JP2003165717A - Silica gel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a new silica gel excellent in heat resistance, resistance to water and the like. <P>SOLUTION: The method for producing the silica gel comprises hydrolyzing a silicon alkoxide and subjecting to a hydrothermal treatment without substantilly aging a resultant hydrogel. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel silica gel having excellent heat resistance and water resistance.

[0002]

BACKGROUND OF THE INVENTION Silica gel has been widely used as a desiccant for a long time, but recently, its use has expanded to catalyst carriers, separating agents, adsorbents and the like. Therefore, the requirements for the performance of silica gel have been diversified according to each application.
The performance of silica gel is greatly affected by physical properties such as surface area, pore diameter, pore volume, and pore diameter distribution of silica gel, and these physical properties are greatly influenced by silica gel production conditions.

The most common method for producing this silica gel is to hydrolyze an alkali silicate salt such as sodium silicate with a mineral acid to gelate the obtained silica hydrosol,
Although it is a drying method, many proposals have been made on the details of the production method in order to improve the performance of silica gel.
For example, in Japanese Patent Laid-Open No. 62-113713, a silica hydrosol produced by the reaction of an alkaline silicate aqueous solution with a mineral acid is gelled, treated with an acid solution having a pH of 2.5 or less, washed with water and then subjected to a buffering action. PH in an aqueous solution containing
A method of producing silica gel having a narrow pore distribution by adjusting to 9 and performing hydrothermal treatment has been proposed.

Further, in Japanese Patent Laid-Open No. 9-30809,
A method has been proposed in which the silica hydrogel is dried by batchwise fluidized drying, followed by hydrothermal treatment. A change in the performance of the silica gel obtained by this method is recognized, and silica gel having a sharper pore distribution is obtained. However,
It has not been possible to sufficiently change the pore volume, the specific surface area, and the average pore diameter, which is not a sufficient method for obtaining silica gel having a desired physical property range.

On the other hand, the silica gel obtained from the above-mentioned alkali silicate salt as a raw material usually contains sodium, calcium, magnesium, titanium,
It contains a considerable amount of impurities such as aluminum and zirconium. The total amount of metallic impurities in silica gel has a great influence on the performance of silica gel, even if the content thereof is a very small amount of several hundred ppm. For example, 1) promotes crystallization of silica gel at high temperature, and 2) promotes hydrothermal reaction of silica gel in the presence of water to increase pore diameter and pore volume, decrease specific surface area, and reduce pore distribution. 3) These impurities bring about expansion, and since these impurities lower the sintering temperature, heating the silica gel containing them accelerates the reduction of the specific surface area. And, such an influence is particularly strong in impurities of alkali metals and alkaline earth metals. Furthermore, if titanium or aluminum is present as an impurity on the surface of silica gel or in a siloxane bond, the number of acid points increases, and silica gel itself may exhibit an undesired catalytic action when used as a catalyst carrier or adsorbent.

KIM et al. (Ultrastable Mesostructured
In Silica Vesicles Science, 282, 1302) (1998), removal of gemini surfactant after formation of supramolecular structure consisting of hydrogen bond between electrically neutral gemini surfactant and silica precursor. Depending on the heat resistance (1000
C.), water resistant (at 100.degree. C. for 150 hours or more), for the production of mesoporous molecular sieves.

As a method of producing silica gel containing no impurities, a method of purifying a gel obtained by neutralizing an alkali silicate salt and a method of hydrolyzing a silicon alkoxide are known. In particular, the latter method is Since silicon alkoxide can be purified by distillation or the like, it is possible to obtain highly pure silica gel relatively easily. However, the silica gel obtained from the silicon alkoxide by the sol-gel method generally has a small average pore diameter and a wide pore distribution. Further, even if the silica gel is subjected to hydrothermal treatment, no remarkable improvement in performance has been reported.

[0008]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the object of the present invention is not only to have a large pore volume and specific surface area but also to have a narrow pore distribution, heat resistance and water resistance. It is to provide an excellent method for producing silica gel.

