Method for preparing ultra-high purity ethylene carbonate

Abstract

The present invention relates to a method for preparing ultra-high purity ethylene carbonate, the method comprising: a step of esterifying ethylene oxide and carbon dioxide in the presence of a catalyst to prepare ethylene carbonate; a DEG removal step of converting diethylene glycol (DEG), which is a by-product of the esterification reaction, into monoethylene glycol (MEG) by using pseudobohemite; and an impurity removal step of removing impurities including moisture and the MEG converted from DEG by distilling a product of the DEG removal step under reduced pressure.

Description

Method for producing ultra-high purity ethylene carbonate

[0001] The present invention relates to a method for producing ultra-high purity ethylene carbonate.

[0002] Ethylene carbonate (EC), used as an organic solvent for battery electrolytes, is typically manufactured through an esterification reaction using ethylene oxide (EO) and carbon dioxide (CO2) as raw materials. However, during the process of manufacturing EC from EO and CO2, monoethylene glycol (MEG) is generated through the hydration reaction of EO with a trace amount of water, and diethylene glycol (DEG) is generated through the reaction of EC and MEG, and by-products are also generated through the hydrolysis reaction of EC.

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

[0004] [Reaction Formula 1]

[0005]

[0006] Furthermore, the side reactions in the manufacturing process of EC are as shown in the following reaction formulas 2-1 to 2-3, and accordingly, removal of MEG and DEG is required.

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

[0008]

[0009] [Reaction Scheme 2-2] - Reaction of EC and MEG

[0010]

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

[0012]

[0013] Among the above by-products, DEG has a boiling point of 244 to 245°C, which is very similar to that of EC, which has a boiling point of 243 to 244°C, and therefore cannot be separated and purified through general reduced pressure distillation. Therefore, a method of adsorbing dihydric alcohols using activated carbon or the like can be used, but this is insufficient to obtain ultra-high purity EC.

[0014] In particular, dihydric alcohols and moisture within EC react with lithium salts within lithium batteries to produce hydrofluoric acid, and the remaining moisture reacts with EC to produce MEG and CO2, causing battery expansion and swelling. Therefore, in order to apply EC as an organic solvent for lithium battery electrolytes, a method for producing ultra-high-purity EC purified of moisture and impurities is required.

[0015] [Prior Art Literature]

[0016] [Patent Document]

[0017] (Patent Document 1) Republic of Korea Patent Publication No. 10-0809877

[0018] The present invention seeks to provide a method for producing ultra-high purity ethylene carbonate.

[0019] One embodiment of the present invention provides a method for producing ultra-high purity ethylene carbonate, comprising: a step of producing ethylene carbonate by esterifying ethylene oxide and carbon dioxide in the presence of a catalyst; a DEG removal step of converting diethylene glycol (DEG), a by-product of the esterification reaction, into monoethylene glycol (MEG) using pseudoboehmite; and an impurity removal step of removing impurities including MEG converted from DEG and moisture by distilling the product of the DEG removal step under reduced pressure.

[0020] The method for producing ultra-high purity ethylene carbonate according to the present invention has the advantage of being able to effectively remove DEG, an impurity having a boiling point similar to that of ethylene carbonate. In addition, the method for producing ultra-high purity ethylene carbonate according to the present invention can obtain ultra-high purity ethylene carbonate having a moisture content of 10 ppm or less and a purity of 99.99% or more through reduced pressure distillation.

[0021] Hereinafter, the present invention will be described in detail.

[0022] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless specifically stated otherwise.

[0023] Hereinafter, the present invention will be described in detail.

[0024] One embodiment of the present invention provides a method for producing ultra-high purity ethylene carbonate, comprising: a step of producing ethylene carbonate by esterifying ethylene oxide and carbon dioxide in the presence of a catalyst; 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 removing impurities including MEG converted from DEG and moisture by distilling the product of the DEG removal step under reduced pressure.

