JPH09248458A - Catalyst and method for exhaust gas-purifying - Google Patents
Catalyst and method for exhaust gas-purifyingInfo
- Publication number
- JPH09248458A JPH09248458A JP8060896A JP6089696A JPH09248458A JP H09248458 A JPH09248458 A JP H09248458A JP 8060896 A JP8060896 A JP 8060896A JP 6089696 A JP6089696 A JP 6089696A JP H09248458 A JPH09248458 A JP H09248458A
- Authority
- JP
- Japan
- Prior art keywords
- exhaust gas
- carrier
- catalyst
- purifying
- mgo
- 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
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車などの内燃
機関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、さらに詳しくは、酸素過剰の排ガス、すなわち
排ガス中に含まれる一酸化炭素（ＣＯ）、水素（Ｈ2 ）
及び炭化水素（ＨＣ）等の還元性成分を完全に酸化する
のに必要な酸素量より過剰の酸素を含む排ガス中の、窒
素酸化物（ＮＯx ）を効率良く還元浄化できる排ガス浄
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 internal combustion engine such as an automobile. More specifically, the present invention relates to exhaust gas with excess oxygen, that is, carbon monoxide (CO) contained in the exhaust gas. ), Hydrogen (H 2 )
And an exhaust gas purifying catalyst capable of efficiently reducing and purifying nitrogen oxides (NO x ) in exhaust gas containing oxygen in excess of the oxygen amount necessary for completely oxidizing reducing components such as hydrocarbons (HC). .
【０００２】[0002]
【従来の技術】従来より自動車の排ガス浄化用触媒とし
て、理論空燃比（ストイキ）において排ガス中のＣＯ及
びＨＣの酸化とＮＯx の還元とを同時に行って浄化する
三元触媒が用いられている。このような三元触媒として
は、例えばコーディエライトなどからなる耐熱性基材に
γ−アルミナからなる多孔質担体層を形成し、その多孔
質担体層に白金（Ｐｔ）、ロジウム（Ｒｈ）などの触媒
貴金属を担持させたものが広く知られている。また、酸
素吸蔵能をもつセリア（セリウム酸化物）を併用し、低
温活性を高めた三元触媒も知られている。2. Description of the Related Art Conventionally, as a catalyst for purifying exhaust gas of automobiles, a three-way catalyst has been used which purifies CO and HC in exhaust gas at the stoichiometric air-fuel ratio by simultaneously oxidizing and reducing NO x . . As such a three-way catalyst, for example, a porous carrier layer made of γ-alumina is formed on a heat-resistant substrate made of cordierite or the like, and platinum (Pt), rhodium (Rh), or the like is formed on the porous carrier layer. What carried the catalyst noble metal is widely known. Further, a three-way catalyst using ceria (cerium oxide) having an oxygen storage ability and having enhanced low-temperature activity is also known.
【０００３】一方、近年、地球環境保護の観点から、自
動車などの内燃機関から排出される排ガス中の二酸化炭
素（ＣＯ2 ）が問題とされ、その解決策として酸素過剰
雰囲気において希薄燃焼させるいわゆるリーンバーンが
有望視されている。このリーンバーンにおいては、燃費
が向上するために燃料の使用が低減され、その燃焼排ガ
スであるＣＯ2 の発生を抑制することができる。On the other hand, in recent years, from the viewpoint of protecting the global environment, carbon dioxide (CO 2 ) in exhaust gas discharged from internal combustion engines such as automobiles has become a problem, and as a solution to this problem, so-called lean combustion in which lean combustion is performed in an oxygen excess atmosphere is performed. Burn is promising. In this lean burn, the use of fuel is reduced to improve fuel efficiency, and the generation of CO 2 , which is the combustion exhaust gas, can be suppressed.
【０００４】これに対し、従来の三元触媒は、空燃比が
理論空燃比（ストイキ）において排ガス中のＣＯ，Ｈ
Ｃ，ＮＯx を同時に酸化・還元し浄化するものであっ
て、リーンバーン時の排ガスの酸素過剰雰囲気下におい
ては、ＮＯx の還元除去に対して充分な浄化性能を示さ
ない。このため、酸素過剰雰囲気下においてもＮＯx を
浄化しうる触媒及び浄化システムの開発が望まれてい
た。On the other hand, in the conventional three-way catalyst, when the air-fuel ratio is the stoichiometric air-fuel ratio (stoichiometric), CO, H in the exhaust gas
It purifies by oxidizing and reducing C and NO x at the same time, and does not show sufficient purification performance for reducing and removing NO x in an oxygen excess atmosphere of exhaust gas during lean burn. Therefore, it has been desired to develop a catalyst and a purification system that can purify NO x even in an oxygen excess atmosphere.
【０００５】そこで本願出願人は、先にＢａなどのアル
カリ土類金属とＰｔをアルミナなどの多孔質担体に担持
した排ガス浄化用触媒（例えば特開平５−１６８８６０
号公報）を提案している。この排ガス浄化用触媒を用
い、空燃比をリーン側からパルス状にストイキ又はリッ
チ側となるように制御する（以下、過渡燃焼という）こ
とにより、リーン側ではＮＯx がアルカリ土類金属（Ｎ
Ｏx 吸蔵元素）に吸蔵され、それがストイキ又はリッチ
側でＨＣやＣＯなどの還元性成分と反応して浄化される
ため、リーンバーンにおいてもＮＯx を効率良く浄化す
ることができる。Accordingly, the applicant of the present application has previously proposed an exhaust gas purifying catalyst in which an alkaline earth metal such as Ba and Pt are supported on a porous carrier such as alumina (for example, Japanese Patent Application Laid-Open No. 5-168860).