[0009]

The object of the present invention relates to a method for producing silica gel in which a silicon alkoxide is hydrolyzed and the resulting hydrogel is hydrothermally treated without substantially aging it.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The silica gel of the present invention has a pore volume and a specific surface area in a range larger than usual, and the pore volume is 0.6 to 1.6 ml / g, preferably measured by a nitrogen gas adsorption / desorption method. Is 0.8 to 1.6 ml / g. The specific surface area is 300 to 1000 m ² / g, more preferably 30.
0 to 900 m ² / g, particularly preferably 400 to 900 m ²
/ G. These pore volume and specific surface area are measured by the BET method by adsorption and desorption of nitrogen gas.

Furthermore, the silica gel of the present invention was characterized by E.V. based on the isothermal desorption curve measured by the nitrogen gas adsorption / desorption method. P. Barr
ett, L .; G. Joyner, P.M. H. Haklen
da, J .; Amer. Chem. Soc. , Vol. 7
3,373 (1951), the pore distribution curve calculated by the BJH method, that is, the differential nitrogen gas adsorption amount (ΔV / Δ (logd); V is the nitrogen gas adsorption with respect to the pore diameter d (nm). The most frequent diameter (Dma
x) is less than 20 nm and the lower limit is not particularly limited,
It is preferably 2 nm or more. This means that the mode diameter (Dmax) of the silica gel of the present invention is in a range smaller than that of ordinary silica gel.

In the silica gel of the present invention, the volume of pores in the range of ± 20% of the above-mentioned mode diameter (Dmax) value is
It is also characterized in that it is usually at least 50%, preferably at least 60% of the total pore volume. Further, the volume of pores within the range of ± 20% of the value of the mode diameter (Dmax) is usually 90% or less of the total pore volume. This is
It means that the silica gel of the present invention is uniform in pores near the mode diameter (Dmax).

With respect to such characteristics, the silica gel of the present invention has a mode diameter (Dma) calculated by the above BJH method.
The differential pore volume ΔV / Δ (logd) in x) is usually 2.0 to 20.0 ml / g, especially 5.0 to 12.0 m.
1 / g is preferable (in the above formula, d
Is the pore diameter (nm), and V is the nitrogen gas adsorption volume. ). When the differential pore volume ΔV / Δ (logd) is included in the above range, it can be said that the absolute amount of pores aligned near the mode diameter (Dmax) is extremely large.

The silica gel obtained by the production method of the present invention is amorphous, that is, no crystalline structure is observed, in view of its three-dimensional structure in addition to the characteristics of the pore structure described above. It has characteristics. This means that when the silica gel obtained by the production method of the present invention is analyzed by X-ray diffraction, substantially no crystalline peak is observed. In the present invention, silica gel that is not amorphous means 6 angstrom (Å Un
It indicates at least one peak of the crystal structure at a position beyond its ds-pacing). Amorphous silica gel is much more excellent in water resistance than crystalline silica gel.

In addition, a series obtained by the manufacturing method of the present invention
The structure of kagel was analyzed by solid-state Si-NMR.
But you can get characteristic results. That is, solid-state Si-NMR
Then, in the silica gel obtained by the production method of the present invention, -O
Si (Q ³) And -OSi bond four
Si (Q^Four) And "Q^Four/ Q³Value of
It is usually 1.3 or more, preferably 1.5 or more. general
To "Q^Four/ Q³The higher the value of, the higher its thermal stability.
It is said to be good. "Q^Four/ Q³Is usually 10
It is the following.

The final characteristic of the silica gel obtained by the production method of the present invention is that the total content of metal impurities excluding silicon constituting the skeleton of the silica gel is usually 500 p.
pm or less, preferably 100 ppm or less, more preferably 10 ppm or less, most preferably 1 ppm or less, which is extremely high purity. The fact that the influence of impurities is small is one of the major factors that allow silica gel obtained by the production method of the present invention to exhibit excellent properties such as heat resistance and water resistance.

