Photocatalytic material and gas purification device

Abstract

To provide a photocatalyst body that can prevent a photocatalyst from falling off, and gas purifying device.SOLUTION: A photocatalyst body according to one embodiment includes: a substrate; and a photocatalyst joined to the substrate through a joint including a silicon compound. The photocatalyst body satisfies the following formula: 0.3≤M(mass%) / S(mass%)≤8, where M(mass%) is a mass percentage of the photocatalyst, and S(mass%) is a mass percentage of silicon (Si) included in the joint.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Embodiments of the present invention relate to a photocatalyst medium and a gas purification device.

Background Art

[0002] Reflecting the increasing awareness of health, there is a growing demand for gas purification (e.g., air purification) in so-called enclosed spaces such as inside trains, automobiles, refrigerators, and living spaces. For example, there is an increasing demand for removing VOCs (Volatile Organic Compounds) such as ammonia, ethylene, and acetaldehyde contained in the atmosphere, and for deodorizing the atmosphere.

[0003] Therefore, a gas purification device has been proposed that includes a frame having a space inside which the gas to be treated flows, and a light source and a photocatalyst medium arranged side by side inside the frame. Generally, the photocatalyst medium has a substrate formed using a plurality of glass fibers and a plurality of photocatalysts supported on the substrate. By using such a gas purification device, VOCs and the like contained in the gas can be removed by active oxygen species generated by the photocatalytic action.

[0004] [[ID=2०]]Here, since the photocatalyst medium is provided in the space through which the gas to be treated flows, the plurality of photocatalysts supported on the substrate are exposed to the gas flow. Therefore, if the bonding force between the photocatalyst and the substrate is weak, the photocatalyst may fall off from the substrate. Therefore, a technique using a silicon compound as a binder for the photocatalyst has been proposed.

[0005] However, in recent years, an increase in the treatment flow rate has been demanded, and the flow velocity of the gas to be treated has become faster, and the flow rate of the gas to be treated has a tendency to increase. Therefore, the force applied to the photocatalyst becomes even greater, and there is a risk that the photocatalyst may easily fall off. Therefore, the development of a technique that can further suppress the detachment of the photocatalyst has been desired.

Prior Art Documents

[0006] [Patent Document 1] Patent No. 6630512 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide a photocatalytic body and a gas purification device that can suppress the shedding of the photocatalyst. [Means for solving the problem]

[0008] The photocatalytic body according to the embodiment comprises a substrate and a photocatalyst bonded to the substrate via a bonding portion containing a silicon compound. The substrate is in the form of a sheet and has multiple linear bodies containing metal woven into it. The diameter of the linear bodies is between 0.016 mm and 2.0 mm. The aforementioned photocatalyst is Below The following equation is satisfied. 0.3 ≤ M(mass%) / S(mass%) ≤ 8 M (mass%) is the mass percentage of the photocatalyst. S (mass%) is the mass percentage of silicon (Si) contained in the joint. [Effects of the Invention]

[0009] According to embodiments of the present invention, it is possible to provide a photocatalytic body that can suppress the shedding of the photocatalyst, and a gas purification device. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic perspective view of the gas purification device as seen from the intake side. [Figure 2] This is a schematic perspective view of the gas purification device as seen from the exhaust side. [Figure 3] Figure 1 is a schematic cross-sectional view of the gas purification device in the direction of line AA. [Figure 4]This graph illustrates the relationship between the photocatalyst shedding rate and the mass ratio of the photocatalyst to the junction. [Modes for carrying out the invention]

[0011] The embodiments will be illustrated below with reference to the drawings. In each drawing, similar components are denoted by the same reference numerals, and detailed descriptions will be omitted as appropriate. Figure 1 is a schematic perspective view of the gas purification device 1 as seen from the intake side. Figure 2 is a schematic perspective view of the gas purification device 1 as seen from the exhaust side. Figure 3 is a schematic cross-sectional view of the gas purification device 1 in Figure 1 along the AA line. As shown in Figures 1 to 3, the gas purification device 1 includes, for example, a frame 2, a filter 3, a fan 4, a light source 5, and a photocatalyst 6.

[0012] Frame 2 is box-shaped. When viewed from the intake side of gas G, the outline of frame 2 can be, for example, a rectangle. In this case, the outline of frame 2 can also be, for example, a polygon. However, considering the attachment and detachment of the photocatalyst 6 and space efficiency, it is preferable that the outline of frame 2 be a rectangle.

