JPH09206559A - Contact reducing method of nitrogen oxides - Google Patents
Contact reducing method of nitrogen oxidesInfo
- Publication number
- JPH09206559A JPH09206559A JP8017991A JP1799196A JPH09206559A JP H09206559 A JPH09206559 A JP H09206559A JP 8017991 A JP8017991 A JP 8017991A JP 1799196 A JP1799196 A JP 1799196A JP H09206559 A JPH09206559 A JP H09206559A
- Authority
- JP
- Japan
- Prior art keywords
- catalyst
- nitrogen
- nitrogen oxides
- exhaust gas
- silver
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、炭化水素を還元剤
として用いる窒素酸化物の接触還元方法に関し、詳しく
は、工場、自動車等から排出される排ガスの中に含まれ
る有害な窒素酸化物を安定して高い除去率にて還元除去
することができる窒素酸化物の接触還元方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for catalytic reduction of nitrogen oxides using hydrocarbons as a reducing agent, and more specifically, it removes harmful nitrogen oxides contained in exhaust gas discharged from factories, automobiles and the like. The present invention relates to a method for catalytic reduction of nitrogen oxides, which enables stable reduction and removal at a high removal rate.
【０００２】[0002]
【従来の技術】従来、排ガス中に含まれる窒素酸化物
は、窒素酸化物を酸化した後、アルカリに吸収させる方
法や、アンモニア、水素、一酸化炭素、炭化水素等の還
元剤を用いて、窒素に変換する方法等によって除去され
ている。しかしながら、前者の方法によれば、生成する
アルカリ廃液を処理して、公害の発生を防止する方策が
必要である。他方、後者の方法によれば、還元剤として
アンモニアを用いるときは、これが排ガス中の硫黄酸化
物と反応して塩類を生成し、その結果、触媒の還元活性
が低下する問題がある。また、水素、一酸化炭素、炭化
水素等を還元剤として用いる場合でも、これらが低濃度
に存在する窒素酸化物よりも高濃度に存在する酸素と反
応するので、窒素酸化物を低減するためには、多量の還
元剤を必要とするという問題がある。2. Description of the Related Art Conventionally, nitrogen oxides contained in exhaust gas are obtained by oxidizing the nitrogen oxides and then absorbing them into an alkali, or by using a reducing agent such as ammonia, hydrogen, carbon monoxide, or a hydrocarbon. It has been removed by a method of converting to nitrogen. However, according to the former method, it is necessary to take measures for treating the generated alkaline waste liquid to prevent the occurrence of pollution. On the other hand, according to the latter method, when ammonia is used as the reducing agent, it reacts with the sulfur oxide in the exhaust gas to form salts, and as a result, the reduction activity of the catalyst is reduced. Further, even when hydrogen, carbon monoxide, hydrocarbons, and the like are used as a reducing agent, since they react with oxygen present at a higher concentration than nitrogen oxide present at a lower concentration, it is necessary to reduce nitrogen oxides. However, there is a problem that a large amount of a reducing agent is required.
【０００３】このため、最近では、還元剤の不存在下に
窒素酸化物を触媒にて直接分解する方法も提案されてい
るが、しかし、従来、知られているそのような触媒は、
窒素酸化物の分解活性が低いために、実用に供し難いと
いう問題がある。また、炭化水素や含酸素化合物を還元
剤として用いる新たな窒素酸化物接触還元用触媒とし
て、Ｈ型ゼオライトやＣｕイオン交換ＺＳＭ−５等が提
案されており、なかでも、Ｈ型ＺＳＭ−５（ＳｉＯ2 ／
Ａｌ2 Ｏ3 モル比＝３０〜４０）が最適であるとされて
いる。しかしながら、このようなＨ型ＺＳＭ−５でも、
未だ十分な還元活性を有するものとはいい難く、特に、
ガス中に水分が含まれるとき、ゼオライト構造体中のア
ルミニウムが脱アルミニウムして、性能が急激に低下す
るので、一層高い還元活性を有し、更に、ガスが水分を
含有する場合にも、すぐれた耐久性を有する窒素酸化物
接触還元用触媒が要望されている。[0003] For this reason, recently, a method of directly decomposing nitrogen oxides with a catalyst in the absence of a reducing agent has been proposed.
There is a problem that it is difficult to put into practical use due to low decomposition activity of nitrogen oxides. Further, as a new catalyst for catalytic reduction of nitrogen oxides using a hydrocarbon or an oxygen-containing compound as a reducing agent, H-type zeolite, Cu ion-exchange ZSM-5, and the like have been proposed. Among them, H-type ZSM-5 ( SiO 2 /
Al 2 O 3 molar ratio = 30 to 40) is considered to be optimal. However, even with such an H-type ZSM-5,
It is still difficult to say that it has sufficient reducing activity.
When moisture is contained in the gas, the aluminum in the zeolite structure is dealuminated and the performance is sharply reduced, so that it has a higher reduction activity, and is excellent even when the gas contains moisture. There is a demand for a catalyst for catalytic reduction of nitrogen oxides having improved durability.
【０００４】[0004]
【発明が解決しようとする課題】そこで、銀又は銀酸化
物を無機酸化物に担持させてなる触媒も提案されている
が、そのような触媒は、酸化活性が高く、窒素酸化物に
対する選択反応性が低いために、窒素酸化物の除去率が
低い。また、触媒が窒素酸化物の分解活性を有する温度
域が高いので、排ガス中の窒素酸化物を有効に分解する
には、排ガスを予め加熱することが必要であって、実用
化には問題がある。更に、銀又は銀酸化物を無機酸化物
に担持させてなる触媒は、硫黄酸化物の共存下での触媒
活性の劣化が著しいという問題もある（特開平５−３１
７６４７号公報）。そのうえ、従来の窒素酸化物接触還
元用触媒は、一般に、耐熱性が十分ではなく、用途によ
っては、一層の耐熱性が強く要望されている。Accordingly, a catalyst comprising silver or silver oxide supported on an inorganic oxide has been proposed. However, such a catalyst has a high oxidation activity and a selective reaction to nitrogen oxide. The removal rate of nitrogen oxides is low because of low properties. Further, since the temperature range in which the catalyst has a decomposition activity of nitrogen oxides is high, it is necessary to preheat the exhaust gas in order to effectively decompose the nitrogen oxides in the exhaust gas, which poses a problem in practical use. is there. Further, the catalyst in which silver or silver oxide is supported on an inorganic oxide has a problem that the catalytic activity is significantly deteriorated in the presence of sulfur oxide (Japanese Patent Laid-Open No. 5-31).
