JP2005334791A - Catalyst for cleaning exhaust gas and oxygen storage material for the catalyst - Google Patents
Catalyst for cleaning exhaust gas and oxygen storage material for the catalyst Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 65
- 239000007789 gas Substances 0.000 title claims description 65
- 239000001301 oxygen Substances 0.000 title claims description 41
- 229910052760 oxygen Inorganic materials 0.000 title claims description 41
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims description 36
- 239000011232 storage material Substances 0.000 title claims description 12
- 238000004140 cleaning Methods 0.000 title abstract 4
- 239000011164 primary particle Substances 0.000 claims abstract description 40
- 239000013078 crystal Substances 0.000 claims abstract description 20
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 15
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 14
- 239000012634 fragment Substances 0.000 claims abstract description 13
- 230000003197 catalytic effect Effects 0.000 claims abstract description 8
- 239000002131 composite material Substances 0.000 claims description 63
- 229910052751 metal Inorganic materials 0.000 claims description 17
- 239000002184 metal Substances 0.000 claims description 17
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 abstract description 3
- 239000010948 rhodium Substances 0.000 description 46
- 238000000746 purification Methods 0.000 description 30
- 238000003860 storage Methods 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 13
- 230000001965 increasing effect Effects 0.000 description 13
- 238000005245 sintering Methods 0.000 description 9
- 239000000843 powder Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000010410 layer Substances 0.000 description 6
- 230000002950 deficient Effects 0.000 description 5
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 4
- 230000032683 aging Effects 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 4
- 238000000635 electron micrograph Methods 0.000 description 4
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- 239000002002 slurry Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- -1 that is Substances 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 3
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 3
- 238000000975 co-precipitation Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 229910052878 cordierite Inorganic materials 0.000 description 3
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 238000005470 impregnation Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 229910052703 rhodium Inorganic materials 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 2
- 235000019341 magnesium sulphate Nutrition 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- CFYGEIAZMVFFDE-UHFFFAOYSA-N neodymium(3+);trinitrate Chemical compound [Nd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O CFYGEIAZMVFFDE-UHFFFAOYSA-N 0.000 description 2
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 2
- 150000002926 oxygen Chemical class 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 2
- 239000011163 secondary particle Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
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- 239000010970 precious metal Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 238000005118 spray pyrolysis Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Abstract
Description
本発明は排気ガス浄化用触媒及び同触媒用酸素吸蔵材に関する。 The present invention is an oxygen storage material regarding catalyst for purifying exhaust gases and the catalyst.
自動車の排気ガスを浄化するための三元触媒は、一般にはサポート材としてのアルミナ及びセリアを担体にコーティングした後、Ｐｔ、Ｐｄ、Ｒｈ等の触媒金属を当該コート層に含浸させて焼成することによって形成されている。また、排気ガス浄化用触媒に関し、排気ガスをその低温時から高温時まで安定して浄化できるようにするとともに、触媒の耐熱を向上させるべく、中空状酸化物粉末と中実状酸化物粉末とを含むサポート材に触媒金属を担持させるという提案が知られている（特許文献１参照）。 A three-way catalyst for purifying automobile exhaust gas is generally obtained by coating a support with alumina and ceria as support materials, and then impregnating the coating layer with a catalyst metal such as Pt, Pd, Rh, and firing. Is formed by. Further, regarding the exhaust gas purification catalyst, the exhaust gas can be stably purified from the low temperature to the high temperature, and in order to improve the heat resistance of the catalyst, a hollow oxide powder and a solid oxide powder are used. suggestion supporting the catalyst metal are known to support material containing (see Patent Document 1).
すなわち、この提案の中空状酸化物粉末は、Ｌａを含有するＡｌ2Ｏ3からなり、これにＲｈが含浸法によって担持されている。また、特許文献１には、中空状酸化物粉末の殻壁の厚さは１００ｎｍ以下であることが望ましく、５０ｎｍ以下、さらには２０ｎｍ以下であることがより望ましいこと、中空状酸化物粉末は外径が２０〜２０００ｎｍであり、１０〜２０００ｎｍの細孔をもつこと、中空状酸化物粉末の粒子はＡｌ，Ｔｉ及びＺｒから選ばれる少なくとも一種の元素の酸化物又は複合酸化物から形成すること、比表面積は２０ｍ2／ｇ以上であることが望ましい、と記載されている。 That is, the proposed hollow oxide powder is made of Al 2 O 3 containing La, and Rh is supported by the impregnation method. Patent Document 1 discloses that the thickness of the shell wall of the hollow oxide powder is desirably 100 nm or less, more desirably 50 nm or less, and further desirably 20 nm or less. Having a diameter of 20 to 2000 nm and having pores of 10 to 2000 nm, the hollow oxide powder particles being formed of an oxide or composite oxide of at least one element selected from Al, Ti and Zr; It is described that the specific surface area is desirably 20 m 2 / g or more.
