JPH0616596A - Separation of dimethyl carbonate from methanol - Google Patents

Abstract

PURPOSE:To accomplish efficient separation for a mixture containing a useful compound for e.g. a carbonylating agent, by extracting a mixture of methanol and dimethyl carbonate with a solvent higher in boiling point than the latter compound followed by drawing the resulting liquid extract as bottoms and the methanol as overhead product. CONSTITUTION:In separating dimethyl carbonate from methanol by distillation of a mixture comprising these two compounds, this mixture is fed into a distillation column where an organic solvent (e.g. phenol) higher in boiling point than the dimethyl carbonate is used for extracting the dimethyl carbonate to extract the dimethyl carbonate in this solvent, and the resulting liquid substance comprising the dimethyl carbonate and the solvent is drawn as bottoms, while the distillate consisting mainly of the methanol is drawn as overhead product. With this extracting distillation process, dimethyl carbonate useful as e.g. a carbonylating agent in the organic synthesis sector for medicines, pesticides, or dyes can efficiently be separated from methanol.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components.

[0002]

BACKGROUND OF THE INVENTION Dimethyl carbonate is used not only as a carbonylating agent, carbomethoxylating agent and methylating agent in the field of organic synthesis of medicines, agricultural chemicals and dyes, but also as an oxygen additive for gasoline, octane number improver and organic solvent. Is useful as This dimethyl carbonate is usually produced by reacting methanol or a methanol derivative with phosgene, carbon monoxide and an oxidizing agent, a carbonylating agent such as a cyclic carbonate. However, in any of these production methods, methanol, which is usually a raw material, and dimethyl carbonate, which is a product, are present as a mixture, and when they are separated by distillation, it is difficult to form an azeotropic mixture for separation. It is well known.

As an azeotropic mixture containing methanol and dimethyl carbonate as main components or a method for separating methanol and dimethyl carbonate from the mixture, conventionally,
Azeotropic distillation and pressure distillation are well known, but extractive distillation has hardly been known. The method by azeotropic distillation is a method of adding a third component (azeotrope-forming agent) that is azeotropic with methanol, changing the azeotropic composition ratio of methanol and dimethyl carbonate, or eliminating azeotrope. In this method, a distillate containing as a main component and an azeotrope-forming agent is withdrawn from the upper part of the distillation column, and a liquid substance containing dimethyl carbonate as the main component is withdrawn from the lower part of the distillation column. As such an azeotropic distillation method, for example, in JP-A-54-41820, methanol is azeotropically distilled using an aliphatic hydrocarbon having a carbon number of 5 to 10 as an azeotrope-forming agent to obtain 40 to 60% of dimethyl carbonate. A method of separating with a yield of is disclosed. In Japanese Patent Publication No. 62-8091, benzene is azeotroped with methanol to separate the by-produced methanol and the starting dimethyl carbonate when diphenyl carbonate is produced by transesterification of dimethyl carbonate and phenol. Used as a material former,
A method of distilling off methanol as a mixture with benzene is disclosed.

The pressure distillation method is a method utilizing the fact that the azeotropic composition ratio of methanol and dimethyl carbonate can be changed by changing the operating pressure during distillation. For example, in JP-A-51-108019, pressurization is performed. A method of distilling under the conditions and increasing the concentration of methanol in the azeotrope of dimethyl carbonate and methanol distilled at the top of the column and extracting only dimethyl carbonate from the bottom of the column is disclosed in JP-A-2-212456. The combined first column is operated at a higher pressure than the second column, and dimethyl carbonate is obtained from the bottom of the first column and methanol is obtained from the bottom of the second column by utilizing the concentration difference of the azeotropic composition at each pressure. A method for separating a mixture of dimethyl carbonate and methanol is disclosed.

The only known method by extractive distillation is to use a large amount of water as an extraction solvent and extract methanol with water to obtain a liquid substance containing water-methanol as a bottom component. Is taken out, and a distillate rich in dimethyl carbonate is taken out as a column top component (Japanese Patent Laid-Open No. 50-77319). Therefore, conversely, using an organic solvent as an extraction solvent, dimethyl carbonate is extracted into the organic solvent and taken out as a liquid substance containing dimethyl carbonate as a column bottom component and the organic extraction solvent as a main component, and methanol as a main component. An extractive distillation method in which methanol and dimethyl carbonate are separated by extracting the distillate thus obtained from the upper part of the distillation column has not been known at all.

