Carbonate manufacturing method

Abstract

The present invention relates to a method for producing carbonate. The method for producing carbonate of the present invention can effectively produce high purity EMC and DEC with high DMC conversion. The method of the present invention can reduce the load of the heat exchanger, thereby saving energy costs and maintenance costs.

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbonate. Specifically, the present invention relates to a method for purifying a target product to a high purity from a product of a carbonate production reaction. [Background technology]

[0002] Ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are the main organic solvents used in battery electrolytes. EMC and DMCDEC are produced by the transesterification of dimethyl carbonate (DMC) and ethanol (EtOH). This reaction is reversible and can be carried out in the presence of a catalyst. The following reaction scheme 1 shows this reaction (where MeOH is the abbreviation for methanol): [ka]

[0003] Catalysts used in this reaction include highly active base catalysts (e.g., NaOH, KOH). However, base catalysts have low solubility in organic solvents, especially carbonates, and are therefore insoluble in DMC, EMC, and DEC. Therefore, base catalysts cause column plugging, which can lead to process failures in the reactive distillation or purification process. Typically, the catalyst used in this reaction is removed before subsequent processes (e.g., separation and purification) are carried out to produce carbonate. This problem primarily occurs in fluidized-bed reactors.

[0004] Patent Document 1 introduces a method for producing carbonate using DMC, alcohol, and a sodium methoxide catalyst. Patent Document 1 produces EMC and DEC by reactive distillation. Patent Document 1 proposes installing a strainer to separate the solid (catalyst) at the downstream of the distillation column where the reactive distillation is carried out, thereby efficiently removing the catalyst. However, when alcohol is distilled in a reactive distillation column, the catalyst precipitates during the process. Therefore, the precipitated catalyst accumulates inside the distillation column, causing clogging of the column. Patent Document 1 also uses two additional reactive distillation columns (second and third reactive distillation columns) in addition to the distillation column (first reactive distillation column) used for reactive distillation to recover the product EMC and DEC. Here, DEC is obtained at the bottom of the second reactive distillation column, and EMC is obtained at the bottom of the third distillation column. Obtaining the product at the bottom of the distillation column contains metals and impurities generated during the process, making it difficult to obtain high-purity carbonate. Applying such carbonate to a lithium-ion battery increases battery resistance. Furthermore, in order to initially obtain DEC (boiling point: 125.8°C), which has a higher boiling point than EMC (boiling point: 107°C), a higher heat (transfer) load and heat transfer coefficient are required in the heat exchanger after the reaction. Therefore, the method of Patent Document 1 increases energy costs.

[0005] Patent Document 2 introduces a method for producing carbonate by extractive distillation using a gel-type strongly basic anion exchange resin catalyst as a transesterification catalyst. Extractive distillation requires a separation step to separate the product using an extractant, which increases equipment and energy costs. In addition, ion exchange resin catalysts typically have low strength, which leads to rapid deactivation due to loss of exchange groups and the formation of fine powder. As a result, the pressure inside the reactor also increases, requiring periodic catalyst replacement. Furthermore, because trace amounts of extractant may be present in the carbonate, additional steps are required to increase purity.

[0006] Therefore, research is needed into a method that can effectively produce high-purity EMC and DEC with a high DMC conversion rate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] CN103804124B [Patent Document 2] KR10-2011-0105379A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to effectively produce high-purity EMC and DEC at a high DMC conversion rate.

[0009] The present invention aims to reduce the load on the heat exchanger and save energy and maintenance costs. [Means for solving the problem]