The production method of the silica gel of the present invention having the physical properties as described above should not be limited except that it is not aged substantially before the hydrothermal treatment, and an alkali silicate salt is hydrolyzed. The obtained silica hydrogel or the silica hydrogel obtained by hydrolyzing a silicon alkoxide can be produced by applying a hydrothermal treatment, and preferably a method of hydrolyzing a silicon alkoxide.

The silicon alkoxide used as a raw material for the silica gel of the present invention is a lower one having 1 to 4 carbon atoms such as trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Examples thereof include tri- or tetra-alkoxysilanes having an alkyl group or oligomers thereof, but tetramethoxysilane, tetraethoxysilane and oligomers thereof are preferable. Since the above silicon alkoxides can be easily purified by distillation, they are suitable as a raw material for high-purity silica gel. The total content of metal impurities in the silicon alkoxide is usually preferably 100 ppm or less, more preferably 10 ppm or less. The content of metal impurities can be measured by the same method as the method for measuring impurities in silica gel.

The hydrolysis of silicon alkoxide is usually 2 to 20 mol per mol of silicon alkoxide.
It is preferably carried out using 3 to 10 mol, particularly preferably 4 to 8 mol of water. Hydrolysis of silicon alkoxides produces silica hydrogels and alcohols. This hydrolysis reaction is usually from room temperature to about 100 ° C., but it can be carried out at a higher temperature by maintaining the liquid phase under pressure. The reaction time depends on the composition of the reaction solution (the type of silicon alkoxide and the molar ratio with water) and the reaction temperature, and the time until gelation differs, so it is not unconditionally specified. The reaction time is 6M hydrogel fracture stress
It is a time that does not exceed Pa. In addition, hydrolysis can be promoted by adding an acid, an alkali, a salt, or the like as a catalyst to the reaction system. However, the use of such additives is not very preferable in the production of the silica gel of the present invention, as it will cause aging of the hydrogel formed, as will be described later.

In the above hydrolysis reaction of the silicon alkoxide, the silicon alkoxide is hydrolyzed to produce a silicate, and subsequently, the condensation reaction of the silicate occurs, the viscosity of the reaction solution increases, and finally the gelation occurs. It becomes silica hydrogel. In order to produce the silica gel of the present invention, it is important to perform hydrothermal treatment immediately without substantially aging so that the hardness of the silica hydrogel produced by the above hydrolysis does not increase. Hydrolysis of silicon alkoxide produces a soft silica hydrogel. Stable aging or drying of this hydrogel is followed by hydrothermal treatment to finally obtain silica gel with controlled pore characteristics. According to the above method, it is not possible to produce silica gel having physical properties defined in the present invention.

Immediately performing hydrothermal treatment on the hydrogel of silica produced by hydrolysis without substantially aging means that the soft state immediately after the hydrogel of silica is maintained is maintained. , Which means to be subjected to the following hydrothermal treatment. It is not preferable to add an acid, an alkali, a salt or the like to the hydrolysis reaction system of the silicon alkoxide, or to make the temperature of the hydrolysis reaction too strict, because the aging of the hydrogel proceeds. Further, in the post-treatment after the hydrolysis, washing, drying, leaving and the like should not take more temperature and time than necessary.

As a means for specifically confirming the aging state of the hydrogel, the hardness of the hydrogel measured by the method as described in Examples below can be referred to. That is,
By subjecting a hydrogel in a soft state having a breaking stress of usually 6 MPa or less, preferably 3 MPa or less, more preferably 2 MPa or less to hydrothermal treatment, silica gel having physical properties defined by the present invention can be obtained.

