Process for producing dialkyl carbonate and apparatus for producing dialkyl carbonate

Abstract

A method for manufacturing a dialkyl carbonate, wherein the method comprises two separation and purification steps (I) and (II), wherein in step (I), a mixture (A) is purified... T The concentration of dialkyl carbonate in the column is 25.00% to 95.00% by mass, and the bottom temperature is above 115°C. In process (II), the bottom component (B) B The concentration of dialkyl carbonate in the fraction was 99.00%–99.95% by mass, and the side fraction (B) s The purity of the dialkyl carbonate in the product is above 99.99% by mass.

Description

Technical Field

[0001] This invention relates to a method for manufacturing dialkyl carbonate and an apparatus for manufacturing dialkyl carbonate. Background Technology

[0002] In recent years, dialkyl carbonates have been used as a major component of lithium-ion battery electrolytes. With the development of the electronics and clean energy vehicle industries, the importance of lithium-ion battery electrolytes is increasing, and consequently, the market demand for high-purity dialkyl carbonates used in lithium-ion battery electrolytes has risen significantly. Industrial-grade dialkyl carbonates contain impurities such as water, methanol, ethanol, methyl ethyl carbonate, and heavy components. Alcohols and water affect the lifespan of lithium-ion batteries, while heavy components cause electrolyte discoloration. Therefore, dialkyl carbonates used in lithium-ion battery electrolytes require further reduction of these impurities to achieve extremely high purity (purity of 99.99% by mass or higher).

[0003] Several methods have been proposed for manufacturing high-purity dimethyl carbonate for lithium-ion battery electrolytes. For example, one proposed method involves a two-column distillation system. Industrial-grade (99.95% by mass) dimethyl carbonate is fed into the first column, and high-purity (99.99% by mass or higher) dimethyl carbonate is obtained by side distillation from the second column (see, for example, Patent Documents 1 and 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Chinese Patent Application Publication No. 107311864

[0007] Patent Document 2: Description of Chinese Patent Application Publication No. 105384639 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, in the methods described in Patent Documents 1 and 2, the reflux ratios of the first and second distillation columns are both as high as 20 to 40, which requires a large amount of heat to produce high-purity dialkyl carbonate for lithium-ion battery electrolytes, leaving room for improvement.

[0010] For example, by distilling the crude dialkyl carbonate obtained through the manufacturing process using a first distillation column, a dialkyl carbonate with a purity of 99.00% to 99.95% by mass is obtained. This purity of dialkyl carbonate is used as an industrial-grade dialkyl carbonate for various industrial applications.

[0011] Next, in a second distillation column, dialkyl carbonate with a purity of 99.00% to 99.95% by mass is introduced to obtain high-purity dialkyl carbonate with a purity of 99.99% by mass or higher. This high-purity dialkyl carbonate has a purity suitable for use as an electrolyte in lithium-ion batteries. Particularly noteworthy is the high heat consumption required in the second distillation column for obtaining the high-purity dialkyl carbonate, in order to achieve the desired purity.

[0012] Therefore, the object of the present invention is to provide a method and apparatus for manufacturing dialkyl carbonate that reduces the heat consumption in the separation and purification process of obtaining high-purity dialkyl carbonate with a purity of 99.99% or higher from dialkyl carbonate with a purity of 99.00% to 99.95% by mass.

[0013] means for solving problems

[0014] To solve the above-mentioned problems, the inventors conducted in-depth research and discovered that by reducing the purity of the dialkyl carbonate supplied to the first distillation column for purifying dialkyl carbonate instead of increasing it, and by adjusting the bottom temperature of the first distillation column to above 115°C, it is possible to separate and purify high-purity dialkyl carbonate (99.99% by mass) from dialkyl carbonate with a purity of 99.00% to 99.95% by mass in the second distillation column with reduced heat consumption, i.e., with a small reflux ratio. This completes the present invention.

[0015] That is, the present invention relates to the following embodiments.

[0016] <1>

[0017] A method for manufacturing a dialkyl carbonate, wherein the method comprises the following steps:

[0018] (I) First separation and purification step (I), wherein a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohol is separated. T The product is continuously supplied to a continuous multi-stage distillation column B1, where the top component (B1), which is mainly composed of aliphatic monohydric alcohols, is distilled. T ) is continuously drawn from the top of the column, and the bottom component (B), which is mainly composed of dialkyl carbonate, is drawn off. B It is continuously drawn from the bottom of the tower;

[0019] (II) Second separation and purification step (II), wherein the bottom component (B1) mainly composed of dialkyl carbonate is continuously drawn from the bottom of the continuous multi-stage distillation column B1. B The side fraction (B) with dialkyl carbonate as the main component is continuously supplied to a continuous multistage distillation column B2 with a side outlet, and the side fraction (B) with dialkyl carbonate as the main component is supplied continuously.s It can be continuously extracted from the side outlet.

[0020] In the process (I), a low-purity dialkyl carbonate mixture (A) is fed to the continuous multi-stage distillation column B1. T The concentration of dialkyl carbonate in the distillation column B1 is 25.00% to 95.00% by mass, and the bottom temperature of the continuous multistage distillation column B1 is above 115°C.

[0021] In the process (II), the bottom component (B) supplied to the continuous multi-stage distillation column B2 B The concentration of dialkyl carbonate in the product is 99.00% to 99.95% by mass.

[0022] In the process (II), the side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The purity of the dialkyl carbonate in the product is above 99.99% by mass.

[0023] <2>

[0024] according to <1> The manufacturing method wherein step (I) is carried out in the presence of a compound containing Fe.

[0025] <3>

[0026] according to <2> The manufacturing method, wherein in step (I), the Fe-containing compound and the low-purity dialkyl carbonate mixture (A) T The contact surface area is 1.0 × 10⁻⁶. -3 m 2 • Minutes / (kg / hour) or more.

[0027] <4>

[0028] according to <2> or <3> The manufacturing method wherein step (I) is performed in the presence of ferrous oxide (II).

[0029] <5>

[0030] according to <1> ~ <4> The manufacturing method described in any one of the following statements, wherein the side fraction (Bside fraction) drawn from the side outlet of the continuous multi-stage distillation column B2... s The content of high-boiling-point compounds in the sample is less than 30 ppm by mass.

[0031] <6>

[0032] according to <1> ~ <5> The manufacturing method described in any one of the following statements, wherein the side fraction (Bside fraction) drawn from the side outlet of the continuous multi-stage distillation column B2... s The metal content in the sample is less than 1 ppm by mass.

[0033] <7>

[0034] according to <1> ~ <6> The manufacturing method described in any one of the following statements, wherein the side fraction (Bside fraction) drawn from the side outlet of the continuous multi-stage distillation column B2... s The water content in the sample is below 30 ppm by mass.

[0035] <8>

[0036] according to <1> ~ <7> The manufacturing method described in any one of the following statements, wherein the side fraction (Bside fraction) drawn from the side outlet of the continuous multi-stage distillation column B2... s The combined content of methanol and ethanol in the product is less than 20 ppm by mass.

[0037] <9>

[0038] according to <1> ~ <8> The manufacturing method described in any one of the following statements, wherein the side fraction (Bside fraction) drawn from the side outlet of the continuous multi-stage distillation column B2... s The content of 2-methoxyethanol in the product is less than 50 ppm by mass.

[0039] <10>

[0040] according to <1> ~ <9> The manufacturing method described in any one of the above statements, wherein the low-purity dialkyl carbonate mixture (A) supplied to the continuous multi-stage distillation column B1 is... T The temperature should be adjusted to 100℃~150℃.

[0041] <11>

[0042] according to <10> The manufacturing method described herein, wherein the low-purity dialkyl carbonate mixture (A) is heated using a heater. T Heating, the time from the heater to the supply to the continuous multistage distillation column B1 is less than 5 minutes.

[0043] <12>

[0044] according to <1> ~ <11> The manufacturing method described in any one of the following statements, wherein the top component (Btop) continuously drawn from the top of the continuous multi-stage distillation column B1 is... T Condensation occurs at a reflux tank temperature of 100℃~150℃.

[0045] <13>

[0046] according to <1> ~ <12> In any one of the manufacturing methods, the continuous multi-stage distillation column B2 has an upper straight column section, a lower straight column section, and a conical section connecting the upper straight column section and the lower straight column section, wherein the diameter of the lower straight column section is larger than the diameter of the upper straight column section.

[0047] The side outlet of the continuous multi-stage distillation column B2 is located in the conical section.

[0048] <14>

[0049] according to <13> In the manufacturing method described above, in the continuous multi-stage distillation column B2, the diameter D of the upper section of the column is... 21 (cm) and the tower diameter D of the straight tower body at the lower section of the tower. 22 The ratio of (cm) satisfies the condition of equation (ii):

[0050] 0.2 <D 21 / D 22 <1.0……(ii).

[0051] <15>

[0052] according to <1> ~ <14> In any one of the manufacturing methods, in the continuous multi-stage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 5 minutes or more.

[0053] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i).

[0054] <16>

[0055] according to <1> ~ <15> In any one of the manufacturing methods, wherein, in the continuous multi-stage distillation column B2, the side fraction (B) is extracted in a gaseous state. s ).

[0056] <17>

[0057] according to <1> ~ <16> In any one of the manufacturing methods, the internal components of the continuous multi-stage distillation column B1 are trays and / or packing.

[0058] <18>

[0059] according to <1> ~ <17> In any one of the manufacturing methods, the reflux ratio of the continuous multi-stage distillation column B1 is 0.5 to 5.

[0060] <19>

[0061] according to <1> ~ <18> In any one of the manufacturing methods, the reflux ratio of the continuous multi-stage distillation column B2 is 0.2 to 4.

[0062] <20>

[0063] according to <1> ~ <19> The manufacturing method described in any one of the following statements, wherein the bottom component (B) of the continuous multi-stage distillation column B1 B In the dialkyl carbonate, the content of 2-methoxyethanol is less than 100 ppm by mass.

[0064] <21>

[0065] according to <1> ~ <20> In any of the manufacturing methods described above, the bottom component (B) of the continuous multi-stage distillation column B1 is... B The components (B1) are directly supplied to the continuous multi-stage distillation column B2, or the bottom components (B2) of the continuous multi-stage distillation column B1 are supplied directly to the continuous multi-stage distillation column B2. B It is supplied to an industrial-grade dialkyl carbonate tank, and then from the tank to a continuous multistage distillation column B2.

[0066] <22>

[0067] according to <1> ~ <21> In any one of the manufacturing methods, the bottom component (B) of the continuous multi-stage distillation column B1 is... B The content of high-boiling-point compounds in the product is above 0.1 ppm by mass.

[0068] <23>

[0069] according to <1> ~ <22> The manufacturing method described in any one of the following methods comprises the step of reacting a cyclic carbonate with an aliphatic monohydric alcohol to obtain a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate. T ).

[0070] <24>

[0071] according to <1> ~ <23> The manufacturing method described in any one of the following steps comprises: continuously feeding a cyclic carbonate and an aliphatic monohydric alcohol into a continuous multistage distillation column A containing a catalyst, wherein the reaction and distillation are carried out simultaneously in the column, and a low-purity dialkyl carbonate mixture (A) containing the generated dialkyl carbonate and unreacted aliphatic monohydric alcohol is disposed of. T It is continuously drawn from the top of the tower.

[0072] <25>

[0073] An apparatus for manufacturing dialkyl carbonate, wherein the apparatus comprises:

[0074] A continuous multistage distillation column B1, wherein a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohol is continuously fed into the continuous multistage distillation column B1. T ), the top component (B) of the column, which is mainly composed of aliphatic monohydric alcohols. T ) is continuously drawn from the top of the column, and the bottom component (B), which is mainly composed of dialkyl carbonate, is drawn off. B It is continuously drawn from the bottom of the tower;

[0075] A continuous multistage distillation column B2, wherein a bottom component (B1) mainly composed of dialkyl carbonate, continuously drawn from the bottom of the continuous multistage distillation column B1, is continuously supplied to the continuous multistage distillation column B2. B Furthermore, the continuous multistage distillation column B2 continuously extracts a side fraction (B2) whose main component is dialkyl carbonate. s The side drawer opening,

[0076] The bottom temperature of the continuous multi-stage distillation column B1 can be set to above 115°C.

[0077] The manufacturing apparatus is configured to contain a Fe-containing compound within the continuous multi-stage distillation column B1.

[0078] <26>

[0079] according to <25> The manufacturing apparatus is configured to supply ferrous oxide (II) into the continuous multistage distillation column B1.

[0080] <27>

[0081] according to <25> or <26> The manufacturing apparatus, wherein the material inside the continuous multi-stage distillation column B1 is carbon steel.

[0082] <28>

[0083] according to <25> to <27> The manufacturing apparatus described in any one of the following statements, wherein the manufacturing apparatus includes a heater, the heater controlling the low-purity dialkyl carbonate mixture (A) supplied to the continuous multistage distillation column B1. T Heating is performed.

[0084] <29>

[0085] according to <25> to <28> The manufacturing apparatus as described in any one of the following descriptions, wherein the continuous multi-stage distillation column B2 has an upper straight column section, a lower straight column section, and a conical section connecting the upper straight column section and the lower straight column section, wherein the diameter of the lower straight column section is larger than the diameter of the upper straight column section.

[0086] The side outlet of the continuous multi-stage distillation column B2 is located in the conical section.

[0087] <30>

[0088] according to <29> The manufacturing apparatus, wherein in the continuous multi-stage distillation column B2, the diameter D of the upper section of the straight column body... 21 (cm) and the tower diameter D of the straight tower body at the lower section of the tower. 22 The ratio of (cm) satisfies the condition of equation (ii):

[0089] 0.2 <D 21 / D 22 <1.0……(ii).

[0090] <31>

[0091] according to <25> ~ <30> The manufacturing apparatus according to any one of the following methods, wherein the internal components of the continuous multi-stage distillation column B1 are trays and / or packing.

[0092] <32>

[0093] according to <25> ~ <31> The manufacturing apparatus described in any one of the following statements, wherein the bottom component (B) of the continuous multi-stage distillation column B1 is... B The components (B1) are directly supplied to the continuous multi-stage distillation column B2, or the bottom components (B2) of the continuous multi-stage distillation column B1 are supplied directly to the continuous multi-stage distillation column B2. B It is supplied to an industrial-grade dialkyl carbonate tank, and then from the tank to a continuous multistage distillation column B2.

[0094] Invention Effects

[0095] According to the present invention, a method and apparatus for manufacturing dialkyl carbonate that reduce the heat consumption in the separation and purification process of obtaining high-purity dialkyl carbonate with a purity of 99.99% or higher from dialkyl carbonate with a purity of 99.00% to 99.95% by mass can be provided. Attached Figure Description

[0096] Figure 1 This is a schematic diagram illustrating an example of the flow of two separation and purification steps (I) and (II) in the method for manufacturing dialkyl carbonate of the present invention.

[0097] Figure 2 This is a schematic diagram illustrating an example of the flow of two separation and purification steps (I) and (II) in the method for manufacturing dialkyl carbonate of the present invention.

[0098] Figure 3 This is a schematic diagram illustrating an example of a continuous multi-stage distillation column. Detailed Implementation

[0099] Hereinafter, embodiments of the present invention (hereinafter referred to as "this embodiment") will be described in detail with reference to the accompanying drawings as needed. However, the present invention is not limited thereto and various modifications can be made without departing from its spirit.

[0100] The method for manufacturing dialkyl carbonate in this embodiment includes the following steps:

[0101] (I) First separation and purification step (I), wherein a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohol is separated. T The product is continuously supplied to a continuous multi-stage distillation column B1, where the top component (B1), which is mainly composed of aliphatic monohydric alcohols, is distilled. T ) is continuously drawn from the top of the column, and the bottom component (B), which is mainly composed of dialkyl carbonate, is drawn off. B It is continuously drawn from the bottom of the tower;

[0102] (II) Second separation and purification step (II), wherein the bottom component (B1) mainly composed of dialkyl carbonate is continuously drawn from the bottom of the continuous multi-stage distillation column B1. B The side fraction (B), which is mainly composed of dialkyl carbonate, is continuously supplied to a continuous multistage distillation column B2 with a side outlet (hereinafter also referred to as the "side fraction outlet"), and the side fraction (B) is supplied to the column. s It can be continuously extracted from the side outlet.

[0103] In the process (I), a low-purity dialkyl carbonate mixture (A) is fed to the continuous multi-stage distillation column B1. T The concentration of dialkyl carbonate in the distillation column B1 is 25.00% to 95.00% by mass, and the bottom temperature of the continuous multistage distillation column B1 is above 115°C.

