Method for producing carbonate

Abstract

The present invention relates to a method for producing a carbonate. According to the method of the present invention, it is possible to suppress clogging of a column that occurs in the carbonate production process, specifically in the purification process.

Description

Technical Field

[0001] The present invention relates to a method for producing carbonate. Specifically, the present invention relates to a method for efficiently removing a catalyst used in a carbonate formation reaction.

Background Art

[0002] As the organic solvent of the battery electrolyte, mainly ethyl methyl carbonate (hereinafter referred to as "EMC") and diethyl carbonate (hereinafter referred to as "DEC") are used. EMC and DEC are produced by the transesterification reaction (ester exchange reaction) of dimethyl carbonate (hereinafter referred to as "DMC") and ethanol (hereinafter referred to as "EtOH"). This reaction is also a reversible reaction. Further, the reaction can be carried out in the presence of a catalyst. As this catalyst, mainly sodium methoxide (hereinafter referred to as "SME") is used. The following Reaction Formula 1 is the reaction formula (where MeOH is methanol).:

Chemical formula

[0003] SME has low solubility in carbonate compounds. That is, SME has low solubility in DMC as a reactant and EMC and DEC as products. Therefore, unless it is extracted separately, SME acts as a cause of process failure. Therefore, it is necessary to efficiently remove SME contained in the product stream of the reaction before purifying the product stream of the reaction.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention aims to provide a method capable of suppressing column plugging (a phenomenon in which a tube or the like is clogged by solid components) occurring in a carbonate production process, specifically, a carbonate purification process.

Means for Solving the Problems

[0005] The method for producing carbonate of the present invention includes a first step of inducing a transesterification reaction in a raw material mixture containing dimethyl carbonate and ethanol in the presence of a catalyst to produce a product containing ethyl methyl carbonate and diethyl carbonate, a second step of distilling the product in a distillation column to obtain a top stream and a bottom stream of the distillation column, and a third step of filtering the bottom stream of the distillation column, wherein the bottom stream of the distillation column contains a catalyst having an average particle size (D50) of more than 1 μm.

Advantages of the Invention

[0006] According to the method of the present invention, clogging of the column occurring in the carbonate production process, specifically in the purification process of the carbonate, can be suppressed.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

[0009] When the reaction according to the above Reaction Formula 1 is carried out, the reaction product solution contains the products EMC, DEC and MeOH and the unreacted reactants DMC and EtOH. Further, the product solution also contains the catalyst used in the reaction. Furthermore, as described above, the SME applied as the catalyst for the reaction has a low solubility in the carbonate which is the main component of the reaction product stream. Therefore, if the reaction product is introduced into the purification process without removing the catalyst, the catalyst will act as a cause of defects in the purification process.

[0010] The present invention aims to remove a catalyst from the reaction product using a filtration device such as a filter, and further enables the easy removal of this catalyst even with a general-purpose filter.

[0011] The method of the present invention proceeds in at least three steps. Also, FIG. 1 is a flowchart of the steps for proceeding with the method of the present invention.

[0012] The method of the present invention induces a transesterification reaction in a raw material mixture containing dimethyl carbonate and ethanol in the presence of a catalyst to produce a product containing ethyl methyl carbonate and diethyl carbonate. This process proceeds as shown in FIG. 1 above. Specifically, DMC and EtOH produce EMC, DEC, and MeOH through a transesterification reaction in the presence of a catalyst.

[0013] In one embodiment, it is possible to control the conversion rate of DMC as a reactant, the selectivities of EMC and DEC as products, etc. at the mixing ratio of the reactants in the raw material. That is, by adjusting the raw material composition, the selectivity of a specific target product can also be increased. Here, selectivity can mean the ratio of the amount of the target product to the total amount of the products. Specifically, the selectivity of EMC means the ratio of EMC to the sum of EMC and DEC. Also, the selectivity of DEC means the ratio of DEC to the sum of EMC and DEC.

[0014] On the other hand, in market forecast data for EMC and DEC, it is said that the future demand for EMC will be about five times or more higher than that for DEC. Considering this, when using the same raw material, it is advantageous to produce EMC with high selectivity. In one embodiment, the raw material mixture can contain DMC and EtOH in a molar ratio (EtOH / DMC) within the range of 0.5 to 8.0.

