JPH11156195A - Oxide catalytic material for nitrogen oxide decomposition and method for decomposing and removing nitrogen oxide - Google Patents
Oxide catalytic material for nitrogen oxide decomposition and method for decomposing and removing nitrogen oxideInfo
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- JPH11156195A JPH11156195A JP9324966A JP32496697A JPH11156195A JP H11156195 A JPH11156195 A JP H11156195A JP 9324966 A JP9324966 A JP 9324966A JP 32496697 A JP32496697 A JP 32496697A JP H11156195 A JPH11156195 A JP H11156195A
- Authority
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- Prior art keywords
- oxide
- exhaust gas
- decomposing
- catalytic material
- decomposition
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、定置式の工場の各
種工業炉や発電所用の内燃機関、及び移動式の自動車等
内燃機関等の各種排気ガス中に含まれる窒素酸化物（Ｎ
Ｏ）を直接、窒素（Ｎ2 ）と酸素（Ｏ2 ）に分解するこ
とが可能な酸化物触媒材料並びにこれを用いて各種排気
ガス中のＮＯを還元剤を用いずに直接、Ｎ2 とＯ2 に分
解して除去する方法に関するもので、とりわけ排気ガス
中の炭化水素濃度が低いリーンバーンエンジン等の自動
車排気ガス浄化用として好適な窒素酸化物分解用酸化物
触媒材料並びに該酸化物触媒材料を用いて排気ガス中の
ＮＯを直接、Ｎ2 とＯ2 に分解して除去する方法に関す
るものである。The present invention relates to nitrogen oxides (N) contained in various exhaust gases from internal combustion engines for various industrial furnaces and power plants in stationary factories and internal combustion engines for mobile automobiles.
O) is an oxide catalyst material capable of directly decomposing O) into nitrogen (N 2 ) and oxygen (O 2 ), and is used to directly reduce NO in various exhaust gases to N 2 without using a reducing agent. The present invention relates to a method for decomposing and removing O 2 , particularly an oxide catalyst material for decomposing nitrogen oxides and an oxide catalyst suitable for purifying automobile exhaust gas such as lean burn engines having a low hydrocarbon concentration in exhaust gas. The present invention relates to a method for directly decomposing NO in exhaust gas into N 2 and O 2 by using a material and removing it.
【０００２】[0002]
【従来の技術】従来より、定置式の前記各種工業炉や内
燃機関、及び移動式の自動車に代表される内燃機関等か
ら排出される排気ガス中に含まれるＮＯは、人体に悪影
響を及ぼすだけでなく、酸性雨及び光化学スモッグの原
因物質であるため、その大気中への放出は大きな環境問
題になっている。2. Description of the Related Art Conventionally, NO contained in exhaust gas discharged from various stationary industrial furnaces and internal combustion engines, and internal combustion engines typified by mobile automobiles, has only a bad effect on the human body. In addition, since it is a causative substance of acid rain and photochemical smog, its release into the atmosphere is a major environmental problem.
【０００３】そこで、前記排気ガス中に含有されるＮＯ
の除去方法としては、かねてより主に接触還元法が用い
られており、例えば、前記工場及び発電所等のＮＯの固
定発生源には排気ガス中に多量の酸素を含有することか
ら、還元剤としてアンモニアを用い、バナジア（Ｖ2 Ｏ
5 ）／チタニア（ＴｉＯ2 ）触媒によりＮＯを還元除去
している。Therefore, the NO contained in the exhaust gas
As a method for removing NO, a catalytic reduction method has been mainly used for a long time. For example, since a fixed NO emission source such as the factory and the power plant contains a large amount of oxygen in the exhaust gas, a reducing agent is used. Using ammonia as vanadia (V 2 O
5 ) / NO is reduced and removed by a titania (TiO 2 ) catalyst.
【０００４】一方、自動車等の移動発生源には、排気ガ
ス中の酸素量が少ないため、該排気ガス中に残存する未
燃の一酸化炭素（ＣＯ）及び炭化水素（Ｃx Ｈy ）を還
元剤として用い、三元触媒によりＮＯを還元除去してい
る。[0004] On the other hand, undesired carbon monoxide (CO) and hydrocarbons (C x H y ) remaining in the exhaust gas are removed from the mobile sources such as automobiles because the amount of oxygen in the exhaust gas is small. It is used as a reducing agent, and NO is reduced and removed by a three-way catalyst.
