JPH03157125A - Deodorizing method with photocatalyst - Google Patents

Abstract

PURPOSE:To effectively decompose a malodor by the action of a photocatalyst by supporting a semiconductor on a cubic porous body, passing gas contg. the malodor through the resulting photocatalyst and irradiating the semiconductor with light. CONSTITUTION:A cubic porous body of ceramics, etc., produced from a fibrous structure as starting material is dipped in a titania sol to impregnate the sol into the porous body and this porous body is dried and heat-treated to support titanium oxide to obtain a photocatalyst 1. The resulting photocatalyst 1 is set on the bottom of a stainless reactor 2 so that the photocatalyst confronts a window 3 of a quartz sheet and a UV lamp 4 is laid just above the window 3. Gas contg. a malodor and air are allowed to flow in the reactor 2 and the lamp 4 is put on to irradiate the photocatalyst 1 with light. The gas comes in very satisfactory contact with the photocatalyst and the decomposition reaction of the malodor with the photocatalyst proceeds efficiently without shielding UV.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for deodorizing bad odors (cooking odor, food odor, tobacco odor, body odor, bed and toilet odor, etc.) in homes and offices using a photocatalyst.

Conventional technology The components of bad odors that occur in homes and offices (cooking odor, food odor, tobacco odor, body odor, pets, the back of the toilet, etc.) are as follows:
Nitrogen compounds (ammonia, amines, indole, skatole, etc.), sulfur compounds (hydrogen sulfide, methyl mercaptan, methyl sulfide, methyl disulfide, dimethyl disulfide, etc.), aldehydes (formaldehyde, acetaldehyde, etc.), ketones (acetone, etc.) ), alcohol (
There are a wide variety of substances, including methanol, ethanol, etc.), fatty acids, and aromatic compounds.

Conventionally, methods for removing such bad odors include a method of chemically reacting a malodorous substance with a drug to change it into an odorless substance, a method of masking the malodorous substance with an air freshener, a method of adsorbing the malodorous substance with activated carbon or zeolite, etc. There were also methods that used a combination of these methods. However, once these were used up or their deodorizing ability decreased, they had to be replaced with new ones. In particular, with adsorbents and deodorizers whose appearance does not change even after their deodorizing performance is exhausted, the decision to replace them is based on the sense of how well the odor has been removed, or it has been decided to replace them after approximately the period of use. It was also troublesome. Therefore, attempts have been made to deodorize using photocatalytic action. This technology takes advantage of the property of semiconductors such as titanium oxide when irradiated with ultraviolet rays, which excites them and oxidizes and decomposes organic substances.It decomposes all kinds of bad odors, including aldehydes, which are difficult to deodorize with the commonly used activated carbon. However, it maintains its performance for a long period of time, and requires very little or no maintenance other than replacing the ultraviolet lamp.

Problems to be Solved by the Invention Factors that determine the ability of the photocatalyst to decompose malodors include the intensity of ultraviolet rays, the amount of catalyst, and the contact efficiency between malodor and catalyst. Therefore, if the amount of catalyst is increased or guide fins are installed to improve the contact efficiency between the bad odor and the catalyst, the ultraviolet rays irradiated to the catalyst will be blocked, creating areas of weak light or shadows, which will actually make the reaction proceed more efficiently. There wasn't,
On the other hand, there was a problem in that it was difficult to make the decomposition reaction proceed efficiently and speed up the deodorization rate, such as the production of smelly intermediate products.

The present invention is intended to solve the above-mentioned conventional problems, and its first object is to provide a method for effectively decomposing bad odors through photocatalytic action. Further, in relation to the first object, a second object is to provide a second method for effectively decomposing bad odors.

Means for Solving the Problems The first means for achieving the above-mentioned first objective is to:
This is a deodorizing method using a photocatalyst in which the semiconductor is irradiated with light to activate the semiconductor. A second means for achieving the second objective is to allow the gas to pass through the porous body in the coexistence of a three-dimensional porous body carrying a semiconductor and a gas containing a bad odor, and to further illuminate the semiconductor. This is a deodorizing method using a photocatalyst that activates semiconductors by irradiating them.