[0010] The method for producing carbonate in the present invention includes a first step in which a raw material containing dimethyl carbonate and ethanol is introduced into a fixed-bed reactor system and a transesterification reaction of the raw material is induced to produce a product containing ethyl methyl carbonate, diethyl carbonate, and methanol; and a second step in which a reactor effluent containing the product and unreacted portions of the raw material is separated into a first separation system. By a second stage, separating the first separation system bottoms stream to obtain a first separation system overhead stream containing primarily ethanol, methanol, and dimethyl carbonate, and a first separation system bottoms stream containing primarily diethyl carbonate and ethyl methyl carbonate; By a third stage, separating the second separation system bottom stream from the second separation system to obtain an overhead stream containing primarily ethyl methyl carbonate and a bottom stream from the second separation system containing primarily diethyl carbonate; and Byand a fourth stage of separating the diethyl carbonate from the first separation system to obtain a third separation system overhead stream containing diethyl carbonate as a main component, wherein in any one of the second stage to the fourth stage, the reflux ratio of any one of the first separation system to the third separation system is set within a range of 0.5 to 5. [Effects of the Invention]

[0011] The carbonate production method of the present invention can effectively produce high-purity EMC and DEC at a high DMC conversion rate.

[0012] The method of the present invention can reduce the load on the heat exchanger, saving energy and maintenance costs. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a process schematic diagram of a method for producing a carbonate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The contents of this application are explained in more detail below.

[0015] The present invention relates to a method for producing carbonates. Specifically, the present invention relates to a method for producing liquid carbonates or carbonate-based solvents. The present invention aims to obtain carbonates with high purity. The present invention also aims to facilitate the process of obtaining carbonates with high energy efficiency and low cost.

[0016] In the present invention, a carbonate is produced by the transesterification of DMC and ethanol. To this end, the present invention mainly involves the transesterification of DMC and ethanol and the purification of the reaction product.

[0017] To this end, the method of the present invention proceeds in at least four stages.

[0018] In the first stage of the method of the present invention, a feedstock containing dimethyl carbonate and ethanol is introduced into a fixed-bed reactor system, and a transesterification reaction of the feedstock is induced to produce a product containing ethyl methyl carbonate, diethyl carbonate, and methanol.

[0019] Products including ethyl methyl carbonate, diethyl carbonate, and methanol can be produced via transesterification of dimethyl carbonate with ethanol.

[0020] Reactors that use catalysts are broadly divided into two types: the first is a fluidized bed reactor, and the second is a fixed bed reactor.

[0021] In a fluidized bed reactor, the catalyst literally flows within the reactor. Therefore, the catalyst may be contained in the product, and it is necessary to remove the catalyst before feeding the product into the separation or purification process. If the catalyst is not removed, column clogging will occur, which will cause problems in the separation and / or purification process.

[0022] In a fixed-bed reactor, the catalyst is present in a fixed state within the reactor. Therefore, even after the reaction is completed, the catalyst remains in the reactor, and the product does not contain the catalyst. Therefore, when a fixed-bed reactor is used, a separate process for removing the catalyst is not required. In the present invention, a fixed-bed reactor is used. As a result, the method of the present invention does not require a process for removing the catalyst applied to the reaction, and there is no risk of the above-mentioned problems caused by the catalyst occurring.

[0023] In the present invention, the raw materials prepared as described above are introduced into a reactor system. In this specification, the term "reactor system" is used as a general concept that includes not only a reactor but also other equipment associated with the reactor or other additional reactors. That is, a reactor system includes a single reactor and other equipment associated therewith, multiple reactors, or multiple reactors and other equipment associated therewith.

[0024] In the method of the present invention, the transesterification reaction of the raw materials, dimethyl carbonate and ethanol, is carried out in the reactor system. As a result, a product containing ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methanol (MeOH) is produced. This product, along with unreacted raw materials, is discharged as reactor effluent from the reactor system. As mentioned above, since the method of the present invention uses a fixed-bed reactor, the reactor effluent does not need to contain a catalyst.

[0025] In the second stage of the method of the present invention, the reactor effluent containing the product and the unreacted portion of the raw material is separated. Specifically, the method of the present invention comprises separating the reactor effluent containing the product and the unreacted portion of the raw material through a first separation system. By and separating the effluent from the reactor effluent to obtain a first separation system overhead stream containing ethanol, methanol, and dimethyl carbonate as main components and a first separation system bottom stream containing diethyl carbonate and ethyl methyl carbonate as main components. More specifically, in the second stage of the method of the present invention, the reactor effluent is supplied to a first separation system, and the low boiling point components of the reactor effluent are discharged from the top of the first separation system and the high boiling point components of the reactor effluent are discharged from the bottom of the first separation system.

