JP2001259433A - Photocatalyst and method of manufacturing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalyst essentially comprising titanium oxide and a method of manufacturing the photocatalyst which can be used in the visible ray region by shifting the optical absorption edge to the visible ray side. SOLUTION: The photocatalyst consists of titanium oxide containing 0.001 to 0.5 at.% aluminum. The photocatalyst is manufactured by preparing a gel from a sol of titanium alkoxide with addition of aluminum alkoxide and calcining the gel. The photocatalyst is obtained in a powdery state or film state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photocatalyst and a method for producing the same. More specifically, the present invention relates to a photocatalyst containing titanium oxide as a main component and a method for producing the same.

[0002]

2. Description of the Related Art Environmental problems such as water, air, and soil pollution have been increasing year by year, and pollutants such as chemicals of anthropogenic origin, particularly organic solvents, pesticides, and surfactants, and viruses that adversely affect the human body. It is desired to remove bacteria and the like.

[0003] In order to remove these contaminants and pathogens, treatment with ultraviolet rays or ozone is performed.
Degradation products remain after the treatment, and their decomposition ability is insufficient. In addition, there is a concern that endocrine disrupting substances, so-called environmental hormones, and other substances that adversely affect the human body may be produced.

On the other hand, a method of decomposing these chemical substances using a photocatalyst represented by titanium oxide is clean because no chemicals or the like are used, and can use light energy such as sunlight. This is an environmental purification method that has attracted particular attention in recent years.

[0005] Since titanium oxide used as a photocatalyst has a band gap of about 3 eV, it is possible to use only light having a shorter wavelength than the corresponding ultraviolet region. Sunlight has less components in this wavelength range, and inexpensive fluorescent lamps have less this component. Therefore, a black light blue fluorescent lamp having an emission peak near 350 nm of ultraviolet light is often used as a light source for a photocatalyst.

[0006] In order to further increase the utilization efficiency of the light source and to manufacture a low-priced product, it is required to make the bandgap narrow, that is, to move the light absorption end to the visible light side to make the light visible. In this connection, for example, ion implantation of chromium atoms into titanium oxide (JP-A-11-197512, etc.), a method of controlling the oxygen composition ratio of a titanium oxide photocatalyst, and visualization by a plasma treatment method have been attempted. However, these methods not only require expensive equipment, but also have drawbacks such as a complicated manufacturing process and a need for a post-processing step in many cases.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photocatalyst containing titanium oxide as a main component, the light absorption end of which is moved to the visible light side to make it visible, and a method for producing the same. To provide.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Achieved by a photocatalyst consisting of titanium oxide containing 0.001 to 0.5 atomic% of aluminum, the production of which is carried out by calcining a gel prepared from a sol obtained by adding aluminum alkoxide to titanium alkoxide,
The photocatalyst is obtained as a powder or a film.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In producing a photocatalyst, first, a sol in which an aluminum alkoxide is added to a titanium alkoxide is formed. As the titanium alkoxide, for example, tetra-lower alkoxytitanium such as tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetraisobutoxytitanium, or tetra-n-butoxytitanium is used.
As the aluminum alkoxide, tri-lower alkyl aluminum such as trimethoxy aluminum, triethoxy aluminum, triisopropoxy aluminum and tri-n-butoxy aluminum is used.

The titanium alkoxide and the aluminum alkoxide have an aluminum composition ratio of 0.001 to 0.5 atomic%, preferably about 0.01%, in the finally obtained photocatalyst.
It is used by mixing at a ratio of up to 0.3 atomic%.

The solvents for these alkoxides include:
Alcohols such as methanol, ethanol, isopropanol and 2-methoxyethanol are used. The two types of alkoxides include a method of adding an aluminum alkoxide to an alcohol solvent of titanium alkoxide, a method of dissolving a mixture of titanium alkoxide and aluminum alkoxide in an alcohol solvent, and mixing an alcohol solution of titanium alkoxide and an alcohol solution of aluminum alkoxide. After the alkoxide mixture solution is formed by an arbitrary method such as the above method, it is hydrolyzed in the presence of an acid catalyst such as hydrochloric acid or acetic acid to form a sol. These catalysts are also used as alcohol solutions and the like. In forming the sol, an alcoholamine such as diethanolamine or triethanolamine or a water-soluble polymer such as polyvinylpyrrolidone can be added and used, whereby a uniform and stable hydrolyzed sol can be obtained. it can.

The obtained sol is dried and gelled in this state, pulverized, and then heat-treated at about 300 to 700 ° C., preferably about 400 to 700 ° C. for about 10 minutes to about 3 hours. Thus, a powdery photocatalyst is obtained. In addition, this sol
A film-shaped photocatalyst can be obtained by attaching it on a heat-resistant substrate (carrier) such as a plate, a rod, a tube, or a bead by a dipping method, a spraying method, a copin coating method, or the like, and firing it under the above-described heating conditions.

