JPH09239276A - Exhaust gas cleaning catalyst - Google Patents

Exhaust gas cleaning catalyst

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Publication number
JPH09239276A
JPH09239276A JP4739196A JP4739196A JPH09239276A JP H09239276 A JPH09239276 A JP H09239276A JP 4739196 A JP4739196 A JP 4739196A JP 4739196 A JP4739196 A JP 4739196A JP H09239276 A JPH09239276 A JP H09239276A
Authority
JP
Japan
Prior art keywords
zeolite
exhaust gas
catalyst
powder
water vapor
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
JP4739196A
Other languages
Japanese (ja)
Inventor
Makoto Misonoo
誠 御園生
Yoshifumi Hirao
佳史 平尾
Shuji Yokoyama
周史 横山
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.)
Toyota Motor Corp
Original Assignee
Toyota Motor Corp
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 Toyota Motor Corp filed Critical Toyota Motor Corp
Priority to JP4739196A priority Critical patent/JPH09239276A/en
Publication of JPH09239276A publication Critical patent/JPH09239276A/en
Pending legal-status Critical Current

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Abstract

PROBLEM TO BE SOLVED: To obtain a catalyst capable of selectively reducing NOx for cleaning to N2 at a high conversion rate even in the presence of a vapor by mixing a zeolite powder bearing tin with a manganese oxide powder. SOLUTION: An exhaust gas cleaning catalyst which is useful when a reducing agent is injected into an exhaust gas to clean NOx by reduction, is prepared by mixing a zeolite powder bearing Sn with Mn2 O3 powder. In this case, zeolite is crystalline aluminosilicate expressed by the formula xM2 /n.Al2 O3 .ySiO2 as is well-known, and should preferably have SiO2 /Al2 O3 molar ratio of 10-200. In addition, the surface pore of the zeolite should be small enough to not allow the penetration of a polycyclic aromatic hydrocarbon compound, measuring 10Å or less. Thus, coke is hardly generated, and the structure breakdown and the catalytic activity deterioration by the blocking of pores are prevented from occurring.

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】本発明は自動車などから排出
される排ガスを浄化する排ガス浄化用触媒に関し、詳し
くは排ガス中に炭化水素などの還元剤を注入してNOx
を還元浄化する場合に有用な排ガス浄化用触媒に関す
る。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst for purifying exhaust gas emitted from an automobile or the like, and more specifically to NO x by injecting a reducing agent such as hydrocarbon into the exhaust gas.
The present invention relates to an exhaust gas-purifying catalyst useful for reducing and purifying exhaust gas.

【0002】[0002]

【従来の技術】自動車用内燃機関の排気ガス浄化用触媒
としては、従来よりモノリス触媒、ペレット触媒が広く
用いられている。これらの排気ガス浄化用触媒は、活性
アルミナなどの触媒担持層に触媒金属を担持した構成で
ある。ここで触媒金属としては、Pt、Pd、Rhなど
が一種または二種以上用いられている。そして排気ガス
中のHC、COを酸化し、NOx を還元して、この3成
分を同時に浄化しているので、三元触媒と称されてい
る。
2. Description of the Related Art Monolith catalysts and pellet catalysts have been widely used as exhaust gas purifying catalysts for automobile internal combustion engines. These exhaust gas purifying catalysts have a structure in which a catalyst metal is supported on a catalyst supporting layer such as activated alumina. As the catalyst metal, Pt, Pd, Rh, etc. are used alone or in combination of two or more. It is called a three-way catalyst because it oxidizes HC and CO in the exhaust gas and reduces NO x to purify these three components at the same time.

【0003】ところで低燃費化や排出炭酸ガス低減の目
的から、自動車の内燃機関では燃料を希薄燃焼させるこ
とが必要となっている。この場合には排気ガス中の酸素
濃度が理論値(排気ガス中の未燃焼成分を完全に酸化す
るのに必要な最小酸素濃度)より大きいリーン側とな
り、上記三元触媒では排気ガス中のNOx を還元除去す
ることができないという欠点がある。またディーゼルエ
ンジンにおいては、多量の空気を用いて燃焼させている
ことから排気ガス中の酸素濃度が大きくなり、同様にN
x の浄化が困難である。
By the way, for the purpose of reducing fuel consumption and reducing carbon dioxide gas emission, it is necessary to burn fuel lean in an internal combustion engine of an automobile. In this case, the oxygen concentration in the exhaust gas becomes leaner than the theoretical value (the minimum oxygen concentration required to completely oxidize the unburned components in the exhaust gas), and the three-way catalyst causes NO in the exhaust gas to rise. The drawback is that x cannot be reduced and removed. Further, in a diesel engine, since a large amount of air is used for combustion, the oxygen concentration in the exhaust gas becomes large, and similarly,
Purification of O x is difficult.

