WO2014083729A1 - Macro-porous monolith and method for producing same - Google Patents

Abstract

In a production method disclosed in the present invention, the hydrolysis and polymerization of a silicon compound having a hydrolysable functional group by a sol-gel method and the phase separation of a solution system containing the compound are allowed to proceed in the system to form a gel which is composed of a skeletal phase containing a polymer of the compound at a high concentration and having fine pores formed therein and a solution phase containing a solvent of the system at a high concentration and which has a co-continuous structure composed of the two phases, and subsequently the gel is dried. In this manner, a macro-porous monolith having a (meso pore)-(macro pore) layered porous structure in which the skeletal phase serves as a skeleton, each of the fine pores is a meso pore, and the solution phase serves as a macro pore can be produced. In the method, the silicon compound is a hydrogenated silicon compound having a Si-H bond in the molecule. On the surface of the skeleton and in the inside of the meso pore in the macro-porous monolith, hydrogen sites each derived from the Si-H bond are distributed.

Description

Macroporous monolith and method for producing the same

The present invention relates to a macroporous monolith, more specifically, a macroporous monolith having a co-continuous structure of a skeleton and macropores and a hierarchical porous structure of mesopores and macropores, and a method for producing the same.

A porous monolith having pores made of an inorganic material such as silica is known. Such monoliths are widely used in chromatographic separation columns, enzyme carriers, catalyst carriers and the like. For the production of such a porous monolith, a sol-gel method which is a liquid phase reaction in a solution system is generally used. The sol-gel method is based on a sol-gel reaction, that is, hydrolysis and polymerization (polycondensation) of the compound, starting from an inorganic low-molecular compound having a hydrolyzable functional group dispersed in a dispersion medium. Typically, a method of obtaining an oxide aggregate or polymer is shown. The inorganic low molecular weight compound as a starting material is, for example, a metal alkoxide represented by tetraalkoxysilane and a metal salt having a hydrolyzable functional group. Conventional common porous monoliths have only mesopores (pores with a diameter of less than 50 nm). Such a porous monolith does not necessarily satisfy the properties desired for various applications.

Unlike this, Patent Literature 1 has a through-hole having a large pore diameter and a pore having a smaller pore diameter formed on the wall surface of the through-hole, and the through-hole and the skeleton exhibit a co-continuous structure. Sex monoliths are disclosed. According to the porous monolith having such a hierarchical porous structure, for example, a chromatographic separation column having a small pressure loss while maintaining a high separation performance is realized. Is difficult to realize and realizes properties desired for various applications as a porous monolith. A porous monolith having a hierarchical porous structure can be obtained, for example, by the progress of a sol-gel reaction combined with a phase separation process.

Non-Patent Documents 1 and 2 disclose fine particles that are not porous monoliths but have mesopores and that have Si—H bonds in the fine particles. Non-Patent Document 2 describes that silver nanoparticles can be formed in mesopores by reducing the salt of silver (I) with the fine particles.

Japanese Patent Laid-Open No. 6-25534 JP 7-41374 A

Z. Y. Xie et al., "Periodic mesoporous hydridosilica--synthesis of an" impossible "material and its thermal transformation into brightly photoluminescent periodic mesoporous nanocrystal silicon-silica composite", Journal of Americancie 5094-5102 O. Dag et al., "Spatially confined redox chemistry in periodic mesoporous hydridosilica-nanosilver grown in reducing nanopores", Journal of American Chemical Society, 2011, 133, pp. 17454-17462

The present invention aims to provide a macroporous monolith having a hierarchical porous structure, a macroporous monolith having an unconventional structure, and a method for producing the same.

In the method for producing a macroporous monolith of the present invention (first production method), in a solution system containing a silicon compound having a hydrolyzable functional group, hydrolysis and polymerization of the silicon compound by a sol-gel method, and By proceeding with phase separation of the system, it is composed of a skeleton phase rich in the silicon compound polymer and having pores with openings on the surface, and a solution phase rich in the solvent of the system, Forming a gel having a co-continuous structure of a skeleton phase and a solution phase; drying the formed gel; forming the skeleton phase as a skeleton, and forming the pores as mesopores having openings on the surface of the skeleton; A macroporous monolith having a hierarchical porous structure of the mesopores and macropores having a macropore as a phase is obtained. Here, in the method, the silicon compound is a silicon hydride compound having at least one Si—H bond in the molecule, and the Si— is formed on the surface of the skeleton and the inside of the mesopores as the monolith. A macroporous monolith in which hydrogen sites based on H bonds are distributed is obtained.

The macroporous monolith of the present invention (first macroporous monolith) has a skeleton composed of hydrido silica and macropores showing a co-continuous structure with the skeleton, and the skeleton has a surface on the skeleton. The mesopores having openings are formed in the structure, thereby having a hierarchical porous structure of the mesopores and macropores, and hydrogen sites based on Si—H bonds are formed on the surface of the skeleton and inside the mesopores. A distributed macroporous monolith.

In another aspect of the method for producing a macroporous monolith according to the present invention (second production method), the macroporous monolith has a skeleton composed of hydrido silica and a macropore showing a co-continuous structure with the skeleton, A mesopore having an opening on the surface of the skeleton is formed in the skeleton, thereby having a hierarchical porous structure of the mesopores and macropores, and Si—H is formed on the surface of the skeleton and inside the mesopores. The metal is reduced at the hydrogen sites in the macroporous monolith by contacting the macroporous monolith with distributed hydrogen sites based on the bonds with a solution containing a metal salt whose standard electrode potential is just greater than hydrogen. And the nanoparticle comprised from the said metal is formed, and the macroporous monolith by which the said nanoparticle is arrange | positioned at least inside the said mesopore is obtained.

Another aspect of the macroporous monolith of the present invention (second macroporous monolith) has a skeleton composed of hydrido silica or silica gel, and macropores showing a co-continuous structure with the skeleton. The mesopores having openings on the surface of the skeleton are formed in the skeleton, thereby having a hierarchical porous structure of the mesopores and macropores, and a standard electrode potential is at least inside the mesopores. A monolith in which nanoparticles composed of a metal that is larger than hydrogen are arranged.

According to the present invention, it is possible to provide a macroporous monolith having a hierarchical porous structure, a macroporous monolith having a structure that has not existed before, and a method for manufacturing the same.

1A to 1E are scanning electron microscope (SEM) observation images showing the structure of the porous monolith produced in Example 1. FIG. FIG. 1 (f) is an image showing the appearance of the first macroporous monolith produced in Example 1. FIG. 2 is a diagram showing the results of pore distribution measurement by mercury porosimetry for the first macroporous monolith produced in Example 1. FIG. 3 is a diagram showing the results of measurement of pore distribution by the nitrogen gas adsorption method for the first macroporous monolith produced in Example 1. FIG. 4A is a diagram showing the results of Fourier transform infrared spectroscopy (FT-IR) measurement on the first macroporous monolith produced in Example 1. FIG. FIG. 4B is a diagram showing a measurement result of Raman spectroscopy for the first macroporous monolith produced in Example 1. FIG. 4C is a diagram showing the measurement results of thermogravimetric-differential thermal analysis (TG-DTA) for the first macroporous monolith produced in Example 1. 4D is a diagram showing the results of solid-state ²⁹ Si CP / MAS NMR measurement for the first macroporous monolith prepared in Example 1. FIG. FIG. 5A shows the results of FT-IR measurement on the monolith after immersion of the first macroporous monolith in an aqueous silver nitrate solution to reduce silver ions in Example 2, and the FT-IR for the monolith before immersion. It is a figure shown together with a measurement result. FIG. 5B shows the results of FT-IR measurement on a monolith after immersion of the first macroporous monolith in an aqueous chloroauric acid tetrahydrate solution to reduce gold ions in Example 2. It is a figure shown with the FT-IR measurement result with respect to the said monolith. FIG. 5C is a graph showing FT-IR measurement results for the monolith after immersion of the first macroporous monolith in an aqueous palladium nitrate solution to reduce palladium ions in Example 2. It is a figure shown together with an IR measurement result. FIG. 5D shows the FT-IR measurement results for the monolith after immersion of the first macroporous monolith in the aqueous solution of chloroplatinic acid hexahydrate in Example 2 to reduce platinum ions. It is a figure shown with the FT-IR measurement result with respect to the said monolith. FIG. 6A is a diagram showing the results of wide-angle X-ray diffraction (XRD) measurement on a monolith after the first macroporous monolith is immersed in an aqueous solution of a metal salt to reduce metal ions in Example 2. . FIG. 6B is a diagram showing XRD measurement results (difference in equivalents of silver ions to be reduced) after immersion of the first macroporous monolith in an aqueous silver nitrate solution to reduce silver ions in Example 2. is there. FIG. 6C shows the XRD measurement results for the monolith after immersion of the first macroporous monolith in a chloroauric acid aqueous solution to reduce the gold ion in Example 2 (difference in equivalence of gold ions to be reduced). FIG. FIG. 6D is a graph showing XRD measurement results (difference in equivalence of palladium ions to be reduced) for the monolith after the first macroporous monolith was immersed in an aqueous palladium nitrate solution to reduce palladium ions in Example 2. It is. FIG. 6E shows the XRD measurement results for the monolith after the first macroporous monolith was immersed in a chloroplatinic acid aqueous solution to reduce platinum ions in Example 2 (difference in equivalence of platinum ions to be reduced). FIG. FIG. 7 shows the average particle diameter (difference of metal types) of metal nanoparticles that were reduced and deposited on the monolith by immersing the first macroporous monolith in an aqueous solution of a metal salt in Example 2. FIG. FIGS. 8A to 8D are diagrams showing high-angle scattering dark field (scanning transmission electron microscope) images (HAADF-STEM images) for the second macroporous monolith produced in Example 2. FIG. FIG. 9 is a view showing an SEM image of the second macroporous monolith produced in Example 2. FIG. FIG. 10 is a graph showing the amount of nitrogen gas adsorbed by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 2. FIG. 11 is a graph showing the result of pore distribution measurement by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 2. FIG. 12 is a diagram showing changes in color tone of the solution and the monolith when the first macroporous monolith is immersed in a solution containing a metal salt in Example 3. FIG. 13 is a graph showing the results of wide-angle X-ray diffraction (XRD) measurement for the second macroporous monolith produced in Example 3. FIG. 14 is a diagram showing the results of X-ray photoelectron spectroscopy (XPS) measurement on the second macroporous monolith produced in Example 3. FIG. 15 is a diagram showing the measurement results of ²⁹ Si solid-state NMR for the second macroporous monolith produced in Example 3. FIG. 16 is a view showing an SEM observation image of the second macroporous monolith produced in Example 3. 17 is a diagram showing a HAADF-STEM image of the second macroporous monolith produced in Example 3. FIG. 18 is a graph showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 3. FIG. FIG. 19 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 3. FIG. 20 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 3. FIG. 21 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 3. FIG. 22 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 4. FIG. 23A is a diagram showing a HAADF-STEM image of the second macroporous monolith produced in Example 4. FIG. FIG. 23B is a diagram showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 4. FIG. 24A is a diagram showing a HAADF-STEM image of the second macroporous monolith produced in Example 4. FIG. 24B is a graph showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 4. FIG. 24C is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 4. FIG. 24D is a diagram showing an SEM observation image of the second macroporous monolith produced in Example 4. FIG. 25A is a diagram showing a HAADF-STEM image of the second macroporous monolith produced in Example 4. FIG. 25B is a diagram showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 4. FIG. 26 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 5. FIG. 27A is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 5. FIG. FIG. 27B is a diagram showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 5. FIG. 28 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 5. FIG. 29 is a diagram showing the XPS measurement results for the second macroporous monolith produced in Example 5. FIG. FIG. 30 is a diagram showing an SEM observation image of the second macroporous monolith produced in Example 5. FIG. 31 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 5. FIG. 32A is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 5. FIG. 32B is a graph showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 5. FIG. 33 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 5. FIG. 34 is a view showing an SEM observation image of the second macroporous monolith produced in Example 5. FIG. 35 is a diagram showing an average particle diameter of metal nanoparticles in the second macroporous monolith produced in Example 5. FIG. 36 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 6. FIG. 37A is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 6. FIG. 37B is a diagram showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 6. FIG. 38 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 6. FIG. 39 is a diagram showing the XPS measurement results for the second macroporous monolith produced in Example 6. 40 is a view showing an SEM observation image of the second macroporous monolith produced in Example 6. FIG. FIG. 41 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 6. FIG. 42A is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 6. 42B is a diagram showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 6. FIG. FIG. 43 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 6. FIG. 44 is a diagram showing the XPS measurement results for the second macroporous monolith produced in Example 6. FIG. 45 is a view showing an SEM observation image of the second macroporous monolith produced in Example 6. FIG. 46 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 6. FIG. 47A is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 6. FIG. 47B is a graph showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 6. FIG. 48 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 6. FIG. 49 is a diagram showing XPS measurement results for the second macroporous monolith produced in Example 6. 50 is a view showing an SEM observation image of the second macroporous monolith produced in Example 6. FIG. FIG. 51 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 6. FIG. 52A is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 6. FIG. 52B is a diagram showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 6. FIG. 53 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 6. FIG. 54 is a diagram showing XPS measurement results for the second macroporous monolith produced in Example 6. FIG. 55 is a view showing an SEM observation image of the second macroporous monolith produced in Example 6. FIG. 56 is a diagram showing the XRD measurement results for the second macroporous monolith produced in Example 7. FIG. 57 is a diagram showing an HAADF-STEM observation image of the second macroporous monolith produced in Example 7. FIG. 58 is a graph showing the particle size distribution of metal nanoparticles in the second macroporous monolith produced in Example 7. FIG. 59 is a diagram showing the measurement results of the pore distribution by the nitrogen gas adsorption method for the second macroporous monolith produced in Example 7. FIG. 60 shows the XPS measurement results for the second macroporous monolith produced in Example 7. 61 is a view showing an SEM observation image of the second macroporous monolith produced in Example 7. FIG. 62 is a diagram showing the average particle diameter of metal nanoparticles in the second macroporous monolith produced in Example 7. FIG. FIG. 63 is a diagram showing a change in ultraviolet absorption spectroscopy accompanying the progress of the reaction in an example of a 4-nitrophenol reduction reaction performed in Example 8. FIG. 64 is a diagram showing the fluid reaction system prepared in Example 8 and the reduction reaction of 4-nitrophenol to 4-aminophenol using the system.