[0026] The stream exiting the top of the separation system is referred to herein as the separation system overhead stream.

[0027] The stream exiting the bottom of the separation system is referred to herein as the separation system bottoms stream.

[0028] The low-boiling point components contained in the reactor effluent mainly comprise ethanol, methanol, and dimethyl carbonate, and the high-boiling point components contained in the reactor effluent mainly comprise diethyl carbonate and ethyl methyl carbonate.

[0029] In this specification, containing a specific component as a main component may mean that the component is contained in an amount of 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, or 99% by weight or more based on the total weight, or less than 100% by weight or approximately 100% by weight.

[0030] Furthermore, in this specification, the term "separation system" is used as a concept that encompasses not only a separation column, which is a tower-shaped structure that advances the separation process, but also a reboiler that reheats a portion of the bottom stream that is refluxed to the separation column, and a cooler that cools a portion of the top stream that is refluxed to the separation column (or a condenser that condenses the stream).

[0031] In the third stage of the method of the present invention, the bottom stream of the first separation system is separated. Specifically, in the third stage of the method of the present invention, the bottom stream of the first separation system is separated into a second separation system. By and separating the first and second separation system top streams containing ethyl methyl carbonate as a major component and the second separation system bottom streams containing diethyl carbonate as a major component. More specifically, in the second stage of the method of the present invention, the bottom stream of the first separation system is fed to a second separation system, and the second separation system By The bottoms stream of the first separation system is separated to provide a second separation system overhead stream containing primarily ethyl methyl carbonate and a second separation system bottoms stream containing primarily diethyl carbonate.

[0032] In the fourth stage of the method of the present invention, the bottom stream of the second separation system is separated. Specifically, in the fourth stage of the method of the present invention, the bottom stream of the second separation system is separated into a third separation system. ByIn the fourth step, the bottom stream of the second separation system is separated into a third separation system and a third separation system, which is mainly composed of diethyl carbonate. By The third separation system is separated into an overhead stream containing diethyl carbonate as a low boiling point component as a main component and a bottom stream containing heavies as a high boiling point component as a main component. That is, in the fourth stage, the present invention provides a third separation system in which the bottom stream from the second separation system is supplied to the third separation system, and the third separation system is separated into an overhead stream containing diethyl carbonate as a low boiling point component as a main component and a bottom stream from the third separation system containing heavies as a high boiling point component as a main component. By The bottom stream from the second separation system is separated to obtain an overhead stream from a third separation system containing diethyl carbonate as a major component.

[0033] The second to fourth steps are different from conventional methods in that high-boiling components are separated and discharged first. In these steps, low-boiling components are separated and discharged first. This reduces the load on the heat exchanger required for separation, thereby reducing energy and maintenance costs.

[0034] Furthermore, in the present invention, high-purity carbonate of 99.9% or more can be obtained only by appropriately adjusting the operating conditions of the separation system. Specifically, in the method of the present invention, in any of the second to fourth stages, the reflux ratio of any of the first to third separation systems is set within the range of 0.5 to 5. That is, the reflux ratio of at least one of the separation systems used in the present invention must be adjusted as described above. In another embodiment, in two or more of the second to fourth stages, the reflux ratio of two or more of the first to third separation systems can be set within the range of 0.5 to 5.

[0035] Even when the method of the present invention is applied, various problems arise if the reflux ratio of the entire separation system is outside the above range. Specifically, if the reflux ratio of the entire separation system is less than 0.5, the ratio of the reflux liquid volume to the effluent volume at the top of the column is low, which increases the amount of product effluent, but makes it difficult to obtain high-purity carbonate. Also, if the reflux ratio of the entire separation system exceeds 5, the ratio of the reflux liquid volume to the effluent volume at the top of the column increases, making it possible to obtain high-purity carbonate, but the low effluent volume increases the time required to obtain the product, resulting in increased operating costs.

