JP7043072B2 - Gold composite material, its manufacturing method and gold nanocatalyst - Google Patents

Description

The present invention relates to a novel gold composite material having higher catalytic activity than a conventional gold nanoparticle catalyst, a method for producing the same, and a gold nanocatalyst using the same.

It is known that gold exhibits high catalytic ability when supported on a carrier as nanoparticles, and various gold nanoparticle catalysts have been proposed.

For example, in Patent Document 1, as the base metal oxide of the carrier supporting the gold nanoparticles, the base metal oxide is one or more selected from the group consisting of MoO ₃ and CuO, or a composite containing one or more of them. A gold nanocatalyst has been proposed that can selectively produce acetaldehyde from ethanol in the gas phase by selecting an oxide.

Further, Patent Document 2 discloses that a surface gold immobilization catalyst in which gold nanoparticles are immobilized on a carrier surface is used as a catalyst used in the production of a pyridine compound, and hydroxy is used as the surface gold immobilization catalyst. Disclosed that apatite (HAP), titania (TiO ₂ ), alumina (Al ₂ O ₃ ), magnesia (MgO), silica (SiO ₂ ), ceria (CeO ₂ ), activated carbon (C) and the like are used as carriers. There is.

JP-A-2015-178525 Japanese Unexamined Patent Publication No. 2012-121844

However, it may not be possible to say that sufficient catalytic activity is still obtained for the particles carrying the gold nanoparticles according to the above proposal, such as cases where the activity is insufficient or there are few reaction systems to which the particles can be applied. ..
Therefore, an object of the present invention is to provide a novel gold composite material having higher catalytic activity than a conventional gold nanoparticle catalyst, a method for producing the same, and a gold nanocatalyst using the same.

As a result of diligent studies to solve the above-mentioned problems, the present inventors expected that if the carrier is an acidic substance, the behavior different from that of the conventional catalyst can be obtained, and the above-mentioned problems can be solved. As a result of various studies on a method for producing a gold composite material in which gold fine particles are supported on an acidic carrier that cannot be produced, among many production methods, a colloidal solution of gold fine particles is prepared in advance to be acidic. It has been found that a gold composite material obtained by supporting gold fine particles on an acidic carrier can be obtained by a method of reacting with a metal oxide, and the present invention has been completed.

That is, the present invention has been made based on the above findings, and is as follows.
1. 1. A gold composite material composed of a carrier and gold fine particles supported on the carrier.
The gold composite material, wherein the carrier is an acidic solid metal oxide.

2. 2. The solid metal oxide
1. The gold composite material according to 1 above, which is one or more selected from the group consisting of niobium oxide, polyoxometallate, tungsten oxide, tantalum oxide, molybdenum oxide, and vanadium oxide.
3. 3. 1. The gold composite material according to 1, wherein the supported gold fine particles have a particle size of 5 nm or less.
4. 1. The gold composite material according to 1, wherein the specific surface area of the solid metal oxide is 20 m ² / g or more.
5. The gold composite material according to claim 4, wherein the density of the gold fine particles supported on the carrier is 2 μmol · m ^-2 or less.
6. The solid metal oxide is a crystal structure formed by crystal lattices constituting the solid metal oxide, and is a lattice point formed by one crystal lattice or a group of a plurality of crystal lattices. And the voids formed around the lattice points, the voids having normal voids having the same size as each lattice point or the crystal lattice, and large voids larger than each lattice point. The gold composite material according to 1 as a feature.
7. 6. The gold composite material according to 6, wherein the capacity of the large void (mesopore capacity) is 0.1 cm ³ / g or more.
A gold nanocatalyst comprising the gold composite material according to any one of 8.1 to 7 and used for oxidation of components derived from biomass.
The method for producing a gold composite material according to 9.1.
It is provided with a supporting step of supporting gold fine particles using an acidic solid metal oxide and a gold colloidal solution.
In the above loading step,
As the solid metal oxide, one having a high specific surface area of 20 m ² / g or more is used.
A method for producing a gold composite material, which comprises using a gold colloidal solution containing gold particles having a particle size of 5 nm or less as the gold colloidal solution.
A gold nanocatalyst for an oxidation reaction of an organic compound, which comprises the gold composite material described in 10.1.

