JP6226341B2 - Gold cluster catalyst - Google Patents

Description

  The present invention relates to a gold cluster catalyst, and more particularly, to a gold cluster catalyst capable of performing a reaction with high selectivity.

Solid catalysts were industrialized in the early 20th century, and have since contributed to the development of inorganic chemical industry, coal chemical industry and petrochemical industry. Solid catalysts can be roughly classified into three types: metal sulfides used for hydrodesulfurization of petroleum, metal oxides used for selective oxidation of unsaturated hydrocarbons, and metals used for automobile exhaust gas purification. Among them, noble metals are highly versatile because they can be used for oxidation and reduction reactions. In particular, palladium and platinum are typical examples.
Gold is a particularly stable metal among precious metals and has been considered a metal with poor activity as a catalyst, but exhibits excellent catalytic activity when supported on a base metal oxide as nanoparticles having a diameter of 5 nm or less. The inventor has found the world first (Non-Patent Document 1). It exhibits high performance not possible with palladium or platinum catalysts in CO oxidation at room temperature, gluconic acid synthesis by oxygen oxidation of aqueous glucose solution, hydrogen peroxide synthesis from hydrogen and oxygen, and one-pot synthesis of azobenzene from nitrobenzene.

  Various catalysts using these noble metals have been proposed. For example, Patent Documents 1 and 2 propose a noble metal-containing catalyst having selectivity in a specific reaction.

JP 2007-301470 A

JP 2007-90164 A

(M. Haruta, Chem. Lett. 1987)

  However, the catalyst according to the above proposal has not yet been able to control the reaction with sufficient selectivity, and the target product cannot be obtained at a high reaction rate by suppressing the formation of by-products. Therefore, there is a demand for the development of a catalyst that can control the reaction with high selectivity.

  Accordingly, an object of the present invention is to provide a gold cluster catalyst capable of promoting and controlling a chemical reaction with high catalytic activity and selectivity.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have the possibility that a specific diameter and number of atoms exhibit a particularly outstanding performance regarding the catalytic activity and selectivity of gold nanoparticles and clusters. As a result of various investigations, bare gold nanoparticles and clusters that were not protected or stabilized by organic ligands were dispersed and immobilized in metal oxides, carbon materials, or polymer materials. As a result of further investigation and investigation, it was found that excellent catalytic activity and / or selectivity for various chemical reactions can be obtained by selecting the optimum diameter or specific number of atoms in the catalyst. Succeeded in producing a gold cluster catalyst supporting a gold cluster composed only of gold atoms from which the children were removed, and found that such a gold cluster catalyst can achieve the above-mentioned purpose. This has led to the completion of the present invention.
That is, the present invention provides the following inventions.
1. A gold cluster catalyst in which a cluster formed by assembling a plurality of gold atoms is supported on a carrier,
The cluster has a particle size of 10 nm or less, and the cluster is substantially composed of only gold atoms;
The number of gold atoms constituting the cluster is a number selected from the group consisting of 11, 55, 101;
A gold cluster catalyst used as a hydrogenation catalyst for organic compounds containing oxygen atoms.
2. The raw material component of the gold cluster catalyst is a gold cluster compound stabilized with an organic ligand and having a gold atom with a predetermined number of atoms, and the removal rate of the organic ligand due to the gold cluster compound is 90 2. The gold cluster catalyst according to 1, wherein the gold cluster catalyst is at least% cluster.
3. 3. The gold cluster catalyst according to 1 or 2, wherein the support is made of ceria or zirconia.

The gold cluster catalyst of the present invention is capable of synthesizing various compounds with high selectivity.

FIG. 1 is a perspective view schematically showing an oxygen plasma processing apparatus used for producing the gold cluster catalyst of the present invention. FIG. 2 is an electron micrograph (drawing substitute photograph) of the gold cluster catalyst obtained in Example 1. FIG. 3 is a histogram showing the gold cluster size obtained in Example 1. FIG. 4 is an electron micrograph (drawing substitute photograph) of the phosphine-protected Au cluster obtained as an intermediate substance in Example 1. FIG. 5 is a histogram showing the size of the phosphine-protected Au cluster obtained as an intermediate material in Example 1. FIG. 6 is an FT-IR chart of the gold cluster catalyst obtained in Example 1 and Example 7. 7 is an electron micrograph (drawing substitute photograph) of a phosphine-protected Au cluster obtained as an intermediate substance in Example 2. FIG. FIG. 8 is a histogram showing the size of the phosphine-protected Au cluster obtained as an intermediate material in Example 2. FIG. 9 is an electron micrograph (drawing substitute photograph) of the phosphine-protected Au cluster obtained as an intermediate substance in Example 3. FIG. 10 is a histogram showing the size of the phosphine-protected Au cluster obtained as an intermediate material in Example 3. FIG. 11 is a bar graph showing the results of a test to see the catalytic activity of the catalyst obtained in the example. FIG. 12 is a bar graph showing the results of a test to see the catalytic activity of the catalyst obtained in the example.