【０００５】そのようなＮＯの還元除去方法に用いられ
る三元触媒としては、例えば、パラジウム（Ｐｄ）、白
金（Ｐｔ）、ロジウム（Ｒｈ）等の貴金属をγ−アルミ
ナ（Ａｌ2 Ｏ3 ）で被覆したコージェライト等の耐火性
担体に担持したものが用いられていた。As a three-way catalyst used in such a NO reduction reduction method, for example, a noble metal such as palladium (Pd), platinum (Pt), rhodium (Rh) is converted to γ-alumina (Al 2 O 3 ). Those supported on a coated refractory carrier such as cordierite have been used.
【０００６】しかしながら、前記固定発生源のＮＯ除去
方法として用いられているアンモニアによる接触還元法
は、アンモニアが高価でかつ危険であり、その取り扱い
に十分な注意が必要であるという理由から、移動発生源
には用いることができなかった。[0006] However, the catalytic reduction method using ammonia, which is used as a method for removing NO from the fixed generation source, involves the problem that ammonia is expensive and dangerous, and requires sufficient care in its handling. It could not be used as a source.
【０００７】他方、自動車等の移動発生源においても、
現在、省エネルギ−化のために注目されている希薄燃焼
エンジン（リーンバーンエンジン）では、排気ガス中の
未燃の一酸化炭素及び炭化水素量が極端に少ないため、
ＮＯの還元作用を示さないという問題が残されている。[0007] On the other hand, in a mobile source such as an automobile,
At present, in lean-burn engines (lean-burn engines), which are attracting attention for energy saving, the amounts of unburned carbon monoxide and hydrocarbons in exhaust gas are extremely small.
There remains a problem of not exhibiting the reducing action of NO.
【０００８】かかる問題を解決するためには還元剤を使
用せずにＮＯを除去することが最も簡単で理想的である
ことから、かねてより銅イオン交換ゼオライト触媒を用
いることが提案されていたが、水蒸気存在下では活性が
著しく劣化し、最も要求されている６００℃前後での水
蒸気を含有する排気ガス条件下では、前記ＮＯの分解除
去能力が低く、実用上、使用できないという欠点があっ
た。In order to solve such a problem, since it is easiest and ideal to remove NO without using a reducing agent, it has been proposed to use a copper ion exchanged zeolite catalyst for some time. However, the activity is significantly deteriorated in the presence of water vapor, and under exhaust gas conditions containing water vapor at around 600 ° C., which is the most required, the ability to decompose and remove NO is low, and there is a drawback that it cannot be used practically. .
【０００９】そこで、ＮＯをＮ2 とＯ2 に直接分解する
他の方法として、パラジウムに金、銀を混合してＡｌ2
Ｏ3 に担持した触媒材料が提案されている（Ｒ．Ｊ．Ｗ
ｕｅｔ ａｌ．／Ａｐｐｌｉｅｄ Ｃａｔａｌｙｓｉｓ
Ｂ：Ｅｎｖｉｒｏｎｍｅｎｔａｌ ６（１９９５）参
照）。Therefore, as another method of directly decomposing NO into N 2 and O 2 , gold and silver are mixed with palladium to form Al 2
A catalyst material supported on O 3 has been proposed (RJW).
uet al. / Applied Catalysis
B: Environmental 6 (1995)).
【００１０】[0010]
【発明が解決しようとする課題】しかしながら、前記提
案では水蒸気が存在しない排気ガス条件下ではＮＯをＮ
2 とＯ2 に直接分解できるとされているものの、水蒸気
存在下では確認されておらず、触媒材料として実用的な
水蒸気存在下での６００℃前後の温度範囲における触媒
活性が未だ不十分であるという課題があった。However, in the above-mentioned proposal, NO is converted to N under exhaust gas conditions in which no steam is present.
Although it is said that it can be directly decomposed into 2 and O 2 , it has not been confirmed in the presence of steam, and the catalytic activity in the temperature range of about 600 ° C. in the presence of steam which is practical as a catalyst material is still insufficient. There was a problem that.
【００１１】[0011]
【発明の目的】本発明は前記課題に鑑み成されたもの
で、その目的は、工場や発電所等の固定発生源から排出
される各種排気ガス、及び自動車に代表される移動発生
源、とりわけ希薄燃焼エンジン（リーンバーンエンジ
ン）の排気ガス中に含まれるＮＯを、６００℃前後の高
温の水蒸気を含有する排気ガス条件下でも、還元剤を用
いずに高い触媒活性で直接、Ｎ2 とＯ2 に分解除去する
ことができる有用な触媒材料並びにそれを用いたＮＯの
分解除去方法を提供するものである。SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide various exhaust gases emitted from fixed sources such as factories and power plants, and mobile sources represented by automobiles, especially NO contained in the exhaust gas of a lean burn engine (lean burn engine) is directly converted into N 2 and O 2 with high catalytic activity without using a reducing agent even under exhaust gas conditions containing high-temperature steam around 600 ° C. It is intended to provide a useful catalyst material which can be decomposed and removed into 2, and a method for decomposing and removing NO using the same.
