JPH1135314A - Production of inorganic porous body with large pore diameter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a porous body having large pore diameters and sharp distribution of pore diameters without changing the outer shape from an inorg. porous body having small pore diameters and wide distribution of pore diameters by impregnating the inorg. porous body with an inorg. salt soln., drying, calcining and removing the inorg. salt component. SOLUTION: An inorg. porous body, preferably a silica gel, is impregnated with an aq. soln. of inorg. salts (e.g. ammonium molybdate). The inorg. salts are one or more kinds selected from inorg. salts the oxides of which to be produced by calcining preferably have a melting point of 400 to 800 deg.C and/or one or more kinds selected from molybdates, molybdenum oxide, mixtures of molybdates or molybdenum oxide and phosphates, phosphates, alkali metal chlorides, alkali metal sulfates and mixtures of these with alkaline earth metal salts. Then the body is dried and calcined preferably at a temp. higher than the melting point of the oxides of the inorg. salts to be produced and lower than the temp. which is higher by 200 deg.C than the melting point, and then the inorg. salt component is removed preferably by using 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 an inorganic porous material having a large pore size and a sharp pore size distribution.

[0002]

2. Description of the Related Art Inorganic porous materials are conventionally used as catalyst carriers, adsorbents,
It is used for applications such as filtration media. The reason why inorganic porous materials are used in such fields is that the rigidity of inorganic materials, heat resistance,
It is considered to be excellent in chemical resistance. on the other hand,
There are various and precise requirements for the properties of the pores of the inorganic porous material depending on the application. In particular, in a chromatographic carrier, a catalyst carrier, a molecular sieve, a functional group-fixed matrix, a material for porous molding, etc., more uniform macropores (the macropores in the present invention mean large pores having a pore diameter of 1000 mm or more). ) Is advantageous, and materials with even higher porosity are strongly desired.

Conventionally, inorganic porous materials include silica gel and porous glass. Silica gel is usually made into a silica hydrogel by the reaction of sodium silicate and sulfuric acid or hydrochloric acid,
It is manufactured by washing with water, drying and, if necessary, baking. The silica gel thus obtained has a characteristic such that the pore size distribution is wide or the pore size is small (several hundred square meters). Proposals concerning a method for producing silica gel include, for example, JP-A-58-104017 and JP-A-47-5.
No. 817 publication.

[0004] Further, the porous glass is obtained by melting a borosilicate glass having a specific composition, molding, and then heat-treating the borosilicate glass within a certain temperature range to cause phase separation, followed by acid treatment and washing with water to remove the eluted phase. It is manufactured by drying. Such a porous glass typically contains boric anhydride and sodium oxide as constituents in addition to 96% of silicic anhydride, and thus has a limitation in chemical resistance of acids and the like. Generally, the pore volume is small. Such a porous glass manufacturing method is described in, for example, U.S. Pat. No. 2,106,744 (1934) and 4,
657,875 (1987).

[0005]

DISCLOSURE OF THE INVENTION The present invention is based on an inorganic porous material having a relatively small pore size and an inorganic large porous material having a structure with a larger pore size and a sharp pore size distribution. It is an object of the present invention to propose a method for producing a porous large-diameter porous body, and further to propose a method for producing an inorganic large-porous porous body capable of obtaining an inorganic large-porous porous body having excellent rigidity and chemical resistance. I do.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have accomplished the present invention. That is, the present invention is as follows. 1. A method for producing an inorganic large pore porous body, wherein an inorganic porous body is impregnated with an aqueous solution of an inorganic salt, dried and fired, and then an inorganic salt component is removed. 2. The inorganic porous material is silica gel, and the melting point of the oxide of the inorganic salt generated by firing the inorganic salt is from 400 ° C to 800 ° C.
C. is a kind of one kind of inorganic salt or a mixture of two or more kinds of inorganic salts, and the temperature at the time of firing is not lower than the melting point of the oxide of the inorganic salt generated by firing and not higher than 200 ° C. higher than the melting point. . 3. The method for producing an inorganic large-pore-diameter porous body according to 1.). 3. Inorganic salts are molybdate-based, molybdenum oxide-based,
Selected from the group consisting of molybdate or molybdenum oxide and phosphate mixtures, phosphates, alkali metal chlorides, alkali metal sulfates, and mixtures of these with alkaline earth metal salts At least one kind Or 2. 3. The method for producing an inorganic large-pore-diameter porous body according to 1.).

