Process and apparatus for purifying vinylene carbonate by dynamic melt crystallization

Abstract

The present application belongs to the technical field of vinylene carbonate preparation, and particularly relates to a process and device for purifying vinylene carbonate by a dynamic melt crystallization method. In the present application, the structure of a crystallization kettle required in a cooling crystallization process is improved, a straight pipe type crystallization pipe is adjusted to a spiral pipe type crystallization pipe, and dynamic circulating cooling crystallization and melt crystallization are combined to purify vinylene carbonate, so that electronic grade vinylene carbonate is successfully obtained. The present application has the following beneficial effects: on the one hand, the heat exchange area of the crystallization kettle is significantly improved by improving the crystallization kettle pipeline, and the dynamic circulating cooling crystallization mode is used to greatly avoid the occurrence of the spiral pipe blockage problem; on the other hand, the problems of a long sweating period, low single-pass yield, and the need for multiple crystallizations in the traditional static melt crystallization process are avoided, and the yield of the obtained product vinylene carbonate is more than 63%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vinylene carbonate preparation, and particularly relates to a process and device for purifying vinylene carbonate by a dynamic melt crystallization method. BACKGROUND

[0002] Vinylene carbonate (VC) is a colorless transparent liquid and is an important intermediate for synthesizing medicines, plant protection agents, resin paints and other various chemicals. Electronic-grade vinylene carbonate refers to vinylene carbonate with higher purity (content reaching 99.999% or above) and better quality, which is mainly used as an additive for lithium battery electrolyte. Electronic-grade vinylene carbonate is a new type of organic film-forming additive and overcharge protection additive for lithium ion batteries, has good high and low temperature performance and anti-gas swelling function, and can significantly improve the capacity and cycle life of the battery.

[0003] Electronic-grade vinylene carbonate is generally obtained by further refining and removing impurities from industrial-grade vinylene carbonate. At present, electronic-grade vinylene carbonate is mainly prepared by combining rectification and melt crystallization processes. However, in the purification process, melt crystallization is mostly static crystallization and is operated in a batch mode, which is divided into three steps of crystallization, sweating and melting. This process has the disadvantages of long process time and low yield, which has become a bottleneck restricting the industrial production of electronic-grade vinylene carbonate. SUMMARY

[0004] In order to solve the above technical problems, the application provides a process for purifying vinylene carbonate by a dynamic melt crystallization method, which comprises the following steps:

[0005] S1, crude vinylene carbonate solution is transported from the raw material tank to the crystallization kettle, at the same time, the cooling water circulation of the crystallization kettle is started, and the dynamic circulation cooling crystallization operation of the crude vinylene carbonate entering the crystallization kettle is started;

[0006] S2, when the feed amount of the crude vinylene carbonate solution accounts for 50-85% of the volume of the crystallization kettle, the feeding is stopped, and the cooling water circulation operation of the crystallization kettle in S1 is stopped, then the uncrystallized vinylene carbonate mother liquor in the crystallization kettle is discharged back to the raw material tank;

[0007] S3, after the operation in S2 is completed, the hot water circulation of the crystallization kettle is started, the crystallized vinylene carbonate solid in the crystallization kettle is melted, then the melted vinylene carbonate melt is discharged to the product tank, and high-purity vinylene carbonate product is obtained.

[0008] In the above process, preferably, in S1, the feeding temperature of the crude vinylene carbonate solution transported from the raw material tank to the crystallization kettle is 25-30℃, and the feeding speed is 100-300 mL / min.

[0009] Preferably, in S1, the crystallization kettle is used once every 100-600 s for each particle in the vinylene carbonate solution.

[0010] Preferably, in S1, the inlet temperature of the cooling water is 5-30℃, the outlet temperature is 10-35℃, the gradient cooling is implemented in the process of dynamic circulation cooling crystallization, the cooling rate is 5-10℃ / h, and the time length of the dynamic circulation cooling crystallization is 0.5-6 h.

[0011] Preferably, in S2, the mass of the uncrystallized vinylene carbonate mother liquor accounts for 20-60% of the initial mass of the vinylene carbonate raw material storage tank.

