JP4610135B2 - Photocatalyst carrier and method for producing porous substrate - Google Patents
Photocatalyst carrier and method for producing porous substrate Download PDFInfo
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- JP4610135B2 JP4610135B2 JP2001250848A JP2001250848A JP4610135B2 JP 4610135 B2 JP4610135 B2 JP 4610135B2 JP 2001250848 A JP2001250848 A JP 2001250848A JP 2001250848 A JP2001250848 A JP 2001250848A JP 4610135 B2 JP4610135 B2 JP 4610135B2
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- alumina
- silicon carbide
- titanium oxide
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- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 26
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Images
Description
【０００１】
【発明の属する技術分野】
この発明は、空気中の臭気物質や有害物質を分解除去する光触媒担持体とその製法に関する。
【０００２】
【従来の技術】
従来、異臭物質、有害物質を含んだ空気を二酸化チタン等の光反応性半導体に接触させて、紫外光を照射し、半導体表面において悪臭物質、有害物質を分解、除去する装置は公知であり、空気清浄機やルームエアコンに利用されている。これらの装置に使用される光反応性半導体を担持した光触媒フィルターには、主として二酸化チタンが光反応性半導体として採用され、二酸化チタンの微粒子を漉き込んだ酸化チタン含有紙をコルゲート加工して通気性を有する蜂の巣（ハニカム）状に形成したものが一般的である。
【０００３】
しかしながら、かかる酸化チタン含有紙からなる紙質コルゲートハニカムフィルターは、活性炭等の吸着助剤を酸化チタンと共に含浸させて初期吸着力を増大させ得る利点はあるが、基質が脆弱で吸着飽和後の水洗による再賦活処理ができない欠点を有している。そこで、このような紙質ハニカムの脆弱な基質の改善として、耐久性のあるセラミック質もしくは金属質の剛性基材の利用が提案されている。これら剛性基材への酸化チタンの担持は、焼付による触媒成膜を必要とし、漉き込みのような安易な手段で酸化チタンを担持可能な紙質ハニカムに比して酸化チタンの担持工程に難を要するが、水洗による再賦活処理を容易に行い得る利点を有している。
【０００４】
このような剛性基材を使用した光触媒担持体として先に、特願２０００−８３５０５に示す発明を提案してあり、これは、セラミック質の剛性基材に、細孔性気孔に富み且つ高い膜強度を有する高活性の光反応性半導体を定着した光触媒担持体を得るという優れた効果を奏するものである。
【０００５】
【発明が解決しようとする課題】
上記特許出願の発明では、セラミック質の多孔性基材を、アルミナ質、アルミナシリカ質、コージライト質又は炭化珪素質のいずれか１つから形成している。
【０００６】
そのアルミナ質による基材は、高硬度、耐摩擦性をもち、熱力学的に安定で耐熱性に優れ、耐酸化性も高く、高い比表面積を有する特徴をもつが、イオン結合性セラミックであるこの物質は構造が緻密に構成されているため、温度が高くなるとそれぞれの原子の熱振動の振幅が加え合わされて、比較的大きな膨張を生じる。このため、熱膨張係数が大きく、熱衝撃に弱い。アルミナと酸化チタンは両者とも酸化物セラミックスであり、熱膨張係数が近い、濡れ性がよいなどの理由から接合が良好で、基材であるアルミナの表面が非常にポーラスなために高い比表面積を得られるという特性を得られるが、焼成時にアルミナに熱負荷がかかると、前記のように熱衝撃に弱いという性質から、基材が破損してしまう割合が高くなる。
