JP3136339B2 - Titanium oxide photocatalyst and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium oxide photocatalyst having high photocatalytic activity and a method for producing the same. More specifically, the present invention is, for example, 400 W
0.3 g of a photocatalyst of the present invention and an aqueous methanol solution (methanol: water = 1: 3) under ultraviolet light irradiation by a high-pressure mercury lamp
To a method of photocatalytic activity to produce better high titanium oxide photocatalyst and efficiency this indicates a volume ratio) 600 cm ³ per hour 200 cm ³ or more hydrogen gas generation amount.

[0002]

2. Description of the Related Art Titanium oxide has been conventionally known as a photodecomposition catalyst for water that causes charge separation by light irradiation and converts light energy into chemical energy. It has been attracting attention as a photocatalyst that has the deodorizing, antibacterial, and antifouling effects of decomposing organic substances by utilizing organic compounds. It is known that the photocatalytic activity varies depending on the crystal type, and the activity of anatase-type titanium oxide tends to be the highest. However, when air heating treatment is applied to crystallization, the specific surface area decreases due to an increase in particle size, etc.
The problem is that the activity is reduced. Also,
Heat treatment at 400 ° C. or higher is required for crystallization to anatase. At this time, a large amount of heat energy is required. Therefore, it is desired to develop a synthesis process under mild conditions instead of the heat treatment operation. ing.

[0003] In recent years, the hydrothermal synthesis method has attracted attention as a soft chemistry process that can be synthesized under higher temperature conditions by conventional solid-phase synthesis methods under milder temperature conditions. As an attempt to crystallize anatase from amorphous titanium oxide using hydrothermal reaction, an example using amorphous titanium oxide obtained by hydrolyzing titanium tetraethoxide as a starting material has been reported. I have. It has been revealed that crystallization to anatase proceeds at 400 ° C. or higher in a heating atmosphere containing no water, whereas crystallization to anatase occurs at 250 ° C. under a steam pressure of 98 kPa. Also, under hydrothermal conditions where a large amount of water at 250 ° C. exists, many anatase crystal nuclei are generated,
Since each crystal nucleus cannot grow large, 11 nm
It is reported that crystals of the order of magnitude are produced (High Pressure Symposium Proceedings, P320, pp117 (1995)). However, detailed hydrothermal temperature conditions and the photocatalytic activity of the obtained anatase crystal have not been studied.

In addition, an amorphous titanium oxide obtained by hydrolyzing titanium tetraethoxide is used as a starting material, and the effect of a solvent on crystallization in a high-temperature solvent has been studied. It has been reported that crystallization proceeds more easily than hexane (M
RS Proceedings, pp 510 (1997)) report that anatase crystallized in high-temperature water has lower photocatalytic activity than that crystallized in other solvents. In this case as well, after the titanium tetraethoxide as a raw material is hydrolyzed, solid-liquid separation, washing, and heat treatment of the dried amorphous titanium oxide in a high-temperature solvent are disadvantageous in that the synthesis operation becomes complicated. .

[0005]

SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of the conventional titanium oxide photocatalysts, has excellent photocatalytic activity, and is economically advantageous because it can be easily produced by a simple operation. The purpose of the present invention is to provide a photocatalyst.

[0006]

The present inventors have conducted intensive studies on titanium oxide useful as a photocatalyst.
Reacting titanium tetraalkoxide with water, producing a hydrolyzate of titanium oxide, and finding that an anatase-type titanium oxide excellent in photocatalytic activity can be obtained by performing heat treatment under hydrothermal conditions together with the mother liquor,
Based on this finding, the present invention has been completed.