7647 publication). In addition, conventional catalysts for catalytic reduction of nitrogen oxides generally do not have sufficient heat resistance, and there is a strong demand for even higher heat resistance depending on the application.
【０００５】そこで、本発明者らは、既に、固体酸担体
にアルミン酸銀を担持させてなる窒素酸化物接触還元用
触媒を提案しており（特願平７−３０６０７０号）、こ
の触媒は、上記問題点を改善しているものの、窒素酸化
物の還元率の点で、尚、十分とはいえない。本発明は、
上述したような事情に鑑みてなされたものであって、そ
の目的とするところは、炭化水素を還元剤として用いる
窒素酸化物の接触還元方法であって、酸素や硫黄酸化物
や水分の共存下においても、多量の還元剤を用いること
なく、排ガス中の窒素酸化物を安定して且つ効率よく接
触還元することができる窒素酸化物の接触還元方法を提
供することにある。Therefore, the present inventors have already proposed a catalyst for catalytic reduction of nitrogen oxides, which comprises a solid acid carrier on which silver aluminate is supported (Japanese Patent Application No. 7-306070). Although the above problems are improved, the reduction rate of nitrogen oxides is still insufficient. The present invention
The present invention has been made in view of the above-mentioned circumstances, and its object is a method for catalytic reduction of nitrogen oxides using a hydrocarbon as a reducing agent, in the presence of oxygen, sulfur oxides, and water. Also in the above, it is to provide a method for catalytic reduction of nitrogen oxides, which can stably and efficiently catalytically reduce nitrogen oxides in exhaust gas without using a large amount of reducing agent.
【０００６】[0006]
【課題を解決するための手段】本発明は、排ガスに含ま
れる窒素酸化物を触媒の存在下に還元剤として炭化水素
を用いて接触還元する方法において、第１段階として、
排ガスを窒素酸化物酸化触媒（以下、酸化触媒又は第１
触媒ということがある。）に接触させて、排ガスに含ま
れる一酸化窒素（ＮＯ）を二酸化窒素（ＮＯ2 ）に酸化
し、次いで、このような排ガスに炭化水素を加え、第２
段階として、この排ガスを銀、酸化銀及びアルミン酸銀
から選ばれる窒素酸化物還元触媒（以下、還元触媒又は
第２触媒ということがある。）に接触させて、窒素酸化
物を窒素に還元することを特徴とする。The present invention is a method for catalytically reducing nitrogen oxides contained in exhaust gas by using hydrocarbon as a reducing agent in the presence of a catalyst.
The exhaust gas is converted into a nitrogen oxide oxidation catalyst (hereinafter, the oxidation catalyst or the first
Sometimes called a catalyst. ) To oxidize nitric oxide (NO) contained in the exhaust gas into nitrogen dioxide (NO 2 ), and then add hydrocarbons to such exhaust gas,
As a step, this exhaust gas is brought into contact with a nitrogen oxide reduction catalyst (hereinafter, sometimes referred to as a reduction catalyst or a second catalyst) selected from silver, silver oxide and silver aluminate to reduce the nitrogen oxides to nitrogen. It is characterized by
【０００７】[0007]
【発明の実施の形態】本発明の方法によれば、第１段階
として、排ガスを窒素酸化物酸化触媒に接触させて、排
ガスに含まれる一酸化窒素（ＮＯ）を二酸化窒素（ＮＯ
2 ）に酸化する。一酸化窒素に比べて、二酸化窒素は、
後述する還元触媒による還元反応において、還元剤であ
る炭化水素との選択反応性によりすぐれるので、第２段
階における窒素酸化物の接触還元に先立って、このよう
に、第１段階において、予め一酸化窒素を二酸化窒素に
酸化することによって、排ガスに含まれる窒素酸化物の
除去率を高めることができる。According to the method of the present invention, as a first step, the exhaust gas is brought into contact with a nitrogen oxide oxidation catalyst so that nitric oxide (NO) contained in the exhaust gas is converted into nitrogen dioxide (NO).
2 ) to oxidize. Compared to nitric oxide, nitrogen dioxide
In the reduction reaction by the reduction catalyst described later, since it is superior due to the selective reactivity with the hydrocarbon that is the reducing agent, prior to the catalytic reduction of nitrogen oxides in the second step, in this way, in the first step, it is possible By oxidizing nitrogen oxide to nitrogen dioxide, the removal rate of nitrogen oxides contained in the exhaust gas can be increased.
【０００８】上記酸化触媒、即ち、第１触媒としては、
特に、限定されるものではないが、好ましくは、白金、
マンガン、パラジウム、ロジウム、イリジウム、ルテニ
ウム及び銅から選ばれる金属又はその酸化物からなる触
媒が用いられる。これら金属又はその酸化物は、通常、
比表面積の大きい酸化物、例えば、アルミナ、シリカ、
シリカ−アルミナ、ジルコニア、チタニア、ゼオライト
等の固体酸担体に担持されて用いられる。上記金属又は
その酸化物をこのような担体に担持させるには、従来よ
り知られているイオン交換法や含浸法等、適宜の方法に
よればよい。As the above-mentioned oxidation catalyst, that is, the first catalyst,
Although not particularly limited, preferably platinum,
A catalyst composed of a metal selected from manganese, palladium, rhodium, iridium, ruthenium and copper or an oxide thereof is used. These metals or their oxides are usually
Oxides with a large specific surface area, such as alumina, silica,
It is used by being supported on a solid acid carrier such as silica-alumina, zirconia, titania or zeolite. In order to support the above metal or its oxide on such a carrier, an appropriate method such as a conventionally known ion exchange method or impregnation method may be used.
【０００９】上記金属又はその酸化物の担体への担持
量、即ち、上記金属又はその酸化物と担体の重量に対す
る上記金属又はその酸化物の割合は、用いる金属種や触
媒が置かれる反応条件にもよるが、また、必ずしも限定
されるものではないが、通常、金属換算にて、0.００１
〜１０重量％の範囲であり、好ましくは、0.１〜５重量
％の範囲である。上記金属又はその酸化物の担体への担
持量が0.００１重量％よりも少ないときは、上述したよ
うな一酸化窒素を二酸化窒素に酸化する能力が不十分で
ある。しかし、担持量が１０重量％を越えても、一酸化
窒素を二酸化窒素に酸化する能力がそれに見合って増大
するものでもなく、経済性の点からも不利である。The amount of the above-mentioned metal or its oxide supported on the carrier, that is, the ratio of the above-mentioned metal or its oxide to the weight of the above-mentioned metal or its oxide and the carrier depends on the metal species used and the reaction conditions under which the catalyst is placed. Although it is not limited to this, it is usually 0.001 in terms of metal.
