TW201420182A - Transition metal compound-loaded titanium oxide - Google Patents

Abstract

Provided is a transition metal compound-loaded titanium oxide that has excellent responsivity to visible light, and offers excellent photocatalytic capability. This transition metal compound-loaded titanium oxide has a transition metal compound loaded on crystalline titanium oxide, the transition metal compound-loaded titanium oxide being characterized by having an average minor axis of 50 nm or less and an average aspect ratio (major axis/minor axis) of 1.5 or more. Preferably, the crystalline titanium oxide is a rutile-type titanium oxide having crystal faces (110) and (111) and/or a rutile-type titanium oxide having crystal faces (110), (111), and (001).

Description

Titanium oxide carrying a transition metal compound

The present invention relates to a transition metal compound-loaded titanium oxide obtained by supporting a transition metal compound on titanium oxide. The above-described titanium oxide carrying a transition metal compound is excellent in response to visible light and exhibits excellent photocatalytic activity.

The titanium oxide carrying the transition metal compound has photocatalytic activity, and exhibits strong oxidizing power by irradiating light such as visible light or ultraviolet light, and can decompose harmful chemicals into water or carbon dioxide, and carry a transition metal by coating or mixing. The suspension of the titanium oxide of the compound imparts antibacterial, anti-mildew, deodorization, air purification, water purification, and antifouling effects to the object to be coated or the mixture to be coated. Further, it is known that when the titanium oxide carrying the transition metal compound contains an ionic impurity such as a halogen ion, the responsiveness to ultraviolet light and visible light is lowered.

The titanium oxide carrying the transition metal compound is known to be produced by the following procedure (see Patent Documents 1, 2, etc.).

1. A titanium oxide production step in which a titanium compound is hydrothermally treated to obtain a titanium oxide suspension.

2. A step of supporting a transition metal compound carrying a transition metal compound-loaded titanium oxide suspension by adding a transition metal compound to a titanium oxide suspension.

3. A purification step of reducing the content of ionic impurities by applying a suspension of a transition metal compound-containing titanium oxide to a titanium oxide suspension using a full filtration method, a vacuum filtration method, or a centrifugal separation treatment.

However, in the above-mentioned method, in the purification step, the transition metal compound-loaded titanium oxide is densified by solid-liquid separation, and the exposure amount of the high active surface is lowered, so that a transition having sufficient photocatalytic activity is not obtained. The problem of titanium oxide of metal compounds. Further, once the tungsten oxide carrying the transition metal compound, which has been densified, is redispersed after being subjected to a pulverization treatment or the like, satisfactory photocatalytic activity is not obtained.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 10-158015

[Patent Document 2] Japanese Laid-Open Patent Publication No. 62-235215

Accordingly, an object of the present invention is to provide a transition metal compound-containing titanium oxide which is excellent in response to visible light and exhibits excellent photocatalytic activity.

As a result of intensive investigation to solve the above problems, the inventors of the present invention have found that a rod-shaped titanium oxide carrying a transition metal compound is subjected to solid-liquid separation treatment by centrifugal separation or the like, and once pulverized, even after pulverization Decentralized, rod-shaped crystal structure will also be cut off And because of the following 1, 2, etc., the photocatalytic activity in the visible light region is remarkably lowered.

1. The average aspect ratio of the titanium oxide carrying the transition metal compound becomes smaller and becomes closer to a spherical shape, so that the separation between the oxidation reaction field and the reduction reaction field is lowered, and the reverse reaction or side reaction cannot be avoided. Go on.

2. The titanium oxide sheet which does not carry a transition metal compound is produced by cutting a rod-like crystal structure, and the titanium oxide sheet becomes unable to exhibit visible light responsiveness.

Further, it has been found that, in the purification step, if the membrane filtration treatment by the cross flow filtration method is used instead of the solid-liquid separation treatment such as centrifugation, the titanium oxide carrying the transition metal compound may not be compacted. The state in which the rod-like crystal structure is maintained is effective in removing ionic impurities, and the content of the ionic impurities is extremely low, and the rod-shaped titanium oxide carrying the transition metal compound is obtained. Further, it has been found that when the reaction system is stirred during hydrothermal treatment, a transition metal compound-containing titanium oxide having an average short diameter and a small average aspect ratio can be obtained. Further, it has been found that the transition metal compound-containing titanium oxide obtained as described above is excellent in responsiveness to visible light and exhibits excellent photocatalytic activity. The present invention has been completed in light of these findings.

That is, the present invention provides a transition metal compound-containing titanium oxide which is a transition metal compound-supporting titanium oxide carrying a transition metal compound in a crystalline titanium oxide, and has an average minor axis of 50 nm or less and an average aspect ratio. (long diameter / short diameter) is 1.5 or more.

The crystalline titanium oxide has a crystal face (110) and The rutile-type titanium oxide of the crystal face (111) and/or the rutile-type titanium oxide having a crystal face (110), a crystal face (111), and a crystal face (001) are preferred.

The specific surface area is preferably 10 m ² /g or more.

The present invention provides a titanium oxide having an average minor axis of 50 nm or less and an average aspect ratio (long diameter/short diameter) of 1.5 or more.

The transition metal compound-containing titanium oxide of the present invention has an average minor axis of 50 nm or less and an average aspect ratio (long diameter/short diameter) of 1.5 or more. Therefore, it is excellent in responsiveness to visible light, and absorbs light from ordinary living spaces such as sunlight or incandescent lamps, fluorescent lamps, and LEDs, and decomposes harmful chemicals into water or carbon dioxide. That is, the transition metal compound-containing titanium oxide suspension of the present invention can be suitably used as a photocatalyst for LED illumination. In addition, it can be applied to various antibacterial and anti-mildew, deodorization, air purification, water purification, etc., and can be widely applied to environmental purification and home appliances in public facilities such as indoor wallpapers or furniture, hospitals, schools, etc. The high functionality of the products.

001‧‧‧ Crystallized surface

110‧‧‧ Crystallized surface

111‧‧‧ Crystallized surface

Fig. 1 is a schematic view showing an example of membrane filtration by a sweeping method.

Fig. 2 is a schematic view showing an example of reverse cleaning by membrane filtration by a sweeping method.

Fig. 3 is a perspective view of a rod-shaped rutile-type titanium oxide having a crystal face (110) (111) and a rod-shaped rutile-type titanium oxide having a crystal face (110) (111) (001).

Fig. 4 is a photograph (×200000, scale: 100 nm) of the iron compound-loaded titanium oxide obtained in Example 2, which was imaged by an electric field emission type scanning electron microscope.

[Formation of the Invention]

[Titanium oxide carrying a transition metal compound]

The transition metal compound-containing titanium oxide of the present invention is characterized in that the transition metal compound is supported on the crystalline titanium oxide, and the average short diameter is 50 nm or less, and the average aspect ratio (long diameter/short diameter) is 1.5 or more.

The titanium oxide carrying the transition metal compound has an average minor axis of 50 nm or less, preferably 5 to 40 nm, particularly preferably 5 to 30 nm, and most preferably 10 to 25 nm. When the average short diameter is larger than the above range, the separation between the oxidation reaction field and the reduction reaction field is lowered, and the reverse reaction or the side reaction is unavoidable, and the photocatalytic activity is lowered, which is not preferable.

Further, the average aspect ratio (long diameter/short diameter) of the titanium oxide carrying the transition metal compound is 1.5 or more, preferably 1.5 to 100, more preferably 1.5 to 50, and particularly preferably 1.5 to 20, most preferably 2~15. When the average aspect ratio is less than the above range, the separation between the oxidation reaction field and the reduction reaction field is lowered, and the reverse reaction or the side reaction is unavoidable, and the photocatalytic activity is lowered, which is not preferable.

Further, in the present invention, the average short diameter and the average aspect ratio are values obtained by the following measurement methods for the samples obtained by the following production methods.

<Sample preparation method>

1. Put a small amount (about half of the size of the spoon) The titanium oxide of the metal compound was added to a 9 mL glass sample vial, and 7 mL of ethanol was added thereto, and ultrasonic waves were applied for 5 minutes in an ultrasonic cleaner to disperse into ethanol to obtain an ethanol dispersion.

