Carbonate manufacturing method

Abstract

The present invention relates to a method for producing carbonate. According to the method of the present invention, the conversion rate of DMC and the selectivity of EMC can be increased in the transesterification reaction of DMC and EtOH.

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbonates. [Background technology]

[0002] Ethyl methyl carbonate (hereinafter referred to as "EMC") and diethyl carbonate (hereinafter referred to as "DEC") are mainly used as organic solvents for battery electrolytes. EMC and DEC are produced by transesterification using dimethyl carbonate (hereinafter referred to as "DMC") and ethanol (hereinafter referred to as "EtOH") as raw materials. This reaction is also reversible. The reaction can also proceed in the presence of a catalyst. A basic catalyst can be used as this catalyst, and a typical example is sodium methoxide (hereinafter referred to as "SME"). The reaction is summarized in the following reaction formula 1: [ka]

[0003] Market forecasts for EMC and DMC indicate that future demand for EMC will be five times higher than that for DEC, so it is necessary to produce highly selective EMC using the same raw materials.

[0004] Conventional techniques (e.g., Patent Documents 1 and 2) use reactive distillation equipment to produce DMC and EMC. These techniques can achieve high DMC conversion rates. However, as the DMC conversion rate increases, the selectivity for DEC rather than EMC also increases. Therefore, it is difficult to increase the selectivity for EMC using these techniques. Furthermore, the operation of these techniques is complicated.

[0005] Therefore, there is a need to develop methods to enhance the selectivity of EMC in the reaction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] CN103804124B [Patent Document 2] KR10-1668571B Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to simultaneously increase the conversion rate of DMC and the selectivity of EMC in the transesterification reaction of DMC and EtOH. [Means for solving the problem]

[0008] The carbonate production method of the present invention includes a first step of producing a raw material mixture containing dimethyl carbonate and ethanol, and a second step of inducing a transesterification reaction in the raw material mixture to produce a product containing ethyl methyl carbonate and diethyl carbonate, wherein diethyl carbonate is further added to the raw material mixture in the first step. [Effects of the Invention]

[0009] The method of the present invention can increase the conversion of DMC and the selectivity of EMC in the transesterification reaction of DMC and EtOH. [Brief explanation of the drawings]

[0010] [Figure 1] 1 shows a method of an embodiment of the present invention in which DEC is further included in the raw material mixture. DETAILED DESCRIPTION OF THE INVENTION

[0011] The contents of this application are explained in more detail below.

[0012] The present invention relates to a method for producing a carbonate. Specifically, the present invention relates to a method for producing a mixture of carbonates containing EMC and DEC. More specifically, the present invention relates to a method for improving the selectivity of EMC in the mixture. Hereinafter, the method for producing a carbonate of the present invention may be referred to as the "method of the present invention."

[0013] As used herein, the term "selectivity" refers to the proportion of the target product among all products in a chemical reaction that produces multiple products.

[0014] In the present invention, of the products of the transesterification reaction of DMC and EtOH, EMC, DEC, and methanol (hereinafter referred to as "MeOH"), is the target product, EMC. Furthermore, the EMC selectivity in the present invention means the ratio of EMC to the sum of EMC and DEC. Furthermore, the DEC selectivity in the present invention means the ratio of DEC to the sum of EMC and DEC.

[0015] The process of the present invention produces carbonates in at least two stages.

[0016] In the first step of the method of the present invention, a raw material mixture containing DMC and EtOH is produced. As will be described later, the present invention recognizes that the selectivity of the target product, EMC, is determined by the equilibrium of the chemical reaction of the raw materials, and that this equilibrium is controlled by the composition of the reactants in the raw material mixture.

[0017] In the second step of the method of the present invention, the raw material mixture is subjected to a transesterification reaction to produce a product containing EMC and DEC. The product may further contain MeOH, as shown in Reaction Scheme 1. A battery electrolyte uses the EMC and DEC as a solvent. EMC is the target product of the method of the present invention.

