JP7141980B2 - Connected mesoporous silica particles and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to connected mesoporous silica particles and a method for producing the same, and more particularly to novel connected mesoporous silica particles having an average primary particle size, pore size, pore volume, and tap density within specific ranges and a method for producing the same. .

Mesoporous silica is a material with nano-sized pores and a high specific surface area. Mesoporous silica utilizes these characteristics to
(a) a catalyst carrier;
(b) an adsorbent;
(c) thermal insulation;
(d) molds for producing mesoporous materials;
etc. is being considered.
When mesoporous silica is put to practical use, it is important to control its morphology, and various studies have been made heretofore. So far, various types of mesoporous silica have been synthesized, such as film-like, spherical (see Patent Document 1 and Non-Patent Document 1), and polygonal (see Non-Patent Document 2). In addition, many reports have been made on the synthesis of structures in which they are linked.

When mesoporous silica is used for certain applications, not only the morphology of mesoporous silica but also its average primary particle size, pore size, pore volume, tap density, etc. may be important factors. However, there have been no examples of the synthesis of mesoporous silica having a specific average primary particle size, pore size, pore volume, and tap density.

Japanese Patent Application Laid-Open No. 2004-002161

Chemistry of Materials, 2003, 15, 4247-4256 Journal of the American Chemical Society, 1992, 114, 10834-10843

The problem to be solved by the present invention is to provide connected mesoporous silica particles having a specific average primary particle size, pore size, pore volume, and tap density, and a method for producing the same.
Another problem to be solved by the present invention is that it can be used for various applications requiring low density, or can be used as a template for synthesizing various mesoporous materials requiring low density. It is an object of the present invention to provide possible linked mesoporous silica particles and a method for producing the same.

In order to solve the above problems, the gist of the connected mesoporous silica particles according to the present invention is to have the following configuration.
(1) The linked mesoporous silica particles have a structure in which primary particles made of mesoporous silica are linked.
(2) the linked mesoporous silica particles,
The average primary particle size is 7 nm or more and 300 nm or less,
Pore diameter is 2 nm or more and 50 nm or less,
Pore volume is 0.2 mL / g or more and 3.0 mL / g or less,
The tap density is 0.05 g/cm ³ or more and 0.2 g/cm ³ or less.

The gist of the method for producing linked mesoporous silica particles according to the present invention is to have the following configuration.
(1) The method for producing the linked mesoporous silica particles includes
a polymerization step of condensation polymerization of the silica source in a reaction solution containing a silica source, a surfactant and an alkali catalyst to obtain precursor particles;
a drying step of separating and drying the precursor particles from the reaction solution;
and a calcining step of calcining the precursor particles to obtain the connected mesoporous silica particles according to the present invention.
(2) the reaction solution is
the concentration of the surfactant is 0.03 mol/L or more and 0.3 mol/L or less;
The concentration of the silica source is 0.05 mol/L or more and 0.45 mol/L or less.

Mesoporous silica is usually synthesized by polycondensing a silica source in a reaction solution containing a silica source, a surfactant and a catalyst. At this time, if the concentration of the surfactant and the concentration of the silica source in the reaction solution are each limited to a specific range, a structure in which primary particles made of mesoporous silica are connected, and an average primary particle diameter, Connected mesoporous silica particles can be synthesized that have pore sizes, pore densities, and tap densities within specific ranges.

Since the connected mesoporous silica particles according to the present invention have a low tap density, they can be used in various applications requiring low density. Alternatively, it can be used as a template for synthesizing various mesoporous materials that require low density.

1 is an SEM photograph of a sample synthesized in Example 1. FIG. 4 is an SEM photograph of a sample synthesized in Example 2. FIG. 4 is a SEM photograph of a sample synthesized in Example 3. FIG. 4 is an SEM photograph of a sample synthesized in Example 4. FIG. 4 is a SEM photograph of a sample synthesized in Example 5. FIG.

4 is an SEM photograph of a sample synthesized in Comparative Example 1. FIG. 4 is a SEM photograph of a sample synthesized in Comparative Example 2. FIG. 4 is an SEM photograph of a sample synthesized in Comparative Example 3. FIG. 4 is an SEM photograph of a sample synthesized in Comparative Example 4; 4 is a SEM photograph of a sample synthesized in Example 6. FIG. 4 is an SEM photograph of a sample synthesized in Example 7. FIG. 10 is a SEM photograph of a sample synthesized in Example 8. FIG.

