WO2010110447A1 - Mesoporous silica-supported gold cluster, catalyst comprising same, and process for producing same - Google Patents

Mesoporous silica-supported gold cluster, catalyst comprising same, and process for producing same Download PDF

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WO2010110447A1
WO2010110447A1 PCT/JP2010/055434 JP2010055434W WO2010110447A1 WO 2010110447 A1 WO2010110447 A1 WO 2010110447A1 JP 2010055434 W JP2010055434 W JP 2010055434W WO 2010110447 A1 WO2010110447 A1 WO 2010110447A1
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mesoporous silica
gold
supported
range
silica
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PCT/JP2010/055434
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French (fr)
Japanese (ja)
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達哉 佃
永梅 劉
寛規 角山
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国立大学法人北海道大学
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/52—Gold
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
    • B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
    • B01J29/0316—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing iron group metals, noble metals or copper
    • B01J29/0325—Noble metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B01J35/30—
    • B01J35/393—
    • B01J35/618—
    • B01J35/647—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating

Definitions

  • the present invention relates to a mesoporous silica-supported gold cluster, a catalyst using the same, and a method for producing the same.
  • Nano-sized gold catalysts supported on metal oxides have attracted attention.
  • silica By immobilizing the gold catalyst on the carrier, there is an advantage that it can be recovered from the reaction system and reused.
  • silica can be used as a support, there is an advantage that a gold cluster catalyst which is superior in safety and economy can be produced.
  • Mono-dispersed gold clusters of less than 5 nm supported on silica are ideal materials for studying the intrinsic catalytic activity of gold clusters. This is because silica is catalytically inactive and its interaction with clusters is relatively weak.
  • Non-Patent Documents 1 and 2 such as coprecipitation method (DP) and impregnation support method (IP) cannot be used. .
  • Non-patent Document 3 As a method of supporting the gold cluster on the metal oxide, monodispersed gold nanoparticles (average particle size 3.5 ⁇ 0.5, 6.3 ⁇ 0.5, 8.2 ⁇ 0.9 nm) protected with alkanethiol are prepared in advance, and this is prepared using an organic solvent ( It is adsorbed on metal oxides (tungsten oxide, soot zeolite, silica, titania, zirconia, tin oxide, iridium oxide, iron oxide, alumina, zinc oxide, nickel oxide) in chloroform and dichloromethane).
  • metal oxides tungsten oxide, soot zeolite, silica, titania, zirconia, tin oxide, iridium oxide, iron oxide, alumina, zinc oxide, nickel oxide
  • a method of preparing supported monodispersed gold nanoparticles by firing for a time is known (Non-patent Document 3). In Non-Patent Document 3, the catalytic activity of the supported mono
  • a gold 55-mer (Au55, particle size 1.4 nm) protected with triphenylphosphine was synthesized in advance and adsorbed onto silica in an organic solvent (dichloromethane).
  • a method of preparing supported monodispersed gold nanoparticles by firing for a time is known (Non-Patent Document 4).
  • the average particle size was 1.4 nm.
  • the catalytic activity for partial oxidation of styrene in toluene at 100 ° C. was evaluated.
  • Patent Document 1 discloses a composite of cerium-containing mesoporous silica and noble metal ultrafine particles, a method for producing the composite, a method for oxidative removal of trace carbon monoxide using the composite as a catalyst, and an alcohol.
  • a method for the synthesis of ketones by oxidative dehydrogenation of the class is disclosed.
  • the composite is characterized in that ultrafine gold particles are supported on mesoporous silica containing cerium, and the diameter of the ultrafine particles is in the range of 0.5 to 5 nm, and the total number of particles is almost the same. Is included.
  • Example 2 as a result of measuring the particle size of the gold particles in the catalyst used in Example 1, the range of 0 to 0.5 nm is 1% of the total number of particles, and the range of 0.5 to 1 nm. Is 16% of the total number of particles, 51% of the total number of particles in the range of 1 to 1.5 nm, 21% of the total number of particles in the range of 1.5 to 2.0 nm, 2.0 to 2.5 nm The range was 9% of the total number of particles, and the range of 2.5 to 3.0 nm was 2% of the total number of particles.
  • Patent Document 1 describes a method of supporting ultrafine gold particles on mesoporous silica containing cerium.
  • an alkaline solution is added to an aqueous solution of chloroauric acid to adjust the pH value to a range of 7.0 or more and less than 10.0, thereby changing chloroauric acid to a state in which hydroxide ions are coordinated.
  • the surface of the mesoporous silica is a precursor of the ultrafine gold particles with an electrical affinity.
  • a method of adsorbing a gold complex coordinated with hydroxide ions is used.
  • Patent Document 1 The entire description of Patent Document 1 and Non-Patent Documents 1 to 8 is specifically incorporated herein by reference.
  • Non-patent Document 5 Non-patent Document 5
  • silica one of the most common catalyst supports, is difficult to prepare, so there is no information on the size effect of the gold catalyst.
  • the general methods such as the coprecipitation method and the impregnation support method described above, it is impossible to suppress the particle size to 5 nm or less, and a wide distribution occurs in the size.
  • the gold ultrafine particles are supported on mesoporous silica containing cerium, so that the diameter of the gold ultrafine particles is within the range of 0.5 to 5 nm, and most of the total number of particles is included.
  • a complex is provided.
  • the number of ultrafine gold particles is 17% of the total number of particles when the diameter is in the range of 0 to 1 nm, whereas the total number of gold particles is within the range of 1 to 3.0 nm. 83%. That is, even with this method, it is still difficult to make the size of gold ultrafine particles smaller than 1 nm.
  • an object of the present invention is to provide a method for preparing a silica-supported gold cluster in the sub-nanometer to several nanometer region, and thereby to provide a sub-nanometer silica-supported gold cluster that has never been obtained. Furthermore, another object of the present invention is to provide a catalyst using a silica-supported gold cluster in the sub-nanometer range to a few nanometer range.
  • the present inventors have made various studies to achieve the above object, and as a result, by using triphenylphosphine-protected gold 11-mer (Au 11 , particle size 0.8 nm) as a starting material, sub-nanometers to several nanometers are obtained. We have found that a silica-supported gold cluster in the region can be prepared and completed the present invention.
  • the present invention for achieving the above object is as follows.
  • [1] A composite of gold clusters and mesoporous silica composed of mesoporous silica in which gold clusters having a particle size in the range of 0.8 to 1.0 nm are supported in pores.
  • [2] The composite according to [1], wherein the mesoporous silica has a pore diameter in the range of 2 to 50 nm.
  • Au 11 : TTP is the production method according to [7], wherein at least one of or both of [Au 11 (TPP) 8 Cl 2 ] + and Au 11 (TPP) 7 Cl 3 is included. [9] The production method according to [7] or [8], wherein Au 11 : TTP is mixed in an amount of 0.1 to 2.5 parts by mass with respect to 100 parts by mass of mesoporous silica. [Ten] The method according to any one of [7] to [9], wherein the firing is performed at a temperature in the range of 180 to 220 ° C.
  • the present invention it is possible to provide a method for preparing a silica-supported gold cluster in the sub-nanometer to several nanometer region, thereby providing a sub-nanometer silica-supported gold cluster that has not been obtained conventionally.
  • a catalyst using a silica-supported gold cluster in the sub-nanometer to several nanometer range it is possible to provide a method for preparing a silica-supported gold cluster in the sub-nanometer to several nanometer region.
  • FIG. 1 shows the results of thermogravimetric analysis of gold 11-mer (Au 11 ) (Au 11 : TPP) synthesized in Reference Example 1.
  • FIG. 2 shows the results of examining the dependence of the firing time on the size of the gold cluster by diffuse reflectance spectroscopy when SBA-15 shown in Reference Example 2 is used as the carrier.
  • FIG. 3 shows the case where SBA-15 (Reference Example 2), MCF (Reference Example 3) and HMS (Reference Example 4) are used as carriers and silica (SiO 2 ) is used as a reference, and the firing time is 2 hours. It is the result of having investigated the dependence of the support
  • FIG. 1 shows the results of thermogravimetric analysis of gold 11-mer (Au 11 ) (Au 11 : TPP) synthesized in Reference Example 1.
  • FIG. 2 shows the results of examining the dependence of the firing time on the size of the gold cluster by diffuse reflectance spect
  • FIG. 4 shows TEM photographs and EXAFS results for samples with different firing times and carriers.
  • FIG. 5 shows TEM photographs and gold cluster sizes for samples with different firing times and carriers.
  • FIG. 6 shows an FT-IR spectrum of a sample obtained using SBA-15 (Reference Example 2) as a carrier and a firing time of 2 hours.
  • FIG. 7 shows HAADF-STEM (High-angle annular dark-field scanning transmission electromicroscopy) images and gold cluster particle size distributions at firing times of 2, 8, and 16 hours.
  • Au 11 supported on SBA-15 with a firing time of 2 hours is 0.16Au 11 -SBA (2)
  • 8 hours is 0.16Au 11 -SBA (8)
  • 16 hours is 0.16Au 11 -SBA (16). Represent each.
  • FIG. 8 shows the results of a diffuse reflection UV-vis microscope.
  • a) is 0.16Au 11 -SBA (2)
  • b) is 0.16Au 11 -SBA (8)
  • c) is 0.16Au 11 -SBA (16).
  • FIG. 9 shows the results of catalytic activity for the oxidation reaction of benzyl alcohol in Example 5.
  • A shows the relationship of log [1 / (1-X)] to the reaction time.
  • a) is 0.16Au 11 -SBA (2)
  • b) is 0.16Au 11 -SBA (8)
  • c) is 0.16Au 11 -SBA (16).
  • B shows the relationship of the normalized reaction rate constant to the diameter of the Au 11 cluster.
  • the present invention relates to a composite of gold clusters and mesoporous silica, which is composed of mesoporous silica in which gold clusters having a particle size (average particle diameter) in the range of 0.8 to 1.0 nm are supported in pores.
  • the gold clusters supported in the pores are made of gold 11-mer (Au 11 ), and the particle size of the gold 11-mer is 0.8 nm. Is not wide). Accordingly, although depending on the production conditions, the particle size (average particle diameter) of the gold cluster supported on the composite of the present invention is 0.8 nm or more and 1.0 nm or less.
  • gold clusters having a particle size exceeding 1.0 nm (individual) are also supported. However, even if it is supported, it is 30% or less. Conversely, gold clusters with particle sizes (individual) in the range of 0.8 to 1.0 nm are 70% or more of the supported gold clusters.
  • the gold cluster supported on the composite of the present invention is much finer than the gold particles supported on the composite containing gold particles described in Patent Document 1.
  • the composite of the present invention is a composite comprising a gold cluster and mesoporous silica, in other words, a gold cluster supported on mesoporous silica.
  • the particle size (average particle diameter) of the gold cluster is in the range of 0.8 to 1.0 nm.
  • a silica particle carrying a gold cluster is known, and the gold cluster has a mean particle size of 1.4 nm.
  • the pore diameter of mesoporous silica supporting gold clusters is in the range of 2 to 50 nm.
  • Mesoporous silica is porous silica having uniform and regular pores (mesopores) generally made of silicon dioxide (silica). It has pores with an almost uniform diameter called the mesopore region, ranging from 2 to 50 nm, and may have various characteristics depending on the network mode (spatial symmetry) created by the pores and the manufacturing method. It is a known group of porous materials.
  • This porous silica is one of the substances that are expected to be used as a structural member such as a separation adsorbent, a chromatography filler, a wastewater treatment agent, a catalyst, etc. due to the characteristics such as pore diameter and large surface area. It is.
  • mesopores pores with a diameter of 2 to 50 nm are defined as mesopores in the catalyst field.
  • Several methods for synthesizing mesoporous silica are known, and a sol-gel method using a surfactant as a template can be exemplified. It is known that mesoporous silica prepared using a cationic surfactant can take various types of networks (spatial symmetry) created by various pores depending on the type of the cationic surfactant (Non-patent literature). 8). In the present invention, known mesoporous silica can be used as it is.
