JPH0615427B2 - Inorganic porous body and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an inorganic porous material having a uniform entanglement structure of pores and constituent skeletons (spherical or spherical with a uniform particle size), and a method for producing the same. .

[Conventional technology]

The inorganic porous material has been conventionally used for applications such as a catalyst carrier, an adsorbent, and a filtration material. It is considered that the reason why the inorganic porous material is used in such a field is that the inorganic material is excellent in rigidity, heat resistance and chemical resistance. On the other hand, the demands on the characteristics of the pores of the inorganic porous material have become diverse and precise depending on the application. Particularly, in a chromatographic carrier, a catalyst carrier, a molecular sieve, a functional group-immobilized matrix, a porous molding material and the like, more uniform macropores (the macropores in the present invention are 10
It means a hole having a hole diameter of 00Å or more. ) Is advantageous, and a material having a higher porosity is strongly desired.

Conventionally, silica gel, porous glass, etc. have been used as the inorganic porous material. Silica gel is usually produced by reacting sodium silicate with sulfuric acid or hydrochloric acid to give silica hydrogel through silica gel, washing with water, drying and, if necessary, firing. The silica gel thus obtained has excellent properties such as a wide pore size distribution or a small pore size (several hundred liters). The method for producing silica gel is described in, for example, JP-A-58.
-1004017 and JP-A-47-5817.

In addition, porous glass is formed by melting borosilicate glass of a specific composition, heat-treating it within a certain temperature range to cause phase separation, and then acid-treating and washing with water to remove the eluted phase and further drying. Manufactured. Such porous glass is
Typically, in addition to 96% silicic acid anhydride, boric acid anhydride and sodium oxide are included as constituent components, so that not only the chemical resistance of acids and the like is limited, but also the pore volume is generally small. The porous glass manufacturing method is described in, for example, US Pat.
06, 744 (1934).

[Problems to be solved by the invention]

The present invention provides an answer to the requirement for the pore characteristics of such an inorganic porous material. In addition, the present invention provides an inorganic porous material having particularly excellent rigidity and chemical resistance.

[Means and Actions for Solving Problems]

As a result of intensive studies to overcome such limitations of the prior art, the inventors have found that there is a structure similar to the structure by spinodal decomposition, which has substantially silicic acid anhydride as a structural unit, and has not been found in the past. The present invention was accomplished by devising a non-porous inorganic material and a method for producing the same. According to the present invention, in particular, a high porosity while maintaining its rigidity is possible, and a great effect is expected in a field of use such as a chromatographic carrier, a catalyst carrier and a molecular sieve.

The feature of the present invention is that the pores and the constituent skeleton are uniformly entangled with each other, and the total pore volume when the pore diameter (D) is in the range of 1/2 ≦ D ≦ 2 is the total pore volume. 80% or more,
Furthermore, the constituent skeleton diameter (D ') The sum of the constituent skeleton volumes within the range of 8 is the total constituent skeleton volume
It is 0% or more. Here, the "average pore diameter ()" is a pore diameter selected so that the volume occupied by pores larger than the pore diameter is equal to the volume occupied by pores smaller than the pore diameter.

Is a skeleton diameter selected so that the volume occupied by the skeleton larger than the skeleton diameter is equal to the volume occupied by the skeleton smaller than the skeleton diameter. This feature is clearly shown in the figures attached to the examples. The second feature is that the average pore diameter is 1000Å to 50000Å. Outside of this range, it is difficult to obtain the above uniform entangled structure. Furthermore, the third feature is that the inorganic porous material substantially contains silicic acid anhydride as a constituent unit. Here, it is meant that the substantial part forming the skeleton of the inorganic porous material is a three-dimensional polymer containing 98% or more by weight of silicic acid anhydride as a constituent unit. If the content of silicic acid anhydride is less than 98%, impurities (inorganic salts and inorganic oxides) mixed with each other reduce chemical resistance, particularly acid resistance.

The weight percentage in this case is calculated in a dry state containing no volatile substances such as water.

The characteristics of the pores of the inorganic porous material obtained in the present invention are measured by the mercury penetration method. That is, the pore diameter and the volume of the pore in the pore diameter configuration are respectively determined by the pressure and the amount of pressure when the pressurized mercury is pressed into the pore. The average skeleton diameter is measured by the hydrofluoric acid dissolution method and the subsequent mercury intrusion method. That is, a bifunctional compound such as divinylbenzene and a radical-polymerizable compound such as styrene are put in a liquid into the pores of the inorganic porous material and polymerized to form a three-dimensional cross-linked polymer.
The inorganic porous material constituent is dissolved by treating with a 0% aqueous solution of hydrofluoric acid, and then the constituent skeleton diameter of the inorganic porous material constituent is measured as pores by the mercury porosimetry.

