Method for producing carbonic acid diester

Abstract

To provide a method for efficiently producing a carbonic acid diester by using carbon dioxide as a carbonyl source.SOLUTION: A method for producing a carbonic acid diester, comprising the step of reacting an alkoxysilane represented by the formula (A) with carbon dioxide: wherein each R1 is independently an optionally substituted hydrocarbyl group; each R2 is independently an optionally substituted hydrocarbyl group; n is an integer of 1 to 3; and R1, OR1, or R1 and OR1 bonded to the same Si atom may be bonded to each other to form a ring. ).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a carbonic acid diester. [Background technology]

[0002] Carbonate diesters are widely used as solvents for electrolytes and the like, alkylating agents, carbonylating agents, gasoline additives, diesel fuel additives, and raw materials for polymers such as polycarbonates.

[0003] As a method for producing a carbonate diester, a method of reacting phosgene with an alcohol is widely known and has been industrialized. However, this method has problems such as corrosion of the equipment due to the by-product hydrochloric acid and the need to use phosgene, which is highly toxic and corrosive. Therefore, development of a method for producing a carbonate diester using carbon dioxide as a carbonyl source instead of phosgene is underway.

[0004] For example, Patent Document 1 discloses a method for producing an organic carbonate by reacting an alcohol, carbon dioxide, and an alkyl halide in an ionic liquid. Furthermore, Patent Document 2 discloses a method for producing an organic carbonate using tetraethoxysilane as the alkoxysilane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Chinese Patent Application Publication No. 111362800 [Patent Document 2] Patent Publication No. 2021-183566 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the method described in Patent Document 1 solves the above-mentioned problems caused by the use of phosgene, the problem of needing to use methyl iodide and alkyl halide as sacrificial reagents, which have a large environmental impact, remains. Furthermore, the method described in Patent Document 2 can produce organic carbonates, but there is room for improvement in production efficiency. Under these circumstances, there is a need to develop a new method for efficiently producing carbonate diesters, in order to increase the degree of freedom in selecting production methods.

[0007] An object of the present disclosure is to provide a method for efficiently producing a carbonate diester using carbon dioxide as a carbonyl source. [Means for solving the problem]

[0008] The inventors of the present disclosure have found that a carbonic acid diester can be efficiently produced by reacting an alkoxysilane having an isocyanurate skeleton with carbon dioxide.

[0009] [1] A method for producing a carbonate diester, comprising a reaction step of reacting an alkoxysilane represented by formula (A) with carbon dioxide. [ka] (In the formula, R 1 each independently represents a hydrocarbon group which may have a substituent; R 2 each independently represents a hydrocarbon group which may have a substituent; n is an integer of 1 to 3; R bonded to the same Si atom 1 Comrades, OR 1 Peers or R 1 and OR 1 may be bonded to each other to form a ring. [2] The method for producing a carbonate diester according to [1], wherein the reaction step is carried out in the presence of a metal catalyst. [3] The method for producing a carbonate diester according to [2], wherein the metal catalyst contains one or more metals selected from the group consisting of metals of Group 4 of the periodic table and metals of Group 14 of the periodic table. [4] The method for producing a carbonic acid diester according to [2] or [3], wherein the metal catalyst is a metal alkoxide. [5] [4] The method for producing a carbonic acid diester according to [4], wherein the metal alkoxide is at least one selected from the group consisting of zirconium alkoxide, tin alkoxide, and titanium alkoxide. [6] The method for producing a carbonate diester according to any one of [1] to [5], wherein a polymer having a constitutional unit represented by formula (C) is produced in the reaction step. [ka] [ka] (In the formula, R 1 and R 2 are R in formula (A), respectively. 1 and R 2 each Y independently represents a group represented by formula (c1) to (c3); p is an integer of 0 to 2; q is 0 or 1; and the wavy line represents R 2 represents the bonding position with another structural unit; * represents the bonding position with another structural unit.) [7] The method for producing a carbonate diester according to any one of [1] to [6], wherein the reaction step is carried out under a temperature condition of 80°C or higher and 250°C or lower. [8] The method for producing a carbonate diester according to any one of [1] to [7], wherein the initial pressure of carbon dioxide (at 25°C) in a reactor in which the reaction is carried out is 1.0 MPa or more and 15.0 MPa or less. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a method for efficiently producing a carbonate diester using carbon dioxide as a carbonyl source. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the relationship between the initial pressure of carbon dioxide and the yield of carbonate diester in the reaction steps of Examples 1 to 5 (black) and Comparative Examples 1 to 5 (white). [Figure 2] 1 is a graph showing the relationship between the reaction temperature and the yield of carbonate diester in the reaction steps of Examples 1, 6 to 8 (black) and Comparative Examples 1, 6 to 8 (white). [Figure 3] 1 is a MALDI-TOFMS spectrogram of the reaction mixture residue in an example. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present disclosure will be described in detail below. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present disclosure, and the present disclosure is not limited to these contents, and can be implemented in various modifications within the scope of its gist.

[0013] In the present disclosure, the range "X to Y" means "X or more and Y or less." Furthermore, when a numerical range expressed as "X to Y" or "X or more and Y or less" is stated in stages (for example, in order of preference), the upper and lower limits of each numerical range can be combined in any way.

[0014] In the present disclosure, a description such as "X such as x1, x2, and x3" lists x1, x2, and x3 as examples of X, and does not mean that X is limited to x1, x2, x3, and the like.

[0015] One embodiment of the present disclosure relates to a method for producing a carbonate diester, which includes a reaction step of reacting an alkoxysilane having an isocyanurate skeleton with carbon dioxide. This will be explained in more detail.

[0016] 1.Reaction process 1-1.Alkoxysilane In the production method according to this embodiment, the alkoxysilane used as a raw material for the carbonate diester is not particularly limited as long as it is a compound represented by formula (A), and can be appropriately selected depending on the carbonate diester to be produced. The alkoxysilane may be used alone, or two or more types may be used in any combination and ratio.