An embodiment of the present invention will be described in detail below.
[1. Linked Mesoporous Silica Particles]
The connected mesoporous silica particles according to the present invention have the following configuration.
(1) The linked mesoporous silica particles have a structure in which primary particles made of mesoporous silica are linked.
(2) the linked mesoporous silica particles,
The average primary particle size is 7 nm or more and 300 nm or less,
Pore diameter is 2 nm or more and 50 nm or less,
Pore volume is 0.2 mL / g or more and 3.0 mL / g or less,
The tap density is 0.05 g/cm ³ or more and 0.2 g/cm ³ or less.

[1.1. structure]
In the present invention, "connected mesoporous silica particles" refer to particles (secondary particles) having a structure in which primary particles of mesoporous silica are connected.
"Mesoporous silica" refers to particles of silica having mesopores and having an aspect ratio of 3 or less.

[1.2. Average primary particle size]
The term "average primary particle size" refers to the average length of primary particles in the minor axis direction. The term "short axis direction length" refers to the length in the direction perpendicular to the longest direction (major axis direction) of the primary particles.
In general, if the average primary particle size is too small, the cohesive force between particles will be too strong and the tap density will be too high. Therefore, the average primary particle size should be 7 nm or more. The average primary particle size is preferably 9 nm or more, more preferably 12 nm or more, still more preferably 20 nm or more, still more preferably 50 nm or more, still more preferably 80 nm or more.
On the other hand, if the average primary particle size is too large, the tap density becomes excessively high because the gaps between the particles are reduced. Therefore, the average primary particle size should be 300 nm or less. The average primary particle size is preferably 280 nm or less, more preferably 250 nm or less.

[1.3. Pore diameter]
"Pore size" refers to the average value of mesopores contained in primary particles, and does not include the size of voids between primary particles.
Generally, when the pore size becomes too small, the molecules that can be adsorbed are severely limited. Therefore, the pore size should be 2 nm or more. The pore diameter is preferably 2.5 nm or more, more preferably 3 nm or more.
On the other hand, if the pore size is too large, the ability to retain adsorbed substances will be lacking. Therefore, the pore size should be 50 nm or less. The pore diameter is preferably 40 nm or less, more preferably 30 nm or less.

[1.4. Pore capacity]
"Pore volume" refers to the volume of mesopores contained in primary particles, and does not include the volume of voids between primary particles.
Generally, when the pore volume becomes too small, the number of molecules that can be adsorbed is limited. Therefore, the pore volume should be 0.2 mL/g or more. The pore volume is preferably 0.25 mL/g or more, more preferably 0.3 mL/g or more.
On the other hand, if the pore volume is too large, the mechanical strength is poor. Therefore, the pore volume should be 3.0 mL/g or less. The pore volume is preferably 2.8 mL/g or less, more preferably 2.5 mL/g or less.

[1.5. tap density]
"Tap density" refers to a value measured according to JIS Z 2512.
In general, if the tap density is too low, the mechanical strength will be poor. Therefore, the tap density should be 0.05 g/cm ³ or more. The tap density is preferably 0.06 g/cm ³ or more, more preferably 0.07 g/cm ³ or more.
On the other hand, if the tap density is too high, the space between particles will decrease, restricting the movement of adsorbed substances. Therefore, the tap density should be 0.2 g/cm ³ or less. The tap density is preferably 0.19 g/cm ³ or less, more preferably 0.18 g/cm ³ or less.

[2. Method for producing linked mesoporous silica particles]
The method for producing linked mesoporous silica particles according to the present invention comprises:
a polymerization step of condensation polymerization of the silica source in a reaction solution containing a silica source, a surfactant and a catalyst to obtain precursor particles;
a drying step of separating and drying the precursor particles from the reaction solution;
and a calcining step of calcining the precursor particles to obtain the connected mesoporous silica particles according to the present invention.
The method for producing linked mesoporous silica particles according to the present invention may further comprise a diameter-expanding step of subjecting the dried precursor particles to a diameter-expanding treatment.

[2.1. Polymerization process]
First, the silica source is polycondensed in a reaction solution containing a silica source, a surfactant and a catalyst to obtain precursor particles (polymerization step).

