JPH0323211A - Production of silica gel having large pore diameter - Google Patents

Abstract

PURPOSE:To easily obtain silica gel having a large pore diameter and satisfactory pore distribution by treating porous silica impregnated with phosphoric acid having a prescribed concn. at a prescribed temp. and by washing the silica with an aq. ammonia soln., etc. CONSTITUTION:Porous silica is impregnated with phosphoric acid having 2-50wt.% concn. (expressed in terms of P2O5). The silica is heat-treated at 100-700 deg.C and washed with an aq. ammonia soln., an aq. soln. of a strong org. base or dil. hydrochloric acid or washed with the ammonia or base soln. and further washed with the hydrochloric acid.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a large pore size silica gel, and more particularly, to a method for preparing a large pore size silica gel with high strength and a sharp pore distribution. It is something.

(Prior art) The field in which silica gel with a large pore size of 50 nm (500 A') or more is required has expanded significantly in recent years, and it is widely used as a catalyst support, liquid chromatography (particularly in the field of biochemistry), and other applications. ing.

The manufacturing method is also a method of adding inorganic substances and high-temperature heat treatment (
West German Patent No. 2,042,910, Japanese Unexamined Patent Publication No. 1973-
5811), hydrothermal treatment method (one example is West German Patent No. 2,225,452, Japanese Patent Publication No. 61-2048)
7), organic matter-added silica coacervate calcination method (U.S. Patent No. 3,855,172, Japanese Patent Publication No. 54-9588,
Japanese Patent Publication No. 617858), a method of gelling colloidal silica (or polytetraethoxysilane, etc.) with a surfactant in a polar solvent (Japanese Patent Publication No. 58-1040)
No. 17, West German Patent No. 2,155,281), or an improved olefin hydrogenation catalyst impregnated with phosphoric acid and passed through steam to improve its strength (US Pat. No. 2,960, No. 477, 3,917,72
No. 1) etc. are conventionally known.

(Problem to be Solved by the Invention) However, in any of the above methods, it is currently quite difficult to prepare a material with good physical properties and strength. In other words, the pore distribution is poor or the pore diameter is ionm.
At a certain level or more, the pore structure changes drastically and the strength decreases. Furthermore, West German Patent No. 2,042,91
As in the case of No. 0, the silica gel produced may contain crystallized material or be weak due to the high temperature treatment or the atmosphere, and furthermore, due to the high temperature oxidizing atmosphere, the equipment used may This includes the problem that the damage may be large.

Porous silica, which is solid silica with pores (mainly solid silica is in an amorphous state), is used as a raw material, but it may change to crystalline silica in high-temperature treatment methods.
In order to prepare a good chromatographic packing material from non-quality (amorphous) silica, it is desirable to use a low temperature treatment method.

An object of the present invention is to provide a method for preparing large pore size silica gel with a good pore distribution using a simple process.

(Means for Solving the Problems) In order to achieve the above objectives, the present invention selects optimal additives and further improves the surface and pore distribution of the product.
It also undergoes finishing treatment to improve strength.

That is, the present invention is characterized in that porous silica is impregnated with phosphoric acid, heated for 521 days, and then washed with aqueous ammonia, a strong organic base aqueous solution, or dilute hydrochloric acid, and further treated with aqueous ammonia or a strong organic base aqueous solution. This is a method for producing large pore size silica gel, which is characterized in that the washed silica gel is then washed with dilute hydrochloric acid.

Porous silica, which is the raw material of the present invention, can be obtained by, for example, reacting an aqueous alkali metal silicate solution with an aqueous mineral acid solution, washing a silica hydride gel, and then drying it by heating. 100μ. Pore volume 0.3-1.5d/
g, specific surface area 300-500rtt/Q, pore diameter 20
Examples include spherical silica gel of about 500A.

The degree of phosphoric acid used for impregnation is 2 to 50% by weight, preferably 5 to 25% by weight, calculated as P205. The porous silica impregnated with phosphoric acid can then be pre-dried at a temperature that does not cause much reaction (approximately 90° C.) and dispersed in a sieve to obtain a product with better pore distribution. The subsequent heat treatment is carried out at 100 to 700°C, preferably 150 to 600°C, for 3 to 50 hours to obtain a silica gel with large pores.

