JP5238385B2 - Visible light responsive fibrous photocatalyst and purification device - Google Patents

Description

  The present invention relates to a photocatalyst having a photocatalyst material supported on a carrier, a method for producing the photocatalyst, and a purification device using the photocatalyst, and particularly to a photocatalyst having a large specific surface area.

Conventionally, a technique for purifying water and air with a photocatalyst under ultraviolet light irradiation is known. As photocatalysts, oxide semiconductors, especially titanium oxide (TiO ₂ ), are known to be safe compounds that have excellent catalytic action, are chemically stable, and have a low possibility of elution and environmental pollution. Yes.

Various kinds of environmental pollutants are decomposed and removed by utilizing the photocatalytic action of titanium oxide. For example, it is used for purification of water, decomposition of malodorous substances such as ammonia, aldehydes and amines in water, sterilization of fungi, algae killing of algae and the like.
For air and gas treatment, for example, decomposition of malodorous substances such as toilet urine odor, pet odor and cigarette odor, or decomposition of environmental pollutants such as nitrogen compounds, sulfide compounds and dioxins discharged from incinerators The photocatalytic action of titanium oxide is also used for removal.

  When titanium oxide is used as a photocatalyst for various applications, it is common to support other inorganic materials as carriers. In the present specification, a complex composed of a carrier and a photocatalytic material carried on the carrier is simply referred to as a “photocatalyst”.

Many attempts have been made to efficiently exhibit the photocatalytic action by making the photocatalyst body porous and increasing the specific surface area with which the photocatalyst material can come into contact with the object to be treated.
For example, Patent Document 1 discloses that a ceramic porous body mainly composed of ceramics, cement, foamed concrete, brick, silica, alumina, zirconia, silicon carbide, silicon nitride, barium titanate or the like is preferable as a carrier. What is described as a porous material in this publication is a material in which the above-mentioned various inorganic materials are crushed by a crusher such as a jaw crusher into pieces of several mm to several tens mm, typically 1 to 100 mm, in the form of strips or granules. It is.

As another example, Patent Document 2 discloses that activated carbon, zeolite, silica gel, alumina, pearlite, and porous glass are used as carriers, and that activated carbon is particularly preferable. As a method for producing activated carbon, an activated carbon raw material from which coconut shells are dried and fine powder is removed is put into a rotary kiln (550 to 650 ° C.), and in a red hot state, steam, carbon dioxide (CO _{2 in} combustion gas) and oxygen ( Granular activated carbon is obtained by activation at a temperature of 850 to 950 ° C. in a mixed atmosphere of O ₂ ) in the combustion air.

Patent Document 3 shows an example in which a thin film of titanium oxide is formed on an inorganic paper mainly composed of silicon carbide, silica glass, activated carbon, zeolite, and sepiolite.
Patent Documents 4 and 5 show an example of a water purification device using a photocatalyst using activated carbon, activated alumina, silica gel, and porous glass as a carrier, and an example of an exhaust gas purification device.

Patent Document 6 shows examples of nickel cadmium, stainless steel, vermalloy, aluminum alloy, copper porous metal carrier, and activated carbon, activated alumina, silica gel, porous glass granular ceramic, clay porous ceramic carrier. Yes.
Patent Document 7 shows an example of an exhaust gas treatment apparatus using a photocatalyst in which activated carbon, activated alumina, silica gel, and porous glass are used as a carrier.

  However, the conventional porous photocatalysts such as these have a large specific surface area because they are opaque to ultraviolet light, although they are porous to increase the specific surface area. The processing power that was expected was not obtained. In addition, conventional porous photocatalysts such as these generally have problems such as low heat resistance, chemical resistance, chemical stability, and low mechanical strength. In particular, it could not withstand use under harsh conditions.

  Also, when many impurities are contained, for example, in the purification of water, the impurity elements contained in the carrier are eluted and mixed into the purified water because the impurity element content of the carrier is large and the chemical stability is low. There are many things to do. Or, in the purification of air, since the impurity element content of the carrier is large and the carrier is a crushed powder, the impurity element-containing fine powder contained in the carrier often mixes with the purified air. . In particular, when the gas to be treated contains a corrosive gas at a high temperature, secondary impurities are generated due to deterioration of the carrier.

  In addition, since titanium oxide has a high energy band gap structure (3.2 eV), it absorbs only ultraviolet light having a short wavelength, and hardly causes a catalytic reaction by visible light. The development and application of visible light responsive titanium oxide photocatalysts that can effectively use visible light, which occupies most of indoor light and sunlight, are currently important research subjects.

  Various methods for producing such visible light responsive titanium oxide powder have been proposed. For example, Patent Documents 8 and 9 describe a production method in which a photocatalyst such as titanium dioxide is chemically doped with metal ions such as vanadium, chromium, and manganese. However, the photocatalyst chemically doped with a metal cation such as vanadium as described above has a photocatalytic activity in visible light, but a decrease in the photocatalytic activity in ultraviolet light originally possessed by the photocatalyst before doping is observed. There are many. This is because newly introduced metal ions aggregate on the surface of the photocatalyst to form a new impurity energy level, which becomes a recombination center of holes and electrons generated by ultraviolet light irradiation, resulting in a decrease in photocatalytic activity. It is estimated.

  Patent Document 10 discloses a production method in which a transition metal such as vanadium, chromium, or manganese is ion-implanted into a titanium dioxide photocatalyst. In the photocatalyst implanted with transition metal ions, the implanted transition metal ions are uniformly implanted at an appropriate depth inside without deteriorating the surface structure of titanium dioxide. While maintaining the photocatalytic activity, visible light also exhibits photocatalytic activity. However, the ion implantation manufacturing method requires a large-scale manufacturing apparatus, strict manufacturing process control, and the like, and has problems in both productivity and cost.

  Patent Document 11 shows that a composite fine particle of a metal oxide containing nitrogen and titanium oxide can be obtained in a high yield as a photocatalytic material that also responds to visible light. Patent Document 12 shows that titanium oxide fine particles containing nitrogen can be obtained in a high yield as this similar invention. However, since the photocatalyst made of titanium oxide shown in these documents is in the form of fine particles, it cannot be directly mounted on a photocatalytic reaction device (unit) and used for exhaust gas treatment or wastewater treatment.

JP 2004-230301 A JP 2006-110470 A JP 2004-305883 A JP 2003-181475 A JP 2002-35551 A Japanese Patent Laid-Open No. 2001-232206 JP 2001-170453 A JP-A-9-192896 JP 2000-237598 A JP-A-9-262482 JP 2005-138008 A JP 2005-139020 A

  The present invention has been made in view of the above-described problems, and can provide a photocatalyst capable of efficiently exhibiting photocatalytic action under irradiation of not only ultraviolet light but also visible light, a method for producing the same, and such a photocatalyst. An object of the present invention is to provide a purifying apparatus using the above.

The present invention has been made to solve the above-described problems, and includes at least a fibrous silica glass support composed of silica glass fibers, and a metal oxide formed on the surface of the fibrous silica glass support as a main component. A fibrous photocatalyst comprising a coating of a photocatalyst material, wherein the photocatalyst material further includes any one of transition metal elements other than the metal element constituting the main component metal oxide and / or nitrogen as an additional element contain, are those having a visible light responsive, the fibrous photocatalyst is, that provides visible light responsive fibrous photocatalyst characterized by functioning as a photocatalyst having visible light responsiveness.

Such a visible light responsive fibrous photocatalyst is a fibrous photocatalyst capable of generating a photocatalytic action not only by ultraviolet light but also by visible light irradiation.
In addition, since the carrier is made of silica glass fiber having high light transmittance, it has high light transmittance, and since it is fibrous, it has high air permeability and water permeability, and the photocatalyst material and the object to be treated are It can be set as the photocatalyst body with a large specific surface area which can be contacted. And by having these characteristics simultaneously, a photocatalytic action can be exhibited efficiently.
Moreover, since it is a fibrous photocatalyst, it is less likely to scatter than a particulate photocatalyst and is easy to handle. Moreover, it can be easily formed into an arbitrary shape as compared with the bulk photocatalyst body, and can be easily filled into a container of an arbitrary shape.
Further, since it is a fibrous photocatalyst, the packing density and the porosity can be easily set arbitrarily according to the purpose. Moreover, it can be made into cloth shape, wool shape, felt shape, etc. according to a use.
In addition, when the support is made of silica glass fiber, a visible light responsive fibrous photocatalyst having high chemical stability and high heat resistance can be obtained.

