JP3831888B2 - Photocatalyst unit and apparatus using the same - Google Patents

Photocatalyst unit and apparatus using the same Download PDF

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JP3831888B2
JP3831888B2 JP07898199A JP7898199A JP3831888B2 JP 3831888 B2 JP3831888 B2 JP 3831888B2 JP 07898199 A JP07898199 A JP 07898199A JP 7898199 A JP7898199 A JP 7898199A JP 3831888 B2 JP3831888 B2 JP 3831888B2
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photocatalyst
light
region
gap
unit
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JP2000271486A (en
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泰良 加藤
輝史 宮田
豊 武田
公一 横山
英治 宮本
雅敏 藤澤
尚美 今田
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Mitsubishi Power Ltd
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Babcock Hitachi KK
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Description

【0001】
【発明の属する技術分野】
本発明は、排ガスもしくは廃液の処理装置に用いる板状光触媒体を積層した光触媒ユニット及びそれを用いる装置に係り、特に少ないエネルギーで効率よく排ガス、廃液中の有害物を分解、除去するのに好適な光触媒ユニット及び装置に関する。
【0002】
【従来の技術】
酸化チタン(TiO2)に波長の小さい光が照射されると強い酸化能を示すことは古くから知られている(触媒学会編、元素別触媒便覧p256(1977)など)。酸化チタンの光触媒機能を利用して、近年、廃水や排ガス中の各種有機物(NOx)除去へ利用する試みが種々の分野で盛んに行われ、トンネル内の排ガス浄化や、ダイオキシンを含む廃水の浄化などへ適用する発明が多数なされている。特に、光触媒を用いると光を照射するだけで各種有害有機物や窒素酸化物が容易に分解して除去できるため、揮発性有機物(VOC)の除去やシックハウスの原因物質(新建材から生じる有害成分)の除去などへの応用が精力的に進められている。
それらに用いられる酸化チタン触媒の形状は、微粉状(特開平6-12689号など)、ガラスや金属にコーティングされた形状(特開平7-10378号等)の他、ガラス繊維織布にコーティングしたフェルト状(特開平7-96202号)など種々のものが知られている。
また、触媒の充填方法に関しても数多くの方式が検討されている。中でも平板光触媒を多数積層して用いる方法(特開平10-286436号)では、その装置は、平板光触媒の積層体の横に積層方向に延びる管状光源を配置し、隣り合う平板光触媒と平板光触媒間の隙間に光を照射し、また隣り合う平板光触媒同士間のスペーサを実質的に無くして陰の発生を抑制するように構成して、光を有効に利用する。この装置では処理する排ガスを隣り合う平板光触媒間を通じて流すので、該ガス流の圧損が小さく排ガス浄化能にも優れている。
【0003】
一方、発明者らは、上記特開平10-286436号と同様に光を有効に利用するという観点から、スペーサ形状及び光源との配置関係から陰の発生を最小限に抑えた平板状触媒を用いた触媒装置を開発した。
【0004】
【発明が解決しようとする課題】
上記従来技術の中、図7に示すように平板または平板光触媒体を隙間をあけて積層したユニットは、ガス流の圧力損失が少なく、光源と光触媒との配置の工夫から光エネルギーの利用効率が従来に比べれば高いものの、積層した光触媒の全面を有効に利用するという観点からは十分とは言えなかった。
【0005】
即ち、本発明者らが検討した結果によれば、管状光源を、積層ユニットの横の方に平板光触媒体の面に直交する方向、言い換えれば積層方向に配置した場合、平板光触媒体間の隙間の入口近傍にしか光が十分に照射されない。例えば、積層した平板光触媒体のピッチ(ないし隙間)5mmの時には、隙間入口から約1cmまでは光照射強度が高いが、それ以降の強度は相当小さくなる。その結果、隙間入口から離れて光量の少ない所に位置する光触媒は、必ずしも有効に利用されていなかった。
【0006】
本発明の目的は、平板光触媒体間の隙間の入口近傍しか光が照射されないという問題を解決して、光触媒全体を有効に利用できる高性能な光触媒ユニット及びそれを用いた光触媒装置を実現することにある。
【0007】
【課題を解決するための手段】
本発明は、上記目的を達成するために、光触媒を担持した複数枚の平板光触媒体または一部に突起を有する複数枚の平板光触媒体を隙間をもって積層してなり、前記隙間に対して光が照射され前記隙間に供給される流体に含まれる有害成分を分解する光触媒ユニットにおいて、前記平板光触媒体または一部に突起を有する平板光触媒体は、その表面及び裏面にそれぞれ、光触媒を担持した光触媒領域と金属面でなる光反射領域とを分散して有する第1の光触媒ユニットを提案する。第1の光触媒ユニットにおいては、光触媒領域及び光反射領域はそれぞれ帯状に交互に形成されているか、あるいは格子の桝目を交互に占めるように形成されているか、あるいは光触媒領域が光反射領域中に分布して点在するように形成されていることが好ましい。
【0008】
また、本発明の第2の光触媒ユニットは、第1の光触媒ユニットにおける光触媒体、すなわち表裏両面にそれぞれ光触媒領域及び光反射領域を有する光触媒体の代わりに、一方の面に光触媒を担持した光触媒領域を、他方の面に金属面でなる光反射領域を有する光触媒体を、光触媒領域と光反射領域が対向するように積層したものである。