【0004】そこで近年、ゼオライトを利用したゼオラ
イト系触媒が注目され、本願出願人らはNOx の浄化性
能に優れたゼオライト系触媒をいくつか提案している。
例えば特開平1−130735号公報では、ゼオライト
に遷移金属をイオン交換担持した排気ガス浄化用触媒を
開示している。この触媒によれば、ゼオライトの細孔中
に遷移金属の活性サイトが存在し、そこにNOx が吸着
して反応を起こし浄化される。なお、遷移金属としては
銅(Cu)が好ましい。
Therefore, in recent years, zeolite-based catalysts utilizing zeolite have been drawing attention, and the applicants of the present application have proposed some zeolite-based catalysts having excellent NO x purification performance.
For example, JP-A-1-130735 discloses an exhaust gas purifying catalyst in which a transition metal is ion-exchanged and supported on zeolite. According to this catalyst, an active site of a transition metal exists in the pores of zeolite, and NO x is adsorbed to the active site to cause a reaction and purification. Copper (Cu) is preferable as the transition metal.

【0005】また、特開平3−89942号公報では、
ゼオライトに希土類元素と銅(Cu)を担持してなる排
気ガス浄化用触媒を開示している。特開平3−2021
57号公報では、ゼオライトにアルカリ土類金属と、希
土類元素と、銅(Cu)を担持してなる排気ガス浄化用
触媒を開示している。さらに特開平2−149317号
公報には、水素型のゼオライトにCu,Mn,Fe,N
i,Co,Rh,Pd,Pt,V,及びMoから選ばれ
る元素を担持したゼオライト系触媒が開示されている。
Further, in Japanese Patent Application Laid-Open No. 3-89942,
Disclosed is an exhaust gas purifying catalyst in which a rare earth element and copper (Cu) are supported on zeolite. JP-A-3-2021
Japanese Patent Publication 57 discloses an exhaust gas purifying catalyst in which an alkaline earth metal, a rare earth element, and copper (Cu) are supported on zeolite. Further, in Japanese Patent Laid-Open No. 2-149317, Cu, Mn, Fe, N is added to hydrogen type zeolite.
A zeolite-based catalyst carrying an element selected from i, Co, Rh, Pd, Pt, V, and Mo is disclosed.

【0006】また、酸素過剰雰囲気の排ガスに軽油やプ
ロパンなどの還元剤を注入し、この還元剤によりNOx
を選択的に窒素(N2 )に還元して浄化する方法が種々
検討されている。例えば特公平5−16887号公報に
は、プロトン型ゼオライト、アルカリ金属型ゼオライト
又は酸性を有する金属酸化物から選ばれる触媒を用い、
炭化水素の存在下で酸素過剰雰囲気の排ガス中のNOx
を浄化する方法が記載されている。
Further, a reducing agent such as light oil or propane is injected into the exhaust gas in an oxygen excess atmosphere, and this reducing agent causes NO x.
Various methods for purifying nitrogen by selectively reducing it to nitrogen (N 2 ) have been studied. For example, Japanese Examined Patent Publication No. 5-16887 uses a catalyst selected from a proton type zeolite, an alkali metal type zeolite or an acidic metal oxide,
NO x in exhaust gas in an oxygen excess atmosphere in the presence of hydrocarbons
A method of purifying is described.

