JP2006347849A - Core-shell type spherical silica-based mesoporous body and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a core-shell type spherical silica-based mesoporous body having mesopores modified with different organic functional groups in a hierarchical state. <P>SOLUTION: The method for producing the silica-based mesoporous body includes: a first process for depositing core particles, in each of which a surfactant of an alkyl ammonium halide expressed by general formula (1) is introduced in a first silica, by mixing the surfactant and a first silica raw material in a basic solvent; a second process for obtaining porous precursor particles by stacking a shell layer, in which the surfactant is introduced in a second silica, on the outer side of each core particle by adding a second silica raw material into the solvent and mixing them; and a third process for obtaining the core-shell type spherical silica-based mesoporous body by removing the surfactant contained in the porous precursor particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a core-shell type spherical silica mesoporous material and a method for producing a core-shell type spherical silica mesoporous material.

  In recent years, silica-based mesoporous materials in which meso-sized pores (mesopores) having a pore diameter of about 1 to 50 nm are regularly arranged have attracted attention as materials for adsorbing and storing various substances. Studies on the synthesis and functional development of such silica-based mesoporous materials have been actively conducted.

  For example, G. Van Tendeloo et al. Reported a method for producing a spherical porous body having pores arranged radially using tetraethoxysilane and cetyltrimethylammonium salt (G. Van Tendeloo, O. I. Lebedev, O. Collart). , P. Cooland EF Vansant, “J. Phys. Condens. Matter”, Vol. 15, 2003, p3037-p3046 (Non-patent Document 1)). In JP-A-2005-89218 (Patent Document 1), a silica raw material and a specific surfactant are mixed in a specific solvent, and the surfactant is introduced into the silica raw material. Spherical silica-based mesoporous material comprising a first step of obtaining porous precursor particles and a second step of removing the surfactant contained in the porous precursor particles to obtain a spherical silica-based mesoporous material A method for manufacturing a body is disclosed. With the methods described in Non-Patent Document 1 and Patent Document 1, it was possible to synthesize a spherical silica-based mesoporous material in which pores are radially arranged from the center of the sphere toward the outside. Further, in such a spherical silica-based mesoporous material, it was possible to introduce an organic functional group into the pores using an alkoxysilane having an organic functional group.

However, in such methods described in Non-Patent Document 1 and Patent Document 1, basically only one type of organic functional group can be introduced into the resulting spherical silica-based mesoporous material, When other types of organic functional groups described above were introduced, the organic functional groups were not site-specific but randomly introduced in the resulting spherical silica-based mesoporous material. Thus, in the methods described in Non-Patent Document 1 and Patent Document 1, a spherical silica-based mesoporous material modified with different organic functional groups in a hierarchical manner cannot be obtained. Introduce several different dyes at the desired site of the material and conduct electron transfer between these different kinds of dyes, or separate the adsorption region and the active site region to allow the oxidation-reduction catalytic reaction to proceed simultaneously It was not possible to obtain a spherical silica-based mesoporous material that can be used. Further, in the methods described in Non-Patent Document 1 and Patent Document 1, there is a limit to the increase in the particle size of the obtained spherical silica mesoporous material, and the particle size of the conventional spherical silica mesoporous material is realistic. The maximum was about 1 μm.
JP 2005-89218 A G. Van Tendeloo, O.D. I. Lebedev, O.M. Collart, P.M. Cooland E.M. F. Vansant, “J. Phys. Condens. Matter”, Vol. 15, 2003, p3037-p3046

  The present invention has been made in view of the above-described problems of the prior art, and has a core-shell type spherical silica-based mesoporous material having mesopores modified with different organic functional groups in a hierarchical manner, and a particle diameter larger than that of the conventional one. Provide a method for producing a core-shell type spherical silica-based mesoporous material that can efficiently and reliably produce a large core-shell type spherical silica-based mesoporous material, and is modified with different organic functional groups in a hierarchical manner Another object of the present invention is to provide a core-shell type spherical silica-based mesoporous material having mesopores and capable of exhibiting different properties depending on the positions of the pores in the same particle.

  As a result of intensive studies to achieve the above object, the present inventors have mixed a specific alkyl ammonium halide having a long-chain alkyl group and a first silica raw material at a specific ratio in a basic solvent. In addition, after the core particles are precipitated, the second silica raw material is further introduced, so that new particles made of the second silica are not generated but are selectively formed on the surface of the core particles. As a result of the condensation reaction of the silica raw material, a core-shell type spherical silica-based mesoporous material in which a shell layer is laminated on the outside of the core particles can be obtained, and the above object is achieved. It came to be completed.

  That is, the manufacturing method of the core-shell type spherical silica mesoporous material of the present invention has the following general formula (1) as a surfactant:

[Wherein R ¹ , R ² and R ³ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms, X represents a halogen atom, and n represents an integer of 7 to 25, respectively. ]
In the basic solvent, the surfactant and the first silica raw material are used in a basic solvent, and the content ratio of the surfactant to the silicon atom in the first silica raw material (surface active First agent / silicon atom in the first silica raw material) in a range of 0.1 to 20 in molar ratio to precipitate the core particles having the surfactant introduced into the first silica. Process,
After the core particles have been precipitated, the second silica raw material is mixed in the solvent, and a shell layer in which the surfactant is introduced into the second silica is laminated outside the core particles, A second step of obtaining porous precursor particles in which the surfactant is introduced into the core particles and the shell layer;
A third step of removing the surfactant contained in the porous precursor particles and obtaining a core-shell type spherical silica-based mesoporous material comprising the core particles and the shell layer;
It is the method characterized by including.

  The solvent according to the present invention is preferably a mixed solvent of water and alcohol having an alcohol content of 85% by volume or less.

  In the present invention, the first silica raw material and the second silica raw material may be the same or different, and each is preferably an alkoxysilane.

The core-shell type spherical silica-based mesoporous material of the present invention includes core particles made of the first silica,
The first silica is composed of a second silica having a different composition, and a shell layer laminated on the outside of the core particles;
It is characterized by having.

  In the core-shell type spherical silica mesoporous material of the present invention, the shell layer is formed of a plurality of silica layers, and at least one of the plurality of silica layers is the first silica. It is preferable that they are made of silica having different compositions.

  Furthermore, in the core-shell type spherical silica mesoporous material of the present invention, it is preferable that the first silica and the second silica are made from alkoxysilanes having different compositions as raw materials.

  The reason why the above object is achieved by the method for producing a core-shell type spherical silica mesoporous material of the present invention is not necessarily clear, but the present inventors speculate as follows. That is, first, in a basic solvent, when the surfactant and the first silica raw material are mixed in the molar ratio range, after the condensation of the first silica raw material proceeds to some extent, the first silica raw material and the interface are mixed. The active agent is complexed to generate core particles in which the surfactant is introduced into the first silica. Then, after the core particles into which the surfactant is introduced into the first silica are precipitated, a second silica raw material is further added. As a result, the second silica raw material added in a state where the condensation has not progressed at all, selectively undergoes a condensation reaction on the surface of the core particle, and the second silica and the surfactant are combined on the surface of the core particle. Is done. Therefore, by adding the second silica raw material after the core particles are precipitated, new shells made of the second silica are not generated, and the shell layer made of the second silica is formed outside the core particles. The present inventors speculate that stacked particles are generated. In such a reaction process, when a second silica raw material having a composition different from that of the first silica raw material is added after the core particles are precipitated, the core particles made of the first silica and the second silica are added. For example, a core-shell type spherical silica-based mesoporous material whose pores are modified with hierarchically different organic functional groups can be obtained. On the other hand, when the second silica raw material having the same composition as the first silica raw material is added, a shell layer made of the same silica as the core particles can be laminated. The particle diameter of the modified spherical silica mesoporous particles can be increased.

  According to the present invention, a core-shell type spherical silica-based mesoporous material having mesopores modified with different organic functional groups in a hierarchical manner and a core-shell-type spherical silica-based mesoporous material having a larger particle diameter than conventional ones can be efficiently obtained. And it becomes possible to manufacture reliably. In addition, according to the present invention, the core-shell type spherical silica-based mesopores have mesopores modified with different organic functional groups in a hierarchical manner, and can exhibit different properties depending on the location of the pores in the same particle. A porous body can be provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

[Method for producing core-shell type spherical silica mesoporous material]
First, the manufacturing method of the core-shell type spherical silica-based mesoporous material of the present invention will be described by dividing it into first to third steps.

