JPH09183744A - Continuous production of dialkyl carbonate and diol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously produce a dialkyl carbonate and a diol in a short reaction time at high reaction rate, yield and selectivity, by using an easily available aliphatic alcohol containing a dialkyl carbonate, and a cyclic carbonate. SOLUTION: This method for producing a dialkyl carbonate and a diol, is to react a cyclic carbonate with an aliphatic alcohol at the first continuous multistage distillation tower, take out a low boiling point fraction containing the dialkylcarbonate from the top of the tower, continuously take out a high boiling fraction containing the diol and the cyclic carbonate from the lower part of the tower and feed to the second continuous multistage distillation tower. A low boiling fraction containing an azeotropic mixture of the cyclic carbonate with the diol is taken out from the top of the distillation tower and is recycled to the first continuous multistage distillation tower and the diol is continuously taken out from the lower part of the tower of the second continuous multistage distillation tower.

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. 3,642,85]
No. 8, JP-A-54-48715 (US Pat. No. 4,181,676), tertiary aliphatic amine [JP-A-51-212025 (US Pat.
62,884)], a thallium compound [JP-A-5
4-48716 (U.S. Pat. No. 4,307,032)
Specification)], tin alkoxides (JP-A-54-630).
No. 23), zinc, aluminum and titanium alkoxides (JP-A-54-148726), a composite catalyst comprising a Lewis acid and a nitrogen-containing organic base (JP-A-55-64).
550), phosphine compounds (JP-A-55-64)
No. 551), quaternary phosphonium salt (JP-A-56-1)
No. 0144), cyclic amidines (JP-A-59-106).
436), a compound of zirconium, titanium and tin [JP-A-63-41432 (US Pat. No. 4,6).
No. 61,609)], a solid strong basic anion exchanger having a quaternary ammonium group (JP-A-63-2380).
No. 43), ion exchange resins having tertiary amine or quaternary ammonium groups, strongly acidic or weakly acidic ion exchange resins, alkali metal or alkaline earth metal silicates impregnated in silica, ammonium exchanged zeolites. Solid catalysts selected from [JP-A-64-31737 (US Pat. No. 4,691,041)], 3
A homogeneous catalyst (US Pat. No. 4,734,518) selected from secondary phosphine, tertiary arsine, tertiary stibine, divalent sulfur or selenium compounds has been proposed.

Four reaction systems have been proposed so far. These four reaction systems are used in the most representative reaction example, the method for producing dimethyl carbonate and ethylene glycol from ethylene carbonate and methanol.

That is, in the first method, ethylene carbonate, methanol and a catalyst are charged into an autoclave which is a batch type reaction vessel, and the reaction is carried out by maintaining a reaction temperature above the boiling point of methanol under pressure for a predetermined reaction time. It is a complete batch reaction system [US Pat. No. 3,642,858, JP-A-54-48].
715 (US Pat. No. 4,181,676), JP-A-54-63023, JP-A-54-1.
48726, JP-A-55-64550, JP-A-55-6455, and JP-A-56-10144].

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 into 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 method, in order to supplement the methanol that is azeotropically distilled with the dimethyl carbonate that is formed, methanol is continuously or batchwise added to the reaction vessel, but in any case, In this system, the reaction proceeds only in a batch-type reaction vessel 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 the 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. 3,80
3,201), 17 mol (JP-A 1-3110).
54), 22 mol [JP-A-51-122025 (US Pat. No. 4,062,884)], 2
A large excess of 3 mol of methanol [JP-A-54-48716 (US Pat. No. 4,307,032)] is used.

In the third method, a mixed solution of ethylene carbonate and methanol is continuously supplied to a tubular reactor maintained at a predetermined reaction temperature, and unreacted ethylene carbonate and 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. 4,6
61,609), U.S. Pat. No. 4,734,51.
No. 8] and a method using a heterogeneous catalyst fixed in a tubular reactor [JP-A-63-238043].
JP-A-64-31737 (US Pat. No. 4,69
1,041 specification)].

Since the reaction for producing dimethyl carbonate and ethylene glycol by the reaction between 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 It is impossible to raise the equilibrium reaction rate above the temperature. For example, JP-A-63-41432 (US Pat. No. 4,661,
According to Example 1 of the specification (No. 609), the reaction rate of ethylene carbonate is 25% in the flow reaction at 130 ° C. using the raw material having the 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.
The method of 1737 (US Pat. No. 4,691,041) uses a large number of equipments for separation, purification, recovery and recirculation.

The fourth method is a reactive distillation method, that is, ethylene carbonate and methanol are continuously fed into a multi-stage distillation column, and the reaction is carried out 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 for separating a certain dimethyl carbonate and ethylene glycol [JP-A-4-198141, JP-A-5-2138]
30 (German Patent No. 4129316)].

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 (1) a complete batch reaction system and (2) a distillation column at the top. There are four methods, a batch reaction method using the reaction kettle provided, (3) a liquid flow reaction method using a tubular reactor, and (4) reactive distillation method. However, since the transesterification reaction is a reversible equilibrium reaction, it is short. It was very difficult in any method to complete the reaction in time. That is, (1),
In the case of (3), the upper limit of the reaction rate of the cyclic carbonate is determined by the charged composition and the 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 diol from this reaction solution,
Usually, a distillation separation method is 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 accelerates the decomposition of ethylene carbonate, so that it usually has to be distilled off under reduced pressure to form an azeotrope (McKetta, "Enc.
Cyclopedia of Chemical Pro
cessing and Design "vol.2
0, p. 194, Marcel Dekker, 19
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 by using an extremely large amount of the aliphatic monoalcohol, which results in a long reaction. Need time.
In the case of (4), it is possible to proceed the reaction at a higher reaction rate as compared with (1), (2) and (3), and in fact, use a large amount of pure aliphatic monoalcohol. An example in which the reaction rate of ethylene carbonate reaches 100% is also described. However, as the reaction rate increases, the concentration of cyclic carbonate in the reaction solution gradually dilutes and the reaction rate decreases, so a large number of distillation / reaction stages are required to complete the reaction, and as a result, the reaction time (residence) Time) becomes longer.

