JP2852418B1 - Production method of carbonate ester - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a method capable of industrially producing a carbonic acid ester 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, comprising reacting carbon dioxide with an acetal compound in the presence of a metal alkoxide and a halide.

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.

[0003]

Accordingly, the present invention provides
It is an object of the present invention to provide a method capable of industrially producing a carbonic acid ester using carbon dioxide which is toxic and corrosive and is obtained at extremely low cost as a carbonylating agent.

[0004]

The present inventors have conducted intensive studies to solve the problems of the above-mentioned conventional methods. As a result, when carbon dioxide and an acetal compound are reacted in the presence of a metal alkoxide and a halide, a carbonate ester is obtained. Was found, and the present invention was accomplished based on this finding. That is, the present invention provides (1) a method for producing a carbonate, comprising reacting carbon dioxide with an acetal compound in the presence of a metal alkoxide and a halide;
(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 or a rare earth element, and (3) the halide is a quaternary phosphonium salt, an alkali metal salt or quaternary metal. (4) The method for producing a carbonate according to (1) or (2), which is a quaternary ammonium salt, (4) carbon dioxide and an acetal in the presence of a halide selected from quaternary phosphonium salts, alkali metal salts and quaternary ammonium salts. (5) a method for producing a carbonate ester, which comprises reacting a compound.
The method for producing a carbonate according to (3) or (4), wherein the alkali metal salt is used together with a crown ether compound,
And (6) reacting carbon dioxide with an acetal compound in the presence of a Lewis acid, (1), (2),
(3) A method for producing a carbonate according to (4) or (5).

[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).

[0006] Formula ^{(I) R 1 R 2 C} (OR 3) 2 ( wherein, R ¹ and R ² represents hydrogen, an alkyl group, an aralkyl group, an aryl group or a dialkylamino group, R ³
Represents an alkyl group, an aralkyl group or an aryl group. )

In the general formula (I), the alkyl groups represented by R ¹ , R ² and R ³ are preferably lower alkyl groups, and more preferably have 1 to 4 carbon atoms. Specific examples include methyl, ethyl, n-propyl, n-butyl and the like. The aralkyl group represented by R ¹ , R ² and R ³ preferably has 7 to 20 carbon atoms, more preferably 7 to 12 carbon atoms, such as benzyl and phenethyl. R ^1, R ² and aryl groups preferably having 6 to 14 carbon atoms represented by R ^3, an even more preferably 6-10, such as phenyl, tolyl, anisyl,
Naphthyl and the like. The dialkylamino group represented by R ¹ and R ² is preferably a dialkylamino group substituted with a lower alkyl group, and examples include a dimethylamino group and a diethylamino group. More specifically, such acetal compounds include, for example, benzaldehyde dimethyl acetal, acetaldehyde dimethyl acetal, formaldehyde dimethyl acetal, acetone dimethyl acetal, acetone diethyl acetal, acetone dibenzyl acetal, diethyl ketone dimethyl acetal, benzophenone dimethyl acetal, benzylphenyl Ketone dimethyl acetal, cyclohexanone dimethyl acetal, acetophenone dimethyl acetal, 2,
2-dimethoxy-2-phenylacetophenone, 4,4
-Dimethoxy-2,5-cyclohexadien-1-one, dimethylacetamide dimethylacetal, dimethylformamide dimethylacetal, dimethylformamide diethylacetal, dimethylformamide dibenzylacetal and the like.

The reaction of the present invention can be performed in the presence of a metal alkoxide and a halide. The metal alkoxide used here is represented by the following general formula (II) or general formula (III)
It is represented by

Formula (II) (R ⁴ ) _n M (OR ⁵ ) _4-n (wherein R ⁴ and R ⁵ represent an alkyl group, an aralkyl group, an alkenyl group or an aryl group, and n is 0 to 3) And M represents a metal atom.) General formula (III) (R ⁴ ) _m M '(OR ⁵ ) _3-m (wherein R ⁴ and R ⁵ have the same meanings as in general formula (II)) Yes, m
Represents an integer of 0 to 2. M ′ represents a rare earth element. )

The alkyl groups represented by R ⁴ and R ⁵ are preferably lower alkyl groups, and more preferably have 1 to 4 carbon atoms. Specifically, for example, methyl, ethyl, n
-Butyl, isopropyl, hexyl, cyclohexyl and the like. The aralkyl group represented by R ⁴ or R ⁵ preferably has 7 to 12 carbon atoms, and specific examples include benzyl, phenethyl, naphthylmethyl, 2-naphthylethyl and the like. The alkenyl group represented by R ⁴ or R ⁵ preferably has 2 to 10 carbon atoms and may be either a chain or a ring. Specifically, for example, cyclopentadienyl, pentamethylcyclopentadienyl, indenyl,
Vinyl, allyl and the like. The aryl group represented by R ⁴ or R ⁵ preferably has 6 to 14 carbon atoms,
For example, phenyl, tolyl, anisyl, naphthyl and the like can be mentioned. The metal atom represented by M is not particularly limited, but is preferably tin, titanium or zirconium. Further, these metal alkoxides can also be used by being generated by reacting a corresponding metal halide with an alkali metal alkoxide such as sodium methoxide or magnesium methoxide in a system. Specific examples of the metal alkoxide are shown below, but the present invention is not limited to these.