(First step)
In the method for producing a core-shell type spherical silica mesoporous material of the present invention, first, in a basic solvent, a surfactant and a first silica raw material are contained in the silicon contained in the first silica raw material. In the first silica, the content ratio of the surfactant to the atoms (surfactant / silicon atoms contained in the first silica raw material) is 0.1 to 20 in a molar ratio. The core particles into which the surfactant is introduced are precipitated (first step).

  In the present invention, the term “precipitation” refers to the time when the diffraction peak on the 100 plane of hexagonal pores begins to appear by X-ray diffraction measurement of the reaction solution, and the diffraction peak gradually increases. The time when it reaches a certain value is defined as the end time of deposition.

  The first silica raw material used in the present invention is not particularly limited as long as it can form a silicon oxide (including a silicon composite oxide) by reaction, but the reaction efficiency and physical properties of the obtained silicon oxide are not limited. From the viewpoint, it is preferable to use alkoxysilane, sodium silicate, layered silicate, silica, or any mixture thereof, and it is more preferable to use alkoxysilane.

  Examples of the alkoxysilane include tetraalkoxysilane having 4 alkoxy groups, trialkoxysilane having 3 alkoxy groups, and dialkoxysilane having 2 alkoxy groups. The type of such an alkoxy group is not particularly limited, but those having a relatively small number of carbon atoms in the alkoxy group such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group (about 1 to 4 carbon atoms) From the viewpoint of reactivity. In addition, when the alkoxysilane has 3 or 2 alkoxy groups, an organic group, a hydroxyl group, or the like may be bonded to the silicon atom in the alkoxysilane, and the organic group is an amino group, a mercapto group, or the like. It may further have a functional group.

  Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and dimethoxydiethoxysilane. Examples of the trialkoxysilane include methyltrimethoxysilane and propyltrimethoxy. Silane, hexyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, allyltrimethoxysilane, vinyltrimethoxysilane, cyanopropyltrimethoxysilane, 3-bromopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 2 -(3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-iodopropyltrimethoxysilane, 3- Lucaptopropyltrimethoxysilane, trimethoxy [2- (7-oxabicyclo [4,1,0] hept-3-yl) ethyl] silane, 1- [3- (trimethoxysilyl) propyl] urea, N- [ 3- (trimethoxysilyl) propyl] aniline, trimethoxy [3-phenylaminopropyl] silane, acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, trimethoxy [2-phenylethyl] silane, trimethoxy (7-octene- 1-yl) silane, trimethoxy (3,3,3-trifluoropropyl) silane, 3- [2- (2-aminoethylamino) ethylamino] propyltrimethoxysilane, [3- (2-aminoethylamino) Propyl] trimethoxysilane, 3-aminopropyltrime Xysilane, 3-diethylaminopropyltrimethoxysilane, bis (3-methylamino) propyltrimethoxysilane, N, N-dimethylaminopropyltrimethoxysilane, N- [3- (trimethoxysilylpropyl) ethylenediamine, trimethoxy (3- Methylamino) propylsilane, methyltriethoxysilane, propyltriethoxysilane, hexyltriethoxysilane, octadecyltriethoxysilane, phenyltriethoxysilane, allyltriethoxysilane, (1-naphthyl) triethoxysilane, [2- (cyclo Hexenyl) ethyl] triethoxysilane, 3-aminopropyltriethoxysilane, 3- [bis (2-hydroxyethyl) amino] propyltriethoxysilane, 3-chloropropyltriethoxysila 3-glycidyloxypropyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 4-chlorophenyltriethoxysilane, (bicyclo [2,2,1] hept-5-en-2-yl) triethoxysilane, chloro Methyltriethoxysilane, pentafluorophenyltriethoxysilane, 3- (triethoxysilyl) propionitrile, 3- (triethoxysilyl) propyl isocyanate, bis [3-triethoxysilylpropyl] tetrasulfide, triethoxy (3-isocyanate) Natopropyl) silane, triethoxy (3-thioisocyanatopropyl) silane and the like. Examples of the dialkoxysilane include dimethoxydimethylsilane, diethoxydimethylsilane, diethoxy-3-glycidoxypropylmethylsilane, dimethoxydiphenylsilane, and dimethoxymethylphenylsilane.

  Such alkoxysilanes can be used alone or in combination of two or more. Moreover, the alkoxysilane having 2 to 4 alkoxy groups described above can be used in combination with a monoalkoxysilane having one alkoxy group. Examples of the monoalkoxysilane that can be used in this way include trimethylmethoxysilane, trimethylethoxysilane, and 3-chloropropyldimethylmethoxysilane.

  The alkoxysilane generates a silanol group by hydrolysis, and the generated silanol groups condense to form a silicon oxide. In this case, an alkoxysilane having a large number of alkoxy groups in the molecule has many bonds generated by hydrolysis and condensation. Therefore, in the present invention, tetraalkoxysilane having a large number of alkoxy groups is preferably used as alkoxysilane, and tetramethoxysilane or tetraethoxysilane is particularly preferably used as tetraalkoxysilane from the viewpoint of reaction rate.

As sodium silicate used as the first silica raw material in the present invention, sodium metasilicate (Na ₂ SiO ₃ ), sodium orthosilicate (Na ₄ SiO ₄ ), sodium disilicate (Na ₂ Si ₂ O ₅ ), Examples thereof include sodium tetrasilicate (Na ₂ Si ₄ O ₉ ). As the sodium silicate, in addition to such a single substance, water glass (Na ₂ O · nSiO ₂ , n = 2 to 4) or the like having a different composition depending on the case can be used.

As the layered silicate, kanemite (NaHSi ₂ O ₅ .3H ₂ O), sodium disilicate crystal (α, β, γ, δ-Na ₂ Si ₂ O ₅ ), macatite (Na ₂ Si ₄ O ₉ · 5H ₂₎ O), Aia light _{(Na 2 Si 8 O 17 ·} xH 2 O), magadiite _{(Na 2 Si 14 O 17 ·} xH 2 O), kenyaite _{(Na 2 Si 20 O 41 ·} xH 2 O) , and the like . Further, a layer obtained by treating clay minerals such as sepiolite, montmorillonite, vermiculite, mica, kaolinite and smectite with an acidic aqueous solution to remove elements other than silica can be used as the layered silicate.

  The silica used as the first silica raw material in the present invention includes precipitated silica such as Ultrasil (Ultrasil), Cab-O-Sil (Cabot), HiSil (Pittsburgh Plate Glass); colloidal silica; Aerosil (Degussa) -Huls) and the like.

  The above-mentioned first silica raw material can be used alone or in combination of two or more. However, when two or more types of first silica raw materials are used, the reaction conditions during production may be complicated. Therefore, in the present invention, it is preferable to use a single first silica raw material.

  The surfactant used in the present invention is represented by the following general formula (1):

[Wherein R ¹ , R ² and R ³ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms, X represents a halogen atom, and n represents an integer of 7 to 25, respectively. ]
It is an alkylammonium halide represented by.

Thus, R < ¹ >, R < ² >, R < ³ > in General formula (1) may be same or different, and respectively shows a C1-C3 alkyl group. Examples of such an alkyl group include a methyl group, an ethyl group, and a propyl group, and these may be mixed in one molecule. From the viewpoint of symmetry of the surfactant molecule, R ¹ , R ² , R ³ Are preferably the same. When the symmetry of the surfactant molecule is excellent, aggregation of the surfactants (formation of micelles, etc.) tends to be facilitated. ^Furthermore, R ^1, it is preferable that at least one of R 2, ^{R 3} is a methyl ^group, and more preferably all of R ^1, R 2, ^{R 3} is a methyl group.

  Moreover, n in General formula (1) shows the integer of 7-25, and it is more preferable that it is an integer of 11-17. In the case of the alkyl ammonium halide having n of 6 or less, spherical core particles can be obtained, but the formation of pores is difficult because the aggregating action of the surfactant is insufficient. On the other hand, in the case of the alkyl ammonium halide having n of 26 or more, the hydrophobic interaction of the surfactant is too strong, so that a layered compound is formed and spherical core particles cannot be obtained.

