JP2022156941A - Method for producing carbonate - Google Patents

Abstract

To provide a method for readily producing carbonate by a reaction between carbon dioxide and carboxylic acid orthoester.SOLUTION: A method for producing carbonate includes a reaction step for reacting carbon dioxide with carboxylic acid orthoester to produce carbonate in the presence of cerium oxide.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbonate ester.

Carbonic acid esters are raw materials for polycarbonates, polyurethanes, and the like, and are also useful compounds having a wide range of uses such as solvents, fuel additives, various detergents, and electrolytes for lithium ion batteries.
As a method for producing a carbonate ester, a production method by reacting carbon dioxide with a carboxylic acid orthoester in the presence of a homogeneous catalyst is known (see, for example, Patent Documents 1 and 2).
Also proposed is a method of producing a carbonate ester by reacting carbon dioxide and alcohol in the presence of a solid catalyst and benzonitrile (see, for example, Patent Documents 3 and 4).

JP-A-11-35521 JP-A-7-224010 JP 2016-216363 A WO2019/138993

Conventional methods for producing carbonic acid esters using homogeneous catalysts or benzonitrile or the like have the problem that separation and purification after carbonic acid ester formation is complicated. An object of the present invention is to provide a method for easily producing a carbonic acid ester by reacting carbon dioxide with a carboxylic acid orthoester.

上記式中、Ｒ^１は、それぞれ独立して、置換基を有していてもよいアルキル基であり；Ｒ^２は、水素原子又は置換基を有していてもよい炭化水素基である。
［３］
前記式（Ａ）において、Ｒ^１の全てが炭素数１～６のアルキル基であり；Ｒ^２が水素原子、ハロゲノ基を有していてもよい炭素数１～２０のアルキル基又は炭素数６～２０のアリール基である、［２］に記載の炭酸エステルの製造方法。
［４］
前記反応工程をアルコールの存在下で行う、［１］～［３］のいずれかに記載の炭酸エステルの製造方法。 The present inventors have made intensive studies to solve the above problems, and as a result, found that a carbonic acid ester is produced by the reaction of carbon dioxide and a carboxylic acid orthoester in the presence of cerium oxide. completed.
The present invention provides the following specific aspects and the like.
[1]
A method for producing a carbonic acid ester, comprising a reaction step of reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide to produce a carbonic acid ester.
[2]
The method for producing a carbonic acid ester according to [1], wherein the carboxylic acid orthoester is a compound represented by formula (A), and the carbonic acid ester is a compound represented by formula (B).

In the above formula, R ¹ is each independently an optionally substituted alkyl group; R ² is a hydrogen atom or an optionally substituted hydrocarbon group.
[3]
In the above formula (A), all of R ¹ are alkyl groups having 1 to 6 carbon atoms; R ² is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a halogeno group, or The method for producing a carbonate ester according to [2], which is an aryl group of ~20.
[4]
The method for producing a carbonate ester according to any one of [1] to [3], wherein the reaction step is performed in the presence of alcohol.

According to the present invention, a carbonic acid ester can be easily produced by reacting carbon dioxide and a carboxylic acid orthoester. After the reaction, the catalyst and the carbonate ester can be easily separated by filtration or the like, and the catalyst can be used repeatedly. The by-product is the corresponding carboxylic acid ester, which can also be easily separated from the target carbonic acid ester by distillation. In particular, when the reaction is carried out in the presence of alcohol, the carboxylic acid orthoester serves not only as a raw material but also as a dehydrating agent that produces a carbonate ester in the reaction of the alcohol and carbon dioxide, resulting in a high yield of the carbonate ester. be done.

In describing the details of the present invention, specific examples will be given, but the present invention is not limited to the following contents as long as they do not deviate from the gist of the present invention, and can be implemented with appropriate modifications.

Method for Producing Carbonate Ester A method for producing a carbonate ester according to an embodiment of the present invention is characterized by including a reaction step of reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide to produce a carbonate ester. do.

