Process for the production of ultra-high purity ethylene carbonate

Abstract

The present invention provides a method for manufacturing ultra-high purity ethylene carbonate, comprising: a step of esterifying ethylene oxide with carbon dioxide in the presence of a catalyst to produce ethylene carbonate; a DEG removal step of converting a byproduct of the esterification reaction, diethylene glycol (DEG), into monoethylene glycol (MEG) using pseudo-boehmite; and an impurity removal step of performing vacuum distillation on a product of the DEG removal step to remove impurities including MEG converted from DEG and moisture.

Description

Technical Field

[0001] This invention relates to a method for manufacturing ultra-high purity ethylene carbonate. Background Technology

[0002] Ethyl carbonate (EC), used as an organic solvent in battery electrolytes, is typically manufactured via esterification of ethylene oxide (EO) and carbon dioxide (CO2). However, during the production of EC from EO and CO2, EO hydration due to trace amounts of water generates monoethylene glycol (MEG), EC reacts with MEG to produce diethylene glycol (DEG), and hydrolysis of EC also produces byproducts.

[0003] Specifically, the synthesis reaction of EC is shown in the following reaction formula 1.

[0004] [Reaction Formula 1]

[0005]

[0006] Furthermore, the side reactions in the EC manufacturing process are shown in reaction formulas 2-1 to 2-3 below, thus requiring the removal of MEG and DEG.

[0007] [Reaction 2-1] - Hydration reaction of EO

[0008]

[0009] [Reaction 2-2] - Reaction of EC with MEG

[0010]

[0011] [Reaction 2-3] - Hydrolysis reaction of EC

[0012]

[0013] Among the aforementioned byproducts, DEG has a boiling point of 244°C to 245°C, which is very similar to that of EC, which has a boiling point of 243°C to 244°C. Therefore, it cannot be separated and purified by conventional vacuum distillation. While methods such as activated carbon adsorption of diols can be used, in reality, this method is insufficient for obtaining ultra-high purity EC.

[0014] In particular, the diols and water in EC react with lithium salts in lithium batteries to form hydrofluoric acid, while residual water reacts with EC to produce MEG and CO2, thus posing a problem of battery swelling and swelling. Therefore, in order to use EC as an organic solvent for lithium battery electrolytes, a method for manufacturing ultra-high purity EC after purifying water and impurities is needed.

[0015] Existing technical documents

[0016] Patent documents

[0017] Patent Document 1: Korean Patent Publication No. 10-0809877 Summary of the Invention

[0018] Technical issues

[0019] The present invention aims to provide a method for manufacturing ultra-high purity ethylene carbonate.

[0020] Technical solution

[0021] One embodiment of the present invention provides a method for manufacturing ultra-high purity ethylene carbonate, comprising: an esterification reaction of ethylene oxide and carbon dioxide in the presence of a catalyst to produce ethylene carbonate; a DEG removal step of converting diethylene glycol (DEG), a byproduct of the esterification reaction, into monoethylene glycol (MEG) using pseudoboehmite; and an impurity removal step of subjecting the product of the DEG removal step to vacuum distillation to remove impurities including MEG converted from DEG and water.

[0022] The effects of the invention

[0023] The method for manufacturing ultra-high purity ethylene carbonate of the present invention has the advantage of effectively removing DEG, an impurity with a similar boiling point to ethylene carbonate. Furthermore, the method for manufacturing ultra-high purity ethylene carbonate of the present invention can obtain ultra-high purity ethylene carbonate with a water content of less than 10 ppm and a purity of more than 99.99% by vacuum distillation. Detailed Implementation

[0024] The present invention will now be described in detail.

[0025] In this specification, when a part is referred to as "containing" a constituent element, unless otherwise stated, it means that other constituent elements may be included, rather than excluded.

[0026] The present invention will now be described in detail.

[0027] One embodiment of the present invention provides a method for manufacturing ultra-high purity ethylene carbonate, comprising: an esterification reaction of ethylene oxide and carbon dioxide in the presence of a catalyst to produce ethylene carbonate; a DEG removal step of converting diethylene glycol (DEG), a byproduct of the esterification reaction, into monoethylene glycol (MEG) using boehmite; and an impurity removal step of subjecting the product of the DEG removal step to vacuum distillation to remove impurities including MEG converted from DEG and water.

[0028] According to one embodiment of the present invention, the step of producing the ethylene carbonate is carried out by an esterification reaction of ethylene oxide and carbon dioxide in the presence of a catalyst. As a catalyst used in this process, various catalysts such as solid acid catalysts, alkali metal salt catalysts, and homogeneous organometallic catalysts can be used, which are widely known in the art.