2. The obtained ethanol dispersion liquid was taken up by a glass pipette, dropped on a sample stage for SEM, and naturally dried, and then subjected to platinum vapor deposition for 30 seconds.

<Measurement method>

An electric field emission type scanning electron microscope (trade name "FE-SEM JSM-6700F", manufactured by Nippon Denshi Co., Ltd., acceleration voltage: 15 kV, WD: about 3 mm, magnification: 200,000 times), random observation of crystal particles, extraction of representative In the three SEM photographs taken, the appearance of the extracted SEM photograph is extremely large or small, and 30 particles with well-defined particles centered on the average size of the particles are printed on the OHP sheet. For the particles, use the map. The analysis software (product name "WinROOF Version 5.6", manufactured by Mitani Corporation) is used to obtain each of the short diameters (widths orthogonal to the maximum long diameter), and the values are averaged as the average short diameter. Further, the average long diameter (maximum long diameter) was obtained in the same manner, and the ratio (average long diameter/average short diameter) was defined as an average aspect ratio.

Examples of the crystalline titanium oxide include a rutile type, an anatase type, and a brookite type titanium oxide. In the present invention, from the viewpoint of exposing a stable crystal surface, rutile-type or anatase-type titanium oxide is preferable (from the viewpoint of exhibiting more excellent photocatalytic activity, rutile-type titanium oxide is more preferable, particularly preferably A rutile-type titanium oxide having a crystal face (110) and a crystal face (111) and/or a rutile-type titanium oxide having a crystal face (110), a crystal face (111), and a crystal face (001).

Transition metal compound, for example, a transition metal ion State loading of transition metal monomers, transition metal salts, transition metal oxides, transition metal hydroxides, or transition metal complexes. The amount of the transition metal compound supported is, for example, 50 ppm or more, preferably 100 ppm or more, more preferably 200 ppm or more, particularly preferably 300 ppm or more, and most preferably 500 ppm or more. The upper limit of the amount of the transition metal compound supported is, for example, about 5,000 ppm, preferably 3,000 ppm, and particularly preferably 2,000 ppm. When the amount of the transition metal compound supported is less than the above range, the visible light responsiveness tends to decrease. On the other hand, when the amount of the transition metal compound supported is higher than the above range, the reverse electron transfer of the injected electrons or the like causes the excited electrons to not function effectively, and the photocatalytic activity tends to decrease.

The transition metal compound is selectively supported on the surface of the crystalline titanium oxide, and the separation property of the reaction field between the oxidation reaction and the reduction reaction can be further improved, and the recombination of the excited electrons and the hole can be suppressed by the foregoing. It is preferable to suppress the progress of the reverse reaction and to greatly enhance the activity of the photocatalyst, and it is preferable to selectively carry the transition metal compound on the oxidation reaction surface.

In the present invention, the transition metal compound is carried in a "surface selective" manner, and refers to a specific surface (for example, a specific surface) of the crystal faces of the crystallized titanium oxide having two or more surfaces. One side or two sides, etc.) are carried in an amount exceeding 50% of the transition metal compound (preferably 70% or more, particularly preferably 80% or more). Furthermore, the upper limit of the face selection rate is 100%. The surface selectivity can be determined by confirming the signal derived from the transition metal compound on each crystal face by using a transmission electron microscope (TEM) or an energy dispersive fluorescent X-ray analyzer (EDX).

The transition metal compound may have an absorption spectrum in the visible light region and may inject electrons into the conduction band in the excited state. However, in the present invention, the third to eleventh element compounds of the periodic table are preferred, and the periodic table is The element of the 8th to 11th element is particularly preferred, and particularly preferably an iron compound or a platinum compound, and most preferably a trivalent iron compound (Fe ³⁺ ). Since the trivalent iron compound (Fe ³⁺ ) is easily adsorbed to titanium oxide, and the divalent iron compound (Fe ²⁺ ) has a property of being not easily adsorbed, it is easier to use surface selectivity by utilizing this property. Ground carrying.

The specific surface area of the titanium oxide carrying the transition metal compound is, for example, 10 m ² /g or more. The lower limit of the specific surface area is preferably 30 m ² /g, more preferably 50 m ² /g, particularly preferably 60 m ² /g, and most preferably 70 m ² /g. The upper limit of the specific surface area, for example, 200m ² / g, preferably from 150m ² / g, particularly preferably 100m ² / g.

The specific surface area of the titanium oxide contains a transition metal compound of, for example, 10 ~ 200m ² / g, preferably 10 ~ 150m ² / g, more preferably 30 ~ 150m ² / g, particularly preferably 50 ~ 100m ² / g, more preferably 60 to 100 m ² /g, most preferably 70 to 100 m ² /g. The titanium oxide carrying the transition metal compound having a specific surface area in the above range exhibits an excellent photocatalytic activity because the amount of exposure of the high active surface is increased.

The specific surface area is a sample obtained by degassing a transition metal compound-containing titanium oxide at 100 ° C (under vacuum) for 60 minutes, using a high-speed specific surface area ‧ pore size distribution measuring apparatus (trade name "NOVA-1200", Quantachtome Co., Ltd., the average of the values obtained by changing the sample twice under the following conditions.

<Specific surface area measurement conditions>

Measuring principle: constant volume method (blank correction type)

Detection method: relative pressure (using the ratio of the adsorption equilibrium pressure (P) to the saturated vapor pressure (P ₀ ) in the sample box of the pressure transducer) and the amount of adsorbed gas (by using the pressure transducer to detect and utilize the heat Manifold temperature detection of resistance calculates the amount of injected gas for an ideal gas)

Adsorbed gas: nitrogen gas

Box size: small pellet box (box capacity: 1.8cm ³ , trunk outer diameter: 9mm)

Measurement item: 3 points on the adsorption side of P/P ₀ = _{0.1, 0.2,} 0.3

Analytical project: specific surface area using the BET multipoint method

The transition metal compound-containing titanium oxide of the present invention exhibits excellent visible light responsiveness, and exhibits excellent photocatalytic activity by light irradiation, and decomposes harmful chemicals into water or carbon dioxide, thereby exhibiting antibacterial and antifungal properties. Deodorization, air purification, water purification, anti-fouling and other effects.

For example, the amount of CO ₂ produced when the toluene is oxidized by using the above-described transition metal compound-containing titanium oxide (200 mg) is, for example, 300 ppm or more. Moreover, the amount of CO ₂ produced when the methanol is oxidized is, for example, 500 ppm or more, preferably 600 ppm or more, more preferably 700 ppm or more, and particularly preferably 750 ppm or more.

Further, the method for measuring the amount of CO ₂ produced when the toluene is oxidized is as follows.

200 mg of titanium oxide carrying a transition metal compound was spread on a glass dish, placed in a reaction container (Tedlar bag, material: fluorinated ethylene resin), and 125 ppm of toluene gas (100 ppm) was blown into the reaction container. After the adsorption of the toluene gas to the titanium oxide carrying the transition metal compound was balanced, light irradiation (LED, light intensity: 2.5 W/cm ² , wavelength of light: 455 nm) was carried out at room temperature (25 ° C), and the light was measured. The amount of CO ₂ produced after 24 hours from the start of irradiation.

Further, the method for measuring the amount of CO ₂ produced when the methanol is oxidized is as follows.

200 mg of titanium oxide carrying a transition metal compound was spread on a glass dish, placed in a reaction container (Tedlar bag, material: fluorinated ethylene resin), and 125 ppm of methanol gas (125 mL) was blown into the reaction container. After the adsorption of the methanol gas to the titanium oxide carrying the transition metal compound is balanced, light irradiation (LED, light intensity: 2.5 W/m ² , wavelength of light: 455 nm) is performed at room temperature (25 ° C), and the light is measured. The amount of CO ₂ produced after 24 hours from the start of irradiation.

