KR101683774B1 - Porous Silica Spheres Having Various Pore Structural Tunability and Method of Preparing the Same - Google Patents

Abstract

The present invention relates to a spherical porous silica having various pore structural characteristics and a method for producing the same. The mesoporous and skeletal structure of a synthesized silica sample can be controlled according to the synthesis conditions, By the phase separation with the solvent in the colloidal suspension, it is possible to produce the hierarchical porous silica in which the macropores are formed in the mesoporous silica spheres so as to further control the pore size and distribution.

Description

TECHNICAL FIELD [0001] The present invention relates to spherical porous silica having various pore structural characteristics, and to a method for producing the porous silica.

The present invention relates to a spherical porous silica and a process for producing the same, and more particularly, to a process for preparing a microporous silica colloid by synthesizing a micro silica colloid as a basic unit constituting porous silica, and applying an aerosol process to the micro silica colloidal suspension, The present invention relates to a spherical porous silica capable of controlling pore structural characteristics and a method for producing the same.

Silica (SiO ₂ ) is a silicon dioxide (Si), which is composed of silicon and oxygen, which are the most elements of the crustal elements. They are present in various types of minerals on the earth or are produced by various synthetic methods. In addition, silica can be applied to various fields such as an adsorbent, a drug carrier, a gas separator, a catalyst support, and a sensor as a porous material having a lot of pores inside the material. In order to obtain optimum and best performance in this field, Controlling the porosity is technically very important. In particular, silica with a pore structure of mesoporosity (2 nm <pore size <50 nm) has a faster Knudsen diffusion than microporous (pore size <2 nm) materials, And has been attracting widespread attention because it is possible to store and apply it.

Among the various synthetic methods for synthesizing mesoporous silica, the supramolecular templating method, which can control the pore structure properly, has been most widely used since it was developed by Mobil Inc. in the early 1990s (CT Kresge et al. Nature , 359: 710 (1992)). MCM-41-based materials (M41S) synthesized by this method have wide specific surface area, regular pore arrangement, and uniform pore size distribution.

The mesoporous structure of these regularly ordered materials is synthesized using ionic surfactants as templates. Amphoteric surfactants dissolve in water to form a micelle-like macromolecule, with the hydrophilic head forming the outer surface and the hydrophobic tail being centered. Then, the silicate ions in the solution are located at the outer portion of the micelle which is the hydrophilic head portion of the surfactant, and the silicate ions are polymerized to form a condensed silica structure (JS Beck et al., Chem. Mater . 6 : 1816 (1994)). The synthesized silica-surfactant composite is subjected to a calcination process to form a mesoporous silica having a uniform mesopore distribution. The size, shape and connectivity of the mixture of silicate and micelle can vary depending on the structure of the surfactant, the additives to be added, and the synthesis temperature, which means that the pore structure of the synthesized mesoporous silica can be controlled.

U.S. Patent Nos. 6,027,706 and 6,054,111 disclose mesoporous materials prepared using amphiphilic block copolymers, which are nonionic surfactants of the neutral series.

In the case of zeolite, in general, an inorganic or organic molecule acts as a template material to induce the pore structure, whereas a mesoporous material induces pores in a micelle structure in which a plurality of surfactant molecules are collected rather than a single molecule .

The mesopore size of the synthesized mesoporous silica was controlled by controlling the carbon chain length of the hydrophobic tail portion of the surfactant located at the center of the micelle from 12 to 22 (M. Kruk et al. , J. Phys. Chem. B. , 104: 292 (2000)). As a template for the macromolecular casting method, meso pore size can be adjusted up to 30 nm by using a large amphoteric block copolymer as compared to a small surfactant (D. Zhao et al., Science , 279: 548 )). These macromolecular casting processes have been applied not only to silica but also to the formation of mesoporous structures of other metal oxides, metal sulfides and metal phosphates.

Although such a macromolecular casting method allows a compound to easily change the skeleton and pore structure of a substance and to produce a uniform array of mesopores, the surfactants and block copolymers used as templates are very expensive . Because these organic templates are expensive materials, the manufacturing process using them dramatically increases the cost of producing the composite. In addition, in order to generate the proper mutual attraction between the silicate and the organic surfactant in the synthesis solution, the synthesis should proceed under generally very strong basic or acidic conditions, thereby producing synthetic waste which is further harmful to the environment. Therefore, there is a need for new synthetic methods for economical and environmentally friendly mesoporous silica, which overcome the limitations of conventional mesoporous silica synthesis methods and enable the compounds to be used in real industries.

As a result of intensive efforts, the present inventors have found that a colloidal suspension of micro silica having a diameter of 1 to 200 nm is synthesized, and an aerosol process is applied to the colloidal suspension, It was confirmed that spherical mesoporous silica can be produced, and the present invention was completed.