In this case, the photocatalyst material is the a metal oxide is titanium oxide of the main component, it is not preferable are those containing either one and / or nitrogen transition metal elements other than titanium as the additional element . Then, a transition metal element other than the titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, palladium, silver, platinum, cerium, have preferably be at least one selected from the group consisting of neodymium.
If the photocatalyst material used in the present invention comprises such a component, a photocatalyst having a higher photocatalytic action can be obtained particularly in the visible light region.

In the visible light responsive fibrous photocatalyst of the present invention, among the elements contained in the fibrous silica glass carrier, the content of each of the alkali metal elements Li, Na, and K is 100 wt. ppb or less, and the content of each of the alkaline earth metal elements Mg and Ca is 50 wt. ppb or less is Ru may be a visible light responsive fibrous photocatalyst.
Thus, if various metal elements are contained as described above among the elements contained in the fibrous silica glass support, a fibrous silica glass support having a sufficiently high purity can be obtained. And, if such a fibrous silica glass carrier having a very small amount of impurity metal elements and a sufficiently high purity, deterioration (devitrification) of the fibrous silica glass carrier due to recrystallization or the like is effectively prevented. It is also possible to prevent the release of impurities into the environment when using the visible light responsive photocatalytic material.

Further, the silica glass fibers, fiber diameter 5 to 300 .mu.m, it is not preferable is that 100mm or more in length.
As described above, if the fiber diameter of the silica glass fiber according to the visible light responsive fibrous photocatalyst of the present invention is 5 μm or more, the silica glass fiber can have sufficient strength, and thus is cut and becomes particle-like. Can be prevented, and can be handled more easily. Moreover, if the fiber diameter is 300 μm or less, the strength of the fiber is moderate without being too strong, and can be handled more easily.
The fiber diameter in the present specification means a value corresponding to the diameter when the cross-sectional area of the fiber is converted on the assumption that the cross-sectional shape of the fiber is a true circle, in accordance with the definition usually used. It is defined even if the cross-sectional shape is not a perfect circle.
Moreover, if the length of the silica glass fiber of the visible light responsive fibrous photocatalyst of the present invention is 100 mm or more, the visible light responsive fibrous photocatalyst can be easily handled.

Further, the silica glass fibers, it is not preferable fiber curl radius is less than 200 mm.
Thus, if the fiber curl radius of the silica glass fiber is 200 mm or less, the silica glass fiber can have an appropriate curl, and it is easier to handle the visible light responsive fibrous photocatalyst in a lump. can do.

In addition, the present invention provides at least a photocatalytic reactor, any one of the above visible light responsive fibrous photocatalysts contained in the photocatalytic reactor, and a light source that emits light including at least ultraviolet light and visible light. And irradiating the visible light responsive fibrous photocatalyst with the light beam with the light source, and passing the object to be processed through the photocatalytic reactor containing the visible light responsive fibrous photocatalyst, that provides purifying apparatus, characterized in that the purification treatment of the object to be processed by the action.

  If it is such a purification device comprising the visible light responsive fiber photocatalyst according to the present invention, the visible light responsive fiber that can efficiently exhibit the photocatalytic action not only by ultraviolet rays but also by irradiation with visible light. Therefore, it is possible to provide a purification device having a high processing capacity.

The present invention includes at least a step of producing a fibrous silica glass support composed of silica glass fibers, a step of forming a metal oxide film serving as a photocatalytic material on the surface of the fibrous silica glass support, that provides a method of manufacturing a visible-light-responsive fibrous photocatalyst which comprises a step of performing nitrogen doping treatment to a fibrous silica glass support to form a coating of metal oxides.

  If it is a manufacturing method of such a visible-light-responsive type fiber photocatalyst body, it has a fibrous silica glass support | carrier and the metal oxide formed in the surface as a main component, nitrogen is contained, and visible light responsiveness is shown. A visible light responsive fibrous photocatalyst that functions as a photocatalyst having visible light responsiveness can be produced.

In this case, the metal oxide, have preferably be an oxide of titanium.
Thus, if the metal oxide which is the main component of the photocatalytic material is titanium oxide, a photocatalyst having a higher photocatalytic action can be obtained.

The present invention also includes a step of producing a fibrous silica glass carrier comprising at least silica glass fibers, and a coating of a photocatalytic material having visible light responsiveness on the surface of the fibrous silica glass carrier. And a step of forming a coating containing any one of transition metal elements other than the metal elements constituting the metal oxide as an additive metal element. A method for producing a visible light responsive fibrous photocatalyst is provided. you.

  If it is a manufacturing method of such a visible-light-responsive type fibrous photocatalyst body, it is the fibrous silica glass support | carrier and the metal element formed in the surface other than the metal element which has a metal oxide as a main component and comprises this metal oxide Thus, a visible light responsive fibrous photocatalyst that functions as a photocatalyst having visible light responsiveness can be produced.

In this case, the metal oxide may be titanium oxide, and the additive metal element may be at least one of vanadium, chromium, manganese, iron, cobalt, nickel, copper, palladium, silver, platinum, cerium, and neodymium. It has preferred.
By using such a photocatalytic material component, a photocatalyst having a higher photocatalytic activity particularly in the visible light region can be obtained.

In this case, the visible light responsive fibrous photocatalyst produced, further, Ru can be performed nitrogen doping treatment.
Thus, as described above, a visible light responsive fiber manufactured to have a photocatalytic material coating containing a metal oxide as a main component and a transition metal element other than the metal element constituting the metal oxide added. Further, the nitrogen-like photocatalyst can be subjected to nitrogen doping treatment.

In the method of manufacturing the visible-light-responsive fibrous photocatalyst of the present invention, the nitrogen doping treatment, an ammonia-containing atmosphere, Ru can be done by performing a heat treatment at 400 ° C. to 700 ° C..
Nitrogen doping can be performed more appropriately by performing nitrogen doping under such conditions.

In the method for producing a visible light responsive fibrous photocatalyst of the present invention, the production of the fibrous silica glass support is performed by forming a transparent silica glass base material by a flame hydrolysis method using at least a silicon compound as a raw material. a step of the step of processing the transparent silica glass base material rod body, to melt the transparent silica glass rod-like body, have preferably be carried out by a step in drawing the fibrous producing silica glass fibers .
If a fibrous silica glass carrier is produced through such steps, a fibrous carrier made of high-purity silica glass can be more easily produced.

  As described above, the visible light responsive fibrous photocatalyst and the method for producing a visible light responsive fibrous photocatalyst according to the present invention can generate photocatalytic action not only by ultraviolet light but also by visible light irradiation. It can be set as a fibrous photocatalyst. In addition, since the support is made of silica glass fiber, it has high light permeability, high air permeability and water permeability, and has a large specific surface area that allows the photocatalyst material and the object to be processed to contact each other. It can be set as a photocatalyst.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
As described above, the conventional photocatalyst has a problem that the processing capability as expected from the large specific surface area is not obtained although the device has been devised to increase the specific surface area.

In order to solve these problems, the present inventors have conducted the following studies.
For example, although the support | carrier which comprises the photocatalyst body described in patent document 1 is a porous body as mentioned above, it crushes various inorganic materials and makes it 1-100 mm strip shape or a granular form. Because it is in the form of particles, even if it is irradiated with visible light or ultraviolet light from the outside of the carrier to promote the photoreaction, it is diffusely reflected on the surface of the carrier particles, and the light does not reach the inside of the photocatalyst sufficiently. . Further, impurities such as metals are inevitably mixed by the pulverization process, and the purity cannot be kept high. Since impurities enter in this way, the heat resistance, chemical resistance, and chemical stability become even lower.
In addition, conventional carriers generally have no visible light or ultraviolet light permeability, and photochemical reactions using photocatalysts with a large specific surface area mainly occur only on the surface layer of these photocatalysts. However, the efficiency was low.

Therefore, the present inventors firstly used a fine powder photocatalyst and a fiber having a high transmittance of visible light or ultraviolet light compared to a photocatalyst produced by sintering fine powder and having a large specific surface area. It was considered that a glassy silica glass support was prepared and used as a fibrous photocatalyst.
Such a photocatalyst was considered to have a high ultraviolet transmittance and allow the object to be processed to pass through the gaps between the fibers, so that the photocatalytic action can be effectively exhibited.

