Direct synthesis preparation method of ethylene carbonate

Abstract

The invention relates to the technical field of ethylene carbonate, in particular to a direct synthesis preparation method of ethylene carbonate, which comprises the following steps: S1, raw material preparation: the raw materials comprise ethylene oxide, carbon dioxide and a catalyst, the mass ratio of ethylene oxide to carbon dioxide to the catalyst is 1: (1.2-1.4): (0.006-0.008), the catalyst is prepared from modified quaternary ammonium salt, modified ferroferric oxide and a solvent, and the solvent is a solvent; the mass ratio of the modified quaternary ammonium salt to the modified ferroferric oxide to the solvent is 1: (0.2-0.4): (2-3). According to the method, the catalytic activity of quaternary ammonium salt on the reaction of ethylene oxide and carbon dioxide can be enhanced through treatment of the polyhexamethylene biguanide solution, side reactions can be reduced through high catalytic activity, ethylene oxide and carbon dioxide are promoted to react more efficiently to generate ethylene carbonate, and therefore the purity and yield of a synthesized product are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene carbonate, and specifically provides a direct synthesis preparation method of ethylene carbonate. Background Art

[0002] Ethylene carbonate is an important organic compound. It is a colorless transparent liquid at room temperature with a slight ether smell. It has characteristics such as a high dielectric constant and good chemical stability, and is widely used in multiple fields. In the lithium battery industry, it is often used as an electrolyte solvent, which can effectively improve the battery performance.

[0003] In the prior art, in the synthesis and preparation process of ethylene carbonate, the selected catalyst has a low selectivity for the reaction to generate ethylene carbonate, and various by-products are easily generated during the reaction. These by-products are mixed into the product, resulting in a decrease in purity. Based on this, the present invention provides a direct synthesis preparation method of ethylene carbonate. Summary of the Invention

[0004] The purpose of the present invention is to provide a direct synthesis preparation method of ethylene carbonate. The ethylene carbonate prepared by the present invention not only has good purity performance but also has excellent yield performance.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A direct synthesis preparation method of ethylene carbonate, including the following steps:

[0006] S1: Raw material preparation. The raw materials include ethylene oxide, carbon dioxide, and a catalyst. The mass ratio of ethylene oxide, carbon dioxide, and the catalyst is 1:(1.2 - 1.4):(0.006 - 0.008). The catalyst is prepared from a modified quaternary ammonium salt, modified iron tetroxide, and a solvent. The mass ratio of the modified quaternary ammonium salt, modified iron tetroxide, and the solvent is 1:(0.2 - 0.4):(2 - 3);

[0007] S2: Preliminary reaction. Ethylene oxide, carbon dioxide, and the catalyst are added to a reaction kettle for treatment to obtain a base material;

[0008] S3: Preparation treatment. The base material is purified to obtain ethylene carbonate.

[0009] Further, the modified quaternary ammonium salt is prepared by the following method: A quaternary ammonium salt, polydimethyldiallylammonium chloride, and water are added to a beaker and mixed. After mixing evenly, a mixed solution is added, and the water bath is heated to 60 - 70 °C and kept at a constant temperature for 2 - 4 h. The obtained product is subjected to filtration treatment, and the solid matter retained after filtration is sent into an oven. The oven is set at 60 - 80 °C for drying treatment for 1 - 2 h to obtain a powder. The powder is mixed with a polyhexamethyl biguanide solution and reacted at 0 - 6 °C for 2 - 4 h. The obtained product is sent into an oven. The oven is set at 40 - 60 °C for drying treatment for 4 - 6 h to obtain the modified quaternary ammonium salt.

[0010] Further, the mass ratio of quaternary ammonium salt, polydimethyldiallylammonium chloride, and water is 1:(0.2 - 0.4):(2 - 3), the mass ratio of the powder material to the polyhexamethylbiguanide solution is 1:(0.4 - 0.6), and the mass concentration of the polyhexamethylbiguanide solution is 2 - 4%.

[0011] Further, the modified iron oxide is selected from nano - iron oxide as the raw material, and the particle size of the nano - iron oxide is 2 - 10 nm.