[0012] In the purification method of the vinylene carbonate provided by the application, if a conventional stainless steel crystallization kettle is used, the thickness of the vinylene carbonate crystallization layer cannot be seen in the equipment, and therefore, in the application, the thickness of the crystallization layer is calculated by using the amount of the uncrystallized mother liquor.

[0013] In the application, the crude vinylene carbonate entering the crystallization kettle is subjected to dynamic circulation cooling crystallization and melt crystallization by using the new process of dynamic melt crystallization, the whole process does not need long sweating operation, the problems existing in the traditional static melt crystallization purification process, such as long sweating process time, multiple inspection of sweat, and difficult control of the sweating process, are solved, the method of the application can be used for continuous purification, the loss in the multiple sweating inspection process can be avoided, and the yield of the vinylene carbonate is greatly improved.

[0014] Further, the application further provides a device used in the process of the dynamic melt crystallization method for purifying the vinylene carbonate, which comprises: a feed circulating pump, a raw material storage tank, a product storage tank, a discharge pump, and a crystallization kettle; the feed circulating pump is connected with the raw material storage tank and the crystallization kettle, and is used for conveying the crude vinylene carbonate solution raw material in the raw material storage tank to the crystallization kettle; the crystallization kettle is provided with a heat exchange medium inlet and a heat exchange medium outlet.

[0015] The bottom outlet of the crystallization kettle is connected with a three-way valve, and the three-way valve and the connected pipelines are respectively connected with the raw material storage tank and the product storage tank; wherein, the uncrystallized vinylene carbonate mother liquor and the unqualified vinylene carbonate product flowing out of the crystallization kettle re-enter the raw material storage tank through the pipelines, so as to realize the operation of the dynamic circulation cooling crystallization of the crude vinylene carbonate; finally, the qualified vinylene carbonate melt liquid in the crystallization kettle enters the product storage tank through the pipelines, and is discharged through the discharge pump.

[0016] In the above device, preferably, the crystallization kettle is composed of a shell and a spiral pipe spirally wound in the shell.

[0017] Preferably, the spiral pipe spirally wound in the shell of the crystallization kettle has a spiral height of 0.3-0.8 m, a spiral diameter of 0.2-0.3 m, and a pipe inner diameter of 10-20 mm.

[0018] More preferably, the spiral pipe spirally wound in the crystallization kettle has a spiral height of 0.5 m, a spiral diameter of 0.3 m, and a pipe inner diameter of 20 mm.

[0019] Preferably, the shell of the crystallization kettle and the spiral pipe spirally wound in the shell are made of transparent glass or stainless steel.

[0020] Preferably, when the shell of the crystallization kettle and the spiral pipe spirally wound in the shell are made of transparent glass, a camera is arranged at 15-30 cm outside the center line of the crystallization kettle, and the height of the camera can be adjusted as needed.

[0021] In the present application, a heat exchange medium inlet and a heat transfer medium outlet are arranged on the crystallization kettle. During dynamic circulation cooling crystallization, cooling medium is introduced to cool the raw material in the spiral pipe spirally wound in the crystallization kettle, so that the crude vinylene carbonate is crystallized and adheres to the inner wall of the spiral pipe.

[0022] In the present application, if a conventional crystallization kettle made of stainless steel is used, the thickness of the vinylene carbonate crystalline layer cannot be observed in the equipment, and thus the thickness of the crystalline layer can only be calculated by using the amount of uncrystallized mother liquor. The mass of uncrystallized vinylene carbonate mother liquor is controlled to account for 20-60% of the initial mass of the vinylene carbonate raw material storage tank.

[0023] Of course, in the laboratory small test stage, in order to more conveniently observe the crystallization of the crude vinylene carbonate in the crystallization kettle, the shell of the crystallization kettle and the spiral pipe spirally wound in the shell are made of transparent glass, and a camera is arranged outside the shell. Thus, the thickness of the crystalline layer in the crystalline pipe can be estimated by comparing the photos taken by the camera and combining related software, so as to further determine the length of the dynamic cooling crystallization time and avoid the blockage of the inner wall of the crystalline pipe caused by the too large thickness of the crystalline layer due to the too long crystallization time.