[0104] In the process (II), the bottom component (B) supplied to the continuous multi-stage distillation column B2 B The concentration of dialkyl carbonate in the product is 99.00% to 99.95% by mass.

[0105] In the process (II), the side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The purity of the dialkyl carbonate in the product is above 99.99% by mass.

[0106] The method for producing dialkyl carbonate according to this embodiment, by having the above-described structure, can reduce the heat consumption in the separation and purification process for obtaining high-purity dialkyl carbonate with a purity of 99.99% or higher from dialkyl carbonate with a purity of 99.00% to 99.95% by mass. For example, separation and purification can be performed with a small reflux ratio, thus reducing heat consumption.

[0107] Typically, to improve the purity of the final dialkyl carbonate, the low-purity dialkyl carbonate mixture (A) supplied to the continuous multistage distillation column B1 should be increased beforehand. T The concentration of dialkyl carbonate in the ester (e.g., as described in Patent Documents 1 and 2, with a purity of 99.95% by mass) is relatively low. However, in the method for manufacturing dialkyl carbonate in this embodiment, it was surprisingly found that by setting the concentration of the dialkyl carbonate to a lower range than previously described above, it is possible to manufacture high-purity dialkyl carbonate with a purity of 99.99% by mass or higher from dialkyl carbonate with a purity of 99.00% to 99.95% by mass in a manner that reduces heat consumption.

[0108] The mechanism by which this effect is observed is not yet clear, but the inventors speculate as follows. The low-purity dialkyl carbonate mixture (A) supplied to the continuous multi-stage distillation column B1... T Dialkyl carbonates typically contain aliphatic monohydric alcohols, trace amounts of alkoxy alcohols, and trace amounts of aliphatic carbonate ethers as impurities. 2ME (2-methoxyethanol) is not easily separated from dialkyl carbonates by distillation; therefore, a large amount of heat consumption, i.e., a high reflux ratio, is required to purify dialkyl carbonates containing such impurities to a purity of 99.99% by mass or higher. In the method for manufacturing dialkyl carbonates according to this embodiment, in step (I), a low-purity dialkyl carbonate mixture (A) supplied to a continuous multi-stage distillation column B1 is... T The concentration of dialkyl carbonate in the mixture is set in a low range of 25.00% by mass to 95.00% by mass, and the bottom temperature of the column for distillation separation of aliphatic monohydric alcohol and dialkyl carbonate is set at a high temperature (e.g., above 115°C). By reducing the concentration of dialkyl carbonate in the feed mixture and increasing the bottom temperature, 2ME, which is an obstacle to the high purity of dialkyl carbonate, can be converted into a high-boiling-point compound. It is believed that the high-boiling-point compound can be easily separated from dialkyl carbonate by distillation. Therefore, in the continuous multistage distillation column B2 of step (II), the purity of dialkyl carbonate can be increased to above 99.99% by mass by reducing the reflux ratio and the heat consumption.

[0109] Side fraction (B) s There is no particular upper limit to the purity of dialkyl carbonates in (e.g., 99.999% by mass).

[0110] It should be noted that, in this embodiment, the main component refers to the component with the highest mass ratio. The main component is the component with a mass ratio of 30% or more, preferably 40% or more, and more preferably 50% or more.

[0111] In the manufacturing method of this embodiment, two separation and purification steps (I) and (II) are performed to separate high-purity dialkyl carbonate with a purity of 99.99% by mass or higher.

[0112] In the manufacturing method of this embodiment, the two separation and purification steps (I) and (II) are preferably, for example, as follows: Figure 1 The diagram shows a first separation and purification step (I), wherein a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohol is separated. T The product is continuously supplied to the first continuous multi-stage distillation column B1, where the top component (B1), which is mainly composed of aliphatic monohydric alcohols, is distilled. T ) is continuously drawn from the top of the column, and the bottom component (B), which is mainly composed of dialkyl carbonate, is drawn off. B The bottom component (B1), which is mainly composed of dialkyl carbonate, is continuously drawn from the bottom of the continuous multi-stage distillation column B1; and the second separation and purification step (II) involves continuously drawing the bottom component (B1) from the bottom of the column B1. B The product is continuously supplied to a second continuous multistage distillation column B2, which has a side outlet, and the top component (B2) is used as a low-boiling-point component. t The side fraction (B), mainly composed of dialkyl carbonate, is continuously drawn out from the top of the column. s ) is continuously drawn out from the side outlet, and the bottom component (B), which is a high-boiling-point component, is drawn out from the bottom of the column. b It is continuously drawn out from the bottom of the tower.

[0113] [First Separation and Purification Step (I)]

[0114] In the method for manufacturing dialkyl carbonate in this embodiment, step (I) is a first separation and purification step, wherein a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohol is separated. T The product is continuously supplied to a continuous multi-stage distillation column B1, where the top component (B1), which is mainly composed of aliphatic monohydric alcohols, is distilled. T ) is continuously drawn from the top of the column, and the bottom component (B), which is mainly composed of dialkyl carbonate, is drawn off. B It is continuously drawn out from the bottom of the tower.

[0115] The following is a detailed description of process (I).

[0116] In process (I), a low-purity dialkyl carbonate mixture (A) is supplied to continuous multi-stage distillation column B1. T The concentration of dialkyl carbonate in the mixture is 25.00% to 95.00% by mass, preferably 30.00% to 90.00% by mass, and more preferably 35.00% to 85.00% by mass. Low-purity dialkyl carbonate mixture (A)T The concentration of dialkyl carbonate in (A) refers to a mixture of low-purity dialkyl carbonates (A). T The purity of dialkyl carbonate.

[0117] There are no particular limitations on the dialkyl carbonate esters; examples include dimethyl carbonate and diethyl carbonate. Among these, dimethyl carbonate is preferred.

[0118] There are no particular limitations on the aliphatic monohydric alcohol; examples include methanol and ethanol. Among these, methanol is preferred.

[0119] In a low-purity dialkyl carbonate mixture (A) T In this context, there are no particular restrictions on the components other than dialkyl carbonates and aliphatic monohydric alcohols. For example, it can contain alkoxy alcohols, aliphatic carbonate ethers, epoxides, carbon dioxide, etc. As for alkoxy alcohols, there are no particular restrictions; for example, 2-methoxyethanol (hereinafter also referred to as "2ME") can be included. As for aliphatic carbonate ethers, there are no particular restrictions; for example, ethylene glycol monomethyl ether carbonate (hereinafter also referred to as "EMMC") can be included. As for epoxides, there are no particular restrictions; for example, ethylene oxide can be included.

[0120] Low-purity dialkyl carbonate mixture (A) T The concentration of aliphatic monohydric alcohol in the product is preferably 5.00% to 75.00% by mass, more preferably 10.00% to 70.00% by mass, and even more preferably 15.00% to 65.00% by mass.

[0121] Low-purity dialkyl carbonate mixture (A) T The concentration of 2-methoxyethanol in the product is preferably 0.00% to 1.00% by mass, more preferably 0.00% to 0.80% by mass, and even more preferably 0.00% to 0.60% by mass.

[0122] Low-purity dialkyl carbonate mixture (A) T The carbon dioxide content in the product is preferably 0.00 to 1.00% by mass, more preferably 0.00% to 0.50% by mass, and even more preferably 0.00% to 0.10% by mass.

[0123] Furthermore, the bottom temperature of the continuous multistage distillation column B1 is 115°C or higher, preferably 140°C to 250°C, and more preferably 180°C to 220°C. With the bottom temperature of the continuous multistage distillation column B1 within this range, 2ME, which is an obstacle to the high purity of dialkyl carbonate, can be converted into a high-boiling-point compound, thus reducing heat consumption in the continuous multistage distillation column B2 of step (II).

[0124] In the continuous multistage distillation column B1, the liquid residence time calculated by the following formula (i) is preferably 5 minutes or more, more preferably 10 minutes to 150 minutes, and even more preferably 15 minutes to 120 minutes. When the liquid residence time in the continuous multistage distillation column B1 is within the above range, it results in a higher conversion rate of 2ME and a higher bottom component (B0) drawn from the continuous multistage distillation column B1. B The residual concentration of 2ME in ) tends to be lower (e.g., below 10 ppm by mass).

[0125] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0126] Process (I) is preferably carried out in the presence of a compound containing Fe.

[0127] For example, it is preferable that a Fe-containing compound is present inside or on the surface of the continuous multi-stage distillation column B1. When step (I) is carried out in the presence of the Fe-containing compound, the reaction of converting 2ME, which is an obstacle to the high purity of dialkyl carbonate, into a high-boiling-point compound can be further promoted. As a result, it is easier to achieve a final dialkyl carbonate purity of, for example, 99.99% by mass or more, and it is possible to produce dialkyl carbonate with such high purity (99.99% by mass or more) with less steam, i.e., a small reflux ratio.

[0128] There are no particular limitations on compounds containing Fe; examples include iron oxides. Ferrous(II) oxide is an example of an iron oxide.

[0129] From the viewpoint of further promoting the reaction that converts 2ME into high-boiling-point compounds, it is preferable to increase the purity of the dialkyl carbonate mixture (A). T The contact surface area between the Fe-containing compound and the Fe-containing compound. More specifically, the Fe-containing compound in step (I) and the low-purity dialkyl carbonate mixture (A) T The preferred contact surface area is 1.0 × 10⁻⁶. -3 m 2 • Minutes / (kg / hour) or more. The preferred contact surface area is 1.5 × 10⁻⁶. -3 m 2 • 1 minute / (kg / hour) or more, preferably 2.0 × 10 -3 m 2 • Minutes / (kg / hour) or more. There is no particular upper limit to the contact surface area, for example, 10,000 × 10⁻⁶. -3 m 2 • Less than minutes / (kg / hour).

[0130] When a powder containing a compound with Fe is added, the contact surface area is calculated using the following formula.

[0131] Contact surface area (m²) 2 •min / (kg / hour))=[(surface area of ​​average particle size of added powder)(m 2 [×Liquid residence time in tower (minutes)] / Supply flow rate (kg / hour)

[0132] The residence time of the liquid in the above-mentioned column is calculated by the following formula.

[0133] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component)

[0134] In addition, when the distillation tower material, such as the inner wall, contains compounds containing Fe, the contact surface area can be calculated using the following formula.

[0135] Contact surface area (m²) 2 • minutes / (kg / hour)) = [(BTM capacity, internal tower area in contact with liquid (m²)] 2 [×(residence time in tower (minutes)) / (supply flow rate (kg / hour))]

[0136] The material inside distillation column B1 is carbon steel. During equipment shutdown and assembly, ferrous oxide (II) can be generated on the surface by the incoming oxygen. Normally, carbon steel is not used for high-purity material purification, but in this embodiment, by using carbon steel as the material inside distillation column B1, heat consumption can be reduced in the separation and purification of high-purity dialkyl carbonate in distillation column B2. Examples of materials for distillation column B1 include the inner wall surface of distillation column B1.

[0137] The internal components of the recovery section and concentration section of the continuous multistage distillation column B1 are preferably trays and / or packing, with trays being more preferred. There are no restrictions on the type of tray; for example, bubble cap trays, perforated trays, corrugated trays, heavy-disc floating valve trays, floating valve trays, counter-current trays, S-shaped trays, Superfrac trays, Maxfrac trays, dual-flow trays, grid trays, cross-flow grid trays, Kittel trays, etc., are preferred. In cases where the continuous multistage distillation column has a layer with a low concentration of 2ME and where no substantial reaction occurs (e.g., the layer above the feed liquid introduction layer), a distillation column filled with packing in this layer is also preferred; that is, a multistage distillation column that simultaneously possesses a tray section and a packing-filled section. There are no particular limitations on the packing material used; for example, random packing materials such as Raschig rings, Lessin rings, Pall rings, Bell saddle rings, rectangular saddle rings, Dixon packing, McMahon packing, and Helipak are preferred; while structured packing materials such as Mellapak, Gempak, Techno-pack, Flexipac, Sulzer packing, Goodroll packing, and Glitsch grid are preferred. When the internal components of the recovery section and the concentration section of the continuous multistage distillation column B1 are each trays and / or packing materials, it is easier to achieve a high purity (purity ≥ 99.99% by mass) of the final dialkyl carbonate, for example, suitable for use as a lithium-ion battery electrolyte. Furthermore, it is possible to produce such high-purity (purity ≥ 99.99% by mass) dialkyl carbonate from industrial-grade dialkyl carbonate in a manner that further reduces the heat of supply (small reflux ratio).

[0138] The reflux ratio of the continuous multistage distillation column B1 is preferably 0.5 to 20, more preferably 0.8 to 15, and even more preferably 1 to 5. In the method for producing dialkyl carbonate in this embodiment, by setting a small reflux ratio in this way, the reaction of converting 2ME into high-boiling-point compounds can be further promoted, and the heat consumption in the subsequent second separation and purification step (II) can be reduced.

[0139] The bottom component (B) of the continuous multi-stage distillation column B1 B In this product, the concentration of dialkyl carbonate is 99.00% to 99.95% by mass. Additionally, the bottom composition of continuous multi-stage distillation column B1 (B...) B In the product, the content of 2-methoxyethanol is preferably less than 100 ppm by mass, more preferably less than 50 ppm by mass, and even more preferably less than 10 ppm by mass. The bottom component (B) of the continuous multi-stage distillation column B1... B In this context, there is no lower limit to the content of 2-methoxyethanol, for example, it can be 0 ppm by mass. When the bottom component of continuous multi-stage distillation column B1 (B...)... BWhen the purity of the dialkyl carbonate and the content of 2-methoxyethanol in the dialkyl carbonate are within the above-mentioned range, it is easier to make the final dialkyl carbonate have a high purity (purity of 99.99% by mass or more) that is suitable for use as a lithium-ion battery electrolyte, for example. Moreover, it is more likely to produce such high-purity (purity of 99.99% by mass or more) dialkyl carbonate from industrial-grade dialkyl carbonate with less heat consumption (small reflux ratio).

[0140] The bottom component (B) of the continuous multi-stage distillation column B1 B In the distillation process, the content of the high-boiling-point compound is preferably 0.1 ppm by mass or more, more preferably 1 ppm by mass or more, and even more preferably 100 ppm by mass or more. The high-boiling-point compound is considered to be a substance obtained by converting 2-methoxyethanol, which is not easily separated from dialkyl carbonate during distillation; therefore, the content of this high-boiling-point compound can be within the above-mentioned range. That is, when the bottom component (B...) of the continuous multi-stage distillation column B1... B When the content of high-boiling-point compounds in the product is within the above-mentioned range, it is easier to achieve a high purity (purity of 99.99% by mass or more) in the final dialkyl carbonate, for example, that is suitable for use as a lithium-ion battery electrolyte. Moreover, it is more likely to produce such high-purity (purity of 99.99% by mass or more) dialkyl carbonate from industrial-grade dialkyl carbonate with less heat consumption (small reflux ratio).

[0141] The bottom component (B) of the continuous multi-stage distillation column B1 B In this context, there is no upper limit to the content of high-boiling-point compounds, for example, it is 1.0% by mass.

[0142] In this embodiment, "high-boiling-point compound" refers to a compound that has a boiling point at a pressure of 760 mmHg that is more than 100°C higher than the boiling point of the dialkyl carbonate, which is the main component. It should be noted that, here, "main component" refers to the bottom component (B1) of the continuous multi-stage distillation column B1. B It is the component with the highest proportion of dialkyl carbonates contained in ).

[0143] It should be noted that, in this embodiment, the concentration of dialkyl carbonate and the content of each component can be determined by the methods described in the examples below.

[0144] In process (I), in order to process a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohols... T Distillation separates the top component (B) into a column containing mainly aliphatic monohydric alcohols. T ) and bottom components (B) with dialkyl carbonate as the main component B ), using a continuous multistage distillation column B1.

[0145] The continuous multistage distillation column B1 in process (I) preferably has the ability to stably separate large quantities of low-purity dialkyl carbonate mixtures (A) with a specified separation efficiency over a long period of time. T The function of separating dialkyl carbonates is desired, and therefore, it is preferable to simultaneously satisfy various conditions.

[0146] In this embodiment, a mixture of dialkyl carbonate and low-purity dialkyl carbonate of aliphatic monohydric alcohol (A) is used. T The product is continuously supplied to the continuous multi-stage distillation column B1, where the top component (B1), which is mainly composed of aliphatic monohydric alcohols, is distilled. T The bottom component (B), which is mainly composed of dialkyl carbonate, is continuously extracted from the top of the column (preferably in gaseous state). B The low-purity dialkyl carbonate mixture (A) is continuously drawn from the bottom of the column (preferably in liquid form). T When supplying the low-purity dialkyl carbonate mixture (A) to the continuous multi-stage distillation column B1, it can be supplied in either gaseous or liquid form. T Before being supplied to the continuous multi-stage distillation column B1, it is preferable to heat or cool the liquid to a temperature close to the temperature of the liquid near the supply port of the distillation column B1.