【0009】
また、本発明の第3の光触媒ユニットは、第1の光触媒ユニットにおける光触媒体、すなわち表裏両面にそれぞれ光触媒領域及び光反射領域を有する光触媒体の代わりに、板の両面に光触媒を担持してなる板状光触媒体と、板の両面が金属面で形成された光反射体と、を交互に積層したものである。
【0010】
さらに、本発明の目的を達成するために、本発明の光触媒装置は、被処理流体の流路を内部に形成する容器と、流路内に設置された上記第1〜第3の何れかに光触媒ユニットと、この光触媒ユニットの近傍から光触媒体間の隙間に光を照射する光源とを備え、被処理流体を隙間に沿う方向に流すようにしたものである。
【0011】
上記第1の光触媒ユニットにおける光の伝播及び光触媒の作用について図4を用いて説明する。一般に、金属は光触媒の励起に必要な近紫外以下の波長の光の反射率が高いため、金属面でなる光反射領域は光をよく反射する。したがって、図4(A)に示すように、照射された光線5の一部は光触媒領域2に衝突して光触媒の活性化に利用されるが、光反射領域1に照射された光線5は反射されて、積層された光触媒体間の隙間のより奥に向かって進行する。その過程で、光触媒領域2の光触媒成分と衝突した光から逐次利用されるので、光触媒体の広い範囲に均一に光が照射されるようになる。その結果、広い範囲で光により発生した活性種は、排ガスまたは廃水などの被分解物により速やかに消費されるようになり、光触媒体全体が活性化する。一方、図4(B)に示す従来の光触媒体の場合、光触媒体間の隙間に入射した光線5は、積層された他の光触媒体に遮られるために隙間の入口部分にしか到達できない。また、光触媒体表面は全面が光触媒成分で覆われており、通常、光触媒成分は紫外域や近紫外域の光の吸収率が高いため、照射された光線5の大半は隙間の入口近傍で吸収されるので反射は殆ど起こらない。その結果、光により励起され有害物などの分解に必要な活性種は、触媒層隙間の入口部分に集中することになる。また、光触媒の活性種には寿命があり、速やかに有害物との反応に利用されなければ熱エネルギーなどに変化して消滅する性質がある。これらが原因して、隙間の入口近傍に大量の活性種が局在するため、反応物の拡散による物質移動速度が活性種の発生速度に追いつかず、活性種が有効に利用されず消滅する頻度が大きい。このことが、光触媒の活性化を阻害している。
【0012】
ここで、本発明にかかる光触媒体を構成する部材について説明しておきたい。光反射領域を構成する部材及び光触媒領域の光触媒を担持する担体として、一枚の金属基板を用いる。金属基板は、鉄、アルミニウム、各種ステンレス金属、ジュラルミンなど軽金属合金など、金属光沢有する態様のもので、使用環境下で腐食や錆を発生しないものが良い。それらの使用の形態は、板状のまま、もしくは板状のものに機械加工により表面に凹凸加工やメタルラス加工などが施された状態、あるいは、線状金属を織った網状など、種々の形態のものが用いられる。
光触媒としては、酸化チタンを主成分とするものを用い、硫酸法、ゾルゲル法、気相法などで調整されたアナターゼ型またはルチール型の酸化チタン単独、もしくはそれらにPt、Pdなどの貴金属、Vなどの遷移金属元素を添加したものなどが使用できる。それら各種光触媒成分は、そのまま、またはシリカゾル、過酸化チタンなどの無機結合剤、またはポリエチレン、ポリビニールアルコール、ポリエチレングリコール、テフロンなどの樹脂ディスパージョンなど有機結合剤とともに、ゾル状またはスラリ状にして、金属基板の表面にコーティングされ、必要に応じて焼成や水洗などが行われる。光触媒成分は、図1に例を示すように(1)光触媒成分コーティングされた部分と、金属面が露出する部分が帯状、千鳥状に配置された状態に、(2)金属基板の表面もしくは裏面の一方にのみコーティングされた状態に、また(3)図示しないが、複数枚積層された光触媒体のうち一部の光触媒体両面にされた状態に形成される。
触媒をコーティングする厚さは、大きくても構わないが、通常0.1mm〜数十μm程度にすることが好結果を与えやすい。あまり厚みが大きいと剥離し易くなり、薄すぎると触媒成分が不足して性能が低下する傾向がある。
光触媒体の積層方法については、触媒成分をコーティングした板状や網状の光触媒体を、図2に示すように、(A)平板、(B)平板の一部に波上凹凸の線状突起を形成したもの、(C)平板一部に角状凹凸の線状突起を形成したもの、(D)平板の一部に山状凹凸の線状突起を形成したものなどに成形して用い、図3に示すように積層して、光触媒ユニットを構成する。なお、図2に示す成形は、触媒コーティング後でもよいし、コーティングに先立ち行われていもよい。また、必要なら、図1に示す光触媒体等を混用してユニットとしても差し支えない。
【0013】
本発明の光触媒ユニットを実際の装置で使用するに当たっては、光源と光触媒体の配置が重要であり、管状光源を用いる場合には、光触媒ユニットの横側に、管状の長手方向と平板状触媒との面が直交するように配置するとよい。光触媒体はその線状突起が光の照射方向と平行になるように配置する。もちろん、光源の配置がこれ以外の場合であっても、本発明の効果は発現されるが、上記光源−触媒配置がより効果が大きい傾向にある。
【0014】
更に、本発明にかかる光触媒体の基板構成が光触媒体の全体である必要はなく、例えば金属基板とセラミックス製光触媒体の組み合わせのように、全体の一部に用いられてもかまわない。
【0015】
【発明の実施の形態】
以下、具体例を用いて本発明を詳細に説明する。
(実施の形態1)
厚さ0.2mmのステンレス鋼SUS430の薄板をローラプレスを用いて図5に示す形状、寸法に成形し、200mm幅×100mm長に切断した成形基板を用意した。これとは別にSUS430の薄板を200mm幅×100mm長に切断した平板基板を用意した。加工時の油脂成分を取り除くため、アセトン中につけて脱脂し、大気中で乾燥した。
一方、重合度700のポリビニールアルコール(クラレポバール107)13gを水100mlに溶かし、これに弱アルカリ性シリカゾル(日産化学製シリカゾル−N)650gに加えた。この溶液に微粒アナターゼ型酸化チタン(デグッサ製P-25 、表面積50m/g)を200g添加し攪拌して、第1のスラリを得た。
