JP2005161242A - Photocatalyst-coated pipe, its production method, and contaminant decomposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst-coated pipe with high mechanical strength of a photocatalyst layer, high durability, and a high decomposing and purifying action of contaminants; a production method efficiently producing it; and contaminants decomposition method using the photocatalyst-coated pipe. <P>SOLUTION: In this production method of the photocatalyst-coated pipe, titanium compound vapor and oxygen are introduced into a pipe, the pipe is heated from outside to produce titanium oxide, titanium oxide particles are sintered on an inner wall of the pipe and carried thereon, to provide the photocatalyst-coated pipe. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photocatalyst coating conduit provided with a photocatalytic coating made of titanium oxide on the inner wall of a pipe, a manufacturing method thereof, and a pollutant decomposition method using the photocatalyst coating conduit.

Titanium oxide (TiO ₂ ) particles have been widely used as white pigments in paints, cosmetics and food additives. In addition, the use for the decomposition of nitrogen oxides (NOx) that cause air pollution and the decomposition of organic solvents that cause water pollution by the photocatalytic action exhibited by titanium oxide has been studied.

  Conventionally, as a method of decomposing contaminants such as gas and water using a titanium oxide photocatalyst in a flow system, a photocatalyst coating made of titanium dioxide has been applied to the inner wall of the translucent pipe, and the purification object such as gas and water is inside. Has been proposed (see, for example, Patent Document 1).

As a method of supporting a photocatalyst such as titanium dioxide on the surface of a substrate, a method of photocatalytic coating of titanium oxide particles or titanium oxide precursor synthesized in advance by a dip method or a spray method is performed.
JP-A-8-294687

However, the conventional method of coating the surface of the base material with titanium oxide particles or titanium oxide precursors synthesized in advance has a low mechanical strength and poor durability of the photocatalyst layer obtained by coating. It was insufficient for use in decomposing contaminants with a photocatalyst while flowing continuously for a period of time.
Moreover, since the photocatalyst layer obtained by the coating of the conventional method contains an inorganic binder or the like, it has a low ability to decompose and purify contaminants.

  The present invention has been made in view of the above circumstances, and a photocatalyst coating conduit having a high mechanical strength of the photocatalyst layer, excellent durability, and a high ability to decompose and purify pollutants, a manufacturing method for efficiently producing the same, and the photocatalyst coating conduit The purpose is to provide a pollutant decomposition method using

In order to achieve the above object, the present invention introduces titanium compound vapor and oxygen into a pipe, heats the pipe from outside to synthesize titanium oxide, and sinters and carries titanium oxide particles on the inner wall of the pipe. Provided is a method for producing a photocatalyst-coated conduit characterized by obtaining a photocatalyst-coated conduit.
In the method for producing a photocatalyst-coated conduit of the present invention, it is preferable to use a pipe made of a material having translucency with respect to excitation light that activates the photocatalyst.
In this case, it is preferable to use a quartz glass pipe as the pipe.
In the method for producing a photocatalyst-coated conduit according to the present invention, the titanium compound is preferably titanium tetrachloride.
Further, when heating from the outside of the pipe, it is preferable to heat the outside of the pipe while reciprocating the oxyhydrogen burner flame in the longitudinal direction of the pipe.
Furthermore, it is preferable to synthesize titanium oxide and sinter to the inner wall of the pipe while rotating the pipe.
In the method for producing a photocatalyst-coated conduit of the present invention, the synthesis temperature and sintering temperature of titanium oxide are preferably in the range of 850 to 1500 ° C.
In the method for producing a photocatalyst-coated conduit according to the present invention, a silica glass material vapor is introduced into a pipe, heated from the outside of the pipe to provide an optical waveguide layer on the inner wall of the pipe, and then the inner wall of the optical waveguide layer is coated with the photocatalyst You can also.

