JPH0826716A - Production of porous spherical silica particle - Google Patents

Abstract

PURPOSE:To obtain perfectly spherical silica particles having a satisfactory particle size distribution by converting a silica sol into silica gel in an aq. soln. contg. carboxylic acid (salt) and an aliphatic nitrile compd. CONSTITUTION:A soln. of tetraalkoxysilane or water glass having 1.0-0.1mol/l concn. is hydrolyzed in the presence of a catalyst such as an aq. ammonia soln. or. gaseous ammonia to prepare a silica sol. This silica sol is brought into a reaction at 0-80 deg.C for 1.5-2.0hr in an aq. soln. contg. carboxylic acid (salt) and an aliphatic nitrile compd. to obtain the objective porous spherical silica particles having 1.5-5.0mum average particle diameter, 200-400m<2>/g specific surface area and 50-65% porosity. The carboxylic acid is contained in the aq. soln. in a molar ratio of 0.1-0.001 to the tetraalkoxysilane or water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing porous spherical silica particles, and more particularly to a method for producing porous spherical silica particles containing silica having a good particle size distribution (uniform particle size) as a main component. . The porous spherical particles containing silica as a main component and having a good particle size distribution are useful as a packing material for liquid chromatography, a catalyst carrier, a molecular sieve and the like.

[0002]

2. Description of the Related Art The following method is known as a method for producing porous spherical silica particles used as a packing material for liquid chromatography. A colloidal silica particle sol is formed in a polar liquid, formaldehyde and urea or melamine are added and polymerized to form spherical particles. Then, a method of burning organic matter at 550 ° C. to obtain porous spherical particles (Japanese Patent Publication No. 54-9588, Japanese Patent Publication No. 60-35173, and Japanese Patent Publication No. 61-78).
58). Method for producing porous spherical particles by partially hydrolyzing and polycondensing tetraalkoxysilane, and then further gelling with an alkaline solvent in an organic solvent (USP 3,667,909,
JP-A-50-140397). Here, ethanol, an ethanol-heptane mixed catalyst, or the like is used as the organic solvent. A method for producing porous spherical particles by subjecting a silica sol to a surfactant in an organic solvent to emulsify it and performing gelation reaction (JP-B-4-63810, JP-B-62-19362, JP-B-3-23486, JP-A-63- 162518). The organic solvent in this case is a linear unsaturated hydrocarbon (hexene, octene, heptene, etc.), a linear unsaturated halogenated hydrocarbon (1.2 dichloroethylene, trichlene, tetrachloroethylene, etc.), toluene, hexane, heptane, cyclohexane, benzene. , Xylene, chloroform, carbon tetrachloride, liquid paraffin and the like.

ZrO is added to impart alkali resistance.
₂ and TiO ₂ mixed porous spherical particles SiO ₂ —ZrO
₂ , SiO ₂ —TiO ₂ is also known. The production method is a method in which each mixed sol is gelled with an ammonia catalyst (JP-A-62-67450). SiO ₂ , ZrO ₂
Spray dry the mixture of colloids to make porous SiO
A method for producing _2- ZrO ₂ spherical particles is also known (JP-A-2-143159). Hydrolysis of methanol solution of tetramethyl orthosilicate with hydrochloric acid, addition of tributylborate and sodium acetate or sodium citrate, followed by vigorous stirring, and extruding from a porous silica tube into kerosene containing dissolved surfactant to form porous silica spheres. Methods for producing particles are also known (H. Mori et al.,
J. Ceram. Soc. Jpn., 101 , 1108 (1993)).

[0004]

Although porous spherical particles can be obtained by any of the conventional methods, the particle size distribution is not so good. Also known is a method of hydrolyzing and polycondensing tetraalkoxysilane with an ammonia catalyst to synthesize monodisperse spherical silica particles having a very good particle size distribution (W. Stoeber,
J. Colloid & Interface Sci., 26 , 62 (1968)). However, although the silica particles obtained by this method have a good particle size distribution, they are non-crystalline, non-porous particles, and are true spherical particles whose specific surface area is almost equal to the value calculated from the particle size. In view of the above situation, an object of the present invention is to obtain spherical silica particles having a good particle size distribution and being porous. Such particles are ideal as packings for liquid chromatography, catalyst supports, and molecular sieves.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that by forming a gel containing silica as a main component in the presence of a specific organic compound, The present invention has been achieved by finding that silica particles that are porous and have a good particle size distribution can be obtained. That is, the present invention is a method for producing porous spherical silica particles, characterized in that silica sol is silica gel in an aqueous solution containing a carboxylic acid or a carboxylic acid salt and an aliphatic nitrile compound.

In this case, a one-step method of hydrolyzing tetraalkoxysilane or water glass as a main component in an aqueous solution containing a carboxylic acid or a carboxylic acid salt and an aliphatic nitrile compound to produce silica sol and grow the gel is described. It is advantageous. Further, the carboxylic acid or carboxylic acid salt and the aliphatic nitrile compound may be added after partial hydrolysis of the tetraalkoxysilane or water glass.