[0147] In addition, this low-purity dialkyl carbonate mixture (A) T The location where the product is supplied to the continuous multistage distillation column B1 is preferably near the area between the recovery section and the concentration section. The continuous multistage distillation column B1 preferably has a reboiler and a reflux device for heating the distillate.

[0148] In this embodiment, the low-purity dialkyl carbonate mixture (A) is used. T Preferably, it is supplied to a continuous multi-stage distillation column B1 at a rate of approximately 2 tons / hour or more for distillation and separation, and the top component (B) of the column is used as a low-boiling-point mixture. T The bottom component (B1) is continuously drawn from the top of the distillation column B1 and becomes part of the high-boiling-point mixture. B It is continuously drawn from the lower part of the distillation column B1.

[0149] In process (I), the top component (B), which is a low-boiling-point mixture, can be made... T The concentration of the aliphatic monohydric alcohol in the product is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more. Top component (B) T There is no particular upper limit to the concentration of the aliphatic monohydric alcohol in the mixture, for example, 100% by mass. Furthermore, the top component (B) of the low-boiling-point mixture... TThe alcohols separated from the main components of the mixture are preferably in an amount of 300 kg / h or more, preferably 350 kg / h or more, and more preferably 400 kg / h or more. This is the top component (B) of the low-boiling-point mixture. T The other components of the product are mainly dialkyl carbonates, so it can be reused directly as an aliphatic monohydric alcohol reacting with cyclic carbonates, or mixed with alcohols recovered in other processes and reused as an aliphatic monohydric alcohol reacting with cyclic carbonates. This method is one of the preferred embodiments of this invention. If the amount of recovered alcohols alone is insufficient, new aliphatic monohydric alcohols are added.

[0150] Additionally, the bottom component (B) that is separated in process (I) as a high-boiling-point mixture B The main component of the product is dialkyl carbonate, and the content of unreacted aliphatic monohydric alcohol is preferably less than 1% by mass, more preferably less than 0.8% by mass, and even more preferably less than 0.6% by mass. Bottom component (B) B There is no particular limit to the lower limit of the content of unreacted aliphatic monohydric alcohols in the product, for example, it can be 0 by mass.

[0151] Furthermore, in a preferred embodiment of this invention, halogen-free raw materials and catalysts are used to carry out the reaction, thus ensuring that the resulting dialkyl carbonate is completely free of halogens. Therefore, in this embodiment, the halogen content is preferably 0.1 ppm by mass or less, more preferably 1 ppb by mass or less (beyond the detection limit of ion chromatography).

[0152] The bottom pressure in the continuous multistage distillation column B1 operating in process (I) varies depending on the composition of the column and the bottom temperature used, and is preferably 0.1 MPaG to 3.0 MPaG, more preferably 0.15 MPaG to 2.5 MPaG, and even more preferably 0.2 MPaG to 2.0 MPaG.

[0153] There are no particular restrictions on the materials used to construct the continuous multistage distillation column B1 used in process (I). For example, from the perspective of the quality of the dialkyl carbonates and diols produced and separated, metal materials such as carbon steel and stainless steel are preferred.

[0154] [Process (II)]

[0155] In the method for manufacturing dialkyl carbonate in this embodiment, step (II) is a second separation and purification step, wherein the bottom component (B1), which is mainly composed of dialkyl carbonate, is continuously drawn from the bottom of the continuous multi-stage distillation column B1 in step (I) described above. B The side fraction (B) with dialkyl carbonate as the main component is continuously supplied to a continuous multistage distillation column B2 with a side outlet, and the side fraction (B) with dialkyl carbonate as the main component is supplied continuously. sIt can be continuously extracted from the side outlet.

[0156] In the second separation and purification step, the top component (B), which is a low-boiling-point component, can be separated. t The component is continuously drawn from the top of the column. Additionally, in the second separation and purification step, the bottom component (B), which is a high-boiling-point component, can be extracted from the bottom of the column. b It is continuously drawn out from the bottom of the tower.

[0157] The following is a detailed description of process (II).

[0158] In process (II), the bottom component (B) supplied to the continuous multi-stage distillation column B2 is... B The concentration of dialkyl carbonate in the product is 99.00% to 99.95% by mass, preferably 99.2% to 99.95% by mass, and more preferably 99.4% to 99.95% by mass. When the bottom composition of the continuous multi-stage distillation column B1 (B... B When the concentration of dialkyl carbonate in the product is within the above range, it is easy to make the final dialkyl carbonate have a purity of 99.99% by mass or higher, which is suitable for use as a lithium-ion battery electrolyte. Moreover, it is possible to produce such high-purity dialkyl carbonate with a purity of 99.99% by mass or higher from industrial-grade dialkyl carbonate with less heat consumption, i.e., a small reflux ratio.

[0159] In process (II), the side fraction (B) drawn from the side outlet of the continuous multistage distillation column B2 is... s The dialkyl carbonate in the product has a purity of 99.99% by mass or higher. Such high-purity dialkyl carbonate can be used, for example, as an electrolyte in lithium-ion batteries.

[0160] The bottom temperature of the continuous multistage distillation column B2 is preferably below 120°C, more preferably 60°C to 110°C, and even more preferably 65°C to 105°C. When the bottom temperature of the continuous multistage distillation column B2 is within the above range, it is possible to use the steam generated by heat exchange through the condenser at the top of the multistage distillation column B1 to heat the column. This allows for the production of high-purity dialkyl carbonate with a purity of 99.99% by mass or higher, suitable for use as a lithium-ion battery electrolyte, from dialkyl carbonate with a purity of 99.0% by mass or higher (e.g., industrial grade) in a manner that further reduces the amount of heat supplied from the outside.

[0161] The side fraction (B) drawn from the side outlet of the continuous multistage distillation column B2 sIn the dialkyl carbonate production process, the content of high-boiling-point compounds is preferably 30 ppm by mass or less, more preferably 25 ppm by mass or less, and even more preferably 20 ppm by mass or less. Obviously, for example, when purification is performed solely using a continuous multi-stage distillation column B1 to achieve a final dialkyl carbonate purity of 99.99% by mass or more and then withdrawn from the bottom of the column, high-boiling-point compounds are present in the dialkyl carbonate. In applications such as lithium-ion batteries, these high-boiling-point compounds can cause performance degradation, and therefore it is desirable to remove them. According to the method for manufacturing dialkyl carbonate of this embodiment, by proceeding through two steps (I) and (II), the content of high-boiling-point compounds can be reduced while suppressing heat consumption. It should be noted that the definition of "high-boiling-point compound" is as described above.

[0162] The side fraction (B) drawn from the side outlet of continuous multistage distillation column B2 s The metal content in the dialkyl carbonate is preferably 1 ppm by mass or less, more preferably 0.8 ppm by mass or less, and even more preferably 0.6 ppm by mass or less. Obviously, for example, when purification is performed solely using a continuous multi-stage distillation column B1 to achieve a final dialkyl carbonate purity of 99.99% by mass or more and then withdrawn from the bottom of the column, the dialkyl carbonate contains metal. In applications such as lithium-ion batteries, this metal can cause performance degradation, and therefore it is desirable to remove it. According to the method for manufacturing dialkyl carbonate of this embodiment, by proceeding through two steps (I) and (II), the metal content can be reduced while suppressing heat consumption.

[0163] The side fraction (B) drawn from the side outlet of continuous multistage distillation column B2 s The water content in the dialkyl carbonate is preferably 30 ppm by mass or less, more preferably 25 ppm by mass or less, and even more preferably 20 ppm by mass or less. When used as an electrolyte for lithium-ion batteries, moisture can cause performance degradation, so it is desirable to remove this moisture. According to the method for manufacturing dialkyl carbonate of this embodiment, by performing steps (I) and (II), the moisture content can be reduced while suppressing heat consumption.

[0164] The side fraction (B) drawn from the side outlet of continuous multistage distillation column B2 s The combined content of methanol and ethanol in the ester is preferably below 20 ppm by mass. High-purity dialkyl carbonates with such content within the above range are extremely useful, for example, as lithium-ion battery electrolytes.

[0165] The side fraction (B) drawn from the side outlet of continuous multistage distillation column B2 sThe 2ME content in the dialkyl carbonate is preferably 50 ppm by mass or less, more preferably 40 ppm by mass or less, and even more preferably 30 ppm by mass or less. When used as an electrolyte for lithium-ion batteries, 2ME causes performance degradation, so it is desirable to remove 2ME. According to the method for manufacturing dialkyl carbonate of this embodiment, by passing through two steps (I) and (II), in step (I) 2ME is converted to high-boiling-point compounds and thoroughly removed, and then further purified in step (II), the 2ME content can be reduced to an extremely low level, reducing the 2ME content while suppressing heat consumption. In the side fraction (B) s In this study, there are no specific restrictions on the lower limits of the contents of high-boiling-point compounds, 2ME, metals, water, methanol, and ethanol, for example, 0 ppm by mass.

[0166] In the continuous multi-stage distillation column B2, it is preferable to extract the side fraction (B) in gaseous state. s In continuous multistage distillation column B2, when the side fraction (B) is extracted in gaseous state... s When ), it has the effect of suppressing the side fraction (B) s The tendency of high-boiling-point components and metal content in dialkyl carbonates.

[0167] The reflux ratio of the continuous multistage distillation column B2 is preferably 0.2 to 4, more preferably 0.6 to 2.0, and even more preferably 0.8 to 1.5. In the method for producing dialkyl carbonate in this embodiment, by setting a small reflux ratio in this way, heat consumption can be reduced, and the purity of the final dialkyl carbonate can be made to a high purity of 99.99% by mass or more, for example, a purity suitable for use as a lithium-ion battery electrolyte.

[0168] In the continuous multistage distillation column B2, the column diameter D above the side outlet is... 21 (cm) and the tower diameter D below the side outlet 22 The ratio of (cm) preferably satisfies the condition of equation (ii) below. When D 21 / D 22 When the conditions of formula (ii) are met, there is a tendency to produce high-purity dialkyl carbonates with a purity of 99.99% by mass or more, which are used as electrolytes for lithium-ion batteries, for example, with less heat consumption, i.e. a smaller reflux ratio.

[0169] 0.2 <D 21 / D 22 <1.0……(ii)

[0170] Starting from the same point of view, D 21 / D 22 More preferably, it is 0.3 to 1.0.

[0171] In process (II), in order to continuously extract the bottom component (B1) of dialkyl carbonate as the main component from the bottom of the continuous multi-stage distillation column B1, B Distillation separated a side fraction (B) with dialkyl carbonate as the main component. s The continuous multistage distillation column B2 is used. The components at the bottom of the column (B) can be further extracted using the continuous multistage distillation column B2. B Distillation separates the top component (B) which is a low-boiling-point component. t ) and the bottom component of the tower (B) as a high-boiling-point component b ).

[0172] The recovery section and concentration section of the continuous multistage distillation column B2 in step (II) are preferably distillation columns having the aforementioned trays and / or packing as internal components. Multistage distillation columns that simultaneously have tray sections and packed sections can also be used.

[0173] It should be noted that the theoretical number of internal components that combine the recovery section and the concentration section of the continuous multi-stage distillation column B2 is preferably 3 to 40 layers.

[0174] In this embodiment, the internal components refer to the parts in the distillation column where gas-liquid contact actually occurs. There are no particular limitations on the trays used; for example, bubble cap trays, perforated trays, corrugated trays, heavy-disc floating valve trays, floating valve trays, counter-current trays, S-shaped trays, Superfrac trays, Maxfrac trays, dual-flow trays, grid trays, cross-flow grid trays, and Kittel trays are preferred. There are no particular limitations on the packing materials used; for example, random packing materials such as Raschig rings, Lessin rings, Pall rings, Bell saddle rings, rectangular saddle rings, Dixon packing, McMahon packing, and Helipak are preferred; structured packing materials such as Mellapak, Gempak, Techno-pack, Flexipac, Sulzer packing, Goodroll packing, and Glitsch grid are preferred.

[0175] In this embodiment, it is preferable to continuously extract the bottom component (B1) of the continuous multi-stage distillation column B1, which is mainly composed of dialkyl carbonate. B ) is continuously supplied to continuous multi-stage distillation column B2, and the top component (B) which is the low-boiling-point component is then produced. t The side fraction (B), mainly composed of dialkyl carbonate, is continuously drawn out from the top of the column. s ) is continuously drawn out from the side outlet, and the bottom component (B), which is a high-boiling-point component, is drawn out from the bottom of the column. b ) is continuously drawn from the bottom of the column. This is to ensure that the bottom component (B) is extracted from the bottom of the column. BBefore being supplied to the continuous multistage distillation column B2, the liquid is conditioned to a temperature close to that of the liquid near the supply port of the distillation column B2, and preferably heated or cooled.

[0176] In addition, the bottom component (B) B The location where the product is supplied to the continuous multistage distillation column B2 is preferably near the area between the recovery section and the concentration section. The continuous multistage distillation column B2 preferably has a reboiler and a reflux device for heating the distillate.

[0177] In this embodiment, the bottom component (B) of the tower is... B Preferably, at a rate of approximately 2 tons / hour or more, the distillate is drawn from continuous multistage distillation column B1 and fed into continuous multistage distillation column B2 for distillation separation. The top component (Btop), representing the low-boiling-point component, is continuously drawn from the upper part of distillation column B2. t The bottom component (B2), which is a high-boiling-point component, is continuously extracted from the bottom of the distillation column B2. b ).

[0178] The top component of the column (B) is a low-boiling-point component. t The other components of the product are mainly dialkyl carbonates, so it can be reused directly as an aliphatic monohydric alcohol reacting with cyclic carbonates, or mixed with alcohols recovered in other processes and reused as an aliphatic monohydric alcohol reacting with cyclic carbonates. This method is one of the preferred embodiments of this invention. If the amount of recovered alcohols alone is insufficient, it is preferable to add new aliphatic monohydric alcohols.

[0179] Bottom composition of continuous multistage distillation column B1 (B B It is preferred to supply directly to the continuous multistage distillation column B2, or to the industrial-grade dialkyl carbonate tank, and then from the tank to the continuous multistage distillation column B2.

[0180] As a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate and aliphatic monohydric alcohol used in process (I). T There are no particular restrictions. For example, it can be a mixture obtained by simultaneously reacting and distilling cyclic carbonates and aliphatic monohydric alcohols in a continuous multistage distillation column in the presence of a catalyst, or it can be a commercially available dialkyl carbonate, or it can be a component separated from a distillation column in the dialkyl carbonate manufacturing process.

[0181] [Process (α)]

[0182] The method for manufacturing dialkyl carbonates in this embodiment preferably includes step (α), in which a cyclic carbonate is reacted with an aliphatic monohydric alcohol to obtain a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonates. T ).

[0183] Furthermore, step (α) is preferably the following step: cyclic carbonate and aliphatic monohydric alcohol are continuously fed into a continuous multi-stage distillation column A containing a catalyst, where the reaction and distillation are carried out simultaneously, and a low-purity dialkyl carbonate mixture (A) containing the generated dialkyl carbonate and unreacted aliphatic monohydric alcohol is collected. T It is continuously drawn from the top of the tower.

[0184] Furthermore, step (α) is more preferably performed by passing a high-boiling-point reaction mixture (A) containing diols. B The process of continuously producing dialkyl carbonates and diols by continuously drawing out the product from the bottom of the column using reactive distillation.

[0185] The following is a detailed explanation of process (α).

[0186] The reaction in step (α) is a reversible equilibrium transesterification reaction, represented by the following formula, from cyclic carbonate (A) and aliphatic monohydric alcohol (B) to produce dialkyl carbonate (C) and dihydric alcohol (D).

[0187]

[0188] (where R is in the formula) 1 This indicates a divalent group -(CH2)m- (m is an integer from 2 to 6), in which one or more hydrogen atoms can be replaced by alkyl or aryl groups with 1 to 10 carbon atoms. Additionally, R... 2 (This refers to a monovalent aliphatic group having 1 to 12 carbon atoms, where one or more hydrogen atoms can be replaced by an alkyl or aryl group having 1 to 10 carbon atoms.)

[0189] The cyclic carbonate used as a raw material in step (α) is a compound represented by (A) in the above formula, without particular restrictions. For example, alkyl carbonate esters such as ethylene carbonate and propylene carbonate are preferred; 1,3-dioxane-2-one, 1,3-dioxane-2-hepta-one, etc. From the perspective of ease of acquisition, ethylene carbonate and propylene carbonate are further preferred, and ethylene carbonate is particularly preferred.

