JP2009131751A - Photocatalyst activation device and method of using the same - Google Patents

Abstract

The reaction rate of a photocatalytic reaction is increased.
A photocatalytic activation device includes a photocatalytic layer made of or carrying a photocatalytic material, an excitation light source capable of irradiating light for activating the photocatalytic material of the photocatalytic layer, and a photocatalytic layer. The heating means 16 for heating the contact surface of 10 and the gas to be processed is provided. Thereby, the contact between the photocatalyst and the target gas is improved, and there is an advantage that the reaction can be promoted and the effect can be exhibited in a shorter time.
[Selection] Figure 2

Description

  The present invention relates to a photocatalytic activation device utilizing a photocatalytic reaction and a method of using the same.

The photocatalyst is activated by an excitation light source to cause a photocatalytic reaction, exhibits deodorization / deodorization, antibacterial / sterilization, antifouling / antifogging effects, and is used for malodor removal, air purification, sterilization, sterilization, etc. (Non-Patent Document 1). As reactants that cause a photocatalytic reaction, titanium oxide (TiO ₂ ) is known in addition to semiconductors such as gallium phosphide (GaP) and gallium arsenide (GaAs). In particular, titanium oxide is widely used because it is chemically very stable, does not cause a photolytic reaction, has a relatively small band gap energy, and can absorb and react with ultraviolet rays close to visible light. A deodorizing apparatus has been developed that uses such titanium oxide to irradiate ultraviolet rays to cause a photocatalytic reaction to deodorize a gas to be treated (for example, Patent Documents 1 and 2). As an ultraviolet light source for titanium oxide, a black light, a mercury lamp, an LED, or the like is used, and any light source generates heat according to its type and output.

Conventionally, electrochemical reactions are considered to be independent of temperature, and photoexcitation with ultraviolet light is also considered in the photocatalytic reaction, which is one type thereof. Even if the rate constant of the photocatalytic reaction increases as the temperature rises, the amount of adsorption of the target gas decreases as the temperature rises, so the effect of heating cannot be expected. For this reason, the conventional photocatalyst activation device is provided with a protection mechanism that prevents heat from the heat source and the heating element from propagating to the photocatalyst. Countermeasures against heat have been taken.
JP 2002-98375 A Japanese Patent Laid-Open No. 2006-296811 Nosaka, Nosaka, “Introductory Photocatalyst” Tokyo Books p. 105-106 (2004)

  In recent years, many products using the above-described photocatalytic reaction, in particular, deodorizing and deodorizing effects have appeared. However, since the photocatalytic reaction is a relatively weak reaction and the surface area of the photocatalytic substance is small, an improvement for further improving the deodorizing / deodorizing performance is required. In particular, there is a demand for a structure capable of exhibiting deodorizing / deodorizing performance in a short time so that the effectiveness of such a photocatalyst can be easily understood by the user. In particular, the deodorization rate of the photocatalytic reaction using titanium dioxide, which is widely used, has a problem that it is slower than other deodorization methods such as a cleaning method and an adsorption method. In addition, the deodorization by the titanium dioxide photocatalyst has a problem that the decomposition efficiency decreases as the gas concentration of the target gas decreases.

  The present invention has been made in view of such problems, and a main object of the present invention is to provide a photocatalyst activation device and a method of using the photocatalyst that can perform a photocatalytic reaction more effectively.

  According to the first photocatalytic activation device of the present invention, a photocatalytic layer made of or carrying a photocatalytic substance, an excitation light source capable of irradiating light for activating the photocatalytic substance of the photocatalytic layer, It is a photocatalyst activation apparatus provided with this, Comprising: The heating means for heating the contact surface of the said photocatalyst layer and gas to be processed can be further provided. Thereby, the contact between the photocatalyst and the target gas is improved, and there is an advantage that the reaction can be promoted and the effect can be exhibited in a shorter time.

