Photocatalyst carrier

Abstract

To provide a photocatalyst support with a high deodorization effect.SOLUTION: A photocatalyst support according to one embodiment of the present invention comprises a substantially plate-form substrate that is formed from a porous ceramic material, and a photocatalyst that is supported on the surface of the substrate and inside pores therein. The open pore ratio of the ceramic material is 35-75% inclusive, the ceramic material includes large pores having a diameter of 100-1000 μm inclusive, and small pores having a diameter of 10 μm or lower are opened in the inner wall surfaces of the large pores.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a photocatalyst carrier.

Background Art

[0002] Deodorizing devices that obtain a deodorizing effect by decomposing organic substances using a photocatalyst such as titanium oxide have been put into practical use. Such a deodorizing device includes: a photocatalyst carrier obtained by supporting a photocatalyst on the surface of a base material; a light source that emits light for activating the photocatalyst on the photocatalyst carrier; and an airflow generating means that sucks in ambient air and brings it into contact with the photocatalyst. In order to efficiently bring air into contact with the photocatalyst, it has been proposed to use a porous ceramic material as the base material of the photocatalyst carrier (see, for example, Patent Document 1).

[0003] When selecting a ceramic material to be used as the base material of a photocatalyst carrier, emphasis is placed on the material composition that determines mechanical properties, and the porosity which serves as an indicator of the surface area and consequently the air contact efficiency. Regarding porosity, Patent Document 1 describes that a ceramic porous body with a porosity of 85% is used.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] Patent Document 1 achieves high porosity while ensuring mechanical strength by using a multilayer material. Pores include open pores (continuous pores) and closed pores (independent pores), and it is unclear what pore ratio the porosity in Patent Document 1 refers to. However, regardless of the value of the porosity in Patent Document 1, it is difficult to significantly increase the porosity of ceramic materials above the value in Patent Document 1 when considering mechanical strength. Therefore, a different approach is needed to further improve the deodorizing effect. In view of these circumstances, the object of the present invention is to provide a photocatalyst carrier with a high deodorizing effect. [Means for solving the problem]

[0006] A photocatalyst support according to one aspect of the present invention comprises a roughly plate-shaped substrate made of a porous ceramic material, and a photocatalyst supported on the surface and inside the pores of the substrate, wherein the open porosity of the ceramic material is 35% or more and 75% or less, and the ceramic material has air pores with a diameter of 100 μm or more and 1000 μm or less, and small pores with a diameter of 10 μm or less open on the inner wall surface of the air pores.

[0007] In the photocatalyst support described above, the number of air pores within a 1.8 mm × 1.8 mm area in the cross-section of the ceramic material may be 8 or more and 50 or less.

[0008] In the photocatalyst support described above, the substrate has a plurality of through holes that penetrate in the thickness direction, the diameter of the through holes is 0.7 mm or more and 2.0 mm or less, and the area ratio of the through holes in the substrate may be 20% or more and 50% or less.

[0009] In the photocatalyst support described above, the photocatalyst mainly consists of titanium dioxide, and the amount of photocatalyst supported is 0.04 g / cm³. 3 More than 0.15g / cm 3 The following is also acceptable.

[0010] A method for producing a photocatalyst carrier according to another aspect of the present invention comprises the steps of: immersing a roughly plate-shaped substrate made of a porous ceramic material in a photocatalyst dispersion in which photocatalyst particles are dispersed in a solvent; drying the substrate; and firing the substrate, wherein the open porosity of the ceramic material is 35% or more and 75% or less, and the ceramic material has air pores with a diameter of 100 μm or more and 1000 μm or less, and small pores with a diameter of 10 μm or less are opened on the inner wall surface of the air pores. [Effects of the Invention]

[0011] According to the present invention, a photocatalyst carrier with high deodorizing effect can be provided. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic perspective view showing a photocatalyst support according to one embodiment of the present invention. [Figure 2] Figure 1 is a flowchart showing the procedure for manufacturing the photocatalyst support. [Figure 3] This is a cross-sectional SEM image of the substrate of prototype 1. [Figure 4] This is a cross-sectional SEM image of the substrate of prototype 7. [Figure 5] This is a cross-sectional SEM image of the substrate of prototype 8. [Figure 6] This is a cross-sectional SEM image of the substrate of prototype 9. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic perspective view showing a photocatalyst support 1 according to one embodiment of the present invention.

