JP6263123B2 - Transition metal compound-supported titanium oxide - Google Patents

Description

  The present invention relates to a transition metal compound-supported titanium oxide obtained by supporting a transition metal compound on titanium oxide. The transition metal compound-supported titanium oxide has excellent responsiveness to visible light and can exhibit excellent photocatalytic ability.

  Transition metal compound-supported titanium oxide has photocatalytic activity, and can exhibit strong oxidizing power when irradiated with light such as visible light and ultraviolet light, and can decompose harmful chemical substances into water and carbon dioxide. By applying or mixing a suspension of transition metal compound-supported titanium oxide, antibacterial, antifungal, deodorizing, air purification, water purification, and antifouling effects can be imparted to the coated body or mixture. . And when ionic impurities, such as a halogen ion, are contained in transition metal compound carrying | support titanium oxide, it is known that the response with respect to an ultraviolet-ray and visible light will fall.

It is known that transition metal compound-supported titanium oxide can be produced through the following steps (see Patent Documents 1 and 2, etc.).
1. 1. Titanium oxide production process for obtaining a titanium oxide suspension by hydrothermal treatment of a titanium compound 2. Transition metal compound supporting step for obtaining a transition metal compound supporting titanium oxide suspension by adding a transition metal compound to the titanium oxide suspension. A purification process that reduces the content of ionic impurities by subjecting the transition metal compound-supported titanium oxide suspension to solid or liquid separation by subjecting it to a treatment such as pressure or vacuum filtration using a filtration method or centrifugation. In the above method, since the transition metal compound-supported titanium oxide is consolidated by solid-liquid separation in the purification step and the exposed amount of the highly active surface is reduced, the transition metal compound-supported titanium oxide having sufficient photocatalytic ability cannot be obtained. That was the problem. Furthermore, the transition metal compound-supported titanium oxide once consolidated has not been able to obtain satisfactory photocatalytic ability even after being subjected to pulverization and the like and then redispersed.

Japanese Patent Laid-Open No. 10-158015 Japanese Patent Laid-Open No. 62-235215

  Accordingly, an object of the present invention is to provide a transition metal compound-supported titanium oxide that has excellent responsiveness to visible light and exhibits excellent photocatalytic activity.

As a result of intensive investigations by the present inventors to solve the above problems, the rod-shaped transition metal compound-supported titanium oxide is once consolidated by being subjected to a solid-liquid separation process such as centrifugation, and then pulverized. It was found that even when re-dispersed, the rod-like crystal structure was cut, and the photocatalytic ability in the visible light region was remarkably lowered due to the following reasons 1, 2 and the like.
1. 1. Since the average aspect ratio of the transition metal compound-supported titanium oxide is small and the shape is closer to a sphere, the separation between the oxidation reaction field and the reduction reaction field is reduced, and the progress of the reverse reaction and side reaction is unavoidable. The rod-like crystal structure is cut to produce a piece of titanium oxide that does not carry a transition metal compound, and the piece of titanium oxide cannot exhibit visible light responsiveness.

  In the purification process, when a membrane filtration process using a cross-flow filtration method is employed instead of a solid-liquid separation process such as centrifugation, the rod-like crystal structure is maintained without compacting the transition metal compound-supported titanium oxide. It has been found that ionic impurities can be efficiently removed in a state, the content of ionic impurities is extremely low, and a rod-shaped transition metal compound-supported titanium oxide can be obtained. Furthermore, it has been found that when the reaction system is stirred during hydrothermal treatment, a transition metal compound-supported titanium oxide having an extremely small average minor axis and a large average aspect ratio can be obtained. And it discovered that the transition metal compound carrying | support titanium oxide obtained in that way was excellent in the responsiveness with respect to visible light, and could exhibit the outstanding photocatalytic ability. The present invention has been completed based on these findings.

  That is, the present invention is a transition metal compound-supported titanium oxide in which a transition metal compound is supported on crystalline titanium oxide, having an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. A transition metal compound-supported titanium oxide is provided.

  Examples of the crystalline titanium oxide include rutile type titanium oxide having a crystal plane (110) and a crystal plane (111) and / or rutile type oxide having a crystal plane (110), a crystal plane (111) and a crystal plane (001). Titanium is preferred.

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

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

  The transition metal compound-supported titanium oxide of the present invention has an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. Therefore, it has excellent responsiveness to visible light, and can absorb light in normal living spaces such as sunlight, incandescent lamps, fluorescent lamps, and LEDs, and decompose harmful chemical substances into water and carbon dioxide. That is, the transition metal compound-supported titanium oxide suspension of the present invention can be suitably used as a photocatalyst for LED illumination. And it can be applied in various ways such as antibacterial and antifungal, deodorization, air purification, water purification, etc., indoor wallpaper, furniture, environmental purification in homes, hospitals, schools and other public facilities, high functionality of home appliances Application to a wide range is possible.

It is the schematic which shows an example of the membrane filtration by a crossflow system. It is the schematic which shows an example of the back washing | cleaning in the membrane filtration by a crossflow system. It is a perspective view of a rod-shaped rutile type titanium oxide having a crystal plane (110) (111) and a rod-shaped rutile type titanium oxide having a crystal plane (110) (111) (001). It is the photograph (x200000, scale bar: 100 nm) of the iron compound carrying | support titanium oxide obtained in Example 2 image | photographed using the field emission type | mold scanning electron microscope.

[Transition metal compound-supported titanium oxide]
The transition metal compound-supported titanium oxide of the present invention is characterized in that the transition metal compound is supported on crystalline titanium oxide, the average minor axis is 50 nm or less, and the average aspect ratio (major axis / minor axis) is 1.5 or more. To do.

  The average minor axis of the transition metal compound-supported titanium oxide is 50 nm or less, preferably 5 to 40 nm, particularly preferably 5 to 30 nm, and most preferably 10 to 25 nm. If the average minor axis exceeds the above range, the separation between the oxidation reaction field and the reduction reaction field is lowered, the reverse reaction and the side reaction cannot be avoided, and the photocatalytic ability is lowered.

  The average aspect ratio (major axis / minor axis) of the transition metal compound-supported titanium oxide 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. If the average aspect ratio is less than the above range, the separation between the oxidation reaction field and the reduction reaction field is lowered, the reverse reaction and the side reaction cannot be avoided, and the photocatalytic ability is lowered.

In the present invention, the average minor axis and the average aspect ratio are values obtained by the following measuring method for samples obtained by the following adjusting method.
<Sample preparation method>
1. Place a small amount (about half of the earpick size spatula) of the transition metal compound-supported titanium oxide in a 9 mL glass sample bottle, add 7 mL of ethanol, and disperse the ultrasonic wave in ethanol over 5 minutes using an ultrasonic cleaner. An ethanol dispersion is obtained.
2. One drop of the obtained ethanol dispersion is taken with a glass spoid, dropped on a sample stage for SEM and allowed to dry naturally, and then platinum deposition is performed for 30 seconds.
<Measurement method>
Using a field emission scanning electron microscope (trade name “FE-SEM JSM-6700F”, manufactured by JEOL Ltd., acceleration voltage: 15 kV, WD: about 3 mm, magnification: 200,000 times), crystal grains are randomly selected. Observe, extract three representative points, and 30 particles that are not extremely large or small in appearance in the entire extracted SEM photograph and have a clear outline centered on average-sized particles Are extracted and transferred to an OHP sheet, and for each of these particles, an image analysis software (trade name “WinROOF Version 5.6”, manufactured by Mitani Corp.) is used to obtain each minor axis (width orthogonal to the maximum major axis). These values were averaged to obtain an average minor axis. Further, the average major axis (maximum major axis) was determined by the same method, and the ratio (average major axis / average minor axis) was taken as the average aspect ratio.

