JP3214576B2 - Separation method of methanol and dimethyl carbonate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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]

2. Description of the Related Art Dimethyl carbonate is used not only as a carbonylating agent, a carbomethoxylating agent and a methylating agent in the field of organic synthesis such as pharmaceuticals, agricultural chemicals and dyes, but also as an additive for gasoline, an octane improver, and an organic solvent. Useful as This dimethyl carbonate is usually produced by reacting methanol or a methanol derivative with phosgene, carbon monoxide, and a carbonylating agent such as an oxidizing agent or a cyclic carbonate. However, in any of these production methods, usually, methanol, which is a raw material, and dimethyl carbonate, which is a product, exist as a mixture, and when they are separated by distillation, an azeotrope is generated, which is difficult to separate. It is well known.

As a method for separating methanol and dimethyl carbonate from an azeotrope or a mixture containing methanol and dimethyl carbonate as main components,
A method by azeotropic distillation and a method by pressure distillation are well known, but a method by extractive distillation was hardly known. The method of azeotropic distillation is a method of adding a third component (azeotrope-forming agent) azeotropic with methanol, changing the azeotropic composition ratio of methanol and dimethyl carbonate, or eliminating azeotropic distillation. This is a method in which a distillate mainly composed of a distillate and an azeotrope-forming agent is extracted from the upper part of the distillation column, and a liquid substance mainly composed of dimethyl carbonate is extracted from the lower part of the distillation column to separate the distillate. As such an azeotropic distillation method, for example, in Japanese Patent Application Laid-Open No. 54-41820, methanol is azeotropically distilled by using an aliphatic hydrocarbon having 5 to 10 carbon atoms as an azeotrope and dimethyl carbonate is reduced to 40 to 60%. Are disclosed. Japanese Patent Publication No. Sho 62-8091 discloses that when diphenyl carbonate is produced by transesterification of dimethyl carbonate and phenol, benzene is azeotropically mixed with methanol in order to separate the by-produced methanol from the raw material dimethyl carbonate. Used as a substance forming agent,
A method is disclosed in which methanol is distilled off as a mixture with benzene.

The method using pressure distillation 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, Japanese Patent Application Laid-Open No. A method of distilling under the conditions and increasing the methanol concentration in the azeotrope of methanol and dimethyl carbonate distilled off at the top of the column to extract only dimethyl carbonate from the bottom of the column, and JP-A-2-212456 discloses that two distillation columns are used. The 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 method known as the extractive distillation method 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 main component as a bottom component. And a distillate rich in dimethyl carbonate is taken out as a top component (JP-A-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 and the organic extraction solvent as main components as a bottom component, and methanol as a main component. The extractive distillation method of separating methanol and dimethyl carbonate by extracting the distillate from the upper part of the distillation column has not been known at all.

[0006]

In the conventionally known method for producing dimethyl carbonate, the reaction is usually carried out in an excess of methanol in order to improve and improve the reaction yield of dimethyl carbonate. Therefore, not only must methanol and dimethyl carbonate be separated after the reaction, but also the economical production method cannot be achieved unless the separated methanol is recycled to the reaction zone as a raw material. Typically, methanol and dimethyl carbonate form 70% and 30% by weight azeotropes, respectively, at normal pressure. By changing the azeotropic composition and reducing the amount of excess dimethyl carbonate contained in methanol and recycled, not only the loss during purification and recycling is reduced, but also the reaction yield can be increased, In addition, it is naturally preferable that the equipment can be prevented from being enlarged.

However, in the above-mentioned known method, when methanol and dimethyl carbonate are separated from an azeotropic mixture or a mixture containing methanol and dimethyl carbonate as main components, high-purity methanol and dimethyl carbonate are obtained at a high recovery rate. However, since the distillation operation is performed under pressure, a large-diameter high-pressure distillation column is required, the equipment cost is increased, and disadvantages are unavoidable when the method is carried out on an industrial scale.

In the method using an azeotrope-forming agent with methanol, it is necessary to separate a new azeotrope in order to recycle methanol, so that it cannot be a very simple process and the reaction yield is improved. This necessitates an increase in energy for boiling and distilling off a large excess of methanol used as an azeotrope and an increase in the size of the separation column for methanol and an azeotrope-forming agent. 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 present inventors have conducted intensive studies on a method for separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components. The inventors have found a separation method capable of obtaining high-purity methanol and dimethyl carbonate at a high recovery rate by an extractive distillation method of extracting into an extraction solvent, and have completed the present invention.