  • various types of mesoporous silica can be used as a carrier.
  • the mesoporous silica has a pore diameter of 2 to 50 nm.
  • mesoporous silica having various pore diameters can be used depending on the type of catalytic reaction.
  • the pore diameter of mesoporous silica is preferably in the range of 2 nm or more.
  • the BET specific surface area of mesoporous silica is not particularly limited, but can be, for example, in the range of 500 to 1300 m 2 / g.
  • the BET specific surface area of mesoporous silica is preferably in the range of 600 to 1200 m 2 / g.
  • the amount of gold clusters supported in the pores of mesoporous silica is not particularly limited, but can be, for example, in the range of 0.1 to 2.5% by mass. If the amount of gold clusters supported becomes too large, the entire amount becomes difficult to be supported in the pores, so the upper limit is about 2.5% by mass. Further, if the amount of gold clusters supported is too large, the particles of gold clusters may become too large during aggregation for the production of the composite. From such a viewpoint, the supported amount of the gold cluster is preferably in the range of 0.1 to 0.5% by mass.
  • the present invention also includes a catalyst comprising the composite of the gold cluster of the present invention and mesoporous silica.
  • the composite used for the catalyst is as described above.
  • the catalyst of the present invention can be used for an oxidation reaction, for example.
  • examples thereof include oxidation reactions of primary alcohols such as benzyl alcohol and secondary alcohols such as 1-indanol.
  • the catalyst of the present invention When the catalyst of the present invention is used for an alcohol oxidation reaction, it can be carried out as follows. A composite of gold clusters and mesoporous silica is mixed and stirred with alcohol in an aqueous solution of K 2 CO 3 . This is irradiated with microwaves, and when the temperature reaches 80 ⁇ 2 ° C., hydrogen peroxide is added. However, the temperature at which hydrogen peroxide is added is not intended to be limited to 80 ⁇ 2 ° C., and may be appropriately set within a range of 50 to 90 ° C., for example, in consideration of the type of catalyst of the present invention and the type of alcohol Can do. The reaction is stopped by adding hydrochloric acid and the product is extracted with ethyl acetate. The extracted organic phase is dried over sodium sulfate and identified and quantified by gas chromatography.
  • the present invention also includes a method for producing a composite of the gold cluster and mesoporous silica of the present invention.
  • This manufacturing method is (1) A step of mixing mesoporous silica and trimeric phosphine-protected 11-mer gold clusters (hereinafter referred to as Au 11 : TTP) in a solvent to adsorb Au 11 : TTP to mesoporous silica; When (2) a step of firing at least a part of triphenylphosphine by firing Au 11 : mesoporous silica adsorbed with TTP; Is included.
  • Au 11 trimeric phosphine-protected 11-mer gold clusters
  • Au 11 : TTP an 11-mer gold cluster (hereinafter referred to as Au 11 : TTP) protected with triphenylphosphine is used.
  • the 11-mer gold cluster protected with triphenylphosphine can be synthesized from a commercially available Au (I) (TPP) Cl complex as described in Reference Example 1 described later.
  • Au 11 : TTP obtained by the method shown in Reference Example 1 contains at least one or both of [Au 11 (TPP) 8 Cl 2 ] + and Au 11 (TPP) 7 Cl 3 .
  • Au 11 : TTP can be used.
  • Mesoporous silica and Au 11 : TTP are mixed in a solvent at a predetermined ratio to adsorb Au 11 : TTP to mesoporous silica.
  • Au 11 : TTP can be mixed in the range of 0.1 to 2.5 parts by mass with respect to 100 parts by mass of mesoporous silica.
  • Au 11 : TTP is favorably adsorbed to mesoporous silica, and the degree of adsorption can be determined by the color change of the mixed solution (change from colored to colorless).
  • the solvent for example, dichloromethane, chloroform, ethanol mixture thereof and the like can be used. In particular, it is preferable to use a mixture of three solvents, dichloromethane, chloroform, and ethanol, from the viewpoint of efficiently and uniformly adsorbing Au 11 : TTP.
  • the mesoporous silica adsorbed with Au 11 : TTP is baked to remove at least a part of triphenylphosphine.
  • the firing conditions can be appropriately determined depending on the state of thermal desorption of triphenylphosphine from Au 11 : TTP. As shown in FIG. 1, in the Au 11 : TTP synthesized in Reference Example 1, triphenylphosphine is thermally desorbed at a temperature around 200 ° C. Considering this point, the firing can be performed at a temperature in the range of 180 to 220 ° C., for example.
  • the firing temperature not only affects the degree of elimination (removal) of triphenylphosphine, but also affects the particle size of the gold clusters supported in the mesoporous silica pores. As a tendency, the lower the temperature and the shorter the heating time, the smaller the gold cluster particle size. Conversely, the higher the temperature and the longer the heating time, the larger the gold cluster particle size. Considering these points, the heating temperature and time for firing are appropriately determined. However, the calcination is preferably carried out under conditions that remove substantially all of the adsorbed triphenylphosphine.
  • the heating time is in the range of 2 to 16 hours, so that substantially all of the triphenylphosphine can be removed and the particle size of the gold cluster is reduced, for example, 3 nm
  • a composite of gold clusters and mesoporous silica composed of mesoporous silica in which at least a part of gold clusters having a particle size of 3 nm or less is supported in the pores can be produced.
  • the composite of the produced gold cluster and mesoporous silica is used as it is as a catalyst.
  • the mesoporous silica having a large surface area is used as the support, the density of the adsorbed Au 11 can be suppressed. Therefore, for example, the particle size of the gold cluster can be 1 nm or less, and Au 11 is also characterized in that the size is uniform at the atomic level.
  • TTP which is an Au 11 precursor having a uniform size at the atomic level
  • an agglomeration process can be uniformly generated and the dispersibility of the gold cluster can be maintained. As a result, it can be controlled to a relatively small size.
  • Reference example 3 MCFS synthesis 1. 2 g of amphiphilic polymer P123 was added to 2M HCl solution (75 mL) and stirred at 40 ° C. for 4 hours. 2. 1 g of TMB (1,3,5-trimethylbenzene) was added and stirred at 40 ° C. for 2 hours. 3. 4.25 g of TEOS (tetraethoxysilane) was added and stirred at 40 ° C. for 24 hours. 4. Placed in an 80 ° C autoclave for 1 day. 5. Filtered and dried. 6. Baked at 500 ° C. for 6 hours in air to obtain mesoporous silica MCFS.
  • TMB 1,3,5-trimethylbenzene
  • TEOS tetraethoxysilane
  • Reference example 4 HMS synthesis method 1. Add 270 mL water to 11.5 M HCl solution (47 mL). 2. 4.74 g of CTAB (Cetyl Trimethyl Ammonium Bromide) was added and stirred at room temperature until dissolved. 3. 20.8 g of TEOS (tetraethoxysilane) was added and stirred at 40 ° C. for 24 hours. 4. Allowed to stand at room temperature for 48 hours. 5. Filter and dry. 6. Baked at 600 ° C. for 6 hours in air to obtain mesoporous silica HMS.
  • CTAB Cetyl Trimethyl Ammonium Bromide
  • Table 1 shows the BET specific surface area, total pore volume, and BJH adsorption pore diameter of the mesoporous silica synthesized in Reference Examples 2 to 4.
  • Example 1 Supporting gold on mesoporous silica 5 mg of gold 11-mer (Au 11 ) prepared in Reference Example 1 was dissolved in 24 mL of dichloromethane, and then 1 g of mesoporous silica prepared in any of Reference Examples 2 to 4 was added to this solution. Added and stirred for 2 hours. After stirring, it was filtered to obtain mesoporous silica adsorbing gold 11-mer (Au 11 ). Due to the difference in color (difference in absorption spectrum) between the solution before adsorption and the filtrate obtained after filtration, the gold 11-mer (Au 11 ) contained in the solution was adsorbed to almost 100% mesoporous silica. I understood.
  • the obtained mesoporous silica adsorbing the gold 11-mer (Au 11 ) was baked at 200 ° C. From the results of thermogravimetric analysis of gold 11-mer (Au 11 ) shown in FIG. 1, the firing temperature was set to 200 ° C.
  • FIG. 2 shows the result of examining the dependence of the firing time on the size of the gold cluster by diffuse reflectance spectroscopy when SBA-15 shown in Reference Example 2 is used as a carrier. As shown in FIG. 2, the peak of surface plasmon absorption increases with the firing time, and it can be seen that the size gradually increases.
  • FIG. 3 shows the result of examining the dependence of the carrier on the size of the material by diffuse reflectance spectroscopy.
  • FIG. 3 shows that agglomeration accompanying firing can be suppressed by using mesoporous silica as a carrier.
  • FIG. 4 shows TEM photographs and EXAFS results for samples with different firing times and carriers
  • FIG. 5 shows TEM photographs and gold particle sizes.
  • FIG. 4 shows that the gold cluster obtained by firing Au 11 : TPP adsorbed on SBA-15 for 2 hours is so small that it cannot be observed by TEM.
  • the average coordination number determined by EXAFS is 5.8 ⁇ 2.0, which corresponds to the value of face-centered cubic particles having a diameter of about 0.8 nm.
  • FIG. 6 shows an FT-IR spectrum of a sample obtained by using SBA-15 (Reference Example 2) as a carrier and a firing time of 2 hours. From FIG. 6, since the peak attributed to the organic ligand disappeared upon firing, the removal of the ligand was confirmed.
  • Example 2 When the catalytic activity for the oxidation reaction of benzyl alcohol was investigated, benzoic acid was obtained as the main product. In addition, the gold catalyst obtained showed higher activity than that of a particle size of 10 nm or more prepared by the conventional method, and the sub-nanometer size gold cluster showed the highest activity.
  • the oxidation reaction of benzyl alcohol was performed using a temperature-controlled microwave apparatus. Benzyl alcohol (31.0 mg, 0.25 mmol), K 2 CO 3 (103.7 mg, 0.75 mmol), and H 2 O (10 mL) were added to the test tube. After sonication for 2 minutes, 1% catalyst (100 mg) was added to the reaction substrate and vigorously stirred (1000 rpm). When the temperature reached 80 ⁇ 2 ° C., 0.5 ml of 30% H 2 O 2 was added. After 90 minutes, the reaction was quenched with 2 M HCl. The product was extracted 3 times with AcOEt (10 mL). The extracted organic phase was dried over Na 2 SO 4 , diluted to 100 mL, and analyzed by gas chromatography (Shimadzu, GC-2014). The results (conversion and selectivity) are shown in Table 2.
  • the catalyst of the present invention shows higher activity than the gold catalysts prepared by the conventional method (0.5Au / SBA (IP), 0.5Au / SBA (DP)), and the gold particle size decreases. It can be seen that the activity increases. Furthermore, the relative production of aldehyde (1) increased with increasing gold particle size. From the results of EXAFS shown in FIG. 4, the gold particle size is the smallest when the firing time is 2 hours and is about 0.8 nm, and when it is 8 hours, it is about 1.0 nm. Furthermore, when the firing time is 16 hours, it can be seen from the histogram shown in FIG. 5 that the gold particle size increases to 2.8 ⁇ 0.6 nm (average value and standard deviation).
  • Example 3 Examination of reusability (1) The reusability of 0.5Au 11 -SBA (2h) was investigated. After completion of the reaction, 0.5Au 11 -SBA (2h) catalyst was recovered from the reaction mixture by filtration, washed well with acetone and dried. The catalyst thus recovered was reused in the next run under the same conditions as in Example 2. The results (conversion and selectivity) are shown in Table 3.
  • Example 4 Supporting gold on mesoporous silica 4 mg (corresponding to 0.16% by mass) of the gold 11-mer (Au 11 ) (diameter 0.8 nm) prepared in Reference Example 1 was mixed with 24 mL of a mixed solvent of dichloromethane and ethanol (CH 2 Cl 2 / C 2 was dissolved in H 5 OH (80/20)), then added mesoporous silica SBA-15 of 1g prepared in reference example 2 to this solution was stirred for 2 hours. After stirring, it was filtered to obtain mesoporous silica adsorbing gold 11-mer (Au 11 ).
