JP2017144397A - Catalyst for converting carbon dioxide, and method for producing compound containing carboxyl group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst that enables a compound such as an unsaturated carboxylic acid to be efficiently produced with carbon dioxide as a raw material with long-term stability.SOLUTION: In the catalyst including a transition metal complex supported on a porous support having a communication hole structure, the transition metal complex has the activity of catalyzing reaction of carbon dioxide as a starting material, the porous support has a mode diameter of 0.8 nm or more in a logarithmic differentiation void volume distribution (dV/dlog (D)), and in the porous support, the total of the volumes of voids within a range between the mode diameter -2 nm and the mode diameter +2 nm is 80% or more of the total void volume.SELECTED DRAWING: None

Description

  The present invention relates to a carbon dioxide conversion catalyst and a method for producing a carboxyl group-containing compound.

In recent years, many methods of using CO ₂ as a raw material for chemical synthesis have been proposed for the purpose of reducing greenhouse gases such as carbon dioxide (CO ₂ ). As one of them, it has been proposed to produce unsaturated carboxylic acids such as acrylic acid using CO ₂ and alkene as raw materials.

For example, a method of producing an acrylate by reacting CO ₂ and ethylene in the presence of a homogeneous catalyst containing a nickel complex and a base and a base has been proposed (Non-patent Document 1). In this method, an olefin-nickel complex and CO ₂ are reacted in a tetrahydrofuran (THF) solvent to form a nickelalactone complex, and then an acrylate complex is obtained by cleavage of the lactone ring. The acrylate ligand is replaced with an olefin ligand to release acrylate (sodium acrylate).
Further, as a homogeneous catalyst, a method of reacting CO ₂ with ethylene using a zero-valent molybdenum complex having a tri-phosphine ligand has also been reported (Non-Patent Document 2).

Further, in Patent Document 1, a) a transition metal-alkene complex is reacted with CO ₂ to produce a metallalactone, and b) a metallalactone is converted into an alkali metal hydroxide or alkaline earth metal hydroxide and an alkali metal superbase. Or an alkali metal salt of an α, β-ethylenically unsaturated carboxylic acid or an adduct of an alkaline earth metal salt and a transition metal complex by reacting with a base selected from alkaline earth metal superbases, and c ) React the transition metal-alkene complex by reacting the adduct with the alkene to release the alkali metal salt or alkaline earth metal salt of the α, β-ethylenically unsaturated carboxylic acid. Methods for preparing alkali metal salts or alkaline earth metal salts of carboxylic acids are disclosed.
Patent Document 2 discloses a method for producing a β-unsaturated carboxylic acid or a salt thereof by reacting a metallalactone intermediate in the presence of a halide in a solvent.

US Pat. No. 8,697,909 International Publication No. 2014/198469

Lejkowski, M. L. et al., “The first catalytic synthesis of an acrylate from CO2 and an alkene-A rational approach”, Chem. Eur. J. 18, 14017-14025 (2012) Hanna et al., “Ancillary Ligand Effects on Carbon Dioxide-Ethylene Coupling at Zerovalent Molybdenum”, Organometallics, 2014, 33, 3425-3432

However, in any of the conventional methods as described above, the solubility of CO _{2 in} a solvent (THF) is low. For example, the ratio of the solubility of ethylene and CO ₂ (the solubility of ethylene: the solubility of CO ₂ ) is 10 : About 1 to 5: 1. Therefore, the CO ₂ gas as a raw material cannot be brought into contact with the catalyst in a sufficient amount. Furthermore, CO ₂ and alkenes have low affinity with metal complexes. Due to such low solubility and low affinity, the conventional method has a problem that sufficient catalytic activity cannot be achieved. Further, in the conventional method, the catalyst is agglomerated due to frequent ligand exchange reaction, so that the catalyst life is short, and since the catalyst and the product are soluble in the solvent, it is difficult to recover the product. There was a problem. Therefore, the development of techniques that allow carrying out the production of unsaturated carboxylic acids from CO ₂ and alkene at an industrial level has been desired.
The present invention has been made in view of the above circumstances, and provides a catalyst that enables efficient and stable long-term production of a compound such as an unsaturated carboxylic acid using CO ₂ as a raw material. For the purpose.

