JP4488191B2 - Method for producing spherical silica-based mesoporous material - Google Patents

Description

  The present invention relates to a method for producing a spherical silica mesoporous material made of a silica-based material having a skeleton formed mainly of silicon atoms and oxygen atoms.

  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. Research on the synthesis and functional development of such silica-based mesoporous materials has been actively conducted.

  For example, Grun et al. Have reported a method for producing spherical porous bodies from alkylamine and tetraethoxysilane (M. Grun et al., Stud. Surf. Sci. Catal., 128, 155 (2000) (non- Patent Document 1)). In JP-A-10-328558 (Patent Document 1), a spherical porous body is obtained by reacting alkoxysilane under an acidic condition in an aqueous solution containing a surfactant such as an alkyltrimethylammonium salt. It is disclosed. Furthermore, in Japanese Patent Application Laid-Open No. 2002-29733 (Patent Document 2), an alkyl ammonium halide having a specific structure is used as a surfactant, and the surfactant and the silica raw material are dissolved in water so as to have a specific concentration. It is described that it is possible to improve the content ratio of the spherical porous body and the uniformity of the particle diameter of the spherical porous body by the method of reacting under basic conditions.

  Inventors of the present invention, Yano and Fukushima, have high particle size uniformity using alkyltrimethylammonium chloride having a long-chain alkyl group as a surfactant and a mixed solvent of water and methanol as a reaction solvent. A method for producing a spherical silica-based mesoporous material has been reported (K. Yano and Y. Fukushima, J. Mater. Chem., 14, 1579-1584 (April, 2004) (non-patent document 2)).

However, in any of the above conventional methods, only one type of monodisperse particles can be obtained. Therefore, when two types of spherical silica-based mesoporous materials having different particle diameters are mixed to improve the packing property, the spherical silica-based mesoporous materials having the respective particle diameters are synthesized separately and then uniform. In this case, there is a problem that the particles are aggregated and cannot be redispersed.
JP-A-10-328558 JP 2002-29733 A M. Grun et al., Stud. Surf. Sci. Catal., 128, 155 (2000) K. Yano and Y. Fukushima, J. Mater. Chem., 14, 1579-1584 (April, 2004)

  This invention is made | formed in view of the subject which the said prior art has, and aims at providing the method which can manufacture simultaneously several types of spherical silica type mesoporous bodies from which a particle size differs.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have selected a silica raw material, a water-soluble polymer solution, or a polar solvent having a dielectric constant of 33 or more at a specific addition time from the start of the reaction to the end of the reaction. It was found that the above-described object can be achieved by adding any of the above, and the present invention has been completed.

That is, the present invention
A first step of mixing a silica raw material and a surfactant in a solvent to obtain porous precursor particles obtained by introducing the surfactant into the silica raw material;
A second step of obtaining a spherical silica-based mesoporous material by removing the surfactant contained in the porous material precursor particles;
In which a quaternary ammonium salt having a long-chain alkyl group having 8 to 26 carbon atoms is used as the surfactant, the following formula (1):
T ₁ <t <T ₂ (1)
[In formula (1), T ₁ represents the deposition start time, T ₂ represents the reaction end time, and t represents the addition time. ]
In the addition time t satisfying the condition represented by the formula, any additional component selected from the group consisting of a silica raw material, a water-soluble polymer solution and a polar solvent having a dielectric constant of 33 or more is added. It exists in the manufacturing method of different types of spherical silica type mesoporous materials.

  In the method for producing a spherical silica mesoporous material of the present invention, the silica raw material added at the addition time t is preferably at least one selected from the group consisting of monoalkoxysilane, dialkoxysilane and trialkoxysilane. Examples of the water-soluble polymer solution added at the addition time t include polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyacrylamine, polyvinylpyrrolidone, isoprene sulfonic acid, polyalginic acid, hydroxyethyl cellulose, and proteins. At least one aqueous solution selected from the group consisting of polysaccharides and DNA is preferred. Further, the polar solvent added at the addition time t is preferably at least one selected from the group consisting of water, glycerin, ethylene glycol and acetonitrile.

  In the method for producing a spherical silica-based mesoporous material of the present invention, the addition amount of the silica raw material added at the addition time t is 10 to 300 parts by weight with respect to 100 parts by weight of the initial silica raw material. preferable. Moreover, it is preferable that the addition amount of the said water-soluble polymer solution added at the said addition time t is 1-500 weight part with respect to 100 weight part of initial silica raw materials in conversion of solid content. Furthermore, it is preferable that the addition amount of the polar solvent added at the addition time t is 50 to 1000 parts by weight with respect to 100 parts by weight of the initial silica raw material.