[0012] Further, the modified iron oxide is prepared by the following method: Nano - iron oxide and aqueous citric acid solution are added to a reaction kettle. The reaction kettle is set at 200 - 300 r / min and stirred for 20 - 30 min. During the stirring process, the temperature is set at 50 - 60 °C. After the stirring treatment is completed, it is cooled to room temperature. The obtained product is washed with deionized water, then added to an oven and dried at 40 - 60 °C for 6 - 8 h. The dried product and sodium borohydride solution are added to a water bath kettle and stirred for 40 - 50 min under the condition of an ice - water bath. The obtained product is washed with deionized water to obtain the modified iron oxide.

[0013] Further, the mass ratio of nano - iron oxide to aqueous citric acid solution is 1:(2 - 4), the mass concentration of the aqueous citric acid solution is 10 - 20%, the concentration of the sodium borohydride solution is 0.6 - 1 mol / L, and the mass of the sodium borohydride solution is 10 - 20% of the mass of the nano - iron oxide.

[0014] Further, the solvent is prepared by mixing N,N - dimethylformamide and toluene, and the mass ratio of N,N - dimethylformamide to toluene is 1:(2 - 4).

[0015] Further, the method of the preliminary reaction is: Ethylene oxide, carbon dioxide, and a catalyst are added to a reaction kettle. The reaction kettle is set at a pressure of 2 - 4 MPa, a temperature of 120 - 200 °C, and a reaction time of 16 - 22 min. The obtained product is the base material.

[0016] Further, the method of the preparation treatment is: The base material is subjected to distillation treatment. The obtained product is added to a crystallizer and cooled by a jacket cooling method, and circulating cooling water is passed through. The temperature is decreased to 10 - 15 °C at a rate of 1 - 3 °C / min. The obtained product is added to an oven, and the oven is set at 40 - 60 °C for drying treatment for 2 - 4 h to obtain ethylene carbonate.

[0017] Further, the distillation treatment is set at a pressure of 6 - 10 kPa, a heating rate of 2 - 6 °C / min, and heated to 120 - 140 °C.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. In the present invention, during the synthesis and preparation of ethylene carbonate, the catalyst is treated. Among them, the quaternary ammonium salt is modified after reacting with poly(dimethyldiallylammonium chloride) and polyhexamethylene biguanide solution. Poly(dimethyldiallylammonium chloride) can increase the stability and dispersibility of the quaternary ammonium salt, enabling it to better play a catalytic role in the reaction system. The treatment with polyhexamethylene biguanide solution can enhance the catalytic activity of the quaternary ammonium salt for the reaction of ethylene oxide and carbon dioxide. The high catalytic activity can reduce the occurrence of side reactions, prompting ethylene oxide and carbon dioxide to react more efficiently to produce ethylene carbonate, thereby improving the purity and yield of the synthesized product.

[0020] 2. In the present invention, by adding nano-ferroferric oxide, nano-ferroferric oxide has a large specific surface area and high surface energy, which can provide more active sites and accelerate the reaction rate. After being modified with citric acid aqueous solution and sodium borohydride solution, the surface properties of nano-ferroferric oxide are optimized, further improving its catalytic activity and selectivity. During the reaction preparation process, it can provide more active sites, accelerate the reaction rate, make the reaction more complete, improve the yield, and at the same time help reduce the generation of impurities and improve the purity. Specific Embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0022] It should be noted that the raw materials used in the following embodiments are all commercially available raw materials.

[0023] Example 1:

[0024] S1: Raw material preparation. The raw materials include ethylene oxide, carbon dioxide, and a catalyst. The mass ratio of ethylene oxide, carbon dioxide, and the catalyst is 1:1.2:0.006. The catalyst is prepared from a modified quaternary ammonium salt, modified ferroferric oxide, and a solvent. The mass ratio of the modified quaternary ammonium salt, modified ferroferric oxide, and the solvent is 1:0.2:2;

[0025] The modified quaternary ammonium salt is prepared by the following method: The quaternary ammonium salt, polydimethyldiallylammonium chloride, and water are added to a beaker and mixed. After mixing evenly, the mixed solution is added. The water bath is heated to 60 °C and kept at a constant temperature for 2 h. The obtained product is filtered. The solid matter is retained after the filtration treatment. The solid matter is sent into an oven, and the oven is set to dry at 60 °C for 1 h to obtain a powder. The powder is mixed with a polyhexamethylene biguanide solution and reacted at 0 °C for 2 h. The obtained product is sent into an oven, and the oven is set to dry at 40 °C for 4 h to prepare the modified quaternary ammonium salt. The mass ratio of the quaternary ammonium salt, polydimethyldiallylammonium chloride, and water is 1:0.2:2, the mass ratio of the powder to the polyhexamethylene biguanide solution is 1:0.4, and the mass concentration of the polyhexamethylene biguanide solution is 2%;

