JP2000325452A - Energy saving type air purifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose harmful substances in air in a working area, and improve the environment of a living space by an inexpensive device by providing a catalyst the major component of which is titanium oxide, and which is activat ed by a noble metal, or the like, a low-powdered light source, and a power source of a small capacity to make the light source emit light. SOLUTION: This device decomposes and detoxifies harmful substances in air using a catalyst the major component of which is titanium oxide, and which is activated by a noble metal by optically activating it, and the air purifier is constituted by providing a low-powered light source to optically activate the catalyst, and a power source to make the light source emit light. For example, a cylindrical catalyst case both ends of which are open is manufactured from an aluminum pipe or a square pipe the wall surface of which is a mesh- form, and an LED is attached on the internal surface. Then, the purifier is stood at the corner in a room, and by the draft action together with the excitation of the catalyst, contaminated air in the room is convection-circulated through the inside of the case. Then, when the outside is bright, the purifying action is displayed on the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a device for purifying air inside a living room or an automobile or the like in an urban area or the like, in particular, a photo-activated catalyst mainly composed of titanium oxide and activated by a noble metal. The present invention relates to an apparatus for decomposing and detoxifying harmful substances in air.

[0002]

2. Description of the Related Art In general, the outside air at intersections of busy city areas and the air in residential areas near roads are contaminated with many organic and inorganic harmful substances. Their main thing for example, ozone O _3: 300ppb~500ppb carbon monoxide CO: 5,000ppb~20ppm olefins such _{C n H 2n (n = 2~20} ): 400ppb~3000ppb nitrogen oxides NOx: 500ppb~10ppm etc. , still, on the order of 20Ppb～50ppb, aldehyde R-CHO ether CH ₂ -O-CH ₂ butylene C ₄ H ₈ ketones RCOR methane CH ₄ methyl alcohol CH ₃ OH ethylene -CH ₂ - and the like are detected .

[0003] These substances are harmful to health and cause various allergic symptoms, asthma, lung cancer and the like. Therefore, it is necessary to detoxify them. It only captures airborne dust in the air, and those that can decompose and remove these harmful gases include those that require large amounts of power and devices that use sunlight. However, no other low-energy process has been proposed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inexpensive and safe consumer that can be used to decompose harmful substances in the air in a person's room or work place and improve the environment of living space. An object of the present invention is to provide an air purification device for use in a vehicle.

For the purpose of removing harmful gases as described above,
Catalysts commonly used industrially or for vehicle exhaust
As, Au, Pa, Pt, Rn, Ru, Ti, Mn, Cu, W, Al,
Zr, Ce, Tb, Sm, Er, La, Dy, etc. and these oxides
Some CuO, TiO_Two, WO_Three, Mn _TwoO_Three, Mn₈O₁₆, A1_TwoO_Three, Z
rO_Two, MnO_Two, Ce_TwoO_Three, Tb_TwoO_Three, Sm_TwoO_Three, Er_TwoO_Three, La_TwoO
_Three, Dy_TwoO_ThreeAre known, and these are suitable for the purpose of use.
Together, alone or in combination, and as needed
It is used by being activated by electromagnetic waves.

As particularly useful prior arts, a TiO ₂ photocatalyst was announced in 1972 and a noble metal activated photocatalyst was announced in 1979. These applied technologies were also shared with solid carbon in 1980, and carbohydrates were used. Decomposition of proteins in 1980
The decomposition of fatty polymers was published in 1981, respectively. In particular, activation by metal particles having a size in the range of 1 to 10 nm and various methods for producing TiO ₂ are also known. Combination with other Ag and rare earth, further WO ₃ system, Fe ₂ O ₃ system, CdS
Many combinations, such as a system and a MoS system, have also been announced. These are all technologies that became known in the 1980s.

