronic grade ethylene carbonate by falling film crystallization. The ethylene carbonate raw material is added from the top of the crystallizer and circulated between the crystallizer and the ethylene carbonate raw material storage tank at a certain flow rate. The crystallization is carried out in a step-by-step cooling mode, and the uncrystallized ethylene carbonate residual liquid is discharged and transported to the recovery device. The crystal layer is melted in a step-by-step heating and sweating manner, the sweating liquid is cut in a certain proportion, and the sweating liquid and residual liquid are recovered and sent back to the crystallizer. The molten material liquid is returned to the raw material storage tank, and the secondary falling film crystallization is repeated to obtain electronic grade ethylene carbonate. This method can prepare ethylene carbonate with a purity higher than 99.99%, but requires secondary falling film crystallization, high energy consumption, and high sweat cutting ratio, and the product has a low yield after primary crystallization.

Chinese patent application CN107501230A provides a device and method for preparing electronic-grade ethylene carbonate by coupling crystallization and rectification. The method utilizes the combination of falling film crystallization and rectification process to continuously transport the raw materials of the raw material tank to the crystallizer, and the cooling The medium is cooled and crystallized to a certain thickness of the crystal layer, the feeding is stopped, the temperature is raised and sweating, the sweating liquid after crystallization is collected and transported to the rectification tower, the top product of the tower enters the second product tank, and the product of the tower kettle is recycled back to the crystallization raw material tank. The crystals are melted into liquid and transported to the first product tank. The application realizes the recycling of the raw material liquid, and finally obtains an electronic grade ethylene carbonate product with a content of more than 99.99%. The method enters the crystallizer to separate and purify the impurities with low removal rate. In order to obtain high-purity products, the discharge amount of residual liquid and perspiration liquid is large, resulting in a low yield of primary crystallization, and the obtained perspiration liquid and residual liquid need to undergo multiple cycle crystallization , high energy consumption. At the same time, due to the low impurity removal rate during the reaction process, it is easy to change color in the presence of oxygen and high temperature, which will cause the capacity of the battery to decay and the cycle life to decrease when it enters the electrolyte product.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the application provides a purification method and a purification device of electronic grade ethylene carbonate, the specific scheme is as follows:

A method for purifying electronic grade ethylene carbonate, comprising the steps:

S1: seeding the ethylene carbonate with a purity of 99.90% to 99.98% at 20 to 28°C, and complete the seeding when the temperature of the material drops to 31 to 32°C;

S2: after the seeding is completed, the temperature is raised to 36-37° C. and then kept at a constant temperature, and the time from heating up to the end of the constant temperature is 25-30 min;

S3: cooling and crystallization after the constant temperature is completed, and after the cooling and crystallization is completed, the temperature is kept constant for 0.5 to 3 hours to obtain crystallized and uncrystallized mother liquors, and the obtained crystals and uncrystallized mother liquors are separated;

S4: the crystallization of the step S3 is gradually heated up and sweated, and the obtained sweating liquid is subjected to the next round of crystallization;

S5: after the sweating is completed, the temperature is raised to melt the sweated crystals to obtain the first product with a purity greater than 99.995%;

S6: Perform two rectifications on the uncrystallized mother liquor in the step S3 to obtain a second product with a purity greater than 99.990%.

In some embodiments of the present application, the cooling rate of the cooling crystallization in the step S3 is 0.25-1.0°C/h, the end temperature is 32-34°C, and the crystallization time is 5-20h.

In some embodiments of the present application, in the step S4, the heating rate of the temperature rise and sweating is 3-5°C/h, and the end temperature is 34-36.5°C.

In some embodiments of the present application, the temperature of crystal melting in the step S5 is 40-50°C.

In some embodiments of the present application, the material feeding rate during seeding in the step S1 is 1.0 t/h to 5.0 t/h.

In some embodiments of the present application, the vacuum degrees during the two rectifications in the step S6 are respectively -99.9-99.0KPa, and the temperatures are respectively 140-150°C.

The application also provides a purification device used in the above-mentioned purification method, including a falling film crystallizer, a sweating liquid tank, a mother liquor tank, a first product tank, a second product tank, a third rectifying column and a second rectifying column;

The falling film crystallizer is respectively connected with the feeding ports of the sweating liquid tank, the mother liquor tank and the first product tank through the first discharging pipeline;

The sweating liquid tank is connected with the feed port of the falling film crystallizer through a circulating pipeline;

The mother liquor tank is connected with the third rectifying tower through the second discharge pipeline;

The mother liquor tank, the third rectifying tower, the second rectifying tower and the second product tank are connected successively;

During operation, the raw material ethylene carbonate is first seeded and crystallized in the falling film crystallizer to obtain crystalline and uncrystallized ethylene carbonate, and the uncrystallized ethylene carbonate enters the mother liquor tank through the first discharge line, and the uncrystallized ethylene carbonate in the mother liquor tank is Ethylene carbonate enters the third rectification tank and the second rectification tank successively through the second discharge line for rectification and enters the second product tank; the crystallization is carried out in the falling film crystallizer to heat up and sweat, and the obtained sweat liquid passes through the first outlet. The material pipeline enters the sweating liquid tank, and the sweating liquid in the sweating liquid tank enters the falling film crystallizer through the circulation pipeline; the remaining crystals after sweating are melted and enter the first product tank.