The gold composite material of the present invention is a novel composite material, and has higher catalytic activity than a conventional gold nanoparticle catalyst as a catalyst.
Further, the method for producing a gold composite material of the present invention can easily and easily produce the gold composite material of the present invention, which has been considered difficult to produce in the past.
Further, the gold nanocatalyst of the present invention has high catalytic activity.

FIG. 1 is a surface photograph (drawing substitute photograph) of the gold composite material obtained in Example 1 by TEM. FIG. 2 is a chart showing the CO oxidation reaction results of the gold composite material obtained in Example 1. FIG. 3 is a chart showing the CO oxidation reaction results of the gold composite material obtained in Example 2. FIG. 4 is a chart showing the relationship between the specific surface area of the carrier and the catalytic activity in Example 4. FIG. 5 is a chart showing the relationship between gold density and catalytic activity in Example 4.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
The gold composite material of the present invention is a gold composite material composed of a carrier and gold fine particles supported on the carrier, and the carrier is an acidic solid metal oxide.
<Carrier>
The carrier used in the present invention is an acidic solid metal oxide.
Here, "acidic" means that the pH of the isoelectric point is 5 or less in the present specification.
Specific examples of the acidic solid metal oxide include the following compounds.
Niobide oxide, polyoxometalate (specifically, for example, silicotungstic acid, molybdenum acid, phosphotungstic acid, phosphomolybdic acid, ammonium molybdate, ammonium tungstate, etc.) Tungsten oxide, tantalum oxide, molybdenum oxide, vanadium oxide, etc. ..
Among them, one or more selected from the group consisting of niobium oxide, polyoxometallate, tungsten oxide, tantalum oxide, molybdenum oxide, and vanadium oxide is particularly preferably used.
The shape of the carrier is not particularly limited, but it is preferable that it has a complicated three-dimensional structure, and particularly in niobium oxide, polyoxometallate, tungsten oxide, tantalum oxide, molybdenum oxide, and vanadium oxide, MO ₄ tetrahedron is used. In a basic unit consisting of a body, MO ₅ tetrahedron, MO ₆ hexahedron or MO ₅ trihedral, oxygen atoms are bridged between the basic units by dehydration condensation reaction and bonded via apex, ridge or surface. It is preferably a structure. Among these, niobium oxide obtained by hydrothermal reaction is particularly preferable because of its high catalytic activity. In the present invention, the specific surface area of the carrier is preferably 20 to 500 m ² / g, more preferably 100 to 300 m ² / g, and the specific surface area is 150 to 300 m ² / g. Is the most preferable. As described above, it has been found that gold fine particles are supported even with the above-mentioned acidic solid metal oxide when preferably having a specific specific surface area and further having a complicated three-dimensional structure. It greatly contributed to the completion of the present invention.
The particle size of the carrier is preferably 5 to 1000 nm in average particle size, and more preferably 5 to 500 nm.
Here, the specific surface area and the average particle size of the carrier are measured as follows.
-The specific surface area of the carrier was measured using a high-precision gas adsorption amount measuring device manufactured by Microtrac Bell. 0.2 g of the carrier was set in the reactor, and the pretreatment temperature was set to 300 ° C. for 2 hours. The nitrogen adsorption isotherm was measured at the liquid nitrogen temperature and calculated by the BET method.
-A gold-supported sample was measured with an average particle size transmission electron microscope (manufactured by JEOL Ltd.). Specifically, the sample was prepared by ultrasonically dispersing it in ethanol and dropping it on a microgrid. The average particle size of gold was calculated by calculating the diameters of 200 or more gold particles and obtaining the average value of these.

The solid metal oxide is a crystal structure formed by crystal lattices constituting the solid metal oxide, and is a lattice point formed by one crystal lattice or a group of a plurality of crystal lattices. And voids formed around the grid points, the voids have normal voids having the same size as each grid point or the crystal lattice, and large voids larger than each grid point. preferable.
Here, the crystal lattice means each atom or molecule constituting the solid metal oxide, and the lattice point usually means the connection point of each atom or molecule in the aggregate of these atoms or molecules.
The volume of the large void (mesopore volume) is preferably 0.1 cm ³ / g or more.
It is more preferably 0.2 to 0.7 cm ³ / g.
Here, the mesopore volume is the BJH method (EP Barrett, LG Joyner, PH Halenda: J. Am. Calculated according to Chem. Soc., 73, 373 (1951)).