That is, the present invention provides a method for separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components by distillation.
Organic solvent with a higher boiling point than dimethyl carbonate (however,
Excludes dimethyl oxalate. ) Is used as an extraction solvent for dimethyl carbonate, and dimethyl carbonate is extracted into the organic solvent, whereby dimethyl carbonate and a liquid substance containing the organic solvent as main components are taken out from the lower portion of the distillation column as a bottom component, and methanol is mainly extracted. This is a method for separating methanol and dimethyl carbonate by extractive distillation, wherein a distillate as a component is taken out from the top of the distillation column as a top component.

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

The aromatic hydroxy compound, which is an extraction solvent preferably used in the present invention, is an aromatic hydroxy compound represented by the general formula (1) of Chemical formula 1 wherein a hydroxy group is directly bonded to an aromatic group. If it is, what kind of thing may be used.

[0013]

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Examples of such Ar ¹ include phenyl, tolyl (each isomer), xylyl (each isomer), trimethylphenyl (each isomer), tetramethylphenyl (each isomer), and ethylphenyl (each isomer). Isomer), propylphenyl (each isomer), butylphenyl (each isomer),
Phenyl groups and various alkylphenyl groups such as diethylphenyl (each isomer), methylethylphenyl (each isomer), pentylphenyl (each isomer), hexylphenyl (each isomer), cyclohexylphenyl (each isomer) Various alkoxyphenyl groups such as methoxyphenyl (each isomer), ethoxyphenyl (each isomer), butoxyphenyl (each isomer); fluorophenyl (each isomer), chlorophenyl (each isomer), bromophenyl (each isomer) Various halogenated phenyl groups such as chloro (methyl) phenyl (each isomer), dichlorophenyl (each isomer); naphthyl (each isomer), methylnaphthyl (each isomer), dimethylnaphthyl (each isomer) Isomers), chloronaphthyl (each isomer), methoxynaphthyl (each isomer), cyanonaphthyl (each isomer) ) And the like, and naphthyl groups and substituted naphthyl groups; pyridyl (each isomer), cumaryl (each isomer), quinolyl (each isomer), methylpyridyl (each isomer), chloropyridyl (each isomer), methylcumaryl ( 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), and 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)
And the like.

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

[0017]

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Examples of such 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 And alicyclic groups such as cycloheptyl; benzyl, phenethyl (each isomer), phenylpropyl (each isomer), phenylbutyl (each isomer), methylbenzyl (each isomer)
And aralkyl groups. In these alkyl groups, alicyclic groups, and aralkyl groups, other substituents, for example, lower alkyl groups, lower alkoxy groups, cyano groups, halogens, and may have an unsaturated bond. You may.

Examples of such alkyl aryl ethers include, for example, 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 tolyl ether (each isomer), nonyl (ethylphenyl) ether (each isomer), decyl (butylphenyl) ether (each isomer) Isomer), 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 Ruether (each isomer), methyl ( (Methylphenyl) ether (each isomer), methyl (chlorophenyl) ether (each isomer), methyl (nitrophenyl) ether (each isomer), methyl (methoxyphenyl) ether (each isomer), methyl cumyl ether (each isomer) Each isomer), methyl (naphthyl) ether (each isomer), methyl (pyridyl) ether (each isomer), ethyl cumyl ether (each isomer), methyl (benzoylphenyl) ether (each isomer), ethyl xylyl Methyl ether (each isomer), benzyl xylyl ether, methyl (hydroxyphenyl) ether (each isomer), metrubiphenyl ether (each isomer), methyl (hydroxybiphenyl) ether (each isomer), methyl-2- (hydroxyphenyl) ) Propylphenyl ether (each isomer)

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

[0021]

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Examples of the dialkyl carbonate having R ¹ and R ² include, for example, 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), (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 an extraction solvent preferably used in the present invention is represented by the following general formula (4).

