Method for producing carbonate having ethyl group and method for producing methanol

Abstract

A method for producing ethyl methyl carbonate, the method comprising a reaction step for reacting a raw material composition containing ethanol and dimethyl carbonate to obtain a reaction composition containing ethyl methyl carbonate, and a first separation step for separating at least a portion of the reaction composition into a fraction AL that contains methanol as a main component and a fraction AH that contains dimethyl carbonate and ethanol as main components by using a distillation column. The method also comprises a step for returning, to the reaction step, the fraction AH as a portion of the raw material composition. The fraction AH contains 0.4-6.0 wt% of methanol in the fraction AH. The raw material composition contains 0.1-8.0 wt% of methanol with respect to the total amount of the raw material composition.

Description

Method for producing carbonate having an ethyl group and method for producing methanol

[0001] The present invention relates to a method for producing ethyl methyl carbonate.

[0002] Ethyl methyl carbonate used as an organic solvent for a battery electrolyte is widely known to be produced through a transesterification reaction between dimethyl carbonate and ethanol (for example, Patent Document 1 and Patent Document 2).

[0003] International Publication No. WO2022 / 114592, International Publication No. WO2022 / 114576

[0004] Since the above reaction is an equilibrium reaction, unreacted raw materials of dimethyl carbonate and ethanol remain in the reaction solution. However, in the process for recovering the unreacted raw materials, there is a problem of poor energy efficiency due to azeotropy between dimethyl carbonate and methanol, azeotropy between dimethyl carbonate and ethanol, etc.

[0005] Further, since the above reaction produces methanol as a by-product, it is necessary to recover the by-product methanol. However, since the boiling points of methanol and ethanol are close and separation is difficult, there is a problem that the ethanol concentration is high and the quality is poor in the process for recovering the by-product methanol.

[0006] Furthermore, the above reaction is a sequential reaction and produces diethyl carbonate as a by-product, and there is a problem that the yield of ethyl methyl carbonate cannot be increased.

[0007] An object of the present invention is to provide a method for producing ethyl methyl carbonate and a method for producing methanol that can recover by-product methanol with high energy efficiency and reduce the ethanol concentration in methanol to recover high-purity methanol.

[0008] The present inventor has found that the above problems can be solved by allowing a predetermined amount of methanol to be present in ethanol during the recovery of ethanol and using it again as a part of the raw material composition.

[0009] That is, the present invention includes the following embodiments. <1> A method for producing ethyl methyl carbonate, comprising: a reaction step of reacting a raw material composition containing dimethyl carbonate and ethanol to obtain a reaction composition containing ethyl methyl carbonate; and at least a part of the reaction composition is separated by a distillation column into a fraction A mainly composed of methanol Ｌ and a fraction A mainly composed of dimethyl carbonate and ethanol Ｈ in a first separation step; and having a step of returning the fraction A Ｈ as a part of the raw material composition to the reaction step; wherein the fraction A Ｈ contains 0.4 wt% or more and 6.0 wt% or less of methanol in the fraction A Ｈ and the raw material composition contains 0.1 wt% or more and 8.0 wt% or less of methanol based on the total amount of the raw material composition. A method for producing ethyl methyl carbonate. <2> The method for producing ethyl methyl carbonate according to <1>, having a second separation step of separating at least a part of the fraction A Ｌ by a distillation column at a top pressure of 0.7 MPaG or more into a fraction B containing 80 wt% or more of methanol and 0.1 wtppm or more and 0.15 wt% or less of ethanol Ｌ and a fraction B containing 90 wt% or more of dimethyl carbonate Ｈ . <3> In the first separation step, the fraction A Ｌ contains 1 wtppm or more and 0.15 wt% or less of ethanol, and the fraction A ＨThe method for producing ethyl methyl carbonate according to <1> or <2>, wherein the feed for the distillation column in the first separation step contains dimethyl carbonate in a total of 80 wt% or more. <4> The method for producing ethyl methyl carbonate according to any one of <1> to <3>, wherein the weight ratio of ethyl methyl carbonate / diethyl carbonate in the reaction composition is 3.0 or more and 10.0 or less. <5> The method for producing ethyl methyl carbonate according to any one of <1> to <4>, wherein the reaction step uses an alkali metal compound as a catalyst. <6> The method for producing ethyl methyl carbonate according to any one of <1> to <5>, wherein the feed for the distillation column in the first separation step contains dimethyl carbonate in a total of 15 wt% or more and 75 wt%, ethanol in a total of 5 wt% or more and methanol in a total of 10 wt% or more and methanol in the feed is 90 wt% or more. <7> The method for producing ethylmethyl carbonate according to <2>, wherein the feed to the distillation column in the second separation step contains ethanol in an amount of 0.1 wt ppm to 0.15 wt%, dimethyl carbonate in an amount of 20 wt% to 50 wt%, and methanol in an amount of 50 wt% to 80 wt%. <8> The raw material composition comprises dimethyl carbonate containing 0.01 wt% or more methanol as an impurity, and fraction A Ｈ A method for producing ethylmethyl carbonate according to any one of <1> to <7>, which is a mixture of the above. <9> The fraction A Ｈ A method for producing ethyl methyl carbonate according to any one of <1> to <8>, comprising a fifth separation step in which the material is distilled in a distillation column from which it can be extracted through a side cut, and separated into a top fraction, a side cut fraction, and a bottom fraction, and the top fraction and the bottom fraction from the fifth separation step are returned to the reaction step as part of the raw material composition. <10> The fraction B Ｈ A method for producing ethyl methyl carbonate according to any one of <1> to <9>, wherein the fraction B is returned to the reaction step as part of the raw material composition. <11> The fraction B ＨA method for producing ethyl methyl carbonate according to <2>, comprising a fourth separation step of separating the fraction A into a top fraction and a bottom fraction by a distillation column, and returning the bottom fraction from the fourth separation step to the reaction step as part of the raw material composition. <12> The fraction A Ｌ A method for producing ethyl methyl carbonate according to any one of <1> to <11>, comprising a third separation step of separating the reaction composition into a top fraction and a bottom fraction by a distillation column, and supplying the bottom fraction from the third separation step as a feed for the second separation step. <13> A method for producing ethyl methyl carbonate according to any one of <1> to <12>, wherein the reaction step is carried out by a stirred reactor or a plug-flow reactor, the reaction composition obtained by the reaction step is distilled by a distillation column to separate a fraction L mainly composed of dimethyl carbonate and methanol from a fraction H mainly composed of ethyl methyl carbonate, and the fraction L is supplied to the first separation step. <14> A method for producing ethylmethyl carbonate according to any one of <1> to <13>, wherein the reaction step is carried out in a reaction distiller, the bottom liquid of the reaction distiller in the reaction step is distilled in a distillation column to separate fraction H mainly composed of ethylmethyl carbonate, and fraction L mainly composed of dimethyl carbonate and methanol, which distills from the top of the reaction distiller, is supplied to the first separation step. <15> Fraction B Ｌ A method for producing ethyl methyl carbonate according to <2>, comprising the step of synthesizing dimethyl carbonate using as a raw material. <16> A method for producing ethyl methyl carbonate according to any one of <1> to <15>, further comprising the step of purifying methanol contained in the fraction distilled off in at least one step. <17> A method for producing methanol according to any one of <1> to <16>, further comprising the step of purifying methanol contained in the fraction distilled off in at least one step.