In some embodiments of the present application, a crystallization tube, a material circulation pump and a cooling system are installed inside the falling film crystallizer.

In some embodiments of the present application, a first rectification column is further included, and the first rectification column is connected to the falling film crystallizer.

Compared with the prior art, the present application has achieved the following technical effects:

The method for purifying electronic-grade ethylene carbonate provided by the present application includes seeding before cooling and crystallization, and providing crystal seeds for crystallization, so that the crystallization is easy to carry out, and the encapsulation impurities in the crystal are less, thereby improving the electronic-grade ethylene carbonate. Purity and Yield. After seeding, cooling and crystallization are carried out, and the substances with similar boiling points to ethylene carbonate, azeotropes and heat-sensitive substances can be removed by using the different melting points, which can effectively remove trace impurities, so that the impurity removal rate is high, and the single impurity content is high. ≤5ppm, high-purity ethylene carbonate can be obtained, thereby effectively improving the performance of the electrolyte. Comparing Example 2 and Comparative Example 2, it can be seen that the purification method provided by the present application has a 5% higher yield of primary crystallization than Comparative Example 2, and less perspiration fluid discharge, thereby reducing the number of perspiration fluid cycles and reducing energy consumption. At the same time, the electronic grade ethylene carbonate prepared by the present application has less impurity content and less discoloration of the electronic grade ethylene carbonate, so that the battery life can be improved. After cooling and crystallization, the uncrystallized mother liquor is enriched with various organic alcohols, aldehydes, ketones and other impurities with similar boiling points and properties to ethylene carbonate. In the present application, the uncrystallized mother liquor after cooling and crystallization is rectified twice, and impurities are further removed by rectification, and a second product with a purity greater than 99.99% is obtained from the second rectifying tower. At the same time, the sweating liquid is returned to the falling film crystallizer, and the raw material liquid is recycled to improve the total yield.

Description of drawings

Fig. 1 is the schematic flow sheet of the purification method of electronic grade ethylene carbonate of a kind of embodiment of the application;

2 is a schematic structural diagram of a purification device according to an embodiment of the application;

3 is a schematic structural diagram of a purification device according to another embodiment of the present application;

Wherein 1, the first rectification column; 2, the second rectification column; 3, the falling film crystallizer; 31, the first discharge pipeline; 311, the first route; 312, the second route; 313, the third route; 4. Perspiration tank; 41. Circulation pipeline; 5. Mother liquor tank; 51. Second discharge pipeline; 6. Third distillation column; 7. First product tank; 8. Second product tank; 9. Buffer tank .

Detailed ways

The technical solutions of the present application will be described in detail below in conjunction with specific embodiments, however, it should be understood that elements, structures and features in one embodiment can also be beneficially combined into other embodiments without further description.

It will be appreciated that although the figures may show a particular order of method steps, the order of the steps may differ from that depicted. Furthermore, two or more steps may be performed concurrently or with partial concurrence. Such variations will depend on the software and hardware chosen and designer choice. All such variations are within the scope of this disclosure.

In the description of the present application, it should be understood that the terms "first", "second", etc. are only used for description purposes, and cannot be interpreted as indicating or implying relative importance or implying the number of indicated technical features . Thus, a feature defined as "first", "second", etc., may expressly or implicitly include one or more of that feature.

In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it may be a fixed connection, a detachable connection, or an integrated connection. Ground connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood in specific situations.

The described embodiments are only to describe the preferred embodiments of the present application, not to limit the scope of the present application. On the premise of not departing from the design spirit of the present application, various modifications made by those of ordinary skill in the art to the technical solutions of the present application and improvements, shall fall within the scope of protection determined by the claims of this application.

As shown in Figure 1, it is a purification method of electronic grade ethylene carbonate according to an embodiment of the application, comprising the steps:

S1: seeding the ethylene carbonate with a purity of 99.90% to 99.98% under the environmental conditions of 20 to 28°C, and complete the seeding when the temperature of the material is lowered to 31 to 32°C;

S2: after the seeding is completed, the temperature is raised to 36-37° C. and then kept at a constant temperature, and the time from heating up to the end of the constant temperature is 25-30 min;

S3: cooling and crystallization after the constant temperature is completed, and after the cooling and crystallization is completed, the temperature is kept constant for 0.5 to 3 hours to obtain crystallized and uncrystallized mother liquors, and the obtained crystals and uncrystallized mother liquors are separated;

S4: the crystallization of the step S3 is gradually heated up and sweated, and the obtained sweating liquid is carried out to the next round of crystallization;

S5: after the sweating is completed, the temperature is raised to melt the sweated crystals to obtain the first product with a purity greater than 99.995%;

S6: Perform two rectifications on the uncrystallized mother liquor in the step S3 to obtain a second product with a purity greater than 99.990%.

