JP5463861B2 - Exhaust gas purification catalyst - Google Patents
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Description
本発明は、排気ガス浄化用触媒に関する。 The present invention relates to an exhaust gas purification catalyst.
エンジン排気ガス中のＨＣ（炭化水素）、ＣＯ及びＮＯｘ（窒素酸化物）を浄化する触媒は約２００℃から約１１００℃までの広範な温度域で高い浄化率を有することが求められる。そのため、Ｐｔ、Ｐｄ、Ｒｈ等の希少金属を触媒金属として用いるとともに、これら触媒金属を活性アルミナ、酸化ジルコニウム、或いは酸素吸蔵放出能を有するＣｅ系酸化物等の耐熱性酸化物粒子に担持させた状態で担体上の触媒層に含ませることが行なわれている。しかし、触媒が高温の排気ガスに晒されると、少しずつではあるが、触媒金属が凝集してその表面積が低下し、触媒性能が低下することが知られている。そのため、通常はこの凝集を見越して触媒金属を触媒層に多めに含ませることがなされている。 A catalyst that purifies HC (hydrocarbon), CO, and NOx (nitrogen oxide) in engine exhaust gas is required to have a high purification rate in a wide temperature range from about 200 ° C. to about 1100 ° C. Therefore, rare metals such as Pt, Pd, and Rh are used as catalyst metals, and these catalyst metals are supported on heat-resistant oxide particles such as activated alumina, zirconium oxide, or Ce-based oxides having oxygen storage / release ability. In this state, the catalyst layer on the support is included. However, it is known that when the catalyst is exposed to high-temperature exhaust gas, the catalytic metal is agglomerated and its surface area is reduced, and the catalytic performance is lowered. For this reason, usually, a large amount of catalyst metal is included in the catalyst layer in anticipation of this aggregation.
一方、最近では、触媒金属が凝集しないようにする工夫もなされ、例えば、特許文献１，２には、ＲｈをＣｅＺｒ系複合酸化物にドープさせるとともに、一部の触媒金属をその複合酸化物の表面に露出させることが記載されている。かかるＲｈドープＣｅＺｒ系複合酸化物によれば、Ｒｈの凝集が抑制されるだけでなく、ＣｅＺｒ系複合酸化物の酸素吸蔵放出量の増大及び酸素吸蔵放出速度の向上も同時に実現される。これは、排気ガス空燃比（Ａ／Ｆ）の変動があっても、触媒まわりを排気ガスの浄化に好適なストイキ近傍の雰囲気に素早く戻すことができるという、自動車ならではの課題解決に大きな効果を奏する。
On the other hand, recently, a device has been devised to prevent the catalyst metal from agglomerating. For example,
また、排気ガス浄化用触媒では、主に酸化触媒能が利用されるＰｔやＰｄと、主に還元触媒能が利用されるＲｈとを組み合わせることがなされている。例えば、ＰｔとＲｈ、ＰｄとＲｈ、という二種の触媒金属を組み合わせたバイメタル触媒、或いはＰｔ、Ｐｄ及びＲｈの組み合わせであるトリメタル触媒が知られている。上記特許文献１，２ではＰｔやＰｄは活性アルミナに担持されている。
Further, in the exhaust gas purifying catalyst, Pt or Pd that mainly uses oxidation catalytic ability is combined with Rh that mainly uses reduction catalytic ability. For example, a bimetallic catalyst in which two types of catalytic metals Pt and Rh and Pd and Rh are combined, or a trimetallic catalyst that is a combination of Pt, Pd, and Rh is known. In
また、特許文献３には、貴金属を含有するペロブスカイト型複合酸化物を排気ガス浄化用触媒に利用することが記載されている。それは、例えば、Ｐｄを含有するペロブスカイト型複合酸化物が担持されたＬａ含有θアルミナと、Ｐｔ及びＲｈが担持されたジルコニア系複合酸化物と、Ｐｔが担持されたセリア系複合酸化物と、Ｐｔ及びＲｈが担持されたθアルミナとを混合したものである。上記貴金属を含有するペロブスカイト型複合酸化物については、一般式ＡＢ１−ｍＮｍＯ３（Ａは希土類元素及びアルカリ土類金属から選ばれる少なくとも１種、Ｂは遷移元素及びＡｌから選ばれる少なくとも１種、ＮはＲｈ、Ｐｄ及びＰｔから選ばれる少なくとも１種、０＜ｍ＜０．５）で表されている。 Patent Document 3 describes that a perovskite complex oxide containing a noble metal is used as an exhaust gas purifying catalyst. For example, a La-containing θ-alumina supporting a perovskite-type composite oxide containing Pd, a zirconia-based composite oxide supporting Pt and Rh, a ceria-based composite oxide supporting Pt, and Pt And θ alumina on which Rh is supported. The perovskite complex oxide containing the noble metal has a general formula AB 1-m N m O 3 (A is at least one selected from rare earth elements and alkaline earth metals, B is at least selected from transition elements and Al). One, N is represented by at least one selected from Rh, Pd and Pt, 0 <m <0.5).
上述の如きペロブスカイト型複合酸化物は酸素イオン伝導性を有することが知られており、酸素の吸蔵（吸着）放出能に関し、ペロブスカイト型複合酸化物とＣｅ系複合酸化物とを比較すると、両者は次の関係にある。 The perovskite complex oxide as described above is known to have oxygen ion conductivity, and when comparing the perovskite complex oxide with the Ce-based complex oxide in terms of oxygen storage (adsorption) release, It has the following relationship.
(1) 酸素吸蔵放出量 ペロブスカイト型複合酸化物＞Ｃｅ系複合酸化物
(2) 酸素吸蔵放出速度 ペロブスカイト型複合酸化物＜Ｃｅ系複合酸化物
(3) 放出酸素 ペロブスカイト型複合酸化物；普通の酸素分子
Ｃｅ系複合酸化物；活性酸素
また、上記(2)にも関連するが、Ｃｅ系複合酸化物は、リーン（酸素過剰雰囲気）で酸素を吸蔵し、リッチ（酸素不足雰囲気）で酸素を放出するのに対し、ペロブスカイト型複合酸化物は、リーンで周囲から酸素を取り込み、リッチでその酸素を放出する傾向があるものの、Ｃｅ系複合酸化物に比べて、雰囲気の変化に対する酸素の吸蔵・放出の応答性が低い。
(1) Oxygen storage / release amount Perovskite complex oxide> Ce complex oxide
(2) Oxygen storage / release rate Perovskite complex oxide <Ce complex oxide
(3) Released oxygen Perovskite complex oxide; Ordinary oxygen molecule
Ce-based composite oxide; active oxygen Although related to (2) above, Ce-based composite oxide absorbs oxygen in a lean (oxygen-rich atmosphere) and releases oxygen in a rich (oxygen-deficient atmosphere). On the other hand, the perovskite complex oxide tends to take in oxygen from the surroundings in a lean manner and release the oxygen in a rich manner, but it does not absorb and release oxygen in response to changes in the atmosphere compared to Ce-based complex oxides. Responsiveness is low.
以上から、本発明は、ペロブスカイト型複合酸化物を排気ガス浄化用触媒に利用するにあたって、その酸素吸蔵放出速度が遅い点、雰囲気のリーン・リッチ変化に対する応答性が低い点、放出される酸素の活性が低い点を考慮して、排気ガス浄化用触媒の性能改善を図ることを課題とする。 From the above, the present invention uses a perovskite complex oxide as an exhaust gas purifying catalyst, has a low oxygen storage / release rate, a low response to lean / rich changes in the atmosphere, In view of the low activity, it is an object to improve the performance of the exhaust gas purifying catalyst.
本発明は、上記課題を解決するために、ペロブスカイト型複合酸化物とＲｈドープＣｅＺｒ系複合酸化物とを組み合わせた。 In order to solve the above problems, the present invention combines a perovskite complex oxide and a Rh-doped CeZr-based complex oxide.