【０００７】
また、炭化珪素質による基材は、共有結合性が高いため難焼結性であるが、科学的安定度が高く、耐熱性、耐食性に優れ、高硬度、耐摩擦性である。そして、共有結合性の物質は個々の原子の熱振動の振幅の一部が結合角の変化によって吸収されるので、原子間距離の増加が小さく、したがって熱膨張の程度が低い。その熱膨張係数は、非酸化物セラミックスの中のでも窒化珪素、サイアロンなどよりやや高い程度であり、また、熱伝導率が高いので熱衝撃に強い。このような炭化珪素の低熱膨張性、高熱伝導率の特性から、酸化チタン塗工後に５００℃焼成した場合でも基材破損率は低い。しかし、酸化チタンに対し熱膨張係数の差が大きいため、冷却過程において両者の間に引っ張り応力が強く発生し、酸化チタン膜にクラックが生じやすい。
【０００８】
以上のように、アルミナ質又は炭化珪素質の基材と酸化チタンという異種セラミックス間の接合においては、焼成時に、熱衝撃特性に起因して基材に破損が生じたり、あるいは、熱膨張係数の違いに起因して接合部分に応力が発生し、接合剥離や、引っ張り応力に負けるセラミックス側で破損が生じるなどの不具合が起こり得る。この発明はこのような課題を解決するものであり、光触媒担持体の多孔性基材について、より損傷し難い材質を提案することを目的とする。
【０００９】
【課題を解決するための手段】
上記課題を解決するためにこの発明が採った手段は、酸化チタンを主成分とした光反応性半導体をセラミック質の多孔性基材に塗工し、乾燥凝固させた膜を焼成して、微細孔性の膜を形成してなる光触媒担持体において、そのセラミック質の多孔性基材を、炭化珪素質の骨格多孔体上にアルミナ質の膜を形成した構造とすることを特徴としている。なお、このような発明における光反応性半導体の形成態様としては、上述の特願２０００−８３５０５に示す発明を流用するのがよい。
【００１０】
炭化珪素質は高強度特性をもつ一方で熱膨張係数の違いから酸化チタンにクラックが生じやすいという弱点をもつが、その熱膨張係数の違いという弱点を、酸化チタンと炭化珪素の中間程度の熱膨張係数をもつアルミナ質の緩衝層を形成することで補うものである。つまり、熱膨張係数の小さい炭化珪素と熱膨張係数の大きい酸化チタンとの間に、これらの中間程度の熱膨張係数をもつアルミナの緩衝層を形成することにより、この緩衝層が熱膨張係数の差を吸収し、酸化チタンの塗工、焼成時における残留応力を低減し、基材の破損、チョーキングの発生を抑制する。
【００１１】
このような炭化珪素質の骨格多孔体上にアルミナ質の膜を形成してなるセラミック質の多孔性基材の製造方法として本発明では、発泡体に炭化珪素スラリーを含浸させてから乾燥させ、この乾燥後の未焼成の骨格多孔体にアルミナを塗工して乾燥させた後、これら炭化珪素及びアルミナを同時焼成することを特徴とした製造方法を提案する。その乾燥温度域は１０００℃未満、好ましくは３５０〜７００℃が適しており、焼成温度域は１０００℃以上、好ましくは１３００〜１５００℃が適している。
【００１２】
従来一般的に知られている基材の製法では、複数のセラミック質を積層する場合、１つのセラミック質についてそれぞれ乾燥・焼成の工程を実施するのが慣用手段となっている。すなわち、第１のセラミックスの塗工（たとえばディップコーティング）→乾燥→焼成→冷却→第２のセラミックスの塗工→乾燥→焼成→冷却の過程を経ることになる。これに対し、この発明の製法では、発泡体としてたとえば軟質ポリウレタン発泡体を裁断し、これに炭化珪素スラリーを含浸させた後に乾燥させて発泡体を除去することで骨格多孔体を生成する。そして、その乾燥後の未焼成の骨格多孔体にアルミナをたとえばディップコーティングして乾燥させ、続いて、このアルミナとその下の炭化珪素とを同時に焼成するという手段をとっている。つまり、第１のセラミックスの塗工→乾燥→第２のセラミックスの塗工→乾燥→同時焼成→冷却という過程になっている。
【００１３】
