JP2003340284A - Exhaust gas cleaning catalyst and catalyst coated structure thereof and exhaust gas cleaning method - Google Patents

Exhaust gas cleaning catalyst and catalyst coated structure thereof and exhaust gas cleaning method

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Publication number
JP2003340284A
JP2003340284A JP2002148932A JP2002148932A JP2003340284A JP 2003340284 A JP2003340284 A JP 2003340284A JP 2002148932 A JP2002148932 A JP 2002148932A JP 2002148932 A JP2002148932 A JP 2002148932A JP 2003340284 A JP2003340284 A JP 2003340284A
Authority
JP
Japan
Prior art keywords
catalyst
exhaust gas
gas cleaning
combustion exhaust
purifying catalyst
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
Application number
JP2002148932A
Other languages
Japanese (ja)
Inventor
Masashi Sugiyama
正史 杉山
Kengo Soda
健吾 曽田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sumitomo Metal Mining Co Ltd
Original Assignee
Sumitomo Metal Mining Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Sumitomo Metal Mining Co Ltd filed Critical Sumitomo Metal Mining Co Ltd
Priority to JP2002148932A priority Critical patent/JP2003340284A/en
Publication of JP2003340284A publication Critical patent/JP2003340284A/en
Pending legal-status Critical Current

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  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an exhaust gas cleaning catalyst having an excellent NOx removal capacity and durability in combustion exhaust gas containing sulfur oxide and not lowering in denitration capacity even if the temperature of the exhaust gas has a relatively low temperature of about 300-400°C, and to provide an exhaust gas cleaning method. <P>SOLUTION: The exhaust gas cleaning catalyst comprising a mixture of a first catalyst containing titania and iridium and a second catalyst containing sulfuric acid treated zirconia and palladium or a catalyst coated structure obtained by applying this catalyst to a support substrate having an integrated structure comprising a refractory material having a large number of through- holes is used to bring the oxygen excessive combustion exhaust gas containing sulfur oxide into contact with combustion exhaust gas in the presence of methanol to reduce and remove nitrogen oxides. <P>COPYRIGHT: (C)2004,JPO

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【発明の属する技術分野】本発明は、ボイラー、ディー
ゼルエンジン発電機、またはディーゼルエンジン自動車
からの排ガスのような、酸素濃度の高い燃焼排ガス中に
含まれる窒素酸化物の除去に有効な排ガス浄化用触媒、
並びにその触媒を使用する排ガス浄化方法に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exhaust gas purification for removing nitrogen oxides contained in combustion exhaust gas having a high oxygen concentration, such as exhaust gas from a boiler, a diesel engine generator, or a diesel engine automobile. catalyst,
And a method for purifying exhaust gas using the catalyst.

【0002】[0002]

【従来の技術】工場、発電設備、自動車等から排出され
る各種の燃焼排ガス中には、燃焼生成物である水や二酸
化炭素と共に、一酸化窒素や二酸化窒素などの窒素酸化
物(NOx)が含まれている。NOxは人体、特に呼吸
器系に悪影響を及ぼすばかりでなく、地球環境保全の上
から問題視される酸性雨の原因の1つとなっている。そ
のため、これら各種の燃焼排ガスから窒素酸化物を効率
よく除去する技術の開発が望まれている。
2. Description of the Related Art Nitrogen oxides (NOx) such as nitric oxide and nitrogen dioxide are contained in various combustion exhaust gases emitted from factories, power generation facilities, automobiles, etc., as well as water and carbon dioxide which are combustion products. include. NOx not only adversely affects the human body, especially the respiratory system, but is one of the causes of acid rain, which is regarded as a problem from the viewpoint of global environmental protection. Therefore, development of a technique for efficiently removing nitrogen oxides from these various combustion exhaust gases is desired.

【0003】従来、酸素過剰雰囲気下でNOxを還元除
去する方法としては、V−TiO触媒を用い、
アンモニア(NH)を還元剤として還元除去する方法
がよく知られている。しかし、この方法においては、臭
気が強く有害なアンモニアを用いるため取り扱いが容易
でなく、また未反応のアンモニアの排出を防ぐために特
別な装置を必要とし、設備が大型化することから、小規
模な排ガス発生源や移動型発生源への適用には不向きで
あるうえ、経済性においても好ましいものではなかっ
た。
Conventionally, as a method for reducing and removing NOx in an atmosphere of excess oxygen, a V 2 O 5 —TiO 2 catalyst has been used,
A method of reducing and removing ammonia (NH 3 ) using a reducing agent is well known. However, this method uses ammonia, which has a strong odor and is harmful, so that it is not easy to handle, and a special device is required to prevent the discharge of unreacted ammonia, and the equipment becomes large. It is not suitable for application to an exhaust gas source or a mobile source, and it is not economically preferable.

