A method for synthesizing vinylene carbonate by low-temperature oxidation

Abstract

The present invention relates to a method for synthesizing vinylene carbonate by low-temperature oxidation, characterized in that vinylene carbonate is used as a raw material, ozone is used as an oxidant, a tubular reactor is used as a reaction device for reaction, and the material after the reaction enters a product separation unit to obtain high-purity vinylene carbonate. The present invention adopts a one-step oxidation method to obtain highly selective vinylene carbonate, avoiding the problems of serious pollution, poor safety, low yield, high cost, etc. of the existing chlorination-dechlorination two-step process. The reaction temperature of the method for synthesizing vinylene carbonate by low-temperature oxidation of the present invention is 40-80°C, and the VC yield is 42.3-83.2%. When the temperature is 50-60°C, the VC yield is above 70%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and in particular relates to a method for synthesizing vinylene carbonate by low-temperature oxidation. Background Art

[0002] Vinylene carbonate is an important polymer intermediate and a key additive in lithium battery electrolyte. In recent years, the demand for lithium-ion batteries, especially lithium-ion power batteries, has grown rapidly, and the demand for vinylene carbonate has also grown rapidly. At present, the industrial production of vinylene carbonate is based on vinylene carbonate as a raw material, which is photocatalytically chlorinated to chloroethylene carbonate, and then dechlorinated under the action of triethylamine to synthesize vinylene carbonate, and the crude product is subjected to vacuum distillation and crystallization to obtain the product. The main disadvantages of this process are long reaction time, low reaction yield, more by-products, obvious three wastes, impurities wrapped in the product obtained by crystallization, and it is difficult to further improve the purity. Due to the particularity of the process and the chlorine raw material, the production capacity of vinylene carbonate has grown slowly, resulting in a rapid increase in the price of vinylene carbonate in recent years. Therefore, how to cleanly and efficiently selectively prepare high-purity vinylene carbonate is a key technical problem that the industry needs to solve urgently. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention aims to provide a method for synthesizing vinylene carbonate by low-temperature oxidation. The catalyst involved in the method is cheap, easy to obtain, and highly active. The reaction time is short, and continuous production can be achieved.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] The invention provides a method for synthesizing vinylene carbonate by low-temperature oxidation, which uses vinylene carbonate as a raw material, ozone as an oxidant, and a tubular reactor as a reaction device for reaction, and the materials after the reaction enter a product separation unit to obtain high-purity vinylene carbonate.

[0006] In some embodiments of the present invention, the molar ratio of ethylene carbonate to ozone is between 1:1 and 1:5, preferably 1:1 to 1:2.

[0007] In some embodiments of the present invention, fillers are packed in the tubular reactor to increase the gas-liquid contact area and improve the mass transfer rate.

[0008] In some embodiments of the present invention, the reaction pressure is normal pressure, and the reaction temperature is 40-100°C, preferably 40-60°C.

[0009] In some embodiments of the present invention, the product separation unit comprises a gas-liquid separation tank, a primary vacuum distillation tower, a secondary vacuum distillation tower and an ozone absorption tank.

[0010] Furthermore, the separation process of the product separation unit is:

[0011] The outlet material of the tubular reactor is separated by a gas-liquid separation tank, the gaseous material is treated by an ozone absorption tank and then discharged, the liquid material enters a primary vacuum distillation tower, water vapor and other light component by-products are extracted from the top of the primary vacuum distillation tower, and the bottom material of the primary vacuum distillation tower enters a secondary vacuum distillation tower to further separate vinylene carbonate and unreacted vinyl carbonate.

[0012] In some embodiments of the present invention, during the separation process of the product separation unit, the ozone absorption tank contains a sodium thiosulfate solution.

[0013] In some embodiments of the present invention, during the separation process of the product separation unit, the bottom temperature of the first vacuum distillation tower is 40-80°C, preferably 50-70°C, and the absolute pressure at the top of the tower is 0-20 kPa, preferably 5-10 kPa.

[0014] In some embodiments of the present invention, during the separation process of the product separation unit, the bottom temperature of the secondary vacuum distillation tower is 70-120°C, preferably 80-100°C, and the absolute pressure at the top of the tower is 0-20 kPa, preferably 5-10 kPa.

[0015] In some embodiments of the present invention, during the separation process of the product separation unit, vinylene carbonate is obtained at the top of the secondary vacuum distillation tower, and unreacted vinyl carbonate is obtained at the bottom of the tower.

[0016] The invention provides a method for synthesizing vinylene carbonate by low-temperature oxidation. The method is a continuous synthesis method and involves the following steps: vinylene carbonate enters a reactor through a liquid delivery pump; O3 is generated by an ozone generator and then delivered to the reactor; in the reactor, vinylene carbonate is oxidized by ozone to generate vinylene carbonate; and the product is subjected to multi-stage vacuum distillation after gas-liquid separation to obtain pure vinylene carbonate.