[0029] As previously mentioned, ethylene carbonate, produced from ethylene oxide and carbon dioxide, produces ethylene glycol (MEG) through the hydration of ethylene oxide and hydrolysis of ethylene carbonate caused by trace amounts of water. Furthermore, the reaction of ethylene carbonate with MEG yields diethylene glycol (DEG). This byproduct can negatively impact the commercial viability of ethylene carbonate; therefore, maximizing the removal of this byproduct to obtain ultra-high purity ethylene carbonate is crucial. However, DEG and ethylene carbonate have similar boiling points, making separation and purification via conventional vacuum distillation impossible. To address this, the present invention provides a method for converting DEG in ethylene carbonate into MEG, enabling efficient removal of DEG via vacuum distillation.

[0030] Specifically, according to one embodiment of the present invention, a DEG removal step is included: converting diethylene glycol (DEG), a byproduct of the esterification reaction, into monoethylene glycol (MEG) using boehmite. In the DEG removal step, boehmite is used as a catalyst, and the diethylene glycol (DEG) can be converted into monoethylene glycol (MEG) through the hydroxyl groups on the surface of boehmite.

[0031] According to one embodiment of the present invention, the reaction mechanism in the DEG removal step using the pseudoboehmite (labeled as Pseudo-AlO-OH in the following reaction formula) can be described as follows.

[0032] Step 1: Pseudo-AlO-OH + H2O → Pseudo-AlO-OH2+ + -OH -

[0033] Step 2: C4H 10 O3(DEG) + -OH - → C-2H6O2 + C-2H5O2 - + Pseudo-AlO-OH2 +

[0034] Step 3: Pseudo-AlO-OH + 2C-2H6O2

[0035] Through the catalytic action described above, DEG in ethylene carbonate is converted into MEG. Boehmite has a large number of hydroxyl groups on its surface and a large specific surface area, thus enabling a high conversion efficiency of DEG.

[0036] According to one embodiment of the present invention, when the DEG content in the ethylene carbonate is 151 ppm or less, the content of the pseudoboehmite can be adjusted to 5 to 50 parts by weight relative to 100 parts by weight of the ethylene carbonate. Specifically, when the DEG content in the ethylene carbonate is 151 ppm or less, the content of the pseudoboehmite relative to 100 parts by weight of the ethylene carbonate can be 15 to 45 parts by weight, 20 to 45 parts by weight, 25 to 45 parts by weight, or 30 to 45 parts by weight. Within the above ranges, a high DEG conversion efficiency can be achieved without loss of ethylene carbonate.

[0037] According to one embodiment of the present invention, the DEG removal step can be performed for 10 to 60 minutes within a temperature range of 35°C to 55°C. Specifically, the DEG removal step can be performed at 40°C to 55°C, 45°C to 55°C, or approximately 50°C. Furthermore, the DEG removal step can be performed for 20 to 40 minutes, or approximately 30 minutes. Within the above temperature range and / or reaction time range, there is an advantage in preventing excessive energy input and effectively removing DEG.

[0038] According to one embodiment of the present invention, the conversion rate of diethylene glycol (DEG) to monoethylene glycol (MEG) in the DEG removal step can be at least 85%. This conversion rate can be achieved by appropriately adjusting the reaction temperature and time according to the boehmite content. More preferably, the conversion rate of diethylene glycol (DEG) to monoethylene glycol (MEG) in the DEG removal step can be at least 87%, 89%, or 90%.

[0039] The method for producing ultra-high purity ethylene carbonate of the present invention can substantially completely remove DEG from ethylene carbonate through the aforementioned DEG removal step, converting DEG in ethylene carbonate into MEG, thereby allowing the DEG to be easily removed from ethylene carbonate by vacuum distillation.

[0040] According to one embodiment of the present invention, the impurity removal step may include: a first vacuum distillation step to remove impurities including monoethylene glycol (MEG) and water by using a side-stream sample; and a second vacuum distillation step to further remove ethylene oxide (EO) and water by subjecting the side-stream sample product, which has been used to remove impurities once by the first vacuum distillation, to vacuum distillation at a lower temperature than that of the first vacuum distillation step.

[0041] According to one embodiment of the present invention, in the first vacuum distillation step, a side-stream sample can be used to remove light impurities including water, MEG, and EO through a light-cut fraction, and heavy impurities including heavy metals and boehmite can be removed through a heavy-cut fraction, thereby purifying ethylene carbonate. Then, the ethylene carbonate purified by the side-stream sample can be subjected to vacuum distillation to obtain ultra-high purity ethylene carbonate.