As a result of diligent research, the present inventors have found that carbon dioxide (CO ₂ ) and other substances such as alkenes are present in the presence of a catalyst in which a transition metal complex is supported on a porous support having a specific pore distribution. It is found that a reaction field with a high concentration of CO ₂ is formed in the pores of the carrier by the reaction, and the synthesis of the target compound can be carried out efficiently and stably for a long period of time. The invention has been completed.
That is, the present invention has the following configuration.
[1] A catalyst in which a transition metal complex is supported on a porous carrier having a communicating pore structure,
The transition metal complex has an activity of catalyzing a reaction using carbon dioxide as a starting material;
The porous carrier has a mode diameter of Log differential pore volume distribution (dV / dlog (D)) of 0.8 nm or more, and the total pore volume within the range of the mode diameter ± 2 nm is A carbon dioxide conversion catalyst characterized by being 80% or more of the total pore volume.
[2] The carbon dioxide conversion according to [1], wherein the porous carrier has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, and sulfur. catalyst.
[3] The porous support is at least one selected from the group consisting of silica, alumina, carbon, zeolite, activated carbon, a clay sintered body, and an organometallic structure. Catalyst for carbon dioxide conversion.
[4] The carbon dioxide conversion catalyst as described in [3], wherein the porous carrier is an organometallic structure.
[5] The carbon dioxide conversion catalyst according to [4], wherein the organometallic structure is a zeolite type imidazolate skeleton.
[6] Any one of [1] to [5], wherein the porous carrier has a carbon dioxide adsorption amount per unit weight of 20 to 400 ml / g measured by a constant volume gas adsorption method. The catalyst for carbon dioxide conversion described in 1.
[7] A carboxyl group-containing compound obtained by reacting carbon dioxide with another substance in the presence of the catalyst according to any one of [1] to [6] Manufacturing method.
[8] The method for producing a carboxyl group-containing compound according to [7], wherein the other substance is an alkene, and the carboxyl group-containing compound is an unsaturated carboxylic acid.
[9] The method for producing a carboxyl group-containing compound as described in [7], wherein the other substance is ethylene and the carboxyl group-containing compound is (meth) acrylic acid.

According to the catalyst of the present invention, it is possible to efficiently and stably produce a compound such as an unsaturated carboxylic acid using CO ₂ as a raw material for a long period of time.

Hereinafter, the present invention will be described in detail.
<Catalyst for carbon dioxide conversion>
The catalyst of the present invention is a catalyst in which a transition metal complex is supported on a porous carrier having a communicating pore structure.

(Transition metal complex)
The transition metal complex is not particularly limited as long as it can catalyze the reaction of CO ₂ with other raw material compounds in order to obtain a desired compound. For example, Non-Patent Documents 1 and 2 and Patent Document Known transition metal complexes such as described in 1 and 2 can be used.
In general, transition metal complexes include, as active metals, elements belonging to Group 4 of the periodic table (preferably Ti, Zr), elements belonging to Group 6 (preferably Cr, Mo, W), and elements belonging to Group 7 (preferably Is selected from the group consisting of elements belonging to Group 8 (preferably Fe, Ru), elements belonging to Group 9 (preferably Co, Rh), and elements belonging to Group 10 (preferably Ni, Pd, Pt). At least one element. Of these, nickel, molybdenum, cobalt, iron, rhodium, ruthenium, palladium, platinum, rhenium and tungsten are preferred, nickel, molybdenum, palladium, platinum, cobalt, iron, rhodium and ruthenium are more preferred, and nickel and palladium are particularly preferred. preferable.

The ligand of the transition metal complex may be monodentate or multidentate, such as bidentate, tridentate, etc., but leave the coordination site on the metal for CO ₂ as the starting material and the compound to be reacted therewith. It is desirable to select an appropriate ligand. For example, when the active metal is nickel, a bidentate ligand is preferably used, and when cobalt is used, a tridentate ligand is preferably used.

  The ligand may include at least one phosphorus atom, nitrogen atom, oxygen atom, and / or carbene group coordinated to the transition metal. The ligand can be selected from, for example, phosphines, phosphites, amines, and N-heterocyclic carbenes. The ligand preferably comprises at least one phosphorus atom and / or amine and / or carbene group coordinated to the transition metal, and comprises at least one phosphorus atom and / or amine coordinated to the transition metal. More preferred.

  When the ligand contains at least one phosphorus atom coordinated to the transition metal, it is preferred that at least one group is bonded to the phosphorus atom via a secondary or tertiary carbon atom. More preferably, at least two groups are bonded to the phosphorus atom via a secondary or tertiary carbon atom. Suitable groups attached to the phosphorus atom via a secondary or tertiary carbon atom are, for example, adamantyl, tert-butyl, cyclohexyl, sec-butyl, isopropyl, phenyl, tolyl, xylyl, mesityl, naphthyl, Fluorenyl or anthracenyl. Of these, a group having a high electron donating property is desirable, and specifically, tert-butyl and cyclohexyl are preferable.

  When the ligand comprises at least one N-heterocyclic carbene that coordinates to the transition metal, preferably at least one group is bonded to at least one α-nitrogen atom of the carbene group via a tertiary carbon atom. ing. A suitable group bonded to the nitrogen atom via a tertiary carbon atom is, for example, adamantyl or tert-butyl, preferably tert-butyl.