このように同時焼成を行うことにより、その高温で、炭化珪素とアルミナとの間に界面反応が起こってムライト（３Ａｌ２Ｏ３・２ＳｉＯ２）が形成され、強固な結合を得ることができる。そして、この表面酸化膜は基本的にアルミナの表面物性をもつため、上述のように酸化チタンとの接合が良好である。したがって、炭化珪素の熱特性から破損の少ない基材を得られるとともに、緩衝層としてのムライト層の存在により、酸化チタンの付きがよくて剥がれ難くなり、クラックの発生も抑制される。そしてさらに、焼成及び冷却の工程が少ない分、熱衝撃を抑えられるし、工程のスリム化も達成される。
【００１４】
【発明の実施の形態】
以下、具体的実施例と試験例を示して本発明の好適な実施の形態を説明する。
【００１５】
【実施例】
二酸化チタン含有ゾル液を３種類の多孔性基材（寸法：２４５ｍｍ×２９５ｍｍ×ｔ２０ｍｍ・数量：各３０枚）に塗工して焼成し、試料とした。完成した試料の二酸化チタン添着量の平均値（ｇ／ｍ２）、膜硬度（Ｈ）、破損率（％）を測定した。なお、膜硬度の測定はＪＩＳ Ｋ５４００の規定に準拠して行っている。この結果を表１に示す。
【表１】
試料Ａ〜Ｃの内訳は、試料Ａが、多孔性基材としてアルミナセラミック多孔体（Ａｌ２Ｏ３：７６％・ＳｉＯ２：１９％・空孔率：８５％）を使用したもの、試料Ｂが、多孔性基材として炭化珪素セラミック多孔体（ＳｉＣ：６７％・Ａｌ２Ｏ３：１２％・ＳｉＯ２：１９％・空孔率：８５％）を使用したもの、そして試料Ｃが、炭化珪素−アルミナセラミック複合多孔体（炭化珪素セラミック多孔体の上に５０〜１５０μｍのアルミナ膜を形成）を使用したものである。表１からわかるとおり、試料Ｃは、試料Ａに対しては破損率で優れ、試料Ｂに対しては酸化チタンの添着量及び硬度で優っている。
【００１７】
本発明に係る光触媒担持体である試料Ｃの製法では、まず、軟質ポリウレタン発泡体を裁断して炭化珪素セラミックススラリーを含浸させ、これを３５０〜７００℃で乾燥させることで発泡体を除去し骨格多孔体とする。そして、未焼成のまま骨格多孔体にアルミナをディップコーティングした後に３５０〜７００℃で乾燥させ、そして該アルミナ塗工・乾燥後の多孔性基材を１３００〜１５００℃で焼成し、次いで冷却する。このように炭化珪素及びアルミナを同時焼成する工程とすることにより、表２に示す効果を得られている。すなわち、製造時間短縮と歩留りの向上が達成されている。
【表２】
【試験例１】
試料Ａ〜Ｃの各基材における表面多孔性を確認するために、二酸化チタンを塗工する前の多孔性基材表面についてＳＥＭ観察した写真を、図１〜図３に示す。
【００１９】
【試験例２】
試料Ａ〜Ｃを表３に示す小型の試験機にフィルターとして搭載し、この試験機をステンレス製６ｍ３の密閉試験室に設置して、アンモニア臭気を５ｐｐｍ前後まで充填してから循環送風運転を開始した。そして、所定の経過時間毎に濃度をガス検知管（ガステック社製）によって測定した。これを表４に示す。
【表３】
この結果において、本発明に係るフィルターＣは、フィルターＡ，Ｂの中間の性能を示した。これは、光触媒担持体として優れた機能を維持しながら基材の強度を強くすることができたことを示している。
【００２１】
【試験例３】
よく「タマネギが腐ったような臭い」と表現される含硫無機化合物に硫化水素があるが、この物質はｐｐｂレベルの低濃度で臭気が確認されるほどのものである。光触媒法はこの脱臭にも非常に有効なので、これについても、試験例２と同様の試験条件にてフィルターＡ〜Ｃの性能を確認・比較した。なお、硫化水素の初期濃度は１．５ｐｐｍである。その結果を表５に示す。
【表５】
表５より、本発明に係るフィルターＣがｐｐｂレベルの領域で非常に成績のよいことがわかる。この表５の結果及び先の表４の結果から、性能については非常に高水準にあることがわかる。一般に、アンモニア、硫化水素といった無機化合物の除去の際、フィルター表面に生成し残留する硝酸塩，硫酸鉛等の副生成物により性能が劣化することはよく知られている。そのため、実機での稼働となった場合、どうしてもフィルター洗浄のメンテナンスを頻繁に行わなければならないが、過去の例から、このメンテナンス作業においてフィルターが破損してしまうことが多々あった。しかし、本発明に係るフィルターであれば、上記のように強度的に優れているので耐久性に富み、より寿命の長いフィルターを提供することができる。
【００２３】
【試験例４】
