Photocatalyst, its production and photocatalytic reaction method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a photocatalyst capable of exhibiting catalytic activity even by irradiation with visible light, a method for producing the photocatalyst, a decomposition reaction of nitrogen oxides under visible light irradiation, and an isomerization reaction of butene by the photocatalyst. It is related to photocatalytic reaction methods such as, and more specifically, it is related to photocatalysts in which specific metal ions are introduced into titanium oxide by applying an ion injection method that introduces metal ions by irradiating accelerated high-energy metal ions. Is.

【0002】

[Conventional technology]

The photocatalytic reaction with titanium oxide has attracted attention as an environment-friendly process that cleanly converts light energy into chemical energy at room temperature, and applied research for environmental purification is being actively conducted. In particular, research on adsorbing dyes to titanium oxide in order to use ultrafine particles to improve the photocatalytic activity of titanium oxide, addition of metals such as Pt, Ag, and Ni, and light in the visible light region (about 400 nm to 800 nm). And so on.

【0003】

However, although conventional photocatalysts work in the ultraviolet light region with a wavelength shorter than about 380 nm, it has been considered impossible to perform a steady photocatalytic reaction in the visible light region with a long wavelength. For example, examples of conventional photocatalytic reactions using titanium oxide include nitrogen oxide decomposition reactions and butene isomerization reactions, but these photocatalytic reactions proceed efficiently only under ultraviolet light irradiation. For this reason, only about 5% of ultraviolet light can be used with sunlight alone, and in order to actually cause a reaction, a light source capable of irradiating ultraviolet light such as a mercury lamp is required separately.

【0004】

[Problems to be Solved by the Invention]

The present invention has been made under such circumstances, and an object of the present invention is to provide a photocatalyst that shifts the light absorption band of titanium oxide to the visible light region and operates stably even in the visible light region. , And to provide a photocatalytic reaction method such as a decomposition reaction of nitrogen oxide and an isomerization reaction of butene by irradiating this photocatalyst with light from ultraviolet light to visible light in the presence of nitrogen oxide, butene and the like. ..

【0005】

[Means for solving problems]

As a result of diligent studies to solve the above problems, the present inventors have focused on the ion implantation method used as a means of doping in the semiconductor field, and have focused on the electronic state of the catalyst by ion implantation into various catalyst materials. After investigating the modification of the above, and further examining the implantation of various metal ions into titanium oxide and investigating the effect of the metal ions on the photocatalytic properties, surprisingly, a specific metal ion was introduced into titanium oxide. The resulting photocatalyst absorbs light not only in the ultraviolet light region but also in the visible light region (about 400 nm to 800 nm), which has been impossible until now, and the nitrogen oxides under visible light irradiation. It has been found that it exhibits activity at room temperature in various photocatalytic reactions such as decomposition and isomerization reaction of butene, and the present invention has been completed based on this finding.

【0006】

That is, the present invention contains 1 × 10 ions of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt.¹⁵It provides a photocatalyst characterized by being contained from the surface to the inside of titanium oxide at a ratio of ion / g-titanium oxide or more. Further, the present invention accelerates the ion of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt to a high energy of 30 KeV or more. The present invention provides a method for producing a photocatalyst, which comprises irradiating titanium oxide and introducing the metal ions into titanium oxide. Furthermore, the present invention provides a photocatalytic reaction method characterized by irradiating visible light to carry out a photoreaction in the presence of the above-mentioned photocatalyst. Below, the present onset described a bright in detail.

【0007】

The photocatalyst of the present invention contains titanium oxide containing a specific metal ion. The metal ion introduced into titanium oxide is an ion of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt, preferably Cr, V, Fe, Ni, Mn, particularly preferably Cr, V. The charge of the metal ion is not particularly limited, but usually exists in a monovalent state when the metal ion before injection is accelerated. After injection, metal ions are present as 1 to 5 valences in titanium oxide. These metal ions may be used alone or in combination of two or more.