  According to the second photocatalyst activation device, the heating means can heat the photocatalyst layer and / or the target gas. Thereby, contact with a photocatalyst layer and object gas can be promoted effectively.

  Moreover, according to the 3rd photocatalyst activation device, the temperature control means for controlling the surface temperature of the contact surface heated with the said heating means to the temperature range of 30-120 degreeC can be provided further. Thereby, the reaction between the photocatalyst and the target gas can be further promoted, and the effect of the photocatalytic reaction such as deodorization and deodorization can be exhibited in a short time.

  Furthermore, according to the third photocatalyst activation device, the heat generated by the excitation light source can be used as the heating means. Thus, by using the heat generated by the excitation light source or in combination with other heat sources, a photocatalytic reaction with low power consumption and improved energy efficiency can be realized.

  Furthermore, according to the fourth photocatalyst activation device, the photocatalytic substance can contain titanium oxide. Thereby, as a stable photocatalytic substance, the persistence of the photocatalytic effect can be enhanced.

  Furthermore, according to the method of using the fifth photocatalyst activation device, a photocatalyst layer made of or carrying a photocatalyst material, an excitation light source capable of irradiating light for activating the photocatalyst material of the photocatalyst layer, A method of using a photocatalyst activation device comprising: a step of bringing a gas to be treated into contact with the photocatalyst layer; heating a contact surface between the photocatalyst layer and the gas to be treated; And a step of controlling the surface temperature within a temperature range of 30 to 120 ° C. Thereby, the contact between the photocatalyst and the target gas is improved, and there is an advantage that the reaction can be promoted and the effect can be exhibited in a shorter time.

  Furthermore, according to the sixth method for using the photocatalyst activation device, the method further includes a step of firing the photocatalytic substance in advance at a temperature of 500 to 650 ° C. prior to the step of bringing the gas to be treated into contact with the photocatalyst layer. it can. Thereby, the crystallization of the photocatalytic substance progresses, and the effect of improving the photocatalytic reaction is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a photocatalyst activation device and a method for using the photocatalyst activation device for embodying the technical idea of the present invention. Not specific to anything. Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the constituent members described in the embodiments are not intended to limit the scope of the present invention only to the description unless otherwise specified. It is just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and symbol indicate the same or the same members, and detailed description thereof will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing. In addition, the contents described in some examples and embodiments may be used in other examples and embodiments.

  As described above, the temperature dependence on the reaction rate of the photocatalyst is complicated by the addition of the element of recombination of electrons and holes, and therefore, little research has been conducted focusing on this point. In view of such circumstances, the present inventor has conducted various studies on temperature dependence, and as a result, has found that temperature control is effective in order to improve the photocatalytic reaction, and has achieved the present invention.

  In order to improve the photocatalytic reaction, specifically, to increase the reaction rate, the photocatalytic reaction itself is promoted, or the adsorption of the target gas to the surface of the photocatalytic substance is promoted to increase the reactivity. Can be considered. Regarding the latter, the photocatalytic substance exerts the photocatalytic effect when the target gas is adsorbed, and it is based on the idea that the effects such as deodorization are not sufficiently exhibited when sufficient adsorption is not performed. As a result of the inventors' research, the latter method was found to be effective.

Utilizing this property, it is possible to achieve high efficiency of photocatalyst activation devices such as deodorizing / deodorizing devices, sterilizing devices, and antifouling devices using the decomposition and sterilizing action of organic substances using photocatalytic reactions. Hereinafter, as an embodiment of the present invention, focusing on a deodorizing / air purifying function widely used as a photocatalyst activation device, an example in which the present invention is applied to a malodor purification device that purifies malodor will be described with reference to FIG. This will be described based on the block diagram. The photocatalytic activation device 100 shown in this figure includes a photocatalytic layer 10 made of or carrying a photocatalytic substance, an excitation light source 12 fixed at a position where the photocatalytic layer 10 can be irradiated with light, and an excitation light source 12. It has a drive circuit 14 for driving, a heating means 16 for heating the photocatalyst layer 10, a temperature control means 17 for controlling the temperature of the contact portion, and a power source 18 for driving them.
(Excitation light source 12)

  The excitation light source 12 selects a type that can irradiate the wavelength of excitation light that causes the photocatalytic reaction of the photocatalytic substance according to the selected photocatalytic substance. For example, a light emitting diode (LED), a semiconductor laser (LD), a mercury lamp, a halogen lamp, a black light, a germicidal lamp, or the like can be used. In particular, when used as a heat source to be described later, waste heat can be used efficiently by using the excitation light source 12 having a high calorific value.