近年、ホルムアルデヒドに代表される揮発性有機化合物（ＶＯＣ）の毒性が指摘されている。各種工業においても、悪臭防止法及びＰＲＴＲ法の制定によって、数多くの有害ガス状物質の処理をしなければならない状況になってきた。そこで、本発明の光触媒担持体が有機性ガスに対しても有効であるかどうか確認するため、代表的な有機性ガスのアセトアルデヒドを除去対象として試験を行った。
【００２４】
上記のフィルターＡ〜Ｃを表６及び図４に示す試験機に搭載し、該試験機をステンレス製３０ｍ３の密閉試験室に設置した。そして、アセトアルデヒド臭気を５ｐｐｍ前後まで充填した後に循環送風運転を開始し、所定の経過時間毎にアセトアルデヒド濃度を１３１２型マルチガスモニター（ＩＮＯＶＡ社製）によって測定した。その結果を表７に示す。
【表６】
表７から、フィルターＡ〜Ｃの３種とも、若干の除去速度の差こそあれ、ｐｐｍレベルでの除去速度は同等にみえる。ただし、１ｐｐｍを割ってからのｐｐｂレベルになってくると、やはり表面がより多孔質であるＡとＣのフィルターが性能を発揮している。基本的に低濃度領域での酸化チタン表面反応は１次反応としてみられるが、この領域において反応速度は酸化チタン表面に接触あるいは吸着する物質の濃度に比例する。本試験では装置に供給される空気量がほぼ一定であるので、除去公効率の大小は、より多くの物質を取り込める大表面積をもつか否かという点で決定されている。
【００２６】
【発明の効果】
この発明によると、炭化珪素質とアルミナ質とを混合した基材、すなわち炭化珪素質による骨格多孔体をアルミナ質で覆った構造の多孔性基材としたことにより、多孔質で割れ難く、光反応性半導体としての酸化チタン膜のクラック発生、剥離を抑制できるという大きな利点を得られ、高信頼性、長寿命の光触媒担持体を提供することができるようになる。また、その製法に同時焼成という手法を取り入れることにより、歩留り向上、時間短縮が可能となり、コストダウンにも貢献する。
【図面の簡単な説明】
【図１】実施例の試料Ａについて、酸化チタン塗工前の基材表面を観察したＳＥＭ写真。
【図２】実施例の試料Ｂについて、酸化チタン塗工前の基材表面を観察したＳＥＭ写真。
【図３】実施例の試料Ｃについて、酸化チタン塗工前の基材表面を観察したＳＥＭ写真。
【図４】試験例４で使用した試験機の構造を示した概略断面図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photocatalyst carrier that decomposes and removes odorous substances and harmful substances in the air and a method for producing the same.
[0002]
[Prior art]
Conventionally, an apparatus for contacting a photoreactive semiconductor such as titanium dioxide with air containing odorous substances and harmful substances, irradiating ultraviolet light, and decomposing and removing malodorous substances and harmful substances on the semiconductor surface is known. Used for air purifiers and room air conditioners. The photocatalytic filter carrying the photoreactive semiconductor used in these devices mainly uses titanium dioxide as the photoreactive semiconductor, and corrugated titanium oxide-containing paper containing fine particles of titanium dioxide for breathability. In general, it is formed in the shape of a honeycomb having honeycomb.