[0190] Furthermore, the aliphatic monohydric alcohol used as another raw material is the compound represented by (B) in the above formula, and it is preferable to use an aliphatic monohydric alcohol with a boiling point lower than that of the dihydric alcohol produced. Therefore, specific examples of aliphatic monohydric alcohols can vary depending on the type of cyclic carbonate used, and for example: methanol, ethanol, propanol (various isomers), allyl alcohol, butanol (various isomers), 3-buten-1-ol, pentanol (various isomers), hexanol (various isomers), heptanol (various isomers), octanol (various isomers), nonanol (various isomers), decanol (various isomers), undecanool (various isomers), dodecanool (various isomers), cyclopentanol, cyclohexanol, cycloheptan ... Octanol, methylcyclopentanol (various isomers), ethylcyclopentanol (various isomers), methylcyclohexanol (various isomers), ethylcyclohexanol (various isomers), dimethylcyclohexanol (various isomers), diethylcyclohexanol (various isomers), phenylcyclohexanol (various isomers), benzyl alcohol, phenethyl alcohol (various isomers), phenylpropanol (various isomers), etc. In addition, these aliphatic monohydric alcohols can be substituted by halogens, lower alkoxy groups, cyano groups, alkoxycarbonyl groups, aryloxycarbonyl groups, acyloxy groups, nitro groups, etc.

[0191] Among such aliphatic monohydric alcohols, alcohols with 1 to 6 carbon atoms are preferred, and alcohols with 1 to 4 carbon atoms, such as methanol, ethanol, propanol (various isomers), and butanol (various isomers), are even more preferred. When ethylene carbonate or propylene carbonate is used as a cyclic carbonate, methanol or ethanol is preferred, and methanol is particularly preferred.

[0192] In step (α), the catalyst is present in the reactive distillation column A. The method for presenting the catalyst can be any method without particular limitation. For example, in the case of a homogeneous catalyst dissolved in the reaction liquid under reaction conditions, the catalyst can be present in the liquid phase within the reactive distillation column by continuously supplying the catalyst into the column. Alternatively, in the case of a heterogeneous catalyst that is not dissolved in the reaction liquid under reaction conditions, the catalyst can be present in the reaction system by placing a solid catalyst within the reactive distillation column. A combination of these methods is also possible.

[0193] When a homogeneous catalyst is continuously supplied to the reactive distillation column, it can be supplied simultaneously with cyclic carbonates and / or aliphatic monohydric alcohols, or it can be supplied to a location different from the feedstock. Since the actual reaction zone within the distillation column is the area downwards from the catalyst supply point, it is preferable to supply the catalyst to the region between the top of the column and the feedstock supply point. Furthermore, the number of catalyst layers is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more.

[0194] Furthermore, when using a heterogeneous solid catalyst, the number of catalyst layers is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more. Solid catalysts that also function as packing material in a distillation column can also be used.

[0195] As a catalyst used in process (α), a wide variety of catalysts known to date can be used. Specific examples of catalysts are not particularly limited, and examples include:

[0196] Alkali metals and alkaline earth metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, and barium;

[0197] Alkaline compounds such as hydrides, hydroxides, alkoxides, aromatic oxides, and amino compounds of alkali metals and alkaline earth metals;

[0198] Alkaline compounds such as carbonates, bicarbonates, and organic acid salts of alkali metals and alkaline earth metals;

[0199] Tertiary amines such as triethylamine, tributylamine, trihexylamine, and benzyldiethylamine;

[0200] N-alkylpyrrole, N-alkylindole azole, N-alkylimidazolium, N-alkylpyrazole Nitrogen-containing heterocyclic aromatic compounds such as diazoles, pyridines, alkylpyridines, quinolines, alkylquinolines, isoquinolines, alkylisoquinolines, acridines, alkylacridines, phenanthroline, alkylphenanthroline, pyrimidines, alkylpyrimidines, pyrazines, alkylpyrazines, triazines, and alkyltriazines;

[0201] Cyclic amidines such as diazabicycloundecene (DBU) and diazabicyclononene (DBN);

[0202] Thallium compounds, including thallium oxide, thallium halide, thallium hydroxide, thallium carbonate, thallium nitrate, thallium sulfate, and organic acid salts of thallium;

[0203] Tin compounds such as tributylmethoxytin, tributylethoxytin, dibutyldimethoxytin, diethyldiethoxytin, dibutyldiethoxytin, dibutylphenoxytin, diphenylmethoxytin, dibutyltin acetate, tributyltin chloride, and tin 2-ethylhexanoate;

[0204] Zinc compounds such as zinc dimethoxy, zinc diethoxy, zinc ethylenedioxy, and zinc dibutoxy.

[0205] Aluminum compounds such as trimethoxyaluminum, triisopropoxyaluminum, and tributoxyaluminum;

[0206] Titanium compounds such as tetramethoxytitanium, tetraethoxytitanium, tetrabutoxytitanium, dichlorodimethoxytitanium, tetraisopropoxytitanium, titanium acetate, and titanium acetylacetonate;

[0207] Trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tributylmethylhalogenated Trioctylbutylhalogenation Triphenylmethylhalogenated Phosphorus compounds;

[0208] Zirconium compounds such as zirconium halides, zirconium acetylacetonate, zirconium alkoxy, and zirconium acetate;

[0209] Lead and lead-containing compounds, such as lead oxides like PbO, PbO2, and Pb3O4;

[0210] Lead sulfides such as PbS, Pb2S3, and PbS2;

[0211] Lead hydroxides such as Pb(OH)2, Pb3O2(OH)2, Pb2[PbO2(OH)2], and Pb2O(OH)2;

[0212] Pimine salts such as Na2PbO2, K2PbO2, NaHPbO2, and KHPbO2;

[0213] Lead salts such as Na2PbO3, Na2H2PbO4, K2PbO3, K2[Pb(OH)6], K4PbO4, Ca2PbO4, and CaPbO3;

[0214] Lead carbonates and their basic salts, such as PbCO3 and 2PbCO3·Pb(OH)2;

[0215] Pb(OCH3)2, (CH3O)Pb(OPh), Pb(OPh)2 and other alkoxy lead and aryloxy lead compounds;

[0216] Lead salts and their carbonates or basic salts of organic acids such as Pb(OCOCH3)2, Pb(OCOCH3)4, and Pb(OCOCH3)2·PbO·3H2O;

[0217] Organolead compounds such as Bu4Pb, Ph4Pb, Bu3PbCl, Ph3PbBr, Ph3Pb (or Ph6Pb2), Bu3PbOH, PH2PbO, etc. (Bu represents butyl, Ph represents phenyl);

[0218] Lead alloys such as Pb-Na, Pb-Ca, Pb-Ba, Pb-Sn, and Pb-Sb;

[0219] Lead minerals such as galena, and hydrates of these lead compounds.

[0220] These compounds can be used as homogeneous catalysts when dissolved in reactants, reaction mixtures, or byproducts, and as solid catalysts when insoluble in reactants, reaction mixtures, or byproducts. Furthermore, using a mixture obtained by pre-dissolving these compounds in reactants, reaction mixtures, or byproducts, or by dissolving them through reaction, as a homogeneous catalyst is also a preferred method.

[0221] In addition, ion exchange resins such as anion exchange resins with tertiary amine groups, ion exchange resins with amide groups, ion exchange resins with at least one of the exchange groups of sulfonic acid groups, carboxylic acid groups, and phosphate groups, and solid strong basic anion exchange resins with quaternary ammonium groups as exchange groups are used as catalysts; and solid inorganic compounds such as silica, silica-alumina, silica-magnesium oxide, aluminosilicates, gallium silicate, various zeolites, various metal exchange zeolites, and ammonium exchange zeolites are used as catalysts.

[0222] As a solid catalyst, a solid strong basic anion exchanger having quaternary ammonium groups as exchange groups is particularly preferred. There are no particular limitations on such a solid strong basic anion exchanger; examples include: strong basic anion exchange resins having quaternary ammonium groups as exchange groups, cellulose strong basic anion exchangers having quaternary ammonium groups as exchange groups, and inorganic carrier-supported strong basic anion exchangers having quaternary ammonium groups as exchange groups. There are no particular limitations on the strong basic anion exchange resin having quaternary ammonium groups as exchange groups; styrene-based strong basic anion exchange resins are preferred. Styrene-based strong basic anion exchange resins are strong basic anion exchange resins with a copolymer of styrene and divinylbenzene as the matrix and having quaternary ammonium groups (type I or type II) as exchange groups, and are schematically represented, for example, by the following formula.

[0223]

[0224] In the above formula, X represents an anion, and typically, X is a ion selected from F. - Cl - ,Br - I - HCO3 - CO3 2- CH3CO2 - HCO2 - IO3 - BrO3 - ClO3 - At least one anion, preferably selected from Cl, is used. - ,Br - HCO3 - CO32- At least one anion is present in the resin matrix. Furthermore, the resin matrix can be either gel-type or macroporous (MR-type), with the MR-type being particularly preferred due to its high resistance to organic solvents.

[0225] There are no particular limitations on the type of cellulose strong basic anion exchanger having a quaternary ammonium group as an exchange group. For example, cellulose with an exchange group of -OCH2CH2NR3X can be obtained by trialkylaminoethylating some or all of the -OH groups of cellulose. Here, R represents an alkyl group, typically methyl, ethyl, propyl, butyl, etc., with methyl and ethyl being preferred. Additionally, X represents the anion as described above.

[0226] Inorganic carrier-supported strong basic anion exchangers with quaternary ammonium groups as exchange groups that can be used in process (α) refer to those that introduce quaternary ammonium groups -O(CH2) by modifying part or all of the surface hydroxyl groups -OH of the inorganic carrier. n The substance is NR3X. Wherein, R and X are as described above. n is typically an integer from 1 to 6, preferably n = 2. As an inorganic support, silica, alumina, silica-alumina, titanium dioxide, zeolite, etc., can be used, with silica, alumina, and silica-alumina being preferred, and silica being particularly preferred. Any method can be used to modify the surface hydroxyl groups of the inorganic support.

[0227] Commercially available solid strong-base anion exchangers with quaternary ammonium groups as exchange groups can also be used. In this case, they can also be used as transesterification catalysts after pretreatment with the desired anionic species through ion exchange.

[0228] Furthermore, it is preferable to use solid catalysts comprising macroporous and gel-type organic polymers bonded with heterocyclic groups containing at least one nitrogen atom, or inorganic supports bonded with heterocyclic groups containing at least one nitrogen atom, as transesterification catalysts. Alternatively, solid catalysts obtained by further quaternizing some or all of the nitrogen-containing heterocyclic groups of these substances can also be used. It should be noted that solid catalysts such as ion exchangers can also function as packing materials in this embodiment.

[0229] The amount of catalyst used in step (α) varies depending on the type of catalyst used. When a homogeneous catalyst dissolved in the reaction solution under reaction conditions is continuously supplied, it is expressed as a ratio to the total mass of the cyclic carbonate and aliphatic monohydric alcohol supplied as raw materials, preferably in an amount of 0.0001% to 50% by mass, more preferably 0.005% to 20% by mass, and even more preferably 0.01% to 10% by mass. Furthermore, when a solid catalyst is used in the distillation column, a catalyst amount of preferably 0.01% to 75% by volume, more preferably 0.05% to 60% by volume, and even more preferably 0.1% to 60% by volume, is preferred relative to the empty volume of the distillation column.

[0230] In step (α), when cyclic carbonates are continuously supplied to a continuous multistage distillation column A, which serves as a reactive distillation column, it is preferable to supply the cyclic carbonates to a specific layer. That is, it is preferable to continuously introduce the cyclic carbonates, which are used as raw materials, into the continuous multistage distillation column from one or more inlets located between the third layer from the top and the (n / 3)th layer from the top. It is important that the layers above the cyclic carbonate inlets are free of high-boiling-point compounds such as cyclic carbonates and diols in the top composition. In this sense, the layers above the cyclic carbonate inlets are preferably three or more, more preferably four to ten, and even more preferably five to eight.

[0231] The preferred cyclic carbonate used in step (α) is, for example, a halogen-free cyclic carbonate produced by reacting alkyl oxidants such as ethylene oxide, propylene oxide, and styrene oxide with carbon dioxide. Therefore, cyclic carbonates containing small amounts of these raw material compounds, diols, etc., can also be used as raw materials for step (α).

[0232] In step (α), the supplied raw materials may contain dialkyl carbonates and / or diols as products. Expressed as a mass percentage of dialkyl carbonate in the aliphatic monohydric alcohol / dialkyl carbonate mixture, the content of dialkyl carbonate is preferably 0% to 40% by mass, more preferably 0% to 30% by mass, and even more preferably 0% to 20% by mass. Expressed as a mass percentage of diols in the cyclic carbonate / diol mixture, the content of diols is preferably 0% to 10% by mass, more preferably 0% to 7% by mass, and even more preferably 0% to 5% by mass.

[0233] In the industrial implementation of the reaction in step (α), it is preferable to use, in addition to using the cyclic carbonates and / or aliphatic monohydric alcohols newly introduced into the reaction system, substances recovered in steps (I), (II), and / or other steps that are mainly composed of cyclic carbonates and / or aliphatic monohydric alcohols as their raw materials. For example, the top component (B) separated and purified in step (I) T ) is usually a mixture of aliphatic monohydric alcohols and dialkyl carbonates, therefore it is preferable to use this top component (B) T The method for manufacturing dialkyl carbonate in this embodiment can achieve the above-described operation by reusing it as part of the raw materials in step (α). This is one of the preferred methods for manufacturing dialkyl carbonate in this embodiment. Other steps include, for example, a step of manufacturing diaryl carbonate from dialkyl carbonate and aromatic monohydroxy compounds, in which an aliphatic monohydric alcohol is generated as a byproduct and recovered. The recovered aliphatic monohydric alcohol generated as a byproduct usually contains dialkyl carbonate. In addition, the recovered aliphatic monohydric alcohol generated as a byproduct sometimes contains aromatic monohydroxy compounds, alkylaryl ethers, small amounts of alkyl carbonate aryl esters, diaryl carbonates, etc. In this embodiment, the aliphatic monohydric alcohol generated as a byproduct can be used directly as a raw material, or it can be used as a raw material after reducing the amount of substances with a boiling point higher than the aliphatic monohydric alcohol by distillation or the like.

[0234] In step (α), when aliphatic monohydric alcohols are continuously supplied to a continuous multistage distillation column A, which serves as a reactive distillation column, it is preferable to supply the aliphatic monohydric alcohols to a specific layer. For example, it is preferable to continuously introduce the aliphatic monohydric alcohols used as raw materials into the continuous multistage distillation column A from the (n / 3)th layer from the top to the (2n / 3)th layer from the top. If the aliphatic monohydric alcohols used as raw materials in step (α) contain a specific amount of dialkyl carbonate, it is preferable to set their inlet at the aforementioned specific layer. More preferably, it is preferable to continuously introduce the aliphatic monohydric alcohols into the continuous multistage distillation column from the (2n / 5)th layer from the top to the (3n / 5)th layer from the top.

[0235] The feedstock is continuously supplied to the distillation column in liquid, gaseous, or liquid-gas mixture form. In addition to supplying the feedstock to the distillation column in this manner, it is also preferred to intermittently or continuously supply gaseous feedstock from the central and / or lower part of the distillation column. Furthermore, it is also preferred to continuously supply cyclic carbonates in liquid or gas-liquid mixtures to the distillation column in a layer above the layer containing the catalyst, and to continuously supply aliphatic monohydric alcohols in gaseous and / or liquid form from one or more inlets provided in the aforementioned layers of the distillation column. Moreover, it is preferable that these feedstocks contact the catalyst in a region of the distillation column, preferably 5 or more layers, more preferably 7 or more layers, and even more preferably 10 or more layers.

[0236] In step (α), the ratio of cyclic carbonate to aliphatic monohydric alcohol supplied to the reactive distillation column varies depending on the type or amount of transesterification catalyst and the reaction conditions. Preferably, the aliphatic monohydric alcohol is supplied in a molar ratio of 0.01 to 1000 times the cyclic carbonate. To improve the reaction rate of the cyclic carbonate, it is preferable to supply an excess of aliphatic monohydric alcohol of 2 moles or more; however, if an excessive amount of aliphatic monohydric alcohol is used, the equipment needs to be enlarged. In this sense, the molar ratio of aliphatic monohydric alcohol to cyclic carbonate is preferably 2 to 20, more preferably 3 to 15, and even more preferably 5 to 12. It should be noted that when a large amount of unreacted cyclic carbonate remains, it reacts with the diol as a product to generate polymers such as dimers and trimers as byproducts. Therefore, in industrial applications, it is preferable to minimize the amount of unreacted cyclic carbonate remaining.