[0018] In the method of the present invention, the feed mixture further contains a non-target product in the first step. By adding the non-target product to the feed, the production of the target product can be increased at the same reactant conversion rate according to Le Chatelier's principle. That is, in the present invention, the feed mixture further contains DEC in the first step. This can increase the selectivity of EMC at the same reactant conversion rate.

[0019] The method for adding the non-target product, DEC, to the raw material mixture is not particularly limited, but examples of such a method include recycling DEC from the product obtained after the second step and supplying it to the raw material, or separately preparing DEC and adding it to the raw material.

[0020] That is, in one embodiment, the first step may further include adding the DEC produced in the second step to the raw material mixture. Specifically, the first step may include refluxing the diethyl carbonate produced in the second step and further including it in the raw material mixture.

[0021] Figure 1 shows a simplified scheme for this. The DEC resupply scheme shown in Figure 1 will be explained in more detail. First, DMC, EtOH, and a catalyst are introduced into a reactor, and then reacted to produce EMC, DEC, and MeOH. The resulting product stream is sent to a first distillation column (Column 1). In the first distillation column, EMC, a low-boiling compound, is separated from the top of the column. The remaining product is then sent to a second distillation column (Column 2). In the second column, heavier components are extracted from the bottom, and DEC is extracted from the top. The overhead DEC can then be recycled or refluxed back to the reactor, allowing the feed mixture to further contain DEC, an undesired product. The steps shown in Figure 1 are illustrative; the actual process for carrying out the method of the present invention may also include additional distillation columns for separating unreacted materials and / or alcohols (e.g., methanol and ethanol).

[0022] In another embodiment, the first step may further include adding (another) DEC other than the DEC produced in the second step, for example, DEC that is separately produced or prepared, to the raw material mixture.

[0023] As mentioned above, the selectivity of the target product of the present invention does not change significantly depending on the reaction temperature or the amount of catalyst used in the present invention, but can change depending on the composition of the reactants contained in the raw material mixture. In order to achieve the objective of the present invention, i.e., to maximize the conversion rate of the reactant DMC and the selectivity of the target product EMC, the ratio of materials contained in the raw material of the present invention can also be appropriately adjusted.

[0024] In one embodiment, the number of moles (mol DMC ) and the number of moles of ethanol (mol EtOH) may be in the range of 0.2 to 10. In other embodiments, the lower limit of the ratio may be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0. In other embodiments, the upper limit of the ratio may be 9, 8, 7, 6, 5, 4, 3, 2, or 1.

[0025] In one embodiment, the proportion of DEC further contained in the raw material mixture may also be appropriately adjusted. Meanwhile, since DEC directly affects the conversion rate of the reactant DMC and the conversion rate of the target product EMC, the amount of DEC added may be further adjusted when the ratio of the reactant DMC to the other reactant EtOH is within a specific range.

[0026] In one embodiment, the number of moles (mol DMC ) and the number of moles of ethanol (mol EtOH ) may be in the range of 0.9 to 1.1, and in this case, the molar ratio of the diethyl carbonate (mol DEC ) and the number of moles of dimethyl carbonate (mol DEC ) and the ratio (mol DEC / mol DMC ) may be in the range of 0.01 to 0.2. In another embodiment, the ratio may be in the range of 0.014 to 0.016. For reference, as mentioned above, the molar ratio of DEC to DMC may vary depending on the ratio of DMC to EtOH in the raw materials. In one embodiment, the second step, i.e., the transesterification of DMC and EtOH in the feedstock, can proceed under certain conditions.

[0027] As described above, the raw materials used in the method of the present invention include DMC and EtOH, and the reaction between them can be carried out in the presence of a catalyst. In one embodiment, the catalyst can be a basic catalyst. Specifically, the basic catalyst can include sodium methoxide, sodium hydroxide, sodium ethoxide, potassium hydroxide, potassium ethoxide, potassium methoxide, or a combination thereof. More specifically, the basic catalyst can be sodium methoxide.