If a UV-LED capable of irradiating ultraviolet rays is used, a photocatalyst activation device having low power consumption, long life, and excellent reliability and stability compared to a mercury lamp or the like can be realized. Furthermore, the advantage that the excitation light source 12 including the lighting circuit can be reduced in size by using the LED is also obtained. In particular, the conventional odor purifier using a titanium dioxide photocatalyst used a mercury lamp, black light, etc. as an ultraviolet light source, so its size was about the same as a commercially available air conditioner air cleaner, but its volume can be greatly reduced, Also, because of its long life, maintenance work such as valve replacement can be eliminated. As the emission wavelength of the LED, one that emits light including ultraviolet rays of 360 to 400 nm can be used. The number of light emitting elements such as LEDs may be one, or a large number may be arranged in parallel.
(Photocatalytic substance)

As the photocatalytic substance, a semiconductor-based substance is used, and preferably, a substance having a small effect of elution by a photodissolution reaction and a high effect sustainability is used. Here, titanium oxide was used as a photocatalytic substance having a relatively small band gap energy and capable of being excited by ultraviolet rays close to visible light.
(Titanium oxide)

The reaction mechanism of titanium oxide will be described below. Titanium oxide has three crystal forms: rutile, anatase, and brookite. Brookite is unstable compared to others and it is difficult to synthesize pure crystals. Rutile is widely used as a pigment in paints, and anatase is mainly used as a photocatalyst. Titanium oxide exhibits n-type semiconductivity, and its application to solar energy conversion materials has attracted attention as a material for photoelectrodes and photocatalysts. A general photochemical reaction occurs by photoexcitation of a reaction substrate. On the other hand, the photocatalytic reaction of titanium oxide absorbs light (ultraviolet light) energy over a band gap of about 3 to 3.2 eV, and in the conduction band, the electron (e ⁻ ) Holes (h ⁺ ) are generated.

[Chemical 1]
TiO ₂ + near UV → e ^- (electron) + h ⁺ (holes)

The electrons reduce oxygen to produce superoxide ions (O ²⁻ ). Thereafter, superoxide ions react with moisture to generate hydroxyl radicals through hydrogen peroxide. Holes are also involved in hydroxyl radical generation. This is shown in the following equation.

[Chemical 2]
O ₂ + e ⁻ → O ²⁻
O ^2- + 2H ⁺ → H ₂ O ₂
H ₂ O ₂ + e ⁻ + H ⁺ → OH + H ₂ O
h ⁺ + H ₂ O → OH + OH ⁻

Hydroxyl radicals, superoxide ions, and the like are called active oxygens, and hydroxyl radicals have the highest reactivity and the strongest oxidizing power. For this reason, it decomposes all organic substances into water and carbon dioxide.
(Photocatalyst layer 10)

The photocatalyst material itself is granulated and fired, or the photocatalyst material is supported on other members such as cloth, ceramics, and metal to form the photocatalyst layer 10. For carrying, for example, a binder can be used.
(Drive circuit 14)