[0025] According to one embodiment of the present invention, the step of producing ethylene carbonate is a reaction that occurs through an esterification reaction of ethylene oxide and carbon dioxide in the presence of a catalyst. Various catalysts can be used as the catalyst, such as a solid acid catalyst, an alkali metal salt catalyst, and a homogeneous organic metal catalyst, which are widely known in the art.

[0026] As mentioned above, ethylene carbonate, which is manufactured from ethylene oxide and carbon dioxide as raw materials, produces monoethylene glycol (MEG) through the hydration reaction of ethylene oxide with a small amount of water and the hydrolysis of ethylene carbonate, and diethylene glycol (DEG) is produced when ethylene carbonate and monoethylene glycol (MEG) react. Since such by-products can lower the marketability of ethylene carbonate, it is important to remove them as much as possible to obtain ultra-pure ethylene carbonate. However, since diethylene glycol (DEG) has the same or similar boiling point as ethylene carbonate, separation and purification through general reduced pressure distillation is impossible. Therefore, the present invention provides a means for converting diethylene glycol (DEG) in ethylene carbonate into monoethylene glycol (MEG) and effectively removing it through reduced pressure distillation.

[0027] Specifically, according to one embodiment of the present invention, a DEG removal step is included, which converts diethylene glycol (DEG), a by-product of the esterification reaction, into monoethylene glycol (MEG) using pseudoboehmite. The DEG removal step can convert diethylene glycol (DEG) into monoethylene glycol (MEG) through hydroxyl groups on the surface of pseudoboehmite using pseudoboehmite as a catalyst.

[0028] According to one embodiment of the present invention, the reaction mechanism in the DEG removal step using the pseudoboehmite (represented as Pseudo-AlO-OH in the reaction formula below) may be as follows.

[0029] - Step 1: Pseudo-AlO-OH + H2O → Pseudo-AlO-OH2 + + -OH -

[0030] - Step 2: C4H 10 O3(DEG) + -OH- → C-2H6O2+ C-2H5O2 - + Pseudo-AlO-OH2 +

[0031] - Step 3: Pseudo-AlO-OH + 2C-2H6O2

[0032] Through the catalytic action described above, DEG in ethylene carbonate is converted to MEG, and pseudoboehmite has a large number of hydroxyl groups on its surface and a large specific surface area, so it can achieve a high conversion efficiency of DEG.

[0033] According to one embodiment of the present invention, the content of the pseudoboehmite may be adjusted to 5 parts by weight to 50 parts by weight with respect to 100 parts by weight of ethylene carbonate when the DEG content in the ethylene carbonate is 151 ppm or less. Specifically, the content of the pseudoboehmite may be 15 parts by weight to 45 parts by weight, 20 parts by weight to 45 parts by weight, 25 parts by weight to 45 parts by weight, or 30 parts by weight to 45 parts by weight with respect to 100 parts by weight of ethylene carbonate when the DEG content in the ethylene carbonate is 151 ppm or less. Within the above range, a high conversion efficiency of DEG can be achieved without loss of ethylene carbonate.

[0034] According to one embodiment of the present invention, the DEG removal step may be performed at a temperature range of 35°C to 55°C for 10 to 60 minutes. Specifically, the DEG removal step may be performed at 40°C to 55°C, 45°C to 55°C, or about 50°C. In addition, the DEG removal step may be performed for 20 to 40 minutes, or about 30 minutes. Within the above temperature range and / or reaction time range, there is an advantage in that excessive energy input can be prevented and DEG can be effectively removed.

[0035] According to one embodiment of the present invention, the conversion rate of diethylene glycol (DEG) into monoethylene glycol (MEG) in the DEG removal step may be at least 85%. The conversion rate may be achieved by appropriately adjusting the reaction temperature and time depending on the content of pseudoboehmite. More preferably, the conversion rate of diethylene glycol (DEG) into monoethylene glycol (MEG) in the DEG removal step may be at least 87%, or 89%, or 90%.

[0036] The method for producing ultra-high purity ethylene carbonate according to the present invention can substantially remove all of the DEG in ethylene carbonate through the above-described DEG removal step, and the DEG in ethylene carbonate is converted to MEG, which can be easily removed from the ethylene carbonate through reduced pressure distillation.