It is in the range of 10 to 10% by weight, and preferably in the range of 0.1 to 5% by weight. When the amount of the above metal or its oxide supported on the carrier is less than 0.001% by weight, the above-described ability to oxidize nitric oxide to nitrogen dioxide is insufficient. However, even if the supported amount exceeds 10% by weight, the ability to oxidize nitric oxide to nitrogen dioxide does not increase correspondingly, which is also disadvantageous from the economical point of view.
【００１０】第１段階において、一酸化窒素を含む排ガ
スをこのような第１触媒に接触させる際の空間速度は、
酸化率の観点からは、低ければ低いほどよいが、しか
し、一酸化窒素を実用的に効率よく酸化する観点から
は、通常、５００００〜５０００００hr-1の範囲であ
る。In the first stage, the space velocity in contacting the exhaust gas containing nitric oxide with such a first catalyst is
From the viewpoint of the oxidation rate, the lower the better, the better, but from the viewpoint of effectively oxidizing nitric oxide practically, it is usually in the range of 50,000 to 500,000 hr −1 .
【００１１】本発明の方法によれば、このように、排ガ
スを第１触媒に接触させて、排ガスに含まれる一酸化窒
素を二酸化窒素とした後、このような排ガスに還元剤で
ある炭化水素を加え、これを第２触媒に接触させること
によって、上記二酸化窒素を効率よく窒素に還元するこ
とができ、延いては、排ガス中の窒素酸化物の除去率を
高めることができる。According to the method of the present invention, the exhaust gas is brought into contact with the first catalyst in this way to convert nitrogen monoxide contained in the exhaust gas into nitrogen dioxide, and then the hydrocarbon as a reducing agent is added to the exhaust gas. And by contacting it with the second catalyst, the nitrogen dioxide can be efficiently reduced to nitrogen, which in turn can increase the removal rate of nitrogen oxides in the exhaust gas.
【００１２】上記炭化水素からなる還元剤としては、例
えば、気体状のものとして、メタン、エタン、プロパ
ン、プロピレン、ブチレン等の炭化水素ガス、液体状の
ものとして、ペンタン、ヘキサン、オクタン、ヘプタ
ン、ベンゼン、トルエン、キシレン等の単一成分系の炭
化水素、ガソリン、灯油、軽油、重油等の鉱油系炭化水
素等を用いることができる。特に、本発明においては、
上記したなかでも、エチレン、プロピレン、イソブチレ
ン、１−ブテン、２−ブテン等の低級アルケン、プロパ
ン、ブタン等の低級アルカン、軽油等が還元剤として好
ましく用いられる。これら炭化水素は、単独で用いても
よく、又は必要に応じて二種以上併用してもよい。Examples of the reducing agent composed of the above hydrocarbons include hydrocarbon gases such as methane, ethane, propane, propylene and butylene as gaseous substances, and pentane, hexane, octane and heptane as liquid substances. Single-component hydrocarbons such as benzene, toluene, xylene, and mineral oil hydrocarbons such as gasoline, kerosene, light oil, and heavy oil can be used. In particular, in the present invention,
Among the above, lower alkenes such as ethylene, propylene, isobutylene, 1-butene and 2-butene, lower alkanes such as propane and butane, and light oil are preferably used as the reducing agent. These hydrocarbons may be used alone or in combination of two or more as needed.
【００１３】上記還元剤としての炭化水素は、用いる具
体的な炭化水素によって異なるが、通常、排ガス中の窒
素酸化物（実質的に、一酸化窒素と二酸化窒素とからな
る。）に対するモル比にて、0.１〜２程度の範囲にて用
いられる。炭化水素の使用量が窒素酸化物に対するモル
比にて、0.１未満であるときは、窒素酸化物に対して十
分な還元活性を得ることができず、他方、モル比が２を
越えるときは、未反応の炭化水素の排出量が多くなるた
めに、窒素酸化物の接触還元処理の後に、これを回収す
るための後処理が必要となる。The hydrocarbon as the reducing agent varies depending on the specific hydrocarbon used, but is usually in a molar ratio with respect to the nitrogen oxides in the exhaust gas (substantially consisting of nitric oxide and nitrogen dioxide). Therefore, it is used in the range of about 0.1 to 2. When the amount of the hydrocarbon used is less than 0.1 in terms of the molar ratio to the nitrogen oxides, sufficient reduction activity for the nitrogen oxides cannot be obtained. On the other hand, when the molar ratio exceeds 2, Since a large amount of unreacted hydrocarbons is emitted, a post-treatment for recovering the nitrogen oxides after the catalytic reduction treatment of the nitrogen oxides is required.
【００１４】尚、排ガス中に存在する燃料等の未燃焼物
乃至不完全燃焼生成物、即ち、炭化水素類やパティキュ
レート類等も還元剤として有効であり、これらも本発明
における炭化水素に含まれる。このことから、見方を変
えれば、本発明の方法は、排ガス中の炭化水素類やパテ
ィキュレート類等を減少させ、又は除去する方法として
も有用であるということができる。It should be noted that unburned substances or incompletely burned products such as fuel existing in the exhaust gas, that is, hydrocarbons and particulates are also effective as reducing agents, and these are also included in the hydrocarbon of the present invention. Be done. From this point of view, it can be said that the method of the present invention is also useful as a method for reducing or removing hydrocarbons and particulates in exhaust gas.
【００１５】第２触媒は、銀、酸化銀又はアルミン酸銀
から選ばれるものである。これらのうち、銀及び酸化銀
は、通常、比表面積の大きい酸化物、例えば、アルミ
ナ、シリカ、シリカ−アルミナ、ジルコニア、チタニ
ア、ゼオライト等の固体酸担体に担持されて用いられ
る。これらのなかでは、特に、耐熱性にすぐれると共
に、担持効果にすぐれるアルミナが好ましく用いられ
る。The second catalyst is selected from silver, silver oxide or silver aluminate. Of these, silver and silver oxide are usually used by being supported on an oxide having a large specific surface area, for example, a solid acid carrier such as alumina, silica, silica-alumina, zirconia, titania, or zeolite. Among these, alumina is particularly preferably used because it has excellent heat resistance and an excellent supporting effect.
