Method for preparing carbonate

Abstract

The present invention relates to a method for preparing carbonate, the method comprising the steps of: supplying a raw material containing dimethyl carbonate and ethanol to an esterification reactor; inducing transesterification of the raw material in the presence of a sodium alkoxide-based catalyst to obtain an esterification product including ethylmethylcarbonate, diethylcarbonate, and methanol; supplying the esterification product to a distillation column to produce a top stream containing alcohol and a bottom stream containing a carbonate-based compound and the residual sodium alkoxide-based catalyst; filtering the bottom stream with a filter to remove the residual sodium alkoxide-based catalyst and obtain a catalyst-removed stream; and supplying the top stream and the catalyst-removed stream to a purification column so as to obtain a carbonate product, wherein the content of alcohol in the bottom stream is controlled to 6 wt % or less.

Description

Method for manufacturing carbonate

[0001] The present invention relates to a method for manufacturing carbonate.

[0002] Ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), which are used as organic solvents for battery electrolytes, are manufactured through an ester exchange reaction using dimethyl carbonate (DMC) and ethanol (EtOH) as raw materials, and sodium methoxide (NaOCH3, SME), which has excellent activity as a catalyst, is mainly used.

[0003] However, the above SME has low solubility in organic solvents and does not dissolve in DMC, EMC, and DEC, which causes column plugging in reaction distillation or purification processes, thereby becoming a cause of process trouble.

[0004] For example, Patent Document 1 discloses the production of EMC and DEC through reactive distillation using DMC, alcohol, and a catalyst, and the separation of the catalyst by including a strainer at the downstream end of the reactive distillation column. However, this process has a problem in that as alcohol is distilled in the reactive distillation column and the catalyst precipitates, powder accumulates in the packing inside the column, causing plogging.

[0005] Accordingly, in order to solve the aforementioned problems, research is needed on a method to efficiently remove the catalyst in the carbonate purification process.

[0006] [Prior Art Literature]

[0007] [Patent Literature]

[0008] (Patent Document 1) CN 103804124 B

[0009] The present invention aims to provide a method for producing carbonates that can prevent column plugging caused by catalyst precipitation by controlling the alcohol content in the bottom stream supplied to the filter section through distillation, in a method for producing EMC and DEC by reacting DMC with EtOH.

[0010] However, the technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0011] One embodiment of the present invention provides a method for producing carbonates, comprising the steps of: supplying a raw material containing dimethyl carbonate and ethanol to an esterification reactor; inducing an ester exchange reaction of the raw material in the presence of a sodium alkoxide-based catalyst to obtain an esterification product containing ethylmethyl carbonate, diethyl carbonate, and methanol; supplying the esterification product to a distillation tower to produce a top stream containing alcohol and a bottom stream containing a carbonate-based compound and a residual sodium alkoxide-based catalyst; introducing the bottom stream into a filter section to remove the residual sodium alkoxide-based catalyst and obtaining a catalyst-removed stream; and supplying the top stream and the catalyst-removed stream to a purification tower to obtain a carbonate product, wherein the alcohol content in the bottom stream is controlled to be 6 weight% or less.

[0012] The method for manufacturing carbonate according to the present invention can increase the removal efficiency of sodium alkoxide-based catalysts in the filter process by controlling the alcohol content in the bottom stream introduced into the filter section through distillation to a value below a specific value.

[0013] The present invention can accurately predict the removal efficiency of sodium alkoxide-based catalysts in a filter process.

[0014] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below.

[0015] Figure 1 is a schematic diagram showing a carbonate manufacturing process according to the present invention.

[0016] Figure 2 is a graph showing the efficiency of the filter according to the alcohol content in the bottom flow introduced into the filter section.

[0017] Figure 3 is a graph showing the Na content in the catalyst removal stream after filtration according to the alcohol content in the bottom stream introduced into the filter section.

[0018] In this specification, when a part is described as "comprising" a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0019] The inventors recognized that in the purification process of carbonates, the existing purification process has a problem in which a catalyst precipitates during the distillation process, causing column plugging. As a result of continuing research on this, they developed a method for manufacturing carbonates as follows.

[0020] The present invention will be described in detail below.

[0021] One embodiment of the present invention provides a method for producing carbonates, comprising the steps of: supplying raw materials including dimethyl carbonate (DMC) and ethanol (EtOH) to an esterification reactor; inducing an ester exchange reaction of the raw materials in the presence of a sodium alkoxide-based catalyst to obtain an esterification product including ethylmethyl carbonate (EMC), diethyl carbonate (DEC), and methanol (MeOH); supplying the esterification product to a distillation tower to produce a top stream containing alcohol and a bottom stream containing a carbonate-based compound and a residual sodium alkoxide-based catalyst; introducing the bottom stream into a filter section to remove the residual sodium alkoxide-based catalyst and obtaining a catalyst-removed stream; and supplying the top stream and the catalyst-removed stream to a purification tower to obtain a carbonate product, wherein the alcohol content in the bottom stream is controlled to be 6 weight% or less.