[0007] The present invention for solving the above problems comprises the following technical means. (1) mixing titanium tetraalkoxide with water,
A reaction that produces a precipitate and is treated under hydrothermal conditions.
The product is filtered, washed with water and dried if necessary.
Obtained by immersing in a solution containing
A that titanium oxide photocatalyst, the number of basic structures, the x in the general formula _{TiO 2 · xH 2 O · yPt} ( wherein 0-1. The number excluding 0 5, y is greater than 0 and less than 0.05 The titanium oxide photocatalyst represented by this. (2) The titanium oxide photocatalyst according to the above (1), wherein the crystal structure of the titanium oxide as a carrier is anatase. (3) mixing titanium tetraalkoxide with water;
A precipitate is formed, and the reaction product obtained by treatment under hydrothermal conditions is filtered, washed with water, dried if necessary, immersed in a platinum-containing solution, and irradiated with ultraviolet light. Is represented by a general formula TiO ₂ .xH ₂ O.yPt (where x is a number excluding 0 from 0 to 1.5, and y is a number greater than 0 and less than 0.05). A method for producing a titanium oxide photocatalyst. (4) mixing titanium tetraalkoxide with water;
A precipitate is formed, and the reaction product obtained by treatment under hydrothermal conditions is filtered, washed with water, dried if necessary, immersed in a platinum-containing solution, and irradiated with ultraviolet light. The method for producing a titanium oxide photocatalyst according to the above (3), wherein the crystal structure of the titanium oxide as the carrier to be converted is anatase. (5) The method for producing a titanium oxide photocatalyst according to the above (3) or (4), wherein ethoxide, propoxide, or butoxide is used as a raw material as the titanium tetraalkoxide. (6) The method for producing a titanium oxide photocatalyst according to the above (3), (4) or (5), wherein the hydrothermal treatment temperature is 100 ° C. or higher. (7) The method for producing a titanium oxide photocatalyst according to the above (3), (4), (5) or (6), wherein the hydrothermal treatment time is 6 hours or more.

That is, in the present invention, the basic structure is represented by a general formula TiO ₂ .xH ₂ O.yPt (where x is a number other than 0 from 0 to 1.5, and y is greater than 0 and less than 0.05. The present invention provides a titanium oxide photocatalyst represented by the following formula: According to the present invention, the titanium oxide photocatalyst generates a precipitate from the titanium tetraalkoxide and the aqueous solution, which is subjected to hydrothermal treatment together with the mother liquor, and the obtained slurry is filtered, washed with water, dried, and then obtained. It can be produced by reacting the obtained titanium oxide with a chloroplatinic acid solution under irradiation with a high-pressure mercury lamp. Here, platinic acid is a raw material for platinum as a cocatalyst, and when titanium oxide is suspended in an aqueous solution of chloroplatinic acid and irradiated with light, electrons generated by photoexcitation reduce chloroplatinic acid ions to form titanium oxide on the titanium oxide. To precipitate platinum fine particles. This reaction can be confirmed by the white titanium oxide powder gradually changing to gray.

[0009]

Next, the present invention will be described in more detail. The titanium oxide photocatalyst of the present invention has a basic structure represented by the general formula TiO ₂ .xH ₂ O.yPt. In the general formula, x is a number excluding 0 from 0 to 1.5, and y is greater than 0 and 0.5.
It is a number less than 05. A composite compound having such a basic structure has good photocatalytic activity.

[0010] Such a titanium oxide photocatalyst can be produced by sequentially performing (1) a step of forming a titanium oxide and (2) a step of supporting platinum.

In the step (1) of forming titanium oxide, titanium oxide can be produced by subjecting titanium tetraalkoxide to a hydrothermal treatment step. The amount of water to be added is not less than the stoichiometric amount necessary for hydrolysis of titanium tetraalkoxide. Next, a titanium tetraalkoxide solution is prepared. Examples of the titanium tetraalkoxide include ethoxide, propoxide, butoxide and the like.

The titanium tetraalkoxide solution is dropped into the aqueous solution to form a precipitate. Even if the aqueous solution is dropped into the alkoxide titanate solution, a precipitate can be obtained. The amount of titanium tetraalkoxide to be mixed is 100% or less, preferably 10% or less as a molar ratio to water. The obtained precipitate can be subjected to hydrothermal treatment together with the mother liquor using a sealed container such as a Teflon inner cylinder type reaction vessel, a glass ampule, an autoclave, or the like. Preferably, the treated product is filtered to remove by-product solutes by washing with water. In this case, if a solid-liquid separation and washing method equivalent to that of filtration, washing with water is used, an appropriate method may be used in the same manner. it can.
The precipitate to be subjected to the platinum loading step does not need to be particularly dried, but may be used after drying if necessary.