  • FIG. 7 shows the HAADF-STEM (High-angle annular dark-field scanning transmission electromicroscopy) images and the gold cluster particle size distribution at firing times of 2, 8, and 16 hours.
  • Au 11 supported on SBA-15 with a firing time of 2 hours is 0.16Au 11 -SBA (2)
  • 8 hours is 0.16Au 11 -SBA (8)
  • 16 hours is 0.16Au 11 -SBA (16). write.
  • the particle size of the gold cluster was evaluated by HAADF-STEM and diffuse reflectance UV-vis spectroscopy.
  • the average particle size was 0.8 ⁇ 0.3 nm at a firing time of 2 hours, 1.5 ⁇ 0.6 nm at a firing time of 8 hours, and 1.9 ⁇ 1.0 nm at a firing time of 16 hours.
  • FIG. a) is 0.16Au 11 -SBA (2)
  • b) is 0.16Au 11 -SBA (8)
  • c) is 0.16Au 11 -SBA (16).
  • the surface plasmon band of the gold cluster was not found for 0.16Au 11 -SBA (2), but it became clear as the firing time became longer. This tendency coincides with the result of HAADF-STEM.
  • Au 11 clusters aggregated into large particles by heat-induced migration.
  • 0.16Au 11 -SBA (2) the firing time was short and there was little opportunity for aggregation, and as a result, the Au 11 cluster was maintained as it was.
  • Example 5 The catalytic activity of 0.16Au 11 -SBA (2), 0.16Au 11 -SBA (8), and 0.16Au 11 -SBA (16) obtained in Example 4 for the oxidation reaction of benzyl alcohol was the same as in Example 3.
  • Table 4 shows rate constants k and k ′ in addition to the yields of benzyl alcohol (1) as a raw material and benzaldehyde (2) and benzoic acid (3) as products.
  • k is a value normalized by the surface area of the corresponding cluster on the assumption that the diameter is spherical as shown in FIG.
  • k ′ is a value normalized by a relative rate constant of 0.16Au 11 -SBA (2), and is also shown in B of FIG. k ′ indicates that the Au 11 cluster having the smallest average particle diameter (0.8 nm) has higher catalytic activity than the large Au 11 cluster (1.5 nm and 1.9 nm).
  • Example 6 Examination of reusability (2) The reusability of 0.16Au 11 -SBA (2) obtained in Example 4 was examined. After completion of the reaction, 0.16Au 11 -SBA (2) catalyst was recovered from the reaction mixture by filtration, washed well with acetone and dried. The catalyst thus recovered was reused in the next run under the same conditions as in Example 2. However, 0.5 ml of 30% H 2 O 2 was added when the temperature reached 60 ⁇ 2 ° C. The results (yield) are shown in Table 5. From the results of Table 5, it was found that, at 60 ° C., it can be repeatedly used up to 4 times without losing the catalytic activity.
  • Example 7 Oxidation of primary and secondary alcohols About 0.16Au 11 -SBA (2) obtained in Example 4, the oxidation of various primary alcohols or secondary alcohols was examined. The reaction conditions were the same as in Example 2. However, 0.5 ml of 30% H 2 O 2 was added when the temperature reached 60 ⁇ 2 ° C. The results (recovery rate and yield) are shown in Table 6.
  • the present invention is useful in the catalyst utilization field.

Abstract

Disclosed are: a process for preparing a silica-supported gold cluster having a size of the order ranging from a subnanometer to several nanometers; a silica-supported gold cluster having a size of the order of a subnanometer; and a catalyst comprising silica-supported gold clusters having a size of the order ranging from a subnanometer to several nanometers. Specifically disclosed are: a complex which comprises a mesoporous silica and gold clusters having a particle size of 0.8 to 1.0 nm and supported in pores of the mesoporous silica; a catalyst comprising the complex; and a process for producing a gold cluster-mesoporous silica complex comprising a mesoporous silica and gold clusters having a particle size of 3 nm or less and supported in pores of the mesoporous silica, which comprises the steps of mixing a mesoporous silica and triphenylphosphine-protected 11-mer gold clusters (referred to as "Au11:TTP", hereinbelow) together in a solvent to allow the Au11:TTP to be adsorbed on the mesoporous silica, and firing the mesoporous silica having Au11:TTP adsorbed thereon to remove at least a portion of the triphenylphosphine.

Description

メソポーラスシリカ担持金クラスターとこれを用いる触媒およびこれの製造方法Mesoporous silica-supported gold cluster, catalyst using the same, and method for producing the same 関連出願の相互参照Cross-reference of related applications
　本出願は、２００９年３月２６日出願の日本特願２００９０－７６９７２号の優先権を主張し、その全記載は、ここに特に開示として援用される。 This application claims the priority of Japanese Patent Application No. 20090-76972 filed on Mar. 26, 2009, the entire description of which is specifically incorporated herein by reference.
　本発明は、メソポーラスシリカ担持金クラスターとこれを用いる触媒およびこれの製造方法に関する。 The present invention relates to a mesoporous silica-supported gold cluster, a catalyst using the same, and a method for producing the same.
　金属酸化物に担持したナノサイズの金の触媒が近年注目されている。金触媒は担体に固定化されることにより、反応系から回収でき再使用できるという利点がある。さらに、担体としてシリカを使用できれば、安全性や経済的に優位な金クラスター触媒を製造できるという利点もある。シリカに担持された5nm未満の単分散金クラスターは、金クラスターの本質的な触媒活性についての研究のための理想的な材料である。なぜなら、シリカは触媒的に不活性であり、クラスターとの相互作用も比較的弱いからである。しかし、そのような小さい金クラスターをシリカに担持することは、共沈法 (DP)や含浸担持法(IP)のような従来法(非特許文献1、2)は使えないため、容易ではない。 In recent years, nano-sized gold catalysts supported on metal oxides have attracted attention. By immobilizing the gold catalyst on the carrier, there is an advantage that it can be recovered from the reaction system and reused. Furthermore, if silica can be used as a support, there is an advantage that a gold cluster catalyst which is superior in safety and economy can be produced. Mono-dispersed gold clusters of less than 5 nm supported on silica are ideal materials for studying the intrinsic catalytic activity of gold clusters. This is because silica is catalytically inactive and its interaction with clusters is relatively weak. However, it is not easy to support such small gold clusters on silica because conventional methods (Non-Patent Documents 1 and 2) such as coprecipitation method (DP) and impregnation support method (IP) cannot be used. .
　金クラスターを金属酸化物に担持する方法としては、アルカンチオールで保護した単分散金ナノ粒子（平均粒径3.5±0.5、6.3±0.5、8.2±0.9nm）をあらかじめ調製し、これを有機溶媒（クロロホルム、ジクロロメタン）中で金属酸化物（酸化タングステン、 ゼオライト、シリカ、チタニア、ジルコニア、酸化スズ、酸化イリジウム、酸化鉄、アルミナ、酸化亜鉛、酸化ニッケル）に吸着させ、これを空気中300℃で1時間焼成することによって、担持単分散金ナノ粒子を調製する方法が知られている(非特許文献3)。非特許文献3では、この担持単分散金ナノ粒子の200℃におけるエタノールの酸素酸化反応に対する触媒活性が評価された。 As a method of supporting the gold cluster on the metal oxide, monodispersed gold nanoparticles (average particle size 3.5 ± 0.5, 6.3 ± 0.5, 8.2 ± 0.9 nm) protected with alkanethiol are prepared in advance, and this is prepared using an organic solvent ( It is adsorbed on metal oxides (tungsten oxide, soot zeolite, silica, titania, zirconia, tin oxide, iridium oxide, iron oxide, alumina, zinc oxide, nickel oxide) in chloroform and dichloromethane). A method of preparing supported monodispersed gold nanoparticles by firing for a time is known (Non-patent Document 3). In Non-Patent Document 3, the catalytic activity of the supported monodispersed gold nanoparticles for the oxygen oxidation reaction of ethanol at 200 ° C. was evaluated.
　その他の例として、トリフェニルホスフィンで保護した金55量体（Au55、粒径1.4nm）をあらかじめ合成し、これを有機溶媒（ジクロロメタン）中でシリカに吸着させ、これを真空中200℃で2時間焼成することによって、担持単分散金ナノ粒子を調製する方法が知られている(非特許文献4)。担持単分散金ナノ粒子は、サイズを透過電子顕微鏡によって観測した結果、平均粒径1.4nmであった。100℃トルエン中におけるスチレンの部分酸化反応に対する触媒活性が評価された。 As another example, a gold 55-mer (Au55, particle size 1.4 nm) protected with triphenylphosphine was synthesized in advance and adsorbed onto silica in an organic solvent (dichloromethane). A method of preparing supported monodispersed gold nanoparticles by firing for a time is known (Non-Patent Document 4). As a result of observing the size of the supported monodispersed gold nanoparticles with a transmission electron microscope, the average particle size was 1.4 nm. The catalytic activity for partial oxidation of styrene in toluene at 100 ° C. was evaluated.
　また、特許文献1には、セリウムを含有するメソポーラスシリカと貴金属の超微粒子の複合体、その複合体の製造方法、並びにその複合体を触媒に用いた微量一酸化炭素の酸化的除去方法及びアルコール類の酸化的脱水素反応によるケトン類の合成方法が開示されている。前記複合体は、金の超微粒子を、セリウムを含有するメソポーラスシリカに担持させたことを特徴とするものであり、前記超微粒子の直径は、０．５～５ｎｍの範囲に全粒子数の殆どが含まれる。実施例２によれば、実施例１で用いた触媒中の金粒子の粒径の測定の結果、０～０．５ｎｍの範囲には全粒子数の１％、０．５～１ｎｍの範囲には全粒子数の１６％、１～１．５ｎｍの範囲には全粒子数の５１％、１．５～２．０ｎｍの範囲には全粒子数の２１％、２．０～２．５ｎｍの範囲には全粒子数の９％、２．５～３．０ｎｍの範囲には全粒子数の２％であった。 Patent Document 1 discloses a composite of cerium-containing mesoporous silica and noble metal ultrafine particles, a method for producing the composite, a method for oxidative removal of trace carbon monoxide using the composite as a catalyst, and an alcohol. A method for the synthesis of ketones by oxidative dehydrogenation of the class is disclosed. The composite is characterized in that ultrafine gold particles are supported on mesoporous silica containing cerium, and the diameter of the ultrafine particles is in the range of 0.5 to 5 nm, and the total number of particles is almost the same. Is included. According to Example 2, as a result of measuring the particle size of the gold particles in the catalyst used in Example 1, the range of 0 to 0.5 nm is 1% of the total number of particles, and the range of 0.5 to 1 nm. Is 16% of the total number of particles, 51% of the total number of particles in the range of 1 to 1.5 nm, 21% of the total number of particles in the range of 1.5 to 2.0 nm, 2.0 to 2.5 nm The range was 9% of the total number of particles, and the range of 2.5 to 3.0 nm was 2% of the total number of particles.
　さらに、特許文献１には、セリウムを含有するメソポーラスシリカに金の超微粒子を担持する方法が記載されている。この方法、塩化金酸の水溶液にアルカリ溶液を添加してｐＨ値を７．０以上１０．０未満の範囲に調整して塩化金酸を水酸化物イオンが配位した状態に変化させ、その溶液中にセリウムを含有するメソポーラスシリカを分散させるか又はその溶液とセリウムを含有メするソポーラスシリカとを接触させることにより、メソポーラスシリカ表面に電気的親和力で前記金の超微粒子の前駆体である水酸化物イオンが配位した金錯体を吸着させる方法を用いる。 Furthermore, Patent Document 1 describes a method of supporting ultrafine gold particles on mesoporous silica containing cerium. In this method, an alkaline solution is added to an aqueous solution of chloroauric acid to adjust the pH value to a range of 7.0 or more and less than 10.0, thereby changing chloroauric acid to a state in which hydroxide ions are coordinated. By dispersing mesoporous silica containing cerium in a solution or bringing the solution into contact with mesoporous silica containing cerium, the surface of the mesoporous silica is a precursor of the ultrafine gold particles with an electrical affinity. A method of adsorbing a gold complex coordinated with hydroxide ions is used.
