JP3049312B2 - Crosslinked titanium-niobium layered composite oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photocatalyst and an adsorbent useful for photochemical conversion, synthetic chemistry using light, removal treatment of environmental pollutants, and the like, and a method for producing the same. More specifically, the present invention relates to a method for manufacturing a more excellent material by modifying the interlayer using K [TiNbO ₅ ].

[0002]

_2. Description of the Related Art Since 1969, much research has been conducted on a semiconductor photocatalytic reaction using a metal compound having photoresponsive semiconductor characteristics represented by titanium oxide (TiO ₂ ). Its potential utility is becoming apparent.

A metal compound having the above-mentioned photoresponsive semiconductor properties absorbs light having an energy equal to or greater than the value of a “forbidden band” which is an energy gap between a valence band and a conduction band in a crystal molecule. Electrons in the electronic band are photoexcited into the conduction band, producing free electrons in the conduction band and holes in the valence band. If these can cause reduction and oxidation reactions, respectively, the photocatalytic reaction proceeds. . However, in order for photodecomposition of water to occur by the semiconductor photocatalyst, the bandwidth of the semiconductor is determined by the electrolytic pressure of water (theoretical value: 1.23).
V), and the ability of the conductor electrons to reduce water and the valence band holes to oxidize water. That is, the lower end of the conduction band must be located on the minus side of the hydrogen generation potential from water, and the upper end of the valence band must be located on the plus side of the oxygen generation potential. Due to this limitation, the types of semiconductors that can completely decompose water theoretically are limited.

[0004] As a method for producing a photocatalyst mainly containing the above metal compound (TiO ₂ ), an inorganic material powder is used.
A method of directly sintering at a high temperature, by chemical treatment, in order to impart more excellent photoresponsiveness to the semiconductor, after adsorbing an aqueous solution of a metal or metal compound on the semiconductor, and then adsorbing the metal or metal compound on the semiconductor material A method of oxidizing, reducing, or partially oxidizing after reduction, a sol-gel method, and the like have been known.

In the photocatalyst using a metal compound having the above-mentioned photoresponsive semiconductor characteristics, the semiconductor has a too large bandwidth, so that it cannot absorb the visible light portion of sunlight but absorbs almost only ultraviolet light. Further, there is a problem that electrons and holes generated by excitation by light energy are easily recombined, and the reaction quantum yield in various reaction systems is not easily increased.

Recently, layered composite oxides have been reported as photocatalysts having photoresponsive semiconductor properties. One attractive point when using a layered composite oxide as a photocatalyst is that various combinations of the elements used are possible.

In general, when a highly functional photocatalyst, for example, a catalyst for completely decomposing water into hydrogen and oxygen by visible light, is prepared using a layered composite oxide, it is important how the layers are modified. It becomes a problem. However, since the interlayer charge density is high, it is difficult to increase the interlayer distance, it is difficult to modify the interlayer, and it is difficult to obtain a high-performance catalyst.

[0008]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a crosslinked layered composite oxide useful as a high-performance photocatalyst by modifying the interlayer by increasing the interlayer distance of the layered composite oxide. The purpose of the present invention is to provide a method for efficiently producing a.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies on a method of modifying the interlayer of a layered composite oxide, and as a result, using a layered composite oxide prepared by a high-temperature reaction,
After this is subjected to a proton exchange treatment, a long-chain alkylamine intercalation treatment, a treatment with tetraalkoxysilane, and a calcination treatment are sequentially performed, whereby a crosslinked layered composite oxide having pillars of silica between layers can be easily obtained. This led to the completion of the present invention based on this finding.

[0010] That is, the present invention provides an A having a layered structure.
[TiNbO ₅ ] (A = K, Rb, Tl, Cs) by increasing the distance between the layers of the composite oxide by physically extending columns and then modifying the layer space, Provided is a method for producing an interlayer crosslinked catalyst having a surface area, a high activity and a high stability.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, a compound represented by A [TiNbO ₅ ] (A = K, Rb, Tl, Cs) is used as a layered composite oxide. It is prepared by a high temperature reaction.

As an example, the layered composite oxide of K [TiNbO ₅ ] can be prepared by a commonly used method, for example, mixing niobium oxide, titanium oxide and potassium carbonate powders at predetermined ratios, and mixing this powder mixture. It is prepared by baking at 950 to 1100 ° C. in an oxygen-containing gas atmosphere such as air.

In the method of the present invention, it is necessary to first apply a proton exchange treatment to the layered composite oxide thus prepared. Next, a long-chain alkylamine is intercalated into the proton exchange layered composite oxide. The long-chain alkylamine used at this time is preferably one having about 5 to 15 carbon atoms, particularly n
-Hexylamine is preferred. This intercalation reaction can be performed by contacting the long-chain alkylamine with the proton-converted layered composite oxide at room temperature for about 50 to 200 hours in an appropriate solvent such as a lower alcohol. By this reaction, the long-chain alkylamine is intercalated between the layers of the layered composite oxide, and the interlayer distance is increased.

Next, tetraalkoxysilane is reacted with the layered composite oxide in which the long-chain alkylamine has been intercalated as described above. As the tetraalkoxysilane used at this time, those in which the alkoxyl group is a lower alkoxyl group such as an ethoxy group, an n-propoxy group, and an isopropoxy group are preferable, and tetraethoxysilane is particularly preferable. This reaction is generally 40-80
This is performed at about 50 ° C. for about 50 to 200 hours.