[0237] In the method for manufacturing dialkyl carbonate of this embodiment, it is preferable to continuously produce (step (α)) and separate and purify (steps (I) and (II)) more than 2 tons of dialkyl carbonate per hour. For this purpose, the minimum amount of cyclic carbonate continuously supplied is preferably 2.2 P tons / hour, more preferably 2.1 P tons / hour, and even more preferably 2.0 P tons / hour, relative to the amount of dialkyl carbonate to be produced (P tons / hour). In addition, in a further preferred case, it is possible to produce less than 1.9 P tons / hour.

[0238] The continuous multistage distillation column A in process (α) is not merely a condition for simple distillation function, but a continuous multistage distillation column that combines the conditions for simple distillation function with the conditions required to stably carry out the reaction with high reaction rate and high selectivity. Specifically, it is preferred to be a continuous multistage distillation column that satisfies the following conditions.

[0239] The continuous multi-stage distillation column is a cylindrical column body with a length L0 (cm) and inner diameter D0 (cm) satisfying the following formulas (1) to (6), and an internal plate column with n layers of perforated plates, wherein the upper part of the column at or near the top of the column has an inner diameter d. 01 A gas extraction port (cm) has an inner diameter d at the bottom of the tower or near the bottom of the tower. 02 The liquid outlet (cm) has one or more first inlets at the lower part of the gas outlet and at the upper and / or middle part of the tower, and one or more second inlets at the upper part of the liquid outlet and at the middle and / or lower part of the tower.

[0240] 2100≤L0≤8000 Equation (1)

[0241] 180≤D0≤2000 Equation (2)

[0242] 4≤L0 / D0≤40 Equation (3)

[0243] 20≤n0≤120 Equation (4)

[0244] 3≤D0 / d 01 ≤20 Equation (5)

[0245] 5≤D0 / d 02 ≤30 Equation (6)

[0246] It should be noted that, in this embodiment, the term "top of the tower or upper part of the tower near the top of the tower" refers to the portion extending downwards from the top of the tower by approximately 0.25L0, and the term "bottom of the tower or lower part of the tower near the bottom of the tower" refers to the portion extending upwards from the bottom of the tower by approximately 0.25L0. Furthermore, "L0" is as defined above.

[0247] Using a continuous multistage distillation column that simultaneously satisfies equations (1), (2), (3), (4), (5), and (6), it is possible to produce dialkyl carbonates and / or diols from cyclic carbonates and aliphatic monohydric alcohols at an industrial scale of preferably 2 tons per hour or more with high reaction rate, high selectivity, and high productivity, for example, more than 1,000 hours, preferably more than 3,000 hours, and even more preferably more than 5,000 hours, for a long time and with greater stability.

[0248] When L0 (cm) is 2100 or higher, the reaction rate increases, thus enabling the aforementioned production volume. Furthermore, to reduce equipment costs while ensuring the reaction rate can achieve the aforementioned production volume, L0 is preferably 8000 or lower. A more preferred range for L0 (cm) is 2300 ≤ L0 ≤ 6000, and even more preferably 2500 ≤ L0 ≤ 5000.

[0249] The aforementioned production volume can be achieved when D0 (cm) is 180 or higher. Furthermore, in order to reduce equipment costs while achieving the target production volume, D0 is preferably 2000 or lower. A more preferred range for D0 (cm) is 200 ≤ D0 ≤ 1000, and even more preferably 210 ≤ D0 ≤ 800.

[0250] When L0 / D0 is 4 or higher and 40 or lower, stable operation becomes easier. In particular, when L0 / D0 is 40 or lower, it is possible to suppress the increase of the pressure difference between the top and bottom of the column. Therefore, not only is long-term stable operation easier, but the temperature at the bottom of the column can also be maintained without increasing it. Thus, it tends to suppress side reactions and improve selectivity. A more preferred range for L0 / D0 is 5 ≤ ​​L0 / D0 ≤ 30, and even more preferably 7 ≤ L0 / D0 ≤ 20.

[0251] When n0 is 10 or higher, the reaction rate increases, thus enabling the aforementioned production volume. Furthermore, to reduce equipment costs while ensuring a reaction rate that achieves the target production volume, n0 is preferably 120 or lower. Additionally, when n0 is 120 or lower, it is possible to suppress an increase in the pressure difference between the top and bottom of the column, thus facilitating long-term stable operation and avoiding raising the temperature at the bottom of the column, thereby tending to suppress side reactions and improve selectivity. A more preferred range for n0 is 30 ≤ n0 ≤ 100, and even more preferably 40 ≤ n0 ≤ 90.

[0252] When D0 / d 01 When the value is above 3, not only do equipment costs become cheaper, but the amount of gas components escaping outside the system can also be suppressed, thus making stable operation easier. 01 When the value is below 20, the extraction rate of gas components becomes relatively larger, which not only makes stable operation easier but also tends to increase the reaction rate. A more preferred D0 / d 01 The range is 4≤D0 / d 01 ≤15, further preferably 5≤D0 / d 01 ≤13.

[0253] When D0 / d 02 When the value is above 5, not only do equipment costs become cheaper, but the liquid extraction volume also decreases relatively, making stable operation easier. 02 When the value is below 30, it can suppress the rapid increase in flow velocity at the liquid extraction outlet or in the pipeline, making it less prone to erosion and thus inhibiting corrosion of the device. A more preferred D0 / d 02 The range is 7≤D0 / d 02 ≤25, further preferably 9≤D0 / d 02 ≤20.

[0254] Furthermore, in this embodiment, it is known that d 01 With the d02 The case that satisfies equation (7) is a further preferred option.

[0255] 1≤d 01 / d 02 ≤5 Equation (7)

[0256] In this embodiment, long-term stable operation means that for more than 1,000 hours, preferably more than 3,000 hours, and even more preferably more than 5,000 hours, there is no overflow or leakage, or blockage or corrosion of the pipeline. It can operate continuously in a stable state based on the operating conditions, and produce a specified amount of dialkyl carbonate and diols while maintaining high reaction rate, high selectivity and high productivity.

[0257] In step (α), there is a preference for consistently producing dialkyl carbonates and / or diols at a high productivity of 2 tons per hour or more with high selectivity over a long period. More preferably, dialkyl carbonates and diols are produced at 3 tons per hour or more and 1.95 tons per hour or more, respectively; even more preferably, at 4 tons per hour or more and 2.6 tons per hour or more, respectively. Furthermore, in step (α), the parameters L0, D0, L0 / D0, n0, and D0 / d in this continuous multi-stage distillation column are... 01 、D0 / d 02 The corresponding values ​​are 2300≤L0≤6000, 200≤D0≤1000, 5≤L0 / D0≤30, 30≤n0≤100, and 4≤D0 / d. 01 ≤15、7≤D0 / d 02 When the concentration is ≤25, there is a tendency to produce dialkyl carbonates at a rate of 2.5 tons per hour or more, preferably 3 tons per hour or more, and even more preferably 3.5 tons per hour or more, and diols at a rate of 1.6 tons per hour or more, preferably 1.95 tons per hour or more, and even more preferably 2.2 tons per hour or more. Furthermore, in process (α), the values ​​of L0, D0, L0 / D0, n0, and D0 / d in this continuous multi-stage distillation column are... 01 、D0 / d 02 The corresponding values ​​are 2500≤L0≤5000, 210≤D0≤800, 7≤L0 / D0≤20, 40≤n0≤90, and 5≤D0 / d. 01 ≤13、9≤D0 / d 02 In the case of ≤20, there is a tendency to be able to produce more than 3 tons per hour, preferably more than 3.5 tons per hour, and more preferably more than 4 tons per hour of dialkyl carbonates and more than 1.95 tons per hour, preferably more than 2.2 tons per hour, and more preferably more than 2.6 tons per hour of diols.

[0258] In this embodiment, the selectivity of dialkyl carbonates and diols refers to the selectivity of the reacted cyclic carbonates. In this embodiment, a high selectivity of 95% or more is preferred, a high selectivity of 97% or more is more preferred, and a high selectivity of 99% or more is even more preferred. Furthermore, the reaction rate mentioned in this embodiment generally refers to the reaction rate of the cyclic carbonates. In this embodiment, the reaction rate of the cyclic carbonates is preferably 95% or more, more preferably 97% or more, even more preferably 99% or more, even more preferably 99.5% or more, and even more preferably 99.9% or more.

[0259] The continuous multistage distillation column A used in step (α) is preferably a plate-type distillation column with trays as internal components. In this embodiment, the internal components refer to the parts in the distillation column where gas-liquid contact actually occurs. There are no particular limitations on such trays; examples include: bubble cap trays, perforated trays, corrugated trays, heavy-disc floating valve trays, floating valve trays, counter-current trays, S-shaped trays, Superfrac trays, Maxfrac trays, dual-flow trays, grid trays, cross-flow grid trays, Kittel trays, etc. It should be noted that in step (α), a multistage distillation column that simultaneously has a portion of the tray section filled with packing and the tray section itself can also be used. There are no particular limitations on such packing materials; examples include: Raschig rings, Lessin rings, Pall rings, Bell saddle rings, rectangular saddle rings, Dixon packing, McMahon packing, Helipak, and other random packing materials; and Mellapak, Gempak, Techno-pack, Flexipac, Sulzer packing, Goodroll packing, Glitschgrid, and other structured packing materials. It should be noted that the term "number of layers n (n0, n1, n2, etc.) of internal components" used in this embodiment refers to the number of trays in the case of trays, and the theoretical number of layers in the case of packing materials. Therefore, in the case of a multi-stage distillation column having both a tray section and a packing-filled section, the number of layers n is the sum of the number of trays and the theoretical number of layers.

[0260] In the reaction of cyclic carbonates with aliphatic monohydric alcohols in step (α), any of the following can be used: a plate-type continuous multistage distillation column with internal components comprising trays having a predetermined number of layers and / or a packed column-type continuous multistage distillation column; more preferably, a plate-type distillation column with trays as internal components. Furthermore, porous plate trays with perforated plate sections and downcomer sections are particularly advantageous in terms of functionality versus equipment cost. Moreover, it is preferable that the porous plate tray has a permeable layer of trays per 1m³. 2 The porous plate has 100 to 1000 holes per square meter of surface area. More preferably, each meter contains... 2The number of holes in this perforated plate is between 120 and 900, more preferably between 150 and 800. Furthermore, the cross-sectional area of ​​each hole in this perforated plate is preferably 0.5 cm². 2 ~5cm 2 More preferably, the cross-sectional area of ​​each hole is 0.7 cm². 2 ~4cm 2 Further preferred size is 0.9cm 2 ~3cm 2 Furthermore, this perforated tray is particularly preferred for every 1m... 2 The porous plate has 100 to 1000 holes in its surface area, and each hole has a cross-sectional area of ​​0.5 cm². 2 ~5cm 2 The number of holes in the porous plate can be the same or different in all porous plates.

[0261] In this embodiment, the aperture ratio of the perforated trays in the continuous multistage distillation column A refers to the ratio of the total area (total cross-sectional area of ​​the openings) of each tray in the continuous multistage distillation column A through which gas and liquid can pass to the area of ​​the tray having those openings. It should be noted that, for trays with downcomers, the area of ​​the portion that substantially foams, excluding that portion, is used as the tray area.

[0262] The aperture ratio of the perforated trays in the continuous multi-stage distillation column A is preferably in the range of 1.5% to 15%. When the aperture ratio is 1.5% or higher, the equipment can be scaled down relative to the required production volume, resulting in lower equipment costs and shorter residence times, which helps suppress side reactions (e.g., the reaction between diols as reaction products and unreacted cyclic carbonates). Furthermore, when the aperture ratio is 15% or lower, the residence time in each tray is longer, thus reducing the number of trays required to achieve high reaction rates, and no adverse effects occur even when increasing n0. In this sense, a preferred aperture ratio range is 1.7% to 8.0%, and more preferably in the range of 1.9% to 6.0%.

[0263] It should be noted that the opening ratios of all trays in the continuous multi-stage distillation column A can be the same or different. In this embodiment, it is generally preferred to use a multi-stage distillation column where the opening ratio of the upper trays is greater than that of the lower trays.

[0264] In step (α), cyclic carbonates and aliphatic monohydric alcohols, as raw materials, are continuously fed into a continuous multi-stage distillation column A containing a catalyst. In this column, reaction and distillation occur simultaneously, resulting in a low-purity dialkyl carbonate mixture (A) containing the generated dialkyl carbonate. T The high-boiling-point reaction mixture (A) containing diols is continuously drawn out from the top of the column (preferably in gaseous state).B It is continuously drawn from the bottom of the column (preferably in liquid form), thereby continuously producing dialkyl carbonates and diols.

[0265] The reaction time of the transesterification reaction in step (α) is considered to be equivalent to the average residence time of the reaction liquid in the continuous multi-stage distillation column A. The residence time varies depending on the shape or number of layers of the internal components of the distillation column A, the amount of raw material supplied, the type or amount of catalyst, the reaction conditions, etc., and is preferably 0.1 hours to 20 hours, more preferably 0.5 hours to 15 hours, and even more preferably 1 hour to 10 hours.

[0266] The reaction temperature varies depending on the type of raw material compound used and the type or amount of catalyst, and is preferably between 30°C and 300°C. Increasing the reaction temperature is preferable to improve the reaction rate, but high reaction temperatures can also easily lead to side reactions. A preferred reaction temperature is in the range of 40°C to 250°C, more preferably in the range of 50°C to 200°C, and even more preferably in the range of 60°C to 150°C. In this embodiment, the bottom temperature is preferably set below 150°C, more preferably below 130°C, even more preferably below 110°C, and even more preferably below 100°C for reactive distillation. Furthermore, the reaction pressure varies depending on the type or composition of the raw material compound used, the reaction temperature, etc., and can be any of reduced pressure, atmospheric pressure, or pressurized pressure, preferably between 1 Pa and 2 × 10⁻⁶ Pa. 7 Within the range of Pa, more preferably within 10 Pa. 3 Pa~10 7 Within the range of Pa, and more preferably within 10 Pa. 4 Pa ~ 5 × 10 6 It is carried out within the range of Pa.

[0267] Example

[0268] The present invention will now be described in more detail using examples and comparative examples. The present invention is not limited to the following examples.

[0269] [Purity of dialkyl carbonate]

[0270] The purity of dialkyl carbonates was determined by gas chromatography. The analysis using gas chromatography was performed according to GB / T33107-2016.

[0271] [Content of 2-methoxyethanol and high-boiling-point compounds]

[0272] The contents of 2-methoxyethanol and high-boiling-point compounds were determined by gas chromatography. The analysis using gas chromatography was performed according to GB / T 33107-2016.

[0273] [Methanol and ethanol content]

[0274] The contents of methanol and ethanol were determined by gas chromatography. The analysis using gas chromatography was performed in accordance with GB / T33107-2016.

[0275] [Water content]

[0276] Water content was determined by coulometric titration. The analysis using coulometric titration was performed according to JIS K2275-3.

[0277] [Metal content]

[0278] The content of metal components was determined by ICP method. The analysis using ICP method was performed according to JIS G 1258.

[0279] [Example 1]

[0280] Process (α)

[0281] <Continuous Multistage Distillation Column A>

[0282] A plate-type distillation column with trays as internal components is used as a continuous multi-stage distillation column A.

[0283] Reactive distillation

[0284] Liquid ethylene carbonate (99.95% by mass) is continuously introduced into distillation column A at a rate of 3.04 tons / hour from the inlet located at the 55th layer from the bottom. Gaseous methanol (containing 8.95% by mass dimethyl carbonate) and liquid methanol (containing 6.66% by mass dimethyl carbonate) are continuously introduced into the distillation column at a rate of 9.8 tons / hour from the inlet located at the 31st layer from the bottom. The molar ratio of the feedstock introduced into the distillation column is methanol / ethylene carbonate = 12.7.

[0285] The catalyst was prepared using a solution of 4.8 tons of ethylene glycol in 2.5 tons of KOH (48% by mass aqueous solution), heated to approximately 130°C, slowly depressurized, and heated at approximately 1300 Pa for approximately 3 hours to obtain a homogeneous solution. This catalyst solution was continuously introduced into the distillation column through an inlet located at the 54th layer from the bottom (K concentration: 0.1% by mass relative to the supplied ethylene carbonate). The temperature at the bottom of the column was 98°C, and the pressure at the top was approximately 1.118 × 10⁻⁶. 5 Reactive distillation was carried out continuously under the conditions of Pa and reflux ratio of 0.42.