[0015] As described above, the reaction according to the formula described in Reaction Formula 1 is an ester exchange reaction. In this specification, inducing a reaction means appropriately adjusting conditions such as the temperature and pressure of the raw materials to induce the components contained in the raw materials to react. In the present invention, the conditions for inducing the reaction can be appropriately adjusted. For example, in the present invention, the reaction temperature can be appropriately controlled, or the content of the catalyst added can be appropriately controlled to try to induce the reaction quickly. However, this does not significantly affect the composition of the final reaction product. The composition of the final reaction product can be greatly affected by the composition of the reactants in the raw materials.

[0016] In one embodiment, the present invention can carry out the first stage in a specific reactor. For example, the present invention can carry out the first stage in a continuous stirred tank reactor (CSTR). When using a CSTR, it is easy to adjust the raw material composition. Since it is easy to adjust the raw material composition, the composition of the product can also be easily controlled to the target level. As described above, among the composition of the reactants, the amount of catalyst added, and the reaction temperature, the amount of catalyst added and the reaction temperature do not significantly affect the composition of the product.

[0017] Also, the present invention can be carried out in the presence of a catalyst in the first stage. In one embodiment, the catalyst may be an acidic catalyst or a basic catalyst, and a basic catalyst is more suitable. Specifically, the basic catalyst can include sodium methoxide, sodium hydroxide, sodium ethoxide, potassium methoxide, potassium hydroxide, potassium ethoxide, or a combination thereof. More specifically, the basic catalyst may be sodium methoxide. The SME catalyst is suitable for promoting the ester exchange reaction between DMC and EtOH.

[0018] In one embodiment, the appropriate dosage of the catalyst can also be adjusted. However, in the reaction of the present invention, increasing the appropriate dosage of the catalyst only affects the reaction rate and does not significantly affect the composition of the final product.

[0019] Through the process of purifying the target product from the reaction product, the target product can be obtained. At this time, if the reaction product is put into a device such as a purification column without any separate treatment, the purification process may not proceed smoothly. This is due to the catalyst contained in the reaction product. The catalyst must be removed before purifying the reaction product.

[0020] As a method for removing a catalyst that usually exists in a solid form, since it has pores smaller than the catalyst, a filtration method can be applied in which the liquid is passed through and the catalyst is filtered.

[0021] Carbonate-based compounds (such as DMC, EMC, DEC, etc.) cannot dissolve the catalyst (such as SME) applied in the present invention well. However, alcohol can dissolve the catalyst well. As can be confirmed from the above reaction formula, the reaction product may also contain alcohol (MeOH and unreacted EtOH). Therefore, the product flowing out from the reactor can contain the catalyst dissolved by alcohol. In this case, it is not easy to remove the catalyst by a filtration method such as a filter.

[0022] If a filter or the like with excellent filtration performance is introduced by having a smaller pore size, a catalyst with a very small size can also be filtered. However, if the pore size is small, the flow of the fluid flowing through the process is not smooth, so the operating pressure increases, and the process cost also increases as the operating pressure increases. In addition, since most filters are consumables, it is also difficult to replace relatively expensive filters regularly.

[0023] Therefore, it is necessary to make it easier to filter the catalyst even with a filter of normal performance. Also, this can be achieved by increasing the size of the catalyst present in the product stream. In the present invention, an additional step is further advanced before filtering the reaction product. Specifically, in the second step of the method of the present invention, the product is distilled in a distillation column to obtain a top stream and a bottom stream of the distillation column. Specifically, in the second step of the method of the present invention, the product is fed into a distillation column, the product is distilled, and a top stream and a bottom stream of the distillation column are obtained.

[0024] As a result of the distillation, the top stream flowing out of the distillation column mainly contains components with relatively low boiling points, and the bottom stream flowing out of the distillation column mainly contains components with relatively high boiling points. Since the distillation process corresponds to the separation of a gas-gas mixture, a liquid-liquid mixture, or a gas-liquid mixture, the catalyst should accumulate at the bottom of the distillation column. That is, the bottom stream of the distillation column contains the catalyst. Here, the catalyst particles present in the reaction product can aggregate to an appropriate size.