すなわち、上記課題を解決する第１の手段は、ＣｅとＺｒとを含有するＣｅＺｒ系複合酸化物粒子にＲｈが固溶しているＲｈドープＣｅＺｒ系複合酸化物粉末と、耐熱性粒子にＰｔ及びＰｄの少なくとも一方の貴金属が担持された貴金属担持耐熱性粉末とが担体上の触媒層に含まれている排気ガス浄化用触媒であって、
上記触媒層は、単層又は複数の層よりなり、さらに、ペロブスカイト型複合酸化物粉末を含有し、該ペロブスカイト型複合酸化物粉末と上記ＲｈドープＣｅＺｒ系複合酸化物粉末とは、同じ層中に混在し、若しくは隣接する二層に分かれており、
上記貴金属を担持する耐熱性粒子は、Ｌａを含有する活性Ａｌ ２ Ｏ ３ 粒子、ＢａＳＯ ４ 粒子、並びにＣｅＺｒ系複合酸化物とＡｌ ２ Ｏ ３ との複合化物粒子から選ばれる少なくとも一種であることを特徴とする。
That is, the first means for solving the above problem is that Rh-doped CeZr-based composite oxide powder in which Rh is solid-solved in CeZr-based composite oxide particles containing Ce and Zr, and Pt and An exhaust gas purifying catalyst comprising a noble metal-supported heat-resistant powder on which at least one noble metal of Pd is supported and contained in a catalyst layer on a carrier,
The catalyst layer is composed of a single layer or a plurality of layers, and further contains a perovskite-type composite oxide powder. The perovskite-type composite oxide powder and the Rh-doped CeZr-based composite oxide powder are in the same layer. It is mixed or divided into two adjacent layers ,
The heat-resistant particles supporting the noble metal are at least one selected from active Al 2 O 3 particles containing La , BaSO 4 particles, and composite particles of CeZr-based composite oxide and Al 2 O 3. Features.
これにより、ペロブスカイト型複合酸化物粉末から酸素が放出されたとき、その一部がＲｈドープＣｅＺｒ系複合酸化物粉末に吸蔵され、リッチ雰囲気になったときに該ＲｈドープＣｅＺｒ系複合酸化物粉末から活性酸素となって放出される。或いは、ペロブスカイト型複合酸化物粉末から放出される酸素が、ＲｈドープＣｅＺｒ系複合酸化物粉末から放出される活性酸素との反応により、活性が高い状態になる。このように、ＲｈドープＣｅＺｒ系複合酸化物粉末の存在によって、ペロブスカイト型複合酸化物粉末から放出される酸素の活性化が図れる。 As a result, when oxygen is released from the perovskite complex oxide powder, a part of the oxygen is occluded in the Rh-doped CeZr-based complex oxide powder, and when the rich atmosphere is reached, the Rh-doped CeZr-based complex oxide powder Released as active oxygen. Alternatively, the oxygen released from the perovskite complex oxide powder becomes highly active due to the reaction with the active oxygen released from the Rh-doped CeZr composite oxide powder. Thus, the oxygen released from the perovskite complex oxide powder can be activated by the presence of the Rh-doped CeZr-based complex oxide powder.
ここに、Ｒｈが固溶していないＣｅＺｒ系複合酸化物粉末、或いはその表面にＲｈを担持したＣｅＺｒ系複合酸化物粉末も、吸蔵した酸素を活性酸素として放出するが、その吸蔵放出速度はＲｈドープＣｅＺｒ系複合酸化物粉末に比べて遅く、そのため、ペロブスカイト型複合酸化物粉末から放出される酸素の活性化に充分な効果を発揮し得ない。すなわち、ＲｈドープＣｅＺｒ系複合酸化物粉末の場合は、その酸素吸蔵放出速度が速いためにペロブスカイト型複合酸化物粉末から放出される酸素の活性化が効率良く図れるものである。従って、ペロブスカイト型複合酸化物粉末から放出される酸素が、貴金属担持耐熱性粉末のＰｔ又はＰｄによるＨＣやＣＯの酸化に有効に利用され、ＨＣやＣＯの酸化、これに伴うＮＯｘの還元が効率良く進む。 Here, CeZr-based composite oxide powder in which Rh is not dissolved, or CeZr-based composite oxide powder supporting Rh on its surface also releases the stored oxygen as active oxygen, but the storage-release rate is Rh It is slower than the doped CeZr-based composite oxide powder, and therefore cannot sufficiently exhibit the effect of activating oxygen released from the perovskite-type composite oxide powder. That is, in the case of the Rh-doped CeZr-based composite oxide powder, the oxygen released from the perovskite-type composite oxide powder can be activated efficiently because of its high oxygen storage / release rate. Therefore, the oxygen released from the perovskite complex oxide powder is effectively utilized for the oxidation of HC and CO by Pt or Pd of the noble metal-supported heat-resistant powder, and the oxidation of HC and CO and the accompanying reduction of NOx are efficient. Proceed well.
また、ペロブスカイト型複合酸化物粉末は、酸素の吸蔵放出速度は遅いものの、酸素の吸蔵放出量が多い。このため、エンジンの燃料カット時など排気ガスが比較的長い時間リーンになるときに、酸素がペロブスカイト型複合酸化物粉末に吸蔵され、ＲｈドープＣｅＺｒ系複合酸化物粉末まわりや貴金属担持耐熱性粉末まわりが酸素過剰雰囲気になることが抑制される。よって、これら触媒成分によるＮＯｘの還元に有利になる。 In addition, the perovskite complex oxide powder has a large oxygen storage / release amount although the oxygen storage / release rate is slow. For this reason, oxygen is occluded in the perovskite type complex oxide powder when the exhaust gas leans for a relatively long time, such as when the engine is cut, and around the Rh-doped CeZr-based complex oxide powder and the noble metal-supported heat-resistant powder. Is suppressed to an oxygen-excess atmosphere. Therefore, it is advantageous for the reduction of NOx by these catalyst components.
そうして、上記貴金属を担持する耐熱性粒子を、Ｌａを含有する活性Ａｌ２Ｏ３粒子、ＢａＳＯ４粒子、並びにＣｅＺｒ系複合酸化物とＡｌ２Ｏ３との複合化物粒子から選ばれる少なくとも一種としたから、良好な触媒性能と耐熱性が得られる。耐熱性粒子としては、Ｌａ含有Ａｌ２Ｏ３粒子が最も好ましく、これにＣｅＺｒ系複合酸化物とＡｌ２Ｏ３との複合化物粒子、及びＢａＳＯ４粒子が順に続く。 Then, at least one heat-resistant particles supporting the precious metal, active Al 2 O 3 particles containing La, selected from composite compound particles of BaSO 4 particles, and CeZr-based mixed oxide and Al 2 O 3 since was, good good catalyst performance and heat resistance can be obtained. As the heat-resistant particles, La-containing Al 2 O 3 particles are most preferable, followed by composite particles of CeZr-based composite oxide and Al 2 O 3 and BaSO 4 particles in this order.
Ｌａ含有Ａｌ２Ｏ３粒子の場合、その耐熱性が高く且つ多数の細孔を有し表面積が大であることから、ＰｔやＰｄを高分散に担持することができ、該ＰｔやＰｄのシンタリングが抑制される。ＣｅＺｒ系複合酸化物とＡｌ２Ｏ３との複合化物粒子は、ＣｅＺｒ系複合酸化物一次粒子とＡｌ２Ｏ３一次粒子とが凝集してなるものであり、Ａｌ２Ｏ３一次粒子が立体障害となることによってＣｅＺｒ系複合酸化物一次粒子のシンタリングが抑制され、長期間の使用によっても高い比表面積が維持される。ＢａＳＯ４粒子の場合、活性Ａｌ２Ｏ３ほどの大きな比表面積は備えていないが、高温の排気ガスに晒されても、比表面積の低下が実質的になく、ＰｔやＰｄのサポート材としては極めて安定であり、しかも、エンジンオイルから排気ガス中に混入するＰ、Ｚｎ、Ｓによる被毒（触媒の劣化）も少なくなる。 In the case of La-containing Al 2 O 3 particles, Pt and Pd can be supported in a highly dispersed state because of its high heat resistance, a large number of pores, and a large surface area. The ring is suppressed. Composite compound particles of CeZr-based mixed oxide and Al 2 O 3 is for the CeZr-based mixed oxide primary particles and Al 2 O 3 primary particles formed by agglomerating, Al 2 O 3 primary particles steric hindrance As a result, sintering of the CeZr-based composite oxide primary particles is suppressed, and a high specific surface area is maintained even after long-term use. In the case of BaSO 4 particles, the specific surface area as large as active Al 2 O 3 is not provided, but even when exposed to high-temperature exhaust gas, the specific surface area does not substantially decrease, and as a support material for Pt and Pd, It is extremely stable, and poisoning (deterioration of the catalyst) due to P, Zn, and S mixed from the engine oil into the exhaust gas is reduced.
