Zirconium alkoxide-supported metal oxide, method for producing zirconium alkoxide-supported metal oxide, and method for producing carbonic acid diester

Abstract

Provided is a zirconium alkoxide-supported metal oxide that contains a carrier and a zirconium alkoxide supported on the carrier, and in which the carrier is a metal oxide.

Description

Zirconium alkoxide-supported metal oxide, method for producing zirconium alkoxide-supported metal oxide, and method for producing carbonate diester

[0001] The present disclosure relates to a zirconium alkoxide-supported metal oxide, a method for producing a zirconium alkoxide-supported metal oxide, and a method for producing a carbonate diester.

[0002] Zirconium alkoxides are compounds that are used as catalysts for various organic synthesis reactions.

[0003] For example, Patent Document 1 proposes a method for producing an organic carbonate by reacting an alkoxysilane with carbon dioxide using a zirconium alkoxide as a catalyst.

[0004] Japanese Patent Application Laid-Open No. 2021-183566

[0005] In organic synthesis using zirconium alkoxide as a catalyst, the zirconium alkoxide is generally used in a dissolved state in the reaction solution and discarded without being recovered after the reaction.

[0006] In recent years, with increasing awareness of reducing environmental impact, active development of heterogeneous catalysts that can be separated and recovered after reaction has been underway. An object of the present disclosure is to provide a novel zirconium alkoxide material that can be used as a heterogeneous catalyst.

[0007] The inventors of the present disclosure have found that the above-mentioned problems can be solved by using a metal oxide or a metal oxide composite as a support and supporting a zirconium alkoxide thereon.

[0008] [1] A zirconium alkoxide-supported metal oxide comprising a carrier and a zirconium alkoxide supported on the carrier, wherein the carrier is a metal oxide. [2] The zirconium alkoxide-supported metal oxide according to [1], wherein the zirconium alkoxide is a compound represented by general formula (I). (R １ ) ４－ｐ Zr(OR １ ) ｐ (I) (R １are each independently a hydrocarbon group which may have a substituent; and p is an integer of 1 or more and 4 or less.) [3] The zirconium alkoxide-supported metal oxide according to [1] or [2], wherein the metal oxide comprises an oxide of one or more metals selected from the group consisting of rare earth metals, metals of Group 4 of the periodic table, metals of Group 13 of the periodic table, and metals of Group 14 of the periodic table. [4] The zirconium alkoxide-supported metal oxide according to any one of [1] to [3], wherein the support is a core-shell type particle. [5] The zirconium alkoxide-supported metal oxide according to [4], wherein the core of the core-shell type particle is silica and the shell of the core-shell type particle is ceria. [6] The zirconium alkoxide-supported metal oxide according to [4] or [5], wherein the content of the core relative to the total amount of the core-shell type particles is 10% by weight or more and 99% by weight or less, and the content of the shell relative to the total amount of the core-shell type particles is 1% by weight or more and 90% by weight or less. [7] The zirconium alkoxide-supported metal oxide according to any one of [1] to [6], wherein the amount of the zirconium alkoxide supported is 1% by weight or more and 20% by weight or less based on the total amount of the zirconium alkoxide-supported metal oxide. [8] The zirconium alkoxide-supported metal oxide according to any one of [1] to [7], which is a catalyst used in a reaction for synthesizing a carbonate diester from an alkoxysilane and carbon dioxide. [9] A method for producing a zirconium alkoxide-supported metal oxide, comprising a supporting step of contacting a support with a solution containing zirconium alkoxide and then removing the solvent from the solution to support the zirconium alkoxide on the support, wherein the support is a metal oxide.

[10] The method for producing a zirconium alkoxide-supported metal oxide according to [9], wherein the zirconium alkoxide is a compound represented by general formula (I). (R １ ) ４－ｐ Zr(OR １ ) ｐ (I) (R １are each independently a hydrocarbon group which may have a substituent; and p is an integer of 1 or more and 4 or less.)

[11] A method for producing a zirconium alkoxide-supported metal oxide according to [9] or

[10] , wherein the metal oxide comprises an oxide of one or more metals selected from the group consisting of rare earth metals, metals of Group 4 of the periodic table, metals of Group 13 of the periodic table, and metals of Group 14 of the periodic table.

[12] A method for producing a zirconium alkoxide-supported metal oxide according to any of [9] to

[11] , wherein the support is a core-shell type particle.

[13] A method for producing a zirconium alkoxide-supported metal oxide according to

[12] , wherein the core of the core-shell type particle is silica and the shell of the core-shell type particle is ceria.

[14] A method for producing a carbonate diester, comprising a reaction step of reacting an alkoxysilane with carbon dioxide in the presence of the zirconium alkoxide-supported metal oxide according to any of [1] to [8].

[15] The method for producing a carbonic acid diester according to

[14] , wherein the alkoxysilane is at least one selected from the group consisting of compounds represented by general formula (A1) and compounds represented by general formula (A2). (R ａ２ ) ４－ｎ１ Si(OR ａ１ ) ｎ１ (A1) R ａ３ [Si(R ａ２ ) ３－ｎ２ (OR ａ１ ) ｎ２ ] ｍ (A2) (R ａ１ are each independently a hydrocarbon group which may have a substituent; R ａ２ are each independently a hydrocarbon group which may have a substituent; R ａ３ are each independently a hydrocarbon group which may have a substituent; n1 is an integer of 1 or more and 4 or less; n2 is an integer of 1 or more and 3 or less; m is an integer of 2 or more and 20 or less; when n1 is an integer of 2 or more and 4 or less, two OR ａ１ R ａ１ may be bonded to each other to form a ring; when n1 is an integer of 1 or more and 3 or less, OR ａ１ R in the group ａ１and R ａ２ may be bonded to each other to form a ring; when n2 is 2 or 3, two OR ａ１ R ａ１ may be bonded to each other to form a ring; when n2 is 1 or 2, OR ａ１ R in the group ａ１ and R ａ２ may be bonded to each other to form a ring.)

[0009] According to the present disclosure, it is possible to provide a novel zirconium alkoxide material that can be used as a heterogeneous catalyst.

[0010] 1 is a graph showing the evaluation results of the reusability of catalysts in Examples.

[0011] 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.

[0012] In the present disclosure, unless otherwise specified, the expressions "X or more and Y or less" and "X to Y" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. When the lower limit and upper limit of a numerical range are stated separately, the numerical range can be a combination of any lower limit and any upper limit.

[0013] In the present disclosure, the terms "content of X" and "amount of X used" mean "total content of X" and "total amount of X used," respectively, unless otherwise specified, when two or more types of X are used in combination. In the present disclosure, the term "X such as x1, x2, and x3" refers to x1, x2, and x3 as examples of X, and does not mean that X is limited to x1, x2, x3, and the like.

[0014] 1. Zirconium Alkoxide-Supported Metal Oxide The zirconium alkoxide-supported metal oxide according to the first embodiment of the present disclosure includes a support and zirconium alkoxide supported on the support, the support being a metal oxide. The zirconium alkoxide-supported metal oxide according to this embodiment is not limited in its application, but can be suitably used as a heterogeneous catalyst for organic synthesis reactions. Examples of organic synthesis reactions include, but are not limited to, reactions using zirconium alkoxide as a catalyst, such as the synthesis of a carbonate diester from an alkoxysilane and carbon dioxide, which will be described later. Furthermore, the zirconium alkoxide-supported metal oxide according to this embodiment can be easily separated, recovered, and reused after the reaction, and is therefore expected to contribute to reducing environmental impact.

[0015] 1-1. Support The zirconium alkoxide-supported metal oxide contains a metal oxide as a support. The support may be a support consisting of only one type of metal oxide, or may be a metal oxide composite containing two or more types of metal oxides. Furthermore, the metal oxide may be an oxide of one type of metal, or may be a composite oxide of two or more metals.

[0016] In the present disclosure, the term "metal" also includes metalloids, such as boron, silicon, germanium, arsenic, selenium, tin, antimony, tellurium, bismuth, polonium, and astatine.