【００１２】[0012]
【課題を解決するための手段】本発明は前記課題に鑑み
成されたもので、β−Ｇａ2 Ｏ3 とＰｄＯの２結晶相か
ら成る酸化物に対してＡｌ2 Ｏ3 を適量添加することに
より、得られた酸化物材料は、６００℃を超え８００℃
に至る高温の水蒸気を含有した排気ガス条件下でもＮＯ
の直接分解反応に高い活性を示し、特に、希薄燃焼方式
の内燃機関から放出される還元剤がほとんど存在しない
ＮＯを含有する水蒸気を含有した排気ガス中において
も、該ＮＯを直接Ｎ2 とＯ2 に効果的に分解して浄化す
ることができることを確認し、本発明に至った。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to add an appropriate amount of Al 2 O 3 to an oxide composed of two crystal phases of β-Ga 2 O 3 and PdO. As a result, the obtained oxide material exceeds 600 ° C. and 800 ° C.
NO even under exhaust gas conditions containing high temperature steam up to
Has a high activity in the direct decomposition reaction of NO. Particularly, even in exhaust gas containing NO and containing steam containing almost no reducing agent released from a lean burn type internal combustion engine, the NO is directly converted into N 2 and O 2. The present inventors have confirmed that they can be effectively decomposed and purified into 2 and have led to the present invention.
【００１３】即ち、本発明の窒素酸化物分解用酸化物触
媒材料は、結晶相としてＧａとＰｄの原子比ｎ（Ｇａ／
Ｐｄ）が１．０〜５．０であるβ−Ｇａ2 Ｏ3 とＰｄＯ
から構成される酸化物に対し、Ａｌ2 Ｏ3 を１０〜６０
重量％添加して成ることを特徴とするものである。That is, the oxide catalyst material for decomposing nitrogen oxides of the present invention has an atomic ratio n (Ga / Pd) of Ga and Pd as a crystal phase.
Β-Ga 2 O 3 having Pd) of 1.0 to 5.0 and PdO
To oxides composed of the Al 2 O 3 10 to 60
% By weight.
【００１４】更に、本発明の窒素酸化物分解除去方法
は、β−Ｇａ2 Ｏ3 とＰｄＯの２結晶相から構成される
酸化物であり、含有するＧａとＰｄの原子比ｎ（Ｇａ／
Ｐｄ）が１．０〜５．０で、４０〜９０重量％の前記酸
化物に、１０〜６０重量％の割合のＡｌ2 Ｏ3 を添加し
て成る窒素酸化物分解用酸化物触媒材料を用い、該触媒
材料とＮＯを含む排気ガスを接触させ、還元剤を用いず
にＮＯをＮ2 とＯ2 に直接分解除去することを特徴とす
るものである。Further, the method for decomposing and removing nitrogen oxides of the present invention is an oxide composed of two crystal phases of β-Ga 2 O 3 and PdO, and has an atomic ratio n (Ga / Pd) of Ga and Pd contained therein.
Pd) is at 1.0 to 5.0, the oxide of 40 to 90 wt%, nitrogen oxides cracking oxide catalyst material formed by adding Al 2 O 3 ratio of 10 to 60 wt% The catalyst material is brought into contact with an exhaust gas containing NO, and NO is directly decomposed and removed into N 2 and O 2 without using a reducing agent.
【００１５】[0015]
【作用】本発明の窒素酸化物分解用酸化物触媒材料並び
に窒素酸化物分解除去方法によれば、触媒材料がβ−Ｇ
ａ2 Ｏ3 とＰｄＯの２結晶相から構成される酸化物にＡ
ｌ2 Ｏ3 を添加したものであることから、前記β−Ｇａ
2 Ｏ3 結晶相の上にＮＯが解離吸着し、更にＰｄＯ結晶
相によりＮ−Ｏ間の結合力が弱められることにより、Ｎ
Ｏの直接分解活性が発現すると共に、Ａｌ2 Ｏ3 を共存
させることにより、β−Ｇａ2 Ｏ3 とＰｄＯが良く分散
化されるため、ＮＯ分解の活性点が増大し、その結果、
水蒸気の吸着による阻害が抑制され、８００℃に及ぶ高
温で水蒸気が共存していても高い触媒活性を示すもので
ある。According to the oxide catalyst material for decomposing nitrogen oxides and the method for decomposing and removing nitrogen oxides of the present invention, the catalyst material is β-G
A is an oxide composed of two crystal phases of a 2 O 3 and PdO.
l 2 O 3 , the β-Ga
NO is dissociated and adsorbed on the 2 O 3 crystal phase, and the bonding force between N and O is weakened by the PdO crystal phase.