Hereinafter, the present invention will be described in more detail.
The gold cluster catalyst of the present invention (first invention) is stabilized by an organic ligand, and is subjected to post-treatment by supporting a plurality of gold cluster compounds having a predetermined number of atoms on the carrier. A cluster formed by assembling a plurality of particles is supported on a carrier, the particle diameter of the cluster is within a specific range, and the cluster is substantially composed of only gold atoms.
Hereinafter, the gold cluster catalyst of the present invention will be described in more detail.

<Carrier>
The carrier can be used without particular limitation as long as it can support gold nanoparticles in which 200 to tens of thousands of gold atoms are aggregated, or a gold cluster in which not more than 200 atoms are aggregated. for example, the examples of its _{constituents, MgO, Al 2 O 3,} SiO 2, CaO, TiO 2, V 2 O 5, Cr 2 O 3, MnOx, Fe 2 O 3, Co 3 O 4, NiO, CuO _{, ZnO, SrO, ZrO 2,} Nb 2 O 5, MoO 3, SnO 2, BaO, La 2 O 3, CeO 2, Bi 2 O 5, CeO 2 -ZrO 2 ( weight ratio 1: 1, 1: 3) And base metal oxides and composite oxides.
Among them, ZrO ₂ (zirconia) and CeO ₂ (ceria) can be particularly preferably used. In particular, ceria is considered to have a strong interaction with the gold cluster, and the gold cluster does not aggregate and remains as it is (as it should be) ) It is preferable because it is supported on a carrier and can provide specific catalytic properties. Moreover, a commercial item can also be used as ceria, for example, CeO ₂ -1 Shin-Etsu Chemical Co., Ltd. BET (specific surface area, m ² / g) 161, CeO ₂ -2 first rare element chemical industry BET 166, CeO ₂ -3 Sakura BET25.4 etc. can be mentioned. Furthermore, a metal oxide having a regular porous structure can also be used as a support. Examples thereof include titanosilicalite-1 (TS-1) having micropores of 2 nm or less, and MCM-41 and SBA-15, which are silica having mesopores of 2 nm or more.
The carrier may have various shapes such as a spherical shape, a plate shape, a flower shape, and a rod (rod) shape.
The carrier has an average particle diameter of preferably 1 nm to 1 μm, and more preferably 10 nm to 100 nm. Moreover, it is preferable that it is 4-20 times the particle diameter of the said gold | metal | money cluster carry | supported. In the case of a plate shape, a flower shape, or a rod (rod) shape, the thickness is preferably 5 nm to 100 nm.

<Gold cluster>
The gold cluster catalyst of the present invention is a gold cluster catalyst having a particle diameter of the gold cluster of 10 nm or less, preferably 0.8 to 5.0 nm, particularly preferably 0.8 to 2.0 nm. And Here, the said particle diameter shows the longest particle diameter of a gold cluster particle.
Further, if the particle diameter exceeds 10 nm, the catalytic activity is lowered, so it is necessary to be within the above range. In the present specification, the gold cluster supported on the carrier is “a cluster consisting almost of gold atoms” means that the organic ligand is at least 90% (of the originally introduced organic ligand). This means a gold cluster removed as a percentage of the number of molecules), particularly preferably a cluster from which 95% or more has been removed.
The gold cluster is formed by assembling a plurality of gold atoms formed by supporting a plurality of gold cluster compounds stabilized by an organic ligand and having a predetermined number of gold atoms on the support, and then treating them. By this treatment, the organic ligand is removed, and a gold cluster consisting only of gold atoms is supported on the carrier. By removing the organic ligand in this way, there is no interfering action of the catalytic activity by the organic ligand, and higher catalytic activity can be obtained.
In this case, the predetermined number of atoms is preferably a number selected from the group consisting of 11, 13, 55, 101, and 147, and particularly a number selected from the group consisting of 11, 55, and 101. Particularly preferred.
As described above, the gold cluster composed of only gold atoms is not particularly limited as long as it is composed of only a predetermined number of gold atoms, but in order to have a thermally stable property, it is a hemispherical carrier. It is preferable to have a shape that is closely attached to each other.