The present invention also provides a photocatalyst-coated conduit manufactured by the method for manufacturing a photocatalyst-coated conduit.
Furthermore, the present invention provides a pollutant decomposition method characterized by flowing a treatment fluid through the photocatalyst coating conduit and irradiating the photocatalyst coating with excitation light that activates the photocatalyst to decompose the contaminant in the treatment fluid. I will provide a.

According to the method for producing a photocatalyst-coated conduit of the present invention, it is possible to efficiently produce a photocatalyst-coated conduit having a high mechanical strength, excellent durability, and high ability to decompose and purify contaminants.
The photocatalyst-coated conduit of the present invention has a high photocatalytic activity of the photocatalyst coating formed on the inner wall, and is suitable for applications such as decomposing contaminants by photocatalysis, and at the same time has a high hydrophilicity, so that it has a sufficient self-cleaning function Also have. Therefore, it is possible to suppress degradation of the decomposition and purification function due to contaminants adhering to the surface of the photocatalyst during decomposition of the fluid to be processed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first example of a production apparatus suitable for the method for producing a photocatalyst-coated conduit according to the present invention. The manufacturing apparatus includes a pipe 1 that is rotatably attached, an oxyhydrogen flame burner 2 that heats the outer surface of the pipe 1, and a pipe 3 that supplies oxygen and a titanium compound vapor in a mixed state inside the pipe 1. And a bubbler 5 for supplying a carrier gas such as argon to a container containing the titanium compound 4 and supplying a titanium compound vapor via the pipe 3.

  This manufacturing apparatus synthesizes titanium oxide in the pipe 1 by introducing oxygen and a titanium compound vapor into the pipe 1 through the pipe 3 and heating the pipe 1 with the flame of the oxyhydrogen burner 2. At the same time, the titanium oxide particles are sintered and supported on the inner wall of the pipe 1 to produce a photocatalyst coating conduit 10 having a photocatalyst coating made of titanium oxide on the inner wall. Although the thickness of this photocatalyst coating is not specifically limited, For example, it is preferable to set it as about 0.1-10.0 micrometers. This photocatalytic coating is desirably provided with a uniform thickness over the entire inner wall of the pipe 1, but is not limited to this, and is provided only on the half side of the inner wall of the pipe. It can also be provided in a shape such as a shape.

  For example, titanium tetrachloride can be used as the titanium compound 4 as a raw material of titanium oxide, and can be supplied in a vapor phase by bubbling or baking. When titanium tetrachloride is used as the titanium compound 4 and the raw material is supplied by bubbling, keeping the bubbler 5 at 60 ° C. or higher keeps the vapor pressure suitable for transfer, and the production efficiency is good and industrially desirable. . In this case, it is desirable that the pipe 3 be kept at a bubbler keeping temperature or higher so that titanium tetrachloride is not liquefied.

The titanium oxide coated on the inner wall of the pipe 1 is pure TiO ₂ and, for example, one or more dopants such as P, N, Si, and B are added to add visible light activity and special activity. You can also FIG. 2 is a block diagram showing a second example of a manufacturing apparatus suitable for the method of manufacturing a photocatalyst-coated conduit according to the present invention. This manufacturing apparatus includes the same components as the manufacturing apparatus shown in FIG. In order to add the dopant, a dopant bubbler 7 containing silicon tetrachloride 6, an ammonia gas cylinder 9 for adding N, and a pipe 8 for introducing these dopants into the pipe 1 are provided. ing.

  The pipe 1 is for decomposing and purifying contaminants by photocatalytic action while circulating a fluid to be treated such as exhaust gas and wastewater, and the size and material can be selected according to the application. However, it is necessary to select a material that can withstand the amount of heat when it is exposed to an oxyhydrogen flame and synthesizes titanium oxide from a titanium compound. For example, when titanium tetrachloride is used as the titanium oxide raw material, the synthesis temperature is preferably 850 ° C. to 1500 ° C. in order to obtain a high photocatalytic activity. Can be used.