The excitation light source 12 is driven by a drive circuit 14. When a fluorescent lamp such as a black light is used as the excitation light source 12, a lighting circuit for the fluorescent lamp is prepared. The drive circuit 14 in the case where an LED is used as the excitation light source 12 can be a switching circuit that turns the LED on / off using an FET or the like. The drive circuit 14 can light the excitation light source 12 in a pulsed manner in addition to continuously lighting the pumping light source 12. For such a pulse lighting application, a semiconductor light emitting element such as an LED is most preferable. Compared with the case of continuous irradiation with ultraviolet light, by performing pulse irradiation, a new reactant can be supplied during the extinguishing time, and the photocatalytic reaction can be performed efficiently. In particular, the adsorption of organic substances on the photocatalyst surface is performed more efficiently when the light is turned off than when it is turned on, and the photolysis is performed in a short time. . The turn-off time is preferably the same as or shorter than the turn-on time. In addition, by reducing the duty ratio, power saving can be achieved, which can be realized even by battery driving. In the case of pulse lighting, for example, a pulse drive circuit included in the drive circuit adjusts the amount of current supplied to the LED and the lighting cycle. Further, PWM control capable of adjusting the duty ratio that defines the LED ON time is performed. The duty ratio is the ratio of the LED irradiation time to the pulse period (lighting time / cycle). For example, the pulse control circuit can change the pulse period from 120 μs to 999 s, can change the current amount per LED element at a maximum of 100 mA, and the timer from 0.5 to 9.5 h at intervals of 0.5 h. This photocatalytic activation device activates a photocatalytic substance by driving an LED with a drive circuit and irradiating the photocatalytic substance with excitation light. The photocatalytic efficiency is improved by adjusting the lighting cycle and the duty ratio.
(Power supply 18)

The drive circuit 14 is connected to a power source 18. The power source 18 may be a primary battery, a secondary battery, or the like when using the excitation light source 12 with low power consumption in addition to a commercial power source. As a result, it is possible to realize a photocatalyst activation device that does not require connection of a power supply line and is easy to handle, and a portable photocatalyst activation device that can be used in a place without power supply equipment. Further, a solar cell can be used as the power source 18. In the daytime, it is possible to drive continuously by day and night by using the ultraviolet light contained in the sunlight to excite light and storing the electric power in the solar cell and using the stored electric power in the nighttime. Needless to say, it is possible to employ a configuration in which either a commercial power source, a storage battery, or a solar cell is used in combination as the power source 18 or these can be switched for use.
(Heating means 16)

  The heating means 16 is supplied with power from the power source 18 and heats the contact surface between the photocatalyst layer 10 and the gas to be processed. An electric heater or the like can be used as such a heating means 16. In the example of FIG. 1, the photocatalyst layer 10 is directly heated by the heating means 16, but the target gas side that contacts the photocatalyst layer surface may be heated. A heat exchanger can be used as such a heating means. Moreover, the heating means for photocatalyst layers which heats a photocatalyst layer, and the heating means for object gas which heats object gas can be provided separately, and these can also be used together. Regardless of the configuration, by heating the contact surface between the photocatalyst layer 10 and the target gas with the heating means 16, adsorption is promoted, and the photocatalytic reaction is efficiently promoted over a wide area. In addition, since heat flow is generated by heating the contact surface or the reaction environment, this also promotes adsorption. That is, if decomposition occurs at the contact portion between the photocatalytic substance and the organic substance, the adsorption of the new organic substance may be hindered due to the influence of the resulting gas. Becomes easy to adsorb. Further, when more organic substances are adsorbed on the photocatalytic substance, the photocatalytic reaction becomes active and the decomposition is promoted. In addition, the malodorous gas can be circulated and purified by the heat flow in a particularly narrow space.

  The driving of the heating unit 16 is controlled by the temperature control unit 17. The temperature control means 17 controls the operation of the heating means 16 so as to maintain the surface temperature of the contact surface within a preferable range. A preferable surface temperature is 30 ° C to 120 ° C, more preferably 50 ° C to 100 ° C, and still more preferably 60 ° C to 80 ° C. By maintaining in this temperature range, the effect of improving the photocatalytic efficiency can be obtained. The main reason for the improvement of the photocatalytic efficiency by such temperature is whether the photocatalytic reaction is promoted by heating or the adsorption of the target gas and the photocatalytic layer on the surface of the contact surface is promoted. It is done. In a long-term decomposition experiment with a visible light responsive photocatalyst using a normal fluorescent lamp conducted by the present inventor, the reaction rate did not change depending on the presence or absence of heating. It is considered that the reaction promotion by heating is not the promotion of the photocatalytic reaction itself but the improvement of contact with the target gas. In particular, since the target gas is thermally vibrated by heating, it is presumed that the target gas is stirred on the surface of the photocatalyst layer on the contact surface, trapped, and the reaction proceeds.