上記2種類の金属基板に、第1のスラリを長手方向と平行に幅約5mm間隔で縞模様に(図1(A)参照)に、薄く刷毛により塗布した後、100℃で乾燥して固化させた。その後、余剰有機バインダを除去するため、流水に晒してバインダを溶解除去後、100℃で乾燥して光触媒体を得た。得られた2種類の形状の光触媒体を幅200mm、奥行き100mm、高さ300mmの金属枠に交互に積層し(図3(A)参照)、光触媒ユニットを作製した。
実施の形態1の光触媒ユニットを一対用い、図6に示す試験装置でベンゼンの光分解反応性能を測定した。測定条件を表1に示す。試験装置は、一端にガス入口を、他端にガス出口を有し内部に流路を有する容器20と、容器20内の流路に順に配置された分散板8、光触媒ユニット6、管状光源7及びもう一つの光触媒ユニット6と、容器のガス入口に接続されベンゼン10ppmを含む空気を模擬排ガスとして容器20に供給するファン9とから構成されている。分散板8は排ガスを流路断面に分散して供給するものである。また、管状光源7(例えば蛍光灯)は、光触媒ユニット6の幅方向中心に、かつ光触媒ユニット6内の光触媒体の積層方向に延びて設置されている。また光触媒体はその線状突起の長手が光の照射方向と平行になるように配置されている。
【0016】
【表1】

Figure 0003831888
実施の形態1の光触媒ユニットを用いた試験の結果は、後述の表2に示すように、ベンゼン分解率が69%であった。
【0017】
(実施の形態2)
重合度700のポリビニールアルコール(クラレポバール107)13gを水100mlに溶かし、これに弱アルカリ性シリカゾル(日産化学製シリカゾル−N)650gに加えた。この溶液に微粒アナターゼ型酸化チタン(デグッサ製P-25 、表面積50m/g)を170g添加し攪拌して、第2のスラリを得た。
【0018】
実施の形態1で用いた2種類の金属基板表面に、第2の上記スラリを塗装用霧吹き機を用いて噴霧し、基板全面に分布しかつ基板面積の約半分程度がスラリの微細な液滴で覆われる状態(図1(C)参照)にした。この光触媒体を、実施の形態1と同様の条件で、乾燥、水洗、乾燥、枠組みをして光触媒ユニットを得た。この実施の形態2の光触媒ユニットを一対用い、実施の形態1と同様にして、図6に示す試験装置でベンゼンの光分解反応性能を測定した。実施の形態2の光触媒ユニットを用いた試験の結果は、後述の表2に示すように、ベンゼン分解率が72%であった。
【0019】
(実施の形態3)
実施の形態1における金属基板の中、平板状金属基板の両面全面に触媒スラリを塗布した光触媒体を得た。一方、図5に示す形状に成形した金属基板には触媒を塗布せず全面金属面が露出している状態の金属基板を得た。これらの光触媒体及び金属基板を、実施の形態1と同様に、交互に積層して光触媒ユニットを作製した。
この実施の形態3の光触媒ユニットを一対用い、実施の形態1と同様にして、ベンゼンの光分解反応性能を測定した。実施の形態3の光触媒ユニットを用いた試験の結果は、後述の表2に示すように、ベンゼン分解率が62%であった。
【0020】
(実施の形態4)
実施の形態1で用いた2種類の金属基板の片面全体に触媒スラリを塗布し、他の面全体を金属面が露出した光触媒体を作製し(図1(D)参照)、光触媒面と金属面が対向するように積層し、他は同様にして光触媒ユニットを得た。
実施の形態4の光触媒ユニットを一対用い、実施の形態1と同様にして、ベンゼンの光分解反応性能を測定した。実施の形態4の光触媒ユニットを用いた試験の結果は、後述の表2に示すように、ベンゼン分解率が74%であった。
【0021】
(実施の形態5)
実施の形態1で用いた0.2mmSUS基板に代えて、これを幅約2mmの大きさのメタルラスを施した(薄板に細かい切れ目を交互に入れ引っ張って金網状に広げた)網状金属板(エキスパンドメタル)を用い、これに光触媒を縞模様に形成し、他は実施の形態1と同様にして光触媒ユニットを調製した。
実施の形態5の光触媒ユニットを一対用い、実施の形態1と同様にして、ベンゼンの光分解反応性能を測定した。実施の形態5の光触媒ユニットを用いた試験の結果は、後述の表2に示すように、ベンゼン分解率が65%であった。
【0022】
(実施の形態6)
重合度1700のポリビニールアルコール(クラレポバール117)130gを水1000mlに溶かし、これに弱アルカリ性シリカゾル(日産化学製シリカゾル−N)6500gに加えた。この溶液に微粒アナターゼ型酸化チタン(デグッサ製P-25 、表面積50m/g)を2500g添加して攪拌し、粘ちょうな第3のスラリを得た。このスラリを、繊維径6μmのE-ガラス繊維2000本を1インチ当たり8本で平織りした網状織布に含浸した後、加熱成形金型の間に挟んで乾燥し、図5の形状に成形した後、切断して200mm幅×100mm長の網状乾燥体を得た。一方、これとは別に、厚み0.3mmのアルミニウムの薄板を200mm幅×100mm長に切断した金属板を作製した。上記で調製した、触媒体及び金属板を実施の形態1と同様の方法で交互に積層し、光触媒ユニットを作製した。
【0023】
実施の形態6の光触媒ユニットを一対用い、実施の形態1と同様にして、ベンゼンの光分解反応性能を測定した。実施の形態6の光触媒ユニットを用いた試験の結果は、後述の表2に示すように、ベンゼン分解率が57%であった。
【0024】
(比較例)
実施の形態1における触媒スラリの塗布方法を一部から全面に変え、基板全体が触媒で覆われた触媒体を調製し、他は同様にして触媒体ユニットを調製した。この比較例で得られた光触媒ユニットを各々一対用い、実施の形態1と同様にして、ベンゼンの光分解反応性能を測定した。比較例の光触媒ユニットを用いた試験の結果は、表2に示すように、ベンゼン分解率が36%であった。
【0025】
【表2】
Figure 0003831888
表2にまとめたベンゼン分解率をみると、実施の形態1〜6の光触媒ユニットは57〜74%と高いベンゼン分解率を示しているのに対し、比較例は36%と低い値を示している。比較例で用いた光触媒体は表裏全面が触媒成分で覆われたものである。一方、本発明の各実施例で用いた光触媒体は光触媒領域と光反射領域と有するもので、触媒成分で覆われた面積は比較例の場合の半分程度と低いにも拘わらず、表2に示すように高い性能が得られており、触媒面が触媒機能を有する部分と光の反射機能を有する部分とで構成された光触媒体が触媒性能の向上に極めて有効な手段であることは明白である。
