JP3899054B2 - Highly efficient ozonolysis porous material and method for producing the same - Google Patents
Highly efficient ozonolysis porous material and method for producing the same Download PDFInfo
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- JP3899054B2 JP3899054B2 JP2003205033A JP2003205033A JP3899054B2 JP 3899054 B2 JP3899054 B2 JP 3899054B2 JP 2003205033 A JP2003205033 A JP 2003205033A JP 2003205033 A JP2003205033 A JP 2003205033A JP 3899054 B2 JP3899054 B2 JP 3899054B2
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- 238000005949 ozonolysis reaction Methods 0.000 title claims description 35
- 239000011148 porous material Substances 0.000 title claims description 15
- 238000004519 manufacturing process Methods 0.000 title claims description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical group [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims description 48
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 29
- 239000013078 crystal Substances 0.000 claims description 25
- 239000011572 manganese Substances 0.000 claims description 22
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims description 18
- HBTFASPVVFSRRI-UHFFFAOYSA-N manganese(2+);dinitrate;hydrate Chemical compound O.[Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O HBTFASPVVFSRRI-UHFFFAOYSA-N 0.000 claims description 16
- 239000000919 ceramic Substances 0.000 claims description 14
- 238000000354 decomposition reaction Methods 0.000 claims description 14
- 239000007864 aqueous solution Substances 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- HJGMWXTVGKLUAQ-UHFFFAOYSA-N oxygen(2-);scandium(3+) Chemical group [O-2].[O-2].[O-2].[Sc+3].[Sc+3] HJGMWXTVGKLUAQ-UHFFFAOYSA-N 0.000 claims description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 150000001875 compounds Chemical class 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 3
- 230000008018 melting Effects 0.000 claims description 3
- 238000010304 firing Methods 0.000 claims description 2
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical group [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 claims 1
- 238000000034 method Methods 0.000 description 18
- 238000010438 heat treatment Methods 0.000 description 16
- 239000003054 catalyst Substances 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 230000003197 catalytic effect Effects 0.000 description 7
- 238000002441 X-ray diffraction Methods 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 6
- YMKHJSXMVZVZNU-UHFFFAOYSA-N manganese(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YMKHJSXMVZVZNU-UHFFFAOYSA-N 0.000 description 5
- 238000005452 bending Methods 0.000 description 4
- 238000004523 catalytic cracking Methods 0.000 description 4
- 239000006260 foam Substances 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 229910052596 spinel Inorganic materials 0.000 description 3