【0007】[0007]

【発明が解決しようとする課題】ところが還元剤を用い
てNOx を選択的に還元浄化する触媒であっても、NO
x のN2 への転化率は十分とはいえなかった。近年の研
究によれば、このように転化率の向上を阻害する大きな
要因の一つに、水蒸気による反応阻害があることがわか
っている。つまり水蒸気の存在しない雰囲気であればN
x を高い転化率でN2 へ選択的に還元浄化できるのに
対し、水蒸気の存在する雰囲気では転化率が大きく低下
するという現象があることがわかっている。
However, using a reducing agent
NOxEven if the catalyst selectively reduces and purifies NO
xNTwoThe conversion rate to was not sufficient. Recent research
According to research, it is
We understand that one of the factors is the inhibition of the reaction by water vapor.
ing. In other words, if the atmosphere does not contain water vapor, N
OxWith a high conversion rateTwoEven though it can be selectively reduced and purified
On the other hand, the conversion rate decreases significantly in the atmosphere containing water vapor.
It is known that there is a phenomenon of doing.

【0008】そして自動車からの排ガス中には多くの水
蒸気が含まれているから、水蒸気の存在下でもNOx
効率良く還元浄化できる触媒の開発が望まれている。本
発明はこのような事情に鑑みてなされたものであり、水
蒸気の存在下においても高い転化率でNOx をN2 に選
択的に還元浄化できる触媒を提供することを目的とす
る。
Since a large amount of water vapor is contained in exhaust gas from automobiles, it is desired to develop a catalyst that can efficiently reduce and purify NO x even in the presence of water vapor. The present invention has been made in view of such circumstances, and an object thereof is to provide a catalyst capable of selectively reducing and purifying NO x to N 2 at a high conversion rate even in the presence of water vapor.

【0009】[0009]

【課題を解決するための手段】上記課題を解決する本発
明の排ガス浄化用触媒の特徴は、錫(Sn)を担持した
ゼオライト粉末と、酸化マンガン(Mn2 3 )粉末と
を混合してなることにある。
The characteristics of the exhaust gas purifying catalyst of the present invention for solving the above-mentioned problems are that a zeolite powder carrying tin (Sn) and manganese oxide (Mn 2 O 3 ) powder are mixed. Is to be.

【0010】[0010]

【発明の実施の形態】ゼオライトは周知のように一般式
xM2 /n・Al2 3 ・ySiO2 で表される結晶性
アルミノケイ酸で、M(n価の金属)、x、yの違いに
よって、結晶構造中の細孔径が異なり、多くの種類のも
のが市販されている。またSi4+の一部をAl3+で置換
しているため正電荷が不足し、その不足を補うためNa
+ 、K + などの陽イオンを結晶内に保持する性質がある
ため、高い陽イオン交換能をもっている。
BEST MODE FOR CARRYING OUT THE INVENTION As is well known, zeolite has the general formula
xMTwo/ N ・ AlTwoOThree・ YSiOTwoCrystallinity
With alumino-silicic acid, the difference between M (n-valent metal), x and y
Therefore, the pore size in the crystal structure is different, and many types
Are commercially available. Also Si4+Part of Al3+Replace with
Therefore, there is a shortage of positive charge, and to compensate for the shortage, Na
+, K +Has the property of holding cations such as
Therefore, it has a high cation exchange capacity.

【0011】本発明で用いるゼオライトのSiO2 /A
2 3 のモル比は、10〜200が望ましい。10よ
り少ないと500℃以上の高温下での熱安定性が悪くな
る。また200より大きくなるとイオン交換点が減少す
るため、イオン交換の減少すなわち触媒活性が低下する
ようになる。熱劣化はアルミニウム周辺の構造変化が主
因と推定されるので、特に高温での耐久性を確保したい
場合にはモル比が20以上のゼオライトを用いることが
好ましい。特にモル比が20〜200のZSM−5を用
いることが推奨される。
The SiO 2 / A of the zeolite used in the present invention
The molar ratio of l 2 O 3 is preferably 10 to 200. If it is less than 10, the thermal stability at a high temperature of 500 ° C. or higher deteriorates. On the other hand, when it is more than 200, the ion exchange point is decreased, so that the ion exchange is decreased, that is, the catalytic activity is decreased. Since it is estimated that the thermal deterioration is mainly due to the structural change around aluminum, it is preferable to use zeolite with a molar ratio of 20 or more, especially when it is desired to ensure durability at high temperatures. In particular, it is recommended to use ZSM-5 with a molar ratio of 20-200.