  Furthermore, as a heat source for heating the contact surface, the heat generated by the excitation light source 12 can be used instead of or in addition to the heating means. The excitation light source generally generates heat. In particular, mercury lamps and halogen lamps generate a large amount of heat. Therefore, the heat generated by the excitation light source can be used as it is for heating the photocatalyst layer, which is preferable.

The photocatalyst layer 10 is placed on the stage. In the example of FIG. 1, the photocatalyst layer 10 is fixed on the heating means 16. In addition, you may provide the vibration provision means to vibrate a photocatalyst layer. Thereby, the surface area of the photocatalyst layer and the target of the photocatalytic reaction can be increased, and the photocatalytic reaction can be further promoted. The vibration applying means is a low-frequency vibrator and can vary the frequency from 0 to 300 Hz. By adding fine vibration, the contact probability between the photocatalyst layer and the target of the photocatalytic reaction can be increased, and the photocatalytic reaction can be further promoted. In particular, it is possible to improve the decomposition rate in a low concentration range where it is difficult to decompose and remove organic substances such as malodorous gases.
(Example)

Hereinafter, as an example, using the malodor purification apparatus of FIG. 1, a target gas containing a malodorous substance was sealed, the time change of the concentration of the gas irradiated with ultraviolet rays was measured, and the respective decomposition rates were observed.
(Gas concentration measurement)

Here, a gas detector tube (detector tube type gas measuring device) was used as an instrument for measuring and analyzing the gas concentration. A gas detector tube is a device that measures the concentration of the target gas. The surface of the glass tube is filled with a granular detector that changes color in response to the target gas and is tightly packed into a glass tube with a constant inner diameter. Is printed with a density scale. The detection agent to be filled is coated with each reagent on a granular material such as silica gel or alumina as a desiccant, and the reagent reacts only with the gas to be measured to show a clear discoloration layer and is stable over a long period of time. What is used is used.
(Odorous substance)

In this example, acetaldehyde was used. Acetaldehyde (CH ₃ CHO) is a colorless chemical substance with an irritating odor, has a boiling point of 20.8 ° C. and a melting point of −123.3 ° C., and is synthesized by a method such as ethylene oxidation. It becomes a raw material for producing molecules and the like. Emissions to the atmosphere include acetaldehyde production processes, a substance production process using acetaldehyde as a raw material, automobile exhaust gas, and tobacco smoke. It is designated as a specific malodorous substance as a substance causing bad odor. The concentration at which odor can be detected (detection threshold concentration) is 0.002 ppm, and the concentration range (odor intensity 2.5 to 3.5) that can be established as a regulation standard by the prefectural governor by the Odor Control Act is 0.05 to 0.00. 5 ppm. Moreover, the malodor purification apparatus which introduce | transduces acetaldehyde was set as the structure arrange | positioned in the environment which enclosed target gas in the enclosed space as shown in FIG.

Moreover, anatase type titanium dioxide (TiO ₂ ) PC-500 powder manufactured by MILLENNIUM was used as a photocatalytic substance. Here, as pre-treatment before introduction into the apparatus, granulated by kneading with water and then calcined at 600 ° C. to 900 ° C. and raw powder not calcined were used. Further, three types of commercially available visible light responsive photocatalysts from other companies were used. The particles of the sample thus prepared are microspherical and contain titanium dioxide as a main component. The specific surface area of titanium dioxide decreases as the firing temperature increases. The results of specific surface area measurement by the BET method are as follows: PC-500 raw powder is 265 m ² / g, 600 ° C. calcined sample is 43 m ² / g, 700 ° C. calcined sample is 29 m ² / g, 900 ° C. calcined sample is 4.2 m ² / g, and the visible light responsive photocatalyst was 89 m ² / g. About 0.13 g of each photocatalyst thus obtained was placed in a stainless steel dish having an inner diameter of 60 mm, dispersed in water, and dried at 100 ° C.

