JPH09176061A - Continuous production of dialkyl carbonate and diol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a dialkyl carbonate and diols of high purity can continuously be produced in a short reactional time in a high yield. SOLUTION: A cyclic carbonate is reacted with an aliphatic monohydric alcohol in a continuous multistage distillation column equipped with a transesterification reactor on the outside thereof to take out low-boiling components containing a dialkyl carbonate from the column top. High-boiling components containing a diol and the cyclic carbonate are continuously taken out of the column bottom and continuously fed to a continuous hydrolytic reactor to hydrolyze the unreacted cyclic carbonate. Thereby, the diol is continuously produced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for continuously producing a dialkyl carbonate and a diol by reacting a cyclic carbonate with an aliphatic monoalcohol.

[0002]

2. Description of the Related Art Several proposals have been made for a method for producing a dialkyl carbonate and a diol from a reaction of a cyclic carbonate and an aliphatic monoalcohol, but most of them are related to a catalyst. As such a catalyst, for example, an alkali metal or a basic compound containing an alkali metal [US Pat. No. 3,642,858, JP-A-54-48715 (US Pat.
No. 181676)], tertiary aliphatic amine [JP-A-51-1222025 (US Pat. No. 4,062,884).
Specification)], a thallium compound [JP-A-54-4871]
No. 6 (US Pat. No. 4,307,032)], tin alkoxides (JP-A No. 54-63023), and zinc, aluminum, and titanium alkokinds (JP-A No. 5).
4-148726), a composite catalyst composed of a Lewis acid and a nitrogen-containing organic base (JP-A-55-64550),
A phosphine compound (JP-A-55-64551),
Quaternary phosphonium salt (JP-A-56-10144), cyclic amidine (JP-A-59-106436), zirconium, titanium and tin compounds [JP-A-63-41432 (US Pat. No. 4,661,609). Description)] A solid strong basic anion exchanger having a quaternary ammonium group (Japanese Patent Laid-Open No. 63-238043),
A solid selected from an ion exchange resin having a tertiary amine or quaternary ammonium group, a strongly acidic or weakly acidic ion exchange resin, an alkali metal or alkaline earth metal silicate impregnated in silica, and an ammonium exchanged zeolite. Catalyst [JP-A-64-31737 (US Pat. No. 4,691,041)] Homogeneous catalyst selected from tertiary phosphine, tertiary arsine, tertiary stibine, divalent sulfur or selenium compound (US Patent No. 4734518
No.) and the like have been proposed.

Four reaction systems have been proposed so far. These four reaction systems are used in the most typical reaction example, which is a method for producing dimethyl carbonate and ethylene glycol from ethylene carbonate and methanol. That is, the first method is a complete batch reaction in which ethylene carbonate, methanol and a catalyst are charged into an autoclave which is a batch type reaction vessel, and the reaction is carried out at a reaction temperature above the boiling point of methanol under pressure for a predetermined reaction time. Reaction system [US Pat. No. 3,642,858, JP-A-54-48715 (US Pat. No. 418)
1676), JP-A-54-63023,
JP-A-54-148726, JP-A-55-645
50, JP-A-55-6455, JP-A-56
-10144 publication].

The second method uses an apparatus in which a distillation column is provided in the upper part of a reaction kettle, and ethylene carbonate, methanol and a catalyst are charged in a reaction vessel and heated to a predetermined temperature to proceed the reaction. Let In this case, the produced dimethyl carbonate and methanol form the lowest azeotrope (boiling point 63 ° C./760 mmHg), so this azeotrope is methanol (boiling point 64.6 ° C. /
760 mmHg). In this system, a distillation column is provided for separating the azeotrope and methanol. That is, the dimethyl carbonate vapor and methanol vapor evaporated from the reaction kettle are separated into an azeotropic mixture vapor and liquid methanol while rising in the distillation column,
The vapor of the azeotropic mixture is distilled off from the top of the distillation column, and liquid methanol is flowed down and returned to the reaction vessel to be used in the reaction. Further, in this system, in order to supplement the methanol that is azeotropically distilled with the dimethyl carbonate that is produced, methanol is continuously or batchwise added to the reaction vessel, but in any case, In this system, the reaction is allowed to proceed only in a batch reactor in which the catalyst, ethylene carbonate and methanol are present. Therefore, the reaction is batch type, and the reaction is carried out under reflux for a long time of 3 to 20 hours.

In this system, one product, dimethyl carbonate, is continuously withdrawn from the reaction system, while the other product, ethylene glycol, is unreacted with ethylene in the presence of a catalyst. It will stay with the carbonate for a long time. In order to suppress the side reaction due to long-term retention of ethylene glycol and ethylene carbonate and prevent the decrease in selectivity, it is necessary to use a large excess of methanol with respect to ethylene carbonate batch-wise charged in the reaction vessel. In fact, in the methods proposed so far, 14 moles per mole of ethylene carbonate (or propylene carbonate) (US Pat.
No. 201), 17 moles (JP-A 1-311054)
JP-A No. 51-122025 (US Pat. No. 4,062,884), 23 mol [JP-A No. 54-48716 (US Pat. No. 4307).
No. 032)]], a large excess of methanol is used.

[0006] In the third method, a mixed solution of ethylene carbonate and methanol is continuously supplied to a pipette reactor kept at a predetermined reaction temperature, and unreacted ethylene carbonate, methanol and products are discharged from the other outlet. It is a continuous reaction system in which a reaction mixture containing a certain dimethyl carbonate and ethylene glycol is continuously withdrawn in a liquid state.
Two methods are used depending on the form of the catalyst used.
That is, a method in which a homogeneous catalyst is used to pass through a tubular reactor together with a mixed solution of ethylene carbonate and methanol, and after the reaction, the catalyst is separated from the reaction mixture [JP-A-63-41432 (US Pat. 4661
No. 609), U.S. Pat. No. 4,734,518], and a method using a heterogeneous catalyst fixed in a tubular reactor [JP-A-63-238043 and JP-A-6-38043].
4-31737 (U.S. Pat. No. 4,691,041)]. Since the reaction of producing dimethyl carbonate and ethylene glycol by the reaction of ethylene carbonate and methanol is an equilibrium reaction, in the continuous flow reaction system using this tubular reactor, the reaction rate of ethylene carbonate is determined by the feed composition ratio and the reaction temperature. It is impossible to raise the reaction rate above the equilibrium reaction rate. For example, JP-A-63-41432 (US Pat. No. 466)
According to Example 1 of (1609 specification), the reaction rate of ethylene carbonate is 25% in the flow reaction at 130 ° C. using a raw material having a charged molar ratio of methanol / ethylene carbonate = 4/1. This means that a large amount of unreacted residual ethylene carbonate and methanol in the reaction mixture must be separated and recovered and recycled to the reactor.
1737 (US Pat. No. 4,691,104)
In this method, a lot of equipments for separation, purification, recovery and recycling are used.

The fourth method is a reactive distillation method, that is, ethylene carbonate and methanol are continuously fed into a multi-stage distillation column to carry out a reaction in the presence of a catalyst in a plurality of stages of the distillation column, and at the same time, a product is produced. A continuous production method in which a certain dimethyl carbonate and ethylene glycol are separated [JP-A-4-198141 and JP-A-4-2302].
43, JP-A-5-213830 (German Patent 4129316) and JP-A-6-9507 (German Patent 4216121)].

As described above, the methods proposed so far for producing a dialkyl carbonate and a diol from a cyclic carbonate and an aliphatic monoalcohol are as follows: Batch reaction method using a reaction kettle (3) Liquid flow reaction method using a tubular reactor (4) Reactive distillation method, each of which has the following problems.

That is, in the cases of (1) and (3), the upper limit of the reaction rate of the cyclic carbonate is determined by the charged composition and temperature, so that the reaction cannot be completely terminated.
When the reaction rate of the cyclic carbonate is less than 100%, the cyclic carbonate and the diol coexist in the reaction solution.
To obtain the diol from this reaction solution, a distillation separation method is usually used. For example, in the case of producing dimethyl carbonate and ethylene glycol from ethylene carbonate and methanol, if the pressure is 72 torr or more, an azeotropic mixture is not formed. Therefore, it is possible to separate ethylene carbonate and ethylene glycol only by distillation separation.
In this case, if the distillation temperature is too high, ethylene glycol will accelerate the decomposition of ethylene carbonate,
It usually must be distilled off under reduced pressure to form an azeotrope (McKetta, "Enclosed").
ia of Chemical Processing
and Design "vol. 20, p. 194,
Marcel Dekker, 1984). Therefore, it is difficult to quantitatively obtain unreacted ethylene carbonate and the product ethylene glycol from the reaction mixture. Therefore, conventionally, a method for obtaining ethylene glycol from this azeotropic mixture has been proposed. For example, in the method described in Example 50 of JP-A-64-31737, the reaction vessel distillate is distilled in a distillation column (B) to obtain a low boiling point fraction consisting of methanol and dimethyl carbonate, and ethylene glycol. And a bottom liquid containing ethylene carbonate, and the bottom liquid is distilled in a distillation column (D) to separate a bottom liquid containing ethylene carbonate and an ethylene glycol / ethylene carbonate azeotrope. Further, the bottom liquid composed of ethylene carbonate is circulated to the reaction vessel again, and the diol is obtained by hydrolyzing the ethylene glycol / ethylene carbonate azeotrope to convert the cyclic carbonate into the diol. However, this method has a problem that the reaction rate is low and the amount of ethylene carbonate circulated is large.

Further, in the case of (2), in order to increase the reaction rate of the cyclic carbonate, the dialkyl carbonate produced must be distilled off using an extremely large amount of aliphatic monoalcohol, which results in a long reaction. Need time.
In the case of (4), compared to (1), (2), and (3), it is possible to proceed the reaction at a higher reaction rate,
In fact, examples of 100% ethylene carbonate conversion are also described. However, no examples have been known in which a dialkyl carbonate or a diol was obtained in a high yield without using a pure aliphatic monoalcohol.

On the other hand, the dimethyl carbonate produced by the method (4) distills out as a low boiling point component together with unreacted methanol. Since dimethyl carbonate and methanol form an azeotropic mixture, a special separation method such as distillation under pressure (Japanese Patent Laid-Open No. 51-108019) is used to obtain dimethyl carbonate from the distillate. ing. Although dimethyl carbonate free of methanol is usually obtained by this separation method, it is difficult to obtain pure methanol substantially free of dimethyl carbonate because methanol is obtained as a mixture with dimethyl carbonate. For example, in the examples of JP-A-51-108019, a mixture of methanol / dimethyl carbonate (weight concentration ratio: 70/30) is used.
Was separated by distillation to obtain pure dimethyl carbonate as a bottom component, but the top fraction was methanol /
Dimethyl carbonate mixture (weight concentration ratio: 95/5)
Only got it.

As described above, since an extra separation step is required to obtain a pure aliphatic monoalcohol, an industrial method for producing dimethyl carbonate is not pure methanol but this methanol / dimethyl carbonate mixture. Is highly desirable. However, in the method (4), almost no example is known in which a methanol / dimethyl carbonate mixture is used as a raw material. The only exception is Example 5 of JP-A-5-213830, which uses an aliphatic monoalcohol / dialkyl carbonate mixture (weight concentration ratio = 70/30) to obtain an ethylene carbonate conversion rate of 62.8%. Only obtained (conversion calculated from bottom composition).