【0004】近年、酸素過剰の希薄燃焼排ガス中に残存
する未燃焼の炭化水素を還元剤として用いることによ
り、NOxの還元反応を促進させることができるという
報告がなされた。それ以来、この反応を促進するための
触媒が種々開発され、例えば、アルミナやアルミナに遷
移金属を担時した触媒などが、炭化水素を還元剤として
用いるNOxの還元除去反応に有効であるとする数多く
の報告がなされている。
In recent years, it has been reported that the reduction reaction of NOx can be promoted by using unburned hydrocarbons remaining in the lean-burn exhaust gas with excess oxygen as a reducing agent. Since then, various catalysts for accelerating this reaction have been developed. For example, alumina and a catalyst in which a transition metal is supported on alumina are effective for the reduction and removal reaction of NOx using hydrocarbon as a reducing agent. Many reports have been made.

【0005】[0005]

【発明が解決しようとする課題】このような炭化水素を
還元剤として酸素過剰の燃焼排ガス中の窒素酸化物を還
元除去する触媒として、アルミナやアルミナに遷移金属
を担時した触媒のほか、特開平4−284848号公報
には0.1〜4重量%のCu、Fe、Cr、Zn、N
i、又はVを含有するアルミナ若しくはシリカ−アルミ
ナからなる還元触媒が報告されている。
As a catalyst for reducing and removing nitrogen oxides in exhaust gas with excess oxygen by using such a hydrocarbon as a reducing agent, in addition to a catalyst in which a transition metal is supported on alumina or alumina, In Kaihei 4-284848, 0.1 to 4% by weight of Cu, Fe, Cr, Zn, N is disclosed.
Reduction catalysts made of alumina or silica-alumina containing i or V have been reported.

【0006】また、Ptをアルミナに担時した触媒を用
いると、NOxの還元反応が200〜300℃程度の低
温領域で進行することが、特開平4−267946号公
報、特開平5−68855号公報、特開平5−1039
49号公報などに報告されている。しかし、これらの貴
金属担持触媒は、還元剤である炭化水素の燃焼反応が過
度に促進されたり、地球温暖化の原因物質の1つとされ
ているNOが多量に副生し、無害なNへの還元反応
を選択的に進行させることが困難であるといった欠点を
有していた。
When a catalyst in which Pt is supported on alumina is used, the reduction reaction of NOx proceeds in a low temperature range of about 200 to 300 ° C., as disclosed in JP-A-4-267946 and JP-A-5-68855. Japanese Patent Laid-Open No. 5-1039
It is reported in Japanese Patent Publication No. 49 and the like. However, in these noble metal-supported catalysts, the combustion reaction of hydrocarbon as a reducing agent is excessively promoted, and a large amount of N 2 O, which is one of the causative agents of global warming, is produced as a by-product, and harmless N It has a drawback that it is difficult to selectively proceed the reduction reaction to 2 .

【0007】更に、特開平4−281844号公報に
は、アルミナなどに銀を担持した触媒が、酸素過剰雰囲
気下で炭化水素を還元剤として、NOxの還元反応を選
択的に進行させることが開示されている。その後、銀を
含有する触媒を用いる類似のNOxの還元除去方法が、
特開平4−354536号公報、特開平5−92124
号公報、特開平5−92125号公報、及び特開平6−
277454号公報などに開示されている。
Further, JP-A-4-281844 discloses that a catalyst in which silver is supported on alumina or the like selectively causes a reduction reaction of NOx by using hydrocarbon as a reducing agent in an oxygen excess atmosphere. Has been done. Then, a similar NOx reduction and removal method using a silver-containing catalyst was performed.
JP-A-4-354536, JP-A-5-92124
JP-A-5-92125 and JP-A-6-92125.
It is disclosed in Japanese Patent Publication No. 277454.

【0008】しかし、上記した従来の脱硝触媒を用いた
排ガス浄化方法は、硫黄酸化物を含む燃焼排ガス中では
NOxの除去性能が低下しやすく、実用的な耐久性が不
十分であるという問題があった。また、300℃〜40
0℃程度の比較的低温の場合、NOxの除去性能が低下
しやすいという問題もあった。
However, the above-mentioned conventional exhaust gas purification method using a denitration catalyst has a problem that the NOx removal performance is easily deteriorated in the combustion exhaust gas containing sulfur oxides and the practical durability is insufficient. there were. Also, 300 ° C to 40
At a relatively low temperature of about 0 ° C., there is also a problem that the NOx removal performance tends to deteriorate.

【0009】本発明は、このような従来の事情に鑑み、
硫黄酸化物を含む燃焼排ガスにおいても優れたNOxの
除去性能と耐久性を有し、燃焼排ガス温度が300℃〜
400℃程度の比較的低温でも脱硝性能が低下しない排
ガス浄化用触媒、及びそれを用いた排ガス浄化方法を提
供することを目的とする。
The present invention has been made in view of such conventional circumstances.
It has excellent NOx removal performance and durability even in combustion exhaust gas containing sulfur oxides, and the combustion exhaust gas temperature is 300 ° C to
An object of the present invention is to provide an exhaust gas purifying catalyst that does not deteriorate in denitration performance even at a relatively low temperature of about 400 ° C., and an exhaust gas purifying method using the same.