In the present application, ethylene carbonate with a purity of 99.90% to 99.98% is seeded at a temperature of 20 to 28°C, and the seeding is terminated when the temperature of the material drops to 31 to 32°C. When the temperature of the material drops to 31～32℃, the crystallization will release the heat of solidification, and the temperature will rebound. This rebound temperature is the final cooling temperature, and the seeding is completed. In this embodiment, the source of the ethylene carbonate having a purity of 99.90% to 99.98% is not particularly limited. For example, the ethylene carbonate with a purity of 99.90% to 99.98% is prepared by addition reaction of ethylene oxide and carbon dioxide as raw materials to obtain a crude product of ethylene carbonate, and the crude product is flashed through a flash tank to flash unreacted carbon dioxide. After entering the thin film evaporator, the gas phase is condensed and then enters the first rectifying tower for rectification. In this embodiment, the feeding rate during the seeding is preferably 1.0 t/h to 5.0 t/h, more preferably 2.0 t/h. In this embodiment, the temperature of the seeding is preferably 25°C. In this embodiment, quenching is used to seed crystals under the conditions of 20-28° C. to form seeds in the crystallizer, which is beneficial for the crystallization process to be carried out on the seeds.

After the seeding is completed, the temperature is raised to 36-37° C. and then kept at a constant temperature, and the time from heating to the end of the constant temperature is 25-30 min. In this embodiment, seeding can crystallize the crude ethylene carbonate, and after the crystals are obtained, the temperature is raised to 36-37° C. to melt the excess crystals, and a small amount of crystals are retained as seed crystals. Since the melting temperature of impurities is lower than the melting temperature of ethylene carbonate, the impurities melt faster in the process of melting excess crystals, reducing the coating of impurities in the seeds, thereby improving the purity of the seeds, and the purity of the seeds is improved. Thereby, the crystallization purity is improved, and finally the purity of the first product is improved.

After the constant temperature is completed, the cooling crystallization is carried out, and after the cooling crystallization is completed, the constant temperature is kept for 0.5 to 3 hours, and the obtained crystal and uncrystallized mother liquor are separated. In this embodiment, the cooling rate of the cooling crystallization is preferably 0.25-1.0°C/h, more preferably 0.5°C/h; the end temperature is preferably 32-34°C, more preferably 32°C; the crystallization time is preferably 5 ~20h, more preferably 10h; the constant temperature time is preferably 1h.

After the crystals are obtained, the crystals are heated up and sweated in a step-by-step manner, and the obtained sweating liquid is subjected to the next round of crystallization, that is, the cooling crystallization in step S3. In this embodiment, the heating rate of the temperature-raising perspiration is preferably 3-5°C/h, more preferably 4°C/h; the end temperature is preferably 34-36.5°C, more preferably 35°C. In this embodiment, the purity of the obtained perspiration fluid is 99.9910 to 99.9920%. In this embodiment, the next round of crystallization of the perspiration liquid can make the material recycled and improve the utilization rate of the raw material.

After sweating, the temperature is raised to melt the crystals remaining after sweating to obtain a first product with a purity greater than 99.995%. In the present invention, the temperature at which the crystals are melted is preferably 40 to 50°C, and more preferably 45°C.

After cooling and crystallization to obtain crystallized and uncrystallized mother liquor, the uncrystallized mother liquor is rectified twice to obtain a second product with a purity greater than 99.99%. In this embodiment, the purity of the mother liquor obtained after cooling and crystallization is 99.97-99.98%. In the present invention, the degree of vacuum during the two rectifications is preferably -99.9 to -99.0KPa, more preferably -99.9KPa; the temperature is preferably 140 to 150°C, more preferably 145°C.

In this embodiment, the determination standard of the electronic grade ethylene carbonate is evaluated by HG/T5391-2018.

As shown in FIG. 2, another embodiment of the present application provides a purification device used in the above-mentioned purification method, including a falling film crystallizer 3, a sweating liquid tank 4, a mother liquor tank 5, a first product tank 7, a second product Tank 8, the third rectifying column 6 and the second rectifying column 2;

The falling film crystallizer 3 is respectively connected with the feed ports of the sweating liquid tank 4, the mother liquor tank 5 and the first product tank 7 through the first discharge line 31;

The sweating liquid tank 4 is connected with the feed port of the falling film crystallizer 3 through the circulation line 41;

Described mother liquor tank 5 is connected with the 3rd rectifying tower 6 by the 2nd discharge pipeline 51;

Described mother liquor tank 5, the third rectifying tower 6, the second rectifying tower 2 and the second product tank 8 are connected successively;