  On the other hand, it is thought that transparent silica gel particles can be used in the same way. However, in the case of silica gel with a large particle size, even if this is used as a carrier, the air or water of the purified product flows through the gaps between the particles. This makes it difficult to enter the pores inside the silica gel particles, resulting in poor photocatalytic reaction efficiency. On the other hand, in the case of silica gel with fine particles, clogging occurs during the treatment of air or water, or ultraviolet light is difficult to enter inside the particles, resulting in poor photocatalytic reaction efficiency.

  In addition, although the manufacturing method of fibrous silica glass is known for a long time, as a recent literature, JP, 2004-99376, JP, 2004-99377, JP, 2004-352576, A JP, 2006, is mentioned. JP-A No. 27960 and JP-A No. 2006-282401.

  However, these recent inventions related to fibrous silica glass relate to synthetic silica glass fibers, yarns and fabrics used for multilayer printed wiring, and particularly to low dielectric constant and low loss printed circuit boards necessary for high frequency circuits of 1 GHz or higher. Is.

Japanese Patent Application Laid-Open No. 2006-231171 discloses a method of reducing nitrogen oxide (NO) to nitrogen by a photocatalyst and urea under irradiation of visible light from ultraviolet rays. Among these, activated carbon, activated carbon fiber, titanium oxide, alumina, silica gel, and quartz wool are considered as urea carriers.
However, the quartz wool of this document is originally considered as a carrier for urea and is not a carrier for titanium oxide.

  Based on these findings, the present inventors prepared a fibrous silica glass support to impart visible light or ultraviolet light transmittance, air permeability, and water permeability to the photocatalyst, and then produced the fibrous silica glass. It has been found that a visible light-responsive fibrous photocatalyst is produced by performing a treatment for forming a coating film of a material to be a photocatalyst having a visible light response on the surface of the carrier. And according to such a manufacturing method, it can be set as a photocatalyst body which has high light permeability, high air permeability and water permeability, and a large specific surface area that allows the photocatalyst material and the object to be processed to come into contact with each other. The present invention has been completed by conceiving what can be done.

In addition, when the carrier contains a large amount of impurities, such as conventional powder and sintered body carriers, for example, in the purification of water, the carrier contains a large amount of impurity elements and the chemical stability is low. In many cases, impurity elements contained in these carriers are eluted and mixed in the purified water. Alternatively, in the purification of air, since the carrier has a large impurity element content and the carrier is crushed powder or a lump of sintered powder, the impurity element contained in these carriers in the purified air In many cases, the contained fine powder is mixed. In particular, when the gas to be treated contains a corrosive gas at a high temperature, secondary impurities may be generated due to deterioration of the carrier.
In addition to the problem of fine powder photocatalysts being easily scattered, the heat resistance, chemical resistance, chemical stability, etc. are generally low, and it is used for a long time, especially under ultraviolet irradiation. It could not withstand use under harsh conditions such as treating hot fluids.
In addition, the hard lump photocatalyst has difficulty in processability.

  On the other hand, if it is a visible light responsive fibrous photocatalyst having a visible light responsive photocatalyst film formed on the surface of the fibrous silica glass carrier as in the present invention, it is excellent in processability. In addition, since the material of the carrier is silica glass, it is possible to obtain a photocatalyst that has good light transmittance of visible light or ultraviolet light, and has high chemical stability and heat resistance.

Further, the visible light responsive fibrous photocatalyst of the present invention can generate a photocatalytic action not only by ultraviolet light but also by irradiation with visible light. For example, the amount of ultraviolet light contained in sunlight is small compared to the total light energy, but the photocatalytic action is large compared to visible light. Accordingly, it is important to develop a photocatalyst having high responsiveness even in visible light while maintaining the ultraviolet photocatalytic action inherent in photocatalytic materials such as titanium oxide (TiO ₂ ). For example, in various mercury lamps, a large amount of visible light is generated in addition to ultraviolet light, and it is very important to develop a photocatalyst that exhibits high responsiveness not only in ultraviolet light but also in visible light.

  The greatest feature of the visible light responsive fibrous photocatalyst of the present invention is that ultraviolet light and visible light irradiated on the surface of the photocatalyst are transmitted and scattered to the inside. Accordingly, even a photocatalyst having a large volume can efficiently cause a photocatalytic reaction not only on the surface but also inside. Such a thing brings about the improvement of the photoreaction efficiency which cannot be achieved with the photocatalyst which carried the conventional opaque ceramics as a support | carrier and carry | supported the photocatalyst material.

  Titanium oxide generates a photocatalytic action by absorbing ultraviolet light having a wavelength of about 400 nm or less. Titanium oxide is a kind of semiconductor, and a semiconductor is usually a nonconductor that does not conduct electricity, but it conducts electricity when irradiated with light. However, any light is not necessary, and light with a certain level of energy is required. This energy is called bandgap energy and varies depending on the type of semiconductor. When the titanium oxide is irradiated with ultraviolet light having a band gap energy or higher, electrons in the valence band move to a conduction band having a high energy level and can move. When electrons move to the conduction band, a hole is formed in the valence band, from which electrons are removed, and this hole has a positive charge and is called a hole. Electrons and holes are generated simultaneously, electrons have a strong reducing power, and holes have a strong oxidizing power. This is the basic mechanism of photocatalysis.

  Titanium oxide doped with a transition metal element other than nitrogen or titanium absorbs not only ultraviolet light having a wavelength of 400 nm or less but also visible light having a wavelength of about 800 nm or less, thereby generating a larger photocatalytic action. Although the detailed mechanism of visible light responsiveness by doping transition metal elements other than nitrogen and titanium into titanium oxide has not been fully elucidated, anyway, transition metals other than nitrogen and titanium Visible light responsiveness is produced by doping the element.

  Hereinafter, the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.

(Manufacturing method 1)
First, a method for producing a visible light responsive fibrous photocatalyst comprising a coating containing a metal oxide as a main component and at least nitrogen as an additive element as a photocatalyst material coating will be described.
FIG. 1 shows an example of a method for producing a visible light responsive fibrous photocatalyst according to the present invention.
First, the fibrous silica glass support | carrier 11 which consists of a silica glass fiber as shown to Fig.1 (a) is produced (process 1a). 1A-1 schematically shows a cross section along the fiber axial direction, and FIG. 1A-2 schematically shows a cross section perpendicular to the fiber axial direction.

  This fibrous silica glass support is obtained by a known method (for example, “Application Technology of High-Purity Silica” (CMC Co., Ltd., issued on March 1, 1991, P. 202, Chapter 5 Silica Fiber and its Application)). For example, it is preferable to prepare by the following method.

First, a transparent silica glass base material is formed as follows (step 1).
A high-purity silicon compound such as SiCl ₄ is used as a raw material, and a transparent silica glass base material is formed by flame hydrolysis using oxyhydrogen gas or propane gas. The flame hydrolysis method performed here is a direct melting method which is a method for obtaining a transparent silica glass base material directly at a high temperature (1700 ° C. or higher), or a white opaque soot body at a relatively low temperature (about 500 to 1000 ° C.). Then, a method such as a soot method, which is a method for obtaining a transparent silica glass base material by heating and melting under reduced pressure, can be appropriately selected. The transparent silica glass base material may be manufactured using a manufacturing method other than the flame hydrolysis method. However, according to the flame hydrolysis method, a higher-purity product can be obtained and the concentration of OH groups can be easily adjusted. Therefore, it is preferable.

Next, the above-described transparent silica glass base material is processed into a rod-shaped body as follows (step 2). Thereby, it becomes easy to perform the drawing process to the fiber shape in the next step 3.
For example, the transparent silica glass base material is stretched into a rod-like body having a diameter of about 5 to 10 mm and a length of about 500 to 2000 mm by heat processing for softening by heating. When such a processing method is adopted, the vertical cross-sectional shape with respect to the axial direction of the transparent silica glass rod-like body tends to be close to a perfect circle or an ellipse.
Further, the transparent silica glass base material may be processed by a cutting machine, and if necessary, processed into an elongated rod-like body whose vertical cross-sectional shape with respect to the axial direction is a square, rectangle, triangle or other polygon. As dimensions, the total length of the sides of the polygon is about 10 to 50 mm and the length is about 500 to 2000 mm. By making the vertical cross-sectional shape polygonal, an appropriate bend (fiber curl) can be formed in the fiber by drawing (drawing process) into the fiber shape in the next step 3.