[0014] The photocatalyst carrier 1 comprises a roughly plate-shaped substrate made of a porous ceramic material, and a photocatalyst supported on the surface and inside the pores of the substrate.

[0015] By using a porous ceramic or a ceramic material having both pores of 100 µm or larger and fine pores of 10 µm or smaller as the substrate of the photocatalyst carrier 1, organic substances in air can be primarily adsorbed and held, and the adsorbed organic substances can be decomposed over time by the catalytic effect of the photocatalyst, thereby increasing the deodorizing effect.

[0016] The ceramic material forming the substrate preferably contains silica, which is relatively inexpensive and can improve mechanical properties, as a main component, and preferably contains less expensive alumina. Specifically, as the lower limit of the total content of silica and alumina, 60% or more is preferable, and 80% is more preferable, in order to suppress cost. On the other hand, as the upper limit of the total content of silica and alumina, 98% is preferable, and 97% is more preferable, in order to allow inclusion of additives that optimize the physical properties of the material. Further, as the lower limit of the ratio of silica to alumina, 1.0 is preferable, and 1.2 is more preferable, in order to improve strength. On the other hand, as the upper limit of the ratio of silica to alumina, 3.0 is preferable, and 2.5 is more preferable, in order to suppress cost.

[0017] As the lower limit of the open porosity of the ceramic material forming the substrate, 35% is preferable, 40% is more preferable, and 50% is even more preferable. On the other hand, as the upper limit of the open porosity of the ceramic material forming the substrate, 75% is preferable, and 70% is more preferable. By setting the open porosity of the ceramic material to be not less than the above lower limit, the amount of the photocatalyst supported inside the pores of the substrate can be increased, so that the deodorizing effect of the photocatalyst carrier 1 (the effect of decomposing organic substances by the catalytic effect of the photocatalyst) can be enhanced. Further, by setting the open porosity of the ceramic material to be not more than the above upper limit, the mechanical strength of the substrate can be ensured. The "open porosity" is measured in accordance with the boiling method specified in JIS-R1634 (1998).

[0018] The ceramic material forming the base material has large pores with a diameter of 100 µm or more and 1000 µm or less, and small pores with a diameter of 10 µm or less. It is preferable that the pore diameter existence density distribution of the ceramic material has a peak in the range of 100 µm or more and 1000 µm or less, and a peak in the range of 10 µm or less. In the ceramic material, the small pores preferably open also on the inner wall surfaces of the large pores. If the pore diameter is too large, the specific surface area of the porous ceramic decreases, which reduces the adsorption capacity for organic substances and decreases the supported amount of the photocatalyst. Conversely, if the pore diameter is too small, the problem occurs that the photocatalyst dispersion liquid does not penetrate into fine portions, resulting in a reduced supported amount of the photocatalyst. The presence of large pores with a pore diameter of 100 µm or more and 1000 µm or less allows the photocatalyst dispersion liquid to penetrate into the interior, enabling efficient supporting of the photocatalyst. Furthermore, if small pores with a pore diameter of 10 µm or less are mixed, the photocatalyst dispersion liquid that has entered the large pores can easily penetrate into the small pores, so that the photocatalyst can be uniformly supported even in deep parts of the base material, which further improves the deodorization efficiency. From this viewpoint, it is preferable that 8 or more and 50 or less large pores exist in a square range of 1.8 mm × 1.8 mm of a cross-section of the porous ceramic. The term "pore diameter" refers to the average value of the major axis and minor axis of each pore in a scanning electron microscope image of a cross-section of the ceramic material. More specifically, the ceramic material was processed into a rod shape having a cross-section of about 10×10 mm, this rod was cut using a band saw, the surface was coated with an ion sputtering apparatus, and then the cross-section was photographed with a scanning electron microscope. For the scanning electron microscope, S3400 manufactured by Hitachi High-Tech Corporation was used, and images were captured at 15 kV.

[0019] As the lower limit of the thickness of the base material, 8 mm is preferable and 10 mm is more preferable in order to ensure strength. On the other hand, as the upper limit of the thickness of the base material, 20 mm is preferable and 15 mm is more preferable, so that light can be irradiated to the photocatalyst inside the pores to activate the catalytic action.