（上記式中、Ｒ^１は、それぞれ独立して、置換基を有していてもよいアルキル基であり；Ｒ^２は、水素原子又は置換基を有していてもよい炭化水素基である。）
具体的には、例えば、二酸化炭素にオルト酢酸トリエチルを反応させて、ジエチルカーボネートと酢酸メチルを生成する反応が挙げられる。
本発明者らは、二酸化炭素とカルボン酸オルトエステルからの炭酸エステルの直接合成について検討し、酸化セリウムの存在下で、簡便に炭酸エステルを製造できることを見出した。この直接合成の反応メカニズムは以下のように推定される。まず、酸化セリウムとカルボン酸オルトエステルとが反応し、Ｃｅ－Ｏ－Ｒ^１というアルコキシ基部位を有する化学種が酸化セリウム表面に生成する。このアルコキシ基部位のＣｅ－Ｏ結合に対して二酸化炭素分子が挿入し、Ｃｅ－Ｏ－（Ｃ＝Ｏ）－Ｏ－Ｒ^１というカルボニル基（Ｃ＝Ｏ）を持つ化学種となる。このカルボニル基（Ｃ＝Ｏ）に対して、カルボン酸オルトエステル由来のもう一つのＲ^１Ｏ基が求核的に反応して、生成物である炭酸エステル（Ｂ）と、副生成物であるカルボン酸エステルを生成し、酸化セリウムが再生する。本実施形態に係る製造方法は、二酸化炭素を有効活用でき、また、ホスゲンを用いる合成法の代替となり得る、低環境負荷の炭酸エステルの製造方法である。
以下、「カルボン酸オルトエステル」、反応条件等について説明する。本明細書では、
酸化セリウムの存在下、二酸化炭素とカルボン酸オルトエステルとを反応させ炭酸エステルを生成する反応工程を、単に「反応工程」ともいう。 A reaction in which carbon dioxide and a carboxylic acid orthoester are reacted to form a carbonate ester is represented, for example, by the following reaction formula.

(In the above formula, R ¹ is each independently an optionally substituted alkyl group; R ² is a hydrogen atom or an optionally substituted hydrocarbon group. )
Specifically, for example, a reaction of reacting carbon dioxide with triethyl orthoacetate to produce diethyl carbonate and methyl acetate can be mentioned.
The present inventors have studied the direct synthesis of carbonic acid esters from carbon dioxide and carboxylic acid orthoesters, and found that carbonic acid esters can be easily produced in the presence of cerium oxide. The reaction mechanism of this direct synthesis is presumed as follows. First, cerium oxide reacts with a carboxylic acid orthoester to generate a chemical species Ce--O--R ¹ having an alkoxy group site on the surface of the cerium oxide. A carbon dioxide molecule is inserted into the Ce—O bond of this alkoxy group site, resulting in a chemical species having a carbonyl group (C=O) called Ce—O—(C═O)—OR ¹ . Another R ¹ O group derived from a carboxylic acid orthoester reacts nucleophilically with this carbonyl group (C═O) to give a product carbonate ester (B) and a by-product A carboxylic acid ester is produced and cerium oxide is regenerated. The production method according to the present embodiment is a method for producing a carbonic acid ester with low environmental load, which can effectively use carbon dioxide and can be an alternative to a synthesis method using phosgene.
The "carboxylic acid orthoester", reaction conditions and the like are described below. Herein,
A reaction step of reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide to produce a carbonate ester is also simply referred to as a “reaction step”.

<Carboxylic acid orthoester>
Carboxylic acid orthoesters used in the present invention are not particularly limited as long as they are compounds having three alkoxy groups on the same carbon. The three alkoxy groups may be the same or different. Also, the alkyl group of the alkoxy group may be linear or branched, and may be substituted or unsubstituted.

（式（Ａ）中、Ｒ^１は、それぞれ独立して、置換基を有していてもよいアルキル基であり；Ｒ^２は、水素原子又は置換基を有していてもよい炭化水素基である。） Carboxylic acid orthoesters preferably include compounds represented by formula (A).