The transition metal compound-containing titanium oxide of the present invention exhibits excellent light responsiveness as described above, that is, has responsiveness to light in a wide wavelength range from the ultraviolet region to the visible region, and thus absorbs The light of normal living space such as sunlight, incandescent lamps, fluorescent lamps, and LEDs exhibits high catalytic activity and decomposes harmful chemicals into water or carbon dioxide, and can exhibit antibacterial properties (bacteria, actinomycetes, fungi, algae, etc.) Sterilization, algae killing, mildew proofing, deodorization (for example, deodorization of sulfur-containing substances such as ammonia, amines, methyl mercaptan, hydrogen sulfide, etc., malodorous gases such as acetic acid, aldehydes, and ethylene), air purification , water purification, anti-fouling and other effects. Further, the transition metal compound-containing titanium oxide of the present invention can be applied or mixed by a state in which a binder, a solvent, a dispersant, a tackifier, a surfactant, or the like is mixed, if necessary, to coat the object to be coated. Or the mixture gives the aforementioned effects.

Titanium oxide carrying a transition metal compound as the present invention Examples of the coated body and the mixture to be coated include building materials, exterior decoration, architectural interior decoration, architectural coatings, walls, wallpapers, floors, window frames, window glass, crystallized glass, glass, screen windows, and rainwater drainage. Sinks, sunshine heat reflective sheets, letter boxes, structural members, paving materials, display panels, traffic signs, road traffic sign reflectors, flat panel displays, display filters, road display materials, road decorative panels, fences, doors , tunnels, road lighting fixtures, soundproof walls, grilles, tunnel interiors, road mirrors, plastic sheet greenhouse roofs, bridges, bridge safety barriers, cars, trains, ships, interiors and exteriors, painting, vehicles Use wheel, railway vehicle body structure, vehicle parts, mechanical devices or articles, ‧ dust cover, painting, various display devices, advertising towers, insulators, solar panels, solar battery covers, solar water heaters, heat shields, Fuel cells, optical fibers, vehicle lighting covers, fishing nets, ropes, hoses, bottom members, anti-algae, shoes, handbags, blinds, curtains Wall coverings, screens, paper sliding windows, plastic sliding windows, paper sliding doors, synthetic leather, tablecloths, clothing, raincoats, stationery, books, notebooks, paper, cartons, vehicles or home appliances, etc. Utensils, musical instruments, fishing tackles, interior decorations, plastic containers, cards, tents, timber, columns, ceilings, wooden walls, etc., construction materials, furniture, printed plywood, interior panels, artificial flowers, foliage plants, artificial Plants, swimming pools, baths, rivers, rivers, factory drainage, living drainage, groundwater, pools, artificial rivers, water treatment fillers, mirrors, washbasins, ceramic tiles, tile joints, bathtubs, bathroom components, toilet floors Finished materials, in-house anti-infective disease internal components, kiln industry multi-function materials, glaze medicine, refrigerator inner and outer walls, pedestal, kitchen panel, flow table, microwave oven, cooking container, ventilation Installation, air conditioning, heat exchangers, various filters, toilets, fibers, non-woven fabrics, masks, clothing, bedding, hats, hard hats, door mats, carpets, medical equipment, food, forks, knives, spoons, utensils, packaging materials , plastic wrap, food preservation container, food cleaning device, water purifier, kitchen waste treatment device, melamine decorative board, carpet, lighting device, lighting fixture, lighting, lighting umbrella, black light, antifouling paint, Various films such as filters and agricultural vinyl films, sheets, super-hydrophilic films, grass-proof sheets, electronic parts, electrical products, electronic equipment, corona charging devices, plasma generating devices, ozone generating devices, exposure devices, humidification , hand dryer, scalp care device, vacuum cleaner, telephone, mobile phone, portable equipment, touch panel display, organic EL components, flat panel display, inkjet recording device, air cleaner, refrigeration machine, dust collector, Decorations, mechanical parts, disks, display cases, cover glass for instruments, cameras, glasses, lenses for cameras, lenses for glasses, Contact lenses, whitening agents, oral ‧ dental material, the dental bleaching material, implants, oral appliances, cosmetics, shampoo and the like.

(Manufacturing method of titanium oxide carrying transition metal compound)

The transition metal compound-containing titanium oxide of the present invention can be produced, for example, by the following procedure.

(Step of producing crystalline titanium oxide)

The step of producing a crystalline titanium oxide is a step of obtaining crystalline titanium oxide from a titanium compound. As a method for producing crystalline titanium oxide, a conventionally known method can be employed. For example, bar-shaped rutile-type titanium oxide is hydrothermally treated by using a titanium compound in an aqueous medium (for example, water or a mixture of water and a water-soluble organic solvent) [for example, 100 to 220 ° C for 2 to 48 hours (more Good for 2~15 hours, especially for 5~15 hours)] but can be synthesized. Further, when a halide is added and/or stirred (for example, a power required for stirring Pv: 0.1 to 1500 W/m ³ ) during hydrothermal treatment, the size and surface area of the obtained particles can be adjusted, which is preferable.

Examples of the titanium compound include a trivalent titanium compound and a tetravalent titanium compound. Examples of the trivalent titanium compound include titanium trihalide such as titanium trichloride or titanium tribromide. As the trivalent titanium compound of the present invention, titanium trichloride (TiCl ₃ ) is preferred from the viewpoint of being inexpensive and easily available.

In addition, examples of the tetravalent titanium compound of the present invention include a compound represented by the following formula (1).

Ti(OR) _t X _4-t (1) (wherein R represents a hydrocarbon group, and X represents a halogen atom. _t represents an integer of 0 to 3)

Examples of the hydrocarbon group of R in the formula (1) include a C _1-4 aliphatic group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a n-butyl group, a second butyl group, and a third butyl group. Hydrocarbyl group and the like.

Examples of the halogen atom of X in the formula (1) include chlorine, bromine, and iodine.

Examples of the tetravalent titanium compound as described above include titanium tetrahalide such as TiCl ₄ , TiBr ₄ , and TiI ₄ ; Ti(OCH ₃ )Cl ₃ , Ti(OC ₂ H ₅ )Cl ₃ , and Ti(OC). _{4 H 9) Cl 3, Ti} (OC 2 H 5) Br 3, Ti (OC 4 H 9) Br 3 , etc. trihalide, alkoxy _{titanium; Ti (OCH 3) 2 Cl} 2, Ti (OC 2 H 5) Titanium dihalide dihalide such as ₂ Cl ₂ , Ti(OC ₄ H ₉ ) ₂ Cl ₂ , Ti(OC ₂ H ₅ ) ₂ Br ₂ or the like; Ti(OCH ₃ ) ₃ Cl, Ti(OC ₂ H ₅ ) ₃ Cl, Ti(OC ₄ H ₉ ) ₃ Cl, Ti(OC ₂ H ₅ ) ₃ Br or the like monohalogenated titanium alkoxide. As the tetravalent titanium compound of the present invention, titanium tetrahalide is preferred from the viewpoint of being inexpensive and easily available, and particularly titanium tetrachloride (TiCl ₄ ) is preferred.

The rod-shaped rutile-type titanium oxide obtained by hydrothermal treatment can be purified by a conventionally known method, for example, filtration, concentration, distillation, extraction, crystallization, recrystallization, column chromatography, or a combination thereof. . In the present invention, the membrane filtration is carried out by the following sweeping method, and the crystal structure of the titanium oxide can be maintained, and the content of the ionic impurities can be reduced, and the pulverization treatment or the like is not required, and the transition metal compound can be directly applied. The step of obtaining a titanium oxide having a high transition metal compound is preferable.

The average diameter of the crystalline titanium oxide obtained by the above method is 50 nm or less, preferably 5 to 40 nm, particularly preferably 5 to 30 nm, and most preferably 10 to 25 nm.

Further, the average aspect ratio (long diameter/short diameter) of the crystalline titanium oxide obtained by the above method is 1.5 or more, preferably 1.5 to 100, more preferably 1.5 to 50, particularly preferably 1.5 to 20, most preferably It is 2~15.