Next, as described below, the above-described transparent silica glass rod-like body is melted and drawn into a fiber shape to produce silica glass fibers (step 3).
For example, 10 to 30 synthetic transparent silica glass rods having a diameter of 5 to 10 mm obtained in Step 2 are juxtaposed and heated by propane or the like, direct electric resistance heating by a heater, high frequency induction heating, or melt softening Then, it is drawn (drawn) to obtain a silica glass fiber having a fiber diameter of about 300 μm or less. In addition, you may combine multiple said methods for the heating method in the case of melt drawing.
It may be cooled as it is, and it may be a continuous glass (long fiber) silica glass fiber, but after that, by further spraying a high-speed fluid (for example, jet blowing with a flame), a wool shape having a fiber diameter of about 5 to 100 μm ( (Short fiber) silica glass fiber may be produced.

By passing through the above steps, the fibrous silica glass support 11 as shown in FIG. 1A can be produced.
Moreover, it is good also as a fibrous silica glass support | carrier as a form called a strand, a yarn, a cloth | cross, etc. by converging, spinning, or braiding a silica glass fiber. In addition, as a form of the fibrous silica glass support according to the present invention, various forms that can be generally taken by the silica glass fiber can be appropriately selected.

In the fibrous silica glass support, the size of one silica glass fiber is preferably 5 to 300 μm in diameter (fiber diameter) and 100 mm or more in length (fiber length) for the following reasons.
As described above, the fiber diameter in the present specification means a value corresponding to the diameter when the cross-sectional area of the fiber is converted on the assumption that the cross-sectional shape of the fiber is a perfect circle. is there. Moreover, the limitation of the said preferable fiber diameter and fiber length can be prescribed | regulated by the average (average fiber diameter, average fiber length) of many silica glass fibers.

As described above, the fiber diameter of the silica glass fiber according to the visible light responsive fibrous photocatalyst of the present invention is preferably 5 μm or more. In this way, the strength of the silica glass fiber can be sufficiently secured, so that it can be prevented from being cut and become particle-like, and can be handled more easily. Moreover, if a fiber diameter is 300 micrometers or less, the intensity | strength of a fiber is not too strong, it is moderate, and it can be made easier to handle.
Moreover, if the length of the silica glass fiber according to the visible light responsive fibrous photocatalyst of the present invention is 100 mm or more, when the visible light responsive fibrous photocatalyst is collectively made into a cottony lump, A visible light responsive fibrous photocatalyst that can be easily united and handled is preferable. Moreover, if the length of this silica glass fiber is 3000 mm or less, when the fibrous photocatalysts are put together into a cotton-like lump, it can be moderately easily bundled and a fibrous photocatalyst that is easier to handle can be obtained. Therefore, it is preferable.

The fiber diameter of the silica glass fiber can be controlled by controlling the feed speed of the rod-shaped body, the fiber pulling speed, the amount of flame, the temperature, etc., when the silica glass rod-shaped body is drawn into silica glass fibers.
Moreover, when making the fiber length of a silica glass fiber into a short fiber, it can be controlled by the flow rate etc. at the time of spraying a high-speed fluid, for example. Moreover, when setting it as a continuous fiber, after winding up, it can adjust by cutting | disconnecting by moderate length.

The OH group in the silica glass fiber is 1-1000 wt. It is preferable to contain about ppm, 1-100 wt. More preferably, it is about ppm. In this way, the UV resistance is improved, and in particular, it is possible to prevent a decrease in light transmittance and deterioration in strength. Moreover, peeling of the photocatalyst material film caused by this deterioration can be suppressed.
This is because the OH group terminates the network structure (network structure) of Si atoms and O atoms of the silica (network terminator), and the silica glass structure is stabilized (relaxed) by being present in an appropriate amount. This is because the bond angle of O—Si can be set to a stable value, and as a result, deterioration due to ultraviolet irradiation can be suppressed.

Further, in the above step 2, when the transparent silica glass base material is processed into an elongated rod-like body whose vertical cross-sectional shape with respect to the axial direction is square, rectangular, triangular or other polygonal shape, when drawn into a silica glass fiber The vertical cross-sectional shape of the silica glass fiber tends to be a square, rectangle, triangle or other polygonal shape. With such a cross-sectional shape, an appropriate bend (fiber curl) can be formed in the silica glass fiber. The fibers of the fibrous silica glass carrier are preferably curled rather than straight from the viewpoint of ease of handling the carrier in a lump.
The degree of curling can be judged from the shape after the fiber is dropped from above onto a silica glass plate dried in an atmosphere of air at room temperature of 25 ° C. and a relative humidity of 50% or less.
In this case, the radius of curvature of the silica glass fiber, that is, the fiber curl radius is preferably 200 mm or less, and more preferably 100 mm or less. The lower limit of the preferred range of the fiber curl radius is not particularly limited, but can be determined according to ease of handling and the like, for example, about 10 mm.

  The method for producing a fibrous silica glass carrier as described above is preferable because it can be a fibrous carrier made of silica glass with extremely high purity.

As described above, after producing the fibrous silica glass support 11 as shown in FIG. 1A, next, as shown in FIG. 1B, the surface of the fibrous silica glass support 11 is formed. Then, a metal oxide film 12 to be a photocatalytic material is formed (step 1b). The fibrous silica glass carrier 11 on which the metal oxide coating 12 is formed may be hereinafter referred to as an intermediate composite 13.
1B-1 schematically shows a cross section along the fiber axial direction, and FIG. 1B-2 schematically shows a cross section perpendicular to the fiber axial direction.

Examples of the metal oxide used as the photocatalyst material for the present invention include titanium oxide, zinc oxide, zirconium oxide, and the like. Titanium oxide is preferred for reasons such as high photocatalytic activity. Titanium oxide includes pure anhydrous titanium oxide (TiO ₂ ) and various hydrates. Moreover, a dopant, a binder, etc. may be included.
As the titanium oxide used in the practice of the present invention, an anatase type crystal structure having high photocatalytic activity (anatase type titanium oxide) is particularly preferable.
In the following, as a preferred example, a case where a titanium oxide film is formed in Step 1b will be mainly described.

  The metal oxide film 12 can be formed by the following method, for example. There are roughly two types, that is, a dry method and a wet method.

The first method is vapor deposition of a metal oxide on the surface of a fibrous silica glass support (dry method). As a vapor deposition method, titanium oxide (TiO ₂ ) may be deposited by a film forming technique such as a sputtering method, a glow discharge method, a thermal vapor deposition method, a vacuum vapor deposition method, a chemical vapor deposition method (CVD method), or an ion plating method. it can. In view of technical ease and cost, the thermal evaporation method is particularly preferable. The titanium oxide formed as a film is preferably titanium dioxide (TiO ₂ ), and the structure is preferably anatase titanium oxide.

The second method is a solution of an organometallic compound that becomes a precursor of a metal oxide, or a dispersion of fine particles made of a compound that becomes a precursor of a metal oxide (in the case of titanium oxide, a solution of an organotitanium compound or (Titanium oxide dispersion) is impregnated with a fibrous silica glass carrier and then heat-dried (dip coating method, wet method).
For example, a fibrous silica glass carrier is immersed and impregnated in a sol solution of titanium oxide (TiO ₂ ) prepared by hydrolysis of an organic titanium compound in the presence of an acid catalyst, then pulled up at a constant speed and dried, about 300 to 700 ° C. Bake with heat. In order to produce a uniform and high-quality titanium oxide film, it is preferable to repeat the above-described steps of immersion, impregnation, drying, and baking a plurality of times. Examples of the organic titanium compound include titanium such as titanium ethoxide [Ti (OC ₂ H ₅ ) ₄ ], titanium proxy [Ti (OC ₃ H ₇ ) ₄ ], titanium bromide [Ti (OC ₄ H ₉ ) ₄ ]. Alkoxides can be used. As the acid catalyst, for example, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, or organic acids such as oxalic acid, lactic acid, and acetic acid can be used.

  The amount of the metal oxide formed and supported on the surface portion of the fibrous silica glass support in this step 1b is not particularly limited, and its use and purpose, the material form of gas or liquid of the object to be treated, etc. It can be appropriately selected depending on the case. Generally, fibrous silica glass support 100 wt. % To 0.1 to 50 wt. % Can be supported as a coating.

As described above, the fibrous silica glass support 11 (intermediate composite 13) on which the metal oxide film 12 as shown in FIG. 1B is formed is subjected to nitrogen doping (step 1c).
1C-1 schematically shows a cross section along the fiber axial direction, and FIG. 1C-2 schematically shows a cross section perpendicular to the fiber axial direction.