上記ペロブスカイト型複合酸化物粉末は、当該ペロブスカイト型複合酸化物粒子にＰｔ、Ｐｄ及びＲｈから選ばれる少なくとも一種が担持されてなるものであることが好ましい。これにより、ペロブスカイト型複合酸化物粉末の酸素吸蔵放出性能が高まるとともに、排気ガスの浄化に有利になる。 The perovskite complex oxide powder is preferably formed by supporting at least one kind selected from Pt, Pd and Rh on the perovskite complex oxide particles. As a result, the oxygen storage / release performance of the perovskite complex oxide powder is enhanced, and it is advantageous for purification of exhaust gas.
上記課題を解決する第２の手段は、ＣｅとＺｒとを含有するＣｅＺｒ系複合酸化物粒子にＲｈが固溶しているＲｈドープＣｅＺｒ系複合酸化物粉末と、耐熱性粒子にＰｔ及びＰｄの少なくとも一方の貴金属が担持された貴金属担持耐熱性粉末とが担体上の触媒層に含まれている排気ガス浄化用触媒であって、 A second means for solving the above problem is that Rh-doped CeZr-based composite oxide powder in which Rh is solid-solved in CeZr-based composite oxide particles containing Ce and Zr, and heat-resistant particles of Pt and Pd. An exhaust gas purifying catalyst comprising a noble metal-supporting heat-resistant powder on which at least one noble metal is supported and contained in a catalyst layer on a carrier,
上記触媒層は、単層又は複数の層よりなり、さらに、ペロブスカイト型複合酸化物粉末を含有し、該ペロブスカイト型複合酸化物粉末と上記ＲｈドープＣｅＺｒ系複合酸化物粉末とは、同じ層中に混在し、若しくは隣接する二層に分かれており、 The catalyst layer is composed of a single layer or a plurality of layers, and further contains a perovskite-type composite oxide powder. The perovskite-type composite oxide powder and the Rh-doped CeZr-based composite oxide powder are in the same layer. It is mixed or divided into two adjacent layers,
上記ペロブスカイト型複合酸化物粉末は、当該ペロブスカイト型複合酸化物粒子にＰｔ、Ｐｄ及びＲｈから選ばれる少なくとも一種が担持されてなるものであることを特徴とする。 The perovskite complex oxide powder is characterized in that at least one selected from Pt, Pd and Rh is supported on the perovskite complex oxide particles.
これにより、上記第１の手段と同じく、ペロブスカイト型複合酸化物粉末から放出される酸素の活性化が図れ、この酸素が貴金属担持耐熱性粉末のＰｔ又はＰｄによるＨＣやＣＯの酸化に有効に利用され、ＨＣやＣＯの酸化、これに伴うＮＯｘの還元が効率良く進む。また、排気ガスが比較的長い時間リーンになるときに、ＲｈドープＣｅＺｒ系複合酸化物粉末まわりや貴金属担持耐熱性粉末まわりが酸素過剰雰囲気になることが抑制されるため、これら触媒成分によるＮＯｘの還元に有利になる。 As a result, the oxygen released from the perovskite complex oxide powder can be activated as in the first means, and this oxygen is effectively used for the oxidation of HC and CO by Pt or Pd of the noble metal-supported heat-resistant powder. Thus, the oxidation of HC and CO and the accompanying reduction of NOx proceed efficiently. Further, when the exhaust gas is lean for a relatively long time, it is suppressed that the atmosphere around the Rh-doped CeZr-based composite oxide powder and the noble metal-supported heat-resistant powder is in an oxygen-excess atmosphere. It is advantageous for reduction.
そうして、ペロブスカイト型複合酸化物粉末は、当該ペロブスカイト型複合酸化物粒子にＰｔ、Ｐｄ及びＲｈから選ばれる少なくとも一種が担持されてなるから、その酸素吸蔵放出性能が高まるとともに、排気ガスの浄化に有利になる。 Thus, since the perovskite type complex oxide powder has at least one selected from Pt, Pd and Rh supported on the perovskite type complex oxide particles, its oxygen storage / release performance is enhanced and the exhaust gas is purified. To be advantageous.
好ましい実施形態では、上記触媒層が上下に隣接するように積層された上層と下層とを有し、上層にＲｈドープＣｅＺｒ系複合酸化物粉末が含まれ、下層にペロブスカイト型複合酸化物粉末が含まれている。これにより、下層のペロブスカイト型複合酸化物粉末から放出される酸素が上層に入っていくため、該上層のＲｈドープＣｅＺｒ系複合酸化物粉末が当該酸素の活性化に効率良く働く。 In a preferred embodiment, the catalyst layer has an upper layer and a lower layer laminated so as to be adjacent to each other, the upper layer includes an Rh-doped CeZr-based complex oxide powder, and the lower layer includes a perovskite-type complex oxide powder. It is. As a result, oxygen released from the lower perovskite complex oxide powder enters the upper layer, so that the upper Rh-doped CeZr-based composite oxide powder efficiently works to activate the oxygen.
また、上記ペロブスカイト型複合酸化物粉末は、Ｒｈ以外の触媒金属（例えば、Ｐｔ、Ｐｄ等）が固溶したペロブスカイト型複合酸化物粉末であることが好ましい。触媒金属の固溶により、ペロブスカイト型複合酸化物粉末の酸素吸蔵放出性能が高まるとともに、排気ガスの浄化に有利になる。 The perovskite complex oxide powder is preferably a perovskite complex oxide powder in which a catalyst metal other than Rh (eg, Pt, Pd, etc.) is dissolved. The solid solution of the catalyst metal enhances the oxygen storage / release performance of the perovskite-type composite oxide powder, and is advantageous for purification of exhaust gas.
以上のように、本発明によれば、担体上の触媒層がＲｈドープＣｅＺｒ系複合酸化物粉末と貴金属担持耐熱性粉末とペロブスカイト型複合酸化物粉末とを含有し、且つその触媒層が単層又は複数の層よりなり、ペロブスカイト型複合酸化物粉末とＲｈドープＣｅＺｒ系複合酸化物粉末とは、同じ層中に混在し、若しくは隣接する二層に分かれており、ＲｈドープＣｅＺｒ系複合酸化物粉末によって、ペロブスカイト型複合酸化物粉末から放出される酸素の活性化が図れるため、該ペロブスカイト型複合酸化物粉末から放出される酸素が、貴金属担持耐熱性粉末のＰｔ又はＰｄによるＨＣやＣＯの酸化に有効に利用されることになり、ＨＣやＣＯの酸化、これに伴うＮＯｘの還元が効率良く進み、しかも、排気ガスが比較的長い時間リーンになるときに、ＲｈドープＣｅＺｒ系複合酸化物粉末まわりや貴金属担持耐熱性粉末まわりが酸素過剰雰囲気になることが抑制され、これら触媒成分によるＮＯｘの還元に有利になる。 As described above, according to the present invention, the catalyst layer on the support contains the Rh-doped CeZr-based composite oxide powder, the noble metal-supported heat-resistant powder, and the perovskite-type composite oxide powder, and the catalyst layer is a single layer. Alternatively, the perovskite-type composite oxide powder and the Rh-doped CeZr-based composite oxide powder are mixed in the same layer or divided into two adjacent layers, and the Rh-doped CeZr-based composite oxide powder. As a result, the oxygen released from the perovskite complex oxide powder can be activated, so that the oxygen released from the perovskite complex oxide powder is used to oxidize HC and CO by Pt or Pd of the noble metal-supported heat-resistant powder. It will be used effectively, the oxidation of HC and CO, and the accompanying reduction of NOx will proceed efficiently, and the exhaust gas will be lean for a relatively long time. When the, Rh-doped CeZr-based mixed oxide powder around or precious-metal-supporting heat-resistant powder around is suppressed to become an oxygen-rich atmosphere, which is advantageous in the reduction of NOx by these catalyst components.
そうして、第１の手段に係る発明によれば、上記貴金属担持耐熱性粉末は、その貴金属を担持する耐熱性粒子が、Ｌａを含有する活性Ａｌ Thus, according to the invention relating to the first means, the noble metal-supported heat-resistant powder has an active Al in which the heat-resistant particles supporting the noble metal contain La. ２2 ＯO ３3 粒子、ＢａＳＯParticles, BaSO ４4 粒子、並びにＣｅＺｒ系複合酸化物とＡｌParticles, and CeZr-based composite oxide and Al ２2 ＯO ３3 との複合化物粒子から選ばれる少なくとも一種であるから、良好な触媒性能と耐熱性が得られる。Therefore, good catalytic performance and heat resistance can be obtained.