ところで、上記セリアは、三元触媒においては酸素吸蔵材として働き、当該触媒が有効に働く空燃比領域を拡大するが、耐熱性が低いという問題がある。これに対して、触媒の耐熱性向上のために、セリアとジルコニアとを複合させた複合酸化物を触媒貴金属のサポート材として用いることは知られている。
本出願人は、先にＣｅとＺｒとを含有し結晶格子又は原子間に触媒金属を配置してなる複合酸化物を共沈法によって製造する方法を開発し、提案している（特願２００３−３７９８３９号，出願人：マツダ株式会社）。この複合酸化物によれば、排気ガスの熱による触媒金属のシンタリングや表面に存在する触媒金属の埋没が抑えられ、すなわち、触媒の耐熱性が向上するとともに、酸素吸蔵能（吸蔵速度及び吸蔵量）が高まる。従って、触媒金属量を少なくしても、排気ガス浄化におけるライトオフ性能及び高温浄化性能を向上させることができた。 The applicant has developed a method for producing a composite oxide formed by arranging the catalytic metal between containing Ce and Zr above the crystal lattice or atom by a coprecipitation method, proposed (Japanese Patent Application No. 2003 -379839, applicant: Mazda Motor Corporation). According to this composite oxide, sintering of the catalyst metal due to the heat of the exhaust gas and burying of the catalyst metal existing on the surface are suppressed, that is, the heat resistance of the catalyst is improved and the oxygen storage capacity (storage speed and storage speed) is increased. amount) is increased. Therefore, even if the amount of catalyst metal is reduced, the light-off performance and the high-temperature purification performance in exhaust gas purification can be improved.
しかし、共沈法で得られる複合酸化物では、その結晶子（一次粒子）の微細化にも限界があり、触媒金属の添加量を少なくすると、結晶子表面に露出して排気ガスの酸化・還元に直接働く（触媒作用をする）触媒金属量が少なくなる。また、二次粒子も多数の一次粒子が凝集してなるものであるため、内部に埋もれている一次粒子は排気ガスと充分に接触しないという問題があった。これは、後出比較例に示すとおり、高温に晒した場合、比較的小さなＢＥＴ比表面積がさらに低下することから、凝集した中実状複合酸化物同士がシンタリングを起こしやすいことに原因があると考えられる。 However, the composite oxide obtained in the coprecipitation method, there is a limit to miniaturization of the crystallite (primary particle), if reducing the amount of catalyst metal, oxide-exhaust gas is exposed to the crystallite surface acting directly reducing (catalyze) the catalytic amount of metal is reduced. Moreover, since they are the secondary particles also are a number of primary particles formed by agglomerating primary particles which are buried in the interior has a problem that does not sufficiently contact with the exhaust gas. This is because the relatively small BET specific surface area is further reduced when exposed to a high temperature as shown in the comparative example described later, so that the aggregated solid complex oxides are likely to cause sintering. Conceivable.
つまり、Ｒｈは、その一部が後述のように一次粒子（結晶子）の結晶格子又は原子間に配置されることによって酸素吸蔵量の増大等、酸素吸蔵能の向上に寄与するとともに、残りの一部が一次粒子表面に露出していることによって排気ガスと接触して浄化性能の向上に寄与するが、シンタリングによって粗大化した粒子内部にＲｈが埋没する結果、粒子表面に露出して排気ガス浄化性能に寄与するＲｈ量が少なくなるという問題があった。そのため、排気ガス浄化性能をさらに高めることが難しかった。 That, Rh is increased like the oxygen storage amount by being disposed between the crystal lattice or atom of the part as described later primary particles (crystallites), contributes to the improvement of the oxygen storage capacity, the remaining Although part of the surface is exposed to the primary particle surface, it contributes to the improvement of the purification performance by contacting with the exhaust gas. However, as a result of Rh being buried inside the particle coarsened by sintering, it is exposed to the particle surface and exhausted. there is a problem that contributes Rh amount on the gas purification performance is reduced. Therefore, it was difficult to further improve the exhaust gas purification performance.