[0017] The shape of the metal oxide is not particularly limited and may be any shape such as particles, fibers, films, plates, etc., but particles or fibers are preferred, and particles are more preferred.

[0018] When the metal oxide has a particulate shape, the average particle size of the particles is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 20 nm or more, still more preferably 50 nm or more, and is preferably 1,000 μm or less, more preferably 500 μm or less, even more preferably 100 μm or less, still more preferably 1,000 nm or less, and particularly preferably 500 nm or less. That is, suitable ranges for the average particle size of the metal oxide particles include, for example, 5 nm or more and 1,000 μm or less, 10 nm or more and 500 μm or less, 10 nm or more and 100 μm or less, 20 nm or more and 1,000 nm or less, and 50 nm or more and 500 nm or less.

[0019] In the present disclosure, the "average particle size" is the 50% particle size D50 (median size) in the volume-based cumulative particle size distribution measured with a laser diffraction particle size analyzer.

[0020] The specific surface area of ​​the metal oxide is not particularly limited, but is preferably 0.4 m ２ / g or more, more preferably 5m ２ / g or more, more preferably 50m ２ / g or more, and even more preferably 100m ２ / g or more, particularly preferably 200m ２ / g or more, and preferably 1,000m ２ / g or less, more preferably 800m ２ / g or less, more preferably 600m ２ / g or less, and even more preferably 500m ２ / g or less, particularly preferably 400m ２ That is, the preferred range of the specific surface area of ​​the metal oxide is, for example, 0.4 m ２ / g or more 1,000m ２ / g or less, 5m ２ / g or more 800m ２ / g or less, 50m ２ / g or more 600m ２ / g or less, 100m ２ / g or more 500m ２ / g or less, and 200m ２ / g or more 400m ２ / g or less.

[0021] In the present disclosure, the specific surface area of ​​a metal oxide is measured by a nitrogen adsorption method using a specific surface area and pore size distribution measuring device (for example, "BELSROP MINI X" manufactured by Microtrac-Bell Corporation).

[0022] The metal oxide is not particularly limited, but in order to use the zirconium alkoxide-supported metal oxide as a heterogeneous catalyst, it is preferable that the metal oxide is insoluble or poorly soluble in organic solvents and aqueous solvents. Such a metal oxide is preferably an oxide of one or more metals selected from the group consisting of rare earth metals, Group 4 metals of the periodic table, Group 13 metals, and Group 14 metals of the periodic table, and more preferably an oxide of one or more metals selected from the group consisting of rare earth metals and Group 14 metals of the periodic table. When the metal oxide is a metal oxide composite, it is preferable that the metal oxide composite is a composite of two or more of the above metal oxides.

[0023] Rare earth metals include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, preferably cerium.

[0024] Group 4 metals of the periodic table include titanium, zirconium, hafnium, and rutherfordium, preferably titanium or zirconium.

[0025] The metals of Group 13 of the periodic table include aluminum, gallium, indium, thallium, and nihonium, with aluminum being preferred.

[0026] The metals of Group 14 of the periodic table include silicon, germanium, tin, lead, and flerovium, with silicon being preferred.

[0027] Specific examples of metal oxides include magnesium oxide (MgO), calcium oxide (CaO), and vanadium oxide (V ２ O ５ ), niobium oxide (Nb２ O ５ ), tantalum oxide (Ta ２ O ５ ), iron (II) oxide (FeO), iron (III) oxide (Fe ２ O ３ ), copper(I) oxide (Cu ２ O), copper (II) oxide (CuO), zinc oxide (ZnO), ceria (CeO ２ ), zirconia (ZrO ２ ), titania (TiO ２ ), alumina (Al ２ O ３ ), and silica (SiO ２ ), and ceria (CeO ２ ), zirconia (ZrO ２ ), titania (TiO ２ ), alumina (Al ２ O ３ ), and silica (SiO ２ ) are particularly preferred.

[0028] When the metal oxide is a metal oxide composite, the metal oxide composite may be a composite in which two or more metal oxides are mixed uniformly or non-uniformly, or may be a multilayer structure in which layers of each metal oxide are stacked, but a multilayer structure is preferred. In particular, when the support has a particulate shape, the support is preferably a core-shell type particle among multilayer structures. Core-shell type particles are particles having a core composed of one metal oxide and a shell composed of another metal oxide.

[0029] The combination of the metal oxide constituting the core of the core-shell type particle and the metal oxide constituting the shell is not particularly limited, and for example, the above-mentioned metal oxides can be arbitrarily combined. That is, the core-shell type particle can be made of magnesium oxide (MgO), calcium oxide (CaO), vanadium oxide (V), ２ O ５ ), niobium oxide (Nb ２ O ５ ), tantalum oxide (Ta ２ O ５ ), iron (II) oxide (FeO), iron (III) oxide (Fe ２ O３ ), copper(I) oxide (Cu ２ O), copper (II) oxide (CuO), zinc oxide (ZnO), ceria (CeO ２ ), zirconia (ZrO ２ ), titania (TiO ２ ), alumina (Al ２ O ３ ), and silica (SiO ２ ), and ceria (CeO ２ ), zirconia (ZrO ２ ), titania (TiO ２ ), alumina (Al ２ O ３ ), or silica (SiO ２ ) are particularly preferred.

[0030] Suitable core-shell particles include silica (SiO ２ ) or titania (TiO ２ ) and a core made of ceria (CeO ２ ), zirconia (ZrO ２ ), titania (TiO ２ ), alumina (Al ２ O ３ ), or silica (SiO ２ ) and a shell made of silica (SiO ２ ) or titania (TiO ２ ) and a core made of ceria (CeO ２ ), and a core made of silica and a shell made of ceria (CeO ２ It is more preferable that the zirconium alkoxide-supported metal oxide using such core-shell type particles as a carrier is expected to exhibit high catalytic activity in the carbonic acid diester synthesis reaction described below.

[0031] The content of the core relative to the total weight of the core-shell type particles is preferably 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more, still more preferably 20% by weight or more, and is preferably 99% by weight or less, more preferably 95% by weight or less, even more preferably 90% by weight or less, still more preferably 80% by weight or less, particularly preferably 70% by weight or less, and most preferably 60% by weight or less. That is, suitable ranges of the content of the core relative to the total weight of the core-shell type particles include, for example, 5% by weight or more and 99% by weight or less, 10% by weight or more and 95% by weight or less, 10% by weight or more and 90% by weight or less, 15% by weight or more and 80% by weight or less, 15% by weight or more and 70% by weight or less, and 20% by weight or more and 60% by weight or less.

[0032] The content of the shell relative to the total amount of the core-shell type particles is preferably 1% by weight or more, more preferably 5% by weight or more, even more preferably 10% by weight or more, still more preferably 20% by weight, particularly preferably 30% by weight or more, and most preferably 40% by weight or more, and is preferably 95% by weight or less, more preferably 90% by weight or less, even more preferably 85% by weight or less, and still more preferably 80% by weight or less. That is, suitable ranges of the content of the shell relative to the total amount of the core-shell type particles include, for example, 1% by weight or more to 95% by weight or less, 5% by weight or more to 90% by weight or less, 10% by weight or more to 90% by weight or less, 20% by weight or more to 85% by weight or less, 30% by weight or more to 85% by weight or less, and 40% by weight or more to 80% by weight or less.

[0033] By setting the content ratio of the core to silica within the above range, when the zirconium alkoxide-supported metal oxide is used as a catalyst for the carbonic acid diester synthesis reaction described below, high catalytic activity can be maintained even if it is recovered and reused after the reaction. As shown in the examples described below, the maintenance of catalytic activity is high when the core content is 20% by weight or more and 60% by weight or less and the shell content is 40% by weight or more and 80% by weight relative to the total amount of the core-shell type particles, and is particularly high when the core content is 20% by weight or more and 40% by weight or less and the shell content is 60% by weight or more and 80% by weight relative to the total amount of the core-shell type particles. ２), this tendency is particularly strong in core-shell type particles in which the shell is formed of ceria.

[0034] The content ratio of the core and silica in the core-shell particles is measured by X-ray fluorescence analysis (XRF).

