JP3005684B1 - Method for producing carbonate ester - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a method capable of industrially producing a carbonic acid ester in high yield using carbon dioxide which is toxic and corrosive and which can be obtained at a very low cost without using it as a carbonylating agent. SOLUTION: A method for producing a carbonate ester in which carbon dioxide and an acetal compound are reacted under a pressure condition of 800 atm or more in the presence of a metal alkoxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a carbonate ester using carbon dioxide.

[0002]

2. Description of the Related Art Carbonic esters are useful as raw materials for polycarbonate production, gasoline additives for improving octane number, diesel fuel additives for reducing particles in exhaust gas, alkylating agents, carbonylating agents, solvents and the like. Compound. As a conventional method for producing a carbonate ester, first, there is a method in which phosgene is reacted with an alcohol as a carbonylating agent.
Use of phosgene, which is extremely toxic and corrosive, requires careful handling such as transport and storage.
Significant costs were incurred for maintenance and management of manufacturing facilities, waste disposal, and ensuring worker safety. An oxidative carbonylation method in which carbon monoxide is reacted with alcohol and oxygen as a carbonylating agent is also known. However, in this method, since highly toxic carbon monoxide is used at a high pressure, safety of workers is secured. Therefore, there is a disadvantage in that side reactions such as generation of carbon dioxide by oxidation of carbon monoxide occur. For this reason, there is a demand for the development of a method for producing a carbonate ester more safely and inexpensively.
A method has been proposed in which carbon dioxide is reacted with alcohol as a carbonylating agent (Applied Catalysis, 1996).
Year, Volume 142, L1; Collect. Czech. Chem. Commu
n., 1995, 60, 687, etc.). But,
Both methods have a very low catalytic activity with a turnover number of about two or three, and have a problem that generated water decomposes the catalyst and inhibits the reaction. A method for producing a carbonate ester from the reaction between carbon dioxide and a carboxylic acid orthoester has also been proposed (JP-A-7-244010).
However, the raw materials are expensive, the yield is not sufficient, and there is a problem in industrial implementation. On the other hand, the present inventors have proposed a method for producing a carbonate by reacting carbon dioxide with an acetal compound in the presence of a metal alkoxide and a halide (Japanese Patent No. 2852418). This method uses carbon dioxide which is obtained at very low cost without toxicity and corrosiveness as a carbonylating agent, and is an industrially advantageous method for producing a carbonate ester. The method of the present invention further improves the method proposed by the present inventor in terms of yield and the like.

[0003]

Accordingly, the present invention provides
It is an object of the present invention to provide a method capable of industrially producing a carbonic ester in high yield using carbon dioxide which is obtained at very low cost without toxicity and corrosiveness as a carbonylating agent.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the problems of the above-mentioned conventional method, and as a result, it has been found that carbon dioxide and an acetal compound are reacted under high pressure in the presence of a metal alkoxide. Was found to be obtained in remarkably high yield, and the present invention was accomplished based on this finding. That is, the present invention relates to (1) a method in which carbon dioxide and an acetal compound are reacted with each other in the presence of a metal alkoxide.
(2) The method for producing a carbonate according to (1), wherein the metal alkoxide is an alkoxide of a metal selected from tin, titanium, zirconium and rare earth elements. An object of the present invention is to provide a method for producing an ester, and (3) a method for producing a carbonate according to (1) or (2), wherein carbon dioxide is reacted with an acetal compound in the presence of a Lewis acid.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, carbonic acid ester is produced by reacting carbon dioxide with an acetal compound. Acetal compounds that can be used in the present invention,
It is represented by the following general formula (I).

Formula (I) R¹R²C (OR³)₂  (Where R¹And R²Is hydrogen, alkyl group, aralkyl
A group, an aryl group or a dialkylamino group,³
Represents an alkyl group, an aralkyl group or an aryl group.
You. )

In the general formula (I), R¹, R²And R³In table
The alkyl group referred to is preferably a lower alkyl group.
And more preferably has 1 to 4 carbon atoms. In particular
For example, methyl, ethyl, n-propyl, n-butyl and the like
Is mentioned. Also, R¹, R ²And R³Represented by
The aralkyl group preferably has 7 to 20 carbon atoms, more preferably
For example, benzyl, phenethyl, etc.
And so on. R¹, R²And R³Ants represented by
The hydroxyl group preferably has 6 to 14 carbon atoms, more preferably
6-10, for example, phenyl, tolyl, anisyl,
Naphthyl and the like. Also, R¹And R²Represented by
The dialkylamino group is preferably lower alkyl.
A dialkylamino group substituted with
Examples include a tylamino group and a diethylamino group. This
More specifically, as an acetal compound such as
For example, benzaldehyde dimethyl acetal, acetoa
Aldehyde dimethyl acetal, formaldehyde di
Methyl acetal, acetone dimethyl acetal,
Seton diethyl acetal, acetone dibenzyla
Cetal, diethyl ketone dimethyl acetal, ben
Zofenone dimethyl acetal, benzylphenylke
Ton-dimethyl acetal, cyclohexanone dimethyl
Acetal, acetophenone dimethyl acetal, 2,
2-dimethoxy-2-phenylacetophenone, 4,4
-Dimethoxy-2,5-cyclohexadiene-1-o
Dimethylacetamide dimethylacetal,
Cylformamide dimethyl acetal, dimethylform
Muamide Diethyl acetal, dimethylformamide
 Dibenzyl acetal and the like.

