Metal support and method for producing same, calcined body of metal support and method for producing same, reaction catalyst, and cation-modified carrier and method for producing same

Abstract

Disclosed is a metal support comprising: a cation-modified carrier comprising a carrier containing a metal oxide or carbon and polyvalent cations disposed on the carrier; and a metal-substituted polyoxometalate supported on the cation-modified carrier. The polyvalent cations include metal atoms. The metal-substituted polyoxometalate has a polyoxometalate having a missing site and a substituting metal atom introduced into the missing site.

Description

Metal carrier and method for producing same, calcined metal carrier and method for producing same, reaction catalyst, and cation-modified carrier and method for producing same

[0001] The present disclosure relates to a metal support containing a polyoxometalate and a method for producing the same, a calcined metal support and a method for producing the same, a reaction catalyst, and a cation-modified support and a method for producing the same.

[0002] Polyoxometalate compounds having metal-substituted polyoxometalates have been proposed as reaction catalysts for use in various chemical reactions such as photocatalysis (Patent Document 1).

[0003] International Publication No. 2020 / 009166

[0004] The present disclosure relates to a metal support having a metal-substituted polyoxometalate supported on a support, which can exhibit high catalytic activity.

[0005] The present disclosure includes at least the following: [1] A metal support comprising: a cation-modified support comprising a support containing a metal oxide or carbon and polyvalent cations disposed on the support; and a metal-substituted polyoxometalate supported on the cation-modified support, wherein the polyvalent cations comprise metal atoms, and the metal-substituted polyoxometalate comprises a polyoxometalate having defect sites and substituted metal atoms introduced into the defect sites. [2] The metal support according to [1], wherein the support comprises at least one material selected from the group consisting of titanium oxide, aluminum oxide, aluminosilicate, and tin oxide. [3] A reaction catalyst comprising the metal support according to [1] or [2]. [4] A calcined product of the metal support according to [1] or [2]. [5] A reaction catalyst comprising the calcined product according to [4]. [6] A cation-modified support comprising: a support containing a metal oxide or carbon; and polyvalent cations disposed on the support, wherein the polyvalent cations comprise metal atoms. [7] A method for producing a cation-modified support according to [6], comprising supporting polyvalent cations on a support containing a metal oxide or carbon in a dispersion containing the support and a dispersion medium. [8] The method according to [7], wherein the dispersion medium is alkaline. [9] A method for producing a metal support, comprising supporting a metal-substituted polyoxometalate on the cation-modified support according to [6] to form a metal support, the metal-substituted polyoxometalate having a polyoxometalate having defect sites and a substitutional metal atom introduced into the defect sites.

[10] A method for producing a calcined metal support, comprising calcining the metal support according to [1] or [2].

[0006] The present invention provides a metal support and a calcined product thereof that have a metal-substituted polyoxometalate supported on a support and exhibit high catalytic activity. In a dispersion containing the metal support, the metal-substituted polyoxometalate is stably supported on the support and is unlikely to be eluted into the dispersion medium. Therefore, the metal support or its calcined product can be easily recovered and reused after use. Even when reused, the metal support and its calcined product can maintain high catalytic activity.

[0007] 1 is a schematic diagram showing an example of a metal support; 2 is a diagram showing ultraviolet-visible absorption spectra of a filtrate obtained by filtering a dispersion containing a metal support, and a solution of a metal-substituted polyoxometalate compound; ３１ 1 shows P-NMR spectra of an aluminum polyoxocation / metal-substituted polyoxometallate composite and FT-IR spectra of a metal-substituted polyoxometallate.

[0008] The present invention is not limited to the following examples.