【0008】

The amount of metal ions introduced into titanium oxide is 1 x 10¹⁵Ion / g-Titanium oxide or higher. The unit of the amount of metal ions introduced is the number of metal ions per 1 g of titanium oxide. The amount of metal ions introduced is 1 x 10¹⁵If it is less than ion / g-titanium oxide, the effect of absorbing light in the visible light region and exhibiting photocatalytic activity cannot be obtained. The upper limit of the amount of metal ions introduced is not particularly limited, but the amount of metal ions introduced is 1 × 10.²¹If the amount exceeds ion / g-titanium oxide, the effect of exhibiting the photocatalytic activity may not be obtained, which is not preferable. The preferable range of the amount of metal ions introduced varies depending on the type of metal ions, but is usually 1 × 10.¹⁶~5×10¹⁸The ion / g-titanium oxide range is preferred, especially 1x10.¹⁶~5×10¹⁷The ion / g-titanium oxide range is preferred.

【0009】

The metal ions introduced into the base material titanium oxide may be present on the surface of titanium oxide, but it is preferable that most of the metal ions are present inside the titanium oxide, and 90% or more of the metal ions are of titanium oxide. It is more preferable that it is present inside, and it is preferable that 95% or more of the metal ions are present inside the titanium oxide, and it is particularly preferable that 99% or more of the metal ions are present inside the titanium oxide. Further, the metal ion introduced into the titanium oxide preferably exists between the surface and the depth of 1000 Å, and particularly preferably exists between the surface and the depth of 300 Å. Further, it is preferable that the metal ions introduced into the titanium oxide are uniformly dispersed. The titanium oxide used as the base material is TiO.₂, SrTiO₃And so on. The crystal form of titanium oxide is not particularly limited, and anatase type, rutile type, and various other types can be used. The photocatalyst of the present invention contains titanium oxide containing a specific amount of the metal ion from the surface to the inside of the titanium oxide as a component, but another photocatalyst may be used in combination, or another base material may be used. It may be contained. The shape of the photocatalyst of the present invention may be in various forms, and examples thereof include powders, particles, pellets, and membranes, and powders are preferable. The average particle size of the photocatalyst powder is not particularly limited, but is usually in the range of 1 to 1000 nm, preferably in the range of 1 to 500 nm, and particularly preferably in the range of 5 to 50 nm. The photocatalyst of the present invention may be used as it is, or a mixture of a photocatalyst and a binder may be applied to form a film, or the photocatalyst may be supported on a support such as paper.

【0010】

In the method for producing a photocatalyst of the present invention, ions of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt are converted to high energy of 30 KeV or more. Accelerate and irradiate titanium oxide. The energy of the metal ion is 30 KeV or more, preferably in the range of 50 to 400 KeV, and particularly preferably in the range of 100 to 200 KeV. In the preferred range, the metal ion implantation can be dispersed more uniformly, and the structural destruction due to the metal ions of the catalyst can be easily prevented. The preferred range of metal ion irradiation dose varies depending on the type of metal ion, but is usually 1 × 10.¹⁴~1×10¹⁹Ion / cm²The range of is preferable, especially 1 × 10¹⁶~1×10¹⁷Ion / cm²The range of is preferable. The unit of irradiation amount of metal ions is irradiation area 1 cm.²Shows the number of metal ions per hit.

【0011】

The method for introducing metal ions used to obtain the photocatalyst of the present invention is an ion implantation method used as a means for doping impurities in the semiconductor field, and irradiates a semiconductor sample with accelerated high-energy metal ions. As a result, metal ions are implanted into the semiconductor to modify the electronic state of the semiconductor. The ion implantation method is also used for surface modification of metal materials such as steel.

【0012】

The shape of titanium oxide used in the method for producing a photocatalyst of the present invention is not particularly limited, but is preferably in the form of powder. The average particle size of the titanium oxide powder is not particularly limited, but is usually in the range of 1 to 1000 nm, preferably in the range of 1 to 500 nm, and particularly preferably in the range of 5 to 50 nm.