As the conditions for this hydrothermal treatment, the state of water may be liquid or gas, and may be diluted with a solvent or other gas, but liquid water is preferably used. The silica hydrogel is usually 0.1 to 10 times by weight, preferably 0.5 to 5 times by weight, particularly preferably 1 times.
~ 3 times by weight of water is added to form a slurry, usually 40 ~ 2
At a temperature of 50 ° C., preferably 50 to 200 ° C., usually 0.
It is carried out for 1 to 100 hours, preferably 1 to 10 hours.
Water used for hydrothermal treatment may include lower alcohols, methanol, ethanol, propanol and the like. Further, this hydrothermal treatment method is also applied to a material in which silica gel is formed in a film or layer form on a substrate such as particles, a substrate, or a tube for the purpose of producing a membrane reactor or the like. It is also possible to carry out hydrothermal treatment by changing the temperature conditions using a reactor for hydrolysis reaction, but the optimum conditions are usually different between the hydrolysis reaction and the subsequent hydrothermal treatment. Obtaining the silica gel of the present invention is generally difficult.

Under the above hydrothermal treatment conditions, when the temperature is raised, the resulting silica gel tends to have a large pore size and a large pore volume. Further, with the treatment time, the specific surface area of the obtained silica gel tends to gradually decrease after reaching the maximum once. Based on the above tendency, it is necessary to appropriately select the conditions according to the desired physical property values, but since hydrothermal treatment is for the purpose of changing the physical properties of silica gel, it is usually higher temperature conditions than the above hydrolysis reaction conditions. Preferably.

If the temperature and time of hydrothermal treatment are set outside the above ranges, it will be difficult to obtain the silica gel of the present invention. For example, if the temperature of the hydrothermal treatment is too high, the pore size and pore volume of silica gel become too large, and the pore distribution also widens. On the other hand, if the temperature of the hydrothermal treatment is too low, the resulting silica gel has a low degree of cross-linking, poor thermal stability, no peak appears in the pore distribution, and the above-mentioned solid Si
Q ⁴ / Q ³ value becomes extremely small at -NMR.

When the hydrothermal treatment is performed in ammonia water, the same effect can be obtained at a lower temperature than when the hydrothermal treatment is performed in pure water. Further, when hydrothermal treatment is carried out in ammonia water, the silica gel finally obtained generally becomes hydrophobic as compared with the case of treatment in pure water, but it is usually 30 to 250 ° C., preferably 40 to 200 ° C. Hydrothermal treatment at high temperature makes it particularly hydrophobic. The ammonia concentration in the ammonia water here is preferably 0.001 to 10
%, Particularly preferably 0.005 to 5%.

The hydrothermally treated silica hydrogel is usually dried at 40 to 200 ° C, preferably 60 to 120 ° C. The drying method is not particularly limited, and may be a batch type or a continuous type, and can be dried under normal pressure or reduced pressure. If necessary, when the carbon content derived from the raw material silicon alkoxide is contained, it is usually 4
It can be removed by firing at 00 to 600 ° C. Further, in order to control the surface condition, firing may be performed at a temperature of up to 900 ° C. Further, the silica gel of the present invention finally obtained is obtained by pulverizing and classifying as required.

Silica gel having a crystal structure tends to have poor thermal stability in water, and when the silicon alkoxide is hydrolyzed in the presence of a template such as a surfactant used to form pores in the gel, The gel easily contains a crystalline structure. Therefore, in the present invention, it is preferable to hydrolyze in the absence of a template such as a surfactant, that is, under the condition that they do not exist in an amount sufficient to exert the function as a template.

[0029]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. (1) Hardness measurement of silica hydrogel 6 with silicon alkoxide in a 5 L separable flask
After reacting with a molar amount of water and the temperature of the reaction solution reached the boiling point of the alcohol produced by the reaction, the reaction solution was extracted from the flask, and the extracted reaction solution was put into a 50 cc glass screw tube at a certain amount (at the liquid depth). 20 mm), sealed and kept in a water bath controlled at a substantially constant temperature, and the puncture strength was measured by a digital force gauge (manufactured by A & D Co., Ltd., model:
AD-4935). A probe (a round bar made of stainless steel and having a diameter of 5 mm) is attached to the measuring instrument,
The hydrogel retained in the container is crushed by being pushed slowly into the hydrogel. The breaking stress was defined as the maximum stress value shown until the hydrogel was compressed and broken. The measurement results are shown in FIG.
FIG. 1 is a plot of the common logarithm of the aging time of silica hydrogel on the horizontal axis and the fracture stress on the vertical axis. Figure 1
It can be seen that the fracture stress increases with the aging time and that the aging rate depends on the temperature.