[0003]
However, the paper corrugated honeycomb filter made of such a paper containing titanium oxide has an advantage that the initial adsorbing power can be increased by impregnating the adsorbing aid such as activated carbon with titanium oxide, but the substrate is fragile and is washed by washing after adsorption saturation It has the disadvantage that it cannot be reactivated. Therefore, the use of a durable ceramic or metallic rigid base material has been proposed as an improvement of the brittle substrate of such a paper honeycomb. Titanium oxide support on these rigid substrates requires catalyst film formation by baking, making the titanium oxide support process more difficult than a paper honeycomb that can support titanium oxide by an easy means such as squeezing. In short, it has an advantage that the reactivation process by washing with water can be easily performed.
[0004]
As a photocatalyst carrier using such a rigid substrate, the invention shown in Japanese Patent Application No. 2000-83505 has been proposed. This is because a ceramic rigid substrate, a porous film rich in porous pores and high in thickness. It has an excellent effect of obtaining a photocatalyst carrier on which a highly active photoreactive semiconductor having strength is fixed.
[0005]
[Problems to be solved by the invention]
In the invention of the above patent application, the ceramic porous substrate is formed of any one of alumina, alumina siliceous, cordierite, or silicon carbide.
[0006]
The base material made of alumina has high hardness, friction resistance, thermodynamic stability, excellent heat resistance, high oxidation resistance, and high specific surface area, but is an ion-bonded ceramic. Since this substance has a dense structure, when the temperature rises, the amplitude of thermal vibration of each atom is added to cause a relatively large expansion. For this reason, a thermal expansion coefficient is large and it is weak to a thermal shock. Alumina and titanium oxide are both oxide ceramics and have good bonding due to their close thermal expansion coefficient and good wettability. The surface of alumina, which is the base material, is extremely porous, so it has a high specific surface area. Although the characteristic that it is obtained can be obtained, if a heat load is applied to alumina during firing, the ratio of the substrate to breakage increases due to the property of being weak against thermal shock as described above.
[0007]
In addition, the substrate made of silicon carbide is difficult to sinter because of its high covalent bonding property, but has high scientific stability, excellent heat resistance and corrosion resistance, and high hardness and friction resistance. In addition, since a part of the thermal vibration amplitude of each atom is absorbed by a change in the bond angle, the covalent substance has a small increase in interatomic distance, and thus the degree of thermal expansion is low. The coefficient of thermal expansion is slightly higher than that of silicon nitride, sialon, etc., among non-oxide ceramics, and is highly resistant to thermal shock because of its high thermal conductivity. Due to the low thermal expansion property and high thermal conductivity of silicon carbide, the substrate damage rate is low even when baked at 500 ° C. after titanium oxide coating. However, since the difference in thermal expansion coefficient with respect to titanium oxide is large, a tensile stress is strongly generated between the two during the cooling process, and a crack is easily generated in the titanium oxide film.
[0008]
As described above, in bonding between an alumina or silicon carbide base material and dissimilar ceramics such as titanium oxide, the base material may be damaged due to thermal shock characteristics or may have a thermal expansion coefficient during firing. Due to the difference, stress is generated in the joint portion, and there may be problems such as joint peeling and damage on the ceramic side that is subject to tensile stress. This invention solves such a subject, and it aims at proposing the material which is hard to damage about the porous base material of a photocatalyst carrier.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention adopts a method in which a photoreactive semiconductor mainly composed of titanium oxide is applied to a porous ceramic substrate, and the dried and solidified film is baked to obtain fine particles. The photocatalyst carrier formed by forming a porous film is characterized in that the ceramic porous substrate has a structure in which an alumina film is formed on a silicon carbide skeleton porous body. In addition, as a formation aspect of the photoreactive semiconductor in such invention, it is good to divert the invention shown in the above-mentioned Japanese Patent Application No. 2000-83505.
[0010]
Although silicon carbide has high strength characteristics, it has a weak point that cracks are likely to occur in titanium oxide due to the difference in thermal expansion coefficient. However, the weakness of the difference in thermal expansion coefficient is considered to be about half the heat between titanium oxide and silicon carbide. It is supplemented by forming an alumina buffer layer having an expansion coefficient. That is, by forming an alumina buffer layer having an intermediate thermal expansion coefficient between silicon carbide having a small thermal expansion coefficient and titanium oxide having a large thermal expansion coefficient, the buffer layer has a thermal expansion coefficient of Absorbs the difference, reduces the residual stress at the time of titanium oxide coating and firing, and suppresses breakage of the base material and occurrence of choking.