[0042] According to one embodiment of the present invention, the first vacuum distillation step can utilize a side-cut organic solvent purification apparatus consisting of a round-bottom flask, a Dean-Stark water separator, a cooling water circulation system, a column packing, and a reflux condenser. For example, in the first vacuum distillation step, ethylene carbonate is distilled under reduced pressure using a Dean-Stark glassware, and the product is collected in an upper flask for light-cut removal. Then, the flask is replaced and further vacuum distilled to obtain purified ethylene carbonate in the flask, while other heavy impurities settle to the bottom of the reactor for heavy-cut removal.

[0043] According to one embodiment of the present invention, the first vacuum distillation step can be carried out for 4 to 10 hours in a temperature range of 45°C to 160°C.

[0044] Because the first vacuum distillation step using the side stream is carried out in a high-temperature atmosphere (e.g., about 85°C), ethylene carbonate may decompose, resulting in the presence of ethylene oxide as an impurity. Therefore, it is necessary to further perform vacuum distillation at a temperature lower than that of the first vacuum distillation step, i.e., a temperature higher than the freezing point of ethylene oxide, to remove light impurities such as ethylene oxide and water. In this regard, the impurity removal step in the method for manufacturing ultra-high purity ethylene carbonate of the present invention may include a first vacuum distillation step and a second vacuum distillation step.

[0045] According to one embodiment of the present invention, the second vacuum distillation step can be carried out for 30 to 120 minutes within a temperature range of 35°C to 55°C. When the temperature exceeds this range, ethylene carbonate may decompose to form ethylene oxide. The aforementioned temperature range is above the boiling point of water under reduced pressure (approximately -40°C to -16°C), allowing for simultaneous water removal. Furthermore, within the aforementioned time range, it has the advantages of reducing unnecessary process time and effectively removing both water and ethylene oxide.

[0046] When the method for manufacturing ultra-high purity ethylene carbonate of the present invention is used, ultra-high purity ethylene oxide with a moisture content of less than 10 ppm, an ethylene oxide (EO) content of less than 30 ppm, a MEG content of less than 20 ppm, and a DEG content of less than 30 ppm can be obtained.

[0047] The present invention will be described in detail below through embodiments. However, the embodiments of the present invention can be modified into many other forms, and the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments in this specification are provided to illustrate the present invention more completely to those skilled in the art.

[0048] [Example 1]

[0049] 100g of ethylene carbonate, manufactured from ethylene oxide and carbon dioxide, was mixed with boehmite (specific surface area: 317.1m³). 2 / g, Pore Volume (N2-isotherm): 0.6307ml / g) After adding 30g, a DEG conversion reaction was carried out at approximately 50°C for approximately 30 minutes. The untreated ethylene carbonate and the product were collected, and the contents of MEG and DEG were determined by GC analysis. In this GC analysis, acetone and ethylene carbonate (EC) were mixed at a volume ratio of 1:2 for analysis.

[0050] [Comparative Example 1-1]

[0051] Application of boehmite (specific surface area: 40.6 m²) 2 / g, pore volume (N2-isotherm): 0.1594ml / g) was used to replace boehmite. Otherwise, the DEG conversion reaction was carried out using the same method as in Example 1, and the contents of MEG and DEG were determined by GC analysis of the product after the reaction.

[0052] [Comparative Examples 1-2]

[0053] The molecular sieve used was M / S 4A (Sigma Aldrich, product name: MolecularSieves (4A, 8-12 mesh), with a specific surface area of ​​44.0 m². 2 / g, pore volume (N2-isotherm): 0.1028ml / g) was used to replace boehmite. Otherwise, the DEG conversion reaction was carried out using the same method as in Example 1, and the products after the reaction were taken and the contents of MEG and DEG were determined by GC analysis.

[0054] The results of the DEG conversion reaction of Example 1 and Comparative Examples 1-1 and 1-2 are shown in Table 1 below.

[0055] [Table 1]

[0056]

[0057] Table 1 confirms that Example 1, using boehmite, exhibits a very high DEG conversion rate compared to Comparative Examples 1-1 and 1-2, which use other substances, such as boehmite or molecular sieves. This is due to the high specific surface area and hydroxyl content of boehmite, demonstrating that boehmite is a highly effective catalyst for DEG conversion (DEG removal).

[0058] [Example 2]

[0059] 50g of ethylene carbonate, manufactured from ethylene oxide and carbon dioxide, was mixed with boehmite (specific surface area: 317.1m³). 2 / g, pore volume (N2-isotherm): 0.6307ml / g) After adding 15g, a DEG conversion reaction was carried out at approximately 50°C for about 30 minutes. The untreated ethylene carbonate and the product were collected, and the contents of MEG and DEG were determined by GC analysis. In this GC analysis, acetone and ethylene carbonate (EC) were mixed at a volume ratio of 1:2 for analysis.