特開2008-280184号公報JP 2008-280184 A
　特許文献１及び非特許文献１～８の全記載は、ここに特に開示として援用される。 The entire description of Patent Document 1 and Non-Patent Documents 1 to 8 is specifically incorporated herein by reference.
　これまで、高分子保護金クラスターや酸化物担持金クラスターに関する研究において、金クラスターのサイズを1nmよりも小さくすると酸素酸化反応に対する触媒活性が急激に増大することが報告されている(非特許文献5-7)。しかし、最も一般的な触媒担体の一つであるシリカについては、調製が困難なことから、金触媒のサイズ効果に関する情報は皆無である。例えば、前述の共沈法や含浸担持法などの一般的な方法では、粒径を5nm以下に抑えることは不可能であり、しかもサイズには幅広い分布が発生してしまう。 So far, in research on polymer-protected gold clusters and oxide-supported gold clusters, it has been reported that the catalytic activity for oxygen oxidation reaction increases rapidly when the size of the gold clusters is smaller than 1 nm (Non-patent Document 5). -7). However, silica, one of the most common catalyst supports, is difficult to prepare, so there is no information on the size effect of the gold catalyst. For example, in the general methods such as the coprecipitation method and the impregnation support method described above, it is impossible to suppress the particle size to 5 nm or less, and a wide distribution occurs in the size.
　特許文献１に記載の方法では、金の超微粒子を、セリウムを含有するメソポーラスシリカに担持させることで、金の超微粒子の直径が０．５～５ｎｍの範囲に全粒子数の殆どが含まれる複合体が提供される。しかし、金の超微粒子数は、直径が０～１ｎｍの範囲には合計で全粒子数の１７％であるのに対して、直径が１～３．０ｎｍの範囲には合計で全粒子数の８３％であった。即ち、この方法でも、金の超微粒子のサイズを１ｎｍより小さくすることは依然として難しい。また、特許文献１に記載の方法では、セリウムを含有するメソポーラスシリカに担持させることが必要であり、セリウムを含有させる操作を余計に必要とする。 In the method described in Patent Document 1, the gold ultrafine particles are supported on mesoporous silica containing cerium, so that the diameter of the gold ultrafine particles is within the range of 0.5 to 5 nm, and most of the total number of particles is included. A complex is provided. However, the number of ultrafine gold particles is 17% of the total number of particles when the diameter is in the range of 0 to 1 nm, whereas the total number of gold particles is within the range of 1 to 3.0 nm. 83%. That is, even with this method, it is still difficult to make the size of gold ultrafine particles smaller than 1 nm. Moreover, in the method of patent document 1, it is necessary to carry | support on the mesoporous silica containing cerium, and operation which contains cerium is needed extra.
　そこで、本発明の目的は、サブナノメートルから数ナノメートル領域のシリカ担持金クラスターを調製する方法を提供すること、それにより、従来得られたことがない、サブナノメートルのシリカ担持金クラスターを提供すること、さらには、サブナノメートルから数ナノメートル領域のシリカ担持金クラスターを用いた触媒を提供することにある。 Accordingly, an object of the present invention is to provide a method for preparing a silica-supported gold cluster in the sub-nanometer to several nanometer region, and thereby to provide a sub-nanometer silica-supported gold cluster that has never been obtained. Furthermore, another object of the present invention is to provide a catalyst using a silica-supported gold cluster in the sub-nanometer range to a few nanometer range.
　本発明者らは、上記目的を達成すべく種々検討し、その結果、トリフェニルホスフィン保護金11量体（Au11、粒径0.8nm）を出発物質として用いることで、サブナノメートルから数ナノメートル領域のシリカ担持金クラスターを調製することができることを見出し、本発明を完成した。 The present inventors have made various studies to achieve the above object, and as a result, by using triphenylphosphine-protected gold 11-mer (Au 11 , particle size 0.8 nm) as a starting material, sub-nanometers to several nanometers are obtained. We have found that a silica-supported gold cluster in the region can be prepared and completed the present invention.
　上記目的を達成する本発明は以下のとおりである。
[1]
粒子サイズが0.8～1.0nmの範囲にある金クラスターを細孔内に担持したメソポーラスシリカからなる、金クラスターとメソポーラスシリカの複合体。
[2]
メソポーラスシリカの細孔径は、2～50nmの範囲である[1]に記載の複合体。
[3]
メソポーラスシリカのBET比表面積は500～1300m2/gの範囲である[1]または[2]に記載の複合体。
[4]
金クラスターの担持量は、0.1～0.5質量%の範囲である[1]～[3]のいずれかに記載の複合体。
[5]
[1]～[4]のいずれかに記載の金クラスターとメソポーラスシリカの複合体からなる触媒。
[6]
触媒は、アルコール酸化反応用である[5]に記載の触媒。
[7]
メソポーラスシリカとトリフェニルホスフィンで保護した１１量体の金クラスター(以下、Au11:TTPと表す))とを溶媒中で混合して、Au11:TTPをメソポーラスシリカに吸着させる工程、
Au11:TTPを吸着したメソポーラスシリカを焼成してトリフェニルホスフィンの少なくとも一部を除去する工程、
を含む、粒子サイズが3nm以下の金クラスターの少なくとも一部を細孔内に担持したメソポーラスシリカからなる、金クラスターとメソポーラスシリカの複合体の製造方法。
[8]
Au11:TTPは、少なくとも[Au11(TPP)8Cl2]+およびAu11(TPP)7Cl3の一方または両方を含む[7]に記載の製造方法。
[9]
Au11:TTPをメソポーラスシリカ100質量部に対して0.1～2.5質量部の範囲で混合する[7]または[8]に記載の製造方法。
[10]
焼成は、180～220℃の範囲の温度で行う[7]～[9]のいずれかに記載の製造方法。
[11]
焼成は、吸着しているトリフェニルホスフィンの実質的に全部を除去する条件で実施する[7]～[10]のいずれかに記載の製造方法。
[12]
メソポーラスシリカは、細孔径が2～50nmの範囲である[7]～[11]のいずれかに記載の製造方法。 The present invention for achieving the above object is as follows.
[1]
A composite of gold clusters and mesoporous silica composed of mesoporous silica in which gold clusters having a particle size in the range of 0.8 to 1.0 nm are supported in pores.
[2]
The composite according to [1], wherein the mesoporous silica has a pore diameter in the range of 2 to 50 nm.
[3]
The composite according to [1] or [2], wherein the BET specific surface area of mesoporous silica is in the range of 500 to 1300 m 2 / g.
[Four]
The composite according to any one of [1] to [3], wherein the supported amount of the gold cluster is in the range of 0.1 to 0.5% by mass.
[Five]
[1] A catalyst comprising a composite of a gold cluster and mesoporous silica according to any one of [4].
[6]
The catalyst according to [5], which is used for an alcohol oxidation reaction.
[7]
A step of mixing mesoporous silica and trimeric phosphine-protected 11-mer gold cluster (hereinafter referred to as Au 11 : TTP) in a solvent to adsorb Au 11 : TTP to mesoporous silica;
Calcination of Au 11 : TTP adsorbed mesoporous silica to remove at least a part of triphenylphosphine,
A method for producing a composite of gold clusters and mesoporous silica, comprising mesoporous silica in which at least a part of gold clusters having a particle size of 3 nm or less is supported in pores.
[8]
Au 11 : TTP is the production method according to [7], wherein at least one of or both of [Au 11 (TPP) 8 Cl 2 ] + and Au 11 (TPP) 7 Cl 3 is included.
[9]
The production method according to [7] or [8], wherein Au 11 : TTP is mixed in an amount of 0.1 to 2.5 parts by mass with respect to 100 parts by mass of mesoporous silica.
[Ten]
The method according to any one of [7] to [9], wherein the firing is performed at a temperature in the range of 180 to 220 ° C.
[11]
The method according to any one of [7] to [10], wherein the calcination is performed under a condition that substantially all of the adsorbed triphenylphosphine is removed.
[12]
The method according to any one of [7] to [11], wherein the mesoporous silica has a pore diameter in the range of 2 to 50 nm.
　本発明によれば、サブナノメートルから数ナノメートル領域のシリカ担持金クラスターを調製する方法を提供することができ、それにより、従来得られたことがない、サブナノメートルのシリカ担持金クラスターを提供すること、さらには、サブナノメートルから数ナノメートル領域のシリカ担持金クラスターを用いた触媒を提供することができる。 According to the present invention, it is possible to provide a method for preparing a silica-supported gold cluster in the sub-nanometer to several nanometer region, thereby providing a sub-nanometer silica-supported gold cluster that has not been obtained conventionally. In addition, it is possible to provide a catalyst using a silica-supported gold cluster in the sub-nanometer to several nanometer range.
　本発明では、これまで報告例のないサブナノメートル金クラスターのシリカ上への担持に成功した。尚、サイズが極めて微小であるため通常の透過型電子顕微鏡では観測できないので、広域X線吸収端微細構造解析によって金と金の平均配位数に基づいて評価した。 In the present invention, a sub-nanometer gold cluster that has not been reported so far has been successfully supported on silica. Since the size is extremely small and cannot be observed with a normal transmission electron microscope, evaluation was performed based on the average coordination number of gold and gold by a wide-area X-ray absorption edge fine structure analysis.
　また、通常のシリカ吸着では焼成によって凝集が観測されたが、メソポーラスシリカを利用することで、焼成後の粒子凝集を抑えながら有機配位子の除去に成功した。 In addition, agglomeration was observed by firing in normal silica adsorption, but by using mesoporous silica, organic ligands were successfully removed while suppressing particle aggregation after firing.
図１は、参考例１で合成した金１１量体(Au11)(Au11:TPP)の熱重量分析の結果である。FIG. 1 shows the results of thermogravimetric analysis of gold 11-mer (Au 11 ) (Au 11 : TPP) synthesized in Reference Example 1. 図２は、担体として参考例2に示すSBA-15を用いた場合の金クラスターのサイズに対する焼成時間の依存性を拡散反射分光法で調べた結果である。FIG. 2 shows the results of examining the dependence of the firing time on the size of the gold cluster by diffuse reflectance spectroscopy when SBA-15 shown in Reference Example 2 is used as the carrier. 図３は、担体としてSBA-15(参考例2)、MCF(参考例3)およびHMS(参考例4)、さらには参照としてシリカ(SiO2)をそれぞれ用いて焼成時間を2時間とした場合の、金クラスターのサイズに対する担体の依存性を拡散反射分光法で調べた結果である。FIG. 3 shows the case where SBA-15 (Reference Example 2), MCF (Reference Example 3) and HMS (Reference Example 4) are used as carriers and silica (SiO 2 ) is used as a reference, and the firing time is 2 hours. It is the result of having investigated the dependence of the support | carrier with respect to the size of a gold cluster by diffuse reflection spectroscopy. 図４は、焼成時間および担体が異なるサンプルについてのTEM写真とEXAFS結果を示す。FIG. 4 shows TEM photographs and EXAFS results for samples with different firing times and carriers. 図５は、焼成時間および担体が異なるサンプルについてのTEM写真と金クラスターのサイズを示す。FIG. 5 shows TEM photographs and gold cluster sizes for samples with different firing times and carriers. 図６は、担体としてSBA-15(参考例２)を用い、焼成時間を２時間として得たサンプルのFT-IRスペクトルを示す。FIG. 6 shows an FT-IR spectrum of a sample obtained using SBA-15 (Reference Example 2) as a carrier and a firing time of 2 hours. 図７は、焼成時間2時間、8時間及び16時間におけるHAADF-STEM(High-angle annular dark-field scanning transmission electro microscopy)画像及び金クラスターの粒度分布を示す。便宜上、焼成時間2時間のSBA-15に担持されたAu11を0.16Au11-SBA(2)、8時間を0.16Au11-SBA(8)及び16時間を0.16Au11-SBA(16)とそれぞれ表記する。FIG. 7 shows HAADF-STEM (High-angle annular dark-field scanning transmission electromicroscopy) images and gold cluster particle size distributions at firing times of 2, 8, and 16 hours. For convenience, Au 11 supported on SBA-15 with a firing time of 2 hours is 0.16Au 11 -SBA (2), 8 hours is 0.16Au 11 -SBA (8), and 16 hours is 0.16Au 11 -SBA (16). Represent each. 図８は、拡散反射UV-vis 顕微鏡の結果を示す。a)が0.16Au11-SBA(2)、b)が0.16Au11-SBA(8)、c)が0.16Au11-SBA(16)である。FIG. 8 shows the results of a diffuse reflection UV-vis microscope. a) is 0.16Au 11 -SBA (2), b) is 0.16Au 11 -SBA (8), and c) is 0.16Au 11 -SBA (16). 図９は、実施例５におけるベンジルアルコールの酸化反応に対する触媒活性の結果を示す。Ａは反応時間に対するlog[1/(1-X)]の関係を示す。a)が0.16Au11-SBA(2)、b)が0.16Au11-SBA(8)、c)が0.16Au11-SBA(16)である。BはAu11クラスターの直径に対す規格化した反応速度定数の関係を示す。FIG. 9 shows the results of catalytic activity for the oxidation reaction of benzyl alcohol in Example 5. A shows the relationship of log [1 / (1-X)] to the reaction time. a) is 0.16Au 11 -SBA (2), b) is 0.16Au 11 -SBA (8), and c) is 0.16Au 11 -SBA (16). B shows the relationship of the normalized reaction rate constant to the diameter of the Au 11 cluster.
