JP2955866B2 - Method for producing dialkyl carbonate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a dialkyl carbonate.

More specifically, the present invention provides a method for producing a dialkyl carbonate, comprising reacting a cyclic carbonate and an alcohol in the presence of a solid basic anion exchange resin, using a raw material having a water concentration of 160 ppm or less at a relatively low temperature. About.

(Prior Art) As a method for producing a dialkyl carbonate by reacting a cyclic carbonate and an alcohol in the presence of a catalyst, a method using a tertiary aliphatic amine as a catalyst,
Mainly uniform such as a method using an alkali metal or an alkali metal compound, a method using a thallium compound, a method using a tin alkoxide, a method using a composite catalyst composed of a Lewis acid and a nitrogen-containing organic base, a method using a quaternary phosphonium salt, and the like. Based catalysts have been used.

In this case, there is a problem that it is difficult to separate the catalyst and the reaction mixture.

On the other hand, as a method for using a heterogeneous catalyst which can easily separate the catalyst and the reaction mixture, a method using a basic exchange resin containing a tertiary aliphatic amine group (Japanese Patent Publication No. 59-28)
542), a method using a strongly basic exchange resin containing a quaternary ammonium group (JP-A-63-238043),
A method using a basic or acidic exchange resin, silicates containing alkali and alkaline earth metals, etc.
No. 31,737) and a method using a silica-titania solid acid catalyst (Japanese Patent Publication No. Sho 61-5467).

(Problems to be Solved by the Invention) In a method for producing a dialkyl carbonate by a reaction between a cyclic carbonate and an alcohol using a known heterogeneous catalyst, a relatively high reaction temperature is required for catalytic activity. It also causes deterioration of the exchange resin having a low heat-resistant temperature. In addition, there is a problem that a side reaction such as dehydration condensation of glycol occurs during the reaction, resulting in a decrease in selectivity.

(Means for Solving the Problems) The present inventors have conducted intensive studies on a method for producing a dialkyl carbonate from a cyclic carbonate and an alcohol, and as a result, using a solid basic anion exchange resin as a catalyst and using a raw material having a water concentration of 160 ppm or less. As a result, they have found that dialkyl carbonate can be produced stably at a very high yield and for a long time even at a relatively low temperature.

That is, the present invention provides a quaternary ammonium group or a tertiary amine group as a functional group, and in the presence of a solid basic anion exchange resin containing a carbonate group and / or a hydrogen carbonate group, to reduce the water concentration to 160 ppm or less. A method for producing a dialkyl carbonate, characterized in that a reaction is performed using a starting material containing a cyclic carbonate and an alcohol.

Examples of the cyclic carbonate used in the present invention include, for example, alkylene carbonates such as ethylene carbonate and propylene carbonate, 1,3-dioxacyclohex-2-one, and 1,3-dioxacyclohepta-2-one. However, ethylene carbonate and propylene carbonate are preferably used from the viewpoint of easy availability.

Examples of the alcohol include aliphatic alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and 1-methylethyl alcohol; and monohydric alcohols having 1 to 12 carbon atoms such as alicyclic alcohols such as cyclohexanol. .

Examples of the catalyst used in the present invention include a strongly basic anion exchange resin having a quaternary ammonium group as a functional group, and a weakly basic anion exchange resin having a tertiary amine as a functional group. Or one having a hydrogen carbonate root. As the resin matrix, any of a styrene-based gel type and a macroreticular type (MR type) can be used, but the MR type is preferable because of high organic solvent resistance.

As the solid strong basic anion exchange resin and the solid weak basic anion exchange resin having a quaternary ammonium group or a tertiary amine group as a functional group, commercially available ones can also be used. In such a case, it is preferable to perform ion exchange with a desired anionic species in advance as a pretreatment, and then use the catalyst as a catalyst after dehydration.

The use form of the above-mentioned anion exchange resin is usually used as fine powder or spherical particles having an average particle diameter of 0.2 to 10 mm.

As a mode of the reaction, a commonly used method such as a fluidized bed system, a fixed bed system, and a stirring system can be used. In addition, any of a flow-type method and a batch-type method may be used, and the separation of the reaction solution and the catalyst can be easily performed.

In practicing the present invention, the reaction temperature is usually from 0 to 120.
C. is used, but sufficient yield can be obtained even at a relatively low temperature of 0 to 45.degree. C., more preferably 15 to 40.degree.

The reaction time may vary depending on the type and composition of the cyclic carbonate and alcohol as the raw materials, and the reaction temperature.
For example, when a flow reaction is performed, expressed in terms of the liquid hourly space velocity (LHSV) with respect to the total feed liquid, usually 0.05 to 40 hr ^-1 , preferably 0.1 to 20 hr ^-1 , more preferably 0.2 to 10 hr ^{-1 is} used. Is done. In the case of a batch reaction, usually 0.05 to 60 hours
^-1 , preferably 0.1 to 40 hr ^-1 , more preferably 0.2 to 20 hr ^-1
hr ^-1 is used.