During work, the raw material ethylene carbonate firstly carries out seeding and cooling crystallization in the falling film crystallizer 3 to obtain crystallization and uncrystallized ethylene carbonate, and the uncrystallized ethylene carbonate enters the mother liquor tank 5 through the first discharge line 31, and the mother liquor tank The uncrystallized ethylene carbonate in 5 enters the third rectifying tower 6 and the second rectifying tower 2 successively through the second discharge line 51 for rectification and enters the second product tank 8; Crystallization is carried out in the falling film crystallizer 3 Warm up and sweat, the obtained sweating liquid enters the sweating liquid tank 4 through the first discharge line 31, and the sweating liquid in the sweating liquid tank 4 enters the falling film crystallizer 3 through the circulation pipeline 41 again; A product tank 7.

In this embodiment, a crystallizing tube, a plate heat exchanger, a material circulation pump and a cooling system are preferably installed inside the falling film crystallizer 3 . In this embodiment, the discharge pipeline of the falling film crystallizer 3 is preferably divided into three paths, the first path 311 is connected with the first product tank 7, the second path 312 is connected with the mother liquor tank 5, and the third path 313 is connected with the mother liquor tank 5. The sweat tank 4 is connected.

In this embodiment, the purification device preferably further comprises a first rectification column 1, and the first rectification column 1 is connected with the falling film crystallizer 3, so that the ethylene carbonate obtained by the rectification of the first rectification column 1 The crude product is input from the side line of the first rectifying tower 1, and is added from the top of the falling film crystallizer 3 for cooling and crystallization. In this embodiment, it is preferable to use inert gas protection when adding raw materials to the falling film crystallizer 3 .

As shown in FIG. 3 , in this embodiment, the purification device preferably further includes a buffer tank 9 . The buffer tank 9 is respectively connected with the falling film crystallizer 3 and the first product tank 7, and the product obtained after the remaining crystals melted after sweating are output from the falling film crystallizer 3 and preferably enter the buffer tank 9 for buffering, and then enter the buffer tank 9. First product tank 7 . In this embodiment, the first purpose of setting the buffer tank is to ensure that each index of the crystallization product is qualified and then enter the product tank, so as to avoid the product index fluctuation caused by unstable operation and contaminate the product tank. After passing the test, it is transferred to the product tank through the pump, which saves the total operation time of the crystallization process.

In this embodiment, the falling film crystallizer 3, the sweating liquid tank 4, the mother liquor tank 5, the first product tank 7, the second product tank 8, the third rectification column 6, the second rectification column 2 and the first The inlet and outlet pipelines of a rectifying tower 1 are all provided with valves to control the inlet and outlet materials.

In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present application.

Example 1

In this example, the ethylene carbonate with a purity of 99.90% to 99.98% is prepared by addition reaction of ethylene oxide and carbon dioxide as raw materials to obtain a crude product of ethylene carbonate, and the crude product is flashed out in a flash tank. The unreacted carbon dioxide enters the thin film evaporator, and the gas phase condenses and enters the first rectifying tower for rectification.

(1) seeding and cooling crystallization: under the protection of inert gas, take the ethylene carbonate crude product (mass fraction of 99.98% ethylene carbonate crude product) produced by the side line of the first rectifying tower and add it from the top of the falling film crystallizer, enter The feeding rate is 1.5t/h. After the feeding is completed, the material circulation pump is turned on, the cooling system is turned on, and a cold source of 20 °C is used to stimulate the material to crystallize. When the material temperature drops to 31 to 32 °C, it will rebound. After cooling to the final temperature, the seeding is completed. After the seeding is completed, the temperature control plate heat exchanger is switched, and the circulating water is rapidly heated to 36 ° C by steam, and the temperature is kept constant after the temperature is raised to 36 ° C (the time from heating up to the constant temperature to end this process is 25min, and the excess produced by the explosion will be The crystals are partially melted, leaving a small amount of crystals on the surface of the heat exchange tube as seeds). After the constant temperature is over, the material is crystallized in the crystallizer by a gradual cooling method, and a crystal layer is formed on the wall of the crystallizer. Time 1h, obtain crystallized and uncrystallized ethylene carbonate mother liquor (the purity of uncrystallized ethylene carbonate mother liquor is 99.97%); Uncrystallized ethylene carbonate mother liquor is discharged from the crystallizer outlet, and transported to the mother liquor tank, as The raw material enters the third rectifying tower.

(2) warming up and sweating: the crystallization of step (1) is melted in a stepwise warming and sweating manner, the temperature rising rate is 3°C/h, the end point temperature of sweating is 36°C, and the sweating liquid (the purity of the sweating liquid is 99.9910%) is discharged to Perspiration tank.

(3) Crystallization melting: After sweating, continue to increase the temperature, so that all the remaining crystals after sweating are melted into liquid (the temperature during the melting process of crystals is 40°C), and the product is discharged from the bottom of the falling film crystallizer into the buffer tank , and then transported to the first product tank.