また、第２の手段に係る発明によれば、上記ペロブスカイト型複合酸化物粉末は、当該ペロブスカイト型複合酸化物粒子にＰｔ、Ｐｄ及びＲｈから選ばれる少なくとも一種が担持されてなるから、その酸素吸蔵放出性能が高まるとともに、排気ガスの浄化に有利になる。 Further, according to the invention relating to the second means, the perovskite complex oxide powder is formed by supporting at least one kind selected from Pt, Pd and Rh on the perovskite complex oxide particles. The emission performance is enhanced and it is advantageous for purification of exhaust gas.
以下、本発明を実施するための形態を図面に基づいて説明する。尚、以下の好ましい実施形態の説明は、本質的に例示に過ぎず、本発明、その適用物或いはその用途を制限することを意図するものではない。
＜実施形態１＞
図１に示すエンジンの排気ガス浄化用触媒において、１はハニカム担体であり、該ハニカム担体１のセル壁面１ａに触媒層２が形成されている。この触媒層２は、酸素吸蔵放出能を有するＲｈドープＣｅＺｒ系複合酸化物粉末と貴金属担持耐熱性粉末とペロブスカイト型複合酸化物粉末とを混合状態で含有する。
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.
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In the engine exhaust gas purification catalyst shown in FIG. 1,
ＲｈドープＣｅＺｒ系複合酸化物粉末は、ＣｅとＺｒとを含有するＣｅＺｒ系複合酸化物粒子にＲｈが固溶したものである。このＣｅＺｒ系複合酸化物粒子は、さらにＮｄ、Ｐｒ、Ｌａ及びＹから選ばれる少なくとも一種を含有するものとすることができ、又はＡｌ２Ｏ３が複合されたものとすることができる。Ａｌ２Ｏ３が複合されたＣｅＺｒ系複合酸化物粒子（二次粒子）は、ＣｅＺｒ系複合酸化物の一次粒子とＡｌ２Ｏ３の一次粒子とが凝集してなるものである。 The Rh-doped CeZr-based composite oxide powder is obtained by dissolving Rh in CeZr-based composite oxide particles containing Ce and Zr. The CeZr-based composite oxide particles may further contain at least one selected from Nd, Pr, La, and Y, or may be a composite of Al 2 O 3 . CeZr-based composite oxide particles (secondary particles) in which Al 2 O 3 is composited are formed by agglomeration of primary particles of CeZr-based composite oxide and primary particles of Al 2 O 3 .
貴金属担持耐熱性粉末は、耐熱性酸化物粒子にＰｔ及びＰｄの少なくとも一方の貴金属が担持されたものである。その耐熱性粒子は、Ｌａを含有する活性Ａｌ２Ｏ３粒子（Ｌａ含有Ａｌ２Ｏ３）、ＢａＳＯ４粒子、並びにＣｅＺｒ系複合酸化物とＡｌ２Ｏ３との複合化物粒子（ＣｅＺｒＡｌ）から選ばれる少なくとも一種とすることができる。 The noble metal-supported heat-resistant powder is obtained by supporting at least one of Pt and Pd on a heat-resistant oxide particle. The heat-resistant particles are selected from La-containing active Al 2 O 3 particles (La-containing Al 2 O 3 ), BaSO 4 particles, and composite particles of CeZr-based composite oxide and Al 2 O 3 (CeZrAl). Can be at least one kind.
ペロブスカイト型複合酸化物粉末は、一般式ＡＢＯ３で表され、Ａは希土類元素及びアルカリ土類金属から選ばれる少なくとも１種、Ｂは遷移元素から選ばれる少なくとも１種である。好ましいのは、ＬａＧａＯ３系のペロブスカイト型複合酸化物粉末であり、そのＡサイト（Ｌａサイト）及びＢサイト（Ｇａサイト）の少なくとも一方に２Ａ族元素が固溶していることである。特にＡサイトにＳｒが固溶し、ＢサイトにＭｇが固溶していることが好ましい。 The perovskite complex oxide powder is represented by the general formula ABO 3 , wherein A is at least one selected from rare earth elements and alkaline earth metals, and B is at least one selected from transition elements. Preference is given to LaGaO 3 -based perovskite complex oxide powders in which the group 2A element is in solid solution at least one of its A site (La site) and B site (Ga site). In particular, it is preferable that Sr is dissolved in the A site and Mg is dissolved in the B site.
或いは、触媒金属を含有するペロブスカイト型複合酸化物粉末も好ましい。例えば一般式ＡＢ１−ＸＣＸＯ３（ＡはＬａ、Ｓｒ、Ｃｅ、Ｂａ又はＣａのうちの少なくとも一種、ＢはＣｏ、Ｆｅ、Ｎｉ、Ｃｒ、Ｍｎ又はＭｇのうちの少なくとも一種、ＣはＰｔ又はＰｄのうちの少なくとも一種、０．０５≦Ｘ≦０．２）で表されるペロブスカイト型複合酸化物粉末である。 Alternatively, a perovskite complex oxide powder containing a catalyst metal is also preferable. For example, the general formula AB 1-X C X O 3 (A is at least one of La, Sr, Ce, Ba or Ca, B is at least one of Co, Fe, Ni, Cr, Mn or Mg, and C is It is a perovskite type complex oxide powder represented by at least one of Pt and Pd, 0.05 ≦ X ≦ 0.2).
[実施例及び比較例]
−ＲｈドープＣｅＺｒ系複合酸化物粉末−
ＲｈドープＣｅＺｒ系複合酸化物粉末として、ＣｅＺｒＮｄ複合酸化物粒子にＲｈが固溶したＲｈ−ＣｅＺｒＮｄ粉末を準備した。すなわち、Ｃｅ、Ｚｒ、Ｎｄ及びＲｈの各硝酸塩を含む溶液にアンモニア水を攪拌しながら添加して中和させ、得られた共沈物を水洗した後、大気雰囲気において１５０℃の温度で一昼夜乾燥させ、粉砕し、さらに５００℃の温度に２時間保持する焼成を行なうことにより、当該Ｒｈ−ＣｅＺｒＮｄ粉末を得た。ドープされたＲｈのうちの少なくとも一部は当該複合酸化物粒子の表面に露出している。このＲｈドープＣｅＺｒ系複合酸化物のＲｈを除く組成比はＣｅＯ２：ＺｒＯ２：Ｎｄ２Ｏ３＝４５：４５：１０（質量％）であり、Ｒｈドープ量は０．１質量％である。
[Examples and Comparative Examples]
-Rh-doped CeZr-based composite oxide powder-
As the Rh-doped CeZr-based composite oxide powder, an Rh—CeZrNd powder in which Rh was dissolved in CeZrNd composite oxide particles was prepared. That is, ammonia water is added to a solution containing nitrates of Ce, Zr, Nd, and Rh with neutralization while stirring, and the resulting coprecipitate is washed with water, and then dried in an air atmosphere at a temperature of 150 ° C. overnight. The obtained Rh—CeZrNd powder was obtained by firing, pulverizing, and firing at a temperature of 500 ° C. for 2 hours. At least a part of the doped Rh is exposed on the surface of the composite oxide particle. The composition ratio of the Rh-doped CeZr-based composite oxide excluding Rh is CeO 2 : ZrO 2 : Nd 2 O 3 = 45: 45: 10 (mass%), and the Rh doping amount is 0.1 mass%.
−貴金属担持耐熱性粉末−
貴金属担持耐熱性粉末として、各々Ｐｄを担持したＬａ含有Ａｌ２Ｏ３、ＢａＳＯ４、及びＣｅＺｒＡｌ、並びに各々Ｐｔを担持したＬａ含有Ａｌ２Ｏ３、ＢａＳＯ４、及びＣｅＺｒＡｌの各粉末を準備した。ＣｅＺｒＡｌは次の方法によって得た。すなわち、硝酸Ａｌ水溶液にアンモニア水を攪拌しながら添加して、アルミナ粒子の前駆体である水酸化Ａｌの沈殿を得た。この沈殿を生じた溶液に、アンモニア水溶液を添加した後、Ｃｅ及びＺｒの各硝酸塩水溶液を添加して混合し、Ｃｅ及びＺｒの各水酸化物の共沈物と上記水酸化Ａｌとの混合物を得た。この混合沈殿物を水洗し、大気雰囲気において１５０℃の温度で一昼夜乾燥させ、粉砕し、さらに５００℃の温度に２時間保持する焼成を行なった。これにより、Ｃｅ及びＺｒを含有するＣｅＺｒ複合酸化物の一次粒子とアルミナの一次粒子とが凝集してなる当該ＣｅＺｒＡｌ粉末を得た。その組成比はＣｅＯ２：ＺｒＯ２：Ａｌ２Ｏ３＝２５：２５：５０（質量％）である。また、Ｌａ含有Ａｌ２Ｏ３は、Ｌａ２Ｏ３を４質量％含有するものである。
-Precious metal-supported heat-resistant powder-
Noble metal-supporting heat-resistant powder, each containing La carrying Pd Al 2 O 3, BaSO 4 , and CeZrAl, and La-containing carrying each Pt Al 2 O 3, BaSO 4 , and were prepared powders of CeZrAl. CeZrAl was obtained by the following method. That is, ammonia water was added to an aqueous solution of Al nitrate while stirring to obtain a precipitate of Al hydroxide, which is a precursor of alumina particles. An aqueous ammonia solution is added to the solution resulting from the precipitation, and then an aqueous nitrate solution of Ce and Zr is added and mixed. The coprecipitate of Ce and Zr hydroxide and the above-mentioned Al hydroxide is mixed. Obtained. The mixed precipitate was washed with water, dried in an air atmosphere at a temperature of 150 ° C. for a whole day and night, pulverized, and further calcined at a temperature of 500 ° C. for 2 hours. Thereby, the CeZrAl powder obtained by agglomerating primary particles of CeZr composite oxide containing Ce and Zr and primary particles of alumina was obtained. The composition ratio is CeO 2 : ZrO 2 : Al 2 O 3 = 25: 25: 50 (mass%). La-containing Al 2 O 3 contains 4% by mass of La 2 O 3 .