[0013] For example, the frame 2 has a rectangular parallelepiped shape and has a space inside through which the gas G to be treated flows. A light source 5 and a photocatalyst 6 are provided inside the frame 2. A hole 2a is provided at one end of the frame 2 (the intake end). The hole 2a serves as the inlet for the gas G to be treated. A hole 2b is provided at the other end of the frame 2 (the exhaust end). The hole 2b is opposite to the hole 2a. The hole 2b serves as the outlet for the treated gas G. Therefore, an airflow can be formed inside the frame 2, flowing from the hole 2a to the hole 2b.

[0014] The gas G mainly consists of, for example, air and contains the substance to be treated. The substance to be treated may be any substance that can be purified by photocatalytic action. The substance to be treated can be, for example, VOCs such as ammonia, ethylene, and acetaldehyde.

[0015] As shown in FIG. 3, brackets 2c and 2d are provided inside the frame 2. A photocatalyst body 6 is detachably provided on the bracket 2c. The bracket 2c holds the peripheral portion of the photocatalyst body 6. A light source 5 is detachably provided on the bracket 2d. The bracket 2d holds the peripheral portion of the light source 5.

[0016] Also, the side portion of the frame 2 is open. A lid 2e can be detachably provided at the opening of the side portion of the frame 2. The photocatalyst body 6 and the light source 5 can be detached and attached through the opening of the side portion of the frame 2. In addition, a connector 2f for making an electrical connection between the light source 5 and a lighting circuit, a power source, etc. provided outside the gas purification device 1 can be provided on the side portion of the frame 2 or the like.

[0017] There is no particular limitation on the materials of the frame 2 and the lid 2e. The materials of the frame 2 and the lid 2e can be, for example, metal. The metal can be, for example, iron, stainless steel, aluminum alloy, etc. When the materials of the frame 2 and the lid 2e are metal, the frame 2 and the lid 2e can be formed by, for example, sheet metal processing. Note that the frame 2 and the lid 2e illustrated in FIGS. 1 to 3 are metal-made frame 2 and lid 2e formed by sheet metal processing or the like.

[0018] The materials of the frame 2 and the lid 2e can also be, for example, thermoplastic resin. The thermoplastic resin can be, for example, ABS resin (acrylonitrile-butadiene-styrene copolymer synthetic resin), polypropylene resin, acrylic resin (polymethyl methacrylate resin), etc. When the materials of the frame 2 and the lid  2e are thermoplastic resin, the frame 2 and the lid 2e can be formed by, for example, injection molding.

[0019] Filter 3 covers the hole 2a provided at the intake-side end of the frame 2. As shown in FIGS. 1 and 3, the filter 3 can be detachably provided at the intake-side end of the frame 2 by means of a bracket 3a. The bracket 3a is in a frame shape and holds the peripheral portion of the filter 3. A hole is provided in the central portion of the bracket 3a, and the central portion of the filter 3 is exposed inside the hole. Therefore, the gas G can be introduced into the frame 2 through the filter 3.

[0020] The filter 3 suppresses dust and the like outside the frame 2 from being sucked into the frame 2. The filter 3 can be provided, for example, to remove dust of such a size that it can be visually confirmed. The filter 3 can be, for example, a plain-woven wire mesh made of stainless steel (wire diameter φ0.1 mm, 100 mesh).

[0021] The fan 4 is connected to the hole 2b provided at the exhaust-side end of the frame 2. As shown in FIGS. 1 to 3, the fan 4 can be detachably provided at the exhaust-side end of the frame 2. The fan 4 discharges the gas G inside the frame 2 to the outside of the frame 2 through the hole 2b. Therefore, a flow of the gas G from the filter 3 side toward the fan 4 side can be formed inside the frame 2. The fan 4 can be, for example, a sirocco fan or the like.

[0022] The light source 5 is provided inside the frame 2 and irradiates the photocatalyst 6 with light having a predetermined wavelength. Although the light source 5 illustrated in FIG. 3 is provided with a light-emitting element 5b, the light source 5 may be any one that can irradiate light having a predetermined wavelength. For example, the light source 5 may have a discharge lamp that irradiates light having a predetermined wavelength. In the following, as an example, the light source 5 having the light-emitting element 5b will be described.