(Overall form of gold cluster catalyst)
The gold cluster catalyst of the present invention in which the gold cluster is supported on the carrier is one in which the above-described gold cluster is fixed to the above-mentioned carrier by the interaction of both.
The size and shape of the gold cluster catalyst as a whole are not particularly limited as long as it is formed of the above support and gold clusters, but the average particle diameter is preferably 1 nm to 10 nm.
The weight ratio of the gold atom to the carrier in the gold cluster catalyst is preferably 0.1 to 5.0 parts by weight of gold atoms with respect to 100 parts by weight of the carrier.

<Manufacturing method>
The method for producing a gold cluster catalyst according to the present invention comprises a plasma treatment step of oxygen plasma treatment after a plurality of gold cluster compounds stabilized by an organic ligand and having gold atoms having a predetermined number of atoms are supported on a carrier. It can be implemented by doing.
This will be further described below.

(pre-process)
In the present invention, prior to the plasma treatment step, a gold cluster compound production step of producing a gold cluster compound having a predetermined number of atoms and stabilized by an organic ligand can be performed.
The gold cluster compound production step can be performed, for example, by reacting a gold halide compound such as chloroauric acid tetrahydrate with a series of phosphine compounds such as triphenylphosphine at 0 to 50 ° C.
In the said gold cluster compound manufacturing process, in order to set it as the desired number of gold atoms, it changes with numbers of atoms, and it can respectively carry out according to a well-known synthesis method. For example, a chloro (triphenylphosphine) Au ₁₁ cluster having 11 atoms (a cluster of Au ₁₁ protected by phosphine, hereinafter, when a number is written with a subscript to the right of Au, such as Au ₁₁ Represents the number of gold atoms in the cluster), sodium borohydride is allowed to act on chloro (triphenylphosphine) Au, and borane-tetrahydrofuran complex (THF) is obtained to obtain the Au ₅₅ cluster. (BH ₃ -THF complex) is allowed to act and Au ₁₀₁ clusters are obtained by adding triphenylphosphine to the reaction solution of chloroauric acid and tetraoctylammonium bromide (TOAB). Can do.

(Plasma treatment process)
Examples of the gold cluster compound containing a predetermined number of gold atoms obtained by the preceding step include Au ₁₁ cluster protected with phosphine, Au ₁₀₁ cluster protected with phosphine, and the like.
Examples of the method for supporting the gold cluster compound on the carrier include a solid phase mixing method and a wet mixing method.
The solid phase mixing method can be carried out by mixing the gold cluster compound and the carrier with a mortar and the like, and then baking with air at 100 to 400 ° C. for 1 to 10 hours.
The above-mentioned wet mixing method is performed by mixing the carrier and the gold cluster compound using a mixing device such as a ball mill in a system to which a solvent is added, and then performing air firing in an electric furnace at 100 to 400 ° C. for 1 to 10 hours. Can do.

And the manufacturing method of this invention is characterized by performing the plasma treatment process which performs oxygen plasma treatment to the gold cluster compound carrying | support material formed by carrying | supporting a gold cluster compound on a support | carrier.
That is, the gold cluster catalyst of the present invention is preferably obtained by carrying the plasma treatment after a gold complex compound comprising a predetermined number of gold atoms is supported on the carrier.
The plasma treatment can be performed using, for example, the apparatus shown in FIG.
The apparatus 1 shown in FIG. 1 includes a reaction vessel 10, a sample mounting table 20, a plasma spray 30, an oxygen injection tube 40, and a suction tube 50 that sucks air in the vessel. Such an apparatus is based on the principle of plasma processing described in JP 2008-49282 A, JP 2008-49280 A, and the like.
After the sample is placed on the sample mounting table 20, oxygen is applied under the conditions of frequency 1 to 100 kHz, voltage (input voltage) 10 to 100 V (actual applied voltage is 10 kV to 20 kV), and power consumption 1 to 10 W. While injecting from the oxygen injection tube 40, plasma is irradiated while suctioning the internal gas from the suction tube 50. At this time, the irradiation time is arbitrary depending on the weight of the sample, but is preferably 1 to 10 minutes with respect to 1 g of the weight.

