JP3124400B2 - Method for producing carbonic acid diester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a dialiphatic carbonate, and more particularly to a method for producing a dialiphatic carbonate with a high yield and a high selectivity from an aliphatic alcohol and carbon dioxide. . Dialiphatic carbonate is a very useful compound as a raw material for organic synthesis of pharmaceuticals, agricultural chemicals and the like, and as an intermediate for the production of polycarbonate, urethane and the like.

[0002]

2. Description of the Related Art As a method of producing a carbonate ester, a method of reacting phosgene with an alcohol has been industrially used for a long time. However, this method requires the use of highly toxic phosgene and the reaction between alcohol and phosgene. There are drawbacks such as a large amount of by-produced hydrochloric acid which is highly corrosive in the reaction. Therefore, there has been a strong demand for a method for producing a carbonate ester that does not use phosgene.

As a production method without using phosgene, a method of synthesizing a carbonate ester from an alcohol, carbon monoxide and oxygen has been proposed and proposed (for example, Japanese Patent Publication No. Sho 6 (1988)).
No. 1-8816, WO-87 / 7601).
These are methods in which a palladium compound and a copper compound are used as catalysts, and a carbonate ester is synthesized in a liquid phase by an enzyme acid compound of alcohol and carbon monoxide. Since the reaction with the enzyme must be performed outside the explosion range, there is a danger in operation. In addition, since a halide is used as a catalyst, there is a restriction on an apparatus for corrosion, so that the method is not necessarily industrially advantageous.

There have also been proposed various methods for obtaining a carbonic ester by enzymatically oxidizing a nitrite and carbon monoxide on a catalyst carrying a platinum group compound (see, for example, Japanese Patent Application Laid-Open No. 60-181051). However, the danger of explosion due to the use of toxic carbon monoxide as in the previous method and the use of molecular enzymes cannot be avoided.

On the other hand, there has been proposed a method of synthesizing a carbonate by reacting ethylene carbonate obtained by a reaction between ethylene oxide and carbon dioxide with an alcohol in the presence of various transesterification catalysts (for example, Japanese Patent Application Laid-Open No. Sho 54 (1979)). ―
However, this method is not suitable as a method for producing only a carbonate ester because diethylene glycol is by-produced.

As a method for producing a carbonate ester free from the above-mentioned problems, a method for directly obtaining a dialiphatic carbonate from an aliphatic alcohol and carbon dioxide has been studied.

[0007] However, there are only a few examples of a method for directly obtaining a dialiphatic carbonate from an aliphatic alcohol and carbon dioxide gas.

That is, in Japanese Patent Application Laid-Open No. 54-3012, a tin compound, a titanium compound and a zirconium compound are used as catalysts. As another problem, it is pointed out that the catalyst is deactivated by water generated stoichiometrically by the reaction.

Further, in Japanese Patent Application Laid-Open No. 58-134053, a method of removing water with a molecular sieve or the like is used, but the catalyst itself such as alkoxides of tin, titanium and zirconium is particularly enhanced by the presence of water. It is presumed that under the conditions of the given temperature, it becomes a hydrolyzed hydroxide or oxide and loses catalytic activity.

[0010]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for producing carbonic diesters in a safe and economically advantageous manner. That is, an object of the present invention is to provide a method for efficiently producing a carbonic acid diester by using a catalyst having a high selectivity and being hardly deactivated.

[0011]

That is, the present invention provides a method for producing a dialiphatic carbonate, which comprises reacting an aliphatic alcohol with carbon dioxide in the presence of a thallium compound.

The thallium compound has a characteristic chemical property that liberates water from a hydroxide and an alcohol to form an alkoxide, and the present inventors have focused on this characteristic chemical property and conducted various studies. As a result, the present invention has been completed.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing a carbonate, and more particularly to a reaction for producing a dialiphatic carbonate.

The reaction of a dialiphatic carbonate by the reaction between an aliphatic alcohol and carbon dioxide is already known and is represented by the following reaction formula.

[0016]

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Since this reaction uses carbon dioxide, which is an inert compound, the esterification reaction is said to have an equilibrium depending on the source system, and this reaction is performed by calculating the standard energy of formation of each compound of the reaction source system and the production system. It is expected that high yields cannot be achieved unless the product water is continuously removed and dominated by equilibrium as inferred from.

On the other hand, in order for this reaction to proceed catalytically, it is considered to be a catalytically active species. The metal alcoholate must be regenerated, but as it is already known, it has been considered effective for this reaction (Japanese Patent Application Laid-Open No. 54-301).
No. 2) It is known that an alkoxy compound of titanium, tin or zirconium is liable to be decomposed into a hydroxide or an oxide upon contact with water.
This involves the problem of catalyst deactivation due to the water produced.

Thalium alcoholate, which is an example of the catalyst used in the present invention, is formed by the reaction of thallium hydroxide with alcohol and has a unique chemical property of liberating water (cited Menzies). RCJ Chem.Soc. (Londo
n), 1931,1571) Therefore, when used as a catalyst in this reaction,
It is expected that the water generated by the reaction is less likely to be deactivated.

The present inventors first confirmed that the reaction proceeded catalytically using thallium (I) ethoxide with the production of diethyl carbonate as a catalyst by the reaction of ethanol and carbon dioxide gas, and further confirmed that other monovalent thallium compounds Have been found to be equally effective.