[0037] According to one embodiment of the present invention, the impurity removal step may include a first reduced pressure distillation step for removing impurities including monoethylene glycol (MEG) and moisture using a side cut; and a second reduced pressure distillation step for further removing ethylene oxide (EO) and moisture by distilling the side cut product from which impurities have been primarily removed through the first reduced pressure distillation at a temperature lower than that of the first reduced pressure distillation step.

[0038] According to one embodiment of the present invention, the first reduced pressure distillation step can purify ethylene carbonate by removing light impurities including moisture, MEG, and EO through a light cut and removing heavy impurities such as heavy metals and pseudoboehmite through a heavy cut using a side cut. Then, the ethylene carbonate purified through the side cut can be subjected to reduced pressure distillation to obtain ultra-high purity ethylene carbonate.

[0039] According to one embodiment of the present invention, the first reduced pressure distillation step may use a side-cut organic solvent purification device consisting of a round flask, a Dean-stark, a cooling water circulation device, a column packing, and a reflux condenser. For example, the first reduced pressure distillation step uses a Dean-stark glass to distill ethylene carbonate under reduced pressure, and obtains and removes (light-cut) the product in the upper flask. Then, when the flask is changed and additional reduced pressure distillation is performed, purified ethylene carbonate is obtained in the flask, and other heavy impurities (heavier) settle to the bottom of the reactor and are removed (heavy-cut).

[0040] According to one embodiment of the present invention, the first reduced pressure distillation step may be performed at a temperature range of 45°C to 160°C for 4 to 10 hours.

[0041] Since the first reduced pressure distillation step using the above side cut is performed under a high temperature atmosphere (for example, about 85° C.), ethylene carbonate may be decomposed and ethylene oxide may exist as an impurity. Therefore, it is necessary to additionally perform reduced pressure distillation at a temperature lower than the first reduced pressure distillation step, that is, at a temperature higher than the freezing point of ethylene oxide, to remove light impurities such as ethylene oxide and moisture. Accordingly, the impurity removal step in the method for producing ultra-high purity ethylene carbonate according to the present invention may include the first and second reduced pressure distillation steps.

[0042] According to one embodiment of the present invention, the second reduced pressure distillation step may be performed at a temperature range of 35°C to 55°C for 30 to 120 minutes. If the temperature range is exceeded, a problem may arise in which ethylene carbonate may decompose and ethylene oxide may be generated. The temperature range is higher than the boiling point of water under reduced pressure (about -40°C to -16°C), so that moisture removal can be performed simultaneously. In addition, there is an advantage in that unnecessary time in the process can be reduced within the time range, and moisture and ethylene oxide can be sufficiently removed.

[0043] When using the method for producing ultra-high purity ethylene carbonate according to the present invention, ultra-high purity ethylene oxide having a moisture content of 10 ppm or less, an ethylene oxide (EO) content of 30 ppm or less, an MEG content of 20 ppm or less, and a DEG content of 30 ppm or less can be obtained.

[0044] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0045] [Example 1]

[0046] After adding 30 g of pseudoboehmite (specific surface area: 317.1 m2 / g, Pore Volume (N2-isotherm): 0.6307 ml / g) to 100 g of ethylene carbonate manufactured from ethylene oxide and carbon dioxide as raw materials, a DEG conversion reaction was performed at a temperature of approximately 50 ℃ for approximately 30 minutes. The ethylene carbonate before the reaction and the product after the reaction were collected and analyzed by GC to measure the contents of MEG and DEG. At this time, the GC analysis was performed by mixing acetone and ethylene carbonate (EC) in a volume ratio of 1:2.