The amount ratio of the cyclic carbonate and the alcohol as raw materials is
Can be used in a wide range. However, if the molar ratio of alcohol to cyclic carbonate is too large, the amount of alcohol to be recovered is large, which is not practical. On the other hand, if the molar ratio is too small, the conversion rate of the cyclic carbonate becomes low, so that it is not practical to increase the recovery amount.

Therefore, the molar ratio of the alcohol to the starting material cyclic carbonate is usually 0.05 to 100, preferably 0.1 to 40, more preferably 0.2 to 20.

In the method of the present invention, the amount of water in the raw material has a large effect on the yield of dialkyl carbonate, particularly under low-temperature conditions, and this effect is large, and when the amount of water exceeds 200 ppm, the catalytic performance significantly decreases, and the dialkyl carbonate The yield decreases. Therefore, the water concentration in the raw material is 16
0 ppm or less, preferably, 130 ppm or less, more preferably,
It is necessary to make it 100 ppm or less.

In the raw materials, in addition to cyclic carbonate and alcohol,
For example, it may contain a recycle reaction intermediate, if desired, a solvent, etc., and the water content needs to be the above-mentioned concentration with respect to all the supply liquid supplied to these reaction sites.

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to only these Examples.

The conversion, selectivity, and yield shown in the examples are numerical values calculated by the following formulas.

In this reaction, a mono-substituted monoalkyl-substituted carbonate is produced as a reaction intermediate, and this was regarded as a cyclic carbonate as a raw material equivalent.

Example 1 (Preparation of catalyst) Dowex MSA-1 [Dow Chemical Co., Ltd., styrene
Anion exchange resin (Type I) made of strong base Anion species Cl ]
Pretreatment is carried out by the method described below,
I was sorry.

250 ml of Dowex MSA-1 was added to a 1N aqueous solution of NAOH 50
After stirring in 0 ml for 1 hour, it was filtered and washed with 2,000 ml of water.

, And then washed with water up to PH7.

Further, the mixture was stirred in 500 ml of a 1N Na ₂ CO ₃ aqueous solution for 1 hour, filtered, and washed with 2,000 ml of water.

After the above operation was repeated twice more, the resultant was washed with water up to PH7.

The resin subjected to the above treatments (1) to (4) was placed in 500 ml of dehydrated methanol, stirred for 10 minutes, and the operation of decantation was repeated to dehydrate the resin. Thereafter, the resin was stored in dehydrated methanol to obtain catalyst A.

(Reaction) The catalyst A obtained above was put into a tubular reactor (outer diameter 12.7 mm, inner capacity
20ml), immersed in oil bath, 20 ℃, 1kg / cm ²
First, methanol was sent. Then, adjust the water concentration to 100p
pm, a mixed raw material of ethylene carbonate and methanol (methanol / ethylene carbonate molar ratio =
The flow was switched to 2), and the liquid feeding was started at a flow rate of 40 ml / hr (LHSV = 2). When the reaction system becomes steady, analysis of the reaction solution is performed.
The measurement was carried out by a temperature-raising gas chromatograph (column temperature: from 60 ° C. to 220 ° C. at 10 ° C./min, detector FID) equipped with a 2 m PEG20M glass column.

As a result, the conversion of ethylene carbonate was 45%, the selectivity of dimethyl carbonate was 99% or more, and dimethyl carbonate showed almost equilibrium yield. In addition, production of CO _{2 as} a by-product of the reaction was not observed.

Example 2 A reaction was carried out in the same manner using the same catalyst A and a raw material having a water concentration of 100 ppm as in Example 1, except that the reaction was carried out at a feed rate of the raw materials of 100 ml / hr (LHSV = 5). . The results are shown in Table 1. As a result, dimethyl carbonate was obtained at an extremely high yield, and production of CO _{2 as} a by-product of the reaction was not observed.

Example 3 The same procedure as in Example 1 was carried out except that the reaction was carried out at a reaction temperature of 40 ° C. and a reaction pressure of 5 kg / cm ² , and a catalyst A and a water concentration of 100 p.
The reaction was carried out in the same manner using the raw material of pm. The results are shown in Table 1. In addition, production of CO _2, a by-product of the reaction, was not observed.

Example 4 The same procedure as in Example 1 was carried out except that the reaction was carried out at a reaction temperature of 60 ° C. and a reaction pressure of 5 kg / cm ² , and a water concentration of 100 p
The reaction was carried out in the same manner using the raw material of pm. The results are shown in Table 1. A small amount of CO ₂ , a by-product of the reaction, was detected.