【0010】[0010]

【課題を解決するための手段】上記目的を達成するた
め、本発明は、酸素過剰の燃焼排ガス中の窒素酸化物を
還元除去する触媒であって、チタニアとイリジウムを含
有する第1触媒と、硫酸処理ジルコニアとパラジウムを
含有する第2触媒との混合物からなることを特徴とする
排ガス浄化用触媒を提供するものである。
To achieve the above object, the present invention is a catalyst for reducing and removing nitrogen oxides in oxygen-rich combustion exhaust gas, which comprises a first catalyst containing titania and iridium, An exhaust gas purifying catalyst comprising a mixture of a sulfuric acid-treated zirconia and a second catalyst containing palladium.

【0011】上記本発明の排ガス浄化用触媒において
は、前記第1触媒に対する第2触媒の混合割合が3〜5
重量倍であることが好ましい。
In the above exhaust gas purifying catalyst of the present invention, the mixing ratio of the second catalyst to the first catalyst is 3 to 5.
It is preferably a weight times.

【0012】また、本発明は、上記排ガス浄化用触媒
と、多数の貫通孔を有する耐火性材料からなる一体構造
の支持基質とからなり、支持基質の少なくとも貫通孔内
表面に前記触媒が被覆されていることを特徴とする排ガ
ス浄化用触媒被覆構造体を提供する。
Further, the present invention comprises the above exhaust gas purifying catalyst and a supporting substrate having an integral structure made of a refractory material having a large number of through holes, and at least the inner surface of the through holes of the supporting substrate is coated with the catalyst. A catalyst coating structure for exhaust gas purification is provided.

【0013】更に、本発明は、上記排ガス浄化用触媒又
は排ガス浄化用触媒被覆構造体に、硫黄酸化物を含む酸
素過剰の燃焼排ガスをメタノールの存在下で接触させ、
燃焼排ガス中の窒素酸化物を還元除去することを特徴と
する排ガス浄化方法を提供するものである。
Further, the present invention comprises contacting the exhaust gas-purifying catalyst or the exhaust-gas-purifying catalyst coating structure with oxygen-rich combustion exhaust gas containing sulfur oxides in the presence of methanol,
An exhaust gas purification method characterized by reducing and removing nitrogen oxides in combustion exhaust gas.

【0014】[0014]

【発明の実施の形態】本発明における排ガス浄化用触媒
は、第1触媒と第2触媒を混合してなる触媒であって、
第1触媒はチタニア(TiO)とイリジウム(Ir)
を含有し、第2触媒は硫酸処理ジルコニア(ZrO
とパラジウム(Pd)を含有している。第1触媒と第2
触媒の混合割合は、第1触媒よりも第2触媒を多くする
ことが脱硝性能の点で好ましく、具体的には第1触媒に
対する第2触媒の好ましい混合割合は重量比で3〜5倍
の範囲である。第2触媒の混合割合が第1触媒に対して
重量比で3倍未満では脱硝性能が低下し、5倍を超える
場合には第1触媒の含有量が少なくなるため、脱硝反応
進行時の1ステップとして重要なNOxの酸化性能が不
十分となり、その結果として脱硝性能が低下する。
BEST MODE FOR CARRYING OUT THE INVENTION The exhaust gas purifying catalyst according to the present invention is a catalyst obtained by mixing a first catalyst and a second catalyst,
The first catalyst is titania (TiO 2 ) and iridium (Ir)
The second catalyst contains sulfuric acid-treated zirconia (ZrO 2 ).
And palladium (Pd). First catalyst and second
From the standpoint of denitration performance, it is preferable that the mixing ratio of the catalyst be larger than that of the first catalyst in terms of denitration performance. Specifically, the mixing ratio of the second catalyst to the first catalyst is 3 to 5 times by weight. It is a range. If the mixing ratio of the second catalyst is less than 3 times the weight ratio of the first catalyst, the denitrification performance will be reduced, and if it exceeds 5 times, the content of the first catalyst will be small. The NOx oxidation performance, which is important as a step, becomes insufficient, and as a result, the denitration performance decreases.

【0015】第1触媒におけるチタニアの構造は特に限
定されず、アナタ−ゼ型、ルチル型、又はこれらの混合
状態が挙げられる。また、第1触媒に含有されるイリジ
ウムの状態は特に限定されず、金属状態、酸化物状態、
又はこれらの混合状態が挙げられ、出発原料も特に限定
されない。第1触媒中のイリジウムの含有量は、金属換
算で0.1〜10重量%が好ましく、0.1〜5重量%が
更に好ましい。イリジウムの含有量が0.1重量%未満
では脱硝反応進行時の1ステップとして重要なNOxの
酸化性能が不十分であり、一方10重量%を超えると脱
硝性能が低下する。
The structure of titania in the first catalyst is not particularly limited, and examples thereof include anatase type, rutile type, or a mixed state thereof. Further, the state of iridium contained in the first catalyst is not particularly limited, and may be a metal state, an oxide state,
Alternatively, a mixed state thereof may be mentioned, and the starting material is not particularly limited. The content of iridium in the first catalyst is preferably 0.1 to 10% by weight, and more preferably 0.1 to 5% by weight in terms of metal. If the content of iridium is less than 0.1% by weight, the NOx oxidation performance, which is important as one step in the progress of the denitration reaction, is insufficient, while if it exceeds 10% by weight, the denitration performance deteriorates.