[0024] Further, in the actual production process, the processing capacity of the crystallization kettle equipment can be controlled by adjusting the spiral height, spiral diameter and pipe inner diameter of the spiral pipe spirally wound in the crystallization kettle.

[0025] The present application has the following beneficial effects:

[0026] (1) A novel purification process for electronic grade vinylene carbonate is provided, namely, by using dynamic cyclic cooling crystallization and melt crystallization, the problems of excessively long sweating cycle, low single-pass yield, and need for multiple crystallizations in the traditional static melt crystallization purification process of vinylene carbonate are solved. The purity of the obtained finished vinylene carbonate can reach 99.99%, and the yield is above 63%. The purification process provided by this invention can be continuously purified, breaking the shackles in the scale increase of electronic grade vinylene carbonate production capacity.

[0027] (2) The present invention improves the crystallization vessel structure in the purification process of vinylene carbonate. The internal structure of the crystallization vessel is changed from the traditional tubular pipeline to a spiral winding spiral tube structure. The length-diameter relationship of the pipeline is reasonably adjusted, which significantly improves the heat exchange area of ​​the crystallization vessel. At the same time, by means of dynamic circulation cooling crystallization and reasonable control of crude product crystallization, the cooling cycle time of dynamic circulation is reasonably adjusted, avoiding the problem of blockage of the winding pipeline.

[0028] (3) In this invention, the shell of the crystallization vessel and the spiral tube inside the shell are made transparent, which is beneficial to clearly determine the crystallization thickness of crude vinylene carbonate in the crystallization vessel. Attached Figure Description

[0029] Figure 1 This is the apparatus used in the dynamic melt crystallization purification process of vinylene carbonate in Embodiment 1 of the present invention;

[0030] Among them, 1-feed circulation pump, 2-raw material storage tank, 3-product storage tank, 4-discharge pump, 5-crystallization kettle, 6-heat exchange medium inlet, 7-heat exchange medium outlet, and 8-camera.

[0031] Figure 2 This is a schematic diagram of the spiral tube inside the crystallization vessel in Embodiment 1 of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.

[0033] Example 1

[0034] The apparatus used in a dynamic melt crystallization process for purifying vinylene carbonate is shown in the attached diagram. Figure 1 As shown, the device includes: a feed circulation pump 1, a raw material storage tank 2, a product storage tank 3, a discharge pump 4, and a crystallization kettle 5; the feed circulation pump 1 is connected to the raw material storage tank 2 and the crystallization kettle 5, and is used to transport the crude vinylene carbonate solution raw material in the raw material storage tank 2 to the crystallization kettle 5.

[0035] The crystallization kettle 5 is provided with a heat exchange medium inlet 6 and a heat exchange medium outlet 7.

[0036] The bottom outlet of the crystallization kettle 5 is connected with a three-way valve, which is connected with the raw material storage tank 2 and the product storage tank 3 through pipes; wherein, the uncrystallized vinylene carbonate mother liquor and unqualified vinylene carbonate product flowing out of the crystallization kettle 5 re-enter the raw material storage tank 2 through the pipes, so as to realize the dynamic circulating cooling crystallization operation of the crude vinylene carbonate product; finally, the qualified vinylene carbonate melt in the crystallization kettle 5 enters the product storage tank 3 through the pipes, and is discharged through the discharge pump 4.

[0037] The shell of the crystallization kettle 5 and the spiral pipe spirally wound in the shell in the embodiment are both made of transparent glass material.

[0038] A structural diagram of the spiral pipe spirally wound in the shell of the crystallization kettle is shown in FIG. 2. Figure 2 As shown in FIG. 2, the spiral pipe has a spiral height of 0.5 m, a spiral diameter of 0.3 m, and an inner diameter of 20 mm.

[0039] In addition, a camera 8 is arranged at a position 30 cm outside the center line of the crystallization kettle 5, and the camera 8 can be adjusted up and down according to actual needs.