Therefore, in order to convert the cyclic carbonate substantially completely in the method (4), as shown in JP-A-6-9507, only a dialkyl carbonate / aliphatic monoalcohol mixture is used. Instead, it was necessary to supply pure aliphatic monoalcohol. However, for that purpose, a complicated step of separating the methanol / dimethyl carbonate azeotrope to obtain methanol substantially free of dimethyl carbonate (for example, a method of combining two distillation columns having different operating pressures: JP-A No. 2-2980) -212456) is required separately. In fact, in JP-A-6-9507, the pure aliphatic monoalcohol obtained by this method is used.

Furthermore, since the method (4) is a method of obtaining a dialkyl carbonate and a diol by using a reversible equilibrium reaction, a cyclic aliphatic carbonate is substantially 100% converted by using a pure aliphatic monoalcohol. Even in some cases, traces of unreacted cyclic carbonate will essentially remain. Therefore, rectification separation is required to obtain a highly pure diol.

Thus, no method has been proposed so far in which a cyclic carbonate is reacted at a high conversion rate to produce a highly pure dialkyl carbonate and a diol in a short reaction time with a high yield and continuously. It was

[0016]

SUMMARY OF THE INVENTION There is no such drawback as the methods proposed so far, and a cyclic carbonate is reacted at a high conversion rate, and a highly pure dialkyl carbonate and a diol are reacted in a short time. It is an object of the present invention to provide a method of continuously producing in good yield in time.

[0017]

As a result of intensive studies, the inventors of the present invention have found that a continuous transesterification reaction using a continuous multistage distillation column provided with an external transesterification reactor and a continuous hydrolysis reaction apparatus using a continuous hydrolysis reaction apparatus are performed. It has been found that a diol substantially free of cyclic carbonate can be easily obtained by combining hydrolysis reactions, and the present invention has been completed based on this finding.

That is, the present invention is as follows. 1. When a dialkyl carbonate and a diol are continuously produced from a cyclic carbonate and an aliphatic monoalcohol, (i) the cyclic carbonate and the aliphatic monoalcohol as raw material compounds are continuously supplied to a continuous multistage distillation column, Is discharged from a side outlet provided in the middle stage and / or the lowest stage of the distillation column, introduced into a transesterification reactor provided outside the distillation column, and allowed to exist in the reactor. After reacting by contacting the transesterification catalyst and the raw material compound, the esterification catalyst is circulated to a continuous multistage distillation column by introducing it into a circulation inlet provided in a stage above the stage having the outlet, A dialkylcarbonate produced while reacting in the transesterification reactor or both in the reactor and in the continuous multistage distillation column. Low boiling component with continuously withdrawn from the top of continuous multistage distillation column, a first step of extracting the lower portion of the column extraction was continuously from a lower portion of the column containing the product diol and unreacted cyclic carbonate containing, (i
i) The bottom product of the first step containing unreacted cyclic carbonate and water are continuously supplied to a continuous hydrolysis reactor, and the unreacted cyclic carbonate is continuously supplied in the continuous hydrolysis reactor. A method for continuously producing a dialkyl carbonate and a diol, which comprises a second step of continuously extracting a reaction liquid containing a produced diol from the continuous hydrolysis reaction device while hydrolyzing. 2. A method for continuously producing the above dialkyl carbonate and diol, wherein a mixture of a dialkyl carbonate and an aliphatic monoalcohol is supplied to a continuous multistage distillation column instead of the aliphatic monoalcohol. 3. A method for continuously producing the dialkyl carbonate and the diol according to 1 or 2 above using a continuous multi-stage distillation column in the presence of a transesterification catalyst. 4. When continuously supplying the cyclic carbonate and the aliphatic monoalcohol to the continuous multi-stage distillation column, the cyclic carbonate is continuously supplied to the upper part of the continuous multi-stage distillation column, and the aliphatic monoalcohol is gaseous to the lower part of the continuous multi-stage distillation column. The method for continuously producing the above-mentioned 1, 2 or 3 dialkyl carbonate and diol, which are continuously supplied by the method. 5. When the unreacted cyclic carbonate is continuously hydrolyzed, the hydrolysis is performed in the presence of a hydrolysis catalyst composed of a solid catalyst and / or a homogeneous catalyst.
A method for continuously producing 3 or 4 dialkyl carbonate and diol. 6. Prior to continuously supplying the lower column withdrawal product of the first step to the continuous hydrolysis reactor, the lower column withdrawal product is continuously fed to a low boiling point component separation column composed of a continuous multi-stage distillation column to obtain an aliphatic monoester. A low-boiling component containing alcohol and dialkyl carbonate is continuously withdrawn from the upper part of the low-boiling component separation column, and a high-boiling component containing diol and cyclic carbonate is withdrawn from the lower part of the low-boiling component separation column. The extract from the upper part of the separation column is circulated by continuously supplying it to the continuous multistage distillation column of the first step, while the extract from the lower part of the low boiling point component separation column is supplied to the continuous hydrolysis reactor. A method for continuously producing the above-mentioned 1, 2, 3, 4 or 5 dialkyl carbonate and diol. 7. The continuous hydrolysis reactor is a continuous hydrolysis reactor consisting of a tubular reactor or a tank reactor, and the reaction liquid containing the produced diol and carbon dioxide gas is continuously supplied to a diol separation column consisting of a continuous multistage distillation column. Then, the low boiling point component containing carbon dioxide is continuously extracted from the upper part of the diol separation column, and the diol is continuously extracted from the lower part of the diol separation column. A method for continuously producing carbonate and diol. 8. The continuous hydrolysis reaction device is a continuous hydrolysis reaction column consisting of a continuous multi-stage distillation column, and the low boiling point component containing carbon dioxide gas produced is continuously withdrawn from the upper portion of the continuous hydrolysis reaction column, and the diol is the continuous hydrolysis reaction. A method for continuously producing the above-mentioned 1,2,3,4,5, or 6 dialkyl carbonate and diol which are withdrawn from the lower part of the reaction tower. 9. When the product extracted from the lower part of the low boiling point component separation column is supplied to the continuous hydrolysis reaction column, the product extracted from the lower part is supplied to the upper part of the continuous hydrolysis reaction column above the position for extracting the diol. A method for continuously producing carbonate and diol. 10. A method for continuously producing a dialkyl carbonate and a diol according to 8 or 9 above, wherein water is supplied to an upper portion from a diol extraction port when water is continuously supplied to a continuous hydrolysis reaction tower. 11. A cyclic carbonate and a diol are compounds that form a minimum azeotrope, and before the material extracted from the lower part of the low boiling point component separation column is fed to the continuous hydrolysis reactor,
The substance extracted from the lower part of the low boiling point component separation column is supplied to an azeotropic separation column comprising a continuous multi-stage distillation column, the diol is continuously extracted from the lower part of the azeotropic separation column, and the minimum amount of cyclic carbonate and diol is obtained. The low boiling point component consisting of an azeotropic mixture is continuously withdrawn from the upper part of the azeotropic separation column, and the substance withdrawn from the upper part of the azeotropic separation column and water are continuously supplied to a continuous hydrolysis reactor. A method for continuously producing a dialkyl carbonate and a diol. 12. A method for continuously producing the dialkyl carbonate and the diol according to 11 above, which comprises supplying a hydrolysis reaction solution from a continuous hydrolysis reaction apparatus to an azeotropic separation column. 13. The continuous hydrolysis reaction apparatus is a continuous hydrolysis reaction tower consisting of a continuous multi-stage distillation tower, and a low boiling point component containing an aliphatic monoalcohol, a dialkyl carbonate and carbon dioxide gas is continuously extracted from the upper part of the continuous hydrolysis reaction tower. It is circulated by supplying it to the continuous multi-stage distillation column of the first step, and the diol is extracted from the lower part of the continuous hydrolysis reaction column as described above, 1, 2, 3, 4, 5, 6, 8, 9, 1.
A method for continuously producing 0, 11 or 12 dialkyl carbonate and a diol. 14． A method for continuously producing the above-mentioned 13 dialkyl carbonate and diol, which are supplied to the continuous multi-stage distillation column of the first step after removing carbon dioxide gas or carbon dioxide gas and water from the product extracted from the upper part of the continuous hydrolysis reaction column. 15. The method for continuously producing the dialkyl carbonate and the diol according to 13 above, wherein the lower-column extract of the first step is supplied to the continuous hydrolysis column, and the lower-column extract is supplied above the diol extraction port.

The method of the present invention allows the reaction to proceed in a shorter reaction time and obtains a highly pure diol as compared with a conventional method, for example, a method using only a continuous multi-stage distillation column. The reason seems to be as follows. In the reaction of the present invention, a dialkyl carbonate (C) and a diol (D) are produced from an annulation carbonate (A) and an aliphatic monoalcohol (B).
It is a reversible equilibrium transesterification reaction represented by the following general formula (I).

[0020]

Embedded image

[Wherein R ¹ is a divalent group-(CH ₂ ) _m
(M is an integer of 2 to 6) and one or more hydrogens thereof may be substituted with an alkyl group having 1 to 10 carbons or an aryl group. R ² is 1 having 1 to 12 carbon atoms
Represents a valent aliphatic group in which at least one hydrogen has 1 carbon atom
It may be substituted with an alkyl group or aryl group of 10. This transesterification reaction usually proceeds in the liquid phase. Therefore, in order to shorten the reaction time, the low boiling point product of the dialkyl carbonate and the diol produced as a result of the reaction is used in the reaction solution. It needs to be removed from the inside as quickly as possible.

However, in the reaction system described in the prior art, the reaction time cannot be shortened by any means when the cyclic carbonate is substantially 100% converted. Since the conversion rate of the cyclic carbonate gradually decreases as the reaction proceeds and the concentration of the cyclic carbonate decreases, the higher the reaction rate of the cyclic carbonate, the longer the reaction time. This is because it is necessary to react with a large amount of aliphatic alcohol for a long time in order to completely react the cyclic carbonate. Moreover, even when the cyclic carbonate is substantially 100% converted by using a pure aliphatic monoalcohol, a small amount of unreacted cyclic carbonate remains as described above, and therefore it is difficult to obtain a highly pure diol. Distillation separation becomes necessary.

On the other hand, in the method of the present invention, in the reactor of the continuous multistage distillation column equipped with the transesterification reactor outside,
Or, in the reactor and the distillation column, in the transesterification reaction of the cyclic carbonate and the aliphatic monoalcohol, by reacting without increasing the conversion rate unnecessarily, reduction of the amount of the aliphatic monoalcohol and reaction time Can be shortened. Further, since the unreacted cyclic carbonate is eliminated by the hydrolysis reaction, a highly pure diol can be obtained without requiring a complicated separation step of separating the cyclic carbonate.