【0012】水素型のゼオライトでは、ゼオライトから
の脱アルミニウムが容易に起こるため耐久性が低下する
ので、Na型を用いるのが好ましい。またゼオライト表
面の細孔は、10オングストローム以下と小さいことが
望ましい。細孔を多環芳香族炭化水素化合物の入り込め
ない大きさとすることによりコークが生成しにくくな
り、細孔閉塞による構造破壊や触媒活性低下も防止でき
る。
[0012] In the hydrogen type zeolite, dealumination from the zeolite easily occurs and the durability is lowered. Therefore, it is preferable to use the Na type. Further, it is desirable that the pores on the surface of zeolite are as small as 10 angstroms or less. By making the pores of a size that does not allow the polycyclic aromatic hydrocarbon compound to enter, it becomes difficult for coke to form, and it is also possible to prevent structural destruction and catalyst activity deterioration due to pore clogging.

【0013】上記ゼオライトに担持されているSnの担
持量は、ゼオライト中のアルミニウム元素に対してモル
比で0.1〜3の範囲とすることが望ましい。Snの担
持量がこれより少ないと反応速度が遅くなり、これより
多く担持するとプロペンなどの炭化水素のみ酸化され窒
素添加率が低下する場合がある。なお、ゼオライトへの
Snの担持法は、従来のゼオライト系触媒と同様に吸着
法や含浸法によるイオン交換担持法を利用できる。
The amount of Sn supported on the zeolite is preferably in the range of 0.1 to 3 in molar ratio with respect to the aluminum element in the zeolite. If the supported amount of Sn is less than this, the reaction rate becomes slow, and if the supported amount of Sn is more than this, only hydrocarbons such as propene may be oxidized and the nitrogen addition rate may decrease. As a method for supporting Sn on zeolite, an ion exchange supporting method such as an adsorption method or an impregnation method can be used as in the case of a conventional zeolite-based catalyst.

【0014】このSn担持ゼオライト粉末の粒径は、平
均粒径として1μm以下であることが望ましい。平均粒
径がこれより大きくなると反応速度が遅くなり、NOx
浄化率が低下する。Sn担持ゼオライト粉末と酸化マン
ガン粉末との混合比率は、重量比でSn担持ゼオライト
/Mn2 3 =0.1〜10の範囲が望ましい。この比
率がこれより小さくなると高温における窒素添加率が低
下し、これより大きくなると低温における窒素添加率が
減少する。
The Sn-supported zeolite powder preferably has an average particle size of 1 μm or less. If the average particle size is larger than this, the reaction rate becomes slower, and NO x
Purification rate decreases. The mixing ratio of the Sn-supporting zeolite powder and the manganese oxide powder is preferably in the range of Sn-supporting zeolite / Mn 2 O 3 = 0.1 to 10 by weight ratio. If this ratio is smaller than this, the nitrogen addition rate at high temperatures is reduced, and if it is larger than this, the nitrogen addition rate at low temperatures is reduced.

【0015】また酸化マンガン粉末の粒径は、平均粒径
として1μm以下であることが望ましい。平均粒径がこ
れより大きくなるとNOからNO2 への酸化が減少する
ことにより、NOx 浄化性能が低下する。本発明の排ガ
ス浄化用触媒は、Sn担持ゼオライト粉末と酸化マンガ
ンとの混合粉末をモノリス担体基材やメタル担体基材に
コートして用いることができる。また混合粉末自体をペ
レット形状やハニカム形状に成形して用いることもでき
る。
The manganese oxide powder preferably has an average particle size of 1 μm or less. If the average particle size is larger than this, the oxidation of NO to NO 2 is reduced, and the NO x purification performance is reduced. The exhaust gas purifying catalyst of the present invention can be used by coating a mixed powder of Sn-supported zeolite powder and manganese oxide on a monolith carrier base material or a metal carrier base material. Further, the mixed powder itself can be molded into a pellet shape or a honeycomb shape and used.