  Furthermore, X in the general formula (1) represents a halogen atom. The type of such a halogen atom is not particularly limited, but X is preferably a chlorine atom or a bromine atom from the viewpoint of easy availability.

Therefore, as the surfactant represented by the general formula (1), all of R ¹ , R ² and R ³ are methyl groups and alkyltrimethylammonium halides having a long-chain alkyl group having 8 to 26 carbon atoms. Among them, octyltrimethylammonium halide, decyltrimethylammonium halide, dodecyltrimethylammonium halide, tetradecyltrimethylammonium halide, hexadecyltrimethylammonium halide, octadecyltrimethylammonium halide, eicosyltrimethylammonium halide, docosyltrimethylammonium halide are preferred. Is more preferable.

  Such a surfactant forms a complex in the solvent together with the first silica raw material. The silica raw material in the composite is changed to silicon oxide (first silica) by the reaction, but the surfactant is present because silicon oxide is not generated in the portion where the surfactant is present. A hole will be formed in the part. That is, the surfactant is introduced into the silica raw material and functions as a template for pore formation. In the present invention, the surfactant can be used alone or in combination of two or more, but as described above, the surfactant acts as a template for forming pores in the reaction product of the silica raw material, Since the type greatly affects the pore shape of the porous body, it is preferable to use only one type of surfactant in order to obtain a more uniform spherical porous body.

  In the present invention, the content ratio of the surfactant to the silicon atoms in the first silica raw material (surfactant / silicon atoms in the first silica raw material) is 0.1 to 20 (preferably 0.2 to 10). When the content ratio of such a surfactant is less than 0.1, a sufficient core particle cannot be obtained because the amount of the surfactant to be a template is insufficient. Thus, in the present invention, since the surfactant functions as a template (template) for pores, the surfactant is contained with respect to the silicon atoms contained in the first silica raw material. The ratio is at least greater than that required to form pores. Moreover, when the content ratio of the surfactant exceeds 20, the formation of particles is inhibited, so that it becomes difficult to obtain uniform particles.

  Here, excess surfactant more than the amount of surfactant necessary to form pores prevents aggregation between the precipitated core particles, and additionally adds a second silica raw material to be described later. The porous precursor particles obtained in this way are used for pore formation. That is, by controlling the content ratio (molar ratio) of the surfactant to the silicon atoms in the first silica raw material as described above, uniform core particles (spherical bodies) are generated and grown. In addition, when the second silica raw material is mixed after the core particles are precipitated, the amount of surfactant necessary for forming the pores of the shell layer is present, so that the porous body has uniform pores. Generation and growth of precursor particles can be realized. Further, by controlling the content ratio (molar ratio) as described above, the particle diameter of the obtained porous precursor particles is highly uniformly controlled in combination with the use of a mixed solvent described later. It is also possible.

  In the present invention, the first silica raw material and the surfactant are mixed in a basic solvent. In general, the silica raw material reacts under basic and acidic conditions and changes to silicon oxide. However, when the content ratio of the surfactant is controlled as described above, Then the reaction hardly progresses. Therefore, in this invention, a silica raw material is made to react in a basic solvent. In addition, when the silica raw material is reacted under basic conditions, the reaction point of silicon atoms is increased when the reaction is performed under basic conditions, and a silicon oxide having excellent physical properties such as moisture resistance and heat resistance is obtained. In this respect, mixing under basic conditions is also advantageous.

  The pH value of such a basic solvent is preferably 7.5 to 13, and more preferably 8 to 12. When such a pH value is less than the lower limit, pore formation of the core particles tends to be difficult, and on the other hand, when the upper limit is exceeded, the precipitation amount of the core particles tends to decrease. In addition, the method for adjusting the pH value of such a basic solvent is not particularly limited, but a method of appropriately adjusting the pH value by adding a basic substance such as an aqueous sodium hydroxide solution to the solvent described later can be mentioned. .

  As such a solvent, it is preferable to use a mixed solvent of water and alcohol. Examples of such an alcohol include methanol, ethanol, isopropanol, n-propanol, ethylene glycol, and glycerin, and methanol or ethanol is preferable from the viewpoint of solubility of the first silica raw material.

  Moreover, as such a mixed solvent, it is more preferable to use a water / alcohol mixed solvent having an alcohol content of 85% by volume or less. Furthermore, among such a mixed solvent of water and alcohol, it is possible to realize generation and growth of uniform spheres, and the core particles in which the surfactant is introduced into the obtained first silica raw material From the viewpoint that the diameter can be controlled highly uniformly, it is more preferable to use a mixed solvent having an alcohol content of 45 to 80% by volume, and a mixture having an alcohol content of 50 to 70% by volume. It is particularly preferable to use a solvent. When the alcohol content is less than 45% by volume, it is difficult to control the particle size and particle size distribution, and the uniformity of the particle size of the obtained core particles tends to be low, while the alcohol content is low. When it exceeds 80% by volume, it is difficult to control the particle size and particle size distribution, and the uniformity of the particle size of the obtained core particles tends to be low.

  Further, in the present invention, by changing the ratio of water and alcohol, it is possible to easily control the particle size of the core particle while maintaining a high uniformity of the particle size of the core particle. become. For example, when the ratio of water is high, the core particles are likely to precipitate, so that core particles with a small particle diameter can be obtained. Conversely, when the ratio of alcohol is high, core particles with a large particle diameter can be obtained.

  The reaction conditions (reaction temperature, reaction time, etc.) in the first step are not particularly limited, and the reaction temperature is, for example, −20 ° C. to 100 ° C. (preferably 0 ° C. to 80 ° C., more preferably 10 ° C. to 40 ° C.). In addition, the reaction is preferably allowed to proceed with stirring. Specific reaction conditions are preferably determined based on the type of silica raw material used.

  For example, when alkoxysilane is used as a silica raw material, core particles can be obtained as follows. First, a basic solution containing a surfactant is prepared by adding a surfactant and a basic substance to the mixed solvent of water and alcohol described above, and alkoxysilane is added to this solution. Since the added alkoxysilane is hydrolyzed (or hydrolyzed and condensed) in the solution, core particles (white powder) are deposited several seconds to several tens of minutes after the addition. In this case, the reaction temperature is preferably 0 ° C to 80 ° C, more preferably 10 ° C to 40 ° C. The solution is preferably stirred.

  Moreover, when using silica raw materials other than alkoxysilane (sodium silicate, layered silicate or silica) as the first silica raw material, the first silica raw material is mixed with a mixed solvent of water and alcohol containing a surfactant. A basic solution such as a sodium hydroxide aqueous solution is further added to prepare a uniform solution so that the amount is about equimolar with the silicon atoms in the first silica raw material. Thereafter, the core particles can be produced by a method in which a dilute acid solution is added 1/2 to 3/4 times moles of silicon atoms in the first silica raw material.

(Second step)
Next, in the method for producing the core-shell type spherical silica-based mesoporous material of the present invention, after the core particles are precipitated, a second silica raw material is mixed in the solvent, and the interface is incorporated in the second silica. The shell layer into which the activator is introduced is laminated on the outer side of the core particle to obtain porous precursor particles in which the surfactant is introduced into the core particle and the shell layer (second step).

  As a kind of silica raw material which can be used for the 2nd silica raw material concerning this invention, the thing similar to the above-mentioned 1st silica raw material is mentioned, Especially, it is more preferable to use alkoxysilane. In addition, as the second silica raw material used in the present invention, the silica raw material can be used alone, or two or more kinds can be used in combination.

  Further, as the second silica raw material used in the present invention, a silica raw material having the same composition as that of the first silica raw material may be used, or a silica raw material having a composition different from that of the first silica raw material may be used. It may be used. When a second silica material having the same composition as that of the first silica material is used, a shell layer made of silica having the same composition can be laminated on the outside of the core particles. It becomes possible to increase the particle size of the body particles. On the other hand, when a silica raw material having a composition different from that of the first silica raw material is mixed as the second silica raw material, the second silica having a composition different from that of the first silica is outside the core particles made of the first silica. It is possible to obtain a core-shell type spherical silica-based mesoporous material in which a shell layer made of is laminated.