[0009] Fig. 1 is a schematic diagram showing an example of a metal support. The metal support 20 shown in Fig. 1 includes a support 1, a cation-modified support 5 containing a polyvalent cation 3, and a metal-substituted polyoxometalate 15 supported on the cation-modified support 5. The polyvalent cation 3 contains a metal atom and is disposed on the support 1. The metal-substituted polyoxometalate 15 includes a polyoxometalate 7 having defect sites 10 and a substituted metal atom M introduced into the defect sites 10. １ , M ２ The polyvalent cation 3 is interposed between the support 1 and the metal-substituted polyoxometallate 15, thereby supporting the metal-substituted polyoxometallate 15 on the cation-modified support 5. The metal support 20 may further have a counter cation (e.g., a cesium cation) of the metal-substituted polyoxometallate 15. The metal support 20 is mainly composed of a substituted metal atom M １ , M ２ can be used as a reaction catalyst based on the catalytic activity of

[0010] The carrier 1 contains a metal oxide or carbon. The carrier 1 may be, for example, particles, and the shape thereof is not particularly limited. When the carrier 1 is particles, the particle diameter (maximum width) may be 100 μm or less.

[0011] The carrier 1 contains a metal oxide or carbon. The carrier 1 containing a metal oxide or carbon can stably support the polyvalent cation 3 mainly through electrostatic interaction. The proportion of the metal oxide and carbon in the carrier 1 is, for example, 50% by mass or more, 60% by mass or more, based on the mass of the carrier 1. It may also be 70% by mass or more, 80% by mass or more, or 90% by mass or more, or 100% by mass or less. The carrier 1 may contain at least one selected from the group consisting of titanium oxide, aluminum oxide, aluminosilicates, and tin oxide. In this specification, metal silicates such as aluminosilicates are also classified as metal oxides.

[0012] The polyvalent cation 3 is supported on the surface of the support 1 through electrostatic interaction with the support 1, and can also hold the metal-substituted polyoxometalate 15 through electrostatic interaction. In the example of FIG. 1 , the polyvalent cation 3 is an aluminum polyoxocation (aluminum-13 cluster). However, the polyvalent cation 3 constituting the cation-modified support 5 is not limited to polyoxocations such as aluminum polyoxocations, and can be any divalent or higher cation containing a metal atom. Other examples of the polyvalent cation 3 include beryllium ions, magnesium ions, calcium ions, strontium ions, barium ions, lanthanoid ions, actinoid ions, zinc ions, cadmium ions, tin ions, lead ions, transition metal ions, gallium polyoxocations, and aluminum polyoxocations containing tungsten, germanium, gallium, silicon, or the like.

[0013] The amount of polyvalent cations 3 disposed on the support 1 may be, for example, 0.001% by mass or more and 99.9% by mass or less based on the mass of the support 1.

[0014] In the example of FIG. 1, the metal-substituted polyoxometallate 15 is a polyoxometallate 7 having one defect site 10 and two substitutional metal atoms M １ , M ２ and a substitutional metal atom M １ , M ２ An organic ligand L coordinated to １, L ２ The number of substitutional metal atoms introduced into one defect site is not particularly limited and can be, for example, 1 or 2. When one metal-substituted polyoxometallate 15 has multiple substitutional metal atoms, these substitutional metal atoms may be the same or different.

[0015] The metal-substituted polyoxometalate constituting the metal support is not limited to the example shown in FIG. 1 . Polyoxometalates are generally anions formed by condensation of oxoacids of transition metal atoms, and may contain heteroatoms that are elements different from the transition metal atoms. A polyoxometalate containing a heteroatom contains, for example, a heteroatom, multiple transition metal atoms, and multiple oxygen atoms bonded to the heteroatom or the transition metal atom. In this polyoxometalate, generally, multiple transition metal atoms are bonded to the heteroatom via oxygen atoms. One molecule of a polyoxometalate compound usually contains one heteroatom. The polyoxometalate compound may form a hydrate.

[0016] The polyoxometallates can be, for example, Keggin-type, Dawson-type, Anderson-type, or Waugh-type, although in this disclosure the polyoxometallates are most typically Keggin-type.