Hereinafter, the present invention will be described in detail. One of the features of the present invention is to use an existing inorganic porous material as a starting material. The inorganic porous body is not particularly limited, for example,
Examples of the inorganic porous material include silica, alumina, silica-alumina, titania, zirconia, and a mixture of two or more thereof. Among them, the porous silica material is most commonly used as represented by silica gel, and is preferable because of the high acid resistance of silica. The shape of the inorganic porous body is not particularly limited, but particles such as silica gel, pellets, and various molded bodies can be used. Hereinafter, a description will be given using silica as an example.

The inorganic salt used in the present invention is (1) a compound having a high affinity for silica, which is an inorganic porous material, and is easily compatible with the inorganic salt.
Compounds that exhibit a melting point between ° C. are preferred. Large pores tend to be obtained when the melting point is lower than the lower limit, and macropores formed when the melting point is lower than the upper limit tend to be maintained. The sintering operation is performed at a temperature higher than the temperature at which the sintering of silica proceeds. The conditions (1) and (2) are closely related to the sintering temperature. Because, at the sintering temperature, the added inorganic salt is melted to be in a liquid state, and furthermore, the interaction works at the interface between the liquid phase of the inorganic salt and the solid of silica,
This is because it is considered that the structure of the present invention is formed. Any inorganic salt that satisfies the above conditions (1) and (2) can be used, but particularly preferred specific examples are molybdate, molybdenum oxide, molybdate or molybdenum oxide and phosphate. It is composed of a mixture system, a phosphate system, an alkali metal chloride system such as sodium chloride and potassium chloride, an alkali metal sulfate system such as potassium sulfate, and a mixture system thereof with an alkaline earth metal salt such as calcium chloride. It is effective that it is at least one selected from the group. As for molybdenum oxide, it is difficult to use molybdenum oxide as it is because its solubility in water is small, and it is oxidized during sintering and changes to molybdenum oxide, and the form of ammonium molybdate which is highly soluble in water is also used. It is preferable to use them. Further, a salt containing each element of molybdenum, phosphorus and sodium is preferable.

[0009] The first step in producing a silica inorganic large pore porous material is to prepare an aqueous solution of an inorganic salt. Although water is used as the solvent, water is selected from the viewpoint of environmental safety. Other solvents, for example, polar solvents such as alcohols and dimethylformamide can also be used as long as they can dissolve the inorganic salt. The concentration of the solution is between 0.1% and 80% by weight, preferably between 5% and 80% by weight. When the concentration is higher than the lower limit, the inorganic salt is easily contained in the porous silica body by one impregnation / drying of the porous silica body, and the phase separation is facilitated. Therefore, the necessity of repeating the impregnation and drying steps is reduced, which is efficient.

Next, an aqueous solution of an inorganic salt is impregnated into the porous silica. The amount (volume) of the aqueous solution of the inorganic salt is 50 to 100%, preferably 60 to 90% of the pore amount (volume) of the silica porous material used.
It is. If the amount is less than the lower limit, the aqueous solution of the inorganic salt easily enters the pores of the porous silica material as a whole, and it is difficult for spots to occur. On the other hand, when the content is 100% or less, the inorganic salt aqueous solution hardly exists outside the porous silica material, the dissolved inorganic salt is effectively used, and when the silica porous material is particles, it is hard to cause coalescence. The porous silica is brought into contact with an aqueous solution of an inorganic salt under atmospheric pressure or reduced pressure. When the porous silica is a powder, the powder is mixed in a state of contact with an aqueous solution of an inorganic salt. The method of mixing is not limited, but an evaporator can be used or various mixers can be used. The mixing time is until the inorganic salt aqueous solution enters the porous silica material, and is, for example, 0.5 to 1 hour. When the porous silica body is a molded body, impregnation can be performed by bringing an inorganic salt aqueous solution into contact with the surface of the molded body.

