JP4038877B2 - Photocatalyst for air purification - Google Patents
Photocatalyst for air purification Download PDFInfo
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- JP4038877B2 JP4038877B2 JP14089798A JP14089798A JP4038877B2 JP 4038877 B2 JP4038877 B2 JP 4038877B2 JP 14089798 A JP14089798 A JP 14089798A JP 14089798 A JP14089798 A JP 14089798A JP 4038877 B2 JP4038877 B2 JP 4038877B2
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- photocatalyst
- adsorbent
- air purification
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- Disinfection, Sterilisation Or Deodorisation Of Air (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、空気中の炭化水素、窒素化合物、硫黄化合物などの悪臭物質を吸着する吸着剤と、紫外線を当てることによってそれらを酸化分解する光触媒とを組み合わせた空気浄化用光触媒体に関するものであり、特に吸着剤と光触媒の混合比を重視した空気浄化用光触媒体に関するものである。
【０００２】
【従来の技術】
空気浄化用光触媒体は、酸化チタンなどの光触媒を単独で使用したものが一般的であり、その構成や接合方法を工夫したものが従来から種々提案されている。しかしながら光触媒を単独で使用したものでは、分解速度が遅いため悪臭物質をすぐに除去するのには不向きである。
【０００３】
また、その中で最近、光触媒と吸着剤を組み合わせたハイブリッド型の吸着再生型脱臭を行うという空気浄化用光触媒体の提案がある。しかしながら、この空気浄化用光触媒体は、吸着剤と光触媒を単純に混ぜ合わせただけのものであり、悪臭物質が吸着剤に吸着した後、表面拡散により光触媒へ移動し紫外線を照射することで悪臭物質を分解するものである。
【０００４】
【発明が解決しようとする課題】
しかしながら、前記従来の空気浄化用光触媒体は、吸着剤の比表面積が大きい活性炭を使用すれば、その吸着力が強すぎて光触媒によって再生されない。さらに吸着剤と光触媒を単純に混ぜ合わせただけのものであり、吸着剤の量と光触媒の量が適当でないため、その作用が十分ではなく吸着物質が吸着剤に吸着したままの状態になりやすく、使用を続けると、吸着剤の劣化が起こり元に戻らないという課題を有していた。そのためその使用は永久的ではなく、結果的に空気浄化用光触媒体の交換をしなければ使用できなかった。
【０００５】
【課題を解決するための手段】
本発明は上記課題を解決するためのものであり、吸着剤の比表面積を限定し、さらに吸着剤と光触媒の量を調整することで吸着剤の劣化を防ぐものである。粉末状の光触媒と粉末状の吸着剤を混ぜ合わせるときに、光触媒の量を多くなるように調製された空気浄化用光触媒体とした。
【０００６】
上記発明によれば、吸着剤によって吸着された悪臭物質が光触媒の効果によって効率よく分解されるように、吸着剤を比表面積の小さい方に限定し、粉末状の光触媒の量と粉末状の吸着剤の量を最適化したため、光触媒によって分解される悪臭物質の量が増加し、吸着剤に吸着されたままの悪臭物質の残存量が少なくなり、吸着剤を再生させることができる。これを繰り返すことで永久的に使用することができる。
【０００７】
この効果を詳細に説明する。一般的に吸着剤は悪臭物質と同時に水も吸着することができる。一方、光触媒は紫外線を照射することによって励起され、その表面に正孔が生じる。この正孔は＋３．０Ｖという非常に高い酸化電位を持ち、さまざまな化合物を酸化することができる。この光触媒の表面にはわずかでも水が存在すれば、その水が光励起でできた正孔と反応して水酸ラジカルを生じる。この水酸ラジカルは短寿命ではあるが、いろいろなものを酸化できる活性化学種である。この水酸ラジカルは、有機化合物と反応すると最終的には二酸化炭素と水に分解される訳である。つまり光触媒の表面には水が必要となる訳である。本発明では光触媒と吸着剤を適度に混合することによって、その水をより効率よく光触媒の表面にもってくることができるようにした。
【０００８】
一方、光触媒と吸着剤の混合物において、吸着剤に吸着された物質は表面拡散により、光触媒上に移動し分解される。しかし、光触媒の量と吸着剤の量を最適なものにしなければ、この表面拡散は起こらず吸着物質が吸着剤に残ったままになる。この表面拡散を起こりやすくするためには、吸着剤と光触媒との間で吸着物質の濃度勾配が大きくなければならない。
【０００９】