[複合体]
　本発明は、粒子サイズ (平均粒子径)が0.8～1.0nmの範囲の金クラスターを細孔内に担持したメソポーラスシリカからなる、金クラスターとメソポーラスシリカの複合体に関する。細孔内に担持した金クラスターは、原料は、金１１量体(Au11)であり、金１１量体の粒径は0.8nmである(金１１量体は単一化学種のため粒径に幅はない)。従って、製造条件にもよるが、本発明の複合体に担持されている金クラスターの粒子サイズ (平均粒子径)は、0.8nm以上であり、かつ1.0nm以下である。1.0nm以下は、粒子サイズ (平均粒子径)であるので1.0nm超える粒子サイズ(個別)を有する金クラスターも担持されている。しかし、担持されていたとしても、30%以下である。逆に粒子サイズ(個別)が0.8～1.0nmの範囲の金クラスターは、担持されている金クラスターの70%以上である。本発明の複合体に担持された金クラスターは、特許文献1に記載の金粒子を含有する複合体に担持された金粒子より遥かに細かい。 [Complex]
The present invention relates to a composite of gold clusters and mesoporous silica, which is composed of mesoporous silica in which gold clusters having a particle size (average particle diameter) in the range of 0.8 to 1.0 nm are supported in pores. The gold clusters supported in the pores are made of gold 11-mer (Au 11 ), and the particle size of the gold 11-mer is 0.8 nm. Is not wide). Accordingly, although depending on the production conditions, the particle size (average particle diameter) of the gold cluster supported on the composite of the present invention is 0.8 nm or more and 1.0 nm or less. Since 1.0 nm or less is a particle size (average particle diameter), gold clusters having a particle size exceeding 1.0 nm (individual) are also supported. However, even if it is supported, it is 30% or less. Conversely, gold clusters with particle sizes (individual) in the range of 0.8 to 1.0 nm are 70% or more of the supported gold clusters. The gold cluster supported on the composite of the present invention is much finer than the gold particles supported on the composite containing gold particles described in Patent Document 1.
　本発明の複合体は、金クラスターとメソポーラスシリカからなる複合体であり、換言すれば、メソポーラスシリカに担持した金クラスターである。但し、金クラスターの粒子サイズ(平均粒子径)は0.8～1.0nmの範囲である。非特許文献4に記載のように、シリカ粒子に金クラスターを担持したものは知られており、この金クラスターの粒子サイズは、平均粒径1.4nmであった。 The composite of the present invention is a composite comprising a gold cluster and mesoporous silica, in other words, a gold cluster supported on mesoporous silica. However, the particle size (average particle diameter) of the gold cluster is in the range of 0.8 to 1.0 nm. As described in Non-Patent Document 4, a silica particle carrying a gold cluster is known, and the gold cluster has a mean particle size of 1.4 nm.
　メソポーラスシリカの細孔内に、粒子サイズ (平均粒子径)が0.8～1.0nmの範囲の金クラスターを担持した、メソポーラスシリカ担持金クラスターは知られていない。 There is no known mesoporous silica-supported gold cluster in which gold clusters having a particle size (average particle diameter) in the range of 0.8 to 1.0 nm are supported in the pores of mesoporous silica.
　金クラスターを担持するメソポーラスシリカの細孔径は、2～50nmの範囲である。メソポーラスシリカは、一般に二酸化ケイ素(シリカ)を材料とする均一で規則的な細孔(メソ孔)を有する多孔質シリカである。メソポア領域と呼ばれる、2から50nmの領域の大きさのほぼ均一な直径の細孔を有し、細孔の作るネットワークの様式（空間対称性）や製造方法等によって、様々な特性を有することが知られている多孔質物質群である。この多孔質シリカは、細孔の直径、広い表面積等の特性から、例えば、分離吸着剤、クロマトグラフィー充填剤、排水処理剤、触媒等の構造部材として多くの用途が期待される物質の一つである。 The pore diameter of mesoporous silica supporting gold clusters is in the range of 2 to 50 nm. Mesoporous silica is porous silica having uniform and regular pores (mesopores) generally made of silicon dioxide (silica). It has pores with an almost uniform diameter called the mesopore region, ranging from 2 to 50 nm, and may have various characteristics depending on the network mode (spatial symmetry) created by the pores and the manufacturing method. It is a known group of porous materials. This porous silica is one of the substances that are expected to be used as a structural member such as a separation adsorbent, a chromatography filler, a wastewater treatment agent, a catalyst, etc. due to the characteristics such as pore diameter and large surface area. It is.
　また、IUPACでは触媒分野において、直径2～50nmの細孔をメソ孔と定義している。メソポーラスシリカの合成方法はいくつか知られており、界面活性剤を鋳型としたゾルゲル法が例示できる。カチオン性界面活性剤を用いて調製されるメソポーラスシリカは、カチオン性界面活性剤の種類により様々な細孔の作るネットワークの様式（空間対称性）をとり得ることが知られている(非特許文献8)。本発明では公知のメソポーラスシリカをそのまま利用することができる。 In IUPAC, pores with a diameter of 2 to 50 nm are defined as mesopores in the catalyst field. Several methods for synthesizing mesoporous silica are known, and a sol-gel method using a surfactant as a template can be exemplified. It is known that mesoporous silica prepared using a cationic surfactant can take various types of networks (spatial symmetry) created by various pores depending on the type of the cationic surfactant (Non-patent literature). 8). In the present invention, known mesoporous silica can be used as it is.
　本発明の複合体では、種々のタイプのメソポーラスシリカを担体として用いることができる。メソポーラスシリカの細孔径は、直径2～50nmであるが、本発明の複合体が触媒に用いられる場合には、触媒反応の種類に応じて、種々の細孔径のメソポーラスシリカを用いることができる。メソポーラスシリカの細孔径は、好ましくは2nm以上の範囲である。メソポーラスシリカのBET比表面積は、特に制限はないが、例えば、500～1300m2/gの範囲であることができる。メソポーラスシリカのBET比表面積は、好ましくは600～1200m2/gの範囲である。 In the composite of the present invention, various types of mesoporous silica can be used as a carrier. The mesoporous silica has a pore diameter of 2 to 50 nm. When the composite of the present invention is used as a catalyst, mesoporous silica having various pore diameters can be used depending on the type of catalytic reaction. The pore diameter of mesoporous silica is preferably in the range of 2 nm or more. The BET specific surface area of mesoporous silica is not particularly limited, but can be, for example, in the range of 500 to 1300 m 2 / g. The BET specific surface area of mesoporous silica is preferably in the range of 600 to 1200 m 2 / g.
　メソポーラスシリカの細孔内への金クラスターの担持量は、特に制限はないが、例えば、0.1～2.5質量%の範囲であることができる。金クラスターの担持は、多くなりすぎると、全量が細孔内に担持されにくくなることから、上限は2.5質量%程度である。また、金クラスターの担持量が多くなりすぎると、複合体製造のための焼成の際に、凝集して金クラスターの粒子が大きくなり過ぎるおそれがある。そのような観点から、金クラスターの担持量は、好ましくは0.1～0.5質量%の範囲である。 The amount of gold clusters supported in the pores of mesoporous silica is not particularly limited, but can be, for example, in the range of 0.1 to 2.5% by mass. If the amount of gold clusters supported becomes too large, the entire amount becomes difficult to be supported in the pores, so the upper limit is about 2.5% by mass. Further, if the amount of gold clusters supported is too large, the particles of gold clusters may become too large during aggregation for the production of the composite. From such a viewpoint, the supported amount of the gold cluster is preferably in the range of 0.1 to 0.5% by mass.
[触媒]
　本発明は、上記本発明の金クラスターとメソポーラスシリカの複合体からなる触媒も包含する。触媒に用いる複合体は、上記のとおりである。 [catalyst]
The present invention also includes a catalyst comprising the composite of the gold cluster of the present invention and mesoporous silica. The composite used for the catalyst is as described above.
　本発明の触媒は、例えば、酸化反応用であることができる。例えば、ベンジルアルコールなどの1級アルコールや1-インダノールなどの2級アルコールの酸化反応を挙げることができる。 The catalyst of the present invention can be used for an oxidation reaction, for example. Examples thereof include oxidation reactions of primary alcohols such as benzyl alcohol and secondary alcohols such as 1-indanol.
　本発明の触媒をアルコールの酸化反応に用いる場合には、以下のように行うことができる。金クラスターとメソポーラスシリカの複合体をK2CO3の水溶液中でアルコールと、混合・撹拌する。これにマイクロ波を照射し、温度が80±2℃に達したところで、過酸化水素を加える。但し、過酸化水素を加える温度は80±2℃に限定される意図ではなく、本発明の触媒の種類やアルコールの種類等を考慮して、例えば、50～90℃の範囲に適宜設定することができる。塩酸を加えて反応を止め、生成物を酢酸エチルで抽出する。抽出した有機相を硫酸ナトリウム乾燥し、ガスクロマトグラフィーにより同定・定量を行う。 When the catalyst of the present invention is used for an alcohol oxidation reaction, it can be carried out as follows. A composite of gold clusters and mesoporous silica is mixed and stirred with alcohol in an aqueous solution of K 2 CO 3 . This is irradiated with microwaves, and when the temperature reaches 80 ± 2 ° C., hydrogen peroxide is added. However, the temperature at which hydrogen peroxide is added is not intended to be limited to 80 ± 2 ° C., and may be appropriately set within a range of 50 to 90 ° C., for example, in consideration of the type of catalyst of the present invention and the type of alcohol Can do. The reaction is stopped by adding hydrochloric acid and the product is extracted with ethyl acetate. The extracted organic phase is dried over sodium sulfate and identified and quantified by gas chromatography.
[複合体の製造方法]
　本発明は、上記本発明の金クラスターとメソポーラスシリカの複合体の製造方法も包含する。この製造方法は、
(1)メソポーラスシリカとトリフェニルホスフィンで保護した１１量体の金クラスター(以下、Au11:TTPと表す))とを溶媒中で混合して、Au11:TTPをメソポーラスシリカに吸着させる工程、と
(2)Au11:TTPを吸着したメソポーラスシリカを焼成してトリフェニルホスフィンの少なくとも一部を除去する工程、
とを含むものである。 [Production method of composite]
The present invention also includes a method for producing a composite of the gold cluster and mesoporous silica of the present invention. This manufacturing method is
(1) A step of mixing mesoporous silica and trimeric phosphine-protected 11-mer gold clusters (hereinafter referred to as Au 11 : TTP) in a solvent to adsorb Au 11 : TTP to mesoporous silica; When
(2) a step of firing at least a part of triphenylphosphine by firing Au 11 : mesoporous silica adsorbed with TTP;
Is included.