[0017] A mononuclear metal-substituted polyoxometalate having a Keggin-type polyoxometalate having one defect site and one substituted metal atom introduced therein can be represented, for example, by the formula (1): [XM １１ O ３９ {M １ (L １ ) ｐ ] ｎ－ In the formula, X represents a heteroatom, M represents a transition metal atom, and M １ represents a substituting metal atom, and L １ is a substituted metal atom M １represents an organic ligand coordinated to M. n represents an integer of 1 to 10. When M is a tungsten atom (W), n is usually 3, 4, or 5. For example, when X is a phosphorus atom, n is 5, when X is a silicon atom or a germanium atom, n is 6, and when X is a boron atom or an aluminum atom, n is 7. p is 1 or 2, and one substituted metal atom M １ An organic ligand L coordinated to １ Generally, the number of organic ligands L １ When is a monodentate ligand, p is 2, and the organic ligand L １ When is a bidentate ligand, p is 1. Here, the term bidentate ligand is used to include chelating ligands.

[0018] The heteroatoms may be selected from, for example, phosphorus atoms (P), silicon atoms (Si), germanium atoms (Ge), aluminum atoms (Al), and boron atoms (B).

[0019] Examples of the transition metal atom include tungsten atoms (W) and molybdenum atoms (Mo). Among these, when the transition metal atom is a tungsten atom, the metal support tends to exhibit even higher activity as a reaction catalyst.

[0020] A binuclear metal-substituted polyoxometalate having a Keggin type polyoxometalate having one defect site and two substituted metal atoms introduced therein can be represented, for example, by the formula (2): [XM １１ O ３９ {M １ (L １ ) ｐ}{{M ２ (L ２ ) ｑ ] ｎ－ ... (2) In formula (2), X, M, and p are defined as in formula (1). When X is a phosphorus atom, n is 3; when X is a silicon atom or a germanium atom, n is 4; and when X is a boron atom or an aluminum atom, n is 5. M １ and M ２ each independently represents a substituting metal atom; L １ and L ２each independently represents an organic ligand, and p and q each independently represent 1 or 2. １ , L ２ When is a monodentate ligand, p and q are 2, and the organic ligand L １ , L ２ When is a bidentate ligand, p and q are 1. Here, bidentate ligand is also used as a term including chelating ligands.

[0021] The polyoxometallate 7 illustrated in Fig. 1 is a Keggin-type polyoxometallate having one defect site 10, which is composed of one basic unit 7A formed by heteroatoms and oxygen atoms and eleven basic units 7B arranged around the basic unit 7A and formed by transition metal atoms and oxygen atoms. ４ (X represents a heteroatom), and has a tetrahedral structure. ６ (wherein M represents a transition metal atom), and has an octahedral structure.

[0022] The substituting metal atom introduced into the vacancy site of the polyoxometalate may be, for example, a noble metal, and may be at least one selected from platinum, palladium, rhodium, iridium, and ruthenium. The substituting metal atom may be divalent platinum, divalent palladium, or a combination thereof. For example, one of the substituting metal atoms M １ is divalent platinum, and the other substituting metal atom M ２ may be divalent palladium.

[0023] organic ligand L １ , L ２ are two ammonia (NH ３ ), two alkylamines having 1 to 3 carbon atoms, one ethylenediamine, a nitrogen-containing heteroaromatic compound (e.g., 2,2'-bipyridine), or a bidentate ligand having an aliphatic heterocycle containing two nitrogen atoms coordinately bonded to one substituted metal atom.

[0024] The alkylamine having 1 to 3 carbon atoms may be, for example, methylamine, ethylamine, or n-propylamine.

[0025] organic ligand L １ or L ２ The aliphatic heterocycle of the bidentate ligand may contain two nitrogen atoms and two or three carbon atoms consecutively arranged between the two nitrogen atoms as atoms constituting the ring. Examples of organic ligands having such aliphatic heterocycles include compounds represented by the following formulas (L1), (L2), (L3) and (L4). In these formulas, R １ and R ２ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms (for example, a methyl group).

[0026]

[0027] The amount of the metal-substituted polyoxometalate supported on the cation-modified support 5 may be, for example, 0.001% by mass or more and 99.9% by mass or less based on the mass of the support 1 .

[0028] Metal support 20 can be produced, for example, by a method including supporting polyvalent cations 3 on support 1 in a dispersion containing support 1 and a dispersion medium to form cation-modified support 5, and supporting metal-substituted polyoxometalate 15 on cation-modified support 5 to form metal support 20. Polyvalent cations may be generated from a metal compound (e.g., aluminum chloride) that is a precursor of the polyvalent cation in a dispersion containing support 1.

