JP7652373B2 - Carbonate ester manufacturing method - Google Patents

Description

The present invention relates to a method for producing carbonate esters.

Carbonate esters are useful compounds that are used as raw materials for polycarbonates and polyurethanes, and also have a wide range of applications, such as solvents, fuel additives, various cleaning agents, and electrolytes for lithium-ion batteries.
As a method for producing a carbonate ester, a production method involving 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, a method for producing a carbonate ester by reacting carbon dioxide with an alcohol in the presence of a solid catalyst and benzonitrile or the like has been proposed (see, for example, Patent Documents 3 and 4).

Japanese Patent Application Publication No. 11-35521 Japanese Patent Application Publication No. 7-224010 JP 2016-216363 A WO2019/138993

Conventional methods for producing carbonate esters using homogeneous catalysts or benzonitrile, etc., have the problem that separation and purification after the production of carbonate esters is complicated. The objective of the present invention is to provide a method for easily producing carbonate esters 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。 Means for Solving the Problems The present inventors have conducted extensive research to solve the above problems and have discovered that a carbonate ester is produced by reaction of carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide, thereby completing the present invention.
The present invention provides the following specific embodiments.
[1]
A method for producing a carbonate ester, comprising a reaction step of reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide to produce a carbonate ester.
[2]
The method for producing a carbonate ester according to [1], wherein the carboxylic acid orthoester is a compound represented by formula (A), and the carbonate ester is a compound represented by formula (B).

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

According to the present invention, a carbonate ester can be easily produced by reacting carbon dioxide with 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 reused. The by-product is the corresponding carboxylic acid ester, which can also be easily separated from the target carbonate 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 to generate a carbonate ester by the reaction of alcohol with carbon dioxide, and the carbonate ester can be obtained in high yield.

Specific examples will be given to explain the details of the present invention, but the invention is not limited to the following content and can be modified as appropriate without departing from the spirit of the invention.

Method for Producing Carbonate Ester A method for producing a carbonate ester according to one 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.

（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。 The reaction of carbon dioxide with a carboxylic acid orthoester to produce a carbonate ester is represented, for example, by the following reaction formula.

(In the above formula, each ^R1 is independently an alkyl group which may have a substituent; and ^each R2 is a hydrogen atom or a hydrocarbon group which may have a substituent.)
Specifically, for example, a reaction in which carbon dioxide is reacted with triethyl orthoacetate to produce diethyl carbonate and methyl acetate can be mentioned.
The present inventors have investigated the direct synthesis of a carbonate ester from carbon dioxide and a carboxylic acid orthoester, and have found that a carbonate ester can be easily produced in the presence of cerium oxide. The reaction mechanism of this direct synthesis is presumed to be as follows. First, cerium oxide reacts with a carboxylic acid orthoester to generate a chemical species having an alkoxy group moiety, Ce-O-R ^1, on the surface of the cerium oxide. A carbon dioxide molecule is inserted into the Ce-O bond of this alkoxy group moiety, resulting in a chemical species having a carbonyl group (C=O), Ce-O-(C=O)-O-R ^1. Another R ¹ O group derived from the carboxylic acid orthoester nucleophilically reacts with this carbonyl group (C=O), producing a product carbonate ester (B) and a by-product carboxylic acid ester, and regenerating cerium oxide. The production method according to this embodiment is a method for producing a carbonate ester with low environmental impact, which can effectively utilize carbon dioxide and can be an alternative to a synthesis method using phosgene.
The "carboxylic acid orthoester" and reaction conditions will be described below.
The reaction process in which carbon dioxide and a carboxylic acid orthoester are reacted with each other in the presence of cerium oxide to produce a carbonate ester is also simply referred to as the "reaction process".

<Carboxylic acid orthoester>
The carboxylic acid orthoester used in the present invention is not particularly limited as long as it is a compound having three alkoxy groups on the same carbon. The three alkoxy groups may be the same or different. 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。） The carboxylic acid orthoester is preferably a compound represented by the formula (A).

(In formula (A), each R ¹ is independently an alkyl group which may have a substituent; and each R ² is a hydrogen atom or a hydrocarbon group which may have a substituent.)