Since the unreacted cyclic carbonate is converted to a diol by hydrolysis, the unreacted cyclic carbonate to be hydrolyzed does not contribute to the yield of dialkyl carbonate, but the dialkyl carbonate selectivity based on the consumed methanol is high. For example, this does not constitute a disadvantage in implementing the present invention. Rather, the produced diol has a larger molar amount than the produced dialkyl carbonate, and in this range, it is a preferable method in that the desired amount ratio of the dialkyl carbonate and the diol can be produced.

Further, in the present invention, the reaction is carried out in the first step at a conversion rate of the cyclic carbonate of less than 100%. Therefore, the pure aliphatic monoalcohol, which was indispensable for reacting the cyclic carbonate at a conversion of substantially 100% in the conventional reactive distillation method, is not always necessary in the present invention, and the aliphatic monoalcohol and the dialkyl are not necessarily required. A mixture of carbonates can be used to react the cyclic carbonates at 100% conversion.

The continuous multi-stage distillation column used in the first step of the present invention is a distillation column having a plurality of stages with two or more stages of distillation, and any column capable of continuous distillation can be used. It may be one. The term "stage" as used in the present invention means a theoretical stage, and in the case of a distillation column having no physical stage such as a packed column, the H. E. FIG. T. P. The value obtained by dividing the filling height by (height per theoretical plate) is used as the number of plates. Examples of such a continuous multi-stage distillation column include a tray column type using trays such as bubble trays, perforated plate trays, valve trays, countercurrent trays, Raschig rings, Lessing rings, Pall rings, Berlu saddles, and interludes. Use any type of column that is normally used as a continuous multi-stage distillation column, such as a packed column type filled with various packing such as Rox saddle, Dickson packing, McMahon packing, Helipack, Sulzer packing, Melapack, etc. can do. Further, a distillation column having both a tray portion and a portion filled with packing material is also preferably used. When a solid catalyst is used, a packed column distillation column in which the solid catalyst is a part or all of the packing is also preferably used. Further, the continuous multi-stage distillation column used in the first step of the present invention may be the above-mentioned distillation column alone, or may be a combination of a plurality of the distillation columns connected in series or in parallel. it can.

In the method of the present invention, the side extraction ports provided on the sides of the continuous multi-stage distillation column can be provided as many as required between the middle stage and / or the bottom stage of the distillation column. Further, the circulation introducing port may be provided above the corresponding side extracting port, and the necessary number can be provided. When a plurality of side withdrawal ports are provided, the liquids withdrawn from two or more different side withdrawal ports can be combined and introduced into the transesterification reactor, or when a plurality of transesterification reactors are used, It is also possible to join the reaction solutions extracted from two or more different transesterification reactors and then to introduce them into the circulation inlet. Moreover, these can also be combined.

Preferably, the number of transesterification reactors provided outside the continuous multistage distillation column is two or more, and the stage provided with a side outlet from the continuous multistage distillation column connected to the transesterification reactors. Are different from each other, and more preferably, there are two or more transesterification reactors provided outside the continuous multistage distillation column, and a stage provided with a side outlet from the distillation column connected to the reactor. Are different from each other, and the stages of the circulation inlets provided in the distillation column for circulating from the reactor to the distillation column are different stages.

In the present invention, a transesterification reactor is provided between the side withdrawal port of the continuous multi-stage distillation column and the circulation inlet port of the distillation column, but this transesterification reactor may be of the flow type. It can be anything
For example, a tubular reactor, a tank reactor or the like is used. The cyclic carbonate used as a raw material in the present invention is a compound represented by the above (A), and examples thereof include alkylene carbonates such as ethylene carbonate and propylene carbonate, and 1,3-dioxacyclohexa-
2-one, 1,3-dioxacyclohepta-2-one and the like are preferably used, ethylene carbonate and propylene carbonate are more preferably used from the viewpoint of easy availability, and ethylene carbonate is particularly preferably used.

The aliphatic monoalcohol as the other raw material is a compound represented by the above (B), which has a lower boiling point than the diol produced. Therefore, for example, methanol, ethanol, propanol (each isomer), allyl alcohol, butanol (each isomer), 3-buten-1-ol, amyl alcohol (each) may vary depending on the kind of the cyclic carbonate used. Isomer), hexyl alcohol (each isomer), heptyl alcohol (each isomer), octyl alcohol (each isomer), nonyl alcohol (each isomer), decyl alcohol (each isomer), undecyl alcohol (each isomer) Body), dodecyl alcohol (each isomer), cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, methylcyclopentanol (each isomer), ethylcyclopentanol (each isomer), methylcyclohexanol (each isomer) Isomer), ethylcyclohexanol (each different Body), dimethyl cyclohexanol (isomers), diethyl cyclohexanol (isomers), phenylcyclohexanol (isomers), benzyl alcohol, phenethyl alcohol (isomers), phenyl propanol (isomers)
In addition, in these aliphatic monoalcohols, halogen, a lower alkoxy group, a cyano group,
Alkoxycarbonyl group, aryloxycarbonyl group,
It may be substituted with a substituent such as an acyloxy group or a nitro group.

Among such aliphatic monoalcohols, alcohols having 1 to 6 carbon atoms are preferably used, and when ethylene carbonate is used as the cyclic carbonate, methanol, ethanol and propanol are particularly preferable. (Each isomer) and butanol (each isomer) having 1 to 4 carbon atoms. The process of the present invention is carried out by carrying out the reaction represented by the general formula (I) in a transesterification reactor in the presence of a catalyst, or in a continuous multistage distillation column together with a transesterification reactor in the presence of a catalyst, and at the same time, by the reaction, It is also one of the features of the present invention to use a reactive distillation system in which the low boiling point product that comes in is separated from the reaction system by distillation.

In the method of the present invention, it is necessary that at least the transesterification catalyst is present in these transesterification reactors, and in addition, it is preferable that the transesterification catalyst is also present inside the continuous multistage distillation column. .
Any method may be used as the method for allowing the transesterification catalyst to exist in the transesterification reactor in the first step or in the reaction system including the transesterification reactor and the continuous multistage distillation column. In the case of a homogeneous catalyst that dissolves in the reaction solution below, the ester exchange catalyst may be present in the reaction system by continuously supplying the transesterification catalyst to the transesterification reactor and / or the continuous multistage distillation column. In the case of a heterogeneous catalyst that can or does not dissolve in the reaction solution under the reaction conditions, the solid catalyst is placed only in the transesterification reactor or both in the transesterification reactor and the continuous multistage distillation column. As a result, a transesterification catalyst can be present in the reaction system. A method in which these are used in combination, for example, a method in which a solid catalyst is placed in the reactor and / or the distillation column and then a homogeneous catalyst is used may be used.

The homogeneous catalyst is used in the transesterification reactor and / or
Alternatively, when continuously supplied to the continuous multi-stage distillation column, they may be supplied simultaneously with the cyclic carbonate and / or the aliphatic alcohol, or may be supplied at a position different from the starting material. Further, when a heterogeneous solid catalyst is used, it is also preferable to fill the distillation column with a solid catalyst that also has the effect of packing the distillation column.

The transesterification catalyst used in the present invention
Various media known so far are used as the medium.
can do. For example, lithium, sodium,
Lithium, rubidium, cesium, magnesium, calci
Alkali metals such as um, strontium and barium, and
And alkaline earth metals; alkali metals and alkaline earth
Metal hydrides, hydroxides, alkoxides,
Basic compounds such as reeloxides and amidates
Kinds; Alkali metal and alkaline earth metal carbonates,
Basic compounds such as bicarbonates and organic acid salts;
Luamine, tributylamine, trihexylamine,
Tertiary amines such as benzyl diethylamine; N-alkyl
Pyrrole, N-alkylindole, oxazole, N
-Alkylimidazole, N-alkylpyrazole, o
Oxadiazole, pyridine, alkyl pyridine, quinoli
, Alkyl quinoline, isoquinoline, alkyl isoki
Norrin, acridine, alkyl acridine, phenanthate
Lorin, alkylphenanthroline, pyrimidine, al
Kirpyrimidine, pyrazine, alkylpyrazine, thoria
Nitrogen-containing heteroaromatic compounds such as gin and alkyltriazine
Kinds; diazabicycloundecene (DBU), diazabicis
Cyclic amidines such as chrononene (DBN);
System, thallium halide, thallium hydroxide, tariu carbonate
Organic acid salts of aluminum, thallium nitrate, thallium sulfate, thallium
Compounds such as thallium compounds; tributylmethoxytin, tri
Butylethoxytin, dibutyldimethoxytin, diethyldi
Ethoxytin, dibutyldiethoxytin, dibutylphenoxy
Sitin, diphenylmethoxytin, dibutyltin acetate, sodium chloride
Tin compounds such as ribyl tin and tin 2-ethylhexanoate;
Dimethoxyzinc, diethoxyzinc, ethylenedioxy
Zinc compounds such as lead and dibutoxyzinc; aluminum
Remethoxide, aluminum triisopropoxide,
Aluminum compounds such as luminium tributoxide;
Tetramethoxy titanium, tetraethoxy titanium, tetra
Butoxy titanium, dichlorodimethoxy titanium, tetry
Sopropoxy titanium, titanium acetate, titanium acetylacetate
Titanium compounds such as tonato; trimethylphosphine,
Triethylphosphine, tributylphosphine, trif
Phenylphosphine, tributylmethylphosphonium hara
Id, trioctylbutylphosphonium halide, tri
Phosphorus compounds such as phenylmethylphosphonium halides
Kinds; Zirconium halide, Zirconium acetylate
Setonate, zirconium alkoxide, zirconium acetate
Zirconium compounds such as um; lead and compounds containing lead
Items such as PbO, PbO_Two, Pb_ThreeO_FourAcid such as
Lead compounds; PbS, Pb_TwoS_Three, PbS_TwoSuch as lead sulfide
Kinds; Pb (OH)_Two, Pb_ThreeO_Two(OH)_Two, Pb
_Two[PbO_Two(OH)_Two], Pb_TwoO (OH)_TwoSuch as
Lead hydroxides; Na_TwoPbO_Two, K_TwoPbO_Two, NaHP
bO_Two, KHPbO _TwoNamarites such as Na_TwoP
bO_Three, Na_TwoH_TwoPbO_Four, K_TwoPbO_Three, K_Two[P
b (OH)₆], K_FourPbO_Four, Ca_TwoPbO_Four, Ca
PbO_ThreeLead salts such as PbCO_Three2PbCO_Three・
Pb (OH)_TwoLead carbonates and their basic salts
Kinds; Pb (OCH_Three)_Two, (CH_ThreeO) Pb (OP
h), Pb (OPh)_TwoAlkoxy lead, such as Ally
Leoxyleads; Pb (OCOCH_Three)_Two , Pb (OCOC
H_Three)_Four, Pb (OCOCH_Three)_Two・ PbO ・ 3H_TwoO
Lead salts of organic acids such as and their carbonates and basic salts; B
u_FourPb, Ph_FourPb, Bu _ThreePbCl, Ph_ThreePbB
r, Ph_ThreePb (or Ph₆Pb_Two), Bu_ThreePbO
H, Ph_TwoOrganic lead compounds such as PbO (Bu is butyl
Group, Ph represents a phenyl group); Pb-Na, Pb-C
a, Pb-Ba, Pb-Sn, Pb-Sb, etc.
Golds; lead minerals such as houenite and senenite, and
And hydrates of these lead compounds; having a tertiary amino group
Anion exchange resin, ion exchange resin having an amide group,
Less of sulfonic acid groups, carboxylic acid groups, and phosphoric acid groups
Ion exchange resin having both one exchange group, quaternary anion
Solid strong basic anion having monium group as exchange group
Ion exchangers such as exchangers; silica, silica-aluminum
Na, silica-magnesia, aluminosilicate, galiu
Musisilicate, various zeolites, various metal exchange Zeora
Of solids such as iron oxides and ammonium exchanged zeolites
Organic compounds and the like are used. Especially preferred as solid contact
It is often used with a quaternary ammonium group as an exchange group
Is a solid strong base anion exchanger having
For example, the quaternary ammonium group is exchanged.
Strongly basic anion exchange resin having a quaternary group
Cellulose having a monium group as an exchange group
Nion exchanger, quaternary ammonium group as exchange group
Inorganic carrier-supporting strong basic anion exchangers
I can do it.