[0286] A mixture of low-purity dimethyl carbonate (A) is continuously drawn from the top of the tower at a rate of 14.2 tons per hour. TThe concentrations of dimethyl carbonate, methanol, 2-methoxyethanol (hereinafter also referred to as "2ME"), and carbon dioxide in the column are 4.13 tons / hour, 10.08 tons / hour, 3.1 kg / hour, and 2.1 kg / hour (total: 14.2 tons / hour). The concentration of dimethyl carbonate is approximately 29% by mass. The liquid continuously drawn from the bottom of the column at a rate of 2.8 tons / hour contains 2.2 tons / hour of ethylene glycol, 0.6 tons / hour of methanol, and 5 kg / hour of unreacted ethylene carbonate.

[0287] Process (I)

[0288] <Continuous Multistage Distillation Column B1>

[0289] As a continuous multistage distillation column B1, it is made of carbon steel, and perforated trays are used as internal components in both the recovery and concentration sections. The contact surface area between the liquid phase and the carbon steel within the continuous multistage distillation column B1 is 2.8 × 10⁻⁶. -3 m 2 It is carried out under the condition of minutes / (kg / hour).

[0290] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0291] A mixture of low-purity dimethyl carbonate (A) containing 4.13 tons / hour of dimethyl carbonate, 10.08 tons / hour of methanol, 3.1 kg / hour of 2-methoxyethanol (hereinafter also referred to as "2ME"), and 2.1 kg / hour of carbon dioxide (total: 14.2 tons / hour, dimethyl carbonate concentration: approximately 29% by mass) T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 207°C, a bottom pressure of about 1.46 MPa, and a reflux ratio of 3.0.

[0292] The top component (B) continuously extracted from the top of the continuous multi-stage distillation column B1 at a rate of 10.59 tons / hour T It contains 10.07 tons / hour of methanol, 0.52 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) T The methanol concentration in the product was 95.1% by mass.

[0293] In addition, the bottom component (B) continuously extracted from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.62 tons / hour B It contains 3.61 tons / hour of dimethyl carbonate, 7.2 kg / hour of methanol, 0.14 kg / hour of 2ME, and 3.6 kg / hour of high-boiling-point compounds. The purity of dimethyl carbonate is 99.8% by mass.

[0294] It should be noted that, in the embodiments, compounds having a boiling point more than 100°C higher than that of dimethyl carbonate at a pressure of 760 mmHg are considered as high-boiling-point compounds.

[0295] Additionally, at the bottom of the tower, the component (B) B In the sample, the content of 2-methoxyethanol was 39 ppm by mass, and the content of high-boiling-point compounds was 841 ppm by mass.

[0296] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0297] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0298] Process (II)

[0299] <Continuous Multistage Distillation Column B2>

[0300] A continuous multistage distillation column made of stainless steel and featuring a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0301] <Bottom of the tower (B) B Distillation separation

[0302] The bottoms component (B) obtained in process (I) will contain 3.61 tons / hour of dimethyl carbonate, 7.2 kg / hour of methanol, 0.14 kg / hour of 2ME, and 3.6 kg / hour of high-boiling compounds (total: 3.62 tons / hour, dimethyl carbonate purity: approximately 99.8% by mass). B The feed is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 2.0.

[0303] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 176 kg / hour t It contains 169 kg / h of dimethyl carbonate and 7.1 kg / h of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 23.6 kg / h. bIt contains 20.0 kg / hour of dimethyl carbonate, 0.1 kg / hour of 2ME, and 3.5 kg / hour of high-boiling-point compounds.

[0304] In addition, the side fraction (B) continuously extracted in gaseous state at a rate of 3.42 tons / hour from the side outlet of the continuous multi-stage distillation column B2 s It contains 3.42 tons / hour of dimethyl carbonate, 0.06 kg / hour of methanol, 0.04 kg / hour of 2ME, 0.00034 kg / hour of high-boiling-point compounds, 0.00013 kg / hour of iron, and 0.012 kg / hour of water. The purity of dimethyl carbonate is 99.991% by mass.

[0305] Furthermore, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 247 kW / t. As can be seen from the above, in Example 1, dimethyl carbonate with a purity of over 99.99% by mass can be produced with minimal heat consumption, i.e., a small reflux ratio.

[0306] Additionally, in the side fraction (B) s In the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0307] [Example 2]

[0308] Process (I)

[0309] <Continuous Multistage Distillation Column B1>

[0310] As a continuous multi-stage distillation column B1, S-shaped trays are used as internal components in both the recovery section and the concentration section.

[0311] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0312] A mixture of low-purity dimethyl carbonate (A) containing 3.86 tons / hour of dimethyl carbonate, 4.16 tons / hour of methanol, 1.76 kg / hour of 2ME, and 2.1 kg / hour of carbon dioxide (total: 8.02 tons / hour, dimethyl carbonate concentration: approximately 48% by mass) T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 207°C, a bottom pressure of about 1.46 MPa, and a reflux ratio of 2.0.

[0313] The top component (B1) continuously extracted from the top of the continuous multi-stage distillation column B1 at a rate of 4.38 tons per hour TIt contains 4.14 tons / hour of methanol, 0.24 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) T The methanol concentration in the sample was 94.5% by mass.

[0314] In addition, the bottom component (B2) continuously extracted from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.64 tons / hour B It contains 3.62 tons / hour of dimethyl carbonate, 24.0 kg / hour of methanol, and 2.06 kg / hour of high-boiling-point compounds. The purity of dimethyl carbonate is 99.3% by mass.

[0315] Additionally, at the bottom of the tower, the component (B) B In this mixture, the content of 2-methoxyethanol is 0 ppm by mass, and the content of high-boiling-point compounds is 566 ppm by mass.

[0316] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0317] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0318] Process (II)

[0319] <Continuous Multistage Distillation Column B2>

[0320] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0321] <Bottom of the tower (B) B Distillation separation

[0322] The bottoms component (B) obtained in process (I) will contain 3.62 tons / hour of dimethyl carbonate, 24.0 kg / hour of methanol, and 2.06 kg / hour of high-boiling compounds (total: 3.64 tons / hour, dimethyl carbonate purity: approximately 99.3% by mass). B The feed is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 2.0.

[0323] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 148 kg / hour t The distillation process includes 124 kg / hour of dimethyl carbonate and 23.9 kg / hour of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 24.5 kg / hour. b It contains 21.6 kg / hour of dimethyl carbonate and 2.06 kg / hour of high-boiling-point compounds.

[0324] Additionally, the side fraction (B) continuously extracted in gaseous form at a rate of 3.47 tons / hour from the side outlet of the continuous multi-stage distillation column B2 s It contains 3.47 tons / hour of dimethyl carbonate and 0.07 kg / hour of methanol. The purity of the dimethyl carbonate is 99.998% by mass.

[0325] Furthermore, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 240 kW / t. Therefore, in Example 2, dimethyl carbonate with a purity of over 99.99% by mass can be produced with minimal heat consumption (small reflux ratio).

[0326] Additionally, in the side fraction (B) s In the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0327] [Example 3]

[0328] Process (I)

[0329] <Continuous Multistage Distillation Column B1>

[0330] As a continuous multi-stage distillation column B1, porous trays are used as internal components in both the recovery section and the concentration section.

[0331] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0332] A mixture of low-purity dimethyl carbonate (A) containing 3.86 tons / hour of dimethyl carbonate, 0.48 tons / hour of methanol, 0.91 kg / hour of 2ME, and 2.1 kg / hour of carbon dioxide (total: 4.35 tons / hour, dimethyl carbonate concentration: approximately 89% by mass) T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 207°C, a bottom pressure of about 1.46 MPa, and a reflux ratio of 2.0.

[0333] The top component (B) continuously drawn from the top of the continuous multi-stage distillation column B1 at a rate of 0.56 tons / hour T It contains 0.46 tons / hour of methanol, 0.10 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) T The methanol concentration in the sample was 82.1% by mass.

[0334] In addition, the bottom component (B2) continuously extracted from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.78 tons / hour B It contains 3.76 tons / hour of dimethyl carbonate, 16.5 kg / hour of methanol, and 1.07 kg / hour of high-boiling-point compounds. The purity of dimethyl carbonate is 99.6% by mass.

[0335] Additionally, at the bottom of the tower, the component (B) B In this compound, the content of 2-methoxyethanol is 0 ppm by mass, and the content of high-boiling-point compounds is 283 ppm by mass.

[0336] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0337] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0338] Process (II)

[0339] <Continuous Multistage Distillation Column B2>

[0340] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0341] <Bottom of the tower (B) B Distillation separation

[0342] The bottoms component (B) obtained in process (I) will contain 3.76 tons / hour of dimethyl carbonate, 16.5 kg / hour of methanol, and 1.07 kg / hour of high-boiling compounds (total: 3.78 tons / hour, dimethyl carbonate purity: approximately 99.6% by mass). B The feed is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 2.0.

[0343] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 174 kg / hour t It contains 158 kg / h of dimethyl carbonate and 16.4 kg / h of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 24.9 kg / h. b It contains 23.8 kg / hour of dimethyl carbonate and 1.07 kg / hour of high-boiling-point compounds.

[0344] Additionally, the side fraction (B) continuously extracted in gaseous form at a rate of 3.58 tons / hour from the side outlet of the continuous multistage distillation column B2. s It contains 3.58 tons / hour of dimethyl carbonate and 0.06 kg / hour of methanol. The purity of the dimethyl carbonate is 99.998% by mass.

[0345] Furthermore, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 244 kW / t. Therefore, in Example 3, dimethyl carbonate with a purity of over 99.99% by mass can be produced with minimal heat consumption (small reflux ratio).

[0346] Additionally, in the side fraction (B) s In the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0347] [Example 4]

[0348] Process (I)

[0349] <Continuous Multistage Distillation Column B1>

[0350] As a continuous multi-stage distillation column, B1 is made of carbon steel, and perforated trays are used as internal components in both the recovery section and the concentration section.

[0351] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0352] A mixture of low-purity dimethyl carbonate (A) containing 4.13 tons / hour of dimethyl carbonate, 10.08 tons / hour of methanol, and 2.1 kg / hour of carbon dioxide (total: 14.2 tons / hour, dimethyl carbonate concentration: approximately 29% by mass) T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 207°C, a bottom pressure of about 1.46 MPa, and a reflux ratio of 3.0.

[0353] The top component (B) continuously extracted from the top of the continuous multi-stage distillation column B1 at a rate of 10.59 tons / hour T It contains 10.07 tons / hour of methanol, 0.52 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) T The methanol concentration in the product was 95.1% by mass.

[0354] In addition, the bottom component (B) continuously extracted from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.62 tons / hour B It contains 3.61 tons / hour of dimethyl carbonate, 7.2 kg / hour of methanol, and 1.8 kg / hour of high-boiling-point compounds. The purity of dimethyl carbonate is 99.8% by mass.

[0355] It should be noted that, in the embodiments, compounds having a boiling point more than 100°C higher than that of dimethyl carbonate at a pressure of 760 mmHg are considered as high-boiling-point compounds.

[0356] Additionally, at the bottom of the tower, the component (B) B In this compound, the content of 2-methoxyethanol is 0 ppm by mass, and the content of high-boiling-point compounds is 499 ppm by mass.

[0357] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0358] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0359] Process (II)

[0360] <Continuous Multistage Distillation Column B2>

[0361] A continuous multistage distillation column made of stainless steel and featuring a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0362] <Bottom of the tower (B) B Distillation separation

[0363] The bottoms component (B) obtained in process (I) will contain 3.61 tons / hour of dimethyl carbonate, 7.2 kg / hour of methanol, and 1.8 kg / hour of high-boiling compounds (total: 3.62 tons / hour, dimethyl carbonate purity: approximately 99.8% by mass). B It is continuously supplied from the inlet to the continuous multi-stage distillation column B2.

[0364] The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of approximately 92°C, a bottom pressure of approximately 3 kPa, and a reflux ratio of 2.0.

[0365] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 182 kg / h t It contains 169 kg / h of dimethyl carbonate and 7.1 kg / h of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 23.6 kg / h. b It contains 20.0 kg / hour of dimethyl carbonate and 1.8 kg / hour of high-boiling-point compounds.

[0366] In addition, the side fraction (B) continuously extracted in gaseous state at a rate of 3.42 tons / hour from the side outlet of the continuous multi-stage distillation column B2 s It contains 3.42 tons / hour of dimethyl carbonate and 0.1 kg / hour of methanol. The purity of the dimethyl carbonate is 99.997% by mass.

[0367] Furthermore, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 247 kW / t. Therefore, in Example 4, dimethyl carbonate with a purity of over 99.99% by mass can be produced with minimal heat consumption (small reflux ratio).

[0368] Additionally, in the side fraction (B) s In the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0369] [Example 5]

[0370] Process (I)

[0371] <Continuous Multistage Distillation Column B1>

[0372] As a continuous multi-stage distillation column B1, stainless steel is used as the material. In addition, perforated trays are used as internal components in both the recovery section and the concentration section. Furthermore, ferrous oxide (II) powder is mixed with the feed liquid and fed into the distillation column at a rate of 0.83 kg / hour.

[0373] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0374] A mixture of low-purity dimethyl carbonate (A) containing 3.86 tons / hour of dimethyl carbonate, 4.16 tons / hour of methanol, 1.76 kg / hour of 2-methoxyethanol (hereinafter also referred to as "2ME"), and 2.1 kg / hour of carbon dioxide (total: 8.02 tons / hour, dimethyl carbonate concentration: approximately 48% by mass) T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 207°C, a bottom pressure of about 1.46 MPa, and a reflux ratio of 2.0.

[0375] The top component (B1) continuously extracted from the top of the continuous multi-stage distillation column B1 at a rate of 4.38 tons per hour T It contains 4.14 tons / hour of methanol, 0.24 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) T The methanol concentration in the sample was 94.5% by mass.

[0376] In addition, the bottom component (B2) continuously extracted from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.64 tons / hour B It contains 3.62 tons / hour of dimethyl carbonate, 24.0 kg / hour of methanol, 2.1 kg / hour of high-boiling-point compounds, and 0.83 kg / hour of ferrous(II) oxide. The purity of dimethyl carbonate is 99.26% by mass.

[0377] It should be noted that, in the embodiments, compounds having a boiling point more than 100°C higher than dimethyl carbonate at a pressure of 760 mmHg are considered high-boiling-point compounds. Additionally, the composition at the bottom of the column (B) B In this compound, the content of 2-methoxyethanol is 0 ppm by mass, and the content of high-boiling-point compounds is 577 ppm by mass.

[0378] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0379] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0380] Process (II)

[0381] <Continuous Multistage Distillation Column B2>

[0382] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0383] <Bottom of the tower (B) B Distillation separation

[0384] The bottoms composition (B) obtained in process (I) will contain 3.62 tons / hour of dimethyl carbonate, 24.0 kg / hour of methanol, 2.1 kg / hour of high-boiling compounds, and 0.83 kg / hour of ferrous oxide (II) (total: 3.64 tons / hour, dimethyl carbonate purity: approximately 99.26% by mass). B The feed is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 2.0.

[0385] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 148 kg / hour t It contains 124 kg / hour of dimethyl carbonate and 23.9 kg / hour of methanol.

[0386] In addition, the bottom component (B) continuously extracted from the bottom of the continuous multi-stage distillation column B2 at a rate of 24.5 kg / hour b It contains 21.6 kg / hour of dimethyl carbonate, 2.1 kg / hour of high-boiling-point compounds and 0.83 kg / hour of ferrous oxide (II).

[0387] Additionally, the side fraction (B) continuously extracted in gaseous form at a rate of 3.47 tons / hour from the side outlet of the continuous multi-stage distillation column B2 s It contains 3.47 tons / hour of dimethyl carbonate and 0.07 kg / hour of methanol. The purity of the dimethyl carbonate is 99.998% by mass.

[0388] Furthermore, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 240 kW / t. Therefore, in Example 5, dimethyl carbonate with a purity of over 99.99% by mass can be produced with minimal heat consumption (small reflux ratio).

[0389] Additionally, in the side fraction (B) sIn the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0390] [Example 6]

[0391] Process (I)

[0392] <Continuous Multistage Distillation Column B1>

[0393] As a continuous multi-stage distillation column B1, stainless steel is used as the material. In addition, perforated trays are used as internal components in both the recovery section and the concentration section. Furthermore, ferrous oxide (II) powder is mixed with the feed liquid and fed into the distillation column at a rate of 0.83 kg / hour.