Issue gazette). By using this exhaust gas purifying catalyst to control the air-fuel ratio from the lean side to the stoichiometric or rich side in a pulse form (hereinafter referred to as transient combustion), NO x on the lean side is alkaline earth metal (N
O x storage element) is inserted in it to be cleaned reacts with the reducing components such as HC and CO in the stoichiometric or rich side, it is possible to efficiently purify NO x even in the lean burn.
【０００６】[0006]
【発明が解決しようとする課題】ところが、上記した特
開平５−１６８８６０号公報に開示されたような排ガス
浄化用触媒においては、６００℃以上、特に７００℃以
上の高温に曝された場合には、過渡燃焼におけるＮＯx
浄化性能が低下するという不具合があることが明らかと
なった。However, in the exhaust gas purifying catalyst disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-168860, when exposed to a high temperature of 600 ° C. or more, especially 700 ° C. or more, , NO in the transient combustion x
It became clear that there was a problem that the purification performance was reduced.
【０００７】この原因は、高温域において例えばＢａと
アルミナとの間に固相反応が生じ、ＢａＡｌ2 Ｏ4 が生
成することによって、担体の比表面積が低下するととも
にＢａのＮＯx 吸蔵能が低下することに起因すると考え
られている。本発明はこのような事情に鑑みてなされた
ものであり、高温域におけるＮＯx吸蔵元素と担体との
間の反応を防止することにより、過渡燃焼におけるＮＯ
x 浄化性能を向上させることを目的とする。The cause of this is that a solid phase reaction occurs between, for example, Ba and alumina in a high temperature range, and BaAl 2 O 4 is produced, whereby the specific surface area of the carrier is reduced and the NO x storage capacity of Ba is reduced. It is believed that this is due to The present invention has been made in view of such circumstances, and by preventing the reaction between the NO x storage element and the carrier in the high temperature range, NO in transient combustion is obtained.
x The purpose is to improve purification performance.
【０００８】[0008]
【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、酸素過剰の雰囲気下で
排ガス中の窒素酸化物（ＮＯx ）、一酸化炭素（ＣＯ）
及び炭化水素（ＨＣ）を浄化する排ガス浄化用触媒であ
って、ＭｇＯ・ｎＡｌ2 Ｏ3 で表される複合酸化物から
なる担体と、アルカリ金属、アルカリ土類金属及び希土
類元素の中から選ばれ担体に担持されたＮＯx 吸蔵元素
と、担体に担持された触媒貴金属と、を含んでなること
にある。The features of the exhaust gas-purifying catalyst of the present invention for solving the above-mentioned problems are that nitrogen oxide (NO x ) and carbon monoxide (CO) in exhaust gas in an atmosphere of excess oxygen.
And a catalyst for purifying exhaust gas for purifying hydrocarbons (HC), which is selected from the group consisting of composite oxides represented by MgO.nAl 2 O 3 and alkali metals, alkaline earth metals and rare earth elements. It comprises a NO x storage element carried on a carrier and a catalytic noble metal carried on the carrier.
【０００９】また本発明の排ガス浄化方法の特徴は、請
求項３に記載のように、酸素過剰の雰囲気下で排ガス中
の窒素酸化物（ＮＯx ）、一酸化炭素（ＣＯ）及び炭化
水素（ＨＣ）を浄化する排ガス浄化方法であって、Ｍｇ
Ｏ・ｎＡｌ2 Ｏ3 で表される複合酸化物からなる担体
と、アルカリ金属、アルカリ土類金属及び希土類元素の
中から選ばれ担体に担持されたＮＯx 吸蔵元素と、担体
に担持された触媒貴金属と、を含んでなる排ガス浄化用
触媒に排ガスを接触させることにある。Further, the feature of the exhaust gas purification method of the present invention is that, as described in claim 3, nitrogen oxide (NO x ), carbon monoxide (CO) and hydrocarbon ( HC) for purification of exhaust gas,
A carrier composed of a composite oxide represented by O.nAl 2 O 3 , a NO x storage element supported on a carrier selected from alkali metals, alkaline earth metals and rare earth elements, and a catalyst supported on the carrier Exhaust gas is brought into contact with an exhaust gas-purifying catalyst containing a noble metal.
【００１０】なお本発明においては、請求項２及び請求
項４に記載のように、ＮＯx 吸蔵元素としてＢａを用い
た時に最も大きな効果が得られる。In the present invention, the greatest effect is obtained when Ba is used as the NO x storage element as described in claims 2 and 4.