As the strong basic anion exchange resin having a quaternary ammonium group as an exchange group, for example, a styrene strong basic anion exchange resin and the like are preferably used. The styrene-based strongly basic anion exchange resin is a strongly basic anion exchange resin having a quaternary ammonium (I type or II type) as an exchange group with a copolymer of styrene and divinylbenzene as a matrix. It is shown schematically by a formula.

[0036]

Embedded image

In the above formula, X represents an anion, usually X
As F^-, Cl^-, Br^-, I^-, HCO_Three ^-,
CO_Three ^2-, CH_ThreeCO_Two ^-, HCO_Two ^-, IO_Three ^-, B
rO _Three ^-, ClO_Three ^-At least one selected from
Is used, preferably Cl.^-, Br^-, H
CO_Three ^-, CO_Three ^2-At least one selected from
Anions are used. The structure of the resin matrix
Is gel type or macro reticular type (MR type)
Can be used, but the MR type is special because of its high resistance to organic solvents.
Preferred.

The cellulose strongly basic anion exchanger having a quaternary ammonium group as an exchange group is, for example, -OCH ₂ CH ₂ obtained by trialkylaminoethylation of a part or all of -OH groups of cellulose. N
An example is cellulose having an exchange group of R ₃ X. However, R represents an alkyl group, and is usually methyl, ethyl,
Propyl, butyl and the like are used, preferably methyl,
Ethyl is used. Further, X is as described above.

The quaternary ammo which can be used in the present invention
Inorganic carrier-supported strong base having a hydrogen group as an exchange group
Ionic anion exchanger refers to a hydroxyl group -OH on the surface of an inorganic carrier.
By modifying some or all of the quaternary ammonium
Um group-O (CH_Two)_nNR _ThreeMeans that introduced X
I do. However, R and X are as described above. n is usually
It is an integer of 1 to 6, and preferably n = 2. Mineral
As the carrier, silica, alumina, silica-alumina, titanium
Tania, zeolite, etc. can be used and are preferred
Cubic silica, alumina, and silica-alumina are used.
Silica is preferably used. Surface water of inorganic carrier
Any method can be used as a method for modifying the acid group.
Wear. For example, an inorganic carrier and amino alcohol HO (C
H_Two)_nNR_TwoThe dehydration reaction in the presence of a base catalyst.
And then halogenated
Alkyl RX '(X' represents halogen, usually Cl,
Br, I, etc. are used) to react with —O (C
H_Two)_nNR_ThreeX ′ group. Furthermore, anion exchange
By carrying out a quaternary anion having a desired anion X
Monium group --O (CH_Two)_nNR_ThreeLet be X. Also, n
= 2, the inorganic carrier is N, N-dialkylazide.
By treatment with lysine, N, N-dialkylamido
Noethoxylated to -OCH_TwoCH_TwoNR_TwoAfter base
In addition, according to the above method, -O (CH_Two)_nNR_ThreeX group
It is.

As the solid strong basic anion exchanger having a quaternary ammonium group as an exchange group, a commercially available one can be used. In that case, it can be used as a transesterification catalyst after performing ion exchange with a desired anion species in advance as a pretreatment. Also, at least 1
Transesterification of solid catalysts consisting of macroreticular and gel-type organic polymers having heterocyclic groups containing 1 nitrogen atom, or inorganic carriers having heterocyclic groups containing at least 1 nitrogen atom It is preferably used as a catalyst. Further, a solid catalyst in which some or all of these nitrogen-containing heterocyclic groups are quaternized is also used.

In the first step of the present invention, an aliphatic monoalcohol or a mixture of an aliphatic monoalcohol and a dialkyl carbonate and a cyclic carbonate are continuously fed to the continuous multistage distillation column as raw material compounds.
It may be directly introduced into the continuous multi-stage distillation column, or these raw material compounds may be introduced into the transesterification reactor and introduced into the continuous multi-stage distillation column as a reaction liquid. Further, these raw material compounds can be introduced separately and / or in a mixed manner, and when a cyclic carbonate or a mixture of a cyclic carbonate and an aliphatic monoalcohol is introduced, from any number of introduction ports, It can be introduced into the same or upper stage as the lowermost circulation outlet provided in the continuous multistage distillation column and / or into any transesterification reactor. When introducing the aliphatic monoalcohol, it can be introduced into any stage and / or any transesterification reactor of the continuous multistage distillation column from any number of inlets.

The raw material compounds are supplied in the form of liquid, gas or a mixture of liquid and gas. In this way, in addition to continuously feeding the raw material compound into the continuous multi-stage distillation column and / or the reactor, an additional gaseous raw material compound is intermittently or continuously fed from the lower part of the distillation column. Is also a preferred method. The cyclic carbonate is continuously fed in a liquid or gas-liquid mixed state to the uppermost transesterification reactor and / or the stage above the side outlet to the uppermost transesterification reactor, and the aliphatic monoalcohol is supplied. It is also preferable to continuously feed the lowermost transesterification reactor in a liquid, gaseous or gas-liquid mixed state. In this case, it does not matter if the aliphatic monoalcohol is contained in the cyclic carbonate supplied from above.

These feed materials may contain the product dialkyl carbonate or diol. The diol contained in the cyclic carbonate is usually used in an amount of 0.0001 to 80% by weight, preferably 0.001 to 80% by weight, which is expressed as a weight percentage of the diol in the cyclic carbonate / diol mixture. Further, the dialkyl carbonate contained in the aliphatic monoalcohol is usually expressed by weight% of the dialkyl carbonate in the aliphatic monoalcohol / dialkyl carbonate mixture,
0.0001 to 50% by weight, preferably 0.001 to 3
Used at 0% by weight.

The amount ratio of cyclic carbonate and aliphatic monoalcohol supplied to the continuous multi-stage distillation column in the first step varies depending on the type and amount of transesterification catalyst and reaction conditions, but usually the cyclic carbonate in the feedstock. The molar ratio of aliphatic monoalcohols to carbonate is 0.01 to 10
It is preferable to supply in the range of 00 times. In order to increase the reaction rate of the cyclic carbonate, it is preferable to supply the aliphatic monoalcohol in an excess amount of 2 times mol or more, but if it is used in an excessively large amount, it is necessary to enlarge the device. In this sense, it is particularly preferable that the aliphatic monoalcohol is used in a molar amount of 2 to 20 times.

In the present invention, the low boiling point component containing the dialkyl carbonate produced in the continuous multistage distillation column of the first step and in the transesterification reactor is liquid, gaseous or liquid and gas from the upper part of the continuous multistage distillation column. Is continuously extracted as a mixture with. The extract may be a dialkyl carbonate alone, a mixture of an aliphatic monoalcohol and a cyclic carbonate, or may contain a small amount of a high boiling point product.

The outlet for withdrawing the low boiling point component containing the dialkyl carbonate from the continuous multi-stage distillation column in the first step is preferably provided with an outlet for the gaseous substance between the raw material supply position and the top of the column or at the top of the column, It is particularly preferable to provide it at the top of the tower. You may perform what is called a reflux operation which returns a part of low boiling point component extracted in this way to the upper part of the said distillation column. When the reflux ratio is increased by this reflux operation, the distillation efficiency of the low boiling point product into the vapor phase is increased, so that the concentration of the low boiling point product in the gas component to be extracted can be increased. However, if the reflux ratio is increased too much, the required heat energy becomes large, which is not preferable. Therefore, the reflux ratio is usually 0 to 10, and preferably 0 to 5.

The diol produced by the method of the present invention is continuously withdrawn from the lower part of the continuous multistage distillation column of the first step as a liquid, a gas or a mixture of liquid and gas.
In the present invention, the upper part of the continuous multi-stage distillation column refers to a range from the top of the distillation column to a position at a height of ½ of the column height,
The top of the tower is also included. Further, the lower part of the continuous multi-stage distillation column refers to the range from the column bottom of the distillation column to a position at a height half the column height, and the column bottom is also included.

In the present invention, the column bottom extract means the diol produced and unreacted with the diol which is continuously withdrawn in liquid and / or gas form from the bottom of the continuous multi-stage distillation column of the first step of the present invention. And a cyclic alkyl carbonate, and may contain an aliphatic monoalcohol or an aliphatic monoalcohol and a dialkyl carbonate. First
If the cyclic carbonate / diol ratio in the bottom extract of the continuous multistage distillation column in the step is too large, the continuous hydrolysis reaction device in the second step becomes large, which is not preferable.
Further, when the cyclic carbonate / diol ratio in the bottom extract is too small, in order to increase the conversion rate of the cyclic carbonate in the continuous multi-stage distillation column, a longer reaction time and a larger amount of aliphatic monoalcohol are used. Need. Therefore, the amount of cyclic carbonate in the bottom extract of the distillation column is usually 0.001 to 0.4, expressed as the molar ratio of cyclic carbonate to diol.
Preferably 0.01 to 0.3, more preferably 0.0.
It is 2 to 0.2.

When a transesterification catalyst having a high boiling point which can be dissolved in the reaction solution under the reaction conditions is used, the catalyst is contained in the extract at the bottom of the column. The outlet for withdrawing the bottom product from the continuous multi-stage distillation column of the first step is provided at the bottom of the column, and particularly preferably at the bottom of the column. The bottom column extract thus extracted may be returned to the bottom of the continuous multistage distillation column in a gaseous or gas-liquid mixture state by heating a part of it with a reboiler.

The amount of the transesterification catalyst used in the present invention varies depending on the kind of the catalyst used, but when the catalyst is continuously supplied to the continuous multistage distillation column and the transesterification reactor in the first step, It is usually used in an amount of 0.0001 to 50% by weight, which is expressed as a ratio with respect to the total weight of the feedstock cyclic carbonate and the aliphatic monoalcohol. When a solid catalyst is used, it is usually 10 to 100% by volume, preferably 50 to 100% by volume with respect to the inner volume of the reactor. Further, when the solid catalyst is installed in the distillation column for use, the solid catalyst has a volume of 0.
A catalyst amount of 01 to 75% by volume is preferably used.