It is an object of the present invention to provide a spherical porous silica capable of controlling pore structural properties and a method for producing the same.

It is another object of the present invention to provide an adsorbent, catalyst support, drug carrier or separator comprising spherical porous silica capable of controlling pore structural properties.

In order to achieve the above object, the present invention provides spherical porous silica comprising spherical micro silica colloid particles aggregated.

The present invention also provides a method of making spherical porous silica comprising the steps of:

(a) preparing a micro silica colloidal suspension having a diameter of 1 to 200 nm on a sol;

(b) converting said suspension into a sprayable aerosol droplet form and spraying; And

(c) heat treating the sprayed aerosol droplets in an aerosol reactor to produce mesoporous silica.

The present invention also provides an adsorbent, a catalyst support, a drug carrier or a separator, characterized in that they comprise the spherical porous silica.

 The spherical mesoporous silica according to the present invention may have various pore structure characteristics such as mesopores and skeletal structures depending on synthesis conditions of colloidal suspensions synthesized by size.

By adding alkanes having different carbon chain lengths to the micro silica colloidal suspension, it is possible to synthesize a hierarchical porous silica having macropores added thereto. Since the aerosol method is used, mass production of mesoporous silica is possible, Porous and Hierarchical Porous Silica Spherical Samples Not only can be used as adsorbents, catalyst supports and drug delivery materials, but also as basic monomers constituting more complex nanostructured materials.

1 is a schematic diagram showing a process of synthesizing a micro silica colloidal suspension by applying a method of synthesizing a silica colloidal suspension according to a first embodiment of the present invention.
FIG. 2 is a graph showing the results obtained by applying dynamic light scattering (DLS) to samples synthesized with different particle sizes by varying the molarity of ammonia in the synthesis composition of micro silica colloidal suspensions according to Example 1 of the present invention A graph showing the correlation between the particle size of one silica colloid and the molar concentration of ammonia
FIG. 3 is a graph showing the results obtained by converting the synthesized microcolumn silica colloidal suspension according to Example 1 of the present invention into an aerosol by injecting the synthesized silica colloidal suspension into an ultrasonic atomizer portion of an aerosol reactor and then passing the aerosol through a high temperature furnace, Lt; RTI ID = 0.0 &gt; a &lt; / RTI &gt; hierarchical porous silica spheres.
Fig. 4 is a graph showing the results of measurement of mesoporous silica spherical samples (Si-7.2 (573), Si-15 (SiO2)) having various mesoporosity and specific surface area according to the size of silica colloid and the temperature of an aerosol reactor according to Example 2 of the present invention 573), Si-29 (573), Si-7.2 (773), Si-15 (773) and Si-29 (773).
5 is a graph showing the results of measurement of mesoporous silica spherical samples (Si-3.0 (573), Si-29 (573), and Si- 573), Si-3.0 (773) and Si-29 (773).
Fig. 6 is a graph showing the results of measurement of mesoporous silica spherical samples (Si-3.0 (573), Si-7.2 (573), and Si- Nitrogen physical adsorption isotherms of Si-15 (573), Si-15 (573), Si-29 (573), Si-3.0 (773), Si- (Nitrogen physisorption isotherm).
7 is a graph showing the results of measurement of mesoporous silica spherical samples (Si-3.0 (573), Si-7.2 (573), and Si- Mesopore size distribution of Si-15 (573), Si-15 (573), Si-29 (573), Si-3.0 (773), Si- FIG.
8 is a graph showing the results of measurement of mesoporous silica spherical samples (Si-3.0 (573), Si-7.2 (573), and Si- 573), Si-15 (573), Si-29 (573), Si-3.0 (773), Si-7.2 (773), Si- A graph of Brunauer-Emmett-Teller (BET) specific surface area and mesopore volume values.
FIG. 9 is a graph showing the results of measurement of the permeability and permeability of the heavily porous silica spherical samples synthesized by the aerosol method after injecting dodecane and icosane in an alkane as an additive into an ultra-small silica colloidal suspension, respectively, according to Example 3 of the present invention (SEM) image of hiSi (12), hiSi (20).
FIG. 10 is a graph showing the results of measurement of the permeability and permeability of hemi-porous silica spherical samples synthesized by aerosol method after putting dodecane and icosane in an alkane as an additive into an ultra-small silica colloidal suspension, respectively, according to Example 3 of the present invention (TEM) image of hiSi (12), hiSi (20).
Fig. 11 is a graph showing the results obtained by adding an alkane dodecane and icosane as an additive to an ultra-small silica colloidal suspension, respectively, according to Example 3 of the present invention, and then using the aerosol method to synthesize the hierarchical porous silica spherical samples , The mechanism of the phase separation between ethanol and each alkane in the aerosol reactor is different from each other and different macro-porosity is formed.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein and the experimental methods described below are well known and commonly used in the art. Duplicate descriptions of the same components are omitted if they are not important.