  Examples of the crystalline titanium oxide include a rutile type, anatase type, brookite type titanium oxide and the like. In the present invention, among them, a rutile type or anatase type titanium oxide (a rutile type titanium oxide is more preferable and particularly preferable in terms of being able to exhibit more excellent photocatalytic ability in that a stable crystal face is exposed. Are preferably rutile-type titanium oxide having crystal face (110) and crystal face (111) and / or rutile-type titanium oxide having crystal face (110), crystal face (111) and crystal face (001).

  The transition metal compound is supported in the state of, for example, a transition metal ion, a transition metal simple substance, a transition metal salt, a transition metal oxide, a transition metal hydroxide, or a transition metal complex. The loading amount of the transition metal compound 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 loading amount of the transition metal compound is, for example, about 5000 ppm, preferably 3000 ppm, particularly preferably 2000 ppm. When the loading amount of the transition metal compound is below the above range, the visible light responsiveness tends to decrease. On the other hand, when the amount of the transition metal compound supported exceeds the above range, excited electrons do not act effectively due to reverse electron transfer of injected electrons and the photocatalytic ability tends to decrease.

  The transition metal compound is supported on the surface of the crystalline titanium oxide in a surface-selective manner, so that the separation of the reaction field between the oxidation reaction and the reduction reaction can be further improved, thereby recombination of excited electrons and holes. It is preferable in that the reverse reaction can be suppressed and the photocatalytic activity can be dramatically improved. In particular, it is preferable that the transition metal compound is selectively supported on the oxidation reaction surface.

  In the present invention, the transition metal compound is “face-selectively” supported means that the amount exceeding 50% (preferably 70% or more, particularly preferably 80% or more) of the transition metal compound is the two faces of crystalline titanium oxide. Among the above crystal planes, it means that it is supported on a specific plane (for example, one specific plane or two planes) instead of all the planes. Note that the upper limit of the surface selectivity is 100%. The surface selectivity can be determined by confirming a signal derived from a transition metal compound on each crystal plane using a transmission electron microscope (TEM) or an energy dispersive X-ray fluorescence analyzer (EDX).

Any transition metal compound may be used as long as it has an absorption spectrum in the visible light region and can inject electrons into the conduction band in an excited state. Compounds are preferred, among which group 8 to 11 element compounds of the periodic table, particularly preferably iron compounds or platinum compounds, and most preferably trivalent iron compounds (Fe ³⁺ ). The trivalent iron compound (Fe ³⁺ ) is easily adsorbed on titanium oxide, and the divalent iron compound (Fe ²⁺ ) has a characteristic that it is difficult to adsorb. Because it can.

The specific surface area of the transition metal compound-supported titanium oxide 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 is, for example, 200 m ² / g, preferably 150 m ² / g, particularly preferably 100 m ² / g.

The specific surface area of the transition metal compound supported titanium oxide, for example, 10 to 200 m ² / g, preferably 10 to 150 m ² / g, more preferably 30 to 150 m ² / g, more preferably 50 to 100 m ² / g, in particular preferably 60~100m ² / g, most preferably 70~100m ² / g. Since the transition metal compound-supported titanium oxide having a specific surface area in the above range increases the amount of exposure of the highly active surface, it can exhibit excellent photocatalytic ability.

  The specific surface area was measured using a high-speed specific surface area / pore diameter distribution measuring device (trade name “NOVA-1200”, Quantachtome.) For a sample obtained by degassing a transition metal compound-supported titanium oxide at 100 ° C. (under vacuum) for 60 minutes. It is the average of the values obtained by measuring the sample twice under the following conditions using Co).

<Specific surface area measurement conditions>
Measuring principle: Constant volume method (blank correction type)
Detection method: Relative pressure (ratio of adsorption equilibrium pressure (P) and saturated vapor pressure (P ₀ ) in sample cell by pressure transducer) and adsorbed gas amount (ideal gas from pressure detection by pressure transducer and manifold temperature detection by thermistor) Calculate the amount of injected gas)
Adsorption gas: Nitrogen gas Cell size: Small pellet cell (cell capacity: 1.8 cm ³ , stem outer diameter: 9 mm)
Measurement item: 3 points on the adsorption side of P / P ₀ = 0.1, 0.2, 0.3 Analysis item: Specific surface area by BET multipoint method

  The transition metal compound-supported titanium oxide of the present invention is excellent in visible light responsiveness, exhibits excellent photocatalytic ability by light irradiation, and decomposes harmful chemical substances into water and carbon dioxide, thereby providing antibacterial, antifungal, deodorizing, Various effects such as air purification, water purification, and antifouling can be exhibited.

For example, the amount of CO ₂ produced when toluene is oxidized using the transition metal compound-supported titanium oxide (200 mg) is, for example, 300 ppm or more. The amount of CO ₂ produced when 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.

The measurement method of the amount of CO ₂ generated upon oxidizing the toluene is as follows.
200 mg of transition metal compound-supported titanium oxide is spread on a glass dish and placed in a reaction vessel (Tedlar bag, material: vinyl fluoride resin), and 125 mL of 100 ppm toluene gas is blown into the reaction vessel. After the adsorption of toluene gas to transition metal compound-supported titanium oxide reaches equilibrium, light irradiation (LED, light intensity: 2.5 W / cm ² , light wavelength: 455 nm) is performed at room temperature (25 ° C.) The amount of CO ₂ produced 24 hours after the start of irradiation is measured.

The method of measuring the amount of CO ₂ generated upon oxidizing the methanol, is as follows.
200 mg of transition metal compound-supported titanium oxide is spread on a glass dish and placed in a reaction vessel (Tedlar bag, material: vinyl fluoride resin), and 125 mL of 800 ppm of methanol gas is blown into the reaction vessel. After the adsorption of methanol gas to the transition metal compound-supported titanium oxide reaches equilibrium, light irradiation (LED, light intensity: 2.5 W / m ² , light wavelength: 455 nm) is performed at room temperature (25 ° C.) The amount of CO ₂ produced 24 hours after the start of irradiation is measured.