- 239000011029 spinel Substances 0.000 description 3
- 239000011800 void material Substances 0.000 description 3
- 239000002918 waste heat Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000001954 sterilising effect Effects 0.000 description 2
- 238000004659 sterilization and disinfection Methods 0.000 description 2
- -1 transition metal salt Chemical class 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 238000004887 air purification Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000004332 deodorization Methods 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 235000012055 fruits and vegetables Nutrition 0.000 description 1
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- 125000001475 halogen functional group Chemical group 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
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- 150000002697 manganese compounds Chemical class 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
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- HYXGAEYDKFCVMU-UHFFFAOYSA-N scandium oxide Chemical compound O=[Sc]O[Sc]=O HYXGAEYDKFCVMU-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
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Description
【０００１】
【発明の属する技術分野】
本発明は、空気中のオゾンを分解して人体に無害の空気とするためのオゾン分解用多孔体とその製造方法に関する。
【０００２】
【従来の技術】
近年、静電複写機やレーザープリンター等のオゾンを発生する事務用機器が普及し、また、上水の浄化及び殺菌、室内の空気清浄及び脱臭、青果物の鮮度保持等、各種殺菌の目的のためにオゾンを利用する技術が普及するのに伴い、大気中にオゾンが放出される機会が増加している。そのため、オゾンの無害化を目的とした高効率の分解手段の必要性が高まっている。
【０００３】
従来からオゾンを分解する手段として、活性炭処理法、加熱分解法および接触分解法などがある。 このうち、接触分解法は触媒を利用してオゾンを分解する方法であり、他の二方法と比較して、安全性が高く、常温で処理可能であり、装置が小型にできるなどの多くの利点を有する。
【０００４】
接触分解法で使用されるオゾン分解触媒としては、コストと性能面から酸化マンガン系のものが従来から使用されている。酸化マンガンをオゾンの接触分解触媒として使用するに際して、接触面積を大きくして触媒能を増大させるため、繊維状もしくはフォーム状やハニカム状の多孔質状担体に酸化マンガン微粉末及びその他の成分を塗布する方法などが多数提案されている。
【０００５】
特許文献１や特許文献２には、酸化マンガンを担体に固着させるために、有機系結合剤または無機系結合剤が用いる例が挙げられており、これら結合剤と水やアルコールなどの溶媒で酸化マンガン粉末をスラリー状にしたものを担体に含浸・塗布し、その後、溶媒を乾燥、除去したものを触媒として用いることが紹介されている。
【０００６】
しかしながら、この方法は、酸化マンガン粉末の塗布面における均一性や固着性に劣り、オゾン分解能が使用中に徐々に低下していくという問題があった。また、いずれの結合剤も空気中の水分を多量に吸着する性質があるため、酸化マンガンのオゾン分解触媒能を阻害するという欠点もある。
【０００７】
また、特許文献３は、多孔質状の担体を硝酸マンガン等のマンガン化合物の希薄な溶液に浸漬した後、空気中で３００ 〜 ５００℃の温度範囲まで加熱し、担体表面にマンガン酸化物を生成付着させることを開示している。この方法によれば、担体表面に酸化マンガン微粒子を付着塗布させるときの均一性や固着性は改善されている。しかしながら、この方法で作成されたオゾン分解用多孔体は、そのオゾン分解機能が、実用的に未だ十分なレベルに到達しているとは言い難く、加えて短時間の使用において急速に劣化していく問題を有している。
【０００８】
【特許文献１】
特開平５-７７７６号公報
【０００９】
【特許文献２】
特開平５-２６１２９４号公報
【００１０】
【特許文献３】
特開昭６３-１９７５２４号公報
【００１１】
【発明が解決しようとする課題】
本発明は、上記従来のオゾン分解用多孔体の問題を解消するもので、通気性能の優れた多孔質状担体の表面に、安価で優れたオゾン分解触媒能を有するマンガン酸化物を、結合材を使用することなく均一に、かつ、強固に付着させることによって高効率で長寿命のオゾン分解用多孔体を提供する。
【００１２】
【課題を解決するための手段】
本発明は、三次元網目構造を有するセラミックスの多孔質状担体に、硝酸マンガン水和物の結晶を融解した硝酸マンガン水溶液、または、硝酸マンガン水和物の結晶を水もしくはアルコールで希釈した硝酸マンガン水溶液の希釈溶液を含浸し、乾燥したのち、融点以下に維持して硝酸マンガン水和物を固化し、さらに、５００〜７００℃の温度域まで昇温し焼成して得られた高効率オゾン分解用多孔体であって、前記の多孔質状担体の骨格表面にはマンガン酸化物またはマンガン酸化物を主成分とする化合物が固着してなり、この固着した化合物の結晶構造は酸化スカンジウム構造のＣ型Ｍｎ２Ｏ３であることを特徴とする。これによってオゾン分解用多孔体の分解効率の向上と長寿命化を達成した。さらには、マンガン硝酸塩をオゾン分解触媒の出発原料として用いた場合には、触媒担体への付着性状がより改善され、それに伴いオゾン分解効率が向上する。