  Furthermore, in the method for producing a spherical silica mesoporous material of the present invention, the initial concentration of the surfactant in the solvent is 0.005 to 0.02 mol / L, and the initial concentration of the silica raw material is converted to Si concentration. And 0.005 to 0.05 mol / L. Moreover, it is preferable to use the mixed solvent of water and alcohol whose alcohol content is 80 volume% or less as an initial solvent for mixing the said silica raw material and the said surfactant.

  In the present invention, a plurality of types having different particle diameters by adding any one of a silica raw material, a water-soluble polymer solution, and a polar solvent having a dielectric constant of 33 or more at a specific addition time from the start of reaction to the end of reaction. The reason why the spherical silica-based mesoporous material is simultaneously generated is not necessarily clear, but the present inventors speculate as follows. That is, when the silica raw material and the surfactant are mixed in a solvent, condensation of the silica raw material proceeds from a solution in which the surfactant and the silica raw material are uniformly dissolved, and the silica raw material and the surfactant are mixed. As a composite, porous precursor particles are deposited. As a result of detailed investigations by the present inventors regarding the precipitation of such particles, the porous body precursor particles have nuclei generated at the same time and the growth rate is the same as generally considered for the production of monodisperse particles. It was found that the particles are not produced in the course of completing the reaction at the same time but are produced by a special process in which particles of a certain size are successively produced as time passes. Therefore, when any one of a silica raw material, a water-soluble polymer solution, or a polar solvent having a dielectric constant of 33 or more is added at a specific addition time from the start of the reaction to the end of the reaction, the size of particles generated before and after the addition is increased. Therefore, the present inventors speculate that a plurality of types of monodispersed spherical silica-based mesoporous materials having different particle sizes are generated simultaneously.

  According to the present invention, it is possible to simultaneously produce a plurality of types of spherical silica mesoporous materials having different particle sizes. Therefore, according to the method for producing a spherical silica-based mesoporous material of the present invention, when two types of spherical silica-based mesoporous materials having different particle diameters are mixed to improve packing properties, they are synthesized separately. Compared to the conventional method of uniformly mixing, the uniformity of the resulting mixture can be improved efficiently and reliably, and the manufacturing process can be shortened and the manufacturing cost can be reduced.

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

(First step)
In the method for producing a spherical silica-based mesoporous material according to the present invention, first, a porous precursor particle obtained by mixing a silica raw material and a surfactant in a solvent and introducing the surfactant into the silica raw material. (First step).

  The initial 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 a reaction, but the viewpoint of the reaction efficiency and the physical properties of the obtained silicon oxide. Therefore, it is preferable to use alkoxysilane, sodium silicate, layered silicate, silica, or any mixture thereof, and it is more preferable to use alkoxysilane.

  As the alkoxysilane, tetraalkoxysilane having 4 alkoxy groups, trialkoxysilane having 3 alkoxy groups, or dialkoxysilane having 2 alkoxy groups can be used. The type of alkoxy group is not particularly limited, but those having a relatively small number of carbon atoms in the alkoxy group (such as those having about 1 to 4 carbon atoms) such as methoxy group, ethoxy group, propoxy group, butoxy group, etc. This is advantageous in terms of reactivity. Further, 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 tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and dimethoxydiethoxysilane. Examples of trialkoxysilane include trimethoxysilanol, triethoxysilanol, and trimethoxymethylsilane. , Trimethoxyvinylsilane, triethoxyvinylsilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, phenyl Trimethoxysilane, phenyltriethoxysilane, γ- (methacryloxypropyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Orchids. Examples of dialkoxysilane include dimethoxydimethylsilane, diethoxydimethylsilane, diethoxy-3-glycidoxypropylmethylsilane, dimethoxydiphenylsilane, and dimethoxymethylphenylsilane.

  Although the said alkoxysilane can also be used independently, it can also be used in combination of 2 or more types. 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.

  Alkoxysilane generates a silanol group by hydrolysis, and the generated silanol groups are condensed 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.

Examples of sodium silicate used as an initial silica raw material in the present invention include sodium metasilicate (Na ₂ SiO ₃ ), sodium orthosilicate (Na ₄ SiO ₄ ), sodium disilicate (Na ₂ Si ₂ O ₅ ), four Examples thereof include sodium silicate (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.

  Examples of silica used as an initial silica raw material in the present invention include precipitated silicas such as Ultrasil (Ultrasil), Cab-O-Sil (Cabot), HiSil (Pittsburgh Plate Glass); colloidal silica; Aerosil (Degussa- And fumed silica such as Huls).

  The above-mentioned initial silica raw materials can be used alone or in combination of two or more.

  The surfactant used in the present invention is a quaternary ammonium salt having a long-chain alkyl group having 8 to 26 carbon atoms. Among them, an alkyl ammonium halide represented by the following general formula (2) is preferable.