The falling liquid velocity and the ascending vapor velocity in the continuous multistage distillation column in the first step are usually different depending on the type of the distillation column used and, if a packed column is used, the type of packing. It is implemented within the range that does not cause flooding. In the first step, a part or most of the liquid flowing down the side outlet of the continuous multi-stage distillation column is withdrawn from the side outlet provided in the middle stage and / or the lowest stage. , Is introduced into the transesterification reactor. Residence time in the reactor is usually 0.00
It is carried out for 1 to 100 hours, preferably 0.003 to 50 hours, more preferably 0.01 to 10 hours.

In the present invention, in addition to the reaction in the transesterification reactor, the reaction can also be carried out in the continuous multistage distillation column,
This is the preferred method. In this case, the amount of dialkyl carbonate produced also depends on the amount of holdup liquid in the continuous multistage distillation column. That is, when the distillation column having the same column height and the same column diameter is used, a distillation column having a large amount of hold-up liquid is preferable in that the residence time of the reaction liquid, that is, the reaction time can be made relatively long. However, when the amount of the hold-up liquid is too large, the retention time becomes long, so that a side reaction proceeds or flooding easily occurs. Therefore, the hold-up liquid amount of the continuous multi-stage distillation column of the first step may vary depending on the distillation conditions and the type of the distillation column, but is expressed by the volume ratio of the hold-up liquid amount to the empty column volume of the distillation column, Usually 0.005
It will take place at 0.75.

Further, the average residence time of the reaction liquid in the continuous multi-stage distillation column of the first step varies depending on the reaction conditions, the type of the distillation column and the internal structure (for example, types of trays and packings), Usually 0.001 to 50 hours, preferably 0.01 to
It is 10 hours, more preferably 0.05 to 5 hours. The reaction temperature of the transesterification reaction is the temperature in the transesterification reactor of the first step, or in the transesterification reactor and in the continuous multistage distillation column, and varies depending on the type of raw material compound used and the reaction pressure. It depends on whether it is the reaction temperature in the vessel or the reaction temperature in the continuous multi-stage distillation column, but it is usually 0 to 350 ° C., preferably 20 to 2
It is in the range of 00 ° C. The reaction pressure may be any of reduced pressure, normal pressure and increased pressure, and is usually expressed as an absolute pressure of 0.
00001 to 20 kg / cm ² , preferably 0.01
-10 kg / cm ² , more preferably 0.1-5 kg
/ Cm ² .

In the method of the first step, since the transesterification reactor is provided outside the continuous multi-stage distillation column, reaction conditions of temperature and pressure different from the distillation conditions (temperature and pressure) can be adopted, and two or more units are used. Each of the reactors is characterized in that different reaction conditions can be adopted. It is also possible to circulate the unreacted cyclic carbonate to the continuous multistage distillation column by supplying a part of the column bottom extract of the first step to the continuous multistage distillation column of the first step. At that time, the position of the inlet for supplying the extract from the lower part of the column to the continuous multi-stage distillation column is not particularly limited, but it is preferably supplied to the upper part of the distillation column.

When the lower column withdrawal product of the first step is fed to the continuous hydrolysis reaction device in the second step, the lower column withdrawal product can be directly fed to the continuous hydrolysis reaction device, or a separating device is used. It is also possible to separate a specific component or components from the column bottom extract individually or as a mixture, and then supply the component containing unreacted cyclic carbonate to the continuous hydrolysis reactor. Examples of such a separation device for the column bottom extract in the first step include a distillation separation device, an extractive distillation separation device, a liquid-liquid extraction separation device, a crystallization separation device, an adsorption separation device,
A membrane separator or the like can be used. Each of these separation devices may be composed of a plurality of devices of the same type, or a combination of a plurality of types of separation devices can be used. Among these separators, a distillation separator is mentioned as a particularly preferable separator.

When a distillation separator is used as a separating device for the lower column withdrawal product in the first step, the lower column withdrawal product is introduced into the distillation and separating device and unreacted cyclic carbonate, diol, etc. contained in the lower column withdrawal product Can be separated into a single fraction or a fraction consisting of a mixture of these components and a bottom liquid. An azeotropic mixture may be obtained as a fraction depending on the kind of the raw material compound. In this way, after the column bottom extract of the first step is separated into each fraction and the bottom liquid by using the distillation separator, the fraction containing the unreacted cyclic carbonate and the bottom liquid are continuously hydrolyzed. Is supplied to. As this distillation separation apparatus, the same continuous multi-stage distillation column as that which can be used in the continuous multi-stage distillation column of the first step can be used alone or in combination.

When a transesterification catalyst which is soluble in the reaction solution under the reaction conditions is used, a fraction containing the transesterification catalyst and / or the bottom liquid is obtained, and a part or all of the fraction is used in the first step. It can also be circulated by supplying it to a multistage distillation column. That is, the following two methods can be mentioned as preferable methods for separating the column bottom extract in the first step using a distillation separator and supplying it to the continuous hydrolysis reaction apparatus in the second step. 1. Before continuously feeding the lower column extract containing the low boiling point components of the aliphatic monoalcohol and dialkyl carbonate in the first step to the continuous hydrolysis reactor, the lower column extract is composed of a continuous multi-stage distillation column. The low boiling point component containing the aliphatic monoalcohol and dialkyl carbonate remaining in the extract at the bottom of the column is continuously withdrawn from the upper part of the low boiling point component separation column while continuously supplying to the boiling point component separation column. A high boiling point component containing a cyclic carbonate is extracted from the lower part of the low boiling point component separation column, and the product extracted from the upper part of the low boiling point component separation column is circulated by continuously supplying it to the continuous multistage distillation column of the first step,
On the other hand, a method of supplying a product extracted from the lower part of the low boiling point component separation column to a continuous hydrolysis reaction device. When the substance extracted from the upper part of the low boiling point component separation column is continuously supplied to the continuous multi-stage distillation column of the first step, it may be directly introduced into the continuous multi-stage distillation column or may be introduced into the transesterification reactor. These components may be introduced and then introduced as a reaction solution into the distillation column. As the low boiling point component separation column, the same continuous multi-stage distillation column as that used in the first multi-stage distillation column can be used. 2. The cyclic carbonate and the diol are compounds that form the lowest azeotropic mixture, and when the product extracted from the lower part of the low boiling point component separation column is fed to the continuous hydrolysis reaction device, it is extracted from the lower part of the low boiling point component separation column. The product is fed to an azeotropic separation column consisting of a continuous multi-stage distillation column, diol is continuously withdrawn from the lower part of the azeotropic separation column, and a low boiling point component consisting of a minimum azeotropic mixture of cyclic carbonate and diol is added to the azeotropic separation column. Continuously withdraw from the top of the boiling separation tower,
A method in which the substance extracted from the upper part of the azeotropic separation column and water are continuously supplied to a continuous hydrolysis reaction device. As the azeotropic separation column, the same continuous multistage distillation column as that which can be used in the continuous multistage distillation column of the first step can be used.

In the second step of the present invention, the bottom product of the first step containing unreacted cyclic carbonate and the water are continuously supplied to a continuous hydrolysis reaction apparatus, and the continuous hydrolysis reaction apparatus does not The reaction cyclic carbonate is continuously hydrolyzed, and the reaction liquid containing the produced diol is continuously withdrawn from the continuous hydrolysis reaction apparatus. When separating the lower column withdrawal product of the first step with a separating device, the component containing unreacted cyclic carbonate obtained by the separating device is used instead of the lower column withdrawing product.

As the continuous hydrolysis reaction apparatus used in the second step, any apparatus can be used as long as it is a reaction apparatus capable of continuously reacting the cyclic carbonate and water in the coexistence. Usually, a tubular reactor; a tank reactor; a tower reactor such as a distillation tower reactor or a bubble tower reactor; a fluidized bed reactor etc. are used, and preferably a tubular reactor or a tank reactor. A reactor or a distillation column type reactor is used.

As the distillation column reactor used as the continuous hydrolysis reactor, the same continuous multistage distillation column as that used for the continuous multistage distillation column in the first step can be used. A hydrolysis catalyst may be used in the second step. The hydrolysis catalyst may be any catalyst that can produce a diol by reacting a cyclic carbonate with water, and various known catalysts can be used. For example, mineral acids such as nitric acid, hydrochloric acid and sulfuric acid; alkali metals and alkaline earth metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium; hydrides of alkali metals and alkaline earth metals. , Alkoxides,
Basic compounds such as aryloxides and amidides; alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, rubidium hydroxide and cesium hydroxide; magnesium hydroxide, calcium hydroxide, strontium hydroxide and the like Alkaline earth metal hydroxide; sodium carbonate,
Alkali metal carbonates such as potassium carbonate; Alkali metal bicarbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate; Organic acid salts of alkali metals and alkaline earth metals; Sodium molybdate, potassium molybdate, sodium tungstate, tungstic acid Inorganic acid salt such as potassium; Organic acid ester such as carboxylic acid ester and sulfonic acid ester; Composite catalyst consisting of Lewis acid and nitrogen-containing organic base; Organic antimony compound; Quaternary phosphonium salt; Quaternary ammonium salt; Triethylamine, Tertiary amines such as tributylamine, trihexylamine, benzyldiethylamine; synthetic zeolite, hydrotalcite, organic ion exchange resin, activated alumina, silica alumina, alumina loaded with copper compound or silica alumina, loaded with zinc compound Solid catalysts such as alumina or silica-alumina can be used.

When the transesterification catalyst in the first step is soluble in the reaction solution under the reaction conditions and the catalyst also has a function as a hydrolysis catalyst, When the bottom product of the first step is fed to the continuous hydrolysis reactor without separation, the transesterification catalyst used in the first step can be used as it is as the hydrolysis catalyst in the second step. ． When the column lower extract in the first step is separated using a distillation separator, a part or the whole of the fraction containing the ester catalyst or the bottom solution can be used as the hydrolysis catalyst in the second step.

The amount of hydrolysis catalyst used in the present invention is
Depending on the type of hydrolysis catalyst used, when the hydrolysis catalyst is continuously supplied to the continuous hydrolysis reaction apparatus, the weight concentration of the hydrolysis catalyst relative to the cyclic carbonate supplied to the continuous hydrolysis reaction apparatus is Expressed as
It is usually used in an amount of 0.0001 to 50% by weight. When the solid catalyst is used by being installed in a continuous hydrolysis reaction device, it is used in an amount of 10 to 75% by volume based on the empty column volume of the distillation column.
The catalytic amount of is preferably used.

As the water used in the second step, any water can be used, and ion exchange water, condensed water of steam or the like is usually used. The amount of water with respect to the cyclic carbonate can be reduced to a stoichiometric amount, and may be less than that depending on the reaction mode, but from a practical point of view, it is usually 1 to 100 mole times the stoichiometric amount or more, preferably 1.
It is used in an amount of 01 to 50 times by mole, more preferably 1.01 to 10 times by mole.

