Process for preparing heterolinear carbonates using a catalyst having excellent solubility

Abstract

Provided is a method for producing a heterogeneous linear carbonate, including a step of performing transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of a catalyst selected from one or more of lithium methoxide (LME), lithium ethoxide (LEE), sodium methoxide (SME), sodium hydroxide (NaOH), and a mixture thereof, the catalyst being introduced in a state of being dissolved in a sulfoxide-based solvent.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a heterogeneous linear carbonate using a catalyst having excellent solubility. BACKGROUND

[0002] Ethyl Methyl Carbonate (EMC), Diethyl Carbonate (DEC) used as an organic solvent for battery electrolyte solution, a common method for preparing is a method of preparing by transesterification reaction of Dimethyl Carbonate (DMC) and ethanol.

[0003] At this time, a catalyst is used in the reaction, and as the catalyst, Sodium Methoxide (NaOCH3, SME) and Sodium Hydroxide (NaOH) having excellent activity are mainly used. However, the SME or NaOH has a problem of low solubility in an organic solvent, and thus cannot be dissolved in DMC, EMC, DEC, and thus causes column plugging in a reaction distillation process or a purification process, and becomes a cause of a process problem.

[0004] In relation to this, in Patent Document 1, DMC, alcohol, and a catalyst are used, and EMC and DEC are prepared by a reaction distillation method, and as can be seen with reference to the attached drawing, although a strainer for separating a solid phase is provided in the rear section of the reaction distillation column, if alcohol is distilled from the reaction distillation column, the catalyst is finally precipitated, and thus fine powder is accumulated on a gasket in the column, and plugging can still occur.

[0005] Further, in Patent Document 2, it is described that a high ratio of DEC is prepared by using the SME catalyst and reaction distillation, in which the inside of the reaction distillation column is composed of a porous tray, and the catalyst is injected in a state of being mixed with SME and alcohol such as ethanol, but this method also has a problem that, after alcohol is distilled from the inside of the reaction distillation column, the catalyst is precipitated in the concentrated solution at the lower end, and thus plugging occurs, and even if the catalyst is transferred to a separation process in the rear section, a problem can occur in the inside of an EMC purification column, and in the case of purifying DEC, DEC can be lost due to the precipitated SME.

[0006] Therefore, there is an urgent need to develop a method for effectively preparing a heterogeneous linear carbonate for a battery electrolyte solution, which can solve the above problems.

[0007] (Patent Document 1) Chinese Patent Publication No. 103804124

[0008] (Patent Document 2) Korean Patent Publication No. 10-1668571 SUMMARY

[0009] The present application provides a preparation method of a heterogeneous linear carbonate, which uses a sulfoxide-based solvent having excellent catalyst solubility, and does not precipitate the catalyst in a purification process, thereby reducing maintenance costs and enabling reuse of the catalyst, thus having excellent economic efficiency.

[0010] One embodiment of the present application provides a preparation method of a heterogeneous linear carbonate, which includes a step of performing an ester exchange reaction of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of a catalyst selected from one or more of lithium methoxide (LME), lithium ethoxide (LEE), sodium methoxide (SME), sodium hydroxide (NaOH), and a mixture thereof, the catalyst being introduced in a state of being dissolved in a sulfoxide-based solvent.

[0011] The preparation method of the heterogeneous linear carbonate of the present application has the effect of effectively preventing the catalyst from being precipitated during distillation by introducing the catalyst in a state of being dissolved in a sulfoxide-based solvent having excellent catalyst solubility during the ester exchange reaction, thereby minimizing process problems by preventing column clogging, thereby reducing maintenance costs and significantly improving the reuse efficiency of the catalyst. DETAILED DESCRIPTION

[0012] In the present specification, when a certain part "comprises" a certain constitutional element, unless particularly stated otherwise, it means that other constitutional elements are not excluded, but means that other constitutional elements can be further included.

[0013] In the present specification, the unit "wt%" can mean a weight ratio of a prescribed component in the entire components.

[0014] Hereinafter, the present application will be described in detail.

[0015] One embodiment of the present application provides a preparation method of a heterogeneous linear carbonate, the preparation method including a step of performing transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of a catalyst selected from one or more of lithium methoxide (LME), lithium ethoxide (LEE), sodium methoxide (SME), sodium hydroxide (NaOH), and a mixture thereof, the catalyst being introduced in a state of being dissolved in a sulfoxide solvent.