そこで、本発明の課題は、触媒金属量を少なくしても、触媒の耐熱性を損なうことなく、その排気ガス浄化性能をさらに高めることができるようにすることにある。 Accordingly, an object of the present invention is to make it possible to further improve the exhaust gas purification performance without impairing the heat resistance of the catalyst even if the amount of catalyst metal is reduced.
本発明は、このような課題に対して、上記ＣｅとＺｒとを含有し且つ触媒金属が結晶格子又は原子間に存する複合酸化物を中空の殻及びその破片のいずれかの形態で触媒に用いるようにした。 The present invention is, with respect to this problem, used for the catalyst in either a composite oxide hollow shell and debris and catalyst metal containing the above Ce and Zr are existing in between crystal lattice or atomic It was so.
すなわち、請求項１に係る発明は、触媒担体上に形成された触媒層に、Ｃｅ及びＺｒを含有する複合酸化物と、Ａｌ2Ｏ3と、少なくとも一種類の触媒金属とが含まれている排気ガス浄化用触媒であって、
上記一種類の触媒金属はＲｈであり、
上記複合酸化物の少なくとも一部は、中空の殻及びその破片の少なくとも一方の形態となって上記触媒層に存在し、
上記中空の殻又はその破片を構成する一次粒子の結晶格子又は原子間に上記Ｒｈの少なくとも一部が配置されていることを特徴とする。
That is, in the invention according to claim 1, the catalyst layer formed on the catalyst carrier includes a composite oxide containing Ce and Zr, Al 2 O 3 , and at least one kind of catalyst metal. a exhaust gas purifying catalyst,
The one type of catalytic metal is Rh,
At least a part of the composite oxide is present in the catalyst layer in the form of at least one of a hollow shell and fragments thereof,
At least a part of the Rh is disposed between crystal lattices or atoms of primary particles constituting the hollow shell or fragments thereof.
従って、上記複合酸化物の結晶格子又は原子間に配置されたＲｈは、Ｒｈ同士の接触が抑制された状態にあるから、高熱に晒されてもシンタリングを生じ難くなる。また、Ｒｈが結晶格子又は原子間に配置された当該複合酸化物は、その雰囲気が酸素過剰になると、速やかに酸素を吸蔵するとともに、酸素吸蔵量も多くなる。 Therefore, Rh disposed between the crystal lattice or atom of said composite oxide, because a state in which the contact is suppressed and Rh each other, even when exposed to high heat hardly occurs sintering. In addition, the complex oxide in which Rh is disposed between crystal lattices or between atoms quickly absorbs oxygen and increases the amount of oxygen stored when the atmosphere is excessive in oxygen.
なお、Ｒｈ以外の触媒金属としては、ＰｔやＰｄ等が含浸法等で触媒層に含有されることが好ましい。或いは更にＲｈが含浸法等で触媒層に含有されてもよい。 As the catalyst metal other than Rh, it is preferable that Pt or Pd, is contained in the catalyst layer in the impregnation method or the like. Or even Rh may be contained in the catalyst layer in the impregnation method or the like.
そうして、上記中空の殻及びその破片のいずれかの形態になっている複合酸化物は、中実の塊状となっている場合に比べて、表面（殻の外面及び内面を含む）に露出する一次粒子が多くなるとともに、排気ガスが当該複合酸化物の殻壁を通り抜けやすくなる。よって、一次粒子の表面に露出しているＲｈが排気ガスと接触し易くなるから、排気ガスの浄化性能が高まる。 Thus, the composite oxide in the form of any one of the hollow shell and its fragments is exposed on the surface (including the outer surface and the inner surface of the shell) as compared to a solid lump. with primary particles increases to, exhaust gas tends through the shell wall of the composite oxide. Therefore, Rh exposed on the surface of the primary particles can easily come into contact with the exhaust gas, so that the exhaust gas purification performance is enhanced.
請求項２に係る発明は、請求項１において、
Ｒｈが結晶格子又は原子間に配置された上記一次粒子の平均結晶子径が１０ｎｍ未満であることを特徴とする。
The invention according to claim 2, in claim 1,
Rh is, wherein the average crystallite size of the crystal lattice or arranged the primary particles between atoms is less than 10 nm.