In order to produce the inorganic porous material of the present invention, silicic acid anhydride forming the substantial part of the inorganic porous material and a specific inorganic salt or a mixture of inorganic salts serving as a template for forming the pores are used. Silicic anhydride is supplied in the form of silica sol. The usual concentration is 10 to 50% by weight relative to water, preferably 20 to 4
It is 0%. Other forms, such as powdered silicic anhydride dispersed in water, or a dispersion of gelled silica in water, may be used, but generally do not give good results. The inorganic salt used in the present invention is (1) a compound having a high affinity with silicic acid anhydride and easily adaptable to it, and (2) having a melting point between 400 ° C and 800 ° C during sintering after mixing with silicic acid and drying. The compounds shown are preferred. The sintering operation is carried out at a temperature higher than the temperature at which the silicic acid sintering advances, as described in (1) above.
The conditions of (2) and (2) are closely related to the sintering temperature. This is because the added inorganic salt is melted to be in a liquid state at the sintering temperature, and further, the interaction acts at the interface between the liquid phase of the inorganic salt and the solid of silicic acid anhydride. This is because it is considered that the structure described in the range is formed.

Although all the inorganic salts satisfying the above conditions (1) and (2) can be used, particularly preferable specific examples include molybdate, molybdenum oxide, and molybdenum oxide or molybdate and phosphoric acid. A salt mixture system, an alkali metal chloride such as sodium chloride and potassium chloride, an alkali metal sulfate such as potassium sulfate, and a mixture thereof with an alkaline earth metal salt such as calcium chloride are effective. Regarding molybdenum oxide type, it is difficult to use as it is because the solubility of molybdenum oxide in water is small, and in the form of ammonium molybdate, which is oxidized during sintering to molybdenum oxide and has high solubility in water. It is preferable to use.

Such an inorganic salt is mixed with the silica sol as an aqueous solution or an acidic solution. The pH of the working solution is 0 to 10, particularly preferably 1 to 5. When the pH is below this range, the acidity is strong, so the acid resistance of the material of the synthesizing apparatus is required, and above this range, the formed silica gel is dissolved.
The amount of the inorganic salt is not particularly limited, but is usually 0.5 to 10 times the volume of silicic anhydride (pore volume 0.2 to 4.5 ml /
g), preferably 1 to 6 times (pore volume 0.4 to
The range is 2.8 ml / g). If the amount of the inorganic salt is less than this range, the pore volume will be small and the properties of the inorganic porous material cannot be fully utilized. On the other hand, if it exceeds this range, the fracture strength of the inorganic porous material is significantly reduced, which is not preferable.

The first step for producing an inorganic porous material is to mix silica sol with a predetermined amount of an aqueous solution of an inorganic salt. At this time, in order to prevent the generation of silica gel and maintain the homogeneity of the aqueous mixture, it is preferable to acidify the mixture with a mineral acid before or after mixing.

The second step is to heat the mixture to 50-300 ° C, preferably 60-250 ° C and dry it by evaporating the water. In this drying step, a desired shape can be formed by using a heating container, heating plate, spray dryer or the like having a desired shape. Particularly, by using a spray dryer, a spherical inorganic porous material having a certain particle size distribution can be synthesized, and further, by using a uniform granulating device utilizing ultrasonic waves (Japanese Patent Laid-Open No. 59-95925), 20
A spherical inorganic porous material having a uniform particle size having a particle size of 0 μ or more can be synthesized. Such a spherical inorganic porous material is very useful in using a column packing material or the like. What is more, the packing state is more uniform because of the spherical shape than in the general crushable packing material, and it becomes a high performance column. In the case of a spherical inorganic porous material having a uniform particle size, the filling uniformity is further improved,
Higher performance can be achieved. It is preferable that the inorganic porous material of the present invention does not contain a heteromorphic substance or a foreign substance as much as possible. However, it is possible to allow the inclusion of impurities within a range that does not substantially change the properties of the inorganic porous material of the present invention. The time required for dewatering and drying varies depending on the drying temperature, method and size of the molded product, but is usually 1 second to 30 minutes. The third stage is firing. The firing temperature is usually between 400 and 1000 ° C. However, in order to achieve a given average pore size and narrow pore size distribution, the inorganic salt used must be melted and the temperature must not exceed 200 ° C. above the melting point of the inorganic salt. If it is lower than the melting point of the inorganic salt, the average pore size becomes remarkably small, and at a temperature higher than the melting point by 200 ° C. or more, the average pore size becomes too large. The firing time is usually 1
It is more than an hour, preferably 2 to 10 hours. The fourth stage is desalting. This is to remove the inorganic salt melted by calcination after cooling and solidifying it with a neutral or acidic aqueous solution. By this operation, the portion where the inorganic salt is removed remains as a hole. The aqueous solution used is neutral water or acidic water depending on the type and amount of the inorganic salt used. Alkaline water is unsuitable for dissolving the silicon oxide which is the skeleton of the inorganic porous material. The volume of the aqueous liquid is at least 5 times the volume of the fired product that is usually treated.

The obtained inorganic porous material is washed with water and dried if necessary, and then used.

〔Example〕

 Hereinafter, specific embodiments of the present invention will be shown by examples.