R ¹ , R ² and R ³ in the general formula (2) may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms. 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, but R ¹ , R ² , R ^{3 are used} from the viewpoint of symmetry of the surfactant molecule. 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 (2) shows the integer of 7-25, and it is more preferable that it is an integer of 9-17. With the alkylammonium halide having n of 6 or less, it becomes difficult to obtain a porous body. On the other hand, in the case of the alkylammonium halide having n of 26 or more, the hydrophobic interaction of the surfactant is too strong, so that a layered compound is generated and a spherical porous body cannot be obtained.

  Furthermore, X in the general formula (2) represents a halogen atom, and the kind 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 (2), alkyltrimethylammonium halides in which all of R ¹ , R ² and R ³ are methyl groups and have 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 a solvent together with the silica raw material. The silica raw material in the composite is changed to silicon oxide by the reaction, but silicon oxide is not generated in the part where the surfactant is present, so pores are formed in the part where the surfactant is present. Will be. 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.

  In the present invention, the initial solvent used as a reaction solvent for mixing the silica raw material and the surfactant is not particularly limited and may be water, but a mixed solvent of water and alcohol may be used. preferable. Examples of such alcohol include methanol, ethanol, isopropanol, n-propanol, ethylene glycol, and glycerin, and methanol or ethanol is preferable from the viewpoint of solubility of the silica raw material.

  Further, when such a mixed solvent of water and alcohol is used, it is more preferable to use a water / alcohol mixed solvent having an alcohol content of 80% by volume or less. Thus, by using the mixed solvent containing alcohol, generation and growth of a more uniform spherical body is realized, and the particle diameter of the resulting spherical silica-based mesoporous body is highly uniformly controlled. There is a tendency. If the alcohol content exceeds 80% by volume, it tends to be difficult to control the particle size and particle size distribution.

  When such a mixed solvent of water and alcohol is used, the particle diameter of the obtained spherical silica mesoporous material can be easily controlled by changing the ratio of water and alcohol. That is, when the ratio of water is high, the porous body is likely to precipitate, so the particle size becomes small. Conversely, when the ratio of alcohol is high, a porous body having a large particle size tends to be obtained.

  In the present invention, when the porous material precursor particles are obtained by mixing the silica raw material and the surfactant in the solvent, the initial concentration of the surfactant described above is 0.005 based on the total volume of the solution. To 0.02 mol / L (more preferably 0.01 to 0.02 mol / L), and the initial concentration of the silica raw material described above is 0.005 to 0.05 mol / in terms of Si concentration based on the total volume of the solution. L (more preferably 0.008 to 0.03 mol / L) is preferable. Thus, by strictly controlling the concentrations of the surfactant and the silica raw material, the generation and growth of a more uniform spherical body is realized, and the particle diameter of the resulting spherical silica-based mesoporous material is highly uniformly controlled. Tend to be. When the initial concentration of the surfactant is less than 0.005 mol / L, there is a tendency that a good porous body cannot be obtained due to a lack of the amount of the surfactant to be a template. When the concentration exceeds 0.02 mol / L, there is a tendency that a porous body having a spherical shape cannot be obtained at a high ratio. In addition, when the initial concentration of the silica raw material is less than 0.005 mol / L, there is a tendency that a porous body having a spherical shape cannot be obtained at a high ratio, while the initial concentration of the silica raw material is 0.05 mol / L. When it exceeds L, there is a tendency that a good porous body cannot be obtained because the ratio of the surfactant to be the template is insufficient.

  Furthermore, in the present invention, the ratio (molar ratio) of the initial concentration of the surfactant to the initial concentration (converted to Si concentration) of the silica raw material is preferably 0.2 to 3, preferably 0.4 to 2. .6 is more preferable, and 0.5 to 2.5 is particularly preferable. If this ratio is less than the lower limit, the ratio of the surfactant to be a template is insufficient, and thus a good porous body tends not to be obtained. On the other hand, if the ratio exceeds the upper limit, the shape is spherical. It tends to be impossible to obtain a porous material at a high ratio.

  Moreover, in this invention, when mixing the said silica raw material and the said surfactant, it is preferable to mix on basic conditions. Silica raw materials generally react under basic and acidic conditions and change to silicon oxide, but the reaction hardly proceeds under acidic conditions when the concentration of silica raw material and surfactant is low. There is a tendency. Therefore, in the present invention, it is preferable to react the silica raw material under basic conditions. 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.

  In order to make the solvent basic, a basic substance such as an aqueous sodium hydroxide solution is usually added. There are no particular restrictions on the basic conditions during the reaction, but the value obtained by dividing the alkali equivalent of the basic substance to be added by the number of moles of silicon atoms in the total silica raw material should be 0.1 to 0.9. Preferably, it is more preferably 0.2 to 0.5. When the value obtained by dividing the alkali equivalent of the basic substance to be added by the number of moles of silicon atoms in the total silica raw material is less than 0.1, the yield tends to decrease, and on the other hand, it exceeds 0.9. In such a case, the formation of the porous body tends to be difficult.