[0006]

In the conventionally known methods for producing dimethyl carbonate, in order to improve and improve the reaction yield of dimethyl carbonate, it is usual to carry out the reaction in the presence of excess methanol. Therefore, not only is it necessary to separate the methanol and the produced dimethyl carbonate after the reaction, but an economical production method cannot be achieved unless the separated methanol is used as a raw material for recycling in the reaction zone. Normally, methanol and dimethyl carbonate form an azeotrope at 70% and 30% by weight, respectively, under normal pressure. By changing the azeotropic composition and reducing the amount of extra dimethyl carbonate contained in methanol and recycled, not only the loss during purification and recycling decreases but also the reaction yield can be increased. Further, it is naturally preferable that the equipment can be prevented from increasing in size.

However, according to the above-mentioned known method, high-purity methanol and dimethyl carbonate can be obtained at a high recovery rate when separating methanol and dimethyl carbonate from an azeotropic mixture or mixture containing methanol and dimethyl carbonate as main components. However, it requires a large-diameter high-pressure distillation column to carry out the distillation operation under pressure, resulting in a large equipment cost and inevitable disadvantages when it is carried out on an industrial scale.

In addition, the method using an azeotrope-forming agent with methanol requires a new azeotrope to be separated for recycling methanol, and thus cannot be a very simple process, and the reaction yield is improved. From the necessity of the above, it brings about an increase in energy for burning and distilling off methanol used in a large excess as an azeotropic mixture, and an increase in the size of the separation column for the azeotrope-forming agent with methanol. An object of the present invention is to establish a separation method for obtaining high-purity methanol and dimethyl carbonate at a high recovery rate when separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components by distillation.

[0009]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a method for separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components, and as a result, have hitherto been known to use dimethyl carbonate as an organic system. The present invention has been completed by finding a separation method capable of obtaining high-purity methanol and dimethyl carbonate with a high recovery rate by an extractive distillation method of extracting in an extraction solvent.

That is, in the present invention, when separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components by distillation,
An organic solvent having a boiling point higher than that of dimethyl carbonate is used as an extraction solvent for dimethyl carbonate, and dimethyl carbonate is extracted into the organic solvent to distill a liquid substance containing dimethyl carbonate and the organic solvent as main components as a bottom component. It is a method for separating methanol and dimethyl carbonate by an extractive distillation method, which is characterized in that a distillate containing methanol as a main component is taken out from the upper part of a distillation column as a column top component.

In carrying out the present invention, the organic solvent used as a solvent for extracting dimethyl carbonate needs to have a boiling point higher than that of dimethyl carbonate, and preferably has a high ability to extract dimethyl carbonate. As such an extraction solvent, one kind or two or more kinds selected from aromatic hydroxy compounds, alkylaryl ethers, dialkyl carbonates, alkylaryl carbonates, alkylene carbonates, diaryl carbonates and alicyclic alcohols are particularly preferably used. To be

The aromatic hydroxy compound, which is the extraction solvent preferably used in the present invention, is represented by the general formula (1) of Chemical formula 1, and the hydroxy group is directly bonded to the aromatic group. So long as it is any type.

[0013]

[Chemical 1]

Examples of such Ar ¹ include phenyl, tolyl (each isomer), xylyl (each isomer), trimethylphenyl (each isomer), tetramethylphenyl (each isomer), ethylphenyl (each isomer). Body), propylphenyl (each isomer), butylphenyl (each isomer),
Phenyl groups such as diethylphenyl (each isomer), methylethylphenyl (each isomer), pentylphenyl (each isomer), hexylphenyl (each isomer), cyclohexylphenyl (each isomer) and various alkylphenyl groups Various alkoxyphenyl groups such as methoxyphenyl (each isomer), ethoxyphenyl (each isomer), butoxyphenyl (each isomer); fluorophenyl (each isomer), chlorophenyl (each isomer), bromophenyl ( Various phenyl groups such as isomers), chloro (methyl) phenyl (each isomer), dichlorophenyl (each isomer); naphthyl (each isomer), methylnaphthyl (each isomer), dimethylnaphthyl (each) Isomer), chloronaphthyl (each isomer), methoxynaphthyl (each isomer), cyanonaphthyl (each isomer) ) Etc. naphthyl groups and substituted naphthyl groups; pyridyl (each isomer), coumaryl (each isomer), quinolyl (each isomer), methylpyridyl (each isomer), chlorpyridyl (each isomer), methylcoumaryl ( And various substituted and unsubstituted heteroaromatic groups such as each isomer) and methylquinolyl (each isomer).