【0013】

The photocatalyst of the present invention absorbs light not only in the ultraviolet light region but also in the visible light region (about 400 to 800 nm), which has been impossible until now. Therefore, the photocatalyst of the present invention can be used to irradiate visible light from ultraviolet light to carry out a photoreaction. The light used in the photocatalytic reaction method of the present invention is light from ultraviolet light to visible light, and may be only ultraviolet light or only visible light. Further, light having a specific wavelength of visible light may be selected from ultraviolet light and irradiated. As long as visible light is emitted from ultraviolet light, light outside this range, such as far-ultraviolet light and infrared light, may be included. The preferred range of wavelengths of ultraviolet to visible light used in the photocatalytic reaction method of the present invention is in the range of 250 to 500 nm. The irradiation intensity of ultraviolet light to visible light used in the photocatalytic reaction method of the present invention is not particularly limited and may be appropriately selected according to the type of photocatalytic reaction.

【0014】

The amount of the photocatalyst used in the photocatalytic reaction method of the present invention is not particularly limited and may be appropriately selected according to the reaction system, but is usually 0.01 to 10,000 g per mole of the raw material. Examples of the photocatalytic reaction of the present invention include a method for decomposing nitrogen oxides by irradiating a photocatalyst with light from ultraviolet light to visible light in the presence of nitrogen oxide to carry out a decomposition reaction, and a method for decomposing nitrogen oxides from ultraviolet light to visible light. Examples thereof include a method for isomerization of butene, which comprises irradiating a photocatalyst with light in the presence of butene to carry out an isomerization reaction. Examples of the isomerization reaction of butene include isomerization between cis-2-butene and 1-butene, and isomerization between cis-2-butene and trans-2-butene.

【0015】

Further, as other examples of the photocatalytic reaction of the present invention, for example, a photoisomerization reaction of an alkene other than the above-mentioned isomerization reaction of butene, a photohydrogen with water of an alkene / alkyne such as ethane or methane production from propylene and water. Chemical decomposition reaction, photooxidation reaction of alcohol such as aldehyde / ketone formation from 2-propanol, secondary amine formation reaction from primary amine, photoamino acid synthesis reaction such as glycine / alanine from methane / water / ammonia, CO + H₂O H₂+ CO₂Various photocatalytic reactions such as photo-water-gas shift reaction and photo-reverse water-gas shift reaction can be mentioned. From the viewpoint of inexhaustible and clean conversion and storage of solar energy, a photocatalytic reaction that uses sunlight and reduces and fixes carbon dioxide with water to lead to useful organic compounds can be mentioned. Specifically, it is a methane synthesis reaction from carbon dioxide and water, a methanol synthesis reaction, a formaldehyde synthesis reaction, and the like. Similarly, photodecomposition of water into hydrogen and oxygen using light in the visible light region uses solar energy because it uses non-depleting energy sources, inexhaustible and inexpensive raw materials, is storable, and does not pollute the environment. Is an ideal and effective way to use.

【0016】

The photocatalyst of the present invention can be applied to various applications by utilizing its photocatalytic properties. For example, nitrogen oxides emitted from various combustion engines are desired to develop effective removal means because they have a direct adverse effect on the human body and can cause photochemical smog and acid rain. However, by using the photocatalyst of the present invention, these decompositions and removals are possible. That is, by applying it to the outer wall or painting of buildings, painting of roads and automobiles, window glass, etc., nitrogen oxides are decomposed and removed into nitrogen and oxygen to make them harmless under sunlight or some light source such as electric lamps. To. Further, it becomes possible to purify water by decomposing harmful substances in water with the photocatalyst of the present invention. Examples of harmful substances in water include trihalomethanes. The photocatalytic reaction method of the present invention can be carried out at room temperature, but is not limited thereto, and can usually be carried out in the range of 0 to 200 ° C.

【0017】

[Action]

The photocatalytic reaction mechanism of the photocatalyst of the present invention is not clear at present, but a catalyst containing titanium oxide as a main component by an impregnation method, a co-precipitation method, an alkoxide method, etc., which are conventionally performed catalyst preparation techniques, can be used. In the method of introducing a metal, the effect of the present invention of absorbing light in the visible light region and exhibiting photocatalytic activity is not exhibited at all. Therefore, metal ions are introduced into the photocatalyst of the present invention in a homogeneous and highly dispersed manner. It is thought that this is due to the fact that there is. In other words, when metal ions are introduced in a homogeneous and highly dispersed manner, the electronic state of titanium oxide is perturbed and visible light can be absorbed, and this light absorption causes electrons and holes in titanium oxide. Of the electrons and holes generated by light irradiation, the electrons move to the metal sites on the surface, where the reduction reaction proceeds efficiently due to the catalytic action of the metal, so that the holes also efficiently proceed with the oxidation reaction on titanium oxide. As a result, the photocatalytic reaction is expected to proceed efficiently.