Specific examples of the ligand containing at least one phosphorus atom that can be used in the present invention include monodentate ligands such as trialkylphosphine such as trimethylphosphine; tricycloalkylphosphine such as tricyclohexylphosphine (PCy3). A triarylphosphine such as triphenylphosphine and tri (4-fluoromethylphenyl) phosphine; a triheteroarylphosphine such as tri-2-furanylphosphine; a phosphorane ligand such as triphenylphosphine oxide; Bidentate ligands include bis (diphenylphosphino) methane (dppm), 1,2-bis (diphenylphosphino) ethane (dppe), 1,3-bis (diphenylphosphino) propane (dppp), 1, 4-bis (diphenylphosphino) buta (Dppb), 1,5-bis (diphenylphosphino) pentane (dpppe), 1,6-bis (diphenylphosphino) hexane, 1,1′-bis (diphenylphosphino) ferrocene, 1,2-bis ( Dipentafluorophenylphosphino) ethane, 1,2-bis (dicyclohexylphosphino) ethane, 1,3-bis (dicyclohexylphosphino) propane, 1,4-bis (dicyclohexylphosphino) butane, 1,2-bis (Di-t-butylphosphino) ethane, 1,2-bis (diphenylphosphino) benzene, 1,2-bis (bis (3,5-dimethylphenyl) phosphino) ethane, 1,3-bis (bis ( 3,5-dimethylphenyl) phosphino) propane, 1,4-bis (bis (3,5-dimethylphenyl) phosphino) Tan, 1,2-bis (cyclohexylphosphino) ethane, 1,4-bis (bis (3,5-di-t-butylphenyl) phosphino) butane, 1,4-bis (bis (3,5-dimethoxy) Phenyl) phosphino) butane, 2,2′-bis (diphenylphosphino) -1,1′-binaphthyl, 2,2′-bis (bis (3,5-dimethylphenyl) phosphino) -1,1′-binaphthyl , (2S, 3S)-(−)-bis (diphenylphosphino) butane, (S, S) -1,2-bis [(2-methoxyphenyl) phenylphosphino] ethane ((S, S) -DIPAMP ), (R, R)-(−)-2,3-bis (tert-butylmethylphosphino) quinoxaline (QuinoxP *), (R, R) -1,2-bis (tert-butylmethylphosphino) Ben Zen (BenzP *), 1,1,1-tris (diphenylphosphinomethyl) ethane, 1,1,1-tris (bis (3,5-dimethylphenyl) phosphinomethyl) ethane, 1,1,1- Tris (diphenylphosphino) methane, tris (2-diphenylphosphinoethyl) phosphine, (oxydi-2,1-phenylene) bis (diphenylphosphine), 4,5-bis (diphenylphosphino) -9,9-dimethyl Xanthene, 4,5-bis (diphenylphosphino) -9,9-dimethylxanthene, and the like. Examples of the tridentate ligand include bis (2-diphenylphosphinoethyl) phenylphosphine, 1,1,1. -Tris (diphenylphosphinomethyl) ethane, etc., and examples of the tetradentate ligand include tris (2-diphenylphosphinoe). Til) phenylphosphine and the like. Of these, 1,2-bis (diphenylphosphino) ethane (dppe), 1,2-bis (dicyclohexylphosphino) ethane, 1,2-bis (di-t-butylphosphino) ethane, and BenzP ^* are preferable. .

  In addition to the above ligands, transition metal complexes can be halides, amines, amides, oxides, phosphides, carboxylates, acetylacetonates, aryl sulfonates or alkyl sulfonates, hydrides, carbon monoxide, olefins. , Dienes, cycloolefins, nitriles, aromatic and heterocyclic aromatics, ethers, phosphorus trifluoride, phospholes, phosphabenzenes, and monodentate, bidentate, and polydentate phosphinites, phosphonites, phosphoramidites, and phosphite coordination It may also have at least one further ligand selected from the children.

（式中、Ｎｉはニッケル原子を表し、Ｐはリン原子を表し、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４はそれぞれ独立してアルキル基、シクロアルキル基又はアリール基を表す。） Specific examples of the transition metal complex that can be suitably used in the present invention include those represented by the following formula (1).

(In the formula, Ni represents a nickel atom, P represents a phosphorus atom, and R ¹ , R ² , R ³ , and R ⁴ each independently represents an alkyl group, a cycloalkyl group, or an aryl group.)

Examples of the alkyl group, cycloalkyl group and aryl group as R ¹ , R ² , R ³ and R ^{4 in} formula (1) include those described later.

In the present invention, the expression “alkyl” includes straight-chain and branched alkyl groups. The alkyl group _is preferably a C 1 _{-C 20} alkyl _group, more preferably a C 1 _{-C 12} alkyl _group, more preferably C 1 -C ₈ alkyl _group, C 1 -C ₄ alkyl group is particularly preferred. Specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, 2-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-pentyl group, 2-methylbutyl group, 3-methylbutyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, 2-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethylbutyl group, 2- Tylbutyl group, 1-ethyl-2-methylpropyl group, n-heptyl group, 2-heptyl group, 3-heptyl group, 2-ethylpentyl group, 1-propylbutyl group, n-octyl group, 2-ethylhexyl group , 2-propylheptyl group, nonyl group, and decyl group.

In addition, the expression “alkyl” generally includes substituted alkyl groups having 1 to 5, preferably 1 to 3, and more preferably 1 substituent. Preferred examples of the substituent are selected from an alkoxy group, a cycloalkyl group, an aryl group, a heteroaryl group, a hydroxyl group, a halogen, a NE ¹ E ² group, a NE ¹ E ² E ³⁺ group, a carboxylate, and a sulfonate. The When the substituted alkyl group is a perfluoroalkyl group, a preferred example thereof is trifluoromethyl. The E ¹ group, E ² group, and E ³ group are each independently selected from hydrogen, an alkyl group, a cycloalkyl group, and an aryl group. The NE ¹ E ² group is an N, N-dimethylamino group, an N, N-diethylamino group, an N, N-dipropylamino group, an N, N-diisopropylamino group, or an N, N-di-n-butylamino group. N, N-di-tert-butylamino group, N, N-dicyclohexylamino group, or N, N-diphenylamino group is preferable.