[0010] According to the present invention, it is possible to provide a method for producing ethyl methyl carbonate and a method for producing methanol that allows for the recovery of by-product methanol with high energy efficiency, and the recovery of high-purity methanol by lowering the ethanol concentration in methanol.

[0011] Figure 1 is a schematic diagram of the manufacturing equipment used in the method for producing ethyl methyl carbonate according to this embodiment. Figure 2 is a schematic diagram of the manufacturing equipment used in the method for producing ethyl methyl carbonate according to this embodiment. Figure 3 is a schematic diagram of the manufacturing equipment used in the method for producing ethyl methyl carbonate according to this embodiment. Figure 4 is a schematic diagram of the manufacturing equipment used in the method for producing ethyl methyl carbonate according to this embodiment.

[0012] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to those shown.

[0013] This embodiment is a method for producing ethyl methyl carbonate, comprising: a reaction step (for example, a process in reactor R) in which a raw material composition containing dimethyl carbonate and ethanol is reacted to obtain a reaction composition containing ethyl methyl carbonate; and a fraction A mainly composed of methanol obtained by distilling the reaction composition in a distillation column. Ｌ And fraction A, which mainly consists of dimethyl carbonate and ethanol. Ｈ The process includes a first separation step (for example, the process of distillation column 1) which separates the fraction A Ｈ The process includes a step of returning the fraction A to the reaction step as part of the raw material composition, Ｈ This is the aforementioned fraction A ＨThe present invention relates to a method for producing ethyl methyl carbonate, wherein the raw material composition contains 0.4 wt% to 6.0 wt% methanol, and the raw material composition contains 0.1 wt% to 8.0 wt% methanol relative to the total amount of the raw material composition. With the above configuration, it is possible to provide a method for producing ethyl methyl carbonate that allows for the recovery of by-product methanol with high energy efficiency, and the recovery of high-purity methanol by lowering the ethanol concentration in the methanol.

[0014] In the method for producing ethyl methyl carbonate according to this embodiment, surprisingly, the yield of ethyl methyl carbonate can be increased by including methanol, a by-product of the main reaction, within a predetermined concentration range in the raw material composition supplied to the reactor. Furthermore, it has been found that the first separation step, in which unreacted raw materials such as dimethyl carbonate in the reaction solution are recycled and the by-product methanol is recovered, can be achieved with high energy efficiency, and the ethanol concentration in the recovered by-product methanol can be reduced, thereby achieving high purity. The mechanism by which these effects are exhibited is that this reaction is a sequential reaction of the equilibrium reaction transesterification reaction, in which the first transesterification reaction produces ethyl methyl carbonate (hereinafter also called "EMC") and methanol (hereinafter also called "MeOH") from dimethyl carbonate (hereinafter also called "DMC") and ethanol, and the second transesterification reaction produces DEC and MeOH from EMC and ethanol (hereinafter also called "EtOH"). Therefore, the more MeOH, a by-product, is added as a raw material, the less DEC is produced and the higher the selectivity of EMC. On the other hand, the conversion rate of DMC decreases, so the amount of unreacted DMC and EtOH in the raw materials increases, and the energy required for the process of recovering the unreacted raw materials and MeOH increases. This conflicting relationship between EMC selectivity and energy efficiency suggests that there is an optimal MeOH concentration in the raw material composition.