【００１４】
本発明における多孔質状担体は、十分な通気性を確保するため連続した開口空隙を有し、その空隙横断面の円換算直径の平均値が、０.１〜１０ ｍｍの範囲内にあることが望ましい。その空隙の直径が０.１ ｍｍ以下では、通気抵抗が著しく増大し、実用的ではない。また、１０ｍｍ以上では、単位体積中の空気通気孔の表面積が限られることになり、触媒との十分な接触が得られず、オゾン分解能において劣る。
【００１５】
多孔質状担体を構成する材質としては、５００ 〜 ７００℃の熱処理温度に耐えられるものであればとくに限定されない。例えば、多孔質ガラスや多孔質セラミックス等が使用できるが、硬度や強度の点から多孔質セラミックスが好ましい。 セラミックスの材質としては、アルミナ、コージエライト、ムライト、ジルコニア、窒化ケイ素、炭化ケイ素等が使用できる。
【００１６】
多孔質状担体としては、開口空隙が三次元網目構造を有するセラミックスを使用し、三次元網目構造の隙間は複数の不規則経路となっているために、通過するオゾンガスは、担体での滞留時間が長くなり、オゾンとマンガン酸化物との接触時間が多くなるため触媒性能が向上する。
【００１７】
三次元網目構造の孔のサイズを規定する単位として、１インチの直線上を通過するセルの数をセル数として＃Ｎと表記する。Ｎはセルの数である。すなわち、孔のサイズが小さいほどセル数は大きくなる。本発明の場合、セル数は＃３から＃２０の範囲がより好ましく、最大＃６０までである。＃３より小さい場合は、一つの孔サイズが大きくなり、担体でのガス滞留時間が短くなりオゾンの分解効率が劣る。また＃６０より大きい場合、担体製造方法上も空隙部を形成する骨格部の厚みが十分とれずに担体の強度が確保できない。
【００１８】
多孔体にとって大事な通気特性を示す指標として見かけ空孔率がある。本発明のオゾン分解用多孔体の場合、＃３〜＃２０で８０％程度、＃４０〜＃６０で７０％程度の空孔率を示す。この見掛け空孔率は、以下の計算式で求められる。
【００１９】
（１−多孔体の嵩密度／使用原料の焼結体の理論密度）×１００％
触媒物質の固着強度を、結合剤を用いることなく高温で焼成することにより高める方法が考えられるが、金属酸化物を焼結させるためには、通常１０００℃以上の高温による熱処理が必要となる。しかしながら、この温度域では、酸化マンガンはＭｎ３Ｏ４の化学式で示される歪んだスピネル構造を有する形態を取る。このＭｎ３Ｏ４の分子構造では２価と３価のＭｎが混合しており、この場合、２価のＭｎがオゾンによって酸化されて３価になると元に戻らないため触媒能が低い。
【００２０】
触媒物質として優れた酸化マンガンを担体表面に強固に付着させるためには、酸化マンガンの前駆体として硝酸マンガン溶液を使用し、これを担体に塗布し、含浸した後に適切な温度条件で熱処理することが効果的である。
【００２１】
硝酸マンガン溶液は、その濃度は特に規定されないが、通常は、硝酸マンガン水和物Ｍｎ(ＮＯ３)２・ｎＨ２０ (ｎ=１,２,３,４,５,６)の結晶を融解して用いる。硝酸マンガン水和物の結晶は２５.８℃以上の温度で融解し、それ自身の持つ結晶水に自己溶解し、やや粘性のある硝酸マンガン水溶液を生成する。そのため、有機系や無機系バインダーを用いることなく、前記多孔質担体に容易に一定量を塗布含浸することが可能となる。また、塗布含浸後の余分な水溶液は、エアガンで除去した後、融点の ２５.８℃以下に一旦保持することにより、得られた硝酸マンガン塩は直ぐに固化する。したがって、従来のスラリーを用いる場合のような乾燥工程を必要としない。
【００２２】
硝酸マンガン水和物には、前記自己溶解性を阻害しない範囲内で、遷移金属塩、希土類金属塩のようにオゾン分解能を有する塩をオゾン分解能改善の目的で添加しても良い。
【００２３】
また、硝酸マンガン溶液には、硝酸マンガン水和物Ｍｎ(ＮＯ３)２・ｎＨ２０ (ｎ=１,２,３,４,５,６)を、水もしくはアルコールで希釈した希薄溶液として用いることもできる。この希薄溶液を用いる場合には、前記自己溶解した硝酸マンガン水溶液と同様に、多孔質担体に含浸させた後、自然乾燥させて水分やアルコール分を蒸発させたのち、２５.８℃以下に維持することで硝酸マンガン水和物が固化する。この方法では硝酸マンガン水和物は、自己溶解した硝酸マンガン水溶液単体ほどに効率よく付着膜厚を形成できないが、この操作を多数回くりかえすことでより精密な膜厚制御が可能になる。
【００２４】
多孔質状担体にマンガン硝酸塩溶液を含浸せしめると、担体表面からある程度の深さまで入り込むが、２５.８℃以下の温度に一旦下げれば、大部分の硝酸マンガン塩は水和物結晶として表面に留まっている。この状態で加熱を開始すると、硝酸マンガン水和物結晶は自身の結晶水に溶解後、結晶水を蒸散し、溶融塩の状態に変化する。この硝酸マンガン溶融塩は、すべての物質に対して良好な濡れ性を発揮し、多孔質状担体の骨格材料表面に均一な被膜を生成する。さらに加熱を続ける過程で、硝酸マンガン溶融塩は、徐々にＮＯxを発生しながら分解して最終的に酸化マンガンに変化するが、その時の強い酸化作用が担体表面を活性化し、均一な酸化マンガン膜が担体表面と強固に結合するという結果を生む。
【００２５】
加熱処理では５００〜７００℃の温度域まで昇温する。この温度域まで加熱することによって、担体骨格表面に付着した酸化マンガンの結晶構造は、Ｃ型Ｍｎ２Ｏ３の酸化スカンジウム構造を呈する。
【００２６】
この酸化スカンジウム構造の酸化マンガンであるＣ型Ｍｎ２Ｏ３は、オゾンと接触するとその強力な酸化作用により、その表面がＭｎＯ２に変化するが、酸化スカンジウム構造（Ｃ型）ではＭｎＯ２は不安定なため、速やかにＭｎ２Ｏ３に戻り、その際に生じた活性酸素がオゾンと反応して酸素分子に分解する。
【００２７】
本発明のオゾン分解用多孔体においては、酸化スカンジウム構造の結晶は、Ｘ線回折法で分析したときに母材であるアルミナの回折ピークの他に現れる大部分のピークがＣ型Ｍｎ２Ｏ３のものであればよい。
【００２８】
本発明のオゾン分解用多孔体における分解−成膜過程における熱処理温度は、最終到達温度が５００ 〜 ７００℃の範囲内でなければならない。５００℃未満では、仮に処理時間を長くしても、その結晶構造を酸化スカンジウム構造（Ｃ型）にすることができない。また、７００℃以上では、酸化マンガンの結晶粒径が大きくなって表面積が減少し、さらに、歪んだスピネル構造を形成することになり、Ｍｎ３Ｏ４ の結晶が増え、十分なオゾン分解効率を得ることができない。処理温度が５００ 〜 ７００℃の範囲内では、その最適処理時間は適宜変化させることができる。熱処理雰囲気としては、大気中でよいが、必要に応じてその酸素分圧を変化させても良い。