  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.). Further, the reaction is preferably allowed to proceed with stirring. Specific reaction conditions are preferably determined based on the type of silica raw material used.

  That is, when using alkoxysilane as a silica raw material, for example, porous precursor particles can be obtained as follows. First, a surfactant and a basic substance are added to a mixed solvent of water and alcohol to prepare a basic solution of the surfactant, and alkoxysilane is added to this solution. Since the added alkoxysilane is hydrolyzed (or hydrolyzed and condensed) in the solution, a white powder is 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.

  After the precipitate is deposited, the solution is further stirred at 0 ° C. to 80 ° C. (preferably 10 ° C. to 40 ° C.) for 1 hour to 10 days to advance the reaction of the silica raw material. After the completion of stirring, the porous precursor particles according to the present invention can be obtained by allowing the system to stand overnight at room temperature as necessary, stabilizing the system, and filtering and washing the resulting precipitate as necessary.

When silica raw material other than alkoxysilane (sodium silicate, layered silicate or silica) is used as the silica raw material, the silica raw material is added to a mixed solvent of water and alcohol containing a surfactant. A basic solution such as an aqueous sodium hydroxide solution is further added to prepare a uniform solution so as to have an equimolar amount with respect to the silicon atoms. Thereafter, the porous precursor particles according to the present invention can be produced by a method in which a dilute acid solution is added in a molar amount of 1/2 to 3/4 times the silicon atoms in the silica raw material. The basic substance requires an excessive amount for the purpose of breaking a part of the Si— (O—Si) ₄ bond already formed in the silica raw material, but the excess must be neutralized 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.

The first step for obtaining the porous precursor particles in which the surfactant is introduced into the silica raw material has been described above. In the present invention, in the first step, the following formula (1) :
T ₁ <t <T ₂ (1)
[In formula (1), T ₁ represents the deposition start time, T ₂ represents the reaction end time, and t represents the addition time. ]
It is important to add any additional component selected from the group consisting of a silica raw material, a water-soluble polymer solution, and a polar solvent having a dielectric constant of 33 or more at an addition time t that satisfies the condition represented by:

  In this way, when a specific additional component is added at a specific addition period from the start of the reaction to the end of the reaction, the size of the particles generated before and after the addition is different. The body precursor particles are generated at the same time. Moreover, it becomes possible to control the particle diameter of the obtained spherical silica-based mesoporous material by changing the timing of adding such additional components. That is, if the addition time is advanced, the particle size of the larger particle size among the plurality of types of particles becomes smaller, and the particle size of the smaller particle size among the plurality of types of particles tends to increase. . On the other hand, when the addition time is delayed, the particle size of the larger particle size among the plurality of types of particles increases, and the particle size of the smaller particle size among the plurality of types of particles tends to decrease. .

Note that timing of adding the additional component (t), which may be a later than deposition starting time _{(T 1),} to be later than (1/20) _{T 1} or more deposition starting time _{(T 1)} More preferred. Further, timing of addition of the additional component (t) is that it may be a pre-reaction end time _{(T 2),} which is before the completion of the reaction time _{(T 2) (1/20) T} 2 or more More preferred. That is, the addition time t is expressed by the following formula (3):
{T ₁ + (1/20) T ₁ } ≦ t ≦ {T ₂ − (1/20) T ₂ } (3)
It is more preferable to satisfy.

The “deposition start time (T ₁ )” here refers to the time from the start of the reaction until the scattering intensity of the reaction solution rises. Specifically, for example, the increase rate of the scattering intensity is 2% / It corresponds to the time of the moment when it becomes larger than sec. Furthermore, “reaction completion time (T ₂ )” refers to the time from the start of the reaction until the scattering intensity of the reaction solution becomes constant. Specifically, for example, the increase rate of the scattering intensity is 1% / sec. It corresponds to the time of the moment. The reaction start time {reaction start time (T ₀ )} means that all substances necessary for the reaction such as the silica raw material and the surfactant were added to the solvent to start the reaction. Say time. Further, the scattering intensity of such a reaction solution can be measured by a light scattering photometer such as SALD-7000 laser diffraction particle size analyzer manufactured by Shimadzu Corporation.

  In the present invention, the silica raw material added at the addition time t may be the same as or different from the initial silica raw material described above, but from the viewpoint of reducing the number of reaction points, monoalkoxy At least one selected from the group consisting of silane, dialkoxysilane and trialkoxysilane is preferred, and monoalkoxysilane is particularly preferred. Examples of such monoalkoxysilane include trimethylmethoxysilane, trimethylethoxysilane, and 3-chloropropyldimethylmethoxysilane.

  Moreover, it is preferable that the addition amount of the silica raw material added at the said addition time t is 10-300 weight part with respect to 100 weight part of initial silica raw materials. If the addition amount of the silica raw material as an additional component is less than the above lower limit, a plurality of types of spherical silica mesoporous bodies having different particle sizes tend to be difficult to obtain. Tend to generate.