【0016】次に、第2触媒における硫酸処理ジルコニ
アは、例えば、市販の水酸化ジルコニアに硫酸アンモニ
ウムの水溶液を含浸した後、空気中にて500〜600
℃で焼成することによって得られる。また、第2触媒に
含まれるパラジウムの状態も特に限定されず、金属状
態、酸化物状態、又はこれらの混合状態であって良く、
出発原料も特に限定されない。この第2触媒中のパラジ
ウムの含有量は、イリジウムの場合と同様に脱硝性能の
点から、金属換算で0.05〜5重量%が好ましく、0.
1〜2重量%が更に好ましい。
Next, the sulfuric acid-treated zirconia in the second catalyst is, for example, 500 to 600 in air after impregnating commercially available zirconia hydroxide with an aqueous solution of ammonium sulfate.
Obtained by firing at ° C. The state of palladium contained in the second catalyst is not particularly limited, and may be a metal state, an oxide state, or a mixed state thereof,
The starting material is also not particularly limited. From the viewpoint of denitration performance, the palladium content in the second catalyst is preferably 0.05 to 5% by weight in terms of metal, as in the case of iridium, and is preferably 0.05% by weight.
1-2% by weight is more preferable.

【0017】これら第1触媒と第2触媒の製造方法につ
いては、いずれも特に限定されるものではなく、従来か
ら行われている手法を採用することができる。例えば、
吸着法、ポアフィリング法、インシピエントウェットネ
ス法、蒸発乾固法、スプレー法などの含浸法、混練法、
物理混合法、及びこれらを組み合わせた法など、通常採
用されている公知の方法を用いることができる。
The method for producing the first catalyst and the second catalyst is not particularly limited, and a conventional method can be adopted. For example,
Adsorption method, pore filling method, incipient wetness method, evaporation dryness method, impregnation method such as spray method, kneading method,
Well-known methods that are usually adopted can be used, such as a physical mixing method and a method combining these methods.

【0018】また、上記した触媒製造の際には、その乾
燥温度は通常80〜120℃程度が好ましい。また、焼
成温度としては300〜900℃が好ましく、400〜
700℃程度が更に好ましい。このときの雰囲気につい
ても、触媒組成に応じて、空気、不活性ガス、酸素、水
蒸気などの雰囲気を適宜選択すればよく、また各雰囲気
を一定時間毎に交互に代えてもよい。
In the above-mentioned catalyst production, the drying temperature is usually preferably about 80 to 120 ° C. The firing temperature is preferably 300 to 900 ° C., and 400 to 900 ° C.
About 700 ° C. is more preferable. Regarding the atmosphere at this time, an atmosphere such as air, an inert gas, oxygen, or steam may be appropriately selected according to the catalyst composition, and each atmosphere may be alternately changed at regular intervals.

【0019】第1触媒と第2触媒を混合してなる排ガス
浄化用触媒は、通常のごとく、粉末状態のまま一定形状
の容器内に充填され、又は所定の形状に成形した成形体
をそのまま若しくは一定形状の容器内に充填して使用す
ることができる。
The exhaust gas-purifying catalyst obtained by mixing the first catalyst and the second catalyst is, as usual, filled in a container in a fixed shape in a powder state, or a molded body molded into a predetermined shape as it is or It can be used by filling it in a container having a fixed shape.

【0020】触媒を所望形状の成形体とするには、粉末
状の触媒をメチルセルロースなどの適当なバインダーと
混合し、あるいはバインダーなしで、所望の形状のダイ
スを有する成型機により押出成形する。また、触媒の形
状は特に制限されず、例えば、球状、ハニカム状、ペレ
ット状、リング状など種々の形状であってよい。また、
これらの形状をなす触媒の大きも、使用条件に応じて任
意に選択すればよい。
In order to make the catalyst into a molded product having a desired shape, the powdery catalyst is mixed with a suitable binder such as methyl cellulose, or is extruded without a binder using a molding machine having a die having a desired shape. The shape of the catalyst is not particularly limited, and may be various shapes such as spherical shape, honeycomb shape, pellet shape, and ring shape. Also,
The size of the catalyst having these shapes may be arbitrarily selected according to the usage conditions.