Example 5 The same procedure as in Example 1 was carried out except that the reaction was carried out at a reaction temperature of 90 ° C. and a reaction pressure of 5 kg / cm ² , and a water concentration of 100 p.
The reaction was carried out in the same manner using the raw material of pm. The results are shown in Table 1. Also, at this time, the reaction by-product CO
₂ was produced in an amount of 0.08 mol% with respect to the raw material ethylene carbonate.

As shown in Examples 1 to 5, the lower the reaction temperature, the higher the conversion of ethylene carbonate.

Example 6 A reaction was carried out by the same method using the same catalyst A as in Example 1 except that the reaction was carried out with the water content of a mixed raw material of ethylene carbonate and methanol being 150 ppm. The results are shown in Table-2.

Comparative Example 1 A reaction was carried out by the same method using the same catalyst A as in Example 1 except that the reaction was carried out at a water concentration of a mixed raw material of ethylene carbonate and methanol of 200 ppm. The results are shown in Table-2.

Comparative Example 2 (Preparation of catalyst) Catalyst B having a chlorine group by the same method as in Example 1 except that 1N HCl was used instead of 1N Na ₂ CO ₃ aqueous solution.
I got

(Reaction) Except that the catalyst B was used, the same water concentration of 100 p as in Example 1 was used.
The reaction was carried out in the same manner using the raw material of pm. As a result, generation of dimethyl carbonate was not recognized.

Example 7 The catalyst preparation of Amberlyst A-21 (a tertiary aliphatic amine type (free base type) weakly basic anion exchange resin manufactured by Rohm and Haas Company) was carried out in the same manner as in Example 1, and A catalyst C having a root was obtained.

(Reaction) Except for using the catalyst C, the same water concentration of 100 p as in Example 1 was used.
The reaction was carried out in the same manner using the raw material of pm. As a result, the conversion of ethylene carbonate was 27%, and the selectivity of dimethyl carbonate was 99% or more.

Comparative Example 3 The reaction was carried out by the same method using the same Amberlyst A-21 catalyst as in Example 8, except that the water concentration of the mixed raw material of ethylene carbonate and methanol was changed to 200 ppm and the reaction was carried out. As a result, the conversion of ethylene carbonate was 2%, and the selectivity of dimethyl carbonate was 99% or more.

Example 8 Using the catalyst A, a reaction was performed in the same manner as in Example 1 except that the water concentration of the mixed raw material of ethylene carbonate and methanol was 100 ppm, and the reaction was continued for 1,000 hours. Table 3 shows the results.
It was shown to.

Example 9 A 500 ml autoclave was charged with 50 ml of catalyst A, 230 g of a mixed material of ethylene carbonate and methanol (mole ratio of methanol / ethylene carbonate = 2, water concentration 100 ppm), and N ₂ purge was performed several times. Stirring was started to carry out the reaction. After a lapse of 60 minutes, the reaction mixture was analyzed. As a result, the conversion of ethylene carbonate was 45% and the selectivity of dimethyl carbonate was 99% or more.

Example 10 The same catalyst A as in Example 1 was used except that the reaction temperature was changed from 20 ° C. to 40 ° C., and ethylene carbonate was changed to propylene carbonate (mole ratio of methanol / propylene carbonate = 2), and the raw material water concentration was 100 ppm. The reaction was performed in the same manner as described above. As a result, the conversion of propylene carbonate was 40%, and the selectivity of dimethyl carbonate was 99%.

Example 11 The same catalyst A as in Example 1 was used except that the reaction temperature was changed to 20 ° C. to 40 ° C., and methanol was changed to ethanol (molar ratio of ethanol / ethylene carbonate = 2), and the raw material water concentration was set to 100 ppm. The reaction was performed in a similar manner. As a result, the conversion of ethylene carbonate was 41%, and the selectivity of diethyl carbonate was 99%.

(Effect of the Invention) According to the present invention, a dialkyl carbonate can be obtained in a high yield and a high selectivity under mild reaction conditions using a cyclic carbonate and an alcohol as raw materials.

In addition, industrial advantages such as stable production for a long period of time because catalyst hardly deteriorates are extremely large.

Claims (4)

(57) [Claims] 1. A raw material containing a cyclic carbonate and an alcohol in the presence of a solid basic anion exchange resin having a quaternary ammonium group or a tertiary amine group as a functional group and containing a carbonate group and / or a hydrogen carbonate group. A method for producing a dialkyl carbonate, wherein a raw material having a water concentration of 160 ppm or less is used. 2. The method according to claim 1, wherein a raw material having a water concentration of 130 ppm or less is used. 3. The method according to claim 1, wherein a raw material having a water concentration of 100 ppm or less is used. 4. The method according to claim 1, wherein the reaction temperature is 0 to 120 ° C.