[0024]

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Examples of such an alkylaryl carbonate include methyl phenyl carbonate, ethyl phenyl carbonate, propyl phenyl carbonate (each isomer), allyl phenyl carbonate, butyl phenyl carbonate (each isomer), and pentyl phenyl carbonate (each isomer) ), Hexyl phenyl carbonate (each isomer), heptyl phenyl carbonate (each isomer), octyl tolyl carbonate (each isomer), nonyl (ethylphenyl) carbonate (each isomer), decyl (butylphenyl) carbonate (each isomer) Isomer), methyl tolyl carbonate (each isomer), ethyl tolyl carbonate (each isomer), propyl tolyl carbonate (each isomer), butyl tolyl carbonate (each isomer), allyl tolyl carbonate Carbonate (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 an extraction solvent preferably used in the present invention is represented by the following general formula (5).

[0027]

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

[0029]

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

[0031]

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Specific examples of such an alicyclic alcohol include cyclopentanol, cyclohexanol, methylcyclohexanol and the like. Preferably, these extraction solvents do not substantially form a minimum azeotrope with dimethyl carbonate under distillation conditions.
Further, those which do not form a new azeotrope with methanol are more preferable. The use of two or more types of extraction solvents is optional as long as the purity of methanol and dimethyl carbonate is not reduced, but one type is usually used in order to simplify the separation of the extraction solvent in a later step.

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

These extraction solvents are supplied from the upper part of the extraction distillation zone of methanol and dimethyl carbonate in the distillation column, are brought into gas-liquid contact with the vapor mainly composed of methanol and dimethyl carbonate, and are subjected to extractive distillation to extract the methanol in the vapor. By increasing the concentration, methanol and dimethyl carbonate can be separated. One 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 to be brought into gas-liquid contact with the vapor containing methanol and dimethyl carbonate in the distillation column, and the more the number of stages in the distillation column, the more the distillate is distilled off from the top of the distillation column. Although the purity of methanol is improved, when used in an excessively large amount, not only the extractive distillation column but also the apparatus for separating dimethyl carbonate from the extraction solvent and dimethyl carbonate becomes large, and the amount of utility used increases. 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 steam. Preferably at least 4% by weight.
More preferably, it is present in an amount of 0% by weight or more.

It is also possible to carry out extractive distillation under pressurized conditions within an allowable range to reduce 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 enrichment section. The extraction solvent thus supplied is brought into gas-liquid contact with methanol and dimethyl carbonate in the extraction distillation column to extract dimethyl carbonate, and moves downward of the extraction distillation column while increasing the dimethyl carbonate concentration in the liquid phase. The mixture containing methanol and dimethyl carbonate as main components may be supplied to the extractive distillation column in liquid or gaseous form. In the stage below the methanol and dimethyl carbonate mixture supply section, that is, in the methanol recovery section, extractive distillation is performed in the number of distillation stages necessary for sufficiently lowering the methanol concentration in the liquid phase, and then dimethyl carbonate and the extraction solvent are extracted from the bottom of the column. Extracted as a mixture. The mixture 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 is separated into dimethyl carbonate and the extraction solvent. At this time, dimethyl carbonate is obtained as a distillate at the top of the distillation column for separation, and the extraction solvent is obtained as a bottom liquid. The separated extraction solvent is recycled to the extraction distillation column again and used for separation of methanol and dimethyl carbonate. At this time, if impurities are accumulated in the extraction solvent, a part of the extraction solvent may be used if necessary. It is optional to take out or supply additional extraction solvent. Further, depending on the type of the extraction solvent, dimethyl carbonate and the extraction solvent can be supplied to the next step without separation and used. On the other hand, the methanol concentration in the vapor phase at the upper part of the extractive distillation column is sufficiently increased, and by distilling this from the upper part of the distillation column, a distillate mainly composed of methanol is obtained as a top component. If an extraction solvent is present in the top component, it is separated from the extraction solvent in the distillation zone corresponding to the extraction solvent recovery section having a sufficient number of theoretical plates for distillation and separation of the extraction solvent and methanol as necessary. Extracting from the top is also a preferred method. FIG. 2 shows an example of a process chart showing an embodiment of the present invention.