On the other hand, the dimethyl carbonate produced by the method (4) is distilled as a low boiling point component together with unreacted methanol. Since dimethyl carbonate and methanol form an azeotrope, distillation is carried out under pressure to obtain dimethyl carbonate (JP-A-51-10).
No. 8019), a special separation method is used. Although dimethyl carbonate containing no methanol is usually obtained by this separation method, methanol is obtained as a mixture with dimethyl carbonate, and therefore it is difficult to obtain methanol containing substantially no dimethyl carbonate. For example, the above-mentioned JP-A-51-1080
In the example of JP-A-19, the methanol / dimethyl carbonate mixture (weight ratio: 70/30) is separated by distillation to obtain pure dimethyl carbonate as a column bottom component, but methanol / dimethyl carbonate is used as the overhead fraction. Only a mixture (weight ratio: 95/5) is obtained. Therefore, in the industrial dimethyl carbonate production method,
It is preferred that this methanol / dimethyl carbonate mixture can be used as a raw material as the aliphatic monoalcohol.

However, in the method (4), when a methanol / dimethyl carbonate mixture is used as an aliphatic monoalcohol as a raw material, the reaction rate is remarkably reduced (Example 5 in JP-A-5-213830). However, the reaction cannot be terminated. It is therefore presumed that it is necessary to feed a dialkyl carbonate-free aliphatic monoalcohol in order to achieve a substantially complete conversion of the cyclic carbonate in this process, for which a methanol / dimethyl carbonate azeotrope is used. To obtain methanol substantially free of dimethyl carbonate (for example, a method of combining two distillation columns with different operating pressures)
-212456) is required separately. As described above, no method has been proposed so far in which a cyclic carbonate is substantially 100% converted in a short reaction time to continuously produce a dialkyl carbonate and a diol with a high yield and a high selectivity.

[0016]

DISCLOSURE OF THE INVENTION According to the present invention, an aliphatic monoalcohol and a cyclic carbonate containing 0 to 40% by weight of a dialkyl carbonate, which are industrially easily available, are used as raw materials, and a dialkyl carbonate and a diol are increased. It is an object of the present invention to provide a method for continuous production with high yield and high selectivity.

[0017]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that 0 to 4 which are industrially easily available as a raw material.
In producing an alkyl carbonate and a diol using an aliphatic monoalcohol containing 0% by weight of a dialkyl carbonate and a cyclic carbonate, the reaction solution obtained by the reactive distillation method using a continuous multistage distillation column is distilled. , A low-boiling fraction consisting of methanol / dimethyl carbonate / ethylene glycol / ethylene carbonate and an ethylene glycol fraction substantially free of ethylene carbonate are obtained, and this low-boiling fraction is recycled to the continuous multistage distillation column. It was found that it is possible to convert ethylene carbonate substantially completely by carrying out the above, and the present invention has been completed based on this finding.

That is, the present invention is as follows.
A first invention is a cyclic carbonate which forms a minimum azeotrope with the diol when a dialkyl carbonate and a diol are continuously produced from the cyclic carbonate and an aliphatic monoalcohol. A continuous process for the production of dialkyl carbonates and diols, characterized in that it comprises a second step.

First step: 0-4 in the first continuous multi-stage distillation column
An aliphatic monoalcohol containing 0% by weight of dialkyl carbonate and a cyclic carbonate are continuously supplied,
The reaction is carried out by contacting with the catalyst present in the distillation column, and at the same time, the low boiling point component including the dialkyl carbonate produced by the reaction is continuously withdrawn from the upper part of the distillation column, and the produced diol and unreacted diol The lower column extract containing the cyclic carbonate of the reaction is continuously withdrawn from the lower column. Second step: The lower column extract of the first step is continuously supplied to the second continuous multi-stage distillation column, and the low boiling point upper column extract containing the lowest azeotropic mixture of cyclic carbonate and diol is added to the upper part of the distillation column. And is circulated to the first continuous multi-stage distillation column and diol is continuously extracted from the lower part of the second continuous multi-stage distillation column.

The second invention is the continuous production method of the dialkyl carbonate and the diol of the first invention, wherein the cyclic carbonate is ethylene carbonate. Third
Of the invention, the composition ratio of the cyclic carbonate and the diol extracted from the lower part of the first continuous multi-stage distillation column is 0.001 expressed as the weight ratio of the cyclic carbonate to the diol.
A continuous process for the production of the dialkyl carbonate and diol of 2 above, which is in the range of 0.2.

The method of the present invention can convert substantially 100% of the cyclic carbonate in a short reaction time as compared with the conventional method, for example, the method using only the continuous multi-stage distillation column. It seems that the reason is as follows. The reaction of the present invention is a reversible equilibrium reaction represented by the following general reaction formula (1) in which a dialkyl carbonate (C) and a diol (D) are produced from a cyclic carbonate (A) and an aliphatic monoalcohol (B). Is.

[0022]

Embedded image [Here, R ¹ is a divalent group — (CH ₂ ) _m — (m is 2 to
6 is an integer of 6 and one or more hydrogen has 1 to 1 carbon atoms.
It may be substituted with an alkyl group or an aryl group of 0. R ² represents a monovalent aliphatic group having 1 to 12 carbon atoms, and one or more hydrogens thereof may be substituted with an alkyl group or aryl group having 1 to 10 carbon atoms. ]

Since this reaction usually proceeds in the liquid phase, in order to shorten the reaction time, the low boiling point product among the dialkyl carbonate and diols produced as a result of the reaction is used as the reaction liquid. It needs to be removed from the inside as quickly as possible. However, the prior art (Japanese Patent Laid-Open No. 5-2138)
No. 30, JP-A-6-9507), a large amount of aliphatic monoalcohol is used in an attempt to convert 100% of the cyclic carbonate in one pass. I could not shorten the reaction time because I had to do it. As the reaction proceeds and the concentration of diol increases, the reverse reaction rate increases. Therefore, the higher the conversion rate of cyclic carbonate, the larger amount of aliphatic monoalcohol is used to generate dialkyl carbonate. This is because it needs to be removed from the inside.