In this invention, after performing the said plasma treatment process, the baking process which bakes in air at 100-800 degreeC can also be performed.
As for the said baking in the air, temperature conditions become like this. Preferably it is 100-800 degreeC, More preferably, it is 200-400 degreeC. If the temperature is less than 100 ° C, the organic ligand may not be removed by combustion, and the catalytic activity may be suppressed. If the temperature exceeds 800 ° C, the gold clusters and gold nanoparticles may be melted and become large particles. It is not preferable. The firing time is preferably 1 to 10 hours, and more preferably 2 to 4 hours.
Moreover, baking can be performed in air using an electric furnace.
Moreover, hydrogen reduction can also be performed. In particular, when a polymer material is used as the carrier, it is useful because the firing temperature cannot be raised to 200 ° C. or higher. Hydrogen reduction can be performed under the following conditions using a known apparatus.
conditions:
Gas flow rate: 10-30 ml / min
_{Ar: H 2 = 30: 1~0} : 1
Firing temperature: 100-400 ° C
Temperature rising time: 0.5-3 hours Firing time: 1-3hours
(Post-process)
The gold cluster catalyst obtained as described above can be subjected to a post-process, for example, by performing a purification treatment using a technique usually used when a gold compound is obtained.

<How to use>
As described above, the gold cluster catalyst of the present invention is a gold catalyst in which a cluster in which a plurality of gold atoms are assembled is supported on a carrier, and is a gold complex compound comprising gold atoms having a predetermined number of atoms. Is a gold catalyst obtained by carrying out plasma treatment after the above-mentioned cluster is supported on the carrier, and is preferably used as a hydrogenation catalyst for an oxygen atom-containing organic compound.
Below, the usage method of the gold | metal cluster catalyst of this invention is demonstrated.
The gold cluster catalyst of the present invention can be used in the production of various compounds, and in that case, the target compound can be obtained with high reaction selectivity. Among them, as a hydrogenation catalyst for oxygen atom-containing organic compounds as described below, It can be preferably used.

特に、金原子数が１０１の金クラスターを含有する金クラスター触媒が有用である。 (Hydrogenation of cinnamaldehyde)
The gold cluster catalyst of the present invention is effective as a hydrogenation catalyst for producing cinnamyl alcohol (2) by hydrogenating cinnamaldehyde (1 in the following chemical reaction formula) by the reaction shown in the following formula.

In particular, a gold cluster catalyst containing a gold cluster having 101 gold atoms is useful.

特に、金原子数が１１の金クラスターを含有する金クラスター触媒が有用である。 (One-pot synthesis of azobenzene from nitrobenzene)
The gold cluster catalyst of the present invention is prepared by ONE-POT synthesis of azobenzene (3) from nitrobenzene (1) by the reaction shown in the following formula (by putting the reactants into one reaction vessel (usually a flask) all at once or sequentially. It is useful as a catalyst used in the case of a synthesis method for performing a multi-stage reaction.

In particular, a gold cluster catalyst containing a gold cluster having 11 gold atoms is useful.

特に、金原子数が１１の金クラスターを含有する金クラスター触媒および平均粒子径４．２ｎｍの金ナノ粒子触媒が有用である。
本発明の金クラスター触媒は、上述の各反応系以外でもシクロヘキサノールの酸素酸化反応など種々反応系で応用可能である。 (Synthesis of aniline by hydrogenation of nitrobenzene)
The gold cluster catalyst of the present invention is useful as a catalyst used when synthesizing aniline from nitrobenzene by the reaction shown in the following formula.

In particular, a gold cluster catalyst containing a gold cluster having 11 gold atoms and a gold nanoparticle catalyst having an average particle diameter of 4.2 nm are useful.
The gold cluster catalyst of the present invention can be applied to various reaction systems such as an oxygen oxidation reaction of cyclohexanol other than the above reaction systems.

The specific surface area of the gold cluster catalyst is preferably 50 to ²⁰⁰ m ² / g.

  The particle diameter is a diameter in the case of spherical particles, and a long diameter in the case of particles of other shapes. It can be obtained by calculating an average value.

<Third component>
Moreover, you may mix | blend another component with the gold cluster catalyst of this invention in the range which does not impair the desired effect of this invention other than the above-mentioned support | carrier and gold cluster.