【0021】また、第1触媒と第2触媒を混合してなる
排ガス浄化用触媒は、支持基質上に触媒を被覆させた触
媒被覆構造体として使用することができる。好ましい触
媒被覆構造体は、多数の貫通孔を有する耐火性材料で構
成された一体構造の支持基質の少なくとも貫通孔内表面
に、例えばウォッシュコート法などの公知の方法により
触媒を被覆したものである。
Further, the exhaust gas-purifying catalyst obtained by mixing the first catalyst and the second catalyst can be used as a catalyst coating structure in which a supporting substrate is coated with the catalyst. A preferred catalyst-coated structure is a monolithic support substrate composed of a refractory material having a large number of through holes, at least the inner surface of the through holes being coated with a catalyst by a known method such as a wash coating method. .

【0022】触媒被覆構造体に用いられる支持基質は、
多数の貫通孔が設けられており、使用時に貫通孔が排ガ
ス流通方向に沿うように配置される。支持基質の開孔率
は、排ガス流通方向に垂直な断面において60〜90%
の範囲が好ましい。支持基質の材料としては、コージェ
ライト等のセラミックスや、ステンレス鋼等の金属を使
用することができる。また、その形状についても、ハニ
カム状や連続フォーム状など、従来から慣用のものが使
用できる。
The support substrate used in the catalyst coated structure is
A large number of through holes are provided, and the through holes are arranged along the exhaust gas flow direction during use. The porosity of the supporting substrate is 60 to 90% in a cross section perpendicular to the exhaust gas flow direction.
Is preferred. As the material of the supporting substrate, ceramics such as cordierite and metals such as stainless steel can be used. Also, regarding the shape, a conventionally used one such as a honeycomb shape or a continuous foam shape can be used.

【0023】本発明の排ガス浄化方法は、上記した排ガ
ス浄化用触媒又は排ガス浄化用触媒被覆構造体に、燃焼
排ガスをメタノールの存在下で接触させれば良い。還元
剤として排ガス中に添加するメタノールの量は、操業上
求められる脱硝率及びランニングコストに応じて適宜選
択すればよいが、通常は窒素酸化物に対するモル比とし
て0.5〜5程度が好ましい。
In the exhaust gas purification method of the present invention, the combustion exhaust gas may be brought into contact with the above-mentioned exhaust gas purification catalyst or exhaust gas purification catalyst coating structure in the presence of methanol. The amount of methanol added to the exhaust gas as a reducing agent may be appropriately selected according to the denitration rate and running cost required for operation, but normally, the molar ratio to nitrogen oxide is preferably about 0.5 to 5.

【0024】希薄空燃比で運転される内燃機関からの燃
焼排ガスは、一般に、CO、HC(炭化水素)及びH
といった還元性成分と、NOx及びOといった酸化性
成分とを含有するが、両者相互の完全な酸化還元反応に
必要な化学量論量よりも過剰量の酸素を含有している。
このような酸素過剰の条件下で燃焼排ガスが本発明の触
媒と接触することにより、NOxはNとHOにまで
還元分解されると同時に、HCなどの還元剤もCO
Oに完全酸化される。
Combustion exhaust gas from an internal combustion engine operated at a lean air-fuel ratio is generally CO, HC (hydrocarbon) and H 2
And a oxidative component such as NOx and O 2, but contains an excess of oxygen in excess of the stoichiometric amount required for a complete redox reaction between them.
By contacting the combustion exhaust gas with the catalyst of the present invention under such an excess oxygen condition, NOx is reductively decomposed to N 2 and H 2 O, and at the same time, a reducing agent such as HC is also reduced to CO 2 and H 2 O. It is completely oxidized to O.

【0025】本発明の触媒を用いた排ガス浄化方法にお
けるガス空間速度(SV)は、特に限定されるものでは
ないが、1,000/h以上で100,000/h以下と
することが好ましい。
The gas space velocity (SV) in the exhaust gas purification method using the catalyst of the present invention is not particularly limited, but it is preferably 1,000 / h or more and 100,000 / h or less.

【0026】[0026]

【実施例】(1)触媒の製造 四塩化イリジウム水和物0.19gを含む120mlの
水溶液に、市販のチタニア10gを浸漬した後、80℃
で蒸発乾固した。これを更に110℃で乾燥した後、空
気中にて500℃で3時間焼成して、Ir/TiO
らなる触媒1を得た。尚、この触媒1における金属換算
でのIr含有量は、触媒1全体の重量に対して1重量%
である。また、金属換算でのIr含有量を3重量%とし
た以外は上記と同様にして、Ir/TiOからなる触
媒2を調整した。
Example (1) Preparation of catalyst After immersing 10 g of commercially available titania in 120 ml of an aqueous solution containing 0.19 g of iridium tetrachloride hydrate, 80 ° C.
It was evaporated to dryness. This was further dried at 110 ° C. and then calcined in air at 500 ° C. for 3 hours to obtain a catalyst 1 composed of Ir / TiO 2 . The Ir content of the catalyst 1 in terms of metal is 1% by weight based on the total weight of the catalyst 1.
Is. Further, a catalyst 2 composed of Ir / TiO 2 was prepared in the same manner as above except that the Ir content in terms of metal was 3% by weight.