[0008] The reaction of the present invention can be carried out in the presence of a metal alkoxide. The metal alkoxide used here is represented by the following general formula (II) or (III).

Formula (II) (R⁴)_nM (OR⁵)_4-n  (Where R⁴And R⁵Represents an alkyl group, an aralkyl group,
Represents a alkenyl group or an aryl group, and n is an integer of 0 to 3
Represents M represents a metal atom. General formula (III) (R⁴)_mM '(OR⁵)_3-m  (Where R⁴And R⁵Is synonymous with general formula (II), and m
Represents an integer of 0 to 2. M 'represents a rare earth element
You. )

R⁴, R⁵An alkyl group represented by
Or a lower alkyl group, more preferably a carbon number
1 to 4. Specifically, for example, methyl, ethyl, n
-Butyl, isopropyl, hexyl, cyclohexyl
And so on. R⁴, R⁵Aralkyl group represented by
Preferably has 7 to 12 carbon atoms, and specifically
, Phenethyl, naphthylmethyl, 2-naphthylethyl
And the like. R ⁴, R⁵Alkenyl represented by
The group preferably has 2 to 10 carbon atoms and is linear or cyclic.
It may be shifted. Specifically, for example, cyclopentadienyl
Pentamethylcyclopentadienyl, indenyl,
Vinyl, allyl and the like. R⁴, R⁵Represented by
The aryl group preferably has 6 to 14 carbon atoms,
Examples include phenyl, tolyl, anisyl, and naphthyl.
I can do it. The metal atom represented by M is particularly limited.
However, tin, titanium and zirconium are preferred. Ma
In addition, these metal alkoxides have the halo of the corresponding metal.
Genides and sodium methoxide or magnesium methoki
Reaction with alkali metal alkoxides such as sides in the system
It can also be generated and used. Below gold
Specific examples of the genus alkoxide are given, but the present invention
It is not limited.

[0011] Sn (OMe)₄  Bu₂Sn (OMe)₂  Bu₂Sn (OEt)₂  Bu₂Sn (OBu)₂  Bu₃Sn (OMe) Ti (OMe)₄  Ti (Oi-Pr)₄  Ti (OBu)₄  Cp₂Ti (OMe)₂  Cp₂Ti (OPh)₂  Cp^* ₂Ti (OMe)₂  Zr (OMe)₄  Zr (Oi-Pr)₄  Zr (OBu)₄  Cp₂Zr (OMe)₂  Cp₂Zr (OPh)₂  Cp^* ₂Ti (OMe)₂  La (Oi-Pr)₃  Sc (Oi-Pr)₃  (Me: methyl, Et: ethyl, i-Pr: isopropyl
, Bu: n-butyl, Cp: cyclopentadienyl,
Ph: phenyl, Cp^*： Pentamethylcyclopentadi
Enil)

In the present invention, a halide may be used as a co-catalyst in addition to the above-mentioned metal alkoxide, but this is not always necessary in the present invention. Examples of such halides include quaternary phosphonium salts, quaternary ammonium salts, alkali metal salts or bis (triphenylphosphoranylidene) ammonium salts. As the quaternary phosphonium salt, a tetraalkylphosphonium salt, a tetraarylphosphonium salt and the like can be used, and specific examples include a tetrabutylphosphonium salt and a tetraoctylphosphonium salt. As the quaternary ammonium salt, a tetraalkylammonium salt, a tetraarylammonium salt, and the like can be used, and specific examples include a tetrabutylammonium salt, a tetraoctylammonium salt, and a myristyltrimethylammonium salt. Examples of the alkali metal salt include a potassium salt and a sodium salt. Examples of the halogen of such a halide include chlorine, bromine and iodine, with iodine being preferred. When an alkali metal salt is used as the halide, the solubility is low. Therefore, it is preferable that a crown ether compound, a cryptand, or the like be coexisted as the host compound, and it is more preferable that a crown ether compound be coexisted. Examples of the crown ether compound include 9-crown-3, 12-crown-4, 15-crown-5, and 18-crown-6, and may have a substituent. Further, a complex compound of such a crown ether compound and lithium, sodium, potassium or the like can also be used. Specific examples of the cryptand include [2.2.1] -cryptand and [2.2.2] -cryptand, and complexes with these metal ions can also be used.