[0026] The modified iron oxide is prepared by using nano iron oxide as a raw material. The particle size of the nano iron oxide is 2 nm. The modified iron oxide is prepared by the following method: The nano iron oxide and the citric acid aqueous solution are added to a reaction kettle. The reaction kettle is set to 200 r / min and stirred for 20 min. During the stirring process, the temperature is set to 50 °C. After the stirring treatment is completed, it is cooled to room temperature. The obtained product is washed with deionized water, and then added to an oven, which is set to dry at 40 °C for 6 h. The dried product and the sodium borohydride solution are added to a water bath kettle and stirred under the condition of an ice-water bath for 40 min. The obtained product is washed with deionized water to prepare the modified iron oxide. The mass ratio of the nano iron oxide to the citric acid aqueous solution is 1:2, the mass concentration of the citric acid aqueous solution is 10%, the concentration of the sodium borohydride solution is 0.6 mol / L, and the mass of the sodium borohydride solution is 10% of the mass of the nano iron oxide;

[0027] The solvent is prepared by mixing N,N-dimethylformamide and toluene. The mass ratio of N,N-dimethylformamide to toluene is 1:2;

[0028] S2: Preliminary reaction, ethylene oxide, carbon dioxide, and a catalyst are added to a reaction kettle for treatment to obtain a base material;

[0029] The method of the preliminary reaction is: Ethylene oxide, carbon dioxide, and a catalyst are added to a reaction kettle. The reaction kettle is set to a pressure of 2 MPa, a temperature of 120 °C, and a reaction time of 16 min. The obtained product is the base material;

[0030] S3: Preparation treatment, the base material is purified to obtain ethylene carbonate;

[0031] The preparation method is as follows: The base material is subjected to distillation treatment. The obtained product is added into a crystallizer, and the jacket cooling method is adopted. Circulating cooling water is introduced, and the temperature is decreased to 10°C at a rate of 1°C / min. The obtained product is added into an oven, and the oven is set at 40°C for drying treatment for 2 h to obtain ethylene carbonate. The set pressure for the distillation treatment is 6 kPa, and the heating rate is 2°C / min, and the temperature is raised to 120°C.

[0032] Example 2:

[0033] S1: Raw material preparation. The raw materials include ethylene oxide, carbon dioxide, and a catalyst. The mass ratio of ethylene oxide, carbon dioxide, and the catalyst is 1:1.3:0.007. The catalyst is prepared from a modified quaternary ammonium salt, modified iron tetroxide, and a solvent. The mass ratio of the modified quaternary ammonium salt, modified iron tetroxide, and the solvent is 1:0.3:2.5;

[0034] The modified quaternary ammonium salt is prepared by the following method: The quaternary ammonium salt, polydimethyldiallylammonium chloride, and water are added into a beaker and mixed. After mixing evenly, the mixed solution is added, and the temperature is raised to 65°C in a water bath and kept at a constant temperature for 3 h. The obtained product is subjected to filtration treatment, and the solid matter is retained during the filtration treatment. The solid matter is sent into an oven, and the oven is set at 70°C for drying treatment for 1.5 h to obtain a powder. The powder is mixed with a polyhexamethylene biguanide solution and reacted at 3°C for 3 h. The obtained product is sent into an oven, and the oven is set at 50°C for drying treatment for 5 h to obtain the modified quaternary ammonium salt. The mass ratio of the quaternary ammonium salt, polydimethyldiallylammonium chloride, and water is 1:0.3:2.5, the mass ratio of the powder to the polyhexamethylene biguanide solution is 1:0.5, and the mass concentration of the polyhexamethylene biguanide solution is 3%;

