KR20000051813A - The preparation of non-symmetric dialkyated carbonates - Google Patents

Abstract

PURPOSE: A process for preparing an asymmetrical chain carbonic acid ester by using a specific catalyst comprising an alkoxide salt of the group IA as a catalytically active component is provided which produces the title compound in a high yield without side products. CONSTITUTION: A process comprises subjecting two kinds of symmetrical chain carbonic acid esters to interesterification in the presence of a specific catalyst, wherein the amount of specific catalyst to be used as a reaction catalyst is 0.0001 to 5% by weight of an alkoxide salt of the group IA. The symmetrical chain carbonic acid esters are selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate and dibutyl carbonate. The asymmetrical chain carbonic acid ester is useful as a solvent, a reagent for various organic syntheses and especially a solvent for a secondary battery of lithium ion. The process has an advantage of having almost no loss by the decomposition of a reactant even when a reaction mixture is subjected to separation in a distillation apparatus after reaction.

Description

Method for preparing asymmetric linear carbonate ester {THE PREPARATION OF NON-SYMMETRIC DIALKYATED CARBONATES}

The present invention relates to a method for producing an asymmetric linear carbonate, and more particularly, using an alkoxide salt of group IA element as a catalyst when preparing an asymmetric linear carbonate by reacting two different symmetric linear carbonates under a catalyst. It relates to a method for producing an asymmetric linear carbonate, characterized in that.

As a conventional method for producing asymmetric linear carbonate ester, a carbonate ester is obtained by reacting different alcohols with chloroacetic acid ester produced by the dehydrochlorination reaction of phosgene and an alcohol as shown in the following [Formula 1] to perform dehydrochlorination reaction The way is.

Here, R ₁ and R ₂ are each different alkyl groups.

However, the above method is difficult to be carried out on a large scale, considering that hydrogen chloride is generated and the reactant phosgene is a highly toxic compound. Therefore, in order to prepare an asymmetric linear carbonate ester, a transesterification reaction is generally used. Such transesterification reaction may be performed by reacting a symmetric linear carbonate ester with an alcohol having another alkyl group as shown in [Formula 2] below, There is a method of reacting two different symmetric linear carbonate esters as in the formula (3).

Provided that each of R ₁ and R ₂ is an alkyl group having a different carbon number.

Provided that each of R ₁ and R ₂ is an alkyl group having a different carbon number.

As an example of a method for preparing an asymmetric linear carbonate from a transesterification reaction between a symmetric linear carbonate and an alcohol as in [Formula 2], Japanese Patent Laid-Open No. 94-16660 uses a metal carbonate, K ₂ CO ₃ , as a catalyst. Presenting. However, this method is of low industrial value because of the low activity of the catalyst and the production of alcohol as a by-product. That is, the selection of the catalyst is also a problem, but the reaction between the symmetric linear carbonate ester and the alcohol, such as [Formula 2], produces an alcohol R ₁ OH as a by-product, so the yield and productivity are lower than those of the Formula [3]. It becomes a disadvantage. Therefore, among the methods for producing asymmetric linear carbonate esters through transesterification reaction, the method of producing by reacting two different symmetric linear carbonate esters can be said to be a practical method in terms of yield and productivity.

As an example, Japanese Patent Laid-Open No. 97-328453 proposes a method for preparing an asymmetric linear carbonate by exchanging two different symmetric linear carbonates with mutual alkyl groups using a Group IIIA oxide catalyst without using alcohol as a reactant. have. However, in this method, since the catalyst used is a heterogeneous oxide catalyst, it is low in terms of economical value because it requires a reaction time of 30 hours or more under a harsh reaction environment, for example, 5-10 atm and 140 ° C. Therefore, when preparing an asymmetric linear carbonate ester from two different symmetric linear carbonate esters, there is a strong demand for improving the catalytic activity so that the reaction rate of the transesterification reaction can be increased to improve the yield.

An object of the present invention is to solve the above problems, in the production of asymmetric linear carbonate by reacting two different symmetric linear carbonate ester under a catalyst, alkoxide salt of group IA element 0.0001 to 5 weight as a reaction catalyst It is to provide a method for producing an asymmetric linear carbonate, characterized in that the use of%.