The reaction conditions of the continuous hydrolysis reaction apparatus will vary depending on the presence or absence of a hydrolysis catalyst and the type and amount of the hydrolysis catalyst, if used, but the reaction temperature is usually
It is carried out at 50 to 300 ° C., preferably 80 to 250 ° C., more preferably 100 to 200 ° C., and the reaction time depends on the presence or absence of a hydrolysis catalyst, the type and amount of the hydrolysis catalyst when used, and the reaction. Although it depends on the temperature, it is usually expressed as an average residence time of 0.001 to 50 hours, preferably 0.01 to 10 hours, and more preferably 0.02.
~ 5 hours. The reaction pressure varies depending on the reaction temperature used, but it is usually 0.01 to 20 in terms of absolute pressure.
0 kg / cm ² , preferably 0.1-100 kg / cm
Done in ² .

The reaction liquid containing the diol produced in the second step of the present invention is continuously withdrawn from the continuous hydrolysis reaction apparatus. By distilling and separating the reaction solution, a diol fraction having a high purity and a fraction containing carbon dioxide as a by-product can be separated. When the reaction liquid contains unreacted cyclic carbonate, aliphatic monoalcohol, and product dialkyl carbonate, these components are separated by distillation, and then these components are circulated in the continuous multistage distillation column of the first step. You can In this case, the components may be directly introduced into the distillation column, or these components may be introduced into a transesterification reactor and introduced into the distillation column as a reaction liquid.

When unreacted water is contained in the reaction solution containing the diol produced in the second step, water is obtained as a distillate when the reaction solution is separated by distillation, and the water fraction is separated into It can be recycled to a two-step continuous hydrolysis reactor and used again. When a cyclic carbonate and a diol are compounds that form a minimum azeotropic mixture, and when an azeotropic separation column is used, from the lowest azeotropic mixture of the cyclic carbonate and the diol continuously extracted from the upper part of the azeotropic separation column. It is also possible to supply the reaction liquid obtained by supplying the low boiling point component to the continuous hydrolysis reaction device and reacting the same with the low boiling point component again to the azeotropic separation column.

When a continuous hydrolysis reactor consisting of a tubular reactor or a tank reactor is used as the continuous hydrolysis reactor in the second step, the reaction liquid containing the produced diol and carbon dioxide gas is continuously multistage distillation column. Is continuously supplied to the diol separation column consisting of the diol separation column, and the low boiling point component containing carbon dioxide produced is continuously extracted from the upper part of the diol separation column and the diol produced is continuously extracted from the lower part of the diol separation column. You can also As the diol separation column, the same continuous multi-stage distillation column that can be used in the first multi-stage distillation column can be used.

When a continuous hydrolysis reaction tower which is a distillation tower type reactor is used as the continuous hydrolysis reaction apparatus in the second step, the continuous hydrolysis reaction tower may also have a function as a distillation separator. It is possible to continuously withdraw the low-boiling-point component containing carbon dioxide gas produced at that time from the upper part of the continuous hydrolysis tower, and the produced diol from the lower part of the continuous hydrolysis reaction tower. Furthermore, when the extract at the bottom of the tower in the first step contains aliphatic monoalcohol and dialkyl carbonate, it contains aliphatic monoalcohol, dialkyl carbonate and carbon dioxide from the upper part of the continuous hydrolysis reaction tower, and contains water. A low boiling point component which may be used is continuously withdrawn from the upper part of the continuous hydrolysis reaction column and is circulated by being supplied to the continuous multistage distillation column of the first step, and the diol produced is withdrawn from the lower part of the continuous hydrolysis reaction column. You can also Further, when water is supplied to the continuous hydrolysis reaction tower, water may be supplied to the upper part of the diol withdrawal port of the continuous hydrolysis reaction tower.
Further, the position of the inlet of the lower column withdrawal product containing unreacted cyclic carbonate to the continuous hydrolysis reaction column is not particularly limited, but the lower column withdrawal product is supplied above the diol withdrawal port. Doing is also a preferred method.

In the present invention, it is not always necessary to use a solvent, but (1) to facilitate the reaction operation,
(2) An inert solvent suitable for the purpose of efficiently obtaining dialkyl carbonate or diol by performing azeotropic distillation or extractive distillation, for example, ethers, aliphatic hydrocarbons, aromatic hydrocarbons , Halogenated aliphatic hydrocarbons, halogenated aromatic hydrocarbons and the like can be used as a reaction solvent, an azeotropic agent or an extractant.

An inert gas such as nitrogen, helium or argon may be allowed to coexist in the reaction system as a substance inert to the reaction, or continuous multistage distillation for the purpose of accelerating the distillation of the low boiling point product to be produced. From the lower part of the column, the above-mentioned inert gas or the low-boiling organic compound inert to the reaction may be introduced in a gaseous state.

[0071]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below. In each of the following examples, the yield of ethylene glycol is a value based on the charged ethylene carbonate, the selectivity of ethylene glycol is a value based on the consumed ethylene carbonate, and the yield of dimethyl carbonate is based on the charged ethylene carbonate. Numerical value, selectivity of dimethyl carbonate is based on consumed methanol.

[0072]

Example 1 Using the apparatus shown in FIG. 1, dimethyl carbonate (DMC) and ethylene glycol (E) from ethylene carbonate (EC) and methanol (MeOH).
G) was produced continuously. The number of transesterification reactors is 4
Group. The internal volumes of the transesterification reactors A, B, C and D are 500 ml, 250 ml, 250 ml and 2 respectively.
It is 50 ml. The continuous multi-stage distillation column 1 is a packed column having a column height of 2 m and a column inner diameter of 32 mm, and stainless Dickson packing (6 mmφ) was used as the packing material. As shown in FIG. 1, a side outlet and an inlet to the transesterification reactor were provided between the position 10 cm from the top of the distillation column and the position 50 cm from the bottom of the distillation column. The transesterification reactor has stainless Dickson packing (6
mmφ).

EC (raw material 1) was introduced into the transesterification reactor A while being preheated to 70 ° C. from the conduit 2 through the conduit 2 at a flow rate of 120 g / h, and sodium hydroxide (3) was added.
A wt% ethylene glycol solution (catalyst) was continuously fed in a liquid state through a conduit 2'at a flow rate of 11 g / h, and MeOH was added.
And a mixture of DMC (weight ratio: MeOH / DMC = 95/5) (raw material 2) at a flow rate of 314 g / h, with a conduit 5
Was continuously fed in a gaseous state through an evaporator 6 '. The continuous multi-stage distillation column 1 was operated at atmospheric pressure, and the top temperature was 64 ° C. The temperature of the transesterification reactor is 70 ° C., the flow rate of the circulating liquid to the transesterification reactor is 1 liter / h, and the pressure of the transesterification reactor is about 5 kg / cm ^2. -G is set. The liquid flowing down in the continuous multi-stage distillation column is extracted from a side extraction port provided in the middle of the distillation column,
It was introduced into each transesterification reactor. The reaction liquid in which the reaction proceeded in the transesterification reactor and the concentrations of dimethyl carbonate and ethylene glycol were increased was circulated from the inlet to the distillation column. The liquid flowing down in the distillation column is
The concentration of dimethyl carbonate as a product and ethylene carbonate as a raw material decreased as the vapor-liquid contact was made with the vapor rising from the bottom of the distillation column toward the top of the column.

The gaseous component distilled from the column top 4 is condensed by the condenser 7.
At the reflux ratio (reflux ratio of 2), and the other is extracted at the top of the column (62.6 wt% MeOH and 3 DMC).
(Including 7.4 wt%) at a flow rate of 347 g / h. The bottom liquid was heated by the reboiler 6. A part of the circulating bottom liquid (containing 57.3% by weight of EG and 6.1% by weight of EC) was withdrawn from the conduit 9 at a flow rate of 137 g / h and filled with Dixon packing (3φ) as a packing material. Was supplied to a position 40 cm from the top of the low boiling point component separation column 10 composed of a packed column having an inner diameter of 2.5 cm and a filling height of 120 cm. Low boiling point component separation tower 10 has a top pressure of 10 t
It was operated at an orr and a bottom temperature of 101 ° C. The gaseous component distilled from the top of the column is condensed in the condenser 13, a part of it is refluxed through the conduit 14, and the rest is flowed through the evaporator 15 to a position 100 cm from the top of the continuous multistage distillation column 1. 39
It was circulated in gaseous form at g / h. The bottom liquid of the low boiling point component separation column 10 was heated by the reboiler 18, and a part thereof was withdrawn from the conduit 20 at a flow rate of 11 g / h. Low boiling point component separation tower 10
A gaseous fraction consisting of EG and EC is withdrawn at a flow rate of 87 g / h from an outlet provided at a position 90 cm from the top of the column, condensed in a condenser 21, and a side withdrawal liquid (EG is 90.3% by weight, EC of 9.7% by weight) was obtained.

The side withdrawal liquid condensed in the condenser 21 together with the top withdrawal liquid of the diol separation column 23 introduced through the conduit 34 and the water introduced through the conduit 35
Continuous hydrolysis reactor 37 (inside diameter 7.
5 mm, 30 cm in length, and filled with spherical activated alumina having a diameter of 2 to 4 mm). The internal pressure of the continuous hydrolysis reactor 37 was kept at 25 kg · cm ² −G.
Water was supplied so that the water / EC weight ratio at the reactor inlet was kept at 0.5. The reaction liquid passes through a conduit 38 and a gas-liquid separator 39.
Carbon dioxide was obtained from conduit 40 and a mixture of EG and water from conduit 22. This mixture of EG and water was passed through a conduit 22 and filled with Dickson packing (3φ) as a filling material, inner diameter 2.5 cm, filling height 120 c.
40 from the top of the diol separation tower 23, which is a packed tower of m.
supplied to the position of cm.

The diol separation tower 23 has a top pressure of 20 torr.
The gaseous component, which is operated at r and distills from the top of this column, is condensed in the condenser 26, a part of which is refluxed via the conduit 27, and the rest is circulated to the continuous hydrolysis reactor 37 via the conduit 34. The bottom liquid of the diol separation column 23 is reboiler 30.
Heated in. The bottom temperature was 110 ° C. A gaseous fraction was withdrawn at a flow rate of 85 g / h from a side extraction port provided at a position 90 cm from the top of the diol separation column 23, and condensed in a condenser 33 to produce EG as a side extraction liquid (with an EC content of 0). .1 ppb or less) was obtained. This result shows that the conversion rate of EC is 100%, the DMC yield is 93%, the DMC selectivity is 99% or more, the EG with an extremely high purity is 99% or more, and the EG selectivity is 99% or more. It has been shown.