[0016] In the present application, the heterogeneous linear carbonate refers to a carbonate different from the dimethyl carbonate, and in detail, refers to an asymmetric linear carbonate and a symmetric linear carbonate, and more in detail, refers to ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0017] The preparation of the ethyl methyl carbonate and the diethyl carbonate is not limited, and can be performed by a method of using a reactive distillation column or a method of performing a reaction in a continuous stirred tank reactor (CSTR) and performing distillation in a distillation column, and in detail, since the composition of the ethyl methyl carbonate and the diethyl carbonate depends on the ratio of the dimethyl carbonate and the ethanol as an equilibrium reaction, the transesterification reaction can be performed in the CSTR so as to easily produce the ethyl methyl carbonate and the diethyl carbonate in a desired composition ratio as long as the ratio of the initially introduced dimethyl carbonate and ethanol is fixed.

[0018] This is because, in the case of the reaction distillation, since the ratio of the dimethyl carbonate and the ethanol varies in each stage, a harsh operation is required to obtain the ethyl methyl carbonate and the diethyl carbonate in a desired composition ratio.

[0019] In the CSTR, the dimethyl carbonate and the ethanol can be subjected to a transesterification reaction in the presence of a transesterification catalyst, thereby obtaining a target product. More specifically, when the dimethyl carbonate, the ethanol, and the catalyst as a preparation raw material are continuously supplied to the CSTR, the reactants generated in the reactor are discharged as a discharge stream, and then introduced into a distillation column to be distilled, thereby selectively separating and obtaining the ethyl methyl carbonate and the diethyl carbonate as a target product.

[0020] The catalyst used in the transesterification reaction can be one or more selected from the group consisting of lithium methoxide (LME), lithium ethoxide (LEE), sodium methoxide (SME), sodium hydroxide (NaOH), and a mixture thereof, and more specifically, one or more selected from the group consisting of sodium methoxide (SME) having excellent activity, sodium hydroxide (NaOH), and a mixture thereof.

[0021] However, as described above, such a catalyst has a problem in that it is not dissolved in dimethyl carbonate as a reaction raw material, ethyl methyl carbonate as a target product, diethyl carbonate, and the like, due to low solubility in an organic solvent, and thus has a problem in that it causes column clogging in a reaction process or a purification process.

[0022] Accordingly, the inventors of the present application have intensively studied a method capable of effectively solving such a problem, and as a result, have found that when the catalyst is put in a state of being dissolved in a polar solvent having excellent solubility, the problem can be solved to exert the following effects: that is, the catalyst is hardly precipitated to reduce maintenance costs, and the catalyst can be reused, so that the economic efficiency is excellent.

[0023] At this time, the polar solvent can be a sulfoxide-based solvent, and more specifically, the sulfoxide-based solvent can be represented by the following Chemical Formula 1.

[0024] [Chemical Formula 1]

[0025] R1-S(=O)-R2

[0026] In the Chemical Formula 1,

[0027] R1 and R2 are each independently a substituted or unsubstituted C1-C10 alkyl group, a C3-C8 cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group.

[0028] More specifically, the sulfoxide-based solvent can be dimethyl sulfoxide (DMSO) in which R1 and R2 are methyl groups.

[0029] As described above, dimethyl sulfoxide has high solubility for the catalyst. Thus, when the catalyst is dissolved in the solvent to be used, precipitation of the catalyst can be prevented, and thus the clogging problem can be effectively solved.

[0030] Further, since the catalyst in a state of being dissolved in the solvent is not precipitated, the catalyst can be directly reused after the target product is obtained by the purification process, and thus the process efficiency is improved in the continuous reaction process, and thus is more preferable.

[0031] The catalyst can be used in a state of being dissolved in the sulfoxide-based solvent at a content of 0.1% by weight or more and 3% by weight or less, specifically 0.1% by weight or more and 2% by weight or less, and more specifically 0.5% by weight or more and 1% by weight or less.

[0032] That is, a solution in which 0.1% by weight or more and 3% by weight or less, specifically 0.1% by weight or more and 2% by weight or less, and more specifically 0.5% by weight or more and 1% by weight or less of the catalyst is included based on the total weight of the solution in which the catalyst is dissolved in the solvent can be used.