[2.1.1. silica source]
In the present invention, the type of silica source is not particularly limited. Examples of silica sources include
(a) tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, tetraethyleneglycooxysilane;
(b) trialkoxysilanes such as 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane;
and so on. Any one of these may be used as the silica source, or two or more may be used in combination.

[2.1.2. Surfactant]
When the silica source is polycondensed in the reaction solution, if a surfactant is added to the reaction solution, the surfactant forms micelles in the reaction solution. Since hydrophilic groups are gathered around the micelles, the silica source is adsorbed on the surfaces of the micelles. Further, the micelles to which the silica source is adsorbed self-organize in the reaction solution, and the silica source undergoes polycondensation. As a result, pores caused by micelles are formed inside the primary particles. The pore size can be controlled (from 1 to 50 nm) primarily by the molecular length of the surfactant.

In the present invention, an alkyl quaternary ammonium salt is used as the surfactant. An alkyl quaternary ammonium salt refers to a compound represented by the following formula (a).
CH ₃ —(CH ₂ ) _n —N ⁺ (R ₁ )(R ₂ )(R ₃ )X ^— (a)

(a) In the formula, R ₁ , R ₂ and R ₃ each represent an alkyl group having 1 to 3 carbon atoms. R ₁ , R ₂ and R ₃ may be the same or different. R ₁ , R ₂ and R ₃ are all preferably the same in order to facilitate aggregation (micelle formation) between alkyl quaternary ammonium salts. Furthermore, at least one of R ₁ , R ₂ and R ₃ is preferably a methyl group, and all are preferably methyl groups.
(a) In formula, X represents a halogen atom. Although the type of halogen atom is not particularly limited, X is preferably Cl or Br in terms of availability.

(a) In the formula, n represents an integer of 7-21. In general, the smaller the value of n, the smaller the diameter of the mesopores at the center of the spherical mesoporous body. On the other hand, the larger the value of n, the larger the central pore size. As a result, a layered compound is produced and a mesoporous body cannot be obtained. n is preferably 9-17, more preferably 13-17.

Among those represented by formula (a), alkyltrimethylammonium halide is preferred. Examples of alkyltrimethylammonium halides include hexadecyltrimethylammonium halide, octadecyltrimethylammonium halide, nonyltrimethylammonium halide, decyltrimethylammonium halide, undecyltrimethylammonium halide and dodecyltrimethylammonium halide.
Among these, alkyltrimethylammonium bromide and alkyltrimethylammonium chloride are particularly preferred.

When synthesizing linked mesoporous silica particles, one type of alkyl quaternary ammonium salt may be used, or two or more types may be used. However, since the alkyl quaternary ammonium salt serves as a template for forming mesopores in the primary particles, its type has a great influence on the shape of the mesopores. In order to synthesize silica particles having more uniform mesopores, it is preferable to use one type of alkyl quaternary ammonium salt.

[2.1.3. catalyst]
When polycondensing a silica source, a catalyst is usually added to the reaction solution. When synthesizing particulate mesoporous silica, it is preferable to use an alkali such as sodium hydroxide or aqueous ammonia as the catalyst.

[2.1.4. solvent]
As the solvent, water, an organic solvent such as alcohol, a mixed solvent of water and an organic solvent, or the like is used.
alcohol is
(1) monohydric alcohols such as methanol, ethanol and propanol;
(2) dihydric alcohols such as ethylene glycol;
(3) trihydric alcohols such as glycerin;
Either one is fine.
When a mixed solvent of water and an organic solvent is used, the content of the organic solvent in the mixed solvent can be arbitrarily selected depending on the purpose. In general, adding an appropriate amount of organic solvent to the solvent facilitates control of particle size and particle size distribution.

[2.1.5. Composition of Reaction Solution]
The composition of the reaction solution affects the external shape and pore structure of mesoporous silica to be synthesized. In particular, the concentration of the surfactant and the concentration of the silica source in the reaction solution have a great effect on the average primary particle size, pore size, pore volume and tap density of the connected mesoporous silica particles.

[A. Surfactant concentration]
If the concentration of the surfactant is too low, the deposition rate of the particles becomes slow, and a structure in which the primary particles are connected cannot be obtained. Therefore, the surfactant concentration should be 0.03 mol/L or more. The surfactant concentration is preferably 0.035 mol/L or more, more preferably 0.04 mol/L or more.