[0028] In addition, the present invention allows the reaction to be carried out in a specific reactor. Chemical reactors are broadly divided into batch reactors and continuous flow reactors. Continuous flow reactors are further divided into continuously stirred tank reactors (CSTRs) and plug flow reactors (PFRs). In reactions involving a catalyst, the PFRs can function as packed bed reactors (PBRs). In the present invention, the type of reactor used to carry out the transesterification reaction is not particularly limited. That is, the second stage may be carried out in a batch reactor or a continuous reactor. In one embodiment, the second stage may be carried out in a PBR or a CSTR. Specifically, the second stage may be carried out in a CSTR.

[0029] As described above, the catalyst content does not affect the selectivity of the target product of the present invention, but it may be appropriately adjusted to shorten the time required to achieve that selectivity. In one embodiment, the amount of the basic catalyst used in the second step may be in the range of 0.02 to 1 part by weight per 100 parts by weight of dimethyl carbonate in the raw material mixture. In another embodiment, the lower limit of the amount of the basic catalyst used may be 0.05 parts by weight, 0.07 parts by weight, or 0.1 parts by weight. In another embodiment, the upper limit of the amount of the basic catalyst used may be 0.9 parts by weight, 0.8 parts by weight, 0.7 parts by weight, 0.6 parts by weight, 0.5 parts by weight, 0.4 parts by weight, 0.3 parts by weight, 0.2 parts by weight, or 0.1 parts by weight.

[0030] As mentioned above, the temperature of the transesterification reaction does not affect the selectivity of the target product of the present invention, but it should be appropriately adjusted to shorten the time required to achieve that selectivity. In one embodiment, the second step may be carried out at a temperature within a range of 30°C to 100°C. In another embodiment, the lower limit of the temperature for the second step may be 35°C, 40°C, 45°C, or 50°C. In another embodiment, the upper limit of the temperature for the second step may be 90°C, 80°C, 70°C, 60°C, 55°C, or 50°C. [Example]

[0031] The present invention will be described in more detail below through examples, which, however, are not intended to limit the scope of the present invention.

[0032] [Experimental Example 1] Qualitative and quantitative analysis Qualitative and quantitative analysis of the products was performed by GC (gas chromatography). 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 In Chromass YL6500GC product, with an Agilent DB-1 30 m x 0.32 mm GC column and an FID detector. The DMC conversion was measured as the mole percent of DMC consumed relative to the DMC feed amount. The EMC selectivity was measured as the mole percent of EMC produced relative to the total amount of EMC and DEC. The DCE selectivity was measured as the mole percent of DEC produced relative to the total amount of EMC and DEC.

[0033] [Experimental Example 2] Reaction of -DMC and EtOH The reaction shown in Reaction Scheme 1 was carried out in a 500 mL reactor. The contents of DMC, EtOH, and SME catalyst, and the reactor temperature were adjusted as shown in Table 1 below. The selectivities of EMC and DEC thus produced are also shown in Table 1 below.

[0034] [Table 1]

[0035] Table 1 shows that the selectivity of EMC in the transesterification reaction of DMC and EtOH varies greatly depending on the composition of the reactants, i.e., the molar ratio between EtOH and DMC. Table 1 also shows that the selectivity of EMC in the transesterification reaction of DMC and EtOH remains unchanged even when the catalyst concentration and reaction temperature are changed. Therefore, in order to increase the selectivity of the target product, EMC, it may be necessary to change at least the composition of the raw material mixture.

[0036] [Example 1] A 500 mL reactor was mixed with 90.08 g (1 mol) of DMC, 46.07 g (1 mol) of EtOH, and 1.7 g (0.0144 mol) of DEC. The mixture was then stirred at 500 rpm while the temperature was raised to 50°C, and 0.1 wt% of NaOCH3 catalyst was added relative to the weight of DMC. The reaction was carried out for 1 hour. After the reaction was completed, samples were taken from the reactor and the concentrations of DMC, EMC, and DEC were measured by GC analysis. The results showed a DMC conversion of 53.1%, an EMC selectivity of 85%, and a DEC selectivity of 15%.