【0027】一方、硫酸アンモニウム10gを含む12
0ミリリットルの水溶液に、水酸化ジルコニウム80g
を浸漬した後、80℃で蒸発乾固した。これを更に11
0℃で乾燥した後、空気中にて550℃で3時間焼成し
て、硫酸処理ZrOを得た。この硫酸処理ジルコニア
20gを、硝酸パラジウム水溶液(Pd:10%)0.
4gを50mlの純水で希釈した溶液に浸漬し、80℃
で蒸発乾固及び110℃で乾燥した後、空気中にて50
0℃で焼成して、Pd/硫酸処理ZrOからなる触媒
3を得た。尚、この触媒3における金属換算でのPd含
有量は、触媒3全体の重量に対して0.2重量%であ
る。
On the other hand, 12 containing 10 g of ammonium sulfate
80 ml of zirconium hydroxide in 0 ml of aqueous solution
Was dipped and then evaporated to dryness at 80 ° C. This is 11 more
After drying at 0 ° C., it was calcined in air at 550 ° C. for 3 hours to obtain sulfuric acid-treated ZrO 2 . 20 g of this sulfuric acid-treated zirconia was added to a palladium nitrate aqueous solution (Pd: 10%) of 0.
Immerse 4g in a solution diluted with 50ml pure water,
After evaporating to dryness and drying at 110 ° C in air, 50
It was calcined at 0 ° C. to obtain a catalyst 3 composed of Pd / sulfuric acid treated ZrO 2 . The Pd content in terms of metal in the catalyst 3 is 0.2% by weight based on the weight of the entire catalyst 3.

【0028】上記のように得られた触媒1と触媒3を、
触媒1:触媒3の重量比が1:4となるように物理混合
することにより触媒Aを製造した。また、触媒2と触媒
3を、触媒2:触媒3の重量比が1:4となるように物
理混合して触媒Bを製造した。
The catalyst 1 and the catalyst 3 obtained as described above are
Catalyst A was prepared by physically mixing the catalyst 1: catalyst 3 in a weight ratio of 1: 4. Further, the catalyst 2 and the catalyst 3 were physically mixed so that the weight ratio of the catalyst 2 to the catalyst 3 was 1: 4, to prepare the catalyst B.

【0029】次に、60gの上記触媒Aを、シリカゾル
(SiO固形分20重量%)4g及び水120mlと
共にボールミルポットに仕込み、湿式粉砕してスラリー
を得た。このスラリー中に、市販の400cpsi(セ
ル/inch)コージェライトハニカム基質から刳り
抜いた直径1インチ×長さ2.5インチの円筒状コアを
浸漬し、引き上げた後余分のスラリーをエアーブローで
除去して乾燥した。その後、500℃で30分間焼成
し、ハニカム1リットル当りドライ換算で120gの固
形分を被覆した触媒被覆構造体を作製し、このハニカム
状触媒被覆構造体を触媒Cとした。
Next, 60 g of the above catalyst A was charged into a ball mill pot together with 4 g of silica sol (SiO 2 solid content 20% by weight) and 120 ml of water, and wet pulverized to obtain a slurry. Into this slurry, a cylindrical core with a diameter of 1 inch and a length of 2.5 inches hollowed out from a commercially available 400 cpsi (cell / inch 2 ) cordierite honeycomb substrate was immersed, and after pulling up, the excess slurry was air blown. Removed and dried. Then, it was fired at 500 ° C. for 30 minutes to prepare a catalyst-coated structure coated with 120 g of solid content per liter of honeycomb in terms of dry matter, and this honeycomb-shaped catalyst-coated structure was designated as catalyst C.

【0030】(2)脱硝性能の評価 上記のごとく製造した触媒A〜B及び触媒1又は3を用
いて、その脱硝性能を評価した。まず、これらの各触媒
を加圧成型した後、粉砕して粒度を350〜500μm
に整粒した。得られた各触媒粉末1.2gを、それぞれ
内径7mmのパイレックス(登録商標)製ガラス反応管
に充填し、これを常圧固定床流通反応装置に装着した。
(2) Evaluation of denitration performance Using the catalysts A to B and the catalyst 1 or 3 produced as described above, the denitration performance was evaluated. First, each of these catalysts is pressure-molded and then pulverized to have a particle size of 350 to 500 μm.
The particles were sized. Each of the obtained catalyst powders (1.2 g) was filled in a Pyrex (registered trademark) glass reaction tube having an inner diameter of 7 mm, and the glass reaction tube was mounted in an atmospheric fixed bed flow reactor.