A first aspect of the present disclosure has a skeleton composed of hydrido silica and macropores showing a co-continuous structure with the skeleton; mesopores having openings on the surface of the skeleton are formed in the skeleton And having a hierarchical porous structure of the mesopores and macropores; and providing a macroporous monolith in which hydrogen sites based on Si—H bonds are distributed on the surface of the skeleton and inside the mesopores .

In a second embodiment, in a solution system containing a silicon compound having a hydrolyzable functional group, hydrolysis and polymerization of the silicon compound by a sol-gel method and phase separation of the system are advanced, thereby It is composed of a polymer-rich skeleton phase with open pores on the surface and a solution phase rich in the solvent of the system, and forms a gel having a co-continuous structure of the skeleton phase and solution phase. Drying the formed gel; using the skeleton phase as a skeleton, the pores as mesopores having openings on the surface of the skeleton, and the solution phase as macropores. A method of obtaining a macroporous monolith having a hierarchical porous structure, wherein the silicon compound is a silicon hydride compound having at least one Si—H bond in the molecule, As monoliths, the interior surface and the mesopores of the framework to obtain a monolith hydrogen sites based on the Si-H bonds are distributed to provide a method for producing a macroporous monolith.

The third aspect provides a method for producing a macroporous monolith in addition to the second aspect, wherein the silicon hydride compound is trialkoxysilane.

The fourth aspect provides a method for producing a macroporous monolith, wherein, in addition to the second or third aspect, the alkoxy group of the trialkoxysilane is at least one selected from a methoxy group, an ethoxy group, and a propoxy group. To do.

The fifth aspect provides a method for producing a macroporous monolith, in addition to any of the second to fourth aspects, wherein the solution system is weakly acidic and contains alcohol.

The sixth aspect has a skeleton composed of hydrido silica or silica gel, and macropores showing a co-continuous structure with the skeleton, and mesopores having openings on the surface of the skeleton are formed in the skeleton. Thus, a macroporous structure having a hierarchical porous structure of the mesopores and macropores, and at least inside the mesopores, nanoparticles composed of a metal whose standard electrode potential is positively larger than hydrogen are arranged. Provide a sex monolith.

The seventh aspect has a skeleton composed of hydrido silica and a macropore showing a co-continuous structure with the skeleton, and mesopores having openings on the surface of the skeleton are formed in the skeleton. A macroporous monolith having a hierarchical porous structure of the mesopores and macropores, in which hydrogen sites based on Si—H bonds are distributed on the surface of the skeleton and inside the mesopores, and a standard electrode potential is Contacting with a solution containing a metal salt that is larger than hydrogen to reduce the metal at the hydrogen sites in the macroporous monolith to form nanoparticles composed of the metal, at least the meso Provided is a method for producing a macroporous monolith, which obtains a macroporous monolith in which the nanoparticles are arranged inside pores.

In an eighth aspect, in addition to the seventh aspect, a macroporous monolith in which hydrogen sites based on the Si—H bond are distributed is formed by the production method according to any one of the second to fifth aspects. A manufacturing method is provided.

In a ninth aspect, in addition to the seventh or eighth aspect, there is provided a method for producing a macroporous monolith, wherein the metal is at least one selected from platinum, palladium, gold, silver, copper, ruthenium, rhodium and mercury. provide.

In a tenth aspect, in addition to the seventh or eighth aspect, the metal is at least two kinds selected from platinum, palladium, gold, silver, copper, ruthenium, rhodium and mercury, and the nanoparticles are the at least 2 Provided is a method for producing a macroporous monolith that is a particle composed of an alloy or solid solution of a seed metal.

In this specification, “macropore” means a pore having a pore diameter (pore diameter) of 50 nm or more according to the proposal by IUPAC, and “mesopore” means a macropore and a micropore (pore having a pore diameter of less than 2 nm). ), That is, a pore having a pore diameter in the range of 2 nm or more and less than 50 nm. The pore size and average pore size of the pores are selected based on the expected pore size and average pore size, for example, general pore distribution measurement, for example, pore distribution measurement by mercury intrusion method for macropores, mesopores Can be obtained by measuring the pore distribution by a nitrogen gas adsorption method.

[First production method and first macroporous monolith]
In the first production method, in a solution system containing a silicon compound having a hydrolyzable functional group, hydrolysis and polymerization (polycondensation) of the silicon compound by sol-gel method and phase separation of the solution system proceed. By this, the process (gelation process) of forming the gel comprised from a skeleton phase and a solution phase is included. The skeleton phase of the gel formed in the gelation step is rich in the above-mentioned silicon compound polymer (hydrolyzate polycondensate). In the skeletal phase, pores having openings on the surface (pores that become mesopores after the gel is dried) are formed. However, not all of the pores have openings on the surface of the skeleton phase. The same applies to the mesopores after drying. The solution phase is rich in the solvent of the solution system, and the concentration of the polymer in the solution phase is relatively lower than the concentration in the skeleton phase. The skeletal phase and the solution phase generated through the phase separation process have a continuous three-dimensional network structure and are intertwined with each other, that is, the gel formed in the gelation process has a co-continuous structure of the skeleton phase and the solution phase. Have.

The first production method further includes a step (drying step) of drying the gel formed in the gelation step. Through the drying step, a first macroporous monolith (first monolith) is obtained. In the drying step, a first monolith skeleton is formed from the gel skeleton phase, and a first monolith macropore is formed from the solution phase. In the first monolith, corresponding to the structure of the skeleton phase and the solution phase of the gel, the skeleton and the macropores each have a continuous three-dimensional network structure and are intertwined with each other, that is, the first monolith is It has a co-continuous structure of macropores. As a result, the first monolith has a more uniform skeleton structure and superior mechanical properties such as strength as compared with a porous body formed by stochastic aggregation and binding of a plurality of polymer particles.

In addition to this, the first monolith has mesopores having openings on the surface of the skeleton. Mesopores are formed from the pores present in the skeleton phase of the gel through a drying process. Having an opening on the surface of the skeleton means having an opening on the wall surface of the macropore, that is, the first monolith has a hierarchical porous structure of macropores and mesopores having different pore diameters. In the present specification, a monolith having a co-continuous structure of a skeleton and macropores and having a hierarchical porous structure of such mesopores and macropores is referred to as a macroporous monolith. Hierarchical porous structure, for example, a chromatographic separation column that has a high specific surface area, that is, a high resolution, is secured by a mesopore with a small pore size while suppressing an increase in pressure loss due to a macropore with a large pore size. As a porous monolith, characteristics desired for various applications are realized.

In the first production method, a silicon hydride compound (silyl hydride compound) having a hydrolyzable functional group and having at least one Si—H bond in the molecule is used as the silicon compound. As a first monolith, a monolith in which hydrogen sites based on Si—H bonds are distributed (Si—H groups are distributed) on the surface of the skeleton and inside the mesopores is obtained. The Si—H groups distributed in the first monolith are derived from the silicon hydride compound that is the starting material of the first production method. The Si—H group has a reduction activity, particularly a reduction activity applicable to various organic reactions, and the first macro that can be used for various applications that can use the reduction activity by the first production method. A porous monolith is obtained.

Such a macroporous monolith cannot be obtained, for example, by agglomerating and binding fine particles formed by hydrolysis and polymerization of a silicon compound having a hydrolyzable functional group. Monoliths with a hierarchical porous structure of mesopores and macropores cannot be produced or are very difficult by fine particle binding. Even if hydrogen particles based on Si—H bonds are distributed and fine particles made of a polycondensate of a hydrolyzate of a silicon compound are prepared, and the fine particles are aggregated and bound, the silicon oxide is mainly used. Since the Si—H groups are easily decomposed by the high heat necessary for binding of the polycondensate as a component, all the Si—H groups are lost in the obtained binder.

The first macroporous monolith is realized for the first time by the first production method employing the sol-gel method in combination with the phase separation process. The skeleton of the first macroporous monolith is hydrido silica, which is a polycondensate of a hydrolyzate of the above silicon hydride compound, in which hydrogen sites based on Si—H bonds are distributed on the surface and inside of mesopores. (Hydrogenated silica). Hydride silica is common to ordinary silica gel in that it has a three-dimensional bond composed of a siloxane bond (Si—O—Si bond), but is different in that the hydrogen sites (Si—H groups) are distributed. ing. When Si—H groups of hydrido silica are oxidized or decomposed, Si—OH groups or Si—O—Si bonds are formed, and hydrido silica becomes ordinary silica gel.

In other words, the first macroporous monolith has a skeleton composed of hydrido silica and macropores indicating a co-continuous structure of the skeleton, and mesopores having openings on the surface of the skeleton in the skeleton. By being formed, it is a macroporous monolith having a hierarchical porous structure of mesopores and macropores, in which hydrogen sites based on Si—H bonds are distributed on the surface of the skeleton and inside the mesopores.

The distribution density of the hydrogen sites distributed on the surface of the skeleton and the mesopores in the first macroporous monolith has, for example, a silicon hydride compound and a Si—H bond as a silicon compound having a hydrolyzable functional group. This can be controlled by changing the mixing ratio of the two compounds in the solution system to a solution system containing a silicon compound (for example, silicon alkoxide). Moreover, after forming a 1st macroporous monolith, it is controllable also by converting a part of hydrogen site which the said monolith has into another functional group. An example of the conversion is the progress of the reaction between the Si—H group and the alcohol R—OH catalyzed by a zinc compound. In this case, the Si—H group is converted into an Si—OR group, and the first macroporous The distribution density of Si—H groups in the conductive monolith is lowered.

The silicon hydride compound is not limited as long as it has at least one Si—H bond in the molecule. The silicon hydride compound is preferably a compound having one Si—H bond. In the latter case, the remaining three bonds with the Si atom are preferably bonds between the Si atom and a hydrolyzable functional group.

The silicon hydride compound has a hydrolyzable functional group. The functional group is preferably at least one selected from an alkoxy group, an ethylene glycoxy group, and a glyceroxy group, and more preferably an alkoxy group from the viewpoint of hydrolysis rate. The alkoxy group is, for example, at least one selected from a methoxy group, an ethoxy group, and a propoxy group, and a sufficient rate can be obtained for hydrolysis of the silicon hydride compound. Therefore, at least one selected from a methoxy group and an ethoxy group Species are more preferred. When the silicon hydride compound has two or more hydrolyzable functional groups, it is preferable that all the functional groups are of the same type from the viewpoint of easy control of the sol-gel reaction.