It is known that when a working semiconductor material, a non-oxidizing compound, and a gas containing oxygen coexist, when the semiconductor material is irradiated with ultraviolet rays, the non-oxidizing compound is oxidized and decomposed. In particular, much research has been conducted on titanium oxide. The working principle of this photocatalysis is that electrons in the valence band in the semiconductor absorb ultraviolet light and are excited to the conduction band, and the holes in the valence band generated there react with the hydroxyl groups (OH groups) on the catalyst surface. It is assumed that the electrons excited in the conductor react with oxygen (0) to generate highly active OH radicals, 0 radicals, and 0 gates, which oxidize and decompose non-oxidizing compounds. When applying this photocatalytic effect to a deodorizing device, what is important is that the ultraviolet rays emitted from the electric lamp are used efficiently and that the bad odor comes into sufficient contact with the semiconductor catalyst layer. Regarding the former, it is necessary to consider semiconductor materials. Here, we conducted various studies regarding the latter.

As a result, by using the first method, which is a catalyst in which a semiconductor is supported on a three-dimensional porous body, the surface area of the catalyst can be expanded (and turbulent flow can be generated on the catalyst surface, which can reduce the odor and the catalyst). The second method uses the air permeability of the three-dimensionally porous catalyst to transport gases containing bad odors through the catalyst. By allowing the odor to pass through and flow, the efficiency of contact between the foul odor and the catalyst is further improved.

Embodiment Next, an embodiment of the present invention will be described based on FIGS. 1 to 7.

(Example 1) Figures 1 and 2 are semiconductors (titanium oxide) used in the present invention.
FIG. 1 is a plan view photograph, and FIG. 2 is a cross-sectional photograph. The porous body used in this example is an alumina ceramic fiber porous body manufactured by Asahi Kasei Industries, which uses a fibrous structure (woven or knitted fabric) as a starting material, and is a woven fabric with an opening of about 1°5 nu++ and a pitch of about 2.5 mm. Approximately 3m thick, with two tiers that close the openings.
+n. Next, this porous body was impregnated with titania sol by dipping, and after drying, it was heat-treated at 400° C. to 700° C. to support titanium oxide, thereby obtaining a photocatalyst 1. The amount of titanium oxide supported here was 403 g/d.

An experimental example using the catalyst of this example will be described below. Figure 3 shows a flow-type measuring device that measures the decomposition rate in one pass of the photocatalytic reaction. 2 is a reactor made of stainless steel, and a photocatalyst 1-1 with a width of 30.5 mm and a length of 120 mm was set on the bottom, and a window 3 of a quartz plate was placed opposite to the photocatalyst 1-1. Light is irradiated from directly above the window 3 with an ultraviolet lamp 4. 5-1.
Reference numeral 5-2 denotes a baffle plate, and there is a gap of 5 mm below both plates, so that the gas flows as close to the photocatalyst 1-1 as possible. 6 is a cylinder containing foul-smelling gas, 7 is a cylinder containing air, 8-1.8-2 is a regulator that adjusts the pressure of the gas discharged from each cylinder, 9-
1.9-2 is a flow rate regulator, 10 is a mixer that stirs and mixes two types of gas uniformly, 12 is a three-way cock that switches between the bypass side and the reaction side, and 13, 14, and 15 are rubber plugs for gas sampling. It is. Further, numeral 11 is a pipe connecting each element part, and is made of glass, fluorine resin, or stainless steel. Here, the power consumption of ultraviolet lamp 4 is 10
With the W germicidal lamp GL-10, the ultraviolet intensity on the surface of the photocatalyst 11 is 3. It was set to Oo+W/cnf (the intensity at a wavelength of 250t+m was measured). In addition, the flow rate regulator 9-1.9- is used so that the total flow rate of gas is 2e/min.
Adjusted with 2. Next, the operation of this flow-type measuring device will be explained. After setting the photocatalyst 1-1 in the reactor 2 and opening the three-way cock 12 to the bypass side, open the cylinders 6 and 7.
The opening releases foul-smelling gas and air, and the flow rate regulators 9-1 and 9-
Set the flow rate in Step 2, and leave it for a while to stabilize the gas flow. From time to time, sample the gas from the rubber stopper 13 with a syringe, analyze it with gas chromatography, and measure the concentration. The gas concentration is finely adjusted in step 9-2. When the mixed gas stabilizes at the set flow rate and set concentration, the ultraviolet lamp 4 is turned on and the photocatalyst 1-1 is irradiated for 5 minutes.