(In formula (A), R ¹ is each independently an optionally substituted alkyl group; R ² is a hydrogen atom or an optionally substituted hydrocarbon group; be.)

( ^R1 )
Each R ¹ is independently an optionally substituted alkyl group.
Although the number of carbon atoms in the alkyl group of R ¹ is not particularly limited, it is usually 1 or more, and is usually 30 or less, preferably 24 or less, more preferably 20 or less, still more preferably 12 or less, and particularly preferably 6 or less. . Alkyl groups may be linear or branched.
Examples of unsubstituted alkyl groups represented by R ¹ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group and tert-butyl group. group, n-pentyl group, iso-pentyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-docosyl group and the like.
Examples of substituents that R ¹ may have include halogeno group, alkylthio group, amino group, imino group, amidino group, pyrrolyl group, triazine ring, triazole ring, benzotriazolyl group, imidazolyl group, benz imidazolyl group, quinolyl group, pyridyl group, pyrimidine group, pyrazinyl group, quinazolinyl group, quinoxalinyl group, purinyl group, piperidinyl group, piperazinyl group, pyrrolidinyl group, pyrazolyl group, aniline group, azo group, diazo group, azide group, cyano group , an amide group, an imide group, a urea group, a group containing an isocyanuric structure, a nitro group, a nitroso group, a cyanate group, an isocyanate group, a morpholino group, a lactam ring, and the like.
From the viewpoint of product versatility and availability, R ¹ is preferably an unsubstituted alkyl group, and it is particularly preferred that all of R ¹ are C 1-6 alkyl groups.

( ^R2 )
R ² is a hydrogen atom or an optionally substituted hydrocarbon group. As used herein, the term "hydrocarbon group" is not limited to a linear saturated hydrocarbon group, and may have a carbon-carbon unsaturated bond, or may have a branched structure. , may have a cyclic structure.
The number of carbon atoms in the hydrocarbon group of R ² is not particularly limited, but it is usually 1 or more, and usually 30
Below, preferably 20 or less, more preferably 12 or less.
Examples of unsubstituted hydrocarbon groups represented by R ² include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group, tert- butyl group, n-pentyl group, iso-pentyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group , n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-docosyl group; cyclopropyl group, cyclobutyl cycloalkyl groups such as groups, cyclopentyl groups, and cyclohexyl groups; , 1-anthryl group, 2-anthryl group, 9-anthryl group, 1-pyrenyl group, 2-pyrenyl group, 4-pyrenyl group, 1-triphenylenyl group, 2-triphenylenyl group and the like.
Examples of the substituent that R ² may have include those exemplified as the substituent that R ¹ may have.
From the viewpoint of availability, R ² is particularly preferably a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a halogeno group, or an aryl group having 6 to 20 carbon atoms.

Specific examples of carboxylic acid orthoesters include orthoformates such as trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, triisopropyl orthoformate, tributyl orthoformate, and diethylphenyl orthoformate. orthoacetic esters such as trimethyl orthoacetate, triethyl orthoacetate, tripropyl orthoacetate, tributyl orthoacetate, triethyl orthochloroacetate, and triethyl orthodichloroacetate; orthopropionate esters such as trimethyl orthopropionate and triethyl orthopropionate; orthobutyric acid orthobutyric acid esters such as trimethyl and trimethyl orthoisobutyrate; orthovaleric acid esters such as trimethyl orthovalerate and triethyl orthovalerate; and orthobenzoic acid esters such as trimethyl orthobenzoate and triethyl orthobenzoate.
The amount of the carboxylic acid orthoester to be used (the amount to be charged) is not particularly limited, and may be appropriately determined according to the size of the reaction vessel. Moreover, the carboxylic acid orthoester may be a commercially available product, or may be synthesized and used.