On the other hand, if the concentration of the surfactant is too high, the precipitation rate of the particles becomes too fast, and the primary particle diameter easily exceeds 300 nm. Therefore, the surfactant concentration should be 0.3 mol/L or less. The surfactant concentration is preferably 0.28 mol/L or less, more preferably 0.26 mol/L or less, still more preferably 0.20 mol/L or less, still more preferably 0.18 mol/L or less, More preferably, it is 0.16 mol/L or less.

[B. Concentration of silica source]
If the concentration of the silica source is too low, the deposition rate of particles will be slow, and a structure in which the primary particles are connected cannot be obtained. Alternatively, the surfactant may be excessive and uniform mesopores may not be obtained. Therefore, the silica source concentration should be 0.05 mol/L or more. The silica source concentration is preferably 0.06 mol/L or more, more preferably 0.07 mol/L or more.

On the other hand, if the concentration of the silica source is too high, the precipitation rate of particles becomes too fast, and the primary particle diameter easily exceeds 300 nm. Alternatively, sheet-like particles may be obtained instead of spherical particles. Therefore, the silica source concentration should be 0.45 mol/L or less. The silica source concentration is preferably 0.44 mol/L or less, more preferably 0.43 mol/L or less.

[C. Concentration of catalyst]
In the present invention, the catalyst concentration is not particularly limited. In general, too low a concentration of catalyst slows down the deposition rate of the particles. On the other hand, if the catalyst concentration is too high, the particle precipitation rate will increase. The optimum concentration of the catalyst is preferably selected according to the type of silica source, the type of surfactant, target physical properties, and the like.

[2.1.6 Reaction conditions]
A silica source is added in a solvent containing a predetermined amount of surfactant for hydrolysis and polycondensation. Thereby, the surfactant functions as a template, and precursor particles containing silica and surfactant are obtained.
As for the reaction conditions, optimum conditions are selected according to the type of silica source, the particle size of the precursor particles, and the like. In general, the preferred reaction temperature is -20 to 100°C. The reaction temperature is more preferably 0 to 80°C, more preferably 10 to 40°C.

[2.2. Drying process]
Next, the precursor particles are separated from the reaction solution and dried (drying step).
Drying is performed to remove the solvent remaining in the precursor particles. Drying conditions are not particularly limited as long as the solvent can be removed.

[2.3. diameter expansion]
Next, if necessary, the dried precursor particles may be subjected to diameter-expanding treatment (diameter-expanding step). "Diameter-enlarging treatment" refers to treatment for enlarging the diameter of mesopores in primary particles.
Specifically, the diameter-expanding treatment is performed by subjecting the synthesized precursor particles (from which the surfactant has not been removed) to a hydrothermal treatment in a solution containing a diameter-expanding agent. This treatment can enlarge the pore size of the precursor particles.

Examples of diameter-enlarging agents include
(a) hydrocarbons such as trimethylbenzene, triethylbenzene, benzene, cyclohexane, triisopropylbenzene, naphthalene, hexane, heptane, octane, nonane, decane, undecane, dodecane;
(b) acids such as hydrochloric acid, sulfuric acid, nitric acid;
and so on.
The reason why the pore diameter is enlarged by hydrothermal treatment in the presence of hydrocarbons is that silica rearrangement occurs when the pore-enlarging agent is introduced from the solvent into the pores of the more hydrophobic precursor particles. It is considered to be for
Further, the reason why the pore size is enlarged by the hydrothermal treatment in the coexistence of an acid such as hydrochloric acid is considered to be the progress of dissolution and reprecipitation of silica in the interior of the primary particles. Optimizing the manufacturing conditions results in the formation of radial pores inside the silica. When this is hydrothermally treated in the presence of an acid, dissolution and reprecipitation of silica occur, and radial pores are converted into continuous pores.

Conditions for the diameter-expanding treatment are not particularly limited as long as the desired pore diameter can be obtained. Generally, it is preferable to add a diameter-enlarging agent to the reaction solution in an amount of about 0.05 mol/L to 10 mol/L, and to perform hydrothermal treatment at 60 to 150°C.