By expressing the direct decomposition activity of O and coexisting with Al 2 O 3 , β-Ga 2 O 3 and PdO are well dispersed, so that the active site of NO decomposition increases, and as a result,
Inhibition due to the adsorption of water vapor is suppressed, and high catalytic activity is exhibited even at the high temperature of 800 ° C. even when water vapor coexists.
【００１６】[0016]
【発明の実施の形態】以下、本発明の窒素酸化物分解用
酸化物触媒材料並びに窒素酸化物分解除去方法について
詳細に説明する。BEST MODE FOR CARRYING OUT THE INVENTION The oxide catalyst material for decomposing nitrogen oxides and the method for decomposing and removing nitrogen oxides of the present invention will be described in detail below.
【００１７】本発明の窒素酸化物分解用酸化物触媒材料
は、β−Ｇａ2 Ｏ3 とＰｄＯの２つの結晶相から構成さ
れる酸化物であり、該結晶相は触媒活性の低下を防止す
るためには前記ＧａとＰｄの原子比ｎ（Ｇａ／Ｐｄ）が
１．０〜５．０の比率から成ることが必要であり、特に
前記触媒活性の点からは前記原子比ｎは２．０〜４．０
の範囲がより望ましく、とりわけ２．５〜３．５の範囲
が最も望ましい傾向を示す。The oxide catalyst material for decomposing nitrogen oxides of the present invention is an oxide composed of two crystal phases, β-Ga 2 O 3 and PdO, and this crystal phase prevents a decrease in catalytic activity. For this purpose, it is necessary that the atomic ratio n (Ga / Pd) of Ga and Pd is in the range of 1.0 to 5.0, and particularly from the viewpoint of the catalytic activity, the atomic ratio n is 2.0. ~ 4.0
Is more desirable, and especially the range of 2.5 to 3.5 shows the most desirable tendency.
【００１８】また、前記酸化物に添加するＡｌ2 Ｏ3 の
量が１０重量％より少なく、即ち前記酸化物の量が９０
重量％より多くなると、水蒸気による反応阻害効果が発
現せず、一方、Ａｌ2 Ｏ3 の量が６０重量％を越える
と、即ち前記酸化物の量が４０重量％未満になると、触
媒活性が低下することから、Ａｌ2 Ｏ3 の添加量は１０
〜６０重量％に限定され、特に耐水性の点からは２０〜
５０重量％がより好ましく、更に３０〜４０重量％が最
も望ましい傾向を示す。Further, the amount of Al 2 O 3 added to the oxide is less than 10% by weight, that is, the amount of the oxide is 90%.
When the amount is more than 60% by weight, the effect of inhibiting the reaction by water vapor is not exhibited. On the other hand, when the amount of Al 2 O 3 exceeds 60% by weight, that is, when the amount of the oxide is less than 40% by weight, the catalytic activity decreases. Therefore, the addition amount of Al 2 O 3 is 10
To 60% by weight, especially from the viewpoint of water resistance.
50% by weight is more preferable, and 30 to 40% by weight shows the most desirable tendency.
【００１９】従って、前記Ａｌ2 Ｏ3 を添加したβ−Ｇ
ａ2 Ｏ3 とＰｄＯの２つの結晶相で構成される酸化物か
ら成る窒素酸化物分解用酸化物を、ＮＯを含有した還元
ガスが存在しない水蒸気を含む排気ガスと接触させる
と、該排気ガス中のＮＯをＮ2とＯ2 に直接分解する優
れた特性を有することが認められる。Accordingly, β-G to which Al 2 O 3 is added
When a nitrogen oxide decomposing oxide composed of an oxide composed of two crystal phases of a 2 O 3 and PdO is brought into contact with an exhaust gas containing water vapor in which a reducing gas containing NO does not exist, the exhaust gas It is recognized that it has an excellent property of directly decomposing NO in the mixture into N 2 and O 2 .
【００２０】次に、本発明の窒素酸化物分解用酸化物触
媒材料の製造方法について、その一例を以下に詳述す
る。Next, an example of the method for producing the oxide catalyst material for decomposing nitrogen oxides of the present invention will be described in detail below.