[0035] 1-2. Zirconium Alkoxide The zirconium alkoxide supported on the metal oxide is not particularly limited, but a preferred example is a tetravalent zirconium alkoxide represented by the general formula (I): (R １ ) ４－ｐ Zr(OR １ ) ｐ (I)

[0036] In general formula (I), R １ are each independently a hydrocarbon group which may have a substituent.

[0037] R １ The number of carbon atoms in the hydrocarbon group which may have a substituent and is represented by the formula (I) is not particularly limited, but is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 12 or less, and even more preferably 8 or less. １ Suitable ranges for the number of carbon atoms in the hydrocarbon group represented by the formula (I) include, for example, ranges of 1 or more and 20 or less, 1 or more and 12 or less, and 2 or more and 8 or less. In the present disclosure, when the X group has a substituent, the number indicated as the number of carbon atoms in the X group or the like does not include the number of carbon atoms in the substituent.

[0038] R １Examples 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, a 2-ethylhexyl 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-icosyl group. cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and aromatic hydrocarbon 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.

[0039] R １ when the hydrocarbon group represented by the formula (I) has a substituent, examples of the substituent include a deuterium atom; an alkyl group 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; a cycloalkyl group having from 3 to 6 carbon atoms, such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group; an aromatic hydrocarbon group having from 6 to 12 carbon atoms, such as a phenyl group, a 1-naphthyl group, and a 2-naphthyl group; an oxygen-containing heterocyclic group, such as a furanyl group; a sulfur-containing heterocyclic group, such as a thienyl group; a heterocyclic group such as a nitrogen-containing heterocyclic group, such as a pyrrolyl group and a pyridyl group; a halogen atom, such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; an isocyanate group; a cyano group; an amino group; an amide group; and a nitro group.

[0040] Therefore, R １ When the hydrocarbon group represented by the formula (I) has a substituent, R １Preferred examples of the alkyl group include aralkyl groups such as benzyl, phenethyl, 1-naphthylmethyl, and 2-naphthylmethyl; cycloalkylalkyl groups such as cyclohexylmethyl; hydrocarbon groups having an oxygen-containing heterocycle such as furfuryl; hydrocarbon groups having a sulfur-containing heterocycle such as thienylmethyl; and hydrocarbon groups having a nitrogen-containing heterocycle such as pyridylmethyl.

[0041] R １ is preferably an alkyl group, more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, even more preferably a methyl group or an ethyl group, and particularly preferably an ethyl group.

[0042] In general formula (I), p is usually an integer of 1 or more and 4 or less, preferably an integer of 2 or more and 4 or less, and more preferably 4.

[0043] Specific examples of the tetravalent zirconium alkoxide represented by general formula (I) include tetramethoxyzirconium, tetraethoxyzirconium, tetraallyloxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetraisobutoxyzirconium, tetra-sec-butoxyzirconium, tetra-tert-butoxyzirconium, tetra-n-pentyloxyzirconium, tetracyclopentyloxyzirconium, tetrahexyloxyzirconium, tetracyclohexyloxyzirconium, tetrabenzyloxyzirconium, tetraoctyloxyzirconium, tetrakis(2-ethylhexyloxy)zirconium, tetradecyloxyzirconium, tetradodecyloxyzirconium, tetrastearyloxyzirconium, tetrakis(8-hydroxyoctyl bis(2-ethylhexyloxy)bis(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.Of these, the tetravalent zirconium alkoxide is preferably at least one selected from the group consisting of tetramethoxyzirconium, tetraethoxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetraisobutoxyzirconium, tetra-sec-butoxyzirconium, tetra-tert-butoxyzirconium, tetra-n-pentyloxyzirconium, tetrahexyloxyzirconium, tetraoctyloxyzirconium, tetrakis(2-ethylhexyloxy)zirconium, tetradecyloxyzirconium, tetradodecyloxyzirconium, and tetrastearyloxyzirconium, and tetramethyloxyzirconium is particularly preferred. More preferred is one or more selected from the group consisting of tetramethoxyzirconium, tetraethoxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetraisobutoxyzirconium, tetra-sec-butoxyzirconium, and tetra-tert-butoxyzirconium, even more preferred is one or more selected from the group consisting of tetramethoxyzirconium, tetraethoxyzirconium, tetra-n-propoxyzirconium, and tetra-n-butoxyzirconium, even more preferred is one or more selected from the group consisting of tetramethoxyzirconium and tetraethoxyzirconium, and particularly preferred is tetraethoxyzirconium.

[0044] The carrier may have one zirconium alkoxide supported thereon, or two or more zirconium alkoxides supported thereon. When two or more zirconium alkoxides are supported on the metal oxide, the combination and ratio of the zirconium alkoxides are not particularly limited.

[0045] The amount of zirconium alkoxide supported is not particularly limited and may be set depending on the application of the zirconium alkoxide-supported metal oxide, but is preferably 1 wt % or more, more preferably 2 wt % or more, even more preferably 3 wt % or more, still more preferably 5 wt % or more, and is preferably 20 wt % or less, more preferably 15 wt % or less, and even more preferably 10 wt % or less, relative to the total amount of zirconium alkoxide-supported metal oxide (i.e., when the total amount of zirconium alkoxide-supported metal oxide is taken as 100 wt %). That is, suitable ranges for the amount of zirconium alkoxide supported relative to the total amount of zirconium alkoxide-supported metal oxide include, for example, 1 wt % to 20 wt %, 2 wt % to 15 wt %, 3 wt % to 10 wt %, and 5 wt % to 10 wt %.

[0046] The amount of zirconium alkoxide supported is measured by X-ray fluorescence analysis (XRF).

[0047] 1-3. Method for Producing Zirconium Alkoxide-Supported Metal Oxide The method for producing the zirconium alkoxide-supported metal oxide according to this embodiment is not particularly limited, but is preferably a production method including a supporting step of bringing a solution containing zirconium alkoxide into contact with a support and then removing the solvent from the solution to cause the support to support the zirconium alkoxide.

[0048] The solvent for the zirconium alkoxide solution used in the supporting step is not particularly limited as long as it can dissolve the zirconium alkoxide and does not dissolve the metal oxide carrier. Examples of such solvents include aliphatic hydrocarbon solvents such as n-hexane, n-octane, n-decane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, o-xylene, m-xylene, and p-xylene; and alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol, and diethylene glycol. Of these, aromatic hydrocarbon solvents are preferred, and toluene is more preferred.

[0049] The concentration of the zirconium alkoxide in the zirconium alkoxide solution is not particularly limited and may be set depending on the type of zirconium alkoxide, the amount of zirconium alkoxide supported, etc., but is preferably 0.1% by weight or more, more preferably 3% by weight or more, and is preferably 50% by weight or less, more preferably 20% by weight or less. That is, suitable ranges for the concentration of the zirconium alkoxide in the zirconium alkoxide solution include, for example, ranges of 0.1% by weight or more and 50% by weight or less, and 3% by weight or more and 20% by weight or less.

[0050] In the supporting step, the method for contacting the metal oxide with the zirconium alkoxide solution is not particularly limited, and examples thereof include a method of mixing the zirconium alkoxide solution with the metal oxide. In addition, the method for removing the solvent in the supporting step is not particularly limited, and examples thereof include a method of distilling off the solvent and drying under reduced pressure.

[0051] 2. Method for Producing Carbonate Diester The second embodiment of the present disclosure is a method for producing a carbonate diester, which includes a reaction step of reacting an alkoxysilane with carbon dioxide in the presence of the zirconium alkoxide-supported metal oxide according to the first embodiment of the present disclosure. In this embodiment, the reaction of the alkoxysilane with carbon dioxide does not produce water as a by-product, and therefore the carbonate diester can be obtained without using a dehydrating agent, which is industrially useful.