[2.4. Firing process]
Next, after performing a diameter-expanding treatment as necessary, the precursor particles are sintered (sintering step). Thereby, the connected mesoporous silica particles according to the present invention are obtained.
Firing is performed to dehydrate and crystallize the precursor particles in which OH groups remain, and to thermally decompose the surfactant remaining in the mesopores. The baking conditions are not particularly limited as long as dehydration/crystallization and thermal decomposition of the surfactant are possible. Firing is usually carried out by heating at 400° C. to 700° C. for 1 hour to 10 hours in the atmosphere.

[3. action]
Mesoporous silica is usually synthesized by polycondensing a silica source in a reaction solution containing a silica source, a surfactant and a catalyst. At this time, if the concentration of the surfactant and the concentration of the silica source in the reaction solution are each limited to a specific range, a structure in which primary particles made of mesoporous silica are connected, and an average primary particle diameter, Connected mesoporous silica particles can be synthesized that have pore sizes, pore densities, and tap densities within specific ranges.

Since the connected mesoporous silica particles according to the present invention have a low tap density, they can be used in various applications requiring low density. Alternatively, it can be used as a template for synthesizing various mesoporous materials that require low density.

(Example 1)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28 g and 1N sodium hydroxide solution: 68.6 mL were added to a mixed solution consisting of water: 388 g, methanol: 172 g, and ethylene glycol: 172 g. When 53.6 g of tetramethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of hexadecyltrimethylammonium chloride used as a surfactant was 0.106 mol/L, and the molar concentration of tetramethoxysilane used as a silica source was 0.425 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 4 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 2 nm, and the pore volume was 0.56 mL/g. Also, the tap density was 0.16 g/cm ³ . FIG. 1 shows an SEM photograph of the sample synthesized in Example 1. As shown in FIG. From FIG. 1, it can be seen that the primary particles are connected. The average particle size of primary particles was 0.21 μm.

(Example 2)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28.2 g and 1N sodium hydroxide solution: 27.4 mL were added to a mixed solution of water: 965 g and methanol: 600 g. When 28.9 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.05 mol/L, and the molar concentration of the silica source was 0.079 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 2 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 2.3 nm, and the pore volume was 0.87 mL/g. Also, the tap density was 0.16 g/cm ³ . FIG. 2 shows an SEM photograph of the sample synthesized in Example 2. As shown in FIG. From FIG. 2, it can be seen that the primary particles are connected. The average particle size of primary particles was 0.28 μm.

(Example 3)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28.2 g and 1N sodium hydroxide solution: 27.4 mL were added to a mixed solution consisting of water: 965 g, methanol: 300 g, and ethylene glycol: 300 g. When 28.9 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.053 mol/L, and the molar concentration of the silica source was 0.084 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 2 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 2.36 nm, and the pore volume was 0.63 mL/g. Also, the tap density was 0.17 g/cm ³ . FIG. 3 shows an SEM photograph of the sample synthesized in Example 3. As shown in FIG. From FIG. 3, it can be seen that the primary particles are connected. The average particle size of primary particles was 0.047 μm.

(Example 4)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28.2 g and 1N sodium hydroxide solution: 27.4 mL were added to a mixed solution consisting of water: 965 g, methanol: 300 g, and ethylene glycol: 300 g. When 28.9 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.053 mol/L, and the molar concentration of the silica source was 0.084 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 2 L of water. After filtration again, the residue was dried in an oven at 45°C. 10 g of the dried sample was dispersed in a mixed solution of 300 mL of ethanol and 300 mL of water, and after adding 22.5 g of trimethylbenzene, the mixture was heated in an autoclave at 100° C. for 3 days. After filtering and washing the autoclaved sample, the organic component was removed by firing the sample at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 7.3 nm, and the pore volume was 1.45 mL/g. Also, the tap density was 0.14 g/cm ³ . FIG. 4 shows an SEM photograph of the sample synthesized in Example 4. As shown in FIG. From FIG. 4, it can be seen that the primary particles are connected. The average particle size of the primary particles was 0.064 μm.

