Process for producing heterogeneous linear carbonates incorporating a catalytic filtering step

Abstract

The present invention relates to a method for producing a cellulose ester-transferase comprising the steps of: carrying out a transesterification reaction of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of a catalyst; and filtering the product obtained by the transesterification reaction through a filter.

Description

[Technical field]

[0001] The present invention relates to a process for the preparation of heterogeneous linear carbonates incorporating a catalytic filtering step. [Background technology]

[0002] Ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) used as organic solvents in battery electrolytes are generally produced by a transesterification reaction between dimethyl carbonate (DMC) and ethanol.

[0003] In this case, a catalyst is used during the reaction. The catalyst is sodium methoxide (NaOCH), which has excellent activity. 3 The main substances used are sodium hydroxide (NaOH) and sodium hydrate (SME).

[0004] However, the SME or NaOH has a problem that it has low solubility in organic solvents and is insoluble in DMC, EMC, and DEC, which induces column plugging in the reactive distillation process or purification process, causing process troubles.

[0005] In this regard, Patent Document 1 discloses a method for producing EMC and DEC by reactive distillation using DMC, alcohol, and a catalyst. Referring to the drawing, a strainer for separating a solid phase is provided at the rear of the reactive distillation tower. However, when alcohol is distilled in the reactive distillation tower, the catalyst eventually precipitates, and the powder accumulates on the packing inside the tower, which still induces plugging.

[0006] Furthermore, Patent Document 2 describes the use of the SME catalyst and reactive distillation to produce a high percentage of DEC. The inside of the reactive distillation tower is made up of porous trays, and the catalyst is injected in a mixed state of SME and alcohol such as ethanol. However, even with this method, when alcohol is distilled inside the reactive distillation tower, the catalyst precipitates from the concentrated liquid at the bottom, inducing plugging. Even if the catalyst is transferred to the downstream separation process, not only are problems expected inside the EMC purification tower, but there is also the problem of DEC loss occurring during DEC purification due to the precipitated SME.

[0007] Therefore, there is a need to study methods that can solve the above problems and effectively prepare various linear carbonates for battery electrolytes. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] China Patent Publication No. 103804124 [Patent Document 2] Korean Patent Publication No. 10-1668571 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a method for producing various linear carbonates, which can produce the target compound in excellent yield by introducing a catalyst filtering step into the synthesis to produce the various linear carbonates, since the catalyst is not precipitated during the purification process. [Means for solving the problem]

[0010] One embodiment of the present invention relates to a method for producing a dimethyl carbonate (DMC)-ethanol (EtOH) transesterification reaction in the presence of a catalyst, and filtering the product obtained by the transesterification reaction through a filter. Effect of the Invention

[0011] The method for producing heterogeneous linear carbonates according to the present invention solves the problem of low catalyst solubility by introducing a catalyst filtering step into the product obtained by transesterification, and can prevent column plugging due to catalyst precipitation that may occur in the purification process, thereby minimizing process problems and thereby reducing maintenance costs.

[0012] In addition, by using a CSTR for the transesterification reaction, it is easy to adjust the production ratio of the desired different linear carbonates by adjusting the ratio of the raw materials dimethyl carbonate and ethanol.

[0013] In addition, when ethanol and a catalyst are mixed in advance in a pre-reactor and then charged into a CSTR, the reaction rate can be increased, and productivity can be improved. BEST MODE FOR CARRYING OUT THEINVENTION

[0014] In this specification, when any part is said to "comprise" a certain component, this does not mean to exclude other components, but means that it may further include other components, unless specifically stated to the contrary.

[0015] In this specification, the unit "wt %" may refer to the weight percentage of a certain component in the total components.

[0016] The present invention will be described in detail below.

[0017] One embodiment of the present invention relates to a method for producing a dimethyl carbonate (DMC)-ethanol (EtOH) transesterification reaction in the presence of a catalyst, and filtering the product obtained by the transesterification reaction through a filter.

[0018] In the present invention, the different linear carbonates refer to carbonates different from the dimethyl carbonate, specifically, asymmetric linear carbonates and symmetric linear carbonates, and more specifically, ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0019] The catalyst used in the transesterification reaction may generally be one 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, may be one or more selected from the group consisting of sodium methoxide (SME), sodium hydroxide (NaOH), and a mixture thereof, each of which has excellent activity.