Next, switch the three-way cock 12 to open to the reaction side and leave it for 5 minutes, then open the inlet rubber stopper 14 and the outlet rubber stopper 1.
Sample the gas using a syringe from 5 and analyze the concentration using gas chromatography. Concentration measurements are taken at 10 minute intervals for 120 minutes. By substituting the gas concentrations at the inlet and outlet into the following equation, the decomposition rate of the malodorous gas in the photocatalyst 1-1 is determined.

b m = (1) It is. Here, as photocatalyst 1-1, the decomposition rates were compared and measured for the case of photocatalyst 1 having a three-dimensional porous body and the case of using a flat photocatalyst. The flat photocatalyst used for comparison was prepared by dipping and impregnating titania sol into alumina-siliceous ceramic paper with a thickness of 0.51 f1 m, drying it and then heat-treating it at 400°C to 700°C to add 300 g of titanium oxide. /J carried. The decomposition rates were measured for 1 spptn of acetaldehyde and 20 ppm of methyl mercaptan as malodorous gases. The results are shown in Table 1.

Note: A, A = acetaldehyde M, M = methyl mercaptan In this way, by making the photocatalyst into a sterically porous body, the decomposition rate is improved by more than 40%.

(Example 2) Another example of the present invention is shown in FIGS. 4 and 5. FIG. 4 is a longitudinal cross-sectional view, and FIG. 5 is a cross-sectional view. 28 and 29 are ultraviolet lamps, 30 are sockets for ultraviolet lamps 28 and 29, 21 and
22 and 23 are ultraviolet lamps 28 and 23 perpendicular to the flow of foul-smelling air.
A three-dimensional porous photocatalyst provided in parallel to 29, 24.
25, 26, and 27 are three-dimensional porous photocatalysts fixed to a casing 37 in parallel to the flow of foul-smelling air; 36 is a pre-filter that collects dust; 31, 32 are cross-flow fans; 33 and 34 are the aforementioned A motor for the fan, 35 is a suction grill, and 38 is a blowout grill. The photocatalyst 2
1 to 27 are the same catalysts as in Example 1, and 21, 22, and
23 is 400imX 130111m, 24-25 is 2
60+++m x 130+yun, 26/27 is 26
0mm x 400ml11, total catalyst area is 3640c
nt.

The ultraviolet lamps 28 and 29 may be of any type as long as they can emit light containing ultraviolet light, and the ultraviolet light to be emitted may be far ultraviolet light or near ultraviolet light. Examples of such electric lights include low-pressure mercury lamps, high-pressure mercury lamps, and ultra-high-pressure mercury lamps. These lights can be used alone (or in combination).

Here, we will introduce the germicidal lamp GL-15 (wavelength 25) with a power consumption of 15W.
Two ultraviolet rays (3.7 nm, ultraviolet output 3.2 W) were used.

In the above configuration, the ultraviolet lamps 28 and 29 are turned on, and the
When the cross-flow fan 32 is operated, air containing bad odor is sucked in through the suction grill 35, and dust is first collected by the pre-filter 36. Next, the foul-smelling air passes through the photocatalysts 21 to 23 and flows, and organic substances such as foul-smelling gases are removed.
It comes into contact with the photocatalysts 21 to 27 of the three-dimensional porous body excited by the ultraviolet rays from the ultraviolet lamps 28 and 29, and is decomposed.

