JPH10338516A - Production of metal oxide intercalated into clay mineral - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deposition and dispersion of a metal oxide on the surface of a grain which has been inevitable in the conventional method and to provide a method for producing the metal oxide capable of being dispersed and confined in the layer structure of a clay mineral and intercalated into the clay mineral. SOLUTION: A metal oxide intercalated into a clay mineral is produced by this method. The clay mineral is swollen and diluted with water to form a sol. An organometallic compd. is added to an aq. soln. contg. org. acid to form a metallic compd.-contg. sol. The sol of the swollen clay mineral is added to the metallic compd.-contg. sol and agitated to intercalate the metallic compd. into the layer of the clay mineral. The clay mineral with the metallic compd. intercalated into the layer is washed, dehydrated, dried and calcined.

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 a metal oxide intercalated in a clay mineral, and more particularly, to a method of intercalating a metal oxide into a gap between the layers while maintaining a layered structure of the clay mineral. To a manufacturing method that can be performed.

[0002]

2. Description of the Related Art In a technique for intercalating a metal oxide into a clay mineral, which has been reported, a metal oxide precursor peptized / stabilized with a strong acid such as hydrochloric acid is used to swell the clay mineral. Sol (Bull. Che.
m. Soc. Jpn. , 65, 2494-2500 (1
992), Journal1 of Porous Ma
terials, 1, 29-41 (1995)).

[0003] In a mixture of a clay mineral and a metal oxide obtained by such a method, it is difficult to obtain a diffraction peak due to an interlayer crosslinked structure by X-ray diffraction. This prevents the metal oxide precursor from infiltrating between the layers because the clay mineral is agglomerated in the acidic solution, and the strongly acidic hydrochloric acid elutes not only the interlayer metal ions of the clay mineral but also the metal ions in the sheet. Therefore, it is considered that the clay mineral cannot maintain its layered structure, and as a result, loses its characteristic as a layered structure.

[0004] Accordingly, the resulting metal oxide has a large specific surface area and a relatively sharp pore distribution, but mainly deposits and aggregates in the voids and surfaces of the card house structure. In the catalytic reaction, in order to control the molecular size of the reactant and the product and to provide selectivity, it is desirable that the catalyst component be dispersed only within the pores. Therefore, an effect in terms of selectivity of a catalytic reaction utilizing a pore structure, that is, so-called shape selectivity, cannot be sufficiently obtained.

[0005] When the catalyst component is carried on the surface of the inorganic substrate or formed into a thin film, the component contained in the substrate may lower the catalytic performance in some cases. Further, when a thin film is formed on the surface of a plastic, or is dispersed in a paper or cloth by weaving or weaving, if the catalyst component is in direct contact, the organic matter may be decomposed / degraded. As a method of preventing these, the metal oxide of the catalyst component is intercalated with the clay mineral which is an inert substance to cover / block, but the effect is not sufficiently obtained because a large amount of the metal oxide is dispersed on the aggregated particle surface. .

[0006]

In a catalytic reaction, the molecular size of a reactant and a product can be controlled and limited by limiting the reaction site to the inside of a pore. Also, by coating the catalyst component with a clay mineral, decomposition / deterioration of the support can be prevented even when functioning as a photocatalyst.

Accordingly, it is an object of the present invention to prevent the deposition / dispersion of metal oxide precursors on the particle surface, which cannot be avoided by the conventional methods, and to disperse and trap only the clay mineral in a layered structure. An object of the present invention is to provide a method for producing a metal oxide intercalated into a mineral.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a sol of a clay mineral having a layered structure sufficiently swollen with water is converted into an organic metal containing an organic acid. By adding the compound oxide to the compound-containing sol, the present invention has been completed in which the metal oxide can be intercalated into the gap between the layers while maintaining the layer structure of the clay mineral.

That is, the present invention relates to a method for producing a metal oxide intercalated in a clay mineral, comprising the following steps: (a) a step of swelling and diluting a clay mineral having a layered structure with water to form a sol; (B) adding an organometallic compound to an aqueous solution containing an organic acid to form a metal compound-containing sol; (c) adding the swelled clay mineral sol to the metal compound-containing sol and stirring; A step of intercalating the metal compound between the layers of the swollen clay mineral, and (d) a step of washing, dehydrating, drying and firing the clay mineral in which the metal compound is intercalated between the layers. It is characterized by the following.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The production method of the present invention will be described below in detail. In the method of the present invention for producing a metal oxide intercalated into a clay mineral, first, the clay mineral is swollen with water to take in sufficient interlayer water into the clay mineral to form a sol having a maximum interlayer gap. In addition, an organometallic compound which is a metal oxide precursor is separately added to an aqueous solution containing an organic acid, mixed and stirred to peptize to obtain a stable sol.

