Carbonate manufacturing method

Abstract

The present invention relates to a method for producing carbonate. The method of the present invention can safely remove a catalyst used in a carbonate production reaction. The method of the present invention can prevent defects that may occur due to the catalyst in a step of purifying the product of the carbonate production reaction. The method of the present invention can produce carbonate in high yield.

Description

[Technical Field]

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

[0002] Specifically, the present invention relates to a method for efficiently removing a catalyst used in a carbonate production reaction. [Background technology]

[0003] Ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mainly used as organic solvents for battery electrolytes. EMC and DEC are produced by transesterification of dimethyl carbonate (DMC) and ethanol (EtOH). This reaction is reversible. This reaction can also be carried out in the presence of a catalyst. In this case, a basic catalyst is usually used. The following reaction scheme 1 shows this reaction (where MeOH is an abbreviation for methanol): [ka]

[0004] The reaction uses a basic catalyst (a metal salt containing, for example, an alkali metal or alkaline earth metal) as a catalyst. The catalyst has low solubility in carbonate, which is the reactant or product of the reaction. Therefore, if the catalyst is not removed separately, defects will occur in subsequent processes because the precipitated catalyst will cause column plugging or fouling in subsequent processes.

[0005] One method of removing the catalyst has been to filter it, but if the size of the catalyst is smaller than the pore size of the filter, or if the alcohol (methanol) contained in the reaction product dissolves the catalyst, the catalyst cannot be filtered out with the filter.

[0006] In addition, the catalyst used in the reaction includes sodium methoxide or sodium ethoxide, which are strongly basic and water-phobic substances, and therefore, if the catalyst is removed using a filter or the like or is exposed to the atmosphere during replacement, stability problems may arise.

[0007] Patent Document 1 describes the production of dimethyl carbonate through reactive distillation using a NaOCH3 catalyst and the removal of the catalyst using a sintered metal filter. However, since Patent Document 1 uses a filter to remove the catalyst, the catalyst may be exposed to the atmosphere or moisture during the filter replacement process, which may pose a safety issue. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] CN104557554A Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to safely remove the catalyst used in the carbonate production reaction.

[0010] The present invention aims to prevent defects that may occur due to catalysts in the process of purifying the product of a carbonate production reaction.

[0011] The present invention is directed to producing carbonates in high yield. [Means for solving the problem]

[0012] The carbonate production method of the present invention includes a reaction step in which raw materials containing dimethyl carbonate and ethanol are reacted in the presence of a catalyst to produce a product containing ethyl methyl carbonate and diethyl carbonate; a catalyst neutralization step in which a catalyst remover is added to the product to produce a neutralization salt of the catalyst and the catalyst remover; and a neutralization salt removal step in which the neutralization salt is removed, wherein the catalyst remover has a pKa value of 2.0 or less. [Effects of the Invention]

[0013] The method of the present invention can safely remove the catalyst used in the carbonate production reaction.

[0014] The method of the present invention can prevent defects that may occur due to the catalyst in the step of purifying the product of the carbonate production reaction.

[0015] The process of the present invention can produce carbonates in high yields. DETAILED DESCRIPTION OF THE INVENTION

[0016] The contents of this application are explained in more detail below.

[0017] As described above, the present invention aims to efficiently recover or remove a catalyst used in the reaction to produce carbonate, specifically, ethyl methyl carbonate and diethyl carbonate. As a result, the product can be obtained with high purity. Furthermore, the present invention allows the catalyst to be safely removed. The carbonate thus produced can be usefully used as a solvent for secondary battery electrolytes.

[0018] As described above, the product of the reaction in the present invention cannot dissolve the catalyst used in the reaction. If the reaction is carried out without removing the catalyst, the catalyst will precipitate and clog pipes, causing column clogging or fouling, which can lead to process failures. While filtering the catalyst can be attempted, the catalyst may dissolve in the alcohol by-product of the reaction, allowing the dissolved catalyst to pass through the filter. Because the product stream containing the dissolved catalyst can also cause downstream process failures, it is necessary to remove the dissolved catalyst. Furthermore, because the catalyst used in the above reaction is a water-phobic material, exposing the catalyst to the atmosphere during filter replacement, for example, can pose a safety risk.