実施の形態1、2では、光触媒体の対向面はそれぞれ光触媒領域と光反射領域とを混在して有している。一方、実施の形態3と4では、対向する一つの面が光触媒領域で他の面が光反射領域で構成されている。実施の形態1〜4の光触媒ユニットがいずれも高い触媒性能を示していることからも分かるように、触媒機能を有する部分と光の反射機能を有する部分とを別々の面に設け、触媒機能を用いる平板と光の反射機能を有する平板の組み合わせのように別機能を有する構造物の組み合わせによっても、優れた触媒性能を達成することができる。
また、実施の形態5のようにメタルラス加工を施し多数の穴のあいた金属基板に光触媒を担持させた光触媒体や、実施の形態6のように網状織布に光触媒を担持させた光触媒体のように、光触媒を担持する面が平面で構成されていないもの、あるいは、光の反射機能を有する金属基板と酸化物で構成された触媒との組み合わせによっても、高い値が得られており、本発明の適用範囲が広いことを示している。
以上説明したように、本発明により、触媒自身の陰により触媒全体を使用できないという光の直進性に起因した本質的な問題を改善することができ、その結果、触媒性能を飛躍的に向上させることが可能になる。これまで、光触媒反応はエネルギー効率が悪く、家電等民生機器の補助手段としての用途に限られる傾向にあったが、本発明により大型かつ省エネルギーの光触媒反応器を実現できるようになり工業技術の発展への効果も大きい。
【0026】
【発明の効果】
本発明によれば、光触媒ユニットを、板の両面に光触媒を担持した光触媒領域と金属面でなる光反射領域とを分散して有する複数の光触媒体を隙間をあけて積層して構成したので、隙間に入射した光線は光反射領域で反射しながら隙間の奥深く進行し、その結果、広い範囲で光により発生した活性種は、隙間に流入した排ガスまたは廃水などの被分解物により速やかに消費されるようになり、光触媒体全体を活性化することができ、高性能な光触媒ユニットが得られる 。
【0027】
また、光触媒ユニットを、積層した板状光触媒体の対向面の一方を光触媒領域とし、他方を光照射領域とするように構成しても、上記同様に高性能な光触媒ユニットが得られる 。
【図面の簡単な説明】
【図1】本発明にかかる光触媒体に形成した光触媒のパターンを示す図である。
【図2】本発明にかかる光触媒体の基板の形状を示す図である。
【図3】本発明の光触媒ユニットにおける光触媒体の積層例を示す図である。
【図4】本発明の光触媒ユニットにおける光の進行経路を説明する図である。
【図5】本発明の実施の形態で作成した光触媒体の形状寸法を示す図である。
【図6】本発明の光触媒ユニットの触媒性能を測定した試験装置を示す図である。
【図7】従来技術の問題点を説明するための補足図である。
【符号の説明】
1 光反射領域
2 光触媒領域
3 平板触媒
4 成形触媒
5 光線
6 光触媒ユニット
7 光源
8 分散板
9 ファン
10 平板触媒[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photocatalyst unit in which plate-like photocatalysts used in an exhaust gas or waste liquid treatment apparatus are stacked and an apparatus using the photocatalyst unit, and particularly suitable for efficiently decomposing and removing harmful substances in exhaust gas and waste liquid with a small amount of energy. The present invention relates to a photocatalytic unit and apparatus.
[0002]
[Prior art]
It has been known for a long time that titanium oxide (TiO 2 ) is irradiated with light having a small wavelength (eg, Catalysis Society, edited by Elemental Catalysts p256 (1977)). In recent years, many attempts have been made to remove various organic substances (NOx) in wastewater and exhaust gas by utilizing the photocatalytic function of titanium oxide, purifying exhaust gas in tunnels, and purifying wastewater containing dioxin. Many inventions are applied to the above. In particular, when a photocatalyst is used, various harmful organic substances and nitrogen oxides can be easily decomposed and removed by simply irradiating light. Therefore, removal of volatile organic substances (VOC) and substances causing sick house (harmful components arising from new building materials) Application to the removal of water is energetically advanced.
The shape of the titanium oxide catalyst used for them is fine powder (JP-A-6-12689, etc.), coated with glass or metal (JP-A-7-10378, etc.), and coated on a glass fiber woven fabric. Various types such as felt (Japanese Patent Laid-Open No. 7-96202) are known.