Next, in the platinum loading step (2), a platinum-containing solution is first prepared. The concentration of the platinum-containing solution can be arbitrarily adjusted according to the amount of the complex carried, but (1)
0.1 to 10 w with respect to the weight of the precipitate obtained in the step
t%, preferably in the range of 1 to 3 wt%. For example, if 2 wt% of platinum is supported, y in the basic formula
Is about 0.008. At room temperature,
Add the precipitate, 1-24 hours, preferably 3-10 hours,
Stir in an internal irradiation reaction tube using a 400 W high pressure mercury lamp. The product after the reaction is separated by filtration, washed with water, washed with ethanol and dried. For drying, a general dryer or a desiccator containing a desiccant is used, for example, at room temperature to 50 ° C. Further, it can be dried by a spray drying method or a freeze drying method. The product obtained shows a fine granular morphology. After being formed into an arbitrary shape before drying, it may be dried.

The titanium oxide photocatalyst thus obtained can be confirmed by chemical analysis, X-ray diffraction, thermal analysis, infrared spectroscopy, measurement with a scanning electron microscope or the like. For example, the X value can be obtained from the weight loss of the thermobalance of the adsorbed water corresponding to the DTA endothermic peak having a peak near 60 ° C. by thermal analysis. The photocatalytic activity can be evaluated, for example, by examining the rate of hydrogen gas generation by photolysis of water containing methanol. Normally, the hydrogen generation potential of titanium oxide is close to the reduction potential of water, so the hydrogen generation rate is extremely low. Therefore, it is necessary to increase the activity by supporting a promoter such as platinum and introducing a reagent that promotes the reduction reaction, and methanol acts as a sacrificial agent for the reduction reaction.

The production of the titanium oxide photocatalyst of the present invention can be easily confirmed by, for example, X-ray diffraction measurement. When measured using a copper tube and a nickel filter,
The precipitate obtained in the step (1) is 2θ = 25.3 °, 3
7.8 °, 48.1 °, 53.9 °, 55.1 ° and 6
At 2.7 °, the anatase (101) and (00)
4), (200), (105), (211) and (20)
4) A peak corresponding to the diffraction line is observed, but the diffraction line peak intensity changes depending on the synthesis conditions such as the processing temperature and time. (101) The crystallite size can be estimated from the half width of the diffraction line. The form of the titanium oxide photocatalyst of the present invention can be observed as an aggregate of fine particles by a scanning electron microscope.

[0016]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Comparative Example 1 4 ml of titanium tetraisopropoxide was added to distilled water 2
After 0 hours, the mixture was stirred for 3 hours and aged as it was. The precipitate was separated by filtration, washed with water, and dried to obtain 1 g of product of Comparative Example 1. An X-ray diffraction image of the product of Comparative Example 1 showed an amorphous X-ray diffraction image.

Example 1 4 ml of titanium tetraisopropoxide and 20 ml of distilled water were added to a pressure-resistant Teflon container, and the container was sealed.
Shake using a shaker for minutes. Place the pressure-resistant Teflon container in a thermostat or an electric furnace,
Hold for hours. The pressure-resistant Teflon container was taken out, allowed to cool, and the precipitate was separated by filtration, washed with water, and dried. Next, 500 ml of a 2 × 10 ⁻⁴ M platinic acid solution and 1 g of the precipitate were added to an internal irradiation type photochemical reaction vessel, and irradiation was performed at room temperature for about 5 hours using a 400 W high pressure mercury lamp. Platinic acid was reacted on the assumption that the amount of platinum carried was 2 wt% (y = 0.
008). The reaction product is separated by filtration, washed with water, washed with ethanol, and then dried at room temperature using a desiccator.
Inventive product 1 was obtained. According to the X-ray diffraction results of the obtained product of the present invention, (101), (00)
4), (200), (105), (211) and (20)
2θ = 25.3 °, which is considered to correspond to 4), 37.
8 °, 48.1 °, 53.9 °, 55.1 ° and 62.
A broad peak was observed at 7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 19.7 nm. The specific surface area was 182 m ² g ⁻¹ . The value of x obtained from the thermogravimetric weight loss value is 1.08, and the value of y is 0.00
It was 8.