[0047] [Comparative Example 1-1]

[0048] A DEG conversion reaction was performed in the same manner as in Example 1, except that boehmite (specific surface area: 40.6 m2 / g, Pore Volume (N2-isotherm): 0.1594 ml / g) was used instead of pseudoboehmite, and the product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0049] [Comparative Example 1-2]

[0050] Except that M / S 4A molecular sieve (Sigma aldrich, product name: Molecular Sieves (4A, 8-12 mesh), specific surface area: 44.0 ㎡ / g, Pore Volume (N2-isotherm): 0.1028 ml / g) was used instead of pseudoboehmite, the DEG conversion reaction was performed in the same manner as in Example 1, and the product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0051] The results of the DEG conversion reaction according to the above Example 1 and Comparative Examples 1-1 and 1-2 were as shown in Table 1 below.

[0052] MEG content DEG content DEG conversion rate Initial EC 3 10 ppm 151 ppm - Example 1 464 ppm 12 ppm 92.1% Comparative Example 1 1419 ppm 50 ppm 66.9% Comparative Example 1 2406 ppm 61 ppm 59.6%

[0053] According to Table 1, it was confirmed that Example 1 using pseudoboehmite showed a very high DEG conversion rate compared to Comparative Examples 1-1 and 1-2 using other materials, such as boehmite or molecular sieves. This is due to the high specific surface area and hydroxyl group content of pseudoboehmite, and it can be seen that pseudoboehmite is a very effective material as a catalyst for DEG conversion (DEG removal).

[0054] [Example 2]

[0055] After adding 15 g of pseudoboehmite (specific surface area: 317.1 m2 / g, Pore Volume (N2-isotherm): 0.6307 ml / g) to 50 g of ethylene carbonate manufactured from ethylene oxide and carbon dioxide as raw materials, a DEG conversion reaction was performed at a temperature of approximately 50°C for approximately 30 minutes. The ethylene carbonate before the reaction and the product after the reaction were collected and analyzed by GC to measure the contents of MEG and DEG. At this time, the GC analysis was performed by mixing acetone and ethylene carbonate (EC) in a volume ratio of 1:2.

[0056] [Example 2-1]

[0057] A DEG conversion reaction was performed in the same manner as in Example 2, except that 5 g of pseudoboehmite was added and the reaction time was changed to about 10 minutes, about 30 minutes, and about 60 minutes, respectively. The product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0058] [Example 2-2]

[0059] Except that 10 g of pseudoboehmite was added, the DEG conversion reaction was performed in the same manner as in Example 2, and the product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0060] [Example 2-3]

[0061] Except that 25 g of pseudoboehmite was added, the DEG conversion reaction was performed in the same manner as in Example 2, and the product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0062] The results of the DEG conversion reaction according to the above Examples 2, 2-1 to 2-3 were as shown in Table 2 below.

[0063] Pseudoböhemia content (relative to 100 parts by weight of EC) Reaction time MEG content DEG content DEG conversion Initial EC--585 ppm 114 ppm - Example 2 30 parts by weight 30 min 704 ppm 12 ppm 89.5% Example 2 - 110 parts by weight 10 min 618 ppm 86 ppm 24.5% 30 min 660 ppm 50 ppm 56.1% 60 min 673 ppm 39 ppm 65.8% Example 2 - 220 parts by weight 30 min 700 ppm 15 ppm 86.8% Example 2 - 350 parts by weight 30 min 718 ppm N.D. 100%

[0064] Referring to Table 2, it can be seen that as the DEG removal reaction time using pseudoboehmite increases, the conversion rate of DEG increases. However, when the content of pseudoboehmite is 10 parts by weight relative to EC, it was difficult to achieve a high DEG conversion rate even if the reaction time was increased. In order to achieve a DEG conversion rate of 85% or more during a reaction time of about 30 minutes, it was effective to set the content of pseudoboehmite to 20 parts by weight or more relative to EC, and when the content of pseudoboehmite was 50 parts by weight relative to EC, the DEG conversion rate was 100%, which was effective for DEG removal, but it was confirmed that the problem of a decrease in the yield of EC occurred. Therefore, it was found that the preferable content of pseudoboehmite in the DEG removal step is 20 to 45 parts by weight relative to EC, or 25 to 45 parts by weight relative to EC. Additionally, the reaction time in the DEG removal step was set between 10 and 60 minutes, but considering process efficiency, approximately 30 minutes was appropriate.