(1)吸着工程
　金クラスターの原料としては、トリフェニルホスフィンで保護した１１量体の金クラスター(以下、Au11:TTPと表す)を用いる。トリフェニルホスフィンで保護した１１量体の金クラスターは、後述する参考例1に記載するように、市販のAu(I)(TPP)Cl錯体を原料として合成できる。参考例1で示す方法で得られるAu11:TTPは、少なくとも[Au11(TPP)8Cl2]+およびAu11(TPP)7Cl3の一方または両方を含むものである。但し、本発明では、この混合物に限らず、Au11:TTPとして用いることができる。 (1) Adsorption process As a raw material of the gold cluster, an 11-mer gold cluster (hereinafter referred to as Au 11 : TTP) protected with triphenylphosphine is used. The 11-mer gold cluster protected with triphenylphosphine can be synthesized from a commercially available Au (I) (TPP) Cl complex as described in Reference Example 1 described later. Au 11 : TTP obtained by the method shown in Reference Example 1 contains at least one or both of [Au 11 (TPP) 8 Cl 2 ] + and Au 11 (TPP) 7 Cl 3 . However, in the present invention, not only this mixture but also Au 11 : TTP can be used.
　メソポーラスシリカとAu11:TTPとを、所定の比率で、溶媒中で混合してAu11:TTPをメソポーラスシリカに吸着させる。例えば、Au11:TTPをメソポーラスシリカ100質量部に対して0.1～2.5質量部の範囲で混合することができる。Au11:TTPは、メソポーラスシリカに対して良好に吸着され、吸着の具合は、混合液の色の変化(有色から無色への変化)で判断することができる。溶媒としては、例えば、ジクロロメタン、クロロホルム、およびそれらのエタノール混合物等を用いることができる。特に、ジクロロメタン、クロロホルム、およびエタノールの3種類の溶媒の混合物を用いることがAu11:TTPを効率的かつ均一に吸着させるという観点から好ましい。 Mesoporous silica and Au 11 : TTP are mixed in a solvent at a predetermined ratio to adsorb Au 11 : TTP to mesoporous silica. For example, Au 11 : TTP can be mixed in the range of 0.1 to 2.5 parts by mass with respect to 100 parts by mass of mesoporous silica. Au 11 : TTP is favorably adsorbed to mesoporous silica, and the degree of adsorption can be determined by the color change of the mixed solution (change from colored to colorless). As the solvent, for example, dichloromethane, chloroform, ethanol mixture thereof and the like can be used. In particular, it is preferable to use a mixture of three solvents, dichloromethane, chloroform, and ethanol, from the viewpoint of efficiently and uniformly adsorbing Au 11 : TTP.
　Au11:TTPのメソポーラスシリカに対する吸着量は、多くなりすぎると、シリカに吸着したAu11から焼成によって有機分子であるトリフェニルホスフィンを除去する際に裸の金クラスターが移動し凝集する確率が高くなる傾向がある。そこで、本発明では、ある程度、Au11:TTPの吸着密度を下げることが好ましく、それによって、焼成工程において、裸の金クラスターが移動し凝集する確率を抑え、結果として、粒子サイズの小さい金クラスターの生成を可能にしている。 If the amount of Au 11 : TTP adsorbed on mesoporous silica is too large, there is a high probability that bare gold clusters will migrate and aggregate when removing triphenylphosphine, an organic molecule, by firing from Au 11 adsorbed on silica. Tend to be. Therefore, in the present invention, it is preferable to reduce the adsorption density of Au 11 : TTP to some extent, thereby suppressing the probability that a bare gold cluster moves and aggregates in the firing step, and as a result, a gold cluster having a small particle size. Is possible.
(2)除去する工程
　次いで、Au11:TTPを吸着したメソポーラスシリカを焼成してトリフェニルホスフィンの少なくとも一部を除去する。焼成条件は、Au11:TTPからのトリフェニルホスフィンの熱脱離の状況により適宜決定できる。図1に示すように、参考例1で合成したAu11:TTPは、200℃前後の温度で、トリフェニルホスフィンが熱脱離する。この点を考慮すると、焼成は、例えば、180～220℃の範囲の温度で行うことができる。また、焼成温度は、トリフェニルホスフィンの脱離(除去)の程度に影響を与えるだけでなく、メソポーラスシリカ細孔内に担持されている金クラスターの粒子サイズにも影響を与える。傾向としては、低温であるほど、また加熱が短時間であるほど、金クラスターの粒子サイズは小さく、逆に、高温であるほど、また加熱が長時間になるほど金クラスターの粒子サイズは大きくなる。これらの点を考慮して、焼成のための加熱温度と時間は、適宜決定される。但し、焼成は、吸着しているトリフェニルホスフィンの実質的に全部を除去する条件で実施することが好ましい。 (2) Removing Step Next, the mesoporous silica adsorbed with Au 11 : TTP is baked to remove at least a part of triphenylphosphine. The firing conditions can be appropriately determined depending on the state of thermal desorption of triphenylphosphine from Au 11 : TTP. As shown in FIG. 1, in the Au 11 : TTP synthesized in Reference Example 1, triphenylphosphine is thermally desorbed at a temperature around 200 ° C. Considering this point, the firing can be performed at a temperature in the range of 180 to 220 ° C., for example. The firing temperature not only affects the degree of elimination (removal) of triphenylphosphine, but also affects the particle size of the gold clusters supported in the mesoporous silica pores. As a tendency, the lower the temperature and the shorter the heating time, the smaller the gold cluster particle size. Conversely, the higher the temperature and the longer the heating time, the larger the gold cluster particle size. Considering these points, the heating temperature and time for firing are appropriately determined. However, the calcination is preferably carried out under conditions that remove substantially all of the adsorbed triphenylphosphine.
　例えば、加熱温度が200℃の場合には、加熱時間は2～16時間の範囲であることが、実質的に全てのトリフェニルホスフィンを除去でき、かつ金クラスターの粒子サイズを小さく、例えば、3nm以下、好ましくは1nm以下にコントロールできるという観点から適当である。焼成時間を2～16時間の範囲で調整することによって、平均粒径を0.8～3nmの範囲で制御でき、焼成時間を2～8時間の範囲で調整することによって、平均粒径を0.8～1.0nmの範囲で制御できる。 For example, when the heating temperature is 200 ° C., the heating time is in the range of 2 to 16 hours, so that substantially all of the triphenylphosphine can be removed and the particle size of the gold cluster is reduced, for example, 3 nm Hereinafter, it is suitable from the viewpoint of preferably controlling to 1 nm or less. By adjusting the firing time in the range of 2-16 hours, the average particle size can be controlled in the range of 0.8-3 nm, and by adjusting the firing time in the range of 2-8 hours, the average particle size can be controlled in the range of 0.8-1.0. Can be controlled in the nm range.
　上記工程により、粒子サイズが3nm以下の金クラスターの少なくとも一部を細孔内に担持したメソポーラスシリカからなる、金クラスターとメソポーラスシリカの複合体を製造することができる。製造された金クラスターとメソポーラスシリカの複合体は、そのまま、触媒として使用される。 According to the above process, a composite of gold clusters and mesoporous silica composed of mesoporous silica in which at least a part of gold clusters having a particle size of 3 nm or less is supported in the pores can be produced. The composite of the produced gold cluster and mesoporous silica is used as it is as a catalyst.
　本発明では、担体として表面積の大きいメソポーラスシリカを用いているため、吸着するAu11の密度を抑えることができる。そのため、例えば、金クラスターの粒子サイズを1nm以下にすることも可能であり、さらにAu11は原子レベルでサイズが揃っているという特徴もある。 In the present invention, since the mesoporous silica having a large surface area is used as the support, the density of the adsorbed Au 11 can be suppressed. Therefore, for example, the particle size of the gold cluster can be 1 nm or less, and Au 11 is also characterized in that the size is uniform at the atomic level.
　さらに本発明の製造方法では、原子レベルでサイズを揃えたAu11前駆体であるAu11:TTPを加熱処理することで、凝集過程を均一に生じさせ、金クラスターの分散性を維持でき、その結果、比較的小さいサイズに制御することができる。 Furthermore, in the production method of the present invention, by performing heat treatment of Au 11 : TTP, which is an Au 11 precursor having a uniform size at the atomic level, an agglomeration process can be uniformly generated and the dispersibility of the gold cluster can be maintained. As a result, it can be controlled to a relatively small size.
　以下、本発明を実施例によりさらに詳細に説明する。 Hereinafter, the present invention will be described in more detail with reference to examples.
参考例１
トリフェニルホスフィン（TPP）で保護された金１１量体の合成法
1. Au(I)(TPP)Cl錯体470mgをエタノール（20mL）に加え30分撹拌した。
2. 水素化ホウ素ナトリウム（35.9mg）をエタノール（7.5mL）に溶かし、これを一気に上述の液に加え、3時間撹拌した。
3. これにヘキサンを500mL加え、24時間静置した。
4. ろ過し、数回ヘキサンで洗浄し、乾かした。
5. 110mg程度の金１１量体(Au11)が得られた。 Reference example 1
Synthesis of gold 11-mer protected with triphenylphosphine (TPP)
1. 470 mg of Au (I) (TPP) Cl complex was added to ethanol (20 mL) and stirred for 30 minutes.
2. Sodium borohydride (35.9 mg) was dissolved in ethanol (7.5 mL) and added to the above solution all at once and stirred for 3 hours.
3. To this was added 500 mL of hexane and allowed to stand for 24 hours.
4. Filtered, washed several times with hexane and dried.
5. About 110 mg of gold 11-mer (Au 11 ) was obtained.
　金１１量体(Au11)の熱重量分析の結果を図1に示す。熱重量分析の結果は、金１１量体(Au11)として[Au11(TPP)8Cl2]+とAu11(TPP)7Cl3のどちらを想定しても、配位子がほぼ完全に除去されていることを示唆した。 The results of thermogravimetric analysis of gold 11-mer (Au 11 ) are shown in FIG. The results of thermogravimetric analysis show that the ligand is almost complete regardless of whether [Au 11 (TPP) 8 Cl 2 ] + or Au 11 (TPP) 7 Cl 3 is used as the gold 11mer (Au 11 ). Suggested that it has been removed.
参考例２
SBA-15の合成法
1. 2M HCl溶液（75mL）に、両親媒性高分子P123（ポリエチレンオキサイドとポリプロピレンオキサイドのブロックポリマー）2gを加え、40℃で4時間撹拌した。
2. TEOS（テトラエトキシシラン）4.25gを加え、40℃で24時間撹拌した。
3. 80℃のオートクレーブに1日置いた。
4. ろ過し、乾かした。
5. 空気中500℃で6時間焼成して、メソポーラスシリカSBA-15を得た。 Reference example 2
Synthesis method of SBA-15
1. 2 g of amphiphilic polymer P123 (polyethylene oxide and polypropylene oxide block polymer) was added to 2 M HCl solution (75 mL) and stirred at 40 ° C. for 4 hours.
2. 4.25 g of TEOS (tetraethoxysilane) was added and stirred at 40 ° C. for 24 hours.
3. Placed in an autoclave at 80 ° C for 1 day.
4. Filtered and dried.
5. Sintered at 500 ° C. for 6 hours in air to obtain mesoporous silica SBA-15.
参考例３
MCFSの合成法
1. 2M HCl溶液（75mL）に、両親媒性高分子P123を2g加え、40℃で4時間撹拌した。
2. 1gのTMB（1,3,5-トリメチルベンゼン）を加え、40℃で2時間撹拌した。
3. TEOS（テトラエトキシシラン）4.25gを加え、40℃で24時間撹拌した。
4. 80℃のオートクレーブに1日置いた。
5. ろ過し、乾かした。
6. 空気中500℃で6時間焼成して、メソポーラスシリカMCFSを得た。 Reference example 3
MCFS synthesis
1. 2 g of amphiphilic polymer P123 was added to 2M HCl solution (75 mL) and stirred at 40 ° C. for 4 hours.