[0011]
In the present invention as a method for producing a ceramic porous substrate formed by forming an alumina film on such a silicon carbide skeletal porous body, the foam is impregnated with a silicon carbide slurry and dried. A manufacturing method is proposed in which alumina is applied to the unsintered skeletal porous body after drying and dried, and then these silicon carbide and alumina are simultaneously fired. The drying temperature range is less than 1000 ° C, preferably 350 to 700 ° C, and the firing temperature range is 1000 ° C or higher, preferably 1300 to 1500 ° C.
[0012]
In a conventionally known method for producing a base material, when laminating a plurality of ceramic materials, it is a conventional means to carry out drying and firing processes for each ceramic material. That is, the first ceramic coating (for example, dip coating) → drying → firing → cooling → second ceramic coating → drying → firing → cooling. On the other hand, in the production method of the present invention, for example, a soft polyurethane foam is cut as a foam, impregnated with a silicon carbide slurry, and then dried to remove the foam to produce a skeletal porous body. Then, the dried unsintered skeletal porous body is dried by, for example, dip-coating alumina, and then the alumina and the underlying silicon carbide are fired simultaneously. In other words, the first ceramic coating → drying → second ceramic coating → drying → co-firing → cooling.
[0013]
By performing co-firing in this way, an interface reaction occurs between silicon carbide and alumina at that high temperature, and mullite (3Al 2 O 3 · 2SiO 2 ) is formed, and a strong bond can be obtained. Since this surface oxide film basically has the surface physical properties of alumina, the bonding with titanium oxide is good as described above. Therefore, a base material with little breakage can be obtained from the thermal characteristics of silicon carbide, and the presence of the mullite layer as a buffer layer makes it difficult to peel off titanium oxide and suppresses the occurrence of cracks. Furthermore, the thermal shock can be suppressed and the process can be slimmed down because there are few firing and cooling processes.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to specific examples and test examples.
[0015]
【Example】
The titanium dioxide-containing sol solution was applied to three types of porous substrates (dimensions: 245 mm × 295 mm × t20 mm, quantity: 30 sheets each) and baked to prepare a sample. The average value (g / m 2 ), film hardness (H), and breakage rate (%) of the titanium dioxide deposition amount of the completed sample were measured. The film hardness is measured in accordance with JIS K5400. The results are shown in Table 1.
[Table 1]
The breakdown of Samples A to C is that Sample A uses an alumina ceramic porous body (Al 2 O 3 : 76%, SiO 2 : 19%, porosity: 85%) as a porous substrate, Sample B but silicon carbide porous ceramic body as a porous substrate (SiC: 67% · Al 2 O 3: 12% · SiO 2: 19% · porosity: 85%) as was used, and sample C are carbonized A silicon-alumina ceramic composite porous body (a 50 to 150 μm alumina film is formed on a silicon carbide ceramic porous body) is used. As can be seen from Table 1, Sample C is superior in breakage rate to Sample A, and superior to Sample B in the amount of titanium oxide attached and the hardness.
[0017]
In the method for producing Sample C, which is a photocatalyst carrier according to the present invention, first, a flexible polyurethane foam is cut and impregnated with a silicon carbide ceramic slurry, and dried at 350 to 700 ° C. to remove the foam and to form a skeleton. A porous body is used. Then, after dip-coating alumina on the skeletal porous body without firing, it is dried at 350 to 700 ° C., and the porous substrate after the alumina coating / drying is fired at 1300 to 1500 ° C. and then cooled. Thus, the effect shown in Table 2 is acquired by setting it as the process which bakes silicon carbide and an alumina simultaneously. That is, shortening of manufacturing time and improvement of yield are achieved.
[Table 2]
[Test Example 1]
In order to confirm the surface porosity in each base material of Samples A to C, photographs obtained by SEM observation of the porous base material surface before applying titanium dioxide are shown in FIGS.