In addition, a number of methods have been examined for the catalyst filling method. In particular, in the method of using a large number of stacked flat photocatalysts (Japanese Patent Laid-Open No. 10-286436), the apparatus arranges a tubular light source extending in the stacking direction next to the flat photocatalyst laminate, and between the adjacent flat photocatalysts. The light is effectively used by irradiating light in the gaps between them and by substantially eliminating the spacers between the adjacent flat plate photocatalysts to suppress the generation of shadows. In this apparatus, since the exhaust gas to be treated is caused to flow through the adjacent flat plate photocatalysts, the pressure loss of the gas flow is small and the exhaust gas purification ability is excellent.
[0003]
On the other hand, the inventors use a flat catalyst that minimizes the occurrence of shadows from the viewpoint of the spacer shape and the arrangement relationship with the light source, from the viewpoint of effectively using light as in JP-A-10-286436. Developed a catalytic device.
[0004]
[Problems to be solved by the invention]
Among the above-mentioned conventional techniques, as shown in FIG. 7, a unit in which flat plates or flat photocatalysts are stacked with a gap therebetween has little pressure loss of gas flow, and light energy utilization efficiency is improved due to the arrangement of the light source and the photocatalyst. Although it is higher than before, it was not sufficient from the viewpoint of effectively utilizing the entire surface of the laminated photocatalyst.
[0005]
That is, according to the results examined by the present inventors, when the tubular light source is disposed in the direction perpendicular to the plane of the flat photocatalyst body on the side of the stacked unit, in other words, in the stacking direction, the gap between the flat plate photocatalyst bodies is Light is sufficiently irradiated only in the vicinity of the entrance. For example, when the pitch (or gap) of the laminated flat photocatalyst bodies is 5 mm, the light irradiation intensity is high up to about 1 cm from the gap entrance, but the intensity thereafter is considerably small. As a result, the photocatalyst located away from the gap entrance and in a place with a small amount of light has not necessarily been effectively used.
[0006]
The object of the present invention is to solve the problem that light is irradiated only in the vicinity of the entrance of the gap between the flat photocatalysts, and to realize a high-performance photocatalytic unit that can effectively use the entire photocatalyst and a photocatalytic device using the same. It is in.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a plurality of flat plate photocatalysts carrying a photocatalyst or a plurality of flat plate photocatalysts having protrusions in a part thereof with a gap , and light is transmitted to the gaps . In the photocatalyst unit for decomposing harmful components contained in the fluid that is irradiated and supplied to the gap , the flat photocatalyst body or the flat photocatalyst body having a projection on a part thereof is a photocatalytic region that carries a photocatalyst on the front surface and the back surface, respectively. And a first photocatalytic unit having a light reflection region made of a metal surface dispersed therein. In the first photocatalyst unit, the photocatalyst regions and the light reflection regions are alternately formed in a strip shape, or are formed so as to occupy the lattice cells alternately, or the photocatalyst regions are distributed in the light reflection regions. And it is preferable that it is formed so as to be scattered.
[0008]
Further, the second photocatalyst unit of the present invention is a photocatalyst region in which the photocatalyst is supported on one side instead of the photocatalyst in the first photocatalyst unit, that is, the photocatalyst having the photocatalyst region and the light reflection region respectively on the front and back surfaces. The photocatalyst having a light reflection region made of a metal surface on the other surface is laminated so that the photocatalyst region and the light reflection region face each other.
[0009]
In addition, the third photocatalyst unit of the present invention carries the photocatalyst on both sides of the plate instead of the photocatalyst in the first photocatalyst unit, that is, the photocatalyst having the photocatalyst region and the light reflection region on both the front and back surfaces, respectively. A plate-like photocatalyst and a light reflector in which both surfaces of the plate are formed of metal surfaces are alternately laminated.
[0010]
Furthermore, in order to achieve the object of the present invention, a photocatalyst device of the present invention includes a container that forms a flow path of a fluid to be treated inside, and any one of the first to third installed in the flow path. A photocatalyst unit and a light source that irradiates light into the gap between the photocatalyst bodies from the vicinity of the photocatalyst unit are provided so that the fluid to be treated flows in a direction along the gap.
[0011]
The light propagation and the action of the photocatalyst in the first photocatalyst unit will be described with reference to FIG. In general, metal has a high reflectance of light having a wavelength of near-ultraviolet or less necessary for excitation of the photocatalyst, so that a light reflection region formed of a metal surface reflects light well. Therefore, as shown in FIG. 4A, a part of the irradiated light beam 5 collides with the photocatalyst region 2 and is used for activation of the photocatalyst, but the light beam 5 irradiated on the light reflection region 1 is reflected. Then, it proceeds toward the back of the gap between the stacked photocatalysts. In this process, since light that collides with the photocatalyst component in the photocatalyst region 2 is sequentially used, light is uniformly irradiated over a wide range of the photocatalyst body. As a result, active species generated by light in a wide range are quickly consumed by the decomposables such as exhaust gas or waste water, and the entire photocatalyst is activated. On the other hand, in the case of the conventional photocatalyst shown in FIG. 4B, the light beam 5 incident on the gap between the photocatalysts can reach only the entrance portion of the gap because it is blocked by the other stacked photocatalysts. Further, the entire surface of the photocatalyst is covered with a photocatalyst component, and since the photocatalyst component usually has a high absorption rate of light in the ultraviolet region and near ultraviolet region, most of the irradiated light beam 5 is absorbed near the entrance of the gap. Therefore, almost no reflection occurs. As a result, active species that are excited by light and necessary for decomposition of harmful substances and the like are concentrated at the entrance of the catalyst layer gap. In addition, the active species of the photocatalyst have a life and have the property of being changed to heat energy or the like if they are not rapidly used for reaction with harmful substances. Because of these, a large amount of active species are localized near the entrance of the gap, so the mass transfer rate due to the diffusion of reactants cannot keep up with the generation rate of the active species, and the frequency at which the active species are not effectively used and disappears. Is big. This inhibits the activation of the photocatalyst.