[0036] As used herein, the reflux ratio (R) refers to the ratio of the amount of reflux liquid to the amount of effluent liquid. That is, the amount of liquid returning to a particular column or reactor based on the amount of liquid discharged from the column or reactor can be referred to as the reflux ratio.

[0037] FIG. 1 shows a simplified diagram of the process of the method of the present invention. The contents of FIG. 1 can be summarized as follows: Drum (A) is a container for storing a solution (such as sulfuric acid / NaOH) for reusing the ion exchange resin. Drum (A) allows the solution to be circulated to regenerate the ion exchange resin when its efficiency decreases. Reactor (B) is a reactor system. Reactor (B) operates by connecting multiple fixed-bed reactors in series. The lower-stage material discharged from the reactor is sent to the first separation system (C). DMC / MeOH / EtOH is obtained from the upper stage of the first separation system (C), and EMC / DEC is obtained from the lower stage. EMC is recovered from the upper stage of the second separation system (D). The lower-stage effluent is sent to the third separation system (E). DEC is recovered from the upper stage of the third separation system (E), and the heavier material in the lower stage of the third separation system is discarded.

[0038] In one embodiment, the mixing ratio of the reactants (DMC and EtOH) in the feedstock may also be appropriately adjusted. For example, the ratio (EtOH / DMC) of the weight of dimethyl carbonate (DMC) to the weight of ethanol (EtOH) in the feedstock may be within the range of 0.1 to 10. In other embodiments, the ratio (EtOH / DMC) may be 0.15 or greater or 0.2 or greater, or 9 or less, 8 or less, 7 or less, 6 or less, or 5 or less. Within these ranges, the reactants can be appropriately contacted with the catalyst to react, thereby reducing energy waste in the purification process. Additionally, the ratio between these reactants may also be adjusted depending on the target product. For example, due to the high demand for DEC, it is common to set the composition to increase selectivity for this target product, but this is because demand for EMC is expected to increase in the future.

[0039] The reactor system can also be designed appropriately.

[0040] In one embodiment, the fixed-bed reactor may be a fixed-bed reactor packed with an ion exchange resin catalyst. By applying an appropriate ion exchange resin catalyst, contact with the reactants can be maximized. As a result, the target product, carbonate, can be produced at a fast reaction rate and high reaction efficiency. In one embodiment, the ion exchange resin catalyst may be a basic ion exchange resin catalyst or an acidic ion exchange resin catalyst. Specifically, the ion exchange resin catalyst may be a basic ion exchange resin catalyst.

[0041] Acidic ion exchange resins are divided into strong acid ion exchange resins and weak acid ion exchange resins. Generally, a strong acid ion exchange resin catalyst can be used, and the resin catalyst can have a sulfonate ion as the exchange group and a hydrogen ion as the ion type.

[0042] Basic ion exchange resin catalysts are divided into weakly basic ion exchange resin catalysts and strongly basic ion exchange resin catalysts. Strongly basic ion exchange resin catalysts are classified into anion (Br - ), thiocyanate (SCN-) anion, chloride anion (Cl - ), acetate anion (acetate, CH3COO - ), hydroxyl group anion (OH - ), fluorine anion (F - The weakly basic ion exchange resin catalyst may have a citrate anion (C3H5O(COO)3) as an ionic form. 3- ), sulfonate (sulfate, SO4 2- ) etc.

[0043] In one embodiment, the ion exchange resin catalyst may be a porous ion exchange resin catalyst or a gel ion exchange resin catalyst. Specifically, the ion exchange resin catalyst may be a porous ion exchange resin catalyst. Porous ion exchange resins have many (approximately 10 to 1,000) macropores on their surface, making them more chemically stable than gel resins. In addition, porous ion exchange resins have a large surface area, which can maximize the contact area with the reactants.