[0020] The substrate, and thus the photocatalyst carrier 1, has a plurality of through-holes 11 that penetrate in the thickness direction. The through-holes 11 act as air passages, reducing air pressure loss and thereby suppressing the load on the fan that forms the airflow. By reducing the diameter of the through-holes 11, air enters from the inner circumferential surface of the through-holes 11 into the pores of the outer substrate, thereby promoting the deodorizing effect. It is preferable that such through-holes 11 are formed regularly at equal intervals over almost the entire surface of the photocatalyst carrier 1, excluding the outer edge.

[0021] The lower limit of the diameter of the through-hole 11 is preferably 0.7 mm, and more preferably 1.0 mm, in order to facilitate its formation. On the other hand, the upper limit of the diameter of the through-hole 11 is preferably 2.0 mm, and more preferably 1.5 mm, in order to prevent air from passing through without contacting the photocatalyst. The lower limit of the area ratio of the through-hole 11 in the substrate is preferably 20%, and more preferably 25%, in order to sufficiently reduce pressure loss. On the other hand, the upper limit of the area ratio of the through-hole 11 in the substrate is preferably 50%, and more preferably 40%, in order to promote contact between air and the photocatalyst. Note that "diameter" refers to the equivalent diameter of a circle, that is, the diameter of a circle with the same area.

[0022] The photocatalyst preferably has titanium dioxide, more specifically anatase-type titanium dioxide, as its main component, as it exhibits excellent photocatalytic effects. The particle size (median diameter) of the photocatalyst is preferably between 50 nm and 400 nm so that it can be introduced into the pores of the substrate.

[0023] The photocatalyst is supported almost uniformly across the entire substrate. The lower limit for the amount of photocatalyst supported per volume of the photocatalyst support 1 (including the internal space of the through-holes 11) is 0.04 g / cm³ to obtain a sufficient deodorizing effect. 3 Preferably, 0.06 g / cm³ 3 This is more preferable. On the other hand, the upper limit for the amount of photocatalyst supported per volume of the photocatalyst support 1 is 0.15 g / cm³ in order to evenly support the photocatalyst without clogging the pores of the ceramic substrate. 3 Preferably, 0.10 g / cm³ 3 This is preferable.

[0024] The photocatalyst carrier 1, having the above configuration, holds the photocatalyst evenly and at a relatively high density throughout its interior, allowing it to effectively decompose organic matter in the air through the catalytic action of the photocatalyst, thus providing a high deodorizing effect.

[0025] The photocatalyst carrier 1 is manufactured by one embodiment of the photocatalyst carrier manufacturing method according to the present invention, as shown in Figure 2. The photocatalyst carrier 1 can be manufactured by a method comprising the steps of forming a substrate (step S1: substrate formation step), immersing the substrate in a photocatalyst dispersion (step S2: immersion step), drying the substrate (step S3: drying step), and calcining the substrate (step S4: calcination step).

[0026] In the substrate formation step S1, a substrate having the desired porosity and pore diameter, as well as the required external shape, is formed. In the substrate formation step, a powder that decomposes at the ceramic firing temperature is mixed with a well-known ceramic raw material and molded. By firing this molded body, a porous ceramic can be formed that contains a mixture of large pores with a diameter of 100 μm to 1000 μm and small pores with a diameter of 10 μm or less, which are not found in general ceramic materials, as described above. As the powder material that forms the pores, materials that decompose at high temperatures, such as sake lees, rice bran, soybean meal, coal, charcoal, and plastics, can be used. The particle size of the powder material that determines the diameter of the pores can be adjusted by adjusting the mixing conditions of a mixing machine such as a kneader or extruder.

[0027] In the immersion step of step S2, the substrate, which is formed from a porous ceramic material as described above, is immersed in a photocatalytic dispersion in which photocatalytic particles are dispersed in a solvent, thereby impregnating the substrate with the photocatalytic dispersion. Since the substrate is formed from a ceramic material having large pores and small pores, the photocatalytic dispersion penetrates evenly into the interior of the substrate. As the solvent for the photocatalytic dispersion, for example, 2-propanol, water, etc., can be used. The photocatalytic concentration in the photocatalytic dispersion is preferably 10% to 40% in order to ensure penetration into the interior of the substrate while introducing the photocatalyst at a sufficient density. The photocatalytic dispersion may also contain a binder that promotes the adhesion of the photocatalytic particles to the substrate.