  When the photocatalyst coating conduit 10 obtained by applying the photocatalyst coating to the inner wall of the pipe is used to circulate a fluid to be treated such as exhaust gas or waste water to decompose and purify pollutants, the light source for exciting the photocatalyst is usually It will be installed inside the photocatalyst coating conduit 10. However, there is a problem in that the amount of light itself is reduced by blocking the irradiation of light from the light source to the photocatalyst due to contaminants contained in the fluid to be treated, or by attaching contaminants to the surface of the light source. On the other hand, if the excitation light is irradiated from the outside of the photocatalyst coating conduit 10, the above problem is solved. Therefore, in a preferred embodiment of the present invention, a photocatalyst-coated conduit 10 that can solve the above problem can be manufactured by using a pipe that is transparent to the excitation light of the photocatalyst. For example, since a quartz glass tube has high translucency in the excitation light region of a photocatalyst such as ultraviolet light, it is desirable to use a quartz glass tube as a pipe.

  When heating from the outside of the pipe 1 with the flame of the oxyhydrogen burner 2, if the oxyhydrogen burner flame is moved at a constant speed along the longitudinal direction of the pipe, the inner wall of the pipe can be continuously coated with titanium oxide. Is desirable. This moving speed needs to be adjusted by the titanium compound used for the raw material and the synthesis temperature. For example, when titanium tetrachloride is used as a raw material and the synthesis temperature is 1300 ° C., the moving speed of the oxyhydrogen burner flame is preferably in the range of 0.1 to 5.0 m / min. If the moving speed is less than 0.1 m / min, the sintering of the titanium oxide proceeds too much, the adsorption capacity of the resulting coating film decreases, and the photocatalytic activity is changed from anatase-type titanium oxide crystal to rutile-type crystal by excessive heating. This is not desirable. On the other hand, when the moving speed exceeds 5.0 m / min, the sintering action is insufficient, the adhesion of the titanium oxide coating film to the inner wall of the pipe is weak, and there is a possibility of causing problems such as peeling.

  Also, during the synthesis and sintering of titanium oxide, the pipe 1 is heated with an oxyhydrogen burner flame while rotating, so that the inside of the pipe 1 is uniformly heated in the radial direction and the inner wall of the pipe is uniformly coated with titanium oxide. Therefore, the photocatalyst coating conduit 10 having a stable decomposition action can be manufactured. The rotation speed is preferably 20 to 70 rpm. If it is rotated more slowly than this, uniform heating in the pipe radial direction cannot be achieved. Further, since sufficiently uniform heating is performed at about 70 rpm, no further effect can be expected even if it is rotated faster than this.

  Also, by using a quartz glass tube for the pipe, introducing a glass material capable of providing a refractive index distribution in quartz glass such as silicon tetrachloride and germanium tetrachloride into the pipe, and heating while moving the oxyhydrogen burner flame, An optical waveguide layer having a predetermined optical refractive index distribution may be provided on the inner wall of the pipe, and a titanium oxide coating may be applied thereon. The optical waveguide layer is composed of one or a plurality of glass layers having different refractive indexes, and can be continuously formed by the above-described manufacturing method. By switching the raw material to be introduced from the glass material to the titanium oxide material, the photocatalytic coating can be produced in one step, which is industrially advantageous.

  Further, the optical waveguide layer is formed, excitation light is incident on the optical waveguide layer at the end face of the pipe, the titanium oxide photocatalyst is activated by the leakage light from the optical waveguide layer, and the contaminants can be decomposed and purified. By forming a predetermined refractive index distribution in the optical waveguide layer, it is possible to expose the excitation light uniformly in the longitudinal direction of the pipe, or it is possible to expose the excitation light with a desired light amount at a desired position. The thickness of the optical waveguide layer used for this purpose is not particularly limited as long as it can guide the excitation light along the longitudinal direction of the pipe, but is preferably about 10.0 μm to 2.0 cm, for example. A structure in which an optical waveguide layer made of a material with a higher refractive index is formed on the inner surface side of the quartz glass tube, the optical waveguide layer becomes the core, and the quartz glass tube on the outer periphery becomes the cladding, and in the longitudinal direction of the pipe Excitation light can be guided efficiently, and by providing a photocatalytic coating made of titanium oxide having a high refractive index on the inner surface of the optical waveguide layer, the excitation light leaks from the optical waveguide layer to the photocatalytic coating side.