  The particle diameter of the core-shell type spherical silica-based mesoporous material thus obtained is not particularly limited and can be adjusted according to the intended use. For example, the particle diameter is about 0.1 to 5 μm. It is also possible. Such adjustment of the particle diameter can be performed by appropriately adjusting the conditions of the solvent, the mixing amount of the second silica raw material, and the like.

  Further, the method of mixing the second silica raw material in the present invention is not particularly limited, and after the core particles have been precipitated, the addition of the second silica raw material in addition to the method of adding the second silica raw material all at once. And the like, and a method of repeatedly adding the second silica raw material continuously. By mixing the second silica raw material in this way, the second silica raw material is added to the solvent in a state in which condensation does not proceed at all. A shell layer in which the surfactant is introduced into the second silica can be laminated outside the core particles.

  As a preferred example of such a mixing method, a method of repeatedly adding the second silica raw material as described above in a plurality of times will be described below. As a suitable method for repeatedly adding the second silica raw material in a plurality of times, first, the silica raw material (i) selected from the second silica raw materials is mixed, and the core particles are mixed. A method of mixing a silica raw material (ii) other than the silica raw material (i) selected from the second silica raw materials after laminating a silica layer made of silica (i) on the surface can be mentioned. . After laminating a silica layer made of silica (i) on the surface of the core particles in this way, other silica raw materials (ii) other than the silica raw material (i) selected from the second silica raw materials are mixed. Thus, a shell layer including a silica layer made of silica (i) and a silica layer made of silica (ii) can be laminated on the outside of the core particles. In addition, the method of repeating the addition of the second silica raw material in a plurality of times is not limited to such a method, and for example, it is possible to repeat such a step two or more times. . Further, when a plurality of layers made of the second silica raw material are laminated on the surface of the core particle in this way, a part of the layer is made of the second silica having the same composition as the first silica. It can also be a layer. Further, in the method of repeatedly adding the second silica raw material in a plurality of times, it is possible to add only the second silica raw material having the same composition as the first silica raw material. In this case, a core-shell type spherical silica-based mesoporous material having a large particle size made of the same silica raw material can be obtained.

  In addition, the mixing amount of the second silica raw material includes silicon atoms contained in the second silica raw material with respect to silicon atoms already contained in the first silica raw material already contained in the solvent. The molar ratio is preferably in the range of 0.01 to 2000, and more preferably in the range of 0.05 to 500. If the mixing amount of the second silica raw material is less than the lower limit, the proportion of the shell layer is too small, so that particles having only the characteristics of the core particles tend to be generated. The proportion of particles tends to be reduced, and particles having only the characteristics of a shell layer tend to be produced.

  In addition, when the second silica raw material is mixed and the shell layer into which the surfactant is introduced into the second silica is laminated outside the core particles, for the same reason as in the first step. The pH value of the solvent is preferably 7.5 to 13, and more preferably 8 to 12. From such a viewpoint, a basic substance can be added as necessary in the second step.

  The reaction conditions (reaction temperature, reaction time, etc.) in the second step are not particularly limited, and the reaction temperature is, for example, -20 ° C to 100 ° C (preferably 0 ° C to 80 ° C, more preferably 10 ° C to 40 ° C.). In addition, the reaction is preferably allowed to proceed with stirring. The specific reaction conditions are preferably determined based on the type of the second silica raw material used.

  For example, when alkoxysilane is used as the second silica raw material, after the core particles have been precipitated, the second silica raw material is mixed, and 1 hour at 0 ° C. to 80 ° C. (preferably 10 ° C. to 40 ° C.). By stirring the solution for 10 days, a layer made of the second silica raw material can be laminated outside the core particles. And after finishing the stirring, if necessary, the porous precursor particles according to the present invention are allowed to stand overnight at room temperature to stabilize the system and then filter and wash the precipitate obtained as necessary. Can be obtained.

Moreover, when using silica raw materials (sodium silicate, layered silicate, or silica) other than alkoxysilane as the second silica raw material, the second silica raw material is mixed after the core particles are precipitated, A basic solution such as an aqueous solution of sodium hydroxide is further added to prepare a uniform solution so that it is about equimolar to the silicon atoms in the silica raw material. Then, the porous precursor particle | grains concerning this invention can be manufactured by the method of adding 1 / 2-3 / 4 times mole with respect to the silicon atom in a 1st silica raw material for a diluted acid solution. The basic substance requires an excessive amount for the purpose of cleaving a part of the Si— (O—Si) ₄ bond already formed in the silica raw material, but it is necessary to neutralize the excess with an acid. There is. As the acid, any of inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid may be used.

(Third step)
Next, in the method for producing a core-shell type spherical silica-based mesoporous material of the present invention, the core contained in the porous body precursor particles is removed, and the core shell includes the core particles and the shell layer. A type spherical silica-based mesoporous material is obtained (third step).

  Examples of the method for removing such a surfactant include a method by baking, a method of treating with an organic solvent, and an ion exchange method. In the case of employing such a firing method, the porous precursor particles are heated at 300 to 1000 ° C., preferably 400 to 700 ° C. The heating time may be about 30 minutes, but it is preferable to heat for 1 hour or longer in order to completely remove the surfactant. Moreover, although such baking can be performed in the air, since a large amount of combustion gas is generated, it may be performed by introducing an inert gas such as nitrogen. Moreover, when employ | adopting the method processed with an organic solvent, a porous body precursor particle | grain is immersed in a good solvent with high solubility with respect to the used surfactant, and surfactant is extracted. When the ion exchange method is employed, the porous precursor particles are immersed in an acidic solution (such as ethanol containing a small amount of hydrochloric acid) and stirred while heating at, for example, 50 to 70 ° C. Thereby, the surfactant existing in the pores of the porous precursor particles is ion-exchanged with hydrogen ions. In addition, although hydrogen ions remain in the hole by ion exchange, the problem of blockage of the hole does not occur because the ion radius of the hydrogen ion is sufficiently small.

  The core-shell type spherical silica-based mesoporous material thus obtained is the same outside the core particles when the second silica raw material having the same composition as the first silica raw material is used in the second step. Since the shell layer made of silica is laminated, a core-shell type spherical silica-based mesoporous material having a large particle diameter in which the pores are modified with the same organic functional group can be obtained. On the other hand, when the second silica raw material having a composition different from that of the first silica raw material is used in the second step, the core particles made of the first silica and the shell layer made of the second silica are provided, A core-shell type spherical silica-based mesoporous material whose pores are modified by organic functional groups that are hierarchically different is obtained.

  The core-shell type spherical silica-based mesoporous material in which the pores thus obtained are modified with hierarchically different organic functional groups allows different compounds to be adsorbed in the same particle and simultaneously perform an oxidation reaction and a reduction reaction, A dye can be adsorbed in the same particle to move electrons from the inside to the outside of the particle.

  In the production method of the present invention, as described above, a core-shell type spherical silica mesoporous material with extremely high particle size uniformity can be obtained by adjusting the alcohol concentration and the like in the solvent used. For example, a core-shell type spherical silica meso having extremely high particle size uniformity in which 90% by weight or more (preferably 95% by weight or more) of the total particles obtained has a particle size in the range of ± 10% of the average particle size It is possible to obtain a porous body. And when the particle diameter of such a core-shell type spherical silica mesoporous material is extremely uniform, it can be suitably used as a material used for optical devices such as photonic crystals.

  The term “spherical” as used in the present invention is not limited to a true sphere, but includes a substantially sphere having a minimum diameter of 80% or more (preferably 90% or more) of the maximum diameter. In the case of a substantially spherical body, the particle size is an average value of the minimum diameter and the maximum diameter in principle. Further, the central pore diameter is a curve (pore diameter distribution curve) in which a value (dV / dD) obtained by differentiating the pore volume (V) with respect to the pore diameter (D) is plotted against the pore diameter (D). ) At the maximum peak. The pore size distribution curve can be obtained by the method described below. That is, silica-based mesoporous particles are cooled to a liquid nitrogen temperature (-196 ° C.), nitrogen gas is introduced, the adsorption amount is determined by a constant volume method or a gravimetric method, and then the pressure of the introduced nitrogen gas is gradually increased. And the adsorption amount of nitrogen gas for each equilibrium pressure is plotted to obtain an adsorption isotherm. Using this adsorption isotherm, a pore size distribution curve can be obtained by a calculation method such as Cranston-Inklay method, Dollimore-Heal method, BJH method or the like.