−ペロブスカイト型複合酸化物粉末−
ペロブスカイト型複合酸化物粉末として、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末及びＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末を準備した。
-Perovskite complex oxide powder-
La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder and LaFe 0.98 Pd 0.02 O 3 powder were prepared as the perovskite complex oxide powder.
Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末は次の方法によって得た。すなわち、Ｌａ及びＧａの各硝酸塩と、Ｓｒ及びＭｇの各酢酸塩をイオン交換水に溶解し混合した後、エバポレータを用いて減圧下で蒸発乾固させ、さらにホットプレート上で乾燥させた後、電気炉により４００℃の温度で３時間の仮焼成を行なった。得られた生成物を乳鉢で粉砕した後、電気炉にて１３００℃の温度で２４時間の本焼成を行なうことにより、当該粉末を得た。 La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder was obtained by the following method. That is, each nitrate of La and Ga and each acetate of Sr and Mg were dissolved and mixed in ion-exchanged water, then evaporated to dryness under reduced pressure using an evaporator, and further dried on a hot plate, Pre-baking was performed for 3 hours at a temperature of 400 ° C. in an electric furnace. The obtained product was pulverized in a mortar and then subjected to main baking at a temperature of 1300 ° C. for 24 hours in an electric furnace to obtain the powder.
ＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末は次の方法によって得た。Ｌａ、Ｆｅ及びＰｄの各硝酸塩、並びにクエン酸(無水）を蒸留水に入れて攪拌した後、加熱して溶媒を除去することにより、Ｌａ、Ｆｅ及びＰｄのクエン酸錯体の混合物を得た。このクエン酸錯体混合物を、大気中において、４００℃の温度に２時間加熱保持する仮焼成を行なった後、１０００℃の温度に６時間加熱保持する本焼成を行なった。得られた焼成品を粉砕して当該粉末を得た。 LaFe 0.98 Pd 0.02 O 3 powder was obtained by the following method. La, Fe and Pd nitrates and citric acid (anhydrous) were placed in distilled water and stirred, and then the solvent was removed by heating to obtain a mixture of citrate complexes of La, Fe and Pd. This citric acid complex mixture was calcined in the air at a temperature of 400 ° C. for 2 hours and then calcined at a temperature of 1000 ° C. for 6 hours. The obtained fired product was pulverized to obtain the powder.
−Ｒｈ担持ＣｅＺｒ系複合酸化物粉末−
ＣｅＺｒＮｄ複合酸化物粒子にＲｈを蒸発乾固によって担持させることにより、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末を得た。ＣｅＺｒＮｄ複合酸化物粒子の組成比はＣｅＯ２：ＺｒＯ２：Ｎｄ２Ｏ３＝４５：４５：１０（質量％）であり、Ｒｈ担持量は、０．１質量％となるようにした。
-Rh-supported CeZr composite oxide powder-
Rh-supported CeZr-based composite oxide powder was obtained by supporting Rh on the CeZrNd composite oxide particles by evaporation to dryness. The composition ratio of the CeZrNd composite oxide particles was CeO 2 : ZrO 2 : Nd 2 O 3 = 45: 45: 10 (mass%), and the Rh loading was 0.1 mass%.
−実施例１に係る触媒の調製−
ＲｈドープＣｅＺｒ系複合酸化物粉末と、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末と、貴金属担持耐熱性粉末（Ｐｔ担持Ｌａ含有Ａｌ２Ｏ３、Ｐｔ担持ＢａＳＯ４、Ｐｔ担持ＣｅＺｒＡｌのいずれか一）とを組み合わせて混合し、ハニカム担体にコーティングすることにより、実施例１に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌである。なお、ＲｈドープＣｅＺｒ系複合酸化物粉末など触媒粉末のコーティングは、該触媒粉末にバインダ及び水を加えてスラリー化して行なった（以下、同じ）。
-Preparation of catalyst according to Example 1-
Rh-doped CeZr-based composite oxide powder, La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder, noble metal-supported heat-resistant powder (Pt-supported La-containing Al 2 O 3 , Pt-supported BaSO 4 , Any one of Pt-supported CeZrAl) was mixed in combination and coated on a honeycomb carrier, thereby preparing three types of catalysts having different types of noble metal-supported heat-resistant powder according to Example 1. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-doped CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, 1.0 g / L for Pt, and La 0.9 Sr 0.1 Ga 0. .8 Mg 0.2 O 3 powder is 20 g / L. The coating of the catalyst powder such as the Rh-doped CeZr composite oxide powder was performed by adding a binder and water to the catalyst powder to form a slurry (hereinafter the same).
ハニカム担体としては、いずれもセル壁厚さ３．５mil（８．８９×１０−２ｍｍ）、１平方インチ（６４５．１６ｍｍ２）当たりのセル数６００のコージェライト製であり、直径２５．４ｍｍ、長さ５０ｍｍの円柱形状のもの（容量２５ｍｌ）を用いた。この点は後述する他の実施例及び比較例も同じである。 The honeycomb carrier is made of cordierite having a cell wall thickness of 3.5 mil (8.89 × 10 −2 mm) and 600 cells per square inch (645.16 mm 2 ), and a diameter of 25.4 mm. A cylindrical shape having a length of 50 mm (capacity 25 ml) was used. This also applies to other examples and comparative examples described later.
−実施例２に係る触媒の調製−
Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末に代えてＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末を採用し、他は実施例１と同様にして実施例２に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、ＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Example 2-
In place of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder, LaFe 0.98 Pd 0.02 O 3 powder was employed, and the rest of the same manner as in Example 1 was followed in Example 2. Three types of catalysts with different types of such precious metal-supported heat-resistant powders were prepared. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-doped CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat resistant powder, 1.0 g / L for Pt, and LaFe 0.98 Pd 0.02 O 3. The powder is 20 g / L.
−実施例３に係る触媒の調製−
貴金属担持耐熱性粉末として、Ｐｄ担持Ｌａ含有Ａｌ２Ｏ３、Ｐｄ担持ＢａＳＯ４、Ｐｄ担持ＣｅＺｒＡｌのいずれか一を採用し、他は実施例１と同様にして実施例３に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｄが１．０ｇ／Ｌ、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Example 3-
As the noble metal-supported heat-resistant powder, any one of Pd-supported La-containing Al 2 O 3 , Pd-supported BaSO 4 , and Pd-supported CeZrAl is adopted, and the other noble metal-supported heat resistance according to Example 3 is used. Three types of catalysts with different powder types were prepared. The supported amount per liter of honeycomb carrier is 100 g / L for Rh-doped CeZr-based composite oxide powder, 50 g / L for noble metal-supported heat-resistant powder, 1.0 g / L for Pd, La 0.9 Sr 0.1 Ga 0. .8 Mg 0.2 O 3 powder is 20 g / L.
−比較例１に係る触媒の調製−
ＲｈドープＣｅＺｒ系複合酸化物粉末に代えてＲｈ担持ＣｅＺｒ系複合酸化物を採用し、他は実施例１と同様にして比較例１に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Comparative Example 1-
Instead of the Rh-doped CeZr-based composite oxide powder, an Rh-supported CeZr-based composite oxide was adopted, and the other three types of catalysts differing in the type of noble metal-supported heat-resistant powder according to Comparative Example 1 were used in the same manner as in Example 1. Prepared. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-supported CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, 1.0 g / L for Pt, and La 0.9 Sr 0.1 Ga 0. .8 Mg 0.2 O 3 powder is 20 g / L.
