Process method for improving crystallization yield of electronic-grade dimethyl carbonate

Abstract

The invention relates to the technical field of chemical production, and particularly discloses a process method for improving the crystallization yield of electronic-grade dimethyl carbonate, which comprises the following steps: re-purifying first-grade dimethyl carbonate (the purity is greater than or equal to 99.5%) extracted from a side line of a reactive distillation unit by using a melt crystallization process; the process parameters of three procedures of cooling crystallization, heating sweating and heating melting are mainly preferably selected, and the single-pass crystallization yield of the electronic-grade dimethyl carbonate is more than or equal to 60w% finally; according to the method, the crystallized electronic-grade dimethyl carbonate is further dehydrated by adopting a mesoporous molecular sieve, the water content of the electronic-grade dimethyl carbonate can be less than or equal to 0.003 w% by adopting a continuous feeding mode of 1-2ml / min and controlling the retention time of feed liquid to be 2-3h, and finally, various indexes of an electronic-grade DMC product meet the index requirements in the national standard GB / T 33107-2016. The electronic-grade dimethyl carbonate prepared by the method is high in single-pass crystallization rate and low in water content, materials in each process are effectively utilized, the resource utilization rate of the coal ethylene glycol byproduct DMC is effectively increased, and waste discharge is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, in particular to a process for improving the crystallization yield of electronic-grade dimethyl carbonate. Background Art

[0002] At present, industrial-grade dimethyl carbonate (DMC) is produced as a by-product in the production process of coal-to-ethylene glycol, with a unit consumption of 0.02t / t per ton of product. The specific process is as follows:

[0003] Main reaction:

[0004] 2CO+2CH3ONO==CH3OOCCOOCH3(DMO)+2NO

[0005] Side effects

[0006] CO+2CH3ONO==CH3OCOOCH3(DMC)+2NO

[0007] In order to improve resource utilization, reduce waste emissions, enhance energy conservation and environmental protection capabilities, and maintain green industrial development, it is urgent to optimize raw material utilization, accurately control process parameters, and adopt efficient energy-saving technologies. Among them, how to effectively improve the crystallization rate of dimethyl carbonate is an important part of building an efficient electronic-grade DMC production process, and it is also an urgent problem to be solved. At the same time, with the continuous increase in new energy vehicles today, the demand for lithium-ion battery electrolytes has also continued to expand, prompting a significant increase in the market demand for electronic-grade DMC.

[0008] The Chinese invention patent application with the publication number of CN 115073293 B discloses a method and device for preparing electronic-grade dimethyl carbonate by coupling reactive distillation and crystallization, which relates to the field of chemical production technology. The prior art: the superior dimethyl carbonate is purified by melt crystallization, and trace impurities are effectively removed to obtain electronic-grade dimethyl carbonate with a water content of ≤20ppm and a DMC purity of ≥99.99wt%; wherein the methanol-rich light components and heavy components in the bottom of the reactive distillation unit are returned to the original industrial device for distillation and purification to obtain industrial-grade dimethyl carbonate for further reuse, and the uncrystallized mother liquor and sweating liquid of the crystallization unit are returned to the reactive distillation unit for reuse, and the yield can reach more than 90%.

[0009] The prior art purifies industrial-grade dimethyl carbonate by coupling reactive distillation with melt crystallization, but the specific yield of melt crystallization is not clear (the single-pass crystallization yield in melt crystallization in the prior art is usually <60%). Even if the total yield can be more than 90%, it can only be achieved through multiple reuses, resulting in a significant increase in reaction energy consumption. To this end, we propose a process for improving the crystallization yield of electronic-grade dimethyl carbonate to solve the above problem. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention provides a process for improving the crystallization yield of electronic-grade dimethyl carbonate, thereby solving the problem of how to effectively improve the crystallization rate of dimethyl carbonate.