[0015] The method for producing ethyl methyl carbonate according to this embodiment is carried out, for example, using the apparatus shown in Figure 1, and comprises: a reaction step in which a raw material composition containing dimethyl carbonate and ethanol is reacted in a reactor R to obtain a reaction composition containing ethyl methyl carbonate; a purification step in which the reaction composition is separated by a distillation column (e.g., distillation column 0) into a fraction L mainly composed of dimethyl carbonate and methanol, and a fraction H mainly composed of ethyl methyl carbonate; and a purification step in which fraction H is separated by a distillation column (e.g., distillation column 1) into a fraction A mainly composed of methanol. Ｌ And fraction A, which mainly consists of dimethyl carbonate and ethanol. Ｈ A first separation step separates the fraction A Ｌ Distilled in a distillation column (e.g., distillation column 2), the fraction B contains 80 wt% or more methanol and 1 wt ppm to 0.15 wt% ethanol. Ｌ Fraction B, which contains 90 wt% or more of dimethyl carbonate. Ｈ A second separation step separates the fraction into two parts, and fraction A Ｈ The process includes a step of returning the raw material composition to the reaction step.

[0016] The method for producing ethyl methyl carbonate according to this embodiment is carried out, for example, by the apparatus shown in Figure 2, and in addition to the above-described steps, fraction A Ｌ A third separation step involves separating the mixture into a top fraction and a bottom fraction using a distillation column (for example, distillation column 3), and fraction B Ｈ A fourth separation step involves separating the top fraction and the bottom fraction using a distillation column (for example, distillation column 4), and fraction A Ｈ The process may include one or more of the following steps: a fifth separation step in which the mixture is distilled in a distillation column (for example, distillation column 5) that can be extracted from the side cut, and separated into a top fraction, a side cut fraction, and a bottom fraction.

[0017] In the method for producing ethyl methyl carbonate according to this embodiment, the fraction distilled at any step may be recycled as a raw material. For example, fraction A ＨIn addition, the bottom fraction from the fourth separation step may be returned to the reaction step as part of the raw material composition, and the top fraction and bottom fraction from the fifth separation step may be returned to the reaction step as part of the raw material composition.

[0018] <Reaction Process> In the reaction process, DMC and EtOH are transesterified in a reaction apparatus R to obtain a reaction composition. The reaction composition obtained by this transesterification reaction may contain EMC, DMC, DEC, MeOH, and EtOH.

[0019] The raw materials supplied to reactor R include DMC and EtOH supplied from outside the process, as well as recycled raw materials containing DMC and EtOH. The DMC and EtOH are, for example, unreacted raw materials that distilled out unreacted in reactor R. An alkali metal compound may also be supplied to the reactor as a catalyst, along with the raw materials. The raw materials may be supplied continuously. The raw material composition used in the reaction process is a mixture of DMC and EtOH supplied from outside the process, and recycled raw materials.

[0020] The MeOH content in the raw material composition is 0.1 wt% to 8.0 wt% of the total amount of the raw material composition, preferably 0.2 wt% to 6.0 wt%, more preferably 0.4 wt% to 5.0 wt%, and even more preferably 0.5 wt% to 4.5 wt%. By having MeOH within this range of raw material concentration, energy efficiency can be increased in the process of recovering recycled raw materials and MeOH (for example, the first separation step), the EtOH concentration in the recovered MeOH can be reduced during purification, and the EMC yield can be increased in the reaction step.

[0021] While MeOH may be included in the DMC supplied from outside the process, it is preferable that the content be 1 wt% or less from the viewpoint of the conversion rate in the reaction process.

[0022] Examples of alkali metal compounds used as catalysts include sodium hydroxide, potassium hydroxide, and alkali metal alkoxides. Examples of alkali metal alkoxides include lithium methoxide, lithium ethoxide, sodium methoxide, sodium methoxide, sodium ethoxide, potassium methoxide, and potassium ethoxide. Among these, alkali metal compounds are preferably sodium hydroxide and sodium alkoxide, more preferably sodium methoxide or sodium ethoxide, and even more preferably sodium methoxide, because they are highly active and allow for economical operation at low catalyst concentrations.

[0023] The concentration of the alkali metal compound is preferably 1 wt ppm to 30,000 wt ppm, more preferably 10 wt ppm to 1,000 wt ppm, and even more preferably 25 wt ppm to 500 wt ppm, relative to the total amount of the raw material composition.

[0024] Since a higher selectivity for EMC is preferable, the selectivity for EMC is expressed as the ratio of EMC to DEC produced by the net reaction. This is the ratio of EMC to DEC in the weight of the product, obtained by subtracting the raw materials from the reaction composition extracted from the reaction step, that is, the ratio of EMC to DEC produced by the net reaction (ratio A, represented by formula (A), for example), which is preferably 1.5 or more, more preferably 2.0 to 12.0, and even more preferably 3.0 to 12.0. {(reaction composition flow rate [kg / h]) × (EMC concentration in reaction composition [wt%]) / 100 - (total raw material composition flow rate [kg / h] × (EMC concentration in total raw material composition [wt%]) / 100}÷{(reaction composition flow rate [kg / h]) × (DEC concentration in reaction composition [wt%]) / 100 - (total raw material composition flow rate [kg / h] × (DEC concentration in total raw material composition [wt%]) / 100}...(A) In order to control ratio A to a desirable range, it is preferable to increase the DMC ratio (DMC / EtOH) in the raw material composition. There is no particular upper limit to ratio A, but from the viewpoint of the energy efficiency of the entire process, it is about 10.0 or less.

[0025] (Reaction apparatus R) Examples of reaction apparatus R include a stirred reactor, a plug flow reactor, and a reaction distillation column. Since the catalyst or its reactants tend to precipitate during the reaction process, it is preferable that reaction apparatus R be a stirred reactor or a plug flow reactor.

[0026] The reaction temperature in the reaction step is preferably 40°C to 150°C, more preferably 50°C to 130°C, and even more preferably 60°C to 120°C.

[0027] The pressure in the reaction process may be, for example, atmospheric pressure to 1000 kPaG.