In the present invention, the expression “cycloalkyl” includes monocyclic and polycyclic alkyl groups, especially monocyclic, bicyclic or tricyclic alkyl groups. As the cycloalkyl group, a C _{3 to} C ₂₀ cycloalkyl group is preferable, a C _{4 to} C ₁₂ cycloalkyl group is more preferable, and a C _{5 to} C ₈ cycloalkyl group is still more preferable. Specific examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and an adamantyl group. Further, the expression “cycloalkyl” generally includes substituted cycloalkyl groups having 1 to 5, preferably 1 to 3, and more preferably 1 substituent. These are preferably selected from alkoxy groups, aryl groups, heteroaryl groups, hydroxyl groups, halogens, NE ¹ E ² groups, NE ¹ E ² E ³⁺ groups, carboxylates, and sulfonates. The E ¹ group, E ² group, E ³ group, and NE ¹ E ² group are as described above.

In the present invention, the expression “aryl” includes unsubstituted and also substituted aryl groups, and is preferably a C ₆ -C ₁₈ aryl group. Specific examples thereof include a phenyl group, a tolyl group, a xylyl group, a mesityl group. Group, naphthyl group, fluorenyl group, anthracenyl group, phenanthrenyl group, naphthacenyl group and the like, among which phenyl group and naphthyl group are preferable. When these aryl groups are substituted, they can be alkyl groups, alkoxy groups, carboxylates, trifluoromethyl groups, sulfonates, NE ¹ E ² groups, alkylene-NE ¹ E ² groups, nitro groups, cyano groups, or halogens. It may have 1 to 5 substituents, preferably 1 to 3 substituents, more preferably 1 substituent selected. When the substituted aryl group is a perfluoroaryl group, a preferred example thereof is a pentafluorophenyl group.

In the present invention, the carbonoxylate and the sulfonate are preferably derivatives of a carboxylic acid functional group and a sulfonic acid functional group, respectively, more specifically, a metal carboxylate or metal sulfonate, a carboxylic acid ester or a sulfonic acid ester functional group, Or it is preferably a carboxamide or sulfonamide functional group. Examples of these _are esters of C 1 -C ₄ alkanols, such as methanol, ethanol, n- propanol, isopropanol, n- butanol, sec- butanol, and tert- butanol esters and the like.

  The above description regarding the expressions “alkyl” and “aryl” applies equally to the expressions “alkoxy” and “aryloxy”.

  About the manufacturing method of the said transition metal complex, the well-known manufacturing method as described in the said nonpatent literature 1 and 2 and the patent documents 1 and 2 is employable, for example.

(Porous carrier having a communication hole structure)
The porous carrier having a communicating pore structure used in the present invention has a log differential pore volume distribution (dV / dlog (D)) with a mode diameter of 0.8 nm or more and a mode diameter within a range of ± 2 nm. The total pore volume has a specific pore distribution that is 80% or more of the total pore volume.
In the present invention, the mode diameter of the Log differential pore volume distribution (dV / dlog (D)) is measured by a gas adsorption method. Specifically, based on the measurement results by the gas adsorption method, a distribution curve is obtained by plotting the pore diameter of the sample on the horizontal axis and the pore volume corresponding to the pore diameter in the sample on the vertical axis. The pore diameter at the point where the peak value (maximum frequency) is taken is called the mode diameter.
The pore volume is the total amount of adsorbed gas that has entered the sample by this measurement method, that is, corresponds to the amount of voids in the sample, and in the graph showing the differential pore distribution curve, This corresponds to the area of the lower region. The integral pore distribution curve is a distribution curve in which the integral value of the differential pore distribution curve is displayed with respect to the pore diameter. Therefore, the “total pore volume within the range of mode diameter ± 2 nm” (hereinafter often referred to as “volume ratio of mode diameter pores”) is the lower part of the differential pore distribution curve in the graph. Means the ratio (%) of the area occupied by the portion corresponding to the pores in the range of the mode diameter ± 2 nm in the area of the region (corresponding to the total pore volume).

Although it will not specifically limit if the said mode diameter is 0.8 nm or more, For example, 8-30 nm is preferable and 10-20 nm is more preferable. If the mode diameter is less than the above lower limit value, it becomes difficult to put the transition metal complex into the support when the transition metal complex is supported. As a result, the surface area of the support cannot be fully utilized, or raw materials such as CO ₂ diffuse. As a result, the transition metal complex and the raw material cannot be sufficiently brought into contact with each other, and sufficient catalytic activity may not be exhibited. When the mode diameter exceeds the above upper limit, the specific surface area of the support becomes too small, and when the transition metal complex is supported, the dispersibility is lowered and the production efficiency of the target compound may be lowered.

The volume ratio of the mode diameter pores is not particularly limited as long as it is 80% or more of the total pore volume. For example, 80% or more is preferable, and 85% or more is more preferable. When the volume ratio of the mode diameter pores is less than the above lower limit, the pore diameter distribution becomes non-uniform and it becomes difficult to put the transition metal complex into the inside of the support, and as a result, the surface area of the support cannot be fully utilized, A raw material such as CO ₂ becomes difficult to diffuse, and as a result, the transition metal complex and the raw material cannot be sufficiently brought into contact with each other, so that sufficient catalytic activity may not be exhibited.