[0012]
Here, I would like to explain the members that constitute the photocatalyst body according to the present invention. A single metal substrate is used as a member that constitutes the light reflection region and a carrier that carries the photocatalyst in the photocatalyst region. The metal substrate should have a metallic luster such as iron, aluminum, various stainless steels, light metal alloys such as duralumin, etc. and should not cause corrosion or rust in the usage environment. The form of their use is in various forms, such as a plate-like or a state in which the surface is subjected to uneven processing or metal lath processing by machining, or a net-like woven wire metal. Things are used.
As the photocatalyst, an anatase-type or rutile-type titanium oxide alone or a precious metal such as Pt, Pd, etc. prepared by using a sulfuric acid method, a sol-gel method, a gas phase method, etc. Those added with transition metal elements such as can be used. These various photocatalytic components can be used in the form of a sol or a slurry as they are or with an organic binder such as an inorganic binder such as silica sol and titanium peroxide, or a resin dispersion such as polyethylene, polyvinyl alcohol, polyethylene glycol, and Teflon. The surface of the metal substrate is coated, and firing or washing is performed as necessary. As shown in Fig. 1, the photocatalyst component consists of (1) a photocatalyst component-coated portion and a portion where the metal surface is exposed arranged in a band or zigzag manner. (3) Although not shown, it is formed in a state where it is formed on both sides of a part of the photocatalyst bodies that are laminated.
The thickness for coating the catalyst may be large, but it is usually easy to give good results when the thickness is about 0.1 mm to several tens of μm. If the thickness is too large, it is easy to peel off, and if it is too thin, the catalyst component is insufficient and the performance tends to be lowered.
As for the method of laminating the photocatalyst, a plate-like or net-like photocatalyst coated with a catalyst component is used, as shown in FIG. Formed, (C) a part of a flat plate formed with linear projections with angular irregularities, (D) a part of a flat plate formed with linear projections with ridges and depressions, etc. Laminate as shown in FIG. In addition, the shaping | molding shown in FIG. 2 may be after catalyst coating, and may be performed prior to coating. Further, if necessary, the photocatalyst shown in FIG. 1 may be mixed to form a unit.
[0013]
In using the photocatalyst unit of the present invention in an actual apparatus, the arrangement of the light source and the photocatalyst is important. When a tubular light source is used, a tubular longitudinal direction and a plate-like catalyst are placed on the side of the photocatalyst unit. It is good to arrange so that the planes of The photocatalyst body is arranged so that the linear protrusions are parallel to the light irradiation direction. Of course, even if the arrangement of the light source is other than the above, the effect of the present invention is exhibited, but the above-mentioned light source-catalyst arrangement tends to be more effective.
[0014]
Furthermore, the substrate configuration of the photocatalyst body according to the present invention is not necessarily the entire photocatalyst body, and may be used for a part of the whole, for example, a combination of a metal substrate and a ceramic photocatalyst body.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail using specific examples.
(Embodiment 1)
A thin substrate of stainless steel SUS430 having a thickness of 0.2 mm was formed into the shape and dimensions shown in FIG. 5 using a roller press, and a molded substrate cut to a length of 200 mm × 100 mm was prepared. Separately, a flat substrate obtained by cutting a thin plate of SUS430 into 200 mm width × 100 mm length was prepared. In order to remove the oil and fat component during processing, it was degreased in acetone and dried in the air.
On the other hand, 13 g of polyvinyl alcohol having a polymerization degree of 700 (Kuraray Poval 107) was dissolved in 100 ml of water and added to 650 g of weak alkaline silica sol (silica sol-N manufactured by Nissan Chemical Industries). To this solution, 200 g of fine anatase-type titanium oxide (Degussa P-25, surface area 50 m / g) was added and stirred to obtain a first slurry.
The first slurry is applied to the above-mentioned two types of metal substrates in a striped pattern parallel to the longitudinal direction at intervals of about 5 mm in width (see FIG. 1A), thinly applied with a brush, and then dried at 100 ° C. to solidify. I let you. Thereafter, in order to remove excess organic binder, it was exposed to running water to dissolve and remove the binder, and then dried at 100 ° C. to obtain a photocatalyst. The obtained two types of photocatalyst bodies were alternately stacked on a metal frame having a width of 200 mm, a depth of 100 mm, and a height of 300 mm (see FIG. 3A) to produce a photocatalyst unit.
Using a pair of the photocatalytic units of Embodiment 1, the photodecomposition performance of benzene was measured with the test apparatus shown in FIG. Table 1 shows the measurement conditions. The test apparatus includes a container 20 having a gas inlet at one end and a gas outlet at the other end and having a flow path inside, a dispersion plate 8 arranged in the flow path in the container 20, a photocatalytic unit 6, and a tubular light source 7. And another photocatalyst unit 6 and a fan 9 connected to the gas inlet of the container and supplying air containing 10 ppm of benzene to the container 20 as a simulated exhaust gas. The dispersion plate 8 supplies exhaust gas dispersed in the cross section of the flow path. Further, the tubular light source 7 (for example, a fluorescent lamp) is installed at the center in the width direction of the photocatalyst unit 6 and extending in the stacking direction of the photocatalyst bodies in the photocatalyst unit 6. The photocatalyst body is disposed so that the length of the linear protrusion is parallel to the light irradiation direction.
[0016]
[Table 1]
Figure 0003831888
As a result of the test using the photocatalyst unit of Embodiment 1, the benzene decomposition rate was 69% as shown in Table 2 described later.
[0017]
(Embodiment 2)
13 g of polyvinyl alcohol (Kuraraypoval 107) having a polymerization degree of 700 was dissolved in 100 ml of water, and added to 650 g of weak alkaline silica sol (Nissan Chemical Silica Sol-N). To this solution, 170 g of fine anatase-type titanium oxide (Degussa P-25, surface area 50 m / g) was added and stirred to obtain a second slurry.