[0033] When the content of the catalyst is too high, the catalyst is not completely dissolved in the sulfoxide-based solvent, and thus the catalyst is precipitated in the subsequent process, and thus is not preferable. When the content of the catalyst is too low, the total amount of the solvent to be used is increased, and thus the reaction efficiency can be decreased, and thus is not preferable.

[0034] The catalyst can be used in a state of being dissolved in the sulfoxide-based solvent at a content of 0.1% by weight or more and 3% by weight or less, specifically 0.1% by weight or more and 2% by weight or less, and more specifically 0.5% by weight or more and 1% by weight or less.

[0035] When the content of the catalyst is too high, the catalyst is not completely dissolved in the sulfoxide-based solvent, and thus the catalyst is precipitated in the subsequent process, and thus is not preferable. When the content of the catalyst is too low, the total amount of the solvent to be used is increased, and thus the reaction efficiency can be decreased, and thus is not preferable.

[0036] In addition, the dimethyl carbonate included as the reaction material can be purchased and used as a commercial product, and a dimethyl carbonate obtained by a publicly known method, such as a gas phase contact reaction of carbon monoxide and nitrous acid ester or a reaction of carbon dioxide and alcohol in the presence of a solid catalyst, can be used.

[0037] Further, the ethanol as another reaction material can be directly used as a commercial product, but it is preferable to use ethanol having a water content of 0.20 mass% or less (2000 mass ppm or less) so as not to affect the transesterification reaction of the present application. Among them, the removal of the contained water is performed by a dehydration operation such as a drying agent such as a molecular sieve, anhydrous magnesium sulfate, and / or calcium oxide.

[0038] The amount of ethanol used can be 20% by weight or more and 150% by weight or less, specifically 30% by weight or more and 130% by weight or less, and more preferably 40% by weight or more and 130% by weight or less, based on the weight of dimethyl carbonate.

[0039] When the amount of ethanol used is too small, the reaction cannot be efficiently performed, and on the other hand, when the amount of ethanol used is too large, the operation of removing ethanol after the reaction becomes complicated, and is also not preferable in terms of economy.

[0040] In addition, the reaction temperature of the transesterification reaction is affected by the temperature in the reactor. The reaction temperature can be 30°C or more and 130°C or less, specifically 60°C or more and 120°C or less, and more specifically 80°C or more and 100°C or less, and thus the temperature in the reactor can also be adjusted to this temperature range.

[0041] When the reaction temperature deviates from the above range, the reaction cannot be easily performed when the reaction temperature is too low, and the reaction efficiency is low, and when the reaction temperature is too high, there are problems in that the energy cost increases and the amount of reaction by-products increases, and thus this is not preferable.

[0042] Furthermore, the pressure of the reaction is not greatly limited, and the pressure of the reaction can vary depending on the reaction temperature and the reaction composition, and for example, can be normal pressure to 1000 kPa.

[0043] Thus, when the transesterification reaction is completed in the reactor, an effluent stream including methyl ethyl carbonate and diethyl carbonate is obtained. Furthermore, when this effluent stream is subjected to distillation after filtration, high-purity methyl ethyl carbonate and diethyl carbonate can be obtained.

[0044] Furthermore, according to the present application, when the catalyst is introduced in a state of being dissolved in a sulfoxide-based solvent, the amount of catalyst precipitated is significantly reduced, and thus not only the clogging problem can be solved, but also the catalyst can be reused, and thus the economy is very excellent.

[0045] Hereinafter, in order to specifically explain the present application, examples will be described in detail. However, the examples of the present application can be modified in various forms, and the scope of the present application is not construed as being limited to the examples to be described below. The examples in the present specification are provided in order to more completely explain the present application to those having an average knowledge in the art.

[0046] [Example 1]

[0047] Dimethyl carbonate (DMC) 135.12 g, ethanol (EtOH) 90.16 g, and sodium methoxide solution (SME, 1 wt% included in dimethyl sulfoxide (DMSO)) 13.5 g were used as raw materials, and the raw materials were reacted at 70°C, 1 bar, and 200 rpm for one hour.

[0048] In order to confirm the effect of the present application through a simple experiment, a batch reactor was used to react the raw materials, thereby synthesizing methyl ethyl carbonate and diethyl carbonate.