【００２９】
本発明のオゾン分解用多孔体を使用中に加熱すると、オゾン分解触媒としての活性度は飛躍的に高まる。しかしながら、その際の温度は、使用される外的条件により制御する必要がある。すなわち、余分な廃熱の処理ができるような外的条件では、酸化スカンジウム構造（Ｃ型）の酸化マンガン結晶粒の成長が進行しない温度である７００℃まで理論的には温度を上げることが可能である。結晶粒が大きくなるとそれに応じて全体の表面積が小さくなり触媒能が劣る。例えば、家庭内や事務所において、このような高温条件で使用することは非現実的である。
【００３０】
一般的な用途では、数十℃から百数十℃程度までの加熱に留めておくほうが廃熱処理の観点から好ましい。しかしながら、工場内に設置する等の廃熱を処理できる使用条件においてはこの限りではない。
【００３１】
【発明の実施形態】
以下、本発明の実施形態を実施例に基づいて説明する。
【００３２】
【実施例】
実施例１
５０×５０×２５ ｍｍに加工した三次元網目構造の多孔体セラミックス（黒崎播磨株式会社製セラミックフォーム＃６：白色、純度９８％のアルミナ材質、セル数＃６ 、見かけ空孔率８０ ％、曲げ強度４５ｋｇ/ｃｍ２）を、３０℃で結晶水に溶解した硝酸マンガン６水和物Ｍｎ(ＮＯ３)２・６Ｈ２０に浸漬し、余分な溶液をエアガンで吹き払った後、そのまま室温中(２０℃)に放置し、硝酸マンガン水和物を担体表面に固着した。
【００３３】
次いで、大気中５００、６００、７００℃の各温度まで昇温後、そのまま１時間キープする熱処理を施したものをオゾン分解用多孔体とした。各オゾン分解用多孔体をＸ線回折法で分析した所、図１に示すように、骨材であるアルミナの回折ピークの他に、すべての多孔体において酸化スカンジウム構造（Ｃ型）Ｍｎ２Ｏ３の回折ピークが観察された。
【００３４】
得られたオゾン分解用多孔体のオゾン分解効率を、２５℃で相対湿度 ５０％の条件下、１ ｐｐｍの濃度のオゾンを含む空気を 空間速度ＳＶ = ７２００ (ｈ- １)にてオゾン分解用多孔体に通過させた時のオゾン分解率 を
１００ x（オゾン分解用多孔体通過後のｐｐｍ濃度）／１
によって評価した。 それぞれのオゾン分解率を表１に示す。
【００３５】
実施例２
実施例１と同じく、５０×５０×２５ ｍｍに加工した三次元網目構造の多孔体セラミックス（黒崎播磨株式会社製セラミックフォーム＃１３：白色，純度９８％のアルミナ材質、セル数＃１３、見かけ空孔率８０％、曲げ強度４５ｋｇ/ｃｍ２）を、硝酸マンガン６水和物Ｍｎ(ＮＯ３)２・６Ｈ２Ｏの１０％水溶液に浸漬し、余分な溶液をエアガンで吹き払った後、風乾し、この操作を３回繰り返した。次いで、大気中６００℃まで昇温後１時間キープする熱処理を施したものを、オゾン分解用多孔体とした。本オゾン分解用多孔体をＸ線回折法で分析した所、骨材であるアルミナの回折ピークの他に、酸化スカンジウム構造（Ｃ型）Ｍｎ２Ｏ３の回折ピークが観察された。
【００３６】
本オゾン分解用多孔体のオゾン分解効率を実施例１と同様に評価した結果を表１に示す。硝酸マンガン６水和物の希釈水溶液を使用し、含浸塗布操作を繰り返すことにより酸化マンガンの膜厚制御とセル数を大きくした効果が現れ、実施例１多孔体と比較してオゾン分解率に優れる結果となっている。
【００３７】
比較例１
実施例１と同じく、５０×５０×２５ ｍｍに加工した三次元網目構造の多孔体セラミックス（黒崎播磨株式会社製セラミックフォーム＃６：白色、純度９８％のアルミナ材質、セル数＃６、見かけ空孔率８０％、曲げ強度４５ｋｇ/ｃｍ２）を、３０℃で結晶水に溶解した硝酸マンガン６水和物Ｍｎ(ＮＯ３)２・６Ｈ２０に浸漬し、余分な溶液をエアガンで吹き払った後、２０℃で固化させた。次いで、大気中２００、３００、４００、４５０℃の各温度まで昇温後そのまま１時間キープする熱処理を施したものを、オゾン分解用多孔体とした。各オゾン分解用多孔体をＸ線回折法で分析した所、骨材であるアルミナの回折ピークの他に、２００℃で熱処理した多孔体には非晶質に特有のハローがみられ、３００と４００℃の各温度で熱処理した多孔体にはルチル構造（β型）ＭＮＯ２の回折ピークが観察された。
【００３８】
このオゾン分解用多孔体のオゾン分解効率を実施例１と同様に評価した結果を表１に示す。いずれの多孔体もオゾン分解率が劣る結果となっている。
【００３９】
【表１】
実施例１と同じく、５０×５０×２５ ｍｍに加工した三次元網目構造の多孔体セラミックス（黒崎播磨株式会社製セラミックフォーム＃６：白色、純度９８％のアルミナ材質、セル数＃６、見かけ空孔率８０％、曲げ強度４５ｋｇ/ｃｍ２）を、３０℃で結晶水に溶解した硝酸マンガン６水和物Ｍｎ(ＮＯ３)２・６Ｈ２０に浸漬し、余分な溶液をエアガンで吹き払った後、２０℃で固化させた。次いで、大気中７５０、８００、９００℃の各温度まで昇温後１時間キープする熱処理を施したものを、オゾン分解用多孔体とした。各オゾン分解用多孔体をＸ線回折法で分析した所、骨材であるアルミナの回折ピークの他に、すべての多孔体に、酸化スカンジウム構造（Ｃ型）Ｍｎ２Ｏ３とひずんだスピネル構造を有するＭｎ３Ｏ４の回折ピークが観察された。得られたオゾン分解用多孔体のオゾン分解効率を実施例１と同様に評価した結果を表１に示す。いずれの多孔体も実施例と較べてオゾン分解効率が劣る結果となっている。
【００４０】
【発明の効果】
本発明は、熱処理温度を制御することによって、連続した開口空隙を有する担体骨格表面に酸化マンガンの結晶構造が均一にかつ強固に付着したオゾン分解用多孔体であって、優れた触媒能を有し、機械的衝撃にも強く、長寿命かつ安定した触媒能を発揮する。
【図面の簡単な説明】
【図１】 本発明に係るオゾン分解用多孔体のＸ線回折法による分析結果を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a porous body for ozonolysis for decomposing ozone in the air into harmless air and a method for producing the same .
[0002]
[Prior art]