Example 2 A product 2 of the present invention was obtained according to Example 1 except that the hydrothermal reaction temperature was changed to 150 ° C. According to the X-ray diffraction results of the product of the present invention,
(101), (004) of anatase type titanium oxide,
2θ = 25.3 °, 37.8 °, which are considered to correspond to (200), (105), (211) and (204),
Broad peaks were observed at 48.1 °, 53.9 °, 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 23.0 nm. The specific surface area was 162 m ² g ⁻¹ . The value of x obtained from the thermogravimetric loss value was 0.77, and the value of y was 0.007.

Example 3 A product 3 of the present invention was obtained according to Example 1 except that the hydrothermal reaction temperature was changed to 200 ° C. According to the X-ray diffraction results of the product of the present invention,
According to the X-ray diffraction results of the obtained product of the present invention, (101), (004), (200),
2105 = 25.3 °, 37.8 °, 48.1 °, which are considered to correspond to (105), (211) and (204),
Broad peaks were observed at 53.9 °, 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 27.6 nm. The specific surface area is 129
m ² g ⁻¹ . The value of x obtained from the thermogravimetric weight loss value was 0.51 and the value of y was 0.008.

Example 4 A product 4 of the present invention was obtained according to Example 1 except that the hydrothermal reaction temperature was changed to 250 ° C. According to the X-ray diffraction results of the product of the present invention,
According to the X-ray diffraction results of the obtained product of the present invention, (101), (004), (200),
2105 = 25.3 °, 37.8 °, 48.1 °, which are considered to correspond to (105), (211) and (204),
Broad peaks were observed at 53.9 °, 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 34.5 nm. Specific surface area is 117
m ² g ⁻¹ . The value of x obtained from the thermogravimetric weight loss value was 0.39, and the value of y was 0.007.

Example 5 A product 5 of the present invention was obtained according to Example 1 except that the hydrothermal reaction temperature was changed to 300 ° C. According to the X-ray diffraction results of the product of the present invention,
According to the X-ray diffraction results of the obtained product of the present invention, (101), (004), (200),
2105 = 25.3 °, 37.8 °, 48.1 °, which are considered to correspond to (105), (211) and (204),
Sharp peaks were observed at 53.9 °, 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 92.1 nm. Specific surface area is 41m
It was ² g ^-1 . The value of x obtained from the thermogravimetric weight loss value was 0.3.
16, and the value of y was 0.007.

Example 6 A product 6 of the present invention was obtained according to Example 1 except that the hydrothermal reaction temperature was changed to 400 ° C. The equilibrium pH at the end of the reaction was 6.8. According to the X-ray diffraction results of the product of the present invention, the X-ray diffraction results of the obtained product of the present invention show that the anatase-type titanium oxides (101), (004), (200), (105),
2θ considered to correspond to (211) and (204)
= 25.3 °, 37.8 °, 48.1 °, 53.9 °,
Sharp peaks were observed at 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 115.0 nm. The specific surface area was 6 m ² g ⁻¹ . The value of x obtained from the thermogravimetric weight loss value was 0.14,
The value of y was 0.008.

Comparative Example 2 A platinum-supported product was prepared from commercially available titanium oxide. Comparative Examples Titanium oxides 2 to 4 are reagents of Wako Pure Chemical Industries, Ltd.
They are amorphous type, rutile type, and anatase / rutile mixed type titanium oxide, respectively. Comparative Example Titanium oxide 5 is Merck's titanium oxide, and the crystal type is an anatase type. 500 ml of distilled water and 0.02M in an internal irradiation type photochemical reaction vessel
5 ml of a platinic acid solution was added, and 1 g of the titanium oxide of the comparative example was suspended, and irradiated with a 400 W high-pressure mercury lamp at room temperature for about 5 hours. Platinic acid is 2 wt.
% (Y = 0.008). The reaction product was separated by filtration, washed with water, washed with ethanol, and then dried at room temperature using a desiccator.
5 was obtained.

