JPS62143817A - Production of silica gel for liquid chromatography - Google Patents

Abstract

PURPOSE:To readily produce the titled silica gel at a low cost, by reacting an aqueous solution of an alkali metal silicate with an aqueous solution of a mineral acid, gelatinizing the resultant aqueous solution of silicic acid, treating the aqueous solution with an aqueous solution of ammonia, filtering and washing the filtrate with water, wet pulverizing the resultant hydrogel, spray-drying the pulverized hydrogel, treating the spray-dried hydrogel with a mineral acid and drying the treated hydrogel. CONSTITUTION:An aqueous solution of an alkali metal silicate is reacted with an aqueous solution of a mineral acid to give an aqueous solution of active silicic acid at 3.0-4.0pH in 6.5-11.5wt% SiO2 concentration, which is then gelatinized while stirring. An aqueous solution of ammonia is then added to react with the formed silica hydrogel slurry and the reaction slurry is filtered and washed with water to give hydrogel, which is wet pulverized. The pulverized hydrogel is further spray-dried, treated with an aqueous solution of a mineral acid, washed with water and dried. According to this method, the aimed silica gel, having high performance and smooth surfaces without containing deformed particles and useful as a packing for liquid chromatography is obtained at a low cost by a simple method without using an organic solvent or organic material and further requiring troublesome operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a '-7IJ gel for liquid chromatography.

Silica gel has higher mechanical strength than polymer fillers such as cross-linked dextra/polyacrylamide, and it hardly swells or shrinks due to changes in pH, ionic strength, eluent composition, etc., so it is suitable for liquid chromatography. Widely used as a filler for graphics.

Liquid chromatography is classified into four types, adsorption type, two-partition type, ion conversion type, and molecular sieve type, depending on the principle of separation, and the properties of the packing materials used therein also differ.

That is, in the adsorption type, silica gel is used as it is; in the distribution and ion exchange type, organic compounds such as organic compounds or alcohol compounds are chemically bonded to silica gel; and in the molecular sieve type, silica gel is used as a Used by chemically bonding organic compounds.

[Conventional technology]

Conventionally, spherical silica gel and crushed silica gel are known as silica gel. Spherical silica gel is superior to crushed silica gel in terms of its performance and usage characteristics.

Furthermore, among spherical silica gels, when used as a packing material for liquid chromatography, it is required to strictly control physical properties such as average particle size, surface species, average pore diameter, and pore volume. That is, the average particle diameter is 10 to 50μ
1 surface area 600-500 pi/9. Average pore diameter 80-12
A spherical silica gel having physical properties of OA and pore volume of 08 to 1.2 a//g is desired.

However, such silica gel is not easy to manufacture and is expensive.

Conventionally, the following method is known as a method for obtaining 5-spherical silica gel.

(1) Japanese Patent Publication No. 1987-71515 discloses a method in which a water glass sol is emulsified in an organic solvent containing a first surfactant, and then a second surfactant is applied to form a gel. Are listed.

This method requires a distillation step to separate the organic solvent used for emulsification and silica gel, which is economically disadvantageous.

Furthermore, the physical properties of the obtained gel have not been determined, and its usefulness as a packing material for liquid chromatography is unknown.

(2) Japanese Patent Publication No. 54-9588 describes a method of forming spherical particles using colloidal silica as a binder using an organic material that is miscible with water and capable of being loaded with water.

What is obtained by this method is a mixture of silica sol particles and organic material, and in order to obtain silica gel, the polymerized organic material must be removed by a sintering process at 500° C. or higher and for 4 hours or more. Furthermore, the physical properties of the resulting gel are determined by the type of colloidal silica used as a raw material, and it is difficult to control the desired gel physical properties.

(3) Spray drying is known as a method for obtaining spherical gels without using organic solvents or organic materials as described above.

JP-A-53-65293 proposes a method of spray drying silica sol. However, when the present inventors carried out this method, the product was spherical but hollow or dog-shaped. It was found that silica gel tends to have a -Y appearance.

When silica gel having such γC hollows or large depressions is used as a packing material for liquid and romatoxy, it is not preferable because its strength is insufficient and it tends to break or spread the separated sample.

In Japanese Patent Publication No. 45-7012, a sulfuric acid solution is kelized with gaseous carbonization gas, aged, treated with sulfuric acid, and then spray-dried. 100-10
05-1.25 cc with surface area of 00 r11'79
A method for obtaining silica gel with a pore volume of /9 is described.

Since this method uses gaseous carbon dioxide, it is not easy to control the reaction and it is difficult to control the physical properties of the silica gel obtained.