  Examples of the water-soluble polymer solution added at the addition time t in the present invention include polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyacrylamine, polyvinyl pyrrolidone, isoprene sulfonic acid, polyalginic acid, hydroxyethyl cellulose, and proteins. At least one aqueous solution selected from the group consisting of (gelatin, pectin, etc.), polysaccharides and DNA is preferred, and polyethylene glycol and polyvinyl alcohol are particularly preferred from the viewpoint of little pH change in the reaction system.

  Moreover, it is preferable that the addition amount of the water-soluble polymer solution added at the said addition time t is 1-500 weight part with respect to 100 weight part of initial silica raw materials in conversion of solid content. If the amount of the water-soluble polymer solution added as an additional component is less than the above lower limit, it tends to be difficult to obtain a plurality of types of spherical silica mesoporous materials having different particle diameters. Tends to increase the viscosity and make it impossible to separate the particles. The concentration of the water-soluble polymer solution is not particularly limited, but usually a concentration of about 10 to 200 g / l is preferably used.

  In the present invention, the polar solvent having a dielectric constant of 33 or more added at the addition time t is preferably at least one selected from the group consisting of water, glycerin, ethylene glycol and acetonitrile, and has an affinity for the silicon oxide surface. Glycerin and ethylene glycol are particularly preferable from the viewpoint of increasing the viscosity. In addition, even if it is a polar solvent and a thing with a dielectric constant of less than 33 is used as an additional component, the multiple types of spherical silica type mesoporous body from which particle diameters differ sufficiently will not be obtained.

  Moreover, it is preferable that the addition amount of the polar solvent added at the said addition time t is 50-1000 weight part with respect to 100 weight part of initial silica raw materials. If the amount of the polar solvent added as an additional component is less than the above lower limit, it is difficult to obtain a plurality of types of spherical silica mesoporous materials having different particle diameters. Tends to be obtained.

(Second step)
Next, in the method for producing a spherical silica mesoporous material according to the present invention, the surfactant contained in the porous precursor particles obtained in the first step is removed to obtain a spherical silica mesoporous material. (Second step). Examples of the method for removing the surfactant as described above include a method by baking, a method of treating with an organic solvent, and an ion exchange method.

  In the method by firing, 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. The firing can be performed in the air, but since a large amount of combustion gas is generated, it may be performed by introducing an inert gas such as nitrogen. Moreover, when processing with an organic solvent, a porous body precursor particle is immersed in a good solvent with high solubility with respect to the used surfactant, and surfactant is extracted. In the ion exchange method, the porous precursor particles are immersed in an acidic solution (such as ethanol containing a small amount of hydrochloric acid) and stirred, for example, while heating at 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.

  By the production method of the present invention described above, a homogeneous mixture of a plurality of types of spherical silica-based mesoporous materials having different particle diameters is produced simultaneously. The average particle size of each of the obtained plural types of spherical silica-based mesoporous materials is not particularly limited, but a plurality of types of spherical silica-based mesoporous materials can be suitably produced within the range of the average particle size of 0.01 to 3 μm. It becomes like this. Further, the difference in the average particle size of the plurality of types of spherical silica-based mesoporous materials obtained by the production method of the present invention is not particularly limited, but a plurality of types of spherical silica-based meso having an average particle size difference of 0.2 μm or more A porous body can be suitably manufactured.

  Furthermore, the plurality of types of spherical silica-based mesoporous materials obtained by the production method of the present invention are each monodispersed, that is, the particle size is highly uniform, and the standard deviation of the particle size in each type is 15% or less. A plurality of types of spherical silica-based mesoporous materials can be suitably produced.

  In addition, the central pore diameter of the plurality of types of spherical silica-based mesoporous materials obtained by the production method of the present invention is not particularly limited, but from the viewpoint of facilitating introduction of a pigment having a large molecular weight such as porphyrin into the pores. About 1.8 to 5 nm is preferable.

  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 spherical silica-based mesoporous material obtained by the present invention is produced using the surfactant as a template and the silica source as a raw material, and has a skeleton —Si—O— in which silicon atoms are bonded through oxygen atoms. Basically, it has a highly crosslinked network structure. Such a silica-based material only needs to have silicon atoms and oxygen atoms as main components, and at least a part of the silicon atoms may form a carbon-silicon bond at two or more organic groups. . 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.