The clay mineral used here is a phyllosilicate having a layered structure, such as smectite such as saponite / montmorillonite, vermiculite, and swelling mica. The metal oxide to be intercalated is a general metal oxide having catalytic activity. Among them, oxides such as titanium, zinc, iron, and tin having a photocatalytic function are exemplified. Examples of the organometallic compound include metal alkoxides, acylates and chelates.

As the alkoxide of the metal, for example, titanium tetraisopropoxide, titanium tetranormal butoxide, iron triisopropoxide, iron trinormal butoxide, tin tetranormal butoxide and the like can be used. As the metal acylate, for example, trinormal butoxytitanium monostearate, diisopropoxytitanium distearate and the like can be used. Further, as the metal chelate, for example, propanedioxytitanium bisethylacetoacetate, zinc acetylacetonate and the like can be used.

The organic acid used for stabilizing the sol includes carboxylic acids such as acetic acid, oxalic acid and formic acid. This organic acid is preferably at least equivalent to the organometallic compound and at a concentration of 3 N or less after mixing with the sol. Insufficient equivalent of the organometallic compound is not preferred because the metal oxide precursor sol lacks stability and cannot be intercalated with good reproducibility. On the other hand, when the concentration is higher than 3N, the aggregation of the clay mineral sol becomes remarkable, and the intercalation is inhibited, which is not preferable. The two kinds of sols thus prepared are mixed to replace the interlayer water taken into the clay mineral with the metal oxide precursor sol, and exchange with the exchangeable cation of the clay mineral. Further, the metal oxide precursor is sandwiched in the voids therebetween, and the metal oxide precursor having a cation exchange capacity equal to or more than the cation exchange capacity originally possessed by the clay mineral is intercalated. Next, the clay mineral in which the metal oxide precursor is intercalated in this way is settled by a centrifugal separator, and the sol containing the excess metal oxide precursor that is not intercalated is removed as a suspended portion. Further, the sediment is dispersed / sedimented with ion-exchanged water for washing. The washing with ion-exchanged water is preferably repeated 3 to 10 times with the same volume as the mixed sol.

In the production method of the present invention, the acid used for stabilizing the metal oxide precursor is an organic acid as a weak acid so as not to coagulate the sol of the clay mineral and not to destroy the sheet structure. Organic acids decompose at relatively low temperatures and are removed during the process of heating and oxidizing the metal oxide precursor.

The calcination for thermally decomposing the intercalated metal oxide precursor into an oxide depends on the metal oxide to be produced, but is preferably oxidized by heating in a temperature range of 200 to 850 ° C. The retention time for oxidation is preferably in the range of 1 to 24 hours. The heating rate for oxidation is not particularly limited, and it is preferable to gradually increase the temperature for the purpose of thinning. However, even if rapid heating such as spray drying is performed, the layered structure is not destroyed. In addition, after the oxidation of the intercalated metal oxide precursor, swelling /
It can be diluted to form a sol, and the sol can be used to form a thin film.

The presence / absence of elution of constituent ions is determined by analyzing the composition of the heat-treated product and comparing the ratio between oxides constituting the raw clay mineral. In order to confirm the layered structure, an oriented and thin film is analyzed by X-ray diffraction. If the layer structure is maintained, a diffraction peak indicating the layer structure is obtained. Further, the deposition on the particle surface and the non-uniform dispersibility are determined by the presence or absence of a diffraction peak attributed to the metal oxide.

[0017]

The clay mineral in which the metal oxide is intercalated has been given excellent selectivity due to the characteristic structure of the clay mineral in addition to the catalytic performance of the metal oxide, and is regarded as an excellent solid acid catalyst. These mainly focus on the fact that the metal oxide is inserted between the layers of the clay mineral at the molecular size and the resulting pore structure.

In recent years, fields in which a metal oxide having a catalytic function is required to be covered with an inert substance and not exposed are expanding. A typical example is the field of photocatalysts that exhibit a self-cleaning function.