(Example 5)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28 g and 1N sodium hydroxide solution: 68.6 mL were added to a mixed solution consisting of water: 388 g, methanol: 172 g, and ethylene glycol: 172 g. When 53.6 g of tetramethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The surfactant molar concentration was 0.106 mol/L, and the silica source molar concentration was 0.425 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 4 L of water. After filtration again, the residue was dried in an oven at 45°C. After dispersing 10 g of the dried sample in 600 mL of 2N hydrochloric acid, the dispersion was heated in an autoclave at 150° C. for 3 days. After filtering and washing the autoclaved sample, the organic component was removed by firing the sample at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 8 nm, and the pore volume was 0.66 mL/g. Also, the tap density was 0.11 g/cm ³ . FIG. 5 shows an SEM photograph of the sample synthesized in Example 5. As shown in FIG. From FIG. 5, it can be seen that the primary particles are connected. The average particle size of primary particles was 0.23 μm.

(Comparative example 1)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 35.2 g and 1N sodium hydroxide solution: 22.8 mL were added to a mixed solution of water: 3980 g and methanol: 4000 g. When 18.1 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.012 mol/L, and the molar concentration of the silica source was 0.0095 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 1 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 2.2 nm, and the pore volume was 0.74 mL/g. Also, the tap density was 0.26 g/cm ³ . FIG. 6 shows an SEM photograph of the sample synthesized in Comparative Example 1. As shown in FIG. From FIG. 6, it can be seen that the primary particles are independent. The average particle size of primary particles was 1.07 μm.
The tap density exceeded 0.20 g/cm ³ probably because each primary particle was completely independent and did not have a connected structure.
The primary particles were independent because the concentration of hexadecyltrimethylammonium chloride (0.012 mol/L) as a template and the concentration of tetraethoxysilane (0.0095 mol/L) as a silica source were both low, and the reaction was Probably because it progressed slowly.
Furthermore, the reason why the average primary particle size exceeded 300 nm is considered to be that the concentrations of both the surfactant and the silica source were low and the reaction proceeded slowly.

(Comparative example 2)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28 g and 1N sodium hydroxide solution: 91.2 mL were added to a mixed solution of water: 365 g and ethylene glycol: 344 g. When 53.6 g of tetramethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.114 mol/L and the molar concentration of the silica source was 0.459 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 1 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
FIG. 7 shows an SEM photograph of the sample synthesized in Comparative Example 2. As shown in FIG. From FIG. 7, it can be seen that most of the grains are tabular grains and grains having an aspect ratio of 3 or less are not obtained.
It is considered that the grains became tabular because the concentration of tetramethoxysilane as a silica raw material was high (0.459 mol/L) and grain formation progressed unevenly.

(Comparative Example 3)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 14.1 g and 1N sodium hydroxide solution: 27.4 mL were added to a mixed solution of water: 1957 g and methanol: 1216 g. When 29 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.013 mol/L, and the molar concentration of the silica source was 0.04 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 2 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
FIG. 8 shows an SEM photograph of the sample synthesized in Comparative Example 3. As shown in FIG. From FIG. 8, the particles were independent and no connected particles were obtained.
The primary particles were independent, probably because the concentration of tetraethoxysilane as a silica source was low (0.04 mol/L) and the reaction proceeded slowly.

(Comparative Example 4)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 14.1 g and 1N sodium hydroxide solution: 27.4 mL were added to a mixed solution of water: 965 g and methanol: 508 g. When 29 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of the surfactant was 0.025 mol/L, and the molar concentration of the silica source was 0.079 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 1 L of water. After filtration again, the residue was dried in an oven at 45°C. The organic components were then removed by firing the residue at 550°C.

[2. evaluation]
FIG. 9 shows an SEM photograph of the sample synthesized in Comparative Example 4. As shown in FIG. The average particle size of primary particles was 0.45 μm.
The average primary particle diameter exceeded 300 nm, probably because the concentration of hexadecyltrimethylammonium chloride (0.025 mol/L) as a template was low and the reaction proceeded slowly.