[0017] [ka]

[0018] (R 1 ) In formula (A), R 1 R each independently represent a hydrocarbon group which may have a substituent. 1 Comrades, OR 1 Peers or R 1 and OR 1 and may be bonded to each other to form a ring, but preferably do not form a ring.

[0019] In the present disclosure, the hydrocarbon group includes an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded. The aliphatic hydrocarbon group is not limited to a linear hydrocarbon group, but may have a branched structure, a carbon-carbon unsaturated bond, or a cyclic structure. The aromatic hydrocarbon group may be monocyclic, polycyclic, or fused ring. The aromatic hydrocarbon group may also be a heterocyclic aromatic hydrocarbon group, but is preferably an aromatic hydrocarbon group that does not contain a heteroatom as a ring-constituting atom.

[0020] R 1 The number of carbon atoms in the hydrocarbon group represented by the formula is preferably 1 or more and 30 or less, more preferably 1 or more and 24 or less, even more preferably 1 or more and 12 or less, still more preferably 1 or more and 8 or less, and particularly preferably 2 or more and 4 or less. In the present disclosure, the hydrocarbon group may have a substituent, but the number of carbon atoms in the hydrocarbon group does not include the number of carbon atoms in the substituent.

[0021] R 1 Examples of the unsubstituted hydrocarbon group represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an isobutyl 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- Linear or branched saturated hydrocarbon groups (alkyl groups) such as heptadecyl, n-octadecyl, n-nonadecyl, and n-docosyl groups; alicyclic saturated hydrocarbon groups (cycloalkyl groups) such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups; vinyl, allyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 2-methylallyl, 1-hexenyl, 1-heptenyl, and 1-octenyl unsaturated hydrocarbon groups containing a carbon-carbon double bond (olefin group), such as an acetylenyl group and a 2-methyl-1-propenyl group; unsaturated hydrocarbon groups containing a carbon-carbon triple bond, such as an acetylenyl group and a propargyl group; benzyl group, phenethyl group; aralkyl groups, such as a 1-naphthylmethyl group and a 2-naphthylmethyl group; 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; and nitrogen-containing heterocyclic groups, such as a 2-pyridyl group, a 3-pyridyl group, and a 4-pyridyl group, with alkyl groups being preferred.

[0022] Examples of substituents that the hydrocarbon group may have include deuterium atoms; halogeno groups such as fluoro, chloro, bromo, and iodo; alkyl groups having from 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl; cycloalkyl groups having from 3 to 6 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; aryl groups having from 6 to 10 carbon atoms such as phenyl, 1-naphthyl, and 2-naphthyl; alkoxy groups having from 1 to 4 carbon atoms such as methoxy, ethoxy, isopropyloxy, n-butyloxy, sec-butyloxy, isobutyloxy, and tert-butyloxy; and cycloalkyl groups having from 3 to 6 carbon atoms such as cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, and cyclohexyloxy. aryloxy groups having 6 to 10 carbon atoms, such as a phenoxy group, a 1-naphthyloxy group, and a 2-naphthyloxy group; alkylthio groups having 1 to 4 carbon atoms, such as a methylthio group, an ethylthio group, an n-propylthio group, an isopropylthio group, an n-butylthio group, a sec-butylthio group, an isobutylthio group, and a tert-butylthio group; cycloalkylthio groups having 3 to 6 carbon atoms, such as a cyclopropylthio group, a cyclobutylthio group, a cyclopentylthio group, and a cyclohexylthio group; arylthio groups having 6 to 10 carbon atoms, such as a phenylthio group, a 1-naphthylthio group, and a 2-naphthylthio group; oxygen-containing heterocyclic groups, such as a furanyl group; sulfur-containing heterocyclic groups, such as a thienyl group; nitrogen-containing heterocyclic groups, such as a pyrrolyl group and a pyridyl group; a carboxy group; a hydroxy group; a cyano group; a nitro group, a cyanate group, an isocyanate group, an amino group; an amide group; an imide group; and a urea group.

[0023] The hydrocarbon group preferably has no substituent. When the hydrocarbon group has a substituent, the position of the substituent is not particularly limited. When the hydrocarbon group has a substituent, the number of substituents is not particularly limited, but is preferably 1 to 12, more preferably 1 to 8, and even more preferably 2 to 4 per hydrocarbon group.

[0024] R 1 From the viewpoint of reaction efficiency with carbon dioxide, the hydrocarbon group represented by the following formula (I) which may have a substituent is preferably an unsubstituted alkyl group, more preferably a methyl group or an ethyl group.

[0025] (R 2 ) In formula (A), R 2 each independently represents a hydrocarbon group which may have a substituent.

[0026] R 2 The number of carbon atoms in the hydrocarbon group represented by the formula is preferably 1 or more and 24 or less, more preferably 1 or more and 12 or less, even more preferably 2 or more and 8 or less, and particularly preferably 3 or more and 6 or less.

[0027] R 2 Examples of the unsubstituted hydrocarbon group represented by the formula (I) include alkylene groups such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, and octamethylene; arylene groups such as phenylene and biphenylene; and o-xylylene. alkylenearylenealkylene groups such as an arylene group, an m-xylylene group, and a p-xylylene group; and the like.

[0028] The substituents that the hydrocarbon group may have include R 1 Examples of the substituent that the hydrocarbon group represented by the following formula may have include those exemplified above.

[0029] The hydrocarbon group preferably has no substituent. When the hydrocarbon group has a substituent, the position of the substituent is not particularly limited. When the hydrocarbon group has a substituent, the number of substituents is not particularly limited, but is preferably 1 to 12, more preferably 1 to 8, and even more preferably 2 to 4 per hydrocarbon group.

[0030] R 2From the viewpoint of the reaction efficiency with carbon dioxide, the hydrocarbon group represented by the following formula (I) which may have a substituent is preferably an unsubstituted alkylene group, more preferably a methylene group, an ethylene group, or a trimethylene group, and even more preferably a trimethylene group.