【００１１】[0011]
【発明の実施の形態】本発明の排ガス浄化用触媒では、
担体としてＭｇＯ・ｎＡｌ2 Ｏ3 で表される複合酸化物
を用いている。この複合酸化物の結晶構造としては、γ
−アルミナと同様のスピネル構造をもつものが知られて
いる。この複合酸化物は、アルミナに比べてＮＯx 吸蔵
元素との反応性が低い。したがって本発明の排ガス浄化
用触媒では、高温域における例えばＢａＡｌ2 Ｏ4 の生
成が抑制されるので、比表面積の低下やＮＯx 吸蔵能の
低下が抑制され、過渡燃焼においても高いＮＯx 浄化能
を有する。BEST MODE FOR CARRYING OUT THE INVENTION In the exhaust gas purifying catalyst of the present invention,
A composite oxide represented by MgO.nAl 2 O 3 is used as a carrier. The crystal structure of this composite oxide is γ
-It is known that it has a spinel structure similar to that of alumina. This composite oxide has a lower reactivity with the NO x storage element than alumina. Therefore, in the exhaust gas purifying catalyst of the present invention, the production of BaAl 2 O 4 , for example, in the high temperature range is suppressed, so that the reduction of the specific surface area and the reduction of the NO x storage capacity are suppressed, and the high NO x purification capacity is achieved even in the transient combustion. Have.
【００１２】さらに、この複合酸化物はそれ自体の耐熱
性が高く、高比表面積のものが比較的得やすいため、触
媒担体としての必要条件を備えている。このＭｇＯ・ｎ
Ａｌ2 Ｏ3 からなる複合酸化物において、ｎ＝１のとき
ＭｇＯ・ｎＡｌ2 Ｏ3 はＭｇＡｌ2 Ｏ4 とも表記され、
一般にスピネルと呼ばれており、状態図からはＭｇＯ・
ｎＡｌ2 Ｏ3 への固溶限界である。Further, this composite oxide has a high heat resistance by itself, and it is relatively easy to obtain one having a high specific surface area, and therefore, it has a necessary condition as a catalyst carrier. This MgO · n
In a complex oxide composed of Al 2 O 3 , when n = 1, MgO · nAl 2 O 3 is also expressed as MgAl 2 O 4 ,
It is generally called spinel, and the phase diagram shows MgO.
This is the solid solution limit for nAl 2 O 3 .
【００１３】ｎが１未満のときＭｇのＡｌ2 Ｏ3 への固
溶限界を越えるため、熱履歴を受ければＭｇＯとＭｇＡ
ｌ2 Ｏ4 との２相系になる。この遊離のＭｇＯが存在す
ると、耐熱性が低下するため好ましくない。ｎが１を超
えると、ＭｇＯ・ｘＡｌ2 Ｏ3 とｙＡｌ2 Ｏ3 （１＜
ｘ，ｘ＋ｙ＝ｎ）の２相系になる。ｎが大きくなると、
比表面積は大きくなる傾向があるが、Ａｌ2 Ｏ3 相の割
合が増えるにつれてＮＯx 吸蔵元素との反応が生じやす
くなる。したがって、ｎの範囲としては０．５≦ｎ≦
１．５が好ましく、さらに過酷な熱負荷に対してはｎ＝
１近傍が最も好ましい。When n is less than 1, the solid solubility limit of Mg in Al 2 O 3 is exceeded, so if MgO and MgA are subjected to thermal history.
It becomes a two-phase system with l 2 O 4 . The presence of this free MgO is not preferable because it lowers the heat resistance. When n exceeds 1, MgO.xAl 2 O 3 and yAl 2 O 3 (1 <
It becomes a two-phase system of x, x + y = n). When n becomes large,
Although the specific surface area tends to increase, the reaction with the NO x storage element tends to occur as the proportion of the Al 2 O 3 phase increases. Therefore, the range of n is 0.5 ≦ n ≦
1.5 is preferable, and n = for severe heat load.
The vicinity of 1 is most preferable.
【００１４】この複合酸化物は、それ自体で担体を構成
してもよいし、アルミナ粉末などの表面に被覆したもの
を担体とすることもできる。この複合酸化物の製造法と
しては、アルコキシド等を用いるゾルゲル法、硝酸マグ
ネシウムと硝酸アルミニウム等の混合水溶液とアンモニ
ア水を用いる共沈法、水酸化アルミニウムに酢酸マグネ
シウムを含浸し焼成する方法等が例示される。The composite oxide may form the carrier by itself, or the alumina powder or the like coated on the surface may be used as the carrier. Examples of the method for producing this composite oxide include a sol-gel method using an alkoxide, a coprecipitation method using a mixed aqueous solution of magnesium nitrate and aluminum nitrate and ammonia water, a method of impregnating aluminum hydroxide with magnesium acetate and firing. To be done.
【００１５】また担体の形状は、ペレット、ハニカム形
状など従来と同様に構成することができ、コーディエラ
イト担体基材又はメタル担体基材などにコートして用い
ることができる。ＮＯx 吸蔵元素としては、アルカリ金
属、アルカリ土類金属及び希土類元素から選ばれる少な
くとも一種が用いられる。アルカリ金属としてはリチウ
ム（Ｌｉ）、ナトリウム（Ｎａ）、カリウム（Ｋ）、セ
シウム（Ｃｓ）が挙げられる。また、アルカリ土類金属
とは周期表２Ａ族元素をいい、マグネシウム（Ｍｇ）、
カルシウム（Ｃａ）、ストロンチウム（Ｓｒ）、バリウ
ム（Ｂａ）が挙げられる。また希土類元素としては、ス
カンジウム（Ｓｃ）、イットリウム（Ｙ）、ランタン
（Ｌａ）、セリウム（Ｃｅ）、プラセオジム（Ｐｒ）、
ネオジム（Ｎｄ）などが例示される。中でもＢａが特に
ＮＯx 吸蔵能に優れ、かつＭｇＯ・ｎＡｌ2 Ｏ 3 複合酸
化物を担体とすることによりＢａＡｌ2 Ｏ4 の生成を効
果的に防止することができる。The shape of the carrier is pellet or honeycomb.