−比較例２に係る触媒の調製−
ＲｈドープＣｅＺｒ系複合酸化物粉末に代えてＲｈ担持ＣｅＺｒ系複合酸化物を採用し、他は実施例３と同様にして比較例２に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｄが１．０ｇ／Ｌ、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Comparative Example 2-
Instead of the Rh-doped CeZr-based composite oxide powder, an Rh-supported CeZr-based composite oxide was adopted, and the other three types of catalysts having different types of noble metal-supported heat-resistant powder according to Comparative Example 2 were used in the same manner as in Example 3. Prepared. The supported amount per liter of honeycomb carrier is 100 g / L for the Rh-supported CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, 1.0 g / L for Pd, and La 0.9 Sr 0.1 Ga 0. .8 Mg 0.2 O 3 powder is 20 g / L.
−比較例３に係る触媒の調製−
Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末量を零とし、ＲｈドープＣｅＺｒ系複合酸化物粉末を増量する他は実施例１と同様にして比較例３に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１２０ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌである。
-Preparation of catalyst according to Comparative Example 3-
A noble metal according to Comparative Example 3 in the same manner as in Example 1 except that the amount of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder is set to zero and the amount of Rh-doped CeZr-based composite oxide powder is increased. Three types of catalysts with different types of supported heat-resistant powders were prepared. The supported amount per liter of the honeycomb carrier is 120 g / L for the Rh-doped CeZr composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, and 1.0 g / L for Pt.
−比較例４に係る触媒の調製−
ＲｈドープＣｅＺｒ系複合酸化物粉末量を零とし、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末量を増量する他は実施例１と同様にして比較例４に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が１２０ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌである。
-Preparation of catalyst according to Comparative Example 4-
According to Comparative Example 4 as in Example 1, except that the amount of Rh-doped CeZr-based composite oxide powder is zero and the amount of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder is increased. Three types of catalysts with different types of noble metal-supported heat-resistant powders were prepared. The supported amount per 1 L of honeycomb carrier is 120 g / L for La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder, 50 g / L for noble metal-supported heat-resistant powder, and 1.0 g / L for Pt. It is.
−排気ガス浄化性能評価−
実施例及び比較例の各触媒について、大気雰囲気において１０００℃の温度に２４時間加熱するエージングを行なった。次いで、これら触媒をモデルガス流通反応装置に取り付け、評価用モデルガスによってＨＣ、ＣＯ及びＮＯｘの浄化に関するライトオフ温度Ｔ５０を測定した。Ｔ５０は、触媒に流入するモデルガス温度を常温から漸次上昇させていき、浄化率が５０％に達したときの触媒入口のガス温度である。評価用のモデルガスは、Ａ／Ｆ＝１４．７±０．９とした。すなわち、Ａ／Ｆ＝１４．７のメインストリームガスを定常的に流しつつ、所定量の変動用ガスを１Ｈｚでパルス状に添加することにより、Ａ／Ｆを±０．９の振幅で強制的に振動させた。空間速度ＳＶは６００００ｈ−１、昇温速度は３０℃／分である。
−Evaluation of exhaust gas purification performance−
About each catalyst of an Example and a comparative example, the aging which heats to the temperature of 1000 degreeC in air | atmosphere for 24 hours was performed. Next, these catalysts were attached to the model gas flow reactor, and the light-off temperature T50 relating to the purification of HC, CO, and NOx was measured with the model gas for evaluation. T50 is the gas temperature at the catalyst inlet when the temperature of the model gas flowing into the catalyst is gradually increased from room temperature and the purification rate reaches 50%. The model gas for evaluation was A / F = 14.7 ± 0.9. That is, the A / F is forced at an amplitude of ± 0.9 by adding a predetermined amount of fluctuation gas in a pulse form at 1 Hz while constantly flowing the main stream gas of A / F = 14.7. Vibrated. The space velocity SV is 60000 h −1 , and the heating rate is 30 ° C./min.
結果を表１に示す。なお、表１において、「Ｒｈドープ材」は「ＲｈドープＣｅＺｒ系複合酸化物粉末」、「Ｒｈ担持材」は「Ｒｈ担持ＣｅＺｒ系複合酸化物粉末」、「ＬａＳｒＧａＭｇＯ」は「Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末」、「ＬａＦｅＰｄＯ」は「ＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末」、「Ａｌ2Ｏ3」は「Ａｌ２Ｏ３」、「ＢａＳＯ4」は「ＢａＳＯ４」である。この点は後述する表２も同じである。 The results are shown in Table 1. In Table 1, “Rh-doped material” is “Rh-doped CeZr-based composite oxide powder”, “Rh-supported material” is “Rh-supported CeZr-based composite oxide powder”, and “LaSrGaMgO” is “La 0.9 Sr”. “0.1 Ga 0.8 Mg 0.2 O 3 powder”, “LaFePdO” is “LaFe 0.98 Pd 0.02 O 3 powder”, “Al 2 O 3 ” is “Al 2 O 3 ”, and “BaSO 4” is “ BaSO 4 ”. This also applies to Table 2 described later.
まず、比較例３と比較例４とを比較すると、ＨＣ、ＣＯ及びＮＯｘいずれの浄化に関しても、比較例３の方が比較例４よりもＴ５０は低い。これから、酸素吸蔵放出材としては、ペロブスカイト型複合酸化物粉末よりもＲｈドープＣｅＺｒ系複合酸化物粉末の方が優れているということができる。 First, when Comparative Example 3 and Comparative Example 4 are compared, Comparative Example 3 has a lower T50 than Comparative Example 4 in terms of purification of HC, CO, and NOx. From this, it can be said that the Rh-doped CeZr-based composite oxide powder is superior to the perovskite-type composite oxide powder as the oxygen storage / release material.
次にＣｅＺｒ系複合酸化物粉末とペロブスカイト型複合酸化物粉末との組み合わせについて検討する。貴金属担持耐熱性粉末の貴金属としてＰｔを採用した実施例１と比較例１とを比較すると、Ｐｔを担持する耐熱性粉末の種類が同じであるケースでは、実施例１の方が比較例１よりもＴ５０は低い。また、貴金属としてＰｄを採用した実施例３と比較例２とを比較した場合でも、同じく、実施例３の方が比較例２よりもＴ５０は低い。これから、貴金属担持耐熱性粉末の貴金属がＰｔ、Ｐｄいずれの場合でも、ペロブスカイト型複合酸化物粉末にＲｈドープＣｅＺｒ系複合酸化物粉末を組み合わせると、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末を組み合わせる場合よりも排気ガス浄化性能が高くなることがわかる。 Next, a combination of CeZr-based complex oxide powder and perovskite complex oxide powder will be examined. Comparing Example 1 in which Pt is used as the noble metal-supporting heat-resistant powder and Comparative Example 1, in the case where the kind of the heat-resistant powder supporting Pt is the same, Example 1 is more than Comparative Example 1. T50 is low. Even when Example 3 employing Pd as a noble metal is compared with Comparative Example 2, similarly, Example 3 has a lower T50 than Comparative Example 2. From this, when the noble metal-supported heat-resistant powder is either Pt or Pd, when the Rh-doped CeZr-based composite oxide powder is combined with the perovskite-type composite oxide powder, the Rh-supported CeZr-based composite oxide powder is combined. It can be seen that the exhaust gas purification performance is improved.
実施例１と実施例２とを比較すると、実施例２の方がＴ５０は低い。これから、ペロブスカイト型複合酸化物粉末としては、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末よりもＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末の方が良いことがわかる。 When Example 1 is compared with Example 2, Example 2 has a lower T50. From this, it can be seen that as the perovskite type complex oxide powder, LaFe 0.98 Pd 0.02 O 3 powder is better than La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder. .