[0060] [Example 2-1]

[0061] Add 5g of boehmite and change the reaction time to about 10 minutes, about 30 minutes and about 60 minutes respectively. Otherwise, carry out the DEG conversion reaction in the same way as in Example 2, and take the product after the reaction to determine the content of MEG and DEG by GC analysis.

[0062] [Example 2-2]

[0063] 10g of boehmite was added, and the DEG conversion reaction was carried out using the same method as in Example 2. The product after the reaction was taken and the contents of MEG and DEG were determined by GC analysis.

[0064] [Examples 2-3]

[0065] 25g of boehmite was added, and the DEG conversion reaction was carried out using the same method as in Example 2. The product after the reaction was taken and the contents of MEG and DEG were determined by GC analysis.

[0066] The results of the DEG conversion reactions in Examples 2, 2-1 to 2-3 above are shown in Table 2 below.

[0067] [Table 2]

[0068]

[0069] As shown in Table 2, the DEG conversion rate increases with the increase of the reaction time for DEG removal using boehmite. However, when the boehmite content relative to EC is 10 parts by weight, it is difficult to achieve a high DEG conversion rate even with extended reaction time. To achieve a DEG conversion rate of over 85% within a reaction time of approximately 30 minutes, setting the boehmite content relative to EC to 20 parts by weight or more is effective. When the boehmite content relative to EC is 50 parts by weight, the DEG conversion rate is 100%, which is effective for DEG removal, but a decrease in EC yield is confirmed. Therefore, the preferred boehmite content relative to EC in the DEG removal step is 20 to 45 parts by weight, or 25 to 45 parts by weight. Furthermore, the reaction time in the DEG removal step is set between 10 and 60 minutes; considering process efficiency, approximately 30 minutes is suitable.

[0070] [Example 3]

[0071] Add boehmite (specific surface area: 317.1 m²) to 1 kg of ethylene carbonate produced from ethylene oxide and carbon dioxide. 2 / g, pore volume (N2-isotherm): 0.6307ml / g) After 300g, a DEG conversion reaction was carried out at approximately 50℃ for about 30 minutes. The ethylene carbonate before the reaction and the product after the reaction were taken, and the contents of MEG and DEG were determined by GC analysis. At this time, acetone and ethylene carbonate (EC) were mixed at a volume ratio of 1:2 for GC analysis.

[0072] [Example 3-1]

[0073] The reaction temperature was adjusted to approximately 40°C. Otherwise, the DEG conversion reaction was carried out using the same method as in Example 3. The products after the reaction were collected, and the contents of MEG and DEG were determined by GC analysis.

[0074] [Example 3-2]

[0075] The reaction temperature was adjusted to approximately 40°C and the reaction time was adjusted to 40 minutes. Otherwise, the DEG conversion reaction was carried out using the same method as in Example 3, and the products after the reaction were taken and the contents of MEG and DEG were determined by GC analysis.

[0076] The results of the DEG conversion reactions in Examples 3, 3-1 to 3-2 above are shown in Table 3 below.

[0077] [Table 3]

[0078]

[0079] As shown in Table 3, the catalyst reactivity increases with increasing temperature in the DEG removal reaction, thus increasing the DEG conversion efficiency. However, when the reaction temperature rises to around 60°C, there is a problem of EC loss due to EC decomposition. Therefore, the suitable temperature range for the DEG removal reaction is considered to be 35°C to 55°C, more specifically, around 50°C.

[0080] [Example 4]

[0081] Add boehmite (specific surface area: 317.1 m²) to 1 kg of ethylene carbonate produced from ethylene oxide and carbon dioxide. 2After adding 300g of ethylene carbonate (pore volume (N2-isotherm): 0.6307ml / g), the mixture was stirred at approximately 50°C for about 15 minutes to carry out the DEG conversion reaction. Then, the DEG-removed ethylene carbonate was placed in a Dean-Stark trap and a 2000mL reactor, stirred at 300rpm under 0 Torr reduced pressure, and heated to approximately 85°C. At this point, for the side stream, 40% of the ethylene carbonate was light-cut to remove MEG, EO, water, and other light substances. The Dean-Stark trap was then replaced to collect another 50%, and the remaining 10% was kept in the reactor for heavy-cut. The heavy-cut process removed boehmite residues and other solid components.