[0394] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0395] A mixture of low-purity dimethyl carbonate (A) containing 3.86 tons / hour of dimethyl carbonate, 0.36 tons / hour of methanol, 0.91 kg / hour of 2-methoxyethanol (hereinafter also referred to as "2ME"), and 2.1 kg / hour of carbon dioxide (total: 4.22 tons / hour, dimethyl carbonate concentration: approximately 91% by mass) is prepared. T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 161°C, a bottom pressure of about 0.80 MPa, and a reflux ratio of 10.

[0396] The top component (B) continuously drawn from the top of the continuous multi-stage distillation column B1 at a rate of 0.51 tons / hour T It contains 0.16 tons / hour of methanol, 0.34 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) T The methanol concentration in the sample was 31.4% by mass.

[0397] In addition, the bottom component (B2) continuously extracted from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.73 tons / hour B It contains 3.71 tons / hour of dimethyl carbonate, 15.4 kg / hour of methanol, 1.07 kg / hour of high-boiling-point compounds, and 0.83 kg / hour of ferrous(II) oxide. The purity of dimethyl carbonate is 99.5% by mass.

[0398] It should be noted that, in the embodiments, compounds having a boiling point more than 100°C higher than that of dimethyl carbonate at a pressure of 760 mmHg are considered as high-boiling-point compounds.

[0399] Additionally, at the bottom of the tower, the component (B) B In this compound, the content of 2-methoxyethanol is 0 ppm by mass, and the content of high-boiling-point compounds is 287 ppm by mass.

[0400] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0401] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0402] Process (II)

[0403] <Continuous Multistage Distillation Column B2>

[0404] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0405] <Bottom of the tower (B) B Distillation separation

[0406] The bottoms composition (B) obtained in process (I) will contain 3.71 tons / hour of dimethyl carbonate, 15.4 kg / hour of methanol, 1.07 kg / hour of high-boiling compounds, and 0.83 kg / hour of ferrous oxide (II) (total: 3.73 tons / hour, dimethyl carbonate purity: approximately 99.5% by mass). B The feed is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 2.0.

[0407] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 233 kg / hour t It contains 218 kg / h of dimethyl carbonate and 15.3 kg / h of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 23.5 kg / h. b It contains 21.6 kg / hour of dimethyl carbonate, 1.07 kg / hour of high-boiling-point compounds and 0.83 kg / hour of ferrous oxide (II).

[0408] Additionally, the side fraction (B) continuously extracted in gaseous form at a rate of 3.47 tons / hour from the side outlet of the continuous multi-stage distillation column B2s It contains 3.47 tons / hour of dimethyl carbonate and 0.06 kg / hour of methanol. The purity of the dimethyl carbonate is 99.998% by mass.

[0409] In addition, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 250 kW / t.

[0410] As can be seen from the above, in Example 6, dimethyl carbonate with a purity of 99.99% or more by mass can be produced with less heat consumption (small reflux ratio).

[0411] Additionally, in the side fraction (B) s In the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0412] [Example 7]

[0413] Process (I)

[0414] <Continuous Multistage Distillation Column B1>

[0415] As a continuous multi-stage distillation column B1, stainless steel is used as the material. In addition, perforated trays are used as internal components in both the recovery section and the concentration section. Furthermore, ferrous oxide (II) powder is mixed with the feed liquid and fed into the distillation column at a rate of 0.83 kg / hour.

[0416] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0417] A mixture of low-purity dimethyl carbonate (A) containing 3.86 tons / hour of dimethyl carbonate, 0.22 tons / hour of methanol, 0.91 kg / hour of 2-methoxyethanol (hereinafter also referred to as "2ME"), and 2.1 kg / hour of carbon dioxide (total: 4.08 tons / hour, dimethyl carbonate concentration: approximately 94.5% by mass) is prepared. T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 128°C, a bottom pressure of about 0.20 MPa, and a reflux ratio of 11.

[0418] The top component (B) continuously drawn from the top of the continuous multi-stage distillation column B1 at a rate of 0.40 tons / hour T It contains 0.22 tons / hour of methanol, 0.18 tons / hour of dimethyl carbonate, and 2.1 kg / hour of carbon dioxide. The top component (B) TThe methanol concentration in the sample is 55% by mass. Additionally, the bottom component (B) is continuously drawn from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.68 tons / hour. B It contains 3.68 tons / hour of dimethyl carbonate, 2.61 kg / hour of methanol, 1.07 kg / hour of high-boiling-point compounds, and 0.83 kg / hour of ferrous(II) oxide. The purity of dimethyl carbonate is 99.88% by mass.

[0419] It should be noted that, in the embodiments, compounds having a boiling point more than 100°C higher than that of dimethyl carbonate at a pressure of 760 mmHg are considered as high-boiling-point compounds.

[0420] Additionally, at the bottom of the tower, the component (B) B In this compound, the content of 2-methoxyethanol is 0 ppm by mass, and the content of high-boiling-point compounds is 291 ppm by mass.

[0421] In a continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is 10 minutes.

[0422] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0423] Process (II)

[0424] <Continuous Multistage Distillation Column B2>

[0425] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet is... 21 The tower diameter D below the side outlet 22 D 21 / D 22 The value is 0.6. The theoretical number of layers in this distillation column is 13.

[0426] <Bottom of the tower (B) B Distillation separation

[0427] The bottoms composition (B) obtained in process (I) will contain 3.68 tons / hour of dimethyl carbonate, 2.61 kg / hour of methanol, 1.07 kg / hour of high-boiling compounds, and 0.83 kg / hour of ferrous oxide (II) (total: 3.68 tons / hour, dimethyl carbonate purity: approximately 99.88% by mass). B It is continuously supplied from the inlet to the continuous multi-stage distillation column B2.

[0428] The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of approximately 92°C, a bottom pressure of approximately 3 kPa, and a reflux ratio of 2.0.

[0429] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 115 kg / hour t The distillation process includes 112 kg / h of dimethyl carbonate and 2.57 kg / h of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 20.2 kg / h. b It contains 19.1 kg / h of dimethyl carbonate, 1.07 kg / h of high-boiling-point compounds, and 0.83 kg / h of ferrous(II) oxide. Additionally, a side fraction (B) is continuously drawn in gaseous form at 3.51 tons / h from the side outlet of the continuous multistage distillation column B2. s It contains 3.51 tons / hour of dimethyl carbonate and 0.04 kg / hour of methanol. The purity of the dimethyl carbonate is 99.999% by mass.

[0430] Furthermore, during this continuous operation, the heat (steam) required per ton of side fraction per hour is 234 kW / t. Therefore, in Example 7, dimethyl carbonate with a purity of over 99.99% by mass can be produced with minimal heat consumption (small reflux ratio).

[0431] Additionally, in the side fraction (B) s In the sample, the content of high-boiling-point compounds is less than 20 ppm by mass, the content of 2ME is less than 30 ppm by mass, the content of metals is less than 0.6 ppm by mass, the content of water is less than 20 ppm by mass, and the content of methanol is less than 20 ppm by mass.

[0432] [Comparative Example 1]

[0433] Process (I)

[0434] <Continuous Multistage Distillation Column B1>

[0435] As a continuous multi-stage distillation column B1, porous trays are used as internal components in both the recovery section and the concentration section.

[0436] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0437] A mixture of low-purity dimethyl carbonate (A) containing 4.13 tons / hour of dimethyl carbonate, 2.1 kg / hour of methanol, and 0.43 kg / hour of 2-methoxyethanol (total: 4.13 tons / hour, dimethyl carbonate concentration: 99.95% by mass) TThe feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 109°C, a bottom pressure of about 80 kPa, and a reflux ratio of 1.8.

[0438] The top component (B) of the continuous multi-stage distillation column B1 is continuously drawn from the top 1 at a rate of 465 kg / h. T It contains 2.0 kg / h of methanol and 463 kg / h of dimethyl carbonate. Additionally, the bottom component (B) is continuously drawn from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.61 tons / hour. B The dimethyl carbonate (DMC) contains 3.61 tons / hour of dimethyl carbonate, 0.72 kg / hour of methanol, and 0.43 kg / hour of 2-methoxyethanol. The purity of the DMC is 99.97% by mass. Additionally, the bottom component (B)... B In this mixture, the content of 2-methoxyethanol is 119 ppm by mass, and the content of high-boiling-point compounds is 0 ppm by mass.

[0439] In the continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is approximately 4 minutes.

[0440] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0441] Process (II)

[0442] <Continuous Multistage Distillation Column B2>

[0443] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet... 21 The tower diameter D below the side outlet 22 The ratio of D 21 / D 22 The value is 0.83, and the theoretical number of layers is 13.

[0444] <Bottom of the tower (B) B Distillation separation

[0445] The bottoms component (B) obtained in process (I) will contain 3.61 tons / hour of dimethyl carbonate, 0.72 kg / hour of methanol, and 0.43 kg / hour of 2-methoxyethanol (total: 3.61 tons / hour, dimethyl carbonate purity: 99.97% by mass). B The solution is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 20.

[0446] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 200 kg / hour t It contains 199 kg / h of dimethyl carbonate and 0.72 kg / h of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 11.1 kg / h. b It contains 10.8 kg / h of dimethyl carbonate and 0.33 kg / h of 2-methoxyethanol. Additionally, a side fraction (B) is continuously drawn in gaseous form at a rate of 3.4 tons / h from the side outlet of the continuous multistage distillation column B2. s The sample contained 3.4 tons / hour of dimethyl carbonate and 0.1 kg / hour of 2-methoxyethanol, with the dimethyl carbonate having a purity of 99.997% by mass. Furthermore, in this continuous operation, the heat (vapor) required per ton of side fraction per hour was 465 kW / t. As can be seen from the above, although Comparative Example 1 could produce dimethyl carbonate with a purity of over 99.99% by mass, it required increasing the heat consumption (increasing the reflux ratio).

[0447] Additionally, in the side fraction (B) s In this mixture, the metal content is less than 0.6 ppm by mass, the water content is less than 20 ppm by mass, and the methanol content is less than 1 ppm by mass.

[0448] [Comparative Example 2]

[0449] Process (I)

[0450] <Continuous Multistage Distillation Column B1>

[0451] As a continuous multi-stage distillation column B1, porous trays are used as internal components in both the recovery section and the concentration section.

[0452] Low-purity dimethyl carbonate mixture (A) T Distillation separation

[0453] A mixture of low-purity dimethyl carbonate (A) containing 4.13 tons / hour of dimethyl carbonate, 2.1 kg / hour of methanol, and 0.43 kg / hour of 2-methoxyethanol (total: 4.13 tons / hour, dimethyl carbonate concentration: 99.95% by mass) T The feed is continuously supplied from the inlet to the continuous multistage distillation column B1. The continuous multistage distillation column B1 operates continuously under the conditions of a bottom temperature of about 109°C, a bottom pressure of about 80 kPa, and a reflux ratio of 1.8.

[0454] The top component (B) of the continuous multi-stage distillation column B1 is continuously drawn from the top 1 at a rate of 465 kg / h. TIt contains 2.0 kg / h of methanol and 463 kg / h of dimethyl carbonate. Additionally, the bottom component (B) is continuously drawn from the bottom 2 of the continuous multi-stage distillation column B1 at a rate of 3.61 tons / hour. B It consists of 3.61 tons / hour of dimethyl carbonate, 0.72 kg / hour of methanol, and 0.43 kg / hour of 2-methoxyethanol, with the dimethyl carbonate having a purity of 99.97% by mass. Additionally, the bottom component (B) B In this mixture, the content of 2-methoxyethanol is 119 ppm by mass, and the content of high-boiling-point compounds is 0 ppm by mass.

[0455] In the continuous multistage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is approximately 10 minutes.

[0456] Liquid residence time in the column (minutes) = BTM capacity (liquid volume (kg) retained in the BTM during operation) / BTM extraction flow rate (flow rate (kg / minute) extracted as bottom component) ... (i)

[0457] Process (II)

[0458] <Continuous Multistage Distillation Column B2>

[0459] A continuous multistage distillation column with a side outlet is used as continuous multistage distillation column B2. In this distillation column, the column diameter D above the side outlet... 21 The tower diameter D below the side outlet 22 The ratio of D 21 / D 22 The value is 0.42, and the theoretical number of layers is 17.

[0460] <Bottom of the tower (B) B Distillation separation

[0461] The bottoms component (B) obtained in process (I) will contain 3.61 tons / hour of dimethyl carbonate, 0.72 kg / hour of methanol, and 0.43 kg / hour of 2-methoxyethanol (total: 3.61 tons / hour, dimethyl carbonate purity: 99.97% by mass). B The feed is continuously supplied from the inlet to the continuous multistage distillation column B2. The continuous multistage distillation column B2 operates continuously under the conditions of a bottom temperature of about 92°C, a bottom pressure of about 3 kPa, and a reflux ratio of 2.0.

[0462] The top component (B) continuously extracted from the top of continuous multi-stage distillation column B2 at a rate of 190 kg / hour t It contains 189 kg / hour of dimethyl carbonate and 0.47 kg / hour of methanol. Additionally, the bottom component (B) is continuously drawn from the bottom of continuous multi-stage distillation column B2 at a rate of 34.2 kg / hour. bIt contains 34.0 kg / h of dimethyl carbonate and 0.18 kg / h of 2-methoxyethanol. Additionally, a side fraction (B) is continuously drawn in gaseous form at a rate of 3.4 tons / h from the side outlet of the continuous multistage distillation column B2. s The sample contained 3.4 tons / hour of dimethyl carbonate, 0.21 kg / hour of methanol, and 0.25 kg / hour of 2-methoxyethanol. The purity of the dimethyl carbonate was 99.98% by mass. Furthermore, in this continuous operation, the heat (steam) required per ton of side fraction per hour was 257 kW / t. Therefore, it is clear that in Comparative Example 2, dimethyl carbonate with a purity of 99.99% or higher could not be produced.

[0463] Additionally, in the side fraction (B) s In the sample, the metal content is less than 1 ppm by mass, the water content is less than 30 ppm by mass, and the methanol content is 62 ppm by mass.

[0464] In addition, during long-term continuous operation, the side fraction (B) s In all of them, the metal content was below 0.6 ppm by mass, the water content was below 20 ppm by mass, and the methanol content was above 20 ppm by mass.

[0465] [Example 8]

[0466] Dimethyl carbonate was manufactured under the same manufacturing conditions as in Example 5, except that the amount of ferrous oxide (II) supplied was varied as shown in Table 1. The results of the determination of impurities, etc., are shown in Table 1.

[0467] [Table 1-1]

[0468] Table 1 (1 / 2)

[0469]

[0470] [Table 1-2]

[0471] Table 1 (2 / 2)

[0472]

[0473] [Example 9]

[0474] use Figure 2 The apparatus shown utilizes a low-purity dialkyl carbonate mixture (A) to be introduced into a continuous multi-stage distillation column B1. T The dimethyl carbonate was heated by a heater (not shown) and adjusted to the temperature shown in Table 2. The time from heating to introduction into the continuous multistage distillation column B1 (feed time) was also used. Otherwise, dimethyl carbonate was manufactured under the same manufacturing conditions as in Example 1. The results of the determination of impurities, etc., are shown in Table 2.

[0475] It should be noted that, Figure 2 The device shown has Figure 3 The distillation columns shown, with dimensions D1 = 1.6m, H1 = 26m, D2 = 2.2m, H2 = 10m, D3 = 0.9m, and H3 = 2.5m, are designated as continuous multi-stage distillation columns B1, possessing... Figure 3 The distillation columns shown, with dimensions D1 = 0.85m, H1 = 28m, D2 = 1.3m, and H2 = 12m, are designated as continuous multistage distillation columns B2. Continuous multistage distillation column B1 has a reflux tank D downstream of the top condenser 11. In both continuous multistage distillation columns B1 and B2, H1 is the upper straight section of the column, and H2 is the lower straight section. The section connecting the two is a conical section. In continuous multistage distillation column B2, a side extraction port (side fraction port) is formed on the conical section.

[0476] [Examples 10, 11, and Comparative Examples 3-5]

[0477] In addition to altering the low-purity dimethyl carbonate mixture (A) as described in Table 2 T Except for the heating temperature and the residence time from the heater to the point of introduction, the procedure was performed in the same manner as in Example 9. The results of the determination of impurities, etc., are shown in Table 2.

[0478] [Comparative Example 6]

[0479] Except for the change to the side fraction (Bs2) of the continuous multistage distillation column B2, which is mainly composed of dialkyl carbonate, drawn from the extraction port located in the upper section of the straight column of the continuous multistage distillation column B2, the process was carried out in the same manner as in Example 9. The manufacturing conditions and measurement results are shown in Table 2.