In addition, the spherical silica-based mesoporous material obtained by the present invention preferably contains 60% or more of the total pore volume in the range of ± 40% of the central pore diameter in the pore size distribution curve. The silica-based mesoporous particle satisfying this condition means that the pore diameter is very uniform. Moreover, there is no restriction | limiting in particular about the specific surface area of this spherical silica type mesoporous material, However, It is preferable that it is 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 spherical silica-based 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 its 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 spherical silica-based 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, 1324, 1995). Further, the porous body having a cubic pore arrangement structure means that the arrangement of pores is a cubic structure (JCVartuli, et al., Chem. Mater., 6, 2317, 1994; Q. Huo, et al., Nature, 368, 317, 1994). Further, the porous body having a disordered pore arrangement structure means that the arrangement of the pores is irregular (PTTanev, et al., Science, 267,865, 1995; SABagshaw, 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. According to the present invention, it is possible to obtain a spherical silica-based mesoporous material in which mesopores are arranged from the particle center toward the outside of the spherical particles while maintaining regularity, and such mesoporous materials are obtained. If it is used, the movement of energy and electrons can be accurately caused only in that direction.

  The spherical silica-based mesoporous material obtained by the present invention may be used as a powder, but 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 L of water and 4 L of methanol, 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant) and 22.8 mL of 1N sodium hydroxide were added. Then, 13.2 g (0.011 mol / L) of tetramethoxysilane (silica raw material) was added and stirring was continued. Tetramethoxysilane was completely dissolved, and a white powder was precipitated after about 180 seconds. The time when tetramethoxysilane was added to the reaction solution was the reaction start time (T ₀ = 0), and the deposition start time (T ₁ ) was 3 minutes (180 seconds).

Then, after 4 minutes from the start of the reaction time _{(T 0),} it was added aqueous polyethylene glycol solution (additional component) 500 mL containing polyethylene glycol 20g to the reaction solution. The time when the polyethylene glycol aqueous solution was added was the addition time (t = 4 minutes), and the reaction end time (T ₂ ) was 7 minutes.

  The resulting reaction solution was further stirred at room temperature for 8 hours and allowed to stand overnight (14 hours), and then filtration and washing with deionized water 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. for 6 hours to remove the organic components including the surfactant, thereby obtaining a spherical silica-based mesoporous material.

  An X-ray diffraction pattern of the obtained spherical silica-based mesoporous material is shown in FIG. From the X-ray diffraction pattern shown in FIG. 1, the obtained porous body has high-order peaks, and this powder is a highly ordered honeycomb porous body having a hexagonal pore arrangement structure. It was confirmed that The central pore diameter was 2.3 nm.

  Next, this spherical silica-based mesoporous material was observed with a scanning electron microscope (SEM). The obtained SEM photograph is shown in FIG. The porous bodies observed by SEM were two types of monodispersed spherical particles having different particle diameters, and the average particle diameter and standard deviation of any 100 particles of each kind were 0.65 μm (standard deviation 0. 0). 023 μm) and 0.15 μm (standard deviation 0.01 μm).

(Example 2)
As in Example 1, except that 4.52 g (0.0055 mol / L) of trimethylmethoxysilane was used as an additional component, and the additional component was added to the reaction solution 5 minutes after the reaction start time (T ₀ ). Thus, a spherical silica-based mesoporous material was obtained. In this example, the deposition start time (T ₁ ) was 3 minutes (180 seconds), the addition time (t) was 5 minutes, and the reaction end time (T ₂ ) was 7 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 0.65 μm (standard deviation 0.023 μm) and 0.125 μm (standard deviation 0.01 μm).

(Example 3)
Using a mixed solvent of 3 L of water and 1 L of methanol as a solvent, 15.4 g (0.0137 mol / L) of decyltrimethylammonium bromide as a surfactant, and 200 mL of a polyvinyl alcohol aqueous solution containing 20 g of polyvinyl alcohol as an additional component, the reaction start time ( A spherical silica-based mesoporous material was obtained in the same manner as in Example 1 except that an additional component was added to the reaction solution 4 minutes after T ₀ ). In this example, the deposition start time (T ₁ ) was 1.5 minutes (90 seconds), the addition time (t) was 4 minutes, and the reaction end time (T ₂ ) was 6 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 1.05 μm (standard deviation 0.06 μm) and 0.35 μm (standard deviation 0.04 μm).

Example 4
A mixed solvent of 4.4 L of water and 3.6 L of methanol as a solvent, 32.1 g (0.0137 mol / L) of tetradecyltrimethylammonium chloride as a surfactant, 500 mL of glycerin as an additional component, and a reaction start time (T ₀ ) 4 minutes later, a spherical silica-based mesoporous material was obtained in the same manner as in Example 1 except that an additional component was added to the reaction solution. In this example, the deposition start time (T ₁ ) was 3.3 minutes (200 seconds), the addition time (t) was 4 minutes, and the reaction end time (T ₂ ) was 6.5 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 0.50 μm (standard deviation 0.035 μm) and 0.2 μm (standard deviation 0.02 μm).

(Example 5)
A spherical silica-based mesoporous material was obtained in the same manner as in Example 1 except that an additional component was added to the reaction solution 6 minutes after the reaction start time (T ₀ ). In this example, the deposition start time (T ₁ ) was 3 minutes (180 seconds), the addition time (t) was 6 minutes, and the reaction end time (T ₂ ) was 7 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 0.67 μm (standard deviation 0.025 μm) and 0.1 μm (standard deviation 0.011 μm).