【００１６】アルミナのなかでも、特開平７−１７１３
４７号公報に記載されているように、アルカリ金属及び
アルカリ土類金属の含有量が0.５重量％以下であり、径
６０オングストローム以下の細孔から形成される細孔容
積が0.０６cm3 ／ｇ以上、径８０オングストローム以下
の細孔から形成される細孔容積が0.１cm3 ／ｇ以上であ
るアルミナが特に好ましく用いられる。このような細孔
容積を有する多孔質のアルミナは、還元剤の適度な酸化
を促進し、これに担持されている銀又は酸化銀と協同し
て、窒素酸化物を効果的に接触還元することができる。Among alumina, Japanese Patent Laid-Open No. 7-1713
As described in Japanese Patent No. 47, the content of alkali metals and alkaline earth metals is 0.5% by weight or less, and the volume of pores formed from pores having a diameter of 60 Å or less is 0.06 cm 3. / G and alumina having a pore volume of 0.1 cm 3 / g or more formed from pores having a diameter of 80 Å or less are particularly preferably used. Porous alumina having such a pore volume promotes appropriate oxidation of the reducing agent and cooperates with silver or silver oxide carried thereon to effectively catalytically reduce nitrogen oxides. Can be.
【００１７】このように、銀又は酸化銀からなる第２触
媒は、従来、知られている成形方法によって、それ自体
にて、又は担体に担持させた後、ハニカム状、球状等の
種々の形状に成形することができる。この成形の際に、
成形助剤、成形体補強体、無機繊維、有機バインダー等
を適宜配合してもよい。また、第２触媒は、予め成形さ
れた不活性な基材上にウオッシュコート法等によって被
覆担持させることもできる。上記基材としては、例え
ば、コージエライトのような粘土からなるハニカム構造
体に担持させることができる。更に、必要に応じて、従
来、知られているその他の触媒の任意の調製法によるこ
ともできる。As described above, the second catalyst made of silver or silver oxide can be formed into various shapes such as a honeycomb shape and a spherical shape by a conventionally known molding method by itself or after being supported on a carrier. Can be molded into. During this molding,
A molding aid, a molded body reinforcing material, an inorganic fiber, an organic binder and the like may be appropriately mixed. The second catalyst can also be supported by coating on a preformed inert base material by a washcoat method or the like. As the base material, for example, a honeycomb structure made of clay such as cordierite can be supported. Further, if necessary, any other known method for preparing a catalyst may be used.
【００１８】銀又は酸化銀の担体への担持量は、0.１〜
５重量％の範囲であることが好ましい。担持量が0.１重
量％よりも少ないときは、窒素酸化物の還元活性が十分
でなく、他方、５重量％よりも多いときは、酸化活性が
高すぎて、選択性に劣ることとなる。The amount of silver or silver oxide supported on the carrier is 0.1 to
It is preferably in the range of 5% by weight. When the supported amount is less than 0.1% by weight, the reducing activity of the nitrogen oxide is not sufficient, and when it is more than 5% by weight, the oxidizing activity is too high, resulting in poor selectivity. .
【００１９】第２触媒のうち、アルミン酸銀からなる触
媒は、例えば、次に示す（１）から（４）のいずれかの
方法に従って調製することができる。 （１）固体酸担体を分散させたスリラー中に硝酸銀等の
水溶性銀塩を投入し、スラリーのｐＨを銀水酸化物の生
成しない8.０近傍に維持して、固体酸のイオン交換サイ
トに銀イオンを固定する。ここに、固体酸としてアルミ
ナを用いた場合は、このようにして、銀イオンを固定し
た固体酸を、その銀イオンを固定するのに十分な塩素イ
オンを含有する水溶液、例えば、塩酸水溶液中に浸漬す
ることによって、塩化銀を生成させた後、過剰の塩素イ
オンを水洗等によって除去することによって、先ず、塩
化銀を担持した固体酸触媒を調製する。Among the second catalysts, the catalyst composed of silver aluminate can be prepared, for example, according to any one of the following methods (1) to (4). (1) A water-soluble silver salt such as silver nitrate is charged into a chiller in which a solid acid carrier is dispersed, and the pH of the slurry is maintained at around 8.0 where silver hydroxide is not generated, thereby obtaining a solid acid ion exchange site. The silver ions are immobilized. Here, when alumina is used as the solid acid, the solid acid in which silver ions are fixed in this way is converted into an aqueous solution containing sufficient chloride ions to fix the silver ions, for example, an aqueous hydrochloric acid solution. After immersion to generate silver chloride, excess chloride ions are removed by washing with water or the like to prepare a solid acid catalyst supporting silver chloride.
【００２０】次いで、これを空気等のような酸化雰囲気
下、好ましくは、水蒸気の存在下に、６００〜８００℃
程度、好ましくは、７００〜８００℃程度の温度にて加
熱焼成することによって、アルミン酸銀を生成させれ
ば、アルミン酸銀を担持させてなる固体酸触媒を得るこ
とができる。Then, this is heated at 600 to 800 ° C. in an oxidizing atmosphere such as air, preferably in the presence of water vapor.
If silver aluminate is produced by heating and baking at a temperature of about 700 ° C., preferably about 700 ° C. to 800 ° C., a solid acid catalyst carrying silver aluminate can be obtained.
【００２１】（２）例えば、硝酸アルミニウム等のよう
な固体酸の前駆体である水溶性塩と硝酸銀等のような水
溶性銀塩を均質に混合した水溶液を調製し、この水溶液
を塩素イオンの存在下で中和する等の方法によって、沈
殿物を生成させ、次いで、この沈殿物を濾過、水洗、リ
パルプを繰り返して行なった後、乾燥し、焼成して、固
体酸を生成させると同時に塩化銀をその固体酸に担持さ
せる。次いで、これを上述したと同様にして、酸化雰囲
気下、好ましくは、水蒸気の存在下に、６００〜８００
℃程度、好ましくは、７００〜８００℃程度の温度にて
加熱焼成することによって、アルミン酸銀を生成させれ
ば、アルミン酸銀を担持させてなる固体酸触媒を得るこ
とができる。(2) For example, an aqueous solution is prepared by homogeneously mixing a water-soluble salt which is a precursor of a solid acid such as aluminum nitrate with a water-soluble silver salt such as silver nitrate. A precipitate is formed by a method such as neutralization in the presence, and then the precipitate is repeatedly subjected to filtration, washing with water, and repulping. Silver is supported on the solid acid. Then, in the same manner as described above, in an oxidizing atmosphere, preferably in the presence of steam, 600 to 800
When silver aluminate is produced by heating and baking at a temperature of about [deg.] C., preferably about 700 to 800 [deg.] C., a solid acid catalyst supporting silver aluminate can be obtained.