In the present invention, it has been confirmed that it is possible to produce a spherical mesoporous silica capable of controlling pore structural characteristics according to synthesis conditions by synthesizing a micro silica colloidal suspension and applying an aerosol method.

It has also been found that it is possible to produce spherical, hierarchical porous silica which can control the mesoporosity and macroporosity by adding an additive alkane to the silica colloidal suspension.

Accordingly, the present invention relates to spherical porous silica composed of aggregated spherical microcrystalline silica colloidal particles in one aspect.

The spherical porous silica may be a mesoporous silica or a hierarchical porous silica.

The diameter of the micro silica colloidal particles may be 1 to 50 nm.

The mesoporous silica is a spherical porous silica having a mesopore having a diameter of 2 to 50 nm and a volume of 0.1 to 2 cm ³ / g, a BET specific surface area of 100 to 1000 m ² / g and a diameter of 100 nm to 2 μm .

Also, the hierarchical porous silica is a spherical porous silica having mesopores having a diameter of 2 to 50 nm and a volume of 0.1 to 2 cm ³ / g, a BET specific surface area of 100 to 1000 m ² / g and a diameter of 100 nm to 2 μm Or mesopores having a diameter of from 2 to 50 nm and a volume of from 0.1 to 2 cm ³ / g and having a BET specific surface area of from 100 to 1000 m ² / g And may be a spherical porous silica having macropores of 200 to 1500 nm in a hollow form at the center of a spherical porous silica having a diameter of 100 nm to 2 탆.

The present invention in another aspect relates to a process for preparing spherical porous silica comprising the steps of:

(a) preparing a micro silica colloidal suspension having a diameter of 1 to 200 nm on a sol; (b) converting said suspension into a sprayable aerosol droplet form and spraying; And (c) heat treating the sprayed aerosol droplets in an aerosol reactor to produce mesoporous silica.

In the method of manufacturing spherical porous silica, the step (a) may further include adding an alkane having 6 to 25 carbon atoms to the suspension.

(A) preparing a micro silica colloidal suspension having a size of 1 to 200 nm on a sol; (b) converting said suspension into a sprayable aerosol droplet form and spraying; And (c) heat treating the sprayed aerosol droplets in an aerosol reactor to produce mesoporous silica.

The present invention also provides a method of preparing a microcolumn silica colloidal suspension comprising: (a) preparing a micro silica colloidal suspension having a size of 1 to 200 nm on a sol; (b) adding the additive to the suspension and converting it into a sprayable aerosol droplet form and spraying; And (c) heat treating the sprayed aerosol droplets in an aerosol reactor to produce a hierarchical porous silica.

The micro silica colloidal suspension for producing spherical mesoporous and hierarchical porous silica according to the present invention comprises (i) a silica precursor is added dropwise to a mixed solution of an amine compound and a solvent under agitation and further stirred; (ii) dissolving the alkali silicate in water and then carrying out the polymerization at pH 7 to 10.

The microsuspension silica suspension for producing spherical mesoporous and hierarchical porous silica according to the present invention can be obtained by applying the Stober synthetic method (W. Stet al., J. Colloid Interface Sci. , 26:62 (1968)) as the first synthetic method . A silica precursor of an alkoxysilane such as tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS) or trimethoxymethylsilane (TMOMS), etc. is used to react with ammonia, amino acid, dimethylamine or diethylamine And the alcohol precursor is hydrolyzed by a small amount of water using an alcohol solvent such as methanol, ethanol, propanol, butanol or the like, Colloidal silica is synthesized through a growth process. Stirring of the suspension can be carried out for 6 to 48 hours using a stirrer at a speed of 100 to 1000 rpm or an ultrasonic atomizer with a frequency of 20 to 60 kHz. The size of the synthesized silica colloid is known to be influenced by the concentration and temperature of the silica precursor and ammonia water.

The second synthesis method involves the synthesis of silica colloids in water solvents such as Ludox. Silica colloid is synthesized by dissolving alkali silicate (mainly sodium silicate (water glass)) as a silica precursor in water and adjusting the pH to 7 ~ 10 during polymerization. Stabilizing cation ions such as sodium and ammonium are present in the solution.