In addition, when it is desired to obtain an even larger pore size, the above-mentioned impregnation,
The heat treatment may be repeated, and in this way, it is possible to obtain a large pore size silica gel having an average pore size of 50 nm (500A > several μm), which is the object of the present invention.

Phosphoric acid concentration is less than 2% by weight or heat treatment temperature is 100%
When the temperature is less than 0.degree. C., the degree of evaporation drying due to heating is small, and the effect of increasing the pore diameter is small. Further, if the phosphorus 1m concentration exceeds 50% by weight, excessive dissolution reaction occurs, which is not appropriate.

Further, when the heat treatment temperature exceeds γOO°C, crystallization begins to occur. By the way, as a result of this heat treatment reaction, deposits such as silicon phosphate and silicon pyrophosphate adhere to the pore surfaces of the silica gel, which may cause the gel to be colored brown. It also affects the chromatographic properties. In order to wash away this silicon phosphate or various types of silicon pyrophosphate compounds and create an active silanol surface, washing with dilute hydrochloric acid may be used. , or washing with stirring for about 5 to 10 hours in an aqueous solution of a strong organic base such as 5 to 20% by weight of phenyltrimethylammonium hydroxide, penzyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetraethylammonium hydroxide, guanidine, etc. By doing so, a large pore size silica gel with a good pore distribution can be obtained. Silica gel that has been washed with ammonia water or a strong organic base aqueous solution is further heated and washed at about 90°C in 2 to 5 NmM, so that the pore distribution becomes sharper, the strength of the silica gel itself is greatly improved, and the amount of impurities increases. will also decrease significantly. Other methods such as cleaning with water vapor are also effective, and products with even better physical properties can be produced using these cleaning methods.

The present invention will be explained below with reference to Examples and Comparative Examples.

All percentages in the examples are based on weight.

Example 1 Silica gel 100 (It) (average particle size 7μ (5-10
μ), pore volume 1.02 d/O, specific surface area 423 Td
/ (J. Pore size 69A) in 15% phosphoric acid solution 200 (
Mix with J. After that, remove the remaining supernatant and heat at about 90℃ for 1
After pre-drying for 0 hours and dispersing with a sieve, the mixture was heat-treated at 300°C for 10 hours.

The silica gel after the heat treatment was placed in a 28% N solution 41 for 40 days, heated to about 50° C., stirred for 5 hours, and thoroughly washed until reaction products such as silicon phosphate were removed. Thereafter, it was washed with water, and further heated to about 90° C. in 5N Ichimoku α Solution 41 and washed with stirring for 5 hours. After washing with water, it was dried at 120° C. for 20 hours to obtain 85 g of silica gel. Its physical properties are as follows.

<Physical properties> Pore volume 0. 72d/(It specific surface area
37 butt/g Pore diameter 2239A The pore distribution is shown in FIG. It becomes very sharp compared to the raw material.

Note that these measurements were performed using a mercury borosimeter.

<Measurement of compressive crushing strength, analysis of phosphorus content> Inner diameter 54cm,
A test silica gel was placed in a stainless steel container with a height of 10 cm, and a load was applied using a compression tester, and the pressure at which it began to fracture by 10 to 20% was measured. Table 1 shows the phosphorus content in the silica gel.

Table 1: Measurement of compressive crushing strength, analysis of phosphorus content〉Table 2: Example 2 Using the same raw materials as Example 1, replacing the ammonia water with 10
1 q of 85 g of silica gel having the following physical properties was prepared in the same manner as in Example 1 except that 41% aqueous solution of tetraethylammonium hydroxide was used.

The measurement method is the same as the previous example.

physical properties〉 Pore volume 0. 76dlg Specific surface area 397Ff/g Pore diameter 2400mm The pore distribution is approximately the same as in Example No.