Example 7 Using the obtained products 1 to 6 of the present invention and comparative products 1 to 5, the rate of hydrogen gas generation was measured at a reaction temperature of 30 ° C. 0.3 g of each product and methanol aqueous solution (methanol: water = 1:
600 ml (3 volume ratio) was added to a Pyrex internal irradiation type photochemical reaction vessel, and ultraviolet rays were irradiated using a high-pressure mercury lamp in a thermostat at 30 ° C. The amount of generated gas was measured over time using a gas burette, and after the irradiation was stopped, the gas composition was determined by gas chromatography to calculate the hydrogen gas generation rate. (The results are shown in Table 1.)

[0026]

[Table 1]

Comparative Product 1 without hydrothermal treatment shows a significantly lower rate of hydrogen evolution. On the other hand, in the product of the present invention subjected to the hydrothermal treatment, the hydrogen generation rate increased to 200 ° C. as the hydrothermal temperature increased, and showed a value of 400 ml / h at the maximum. When the hydrothermal temperature is further increased, the hydrogen generation rate tends to decrease.
It has a value exceeding ml / h. Hydrothermal treatment temperature is 10
Since a high rate of hydrogen generation is observed in a product synthesized under a relatively mild condition of 0 to 200 ° C., it is economical, and it is considered to be advantageous because the danger associated with high pressure is reduced. Comparative product 2 with platinum supported on commercially available titanium oxide
No. 5 is 100 m hydrogen generation rate from methanol aqueous solution
The value was around 1 / h, and the activity was not so high, and in some cases, the hydrogen generation rate decreased with the passage of reaction time. On the other hand, the photocatalyst of the present invention has a hydrogen gas generation rate that is 2 to 4 times higher than those of the comparative examples 3 to 5, and the hydrogen gas generation rate does not decrease with the lapse of reaction time. , And has a high photocatalytic activity, and is useful as a water photolysis catalyst.

Example 8 A product 8 of the present invention was obtained in the same manner as in Example 3, except that the hydrothermal reaction time was changed to 6 hours. According to the X-ray diffraction result of the product of the present invention, the X-ray diffraction result of the obtained product of the present invention shows that the anatase-type titanium oxide (101),
2θ = 25.3 ° considered to correspond to (004), (200), (105), (211) and (204);
Broad peaks were observed at 37.8 °, 48.1 °, 53.9 °, 55.1 ° and 62.7 °. (10
1) The crystallite diameter determined from the half width of the diffraction line is 25.1 nm.
Met. The value of x obtained from the thermogravimetric weight loss value was 1.33, and the value of y was 0.008.

Example 9 1 g of the product 9 of the present invention was obtained in the same manner as in Example 3, except that the hydrothermal reaction time was changed to 12 hours. According to the X-ray diffraction result of the product of the present invention, the X-ray diffraction result of the obtained product of the present invention shows that (1)
01), (004), (200), (105), (21)
2θ = 2 considered to correspond to 1) and (204)
5.3 °, 37.8 °, 48.1 °, 53.9 °, 5
Broad peaks were observed at 5.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line is 2
It was 7.6 nm. The value of x obtained from the thermogravimetric weight loss value was 0.52, and the value of y was 0.008.

Example 10 1 g of the product 10 of the present invention was obtained in the same manner as in Example 3 except that the hydrothermal reaction time was changed to 18 hours. According to the X-ray diffraction results of the product of the present invention, the X-ray diffraction results of the obtained product of the present invention show that the anatase-type titanium oxides (101), (004), (200), (105),
2θ considered to correspond to (211) and (204)
= 25.3 °, 37.8 °, 48.1 °, 53.9 °,
Broad peaks were observed at 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 30.7 nm. The value of x obtained from the thermogravimetric weight loss value was 0.80, and the value of y was 0.008.

Example 11 1 g of the product 11 of the present invention was obtained in the same manner as in Example 3, except that the hydrothermal reaction time was changed to 48 hours. According to the X-ray diffraction results of the product of the present invention, the X-ray diffraction results of the obtained product of the present invention show that the anatase-type titanium oxides (101), (004), (200), (105),
2θ considered to correspond to (211) and (204)
= 25.3 °, 37.8 °, 48.1 °, 53.9 °,
Broad peaks were observed at 55.1 ° and 62.7 °. (101) The crystallite diameter determined from the half width of the diffraction line was 39.5 nm. The value of x obtained from the thermogravimetric weight loss value was 0.40, and the value of y was 0.008.