  The core-shell type spherical silica-based mesoporous material obtained by the present invention is manufactured using the surfactant as a template and the first and second silica raw materials as raw materials, and the silicon atom is interposed via an oxygen atom. It has a highly cross-linked network structure based on a bonded skeleton -Si-O-. Such a core-shell type spherical silica-based mesoporous material only needs to have silicon atoms and oxygen atoms as main components, and at least part of the silicon atoms form carbon-silicon bonds at two or more organic groups. It may be what you have. Examples of such an organic group include, but are not limited to, divalent or higher organic groups generated by removing two or more hydrogens from hydrocarbons such as alkanes, alkenes, alkynes, benzenes, and cycloalkanes. Instead, the organic group may have an amide group, amino group, imino group, mercapto group, sulfone group, carboxyl group, ether group, acyl group, vinyl group or the like.

The core-shell type spherical silica-based mesoporous material obtained by the present invention includes a core-shell type spherical silica-based material in which 60% or more of the total pore volume is included in the range of ± 40% of the central pore diameter in the pore size distribution curve. A mesoporous material is preferred. The core-shell type spherical silica-based mesoporous material satisfying such conditions means that the pore diameter is very uniform. Further, the specific surface area of the core-shell type spherical silica-based mesoporous material is not particularly limited, but is preferably 700 m ² / g or more. The specific surface area can be calculated as a BET specific surface area from the adsorption isotherm using the BET isotherm adsorption equation.

  Furthermore, the core-shell type spherical silica mesoporous material obtained by the present invention preferably has one or more peaks at a diffraction angle corresponding to a d value of 1 nm or more in the X-ray diffraction pattern. The X-ray diffraction peak means that a periodic structure having a d value corresponding to the peak angle is present in the sample. Therefore, having one or more peaks at a diffraction angle corresponding to a d value of 1 nm or more means that the pores are regularly arranged at intervals of 1 nm or more.

  In addition, the pores of the core-shell type spherical silica mesoporous material according to the present invention are formed not only on the surface of the porous material but also inside. The arrangement state (pore arrangement structure or structure) of the pores in such a porous body is not particularly limited, but is preferably a 2d-hexagonal structure, a 3d-hexagonal structure, or a cubic structure. Such a pore arrangement structure may have a disordered pore arrangement structure.

  Here, that the porous body has a hexagonal pore arrangement structure means that the arrangement of the pores is a hexagonal structure (S. Inagaki, et al., J. Chem. Soc., Chem. Commun. 680, 1993; S. Inagaki, et al., Bull. Chem. Soc. Jpn., 69, 1449, 1996, Q. Huo, et al., Science, 268, 1234, 1995). Moreover, the porous body having a cubic pore arrangement structure means that the arrangement of the pores is a cubic structure (JC Vartuli, et al., Chem. Mater., 6, 2317, 1994). Q. Huo, et al., Nature, 368, 317, 1994). Further, that the porous body has a disordered pore arrangement structure means that the arrangement of the pores is irregular (PT Tanev, et al., Science, 267, 865, 1995; S; A. Bagshaw, et al., Science, 269, 1242, 1995; R. Ryoo, et al., J. Phys. Chem., 100, 17718, 1996). The cubic structure is preferably Pm-3n, Im-3m or Fm-3m symmetric. The symmetry is determined based on a space group notation. In the present invention, the surfactant to be used has the chemical structure represented by the general formula (1), and the silica raw material is reacted under the conditions as described above. It is easy to obtain one having pores arranged in a two-dimensional hexagonal. Further, according to the present invention, it is possible to obtain a core-shell type spherical silica-based mesoporous material in which mesopores are arranged from the center of the particle toward the outside of the spherical particle while maintaining regularity. If a porous body is used, energy and electron movement can be caused accurately only in that direction.

[Core-shell type spherical silica mesoporous material]
Next, the core-shell type spherical silica mesoporous material of the present invention will be described. That is, the core-shell type spherical silica-based mesoporous material of the present invention includes core particles made of the first silica,
The first silica is composed of a second silica having a different composition, and a shell layer laminated on the outside of the core particles;
It is characterized by having.

  In the core-shell type spherical silica-based mesoporous material of the present invention, the shell layer is made of second silica having a composition different from that of the core particles. Thus, since the composition of the silica constituting the core particle and the shell layer is different from each other, the core-shell type spherical silica-based mesoporous material of the present invention has a core-shell type in which the pores are modified by organic functional groups that are hierarchically different. It is a spherical silica-based mesoporous material. Therefore, the core-shell type spherical silica-based mesoporous material of the present invention performs an oxidation reaction and a reduction reaction at the same time in the same particle, or adsorbs different dyes in the same particle, respectively, and emits electrons from the inside to the outside of the particle. It can be moved. Moreover, such a shell layer may be composed of a single silica layer composed of the second silica or may be composed of a plurality of silica layers.

  Such a core-shell type spherical silica-based mesoporous material of the present invention employs the above-described method for producing a core-shell type spherical silica-based mesoporous material of the present invention, and a first silica raw material, a first silica raw material, Can be produced by using a second silica raw material having a different composition. Therefore, in the core-shell type spherical silica mesoporous material of the present invention, it is preferable that the first silica and the second silica are made of alkoxysilanes having different compositions as raw materials.

  In the core-shell type spherical silica mesoporous material of the present invention, the shell layer may be composed of one silica layer or a plurality of silica layers. When the shell layer is composed of a plurality of silica layers, it is preferable that at least one of the plurality of silica layers is composed of silica having a composition different from that of the first silica. In the present invention, when the shell layer is formed of a plurality of silica layers, the shell layer is modified with hierarchically different organic functional groups and can exhibit various different performances. .

  The core-shell type spherical silica-based mesoporous material of the present invention has characteristics such as the center pore diameter and specific surface area, and the core-shell-type spherical silica obtained by the above-described method for producing the core-shell-type spherical silica-based mesoporous material. It is the same as the system mesoporous material.

  In addition, since the core-shell type spherical silica-based mesoporous material of the present invention is modified with different organic functional groups in the pores of the core particle and the shell layer, the core particle is particularly a reactive site, and the shell layer Is suitable as a material to be used for the catalyst in which the reaction site and the adsorption site are distinguished from each other. Moreover, although the core-shell type spherical silica-based mesoporous material of the present invention may be used as a powder, it may be molded and used as necessary. Any molding means may be used, but extrusion molding, tablet molding, rolling granulation, compression molding, CIP and the like are preferable. The shape can be determined according to the place of use and method, and examples thereof include a columnar shape, a crushed shape, a spherical shape, a honeycomb shape, an uneven shape, and a corrugated plate shape.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
To a mixed solvent of 4 kg of water and 4 kg of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant) and 22.8 g of 1N sodium hydroxide were added. When a mixture (first silica raw material) of 12.1 g (0.0068 mol / L) of tetramethoxysilane and 3.9 g (0.0042 mol / L) of mercaptopropyltrimethoxysilane was added thereto, stirring was continued. After complete dissolution, white powder (core particles) was precipitated after about 180 seconds. Thereafter, after 30 minutes at room temperature, 26.4 g (0.022 mol / L) of tetramethoxysilane (second silica raw material) was added, and the mixture was further stirred for 8 hours at room temperature. -Washing was repeated 3 times to obtain a white powder (porous precursor particles). The white powder was dried with a hot air dryer for 3 days, and then immersed in an ethanol solution containing 3 L of hydrochloric acid having a concentration of 1% to remove the surfactant, thereby obtaining a core-shell type spherical silica mesoporous material.

  The X-ray diffraction pattern of the core-shell type spherical silica-based mesoporous material thus obtained is shown in FIG. From the X-ray diffraction pattern shown in FIG. 1, it was confirmed that the obtained core-shell type spherical silica-based mesoporous material had high-order peaks and was a highly ordered honeycomb porous material.