The silicon hydride compound is preferably a trialkoxysilane (SiH (OR) ₃ : R is an alkyl group) having one Si—H bond in the molecule and three alkoxy groups as hydrolyzable functional groups. is there. When the silicon hydride compound is trialkoxysilane, it is composed of a three-dimensional network with siloxane bonds, and the formation of a skeleton in which the hydrogen sites are distributed on the surface and mesopores is more reliable. The alkoxy group possessed by the trialkoxysilane is preferably at least one selected from a methoxy group, an ethoxy group, and a propoxy group, and is selected from a methoxy group and an ethoxy group because a sufficient rate can be obtained for hydrolysis of the silicon hydride compound. More preferably, at least one selected from the above. From the viewpoint of easy control of the sol-gel reaction, the three alkoxy groups of trialkoxysilane are preferably the same.

The silicon hydride compound is, for example, trimethoxysilane (SiH (OCH ₃ ) ₃ ) or triethoxysilane (SiH (OCH ₂ CH ₃ ) ₃ ).

The formation of the gel in the gelation process is the same as the conventional macroporous monolith except that a silicon hydride compound having at least one Si—H bond in the molecule is used as the silicon compound having a hydrolyzable functional group. It can be carried out in the same manner as the gelation step based on the sol-gel method (conventional gelation step) combined with the phase separation process in the production of

For example, a solution system subjected to a sol-gel reaction involving a phase separation process can contain materials other than a silicon hydride compound and a solvent (dispersion medium) of the compound. The material only needs to be a material included in a solution system in a conventional gelation process. For example, a template component that contributes to the formation of pores of a skeleton phase, a phase separation inducer, and hydrolysis and polycondensation of a silicon compound It is a material that promotes or suppresses. Further, as described above, the solution system may contain a silicon compound having no Si—H bond (for example, silicon alkoxide) as the silicon compound having a hydrolyzable functional group. This silicon compound, together with the silicon hydride compound, forms a first monolith skeleton through hydrolysis and polycondensation by a sol-gel method, phase separation in a solution system, and drying. By including this silicon compound, for example, the distribution density of hydrogen sites distributed on the surface of the skeleton and the inside of the mesopores in the first macroporous monolith can be controlled.

The template component is not necessarily essential, but is preferably added to the solution system in order to ensure the formation of the pores of the skeletal phase (and the skeletal mesopores in the macroporous monolith). The template component is, for example, an amphiphilic compound. The amphiphilic compound is, for example, a cationic surfactant, a nonionic surfactant, and a block copolymer having a hydrophilic part and a hydrophobic part. The cationic surfactant is preferably a surfactant having a hydrophilic part such as a quaternary ammonium salt and a hydrophobic part mainly composed of an alkyl group. Specific examples of amphiphilic compounds are alkyl ammonium halides, polyoxyethylene alkyl ethers, ethylene oxide-propylene oxide-ethylene oxide block copolymers. The amphiphilic compound is preferably one that is uniformly dissolved in a solvent of a solution system.

When the template component is added to the solution system, for example, it is 0.5 to 5.0 g with respect to 0.0167 mol of silicon atoms (1.0 g in terms of anhydrous silica) in the solution system. 0 to 3.0 g is preferable, and 1.5 to 2.5 g is more preferable.

The phase separation inducer is not limited as long as it is a component capable of inducing a sol-gel reaction accompanied by a phase separation process, and a polymer compound that dissolves in a solution solvent such as polyethylene oxide (PEO) is preferable. As the phase separation inducer, polyvinyl pyrrolidone, polystyrene sulfonate sodium salt, polyallylamine hydrochloride, and the above-described materials as a template component can be used (in contrast, PEO also functions as a template component).

The amount of the phase separation inducer added is, for example, 0.01 to 1.0 mol as a monomer, preferably 0.05 to 0.7 mol, with respect to 1 mol of silicon in the solution. More preferred is 0.4 mol.

A material that promotes hydrolysis and polycondensation of a silicon compound is, for example, an acid. The acid is, for example, a mineral acid such as hydrochloric acid, sulfuric acid or nitric acid, and an organic acid such as acetic acid or citric acid. The acid is preferably hydrochloric acid, sulfuric acid or nitric acid.

The material that suppresses hydrolysis and polycondensation of the silicon compound is, for example, alcohol. The alcohol is, for example, methanol, ethanol, or propanol. When the silicon hydride compound has an alkoxy group as a hydrolyzable functional group, an alcohol having the same alkyl group as the alkyl moiety constituting the alkoxy group (parent alcohol: for example, when the silicon hydride compound has a methoxy group) Is preferably methanol). This simplifies the reaction system and increases the controllability of the sol-gel reaction.

The solution solvent is typically water. The amount of water is, for example, 2.0 to 40.0 in terms of molar ratio (water / silicon) to silicon in the solution, preferably 3.0 to 20.0, and more preferably 5.0 to 10.0. More preferred. Excess water inhibits gel formation.

The sol-gel reaction accompanied by the phase separation process proceeds by the completion of the solution system by mixing these materials in the same manner as the gelation step in the production of the conventional macroporous monolith. However, the first production method involves a phase separation process in order to suppress the loss of Si—H bonds of the silicon hydride compound in the gelation step (to suppress the decomposition of Si—H groups). The sol-gel reaction is preferably allowed to proceed under “mild” conditions.

For mild conditions, for example, it is preferable to make the solution system weakly acidic. For this purpose, for example, the amount of acid added to the solution system is preferably 2.0 mM to 500 mM, and preferably 5.0 mM to 200 mM, based on the total solvent typically composed of water (and alcohol). Is more preferably 10 mM to 50 mM (where M = mol / L).

For mild conditions, for example, it is preferable to add alcohol to the solution system, and the amount of alcohol added is, for example, 0.5 to 20.0 in terms of molar ratio (alcohol / silicon) to silicon in the solution. From 1.0 to 10.0, more preferably from 2.0 to 5.0. As described above, the alcohol is preferably a parent alcohol.

Most preferably, the solution system is weakly acidic and contains alcohol.

In the first production method, the gel formed in the gelation step is then dried to become the first macroporous monolith. A drying process can be implemented similarly to the drying process after the gelation process in manufacture of the conventional macroporous monolith. However, when the drying step is carried out in combination with heating, it is preferable to avoid as much as possible that a high temperature at which the Si—H group decomposes is applied to the gel.

The first macroporous monolith has, for example, the following characteristics in addition to the characteristics described above.

(1) The uniformity of the macropore diameter is high. Since macropores are formed through the phase separation process, the macropores have high uniformity in pore diameter. When the liquid is allowed to penetrate into the macroporous monolith, the average pore diameter of the macropores is preferably 1 μm or more. The same applies to the second macroporous monolith.

(2) It has a high specific surface area. Innumerable mesopores formed in the skeleton exhibit a high specific surface area. The specific surface area can be set to, for example, 600 m ³ / g or more, and is 800 m ³ / g or more depending on manufacturing conditions. The center hole diameter of the mesopore is preferably 2 to 10 nm. The same applies to the second macroporous monolith.

(3) Due to the distribution of hydrogen sites based on the Si—H bond (distribution of Si—H groups), a reduction reaction that reduces the substance that has entered the monolith can proceed. In this case, the hydrogen site functions as a reduction site. However, the reduction reaction is limited to the case where the standard electrode potential of the substance before reduction is positively higher than that of hydrogen. The first macroporous monolith is, for example, a reduction reaction of an organic compound or a reduction reaction of a metal compound (a metal compound such as gold, silver, copper, platinum, palladium, ruthenium, rhodium, mercury, rhenium, germanium, thallium). Can be used.

(4) The hydrogen sites are distributed not only on the surface of the skeleton (wall surface of the macropores) but also inside the mesopores. Thereby, a stable and reliable reduction reaction can be realized, and many substances can be reduced per unit weight of the monolith. Further, as shown in the description of the second production method and the second macroporous monolith, it becomes possible to arrange the reduced substance inside the mesopores. For example, the monolith can be used as a catalyst carrier. This is a great advantage when used.

(5) A substance having a Si—H bond (Si—H group) needs to be used with great care in the state of a low molecular compound due to the risk of explosion or combustion. The same applies to the case where a reduction reaction for reducing a substance by contact with the low-molecular compound proceeds. On the other hand, unlike the low-molecular compound, the first macroporous monolith can avoid these risks. This point is very advantageous in industry.

As long as the first macroporous monolith is obtained, the first production method can include any step other than the gelation step and the drying step.

The first macroporous monolith may be manufactured by a method other than the first manufacturing method described above.

The use of the first macroporous monolith is not limited, for example, a separation medium by any functional group modification to the Si—H group, a catalyst carrier by immobilization of a catalyst molecule / enzyme molecule accompanying a reduction reaction, a trace amount accompanying reduction It can be used widely for stabilizing and collecting harmful substances.

[Second production method and second macroporous monolith]
In the second production method, the first macroporous monolith is brought into contact with a solution containing a metal salt whose standard electrode potential E ⁰ is positively larger than hydrogen, whereby the hydrogen in the first macroporous monolith is made. The metal is reduced at the site to form nanoparticles composed of the metal (reduction process). And by this reduction | restoration process, the macroporous monolith (2nd macroporous monolith) by which the nanoparticle comprised from the said metal is arrange | positioned at least inside the mesopore is obtained. Nanoparticles have a length of any one of the vertical, horizontal, and height dimensions of 250 nm or less and 1 nm (where 1 nm is close to the size of one compound molecule or unit cell), preferably 100 nm or less. It means a particle of 1 nm or more. Particles having a length of less than 1 nm in any of the above dimensions are generally referred to as clusters, and particles exceeding 250 nm are generally referred to as fine particles.

The metal is a metal whose standard electrode potential E ⁰ is just larger than hydrogen in a state before reduction (typically in an ionic state in a solution). Examples of the metal include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), copper (Cu), ruthenium (Ru), rhodium (Rh), mercury (Hg), rhenium (Re), It is at least one selected from germanium (Ge) and thallium (Tl), and may be at least one selected from platinum, palladium, gold, silver, copper, ruthenium, rhodium and mercury. However, since mercury is a liquid at normal temperature and pressure, in order to obtain solid nanoparticles of mercury, mercury salt is dissolved in a low melting point solvent and the first macroporous monolith is dissolved in the melting point of mercury (−38 .9 ° C.) or lower. For example, E ⁰ in water at 25 ° C. is hydrogen: 0 V, platinum (Pt ²⁺ ): +1.19 V (+0.74 V as [PtCl ₆ ] ⁻ ), palladium (Pd ²⁺ ): +0.92 V, gold ( Au ³⁺ ): +1.52 V (as [AuCl ₄ ] ⁻ is +1.00 V), silver (Ag ⁺ ): +0.80 V, copper (Cu ²⁺ ): +0.34 V, ruthenium (Ru ²⁺ ): +0.80 V, Rhodium (Rh ³⁺ ): +0.76 V, Mercury (Hg ²⁺ ): +0.85 V, Rhenium (Re ³⁺ ): +0.30 V, Germanium (Ge ⁴⁺ ): +0.12 V, Thallium (Tl ³⁺ ): +0.72 V is there.

In the second production method, the metal reduction reaction proceeds using the hydrogen sites based on Si—H bonds distributed on the surface of the skeleton of the first macroporous monolith and the inside of the mesopores, and the sites exist. Nanoparticles (metal nanoparticles) composed of the metal are deposited on the portion that has been formed. It should be noted that “at least inside the mesopores” means that the nanoparticles arranged on the surface of the skeleton in the macroporous monolith (wall surface of the macropores) are treated after the production of the second macroporous monolith or This is because there is a possibility that it will flow out somewhat depending on the state of use. In the state immediately after reducing the metal, the nanoparticles are also arranged on the surface of the skeleton in the second macroporous monolith. Of course, the nanoparticle did not flow out by the treatment or use after the formation of the second macroporous monolith, and was also reduced to the surface of the skeleton in the second macroporous monolith together with the inside of the mesopores. The metal nanoparticles can be arranged.

The Si—H group obtained by reducing the metal becomes a Si—OH group or a Si—O—Si bond. In other words, the second macroporous monolith has a skeleton composed of hydrido silica or silica gel and macropores indicating a co-continuous structure of the skeleton, and the skeleton has an opening on the surface of the skeleton. By forming pores, it has a hierarchical porous structure of mesopores and macropores, and at least inside the mesopores, nanoparticles composed of a metal whose standard electrode potential is positively larger than hydrogen are arranged. Macroporous monolith.