[0044] Porous ion exchange resins have excellent decolorizing properties, can reduce the time required to wash the ion exchange resin and the amount of washing solvent used in the early stages of the reaction, and have high strength, so that when reused, there is little loss of exchange groups and little formation of fine powder, allowing for a long reuse cycle.

[0045] In one embodiment, the ion exchange resin catalyst may have an exchange capacity of 1 (eq / l-wet resin) or more and 1.5 (eq / l-wet resin) or less. Generally, the higher the cross-linking degree of an ion exchange resin, the greater the exchange group attached to the matrix, resulting in a higher exchange capacity. However, if the cross-linking degree of the ion exchange resin is high, the stronger the bond between the matrix and the exchange group, resulting in fewer exchange groups participating in the reaction, resulting in a lower reaction efficiency. Therefore, within this range of exchange capacity, an appropriate reaction rate and strength against sudden volume changes can be maintained.

[0046] Therefore, it may be most advantageous to apply an ion exchange resin catalyst that satisfies all of the above characteristics. In one embodiment, the fixed bed reactor system includes a fixed bed reactor packed with a basic ion exchange resin catalyst, the basic ion exchange resin may be porous, and the exchange capacity of the basic ion exchange resin may be in the range of 1 (eq / L-wet resin) to 1.5 (eq / L-wet resin).

[0047] In addition, the present invention can appropriately design reactor equipment in the reactor system. The fixed-bed reactor system of the present invention may be a system having a plurality of the fixed-bed reactors. That is, the fixed-bed reactor system may include two or more of the fixed-bed reactors. In addition, in the present invention, the fixed-bed reactor system may include a plurality of the fixed-bed reactors connected in series. Here, connecting a plurality of reactors in series means that the outlet of one reactor is connected to the inlet of the other reactor. In one embodiment, the fixed-bed reactor system may include a plurality of fixed-bed reactors connected in series.

[0048] In the reactor system, the number of fixed-bed reactors can be appropriately adjusted. The fixed-bed reactor system may be a system in which 2 to 10 of the fixed-bed reactors are connected in series.

[0049] Unlike existing methods, the present invention does not require reactive distillation or extractive distillation. That is, the method of the present invention can employ a tray column or a packing column as the separation system. The meanings of tray column and packing column are well known, so a detailed description will be omitted. There is a wealth of theoretical and empirical information related to the design of tray columns and packing columns, which can be used to systematically design separation and purification systems. That is, in one embodiment, the first to third separation systems may all be tray columns or packing columns.

[0050] If the previous step corresponds to a reaction step in the method of the present invention, the subsequent step may be a separation (or purification) step. The operating conditions of the separation system applied in the separation or purification step using the separation system may also be appropriately adjusted.

[0051] The conditions for separation and purification in the second step can also be adjusted appropriately.

[0052] In one example, the fourth stage can be applied to a separation system having a theoretical plate number in the range of 15 to 80 as the first separation system. A system within this range exhibits appropriate plate efficiency and can be manufactured economically. Furthermore, within this range, maintenance is easy and the thermal resin of the separation system can be easily adjusted.

[0053] In one example, the second stage may set the reflux ratio of the first separation system within the range of 0.5 to 5. The effects of setting it in this way are as described above.

[0054] The combination of the first and second stages has the same mechanism as conventional reactive distillation. However, in the third and fourth stages, the target product is discharged through the top of the column in order of boiling point, which is clearly different from the conventional method of discharging the target product through the bottom of the column in the reverse order. In particular, the present invention requires adjusting the operating conditions in each of the second to fourth stages for this purpose.

[0055] In one example, the second stage may set the reboiler temperature of the first separation system to a range of 90° C. to 100° C. In this case, the overhead stream of the first separation system may contain ethanol, methanol, and DMC as main components, and the bottom stream of the first separation system may contain DEC and EMC as main components.

[0056] The conditions for separation and purification in the third step can also be adjusted appropriately.

[0057] In one example, the third stage can be applied to a separation system having a theoretical plate number in the range of 15 to 80 as the second separation system. A separation system having a theoretical plate number in this range can exhibit appropriate plate efficiency and be manufactured economically. Furthermore, a separation system having a theoretical plate number in this range can be easily maintained and the thermal expansion coefficient of the separation system can be easily adjusted.