[0025] The average pore size of the filter used for filtration is usually around 1 μm. Therefore, the second step is carried out so that the average particle size of the catalyst in the bottom stream of the distillation column exceeds 1 μm. Here, the average particle size can mean the D50 particle size. Since the size of the particles formed by the catalyst present in the reaction product without distillation is smaller than this, it is difficult to filter with a filter. Also, even if the size of the particles thus formed is small through distillation, it is the same. That is, the bottom stream of the distillation column contains a catalyst with an average particle size (D50) exceeding 1 μm.

[0026] There can be various methods for setting the size of the aggregating catalyst. In the present invention, as one of them, the residence time of the reaction product stream, which is the substance to be distilled, in the distillation column can be adjusted. That is, the longer the residence time of the reaction product stream to be distilled in the distillation column, the larger the size of the aggregating catalyst particles can be.

[0027] In one embodiment, in the second stage, the residence time of the product may be in the range of 20 minutes to 120 minutes. The average particle size of the catalyst in the desired effluent can be achieved within this range. If the residence time is too long, the size of the distillation column will increase accordingly, and the process cost burden will become large. Therefore, it is important to ensure an appropriate residence time.

[0028] In this specification, the residence time in the distillation column can mean the time from the point when the temperature of the reaction product supplied to the distillation column reaches 80°C to the point when the bottom stream of the distillation column flows out. In one embodiment, in the second stage, the distillation can be carried out at a temperature in the range of 80°C to 100°C. The alcohol content in the bottom stream of the distillation column can be minimized within this temperature range.

[0029] Before purifying the reaction product after distillation is completed, it is impossible to prevent defects in the purification process without filtering the catalyst. Therefore, in the third stage of the method of the present invention, the bottom stream of the distillation column is filtered. The filtration can be carried out using a known filter. As such a filter, a physical filter can be applied. Examples of physical filters include Metal Filter, Metal Sintering Filter, Metal Powder Filter, Paper Filter, PTFE Filter, and Metal Strainer. The present invention does not limit the type of filter.

[0030] In one embodiment, in the third stage, the filtered stream can be purified. Also, the overhead stream flowing out from the distillation column can contain a small amount of high-boiling components. Therefore, the method of the present invention can further include a fourth stage, in which the overhead stream of the distillation column obtained in the second stage and the bottom stream of the distillation column filtered in the third stage can be purified. As a result, the target product can be obtained with high purity. The purification method is not particularly limited, and the purification process can be carried out using a known distillation column or the like.

[0031] In addition to the above content, the method of the present invention can further include all known methods for obtaining the reaction products described in the present invention.

Example

[0032] Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the scope of the present invention.

[0033] [Quantitative analysis] The quantitative analysis of the reaction product was performed using gas chromatography (GC) on a sample obtained by taking 1 g of the product and mixing it with 0.1 g of m-xylene. As the GC instrument, the YL6500GC product of Young In Chromass was used. Here, the GC column was DB-1 30 m * 0.32 mm, and the GC detector was FID.

[0034] [Particle size analysis] The particle size analysis of the catalyst in the bottom effluent of the distillation apparatus was performed using a NanoZS apparatus of Malvern. 1 mL of the effluent sample was collected and analyzed by placing it in the Cell of the apparatus without a pretreatment step.

[0035] [Na content of the filtrate] The Na content in the filtrate after filtering the bottom stream of the distillation apparatus was measured using inductively coupled plasma atomic emission spectrometry (ICP - AES). The Perkinelmer Optima 8300 model was used. 10 g of the effluent sample was mixed with 10 ml of 70% nitric acid and 10 ml of water, heated at 250 °C for 2 hours, and then analyzed.

[0036] [Example 1] The catalyst used in the reaction was filtered according to the following procedure. (1) 90.08 g (1 mol) of DMC and 46.07 g (1 mol) of EtOH were mixed to produce a raw material. (2) The raw material was fed into a 500 mL reactor, and while stirring at 500 rpm, the temperature of the reactor was raised to 50 °C. During this process, the SME catalyst was added so as to be 0.1 wt% based on the weight of DMC. (3) After 1 hour had passed, a sample in the reactor was taken and quantitative analysis was performed on it. At this time, the conversion rate of DMC in the product was 54 mol%, the selectivity of EMC was 82 mol%, and the selectivity of DEC was 18 mol%. (4) The effluent of the reactor was fed into a distillation apparatus, and the distillation of the effluent was advanced. The temperature of the effluent fed into the distillation apparatus was 50 °C. The effluent was heated at a heating rate of 5 °C / min to 100 °C. (5) After 20 minutes had passed since the temperature of the effluent reached 80 °C, the bottom stream of the distillation apparatus was taken, and particle size analysis of the catalyst in the bottom stream was performed. The result of measuring the average particle size (D50) of the catalyst was 1.61 μm. (6) The bottom stream of the distillation apparatus was filtered through a PTFE syringe filter having an average pore size of 1 μm, and the Na content of the filtrate was analyzed. The residual Na content was 16.12 ppm. The Na removal efficiency (%) calculated from this was 94.3%. The Na removal efficiency was calculated according to the following formula 1: [Formula 1] Na removal efficiency (%) = 100 * ((Na input amount (g) - residual Na content (g)) / (Na input amount (g)))