(Example 6)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 28.2 g and 1N sodium hydroxide solution: 13.7 mL were added to a mixed solution consisting of water: 482.5 g, methanol: 152 g, and ethylene glycol: 152 g. When 14.5 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of hexadecyltrimethylammonium chloride used as a surfactant was 0.105 mol/L, and the molar concentration of tetramethoxysilane used as a silica source was 0.083 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 4 L of water. After filtration again, the residue was dried in an oven at 45°C. After dispersing 10 g of the dried sample in 600 mL of 1N sulfuric acid, it was heated in an autoclave at 130° C. for 3 days. After filtration and washing, the organic components were removed by firing at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 5.1 nm, and the pore volume was 1.3 mL/g. Also, the tap density was 0.08 g/cm ³ . FIG. 10 shows an SEM photograph of the sample synthesized in Example 6. As shown in FIG. From FIG. 10, it can be seen that very fine primary particles aggregate to form secondary particles, which are linked together. The average particle size of primary particles was 7.5 nm.

(Example 7)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 14.1 g and 1N sodium hydroxide solution: 13.7 mL were added to a mixed solution of water: 482.5 g and ethylene glycol: 304 g. When 14.5 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of hexadecyltrimethylammonium chloride used as a surfactant was 0.056 mol/L, and the molar concentration of tetramethoxysilane used as a silica source was 0.089 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 4 L of water. After filtration again, the residue was dried in an oven at 45°C. After dispersing 10 g of the dried sample in 600 mL of 1N sulfuric acid, it was heated in an autoclave at 130° C. for 3 days. After filtration and washing, the organic components were removed by firing at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 5.0 nm, and the pore volume was 0.79 mL/g. Also, the tap density was 0.18 g/cm ³ . FIG. 11 shows an SEM photograph of the sample synthesized in Example 7. From FIG. 11, it can be seen that primary particles of several nanometers to ten and several nanometers are connected. The average particle size of primary particles was 12.8 nm.

(Example 8)
[1. Preparation of sample]
Hexadecyltrimethylammonium chloride: 60.1 g and 1N sodium hydroxide solution: 34.2 mL were added to a mixed solution consisting of water: 462 g, ethylene glycol: 152 g, and methanol: 152 g. When 36.2 g of tetraethoxysilane was added to this mixed solution, the solution became cloudy after a while, confirming that particles were synthesized. The molar concentration of hexadecyltrimethylammonium chloride used as a surfactant was 0.227 mol/L, and the molar concentration of tetramethoxysilane used as a silica source was 0.211 mol/L.

After stirring at room temperature for 8 hours, the mixture was filtered and the residue was redispersed in 4 L of water. After filtration again, the residue was dried in an oven at 45°C. After dispersing 10 g of the dried sample in 600 mL of 2N hydrochloric acid, it was heated at 140° C. for 3 days in an autoclave. After filtration and washing, the organic components were removed by firing at 550°C.

[2. evaluation]
The pore diameter obtained from nitrogen adsorption isotherm measurement was 7.0 nm, and the pore volume was 0.85 mL/g. Also, the tap density was 0.19 g/cm ³ . FIG. 12 shows an SEM photograph of the sample synthesized in Example 8. As shown in FIG. From FIG. 12, it can be seen that primary particles of several nanometers to ten and several nanometers are connected. The average particle size of primary particles was 0.114 μm.

Although the embodiments of the present invention have been described in detail above, the present invention is by no means limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention.

The linked mesoporous silica particles according to the present invention can be used as (a) a catalyst carrier, (b) an adsorbent, (c) a heat insulating material, (d) a mold for producing a mesoporous material, and the like.

Claims (2)

Connected mesoporous silica particles having the following composition.
(1) The linked mesoporous silica particles have a structure in which primary particles made of mesoporous silica are linked.
(2) the linked mesoporous silica particles,
The average primary particle size is 7 nm or more and 300 nm or less,
Pore diameter is 2 nm or more and 50 nm or less,
Pore volume is 0.2 mL / g or more and 3.0 mL / g or less,
The tap density is 0.05 g/cm ³ or more and 0.2 g/cm ³ or less. A method for producing linked mesoporous silica particles having the following configuration.
(1) The method for producing the linked mesoporous silica particles includes
a polymerization step of condensation polymerization of the silica source in a reaction solution containing a silica source, a surfactant and an alkali catalyst to obtain precursor particles;
a drying step of separating and drying the precursor particles from the reaction solution;
and a firing step of firing the precursor particles to obtain the linked mesoporous silica particles according to claim 1 .
(2) the reaction solution is
the concentration of the surfactant is 0.03 mol/L or more and 0.3 mol/L or less;
The concentration of the silica source is 0.05 mol/L or more and 0.45 mol/L or less.

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