The use of photocatalysts such as titanium oxide as antibacterial / deodorizing / antifouling materials is expected to expand.
However, the strong oxidizing performance of the photocatalyst, for example, when slicing into paper to impart a catalytic function, the paper fibers are oxidized / decomposed and damaged. In addition, when a catalyst function is provided by directly forming a thin film on glass or a tile surface, sodium or the like contained in glass or glaze lowers the catalyst function.

On the other hand, a method has been adopted in which the surface of a metal oxide having catalytic performance is coated with alumina or silica, or the surface of the metal oxide is previously shielded with these thin films, and the catalyst is thinned thereon. I have.

The metal oxide obtained by the production method of the present invention has this coating / shielding effect because it is confined in the layer structure of the clay mineral. Therefore, it is effective without damaging the paper or fiber when it is made to have an antibacterial / deodorizing function by being woven into paper or woven into fiber.

When used as a cosmetic material for cutting off ultraviolet light utilizing the UV absorption of the photocatalyst, direct contact between the skin and the organic dispersion medium and the photocatalyst is avoided, so that the function as a cosmetic and its durability are excellent. . Even when a thin film is formed on a glass or tile surface to provide a catalytic function, there is no need for a two-layer coating.

The metal oxide particles contained in the conventional thin film sol are agglomerated particles in the order of μm, whereas the clay mineral sol according to the present invention has a metal oxide precursor of nm size. In this case, the metal oxide is intercalated and dispersed in the layered structure, so that a thin film in which the metal oxide is highly dispersed can be obtained by reducing the thickness. A similar effect can be expected in a pyrosol method or a sol-gel method using an organic medium. However, since the clay mineral sol in the production method of the present invention is an aqueous medium, it is excellent in terms of ease of handling and stability. Needless to say, it is also useful as a catalyst and a catalyst carrier having controlled pores.

[0024]

EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these. Example 1 As a clay mineral, 1.0 g of smectite-based saponite (trade name: Smecton-SA, manufactured by Kunimine Industry Co., Ltd., cation exchange capacity: 71.2 meq / 100 g, hereinafter abbreviated as CLAY-S) was dispersed in 100 g of ion-exchanged water. Then 24
The mixture was allowed to stand for a period of time to swell to form a sol. Separately, 20 g of acetic acid was added to 5 g of ion-exchanged water to prepare an 80% acetic acid solution. Next, to the acetic acid solution kept at 50 ° C., 2.82 g of titanium tetraisopropoxide (reagent 1 grade, manufactured by Wako Pure Chemical Industries, Ltd .; hereinafter, abbreviated as Ti-IPO) as an organometallic compound was added to the acetic acid solution ( Acetic acid / Ti-IPO 8.39 equivalents). After stirring this mixed solution for 45 minutes to peptize,
It was allowed to cool and left standing at 25 ° C. for 6 hours.

In the peptized Ti-IPO-containing solution,
Mix the swollen CLAY-S sol (acetic acid concentration
(2.7N) and stirred for 2 hours. Thereafter, the mixture is sedimented and separated by a centrifugal separator at a centrifugal force of 11,000 Xg, further dispersed in ion-exchanged water, and washed by stirring with the same volume as before sedimentation. This was repeated seven times. The obtained precipitate was dried under reduced pressure at room temperature for 24 hours, then heated to 500 ° C. over 6 hours, and kept for 2 hours to be thermally decomposed to obtain a reaction product.

Example 2 8.0 g of CLAY-S was dispersed in 800 g of ion-exchanged water and allowed to stand for 24 hours to swell. Separately, 22.56 g of Ti-IP0 was added to 200 g of an 80% acetic acid solution (acetic acid / Ti-IPO: 8.39 equivalents), and the mixture was stirred at 50 ° C. for 40 minutes, allowed to stand to cool for 2 hours, and peptized sol. And Thereafter, a swelling sol of CLAY-S was added to the sol (acetic acid concentration: 2.7 N), and the mixture was stirred for 20 minutes, and then allowed to stand for 16 hours. A reaction product was obtained by treating in exactly the same manner as in Example 1 except that the sedimentation was changed to 1,500 Xg.