【0016】本発明の排ガス浄化用触媒では、酸化マン
ガン粉末によりNOのNO2 への酸化反応が促進され
る。そして形成されたNO2 及び予め排ガス中に含まれ
ているNO2 2 、Sn担持ゼオライトにより炭化水素な
どの還元剤と反応して還元浄化される。そして本発明の
排ガス浄化用触媒においては、水蒸気の存在は上記反応
を阻害しないばかりか、むしろ反応を促進するように作
用し、きわめて高いNOx 浄化性能が得られる。この理
由はまだ解明されていないが、水蒸気が存在しても酸化
マンガン粉末によるNOの酸化反応活性が低下しないと
いう作用も一つの要因であろうと推察される。
In the exhaust gas purifying catalyst of the present invention, the oxidation reaction of NO to NO 2 is promoted by the manganese oxide powder. And is reduced and purified by NO2 2, Sn supported zeolite contained in NO 2 and advance in the flue gas formed by reaction with a reducing agent such as a hydrocarbon. In the exhaust gas purifying catalyst of the present invention, the presence of water vapor not only hinders the above reaction, but rather acts to promote the reaction, so that an extremely high NO x purification performance is obtained. The reason for this has not been clarified yet, but it is presumed that the effect that the oxidation reaction activity of NO by the manganese oxide powder does not decrease even if water vapor is present may be one factor.

【0017】[0017]

【実施例】以下、実施例及び比較例により本発明を具体
的に説明する。 (実施例1)Na型ゼオライト粉末(「Na−ZSM−
5」,モル比SiO2 /Al2 3=23.8)を蒸留
水に浸漬し、窒素ガスをバブリングしながら一昼夜静置
する。これによりゼオライト中の酸素を除去する。次い
で窒素気流中でゼオライトを取り出し、窒素ガスをバブ
リングしながらSnCl2 の1.3重量%水溶液中に浸
漬して一昼夜静置する。これを24時間乾燥し、Snが
イオン交換担持されたSn担持ゼオライト粉末を得た。
このSn担持ゼオライト粉末は平均粒径が1μmであ
り、元素分析の結果SnのAlに対するモル比(Sn/
Al)は0.5であってイオン交換レベルは100%で
ある。
EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. (Example 1) Na-type zeolite powder ("Na-ZSM-
5 ", molar ratio SiO 2 / Al 2 O 3 = 23.8) is immersed in distilled water, and the mixture is allowed to stand still overnight while bubbling nitrogen gas. This removes oxygen in the zeolite. Next, the zeolite is taken out in a nitrogen stream, and while bubbling nitrogen gas, it is immersed in a 1.3 wt% SnCl 2 aqueous solution and left standing overnight. This was dried for 24 hours to obtain Sn-supporting zeolite powder in which Sn was ion-exchanged and supported.
This Sn-supported zeolite powder has an average particle size of 1 μm, and as a result of elemental analysis, the molar ratio of Sn to Al (Sn /
Al) is 0.5 and the ion exchange level is 100%.

【0018】次に上記Sn担持ゼオライト粉末と、平均
粒径0.3μmの酸化マンガン(Mn2 3 )粉末と
を、重量比で1対1の比率で物理的に混合し、公知の方
法でペレット化して実施例1の触媒を調製した。 (試験)固定床流通式の触媒反応装置を用い、表1に示
す組成のモデルガスをそれぞれ流通させて、水蒸気を含
む場合と含まない場合のNOのN2 への転換率をそれぞ
れ測定した。得られた結果をグラフ化して図1に示す。
なお、測定に当たって、用いた触媒量は0.5gであ
り、空間速度SVは1万h-1である。そして触媒をヘリ
ウム中500℃で2時間保持し、その後段階的に降温さ
せながら各温度での転化率を測定した。
Next, the Sn-supported zeolite powder and the manganese oxide (Mn 2 O 3 ) powder having an average particle size of 0.3 μm are physically mixed at a weight ratio of 1: 1 and the mixture is prepared by a known method. The catalyst of Example 1 was prepared by pelletizing. (Test) Using a fixed bed flow type catalytic reactor, the model gases having the compositions shown in Table 1 were passed through, and the conversion rates of NO to N 2 with and without water vapor were measured. The obtained results are graphed and shown in FIG.
In the measurement, the amount of catalyst used was 0.5 g and the space velocity SV was 10,000 h-1. Then, the catalyst was held in helium at 500 ° C. for 2 hours, and then the conversion rate at each temperature was measured while gradually lowering the temperature.

【0019】[0019]

【表1】 (比較例1)実施例1で調製されたSn担持ゼオライト
粉末のみを用いてペレット化し、比較例1の触媒を調製
した。そして実施例1と同様にして試験を行い、その結
果を図1に示す。
[Table 1] Comparative Example 1 The catalyst of Comparative Example 1 was prepared by pelletizing only the Sn-supported zeolite powder prepared in Example 1. A test was conducted in the same manner as in Example 1, and the results are shown in FIG.