[0020] However, as mentioned above, such catalysts have low solubility in organic solvents, and are insoluble in the reaction raw material dimethyl carbonate and the target products ethyl methyl carbonate and diethyl carbonate, etc., which causes column plugging during the reaction and purification processes.

[0021] As a result of extensive research into a method for effectively solving such problems, the inventors of the present application have found that if the synthetic product obtained by the transesterification reaction is filtered, the catalyst is hardly precipitated during the purification process, and the target products diethyl carbonate and ethyl methyl carbonate can be produced in excellent yields, thus leading to the present invention.

[0022] The filtering step is carried out by filtering a product obtained by the transesterification reaction.

[0023] The filter may have pores with an average diameter of 0.3 to 2 μm, specifically, pores with an average diameter of 0.4 to 1 μm, and more specifically, pores with an average diameter of 0.45 to 0.8 μm.

[0024] The average diameter of the pores of the filter was measured by magnifying the surface of the filter sample by 2,500 times using a scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope), and the major axis length of the surface pores observed in a randomly sampled area (10 μm or more horizontally and 15 μm or more vertically) in the measured photograph was measured as the pore size. The number of measurements was a minimum of 10 or more, and the average pore size obtained after the measurement was calculated.

[0025] If the average diameter is outside the above range and is too small, it takes a long time to filter, whereas if it is too large, the catalyst will pass through the filter together, which is undesirable.

[0026] The material of the filter is not limited as long as it is chemically stable and does not react with the carbonate-based substance, but may be, for example, one or more materials selected from the group consisting of polyethylene, polypropylene, and polytetrafluoroethylene (PTFE), and more specifically, may be made of a polytetrafluoroethylene (PTFE) material.

[0027] In this way, when a compound is filtered through the filter having the above-mentioned pores, catalyst deposition during a reaction or purification process can be prevented, and thus the column plugging problem can be effectively solved.

[0028] Such a catalyst can be added in a state dissolved in an alcohol-based solvent at 0.1 to 3% by weight, specifically 0.1 to 2% by weight, and more specifically 0.5 to 1% by weight.

[0029] That is, based on the total weight of the solution in which the catalyst is dissolved in the solvent, a solution containing the catalyst in an amount of 0.1 to 3 wt %, specifically 0.1 to 2 wt %, and more specifically 0.5 to 1 wt % can be used.

[0030] If the weight percentage of the catalyst is too high outside the above range, the content that is not dissolved in the alcohol-based solvent increases, which is inefficient, whereas if the weight percentage is too low, the total amount of solvent added increases, which increases energy consumption and reduces reaction efficiency, which is undesirable.

[0031] The alcohol solvent may in particular be ethanol.

[0032] The amount of these catalysts used may be 0.001 to 3% by weight, specifically 0.001 to 1% by weight, and more specifically 0.001 to 0.1% by weight, based on the weight of dimethyl carbonate.

[0033] If the amount of catalyst added is too small and outside the above range, the reaction will not proceed efficiently, whereas if the amount of catalyst added is too large, the amount of catalyst added will be large despite the amount of catalyst not being used being large, which is undesirable from the viewpoint of economy.

[0034] In addition, the production of different linear carbonates, i.e., ethyl methyl carbonate and diethyl carbonate, according to the present invention can be carried out by carrying out the reaction in a continuous stirred tank reactor (CSTR) and distilling in a distillation column. Therefore, the transesterification reaction can be carried out by supplying raw materials into a continuous stirred tank reactor (CSTR).

[0035] Specifically, in the CSTR, the dimethyl carbonate and ethanol undergo an exchange reaction in the presence of a transesterification catalyst, from which the target product can be obtained. More specifically, when the raw materials dimethyl carbonate, ethanol, and a catalyst are continuously fed to the CSTR, the reactants produced in the reactor are discharged as an exhaust stream, and then introduced into a distillation column for distillation, whereby the target products ethyl methyl carbonate and diethyl carbonate are selectively separated and obtained.

[0036] In this case, the present invention performs the filtering process before the discharge stream is introduced into the distillation column.

[0037] Alternatively, the catalyst and ethanol may be mixed and supplied to a pre-reactor, and the transesterification reaction may be carried out in a continuous stirred tank reactor (CSTR).