The nitrogen doping treatment is not particularly limited as long as nitrogen is added to the metal oxide film 12, but can be preferably performed by the following treatment.
That is, heat treatment can be performed in a temperature range of 400 ° C. to 700 ° C. in an ammonia (NH ₃ ) gas-containing atmosphere. In this ammonia gas heat treatment, for example, the fibrous silica glass support after the metal oxide film formation treatment is placed in an electric heating furnace in which a silica glass chamber is installed, the inside of the chamber is made an ammonia gas atmosphere, and then the temperature is raised to 600 ° C. After holding for 1 hour, it is cooled to room temperature. Further, if necessary, the inside of the chamber is switched from ammonia gas to nitrogen gas atmosphere, and baking is performed at 200 ° C. to 300 ° C. for about 3 hours. This baking treatment has an effect of physically and chemically stabilizing the nitrogen-doped metal oxide film.

  By performing such nitrogen doping treatment, nitrogen can be added to the metal oxide film 12 to be a photocatalyst material, and visible light responsiveness can be added to the photocatalyst material.

  By passing through the steps 1a, 1b, and 1c as described above, a visible light responsive type containing a metal oxide as a main component and at least nitrogen as an additive element on the surface of the fibrous silica glass support 11 as a photocatalytic material coating. The visible light responsive fibrous photocatalyst body 16 according to the present invention in which the coating film 15 of the photocatalyst material is formed can be manufactured.

(Manufacturing method 2)
Next, a visible light responsive fibrous photocatalyst comprising a coating containing a metal oxide as a main component and a transition metal element other than the metal element constituting the metal oxide as an additive element as a photocatalyst material coating A manufacturing method will be described.
FIG. 2 shows another example of the method for producing a visible light responsive fibrous photocatalyst according to the present invention.
First, the fibrous silica glass support | carrier 11 which consists of a silica glass fiber as shown to Fig.2 (a) is produced (process 2a). 2A-1 schematically shows a cross section along the fiber axial direction, and FIG. 2A-2 schematically shows a cross section perpendicular to the fiber axial direction.
The manufacturing method of this fibrous silica glass support | carrier 11 is the same as that of the process 1a of above-described manufacturing method 1.

Next, as shown in FIG. 2B, the metal oxide is formed on the surface of the fibrous silica glass support 11 as a coating of a photocatalytic material having visible light responsiveness as a metal oxide and an additive metal element. A film 17 containing any one of transition metal elements other than the metal element to be formed is formed (step 2b), and the visible light responsive fibrous photocatalyst 18 according to the present invention is manufactured. The transition metal element as the additive metal element depends on the properties of the object to be processed or the type of light source of the photoreaction, but vanadium, chromium, manganese, iron, cobalt, nickel, copper, palladium, silver, platinum, cerium, Neodymium or the like can be employed.
FIG. 2B-1 schematically shows a cross section along the axial direction of the fiber, and FIG. 2B-2 schematically shows a vertical cross section with respect to the axial direction of the fiber.

As described above, examples of the metal oxide used as the photocatalyst material for the present invention include titanium oxide, zinc oxide, and zirconium oxide. Titanium oxide is preferable because of its high photocatalytic activity. Titanium oxide includes pure anhydrous titanium oxide (TiO ₂ ) and various hydrates.
As the titanium oxide used in the practice of the present invention, an anatase type crystal structure having high photocatalytic activity (anatase type titanium oxide) is particularly preferable.
Below, as a suitable example, the case where the metal oxide of the main component of the photocatalyst material formed in this process 2b is made into a titanium oxide is mainly demonstrated.

  The metal oxide film 17 can be formed by the following method, for example. As in the case of the production method 1 described above, there are roughly two types, that is, a dry method and a wet method.

The first method is vapor deposition of a metal oxide on the surface of a fibrous silica glass support (dry method). As the vapor deposition method, titanium oxide (TiO ₂ ) doped with a small amount of transition metal element other than titanium as an additive metal element is used, sputtering method, glow discharge method, thermal vapor deposition method, vacuum vapor deposition method, chemical vapor deposition method (CVD method). Vapor deposition is performed by a film deposition technique such as ion plating. In view of technical ease and cost, the thermal evaporation method is particularly preferable.

  The second method is a solution of an organometallic compound that becomes a precursor of a metal oxide, or a dispersion of fine particles made of a compound that becomes a precursor of a metal oxide (in the case of titanium oxide, a solution of an organotitanium compound or (Titanium oxide dispersion) is impregnated with a fibrous silica glass carrier and then heat-dried (dip coating method, wet method). And at this time, in order to enhance the catalytic activity of titanium oxide, depending on the characteristics of the object to be treated and the type of light source used for the photoreaction, nitrate or chloride of a transition metal element other than titanium as an additive metal element, A small amount of other compound is mixed with an organic titanium compound or a titanium oxide dispersion.

  This step 2b is the same as the step 1b of the manufacturing method 1 except that the additive metal element is added in both the dry method and the wet method.

  Through the steps 2a and 2b as described above, a metal that has a metal oxide as a main component as a photocatalyst material coating on the surface of the fibrous silica glass support 11 and at least a main component metal oxide as an additive element The visible-light-responsive fibrous photocatalyst body 18 according to the present invention in which the coating film 17 of the visible-light-responsive photocatalyst material containing any one of transition metal elements other than the elements can be produced.

In addition, the visible light responsive fibrous photocatalyst produced through the above steps 2a and 2b can be further subjected to nitrogen doping treatment. That is, nitrogen doping treatment is performed on the visible light responsive fibrous photocatalyst 18 as shown in FIG. 2B (step 2c).
The nitrogen doping conditions are not particularly limited as long as nitrogen is added to the metal oxide film 17, but can be performed in the same manner as in the step 1 c of the manufacturing method 1.

  As described above, according to the method for producing a visible light responsive fibrous photocatalyst according to the present invention, at least a fibrous silica glass carrier composed of silica glass fibers and a surface of the fibrous silica glass carrier are formed. In addition, a fibrous photocatalyst comprising a coating of a photocatalytic material having visible light responsiveness can be produced. In addition, the photocatalytic material having visible light responsiveness includes a metal oxide as a main component, and further includes at least one of transition metal elements other than the metal element constituting the main component metal oxide as an additive element and nitrogen. Contains a kind of element. And this fibrous photocatalyst body functions as a photocatalyst body which has visible light responsiveness.

  Such a visible light responsive fibrous photocatalyst body can be a photocatalyst body that can generate a photocatalytic action not only by ultraviolet light but also by visible light irradiation. In addition, since the support is made of silica glass fiber, it has high light permeability, high air permeability and water permeability, and has a large specific surface area that allows the photocatalyst material and the object to be processed to contact each other. It can be set as a photocatalyst body and can exhibit a photocatalytic action efficiently.

In addition, the visible light responsive fibrous photocatalyst according to the present invention has an alkali metal element Li, Na, K content of 100 wt. ppb or less, particularly 50 wt. ppb or less, the content of each of the alkaline earth metal elements Mg and Ca is 50 wt. ppb or less, particularly 20 wt. ppb or less.
These metal elements are each easily mixed from the worker's human body, building materials, etc., but according to the method for producing a visible light responsive fibrous photocatalyst according to the present invention, visible light response It is possible to suppress the impurity metal element contained in the type fibrous photocatalyst to the above range. In this way, a highly pure fibrous silica glass support with very few impurity metal elements will further increase the transmittance of visible light or ultraviolet light, and the photochemical reaction in water purification treatment or air purification treatment. It can be promoted more. In addition, since the fibrous silica glass carrier is low in impurities, the fibrous silica glass carrier is deteriorated, deteriorated, recrystallized (devitrified) during processing of high-temperature corrosive gas and corrosive wastewater, and the strength reduction caused thereby. In addition, it is possible to effectively prevent a decrease in transmittance and the like, and it is also possible to prevent the release of impurities into the environment when used as a photocatalyst. Such high purity has been extremely difficult to achieve with a conventional method for producing a porous photocatalyst by a sintering method or the like. Therefore, the visible light responsive fibrous photocatalyst of the present invention is excellent in terms of durability.
Such a photocatalyst has heat resistance, chemical resistance, ultraviolet resistance, and weather resistance, and is preferable for exhaust gas treatment at high temperatures, corrosive wastewater treatment, corrosive exhaust gas treatment, and the like.