Sn (OMe) ₄ Bu ₂ Sn (OMe) ₂ Bu ₂ Sn (OEt) ₂ Bu ₂ Sn (OBu) ₂ Bu ₃ Sn (OMe) Ti (OMe) ₄ Ti (Oi-Pr) ₄ Ti (OBu) ₄ Cp ₂ Ti (OMe) ₂ Cp ₂ Ti (OPh) ₂ Cp ^* ₂ Ti (OMe) ₂ Zr (OMe) ₄ Zr (Oi-Pr) ₄ Zr (OBu) ₄ Cp ₂ Zr (OMe) ) ₂ Cp ₂ Zr (OPh) ₂ Cp ^* ₂ Ti (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 ^* : pentamethylcyclopentadienyl)

The halide used above includes a quaternary phosphonium salt, a quaternary ammonium salt, an alkali metal salt and a bis (triphenylphosphoranylidene) ammonium salt. 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 a halide, the solubility is low.
It is preferable that a crown ether compound, a cryptand, and the like coexist as a host compound, and it is more preferable that a crown ether compound coexist. Examples of the crown ether compound include 9-crown-3, 12
-Crown-4, 15-crown-5, 18-crown-6 and the like, 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.
For the cryptand, specifically, for example, [2.2.
1] -cryptand, [2.2.2] -cryptand and the like, and complexes with these metal ions can also be used.

In the present invention, the reaction between carbon dioxide and the acetal compound can be carried out in the presence of a halide selected from quaternary phosphonium salts, alkali metal salts and quaternary ammonium salts. In this case, examples of the quaternary phosphonium salt, alkali metal salt or quaternary ammonium salt include those described above for the halide.

In the production method of the present invention, the reaction can be represented by the following formula. R ¹ R ² C (OR ³ ) ₂ + CO ₂ → R ³ O (CO) OR ³ + R ¹ (CO) R ² (wherein, R ^{1 to} R ³ have the same meaning as described above) The reaction between carbon dioxide and the acetal compound in the above is usually performed at room temperature to 300 ° C, preferably at 80 to 200 ° C.
For 1 to 100 hours. 1-500 atm in the reaction system,
Preferably, the reaction is carried out by charging carbon dioxide so that the pressure becomes 9.5 to 300 atm. A solvent is not particularly required, but a solvent such as hexane, benzene, or methanol can be used. In many cases, use of methanol is preferred from the viewpoint of improving the solubility of a halide. 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,
1 / 10,000 to 1 / 10th of acetal compound
(Mol). The produced carbonate ester can be isolated according to a conventional method such as distillation.

The reaction between carbon dioxide and the acetal compound in the present invention proceeds without a Lewis acid catalyst. However, when the reaction is carried out in the presence of a Lewis acid, the reaction is accelerated and is sometimes preferred. Examples of such Lewis acids include the following compounds. _{BF 3 · OEt 2 La (OSO} 2 CF 3) 3 Sc (OSO 2 CF 3) 3 Ph 3 C + B (C 6 F 5) 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 stirring device, 0.85 mmol of dibutyltin dimethoxide as a metal alkoxide, 0.85 mmol of tetrabutylphosphonium iodide as a halide, 50.0 mmol of acetone dimethyl acetal, and 41 mm of methanol
was charged, and liquefied carbon dioxide gas was charged from a carbon dioxide gas cylinder to adjust the internal pressure to 60 kg / cm ² . Thereafter, the inside of the autoclave was heated to 180 ° C. while stirring, and the internal pressure was reduced to 3 ° C.
After adjusting to 00 kg / cm ² , the reaction was carried out for 24 hours. After cooling, the remaining carbon dioxide gas was released, and the reaction solution was analyzed by gas chromatography. As a result, it was confirmed that dimethyl carbonate was produced in a yield of 5.0% based on the amount of acetone dimethyl acetal charged. Note that 80% of acetone dimethyl acetal was recovered without being reacted. Therefore, the yield of the carbonate based on the reaction acetone dimethyl acetal (conversion) was 25%.

Examples 2 to 4 Acetal compounds, metal alkoxides shown in Table 1 below,
The reaction was carried out in the same manner as in Example 1 using a halide, a Lewis acid and a solvent. The acetal compound was used in the same amount as in Example 1 (50.0 mmol), the amount of other compounds used and the reaction temperature were as shown in Table 1, and the internal pressure was 300.
After adjusting the pressure to atmospheric pressure, the reaction was carried out for 24 hours. As a result, dimethyl carbonate was produced in the yield shown in Table 1 (based on the charged amount of the acetal compound).

[0018]

[Table 1]

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that 50 mmol of methanol was used instead of the acetal compound. The yield of dimethyl carbonate was 0.53% based on methanol.

Comparative Example 2 Dimethyl carbonate was produced in the same manner as in Example 1 except that dibutyltin methoxide and tetrabutylphosphonium iodide were not used, but no dimethyl carbonate was produced (0% yield). .

[0021]

According to the method of the present invention, a carbonate ester can be produced by reacting carbon dioxide with an acetal compound. Carbon dioxide is inexpensive without toxicity and corrosiveness, and the method of the present invention can be suitably carried out industrially.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-3012 (JP, A) JP-A-58-134053 (JP, A) JP-A-7-224010 (JP, A) International Publication 94/22805 (WO, A1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 69/96 B01J 31/26 C07C 68/04 CA (STN) REGISTRY (STN) WPIDS (STN)

Claims (6)

(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 and a halide. 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 halide is a quaternary phosphonium salt, an alkali metal salt or a quaternary ammonium salt. 4. A process for producing a carbonate ester, comprising reacting carbon dioxide with an acetal compound in the presence of a halide selected from quaternary phosphonium salts, alkali metal salts and quaternary ammonium salts. 5. The method for producing a carbonate according to claim 3, wherein an alkali metal salt is used together with the crown ether compound. 6. The method according to claim 1, wherein carbon dioxide and the acetal compound are reacted in the presence of a Lewis acid.
The method for producing a carbonate according to 2, 3, 4 or 5.