(4) Rectification: continuous rectification operation under reduced pressure is adopted, the material in the mother liquor tank is transported to the third rectification tower, the pressure in the tower is -99.9Kpa, the temperature at the bottom of the tower is 145°C, and the light components are removed from the top of the tower Impurities, the tower still removes heavy component impurities, and the side line extracts ethylene carbonate with a mass fraction of 99.97%, which is transported to the second rectifying tower for rectification (the pressure in the tower is -99.9Kpa, and the temperature at the bottom of the tower is 145 ℃), and the side line The second product is obtained and sent to the second product tank.

Gas chromatography was used to measure the purity, impurity type and content, and yield of the products in the first product tank and the second product tank. The specific detection conditions were shown in Table 1, and the specific results were shown in Table 2.

Table 1 Gas chromatography detection conditions

Column model	DB-1701, 30m*0.53mm*0.5um
Injector	260℃
Detector	300℃
Oven temperature program	90℃(0mim)→10℃/min→190℃(0min)→20℃/min→220℃(6min)
Column flow	1ml/min
split ratio	50:1

Table 2 Product quality assessment results in the first and second product tanks of Example 1

	purity(%)	Ethylene glycol (ppm)	Diethylene glycol (ppm)	Yield (%)
first product	99.99693	3.1	0	70

second product

99.99110

5.0

15.0

75

Further, after the perspiration liquid is returned to the falling film crystallizer for cyclic cooling and crystallization, it is determined that the total yield of the entire purification method is 99%.

Example 2

In this example, the ethylene carbonate with a purity of 99.90% to 99.98% is prepared by addition reaction of ethylene oxide and carbon dioxide as raw materials to obtain a crude product of ethylene carbonate, and the crude product is flashed out in a flash tank. The unreacted carbon dioxide enters the thin film evaporator, and the gas phase condenses and enters the first rectifying tower for rectification.

(1) seeding and cooling crystallization: under the protection of inert gas, take the ethylene carbonate crude product (mass fraction is 99.95% ethylene carbonate crude product) produced by the side line of the first rectifying tower and add it from the top of the falling film crystallizer, enter The material rate is 2.0t/h. After the feeding is completed, the material circulation pump is turned on, the cooling system is turned on, and a cold source of 25 °C is used to stimulate the material to crystallize. When the material temperature reaches 31 to 32 °C, the temperature rebounds. Stop seeding , after the seeding is completed, the temperature control plate heat exchanger is switched, and the circulating water is rapidly heated to 36.5 ℃ by steam, and the temperature is kept constant after warming to 36.5 ℃ (the time from the temperature rise to the constant temperature to end the process is 25min, and the explosion generated The excess crystals are partially melted, leaving a small amount of crystals on the surface of the heat exchange tube as seeds). After the constant temperature is over, the material is crystallized in the crystallization tube in a step-by-step cooling manner, and a crystal layer is formed on the wall of the crystallizer. Time 2h, obtain crystallized and uncrystallized ethylene carbonate mother liquor (the purity of uncrystallized ethylene carbonate mother liquor is 99.98%); Uncrystallized ethylene carbonate mother liquor is discharged from crystallizer outlet, and transported to mother liquor tank, as The raw material enters the third rectifying tower.

(2) warming up and sweating: the crystallization of step (1) is melted in a stepwise warming and sweating manner, the temperature rising rate is 4°C/h, the end point temperature of sweating is 36.5°C, and the sweating liquid (the purity of the sweating liquid is 99.9920%) is discharged to Perspiration tank.

(3) Crystal melting: After sweating, continue to raise the temperature, so that the remaining crystals after sweating are all melted into liquid (the temperature in the crystal melting process is 45 ° C), and the product is discharged from the bottom of the falling film crystallizer into the buffer tank , and then transported to the first product tank. Ethylene carbonate in the first product tank was 99.9961% pure, ethylene glycol 3.0 ppm, and diethylene glycol 2.5 ppm.

(4) Rectification: continuous rectification operation under reduced pressure is adopted, the material in the mother liquor tank is transported to the third rectification tower, the pressure in the tower is -99.5Kpa, the temperature at the bottom of the tower is 147°C, and the light components are removed from the top of the tower Impurities, the tower still removes heavy component impurities, and the side line extraction mass fraction is 99.96% ethylene carbonate, which is transported to the second rectifying tower (the pressure in the tower is -99.5Kpa, and the temperature at the bottom of the tower is 147 ° C), and the side line obtains the first rectification tower. The second product is fed into the second product tank.

Adopt gas chromatography to detect and measure the purity, impurity type and content, yield of the product in the first product tank and the second product tank. The specific detection conditions are shown in Table 1 of Example 1, and the specific results are shown in Table 3.