[0040] Embodiment 2

[0041] The device provided in Embodiment 1 is used to purify vinylene carbonate by a dynamic melt crystallization method, and the process specifically includes the following steps:

[0042] S1, the feed circulating pump 1 is started to transport the crude vinylene carbonate solution from the raw material storage tank 2 (crude vinylene carbonate 500 g, purity 98.26%) to the crystallization kettle 5, and the output flow of the feed circulating pump 1 is controlled by the PLC control system, the feed temperature is set to 30°C, and the inlet flow rate of the crude vinylene carbonate solution is 280 mL / min;

[0043] The valves of the heat exchange medium inlet 6 and the heat exchange medium outlet 7 of the crystallization kettle 5 are opened, the cooling medium is introduced into the shell, the raw material crude vinylene carbonate in the spiral pipe in the shell of the crystallization kettle 5 is cooled, and the three-way valve connected with the bottom outlet of the crystallization kettle 5 is opened to connect the raw material storage tank 2 through the pipe, so as to realize the dynamic circulating cooling crystallization operation of the crude vinylene carbonate raw material by circulating the raw material between the raw material storage tank 2 and the crystallization kettle 5;

[0044] During the cooling of the crystallization kettle 5, the inlet temperature of the cooling medium is 10°C, the cooling rate is 4°C / h, and the cooling time is 2 h.

[0045] S2, when the feed amount of the crude vinylene carbonate solution accounts for 85% of the volume of the crystallization kettle, the feed circulating pump 1 is closed, the crude vinylene carbonate raw material is stopped from being transported from the raw material storage tank 2 to the crystallization kettle 5, and the valves of the heat exchange medium inlet 6 and the heat exchange medium outlet 7 of the crystallization kettle 5 are closed, and then the uncrystallized vinylene carbonate mother liquor in the crystallization kettle 5 is discharged back to the raw material storage tank 2 through the three-way valve.

[0046] S3, the valves of the heat exchange medium inlet 6 and the heat exchange medium outlet 7 of the crystallization kettle 5 are opened, the heating medium is introduced into the shell, the crystallized vinylene carbonate in the spiral pipe of the crystallization kettle 5 is warmed, the temperature is kept at 26°C, the residence time is 0.5 h, the crystallized vinylene carbonate layer in the spiral pipe of the crystallization kettle 5 is melted into a vinylene carbonate melt, the bottom outlet three-way valve of the crystallization kettle 5 is opened to communicate with the product storage tank 3, the valve of the raw material storage tank 2 is closed, the temperature is continuously warmed to 30°C, the vinylene carbonate melt obtained in the crystallization kettle 5 is discharged into the product storage tank 3, and when the liquid level of the product storage tank 3 reaches the set value, the discharge pump 4 is started to discharge.

[0047] The vinylene carbonate product obtained by the above purification method is detected by HPLC method, the purity of the product is 99.99%, and the yield is 65.85%.

[0048] In the above experimental process, the crystallization thickness during dynamic circulating cooling crystallization is estimated from the monitoring software and on-site pictures, and it is obtained that the crystal layer thickness in the crystallization pipe is about 3 mm.

[0049] Example 3

[0050] The device provided in Example 1 is used, and the difference from the device in Example 1 is that the spiral height of the spiral pipe in the crystallization kettle 5 is 0.5 m, the spiral diameter is 0.3 m, and the inner diameter of the spiral pipe is 15 mm, and the rest of the device and the connection relationship are the same as in Example 1.

[0051] The process for purifying vinylene carbonate by a dynamic melt crystallization method specifically includes the following steps:

[0052] S1, the feed circulating pump 1 is started to transport the crude vinylene carbonate solution from the raw material storage tank 2 (500 g of crude vinylene carbonate with a purity of 98.26%) to the crystallization kettle 5, and the output flow of the feed circulating pump 1 is controlled by the PLC control system, the feed temperature is set to 35°C, and the inlet flow rate of the crude vinylene carbonate solution is 250 mL / min;

[0053] The valves of the heat exchange medium inlet 6 and the heat exchange medium outlet 7 of the crystallization kettle 5 are opened, the cooling medium is introduced into the shell, the raw product vinylene carbonate in the spiral pipe in the shell of the crystallization kettle 5 is cooled, and the three-way valve connected to the bottom outlet of the crystallization kettle 5 is opened to be connected to the raw material storage tank 2 through the pipeline, so that the raw material is circulated between the raw material storage tank 2 and the crystallization kettle 5, and the dynamic circulating cooling crystallization operation of the raw product vinylene carbonate is realized.