The micro silica colloidal suspension is in the sol state. After the completion of the synthesis, condensation between the colloids does not occur at room temperature. Thus, formation of a secondary porous structure can be carried out by using an aerosol spraying method. Since the synthesized silica colloids are related to the skeleton thickness of the mesoporous silica to be synthesized by the aerosol method, the smaller the silica colloid size, the thinner the skeletal thickness, and the larger the size, the thicker the skeletal thickness. The specific surface area of the composite can be adjusted according to the determined skeleton thickness.

In the present invention, the amine-based material is selected from the group consisting of ammonia, amino acid, primary amine, secondary amine, and tertiary amine structure, preferably ammonia.

In the present invention, the solvent of step (a) may be selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethanediol, propanediol, butanediol, pentanediol, hexanediol or isoproanol And is preferably ethanol.

In the present invention, the silica precursor may be selected from the group consisting of an alkoxysilane, an aminosilane, and an organosilane containing an alkylsilane and an arylsilane. Examples of the alkoxysilane include tetramethylorthosilicate (TMOS), tetra Is selected from the group consisting of tetraethylorthosilicate (TEOS), tetrapropylorthosilicate, tetrabutylorthosilicate and trimethoxymethylsilane (TMOMS), tetraethylorthosilicate, tetramethylorthosilicate, tetramethylorthosilicate, It is preferable to use trimethoxymethylsilane (TMOMS).

The aminosilane may be selected from the group consisting of dialkylaminosilane, trialkylaminosilane such as tripiperidinylsilane, tetraalkylaminosilane, diarylaminosilane, triarylaminosilane, tetraarylaminosilane, and alkyl Silane or arylsilane is preferably C ₁ -C ₂₀ alkylsilane or C ₆ -C ₂₀ arylsilane.

In the present invention, the addition amount of the silica precursor: amine substance: water may be 0.1 to 10: 0.1 to 20: 0.2 to 100 (molar ratio), preferably 0.1 to 1: 0.2 to 1: 0.5 to 5 have.

In the present invention, the size of the silica colloid of the micro silica colloidal suspension may be 1 to 50 nm. When synthesizing a micro silica colloidal suspension, the size of the silica particles can be controlled by the molar concentration of ammonia water.

In the present invention, the temperature of the aerosol reactor is 333 to 1073 K, preferably 373 to 773 K.

In the present invention, the heat treatment time may be 5 to 60 seconds.

In the present invention, the BET specific surface area (100 to 1000 m ² / g) of meso or hierarchical porous silica produced according to the particle size (1 to 50 nm) of the micro silica colloid can be controlled. Since the specific surface area of the mesoporous silica is determined depending on the size of the micro silica colloidal suspension particles, the specific surface area of the mesoporous silica is preferably 100 to 1,000 m &lt; ^{2 &gt;} / minute by selecting the micro silica colloidal suspension having a particle size in the range of 1 to 50 nm. g.

According to one embodiment of the invention, when the synthesis take place in an aerosol reactor, the same temperatures, BET specific surface area of porous silica sample is from 291m ² / g according to shrink to 3nm in the size of the silica colloidal 29nm to 807m ² / g Respectively.

In the present invention, the volume (0.1 to 2 cm ³ / g) and the size (2 to 50 nm) of the mesopores produced according to the temperature (333 to 1073 K) of the aerosol reactor may be controlled.

According to an embodiment of the present invention, a mesoporous silica spheres having a mesopore size smaller than that of the silica nanoparticles in a dense and dense structure are synthesized under a condition of 573 K, at which the temperature of the aerosol reactor is lower, It was confirmed that mesoporous silica spheres with meso pore size were synthesized at relatively high temperature (773K) and mesoporous silica spheres were formed at a relatively low temperature.

In the present invention, mesopore size (2 to 50 nm) and volume (0.1 to 2 cm ³ / g) are controlled according to the size (1 to 50 nm) of the micro silica colloid and the temperature of the aerosol reactor (333 to 1073 K) . &Lt; / RTI &gt;

According to one embodiment of the present invention, it was confirmed that as the size of the silica colloid increases from 3.0 to 29 nm, the mesopore size gradually increases from 3.1 to 12 nm at 573 K when synthesis proceeds in an aerosol reactor at the same temperature, 773K, it was confirmed that it gradually increased to 5.8 ~ 26nm. It was also found that the BET specific surface area of the samples was not influenced even when the temperature of the aerosol reactor was changed. Instead, the mesopore volume varied with the range of the volume of the aerosol reactor (573K, 0.42-0.53cm ³ / g), (773K, 0.75 to 0.92 cm ³ / g).