[0023] At least one light source 5 can be provided. The gas purification device 1 illustrated in Figure 3 has two light sources 5 that are spaced apart from each other and arranged side by side. The light sources 5 are detachably mounted on brackets 2d inside the frame 2. For example, the light sources 5 can be attached to brackets 2d using fastening members such as screws. The light sources 5 face the photocatalyst body 6. The light sources 5 are electrically connected via connectors 2f to lighting circuits, power supplies, etc., located outside the gas purification device 1.

[0024] The light source 5 includes, for example, a substrate 5a and a light-emitting element 5b. The substrate 5a is plate-shaped. The substrate 5a is placed in the gas flow path opposite the photocatalyst 6. Therefore, the presence of the substrate 5a may obstruct the flow of gas G. In this case, multiple holes penetrating in the thickness direction can be provided in the substrate 5a. However, if the size of the holes is small, the pressure loss will be large, which will obstruct the flow of gas G. If the size of the holes is increased, constraints will be placed on the arrangement and number of the light-emitting element 5b and wiring patterns.

[0025] Therefore, as shown in Figure 3, the width dimension of the substrate 5a is made smaller than the width dimension of the photocatalyst 6. In this case, if the "width dimension of the substrate 5a (mm) / width dimension of the photocatalyst 6 (mm)" is less than 0.5, it becomes easier to ensure appropriate gas G flow.

[0026] There are no particular limitations on the material or structure of the substrate 5a. For example, the substrate 5a can be formed from inorganic materials (ceramics) such as aluminum oxide or aluminum nitride, or organic materials such as paper phenol or glass epoxy. Alternatively, the substrate 5a may be a metal core substrate in which the surface of a metal plate is coated with an insulating material.

[0027] If the light-emitting element 5b generates a large amount of heat, it is preferable to form the substrate 5a using a material with high thermal conductivity from the viewpoint of heat dissipation. Examples of materials with high thermal conductivity include ceramics such as aluminum oxide and aluminum nitride, and metal core substrates. Furthermore, the substrate 5a may have a single-layer structure or a multilayer structure.

[0028] The light-emitting element 5b is provided on the surface of the substrate 5a facing the photocatalyst 6. The light-emitting element 5b is electrically connected, for example, to a wiring pattern provided on the surface of the substrate 5a. There are no particular limitations on the form of the light-emitting element 5b. The light-emitting element 5b can be, for example, a surface-mount type light-emitting element such as a PLCC (Plastic Leaded Chip Carrier) type. The light-emitting element 5b can also be, for example, a light-emitting element with lead wires such as a bullet-shaped element. The light-emitting element 5b can also be, for example, a chip-shaped light-emitting element. A chip-shaped light-emitting element can be mounted on a wiring pattern, for example, by COB (Chip On Board). The light-emitting element 5b illustrated in Figure 3 is a surface-mount type light-emitting element.

[0029] The light-emitting element 5b is provided to excite the photocatalyst provided on the photocatalyst body 6. In this case, if the material or composition of the photocatalyst changes, the absorption wavelength range of the photocatalyst will change. Therefore, a light-emitting element 5b that irradiates light of an appropriate wavelength according to the absorption wavelength range of the photocatalyst is selected. For example, if the photocatalyst is an ultraviolet-responsive photocatalyst containing titanium dioxide, the light-emitting element 5b can be a light-emitting diode or laser diode that irradiates ultraviolet light with a peak wavelength of, for example, 315 nm or more and 420 nm or less. Alternatively, if the photocatalyst is a visible-light-responsive photocatalyst such as tungsten oxide, the light-emitting element 5b can be a light-emitting diode, laser diode, or organic light-emitting diode that irradiates visible light with a peak wavelength of, for example, 405 nm or more and 600 nm or less.

[0030] In recent years, in addition to the removal of VOCs, there has been a demand for the sterilization and inactivation of bacteria and viruses. Therefore, it is also possible to provide an additional light-emitting element that emits light having a peak wavelength shorter than the peak wavelength of the light emitted by the light-emitting element 5b. For example, it is also possible to provide an additional light-emitting diode or laser diode that emits ultraviolet light with a peak wavelength of 270 nm or more and 300 nm or less. In this way, it is possible to sterilize and inactivate bacteria and viruses contained in the gas G flowing inside the frame 2, as well as bacteria and viruses attached to the photocatalyst 6 and the inner wall of the frame 2.