The macroporous monolith in which the metal nanoparticles are arranged up to the inside of the mesopore cannot be produced by a conventional method. For example, even if a macroporous monolith is manufactured by a conventional method and a solution containing metal nanoparticles is flowed into the monolith, there is a possibility that the nanoparticles are supported on the surface of the skeleton of the monolith. Nanoparticles do not enter the interior.

In addition to this, in the second macroporous monolith, the reduction reaction of metal ions proceeds inside the mesopores, and metal nanoparticles are generated on the spot. For this reason, metal nanoparticles are formed along the shape of the wall surface of the mesopore, and the nonuniformity of the shape serves as a kind of anchor, and the dropping of the nanoparticle from the mesopore is suppressed. This is a significant industrial advantage when the second macroporous monolith is used, for example, as a catalyst support.

Furthermore, based on the fact that the uniformity of the Si—H group distribution (reduction site distribution) can be increased for the first macroporous monolith, the second macroporous monolith has a metal nanoparticle structure in the second monolith. High uniformity of distribution can be secured. Since the metal reduction reaction proceeds at very fine sites called Si—H groups, it is possible to ensure high uniformity of the composition of the formed metal nanoparticles.

The metal reduction reaction in the reduction process proceeds according to the electrochemical stoichiometric ratio. Therefore, when the amount of hydrogen sites distributed in the first macroporous monolith is the same, for example, platinum, palladium, gold, and silver are reduced to simple substances only by exchanging monovalent charges. The most particles are deposited.

On the other hand, when the equivalent of the metal ion to be reduced is smaller than the equivalent of the hydrogen site distributed in the first macroporous monolith, the hydrogen site remains in the second macroporous monolith after the reduction step. It will be. The remaining hydrogen sites (Si—H groups) can be changed to Si—OH groups by application of heat in the presence of water. That is, the skeleton of the second macroporous monolith may be hydrido silica in which Si—H groups remain, or normal silica gel that has lost Si—H groups.

The reduction step can proceed spontaneously by simply bringing the first macroporous monolith into contact with a solution containing a metal salt to be reduced based on the high reactivity of the Si—H group. At this time, when a solution containing two or more kinds of metal salts is used, nanoparticles of the respective metals and / or nanoparticles of the two or more kinds of metals or solid solution nanoparticles are precipitated, and the second macroporous monolith Placed inside. Which particles are deposited varies depending on the amount of metal ions to be reduced and the distribution density of hydrogen sites in the first macroporous monolith. When the hydrogen sites have a sufficiently large distribution density compared to the amount of metal ions to be reduced, the nanoparticles of each metal are likely to precipitate, and otherwise, nanoparticles of an alloy or a solid solution are likely to precipitate. Further, when the solution contains water, water is involved in the metal reduction reaction, so the amount of water contained in the solution also affects which particles are deposited. When the proportion of water in the solvent of the solution is large, the reduction reaction rate increases, and each metal nanoparticle tends to precipitate individually. On the other hand, when the proportion of water is small, the reduction reaction rate decreases, and nanoparticles of an alloy or a solid solution are likely to precipitate.

When alloy or solid solution nanoparticles are deposited, there is no upper limit to the number of metal species that can be reduced at one time, and multi-component systems such as binary, ternary, or quaternary systems, depending on the number of metal species present in the solution. Alloy nanoparticles or solid solution nanoparticles can be deposited. For example, in the second production method, the metal is at least two kinds selected from platinum, palladium, gold, silver, copper, ruthenium, rhodium and mercury, and the nanoparticles are an alloy or a solid solution of the at least two kinds of metals. May be. Examples of binary systems are Au—Pd system, Au—Pt system, Pd—Rh system, and Pt—Rh system. The Au—Pd-based nanoparticles can be used, for example, for direct synthesis of hydrogen peroxide, oxidation of alcohols and polyols, catalysts for oxidation of phenol and toluene, desulfurization of thiophene, and the like. The Au—Pt-based nanoparticles can be used, for example, as a catalyst for polyol and CO oxidation. Of course, the use of these nanoparticles is not limited to the above example. Examples of ternary systems are Au—Pd—Pt, Au—Pd—Rh, Au—Pt—Rh, and Pd—Pt—Rh. An example of a quaternary system is the Au—Pd—Pt—Rh system.

The reduction step is performed, for example, by immersing the first macroporous monolith in a solution containing a metal salt to be reduced. After the reduction step, for example, the soaked macroporous monolith can be removed from the solution and dried to obtain a second macroporous monolith.

The solution is, for example, an aqueous solution containing water as a main solvent component. Here, the main solvent component means a component having the largest content (for example, weight) among the components constituting the solvent. The solution with which the first macroporous monolith is brought into contact may be an aqueous solution containing only water, or water and a solvent miscible with water (for example, a polar solvent) as long as the effects of the present invention are obtained. An aqueous solution using the mixture as a solvent may be used. Solvents miscible with water include, for example, diols such as methanol, ethanol, propanol, ethylene glycol, triols such as glycerin, acetone, acid amides (formamide, N-methylformamide, N, N-dimethylformamide (DMF) , Acetamide, N-methylacetamide, N, N-dimethylacetamide, etc.), cyclic ethers (propylene oxide, trimethylene oxide, tetrahydrofuran, 1,4-dioxane, etc.), sulfoxide or sulfone (dimethyl sulfoxide (DMSO), dimethyl sulfone) Etc.) and alkoxy alcohols (ethoxyethanol, methoxymethanol, etc.). In addition, as long as the effect of the present invention is obtained, the solution that is brought into contact with the first macroporous monolith contains water but does not constitute a main solvent component, or a trace amount of water derived from moisture absorption or crystal water of a metal salt. Except for, a solution containing substantially no water may be used. The solvent of the solution includes, for example, one or more selected from diols such as methanol, ethanol, propanol, and ethylene glycol, triols such as glycerin, and acetone, or the above-described one solvent or two or more. A mixture of the following solvents. As long as the effect of the present invention is obtained, the solution or the aqueous solution can contain materials other than water, the above-described solvents, and metal salts.

The first macroporous monolith used in the second production method is, for example, a first macroporous monolith formed by the first production method. That is, the first macroporous monolith may be formed by the first manufacturing method described above. In this case, the first macroporous monolith is an intermediate for producing the second macroporous monolith from the silicon compound.

As long as the second macroporous monolith is obtained, the second production method can include any step other than the reduction step.

The second macroporous monolith may be manufactured by a method other than the second manufacturing method described above.

The use of the second macroporous monolith is not particularly limited. The application is, for example, an application using metal nanoparticles arranged in a monolith as a catalyst (as a monolith, an application as a carrier of the catalyst). Specific examples include the use of the second macroporous monolith as a catalyst for organic synthesis, for example, the Suzuki-Miyaura coupling reaction or the Mizorogi-Heck reaction, which is efficiently catalyzed by palladium nanoparticles. When used as a catalyst for organic synthesis, since it is a monolith, there is also an advantage that it can be easily recovered from the reaction system. Furthermore, in the second macroporous monolith, it is not always necessary to perform “support of nanoparticles by ligands (ligands, linkers) such as hydroxyl groups, thiol groups, amino groups”, which is found in many catalyst carriers. Nanoparticles are expected to have unprecedented high activity and suppression of nanoparticle outflow.

Further, since the second monolith has a macroporous-mesoporous hierarchical porous structure, it is based on high fluid permeability by macropores and high activity (for example, catalytic activity) by metal nanoparticles arranged in mesopores. The construction of a highly efficient and high-performance fluid reaction system is also expected.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

(Example 1: Production of first macroporous monolith)
Polyethylene glycol (PEO) in the amount shown in Table 1 (manufactured by Sigma-Aldrich, molecular weight 35000) mixed at a volume ratio of 1: 1, nitric acid with a concentration of 50 mM (manufactured by Kishida Chemical, concentration 65%) and methanol (Kishida Chemical) (Made) 2.5 mL of the mixture was dissolved. Next, after stirring the obtained mixture at room temperature for 30 minutes, 2.1 mL (16.5 mmol) of trimethoxysilane (HTMS) (manufactured by Tokyo Chemical Industry,> 90%) was added to the obtained solution. The mixture was then stirred for 2 minutes, then stirring was stopped and left at room temperature. Gelation began within 15 minutes after standing. Next, the obtained gel was aged at room temperature for 2 days, washed with methanol, and then dried at 40 ° C. for 2 days to obtain a porous monolith. The mixing ratio (molar ratio) of HTMS, methanol, water and nitric acid was 1: 3.7: 8.4: 7.6 × 10 ⁻³ .

The structure of each produced porous monolith was observed using a scanning electron microscope (SEM) (manufactured by JEOL, JSM-6060S). In HY0 to which no PEO was added, a transparent gel was obtained, and no macropores were observed ((a) in FIG. 1). On the other hand, it was confirmed that as the amount of PEO added was increased, the transparency of the gel obtained was reduced and macropores were formed ((a) to (e) in FIG. 1). In samples HY150 and HY210, the formation of macropores having a co-continuous structure with the skeleton was clearly confirmed ((c) and (d) of FIG. 1), and the production of the first macroporous monolith was confirmed. It was. FIG. 1 (f) shows the appearance of the HY210 monolith. FIG. 1 (f) shows a HY210 monolith and a ruler that serves as an index of the size of the monolith. The upper article in the drawing is a cylindrical HY210 monolith. The appearance of HY150 and HY210 was white.

Next, the characteristics of the macropores present in HY150 and HY210 were evaluated using a mercury pore distribution measuring device (manufactured by Cantachrome, Pore Master 60-GT). Each sample was degassed by heating at 200 ° C. for 6 hours prior to measurement. The evaluation results are shown in FIG. As shown in FIG. 2, the pore diameters of the macropores in both monoliths showed a sharp distribution. That is, the first macroporous monolith having a high uniformity of macropore diameter was obtained. The peak of the pore size distribution of the macropores in the HY150 monolith was 3.3 μm, and the peak of the pore size distribution of the macropores in the HY210 monolith was 1.2 μm. In addition, in HY150 and HY210, the amount of PEO added is larger in HY210, but in HY210, the pore diameter of the macropores is decreased while the pore volume is increased compared to HY150.

Next, the characteristics of mesopores and macropores present in HY150 and HY210 were analyzed by pore distribution measurement by a nitrogen gas adsorption method (BELSORP-miniII, manufactured by Nippon Bell). Each sample was degassed by heating at 200 ° C. for 6 hours prior to measurement. The evaluation results are shown in FIG. As shown in FIG. 3, the adsorption-desorption isotherms of HY150 and HY210 showed type IV characteristics, and the presence of mesopores was confirmed. Further, in both HY150 and HY210, as shown in the BJH pore size distribution curve obtained using the adsorption branch, a high BET surface area mainly having small mesopores of less than 10 nm was confirmed (HY150 is 630 m ² / g, HY210 is 800 m ² / g). In the HY210 monolith, the diameter of the largest mesopore (center pore diameter) was 3.2 nm, whereas in the HY150 monolith, it was 2 nm.

Next, spectroscopic characteristics were evaluated for HY210, and its molecular structure and the presence of Si—H bonds were evaluated. Fourier transform infrared spectroscopy (FT-IR) measurement for HY210 was performed using a standard sample mixed with potassium bromide using a Fourier transform infrared spectrophotometer (manufactured by Shimadzu Corporation, IRAffinity-1). Moreover, the Raman spectroscopic measurement was performed using the confocal Raman spectroscopic apparatus (the product made by HORIBA, Xprora). As shown in FIGS. 4A and 4B, a sharp Si—H stretching vibration at a wave number of 2250 cm ⁻¹ was confirmed in both FT-IR and Raman. Further, the FT-IR, and vibration of a strong Si-O-Si at a wavenumber of 1000 ~ 1250 cm ^-1, the vibration of the O-Si-H was observed at a wave number 800 ~ 925 cm ^-1. Since absorption by Si—OH at a wave number of 930 cm ⁻¹ is negligible and negligible, it was confirmed that the Si—H bond of HTMS was left as it was in the produced macroporous monolith. PEO was confirmed to remain in the monolith with a broad peak due to ether units near a wave number of 1750 cm ⁻¹ . In addition to this, it was possible to obtain further knowledge about the structure of the skeleton of the obtained monolith by examining the peak of the FT-IR spectrum. Specifically, the vibration of Si-O-Si and H-Si-O respectively appearing at a wave number of 1150 cm ^-1 and a wavenumber of 875cm ^-1 is due to the ring structure, the 1070 cm ^-1 and 830 cm ^-1 Si- O—Si and H—Si—O vibrations corresponded to random networks. Therefore, from the results of FT-IR, it was found that the skeleton of the HY210 monolith was mainly composed of a random network and a ring structure in which Si—H groups were maintained.