Regarding the distillation column used for the extractive distillation of the present invention, any type of plate column or packed column can be used, regardless of the type. As the tray column, for example, a distillation column having any type of plate columns such as bubble cap, uniflux, float valve, glitch ballast, flexi, sieve, ripple, turbo grid, venturi cascade, and kittel can be used. As a packed tower, for example, Raschig ring, Lessing ring, Bell saddle, Interlock saddle, Terralet, Pole ring, Cascade mini ring, Dickson packing, McMahon packing, Heli pack, Cannon packing, Good low packing, Through packing, etc. A packed distillation column can be used. It is also possible to adopt a form having a shelf portion and a filling portion as needed.

In performing extractive distillation in the present invention,
The descending liquid velocity and the ascending vapor velocity in the extractive distillation column differ depending on the type of extractive distillation column used, and when using a packed column, it depends on the type of packing material. When a tower is used, it is used within a range that does not cause weeping. In the present invention, when the reflux ratio of the extractive distillation column is increased, the effect of distilling methanol into the vapor phase increases, so that 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 from 0 to 10, preferably from 0.1 to 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]

Hereinafter, the present invention will be described in detail 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 a stage corresponding to 15 theoretical plates, and dimethyl carbonate and methanol were fed from the top to a plate corresponding to 30 theoretical plates. And a liquid mainly composed of methanol was extracted from the top of the column, and a mixed liquid mainly composed of dimethyl carbonate and phenol was extracted from the bottom of the column. The distillation column
A column having a diameter of 26 mm and Dickson packing (3 mmφ) packed with 50 theoretical plates is used. The reflux ratio is 0.2.
And

The feed amounts to the distillation column were such that the composition of dimethyl carbonate and methanol was 32 wt% and 68 wt%, respectively, and the mixture was 60 g / hr and phenol was 200 g / hr. When the temperature at the top of the distillation column was stabilized at 65 ° C., the composition of the distillate from the top of the distillation column was measured. As a result, 99.6 wt% of methanol and 0.4 wt% of dimethyl carbonate were obtained.
%Met.

Then, using the distillation apparatus shown in FIG. 3 for the purpose of separating dimethyl carbonate and phenol,
A mixture containing dimethyl carbonate and phenol as main components was supplied to the bottom of the distillation column, and dimethyl carbonate was extracted from the top of the distillation column without being supplied from an intermediate stage of the distillation column. The feed rate of the mixture mainly composed of dimethyl carbonate and phenol to the bottom of the distillation column was 220 g / hr. When the temperature at the top of the distillation column was stabilized, the composition of the distillate from the top of the distillation column As a result, the content of dimethyl carbonate was 97.4 wt% and the content of methanol was 2.6 wt%.

The recovery rates 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 middle stage of the distillation column, and methylphenyl ether was supplied as an extraction solvent. The distillation column has a column diameter of 26 mm and Dixon packing (3
mmφ), which is equivalent to 30 theoretical plates,
The reflux ratio was 0.2.

The feed amounts to the distillation column were a mixture of dimethyl carbonate and methanol of 32 wt% and 68 wt%, respectively, 60 g / hr, and methylphenyl ether of 140 g / hr.
g / hr. When the temperature at the top of the distillation column was stabilized, the composition of the distillate from the top of the distillation column was measured. As a result, 99.7% by weight of methanol and 0.1% of dimethyl carbonate were obtained.
3 wt%.

[0046]

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

[0047]

Example 4 Using the same distillation column as in Example 2, methylphenyl carbonate was supplied to the distillation column as an extraction solvent.
The amount supplied to the distillation column was 60 g of a mixture of dimethyl carbonate and methanol having a composition of 32 wt% and 68 wt%, respectively.
/ Hr, methylphenyl carbonate is 140 g / hr
Met. When the temperature at the top of the distillation column was stabilized, the composition of the distillate from the top of the distillation column was measured.
9.4 wt% and dimethyl carbonate were 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 feed amount to the distillation column was 60 g / h of a mixture of dimethyl carbonate and methanol having a composition of 32 wt% and 68 wt%, respectively.
r, ethylene carbonate was 190 g / hr.
When the temperature at the top of the distillation column was stabilized, the composition of the distillate from the top of the distillation column was measured. As a result, 99.1 wt% of methanol was obtained.
%, 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 feed amount to the distillation column was 60 g / h of a mixture of dimethyl carbonate and methanol having a composition of 32 wt% and 68 wt%, respectively.
r, diphenyl carbonate was 190 g / hr. When the temperature at the top of the distillation column was stabilized, the composition of the distillate from the top of the distillation column was measured.
wt% and 0.8 wt% of dimethyl carbonate.