[0028] When using a stirred reactor and continuously supplying raw materials, it is preferable to withdraw the reaction composition from the stirred reactor. The withdrawal of the reaction composition may be performed continuously.

[0029] <Purification Process> In the purification process, the reaction composition containing DMC, EMC, DEC, and EtOH is separated into fraction L, which mainly consists of dimethyl carbonate and methanol, and fraction H, which mainly consists of ethyl methyl carbonate. The feed containing the reaction composition is supplied to distillation column 0, and fraction L is collected from the top of distillation column 0. T Extract it and use fraction H as the fraction 0 from the bottom of the tower. Ｂ It is also possible to extract the relevant information. Furthermore, the feed to distillation column 0 may include substances other than the reaction composition obtained in the reaction step described above.

[0030] The weight ratio of EMC to DEC in the feed (ratio B, expressed by the following formula (B)) is preferably 1.5 or higher, more preferably 2.0 or higher, and even more preferably 3.0 or higher, from the viewpoint of the selectivity of EMC. (EMC concentration in feed [wt%]) ÷ (DEC concentration in feed [wt%]) ... (B) There is no particular upper limit to ratio B, but from the viewpoint of the energy efficiency of the entire process, it is preferably 12.0 or lower, and more preferably 10.0 or lower.

[0031] The EMC content of fraction L is preferably 0.05 wt% to 10.0 wt%, more preferably 0.1 wt% to 8.0 wt%, and even more preferably 0.5 wt% to 6.0 wt%, relative to the total amount of fraction L.

[0032] The DMC content of fraction H is preferably 0.5 wt% or less, more preferably 0.0001 wt% to 0.4 wt%, and even more preferably 0.001 wt% to 0.25 wt%, relative to the total amount of fraction H.

[0033] The EtOH content of fraction H is preferably 0.1 wt% or less, more preferably 0.01 wt% or less, and even more preferably 0.005 wt% or less, relative to the total amount of fraction H.

[0034] The top pressure of the tower is preferably -95 kPaG to 50 kPaG, more preferably -75 kPaG to 45 kPaG, and even more preferably -61 kPaG to 40 kPaG.

[0035] The fraction L may be supplied to the first separation process or to a cushion tank.

[0036] The fraction H may be supplied to the precision distillation process for obtaining the product EMC, or it may be supplied to a cushion tank. A cushion tank is an intermediate tank that stores the feed product before it reaches the distillation column, and is provided for the purpose of averaging the composition of the feed product.

[0037] <First Separation Step> In the first separation step, at least a portion of the reaction composition (for example, the fraction L mentioned above) is separated by distillation column 1 into a fraction A mainly composed of methanol. Ｌ And fraction A, which mainly consists of dimethyl carbonate and ethanol. Ｈ The mixture is separated into two parts. In the first separation step, a feed containing at least DMC, EtOH, and MeOH is supplied to the distillation column 1, and fraction A is produced. Ｌ As such, fraction 1 is taken from the top of distillation column 1. T Extract and fraction A Ｈ From the base of the tower, fraction 1 Ｂ You can extract it.

[0038] The DMC concentration in the feed to distillation column 1 is preferably 15 wt% to 75 wt%, more preferably 20 wt% to 72 wt%, and even more preferably 25 wt% to 70 wt%, based on the total amount of feed to distillation column 1.

[0039] The EtOH concentration in the feed to distillation column 1 is preferably 5 wt% to 35 wt%, more preferably 6 wt% to 32 wt%, and even more preferably 7 wt% to 30 wt%, relative to the total amount of feed to distillation column 1.

[0040] The MeOH concentration in the feed to distillation column 1 is preferably 10 wt% to 35 wt%, more preferably 12 wt% to 32 wt%, and even more preferably 14 wt% to 30 wt%, relative to the total amount of feed to distillation column 1.

[0041] The total amount of DMC, EtOH, and MeOH in the feed to distillation column 1 is preferably 90 wt% or more, more preferably 95 wt% or more, and even more preferably 98 wt% or more, based on the total amount of feed to distillation column 1.

[0042] Dividend A Ｌ The MeOH concentration is in fraction A. Ｌ Preferably, the amount is 30 wt% to 90 wt% of the total amount, more preferably 40 wt% to 85 wt%, and even more preferably 50 wt% to 80 wt%.

[0043] Dividend A Ｌ The DMC concentration is in fraction A. Ｌ The amount is preferably 10 wt% to 70 wt% of the total amount, more preferably 15 wt% to 60 wt%, and even more preferably 20 wt% to 50 wt%.

[0044] Dividend A Ｌ The EtOH concentration is in fraction A. Ｌ The amount is preferably 0.1 wt ppm to 0.15 wt%, more preferably 0.5 wt ppm to 0.1 wt%, and even more preferably 1 wt ppm to 800 wt ppm relative to the total amount.

[0045] Dividend A Ｈ The sum of the DMC concentration and EtOH concentration is fraction A Ｈ The amount is preferably 80 wt% or more, more preferably 85 wt% or more, and even more preferably 90 wt% or more, relative to the total amount.

[0046] Dividend A ＨThe MeOH concentration is in fraction A. Ｈ The amount of MeOH is preferably 0.4 wt% to 6.0 wt% of the total amount, more preferably 0.6 wt% to 5.5 wt%, and even more preferably 0.7 wt% to 5.2 wt%. By operating the distillation column 1 to achieve this MeOH concentration, the distillation column 1 can be operated with high energy efficiency.

[0047] The top pressure of the tower is preferably -95 kPaG to 50 kPaG, more preferably -75 kPaG to 45 kPaG, and even more preferably -61 kPaG to 40 kPaG.