Next, in order to evaluate the thermal stability of HY210, its thermogravimetric-differential thermal analysis (TG-DTA) was performed. The analysis was performed using a ThermoPlus TG8120 manufactured by Rigaku at a heating rate of 5 ° C./min while constantly supplying air at 100 mL / min. As shown in FIG. 4C, according to the TG and DTA curves, it was found that the weight decreased greatly from 150 ° C. to 200 ° C. and the weight increased from 350 ° C. to 500 ° C. The weight loss is thought to correspond to the combustion of PEO in the monolith. The increase in weight is thought to be due to thermal oxidation of Si—H groups to Si—O—Si bonds and Si—OH groups. According to TG-DTA analysis, the Si—H groups present in the HY210 monolith were found to be thermally stable up to 350 ° C.

Next, the amount of Si—H groups present in the HY210 monolith was evaluated by solid ²⁹ Si CP / MAS NMR measurement. The solid ²⁹ Si CP / MAS NMR measurement was performed by OPENCORE NMR (299.52 MHz for ¹ H, contact time 10 ms, using 5 mm probe (5 kHz)). The fact that the CP (cross polarization) method does not affect the spectrum was separately confirmed by comparison with the spectrum obtained without the CP method. The “T” signal on the NMR spectrum corresponds to Si in HSiX ₃ (X is OSi, OCH ₃ or OH). When Si—H hydrolysis occurs, a “Q” signal appears due to the SiX ₄ unit. As shown in FIG. 4D, in the NMR spectrum obtained, the T ³ peak is much larger than the T ² peak (94.5% T ³ in peak area, 5.5% T ² ), which is HY210 It shows that a high degree of polycondensation of HTMS is performed in the monolith. In addition to this, no Q signal was observed, and it was confirmed that the Si—H group derived from HTMS was preserved in HY210.

(Example 2: Production of second macroporous monolith)
In Example 2, a second macroporous monolith was fabricated in which nanoparticles composed of a single metal were placed.

Of the first macroporous monolith produced above, a part (0.20 g or more) of HY210 was immersed in 20 mL of distilled water and allowed to stand at room temperature for 3 hours to diffuse water into the macropores. Next, an aqueous solution in which a metal salt was dissolved in water was added to the water in which the monolith was immersed, and the mixture was allowed to stand at room temperature for another 3 hours. After mixing the aqueous solution of metal salt, the generation of hydrogen and the change in the color of the monolith according to the type of metal deposited (from white to reddish brown (gold), black brown (silver), etc.) were immediately confirmed. When 3 hours had passed after mixing, hydrogen generation ceased. The supernatant was removed, and the monolith was washed with 20 mL of methanol three times, and then dried at 40 ° C. for 2 hours to obtain a second macroporous monolith. In the column of “Sample Name” in Table 2, the type of metal constituting the metal salt and the molar ratio of the metal to HY210 (metal / HY210) are shown. Silver nitrate (Sigma Aldrich) is used for the silver (Ag) salt, chloroauric acid tetrahydrate (Kishida Chemical) is used for the gold (Au) salt, and palladium nitrate (sum) is used for the palladium (Pd) salt. Koganei Pharmaceutical Co., Ltd. was used, and chloroplatinic acid hexahydrate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the platinum (Pt) salt.

From the reducibility of the Si—H group, the generation of hydrogen, and the change in the color of the monolith, the metal ions contained in the aqueous solution were reduced and the deposition of the metal was estimated. Further, it was estimated that the precipitated particles serve as a catalyst for further oxidation of Si—H groups to Si—OH or Si—O—Si bonds. The oxidation of the Si—H group is considered to follow the following reaction formula (1). M ^{n +} in the formula (1) is Ag ⁺ , Pd ²⁺ , Au ³⁺ or Pt ⁴⁺ .
nO _1.5 Si—H + M ^{n +} + nH ₂ O
→ nO _1.5 Si—OH + M (0) + n / 2H ₂ + nH ⁺ (1)

According to equation (1), after reduction of the metal, the amount of Si—H groups remaining in the monolith is inversely proportional to the amount of reacted metal salt. This was confirmed from the FT-IR measurement results for HY210 monolith after reducing different amounts of AgNO ₃ (see FIG. 5A). Similar results were obtained for other metal salts (see FIG. 5B for Au, FIG. 5C for Pd and FIG. 5D for Pt). Specifically, when the amount of Ag ⁺ plus (Ag ⁺ the amount of which is reduced by the monolith) was increased from _{Ag 1/100} to _{Ag 1/10,} Si-H and intensity of O-Si-H vibrations It decreased and the intensity of Si—OH vibration increased. This indicates that the Si—H group was oxidized to the Si—O bond.

Next, when wide-angle X-ray diffraction measurement was performed on each monolith after reduction of AgNO ₃ , HAuCl ₄ , Pd (NO ₃ ) ₂ or H ₂ PtCl ₆ , the Bragg diffraction peak corresponding to the precipitated particles was obtained. Was confirmed (see FIG. 6A). The diffraction peak intensity was proportional to the amount of metal salt used. That is, it was confirmed that as the amount of the metal salt used increased, the amount of particles arranged in the monolith increased (FIG. 6B for Ag, FIG. 6C for Au, FIG. 6D for Pd, and FIG. 6E for Pt). See). The wide-angle X-ray diffraction measurement was performed using a CuKα ray (wavelength λ = 0.154 nm) as an incident beam with a powder X-ray diffractometer (Rigaku III, RINT Ultimate III).

The particle size (particle size) calculated using the Scherrer equation from the measurement results of wide-angle X-ray diffraction was in the nanometer range in all cases of Ag, Au, Pd and Pt (see Table 3 below). reference). That is, it was confirmed that by bringing the first macroporous monolith into contact with an aqueous solution in which these metal salts are dissolved, the reduction reaction of the metal can proceed to deposit the noble metal nanoparticles in the monolith. Among the above four types of metals, the particle diameters of Ag and Au nanoparticles were relatively large, followed by the particle diameters of Pd and Pt nanoparticles. As shown in Table 3, it was found that the particle size of the nanoparticles calculated from the Scherrer equation did not depend on the concentration of the metal salt in the aqueous solution in which the monolith was immersed, but on the type of metal. . The value of the standard electrode potential of the metal cation was proportional to the particle size of the deposited nanoparticle, and the charge (oxidation number n) of the cation was inversely proportional to the particle size of the nanoparticle. Incidentally, the Si-H Si-O in water ^- oxidation to occur at -1.23 V. This is sufficiently smaller than the standard electrode potential (E ⁰ ) of each metal ion, but since the series of reactions includes a reduction process of hydrogen ions, the standard electrode potential is substantially positive. It is possible to reduce only metal species that take If the metal ion having a large valence does not interact with the Si—H group distributed on the pore surface of hydride silica a plurality of times, the reduction to neutral atoms is not completed. Therefore, even when the hydride silica pore surface is contacted at a similar concentration, a metal having a lower valence is reduced more rapidly and grows to a relatively large particle size. On the other hand, a metal having a high valence has a relatively small particle size because particle growth per unit time is suppressed. For this reason, as the ratio E ⁰ / n in the metal salt increased, the average particle size of the deposited nanoparticles also increased (see FIG. 7).

Next, the size of the deposited nanoparticles and the spatial distribution of the particles in the monolith were evaluated by the high-angle scattering dark field (scanning transmission electron microscope) method (HAADF-STEM). Specifically, after crushing a massive sample with a mortar, the powdered sample was set on a Cu grid. A high-resolution TEM (manufactured by JEOL, JEM-2100F) was scanned at 200 kV using a STEM unit equipped with a spherical aberration corrector (manufactured by CEOS). Thereby, an image having a diameter of 0.1 nm is obtained. During HAADF-STEM imaging, the convergence angle of the probe was set to 25 mrad, and the inner angle of the annular dark field detector was set to a state exceeding 52 mrad.

The observation result of HAADF-STEM is shown in FIG. 8A shows a sample Ag _1/10 , (b) shows a sample Au _1/10 , (c) shows a sample Pd _1/10 , and (d) shows a sample Pt _1/10 . In HAADF-STEM, the contrast of the obtained image is roughly proportional to the square of atomic number Z. Therefore, in the HAADF-STEM image shown in FIG. 8, dispersed metal nanoparticles (Z = 47 Ag, Z = 79 Au, Z = 46 Pd, Z = 78 Pt nanoparticles) It looks brighter than a monolith mainly composed of 1 H, Z = 8 O and Z = 14 Si. As shown in FIG. 8, the nanoparticles were dispersed not only on the surface of the monolith skeleton (wall surface of the macropores) but also inside the skeleton. In FIG. 8, what is indicated as “inside the skeleton” corresponds to this. It is considered that the metal salt solution diffused to the inside of the skeleton through the mesopores, where it was reduced and nanoparticles were deposited. In addition, because there is a spatial restriction on the growth of particles inside the skeleton, it is confirmed that the nanoparticles present inside the skeleton have a smaller particle size and a more irregular shape than the nanoparticles present on the surface of the skeleton. It was done. Further, as shown in Table 3, it was found that a wide range of nanoparticle diameters was realized in the samples Ag _1/10 , Au _1/10 , Pd _1/10 and Pt _1/10 . However, it was 1 nm to 200 nm for Ag _1/10 , and 5 nm to 150 nm for Au _1/10 , but 5 nm to 50 nm for Pd _1/10 , and ₁ nm to 50 nm for Pt _1/10 . The width over which the particle size was distributed changed slightly. This is consistent with the particle size results calculated by Scherrer's equation.

After reducing the metal salt, no cracks were found in the dried second macroporous monolith. As shown in FIG. 9, the monolith maintained the macropore / skeleton co-continuous structure of the HY210 monolith that was the monolith (first macroporous monolith) before reducing the metal salt. From this, it was confirmed that both the first and second macroporous monoliths have high structural stability when carrying out the reduction reaction based on the Si—H bond. 9A shows the sample Ag _1/10 , FIG. 9B shows the sample Au _1/10 , FIG. 9C shows the sample Pd _1/10 , and FIG. 9D shows the sample Pt _1/10 .

The metal nanoparticles deposited by reduction were fixed on the surface and inside of the monolith skeleton, and even when the monolith was washed with water, methanol, ethanol, and hexane, the metal particles did not flow out of the monolith. . Therefore, it was confirmed that the second macroporous monolith can be used as a carrier for metal nanoparticles. Moreover, when the pore distribution measurement by the nitrogen gas adsorption method was performed on the monolith on which the metal nanoparticles were deposited, the state of the first macroporous monolith was obtained as shown in Table 4 below. Maintained a high specific surface area. Also, the adsorption-desorption isotherm of the monolith shows the characteristics of type IV as in the case of the first macroporous monolith as shown in FIGS. 10 and 11, and the mesopores are present as they are. It was confirmed that As the sample Ag _{1/100 was changed} to Ag _1/10 , that is, as the amount of added Ag ⁺ was increased, a slight decrease in the specific surface area of the obtained second macroporous monolith was confirmed. This is probably because some of the mesopores and macropores of the HY210 monolith were blocked by increased Ag nanoparticles.

(Example 3: Production of second macroporous monolith)
In Example 3, a solution containing two kinds of metal salts (HAuCl ₄ and H ₂ PtCl ₆ ) was used, and nanoparticles composed of Au and Pt (Au—Pt binary nanoparticles) were arranged. Two macroporous monoliths were made. Various evaluations and measurements on the second monolith prepared in the following examples were performed in the same manner as in Example 2 unless otherwise specified.

First, in the same manner as in Example 1, a first macroporous monolith corresponding to HY210 was produced. However, the amount of each material used was five times that of Example 1, and aging was performed at room temperature for 24 hours. The mixing ratio of HTMS, methanol, water and nitric acid is the same as in Example 1. The shape of the produced first macroporous monolith was a cylindrical shape having a diameter of 5.5 mm and a length of 225 mm.