[0054] In the process of cooling the crystallization kettle 5, the inlet temperature of the cooling medium is 15℃, the cooling rate is 4℃ / h, and the cooling time is 2h.

[0055] S2, when the feed amount of the crude product vinylene carbonate solution accounts for 85% of the volume of the crystallization kettle, the feed circulating pump 1 is closed, the feed of the crude product vinylene carbonate from the raw material storage tank 2 to the crystallization kettle 5 is stopped, and the valves of the heat exchange medium inlet 6 and the heat exchange medium outlet 7 of the crystallization kettle 5 are closed, then the uncrystallized vinylene carbonate mother liquor in the crystallization kettle 5 is discharged back to the raw material storage tank 2.

[0056] S3, the valves of the heat exchange medium inlet 6 and the heat exchange medium outlet 7 of the crystallization kettle 5 are opened, the heating medium is introduced into the shell, the crystallized vinylene carbonate in the spiral pipe in the crystallization kettle 5 is heated, the temperature is kept at 22℃, the crystallized vinylene carbonate in the spiral pipe in the crystallization kettle 5 melts into vinylene carbonate melt, the three-way valve at the bottom outlet of the crystallization kettle 5 is opened to be connected to the product storage tank 3, the valve of the raw material storage tank 2 is closed, the temperature is continuously increased to 30℃, the vinylene carbonate melt obtained in the crystallization kettle 5 is discharged into the product storage tank 3, and when the liquid level of the product storage tank 3 reaches the set value, the discharge pump 4 is started to discharge.

[0057] The vinylene carbonate product obtained by the method of the embodiment is detected by HPLC, the purity of the product is 99.99%, and the yield is 63.57%.

[0058] In addition, it can be estimated from the monitoring software and the on-site pictures that the thickness of the crystal layer in the crystallization pipe is about 3.5 mm.

[0059] Comparative Example 1

[0060] The process used in the comparative example is the same as that of Example 1, except that a common straight pipe crystallization pipe is used in the crystallization kettle 5 instead of the spiral winding crystallization pipe in Example 1, wherein the pipe height of the common straight pipe crystallization pipe arranged in the crystallization kettle 5 is 0.5 m, and the inner diameter of the pipe is 20 mm.

[0061] The vinylene carbonate product obtained in the comparative example is detected by HPLC, the purity of the product is 98.62%, and the yield is 40.25%.

[0062] Obviously, even after purification, the quality of the vinylene carbonate product is only slightly improved, with purity improved by 98.62%-98.26%=0.36%, which fails to reach the electronic grade and needs to be reprocessed.

[0063] From the monitoring software and the on-site pictures, it can be estimated that the thickness of the crystal layer in the crystallization tube is about 4 mm.

[0064] Comparative Example 2

[0065] The process adopted in the present comparative example is the same as that in Example 2, except that the ordinary straight-tube crystallization tube is used to replace the spiral-wound crystallization tube in Example 1, wherein the tube height of the ordinary straight-tube crystallization tube arranged in the crystallization kettle 5 is 0.5 m, and the inner diameter of the pipeline is 15 mm.

[0066] In addition, the feeding temperature of the crude vinylene carbonate raw material is 30°C, the feeding flow rate is 250 mL / min, and the rest of the operations are the same as those in Example 2.

[0067] The obtained vinylene carbonate product is detected by HPLC, and the purity of the product is 98.5%, and the yield is 39.89%. Obviously, the purity of the product is only slightly improved, i.e. 98.5%-98.26%=0.24%, and the purity is improved by 0.24%, which also fails to meet the electronic grade requirements.

[0068] From the monitoring software and the on-site pictures, it can be estimated that the thickness of the crystal layer in the crystallization tube is about 4 mm.

[0069] In order to more clearly compare the influence of the changes of different process parameters and devices on the purity of the product, the parameter settings and the purity of the obtained product in each example and each comparative example are arranged in the form of a table, which is shown in Table 1 below.