【0031】この装置に、反応管内のガス温度を350
℃〜450℃の下記表1に示す温度に保ちながら、モデ
ル排ガスとしてNO:1000ppm、O:10%、
O:10%、SO:50ppm、メタノール:2
000ppm、残部:N2からなる混合ガスを、空間速
度30,000/hで通過させ、そのときの脱硝性能を
評価した。脱硝性能としての脱硝率を、下記の数式1に
従って算出し、得られた結果を下記表1に示した。
The gas temperature in the reaction tube was set to 350 in this apparatus.
As the model exhaust gas, NO: 1000 ppm, O 2 : 10%,
H 2 O: 10%, SO 2 : 50 ppm, methanol: 2
A mixed gas consisting of 000 ppm and the balance: N2 was passed at a space velocity of 30,000 / h, and the denitration performance at that time was evaluated. The denitration rate as the denitration performance was calculated according to the following mathematical formula 1, and the obtained results are shown in Table 1 below.

【0032】尚、反応管出口のガス組成の分析について
は、NOxの濃度は化学発光式NOx計で測定し、N
O濃度はPorapack Qカラムを装着したガスク
ロマトグラフ・熱伝導度検出器を用いて測定した。いず
れの触媒の場合も、反応管の出口ガス中にNOは殆ど
認められなかった。
Regarding the analysis of the gas composition at the outlet of the reaction tube, the concentration of NOx was measured by a chemiluminescence type NOx meter, and N 2
The O concentration was measured using a gas chromatograph / heat conductivity detector equipped with a Porpack Q column. In the case of any of the catalysts, N 2 O was hardly found in the outlet gas of the reaction tube.

【0033】[0033]

【数1】 [Equation 1]

【0034】また、比較のために、上記触媒2と触媒3
を排ガスの流れ方向に順番に(混合せず)配置した2段
触媒、即ち触媒2/3と触媒3/2(上流側/下流側)
についても、上記と同様に脱硝性能を評価し、その結果
を下記表1に併せて示した。
For comparison, the above catalyst 2 and catalyst 3 are also included.
Two-stage catalysts arranged in order (without mixing) in the exhaust gas flow direction, that is, catalyst 2/3 and catalyst 3/2 (upstream side / downstream side)
The denitration performance was evaluated in the same manner as above, and the results are also shown in Table 1 below.

【0035】更に、上記の触媒Aで被覆されたハニカム
状触媒被覆構造体からなる触媒Cを用い、これを直径1
5mm×長さ32mmの円筒状に調整した後、内径15
mmのステンレス製反応管内に収納して触媒床を構成し
た。この触媒床に対して、上記モデル排ガスを空間速度
6,000/hで通過させた以外は上記と同様にして脱
硝性能を評価し、その結果を下記表1に併せて示した。
Further, a catalyst C composed of a honeycomb-shaped catalyst coating structure coated with the above-mentioned catalyst A was used, which had a diameter of 1
After adjusting to a cylindrical shape of 5 mm × length 32 mm, the inner diameter 15
A catalyst bed was constructed by being housed in a stainless steel reaction tube of mm. Denitration performance was evaluated in the same manner as above except that the model exhaust gas was passed through the catalyst bed at a space velocity of 6,000 / h, and the results are also shown in Table 1 below.

【0036】[0036]

【表1】 [Table 1]

【0037】次に、上記と同じ触媒A、触媒B、及びハ
ニカム状触媒被覆構造体からなる触媒Cを用い、反応管
内のガス温度を350℃の一定に保ちながら、開始初期
から50時間経過後までの脱硝率の径時変化を測定し
た。その際、上記モデル排ガスを空間速度は、触媒Aと
触媒Bについては30,000/h及び触媒Cでは6,0
00/hとした。得られた結果を下記表2に示した。
Next, using the same catalyst A, catalyst B, and catalyst C consisting of a honeycomb-shaped catalyst coating structure as described above, while maintaining the gas temperature in the reaction tube constant at 350 ° C., 50 hours after the initial start, The change in denitration rate with time was measured. At that time, the space velocity of the model exhaust gas was 30,000 / h for catalyst A and catalyst B and 6.0 for catalyst C.
00 / h. The results obtained are shown in Table 2 below.

【0038】[0038]

【表2】 [Table 2]

【0039】上記表1の結果から、触媒1〜3を組合わ
せて混合した本発明例の触媒A〜Cは、触媒1〜3のい
ずれか単独又は混合せずに2段に配置した比較例に比べ
て、多量の硫黄酸化物が共存する排ガスにおいてもNO
xの除去活性が高いことが分る。また、上記表2の結果
から、本発明例の触媒A〜Cは、硫黄酸化物の共存下に
おいても経時的な脱硝性能の低下が少なく、耐久性に優
れることが分る。
From the results shown in Table 1 above, the catalysts A to C of the present invention in which the catalysts 1 to 3 were combined and mixed were comparative examples in which any one of the catalysts 1 to 3 was arranged alone or in two stages. Compared to NO, even in exhaust gas in which a large amount of sulfur oxides coexist
It can be seen that x removal activity is high. Further, from the results in Table 2 above, it can be seen that the catalysts A to C of the examples of the present invention are excellent in durability with little deterioration in denitration performance over time even in the presence of sulfur oxides.