[0031] (n) n is an integer of 1 or more and 3 or less, and is preferably 2 or 3, more preferably 3, from the viewpoint of catalyst turnover number and availability.

[0032] Specific examples of the alkoxysilane represented by formula (A) include the following compounds.

[0033] [ka]

[0034] The alkoxysilane represented by formula (A) may be a commercially available product or may be synthesized. The alkoxysilane represented by formula (A) can be synthesized by a known organic synthesis reaction or a reaction similar thereto. For example, as shown in the examples described below, (R 1 O) n (R 1 ) 3-n Si-R 2 Isocyanate (R 1 , R 2 , and n are R in formula (A), respectively. 1 , R 2 The alkoxysilane represented by formula (A) can be synthesized by trimerization of the above-mentioned alkylsilane (A).

[0035] Carbon dioxide In the reaction step of this embodiment, carbon dioxide (gas) is used as the carbonyl source. Carbon dioxide may be prepared as an industrial gas, or may be separated and recovered from exhaust gases from factories, power plants, etc. Carbon dioxide may be used alone or in combination with gases other than carbon dioxide within a range that does not significantly impair the effects of the present disclosure. Although carbon dioxide may be used in the form of a mixed gas, from the viewpoint of improving reactivity, it is preferable to use carbon dioxide alone (hereinafter, carbon dioxide and the mixed gas may be collectively referred to as a "carbon dioxide-containing gas"). Examples of gases other than carbon dioxide include inert gases such as nitrogen and argon.

[0036] The method for introducing the carbon dioxide-containing gas into the reaction system is not particularly limited, and may be a method of replacing the atmosphere in the reactor with the carbon dioxide-containing gas, or a method of supplying the carbon dioxide-containing gas to the reaction system by bubbling, but a method of replacing the atmosphere in the reactor with the carbon dioxide-containing gas is preferred.

[0037] When introducing a carbon dioxide-containing gas into the reaction system by replacing the atmosphere in the reactor with a carbon dioxide-containing gas, the pressure of carbon dioxide during the reaction (when a mixed gas is used, the partial pressure of carbon dioxide) is preferably 1.0 MPa or more and 20.0 MPa or less, more preferably 2.0 MPa or more and 15.0 MPa or less. In the above case, the initial pressure of carbon dioxide in the reactor (when a mixed gas is used, the initial partial pressure of carbon dioxide) is preferably 0.1 MPa or more and 20.0 MPa or less, more preferably 1.0 MPa or more and 15.0 MPa or less, even more preferably 1.0 MPa or more and 10.0 MPa or less, even more preferably 1.0 MPa or more and 5.0 MPa or less, particularly preferably 1.0 MPa or more and 3.0 MPa or less.

[0038] According to the production method of this embodiment, by using the compound represented by formula (A) as the alkoxysilane, the reaction proceeds efficiently and a carbonate diester can be obtained in high yield even when the initial pressure of carbon dioxide in the reactor and the reaction temperature are low. For example, in the examples described later, even when the initial pressure of carbon dioxide is 3.0 MPa or less, the compound represented by formula (A) (R1 = ethyl group; R 2 = trimethylene group; n = 3), the carbonic acid diester was obtained in a yield more than double that obtained when tetraethoxysilane was used as the alkoxysilane.

[0039] The above pressures refer to absolute pressures. The "initial pressure of carbon dioxide" refers to the pressure (25°C) immediately after the carbon dioxide-containing gas is introduced into the reactor, i.e., at the start of the reaction.

[0040] 1-3. Catalyst In the reaction step, from the viewpoint of shortening the reaction time and improving the yield, the reaction of alkoxysilane with carbon dioxide is preferably carried out in the presence of a metal catalyst, preferably a metal catalyst containing one or more metals selected from the group consisting of metals in Group 4 of the periodic table and metals in Group 14 of the periodic table. The catalyst may be used alone, or two or more may be used in any combination and ratio.

[0041] In this embodiment, the metal catalyst is preferably a metal alkoxide, more preferably one or more selected from the group consisting of Group 4 metal alkoxides and Group 14 metal alkoxides of the periodic table, even more preferably one or more selected from the group consisting of titanium alkoxides, zirconium alkoxides, hafnium alkoxides, and tin alkoxides, even more preferably one or more selected from the group consisting of zirconium alkoxides, tin alkoxides, and titanium alkoxides, and particularly preferably one or more selected from the group consisting of zirconium alkoxides and tin alkoxides.

[0042] More specifically, preferred examples of metal alkoxides include tetravalent metal alkoxides represented by formula (D). (R 3 ) 4-r M(OR 3 ) r (D)

[0043] (R 3 ) In formula (D), R 3 each independently represents a hydrocarbon group which may have a substituent.

[0044] R 3 The number of carbon atoms in the hydrocarbon group represented by the formula is preferably 1 or more and 30 or less, more preferably 1 or more and 24 or less, even more preferably 1 or more and 12 or less, still more preferably 1 or more and 8 or less, and particularly preferably 2 or more and 4 or less.

[0045] R 3 As the unsubstituted hydrocarbon group represented by R 1 The groups exemplified as the unsubstituted hydrocarbon group represented by the following formula are included, and an alkyl group is preferred.

[0046] Examples of substituents that the hydrocarbon group may have include a deuterium atom; halogeno groups such as a fluoro group, a chloro group, a bromo group, and an iodo group; alkyl groups having from 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group; cycloalkyl groups having from 3 to 6 carbon atoms, such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group; aryl groups having from 6 to 10 carbon atoms, such as a phenyl group, a 1-naphthyl group, and a 2-naphthyl group; oxygen-containing heterocyclic groups such as a furanyl group; sulfur-containing heterocyclic groups such as a thienyl group; nitrogen-containing heterocyclic groups such as a pyrrolyl group and a pyridyl group; a cyano group; a nitro group, an isocyanate group, an amino group; and an amide group.