[0019]
[Test Example 2]
Samples A~C mounted as a filter on a small tester shown in Table 3, by installing this tester sealed test chamber of stainless steel 6 m 3, a circulating blower operation of ammonia odor from the filling to around 5ppm Started. And the density | concentration was measured with the gas detection pipe | tube (made by Gastec) every predetermined | prescribed elapsed time. This is shown in Table 4.
[Table 3]
In this result, the filter C according to the present invention showed an intermediate performance between the filters A and B. This indicates that the strength of the substrate could be increased while maintaining an excellent function as a photocatalyst carrier.
[0021]
[Test Example 3]
Hydrogen sulfide is a sulfur-containing inorganic compound often expressed as “smelling smell of onion”, but this substance has such a degree that odor is confirmed at a low concentration of ppb level. Since the photocatalyst method is very effective for this deodorization, the performance of the filters A to C was confirmed and compared under the same test conditions as in Test Example 2. The initial concentration of hydrogen sulfide is 1.5 ppm. The results are shown in Table 5.
[Table 5]
From Table 5, it can be seen that the filter C according to the present invention performs very well in the ppb level region. From the results of Table 5 and the results of Table 4, it can be seen that the performance is at a very high level. In general, when removing inorganic compounds such as ammonia and hydrogen sulfide, it is well known that the performance is deteriorated by by-products such as nitrate and lead sulfate which are generated and remain on the filter surface. For this reason, when the system is actually operated, it is necessary to frequently perform maintenance for cleaning the filter. However, in the past examples, the filter was often damaged in this maintenance work. However, if the filter according to the present invention is excellent in strength as described above, it is possible to provide a filter having high durability and a longer life.
[0023]
[Test Example 4]
In recent years, the toxicity of volatile organic compounds (VOC) represented by formaldehyde has been pointed out. Even in various industries, due to the establishment of the Malodor Control Law and the PRTR Law, it has become a situation that many toxic gaseous substances must be treated. Therefore, in order to confirm whether or not the photocatalyst carrier of the present invention is also effective for organic gas, a test was conducted with a representative organic gas acetaldehyde as an object to be removed.
[0024]
The filters A to C were mounted on a test machine shown in Table 6 and FIG. 4, and the test machine was installed in a stainless steel 30 m 3 sealed test chamber. Then, after the acetaldehyde odor was filled up to about 5 ppm, the circulating air blowing operation was started, and the acetaldehyde concentration was measured with a 1312 type multi-gas monitor (manufactured by INOVA) at every predetermined elapsed time. The results are shown in Table 7.
[Table 6]
From Table 7, all three types of filters A to C seem to have the same removal rate at the ppm level, although there is a slight difference in the removal rate. However, when it reaches the ppb level after dividing 1 ppm, the filters of A and C, which have a more porous surface, exhibit performance. Basically, the titanium oxide surface reaction in the low concentration region is seen as a primary reaction, and in this region, the reaction rate is proportional to the concentration of the substance contacting or adsorbing on the titanium oxide surface. In this test, since the amount of air supplied to the apparatus is almost constant, the magnitude of the removal efficiency is determined by whether or not it has a large surface area that can take in more substances.
[0026]
【The invention's effect】
According to the present invention, since the substrate is a mixture of silicon carbide and alumina, that is, a porous substrate having a structure in which a skeletal porous body made of silicon carbide is covered with alumina, it is porous and difficult to break. A great advantage that crack generation and peeling of the titanium oxide film as a reactive semiconductor can be suppressed is obtained, and a highly reliable and long-life photocatalyst carrier can be provided. In addition, by adopting the simultaneous firing method in the manufacturing method, the yield can be improved and the time can be shortened, which contributes to cost reduction.
[Brief description of the drawings]
FIG. 1 is an SEM photograph of a sample A of an example in which the surface of a base material before being coated with titanium oxide was observed.
FIG. 2 is an SEM photograph observing the surface of a base material before application of titanium oxide for Sample B of Example.
FIG. 3 is an SEM photograph in which the surface of the base material before application of titanium oxide was observed for sample C of the example.
4 is a schematic cross-sectional view showing the structure of a testing machine used in Test Example 4. FIG.