[0035] The modified iron tetroxide selects nano iron tetroxide as the raw material. The particle size of the nano iron tetroxide is 6 nm. The modified iron tetroxide is prepared by the following method: The nano iron tetroxide and a citric acid aqueous solution are added into a reaction kettle. The reaction kettle is set at 250 r / min and stirred for 25 min. During the stirring process, the temperature is set at 55°C. After the stirring treatment is completed, it is cooled to the normal temperature state. The obtained product is washed with deionized water, and then added into an oven, which is set at 50°C for drying treatment for 7 h. The dried obtained product and a sodium borohydride solution are added into a water bath kettle and stirred for 45 min under the condition of an ice water bath. The obtained product is washed with deionized water to obtain the modified iron tetroxide. The mass ratio of the nano iron tetroxide to the citric acid aqueous solution is 1:3, the mass concentration of the citric acid aqueous solution is 15%, the concentration of the sodium borohydride solution is 0.8 mol / L, and the mass of the sodium borohydride solution is 15% of the mass of the nano iron tetroxide;

[0036] The solvent is prepared by mixing N,N-dimethylformamide and toluene. The mass ratio of N,N-dimethylformamide and toluene is 1:3;

[0037] S2: Preliminary reaction. Ethylene oxide, carbon dioxide and a catalyst are added to a reaction kettle for treatment to obtain a base material.

[0038] The method for the preliminary reaction is as follows: Ethylene oxide, carbon dioxide and a catalyst are added to a reaction kettle. The set pressure of the reaction kettle is 3 MPa, the temperature is 160 °C, and the reaction time is 19 min. The obtained product is the base material.

[0039] S3: Preparation treatment. The base material is purified to obtain ethylene carbonate.

[0040] The method for the preparation treatment is as follows: The base material is subjected to distillation treatment. The obtained product is added to a crystallizer. The jacket cooling method is adopted, and circulating cooling water is introduced. The temperature is decreased at a rate of 1 - 3 °C / min to 13 °C. The obtained product is added to an oven. The oven is set at 50 °C for drying treatment for 3 h to obtain ethylene carbonate. The set pressure for the distillation treatment is 8 kPa, and the heating rate is 4 °C / min. The temperature is raised to 130 °C.

[0041] Example 3:

[0042] S1: Raw material preparation. The raw materials include ethylene oxide, carbon dioxide and a catalyst. The mass ratio of ethylene oxide, carbon dioxide and the catalyst is 1:1.4:0.008. The catalyst is prepared from a modified quaternary ammonium salt, modified iron tetroxide and a solvent. The mass ratio of the modified quaternary ammonium salt, modified iron tetroxide and the solvent is 1:0.4:3.

[0043] The modified quaternary ammonium salt is prepared by the following method: A quaternary ammonium salt, poly(dimethyldiallylammonium chloride) and water are added to a beaker and mixed. After mixing evenly, the mixed solution is added. The water bath is heated to 70 °C and kept at a constant temperature for reaction for 4 h. The obtained product is subjected to filtration treatment. The solid matter retained after the filtration treatment is sent into an oven. The oven is set at 80 °C for drying treatment for 2 h to obtain a powder. The powder is mixed with a polyhexamethylene biguanide solution and reacted at 6 °C for 4 h. The obtained product is sent into an oven. The oven is set at 60 °C for drying treatment for 6 h to obtain the modified quaternary ammonium salt. The mass ratio of the quaternary ammonium salt, poly(dimethyldiallylammonium chloride) and water is 1:0.4:3. The mass ratio of the powder to the polyhexamethylene biguanide solution is 1:0.6. The mass concentration of the polyhexamethylene biguanide solution is 4%.

[0044] Modified magnetite selects nano-magnetite as the raw material. The particle size of the nano-magnetite is 10 nm. The modified magnetite is prepared by the following method: The nano-magnetite and the citric acid aqueous solution are added into a reaction kettle. The reaction kettle is set at 300 r / min and stirred for 30 min. During the stirring process, the temperature is set at 60 °C. After the stirring treatment is completed, it is allowed to cool to room temperature. The obtained product is washed with deionized water, and then added into an oven and dried at 60 °C for 8 h. The dried product and the sodium borohydride solution are added into a water bath kettle and stirred for 50 min under the condition of an ice-water bath. The obtained product is washed with deionized water to obtain the modified magnetite. The mass ratio of the nano-magnetite to the citric acid aqueous solution is 1:4. The mass concentration of the citric acid aqueous solution is 10-20%. The concentration of the sodium borohydride solution is 1 mol / L. The mass of the sodium borohydride solution is 20% of the mass of the nano-magnetite;