(Example 6)
Spherical silica was used in the same manner as in Example 1 except that 500 mL of an aqueous polyethylene glycol solution containing 5 g of polyethylene glycol was used as an additional component, and the additional component was added to the reaction solution 4 minutes after the reaction start time (T ₀ ). A system mesoporous material was obtained. In this example, the deposition start time (T ₁ ) was 3 minutes (180 seconds), the addition time (t) was 4 minutes, and the reaction end time (T ₂ ) was 7 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 0.62 μm (standard deviation 0.025 μm) and 0.1 μm (standard deviation 0.011 μm).

(Example 7)
Same as Example 1 except that 18.1 g (0.011 mol / L) of tetraethoxysilane was used as a silica raw material and an additional component was added to the reaction solution after 4 minutes from the deposition start time (T ₁ ). Thus, a spherical silica-based mesoporous material was obtained. In this example, the deposition start time (T ₁ ) was 13.7 minutes (820 seconds), the addition time (t) was 17.7 minutes, and the reaction end time (T ₂ ) was 60 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 0.67 μm (standard deviation 0.025 μm) and 0.25 μm (standard deviation 0.012 μm).

(Example 8)
Using tetradecyltrimethylammonium chloride 32 g (0.014 mol / L) as a surfactant and 500 mL of an aqueous polyethylene glycol solution containing 5 g of polyethylene glycol as an additional component, the additional component was added to the reaction solution 5 minutes after the reaction start time (T ₀ ). A spherical silica-based mesoporous material was obtained in the same manner as in Example 1 except that it was added to. In this example, the deposition start time (T ₁ ) was 3.3 minutes (200 seconds), the addition time (t) was 5 minutes, and the reaction end time (T ₂ ) was 6.5 minutes.

  The obtained spherical silica-based mesoporous material is a uniform mixture of two types of monodispersed spherical particles having different particle sizes. The average particle size of any 100 particles of each type determined from the SEM photograph and its standard The deviations were 0.50 μm (standard deviation 0.05 μm) and 0.17 μm (standard deviation 0.02 μm).

(Comparative Example 1)
A spherical silica-based mesoporous material was obtained in the same manner as in Example 1 except that no additional component was added to the reaction solution.

  An SEM photograph of the obtained spherical silica-based mesoporous material is shown in FIG. The porous body observed by SEM is one kind of monodispersed spherical particles having a single particle size, and the average particle size of 100 arbitrary particles and the standard deviation thereof are 0.65 μm (standard deviation 0.023 μm). Met.

(Comparative Example 2)
Polyethylene containing 35.2 g (0.014 mol / L) of hexadecyltrimethylammonium chloride (surfactant), 22.8 mL of 1N sodium hydroxide, and 20 g of polyethylene glycol with respect to a mixed solvent of 4 L of water and 4 L of methanol. 500 mL of an aqueous glycol solution (additional component) was added. Then, 13.2 g (0.011 mol / L) of tetramethoxysilane (silica raw material) was added and stirring was continued. Tetramethoxysilane was completely dissolved, and a white powder was precipitated after about 170 seconds. In this comparative example, the deposition start time (T ₁ ) was 2.8 minutes (170 seconds), the addition time (t) was 0 minutes, and the reaction end time (T ₂ ) was 6.5 minutes.

  The resulting reaction solution was further stirred at room temperature for 8 hours and allowed to stand overnight (14 hours), and then filtration and washing with deionized water 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. for 6 hours to remove the organic components including the surfactant, thereby obtaining a spherical silica-based mesoporous material.

  The obtained spherical silica-based mesoporous material is one type of monodispersed spherical particles having a single particle size, and the average particle size and standard deviation of any 100 particles determined from the SEM photograph are 0. It was 60 μm (standard deviation 0.028 μm).

(Comparative Example 3)
A spherical silica-based mesoporous material was obtained in the same manner as in Example 1 except that an additional component was added to the reaction solution 1 minute after the reaction start time (T ₀ ). In this example, the deposition start time (T ₁ ) was 3.3 minutes (200 seconds), the addition time (t) was 1 minute, and the reaction end time (T ₂ ) was 7.5 minutes.

  The obtained spherical silica-based mesoporous material is one type of monodispersed spherical particles having a single particle size, and the average particle size and standard deviation of any 100 particles determined from the SEM photograph are 0. It was 65 μm (standard deviation 0.024 μm).

(Comparative Example 4)
25 g of spherical silica-based mesoporous powder obtained in Comparative Example 1 and 25 g of spherical silica-based mesoporous powder with an average particle size of 0.15 μm (standard deviation 0.01 μm) separately synthesized The mixture was mixed by a mill grinder to obtain a mixture of two types of monodispersed spherical particles having different particle sizes.