In recent years, office machines that generate ozone, such as electrostatic copying machines and laser printers, have become widespread, and for various sterilization purposes such as purification and sterilization of clean water, indoor air purification and deodorization, and freshness maintenance of fruits and vegetables. As technology using ozone spreads, the opportunity for ozone to be released into the atmosphere is increasing. For this reason, the need for highly efficient decomposition means aimed at detoxifying ozone is increasing.
[0003]
Conventional means for decomposing ozone include an activated carbon treatment method, a thermal decomposition method, and a catalytic decomposition method. Among them, the catalytic cracking method is a method of decomposing ozone using a catalyst. Compared with the other two methods, the catalytic cracking method is safer, can be treated at room temperature, and can be reduced in size. Have advantages.
[0004]
As the ozonolysis catalyst used in the catalytic cracking method, a manganese oxide catalyst has been conventionally used in terms of cost and performance. When manganese oxide is used as a catalytic cracking catalyst for ozone, fine powder of manganese oxide and other components are applied to a fibrous, foam-like or honeycomb-like porous carrier in order to increase the contact area and increase the catalytic performance. Many methods have been proposed.
[0005]
[0006]
However, this method is inferior in uniformity and adhesion on the coated surface of the manganese oxide powder, and has a problem that the ozone resolution gradually decreases during use. In addition, since any of the binders has a property of adsorbing a large amount of moisture in the air, it also has a drawback of inhibiting the ozonolysis catalytic ability of manganese oxide.
[0007]
Patent Document 3 discloses that a porous carrier is immersed in a dilute solution of a manganese compound such as manganese nitrate and then heated in air to a temperature range of 300 to 500 ° C. to produce manganese oxide on the surface of the carrier. It is disclosed that it is adhered. According to this method, the uniformity and adhesion when the manganese oxide fine particles are applied to the surface of the carrier are improved. However, it is difficult to say that the ozonolysis porous material prepared by this method has yet reached a practically sufficient level, and in addition, it deteriorates rapidly in a short period of use. Have many problems.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-7776
[Patent Document 2]
JP-A-5-261294
[Patent Document 3]
Japanese Patent Laid-Open No. 63-197524
[Problems to be solved by the invention]
The present invention solves the problem of the conventional porous body for ozonolysis, and binds a manganese oxide having an inexpensive and excellent ozonolysis catalytic activity to the surface of a porous carrier having excellent air permeability. A highly efficient and long-lasting porous body for ozonolysis is provided by uniformly and firmly adhering without using any.