As shown in FIG. 1, the heating means 16 has a heater and a heat insulating layer attached to the lower part of the stainless steel petri dish. The heater is connected to the temperature control means 17 and controls the heater so that the temperature of the bottom surface of the stainless steel dish, that is, the photocatalyst layer is 30 to 100 ° C. Moreover, the heat insulation layer was comprised with the material which hardly has gas adsorption | suction. The heating means 16 was sealed in a gas bag and filled with 5 L of clean air. Furthermore, a small amount of concentrated gas was injected so as to be a predetermined gas concentration or more, and after confirming that the gas was uniformly diffused, the decomposition rate by the photocatalyst was examined. Black light was used for ultraviolet irradiation, and the photocatalyst layer was adjusted so that the ultraviolet intensity of the photocatalyst layer was 1 mW / cm ² . Further, in the visible light irradiation experiment of FIG. 7 described later, a fluorescent lamp of 500 Lux and ultraviolet rays of 40-50 μW / cm ² was used.

The acetaldehyde used as the test gas is diluted with air using a test gas preparation tedlar bag to produce acetaldehyde gas, and this concentrated gas is diluted to a concentration according to the purpose, or directly injected into the tedlar bag for treatment. The previous gas was used.
(Example 1)

As described above, first, titanium dioxide without pretreatment (PC-500 raw powder) was used as Example 1, and the surface temperature was set to 20 ° C, 30 ° C, 40 ° C, 60 ° C, 80 ° C, 100 ° C. The graph of FIG. 2 shows the results of measuring the time-dependent change in concentration for each of the set six types by decomposing acetaldehyde. As shown in this figure, the decomposition rate of acetaldehyde was remarkably improved even at a slight temperature increase of 30 ° C. or 40 ° C., compared with the decomposition rate of 20 ° C. Thereafter, although the decomposition rate was improved up to 80 ° C., it decreased to 100 ° C. to the same extent as in the case of 40 ° C. From this, it can be seen that a particularly high decomposition rate can be obtained at a surface temperature of about 30 ° C to 100 ° C.
(Example 2)

In order to further confirm the phenomenon in which the decomposition rate decreases when the surface temperature becomes too high, Example 2 is a pretreatment of titanium dioxide that was fired at 600 ° C. to 900 ° C., and was not fired. The result of measuring the acetaldehyde decomposition at room temperature (20 ° C.) in the same manner using the raw powder is shown in the graph of FIG. From this graph, titanium dioxide fired at 600 ° C. showed the best decomposition rate. Moreover, about 700-800 degreeC showed the decomposition rate similar to a raw powder, On the other hand, what decomposed | disassembled the thing burned at 900 degreeC fell obviously. The reason for this is considered to be that when the firing temperature of titanium dioxide is increased, the surface is smoothed, the specific surface area is reduced, and the adsorption of the target gas is inhibited, so that the reactivity is lowered. For this reason, it can be said that the firing temperature is preferably about 500 to 700 ° C. Also, the reason why the decomposition rate was increased as compared with the raw powder by firing is presumed that the crystallization of the photocatalytic substance has progressed and the photocatalytic reaction has been improved.
(Reference Example 1)