Examples of the aromatic hydroxy compound having Ar ¹ include phenol, cresol (each isomer), xylenol (each isomer), trimethylphenol (each isomer), tetramethylphenol (each isomer). ), Ethylphenol (each isomer), propylphenol (each isomer), butylphenol (each isomer), diethylphenol (each isomer), methylethylphenol (each isomer), methylpropylphenol (each isomer) , Various alkylphenols such as dipropylphenol (each isomer), methylbutylphenol (each isomer), pentylphenol (each isomer), hexylphenol (each isomer), cyclohexylphenol (each isomer); methoxyphenol ( Each isomer), ethoxyphenol (each isomer) Various alkoxy phenols and the like; naphthol (isomers) and various substituted naphthols; hydroxypyridine (isomers), hydroxycoumarin (isomers), hydroxyquinoline (isomers)
Heteroaromatic hydroxy compounds and the like are used.

The alkylaryl ether which is the extraction solvent preferably used in the present invention is represented by the general formula (2)
It is shown by.

[0017]

[Chemical 2]

Examples of R ¹ include methyl, ethyl, propyl (each isomer), allyl, butyl (each isomer), butenyl (each isomer), pentyl (each isomer),
Alkyl groups such as hexyl (each isomer), heptyl (each isomer), octyl (each isomer), nonyl (each isomer), decyl (each isomer), cyclohexylmethyl; cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl Alicyclic groups such as cycloheptyl; benzyl, phenethyl (each isomer), phenylpropyl (each isomer), phenylbutyl (each isomer), methylbenzyl (each isomer)
And aralkyl groups such as In addition, these alkyl groups, alicyclic groups, and aralkyl groups may be substituted with other substituents such as a lower alkyl group, a lower alkoxy group, a cyano group, and a halogen, or have an unsaturated bond. May be.

Examples of such alkyl aryl ethers include methyl phenyl ether, ethyl phenyl ether, propyl phenyl ether (each isomer), allyl phenyl ether, butyl phenyl ether (each isomer), pentyl phenyl ether (each isomer). ), Hexyl phenyl ether (each isomer), heptyl phenyl ether (each isomer), octyl tril ether (each isomer), nonyl (ethylphenyl) ether (each isomer), decyl (butylphenyl) ether (each isomer) Body), methyl tolyl ether (each isomer), ethyl tolyl ether (each isomer), propyl tolyl ether (each isomer), butyl tolyl ether (each isomer), allyl tolyl ether (each isomer), methyl xylyl Ether (each isomer), methyl ( Limethylphenyl) ether (each isomer), methyl (chlorophenyl) ether (each isomer), methyl (nitrophenyl) ether (each isomer), methyl (methoxyphenyl) ether (each isomer), methyl cumyl ether ( Each isomer), methyl (naphthyl) ether (each isomer), methyl (pyridyl) ether (each isomer), ethyl cumyl ether (each isomer), methyl (benzoylphenyl) ether (each isomer), ethyl xylyl Ether (each isomer), benzyl xylyl ether, methyl (hydroxyphenyl) ether (each isomer), metorbiphenyl ether (each isomer), methyl (hydroxybiphenyl) ether (each isomer), methyl-2- (hydroxyphenyl) ) Propyl phenyl ether (each isomer), etc.

The dialkyl carbonate which is the extraction solvent preferably used in the present invention is represented by the general formula (3) of Chemical formula 3.