<Water vapor adsorption performance test>
50 g of the white powder before firing obtained in Examples 1 to 4 and Comparative Example 1 was sealed in a bag made of vinyl chloride, and held at a pressure of 1000 kg / cm ² for 1 minute by a hydrostatic press. Next, the obtained sample was pulverized in a mortar to prepare particles having a particle size of 0.2 to 0.3 mm, and then the organic components including the surfactant were removed by baking in air at 550 ° C. for 6 hours. A porous molded body was obtained.

Further, 50 g of the mixture of spherical silica-based mesoporous powder obtained in Comparative Example 4 was sealed in a bag made of vinyl chloride, and obtained after being held at a pressure of 1000 kg / cm ² for 1 minute by a hydrostatic press. The sample was pulverized in a mortar and aligned to particles having a particle size of 0.2 to 0.3 mm to obtain a porous molded body.

  In this way, the bulk density of each porous molded body and the water vapor adsorption capacity per unit volume at 25 ° C. and a relative humidity of 80% were measured. The obtained results are shown in Table 1.

  As is apparent from the results shown in Table 1, if a spherical silica-based mesoporous material that is a uniform mixture of two types of monodispersed spherical particles having different particle sizes obtained by the production method of the present invention is used, the bulk is increased. It was confirmed that a porous molded body having a high density and a sufficiently large water vapor adsorption capacity can be obtained.

  As described above, according to the present invention, it is possible to simultaneously produce a plurality of types of spherical silica mesoporous materials having different particle sizes. Therefore, according to the method for producing a spherical silica-based mesoporous material of the present invention, it is obtained as compared with the conventional method in which two types of spherical silica-based mesoporous materials having different particle diameters are synthesized separately and then mixed uniformly. The uniformity of the mixture can be improved efficiently and reliably, and the manufacturing process can be shortened and the manufacturing cost can be reduced. Therefore, the method for producing a spherical silica-based mesoporous material of the present invention is to improve the packing property by mixing two types of spherical silica-based mesoporous materials having different particle sizes when obtaining an adsorbent or a catalyst carrier. This is a very useful method.

2 is a diagram showing an X-ray diffraction pattern of a spherical silica-based mesoporous material obtained in Example 1. FIG. 2 is a SEM photograph of a spherical silica-based mesoporous material obtained in Example 1. 3 is a SEM photograph of a spherical silica-based mesoporous material obtained in Comparative Example 1.

Claims (5)

A first step of mixing a silica raw material and a surfactant in a solvent to obtain porous precursor particles obtained by introducing the surfactant into the silica raw material;
A second step of obtaining a spherical silica-based mesoporous material by removing the surfactant contained in the porous material precursor particles;
In which a quaternary ammonium salt having a long-chain alkyl group having 8 to 26 carbon atoms is used as the surfactant, the following formula (1):
T ₁ <t <T ₂ (1)
[In formula (1), T ₁ represents the deposition start time, T ₂ represents the reaction end time, and t represents the addition time. ]
In the addition time t satisfying the condition represented by the formula, any additional component selected from the group consisting of a silica raw material, a water-soluble polymer solution and a polar solvent having a dielectric constant of 33 or more is added. A method for producing different types of spherical silica-based mesoporous materials. The silica raw material added at the addition time t is at least one selected from the group consisting of monoalkoxysilane, dialkoxysilane and trialkoxysilane,
The water-soluble polymer solution added at the addition time t is polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyacrylamine, polyvinyl pyrrolidone, isoprene sulfonic acid, polyalginic acid, hydroxyethyl cellulose, proteins, polysaccharides And at least one aqueous solution selected from the group consisting of DNA,
The polar solvent added at the addition time t is at least one selected from the group consisting of water, glycerin, ethylene glycol and acetonitrile.
The method for producing a spherical silica-based mesoporous material according to claim 1. The addition amount of the silica raw material added at the addition time t is 10 to 300 parts by weight with respect to 100 parts by weight of the initial silica raw material,
The addition amount of the water-soluble polymer solution added at the addition time t is 1 to 500 parts by weight in terms of solid content with respect to 100 parts by weight of the initial silica raw material,
The amount of the polar solvent added at the addition time t is 50 to 1000 parts by weight with respect to 100 parts by weight of the initial silica raw material.
The method for producing a spherical silica-based mesoporous material according to claim 1 or 2.   The initial concentration of the surfactant in the solvent is 0.005 to 0.02 mol / L, and the initial concentration of the silica raw material is 0.005 to 0.05 mol / L in terms of Si concentration. The manufacturing method of the spherical silica type mesoporous material as described in any one of Claims 1-3.   A mixed solvent of water and alcohol having an alcohol content of 80% by volume or less is used as an initial solvent for mixing the silica raw material and the surfactant. The manufacturing method of the spherical silica type mesoporous material as described in any one of these.