In other words, odor-causing substances such as ammonia, nitrogen compounds of amines, hydrogen sulfide, sulfur compounds of mercaptans,
Aldehydes, ketones, alcohols, fatty acids, and aromatic compounds are oxidatively decomposed into carbon dioxide, water, nitrogen oxides, sulfur compounds, etc. The deodorized air is then discharged from the blow-off grille 38. FIG. 7 is a longitudinal sectional view of a comparative example of a deodorizing device using a photocatalyst. 45 and 46 are ultraviolet lamps, 47 are sockets for the ultraviolet lamps, 43 and 44 are cylindrical flat photocatalysts installed parallel to the flow of foul-smelling air and parallel to the ultraviolet lamps, and 42 is a dust collector. A pre-filter, 48 and 49 are sirocco fans, 50 and 51 are motors for the fans, 52 is a suction grill, and 53 is a blowout grill. Further, 55 to 57 are guide plates that guide malodorous air to the photocatalysts 43 and 44. The photocatalysts 43 and 44
is made of the same catalyst as the flat catalyst compared in Example 1,
Both have a diameter of 150+nm x a length of 40011111, and the total catalyst area is 3770 cJ. Also, ultraviolet lamp 45.4
6 is a germicidal lamp GL-15 (wavelength 2) with a power consumption of 15W.
Two ultraviolet rays (53.7 nm, ultraviolet output 3.2 W) were used.

Here, the acetaldehyde and hydrogen sulfide decomposition performance of the above two deodorizing devices was measured by the following method. The deodorizing device of the embodiment of the present invention is placed in an aluminum box having an internal volume of 1 d. Then, acetaldehyde is injected into this box and the initial concentration is adjusted to about 7 ppm. Next, the ultraviolet lamps 28 and 29 are turned on, the motors 33 and 34 are turned on, and the cross flow fans 31 and 32 are turned on to blow ft1 of air.
．． 5 minutes per minute to start the deodorizing device.

Then, the change in the concentration of acetaldehyde in the box 1d is measured. The concentration was measured by gas chromatography using an FID detector. Next, the hydrogen sulfide decomposition performance was measured. In this case as well, the initial concentration was about 7 ppm, and the concentration was measured by gas chromatography using an FPD detector.

Regarding the deodorizing device shown in FIG. 7 as a comparative example, the decomposition performance of acetaldehyde and hydrogen sulfide was measured using the same method. The results of these measurements are shown in FIG. A-C is a decomposition curve of acetaldehyde/hydrogen sulfide of this example, and B-D is a decomposition curve of acetaldehyde/hydrogen sulfide of a comparative example. The example in which the bad odor flows through the three-dimensional porous photocatalyst is compared to the comparative example in which the odor flows along the cylindrical plate-shaped photocatalyst.
The time required for the concentration to reach 1/10 is reduced by 60 to 70%, and the effect of this example is clear.

Effects of the Invention As is clear from the examples described above, in the first method of deodorizing using a photocatalyst, by making the photocatalyst into a three-dimensional porous body, the contact between the photocatalyst and the foul-smelling gas is extremely improved, and ultraviolet rays are blocked. This allows the decomposition reaction of bad odors to proceed efficiently through photocatalytic action. Furthermore, the second method of deodorizing using a photocatalyst allows a gas containing a bad odor to pass through a porous photocatalyst, thereby making the contact between the photocatalyst and the bad-smelling gas much better than the effect of the first method. The decomposition reaction of bad odors can proceed efficiently through photocatalytic action without blocking ultraviolet rays.

[Brief explanation of the drawing]

Medium, 4, 28, 29, 45, 46... UV lamp.

Claims (2)

[Claims] (1) A deodorizing method using a photocatalyst in which the semiconductor is irradiated with light to activate the semiconductor in the coexistence of a three-dimensional porous body supporting a semiconductor and a gas containing a bad odor. (2) A deodorizing method using a photocatalyst, in which a three-dimensional porous body supporting a semiconductor and a gas containing a bad odor coexist, the gas is passed through the porous body, and the semiconductor is further irradiated with light to activate the semiconductor.