On the other hand, in the method of the present invention, the one-pass conversion of the cyclic carbonate in the first continuous multi-stage distillation column is set to less than 100% to cause the reaction in a short reaction time, and thereafter, the unreacted cyclic carbonate is reacted. Is separated by distillation, circulated to the distillation column, and supplied again as a reaction raw material, whereby the reaction rate of the cyclic carbonate can be substantially 100% in a short reaction time.

Further, in order to convert substantially 100% of the cyclic carbonate by the reactive distillation method described in the above-mentioned prior art, it is necessary to use an aliphatic monoalcohol containing no dialkyl carbonate as a raw material. However, in the present invention, since the one-pass conversion is performed at less than 100%, the reaction rate of the cyclic carbonate can be substantially 100% by using the aliphatic monoalcohol containing the dialkyl carbonate.

The first and second continuous multi-stage distillation columns used in the present invention are distillation columns having multi-stages having a theoretical number of distillation stages of 2 or more, and what is required as long as continuous distillation is possible. It may be anything. 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. As the first continuous multi-stage distillation column, the above distillation columns may be used alone, or a plurality of the distillation columns may be connected in series or in parallel to be used in combination.

When a solid catalyst is used in the first continuous multistage distillation column, a packed column type distillation column in which the solid catalyst is a part or all of the packing is also preferably used. The cyclic carbonate used as a raw material in the present invention is a cyclic carbonate represented by the above (A) and forming a minimum azeotrope with the corresponding diol, and for example, ethylene carbonate is preferably used.

The aliphatic monoalcohol, which is the other raw material, is a compound represented by the above (B) and having a boiling point lower than that of 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), butanol (each isomer), and other alcohols having 1 to 4 carbon atoms. In the present invention, the catalyst needs to be present in the first continuous multi-stage distillation column, and in the area where the catalyst is present,
The reaction distillation system is used in which the cyclic carbonate and the aliphatic monoalcohol are brought into contact with each other to allow the reaction to proceed, and at the same time, the low boiling point product is withdrawn from the upper part of the column by distillation.

Any method may be used to allow the catalyst to be present in the first continuous multi-stage distillation column. For example, in the case of a homogeneous catalyst which dissolves in the reaction solution under the reaction conditions, The catalyst can be present in the reaction system by continuously supplying the catalyst to the distillation column, or in the case of a heterogeneous catalyst which does not dissolve in the reaction solution under the reaction conditions, By placing a solid catalyst,
A catalyst may be present in the reaction system, or a combination of these may be used.

When the homogeneous catalyst is continuously supplied to the distillation column, it may be supplied simultaneously with the raw material or may be supplied at a position different from the raw material. Also, at least 1 from the bottom of the tower
The catalyst may be supplied to any position as long as it has more than theoretical stages. However, since the reaction actually proceeds in the distillation column in the region below the catalyst supply position,
It is preferable to feed the catalyst to a region between the top of the column and the feed position. Further, when a heterogeneous solid catalyst is used, the catalyst can be packed in a required amount at any position in the distillation column, and the theoretical layer of the layer in which the catalyst is present may be at least one theoretical stage. , Preferably two or more stages. It is also preferable to use a solid catalyst that also has the effect of packing the distillation column.

The catalyst used in the present invention includes
Various known ones can be used. For example, alkali metals and alkaline earth metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium; hydrides, hydroxides, alkoxides and aryloxides of alkali metals and alkaline earth metals. Basic compounds such as halides and amidates; basic compounds such as alkali metal and alkaline earth metal carbonates, bicarbonates and organic acid salts; triethylamine, tributylamine, trihexylamine, benzyldiethylamine, etc. Tertiary amines; N-alkylpyrrole, N-
Alkylindole, oxazole, N-alkylimidazole, N-alkylpyrazole, oxadiazole, pyridine, alkylpyridine, quinoline, alkylquinoline, isoquinoline, alkylisoquinoline, acridine, alkylacridine, phenanthroline, alkylphenanthroline, pyrimidine, alkylpyrimidine, pyrazine. , Nitrogen-containing heteroaromatic compounds such as alkylpyrazine, triazine and alkyltriazine;

Cyclic amidines such as diazabicycloundecene (DBU) and diazabicyclononene (DBN); organic acid salts of thallium oxide, thallium halide, thallium hydroxide, thallium carbonate, thallium nitrate, thallium sulfate and thallium. Thallium compounds such as tributylmethoxytin, tributylethoxytin, dibutyldimethoxytin, diethyldiethoxytin, dibutylutylenediethoxytin,
Tin compounds such as dibutylphenoxy tin, diphenyl methoxy tin, dibutyl tin acetate, tributyl tin chloride, tin 2-ethylhexanoate; zinc compounds such as dimethoxy zinc, diethoxy zinc, ethylenedioxy zinc, dibutoxy zinc; aluminum trimethoxy , Aluminum triisopropoxide, aluminum tributoxide, and other aluminum compounds; tetramethoxytitanium, tetraethoxytitanium, tetrabutoxytitanium, dichlorodimethoxytitanium, tetraisopropoxytitanium, titanium acetate,
Titanium compounds such as titanium acetylacetonate; phosphorus compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tributylmethylphosphonium halide, trioctylbutylphosphonium halide, triphenylmethylphosphonium halide;