(2) Silica gel analysis method 1) Pore volume and specific surface area The BET nitrogen adsorption isotherm was measured with AS-1 manufactured by Cantachrome to determine the pore volume and specific surface area. Specifically, the pore volume adopts a value when the relative pressure P / P0 = 0.98, and the specific surface area is 3 of P / P0 = 0.1, 0.2, 0.3.
It was calculated using the BET multipoint method from the nitrogen adsorption amount at each point. In addition, the BJH method was used to determine the pore distribution curve and the differential pore volume at the mode diameter (Dmax). The distance between the measured relative pressure points was 0.025. 2) Powder X-ray diffraction RAD-RB device manufactured by Rigaku Denki Co., Ltd. was used to perform measurement using CuKα as a radiation source. The divergence slit was 1/2 deg, the scattering slit was 1/2 deg, and the light receiving slit was 0.15 mm. 3) Content of Metal Impurity Hydrofluoric acid was added to 2.5 g of the sample, and the mixture was heated to dryness and then water was added to make 50 ml. Using this aqueous solution I
CP emission analysis was performed. In addition, sodium and potassium were analyzed by the flame flame method. 4) Solid-state Si-NMR (Q ⁴ / Q ³ value) Using MSL300 solid-state NMR apparatus manufactured by Bruker, resonance frequency 59.2 MHz (7.05 Tesla), 7
mmCP / MAS (Cross Polarizati)
on / Magic Angle Spinning) probe. The sample rotation speed is 50
00 rps. (2) Manufacturing and evaluation of silica gel

Examples 1 to 3 5 L separable flask (with jacket) made of glass and equipped with a water-cooled condenser open to the atmosphere
Then, 1000 g of pure water was charged. While stirring at 80 rpm, 1400 g of tetramethoxysilane was charged into this over 3 minutes. The water / tetramethoxysilane molar ratio is about 6. 50 in the separable flask jacket
Hot water at ℃ was passed. The stirring was continued, and when the contents reached the boiling point, the stirring was stopped. Subsequently, warm water of 50 ° C. was passed through the jacket for about 0.5 hours to gelate the sol produced. Then, the gel was immediately taken out, and the gel was crushed through a nylon net having an opening of 600 microns to obtain a powdery wet gel (silica hydrogel). 450 g of this hydrogel and 450 g of pure water were charged into a 1 L glass autoclave, and hydrothermal treatment was carried out under the conditions shown in Table-1. After hydrothermal treatment for a predetermined time,
No. Filter with 5A filter paper and wash the filter cake without washing with water.
It was dried under reduced pressure at 0 ° C. until a constant weight was obtained.

Table 1 shows the physical properties of the obtained silica gel. The pore size distribution is shown in FIG. 2, the low-angle side of the powder X-ray diffraction spectrum is shown in FIG. 3, and the wide-angle side is shown in FIG. No crystalline peak appears in the powder X-ray diffraction pattern, and no peak on the low angle side (2θ ≦ 5 deg) due to the periodic structure is observed. The impurity concentration of the obtained silica gel was 0.2 ppm of sodium, 0.1 ppm of potassium and 0.2 ppm of calcium in all of Examples 1 to 3, and magnesium, aluminum, titanium and zirconium were not detected. .