[0048] The column bottom temperature in the first separation step is preferably 50°C to 90°C, more preferably 55°C to 85°C, and even more preferably 57°C to 83°C.

[0049] Dividend A Ｌ This can be supplied to either the third separation process or the second separation process.

[0050] Dividend A Ｈ It may be supplied to the fifth separation process, used as recycled material, or more specifically, supplied to a supply tank.

[0051] The distillation column 1 is not particularly limited, but for example, a continuous distillation column can be used. The distillation column 1 is also usually equipped with a reboiler that heats the bottom of the column.

[0052] The distillation column 1 preferably includes trays and / or packing as internals. Internals refer to the parts of the distillation column where gas and liquid actually come into contact. Examples of trays include bubble trays, perforated plate trays, ripple trays, ballast trays, valve trays, counterflow trays, Uniflux trays, Superflax trays, Maxflax trays, DualFloat trays, grid plate trays, TurboGrid plate trays, and Kittel trays. Examples of packing include irregular packings such as Raschig rings, Lessing rings, Pall rings, Berl saddles, Interox saddles, Dixon packings, McMahon packings, and Helipak, and regular packings such as Melapack, Gempack, Technopack, Flexipak, Sulzer packings, Goodroll packings, and GlitchGrid.

[0053] The feed material may be introduced from the middle section of distillation column 1. "Middle section" refers to the part of the distillation column excluding the top and bottom.

[0054] <Second Separation Process> In the second separation process, fraction A Ｌ Distilled in a distillation column at a top pressure of 0.7 MPaG or higher, fraction B containing 80 wt% or more methanol and 1 wt ppm to 0.15 wt% ethanol. Ｌ Fraction B, which contains 90 wt% or more of dimethyl carbonate. Ｈ The mixture is separated into two parts. In the second separation step, the feed containing at least DMC, EtOH, and MeOH is supplied to the distillation column 2, and fraction B is produced. Ｌ As such, from the top of distillation column 2, fraction 2 T Extract and fraction B Ｈ As such, from the base of the tower, 2 Ｂ It is also possible to extract it. Note that the feed may include the by-product MeOH obtained in the reaction step described above.

[0055] The DMC concentration in the feed to distillation column 2 is preferably 20 wt% to 50 wt%, more preferably 25 wt% to 45 wt%, and even more preferably 28 wt% to 40 wt%, relative to the total amount of feed to distillation column 2.

[0056] The EtOH concentration in the feed to distillation column 2 is preferably 0.1 wt ppm or more and 0.15 wt% or less, more preferably 0.5 wt ppm or more and 0.1 wt% or less, and even more preferably 1 wt ppm or more and 800 wt ppm or less, relative to the total amount of feed to distillation column 2.

[0057] The MeOH concentration in the feed to distillation column 2 is preferably 50 wt% to 80 wt%, more preferably 55 wt% to 75 wt%, and even more preferably 58 wt% to 72 wt%, relative to the total amount of feed to distillation column 2.

[0058] Dividend B Ｌ The EtOH concentration is in fraction B. Ｌ The amount is preferably 0.1 wt ppm to 0.15 wt%, more preferably 0.5 wt ppm to 0.1 wt%, and even more preferably 1 wt ppm to 800 wt ppm relative to the total amount.

[0059] Dividend B Ｌ The MeOH concentration is in fraction B. Ｌ The amount is preferably 80 wt% or more, more preferably 83 wt% to 99.99 wt%, and even more preferably 85 wt% to 99.9 wt% of the total amount.

[0060] Dividend B Ｈ The DMC concentration is in fraction B. Ｈ The amount is preferably 90 wt% or more, more preferably 92 wt% or more, and even more preferably 94 wt% or more, relative to the total amount.

[0061] The top pressure of distillation column 2 is 0.7 MPaG or higher. This is to separate MeOH and DMC by distillation to the aforementioned concentrations. Preferably, the top pressure of distillation column 2 is 0.7 MPaG or higher and 2.0 MPaG or lower, more preferably 0.75 MPaG or higher and 1.9 MPaG or lower, and even more preferably 0.8 MPaG or higher and 1.8 MPaG or lower.

[0062] Dividend B Ｌ Since it is high-purity methanol, it can be supplied to the tank and then sold externally, or it can be used as a raw material for synthesizing DMC.

[0063] Dividend B ＨThis material may be supplied to the fourth separation process or to the recycled material supply tank.

[0064] The distillation column 2 is not particularly limited, but for example, a continuous distillation column can be used. The distillation column 1 is usually equipped with a reboiler that heats the bottom of the column.

[0065] The distillation column 2 preferably includes trays and / or packing as internals. Internals refer to the parts of the distillation column where gas and liquid actually come into contact. Examples of trays include bubble trays, perforated plate trays, ripple trays, ballast trays, valve trays, counterflow trays, Uniflux trays, Superflax trays, Maxflax trays, DualFloat trays, grid plate trays, TurboGrid plate trays, and Kittel trays. Examples of packing include irregular packings such as Raschig rings, Lessing rings, Pall rings, Berl saddles, Interox saddles, Dixon packings, McMahon packings, and Helipak, and regular packings such as Melapack, Gempack, Technopack, Flexipak, Sulzer packings, Goodroll packings, and GlitchGrid.

[0066] The higher the internal height (the distance from the bottom to the top of the filled internals), the better the distillation separation performance and the less heat is required for distillation. However, this necessitates increasing the height of the distillation column, resulting in higher capital investment. Therefore, it is preferable to set an appropriate internal height while balancing capital investment and energy costs.

[0067] The feed material may be introduced from the middle section of distillation column 2. "Middle section" refers to the part of the distillation column excluding the top and bottom.