Zirconium compounds such as zirconium halide, zirconium acetylacetonate, zirconium alkoxide, zirconium acetate; lead and lead-containing compounds such as PbO, PbO ₂ , Pb ₃ O ₄
Lead oxides such as PbS, Pb2S3, PbS ₂ and other lead sulfides; Pb (OH) ₂ , Pb ₃ O ₂ (OH) ₂ , P
Lead hydroxides such as b ₂ [PbO ₂ (OH) ₂ ] and Pb ₂ O (OH) ₂ ; Na ₂ PbO ₂ , K ₂ PbO ₂ , NaH
Namarites such as PbO ₂ and KHPbO ₂ ; Na ₂
PbO ₃ , Na ₂ H ₂ PbO ₄ , K ₂ PbO ₃ , K
₂ [Pb (OH) ₆ ], K ₄ PbO ₄ , Ca ₂ Pb
Lead salts such as O ₄ , CaPbO ₃ ; PbCO ₃ , 2P
Lead carbonates such as bCO ₃ .Pb (OH) ₂ and basic salts thereof; Pb (OCH ₃ ) ₂ and (CH ₃ O) Pb
(OPh), Pb (OPh) ₂ and other alkoxy lead compounds,
Aryloxyleads; Pb (OCOCH ₃ ) ₂ , Pb
(OCOCH ₃ ) ₄ , Pb (OCOCH ₃ ) ₂ · PbO
.Lead salts of organic acids such as 3H ₂ O and their carbonates and basic salts;

Bu ₄ Pb, Ph ₄ Pb, Bu ₃ PbC
1, Ph ₃ PbBr, Ph ₃ Pb (or Ph ₆ P
b ₂ ), Bu ₃ PbOH, Ph ₂ PbO and other organic lead compounds (Bu represents a butyl group, Ph represents a phenyl group);
Pb-Na, Pb-Ca, Pb-Ba, Pb-Sn, P
Lead alloys such as b-Sb; lead minerals such as houenite and senaenite, and hydrates of these lead compounds;
An anion exchange resin having a tertiary amino group, an ion exchange resin having an amide group, an ion exchange resin having at least one exchange group of a sulfonic acid group, a carboxylic acid group and a phosphoric acid group, a quaternary ammonium group Ion exchangers such as solid strong basic anion exchanger having an exchange group; silica, silica-alumina, silica-magnesia, aluminosilicate, gallium silicate, various zeolites,
Solid inorganic compounds such as various metal-exchanged zeolites and ammonium-exchanged zeolites are used.

Particularly preferably used as a solid contact is a solid strong basic anion exchanger having a quaternary ammonium group as an exchange group. As such a substance, for example, a quaternary ammonium group is exchanged. A strong basic anion exchange resin, a cellulose strong basic anion exchanger having a quaternary ammonium group as an exchange group, an inorganic carrier-supporting strong basic anion exchanger having a quaternary ammonium group as an exchange group, and the like. To be

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 is 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.

[0038]

Embedded image

In the above formula, X represents an anion, usually X
^{The, F -, Cl -, Br} -, I -, HCO 3 -,
CO ₃ ⁻ , CH ₃ CO ₂ ⁻ , HCO ₂ ⁻ , IO ₃ ⁻ , B
At least one anion selected from rO ₃ ⁻ and ClO ₃ ⁻ is used, preferably Cl ⁻ , Br ⁻ , H.
At least one anion selected from CO ₃ ⁻ and CO ₃ ⁻ is used. As the structure of the resin matrix, either a gel type or a macroreticular type (MR type) can be used, but the MR type is particularly preferable from the viewpoint of high organic solvent resistance.

The cellulose strong 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 the -OH group 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 inorganic carrier-supporting strongly basic anion exchanger having a quaternary ammonium group as an exchange group which can be used in the present invention is a surface hydroxyl group-OH of the inorganic carrier.
It means that the quaternary ammonium group —O (CH ₂ ) _n NR ₃ X is introduced by modifying part or all of the above. However, R and X are as described above. n is usually an integer of 1 to 6, and preferably n = 2. As the inorganic carrier, silica, alumina, silica alumina, titania, zeolite, etc. can be used, preferably silica, alumina, silica-alumina, and particularly preferably silica. As a method for modifying the surface hydroxyl groups of the inorganic carrier, any method can be used. For example, an inorganic carrier and amino alcohol HO (C
H ₂ ) _n NR ₂ is aminoalkoxylated by advancing a dehydration reaction in the presence of a base catalyst, and then alkyl halide RX ′ (X ′ represents halogen, usually Cl,
Br, I, etc. are used) to react with —O (C
H ₂ ) _n NR ₃ X'group. Further, anion exchange is performed to obtain a quaternary ammonium group —O (CH ₂ ) _n NR ₃ X having a desired anion X. Also, n
= In the case of 2, by treating the inorganic support with N, N- dialkyl aziridine, N, after the -OCH ₂ CH ₂ NR ₂ group and N- dialkylamino ethoxylated, by the method described above -O ( CH ₂ ) _n NR ₃ X group.

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 catalyst after performing ion exchange with a desired anion species in advance as a pretreatment. It also comprises a macroreticular or gel-type organic polymer to which a heterocyclic group containing at least one nitrogen atom is bonded, or an inorganic carrier to which a heterocyclic group containing at least one nitrogen atom is bonded. Solid catalysts are also preferably used. Further, a solid catalyst in which some or all of these nitrogen-containing heterocyclic groups are quaternized is also used.

The amount of the catalyst used in the present invention varies depending on the kind of the catalyst used, but when the catalyst is continuously supplied to the reaction zone of the first continuous multi-stage distillation column, the cyclic carbonate as the feedstock is used. It is usually used in an amount of 0.0001 to 50% by weight, which is expressed as a ratio to the total weight of the aliphatic monoalcohol. When the solid catalyst is installed and used in a continuous multi-stage distillation column, a catalyst amount of 0.01 to 75% by volume based on the empty column volume of the distillation column is preferably used.