<Gold particles>
The gold fine particles in the present invention are so-called gold nanoparticles or gold cluster particles supported on the carrier, and the particle size thereof is preferably 5 nm or less, more preferably 0.1 to 2 nm. The above particle size does not mean that all of the supported gold fine particles have the above-mentioned particle size, but means that the gold fine particles having the above-mentioned preferable range of particle size may be supported.
Here, the particle size of the gold fine particles is an average particle size, and the particle size of each gold particle carried on the carrier is visually compared with the particle size of the gold fine particles confirmed by TEM with the reference length. It is calculated and calculated by calculating the average value according to the conventional method.
The content of the gold fine particles in the gold composite material of the present invention is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, and 0.1 to 2% by weight in the entire gold composite material. % Is the most preferable.
The density of the gold fine particles is preferably 2 μmol · m ^-2 or less, more preferably 0.1 to 0.15 μmol · m- ² . This density is particularly effective when the specific surface area of the carrier is in the above-mentioned preferable range, and is particularly effective in that the activity is increased even with a small gold density.
The density is obtained as follows.
Density of gold fine particles = gold carrier amount (% by weight) / 100/197 (molecular weight of gold, g / mol) / specific surface area of carrier (m ² / g)

<Structure>
In the gold composite material of the present invention, the gold fine particles are supported on the surface of the carrier, but when the carrier is a three-dimensional structure as described above, cavities may be formed inside the carrier. In some cases, the gold fine particles may be supported on the surface of the carrier in the cavity.

<Manufacturing method>
The above-mentioned gold composite material of the present invention can be produced by performing the following steps.
That is, it can be obtained by performing a supporting step of supporting gold fine particles using an acidic solid metal oxide and a gold colloidal solution (hereinafter, this production method is referred to as a colloidal method). Since it is the production method of the present invention and is a particularly preferable method as the above-mentioned method for producing the gold composite material of the present invention, the colloidal method will be mainly described below, but the gold composite material of the present invention is carried out. Obtained by a method such as a precipitation reduction method (DP method), a precipitation precipitation method (DR method), a DP urea method, a solid phase mixing method (SG method), or a colloidal precipitation method (One-pot method), which will be described in detail in the examples. You can also do it.
(Supporting process)
In the carrying step, the solid metal oxide having a high specific surface area of preferably 20 m ² / g or more, more preferably 100 m ² / g or more, and more preferably 150 m ² / g or more is used. As the colloidal gold solution, a colloidal gold solution containing gold particles having a particle size of 5 nm or less, preferably 0.5 to 3 nm is used. When the specific surface area is out of the above range and the particle size of the gold particles exceeds 5 nm, the gold fine particles are not supported.
Then, to the colloidal gold solution, preferably 0.01 to 20 parts by weight, more preferably 0.1 to 5 parts by weight of gold is added to 100 parts by weight of the solid metal oxide, and the mixture is stirred to form a suspension. The pH of the suspension is adjusted to 8 to 11 with sodium hydroxide or the like, and the mixture is stirred and mixed for 30 minutes to 2 hours. Then, 50 to 200 parts by weight of sodium hydride was added to 100 parts by weight of gold in the suspension, the suspension was suction-filtered, washed, dried at 60 to 100 ° C., and then 200. By firing in air at ~ 500 ° C. for 2 to 10 hours, a gold composite material in which gold fine particles are supported on the surface of a solid metal oxide can be obtained.
Further, the solid metal oxide and the colloidal gold solution can be produced as follows.
(Manufacturing process of solid metal oxide)
For example, in order to obtain niobium oxide, NH ₄ {NbO (C ₂ O ₄ ) ₂ (H ₂ O)} and nH ₂ O (Nb: 6 mmol) are dissolved in water and 10 to 300 ° C. It can be obtained by hydrothermal synthesis for 30 hours, suction filtration of the obtained solid, drying at 50 to 100 ° C., and heat treatment at 350 to 500 ° C. for 1 to 4 hours.
(Manufacturing process of colloidal gold solution)
The gold colloidal solution can be formed by dissolving a compound that forms a colloid in water in water. As the compound that can be used at this time, tetrachloroauric acid, HAuCl _4, Au (en) ₂ Cl ₃ , etc. (en: ethylenediamine group) can be used, and usually, a toluene solution of this tetrachloroauric acid and tetraoctylam can be used. It can be obtained by putting a toluene solution of ammonium bromide into water in the presence of sodium boron hydride. When HAuCl ₄ is used, it can be obtained by putting a toluene solution of tetraoctylammonium bromide into water together with HAuCl ₄ in the presence of boron hydride-proof sodium. Further, Au (en) ₂ Cl ₃ can be obtained by putting it in water as it is. In addition, sodium borohydride may be added at the time of supporting as described above, and the gold colloidal solution may be prepared without adding in particular in colloidalization.
The concentration of the gold particles in the gold colloidal solution is preferably 0.1 to 20% by weight, more preferably 0.5 to 5% by weight.