The aliphatic alcohol used in the present invention includes monovalent alkanols having 1 to 12 carbon atoms and cycloalkanols, preferably 1 to 12 carbon atoms.
Up to 6 linear or branched primary alcohols are mentioned.
Specific examples include methanol, ethanol, n-propanol, iso-propanol, n-butanol, n-hexanol and the like.
To four lower alcohols are preferable, and among them, methanol and ethanol are most preferable.

These aliphatic alcohols may be used alone or in a mixture of two or more.

It may be diluted with a solvent inert to the reaction. Examples of such a solvent include hydrocarbons such as benzene, toluene, xylene, tetralin and decalin; amide compounds such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone; sulfoxides such as dimethylsulfoxide and sulfolane; and phenols.

The catalyst used in the present invention is a monovalent thallium compound. Examples of such monovalent thallium compounds include thallium (I) alcoholate such as thallium methoxide and thallium ethoxide, thallium (I) formate, thallium (I) acetate, thallium (I) malonate, thallium (I) benzoate, and the like. Thallium (I) organic carboxylate, thallium chloride (I), thallium (I) bromide, thallium iodide (I), thallium (I) nitrate, thallium sulfate (I), thallium phosphate (I), etc. In addition to salts, thallium carbonate (I), thallium hydroxide (I), thallium oxide (I) and the like can be mentioned.

The amount ratio (molar ratio) of the monovalent thallium compound used as the catalyst to the hydroxy compound is usually from 0.001 to 1, preferably from 0.005 to 1, per mole of alcohol.
0.1.

The carbon dioxide gas is usually a gas, but may be used as it is, or may be diluted with an inert gas such as nitrogen or helium.

The pressure of the carbon dioxide used is suitably at least 1 atm. The higher the pressure, the more the equilibrium is overcome and the reaction proceeds, so that a higher reaction rate yield is obtained.

[0028] The reaction temperature is 100 to 350 ° C, preferably 150 to 300 ° C. If the temperature is too low, the reaction rate is low, and if it is too high, the generated carbonate ester may be decomposed, which is not preferable.

As described above, the present reaction is governed by the equilibrium, so that a higher yield can be obtained by continuously removing generated water. It is also possible to use agents.
Molecular sieves having a small pore system often used as such a dehydrating agent may be used.

The reaction is usually carried out in an autoclave, in which alcohol, thallium as a catalyst and carbon dioxide gas are charged, a solvent dehydrating agent is added if necessary, and the mixture is heated and stirred. After completion of the reaction, the product is taken out by a usual method.

[0031]

According to the present invention, the reaction can be carried out equilibrium at a preferable temperature without deactivating the catalyst by water generated in the reaction, and the desired dialiphatic carbonate can be obtained in high yield. , Can be manufactured with high selectivity.

[0032]

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

[0033]

Example 1 In a stainless steel autoclave having a capacity of 100 ml, 20 ml of ethanol and 0.75 g (3.0 mmol) of commercially available thallium ethoxide were put, and the inside was sufficiently replaced with carbon dioxide gas, and carbon dioxide with an initial pressure of 30 kg / cm ² was obtained. Fill with gas. The reaction temperature is raised to 250 ° C. while stirring the inside well, and the mixture is stirred at the same temperature for 5 hours. After the completion of the reaction, the reaction mixture was cooled, the contents were taken out, and analyzed and quantified by gas chromatography. As a result, formation of 757 mg (6.41 mmol) of diethyl carbonate was confirmed. No compounds other than ethanol as a raw material and diethyl carbonate as a product were detected by gas chromatography. This indicates that the target product can be obtained with a high selectivity. The yield was 214% based on 100% of thallium ethoxide used.
It is.

[0034]

Example 2 In the same manner as in Example 1, the reaction was carried out at 200 ° C. for 22 hours using, as a catalyst, 0.75 g of thallium ethoxide and 20 ml of methanol instead of ethanol. After the completion of the reaction, the product was taken out and analyzed by gas chromatography to obtain 67 mg of dimethyl carbonate. Other trace amounts of methyl ethyl carbonate and diethyl carbonate were detected.

[0035]

Example 3 As in Example 1, methanol was reacted at a temperature of 150 ° C. for 70 hours at a temperature of 0.65 g of thallous oxide and an initial pressure of carbon dioxide gas of 30 kg / cm ^{2 as} in Example 1. As a result, 68 mg of dimethyl carbonate was obtained.

[0036]

Example 4 As a catalyst, thallium (I) formate 0.75
g (3 mmol) and reacted at 200 ° C. for 22 hours in the same manner as in Example 1. As a result, 29 mg of dimethyl carbonate was obtained.

[0037]

Examples 5 to 8 In the same manner as in Example 1, 20 ml of ethanol and 30 kg / CO ₂ initial pressure were placed in a 100 ml autoclave.
25 cm ² and thallium (I) ethoxide
React at 0 ° C for 5 hours. After the reaction, the reaction product is cooled down to 150 ° C., the reaction product is opened by opening a valve and trapped by ice-cooling, and the high boiling point containing the catalyst is left in the autoclave.
Then the internal CO ₂ was replaced by cooling to room temperature to 250 ° C. 5 hours were charged with ethanol 20ml and CO ₂ initial pressure 30kg / cm ² again. This operation was repeated four times, and each time, the amount of dimethyl carbonate formed in the trapped reaction product was analyzed by gas chromatography.

The results are shown in Table 1.

[0039]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-70221 (JP, A) JP-A-58-134053 (JP, A) JP-A-54-3012 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C07C 68/04 C07C 69/96

Claims (1)

(57) [Claims] 1. A method for producing a dialiphatic carbonate, which comprises reacting an aliphatic alcohol with carbon dioxide in the presence of a thallium compound.