[0019] The present invention employs a specific catalyst remover to remove the catalyst used in the reaction. The catalyst remover can form a salt with the catalyst. As a result, by applying the method of the present invention, the catalyst used in the carbonate production reaction can be safely removed, allowing for the production of high-purity carbonate. Furthermore, the economic efficiency of the process can be ensured.

[0020] The method for producing carbonate in the present invention comprises at least three stages.

[0021] The method for producing carbonate in the present invention includes a reaction step in which a feedstock including dimethyl carbonate and ethanol is reacted in the presence of a catalyst to produce a product including ethyl methyl carbonate and diethyl carbonate.

[0022] As will be described later, dimethyl carbonate (DMC) and ethanol (EtOH) undergo a transesterification reaction to produce ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) as the main products, and methanol (MeOH) as a by-product.

[0023] The conversion rate of the reactants and the selectivity and yield of the target product may vary depending on the composition of the reactants in the raw materials. Therefore, the composition of the reactants in the raw materials can be adjusted to maximize the type of target product and the conversion rate of the reactants.

[0024] In one embodiment, the raw material may include dimethyl carbonate (DMC) and ethanol (EtOH) in a molar ratio (EtOH / DMC) ranging from 0.2 to 8.0.

[0025] Meanwhile, market forecasts for EMC and DEC indicate that future demand for EMC will be approximately five times higher than that of DEC. Considering this, it would be advantageous to produce EMC with high selectivity when using the same raw materials. In this case, the raw materials may contain DMC and EtOH in a molar ratio (EtOH / DMC) ranging from 0.5 to 2.0.

[0026] Furthermore, since the above-mentioned components are usually present in a liquid state, the raw material obtained by mixing these components may contain a small amount of water. For example, in the stage of producing the raw material, the raw material may be reacted with a water content in the range of 20 ppm to 500 ppm.

[0027] Since the present invention is directed to removing the catalyst remaining in the product, the reactor in which the raw materials are reacted is a reactor in which at least the catalyst remains in the reaction product.

[0028] On the other hand, in a fixed bed reactor, a catalyst is packed and fixed within the reactor. In the present invention, we attempt to remove the catalyst remaining in the product, but in a fixed bed reactor, the catalyst does not remain in the product. Therefore, the reactor described in the present invention is at least not a fixed bed reactor. In other words, the reactor described in the present invention is a reactor that contains at least a catalyst that flows within the reactor. Such a reactor is called a fluidized bed reactor in the industry.

[0029] In the method of the present invention, the reactor can be a continuous flow reactor, which is literally a reactor in which reactants are continuously fed and products are continuously discharged.

[0030] Continuous flow reactors can be broadly classified into two types. First, continuous stirred tank reactors or mixed flow reactors (CSTRs or MFRs) and second, plug flow reactors (PFRs). Of these, CSTRs can maintain a constant composition of components within the reactor. The present invention employs a CSTR as the reactor to promote a uniform reaction. That is, in one embodiment, the reaction step may involve reacting the raw materials in a continuous stirred tank reactor (CSTR).

[0031] The method of the present invention does not particularly limit the design of the reactor, and the design (size, etc.) of the reactor can be determined by comprehensively considering the reaction rate, the yield and / or selectivity of the target product, the conversion rate of the reactants, etc.

[0032] The chemical reaction used in the method of the present invention is the transesterification of DMC and EtOH. The conversion rate, selectivity, and yield of the target product vary depending on the composition of the reactants, the amount of catalyst, and the reaction temperature. The amount of catalyst and the reaction temperature affect the reaction rate.

[0033] On the other hand, as mentioned above, the chemical reaction used in the present invention significantly varies in product composition depending on the composition of the raw reactants. Furthermore, when the reaction is carried out in a specific reactor, such as a CSTR, the composition of the reactants can determine the product composition. In this case, the catalyst content and temperature may not significantly affect the product composition. Changing the catalyst content and temperature only affects the time required to reach the target product composition, but does not affect the final target composition.