<Gold nanocatalyst>
The gold nanocatalyst of the present invention comprises the above-mentioned gold composite material of the present invention and functions as a catalyst for an oxidation reaction of an organic compound. The gold nanocatalyst of the present invention can be used without particular limitation as long as it is an oxidation reaction of an organic compound, but it can be particularly preferably applied to the following reaction systems.
(Applicable reaction system)
・ CO oxidation reaction CO + 1 / 2O ₂ → CO ₂
・ Glucose oxidation C ₆ H ₁₂ O ₆ + 1 / 2O ₂ → C ₆ H ₁₂ O ₇
・ Oxidation of glycerol C ₃ H ₈ O ₃ + 1 / 2O ₂ → C ₃ H ₆ O ₃ (glyceraldehyde) + H ₂ O
C ₃ H ₈ O ₃ + 1 / 2O ₂ → C ₃ H ₆ O ₃ (dihydroxyacetone) + H ₂ O
・ Oxidation of furfural (C ₄ H ₃ O) CHO + 1 / 2O ₂ → (C ₄ H ₃ O) COOH (2-furancarboxylic acid)
・ Oxidation of 5-hydroxymethylfurfural C ₆ H ₆ O ₃ + 3 / 2O ₂ → C ₆ H ₄ O ₅ (2,5-furandicarboxylic acid) + H ₂ O
(Effective concentration)
The catalyst of the present invention can be used in a gas phase reaction system or a liquid phase reaction system with respect to the above organic compounds (CO, glucose, etc.) which are the target substances of the reaction, and the effective concentration thereof is not particularly limited and the reaction is carried out. The amount of the target substance may be sufficient to come into contact with the catalyst.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Example 1]
NH ₄ {NbO (C ₂ O ₄ ) ₂ (H ₂ O)} · nH ₂ O (Nb: 6 mmol) was dissolved in 40 mL of water, and hydrothermal synthesis was carried out at 175 ° C. for 24 hours.
The obtained solid was suction-filtered, dried at 80 ° C., and heat-treated at 400 ° C. for 2 hours to obtain niobium oxide having a higher-order structure (hereinafter referred to as “NbOx-HT”). The BET specific surface area (according to the above-mentioned measuring method) of the obtained NbOx-HT was 208 m ² / g, and the mesopore volume (according to the above-mentioned measuring method) was 0.563 cm ³ / g.
Dissolve Au (en) ₂ Cl ₃ (0.0507 mmol) in 51 mL of water so that the amount of gold charged is 1% by weight, add niobium oxide (1 g) prepared by hydrothermal synthesis, and suspend. The liquid was adjusted.
The pH of the obtained suspension was adjusted to 9 with NaOH and stirred for 1 hour, and NaBH ₄ was added. Then, the suspension was washed by suction filtration, dried at 80 ° C., and then air calcined at 300 ° C. for 4 hours to obtain a gold composite material.
The obtained gold composite material was subjected to X-ray analysis. As a result, it was found that the material was composed of metal oxide and gold.
In addition, the surface was observed with a normal TEM (transmission electron microscope). The results are shown in FIG.
Then, a CO oxidation reaction was carried out using the obtained gold composite material. The reaction was carried out in a fixed bed distribution device, 0.15 g of gold composite material was set, pretreatment was performed at 250 ° C. under an air flow for 1 hour, and 1% CO / air was distributed at 50 mL / min for the reaction. Was done.
Similarly, a gold composite material that supports gold fine particles in amorphous hydrous niobium (Nb ₂ O ₅・ nH ₂ O, purchased from Soekawa Kagaku) and amorphous niobium oxide (Nb ₂ O ₅ , purchased from Wako Pure Chemical Industries, Ltd.). Got When the gold particle size was calculated by the Scherrer equation from the diffraction peak of Au (111) in the XRD pattern, it was 4.9 nm (Au / NbO _x -HT, the above-mentioned gold composite material of the present invention) and 18.5 nm (Au), respectively. / Nb ₂ O ₅ · nH ₂ O), 43.7 nm (Au / Nb ₂ O ₅ ). When Au / NbO _x -HT was observed by TEM, gold fine particles of about 5 nm were supported as shown in FIG. 1, which was consistent with the particle size confirmed by XRD.
Then, a CO oxidation reaction was carried out using the prepared gold composite material. The results are shown in FIG. When only NbO _x -HT was used, the activity was extremely low, and CO was not converted at 250 ° C. On the other hand, it can be seen that the activity is significantly improved when gold is supported on niobium oxide. Compared with the reaction temperature (T _1/2 ) when the conversion rate of CO shows 50%, the gold composite material of the present invention has T _1/2 = 76 ° C. (Au / NbO _x −HT), and Au / Nb ₂ O ₅ · nH ₂ O was T _1/2 = 194 ° C. In addition, Au / Nb ₂ O ₅ had a conversion rate of 29% at 250 ° C.