That is, the present invention provides a method for producing an asymmetric linear carbonate ester, characterized in that the two different symmetric linear carbonate esters are added as a catalyst to an alkoxide salt compound of a group IA element to directly transesterify an alkyl group. will be. Hereinafter, the present invention will be described in more detail.

[Formula 3]

In Formula 3, R ₁ and R ₂ each represent a different linear (Chain-), iso (Iso-), or cyclic (Cyclic) alkyl group, and the carbon number of these alkyl groups is not limited, but 1 to 10, Preferably it is 1-6.

In the present invention, the linear alkyl group may be selected from methyl group, ethyl group, propyl group, butyl group, benzyl group, etc., and isopropyl group, isobutyl group, sec-butyl group as iso alkyl group , tert-butyl group, isoamyl group and the like. In addition, the cyclic alkyl group may be selected from halopropyl group, cyclobutyl group, cyclohexyl group, cycloheptyl group and the like.

The symmetric linear carbonate ester used in the present invention is, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), dibutyl carbonate ( Dibutyl carbonate, hereinafter DBC) may be selected from two. In addition, specific examples of the asymmetric linear carbonate obtained from the symmetric linear carbonate ester include ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). ), And the like. That is, it is preferable to select and use the symmetric linear carbonate according to the final product to be prepared appropriately. For example, when the asymmetric linear carbonate to be obtained is EMC, DMC and DEC are used as the symmetric linear carbonate. Etc. can be mentioned.

As the catalyst used in the present invention, one or two or more kinds of alkoxide salts of the Group IA elements are used and can be represented by MR, where M represents an alkali metal atom and R represents an alkoxide group. Lithium or sodium is particularly suitable as the alkali metal atom, and alkoxide groups generally have one to three carbon atoms. There is no particular limitation on the shape of such catalysts, but it is preferable to use powdered ones for smooth dispersion in the reactants. In addition, in order to increase the activity of the catalyst, it is required to suppress contact with moisture until it is used for the reaction. The amount of catalyst used is 0.0001 to 5% by weight, preferably 0.01 to 1% by weight, regardless of the type of reactor used in the reaction.

There is no particular limitation on the molar ratio between two different symmetric linear carbonates to be the starting materials, and it is desirable to focus on obtaining the maximum yield of the asymmetric linear carbonate as the final product. It can usually be selected within a molar ratio range of 10: 1 to 1:10, which depends on the starting material but reacts in equivalent molar ratios in terms of productivity.

The reaction temperature is not particularly limited, but the reaction temperature is preferably reacted at the boiling point adjacent to the reactant, more preferably 40 to 200 ° C. This is because if the reaction temperature is less than 40 ° C., the production rate of the asymmetric linear carbonate ester as a final product is low, and the productivity is low.

The reaction pressure is not particularly limited either, but is 0 to 20 atm, preferably near atmospheric pressure.

The reaction apparatus for preparing the asymmetric linear carbonate ester which is the final product in the present invention is not particularly limited, and a conventional batch reactor or a continuous reactor may be used. For example, in the case of using a batch reactor to obtain the asymmetric linear carbonate of the present invention, the reaction method is described first, by first adding a symmetric linear carbonate and a catalyst as a reactant to the batch reactor and gradually heated to the reaction temperature until the equilibrium reaction Proceed with the reaction. The reaction degree is sampled at a certain time and analyzed by gas chromatography until the composition of the reaction mixture does not change, the reaction time is 0.1 to 20 hours, preferably 0.5 to 2 hours. After the reaction, the reaction mixture is separated from the symmetric linear carbonate ester which is the unreacted product and the asymmetric linear carbonate ester which is the final product by distillation methods such as normal pressure, atmospheric pressure or reduced pressure. The order of separation is based on the boiling point of the reactants and the final product. For example, when manufacturing EMC by reaction of DMC and DEC, it is separated in the order of DMC, EMC and DEC. After the reaction was completed, unreacted raw materials were recovered and reused. There are almost no by-products other than the final asymmetric linear carbonate ester.

Hereinafter, the present invention will be described in more detail with reference to Examples, which are only intended to help a specific understanding of the present invention, and the present invention is not limited to the following Examples.

Example 1

In the three-liter three-necked round flask, the stirrer and the cooler used a reaction apparatus. 10 mol (900 g) of DMC, 10 mol (1180 g) of DEC, and 0.1 wt% of LiOCH ₃ were added as a catalyst, and the reaction temperature was heated to 110 ° C. The steam produced during the reaction was condensed in the condenser and refluxed to the reactor. After reaching the reaction temperature, the reaction proceeded to equilibrium after 1 hour, and the reaction was terminated. The change in molar ratio of the reaction mixture could not be observed at the reaction time of 1 hour or more.