  Next, this core-shell type spherical silica-based mesoporous material was observed with a scanning electron microscope (SEM). The obtained scanning electron microscope (SEM) photograph is shown in FIG. From the scanning electron microscope (SEM) photograph, the obtained core-shell type spherical silica-based mesoporous material has a spherical particle shape with a uniform particle diameter, and an average particle diameter of 0.9 μm (standard It was confirmed to be monodisperse particles having a deviation of 0.043 μm).

  Next, the core-shell type spherical silica mesoporous material with gold introduced into the pores was observed with a transmission electron microscope. That is, first, 1 g of the core-shell type spherical silica-based mesoporous material obtained as described above was dispersed in 50 g of water, and then 1 g of chloroauric acid was added to the dispersion and stirred for 30 minutes. Suction filtration was performed to obtain particles. Next, after repeating the process of dispersing the particles in 50 g of water adjusted to PH 2.4 and performing washing twice, the resulting particles are dried with a vacuum dryer to introduce gold into the pores. A core-shell type spherical silica-based mesoporous material was obtained. A transmission electron micrograph of the core-shell type spherical silica-based mesoporous material in which gold is introduced into the pores thus obtained is shown in FIG. Such a transmission electron micrograph shows that the inside of the spherical particles is black, so that it is confirmed that gold is introduced only inside the spherical particles, and further, the core-shell type spherical silica-based mesoporous material Since the gold introduced into the pores is fixed by reacting with the mercapto group existing inside the spherical particle, the mercapto group is introduced only inside the core-shell type spherical silica mesoporous material. It was confirmed. From such a fact, the core-shell type spherical silica-based mesoporous material obtained as described above has a core particle modified with a mercapto group and a shell layer having no organic functional group on the outside thereof. It was confirmed to be a core-shell type spherical silica mesoporous material.

(Example 2)
Hexadecyltrimethylammonium chloride (surfactant) 35.2 g (0.014 mol / L) and 1N sodium hydroxide 22.8 g were added to a mixed solvent of 4 kg of water and 4 kg of methanol. When a mixture of 9.2 g (0.0077 mol / L) of tetramethoxysilane and 4.3 g (0.0033 mol / L) of propyltrimethoxysilane (first silica raw material) was added and stirring was continued, complete After about 210 seconds, white powder (core particles) was precipitated. Then, after 30 minutes at room temperature, 13.2 g (0.011 mol / L) of tetramethoxysilane (second silica raw material) was added, and the mixture was further stirred for 8 hours at room temperature and allowed to stand overnight. -Washing was repeated 3 times to obtain a white powder (porous precursor particles). The white powder was dried with a hot air dryer for 3 days, and then immersed in an ethanol solution containing 1.5 L of hydrochloric acid having a concentration of 1% to remove the surfactant to obtain a core-shell type spherical silica mesoporous material. . The spherical silica-based mesoporous material thus obtained does not have an organic functional group outside the core particle modified with a hydrophobic propyl group, as is apparent from the synthesis procedure described above. A core-shell type core-shell type spherical silica-based mesoporous material having a shell layer.

  When the X-ray diffraction pattern of the core-shell type spherical silica-based mesoporous material thus obtained was measured, the measured X-ray diffraction pattern had a higher-order peak. It was confirmed that the spherical silica-based mesoporous material was a highly ordered honeycomb porous material.

  Next, the obtained core-shell type spherical silica-based mesoporous material was observed with a scanning electron microscope. From the scanning electron micrograph obtained by such observation, all of the obtained core-shell type spherical silica-based mesoporous materials have the shape of spherical particles having a uniform particle size, and the average particle size is 0.75 μm ( It was confirmed to be monodisperse particles having a standard deviation of 0.035 μm.

Further, using the obtained core-shell type spherical silica-based mesoporous material, the amount of water vapor adsorbed was measured by changing the relative water vapor pressure (P / P ₀ ) under the temperature condition of 25 ° C. A water vapor adsorption isotherm was derived. The water vapor adsorption isotherm thus obtained is shown in FIG.

(Example 3)
To a mixed solvent of 4 kg of water and 4 kg of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant) and 22.8 g of 1N sodium hydroxide were added. Tetramethoxysilane (first silica raw material) 13.2 g (0.011 mol / L) was added thereto and stirring was continued to completely dissolve. After about 180 seconds, white powder (core particles) had precipitated. . Thereafter, after 30 minutes at room temperature, a mixture (second silica raw material) of 9.2 g (0.0077 mol / L) of tetramethoxysilane and 4.3 g (0.0033 mol / L) of propyltrimethoxysilane was added. The mixture was added and stirred at room temperature for further 8 hours, and then allowed to stand overnight, and filtration and washing were repeated three times to obtain a white powder (porous body precursor particles). The white powder was dried with a hot air dryer for 3 days, and then immersed in an ethanol solution containing 1.5 L of hydrochloric acid having a concentration of 1% to remove the surfactant to obtain a core-shell type spherical silica mesoporous material. . The core-shell type spherical silica-based mesoporous material thus obtained is modified with core particles that do not have an organic functional group and a hydrophobic propyl group on the outside, as is apparent from the aforementioned synthesis procedure. A core-shell type core-shell type spherical silica-based mesoporous material having a shell layer formed thereon.

  When the X-ray diffraction pattern of the core-shell type spherical silica-based mesoporous material thus obtained was measured, the measured X-ray diffraction pattern had a higher-order peak. It was confirmed that the spherical silica-based mesoporous material was a highly ordered honeycomb porous material.

  Next, the obtained core-shell type spherical silica-based mesoporous material was observed with a scanning electron microscope. From the scanning electron micrograph obtained by such observation, all of the obtained core-shell type spherical silica-based mesoporous materials have the shape of spherical particles having a uniform particle size, and the average particle size is 0.82 μm ( It was confirmed to be a monodisperse particle having a standard deviation of 0.039 μm.

Further, using the obtained core-shell type spherical silica-based mesoporous material, the amount of water vapor adsorbed was measured by changing the relative water vapor pressure (P / P ₀ ) under the temperature condition of 25 ° C. A water vapor adsorption isotherm was derived. The water vapor adsorption isotherm thus obtained is shown in FIG.

Example 4
To a mixed solvent of 4 kg of water and 4 kg of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant) and 22.8 g of 1N sodium hydroxide were added. To this was added 13.2 g (0.011 mol / L) of tetramethoxysilane (first silica raw material), and when stirring was continued, it was completely dissolved, and after about 170 seconds, white powder (core particles) had precipitated. . 30 minutes and 60 minutes later, 13.2 g (0.011 mol / L) of tetramethoxysilane (secondary silica raw material) was added, and the mixture was further stirred for 8 hours at room temperature. -Washing was repeated 3 times to obtain a white powder (porous precursor particles). The white powder was dried with a hot air dryer for 3 days, and then immersed in an ethanol solution containing 3 L of hydrochloric acid having a concentration of 1% to remove the surfactant, thereby obtaining a core-shell type spherical silica mesoporous material.

  When the X-ray diffraction pattern of the core-shell type spherical silica-based mesoporous material thus obtained was measured, the measured X-ray diffraction pattern had a higher-order peak, and the obtained core-shell type spherical silica It was confirmed that the system mesoporous material is a highly ordered honeycomb porous material.

  Next, the obtained core-shell type spherical silica-based mesoporous material was observed with a scanning electron microscope. The obtained scanning electron microscope (SEM) photograph is shown in FIG. From the obtained scanning electron micrograph, the obtained core-shell type spherical silica-based mesoporous material has a spherical particle shape with a uniform particle diameter, and has an average particle diameter of 0.80 μm (standard deviation 0.024 μm). ) Monodisperse particles. From these facts, a shell layer made of silica having the same composition can be laminated on the outside of the core particles by using a silica material having the same composition for the first silica material and the second silica material. It was confirmed that the particle diameter of the obtained core-shell type spherical silica-based mesoporous material can be increased.