[0077]

[Comparative Example 1] As shown in FIG.
Example 1 was moved to a position 10 cm below the top 4 of the distillation column 1, which was a packed column filled with a ring (12φ) and having an inner diameter of 2.5 cm and a filling height of 250 cm and which was isothermally controlled at 80 ° C. A raw material similar to the raw material 1 is continuously supplied in liquid form from the conduit 2 through the preheater 3 at a flow rate of 120 g / h,
A mixture similar to the catalyst of Example 1 was continuously fed in liquid form via conduit 2'at a flow rate of 11 g / h. In addition, Example 1
A mixture similar to that of the starting material 2 was continuously fed in a gaseous state at a flow rate of 329 g / h through a vaporizer 6 ′ and a conduit 5 ′ provided 30 cm from the bottom of the column. The distillation column 1 was operated at atmospheric pressure, and the column top temperature was 76 ° C. The gaseous component distilled from the column top 4 is condensed in the condenser 7 and extracted as a column top extraction liquid (containing 62.3 wt% MeOH and 37.7 wt% DMC) in a liquid state at a flow rate of 309 g / h. Was issued. Bottom liquid extracted from the bottom 8 at a flow rate of 151 g / h (including 47.5% by weight of EG and 11.9% by weight of EC)
Is filled with Dickson packing (3φ) as a filling material through the conduit 9, inner diameter 2.5 cm, filling height 120 c
It was supplied to a position 40 cm from the top of the distillation column 50 composed of a packed column of m.

The distillation column 50 is operated at a top pressure of 10 torr, and a gaseous component consisting of a mixture of MeOH and DMC distilled from the top is condensed in a condenser 26, and a part of the gaseous component is refluxed via a conduit 27. , The rest via conduit 34 44
It was withdrawn at a flow rate of g / h. The overhead distillate is Me
It contained 89.7% by weight of OH and 10.3% by weight of DMC. The bottom liquid of the distillation column 50 is heated by the reboiler 30 (the bottom temperature was 137 ° C.), and a part of the liquid was introduced into the conduit 3
It was withdrawn at a flow rate of 2 to 34.7 g / h. The tower bottom extract contained 68 wt% of diethylene glycol and triethylene glycol in total. A gaseous fraction is withdrawn at a flow rate of 72.5 g / h from an extraction port provided at a position 90 cm from the top of the distillation column 50, and condensed in a condenser 33 to form a side extraction liquid EG.
Was obtained (containing 88.4% by weight of EG and 11.6% by weight of EC). This result shows that the conversion rate of EC is 93%,
The DMC yield was 85%, the DMC selectivity was 92%, the EG yield was 76%, the EG selectivity was 82%. Moreover, the obtained EG contained EC, Indicates that it was not obtained.

[0079]

Example 2 Using the apparatus shown in FIG. 3, dimethyl carbonate (DMC) and ethylene glycol (E) were converted from ethylene carbonate (EC) and methanol (MeOH).
G) was produced continuously. Instead of Dickson packing (6φ) packed in the transesterification reactor in Example 1, an anion exchange resin having a quaternary ammonium group as an exchange group [Dowex (trademark) MSA-1, Cl type] was used.
After ion exchange with a 2N-Na ₂ CO ₃ aqueous solution, washing with pure water was repeated, and then washing with dry MeOH was repeated to dehydrate and dry, and about 50% of Cl ⁻ − ions were CO ₃ ^2−. Ion exchanged] was charged as a catalyst for the transesterification reactor, and the EC flow rate was 1
32 g / h, M supplied from conduit 5 at a flow rate of 381 g / h
The composition of the mixture of OH and DMC is MeO in a weight ratio.
H / DMC = 85/15, and the continuous multistage distillation column 1 was operated in the same manner as that used in Example 1 except that the homogeneous catalyst was not supplied. The column top temperature was 64 ° C. The continuous multistage distillation column 1 was operated at atmospheric pressure. The top withdrawal liquid (containing 55.1 wt% MeOH and 44.9 wt% DMC) of the continuous multistage distillation column 1 was withdrawn at a flow rate of 419 g / h. The bottom liquid of the continuous multistage distillation column 1 (including 68.0% by weight of EG and 3.0% by weight of EC) has a flow rate of 13
40 g from the top of the low boiling point component separation column 10 which was extracted at 3 g / h and was the same as the low boiling point component separation column 10 used in Example 1.
supplied to the position of cm.

The low boiling point component separation column 10 was operated in the same manner as the low boiling point component separation column 10 of Example 1 except that the bottom liquid was not extracted from the conduit 20. The top pressure was 10 torr, and the bottom temperature was 102 ° C. The column top withdrawal liquid was circulated in a gaseous state via the evaporator 15 to the same position as in Example 1 of the continuous multistage distillation column 1 at a flow rate of 38.5 g / h. From the side withdrawal port of the low boiling point component separation column 10, a gaseous fraction comprising EG and EC was withdrawn at a flow rate of 94 g / h, condensed in a condenser 21, and the side withdrawal liquid (E
95.8% by weight of G and 4.2% by weight of EC) were obtained. The side extraction liquid condensed in the condenser 21 is the conduit 4
The azeotropic separation column 47 is mixed with the liquid phase part of the gas-liquid separator 39 (the same as that used in Example 1) introduced from No. 1.
Was fed to a position 40 cm from the top of the column.

The azeotropic separation column 47 was similar to the diol separation column 23 of Example 1 and operated in the same manner. The top pressure was 20 torr, and the bottom temperature was 112 ° C.
The liquid discharged from the top of the column was introduced into a continuous hydrolysis reactor 37 (the same as that used in Example 1) heated to 180 ° C. via a conduit 34 together with water introduced from a conduit 35. The internal pressure of the continuous hydrolysis reactor 37 is 26 kg · c
It was kept in m ² -G. Water was supplied so that the water / EC weight ratio at the reactor inlet was maintained at 0.6. The reaction solution is conduit 38
Is introduced into the gas-liquid separator 39 through the pipe and carbon dioxide gas is introduced into the conduit 40.
And a mixture of EG and water was obtained from conduit 41.
Flow rate of 93 g / h from the side outlet of the azeotropic separation tower 47
EG (EC content is 0.1p
pb or less) was obtained. This result shows that the conversion rate of EC is 100.
%, DMC yield 97%, DMC selectivity 99%
As described above, it is shown that EG having an extremely high purity was obtained with a yield of 99% or more and an EG selectivity of 99% or more.

[0082]

Example 3 Using the apparatus shown in FIG. 4, from ethylene carbonate (EC) and methanol (MeOH), dimethyl carbonate (DMC) and ethylene glycol (E) were used.
G) was produced continuously. Each flow rate and each composition of the EC supplied from the conduit 2, the MeOH and DMC supplied from the conduit 5, and the ethylene glycol solution (catalyst) of sodium hydroxide supplied from the conduit 2 ′ were the same as in Example 1, and other conditions Also under the same conditions as in Example 1, the continuous multistage distillation column 1
I drove. The column top temperature was 64 ° C. The continuous multistage distillation column 1 was operated at atmospheric pressure. The top withdrawal liquid of the continuous multi-stage distillation column 1 (62.6% by weight of MeOH and 37.
4% by weight) was withdrawn at a flow rate of 347 g / h.
Bottom liquid of continuous multistage distillation column 1 (57.3 wt% EG, E
(Containing 6.1% by weight of C) is withdrawn at a flow rate of 137 g / h and is supplied to a position 40 cm from the top of the low boiling point component separation column 10 which is the same as the low boiling point component separation column 10 used in Example 1. It was The low boiling point component separation tower 10 has a top pressure of 10 torr,
It was operated at a bottom temperature of 103 ° C. The gaseous component distilled from the top of this column is condensed in the condenser 13, and a part of it is condensed into the conduit 1
The mixture was refluxed via 4 and the rest was circulated in a gaseous state at a flow rate of 39 g / h to a position 120 cm from the top of the continuous multistage distillation column 1 via an evaporator 15. The bottom liquid of the low boiling point component separation column 10 is heated by the reboiler 18, and a part of it is fed from the conduit 20 to the flow rate 9
A column bottom extract (containing 80.2% by weight of EG and 8.6% by weight of EC) was obtained at 8.0 g / h.

The liquid extracted from the bottom of the low boiling point component separation column 10 is passed through a conduit 22 to a continuous hydrolysis reaction column 43 consisting of a packed column filled with Dickson packing (6φ) as a packing material having an inner diameter of 5 cm and a packing height of 150 cm. Supplied to the top of the tower. The continuous hydrolysis reaction tower 43 has a tower top pressure of 190 torr.
It was operated at a tower bottom temperature of 156 ° C. The gaseous component distilled from the top of the column is introduced into the gas-liquid separator 39 after being condensed in the condenser 26, and the carbon dioxide gas is introduced from the conduit 40 and the EG.
A mixture of water and water was obtained from conduit 42. A part of this mixture of EG and water is circulated to the top of the continuous hydrolysis reaction column 43 via the conduit 27, and the rest is 100c from the top of the continuous hydrolysis reaction column 43 together with water introduced from the conduit 35.
It cycled to the m position. Water was fed so that the water / EC weight ratio in conduit 42 remained at 0.5. A gaseous fraction is withdrawn at a flow rate of 84.5 g / h from a side withdrawal port provided at a position 130 cm from the top of the continuous hydrolysis reaction column 43, and condensed with a condenser 33 to produce EG (EC) as a side withdrawal liquid. The content was 0.1 ppb or less). This result indicates that the EC conversion is 100% and the DMC yield is 93 by performing the first step and the second step.
%, DMC selectivity of 99% or more, extremely high purity EG
Was obtained with a yield of 99% or more and an EG selectivity of 99% or more.

[0084]

Example 4 Using the apparatus shown in FIG. 5, dimethyl carbonate (DMC) and ethylene glycol (E) from ethylene carbonate (EC) and methanol (MeOH).
G) was produced continuously. EC flow rate is 120g / h,
A continuous multi-stage distillation column similar to that used in Example 1 except that the flow rate of the mixture of MeOH and DMC (composition: weight ratio MeOH / DMC = 85/15) supplied from the conduit 5 was 307 g / h. 1 was operated in a similar manner. The column top temperature was 64 ° C. The continuous multistage distillation column 1 was operated at atmospheric pressure. Extracted liquid from the top of the continuous multi-stage distillation column 1 (MeO
H contained 53.2 wt% and DMC contained 46.8 wt%) was extracted at a flow rate of 340 g / h. Continuous multi-stage distillation column 1
Bottom liquid (57.3 wt% EG, 7.1 wt% EC
(Including) was extracted at a flow rate of 136 g / h, and Dickson packing (6φ) was filled as the filling material, inner diameter 5c
m was supplied to the position of 90 cm from the top of the continuous hydrolysis reaction column 43 composed of a packed column having a filling height of 250 cm. The continuous hydrolysis reaction column 43 was operated at a column top pressure of 200 torr and a column bottom temperature of 161 ° C. The gaseous component distilled from the top of the column is condensed in the condenser 26 and then introduced into the gas-liquid separator 39, and carbon dioxide gas is introduced from the conduit 40 and also MeOH and D.
A mixture of MC was obtained from conduit 42. MeOH and DM
To remove carbon dioxide from the C mixture, nitrogen gas was bubbled through a conduit 42 at the bottom of the gas-liquid separator. A part of this mixture of MeOH and DMC is refluxed to the top of the continuous hydrolysis reaction column 43 via the conduit 27, and the rest is passed from the top of the continuous multistage distillation column 1 to 12 via the evaporator 15.
It was fed to a position of 0 cm.