[0052] The reaction process is presumed to proceed according to the following mechanism. First, when carbon dioxide reacts with zirconium alkoxide supported on a metal oxide, carbon dioxide is inserted between the bond between the zirconium and the alkoxy group, resulting in the formation of a structure represented by Zr-O-(C=O)-OR, which activates the carbon dioxide molecule. The O-(C=O)-OR moiety in this structure is eliminated together with the alkoxy group bonded to the zirconium, producing the target carbonate diester. Subsequently, the alkoxysilane donates an alkoxy group to the catalyst molecule after elimination of the carbonate diester, converting the alkoxysilane to disiloxane and regenerating catalytically active zirconium alkoxide.

[0053] The alkoxysilane used in the reaction step is not particularly limited and may be selected depending on the carbonate diester to be produced. However, it is preferably one or more alkoxysilanes selected from the group consisting of compounds represented by general formula (A1) and compounds represented by general formula (A2), and more preferably a compound represented by general formula (A1).

[0054] (R ａ２ ) ４－ｎ１ Si(OR ａ１ ) ｎ１ (A1) R ａ３ [Si(R ａ２ ) ３－ｎ２ (OR ａ１ ) ｎ２ ] ｍ (A2)

[0055] In general formula (A1), R ａ１ are each independently a hydrocarbon group which may have a substituent.

[0056] R ａ１ The number of carbon atoms in the hydrocarbon group which may have a substituent, represented by R, is not particularly limited, but is preferably 1 or more, more preferably 2 or more, and is preferably 30 or less, more preferably 24 or less, and even more preferably 12 or less. ａ１ Suitable ranges for the number of carbon atoms in the hydrocarbon group represented by the formula (I) include, for example, 1 or more and 30 or less, 1 or more and 24 or less, and 2 or more and 12 or less.

[0057] R ａ１Examples 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, a 2-ethylhexyl 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-icosyl group. cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; and aromatic hydrocarbon 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.

[0058] R ａ１ when the hydrocarbon group represented by the formula (I) has a substituent, examples of the substituent include a deuterium atom; an alkyl group 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; a cycloalkyl group having from 3 to 6 carbon atoms, such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group; an aromatic hydrocarbon group having from 6 to 12 carbon atoms, such as a phenyl group, a 1-naphthyl group, and a 2-naphthyl group; an oxygen-containing heterocyclic group, such as a furanyl group; a sulfur-containing heterocyclic group, such as a thienyl group; a heterocyclic group such as a nitrogen-containing heterocyclic group, such as a pyrrolyl group and a pyridyl group; a halogen atom, such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; an isocyanate group; a cyano group; an amino group; an amide group; and a nitro group.

[0059] Therefore, R ａ１ When the hydrocarbon group represented by the formula (I) has a substituent, R ａ１Preferred examples of the alkyl group include aralkyl groups such as benzyl, phenethyl, 1-naphthylmethyl, and 2-naphthylmethyl; cycloalkylalkyl groups such as cyclohexylmethyl; hydrocarbon groups having an oxygen-containing heterocycle such as furfuryl; hydrocarbon groups having a sulfur-containing heterocycle such as thienylmethyl; and hydrocarbon groups having a nitrogen-containing heterocycle such as pyridylmethyl.

[0060] R ａ１ From the viewpoint of reaction efficiency, is preferably an alkyl group, more preferably a methyl group or an ethyl group, and even more preferably an ethyl group.

[0061] In general formula (A1), R ａ２ each independently represents a hydrocarbon group which may have a substituent.

[0062] R ａ２ The number of carbon atoms in the hydrocarbon group which may have a substituent, represented by R, is not particularly limited, but is preferably 1 or more, more preferably 2 or more, and is preferably 30 or less, more preferably 24 or less, and even more preferably 12 or less. ａ２ Suitable ranges for the number of carbon atoms in the hydrocarbon group represented by the formula (I) include, for example, 1 or more and 30 or less, 1 or more and 24 or less, and 2 or more and 12 or less.

[0063] R ａ２ Examples of the unsubstituted hydrocarbon group represented by R ａ１ Examples of the unsubstituted hydrocarbon group include those exemplified as follows:

[0064] R ａ２ When the hydrocarbon group represented by the formula (I) has a substituent, the substituent may be R ａ１ The substituents of the hydrocarbon group represented by the formula (I) include those exemplified above, and are preferably an isocyanate group or a cyano group.

[0065] R ａ２ When the hydrocarbon group represented by the formula (I) has a substituent, R ａ２ As for R ａ１ Examples of the hydrocarbon group which may have a substituent include those exemplified as the hydrocarbon group represented by the following formula:

[0066] Rａ２ is preferably a methyl group, an ethyl group, a vinyl group, an allyl group, or a phenyl group from the viewpoints of availability and stability.

[0067] In general formula (A1), n1 is usually an integer of 1 or more and 4 or less, and from the viewpoint of reaction efficiency, it is preferably an integer of 2 or more and 4 or less, more preferably 3 or 4, and even more preferably 4.

[0068] When n1 is an integer of 2 or more and 4 or less, two OR ａ１ R ａ１ When n1 is an integer of 1 or more and 3 or less, OR and ａ１ R in the group ａ１ and R ａ２ may be bonded to each other to form a ring.

[0069] Examples of the alkoxysilane represented by general formula (A1) include monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraalkoxysilane, and tetraalkoxysilane is preferred.

[0070] Specific examples of monoalkoxysilanes include methoxytrimethylsilane, methoxytriethylsilane, methoxytripropylsilane, methoxytriisobutylsilane, methoxytrioctylsilane, methoxytrihexadecylsilane, methoxytrivinylsilane, methoxytriphenylsilane, phenylmethoxydimethylsilane, phenylmethoxydiethylsilane, ethoxytrimethylsilane, ethoxytriethylsilane, ethoxytripropylsilane, ethoxytriisobutylsilane, ethoxytrioctylsilane, ethoxytriphenylsilane, ethoxytrivinylsilane, ethoxytriallylsilane, ethoxydiethylphenylsilane, phenylethoxydipropylsilane, propoxytrimethylsilane, propoxytriethylsilane, propoxytripropylsilane, phenylpropoxydimethylsilane, phenylpropoxydiethylsilane, and phenylpropoxydipropylsilane.

[0071] Specific examples of dialkoxysilanes include dimethoxydimethylsilane, dimethoxydiethylsilane, dimethoxydipropylsilane, phenyldimethoxymethylsilane, dimethoxymethylvinylsilane, dimethoxydiphenylsilane, diethoxydimethylsilane, diethoxydiethylsilane, diethoxydipropylsilane, diethoxymethylphenylsilane, diethoxyethylphenylsilane, diethoxyphenylpropylsilane, dipropoxydimethylsilane, dipropoxydiethylsilane, dipropoxydipropylsilane, phenyldipropoxymethylsilane, phenyldipropoxyethylsilane, phenyldipropoxypropylsilane, dibutoxydimethylsilane, dibutoxydiethylsilane, and phenyldimethoxyethylsilane.

[0072] Specific examples of trialkoxysilanes include trimethoxymethylsilane, trimethoxyethylsilane, trimethoxypropylsilane, trimethoxyisobutylsilane, trimethoxyoctylsilane, trimethoxyhexadecylsilane, triethoxymethylsilane, triethoxyethylsilane, triethoxypropylsilane, triethoxyisobutylsilane, triethoxyoctylsilane, trimethoxyvinylsilane, trimethoxyphenylsilane, triethoxyphenylsilane, triethoxyvinylsilane, triethoxyallylsilane, tripropoxymethylsilane, tripropoxyethylsilane, tripropoxypropylsilane, tripropoxyphenylsilane, 2-cyanoethyltriethoxysilane, and 3-(triethoxysilyl)propyl isocyanate.

[0073] Specific examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetrakis(2-ethylhexyloxy)silane.

[0074] In general formula (A2), R ａ１ and R ａ２ respectively represent R in general formula (A1). ａ１ and R ａ２ The same applies to the preferred embodiments thereof.

[0075] In general formula (A2), R ａ３ are each independently a hydrocarbon group which may have a substituent.