[0018]
The second slurry is sprayed onto the surface of the two types of metal substrates used in the first embodiment by using a spraying sprayer, and the droplets are distributed over the entire surface of the substrate and about half of the substrate area is a fine slurry droplet. (See FIG. 1C). This photocatalyst body was dried, washed with water, dried and framed under the same conditions as in Embodiment 1 to obtain a photocatalyst unit. Using a pair of the photocatalyst units of the second embodiment, the photodecomposition reaction performance of benzene was measured with the test apparatus shown in FIG. 6 in the same manner as in the first embodiment. As a result of the test using the photocatalytic unit of Embodiment 2, the benzene decomposition rate was 72% as shown in Table 2 described later.
[0019]
(Embodiment 3)
Among the metal substrates in Embodiment 1, a photocatalyst was obtained by applying a catalyst slurry to both surfaces of a flat metal substrate. On the other hand, the metal substrate formed into the shape shown in FIG. 5 was obtained by applying no catalyst to the metal substrate with the entire metal surface exposed. These photocatalyst bodies and metal substrates were alternately stacked in the same manner as in Embodiment 1 to produce a photocatalyst unit.
Using a pair of the photocatalyst units of Embodiment 3, the photodecomposition performance of benzene was measured in the same manner as in Embodiment 1. As a result of the test using the photocatalyst unit of Embodiment 3, the benzene decomposition rate was 62% as shown in Table 2 described later.
[0020]
(Embodiment 4)
The catalyst slurry was applied to one entire surface of the two types of metal substrates used in the first embodiment, and a photocatalyst with the metal surface exposed on the other surface was prepared (see FIG. 1D). The photocatalyst unit was obtained in the same manner except that the layers were laminated so that the surfaces face each other.
Using a pair of the photocatalytic units of Embodiment 4, the photodecomposition performance of benzene was measured in the same manner as in Embodiment 1. As a result of the test using the photocatalyst unit of Embodiment 4, the benzene decomposition rate was 74% as shown in Table 2 described later.
[0021]
(Embodiment 5)
In place of the 0.2 mm SUS substrate used in the first embodiment, a metal lath having a width of about 2 mm was applied (although thin cuts were alternately inserted and pulled to expand into a wire mesh) (expanded) A photocatalyst unit was prepared in the same manner as in Embodiment 1 except that a photocatalyst was formed in a striped pattern.
Using a pair of the photocatalytic units of Embodiment 5, the photodecomposition performance of benzene was measured in the same manner as in Embodiment 1. As a result of the test using the photocatalytic unit of Embodiment 5, the benzene decomposition rate was 65% as shown in Table 2 described later.
[0022]
(Embodiment 6)
130 g of polyvinyl alcohol having a degree of polymerization of 1700 (Kuraraypoval 117) was dissolved in 1000 ml of water and added to 6500 g of weak alkaline silica sol (Silica Sol-N manufactured by Nissan Chemical Industries). To this solution, 2500 g of fine anatase-type titanium oxide (P-25 manufactured by Degussa, surface area 50 m / g) was added and stirred to obtain a viscous third slurry. The slurry was impregnated into a net-like woven fabric obtained by plain weaving 2000 E-glass fibers with a fiber diameter of 6 μm at 8 per inch, and then sandwiched between thermoforming molds and dried to form the shape shown in FIG. Then, it cut | disconnected and obtained the reticulated dry body of 200 mm width x 100 mm length. On the other hand, a metal plate was produced by cutting a 0.3 mm thick aluminum thin plate into 200 mm width × 100 mm length. The catalyst bodies and metal plates prepared above were alternately stacked in the same manner as in Embodiment 1 to produce a photocatalytic unit.
[0023]
Using a pair of the photocatalytic units of Embodiment 6, the photodecomposition performance of benzene was measured in the same manner as in Embodiment 1. As a result of the test using the photocatalyst unit of Embodiment 6, the benzene decomposition rate was 57% as shown in Table 2 described later.
[0024]
(Comparative example)
The catalyst slurry coating method in the first embodiment was changed from a part to the entire surface to prepare a catalyst body in which the entire substrate was covered with the catalyst, and the catalyst body unit was prepared in the same manner as the others. Using a pair of the photocatalyst units obtained in this comparative example, the photodecomposition performance of benzene was measured in the same manner as in the first embodiment. As a result of the test using the photocatalytic unit of the comparative example, as shown in Table 2, the benzene decomposition rate was 36%.
[0025]
[Table 2]
Figure 0003831888
Looking at the benzene decomposition rates summarized in Table 2, the photocatalytic units of Embodiments 1 to 6 show a high benzene decomposition rate of 57 to 74%, while the comparative example shows a low value of 36%. Yes. The photocatalyst used in the comparative example has the entire front and back covered with a catalyst component. On the other hand, the photocatalyst used in each example of the present invention has a photocatalyst region and a light reflection region, and the area covered with the catalyst component is as low as about half of that in the comparative example. As shown, high performance is obtained, and it is obvious that a photocatalyst body composed of a part having a catalytic function on the catalyst surface and a part having a light reflecting function is a very effective means for improving the catalytic performance. is there.
In the first and second embodiments, the opposing surface of the photocatalyst body has a mixture of a photocatalyst region and a light reflection region. On the other hand, in Embodiments 3 and 4, one opposing surface is a photocatalytic region and the other surface is a light reflecting region. As can be seen from the fact that each of the photocatalytic units of Embodiments 1 to 4 shows high catalytic performance, a portion having a catalytic function and a portion having a light reflecting function are provided on different surfaces, and the catalytic function is provided. Excellent catalytic performance can also be achieved by a combination of structures having different functions such as a combination of a flat plate to be used and a flat plate having a light reflecting function.