[0038] That is, the catalyst dissolved in ethanol is charged into a pre-reactor together with ethanol as a reaction raw material, and mixed in advance. Then, this mixture and dimethyl carbonate are each supplied to a CSTR to carry out the reaction.

[0039] The inventors of the present application have confirmed that a more rapid reaction rate can be obtained by performing the pre-mixing process in this manner. Here, the mixing of the catalyst and ethanol is a concept that includes a reaction caused by mixing.

[0040] Specifically, the transesterification reaction begins when the OH group of the catalyst attacks the H of ethanol, so if ethanol and the catalyst are mixed together and reacted in advance, it is possible to avoid a decrease in concentration due to dimethyl carbonate, which has a beneficial effect on the reaction rate.

[0041] The dimethyl carbonate contained as the reaction raw material can be a commercially available product, and dimethyl carbonate produced by a known method, such as one obtained by subjecting carbon monoxide and a nitrite ester to a gas-phase catalytic reaction or one obtained by reacting carbon dioxide and an alcohol in the presence of a solid catalyst, can be used.

[0042] As another reaction raw material, ethanol may be used as is, but it is preferable to use ethanol with a water content of 0.20% by mass or less (2000 ppm or less) so as not to affect the transesterification reaction of the present invention. Here, the water content is removed by dehydration using a desiccant such as a molecular sieve, anhydrous magnesium sulfate and / or calcium oxide.

[0043] The amount of ethanol used may be 20 to 150% by weight, specifically 30 to 130% by weight, and more preferably 40 to 130% by weight, based on the weight of dimethyl carbonate.

[0044] If the amount of ethanol added is too small, the reaction will not proceed efficiently, whereas if too much is used, the trouble of removing it after the reaction will increase, and this is undesirable from an economic point of view.

[0045] The reaction temperature of the transesterification reaction is affected by the temperature inside the CSTR reactor. The reaction temperature may be 30 to 130° C., more specifically, 60 to 120° C., and more specifically, 80 to 100° C., and therefore the temperature inside the reactor can also be adjusted within such a temperature range.

[0046] If the reaction temperature is outside the above range and is too low, the reaction does not proceed easily, resulting in low reaction efficiency. If the reaction temperature is too high, the energy cost increases and the amount of reaction by-products produced increases, which is undesirable.

[0047] The pressure of the reaction is not particularly limited and may vary depending on the reaction temperature and the reaction composition, and may be, for example, normal pressure to 1000 kPa.

[0048] Also, the pH of the reaction is maintained in the range of 6 to 9. If necessary, an alkali metal compound or an alkaline earth metal compound can be added to the reaction to maintain the pH. Exemplary alkaline earth metal compounds include, but are not limited to, oxides, hydroxides, carbonates, and carboxylates.

[0049] The reaction time varies depending on the reaction conditions, reactants and other factors that can affect the reaction. Typically, however, the reaction time is 0.5 to 20 hours. In the case of a continuous process using a CSTR, the reaction time (residence time) is determined by the kinetics of the system, which is determined by the pressure, temperature and catalyst used.

[0050] Thus, the transesterification reaction in a CSTR includes the reaction pressure, temperature, reactant concentration, pH, and reaction time appropriate to produce the desired reaction product. Any particular conditions used in the process are not particularly limited and are selected based on the reactants and the compounds produced using the process.

[0051] When the transesterification reaction is completed using the CSTR, a reaction concentrate containing ethyl methyl carbonate and diethyl carbonate is obtained as an exhaust stream, which is then filtered and distilled to obtain high purity ethyl methyl carbonate and diethyl carbonate in excellent yields without catalyst precipitation.

[0052] Furthermore, according to the present invention, when the catalyst is mixed with ethanol in advance and then reacted, the decrease in concentration caused by DMC is avoided, the reaction rate is increased, and this is very economical. EXAMPLES

[0053] Hereinafter, the present invention will be described in detail based on examples in order to specifically explain the present invention. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention is not limited to the examples described below. The examples in the present specification are provided to more completely explain the present invention to those having average knowledge in the art.

[0054] [Example 1] Dimethyl carbonate (DMC) 540.48g, ethanol (EtOH) 360.592g, and sodium methoxide solution (SME, 1wt% in ethanol (EtOH)) 54.048g were injected into a CSTR having a volume of 100ml at a rate of 1.67ml / min to synthesize ethyl methyl carbonate and diethyl carbonate. The reaction was carried out at 70°C, 1bar, 3 hours, and pH 12. After the reaction, 300 g of the product was passed through a filter with a pore diameter of 0.45 μm in the outlet stream and then distilled.