[0058] In one example, in the third stage, the reflux ratio of the second separation system can be set within a range of 0.5 to 5. The effects of setting it in this way are as described above.

[0059] In one example, the third stage may set the temperature of the reboiler of the second separation system within a range of 110° C. to 120° C. In this case, the overhead stream of the second separation system may contain EMC as a main component, and the bottom stream of the second separation system may contain DEC as a main component.

[0060] The conditions for separation and purification in the fourth step can also be adjusted appropriately.

[0061] In one example, the fourth stage can be performed using a separation system having a theoretical plate number in the range of 15 to 80 as the third separation system. A separation system within this range exhibits appropriate plate efficiency and can be manufactured economically. Furthermore, within this range, maintenance is easy and the thermal resin of the separation system can be easily adjusted.

[0062] In one example, in the fourth stage, the reflux ratio of the third separation system can be set within a range of 0.5 to 5. The effects of setting it in this way are as described above.

[0063] In one example, the fourth stage may set the reboiler temperature of the third separation system to a range of 130° C. to 140° C. In this case, the overhead stream of the third separation system may contain DEC as a main component, and the bottom stream of the third separation system may contain remaining heavy components as a main component.

[0064] Meanwhile, the method for producing carbonate of the present invention may further include conventional steps known in the art before or after each of the above steps, in addition to the above steps. [Example]

[0065] The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the scope of the present invention.

[0066] [Gas Chromatography] The purity of the product, the content of impurities and heavy components in the product, were analyzed by gas chromatography (GC). Specifically, 1 g of the target substance was mixed with 0.1 g of m-xylene and GC was performed on the sample. The GC equipment used was a Young Inchromass YL6500GC product, where the GC column was an Agilent DB-1 30 m x 0.32 mm, and the GC detector was an FID.

[0067] [ICP-AES] The metal content of the product was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES). A Perkinelmer Optima 8300 model was used. A 10 g sample of the effluent was mixed with 10 ml of 70% nitric acid and 10 ml of water, heated at 250°C for 2 hours, and then analyzed.

[0068] [color] The color of the product was evaluated by APHA. APHA is also called Hazen or Pt / Co color and refers to the yellowness of a liquid sample. To measure APHA, a Tintometer PFX995 automatic colorimeter was used. After filling the cell to about 3 / 4 of its height with the sample, the sample was placed firmly on the right side, the temperature was set to room temperature, and the READ key was pressed to perform the analysis. After three measurements, the average value was used as the result.

[0069] [Example] A reaction system consisting of four fixed-bed reactors connected in series was prepared. Each reactor was packed with 80 cc (58 g) of a porous, strongly basic anion exchange resin (Samyang, Trilte AMP-18) with trimethylammonium (TMA) ions as the exchanger and chloride ions as the ion type, and an exchange capacity of 1.3 eq / L. The feedstock contained ethanol (EtOH) and DMC at a mass ratio (EtOH / DMC) of 0.8. The system was operated by continuously feeding the feedstock into the reactor system at 2 cc / min while maintaining the system temperature at 70°C.

[0070] The reaction product was fed to a first separation system. The number of plates in the first separation system was 60. Separation was carried out at a reflux ratio of 3, atmospheric pressure, and a reboiler temperature of 93 to 100°C. An effluent containing DMC, EtOH, and MeOH as main components was obtained at the top of the column, and an effluent containing EMC and DEC as main components was obtained at the bottom of the column.

[0071] The bottom stream from the first separation system was fed to a second separation system. The second separation system had 60 stages. Separation was carried out at a reflux ratio of 3, atmospheric pressure, and a reboiler temperature of 110 to 120°C. EMC with a purity of 99.9% or higher and a total metal content of 1 ppm or less was obtained at the top of the second separation system. An effluent containing DEC as the main component was obtained at the bottom of the second separation system.