例えば、同じ量の吸着物質を同じ空間で分解することにする。一方で、吸着剤が多ければ広い空間に吸着物質が吸着され、光触媒との濃度勾配は小さい。他方、吸着剤が少なければ狭い空間に多くの吸着物質が吸着され、光触媒との間の濃度勾配は大きくなる。このことから、吸着剤の再生を最適にする条件は、光触媒が吸着剤よりも多いことが条件となる。
【００１０】
すなわち、光触媒の効果により吸着されていた物質は徐々に分解されるため、吸着剤の吸着効果が復活する。結果としてこの空気浄化用光触媒体は、永久的に吸着再生を繰り返すことができる訳である。
【００１１】
【発明の実施の形態】
請求項１記載の発明は、酸化チタン、酸化タングステン、酸化亜鉛、酸化鉄または酸化バナジウムから成る粉末状光触媒粒子と、比表面積が３００ｍ２／ｇ以下の粉末状活性炭とを混合してなり、前記光触媒粒子の重量をＷｔ、前記粉末状活性炭の重量をＷａとし、その比をＷｔ／Ｗａとした場合、３／２≦Ｗｔ／Ｗａ≦４となるように混合した空気浄化用光触媒体である。
【００１２】
そして、粉末状光触媒粒子と粉末状吸着剤の混合する割合を最適化することにより、吸着剤に吸着する吸着物質が速やかに光触媒粒子の作用によって分解されるようにした。しかも吸着剤としての活性炭は比表面積の小さいものを使用しているので、吸着した物質を脱着しやすいようにしている。
【００１３】
さらに、粉末状吸着剤として活性炭を使用すると、悪臭物質の吸着速度が速いため速やかに脱臭ができる。しかも、活性炭は悪臭物質と同時に空気中の水分も吸着することができ、この水分は光触媒にとって非常に有効に働くことができるため、光触媒による再生を一層高めることができる。
【００１４】
【実施例】
以下、本発明の実施例について説明する。
【００１５】
（実施例１）
本実施例１の空気浄化用光触媒体の製造法について説明する。まず、粉末状光触媒粒子として粉末状の酸化チタンを準備し、さらに比表面積が３００ｍ２／ｇ以下の粉末状吸着剤として粉末状活性炭を準備し、それらを混合して空気浄化用吸着剤混合型光触媒体を形成する。
【００１６】
本発明の効果を判定するため、次の実験を行った。前記製造方法による光触媒と吸着剤の混合比を一定にした上で、吸着剤として活性炭の比表面積を変えた空気浄化用吸着剤混合型触媒体を用いて、４０ｍ３のボックスに入れた。そのボックスにトルエンを１００ｐｐｍ入れ、触媒体に紫外線を照射しながら、１８０分後のトルエンの濃度から得られる、二酸化炭素への転換率を調べた。この値は次式から求められる。
【００１７】
二酸化炭素への転換率（％）＝（１２０分後の二酸化炭素の濃度）／｛１００−（１８０分後のトルエンの濃度）×７｝
トルエンの減少量と二酸化炭素への転換率から総合判断を行った。
その結果を（表１）に示す。
【００１８】
【表１】
次に、光触媒の重量をＷｔ、吸着剤の重量をＷａとしたときに、それらの混合比Ｗｔ／Ｗａを変えて、前記製造方法により空気浄化用吸着剤混合型触媒体を用いた。評価方法は実験１と同様の方法で行った。その結果を（表２）に示す。
【００２０】
【表２】
本発明は、吸着剤の比表面積を最適化し、さらに粉末状光触媒の量と粉末状活性炭の量からそれらの混合比を最適化したために、活性炭に吸着された物質が酸化チタンによって分解されやすくなり、二酸化炭素への転換率を向上させ、活性炭を再生させることができた。
【００２２】
なお、上述した実施例では、光触媒として酸化チタン（ＴｉＯ２）を用いているが、この他にも、酸化タングステン（ＷＯ３）、酸化亜鉛（ＺｎＯ）、酸化鉄（Ｆｅ２Ｏ３）、酸化バナジウム（Ｖ２Ｏ５）等を用いても同様の効果を奏するものである。
【００２３】
【発明の効果】
以上のように本発明によれば、下記の効果が得られる。
【００２４】
本発明によれば、粉末状光触媒粒子と、粉末状吸着剤の混合において、それらの混合比について最適化を行い、さらに粉末状の吸着剤としては、比表面積が３００ｍ２／ｇ以下のものを用いることにより、吸着力を必要最小限に抑えることで、吸着剤の光触媒による再生を行いやすくした。その結果吸着剤に吸着した物質の光触媒による分解率を上げることができるようになった。
【００２５】
また、粉末吸着剤に活性炭を用いているため、悪臭物質の吸着速度が速く、速やかに脱臭できる。しかも同時に水分を吸着し、光触媒による再生を高めることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photocatalyst for air purification that combines an adsorbent that adsorbs malodorous substances such as hydrocarbons, nitrogen compounds, and sulfur compounds in the air with a photocatalyst that oxidizes and decomposes them by applying ultraviolet rays. In particular, the present invention relates to a photocatalyst for air purification that places importance on the mixing ratio of adsorbent and photocatalyst.