Next, the porous silica body containing the inorganic salt aqueous solution is dried. The drying method is not particularly limited, and drying is performed under normal pressure or reduced pressure at normal temperature or while heating. As a result, the inorganic salt enters the pores of the porous silica material, and the volume ratio of the inorganic salt to the pores is 10 to 100%, preferably 30 to 100%, more preferably 50 to 100%.
%. If it is lower than 10%, the pore size is unlikely to be increased by sintering, and if it is higher than 100%, it may cause coalescence in the case of particles. The step of impregnating and drying the aqueous solution of the inorganic salt on the porous silica can be repeated several times to increase the volume ratio of the inorganic salt to the pores. The residual moisture content during drying is not particularly limited, but is preferably 0.1 to 10% by weight. The remaining baking process removes the remaining water,
If more than 10% by weight of water remains, there is a possibility that rapid evaporation occurs during firing and the structure of the porous silica material is broken.

Next, firing is performed. The firing temperature is usually 400 to 1
000 ° C. More preferably, 600 to 800
° C. However, in order to realize a predetermined average pore size and a narrow pore size distribution, it is desirable that the firing temperature be equal to or higher than the melting point of the inorganic salt used and not exceed 200 ° C. higher than the melting point of the inorganic salt. If the sintering temperature is higher than the melting point of the inorganic salt, the average pore size tends to increase, but if the sintering temperature is lower than the melting point of 10 to 20 ° C., the effect may be obtained to some extent. When the sintering temperature is 200 ° C. or lower, which is higher than the melting point of the salt, a desirable average pore diameter is easily obtained. In addition, the melting point in the present invention refers to a melting point of an oxide of an inorganic salt generated by firing the inorganic salt. The firing time is set in relation to the firing temperature. The baking is performed in a short time at a high temperature and for a long time at a low temperature. In consideration of workability and the like, it is preferable to hold at a predetermined temperature for 0.5 to 5 hours. More preferably, it is 1 to 3 hours. Here, for example, when a salt such as ammonium molybdate is used, calcining is performed at about 300 to 400 ° C. to remove ammonia, and then calcining is performed at the above temperature.

Next, inorganic salts are removed from the obtained fired product by washing. Any washing liquid can be used as long as it does not dissolve silica but dissolves an inorganic salt. Although there are acidic solutions of mineral acids such as hydrochloric acid and sulfuric acid, water is particularly preferable in terms of cost and environment. There is no particular limitation on the amount of the washing solution or the washing temperature, and conditions are set for removing 99% by weight or more of the inorganic salt in the porous silica material. It is preferable that the obtained solution of the inorganic salt is reused as necessary, or the inorganic salt is recovered from the solution.

According to the production method of the present invention, it is possible to obtain a porous silica material having a large internal pore diameter without changing its shape. The obtained porous silica material having a large pore diameter is used after being washed with water and dried if necessary. The drying method is not particularly limited. The pore diameter of the porous silica material having a large pore diameter according to the present production method can be changed by setting the firing conditions, and generally a pore diameter of 100 to 2000 nm can be produced.

[0015]

Embodiments of the present invention will be described below in more detail with reference to examples. The pore volume, average pore size, and pore size distribution of the porous body can be measured by a mercury porosimetry. In the present invention, Poremaster 60 manufactured by Qantachrome was used. In addition, the volume average particle diameter of the particles is Microtrac X-10 manufactured by Honeywell.
It was measured at zero.

The melting point of the salt is determined by a differential scanning calorimeter DSC 210
(Manufactured by Seiko Instruments Inc.). The measurement conditions are in air, the heating rate is 5 ° C./min, and the measurement temperature range is 25 to 8
00 ° C. The silica composition of the silica large pore porous material is I
CP (inductively coupled plasma) emission spectrometer IRIS-AP
(Manufactured by Thermojarrell Assy). Specifically, a 50 mg sample was precisely weighed on a platinum dish, 3 g of potassium sodium carbonate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) and 1 g of sodium tetraborate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) were added, and heated with a burner. And dissolved. Next, 15 ml of 6N hydrochloric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added. After boiling on a heater, pure water was added to 250 ml. Then, dilute 10-fold,
Quantification was performed using a P emission analyzer.