[0047] The hydrocarbon group preferably has no substituent. When the hydrocarbon group has a substituent, the position of the substituent is not particularly limited. When the hydrocarbon group has a substituent, the number of substituents is not particularly limited, but is preferably 1 to 12, more preferably 1 to 8, and even more preferably 2 to 4 per hydrocarbon group.

[0048] R 3From the viewpoint of reaction efficiency with carbon dioxide, the hydrocarbon group represented by the formula (I) which may have a substituent is preferably an unsubstituted alkyl group, more preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, or a tert-butyl group, still more preferably an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, or a tert-butyl group, and even more preferably an ethyl group or an n-butyl group. 3 From the viewpoint of producing a single carbonate diester, R in formula (A) 1 It is preferable that the hydrocarbon group is the same as that of the group.

[0049] (M) M represents a metal atom. The metal atom represented by M is preferably a metal of Group 4 or Group 14 of the periodic table, more preferably titanium, zirconium, hafnium, or tin, even more preferably zirconium, tin, or titanium, and even more preferably zirconium or tin.

[0050] (r) r is an integer of 2 or more and 4 or less, and is preferably 2 or 4, more preferably 4, from the viewpoints of catalytic activity and availability.

[0051] Specific examples of the metal alkoxide represented by formula (D) include the following compounds.

[0052] Titanium alkoxides include tetramethoxytitanium, tetraethoxytitanium, tetra Allyloxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetraisobutoxytitanium, tetra-sec-butoxytitanium, tetra-t-butoxytitanium, tetra-n-pentyloxytitanium, tetracyclopentyloxytitanium, tetrahexyloxytitanium, tetracyclohexyloxytitanium, tetrabenzyloxytitanium, tetraoctyloxytitanium, tetrakis(2-ethylhexyloxy)titanium, tetradecyloxytitanium, tetradodecyloxytitanium, tetrastearyloxytitanium, tetrakis(8-hydroxyoctyloxy)titanium, diisopropoxybis(2-ethyl-1,3-hexanediolato)titanium, bis(

[0033] Examples of titanium compounds include tetrakis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanediolato)titanium, tetrakis(2-chloroethoxy)titanium, tetrakis(2-bromoethoxy)titanium, tetrakis(2-methoxyethoxy)titanium, tetrakis(2-ethoxyethoxy)titanium, butoxytrimethoxytitanium, dibutoxydimethoxytitanium, butoxytriethoxytitanium, dibutoxydiethoxytitanium, butoxytriisopropoxytitanium, dibutoxydiisopropoxytitanium, tetraphenoxytitanium, tetrakis(o-chlorophenoxy)titanium, tetrakis(m-nitrophenoxy)titanium, tetrakis(p-methylphenoxy)titanium, and tetrakis(trimethylsilyloxy)titanium.

[0053] Zirconium alkoxides include tetramethoxyzirconium, tetraethoxyzirconium, tetraallyloxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetraisobutoxyzirconium, tetra-sec-butoxyzirconium, tetra-t-butoxyzirconium, tetra-n-pentyloxyzirconium, tetracyclopentyloxyzirconium, tetrahexyloxyzirconium, tetracyclohexyloxyzirconium, tetrabenzyloxyzirconium, tetraoctyloxyzirconium, tetrakis(2-ethylhexyloxy)zirconium, tetradecyloxyzirconium, tetradodecyloxyzirconium, tetrastearyloxyzirconium, and tetrakis(8-hydroxyoctyloxy)zirconium. , diisopropoxybis(2-ethyl-1,3-hexanediolato)zirconium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanediolato)zirconium, tetrakis(2-chloroethoxy)zirconium, tetrakis(2-bromoethoxy)zirconium, tetrakis(2-methoxyethoxy)zirconium, tetrakis(2-ethoxyethoxy)zirconium, butoxytrimethoxyzirconium, dibutoxydimethoxyzirconium, butoxytriethoxyzirconium, dibutoxydiethoxyzirconium, butoxytriisopropoxyzirconium, dibutoxydiisopropoxyzirconium, tetraphenoxyzirconium, tetrakis(o-chlorophenoxy)zirconium, tetrakis(m-nitrophenoxy)zirconium, and tetrakis(p-methylphenoxy)zirconium.

[0054] Examples of hafnium alkoxides include tetramethoxyhafnium, tetraethoxyhafnium, tetraallyloxyhafnium, tetra-n-propoxyhafnium, tetraisopropoxyhafnium, tetra-n-butoxyhafnium, tetraisobutoxyhafnium, tetra-sec-butoxyhafnium, tetra-t-butoxyhafnium, tetra-n-pentyloxyhafnium, tetracyclopentyloxyhafnium, tetrahexyloxyhafnium, tetracyclohexyloxyhafnium, and tetrabenzyloxyhafnium. hafnium, tetraoctyloxyhafnium, tetrakis(2-ethylhexyloxy)hafnium, tetradecyloxyhafnium, tetradodecyloxyhafnium, tetrastearyloxyhafnium, tetrakis(8-hydroxyoctyloxy)hafnium, diisopropoxybis(2-ethyl-1,3-hexanediolato)hafnium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanediolato)hafnium, tetrakis(2-chloroethoxy)hafnium, tetrakis(2-bromoethoxy)hafnium hafnium, tetrakis(2-methoxyethoxy)hafnium, tetrakis(2-ethoxyethoxy)hafnium, butoxytrimethoxyhafnium, dibutoxydimethoxyhafnium, butoxytriethoxyhafnium, dibutoxydiethoxyhafnium, butoxytriisopropoxyhafnium, dibutoxydiisopropoxyhafnium, tetraphenoxyhafnium, tetrakis(o-chlorophenoxy)hafnium, tetrakis(m-nitrophenoxy)hafnium, and tetrakis(p-methylphenoxy)hafnium.

[0055] Examples of tin alkoxides include dibutyldimethoxytin, dibutyldiethoxytin, and dibutyldipropoxytin.