[0072] The bottom stream from the second separation system was fed to a third separation system. The third separation system had 60 plates. Separation was carried out at a reflux ratio of 3, atmospheric pressure, and a reboiler temperature of 130-140°C. DEC with a purity of 99.9% or higher and a total metal content of 1 ppm or less was obtained from the top of the third separation system. The heavy fraction obtained from the bottom of the third separation system was discarded.

[0073] [Comparative Example 1] The same procedure as in Example 1 was carried out, except that the reflux ratios in the first to third separation systems were all set to 0.3.

[0074] Comparative Example 2 The procedure was the same as in Example 1, except that the third separation system was not used and an operation was performed to obtain a bottom stream from the second separation system containing DEC as a main component. The results of Example and Comparative Examples 1 and 2 were compared and are shown in Tables 1 and 2 below.

[0075] [Table 1]

[0076] [Table 2]

[0077] From Table 1, it can be seen that the reflux ratio of the separation system according to the present invention must be satisfied. If the reflux ratio is less than 0.5, the ratio of the reflux liquid volume to the effluent volume at the top of the column is not small, resulting in an increased amount of product effluent. However, it is difficult to obtain carbonate with a purity of 99.9% or higher.

[0078] According to Table 2, if the DEC is extracted from the bottom of the column without using enough separation systems, it is difficult to obtain a high-purity carbonate. In this case, the amount of impurities is high and the APHA value is too high to be used as an organic solvent for lithium-ion batteries. Therefore, considering the high purity, metal content, and APHA value, it is necessary to produce carbonate using the method of the present invention.

Claims

1. a first stage comprising: charging a feedstock comprising dimethyl carbonate and ethanol into a fixed-bed reactor system and inducing a transesterification reaction of the feedstock to produce a product comprising ethyl methyl carbonate, diethyl carbonate, and methanol; a second stage of feeding a reactor effluent containing the product and an unreacted portion of the feedstock to a first separation system, and separating the reactor effluent through the first separation system to obtain a first separation system overhead stream containing primarily ethanol, methanol, and dimethyl carbonate, and a first separation system bottom stream containing primarily diethyl carbonate and ethyl methyl carbonate; a third step of separating the bottoms stream from the first separation system through a second separation system to obtain a second separation system overhead stream comprising primarily ethyl methyl carbonate and a second separation system bottoms stream comprising primarily diethyl carbonate; a fourth stage of separating the bottoms stream of the second separation system through a third separation system to obtain an overhead stream of the third separation system comprising primarily diethyl carbonate; The ratio (EtOH / DMC) of the weight of dimethyl carbonate (DMC) to the weight of ethanol (EtOH) in the raw material is within the range of 0.1 to 10; The second step involves applying a separation system having a number of theoretical stages in the range of 15 to 80 as the first separation system, setting a reflux ratio of the first separation system in the range of 0.5 to 5, and setting a reboiler temperature of the first separation system in the range of 90°C to 100°C, The third step is to apply a separation system having a theoretical number of stages in the range of 15 to 80 as the second separation system, set the reflux ratio of the second separation system in the range of 0.5 to 5, and set the reboiler temperature of the second separation system in the range of 110°C to 120°C; The fourth step is to apply a separation system having a theoretical number of stages in the range of 15 to 80 as the third separation system, set a reflux ratio of the third separation system in the range of 0.5 to 5, and set a reboiler temperature of the third separation system in the range of 130°C to 140°C. A method for producing carbonates.

2. the fixed bed reactor system includes a fixed bed reactor packed with a basic ion exchange resin catalyst; the basic ion exchange resin is porous; The exchange capacity of the basic ion exchange resin is in the range of 1 (eq / L-wet resin) to 1.5 (eq / L-wet resin). A method for producing the carbonate according to claim 1.

3. The fixed bed reactor system includes a plurality of fixed bed reactors connected in series. A method for producing the carbonate according to claim 1.

4. The first separation system to the third separation system are tray columns or packing columns. A method for producing the carbonate according to claim 1.

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