[0017]

Example 1 A volume average particle diameter of 45.8 μm was added to an inorganic porous material.
Silica gel 5D (trade name, manufactured by Fuji Silysia Chemical Ltd.) having a pore volume of 0.750 mL / g, an average pore diameter of 10 nm, and a silica composition of 98.1% was used. 7. 26 g of pure water, 1.6 g of nitric acid (manufactured by Wako Pure Chemical, special grade), 4.3 g of monosodium phosphate (manufactured by Ohira Chemical Industry, industrial use), and ammonium molybdate (manufactured by Nippon Inorganic Chemical Industry, industrial use) 6 g was added to make a homogeneous solution. The melting point of the mixed inorganic salt is 650.
° C. 20 g of silica gel 5D was placed in a 500 mL eggplant-shaped flask, and the above-mentioned inorganic salt aqueous solution 14.8 was added thereto.
mL (98.6% of the pore volume of silica) was added, and the mixture was rotated and mixed using a rotary evaporator for 30 minutes. Then, it dried at 70 degreeC under reduced pressure in a vacuum dryer for 5 hours. 11 mL of the above inorganic salt aqueous solution was added to the silica gel, and the mixture was rotated under the same conditions and dried. further,
9 mL of an inorganic salt aqueous solution was added, and the third rotation mixing and drying were performed. The resulting inorganic salt impregnated silica gel has a pore volume of 0.3
It was 32 mL / g.

10 mL of silica gel impregnated with an inorganic salt was calcined in an electric furnace at 350 ° C. for 1 hour and then at 650 ° C. for 1 hour. This was added to 100 mL of hot water at 60 ° C., and the mixture was held with stirring for 30 minutes. Thereafter, the mixture was filtered with filter paper, washed with excess water, and dried under reduced pressure. The resulting silica large pore porous particles had a volume average particle size of 45.8 μm, a pore volume of 0.999 mL / g,
The average pore diameter was 200 nm, and the silica composition was 99.6%.

[0019]

Example 2 10 mL of the silica gel impregnated with the inorganic salt of Example 1
Was fired in an electric furnace at 350 ° C. for 1 hour and then at 700 ° C. for 1 hour. The obtained fired product was washed and dried under the same conditions as in Example 1. The obtained large pore silica particles had a volumetric particle diameter of 45.8 μm, a pore volume of 0.985 mL / g, an average pore diameter of 350 nm, and a silica composition of 99.2%.

[0020]

According to the manufacturing method of the present invention, a porous body having a large pore diameter and a sharp pore diameter distribution can be produced from an existing inorganic porous body having a small pore diameter and a wide pore diameter distribution without changing the outer shape. As a result, the performance is greatly improved in applications to a chromatographic carrier, a catalyst carrier, a functional group-fixed base, and the like, which are more uniform and macropores are advantageous.

[Brief description of the drawings]

FIG. 1 is a diagram showing the pore size distribution of the silica gel used in the examples and the silica large pore porous materials obtained in Examples 1 and 2.

[Explanation of symbols]

1 is a pore size distribution of silica gel 5D which is a raw material of an example. 2 is a pore size distribution of the silica large pore porous body obtained in Example 1. 3 is a pore size distribution of the silica large pore porous material obtained in Example 2.

Claims (3)

[Claims] 1. A method for producing an inorganic large-pore porous body, wherein an inorganic porous body is impregnated with an aqueous solution of an inorganic salt, dried and fired, and then an inorganic salt component is removed. 2. The inorganic porous material is silica gel, and the melting point of an oxide of the inorganic salt generated by firing the inorganic salt is 400 ° C.
From 800 ° C. to a mixture of one kind of inorganic salt or two or more kinds of inorganic salts, and the temperature at the time of firing is not lower than the melting point of the oxide of the inorganic salt generated by firing and not higher than 200 ° C. higher than the melting point. The method for producing an inorganic large-pore-sized porous body according to claim 1. 3. An inorganic salt comprising a molybdate salt, a molybdenum oxide salt, a molybdate salt or a mixture of molybdenum oxide and a phosphate salt, a phosphate salt, an alkali metal chloride salt,
At least one selected from the group consisting of alkali metal sulfates, and mixtures thereof with alkaline earth metal salts;
The method for producing an inorganic large-pore-sized porous body according to claim 1 or 2, which is a seed.