[0011] To achieve the above object, the present invention provides the following technical solution: a process for improving the crystallization yield of electronic grade dimethyl carbonate, comprising the following steps:

[0012] S1, first weigh a certain amount of primary dimethyl carbonate product raw material;

[0013] S2, pour the raw materials into the crystallization kettle, replace with nitrogen 3 times, and start stirring;

[0014] S3, cooling crystallization: the temperature of the material in the crystallization kettle is reduced to 6°C, and the temperature in the kettle is cooled down after it stabilizes. The low-temperature bath is cooled down at a rate of 1°C / h. When the temperature of the low-temperature bath drops to 2.5°C, the timing is started. After the constant temperature is maintained for 3 hours, the crystallization mother liquor is discharged to the reactive distillation process for reuse;

[0015] S4, heating and sweating: directly raise the temperature of the low-temperature bath to 3°C to enter the sweating stage. When the temperature in the kettle reaches 4°C, keep the constant temperature for 2 hours, and then discharge the sweating liquid to the reaction distillation process for reuse;

[0016] S5, heating and melting: after the sweating is completed, the low temperature bath is heated at a rate of 2.5°C / h until the solid melts, and the electronic grade dimethyl carbonate product is obtained. The weight is weighed to calculate the ratio, that is, the single-pass crystallization yield of electronic grade dimethyl carbonate prepared by the melt crystallization method is calculated;

[0017] S6, molecular sieve dehydration: The electronic grade dimethyl carbonate product obtained by melt crystallization (cooling crystallization, heating sweating, heating melting) is further dehydrated by molecular sieve, and finally the electronic grade DMC product indicators meet the requirements of the national standard GB / T 33107-2016.

[0018] As a preferred technical solution of the present invention, the primary dimethyl carbonate product raw material needs to be subjected to reactive distillation and dehydrogenation treatment.

[0019] As a preferred technical solution of the present invention, the stirring rate of the crystallization kettle in step S2 is 400r / min.

[0020] As a preferred technical solution of the present invention, the step 3, cooling crystallization: adopting programmed cooling to reach the final crystallization temperature, the crystallization temperature range is 2.2-2.7°C, preferably 2.5°C.

[0021] As a preferred technical solution of the present invention, the step 4, heating and sweating: adopting a programmed heating method to reach the final sweating temperature, the sweating temperature range is 3.0-5.5°C, preferably 4.0°C.

[0022] As a preferred technical solution of the present invention, the step 5, heating and melting: the heating and melting are achieved by programmed heating, and the melting temperature ranges from 21.5 to 25.0°C, preferably 24.0°C.

[0023] As a preferred technical solution of the present invention, the single-pass crystallization yield of electronic-grade dimethyl carbonate prepared by the melt crystallization method is ≥60w%.

[0024] As a preferred technical solution of the present invention, the step 6, molecular sieve dehydration: using mesoporous molecular sieve, continuous feeding at 1-2 ml / min, while controlling the residence time of the feed liquid at 2-3 h, the water content of electronic grade dimethyl carbonate can be ≤0.003w%.

[0025] Compared with the prior art, the present invention provides a process for improving the crystallization yield of electronic-grade dimethyl carbonate, which has the following beneficial effects:

[0026] 1. The present invention optimizes the cooling crystallization final temperature, the heating sweating final temperature and the heating melting final temperature in the melt crystallization, and finally selects the best crystallization process parameters, which can significantly improve the single-pass crystallization yield ≥ 60w%; and has good repeatability, effectively improving the resource utilization rate of DMC, a by-product of coal-to-ethylene glycol, and reducing waste emissions.

[0027] 2. The present invention uses a mesoporous molecular sieve to further dehydrate the crystallized electronic-grade dimethyl carbonate: with a continuous feeding mode of 1-2 ml / min and a control of the residence time of the feed liquid at 2-3 h, the water content of the electronic-grade dimethyl carbonate can be ≤0.003w%, and finally the various indicators of the electronic-grade DMC product can meet the requirements of the national standard GB / T 33107-2016. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flowchart of a process for improving the crystallization yield of electronic-grade dimethyl carbonate according to the present invention;

[0029] Figure 2 A simplified process flow diagram of the present invention for improving the crystallization yield of electronic-grade dimethyl carbonate;

[0030] Figure 3 The present invention is a process flow chart of purifying electronic grade dimethyl carbonate (DMC).