As the synthesis proceeds in the aerosol reactor, the condensation and drying rate of the liquid in the aerosol can be controlled. The size and volume of the mesopores formed between the silica colloid, which is the mesoporosity of the spherical mesoporous silica synthesized by using the condensation rate of the aerosol depending on the temperature of the aerosol reactor, . When the synthesis proceeds in an aerosol reactor at the same temperature, the mesopore size may gradually increase as the size of the silica colloid increases. This is due to the fact that the larger the size of the silica colloid, the larger the voids formed between the colloids. Also, when the synthesis using the same size silica colloidal suspension proceeds at the temperature of the other aerosol reactor, the mesopore size and volume may increase when the temperature is high. This may be due to the fact that the evaporation rate of the liquid in the aerosol droplets formed by spraying the silica colloidal suspension is faster at higher temperatures and the condensation is terminated when the gap between the silica colloids is larger.

In the present invention, the carrier gas of the aerosol reactor is selected from the group consisting of nitrogen, helium, argon, oxygen and air, and the flow rate of the carrier gas is in the range of 1 to 5 L / min.

 In the present invention, the additive is added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the silica colloidal suspension.

In the present invention, the alkane preferably has 6 to 25 carbon atoms, such as hexane, heptane, octane, nonene, decane, undecane, dodecane, icocaine, henococaine, doocaine, Tetracosane, pentacosane. Preferably, dodecane or icocane is used.

When an alkane having 6 to 14 carbon atoms is added, it is possible to produce spherical hexagonal porous silica having macropores of 50 to 300 nm size uniformly dispersed in a spherical porous silica structure, while alkane having 18 to 25 carbon atoms The spherical porous silica having a macro pore size of 200 to 1500 nm in a hollow form can be produced at the center of the spherical porous silica structure.

In the synthesis of dodecane with 12 carbon atoms, many small macropores are uniformly formed. In the case of icosane having 20 carbon atoms, it is synthesized as a hollow form, and hexadecane having 16 carbon atoms In the case of hexadecane, the two features are synthesized in a mixed form.

As a preferred embodiment of the alkane having a short carbon chain length of the present invention, when dodecane is used, since the phase separation with ethanol starts late and the attracting and condensing rate between phase separated dodecane is slow, Dodecane, which was present in several places of aerosol droplets, formed small, uniform macropores in the mesoporous silica skeleton. On the other hand, as a preferred example of an alkane having a long carbon chain length, when icocaine is used, the carbon chain length is relatively long and starts from a point where phase separation with ethanol is early, And thus, a large macroscopic pore is formed at the center of the mesoporous silica to form a hollow spherical shape.

The synthesized spherical mesoporous and hierarchical porous silica materials can systematically and easily change the skeletal structure, mesopore, and macropore of the formed sample by controlling the synthesis conditions that can be controlled during the synthesis process. Particularly, by separating the micro silica colloidal suspension synthesis step used as the basic unit of silica to be synthesized and the assembly step to the secondary porous structure using the aerosol method, only the characteristics desired to be controlled among the pore structural properties can be adjusted and derived, can do.

In another aspect, the present invention relates to an adsorbent, a catalyst support, a drug carrier, and a separator, which are produced by including the spherical mesoporous silica or the spherical porous silica.

The synthesized spherical mesoporous and hierarchical porous silica materials have various pore structural characteristics and can synthesize desired pore structures, and thus can be used as an adsorbent for a harmful substance, a catalyst support, a drug delivery system and a separator.

The synthesized spherical mesoporous and hierarchical porous silica materials can be usefully used as an adsorbent, especially as a CO ₂ adsorbent. Other uses for various applications are equally applicable to the use of conventional mesoporous silica, MCM-41 and SBA-15.

[Example]

The present invention will be described in further detail with reference to the following examples. It will be apparent to those skilled in the art, however, that these examples are provided to further illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1 Synthesis of Microsilica Colloidal Suspension

The ultra-small silica colloidal suspension was synthesized by applying the Stokes synthetic method (Fig. 1). TEOS (tetraethyl orthosilicate, 98%, Aldrich) was used as a silica precursor. Ammonia water (28 wt%, Junsei) and ethanol (absolute for analysis, Merck) were used for the synthesis. The microcrystalline silica colloidal suspensions of 3.0, 7.2, 15, and 29 nm in size were prepared as shown in Table 1.

At 298 K, 685.53 g of ethanol was added to a 1000 cm ³ capacity polypropylene bottle, 10.93 g of ammonia water was added, and the mixture was stirred at a constant rate of 400 rpm for 5 minutes. Thereafter, 18.75 g of TEOS was slowly added dropwise to the stirred solution, followed by further stirring at 400 rpm for 12 hours to synthesize a silica colloidal suspension having a uniform size of 3.0 nm.