Next, a part (53 mg, 1 mmol equivalent) of the prepared first macroporous monolith was mixed with water, acetone, chloroauric acid tetrahydrate (HAuCl ₄ ) aqueous solution and platinum chloride in the amounts shown in Table 5 below. Immersion in a mixed solution of an acid hexahydrate (H ₂ PtCl ₆ ) aqueous solution, and at room temperature (Examples 3-1 and 3-2) or 50 ° C. (Example 3-3) for 3 hours (Example 3- 1), left for 12 hours (Example 3-2) or 36 hours (Example 3-3). The standing time in each example was set until the coloring based on the metal ions in the mixed solution before the monolith was immersed disappeared visually. The “metal salt solution” in Table 5 is a solution obtained by mixing an equal volume of a 0.1 M HAuCl ₄ aqueous solution and an 0.1 M H ₂ PtCl ₆ aqueous solution (mixed at a volume ratio of 1: 1). . In any of the examples, generation of hydrogen was confirmed immediately after immersion. After immersion for the above time, the solution was removed and the monolith was washed 3 times with 20 mL of methanol and then dried at 40 ° C. for 2 hours to obtain a second macroporous monolith. The color of the monolith that was white before immersion changed to black after immersion, and the yellow color seen in the mixed solution before immersion of the monolith disappeared by immersion of the monolith, and the solution became transparent (See FIG. 12. FIG. 12 shows the change in color tone of the monolith and the mixed solution in Example 3-3).

From the reducibility of the Si—H group, the generation of hydrogen, and the change in the color of the monolith, the metal ions contained in the aqueous solution were reduced and the deposition of the metal was estimated. The results of wide angle X-ray diffraction measurements performed on the monoliths produced in Examples 3-1 to 3-3 are shown in FIG. FIG. 13 shows the diffraction of the (111), (200), and (220) planes of Au and Pt from the left side of the page.

As shown in FIG. 13, in Example 3-1, in which the proportion of water in the solvent of the metal salt solution is large, the respective diffraction peaks of Au and Pt were confirmed, and each of the Au nanoparticles and the Pt nanoparticles was observed. It was confirmed that they were deposited individually. On the other hand, from Example 3-2 to 3-3, as the proportion of water in the solvent decreases, the individual diffraction peaks of Au and Pt decrease, and instead the peak of the Au—Pt alloy increases, ie It was confirmed that nanoparticles of Au—Pt alloy were precipitated. In particular, in Example 3-3, the individual diffraction peaks of Au and Pt were not confirmed, but only the diffraction peak of the Au—Pt alloy (Au ₁ Pt ₁ alloy) was confirmed. This is because, as shown in the following formula (2), water is involved in the oxidation reaction of the Si—H group of the first monolith and the reduction reaction of the metal in the solution, so the ratio of water in the solvent is large. In Example 3-1, it is considered that the progress of the reaction is fast and the formation of the nanoparticles of each metal is completed before the alloy is formed. On the other hand, in Example 3-3 in which the ratio of water in the solvent is small, the progress rate of the reaction is slow as shown in the immersion that is longer than the other examples of 36 hours at a temperature of 50 ° C. It is believed that there can be a reaction stage where an alloy of Au and Pt is formed before the nanoparticles are formed.
M ₁ ^{x +} + M ₂ ^{y +} + (x + y) H—SiO _1.5 + (x + y) H ₂ O → M ₁ (0) + M ₂ (0) + (x + y) HO—SiO _1.5 + (x + y) / 2H ₂ + (x + y) H ⁺ (2)

In the formula (2), M ₁ ^{x +} and M ₂ ^{y +} are metal ions (Au ³⁺ and Pt ^{4+ in} Example 3).

FIG. 14 shows the measurement result of X-ray photoelectron spectroscopy (XPS) for the second monolith produced in Example 3-3. XPS measurement was performed using an MgPS ray (1253.6 eV) with an XPS measurement device (manufactured by ULVAC-PHI, MT-5500). The measured core level was calibrated with reference to the first component of the carbon (C) 1s core level peak set at 284.6 eV. As shown in FIG. 14, the presence of Au and Pt was confirmed in the monolith.

FIG. 15 shows the results of ²⁹ Si solid state NMR for the second monolith prepared in Example 3-3. As shown in FIG. 15, oxidation of the Si—H group in the first monolith confirmed Q ³ and Q ⁴ signals based on SiX ₄ units (X is OSi, OCH ₃ or OH). Comparison with ²⁹ Si solid state NMR results for the first monolith (see FIG. 4D) confirmed that 28 mol% of the Si—H groups present in the first monolith were oxidized. This amount of oxidation corresponded to the amount of reduced metal salt.

FIG. 16 shows an SEM observation image of the second monolith produced in Example 3-3, together with an SEM observation image of the first monolith before being immersed in the metal salt aqueous solution. The left image in FIG. 16 is an SEM observation image of the first monolith before immersion, and the right image in FIG. 16 is an SEM observation image of the second monolith after immersion. As shown in FIG. 16, the structure of the macroporous monolith was maintained before and after immersion (before and after nanoparticle deposition).

FIG. 17 shows a HAADF-STEM observation image of the second monolith produced in Example 3-3. As shown in the image labeled “f” in FIG. 17, it was confirmed that the metal nanoparticles were dispersed and distributed in the produced monolith. Further, by using an energy dispersive X-ray spectroscopic analysis (EDS) detector together, the distribution of each atom of Si, Au and Pt on the HAADF-STEM image was evaluated. The images labeled “g”, “h”, and “i” in FIG. 17 show the distribution of each atom of Si, Au, and Pt in the region within the dotted line of the image “f”. “G” indicates the distribution of Si atoms, “h” indicates the distribution of Au atoms, and “i” indicates the distribution of Pt atoms. As shown in these images, Au atoms and Pt atoms were distributed at the same position so as to be in contact with the distribution of Si atoms corresponding to the position where the monolith skeleton was present. That is, it was confirmed more clearly that the nanoparticles of the Au—Pt alloy were dispersed and distributed in the monolith.

FIG. 18 shows the particle size distribution of the Au—Pt alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. The particle diameter of the nanoparticles was distributed from 1 nm to 27 nm, the distribution of 5 nm or less was the largest, and the average particle diameter was 5.5 nm.

FIG. 19 shows the result of pore distribution measurement by the nitrogen gas adsorption method for the second monolith produced in Example 3-3. As shown in the adsorption-desorption isotherm in FIG. 19, the monolith showed type IV characteristics like the first macroporous monolith, and it was confirmed that mesopores were present. The BET specific surface area of the monolith was 380 m ² / g. Although it is smaller than the BET specific surface area of the monolith before reduction (HY210), it is considered that the mesopores and macropores of the monolith were partially blocked by the particles due to the precipitation of the nanoparticles.

Next, a second macroporous monolith was produced in the same manner as in Example 3-3 by changing the absolute amounts of HAuCl ₄ and H ₂ PtCl ₆ contained in the metal salt solution. Specifically, the amount of the first macroporous monolith (1 mmol) in which the total amount of the metal ions contained in the mixed solution was used with the 0.1M concentration HAuCl ₄ aqueous solution and the 0.1M concentration H ₂ PtCl ₆ aqueous solution. ) Monolith prepared using a metal salt solution mixed in an equal amount by volume (mixed at a volume ratio of 1: 1) so as to be 0.5 mol% (that is, the absolute amount is 5 μmol) (Example 3-4) ) And the above aqueous solutions so that the total amount of metal ions contained in the solution is 4.0 mol% (that is, the absolute amount is 40 μmol) of the amount (1 mmol) of the first macroporous monolith used. A monolith (Example 3-5) prepared using a metal salt solution mixed in an equal volume was prepared. The results of wide-angle X-ray diffraction measurement for these monoliths are shown in FIG. As shown in FIG. 20, as the absolute amount of the metal salt in the solution in which the first macroporous monolith is immersed is increased, the peak intensity of the X-ray diffraction increases, that is, more metal nanoparticles are precipitated. confirmed. In addition, as shown in FIG. 20, the deposited nanoparticles showed a diffraction peak of Au—Pt alloy (Au ₁ Pt ₁ ).

Next, as shown in Table 6 below, the same procedure as in Example 3-3 was performed except that the composition of the metal salt solution was changed (the mixing ratio of the HAuCl ₄ solution and the H ₂ PtCl ₆ solution was changed). Thus, a second macroporous monolith was produced. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 21), each had the composition shown in Table 6. That is, it was confirmed that the composition of the nanoparticles deposited on the monolith can be controlled by the composition of the metal salt in the solution in which the first macroporous monolith is immersed. Specifically, in the examples shown in Table 6, a second macroporous monolith in which nanoparticles having a composition ranging from Au ₄ Pt ₁ to Au ₁ Pt ₄ were arranged could be produced.

(Example 4: Production of second macroporous monolith)
In Example 4, a solution containing two kinds of metal salts (HAuCl ₄ and PdCl ₂ ) was used, and a second particle in which nanoparticles composed of Au and Pd (binary Au—Pd nanoparticles) were arranged. A macroporous monolith was prepared. PdCl ₂ was manufactured by Tokyo Chemical Industry.

Specifically, HAuCl ₄ and PdCl ₂ were used as metal salts, and the composition of the metal salt solution was changed as shown in Table 7 below (the mixing ratio of the HAuCl ₄ solution and the PdCl ₂ solution was changed). The second macroporous monolith was produced in the same manner as in Example 3-3 except for the above. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 22), each had the composition shown in Table 7. Specifically, in the examples shown in Table 7, a second macroporous monolith in which nanoparticles having a composition ranging from Au ₄ Pd ₁ to Au ₁ Pd ₄ were arranged could be produced.

FIG. 23A shows a HAADF-STEM observation image for the second monolith produced in Example 4-2. As shown in the images on the upper left and upper right of FIG. 23A, it was confirmed that the metal nanoparticles were dispersed and distributed in the monolith produced. The upper right image is an enlarged image of a part of the left image. Further, by using an EDS detector in combination, the distribution of each atom of Au and Pd on the HAADF-STEM image was evaluated. The lower part of FIG. 23A shows the distribution of each atom of Au and Pd in the region within the dotted line of the image on the right side of the upper part from the left side. As shown in these images, Au atoms and Pd atoms were distributed at the same position so as to be in contact with the distribution of Si atoms corresponding to the position where the monolith skeleton was present. That is, it was confirmed more clearly that nanoparticles of Au—Pd alloy (Au ₃ Pd ₁ alloy) were dispersed and distributed in the monolith.

FIG. 23B shows the particle size distribution of the Au—Pd alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 23A. The average particle size obtained from this particle size distribution was 25 nm.

FIG. 24A shows an HAADF-STEM observation image for the second monolith produced in Example 4-4. As shown in the image labeled “a” in FIG. 24A, it was confirmed that metal nanoparticles were dispersed and distributed in the monolith produced. Further, by using an EDS detector together, the distribution of each atom of Si, Au and Pd on the HAADF-STEM image was evaluated. The images labeled “b”, “c”, and “d” in FIG. 24A show the distribution of each atom of Si, Au, and Pd in the region within the dotted line of the image of “a”, respectively. As shown in these images, Au atoms and Pd atoms were distributed at the same position so as to be in contact with the distribution of Si atoms corresponding to the position where the monolith skeleton was present. That is, it was confirmed more clearly that nanoparticles of Au—Pd alloy (Au ₁ Pd ₁ alloy) were dispersed and distributed in the monolith.

FIG. 24B shows the particle size distribution of the Au—Pd alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 24A. The average particle size obtained from this particle size distribution was 11.5 nm.

FIG. 24C shows the measurement result (adsorption-desorption isotherm) of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 4-4. As shown in the adsorption-desorption isotherm, the monolith showed type IV characteristics like the first macroporous monolith, and it was confirmed that mesopores were present. The monolith had a BET specific surface area of 410 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 24D shows an SEM observation image of the second monolith produced in Example 4-4. In the produced second monolith, it was confirmed that the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

FIG. 25A shows a HAADF-STEM observation image for the second monolith produced in Example 4-6. In the drawing, the right image is an enlarged image of a part of the left image. As shown in FIG. 25A, it was confirmed that metal nanoparticles (Au ₁ Pd ₃ alloy nanoparticles according to the XRD results) were dispersed and distributed in the monolith produced.

FIG. 25B shows the particle size distribution of the Au—Pd alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 25A. The average particle size obtained from this particle size distribution was 6.9 nm.

From the particle size distributions shown in FIG. 23B, FIG. 24B, and FIG. 25B, it was confirmed that the particle size of the particles tends to decrease as the composition ratio of Pd in the alloy nanoparticles increases. This corresponds to the tendency that the particle size of the Pd particles is smaller than that of the Au particles when the single metal particles are deposited.