次に貴金属担持耐熱性粉末の耐熱性粒子の種類がＴ５０に及ぼす影響をみると、Ｌａ含有Ａｌ２Ｏ３を用いたときのＴ５０が最も低く、これにＣｅＺｒＡｌ及びＢａＳＯ４が順に続いている。また、耐熱性粒子に担持する貴金属で比較すると、Ｐｄを担持した実施例３の方がＰｔを担持した実施例１よりも、Ｔ５０は低くなっている。
＜実施形態２＞
本実施形態のエンジンの排気ガス浄化用触媒に係る触媒層構造は図２に示されている。ハニカム担体１のセル壁面１ａに形成されている触媒層２は、実施形態１とは違って、上層２ａ及び下層２ｂの二層構造になっている。上層２ａ及び下層２ｂの一方がＲｈドープＣｅＺｒ系複合酸化物粉末と貴金属担持耐熱性粉末とを含有する層となり、他方がペロブスカイト型複合酸化物粉末を含有する層となる。好ましいのは、上層２ａがＲｈドープＣｅＺｒ系複合酸化物粉末と貴金属担持耐熱性粉末とを含有する層となり、下層２ｂがペロブスカイト型複合酸化物粉末を含有する層となることである。
Next, looking at the effect of the kind of heat-resistant particles of the noble metal-supported heat-resistant powder on T50, T50 is the lowest when La-containing Al 2 O 3 is used, followed by CeZrAl and BaSO 4 in this order. Further, when compared with the noble metal supported on the heat-resistant particles, T3 is lower in Example 3 supporting Pd than in Example 1 supporting Pt.
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The catalyst layer structure relating to the exhaust gas purifying catalyst of the engine of this embodiment is shown in FIG. Unlike
[実施例及び比較例]
−実施例４に係る触媒の調製−
Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末をハニカム担体にコーティングして下層２ｂを形成した後、ＲｈドープＣｅＺｒ系複合酸化物粉末と貴金属担持耐熱性粉末（Ｐｔ担持Ｌａ含有Ａｌ２Ｏ３、Ｐｔ担持ＢａＳＯ４、Ｐｔ担持ＣｅＺｒＡｌのいずれか一）とを組み合わせて混合し、下層２ｂの上にコーティングすることにより、上層２ａを形成した。この方法により、実施例４に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌである。
[Examples and Comparative Examples]
-Preparation of catalyst according to Example 4-
After coating the honeycomb carrier with La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder to form the
−実施例５に係る触媒の調製−
Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末に代えてＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末を採用し、他は実施例４と同様にして実施例５に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、ＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Example 5-
In place of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder, LaFe 0.98 Pd 0.02 O 3 powder was adopted, and the same procedure as in Example 4 was applied to Example 5. Three types of catalysts with different types of such precious metal-supported heat-resistant powders were prepared. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-doped CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat resistant powder, 1.0 g / L for Pt, and LaFe 0.98 Pd 0.02 O 3. The powder is 20 g / L.
−実施例６に係る触媒の調製−
実施例５とは逆に、下層がＲｈドープＣｅＺｒ系複合酸化物粉末と貴金属担持耐熱性粉末とを含有し、上層がＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末を含有する構成とする他は、実施例４と同様にして実施例６に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、ＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Example 6-
Contrary to Example 5, the lower layer contains Rh-doped CeZr-based composite oxide powder and noble metal-supported heat-resistant powder, and the upper layer contains LaFe 0.98 Pd 0.02 O 3 powder. In the same manner as in Example 4, three types of catalysts having different types of noble metal-supported heat-resistant powder according to Example 6 were prepared. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-doped CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat resistant powder, 1.0 g / L for Pt, and LaFe 0.98 Pd 0.02 O 3. The powder is 20 g / L.
−実施例７に係る触媒の調製−
ペロブスカイト型複合酸化物粉末として、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末にＰｄを蒸発乾固法によって担持させた粉末を採用し、他は実施例４と同様にして実施例７に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。但し、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末にＰｄを担持させたことに対応させて、貴金属担持耐熱性粉末のＰｔ担持量を減らした。すなわち、ハニカム担体１Ｌ当たりの担持量は、ＲｈドープＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｄ担持Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌであり、貴金属担持耐熱性粉末によるハニカム担体へのＰｔ担持量が０．８ｇ／Ｌ、Ｐｄ担持Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末によるハニカム担体へのＰｄ担持量が０．２ｇ／Ｌである。
-Preparation of catalyst according to Example 7-
As the perovskite-type composite oxide powder, a powder in which Pd is supported on an La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder by evaporation to dryness is used, and the others are the same as in Example 4. Thus, three types of catalysts having different types of noble metal-supported heat-resistant powder according to Example 7 were prepared. However, the amount of Pt supported on the noble metal-supported heat-resistant powder was reduced corresponding to the fact that Pd was supported on the La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 powder. That is, the supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-doped CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, and Pd-supported La 0.9 Sr 0.1 Ga 0.8 Mg 0. .2 O 3 powder is 20 g / L, Pt supported amount on honeycomb carrier by noble metal supported heat resistant powder is 0.8 g / L, Pd supported La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 The amount of Pd supported on the honeycomb carrier by the O 3 powder is 0.2 g / L.
−比較例５に係る触媒の調製−
ＲｈドープＣｅＺｒ系複合酸化物粉末に代えてＲｈ担持ＣｅＺｒ系複合酸化物を採用し、他は実施例４と同様にして比較例５に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Comparative Example 5-
Instead of the Rh-doped CeZr-based composite oxide powder, an Rh-supported CeZr-based composite oxide was adopted, and the other three types of catalysts with different types of noble metal-supported heat-resistant powder according to Comparative Example 5 were used in the same manner as in Example 4. Prepared. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-supported CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, 1.0 g / L for Pt, and La 0.9 Sr 0.1 Ga 0. .8 Mg 0.2 O 3 powder is 20 g / L.
−比較例６に係る触媒の調製−
ＲｈドープＣｅＺｒ系複合酸化物粉末に代えてＲｈ担持ＣｅＺｒ系複合酸化物を採用し、他は実施例５と同様にして比較例６に係る貴金属担持耐熱性粉末の種類が異なる３種類の触媒を調製した。ハニカム担体１Ｌ当たりの担持量は、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末が１００ｇ／Ｌ、貴金属担持耐熱性粉末が５０ｇ／Ｌ、Ｐｔが１．０ｇ／Ｌ、ＬａＦｅ０．９８Ｐｄ０．０２Ｏ３粉末が２０ｇ／Ｌである。
-Preparation of catalyst according to Comparative Example 6-
Instead of the Rh-doped CeZr-based composite oxide powder, an Rh-supported CeZr-based composite oxide was adopted, and the other three types of catalysts with different types of noble metal-supported heat-resistant powder according to Comparative Example 6 were used in the same manner as in Example 5. Prepared. The supported amount per liter of the honeycomb carrier is 100 g / L for the Rh-supported CeZr-based composite oxide powder, 50 g / L for the noble metal-supported heat-resistant powder, 1.0 g / L for Pt, and LaFe 0.98 Pd 0.02 O 3. The powder is 20 g / L.
−排気ガス浄化性能評価−
上記実施例及び比較例の各触媒について、実施形態１と同じ条件でエージングを行ない、同じ条件でＨＣ、ＣＯ及びＮＯｘの浄化に関するライトオフ温度Ｔ５０を測定した。結果を表２に示す。表２において、「Ｐｄ／ＬａＳｒＧａＭｇＯ」は「Ｐｄ担持Ｌａ０．９Ｓｒ０．１Ｇａ０．８Ｍｇ０．２Ｏ３」である。
−Evaluation of exhaust gas purification performance−
About each catalyst of the said Example and comparative example, aging was performed on the same conditions as
表１と表２との比較から、例えば、触媒成分が同じ実施例１と実施例４との比較、実施例２と実施例５，６との比較、比較例１と比較例５との比較から、二層構造にすることにより、排気ガス浄化性能が高まることがわかる。但し、ペロブスカイト型複合酸化物粉末を下層に配置した実施例４，５は対応する実施例１，２に比べてＴ５０の低下が顕著であるが、ペロブスカイト型複合酸化物粉末を上層に配置した実施例６は、対応する実施例２からみて、Ｔ５０の低下度合が小さい。これから、二層構造にする場合は、ペロブスカイト型複合酸化物粉末を下層にすることが好ましいということができる。下層のペロブスカイト型複合酸化物粉末から放出される酸素が上層のＲｈドープＣｅＺｒ系複合酸化物粉末によって効率良く活性化されるためである。 From the comparison between Table 1 and Table 2, for example, the comparison between Example 1 and Example 4 having the same catalyst component, the comparison between Example 2 and Examples 5 and 6, and the comparison between Comparative Example 1 and Comparative Example 5 Thus, it can be seen that the exhaust gas purification performance is enhanced by adopting a two-layer structure. However, in Examples 4 and 5 in which the perovskite type complex oxide powder is disposed in the lower layer, the T50 is significantly lower than in the corresponding Examples 1 and 2, but in the examples in which the perovskite type complex oxide powder is disposed in the upper layer. In Example 6, as seen from the corresponding Example 2, the degree of decrease in T50 is small. From this, it can be said that in the case of a two-layer structure, it is preferable to use a perovskite complex oxide powder as a lower layer. This is because oxygen released from the lower perovskite complex oxide powder is efficiently activated by the upper Rh-doped CeZr-based complex oxide powder.