[0076] R ａ３ The number of carbon atoms in the hydrocarbon group represented by the formula (I) which may have a substituent is not particularly limited, but is preferably 1 or more, more preferably 3 or more, and even more preferably 6 or more, and is preferably 100 or less, more preferably 50 or less, and even more preferably 12 or less. ａ１ Suitable ranges for the number of carbon atoms in the hydrocarbon group represented by the formula (I) include, for example, 1 or more and 100 or less, 3 or more and 50 or less, and 6 or more and 12 or less.

[0077] R ａ３ Examples of the unsubstituted hydrocarbon group represented by the formula (I) include groups in which m hydrogen atoms have been removed from alkanes such as methane, ethane, propane, butane, and hexane; groups in which m hydrogen atoms have been removed from cycloalkanes such as cyclohexane and cyclooctane; and groups in which m hydrogen atoms have been removed from aromatic hydrocarbons such as benzene, biphenyl, terphenyl, naphthalene, and anthracene.

[0078] R ａ３ When the hydrocarbon group represented by the formula (I) has a substituent, the substituent may be R ａ１ and an alkoxy group, and preferably an alkoxy group, an isocyanate group, or a cyano group.

[0079] R ａ３ One or more carbon atoms of the hydrocarbon group represented by R may be replaced by a Si atom. ａ３ When one or more carbon atoms of the hydrocarbon group represented by the formula (I) are replaced with a Si atom, the Si atom may have a substituent.

[0080] In general formula (A2), -Si(R ａ２ ) ３－ｎ２ (OR ａ１ ) ｎ２ The alkoxysilane moiety represented by R ａ３Among the carbon atoms constituting the group, they may be bonded to the same carbon atom or different carbon atoms.

[0081] In general formula (A2), n2 is usually an integer of 1 or more and 3 or less, and is preferably 2 or 3, and more preferably 3, from the viewpoint of reaction efficiency.

[0082] In general formula (A2), m is usually an integer of 2 or more and 20 or less, and in terms of ease of availability of alkoxysilanes, it is preferably an integer of 2 or more and 10 or less, more preferably an integer of 2 or more and 6 or less, and even more preferably an integer of 2 or more and 4 or less.

[0083] When n2 is 2 or 3, two OR groups bonded to the same Si atom ａ１ R ａ１ When n2 is 1 or 2, ORs bonded to the same Si atom may be bonded to each other to form a ring. ａ１ R in the group ａ１ and R ａ２ may be bonded to each other to form a ring.

[0084] When m in general formula (A2) is 2, examples of the alkoxysilane represented by general formula (A2) include alkoxysilanes represented by general formula (A-22).

[0085] When m in general formula (A2) is 3, examples of the alkoxysilane represented by general formula (A2) include alkoxysilanes represented by general formula (A-23).

[0086]

[0087] Examples of the alkoxysilane represented by general formula (A2), i.e., an alkoxysilane having a plurality of alkoxysilane moieties in the molecule, include polyalkoxysilanes in which a plurality of alkoxysilyl groups are bonded to carbon atoms constituting an aliphatic hydrocarbon group, polyalkoxysilanes in which a plurality of alkoxysilyl groups are bonded to an aromatic hydrocarbon group, polyalkoxysilanes in which carbon atoms in the hydrocarbon group are substituted with Si atoms and the Si atoms have alkoxy groups, and polyalkoxysilanes in which carbon atoms in the hydrocarbon group are substituted with Si atoms.

[0088] Specific examples of polyalkoxysilanes in which a plurality of alkoxysilyl groups are bonded to carbon atoms constituting an aliphatic hydrocarbon group include bis(triethoxysilyl)methane, 1,2-bis(trimethoxysilyl)ethane, 1,2-bis(triethoxysilyl)ethane, 1,2-bis(triphenoxysilyl)ethane, 1,3-bis(trimethoxysilyl)propane, 1,3-bis(triethoxysilyl)propane, 1,4-bis(triethoxysilyl)butane, 1,5-bis(triethoxysilyl)pentane, 1,6-bis(triethoxysilyl)hexane, and 1,8-bis(triethoxysilyl)octane, 1,1,2-tris(triethoxysilyl)ethane, and the like.

[0089] Specific examples of polyalkoxysilanes in which multiple alkoxysilyl groups are bonded to an aromatic hydrocarbon group include 1,2-bis(triethoxysilyl)benzene, 1,3-bis(triethoxysilyl)benzene, 1,4-bis(triethoxysilyl)benzene, 1,2,3-tris(triethoxysilyl)benzene, 1,2,4-tris(triethoxysilyl)benzene, 1,3,5-tris(triethoxysilyl)benzene, and 4,4'-bis(triethoxysilyl)biphenyl.

[0090] Specific examples of polyalkoxysilanes in which the carbon atoms of the hydrocarbon groups are substituted with Si atoms and the Si atoms have alkoxy groups include 1,1,1,3,3,5,5,5-octaethoxy-1,3,5-trisilapentane.

[0091] A specific example of a polyalkoxysilane in which the carbon atoms of the hydrocarbon group are substituted with Si atoms is tris(triethoxysilylethyl)methylsilane.

[0092] Of the above, from the viewpoints of availability and reactivity, the alkoxysilane is preferably a compound represented by general formula (A1), more preferably selected from tetramethoxysilane, tetraethoxysilane, diethoxydimethylsilane, ethoxytrimethylsilane, triethoxymethylsilane, triethoxyphenylsilane, triethoxyvinylsilane, triethoxyallylsilane, 2-cyanoethyltriethoxysilane, 3-(triethoxysilyl)propyl isocyanate, 1,2-bis(triethoxysilyl)ethane, and 1,6-bis(triethoxysilyl)hexane, and even more preferably selected from tetramethoxysilane and tetraethoxysilane.

[0093] The alkoxysilane may be a commercially available product or may be synthesized.

[0094] The alkoxysilanes may be used alone or in any combination of two or more in any ratio.

[0095] 2-2. Carbon dioxide In the reaction step, carbon dioxide (gas) is used as a raw material for the carbonate diester. 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 may be used in the form of a mixed gas in which carbon dioxide is mixed with a gas other than carbon dioxide, as long as the effects of the present disclosure are not significantly impaired. However, from the viewpoint of improving reactivity, it is preferable to use carbon dioxide alone. Examples of gases other than carbon dioxide include inert gases such as nitrogen and argon. Hereinafter, carbon dioxide gas and the above mixed gas will be collectively referred to as a "carbon dioxide-containing gas."

[0096] The method for introducing carbon dioxide into the reaction system is not particularly limited, and may be a method of replacing the atmosphere in the reactor with a carbon dioxide-containing gas, or a method of supplying a carbon dioxide-containing gas into the reaction liquid by bubbling.

[0097] When carbon dioxide is introduced into the reaction system by replacing the atmosphere in the reactor with a carbon dioxide-containing gas, the total pressure P ｔis not particularly limited, but from the viewpoint of reaction efficiency, it is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, even more preferably 5.0 MPa or more, and is preferably 20.0 MPa or less, more preferably 15.0 MPa or less, even more preferably 10.0 MPa or less. That is, the total pressure P of the carbon dioxide-containing gas ｔ Suitable ranges for the pressure include, for example, 1.0 MPa or more and 20.0 MPa or less, 2.0 MPa or more and 15.0 MPa or less, and 5.0 MPa or more and 10.0 MPa or less.

[0098] When carbon dioxide is introduced into the reaction system by bubbling, the total pressure P of the carbon dioxide-containing gas is ｔ From the viewpoint of work efficiency, it is preferable that the pressure is approximately the same as atmospheric pressure, that is, (0.1±0.05) MPa.

[0099] Partial pressure P of carbon dioxide gas in carbon dioxide-containing gas ＣＯ２ is not particularly limited, but from the viewpoint of reaction efficiency, it is preferably 0.5 MPa or more, more preferably 1.0 MPa or more, even more preferably 4.0 MPa or more, and is preferably 15.0 MPa or less, more preferably 12.0 MPa or less, even more preferably 10.0 MPa or less. That is, the partial pressure P of carbon dioxide gas in the carbon dioxide-containing gas ＣＯ２ Suitable ranges for the pressure are, for example, 0.5 MPa or more and 15.0 MPa or less, 1.0 MPa or more and 12.0 MPa or less, and 4.0 MPa or more and 10.0 MPa or less.