[0056] Examples of titanium alkoxides include tetramethoxytitanium, tetraethoxytitanium, tetraallyloxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetraisobutoxytitanium, tetra-sec-butoxytitanium, tetra-t-butoxytitanium, tetra-n-pentyloxytitanium, tetracyclopentyloxytitanium, tetrahexyloxytitanium, tetracyclohexyloxytitanium, tetrabenzyloxytitanium, tetraoctyloxytitanium, tetrakis(2-ethylhexyloxy)titanium, tetradecyloxytitanium, tetradodecyloxytitanium, tetrastearyloxytitanium, tetrakis(8-hydroxyoctyloxy)titanium, and diisopropoxybis(2-ethyl-1 ,3-hexanediolato)titanium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanediolato)titanium, tetrakis(2-chloroethoxy)titanium, tetrakis(2-bromoethoxy)titanium, tetrakis(2-methoxyethoxy)titanium, tetrakis(2-ethoxyethoxy)titanium, butoxytrimethoxytitanium, dibutoxydimethoxytitanium, butoxytriethoxytitanium, dibutoxydiethoxytitanium, butoxytriisopropoxytitanium, dibutoxydiisopropoxytitanium, tetraphenoxytitanium, tetrakis(o-chlorophenoxy)titanium, tetrakis(m-nitrophenoxy)titanium, tetrakis(p-methylphenoxy)titanium, and tetrakis(trimethylsilyloxy)titanium.

[0057] In this embodiment, a metal alkoxide may be supplied to the reaction system, or a metal alkoxide may be generated in the reaction system and used as a catalyst. A method for generating a metal alkoxide in the reaction system includes, for example, reacting dibutyltin oxide (BuSnO) with tetraethoxysilane to generate dibutyldiethoxytin (BuSn(OEt)). Furthermore, a tetravalent metal alkoxide can also be generated using a metal alkoxide other than a tetravalent metal alkoxide. Examples of metal alkoxides other than a tetravalent metal alkoxide include sodium methoxide and sodium tert-butoxide. Specific examples of methods for generating tetravalent metal alkoxides using metal alkoxides other than tetravalent metal alkoxides include a method of reacting zirconium tetrachloride (ZrCl4) with sodium ethoxide to generate tetraethoxyzirconium; a method of reacting zirconocene dichloride (Cp2ZrCl2) with sodium ethoxide to generate zirconocene diethoxide; a method of reacting dibutyldichlorotin (Bu2SnCl2) with sodium ethoxide to generate dibutyldiethoxytin; and a method of reacting hafnocenedichloride (Cp2HfCl2) with sodium ethoxide to generate hafnocenediethoxide.

[0058] When metal alkoxide is used as a catalyst, the reaction in the reaction step is thought to proceed according to the following mechanism. The metal alkoxide catalyst reacts with carbon dioxide to generate a compound [MO-(C=O)-OR] in which carbon dioxide is inserted into the bond between the metal and the alkoxy group, activating the carbon dioxide. The [O-(C=O)-OR] part of this molecule is eliminated along with another alkoxy group on the metal, producing the desired product, diene carbonate. After this desorption, the alkoxysilane donates an alkoxy group to the catalyst molecule, regenerating the catalytically active metal alkoxide and completing the catalytic cycle. This catalytic action enables the highly efficient production of carbonic acid diesters by the reaction of carbon dioxide and alkoxysilane.

[0059] The amount (charge amount) of the catalyst such as a metal alkoxide used is not particularly limited, but is preferably 1.0 mol% to 60.0 mol%, more preferably 5.0 mol% to 50.0 mol%, even more preferably 10.0 mol% to 40.0 mol%, still more preferably 15.0 mol% to 30.0 mol%, and particularly preferably 20.0 mol% to 25.0 mol% relative to the alkoxysilane (the amount of catalyst when the charge amount of the alkoxysilane is 100.0 mol%). In the present disclosure, when two or more catalysts are used, the "amount of catalyst used" refers to the total amount of each catalyst used.

[0060] 1-5. Carbonate diester The carbonate diester obtained by the production method according to this embodiment is a compound in which an alkoxy group derived from an alkoxysilane and / or a metal catalyst is bonded to a carbonyl group (—CO—), and is preferably a compound represented by formula (B). In the present disclosure, the term “Y group derived from X” refers to the Y group itself that X has, or a group obtained by decomposing or modifying the Y group that X has during the reaction, and is preferably the Y group itself that X has.

[0061] [ka]

[0062] (R 4 ) OR in formula (B) 4 is an alkoxy group derived from an alkoxysilane, or when a metal alkoxide is used as a catalyst, is either an alkoxy group derived from a metal alkoxide or an alkoxy group derived from an alkoxysilane. 4 are each independently a hydrocarbon group which may have a substituent, and preferably R 1 or R 3 is synonymous with.

[0063] In formula (B), two R 4may be the same or different from each other, but are preferably the same.

[0064] Specific examples of the carbonate diester represented by formula (B) include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0065] 1-6. By-products In the reaction step, the alkoxysilane supplies an alkoxy group to carbon dioxide, or to carbon dioxide and a metal catalyst. The alkoxysilane preferably supplies the alkoxy group and reacts with other alkoxysilanes present in the reaction system, and the catalytic cycle is repeated to produce an alkoxysilane polymer. Such an alkoxysilane polymer has a structural unit represented by formula (C).

[0066] [ka]

[0067] [ka]

[0068] In formula (C), R 2 is R in formula (A). 2 is synonymous with. In formula (C), Y's each independently represent a group represented by formulas (c1) to (c3). Of the three Y's, it is preferred that one or more are a group represented by formula (c1), and it is more preferred that all three are groups represented by formula (c1). In formulas (c1) to (c3), R 1 is R in formula (A). 1 is synonymous with. In the formulas (c1) to (c3), p is an integer of 0 or more and 2 or less, preferably 1 or 2, and more preferably 2. In the formulas (c1) to (c3), q is 0 or 1, and is preferably 1. In the formulas (c1) to (c3), the wavy lines represent R 2* indicates the bonding position to another structural unit.