【0020】(比較例2)実施例1で用いた酸化マンガ
ン粉末のみを用いてペレット化し、比較例2の触媒を調
製した。そして実施例1と同様にして試験を行い、その
結果を図1に示す。 (評価)図1より、酸化マンガン単独の比較例2では、
水蒸気の有無に関わらずN2 はほとんど生成されずNO
の還元浄化は行われない。また比較例1のSn担持ゼオ
ライト単独では、水蒸気が存在する方が転化率が高いも
のの、転化率は高々20%程度である。しかしSn担持
ゼオライトと酸化マンガンを併用した実施例1では、水
蒸気が存在する場合に最大約80%のきわめて高い転化
率を示し、しかも水蒸気が存在する方が高い転化率を示
している。
Comparative Example 2 The catalyst of Comparative Example 2 was prepared by pelletizing only the manganese oxide powder used in Example 1. A test was conducted in the same manner as in Example 1, and the results are shown in FIG. (Evaluation) From FIG. 1, in Comparative Example 2 of manganese oxide alone,
Almost no N 2 is produced regardless of the presence or absence of water vapor, and NO
No reduction purification is performed. Further, in the case of the Sn-supported zeolite alone of Comparative Example 1, the conversion rate is higher in the presence of water vapor, but the conversion rate is at most about 20%. However, in Example 1 in which Sn-supported zeolite and manganese oxide were used together, a very high conversion rate of up to about 80% was shown in the presence of water vapor, and a higher conversion rate was obtained in the presence of water vapor.

【0021】すなわち実施例1の触媒は、水蒸気による
反応阻害がないばかりか、水蒸気の存在により一層反応
が促進されてNOの還元浄化性能にきわめて優れている
ことが明らかであり、Sn担持ゼオライトと酸化マンガ
ンの混合による相乗効果が得られていることが明らかで
ある。なお上記試験においては、モデルガス中のプロペ
ン(C3 6 )はNOの還元反応に消費されるほか、モ
デルガス中の酸素(O2 )により酸化される場合もあ
る。そこでプロペンのCOx への転化率を測定し、その
うちNOの還元によって生成したCOx の割合を算出す
ることにより、プロペンの反応の選択性を知ることがで
きる。
That is, it is clear that the catalyst of Example 1 has not only the inhibition of the reaction by water vapor but also the reaction is further promoted by the presence of water vapor and is extremely excellent in the reduction and purification performance of NO. It is clear that the synergistic effect is obtained by mixing manganese oxide. In the above test, propene (C 3 H 6 ) in the model gas is consumed by the NO reduction reaction and may be oxidized by oxygen (O 2 ) in the model gas. Therefore, the selectivity of the reaction of propene can be known by measuring the conversion rate of propene to CO x and calculating the proportion of CO x produced by the reduction of NO.

【0022】そこで実施例1の触媒について、モデルガ
ス中の水蒸気の分圧を変化させた場合のNOのN2 への
転化率と、プロペンのCOx への転化率を測定し、NO
の還元によって生成したCOx の割合(選択性)を算出
して図2に示す。入りガス温度は350℃、水蒸気分圧
は0〜6%の間で4水準選び、他の条件は上記試験と同
様である。また選択性は次式により算出した。 選択性(%)=100×(NOからプロペンの酸化に消
費された酸素原子数)/(プロペンの酸化に消費された
全酸素原子数) 図2より、NOのN2 への転化率は約1%程度の水蒸気
の存在により急激に増大し、その後は水蒸気分圧の上昇
により徐々に増大している。一方プロペンのCOx への
転化率は、水蒸気がなくとも約90%と高いが、水蒸気
分圧の上昇により緩やかに増大している。しかし選択性
は、約1%程度の水蒸気の存在により急激に増大した後
は水蒸気分圧の上昇により徐々に増大し、NOのN2
の転化率と同様の挙動を示している。つまり水蒸気の存
在によりプロペンとNOとの反応が促進されていること
がわかり、水蒸気の存在によるNOのN2 への転化率の
向上はプロペンとNOとの反応に起因していることが裏
付けられている。
Therefore, for the catalyst of Example 1, the conversion rate of NO to N 2 and the conversion rate of propene to CO x when the partial pressure of water vapor in the model gas was changed were measured.
The ratio (selectivity) of CO x produced by the reduction of is calculated and shown in FIG. The inlet gas temperature is 350 ° C., and the steam partial pressure is 0 to 6%. Four levels are selected, and the other conditions are the same as in the above test. The selectivity was calculated by the following formula. Selectivity (%) = 100 × (number of oxygen atoms consumed for oxidation of propene to NO) / (total number of oxygen atoms consumed for oxidation of propene) From FIG. 2 , the conversion rate of NO to N 2 is about It rapidly increases due to the presence of about 1% water vapor, and then gradually increases due to an increase in the water vapor partial pressure. On the other hand, the conversion rate of propene to CO x is as high as about 90% even without steam, but it gradually increases due to an increase in steam partial pressure. However, the selectivity shows a behavior similar to that of the conversion rate of NO into N 2 after rapidly increasing in the presence of about 1% of steam and then gradually increasing due to the increase of the partial pressure of steam. In other words, it was found that the reaction between propene and NO was promoted by the presence of water vapor, which proves that the improvement in the conversion rate of NO to N 2 due to the presence of water vapor is due to the reaction between propene and NO. ing.