【００２１】本発明の酸化物は、Ｇａ及びＰｄを含有す
る原料粉末又は水溶液を、ＧａとＰｄの原子比ｎ（Ｇａ
／Ｐｄ）が１．０〜５．０の範囲内となるように秤量
し、十分に撹袢混合した後、アンモニア水で中和して得
られた沈殿物を、酸化性雰囲気中、６００〜８００℃の
温度で５〜３０時間熱処理することにより、β−Ｇａ2
Ｏ3 とＰｄＯの２つの結晶相から構成される粉末を作製
した。The oxide of the present invention is obtained by mixing a raw material powder or an aqueous solution containing Ga and Pd with an atomic ratio n (Ga
/ Pd) is weighed so as to be in the range of 1.0 to 5.0, and after sufficiently stirring and mixing, the precipitate obtained by neutralization with aqueous ammonia is subjected to oxidation in an oxidizing atmosphere at 600 to By performing a heat treatment at a temperature of 800 ° C. for 5 to 30 hours, β-Ga 2
A powder composed of two crystal phases of O 3 and PdO was prepared.
【００２２】前記原料粉末としては、Ｇａの場合、例え
ば、Ｇａの酸化物や、熱処理により酸化物を生成するそ
の炭酸塩、硝酸塩、酢酸塩等を用いることができる。As the raw material powder, in the case of Ga, for example, an oxide of Ga, a carbonate, a nitrate, an acetate thereof, etc. which forms an oxide by heat treatment can be used.
【００２３】又、Ｐｄの場合には、特に制限されるもの
ではないが、通常、その硝酸塩類、硫酸塩類、炭酸塩
類、塩酸、臭酸塩類（ハロゲン化物）等の無機塩類、酢
酸塩等の有機塩類、水酸化物、酸化物等が挙げられ、そ
れらＰｄの塩を溶液にする際の溶媒にも特に制限はない
が、通常、水あるいはアルコール、カルボニル化合物等
の有機物を用いることができる。In the case of Pd, although not particularly limited, usually, inorganic salts such as nitrates, sulfates, carbonates, hydrochloric acid, bromates (halides), acetates and the like are used. Examples include organic salts, hydroxides, oxides, and the like. There is no particular limitation on the solvent used when the Pd salt is made into a solution, but usually water or an organic substance such as an alcohol or a carbonyl compound can be used.
【００２４】また前記酸化物は、前記以外に酸化物や他
の金属塩による固相反応法や、金属アルコキシド等のゾ
ル−ゲル法等によっても合成できるものであり、何等こ
れら製造方法に限定されるものではない。The oxide can be synthesized by a solid-phase reaction method using an oxide or another metal salt or a sol-gel method such as a metal alkoxide. Not something.
【００２５】更に、前記製造方法において、いずれも熱
処理は、該熱処理温度が６００℃より低いと結晶化が不
十分となり、逆に８００℃を越えるとＰｄＯが還元され
てしまうため、６００〜８００℃の温度で、酸化雰囲気
中、５〜３０時間行うが、特に低い温度で熱処理するこ
とが粉末の比表面積を高めるために有効であり、実用的
には、比表面積が３５ｍ2 ／ｇ以上となるように設定す
ることが望ましい。Further, in any of the above-mentioned manufacturing methods, in any of the heat treatments, if the heat treatment temperature is lower than 600 ° C., the crystallization becomes insufficient, and if the heat treatment temperature exceeds 800 ° C., PdO is reduced. The heat treatment is performed at a temperature of 5 to 30 hours in an oxidizing atmosphere. Heat treatment at a particularly low temperature is effective for increasing the specific surface area of the powder, and practically, the specific surface area is 35 m 2 / g or more. It is desirable to set as follows.
【００２６】尚、本発明において、前記触媒の熱処理時
間は特に限定されるものではなく、通常、２〜１０時間
で十分であり、又、該熱処理中に温度を段階的に変化さ
せても良い。In the present invention, the heat treatment time of the catalyst is not particularly limited, and usually 2 to 10 hours is sufficient, and the temperature may be changed stepwise during the heat treatment. .