[0045] The solvent is prepared by mixing N,N-dimethylformamide and toluene. The mass ratio of N,N-dimethylformamide to toluene is 1:4;

[0046] S2: Preliminary reaction. Ethylene oxide, carbon dioxide and a catalyst are added into a reaction kettle for treatment to obtain a base material;

[0047] The method of the preliminary reaction is: Ethylene oxide, carbon dioxide and a catalyst are added into a reaction kettle. The reaction kettle is set at a pressure of 4 MPa, a temperature of 200 °C, and a reaction time of 22 min. The obtained product is the base material;

[0048] S3: Preparation treatment. The base material is purified to obtain ethylene carbonate;

[0049] The method of the preparation treatment is: The base material is subjected to distillation treatment. The obtained product is added into a crystallizer and cooled by a jacket cooling method. Circulating cooling water is introduced and cooled to 15 °C at a rate of 3 °C / min. The obtained product is added into an oven and dried at 60 °C for 4 h to obtain ethylene carbonate. The distillation treatment is set at a pressure of 6-10 kPa and a heating rate of 6 °C / min and heated to 140 °C.

[0050] Comparative Example 1. The difference between this comparative example and Example 1 is that: In this comparative example, the preparation treatment is not carried out.

[0051] Comparative Example 2. The difference between this comparative example and Example 1 is that: In this comparative example, an equal amount of quaternary ammonium salt is selected to replace the catalyst.

[0052] Comparative Example 3. The difference between this comparative example and Example 1 is that: In this comparative example, there is no modified magnetite.

[0053] Comparative Example 4. The difference between this comparative example and Example 1 is that: In this comparative example, there is no modified quaternary ammonium salt.

[0054] Performance test: The ethylene carbonate prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 was subjected to performance testing, and the obtained test data was recorded in the following table:

[0055]

[0056] It can be seen that the purity performance and yield performance of the ethylene carbonate prepared in Comparative Examples 1, 2, 3, and 4 are lower than those in Examples 1, 2, and 3; this shows that: by treating the catalyst during the synthesis of ethylene carbonate, among which, the quaternary ammonium salt is modified after reacting with polydimethyldiallylammonium chloride and polyhexamethylene biguanide solution. Polydimethyldiallylammonium chloride can increase the stability and dispersibility of the quaternary ammonium salt, enabling it to play a better catalytic role in the reaction system. The treatment with polyhexamethylene biguanide solution can enhance the catalytic activity of the quaternary ammonium salt for the reaction of ethylene oxide and carbon dioxide. High catalytic activity can reduce the occurrence of side reactions, promoting the more efficient reaction of ethylene oxide and carbon dioxide to produce ethylene carbonate, thereby improving the purity and yield of the synthesized product;

[0057] By adding nano-ferroferric oxide, nano-ferroferric oxide has a large specific surface area and high surface energy, which can provide more active sites and accelerate the reaction rate. After being modified with citric acid aqueous solution and sodium borohydride solution, the surface properties of nano-ferroferric oxide are optimized, further improving its catalytic activity and selectivity. During the reaction preparation process, it can provide more active sites, accelerate the reaction rate, make the reaction more complete, improve the yield, and at the same time help reduce the generation of impurities and improve the purity.

[0058] By comparing and analyzing the relevant data in the table, it can be known that the ethylene carbonate prepared by the present invention not only has good purity performance but also excellent yield performance. This shows that the direct synthesis method of ethylene carbonate provided by the present invention has a broader market prospect and is more suitable for promotion.

[0059] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0060] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A direct synthesis preparation method of ethylene carbonate, characterized in that: It includes the following steps: S1: Raw material preparation. The raw materials include ethylene oxide, carbon dioxide, and a catalyst. The mass ratio of ethylene oxide, carbon dioxide, and the catalyst is 1:(1.2 - 1.4):(0.006 - 0.008). The catalyst is prepared from a modified quaternary ammonium salt, modified iron tetroxide, and a solvent. The mass ratio of the modified quaternary ammonium salt, modified iron tetroxide, and the solvent is 1:(0.2 - 0.4):(2 - 3); S2: Preliminary reaction. Ethylene oxide, carbon dioxide, and the catalyst are added to a reaction kettle for treatment to obtain a base material; S3: Preparation treatment. The base material is subjected to purification treatment to obtain ethylene carbonate.