[0022] FIG. 1 is a schematic diagram showing a process for manufacturing carbonate according to one embodiment of the present invention. Referring to FIG. 1, an esterification product obtained by performing an ester exchange reaction between dimethyl carbonate and ethanol is transferred to a distillation column to generate a top stream and a bottom stream. The bottom stream is introduced into a filter section to perform filtration, and then supplied together with the top stream to a purification column to produce carbonate.

[0023] The above method for manufacturing carbonates can solve the problem of low solubility of the catalyst for DMC, EMC, and DEC and maximize the filtration efficiency of the catalyst in the filter by maintaining the alcohol content in the bottom stream below a specific value to reduce the amount of catalyst dissolved in the alcohol and utilizing filter equipment. Through this, unlike conventional carbonate manufacturing methods which entail column plugging problems, the above method for manufacturing carbonates has the advantage of suppressing column plugging problems caused by catalyst precipitation occurring during the carbonate manufacturing process, thereby enabling the production of economically viable EMC and DEC.

[0024] According to one embodiment of the present invention, the transesterification reaction of dimethyl carbonate and ethanol can be carried out in the presence of a sodium alkoxide-based catalyst, and Figure 1 below illustrates the reaction.

[0025] [Figure 1]

[0026]

[0027] According to one embodiment of the present invention, the esterification reactor in which the ester exchange reaction of dimethyl carbonate (DMC) and ethanol (EtOH) is performed may be a continuous stirred tank reactor (CSTR). When utilizing the CSTR reactor, the ratio of EtOH and DMC is easily controlled, thereby making it easy to achieve the desired production ratios of EMC and DEC.

[0028] According to one embodiment of the present invention, the sodium alkoxide-based catalyst used when performing the ester exchange reaction may include at least one selected from the group consisting of sodium methoxide (SME), sodium hydroxide, sodium ethoxide, sodium isopropoxide, and mixtures thereof, and specifically may be sodium methoxide. The SME catalyst has excellent activity and can promote the ester exchange reaction between DMC and EtOH.

[0029] According to one embodiment of the present invention, the esterification product after the ester exchange reaction is completed may be supplied to a distillation column. Through distillation in the distillation column, the low-boiling point component of the esterification product may be separated into a top stream and the high-boiling point component into a bottom stream. Specifically, the low-boiling point component may include ethanol (reactant) and methanol (product), and the high-boiling point component may include carbonate-based compounds such as DMC (reactant), EMC (product), and DEC (product). Additionally, the bottom stream may include an undistilled alcohol component and the sodium alkoxide-based catalyst.

[0030] According to one embodiment of the present invention, the alcohol content in the bottom stream may be controlled to be 6 weight% or less. The sodium alkoxide-based catalyst used in the transesterification reaction has very low solubility in organic solvents and very high solubility in alcohol. Specifically, since the solubility of the sodium alkoxide-based catalyst in the carbonate-based compound is close to zero, if alcohol is present in the bottom stream, a problem arises where some ionic catalysts dissolve in the alcohol and are not filtered out by the filter, which may cause plugging in the distillation process of the distillation column or the purification process of the purification column. Therefore, to prevent plugging caused by the catalyst, it is necessary to remove as much of the catalyst as possible, and to this end, it is necessary to increase the amount of alcohol distilled in the top stream to reduce the alcohol concentration in the bottom stream. Specifically, by minimizing the alcohol content in the bottom stream to 6 weight% or less, the catalyst removal efficiency in the filter process can be increased, and plugging in the distillation process or purification process can be prevented. Accordingly, there is an advantage in that the maintenance period caused by plugging can be shortened and the operating time can be increased, thereby achieving an increase in production volume.

[0031] According to one embodiment of the present invention, a step of removing residual sodium alkoxide-based catalyst by introducing a bottom stream, in which the alcohol content is controlled to 6 weight% or less, into a filter section may be further performed. Since the sodium alkoxide-based catalyst accumulates at the bottom of the distillation column according to the distillation process, the filter section may be provided at the bottom of the distillation column or may exist as a separate filter section.

[0032] The filter portion may include a filter composed of metal or polymer, and specifically, may include a syringe filter. The material of the filter included in the filter portion is not limited as long as it is a material that has chemical stability and does not react with the carbonate-based compound. Specifically, the filter may be made of at least one material selected from the group consisting of polyethylene, polypropylene, and polytetrafluoroethylene (PTFE). More specifically, the filter may be made of PTFE material.