Claims (4)
セラミック質の多孔性基材として、炭化珪素質の骨格多孔体上にアルミナ質の膜を形成してなる基材を使用したことを特徴とする光触媒担持体。In the photocatalyst carrier formed by coating a photoreactive semiconductor mainly composed of titanium oxide on a ceramic porous substrate, firing the dried and solidified film, and forming a microporous film,
A photocatalyst carrier comprising a substrate formed by forming an alumina film on a silicon carbide skeleton porous body as a ceramic porous substrate.
発泡体に炭化珪素スラリーを含浸させてから乾燥させ、この乾燥後の未焼成の骨格多孔体にアルミナを塗工して乾燥させた後、これら炭化珪素及びアルミナを同時焼成することを特徴とする製造方法。A method for producing a ceramic porous substrate in the photocatalyst carrier according to claim 1,
The foam is impregnated with a silicon carbide slurry and then dried. After drying, the unfired skeletal porous body is coated with alumina and dried, and then the silicon carbide and the alumina are simultaneously fired. Production method.
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| EP1656985A4 (en) * | 2003-04-23 | 2008-10-29 | Nat Inst Of Advanced Ind Scien | Three-dimensional fine cell structured photocatalyst filter responding to visible light and method for production thereof, and clarification device |
| JP2007098197A (en) * | 2005-09-30 | 2007-04-19 | Bridgestone Corp | Manufacturing method of photocatalyst material |
| FR2935908B1 (en) * | 2008-09-12 | 2011-01-14 | Centre Nat Rech Scient | PHOTOCATALYSTS BASED ON THREE-DIMENSIONAL FOAMS STRUCTURED IN CARBIDE AND IN PARTICULAR IN BETA-SIC |
| WO2015003135A2 (en) | 2013-07-05 | 2015-01-08 | Nitto Denko Corporation | Transparent photocatalyst coating and methods of manufacturing the same |
| JP2016528029A (en) | 2013-07-05 | 2016-09-15 | 日東電工株式会社 | Photocatalyst sheet |
| JP6346947B2 (en) | 2013-07-05 | 2018-06-20 | 日東電工株式会社 | Filter element for decomposing pollutants, system for decomposing pollutants and method of using the system |
| JP2015163396A (en) * | 2014-02-03 | 2015-09-10 | 国立大学法人信州大学 | Photocatalyst filter and method for producing the same |
| CN113926441B (en) * | 2021-10-12 | 2023-11-21 | 北京林业大学 | Si doped TiO 2 Nanometer rod grafted photocatalysis coupling self-cleaning modified ceramic membrane and preparation method thereof |
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| JPS61259763A (en) * | 1985-05-14 | 1986-11-18 | Ibiden Co Ltd | Catalyst carrier made of porous silicon carbide sintered body |
| JPH04341787A (en) * | 1991-05-17 | 1992-11-27 | Sharp Corp | Ceramic heater |
| JPH11164877A (en) * | 1997-12-05 | 1999-06-22 | Mizusawa Ind Chem Ltd | Harmful material removing agent and photocatalyst carrier |
| JP2000000809A (en) * | 1998-06-18 | 2000-01-07 | Ngk Insulators Ltd | Thin-walled honeycomb structural body and reinforcing method thereof |
| JP2001259435A (en) * | 2000-03-24 | 2001-09-25 | Seiwa Kogyo Kk | Photocatalyst-supporting body |
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| JPS61259763A (en) * | 1985-05-14 | 1986-11-18 | Ibiden Co Ltd | Catalyst carrier made of porous silicon carbide sintered body |
| JPH04341787A (en) * | 1991-05-17 | 1992-11-27 | Sharp Corp | Ceramic heater |
| JPH11164877A (en) * | 1997-12-05 | 1999-06-22 | Mizusawa Ind Chem Ltd | Harmful material removing agent and photocatalyst carrier |
| JP2000000809A (en) * | 1998-06-18 | 2000-01-07 | Ngk Insulators Ltd | Thin-walled honeycomb structural body and reinforcing method thereof |
| JP2001259435A (en) * | 2000-03-24 | 2001-09-25 | Seiwa Kogyo Kk | Photocatalyst-supporting body |
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