(Example 5: Production of second macroporous monolith)
In Example 5, a solution containing two kinds of metal salts (RhCl ₃ and PdCl ₂ , and RhCl ₃ and H ₂ PtCl ₆ ) was used, and nanoparticles composed of Rh and Pd (Rh—Pd binary nano-particles) were used. And a second macroporous monolith in which nanoparticles composed of Rh and Pt (binary Rh-Pt nanoparticles) are disposed. . RhCl ₃ was manufactured by Tokyo Chemical Industry.

First, except that PdCl ₂ and RhCl ₃ were used as metal salts, and the composition of the metal salt solution was changed as shown in Table 8 below (the mixing ratio of the PdCl ₂ solution and the RhCl ₃ solution was changed) Produced a second macroporous monolith in the same manner as in Example 3-3. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 26), each had the composition shown in Table 8. Specifically, in the examples shown in Table 8, a second macroporous monolith in which nanoparticles having a composition ranging from Pd ₄ Rh ₁ to Pd ₁ Rh ₄ were arranged could be produced.

FIG. 27A shows an HAADF-STEM observation image for the second monolith produced in Example 5-4. In the figure, an image labeled “h” is an enlarged image of a part of the image labeled “g”. As shown in FIG. 27A, it was confirmed that metal nanoparticles (Pd ₁ Rh ₁ alloy nanoparticles according to the XRD results) were dispersed and distributed in the monolith produced.

FIG. 27B shows the particle size distribution of Pd—Rh alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 27A. The average particle size of the Pd ₁ Rh ₁ alloy nanoparticles determined from this particle size distribution was 5.5 nm.

FIG. 28 shows the measurement results of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 5-4. As shown in the adsorption-desorption isotherm in FIG. 28, the monolith showed the characteristics of type IV like the first macroporous monolith, and it was confirmed that mesopores were present. The BET specific surface area of the monolith was 440 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 29 shows the XPS spectrum measurement results for the second monolith produced in Example 5-4. As shown in the spectrum, the presence of Pd and Rh was confirmed in the monolith.

FIG. 30 shows an SEM observation image of the second monolith produced in Example 5-4. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

Next, HPtCl ₆ and RhCl ₃ were used as metal salts, and the composition of the metal salt solution was changed as shown in Table 9 below (the mixing ratio of the H ₂ PtCl ₆ solution and the RhCl ₃ solution was changed). The second macroporous monolith was produced in the same manner as in Example 3-3 except for the above. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 31), each had the composition shown in Table 9. Specifically, in the examples shown in Table 9, a second macroporous monolith in which nanoparticles having compositions ranging from Pt ₄ Rh ₁ to Pt ₁ Rh ₄ were arranged could be produced.

FIG. 32A shows a HAADF-STEM observation image for the second monolith produced in Example 5-11. In the drawing, an image labeled “f” is an enlarged image of a part of the image labeled “e”. As shown in FIG. 32A, it was confirmed that metal nanoparticles (Pt ₁ Rh ₁ alloy nanoparticles according to the XRD results) were dispersed and distributed in the monolith produced.

FIG. 32B shows the particle size distribution of Pt—Rh alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 32A. The average particle size of the Pt ₁ Rh ₁ alloy nanoparticles determined from this particle size distribution was 4.2 nm.

FIG. 33 shows the measurement results of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 5-11. As shown in the adsorption-desorption isotherm in FIG. 33, the monolith showed the characteristics of type IV as in the first macroporous monolith, and it was confirmed that mesopores were present. The monolith had a BET specific surface area of 410 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 34 shows an SEM observation image of the second monolith produced in Example 5-11. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

FIG. 35 shows Example 3-3 (Au ₁ Pt ₁ ), Example 4-4 (Au ₁ Pd ₁ ), Example 5-4 (Pd ₁ Rh ₁ ), and Example 5-11 (Pt ₁ Rh _1). The average particle diameter of each alloy nanoparticle in the 2nd monolith produced by (1) is shown. As shown in FIG. 35, the average particle diameter of the deposited nanoparticles increased as the sum of the ratios E ⁰ / n in the metal salt increased.

(Example 6: Production of second macroporous monolith)
In Example 6, a solution containing three kinds of metal salts ( _three selected from HAuCl ₄ , PdCl ₂ , H ₂ PtCl ₆ and RhCl ₃ ) was used, and nanoparticles composed of Au, Pd and Pt (Au— Pd—Pt ternary nanoparticles), nanoparticles composed of Au, Pd and Rh (Au—Pd—Rh ternary nanoparticles), nanoparticles composed of Au, Pt and Rh (Au— A second macroporous monolith in which nanoparticles composed of Pt—Rh ternary nanoparticles) or nanoparticles composed of Pd, Pt, and Rh (Pd—Pt—Rh ternary nanoparticles) was arranged was prepared.

First, the second macroporosity was obtained in the same manner as in Example 3-3, except that HAuCl ₄ , PdCl ₂ and H ₂ PtCl ₆ were used as metal salts and the composition of the metal salt solution shown in Table 10 below was used. A monolith was made. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 36), it had a composition of Au ₁ Pd ₁ Pt ₁ . FIG. 36 also shows X-ray diffraction profiles of Au alone, Pt alone and Pd alone. By comparing these profiles, it was confirmed that the lattice size changed with the formation of the Au—Pd—Pt alloy. The right profile in FIG. 36 is an enlarged part of the left profile.

FIG. 37A shows a HAADF-STEM observation image for the second monolith produced in Example 6-1. As shown in the image attached with “a” and the image attached with “b” in FIG. 37A, it was confirmed that metal nanoparticles were dispersed and distributed in the produced monolith. . In the drawing, an image labeled “b” is an enlarged image of a part of the image labeled “a”. Further, by using an EDS detector in combination, the distribution of each atom of Si, Au, Pd and Pt on the HAADF-STEM image was evaluated. The images labeled “c”, “d”, “e”, and “f” in FIG. 37A show the distribution of each atom of Si, Au, Pd, and Pt in the region within the dotted line of the image of “b”, respectively. . As shown in these images, the Au atom, the Pd atom, and the Pt atom were distributed at the same position so as to be in contact with the distribution of Si atoms corresponding to the position where the monolith skeleton was present. That is, it was confirmed more clearly that nanoparticles of Au—Pd—Pt alloy (Au ₁ Pd ₁ Pt ₁ alloy) were dispersed and distributed in the monolith.

FIG. 37B shows the particle size distribution of the Au—Pd—Pt alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 37A. The average particle size obtained from this particle size distribution was 13 nm.

FIG. 38 shows the measurement results of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 6-1. As shown in the adsorption-desorption isotherm in FIG. 38, the monolith has the characteristics of type IV like the first macroporous monolith, and it was confirmed that mesopores exist. The BET specific surface area of the monolith was 450 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 39 shows the XPS spectrum measurement results for the second monolith produced in Example 6-1. As shown in the spectrum, the presence of Au, Pd and Pt was confirmed in the monolith.

FIG. 40 shows an SEM observation image of the second monolith produced in Example 6-1. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

Next, the second macroporous monolith was prepared in the same manner as in Example 3-3 except that HAuCl ₄ , PdCl ₂ and RhCl ₃ were used as metal salts and the composition of the metal salt solution shown in Table 11 below was used. Produced. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 41), it had a composition of Au ₁ Pd ₁ Rh ₁ . FIG. 41 also shows X-ray diffraction profiles of Au alone, Rh alone, and Pd alone. From the comparison of these profiles, it was confirmed that the lattice size changed with the formation of the Au—Pd—Rh alloy. The right profile in FIG. 41 is an enlargement of a part of the left profile.

FIG. 42A shows an HAADF-STEM observation image for the second monolith produced in Example 6-2. In the drawing, the right image labeled “h” is an enlarged image of a part of the left image labeled “g”. As shown in FIG. 42A, in the produced monolith, it was confirmed that the metal nanoparticles (Au ₁ Pd ₁ Rh ₁ alloy nanoparticles according to the XRD results) were dispersed and distributed in the monolith. .

FIG. 42B shows the particle size distribution of Au ₁ Pd ₁ Rh ₁ alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 42A. The average particle size of the Au ₁ Pd ₁ Rh ₁ alloy nanoparticles determined from this particle size distribution was 236 nm.

FIG. 43 shows the measurement results of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 6-2. As shown by the adsorption-desorption isotherm in FIG. 43, the monolith has the characteristics of type IV like the first macroporous monolith, and it was confirmed that mesopores exist. The monolith had a BET specific surface area of 315 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 44 shows the XPS spectrum measurement results for the second monolith prepared in Example 6-2. As shown in the spectrum, the presence of Au, Pd and Rh was confirmed in the monolith.

FIG. 45 shows an SEM observation image of the second monolith produced in Example 6-2. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

Next, the second macroporosity was obtained in the same manner as in Example 3-3, except that HAuCl ₄ , H ₂ PtCl ₆ and RhCl ₃ were used as metal salts and the composition of the metal salt solution shown in Table 12 below was used. A monolith was made. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 46), it had a composition of Au ₁ Pt ₁ Rh ₁ . FIG. 46 also shows X-ray diffraction profiles of Au alone, Rh alone, and Pt alone. From the comparison of these profiles, it was confirmed that the lattice size changed with the formation of the Au—Pt—Rh alloy. The right profile in FIG. 46 is an enlarged part of the left profile.

FIG. 47A shows an HAADF-STEM observation image for the second monolith produced in Example 6-3. In the drawing, the right image labeled “j” is an enlarged image of a part of the left image labeled “i”. As shown in FIG. 47A, in the produced monolith, it was confirmed that metal nanoparticles (Au ₁ Pt ₁ Rh ₁ alloy nanoparticles according to the XRD results) were dispersed and distributed in the monolith. .

FIG. 47B shows the particle size distribution of Au ₁ Pt ₁ Rh ₁ alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 47A. The average particle size of the Au ₁ Pt ₁ Rh ₁ alloy nanoparticles determined from this particle size distribution was 5.5 nm.

FIG. 48 shows the measurement results of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 6-3. As shown in the adsorption-desorption isotherm in FIG. 48, the monolith has the characteristics of type IV like the first macroporous monolith, and it was confirmed that mesopores exist. The BET specific surface area of the monolith was 350 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 49 shows the XPS spectrum measurement results for the second monolith produced in Example 6-3. As shown in the spectrum, the presence of Au, Pt and Rh in the monolith was confirmed.

FIG. 50 shows an SEM observation image of the second monolith produced in Example 6-3. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

Next, the second macroporosity was obtained in the same manner as in Example 3-3, except that PdCl ₂ , H ₂ PtCl ₆ and RhCl ₃ were used as metal salts and the composition of the metal salt solution shown in Table 13 below was used. A monolith was made. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 51), it had a composition of Pd ₁ Pt ₁ Rh ₁ . FIG. 51 also shows the X-ray diffraction profiles of Pd alone, Pt alone and Rh alone. From the comparison of these profiles, it was confirmed that the lattice size changed with the formation of the Pd—Pt—Rh alloy. The right profile in FIG. 51 is an enlargement of a part of the left profile.

FIG. 52A shows a HAADF-STEM observation image for the second monolith produced in Example 6-4. In the drawing, the right image labeled “l” is an enlarged image of a part of the left image labeled “k”. As shown in FIG. 52A, in the produced monolith, it was confirmed that metal nanoparticles (Pd ₁ Pt ₁ Rh ₁ alloy nanoparticles according to the XRD results) were dispersed and distributed in the monolith. .

FIG. 52B shows the particle size distribution of the Pd ₁ Pt ₁ Rh ₁ alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. 52A. The average particle size of the Pd ₁ Pt ₁ Rh ₁ alloy nanoparticles determined from this particle size distribution was 7.5 nm.

FIG. 53 shows the result of pore distribution measurement by the nitrogen gas adsorption method for the second monolith produced in Example 6-4. As shown by the adsorption-desorption isotherm in FIG. 53, the monolith has the characteristics of type IV as in the first macroporous monolith, and it was confirmed that mesopores exist. The monolith had a BET specific surface area of 480 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 54 shows the XPS spectrum measurement results for the second monolith produced in Example 6-4. As shown in the spectrum, the presence of Pd, Pt and Rh was confirmed in the monolith.