(R ¹ )
Each R ¹ is independently an alkyl group which may have a substituent.
The number of carbon atoms in the alkyl group of ^R1 is not particularly limited, but is usually 1 or more, and is usually 30 or less, preferably 24 or less, more preferably 20 or less, even more preferably 12 or less, and particularly preferably 6 or less. The alkyl group may be linear or branched.
Examples of the unsubstituted alkyl group represented by ^R1 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-docosyl group.
Examples of the substituent that R ¹ may have include a halogeno group, an alkylthio group, an amino group, an imino group, an amidino group, a pyrrolyl group, a triazine ring, a triazole ring, a benzotriazolyl group, an imidazolyl group, a benzimidazolyl group, a quinolyl group, a pyridyl group, a pyrimidine group, a pyrazinyl group, a quinazolinyl group, a quinoxalinyl group, a purinyl group, a piperidinyl group, a piperazinyl group, a pyrrolidinyl group, a pyrazolyl group, an aniline group, an azo group, a diazo group, an azide group, a 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, and a lactam ring.
From the viewpoints of versatility of the product and easy availability, R ¹ is preferably an unsubstituted alkyl group, and it is particularly preferable that all R ¹ are alkyl groups having 1 to 6 carbon atoms.

( ^R2 )
^R2 is a hydrogen atom or a hydrocarbon group which may have a substituent. In this specification, the term "hydrocarbon group" is not limited to a linear saturated hydrocarbon group, and may have a carbon-carbon unsaturated bond, a branched structure, or a cyclic structure.
The number of carbon atoms in the hydrocarbon group of ^R2 is not particularly limited, but is usually 1 or more, and is usually 30 or less.
It is preferably 20 or less, and more preferably 12 or less.
Examples of the unsubstituted hydrocarbon group represented by ^R2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonyl group, an n-butyl ... Examples of such groups include alkyl groups such as a decyl group and an n-docosyl group; cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group and a cyclohexyl group; and aryl groups such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a 4-phenanthryl group, a 9-phenanthryl group, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a 1-pyrenyl group, a 2-pyrenyl group, a 4-pyrenyl group, a 1-triphenylenyl group and a 2-triphenylenyl group.
Examples of the substituent that ^R2 may have include those exemplified as the substituent that ^R1 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 orthoformic acid esters such as trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, triisopropyl orthoformate, tributyl orthoformate, and diethylphenyl orthoformate; orthoacetate esters such as trimethyl orthoacetate, triethyl orthoacetate, tripropyl orthoacetate, tributyl orthoacetate, triethyl orthochloroacetate, and triethyl orthodichloroacetate; orthopropionic acid esters such as trimethyl orthopropionate and triethyl orthopropionate; orthobutyric acid esters such as trimethyl orthobutyrate 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 used (charged amount) is not particularly limited and may be appropriately determined depending on the size of the reaction vessel. In addition, the carboxylic acid orthoester may be a commercially available product or may be synthesized.

<Carbon dioxide>
In the reaction step, carbon dioxide (gas) is used as a raw material for the carbonate ester. The filling pressure of the carbon dioxide gas is not particularly limited, but the higher the pressure, the higher the yield tends to be. 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 (25°C) of carbon dioxide in the reactor at the start of the reaction. The pressure of carbon dioxide during the reaction is preferably 1 MPa or more, more preferably 2 MPa or more, and preferably 20 MPa or less, more preferably 15 MPa or less. The carbon dioxide used in the reaction step can be not only that prepared as an industrial gas, but also that separated and recovered from exhaust gas from a factory, a power plant, or the like. In addition, the reaction system may contain gases other than carbon dioxide, such as inert gases such as N ₂ and Ar, within a range that does not significantly impair the effects of the present invention.

<Cerium oxide>
The reaction step is carried out in the presence of cerium oxide (CeO ₂ ), which acts as a catalyst.
The amount of cerium oxide used (charged amount) is usually 0.01 equivalents or more, preferably 0.1 equivalents or more, and usually 1 equivalent or less, preferably 0.5 equivalents or less, more preferably 0.3 equivalents or less, relative to 1 equivalent of the orthocarboxylate ester.
The cerium oxide may be a commercially available product or may be synthesized. Cerium oxide has the advantage that it can be recovered and reused as a catalyst after use in the reaction process. For example, after the reaction process is completed, cerium oxide can be separated from the solution of the reaction product mixture by filtration, washed several times with ethanol, and then dried at 110° C. for 1 hour, recovered, and reused.