Further, the specific surface area of the crystalline titanium oxide obtained by the above method is, for example, 10 m ² /g or more. The lower limit of the specific surface area is preferably 30 m ² /g, more preferably 50 m ² /g, particularly preferably 60 m ² /g, and most preferably 70 m ² /g. The upper limit of the specific surface area, for example, 200m ² / g, preferably from 150m ² / g, particularly preferably 100m ² / g.

(Step of carrying a transition metal compound)

The step of supporting the transition metal compound is a step of carrying a transition metal compound supported on the crystalline titanium oxide obtained through the above step to obtain a transition metal compound-containing titanium oxide. The support of the transition metal compound can be carried out, for example, by adding a solution containing a transition metal compound to the crystalline titanium oxide and impregnating it. For example, a trivalent iron compound (Fe ³⁺ ) is ^supported as a transition metal compound as a transition metal compound-containing titanium oxide, and iron (III) nitrate and iron sulfate can be added by adding a suspension of crystalline titanium oxide. III), a solution of iron (III) chloride or the like is obtained by impregnation.

The concentration of the solution containing the transition metal compound is, for example, about 0.1 to 40% by weight, preferably 1 to 40% by weight. Further, the impregnation time is, for example, about 1 minute to 24 hours, preferably 5 minutes to 10 hours.

In the present invention, when the transition metal compound is impregnated, the excitation light is irradiated, and it is preferable that the transition metal compound is selectively and efficiently carried on the specific surface of the crystalline titanium oxide without requiring a large-scale facility or the like. When the excitation light is irradiated, electrons in the valence band of the crystalline titanium oxide are excited to the conduction band, and holes are generated in the valence band, and excited electrons are generated in the conduction band, and the diffusion proceeds to the surface of the particle, and according to each crystal face The characteristic separation excites electrons and holes to form an oxidation reaction surface and a reduction reaction surface. In this state, for example, when a trivalent iron compound is impregnated as a transition metal compound, a trivalent iron compound (Fe ³⁺ ) is adsorbed on the oxidation reaction surface, but a trivalent iron compound in the reduction reaction surface ( Fe ³⁺ ) is reduced to a divalent iron compound (Fe ²⁺ ), and the divalent iron compound (Fe 2+ ) has a property of being difficult to adsorb, and thus is eluted into the solution, and as a result, it is selectively obtained on the oxidation reaction surface. A titanium oxide carrying an iron compound ^supported on an iron compound (Fe ³⁺ ).

The excitation light is light (for example, ultraviolet light) having energy above the band gap energy. As the excitation light irradiation means, for example, an ultraviolet exposure device having a light source that efficiently generates ultraviolet light, such as a medium high pressure mercury lamp, a UV laser, a UV-LED, or an invisible light, or the like can be used. The amount of irradiation of excitation light, for example, 0.1 ~ 300mW / cm ^2, and preferably 0.5 ~ 100mW / cm ^2.

Further, in the present invention, it is preferred to add a sacrificial agent at the time of impregnation. By adding a cockroach, the transition metal compound can be carried at a high selectivity on the specific crystal face of the crystalline titanium oxide. As the sacrificial agent, an organic compound which easily emits electrons by itself is preferable, and examples thereof include alcohols such as methanol and ethanol; carboxylic acids such as acetic acid; ethylenediaminetetraacetic acid (EDTA) and triethanolamine (TEA). Amines, etc.

The amount of the sacrificial agent to be added can be appropriately adjusted, and is, for example, about 0.5 to 20.0% by weight, preferably about 1.0 to 5.0% by weight, based on the suspension of the crystalline titanium oxide. Excipients can also be used in excess.

After the step of carrying the transition metal compound, it is preferred to carry out the purification treatment. In the present invention, the membrane filtration treatment by the sweeping method is carried out, and the ionic impurities are efficiently removed from the state in which the titanium oxide carrying the transition metal compound is not compacted and the rod-like crystal structure is maintained. The content of the impurity is extremely low, and it is preferable that it is a rod-shaped titanium oxide carrying a transition metal compound.

(filtration by membrane with sweeping method)

In the membrane filtration by the sweeping method, the level of the treated layer flows on the surface of the filtration membrane, and while the filtration membrane is prevented from being contaminated by the deposition of the filter residue, one part of the water to be treated is filtered in the flow side direction of the water to be treated. method. By using the above titanium oxide or carrying a transition metal compound The suspension of titanium oxide is applied by membrane filtration using a sweeping method, so that no pulverized filter residue is formed on the surface of the filtration membrane, and ionic impurities are efficiently removed, and titanium oxide or a titanium oxide carrying a transition metal compound can be maintained. The crystal structure also reduces the content of ionic impurities to an extremely low level.

The concentration of the suspension of the titanium oxide or the transition metal compound-loaded titanium oxide which is filtered by the membrane of the sweeping method is, for example, about 0.1 to 40% by weight (preferably 0.1 to 30% by weight). When the concentration of the suspension of titanium oxide or the titanium oxide carrying the transition metal compound is outside the above range, the removal efficiency of the ionic impurities tends to decrease. Moreover, when the concentration of the suspension of titanium oxide or the titanium oxide carrying the transition metal compound is higher than the above range, the viscosity becomes too high, and fouling (clogging) is likely to occur.

When a suspension of titanium oxide or a titanium oxide carrying a transition metal compound is applied to a membrane filtered by a sweeping method, the ionic impurities and the filtrate can be simultaneously separated and removed to obtain a concentrated titanium oxide or an oxidation carrying a transition metal compound. A suspension of titanium.

It is ideal to adjust the concentration ratio to about 1 to 400 times (especially 1 to 20 times, especially 1 to 10 times). When the concentration ratio is higher than the above range, it is difficult to suppress the deposition of the adhering substance on the film surface, and it is difficult to prevent the compaction of the titanium oxide or the titanium oxide carrying the transition metal compound. In addition, since fouling (clogging) occurs in the filtration membrane due to deposition of the adhering substance on the membrane surface, the membrane life is likely to be lowered, and it is necessary to perform reverse cleaning frequently, and the filtration treatment cannot be operated, and filtration is also performed. The tendency for speed to fall easily. On the other hand, when the concentration ratio is less than the above range, the separation efficiency of the ionic impurities is lowered, and the amount of the washing water used tends to increase.

The concentration ratio can be adjusted, for example, by controlling the filtration pressure, the film surface speed (sweep speed) of the suspension of titanium oxide or the transition metal compound-loaded titanium oxide, and the like. The filtration pressure is, for example, about 0.001 to 5.0 MPa, preferably 0.005 to 3 MPa, and particularly preferably 0.01 to 2.0 MPa.

Moreover, the larger the film surface speed of the supply liquid containing the titanium oxide or the suspension of the titanium oxide carrying the transition metal compound, the more the deposition of the adhering substance to the film surface can be suppressed, and the high filtration flow rate (flux) can be obtained. The film surface line speed (sweep speed) is, for example, 0.02 m/s or more and less than 3 m/s, preferably 0.05 m/s or more and less than 1.5 m/s.

The titanium oxide or the suspension of the titanium oxide carrying the transition metal compound, which is concentrated by membrane filtration by a sweeping method, is added with water, and the concentration of the suspension of the titanium oxide or the titanium oxide carrying the transition metal compound is diluted to the above range. And it is preferable to repeat the operation of membrane filtration by the sweeping method again. According to the above, the load of the filtration membrane due to fouling (clogging) or the like can be reduced, and the life of the filtration membrane can be increased, and the content of the ionic impurities can be reduced to an extremely low level.

Fig. 1 is a schematic view showing an example of membrane filtration (circulating membrane filtration method) by means of a sweeping method of a suspension of titanium oxide or a titanium oxide carrying a transition metal compound. The supply liquid of the suspension containing titanium oxide or the titanium oxide carrying the transition metal compound stored in the storage tank is subjected to membrane filtration by a sweep filtration method to obtain concentrated titanium oxide or titanium oxide carrying a transition metal compound. Suspension (concentrate). A suspension of concentrated titanium oxide or titanium oxide carrying a transition metal compound is again circulated to the storage tank and diluted with water for dilution (diluted water). Filtered by sweeping filtration.