【００２２】（３）硝酸アルミニウムのような水溶性ア
ルミニウム塩と硝酸銀のような水溶性銀塩の水溶液に水
和アルミナを浸漬し、上記アルミニウム塩と銀塩とをア
ルミナの細孔に含浸させた後、噴霧乾燥機のような適当
な手段にて乾燥させ、この後、これを前述したように、
酸化雰囲気下、好ましくは、水蒸気の存在下に、６００
〜８００℃程度、好ましくは、７００〜８００℃程度の
温度にて加熱焼成することによって、アルミン酸銀を生
成させれば、アルミン酸銀を担持させてなる固体酸触媒
を得ることができる。(3) Hydrated alumina is immersed in an aqueous solution of a water-soluble aluminum salt such as aluminum nitrate and a water-soluble silver salt such as silver nitrate to impregnate the pores of the alumina with the aluminum salt and the silver salt. Thereafter, it is dried by a suitable means such as a spray dryer, and thereafter, as described above,
In an oxidizing atmosphere, preferably in the presence of steam, 600
By producing a silver aluminate by heating and baking it at a temperature of about -800 ° C, preferably about 700-800 ° C, a solid acid catalyst supporting silver aluminate can be obtained.
【００２３】（４）更に、別の方法として、アルミン酸
ナトリウムのようなアルミン酸アルカリ金属塩とその１
〜４倍当量の硝酸銀の水溶液を噴霧乾燥によって均一に
混合すると共に乾燥させ、得られた粒状物を水分の不存
在下に３００〜８００℃の温度にて共融させることによ
って、アルミン酸銀を得、これを水洗し、過剰の硝酸銀
と硝酸ナトリウムを除去すれば、高純度品を得ることが
できる。このアルミン酸銀とアルミナ等の固体酸とをボ
ールミル等を用いて湿式にて均一に混合粉砕した後、乾
燥させれば、アルミン酸銀を担持させたアルミナを得る
ことができる。(4) As another method, an alkali metal aluminate such as sodium aluminate and the like
By mixing and drying an aqueous solution of silver nitrate equivalent to ４4 times equivalent by spray drying and drying, and eutecticizing the obtained granules at a temperature of 300 to 800 ° C. in the absence of moisture, silver aluminate is obtained. The resulting product is washed with water to remove excess silver nitrate and sodium nitrate, whereby a highly purified product can be obtained. This silver aluminate and a solid acid such as alumina are uniformly mixed and pulverized by a wet method using a ball mill or the like, and then dried, whereby alumina carrying silver aluminate can be obtained.
【００２４】第２触媒の調製においても、固体酸担体と
して、アルミナが好ましく用いられ、なかでも、前述し
たように、アルカリ金属及びアルカリ土類金属の含有量
が0.５重量％以下であり、径６０オングストローム以下
の細孔から形成される細孔容積が0.０６cm3 ／ｇ以上、
径８０オングストローム以下の細孔から形成される細孔
容積が0.１cm3 ／ｇ以上であるアルミナが特に好ましく
用いられる。このような細孔容積を有する多孔質のアル
ミナは、還元剤の適度な酸化を促進し、これに担持され
ているアルミン酸銀と協同して、窒素酸化物を効果的に
接触還元することができる。Also in the preparation of the second catalyst, alumina is preferably used as the solid acid carrier, and among them, as described above, the content of alkali metal and alkaline earth metal is 0.5% by weight or less, The pore volume formed from pores having a diameter of 60 Å or less is 0.06 cm 3 / g or more,
Alumina having a pore volume of 0.1 cm 3 / g or more formed from pores having a diameter of 80 Å or less is particularly preferably used. Porous alumina having such a pore volume promotes appropriate oxidation of the reducing agent and cooperates with silver aluminate carried thereon to effectively catalytically reduce nitrogen oxides. it can.
【００２５】第２触媒において、固体酸担体へのアルミ
ン酸銀の担持量は、0.０１〜１０重量％の範囲であるこ
とが好ましい。アルミン酸銀の担持量が１０重量％を越
えるときは、得られる触媒の酸化力が高すぎて、選択性
に劣り、担持量が0.０１重量％よりも少ないときは、触
媒活性が十分でない。特に、本発明においては、アルミ
ン酸銀の担持量は、0.１〜５重量％の範囲であることが
好ましい。担持量がこの範囲にあるときは、窒素酸化物
の接触還元反応の空間速度依存性が極めて小さいという
すぐれた特性を得ることができる。In the second catalyst, the amount of silver aluminate supported on the solid acid carrier is preferably in the range of 0.01 to 10% by weight. When the supported amount of silver aluminate exceeds 10% by weight, the resulting catalyst has too high oxidizing power and poor selectivity. When the supported amount is less than 0.01% by weight, the catalytic activity is not sufficient. . In particular, in the present invention, the loading amount of silver aluminate is preferably in the range of 0.1 to 5% by weight. When the supported amount is within this range, it is possible to obtain the excellent property that the space velocity dependence of the catalytic reduction reaction of nitrogen oxide is extremely small.
【００２６】第２段階において、主として二酸化窒素か
らなる窒素酸化物と共に炭化水素を含む排ガスをこのよ
うな第２触媒に接触させる際の空間速度は、通常、５０
００〜５００００hr-1の範囲である。第２段階における
触媒は、第１段階における触媒に比べて、酸化活性が小
さく、窒素酸化物との選択性にすぐれるので、高い脱硝
率を得るには、空間速度は小さいことが好ましいが、通
常、実用上、上記の範囲の空間速度が採用される。 本
発明の方法によれば、第１段階及び第２段階における反
応温度は、１５０〜４５０℃の範囲である。必要に応じ
て、第１段階及び第２段階において、反応温度を変えて
もよい。In the second step, the space velocity at which the exhaust gas containing hydrocarbons together with nitrogen oxides mainly consisting of nitrogen dioxide is brought into contact with such a second catalyst is usually 50.
The range is from 00 to 50,000 hr -1 . The catalyst in the second stage has a smaller oxidizing activity and a better selectivity with respect to nitrogen oxides than the catalyst in the first stage. Therefore, in order to obtain a high denitration rate, it is preferable that the space velocity is small. Usually, practically, the space velocity in the above range is adopted. According to the method of the present invention, the reaction temperature in the first step and the second step is in the range of 150 to 450 ° C. If necessary, the reaction temperature may be changed in the first stage and the second stage.
【００２７】本発明によれば、上述したように、第１段
階において、排ガスを酸化触媒に接触させて、排ガスに
含まれる一酸化窒素を二酸化窒素に酸化し、次いで、こ
のような排ガスに炭化水素を加え、第２段階として、こ
の排ガスを銀、酸化銀及びアルミン酸銀から選ばれる窒
素酸化物還元触媒に接触させて、二酸化窒素を窒素に還
元するので、窒素酸化物を安定して且つ効率よく還元分
解することができ、更に、好ましい場合には、低い温度
域においても、窒素酸化物を安定して且つ効率よく還元
分解することができる。According to the present invention, as described above, in the first step, the exhaust gas is brought into contact with the oxidation catalyst to oxidize the nitric oxide contained in the exhaust gas into nitrogen dioxide, and then the exhaust gas is carbonized. Hydrogen is added and, as a second step, this exhaust gas is brought into contact with a nitrogen oxide reduction catalyst selected from silver, silver oxide and silver aluminate to reduce nitrogen dioxide to nitrogen, so that the nitrogen oxide is stabilized and The nitrogen oxide can be efficiently reductively decomposed, and in a preferable case, the nitrogen oxide can be stably and efficiently reductively decomposed even in a low temperature range.