The shape can be configured in the same way as in the past, and the cordiera
It is used by coating it on a metal carrier substrate or a metal carrier substrate.
Can be NOxAlkali gold as an occlusion element
A few selected from genus, alkaline earth metals and rare earth elements
At least one kind is used. Lithium as an alkali metal
(Li), sodium (Na), potassium (K),
Cium (Cs) is mentioned. Also, alkaline earth metal
Is a group 2A element of the periodic table, and magnesium (Mg),
Calcium (Ca), Strontium (Sr), Baliu
(Ba). Moreover, as rare earth elements,
Candium (Sc), Yttrium (Y), Lantern
(La), cerium (Ce), praseodymium (Pr),
Examples include neodymium (Nd). Ba is especially
NOxExcellent storage capacity and MgO / nAlTwoO ThreeComplex acid
By using a compound as a carrierTwoOFourThe generation of
Can be effectively prevented.
【００１６】ＮＯx 吸蔵元素の含有量は、担体１００ｇ
に対して０．０１〜１．０モルの範囲が望ましい。含有
量が０．０１モルより少ないとＮＯx 吸蔵能力が小さく
ＮＯ x 浄化性能が低下し、１．０モルを超えて含有して
も、ＮＯx 吸蔵能力が飽和すると同時にＨＣのエミッシ
ョンが増加するなどの不具合が生じる。触媒貴金属とし
ては、白金（Ｐｔ）、ロジウム（Ｒｈ）、パラジウム
（Ｐｄ）、イリジウム（Ｉｒ）、オスミウム（Ｏｓ）な
どの１種又は複数種を用いることができ、Ｐｔが特に望
ましい。その担持量は、いずれの貴金属でも、担体１０
０ｇ（触媒全体の体積１リットル相当）に０．１〜２０
ｇが好ましく、０．５〜１０ｇが特に好ましい。触媒貴
金属の担持量をこれ以上増加させても活性は向上せず、
その有効利用が図れない。また触媒貴金属の担持量がこ
れより少ないと、実用上十分な活性が得られない。[0016] NOxThe content of occlusion elements is 100 g of carrier
Is preferably in the range of 0.01 to 1.0 mol. Contained
NO when the amount is less than 0.01 molxLow storage capacity
NO xPurification performance decreases, containing more than 1.0 mole
Also NOxEmission of HC at the same time when the storage capacity is saturated
Problems such as increase in the number of devices will occur. As a precious metal catalyst
For, platinum (Pt), rhodium (Rh), palladium
(Pd), iridium (Ir), osmium (Os)
Any one or more can be used, with Pt being particularly desirable
Good. The amount of the carrier is 10 for any precious metal.
0.1 to 20 g (corresponding to 1 liter of the total volume of the catalyst)
g is preferable, and 0.5 to 10 g is particularly preferable. Catalyst
The activity does not improve even if the supported amount of metal is further increased,
It cannot be used effectively. Also, the amount of catalyst precious metal supported is
If it is less than this, sufficient activity cannot be obtained in practical use.
【００１７】なお、ＮＯx 吸蔵元素及び触媒貴金属を担
体に担持させるには、その塩化物や硝酸塩等を用いて、
含浸法、噴霧法、スラリー混合法などを利用して従来と
同様に担持させることができる。また本発明の排ガス浄
化用触媒には、セリウム酸化物又はジルコニアで安定化
されたセリウム酸化物を含有することもできる。このよ
うにすればセリウム酸化物による酸素吸蔵・放出作用に
より、過渡燃焼におけるＮＯx 浄化性能を一層向上させ
ることができる。In order to support the NO x storage element and the catalytic noble metal on the carrier, its chloride or nitrate is used.
The impregnation method, the spraying method, the slurry mixing method and the like can be used to carry the particles in the same manner as in the past. The exhaust gas purifying catalyst of the present invention may also contain cerium oxide or cerium oxide stabilized with zirconia. This makes it possible to further improve the NO x purification performance in transient combustion by the oxygen storage / release action of the cerium oxide.
【００１８】本発明の排ガス浄化方法では、上記した排
ガス浄化用触媒を用い、酸素過剰の雰囲気下の排ガスを
接触させることにより、ＨＣ及びＣＯは触媒貴金属の触
媒作用によって酸化浄化される。またＮＯx はＮＯx 吸
蔵元素に吸蔵される。そして過渡燃焼により一時的にス
トイキ又はリッチ雰囲気の排ガスが供給されると、排ガ
ス中のＮＯx 及び吸蔵されていたＮＯx は、触媒貴金属
の触媒作用により排ガス中のＨＣ及びＣＯなどの還元成
分と反応して還元浄化される。In the exhaust gas purifying method of the present invention, HC and CO are oxidized and purified by the catalytic action of the catalytic noble metal by using the above-mentioned exhaust gas purifying catalyst and contacting the exhaust gas in an atmosphere with excess oxygen. Further, NO x is stored in the NO x storage element. When the exhaust gas temporarily stoichiometric or rich atmosphere by transient combustion is supplied, NO x which had been NO x and storage in the exhaust gas, the reducing components such as HC and CO in the exhaust gas by the catalytic action of the catalyst noble metal It reacts and is reduced and purified.