[0031] In the figure: 1. Crystallization kettle; 2. Distillation tower; 3. Controller; 4. Crystallization drainage tank; 5. Sweating drainage tank; 6. Liquid extraction pump. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Embodiment 1

[0034] Weigh 1057.58 g of primary dimethyl carbonate (dimethyl carbonate treated by reactive distillation and dehydrogenation) product. See Table 1 for composition.

[0035] Table 1 Dimethyl carbonate raw material composition

[0036]

[0037] The raw materials were poured into the crystallization kettle, replaced with nitrogen 3 times, and stirred at a stirring rate of 400r / min. The temperature of the material in the crystallization kettle was reduced to 6°C. After the temperature in the kettle stabilized, the temperature was lowered. The low-temperature bath was cooled at a rate of 1°C / h. When the temperature of the low-temperature bath dropped to 2.5°C, the timing was started. After the constant temperature was maintained for 3h, the crystallization was drained and 396.3g of crude dimethyl carbonate was discharged, accounting for 37.47% of the total mass. The low-temperature bath was directly heated to 3°C and entered the sweating stage. When the temperature in the kettle reached 4°C, the constant temperature was maintained for 2h, and the sweating liquid was discharged. 3.26g of sweating liquid was discharged, accounting for 0.31% of the total mass. After the sweating was completed, the low-temperature bath was raised to a solid melt at a rate of 2.5°C / h, and 648.40g of electronic-grade dimethyl carbonate product was discharged, accounting for 61.31% of the total mass, that is, the single-pass yield of electronic-grade dimethyl carbonate prepared by the melt crystallization method was 61.31%, and the product composition was shown in Table 2. The raw material loss in the whole process was 9.62 g, accounting for 0.91% of the total mass.

[0038] Table 2 Electronic grade dimethyl carbonate raw material composition

[0039]

[0040] Embodiment 2

[0041] Weigh 818.55 g of primary dimethyl carbonate (dimethyl carbonate treated by reactive distillation and dehydrogenation) product. See Table 3 for composition.

[0042] Table 3 Dimethyl carbonate raw material composition

[0043]

[0044] The raw materials were poured into the crystallization kettle, replaced with nitrogen 3 times, and stirred at a stirring rate of 400r / min. The temperature of the material in the crystallization kettle was reduced to 5.2°C. After the temperature in the kettle stabilized, the temperature was lowered. The low-temperature bath was cooled at a rate of 1°C / h. When the temperature of the low-temperature bath dropped to 2.5°C, the timing was started. After the constant temperature was maintained for 3h, the crystallization was drained and 295.11g of crude dimethyl carbonate was discharged, accounting for 36.05% of the total mass. The low-temperature bath was directly heated to 3°C and entered the sweating stage. When the temperature in the kettle reached 4°C, the constant temperature was maintained for 2h, and the sweating liquid was discharged, and 4.75g of sweating liquid was discharged, accounting for 0.58% of the total mass. After the sweating was completed, the low-temperature bath was raised to a solid melt at a rate of 2.5°C / h, and 511.23g of electronic-grade dimethyl carbonate product was discharged, accounting for 62.46% of the total mass, that is, the single-pass yield of electronic-grade dimethyl carbonate prepared by the melt crystallization method was 62.46%, and the product composition was shown in Table 4. The raw material loss in the whole process was 7.46 g, accounting for 0.91% of the total mass.

[0045] Table 4 Electronic grade dimethyl carbonate raw material composition

[0046]

[0047] Embodiment 3

[0048] Weigh 1018.15 g of primary dimethyl carbonate (dimethyl carbonate treated by reactive distillation and dehydrogenation) product. See Table 5 for composition.