[0028] In the drying step S3, the substrate impregnated with the photocatalytic dispersion is dried to adhere photocatalytic particles to the outer surface and inner surface of the pores of the substrate. Since boiling the solvent of the photocatalytic dispersion may cause the photocatalytic particles to detach, it is preferable to dry at a temperature sufficiently lower than the boiling point of the solvent. For example, if the solvent of the catalyst dispersion is 2-propanol, drying can be carried out at room temperature for 24 hours.

[0029] In step S4, the firing process, the substrate, which has been dried with the impregnated catalyst dispersion, is fired to fix the photocatalytic particles to the substrate. The firing conditions can be, for example, heating at 500°C for 1 hour followed by slow cooling to room temperature. Because the substrate has air pores, the photocatalyst after firing tends to form a continuous layer, making it less likely for the photocatalyst to detach from the substrate.

[0030] As described above, by going through the immersion process, drying process, and calcination process, the photocatalyst can be uniformly supported even inside the relatively small-diameter pores of the substrate. The photocatalyst support 1 produced by this method can exhibit a high deodorizing effect as described above.

[0031] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and variations are possible. [Examples]

[0032] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples.

[0033] A variety of substrates made of ceramic material were prepared, and prototype photocatalyst supports 1 to 11 were fabricated using the procedure shown in Figure 2. The substrates mainly consisted of ceramic materials with varying porosity, pore diameter, and through-hole area ratios. As representative examples illustrating the differences in pore shape of the ceramic materials, operating microscope images of prototypes 1, 7, 8, and 9 are shown in Figures 3 to 6. "Total porosity" refers to the volume percentage of all pores, including closed pores, while "vacuum porosity" is the sum of the volume percentages of all pores and through-holes in the material. "Water absorption rate" was measured according to the boiling method of JIS-A1509-3 (2014).

[0034] To evaluate the deodorizing performance of the obtained photocatalyst-supported prototypes, a test was conducted to decompose ammonia and aldehydes in a sealed container, and the time required for decomposition was measured. Table 1 summarizes the composition of the ceramic material, physical properties, geometric information of the substrate, amount of photocatalyst supported, and deodorizing performance of each prototype. In the table, "-" indicates that there is no measurement value, and "120<" indicates that the odor components could not be decomposed in 120 minutes and the test was terminated.

[0035] [Table 1]

[0036] As described above, it was confirmed that the deodorizing effect of the photocatalyst support can be improved by keeping the pore size of the substrate within a certain range. [Explanation of symbols]

[0037] 1. Photocatalyst carrier 11 Through hole

Claims

1. A roughly plate-shaped substrate formed from a porous ceramic material, Supported on the surface and inside the pores of the substrate is a photocatalyst mainly composed of titanium dioxide, Equipped with, The open porosity of the aforementioned ceramic material is 35% or more and 75% or less. The ceramic material has air pores with a diameter of 100 μm or more and 1000 μm or less. The number of air vents within a 1.8 mm × 1.8 mm area in the cross-section of the ceramic material is 8 or more and 50 or less. Small pores with a diameter of 10 μm or less are opened on the inner wall surface of the aforementioned air vent. The amount of photocatalyst supported is 0.04 g / cm³. ３ 0.15g / cm or more ３ The following is the photocatalyst carrier.

2. The substrate has a plurality of through holes that penetrate in the thickness direction, The diameter of the through hole is 0.7 mm or more and 2.0 mm or less. The photocatalyst carrier according to claim 1, wherein the area ratio of the through-holes in the substrate is 20% or more and 50% or less.

3. A process of immersing a roughly plate-shaped substrate made of a porous ceramic material in a photocatalytic dispersion liquid in which photocatalytic particles mainly composed of titanium dioxide are dispersed in a solvent, A step of drying the substrate, A step of firing the aforementioned substrate, Equipped with, The open porosity of the aforementioned ceramic material is 35% or more and 75% or less. The ceramic material has air pores with a diameter of 100 μm or more and 1000 μm or less. The number of air vents within a 1.8 mm × 1.8 mm area in the cross-section of the ceramic material is 8 or more and 50 or less. Small pores with a diameter of 10 μm or less are opened on the inner wall surface of the aforementioned air vent. The amount of photocatalyst supported was 0.04 g / cm³. ３ 0.15g / cm or more ３ The following is a method for manufacturing a photocatalyst support.

Images