【００１９】そして担体はＮＯx 吸蔵元素との反応性が
低いため、高温域においてもＮＯx吸蔵元素との反応が
生じない。したがって本発明の排ガス浄化用触媒では、
ＮＯ x 吸蔵元素本来のＮＯx 吸蔵能が損なわれることが
なく、過渡燃焼においても高いＮＯx 浄化性能が維持さ
れる。また担体は耐熱性に優れ比表面積の低下もほとん
どないため、この面からも耐熱性に優れている。The carrier is NOxReactivity with storage element
NO in the high temperature range because it is lowxThe reaction with the occlusion element
Does not occur. Therefore, in the exhaust gas purifying catalyst of the present invention,
NO xOriginal NO of occlusion elementxThe storage capacity may be impaired
High NO even in transient combustionxPurification performance maintained
It is. In addition, the carrier is excellent in heat resistance and has a small specific surface area.
Since it does not come out, it is also excellent in heat resistance from this aspect.
【００２０】[0020]
【実施例】以下、実施例により本発明を具体的に説明す
るが、本発明の請求項は実施例により何ら制限を受ける
ものではない。 （実施例１） ＜複合酸化物担体の合成・ゾルゲル法＞気相法高純度超
微粒子マグネシア粉末（宇部化学工業（株）製・粒子径
１０〜１４ｎｍ）とアルミニウムイソプロポキシド（Ａ
ｌ［ＯＣＨ（ＣＨ3 ）2 ］3 ）とを、モル比でＭｇ：Ａ
ｌ＝１：２となるようにイソプロピルアルコールに加
え、攪拌しながら８０℃で約３時間還流した。そこへイ
オン交換水を滴下し、加水分解を完結させ、その後３０
分〜１時間還流を続け、その後放冷した。EXAMPLES The present invention will be described in detail below with reference to examples, but the claims of the present invention are not limited to the examples. (Example 1) <Synthesis of composite oxide carrier / sol-gel method> Gas phase method High-purity ultrafine magnesia powder (manufactured by Ube Chemical Industry Co., Ltd., particle diameter 10-14 nm) and aluminum isopropoxide (A)
1 [OCH (CH 3 ) 2 ] 3 ) in a molar ratio of Mg: A
It was added to isopropyl alcohol so that l = 1: 2, and refluxed at 80 ° C. for about 3 hours with stirring. Ion-exchanged water is added dropwise to complete the hydrolysis, then 30
Reflux was continued for minutes to 1 hour and then allowed to cool.
【００２１】次にロータリーエバポレータを用いて溶媒
を除去し、さらに室温で２４時間自然乾燥させた後、１
２０℃の乾燥機中で２４時間乾燥した。最後に大気中８
００℃で３時間焼成し、ＭｇＯ・ｎＡｌ2 Ｏ3 （ｎ＝
１．０）の組成の複合酸化物担体粉末を得た。 ＜触媒の調製＞この担体粉末の所定量を、所定濃度のジ
ニトロジアンミン白金水溶液中に浸漬し、５時間攪拌し
た後に蒸発乾固させ、大気中にて３００℃で３時間焼成
して白金（Ｐｔ）を担持させた。Ｐｔの担持量は、担体
１００ｇ（１Ｌ相当）に対してＰｔが２ｇである。Next, the solvent was removed by using a rotary evaporator, and the product was naturally dried at room temperature for 24 hours, and then 1
It was dried in a dryer at 20 ° C. for 24 hours. Finally in the atmosphere 8
After firing at 00 ° C. for 3 hours, MgO.nAl 2 O 3 (n =
A composite oxide carrier powder having a composition of 1.0) was obtained. <Preparation of catalyst> A predetermined amount of this carrier powder was immersed in an aqueous dinitrodiammine platinum solution having a predetermined concentration, stirred for 5 hours, evaporated to dryness, and calcined in the atmosphere at 300 ° C for 3 hours to obtain platinum (Pt. ) Was carried. The supported amount of Pt is 2 g of Pt with respect to 100 g of carrier (corresponding to 1 L).
【００２２】次に、Ｐｔが担持された担体粉末を、所定
濃度の酢酸バリウム水溶液中に浸漬し、５時間攪拌した
後に蒸発乾固させ、大気中にて３００℃で３時間焼成し
てＮＯx 吸蔵元素としてのバリウム（Ｂａ）を担持させ
た。Ｂａの担持量は、担体１００ｇ（１Ｌ相当）に対し
てＢａが０．３ｍｏｌである。最後に、ＰｔとＢａが担
持された担体粉末を水素気流中にて５００℃で３時間処
理し、実施例１の排ガス浄化用触媒粉末を調製した。Next, the carrier powder carrying Pt was dipped in an aqueous barium acetate solution having a predetermined concentration, stirred for 5 hours, evaporated to dryness, and calcined in the atmosphere at 300 ° C. for 3 hours to NO x. Barium (Ba) as an occlusion element was supported. The supported amount of Ba is 0.3 mol of Ba per 100 g of carrier (corresponding to 1 L). Finally, the carrier powder supporting Pt and Ba was treated in a hydrogen stream at 500 ° C. for 3 hours to prepare an exhaust gas purifying catalyst powder of Example 1.