[0034] Furthermore, since the conversion rate of the reaction does not have to be 100%, the product can contain a predetermined amount of DMC and EtOH contained in the raw material.

[0035] In the method of the present invention, the reaction is carried out in the presence of a catalyst. Catalysts applicable to the reaction may include sodium methoxide (NaOCH3), sodium ethoxide (NaOC2H5), potassium hydroxide (KOH), sodium hydroxide (NaOH), etc. Among these, sodium methoxide (or sodium methoxide, NaOCH3, SME) can be typically used. Carbonate in the reactants or products cannot dissolve the catalyst, but alcohol in the reactants or products can. Therefore, the product contains a predetermined amount of sodium ions (Na + ) which cannot be filtered out with a normal filter and can precipitate during the purification process after the reaction, causing process defects. In addition, since the catalyst is a water-phobic component, if it is attempted to be removed with a filter without a separate treatment as described above, it will be exposed to the atmosphere during the filter replacement process, which can pose a safety risk.

[0036] In one embodiment, the amount of the catalyst used may also be appropriately adjusted. In one embodiment, the reaction step may use a catalyst in a range of 0.02 wt % to 0.2 wt % based on the weight of the dimethyl carbonate. The content of the catalyst may refer to the content of the catalyst itself. For example, the catalyst may be applied as a solution dissolved in a specific solvent. In this case, the content of the catalyst may refer to the content of the catalyst itself excluding the solvent, not the solution.

[0037] The method of the present invention is intended to solve the problems that arise particularly from the use of the above-mentioned catalysts.

[0038] The method for producing carbonate according to the present invention includes a catalyst neutralization step in which a catalyst remover is added to the product to generate a neutralized salt of the catalyst and the catalyst remover. Specifically, in the catalyst neutralization step, the catalyst remover neutralizes with the catalyst to generate a neutralized salt and methanol, ethanol, or water. The remaining components excluding the neutralized salt vary depending on the type of catalyst. The catalyst used in the reaction is typically a basic component, and therefore the catalyst remover capable of neutralizing with the catalyst to generate a salt is an acidic component. Specifically, the catalyst used in the reaction is a strongly basic component, and therefore the catalyst remover capable of neutralizing with the catalyst to generate a salt is a strongly acidic component. Therefore, the catalyst remover used in the method of the present invention has a pKa value of 2.0 or less.

[0039] Although a variety of compounds having a pKa value of 2.0 or less can be used, in the present invention, it may be advantageous to use a dicarboxylic acid compound, more specifically a linear dicarboxylic acid compound, as a catalyst remover. Here, a linear dicarboxylic acid refers to a compound having a structure in which a linear alkylene is present between two carboxyl groups. A typical component of such a linear dicarboxylic acid compound is oxalic acid. In the method of the present invention, oxalic acid was actually used as a catalyst remover.

[0040] In the method of the present invention, since a catalyst remover, which is typically an acidic substance, is applied in the catalyst neutralization step, the pH value of the product to which the catalyst remover is added may also change. In one embodiment, the catalyst neutralization step may involve adding the catalyst remover so that the pH of the product to which the catalyst remover is added falls within a range of 5 to 8.

[0041] Furthermore, the method of the present invention can achieve a desired pH in the product by using a specific component as a catalyst remover, even with a relatively small amount of catalyst remover. In one embodiment, the catalyst neutralization step may involve adding the catalyst remover in an amount ranging from 0.7 to 1 times the weight of the catalyst. Other acidic compounds can be used as catalyst removers, but these require a significant amount to achieve the desired pH in the product.

[0042] The method for producing carbonate according to the present invention includes a neutralization salt removal step for removing the neutralization salt generated in the catalyst neutralization step. By removing the neutralization salt, a reaction product free of the neutralization salt can be produced. The neutralization salt must be removed because it exists as a solid in the reaction product and may cause defects in subsequent processes. That is, in the present invention, the neutralization salt generated by the catalyst must be removed from the product before purifying the product containing the neutralization salt generated by the catalyst to obtain the product.