The total pore volume (total pore volume) in the porous carrier is not particularly limited, but is preferably 0.1 to 2 mL / g, and more preferably 0.2 to 1.5 mL / g, for example. When the total pore volume is less than the above lower limit, the specific surface area of the porous carrier becomes too small, and when the transition metal complex is supported, its dispersibility is lowered, and the catalyst performance may be lowered. If the total pore volume exceeds the above upper limit, the pore diameter becomes too small, and it becomes difficult to put the metal complex in the back when the transition metal complex is supported, resulting in sufficient surface area of the support. The production efficiency of target compounds such as unsaturated carboxylic acids may not be available or it may be difficult for raw materials such as CO ₂ to diffuse and as a result, transition metals and CO ₂ or other raw material compounds cannot be sufficiently contacted. May be low. The total pore volume can be determined by the gas adsorption method described above.

  In the present invention, “having a communicating hole structure” means a structure in which the pores of the porous carrier are formed in a three-dimensional network, and a structure that allows a gas such as carbon dioxide to pass through by having a through hole. Preferably there is. Such a structure can be confirmed, for example, by observation with a scanning electron microscope (SEM).

  The porous carrier preferably has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen and sulfur. Examples of nitrogen-containing functional groups include amino groups, substituted amino groups, amide groups, imino groups, nitro groups, cyano groups, imidazole residues, nitrile groups, pyridyl groups, among these, amino groups, substituted An amino group or an amide group imidazole residue is preferred. Examples of oxygen-containing functional groups include hydroxyl groups, carboxy groups, carbonyl groups, phenolic hydroxyl groups, alkoxy groups (methoxy groups, ethoxy groups, n-propoxy groups, isopropoxy groups, n-butoxy groups, isobutoxy groups, tert-butoxy groups). Group) and the like. Among these, a carbonyl group and an alkoxy group are preferable. Examples of the sulfur-containing functional group include a sulfuric acid group, a thiol group, a sulfide group, and a disulfide group, and among these, a thiol group is preferable.

  Further, the porous carrier is preferably one having carbon dioxide adsorption ability. Specifically, the carbon dioxide adsorption amount per unit weight measured by the gas adsorption method by the constant volume method of the porous carrier is preferably 10 to 800 ml / g, and preferably 15 to 600 ml / g. Is more preferable, and it is still more preferable that it is 20-400 ml / g. When the amount of carbon dioxide adsorbed on the porous carrier is within the above range, a reaction system with a high carbon dioxide concentration can be formed in the pores of the porous carrier, thereby exhibiting high activity as a whole supported catalyst. Can do.

  The heat resistance temperature of the porous carrier is preferably 200 ° C. or higher, more preferably 300 ° C. or higher, and still more preferably 400 ° C. or higher. When the heat resistant temperature is within this range, it becomes possible to effectively prevent the catalyst from being deteriorated during the reaction. Here, the heat resistance temperature is measured by the following method. The porous support was subjected to a heat deterioration test in the atmosphere at a heating temperature of 100, 200, 300, 400, 500, 600 ° C. and a heating time at each temperature of 18 hours, and the porous support was then subjected to Cu-Kα radiation. Powder X-ray diffraction is performed to observe the fracture state of the crystal due to heat, and the maximum heating temperature when the X-ray reflection intensity does not change after the test is defined as the heat resistant temperature.

The specific surface area of the porous carrier is preferably 600 m ² / g or more, and more preferably 800 m ² / g or more. When the specific surface area is in this range, a sufficient amount of the transition metal complex can be supported. Moreover, although there is no restriction | limiting in particular about the upper limit of a specific surface area, it is preferable to set it as 2500 m < ² > / g or less from a viewpoint of industrial productivity and catalyst strength. The “specific surface area” is a BET specific surface area measured by a BET gas adsorption method using nitrogen as an adsorption gas.

The size of the porous carrier is not particularly limited, but those having a particle diameter of 10 to 1000 μm are preferable. If it is less than the said lower limit, it will be easy to scatter and handling will become complicated easily. If the amount exceeds the upper limit, when the transition metal complex is supported, the transition metal complex is less likely to enter the support, the amount of the transition metal complex supported is reduced, and the degree of improvement in catalyst performance may be reduced. The particle size of the porous carrier is adjusted by sieving.
In addition, the porous carrier preferably has a narrowest particle size distribution.
In addition, although a porous support | carrier is normally obtained as a granular material, you may use it, after shape | molding using a binder etc. as needed. Such a molding treatment may be performed simultaneously with the preparation of the carrier, whereby the supported catalyst may be obtained as a molded product having a desired shape, or may be performed after adjusting the granular supported catalyst. The molding process can be performed by a method such as extrusion, compression, tableting, flow, rolling, spraying, etc., and a desired shape, for example, granular, pellet, spherical, cylindrical, plate, ring, clover It can be formed into a shape or the like.

  The type of the porous carrier is not particularly limited as long as it has the specific pore distribution described above, but is a group consisting of silica, alumina, carbon, zeolite, activated carbon, clay sintered body, and organometallic structure. More selected at least one porous material can be used. Among these, from the viewpoint of carbon dioxide adsorption ability, an organometallic structure (Metal-Organic Framework: MOF) is preferable, and a zeolitic imidazolate framework (Zeolitic Imidazolate Framework: ZIF), which is one of the organometallic structures. More preferably.