[0037] [Example 2] Except that particle size analysis was performed 20 minutes after the temperature of the effluent reached 100 °C in step (5), the catalyst was filtered in the same manner as in Example 1. The total residence time was 24 minutes. The results of measuring the average particle size (D50) of the catalyst were 1.67 μm, the residual Na content was 15.07 ppm, and the Na removal efficiency was 94.6%.

[0038] [Example 3] Except that particle size analysis was performed 30 minutes after the temperature of the effluent reached 100 °C in step (5), the catalyst was filtered in the same manner as in Example 1. The total residence time was 34 minutes. The results of measuring the average particle size (D50) of the catalyst were 1.71 μm, the residual Na content was 13.06 ppm, and the Na removal efficiency was 95.4%.

[0039] [Example 4] Except that particle size analysis was performed 90 minutes after the temperature of the effluent reached 100 °C in step (5), the catalyst was filtered in the same manner as in Example 1. The total residence time was 94 minutes. The results of measuring the average particle size (D50) of the catalyst were 3.03 μm, the residual Na content was 4.8 ppm, and the Na removal efficiency was 98.3%.

[0040] Figure 2 shows the results of particle size analysis of Example 1 (maintained at 80 °C for 20 min after reaching 80 °C, residence time 20 min), Example 2 (maintained at 100 °C for 20 min after reaching 100 °C, residence time 24 min), Example 3 (maintained at 100 °C for 30 min after reaching 100 °C, residence time 34 min), and Example 4 (maintained at 100 °C for 90 min after reaching 100 °C, residence time 94 min).

[0041] [Comparative Example] Except that the effluent from the reactor was immediately filtered through a filter without going through the distillation process, the catalyst was filtered in the same manner as in Example 1. Table 1 shows the results of particle size analysis of the comparative example. Here, the average size of the catalyst filtered by the method of the comparative example was about 0.75 μm.

[0042]

Table 1

[0043] Summarizing the above content, the following can be known. (1) Catalyst particles can be deposited during the process of distilling the reaction effluent. (2) By adjusting the distillation time (residence time), the size of the deposited catalyst particles can also be controlled. Specifically, when the distillation time increases appropriately, the size of the deposited catalyst particles also increases. (3) When filtered with a filter having the same pore size, the Na content in the fluid passing through the filter is low when the distillation time is long.

Claims

1. A first step of inducing a transesterification reaction in a raw material mixture containing dimethyl carbonate and ethanol in the presence of a catalyst to produce a product containing ethyl methyl carbonate and diethyl carbonate; A second step of distilling the product in a distillation column at a temperature in the range of 80°C to 100°C to obtain a top stream of the distillation column and a bottom stream of the distillation column; A third step of filtering the bottom stream of the distillation column, wherein the bottom stream of the distillation column contains a catalyst having an average particle size (D50) of more than 1 μm; In the second step, the residence time of the product is in the range of 20 minutes to 120 minutes; The residence time in the distillation column is the time from the point when the temperature of the reaction product supplied to the distillation column reaches 80°C to the point when the bottom stream of the distillation column flows out; A method for producing carbonate.

2. Further comprising a fourth step of purifying by combining the top stream of the distillation column obtained in the second step and the bottom stream of the distillation column filtered in the third step; The method for producing carbonate according to Claim 1.

3. The catalyst contains sodium methoxide, sodium hydroxide, sodium ethoxide, potassium methoxide, potassium hydroxide, potassium ethoxide, or a combination thereof; The method for producing carbonate according to Claim 1.

4. The first step is carried out in a continuous stirred tank reactor; The method for producing carbonate according to Claim 1.

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