2. The method for directly synthesizing ethylene carbonate according to claim 1, characterized in that, The modified quaternary ammonium salt is prepared by the following method: A quaternary ammonium salt, polydimethyldiallylammonium chloride, and water are added to a beaker and mixed. After mixing evenly, a mixed solution is added. The water bath is heated to 60 - 70°C and kept at a constant temperature for reaction for 2 - 4 h. The obtained product is subjected to filtration treatment. The solid matter retained after filtration treatment is sent into an oven. The oven is set to dry at 60 - 80°C for 1 - 2 h to obtain a powder. The powder is mixed with a polyhexamethylene biguanide solution and reacted at 0 - 6°C for 2 - 4 h. The obtained product is sent into an oven. The oven is set to dry at 40 - 60°C for 4 - 6 h to obtain the modified quaternary ammonium salt.

3. The method for directly synthesizing ethylene carbonate according to claim 2, wherein The mass ratio of the quaternary ammonium salt, polydimethyldiallylammonium chloride, and water is 1:(0.2 - 0.4):(2 - 3). The mass ratio of the powder to the polyhexamethylene biguanide solution is 1:(0.4 - 0.6). The mass concentration of the polyhexamethylene biguanide solution is 2 - 4%.

4. The method for directly synthesizing ethylene carbonate according to claim 1, wherein, The modified iron tetroxide selects nano - iron tetroxide as the raw material, and the particle size of the nano - iron tetroxide is 2 - 10 nm.

5. The direct synthesis preparation method of ethylene carbonate according to claim 1, characterized in that, The modified iron tetroxide is prepared by the following method: Nano - iron tetroxide and a citric acid aqueous solution are added to a reaction kettle. The reaction kettle is set to 200 - 300 r / min and stirred for 20 - 30 min. During the stirring process, the temperature is set to 50 - 60°C. After the stirring treatment is completed, it is allowed to cool to room temperature. The obtained product is washed with deionized water, and then added to an oven. The oven is set to dry at 40 - 60°C for 6 - 8 h. The dried product and a sodium borohydride solution are added to a water bath kettle and stirred under the condition of an ice - water bath for 40 - 50 min. The obtained product is washed with deionized water to obtain the modified iron tetroxide.

6. The method for directly synthesizing ethylene carbonate according to claim 5, wherein The mass ratio of nano - iron tetroxide to the citric acid aqueous solution is 1:(2 - 4). The mass concentration of the citric acid aqueous solution is 10 - 20%. The concentration of the sodium borohydride solution is 0.6 - 1 mol / L, and the mass of the sodium borohydride solution is 10 - 20% of the mass of the nano - iron tetroxide.

7. The direct synthesis preparation method of ethylene carbonate according to claim 1, characterized in that, The solvent is prepared by mixing N,N - dimethylformamide and toluene. The mass ratio of N,N - dimethylformamide and toluene is 1:(2 - 4).

8. The method for directly synthesizing ethylene carbonate according to claim 1, characterized in that, The method of the preliminary reaction is: Ethylene oxide, carbon dioxide, and the catalyst are added to a reaction kettle. The reaction kettle is set with a pressure of 2 - 4 MPa, a temperature of 120 - 200°C, and a reaction time of 16 - 22 min. The obtained product is the base material.

9. The direct synthesis preparation method of ethylene carbonate according to claim 1, characterized in that, The method of preparation treatment is as follows: the base material is subjected to distillation treatment, and the obtained product is added into a crystallizer. The jacket cooling method is adopted, and circulating cooling water is introduced. The temperature is decreased to 10 - 15°C at a rate of 1 - 3°C / min. The obtained product is added into an oven, and the oven is set at 40 - 60°C for drying treatment for 2 - 4 h to obtain ethylene carbonate.

10. The method for directly synthesizing ethylene carbonate according to claim 9, characterized in that, The set pressure for distillation treatment is 6 - 10 kPa, and the heating rate is 2 - 6°C / min, and the temperature is raised to 120 - 140°C.

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