[Example 2]
H ₄ [α-SiW ₁₂ O ₄₀ ] and nH ₂ O and Cs ₄ [α-SiW ₁₂ O ₄₀ ] and nH ₂ O (Cs-POM) were synthesized according to a conventional method. The BET specific surface area (according to the above-mentioned measuring method) of the obtained Cs-POM was 175 m ² / g, and the mesopore volume (according to the above-mentioned measuring method) was 0.128 cm ³ / g. The gold supporting step was carried out by using the following colloid mixing method (Sol Immobilization, SI) and solid phase mixing method (Solid Grinding, SG) to obtain a gold composite material. At this time, the amount of gold charged was 1 part by weight with respect to 100 parts by weight of the carrier.
SI method: A gold colloid protected with dodecanethiol was prepared according to a conventional method. This gold colloid was dissolved in 40 mL of hexane and added dropwise to Cs-POM separately dispersed in 50 mL of hexane. After stirring for 1 hour, the mixture was recovered, vacuum dried overnight, and calcined in air at 300 ° C. for 2 hours.
SG method: 1.0 g of Cs-POM and 16.6 mg of [AuMe ₂ (acac)] were mixed in an agate mortar for 20 minutes and calcined in air at 300 ° C. for 4 hours.
A CO oxidation reaction was carried out using the obtained gold composite material. The CO oxidation reaction was carried out using a fixed-bed flow type catalytic reaction apparatus under the conditions of a catalyst amount of 150 mg, 1 volume% CO in air 50 mLmin ^-1 (SV 20,000 mL H ^-1 g _cat ^-1 ). Quantification was performed by GC (TCD).
It was shown that the gold composite materials obtained by either the SI method or the SG method showed high low-temperature activity against the CO oxidation reaction and were useful as a gold nanocatalyst. The temperatures (T _1/2 ) at which the reaction rate was 50% were −67 and −36 ° C., respectively. In particular, the result of the SI method is a very high CO oxidation activity as compared with the 1 wt% Au / MO _x reported so far, and the gold of the present invention using an acidic solid metal oxide as a carrier is used. You can see the superiority of composite materials.
Further, when TEM observation was performed on the obtained gold composite material, gold particles having a diameter of 3-4 nm were mainly observed, and large particles having a diameter of about 10 nm were also observed. It is known that the activity is relatively low, and it does not match the result of the oxidation reaction. Therefore, it is considered that gold clusters that are too small to be observed by TEM are carried.