Conventional gold catalysts have been prepared by dispersing and immobilizing gold precursors directly on a support, and therefore it is inevitable that there are distributions in the diameter and thickness of gold nanoparticles. For this reason, it has been considered that smaller dimensions are usually more advantageous for the effect of size on catalyst properties (activity and selectivity per surface exposed atom). However, when using gold nanoparticles or gold clusters that are monodisperse (standard deviation is within 10% for nanoparticles, and the number of atoms is specified at one level for clusters), the dimensions (thickness) that express specifically excellent catalytic properties And diameter) and the number of atoms (magic number) and gold clusters are reported, and a clear concept, methodology, and catalyst sample production method have been proposed for this dimension specificity. The current situation is not.
Therefore, we are developing a method for producing supported gold nanoparticle catalysts and supported gold cluster catalysts that can define the gold dimensions as much as possible, and searching for specific reaction cases to systematize the dimensional specificity. is the current situation.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not restrict | limited at all to these.

[Example 1] Preparation of gold cluster catalyst having 11 gold atoms (Synthesis of chloro (triphenylphosphine) Au (I))
1 g of chloroauric acid tetrahydrate was added to 35 mL of ethanol in a nitrogen atmosphere and stirred to dissolve to obtain a chloroauric acid solution. 50 ml of an ethanol solution in which 1.364 g of triphenylphosphine was dissolved was added to the chloroauric acid solution in a nitrogen atmosphere to carry out the reaction. The reaction liquid turned from yellow to white and a white precipitate was formed. The precipitate is dissolved in 5 ml of dichloromethane, 120 ml of pentane is slowly added and stored overnight in a freezer to precipitate a white product, which is filtered off with suction and dried in vacuo to give the product (chloro (triphenyl Phosphine) Au (I)) was obtained.

(Synthesis of Au ₁₁ gold cluster compound)
0.25 g of the obtained chloro (triphenylphosphine) Au (I) was dispersed in 20 g of dehydrated ethanol and stirred for 5 minutes. Thereafter, the mixture was stirred for 2 hours while adding 27 mg of sodium borohydride over 20 minutes. The product was placed in hexane (125 ml) and precipitated for 20 hours. This was added to a dichloromethane solution, and then filtered and dried to obtain a phosphine-protected Au ₁₁ cluster having 11 gold atoms.

(Support on carrier)
Next, 16 mg of Au ₁₁ gold cluster compound prepared as described above was dispersed in a solution of 20 ml of CH ₂ Cl ₂ , 1.0 g of ZrO ₂ carrier was added thereto, and the mixture was further stirred and vacuum-dried. Firing was performed in a medium electric furnace at 300 ° C. for 4 hours. By these operations, the Au ₁₁ composite cluster was supported on the ZrO ₂ support to obtain a gold complex compound support.

(Oxygen plasma treatment for removal of organic ligands)
The obtained gold complex compound-supported product was subjected to oxygen plasma treatment before air firing to remove the organic ligand of the gold complex compound, and a gold cluster catalyst in which gold atom clusters were supported on a carrier was obtained. .
The oxygen plasma treatment was performed using the apparatus shown in FIG. 1 under the following conditions.
Oxygen plasma treatment conditions:
Time 2 minutes Sample weight 0.2g
Frequency 29kHz
Voltage 65V
Input power 2.4W

The obtained gold cluster catalyst was observed using a high angle scattering dark field scanning transmission electron microscope (HAADF-STEM) to confirm whether or not the desired gold cluster catalyst was obtained.
The observation was performed according to the following procedure.
First, the obtained gold cluster catalyst is dispersed in a mixed solution (1: 1, weight ratio) of ethanol and dichloromethane solution to obtain a dispersion, and one drop of the dispersion is dropped on a copper grid, and then overnight in a desiccator. Then, vacuum drying was performed at room temperature, and then carbon was vapor-deposited three times from above to create a grid. HAADF-STEM used an apparatus and a brand name “JEM-3200FS” (manufactured by JEOL Ltd.).
As a result, the average particle size was 0.8 ± 0.4 nm.
An electron micrograph of the particles is shown in FIG. 2, and a histogram showing the gold cluster size is shown in FIG.
In addition, for the phosphine-protected Au ₁₁ cluster, an electron micrograph is similarly shown in FIG. 4, and a histogram showing the gold cluster size is shown in FIG.
Next, in order to confirm the removal of the organic ligand adsorbed on the catalyst surface of the obtained gold cluster, the measurement by the FT-IR spectral diffuse reflection method was performed.
FT-IR used the apparatus and brand name "JASCO FT-IR-6100" (made by JASCO Corporation).
The measurement conditions were as follows.
Cumulative count 200 times,
Resolution 2 cm ⁻¹ .
The mirror cell is used for the background.
The obtained diffuse reflection spectrum was converted into a KM absorption spectrum corresponding to the transmission spectrum by the Kubelka-Munk (KM) equation. The removal of the organic ligand was performed by observing the peak of the C—H stretching vibration of FT-IR. As a result, the removal of the organic ligand was confirmed. The obtained FT-IR measurement results are shown in FIG. 6 also shows the measurement results of the gold complex compound-carrying product before the oxygen plasma treatment. From this result, it can be seen that 95% or more of the organic ligand is removed.