Examples of the filtration membrane used for membrane filtration by a sweeping method include an ultrafiltration membrane, a microfiltration membrane, a nanofilter, and a reverse osmosis membrane. In the present invention, from the viewpoint of good separation performance, it is preferred to use an ultrafiltration membrane in particular.

As the ultrafiltration membrane, a material having an average pore diameter of about 1 to 20 nm (preferably 1 to 10 nm) and having a molecular weight of about 1,000 to 300,000 (preferably 1,000 to 50,000) and an average particle diameter of about 1 to 10 nm can be used. The person is more ideal.

The film shape of the ultrafiltration membrane may be, for example, any hollow fiber filtration membrane, tubular membrane, spiral membrane, flat membrane, or the like, but a hollow fiber filtration membrane or a tubular shape is used from the viewpoint of facilitating reverse cleaning. The membrane is ideal.

The inner diameter of the hollow fiber membrane of the hollow fiber type filtration membrane is about 0.1 to 2.0 mm (preferably 0.5 to 1.5 mm) from the viewpoint of prevention of clogging of the pollutants and improvement of the hollow fiber filling rate of the membrane group.

Examples of the material of the filtration membrane include cellulose acetate, polyacrylonitrile, polyfluorene, polyether oxime (PES), polyacrylonitrile, aromatic polyamine, polyvinylidene fluoride, polyvinyl chloride, and poly. A general material such as ethylene, polypropylene, polyimide, or ceramics. In the present invention, cellulose acetate, polyfluorene, polyether oxime (PES), polyacrylonitrile, and aromatic polyamine are particularly preferred.

When a hollow fiber type filtration membrane is used, a method of filtering a suspension of titanium oxide or a titanium oxide carrying a transition metal compound (filtration method) is oxidized on the inner side (inside of the hollow fiber membrane) a method in which a supply liquid of a suspension of titanium or a suspension of titanium oxide carrying a transition metal compound flows to the outside (the outer side of the hollow fiber membrane) (internal pressure filtration method); on the contrary, the titanium oxide or the titanium oxide is contained on the outer side. A method in which a supply liquid of a suspension of a transition metal compound titanium oxide flows and the filtrate flows inward (external pressure filtration method). In the present invention, an internal pressure filtration method is preferable from the viewpoint of maintaining a high membrane surface flow rate.

In the membrane filtration by the sweeping method, in order to prevent the deposition of adhering substances on the membrane surface, reduce the burden on the membrane, and perform long-term membrane filtration, it is preferable to perform intermittent reverse cleaning of the membrane with washing water. . The reverse cleaning system is preferably carried out at a predetermined cycle while controlling the pressure and the flow rate.

The pressure for the reverse washing is, for example, about 0.01 to 3.0 MPa, preferably 0.01 to 2.0 MPa, more preferably 0.01 to 1.0 MPa, particularly preferably 0.01 to 0.5 MPa, and most preferably 0.05 to 0.5 MPa. Further, the flow rate for the reverse cleaning is, for example, about 0.01 to 10 kg/min, preferably 0.05 to 5 kg/min, particularly preferably 0.1 to 5 kg/min [or, for example, 1 × 10 ^-7 to 2 × 10 ^{-4 .} m/sec or so, preferably 8 × 10 ^-7 ~ 9 × 10 ^-5 m / sec, particularly preferably 1 × 10 ^-6 ~ 9 × 10 ^-5 m / sec]. The frequency of the reverse cleaning is preferably about one time in about 0.5 to 3 hours. The time for the reverse cleaning is preferably about 0.5 to 10 minutes.

Further, as the washing water used for the reverse washing, water (for example, purified water, distilled water, pure water, ion-exchanged water, or the like) is preferably used. Further, it is preferable to reuse the diluted water as a suspension of the concentrated transition metal compound-containing titanium oxide by backwashing the washing water passing through the membrane (see Fig. 2).

When the suspension of the titanium oxide is filtered, it is repeatedly filtered by a membrane of a sweeping method until the pH of the filtrate becomes 1 or more (preferably 1 to 7, particularly preferably 2 to 6, preferably 2 to 5.5). . When the membrane filtration by the sweeping method is completed before the pH of the filtrate is in the above range, the removal of ionic impurities (especially hydrogen ions, chloride ions, and titanium ions) is insufficient, and the transition of the transition metal compound becomes difficult. .

Further, when the suspension containing the transition metal compound-containing titanium oxide is filtered, the membrane has a conductivity of 300 μS/cm or less by filtration (for example, 0.5 to 300 μS/cm, preferably 0.5 to 250 μS/). It is preferable to repeat the cm, particularly preferably from 1 to 200 μS/cm. When the membrane filtration by the sweeping method is completed before the conductivity of the filtrate is within the above range, the removal of ionic impurities (especially iron ions and chloride ions) may be insufficient.

a suspension of a transition metal compound-containing titanium oxide obtained by membrane filtration by a sweeping method, followed by drying (for example, FV (1.3 kPa [A]) or less), and performing at 60 ° C for about 15 hours; At a normal pressure (atmospheric pressure), the transition metal compound-containing titanium oxide is obtained at 105 ° C for about 1 hour.

[Examples]

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples.

Example 1

(Preparation of crystalline titanium oxide)

Diluted with titanium tetrachloride aqueous solution (Ti concentration: 16.5 wt% ± 0.5 wt%, chloride ion concentration: 31 wt% ± 2 wt%, manufactured by Toho Titanium Co., Ltd.) in pure water at room temperature (25 ° C). The Ti concentration was made 5.6% by weight. 5650 g of the diluted titanium tetrachloride aqueous solution was placed in a 10 L rug-lined autoclave and sealed. Using the heat medium, it took 2 hours to raise the temperature in the above autoclave to 140 °C. Thereafter, the mixture was stirred at a power required for stirring (Pv value) at 1,360 W/m ³ while being kept at a temperature of 140 ° C and a vapor pressure of the temperature for 5 hours, and then the autoclave was cooled by cooling the heat medium. Cool to below 40 °C. Thereafter, the mixture was further kept at a temperature of 140 ° C and a pressure of a vapor pressure of the temperature for 5 hours, and then the autoclave was cooled by cooling the heat medium. It was confirmed that the temperature in the autoclave was 40 ° C or lower, and 5650 g of the crude titanium oxide suspension (1) was taken out.

(membrane filtration treatment by sweeping method (1))

The obtained crude titanium oxide suspension (1) was diluted to 3 times with pure water, and a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight limit) was used. : 30,000, manufactured by Daicen Membrane Systems Co., Ltd., at room temperature (25 ° C) and a filtration pressure of 0.02 MPa, while adding the same amount of pure water as the filtrate, and performing a filtration treatment by a sweeping method. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the pH of the filtrate became 4.0. Further, the pH was measured using a pH test paper. In this period, the reverse cleaning was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min in a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. Thereafter, the storage of pure water was stopped, and the concentration of titanium oxide was concentrated to obtain a titanium oxide suspension (1-1). When the titanium oxide suspension (1-1) is dried at 105 ° C for 1 hour under normal pressure, a rod-shaped rutile-type titanium oxide having a crystal face (110) and a crystal face (111) is obtained and has a crystal face (110). Titanium oxide (1) of a mixture of a rod-like rutile-type titanium oxide having a crystal face (111) and a crystal face (001) (specific surface area: 77 m ² /g, average aspect ratio: 6, average short diameter: 18 nm) 525g (refer to Figure 3). The photocatalytic activity of the obtained titanium oxide (1) evaluated by the following toluene oxidation method using ultraviolet rays was 625 ppm (decomposition rate: 94%).

(treatment of carrying iron compounds)

To the titanium oxide suspension (1-1) obtained above, 7.5 g of an aqueous solution of ferric chloride (35 wt%) was added, and the mixture was stirred at room temperature (25 ° C) for 30 minutes. Thereafter, 95 g of methanol (1.7 wt% of the titanium oxide suspension) was added, and a 100 W high-pressure mercury lamp was irradiated with ultraviolet rays (UV) for 3 hours (UV irradiation amount: 5 mW/cm ² ) to obtain a suspension of the titanium oxide containing the iron compound. Liquid (1).