Japanese Patent Publication No. 47-3446 discloses a method in which a silica hydrosol with a pH of 96 to 10.9 is prepared by reacting an aqueous alkali metal silicate solution with a mineral acid, gelled, and further reacted with a mineral acid to form an acidic silica gel slurry and spray-dried. has been reported.

In this method, according to the example, 740 m'
Silica gels with very large surface areas ranging from /9 to 965 m'/9 have been obtained. Such a high surface area θ)
Silica gel generally has micropores of 50A or less. When the silica gel is intended to be used as a filler for liquid chromatography, such micropores not only make the 4F less effective for separation, but also cause a decrease in the strength of the silica gel.

Furthermore, in Japanese Patent Publication No. 47-55676, sodium silicate and sulfuric acid are mixed at 23 to 50°C and the pH is 9.8 to 10.4.
A method is described in which a mixed solution is prepared, a hydrogel slurry is formed therein, the pH is lowered to below 5 after aging, the pH is raised to 8-10.2 after aging, and the pH is aged and spray-dried. There is.

The silica gel obtained by this method has a surface area of 0.9 to 1.1511 according to the examples, 194 to 560 b/9.
It has a pore volume of 79, but the average pore diameter is not specified. Furthermore, as mentioned above, there are many ripening steps, and the operation is complicated.

Special Publication No. 43-7012, No. 47-3446.

No. 47-15676 Both methods require that the gel generation step be carried out on the alkaline side, but when the present inventors used slurry that had been similarly gelled on the alkaline side, the cause was unknown. However, it has been found that very brittle gels are often obtained, and gels with many irregularities on the surface or containing irregularly shaped particles other than spherical ones are often obtained. Such silica gel poses no problem as a normal drying agent, but when it is used as an optical filler for liquid chromatography, it is undesirable because it lowers the packing efficiency.

[Problem that the invention seeks to solve]

The object of the present invention is to produce a silica gel that is more efficient and inexpensive than the above-mentioned conventional techniques, has a smooth surface, is free of irregularly shaped particles, and has high performance as a packing material for liquid chromatography. Our goal is to provide the following.

[Means for solving problems]

The gist of the invention is a method for obtaining silica gel by spray drying a drogel slurry obtained by reaction with an aqueous solution of a mineral acid, such as an aqueous alkali metal silicate solution.

a. React an aqueous solution of alkali metal silicate with an aqueous solution of mineral acid to produce Sin at pH 3.0 to 4.0, concentration 6.5 to 11.
．． 5 wt% of active silicic acid is produced b, the silicic acid is gelled under stirring C, reacted with an ammonia aqueous solution, filtered and washed with water d, the resulting hydrogel is wet-pulverized e, and spray-dried. The method for producing silica gel for liquid chromatography is characterized in that the silica gel is brought into contact with an aqueous mineral acid solution and then dried, and the details thereof will be described below.

The alkali gold IIg silicate used in the present invention includes sodium silicate, potassium silicate, etc., but sodium silicate is generally used. As the mineral acid, sulfuric acid, hydrochloric acid, nitric acid, etc. can be used.

Although any method may be used to generate active silicic acid, a method of dropping an alkali metal silicate into mineral acid under elliptical stirring is preferred.

At this time, the final pH is 6.0-40 and the S+Ot concentration is 6.5.
It is necessary to adjust the respective concentrations and mixing ratios of the alkali metal silicate and mineral acid so that the concentration is ~11.5 wt%.

The pH value greatly affects the gelation time, and if the pH is less than 3, it will take a long time to gel, making it impractical. or becomes difficult.

The S IOt concentration of the produced silicic acid ultimately has a significant influence on the average pore size of the resulting silica gel.

That is, when the concentration of Sin is less than 6.5 wt%, the average pore diameter of the obtained silica gel is less than 80A, and the
When the concentration exceeds 11.5 wt%, the average pore diameter of the resulting silica gel exceeds 1d120A, and the gel has low strength.

The active silicic acid production temperature can be carried out in the range of 5 to 60°C, but 30 to 50°C is particularly favorable and practical. If the formation temperature is less than 5°C, gelation will take a long time, whereas if it exceeds 60°C, gelation will proceed rapidly, making it difficult to stably generate active silicic acid.

The aqueous solution of active silicic acid thus obtained is gelled under stirring to produce a slurry of silica hydrogel - the temperature of gelation is not particularly limited, but at low temperatures it may take a long time to complete gelation. On the other hand, at high temperatures, gelation proceeds rapidly and uniform stirring becomes difficult, so a temperature of 20 to 50°C is appropriate. In general, the lower the gelation temperature, the slower the gelation rate and the easier stirring, so for example, gelation Z is started at 20°C, made into a slurry, and then heated to 80°C to complete gelation. This method is also possible.