Example 4 A silica hydrogel was produced in the same manner as in Example 1. 1
450 g of this silica gel and 450 g of 1% by weight aqueous ammonia were added to an L autoclave, and hydrothermal treatment was performed at 60 ° C. for 3 hours without stirring. Various physical properties of the dried silica gel are shown in Table 1, and its pore size distribution is shown in FIG. Comparative Example 1 The silica hydrogel produced in Example 1 was placed in a hermetically sealed container, left to stand in a cool dark place (10 to 15 ° C.) for 2 weeks for aging, and then hydrothermally treated at 60 ° C. for 3 hours in the same manner as in Example 1. Table 1 shows the physical properties of the dried silica gel. Comparative Examples 2 to 4 Silica gel CA for catalyst carrier manufactured by Fuji Silysia Chemical Ltd.
Table 1 shows various physical properties of RIACT G series (crushed)
FIG. 5 shows the pore size distribution of these. Moreover, when the metal impurity concentration of G-6 was measured, it was found that sodium 170p
pm, magnesium 31ppm, aluminum 15pp
m, potassium 23 ppm, calcium 160 ppm, titanium 260 ppm, and zirconium 44 ppm. Comparative Example 5 A part of the silica hydrogel used in Example 1 was treated at 60 ° C.
After vacuum drying for 48 hours in the same manner as in Example 1,
It was hydrothermally treated at 150 ° C. for 3 hours. Table 1 shows the physical properties of the dried silica gel.

[0034]

[Table 1]

(Heat resistance test of silica gel) Example 1,
2, 5 g of each of the silica gel samples of Comparative Examples 2 and 3 was placed in a quartz beaker and heated to a predetermined heat treatment temperature at 200 ° C./minute in an electric furnace in an air atmosphere. After holding at the predetermined heat treatment temperature for 1 hour, the beaker was immediately taken out to room temperature and allowed to cool. BET by nitrogen adsorption and desorption for this sample
The result of measuring the specific surface area by the method is shown in FIG. It can be seen from FIG. 6 that the silica gel of the example has a smaller change in the specific surface area upon heat treatment than the silica gel of the comparative example.

(Test of thermal stability of silica gel in water) Pure water was added to each of the silica gel of Examples 1 to 3 and Comparative Examples 2 to 4 to prepare a 40 wt% slurry. About 40 ml of the slurry prepared above was placed in a stainless steel micro bomb having a volume of 60 ml, sealed, and immersed in an oil bath at 280 ± 1 ° C. for 3 days. A part of the slurry was extracted from the micro bomb and filtered through 5A filter paper. Filter cake is 100
It was vacuum dried at ℃ for 5 hours. The results of measuring the specific surface area of this sample are shown in Table 2.

The powder X-ray pattern of the above sample was measured in the same manner as above except that the divergence slit 1 deg and the scattering slit 1 deg were used. Examples 1-3,
No peak was developed in the silica gel of Comparative Example 2,
It remained an amorphous pattern. On the other hand, in the silica gels of Comparative Examples 3 and 4, 2θ = in the amorphous pattern.
Clear peaks appeared at 20.9 ° and 26.6 °.
Since this peak coincides with the peak of α-Quartz, it is considered that the silica gels of Comparative Examples 3 and 4 are partially crystallized. The fact that these silica gels caused crystallization under high temperature and high pressure hydrothermal conditions and that the specific surface area decreased remarkably was due to the fact that these silica gels contained alkali metal at high concentration and changed in structure and shape. It is thought that this is because it is easy to cause.

(Silica gel crushing strength test) An IR tablet press (tablet diameter 20 mm) is used as a crusher, and the specific surface area and pore volume of the samples before and after crushing are measured by the BET method. Then, the magnitude of change in measured values before and after crushing is evaluated. The fact that the measured values before and after crushing do not change significantly is considered to indicate that the strength of the structural element related to the specific surface area and pore volume of silica gel is high. For the crushing of the above sample, 1.4 ± 0.2 g of the sample was used, and 4.0 t at normal temperature
It was carried out by applying a pressure of on / cm ² for 3 minutes. The results of tests conducted on the silica gels of Example 1 and Comparative Example 2 are shown in Table-3. Whereas the silica gel of Example 1 showed no significant change in specific surface area and pore volume,
The commercially available silica gel of Comparative Example 2 greatly deteriorated after the test.