Here, in order to distinguish the influence of adsorption on the surface of titanium dioxide, the results of Reference Example 1 in which an experiment similar to Example 1 was performed using titanium dioxide powder with different firing temperatures are shown in FIGS. Show. In these figures, FIG. 4 uses titanium dioxide powder at a firing temperature of 600 ° C., FIG. 5 at 800 ° C., and FIG. 6 at 900 ° C. From these figures, the highest decomposition rate was obtained when the firing temperature was 600 ° C., and the decomposition rate decreased as it increased to 800 ° C. and 900 ° C. Even when the firing temperature was 900 ° C., the improvement effect by heating was smaller than that in the case of FIG. 2, but the improvement tendency by the surface temperature could be confirmed. Considering the specific surface area of the powder and raw powder at such a firing temperature, the reason why the decomposition rate increases due to the temperature rise is not the idea of adsorption equilibrium, but the molecular motion of the gas becomes active, and the titanium dioxide surface This is presumed to be due to an increase in temporary acquisition opportunities. In addition, when the temperature of titanium dioxide is 100 ° C. or more, the decomposition rate is decreased because the molecular motion becomes too active and the trapping power is decreased. In the present inventors' test, such a phenomenon becomes remarkable when the surface temperature is higher than 120 ° C.
(Example 3)

In the first place, the cause of the phenomenon that the decomposition reaction is accelerated by the surface temperature is considered to be because the photocatalytic reaction itself is promoted in addition to the increase in the amount of adsorption of the target gas on the contact surface. If the photocatalytic reaction itself is accelerated, it is presumed that the reactivity is improved also in the case of a visible light responsive photocatalyst. Then, as Example 3, the result of having performed a decomposition experiment of acetaldehyde using a visible light responsive photocatalyst and strong visible light (500 Lux, ultraviolet ray 40-50 μW / cm ² ) by a fluorescent lamp is shown in FIG. In this figure, the measurement at 60 ° C. is performed twice. As is apparent from this figure, the decomposition rate at 60 ° C. to 80 ° C. was comparable to that at 20 ° C. From this, it is considered that the temperature rise does not relate to either the photocatalytic reaction rate or the adsorption amount change.
(Reference Example 2)

However, the experiment of FIG. 7 is considered to be an experiment in which the reaction time is longer than in the case of FIG. In order to confirm this point, as Reference Example 2, the result of performing ultraviolet irradiation (1 mW / cm ² ) on the visible light responsive photocatalyst is shown in FIG. This result is almost the same as that shown in FIG. 2, and a noticeable speed-up was also observed in the visible light responsive photocatalyst. From this, it can be concluded that the reason why the decomposition rate of acetaldehyde was increased by the temperature rise was not the photocatalytic reaction was accelerated, but a phenomenon related to adsorption.
Example 4

  If the above idea is applied to photocatalytic reactions with different gas concentrations, it is expected that the temperature effect will appear more conspicuously at a low concentration at which the adsorption is slower than at a high concentration at which the adsorption is performed quickly. In order to confirm this, the results of measuring the decomposition rate with the titanium dioxide raw powder in Example 4 when the acetaldehyde concentration was high (200 ppm), medium (100 ppm), and low (20 ppm) were obtained. These are shown in FIGS. 9 to 11, respectively. As is clear from these figures, it is confirmed that the decomposition rate is improved by heating at all of the high concentration, medium concentration and low concentration, and the improvement of the decomposition rate is remarkable in the low concentration region, particularly less than 4 ppm. did it.

  As described above, it has been confirmed that the target gas can be decomposed at a rate several times higher than usual by heating the surface of the titanium dioxide photocatalyst, thereby demonstrating the usefulness of the present invention. The effect becomes more significant as the concentration of the target gas decreases, and is extremely effective for gas decomposition at a practical level such as a living space. Furthermore, since the heat flow is generated by heating the titanium dioxide photocatalyst, the odor gas can be circulated and purified by the heat flow in a narrow space.

  The photocatalyst activation device and the method of using the same of the present invention are not limited to deodorization / deodorization devices, and can be suitably applied to sterilization devices, antifouling devices, and the like.