<Solvent>
The reaction step may or may not use a solvent, but it is preferable to use a reaction solvent. It is considered that the use of a reaction solvent increases the amount of carbon dioxide dissolved in the reaction mixture, increases the concentration of carbon dioxide in the reaction system, facilitates the reaction, and improves the yield of the carbonate ester.
The type of reaction solvent is not particularly limited, and examples thereof include alcohols such as 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; aromatic hydrocarbons such as benzene, toluene, and xylene; and heterocyclic aromatic hydrocarbons such as pyridine. Examples of the solvent include compounds such as aprotic polar solvents, such as ethyl acetate, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone (NMP); ethers, such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran (THF), and dioxane; nitriles, such as acetonitrile, propionitrile, butyronitrile, benzonitrile, and 2-cyanopyridine; and ketones, such as acetone and isopropyl ketone. One or more of the solvents may be used.

In particular, from the viewpoint of improving the reaction efficiency, it is preferable to carry out the reaction step 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 a carbonate ester and water (formula (2)). This water reacts with the carboxylic acid orthoester to produce a carbonate ester and ethanol (formula (3)). In this way, by carrying out the reaction step in the presence of alcohol, 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 preferable it is to carry out the reaction in the presence of alcohol, and the effect thereof is more pronounced.

The amount of the solvent used is not particularly limited, but is, for example, usually 1 equivalent or more, more preferably 1.5 equivalents or more, even more preferably 2.5 equivalents or more, and particularly preferably 4 equivalents or more, relative to 1 equivalent of the carboxylic acid orthoester, and is usually 20 equivalents or less, preferably 15 equivalents or less, and more preferably 10 equivalents or less.

<Reaction temperature>
The reaction temperature is not particularly limited, but a higher temperature tends to result in a higher yield, and is usually 100° C. or higher, preferably 120° C. or higher, and more preferably 140° C. or higher. The upper limit of the reaction temperature, which depends on the pressure inside the reactor, is usually 250° C. or lower, preferably 230° C. or lower, from the viewpoint of avoiding thermal decomposition of the carbonate ester produced and achieving a high yield. When the reaction temperature is in this range, the carbonate ester can be produced efficiently.

<Reaction time>
The reaction time is not particularly limited and may be appropriately adjusted depending on the reaction temperature, the amount of catalyst, the reaction scale, etc. 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. In this specification, the "reaction time" refers to the time during which the temperature in the reactor is maintained at a predetermined reaction temperature after it has reached 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 to the carboxylic acid orthoester, and may be appropriately selected depending on whether the process is a continuous process or a batch process. In one embodiment of the present invention, the process may be a continuous process or a batch process. In the case of a batch process, the reaction vessel is preferably a sealed reaction vessel (sealed reaction vessel), more preferably a sealed pressure-resistant vessel having a volume 10 to 100 times the volume of the mixture of the carboxylic acid orthoester, cerium oxide, and optionally a solvent, and more preferably a stainless steel autoclave.

<Operation Procedure>
First, the raw material carboxylic acid orthoester and the catalyst cerium oxide are added to a reaction vessel. At this time, it is preferable to carry out the reaction under an inert gas atmosphere such as nitrogen or argon. After the carboxylic acid orthoester and cerium oxide are added to the reaction vessel, the inside of the reaction vessel is filled with the raw material carbon dioxide 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 reaction vessel, or it may be added to the reaction vessel simultaneously with the carboxylic acid orthoester. During the reaction, the reaction vessel may contain an inert gas such as nitrogen or argon within a range that does not significantly impair the effects of the present invention. In addition, it is preferable to stir the mixture during the reaction, and for example, a magnetic stirrer may be used. After the reaction, the mixture is cooled, the remaining gas is discharged, and the reaction product is recovered.

<Other processes>
The method for producing a carbonate ester according to the present embodiment may include any other step in addition to the reaction step. An example of the optional step is a purification step for increasing the purity of the carbonate ester. In the purification step, a purification method usually performed in the field of organic synthesis, such as filtration, adsorption, column chromatography, distillation, etc., can be used. Specifically, when the target carbonate ester is liquid, purification can be performed by, for example, distillation, crystallization, adsorption, etc.
In addition, a step of recovering cerium oxide may 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>
The carbonate ester produced by the present invention is not particularly limited and may be determined depending on the purpose.
When the compound represented by formula (A) is used as a 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 suitably produced.