Finally, a baking treatment is performed at a temperature in the range of 400 to 600 ° C. in an atmosphere of an oxygen-containing gas such as air to burn organic substances in the interlayer. By this baking treatment, a crosslinked layered composite oxide having silica pillars between layers is obtained. This is a porous body, has a large surface area, and has good high-temperature stability.

[0016]

According to the present invention, it is possible to efficiently manufacture a porous body composed of a crosslinked layered composite oxide having silica pillars between layers by using a layered composite oxide and utilizing an intercalation reaction. Can be. This is useful as a highly functional photocatalyst, for example, in the field of synthetic chemistry using photochemical conversion or light, or in the field of removal of environmental pollutants using photocatalysis.

[0017]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples using K [TiNbO ₅ ] as an example. However, the technical scope of the present invention should not be construed as being limited by these examples.

Reference Example 1 Production of K [TiNbO ₅ ] Niobium oxide (V) [Wako Pure Chemical Industries, Ltd., 99.9%
] 0.015 mol, potassium carbonate [Katayama Chemical Industry Co., Ltd., special grade] 0.016 mol and titanium oxide [Katayama Chemical Industry Co., Ltd., special grade] 0.03 mol are mixed well. The product obtained by baking twice in the air at 950 to 1100 ° C. was pulverized, washed sufficiently with distilled water, and dried.
Drying was performed at 10 ° C. to prepare powdery K [TiNbO ₅ ].

[0019] Reference Example 2 K [TiNbO _5] powdered K prepared in proton exchange Reference Example 1 [TiNbO _5] 4.0 g of 6 N nitric acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade) 150 ml solution After proton exchange for 3 days while stirring at room temperature, the mixture was filtered, washed and dried to obtain powdered H [TiNb
O _5] was obtained.

The intercalation reaction above according to Reference Example 3 hexylamine H [TiNbO _5] Powder 3.0 g n-hexylamine
[Wako Pure Chemical Industries, Ltd., first grade] 80ml and ethanol
[Wako Pure Chemical Industries, Ltd., reagent grade] Put into 40 ml of a mixed solution, react at room temperature with stirring for 7 days, then filter, wash and dry to obtain powdered [C ₆ H ₁₃ NH ₃ ] [T
iNbO ₅ ] was obtained.

Reference Example 4 Intercalation Reaction with Tetraethoxysilane 2.5 g of the above powder of [C ₆ H ₁₃ NH ₃ ] [TiNbO ₅ ] was mixed with tetraethoxysilane [Wako Pure Chemical Industries, Ltd., reagent grade] 80
After reacting for 7 days (while adding 20 ml of (C ₂ H ₅ O) ₄ Si during this period) with stirring at 65 ° C.,
The mixture was filtered, washed with ethanol or distilled water, and dried. Thereby, tetraethoxysilane could be introduced between the layers. Next, this was baked at 500 ° C. in air to form a pillar of silica between the layers, thereby producing SiO ₂ —TiNbO ₅ as a crosslinked layered composite oxide.

From the above Reference Examples 1 to 4, the K between the layers of the layered composite oxide K [TiNbO ₅ ] was changed to another by the identification and TEM measurement by XRD,
It was found that the interlayer distance had changed. The details will be described below.

By the proton exchange described in Reference Example 2, K [Ti
When the K between the layers of NbO ₅ ] was changed to protons, the distance between the layers became slightly smaller. However, according to the invention described in Reference Example 3, H [TiNb
O ₅ ] was subjected to an intercalation reaction with n-hexylamine, and the interlayer distance was changed from 0.83 nm to 2.17 nm.
nm. Further, when the support was made up of tetraethoxysilane, the interlayer distance became 2.40 nm. 40
When baked at 0 ° C., 500 ° C., and 600 ° C., the interlayer distances are 1.56 nm, 1.41 nm, and 1.30 n, respectively.
m, and the interlayer distance was slightly reduced with the burning of the organic matter between the layers, but the high-temperature stability of the layered structure was recognized.

[0024]

[Brief description of the drawings]

FIG. 1 X-ray diffraction diagram of the layered compound produced (a) KTiNbO ₅ untreated (b) (a) treated with 6N nitric acid aqueous solution (c) (b) using n-hexylamine Intercalated (d) (c) treated at 450 ° C. (e) (c) n-hexylamine substituted with tetraethoxysilane (f) (e) treated at 400 ° C. (G) (f) treated at 500 ° C (h) (g) treated at 600 ° C The numerical values in the figure indicate the bottom spacing.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-241036 (JP, A) JP-A-8-196912 (JP, A) JP-A-6-48742 (JP, A) JP-A-11-11 139826 (JP, A) Chem. Soc. , Chem. Commun. (1993), (14), 1144-5 = (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 33/00 C01G 1/00 CA (STN)

Claims (1)

(57) [Claims] (1) After subjecting a layered A [TiNbO ₅ ] (A = K, Rb, Tl, Cs) composite oxide to a proton exchange treatment, a long-chain alkylamine is intercalated, and then a tetraalkoxysilane is reacted. 400 to 60 in an oxygen-containing gas atmosphere
A method for producing a layered composite oxide having an interlayer cross-linking structure, wherein a sintering treatment is performed at a temperature of 0 ° C. to generate silica pillars between layers.