Hereinafter, the present invention will be described in detail. The present invention is characterized in that the silica sol is generated and the gel is grown in the presence of a specific organic compound as described above, and the method of forming the silica sol is not particularly limited. The carboxylic acid or carboxylic acid salt and the aliphatic nitrile compound may be added to the preformed silica sol, or these compounds may be present from the stage of hydrolysis of the tetraalkoxysilane or water glass. Compounds to produce silica sol copolymer SiO ₂ units caused by hydrolysis, can be used as long as it grows to silica gel particles, for example tetraalkoxysilanes, may be mentioned water glass, SiO ₂ particles Most preferred is tetraalkoxysilane because it contains no impurities.

Tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetra ter.
t-Butoxysilane, tetrabutoxysilane, etc. can be used. The silica particles of the present invention contain silica as a main component, but ZrO ₂ , TiO _{2 and the} like can be added to the silica particles in a range that does not lose the characteristics of silica, usually in a range of 50% by weight or less. To obtain such composite particles, ZrO ₂ or T
It suffices that iO ₂ or the like is generated by hydrolysis and contained in the silica sol.

As the nitrile compound, a water-soluble aliphatic compound is suitable. With an aromatic compound such as benzonitrile, the reaction liquid has two layers, and spherical particles cannot be obtained. Among the aliphatic nitrile compounds, acetonitrile and propionitrile are particularly preferable.

As the carboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid and other aliphatic acids are effective. Dibasic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid are also effective. Lactic acid, malic acid,
Oxycarboxylic acids such as tartaric acid and citric acid are also effective. Further, aromatic acids such as benzoic acid, phthalic acid, salicylic acid, gallic acid and tannic acid are also effective. Further, as salts of these acids, sodium salts, potassium salts, ammonium salts and the like are effective.

In the hydrolysis of tetraalkoxysilane and the formation of silica sol in the present invention, it is preferable to add a catalyst such as ammonia or aqueous ammonia in order to accelerate the reaction. In the case of water glass, a mineral acid such as hydrochloric acid is used. The concentration of tetraalkoxysilane or water glass is 1.0 mol / 1 to 0.1 mol / 1, preferably 0.1.
It is 7 mol / 1 to 0.3 mol / 1. carboxylic acid/
The molar ratio of tetraalkoxysilane or water glass is 0.1.
〜0.001, preferably 0.06 to 0.02 is suitable. The balance mainly consists of an aliphatic nitrile compound and water. The reaction temperature is 0 ° C to 80 ° C, preferably 20 ° C to 50 ° C.
° C.

A reaction time of 1.5 to 2.0 hours is suitable. After the reaction, the slurry containing the gel is subjected to a conventional method,
The product is obtained by filtering, washing and drying. The porous spherical silica particles are spherical and have a particle size (average) of about 1.5 to
It is in the range of 5.0 μm. The specific surface area is 200-40
It is about 0 m ² / g and the porosity is about 50 to 65%.

[0013]

In the present invention, tetraalkoxysilane and the like are polycondensed by hydrolysis to form a polymer of SiO ₂ . At this time, the mechanism of action of the nitrile group and the carboxyl group is not clear, but the siloxane chain has -C≡N, -COO.
It is presumed that H is not coordinated to form a very long siloxane chain, and appropriately short chains are aggregated in a spherical shape and dehydrated to form a porous spherical silica gel particle. When observing the surface of the spherical particles with a high-resolution SEM, it appears that short string-like particles are entangled to form a sphere. The present invention will be specifically described below with reference to examples.

[0014]

【Example】

Example 1 Acetonitrile 5 in a 1 liter flask
Add 00 ml and distilled water 6.3 ml. Citric acid in the solution - monohydrate _{(HOOCCH 2 C (OH) (} COOH) CH 2 COOH .H 2 O)
2.0 g was added and completely dissolved. 73 g of tetraethoxysilane (TEOS) was added to this mixed solution and stirred. 25% ammonia water 200 when fully homogenized
The stirring was stopped as soon as ml was added. At this point, the concentration of citric acid was 1.35 × 10 ^-2 mol / 1, TEO
The concentration of S was 0.496 mol / 1. The solution immediately turned cloudy due to the addition of aqueous ammonia, but immediately returned to a clear solution. It was observed that white turbidity gradually started after a few minutes, and gel precipitation increased with time, and TEOS was hydrolyzed. These series of reactions were performed at room temperature.
After standing for 2 hours, the slurry was filtered off. Filter cake to 60 ℃
It was thoroughly washed with deionized water. After washing, vacuum drying was performed at 80 ° C. for 5 hours. As a result, a pure white powder was obtained.