  Since the transition metal compound-supported titanium oxide of the present invention can exhibit extremely excellent photoresponsiveness as described above, that is, because it has responsiveness to light in a wide wavelength range from the ultraviolet region to the visible light region, Absorbs light in normal living spaces such as sunlight, incandescent lamps, fluorescent lamps, LEDs, etc., and exhibits high catalytic activity to decompose harmful chemical substances into water and carbon dioxide, thereby providing antibacterial (bacteria and radiation Fungicides, fungicides, algae, etc.), mold prevention, deodorization (for example, deodorization of odorous gases such as ammonia, amines, methyl mercaptan, hydrogen sulfide, etc., acetic acid, aldehydes, ethylene) Various effects such as air purification, water purification, and antifouling can be exhibited. Further, the transition metal compound-supported titanium oxide of the present invention is coated or mixed in a state where a binder, a solvent, a dispersant, a thickener, a surfactant, and the like are mixed as necessary, so that an object to be coated or a mixture is mixed. The above-mentioned effect can be imparted to.

  Examples of the coated body and mixture of the transition metal compound-supported titanium oxide of the present invention include, for example, building materials, building exteriors, building interiors, building paints, walls, wallpaper, floors, window frames, window glass, crystallized glass, Glass, screen door, rain gutter, solar heat reflective sheet, mailbox, structural member, pavement material, display board, traffic sign, road sign reflector, display panel, display filter, road surface indicator, road decorative board, fence, gate , Lighting equipment for tunnels and roads, sound insulation walls, guard rails, tunnel interiors, road mirrors, plastic house ceiling inner surfaces, bridges, bridge fall prevention fences, interior / exterior and painting of automobiles / trains / ships, vehicle wheels, Railroad car structures, vehicle parts, machinery / equipment exterior / dustproof covers / painting, various display devices, advertising towers, insulators, solar panels, solar cell covers, solar water heaters Cover, fuel cell, optical fiber, vehicle lighting cover, fishing net, rope, hose, bottom member, algae, shoes, bag, blind, curtain, wall cloth, screen, shoji, plastic shoji, bag, synthetic leather, Table cloth, clothing, raincoat, stationery, books, notebooks, paper, cardboard, various plastic bodies such as vehicles and home appliances, toys, sports equipment, musical instruments, fishing gear, in-car accessories, plastic containers, cards, tents, timber, timber Architectural materials such as pillars, ceiling boards, and board walls, furniture, printed plywood, interior boards, artificial flowers, foliage plants, artificial plants, pools, baths, rivers, seas, factory wastewater, domestic wastewater, groundwater, ponds, artificial rivers, etc. Fillers for water treatment, mirrors, wash bowls, tiles, tile joints, bathtubs, bathroom parts, toilet floor finishes, hospital parts for hospital infection prevention Ceramics multifunctional material, glaze, refrigerator inner and outer walls, stand, kitchen panel, sink, range, heating cooking container, ventilator, air conditioning, heat exchanger, various filters, toilet bowl, textile, non-woven cloth, mask, clothing, bedding, Hats, helmets, doormats, carpets, medical instruments, food, forks, knives, spoons, tableware, packaging materials, food wraps, food storage containers, dishwashers, water purifiers, garbage disposal equipment, melamine decorative boards, carpets , Lighting equipment, lighting fixtures, lighting lamps, lighting umbrellas, black lights, antifouling paints, filters, agricultural film, etc., super hydrophilic films, grass protection sheets, electronic parts, electrical products, electrical equipment, Corona charger, plasma generator, ozone generator, exposure device, humidifier, hand dryer, scalp care device, vacuum cleaner, telephone, portable terminal, Mobile devices, touch panel displays, organic EL devices / display panels, inkjet recording devices, air purifiers, refrigeration equipment, dust collectors, ornaments, machine parts, magnetic disks, showcases, instrument cover glasses, cameras, glasses, Camera lenses, eyeglass lenses, contact lenses, whitening agents, dental / oral materials, tooth bleaching materials, implants, oral appliances, cosmetics, shampoos, and the like.

(Method for producing transition metal compound-supported titanium oxide)
The transition metal compound-supported titanium oxide of the present invention can be produced, for example, through the following steps.

(Crystalline titanium oxide manufacturing process)
The crystalline titanium oxide production process is a process for obtaining crystalline titanium oxide from a titanium compound. A well-known and commonly used method can be adopted as a method for producing crystalline titanium oxide. For example, the rod-shaped rutile titanium oxide is obtained by hydrothermal treatment [for example, 100 to 220 ° C., 2 to 48 hours (preferably 2 to 48 hours) in a water medium (for example, water or a mixture of water and a water-soluble organic solvent). 15 hours, particularly preferably 5 to 15 hours)]. In addition, when a halide is added and / or stirred during hydrothermal treatment (for example, the required power Pv value for stirring: about 0.1 to 1500 W / m ³ ), the size and surface area of the resulting particles can be adjusted. preferable.

Examples of the titanium compound include a trivalent titanium compound and a tetravalent titanium compound. Examples of the trivalent titanium compound include titanium trihalides such as titanium trichloride and titanium tribromide. As the trivalent titanium compound in the present invention, titanium trichloride (TiCl ₃ ) is preferable because it is inexpensive and easily available.

Moreover, the tetravalent titanium compound in this invention can mention the compound etc. which are represented by following formula (1), for example.
Ti (OR) _t X _4-t (1)
(In the formula, R represents a hydrocarbon group, X represents a halogen atom, and t represents an integer of 0 to 3).

Examples of the hydrocarbon group for R in formula (1) include C _1-4 aliphatic hydrocarbon groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, and the like. Can do.

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

Examples of such tetravalent titanium compounds include titanium tetrahalides such as TiCl ₄ , TiBr ₄ , and Til ₄ ; Ti (OCH ₃ ) Cl ₃ , Ti (OC ₂ H ₅ ) Cl ₃ , and Ti (OC _4). Trihalogenated alkoxytitanium such as H ₉ ) Cl ₃ , Ti (OC ₂ H ₅ ) Br ₃ , Ti (OC ₄ H ₉ ) Br ₃ ; Ti (OCH ₃ ) ₂ Cl ₂ , Ti (OC ₂ H ₅ ) ₂ Dihalogenated dialkoxytitanium such as Cl ₂ , Ti (OC ₄ H ₉ ) ₂ Cl ₂ , Ti (OC ₂ H ₅ ) ₂ Br ₂ ; Ti (OCH ₃ ) ₃ Cl, Ti (OC ₂ H ₅ ) ₃ Cl, Examples thereof include monohalogenated trialkoxytitanium such as Ti (OC ₄ H ₉ ) ₃ Cl and Ti (OC ₂ H ₅ ) ₃ Br. As the tetravalent titanium compound in the present invention, titanium tetrahalide is preferable and titanium tetrachloride (TiCl ₄ ) is particularly preferable because it is inexpensive and easily available.

  The rod-shaped rutile-type titanium oxide obtained by hydrothermal treatment can be purified by a well-known and conventional method, for example, filtration, concentration, distillation, extraction, crystallization, recrystallization, column chromatography, or a combination thereof. it can. In the present invention, in particular, membrane filtration by the following crossflow method can reduce the content of ionic impurities while maintaining the crystal structure of titanium oxide, and there is no need to perform pulverization or the like. This is preferable in that it can be directly subjected to the transition metal compound supporting step, and a titanium oxide capable of highly supporting the transition metal compound can be obtained.