[0021]

[Chemical 3]

Examples of such dialkyl carbonates having R ¹ and R ² include diethyl carbonate, dipropyl carbonate (each isomer), diallyl carbonate, dibutenyl carbonate (each isomer),
Dibutyl carbonate (each isomer), dipentyl carbonate (each isomer), dihexyl carbonate (each isomer), diheptyl carbonate (each isomer), dioctyl carbonate (each isomer), dinonyl carbonate (each isomer), Didecyl carbonate (each isomer), dicyclopentyl carbonate, dicyclohexyl carbonate (each isomer), dicycloheptyl carbonate,
Dibenzyl carbonate, diphenethyl carbonate (each isomer), di (phenylpropyl) carbonate (each isomer), di (phenylbutyl) carbonate (each isomer), di (chlorobenzyl) carbonate (each isomer), di (Methoxybenzyl) carbonate (each isomer), di (methoxymethyl) carbonate, di (methoxyethyl) carbonate (each isomer), di (chloroethyl) carbonate (each isomer), di (cyanoethyl) carbonate (each isomer) ), Methyl ethyl carbonate,
Methyl propyl carbonate (each isomer), methyl butyl carbonate (each isomer), ethyl propyl carbonate (each isomer), ethyl butyl carbonate (each isomer), dibenzyl carbonate and the like are used.

The alkylaryl carbonate, which is the extraction solvent preferably used in the present invention, is represented by the general formula (4).

[0024]

[Chemical 4]

Examples of such alkylaryl carbonates include methylphenyl carbonate, ethylphenyl carbonate, propylphenyl carbonate (each isomer), allylphenyl carbonate, butylphenyl carbonate (each isomer), pentylphenyl carbonate (each isomer). ), Hexyl phenyl carbonate (each isomer), heptyl phenyl carbonate (each isomer), octyl tril carbonate (each isomer), nonyl (ethyl phenyl) carbonate (each isomer), decyl (butyl phenyl) carbonate (each isomer) Body), methyl tolyl carbonate (each isomer), ethyl tolyl carbonate (each isomer), propyl tolyl carbonate (each isomer), butyl tolyl carbonate (each isomer), allyl tolyl carbonate Bonate (each isomer), methyl xylyl carbonate (each isomer), methyl (trimethylphenyl) carbonate (each isomer), methyl (chlorophenyl) carbonate (each isomer), methyl (nitrophenyl) carbonate (each isomer) ), Methyl (methoxyphenyl) carbonate (each isomer), methyl cumyl carbonate (each isomer), methyl (naphthyl) carbonate (each isomer), methyl (pyridyl) carbonate (each isomer), ethyl cumyl carbonate (Each isomer), methyl (benzoylphenyl) carbonate (each isomer), ethyl xylyl carbonate (each isomer),
Benzyl xylyl carbonate, methyl (hydroxyphenyl) carbonate (each isomer), methoxycarbonyloxybiphenyl (each isomer), methyl (hydroxybiphenyl) carbonate (each isomer), methyl-2- (hydroxyphenyl) propylphenyl carbonate ( Each isomer) and the like.

The alkylene carbonate which is the extraction solvent preferably used in the present invention is represented by the general formula (5) of Chemical formula 5.

[0027]

[Chemical 5]

Examples of such alkylene carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, vinyl ethylene carbonate and cyclohexene carbonate. The diaryl carbonate, which is the extraction solvent preferably used in the present invention, is represented by the general formula (6) of Chemical formula 6.

[0029]

[Chemical 6]

Examples of such diaryl carbonates include diphenyl carbonate, ditolyl carbonate (each isomer), phenyltolyl carbonate (each isomer), di (ethylphenyl) carbonate (each isomer), phenyl (ethylphenyl). ) Carbonate (each isomer) and the like. The alicyclic alcohol, which is the extraction solvent preferably used in the present invention, is represented by the general formula (7) of Chemical formula 7.

[0031]

[Chemical 7]

Specific examples of such an alicyclic alcohol include cyclopentanol, cyclohexanol, and methylcyclohexanol. These extraction solvents are preferably those which do not substantially form the lowest azeotrope with dimethyl carbonate under distillation conditions.
Further, those which do not form a new azeotropic mixture with methanol are more preferable. Further, it is optional to use two or more kinds of extraction solvents unless the purity of methanol and dimethyl carbonate is lowered, but usually one kind is used in order to simplify the separation of the extraction solvent in the subsequent step.