Table 3 Product quality assessment results in the first and second product tanks of Example 2

	purity(%)	Ethylene glycol (ppm)	Diethylene glycol (ppm)	Yield (%)
first product	99.99610	3.0	2.5	68
second product	99.99100	6.0	13.0	73

Further, after the perspiration liquid was returned to the falling film crystallizer for cyclic cooling and crystallization, it was determined that the total yield of the entire purification method was 98%.

Example 3

In this example, the ethylene carbonate with a purity of 99.90% to 99.98% is prepared by addition reaction of ethylene oxide and carbon dioxide as raw materials to obtain a crude product of ethylene carbonate, and the crude product is flashed out in a flash tank. The unreacted carbon dioxide enters the thin film evaporator, and the gas phase condenses and enters the first rectifying tower for rectification.

(1) seeding and cooling crystallization: under the protection of inert gas, get the ethylene carbonate crude product (mass fraction is 99.90% ethylene carbonate crude product) of the first rectifying tower side line output and add from the top of the falling film crystallizer, The feeding rate is 5.0t/h. After the feeding is completed, the material circulation pump is turned on, the cooling system is turned on, and a cold source of 28 °C is used to stimulate the material to crystallize for 60 minutes. When the material temperature reaches 31 to 32 °C, the temperature rebounds. After the seeding is completed, the temperature control plate heat exchanger is switched, and the circulating water is rapidly heated to 36 ° C by steam, and the temperature is kept constant after the temperature is raised to 36 ° C (the time from the temperature rise to the constant temperature to end the process is 30min, and the explosion will produce The excess crystals are partially melted, leaving a small amount of crystals on the surface of the heat exchange tube as seeds). After the constant temperature is over, the material is crystallized in the crystallization tube in a step-by-step cooling manner, and a crystal layer is formed on the wall of the crystallizer. Constant temperature time 3h, obtain crystallized and uncrystallized ethylene carbonate mother liquor (the purity of uncrystallized ethylene carbonate mother liquor is 99.97%); Uncrystallized ethylene carbonate mother liquor is discharged from crystallizer outlet, and delivered to mother liquor tank, Enter the third rectifying tower as raw material.

(2) warming up and sweating: the crystallization of step (1) is melted in a stepwise warming and sweating manner, the temperature rising rate is 5°C/h, the end point temperature of sweating is 36.5°C, and the sweating liquid (the purity of the sweating liquid is 99.9910%) is discharged to Perspiration tank.

(3) Crystallization melting: After sweating, continue to raise the temperature, so that the remaining crystals after sweating are all melted into liquid (the temperature during the crystal melting process is 50 ° C), and the product is discharged from the bottom of the falling film crystallizer into the buffer tank , and then transported to the first product tank.

(4) Rectification: continuous rectification operation under reduced pressure is adopted, the material in the mother liquor tank is transported to the third rectification tower, the pressure in the tower is -99.5Kpa, the temperature at the bottom of the tower is 148°C, and the light components are removed from the top of the tower Impurities, the tower still removes heavy component impurities, and the side line extracts ethylene carbonate with a mass fraction of 99.98%, which is transported to the second rectifying tower for rectification (the pressure in the tower is -99.5Kpa, and the temperature at the bottom of the tower is 148 ℃), the side line The second product is obtained and sent to the second product tank.

Adopt gas chromatography to detect and measure the purity, impurity type and content, yield of the product in the first product tank and the second product tank. The specific detection conditions are shown in Table 1 of Example 1, and the specific results are shown in Table 4.

The result of product quality assessment in the first and second product tanks of table 4 embodiment 3

	purity(%)	Ethylene glycol (ppm)	Diethylene glycol (ppm)	Yield (%)
first product	99.99550	5.0	4.0	72
second product	99.99200	6.0	13.0	73

Further, after the perspiration liquid was returned to the falling film crystallizer for cyclic cooling and crystallization, it was determined that the total yield of the entire purification method was 97%.

Example 4

In this example, the ethylene carbonate with a purity of 99.90% to 99.98% is prepared by addition reaction of ethylene oxide and carbon dioxide as raw materials to obtain a crude product of ethylene carbonate, and the crude product is flashed out in a flash tank. The unreacted carbon dioxide enters the thin film evaporator, and the gas phase condenses and enters the first rectifying tower for rectification.