  The average minor axis 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.

  The average aspect ratio (major axis / minor axis) 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. .5-20, most preferably 2-15.

Furthermore, the specific surface area of the crystalline titanium oxide obtained by the said method is 10 m < ² > / g or more, for example. 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 is, for example, 200 m ² / g, preferably 150 m ² / g, particularly preferably 100 m ² / g.

(Transition metal compound loading process)
The transition metal compound-supporting step is a step of obtaining a transition metal compound-supported titanium oxide by supporting a transition metal compound on the crystalline titanium oxide obtained through the above steps. The transition metal compound can be supported, for example, by adding and impregnating crystalline titanium oxide with a solution containing the transition metal compound. For example, a transition metal compound-supported titanium oxide supporting a trivalent iron compound (Fe ³⁺ ) as a transition metal compound is prepared by adding iron (III) nitrate, iron (III) sulfate, iron chloride ( It is obtained by adding and impregnating a solution containing III) and the like.

  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. The impregnation time is, for example, about 1 minute to 24 hours, preferably 5 minutes to 10 hours.

In the present invention, it is possible to irradiate excitation light when impregnating the transition metal compound, and easily and efficiently without requiring a large facility, and the transition metal compound is selectively applied to a specific surface of the crystalline titanium oxide. Is preferable in that it can be supported. When irradiated with excitation light, electrons in the valence band of crystalline titanium oxide are excited in the conduction band, holes are generated in the valence band, and excited electrons are generated in the conduction band, which are diffused to the particle surface. Excited electrons and holes are separated according to the characteristics 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, the trivalent iron compound (Fe ³⁺ ) is adsorbed on the oxidation reaction surface, but on the reduction reaction surface, the trivalent iron compound (Fe ³⁺ ) is reduced to a divalent iron compound (Fe ²⁺ ), and the divalent iron compound (Fe ²⁺ ) has a characteristic that it is difficult to adsorb. An iron compound-supported titanium oxide on which the compound (Fe ³⁺ ) is supported can be obtained.

Excitation light is light (for example, ultraviolet light) having energy higher than the band gap energy. As the excitation light irradiation means, for example, an ultraviolet exposure apparatus having a light source that efficiently generates ultraviolet rays such as a medium / high pressure mercury lamp, a UV laser, a UV-LED, and a black light can be used. The irradiation amount of the excitation light is, for example, about 0.1 to 300 mW / cm ² , preferably 0.5 to 100 mW / cm ² .

  Furthermore, in the present invention, it is preferable to add a sacrificial agent during the impregnation. By adding the sacrificial agent, the transition metal compound can be supported with high selectivity on a specific crystal plane of the crystalline titanium oxide. As the sacrificial agent, it is preferable to use an organic compound that easily emits electrons. For example, alcohols such as methanol and ethanol; carboxylic acids such as acetic acid; ethylenediaminetetraacetic acid (EDTA) and triethanolamine (TEA) And the like.

  The addition amount of the sacrificial agent can be adjusted as appropriate, 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 crystalline titanium oxide. An excessive amount of the sacrificial agent may be used.

  It is preferable to carry out a purification treatment after the transition metal compound supporting step. In the present invention, the membrane filtration treatment by the crossflow method can efficiently remove ionic impurities while maintaining the rod-like crystal structure without compacting the transition metal compound-supported titanium oxide. In view of obtaining a rod-shaped transition metal compound-supported titanium oxide, the content of ionic impurities is extremely low.

(Membrane filtration by cross flow method)
Membrane filtration by the cross flow method means that water to be treated flows parallel to the surface of the filtration membrane, and a part of the water to be treated is moved to the side of the flow of the water to be treated while preventing filtration membrane contamination due to deposition of filter cake. It is a method of filtering. By subjecting the suspension of titanium oxide or transition metal compound-supported titanium oxide to membrane filtration by a crossflow method, ionic impurities can be efficiently removed without forming a compacted filter cake on the surface of the filtration membrane. In addition, the content of ionic impurities can be reduced extremely low while maintaining the crystal structure of titanium oxide or transition metal compound-supported titanium oxide.

  The concentration of the suspension of titanium oxide or transition metal compound-supported titanium oxide subjected to membrane filtration by the cross flow method is, for example, about 0.1 to 40% by weight (preferably 0.1 to 30% by weight). If the concentration of the suspension of titanium oxide or transition metal compound-supported titanium oxide is out of the above range, the removal efficiency of ionic impurities tends to decrease. Moreover, when the density | concentration of the suspension of a titanium oxide or a transition metal compound carrying | support titanium oxide exceeds the said range, a viscosity will become high too much and it will become easy to foul (clog).

  When a suspension of titanium oxide or a transition metal compound-supported titanium oxide is subjected to membrane filtration by a cross flow method, ionic impurities are separated and removed together with the permeate, and the suspension of concentrated titanium oxide or transition metal compound-supported titanium oxide is suspended. A liquid is obtained.

  The concentration ratio is preferably adjusted to about 1 to 400 times (in particular, 1 to 20 times, particularly 1 to 10 times). When the concentration ratio exceeds the above range, it is difficult to suppress the deposition of substances adhering to the film surface, and it tends to be difficult to prevent consolidation of titanium oxide or transition metal compound-supported titanium oxide. In addition, fouling (clogging) occurs in the filtration membrane due to the deposition of adhering substances on the membrane surface, so that the membrane life is likely to be shortened. In some cases, the filtration rate tends to decrease. On the other hand, when the concentration factor is below the above range, the separation efficiency of ionic impurities tends to decrease and the amount of washing water used tends to increase.

  The concentration ratio can be adjusted, for example, by controlling the filtration pressure, the membrane surface linear velocity (cross flow velocity) of the suspension of titanium oxide or the transition metal compound-supported 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.

  Further, the larger the film surface linear velocity of the supply liquid containing the suspension of titanium oxide or transition metal compound-supported titanium oxide, the more the deposition of adhering substances on the film surface is suppressed, and a higher filtration flux (flux) is obtained. The film surface linear velocity (cross flow velocity) 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 suspension of titanium oxide or transition metal compound-supported titanium oxide concentrated through membrane filtration by the cross-flow method has the concentration of the suspension of titanium oxide or transition metal compound-supported titanium oxide within the above range by adding water. It is preferable to repeat the operation of diluting in such a manner and performing membrane filtration again by the crossflow method. Thereby, the load of the filtration membrane due to fouling (clogging) or the like can be reduced, and the content of ionic impurities can be reduced extremely low while improving the lifetime of the filtration membrane.

  FIG. 1 is a schematic view showing an example (circulation type membrane filtration method) of membrane filtration by a cross flow method of a suspension of titanium oxide or a transition metal compound-supported titanium oxide. A supply liquid containing a suspension of titanium oxide or transition metal compound-supported titanium oxide charged in a preparation tank is subjected to membrane filtration by a cross-flow filtration method and concentrated to a suspension of titanium oxide or transition metal compound-supported titanium oxide. (Concentrated liquid) is obtained. The concentrated suspension of titanium oxide or transition metal compound-supported titanium oxide is circulated again to the charging tank, diluted with dilution water (dilution water), and membrane-filtered by a cross-flow filtration method.