Among these extraction solvents, particularly preferred are phenol and / or cresol as the aromatic hydroxy compound, methylphenyl ether and / or methyltolyl ether as the alkylaryl ether, diethyl carbonate as the dialkyl carbonate, and alkylaryl. Examples thereof include methylphenyl carbonate and / or ethylphenyl carbonate as a carbonate, ethylene carbonate and / or propylene carbonate as an alkylene carbonate, diphenyl carbonate as a diaryl carbonate, and cyclohexanol and / or methylcyclohexanol as an alicyclic alcohol.

These extraction solvents are supplied from the upper part of the extractive distillation zone of methanol and dimethyl carbonate in the distillation column and brought into gas-liquid contact with the vapor containing methanol and dimethyl carbonate as the main components to carry out extractive distillation to obtain methanol in the vapor. Methanol and dimethyl carbonate can be separated by increasing the concentration. An example of this separation method is shown in FIG.
Shown in.

In the method of the present invention, the more the amount of the extraction solvent used for vapor-liquid contact with the vapor containing methanol and dimethyl carbonate in the distillation column is used, and the more the number of stages of the distillation column is increased, the more the distillation column is distilled from the top. Although the purity of methanol is improved, if it is used in an excessively large amount, not only the extractive distillation column but also the device for separating the extraction solvent and dimethyl carbonate will be enlarged and the amount of utility will be increased. The extraction solvent in the liquid phase in each stage of the extractive distillation column may have a concentration higher than the azeotropic composition of methanol and dimethyl carbonate, and a concentration higher than the concentration at which methanol can be taken out into the vapor, but in the method of the present invention, it is usually 25 It is preferable to make it exist by weight% or more.
It is more preferable to make it exist in an amount of 0% by weight or more.

It is also possible to carry out extractive distillation under pressure conditions within an allowable range for reducing the amount of extraction solvent. In carrying out the present invention, the extraction solvent is preferably supplied from above the extractive distillation zone of methanol and dimethyl carbonate in the distillation column, that is, the area corresponding to the concentration section. The thus-extracted extraction solvent is brought into gas-liquid contact with methanol and dimethyl carbonate in the extractive distillation column to extract dimethyl carbonate and move to the lower part of the extractive distillation column while increasing the concentration of dimethyl carbonate in the liquid phase. The mixture containing methanol and dimethyl carbonate as a main component may be supplied to the extractive distillation column in either liquid or gas form. In the stage below the mixture supply section of methanol and dimethyl carbonate, that is, in the methanol recovery section, after extractive distillation in the number of distillation stages necessary to sufficiently reduce the methanol concentration in the liquid phase, dimethyl carbonate and the extraction solvent from the bottom of the column It is taken out as a mixed liquid. The mixed solution of dimethyl carbonate and the extraction solvent extracted from the bottom of the column is supplied to a distillation column for separating dimethyl carbonate and the extraction solvent, if necessary, and separated into dimethyl carbonate and the extraction solvent. At this time, dimethyl carbonate is obtained as a column top distillate of the separation distillation column, and the extraction solvent is obtained as a column bottom liquid. The separated extraction solvent is recycled to the extraction distillation column again and used for the separation of methanol and dimethyl carbonate.At this time, if impurities are accumulated in the extraction solvent, a part of the system may be removed as necessary. It is optional to take it out or supply a new extraction solvent. Further, depending on the type of the extraction solvent, it is possible to supply the dimethyl carbonate and the extraction solvent to the next step without separation and use them. On the other hand, the concentration of methanol is sufficiently increased in the vapor phase in the upper part of the extractive distillation column, and by distilling this from the upper part of the distillation column, a distillate containing methanol as a main component is obtained as a top component. If an extraction solvent is present in the overhead component, it is separated from the extraction solvent in a distillation zone corresponding to an extraction solvent recovery section having a theoretical plate number sufficient for distillation separation of the extraction solvent and methanol, if necessary. It is also a preferable method to extract from the top of the tower. FIG. 2 shows an example of a process diagram showing an embodiment of the present invention.