[0082] The side-stream product was then stirred at 300 rpm under reduced pressure at 0 torr and further distilled under reduced pressure for 90 minutes at approximately 50°C to obtain the final ethylene carbonate. The ethylene carbonate before and after the reaction products were analyzed by GC to determine the MEG and DEG contents. In this GC analysis, acetone and ethylene carbonate (EC) were mixed at a volume ratio of 1:2 for analysis.

[0083] [Example 4-1]

[0084] Side-stream distillation (i.e., light and heavy fractions) was performed, but no further vacuum distillation was carried out. Otherwise, the final ethylene carbonate was obtained in the same manner as in Example 4. The ethylene carbonate before reaction and the product after reaction were taken and the contents of MEG and DEG were determined by GC analysis.

[0085] [Example 4-2]

[0086] No side-stream sampling (i.e., light and heavy fractions) and no further vacuum distillation were performed; otherwise, the final ethylene carbonate was obtained in the same manner as in Example 4. The unreacted ethylene carbonate and the post-reaction products were analyzed by GC to determine the MEG and DEG content.

[0087] The impurity content in the final ethylene carbonate of Examples 4, 4-1 to 4-2 above is shown in Table 4 below.

[0088] [Table 4]

[0089]

[0090] In Table 4 above, Example 3, which did not undergo vacuum distillation, is marked to compare the effects of stirring. It can be confirmed that when stirring is performed during the DEG removal reaction as in Example 4, the reaction time is shortened, and a high DEG conversion rate can be achieved. Furthermore, it can be confirmed that in the case of Example 4-1, due to the high-temperature decomposition of EC at 85°C, EO is generated and partially remains. However, through side-stream sampling, the EO is reduced to 55 ppm, MEG is removed to an undetectable level, and the EC purity is 99.9912%. However, it can be confirmed that due to the lack of further vacuum distillation, some EO remains, and moisture is not sufficiently removed. Similarly, it can be confirmed that in the case of Example 4-2, where no side-stream sampling and further vacuum distillation were performed, the EC purity is excellent at 99.9389%, but the moisture content, EO, and MEG are not sufficiently removed. In contrast, it can be confirmed that in Example 4, after using a side stream to collect light and heavy fractions and then performing vacuum distillation, EC with a moisture content of less than 10 ppm, an EO content of 20 ppm, and a purity of 99.9955% can be obtained. Furthermore, the ICP results of ethylene carbonate obtained according to Example 4 are shown in Table 5 below.

[0091] [Table 5]

[0092]

[0093] Referring to Table 5 above, the content of heavy metal elements in the ethylene carbonate obtained according to Example 4 is very low, and the content of Al, a constituent element of boehmite, is at the level of 0.1 ppm, which confirms that the impurities have been purified very well.

Claims

1. A method for manufacturing ultra-high purity ethylene carbonate, comprising: The step of esterifying ethylene oxide with carbon dioxide in the presence of a catalyst to produce ethylene carbonate; The DEG removal step, which utilizes boehmite to convert diethylene glycol (DEG), a byproduct of the esterification reaction, into monoethylene glycol (MEG); and The product of the DEG removal step is subjected to vacuum distillation to remove impurities including MEG converted from DEG and moisture, in an impurity removal step.

2. The method for manufacturing ultra-high purity ethylene carbonate according to claim 1, wherein, When the DEG content in the ethylene carbonate is below 151 ppm, the content of the pseudoboehmite is adjusted to 5 to 50 parts by weight relative to 100 parts by weight of the ethylene carbonate.

3. The method for manufacturing ultra-high purity ethylene carbonate according to claim 1, wherein, The DEG removal step is performed for 10 to 60 minutes at a temperature range of 35°C to 55°C.

4. The method for manufacturing ultra-high purity ethylene carbonate according to claim 1, wherein, The impurity removal step includes: The first vacuum distillation step, utilizing a side stream, removes impurities including monoethylene glycol (MEG) and water; and The side-stream product, which has been purified of impurities by the first vacuum distillation, is subjected to a second vacuum distillation step at a lower temperature than the first vacuum distillation step to further remove ethylene oxide (EO) and water.

5. The method for manufacturing ultra-high purity ethylene carbonate according to claim 4, wherein, The first vacuum distillation step is carried out for 4 to 10 hours at a temperature range of 45°C to 160°C. The second vacuum distillation step is carried out for 30 to 120 minutes in a temperature range of 35°C to 55°C.

6. The method for manufacturing ultra-high purity ethylene carbonate according to claim 1, wherein, The conversion rate of diethylene glycol (DEG) to monoethylene glycol (MEG) in the DEG removal step is at least 85%.

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