[Example 2] Preparation of gold cluster catalyst having 55 gold atoms A gold cluster catalyst was obtained in the same manner as in Example 1 except that Au clusters were prepared as follows. FIG. 7 shows an electron micrograph of the phosphine-protected Au ₅₅ cluster, and FIG. 8 shows a histogram showing the gold cluster size.
(Synthesis of Au ₅₅ cluster)
Chloro (triphenylphosphine) Au (I) (0.25 g) prepared in the same manner as in Example 1 was dissolved by adding 20 ml of benzene in a nitrogen atmosphere and stirring. Subsequently, 3 ml of a borane-tetrahydrofuran complex (THF) (BH ₃ -THF complex) solution was dropped into the solution over 2 hours at room temperature under stirring in a nitrogen atmosphere to obtain a product. The product was taken up in 5 ml of dichloromethane solution, filtered and dried. The final product (Au ₅₅ cluster) was obtained by slowly adding 120 ml of pentane to the product, filtering and drying.

[Example 3] Preparation of gold cluster catalyst having 101 gold atoms A gold cluster catalyst was obtained in the same manner as in Example 1 except that Au clusters were prepared as follows. An electron micrograph of the phosphine-protected Au ₁₀₁ cluster is shown in FIG. 9, and a histogram showing the gold cluster size is shown in FIG.
(Synthesis of Au ₁₀₁ cluster)
Distilled water 50 ml (a solution) in which chloroauric acid (2.54 mmol) was dissolved and 65 ml (b solution) in which tetraoctylammonium bromide (TOAB) (2.93 mmol) was dissolved were prepared. The prepared a solution and b solution were mixed in a nitrogen atmosphere over 30 minutes to carry out a reaction. Since the gold salt produced by the reaction moved from the aqueous layer to the toluene layer, water was removed from the solution using a 50 ml syringe, and the mixture was vigorously stirred at room temperature. After 30 minutes, triphenylphosphine (8.85 mmol) was added to the solution to react. The color of the solution changed from deep red to pale yellow within 5 minutes from the start of the reaction, and became milky white after 1 hour. Subsequently, distilled water (6 ml) in which sodium borohydride (37.3 mmol) was dissolved was quickly added to the solution and reacted at room temperature with stirring for 180 minutes to obtain a product. The final product (Au ₁₀₁ cluster) was obtained by adding pentane (125 ml) to the product, recrystallization, and drying.

[Examples 4 to 6] Preparation of gold cluster catalyst using ceria as support The same procedures as in Examples 1 to 3 except that the support was changed from ZrO ₂ to CeO ₂ -1, and Au ₁₁ , Au ₅₅ , and Au ₁₀₁ were used. A gold cluster catalyst was obtained. The removal rate of the organic ligand in the obtained gold cluster catalyst was 90% or more.

[Examples 7 to 9]
Gold cluster catalysts of Au ₁₁ , Au ₅₅ , and Au ₁₀₁ were obtained in the same manner as in Examples 1 to 3, except that the following baking treatment was performed after the oxygen plasma treatment. The removal rate of the organic ligand was 90% or more.
<Baking treatment>
The gold cluster catalyst after the completion of the oxygen plasma treatment was put into an electric furnace and calcinated at 150 ° C. for 2 hours.
Further, FT-IR was measured in the same manner as in Example 1 for the catalyst obtained in Example 7. The result is shown in FIG. From this result, it can be seen that 95% or more of the organic ligand is removed.