[0029] The dispersion medium for forming the cationically modified support 5 may contain water. The dispersion medium may be alkaline. In particular, a support 1 containing a metal oxide tends to be negatively charged in an alkaline dispersion medium and easily supports multivalent cations 3 stably. The temperature of the dispersion liquid for forming the cationically modified support 5 may be, for example, 20 to 100°C.

[0030] For example, in a dispersion containing the cation-modified support 5, the metal-substituted polyoxometalate 15, and a dispersion medium, the metal-substituted polyoxometalate 15 can be supported on the cation-modified support 5. In this case, the temperature of the dispersion may be, for example, 20 to 100° C. The dispersion medium may contain water.

[0031] A calcined body can also be obtained by calcining a metal support. The calcined body of a metal support typically contains a metal oxide containing a metal (e.g., tungsten) derived from the polyoxometalate and a substituted metal atom. Calcination of the metal support may be carried out in an air atmosphere or an inert gas atmosphere, or may be carried out under atmospheric pressure, reduced pressure, or increased pressure. In this specification, "calcining a metal support" means heating the metal support to an extent that some chemical property is irreversibly changed. For example, heating a metal support to 200°C or higher typically corresponds to calcining the metal support.

[0032] The metal support can be calcined so that at least a portion of the organic ligands bonded to the substituted metal atoms are released. The metal support from which the organic ligands have been released can also exhibit high catalytic activity. From this perspective, the metal support may be calcined until the organic ligands are substantially no longer contained. During calcination, the organic ligands can be easily released by heating the metal support to 200°C or higher. From the same perspective, the heating temperature for calcination may be 250°C or higher. The upper limit of the heating temperature is not particularly limited, but may be 1000°C or lower, or 550°C or lower. The heating time for calcination may be appropriately adjusted so as to enhance the catalytic activity of the calcined body, and may be, for example, 1 to 20 hours.

[0033] The metal support can exhibit excellent durability even at high temperatures. The metal support can be used as various reaction catalysts, such as a photocatalyst, an exhaust gas purification catalyst, or an oxidation-reduction reaction catalyst. When the metal support is used as a photocatalyst in a hydrogen generation device or the like, the support may include, for example, titanium oxide. When the metal support 20 is used as an exhaust gas purification catalyst, the support may include, for example, aluminum oxide or aluminosilicate. When the metal support is used as an oxidation-reduction reaction catalyst for a fuel cell, the support may include, for example, tin oxide or carbon.

[0034] The present invention is not limited to the following examples.

[0035] 1. Platinum-substituted polyoxometalate compound Cs-P-Pt The platinum-substituted polyoxometalate compound Cs-P-Pt (Cs3[α-PW)) has a Keggin-type polyoxometalate, two divalent platinum atoms introduced into the vacancy sites, a metal-substituted polyoxometalate having ammonia coordinated to the platinum, and a cesium cation. 11 O 39 {cis-Pt II (NH3)2}2]·8H2O) was prepared according to the method described in US Pat. No. 5,649,491.

[0036] 2. Cation-modified support Ti-Al 13 0.2006 g of TiO2 powder was dispersed in 100 mL of distilled water. 45 mL of 0.0625 M NaOH aqueous solution was added to the resulting dispersion. Next, while the dispersion was heated in a water bath at 80°C, an AlCl3 solution containing 0.2992 g of AlCl3·6H2O and 30 mL of distilled water was gradually added to the dispersion. After the entire AlCl3 solution was added, the dispersion was stirred for 15 minutes. The dispersion was then suction filtered through a membrane filter, and the solid on the filter was washed with 100 mL of distilled water. The solid on the filter was then dried for 1 hour using a suction airflow. The solid was further freeze-dried for 2 hours to isolate the TiO2-containing carrier and the aluminum polyoxocation ([ε-AlO4Al 12 (OH) 24 (H2O) 12 ] 7+ ) and a cation-modified support Ti-Al 13 0.2041 g of a white powder of the formula (I) was obtained.