  Examples of the filtration membrane used for membrane filtration by the crossflow method include an ultrafiltration membrane, a microfiltration membrane, a nanofilter, and a reverse osmosis membrane. In the present invention, it is particularly preferable to use an ultrafiltration membrane in terms of excellent separation performance.

  As an ultrafiltration membrane, a substance having an average pore size of about 1 to 20 nm (preferably 1 to 10 nm), a molecular weight of about 1000 to 300,000 (preferably 1000 to 50000), and an average particle size of about 1 to 10 nm It is preferable to use one that can be separated.

  The membrane shape of the ultrafiltration membrane may be, for example, any of a hollow fiber type filtration membrane, a tubular membrane, a spiral membrane, a flat membrane, etc. It is preferable to use a mold filtration membrane or a tubular membrane.

  The inner diameter of the hollow fiber membrane in the hollow fiber membrane is about 0.1 to 2.0 mm (preferably 0.5 to 2.0) from the viewpoint of preventing the blocking of contaminants and improving the hollow fiber filling rate of the membrane module. 1.5 mm).

  Examples of the material of the filtration membrane include general cellulose acetate, polyacrylonitrile, polysulfone, polyethersulfone (PES), polyacrylonitrile, aromatic polyamide, polyvinylidene fluoride, polyvinyl chloride, polyethylene, polypropylene, polyimide, ceramic and the like. Can be mentioned. In the present invention, cellulose acetate, polysulfone, polyethersulfone (PES), polyacrylonitrile, and aromatic polyamide are particularly preferable.

  When using a hollow fiber membrane, the method of flowing a suspension of titanium oxide or transition metal compound-supported titanium oxide (filtration method) is the inside (inside the hollow fiber membrane) titanium oxide or transition metal compound-supported oxidation. A feed solution containing a titanium suspension is flowed, and permeate flows toward the outside (outside of the hollow fiber membrane) (internal pressure filtration method), and vice versa. Examples include a method (external pressure filtration method) in which a supply liquid containing a suspension is flowed and permeate flows inward. In the present invention, the internal pressure filtration method is preferable because the membrane surface flow rate can be kept high.

  In membrane filtration by the cross flow method, the deposition on the filtration membrane surface is prevented to reduce the burden on the filtration membrane and the membrane filtration operation is performed for a long time. It is preferable to perform back washing. The reverse cleaning is preferably performed at a predetermined cycle while controlling the pressure and flow rate.

The pressure for back washing is, for example, about 0.01 to 3.0 MPa, preferably 0.01 to 2.0 MPa, particularly preferably 0.01 to 1.0 MPa, and most preferably 0.01 to 0.5 MPa. More preferably, it is 0.05 to 0.5 MPa. The flow rate of backwashing is, for example, about 0.01 to 10 kg / mim, preferably 0.05 to 5 kg / mim, particularly preferably 0.1 to 5 kg / mim [or, for example, 1 × 10 ⁻⁷ to 2. × 10 ⁻⁴ m / sec, preferably 8 × 10 ^{−7 to} 9 × 10 ⁻⁵ m / sec, and particularly preferably 1 × 10 ^{−6 to} 9 × 10 ⁻⁵ m / sec. The frequency of back washing is preferably about once every 0.5 to 3 hours, for example. The back washing time is preferably about 0.5 to 10 minutes.

  In addition, it is preferable to use water (For example, purified water, distilled water, pure water, ion-exchange water, etc.) as washing water used for back washing. Moreover, it is preferable to reuse the wash water that has passed through the membrane by reverse washing as water for diluting the concentrated transition metal compound-supported titanium oxide suspension (see FIG. 2).

  When filtering a suspension of titanium oxide, membrane filtration by the cross flow method has a permeate pH of 1 or more (preferably 1 to 7, particularly preferably 2 to 6, most preferably 2 to 5.5). It is preferable to repeat until it becomes. If membrane filtration by the cross-flow method is completed before the pH of the permeate reaches the above range, removal of ionic impurities (especially hydrogen ions, chlorine ions, titanium ions) becomes insufficient, and it is difficult to carry transition metal compounds. It may become.

  Moreover, when filtering the suspension of transition metal compound carrying | support titanium oxide, the membrane filtration by a cross flow system has the electric conductivity of a permeate | transmission liquid of 300 microS / cm or less (for example, 0.5-300 microsiemens / cm, Preferably it is 0.8. 5 to 250 μS / cm, particularly preferably 1 to 200 μS / cm). If the membrane filtration by the cross flow method is finished before the electric conductivity of the permeate falls within the above range, removal of ionic impurities (particularly, iron ions and chlorine ions) may be insufficient.

  The transition metal compound-supported titanium oxide suspension obtained by membrane filtration by the crossflow method is then dried (for example, under FV (1.3 kPa [A]) or less) at 60 ° C. for 15 hours. Or about 1 hour at 105 ° C. under normal pressure (atmospheric pressure), a transition metal compound-supported titanium oxide can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited by these Examples.

Example 1
(Preparation of crystalline titanium oxide)
At room temperature (25 ° C.), 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.) Ti concentration Was diluted with pure water so as to be 5.6% by weight. The diluted titanium tetrachloride aqueous solution 5650 g was placed in a 10 L tantalum-lined autoclave and sealed. Using a heat medium, the temperature inside the autoclave was raised to 140 ° C. over 2 hours. Thereafter, while stirring at a required power for stirring (Pv value) of 1360 W / m ³ , the temperature was maintained at 140 ° C., pressure: vapor pressure at the temperature for 5 hours, and the autoclave was cooled by cooling the heating medium. Cooled to below ℃. Thereafter, the autoclave was further cooled by maintaining the temperature: 140 ° C., pressure: vapor pressure at that temperature for 5 hours, and then cooling the heating medium. After confirming that the internal temperature of the autoclave was 40 ° C. or less, 5650 g of a crude titanium oxide suspension (1) was taken out.

(Cross flow membrane filtration treatment (1))
The obtained crude titanium oxide suspension (1) was diluted three-fold with pure water to obtain a hollow fiber type ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and filtration pressure of 0.02 MPa, filtered with a cross flow method while adding the same amount of pure water as the amount of permeate. It was. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to the filtration treatment until the pH of the permeate became 4.0. The pH was measured using a pH test paper. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. Thereafter, the preparation of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (1-1). When the titanium oxide suspension (1-1) was dried at 105 ° C. for 1 hour under normal pressure, a rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111), a crystal face (110), 525 g of titanium oxide (1) (specific surface area: 77 m ² / g, average aspect ratio: 6, average minor axis: 18 nm), which is a mixture of rod-shaped rutile-type titanium oxide having crystal face (111) and crystal face (001) Was obtained (see FIG. 3). The photocatalytic ability of the obtained titanium oxide (1) evaluated by the following toluene oxidation method using ultraviolet rays was 625 ppm (decomposition rate: 94%).