Example 12 The photocatalytic activities of the products of the present invention of Examples 3 and 8 to 11 in which the reaction time was changed from 6 hours to 48 hours at a hydrothermal synthesis temperature of 200 ° C. at which the rate of hydrogen evolution was the largest were performed. evaluated. (The results are shown in Table 2.)

[0033]

[Table 2]

The hydrogen gas generation rate of the product 8 of the present invention 8 with a hydrothermal time of 6 hours was 210 ml / h, and the hydrogen gas generation rate tended to increase by increasing the hydrothermal time.
It has a maximum in 4 hours, but has a high hydrogen gas generation rate even in several hours of hydrothermal time. As a synthesis process, it is desirable to be able to produce in a short time, but in the case of hydrothermal synthesis, it is necessary to consider the cooling time of the reaction vessel. In the case of the product of the present invention, after the hydrothermal treatment, the reaction vessel was cooled with cold water, and the cooling time was made as short as possible.However, in practical use, when the cooling time of the reaction vessel was made sufficiently long, heat was applied. It is considered possible to reduce the hydrothermal time to be added.

Example 13 Hydrothermal synthesis was performed by replacing titanium tetrapropoxide as a raw material with titanium tetraethoxide. 20 g of titanium tetraethoxide and 200 ml of distilled water were added to a pressure-resistant Teflon container, sealed, and then placed in a thermostat.
C. for 24 hours. 3. Take out the pressure-resistant Teflon container, allow it to cool, and then separate the precipitate by filtration, wash with water, and dry.
1 g of a titanium oxide precipitate was obtained. In 500 ml of distilled water,
5 ml of a 0.02 M platinic acid solution was added, and the mixture was transferred to an internal irradiation type photochemical reaction vessel, and 1 g of the precipitate was added.
Irradiation was performed using a 400 W high pressure mercury lamp for a time. Platinic acid was reacted under the assumption that the amount of platinum carried was 2 wt% (y = 0.008). The reaction product is filtered, washed with water,
After washing with ethanol, the product was dried at room temperature using a desiccator to obtain a product 13 of the present invention. X of the obtained product of the present invention
According to the results of X-ray diffraction, (10
1), (004), (200), (105), (21)
2θ = 2 considered to correspond to 1) and (204)
5.3 °, 37.8 °, 48.1 °, 53.9 °, 5
Broad peaks were observed at 5.1 ° and 62.7 °. The value of x obtained from the thermogravimetric weight loss value was 0.45,
The value of y was 0.008. 0.3 g of the product 1 of the present invention
3 and 600 ml of a methanol aqueous solution (methanol: water = 1: 3 volume ratio) were added to a Pyrex internal irradiation type photochemical reaction tube, and reacted at 30 ° C. The composition of the generated gas was analyzed using gas chromatography to determine the hydrogen generation rate. The hydrogen generation rate was 300 ml / h, indicating that it had a high photocatalytic activity, indicating that titanium tetraethoxide may be used as a raw material.

Example 14 Hydrothermal synthesis was performed using titanium tetrabutoxide instead of titanium tetrapropoxide as a raw material. 2
0 g of titanium tetrabutoxide and 200 ml of distilled water were added to a pressure-resistant Teflon container, sealed, and then placed in a thermostat.
It was kept at 00 ° C. for 24 hours. Take out the pressure-resistant Teflon container, let it cool down, filter the precipitate, wash it with water, and dry it.
4.3 g of titanium oxide precipitate were obtained. 500 ml of distilled water
Then, 5 ml of a 0.02 M platinic acid solution was added, the mixture was transferred to an internal irradiation type photochemical reaction vessel, 1 g of the precipitate was added, and irradiation was performed at room temperature for about 5 hours using a 400 W high pressure mercury lamp. Platinic acid was reacted under the assumption that the amount of platinum carried was 2 wt% (y = 0.008). The reaction product was separated by filtration, washed with water, and washed with ethanol, and then dried at room temperature using a desiccator to obtain a product 14 of the present invention. According to the X-ray diffraction results of the obtained product of the present invention, (10)
1), (004), (200), (105), (21)
2θ = 2 considered to correspond to 1) and (204)
5.3 °, 37.8 °, 48.1 °, 53.9 °, 55.
Broad peaks were observed at 1 ° and 62.7 °. The value of x obtained from the thermogravimetric weight loss value is 1.1, and y
Was 0.008. 0.3 g of the product 14 of the present invention
And methanol aqueous solution (methanol: water = 1: 3 volume ratio)
600 ml was added to a Pyrex internal irradiation type photochemical reaction tube and reacted at 30 ° C. The composition of the generated gas was analyzed using gas chromatography to determine the hydrogen generation rate. The hydrogen generation rate was 274 ml / h, indicating high photocatalytic activity, indicating that titanium tetrabutoxide may be used as a raw material.