また、表２の実施例４，５と比較例５，６との比較から、二層構造においても、ペロブスカイト型複合酸化物粉末にＲｈドープＣｅＺｒ系複合酸化物粉末を組み合わせると、Ｒｈ担持ＣｅＺｒ系複合酸化物粉末を組み合わせる場合よりも排気ガス浄化性能が高くなることがわかる。また、実施例４と実施例７との比較から、ペロブスカイト型複合酸化物粉末に貴金属を担持させると、排気ガス浄化性能が高まることがわかる。 Further, from the comparison between Examples 4 and 5 and Comparative Examples 5 and 6 in Table 2, even in the two-layer structure, when the Rh-doped CeZr composite oxide powder is combined with the perovskite composite oxide powder, the Rh-supported CeZr system It can be seen that the exhaust gas purification performance is higher than when the composite oxide powder is combined. Further, from comparison between Example 4 and Example 7, it is understood that exhaust gas purification performance is enhanced when a noble metal is supported on the perovskite complex oxide powder.
なお、貴金属担持耐熱性粉末は、実施形態１，２では、貴金属としてＰｔ及びＰｄのいずれかを担持したものであるが、Ｐｔ及びＰｄの両者を担持したものとすることもできる。 In the first and second embodiments, the noble metal-carrying heat-resistant powder carries either Pt or Pd as the noble metal, but may carry both Pt and Pd.
また、上記実施例ではＲｈドープＣｅＺｒ系複合酸化物粉末として、ＣｅＺｒＮｄ複合酸化物粒子にＲｈが固溶したＲｈ−ＣｅＺｒＮｄ粉末を用いたが、Ｎｄに代えてＰｒ、Ｌａ及びＹを用いてもよい。この場合、Ｎｄの硝酸塩をＰｒ、Ｌａ、Ｙ等の硝酸塩に変えることでこれらの少なくとも一種を含有するＲｈドープＣｅＺｒ系複合酸化物粉末が得られる。さらに、ＲｈドープＣｅＺｒ系複合酸化物粉末は、ＣｅＺｒ系複合酸化物の一次粒子とＡｌ２Ｏ３の一次粒子とが凝集してなるものに代えることができる。その製法としては、硝酸Ａｌ水溶液にアンモニア水を攪拌しながら添加して、アルミナ粒子の前駆体である水酸化Ａｌの沈殿を得、この沈殿を生じた溶液に、アンモニア水溶液を添加した後、Ｃｅ、Ｚｒ及びＲｈの各硝酸塩水溶液を添加して混合し、Ｃｅ、Ｚｒ及びＲｈの各水酸化物の共沈物と上記水酸化Ａｌとの混合物とし、さらにこの混合沈殿物を水洗し、大気雰囲気において１５０℃の温度で一昼夜乾燥させ、粉砕し、さらに５００℃の温度に２時間保持する焼成を行なう方法が採用できる。 Further, in the above embodiment, Rh-CeZrNd powder in which Rh is dissolved in CeZrNd composite oxide particles is used as the Rh-doped CeZr-based composite oxide powder, but Pr, La and Y may be used instead of Nd. . In this case, an Rh-doped CeZr-based composite oxide powder containing at least one of these can be obtained by changing Nd nitrate to nitrate such as Pr, La, or Y. Furthermore, the Rh-doped CeZr-based composite oxide powder can be replaced with a product obtained by agglomerating primary particles of CeZr-based composite oxide and primary particles of Al 2 O 3 . As the production method, ammonia water is added to an aqueous solution of Al nitrate while stirring to obtain a precipitate of Al hydroxide, which is a precursor of alumina particles, and after adding an aqueous ammonia solution to the resulting solution, Ce , Zr and Rh nitrate aqueous solutions were added and mixed to form a mixture of Ce, Zr and Rh hydroxide coprecipitates and the above-mentioned Al hydroxide. In this method, it is possible to employ a method of drying at a temperature of 150 ° C. for a whole day and night, pulverizing, and further firing at a temperature of 500 ° C. for 2 hours.
１ ハニカム担体
１ａ セル壁面
２ 触媒層
２ａ 上層
２ｂ 下層
DESCRIPTION OF
Claims (5)
上記触媒層は、単層又は複数の層よりなり、さらに、ペロブスカイト型複合酸化物粉末を含有し、該ペロブスカイト型複合酸化物粉末と上記ＲｈドープＣｅＺｒ系複合酸化物粉末とは、同じ層中に混在し、若しくは隣接する二層に分かれており、
上記貴金属を担持する耐熱性粒子は、Ｌａを含有する活性Ａｌ ２ Ｏ ３ 粒子、ＢａＳＯ ４ 粒子、並びにＣｅＺｒ系複合酸化物とＡｌ ２ Ｏ ３ との複合化物粒子から選ばれる少なくとも一種であることを特徴とする排気ガス浄化用触媒。 Rh-doped CeZr-based composite oxide powder in which Rh is dissolved in CeZr-based composite oxide particles containing Ce and Zr, and noble metal-supported heat-resistant particles in which at least one of Pt and Pd is supported on heat-resistant particles An exhaust gas purifying catalyst contained in the catalyst layer on the carrier,
The catalyst layer is composed of a single layer or a plurality of layers, and further contains a perovskite-type composite oxide powder. The perovskite-type composite oxide powder and the Rh-doped CeZr-based composite oxide powder are in the same layer. It is mixed or divided into two adjacent layers ,
The heat-resistant particles supporting the noble metal are at least one selected from active Al 2 O 3 particles containing La , BaSO 4 particles, and composite particles of CeZr-based composite oxide and Al 2 O 3. A catalyst for exhaust gas purification.
上記触媒層は、単層又は複数の層よりなり、さらに、ペロブスカイト型複合酸化物粉末を含有し、該ペロブスカイト型複合酸化物粉末と上記ＲｈドープＣｅＺｒ系複合酸化物粉末とは、同じ層中に混在し、若しくは隣接する二層に分かれており、 The catalyst layer is composed of a single layer or a plurality of layers, and further contains a perovskite-type composite oxide powder. The perovskite-type composite oxide powder and the Rh-doped CeZr-based composite oxide powder are in the same layer. It is mixed or divided into two adjacent layers,
上記ペロブスカイト型複合酸化物粉末は、当該ペロブスカイト型複合酸化物粒子にＰｔ、Ｐｄ及びＲｈから選ばれる少なくとも一種が担持されてなるものであることを特徴とする排気ガス浄化用触媒。 The exhaust gas purification catalyst, wherein the perovskite complex oxide powder is formed by supporting at least one kind selected from Pt, Pd and Rh on the perovskite complex oxide particles.
上記触媒層は上下に隣接するように積層された上層と下層とを有し、上層に上記ＲｈドープＣｅＺｒ系複合酸化物粉末が含まれ、下層に上記ペロブスカイト型複合酸化物粉末が含まれていることを特徴とする排気ガス浄化用触媒。 In claim 1 or claim 2,
The catalyst layer has an upper layer and a lower layer laminated so as to be vertically adjacent to each other, the upper layer includes the Rh-doped CeZr-based composite oxide powder, and the lower layer includes the perovskite-type composite oxide powder. An exhaust gas purifying catalyst characterized by that.
上記ペロブスカイト型複合酸化物粉末は、Ｒｈ以外の触媒金属が固溶したペロブスカイト型複合酸化物粉末であることを特徴とする排気ガス浄化用触媒。 In any one of Claim 1 thru | or 3,
The exhaust gas purifying catalyst, wherein the perovskite complex oxide powder is a perovskite complex oxide powder in which a catalyst metal other than Rh is dissolved.
上記ペロブスカイト型複合酸化物粉末は、当該ペロブスカイト型複合酸化物粒子にＰｔ、Ｐｄ及びＲｈから選ばれる少なくとも一種が担持されてなるものであることを特徴とする排気ガス浄化用触媒。 In claim 1, claim 3 subordinate to claim 1, claim 4 subordinate to claim 1, or claim 4 subordinate to claim 3 subordinate to claim 1 ,
The exhaust gas purification catalyst, wherein the perovskite complex oxide powder is formed by supporting at least one kind selected from Pt, Pd and Rh on the perovskite complex oxide particles.
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