[0049] [Example 2]

[0050] Methyl ethyl carbonate and diethyl carbonate were synthesized in the same manner as in Example 1, except that sodium hydroxide solution (NaOH, 1 wt% included in dimethyl sulfoxide (DMSO)) 13.5 g was used instead of sodium methoxide solution (SME, 1 wt% included in dimethyl sulfoxide (DMSO)) 13.5 g.

[0051] [Example 3]

[0052] The raw materials were reacted in the same manner as in Example 1, using sodium hydroxide solution (NaOH, 1 wt% included in dimethyl sulfoxide (DMSO)) 13.5 g.

[0053] Then, the concentrated solution in which the reaction was completed was distilled, and the residue was used to re-feed dimethyl carbonate (DMC) 135.12 g and ethanol (EtOH) 103.66 g as raw materials identical to the above raw materials, and to react under the same conditions.

[0054] [Comparative Example 1]

[0055] Methyl ethyl carbonate and diethyl carbonate were synthesized in the same manner as in Example 1, except that sodium methoxide solution (SME, 1 wt% included in ethanol (EtOH)) 13.5 g was used instead of sodium methoxide solution (SME, 1 wt% included in dimethyl sulfoxide (DMSO)) 13.5 g.

[0056] [Comparative Example 2]

[0057] Methyl ethyl carbonate and diethyl carbonate were synthesized in the same manner as in Example 1, except that sodium hydroxide solution (NaOH, 1 wt% included in ethanol (EtOH)) 13.5 g was used instead of sodium methoxide solution (SME, 1 wt% included in dimethyl sulfoxide (DMSO)) 13.5 g.

[0058] [Experimental Example 1]

[0059] The qualitative and quantitative analysis of the consumption of dimethyl carbonate as a raw material for the preparation and the production of ethyl methyl carbonate and diethyl carbonate as target products in Examples 1 to 3 and Comparative Examples 1 and 2 above were performed, and the results are shown in Table 1 below.

[0060] For the qualitative and quantitative analysis, the obtained synthesis was passed through a filter, 1 g of the product passing through the filter was mixed with 0.1 g of m-xylene, and the concentration was measured using gas chromatography (GC) (YL6500GC, manufactured by YOUNG IN Chromass, GC column: DB-1 30 m x 0.53 mm, GC detector: FID). Also, the reaction conversion rate of the raw material dimethyl carbonate was calculated as the ratio of the consumption to the use amount in mol%, and the reaction selectivity of ethyl methyl carbonate and diethyl carbonate as target products was calculated as the ratio of each of the produced ethyl methyl carbonate and diethyl carbonate to the total content of both in mol%.

[0061] Also, the reaction concentrate produced after the reaction was distilled, the residue was filtered using a 0.45 μm syringe filter, and then the weight of the solid particles remaining on the filter was measured, and the results were similarly shown in Table 1.

[0062] [Table 1]

[0063]

[0064] As can be confirmed from Table 1, in the case of performing the reaction according to the method of the present application, the activity of the catalyst was the same as that in the case of performing the conventional method, but the deposition of the catalyst was significantly reduced, and there was almost no deposition amount, and as can be known from Example 3, almost the same activity was obtained even in the case of reusing the catalyst, and it can be confirmed that the reuse efficiency is very excellent.

Claims

1. A method for producing a heterogeneous linear carbonate, comprising a step of performing transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of a catalyst, wherein the catalyst is one or more selected from the group consisting of sodium methoxide, sodium hydroxide (NaOH), and a mixture thereof, the catalyst is put in a state of being dissolved in a sulfoxide solvent, wherein the sulfoxide solvent is dimethyl sulfoxide (DMSO).

2. The method for producing a heterogeneous linear carbonate according to claim 1, wherein the catalyst is put in a state of being dissolved in the sulfoxide solvent at a content of 0.1% by weight or more and 3% by weight or less.

3. The method for producing a heterogeneous linear carbonate according to claim 1, wherein 0.001% by weight or more and 3% by weight or less of the catalyst is put, based on the weight of the dimethyl carbonate.

4. The method for producing a heterogeneous linear carbonate according to claim 1, wherein the transesterification is performed in a continuous stirred tank reactor (CSTR).

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