[0055] [Example 2] Dimethyl carbonate (DMC) 1080.96g, ethanol (EtOH) 721.184g, and sodium methoxide solution (SME, 1wt% in ethanol (EtOH)) 108.096g were injected into a CSTR having a volume of 100ml at a rate of 10g / min to synthesize ethyl methyl carbonate and diethyl carbonate. At this time, the ethanol and SME were mixed in advance in a pre-reactor, and the mixture of the ethanol and SME mixed with the DMC was injected at the time of injection into the CSTR. At this time, the reaction was carried out at 70°C, 1 bar, 1 hour, and pH 12. After the reaction, 300 g of the product was passed through a filter with a pore diameter of 0.45 μm in the outlet stream and then distilled.

[0056] [Comparative Example 1] Ethyl methyl carbonate and diethyl carbonate were synthesized in the same manner as in Example 1, except that a batch reactor was used instead of a CSTR, and the reaction conditions were adjusted to 70° C., 1 bar, 1 hour, and pH 12. In addition, 300 g of the product obtained from the reaction was distilled.

[0057] [Comparative Example 2] Example 2, except that the ethanol and SME were not premixed in the pre-reactor. Ethyl methyl carbonate and diethyl carbonate were synthesized in the same manner as above. After the reaction, 300 g of the product was distilled in the exhaust stream.

[0058] [Experimental Example 1] In the above Examples 1 and 2 and Comparative Examples 1 and 2, qualitative and quantitative analyses were carried out on the consumption amount of the raw material dimethyl carbonate, and the production amount of the target products ethyl methyl carbonate and diethyl carbonate, and the results are shown in Table 1 below.

[0059] The qualitative and quantitative analysis was carried out by taking 1 g of the obtained product, mixing it with 0.1 g of m-Xylene, and then measuring the concentration using gas chromatography (GC) (YL6500GC; YOUNGIN Chromass, GC column: DB-1 30 m x 0.53 mm, GC detector: FID). In addition, the reaction conversion rate of the raw material dimethyl carbonate was calculated in mole % based on the amount consumed relative to the amount used, and the reaction selectivity of the target products ethyl methyl carbonate and diethyl carbonate was calculated in mole % based on the respective contents of the total contents of ethyl methyl carbonate and diethyl carbonate produced, respectively.

[0060] After the distillation was completed, the weight of the solid catalyst in the residue was measured, and the results are shown in Table 1 below.

[0061] [Table 1]

[0062] As can be seen from Table 1, when the method of the present invention, in which the reaction is carried out in a CSTR and a filtering process is introduced, the catalyst activity is the same as when the conventional method is used, but the filtration process significantly reduces catalyst deposition, and the amount of deposition is almost zero.

[0063] Furthermore, when considering Example 2 and Comparative Example 2, it can be seen that when the catalyst is reacted with ethanol in advance and then introduced into the CSTR, the DMC conversion rate is higher in the same reaction time, and the reaction rate is faster.

Claims

1. A step of carrying out a transesterification reaction of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of a catalyst; and filtering the product obtained by the transesterification reaction through a filter. The transesterification reaction is carried out in a continuous stirred tank reactor (CSTR); The catalyst and ethanol are mixed in a pre-reactor and then fed to a continuous stirred tank reactor (CSTR).

2. The method for producing heterogeneous linear carbonates according to claim 1, characterized in that the filter has pores having an average diameter of 0.3 to 2 μm.

3. The method for producing heterogeneous linear carbonates according to claim 1, characterized in that the filter is made of one or more materials selected from the group consisting of polyethylene, polypropylene, and polytetrafluoroethylene (PTFE).

4. The method for producing different linear carbonates according to claim 1, characterized in that the catalyst is added in a state of being dissolved in an alcohol-based solvent at 0.1 to 3 wt %.

5. The method for producing different linear carbonates according to claim 1, wherein the catalyst is added in an amount of 0.001 to 3 wt % based on the weight of dimethyl carbonate.

6. 2. The method for producing heterogeneous linear carbonates according to claim 1, wherein the catalyst is at least one selected from the group consisting of sodium methoxide (SME), sodium hydroxide (NaOH) and mixtures thereof.

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