The stirring means may be of any type as long as it can crush the hydrogel produced when activated silicic acid gels to produce a hydrogel slurry, and a regular paddle-type stirring blade can also be used. However, if necessary, a high-speed stirring device or a kneader can also be used.

An ammonia aqueous solution is added to the generated silica hydrogel slurry and reacted. At this time, the concentration of the slurry is not particularly limited, but if the concentration is high, the viscosity will be high and stirring will be difficult, and if the concentration is low, it will be economically disadvantageous.
A suitable concentration is 5 to 1 wt%.

The higher the pH of the ammonia-treated solution, the larger the average pore diameter and the smaller the surface area of the final silica gel. For example, by adjusting the pH to 8.0 to 90, they can be adjusted to 80 to 120^ and 600 to 500 m/l, respectively.

The reaction temperature is not particularly limited, but a temperature of 60 to 90°C is appropriate since it takes a long time to complete the reaction at low temperatures.

After the reaction is completed, it is filtered and washed with water to remove by-produced alkali metal salts. If spray drying is performed without removing this by-product salt, crystals of the salt will precipitate in the resulting silica gel.
The bore may become uneven or tight.

The resulting filter cake is dispersed in water and then wet-milled.

This pulverization treatment has a large effect on the particle surface condition and shape of the final silica kel. That is, the surface is smooth,
Grinding is essential in order to obtain silica gel that does not contain irregularly shaped particles. As the pulverization method, any wet method may be used, such as a ball mill, vibration mill, stirring ball mill, rod mill, friction disk mill, stone mill type colloidal, etc.

By spray-drying the pulverized silica hydrogel slurry thus obtained, spherical silica gel can be obtained. Spray dryers are generally nozzle type, disc type, and two-fluid type, and any of them can be used.
When sipping Pfr gel with a particle size of about 10 to 50 microns, a disc type is suitable.

The temperature of the hot air for drying may be about io~300°C.

The spherical silica gel obtained by spray drying is subsequently treated with an aqueous mineral acid solution.

This treatment is particularly important when an organic compound is chemically bonded to silica gel and ionic substances such as nucleic acids, amino acids, and amines are to be separated using a partition type or ion exchange type single molecule cylinder type. That is, when the above-described separation was attempted using silica gel obtained without acid treatment, the separation sample phase often adsorbed or was rejected, making it difficult to perform sufficient separation.

Although the mechanism of action of mineral acids on silica gel is unknown, it has been found that by carrying out acid treatment, the decrease in separation ability due to adsorption or exclusion can be significantly improved.

As the mineral acid, sulfuric acid, hydrochloric acid, nitric acid, etc. can be used.

As a treatment method, it may be carried out by dispersing 7 Likakel in an aqueous mineral acid solution and stirring, or it may be carried out at a still temperature. In order to make the effect of this treatment as sufficient as K4z, it is desirable to adjust the concentration of the mineral acid aqueous solution so that the pt[ of the dispersion becomes 4 or less.

The treatment temperature is approximately ¥300 yen, but heating may also be used. The treatment time should be 50 minutes or more to achieve the desired effect.

The silica gel treated with acid in this manner is washed with water and then dried.

By the above method, it is possible to obtain a high-performance silica gel as an optical filler for liquid chromatography, which has a smooth surface and does not contain irregularly shaped particles.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to achieve a smooth surface and a mixture of irregularly shaped particles easily and inexpensively without using an organic solvent or an organic material, and without requiring complicated operations. It is possible to obtain high-performance silica gel as a packing material for liquid chromatography.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 500 g of a sulfuric acid aqueous solution having a concentration of 15 wt% was supplied to a reaction tank installed in a 50° C. constant temperature bath. While stirring the sulfuric acid aqueous solution with a paddle-type stirring blade, approximately 12609 of a sodium silicate aqueous solution having a concentration of 12Wj% was added to the sulfuric acid aqueous solution at pH 3.5.
Active silicic acid with a Sin2 concentration of 8.6 wt% was prepared. After about 10 minutes, the vaginal silicic acid aqueous solution thickened and started to gel. At this time, stirring was continued to complete gelation while crushing the hydrogel to obtain a silica hydrogel slurry.

Silica hydrogel slurry with pure water and a concentration of approximately 8w
Add % ammonia aqueous solution, Sin, 8 degrees approx. 6 w
After adjusting the t% and pH to 80, the reaction was carried out at 80° C. for 2 hours.

After completion of the reaction, it was filtered and washed with water, then dispersed in water and wet-pulverized using a Dyno Mill (manufactured by Quiley A. Batskoe Co., Ltd. →).
Spray drying was performed using a disc type spray dryer set at 0°C.

The obtained silica gel was suspended in an aqueous sulfuric acid solution, and the pH was adjusted to 5.
．． After acid treatment at room temperature for about 1 hour at 0°C, the mixture was filtered, washed with water, and dried at 110°C overnight.