[0069] The weight average molecular weight (Mw) of the polymer having a structural unit represented by formula (C) is not particularly limited, but is 400 or more and 100,000 or less, and preferably 800 or more and 10,000 or less.

[0070] The number average molecular weight (Mn) of the polymer having a structural unit represented by formula (C) is not particularly limited, but is 400 or more and 100,000 or less, and preferably 800 or more and 9,000 or less.

[0071] Specific examples of the constitutional unit represented by formula (C) include the following.

[0072] [ka]

[0073] Because polymers having structural units represented by formula (C) have low solubility, they tend to precipitate during the reaction or post-treatment, and can be easily removed by simple procedures such as filtration or distillation. Therefore, in the production method according to this embodiment, the progress of the reaction can be easily monitored, and the carbonate diester can be easily isolated. Furthermore, in the production method according to this embodiment, the precipitation of the polymer represented by formula (C) during the reaction suppresses the progress of the reverse reaction, which is thought to enable a reaction rate exceeding equilibrium to produce the carbonate diester with high yield. In fact, in the examples described below, it has been shown that when an alkoxysilane represented by formula (A) is used as the alkoxysilane, a carbonate diester can be obtained in higher yield than when a tetraalkoxysilane is used as the alkoxysilane under the same reaction conditions (see Table 1 and Figure 1).

[0074] 1-7.Reaction solvent The reaction may be carried out in a reaction solvent or without a solvent. When the reaction is carried out in a reaction solvent, the amount of carbon dioxide dissolved in the reaction solution increases, the concentration of carbon dioxide in the reaction system increases, and the reaction proceeds more easily, which is thought to result in an improved yield of the carbonate diester. On the other hand, when the reaction is carried out without a solvent, the alkoxysilane and the catalyst come into contact with carbon dioxide more frequently, which is thought to improve the reaction rate and shorten the reaction time, or to enable the reaction at a lower reaction temperature.

[0075] In the present disclosure, "solvent-free" means that no liquid other than the reaction substrate, catalyst, product, and compounds derived therefrom is used.

[0076] When the reaction is carried out in a reaction solvent, the reaction solvent may be used alone or in any combination and ratio of two or more kinds.

[0077] The reaction solvent is not particularly limited, but examples thereof include aliphatic hydrocarbons such as n-hexane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-octadecane, bicyclohexyl, and decalin; benzene, toluene, ethylbenzene, butylbenzene, dodecylbenzene, o-xylene, m-xylene, p-xylene; Examples of suitable solvents include aromatic hydrocarbons such as p-cymene, naphthalene, and biphenyl; partially hydrogenated aromatic hydrocarbons such as cyclohexylbenzene and tetralin; aromatic heterocycles such as pyridine; aprotic polar solvents such as ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, and N-methyl-2-pyrrolidone; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, and 1,4-dioxane; nitriles such as acetonitrile, propionitrile, butyronitrile, benzonitrile, and 2-cyanopyridine; and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and isopropyl ketone.

[0078] The amount of reaction solvent used is not particularly limited, but is, for example, preferably 10% by mass or more and 200% by mass or less, more preferably 20% by mass or more and 100% by mass or less, based on the alkoxysilane.

[0079] 1-8.Reaction temperature The reaction temperature in the reaction step is not particularly limited, but is preferably 80°C or higher and 250°C or lower, more preferably 100°C or higher and 200°C or lower, even more preferably 110°C or higher and 180°C or lower, and even more preferably 120°C or higher and 160°C or lower.

[0080] 1-9.Reaction time The reaction time in the reaction step is not particularly limited and may be adjusted appropriately depending on the reaction temperature, amount of catalyst, reaction scale, etc., and is preferably from 30 minutes to 100 hours, more preferably from 1 hour to 72 hours, even more preferably from 5 hours to 48 hours, still more preferably from 10 hours to 36 hours, and particularly preferably from 15 hours to 24 hours. In the present disclosure, "reaction time" means the time during which the temperature of the reaction system is maintained at a predetermined reaction temperature after the temperature of the reaction system reaches the predetermined reaction temperature.

[0081] 1-10.Reactor The reactor is not particularly limited as long as it is made of a material that is stable against the reagents and reaction products used in the reaction, but is preferably a pressure-resistant vessel, more preferably a stainless steel autoclave.

[0082] 1-11.Operation Procedure The manufacturing method according to this embodiment can be carried out, for example, by the following procedure. First, the raw material alkoxysilane is supplied to a reactor. This operation may be carried out under an air atmosphere or an inert gas atmosphere such as nitrogen or argon, but is preferably carried out under an inert gas atmosphere. Next, the raw material carbon dioxide is charged into the reactor. If a catalyst and / or a reaction solvent is used, these may be supplied to the reactor before introducing carbon dioxide into the reactor, or they may be supplied to the reactor together with the alkoxysilane. During the reaction, the reactor may contain an inert gas such as nitrogen or argon, as long as it does not significantly impair the effects of the present disclosure. It is also preferable to carry out the reaction while stirring the reaction system. The reaction system can be stirred using a stirring means such as a stirring blade or a magnetic stirrer. The stirring speed is not particularly limited, but is preferably 100 rpm or more and 1,000 rpm or less, more preferably 200 rpm or more and 500 rpm or less. After the reaction, the reaction system is cooled, the remaining gas is discharged from the reactor, and the reaction product is recovered.

[0083] 2.Optional process The production method according to this embodiment may include any step other than the reaction step, such as a purification step for increasing the purity of the carbonate diester. The purification method for carbonic acid diester in the purification process includes filtration, adsorption, column chromatography, etc. Purification methods commonly used in the field of organic synthesis, such as filtration and distillation, can be employed. For example, the reaction mixture can be purified by gel permeation chromatography. [Example]

[0084] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure. In the examples, "room temperature" refers to a temperature condition where no intentional heating or cooling is performed, and more specifically refers to a temperature range of 15°C or higher and 35°C or lower.