(Iron compound loading treatment)
To the titanium oxide suspension (1-1) obtained above, 7.5 g of an aqueous iron chloride solution (35% by weight) was added and stirred at room temperature (25 ° C.) for 30 minutes. Thereafter, 95 g of methanol (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet rays (UV) were irradiated for 3 hours using a 100 W high-pressure mercury lamp (UV irradiation amount: 5 mW / cm ² ). A crude iron compound-supported titanium oxide suspension (1) was obtained.

(Membrane filtration by cross flow method (2))
The crude iron compound-supported titanium oxide suspension (1) was diluted three-fold with pure water to form a hollow fiber ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and filtration pressure of 0.02 MPa, filtered with a cross flow method while adding the same amount of pure water as the amount of permeate. It was. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to filtration treatment until the electric conductivity of the permeate reached 200 μS / cm. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. Then, the preparation of pure water was stopped, the iron compound-supported titanium oxide concentration was concentrated, and an iron compound-supported titanium oxide suspension (1-1) was obtained. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank.

Then, it dried at 105 degreeC under normal pressure for 1 hour, and obtained the iron compound carrying | support titanium oxide (1) (specific surface area: 77m < ² > / g, average aspect-ratio: 6, average minor axis: 18nm). The iron compound content of the obtained iron compound-supported titanium oxide (1) was 800 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 734 ppm. Furthermore, the obtained iron compound-supported titanium oxide (1) has a crystal face (110) and a crystal face (111), and a rod-shaped rutile type titanium oxide in which an iron compound is supported only on the crystal face (111). A rod-shaped rutile titanium oxide having a crystal plane (110), a crystal plane (111), and a crystal plane (001), and an iron compound supported on the crystal plane (001) and the crystal plane (111) Met.

Example 2
(Preparation of crystalline titanium oxide)
At room temperature (25 ° C.), 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.) Ti concentration Was diluted with pure water so as to be 5.6% by weight. The diluted titanium tetrachloride aqueous solution 5650 g was placed in a 10 L tantalum-lined autoclave and sealed. Using a heat medium, the temperature inside the autoclave was raised to 140 ° C. over 2 hours. Thereafter, while stirring at a required power (Pv value) of 220 W / m ³ , the autoclave is cooled by holding the temperature: 140 ° C., pressure: vapor pressure at that temperature for 10 hours, and then cooling the heating medium. did. After confirming that the temperature inside the autoclave was 40 ° C. or less, 5650 g of a crude titanium oxide suspension (2) was taken out.

(Cross flow membrane filtration treatment (1))
The obtained crude titanium oxide suspension (2) was diluted three-fold with pure water to obtain a hollow fiber type ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and filtration pressure of 0.02 MPa, filtered with a cross flow method while adding the same amount of pure water as the amount of permeate. It was. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to the filtration treatment until the pH of the permeate became 4.0. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. Thereafter, the preparation of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (2-1). When the titanium oxide suspension (2-1) was dried at 105 ° C. for 1 hour under normal pressure, a rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111), a crystal face (110), As a result, 533 g of titanium oxide (2), which is a mixture of rod-shaped rutile-type titanium oxide having crystal face (111) and crystal face (001), was obtained. The photocatalytic ability of the obtained titanium oxide (2) evaluated by a toluene oxidation method using the following ultraviolet rays was 647 ppm (decomposition rate: 95%).

(Iron compound loading treatment)
To the titanium oxide suspension (2-1) obtained above, 7.5 g of an aqueous iron chloride solution (35% by weight) was added and stirred at room temperature (25 ° C.) for 30 minutes. Thereafter, 95 g of methanol (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet rays (UV) were irradiated for 3 hours using a 100 W high-pressure mercury lamp (UV irradiation amount: 5 mW / cm ² ). A crude iron compound-supported titanium oxide suspension (2) was obtained.

(Membrane filtration by cross flow method (2))
The crude iron compound-supported titanium oxide suspension (2) was diluted twice with pure water, and a hollow fiber ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and filtration pressure of 0.02 MPa, filtered with a cross flow method while adding the same amount of pure water as the amount of permeate. It was. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to filtration treatment until the electric conductivity of the permeate reached 200 μS / cm. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. Then, the preparation of pure water was stopped and the iron compound-supported titanium oxide concentration was concentrated to obtain an iron compound-supported titanium oxide suspension (2-1). During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank.

Thereafter, it was dried at 105 ° C. for 1 hour under normal pressure to obtain 530 g of crystalline iron compound-supported titanium oxide (2) (specific surface area: 78 m ² / g, average aspect ratio: 3, average minor axis: 17 nm). . The iron compound content of the obtained iron compound-supported titanium oxide (2) was 830 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 775 ppm. Further, the obtained iron compound-supported titanium oxide (2) has a crystal face (110) and a crystal face (111), and the rod-shaped rutile type titanium oxide in which the iron compound is supported only on the crystal face (111). A rod-shaped rutile titanium oxide having a crystal plane (110), a crystal plane (111), and a crystal plane (001), and an iron compound supported on the crystal plane (001) and the crystal plane (111) (FIG. 4).

Example 3
Crystalline iron compound-supported titanium oxide (3) in the same manner as in Example 2 except that the electrical conductivity of the permeate was 150 μS / cm in the above (cross-flow filtration process (2)). (Specific surface area: 78.5 m ² / g, average aspect ratio: 3, average minor axis: 16 nm) 530 g was obtained. The iron compound content of the obtained iron compound-supported titanium oxide (3) was 890 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 795 ppm.

Example 4
Crystalline iron compound-supported titanium oxide (4) in the same manner as in Example 2 except that the above-described (filtration treatment by cross-flow method (2)) was repeated until the electric conductivity of the permeate reached 100 μS / cm. (Specific surface area: 79 m ² / g, average aspect ratio: 3, average minor axis: 15 nm) 530 g was obtained. The iron compound content of the obtained iron compound-supported titanium oxide (4) was 950 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 800 ppm.

Example 5
Crystalline iron compound-supported titanium oxide (5) in the same manner as in Example 2 except that the electrical conductivity of the permeate was 50 μS / cm in the above (cross-flow filtration process (2)). (Specific surface area: 80 m ² / g, average aspect ratio: 3, average minor axis: 14 nm) 530 g was obtained. The iron compound content of the obtained iron compound-supported titanium oxide (5) was 1200 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 800 ppm.

Example 6
In the above (iron compound supporting treatment), a crystalline iron compound-supported titanium oxide (35% by weight) was changed in the same manner as in Example 2 except that the amount of iron chloride aqueous solution (35% by weight) was changed from 7.5 g to 6.5 g. 6) 530 g (specific surface area: 76 m ² / g, average aspect ratio: 3, average minor axis: 17 nm) was obtained. The iron compound content of the obtained iron compound-supported titanium oxide (6) was 700 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 780 ppm.

Example 7
In the above (iron compound supporting treatment), a crystalline iron compound-supported titanium oxide (35% by weight) was changed in the same manner as in Example 2 except that the amount of iron chloride aqueous solution (35% by weight) was changed from 7.5 g to 15.0 g. 7) 530 g (specific surface area: 80 m ² / g, average aspect ratio: 3, average minor axis: 16 nm) was obtained. The iron compound content in the obtained iron compound-supported titanium oxide (7) was 2000 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 753 ppm.