In carrying out the present invention, the cyclic carbonate as a raw material and the aliphatic monoalcohol containing 0 to 40% by weight of dialkyl carbonate are fed to the first continuous multistage distillation column as follows. There is no particular limitation, and any method may be used as long as they can be brought into contact with the catalyst in at least one stage, preferably two or more stages of the distillation column.
That is, the cyclic carbonate and the aliphatic monoalcohol are used in the first continuous multi-stage distillation column in a stage satisfying the above conditions.
It can be continuously fed from the required number of inlets.
Further, the cyclic carbonate and the aliphatic monoalcohol may be supplied to the same stage of the distillation column or may be introduced into different stages.

The raw materials are continuously supplied to the distillation column as a liquid, a gas, or a mixture of liquid and gas. In addition to supplying the raw materials to the first continuous multistage distillation column in this manner, it is also a preferable method to additionally supply the gaseous raw materials intermittently or continuously from the lower part of the distillation column. Cyclic carbonate is continuously fed to the distillation column in a liquid or gas-liquid mixed state above the stage where the catalyst is present, and the aliphatic monoalcohol is continuously fed to the lower part of the distillation column in a gaseous state. The method is also a preferable method. In this case, in the cyclic carbonate, even if the aliphatic monoalcohol is contained,
Of course it doesn't matter.

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,
It is used in an amount of 0 to 40% by weight, preferably 0.1 to 30% by weight, more preferably 1 to 20% by weight.

The amount ratio of the cyclic carbonate and the aliphatic monoalcohol supplied to the first continuous multi-stage distillation column may vary depending on the kind and amount of the catalyst and the reaction conditions, but usually the cyclic carbonate in the feedstock is changed. On the other hand, the aliphatic monoalcohol is preferably supplied in a molar ratio of 0.01 to 1000 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 conversion of cyclic carbonate may be less than 100%. However, as the conversion rate of the cyclic carbonate in the first step is approached to 100%, the reactor becomes large and the required amount of the aliphatic monoalcohol becomes too large. Further, in the present invention, when the unreacted cyclic carbonate is circulated to the first continuous multi-stage distillation column, the diol is also circulated as a component of the minimum azeotropic mixture, so that when the conversion is low, the circulation amount of the diol is low. Since it increases, the conversion rate of the transesterification reaction in the continuous multi-stage distillation column becomes low. Also, the conversion rate is very low,
When the cyclic carbonate / diol composition ratio in the lower column extract of the first step is higher than the cyclic carbonate / diol composition ratio of the lowest azeotrope, the diol cannot be extracted from the lower section of the second continuous multistage distillation column. Can not. Therefore, the conversion rate of the cyclic carbonate in the first step of the present invention is usually 83 to 9 though it varies depending on the kind of the cyclic carbonate and the operating pressure of the second continuous multi-stage distillation column.
9.9%, preferably 90 to 99%, more preferably 95 to 99%.

In the present invention, the low boiling point component containing the dialkyl carbonate produced in the first continuous multi-stage distillation column is continuously withdrawn from the upper part of the distillation column in the form of liquid, gas or a mixture of liquid and gas. . The extract may be a dialkyl carbonate alone, a mixture with an aliphatic monoalcohol and / or a cyclic carbonate, or may contain a small amount of a high boiling point product.

The withdrawal port for withdrawing the low boiling point component containing the dialkyl carbonate from the first continuous multi-stage distillation column is preferably provided with an withdrawal port for gaseous substances between the raw material supply position and the column top or at the column top. It is more preferable to provide it. You may perform what is called a reflux operation which returns the-part of the 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 first continuous multi-stage distillation column in the form of liquid, gas or a mixture of liquid and gas. In the present invention, the upper part of the continuous multi-stage distillation column refers to the range from the top of the distillation column to about ½ of the column height, and the top is also included. The lower part of the continuous multi-stage distillation column refers to a range from the bottom of the distillation column to about ½ of the column height, and the column bottom is also included. Further, in the present invention, the column bottom extract in the first step includes a diol produced and a non-reacted cyclic carbonate which is continuously withdrawn from the bottom of the first continuous multi-stage distillation column in a liquid and / or gaseous state. And may contain an aliphatic monoalcohol or an aliphatic alcohol and a dialkyl carbonate.

The composition ratio of cyclic carbonate / diol in the bottom extract of the first continuous multi-stage distillation column is such that when distilling and separating in the second continuous multi-stage distillation column, the fraction consisting of the lowest azeotropic mixture of diol and cyclic carbonate. In addition, the composition ratio must be such that the diol can be obtained as a single fraction from the lower part of the column. Further, when the cyclic carbonate / diol composition ratio in the corresponding lower extract is too small, a larger reactor or more aliphatic monoalcohol is used to increase the conversion rate of the cyclic carbonate in the first continuous multi-stage distillation column. Need quantity. Therefore, although it may vary depending on the type of cyclic carbonate, the amount of diol contained in the raw material, and the operating conditions of the second continuous multi-stage distillation column, it is usually 0.001 to 0 in terms of the weight ratio of cyclic carbonate to diol. .2, preferably 0.0
1 to 0.11, more preferably 0.01 to 0.053
Range.

The withdrawal port for withdrawing the column bottom extract from the first continuous multi-stage distillation column is provided at the bottom of the column, and particularly preferably at the bottom of the column. The extract thus extracted may be returned to the lower part of the distillation column in a gaseous state or in a gas-liquid mixture state by heating the minus part with a reboiler. The falling liquid velocity and the ascending vapor velocity in the first continuous multi-stage distillation column are usually caused by flooding or weeping, although they vary depending on the type of the distillation column to be used and the type of packing when a packed column is used. It is carried out within the range not included.

In the present invention, the reaction mainly occurs in the liquid phase in the continuous multi-stage distillation column in the presence of the catalyst,
The amount of the reaction product formed usually depends on the amount of the holdup liquid in the 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, if the hold-up fluid volume is too high,
Since the residence time becomes long, side reactions easily proceed and flooding easily occurs. Therefore, the hold-up liquid volume of the first continuous multi-stage distillation column used in the present invention may vary depending on the distillation conditions and the type of the distillation column, but the volume ratio of the hold-up liquid volume to the empty column volume of the first continuous multi-stage distillation column. In general, 0.005 to 0.75 is used.