[0050]

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

[0051]

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

[0052]

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

[0053]

According to the extractive distillation of the present invention in which methanol and dimethyl carbonate are separated by distillation, the mixture of methanol and dimethyl carbonate is separated by extracting and extracting dimethyl carbonate with an organic solvent. It is possible to obtain Further, since high-purity methanol can be recycled to the reactor, an efficient dimethyl carbonate production process can be assembled.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the 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.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C07C 69/96 C07C 29/84 C07C 31/04 C07C 68/08

Claims (12)

(57) [Claims] An organic solvent having a boiling point higher than that of dimethyl carbonate (eg, dimethyl oxalate) when separating methanol and dimethyl carbonate from a mixture containing methanol and dimethyl carbonate as main components by distillation.
except for. ) Is used as an extraction solvent for dimethyl carbonate, and dimethyl carbonate is extracted into the organic solvent, whereby dimethyl carbonate and a liquid substance containing the organic solvent as main components are taken out from the lower portion of the distillation column as a bottom component, and methanol is mainly extracted. A method for separating methanol and dimethyl carbonate by extractive distillation, wherein a distillate as a component is taken out from the top of the distillation column as a top component. 2. The extraction solvent for dimethyl carbonate is one or two selected from the group consisting of aromatic hydroxy compounds, alkylaryl ethers, dialkyl carbonates, alkylaryl carbonates, alkylene carbonates, diaryl carbonates, and alicyclic alcohols. The method for separating methanol and dimethyl carbonate by the extractive distillation method according to claim 1, wherein the above is used. 3. An extraction solvent for dimethyl carbonate.
, Aromatic hydroxy compounds, alkyl arylates
, Dialkyl carbonate, alkyl aryl carbonate
, Diaryl carbonate and alicyclic
One or two types selected from the group of cocoa
The extractive distillation according to claim 1, wherein the above is used.
Of separation of methanol and dimethyl carbonate by the method
Law. 4. The method according to claim 1, wherein the aromatic hydroxy compound is phenol or phenol.
And cresols, where alkyl aryl ethers are
Tyl phenyl ether and methyl tolyl ether
Dialkyl carbonate is diethyl carbonate
Yes, alkyl aryl carbonate is methylphenyl
Carbonate, and diaryl carbonate is
Nylcarbonate, Alicyclic alcohol
The extractive distillation method according to claim 3, wherein is cyclohexanol.
Method for separating methanol and dimethyl carbonate by HPLC. 5. The method for separating methanol and dimethyl carbonate by the extractive distillation method according to claim 4 , wherein phenol and / or cresol is used as an extraction solvent for dimethyl carbonate. 6. The method for separating methanol and dimethyl carbonate by extractive distillation according to claim 4 , wherein phenol is used as an extraction solvent for dimethyl carbonate. 7. An extraction solvent for dimethyl carbonate.
And methyl phenyl ether and / or methyl tri
5. The extraction according to claim 4, wherein
Of methanol and dimethyl carbonate
Release method. 8. An extraction solvent for dimethyl carbonate.
Using methyl phenyl ether
Methanol and dimethyl by the extractive distillation method according to claim 4.
Separation method of carbonate. 9. An extraction solvent for dimethyl carbonate.
The use of diethyl carbonate
The methanol and dimethyl cation by the extractive distillation method according to claim 4
-Method for separating carbonate. 10. An extraction solvent for dimethyl carbonate.
The use of methyl phenyl carbonate
5. The method of claim 4, wherein methanol and dimethyl alcohol are extracted.
A method for separating chill carbonate. 11. An extraction solvent for dimethyl carbonate.
Wherein diphenyl carbonate is used.
Methanol and dimethyl by the extractive distillation method according to claim 4.
Separation method of carbonate. 12. An extraction solvent for dimethyl carbonate.
Wherein cyclohexanol is used.
Item 4. Methanol and dimethyl car by the extractive distillation method according to item 4.
How to separate Bonate.