[0012]
[Means for Solving the Problems]
The present invention relates to a porous ceramic carrier having a three-dimensional network structure, a manganese nitrate aqueous solution in which manganese nitrate hydrate crystals are melted, or manganese nitrate hydrate crystals diluted with water or alcohol. High-efficiency ozonolysis obtained by impregnating diluted solution of aqueous solution and drying, solidifying manganese nitrate hydrate by maintaining below melting point, and further heating up to 500 to 700 ° C and baking The porous body is made of manganese oxide or a compound containing manganese oxide as a main component fixed to the surface of the skeleton of the porous carrier, and the crystal structure of the fixed compound is C in a scandium oxide structure. It is the type Mn 2 O 3 . As a result, the decomposition efficiency of the porous body for ozonolysis was improved and the service life was extended. Furthermore, when manganese nitrate is used as a starting material for the ozone decomposition catalyst, the adhesion property to the catalyst carrier is further improved, and accordingly, the ozone decomposition efficiency is improved.
[0014]
The porous carrier in the present invention has continuous open voids in order to ensure sufficient air permeability, and the average value of the circle-converted diameter of the void cross section is within the range of 0.1 to 10 mm. Is desirable. When the diameter of the void is 0.1 mm or less, the ventilation resistance is remarkably increased, which is not practical. On the other hand, if it is 10 mm or more, the surface area of the air vent in the unit volume is limited, and sufficient contact with the catalyst cannot be obtained, resulting in poor ozone resolution.
[0015]
The material constituting the porous carrier is not particularly limited as long as it can withstand the heat treatment temperature of 500 to 700 ° C. For example, porous glass or porous ceramics can be used, but porous ceramics are preferable in terms of hardness and strength. As the ceramic material, alumina, cordierite, mullite, zirconia, silicon nitride, silicon carbide, or the like can be used.
[0016]
As the porous carrier, ceramics with open pores having a three-dimensional network structure are used, and the gaps in the three-dimensional network structure have a plurality of irregular paths. The catalyst performance is improved because the contact time between ozone and manganese oxide is increased.
[0017]
As a unit for defining the size of the hole of the three-dimensional network structure, the number of cells passing on a straight line of 1 inch is expressed as #N as the number of cells. N is the number of cells. That is, the smaller the hole size, the larger the number of cells. In the case of the present invention, the number of cells is more preferably in the range of # 3 to # 20, and is up to # 60. If it is smaller than # 3, one pore size is increased, the gas residence time in the carrier is shortened, and the ozone decomposition efficiency is inferior. On the other hand, if it is larger than # 60, the strength of the carrier cannot be secured because the thickness of the skeleton forming the void is not sufficient in the carrier production method.
[0018]
There is an apparent porosity as an index showing an air permeability characteristic important for a porous body. In the case of the ozonolysis porous material of the present invention, # 3 to # 20 show a porosity of about 80%, and # 40 to # 60 show a porosity of about 70%. This apparent porosity is obtained by the following calculation formula.
[0019]
(1-the bulk density of the porous body / theoretical density of the sintered material used) x 100%
A method of increasing the fixing strength of the catalyst substance by firing at a high temperature without using a binder is conceivable, but in order to sinter the metal oxide, a heat treatment at a high temperature of 1000 ° C. or higher is usually required. However, in this temperature range, manganese oxide takes a form having a distorted spinel structure represented by a chemical formula of Mn 3 O 4 . In the molecular structure of Mn 3 O 4 , divalent and trivalent Mn are mixed. In this case, when divalent Mn is oxidized by ozone and becomes trivalent, it does not return to its original state, so the catalytic ability is low.
[0020]
In order to firmly adhere manganese oxide, which is excellent as a catalyst substance, to the support surface, use a manganese nitrate solution as a manganese oxide precursor, apply it to the support, impregnate it, and then heat-treat at an appropriate temperature condition. Is effective.
[0021]
The concentration of the manganese nitrate solution is not particularly limited, but normally the manganese nitrate hydrate Mn (NO 3 ) 2 · nH 2 0 (n = 1, 2, 3, 4, 5, 6) is melted. And use. Manganese nitrate hydrate crystals melt at a temperature of 25.8 ° C. or higher and self-dissolve in the crystal water of their own to produce a slightly viscous manganese nitrate aqueous solution. Therefore, it is possible to easily apply and impregnate a certain amount of the porous carrier without using an organic or inorganic binder. Further, after removing the excess aqueous solution after the impregnation with an air gun, the obtained manganese nitrate salt is immediately solidified by being temporarily held at a melting point of 25.8 ° C. or lower. Therefore, a drying step as in the case of using a conventional slurry is not required.
[0022]
To the manganese nitrate hydrate, a salt having ozone decomposability, such as a transition metal salt or a rare earth metal salt, may be added for the purpose of improving the ozone decomposability within the range not inhibiting the self-solubility.
[0023]
As the manganese nitrate solution, a manganese nitrate hydrate Mn (NO 3 ) 2 .nH 2 0 (n = 1, 2, 3, 4, 5, 6) is used as a dilute solution diluted with water or alcohol. You can also. When this dilute solution is used, like the self-dissolved manganese nitrate aqueous solution, after impregnating the porous carrier, it is naturally dried to evaporate moisture and alcohol, and then maintained at 25.8 ° C. or lower. By doing so, manganese nitrate hydrate solidifies. In this method, manganese nitrate hydrate cannot form the deposited film thickness as efficiently as the self-dissolved manganese nitrate aqueous solution alone, but more precise film thickness control can be achieved by repeating this operation many times.