【0018】

[Example]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples. In the examples, the amount of metal ions introduced into titanium oxide and the injection metal ions were measured by three-dimensional SIMS (secondary ion mass spectrometry) and XPS (photoelectron spectroscopy).

【0019】

Example 1 Using a 200KeV ion implanter used for doping semiconductor impurities, VAccelerate the ions to an energy of 150 KeV, and use titanium oxide (manufactured by Degussa, trade name: P-25) with an average particle size of 21 nm.Ion irradiation amount is 7.5 × 10¹⁵Ion / cm²Irradiate with titanium oxide to VIons were injected. As a result of measuring the dispersion state of V ions of the photocatalyst composed of titanium oxide into which the obtained V ions were introduced by three-dimensional SIMS and XPS, the amount of V ions introduced was 7.5 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the amount of V ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with V ions prepared as described above was measured as a function of the amount of injected V ions. The obtained absorption spectrum is shown in FIG.

【0020】

Example 2 VV in the same manner as in Example 1 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV VIon irradiation dose: 1.5 x 10¹⁶Ion / cm²As a result of measuring the dispersion state of V ions of the photocatalyst composed of titanium oxide into which the obtained V ions were introduced by three-dimensional SIMS and XPS, the amount of V ions introduced was 1.5 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of V ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with V ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

【0021】

Example 3 VV in the same manner as in Example 1 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV VIon irradiation dose: 3.0 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of V ions of the photocatalyst composed of titanium oxide into which the obtained V ions were introduced by three-dimensional SIMS and XPS, the amount of V ions introduced was 3.0 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of V ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with V ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

【0022】

Comparative example 1 The ultraviolet light to visible light absorption spectrum of titanium oxide (manufactured by Degussa, trade name: P-25) was measured in the same manner as in Example 1. The obtained absorption spectrum is shown in FIG. From Fig. 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band cap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all, but V ions were injected by the ion injection method. It can be seen that visible light absorption of 400 nm or more is occurring on the injected titanium oxide photocatalyst.

【0023】

Example 4 Cr using a 200KeV ion implanter used for doping semiconductor impuritiesAccelerate the ions to energy of 150 KeV, and add Cr to titanium oxide (manufactured by Degussa, trade name: P-25) with an average particle size of 21 nm.Ion irradiation amount is 1 x 10¹⁶Ion / cm²Irradiate with titanium oxide and CrIons were injected. As a result of measuring the dispersion state of Cr ions of the photocatalyst composed of titanium oxide into which the obtained Cr ions were introduced by three-dimensional SIMS and XPS, the amount of Cr ions introduced was 1 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of Cr ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Cr ions prepared as described above was measured as a function of the amount of introduced Cr ions. The obtained absorption spectrum is shown in FIG.

【0024】

Example 5 CrCr in the same manner as in Example 4 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV CrIon irradiation dose: 1.5 x 10¹⁶Ion / cm²As a result of measuring the dispersed state of Cr ions of the photocatalyst composed of titanium oxide into which the obtained Cr ions were introduced by three-dimensional SIMS and XPS, the amount of Cr ions introduced was 1.5 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of Cr ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Cr ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

【0025】

Example 6 CrCr in the same manner as in Example 4 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV CrIon irradiation dose: 12 × 10¹⁶Ion / cm²As a result of measuring the dispersed state of Cr ions of the photocatalyst composed of titanium oxide into which the obtained Cr ions were introduced by three-dimensional SIMS and XPS, the amount of Cr ions introduced was 12 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of Cr ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Cr ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From FIG. 2, as in Comparative Example 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band gap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all. It can be seen that visible light absorption of 400 nm or more occurs on the titanium oxide photocatalyst in which ions are injected by the ion injection method. As described above, it has been clarified that the titanium oxide containing a specific metal ion of the present invention exhibits an optical property that has not been considered in the past, that is, it absorbs light in the visible light region.