(membrane filtration treatment by sweeping method (2))

The titanium oxide suspension (1) containing the iron compound is diluted to 3 times with pure water, and a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000) is used. The Daicen Membrane Systems (manufactured by Daisen Membrane Systems Co., Ltd.) was subjected to a filtration treatment by a sweeping method while adding pure water of the same amount as the filtrate at room temperature (25 ° C) and a filtration pressure of 0.02 MPa. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the conductivity of the filtrate became 200 μS/cm. During this period, the reverse cleaning was carried out for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. Thereafter, the storage of pure water is stopped, and the concentration of the titanium oxide carrying the iron compound is concentrated to obtain a titanium oxide suspension (1-1) carrying the iron compound. During this period, the flow rate of 0.1 MPa and the flow of 2 kg/min are used in a ratio of one hour. Perform reverse cleaning for 1 minute. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank.

Thereafter, the mixture was dried at 105 ° C for 1 hour under normal pressure to obtain a titanium oxide (1) (specific surface area: 77 m ² /g, average aspect ratio: 6, average short diameter: 18 nm) carrying an iron compound. The content of the iron compound of the obtained titanium oxide (1) carrying an iron compound was 800 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 734 ppm. Further, the obtained titanium oxide (1) carrying an iron compound is a rod-shaped rutile-type titanium oxide having a crystal face (110) and a crystal face (111) and carrying only an iron compound on the crystal face (111). And a mixture of rod-shaped rutile-type titanium oxide having a crystal face (110), a crystal face (111), and a crystal face (001), and having an iron compound on the crystal face (001) and the crystal face (111).

Example 2

(Preparation of crystalline titanium oxide)

The titanium tetrachloride aqueous solution (Ti concentration: 16.5 wt% ± 0.5 wt%, chloride ion concentration: 31 wt% ± 2 wt%, manufactured by Toho Titanium Co., Ltd.) was diluted with pure water at room temperature (25 ° C). The Ti concentration was made 5.6% by weight. 5650 g of the diluted titanium tetrachloride aqueous solution was placed in a 10 L rug-lined autoclave and sealed. Using the heat medium, it took 2 hours to raise the temperature in the above autoclave to 140 °C. Thereafter, the mixture was stirred at a power required for stirring (Pv value) of 220 W/m ³ while maintaining the vapor pressure at a temperature of 140 ° C and a temperature of 10 hours, and then the autoclave was cooled by cooling the heat medium. cool down. It was confirmed that the temperature in the autoclave was 40 ° C or lower, and 5650 g of the crude titanium oxide suspension (2) was taken out.

(membrane filtration treatment by sweeping method (1))

The obtained crude titanium oxide suspension (2) was diluted to 3 times with pure water, and a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, Daicen Membrane) was used. The system (manufactured by Systems) was subjected to a filtration treatment by a sweeping method while adding pure water of the same amount as the filtrate at room temperature (25 ° C) and a filtration pressure of 0.02 MPa. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the pH of the filtrate became 4.0. In this period, the reverse cleaning was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min in a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. Thereafter, the storage of pure water was stopped, and the concentration of titanium oxide was concentrated to obtain a titanium oxide suspension (2-1). When the titanium oxide suspension (2-1) is dried at 105 ° C for 1 hour under normal pressure, a rod-shaped rutile-type titanium oxide having a crystal face (110) and a crystal face (111) is obtained and has a crystal face (110). 533 g of titanium oxide (2) of a mixture of a crystalline surface (111) and a rod-shaped rutile-type titanium oxide of a crystal surface (001). The photocatalytic activity of the obtained titanium oxide (2) evaluated by the toluene oxidation method using ultraviolet rays below was 647 ppm (decomposition rate: 95%).

(treatment of carrying iron compounds)

7.5 g of an aqueous solution of ferric chloride (35 wt%) was added to the titanium oxide suspension (2-1) obtained above, and stirred at room temperature (25 ° C) for 30 minutes. Thereafter, 95 g of methanol (1.7 wt% of the titanium oxide suspension) was added, and a 100 W high-pressure mercury lamp was irradiated with ultraviolet rays (UV) for 3 hours (UV irradiation amount: 5 mW/cm ² ) to obtain a suspension of the titanium oxide containing the iron compound. Liquid (2).

(membrane filtration treatment by sweeping method (2))

A titanium oxide suspension (2) containing a crude iron compound is diluted with pure water Released twice, using a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, manufactured by Daicen Membrane Systems), at room temperature (25 ° C) The filtration pressure was 0.02 MPa, and the same amount of pure water as the filtrate was added, and filtration treatment by a sweeping method was performed. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the conductivity of the filtrate became 200 μS/cm. In this period, the reverse cleaning was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min in a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. Thereafter, the storage of pure water is stopped, and the concentration of the titanium oxide carrying the iron compound is concentrated to obtain a titanium oxide suspension (2-1) carrying the iron compound. In this period, the reverse cleaning was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min in a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank.

Thereafter, the mixture was dried at 105 ° C for 1 hour under normal pressure to obtain a crystalline iron oxide (2) (specific surface area: 78 m ² /g, average aspect ratio: 3, average short diameter: 17 nm) 530 g of an iron compound. . The content of the obtained iron compound carrying the iron compound (2) of the iron compound was 830 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 775 ppm. Further, the obtained titanium oxide (2) carrying an iron compound is a rod-shaped rutile-type titanium oxide having a crystal face (110) and a crystal face (111) and carrying only an iron compound on the crystal face (111). a mixture of rod-shaped rutile-type titanium oxide having a crystal face (110), a crystal face (111), and a crystal face (001), and having an iron compound on the crystal face (001) and the crystal face (111) 4 picture).

Example 3

In the above-described (filtering treatment (2) by the sweeping method), the conductivity of the filtrate was changed to 150 μS/cm, and in the same manner as in Example 2, a crystalline iron compound-loaded titanium oxide was obtained. 3) (specific surface area: 78.5 m ² /g, average aspect ratio: 3, average short diameter: 16 nm) 530 g. The content of the iron compound of the obtained titanium oxide (3) carrying the iron compound was 890 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 795 ppm.

Example 4

In the above-described (filtering treatment (2) by the sweeping method), the conductivity of the filtrate was changed to 100 μS/cm, and in the same manner as in Example 2, a crystalline iron compound-loaded titanium oxide was obtained. 4) (specific surface area: 79 m ² /g, average aspect ratio: 3, average short diameter: 15 nm) 530 g. The content of the obtained iron compound carrying the iron compound titanium oxide (4) was 950 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 800 ppm.

Example 5

In the above-described (filtering treatment (2) by the sweeping method), the conductivity of the filtrate was changed to 50 μS/cm, and the same was carried out in the same manner as in Example 2 to obtain a crystalline iron compound-loaded titanium oxide ( 5) (specific surface area: 80 m ² /g, average aspect ratio: 3, average short diameter: 14 nm) 530 g. The content of the iron compound of the obtained iron compound-containing titanium oxide (5) was 1200 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 800 ppm.

Example 6

In the above (treatment of supporting the iron compound), the amount of the ferric chloride aqueous solution (35 wt%) was changed from 7.5 g to 6.5 g, and the same procedure as in Example 2 was carried out to obtain a crystalline iron-loaded compound. Titanium oxide (6) (specific surface area: 76 m ² /g, average aspect ratio: 3, average short diameter: 17 nm) 530 g. The content of the iron compound of the obtained iron compound-containing titanium oxide (6) was 700 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 780 ppm.

Example 7

In the above-mentioned (treatment of supporting the iron compound), the amount of the ferric chloride aqueous solution (35 wt%) was changed from 7.5 g to 15.0 g, and the same procedure as in Example 2 was carried out to obtain a crystalline iron-loaded compound. Titanium oxide (7) (specific surface area: 80 m ² /g, average aspect ratio: 3, average short diameter: 16 nm) 530 g. The content of the iron compound of the obtained iron compound-containing titanium oxide (7) was 2000 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 753 ppm.