Example 8
In the above (preparation of crystalline titanium oxide), a crude titanium oxide suspension (8) was obtained in the same manner as in Example 2 except that the reaction temperature (temperature in the autoclave) was changed from 140 ° C to 120 ° C. The obtained crude titanium oxide suspension (8) was subjected to the above (membrane filtration treatment (1) by the cross flow method) in the same manner as in Example 2 to obtain a titanium oxide suspension (8-1). A rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111) and a rod-like rutile titanium oxide having a crystal face (110), a crystal face (111) and a crystal face (001). 530 g of titanium oxide (8) was obtained. The photocatalytic ability of the obtained titanium oxide (8) evaluated by the toluene oxidation method with the following ultraviolet rays was 600 ppm (CO ₂ generation rate: 90%).

Thereafter, the same as in Example 2 (iron compound supporting treatment) and (membrane filtration treatment by crossflow method (2)) were performed, and crystalline iron compound supporting titanium oxide (8) (specific surface area: 85 m ² / g). , Average aspect ratio: 2, average minor axis: 10 nm). The iron compound content of the obtained iron compound-supported titanium oxide (8) was 780 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 691 ppm.

Example 9
In the above (Preparation of crystalline titanium oxide), a crude titanium oxide suspension (9) was obtained in the same manner as in Example 2 except that the reaction temperature (temperature in the autoclave) was changed from 140 ° C to 160 ° C. The obtained crude titanium oxide suspension (9) was subjected to the above (membrane filtration treatment (1) by cross flow method) in the same manner as in Example 2, to obtain a titanium oxide suspension (9-1). A rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111) and a rod-like rutile titanium oxide having a crystal face (110), a crystal face (111) and a crystal face (001). 530 g of titanium oxide (9) was obtained. The photocatalytic ability of the obtained titanium oxide (9) evaluated by a toluene oxidation method with the following ultraviolet rays was 645 ppm (decomposition rate: 95%).

Thereafter, in the same manner as in Example 2 (iron compound supporting treatment) and (membrane filtration treatment (2) by cross flow method), the crystalline iron compound supporting titanium oxide (9) (specific surface area: 55 m ² / g). , Average aspect ratio: 12, average minor axis: 25 nm). The iron compound content in the obtained iron compound-supported titanium oxide (9) was 820 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 727 ppm.

Example 10
(Preparation of crystalline titanium oxide)
At room temperature (25 ° C.), 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.) Ti concentration Was diluted with pure water so as to be 5.6% by weight. The diluted titanium tetrachloride aqueous solution 5650 g was placed in a 10 L tantalum-lined autoclave and sealed. Using a heat medium, the temperature inside the autoclave was raised to 140 ° C. over 2 hours. After that, while stirring at a required power for stirring (Pv value) of 13 W / m ³ , temperature: 140 ° C., pressure: held for 10 hours under the condition of vapor pressure at that temperature, and then cooling the heat medium to cool the autoclave did. After confirming that the temperature inside the autoclave was 40 ° C. or less, 5650 g of a crude titanium oxide suspension (10) was taken out.

(Cross flow membrane filtration treatment (1))
Without diluting the resulting crude titanium oxide suspension (10) with pure water, a hollow fiber ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut-off: 30,000 , Manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and a filtration pressure of 0.02 MPa, filtration was performed by a cross flow method while adding pure water in the same amount as the permeate. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to the filtration treatment until the pH of the permeate became 4.0. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. This obtained 5650 g of titanium oxide suspension (10-1). When the titanium oxide suspension (10-1) was 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), a crystal face (110), Titanium oxide (10) which is a mixture of rod-shaped rutile type titanium oxide having crystal face (111) and crystal face (001) was obtained. The photocatalytic ability of the obtained titanium oxide (10) evaluated by a toluene oxidation method using the following ultraviolet rays was 647 ppm (decomposition rate: 95%).

(Iron compound loading treatment)
To the titanium oxide suspension (10-1) obtained above, 7.5 g of an aqueous iron chloride solution (35% by weight) was added and stirred at room temperature (25 ° C.) for 30 minutes. Thereafter, 95 g of methanol (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet rays (UV) were irradiated for 3 hours using a 100 W high-pressure mercury lamp (UV irradiation amount: 5 mW / cm ² ). A crude iron compound-supported titanium oxide suspension (10) was obtained.

(Membrane filtration by cross flow method (2))
Without diluting the crude iron compound-supported titanium oxide suspension (10) with pure water, a hollow fiber type ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000 , Manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and a filtration pressure of 0.02 MPa, filtration was performed by a cross flow method while adding pure water in the same amount as the permeate. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to filtration treatment until the electric conductivity of the permeate reached 200 μS / cm. During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. Thereby, an iron compound-supported titanium oxide suspension (10-1) was obtained.

Then, it dried at 105 degreeC under normal pressure for 1 hour, and obtained 530g of crystalline iron compound carrying | support titanium oxide (10) (specific surface area: 76m < ² > / g, average aspect-ratio: 5, average minor axis: 16nm). . The iron compound content of the obtained iron compound-supported titanium oxide (10) was 820 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 778 ppm.

Example 11
(Preparation of crystalline titanium oxide)
At room temperature (25 ° C.), 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.) Ti concentration Was diluted with pure water so as to be 5.6% by weight. 560 g of diluted titanium tetrachloride aqueous solution was placed in a 1 L tantalum-lined autoclave and sealed. Using a heat medium, the temperature inside the autoclave was raised to 140 ° C. over 2 hours. After that, while stirring at a required power for stirring (Pv value) of 13 W / m ³ , temperature: 140 ° C., pressure: held for 10 hours under the condition of vapor pressure at that temperature, and then cooling the heat medium to cool the autoclave did. After confirming that the internal temperature of the autoclave was 40 ° C. or less, 560 g of a crude titanium oxide suspension (11) was taken out.

(Cross flow membrane filtration treatment (1))
The obtained crude titanium oxide suspension (11) was diluted 10-fold with pure water, and a hollow fiber type ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C) and filtration pressure of 0.05 MPa, filtered with a cross flow method while adding pure water in the same amount as the permeate. It was. The concentrate obtained through the filtration treatment was circulated again to the charging tank, and repeatedly subjected to filtration treatment until the pH of the permeate became 2.9. Then, the preparation of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (11-1). During this time, backwashing was performed for 1 minute at a pressure of 0.15 MPa and a flow rate of 0.1 kg / min once per hour. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. When the titanium oxide suspension (11-1) was dried at 60 ° C. under reduced pressure for 15 hours, rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111), a crystal face (110), Titanium oxide (11), which is a mixture of rod-shaped rutile titanium oxide having crystal face (111) and crystal face (001), was obtained. The photocatalytic ability of the obtained titanium oxide (11) evaluated by a toluene oxidation method using the following ultraviolet rays was 617 ppm (CO ₂ generation rate: 93%).