Further, in the present invention, the average residence time of the reaction liquid in the first continuous multi-stage distillation column depends on the reaction conditions, the type of continuous multi-stage distillation column and the internal structure (for example, types of trays and packings).
Although depending on the above, it is usually 0.001 to 50 hours, preferably 0.01 to 10 hours, and more preferably 0.05 to
5 hours. The reaction temperature is a temperature in the first continuous multi-stage distillation column, and is usually 0 to 350 ° C., preferably 20 to 200 ° C., though it varies depending on the type of raw materials used and the reaction pressure. The reaction pressure may be any of reduced pressure, normal pressure and increased pressure, and is usually 0.00001 when expressed as an absolute pressure.
Is about 20 kg / cm ² .

A part of the extract from the lower part of the tower in the first step
The unreacted cyclic carbonate can be circulated to the continuous multi-stage distillation column by supplying it to the continuous multi-stage distillation column. At that time, the position of the inlet for supplying the column bottom extract to the continuous multistage distillation column is not particularly limited, but it is preferably supplied to the upper part of the distillation column.

It is also possible to directly feed the bottom product extracted from the first step to the second step. At this time, when a catalyst that can be dissolved in the reaction solution under the reaction conditions is used, the catalyst used in the first step is directly supplied to the second step. Also,
After the lower column withdrawal product of the first step is introduced into a catalyst separation device and separated into a low boiling point component containing a cyclic carbonate and a diol and a high boiling point component containing a catalyst, a part or all of the low boiling point component is separated into a second It is also a preferred method to circulate by supplying to the continuous multi-stage distillation column, while circulating a part or all of the high boiling point component containing the catalyst to the first continuous multi-stage distillation column. A distillation column or an evaporator is preferably used as the catalyst separation device.

The bottom product of the first step is used as a liquid or a vapor or a mixture of a liquid and a vapor as a liquid or vapor or a mixture of the liquid and vapor from an inlet provided in an arbitrary number in any stage of the second continuous multi-stage distillation column.
It is continuously supplied to a continuous multistage distillation column, and is distilled and separated into each fraction in the distillation column. Unreacted aliphatic monoalcohol and unreacted cyclic carbonate are withdrawn from the upper part of the second continuous multi-stage distillation column as a column top extract in a gaseous or liquid form or a gas / liquid mixture and circulated to the first continuous multi-stage distillation column. It The extract consists of an aliphatic monoalcohol, a cyclic carbonate and a diol, and may contain a small amount of dialkyl carbonate. The outlet of the extract is usually provided in the second continuous multi-stage distillation column, between the inlet of the lower extract of the first step column and the top of the tower or at the top of the tower, preferably at the top of the tower. It is provided. A reflux operation may be carried out in which a part of the column top extract of the second continuous multistage distillation column thus extracted is returned to the top of the distillation column. The reflux ratio is usually 1 to 10, preferably 1 to 5.

The diol is withdrawn from the lower part of the second reactive distillation column as a bottom product of a gaseous or liquid or gas / liquid mixture. The extract may be a diol alone or a mixture containing a diol. It may also contain a catalyst component. The method of extracting the diol in a gaseous state is a preferable method because it can be separated from the high boiling point component. The thermal energy required for the distillation operation is carried out by heating the bottom liquid. The heating is performed by a reboiler provided outside the second continuous multistage distillation column or a heater provided inside the column bottom.

The bottom liquid of the second continuous multi-stage distillation column is mainly composed of diol. When a catalyst that can be dissolved in the reaction liquid under reaction conditions is used, the bottom liquid contains the catalyst component. When carrying out the reaction for a long time, it is necessary to withdraw this catalyst component continuously or batchwise, but in order to reduce the amount of the diol that is withdrawn along with the catalyst component, the catalyst component is concentrated. It is preferable. The degree of enrichment varies depending on the type of catalyst used and the reaction solution, but is usually 0.1 to 50% by weight, preferably 0.5 to 30% by weight, as expressed by the concentration of the catalyst component in the bottom liquid. %.

Concentration of the bottom liquid may be carried out at the bottom of the column, or it may be introduced into a separation device comprising a distillation column or an evaporator and separated into a low boiling point fraction containing a diol and a high boiling point fraction containing a catalyst component. You may. When a catalyst that can be dissolved in the reaction solution under the reaction conditions is used, it is also a preferable method to circulate a part or all of this concentrated bottom liquid as a catalyst by supplying it to the first reactive distillation column. .

The operating pressure in the second step is carried out within a pressure range in which the cyclic carbonate and the diol form a minimum azeotrope, and varies depending on the raw materials used. For example, when ethylene carbonate is used as the cyclic carbonate, it is usually , 50 to 0.01 torr, preferably 50
~ 0.1 torr, more preferably 50 to 1 torr
performed in r. The operating temperature depends on the raw materials used, operating pressure,
Depending on the composition, it is usually 50 to 2 at the temperature at the bottom of the column.
It is carried out at 50 ° C, preferably 70 to 150 ° C. Second
The extract from the upper part of the continuous multi-stage distillation column is circulated to the first continuous multi-stage distillation column, and the position of its inlet may be anywhere other than the bottom of the column, but it is usually between the cyclic carbonate inlet and the column. It is the bottom of the tower.

In a particularly preferred embodiment of the present invention, ethylene carbonate is used as the cyclic carbonate and methanol is used as the aliphatic monoalcohol to produce the corresponding dialkyl carbonate dimethyl carbonate and ethylene glycol. In this case, ethylene carbonate having a high boiling point among the raw materials is continuously in a liquid state in the distillation column through an inlet provided between the stage where the catalyst of the first continuous multistage distillation column is present and the top of the column. Methanol (which may contain a small amount of dimethyl carbonate), which is a low-boiling raw material, is continuously supplied in a gaseous state from the lower part of the column into the distillation column. Then, dimethyl carbonate which is a low boiling point product produced by the reaction is continuously withdrawn from the top of the distillation column. The high-boiling point product, ethylene glycol, is continuously withdrawn in liquid form from the lower part of the first continuous multi-stage distillation column,
It is supplied to a continuous multi-stage distillation column. Ethylene carbonate /
The low boiling point distillate containing the lowest azeotropic mixture of ethylene glycol and methanol is withdrawn from the upper part of the second continuous multi-stage distillation column and circulated to the first continuous multi-stage distillation column, and ethylene glycol is removed from the second continuous multi-stage distillation column. It is continuously withdrawn from the bottom of the tower.