【００２７】次に、前記β−Ｇａ2 Ｏ3 とＰｄＯの２結
晶相から成る酸化物にＡｌ2 Ｏ3 を所定量添加して窒素
酸化物分解用酸化物触媒材料を作製するが、その添加方
法としては、例えばＡｌ2 Ｏ3 とβ−Ｇａ2 Ｏ3 及びＰ
ｄＯから成る酸化物をボールミルや乳鉢で粉砕混合する
方法等が採用でき、均一に分散するようになれば混合方
法は何ら限定されるものではない。Next, a predetermined amount of Al 2 O 3 is added to the oxide composed of the two crystal phases of β-Ga 2 O 3 and PdO to prepare an oxide catalyst material for decomposing nitrogen oxides. As a method, for example, Al 2 O 3 and β-Ga 2 O 3 and P
A method of pulverizing and mixing an oxide composed of dO in a ball mill or a mortar can be adopted, and the mixing method is not particularly limited as long as the oxide is uniformly dispersed.
【００２８】かくして得られた触媒材料とＮＯを含む排
気ガスとを接触させることにより、還元剤を用いること
なくＮＯをＮ2 とＯ2 に直接分解することが可能とな
る。By bringing the catalyst material thus obtained into contact with exhaust gas containing NO, NO can be directly decomposed into N 2 and O 2 without using a reducing agent.
【００２９】[0029]
【実施例】次に、本発明を以下に詳述するようにして評
価した。Next, the present invention was evaluated as described in detail below.
【００３０】先ず、出発原料としてＧａ（ＮＯ3 ）2 ・
９Ｈ2 Ｏ及びＰｄ（ＮＯ3 ）2 の試薬を用い、ＧａとＰ
ｄの金属比が表１に示す組成となるように秤量し、これ
らの試薬を蒸留水中に溶解させ、撹拌しながらアンモニ
ア水で中和し、この時に生成した沈殿物を濾過、洗浄
し、凍結乾燥させた。First, Ga (NO 3 ) 2.
Using 9H 2 O and Pd (NO 3 ) 2 reagents, Ga and P
The metal ratio of d was weighed so as to have the composition shown in Table 1, these reagents were dissolved in distilled water, neutralized with aqueous ammonia while stirring, and the precipitate formed at this time was filtered, washed, and frozen. Let dry.
【００３１】かくして得られた乾燥粉末を大気中、７０
０℃の温度で３０時間、熱処理して比表面積が４０〜５
０ｍ2 ／ｇの酸化物粉末を得た。The dry powder thus obtained is placed in air at 70
Heat treatment at 0 ° C. for 30 hours for specific surface area of 40-5
An oxide powder of 0 m 2 / g was obtained.
【００３２】次に、得られたβ−Ｇａ2 Ｏ3 とＰｄＯか
ら成る酸化物粉末に対して、比表面積が７０ｍ2 ／ｇ以
上のＡｌ2 Ｏ3 粉末を表１に示す割合で添加混合した
後、該混合粉末を金型プレスにより成形し、更に冷間静
水圧成形法により圧縮してから該成形物を解砕して篩別
し、５００μｍを越え、７００μｍ以下に整粒して評価
試料を調製した。Next, Al 2 O 3 powder having a specific surface area of 70 m 2 / g or more was added to the obtained oxide powder composed of β-Ga 2 O 3 and PdO at a ratio shown in Table 1 and mixed. Thereafter, the mixed powder is molded by a mold press, and further compressed by a cold isostatic pressing method, and then the molded product is crushed and sieved. Was prepared.
【００３３】次いで、模擬排気ガスとしてＮＯが３００
０ｐｐｍ、残部がＨｅから成る反応ガスを、該反応ガス
と触媒材料が接触する条件として、空間速度（ＳＶ）を
９０００／ｈｒ．に設定しで前記評価用材料を充填した
触媒層に流し、６００〜８００℃の温度範囲で、水蒸気
を含ませない場合と１０％の水蒸気を共存させた場合で
それぞれ触媒層を通過して生成したＮ2 ガスをガスクロ
マトグラフで測定し、触媒活性を評価した。Next, NO as a simulated exhaust gas was 300
A space gas (SV) of 9000 / hr. Was used as a condition that a reaction gas consisting of 0 ppm and the balance of He was in contact with the catalyst material. Is passed through the catalyst layer filled with the above-mentioned evaluation material at a temperature of 600 ° C. to 800 ° C., and is generated by passing through the catalyst layer in a case where water vapor is not included and in a case where 10% water vapor coexists. The N 2 gas measured was measured by gas chromatography to evaluate the catalytic activity.