[0068] <Third Separation Process> In the third separation process, fraction A Ｌ The mixture is separated into a top fraction and a bottom fraction by a distillation column (for example, distillation column 3). In the third separation step, a feed containing at least DMC and MeOH is supplied to distillation column 3, and the top fraction 3 is obtained from the top of distillation column 3. T Extract the fraction 3 from the base of the tower. Ｂ Extract the following. Note that here is the fraction 3T It is preferable that it contains 1 wt% or more of compounds other than DMC and MeOH. Bottom fraction 3 Ｂ This may be supplied to the second separation process.

[0069] <Fourth Separation Step> In the fourth separation step, fraction B Ｈ The mixture is separated into a top fraction and a bottom fraction by a distillation column. In the fourth separation step, a feed containing at least DMC and MeOH is supplied to the distillation column 4, and the top fraction 4 is obtained from the top of the distillation column 4. T Extract it, and from the base of the tower, 4 fractions Ｂ Extract the following. Note that fraction 4 is here. T It is preferable that it contains 1 wt% or more of compounds other than DMC and MeOH. 4th separation step, bottom fraction 4 Ｂ It is preferable to return the recycled material to the reaction process as part of the raw material composition. Alternatively, the recycled material may be withdrawn from the fourth separation step, supplied to a tank to stabilize its composition, and then supplied to the reactor.

[0070] <Fifth Separation Step> In the fifth separation step, fraction A Ｈ The mixture is distilled using a distillation column that allows extraction from the side cut, and separated into a top fraction, a side-cut fraction, and a bottom fraction. Preferably, the top fraction and bottom fraction from the fifth separation step are returned to the reaction step as part of the raw material composition. Here, impurities are removed by the side-cut fraction, suppressing the accumulation of impurities within the manufacturing equipment system. In the fifth separation step, a feed containing at least DMC, EtOH, and MeOH is supplied to the distillation column 5, and the top fraction 5 is extracted from the top of the distillation column 5. T Remove it and exit through the side opening 5 Ｓ Extract it, and from the base of the tower, 5 Ｂ Extract the impurities. By installing a side-cut distillation column, there is the advantage of reducing the number of distillation columns required for purification. For example, in a fraction containing impurities whose boiling point is between that of DMC and EtOH, by taking EtOH from the top of the column, DMC from the bottom of the column, and extracting the impurities from the side, one side-cut distillation column can be replaced by two distillation columns. Note that fraction 5 ＳIt is preferable that the mixture contains 1 wt% or more of compounds other than DMC, EtOH, and MeOH. Setting the amount to 1 wt% or more can reduce losses.

[0071] After the recycled material is extracted from the fifth separation step, it may be supplied to a tank to stabilize its composition before being supplied to the reactor.

[0072] <Product> According to the manufacturing method of this embodiment, EMC and MeOH are obtained as products. The purity of the EMC obtained by the manufacturing method of this embodiment is preferably 99 wt% or more, more preferably 99.9 wt% or more, and even more preferably 99.99 wt% or more.

[0073] The EtOH content in the EMC obtained by the manufacturing method according to this embodiment is preferably 20 wt ppm or less, more preferably 17 wt ppm or less, and even more preferably 15 wt ppm or less.

[0074] The MeOH content in the EMC obtained by the manufacturing method according to this embodiment is preferably 20 wt ppm or less, more preferably 17 wt ppm or less, and even more preferably 15 wt ppm or less.

[0075] The DMC content in the EMC obtained by the manufacturing method according to this embodiment is preferably 50 wt ppm or less, more preferably 40 wt ppm or less, and even more preferably 30 wt ppm or less.

[0076] Furthermore, the purity and analysis of each major component in the EMC shall be performed by gas chromatography. The gas chromatography analysis shall be carried out in accordance with HG / T 5158-2017.

[0077] <Methanol purification process, methanol production apparatus> As described above, the method for producing ethyl methyl carbonate according to this embodiment makes it possible to recover the by-product methanol with high energy efficiency and to reduce the ethanol concentration in methanol and recover high-purity methanol. From this viewpoint, the production method according to this embodiment can also be called a methanol production method. In the method for producing ethyl methyl carbonate and methanol according to this embodiment, the obtained methanol may be purified prior to the recovery of methanol. That is, in the method for producing ethyl methyl carbonate and methanol according to this embodiment, in the production method according to this embodiment, the fraction distilled off in at least one step (for example, fraction A) Ｌ The invention may further include a step of purifying the methanol contained in the above. The methanol purification step may appropriately use apparatus used for methanol purification, such as a distillation column, to the extent that it does not impair the effects of the present invention.

[0078] The configuration and functions of the manufacturing equipment that can be used in the carbonate manufacturing method will be explained below with reference to Figures 1 to 4.

[0079] As shown in Figure 1, the manufacturing equipment used in the method for producing ethyl methyl carbonate according to this embodiment includes a reactor R1, a distillation column 0, a distillation column 1, a distillation column 2, and a tank 8. The manufacturing equipment has a recycling channel 9 for supplying recycled raw materials from tank 8 to reactor R1. Figure 1 shows an example in which a stirred reactor is used as the reactor. This is preferable because it has a small number of distillation columns and consumes little heat, and is suitable when the purity of the raw materials DMC and EtOH is high, such as 99.99 wt% or higher (for example, 99.999 wt%).

[0080] As shown in Figure 2, the manufacturing equipment used in the method for producing ethyl methyl carbonate according to this embodiment includes a reactor R1, distillation column 0, distillation column 1, distillation column 2, and a tank 8. The manufacturing equipment shown in Figure 2 is an example in which the number of distillation columns is increased compared to the manufacturing equipment shown in Figure 1, and is suitable when using DMC and EtOH with a purity of 99.9 wt% as raw materials.