Analysis of the reaction mixture by gas chromatography resulted in a mixing ratio of DMC / EMC / DEC in a molar ratio of 1: 2: 1, yielding 50% of the desired final product, EMC.

Example 2

Except for using 0.5% by weight of LiOC ₂ H ₅ as the catalyst was carried out in the same manner as in Example 1, the yield of the final product obtained EMC was 50%.

Example 3

Except for using the DMC and DPC as a reaction was carried out under the same conditions as in Example 1 to obtain the final product MPC and the yield was 50%.

Example 4

Except that 0.5 wt% of NaOCH ₃ was used as a catalyst, the same process as in Example 1 was carried out, and the yield of the latest product, EMC, was 47%.

Example 5

The reaction was carried out in the same manner as in Example 4, except that the reaction time was 2 hours, and the yield of the obtained product, EMC, was 50%.

Example 6

Except that 0.5 wt% of NaOC ₂ H ₅ was used as a catalyst, it was carried out in the same manner as in Example 1, and the yield of the obtained final product, EMC, was 44%.

4160 g of the reaction mixture obtained by mixing the reaction mixtures obtained in Examples 1 and 2 were obtained with 1556 g of EMC having a purity of 99% or more when the reflux ratio was maintained at 10 or higher in a theoretical 50-stage atmospheric distillation column. The distillation yield for was 70%.

Comparative Example 1

The reaction product was reacted under the same conditions as in Example 1, except that 10 mol (900 g) of DMC and 10 mol (460 g) of ethanol were used. The EMC yield in the reaction mixture was 42%, and 7.2% of methanol was produced as a by-product. Unreacted ethanol was 5.2%.

Comparative Example 2

The reaction was carried out under the same conditions as in Example 1 except that 3% by weight of Li ₂ CO ₃ was used as the catalyst and the reaction time was 18 hours. The yield of EMC obtained after the reaction was 2.1%.

Comparative Example 3

The reaction product was reacted under the same conditions as in Example 1 except that 10 moles of ethanol was used instead of DEC, and the reaction time was 18 hours. The EMC yield in the reaction mixture was 16%, and 1.7 wt% of methanol was used as a byproduct. % Was produced and 13.5% of unreacted ethanol.

Comparative Example 4

The reaction was carried out under the same conditions as in Example 1, except that 1 wt% of K ₂ CO ₃ was used as the catalyst, and the yield of EMC obtained after the reaction was 0.8%.

Comparative Example 5

The reaction was carried out under the same conditions as in Example 1, except that 2.5 wt% NaOH and the reaction time of 6 hours were used as the catalyst, and the yield of EMC obtained after the reaction was 1.2%.

Comparative Example 6

1 wt% of titanium ethoxide [Ti (OC ₂ H ₅ ) ₄ ] was used as a catalyst and reacted under the same conditions as in Example 1 except that the reaction time was 20 hours. The yield of was 30%.

Comparative Example 7

The reaction was carried out under the same conditions as in Example 1 except that 5 wt% of acid clay was used as the catalyst, and the yield of EMC was 5%.

As described above, when the alkoxide salt compound of group IA element is used as a catalyst for transesterification of two different symmetric linear carbonate esters according to the present invention, no by-products are produced, and a high yield of asymmetric linear carbonate ester compounds is prepared. Could. In addition, even after the reaction, the reaction mixture is transferred to the distillation apparatus to perform the separation of the reaction mixture has the advantage that there is little loss due to decomposition of the reactant.

Claims (3)

In preparing an asymmetric linear carbonate by transesterification under a catalyst with two different symmetric linear carbonates, A method for producing an asymmetric linear carbonate, characterized by using 0.0001 to 5% by weight of an alkoxide salt of a group IA element as a reaction catalyst. The method of claim 1, The symmetric linear carbonate ester is characterized by two different kinds selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate and dibutyl carbonate. Method for producing an asymmetric linear carbonate ester. The method of claim 1, The alkoxide salt of the group IA element is represented by MR, wherein M is lithium or sodium and R is a methoxide group or an ethoxide group.