Comparative Example 1 0.52 g of CLAY-S was dispersed in 51.2 g of ion-exchanged water and stirred for 24 hours to swell. Separately, 12
5.7 g of Ti-IP0 was added dropwise to 5 ml of 1N HCl, and the mixture was stirred at 50 ° C. for 40 minutes to obtain a transparent state, and then allowed to stand still for 6 hours to obtain a sol that had been peptized. next,
This sol is mixed with the swelled CLAY-S sol,
After stirring for minutes, the mixture was allowed to cool for 16 hours. This mixed sol was subjected to centrifugal sedimentation and washing at 11,000 Xg. Hereinafter, a reaction product was obtained by treatment in exactly the same manner as in Example 1.

Comparative Example 2 6.24 g of CLAY-S was dispersed in 619.2 g of ion-exchanged water and allowed to swell for 24 hours. Separately, 19.5 g of Ti-IP0 was added dropwise to 375 ml of 1N-HCl to stabilize and obtain a peptized sol. Next, the sol of CLAY-S swollen was mixed with this sol, stirred for 20 minutes, and then allowed to stand for 2 hours. This mixed sol was subjected to centrifugal sedimentation and washing at 1500 × g. Hereinafter, a reaction product was obtained by treatment in exactly the same manner as in Example 1.

Example 3 CLAY-S of Example 1 was converted to a smectite-type montmorillonite (trade name Knipia-F, manufactured by Kunimine Industries Co., Ltd.)
Cation exchange capacity 115.0 meq / g, hereinafter CLAY
A reaction product was obtained by the same treatment as in Example 1 except that the reaction product was replaced with -M.

Example 4 A reaction product was obtained by treating in exactly the same manner as in Example 2 except that CLAY-S was replaced with CLAY-M.

Comparative Example 3 A reaction product was obtained by performing the same operation as in Comparative Example 1 except that CLAY-S was replaced with CLAY-M.

Comparative Example 4 A reaction product was obtained by the same procedure as in Comparative Example 2 except that CLAY-S was replaced with CLAY-M.

Example 5 An acetic acid solution concentration of 10% (acetic acid / Ti-IPO 1.05
(Equivalent), and a reaction product was obtained by the same operation as in Example 2.

Comparative Example 5 A reaction product was obtained by the same procedure as in Example 2 except that the acetic acid solution concentration was changed to 5% (acetic acid / Ti-IPO 0.52 equivalent).

Comparative Example 6 A reaction product was obtained by the same treatment as in Example 2 except that the concentration of the acetic acid solution was changed to 100% (acetic acid concentration: 3.3 N).

Next, the reactants obtained in Example 1-4 and Comparative Example 1-4 were measured for pore distribution, specific surface area measurement, X-ray diffraction and reflection spectrum, respectively.

[Composition Analysis] Tables 1, 2 and 3 show the results of composition analysis of the reaction products of Example 1-5 and Comparative Example 1-6 obtained by the above-mentioned operations using fluorescent X-rays.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

As is clear from the results in Tables 1 and 2,
Mg and Al with respect to Si of Comparative Example 1-4 were raw material CLAY
It can be seen that a large amount is lost in comparison with -S. When the standing time after mixing is short, the decrease in Mg and Al is slightly alleviated, but the Ti ratio is not large, and the raw material CLAY-S
This suggests that the aggregation of the cells inhibited intercalation.

On the other hand, according to the method of Example 1-4 of the present invention, loss of Mg and Al other than Na of the interlayer metal is small and the layered structure is reduced irrespective of the length of the standing time after mixing. You can see that it has not been destroyed. It can also be seen that the Ti ratio is stable. As is clear from the results in Table 3, when the acetic acid concentration is insufficient with respect to the equivalent of Ti-IPO (Comparative Example 5) or when the concentration is too large (Comparative Example 6), Ti
The content of O ₂ is reduced.

[Measurement of Pore Distribution and Specific Surface Area] The pore radius and the specific surface area were obtained by obtaining an adsorption-desorption isotherm of nitrogen gas by a constant pressure gas adsorption method. Table 4 shows the obtained results. In addition, adsorption of the reaction product obtained in Example 1
The pore distribution determined from the desorption isotherm and the adsorption isotherm are shown in FIGS. 1 and 2, respectively. As is apparent from FIG. 2, the pore radius of the reactant obtained in Example 1 is distributed in an extremely narrow region.