【００２８】[0028]
【実施例】以下に各段階のための触媒の調製例と共に実
施例を挙げて本発明を説明するが、本発明はこれら実施
例により何ら限定されるものではない。EXAMPLES The present invention will be described below with reference to examples along with examples of catalyst preparation for each step, but the present invention is not limited to these examples.
【００２９】（１）第１触媒の調製 調製例１ 塩化白金酸（Ｈ2 ＰｔＣｌ6 ・６Ｈ2 Ｏ）5.３１ｇをイ
オン交換水１００ｍＬに溶解させた。予め１２０℃にて
２４時間乾燥させた平均粒径３ｍｍのγ−アルミナ（住
友化学工業（株）製ＫＨＡ−２４）１００ｍＬを上記塩
化白金酸水溶液に投入し、３０分間攪拌して、アルミナ
の細孔内に塩化白金酸水溶液を十分に含浸させた。(1) Preparation of First Catalyst Preparation Example 1 5.31 g of chloroplatinic acid (H 2 PtCl 6 .6H 2 O) was dissolved in 100 mL of deionized water. 100 mL of γ-alumina (KHA-24 manufactured by Sumitomo Chemical Co., Ltd.) having an average particle diameter of 3 mm, which had been dried in advance at 120 ° C. for 24 hours, was added to the above chloroplatinic acid aqueous solution and stirred for 30 minutes to form alumina fine particles. The pores were thoroughly impregnated with a chloroplatinic acid aqueous solution.
【００３０】次いで、γ−アルミナを塩化白金酸水溶液
から分離し、表面に付着した過剰の水溶液を除去した
後、１００℃で１２時間乾燥させ、更に、空気中、５０
０℃で焼成して、白金をγ−アルミナに１重量％の担持
量で担持させた触媒（Ａ−１）を得た。Next, γ-alumina was separated from the chloroplatinic acid aqueous solution, and after removing the excess aqueous solution adhering to the surface, it was dried at 100 ° C. for 12 hours, and further, in air, 50
It was calcined at 0 ° C. to obtain a catalyst (A-1) in which platinum was supported on γ-alumina in a supported amount of 1% by weight.
【００３１】調製例２ 塩化白金酸に代えて、硝酸マンガン2.８７ｇ用いた以外
は、調製例１と同様にして、二酸化マンガンをγ−アル
ミナに１重量％の担持量で担持させた触媒（Ａ−２）を
得た。 調製例３ 塩化白金酸に代えて、硝酸ロジウム（Ｒｈ（ＮＯ3 ）3
・２Ｈ2 Ｏ）6.３５ｇを用いた以外は、調製例１と同様
にして、ロジウムをγ−アルミナに１重量％の担持量で
担持させた触媒（Ａ−３）を得た。Preparation Example 2 A catalyst prepared by supporting manganese dioxide on γ-alumina at a loading amount of 1% by weight was prepared in the same manner as in Preparation Example 1 except that 2.87 g of manganese nitrate was used instead of chloroplatinic acid. A-2) was obtained. Preparation Example 3 Instead of chloroplatinic acid, rhodium nitrate (Rh (NO 3 ) 3
2H 2 O) was used in the same manner as in Preparation Example 1 except that 6.35 g of rhodium was supported on γ-alumina to give a catalyst (A-3).
【００３２】調製例４ 塩化白金酸に代えて、塩化パラジウム（ＰｄＣｌ2 ）3.
３ｇを用いた以外は、調製例１と同様にして、パラジウ
ムをγ−アルミナに１重量％の担持量で担持させた触媒
（Ａ−４）を得た。 調製例５ 塩化白金酸に代えて、塩化イリジウム（ＩｒＣｌ4 ）１
7.４ｇを用いた以外は、調製例１と同様にして、イリジ
ウムをγ−アルミナに５重量％の担持量で担持させた触
媒（Ａ−５）を得た。Preparation Example 4 Instead of chloroplatinic acid, palladium chloride (PdCl 2 ) 3.
A catalyst (A-4) was obtained in which palladium was supported on γ-alumina in a supported amount of 1% by weight in the same manner as in Preparation Example 1 except that 3 g was used. Preparation Example 5 Instead of chloroplatinic acid, iridium chloride (IrCl 4 ) 1
A catalyst (A-5) was obtained in which iridium was supported on γ-alumina in a supported amount of 5% by weight in the same manner as in Preparation Example 1 except that 7.4 g was used.
【００３３】調製例６ 塩化白金酸に代えて、塩化ルテニウム（ＲｕＣｌ3 ）4.
１ｇを用いた以外は、調製例１と同様にして、ルテニウ
ムをγ−アルミナに１重量％の担持量で担持させた触媒
（Ａ−６）を得た。 調製例７ 塩化白金酸に代えて、硝酸銅（Ｃｕ（ＮＯ3 ）2 ・３Ｈ
2 Ｏ）2.４２ｇを用いた以外は、調製例１と同様にし
て、酸化第二銅をγ−アルミナに１重量％の担持量で担
持させた触媒（Ａ−７）を得た。Preparation Example 6 Instead of chloroplatinic acid, ruthenium chloride (RuCl 3 ) 4.
A catalyst (A-6) in which ruthenium was supported on γ-alumina in a supported amount of 1% by weight was obtained in the same manner as in Preparation Example 1 except that 1 g was used. Preparation Example 7 instead of chloroplatinic acid, copper nitrate (Cu (NO 3) 2 · 3H
2 O) 2.42 g was used, but in the same manner as in Preparation Example 1 to obtain a catalyst (A-7) in which cupric oxide was supported on γ-alumina in a supported amount of 1% by weight.