[0002]
[Prior art]
As the photocatalyst for air purification, a photocatalyst such as titanium oxide is generally used alone, and various types of devices that have been devised in terms of their configuration and joining method have been proposed. However, those using a photocatalyst alone are not suitable for removing malodorous substances immediately because of their slow decomposition rate.
[0003]
Among them, recently, there is a proposal of a photocatalyst for air purification that performs hybrid type adsorption regeneration type deodorization in which a photocatalyst and an adsorbent are combined. However, this air purification photocatalyst is simply a mixture of an adsorbent and a photocatalyst. After the malodorous substance is adsorbed on the adsorbent, it moves to the photocatalyst by surface diffusion and irradiates with ultraviolet rays. It breaks down substances.
[0004]
[Problems to be solved by the invention]
However, if the conventional photocatalyst for air purification uses activated carbon having a large specific surface area of the adsorbent, its adsorbing power is too strong to be regenerated by the photocatalyst. Furthermore, the adsorbent and photocatalyst are simply mixed together, and the amount of adsorbent and the amount of photocatalyst are not appropriate, so the action is not sufficient and the adsorbent is likely to remain adsorbed on the adsorbent. If the use is continued, there is a problem that the adsorbent deteriorates and does not return to its original state. Therefore, its use is not permanent, and as a result, it cannot be used unless the air purification photocatalyst is replaced.
[0005]
[Means for Solving the Problems]
The present invention is to solve the above-mentioned problems, and limits the specific surface area of the adsorbent and further prevents the deterioration of the adsorbent by adjusting the amounts of the adsorbent and the photocatalyst. When the powdery photocatalyst and the powdery adsorbent were mixed, the photocatalyst for air purification was prepared so as to increase the amount of the photocatalyst.
[0006]
According to the above invention, the adsorbent is limited to one having a small specific surface area so that the malodorous substance adsorbed by the adsorbent is efficiently decomposed by the effect of the photocatalyst, and the amount of the powdered photocatalyst and the powdered adsorption Since the amount of the adsorbent is optimized, the amount of malodorous substance decomposed by the photocatalyst increases, the residual amount of malodorous substance that remains adsorbed on the adsorbent decreases, and the adsorbent can be regenerated. It can be used permanently by repeating this.
[0007]
This effect will be described in detail. In general, adsorbents can adsorb water as well as malodorous substances. On the other hand, the photocatalyst is excited by irradiation with ultraviolet rays, and holes are generated on its surface. These holes have a very high oxidation potential of +3.0 V and can oxidize various compounds. If even a small amount of water is present on the surface of the photocatalyst, the water reacts with holes formed by photoexcitation to generate hydroxyl radicals. Although this hydroxyl radical has a short lifetime, it is an active chemical species that can oxidize various things. This hydroxyl radical is ultimately decomposed into carbon dioxide and water when it reacts with an organic compound. That is, water is required on the surface of the photocatalyst. In the present invention, the water can be brought to the surface of the photocatalyst more efficiently by appropriately mixing the photocatalyst and the adsorbent.
[0008]
On the other hand, in the mixture of the photocatalyst and the adsorbent, the substance adsorbed on the adsorbent moves onto the photocatalyst and is decomposed by surface diffusion. However, if the amount of photocatalyst and the amount of adsorbent are not optimized, this surface diffusion does not occur and the adsorbent remains in the adsorbent. In order to facilitate this surface diffusion, the concentration gradient of the adsorbent must be large between the adsorbent and the photocatalyst.
[0009]
For example, the same amount of adsorbed material is decomposed in the same space. On the other hand, if there are many adsorbents, an adsorbent will be adsorbed in a wide space and the concentration gradient with a photocatalyst will be small. On the other hand, if there are few adsorbents, many adsorbents will be adsorbed in a narrow space, and the concentration gradient with the photocatalyst will increase. Therefore, the condition for optimizing the regeneration of the adsorbent is that the photocatalyst is more than the adsorbent.
[0010]
That is, since the substance adsorbed by the photocatalytic effect is gradually decomposed, the adsorbing effect of the adsorbent is restored. As a result, this air purification photocatalyst can permanently repeat the adsorption regeneration.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
First aspect of the present invention, titanium oxide, tungsten oxide, zinc oxide, and powdery photocatalyst particles composed of iron oxide or vanadium oxide, Ri specific surface area name by mixing the following powdered activated carbon 300 meters 2 / g, When the weight of the photocatalyst particles is Wt, the weight of the powdered activated carbon is Wa, and the ratio is Wt / Wa, the photocatalyst for air purification is mixed so that 3/2 ≦ Wt / Wa ≦ 4. .