(In formula (B), each R ¹ is independently an alkyl group which may have a substituent.)

R ¹ is an alkyl group which may have a substituent derived from the compound represented by formula (A), and the explanation for the compound represented by formula (A) is applied.
Specific examples of the compound represented by formula (B) include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, and ethyl methyl carbonate.

The present invention will be explained in more detail below with reference to examples, but these can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited to the specific examples shown below.

Example 1
In a 10 mL SUS autoclave (manufactured by Taiatsu Glass Industry Co., Ltd.) containing a magnetic stirrer, 1.73 g (10.7 mmol) of triethyl orthoacetate (CH ₃ C(OEt) ₃ ) as a carboxylic acid orthoester, 0.368 g (2.14 mmol) of cerium oxide as a catalyst, and 1.97 g (42.8 mmol) of ethanol as a solvent were added under a nitrogen atmosphere, and carbon dioxide gas was charged from a cylinder at a temperature of 25° C. at a pressure indicated by a pressure gauge (PGI-50M-MG10 manufactured by Swagelok FST) to a charging pressure of 5.0 MPa, and the mixture was stirred for 10 minutes and sealed. Thereafter, the inside of the autoclave was heated to a reaction temperature of 160° C. while stirring at 1200 rpm, and reacted for 20 hours to obtain a carbonate ester (diethyl carbonate). The pressure inside the autoclave when the reaction temperature was reached was 8.8 MPa. After cooling, the remaining gas was released, 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. The yield of diethyl carbonate based on the raw material triethyl orthoacetate was 53%. The results are shown in Table 1. In the table, the pressure inside the autoclave when the reaction temperature was reached is referred to as the "reaction pressure".

Example 2
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was 100° C. The results are shown in Table 1.

Example 3
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was 120° C. The results are shown in Table 1.

Example 4
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was 140° C. The results are shown in Table 1.

Example 5
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was 180° C. The results are shown in Table 1.

Example 6
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was 200° C. The results are shown in Table 1.

Example 7
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction temperature was 220° C. The results are shown in Table 1.

Example 8
Diethyl carbonate was produced in the same manner as in Example 1, except that the charging pressure was 1.0 MPa under the reaction conditions of Example 1. The results are shown in Table 1.

<Example 9>
Diethyl carbonate was produced in the same manner as in Example 1, except that the charging pressure was 3.0 MPa, in contrast to the reaction conditions in Example 1. The results are shown in Table 1.

Example 10
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 3 hours under the same reaction conditions as in Example 1. The results are shown in Table 1.

Example 11
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 6 hours under the reaction conditions of Example 1. The results are shown in Table 1.

Example 12
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 16 hours under the same reaction conditions as in Example 1. The results are shown in Table 1.

Example 13
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 24 hours under the same reaction conditions as in Example 1. The results are shown in Table 1.

<Example 14>
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was 48 hours under the same reaction conditions as in Example 1. The results are shown in Table 1.

Example 15
Diethyl carbonate was produced in the same manner as in Example 1, except that the reaction time was changed to 72 hours under the same reaction conditions as in Example 1. The results are shown in Table 1.

<Example 16>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was used as triethyl orthoformate (HC(OEt) ₃ ) instead of triethyl orthoacetate (CH 3 C(OEt) 3 ). The results are shown in Table 1.

<Example 17>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was used instead of triethyl orthopropionate (CH ₃ CH ₂ C(OEt) ₃ ). The results are shown in Table 1.

<Example 18>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was used instead of triethyl orthobutyrate (CH ₃ CH ₂ CH ₂ C(OEt) ₃ ). The results are shown in Table 1.

<Example 19>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthovalerate (CH ₃ CH ₂ CH 2 CH 2 C(OEt) ₃ ) was used instead of triethyl orthovalerate (CH ₃ CH ₂ CH ₂ C(OEt) ₃ ) under the reaction conditions of Example 1. The results are shown in Table 1.

<Example 20>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthobenzoate (C ₆ H ₅ C(OEt) ₃ ) was used instead of triethyl orthoacetate (CH ₃ C(OEt) ₃ ) under the reaction conditions of Example 1. The results are shown in Table 1.