[0031] The above describes the case of a light source 5 having an element-emitting element 5b, but in the case of a light source having a discharge lamp, a discharge lamp and socket can be provided instead of the substrate 5a and the element-emitting element 5b. The discharge lamp can be, for example, a low-pressure mercury lamp or an excimer lamp.

[0032] The photocatalytic body 6 is detachably mounted on the bracket 2c inside the frame 2. For example, the photocatalytic body 6 can be attached to the bracket 2c using fastening members such as screws.

[0033] The photocatalytic body 6 includes, for example, a substrate, a photocatalyst, and a bonding portion. The base material is, for example, a fabric woven with multiple linear elements. For example, the base material may be sheet-like and formed by weaving together multiple glass fibers. Since the base material formed from multiple glass fibers has low rigidity, a frame-like member can be provided to hold the periphery of the base material. Furthermore, in recent years, there has been a demand for increased processing flow rates, and the flow velocity of the gas G being processed is increasing, and the flow rate of the gas G is also tending to increase. Therefore, in order to suppress deformation of the central region of the base material, crossbars or the like can be provided on the frame-like member that holds the periphery of the base material.

[0034] However, if frame-like members or struts are provided, regions will be created where light emitted from the light-emitting element 5b does not enter and gas G cannot flow, which may prevent an increase in the processing flow rate.

[0035] Therefore, when an increase in processing flow rate is required, it is preferable to use a substrate that is sheet-like and has multiple linear bodies containing metal. Such a substrate can be formed, for example, by weaving in linear bodies containing metal. Examples of materials for the linear bodies include stainless steel, nickel, Monel, phosphor bronze, titanium, copper, copper alloys, silver, and silver alloys. The wire diameter (thickness) of the linear bodies is, for example, 0.016 mm or more and 2.0 mm or less. The number of gaps in one inch (25.4 mm), i.e., the mesh count, can be, for example, 500 or less.

[0036] By forming a substrate using such linear materials, the rigidity of the substrate can be increased, thereby increasing the flow rate and velocity of the gas G permeating the substrate. Furthermore, there is no need to provide reinforcing frame-like members or crossbars. As a result, the processing flow rate can be increased.

[0037] A photocatalyst is a granular material that exhibits photocatalytic activity when light of a predetermined wavelength is incident upon it. The type of photocatalyst can be appropriately selected depending on the application of the gas purification device 1 and the substances contained in the gas G. For example, the photocatalyst can be an ultraviolet-responsive photocatalyst or a visible-light-responsive photocatalyst. An ultraviolet-responsive photocatalyst includes, for example, titanium dioxide. A visible-light-responsive photocatalyst includes, for example, tungsten oxide, titanium dioxide doped with nitrogen, or titanium dioxide ion-implanted with dissimilar metals.

[0038] Photocatalysts can also be directly supported on a substrate. However, as shown in Figure 3, since the photocatalyst body 6 is placed in the space through which the gas G to be treated flows, multiple photocatalysts supported on the substrate are exposed to the flow of gas G. In this case, if the bonding force between the photocatalyst and the substrate is weak, the photocatalyst is likely to detach from the substrate. In recent years, there has been a demand for increased processing flow rates, which has led to a trend of faster flow rates and increased flow rates of the gas G being treated. As a result, the force applied to the multiple photocatalysts supported on the substrate becomes even greater, potentially leading to an even greater detachment of the photocatalysts.

[0039] Therefore, the photocatalyst 6 has a bonding portion. The bonding portion is provided between the photocatalyst and the substrate. The bonding portion is provided to increase the bonding strength between the photocatalyst and the substrate. In this case, if the bonding portion contains a silicon compound, the bonding strength between the photocatalyst and the substrate can be effectively increased. Examples of silicon compounds include silicon oxides, silicon nitrides, silicon oxynitrides, silicon carbides, and silicon sulfides. In other words, the photocatalyst is bonded to the substrate via a bonding portion containing a silicon compound.

[0040] Furthermore, if multiple photocatalysts are completely embedded inside the junction, the light irradiated from the light source 5 may not reach the photocatalysts, or the gas G being processed may not be able to come into contact with the photocatalysts. For this reason, at least some of the multiple photocatalysts are exposed from the junction.

[0041] Here, if the mass ratio of the photocatalyst to the junction increases, the number of junctions decreases, making it easier for the photocatalyst to detach. On the other hand, if the mass ratio of the photocatalyst to the junction decreases, the number of junctions increases, so it is thought that it would be less likely for the photocatalyst to detach. However, as a result of diligent research, the inventors have found that if the mass ratio of the photocatalyst to the junction is made too small, it actually makes it easier for the photocatalyst to detach.