[0037] 3. Metal support Cs-P-Pt-Al 13 -TiO2 cation-modified support Ti-Al 13The resulting solution was dispersed in 250 mL of distilled water to form a white dispersion. A clear yellow Cs-P-Pt solution containing 0.0219 g of Cs-P-Pt and 10 mL of distilled water was added, and the dispersion was stirred for 1.5 hours. The dispersion was suction filtered through a membrane filter, and the solid on the filter was washed with 100 mL of distilled water. The solid on the filter was then dried under suction for 1 hour. The solid was again dispersed in 200 mL of distilled water, and the white floating material was removed by decantation. The dispersion was suction filtered through a membrane filter, washed with 100 mL of distilled water, and the solid on the filter was then dried under suction for 1 hour. The solid was then freeze-dried for an additional 2 hours to obtain the cation-modified Ti-Al support. 13 Metal support Cs-P-Pt-Al 13 0.2099 g of a yellowish white powder of -TiO2 was obtained.

[0038] To confirm the elution of platinum, the filtrate obtained by suction filtration of the dispersion was analyzed by UV-visible spectroscopy. 13 Figure 1 shows the UV-visible absorption spectra of the Cs-P-Pt solution and the Cs-P-Pt solution. The filtrate showed almost no Cs-P-Pt absorption, confirming that the Cs-P-Pt was stably supported on the support without substantial elution.

[0039] 4. Analysis of the obtained metal support Cs-P-Pt-Al 13 -TiO2, solid ３１ The metal support was analyzed by P-NMR and elemental analysis. Table 1 shows the results of the elemental analysis. The calculated values ​​shown in Table 1 are values ​​calculated for an example of the estimated composition of the metal support. However, considering that the analyzed sample is not a molecule and analytical errors are also taken into account, the metal support may actually have a composition different from the estimated composition. Figure 3 shows the metal support Cs-P-Pt-Al 13 -TiO2 solid ３１ The P-NMR spectrum shows a clear signal of P originating from Cs-P-Pt, suggesting that Cs-P-Pt is supported on the support while maintaining a fairly uniform orientation. 31P-NMR: δ-13.28ppm (Reference to an external standard of saturated aqueous solution of phosphoric acid)

[0040]

[0041] 5. Calcined supported catalyst Cs-P-Pt-Al 13 The sintered metal support Cs-P-Pt-Al was obtained by heating the sintered TiO2 at 700°C for 5 hours. 13 -TiO2-700-5 was obtained.

[0042] 6. Photocatalytic reaction test Each metal carrier containing the amount of platinum shown in Table 2, 2.5 μmol of Eosin Y, 2.5 μmol of K5SiW 11 {Al(OH)}O 39 A reaction solution for the photocatalytic reaction of generating hydrogen from water was prepared by mixing 10 mL of 7H2O, 10 mL of water, and 100 mM triethanolamine (TEA). The reaction solution was irradiated with light of 440 nm or longer at 25°C, and the amount of hydrogen generated by the photocatalytic reaction was quantified. ２ The amount of produced carbon and the catalyst turnover number (TON, 2 × (H ２ The amount of Pt produced (mol) / Pt atomic weight (mol) was measured. In Table 2, in Test Examples #2 and #5, Cs-P-Pt or its calcined form Cs-P-Pt-700-5 and TiO2 particles were added to the reaction solution. In Test Examples #3 and #6, the metal carrier recovered from the reaction solution after 6 hours of light irradiation in the photocatalytic reaction test of Test Example #1 or #5, washed with water, and freeze-dried was used. In Test Example #7, a photocatalytic reaction test was conducted on a reaction solution containing a commercially available platinum-supported catalyst (Platinum Black) and TiO2 particles.

[0043]

[0044] As shown in Table 2, the metal support Cs-P-Pt-Al 13 -TiO2 and its sintered body Cs-P-Pt-Al 13It was confirmed that TiO2-700-5 exhibited high catalytic activity, and that these metal supports maintained their high catalytic activity after recycling.