[0033] When the filter section includes a filter made of the above material, the average diameter of the pores of the filter may be 0.3 to 2 μm, specifically 0.4 to 1 μm. More specifically, it may be 0.45 to 0.8 μm. If the average diameter is smaller than the above range, filtration may take a long time, and if the average diameter is larger than the above range, there is a problem that the catalyst may not be filtered out and may pass through the filter along with the bottom flow.

[0034] Figure 2 is a graph showing the efficiency of the filter according to the alcohol content in the bottom stream. Referring to Figure 2, as the alcohol content in the bottom stream increases, the efficiency of the filter decreases, and specifically, when the alcohol content in the bottom stream exceeds 6 weight%, the efficiency of the filter decreases rapidly.

[0035] In addition, Figure 3 is a graph showing the Na content in the catalyst removal stream according to the alcohol content in the bottom stream. Referring to Figure 3, as the alcohol content in the bottom stream increases, the Na content in the catalyst removal stream increases. Through this, the following Equation 1 regarding the Na content in the catalyst removal stream according to the alcohol content in the bottom stream can be derived.

[0036] [Equation 1]

[0037] Y = 0.0001*e 23.944X

[0038] (X: Alcohol content (weight fraction) in the bottom stream, Y: Na content (g) in the catalyst removal stream)

[0039] Specifically, the Na content in the catalyst removal stream can be set based on the desired catalyst removal efficiency. If filtration through a filter is not performed after distillation, the Na content in the catalyst removal stream may be up to 100% of the Na content in the introduced catalyst, and the catalyst can be removed such that the Na content in the catalyst removal stream is 0.1% or less of the Na content in the introduced catalyst, depending on the desired catalyst removal efficiency. By predicting the alcohol content in the bottom stream in real time through Equation 1 and adjusting the amount of alcohol distilled in the distillation column accordingly, plugging by the catalyst can be prevented.

[0040] According to one embodiment of the present invention, the top flow and the catalyst removal flow can be supplied to a purification column to obtain a carbonate product. Since the top flow may also contain a small amount of high-boiling point components, additional purification can be performed. The purification column is not particularly limited, and the purification process can be performed using a known distillation column. Through the purification process, alcohol, which is a low-boiling point component, is separated into the top flow of the purification column, and DMC, EMC, and DEC, which are high-boiling point components, are separated into the bottom flow of the purification column, thereby obtaining the desired carbonate products, EMC and DEC, with high purity.

[0041] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0042] [Preparation Example] - Synthesis of Raw Materials

[0043] 450.4 g (5 mol) of DMC and 230.35 g (5 mol) of EtOH were mixed in a 1,000 mL reactor. The mixture was stirred at 500 rpm while the temperature was raised to 50 ℃, and 0.1 wt% of NaOCH3 catalyst relative to the weight of DMC was added, followed by a reaction for 1 hour. After the reaction was completed, a sample was taken from the reactor, and the content of each component was measured via GC analysis. The results showed that the content of each component was as follows:

[0044] MeOH: 15 wt% EtOH: 12 wt% DMC: 32 wt% EMC: 33 wt%, DEC: 8 wt%

[0045] [Example 1]

[0046] 680.75 g of the above raw material was introduced into a 1,000 mL distillation column, and distillation was performed while increasing the temperature to 100 ℃. When the weight of the top stream was 359.52 g, distillation was stopped, and the bottom stream was acquired and its components analyzed. As a result, the alcohol content (MeOH and EtOH) in the bottom stream was approximately 6 wt%. The bottom stream was filtered using a PTFE syringe filter with a pore size of 0.45 μm. Subsequently, the Na content in the catalyst-removed stream obtained after filtration was analyzed using an ICP-AES instrument. The Na content in the catalyst-removed stream was 0.000479 g, and the Na removal efficiency was 99.75%.

[0047] [Example 2]

[0048] The catalyst in the raw material was removed in the same manner as in Example 1, except that distillation was stopped when the weight of the top stream was 449.4 g. The alcohol content in the bottom stream was about 1 wt%, the Na content in the catalyst removal stream was 0.000178 g, and the Na removal efficiency was 99.91%.

[0049] [Comparative Example 1]

[0050] The catalyst in the raw material was removed in the same manner as in Example 1, except that distillation was stopped when the weight of the top stream was 89.88 g. The alcohol content in the bottom stream was about 23 wt%, the Na content in the catalyst removal stream was 0.034306 g, and the Na removal efficiency was 81.99%.

[0051] [Comparative Example 2]

[0052] The catalyst in the raw material was removed in the same manner as in Example 1, except that distillation was stopped when the weight of the top stream was 179.76 g. The alcohol content in the bottom stream was about 19 wt%, the Na content in the catalyst removal stream was 0.013777 g, and the Na removal efficiency was 92.77%.