[0065] [Example 3]

[0066] 300 g of pseudoboehmite (specific surface area: 317.1 m2 / g, Pore Volume (N2-isotherm): 0.6307 ml / g) was added to 1 kg of ethylene carbonate manufactured from ethylene oxide and carbon dioxide as raw materials, and then a DEG conversion reaction was performed at a temperature of approximately 50°C for approximately 30 minutes. The ethylene carbonate before the reaction and the product after the reaction were collected and analyzed by GC to measure the contents of MEG and DEG. At this time, the GC analysis was performed by mixing acetone and ethylene carbonate (EC) in a volume ratio of 1:2.

[0067] [Example 3-1]

[0068] Except that the reaction temperature was adjusted to about 40°C, the DEG conversion reaction was performed in the same manner as in Example 3, and the product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0069] [Example 3-2]

[0070] The DEG conversion reaction was performed in the same manner as in Example 3, except that the reaction temperature was adjusted to about 40°C and the reaction time to 40 minutes, and the product after the reaction was taken and the contents of MEG and DEG were measured through GC analysis.

[0071] The results of the DEG conversion reaction according to the above Examples 3, 3-1 to 3-2 were as shown in Table 3 below.

[0072] Temperature Time MEG Content DEG Content DEG Conversion Rate Initial EC--310 ppm 151 ppm Example 350 ℃ 30 min. 473 ppm 12 ppm 92% Example 3-140 ℃ 30 min. 465 ppm 18 ppm 88% Example 3-240 ℃ 40 min. 470 ppm 14 ppm 90%

[0073] According to Table 3, the higher the temperature of the DEG removal reaction, the greater the catalytic reactivity, leading to a higher DEG conversion efficiency. However, when the reaction temperature increased to approximately 60°C, there was a problem of EC loss due to EC decomposition. Therefore, it is determined that the appropriate temperature range for the DEG removal reaction is 35°C to 55°C, and more specifically, around 50°C.

[0074] [Example 4]

[0075] After adding 300 g of pseudoboehmite (specific surface area: 317.1 m2 / g, Pore Volume (N2-isotherm): 0.6307 ml / g) to 1 kg of ethylene carbonate manufactured from ethylene oxide and carbon dioxide as raw materials, the DEG conversion reaction was performed with stirring at a temperature of about 50 ℃ for about 15 minutes. Then, the ethylene carbonate from which DEG had been removed was placed in a Dean-stark trap and a 2000 mL reactor, stirred at 300 rpm under a reduced pressure of 0 torr, and heated to about 85 ℃. At this time, the side cut was performed by removing MEG, EO, moisture, and other light substances through a light cut of 40% of the ethylene carbonate, replacing the Dean-stark trap to receive 50% again, and leaving the remaining 10% in the reactor for a heavy cut. Pseudoboehmite residues and other solids were removed through heavy-cut.

[0076] Then, the side cut product was stirred at 300 rpm under reduced pressure conditions of 0 torr and further distilled under reduced pressure at a temperature of about 50°C for 90 minutes to obtain the final ethylene carbonate. The ethylene carbonate before the reaction and the product after the reaction were taken and analyzed by GC to measure the contents of MEG and DEG. At this time, the GC analysis was performed by mixing acetone and ethylene carbonate (EC) in a volume ratio of 1:2.

[0077] [Example 4-1]

[0078] The final ethylene carbonate was obtained in the same manner as in Example 4, except that side cuts (i.e., light-cut and heavy-cut) were performed but additional reduced pressure distillation was not performed. The ethylene carbonate before the reaction and the product after the reaction were taken and the contents of MEG and DEG were measured through GC analysis.

[0079] [Example 4-2]

[0080] The final ethylene carbonate was obtained in the same manner as in Example 4, except that side cuts (i.e., light-cut and heavy-cut) were not performed and additional reduced-pressure distillation was not performed. The ethylene carbonate before the reaction and the product after the reaction were taken and the contents of MEG and DEG were measured through GC analysis.

[0081] The content of impurities in the final ethylene carbonate according to the above Examples 4, 4-1 to 4-2 was as shown in Table 4 below.