The distillation column used in the extractive distillation of the present invention may be either a plate column or a packed column regardless of the type. As the plate column, for example, a distillation column having various types of plate plates such as a bubble cap, a uniflux, a float valve, a glitch ballast, a flexi, a sieve, a ripple, a turbo grid, a Venturi cascade, and a kittel can be used. As packing tower, for example, Raschig ring, Lessing ring, Bell saddle, Interlocks saddle, Terralet, Pall ring, Cascade mini ring, Dickson packing, McMahon packing, Helipack, Canon packing, Goodlaw packing, Sluzer packing, etc. A packed distillation column can be used. Moreover, it is also possible to adopt a format having a shelf and a filling section as needed.

In carrying out extractive distillation in the present invention,
The descending liquid velocity and ascending vapor velocity in the extractive distillation column differ depending on the type of extractive distillation column used and the type of packing material when a packed column is used, but usually within the range where flooding does not occur, and trays are used. When using a tower, it is used within the range where weeping does not occur. In the present invention, when the reflux ratio of the extractive distillation column is increased, the distillation effect of methanol in the vapor phase is enhanced, and therefore the purity of methanol extracted from the top of the column can be increased. However, if the reflux ratio is excessively increased, the required heat energy increases, which is not preferable. The reflux ratio is usually 0-10, preferably 0.1-5. The temperature of each part of the extractive distillation column varies depending on the volatility of methanol from the extraction solvent, but the top of the column is preferably close to the boiling point of methanol.

[0039]

EXAMPLES The details of the present invention will be described below with reference to examples.
This does not particularly limit the content of the present invention.

[0040]

Example 1 Using the distillation apparatus shown in FIG. 1, phenol was supplied as an extraction solvent from the top of the distillation column to 15 theoretical plates, and dimethyl carbonate and methanol from the top to 30 theoretical plates. Then, a liquid containing methanol as a main component was withdrawn from the top of the column, and a mixed liquid containing dimethyl carbonate and phenol as a main component was withdrawn from the bottom of the column. Distillation column
A column diameter of 26 mm and a Dickson packing (3 mmφ) packed with 50 theoretical plates were used, and the reflux ratio was 0.2.
And

The amounts supplied to the distillation column were 60 g / hr for a mixed solution of dimethyl carbonate and methanol of 32 wt% and 68 wt%, and 200 g / hr for phenol. When the temperature at the top of the distillation column was stable at 65 ° C., the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 99.6 wt% and dimethyl carbonate was 0.4 wt.
%Met.

Next, using the distillation apparatus shown in FIG. 3 for the purpose of separating dimethyl carbonate and phenol,
A mixed solution containing dimethyl carbonate and phenol as main components was supplied to the bottom of the distillation column, and dimethyl carbonate was withdrawn from the top of the distillation column without being supplied from the intermediate stage of the distillation column. The amount of the mixed solution containing dimethyl carbonate and phenol as the main components supplied to the bottom of the distillation column was 220 g / hr. When the temperature at the top of the distillation column was stable, the composition of the distillate from the top of the distillation column As a result, dimethyl carbonate was 97.4 wt% and methanol was 2.6 wt%.

The recoveries of dimethyl carbonate and methanol were 99.0% and 99.8%, respectively.

[0044]

Example 2 Using the distillation apparatus shown in FIG. 3, dimethyl carbonate and methanol were supplied to the bottom of the distillation column from the intermediate stage of the distillation column as methyl phenyl ether as an extraction solvent. The distillation column has a diameter of 26 mm and a Dickson packing (3
(mmφ) filled with 30 theoretical plates,
The reflux ratio was 0.2.

The amounts supplied to the distillation column were 60 g / hr for a mixed solution of 32 wt% and 68 wt% of dimethyl carbonate and methanol, and 140 for methyl phenyl ether.
It was g / hr. When the temperature at the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 99.7 wt% and dimethyl carbonate was 0.1%.
It was 3 wt%.

[0046]

Example 3 Using the same distillation column as in Example 2, diethyl carbonate was supplied to the distillation column as an extraction solvent. The supply amount to the distillation column is 60 g / h for a mixture of dimethyl carbonate and methanol of 32 wt% and 68 wt% respectively.
The amount of r and diethyl carbonate was 200 g / hr.
When the temperature at the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 99.1 wt.
%, Dimethyl carbonate was 0.9 wt%.