2. 1 g of TMB (1,3,5-trimethylbenzene) was added and stirred at 40 ° C. for 2 hours.
3. 4.25 g of TEOS (tetraethoxysilane) was added and stirred at 40 ° C. for 24 hours.
4. Placed in an 80 ° C autoclave for 1 day.
5. Filtered and dried.
6. Baked at 500 ° C. for 6 hours in air to obtain mesoporous silica MCFS.
参考例４
HMSの合成法
1. 11.5M HCl溶液（47mL）に、水を270mL加える。
2. CTAB(Cetyl Trimethyl Ammonium Bromide)を4.74g加え、室温で溶けるまで撹拌した。
3. TEOS（テトラエトキシシラン）20.8gを加え、40℃で24時間撹拌した。
4. 室温で48時間静置した。
5. ろ過し、乾かす。
6. 空気中600℃で6時間焼成して、メソポーラスシリカHMSを得た。 Reference example 4
HMS synthesis method
1. Add 270 mL water to 11.5 M HCl solution (47 mL).
2. 4.74 g of CTAB (Cetyl Trimethyl Ammonium Bromide) was added and stirred at room temperature until dissolved.
3. 20.8 g of TEOS (tetraethoxysilane) was added and stirred at 40 ° C. for 24 hours.
4. Allowed to stand at room temperature for 48 hours.
5. Filter and dry.
6. Baked at 600 ° C. for 6 hours in air to obtain mesoporous silica HMS.
　参考例２～４で合成したメソポーラスシリカのBET比表面積、総細孔容量およびBJH吸着細孔径を表1に示す。 Table 1 shows the BET specific surface area, total pore volume, and BJH adsorption pore diameter of the mesoporous silica synthesized in Reference Examples 2 to 4.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
実施例１
金のメソポーラスシリカへの担持
　参考例1で調製した金１１量体(Au11)5mgを24mLのジクロロメタンに溶解し、次いで、参考例2～4のいずれかで調製したメソポーラスシリカ1gをこの溶液に添加し、2時間撹拌した。撹拌後濾過して、金１１量体(Au11)を吸着したメソポーラスシリカを得た。吸着前の溶液と濾過後に得られた濾過液との色の違い(吸光スペクトルの違い)から、溶液に含まれていた金１１量体(Au11)はほぼ100%メソポーラスシリカに吸着されたことが分かった。 Example 1
Supporting gold on mesoporous silica 5 mg of gold 11-mer (Au 11 ) prepared in Reference Example 1 was dissolved in 24 mL of dichloromethane, and then 1 g of mesoporous silica prepared in any of Reference Examples 2 to 4 was added to this solution. Added and stirred for 2 hours. After stirring, it was filtered to obtain mesoporous silica adsorbing gold 11-mer (Au 11 ). Due to the difference in color (difference in absorption spectrum) between the solution before adsorption and the filtrate obtained after filtration, the gold 11-mer (Au 11 ) contained in the solution was adsorbed to almost 100% mesoporous silica. I understood.
　上記得られた金１１量体(Au11)を吸着したメソポーラスシリカを200℃で焼成した。図1に示す金１１量体(Au11)の熱重量分析の結果から、焼成温度を200℃に設定した。担体として参考例2に示すSBA-15を用いた場合の、金クラスターのサイズに対する焼成時間の依存性を拡散反射分光法で調べた結果を図2に示す。図2に示す通り、焼成時間とともに表面プラズモン吸収のピークが増大しており、サイズが徐々に増加する様子が分かる。 The obtained mesoporous silica adsorbing the gold 11-mer (Au 11 ) was baked at 200 ° C. From the results of thermogravimetric analysis of gold 11-mer (Au 11 ) shown in FIG. 1, the firing temperature was set to 200 ° C. FIG. 2 shows the result of examining the dependence of the firing time on the size of the gold cluster by diffuse reflectance spectroscopy when SBA-15 shown in Reference Example 2 is used as a carrier. As shown in FIG. 2, the peak of surface plasmon absorption increases with the firing time, and it can be seen that the size gradually increases.
　担体としてSBA-15(参考例2)、MCF(参考例3)およびHMS(参考例4)、さらには参照としてシリカ(SiO2)をそれぞれ用いて焼成時間を2時間とした場合の、金クラスターのサイズに対する担体の依存性を拡散反射分光法で調べた結果を図3に示す。図3から、メソポーラスシリカを担体とすることで焼成に伴う凝集を抑制できることが分かる。 Gold clusters when SBA-15 (Reference Example 2), MCF (Reference Example 3) and HMS (Reference Example 4) are used as carriers and silica (SiO 2 ) is used as a reference and the firing time is 2 hours. FIG. 3 shows the result of examining the dependence of the carrier on the size of the material by diffuse reflectance spectroscopy. FIG. 3 shows that agglomeration accompanying firing can be suppressed by using mesoporous silica as a carrier.
　さらに、焼成時間および担体が異なるサンプルについてのTEM写真とEXAFS結果を図4に示し、TEM写真と金粒子のサイズを図5に示す。図4から、SBA-15に吸着したAu11:TPPを2時間焼成して得られた金クラスターがTEMで観測できないほど小さいことが分かる。また、EXAFSで求めた平均配位数は5.8±2.0であり、直径0.8nm程度の面心立方粒子の値に対応することが分かる。 Further, FIG. 4 shows TEM photographs and EXAFS results for samples with different firing times and carriers, and FIG. 5 shows TEM photographs and gold particle sizes. FIG. 4 shows that the gold cluster obtained by firing Au 11 : TPP adsorbed on SBA-15 for 2 hours is so small that it cannot be observed by TEM. The average coordination number determined by EXAFS is 5.8 ± 2.0, which corresponds to the value of face-centered cubic particles having a diameter of about 0.8 nm.
　図5から、SBA-15に吸着したAu11:TPPを16時間焼成して得られた金クラスターの平均サイズが2.8±0.6nm（平均値と標準偏差）2.5nmであることが分かる。また、他のメソポーラスシリカ上でも平均サイズ3nm程度の単分散粒子が得られていることが確認される。 From FIG. 5, it can be seen that the average size of gold clusters obtained by firing Au 11 : TPP adsorbed on SBA-15 for 16 hours is 2.8 ± 0.6 nm (average value and standard deviation) is 2.5 nm. It is also confirmed that monodisperse particles having an average size of about 3 nm are obtained on other mesoporous silica.
　さらに担体としてSBA-15(参考例2)を用い、焼成時間を2時間として得たサンプルのFT-IRスペクトルを図6に示す。図6から、焼成に伴い有機配位子に帰属されるピークが消失することから、配位子の除去が確認された。 Further, FIG. 6 shows an FT-IR spectrum of a sample obtained by using SBA-15 (Reference Example 2) as a carrier and a firing time of 2 hours. From FIG. 6, since the peak attributed to the organic ligand disappeared upon firing, the removal of the ligand was confirmed.
実施例２
　ベンジルアルコールの酸化反応に対する触媒活性を調べたところ、安息香酸が主生成物として得られた。また、得られた金触媒は従来法で調製した粒径10nm以上のものよりも高い活性を示し、さらにサブナノメートルサイズの金クラスターが最も高い活性を示した。 Example 2
When the catalytic activity for the oxidation reaction of benzyl alcohol was investigated, benzoic acid was obtained as the main product. In addition, the gold catalyst obtained showed higher activity than that of a particle size of 10 nm or more prepared by the conventional method, and the sub-nanometer size gold cluster showed the highest activity.
　ベンジルアルコールの酸化反応は、温度制御されたマイクロ波装置を用いて行った。ベンジルアルコール(31.0 mg、0.25 mmol)、K2CO3(103.7 mg、0.75 mmol)、およびH2O(10 mL)を試験管に加えた。2分間超音波処理した後、反応基質に対して1%の触媒(100 mg)を加え、強撹拌した(1000 rpm)。温度が80±2℃に達したところで、0.5 mlの30% H2O2を加えた。90分間後に反応を2 M HClで停止した。生成物をAcOEt(10 mL)で3回抽出した。抽出した有機相はNa2SO4で乾燥し、100 mLに希釈し、ガスクロマトグラフィー(Shimadzu、 GC-2014)で分析した。結果(転化率および選択率)を表2に示す。 The oxidation reaction of benzyl alcohol was performed using a temperature-controlled microwave apparatus. Benzyl alcohol (31.0 mg, 0.25 mmol), K 2 CO 3 (103.7 mg, 0.75 mmol), and H 2 O (10 mL) were added to the test tube. After sonication for 2 minutes, 1% catalyst (100 mg) was added to the reaction substrate and vigorously stirred (1000 rpm). When the temperature reached 80 ± 2 ° C., 0.5 ml of 30% H 2 O 2 was added. After 90 minutes, the reaction was quenched with 2 M HCl. The product was extracted 3 times with AcOEt (10 mL). The extracted organic phase was dried over Na 2 SO 4 , diluted to 100 mL, and analyzed by gas chromatography (Shimadzu, GC-2014). The results (conversion and selectivity) are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示す結果から、本発明の触媒は、従来法で調製した金触媒（0.5Au/SBA(IP)、0.5Au/SBA(DP)）よりも高い活性を示し、金粒子サイズの減少とともに活性が上昇することが分かる。さらに、金粒子サイズの増加とともに、アルデヒド(1)の相対的な生成量が増加した。尚、図4に示すEXAFSの結果から、金粒子サイズは焼成時間2時間の場合が最もが小さく約0.8nmであり、8時間の場合は約1.0nmである。さらに、焼成時間16時間の場合は、図5に示すヒストグラムから金粒子サイズは2.8±0.6nm（平均値と標準偏差）と大きくなることが分かる。 From the results shown in Table 2, the catalyst of the present invention shows higher activity than the gold catalysts prepared by the conventional method (0.5Au / SBA (IP), 0.5Au / SBA (DP)), and the gold particle size decreases. It can be seen that the activity increases. Furthermore, the relative production of aldehyde (1) increased with increasing gold particle size. From the results of EXAFS shown in FIG. 4, the gold particle size is the smallest when the firing time is 2 hours and is about 0.8 nm, and when it is 8 hours, it is about 1.0 nm. Furthermore, when the firing time is 16 hours, it can be seen from the histogram shown in FIG. 5 that the gold particle size increases to 2.8 ± 0.6 nm (average value and standard deviation).
実施例３
再利用性の検討(1)
　0.5Au11-SBA(2h)についての再利用性を検討した。反応終了後、0.5Au11-SBA(2h)触媒を濾過により反応混合物から回収し、アセトンでよく洗浄し、乾燥した。このように回収した触媒は、次のランで実施例2と同様の条件で再利用された。結果(転化率および選択率)は表3に示す。 Example 3
Examination of reusability (1)
The reusability of 0.5Au 11 -SBA (2h) was investigated. After completion of the reaction, 0.5Au 11 -SBA (2h) catalyst was recovered from the reaction mixture by filtration, washed well with acetone and dried. The catalyst thus recovered was reused in the next run under the same conditions as in Example 2. The results (conversion and selectivity) are shown in Table 3.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表３に示す結果から、本発明の触媒は、活性を実質的に保ったまま再利用ができることが分かる。 From the results shown in Table 3, it can be seen that the catalyst of the present invention can be reused while substantially maintaining its activity.