In the present invention, it is not always necessary to use a solvent, but suitable inert solvents such as ethers, aliphatic hydrocarbons and aromatic hydrocarbons for the purpose of facilitating the reaction operation and the like. , Halogenated aliphatic hydrocarbons,
Halogenated aromatic hydrocarbons and the like can be used as a reaction solvent. In addition, nitrogen, which is inert to the reaction,
An inert gas such as helium or argon may be allowed to coexist in the reaction system, and an inert gas or reaction may be performed from the lower part of the continuous multistage distillation column for the purpose of accelerating the distillation of the low boiling point product to be produced. The active low-boiling organic compound may be introduced in a gaseous state.

[0065]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 Dimethyl carbonate and ethylene glycol were continuously produced from ethylene carbonate and methanol using the apparatus shown in FIG.

Dixon packing (3
20 cm from the top 4 of the first continuous multi-stage distillation column 1 composed of a packed column having an inner diameter of 2 cm and a packing height of 120 cm packed with φ).
To the position of ethylene carbonate, methanol, dimethyl carbonate, sodium hydroxide (weight ratio: ethylene carbonate / methanol / dimethyl carbonate / sodium hydroxide = 29.6 / 65.4 / 4.9 / 0.0
The mixture consisting of 9) (raw material 1) was continuously fed in liquid form from conduit 2 via preheater 3. The bottom liquid of the first continuous multistage distillation column was heated by the reboiler 6. The first continuous multi-stage distillation column was operated at atmospheric pressure.

Gaseous components distilled from the top 4 are condensed in the condenser 7.
It was condensed in, partly refluxed, and then extracted as a liquid. The column bottom liquid extracted from the column bottom 8 was filled with Dixon packing (3φ) as a packing through a conduit 9.
It was fed to a position 20 cm from the top of the second continuous multi-stage distillation column 10 consisting of a packed column having an inner diameter of 2 cm and a packing height of 120 cm.

The second continuous multistage distillation column has a top pressure of 10 torr.
The gaseous component which is operated at r and distills from the top of the column is condensed in a cooler 13, a part of which is refluxed through a conduit 14, and the rest is condensed through a conduit 15 from the top of the first continuous multistage distillation column. It circulated to the position of 60 cm. The bottom liquid of the second continuous multi-stage distillation column was heated by the reboiler 18, and a part thereof was extracted from the conduit 20. This bottom liquid did not contain ethylene carbonate.

The reaction conditions and the results after steady state are shown in Table 1. This result shows that the conversion of ethylene carbonate is 100 by performing the first step and the second step.
%, The yield of ethylene glycol is 99% or more (ethylene glycol selectivity based on ethylene carbonate is 99%
), The yield of dimethyl carbonate is 99% or more (selectivity of dimethyl carbonate based on ethylene carbonate is 99% or more).

(Example 2) The composition of the raw material supplied from the conduit 2 was ethylene carbonate, methanol, dimethyl carbonate, sodium methoxide (weight ratio: ethylene carbonate / methanol / dimethyl carbonate / sodium methoxide = 29.6 / 65). .4 / 4.9 /
0.15) except that the conditions were the same as in Example 1. The reaction conditions and the results after steady state are shown in Table 1.

Comparative Example 1 The apparatus shown in FIG. 2, that is, the apparatus used in Example 1 except for the second continuous multistage distillation column was used, and the circulation from the second continuous distillation column was not performed. Other than that, the reaction was performed in the same manner as in Example 1 (however, the column height of the continuous multistage distillation column 1 was 200 cm). The reaction conditions and the results after steady state are shown in Table 2. As a result, the conversion rate of ethylene carbonate was 91.4%, the yield of ethylene glycol was 89% (the ethylene glycol selectivity was 97% based on ethylene carbonate), and the yield of dimethyl carbonate was 89% (dimethyl carbonate based on ethylene carbonate). The carbonate selectivity is 97%).

Example 3 Using the apparatus shown in FIG. 3, dimethyl carbonate and ethylene glycol were continuously produced from ethylene carbonate and methanol. Dickson packing (3φ) was filled as a filling,
From the ethylene carbonate and sodium hydroxide (weight ratio: ethylene carbonate / sodium hydroxide = 99.7 / 0.3) to the top 4 of the first continuous multi-stage distillation column 1 consisting of a packed column having an inner diameter of 2 cm and a packing height of 120 cm. Is continuously supplied in liquid form from conduit 2 through preheater 3 to obtain a mixture (raw material 2) composed of methanol and dimethyl carbonate (weight ratio: methanol / dimethyl carbonate = 93/7). The reaction was carried out in the same manner as in Example 1 except that the gas was continuously supplied from 5 to the bottom of the column via the evaporator 6. Table 3 shows the reaction conditions and the results after the steady state.

Example 4 Example 3 except that a mixture of ethylene carbonate and diazabicycloundecene (DBU) (weight ratio: ethylene carbonate / DBU = 99.5 / 0.5) was used as the raw material 1. The reaction was carried out in the same manner as in. The reaction conditions and the results after steady state are
It is shown in the table.

(Example 5) Same as Example 3 except that a mixture of ethylene carbonate and sodium methoxide (NaOMe) (weight ratio: ethylene carbonate / NaOMe = 99.5 / 0.5) was used as the raw material 1. The reaction was carried out by the method of. Table 3 shows the reaction conditions and the results after the steady state.