Further, a photocatalyst body in which metal lath processing is performed and a photocatalyst is supported on a metal substrate having a large number of holes as in the fifth embodiment, or a photocatalyst body in which a photocatalyst is supported on a net-like woven cloth as in the sixth embodiment. In addition, a high value can be obtained even if the surface carrying the photocatalyst is not composed of a flat surface, or a combination of a metal substrate having a light reflecting function and a catalyst composed of an oxide. It shows that the application range of is wide.
As described above, according to the present invention, the essential problem caused by the straightness of light that the entire catalyst cannot be used due to the shadow of the catalyst itself can be improved, and as a result, the catalyst performance is dramatically improved. It becomes possible. Up to now, photocatalytic reaction has been inferior in energy efficiency and tended to be limited to use as an auxiliary means for consumer equipment such as home appliances, but the present invention makes it possible to realize a large and energy-saving photocatalytic reactor, and development of industrial technology The effect on is great.
[0026]
【The invention's effect】
According to the present invention, the photocatalyst unit is configured by laminating a plurality of photocatalysts having a photocatalyst region carrying a photocatalyst on both sides of a plate and a light reflection region made of a metal surface with a gap therebetween. Light incident on the gap travels deep inside the gap while reflecting off the light reflecting area, and as a result, the active species generated by light in a wide range are quickly consumed by the decomposables such as exhaust gas or waste water flowing into the gap. Thus, the entire photocatalyst can be activated, and a high-performance photocatalytic unit can be obtained.
[0027]
Moreover, even if the photocatalyst unit is configured such that one of the opposing surfaces of the laminated plate-like photocatalyst bodies is a photocatalyst region and the other is a light irradiation region, a high-performance photocatalyst unit can be obtained as described above.
[Brief description of the drawings]
FIG. 1 is a diagram showing a pattern of a photocatalyst formed on a photocatalyst body according to the present invention.
FIG. 2 is a diagram showing the shape of a substrate of a photocatalyst according to the present invention.
FIG. 3 is a view showing an example of stacking photocatalyst bodies in the photocatalyst unit of the present invention.
FIG. 4 is a diagram illustrating a light traveling path in the photocatalytic unit of the present invention.
FIG. 5 is a diagram showing the shape and size of the photocatalyst produced in the embodiment of the present invention.
FIG. 6 is a view showing a test apparatus for measuring the catalyst performance of the photocatalyst unit of the present invention.
FIG. 7 is a supplementary diagram for explaining a problem of the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light reflection area | region 2 Photocatalyst area | region 3 Flat plate catalyst 4 Molding catalyst 5 Light beam 6 Photocatalyst unit 7 Light source 8 Dispersing plate 9 Fan 10 Flat plate catalyst

Claims (6)

光触媒を担持した複数枚の平板光触媒体または一部に突起を有する複数枚の平板光触媒体を隙間をもって積層してなり、前記隙間に対して光が照射され前記隙間に供給される流体に含まれる有害成分を分解する光触媒ユニットにおいて、
前記平板光触媒体または一部に突起を有する平板光触媒体は、その表面及び裏面にそれぞれ、光触媒を担持した光触媒領域と金属面でなる光反射領域とを分散して有することを特徴とする光触媒ユニット。
A plurality of flat photocatalysts carrying a photocatalyst or a plurality of flat photocatalysts having protrusions on a part thereof are stacked with a gap, and light is irradiated to the gap and is contained in the fluid supplied to the gap. In the photocatalytic unit that decomposes harmful components,
The flat photocatalyst body or the flat photocatalyst body having a protrusion on a part thereof has a photocatalyst region carrying a photocatalyst and a light reflection region composed of a metal surface dispersed on the front and back surfaces, respectively. .
前記光触媒領域及び前記光反射領域はそれぞれ帯状に交互に形成されたことを特徴とする請求項1記載の光触媒ユニット。  The photocatalyst unit according to claim 1, wherein the photocatalyst region and the light reflection region are alternately formed in a band shape. 前記光触媒領域及び前記光反射領域は、格子の桝目を交互に占めるように形成されたことを特徴とする請求項1記載の光触媒ユニット。  The photocatalyst unit according to claim 1, wherein the photocatalyst region and the light reflection region are formed so as to alternately occupy a grid of lattices. 前記光触媒領域は前記光反射領域中に分布して点在することを特徴とする請求項1記載の光触媒ユニット。  The photocatalytic unit according to claim 1, wherein the photocatalytic regions are distributed and scattered in the light reflecting region. 請求項1記載の光触媒ユニット用部品として、板の表面及び裏面にそれぞれ、光触媒を担持した光触媒領域と金属面でなる光反射領域とを分散して有する光触媒体。  2. A photocatalyst body having a photocatalyst region carrying a photocatalyst and a light reflection region made of a metal surface on a front surface and a back surface of the plate as the parts for a photocatalyst unit according to claim 1. 被処理流体の流路を内部に形成する容器と、前記流路内に設置された請求項1ないし4のいずれか一項に記載の光触媒ユニットと、該光触媒ユニットの近傍から前記光触媒体間の隙間に光を照射する光源とからなり、前記被処理流体を前記隙間に沿う方向に流すことを特徴とする光触媒装置。A container that forms a flow path for a fluid to be treated, a photocatalyst unit according to any one of claims 1 to 4 installed in the flow path, and a space between the photocatalyst bodies from the vicinity of the photocatalyst unit. A photocatalyst device comprising a light source for irradiating light to a gap, and causing the fluid to be treated to flow in a direction along the gap.
JP07898199A 1999-03-24 1999-03-24 Photocatalyst unit and apparatus using the same Expired - Fee Related JP3831888B2 (en)

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