[0070] Table 1 Quality of products obtained under different conditions in each experimental group

[0071]

[0072] The data in Table 1 shows that the purity of the vinylene carbonate product obtained by using the crystallization kettle with the spiral-wound crystallization tube and the operation of dynamic melt crystallization in each example is significantly improved, and the purity of the product in Examples 1-2 is more than 99.99%. In addition, the process of dynamic melt crystallization in the present application also avoids the loss of the product to some extent, and the yield of the vinylene carbonate product is more than 63%.

[0073] In the Example 1-2, the product was purified by using a traditional crystallization kettle. The purification degree was low, the thickness of the crystallization layer was large, the product loss was large, and the yield was significantly reduced. The yield of the product in the Example 1-2 was only about 40%, and the waste of raw materials was obviously serious.

Claims

1. A process for purifying vinylene carbonate by a dynamic melt crystallization process, characterized in that, The method comprises the following steps: S1, the crude vinylene carbonate solution is transported from the raw material tank to the crystallization kettle, at the same time, the cooling water circulation of the crystallization kettle is started, the dynamic circulation cooling crystallization operation of the crude vinylene carbonate entering the crystallization kettle is started, the raw material is circulated between the raw material tank and the crystallization kettle; in the process of dynamic circulation cooling crystallization, the cooling medium is introduced, the cooling medium cools the raw material in the spiral pipe winding spirally in the crystallization kettle, so that the crude vinylene carbonate is crystallized and attached to the inner wall of the spiral pipe winding spirally; S2, when the feeding amount of the crude vinylene carbonate solution accounts for 50-85% of the volume of the crystallization kettle, the feeding is stopped, and the cooling water circulation operation of the crystallization kettle in S1 is stopped, then the uncrystallized vinylene carbonate mother liquor in the crystallization kettle is discharged back to the raw material tank; S3, after the operation in S2 is completed, the hot water circulation of the crystallization kettle is started, the crystallized vinylene carbonate solid in the crystallization kettle is melted, then the melted vinylene carbonate melt is discharged to the product tank, and the high-purity vinylene carbonate product is obtained.

2. A process for purifying vinylene carbonate by a dynamic melt crystallization process according to claim 1, characterized in that, In S1, the feeding temperature of the crude vinylene carbonate solution transported from the raw material tank to the crystallization kettle is 25-30℃, and the feeding speed is 100-300 mL / min.

3. A process for purifying vinylene carbonate by a dynamic melt crystallization process as claimed in claim 1, wherein, In S1, each mass point in the vinylene carbonate solution passes through the crystallization kettle once every 100-600 s.

4. A process for purifying vinylene carbonate by a dynamic melt crystallization process as claimed in claim 1, wherein, In S1, when the cooling water circulates, the inlet temperature of the cooling water is 5-30℃, and the outlet temperature is 10-35℃; in the process of dynamic circulation cooling crystallization, gradient cooling is implemented, the cooling rate is 5-10℃ / h, and the time length of dynamic circulation cooling crystallization is 0.5-6 h.

5. A process for purifying vinylene carbonate by a dynamic melt crystallization process as claimed in claim 1, wherein, In S2, the mass of the uncrystallized vinylene carbonate mother liquor accounts for 20-60% of the initial mass of the raw material tank.

6. The apparatus for the purification of vinylene carbonate by a dynamic melt crystallization process according to claim 1, characterized in that, The method comprises the following steps: The crystallization kettle (5) is connected with the raw material tank (2) and the product tank (3) through a three-way valve, and the uncrystallized vinylene carbonate mother liquor and the unqualified vinylene carbonate product flowing out of the crystallization kettle (5) reenter the raw material tank (2) through the pipeline, so that the dynamic circulation cooling crystallization operation of the crude vinylene carbonate is realized; finally, the qualified vinylene carbonate melt in the crystallization kettle (5) enters the product tank (3) through the pipeline, and is discharged through the discharge pump (4).

7. A device for purifying vinylene carbonate by a dynamic melt crystallization process according to claim 6, wherein The crystallization kettle (5) is composed of a shell and a spiral pipe winding spirally in the shell.

8. A device for purifying vinylene carbonate by a dynamic melt crystallization process according to claim 7, wherein The spiral pipe winding spirally in the shell of the crystallization kettle (5) has a spiral height of 0.3-0.8 m, a spiral diameter of 0.2-0.3 m, and an inner diameter of 10-20 mm.

Images