[0007]

SUMMARY OF THE INVENTION An energy-saving air purifying apparatus according to the present invention comprises a catalyst mainly composed of titanium oxide and activated by a noble metal or the like, and a low electric power for photoactivating the catalyst. It has a light source and a small-capacity power supply for causing the light source to emit light. Although there is no particular limitation on the area of the catalyst, is usually 500 cm ² or more, 10000 cm ² or less, preferably 1000 cm ² or more, and 5000 cm ² or less. The driving power of the light source catalyst 1 cm ² per 10μW above, 15W or less, preferably catalyst 1 cm ² per 10μW or more and less 100 .mu.W. If the area of the catalyst is 1000 cm ² or less, the purifying ability is too small, but if it is 10,000 cm ² or more, the thickness of the sheet required to obtain the required strength is usually too large. When purifying a large volume of air, it is preferable to use a plurality of the above sizes rather than one large volume. That is, if the device is large,
This is because the increase in the internal capacity of the device is larger than the catalyst area, and the contact efficiency of the catalyst is relatively reduced.
Also, when a granular catalyst is used, if the size is larger than the above, the air resistance increases, so it is desirable to keep the above-mentioned limit. Further, the catalyst 1 cm ² per the driving power of the light source
If the power is set to 10 μW or less, the processing capacity is excessively reduced, which is inappropriate. However, if the power is set to 15 mW or more, the harmful substance concentration does not decrease so much, and the required power is wasted. It is recommended to use a semiconductor light emitting element such as an LED, an LSD, and an LD as a light source. The reason is that when the light source is turned on and off, the life of other light sources is shortened. This is because the semiconductor light source has an extremely long life even when used under such usage conditions, has an appropriate wavelength, is highly efficient, and easily controls high-frequency light emission.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The catalyst used will be described below. For example, a photocatalyst such as TiO ₂ causes a decomposition reaction by irradiating an electromagnetic wave so that an oxidation potential and a reduction potential of molecules oxidized and decomposed exist between the band gaps of a semiconductor. This is because the electrons of atoms in the valence band of the catalyst are excited and transit to the conduction band, leaving holes in the valence band. Then, a pair of an electron and a hole is generated in the catalyst, and the electron and the hole move in the semiconductor TiO ₂ ,
Electrons are present as (O ₂ ⁻ ) (O ₂ ⁻ ) on the catalyst surface,
Oxide ion and hydroxyl radical (O
H ⁺ ), which acts as a reducing agent and a strong oxide, reacts directly with the organic matter, and reacts with the organic matter CC, CH, C-Cl, H
Reacts with -Cl and the like, causing decomposition reaction of organic substances. The series of actions is like this, but what should be noted here is: 1. Problem of lattice plane defect of TiO ₂ catalyst _2. Problems of many lattice point defects of TiO ₂ catalyst. _3. Problem of uneven crystal size of TiO ₂ catalyst It is about the problem of recombination of electrons and holes.

Here, if the electrons and holes recombine, no decomposing action occurs, and the catalyst becomes extremely inefficient. It is required that both oxidation-reduction reactions occur simultaneously in one catalyst particle. Although these seem at first glance to be contradictory, the above-mentioned problems 1 to 3 can be solved by obtaining a fine catalyst TiO ₂ having a particle size of about 0.1 to 10 nm, and defects can be prevented. This is made possible by forming a size of perfect crystallization. For example, even in the case of precipitation by hydrolysis, complete crystallization can be achieved by precisely controlling the decomposition rate.

First, a polynuclear complex ion solution having Ti chloride ions is used as a starting material to obtain 0.025 mol / liter of Ti.
C ₄ is hydrolyzed at 70 ° C. for 24 hours, urea is added at pH 6.5 and polycondensed to form a colloid nucleus. The particle shape is cubic anatase, and the average particle size is 10 nm (according to the electron microscope image), causing strong interaction between the particles, but the primary particles containing chlorine are mainly agglomerated. The particles are formed in a state where the force for reducing the energy of the particles and the interfacial tension are balanced.

Therefore, it is necessary that the pH of the final concentrated liquid obtained by lowering the concentration of titanium chloride in cubic grain anatase and raising the production temperature be 1-2. Under these conditions, mononuclear hydroxo complex
Form Ti-O-Ti, wash with water, dry and pulverize, fine Ti
Get the O ₂ particles. K ₂ PtC ₆ with TiO ₂ in methanol aqueous solution
Suspend so that the ratio of Pt is 1: 1 by weight, and
While irradiating 276nm light, 100kHz, 6 as stirrer
Irradiation with ultrasonic waves of 0 W (0.1 W / cm ² ) was performed with strong stirring to precipitate Pt on the surface of the titanium oxide particles.