Example 1 185.6 g of sodium phosphate-phosphate was dissolved in 218 g of distilled water. On the other hand, ammonium molybdate 6
4.7 g was dissolved in 161 g water. The above two liquids were added to 200 g of Snowtex-30 (manufactured by Nissan Chemical Industries, Ltd. silica sol) to prepare a uniform liquid. This was spray dried to obtain spherical particles. 230 g of the obtained particles were fired in an electric furnace at 700 ° C. for 2 hours. Then, it was mixed with water 2 and treated at 80 ° C. for 1 hour. It is filtered and dried to obtain an average pore size of 3660Å from 1220Å to 10000.
Pore volume is 1.0 with pores distributed in a narrow range of Å
3 ml / g of spherical silica gel was obtained.

FIG. 1 shows a pore distribution diagram obtained by the mercury intrusion method, and FIG. 2 shows a constituent skeleton diameter distribution diagram obtained by the hydrofluoric acid method-mercury intrusion method. Further, the elemental analysis results of the obtained porous silica gel are SiO ₂ : 98%, MoO ₃ : 1.1%, Na ₂ O: 0.3%, P ₂ O ₅ : 0.
It was 5%.

Example 2 Snowtex-30, 120 g, and potassium chloride 4
A solution in which 8.07 g (0.645 mol), calcium chloride dihydrate 32.05 g (0.218 mol) and concentrated hydrochloric acid (2 ml) were added was added. The prepared slurry liquid was stable at pH 1.20. The melting point of the complex salt used is 670 ° C.
This was spray-dried to obtain 105 g of spherical particles. This was baked at 750 ° C. for 2 hours. This product was treated with 10 times amount of 1N hydrochloric acid aqueous solution at 80 ° C. for 1 hour, and then filtered and dried to obtain porous silica gel particles. The average pore diameter was 1200Å and the pore volume was 0.82 ml / g. The pore distribution diagram is shown in FIG. The elemental analysis results of the obtained porous silica gel were SiO ₂ : 98.7%, KCl: 0.6%, and CaCl ₂ : 0.7%. In addition, Table 1 shows the measurement results of the constituent skeleton diameter distribution.

Example 3 50 g of sodium nitrate and 94 g of diammonium phosphate
Was dissolved in 200 g of water. Snowtech-3 in the solution
286 g of 0 was added to make a uniform solution. The melting point of the oxide system (when fired) of the salt used is 552 ° C. This solution was evaporated to dryness at 200 ° C. while mixing on a hot plate with a heater. 220 g of the obtained powder was calcined at 650 ° C. for 2 hours. Then, the mixture was added to water 2 and stirred at 80 ° C. for 1 hour and dried. The obtained solid has an average pore size of 2700Å,
It was a porous silica gel having a pore volume of 1.12 ml / g. The pore distribution chart is shown in FIG. 4, and the constituent skeleton diameter distribution measurement results are shown in Table 1. The elemental analysis results of the obtained porous silica gel are SiO ₂ : 99.5%, Na ₂ O: 0.4%, P
₂ O ₅ : 0.1%.

[Effects of the Invention] The inorganic porous material of the present invention has a uniform entanglement structure of pores and constituent skeletons as described above, and therefore the pore size and the spatial distribution of pores are uniform. Since it has high strength and substantially contains silicic acid anhydride as a structural unit, it has excellent heat resistance and chemical resistance, and is particularly suitable for use as a chromatographic carrier, catalyst carrier, functional group-immobilized matrix, porous molding material, etc. it can. Further, according to the production method of the present invention, the above excellent inorganic porous material can be easily obtained.

[Brief description of drawings]

FIG. 1 is a pore distribution diagram of the inorganic porous material obtained in Example 1 of the present invention, and FIG. 2 is a constituent skeleton distribution diagram thereof. FIG. 3 is a pore distribution diagram of the inorganic porous material of Example 2. FIG. 4 is a pore distribution diagram of the inorganic porous material of Example 3.

Claims (3)

[Claims] 1. The total pore volume of the pore diameter (D) in the range of 1/2 ≦ D ≦ 2 (which represents the average pore diameter) is 80% or more of the total pore volume, and further, the constitution The total skeleton volume in which the skeleton diameter (D ′) is within the range of 1/2 ′ ≦ D ′ ≦ 2 ′ (where ′ represents the average skeleton diameter) is 80% or more of the total skeleton volume, and the average fine particle Pore size is 1000
An inorganic porous material having a silicic acid anhydride structural unit of up to 50000Å. 2. A silica sol having a melting point of 400 ° C. to 800.
After melting and dehydrating a uniform aqueous mixture consisting of an inorganic salt or an aqueous solution of a mixture of inorganic salts in the range of ℃, the inorganic salt, the inorganic oxide produced by calcination, or the melting point of the mixture or a temperature 200 ° C. higher than the melting point. The method for producing an inorganic porous material having substantially uniform silicic acid as a constituent unit, which has a structure in which pores and constituent skeletons are uniformly entangled, by firing in the range described above and further desalting. 3. A method according to claim 2, wherein a molybdate, molybdenum oxide, molybdate or a mixture of molybdenum oxide and a phosphate, a phosphate, and a potassium chloride-calcium chloride system is used as the inorganic salt. The method for producing an inorganic porous material according to item.