[0024]
When a porous support is impregnated with a manganese nitrate solution, it penetrates from the support surface to a certain depth, but once it is lowered to a temperature of 25.8 ° C. or less, most of the manganese nitrate remains on the surface as hydrate crystals. ing. When heating is started in this state, the manganese nitrate hydrate crystal dissolves in its own crystal water, and then the crystal water is evaporated to change to a molten salt state. This manganese nitrate molten salt exhibits good wettability with respect to all substances, and forms a uniform film on the surface of the skeleton material of the porous carrier. In the process of further heating, the manganese nitrate molten salt gradually decomposes while generating NO x and eventually changes to manganese oxide. The strong oxidizing action at that time activates the surface of the carrier, resulting in uniform manganese oxide. The result is that the membrane is firmly bonded to the support surface.
[0025]
In the heat treatment, the temperature is raised to a temperature range of 500 to 700 ° C. By heating to this temperature range, the crystal structure of manganese oxide attached to the surface of the carrier skeleton exhibits a scandium oxide structure of C-type Mn 2 O 3 .
[0026]
C-type Mn 2 O 3 , which is manganese oxide having a scandium oxide structure, changes its surface to MnO 2 due to its strong oxidizing action when it comes into contact with ozone, but MnO 2 is not present in the scandium oxide structure (C type). Since it is stable, it quickly returns to Mn 2 O 3 and the active oxygen generated at that time reacts with ozone and decomposes into oxygen molecules.
[0027]
In the porous body for ozonolysis of the present invention, most of peaks appearing in addition to the diffraction peak of alumina, which is the base material, are C-type Mn 2 O 3 in the scandium oxide structure crystals when analyzed by X-ray diffraction. If it is a thing.
[0028]
The final heat treatment temperature in the decomposition-film formation process in the ozonolysis porous material of the present invention must be in the range of 500 to 700 ° C. If it is less than 500 degreeC, even if processing time is lengthened, the crystal structure cannot be made into a scandium oxide structure (C type). Further, at 700 ° C. or higher, the crystal grain size of manganese oxide is increased, the surface area is reduced, and a distorted spinel structure is formed. The crystal of Mn 3 O 4 is increased, and sufficient ozone decomposition efficiency is obtained. Can't get. When the treatment temperature is in the range of 500 to 700 ° C., the optimum treatment time can be appropriately changed. The heat treatment atmosphere may be air, but the oxygen partial pressure may be changed as necessary.
[0029]
When the porous body for ozonolysis of the present invention is heated during use, the activity as an ozonolysis catalyst increases dramatically. However, the temperature at that time needs to be controlled by the external conditions used. In other words, under external conditions where excess waste heat can be treated, the temperature can theoretically be raised to 700 ° C., which is the temperature at which the growth of scandium oxide (C type) manganese oxide crystal grains does not proceed. It is. When the crystal grains are increased, the entire surface area is reduced accordingly, and the catalytic ability is deteriorated. For example, it is unrealistic to use it under such high temperature conditions in a home or office.
[0030]
In general applications, it is preferable to keep the heating at about several tens of degrees Celsius to about several hundred tens of degrees Celsius from the viewpoint of waste heat treatment. However, this is not the case in use conditions where waste heat such as installation in a factory can be treated.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0032]
【Example】
Example 1
Porous ceramics with a three-dimensional network structure processed to 50 × 50 × 25 mm (Ceramic foam # 6 manufactured by Kurosaki Harima Co., Ltd., white, alumina material with a purity of 98%, cell number # 6, apparent porosity 80%, bending (Strength 45 kg / cm 2 ) was immersed in manganese nitrate hexahydrate Mn (NO 3 ) 2 · 6H 20 dissolved in crystal water at 30 ° C., and the excess solution was blown off with an air gun, and then at room temperature. (20 ° C.), the manganese nitrate hydrate was fixed on the support surface.
[0033]
Next, after heating up to 500, 600, and 700 ° C. in the atmosphere, a material subjected to heat treatment for keeping for 1 hour as it was was used as a porous body for ozone decomposition. As shown in FIG. 1, each ozonolysis porous material was analyzed by X-ray diffraction. As shown in FIG. 1, in addition to the diffraction peak of alumina as an aggregate, in all porous materials, scandium oxide structure (C type) Mn 2 O Three diffraction peaks were observed.
[0034]
The ozone decomposition efficiency of the resulting ozonolysis for the
Evaluated by. Table 1 shows the respective ozonolysis rates.