  The photocatalyst-coated conduit 10 manufactured in this way can be processed into a desired inner diameter by performing a drawing process after manufacturing, if necessary. For example, when a quartz glass tube is used for a pipe, the portion to be stretched after forming a photocatalytic coating of titanium oxide on the inner wall is heated from the outside to near the glass softening temperature with a heater, an oxyhydrogen flame, etc., and the inner diameter is narrowed by stretching, In addition, the length can be increased.

  The photocatalyst coating conduit 10 obtained by the above method has high photocatalytic activity of the photocatalyst coating formed on the inner wall, and is suitable for applications such as decomposing contaminants by photocatalysis, and at the same time has high hydrophilicity. It also has a sufficient self-cleaning function. Therefore, it is possible to suppress degradation of the decomposition and purification function due to contaminants adhering to the surface of the photocatalyst during decomposition of the fluid to be processed. Examples of pollutants that can be decomposed by the photocatalyst coating conduit 10 include nitrogen oxides (NOx), aldehydes such as acetaldehyde, carboxylic acids such as acetic acid, malodorous components such as sulfur-containing compounds and nitrogen-containing compounds, environmental hormones, Legionella bacteria etc. are mentioned.

[Example 1]
A quartz glass tube with a diameter of 40 mm was installed on the lathe and rotated at 45 rpm. Therefore, titanium tetrachloride vapor 50 sccm and oxygen 1000 sccm were introduced and heated at about 1300 ° C. with an oxyhydrogen burner flame from the outside of the quartz glass tube. The oxyhydrogen burner flame was moved at 2.0 m / min along the longitudinal direction of the quartz glass tube. A titanium oxide film having a thickness of 1.2 μm was formed on the inner wall of the quartz glass tube after the above operation, and a titanium oxide coated pipe having a total length of 1500 mm was obtained.
A 10.0 μmol / L methylene blue aqueous solution was passed through this pipe at a rate of 20 cc / min, and the methylene blue concentration of the solution that passed through the pipe was measured. Before applying the excitation light, the concentration of the solution that passed through the pipe did not change at 10.0 μmol / L, but when irradiated with a black light that emits 365 nm light from the outside of the pipe at an illuminance of 5.0 mW / cm ² , The methylene blue concentration of the solution that passed through was reduced to 0.6 μmol / L, indicating sufficient decomposition and purification ability. There was no damage such as peeling on the titanium oxide photocatalyst layer on the inner wall of the pipe after the experiment, and there was no problem in the mechanical strength of the photocatalyst layer.

[Comparative Example 1]
A titanium oxide coating was applied to the inner wall of quartz glass having a diameter of 40 mm with a commercially available photocatalytic coating solution. This coating was performed by a dip coating method. The thickness of the titanium oxide layer after sufficiently drying was 1.3 μm, and a titanium oxide coated pipe having a total length of 1500 mm was obtained.
A 10.0 μmol / L methylene blue aqueous solution was passed through this pipe at a rate of 20 cc / min, and the methylene blue concentration of the solution that passed through the pipe was measured. Before applying the excitation light, the concentration of the solution that passed through the pipe did not change at 10.0 μmol / L, but when irradiated with a black light that emits 365 nm light from the outside of the pipe at an illuminance of 5.0 mW / cm ² , The concentration of methylene blue in the solution that passed through the tube decreased to 7.8 μmol / L. However, a part of the titanium oxide layer on the inner wall of the pipe peeled off and flowed out together with the solution, and there was a problem in durability of the titanium oxide layer.