The ratio of molar concentration of reactants to particle size Particle Size (nm)          Molar concentration ratio TEOS NH ₃ H ₂ O  EtOH  3.0  0.10  0.20  0.49  16.53  7.2  0.10  0.30  0.73  16.42  15  0.10  0.40  0.97  16.30  29  0.10  0.50  1.21  16.19

The entire synthesis process of the silica colloidal suspensions having different particle sizes was the same as that of synthesizing the silica colloidal suspension having the size of 3.0 nm. In addition, silica colloidal suspensions having larger sizes were also prepared by controlling the molar concentration of the materials used in the synthesis, in particular, the ammonia water to adjust the colloid size and synthesizing the same.

The particle size of the synthesized microcrystalline silica colloids was measured using a dynamic light scattering analysis (DLS). As shown in FIG. 2, the correlation between the molar concentration of ammonia in the solution and the size of the synthesized silica colloid was graphically shown. It can be seen that the size of the synthesized silica colloid increases as the molar concentration of ammonia increases, and the trend line of the graph is represented by a quadratic equation as follows.

y = 267.86 x ² -126.57 x + 20.05 ( y = size of silica colloid, x = molar ammonia concentration)

The value of the coefficient of determination R ² , which can be used to determine how the above quadratic equation corresponds to the measured values, is 0.9795. It was confirmed that the size of the silica colloid to be synthesized could be predicted by using the calculated quadratic equation and that the silica colloid size could be systematically changed and synthesized.

Example 2: Synthesis of mesoporous silica spheres

A silica colloidal suspension having a size of 3.0, 7.2, 15, and 29 nm synthesized in Example 1 was injected into each of a 400 cm ³ batch in an ultrasonic atomizer and sprayed in an aerosol droplet form And the aerosol process was carried out (FIG. 3).

The silica colloidal suspension injected into the ultrasonic atomizer was sprayed at 200 cm ³ per hour and dry nitrogen was used as the carrier gas passing through the aerosol reactor. The flow rate of nitrogen was kept constant at 5,000 cm ³ / min, which is the rate at which the aerosol droplets pass the furnace of the aerosol reactor with the carrier gas in 11 seconds. The sprayed aerosol was dried by passing through a quartz tube in a furnace heated to a temperature of 573 K or 773 K under each condition and the synthesized spherical mesoporous silica was collected by collecting the filter paper located at the rear end of the aerosol reactor .

The synthesized mesoporous silica spheres were named according to the size of the silica colloidal particles of the silica colloidal suspension and the temperature of the aerosol reactor.

(Si- n ( m ), n = particle size of silica colloid, m = temperature of furnace of aerosol reactor)

(573), Si-15 (573), Si-29 (573), Si-3.0 (773), and Si-7.2 (773), Si-15 (773) and Si-29 (773).

All synthesized mesoporous silica was spherical in shape, and the synthesized silica showed a size distribution between 300 and 800 nm (Table 2).

Size distribution of synthesized silica sample S _BET
(m ² / g) V _micro
(cm &lt; ³ &gt; / g) V _meso
(cm &lt; ³ &gt; / g) V _total
(cm &lt; ³ &gt; / g) Mesopore
size (nm) Si-3.0 (573)  807  0.010  0.52  0.53  3.1 Si-7.2 (573)  676  0.010  0.49  0.50  3.8 Si-15 (573)  456  0.013  0.44  0.45  5.8 Si-29 (573)  322  0.014  0.41  0.42  12 Si-3.0 (773)  802  0.010  0.87  0.88  5.8 Si-7.2 (773)  646  0.011  0.91  0.92  9.1 Si-15 (773)  458  0.017  0.85  0.87  16 Si-29 (773)  291  0.017  0.73  0.75  26

In addition, it was confirmed by scanning electron microscope images that microscopic silica colloids, that is, nanoparticles having a uniform size for each sample, act as a basic unit to form large mesoporous silica particles, And consistent with the values measured by dynamic light scattering analysis on a colloidal suspension (FIG. 5). In addition, when the temperature (573, 773K) was applied to the silica colloidal suspensions of the same size by different aerosol reactors in the scanning electron microscope image shown in FIG. 5, the density of silica colloid particles acting as the basic monomers was differently synthesized Respectively. The mesoporous silica spheres with the denser and dense structure of the silica nanoparticles are synthesized under the condition of the lower temperature of the aerosol reactor at 573 K. The silica nanospheres are relatively cemented at the higher temperature of 773 K, It was confirmed that the mesoporous silica spheres having larger and larger voids between the particles and the particles were synthesized.