The reaction in the production method of the present invention is represented by the following formula.
I can do it. R¹R²C (OR³)₂ + CO₂ → R³O (C
O) OR³ + R¹(CO) R²  (Where R¹~ R³Has the same meaning as described above. )

In the present invention, the reaction between carbon dioxide and the acetal compound is usually carried out at room temperature to 300 ° C., preferably at 80 ° C.
Perform at 〜200 ° C. for 1-100 hours. The pressure is 80 in the system.
The treatment is performed at 0 atm or more, preferably at least 1000 atm, particularly preferably at least 1500 atm. The upper limit of the pressure is not particularly limited, and is determined by the manufacturing cost of the pressure-resistant device. No solvent is required, but hexane,
Solvents such as benzene and methanol can also be used, and the use of methanol is often preferred. When methanol is used as the solvent, the amount of methanol used is preferably 0.5 to 1000 mol per 1 mol of the acetal compound. In the method of the present invention, the unreacted acetal compound can be recovered from the reaction system and reused. In the method of the present invention, ketones or aldehydes are by-produced together with the carbonic acid esters. However, ketones and aldehydes are easily converted into acetal compounds by reaction with alcohols, so that they can be recovered and reused. In the present invention, the amount of the metal alkoxide and / or halide used is a so-called catalytic amount, and is usually 1 / 10,000 to 1/10, preferably 1 / 10,000 to 1 mol of the acetal compound. 1 / mole. In particular, according to the method of the present invention, the amount of halide can be reduced to zero, and the amount of metal alkoxide used can be significantly reduced. The produced carbonate ester can be isolated according to a conventional method such as distillation.

[0015] Carbon dioxide and acetalization in the present invention
The reaction of the compound proceeds without a Lewis acid catalyst.
Performing in the presence of an acid accelerates the reaction and may be preferable.
You. Such Lewis acids include, for example,
Compounds are given. BF₃・ OEt₂  La (OSO₂CF₃)₃  Sc (OSO₂CF₃)₃  Ph₃C⁺B (C₆F₅)₄ ⁻  (Et: ethyl, Ph: phenyl)

[0016]

Next, the present invention will be described in more detail with reference to examples. Example 1 In a 20 ml-volume SUS autoclave equipped with a stirrer, 0.17 mmol of dibutyltin dimethoxide as a metal alkoxide and 10 parts of acetone dimethyl acetal were added.
mmol and 8.1 ml of methanol, and charged with liquefied carbon dioxide gas from a carbon dioxide gas cylinder to increase the internal pressure to 60 kg / cm.
Adjusted to ² . Thereafter, the inside of the autoclave was heated to 180 ° C. while stirring, and the internal pressure was increased to 2000 atm.
Allowed to react for hours. After cooling, release the remaining carbon dioxide gas,
When the reaction mixture was analyzed by gas chromatography, the conversion of dimethyl acetal was 89%, and the yield of dimethyl carbonate based on the charged acetal was 88%.

Comparative Example 1 After filling with carbon dioxide, the reaction was carried out in the same manner as in Example 1 except that the reaction pressure was changed to 300 atm, and the reaction was analyzed. The conversion of dimethyl acetal was 27%, and the dimethyl carbonate recovery based on the acetal used was calculated. Rate was 26%. It can be seen that the yield is significantly lower at a reaction pressure of 300 atm than at 2000 atm.

Example 2 The reaction was carried out in exactly the same manner as in Example 1 except that cyclohexanone dimethyl acetal was used in place of acetone dimethyl acetal. Analysis was carried out. The yield of dimethyl carbonate based on the charged acetal was 77%. Also, 1-methylcyclohexene was by-produced at a yield of 0.2%.

Comparative Example 2 After filling with carbon dioxide, the reaction was conducted in exactly the same manner as in Example 2 except that the reaction pressure was changed to 300 atm. The yield of dimethyl carbonate was 21%, and 1-methylcyclohexene was obtained. Was by-produced at a yield of 4.0%. It can be seen that a low reaction pressure not only reduces the yield, but also increases the proportion of undesirable by-products.

[0020]

According to the method of the present invention, by reacting carbon dioxide and an acetal compound under a high pressure, the production of by-products can be suppressed and a carbonate ester can be produced in an extremely high yield. Carbon dioxide is inexpensive without toxicity and corrosiveness, and the method of the present invention can be suitably carried out industrially.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-11-199546 (JP, A) JP-A-11-35521 (JP, A) JP-A-9-249617 (JP, A) JP-A-7-249 224010 (JP, A) Journal of the Chemical Society of Japan, [10] (1975), 1789-1794. (58) Fields investigated (Int. Cl. ⁷ , DB name) (STN) WPIDS (STN)

Claims (3)

(57) [Claims] 1. A method for producing a carbonate ester, comprising reacting carbon dioxide with an acetal compound in the presence of a metal alkoxide under a pressure condition of 800 atm or more. 2. The method for producing a carbonate according to claim 1, wherein the metal alkoxide is an alkoxide of a metal selected from tin, titanium, zirconium and rare earth elements. 3. The method for producing a carbonate according to claim 1, wherein the carbon dioxide and the acetal compound are reacted in the presence of a Lewis acid.