[Example 2]
A φ40 mm quartz glass tube was placed on a lathe and rotated at 45 rpm. Thereto, silicon tetrachloride vapor 20 sccm, germanium tetrachloride vapor 8 sccm, and oxygen 1000 sccm were introduced, and heated at 1150 ° C. with an oxyhydrogen burner flame from the outside of the quartz glass tube. The oxyhydrogen burner flame was moved at 2.0 m / min along the longitudinal direction of the pipe, and was reciprocated from one end to the other end of the quartz glass tube. Next, 50 sccm of titanium tetrachloride vapor and 1000 sccm of oxygen were introduced and heated at about 1300 ° C. with an oxyhydrogen burner flame from the outside of the quartz glass tube. The oxyhydrogen burner flame was moved at 2.0 m / min along the longitudinal direction of the quartz glass tube. A titanium oxide film having a thickness of 1.2 μm was formed on the inner wall of the quartz glass tube after the above operation, and a titanium oxide coated pipe having a total length of 1500 mm was obtained.
When 10.0 μmol / L methylene blue aqueous solution was circulated through this pipe at a rate of 20 cc / min, the optical waveguide layer on the pipe end face was irradiated with xenon lamp light with an illuminance of 1000 mW / cm ² at 365 nm and passed through the pipe. The methylene blue concentration of the obtained solution was reduced to 0.9 μmol / L, and sufficient decomposition and purification ability was shown. There was no damage such as peeling on the titanium oxide photocatalyst layer on the inner wall of the pipe after the experiment, and there was no problem in the mechanical strength of the photocatalyst layer.

It is a block diagram which shows the 1st example of a suitable manufacturing apparatus in the manufacturing method of the photocatalyst coating conduit | pipe of this invention. It is a block diagram which shows the 2nd example of a suitable manufacturing apparatus in the manufacturing method of the photocatalyst coating conduit | pipe of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pipe, 2 ... Oxyhydrogen burner, 3 ... Pipe, 4 ... Titanium compound, 5 ... Bubbler, 6 ... Silicon tetrachloride, 7 ... Bubbler, 8 ... Pipe, 9 ... Ammonia gas cylinder, 10 ... Photocatalyst coating conduit.

Claims (10)

  A photocatalyst characterized in that a titanium compound vapor and oxygen are introduced into a pipe and heated from outside the pipe to synthesize titanium oxide, and titanium oxide particles are sintered and supported on the inner wall of the pipe to obtain a photocatalyst-coated conduit. A method of manufacturing a coating conduit.   2. The method for producing a photocatalyst-coated conduit according to claim 1, wherein a pipe made of a material having translucency with respect to excitation light for activating the photocatalyst is used.   A method for producing a photocatalyst-coated conduit according to claim 1 or 2, wherein a quartz glass pipe is used.   The method for producing a photocatalyst-coated conduit according to any one of claims 1 to 3, wherein the titanium compound is titanium tetrachloride.   The method for producing a photocatalyst-coated conduit according to any one of claims 1 to 4, wherein when heating from the outside of the pipe, the outside of the pipe is heated while reciprocating the oxyhydrogen burner flame in the longitudinal direction of the pipe.   The method for producing a photocatalyst-coated conduit according to any one of claims 1 to 5, wherein the titanium oxide is synthesized and sintered to the inner wall of the pipe while rotating the pipe.   The method for producing a photocatalyst-coated conduit according to any one of claims 1 to 6, wherein the synthesis temperature and sintering temperature of titanium oxide are in the range of 850 to 1500 ° C.   The quartz glass material vapor is introduced into the pipe, heated from the outside of the pipe to provide an optical waveguide layer on the inner wall of the pipe, and then the inner wall of the optical waveguide layer is coated with a photocatalyst. A method for producing a photocatalyst-coated conduit according to claim 1.   The photocatalyst coating conduit | pipe manufactured by the manufacturing method in any one of Claims 1-8. 10. A method for decomposing a pollutant, comprising flowing a treatment fluid through the photocatalyst coating conduit according to claim 9 and irradiating the photocatalyst coating with excitation light that activates the photocatalyst to decompose the contaminant in the treatment fluid. .

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