【0026】

Example 7 Fe using a 200KeV ion implanter used for doping impurities into semiconductorsAccelerate the ions to energy of 150 KeV, and add Fe to titanium oxide (manufactured by Degussa, trade name: P-25) with an average particle size of 21 nm.Ion irradiation amount is 7.5 × 10¹⁵Ion / cm²Irradiate to titanium oxide with FeIons were injected. As a result of measuring the dispersed state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 7.5 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface.

【0027】

Example 8 FeFe is the same as in Example 7 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV FeIon irradiation dose: 1.5 x 10¹⁶Ion / cm²As a result of measuring the dispersed state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 1.5 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface.

【0028】

Example 9 FeFe is the same as in Example 7 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV FeIon irradiation dose: 3.0 × 10¹⁶Ion / cm²As a result of measuring the dispersed state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 3.0 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface.

【0029】

Example 10 Fe using a 200 KeV ion implanter used for doping semiconductor impuritiesAccelerate the ions to energy of 150 KeV, and add Fe to titanium oxide (manufactured by Degussa, trade name: P-25) with an average particle size of 21 nm.Ion irradiation amount is 2.2 x 10¹⁵Ion / cm²Irradiate to titanium oxide with FeIons were injected. As a result of measuring the dispersed state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 2.2 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Fe ions prepared as described above was measured as a function of the amount of injected Fe ions. The obtained absorption spectrum is shown in FIG.

【0030】

Example 11 FeFe is the same as in Example 10 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV FeIon irradiation dose: 6.6 × 10¹⁵Ion / cm²As a result of measuring the dispersed state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 6.6 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Fe ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

【0031】

Example 12 FeFe is the same as in Example 10 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV FeIon irradiation dose: 1.3 × 10¹⁶Ion / cm²As a result of measuring the dispersed state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 1.3 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Fe ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From Fig. 3, with titanium oxide alone, only light absorption in the ultraviolet light region with a band cap value of about 380 nm and about 400 nm or less occurred, and no light absorption in the visible light region occurred, but Fe ions were injected by the ion injection method. It can be seen that visible light absorption of 400 nm or more is occurring on the injected titanium oxide photocatalyst.

【0032】

Example 13 Ni using a 200KeV ion implanter used for doping semiconductor impuritiesAccelerate the ions to an energy of 150 KeV, and use titanium oxide (manufactured by Degussa, trade name: P-25) with an average particle size of 21 nm and Ni.Ion irradiation amount is 2.2 x 10¹⁵Ion / cm²Irradiate with titanium oxide and NiIons were injected. As a result of measuring the dispersion state of Ni ions of the photocatalyst composed of titanium oxide into which the obtained Ni ions were introduced by three-dimensional SIMS and XPS, the amount of Ni ions introduced was 2.2 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Ni ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Ni ions prepared as described above was measured as a function of the amount of introduced Ni ions. The obtained absorption spectrum is shown in FIG.

【0033】

Example 14 NiNi in the same manner as in Example 13 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV NiIon irradiation dose: 6.6 × 10¹⁵Ion / cm²As a result of measuring the dispersion state of Ni ions of the photocatalyst composed of titanium oxide into which the obtained Ni ions were introduced by three-dimensional SIMS and XPS, the amount of Ni ions introduced was 6.6 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Ni ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Ni ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

【0034】

Example 15 NiNi in the same manner as in Example 4 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV NiIon irradiation dose: 1.3 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Ni ions of the photocatalyst composed of titanium oxide into which the obtained Ni ions were introduced by three-dimensional SIMS and XPS, the amount of Ni ions introduced was 1.3 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Ni ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Ni ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From FIG. 4, as in Comparative Example 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band gap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all. It can be seen that visible light absorption of 400 nm or more occurs on the titanium oxide photocatalyst in which ions are injected by the ion injection method. As described above, it has been clarified that the titanium oxide containing a specific metal ion of the present invention exhibits an optical property that has not been considered in the past, that is, it absorbs light in the visible light region.