【0023】なお、水蒸気の有無を交互に繰り返して試
験しても、直前の状態に影響されることなく水蒸気の有
無に応じてほぼ一定の転化率を示すことから、水蒸気が
触媒を化学変化させるとは考えにくく、水蒸気は直接的
にNOのN2 への転化反応に関与していると推察され
る。 (比較例3)SnCl2 水溶液の代わりにCe化合物水
溶液を用いたこと以外は実施例1と同様にして、Snの
代わりにCeを担持したCe担持ゼオライト粉末を調製
した。そして実施例1と同様にしてCe担持ゼオライト
粉末と酸化マンガン粉末とを重量比で1対1に混合し、
同様にペレット化して比較例3の触媒を調製した。
Even when the test is repeated with and without steam, the steam shows a substantially constant conversion rate according to the presence or absence of steam without being affected by the immediately preceding state, so that steam chemically changes the catalyst. It is unlikely that the water vapor is directly involved in the conversion reaction of NO to N 2 . (Comparative Example 3) A Ce-supported zeolite powder carrying Ce instead of Sn was prepared in the same manner as in Example 1 except that the Ce compound aqueous solution was used instead of the SnCl 2 aqueous solution. Then, in the same manner as in Example 1, the Ce-supported zeolite powder and the manganese oxide powder were mixed in a weight ratio of 1: 1,
Similarly, pelletizing was performed to prepare a catalyst of Comparative Example 3.

【0024】(比較例4)Snを担持しないNa型ゼオ
ライト粉末を用いたこと以外は実施例1と同様にして、
Na担持ゼオライト粉末と酸化マンガン粉末とを重量比
で1対1に混合し、同様にペレット化して比較例4の触
媒を調製した。 (試験・評価)比較例3と比較例4の触媒について実施
例1と同様に試験し、水蒸気の存在しない場合と存在す
る場合についてそれぞれ最大転化率を測定した。結果を
表2に示す。
(Comparative Example 4) In the same manner as in Example 1 except that Na-type zeolite powder not supporting Sn was used,
A Na-supported zeolite powder and a manganese oxide powder were mixed in a weight ratio of 1: 1 and pelletized in the same manner to prepare a catalyst of Comparative Example 4. (Test / Evaluation) The catalysts of Comparative Example 3 and Comparative Example 4 were tested in the same manner as in Example 1, and the maximum conversion rates were measured respectively in the absence and presence of water vapor. Table 2 shows the results.

【0025】[0025]

【表2】 表2より、比較例3及び比較例4の触媒では、水蒸気が
存在しない場合には高い転化率を示すものの、水蒸気が
存在すると転化率が大きく低下している。しかし実施例
1では水蒸気が存在する場合に高い転化率を示し、Sn
担持ゼオライトと酸化マンガンの組み合わせがきわめて
特異な性能を示していることがわかる。
[Table 2] From Table 2, the catalysts of Comparative Example 3 and Comparative Example 4 show a high conversion rate in the absence of water vapor, but the conversion rate is greatly reduced in the presence of water vapor. However, Example 1 shows a high conversion in the presence of water vapor,
It can be seen that the combination of supported zeolite and manganese oxide shows extremely unique performance.