[0037]

The present invention relates to a titanium oxide photocatalyst having a high hydrogen gas generation rate and a method for producing the same. The present invention has the following effects. (1) The photohydrogen generation rate is higher than the conventional titanium oxide photocatalyst. (2) It has good chemical resistance and can be used in a wide pH range of pH 1 to 13. (3) It can be obtained in a simple step under relatively mild production conditions. (4) Since the product is fine particles of submicron size or less and is easily dispersed in an aqueous solution, a floating operation such as gas bubbling is not required. (5) A photocatalyst having a specific surface area exceeding 100 m ² g ⁻¹ is obtained.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeo Ebina 2-3-6, Shimizunuma, Miyagino-ku, Sendai, Miyagi Prefecture Izumiso 202 (72) Inventor Takako Nagase 2--8, Miyachiyo, Miyagino-ku, Sendai, Miyagi Prefecture No. 4-101 (72) Inventor Kazuo Torii 1-19-13, Nishinakada, Taihaku-ku, Sendai City, Miyagi Prefecture (56) References JP-A 8-131834 (JP, A) JP-A 8-243390 (JP, A) Masao Kondo et al., “Crystallization behavior and microstructure of monodispersed titanium dioxide particles hydrothermally crystallized”, Journal of the Ceramic Society of Japan (1994), No. 102, No. 8, 742-746 (58) Fields surveyed (Int. Cl. ⁷ , DB name) B01J 21/00-38/74 C01G 23/04-23/08 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. A titanium tetraalkoxide mixed with water.
Combined to form a precipitate, which is obtained by treatment under hydrothermal conditions.
The reaction product was filtered, washed with water, and dried if necessary.
Then, it is immersed in a platinum-containing solution and irradiated with ultraviolet light.
The titanium oxide photocatalyst obtained has a basic structure represented by a general formula TiO ₂ .xH ₂ O.yPt (where x is a number excluding 0 from 0 to 1.5, and y is larger than 0 and smaller than 0.05. The titanium oxide photocatalyst represented by: 2. The titanium oxide photocatalyst according to claim 1, wherein the titanium oxide as a carrier has an anatase crystal structure. 3. Titanium tetraalkoxide is mixed with water to form a precipitate, and a reaction product obtained by treatment under hydrothermal conditions is filtered, washed with water, and dried if necessary. The basic structure characterized by being immersed in a containing solution and irradiating with ultraviolet light is represented by the general formula TiO ₂ .xH ₂ O.yPt (where x is a number excluding 0 of 0 to 1.5 and y is 0) Greater than less than 0.05). 4. Titanium tetraalkoxide is mixed with water to form a precipitate, and the reaction product obtained by the treatment under hydrothermal conditions is filtered, washed with water, and, if necessary, dried. 4. The method for producing a titanium oxide photocatalyst according to claim 3, wherein the titanium oxide as a carrier has an anatase crystal structure, which is immersed in a solution containing the solution and irradiated with ultraviolet light. 5. A titanium tetraalkoxide,
The method for producing a titanium oxide photocatalyst according to claim 3 or 4, wherein ethoxide, propoxide, or butoxide is used as a raw material. 6. The method for producing a titanium oxide photocatalyst according to claim 3, wherein the hydrothermal treatment temperature is 100 ° C. or higher. 7. The hydrothermal treatment time is not less than 6 hours.
A method for producing the titanium oxide photocatalyst described above.