[0042] Figure 4 is a graph illustrating the relationship between the photocatalyst shedding rate and the mass ratio of the photocatalyst to the junction. In Figure 4, the mass ratio of the photocatalyst to the junction is given as "M(mass%) / S(mass%)". M(mass%) is the mass percentage of the photocatalyst. S(mass%) is the mass percentage of silicon (Si) contained in the junction. The mass percentage M (mass%) and mass percentage S (mass%) can be measured, for example, using an electron beam microanalyzer. The mass percentage of each object in a predetermined measurement range of the photocatalyst 6, for example, a region of φ2.0 mm, can be measured and determined. Furthermore, in the photocatalyst shedding test, the photocatalyst body 6, which has a substrate, photocatalyst, and joint, was subjected to a flow rate of 0.5 m³. 3 The samples were exposed to an airflow of 1 / min. Furthermore, the photocatalyst shedding rate was measured within a 200 μm diameter range on the surface of photocatalyst 6.

[0043] As can be seen from Figure 4, if we set "0.3 ≤ M(mass%) / S(mass%) ≤ 8", the photocatalyst shedding rate can be reduced to 0.8% or less. Furthermore, if we set "0.4 ≤ M(mass%) / S(mass%) ≤ 6", the photocatalyst shedding rate can be reduced even further.

[0044] Next, a method for producing the photocatalyst 6 according to this embodiment will be described. In the following example, we will describe the case where the joint contains silicon dioxide (SiO2). Therefore, by replacing silicon dioxide with other silicon compounds, it can be applied to joints containing other silicon compounds.

[0045] First, a dispersion is created by dispersing multiple particles containing silicon dioxide and multiple photocatalysts (for example, multiple particles containing titanium dioxide) in an aqueous solution mainly composed of water. In this case, the mass ratio of multiple photocatalysts to multiple silicon dioxide-containing particles is set to the aforementioned "0.3 ≤ M (mass%) / S (mass%) ≤ 8" or "0.4 ≤ M (mass%) / S (mass%) ≤ 6". The average particle size of multiple silicon dioxide-containing particles can be, for example, 1 μm or less. The average particle size of multiple photocatalysts can be, for example, 1 μm or less.

[0046] Next, a sheet-like substrate is immersed in the dispersion. Next, the immersed substrate is removed from the dispersion. Next, the dispersion liquid remaining on the surface of the substrate is dried to form a bonding area containing silicon dioxide (SiO2) on the surface of the substrate, and multiple photocatalysts are bonded to the substrate via this bonding area. In this manner, the photocatalyst 6 can be manufactured.

[0047] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other. [Explanation of Symbols]

[0048] 1. Gas purification device, 2. Frame, 4. Fan, 5. Light source, 6. Photocatalyst, G. Gas

Claims

1. With the base material; The substrate is bonded to a photocatalyst via a bonding portion containing a silicon compound; It is equipped with, The aforementioned substrate is in the form of a sheet, and a plurality of linear bodies containing metal are woven into it. The diameter of the aforementioned linear body is 0.016 mm or more and 2.0 mm or less. A photocatalyst that satisfies the following formula. 0.3≦M(mass%) / S(mass%)≦8 M (mass%) is the mass percentage of the photocatalyst. S (mass%) is the mass percentage of silicon (Si) contained in the joint.

2. The photocatalytic material according to claim 1, wherein the mesh count of the substrate is 500 or less.

3. The photocatalyst according to claim 1 or 2, satisfying the following formula. 0.4≦M(mass%) / S(mass%)≦6

4. The photocatalyst according to any one of claims 1 to 3, wherein the silicon compound comprises at least one of silicon nitride, silicon oxynitride, silicon carbide, and silicon sulfide.

5. A photocatalyst according to any one of claims 1 to 4; The photocatalyst body is provided with a light source capable of irradiating it with light having a predetermined wavelength; It is equipped with, The light source is a gas purification device that, when the photocatalyst contained in the photocatalyst body is an ultraviolet-responsive photocatalyst, irradiates ultraviolet light with a peak wavelength of 315 nm or more and 420 nm or less, and when the photocatalyst is a visible light-responsive photocatalyst, irradiates visible light with a peak wavelength of 405 nm or more and 600 nm or less.

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