[0082] Stirring EOMEGDEGECMoistureDEG Conversion Initial-1015 ppm310 ppm151 ppm99.7840%--Example 4O20 ppmN.DND99.9955%7.8 ppm100%Example 4-1O55 ppmN.DND99.9912%180 ppm100%Example 4-2O154 ppm487 ppmN.D.99.9389%>180 ppm100%Example 3X190 ppm473 ppm12 ppm99.9336%>180 ppm92%

[0083] In the above Table 4, Example 3 was not subjected to reduced pressure distillation, and is indicated to compare the effects depending on whether stirring was performed. As in Example 4, when stirring was performed during the DEG removal reaction, it was confirmed that the reaction time could be shortened and a high DEG conversion rate could be achieved. In addition, in the case of Example 4-1, EO was generated due to high-temperature decomposition of EC at a high temperature of 85 ℃ and some remained, but through the side cut, EO was reduced to 55 ppm, and MEG was removed to an undetectable level, so it was confirmed that EC had a purity of 99.9912%. However, since additional reduced pressure distillation was not performed, it was confirmed that some EO remained and moisture was not sufficiently removed. Similarly, in the case of Example 4-2, where a side cut and additional reduced pressure distillation were not performed, the purity of EC was excellent at 99.9389%, but it was confirmed that the moisture content and EO and MEG were not sufficiently removed. In contrast, in Example 4, where light-cut and heavy-cut were performed using side cuts and then vacuum distillation was performed, it was confirmed that EC having a purity of 99.9955% with a moisture content of less than 10 ppm and an EO content of 20 ppm could be obtained. Furthermore, the ICP results of ethylene carbonate obtained according to Example 4 were as shown in Table 5 below.

[0084] Al (ppm)Ca(ppm)Cr(ppm)Cu(ppm)Fe(ppm)K(ppm)Na(ppm)Ni(ppm)Pb(ppm)Zn(ppm)Mn(ppm)Mg(ppm)Example 40.100.18N.DND0.430.150.29NDNDNDND0.01

[0085] Referring to Table 5 above, it was confirmed that the ethylene carbonate obtained according to Example 4 had a very low content of heavy metal elements, and the content of Al, a constituent element of pseudoboehmite, was at the level of 0.1 ppm, indicating that impurities were very well purified.

Claims

1. A step of producing ethylene carbonate by esterifying ethylene oxide and carbon dioxide in the presence of a catalyst; A DEG removal step of converting diethylene glycol (DEG), a by-product of the esterification reaction, into monoethylene glycol (MEG) using pseudoboehmite; and An impurity removal step comprising: removing impurities including MEG and moisture converted from DEG by distilling the product of the above DEG removal step under reduced pressure; A method for producing ultra-high purity ethylene carbonate.

2. In claim 1, A method for producing ultra-high purity ethylene carbonate, wherein the content of the pseudoboehmite is adjusted to 5 to 50 parts by weight based on 100 parts by weight of ethylene carbonate when the content of DEG in the ethylene carbonate is 151 ppm or less.

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

4. In claim 1, The above impurity removal step is, A first reduced pressure distillation step, using a side cut to remove impurities including monoethylene glycol (MEG) and moisture; and A method for producing ultra-high purity ethylene carbonate, comprising: a second reduced pressure distillation step of further removing ethylene oxide (EO) and moisture by distilling the side cut product from which impurities have been primarily removed through the first reduced pressure distillation step at a lower temperature than the first reduced pressure distillation step.

5. In claim 4, The first pressure-reduced distillation step is performed at a temperature range of 45°C to 160°C for 4 to 10 hours, A method for producing ultra-high purity ethylene carbonate, wherein the second reduced pressure distillation step is performed at a temperature range of 35° C. to 55° C. for 30 to 120 minutes.

6. In claim 1, A method for producing ultra-high purity ethylene carbonate, wherein the conversion rate of diethylene glycol (DEG) into monoethylene glycol (MEG) in the above DEG removal step is at least 85%.

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