[0480] [Table 2]

[0481]

[0482] [Examples 12, 13, Comparative Examples 7, 8]

[0483] Except for changing the reflux tank temperature of the continuous multistage distillation column B1 as described in Table 3, the process was carried out in the same manner as in Example 9. The manufacturing conditions and measurement results are shown in Table 3.

[0484] [Table 3]

[0485]

[0486] Industrial practicality

[0487] According to the manufacturing method of the present invention, for example, a method is provided to produce high-purity (purity greater than 99.99% by mass) dialkyl carbonates suitable for use as electrolytes in lithium-ion batteries with low heat consumption (small reflux ratio).

[0488] Label Explanation

[0489] B1: First continuous multistage distillation column; B2: Second continuous multistage distillation column; C: Industrial dimethyl carbonate tank; D: Reflux tank; 11: Top condenser of continuous multistage distillation column B1; 12: Reboiler of continuous multistage distillation column B1; 21: Top condenser of continuous multistage distillation column B2; 22: Reboiler of continuous multistage distillation column B2; A T : A mixture of low-purity dialkyl carbonates, used as feedstock to continuous multistage distillation column B1, B T The top components of a continuous multi-stage distillation column B1, whose main component is an aliphatic monohydric alcohol, and B... B The bottom components of B1, a continuous multistage distillation column with dialkyl carbonate as the main component, and B... t The top component of continuous multi-stage distillation column B2, which contains low-boiling-point components, and B... s Bs2: Side fraction of continuous multistage distillation column B2, whose main component is dialkyl carbonate; Bs3: Side fraction of continuous multistage distillation column B2, whose main component is dialkyl carbonate, from the extraction outlet in the comparative example; Bs4: Side fraction of continuous multistage distillation column B2, whose main component is dialkyl carbonate, from the extraction outlet in the comparative example. b : The bottom component of continuous multistage distillation column B2, which contains high-boiling-point components; D1: the inner diameter of the upper straight column section; H1: the length of the upper straight column section; D2: the inner diameter of the lower straight column section; H2: the length of the lower straight column section.

Claims

1. A method for manufacturing a dialkyl carbonate, wherein, The method for manufacturing the dialkyl carbonate includes the following steps: (I) a first separation and purification step (I) in which a low-purity dialkyl carbonate mixture (A T ) containing a dialkyl carbonate and an aliphatic monohydric alcohol is continuously supplied to a continuous multi-stage distillation column B1, a column top component (B T ) containing the aliphatic monohydric alcohol as a main component is continuously withdrawn from the upper portion of the column, and a column bottom component (B B ) containing the dialkyl carbonate as a main component is continuously withdrawn from the lower portion of the column; (II) Second separation and purification step (II), wherein the bottom component (B1) mainly composed of dialkyl carbonate is continuously drawn from the bottom of the continuous multi-stage distillation column B1. B The side fraction (B), which is mainly composed of dialkyl carbonate, is continuously supplied to B2, a continuous multistage distillation column with a side outlet, and the side fraction (B2) is continuously supplied to B2. s It is continuously extracted from the side outlet. In the process (I), a low-purity dialkyl carbonate mixture (A) is fed to the continuous multi-stage distillation column B1. T The concentration of dialkyl carbonate in the mixture is 25.00% to 95.00% by mass, and the low-purity dialkyl carbonate mixture (A) contains dialkyl carbonate. T It also contains alkoxy alcohols, and the bottom temperature of the continuous multi-stage distillation column B1 is above 115°C. In the process (II), the bottom component (B) supplied to the continuous multi-stage distillation column B2 B The concentration of dialkyl carbonate in the product is 99.00%–99.95% by mass. In the process (II), the side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The purity of the dialkyl carbonate in the distillation column B2 is above 99.99% by mass, and the reflux ratio is 0.2 to 2.

0. The process (I) is carried out in the presence of a compound containing Fe.

2. The manufacturing method according to claim 1, wherein, The low-purity dialkyl carbonate mixture (A) supplied to continuous multi-stage distillation column B1 T The concentration of dialkyl carbonate in the product is 30.00% to 90.00% by mass.

3. The manufacturing method according to claim 1, wherein, The low-purity dialkyl carbonate mixture (A) supplied to continuous multi-stage distillation column B1 T The concentration of dialkyl carbonate in the product is 35.00% to 85.00% by mass.

4. The manufacturing method according to claim 1, wherein, The dialkyl carbonate is either dimethyl carbonate or diethyl carbonate.

5. The manufacturing method according to claim 1, wherein, The aliphatic monohydric alcohol is methanol or ethanol.

6. The manufacturing method according to claim 1, wherein, In the low-purity dialkyl carbonate mixture (A) T The product contains aliphatic carbonate ethers, epoxides, and carbon dioxide as components other than dialkyl carbonates, aliphatic monohydric alcohols, and alkoxy alcohols.

7. The manufacturing method according to claim 1, wherein, The alkoxy alcohol is 2-methoxyethanol.

8. The manufacturing method according to claim 6, wherein, The aliphatic carbonate ether is ethylene glycol monomethyl ether carbonate.

9. The manufacturing method according to claim 6, wherein, The epoxide is ethylene oxide.

10. The manufacturing method according to claim 1, wherein, The low-purity dialkyl carbonate mixture (A) T The concentration of the aliphatic monohydric alcohol in the formula is 5.00% by mass to 75.00% by mass.

11. The manufacturing method according to claim 1, wherein, The low-purity dialkyl carbonate mixture (A) T The concentration of the aliphatic monohydric alcohol in the formula is 10.00% by mass to 70.00% by mass.

12. The manufacturing method according to claim 1, wherein, The low-purity dialkyl carbonate mixture (A) T The concentration of the aliphatic monohydric alcohol in the formula is 15.00% by mass to 65.00% by mass.

13. The manufacturing method according to claim 7, wherein, The low-purity dialkyl carbonate mixture (A) T The concentration of 2-methoxyethanol in the product is 0.00% by mass to 1.00% by mass.

14. The manufacturing method according to claim 7, wherein, The low-purity dialkyl carbonate mixture (A) T The concentration of 2-methoxyethanol in the product is 0.00% to 0.80% by mass.

15. The manufacturing method according to claim 7, wherein, The low-purity dialkyl carbonate mixture (A) T The concentration of 2-methoxyethanol in the product is 0.00% to 0.60% by mass.

16. The manufacturing method according to claim 1, wherein, The bottom temperature of the continuous multi-stage distillation column B1 is 140℃~250℃.

17. The manufacturing method according to claim 1, wherein, The bottom temperature of the continuous multi-stage distillation column B1 is 180℃~220℃.

18. The manufacturing method according to claim 1, wherein, The Fe-containing compound in step (I) and the low-purity dialkyl carbonate mixture (A) T The contact surface area is 1.0 × 10⁻⁶. -3 m 2 • Minutes / (kg / hour) or more.

19. The manufacturing method according to claim 18, wherein, The Fe-containing compound in step (I) and the low-purity dialkyl carbonate mixture (A) T The contact surface area is 1.5 × 10⁻⁶. -3 m 2 • Minutes / (kg / hour) or more.

20. The manufacturing method according to claim 18, wherein, The Fe-containing compound in step (I) and the low-purity dialkyl carbonate mixture (A) T The contact surface area is 2.0 × 10⁻⁶. -3 m 2 • Minutes / (kg / hour) or more.

21. The manufacturing method according to claim 18, wherein, When powder containing a compound with Fe is added, the contact surface area is calculated using the following formula: Contact surface area (m²) 2 •min / (kg / hour)) = [(surface area of ​​average particle size of added powder) (m 2 [×Liquid residence time in tower (minutes)] / Supply flow rate (kg / hour) The residence time of the liquid inside the tower is calculated using the following formula: Liquid residence time in the column (minutes) = BTM capacity (kg) / BTM extraction flow rate (kg / minute), where BTM capacity is the liquid volume retained in the BTM during operation, and BTM extraction flow rate is the flow rate extracted as the bottom component of the column.

22. The manufacturing method according to claim 18, wherein, When the distillation column material contains compounds containing Fe, the contact surface area is calculated using the following formula: Contact surface area (m²) 2 • minutes / (kg / hour) = [(BTM volume contact liquid internal column area (m²)] 2 ) × (residence time in tower (minutes)) / (supply flow rate (kg / hour)).

23. The manufacturing method according to claim 1, wherein, The process (I) is carried out in the presence of ferrous oxide (II).

24. The manufacturing method according to claim 1, wherein, The material inside the continuous multi-stage distillation column B1 is carbon steel.

25. The manufacturing method according to claim 1, wherein, The bottom component (B) supplied to continuous multistage distillation column B2 B The concentration of dialkyl carbonate in the product is 99.2% to 99.95% by mass.

26. The manufacturing method according to claim 1, wherein, The bottom component (B) supplied to continuous multistage distillation column B2 B The concentration of dialkyl carbonate in the product is 99.4% to 99.95% by mass.

27. The manufacturing method according to any one of claims 1 to 26, wherein, The bottom temperature of the continuous multi-stage distillation column B2 is below 120°C.

28. The manufacturing method according to claim 27, wherein, The bottom temperature of the continuous multi-stage distillation column B2 is 60℃~110℃.

29. The manufacturing method according to claim 27, wherein, The bottom temperature of the continuous multistage distillation column B2 is 65℃~105℃.

30. The manufacturing method according to any one of claims 1 to 26, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The content of high-boiling-point compounds in the product is less than 30 ppm by mass.

31. The manufacturing method according to claim 30, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The content of high-boiling-point compounds in the product is less than 25 ppm by mass.

32. The manufacturing method according to claim 30, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The content of high-boiling-point compounds in the product is less than 20 ppm by mass.

33. The manufacturing method according to any one of claims 1 to 26, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The metal content in the sample is less than 1 ppm by mass.

34. The manufacturing method according to claim 33, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The metal content in the sample is less than 0.8 ppm by mass.

35. The manufacturing method according to claim 33, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The metal content in the sample is less than 0.6 ppm by mass.

36. The manufacturing method according to any one of claims 1 to 26, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The water content in the sample is below 30 ppm by mass.

37. The manufacturing method according to claim 36, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The water content in the sample is below 25 ppm by mass.

38. The manufacturing method according to claim 36, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The water content in the sample is below 20 ppm by mass.

39. The manufacturing method according to any one of claims 1 to 26, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The combined content of methanol and ethanol in the product is less than 20 ppm by mass.

40. The manufacturing method according to any one of claims 1 to 26, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The content of 2-methoxyethanol in the product is less than 50 ppm by mass.

41. The manufacturing method according to claim 40, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The content of 2-methoxyethanol in the product is less than 40 ppm by mass.

42. The manufacturing method according to claim 40, wherein, The side fraction (B) drawn from the side outlet of the continuous multi-stage distillation column B2 s The content of 2-methoxyethanol in the product is less than 30 ppm by mass.

43. The manufacturing method according to any one of claims 1 to 26, wherein, The low-purity dialkyl carbonate mixture (A) supplied to the continuous multi-stage distillation column B1 T The temperature should be adjusted to 100℃~150℃.

44. The manufacturing method according to claim 43, wherein, The low-purity dialkyl carbonate mixture (A) is heated using a heater. T Heating, the time from the heater to the supply to the continuous multistage distillation column B1 is less than 5 minutes.

45. The manufacturing method according to any one of claims 1 to 26, wherein, The top component (B) continuously drawn from the top of the continuous multi-stage distillation column B1 T Condensation occurs at a reflux tank temperature of 100℃~150℃.

46. ​​The manufacturing method according to any one of claims 1 to 26, wherein, The continuous multi-stage distillation column B2 has an upper straight column section, a lower straight column section, and a conical section connecting the upper and lower straight column sections. The diameter of the lower straight column section is larger than the diameter of the upper straight column section. The side outlet of the continuous multi-stage distillation column B2 is located in the conical section.

47. The manufacturing method according to claim 46, wherein, In the continuous multi-stage distillation column B2, the column diameter D of the upper section of the straight column body... 21 The tower diameter D of the straight tower body in the lower section of the tower. 22 The ratio satisfies the condition of equation (ii): 0.2 <D 21 / D 22 <1.0......(ii) Wherein, the tower diameter D 21 and the tower diameter D 22 The unit is cm.

48. The manufacturing method according to claim 47, wherein, D 21 / D 22 It ranges from 0.3 to 1.

0.

49. The manufacturing method according to any one of claims 1 to 26, wherein, In the continuous multi-stage distillation column B1, the liquid residence time in the column, calculated by the following formula (i), is more than 5 minutes. Liquid residence time in the column (minutes) = BTM capacity (kg) / BTM effluent flow rate (kg / minute) ... (i) Wherein, BTM capacity is the liquid volume retained in the BTM of the tower during operation, and BTM extraction flow rate is the flow rate extracted as the bottom component of the tower.

50. The manufacturing method according to claim 49, wherein, In the continuous multi-stage distillation column B1, the liquid residence time in the column calculated by the above formula (i) is 10 minutes to 150 minutes.

51. The manufacturing method according to claim 49, wherein, In the continuous multi-stage distillation column B1, the liquid residence time in the column calculated by the above formula (i) is 15 minutes to 120 minutes.

52. The manufacturing method according to any one of claims 1 to 26, wherein, In the continuous multi-stage distillation column B2, the side fraction (B) is extracted in gaseous state. s ).

53. The manufacturing method according to any one of claims 1 to 26, wherein, The internal components of the continuous multi-stage distillation column B1 are trays and / or packing.

54. The manufacturing method according to any one of claims 1 to 26, wherein, The reflux ratio of the continuous multistage distillation column B1 is 0.5 to 20.

55. The manufacturing method according to claim 54, wherein, The reflux ratio of the continuous multistage distillation column B1 is 0.8 to 15.

56. The manufacturing method according to claim 54, wherein, The reflux ratio of the continuous multistage distillation column B1 is 1 to 5.

57. The manufacturing method according to any one of claims 1 to 26, wherein, The reflux ratio of the continuous multistage distillation column B2 is 0.6 to 2.

0.

58. The manufacturing method according to any one of claims 1 to 26, wherein, The reflux ratio of the continuous multistage distillation column B2 is 0.8 to 1.

5.

59. The manufacturing method according to any one of claims 1 to 26, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B In the dialkyl carbonate, the content of 2-methoxyethanol is less than 100 ppm by mass.

60. The manufacturing method according to claim 59, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B In the dialkyl carbonate, the content of 2-methoxyethanol is less than 50 ppm by mass.

61. The manufacturing method according to claim 59, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B In the dialkyl carbonate, the content of 2-methoxyethanol is less than 10 ppm by mass.

62. The manufacturing method according to any one of claims 1 to 26, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B The components (B1) are directly supplied to the continuous multi-stage distillation column B2, or the bottom components (B2) of the continuous multi-stage distillation column B1 are supplied directly to the continuous multi-stage distillation column B2. B It is supplied to an industrial-grade dialkyl carbonate tank, and then from the tank to a continuous multistage distillation column B2.

63. The manufacturing method according to any one of claims 1 to 26, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B In the sample, the content of high-boiling-point compounds is above 0.1 ppm by mass.

64. The manufacturing method according to claim 63, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B In the sample, the content of high-boiling-point compounds is above 1 ppm by mass.

65. The manufacturing method according to claim 63, wherein, The bottom component (B) of the continuous multi-stage distillation column B1 B In the sample, the content of high-boiling-point compounds is above 100 ppm by mass.

66. The manufacturing method according to claim 63, wherein, The high-boiling-point compound is a substance obtained by converting 2-methoxyethanol.

67. The manufacturing method according to claim 63, wherein, The high-boiling-point compound is a compound that has a boiling point that is more than 100°C higher than that of dialkyl carbonate at a pressure of 760 mmHg.

68. The manufacturing method according to any one of claims 1 to 26, wherein, The manufacturing method includes the following steps: reacting a cyclic carbonate with an aliphatic monohydric alcohol to obtain a low-purity dialkyl carbonate mixture (A) containing dialkyl carbonate. T ).

69. The manufacturing method according to any one of claims 1 to 26, wherein, The manufacturing method comprises the following steps: continuously feeding cyclic carbonates and aliphatic monohydric alcohols into a continuous multi-stage distillation column A containing a catalyst, where the reaction and distillation are carried out simultaneously, and a low-purity dialkyl carbonate mixture (A) containing the generated dialkyl carbonate and unreacted aliphatic monohydric alcohol is collected. T It is continuously drawn from the top of the tower.

70. The manufacturing method according to claim 69, wherein, The cyclic carbonate is ethylene carbonate or propylene carbonate.

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