【００２３】（実施例２）気相法高純度超微粒子マグネ
シア粉末とアルミニウムイソプロポキシドの混合比をモ
ル比でＭｇ：Ａｌ＝１：２．８としたこと以外は実施例
１と同様にして、ＭｇＯ・ｎＡｌ2 Ｏ3 （ｎ＝１．５）
の組成の複合酸化物担体粉末を調製した。そして同様に
してＰｔとＢａを担持し、同様に水素気流中で処理して
実施例２の排ガス浄化用触媒粉末を得た。(Example 2) The same as Example 1 except that the mixing ratio of the vapor phase high-purity ultrafine magnesia powder and aluminum isopropoxide was Mg: Al = 1: 2.8. , MgO · nAl 2 O 3 (n = 1.5)
A composite oxide carrier powder having the composition of was prepared. Then, Pt and Ba were similarly loaded, and similarly treated in a hydrogen stream to obtain an exhaust gas-purifying catalyst powder of Example 2.
【００２４】（実施例３）気相法高純度超微粒子マグネ
シア粉末とアルミニウムイソプロポキシドの混合比をモ
ル比でＭｇ：Ａｌ＝１：６としたこと以外は実施例１と
同様にして、ＭｇＯ・ｎＡｌ2 Ｏ3 （ｎ＝３．０）の組
成の複合酸化物担体粉末を調製した。そして同様にして
ＰｔとＢａを担持し、同様に水素気流中で処理して実施
例３の排ガス浄化用触媒粉末を得た。Example 3 MgO was prepared in the same manner as in Example 1 except that the mixing ratio of the vapor-phase high-purity ultrafine magnesia powder and aluminum isopropoxide was Mg: Al = 1: 6. A composite oxide carrier powder having a composition of nAl 2 O 3 (n = 3.0) was prepared. Then, Pt and Ba were similarly loaded, and similarly treated in a hydrogen stream to obtain an exhaust gas purifying catalyst powder of Example 3.
【００２５】（実施例４）気相法高純度超微粒子マグネ
シア粉末とアルミニウムイソプロポキシドの混合比をモ
ル比でＭｇ：Ａｌ＝１：１としたこと以外は実施例１と
同様にして、ＭｇＯ・ｎＡｌ2 Ｏ3 （ｎ＝０．５）の組
成の複合酸化物担体粉末を調製した。そして同様にして
ＰｔとＢａを担持し、同様に水素気流中で処理して実施
例３の排ガス浄化用触媒粉末を得た。(Example 4) MgO was prepared in the same manner as in Example 1 except that the mixing ratio of the vapor-phase high-purity ultrafine magnesia powder and aluminum isopropoxide was Mg: Al = 1: 1. A composite oxide carrier powder having a composition of nAl 2 O 3 (n = 0.5) was prepared. Then, Pt and Ba were similarly loaded, and similarly treated in a hydrogen stream to obtain an exhaust gas purifying catalyst powder of Example 3.
【００２６】（比較例）γ−アルミナ粉末を担体とし、
実施例１と同様にしてＰｔとＢａを担持した後水素気流
中で処理して、比較例の排ガス浄化用触媒粉末を得た。 （試験・評価）上記したそれぞれの触媒粉末を耐久試験
装置に充填し、表１に示すリーン側のモデル排ガスとリ
ッチ側のモデル排ガスを、入りガス温度９００℃でリー
ン…リッチを１分…４分で切り替えながら５時間流し
た。Comparative Example Using γ-alumina powder as a carrier,
In the same manner as in Example 1, Pt and Ba were loaded and then treated in a hydrogen stream to obtain an exhaust gas-purifying catalyst powder of a comparative example. (Test / Evaluation) Each of the above-mentioned catalyst powders was filled in an endurance test apparatus, and the lean side model exhaust gas and the rich side model exhaust gas shown in Table 1 were introduced at a gas temperature of 900 ° C. and lean to rich for 1 minute. Flowed for 5 hours while switching in minutes.
【００２７】[0027]
【表１】 そして上記耐久試験後の各触媒粉末について、ＢＥＴ比
表面積を測定するとともに、過渡燃焼を模したモデル排
ガス評価におけるＮＯx 浄化率と粉末Ｘ線回折法による
ＢａＣＯ3 残存率の測定を実施した。[Table 1] Then, the BET specific surface area of each catalyst powder after the durability test was measured, and the NO x purification rate in the model exhaust gas evaluation imitating transient combustion and the BaCO 3 residual rate by the powder X-ray diffraction method were measured.
【００２８】ＮＯx 浄化率は、耐久試験後のそれぞれの
排ガス浄化用触媒粉末０．５ｇを評価装置に充填し、表
２に示すリーン側のモデル排ガスとリッチ側のモデル排
ガスを２分毎に交互に繰り返して流速２Ｌ／ｍｉｎで流
すことにより測定した。入りガス温度は４００℃及び５
００℃の２水準である。結果を表３に示す。なお、ＮＯ
x 浄化率は次式で定義される。Regarding the NO x purification rate, 0.5 g of each exhaust gas purifying catalyst powder after the durability test was filled in the evaluation apparatus, and the lean side model exhaust gas and the rich side model exhaust gas shown in Table 2 were every 2 minutes. The measurement was performed by alternately repeating the flow at a flow rate of 2 L / min. Inlet gas temperature is 400 ° C and 5
There are two levels of 00 ° C. The results are shown in Table 3. Note that NO
x Purification rate is defined by the following equation.