[0017] Compared with the prior art, the present invention adopts a one-step oxidation method to obtain highly selective vinylene carbonate, avoiding the problems of serious pollution, poor safety, low yield, high cost, etc. of the existing chlorination-dechlorination two-step process. The reaction temperature of the low-temperature oxidation method for synthesizing vinylene carbonate of the present invention is 40-80°C, and the VC yield is 42.3-83.2%. When the temperature is 50-60°C, the VC yield is above 70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic diagram of a process flow of synthesizing vinylene carbonate by low-temperature oxidation in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] refer to Figure 1 , is a schematic diagram of the process flow of low-temperature oxidation synthesis of vinylene carbonate, and ozone is prepared by passing oxygen through an ozone generator. Ethylene carbonate (EC) is first stored in an EC storage tank and enters an oxidation reactor (using a tubular reactor) through an EC pump. The method for synthesizing vinylene carbonate by low-temperature oxidation is to use vinylene carbonate as a raw material, ozone as an oxidant, and use a tubular reactor as a reaction device for reaction, and the reacted materials enter a product separation unit, and the product separation unit comprises a gas-liquid separation tank, a primary vacuum distillation tower, a secondary vacuum distillation tower and an ozone absorption tank. Among them, the separation process of the product separation unit is as follows: the outlet material of the tubular reactor is separated by a gas-liquid separation tank, the gas phase material is treated by an ozone absorption tank and then emptied, the liquid phase material enters a primary vacuum distillation tower, water vapor and other light component by-products are extracted from the top of the primary vacuum distillation tower, the bottom material of the primary vacuum distillation tower enters a secondary vacuum distillation tower for further separation, and the top of the secondary vacuum distillation tower obtains vinylene carbonate (pure VC product), and the bottom of the tower obtains unreacted vinyl carbonate.

[0021] Table 1 shows the reaction conditions and yields of synthesizing vinylene carbonate by catalytic oxidation of ethylene carbonate with O3 under different conditions in Examples 1-10. Examples 1-10 in Table 1 were carried out in a tubular reactor, and the products after the reaction were subjected to gas-liquid separation and vacuum distillation to remove water, by-products and unreacted EC in the products, and the components after vacuum distillation were analyzed by gas chromatography, thereby calculating the VC yield.

[0022] In the following Examples 1-10, the ozone absorption tank contains sodium thiosulfate solution. The bottom temperature of the primary vacuum distillation tower is 60°C, and the absolute pressure at the top of the tower is 8 kPa. The bottom temperature of the secondary vacuum distillation tower is 90°C, and the absolute pressure at the top of the tower is 8 kPa.

[0023] Table 1. Yield of synthesizing vinylene carbonate by catalytic oxidation of ethylene carbonate with O3 under different conditions

[0024]

[0025]

[0026] Examples 1-5

[0027] The volume flow rate of ethylene carbonate is 0.1 mL / min, the mass flow rate of O3 is 5 g / h, the reaction temperature is 40-80°C, the product after the reaction is separated into gas and liquid, and then vacuum distilled to obtain pure vinylene carbonate, which is analyzed and quantified by gas chromatography. When the reaction is carried out at 40-80°C, the VC yield is 42.3-83.2%, and when the temperature is 50-60°C, the VC yield is above 70%.

[0028] Examples 6-10

[0029] The volume flow rate of ethylene carbonate is 0.1 mL / min, the mass flow rate of O3 is 10 g / h, the reaction temperature is 40-80°C, the product after the reaction is separated by gas-liquid separation, and then vacuum distillation is performed to obtain pure vinylene carbonate, which is analyzed and quantified by gas chromatography. When the reaction is performed at 40-80°C, the VC yield is 60.6-84.8%, and when the temperature is 50-60°C, the VC yield is above 75%.

[0030] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for synthesizing vinylene carbonate by low temperature oxidation, characterized in that: Using ethylene carbonate as raw material and ozone as oxidant, a tubular reactor is used as a reaction device for reaction, and the materials after the reaction enter the product separation unit to obtain pure vinylene carbonate; The reaction pressure is normal pressure, and the reaction temperature is 40-100°C.

2. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 1, characterized in that: The molar ratio of ethylene carbonate to ozone is between 1:1 and 1:

5.

3. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 2, characterized in that: The molar ratio of ethylene carbonate to ozone is between 1:1 and 1:

2.

4. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 1, characterized in that: Filling the tubular reactor with fillers increases the gas-liquid contact area and improves the mass transfer rate.

5. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 1, characterized in that: The reaction pressure is normal pressure, and the reaction temperature is 40-60°C.

6. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 1, characterized in that: The product separation unit comprises a gas-liquid separation tank, a primary vacuum distillation tower, a secondary vacuum distillation tower and an ozone absorption tank; The separation process of the product separation unit is: The outlet material of the tubular reactor is separated by a gas-liquid separation tank, the gaseous material is treated by an ozone absorption tank and then discharged, the liquid material enters a primary vacuum distillation tower, water vapor and other light component by-products are extracted from the top of the primary vacuum distillation tower, and the bottom material of the primary vacuum distillation tower enters a secondary vacuum distillation tower to further separate vinylene carbonate and unreacted vinyl carbonate.

7. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 6, characterized in that: The ozone absorption tank contains sodium thiosulfate solution.

8. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 6, characterized in that: The bottom temperature of the first-stage vacuum distillation tower is 40-80°C, and the absolute pressure at the top of the tower is 0-20kPa.

9. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 8, characterized in that: The bottom temperature of the first-stage vacuum distillation tower is 50-70°C, and the absolute pressure at the top of the tower is 5-10 kPa.

10. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 6, characterized in that: The bottom temperature of the secondary vacuum distillation tower is 70-120°C, and the absolute pressure at the top of the tower is 0-20kPa.

11. The method for synthesizing vinylene carbonate by low-temperature oxidation according to claim 10, characterized in that: The bottom temperature of the secondary vacuum distillation tower is 80-100°C, and the absolute pressure at the top of the tower is 5-10kPa.

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