[0049] Table 5 Dimethyl carbonate raw material composition

[0050]

[0051] The raw materials were poured into the crystallization kettle, replaced with nitrogen 3 times, and stirred at a stirring rate of 400r / min. The temperature of the material in the crystallization kettle was reduced to 6.9°C. After the temperature in the kettle stabilized, the temperature was lowered. The low-temperature bath was cooled at a rate of 1°C / h. When the temperature of the low-temperature bath dropped to 2.5°C, the timing was started. After the constant temperature was maintained for 3h, the crystallization was drained and 365.95g of crude dimethyl carbonate was discharged, accounting for 35.94% of the total mass. The low-temperature bath was directly heated to 3°C and entered the sweating stage. When the temperature in the kettle reached 4°C, the constant temperature was maintained for 2h, and the sweating liquid was discharged. 6.57g of sweating liquid was discharged, accounting for 0.65% of the total mass. After the sweating was completed, the low-temperature bath was raised to a solid melt at a rate of 2.5°C / h, and 627.65g of electronic-grade dimethyl carbonate product was discharged, accounting for 61.65% of the total mass, that is, the single-pass yield of electronic-grade dimethyl carbonate prepared by the melt crystallization method was 61.65%, and the product composition was shown in Table 6. The raw material loss in the whole process was 17.98 g, accounting for 1.77% of the total mass.

[0052] Table 6 Electronic grade dimethyl carbonate raw material composition

[0053]

[0054] Through the above three groups of experiments, it can be seen that the primary dimethyl carbonate sample can be made into electronic grade dimethyl carbonate product through the melt crystallization process, and the average single-pass crystallization yield is 61.81%, and the repeatability is good.

[0055] In the description of the present invention, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprising a reference structure" do not exclude the presence of other identical elements in the process, method, article or device comprising the elements. It should be noted that, in this article, relational terms such as "first", "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0056] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for improving the crystallization yield of electronic grade dimethyl carbonate, characterized in that: The following steps are involved: S1, first weigh a certain amount of primary dimethyl carbonate product raw material; S2, pour the raw materials into the crystallization kettle, replace with nitrogen 3 times, and start stirring; S3, cooling crystallization: the temperature of the material in the crystallization kettle is reduced to 6°C, and the temperature in the kettle is cooled down after it stabilizes. The low-temperature bath is cooled down at a rate of 1°C / h. When the temperature of the low-temperature bath drops to 2.5°C, the timing is started. After the constant temperature is maintained for 3 hours, the crystallization mother liquor is discharged to the reactive distillation process for reuse; S4, heating and sweating: directly raise the temperature of the low-temperature bath to 3°C to enter the sweating stage. When the temperature in the kettle reaches 4°C, keep the constant temperature for 2 hours, and then discharge the sweating liquid to the reaction distillation process for reuse; S5, heating and melting: after the sweating is completed, the low temperature bath is heated at a rate of 2.5°C / h until the solid melts, and the electronic grade dimethyl carbonate product is obtained. The weight is weighed to calculate the ratio, that is, the single-pass crystallization yield of electronic grade dimethyl carbonate prepared by the melt crystallization method is calculated; S6, molecular sieve dehydration: The electronic grade dimethyl carbonate product obtained by melt crystallization (cooling crystallization, heating sweating, heating melting) is further dehydrated by molecular sieve, and finally the electronic grade DMC product indicators meet the requirements of the national standard GB / T 33107-2016.

2. A process for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The primary dimethyl carbonate product raw material needs to be subjected to reactive distillation and dehydrogenation treatment.

3. A process for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The stirring rate of the crystallization kettle in step S2 is 400 r / min.

4. A device for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The step 3, cooling crystallization: adopting programmed cooling to reach the final crystallization temperature, the crystallization temperature range is 2.2-2.7°C, preferably 2.5°C.

5. A device for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The step 4, heating and sweating: adopting a programmed heating method to reach the final sweating temperature, the sweating temperature range is 3.0-5.5°C, preferably 4.0°C.

6. A device for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The step 5, heating and melting: the temperature is programmed to achieve heating and melting, and the melting temperature range is 21.5-25.0°C, preferably 24.0°C.

7. A device for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The single-pass crystallization yield of electronic-grade dimethyl carbonate prepared by melt crystallization is ≥60w%.

8. A device for improving the crystallization yield of electronic-grade dimethyl carbonate according to claim 1, characterized in that: The step 6, molecular sieve dehydration: using mesoporous molecular sieve, continuous feeding at 1-2 ml / min, while controlling the residence time of the feed liquid at 2-3 hours, the water content of electronic grade dimethyl carbonate can be ≤0.003w%.

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