Example 8

In the above (preparation of crystalline titanium oxide), the reaction temperature (temperature in the autoclave) was changed from 140 ° C to 120 ° C, and a crude titanium oxide suspension (8) was obtained in the same manner as in Example 2, and When the obtained crude titanium oxide suspension (8) was subjected to the above-described membrane filtration treatment (1) by a sweeping method in the same manner as in Example 2, a titanium oxide suspension (8-1) was obtained and obtained as crystals. Titanium oxide of a rod-shaped rutile-type titanium oxide having a surface (110) and a crystal plane (111) and a rod-shaped rutile-type titanium oxide having a crystal face (110), a crystal face (111), and a crystal face (001) (8) 530g. The photocatalytic activity of the obtained titanium oxide (8) evaluated by the toluene oxidation method using ultraviolet rays below was 600 ppm (CO ₂ production rate: 90%).

Then, in the same manner as in the second embodiment, the treatment (the treatment of carrying the iron compound) and the membrane filtration treatment (2) by the sweep method are carried out to obtain a crystalline iron compound (8) carrying an iron compound (specific surface area: 85 m ² /g, average aspect ratio: 2, average short diameter: 10 nm). The content of the iron compound of the obtained iron compound-containing titanium oxide (8) was 780 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 691 ppm.

Example 9

In the above (preparation of crystalline titanium oxide), the reaction temperature (inner autoclave temperature) was changed from 140 ° C to 160 ° C, and the same procedure as in Example 2 was carried out to obtain a crude titanium oxide suspension (9), and When the obtained crude titanium oxide suspension (9) was subjected to the above-described membrane filtration treatment (1) by a sweeping method in the same manner as in Example 2, a titanium oxide suspension (9-1) was obtained and obtained as crystals. Titanium oxide of a rod-shaped rutile-type titanium oxide having a surface (110) and a crystal plane (111) and a rod-shaped rutile-type titanium oxide having a crystal face (110), a crystal face (111), and a crystal face (001) (9) 530g. The photocatalytic activity of the obtained titanium oxide (9) evaluated by the toluene oxidation method using ultraviolet rays below was 645 ppm (decomposition rate: 95%).

Then, in the same manner as in Example 2, the treatment (the treatment of carrying the iron compound) and the membrane filtration treatment (2) by the sweep method were carried out to obtain a crystalline iron compound (9) carrying an iron compound (specific surface area: 55 m ² /g, average aspect ratio: 12, average short diameter: 25 nm). The content of the iron compound of the obtained iron compound-containing titanium oxide (9) was 820 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 727 ppm.

Example 10

(Preparation of crystalline titanium oxide)

The titanium tetrachloride aqueous solution (Ti concentration: 16.5 wt% ± 0.5 wt%, chloride ion concentration: 31 wt% ± 2 wt%, manufactured by Toho Titanium Co., Ltd.) was diluted with pure water at room temperature (25 ° C). The Ti concentration was made 5.6% by weight. 5650 g of the diluted titanium tetrachloride aqueous solution was placed in a 10 L rug-lined autoclave and sealed. Using the heat medium, it took 2 hours to raise the temperature in the above autoclave to 140 °C. Thereafter, the mixture was stirred at a power required for stirring (Pv value) of ¹³ W/m ³ while maintaining the vapor pressure at a temperature of 140 ° C and a pressure for 10 hours, and then the autoclave was cooled by cooling the heat medium. cool down. It was confirmed that the temperature in the autoclave was 40 ° C or lower, and 5650 g of the crude titanium oxide suspension (10) was taken out.

(membrane filtration treatment by sweeping method (1))

The crude titanium oxide suspension (10) which is not diluted with pure water, uses a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, Daicen Membrane Systems (shares) The system was subjected to a filtration treatment by a sweeping method while adding pure water of the same amount as the filtrate at room temperature (25 ° C) and a filtration pressure of 0.02 MPa. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the pH of the filtrate became 4.0. In this period, the reverse cleaning was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min in a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. According to the foregoing, 5650 g of a titanium oxide suspension (10-1) was obtained. When the titanium oxide suspension (10-1) is dried at 105 ° C for 1 hour under normal pressure, a rod-shaped rutile-type titanium oxide having a crystal face (110) and a crystal face (111) is obtained and has a crystal face (110). Crystalline surface (111) and crystal plane Titanium oxide (10) of a mixture of rod-shaped rutile-type titanium oxide of (001). The photocatalytic activity of the obtained titanium oxide (10) evaluated by the toluene oxidation method using ultraviolet rays below was 647 ppm (decomposition rate: 95%).

(treatment of carrying iron compounds)

7.5 g of an aqueous ferric chloride solution (35 wt%) was added to the titanium oxide suspension (10-1) obtained above, and the mixture was stirred at room temperature (25 ° C) for 30 minutes. Thereafter, 95 g of methanol (1.7 wt% of the titanium oxide suspension) was added, and a 100 W high-pressure mercury lamp was irradiated with ultraviolet rays (UV) for 3 hours (UV irradiation amount: 5 mW/cm ² ) to obtain a suspension of the titanium oxide containing the iron compound. Liquid (10).

(membrane filtration treatment by sweeping method (2))

The titanium oxide suspension (10) containing the iron compound is not diluted with pure water, and the hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, Daicen Membrane) is used. The system (manufactured by Systems) was subjected to a filtration treatment by a sweeping method while adding pure water of the same amount as the filtrate at room temperature (25 ° C) and a filtration pressure of 0.02 MPa. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the conductivity of the filtrate became 200 μS/cm. In this period, the reverse cleaning was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min in a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. According to the foregoing, a titanium oxide suspension (10-1) carrying an iron compound was obtained.

Thereafter, it was dried at 105 ° C for 1 hour under normal pressure to obtain a crystalline iron oxide (10) (specific surface area: 76 m ² /g, average aspect ratio: 5, average short diameter: 16 nm) 530 g of an iron compound. . The content of the iron compound of the obtained iron compound-containing titanium oxide (10) was 820 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 778 ppm.

Example 11

(Preparation of crystalline titanium oxide)

The titanium tetrachloride aqueous solution (Ti concentration: 16.5 wt% ± 0.5 wt%, chloride ion concentration: 31 wt% ± 2 wt%, manufactured by Toho Titanium Co., Ltd.) was diluted with pure water at room temperature (25 ° C). The Ti concentration was made 5.6% by weight. 560 g of the diluted titanium tetrachloride aqueous solution was placed in a 1 L lining autoclave and sealed. Using the heat medium, it took 2 hours to raise the temperature in the above autoclave to 140 °C. Thereafter, the mixture was stirred at a power required for stirring (Pv value) of ¹³ W/m ³ while maintaining the vapor pressure at a temperature of 140 ° C and a pressure for 10 hours, and then the autoclave was cooled by cooling the heat medium. cool down. It was confirmed that the temperature in the autoclave was 40 ° C or lower, and 560 g of the crude titanium oxide suspension (11) was taken out.

(membrane filtration treatment by sweeping method (1))

The obtained crude titanium oxide suspension (11) was diluted 10 times with pure water, and a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, Daicen Membrane) was used. The system (manufactured by Systems) was subjected to a filtration treatment by a sweeping method while adding pure water of the same amount as the filtrate at room temperature (25 ° C) and a filtration pressure of 0.05 MPa. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the pH of the filtrate became 2.9. Thereafter, the storage of pure water was stopped, and the concentration of titanium oxide was concentrated to obtain a titanium oxide suspension (11-1). During this period, the reverse cleaning was carried out for 1 minute at a pressure of 0.15 MPa and a flow rate of 0.1 kg/min at a ratio of one hour. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank. When the titanium oxide suspension (11-1) is dried at 60 ° C for 15 hours under reduced pressure, a rod-shaped rutile-type titanium oxide having a crystal face (110) and a crystal face (111) and a crystal face (110) are obtained. A titanium oxide (11) of a mixture of a crystalline surface (111) and a rod-shaped rutile-type titanium oxide of a crystal surface (001). The photocatalytic activity of the obtained titanium oxide (11) evaluated by the toluene oxidation method using ultraviolet rays described below was 617 ppm (CO ₂ production rate: 93%).