[0081] For example, in the method for producing ethyl methyl carbonate according to this embodiment, the reaction step may be carried out in a stirred reactor or a plug-flow reactor, the reaction composition obtained in the reaction step may be distilled in a distillation column to separate a fraction L mainly composed of dimethyl carbonate and methanol from a fraction H mainly composed of ethyl methyl carbonate, and the fraction L may be supplied to the first separation step. The manufacturing equipment shown in Figure 3 is the same as the manufacturing equipment shown in Figure 1, except that a raw material mixer 7 is provided and a plug-flow reactor R2 is used as the reactor. Equipment utilizing a plug-flow reactor is effective when a solid catalyst (for example, a zeolite supported with an alkali metal compound) is used as the catalyst or when the production volume is very small.

[0082] For example, in the method for producing ethyl methyl carbonate according to this embodiment, the reaction step can be carried out using a reaction distiller, the bottom liquid of the reaction distiller in the reaction step can be distilled by a distillation column to separate fraction H mainly composed of ethyl methyl carbonate, and fraction L mainly composed of dimethyl carbonate and methanol, which distills from the top of the reaction distiller column, can be supplied to the first separation step. Figure 4 shows an example of an apparatus suitable when using a reaction distiller R3 as the reactor and using high-purity DMC and EtOH with a purity of about 99.999 wt% as raw materials. When using a reaction distiller, the composition of the reactor outlet is different from that of a stirred reactor or a plug flow reactor, so the configuration of the distillation column is different from that shown in Figures 1 to 3. Specifically, when using a stirred reactor or a plug-flow reactor, the fraction at the reactor outlet is a mixture of MeOH, unreacted EtOH, unreacted DMC, EMC, and DEC (equilibrium composition), whereas when using a reaction distiller, the top composition is MeOH, unreacted EtOH, and unreacted DMC (partially), and the bottom liquid composition is DMC (partially), EMC, and DEC. For this reason, in the apparatus shown in Figure 4, distillation column 0 (a column that mainly separates MeOH, unreacted EtOH, and unreacted DMC (top) from EMC and DEC (bottom)) is eliminated, and distillation column 6 (which separates unreacted DMC (top) from EMC and DEC (bottom)) is provided. The manufacturing equipment shown in Figure 4 is the same as the manufacturing equipment shown in Figure 1 in other configurations.

[0083] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0084] The catalysts used in each example are denoted as follows: 30% KOMe; 30 wt% methanol solution of potassium methoxide; 30% NaOMe; 30 wt% methanol solution of sodium methoxide; 25% NaOEt; 25 wt% ethanol solution of sodium ethoxide.

[0085] [Example 1] Ethyl methyl carbonate was produced using the manufacturing apparatus shown in Figure 1. Reactor R1 was a stirred reactor with a capacity of 12 liters. Distillation columns 0 and 1 had an inner diameter of 80 mm and an internal height of 5.2 m (sum of the upper and lower parts of the feed port). Distillation column 2 had an inner diameter of 50 mm and an internal height of 10.4 m (sum of the upper and lower parts of the feed port). Sulzer Laboratory Packing DX was used for the internals of all three distillation columns: 0, 1, and 2. The raw materials supplied from outside the reaction process (fresh raw materials) DMC and EtOH were both of a purity of 99.99 wt% or higher. The raw material composition, process liquid flow rate, heat quantity, operating conditions, and test results are shown in Table 1.

[0086] [Comparative Example 1] Ethyl methyl carbonate was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1. The raw material composition, process liquid flow rate, heat quantity, operating conditions, and test results are shown in Table 1.

[0087] [Examples 2-1, 2-2, Comparative Example 2] Ethyl methyl carbonate was produced using the manufacturing apparatus shown in Figure 2. Reactor R1, distillation column 0, distillation column 1, and distillation column 2 have the same structure as in Example 1. Distillation columns 3, 4, and 5 have the same structure, with an inner diameter of 50 mm and an internal height of 5.2 m (sum of the upper and lower parts of the feed port). The internals are Sulzer Laboratory Packing DX. The raw materials (fresh raw materials) DMC and EtOH supplied from outside the reaction process had a purity of 99.9 wt% or higher. The raw material composition, process liquid flow rate, heat quantity, operating conditions, and test results are shown in Table 2.

[0088] [Example 3, Comparative Example 3-1, Comparative Example 3-2] Ethyl methyl carbonate was produced using the manufacturing apparatus shown in Figure 3. Except for using a plug-flow reactor R2 equipped with 30 tubes with an inner diameter of 40 mm and a length of 300 mm, and changing the conditions as shown in Table 3, the procedure was carried out in the same manner as in Example 1 to obtain ethyl methyl carbonate. The raw material composition, process liquid flow rate, heat quantity, operating conditions, and test results are shown in Table 3.

[0089] [Example 4, Comparative Example 4] Ethyl methyl carbonate was produced using the manufacturing apparatus shown in Figure 4. Reactor R3 was an Oldershaw reaction distiller with an inner diameter of 50 mm and 60 theoretical plates. Distillation columns 1 and 6 had an inner diameter of 40 mm and an internal height of 5.2 m (sum of the upper and lower parts of the feed port). Distillation column 2 had an inner diameter of 40 mm and an internal height of 10.4 m (sum of the upper and lower parts of the feed port). Sulzer Laboratory Packing DX was used for the internals of all three distillation columns: 6, 1, and 2. The raw materials supplied from outside the reaction process (fresh raw materials) DMC and EtOH were both of a purity of 99.99 wt% or higher. The raw material composition, process liquid flow rate, heat quantity, operating conditions, and test results are shown in Table 4.