実施例４
金のメソポーラスシリカへの担持
　参考例1で調製した金１１量体(Au11)(直径0.8nm)4mg(0.16質量%相当)を24mLのジクロロメタンとエタノールの混合溶媒(CH2Cl2/C2H5OH(80/20))に溶解し、次いで、参考例2で調製した1gのメソポーラスシリカSBA-15をこの溶液に添加し、2時間撹拌した。撹拌後濾過して、金１１量体(Au11)を吸着したメソポーラスシリカを得た。吸着前の溶液と濾過後に得られた濾過液との色の違い(吸光スペクトルの違い)から、溶液に含まれていた金１１量体(Au11)はほぼ100%メソポーラスシリカに吸着されたことが分かった。 Example 4
Supporting gold on mesoporous silica 4 mg (corresponding to 0.16% by mass) of the gold 11-mer (Au 11 ) (diameter 0.8 nm) prepared in Reference Example 1 was mixed with 24 mL of a mixed solvent of dichloromethane and ethanol (CH 2 Cl 2 / C 2 was dissolved in H 5 OH (80/20)), then added mesoporous silica SBA-15 of 1g prepared in reference example 2 to this solution was stirred for 2 hours. After stirring, it was filtered to obtain mesoporous silica adsorbing gold 11-mer (Au 11 ). Due to the difference in color (difference in absorption spectrum) between the solution before adsorption and the filtrate obtained after filtration, the gold 11-mer (Au 11 ) contained in the solution was adsorbed to almost 100% mesoporous silica. I understood.
　上記得られた金１１量体(Au11)を吸着したメソポーラスシリカを真空下、200℃で焼成した。焼成温度を200℃に設定した。焼成時間2時間、8時間及び16時間におけるHAADF-STEM(High-angle annular dark-field scanning transmission electro microscopy)画像及び金クラスターの粒度分布を図7に示す。便宜上、焼成時間2時間のSBA-15に担持されたAu11を0.16Au11-SBA(2)、8時間を0.16Au11-SBA(8)及び16時間を0.16Au11-SBA(16)と表記する。金クラスターの粒度は、HAADF-STEM及び拡散反射UV-vis 顕微鏡(diffuse reflectance UV-vis spectroscopy)にて評価した。平均粒子径は、200粒子以上について測定した結果、焼成時間2時間で0.8±0.3nm、焼成時間8時間で1.5±0.6nm、焼成時間16時間で1.9±1.0nmであった。 The obtained mesoporous silica adsorbing the gold 11-mer (Au 11 ) was baked at 200 ° C. under vacuum. The firing temperature was set to 200 ° C. FIG. 7 shows the HAADF-STEM (High-angle annular dark-field scanning transmission electromicroscopy) images and the gold cluster particle size distribution at firing times of 2, 8, and 16 hours. For convenience, Au 11 supported on SBA-15 with a firing time of 2 hours is 0.16Au 11 -SBA (2), 8 hours is 0.16Au 11 -SBA (8), and 16 hours is 0.16Au 11 -SBA (16). write. The particle size of the gold cluster was evaluated by HAADF-STEM and diffuse reflectance UV-vis spectroscopy. As a result of measuring the average particle diameter of 200 particles or more, the average particle size was 0.8 ± 0.3 nm at a firing time of 2 hours, 1.5 ± 0.6 nm at a firing time of 8 hours, and 1.9 ± 1.0 nm at a firing time of 16 hours.
　拡散反射UV-vis 顕微鏡の結果を図8に示す。a)が0.16Au11-SBA(2)、b)が0.16Au11-SBA(8)、c)が0.16Au11-SBA(16)である。金クラスターの表面プラズモンバンドは0.16Au11-SBA(2)については見られなかったが、焼成時間が長くなると明らかになった。この傾向はHAADF-STEMの結果とも符合し、0.16Au11-SBA(8)及び0.16Au11-SBA(16)においては、Au11クラスターは、熱誘導移動により凝集して大きな粒子になった。それに対して0.16Au11-SBA(2)については焼成時間が短く、凝集の機会が少なく、その結果Au11クラスターがそのまま維持された。 The results of the diffuse reflection UV-vis microscope are shown in FIG. a) is 0.16Au 11 -SBA (2), b) is 0.16Au 11 -SBA (8), and c) is 0.16Au 11 -SBA (16). The surface plasmon band of the gold cluster was not found for 0.16Au 11 -SBA (2), but it became clear as the firing time became longer. This tendency coincides with the result of HAADF-STEM. In 0.16Au 11 -SBA (8) and 0.16Au 11 -SBA (16), Au 11 clusters aggregated into large particles by heat-induced migration. In contrast, for 0.16Au 11 -SBA (2), the firing time was short and there was little opportunity for aggregation, and as a result, the Au 11 cluster was maintained as it was.
実施例５
　実施例４で得られた0.16Au11-SBA(2)、0.16Au11-SBA(8)、及び0.16Au11-SBA(16)のベンジルアルコールの酸化反応に対する触媒活性を、実施例３と同様の方法で調べた。結果を図９及び表４に示す。表４には、原料であるベンジルアルコール(1)と生成物であるベンズアルデヒド(2)及び安息香酸(3)の収率に加えて、速度定数k及びk’を示す。但し、kは図7に示す直径の球状と仮定して対応するクラスターの表面積で規格化した値である。一方、k’は0.16Au11-SBA(2)の相対速度定数で規格化した値であり、図９のBにも示す。k’は平均粒子径(0.8nm)が最も小さいAu11クラスターが、大きいAu11クラスター(1.5nm及び1.9nm)に比べて、高い触媒活性を有することを示す。 Example 5
The catalytic activity of 0.16Au 11 -SBA (2), 0.16Au 11 -SBA (8), and 0.16Au 11 -SBA (16) obtained in Example 4 for the oxidation reaction of benzyl alcohol was the same as in Example 3. We investigated by the method. The results are shown in FIG. Table 4 shows rate constants k and k ′ in addition to the yields of benzyl alcohol (1) as a raw material and benzaldehyde (2) and benzoic acid (3) as products. However, k is a value normalized by the surface area of the corresponding cluster on the assumption that the diameter is spherical as shown in FIG. On the other hand, k ′ is a value normalized by a relative rate constant of 0.16Au 11 -SBA (2), and is also shown in B of FIG. k ′ indicates that the Au 11 cluster having the smallest average particle diameter (0.8 nm) has higher catalytic activity than the large Au 11 cluster (1.5 nm and 1.9 nm).
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
実施例６
再利用性の検討(2)
　実施例４で得られた0.16Au11-SBA(2)についての再利用性を検討した。反応終了後、0.16Au11-SBA(2)触媒を濾過により反応混合物から回収し、アセトンでよく洗浄し、乾燥した。このように回収した触媒は、次のランで実施例2と同様の条件で再利用された。但し、0.5 mlの30% H2O2を加えるのは、温度が60±2℃に達したときとした。結果(収率)は表5に示す。表５の結果から、60℃においては、4回までは触媒活性を失うことなく繰返利用できることが分かった。 Example 6
Examination of reusability (2)
The reusability of 0.16Au 11 -SBA (2) obtained in Example 4 was examined. After completion of the reaction, 0.16Au 11 -SBA (2) catalyst was recovered from the reaction mixture by filtration, washed well with acetone and dried. The catalyst thus recovered was reused in the next run under the same conditions as in Example 2. However, 0.5 ml of 30% H 2 O 2 was added when the temperature reached 60 ± 2 ° C. The results (yield) are shown in Table 5. From the results of Table 5, it was found that, at 60 ° C., it can be repeatedly used up to 4 times without losing the catalytic activity.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
実施例７
　１級及び２級アルコールの酸化
実施例４で得られた0.16Au11-SBA(2)について、種々の１級アルコールまたは２級アルコールの酸化について検討した。反応条件は実施例2と同様とした。但し、0.5 mlの30% H2O2を加えるのは、温度が60±2℃に達したときとした。結果(回収率と収率)は表6に示す。 Example 7
Oxidation of primary and secondary alcohols About 0.16Au 11 -SBA (2) obtained in Example 4, the oxidation of various primary alcohols or secondary alcohols was examined. The reaction conditions were the same as in Example 2. However, 0.5 ml of 30% H 2 O 2 was added when the temperature reached 60 ± 2 ° C. The results (recovery rate and yield) are shown in Table 6.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　本発明は触媒利用分野に有用である。 The present invention is useful in the catalyst utilization field.

Claims (12)

  1. 粒子サイズが0.8～1.0nmの範囲にある金クラスターを細孔内に担持したメソポーラスシリカからなる、金クラスターとメソポーラスシリカの複合体。 A composite of gold clusters and mesoporous silica composed of mesoporous silica in which gold clusters having a particle size in the range of 0.8 to 1.0 nm are supported in pores.
  2. メソポーラスシリカの細孔径は、2～50nmの範囲である請求項1に記載の複合体。 2. The composite according to claim 1, wherein the mesoporous silica has a pore diameter in the range of 2 to 50 nm.
  3. メソポーラスシリカのBET比表面積は500～1300m2/gの範囲である請求項1または2に記載の複合体。 The composite according to claim 1 or 2, wherein the mesoporous silica has a BET specific surface area in the range of 500 to 1300 m 2 / g.
  4. 金クラスターの担持量は、0.1～0.5質量%の範囲である請求項1～3のいずれか1項に記載の複合体。 The composite according to any one of claims 1 to 3, wherein a supported amount of the gold cluster is in a range of 0.1 to 0.5 mass%.
  5. 請求項1～4のいずれか1項に記載の金クラスターとメソポーラスシリカの複合体からなる触媒。 A catalyst comprising a composite of a gold cluster and mesoporous silica according to any one of claims 1 to 4.
  6. 触媒は、アルコール酸化反応用である請求項5に記載の触媒。 6. The catalyst according to claim 5, which is used for an alcohol oxidation reaction.
  7. メソポーラスシリカとトリフェニルホスフィンで保護した１１量体の金クラスター(以下、Au11:TTPと表す))とを溶媒中で混合して、Au11:TTPをメソポーラスシリカに吸着させる工程、
    Au11:TTPを吸着したメソポーラスシリカを焼成してトリフェニルホスフィンの少なくとも一部を除去する工程、
    を含む、粒子サイズが3nm以下の金クラスターの少なくとも一部を細孔内に担持したメソポーラスシリカからなる、金クラスターとメソポーラスシリカの複合体の製造方法。     A step of mixing mesoporous silica and trimeric phosphine-protected 11-mer gold cluster (hereinafter referred to as Au 11 : TTP) in a solvent to adsorb Au 11 : TTP to mesoporous silica;
    Calcination of Au 11 : TTP adsorbed mesoporous silica to remove at least a part of triphenylphosphine,
    A method for producing a composite of gold clusters and mesoporous silica, comprising mesoporous silica in which at least a part of gold clusters having a particle size of 3 nm or less is supported in pores.
  8. Au11:TTPは、少なくとも[Au11(TPP)8Cl2]+およびAu11(TPP)7Cl3の一方または両方を含む請求項7に記載の製造方法。 8. The production method according to claim 7, wherein Au 11 : TTP contains at least one or both of [Au 11 (TPP) 8 Cl 2 ] + and Au 11 (TPP) 7 Cl 3 .
  9. Au11:TTPをメソポーラスシリカ100質量部に対して0.1～2.5質量部の範囲で混合する請求項7または8に記載の製造方法。 9. The production method according to claim 7, wherein Au 11 : TTP is mixed in a range of 0.1 to 2.5 parts by mass with respect to 100 parts by mass of mesoporous silica.
  10. 焼成は、180～220℃の範囲の温度で行う請求項7～9のいずれか1項に記載の製造方法。 The production method according to any one of claims 7 to 9, wherein the firing is performed at a temperature in the range of 180 to 220 ° C.
  11. 焼成は、吸着しているトリフェニルホスフィンの実質的に全部を除去する条件で実施する請求項7～10のいずれか1項に記載の製造方法。 The production method according to any one of claims 7 to 10, wherein the calcination is carried out under conditions for removing substantially all of the adsorbed triphenylphosphine.
  12. メソポーラスシリカは、細孔径が2～50nmの範囲である請求項7～11のいずれか1項に記載の製造方法。 The production method according to any one of claims 7 to 11, wherein the mesoporous silica has a pore diameter in the range of 2 to 50 nm.
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