  The visible light responsive fibrous photocatalyst according to the present invention is accommodated in a photocatalytic reactor, and a visible light response is generated by a light source that emits light including at least ultraviolet light and visible light (hereinafter sometimes referred to as ultraviolet visible light). It is possible to provide a purification device that purifies the object to be treated by photocatalytic action by bringing the object to be treated into contact with the visible light responsive fiber photocatalyst while irradiating the type fibrous photocatalyst with light.

The configuration of the purification device can take various forms. FIG. 3 shows an example in which an ultraviolet-visible light source is disposed at the center of a visible light responsive fibrous photocatalyst as an example of a pollutant gas purifying apparatus including a visible light responsive fibrous photocatalyst and a light source. 3A is a schematic cross-sectional view as viewed from the side of the photocatalytic reaction unit, and FIG. 3B is a schematic cross-sectional view of the AA ′ plane in FIG. 3A. This pollutant gas purifier is covered with a metal (stainless steel, aluminum, etc.) chamber 21, and for example, a silica glass chamber 22 having a spiral partition plate 22a serves as a reactor. Moreover, the ultraviolet visible light source 23 is arrange | positioned in the center part. The visible light responsive fibrous photocatalyst 25 of the present invention is filled in the silica glass chamber 22. By introducing a pollutant gas from the pollutant gas inlet 26 while irradiating the visible light responsive fiber photocatalyst 25 with ultraviolet light and visible light from the ultraviolet visible light source 23, and passing the visible light responsive fiber photocatalyst 25 through The contaminated gas is purified, and the purified gas is discharged from the purified gas outlet 27. The partition plate 22a may not be provided, but by arranging such a spiral partition plate 22a in the reactor, the gas passage distance in the photocatalyst body can be lengthened, and the pollutant gas purification process is effective. Can be done automatically.
The ultraviolet-visible light source 23 may be any light source that can irradiate light including at least ultraviolet light and visible light. However, a medium-pressure mercury lamp, a high-pressure mercury lamp, an excimer lamp, a xenon lamp, a metal halide lamp, a laser diode, and a light-emitting diode. Etc. can be used.

  In addition, as another example of the pollutant gas purification apparatus including the visible light responsive fibrous photocatalyst and the ultraviolet visible light source in FIG. 4, an ultraviolet visible light source is disposed on the outer periphery of the visible light responsive fibrous photocatalyst. An example is shown. 4A is a schematic cross-sectional view of the photocatalytic reaction unit as viewed from the side, and FIG. 4B is a schematic cross-sectional view of the B-B ′ plane in FIG. In this pollutant gas purifier, a silica glass inner tube 34 having a partition plate 34a and an ultraviolet / visible light source 33 are arranged as a reactor in a silica glass outer tube 32 covered with a metal chamber 31. The visible light responsive fibrous photocatalyst 35 of the present invention is disposed in the silica glass inner tube 34. While the visible light responsive fiber photocatalyst 35 in the silica glass inner tube 34 is irradiated with ultraviolet visible light by the ultraviolet visible light source 33, a contaminated gas is introduced from the contaminated gas inlet 36, and the visible light responsive fiber photocatalyst is obtained. The polluted gas is purified by passing through 35, and the purified gas is discharged from the purified gas discharge port 37.

FIG. 5 shows still another example of a pollutant gas purifying apparatus including a visible light responsive fiber photocatalyst and an ultraviolet visible light source. 5A is a schematic cross-sectional view as viewed from above the photocatalytic reaction unit, and FIG. 5B is a schematic cross-sectional view of the CC ′ plane in FIG. 5A. This pollutant gas purification device can be used particularly for an exhaust gas purification processing unit of a vehicle or the like.
In this pollutant gas purifying apparatus, a silica glass photocatalytic reaction chamber 41 is arranged as a photocatalytic reactor inside a cylindrical aluminum exhaust gas treatment unit cover 40 having an elliptical cross section. In addition, ultraviolet visible light sources 43a and 43b are disposed at two locations corresponding to the focal points of the elliptical cross-sectional shape. In addition, a visible light responsive fibrous photocatalyst body 42 is disposed inside the silica glass photocatalytic reaction chamber 41.
Further, exhaust gas discharged from the engine of the vehicle enters the exhaust gas inlet 44 and is purified by a photocatalytic reaction, and is then discharged from the purified gas outlet 45 to the outside. Since the exhaust gas is hot, cooling air enters from the cooling air inlet 46 and exits from the cooling air outlet 47 to protect the light source.

During the vehicle exhaust gas treatment, the exhaust gas introduction port 44 irradiates the visible light responsive fiber photocatalyst 42 in the silica glass photocatalyst reaction chamber 41 with ultraviolet visible light by the ultraviolet visible light sources 43a and 43b. The exhaust gas is purified by introducing a pollutant gas through the visible light responsive fibrous photocatalyst body 42 and the purified gas is discharged from the purified gas discharge port 45. Further, in order to cool the heat generated by the exhaust gas, the cooling air is circulated into the space between the exhaust gas processing unit cover 40 and the photocatalytic reaction chamber 41 by the cooling air inlet 46 and the cooling air outlet 47.
The ultraviolet-visible light sources 43a and 43b may be anything that emits ultraviolet-visible light with high efficiency, but mercury lamps, excimer lamps, metal halide lamps, light-emitting diodes, laser diodes, and the like can be used.

  Such a purification device comprising the visible light responsive fibrous photocatalyst according to the present invention has a high chemical stability and a purification comprising a photocatalyst capable of efficiently exhibiting a photocatalytic action. Since it is an apparatus, it can be set as the purification apparatus which has high durability and high processing capability. Therefore, it can be used as a purification device for removing bad odors and harmful substances in the air, and in particular, it can also be used in harsh environments such as removal of environmental pollutants in high-temperature combustion gas discharged from a thermal reactor. For example, it can be used for the treatment of exhaust gas from incinerators, thermal power plants, automobiles and the like. In particular, if a high-purity silica glass fiber is used as a carrier, it further meets such a purpose. Further, by increasing the efficiency and size of the photocatalytic reaction of the present apparatus, it is possible to take out hydrogen fuel by photocatalytic decomposition reaction of water using sunlight as a light source.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.
Example 1
According to the visible light responsive fiber photocatalyst manufacturing method (manufacturing method 1) as shown in FIG. 1, a visible light responsive fiber photocatalyst was manufactured as follows.

First, a fibrous silica glass support was produced as follows by a soot method by flame hydrolysis using silicon tetrachloride (SiCl ₄ ) as a raw material (step 1a).
By the soot method of the oxyhydrogen flame hydrolysis method using high-purity silicon tetrachloride as a raw material, 30 wt. A high-purity transparent synthetic silica glass base material containing ppm was prepared. By cutting this transparent synthetic silica glass base material, 20 silica glass rods having a size of 3 mm × 10 mm square and a length of 2 m were produced. Next, these 20 silica glass rods are set as raw material rods in a fiber production apparatus, softened and stretched by flame heating in a first gas burner to form thick fibers having a diameter of about 200 to 300 μm, and subsequently to a second gas burner. Then, the fiber was softened and stretched by flame heating to draw a thin fiber having a diameter of about 10 to 50 μm, and at the same time, a short fiber (wool) was produced by jet blow. The diameter of the wool could be controlled by controlling the feed rate of the silica glass rod as the raw material rod, the fiber pulling rate (drawing rate), the flame amount and the temperature control. After accommodating the wool in a winder, the wool was cut to a length of about 200 to 500 mm and mixed to prepare a cottony and lump fibrous high purity silica glass carrier. The fiber curl radius was 50-100 mm.
Further, impurity metal element concentration analysis of the fibrous silica glass support was performed by plasma emission analysis (ICP-AES) and plasma mass spectrometry (ICP-MS).

Next, as described below, a film was formed on the surface of the fibrous silica glass support by dip coating using titanium oxide as a photocatalytic material (step 1b).
A titanium alkoxide serving as a titanium oxide source of the photocatalyst, ethyl alcohol serving as a solvent, and ethylene glycol serving as a stabilizer were mixed to prepare a dip coating solution. Next, the fibrous silica glass carrier previously made in the pressure-resistant glove box and the dip coating liquid in the container are put, and then the fiber is reduced while reducing the pressure in the glove box to 10 ⁻² Torr (about 0.13 Pa) or less. The inside of the glass silica glass support (the gaps between the many silica glass fibers) was degassed, and then the support was put into a dip coating solution while being returned to normal pressure and immersed in a titanium compound solution. After this dip coating operation was repeated 10 times, it was taken out from the glove box, placed in an electric furnace, and baked at 450 ° C. for 1 hour to obtain a transparent film.