Scanning electron microscope (SEM) of the obtained powder
Observation and specific surface area measurement (BET method) were performed. As a result, the average particle size was 3.1 μm (the maximum particle size was 3.5 μm).
m) Specific surface area: 360 m ² / g Porosity: 56.9% Porous spherical SiO ₂ particles having a good average particle size distribution of 1041Å. Photo 1 shows the particle shape and Photo 2 shows the particle surface shape. As can be seen from this photograph, the particles are spherical and have a very good particle size distribution (the particle size is uniform).

Example 2 The same reaction as in Example 1 was carried out except that 2.0 g of benzoic acid (C ₆ H ₅ COOH) was used instead of citric acid monohydrate. Obtained porous spherical S
The iO ₂ particles have an average particle size of 2.5 μm (maximum particle size of 3.0 μm).
m) Specific surface area 318 m ² / g Porosity 55.9% Pore average diameter 820Å.

Example 3 The same reaction as in Example 1 was carried out except that 2.0 g of succinic acid (HOOCCH ₂ CH ₂ COOH) was used instead of citric acid monohydrate. The obtained porous spherical SiO ₂ particles had an average particle diameter of 2.1 μm (maximum particle diameter of 2.5 μm
m) Specific surface area 285 m ² / g Porosity 52.3% Pore average diameter 760Å

Example 4 The same reaction as in Example 1 was carried out except that 3.5 g of sodium salicylate (HOC ₆ H ₄ COONa) was used in place of the citric acid monohydrate. The obtained porous spherical SiO ₂ particles had an average particle diameter of 1.7 μm (maximum particle diameter of 2.0 μm.
m) Specific surface area 295 m ² / g Porosity 58.0% Pore average diameter 800Å

(Embodiment 5) Into a 1 liter flask were placed 500 ml of propitrnitrile and 6.3 ml of distilled water,
2.0 g of citric acid-hydrate was dissolved in the solution. 73 g of tetraethoxysilane was added to this mixed solution and stirred. 25% ammonia water 200 when fully homogenized
ml was added at once and stirring was stopped, and the same operation as in Example 1 was performed. The obtained porous spherical SiO ₂ particles had an average particle diameter of 1.6 μm (maximum particle diameter of 2.1 μm).
m) Specific surface area 342 m ² / g Porosity 60.2% Pore average diameter 735Å

Example 6 The same reaction as in Example 1 was carried out except that 73 g of tetraisopropoxysilane was used instead of tetraethoxysilane. The obtained porous spherical SiO ₂ particles had an average particle diameter of 3.4 μm (maximum particle diameter of 3.8 μm).
m) Specific surface area 319 m ² / g Porosity 62.3% Pore average diameter 552Å

(Example 7) A 1-liter flask was charged with 500 ml of acetonitrile and 12.6 ml of distilled water, and 2.0 g of citric acid hydrate was dissolved in the solution. To this solution, 146 g of tetraethoxysilane was added and stirred. The following operations were performed in exactly the same manner as in Example 1. The obtained porous spherical SiO ₂ particles had an average particle diameter of 2.7 μm (maximum particle diameter of 3.1 μm).
m) Specific surface area 328 m ² / g Porosity 52.6% Pore average diameter 917Å.

Comparative Example 1 The same reaction as in Example 1 was carried out without using any carboxylic acid. Small spherical particles were obtained but were non-porous. Average particle size 0.8μm (maximum particle size 1.0μ
m) Specific surface area 16 m ² / g

[0023]

According to the method of the present invention, silica particles having a large porosity and surface area, and having a spherical shape and a good particle size distribution can be obtained. Therefore, the particles are extremely useful as a packing material for liquid chromatography, a catalyst carrier, a molecular sieve and the like.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (6,000) showing the structure of porous spherical silica particles obtained by the method of the present invention.
Times).

FIG. 2 is a partially enlarged photograph of FIG. 1 (80,000 times).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01N 30/48 K

Claims (5)

[Claims] 1. A method for producing porous spherical silica particles, characterized in that silica sol is silica gel in an aqueous solution containing a carboxylic acid or a carboxylic acid salt and an aliphatic nitrile compound. 2. A method for producing porous spherical silica particles, which comprises hydrolyzing tetraalkoxysilane or water glass as a main component in an aqueous solution containing a carboxylic acid or a carboxylic acid salt and an aliphatic nitrile compound. 3. Tetraalkoxysilane or water glass as a main component is hydrolyzed to form a silica sol, and a carboxylic acid or a carboxylic acid salt and an aliphatic nitrile compound are added to the sol to form silica gel. And a method for producing porous spherical silica particles. 4. The method for producing porous spherical silica particles according to claim 1, wherein the aliphatic nitrile is acetonitrile, propionitrile, or a mixture of both. 5. The method for producing porous spherical silica particles according to claim 2, wherein ammonia or aqueous ammonia is used as a catalyst for the hydrolysis of tetraalkoxysilane.