【0035】

Example 16 Using a 200KeV ion implanter used for doping semiconductor impurities, MnAccelerate the ions to an energy of 150 KeV, and use titanium oxide (manufactured by Degussa, trade name: P-25) with an average particle size of 21 nm, and Mn.Ion irradiation amount is 1 x 10¹⁵Ion / cm²Irradiate with titanium oxide and MnIons were injected. Obtained MnMn, a photocatalyst consisting of titanium oxide into which ions have been introducedAs a result of measuring the dispersion state of ions with three-dimensional SIMS and XPS, MnIontophoresis amount is 1 x 10¹⁶Ion / g-TiO₂And Mn inside between the surface of titanium oxide and a depth of 200 Å from the surfaceIt was confirmed that 99% or more of the iontophoresis amount was dispersed almost uniformly. Mn prepared as aboveIntroduced ultraviolet light to visible light absorption spectrum of photocatalyst consisting of ion-introduced titanium oxide MnIt was measured as a function of the amount of ions. The obtained absorption spectrum is shown in FIG.

【0036】

Example 17 MnMn is the same as in Example 16 except that the ion injection conditions are as follows.A photocatalyst composed of ion-injected titanium oxide was prepared. Acceleration energy: 150KeV MnIon irradiation dose: 3 × 10¹⁵Ion / cm²Obtained MnMn, a photocatalyst consisting of titanium oxide into which ions have been introducedAs a result of measuring the dispersion state of ions with three-dimensional SIMS and XPS, MnIontophoresis amount is 3 x 10¹⁶Ion / g-TiO₂And Mn inside between the surface of titanium oxide and a depth of 200 Å from the surfaceIt was confirmed that 99% or more of the iontophoresis amount was dispersed almost uniformly. Mn prepared as aboveThe ultraviolet to visible light absorption spectra of a photocatalyst composed of ion-introduced titanium oxide were measured. The obtained absorption spectrum is shown in FIG. From FIG. 5, as in Comparative Example 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band gap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all, but Mn. It can be seen that visible light absorption of 400 nm or more occurs on the titanium oxide photocatalyst in which ions are injected by the ion injection method. As described above, it has been clarified that the titanium oxide containing a specific metal ion of the present invention exhibits an optical property that has not been considered in the past, that is, it absorbs light in the visible light region.

【0037】

Example 18 Butene isomerization reaction 250 mg of the Cr iontophoretic titanium oxide photocatalyst prepared in Example 4 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr cis-2-butene was introduced, and the illuminance was 2,000 μW / cm using a mercury lamp that blocked light with a wavelength of 450 nm or less with an optical filter as a light source.²The photocatalyst was irradiated with the light of cis-2-butene in the presence of cis-2-butene, and the isomerization reaction of butene was carried out at room temperature. The reaction product was collected with a microsyringe at regular intervals, and the amount of 1-butene and trans-2-butene produced with respect to the elapsed time was quantified by gas chromatography. The results are shown in Fig. 6.

【0038】

Comparative example 2 The isomerization reaction of cis-2-butene was carried out in the same manner as in Example 18 except that titanium oxide alone used in Comparative Example 1 was used instead of the Cr iontophoretic titanium oxide photocatalyst in Example 18. This result is shown in Fig. 6. As is clear from FIG. 6, under visible light irradiation of about 450 nm or more, the reaction hardly proceeds with titanium oxide alone, whereas by using the Cr ion-introduced titanium oxide photocatalyst of the present invention, cis-2 It can be seen that the isomerization reaction of butene to 1-butene and trans-2-butene proceeds efficiently as a photocatalytic reaction even at room temperature.

【0039】

Example 19 Nitric oxide decomposition reaction 250 mg of the Cr iontophoretic titanium oxide photocatalyst prepared in Example 4 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr nitric oxide was introduced, and the decomposition reaction of nitric oxide was carried out at room temperature using a mercury lamp in which light having a wavelength of 450 nm or less was blocked by an optical filter as a light source. The illuminance of the light at this time is 2,000 μW / cm.²Met. The reaction product is collected in a sampling tube at regular intervals and gas chromatographed N.₂, O₂, N₂OWas quantified with respect to the elapsed time. It was confirmed that nitric oxide decreased according to the amount of product. The results are shown in Fig. 7.