[0090] The effect of each example was evaluated using Equation 3 as the amount of heat required for the recovery process per unit amount of EMC generated. (Total amount of heat required for each recovery process distillation column [kcal / h]) ÷ {(amount of EMC at the reactor outlet [kg / h]) - (amount of EMC in the reactor raw material [kg / h])} ... Equation 3

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Claims

1. A method for producing ethyl methyl carbonate, comprising: a reaction step of reacting a raw material composition containing dimethyl carbonate and ethanol to obtain a reaction composition containing ethyl methyl carbonate; and a step of distilling at least a portion of the reaction composition into a fraction A mainly composed of methanol using a distillation column. Ｌ And fraction A, which mainly consists of dimethyl carbonate and ethanol. Ｈ A first separation step separates the fraction A Ｈ The process includes a step of returning the fraction A to the reaction step as part of the raw material composition, Ｈ This is the aforementioned fraction A Ｈ A method for producing ethyl methyl carbonate, comprising: a raw material composition containing 0.4 wt% to 6.0 wt% methanol, and the raw material composition containing 0.1 wt% to 8.0 wt% methanol relative to the total amount of the raw material composition.

2. The aforementioned fraction A Ｌ At least a portion of it is distilled in a distillation column at a top pressure of 0.7 MPaG or higher to obtain fraction B containing 80 wt% or more methanol and 0.1 wt ppm to 0.15 wt% ethanol. Ｌ Fraction B, which contains 90 wt% or more of dimethyl carbonate. Ｈ A method for producing ethyl methyl carbonate according to claim 1, comprising a second separation step of separating into and .

3. In the first separation step, the fraction A Ｌ contains ethanol at 1 wtppm or more and 0.15 wt% or less, and the fraction A Ｈ contains a total of 80 wt% or more of dimethyl carbonate and ethanol. The method for producing ethyl methyl carbonate according to claim 1.

4. The method for producing ethyl methyl carbonate according to claim 1, wherein the weight ratio of ethyl methyl carbonate / diethyl carbonate in the reaction composition is 3.0 or more and 10.0 or less.

5. The method for producing ethyl methyl carbonate according to claim 1, wherein the reaction step uses an alkali metal compound as a catalyst.

6. The method for producing ethyl methyl carbonate according to claim 3, wherein the feed to the distillation column in the first separation step contains 15 wt% to 75 wt% of dimethyl carbonate, 5 wt% to 35 wt% of ethanol, and 10 wt% to 35 wt% of methanol, and the total amount of dimethyl carbonate, ethanol, and methanol in the feed is 90 wt% or more.

7. The method for producing ethyl methyl carbonate according to claim 2, wherein the feed to the distillation column in the second separation step contains ethanol in an amount of 0.1 wt ppm to 0.15 wt%, dimethyl carbonate in an amount of 20 wt% to 50 wt%, and methanol in an amount of 50 wt% to 80 wt%.

8. The raw material composition comprises dimethyl carbonate containing 0.01 wt% or more methanol as an impurity, and fraction A Ｈ A method for producing ethyl methyl carbonate according to claim 1, wherein the mixture is a mixture of the above.

9. The aforementioned fraction A Ｈ A method for producing ethyl methyl carbonate according to claim 2, comprising a fifth separation step of distilling the material using a distillation column from which it can be extracted through a side cut, and separating it into a top fraction, a side cut fraction, and a bottom fraction, and returning the top fraction and the bottom fraction from the fifth separation step to the reaction step as part of the raw material composition.

10. The aforementioned fraction B Ｈ A method for producing ethyl methyl carbonate according to claim 1, wherein the raw material composition is returned to the reaction step as part of the raw material composition.

11. The aforementioned fraction B Ｈ A method for producing ethyl methyl carbonate according to claim 2, comprising a fourth separation step of separating the material into a top fraction and a bottom fraction by a distillation column, and returning the bottom fraction from the fourth separation step to the reaction step as part of the raw material composition.

12. The aforementioned fraction A Ｌ A method for producing ethyl methyl carbonate according to claim 2, comprising a third separation step of separating the material into a top fraction and a bottom fraction by a distillation column, wherein the bottom fraction from the third separation step is supplied as a feed for the second separation step.

13. The method for producing ethyl methyl carbonate according to claim 1, wherein the reaction step is carried out in a stirred reactor or a plug-flow reactor, the reaction composition obtained in the reaction step is distilled in a distillation column to separate a fraction L mainly composed of dimethyl carbonate and methanol from a fraction H mainly composed of ethyl methyl carbonate, and the fraction L is supplied to the first separation step.

14. The method for producing ethyl methyl carbonate according to claim 1, wherein the reaction step is carried out by a reaction distiller, the bottom liquid of the reaction distiller in the reaction step is distilled by a distillation column to separate fraction H mainly composed of ethyl methyl carbonate, and fraction L mainly composed of dimethyl carbonate and methanol, which distills from the top of the reaction distiller, is supplied to the first separation step.

15. The aforementioned fraction B Ｌ A method for producing ethyl methyl carbonate according to claim 2, comprising the step of synthesizing dimethyl carbonate using as a raw material.

16. The method for producing ethyl methyl carbonate according to claim 1, further comprising the step of purifying methanol contained in the fraction distilled off in at least one step.

17. A method for producing methanol, further comprising a step of purifying methanol contained in a fraction distilled off in at least one step in the method for producing ethyl methyl carbonate according to any one of claims 1 to 16.

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