[0100] Total pressure P of carbon dioxide-containing gas ｔ The partial pressure P of carbon dioxide gas in the carbon dioxide-containing gas ＣＯ２ The ratio (P ＣＯ２ / P ｔ ) is not particularly limited, but is preferably 0.50 or more, more preferably 0.75 or more, and even more preferably 0.90 or more, and is usually 1.00 or less, preferably 0.95 or less. ＣＯ２ / P ｔSuitable ranges of are, for example, 0.50 or more and 1.00 or less, 0.75 or more and 1.00 or less, and 0.90 or more and 0.95 or less.

[0101] The above pressure means absolute pressure. ｔ " and "The partial pressure P of carbon dioxide gas in the carbon dioxide-containing gas ＣＯ２ " means the pressure (25°C) at the start of the reaction.

[0102] 2-3. Zirconium alkoxide-supported metal oxide In the reaction step, the zirconium alkoxide-supported metal oxide according to the first embodiment of the present disclosure is used as a catalyst for the reaction between alkoxysilane and carbon dioxide. Because the zirconium alkoxide-supported metal oxide is a heterogeneous catalyst that is generally not dissolved in the reaction liquid, it can be separated and recovered after the reaction step by simple procedures such as centrifugation and filtration. Furthermore, since the zirconium alkoxide-supported metal oxide can be reused in the production of a carbonate diester after recovery, it is a catalyst with a low environmental impact.

[0103] The zirconium alkoxide-supported metal oxide may be used alone or in any combination of two or more kinds in any ratio.

[0104] In the reaction step, the amount (charge amount) of the zirconium alkoxide-supported metal oxide used may be selected depending on the type of alkoxysilane and the type of zirconium alkoxide-supported metal oxide, and is not particularly limited. Specifically, the amount (charge amount) of the zirconium alkoxide-supported metal oxide used is such that the amount of zirconium alkoxide relative to the substance amount of alkoxysilane is preferably 0.01 mol% or more, more preferably 0.1 mol% or more, even more preferably 0.5 mol% or more, and even more preferably 1.0 mol% or more. Furthermore, the amount (charge amount) of the zirconium alkoxide relative to the substance amount of alkoxysilane is preferably 25.0 mol% or less, more preferably 20.0 mol% or less, even more preferably 15.0 mol% or less, and even more preferably 10.0 mol% or less. That is, suitable ranges of the amount of zirconium alkoxide-supported metal oxide used relative to the amount of alkoxysilane include, for example, 0.01 mol% or more and 25.0 mol% or less, 0.1 mol% or more and 20.0 mol% or less, 0.5 mol% or more and 15.0 mol% or less, and 1.0 mol% or more and 10.0 mol% or less.

[0105] 2-4. Carbonate diester The carbonate diester produced by the production method according to this embodiment is a carbonate diester having two ester groups selected from the group consisting of an ester group derived from an alkoxy group of an alkoxysilane and an ester group derived from an alkoxy group of a zirconium alkoxide. The carbonate diester produced by the production method according to this embodiment is not particularly limited and may be determined depending on its intended use. Examples of intended uses of carbonate diesters include solvents for electrolytic solutions and the like, alkylating agents, carbonylating agents, gasoline additives, diesel fuel additives, and raw materials for polymers such as polyurethane and polycarbonate.

[0106] In the reaction step, it is preferable to use one or more compounds selected from the group consisting of compounds represented by general formula (A1) and compounds represented by general formula (A2) as the alkoxysilane, and it is preferable to use a metal oxide supported with zirconium alkoxide represented by general formula (I) as the zirconium alkoxide-supported metal oxide. Therefore, according to a preferred aspect of this embodiment, a mixture of a carbonate diester represented by general formula (B1), a carbonate diester represented by general formula (B2), and a carbonate diester represented by general formula (B3) can be produced.

[0107]

[0108] OR in general formulas (B1) and (B2) ａ１ is a group derived from the alkoxy group of the alkoxysilane. That is, R ａ１ represents R in general formulas (A1) and (A2). ａ１ The same applies to the preferred embodiments thereof.

[0109] OR in general formulas (B2) and (B3) １ is a group derived from the alkoxy group of zirconium alkoxide. That is, R １ represents R in general formula (I). １ The same applies to the preferred embodiments thereof.

[0110] R ａ１ and R １ and are preferably the same group, in that one type of carbonate diester can be produced by the production method according to this embodiment. In other words, the alkoxy group of the alkoxysilane and the alkoxy group of the zirconium alkoxide are preferably the same group.

[0111] Specific examples of the carbonate diester represented by any one of general formulas (B1) to (B3) include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, di-n-butyl carbonate, ethyl methyl carbonate, ethyl isopropyl carbonate, dicyclohexyl carbonate, divinyl carbonate, diallyl carbonate, methyl propargyl carbonate, and diphenyl carbonate.

[0112] 2-5. Reaction Solvent In the reaction step, the reaction between alkoxysilane and carbon dioxide may be carried out in a reaction solvent or without a solvent, but it is preferable to carry out the reaction without a solvent.

[0113] In this disclosure, "solvent-free" means that no liquid other than the reaction substrates, catalyst, product, and compounds derived therefrom is used. Therefore, for example, even if an alkoxysilane also functions as a solvent, the alkoxysilane is not considered to be a reaction solvent, and the reaction is considered to be carried out "solvent-free."

[0114] Although the type of reaction solvent is not particularly limited, a solvent with high solubility of carbon dioxide is preferred, since it can increase the carbon dioxide concentration in the reaction system and improve the yield of the carbonate diester. Examples of the reaction solvent include aliphatic hydrocarbon solvents such as n-hexane, n-octane, n-decane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, o-xylene, m-xylene, and p-xylene; aromatic heterocyclic compound solvents such as pyridine; aprotic polar solvents such as ethyl acetate, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone (NMP); ether solvents such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran (THF), and dioxane; nitrile solvents such as acetonitrile, propionitrile, butyronitrile, benzonitrile, and 2-cyanopyridine; and ketone solvents such as acetone and isopropyl ketone.

[0115] Of these, the reaction solvent is preferably one or more solvents selected from the group consisting of acetonitrile, N,N-dimethylformamide, tetrahydrofuran, toluene, pyridine, 2-cyanopyridine, and benzonitrile, in terms of improving the reaction efficiency.

[0116] The reaction solvent may be used alone or in any combination of two or more in any ratio.

[0117] The amount of the reaction solvent used is not particularly limited, but is preferably 10 parts by weight or more, more preferably 20 parts by weight or more, and is preferably 200 parts by weight or less, more preferably 100 parts by weight or less, relative to 100 parts by weight of the alkoxysilane. That is, suitable ranges for the amount of the reaction solvent used relative to 100 parts by weight of the alkoxysilane include, for example, from 10 parts by weight to 200 parts by weight and from 20 parts by weight to 100 parts by weight.

[0118] 2-6. Reaction Temperature The reaction temperature in the reaction step is not particularly limited, and is preferably 80°C or higher, more preferably 100°C or higher, even more preferably 120°C or higher, still more preferably 150°C or higher, and is preferably 250°C or lower, more preferably 230°C or lower, even more preferably 210°C or lower, and still more preferably 190°C or lower. That is, suitable ranges of the reaction temperature include, for example, 80°C or higher and 250°C or lower, 100°C or higher and 230°C or lower, 120°C or higher and 210°C or lower, and 150°C or higher and 190°C or lower.

[0119] 2-7. Reaction Time The reaction time in the reaction step is not particularly limited and may be adjusted depending on the reaction temperature, amount of catalyst, reaction scale, and the like. Specifically, the reaction time is preferably 0.5 hours or more, more preferably 1 hour or more, even more preferably 5 hours or more, still more preferably 10 hours or more, and preferably 100 hours or less, more preferably 72 hours or less, even more preferably 48 hours or less, and still more preferably 24 hours or less. That is, suitable ranges of the reaction time include, for example, from 0.5 hours to 100 hours, from 1 hour to 72 hours, from 5 hours to 48 hours, and from 10 hours to 24 hours.