  MOF is a crystalline three-dimensional microporous material synthesized through coordination bonds and self-assembly of metal ions and organic bridging ligands (polydentate ligands). It has uniform micropores and high specific surface area. Have. ZIF, which is a kind of MOF, is a material having a zeolite-like topology that contains zinc (Zn) or cobalt (Co) as a metal and imidazole as an organic bridging ligand. The MOF containing ZIF has a regular pore structure, so that gas can be taken into the pores at a high concentration. Therefore, since the reaction rate of the catalytic reaction that proceeds on the MOF can be increased, the entire supported catalyst can exhibit high activity.

  As MOFs, MOFs having a plurality of metals, metal oxides, metal clusters, or metal oxide cluster structural units are known, but are not limited thereto. The metal can be selected from transition metals and beryllium. More specific examples include zinc (Zn), cadmium (Cd), mercury (Hg), and beryllium (Be). A metal structure unit can be bonded with an organic compound to form a porous structure, and 1,3,5-benzenetribenzoate (BTB) is used as an organic compound (ligand) for bonding adjacent metal structure units. ), 1,4-benzenedicarboxylate (BDC), cyclobutyl 1,4-benzenedicarboxylate (CB BDC), 2-amino 1,4 benzenedicarboxylate (H2N BDC), tetrahydropyrene 2,7-di Carboxylate (HPDC), terphenyl dicarboxylate (TPDC), 2,6 naphthalene dicarboxylate (2,6-NDC), pyrene 2,7-dicarboxylate (PDC), biphenyl dicarboxylate (BDC), Or any dicarboxylate with a phenyl compound can be mentioned.

Specific examples of MOF include MOF-177 including a structure represented by the general formula Zn ₄ O (1,3,5-benzenetribenzoate) ₂ ; general formula Zn ₄ O (1 also known as IRMOF-I , 4-benzenedicarboxylate) MOF-5 including a structure represented by ₃ ; MOF-74 including a structure represented by general formula Mg ₂ (2,5-dihydroxyterephthalic acid); General formula Cu ₂ (3 , 3 ', MOF-505 containing a structure represented by 5,5'-biphenyltetracarboxylic carboxylate); a structure represented by the general formula _Zn 4 O (cyclobutyl 1,4 benzene dicarboxylate) IRMOF- 6, the general formula _Zn 4 O (2-amino-1,4 benzene _{dicarboxylate)} IRMOF-3 contains a structure represented by _3; formula _Zn 4 O (terphenyl dicarboxylate Represented by the general formula _Zn 4 O (2,6-naphthalene _{dicarboxylate) 3; rate) 3} or _Zn 4 O (tetrahydropyrene 2,7- _{dicarboxylate)} IRMOF-11 comprising a structure represented by ₃ IRMOF-8 containing the structure.

Specific examples of ZIF include ZIF-68 including a structure represented by the general formula Zn (benzimidazolate) (2-nitroimidazolate); Zn (cyclobenzimidazolate) (2-nitroimidazolate) ZIF-69 containing the structural that; formula Zn _2; formula Zn (benzimidazolyl _rate) ZIF-9 containing ZIF-7, Co structure represented by (benzimidazolyl _{rate) 2} having a structure represented by ₂ ZIF-11 containing a structure represented by (benzimidazolate); ZIF-90 containing a structure represented by Zn (imidazolate-2-carboxaldehyde) ₂ ; Zn (4-cyanoimidazolate) of general formula (2 ZIF-82 represented by -nitroimidazolate); ZIF represented by the general formula Zn (imidazolate) (2-nitroimidazolate) 70; ZIF-79 represented by the general formula Zn (6-methylbenzimidazolate) (2-nitroimidazolate); and represented by the general formula Zn (6-bromobenzimidazolate) (2-nitroimidazolate) ZIF-81.

  As for the MOF and ZIF, commercially available ones may be used, and known methods described in WO2007 / 117117, Nature 453, 207-211 (8 May 2008), JP2014-156434, etc. May be manufactured.

  The catalyst used in the method of the present invention may contain other components other than the transition metal complex and the porous carrier. Other components are not particularly limited as long as the effects of the present invention are not impaired.

(Catalyst adjustment)
In the present invention, a method for preparing a catalyst (hereinafter simply referred to as “supported catalyst”) by supporting the transition metal complex on the porous carrier is not particularly limited, but these components may be used in any method. To form a complex of at least the transition metal complex and the porous carrier. In the composite, the transition metal complex may be fixed to the surface of the porous carrier or may be included in a porous structure, but at least a part of the transition metal complex is the porous carrier. It is preferable to be included in the porous structure.

As a method for preparing the supported catalyst, a known method can be employed, and examples thereof include the following methods (A) and (B).
(A) A method in which a granular transition metal complex and a porous carrier are physically mixed and then heated.
(B) A method in which a porous carrier is added to a solution of a transition metal complex, and the transition metal complex is impregnated in the porous carrier.
Hereinafter, methods (A) and (B) will be described.