[0085] [Measuring equipment] Nuclear magnetic resonance (NMR) device: Bruker "AVANCE 400" Gas chromatograph (GC): Shimadzu Corporation "GC-2014" Matrix-assisted laser desorption / ionization time-of-flight mass spectrometer (MALDI-TOFMS): Bruker "Autoflex Speed"

[0086] [Synthesis Example 1] [ka]

[0087] 80.3 g (324.5 mmol) of 3-(triethoxysilyl)propyl isocyanate was placed in a 200 mL autoclave vessel and sealed, and the atmosphere inside the autoclave vessel was replaced with nitrogen gas. The reaction solution was reacted at 200°C for 96 hours while stirring, to obtain alkoxysilane 1 (yield 100%). 1 The 1 H NMR spectrum data is shown below.

[0088] 1 H NMR (400 MHz, C6D6): δ 3.68-3.78 (m, 6H+18H), 1.90-1.78 (m, 6H), 1.16-1.07 (t,J = 14 Hz, 27H), 0.65-0.55 (m, 6H). 13 C{ 1 H} NMR (100 MHz, C6D6): δ 148.6, 58.1, 45.0, 21.5, 18.1, 7.7 ppm. 29 Si NMR (79.5 MHz, C6D6): δ -46.7

[0089] Example 1 [ka]

[0090] Zirconium tetraethoxide (2.0 g, 7.4 mmol) and alkoxysilane 1 (26.0 g, 35 mmol, 105 mmol as silicon units) obtained in Synthesis Example 1 were added to an autoclave. While stirring the mixture, carbon dioxide (initial pressure: 5.0 MPa) was charged into the autoclave. The autoclave was placed in a thermal synthesis apparatus preheated to 120°C and heated for 15 hours while stirring at 300 rpm. After the reaction was completed, the autoclave was thoroughly cooled to room temperature, and the residual carbon dioxide was vented from the autoclave. A pale yellow solid precipitated in the resulting reaction mixture. The reaction mixture was distilled under reduced pressure to isolate diethyl carbonate 2. The reaction results are shown in Table 1, Figures 1 and 2.

[0091] The residue after isolating diethyl carbonate 2 was recovered and analyzed by MALDI-TOFMS. The mass spectrogram obtained is shown in Figure 3. In addition to the mass peak of the raw material alkoxysilane 1, a mass peak corresponding to polymer 3 (n ≥ 2) was observed in the mass spectrogram. Polymer 3 is a polymer formed by polymerizing two or more alkoxysilanes 1, and contains a structural unit represented by formula (C) (Y = group represented by formula (c1); p = 2; R 1 = ethyl group) and a polymer with triethoxysilyl terminals. From the above results, it is clear that the pale yellow solid observed in the reaction mixture is a polymer of alkoxysilane 1, which precipitated in the reaction system due to its low solubility.

[0092] Example 2 Except for changing the initial pressure of carbon dioxide to 4.0 MPa, the reaction was carried out under the same conditions as in Example 1. The reaction results are shown in Table 1 and FIG.

[0093] Example 3 Except for changing the initial pressure of carbon dioxide to 3.0 MPa, the reaction was carried out under the same conditions as in Example 1. The reaction results are shown in Table 1 and FIG.

[0094] Example 4 Except for changing the initial pressure of carbon dioxide to 2.0 MPa, the reaction was carried out under the same conditions as in Example 1. The reaction results are shown in Table 1 and FIG.

[0095] Example 5 Except for changing the initial pressure of carbon dioxide to 1.0 MPa, the reaction was carried out under the same conditions as in Example 1. The reaction results are shown in Table 1 and FIG.

[0096] Example 6 The reaction was carried out under the same conditions as in Example 1, except that the reaction temperature was changed to 180° C. The reaction results are shown in Table 1 and FIG.

[0097] Example 7 The reaction was carried out under the same conditions as in Example 1, except that the reaction temperature was changed to 160° C. The reaction results are shown in Table 1 and FIG.

[0098] Example 8 The reaction was carried out under the same conditions as in Example 1, except that the reaction temperature was changed to 140° C. The reaction results are shown in Table 1 and FIG.

[0099] Example 9 The reaction was carried out under the same conditions as in Example 1, except that the reaction temperature was changed to 110° C. The reaction results are shown in Table 1.

[0100] Example 10 The reaction was carried out under the same conditions as in Example 1, except that the reaction temperature was changed to 100° C. The reaction results are shown in Table 1.

[0101] Example 11 Except for changing zirconium tetraethoxide to dibutyltin oxide (3.8 g, 15.3 mmol), the reaction was carried out under the same conditions as in Example 1. The reaction results are shown in Table 1.

[0102] Example 12 The reaction was carried out under the same conditions as in Example 1, except that zirconium tetraethoxide was changed to butyltin oxide (3.8 g, 15.3 mmol) and the reaction time was changed to 67 hours. The reaction results are shown in Table 1.

[0103] Comparative Example 1 [ka]

[0104] The reaction was carried out under the same conditions as in Example 1, except that alkoxysilane 1 was replaced with tetraethoxysilane (TEOS) (21.8 g, 105 mmol). The yield of diethyl carbonate was determined by GC measurement using 1,3,5-trimethylbenzene as the standard substance. The reaction results are shown in Table 1, Figure 1, and Figure 2.

[0105] Comparative Example 2 The reaction was carried out under the same conditions as in Example 2, except that alkoxysilane 1 was replaced with tetraethoxysilane (TEOS) (21.8 g, 105 mmol). The yield of diethyl carbonate was determined by GC measurement using 1,3,5-trimethylbenzene as the standard substance. The reaction results are shown in Table 1 and Figure 1.