<Carbon dioxide>
The reaction step uses carbon dioxide (gas) as a raw material for carbonate ester. The filling pressure of carbon dioxide gas is not particularly limited, but the higher the pressure, the higher the yield tends to be, and it is usually 0.1 MPa or more, preferably 1.0 MPa or more, and usually 10 MPa or less, preferably 5.0 MPa or less. . When the filling pressure is within this range, the carbonate ester can be produced efficiently. In this specification, the "filling pressure" means the pressure of carbon dioxide (25°C) in the reactor at the start of the reaction. Carbon dioxide has a reaction pressure of preferably 1 MPa or higher, more preferably 2 MPa or higher, and preferably 20 MPa or lower, more preferably 15 MPa or lower. The carbon dioxide used in the reaction step can be not only prepared as an industrial gas, but also separated and recovered from exhaust gases from factories, power plants, and the like. The reaction system may contain a gas other than carbon dioxide, such as an inert gas such as N ₂ or Ar, as long as the effects of the present invention are not significantly impaired.

<Cerium oxide>
The reaction step is performed in the presence of cerium oxide (CeO ₂ ). Cerium oxide acts as a catalyst.
The amount of cerium oxide to be used (amount to be charged) is usually 0.01 equivalent or more, preferably 0.1 equivalent or more, and usually 1 equivalent or less, preferably 0.01 equivalent or more, relative to 1 equivalent of the orthocarboxylic acid ester. It is 5 equivalents or less, more preferably 0.3 equivalents or less.
Cerium oxide may be commercially available or may be synthesized. Cerium oxide has the advantage that it can be recovered and reused as a catalyst after being used in the reaction process. For example, after completion of the reaction step, the cerium oxide can be separated from the solution of the reaction product mixture by filtration, washed several times with ethanol, dried at 110° C. for 1 hour, and recovered for reuse.

<Solvent>
The reaction step may or may not use a solvent, but it is preferred to use a reaction solvent. By using a reaction solvent, the amount of carbon dioxide dissolved in the reaction mixture increases, the concentration of carbon dioxide in the reaction system increases, the reaction proceeds more easily, and the yield of the carbonate ester improves. Conceivable.
The type of reaction solvent is not particularly limited, but ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, t-butanol, allyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol. , 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and glycerin; aliphatic hydrocarbons such as butane, hexane, octane, and cyclohexane; aromatics such as benzene, toluene, and xylene Hydrocarbons; heterocyclic aromatic compounds such as pyridine; ethyl acetate, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone (NMP), etc. Ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran (THF), dioxane; Nitriles such as acetonitrile, propionitrile, butyronitrile, benzonitrile, 2-cyanopyridine; Acetone and ketones such as isopropyl ketone. 1 type may be used for a solvent and 2 or more types may be used for it.

Above all, from the viewpoint of improving reaction efficiency, the reaction step is preferably carried out in the presence of alcohol. In the reaction step, the carboxylic acid orthoester functions as a reactant (formula (1)). Carbon dioxide and alcohol react in the presence of cerium oxide to produce carbonate and water (equation (2)). This water reacts with the carboxylic acid orthoester to produce a carbonate and ethanol (formula (3)). By carrying out the reaction step in the presence of alcohol in this manner, the carboxylic acid orthoester functions as both a reactant and a dehydrating agent, and the reaction can be carried out more efficiently. In particular, the longer the alkyl chain of the alkoxy group of the carboxylic acid orthoester, the more preferably the reaction is carried out in the presence of an alcohol, and the effect is remarkably exhibited.

The amount of the solvent used is not particularly limited, but for example, it is usually 1 equivalent or more, more preferably 1.5 equivalents or more, still more preferably 2.5 equivalents or more, particularly preferably 4 equivalents, per 1 equivalent of the carboxylic acid orthoester. It can be used in an equivalent amount or more and usually 20 equivalents or less, preferably 15 equivalents or less, more preferably 10 equivalents or less.