It is a block diagram which shows the photocatalyst activation device which concerns on embodiment of this invention. In the titanium dioxide photocatalytic reaction which concerns on Example 1, it is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration by making surface temperature into 20 to 100 degreeC. In the titanium dioxide photocatalytic reaction which concerns on Example 2, it is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration when a calcination temperature shall be 600 to 900 degreeC or no pretreatment. It is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration by making surface temperature 25 to 80 degreeC in the titanium dioxide photocatalytic reaction which made the calcination temperature which concerns on the reference example 1 600 degreeC. It is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration by making surface temperature 25 to 80 degreeC in the titanium dioxide photocatalytic reaction which made the calcination temperature which concerns on the reference example 1 800 degreeC. It is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration by making surface temperature 25 to 100 degreeC in the titanium dioxide photocatalytic reaction which made the calcination temperature which concerns on the reference example 1 900 degreeC. It is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration by irradiating visible light with the surface temperature of 20 to 80 degreeC in the photocatalytic reaction of the visible light response type photocatalyst concerning Example 3. FIG. It is a graph which shows the result of having measured the time change of the acetaldehyde density | concentration by irradiating an ultraviolet-ray by making surface temperature into 24 to 80 degreeC in the photocatalytic reaction of the visible light response type photocatalyst concerning the reference example 2. FIG. It is a graph which shows the result of having measured the time change of the density | concentration when acetaldehyde density | concentration is made into high density | concentration and surface temperature shall be 25 degreeC-80 degreeC in the titanium dioxide photocatalytic reaction without the pretreatment which concerns on Example 4. FIG. It is a graph which shows the result of having measured the time change of the density | concentration when the acetaldehyde density | concentration is made into medium density | concentration and the surface temperature shall be 25 to 80 degreeC in the titanium dioxide photocatalytic reaction without the pretreatment which concerns on Example 4. FIG. It is a graph which shows the result of having measured the time change of the density | concentration when the acetaldehyde density | concentration is made into a low density | concentration and the surface temperature shall be 25 to 80 degreeC in the titanium dioxide photocatalytic reaction without the pretreatment which concerns on Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Photocatalyst activation apparatus 10 ... Photocatalyst layer 12 ... Excitation light source 14 ... Drive circuit 16 ... Heating means 17 ... Temperature control means 18 ... Power supply

Claims (7)

A photocatalytic layer made of or carrying a photocatalytic material;
An excitation light source capable of irradiating light for activating the photocatalytic substance of the photocatalytic layer;
A photocatalytic activation device comprising:
A photocatalyst activation device comprising heating means for heating a contact surface between the photocatalyst layer and a gas to be treated. In the photocatalyst activation device according to claim 1,
The photocatalyst activation device, wherein the heating means heats the photocatalyst layer and / or the target gas. In the photocatalyst activation device according to claim 1 or 2, further,
A photocatalyst activation device comprising temperature control means for controlling the surface temperature of the contact surface heated by the heating means to a temperature range of 30 to 120 ° C. In the photocatalyst activation device according to any one of claims 1 to 3,
A photocatalyst activation device using heat generated by the excitation light source as the heating means. In the photocatalyst activation device according to any one of claims 1 to 4,
The photocatalyst activation apparatus characterized in that the photocatalytic substance contains titanium oxide. A photocatalytic layer made of or carrying a photocatalytic material;
An excitation light source capable of irradiating light for activating the photocatalytic substance of the photocatalytic layer;
Using a photocatalyst activation device comprising:
Contacting the photocatalyst layer with a gas to be treated;
Heating the contact surface between the photocatalyst layer and the gas to be treated, and controlling the surface temperature of the contact surface to a temperature range of 30 to 120 ° C .;
A method of using a photocatalyst activation device comprising: The method of using the photocatalytic activation device according to claim 6, further comprising:
Prior to the step of bringing the gas to be treated into contact with the photocatalyst layer, the method for producing a photocatalyst activation device includes a step of firing a photocatalyst substance at a temperature of 500 to 700 ° C. in advance.

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