[0012]
Then, by optimizing the mixing ratio of the powder photocatalyst particles and the powder adsorbent, the adsorbed material adsorbed on the adsorbent was quickly decomposed by the action of the photocatalyst particles. Moreover, since activated carbon as the adsorbent has a small specific surface area, the adsorbed substance is easily desorbed.
[0013]
Furthermore, the use of activated carbon as a powdery adsorbent for adsorption rate of the malodorous substances is high can quickly deodorization. In addition, the activated carbon can adsorb moisture in the air at the same time as the malodorous substance, and this moisture can work very effectively for the photocatalyst, so that regeneration by the photocatalyst can be further enhanced.
[0014]
【Example】
Examples of the present invention will be described below.
[0015]
Example 1
A method for producing the air purification photocatalyst of Example 1 will be described. First, powdered titanium oxide is prepared as powdered photocatalyst particles, and powdered activated carbon is further prepared as a powdered adsorbent having a specific surface area of 300 m 2 / g or less. A photocatalyst is formed.
[0016]
In order to determine the effect of the present invention, the following experiment was conducted. The mixing ratio of the photocatalyst and the adsorbent according to the above production method was made constant, and an adsorbent mixed catalyst body for air purification in which the specific surface area of activated carbon was changed as the adsorbent was put in a 40 m 3 box. 100 ppm of toluene was put in the box, and the conversion rate to carbon dioxide obtained from the concentration of toluene after 180 minutes was examined while irradiating the catalyst body with ultraviolet rays. This value is obtained from the following equation.
[0017]
Conversion rate to carbon dioxide (%) = (concentration of carbon dioxide after 120 minutes) / {100− (concentration of toluene after 180 minutes) × 7}
A comprehensive judgment was made based on the amount of toluene reduced and the conversion rate to carbon dioxide.
The results are shown in (Table 1).
[0018]
[Table 1]
Next, when the weight of the photocatalyst is Wt and the weight of the adsorbent is Wa, the mixing ratio Wt / Wa is changed, and the adsorbent mixed catalyst body for air purification is used by the manufacturing method. The evaluation method was the same as in Experiment 1. The results are shown in (Table 2).
[0020]
[Table 2]
In the present invention, the specific surface area of the adsorbent is optimized, and further, the mixing ratio is optimized based on the amount of powdered photocatalyst and the amount of powdered activated carbon, so that the substance adsorbed on the activated carbon is easily decomposed by titanium oxide. It was possible to improve the conversion rate to carbon dioxide and regenerate the activated carbon.
[0022]
In the above-described embodiments , titanium oxide (TiO 2 ) is used as a photocatalyst, but in addition to this, tungsten oxide (WO 3 ), zinc oxide (ZnO), iron oxide (Fe 2 O 3 ), oxidation Even if vanadium (V 2 O 5 ) or the like is used, the same effect can be obtained.
[0023]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
[0024]
According to the onset bright, powdered photocatalyst particles, the mixing of the powdered adsorbent, optimizes for their mixing ratio, the more powdery sorbent, a specific surface area of 300 meters 2 / g or less of those By using, the adsorbent can be easily regenerated with a photocatalyst by minimizing the adsorption power. As a result, the photocatalytic decomposition rate of the substance adsorbed on the adsorbent can be increased.
[0025]
Moreover, since activated carbon is used as the powder adsorbent, the malodorous substance can be adsorbed at a high rate and can be quickly deodorized. At the same time, moisture can be adsorbed and regeneration by the photocatalyst can be enhanced.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14089798A JP4038877B2 (en) | 1998-05-22 | 1998-05-22 | Photocatalyst for air purification |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14089798A JP4038877B2 (en) | 1998-05-22 | 1998-05-22 | Photocatalyst for air purification |
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| Publication Number | Publication Date |
|---|---|
| JPH11333297A JPH11333297A (en) | 1999-12-07 |
| JP4038877B2 true JP4038877B2 (en) | 2008-01-30 |
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| JP4358587B2 (en) * | 2003-09-29 | 2009-11-04 | 東北リコー株式会社 | Method for producing photocatalyst adsorbent and photocatalyst adsorbent |
| JP6857063B2 (en) * | 2017-03-23 | 2021-04-14 | シャープ株式会社 | Complex of photocatalyst and adsorbent |
| CN110180387A (en) * | 2019-07-02 | 2019-08-30 | 苏州仕净环保科技股份有限公司 | A kind of efficient process system polluting gas source |
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