<Reaction temperature>
The reaction temperature is not particularly limited, but there is a tendency that the higher the reaction temperature, the higher the yield. The upper limit of the reaction temperature is usually 250° C. or lower, preferably 230° C. or lower, from the viewpoint of avoiding thermal decomposition of the produced carbonate and realizing a high yield, although it depends on the pressure in the reactor. . When the reaction temperature is within this range, the carbonate ester can be efficiently produced.

<Reaction time>
The reaction time is not particularly limited, and may be appropriately adjusted depending on the reaction temperature, amount of catalyst, reaction scale, and the like. It is usually 30 minutes or more, preferably 1 hour or more, more preferably 3 hours or more, and usually 120 hours or less, preferably 100 hours or less, more preferably 80 hours or less. As used herein, the term “reaction time” refers to the time during which the temperature inside the reactor reaches a predetermined reaction temperature and is maintained at the predetermined reaction temperature.

<Reaction vessel>
The reaction vessel is not particularly limited as long as it is made of a material that is stable with respect to the carboxylic acid orthoester, and is appropriately selected according to the continuous process or batch process. An embodiment of the invention may be a continuous process or a batch process. In the case of a batch process, it is preferably a closed reaction vessel (closed reaction vessel), more preferably a carboxylic acid orthoester and cerium oxide, and optionally a volume of 10 to 100 times the volume of the mixture of solvents. It is a sealed pressure-resistant container, more preferably a stainless steel autoclave.

<Operation procedure>
First, a carboxylic acid orthoester as a raw material and cerium oxide as a catalyst are added to a reaction vessel. At this time, it is preferable to carry out in an inert gas atmosphere such as nitrogen or argon. After adding the carboxylic acid orthoester and cerium oxide to the reactor, the reactor is filled with carbon dioxide as a raw material to create a carbon dioxide atmosphere. When a solvent is used, it may be added to the reaction vessel before carbon dioxide is introduced into the reactor, or it may be added to the reactor simultaneously with the carboxylic acid orthoester. During the reaction, the reaction vessel may contain an inert gas such as nitrogen or argon as long as the effects of the present invention are not significantly impaired. Moreover, it is preferable to stir during the reaction, and for example, a magnetic stirrer can be used. After the reaction, it is cooled, the remaining gas is discharged, and the reaction product is recovered.

<Other processes>
The method for producing a carbonic acid ester according to the present embodiment may include optional steps in addition to the reaction steps described above. Optional steps include a purification step to increase the purity of the carbonate. In the purification step, purification methods commonly used in the field of organic synthesis, such as filtration, adsorption, column chromatography, and distillation, can be employed. Specifically, when the intended carbonate ester is liquid, purification can be carried out, for example, by distillation, crystallization, adsorption, or the like.
A step of recovering cerium oxide may also be provided.

（式（Ｂ）中、Ｒ^１は、それぞれ独立して、置換基を有していてもよいアルキル基である。） <Carbonate ester>
Carbonic acid ester produced by the present invention is not particularly limited, and may be determined depending on the purpose.
When the compound represented by the formula (A) is used as the carboxylic acid orthoester in the production method according to one embodiment of the present invention, the compound represented by the following formula (B) can be produced favorably.

(In formula (B), each R ¹ is independently an optionally substituted alkyl group.)

R ¹ is an optionally substituted alkyl group derived from the compound represented by formula (A), and the description for the compound represented by formula (A) applies.
Specific examples of the compound represented by formula (B) include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethyl methyl carbonate and the like.

The present invention will be described in more detail with reference to examples below, but modifications can be made as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