[0106] Comparative Example 3 The reaction was carried out under the same conditions as in Example 3, except that alkoxysilane 1 was replaced with tetraethoxysilane (TEOS) (21.8 g, 105 mmol). The yield of diethyl carbonate was determined by GC measurement using 1,3,5-trimethylbenzene as the standard substance. The reaction results are shown in Table 1 and Figure 1.

[0107] Comparative Example 4 The reaction was carried out under the same conditions as in Example 4, except that alkoxysilane 1 was replaced with tetraethoxysilane (TEOS) (21.8 g, 105 mmol). The yield of diethyl carbonate was determined by GC measurement using 1,3,5-trimethylbenzene as the standard substance. The reaction results are shown in Table 1 and Figure 1.

[0108] Comparative Example 5 The reaction was carried out under the same conditions as in Example 5, except that alkoxysilane 1 was replaced with tetraethoxysilane (TEOS) (21.8 g, 105 mmol). The yield of diethyl carbonate was determined by GC measurement using 1,3,5-trimethylbenzene as the standard substance. The reaction results are shown in Table 1 and Figure 1.

[0109] Comparative Example 6 The reaction was carried out under the same conditions as in Comparative Example 1, except that the reaction temperature was changed to 180° C. The reaction results are shown in Table 1 and FIG.

[0110] Comparative Example 7 The reaction was carried out under the same conditions as in Comparative Example 1, except that the reaction temperature was changed to 160° C. The reaction results are shown in Table 1 and FIG.

[0111] Comparative Example 8 The reaction was carried out under the same conditions as in Comparative Example 1, except that the reaction temperature was changed to 140° C. The reaction results are shown in Table 1 and FIG.

[0112] [Table 1]

[0113] Comparing Examples 1 to 5 and Comparative Examples 1 to 5, which were identical in reaction conditions except for the type of alkoxysilane, it can be seen that Examples 1 to 5, which used an alkoxysilane represented by formula (A) as the alkoxysilane, each produced a carbonate diester in a higher yield than the Comparative Example, which used a tetraalkoxysilane as the alkoxysilane (see Table 1 and Figure 1). The difference in the yield of the carbonate diester became more pronounced as the initial carbon dioxide pressure became lower. In particular, it was confirmed that Examples 3 to 5, in which the initial carbon dioxide pressure was 3.0 MPa or less, each produced a carbonate diester in a yield more than twice that of Comparative Examples 3 to 5.

[0114] These results indicate that by using the alkoxysilane represented by formula (A) as the alkoxysilane, a polymer having a structural unit represented by formula (C) was produced as a by-product in conjunction with the formation of the carbonate diester, and this polymer precipitated, suppressing the reverse reaction and allowing the reaction to proceed beyond equilibrium. It is assumed that this is the case.

[0115] In the examples, the by-product was a polymer having a structural unit represented by formula (C), which has low solubility, and therefore the carbonate diester could be easily purified by distillation. On the other hand, in the comparative examples, a dimer of tetraethoxysilane, the raw material, was produced as a by-product. Because the tetraethoxysilane dimer is soluble, it was difficult to purify the carbonate diester to a high purity by simple procedures such as filtration and distillation. Therefore, the production method according to the present disclosure can be said to be a method with excellent workability.

[0116] Furthermore, when Examples 1, 6 to 8 and Comparative Examples 1, 6 to 8, which were identical in reaction conditions except for the reaction temperature, were compared, it was found that, under the same temperature conditions, when an alkoxysilane represented by formula (A) was used as the alkoxysilane, a higher yield of carbonate diester was obtained than in the Comparative Example, in which a tetraalkoxysilane was used as the alkoxysilane (see Table 1 and FIG. 2). It was also found that when an alkoxysilane represented by formula (A) was used as the alkoxysilane, a carbonate diester was obtained in good yield even at a low reaction temperature of about 120°C. [Industrial Applicability]

[0117] According to the present disclosure, there is provided a method for efficiently producing a carbonate diester by reacting an alkoxysilane having an isocyanurate skeleton with carbon dioxide. This production method allows the production of a carbonate diester without using phosgene, and therefore has high industrial applicability.

Claims

1. A method for producing a carbonate diester, comprising a reaction step of reacting an alkoxysilane represented by formula (A) with carbon dioxide. 【Chemistry 1】 (In the formula, R １ each independently represents a hydrocarbon group which may have a substituent; R ２ each independently represents a hydrocarbon group which may have a substituent; n is an integer of 1 or more and 3 or less; R １ Comrades, OR １ Friends or R １ and OR １ may be bonded to each other to form a ring.)

2. The method for producing a carbonic acid diester according to claim 1 , wherein the reaction step is carried out in the presence of a metal catalyst.

3. 3. The method for producing a carbonate diester according to claim 2, wherein the metal catalyst contains one or more metals selected from the group consisting of metals of Group 4 and metals of Group 14 of the periodic table.

4. The method for producing a carbonic acid diester according to claim 2 , wherein the metal catalyst is a metal alkoxide.

5. 5. The method for producing a carbonic acid diester according to claim 4, wherein the metal alkoxide is at least one selected from the group consisting of zirconium alkoxide, tin alkoxide, and titanium alkoxide.

6. The method for producing a carbonate diester according to claim 1 , wherein a polymer having a structural unit represented by formula (C) is produced in the reaction step. 【Chemistry 2】 【Transformation 3】 (In the formula, R １ and R ２ respectively represent R in formula (A). １ and R ２ Each Y independently represents a group represented by formula (c1) to (c3); p is an integer of 0 to 2; q is 0 or 1; and the wavy line represents R ２ represents the bonding position with another structural unit.)

7. The method for producing a carbonate diester according to claim 1, wherein the reaction step is carried out at a temperature of 80°C or higher and 250°C or lower.

8. 2. The method for producing a carbonate diester according to claim 1, wherein the initial pressure (25°C) of carbon dioxide in a reactor in which the reaction is carried out is 1.0 MPa or more and 15.0 MPa or less.

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