Example 6 Ethylene carbonate, sodium hydroxide (weight ratio: ethylene carbonate / NaO
Example 3 except that a mixture of H = 99.5 / 0.5) was used as the raw material 1 and a mixture of methanol and dimethyl carbonate (weight ratio: methanol / dimethyl carbonate = 85/15) was used as the raw material 2. The reaction was carried out in the same manner as in. Table 3 shows the reaction conditions and the results after the steady state.

Comparative Example 2 The apparatus shown in FIG. 4, that is, the apparatus used in Example 3 except for the second continuous multistage distillation column was used, and the circulation from the second continuous distillation column was not performed. Other than that, the reaction was performed in the same manner as in Example 3 (however, the tower height of the continuous multistage distillation column 1 was 200 cm). Table 4 shows the reaction conditions and the results after the steady state.

Example 7 Dimethyl carbonate and ethylene glycol were continuously produced from ethylene carbonate and methanol by using the apparatus shown in FIG. From the top 4 to the 5th stage of the first continuous multistage distillation column 1 consisting of an Oldershaw type multistage distillation column having a column diameter of 5 cm and a column height of 160 cm, in which 40 stages of sieve trays having an opening ratio of 2% and a liquid depth of 5 mm were installed. , Ethylene carbonate, sodium hydroxide (weight ratio: ethylene carbonate / sodium hydroxide =
99.9 / 0.1) mixture (raw material 1) into conduit 2
Was continuously supplied in liquid form through the preheater 3. A mixture (raw material 2) composed of a mixture of methanol and dimethyl carbonate (weight ratio: methanol / dimethyl carbonate = 93/7) (raw material 2) was continuously introduced into the bottom of the first continuous multi-stage distillation column in a gaseous state from a conduit 5 through an evaporator 6. Supplied to. The first continuous multi-stage distillation column was operated at atmospheric pressure.

The gaseous component distilled from the top 4 is the condenser 7.
It was condensed in and extracted as a liquid. The bottom liquid withdrawn from the bottom 8 is filled with McMahon packing (6φ) as a filling material through a conduit 9 and has an inner diameter of 50 mm and a filling height of 1
It was fed to a position 20 cm from the top of the second continuous multistage distillation column 10 composed of a 20 cm packed column.

The second continuous multistage reactive distillation column has a top pressure of 10 t.
The gaseous component distilled from the top of the first continuous multi-stage distillation column is operated at orr, and the gaseous component distilled from the top of the column is condensed in a cooler 13 and a part of the gas is refluxed through a conduit 14 and the rest is condensed through a conduit 15 from the top of the first continuous multistage distillation column. It circulated to the position of 20 steps. The bottom liquid of the second continuous multi-stage distillation column was heated by the reboiler 18, and a part thereof was extracted from the conduit 20. This bottom liquid did not contain ethylene carbonate. Ethylene glycol was extracted in a gaseous form from an extraction port provided at a position 80 cm from the top of the second continuous multistage reactive distillation column, and condensed in a condenser 21. The bottom liquid of this column did not contain ethylene carbonate either. Table 5 shows the reaction conditions and the results after the steady state.

Example 8 Methanol and dimethyl carbonate (weight ratio: methanol / dimethyl carbonate =
The reaction was performed in the same manner as in Example 7 except that the mixture consisting of 85/15) was used as the raw material 2. Table 5 shows the reaction conditions and the results after the steady state.

[0081]

[Table 1]

[0082]

[Table 2]

[0083]

[Table 3]

[0084]

[Table 4]

[0085]

[Table 5]

[0086]

Industrial Applicability According to the method of the present invention, an aliphatic monoalcohol containing 0 to 40% by weight of a dialkyl carbonate and a cyclic carbonate which are easily available as raw materials are used to produce a dialkyl carbonate and a diol in a high yield and a high yield. It was possible to manufacture continuously with a selectivity.

[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 3.

FIG. 4 is a schematic diagram of an apparatus used in Comparative Example 2.

FIG. 5 is a schematic diagram of an apparatus used in Example 7.

[Explanation of symbols]

 1: First continuous multi-stage distillation column 3: Preheater 6, 18: Reboiler 6 ': Evaporator 10: Second continuous multi-stage distillation column 7, 13, 21: Condenser

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C07C 68/08 C07C 68/08 69/96 69/96 Z

Claims (3)

[Claims] 1. When continuously producing a dialkyl carbonate and a diol from a cyclic carbonate and an aliphatic monoalcohol, the cyclic carbonate is a cyclic carbonate which forms a minimum azeotrope with the diol. A continuous process for the production of dialkyl carbonates and diols, characterized in that it comprises two steps. First step: An aliphatic monoalcohol containing 0 to 40% by weight of dialkyl carbonate and a cyclic carbonate are continuously supplied to a first continuous multi-stage distillation column and brought into contact with a catalyst present in the distillation column. The low boiling point component containing the dialkyl carbonate produced by the reaction is continuously withdrawn from the upper part of the distillation column at the same time as the reaction is carried out, and the withdrawal product at the lower part of the column containing the produced diol and unreacted cyclic carbonate is removed from the column. Pull out continuously from the bottom. Second step: The lower column extract of the first step is continuously supplied to the second continuous multi-stage distillation column, and the low boiling point upper column extract containing the lowest azeotropic mixture of cyclic carbonate and diol is added to the upper part of the distillation column. And is circulated to the first continuous multi-stage distillation column and diol is continuously extracted from the lower part of the second continuous multi-stage distillation column. 2. The continuous process for producing a dialkyl carbonate and a diol according to claim 1, wherein the cyclic carbonate is ethylene carbonate. 3. The composition ratio of the cyclic carbonate and the diol extracted from the lower part of the first continuous multi-stage distillation column is 0.0 expressed as the weight ratio of the cyclic carbonate to the diol.
A continuous process for the production of dialkyl carbonates and diols according to claim 2, in the range from 01 to 0.2.