[0047]

[Example 4] The same distillation column as in Example 2 was used, and methylphenyl carbonate was supplied to the distillation column as an extraction solvent.
The amount of dimethyl carbonate and the composition of methanol supplied to the distillation column are 32 wt% and 60 wt% of the mixed liquid of 68 wt% respectively.
/ Hr, methyl phenyl carbonate 140g / hr
Met. When the temperature of the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured, and
It was 9.4 wt% and dimethyl carbonate was 0.6 wt%.

[0048]

Example 5 Using the same distillation column as in Example 2, ethylene carbonate was supplied to the distillation column as an extraction solvent. The supply amount to the distillation column is 60 g / h for a mixture of dimethyl carbonate and methanol of 32 wt% and 68 wt% respectively.
r and ethylene carbonate were 190 g / hr.
When the temperature at the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 99.1 wt.
%, Dimethyl carbonate was 0.9 wt%.

[0049]

Example 6 Using the same distillation column as in Example 2, diphenyl carbonate was supplied to the distillation column as an extraction solvent. The supply amount to the distillation column is 60 g / h for a mixture of dimethyl carbonate and methanol of 32 wt% and 68 wt% respectively.
The amount of r and diphenyl carbonate was 190 g / hr. When the temperature of the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 99.2.
wt% and dimethyl carbonate were 0.8 wt%.

[0050]

Example 7 The same distillation column as in Example 2 was used, and cyclohexanol was supplied to the distillation column as an extraction solvent. The amount of dimethyl carbonate and methanol contained in the distillation column was 32 wt% and the mixture of 68 wt% was 60 g / hr.
Cyclohexanol was 190 g / hr. When the temperature at the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 99.0 wt% and dimethyl carbonate was 1.0 wt%.

[0051]

Example 8 Using the same distillation column as in Example 2, cresol was supplied to the distillation column as an extraction solvent. The composition of dimethyl carbonate and methanol is 32 for the supply amount to the distillation column.
The mixed liquid of wt% and 68 wt% was 60 g / hr and cresol was 380 g / hr. When the temperature of the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured. As a result, methanol was 98.4 wt% and dimethyl carbonate was 1.6 wt%.

[0052]

Example 9 The same distillation column as in Example 2 was used, and methyltolyl ether was supplied to the distillation column as an extraction solvent. The supply amount to the distillation column is 60 g / h for a mixture of dimethyl carbonate and methanol of 32 wt% and 68 wt% respectively.
The amount of r and methyl tolyl ether was 280 g / hr.
When the temperature at the top of the distillation column was stable, the composition of the distillate from the top of the distillation column was measured, and as a result, the amount of methanol was 98.1 wt.
%, Dimethyl carbonate was 1.9 wt%.

[0053]

EFFECT OF THE INVENTION In the distillation separation of methanol and dimethyl carbonate according to the present invention, the extractive distillation in which dimethyl carbonate is extracted with an organic solvent allows the separation of a mixture of methanol and dimethyl carbonate to obtain highly pure methanol and dimethyl carbonate. It is possible to obtain Further, since high-purity methanol can be recycled to the reactor, it is possible to assemble an efficient dimethyl carbonate production process.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a separation method of the present invention.

FIG. 2 is a process chart showing an example of an embodiment of the present invention.

FIG. 3 is a schematic view showing another example of the separation method of the present invention.

Claims (2)

[Claims] 1. When separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as a main component by distillation, an organic solvent having a higher boiling point than dimethyl carbonate is used as an extraction solvent for dimethyl carbonate, and dimethyl carbonate is used as the organic solvent. By extracting into the inside, a liquid substance containing dimethyl carbonate and the organic solvent as a main component is taken out from the lower part of the distillation column as a bottom component, and a distillate containing methanol as a main component is taken out from the upper part of the distillation column as a top component. A method for separating methanol and dimethyl carbonate by an extractive distillation method, which is characterized by the above. 2. The solvent for extracting dimethyl carbonate is selected from aromatic hydroxy compounds, alkyl aryl ethers, dialkyl carbonates, alkyl aryl carbonates, alkylene carbonates, diaryl carbonates, and alicyclic alcohols. 1 type or 2
The method according to claim 1, wherein more than one type is used.