<Example 1>
1.73 g (10.7 mmol) of triethyl orthoacetate (CH ₃ C(OEt) ₃ ) as a carboxylic acid orthoester was placed in a 10 mL SUS autoclave (manufactured by Pressure Glass Industry Co., Ltd.) containing a magnetic stirrer under a nitrogen atmosphere. ), 0.368 g (2.14 mmol) of cerium oxide as a catalyst and 1.97 g (42.8 mmol) of ethanol as a solvent are added, and carbon dioxide gas is added from a cylinder at a temperature of 25 ° C., a pressure gauge (manufactured by Swagelok FST) The pressure indicated by PGI-50M-MG10) was used to fill the autoclave to a filling pressure of 5.0 MPa, and the autoclave was held for 10 minutes with stirring and sealed. After that, while stirring the inside of the autoclave at 1200 rpm, the mixture was heated to a reaction temperature of 160° C. and reacted for 20 hours to obtain a carbonate ester (diethyl carbonate). The pressure inside the autoclave when reaching the reaction temperature was 8.8 MPa. After cooling, the remaining gas was discharged, and the reaction product mixture was analyzed by gas chromatography (GC-2014ATF/SPL manufactured by Shimadzu Corporation) using 4-tert-butyltoluene as an internal standard substance. The yield of diethyl carbonate based on the raw material triethyl orthoacetate was 53%. Table 1 shows the results. In the table, the pressure inside the autoclave when reaching the reaction temperature is defined as "reaction pressure".

<Example 2>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was changed to 100°C. Table 1 shows the results.

<Example 3>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was changed to 120°C. Table 1 shows the results.

<Example 4>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was changed to 140°C. Table 1 shows the results.

<Example 5>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was changed to 180°C. Table 1 shows the results.

<Example 6>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was changed to 200°C. Table 1 shows the results.

<Example 7>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was changed to 220°C. Table 1 shows the results.

<Example 8>
Diethyl carbonate was produced in the same manner as in Example 1 except that the filling pressure was changed to 1.0 MPa under the reaction conditions of Example 1. Table 1 shows the results.

<Example 9>
Diethyl carbonate was produced in the same manner as in Example 1, except that the filling pressure was changed to 3.0 MPa under the reaction conditions of Example 1. Table 1 shows the results.

<Example 10>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 3 hours. Table 1 shows the results.

<Example 11>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 6 hours. Table 1 shows the results.

<Example 12>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 16 hours. Table 1 shows the results.

<Example 13>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 24 hours. Table 1 shows the results.

<Example 14>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 48 hours. Table 1 shows the results.

<Example 15>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 72 hours. Table 1 shows the results.

<Example 16>
Production of diethyl carbonate in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced by triethyl orthoformate (HC(OEt) ₃ ) under the reaction conditions of Example 1. did Table 1 shows the results.

<Example 17>
By the same procedure as in Example 1 except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was changed to triethyl orthopropionate (CH ₃ CH ₂ C(OEt) ₃ ) for the reaction conditions of Example 1 The production of diethyl carbonate was carried out. Table 1 shows the results.

<Example 18>
The procedure of Example 1 was repeated except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced with triethyl orthobutyrate (CH ₃ CH ₂ CH ₂ C(OEt) ₃ ) for the reaction conditions of Example 1. produced diethyl carbonate. Table 1 shows the results.

<Example 19>
The reaction conditions of Example 1 were the same as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced by triethyl orthovalerate (CH ₃ CH ₂ CH ₂ CH ₂ C(OEt) ₃ ). Diethyl carbonate was produced by the same operation. Table 1 shows the results.

<Example 20>
By the same procedure as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was changed to triethyl orthobenzoate (C ₆ H ₅ C(OEt) ₃ ) for the reaction conditions of Example 1. The production of diethyl carbonate was carried out. Table 1 shows the results.

<Example 21>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced by triethyl orthochloroacetate (ClCH ₂ C(OEt) ₃ ). manufactured. Table 1 shows the results.

<Example 22>
Diethyl carbonate was prepared in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced by triethyl orthodichloroacetate (Cl ₂ CHC(OEt) ₃ ). was manufactured. Table 1 shows the results.

<Example 23>
Diethyl carbonate was produced in the same manner as in Example 1 except that ethanol was not added as a solvent under the reaction conditions of Example 1. Table 1 shows the results.

<Example 24>
The reaction conditions of Example 1 were the same as in Example 1, except that ethanol was not added as a solvent and triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced with triethyl orthoformate (HC(OEt) ₃ ). Diethyl carbonate was produced by the operation of . Table 1 shows the results.