[0037] [Example 2] Except for changing the amount of DEC used to 5 g (0.0423 mol), the reaction was carried out in the same manner as in Example 1. As a result, the conversion of DMC was 53.4%, the selectivity to EMC was 87.9%, and the selectivity to DEC was 12.1%.

[0038] [Example 3] Except for changing the amount of DEC to 7 g (0.0593 mol), the reaction was carried out in the same manner as in Example 1. The DMC conversion was 53.7%, the selectivity for EMC was 90.1%, and the selectivity for DEC was 9.9%.

[0039] [Example 4] Except for changing the amount of DEC to 13 g (0.1100 mol), the reaction was carried out in the same manner as in Example 1. The DMC conversion was 54.2%, the selectivity for EMC was 95.4%, and the selectivity for DEC was 4.6%.

[0040] [Example 5] Except for changing the amount of DEC to 17.8 g (0.1507 mol), the reaction was carried out in the same manner as in Example 1. The DMC conversion was 54.7%, the selectivity for EMC was 99.9%, and the selectivity for DEC was 0.1%.

[0041] [Comparative Example 1] Except for not adding DEC to the raw material, the reaction was carried out in the same manner as in Example 1. As a result, the DMC conversion was 54%, the selectivity to EMC was 82%, and the selectivity to DEC was 18%.

[0042] Comparative Example 2 The reaction was carried out in the same manner as in Example 1, except that DEC was not added to the raw materials and the molar ratio of EtOH to DMC (EtOH / DMC) was changed to 0.2. As a result, the DMC conversion was 21%, the selectivity to EMC was 96%, and the selectivity to DEC was 4%. The information and results of the Examples and Comparative Examples are summarized in Table 2 below.

[0043] [Table 2]

[0044] Table 2 shows that adding DEC under the same conditions increases the selectivity of EMC (Example 1 and Comparative Example 1). Also, when trying to increase the selectivity of EMC without adding DEC, the conversion rate decreases (Example 4 and Comparative Example 2).

Claims

1. a first stage of producing a feed mixture comprising dimethyl carbonate and ethanol; a second step of inducing a transesterification reaction in the feed mixture to produce a product comprising ethyl methyl carbonate and diethyl carbonate; In the first step, the raw material mixture further contains diethyl carbonate, the second step proceeds in the presence of a basic catalyst comprising sodium methoxide, sodium hydroxide, sodium ethoxide, potassium hydroxide, potassium ethoxide, potassium methoxide, or a combination thereof; In the raw material mixture, the number of moles of dimethyl carbonate (mol ＤＭＣ ) and the number of moles of ethanol (mol ＥｔＯＨ ) and the ratio (mol ＥｔＯＨ / mol ＤＭＣ ) is in the range of 0.9 to 1.1, and the number of moles of diethyl carbonate (mol ＤＥＣ ) and the number of moles of dimethyl carbonate (mol ＤＭＣ ) and the ratio (mol ＤＥＣ / mol ＤＭＣ ) is in the range of 0.0593 to 0.2, The DMC conversion rate is 53.7% or more, and the EMC selectivity is 90.1% or more. A method for producing carbonates.

2. The second stage is carried out in a continuous stirred tank reactor. A method for producing the carbonate according to claim 1.

3. The amount of the basic catalyst used in the second step is within the range of 0.02 parts by weight to 1 part by weight per 100 parts by weight of dimethyl carbonate in the raw material mixture. A method for producing the carbonate according to claim 1.

4. The second stage is carried out at a temperature in the range of 30°C to 100°C. A method for producing the carbonate according to claim 1.

5. In the first step, the diethyl carbonate produced in the second step is refluxed to further include it in the raw material mixture. A method for producing the carbonate according to claim 1.

6. In the first step, diethyl carbonate other than the diethyl carbonate produced in the second step is further added to the raw material mixture. A method for producing the carbonate according to claim 1.

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