As is clear from the above results, it was found that the metal composite material of the present invention, which supports gold fine particles on an acidic solid metal oxide, is useful as a gold nanocatalyst.
In particular, when the solid metal oxide used as a carrier in the present invention is obtained by a hydrothermal reaction, it is a compound having a higher-order structure and has a complicated three-dimensional structure. It was found that excellent catalytic activity is exhibited by supporting gold fine particles on a molecular compound.

[Example 3]
(Solid metal oxide)
The NbO _x -HT obtained in Example 1 was prepared.
In addition, the following solid metal oxides were prepared separately.
・ Nb ₂ O ₅・ nH ₂ O
Purchased from Soekawa Rikagaku BET specific surface area (according to the above-mentioned measurement method) 19 m ² / g, mesopore volume (according to the above-mentioned measurement method) 0.002 cm ³ / g.
・ Nb ₂ O ₅
Purchased from Wako Pure Chemical Industries, Ltd. BET specific surface area (according to the above-mentioned measuring method) 6 m ² / g, mesopore volume (according to the above-mentioned measuring method) 0.001 cm ³ / g.
・ ANO
NH ₄ {NbO (C ₂ O ₄ ) ₂ (H ₂ O)} and nH ₂ O purchased from Aldrich were obtained by calcining at 400 ° C. BET specific surface area (according to the above-mentioned measuring method) 2.3 m ² / g, mesopore volume (according to the above-mentioned measuring method) 0.000 cm ³ / g.
(Supporting gold)
A gold composite material on which gold fine particles were supported was obtained by each of the following methods.
・ DP (precipitation precipitation method), DR (precipitation reduction method)
HAuCl ₄ (0.2478M, 0.0507 mmol) or Au (en) ₂ Cl ₃ (0.0507 mmol) was dissolved in 51 mL of water and NbO _x -HT (1 g) was added. The mixture was stirred for 1 hour while adjusting the pH to 9 with NaOH or aqueous ammonia. Then, the suspension is washed by suction filtration, dried at 80 ° C. or vacuum dried (Vac), and then air-baked (air) at 300 ° C. for 4 hours or under hydrogen (10%) flow (H ₂ ). ) Treatment at 300 ° C. for 4 hours to obtain a gold composite material (gold carrying amount: 1% by weight). (The gold composite material obtained by this method is referred to as DP). In the case of the precipitation reduction method (hereinafter, the composite material obtained by this method is referred to as DR), HAuCl ₄ (0.2478M, 0.0507 mmol) or Au (en) ₂ Cl ₃ (0.0507 mmol). ) Was dissolved in 51 mL of water and NbO _x -HT (1 g) was added. NaBH ₄ was added to pH 7, 9, or 10 after stirring for 1 hour while adjusting with NaOH water. Then, the suspension was washed by suction filtration, dried at 80 ° C., and then air-baked at 300 ° C. for 4 hours to obtain a gold composite material (gold carrying amount: 1% by weight).
・ SG (solid phase mixing method)
Me ₂ Au (acac) (0.0507 mmol) and NbO _x -HT (1 g) were mixed and kneaded in an agate mortar for 20 minutes, and the obtained kneaded product was calcined at 300 ° C. to gold. A composite material was obtained.
-DP urea method HAuCl ₄ (0.2478M, 0.0507 mmol) or Au (en) ₂ Cl ₃ (0.0507 mmol) was dissolved in 51 mL of water, 3.75 g of urea was added, and NbO _x -HT was added. (1 g) was added. The mixture was stirred at 90 ° C. for 4 hours. Then, the suspension was washed by suction filtration, dried at 80 ° C., and then air fired at 300 ° C. for 4 hours to obtain a gold composite material (gold carrying amount: 1% by weight).
・ One-pot (joint precipitation method)
Dissolve NH ₄ {NbO (C ₂ O ₄ ) ₂ (H ₂ O)}, nH ₂ O (Nb: 6 mmol) and HAuCl ₄ or Au (en) ₂ Cl ₃ in 45 mL of water at 175 ° C. Hydrothermal synthesis was carried out for 24 hours to obtain a solid substance. The obtained solid material was suction-filtered and then dried at 80 ° C. to obtain an oxide. After drying, it was heat-treated at 400 ° C. for 2 hours under air to obtain a gold composite material.
-The gold composite material of the present invention in Example 2 of the colloidal mixing method was used. A gold colloid (AuSH-R) protected with dodecanethiol was prepared according to a conventional method. This gold colloid was dissolved in 40 mL of hexane and added dropwise to NbO _x -HT separately dispersed in 50 mL of hexane. After stirring for 1 hour, the mixture was recovered, vacuum dried overnight, and calcined in air or in vacuum at 300 ° C. for 2 hours.
Each of the obtained composite materials was subjected to a CO oxidation reaction in the same manner as in Example 1. The results are shown in Table 1. As is clear from the results shown in Table 1, when only NbOx-HT was used, the activity was extremely low, and CO was not converted at 250 ° C. On the other hand, it can be seen that the activity is significantly improved when gold is supported on niobium oxide. When compared at the reaction temperature (T1 / 2) when the conversion rate of CO is 50%, the gold composite material of the present invention has T1 / 2 = 76 ° C. (No. 8), whereas the comparison target is T1 / 2 = 194 ° C. (No. 11, Au / Nb ₂ O ₅ · nH ₂ O). In addition, Au / Nb ₂ O ₅ (No. 12) had a conversion rate of 29% at 250 ° C.