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

(Membrane filtration by cross flow method (2))
The crude iron compound-supported titanium oxide suspension (11) was diluted 10-fold with pure water, and a hollow fiber type ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES, nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C) and filtration pressure of 0.05 MPa, filtered with a cross flow method while adding pure water in the same amount as the permeate. It was. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to filtration treatment until the electric conductivity of the permeate reached 21 μS / cm. Thereafter, the preparation of pure water was stopped, and the concentration of the iron compound-supported titanium oxide was concentrated to obtain an iron compound-supported titanium oxide suspension (11-1). During this time, backwashing was performed for 1 minute at a pressure of 0.15 MPa and a flow rate of 0.1 kg / min once per hour. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank.

Thereafter, it was dried at 60 ° C. under reduced pressure for 15 hours to obtain 40 g of crystalline iron compound-supported titanium oxide (11) (specific surface area: 71 m ² / g, average aspect ratio: 9, average minor axis: 20 nm). . The iron compound content in the obtained iron compound-supported titanium oxide (11) was 420 ppm. Moreover, the photocatalytic ability evaluated by the toluene oxidation method by the following visible light was 416 ppm, and the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 716 ppm.

Comparative Example 1
(Preparation of crystalline titanium oxide)
At room temperature (25 ° C.), 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.) Ti concentration Was diluted with pure water so as to be 5.6% by weight. 560 g of diluted titanium tetrachloride aqueous solution was placed in a 1 L tantalum-lined autoclave and sealed. Using a heat medium, the temperature inside the autoclave was raised to 140 ° C. over 2 hours. Then, after stirring for 10 hours under the conditions of temperature: 140 ° C., pressure: vapor pressure at that temperature without stirring, the autoclave was cooled by cooling the heating medium. After confirming that the temperature inside the autoclave was 40 ° C. or less, 560 g of a crude titanium oxide suspension (12) was taken out.

The crystalline iron compound-supported titanium oxide (12) (specific surface area: 9 m) was used in the same manner as in Example 11 except that the crude titanium oxide suspension (12) was used instead of the crude titanium oxide suspension (11). ² / g, average aspect ratio: 1.2, average minor axis: 100 nm). The iron compound content of the obtained iron compound-supported titanium oxide (12) was 30 ppm. Moreover, the photocatalytic ability evaluated by the methanol oxidation method by the following visible light was 250 ppm.

<Method for evaluating photocatalytic activity>
(Toluene oxidation method using visible light)
Using the iron compound-supported titanium oxide obtained in the examples as a photocatalyst, toluene was oxidized in the gas phase, and the amount of produced CO ₂ was measured to evaluate the photocatalytic ability.
200 mg of iron compound-supported titanium oxide was spread on a glass dish and placed in a reaction vessel (Tedlar bag, material: vinyl fluoride resin), and 125 mL of 100 ppm toluene gas was blown into the reaction vessel. After the adsorption of toluene gas to the iron compound-supported titanium oxide reached equilibrium, light irradiation (LED, light intensity: 2.5 mW / cm ² , light wavelength: 455 nm) was performed at room temperature (25 ° C.). A gas chromatograph with a flame ionization detector attached to a methanizer (trade name “MT221”, manufactured by GL Science Co., Ltd.) for the amount of CO ₂ produced (CO ₂ concentration in the reaction vessel) 24 hours after the start of light irradiation. Measurement was performed using a trade name “GC-14B” (manufactured by Shimadzu Corporation).

(Methanol oxidation method using visible light)
Using the iron compound-supported titanium oxide obtained in Examples and Comparative Examples as a photocatalyst, methanol was oxidized in the gas phase, and the amount of produced CO ₂ was measured to evaluate the photocatalytic ability.
200 mg of iron compound-supported titanium oxide was spread on a glass dish and placed in a reaction vessel (Tedlar bag, material: vinyl fluoride resin), and 125 mL of 800 ppm of methanol gas was blown into the reaction vessel. After the adsorption of methanol gas to the iron compound-supported titanium oxide reached equilibrium, light irradiation (LED, light intensity: 2.5 W / m ² , light wavelength: 455 nm) was performed at room temperature (25 ° C.). A gas chromatograph with a flame ionization detector attached with a methanizer (trade name “MT221”, manufactured by GL Science Co., Ltd.) for the amount of CO ₂ produced (CO ₂ concentration in the reaction vessel) 24 hours after the start of light irradiation. Measurement was performed using a trade name “GC-14B” (manufactured by Shimadzu Corporation).

(Toluene oxidation method using ultraviolet rays)
Using the titanium oxide obtained in the examples as a photocatalyst, the photocatalytic ability was evaluated by oxidizing toluene in the gas phase and measuring the amount of CO ₂ produced.
200 mg of titanium oxide was spread on a glass dish and placed in a reaction vessel (Tedlar bag, material: vinyl fluoride resin), and 125 mL of 100 ppm toluene gas was blown into the reaction vessel. After the adsorption of toluene gas to titanium oxide reached equilibrium, light irradiation (LED, light intensity: 0.1 mW / cm ² , light wavelength: 365 nm) was performed at room temperature (25 ° C.). A gas chromatograph with a flame ionization detector attached with a methanizer (trade name “MT221”, manufactured by GL Science Co., Ltd.) for the amount of CO ₂ produced (CO ₂ concentration in the reaction vessel) 24 hours after the start of light irradiation. Measurement was performed using a trade name “GC-14B” (manufactured by Shimadzu Corporation).

  The transition metal compound-supported titanium oxide of the present invention has an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. Therefore, it has excellent responsiveness to visible light, and can absorb light in normal living spaces such as sunlight, incandescent lamps, fluorescent lamps, and LEDs, and decompose harmful chemical substances into water and carbon dioxide. That is, the transition metal compound-supported titanium oxide suspension of the present invention can be suitably used as a photocatalyst for LED illumination. And it can be applied in various ways such as antibacterial and antifungal, deodorization, air purification, water purification, etc., indoor wallpaper, furniture, environmental purification in homes, hospitals, schools and other public facilities, high functionality of home appliances Application to a wide range is possible.

Claims (2)

A titanium compound is hydrothermally treated in an aqueous medium while stirring at a required power Pv value of 0.1 to 1500 W / m ³ , and a rutile type titanium oxide having a crystal face (110) and a crystal face (111) and / or Or manufacturing a crystalline titanium oxide which is a rutile type titanium oxide having a crystal face (110), a crystal face (111) and a crystal face (001) ,
A step of obtaining a transition metal compound-supported titanium oxide by supporting an iron compound as a transition metal compound in the produced crystalline titanium oxide;
And a step of purifying the obtained transition metal compound-supported titanium oxide by subjecting it to membrane filtration by a cross flow method,
A transition metal compound-supported titanium oxide containing process,
Transition metal compound-supported titanium oxide, an average minor diameter of 25nm or less and an average aspect ratio (major axis / minor axis) of the production method of the transition metal compound-supported titanium oxide is 1.5 or more. The method for producing a transition metal compound-supported titanium oxide according to claim 1, wherein the specific surface area of the transition metal compound-supported titanium oxide is 10 m ² / g or more.