FIG. 55 shows an SEM observation image of the second monolith produced in Example 6-4. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

(Example 7: Production of second macroporous monolith)
In Example 7, a solution containing four types of metal salts (HAuCl ₄ , H ₂ PtCl ₆ , PdCl ₂ and RhCl ₃ ) was used, and nanoparticles composed of Au, Pt, Pd and Rh (Au—Pt—Pd) were used. A second macroporous monolith in which -Rh quaternary nanoparticles) are arranged was prepared.

Specifically, as in Example 3-3, HAUCl ₄ , PdCl ₂ , H ₂ PtCl ₆ and RhCl ₃ were used as metal salts, and the composition of the metal salt solution shown in Table 14 below was used. Two macroporous monoliths were made. When the composition of the nanoparticles deposited on the produced monolith was evaluated by wide-angle X-ray diffraction measurement (see FIG. 56), it had a composition of Au ₁ Pd ₁ Pt ₁ Rh ₁ . FIG. 56 also shows X-ray diffraction profiles of Au alone, Pd alone, Pt alone and Rh alone. By comparing these profiles, it was confirmed that the lattice size changed with the formation of the Au—Pd—Pt—Rh alloy. The right profile in FIG. 56 is an enlargement of a part of the left profile.

FIG. 57 shows a HAADF-STEM observation image of the second monolith produced in Example 7. As shown in the image labeled “m” in FIG. 57, it was confirmed that in the produced monolith, the metal nanoparticles were dispersed and distributed in the monolith. Further, by using an EDS detector in combination, the distribution of each atom of Si, Au, Pd, Pt and Rh on the HAADF-STEM image was evaluated. Each of Si, Au, Pd, Pt, and Rh in the region within the dotted line of the image “m” is added to the images labeled “n”, “o”, “p”, “q”, and “r” in FIG. Shows the distribution of atoms. As shown in these images, the Au atom, the Pd atom, the Pt atom, and the Rh atom were distributed at the same position so as to be in contact with the distribution of the Si atom corresponding to the position where the monolith skeleton was present. That is, it was confirmed more clearly that nanoparticles of Au—Pd—Pt—Rh alloy (Au ₁ Pd ₁ Pt ₁ Rh ₁ alloy) were dispersed and distributed in the monolith.

FIG. 58 shows the particle size distribution of Au—Pd—Pt—Rh alloy nanoparticles obtained from the HAADF-STEM observation image of FIG. The average particle diameter of the Au—Pd—Pt—Rh alloy nanoparticles obtained from the distribution was 245 nm.

FIG. 59 shows the measurement results of the pore distribution by the nitrogen gas adsorption method for the second monolith produced in Example 7. As shown in the adsorption-desorption isotherm in FIG. 59, the monolith has the characteristics of type IV as in the first macroporous monolith, and it was confirmed that mesopores exist. The monolith had a BET specific surface area of 280 m ² / g. This value is small compared to the BET specific surface area of the monolith before reduction (HY210), which is thought to be because some of the mesopores and macropores of the monolith were blocked by the particles due to precipitation of the nanoparticles. .

FIG. 60 shows the XPS spectrum measurement results for the second monolith produced in Example 7. As shown in the spectrum, the presence of Au, Pd, Pt and Rh was confirmed in the monolith.

FIG. 61 shows an SEM observation image of the second monolith produced in Example 7. From the SEM observation image, it was confirmed that in the produced second monolith, the porous structure of the first monolith was maintained and particles having a large size were not present in the structure.

FIG. 62 shows the average particle diameter of each alloy nanoparticle in the second monolith produced in Examples 6-1 to 6-4 and 7. As shown in FIG. 62, the average particle size of the deposited nanoparticles increased as the total ratio E ⁰ / n in the metal salt increased.

(Example 8: Implementation of reduction reaction using second macroporous monolith as catalyst)
In Example 8, a solution of 4-nitrophenol to 4-aminophenol was obtained using metal nanoparticles arranged in the second macroporous monolith as a catalyst and sodium borohydride (NaBH ₄ ) as a reducing agent. Phase reduction was performed at room temperature.

Specifically, it was performed as follows. First, 0.2 to 0.5 mg of a second macroporous monolith prepared in Examples 2 to 7 and arranged with metal nanoparticles having the composition shown in Table 15 below (a predetermined number of moles with respect to the monolith). Was selected), and this was immersed in 5 mL of a mixed solution of ion-exchanged water and methanol (volume ratio 1: 1). Next, 0.5 mL (equivalent to 0.5 mol) of NaBH ₄ and 0.25 mL (equivalent to 0.1 mol) of 4-nitrophenol were added to the solution, and reduction of 4-nitrophenol with a monolith was performed. The degree to which 4-nitrophenol was reduced was evaluated by withdrawing 0.1 mL of solution at regular time intervals and diluting it in 2 mL of distilled water to measure ultraviolet absorption spectroscopy (UV). In the UV absorption spectrum, in the presence of NaBH ₄ , an absorption peak of 4-nitrophenol is observed around 400 nm and an absorption peak of 4-aminophenol is observed around 300 nm. An example of the change is shown in FIG. The example shown in FIG. 63 is an example using the second macroporous monolith in which 0.92 mol of Au ₁ Pt ₃ alloy nanoparticles are arranged. As shown in FIG. 63, after the addition of NaBH ₄ and 4-nitrophenol, the absorption near 300 nm increases while the absorption near wavelength 400 nm decreases with the passage of time. From this change in absorption, the rate of decrease in the concentration of 4-nitrophenol over time, that is, the reaction constant κ of the reduction reaction can be obtained. For example, κ in the example shown in FIG. 63 is 2.615 / hour. When the metal nanoparticles were Au particles, κ was 0.353 / hour, and when the metal nanoparticles were Pt particles, κ was 0.564 / hour. The reaction constant of Au ₁ Pt ₃ nanoparticles composed of a binary alloy was larger than that of Au nanoparticles and Pt nanoparticles. The absorption peaks in the vicinity of the wavelength of 400 nm shown in FIG. 63 are 0 hour, 0.166 hours, 0.333 hours, 0.500 hours, 0.667 hours, and 0.833 hours from the top. After 1.000 hours and 1.166 hours later. Absorption peaks near the wavelength of 300 nm are as follows, from 0 hours, 0.166 hours, 0.333 hours, 0.500 hours, 0.667 hours, 0.833 hours, and 1.000 hours from the bottom. 1.166 hours later.

For the second monolith, Table 15 shows the ratio (TOF) of the number of moles of reactive molecules (4-nitrophenol) reduced during 1 hour to 1 mole of metal nanoparticles serving as a catalyst. The value of TOF was determined for the case where 4 moles of metal nanoparticles were arranged for each monolith, which is considered to have the highest reaction efficiency. Table 15 also shows the TOF value when a similar reduction reaction was attempted using the HY210 produced in Example 1.

As judged from the TOF values shown in Table 15, in any second macroporous monolith in which metal nanoparticles are arranged, the reduction reaction of 4-nitrophenol proceeds using the nanoparticles as a catalyst. I was able to. Nanoparticles having particularly high ability as a catalyst were nanoparticles of binary alloys of Pd ₃ Rh ₁ , Pd ₁ Rh ₄ , Pt ₁ Rh ₃ and Pt ₁ Rh ₄ .

Next, using a second macroporous monolith on which Pd ₁ Rh ₄ alloy nanoparticles are arranged, a solution containing ₄ -nitrophenol and NaBH ₄ is continuously flowed through the monolith while the 4- A reactor (fluid reaction system) capable of proceeding the reduction reaction of nitrophenol was produced (see FIG. 64). A specific method for producing this reactor is shown below.

First, as in Example 5-7, a second macroporous material having a cylindrical shape (weight: 53 mg) having a length of 22 mm and a diameter of 5 mm, in which 0.04 mmol of Pd ₁ Rh ₄ alloy nanoparticles were arranged. A monolith was made. Next, this was sandwiched between a pair of cylindrical silica monoliths having the same diameter, and inserted into a cylindrical column (made of resin). Silica monolith is a monolith produced by the method described in Kei Morisato et al., Journal of Chromatography A, 1216 (2009) pp. It has a hierarchical porous structure of pores and mesopores.

The reactor thus produced was connected to a high performance liquid chromatography (HPLC) pump so that the flow rate of the fluid flowing in the reactor could be controlled. Then, a separately prepared water / methanol mixed solution containing 50 mmol of 4-nitrophenol and 0.2 mmol of NaBH ₄ (mixing ratio of water and methanol as a medium is 1: 1 by volume) is added to room temperature. In this reactor. The solution flowing out of the reactor was subjected to UV absorption spectrometry, and the reduction reaction rate of 4-nitrophenol to 4-aminophenol was evaluated. As a result, the flow rate was 0.2% / min. A reduction rate of 78% was achieved at 0.0 mL / min.

The macroporous monolith of the present invention and the macroporous monolith obtained by the production method of the present invention are used for the same applications as the conventional macroporous monolith, for example, a chromatographic separation column, an enzyme carrier, a catalyst carrier, etc. be able to.

The present invention can be applied to other embodiments without departing from the intent and essential features thereof. The embodiments disclosed in this specification are illustrative in all respects and are not limited thereto. The scope of the present invention is shown not by the above description but by the appended claims, and all modifications that fall within the meaning and scope equivalent to the claims are embraced therein.

Claims (10)

Having a skeleton composed of hydrido silica and macropores showing a co-continuous structure with the skeleton;
By forming mesopores having openings on the surface of the skeleton in the skeleton, the skeleton has a hierarchical porous structure of the mesopores and macropores,
A macroporous monolith in which hydrogen sites based on Si—H bonds are distributed on the surface of the skeleton and inside the mesopores. In a solution system containing a silicon compound having a hydrolyzable functional group, the silicon compound is rich in the polymer of the silicon compound by advancing hydrolysis and polymerization of the silicon compound by a sol-gel method and phase separation of the system. It is composed of a skeletal phase with pores having openings on the surface and a solution phase rich in the solvent of the system, and forms a gel having a co-continuous structure of the skeleton phase and the solution phase
Drying the gel formed,
A macroporous monolith having a hierarchical porous structure of the mesopores and macropores, wherein the skeleton phase is a skeleton, the pores are mesopores having openings on the surface of the skeleton, and the solution phase is a macropore A method of obtaining
The silicon compound is a silicon hydride compound having at least one Si-H bond in the molecule;
A method for producing a macroporous monolith, wherein a monolith in which hydrogen sites based on the Si—H bond are distributed on the surface of the skeleton and inside the mesopores is obtained as the monolith. The method for producing a macroporous monolith according to claim 2, wherein the silicon hydride compound is trialkoxysilane. The method for producing a macroporous monolith according to claim 3, wherein the alkoxy group of the trialkoxysilane is at least one selected from a methoxy group, an ethoxy group, and a propoxy group. The method for producing a macroporous monolith according to claim 2, wherein the solution system is weakly acidic and contains alcohol. Having a skeleton composed of hydrido silica or silica gel, and macropores showing a co-continuous structure with the skeleton,
By forming mesopores having openings on the surface of the skeleton in the skeleton, the skeleton has a hierarchical porous structure of the mesopores and macropores,
A macroporous monolith in which nanoparticles composed of a metal having a standard electrode potential positively greater than hydrogen are disposed at least inside the mesopores. A mesopore having a skeleton composed of hydridosilica and a macropore showing a co-continuous structure with the skeleton, and having an opening on the surface of the skeleton, the mesopores and A macroporous monolith having a macroporous hierarchical porous structure in which hydrogen sites based on Si—H bonds are distributed on the surface of the skeleton and inside the mesopores,
The metal is reduced at the hydrogen site in the macroporous monolith by contacting a solution containing a metal salt whose standard electrode potential is just greater than that of hydrogen to form nanoparticles composed of the metal. ,
A method for producing a macroporous monolith, which obtains a macroporous monolith in which the nanoparticles are disposed at least inside the mesopores. The method for producing a macroporous monolith according to claim 7, wherein the macroporous monolith in which hydrogen sites based on the Si-H bonds are distributed is formed by the method for producing a macroporous monolith according to claim 2. The method for producing a macroporous monolith according to claim 7, wherein the metal is at least one selected from platinum, palladium, gold, silver, copper, ruthenium, rhodium and mercury. The metal is at least two selected from platinum, palladium, gold, silver, copper, ruthenium, rhodium and mercury;
The method for producing a macroporous monolith according to claim 7, wherein the nanoparticles are particles composed of an alloy or a solid solution of the at least two kinds of metals.

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