In Table 1, each note is as follows.
* 1-7: Catalyst (gold composite material, gold content 1% by weight) 0.15 g, flow rate (flow rate) 50 mLmin ^-1 (1% CO / Air),
The particle size was calculated by the Scherrer formula.

[Example 4]
As shown in the table below, a gold composite material was prepared in the same manner as in the colloidal mixing method of Example 3 except that the type and specific surface area of the carrier were variously changed and the density of the supported gold was also changed. .. The obtained gold composite material was subjected to a CO oxidation reaction in the same manner as in Example 1 to confirm its activity as an oxidation catalyst.
The relationship between the specific surface area of the carrier and the catalytic activity is shown in FIG. 4, and the relationship between the gold density and the catalytic activity is shown in FIG.
The catalyst is 1% by weight Au / Nb ₂ O ₅ (niobium oxide is hydrothermally synthesized, specific surface area 208 m ² / g), the catalyst amount is 0.15 g, and the substrate gas is 1 volume% CO / air. It was set to 50 mL / min. Further, TOF in the figure indicates the CO reaction rate (mol (CO) mol (Au) ^-1 s ^-1 ) per atom of gold at 20 ° C. in a unit time. The gold particle size is calculated by TEM. Table 2 shows the physical characteristics and catalytic activity of the obtained gold composite material. Further, in the table, NbO _x -HT is the same as in Example 3, and the one prepared by hydrothermal synthesis is shown. The mesopore volume of TT-Nb ₂ O ₅ (pseudo-hexagonal crystal) in Table 2 is 0.228 cm ³ / g, and the mesopore volume of TT-Nb ₂ O ₅ (orthorhombic crystal) is 0.359 cm ³ / g. there were. Note that Nb ₂ O ₅ −P is a pyrochlore oxide niobium produced according to the previous report, and Nb ₂ O ₅ · nH ₂ O and Nb ₂ O ₅ are the same as in Example 3, respectively.
Synthesis of TT-Nb ₂ O ₅ (pseudo-hexagonal crystal).
Nb ₂ O ₅ · nH ₂ O (Nb: 0.25 mmol) was dissolved in 45 mL of water and hydrothermal synthesis was carried out at 175 ° C. for 24 hours to obtain a solid substance. The obtained solid material was suction-filtered and then dried at 80 ° C. to obtain an oxide composed of niobium oxide. Then, it was heat-treated at 400 ° C. for 2 hours under air to obtain an acidic solid metal oxide (hereinafter referred to as TT-Nb ₂ O ₅ ).
Synthesis of T-Nb ₂ O ₅ (orthorhombic crystal).
It was obtained by air calcining NbO _x −HT at 650 ° C. for 4 hours (hereinafter referred to as T—Nb ₂ O ₅ ).
Synthesis of Nb ₂ O ₅ -P (pyrochlore type).
Nb ₂ O ₅ · nH ₂ O (Nb: 4 mmol) was dissolved in 45 mL of water and hydrothermal synthesis was carried out at 175 ° C. for 24 hours to obtain a solid substance. The obtained solid material was suction-filtered and then dried at 80 ° C. to obtain an oxide composed of niobium oxide. Then, it was heat-treated at 400 ° C. for 2 hours under air to obtain an acidic solid metal oxide (hereinafter referred to as Nb ₂ O ₅ −P).
As is clear from the results shown in FIGS. 4 and 5, the higher the specific surface area, the higher the catalytic activity, and when the specific surface area is high, the catalytic activity is particularly high when the gold density is 2 or less, particularly 1, 5 or less. It turns out to be expensive.