[Examples 10 to 12]
Au ₁₁ , Au ₅₅ , and Au ₁₀₁ gold cluster catalysts were obtained in the same manner as in Examples 7 to 9 except that the support was changed from ZrO ₂ to CeO ₂ -1 and the calcination temperature was 300 ° C. In the obtained gold cluster catalyst, the particle diameter of the gold cluster was 2 nm or less, and the removal rate of the organic ligand was 90% or more.

[Test Example 1] An autoclave was used in the liquid phase reaction vessel of the azobenzene one-pot synthesis catalyst, and the catalyst obtained in Examples 1 to 12 (Au 0.3 mol% with respect to the substrate) was placed in the autoclave, and nitrobenzene as the substrate. Was added in an amount of 0.5 mmol, 50 μL of dodecane as an internal standard substance, and 3 mL of a solvent were added. The solution after the reaction was filtered through a 0.45 μm membrane filter. The obtained filtrate was subjected to quantitative analysis using Agilent 7890AGC (gas chromatography, trade name, manufactured by Agilent). As a result, high catalytic activity was recognized for any of the catalysts.

[Test Example 2] Hydrogenation of cinnamaldehyde Each of the catalysts obtained in Examples 6 and 12 was placed in an autoclave as a reaction vessel (Au 1 mol% (calculated amount: 1 mol%, actual amount: 0.6 mol%) with respect to the substrate). Then, 0.5 mmol of cinnamaldehyde as a substrate, 25 μL of anisol as an internal standard substance, and 3 mL of a solvent were added, respectively, pressurized with 0.5 MPa of hydrogen, and reacted at 80 ° C. for 22 (25) hours. The solution after the reaction was filtered through a 0.45 μm membrane filter. The obtained filtrate was subjected to quantitative analysis using Agilent 7890AGC (gas chromatography, trade name, manufactured by Agilent).
The result is shown in FIG.
For comparison, catalytic activity was also confirmed for those in which neither oxygen plasma treatment nor firing treatment was performed. The results are also shown.
In FIG. 11, the comparison target is “no pretreatment”, the catalyst of Example 6 is “PL”, and the catalyst of Example 12 is “PL, 300”.
From FIG. 11, the gold cluster catalyst of the present invention obtained by oxygen plasma treatment (the catalyst obtained in Example 6) had a high selectivity for cinnamyl alcohol, which was 83% at the maximum. Further, the catalyst treated with oxygen plasma and treated in air at 300 ° C. (the catalyst obtained in Example 12) had the highest conversion rate of cinnamaldehyde and a high selectivity of cinnamyl alcohol.

[Test Example 3] Hydrogenation of nitrobenzene The catalyst obtained in Example 1 and the catalyst obtained in Example 7 were placed in an autoclave (Au 1 mol% with respect to the substrate), 0.5 mmol of nitrobenzene as the substrate, and internal standard 50 μL of dodecane as a substance and 3 mL of toluene as a solvent were added, respectively, pressurized with 0.5 MPa of hydrogen, and reacted at 60 ° C. for 6 hours. The solution after the reaction was filtered through a 0.45 μm membrane filter. The obtained filtrate was quantitatively analyzed using Agilent 7890AGC. The result is shown in FIG.
For comparison, catalytic activity was also confirmed for those in which neither oxygen plasma treatment nor firing treatment was performed. The results are also shown.
In FIG. 12, the comparison target is “no pretreatment”, the catalyst of Example 1 is “PL”, and the catalyst of Example 7 is “PL, 150”.
As is apparent from the results shown in FIG. 12, it can be seen that the gold catalyst of the present invention (particularly Example 7) exhibits high catalytic activity.

Claims (3)

A gold cluster catalyst in which a cluster formed by assembling a plurality of gold atoms is supported on a carrier,
The cluster has a particle size of 10 nm or less, and the cluster is substantially composed of only gold atoms;
The number of gold atoms constituting the front Symbol cluster is a number selected from the group consisting of 11,55,101,
Gold cluster catalyst used as a hydrogenation catalyst for cinnamaldehyde or nitrobenzene or as a one-pot synthesis catalyst for azobenzene from nitrobenzene . Thin a Nam number of hydrogenation catalysts as gold atoms aldehyde 101, the number 11 der Rukoto of gold atoms from a few are 11 or nitrobenzene gold atoms as nitrobenzene hydrogenation catalyst as a one-pot synthesis catalyst azobenzene The gold cluster catalyst according to claim 1, wherein the catalyst is a gold cluster catalyst. Before Symbol carrier, gold clusters catalyst according to claim 1 or 2 consisting of ceria or zirconia.

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