[0120] 2-8. Reactor The reactor used in the reaction step is not particularly limited as long as it is made of a material that is stable against the raw materials, catalyst, and product, and may be selected depending on the method for introducing the carbon dioxide-containing gas into the reaction system.

[0121] When the introduction of carbon dioxide-containing gas into the reaction system is carried out by replacing the atmosphere in the reactor, the reactor is preferably a sealed reactor (sealed reactor), more preferably a sealed pressure-resistant reactor, and even more preferably a stainless steel autoclave. When the introduction of carbon dioxide into the reaction system is carried out by bubbling, the reactor preferably has a supply pipe for supplying carbon dioxide to the reaction system by bubbling and an exhaust pipe for discharging the gas in the reactor.

[0122] The reactor preferably has a volume 10 to 100 times the volume of a reaction solution containing alkoxysilane, zirconium alkoxide-supported metal oxide, and, if necessary, a reaction solvent. The reactor may be equipped with a magnetic stirrer or stirring blades for stirring the reaction solution.

[0123] 3. Other Steps The production method according to this embodiment may include any other steps in addition to the reaction step. Examples of the optional steps include a purification step for increasing the purity of the carbonate ester, and a catalyst recovery step for recovering the zirconium alkoxide-supported metal oxide from the reaction system after the reaction step.

[0124] As a method for purifying the carbonate diester in the purification step, a purification method commonly used in the field of organic synthesis, such as filtration, adsorption, column chromatography, distillation, etc., can be used. Specifically, a method can be mentioned in which the obtained solid is filtered under a nitrogen atmosphere, washed with diethyl ether or the like, and then vacuum dried.

[0125] The recovery of the zirconium alkoxide-supported metal oxide in the catalyst recovery step can be carried out by solid-liquid separation of the reaction mixture obtained in the reaction step. The method of solid-liquid separation is not particularly limited, and any method such as centrifugation or filtration can be used.

[0126] When the recovered zirconium alkoxide-supported metal oxide is to be reused in the reaction of alkoxysilane with carbon dioxide, it is preferable to wash and dry the zirconium alkoxide-supported metal oxide separated from the reaction mixture.

[0127] An organic solvent can be suitably used for washing the zirconium alkoxide-supported metal oxide. The organic solvent is not particularly limited, but preferred examples include alcohols such as methanol and ethanol; aliphatic hydrocarbons such as normal hexane and cyclohexane; and aromatic hydrocarbons such as toluene. Of these, alcohols are preferred as the organic solvent.

[0128] The present disclosure will be explained in more detail below using examples, but modifications can be made as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure should not be interpreted as being limited by the specific examples shown below. In this disclosure, "room temperature" means a temperature condition in which no artificial heating or cooling is performed, and specifically, a temperature range of 20°C to 30°C.

[0129] <Reactor> Apparatus: Chemist Plaza Chemi Chemi-300 (manufactured by Shibata Scientific Co., Ltd.) Rotation speed: 1200 rpm <Gas chromatography (GC) measurement> Apparatus: GC-2014 (manufactured by Shimadzu Corporation) Detector: FID (flame ionization detector) Column: TC-1 (manufactured by GL Sciences Inc.) Carrier gas: N ２ Internal standard substance: mesitylene Data processing: Lab solutions (Shimadzu Corporation)

[0130] <Pretreatment and Preparation of Metal Oxides> Silica: Silica ("CARiACT Q-10" manufactured by Fuji Silysia Chemical Ltd.) was calcined in an electric furnace at 300°C for 2 hours. Ceria nanopowder: Cerium (IV) oxide nanopowder (manufactured by Sigma-Aldrich; average particle size 25 nm) was calcined in an electric furnace at 600°C for 3 hours. Titania: Titanium (IV) oxide anatase type (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was calcined in an electric furnace at 600°C for 3 hours. Ceria: An aqueous solution of cerium (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dried in an air atmosphere and calcined in an electric furnace at 600°C for 3 hours to prepare ceria.

[0131] Example 1-1: Preparation of zirconium alkoxide-supported metal oxide Toluene was added to zirconium tetraethoxide and heated to reflux to prepare a zirconium tetraethoxide solution. This solution was mixed with ceria prepared from cerium nitrate at room temperature. The solution and ceria were mixed so that the amount of zirconium tetraethoxide was 5 parts by weight per 95 parts by weight of ceria. Toluene was distilled off from the resulting mixture at 40°C under reduced pressure, and the mixture was dried to obtain a zirconium alkoxide-supported metal oxide.

[0132] Examples 1-2 to 1-6: Preparation of zirconium alkoxide-supported metal oxides Zirconium alkoxide-supported metal oxides were obtained in the same manner as in Example 1-1, except that the carriers were changed to those shown in Table 1.

[0133] Example 1-7 Preparation of Zirconium Alkoxide-Supported Metal Oxide (Preparation of Core-Shell Particles) An aqueous solution of cerium (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to silica so that the ceria content relative to the total amount of the core-shell particles after firing was 5 wt %, and the mixture was dried at 120°C in an air atmosphere and then fired at 600°C for 3 hours to obtain core-shell particles.

[0134] (Supporting of zirconium alkoxide) Toluene was added to zirconium tetraethoxide and heated to reflux to prepare a zirconium tetraethoxide solution. This solution was mixed with core-shell type particles at room temperature. At this time, the solution and core-shell type particles were mixed so that the amount of zirconium tetraethoxide was 5 parts by weight per 95 parts by weight of the core-shell type particles. Toluene was distilled off from the obtained mixture at 40°C under reduced pressure conditions, and the mixture was dried to obtain a zirconium alkoxide-supported metal oxide.

[0135] Examples 1-8 to 1-11: Preparation of zirconium alkoxide-supported metal oxides Zirconium alkoxide-supported metal oxides were obtained in the same manner as in Example 1-7, except that in the preparation of the core-shell type particles, the mixing ratio of silica to the aqueous solution of cerium nitrate was changed so that the content of ceria relative to the total amount of the core-shell type particles after firing was as shown in Table 1.

[0136] Example 1-12 Preparation of Zirconium Alkoxide-Supported Metal Oxide A zirconium alkoxide-supported metal oxide was obtained in the same manner as in Example 1-11, except that in the preparation of core-shell type particles, silica was replaced with titania.

[0137]

[0138] <Example 2-1: Production of carbonic acid diester>

[0139] In a nitrogen-filled groove box, 2.0 g of the zirconium alkoxide-supported metal oxide obtained in Example 1-2 and 3.5 mL of tetraethoxysilane (TEOS) were added to a 10 mL SUS autoclave (manufactured by Taiatsu Glass Industry Co., Ltd.) containing a magnetic stirrer. Carbon dioxide gas was charged into the autoclave at 25°C so that the charging pressure inside the autoclave was 5.0 MPa, and the autoclave was maintained for 10 minutes. The reaction solution was then heated to 220°C with stirring and reacted for 6 hours to produce diethyl carbonate.

[0140] After the reaction, the autoclave was cooled to room temperature and the remaining gas was released. Mesitylene was added to the reaction mixture as an internal standard, and a portion of the supernatant was collected and analyzed by GC to determine the yield of diethyl carbonate relative to TEOS. The yield of diethyl carbonate is shown in Table 2.

[0141] Examples 2-2 to 2-5: Production of carbonate diesters Diethyl carbonate was produced in the same manner as in Example 2-1, except that the type and amount of zirconium alkoxide-supported metal oxide used were changed as shown in Table 2. The yield of diethyl carbonate is shown in Table 2.

[0142] Comparative Example 2-1: Production of Carbonic Acid Diester Diethyl carbonate was produced in the same manner as in Example 2-1, except that 0.1 g of zirconium tetraethoxide was used instead of 2.0 g of zirconium alkoxide-supported metal oxide. The yield of diethyl carbonate is shown in Table 2. Note that zirconium tetraethoxide is a homogeneous catalyst rather than a heterogeneous catalyst, and therefore is difficult to recover after the reaction.