As a result, Pt was deposited on the surface of the TiO ₂ particles having a particle size of 10 nm to form a TiO ₂ Pt catalyst. Pt size is T
The order of 1 nm is about 1/10 of that of SiO ₂ , and Pt particles are Ti
About 10 particles could be adhered to the O ₂ particle surface. The catalyst particles are again kneaded with water, extruded from a nozzle having a diameter of 1 mm, cut into a length of 1 mm, formed into a pyret, dried, and sintered at 300 ° C. for 3 hours to have a surface area of about 300 to 400 m ² / g. A granular titanium oxide catalyst was obtained. Note that, in the above description, the object to be processed is granulated in order to improve the flow of the object, but it is needless to say that the object can be formed into a film shape, a plate shape, a scaly shape, or the like. It is also free to use a mixed crystal of TiO ₂ and SiO ₂ or to use the photoexcitation effect of rare earth.

Finally, the problem of electron-hole bonding in the crystal becomes a very important performance as a catalyst. Of course, the retention time varies depending on the depth of the reaction. Considering this point, if the catalyst surface is exposed to electromagnetic waves, reactants generated on the surface are not replenished from the inside, and if the emission rate of electrons and holes is Q,

[0014]

(Equation 1)

If τ is fixed here,

(Equation 2) This shows that the electron and hole emission rates decrease with a time constant.

In practice, the space where the solid surface is exposed to the electromagnetic wave differs when the electron and hole emission layers are multilayered. Since the activation energy of the catalyst changes depending on the amount of emission,

(Equation 3) Becomes

Therefore, when considering the vibration of molecules, it greatly varies depending on the state of crystal formation. On average, however, the time spent on the surface of the electron hole is 10 ⁻² to 10 −10.
^-3 ,

(Equation 4)

Therefore, if the temperature rises from 20 ° C. to 100 ° C., the residence time of the electrons and holes will be from 10 ⁻¹ second to 10 ⁻³ to 10 ⁻³ .
Since it is considered to be about 10 ⁻⁴ seconds, it is recommended that the repetition period of photoexcitation be changed according to the temperature and the residence time of electrons and holes.

The reason why the electromagnetic wave irradiation is pulsed is to operate with lower power. Since the desired repetition frequency of pulse irradiation depends on the temperature T, it is desirable that the pulse irradiation be controlled efficiently as a function of the temperature.

Semiconductor light emitting devices such as LEDs, SLDs, and LDs are advantageous for switching control of the repetition frequency of electromagnetic wave irradiation, and LEDs having a wavelength of about 400 to 430 nm are particularly effective. The output efficiency of electromagnetic waves is 91 cd /
LED is 300 cd / W, which is about 3 times higher than W. Further, when a pulse with a duty factor of about 10%, that is, an on / off ratio of 1: 9, so that electrons and holes are always present, the LED becomes 3000 cd / W, which is about 30 times,
Efficiency is greatly improved. Moreover, according to pulsed irradiation,
Further, the electromagnetic wave density can be increased.

Thus, according to the present invention, the prior art
30 times or more of the efficiency can be obtained. Also,
Speaking of deodorization, odor intensity is I, concentration of odorous substance
To C ₀given that,

(Equation 5) Therefore, deodorization requires a logarithmic catalysis.

[0022]

[Example 1] [Example 1] A tubular catalyst case having both ends opened by an aluminum tube or a square tube having a net-like wall was manufactured, LEDs were mounted on the inner surface, and the LED was mounted on a corner in the room. When the catalyst is excited, the draft action causes contaminated air in the room to convectively circulate through the interior of the case. When the outside is bright, the purifying action is performed on the outside.

For this reason, the upper opening of the case is arranged at a position lower than the ceiling by about 30 cm, and the lower end is arranged so that the suction port comes at a position higher by about 50 cm than the floor surface. In some cases, a bimorph fan of about 0.05 W is inserted into the case to circulate air.