[0043] In one embodiment, in the method of the present invention, the neutralization salt formed by the catalyst is removed in the neutralization salt removal step. In one embodiment, the neutralization salt can be removed by filtration. By passing the reaction product through a filter with an appropriate pore size, the neutralization salt remains on the filter, allowing the neutralization salt to be removed from the product.

[0044] The method according to the present invention may further include a step of separating the product from which the catalyst has been removed based on the above content. Specifically, the method according to the present invention may further include a product separation step of separating ethyl methyl carbonate or diethyl carbonate from the reaction product from which the neutralization salt has been removed.

[0045] The target product of the chemical reaction used in the method of the present invention is carbonate. Currently, DEC is used as a solvent for secondary battery electrolytes, but as mentioned above, there is also a significant demand for EMC. Therefore, the method of the present invention can proceed with a step of separating a specific compound (DEC or EMC) as the target product from the carbonate contained in the product stream depending on its business importance.

[0046] In addition to the above steps, the method according to the present invention may include all other steps known to be required in the process for producing carbonate-based compounds and the process for removing the catalyst used therein. [Example]

[0047] 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.

[0048] [Experimental Example 1] Karl-Fischer The moisture content of the raw materials was measured using the Karl-Fischer method.

[0049] [Experimental Example 2] Dynamic light scattering analysis The average size of the neutralized salts generated by the neutralization reaction of the catalyst remover with the catalyst was measured by dynamic light scattering analysis. Dynamic light scattering analysis was performed using a Malvern NanoZS device. A 1 mL sample of the product from which the neutralized salts were generated was placed in the cell of the device without any pretreatment process and analyzed.

[0050] [Experimental Example 3] Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) The sodium content was measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES), model Optima 8300, manufactured by Perkinelmer. Ten grams 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.

[0051] [Experimental Example 4] Gas chromatography Qualitative and quantitative analysis of the product was performed by gas chromatography (GC). Specifically, 1 g of the product was mixed with 0.1 g of m-xylene and GC was performed on the sample. The GC equipment used was a Young In Chromas YL6500GC product, with a DB-1 30 m*0.32 mm GC column and an FID detector. The conversion of dimethyl carbonate, the main reactant of the raw material, was calculated as the mole percent consumed relative to the amount input. The selectivity of the product diethyl carbonate was calculated as the mole percent of the diethyl carbonate content relative to the total content of ethyl methyl carbonate and diethyl carbonate. The selectivity of the product ethyl methyl carbonate was calculated as the mole percent of the ethyl methyl carbonate content relative to the total content of ethyl methyl carbonate and diethyl carbonate.

[0052] [Example 1] A raw material solution was prepared by mixing 90.1 g (1 mol) of DMC and 46.07 g (1 mol) of EtOH. The water content of the raw material was 65 ppm. A catalyst solution was prepared by dissolving SME catalyst in methanol at a concentration of 30 wt%. The SME catalyst was added to a 500 mL reactor together with the raw material solution at a ratio of 0.04 wt% based on the weight of the raw material DMC.

[0053] The transesterification reaction was carried out for 1 hour under a reactor pressure of 1 bar, a reaction temperature of 50°C, and an agitation speed of 500 rpm. The DMC conversion in the product was 54 mol%, the selectivity for EMC was 82 mol%, and the selectivity for DEC was 18 mol%.

[0054] After the reaction was completed, oxalic acid (OA) was added to the product as a catalyst remover in an amount of 0.82 times the catalyst weight. The pH of the product and the particle size of the solid precipitate were then analyzed. Particle size was measured using a dynamic light scattering (DLS) spectrophotometer. The product was filtered through a PTFE syringe filter with a pore size of 1 μm. The sodium content of the filtered product was measured using ICP.