(Method (A))
In the method (A), a particulate transition metal complex and a porous carrier are physically mixed and then heated to prepare a composition. The method of physically mixing the transition metal complex and the porous carrier is not particularly limited, and can be performed by a usual method such as mixing with a mortar or ball mill.
The heat treatment can be performed by heat treatment under vacuum conditions or in the presence of an inert gas such as He. Heating is preferably performed at 50 to 200 ° C., preferably 60 to 150 ° C., more preferably 80 to 120 ° C. for 24 to 150 hours.

(Method (B))
In the method (B), a porous carrier is added to the transition metal complex solution, the transition metal complex is impregnated in the porous carrier, and then the composition is prepared by heating, distilling, etc. as necessary. To do.

  The solvent is not particularly limited as long as the transition metal complex has good solubility. Examples include aromatic hydrocarbons such as benzene, toluene and xylene, halogenated aromatic hydrocarbons such as chlorobenzene, ethers such as tetrahydrofuran (THF), alcohols such as methanol, ethanol and isopropanol, dimethylformamide, dimethyl sulfoxide, and Water is mentioned. These may be used alone or in combination of two or more. A preferred solvent is THF.

  After the addition of the porous carrier, the mixture can be stirred, heated, the solvent or water is distilled off, and the resulting product is dried (vacuum drying). The heating temperature is preferably 25 to 100 ° C, more preferably 25 to 80 ° C, and further preferably 25 to 60 ° C.

  The amount of the transition metal complex supported in the supported catalyst is determined in consideration of the type of the transition metal complex and the like. For example, the amount is preferably 2 to 40 parts by weight, and 3 to 30 parts by weight with respect to 100 parts by weight of the porous carrier. More preferred is 5 to 20 parts by mass. If the amount is less than the lower limit, the amount of the transition metal complex supported is too small and the activity may be reduced. If the amount exceeds the upper limit, the excess transition metal complex is caused by blocking the pores of the porous carrier. There is a risk of reducing the catalytic activity.

  When the porous carrier is granular, the obtained granular supported catalyst may be used after being molded using a binder or the like, if necessary. The molding process can be performed by a method such as extrusion, compression, tableting, flow, rolling, spraying, etc., and a desired shape, for example, granular, pellet, spherical, cylindrical, plate, ring, clover It can be formed into a shape or the like.

<Method for producing carboxyl group-containing compound>
A carboxyl group-containing compound can be obtained by reacting carbon dioxide with another substance in the presence of the catalyst. For example, an unsaturated carboxylic acid such as (meth) acrylic acid can be produced using an alkene such as ethylene as the other substance. As for specific production steps, reaction conditions, and reaction product recovery methods, known ones described in Non-Patent Documents 1 and 2 and Patent Documents 1 and 2, etc. can be employed. A general explanation will be given by taking an example of producing an unsaturated carboxylic acid by reaction of CO ₂ with an alkene.

(Reaction between CO ₂ and alkene)
Alkenes that can be used in the present invention are, for example, ethylene, propylene, isobutene, butadiene, piperylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene. Of these, ethylene is preferred. These may be gaseous or liquid depending on the type.
CO ₂ can be used in a gaseous, liquid, or supercritical state. Although it is possible to use gas mixtures containing CO ₂ available on an industrial scale, it is desirable that they are substantially free of carbon monoxide.

CO ₂ and alkenes may also contain an inert gas such as nitrogen or a noble gas. However, the content of the inert gas is preferably less than 20% by volume based on the total amount of CO ₂ and alkene in the reactor.

This reaction is preferably performed using a solvent. That is, the reaction is preferably carried out by allowing the supported catalyst to be present in a solvent, introducing CO ₂ and alkene into the solvent, and bringing the catalyst into contact with the supported catalyst. Solvents include aromatic hydrocarbons such as benzene, toluene and xylene, halogenated aromatic hydrocarbons such as chlorobenzene, ethers such as tetrahydrofuran (THF), alcohols such as methanol, ethanol and isopropanol, dimethylformamide, dimethyl sulfoxide, and Water is mentioned. These may be used alone or in combination of two or more. A preferred solvent is THF.

About a reaction system, it may carry out by a batch type, may be carried out by a semibatch type, may be carried out by a continuous type, and may be carried out by the combination of a batch type, a semibatch type, and a continuous type. In the palindromic formula, the reaction is carried out by introducing the supported catalyst, CO ₂ and alkene into the solvent in the reactor. In the case of the semi-batch method, the reaction is carried out by previously charging either the supported catalyst or the raw material (CO ₂ or alkene) into the solvent in the reactor and continuously introducing the remaining raw material into the reactor. . In the case of the continuous type, the reaction is carried out by charging the supported catalyst in the solvent in the reactor and continuously introducing CO ₂ and alkene into the reactor. In the case of continuous operation, the liquid phase of the reaction mixture is supplied while supplying the reaction raw material into a fixed bed method, fluidized bed method, moving bed method, suspension bed method, stirring and mixing type or loop type reactor. It can be carried out by various methods such as an extraction method. When carried out batchwise or continuously using gaseous CO ₂ and alkenes under liquid phase conditions in a stirred and mixed reactor, CO ₂ and alkenes are taken up in the gas phase part of the reactor and You may supply to any one of a liquid phase part, and you may supply to both the gaseous-phase part and liquid phase part of a reactor.
Moreover, about a reaction apparatus, according to the reaction format to employ | adopt, a well-known reaction apparatus can be used suitably.