TiO ₂ PtEr catalyst was applied to the inner surface of a cylindrical case having a mesh wall having an inner diameter of 10 cm and a length of 1.5 m with respect to 3000 cm ² .
g at the rate of 430nm, 3cd LED inside
Are arranged to emit light in a pulsed manner. Floor
It was installed vertically in a room with a 10m x 5m ceiling height of 2.3m, the on-time was set to 0.8msec, the off-time was set to 10msec, and a current of 3.1V, 42mA at a peak value was passed, and the lamp was turned on in a pulse shape. Insert a 3.2V, 0.03W fan into the case, with a capacity of 12.6AH
, And room air of 0.5 m ³ / min was flowed into the case and circulated.

Of particular interest was measured NOx, which is decomposed by its reaction.

Embedded image

As a result of the measurement, the NOx concentration at the entrance of the case was reduced from 11 ppm to 7 ppm at the exit, and after continuous operation for about 41 hours, the average NOx concentration in the entire room became 1.1 ppm. Further, it was also found that the final concentration reached about 10% or less of the removal of various other olefins and O ₃ . Room temperature averaged 26 ° C and humidity was 60%. still,
The room faces an intersection with an average of 140,000 vehicles passing through the city each day. Four people lived normally and were allowed to enter and exit freely.

The above lithium secondary battery was able to be driven without recharging for 10 consecutive days. When a solar cell was used together as an auxiliary power source, it could be used for one month continuously. In both cases, it was proved that the harmful substances could be removed up to about 1/10 of the original concentration almost in the same manner as described above.

Example 2 The above-mentioned finely divided catalyst was mixed with a porous fluororesin so as to have a weight ratio of 50%, kneaded and rolled to form a sheet having a thickness of 0.1 mm.
by molding the m ² attached to 5cm position than the portion of the outdoor lights,
When the catalyst is activated by the light while the external light is lit at night and by sunlight during the day, the average of one day and night is 0.42 μmol / c.
The generation of m ² · h nitric acid was detected. In the case of an outside light, it can be used without a power source on an expressway, an urban road in a traffic congestion area, inside a tunnel, and the like, but it is advantageous to use the solar cell together. It is also effective to incorporate it into the noise barrier of the road.

When mounted on a reflector such as an indoor light or a fluorescent light, these can be used without power supply. In this case, of course, the combined use with a solar cell is effective. The shape of the catalyst can be arbitrarily designed. Furthermore, if a meter for measuring the conductivity, an automatic lighting switch, a buzzer, and the like are attached so that the reaction state can be verified, it can be used more effectively.

This catalyst has a decomposing effect on dioxins, which can be decomposed into chlorides, borides and oxides. It is also effective for CO gas due to incomplete combustion. In this case, a combination in which exhaust gas is washed with water is advantageous. Further, it can be used as a gas mask, and can have a sterilizing action and a deodorizing action even in hospitals and the like. These are extremely effective because they can be driven continuously for one month or more even with a small battery drive.

[0031]

Industrial Applicability The present invention is highly effective as a device capable of decomposing organic substances and the like with very low energy at a high efficiency, decomposing harmful substances in indoor and outdoor air little by little, and purifying continuously. Wide range of applications.

Claims (10)

[Claims] An energy-saving air purification system comprising a catalyst mainly composed of titanium oxide and activated by a noble metal, a low-power light source for photoactivating the catalyst, and a power supply for causing the light source to emit light. apparatus. 2. The driving power of the light source is 10 μm / cm ^{2 of the} catalyst.
2. The air purification device according to claim 1, wherein the air purification device is not less than W and not more than 15 mW. 3. The air purification device according to claim 1, wherein the light source is a semiconductor light emitting device. 4. The air purifying apparatus according to claim 1, wherein the power supply is a pulse power supply. 5. The air purifying apparatus according to claim 1, wherein the repetition frequency of the pulse of the power supply is changed according to the temperature. 6. The catalyst is formed in a tubular shape with both ends open, a light source is disposed inside the simple catalyst, and the tubular catalyst is installed and used so as to cause convection inside and outside thereof.
An air purification device according to any one of claims 1 to 5. 7. The air purification device according to claim 6, wherein a low-energy fan is provided inside the tubular catalyst. 8. The air purification device according to claim 6, wherein a filter is provided in an air intake of the cylindrical catalyst. 9. The air purification device according to claim 1, wherein the catalyst is photoactivated from both front and back surfaces. 10. An air purification device comprising a catalyst mainly composed of titanium oxide and activated by a noble metal, provided on the surface of a reflector of an illumination lamp.