(1) seeding and cooling crystallization: under the protection of inert gas, take the ethylene carbonate crude product (mass fraction of 99.98% ethylene carbonate crude product) produced by the side line of the first rectifying tower and add it from the top of the falling film crystallizer, enter The feeding rate is 1.0t/h. After the feeding is completed, the material circulation pump is turned on, the cooling system is turned on, and a cold source of 20 °C is used to stimulate the material to crystallize. When the material temperature drops to 31-32 °C, it will rebound. After cooling to the final temperature, the seeding is completed. After the seeding is completed, the temperature control plate heat exchanger is switched, and the circulating water is rapidly heated to 37 ° C by steam, and the temperature is kept constant after the temperature is raised to 37 ° C (the time from warming up to the constant temperature to end this process is 30 min, and the excess produced by the explosion will be The crystals are partially melted, leaving a small amount of crystals on the surface of the heat exchange tube as seeds). After the constant temperature is over, the material is crystallized in the crystallizer in a step-by-step cooling manner, and a crystal layer is formed on the crystallizer wall. Time 0.5h, obtain crystallized and uncrystallized ethylene carbonate mother liquor (the purity of uncrystallized ethylene carbonate mother liquor is 99.975%); Uncrystallized ethylene carbonate mother liquor is discharged from the crystallizer outlet, and transported to the mother liquor tank, Enter the third rectifying tower as raw material.

(2) warming up and sweating: the crystallization of step (1) is melted by gradually warming up and sweating, the temperature rising rate is 3°C/h, the end point temperature of sweating is 34°C, and the sweating liquid (the purity of the sweating liquid is 99.9912%) is discharged to Perspiration tank.

(3) Crystallization melting: After sweating, continue to increase the temperature, so that all the remaining crystals after sweating are melted into liquid (the temperature during the melting process of crystals is 40°C), and the product is discharged from the bottom of the falling film crystallizer into the buffer tank , and then transported to the first product tank.

(4) Rectification: continuous rectification operation under reduced pressure is adopted, the material in the mother liquor tank is transported to the third rectification tower, the pressure in the tower is -99.0Kpa, the temperature at the bottom of the tower is 140°C, and the light components are removed from the top of the tower Impurities, the tower still removes heavy component impurities, and the side line extracts ethylene carbonate with a mass fraction of 99.98%, which is transported to the second rectifying tower for rectification (the pressure in the tower is -99.0Kpa, and the temperature at the bottom of the tower is 150 ° C), and the side line The second product is obtained and sent to the second product tank.

Adopt gas chromatography to detect and measure the purity, impurity type and content, yield of the product in the first product tank and the second product tank. The specific detection conditions are as shown in Table 1 of Example 1, and the specific results are shown in Table 5.

Table 5 Product quality assessment results in the first and second product tanks of embodiment 4

	purity(%)	Ethylene glycol (ppm)	Diethylene glycol (ppm)	Yield (%)
first product	99.99600	5.0	4.0	70
second product	99.99250	8.0	13.0	73

Further, after the perspiration liquid was returned to the falling film crystallizer for cyclic cooling and crystallization, it was determined that the total yield of the entire purification method was 97.5%.

Comparative Example 1

Except for the operations of unseeded and crystal-seeded melting, other operation steps are exactly the same as those in Example 2.

Adopt gas chromatography to detect and measure the purity, impurity type and content, yield of the product in the first product tank and the second product tank. The specific detection conditions are as shown in Table 1 of Example 1, and the specific results are shown in Table 6.

Table 6 Results of product quality assessment in the first and second product tanks of Comparative Example 1

	purity(%)	Ethylene glycol (ppm)	Diethylene glycol (ppm)	Yield (%)
first product	99.99410	4.5	6.7	65
second product	99.99100	6.0	13.0	73

Further, after the perspiration liquid was returned to the falling film crystallizer for cyclic cooling and crystallization, the total yield of the entire purification method was determined to be 96%;

It can be seen from the comparison between Example 2 and Comparative Example 1 that, in the purification method provided by the present invention, seeding before cooling and crystallization can reduce the coating of impurities in the crystal, reduce the content of each impurity, and improve the purity of the seed crystal, thereby improving the purity of the crystal. , improve product purity and yield.

Comparative Example 2

The raw materials to be purified are exactly the same as those in Example 2, and they are all crude ethylene carbonate products (the crude ethylene carbonate products with a mass fraction of 99.95%) from the side line of the first rectifying column. Adopt the operation method and conditions of Example 4 in the patent CN107501230A to purify, after rectification, the ethylene carbonate solution obtained at the bottom of the rectification tower is sent back to the raw material tank to stop the purification, and only the yield of the raw material to be purified is detected when the primary crystallization is carried out. Rate. At this moment, adopt gas chromatography to detect and measure the purity and yield of the product in the first product tank and the second product tank, the specific detection conditions are as shown in Table 1 of Example 1, and the specific results are shown in Table 7.

Table 7 Results of product quality assessment in the first and second product tanks of Comparative Example 2

	purity(%)	Ethylene glycol (ppm)	Diethylene glycol (ppm)	Yield (%)
first product	99.9921	8.2	9.5	63
second product	99.9910	6.0	13.0	73

Wherein in Examples 1-4 and Comparative Examples 1-2:

First product yield (%)=first product quality/feeding amount after crystallization;

Second product yield (%) = rectification product quality/feeding amount

Overall yield = total mass of product/total amount of feed.