【００３４】（２）第２触媒の調製 調製例８ 硝酸アルミニウム（Ａｌ（ＮＯ3 ）3 ・９Ｈ2 Ｏ）8.６
９ｇ、硝酸銀3.９４ｇ及び水和アルミナ（水澤化学工業
（株）製）１００ｇを適当量の水と混和して、ペースト
状物を調製した。これを加熱式混練機を用いて混練乾燥
させた後、水分１０重量％を含む空気雰囲気下、８００
℃で３時間加熱焼成して、銀重量換算にて担持量2.５重
量％にてアルミン酸銀を担持させてなるアルミナ粉末触
媒を得た。[0034] (2) Preparation Example 8 aluminum nitrate second catalyst (Al (NO 3) 3 · 9H 2 O) 8.6
9 g, 3.94 g of silver nitrate and 100 g of hydrated alumina (manufactured by Mizusawa Chemical Industry Co., Ltd.) were mixed with an appropriate amount of water to prepare a paste. This was kneaded and dried using a heating kneader, and then dried under an air atmosphere containing 10% by weight of water.
C. for 3 hours to obtain an alumina powder catalyst having silver aluminate supported thereon at a loading of 2.5% by weight in terms of silver weight.
【００３５】このアルミナ粉末触媒６０ｇとシリカゾル
（日産化学工業（株）製スノーテックスＮ）６ｇとを適
当量の水と混和し、これをジルコニアボール１００ｇを
粉砕媒体として遊星ミルで５分間湿式粉砕して、ウオッ
シュコート用スラリーを調製した。このスラリーをセル
数２００セル／平方インチのコージエライト基材に塗布
して、触媒を約１５０ｇ／Ｌの割合で担持させた。この
触媒をＢ−１という。60 g of this alumina powder catalyst and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) were mixed with an appropriate amount of water, and this was wet-ground for 5 minutes with a planetary mill using 100 g of zirconia balls as a grinding medium. To prepare a wash coat slurry. This slurry was applied to a cordierite substrate having a cell number of 200 cells / square inch to carry a catalyst at a rate of about 150 g / L. This catalyst is called B-1.
【００３６】実施例１〜１３（評価試験） 下記の組成を有するガスを第１段階にて第１触媒（Ａ−
１〜７）にて処理した後、このガスに還元剤（炭化水
素）を加え、第２段階にて第２触媒（Ｂ−１）にて処理
して、窒素酸化物含有ガスの窒素酸化物接触還元を行な
い、第１段階において、一酸化窒素の二酸化窒素への転
化率と、第２段階の後の窒素酸化物の除去率とをそれぞ
れケミカルルミネッセンス法にて求めた。結果を表１及
び表２に示す。Examples 1 to 13 (Evaluation test) A gas having the following composition was used in the first stage to produce the first catalyst (A-
1-7), then a reducing agent (hydrocarbon) is added to this gas, and the second catalyst (B-1) is used in the second step to obtain a nitrogen oxide containing nitrogen oxide. Catalytic reduction was performed, and in the first step, the conversion rate of nitric oxide to nitrogen dioxide and the removal rate of nitrogen oxides after the second step were determined by the chemiluminescence method. The results are shown in Tables 1 and 2.
【００３７】（試験条件） （１）ガス組成（第１段階） ＮＯ ５００ｐｐｍ Ｏ2 １０容量％ 水 ６容量％ 窒素 残部 （２）ガス組成（第２段階）(Test conditions) (1) Gas composition (first stage) NO 500 ppm O 2 10% by volume Water 6% by volume Nitrogen balance (2) Gas composition (second stage)
【００３８】第１段階で処理したガスに還元剤（炭化水
素）を５００ｐｐｍ加えた。還元剤として軽油を用いた
場合、軽油はＣ換算でＣ１２とした。） （３）空間速度 第１段階 １０００００、２０００００又は５０００
００（hr-1） 第２段階 １００００、２００００又は５００００
（hr-1） （４）反応温度 １７５℃、２００℃、２５０℃、
３００℃、３５０℃、４００℃又は４５０℃A reducing agent (hydrocarbon) of 500 ppm was added to the gas treated in the first stage. When light oil was used as the reducing agent, the light oil was C12 in terms of C. ) (3) Space velocity 1st stage 100,000, 200,000 or 5000
00 (hr -1 ) 2nd stage 10,000, 20,000 or 50,000
(Hr -1 ) (4) Reaction temperature 175 ° C, 200 ° C, 250 ° C,
300 ° C, 350 ° C, 400 ° C or 450 ° C
【００３９】比較例１〜４（評価試験） 窒素酸化物含有ガスを第１段階（窒素酸化物含有ガスに
還元剤を加えた後、酸化触媒でのみ処理する。）か、又
は第２段階（窒素酸化物含有ガスに還元剤を加えた後、
還元触媒でのみ処理する。）のいずれか一方のみで処理
した以外は、実施例と同様にして、窒素酸化物含有ガス
の窒素酸化物接触還元を行ない、窒素酸化物含有ガスを
第１段階のみで処理した場合には、一酸化窒素への二酸
化窒素への転化率を、また、窒素酸化物含有ガスを第２
段階のみで処理した場合には、窒素酸化物の除去率をそ
れぞれケミカルルミネッセンス法にて求めた。結果を表
１及び表２に示す。Comparative Examples 1 to 4 (Evaluation Test) The nitrogen oxide-containing gas was treated in the first stage (after adding the reducing agent to the nitrogen oxide-containing gas, then treated only with the oxidation catalyst) or in the second stage ( After adding the reducing agent to the nitrogen oxide-containing gas,
Treat with reducing catalyst only. ), Except that only one of the above) was treated, catalytic reduction of nitrogen oxide-containing gas was carried out in the same manner as in Example, and when the nitrogen oxide-containing gas was treated only in the first stage, The conversion of nitrogen dioxide to nitric oxide and the nitrogen oxide containing gas
When the treatment was performed only in stages, the removal rate of nitrogen oxides was obtained by the chemiluminescence method. The results are shown in Tables 1 and 2.
【００４０】[0040]
【表１】 [Table 1]
【００４１】[0041]
【表２】 [Table 2]
【００４２】[0042]
【発明の効果】表１及び表２に示す結果から明らかなよ
うに、本発明の方法によれば、酸素や硫黄酸化物や水分
の共存下においても、多量の還元剤を用いることなく、
排ガス中の窒素酸化物を安定して且つ効率よく接触還元
することができる。また、好ましい態様によれば、低い
温度域で窒素酸化物を高い除去率で除去することができ
る。As is clear from the results shown in Tables 1 and 2, according to the method of the present invention, even in the presence of oxygen, sulfur oxides and water, a large amount of reducing agent is not used.
It is possible to stably and efficiently catalytically reduce nitrogen oxides in exhaust gas. Moreover, according to a preferable aspect, nitrogen oxides can be removed at a high removal rate in a low temperature range.
フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｂ０１Ｊ 23/44 Ｂ０１Ｊ 23/46 Ａ 23/46 ３０１Ａ ３０１ ３１１Ａ ３１１ 23/66 Ａ 23/66 23/72 Ａ 23/72 Ｂ０１Ｄ 53/36 ＺＡＢ (72)発明者 田畑 啓一 大阪府堺市戎島町５丁１番地 堺化学工業 株式会社中央研究所内Continuation of the front page (51) Int.Cl. 6 Identification number Office reference number FI Technical indication location B01J 23/44 B01J 23/46 A 23/46 301A 301 311A 311 23/66 A 23/66 23/72 A 23 / 72 B01D 53/36 ZAB (72) Inventor Keiichi Tabata 5-1, Ebishimacho, Sakai City, Osaka Prefecture Sakai Chemical Industry Co., Ltd. Central Research Laboratory
Claims (4)
下に還元剤として炭化水素を用いて接触還元する方法に
おいて、第１段階として、排ガスを窒素酸化物酸化触媒
に接触させて、排ガスに含まれる一酸化窒素（ＮＯ）を
二酸化窒素（ＮＯ2 ）に酸化し、次いで、このような排
ガスに炭化水素を加え、第２段階として、この排ガスを
銀、酸化銀及びアルミン酸銀から選ばれる窒素酸化物還
元触媒に接触させて、窒素酸化物を窒素に還元すること
を特徴とする窒素酸化物接の触還元方法。1. A method for catalytically reducing nitrogen oxides contained in exhaust gas by using hydrocarbon as a reducing agent in the presence of a catalyst, wherein the exhaust gas is brought into contact with a nitrogen oxide oxidation catalyst as a first step. Is oxidized to nitrogen dioxide (NO 2 ), then hydrocarbon is added to such exhaust gas, and as a second step, the exhaust gas is selected from silver, silver oxide and silver aluminate. And a catalytic reduction method for contacting nitrogen oxides, which comprises reducing the nitrogen oxides to nitrogen by contacting them with a nitrogen oxide reduction catalyst.
ラジウム、ロジウム、イリジウム、ルテニウム及び銅か
ら選ばれる金属又はその酸化物からなる触媒である請求
項１に記載の方法。2. The method according to claim 1, wherein the nitrogen oxide oxidation catalyst is a catalyst composed of a metal selected from platinum, manganese, palladium, rhodium, iridium, ruthenium and copper, or an oxide thereof.
法。3. The method according to claim 1, wherein the hydrocarbon is light oil.
４５０℃の範囲の温度で排ガスを触媒に接触させる請求
項１又は２に記載の方法。4. The method according to claim 1, wherein in the first and second stages,
The method according to claim 1 or 2, wherein the exhaust gas is brought into contact with the catalyst at a temperature in the range of 450 ° C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8017991A JPH09206559A (en) | 1996-02-02 | 1996-02-02 | Contact reducing method of nitrogen oxides |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8017991A JPH09206559A (en) | 1996-02-02 | 1996-02-02 | Contact reducing method of nitrogen oxides |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09206559A true JPH09206559A (en) | 1997-08-12 |
Family
ID=11959202
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8017991A Pending JPH09206559A (en) | 1996-02-02 | 1996-02-02 | Contact reducing method of nitrogen oxides |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09206559A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100347845B1 (en) * | 1999-10-06 | 2002-08-07 | 한국과학기술연구원 | Method of removing malodor by a catalytic wet oxidation |
| US6805849B1 (en) | 1998-02-06 | 2004-10-19 | Johnson Matthey Public Limited Company | System for NOx reduction in exhaust gases |
| US8850802B1 (en) | 2013-03-15 | 2014-10-07 | Daimler Ag | Catalytic reduction of NOx |
| US9073010B2 (en) | 1998-02-06 | 2015-07-07 | Daimler Ag | Catalytic reduction of NOx |
-
1996
- 1996-02-02 JP JP8017991A patent/JPH09206559A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6805849B1 (en) | 1998-02-06 | 2004-10-19 | Johnson Matthey Public Limited Company | System for NOx reduction in exhaust gases |
| US7498010B2 (en) | 1998-02-06 | 2009-03-03 | Johnson Matthey Public Limited Company | Catalytic reduction of NOx |
| US9073010B2 (en) | 1998-02-06 | 2015-07-07 | Daimler Ag | Catalytic reduction of NOx |
| KR100347845B1 (en) * | 1999-10-06 | 2002-08-07 | 한국과학기술연구원 | Method of removing malodor by a catalytic wet oxidation |
| US8850802B1 (en) | 2013-03-15 | 2014-10-07 | Daimler Ag | Catalytic reduction of NOx |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3430422B2 (en) | Catalyst for catalytic reduction of nitrogen oxides | |
| KR20110055082A (en) | The catalysts for selective oxidation of nh3 to n2 and their preparation methods | |
| JP3791968B2 (en) | Method for catalytic reduction of nitrogen oxides | |
| JPH09206559A (en) | Contact reducing method of nitrogen oxides | |
| JP3453239B2 (en) | Catalyst for catalytic reduction of nitrogen oxides | |
| JPH1199319A (en) | Waste gas purifying method | |
| JPH06315635A (en) | Catalytic structure for nitrogen oxide catalytic reduction | |
| JP2609983B2 (en) | Catalyst structure for catalytic reduction of nitrogen oxides | |
| JP3495832B2 (en) | Method for catalytic reduction of nitrogen oxides | |
| JP4132192B2 (en) | Exhaust gas purification method | |
| JP3781830B2 (en) | Method for catalytic reduction of nitrogen oxides | |
| JP3924341B2 (en) | Method for catalytic reduction of nitrogen oxides | |
| JP3872858B2 (en) | Method for producing nitrogen oxide reduction catalyst | |
| JP2618316B2 (en) | Catalyst for catalytic reduction of nitrogen oxides | |
| JP3745988B2 (en) | Method for catalytic reduction of nitrogen oxides and catalyst therefor | |
| JP3985301B2 (en) | Exhaust gas purification catalyst and purification method using the same | |
| JPH1119515A (en) | Catalyst for nitrogen oxide contact reduction | |
| JPH09155163A (en) | Method for catalytic reduction of nitrogen oxides | |
| JPH11197458A (en) | Cleaning of exhaust gas | |
| JPH09201515A (en) | Catalytic reduction method of nitrogen oxides | |
| JPH11114420A (en) | Catalyst for cleaning exhaust gas and method | |
| JPH1157411A (en) | Cleaning method for exhaust gas | |
| JPH1094718A (en) | Catalytic reelection of nitrogen oxide | |
| JP4058503B2 (en) | Exhaust gas purification catalyst layer, exhaust gas purification catalyst coating structure, and exhaust gas purification method using the same | |
| JPH1057771A (en) | Method for catalytically reducing nitrogen oxides |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20040106 |