<Example 25>
The reaction conditions of Example 1 were repeated except that ethanol was not added as a solvent and triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced with triethyl orthopropionate (CH ₃ CH ₂ C(OEt) ₃ ). Diethyl carbonate was produced in the same manner as in Example 1. Table 1 shows the results.

<Example 26>
For the reaction conditions of Example 1, except that ethanol was not added as a solvent and triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was replaced with triethyl orthobutyrate (CH ₃ CH ₂ CH ₂ C(OEt) ₃ ). Diethyl carbonate was produced in the same manner as in Example 1. Table 1 shows the results.

<Example 27>
Ethanol was not added as a solvent to the reaction conditions of Example 1, and triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was changed to triethyl orthovalerate (CH ₃ CH ₂ CH ₂ CH ₂ C(OEt) ₃ ). Diethyl carbonate was produced in the same manner as in Example 1, except for the above. Table 1 shows the results.

<Example 28>
After completion of the reaction in Example 1, cerium oxide (catalyst) was separated from the solution by filtration, washed with ethanol five times, and dried at 110° C. for 1 hour to recover. Using this recovered cerium oxide (catalyst), diethyl carbonate was produced again under the same conditions as in Example 1 (first reuse of catalyst). The same operation was repeated to carry out reuse experiments up to the fourth time. Table 2 shows the results.

<Example 29>
After completion of the reaction in Example 19, cerium oxide (catalyst) was separated from the solution by filtration, washed with ethanol five times, and dried at 110° C. for 1 hour to recover. Using this recovered cerium oxide (catalyst), diethyl carbonate was again produced under the same conditions as in Example 19 (first reuse of catalyst). The same operation was repeated to carry out reuse experiments up to the fourth time. Table 3 shows the results.

From the above examples, it was found that a carbonic acid ester can be easily produced by reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide.
From Examples 1 to 7, it was found that the higher the reaction temperature, the higher the yield of the carbonate ester, and that the higher the reaction temperature than 160° C., the slower the improvement in the yield. When the reaction temperature is higher than 160° C., although the amount of carbonate produced increases, part of the produced carbonate is thermally decomposed, and the improvement in yield slows down.
It was found from Examples 1, 8, and 9 that the yield of carbonate ester was improved by increasing the initial pressure.
From Examples 1 and 10 to 12, it was found that the longer the reaction time, the higher the yield of the carbonate ester.
As shown in Examples 29 and 30, the used cerium oxide can be recovered and reused as a catalyst.
In addition, from Examples 1 and 14 to 28, the yield of the carbonate ester is improved by conducting the reaction in the presence of alcohol, and there is a tendency that the longer-chain orthoester of the carboxylic acid gives a higher yield of the carbonate ester. I understood it.

According to the present invention, a carbonic acid ester can be easily produced by reacting carbon dioxide and a carboxylic acid orthoester. In addition, the carbonate ester obtained by the production method of the present invention is a raw material for polycarbonate, polyurethane, etc., and has a wide range of uses such as solvents, fuel additives, various detergents, and electrolytes for lithium ion batteries. Very useful.

Claims (4)

A method for producing a carbonic acid ester, comprising a reaction step of reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide to produce a carbonic acid ester. 2. The method for producing a carbonic acid ester according to claim 1, wherein the carboxylic acid orthoester is a compound represented by formula (A), and the carbonic acid ester is a compound represented by formula (B).

In the above formula, R ¹ is each independently an optionally substituted alkyl group; R ² is a hydrogen atom or an optionally substituted hydrocarbon group. In the above formula (A), all of R ¹ are alkyl groups having 1 to 6 carbon atoms; R ² is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a halogeno group, or The method for producing a carbonate ester according to claim 2, wherein the aryl group is ∼20. The method for producing a carbonate ester according to any one of claims 1 to 3, wherein the reaction step is performed in the presence of alcohol.