Next, nitrogen dope treatment was performed on the fibrous silica glass support on which the titanium oxide film was formed as follows (step 1c).
About 100 g of a fibrous lump of fibrous silica glass carrier on which a photocatalytic material coating containing titanium oxide was formed was placed in an electric furnace in which a silica glass chamber was installed. Then, ammonia gas diluted with nitrogen gas (nitrogen gas 50 vol.%, Ammonia gas 50 vol.%) Was introduced into the chamber, and ammonia doping treatment was performed at 600 ° C. for 1 hour while flowing at 60 ml / min. Next, the inside of the chamber was changed to a nitrogen gas 100% atmosphere, and a baking process was performed at 300 ° C. for 3 hours to stabilize the added nitrogen.

Thereafter, when this transparent film was examined by X-ray diffraction analysis or the like, it was confirmed that it was anatase-type titanium oxide (TiO ₂ ), and it was observed by a scanning electron microscope (SEM) or the like. It consists of ultrafine particles of titanium oxide of about 5 to 10 nm, has pores of about 2 to 3 nm, and a specific surface area of about 80 m ² / g.

(Example 2)
According to the visible light responsive fibrous photocatalyst production method (manufacturing method 2) as shown in FIG. 2, a visible light responsive fibrous photocatalyst was produced as follows.
First, a fibrous silica glass support was produced in the same manner as in Example 1 (Step 2a).

Next, a film was formed on the surface of the fibrous silica glass support by the dip coating method using titanium oxide as the main component of the photocatalytic material and chromium and vanadium as the additive elements as follows (step 2b). .
Titanium alkoxide as a photocatalyst source and ethyl alcohol as a solvent, ethylene glycol as a stabilizer, reagents such as ethylene glycol, and chromium chloride and vanadium chloride (the amount of each added element in a ratio of 1/100 of each titanium weight) ) To prepare a dip coating solution. Next, the fibrous silica glass carrier previously made in the pressure-resistant glove box and the dip coating liquid in the container are put, and then the fiber is reduced while reducing the pressure in the glove box to 10 ⁻² Torr (about 0.13 Pa) or less. The inside of the glass silica glass support (the gaps between the many silica glass fibers) was degassed, and then the support was put into a dip coating solution while being returned to normal pressure and immersed in a titanium compound solution. After this dip coating operation was repeated 10 times, it was taken out from the glove box, placed in an electric furnace, and baked at 450 ° C. for 1 hour to obtain a transparent film.

When this transparent film was examined by an X-ray diffraction analysis method or the like, it was confirmed that it was anatase-type titanium oxide (TiO ₂ ), and it was observed by a scanning electron microscope (SEM) or the like. It consisted of ultrafine particles of titanium oxide of about 10 to 20 nm, had pores of about 2 to 5 nm, and a specific surface area of 50 m ² / g. Next, by measuring the weight (g) of the fibrous photocatalyst after the titanium oxide film was formed, the photocatalyst weight ratio (%) relative to the silica glass support weight was determined.
Each physical property value was measured in the same manner as in Example 1.

(Example 3)
First, it carried out to the process 2b similarly to Example 2. Furthermore, under the same nitrogen doping treatment conditions as in Example 1, the fibrous silica glass carrier containing titanium oxide and formed with a coating containing vanadium and chromium was subjected to nitrogen doping treatment, and the fibrous photocatalyst and (Step 2c).
Each physical property value was measured in the same manner as in Example 1.

(Comparative Example 1)
A predetermined amount of the same fibrous silica glass support as in Example 1 was prepared. Next, the surface of the fibrous silica glass support was subjected to a film formation treatment using only titanium oxide as a photocatalyst material to produce a fibrous photocatalyst.
Each physical property value was measured in the same manner as in Example 1.

(Comparative Example 2)
Alumina (Al ₂ O ₃ ) ceramic particles having a particle diameter of 1 to 2 mm and a 99.99% purity grade product were used as they were as a carrier, and a titanium oxide film was formed in the same manner as in Comparative Example 1 to obtain a photocatalyst.
This photocatalyst was opaque in appearance.
Each physical property value was measured in the same manner as in Example 1. In addition, since it is powder, the fiber diameter and the fiber length cannot be defined.

  For each of the photocatalysts produced in Examples 1 to 3 and Comparative Examples 1 and 2, the acetaldehyde purification test and the NOx purification test were performed as follows, and the photocatalytic characteristics were measured.

(Photocatalytic performance evaluation (acetaldehyde purification test))
The produced visible light responsive fibrous photocatalyst was evaluated for photocatalytic performance using acetaldehyde photolysis reaction.
First, 120 g of a visible light responsive fibrous photocatalyst body was prepared by molding it into a plate shape having dimensions of 100 mm × 100 mm × 10 mm.
The reactor for visible light responsive fibrous photocatalyst and acetaldehyde shown in FIG. 6 is a closed system device, and a high purity synthetic silica glass container on which the visible light responsive fibrous photocatalyst 57b as a specimen is placed. It is composed of a high-purity synthetic silica glass-made reaction vessel (chamber) 55 and a light source (lamp) 56a. The reaction gas is a total of 660 Torr (about 88 kPa) CH ₃ CHO (1000 vol. Ppm) supplied from the acetaldehyde cylinder 51 and He as a dilution gas, and 100 Torr (about 13 kPa) O ₂ supplied from the oxygen gas cylinder 52. A mixed gas of 760 Torr (about 101 kPa) (approximately the same as atmospheric pressure) was used. As the light source 56a, an intermediate pressure mercury lamp capable of irradiating ultraviolet to visible light was used. In addition, the gas supply side includes gas pressure regulators 53a and 53b, mass flow controllers 54a and 54b, and the like. Further, on the gas discharge side, a gas analyzer (gas chromatograph device) 58, exhaust fans 59a, 59b and the like are provided to analyze the discharged gas.

(Acetaldehyde purification test 1)
The photocatalytic action by ultraviolet to visible light irradiation was evaluated by the following procedure.

(1) A cotton-like specimen (visible light-responsive fibrous photocatalyst) weighing 120 g, dimensions of 100 mm × 100 mm × 10 mm, and a single one are installed in the photocatalytic reaction chamber, the interior is made into an air atmosphere at 25 ° C., and the wavelength is 400 nm. It is held for 6 hours while irradiating with medium pressure mercury lamp light at an output of the following ultraviolet intensity of about 10 mW / cm ² .

(2) After the inside of the reaction chamber was once evacuated to a vacuum of 10 ³ Pa or less, acetaldehyde mixed gas (660 Torr (about 88 kPa) partial pressure of He diluted CH ₃ CHO, 1000 vol.ppm gas and 100 Torr (about 13 kPa)) Partial pressure O ₂ gas) was introduced at 10 ⁵ Pa (approximately atmospheric pressure) and allowed to stand at room temperature of 25 ° C. for 6 hours while flowing at a flow rate of 300 ml / min. At this time, the lamp light source is not lit.

(3) The gas flow of the acetaldehyde mixed gas is stopped, the inside of the reaction chamber (inner volume 5 L) is shut off, and irradiation with a medium pressure mercury lamp is started. The spectral spectrum distribution of the medium pressure mercury lamp is shown in FIG. The intensity of ultraviolet light having a wavelength of 400 nm or less on the surface of the specimen is set to 10 mW / cm ² .

(4) Keep the temperature of the reaction chamber at 25 ° C., continuously irradiate with medium pressure mercury lamp light, and measure the acetaldehyde concentration of the mixed gas after 6 hours by gas chromatography.

The purification rate in this acetaldehyde purification test 1 was determined by the following calculation formula (1).
Purification rate (%) = 100 × {(CH ₃ CHO initial concentration) − (CH ₃ CHO final concentration)} / (CH ₃ CHO initial concentration) (1)

  The purification rate is evaluated as ◎ (very good) when the purification rate is 100 to 90%, ○ (good) when 90 to 70%, △ (somewhat poor) when 70 to 40%, and 40 to 0. In the case of%, it was set as x (defect).