【００２９】ＮＯx 浄化率（％）＝１００×（１−４分
間の出口ガス中のＮＯx 量／４分間の入りガス中のＮＯ
x 量）NO x purification rate (%) = 100 × (NO x amount in outlet gas for 1-4 minutes / NO in incoming gas for 4 minutes)
x amount)
【００３０】[0030]
【表２】 またＢａＣＯ3 残存率は、耐久試験後の各触媒粉末の、
ＢａＣＯ3 とＢａＡｌ 2 Ｏ4 のＸＲＤスペクトルの最強
ピーク高さより、次式により算出した。結果を表３に示
す。[Table 2]Also BaCOThreeResidual rate of each catalyst powder after durability test,
BaCOThreeAnd BaAl TwoOFourStrongest XRD spectrum
It was calculated from the peak height by the following formula. The results are shown in Table 3.
You.
【００３１】ＢａＣＯ3 残存率＝ＢａＣＯ3 ／（ＢａＣ
Ｏ3 ＋ＢａＡｌ2 Ｏ4 ）BaCO 3 residual rate = BaCO 3 / (BaC
O 3 + BaAl 2 O 4 )
【００３２】[0032]
【表３】 表３より、実施例１〜４の複合酸化物ＭｇＯ・ｎＡｌ2
Ｏ3 を担体に用いた場合には、比較例のγ−アルミナを
担体に用いた場合と比較して高いＮＯx 浄化率が得ら
れ、耐熱性に優れていることがわかる。[Table 3] From Table 3, the composite oxides MgO.nAl 2 of Examples 1 to 4
It can be seen that when O 3 is used as the carrier, a higher NO x purification rate is obtained and heat resistance is excellent as compared with the case where γ-alumina of Comparative Example is used as the carrier.
【００３３】比較例は実施例１〜４より比表面積が高い
にもかかわらずＮＯx 浄化率が低下していることから、
上記差異の理由を比表面積の差で説明することは困難で
ある。しかしＢａＣＯ3 残存率をみると、実施例１〜４
の値は比較例より高い値を示している。これより、実施
例１〜４の触媒が耐熱性に優れているのは、担持された
Ｂａと担体との反応が抑制されたことによりＢａのＮＯ
x 吸蔵能の低下が抑制されたことによるものと考えら
れ、これは担体をＭｇとＡｌとの複合酸化物としたこと
に起因していることが明らかである。In the comparative example, although the specific surface area is higher than those in Examples 1 to 4, the NO x purification rate is lowered,
It is difficult to explain the reason for the above difference by the difference in specific surface area. However, looking at the BaCO 3 residual rate, Examples 1 to 4
The value of is higher than that of the comparative example. From this, the catalysts of Examples 1 to 4 are excellent in heat resistance because the reaction between the carried Ba and the carrier is suppressed, and thus the NO of Ba is
It is considered that the decrease in the x storage capacity was suppressed, and it is clear that this is due to the fact that the carrier was a composite oxide of Mg and Al.
【００３４】[0034]
【発明の効果】すなわち本発明の排ガス浄化用触媒及び
排ガス浄化方法によれば、酸素過剰の雰囲気下における
排ガス中のＮＯx 、ＣＯ及びＨＣを効率良く浄化でき
る。また９００℃程度の高温に曝されたとしても、過渡
燃焼において高いＮＯx 浄化率を維持し、きわめて耐熱
性に優れている。According to the exhaust gas purifying catalyst and the exhaust gas purifying method of the present invention, it is possible to efficiently purify NO x , CO and HC in exhaust gas in an oxygen-rich atmosphere. Even when it is exposed to a high temperature of about 900 ° C., it maintains a high NO x purification rate in transient combustion and has excellent heat resistance.
Claims (4)
化物（ＮＯx ）、一酸化炭素（ＣＯ）及び炭化水素（Ｈ
Ｃ）を浄化する排ガス浄化用触媒であって、 ＭｇＯ・ｎＡｌ2 Ｏ3 で表される複合酸化物からなる担
体と、アルカリ金属、アルカリ土類金属及び希土類元素
の中から選ばれ該担体に担持されたＮＯx 吸蔵元素と、
該担体に担持された触媒貴金属と、を含んでなることを
特徴とする排ガス浄化用触媒。An exhaust gas containing nitrogen oxides (NO x ), carbon monoxide (CO) and hydrocarbons (H) in an oxygen-excess atmosphere.
A catalyst for purifying exhaust gas for purifying C), which is a carrier composed of a composite oxide represented by MgO.nAl 2 O 3 and is supported on the carrier selected from alkali metals, alkaline earth metals and rare earth elements The stored NO x storage element,
An exhaust gas-purifying catalyst, comprising a catalyst noble metal supported on the carrier.
とを特徴とする請求項１記載の排ガス浄化用触媒。2. The exhaust gas purifying catalyst according to claim 1, wherein the NO x storage element is barium.
化物（ＮＯx ）、一酸化炭素（ＣＯ）及び炭化水素（Ｈ
Ｃ）を浄化する排ガス浄化方法であって、 ＭｇＯ・ｎＡｌ2 Ｏ3 で表される複合酸化物からなる担
体と、アルカリ金属、アルカリ土類金属及び希土類元素
の中から選ばれ該担体に担持されたＮＯx 吸蔵元素と、
該担体に担持された触媒貴金属と、を含んでなる排ガス
浄化用触媒に前記排ガスを接触させることを特徴とする
排ガス浄化方法。3. Nitrogen oxides (NO x ), carbon monoxide (CO) and hydrocarbons (H) in exhaust gas under an atmosphere of excess oxygen.