【００３４】本実施例では、触媒のＮＯ分解能は前記触
媒層出口側のＮ2 濃度（ｐｐｍ）の２倍の値を触媒層入
口側のＮＯ濃度（ｐｐｍ）で除した百分率を、ＮＯ除去
率（％）とし、各温度でのＮＯ除去率を求めた。In the present embodiment, the NO resolution of the catalyst is expressed by a percentage obtained by dividing twice the value of N 2 concentration (ppm) at the catalyst layer outlet side by the NO concentration (ppm) at the catalyst layer inlet side. (%), And the NO removal rate at each temperature was determined.
【００３５】以上の結果から、６００〜８００℃の温度
範囲で、水蒸気が存在しない条件下及び１０％の水蒸気
が存在する条件下での評価に基づき、本発明による効果
を明確にするために、水蒸気が存在する条件下でのＮＯ
分解活性の最低値が２０％未満のものは不良、最低値が
２０％以上で最高値が５０〜５２％のものを可、５３〜
６６％のものを良、６７％以上のものを優と判定した。From the above results, in order to clarify the effect according to the present invention, based on the evaluation under the condition where steam does not exist and the condition where 10% steam exists in the temperature range of 600 to 800 ° C., NO in the presence of water vapor
If the minimum value of the decomposition activity is less than 20%, it is defective. If the minimum value is 20% or more and the maximum value is 50 to 52%, acceptable.
66% was determined to be good, and 67% or more was determined to be excellent.
【００３６】また、本発明にかかる評価用の触媒材料
は、Ｘ線回折測定（ＸＲＤ）により結晶相を同定し、い
ずれもβ−Ｇａ2 Ｏ3 とＰｄＯの２つの結晶相の存在を
確認した。The crystal phase of the catalyst material for evaluation according to the present invention was identified by X-ray diffraction measurement (XRD), and the presence of two crystal phases, β-Ga 2 O 3 and PdO, was confirmed in each case. .
【００３７】尚、β−Ｇａ2 Ｏ3 とＰｄＯの２つの結晶
相から成る酸化物にＡｌ2 Ｏ3 を添加しないもの、及び
従来のＰｄにＡｕとＡｇを混合してＡｌ2 Ｏ3 に担持し
たものを比較例とした。An oxide composed of two crystal phases of β-Ga 2 O 3 and PdO without adding Al 2 O 3 , or a conventional Pd mixed with Au and Ag and supported on Al 2 O 3 This was used as a comparative example.
【００３８】[0038]
【表１】 [Table 1]
【００３９】表１から明らかなように、比較例であるＡ
ｌ2 Ｏ3 を添加しない試料番号９では水蒸気存在下では
６００℃以上でのＮＯ分解活性が低く、従来のＰｄにＡ
ｕとＡｇを混合してＡｌ2 Ｏ3 に担持した試料番号１９
では、水蒸気を含まない状態でもＮＯ除去率が６００℃
でも１８％と低く、最高値でも６２％であり、実用上、
満足すべきものではない。As is clear from Table 1, the comparative example A
In Sample No. 9 to which l 2 O 3 was not added, the NO decomposition activity at 600 ° C. or higher was low in the presence of water vapor,
Sample No. 19 in which u and Ag were mixed and supported on Al 2 O 3
In this case, the NO removal rate is 600 ° C even without water vapor.
However, it is as low as 18%, and the highest value is 62%.
Not satisfactory.
【００４０】それに対して、本発明ではいずれも、６０
０℃以上８００℃という高温の雰囲気下、水蒸気が共存
していても十分なＮＯ分解活性を示していることが確認
できた。On the other hand, in the present invention, in each case, 60
It was confirmed that under a high temperature atmosphere of 0 ° C. or more and 800 ° C., sufficient NO decomposition activity was exhibited even in the presence of water vapor.
【００４１】[0041]
【発明の効果】以上、詳述したように本発明の窒素酸化
物分解用酸化物触媒材料並びに窒素酸化物分解除去方法
によれば、該酸化物触媒材料は、ＧａとＰｄの原子比ｎ
が１．０〜５．０の比率から成るβ−Ｇａ2 Ｏ3 とＰｄ
Ｏの２つの結晶相で構成される酸化物と、１０〜６０重
量％のＡｌ2 Ｏ3 から成る窒素酸化物を直接分解する触
媒材料であり、該酸化物触媒材料にＮＯを含む還元ガス
が存在しない酸化性排気ガスを接触させることにより、
６００〜８００℃の高温の温度範囲でもＮＯをＮ2 とＯ
2 に直接分解され、水蒸気存在下でも十分なＮＯ分解活
性能力を有していることから、工場や発電所等の固定発
生源は勿論、自動車等の移動発生源からの排気ガス中に
含まれるＮＯを有効に分解除去することができる。As described above in detail, according to the oxide catalyst material for decomposing nitrogen oxide and the method for decomposing and removing nitrogen oxide of the present invention, the oxide catalyst material has an atomic ratio of Ga to Pd of n.