【0040】[0040]

【発明の効果】本発明によれば、酸素過剰の燃焼排ガス
中の窒素酸化物を優れた脱硝率で還元除去する排ガス浄
化用触媒を提供することができる。この本発明の排ガス
浄化用触媒は、硫黄酸化物を含む燃焼排ガスにおいても
優れたNOxの除去性能を維持し、耐久性にも優れてい
る。更に、排ガス温度が300℃〜400℃程度の比較
的低温であっても、脱硝性能が低下することがない。
EFFECTS OF THE INVENTION According to the present invention, it is possible to provide an exhaust gas purifying catalyst that reduces and removes nitrogen oxides in combustion exhaust gas with excess oxygen at an excellent denitration rate. The exhaust gas-purifying catalyst of the present invention maintains excellent NOx removal performance even in combustion exhaust gas containing sulfur oxides, and has excellent durability. Furthermore, even if the exhaust gas temperature is relatively low, such as about 300 ° C to 400 ° C, the denitration performance does not deteriorate.

───────────────────────────────────────────────────── フロントページの続き Fターム(参考) 4D048 AA06 AB02 AB07 AC09 BA07X BA08X BA31X BA33X BA39Y BA41X BA46X BB01 BB02 BB16 BC01 CC50 4G069 AA03 BA04A BA04B BA05A BA05B BA13A BA13B BA17 BB02A BB02B BB10A BB10B BC51A BC51B BC74A BC74B CA02 CA03 CA08 CA13 EA18 EA19 EB12Y EB14Y EC09 EC28 FC08    ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D048 AA06 AB02 AB07 AC09 BA07X                       BA08X BA31X BA33X BA39Y                       BA41X BA46X BB01 BB02                       BB16 BC01 CC50                 4G069 AA03 BA04A BA04B BA05A                       BA05B BA13A BA13B BA17                       BB02A BB02B BB10A BB10B                       BC51A BC51B BC74A BC74B                       CA02 CA03 CA08 CA13 EA18                       EA19 EB12Y EB14Y EC09                       EC28 FC08

Claims (5)

【特許請求の範囲】[Claims] 【請求項1】 酸素過剰の燃焼排ガス中の窒素酸化物を
還元除去する触媒であって、チタニアとイリジウムを含
有する第1触媒と、硫酸処理ジルコニアとパラジウムを
含有する第2触媒との混合物からなることを特徴とする
排ガス浄化用触媒。
1. A catalyst for reducing and removing nitrogen oxides in combustion exhaust gas containing excess oxygen, which is obtained by mixing a first catalyst containing titania and iridium with a second catalyst containing sulfuric acid-treated zirconia and palladium. An exhaust gas purifying catalyst characterized by:
【請求項2】 前記第1触媒に対する第2触媒の混合割
合が3〜5重量倍であることを特徴とする、請求項1に
記載の排ガス浄化用触媒。
2. The exhaust gas-purifying catalyst according to claim 1, wherein a mixing ratio of the second catalyst to the first catalyst is 3 to 5 times by weight.
【請求項3】 請求項1又は2に記載の排ガス浄化用触
媒と、多数の貫通孔を有する耐火性材料からなる一体構
造の支持基質とからなり、支持基質の少なくとも貫通孔
内表面に前記触媒が被覆されていることを特徴とする排
ガス浄化用触媒被覆構造体。
3. The exhaust gas purifying catalyst according to claim 1 or 2, and a supporting substrate having an integral structure made of a refractory material having a large number of through holes, wherein the catalyst is provided on at least the inner surface of the through holes. An exhaust gas-purifying catalyst-coated structure characterized by being coated with.
【請求項4】 請求項1又は2に記載の排ガス浄化用触
媒に、硫黄酸化物を含む酸素過剰の燃焼排ガスをメタノ
ールの存在下で接触させ、燃焼排ガス中の窒素酸化物を
還元除去することを特徴とする排ガス浄化方法。
4. The exhaust gas purifying catalyst according to claim 1 or 2 is contacted with oxygen-rich combustion exhaust gas containing sulfur oxides in the presence of methanol to reduce and remove nitrogen oxides in the combustion exhaust gas. Exhaust gas purification method characterized by the above.
【請求項5】 請求項3に記載の排ガス浄化用触媒被覆
構造体に、硫黄酸化物を含む酸素過剰の燃焼排ガスをメ
タノールの存在下で接触させ、燃焼排ガス中の窒素酸化
物を還元除去することを特徴とする排ガス浄化方法。
5. The exhaust gas-purifying catalyst-coated structure according to claim 3 is contacted with oxygen-rich combustion exhaust gas containing sulfur oxides in the presence of methanol to reduce and remove nitrogen oxides in the combustion exhaust gas. An exhaust gas purification method characterized by the above.
JP2002148932A 2002-05-23 2002-05-23 Exhaust gas cleaning catalyst and catalyst coated structure thereof and exhaust gas cleaning method Pending JP2003340284A (en)

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Country Link
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