The powdery or thin-film photocatalyst obtained by calcination has a composition ratio of aluminum (Ti by X-ray photoelectron spectroscopy).
2p, O1s, calculated from peak area of Al2s orbit)
It is adjusted to be 0.5 atomic%, preferably about 0.01 to 0.3 atomic%. Regardless of the composition ratio of aluminum below or above, the X-ray diffraction pattern of the resulting photocatalyst is of the anatase type, and the decrease in light transmittance measured by the light absorption spectrum starts at about 360 nm or about 375 nm, The absorption only increases at the following wavelengths.

The photocatalyst in the form of a powder or a thin film has a crystal structure derived from titanium oxide and has no aluminum compound portion, and is composed of sunlight, fluorescent light, black light, UV lamp, By irradiating light using a mercury lamp, xenon lamp, or the like as a light source, it absorbs more light than a photocatalyst formed by ordinary means, and is dissolved in water by the redox effect of electrons and holes generated in the photocatalyst. It effectively decomposes endocrine disruptors, organic solvents, nitrogen compounds such as ammonia, pollutants of the environment such as chlorine-containing, bromine or iodine compounds, or harmful substances in the gas phase such as the atmosphere.

[0015]

According to the present invention, when producing a photocatalyst using a general sol-gel method, by adding aluminum alkoxide to the sol, aluminum of 0.5 atomic% or less can be added in a state where the crystal structure is maintained as a main component as it is. Thus, the obtained powder or thin film photocatalyst achieves visible light in which the light absorption edge shifts to the longer wavelength side. Thereby, this photocatalyst has an effect that it can absorb more light using sunlight, a fluorescent lamp, a UV lamp or the like as a light source.

EXAMPLES Next, the present invention will be described with reference to examples.

EXAMPLE To a solution of 0.12 g of aluminum triisopropoxy in 81.07 ml of 2-methoxyethanol, 16.88 ml of tetraisopropoxy was added. This solution (97.95 ml) was mixed with 20 ml of 2-methoxyethanol and 2.05 ml of 1.2N hydrochloric acid to obtain a sol A for preparing a photocatalyst. All of these mixings were performed at room temperature under stirring conditions.

The sol A was poured into a petri dish, dried under room temperature conditions to perform gelation, the gelled product was pulverized in a mortar, and calcined at 500 ° C. for 1 hour in the air to obtain a photocatalyst powder A. . Its X-ray diffraction pattern was of the anatase type.

Further, sol A is dip-coated on a quartz glass plate and dried under room temperature conditions to form a gel film,
It was baked at 500 ° C. for 1 hour in the air to obtain a photocatalytic thin film A. When the light absorption spectrum was measured, the decrease in light transmittance started at about 430 nm, and the absorption increased at wavelengths lower than that. The composition ratio calculated from the peak areas of the Ti2p, O1s, and Al2s orbitals by X-ray photoelectron spectroscopy indicated that aluminum was 0.28 atomic%.

Comparative Example 1 The amount of triisopropoxyaluminum was
Changing to 0.24 g, photocatalyst powder B obtained by the same procedure
Indicates that the X-ray diffraction pattern is of an anatase type, and that the photocatalytic thin film B has a light transmittance decrease of about 3 in the light absorption spectrum.
Starting from 75 nm, absorption becomes larger at wavelengths shorter than that, and aluminum is 0.51 atomic% in the composition ratio calculated from the peak area of Ti2p, O1s, Al2s orbitals by X-ray photoelectron spectroscopy.
Met.

COMPARATIVE EXAMPLE 2 The photocatalyst powder C obtained in the same procedure as described in Example 1 except that triisopropoxyaluminum was not used had an anatase type X-ray diffraction pattern.
The decrease in light transmittance in the light absorption spectrum began at about 360 nm, and absorption increased at wavelengths below that.

[Brief description of the drawings]

FIG. 1 shows photocatalyst powders obtained in Examples and Comparative Examples
It is an X-ray diffraction pattern of A, B and C. The numbers in the figure indicate crystal planes.

FIG. 2 shows photocatalytic thin films obtained in Examples and Comparative Examples.
4 is a graph showing light absorption characteristics of A, B and C.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4D048 AA21 AB03 BA03X BA03Y BA07X BA07Y BA41X BA41Y EA01 4G069 AA03 AA08 AA11 BA04A BA04B BA04C BA37 BA38 BC16A BC16B BE06A BE06B BE06C CA10 CA11 EA0123 EA07 EA07 EA07

Claims (4)

[Claims] 1. A photocatalyst comprising a titanium oxide containing 0.001 to 0.5 atomic% of aluminum. 2. The photocatalyst according to claim 1, wherein a crystal structure derived from the titanium oxide is retained, and the aluminum compound portion has no crystal structure. 3. The method for producing a powdery photocatalyst according to claim 1, wherein the gel prepared by using a sol obtained by adding aluminum alkoxide to titanium alkoxide is calcined. 4. The film-shaped photocatalyst according to claim 1, wherein a sol obtained by adding an aluminum alkoxide to a titanium alkoxide is applied onto a heat-resistant carrier, and the gel film obtained by drying is dried. Production method.