The bottom liquid of the continuous hydrolysis reaction column 43 is heated by the reboiler 30, and a part of the liquid is fed from the conduit 32 at a flow rate of 11 g.
/ H. In addition, water was introduced into the inlet of the reboiler 30. At this time, water was introduced so that the water concentration in the liquid extracted from the top of the continuous hydrolysis reaction column 43 was maintained at 50 ppm or less. 230 from the top of the continuous hydrolysis reaction column 43
From the side outlet provided at the position of cm to the condenser 3
A mixture of EG and a small amount of water was obtained as a side extraction liquid through Step 3. This mixture contained nothing but water and EG. The flow rate without water was 84.5 g / h. This result shows that by performing the first step and the second step, the conversion rate of EC is 100%, the DMC yield is 92%, the DMC selectivity is 99% or more, and the yield of extremely high-purity EG is 99%. % Or higher, and the EG selectivity is 99% or higher.

[0086]

Example 5 Using the apparatus shown in FIG. 6, from ethylene carbonate (EC) and methanol (MeOH), dimethyl carbonate (DMC) and ethylene glycol (E).
G) was produced continuously. EC flow rate is 135g / h,
Using a continuous multi-stage distillation column equipped with an anion exchange resin-filled transesterification reactor in the same manner as used in Example 2 except that MeOH was supplied from the conduit 5 at a flow rate of 327 g / h. I drove. The column top temperature was 64 ° C.
The continuous multistage distillation column 1 was operated at atmospheric pressure. The gaseous component distilled from the column top 4 is condensed in the condenser 7, and is extracted at a flow rate of 365 g / h in a liquid form as a column top extraction liquid (containing 63.7 wt% MeOH and 36.3 wt% DMC). Was issued. The bottom liquid extracted from the bottom 8 at a flow rate of 134 g / h (1.9% by weight of DMC, 68.0% by weight of EG, EC
Is contained in a continuous hydrolysis reactor 37 (used in Example 1) with water introduced at a flow rate of 5.3 g / h from a conduit 35 via a conduit 9. And similar). Continuous hydrolysis reactor 3
The internal pressure of 7 was maintained at 25 kg · cm ² −G. Conduit 38
The reaction liquid was obtained at a flow rate of 140 g / h. When this reaction solution was analyzed, MeOH was 25.1% by weight, DM
The C content was 1.9 wt% and the EG content was 68.1 wt%. Further, no unreacted EC was detected in this reaction solution. This result shows that by performing the first step and the second step, the conversion rate of EC is 100%, the DMC yield is 96%, the DMC selectivity is 99% or more, and EC-free high-purity EG is obtained. Yield 99% or more, EG selectivity 99
It shows that it was obtained in% or more.

[0087]

According to the method of the present invention, a dialkyl carbonate and a highly pure diol can be continuously produced at a high reaction rate from a cyclic carbonate and an aliphatic alcohol.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used in Example 1.

FIG. 2 is a schematic diagram of an apparatus used in Comparative Example 1.

FIG. 3 is a schematic diagram of an apparatus used in Example 2.

FIG. 4 is a schematic diagram of an apparatus used in Example 3.

FIG. 5 is a schematic diagram of an apparatus used in Example 4.

FIG. 6 is a schematic diagram of an apparatus used in Example 5.

[Explanation of symbols]

 1 Continuous multi-stage distillation column 2, 2'conduit 3 Preheater 4 Top 5, 5'cond 6 Reboiler 6'Evaporator 7 Condenser 8 Bottom 9 Separation 10 Low boiling point component separation column 11 Top 12 Cond 13 Condenser 14 Conduit 15 Evaporator 16 Tower bottom 17 Conduit 18 Reboiler 19 Conduit 20 Conduit 21 Condenser 22 Conduit 23 Diol separation column 24 Top 25 Conduit 26 Condenser 27 Conduit 28 Bottom 29 29 Conduit 30 Reboiler 31 Conduit 32 Conduit 33 Condenser 34 Conduit 34 35 conduit 36 conduit 37 continuous hydrolysis reactor 38 conduit 39 gas-liquid separator 40 conduit 41 conduit 42 conduit 43 continuous hydrolysis reaction tower 45 conduit 47 azeotropic separation tower 50 distillation tower 61 inlet port 62 side outlet port 63 inlet port 64 Side outlet 65 Inlet 66 Side outlet 67 Inlet 68 Side outlet Port A Transesterification reactor B Transesterification reactor C Transesterification reactor D Transesterification reactor

Claims (15)

[Claims] 1. When continuously producing a dialkyl carbonate and a diol from a cyclic carbonate and an aliphatic monoalcohol, (i) a cyclic carbonate and an aliphatic monoalcohol which are raw material compounds are continuously supplied to a continuous multistage distillation column. The liquid flowing down in the distillation column is withdrawn from a side outlet provided in the middle stage and / or the lowest stage of the distillation column, and introduced into an ester exchange reactor provided outside the distillation column to carry out the reaction. The above-mentioned continuous multi-stage distillation is performed by bringing the transesterification catalyst present in the vessel into contact with the raw material compound, and then introducing it into a circulation inlet provided in a stage above the stage having the outlet. It is circulated to the column, and while the reaction is carried out in the transesterification reactor or both in the reactor and in the continuous multistage distillation column, the dialky formed is produced. The low boiling point component containing rucarbonate is continuously withdrawn from the upper part of the continuous multi-stage distillation column, and the lower column withdrawal containing the produced diol and unreacted cyclic carbonate is continuously withdrawn from the lower part of the column.
Step, (ii) The lower column withdrawal product of the first step containing unreacted cyclic carbonate and water are continuously supplied to a continuous hydrolysis reaction apparatus, and the unreacted cyclic carbonate is removed in the continuous hydrolysis reaction apparatus. A method for continuously producing a dialkyl carbonate and a diol, which comprises a second step of continuously withdrawing a reaction liquid containing a produced diol from the continuous hydrolysis reaction apparatus while continuously hydrolyzing. 2. The method for continuously producing a dialkyl carbonate and a diol according to claim 1, wherein a mixture of a dialkyl carbonate and an aliphatic monoalcohol is supplied to the continuous multistage distillation column instead of the aliphatic monoalcohol. 3. The method for continuously producing a dialkyl carbonate and a diol according to claim 1, wherein a continuous multi-stage distillation column in the presence of an ester exchange catalyst is used. 4. When the cyclic carbonate and the aliphatic monoalcohol are continuously supplied to the continuous multi-stage distillation column, the cyclic carbonate is continuously supplied to the upper part of the continuous multi-stage distillation column,
The method for continuously producing a dialkyl carbonate and a diol according to claim 1, 2 or 3, wherein the aliphatic monoalcohol is continuously fed to the lower part of the continuous multi-stage distillation column in a gaseous state. 5. The dialkyl according to claim 1, 2, 3 or 4, wherein the unreacted cyclic carbonate is continuously hydrolyzed in the presence of a hydrolysis catalyst composed of a solid catalyst and / or a homogeneous catalyst. A method for continuously producing carbonate and diol. 6. Prior to continuously supplying the lower column withdrawal product of the first step to a continuous hydrolysis reactor, the lower column withdrawal product is continuously supplied to a low boiling point component separation column comprising a continuous multistage distillation column. Then, the low boiling point component containing the aliphatic monoalcohol and the dialkyl carbonate is continuously withdrawn from the upper part of the low boiling point component separation column, and the high boiling point component containing the diol and the cyclic carbonate is withdrawn from the lower part of the low boiling point component separation column. The extract from the upper part of the low boiling point component separation column is circulated by continuously supplying it to the continuous multistage distillation column of the first step, while the extract from the lower part of the low boiling point component separation column is continuously hydrolyzed. A method for continuously producing a dialkyl carbonate and a diol according to claim 1, 2, 3, 4, or 5, which is supplied to a decomposition reactor. 7. The continuous hydrolysis reactor is a continuous hydrolysis reactor consisting of a tubular reactor or a tank reactor, and the reaction liquid containing the produced diol and carbon dioxide gas is a diol separation column consisting of a continuous multi-stage distillation column. A low boiling point component containing carbon dioxide is continuously extracted from the upper part of the diol separation column, and diol is continuously extracted from the lower part of the diol separation column. 5. A method for continuously producing a dialkyl carbonate and a diol according to 5 or 6. 8. The continuous hydrolysis reaction apparatus is a continuous hydrolysis reaction tower comprising a continuous multi-stage distillation column, and the low boiling point component containing carbon dioxide gas produced is continuously withdrawn from the upper portion of the continuous hydrolysis reaction tower to obtain a diol. The method for continuously producing a dialkyl carbonate and a diol according to claim 1, 2, 3, 4, 5, or 6, which is withdrawn from the lower part of the continuous hydrolysis reaction column. 9. When supplying the extract from the lower part of the low boiling point component separation column to the continuous hydrolysis reaction column, the extract from the lower part is supplied above the position for extracting the diol of the continuous hydrolysis reaction column. The method for continuously producing a dialkyl carbonate and a diol according to claim 6. 10. The dialkyl carbonate and the diol according to claim 8 or 9, wherein water is continuously supplied to the upper portion of the diol outlet when the water is continuously supplied to the continuous hydrolysis reaction tower. Manufacturing method. 11. A cyclic carbonate and a diol are compounds that form a minimum azeotropic mixture, and the low boiling point component separation column is supplied to a low boiling point component separation column before the substance extracted from the lower part of the low boiling point component separation column is fed to a continuous hydrolysis reactor. The substance extracted from the lower part of the column is supplied to an azeotropic separation column consisting of a continuous multistage distillation column, and the diol is continuously extracted from the lower part of the azeotropic separation column,
The low boiling point component consisting of the lowest azeotropic mixture of cyclic carbonate and diol is continuously withdrawn from the upper part of the azeotropic separation column, and the substance and water withdrawn from the upper part of the azeotropic separation column are continuously fed to a continuous hydrolysis reactor. A method for continuously producing a dialkyl carbonate and a diol according to claim 6 or 9, which is supplied to 12. The method for continuously producing a dialkyl carbonate and a diol according to claim 11, wherein the hydrolysis reaction liquid of the continuous hydrolysis reaction device is supplied to the azeotropic separation column. 13. The continuous hydrolysis reaction apparatus is a continuous hydrolysis reaction tower comprising a continuous multi-stage distillation column, and a low boiling point component containing an aliphatic monoalcohol, a dialkyl carbonate and carbon dioxide gas is supplied from the upper part of the continuous hydrolysis reaction tower. The diol is withdrawn from the lower part of the continuous hydrolysis reaction column by continuously withdrawing and circulating it by supplying it to the continuous multistage distillation column of the first step.
A method for continuously producing a dialkyl carbonate and a diol according to 8, 9, 10, 11 or 12. 14. The dialkyl carbonate and the diol according to claim 13, which are continuously fed to the continuous multistage distillation column of the first step after removing carbon dioxide gas or carbon dioxide gas and water from the product extracted from the upper part of the continuous hydrolysis reaction column. Manufacturing method. 15. The dialkyl carbonate and the diol according to claim 13, which are continuously supplied to the upper part of the diol withdrawal port when the lower column withdrawal product of the first step is fed to the continuous hydrolysis column. Method of manufacturing.