  Next, the core-shell type spherical silica-based mesoporous material having platinum introduced into the pores was observed with a transmission electron microscope. That is, first, 1 g of the core-shell type spherical silica mesoporous material obtained as described above was dispersed in 20 g of water, and 0.05 g of tetraammineplatinum chloride was added to the dispersion and stirred for 30 minutes. Thereafter, water was removed by a rotary evaporator. Next, the core-shell type spherical silica mesoporous material in which platinum was introduced into the pores was obtained by heating for 2 hours under a temperature condition of 400 ° C. under a nitrogen stream containing 5% hydrogen gas. A transmission electron micrograph of the core-shell type spherical silica-based mesoporous material in which platinum is introduced into the pores thus obtained is shown in FIG. Even in the core-shell type spherical silica mesoporous material synthesized by the method of sequentially laminating the shell layer on the core particles from such transmission electron micrographs, the pores are continuous and radial from the center of the sphere to the outside. It has been confirmed that

(Example 5)
To a mixed solvent of 4 kg of water and 4 kg of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant) and 22.8 g of 1N sodium hydroxide were added. To this was added 13.2 g (0.011 mol / L) of tetramethoxysilane (first silica raw material), and when stirring was continued, it was completely dissolved, and after about 170 seconds, white powder (core particles) had precipitated. . After 30 minutes, 60 minutes, 90 minutes and 120 minutes, 13.2 g (0.011 mol / L) of tetramethoxysilane (second silane raw material) was added, and the mixture was further stirred at room temperature for 8 hours. , And left overnight, filtration and washing were repeated three times to obtain a white powder (porous precursor particles). The white powder was dried with a hot air dryer for 3 days, and then the surfactant was removed by baking at 550 ° C. to obtain a core-shell type spherical silica mesoporous material.

  When the X-ray diffraction pattern of the core-shell type spherical silica-based mesoporous material thus obtained was measured, the measured X-ray diffraction pattern had a higher-order peak, and the obtained core-shell type spherical silica It was confirmed that the system mesoporous material is a highly ordered honeycomb porous material.

  Next, the obtained core-shell type spherical silica-based mesoporous material was observed with a scanning electron microscope. The obtained scanning electron microscope (SEM) photograph is shown in FIG. From the obtained scanning electron micrograph, all of the obtained core-shell type spherical silica-based mesoporous materials have the shape of spherical particles having a uniform particle size, and an average particle size of 1.21 μm (standard deviation 0.035 μm). ) Monodisperse particles. From these facts, a shell layer made of silica having the same composition can be laminated on the outside of the core particles by using a silica material having the same composition for the first silica material and the second silica material. It was confirmed that the particle diameter of the obtained core-shell type spherical silica-based mesoporous material can be increased.

(Example 6)
To a mixed solvent of 3 kg of water and 1 kg of methanol, 15.4 g (0.013 mol / L) of decyltrimethylammonium chloride and 22.8 g of 1N sodium hydroxide were added. To this was added 13.2 g (0.021 mol / L) of tetramethoxysilane (first silica raw material), and when stirring was continued, it was completely dissolved, and after about 100 seconds, white powder (core particles) had precipitated. . Sixty minutes later, 26.4 g of tetramethoxysilane (second silica raw material) was further added, and the mixture was further stirred for 8 hours at room temperature, then left overnight, filtered and washed three times to obtain a white powder (porous material) Precursor particles) were obtained. The white powder was dried with a hot air dryer for 3 days and then calcined at 550 ° C. to remove the surfactant and obtain a core-shell type spherical silica mesoporous material. As a result of observing the obtained core-shell type spherical silica mesoporous material with a scanning electron microscope, it was confirmed to be monodisperse particles having an average particle diameter of 0.85 μm (standard deviation 0.04 μm).

(Example 7)
Tetradecyltrimethylammonium chloride (32.1 g, 0.012 mol / L) and 1N sodium hydroxide (22.8 g) were added to a mixed solvent of 4.4 kg of water and 3.6 kg of methanol. To this was added 13.2 g (0.021 mol / L) of tetramethoxysilane (first silica raw material), and when stirring was continued, it was completely dissolved, and after about 190 seconds, white powder (core particles) had precipitated. . Sixty minutes later, 26.4 g of tetramethoxysilane (second silica raw material) was further added, and the mixture was further stirred for 8 hours at room temperature, then left overnight, filtered and washed three times to obtain a white powder (porous material) Precursor particles) were obtained. The white powder was dried with a hot air dryer for 3 days and then calcined at 550 ° C. to remove the surfactant and obtain a core-shell type spherical silica mesoporous material. As a result of observing the obtained core-shell type spherical silica-based mesoporous material with a scanning electron microscope, it was confirmed to be monodisperse particles having an average particle size of 0.75 μm (standard deviation 0.04 μm).

(Comparative Example 1)
To a mixed solvent of 4 kg of water and 4 kg of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant) and 22.8 g of 1N sodium hydroxide were added. To this, 13.2 g (0.011 mol / L) of tetramethoxysilane was added and stirring was continued to dissolve completely. After about 180 seconds, a white powder precipitated. The mixture was further stirred at room temperature for 8 hours and then left overnight, and filtration and washing were repeated three times to obtain a white powder. The white powder was dried with a hot air dryer for 3 days and then baked at 550 ° C. to remove the surfactant and obtain a spherical silica-based mesoporous material for comparison.

  The spherical silica-based mesoporous material as a comparison thus obtained was observed with a scanning electron microscope (SEM). The obtained scanning electron microscope (SEM) photograph is shown in FIG. From the obtained scanning electron micrograph, the spherical silica-based mesoporous material as a comparison has a spherical particle shape with a uniform particle diameter, and has an average particle diameter of 0.65 μm (standard deviation 0.023 μm). It was confirmed to be monodispersed spherical particles.

Further, by using the obtained spherical silica-based mesoporous material, the amount of water vapor adsorbed was measured by changing the relative water vapor pressure (P / P ₀ ) under the temperature condition of 25 ° C., and the water vapor adsorption at a temperature of 25 ° C. Led isotherm. The water vapor adsorption isotherm thus obtained is shown in FIG.

(Comparative Example 2)
To a mixed solvent of 4 kg of water and 4 kg of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride and 22.8 g of 1N sodium hydroxide were added. A mixture of 9.2 g (0.0077 mol / L) of tetramethoxysilane and 4.3 g (0.0033 mol / L) of propyltrimethoxysilane was added thereto, and the mixture was completely stirred. After about 210 seconds, a white powder was dissolved. Has been deposited. The mixture was further stirred at room temperature for 8 hours and then left overnight, and filtration and washing were repeated three times to obtain a white powder. This white powder was dried with a hot air dryer for 3 days, then immersed in an ethanol solution containing 1 L of hydrochloric acid having a concentration of 1% and heated at a temperature of 60 ° C. to remove the surfactant. A spherical silica-based mesoporous material was obtained.

Using the spherical silica-based mesoporous material thus obtained, the amount of water vapor adsorbed was measured by changing the relative water vapor pressure (P / P ₀ ) under the temperature condition of 25 ° C. A water vapor adsorption isotherm was derived. The water vapor adsorption isotherm thus obtained is shown in FIG.

(Comparative Example 3)
To a mixed solvent of 3 kg of water and 1 kg of methanol, 15.4 g (0.013 mol / L) of decyltrimethylammonium chloride and 22.8 g of 1N sodium hydroxide were added. To this was added 13.2 g (0.021 mol / L) of tetramethoxysilane (first silica raw material), and when stirring was continued, it was completely dissolved, and after about 100 seconds, white powder (core particles) had precipitated. . After stirring at room temperature for 8 hours, the mixture was allowed to stand overnight, and filtration and washing were repeated three times to obtain a white powder (porous precursor particles). The white powder was dried with a hot air dryer for 3 days and then calcined at 550 ° C. to remove the surfactant and obtain a spherical silica mesoporous material. As a result of observing the obtained spherical silica-based mesoporous material with a scanning electron microscope, it was confirmed to be monodisperse particles having an average particle diameter of 0.60 μm (standard deviation 0.024 μm).