The obtained silica gel was spherical, had a smooth surface, and contained almost no irregularly shaped particles.

In terms of physical properties, as shown in Table 1, it was suitable as a packing material for liquid chromatography.

Furthermore, in order to investigate the performance when an organic compound is chemically bonded to silica gel, silica gel 2 obtained by the above method was used.
0g was suspended in xylene 120d, octadecyltrichlorosilane 129 was added, and the mixture was reacted at 60°C for 3 hours.

After the reaction was completed, the product was washed with xylene, then with methanol, and then dried at 80° C. overnight. The obtained gel was packed into a column (diameter 18 x length 300111) and the elution behavior of 1-methylnicotinamide was investigated using a 3 wt % methanol aqueous solution as the mobile phase.As a result, there was almost no adsorption of the sample, and liquid chromatography was performed. It had high performance as a filler.

Example 2 100 g of an aqueous sulfuric acid solution with a concentration of 15 wt% was supplied to a reaction tank installed in a constant temperature bath at 20°C. While stirring the sulfuric acid aqueous solution with a paddle-type stirring blade, approximately 285 g of a 12 wt % silicate solution containing 12 wt % of 5iO = 93 degrees was added, and the pH was 4.
0 and a Sin2 concentration of 8.9 Wt%. After about 50 minutes, the hindlimb silicic acid aqueous solution started to gel.

The hydrogel is gelatinized while being crushed by stirring [8]
The temperature was raised to 0°C to complete gelation.

The obtained silica hydrogel slurry was subsequently prepared in Example 1.
A similar operation was performed to obtain silica gel.

The obtained silica gel was spherical and had a smooth surface, with almost no irregularly shaped particles mixed therein. As for the physical properties, as shown in Table 1, it was suitable as a packing material for liquid chromatography.

Further, in the same manner as in Example 1, octadecyl l-IJ dichlorolane was chemically bonded and the elution behavior of 1-methylnicotinamide was investigated. As a result, there was almost no adsorption of the sample, and it was found to have high performance as a packing material for liquid chromatography.

Comparative Example 1 Approximately 3,419 silicic acid aqueous solution with an Si02 concentration of 12 wt% was added to 200 g of a sulfuric acid aqueous solution with a concentration of 15 wt%, and the Si02 concentration was approximately 12.6 wt at pH 4.0.
The experiment was carried out under the same conditions as in Example 2, except that the activity level was increased.

The obtained silica gel was spherical and had a smooth surface, and did not contain irregularly shaped particles, but as shown in Table 1, it had a large average particle diameter, large pore size, and large pore volume, and was relatively weak.

Comparative Example 2 Same as Example 2, except that Sin, concentration 7.5W
Add 446g of sodium silicate to pH 4.0.
An experiment was conducted by preparing active silicic acid containing 9 degrees and 6.1 wt% of SiQ.

The obtained silica gel had a spherical shape, a smooth surface, and no irregularly shaped particles, but as shown in Table 1, the pore size was small and the pore volume was small.

Comparative Example 3 Same as Example 2, but without adding ammonia,
The test was performed at pH 6 at 80°C overnight.

The obtained silica gel had a spherical shape and a smooth surface, and contained almost no irregularly shaped particles, but had a small pore size as shown in Table 1.

Comparative Example 4 This was carried out in the same manner as in Example 1, but without wet grinding.

Although the obtained silica gel was spherical, the surface was uneven and contained irregularly shaped particles.

Comparative Example 5 This was carried out in the same manner as in Example 1, except that the acid treatment was not performed.

The obtained silica gel was spherical and had a smooth surface, and no irregularly shaped particles were present. In addition, the physical properties were desirable as shown in Table 1, but octadecyltrichlorosilane was further bonded in the same manner as in Example 1.
- As a result of investigating the elution behavior of methylnicotinamide, the sample was adsorbed to the gel and could only be removed from the bath, and it was not able to exhibit sufficient performance as an optical filler for liquid chromatography.

Table 1

Claims (1)

[Claims] (1) In a method for obtaining silica gel by spray drying a silica hydrogel slurry obtained by reacting an aqueous solution of an alkali metal silicate with an aqueous solution of a mineral acid, a. Reacting an aqueous solution of an alkali metal silicate with an aqueous solution of a mineral acid. SiO_2 concentration 6.5-1 at pH 3.0-4.0
1.5 wt% active silicic acid is produced b, the silicic acid is gelled under stirring c, reacted with an aqueous ammonia solution, filtered and washed with water d, the obtained hydrogel is wet-pulverized e, and sprayed. A method for producing silica gel for liquid chromatography, which comprises drying, contacting with an aqueous mineral acid solution, and then drying.