Transmission electron microscopy image analysis was also performed to confirm this fact (Fig. 6). When assembling the micro silica colloidal particles using the aerosol method, the skeleton thickness of the synthesized silica spheres is due to the size of the colloidal particles used. The skeleton referred to herein is a spherical porous silica material, and the silica colloid particles form the skeleton thereof. Silica colloidal particles are dried and condensed to form porous silica spheres. The basic unit that forms the framework of this spherical silica colloidal particles is silica colloidal particles. Therefore, it can be said that the skeleton thickness of the spheres is the same as the size of the silica colloid particles.

However, among the silica spheres synthesized using the same silica colloidal suspension, the transmission electron microscope images of samples synthesized at the higher aerosol reactor temperature of 773 K show that there are more bright domains identified as voids inside the spheres Respectively. It was confirmed that samples with different porosity can be synthesized according to the temperature applied to the aerosol method.

Nitrogen adsorption / desorption analysis was performed to analyze the precise pore structure of synthesized mesoporous silica spheres (FIG. 7). All the samples were confirmed to follow the type IV isotherm of the mesoporous materials, and it was confirmed by t- plot analysis that micro-pores were almost absent (FIG. 4). In order to analyze the mesopore distribution of the samples, the calculated distribution was analyzed by applying the BJH formula (FIG. 8). As the silica colloid size increased from 3.0 to 29 nm, the mesopore size increased gradually from 3.1 to 12 nm at 573 K, and gradually increased from 5.8 to 26 nm at 773 K. Respectively.

Therefore, when the mesoporous silica spheres are synthesized at a higher temperature by the production method of the present invention, it is confirmed that the mesopores are larger and the change of the size of silica colloid particles may have a greater influence on the change of mesopore size And it was confirmed that the mesoporosity can be controlled systematically according to the synthesis conditions.

As shown in FIG. 9, the BET specific surface area and the mesopore volume of the mesoporous silica samples (Si- n ( m )) synthesized in the present invention vary depending on the synthesis conditions, Was increased from 291 m ² / g to 807 m ² / g with decreasing from 29 nm to 3.0 nm. As described above, it was determined that the skeleton thickness of the mesoporous silica samples became thinner as the size of the silica colloid used became smaller, so that the BET specific surface area widened accordingly. In addition, it was confirmed that the BET specific surface area of the samples was hardly affected even when the temperature of the aerosol reactor was changed. As a result, it was confirmed that there was no ripening between the silica colloids acting as the basic unit. Instead meso pore volume was found to have the volume of each of the other range ^{(573K, 0.42-0.53cm 3 / g)} , (773K, 0.75 ~ 0.92cm 3 / g) with the temperature of the aerosol in the reactor.

By combining the above results, it was confirmed that the skeletal thickness and the pore structural characteristics of the synthesized mesoporous silica spheres can be systematically controlled by adjusting the particle size of the micro silica colloid used in the synthesis and the temperature of the aerosol reactor.

Example 3 Synthesis of Silica Spheres Having Hierarchical Porous Pore Structure

1.64 cm ³ (0.80 wt%) of dodecane (TCI) having a carbon chain length of 12 in an alkane was added to 200 cm ³ of a silica colloidal suspension having a size of 7.2 nm in the micro silica-based colloid suspension synthesized in Example 1, (298K) for 3 hours to prepare a homogeneous solution, which was then introduced into an aerosol sprayer. As the carrier gas in the aerosol method, dry nitrogen was used at the same flow rate (5,000 cm ³ / min) and synthesized at a temperature of 573 K in the reactor. As an additive, not only dodecane but also icosane (Aldrich) was synthesized in the same manner as in the above synthesis process using the same amount. The silica spheres thus synthesized were collected on a filter paper. The obtained material was named hierSi (12) and hierSi (20) according to the carbon chain length of the added paraffin.

As shown in FIG. 10, in the case of hierSi (12) synthesized by adding dodecane, a plurality of macropores (50 nm <pore size <200 nm) were synthesized from mesoporous silica Were synthesized in the form existing in skeletal structure. In contrast, in the case of hierSi (20) with icosane, it was confirmed that a large macropore (200 nm < pore size) was present in the mesoporous silica skeleton. These results were also confirmed by the transmission electron microscope image of FIG.

The formation mechanism of the silica spheres having the hierarchical pore structure is judged as phase separation of alkane and ethanol by liquid evaporation in the aerosol during the synthesis process as shown in FIG. Dodecane, which is relatively short in carbon chain length, starts from the moment when the phase separation with ethanol is late, and because the attracting and condensing rate between the phase separated dodecane is slow, until the evaporation is completed, Were found to form small and uniform macropores in the mesoporous silica skeleton. On the other hand, the icocaine starts from the point where the carbon chain length is relatively long and phase separation with ethanol is early, and the attracting force between the phase-separated icocins is strong and forms a large phase at the center of the aerosol droplet, And it was confirmed that it was synthesized as hollow spheres.