(Comparative Example 4)
Tetradecyltrimethylammonium chloride (32.1 g, 0.012 mol / L) and 1N sodium hydroxide (22.8 g) were added to a mixed solvent of 4.4 kg of water and 3.6 kg of methanol. To this was added 13.2 g (0.021 mol / L) of tetramethoxysilane (first silica raw material), and when stirring was continued, it was completely dissolved, and after about 190 seconds, white powder (core particles) had precipitated. . After stirring at room temperature for 8 hours, the mixture was allowed to stand overnight, and filtration and washing were repeated three times to obtain a white powder (porous precursor particles). The white powder was dried with a hot air dryer for 3 days and then calcined at 550 ° C. to remove the surfactant and obtain a spherical silica mesoporous material. As a result of observing the obtained spherical silica-based mesoporous material with a scanning electron microscope, it was confirmed to be monodisperse particles having an average particle diameter of 0.52 μm (standard deviation 0.03 μm).

<Evaluation of the core-shell type spherical silica-based mesoporous material obtained in Examples 1-7 and the spherical silica-based mesoporous material obtained in Comparative Examples 1-4>
As a result of observation by the scanning electron microscope of the core-shell type spherical silica-based mesoporous material obtained in Examples 4 to 7 and the spherical silica-based mesoporous material obtained in Comparative Examples 1, 3, and 4, and FIG. As is apparent from the results shown in 7 and 8, when the production method of the core-shell type spherical silica-based mesoporous material of the present invention is employed (Examples 4 to 7), the average particle diameter is 0.80 μm, 1 Since the core-shell type spherical silica-based mesoporous material having relatively large particle diameters of 21 μm, 0.85 μm, and 0.75 μm has been obtained, the method for producing the core-shell type spherical silica-based mesoporous material of the present invention is used. For example, it was confirmed that the particle diameter of the core-shell type spherical silica-based mesoporous material can be increased.

As is clear from the water vapor adsorption isotherm shown in FIG. 4, the core-shell type spherical silica-based mesoporous material obtained in Example 2 has a relative water vapor pressure (P / P ₀ ) at which vapor condensation starts to occur. It was about 0.6. Further, the core-shell type spherical silica mesoporous material obtained in Example 3 had a relative water vapor pressure (P / P ₀ ) of about 0.55 at which vapor condensation began to occur. On the other hand, in the core-shell type spherical silica mesoporous material obtained in Comparative Example 1, it can be seen that the condensation of water vapor in the pores begins to occur from about 0.5 relative water vapor pressure (P / P ₀ ). Further, in the core-shell type spherical silica-based mesoporous material obtained in Comparative Example 2, water vapor condensation occurs in the pores at a relatively high relative water vapor pressure (P / P ₀ ) of about 0.7. You can see that it is starting.

  From these results, the core-shell type spherical silica-based mesoporous material obtained in Comparative Example 1 is somewhat low because the mesopores do not contain a hydrophobic organic functional group and are relatively hydrophilic. It can be seen that water vapor aggregation begins to occur at the relative water vapor pressure. Moreover, in the core-shell type spherical silica mesoporous material obtained in Comparative Example 2, the mesopores are modified with a hydrophobic organic functional group (propyl group), so that the core-shell obtained in Comparative Example 1 is used. It can be seen that the condensation of water vapor begins to occur at a slightly higher relative water vapor pressure than the type spherical silica-based mesoporous material.

On the other hand, in the core-shell type spherical silica mesoporous material obtained in Example 2, the core particle is modified with a hydrophobic organic functional group, but the shell layer does not contain a hydrophobic organic functional group. Therefore, the shell layer is relatively hydrophilic, and there is agglomeration of steam at a relative water vapor pressure (P / P ₀ ) approximately in the middle of the core-shell type spherical silica-based mesoporous material obtained in Comparative Examples 1 and 2. I understood. In the core-shell type spherical silica mesoporous material obtained in Example 3, the shell layer is modified with a hydrophobic organic functional group, but the core particles do not contain a hydrophobic organic functional group. It is found that the core particles are relatively hydrophilic, and there is agglomeration of vapor at a relative water vapor pressure (P / P ₀ ) approximately in the middle of the core-shell type spherical silica-based mesoporous material obtained in Comparative Examples 1 and 2. It was. Further, the core-shell type spherical silica mesoporous materials obtained in Examples 2 to 3 have the same composition but different pore arrangement, and the core-shell type spherical silica obtained in Example 3 is different. It was found that the mesoporous material has a lower relative water vapor pressure at which water vapor condensation begins to occur. From these facts, even if the composition of the silica raw material forming the core-shell type spherical silica-based mesoporous material is exactly the same, the water vapor adsorption characteristics can be improved by changing the arrangement of the pores modified with the organic functional group. I found it different.

  As described above, according to the present invention, the core-shell type spherical silica-based mesoporous material having mesopores modified with different organic functional groups in a hierarchical manner, and the core-shell type spherical silica-based material having a larger particle diameter than conventional ones. Provided is a method for producing a core-shell type spherical silica-based mesoporous material capable of efficiently and reliably producing a mesoporous material, and has mesopores modified with different organic functional groups in a hierarchical manner It is possible to provide a core-shell type spherical silica-based mesoporous material that can exhibit different properties depending on the pores in the same particle.

  Therefore, since the core-shell type spherical silica-based mesoporous material of the present invention can exhibit different performance between the core particle and the shell layer, different compounds can be adsorbed in the same particle and the oxidation reaction and the reduction reaction can be performed simultaneously or the same. It is useful as a material or the like that can adsorb a dye in the particles and move electrons from the inside to the outside of the particles.

2 is a graph showing an X-ray diffraction pattern of a core-shell type spherical silica-based mesoporous material obtained in Example 1. 2 is a scanning electron microscope (SEM) photograph of the core-shell type spherical silica-based mesoporous material obtained in Example 1. It is a transmission electron micrograph of the core-shell type spherical silica mesoporous material obtained in Example 1 in which gold is introduced into the pores. It is a graph which shows the water vapor | steam adsorption isotherm of the core-shell type spherical silica type mesoporous material obtained in Examples 2-3 and Comparative Examples 1-2. 4 is a scanning electron microscope (SEM) photograph of the core-shell type spherical silica-based mesoporous material obtained in Example 4. It is a transmission electron micrograph of the core-shell type spherical silica-based mesoporous material obtained in Example 1 in which platinum is introduced into the pores. 6 is a scanning electron microscope (SEM) photograph of the core-shell type spherical silica-based mesoporous material obtained in Example 5. 4 is a scanning electron microscope (SEM) photograph of the core-shell type spherical silica-based mesoporous material obtained in Comparative Example 1.

Claims (6)

As a surfactant, the following general formula (1):
[Wherein R ¹ , R ² and R ³ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms, X represents a halogen atom, and n represents an integer of 7 to 25, respectively. ]
In the basic solvent, the surfactant and the first silica raw material are used in a basic solvent, and the content ratio of the surfactant to the silicon atom in the first silica raw material (surface active First agent / silicon atom in the first silica raw material) in a range of 0.1 to 20 in molar ratio to precipitate the core particles having the surfactant introduced into the first silica. Process,
After the core particles have been precipitated, the second silica raw material is mixed in the solvent, and a shell layer in which the surfactant is introduced into the second silica is laminated outside the core particles, A second step of obtaining porous precursor particles in which the surfactant is introduced into the core particles and the shell layer;
A third step of removing the surfactant contained in the porous precursor particles and obtaining a core-shell type spherical silica-based mesoporous material comprising the core particles and the shell layer;
A method for producing a core-shell type spherical silica-based mesoporous material, comprising:   The method for producing a core-shell type spherical silica mesoporous material according to claim 1, wherein the solvent is a mixed solvent of water and alcohol having an alcohol content of 85% by volume or less.   3. The core-shell type spherical silica according to claim 1, wherein the first silica raw material and the second silica raw material may be the same or different and each is an alkoxysilane. For producing a porous mesoporous material. Core particles composed of first silica;
The first silica is composed of a second silica having a different composition, and a shell layer laminated on the outside of the core particles;
A core-shell type spherical silica mesoporous material characterized by comprising:   5. The shell layer is formed of a plurality of silica layers, and at least one of the plurality of silica layers is made of silica having a composition different from that of the first silica. The core-shell type spherical silica-based mesoporous material described in 1.   The core-shell type spherical silica-based mesoporous material according to claim 4 or 5, wherein the first silica and the second silica are made from alkoxysilanes having different compositions.