Comparative Example 1 100g of silica gel (average particle size 15μ (13-18μ
), pore volume 0.96 d/g, specific surface area 374 Trt/
0, pore size 103A) with 200g of 15% phosphoric acid solution.
Mix with. After that, the remaining supernatant was removed and heated to about 90℃ for 1 hour.
After pre-drying for 0 hours, fractionating with a sieve, heat treatment was performed at 150° C. for 10 hours. Next, it was heated to about 90°C in water 41, washed for 5 hours, and then dried at 120°C for 20 hours. The obtained silica gel had the following physical properties. The measurement method is the same as the previous example.

Physical properties〉 Pore volume ratio surface area Pore diameter <Analysis of phosphorus content> Unwashed product after heat treatment P: 7.8% Product washed with water after same treatment P: 0.328% Water washing alone does not clean silicon phosphate, etc. It is difficult to use it as a packing material for liquid chromatography because a considerable amount of part remains that cannot be removed.

Example 3 100 g of silica gel (average particle size 5μ (4-1μ), pore volume 0.97rfJ1/U, specific surface area 420Td/
g, pore size 68A) is mixed with 5% phosphoric acid solution 200Q. Thereafter, the remaining supernatant was removed, pre-dried at about 90°C for 10 hours, dispersed in a sieve, and then heat-treated at 150°C for 10 hours. After washing with water and drying at 120° C. for 20 hours, 90 g of the obtained silica gel is mixed again with 200 g of a 10% phosphoric acid solution.

Afterwards, remove the remaining supernatant and preheat at approximately 90°C for 10 hours.
．． 8γml/Ill 209Td/g 456A After drying and dispersing in a sieve, it was heat-treated at 150°C for 10 hours. The silica gel after heat treatment is heated to 52 2N at about 90℃.
Washed in α solution for 5 hours, then washed with water, then heated to 120°C.
After drying for 20 hours, 83 g of silica gel was obtained. Its physical properties are as follows. The measurement method is the same as the previous example.

Physical properties> Pore volume O, 63 d/g Specific surface area 32 d/g Pore diameter 1118 A The pore distribution is shown in FIG. It becomes very sharp compared to the raw material.

Analysis of silica content, measurement of compressive crushing strength〉 Unwashed product after heat treatment P: 8.8% P: 250 ppm after washing with 2N-H (1' solution) The measured value of compressive crushing strength is that the raw material silica gel is approximately 500 km
cd, about 800k after hydrochloric acid cleaning! II/cIi.

(Operations and Effects of the Invention) As is clear from the above explanation, according to the method of the present invention, large pore diameters (approximately 50
Silica gel with a sharp pore distribution and high strength can be obtained. Note that even if other acids such as salts m, (iiWl, etc.) are used in place of the phosphoric acid used in the present invention, it is not possible to obtain silica gel with a large pore size. Coming is 600-70
The method of the present invention is extremely useful as it is sufficiently effective even at low Calo heat treatment temperatures, as it begins to contain crystallized silica gel at temperatures above about 0°C, which affects its strength and chromatographic properties.

[Brief explanation of drawings]

The drawings are graphs showing the pore distribution curve of the silica gel in the example measured with a porosimeter, and FIG. 1 (A) is the raw material silica gel of Example 1, and FIG. Figure 2 (A> is the raw material silica gel of Example 3, and Figure 2 (8) is the pore distribution curve of the silica gel according to the present invention in Example 3. The horizontal axis is the pore radius, and the vertical axis is the silica gel according to the present invention. represents the volume-based pore distribution.

Claims (5)

[Claims] (1) A method for producing large pore size silica gel, which comprises impregnating porous silica with phosphoric acid, heating it, and then washing it with ammonia water, a strong organic base aqueous solution, or dilute hydrochloric acid. (2) A method for producing large pore size silica gel, which comprises impregnating porous silica with phosphoric acid, heating it, washing it with ammonia water or a strong organic base aqueous solution, and then washing it with dilute hydrochloric acid. (3) Claim 1 wherein the heat treatment temperature is 100 to 700°C.
Or the manufacturing method described in 2. (4) The manufacturing method according to claim 1 or 2, wherein the phosphoric acid concentration (P_2O_5) is 2 to 50% by weight. (5) The manufacturing method according to claim 1 or 2, wherein the concentration of ammonia water is 5 to 30% by weight.