[0044]

[Table 4]

[X-ray Diffraction Analysis] The sample before the heat treatment was oriented on a slide glass, dried, fired at 500 ° C., and subjected to X-ray diffraction analysis to measure the interval between the layered structures.
In addition, what was fired at 500 ° C. in the form of a block was pulverized into X
Subjected to ray diffraction analysis, it was observed crystal structure of Ti0 _2. The obtained results are shown in Tables 4 and 5. FIG. 3 shows a change in the layered structure of the reaction product obtained in Example 1 with increasing temperature. It can be seen that the dried product is slightly wider (1.38 nm) than the interlayer distance (1.18 nm) of the raw clay mineral due to the intercalation. As the temperature rises, the diffraction peak giving this interval becomes smaller and becomes 2.45 nm.
Appears. This is because the metal oxide precursor intercalated between the layers becomes an oxide by firing,
By expanding the interlayer gap as a pillar.

FIG. 4 shows a comparison of the crystal structures of Example 1 and Comparative Example 1. The reaction product obtained in Example 1 is a diffraction peak attributed to sabonite, and the crystal structure can be assigned. No TiO ₂ peak is observed. On the other hand, the reaction product obtained in Comparative Example 1 clearly shows anatase-type TiO ₂
Becomes the diffraction peak.

As is clear from the above results, the reaction product obtained in Example 1 does not have grown TiO ₂ crystals, but exists in a dispersed state while being well intercalated between layers. On the other hand, it can be seen that, in the reaction product obtained in Comparative Example 1, the layered structure was not maintained, and TiO ₂ crystal growth occurred. Acetic acid concentration is Ti-IP
If the equivalent of O is insufficient (Comparative Example 5) or the concentration is too high (Comparative Example 6), the metal oxide precursor is deposited outside the layered structure, and anatase TiO ₂ is observed after firing. Become.

[0048]

[Table 5]

[Measurement of Reflection Spectrum] The reflection spectrum in the ultraviolet-visible region was measured by an ultraviolet-visible spectrophotometer. FIG. 5 shows the results of the reflection spectra of the reaction product (dried product and calcined product), raw material saponite and TiO ₂ (anatase type and rutile type) obtained in Example 1. Table 6 shows the results of comparison of the reflectance (%) for each wavelength. The reactant obtained in Example 1 has a TiO ₂ content of about 50% and is 100% despite being covered by clay mineral.
Since the reflectance is equivalent to that of TiO ₂ , it is understood that the material has excellent UV absorption ability.

As described above, according to the production method of the present invention,
The metal oxide can be intercalated into the interlayer gap while maintaining the layer structure of the clay mineral well. Then, the obtained metal oxide has a large UV absorbing ability while being well shielded by the clay mineral, and can exhibit a function as a photocatalyst.

[0051]

[Table 6]

[Brief description of the drawings]

1 shows an adsorption-desorption isotherm of a metal oxide intercalated in CLAY-S obtained in Example 1. FIG.

FIG. 2 shows a pore distribution obtained from an adsorption isotherm of a metal oxide intercalated in CLAY-S obtained in Example 1.

FIG. 3 shows a change in a layered structure with a rise in temperature in Example 1.

FIG. 4 shows a comparison of crystal structures of Example 1 and Comparative Example 1 by X-ray diffraction analysis.

FIG. 5 shows a reflection spectrum of the metal oxide intercalated into CLAY-S obtained in Example 1 in an ultraviolet-visible region using an ultraviolet-visible spectrophotometer.

Claims (8)

[Claims] 1. A method for producing a metal oxide intercalated in a clay mineral, comprising the following steps: (a) a step of swelling and diluting a clay mineral having a layered structure with water to form a sol; A) adding an organometallic compound to an aqueous solution containing an organic acid to form a metal compound-containing sol; and (c) adding the swelled clay mineral sol to the metal compound-containing sol and stirring to cause the swelling. Intercalating the metal compound between layers of the clay mineral, and (d) washing, dehydrating, drying and firing the clay mineral in which the metal compound is intercalated between the layers. The above method. 2. The method according to claim 1, wherein the clay mineral is a phyllosilicate mineral. 3. The method according to claim 2, wherein the phyllosilicate mineral is smectite, vermiculite or mica. 4. The method according to claim 1, wherein the organic acid is oxalic acid, acetic acid or formic acid. 5. The method according to claim 1, wherein the metal oxide is titanium oxide, zinc oxide, ferric oxide or tin oxide. 6. The method according to claim 1, wherein the organometallic compound is a metal alkoxide, acylate or chelate. 7. The method according to claim 1, wherein the calcination is performed by heating at 200 to 850 ° C. to oxidize. 8. The method according to claim 7, wherein the holding time for the oxidation is 1 to 24 hours.