(treatment of carrying iron compounds)

To the titanium oxide suspension (11-1) obtained above, 0.3 g of an aqueous solution of ferric chloride (35 wt%) was added, and the mixture was stirred at room temperature (25 ° C) for 30 minutes. Thereafter, 9.6 g of methanol (1.7 wt% of the titanium oxide suspension) was added, and ultraviolet rays (UV) were irradiated for 3 hours (UV irradiation amount: 0.9 mW/cm ² ) using a 100 W high-pressure mercury lamp to obtain oxidation of the crude iron compound. Titanium suspension (11).

(membrane filtration treatment by sweeping method (2))

The titanium oxide suspension (11) containing the iron compound is diluted 10 times with pure water, and a hollow fiber type ultrafiltration membrane (trade name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000) is used. The Daicen Membrane Systems (manufactured by Daisen Membrane Systems Co., Ltd.) was subjected to a filtration treatment by a sweeping method while adding pure water of the same amount as the filtrate at room temperature (25 ° C) and a filtration pressure of 0.05 MPa. The concentrated liquid obtained by the filtration treatment was again circulated in the storage tank, and the filtration treatment was repeatedly applied until the conductivity of the filtrate became 21 μS/cm. Thereafter, the storage of pure water is stopped, and the concentration of the titanium oxide carrying the iron compound is concentrated to obtain a titanium oxide suspension (11-1) carrying the iron compound. During this period, in the ratio of 1 hour and 1 time, The backwashing was carried out for 1 minute at a pressure of 0.15 MPa and a flow rate of 0.1 kg/min. The washing water that has passed through the membrane by the reverse washing is circulated in the storage tank.

Thereafter, it was dried at 60 ° C for 15 hours under reduced pressure to obtain a crystalline iron oxide (11) (specific surface area: 71 m ² /g, average aspect ratio: 9, average short diameter: 20 nm) 40 g of an iron compound. . The content of the iron compound of the obtained iron compound-containing titanium oxide (11) was 420 ppm. Further, the photocatalytic activity evaluated by the toluene oxidation method using visible light described below was 416 ppm, and the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 716 ppm.

Comparative example 1

(Preparation of crystalline titanium oxide)

The titanium tetrachloride aqueous solution (Ti concentration: 16.5 wt% ± 0.5 wt%, chloride ion concentration: 31 wt% ± 2 wt%, manufactured by Toho Titanium Co., Ltd.) was diluted with pure water at room temperature (25 ° C). The Ti concentration was made 5.6% by weight. 560 g of the diluted titanium tetrachloride aqueous solution was placed in a 1 L lining autoclave and sealed. Using the heat medium, it took 2 hours to raise the temperature in the above autoclave to 140 °C. Thereafter, the mixture was kept at a temperature of 140 ° C and a vapor pressure of the temperature for 10 hours, and then the autoclave was cooled by cooling the heat medium. It was confirmed that the temperature in the autoclave was 40 ° C or lower, and 560 g of the crude titanium oxide suspension (12) was taken out.

The crude titanium oxide suspension (12) was used instead of the crude titanium oxide suspension (11), and the same procedure as in Example 11 was carried out to obtain a crystalline iron compound (12) carrying an iron compound (specific surface area: 9 m ² /g). , average aspect ratio: 1.2, average short diameter: 100 nm). The content of the iron compound of the obtained titanium oxide (12) carrying an iron compound was 30 ppm. Further, the photocatalytic activity evaluated by the methanol oxidation method using visible light described below was 250 ppm.

<Evaluation method of photocatalytic activity>

(Toluene oxidation using visible light)

The titanium oxide carrying the iron compound obtained in the examples was used as a photocatalyst, and toluene was oxidized in the gas phase, and the amount of CO ₂ produced was measured to evaluate the photocatalytic activity.

200 mg of titanium oxide carrying an iron compound was spread on a glass dish, placed in a reaction container (Tedlar bag, material: fluorinated ethylene resin), and 125 ppm of toluene gas (100 ppm) was blown into the reaction container. After the adsorption of the toluene gas to the titanium oxide carrying the iron compound was balanced, light irradiation (LED, light intensity: ^2.5 mW/cm ² , wavelength of light: 455 nm) was performed at room temperature (25 ° C). Using a gas chromatograph (trade name "GC-14B", manufactured by Shimadzu Corporation) attached to a Methanizer (trade name "MT221", manufactured by GL Sciences Co., Ltd.) with a hydrogen flame free detector, the measurement starts with light irradiation. The amount of CO ₂ produced after 24 hours (the concentration of CO _{2 in the} reaction vessel).

(Methanol oxidation method using visible light)

The titanium oxide carrying the iron compound obtained in the examples and the comparative examples was used as a photocatalyst, and methanol was oxidized in the gas phase, and the amount of CO ₂ produced was measured to evaluate the photocatalytic activity.

200 mg of titanium oxide carrying an iron compound was spread on a glass dish, placed in a reaction container (Tedlar bag, material: fluorinated ethylene resin), and 125 ppm of methanol gas (125 mL) was blown into the reaction container. After the adsorption of the methanol gas to the titanium oxide carrying the iron compound was balanced, light irradiation (LED, light intensity: 2.5 W/m ² , wavelength of light: 455 nm) was performed at room temperature (25 ° C). Using a gas chromatograph (trade name "GC-14B", manufactured by Shimadzu Corporation) with a hydrogen flame free detector attached to the Methanizer (trade name "MT221", manufactured by GL Sciences), the measurement is started by light irradiation. The amount of CO ₂ produced after the hour (the concentration of CO _{2 in the} reaction vessel).

(toluene oxidation method using ultraviolet rays)

By using the titanium oxide obtained in the example as a photocatalyst, toluene was oxidized in the gas phase, and the amount of CO ₂ produced was measured to evaluate the photocatalytic activity.

200 mg of titanium oxide was spread on a glass dish, placed in a reaction container (Tedlar bag, material: fluorinated ethylene resin), and 125 ppm of toluene gas (100 ppm) was blown into the reaction container. After the adsorption of the toluene gas to the titanium oxide was balanced, light irradiation (LED, light intensity: 0.1 mW/cm ² , wavelength of light: 365 nm) was performed at room temperature (25 ° C). Using a gas chromatograph (trade name "GC-14B", manufactured by Shimadzu Corporation) with a hydrogen flame free detector attached to the Methanizer (trade name "MT221", manufactured by GL Sciences), the measurement is started by light irradiation. The amount of CO ₂ produced after the hour (the concentration of CO _{2 in the} reaction vessel).

[Industrial availability]

The transition metal compound-containing titanium oxide of the present invention has an average minor axis of 50 nm or less and an average aspect ratio (long diameter/short diameter) of 1.5 or more. Therefore, it is excellent in responsiveness to visible light, and absorbs sunlight in ordinary living spaces such as sunlight or incandescent lamps, fluorescent lamps, and LEDs, and decomposes harmful chemicals into water or carbon dioxide. That is, this The titanium oxide suspension containing the transition metal compound of the invention can be suitably used as a photocatalyst for LED illumination. In addition, it can be applied to various antibacterial, anti-mildew, deodorization, air purification, water purification, etc., and can be widely applied to environmental purification, home appliances, such as indoor wallpapers or furniture, in public facilities in homes, hospitals, schools, etc. The high functionality of the products.

Claims (4)

A titanium oxide carrying a transition metal compound, which is a transition metal compound-supporting titanium oxide carrying a transition metal compound in a crystalline titanium oxide, having an average minor axis of 50 nm or less and an average aspect ratio (long diameter/short diameter) ) is 1.5 or more. The titanium oxide of a transition metal compound according to claim 1, wherein the crystalline titanium oxide is rutile-type titanium oxide having a crystal face (110) and a crystal face (111) and/or has a crystal face (110) and crystallized Rutile-type titanium oxide on surface (111) and crystal plane (001). The titanium oxide of the transition metal compound as claimed in claim 1 or 2 has a specific surface area of 10 m ² /g or more. A titanium oxide having an average minor axis of 50 nm or less and an average aspect ratio (long diameter/short diameter) of 1.5 or more.