[Example 5]
As shown in Table 3 below, a gold composite material was prepared in the same manner as in the colloidal mixing method of Example 3 except that the types of carriers were variously changed. The carriers used were NbO _x -HT of Example 3, T-Nb ₂ O ₅ of Example 4, JRC-NbO-1 (Catalyst manufactured by CBMM, see catalyst of the Japan Society of Catalysis), JRC-NbO-2 (Catalyst, manufactured by CBMM). Using SiO ₂ (Q-10, manufactured by Fuji Silysia Chemical Ltd.) as a reference catalyst of the Japan Society of Catalysis), the obtained gold composite material was subjected to a CO oxidation reaction in the same manner as in Example 1 to confirm its activity as an oxidation catalyst. did. In addition, the obtained gold composite material (gold nanocatalyst) was used to carry out an oxidation reaction of furfural. The oxidation reaction of furfural was furfural (1 mmol), water (10 mL), NaOH (1 mmol), the obtained gold composite material (gold nanocatalyst) (50 mg), PO ₂ = 5 bar, reaction temperature 40 ° C. The reaction was carried out for 1.5 hours. The reaction rate was measured by GC.
The BET specific surface area of JRC-NbO-1 is 116 m ² / g (according to the above-mentioned measuring method), and the mesopore volume (according to the above-mentioned measuring method) is 0.128 cm ³ / g.
The BET specific surface area of JRC-NbO-2 is 4 m ² / g (according to the above-mentioned measuring method) and the mesopore volume (according to the above-mentioned measuring method) 0.000 cm ³ / g.

Claims (4)

A gold composite material composed of a carrier and gold fine particles supported on the carrier.
The carrier is an acidic solid metal oxide.
The solid metal oxide is niobium oxide and is
The specific surface area of the carrier is 100 to 300 m ² / g, and the specific surface area is 100 to 300 m 2 / g.
The particle size of the supported gold fine particles is 5 nm or less, and the particle size is 5 nm or less.
The density of the gold fine particles supported on the carrier is 2 μmol · m ^-2 or less, and the density is 2 μmol · m-2 or less.
The above niobium oxide is a gold composite material having a mesopore volume measured by the following measuring method of 0.1 cm ³ / g or more.
Measurement method of mesopore volume: Calculated by the BJH method, which obtains the pore diameter from the desorption isotherm, which is the relationship between the relative pressure and the amount of adsorption when the adsorbate is desorbed.
It is made of the gold composite material according to claim 1.
A gold nanocatalyst used to oxidize biomass-derived components.
The method for manufacturing a gold composite material according to claim 1.
It comprises a step of manufacturing a solid metal oxide to obtain an acidic solid metal oxide, and a carrying step of supporting gold fine particles by using the solid metal oxide and a gold colloidal solution.
In the above solid metal oxide manufacturing process, NH ₄ {NbO (C ₂ O ₄ ) ₂ (H ₂ O)} and nH ₂ O are dissolved in water for hydrothermal synthesis, and the obtained solid is suction filtered. After that, it is dried at 50 to 100 ° C. and heat-treated at 350 to 500 ° C. for 1 to 4 hours.
In the above loading step,
As the solid metal oxide, one having a high specific surface area of 100 to 300 m ² / g was used.
A method for producing a gold composite material, which comprises using a gold colloidal solution containing gold particles having a particle size of 5 nm or less as the gold colloidal solution.
A gold nanocatalyst for an oxidation reaction of an organic compound, which comprises the gold composite material according to claim 1.

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