[0035]
Example 2
As in Example 1, porous ceramics having a three-dimensional network structure processed to 50 × 50 × 25 mm (Ceramic foam # 13 manufactured by Kurosaki Harima Co., Ltd .: white, 98% pure alumina material, number of cells # 13, apparent sky 80% porosity and 45 kg / cm 2 bending strength) were immersed in a 10% aqueous solution of manganese nitrate hexahydrate Mn (NO 3 ) 2 · 6H 2 O, and the excess solution was blown off with an air gun, then air-dried This operation was repeated three times. Subsequently, what was heat-processed which heated up to 600 degreeC in air | atmosphere and kept for 1 hour was made into the porous body for ozone decomposition | disassembly. When this porous body for ozonolysis was analyzed by X-ray diffraction, a diffraction peak of scandium oxide structure (C type) Mn 2 O 3 was observed in addition to the diffraction peak of alumina as an aggregate.
[0036]
Table 1 shows the results of evaluating the ozonolysis efficiency of the porous body for ozonolysis in the same manner as in Example 1. By using a dilute aqueous solution of manganese nitrate hexahydrate and repeating the impregnation coating operation, the effect of increasing the film thickness control and the number of cells of manganese oxide appears, and the ozonolysis rate is excellent compared to Example 1 porous body. It is the result.
[0037]
Comparative Example 1
As in Example 1, porous ceramics having a three-dimensional network structure processed to 50 × 50 × 25 mm (Ceramic foam # 6 manufactured by Kurosaki Harima Co., Ltd., white, 98% pure alumina material, number of cells # 6, apparent sky 80% porosity and 45 kg / cm 2 bending strength) were immersed in manganese nitrate hexahydrate Mn (NO 3 ) 2 · 6H 2 0 dissolved in crystal water at 30 ° C., and the excess solution was blown off with an air gun. And then solidified at 20 ° C. Next, a porous body for ozone decomposition was subjected to heat treatment in which the temperature was raised to 200, 300, 400, and 450 ° C. in the atmosphere and kept for 1 hour. When each ozonolysis porous material was analyzed by the X-ray diffraction method, in addition to the diffraction peak of alumina as an aggregate, the porous material heat-treated at 200 ° C. showed a halo peculiar to amorphous, 300 and A rutile structure (β-type) MNO 2 diffraction peak was observed in the porous body heat-treated at each temperature of 400 ° C.
[0038]
The results of evaluating the ozonolysis efficiency of this ozonolysis porous material in the same manner as in Example 1 are shown in Table 1. All the porous bodies are inferior in the ozonolysis rate.
[0039]
[Table 1]
As in Example 1, porous ceramics having a three-dimensional network structure processed to 50 × 50 × 25 mm (Ceramic foam # 6 manufactured by Kurosaki Harima Co., Ltd., white, 98% pure alumina material, number of cells # 6, apparent sky 80% porosity and 45 kg / cm 2 bending strength) were immersed in manganese nitrate hexahydrate Mn (NO 3 ) 2 · 6H 2 0 dissolved in crystal water at 30 ° C., and the excess solution was blown off with an air gun. And then solidified at 20 ° C. Next, a porous body for ozone decomposition was subjected to heat treatment in which the temperature was raised to 750, 800, and 900 ° C. in the atmosphere and kept for 1 hour. When each porous body for ozonolysis was analyzed by the X-ray diffraction method, in addition to the diffraction peak of alumina as an aggregate, all porous bodies had a spinel structure distorted with scandium oxide structure (C type) Mn 2 O 3. A diffraction peak of Mn 3 O 4 with Table 1 shows the results of evaluating the ozonolysis efficiency of the obtained porous body for ozonolysis in the same manner as in Example 1. Any porous body is inferior in ozonolysis efficiency as compared with the Examples.
[0040]
【The invention's effect】
The present invention is a porous body for ozonolysis in which the crystal structure of manganese oxide is uniformly and firmly attached to the surface of a carrier skeleton having continuous open voids by controlling the heat treatment temperature, and has excellent catalytic ability. In addition, it is resistant to mechanical impact, and exhibits long life and stable catalytic ability.
[Brief description of the drawings]
FIG. 1 shows the result of analysis of an ozonolysis porous material according to the present invention by X-ray diffraction.
Claims (2)
前記の多孔質状担体の骨格表面にはマンガン酸化物、または、マンガン酸化物を主成分とする化合物が固着してなり、この固着した化合物の結晶構造は酸化スカンジウム構造のＣ型Ｍｎ２Ｏ３であるオゾン分解用多孔体。A manganese nitrate aqueous solution in which manganese nitrate hydrate crystals are melted on a porous ceramic support having a three-dimensional network structure , or a manganese nitrate aqueous solution in which manganese nitrate hydrate crystals are diluted with water or alcohol. After impregnating and drying, the high-efficiency ozonolysis porous material obtained by solidifying manganese nitrate hydrate by maintaining it below the melting point, and further raising the temperature to a temperature range of 500 to 700 ° C. and firing. And
Manganese oxide skeleton surface of said porous carrier, or a compound whose main component is manganese oxide is then secured, C-type Mn 2 O 3 crystal structure of the fixed and compounds scandium oxide structure der Luo ozone decomposition for the porous body.
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