It can be seen from the comparison between Example 2 and Comparative Example 2 that the purification method provided by the present invention has a 5% higher yield than that of Comparative Example 2 during one crystallization, and the amount of perspiration liquid is less, so that the number of perspiration liquid cycles is less, thereby reducing the amount of sweating. Energy consumption, less impurity content and higher purity.

Example 5

The crystalline products in the first product tank in Examples 1 to 3, Comparative Example 1 and Comparative Example 2 were respectively mixed with the lithium battery electrolyte, and after mixing evenly, they were transferred to a 60°C incubator for preservation, and the color was measured for 24 hours. Spend. Among them, the colorimetric detection adopts the colorimeter detection method, Pt-Co color number. The specific results are shown in Table 8 and Table 8.

Table 8 Discoloration reaction results

	Chroma
Example 1	<5 (no discoloration)
Example 2	<5 (no discoloration)
Example 3	<5 (no discoloration)
Example 4	<5 (no discoloration)
Comparative Example 1	15-20 (pale pink)
Comparative Example 2	20 (pale pink)

As can be seen from Table 8, the electronic grade ethylene carbonate obtained by the purification of the present invention has little discoloration, and the results show that the purified ethylene carbonate of the present invention has high purity and low impurity content, thereby improving battery life.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. The purification method of electronic grade ethylene carbonate, is characterized in that, comprises the steps:

   S1: seeding the ethylene carbonate with a purity of 99.90% to 99.98% at 20 to 28°C, and completes the seeding when the temperature of the material drops to 31 to 32°C;

   S2: after the seeding is completed, the temperature is raised to 36-37° C. and then kept at a constant temperature, and the time from heating up to the end of the constant temperature is 25-30 min;

   S3: cooling and crystallization after the constant temperature is completed, and after the cooling and crystallization is completed, the temperature is kept constant for 0.5 to 3 hours to obtain crystallized and uncrystallized mother liquors, and the obtained crystals and uncrystallized mother liquors are separated;

   S4: the crystallization of the step S3 is gradually heated up and sweated, and the obtained sweating liquid is subjected to the next round of crystallization;

   S5: after the sweating is completed, the temperature is raised to melt the sweated crystals to obtain the first product with a purity greater than 99.995%;

   S6: Perform two rectifications on the uncrystallized mother liquor in the step S3 to obtain a second product with a purity greater than 99.990%.
2. The purification method according to claim 1, wherein the cooling rate of cooling crystallization in the step S3 is 0.25～1.0°C/h, the end temperature is 32～34°C, and the crystallization time is 5～20h.
3. The purification method according to claim 1, characterized in that, in the step S4, the heating rate of the temperature rise and sweating is 3-5°C/h, and the end temperature is 34-36.5°C.
4. The purification method according to claim 1, wherein the temperature at which the crystals melt in the step S5 is 40-50°C.
5. The purification method according to claim 1, wherein the feeding rate during seeding in the step S1 is 1.0t/h～5.0t/h.
6. The purification method according to claim 1, characterized in that, in the step S6, the vacuum degree during the two rectifications is respectively -99.9～-99.0KPa, and the temperature is respectively 140～150°C.
7. The purification device of the purification method according to any one of claims 1 to 6, characterized in that it comprises a falling film crystallizer, a sweating liquid tank, a mother liquor tank, a first product tank, a second product tank, a third rectifying tower and a the second distillation column;

   The falling film crystallizer is respectively connected with the feeding ports of the sweating liquid tank, the mother liquor tank and the first product tank through the first discharging pipeline;

   The sweating liquid tank is connected with the feed port of the falling film crystallizer through a circulation pipeline;

   The mother liquor tank is connected with the third rectifying tower through the second discharge pipeline;

   The mother liquor tank, the third rectifying tower, the second rectifying tower and the second product tank are connected successively;

   During operation, the raw material ethylene carbonate is first seeded and crystallized in the falling film crystallizer to obtain crystalline and uncrystallized ethylene carbonate, and the uncrystallized ethylene carbonate enters the mother liquor tank through the first discharge line, and the uncrystallized ethylene carbonate in the mother liquor tank is Ethylene carbonate then enters the third rectifying tower and the second rectifying tower successively through the second discharge line for rectification and enters the second product tank; crystallization is carried out in the falling film crystallizer to heat up and sweat, and the obtained sweating liquid passes through the first The discharge line enters the sweating liquid tank, and the sweating liquid in the sweating liquid tank enters the falling film crystallizer through the circulation pipeline; the remaining crystals after sweating are melted and enter the first product tank.
8. The purification device according to claim 7, wherein a crystallizer tube, a material circulation pump and a cooling system are installed inside the falling film crystallizer.
9. The purification device according to claim 7, further comprising a first rectification column, the first rectification column is connected with the falling film crystallizer.
10. The purification device according to claim 7, wherein the discharge pipeline of the falling film crystallizer is preferably divided into three paths, the first path is connected with the first product tank, and the second path is connected with the mother liquor tank connected, and the third road is connected with the sweating fluid tank.

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