[0055] [Example 2] The same procedure as in Example 1 was carried out, except that a raw solution having a water content of 94 ppm was prepared and the SME catalyst was added to the reactor in an amount of 0.05 wt % based on the weight of the raw DMC.

[0056] [Example 3] The same procedure as in Example 1 was carried out, except that a raw solution having a water content of 130 ppm was prepared and the SME catalyst was added to the reactor in an amount of 0.067 wt % based on the weight of the raw DMC.

[0057] [Example 4] The same procedure as in Example 1 was carried out, except that a raw solution having a water content of 150 ppm was prepared and the SME catalyst was added to the reactor in an amount of 0.073 wt % based on the weight of the raw DMC.

[0058] [Comparative Example 1] The same process as in Example 1 was carried out, except that a raw material solution with a water content of 91 ppm was prepared, the catalyst solution was added to the reactor at a ratio of 0.05 wt% based on the weight of the raw material DMC, and PPA was added as a catalyst remover in an amount 1.2 times the weight of the catalyst.

[0059] Comparative Example 2 The same process as in Example 1 was carried out, except that a raw material solution with a water content of 65 ppm was prepared, the catalyst solution was added to the reactor at a ratio of 0.04 wt% based on the weight of the raw material DMC, and IPA was added as a catalyst remover in an amount 1.6 times the weight of the catalyst.

[0060] Comparative Example 3 The same process as in Example 1 was carried out, except that a raw material solution with a water content of 130 ppm was prepared, the catalyst solution was added to the reactor at a ratio of 0.07 wt% based on the weight of the raw material DMC, and IPA was added as a catalyst remover in an amount 1.6 times the weight of the catalyst. The raw material compositions and experimental results of the examples and comparative examples are summarized in Table 1.

[0061] [Table 1]

[0062] Table 1 shows that in Examples 1 to 3, in which OA, a linear saturated dicarboxylic acid with a low pKa (acid dissociation constant) of 1.25, was used, the pH of the product decreased from 12 to 7 even with the addition of a small amount of acid. It was also confirmed that the particle size of the neutralized salt generated by the addition of OA was 1 μm or larger.

[0063] Furthermore, the Na content of the filtered product was confirmed to be 0.50-0.64 mg / L, which was similar to the Na content in the raw material. This confirmed that the neutralization salts generated by the addition of OA were completely removed by the filter. However, in the comparative examples using polyphosphoric acid (pKa 2.16) (Comparative Example 1) and isophthalic acid (pKa 3.46) (Comparative Examples 2 and 3), the pH of the product was confirmed to decrease from 12 to approximately 7-8 only after using 1.5-2 times the amount of catalyst remover compared to the examples using OA.

[0064] Furthermore, although the particle size of the neutralized salts produced in the comparative examples was 1 μm or larger, the Na content of the filtered product was 2.83 to 6.18 mg / L. This indicates that the filter was unable to remove all of the neutralized salts produced by the addition of PPA or IPA. This is thought to be because the neutralized salts produced by PPA and IPA have high solubility in water, and the product stream dissolved the neutralized salts.

Claims

1. a reacting step in which a feedstock comprising ethanol and a carbonate consisting of dimethyl carbonate is homogeneously reacted in the presence of a catalyst to produce a product comprising ethyl methyl carbonate and diethyl carbonate; a catalyst neutralization step of adding a catalyst remover to the product to form a neutralized salt of the catalyst and the catalyst remover; a neutralization salt removal step of removing the neutralization salt by filtration; the catalyst remover is oxalic acid; the catalyst is sodium methoxide; The catalyst neutralization step involves adding the catalyst remover in an amount ranging from 0.7 to 1 times the weight of the catalyst so that the pH of the product to which the catalyst remover has been added is within the range of 5 to 8. A method for producing carbonates.

2. The reacting step involves reacting a raw material having a moisture content in the range of 20 ppm to 500 ppm. A method for producing the carbonate according to claim 1.

3. The reacting step uses a catalyst in the range of 0.02 wt % to 0.2 wt % based on the weight of the dimethyl carbonate. A method for producing the carbonate according to claim 1.

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