An exhaust gas purification method for purifying C), which comprises a carrier composed of a complex oxide represented by MgO.nAl 2 O 3 and a carrier selected from alkali metals, alkaline earth metals and rare earth elements. NO x storage element,
An exhaust gas purifying method, characterized in that the exhaust gas is brought into contact with a catalyst for purifying exhaust gas, which comprises a catalyst noble metal supported on the carrier.
とを特徴とする請求項３記載の排ガス浄化方法。4. The exhaust gas purification method according to claim 3, wherein the NO x storage element is barium.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8060896A JPH09248458A (en) | 1996-03-18 | 1996-03-18 | Catalyst and method for exhaust gas-purifying |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8060896A JPH09248458A (en) | 1996-03-18 | 1996-03-18 | Catalyst and method for exhaust gas-purifying |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09248458A true JPH09248458A (en) | 1997-09-22 |
Family
ID=13155588
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8060896A Pending JPH09248458A (en) | 1996-03-18 | 1996-03-18 | Catalyst and method for exhaust gas-purifying |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09248458A (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000084405A (en) * | 1998-08-24 | 2000-03-28 | Degussa Huels Ag | Nitrogen oxides-accumulating material and nitrogen oxides-accumulating catalyst to be prepared therefrom |
| JP2000512907A (en) * | 1997-06-11 | 2000-10-03 | ダイムラークライスラー アクチエンゲゼルシヤフト | Storage catalyst |
| US6372688B1 (en) | 1998-12-28 | 2002-04-16 | Toyota Jidosha Kabushiki Kaisha | Catalyst for purifying an exhaust gas and process for producing the same |
| US6569803B2 (en) | 2000-01-19 | 2003-05-27 | Toyota Jidosha Kabushiki Kaisha | Catalyst for purifying exhaust gas |
| JP2006297237A (en) * | 2005-04-18 | 2006-11-02 | Toyota Motor Corp | Catalyst for cleaning exhaust gas and manufacturing method for the same |
| US7438866B2 (en) | 2001-02-02 | 2008-10-21 | Hitachi, Ltd. | Emission gas purification catalyst and internal combustion engine provided with the catalyst |
| JP2012130895A (en) * | 2010-12-24 | 2012-07-12 | Daihatsu Motor Co Ltd | Catalyst support and catalyst for cleaning exhaust gas |
| JP2012152720A (en) * | 2011-01-28 | 2012-08-16 | Daihatsu Motor Co Ltd | Catalyst carrier and exhaust gas-purifying catalyst |
| US20140331652A1 (en) * | 2011-12-07 | 2014-11-13 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purification device of internal combustion engine |
| JP2015520021A (en) * | 2012-04-26 | 2015-07-16 | ジョンソン、マッセイ、パブリック、リミテッド、カンパニーＪｏｈｎｓｏｎ Ｍａｔｔｈｅｙ Ｐｕｂｌｉｃｌｉｍｉｔｅｄ Ｃｏｍｐａｎｙ | NOX trap composition |
-
1996
- 1996-03-18 JP JP8060896A patent/JPH09248458A/en active Pending
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000512907A (en) * | 1997-06-11 | 2000-10-03 | ダイムラークライスラー アクチエンゲゼルシヤフト | Storage catalyst |
| JP2000084405A (en) * | 1998-08-24 | 2000-03-28 | Degussa Huels Ag | Nitrogen oxides-accumulating material and nitrogen oxides-accumulating catalyst to be prepared therefrom |
| US6372688B1 (en) | 1998-12-28 | 2002-04-16 | Toyota Jidosha Kabushiki Kaisha | Catalyst for purifying an exhaust gas and process for producing the same |
| US6569803B2 (en) | 2000-01-19 | 2003-05-27 | Toyota Jidosha Kabushiki Kaisha | Catalyst for purifying exhaust gas |
| US7438866B2 (en) | 2001-02-02 | 2008-10-21 | Hitachi, Ltd. | Emission gas purification catalyst and internal combustion engine provided with the catalyst |
| JP2006297237A (en) * | 2005-04-18 | 2006-11-02 | Toyota Motor Corp | Catalyst for cleaning exhaust gas and manufacturing method for the same |
| JP4720270B2 (en) * | 2005-04-18 | 2011-07-13 | トヨタ自動車株式会社 | Exhaust gas purification catalyst and method for producing the same |
| JP2012130895A (en) * | 2010-12-24 | 2012-07-12 | Daihatsu Motor Co Ltd | Catalyst support and catalyst for cleaning exhaust gas |
| JP2012152720A (en) * | 2011-01-28 | 2012-08-16 | Daihatsu Motor Co Ltd | Catalyst carrier and exhaust gas-purifying catalyst |
| US20140331652A1 (en) * | 2011-12-07 | 2014-11-13 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purification device of internal combustion engine |
| US9097167B2 (en) * | 2011-12-07 | 2015-08-04 | Toyota Jidosha Kabushiki Kaisha | Exhaust gas purification device of internal combustion engine |
| JP2015520021A (en) * | 2012-04-26 | 2015-07-16 | ジョンソン、マッセイ、パブリック、リミテッド、カンパニーＪｏｈｎｓｏｎ Ｍａｔｔｈｅｙ Ｐｕｂｌｉｃｌｉｍｉｔｅｄ Ｃｏｍｐａｎｙ | NOX trap composition |
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