[0143] Comparative Example 2-2: Production of carbonate diester Diethyl carbonate was produced in the same manner as in Example 2-1, except that 0.3 g of ceria nanopowder was used instead of 2.0 g of zirconium alkoxide-supported metal oxide. The yield of diethyl carbonate is shown in Table 2.

[0144]

[0145] <Example 3-1: Production of carbonic acid diester>

[0146] In a nitrogen-filled groove box, 1.0 g of the zirconium alkoxide-supported metal oxide obtained in Example 1-1 and 3.27 mL of tetraethoxysilane (TEOS) were added to a 10 mL SUS autoclave (manufactured by Taiatsu Glass Industry Co., Ltd.) containing a magnetic stirrer. Carbon dioxide gas was charged into the autoclave at 25°C so that the charging pressure inside the autoclave was 5.0 MPa, and the autoclave was maintained for 10 minutes. The reaction solution was then heated to 180°C with stirring, and the reaction was carried out for 15 hours to produce diethyl carbonate.

[0147] After the reaction, the autoclave was cooled to room temperature and the remaining gas was released. Mesitylene was added to the reaction mixture as an internal standard, and a portion of the supernatant was collected and analyzed by GC to determine the yield of diethyl carbonate based on TEOS. The yield of diethyl carbonate is shown in Table 3.

[0148] Examples 3-2 to 3-9: Production of carbonate diesters Diethyl carbonate was produced in the same manner as in Example 3-1, except that the zirconium alkoxide-supported metal oxide was changed to one shown in Table 3. The yields of diethyl carbonate are shown in Table 3.

[0149] Comparative Example 3-1: Production of carbonate diester Diethyl carbonate was produced in the same manner as in Example 3-1, except that the core-shell particles produced in Example 1-7 were used instead of the zirconium alkoxide-supported metal oxide. The yield of diethyl carbonate is shown in Table 3.

[0150] Comparative Example 3-2: Production of carbonate diester Diethyl carbonate was produced in the same manner as in Example 3-1, except that 0.05 g of zirconium tetraethoxide was used instead of 1.0 g of zirconium alkoxide-supported metal oxide. The yield of diethyl carbonate is shown in Table 3. Note that zirconium tetraethoxide is a homogeneous catalyst rather than a heterogeneous catalyst, and therefore is difficult to recover after the reaction.

[0151]

[0152] Example 4-1: Evaluation of catalyst reusability Diethyl carbonate was produced using the zirconium alkoxide-supported metal oxide obtained in Example 1-6 in the same procedure as in Example 3-1, and then the suspension remaining in the autoclave was washed into a centrifuge tube with TEOS, and the supernatant was removed by centrifugation. TEOS was added to the residue, and after stirring, the mixture was centrifuged again and the supernatant was removed. This procedure was repeated until mesitylene, the internal standard substance, was no longer detected in the supernatant by GC. The zirconium alkoxide-supported metal oxide was then washed and recovered.

[0153] The recovered zirconium alkoxide-supported metal oxide was used again to produce diethyl carbonate in the same manner as in Example 3-1. The recovery of the zirconium alkoxide-supported metal oxide and the subsequent production of dialkyl carbonate were then repeated to evaluate the change in catalytic activity of the zirconium alkoxide-supported metal oxide due to reuse. The results are shown in Figure 1.

[0154] Examples 4-2 to 4-8: Evaluation of catalyst reusability Changes in catalytic activity of zirconium alkoxide-supported metal oxide due to reuse were evaluated in the same manner as in Example 4-1, except that the zirconium alkoxide-supported metal oxide was changed to one shown in Table 4. The results are shown in Figure 1.

[0155]

[0156] According to the present disclosure, a novel zirconium alkoxide-supported metal oxide can be provided, which can be used as a heterogeneous catalyst in organic synthesis reactions.

Claims

1. A zirconium alkoxide-supported metal oxide comprising a carrier and zirconium alkoxide supported on the carrier, wherein the carrier is a metal oxide.

2. The zirconium alkoxide-supported metal oxide according to claim 1, wherein the zirconium alkoxide is a compound represented by the general formula (I). (R １ ) ４－ｐ Zr(OR １ ) ｐ (I) (R １ is each independently a hydrocarbon group which may have a substituent; p is an integer of 1 or more and 4 or less.) 3. The zirconium alkoxide-supported metal oxide according to claim 1, wherein the metal oxide contains an oxide of one or more metals selected from the group consisting of rare earth metals, Group 4 metals of the periodic table, Group 13 metals of the periodic table, and Group 14 metals of the periodic table.

4. The zirconium alkoxide-supported metal oxide according to claim 1, wherein the carrier is a core-shell type particle.

5. The zirconium alkoxide-supported metal oxide according to claim 4, wherein the core of the core-shell type particle is silica and the shell of the core-shell type particle is ceria.

6. The zirconium alkoxide-supported metal oxide according to claim 4, wherein the content of the core with respect to the total amount of the core-shell type particles is 10% by weight or more and 99% by weight or less, and the content of the shell with respect to the total amount of the core-shell type particles is 1% by weight or more and 90% by weight or less.

7. The zirconium alkoxide-supported metal oxide according to claim 1, wherein the supported amount of the zirconium alkoxide is 1% by weight or more and 20% by weight or less with respect to the total amount of the zirconium alkoxide-supported metal oxide.

8. The zirconium alkoxide-supported metal oxide according to claim 1, which is a catalyst used in the reaction for synthesizing a dialkyl carbonate from an alkoxysilane and carbon dioxide.

9. A method for producing a zirconium alkoxide-supported metal oxide, comprising a supporting step of supporting the zirconium alkoxide on the carrier by removing the solvent of the solution after bringing a solution containing zirconium alkoxide into contact with the carrier, wherein the carrier is a metal oxide.

10. The method for producing a zirconium alkoxide-supported metal oxide according to claim 9, wherein the zirconium alkoxide is a compound represented by the general formula (I). (R １ ) ４－ｐ Zr(OR １ ) ｐ (I) (R １ is each independently a hydrocarbon group which may have a substituent; p is an integer of 1 or more and 4 or less.) 11. The method for producing a zirconium alkoxide-supported metal oxide according to claim 9, wherein the metal oxide contains an oxide of one or more metals selected from the group consisting of rare earth metals, Group 4 metals of the periodic table, Group 13 metals of the periodic table, and Group 14 metals of the periodic table.

12. The method for producing a zirconium alkoxide-supported metal oxide according to claim 9, wherein the carrier is a core-shell type particle.

13. The method for producing a zirconium alkoxide-supported metal oxide according to claim 12, wherein the core of the core-shell type particle is silica and the shell of the core-shell type particle is ceria.

14. A method for producing a diester carbonate, comprising a reaction step of reacting an alkoxysilane with carbon dioxide in the presence of the zirconium alkoxide-supported metal oxide according to any one of claims 1 to 8.

15. The method for producing a carbonic acid diester according to claim 14, wherein the alkoxysilane is at least one selected from the group consisting of compounds represented by general formula (A1) and compounds represented by general formula (A2). (R ａ２ ) ４－ｎ１ Si(OR ａ１ ) ｎ１ (A1) R ａ３ [Si(R ａ２ ) ３－ｎ２ (OR ａ１ ) ｎ２ ] ｍ (A2) (R ａ１ are each independently a hydrocarbon group which may have a substituent; R ａ２ are each independently a hydrocarbon group which may have a substituent; R ａ３ are each independently a hydrocarbon group which may have a substituent; n1 is an integer of 1 or more and 4 or less; n2 is an integer of 1 or more and 3 or less; m is an integer of 2 or more and 20 or less; when n1 is an integer of 2 or more and 4 or less, two OR ａ１ R ａ１ may be bonded to each other to form a ring; when n1 is an integer of 1 or more and 3 or less, OR ａ１ R in the group ａ１ and R ａ２ may be bonded to each other to form a ring; when n2 is 2 or 3, two OR ａ１ R ａ１ may be bonded to each other to form a ring; when n2 is 1 or 2, OR ａ１ R in the group ａ１ and R ａ２ may be bonded to each other to form a ring.)

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