[0045] 7. Aluminum Polyoxocation / Metal-Substituted Polyoxometalate Composite: 0.1214 g (0.50 mmol) of AlCl3·6H2O was dissolved in 20 mL of distilled water. 45 mL of 0.025 M NaOH aqueous solution was added to the resulting solution in a water bath at 80°C. The resulting mixture was stirred for 20 minutes to obtain an alkaline AlCl3 solution. 0.1005 g (0.027 mmol) of Cs-P-Pt was dissolved in 40 mL of water at 80°C to obtain a Cs-P-Pt solution. 60 mL of alkaline AlCl3 solution was added to the Cs-P-Pt solution, resulting in the formation of a yellow-white precipitate. The mixture was stirred at room temperature for two days, after which the precipitate was collected by filtration and freeze-dried to obtain the product powder. Figure 4 shows the aluminum polyoxocation / metal-substituted polyoxometalate composite (Al 13 The FT-IR spectra of the aluminum polyoxocations (Cs-P-Pt) and Cs-P-Pt were compared. Comparison of the FT-IR spectra suggested that the aluminum polyoxocations and the metal-substituted polyoxometalates formed complexes through electrostatic interactions. This result suggests that the metal-substituted polyoxometalates are stably supported on the cation-modified support through electrostatic interactions with multivalent cations.

[0046] 1... support, 3... polyvalent cation, 5... cation-modified support, 7... polyoxometalate, 10... defect site, 15... metal-substituted polyoxometalate, 20... metal support, M １ , M ２ ...Substituted metal atom, L １ , L ２ ...Organic ligand.

Claims

1. a cation-modified support comprising a support containing a metal oxide or carbon and a multivalent cation disposed on the support; a metal-substituted polyoxometalate supported on the cation-modified support; Including, the polyvalent cations include beryllium ions, magnesium ions, calcium ions, strontium ions, barium ions, lanthanide ions, actinide ions, zinc ions, cadmium ions, tin ions, lead ions, transition metal ions, aluminum polyoxocations, or gallium polyoxocations; The metal-substituted polyoxometalate is a polyoxometalate having defect sites; a substitutional metal atom introduced into the defect site; having Metal carrier.

2. 2. The metal support according to claim 1, wherein the support comprises at least one selected from the group consisting of titanium oxide, aluminum oxide, aluminosilicate, and tin oxide.

3. A reaction catalyst comprising the metal support according to claim 1 or 2.

4. A sintered body of the metal support according to claim 1 or 2.

5. A reaction catalyst comprising the calcined body according to claim 4.

6. a support comprising a metal oxide or carbon; a multivalent cation disposed on the support; Including, the polyvalent cations include beryllium ions, magnesium ions, calcium ions, strontium ions, barium ions, lanthanide ions, actinide ions, zinc ions, cadmium ions, tin ions, lead ions, transition metal ions, aluminum polyoxocations, or gallium polyoxocations; Cation-modified carriers.

7. 7. A method for producing a cationically modified support according to claim 6, comprising supporting polyvalent cations on a support containing a metal oxide or carbon in a dispersion liquid containing the support and a dispersion medium.

8. The method of claim 7 wherein the dispersion medium is alkaline.

9. a metal-substituted polyoxometalate supported on the cation-modified support of claim 6 to form a metal support; The metal-substituted polyoxometalate is a polyoxometalate having defect sites; a substitutional metal atom introduced into the defect site; having A method for producing a metal support.

10. A method for producing a sintered metal support, comprising sintering the metal support according to claim 1 or 2.

11. a support containing at least one selected from the group consisting of titanium oxide, aluminum oxide, aluminosilicate, and tin oxide, or carbon; a multivalent cation disposed on the support; Including, the polyvalent cation comprises a metal atom; A method for producing a cationically modified support, comprising: The method includes causing a carrier to support a polyvalent cation in a dispersion containing a carrier containing at least one selected from the group consisting of titanium oxide, aluminum oxide, aluminosilicate, and tin oxide, or carbon, and a dispersion medium; The method wherein the dispersion medium is alkaline.