【0040】

Comparative example 3 In Example 19, the decomposition reaction of nitric oxide was carried out in the same manner as in Example 19 except that titanium oxide alone used in Comparative Example 1 was used instead of the Cr iontophoretic titanium oxide photocatalyst. This result is shown in Fig. 7. As is clear from FIG. 7, the reaction does not proceed with titanium oxide alone under visible light irradiation of about 450 nm or more, whereas the Cr of the present inventionIt can be seen that by using the iontophoretic titanium oxide photocatalyst, the decomposition reaction of nitric oxide proceeds efficiently as a photocatalytic reaction even at room temperature.

【0041】

Example 20 Butene isomerization reaction 250 mg of the V-iontophoretic titanium oxide photocatalyst prepared in Example 1 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr cis-2-butene was introduced, and the illuminance was 2,000 μW / cm using a mercury lamp that blocked light with a wavelength of 450 nm or less with an optical filter as a light source.²The photocatalyst was irradiated with the light of cis-2-butene in the presence of cis-2-butene, and the isomerization reaction of butene was carried out at room temperature. The reaction product was collected with a microsyringe at regular intervals, and the amount of 1-butene and trans-2-butene produced with respect to the elapsed time was quantified by gas chromatography. The results are shown in Fig. 8.

【0042】

Comparative example 4 The isomerization reaction of cis-2-butene was carried out in the same manner as in Example 20 except that the titanium oxide used in Comparative Example 1 alone was used instead of the V iontophoresis titanium oxide photocatalyst in Example 20. This result is shown in Fig. 8. As is clear from FIG. 8, the reaction does not proceed with titanium oxide alone under visible light irradiation of about 450 nm or more, whereas by using the V ion-introduced titanium oxide photocatalyst of the present invention, cis-2- It can be seen that the isomerization reaction of butene to 1-butene and trans-2-butene proceeds efficiently as a photocatalytic reaction even at room temperature.

【0043】

Example 21 Nitric oxide decomposition reaction 250 mg of the V-iontophoretic titanium oxide photocatalyst prepared in Example 1 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr nitric oxide was introduced, and the decomposition reaction of nitric oxide was carried out at room temperature using a mercury lamp in which light having a wavelength of 450 nm or less was blocked by an optical filter as a light source. The illuminance of the light at this time is 2,000 μW / cm.²Met. The reaction product is collected in a sampling tube at regular intervals and gas chromatographed N.₂, N₂OWas quantified with respect to the elapsed time. It was confirmed that nitric oxide decreased according to the amount of product. The results are shown in Fig. 9.

【0044】

[Effect of the invention]

Since the photocatalyst of the present invention absorbs light not only in the ultraviolet light region but also in the visible light region, which has been impossible so far, light from ultraviolet light to visible light can be produced in the presence of the photocatalyst of the present invention. It can be irradiated to promote various photoreactions. The photocatalyst, the method for producing a photocatalyst, and the photocatalytic reaction method of the present invention are extremely epoch-making.

[Simple explanation of drawings]

[Figure 1]

It is an ultraviolet light to visible light absorption spectrum of a photocatalyst which is an Example of this invention.

[Figure 2]

It is an ultraviolet light to visible light absorption spectrum of a photocatalyst which is an Example of this invention.

[Fig. 3]

It is an ultraviolet light to visible light absorption spectrum of a photocatalyst which is an Example of this invention.

[Fig. 4]

It is an ultraviolet light to visible light absorption spectrum of a photocatalyst which is an Example of this invention.

[Fig. 5]

It is an ultraviolet light to visible light absorption spectrum of a photocatalyst which is an Example of this invention.

[Fig. 6]

It is a figure which quantified the production amount with respect to the elapsed time of 1-butene and trans-2-butene formation in the butene isomerization reaction method using a photocatalyst which is one Example of this invention.

[Fig. 7]

In the method for decomposing nitric oxide using a photocatalyst, which is an embodiment of the present invention, N₂, O₂, N₂OIt is a figure which quantified the amount of production with respect to the elapsed time of production.

[Fig. 8]

It is a figure which quantified the production amount with respect to the elapsed time of 1-butene and trans-2-butene formation in the butene isomerization reaction method using a photocatalyst which is one Example of this invention.

[Fig. 9]

In the method for decomposing nitric oxide using a photocatalyst, which is an embodiment of the present invention, N₂, N₂OIt is a figure which quantified the amount of production with respect to the elapsed time of production.