[0039]

[Table 2]

[0040]

[Table 3]

High mechanical strength is required for industrially obtained silica gel. If they are used as they are, particles may be broken by contact with each other or with equipment to generate fine powder, which may cause a problem in the operation of equipment involving silica gel. Further, when used as a molded body, it is important that it can withstand the pressure applied at the time of molding, and if it does not have sufficient strength, it will be a molded body in which the original pore characteristics of silica gel are not utilized. Conventional silica gel is not strong enough. As is clear from Table 3, the silica gel of the present invention has sufficient crush strength.

[0042]

INDUSTRIAL APPLICABILITY The novel silica gel of the present invention has excellent heat resistance and water resistance, high stability, and high purity as compared with conventional silica gel. In addition, the silica gel of the present invention can be manufactured using a silicon alkoxide as a raw material in a relatively simple process and in which the silica gel is controlled in a desired physical property range.

The silica gel of the present invention can be used for conventional applications of silica gel, but particularly when it is used as a catalyst carrier, a membrane reactor, etc., performance deterioration is small and it can be used more stably for a long time.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between each aging time and the fracture stress of the hydrogel when the silica hydrogel is aged at each temperature of 35 ° C., 45 ° C. and 55 ° C.

FIG. 2 is a diagram showing a pore distribution of silica gel according to an example of the present invention.

FIG. 3 is a view showing a powder X-ray diffraction spectrum (low-angle side) of silica gel of an example of the present invention.

FIG. 4 is a diagram showing a powder X-ray diffraction spectrum (wide-angle side) of silica gel of an example of the present invention.

FIG. 5 is a diagram showing a pore distribution of a comparative example (commercial silica gel).

FIG. 6 is a diagram showing changes in specific surface area of silica gel of Example of the present invention and silica gel of Comparative Example due to heating.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Yamaguchi             Kitakyushu City Hachiman Nishi Ward, Kurosaki Castle Stone No. 1-1 Mitsubishi             Inside Chemical Co., Ltd. (72) Inventor Takayuki Yoshimori             Kitakyushu City Hachiman Nishi Ward, Kurosaki Castle Stone No. 1-1 Mitsubishi             Inside Chemical Co., Ltd. F term (reference) 4G072 AA28 BB13 CC10 HH30 MM01                       RR05 TT05 TT08 TT09 TT19                       TT30

Claims (10)

[Claims] 1. A silica gel having the following characteristics. (A) Pore volume of 0.6 to 1.6 ml / g, (b) specific surface area of 300 to 1000 m ² / g, (c) modal diameter (Dmax) of pores of less than 20 nm, (d) Dmax. The volume of pores within the range of ± 20% of 50% or more of the total pore volume,
(E) It is amorphous, and (f) the content of metal impurities is 500 ppm or less. 2. The silica gel according to claim 1, which has a pore volume of 0.8 to 1.6 ml / g. 3. The silica gel according to claim 1, which has a specific surface area of 400 to 900 m ² / g. 4. The silica gel according to claim 1, which has a mode diameter (Dmax) of 2 nm or more. 5. The silica gel according to claim 1, wherein the volume of pores within a range of ± 20% of the mode diameter (Dmax) is 60% or more of the total pore volume. 6. The silica gel according to claim 1, wherein the content of metal impurities is 10 ppm or less. 7. The silica gel according to claim 1, wherein the content of metal impurities is 1 ppm or less. 8. The silica gel according to claim 1, which has a differential pore volume at a mode diameter (Dmax) of 2.0 to 20.0 ml / g. 9. The silica gel according to claim 1, which has a Q ⁴ / Q ³ value of 1.3 or more in solid-state Si-NMR. 10. The silica gel according to claim 1, which is produced through a step of hydrolyzing a silicon alkoxide.