In the present invention, when the microcrystalline silica colloidal suspension was synthesized, the particle size of the silica colloid increased as the molar concentration of ammonia water increased, and the particle size could be controlled. When the mesoporous silica spheres were synthesized, It is confirmed that the structure can be controlled by the denser and denser structure, and the comparative sparse arrangement at 773K. In the synthesis of silica spheres with a hierarchical porous structure, macropores were observed when dodecane was added during synthesis, and macropores were found at the center of silica skeleton when icocane was added.

Therefore, it has been confirmed through the results of the present invention that the size and distribution of macropores as well as mesopores can be controlled depending on the type of alkane additive.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the invention will be defined by the claims and their equivalents.

Claims (22)

Wherein the spherical porous silica is composed of agglomerated spherical microcrystalline silica colloidal particles and mesopores having a diameter of 2 to 50 nm and macrocellular pores having a size of 50 to 300 nm are distributed.
A spherical porous silica having mesopores having a diameter of 2 to 50 nm and being present in the form of a macropore hollow having a size of 200 to 1500 nm at the center of the spherical porous silica, .
3. The method according to claim 1 or 2,
A spherical porous silica having a mesopore having a diameter of 2 to 50 nm and a volume of 0.1 to 2 cm ³ / g, a BET specific surface area of 100 to 1000 m ² / g, and a diameter of 100 nm to 2 μm.
The spherical porous silica according to claim 1 or 2, wherein the micro silica colloidal particles have a diameter of 1 to 50 nm.
The spherical porous silica according to claim 1, wherein the spherical porous silica is present in a macro pore hollow shape having a size of 200 to 1500 nm at the center of the spherical porous silica.
A method of making spherical porous silica comprising the steps of:
(a) adding an alkane having 6 to 25 carbon atoms to an ultra-small silica colloidal suspension having a diameter of 1 to 200 nm on a sol;
(b) converting the alkane-added suspension into a sprayable aerosol droplet form and spraying; And
(c) heat treating the sprayed aerosol droplets in an aerosol reactor to produce mesoporous silica.
delete The method according to claim 6, wherein step (a) comprises adding a silica precursor in a dropwise manner to a mixed solution of the amine-based material and the solvent under agitation and further stirring or polymerizing the solution at a pH of 7 to 10 after dissolving the silicate in water Wherein the porous silica is a porous silica.
9. The method of claim 8, wherein the silica precursor is selected from the group consisting of alkoxysilanes, aminosilanes, and organosilanes comprising alkylsilanes and arylsilanes.
The method of claim 9, wherein the alkoxysilane is selected from the group consisting of tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), tetrapropylorthosilicate, tetrabutylorthosilicate, And trimethoxymethylsilane (TMOMS). &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
9. The method according to claim 8, wherein the amount of the silica precursor: amine-based material: water is 0.1 to 10: 0.1 to 20: 0.2 to 100 (molar ratio).
The method of claim 6, wherein the size of the silica colloid of the micro silica colloidal suspension is 1 to 50 nm.
7. The method according to claim 6, wherein the temperature of the aerosol reactor is 333 to 1073K.
The method according to claim 6, wherein the BET specific surface area (100 to 1000 m ² / g) of the spherical porous silica produced according to the particle size (1 to 50 nm) of the micro silica colloid is controlled.
The method according to claim 6, wherein a volume (0.1 to 2 cm ³ / g) and a size (2 to 50 nm) of the mesopores generated according to the temperature (333 to 1073 K) of the aerosol reactor are controlled.
The method according to claim 6, wherein the size (2 to 50 nm) and the volume (0.1 to 2 cm ³ / g) of the mesopores are selected according to the size (1 to 50 nm) of the micro silica colloid and the temperature (333 to 1073 K) &Lt; / RTI &gt;
7. The process of claim 6 wherein the carrier gas of the aerosol reactor is selected from the group consisting of nitrogen, helium, argon, oxygen and air, and the flow rate of the carrier gas is in the range of 1 to 5 L / min. Way.
7. The method according to claim 6, wherein the amount of the alkane having 6 to 25 carbon atoms is 0.1 to 10 parts by weight based on 100 parts by weight of the silica colloidal suspension.
The method according to claim 6, wherein macropores having a size of 50 to 300 nm are distributed in the spherical porous silica structure.
The method according to claim 6, wherein macropores having a size of 200 to 1500 nm are present in a hollow form at the center of the spherical porous silica structure.
An adsorbent comprising spherical porous silica of claim 1 or 2.
A catalyst support comprising the spherical porous silica of claim 1 or 2.

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