Β-Ga 2 O 3 and Pd having a ratio of 1.0 to 5.0
An oxide composed of two crystal phases of O and a catalyst material for directly decomposing nitrogen oxides composed of 10 to 60% by weight of Al 2 O 3 , wherein the oxide catalyst material contains a reducing gas containing NO. By contacting non-existing oxidizing exhaust gas,
NO and N 2 and O even in a high temperature range of 600 to 800 ° C.
It is directly decomposed into 2 and has sufficient NO decomposition activity even in the presence of water vapor, so it is contained in exhaust gas from mobile sources such as automobiles as well as fixed sources such as factories and power plants. NO can be effectively decomposed and removed.
【００４２】その結果、省エネルギー、省資源及び地球
温暖化防止を目標として開発される今後のリーンバーン
エンジン等の各種内燃機関の排気ガスをはじめ、ＮＯを
含有する各種有害物質の浄化に極めて有用なものとな
る。As a result, it is extremely useful for purifying various harmful substances containing NO, including exhaust gas from various internal combustion engines such as lean burn engines which will be developed with the aim of saving energy and resources and preventing global warming. It will be.
Claims (2)
原子比ｎ（Ｇａ／Ｐｄ）が１．０〜５．０であるβ−Ｇ
ａ2 Ｏ3 とＰｄＯの結晶相から成る酸化物が４０〜９０
重量％と、酸化アルミニウム（Ａｌ2 Ｏ3 ）が１０〜６
０重量％とから成ることを特徴とする窒素酸化物分解用
酸化物触媒材料。1. A β-G having an atomic ratio n (Ga / Pd) of gallium (Ga) to palladium (Pd) of 1.0 to 5.0.
oxide comprising a crystal phase of a 2 O 3 and PdO 40 to 90
% By weight and aluminum oxide (Al 2 O 3 )
An oxide catalyst material for decomposing nitrogen oxides, comprising 0% by weight.
原子比ｎ（Ｇａ／Ｐｄ）が１．０〜５．０であるβ−Ｇ
ａ2 Ｏ3 とＰｄＯの結晶相から成る酸化物が４０〜９０
重量％と、酸化アルミニウム（Ａｌ2 Ｏ3 ）が１０〜６
０重量％とから成る窒素酸化物分解用酸化物触媒材料
を、窒素酸化物を含む排気ガスと接触させ、該窒素酸化
物を直接、窒素と酸素に分解することを特徴とする窒素
酸化物分解除去方法。2. A β-G having an atomic ratio n (Ga / Pd) of gallium (Ga) to palladium (Pd) of 1.0 to 5.0.
oxide comprising a crystal phase of a 2 O 3 and PdO 40 to 90
% By weight and aluminum oxide (Al 2 O 3 )
Nitrogen oxide decomposition, characterized in that an oxide catalyst material for nitrogen oxide decomposition consisting of 0% by weight is brought into contact with an exhaust gas containing nitrogen oxide, and the nitrogen oxide is directly decomposed into nitrogen and oxygen. Removal method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9324966A JPH11156195A (en) | 1997-11-26 | 1997-11-26 | Oxide catalytic material for nitrogen oxide decomposition and method for decomposing and removing nitrogen oxide |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9324966A JPH11156195A (en) | 1997-11-26 | 1997-11-26 | Oxide catalytic material for nitrogen oxide decomposition and method for decomposing and removing nitrogen oxide |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH11156195A true JPH11156195A (en) | 1999-06-15 |
Family
ID=18171622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9324966A Pending JPH11156195A (en) | 1997-11-26 | 1997-11-26 | Oxide catalytic material for nitrogen oxide decomposition and method for decomposing and removing nitrogen oxide |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH11156195A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006041170A1 (en) * | 2004-10-15 | 2006-04-20 | Ngk Insulators, Ltd. | Method for producing porous structure |
-
1997
- 1997-11-26 JP JP9324966A patent/JPH11156195A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006041170A1 (en) * | 2004-10-15 | 2006-04-20 | Ngk Insulators, Ltd. | Method for producing porous structure |
| JPWO2006041170A1 (en) * | 2004-10-15 | 2008-05-22 | 日本碍子株式会社 | Method for producing porous structure |
| JP5098333B2 (en) * | 2004-10-15 | 2012-12-12 | 日本碍子株式会社 | Method for producing porous structure |
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