The reaction temperature is preferably 50 to 200 ° C, more preferably 80 to 150 ° C. Moreover, a pressure is 1-10 Mpa in absolute pressure normally, Preferably it is 2-8 Mpa. The molar ratio of CO ₂ and alkene fed to the reactor (CO ₂ / alkene) is usually 8-1, preferably 5-2.

  The obtained reaction product such as acrylic acid can be recovered by a known method such as distillation, but since the heterogeneous catalyst is used in the method of the present invention, the catalyst can be easily separated. Therefore, the reaction product can be easily recovered as compared with the conventional technique in which the reaction is performed in a homogeneous system.

[Example 1]
(1) Synthesis of metal complex catalyst ((dcpe) Ni (COD)) 1,2-bis (dicyclohexylphosphino) ethane (dcpe) (430 mg, 1.02 mmol) in tetrahydrofuran (THF) was mixed with nickel bis-1, The solution was gradually added dropwise to a THF solution of 5-cyclooctadiene (Ni (COD) ₂ ) (280 mg, 1,02 mmol). After stirring at room temperature for 3 hours, THF was distilled off in vacuo. Thereby, a metal complex catalyst ((dcpe) Ni (COD)) was obtained in a yield of 560 mg (yield: 93%).

(2) Synthesis of carrier (ZIF-68, 10.3A)
A mixed solution of 2-nitroimidazole in DMF (0.2 mol / L, 10 mL) and benzimidazole in N, N-dimethylformamide (DMF) (0.2 mol / L, 10 mL) was mixed with Zn (NO ₃ ). ₂ · 4H ₂ O in DMF (0.2mol / L, 10mL) was added to. The mixed solution was sealed and heated at 100 ° C. for 96 hours. The precipitate was filtered and washed with DMF (5 mL) three times. Then, it dried at 50 degreeC and 24 hours in vacuum. As a result, (ZIF-68) used as a carrier was obtained in a yield of 0.1 g (yield: 20%).

(3) Loading of metal complex catalyst on carrier ZIF-68 (50 mg) obtained above was weighed into a sample bottle and suspended in a THF solution of (dcpe) Ni (COD) (0.2 mmol / L). It was. After stirring at room temperature for 48 hours, solids were collected by centrifugation (3000 rpm, 30 minutes). The solid was washed twice with THF and dried at room temperature at 50 ° C. for 24 h. As a result, a supported catalyst was obtained in a yield of 62 mg.

(4) Catalytic reaction The supported catalyst (50 mg) obtained above and the sodium salt of 3-fluorophenol (100 equivalents relative to the catalyst) were introduced into a reaction tube and suspended in 15 mg of THF. The reaction tube was installed in a closed reaction apparatus, and ethylene (0.05 MPa) and carbon dioxide (0.1 MPa) were sequentially introduced. Then, it heated at 80 degreeC for 20 hours. After completion of the reaction, D ₂ O (20 mL, water substituted with deuterium) and 40 mL of diethyl ether were added to the reaction solution, and the product of the D ₂ O layer was analyzed by ¹ H-NMR. The turnover number (TON) obtained from the analysis result was 7.

[Comparative Example 1]
The experiment was conducted in the same manner as in the catalytic reaction of Example 1, except that 1,2-bis (dicyclohexylphosphino) ethane (dcpe) (29.5 mg) was introduced into the reaction tube instead of the supported catalyst. It was. As a result, TON was 3.

Claims (9)

A catalyst in which a transition metal complex is supported on a porous carrier having a communicating pore structure,
The transition metal complex has an activity of catalyzing a reaction using carbon dioxide as a starting material;
The porous carrier has a mode diameter of Log differential pore volume distribution (dV / dlog (D)) of 0.8 nm or more, and the total pore volume within the range of the mode diameter ± 2 nm is A carbon dioxide conversion catalyst characterized by being 80% or more of the total pore volume.   The catalyst for carbon dioxide conversion according to claim 1, wherein the porous carrier has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen and sulfur.   2. The carbon dioxide according to claim 1, wherein the porous carrier is at least one selected from the group consisting of silica, alumina, carbon, zeolite, activated carbon, clay sintered body, and organometallic structure. Conversion catalyst.   The catalyst for carbon dioxide conversion according to claim 3, wherein the porous carrier is an organometallic structure.   5. The carbon dioxide conversion catalyst according to claim 4, wherein the organometallic structure is a zeolite type imidazolate skeleton.   6. The carbon dioxide according to claim 1, wherein the porous carrier has a carbon dioxide adsorption amount per unit weight of 20 to 400 ml / g measured by a constant volume gas adsorption method. Conversion catalyst.   A carboxyl group-containing compound is obtained by reacting carbon dioxide with another substance in the presence of the carbon dioxide conversion catalyst according to any one of claims 1 to 6. Production method.   The method for producing a carboxyl group-containing compound according to claim 7, wherein the other substance is an alkene and the carboxyl group-containing compound is an unsaturated carboxylic acid.   The method for producing a carboxyl group-containing compound according to claim 7, wherein the other substance is ethylene and the carboxyl group-containing compound is (meth) acrylic acid.