(Acetaldehyde purification test 2)
The photocatalytic action by irradiation with only visible light was evaluated.
Specifically, in the same manner as in the acetaldehyde purification test 1, except that in (3) and (4), the lamp light source adjustment filter 56b that absorbs ultraviolet light of 390 nm or less is attached, and the visible light intensity of 400 nm or more on the surface of the specimen is obtained. Medium pressure mercury lamp irradiation was started after adjusting to 5 mW / cm ² , and an irradiation test was performed at a temperature of 25 ° C. for 6 hours.
The calculation and evaluation of the purification rate in this acetaldehyde purification test 2 were the same as in the acetaldehyde purification test 1.

(NOx purification test)
In order to evaluate the purification capacity of the photocatalyst, a nitrogen oxide (NOx) decomposition experiment was performed using an evaluation apparatus such as the conceptual diagram shown in FIG. Specifically, nitric oxide (NO) was used as NOx.
In the cylindrical reaction vessel 65, an ultraviolet / visible light lamp 66 was passed in the center, and a photocatalyst 67 was disposed around the ultraviolet / visible light lamp 66. Other NO100 wt. The system includes a NOx gas cylinder 61, an air gas cylinder 62, a pressure regulator 63a, 63b, mass flow controllers 64a, 64b, various valves, a NOx concentration meter 68, exhaust fans 69a, 69b, and the like that can flow ppm standard gas.
The outer dimensions of the reaction vessel 65 are 120 mm long, 320 mm long, the photocatalyst housing silica glass chamber has an outer diameter of 100 mm, an inner diameter of 20 mm, a length of 300 mm, and a volume of about 2 L, and the input amount of each photocatalyst is 200 g.

The experimental conditions are as follows.
(1) In order to stabilize adsorption, the NOx gas flow is changed to a NO concentration of 1 wt. The measurement was performed at a ppm flow rate of 60 ml / min for 30 minutes.
(2) Next, the ultraviolet-visible light source in the reaction vessel was turned on, and the intensity of ultraviolet rays was 10 mW / cm ² . In this state, NOx gas flow, NO concentration 1 wt. The NO was decomposed by photocatalysis by continuous operation at ppm, gas flow rate 6 L / min, temperature 25 ° C., relative humidity 50%, 3 hours.
The NO purification rate was evaluated based on the numerical value calculated by the following equation (2).

{(NO initial concentration) − (NO purified concentration)} / (NO initial concentration) (2)

  A NO decomposition rate of 90% or more was evaluated as ◎ (very good), 90% to 70% as ◯ (good), 70% to 40% as △ (somewhat poor), and less than 40% as × (bad).

(Weather resistance test)
For each photocatalyst, a continuous weathering experiment was performed at a temperature of 50 ° C. and a humidity of 90% to 500 hours using a low-pressure mercury lamp at a UV irradiation energy density of 10 mW / cm ^2. Microscopic observation was performed. ◯ (good) when no change was detected, △ (somewhat poor) when slight discoloration occurred or detachment of titanium oxide was observed, discoloration was observed, and detachment was observed in 10% or more of titanium oxide Time was evaluated as x (defect).

(Heat resistance test)
Each photocatalyst is placed in an atmospheric furnace equipped with a high-purity alumina heat insulating material and a molybdenum disilicide heater, subjected to a continuous heat resistance experiment at 500 ° C. for 1000 hours, and then visual observation and stereoscopic microscope observation of the photocatalyst Went. Evaluation criteria are the same as in the above weather resistance test: ○ (good) when no change is detected, △ (slightly poor) when slight discoloration occurs or peeling of titanium oxide is observed, discoloration is observed, titanium oxide When 10% or more of peeling was observed, it was evaluated as x (defect).

  For the photocatalysts produced in Examples 1 to 3 and Comparative Examples 1 and 2, the physical property values and the results of characteristic evaluation as a photocatalyst are summarized in Tables 2 and 3 below.

In Examples 1 to 3 and Comparative Example 1, the NOx purification test was better than Comparative Example 2. This is presumably because the support was made of silica glass fiber, so that the transparency to ultraviolet rays was high, and the ultraviolet rays were sufficiently distributed inside the photocatalyst to effectively exhibit the photocatalytic action.
On the other hand, in Comparative Example 2, the NOx purification test was slightly poor. This is considered to be because the photocatalyst in which titanium oxide is supported on the alumina ceramic powder as in Comparative Example 2 does not sufficiently spread the ultraviolet rays.
In Examples 1 to 3, even when only visible light was irradiated (acetaldehyde purification test 2), a better result than Comparative Example 1 was obtained, and the purification ability was high.

  Moreover, the photocatalyst bodies of Examples 1 to 3 and Comparative Example 1 were easy to mold, and in the NOx purification test, it was easy to fill the reaction vessel.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a figure which shows an example of the manufacturing method of the visible light response type | mold fibrous photocatalyst body which concerns on this invention with the conceptual diagram of the structure in each process. It is a figure which shows another example of the manufacturing method of the visible light response type | mold fibrous photocatalyst body which concerns on this invention with the conceptual diagram of the structure in each process. It is the schematic sectional drawing which showed an example of the purification apparatus which comprises the visible light responsive type fiber photocatalyst and the ultraviolet visible light source concerning the present invention. It is the schematic sectional drawing which showed another example of the purification apparatus which comprises the visible light response type | mold fibrous photocatalyst and the ultraviolet visible light source which concern on this invention. It is the schematic sectional drawing which showed another example of the purification apparatus which comprises the visible light response type | mold fibrous photocatalyst and the ultraviolet visible light source which concern on this invention. It is the schematic which showed the acetaldehyde purification test apparatus of an Example as an example of the apparatus which evaluates the processing capacity of a photocatalyst body. It is the schematic which showed the NOx purification test apparatus of the Example as another example of the apparatus which evaluates the processing capacity of a photocatalyst body. It is a graph which shows the relative spectral intensity spectrum (The wavelength 365nm is set to the relative intensity 100) of a medium pressure mercury lamp.

Explanation of symbols

11 ... Fibrous silica glass carrier, 12 ... Metal oxide coating as photocatalytic material,
13 ... Intermediate complex,
15 ... coat of visible light responsive photocatalytic material,
16 ... Visible light responsive fibrous photocatalyst of the present invention,
17 ... coat of visible light responsive photocatalytic material,
18 ... Visible light responsive fibrous photocatalyst of the present invention,
21 ... Metal chamber,
22 ... Silica glass chamber, 22a ... Spiral partition plate,
23 ... UV-visible light source, 25 ... Visible light responsive fibrous photocatalyst,
26 ... Pollutant gas inlet, 27 ... Purified gas outlet,
31 ... Metal chamber, 32 ... Silica glass outer tube, 33 ... UV-visible light source,
34 ... Inner tube made of silica glass, 34a ... Partition plate,
35. Visible light responsive fibrous photocatalyst,
36 ... Pollutant gas inlet, 37 ... Purified gas outlet,
40 ... exhaust gas treatment unit cover, 41 ... photocatalytic reaction chamber,
42 ... Visible light responsive fibrous photocatalyst,
43a, 43b ... UV-visible light source,
44 ... exhaust gas inlet, 45 ... purified gas outlet,
46: Cooling air inlet 47: Cooling air outlet

Claims (2)

at least,
A fibrous silica glass support made of silica glass fibers;
A fibrous photocatalyst comprising a coating of a photocatalytic material mainly composed of titanium oxide formed on the surface of the fibrous silica glass carrier,
The photocatalytic material further contains at least one of vanadium, chromium, manganese, iron, cobalt, nickel, copper, palladium, silver, platinum, cerium, neodymium and nitrogen as additive elements, and has visible light responsiveness. And
Of the elements contained in the fibrous silica glass support, the content of each of the alkali metal elements Li, Na, K is 100 wt. ppb or less, and the content of each of the alkaline earth metal elements Mg and Ca is 50 wt. ppb or less,
The silica glass fiber has an OH group of 1-1000 wt. containing ppm,
The silica glass fiber has a fiber diameter of 5 to 300 μm and a length of 100 mm or more,
The silica glass fiber has a fiber curl radius of 200 mm or less,
The visible light responsive fibrous photocatalyst body, wherein the fibrous photocatalyst body functions as a photocatalyst body having visible light responsiveness. at least,
A photocatalytic reactor;
Housed in photocatalytic reactor, and visible light responsive fibrous photocatalyst according to claim 1,
A light source that emits light including at least ultraviolet light and visible light, and irradiating the visible light responsive fibrous photocatalyst with the light while irradiating the visible light responsive fibrous photocatalyst with the light source. A purification apparatus characterized by passing a treatment object through a photocatalytic reactor and purifying the treatment object by photocatalysis.

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