[0053] [Comparative Example 3]

[0054] The catalyst in the raw material was removed in the same manner as in Example 1, except that distillation was stopped when the weight of the top stream was 269.64 g. The alcohol content in the bottom stream was about 14 wt%, the Na content in the catalyst removal stream was 0.004439 g, and the Na removal efficiency was 97.67%.

[0055] [Experimental Example 1]

[0056] 1. Qualitative Analysis

[0057] The analysis of components within the raw material and the analysis of alcohol content in the bottom stream were performed using gas chromatography (GC). Specifically, GC was performed on a sample in which 1 g of the analyte was taken and mixed with 0.1 g of m-xylene. The GC instrument used was the YL6500GC from Youngin Chromass, where the GC column was a DB-1 30 m * 0.32 mm and the GC detector was an FID.

[0058] 2. Na content in the catalyst removal stream

[0059] The Na content in the catalyst removal stream was measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES). A Perkinelmer Optima 8300 model was used, and 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.

[0060] Classification Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Raw Material (g) 680.75680.75680.75680.75680.75 Top Flow (g) 89.88179.76269.64359.52449.4 Catalyst Removal Flow (g) 590.87500.99411.11321.23231.35 Na Content in Catalyst Removal Flow (g) 0.0343060.0137770.0044390.0004790.000178 Na Content in Input SME (g) 0.1904960.1904960.1904960.1904960.190496 Amount of Na Removed by Filter (g) 0.156 190.176 7190.186 056 0.190 170.190 318 Na removal efficiency (%) in filter 8 1.99 92.77 97.67 99.75 99.91 Alcohol content in bottom stream (wt%) 23 19 14 61

[0061] Referring to Figure 2 and Table 1, it was confirmed that when the alcohol content in the bottom stream exceeds 6%, the efficiency of the filter, which was 99.75% when the alcohol content in the bottom stream was 6%, decreases sharply to 81.99%. Through the examples and comparative examples, it was found that in order to secure a filter efficiency of 99% or more for Na, the alcohol content in the bottom stream must be managed to be 6 wt% or less.

[0062] In addition, referring to Fig. 3 and Table 1, it was confirmed that the Na content in the catalyst removal stream varied depending on the alcohol content in the bottom stream. Furthermore, the results of Fig. 3 accurately followed Equation 1 (R 2 =0.997) was found. In particular, when removing alcohol by distillation in a reaction where the molar ratio of EtOH / DMC is 1 and the content of NaOCH3 catalyst is 0.1 wt% (based on DMC), the efficiency of the filter according to the alcohol content in the bottom stream could be predicted with high accuracy using Equation 1 above.

Claims

1. A step of supplying raw materials containing dimethyl carbonate and ethanol to an ester reactor; A step of inducing an ester exchange reaction of the above raw material in the presence of a sodium alkoxide-based catalyst to obtain an esterification product comprising ethylmethyl carbonate, diethyl carbonate, and methanol; A step of supplying the above esterification product to a distillation column to produce a top stream containing alcohol and a bottom stream containing a carbonate-based compound and a residual sodium alkoxide-based catalyst; A step of introducing the above-mentioned bottom flow into a filter section to remove residual sodium alkoxide-based catalyst and obtaining a catalyst-removed flow; and The method comprises the step of supplying the above top flow and the above catalyst removal flow to a purification tower to obtain a carbonate product; The alcohol content in the above-mentioned bottom flow is controlled to be 6 weight% or less, Method for manufacturing carbonate.

2. In Paragraph 1, The above sodium alkoxide-based catalyst comprises at least one selected from the group consisting of sodium methoxide, sodium hydroxide, sodium ethoxide, sodium isopropoxide, and mixtures thereof. Method for manufacturing carbonate.

3. In Paragraph 1, The Na content in the catalyst removal stream according to the alcohol content in the bottom stream is obtained by the following Equation 1, Method for manufacturing carbonate. [Equation 1] Y = 0.0001*e 23.944X In the above Equation 1, X is the alcohol content (weight fraction) in the bottom stream, and Y is the Na content (g) in the catalyst removal stream.

4. In Paragraph 1, The above filter portion comprises a filter made of at least one material selected from the group consisting of polyethylene, polypropylene, and polytetrafluoroethylene. Method for manufacturing carbonate.

5. In Paragraph 4, The average diameter of the pores of the above filter is 0.3 to 2 μm, Method for manufacturing carbonate.

6. In Paragraph 1, The above-mentioned transesterification reaction is carried out in a continuous stirred tank reactor (CSTR), Method for manufacturing carbonate.

Images