<Example 21>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was used instead of triethyl orthochloroacetate (ClCH ₂ C(OEt) ₃ ). The results are shown in Table 1.

<Example 22>
Diethyl carbonate was produced in the same manner as in Example 1, except that triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was used instead of triethyl orthodichloroacetate (Cl ₂ CHC(OEt) ₃ ). The results are shown in Table 1.

<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. The results are shown in Table 1.

<Example 24>
Diethyl carbonate was produced in the same manner as in Example 1, except that ethanol was not added as a solvent and triethyl orthoacetate (CH ₃ C(OEt) ₃ ) was used as triethyl orthoformate (HC(OEt) ₃ ). The results are shown in Table 1.

<Example 25>
Diethyl carbonate was produced in the same manner as in Example 1, except that ethanol was not added as a solvent and triethyl orthopropionate (CH ₃ CH ₂ C(OEt) ₃ ) was used instead of triethyl orthoacetate (CH ₃ C(OEt) ₃ ). The results are shown in Table 1.

<Example 26>
Diethyl carbonate was produced in the same manner as in Example 1, except that ethanol was not added as a solvent and _triethyl orthoacetate ( _CH3C (OEt) ₃ ) was used as _triethyl orthobutyrate ( _CH3CH2CH2C (OEt) ₃ ). The results are shown in Table 1.

<Example 27>
Diethyl carbonate was produced in the same manner as in Example 1, except that ethanol was not added as a solvent _{and triethyl} orthovalerate ( _{CH3CH2CH2CH2C} (OEt) ₃ ) was used instead of _triethyl orthovalerate ( _{CH3CH2CH2CH2C} (OEt) ₃ ). The results are shown in Table 1.

<Example 28>
After the reaction in Example 1 was completed, the cerium oxide (catalyst) was separated from the solution by filtration, washed five times with ethanol, and then dried at 110° C. for 1 hour to recover it. Using this recovered cerium oxide (catalyst), diethyl carbonate was produced again under the same conditions as in Example 1 (first catalyst reuse). The same operation was repeated, and the reuse experiment was carried out four times. The results are shown in Table 2.

<Example 29>
After the reaction in Example 19 was completed, the cerium oxide (catalyst) was separated from the solution by filtration, washed five times with ethanol, and then 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 19 (first catalyst reuse). The same operation was repeated, and the reuse experiment was carried out four times. The results are shown in Table 3.

From the above examples, it was found that a carbonate 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 increasing the reaction temperature tends to improve the yield of carbonate ester, and the improvement in yield was slow when the reaction was carried out at a temperature higher than 160° C. It is considered that when the reaction temperature is higher than 160° C., the amount of carbonate ester produced increases, but the produced carbonate ester is partially thermally decomposed, and the improvement in yield becomes slow.
It was found from Examples 1, 8 and 9 that the yield of carbonate ester was improved by increasing the initial pressure.
It was found from Examples 1 and 10 to 12 that the yield of carbonate ester tends to improve as the reaction time increases.
As shown in Examples 29 and 30, the cerium oxide used can be recovered and reused as a catalyst.
Furthermore, it was found from Examples 1 and 14 to 28 that the yield of carbonate ester was improved by carrying out the reaction in the presence of alcohol, and that the longer the chain carboxylic acid orthoester, the higher the yield of carbonate ester tended to be.

According to the present invention, carbonate esters can be easily produced by reacting carbon dioxide with carboxylic acid orthoesters. In addition, the carbonate esters obtained by the production method of the present invention are very useful as raw materials for polycarbonates and polyurethanes, and also have a wide range of applications, such as solvents, fuel additives, various cleaning agents, and electrolytes for lithium-ion batteries.

Claims (2)

The method includes a reaction step of reacting carbon dioxide with a carboxylic acid orthoester in the presence of cerium oxide to produce a carbonate ester,
The carboxylic acid orthoester is a compound represented by formula (A),
The method for producing a carbonate ester , wherein the carbonate ester is a compound represented by formula (B) .

In the above formula, R ¹ 's are each independently an alkyl group having 1 to 6 carbon atoms; R ² 's are 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. The method for producing a carbonate ester according to claim 1 , wherein the reaction step is carried out in the presence of an alcohol.