【0026】[0026]

【発明の効果】すなわち本発明の排ガス浄化用触媒によ
れば、水蒸気による反応阻害が生じないばかりか、水蒸
気の存在下できわめて高いNOx 浄化性能を示す。した
がって実際に水蒸気を多く含む自動車排ガスの浄化にき
わめて有用であり、実用におけるNOx の浄化性能にき
わめて優れている。
[Effects of the Invention] That is, the exhaust gas purifying catalyst of the present invention not only does not inhibit the reaction due to water vapor, but also exhibits extremely high NO x purification performance in the presence of water vapor. Therefore, it is actually extremely useful for purifying automobile exhaust gas containing a large amount of water vapor, and is extremely excellent in practical NO x purification performance.

【図面の簡単な説明】[Brief description of drawings]

【図1】本発明の実施例及び比較例の排ガス浄化用触媒
の、NOからN2 への転化率を示すグラフである。
FIG. 1 is a graph showing conversion rates from NO to N 2 of exhaust gas purifying catalysts of Examples and Comparative Examples of the present invention.

【図2】本発明の実施例の排ガス浄化用触媒の、水蒸気
分圧変化に対するNOのN2 への転化率、プロペンのC
x への転化率及び選択性の変化を示すグラフである。
FIG. 2 is a graph showing the conversion rate of NO to N 2 and the C of propene in the exhaust gas purifying catalyst according to the example of the present invention with respect to the partial pressure change of water vapor.
The conversion and selectivity of the change to the O x is a graph showing.

Claims (1)

【特許請求の範囲】[Claims] 【請求項1】 錫(Sn)を担持したゼオライト粉末
と、酸化マンガン(Mn2 3 )粉末とを混合してなる
ことを特徴とする排ガス浄化用触媒。
1. An exhaust gas purifying catalyst comprising a mixture of tin (Sn) -supported zeolite powder and manganese oxide (Mn 2 O 3 ) powder.
JP4739196A 1996-03-05 1996-03-05 Exhaust gas cleaning catalyst Pending JPH09239276A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP4739196A JPH09239276A (en) 1996-03-05 1996-03-05 Exhaust gas cleaning catalyst

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4739196A JPH09239276A (en) 1996-03-05 1996-03-05 Exhaust gas cleaning catalyst

Publications (1)

Publication Number Publication Date
JPH09239276A true JPH09239276A (en) 1997-09-16

Family

ID=12773818

Family Applications (1)

Application Number Title Priority Date Filing Date
JP4739196A Pending JPH09239276A (en) 1996-03-05 1996-03-05 Exhaust gas cleaning catalyst

Country Status (1)

Country Link
JP (1) JPH09239276A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6455463B1 (en) 2001-03-13 2002-09-24 Delphi Technologies, Inc. Alkaline earth/transition metal lean NOx catalyst
US6576587B2 (en) 2001-03-13 2003-06-10 Delphi Technologies, Inc. High surface area lean NOx catalyst
US6624113B2 (en) 2001-03-13 2003-09-23 Delphi Technologies, Inc. Alkali metal/alkaline earth lean NOx catalyst
US6670296B2 (en) 2001-01-11 2003-12-30 Delphi Technologies, Inc. Alumina/zeolite lean NOx catalyst
US6864213B2 (en) 2001-03-13 2005-03-08 Delphi Technologies, Inc. Alkaline earth / rare earth lean NOx catalyst

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6670296B2 (en) 2001-01-11 2003-12-30 Delphi Technologies, Inc. Alumina/zeolite lean NOx catalyst
US6455463B1 (en) 2001-03-13 2002-09-24 Delphi Technologies, Inc. Alkaline earth/transition metal lean NOx catalyst
US6576587B2 (en) 2001-03-13 2003-06-10 Delphi Technologies, Inc. High surface area lean NOx catalyst
US6624113B2 (en) 2001-03-13 2003-09-23 Delphi Technologies, Inc. Alkali metal/alkaline earth lean NOx catalyst
US6864213B2 (en) 2001-03-13 2005-03-08 Delphi Technologies, Inc. Alkaline earth / rare earth lean NOx catalyst

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