このような小さい結晶子径であれば、その表面に露出するＲｈの量が多くなり、排気ガス浄化性能の向上に有利になる。 With such a small crystallite diameter, the amount of Rh exposed on the surface increases, which is advantageous for improving the exhaust gas purification performance.
請求項３に係る発明は、請求項１又は請求項２において、
上記中空の殻は、その直径が０．０５μｍ以上３．０μｍ以下の略球状であり、その殻壁の厚みが５０ｎｍ以下であることを特徴とする。
The invention according to claim 3, in claim 1 or claim 2,
The hollow shell has a substantially spherical shape with a diameter of 0.05 μm or more and 3.0 μm or less, and a thickness of the shell wall is 50 nm or less.
従って、一次粒子同士の接触による粒成長が抑制されるとともに、当該中空殻状複合酸化物のシンタリングも少なくなる。また、上記一次粒子の平均結晶子径が１０ｎｍ未満である場合、殻壁の厚みと該殻壁を構成する一次粒子の平均結晶子径との関係から、殻壁の厚み方向に存在する一次粒子の数が約１０個程度に或いは１０個以下に抑えられるので、排気ガスが殻壁を通り易くなり、排気ガスの浄化性能が高まる。 Therefore, grain growth due to contact between primary particles is suppressed, and sintering of the hollow shell complex oxide is also reduced. Further, when the average crystallite size of the primary particles is less than 10 nm, the relationship between the average crystallite size of the primary particles constituting the thickness and the shell wall of the shell wall, the primary particles present in the thickness direction of the shell wall Therefore, the exhaust gas can easily pass through the shell wall, and the exhaust gas purification performance is enhanced.
請求項４に係る発明は、排気ガス浄化用触媒に含有される酸素吸蔵材であって、
Ｃｅ及びＺｒを含有し且つ結晶格子又は原子間にＲｈが配置されている複合酸化物の一次粒子から構成されていて、
上記一次粒子が凝集して中空の殻及びその破片の少なくとも一方の形態となっていることを特徴とする。
The invention according to claim 4 is an oxygen storage material contained in the exhaust gas purification catalyst,
It is composed of primary particles of a composite oxide containing Ce and Zr and having Rh arranged between crystal lattices or atoms,
The primary particles are aggregated to form at least one of a hollow shell and its fragments.
従って、この酸素吸蔵材によれば、Ｒｈのシンタリングを生じ難くなり且つ優れた酸素吸蔵特性を示すことに加えて、表面に露出する一次粒子が多くなるとともに、排気ガスが当該複合酸化物の殻壁を通り抜け易くなるから、一次粒子の表面に露出しているＲｈが排気ガスと接触し易くなり、排気ガスの浄化性能が高まる。 Therefore, according to the oxygen storage material, in addition to an oxygen-absorbing characteristics becomes and excellent hardly occurs sintering of Rh, together with the primary particles are often exposed to the surface, the exhaust gas of the complex oxide Since it becomes easy to pass through the shell wall, the Rh exposed on the surface of the primary particles can easily come into contact with the exhaust gas, and the purification performance of the exhaust gas is enhanced.
請求項５に係る発明は、請求項４において、
上記複合酸化物の平均結晶子径が１０ｎｍ未満であることを特徴とする。
The invention according to claim 5 is the invention according to claim 4,
An average crystallite size of the composite oxide is less than 10 nm.
従って、酸素吸蔵材表面に露出するＲｈの量が多くなり、排気ガス浄化性能の向上に有利になる。 Therefore, the amount of Rh exposed to the oxygen storage material surface is increased, which is advantageous in improving the exhaust gas purification performance.
以上のように本発明に係る排気ガス浄化用触媒によれば、Ｃｅ及びＺｒを含有しＲｈが結晶格子又は原子間に配置された複合酸化物が中空の殻及びその破片の少なくとも一方の形態になっているから、触媒の耐熱性が向上し、また、表面に露出する一次粒子が多くなるとともに、排気ガスが当該複合酸化物の殻壁を通り抜けやすくなるから、一次粒子の表面に露出しているＲｈが排気ガスと接触し易くなり、排気ガスの浄化性能が高まる。 As described above, according to the exhaust gas purifying catalyst of the present invention, the composite oxide containing Ce and Zr and having Rh arranged between crystal lattices or atoms is in the form of at least one of a hollow shell and its fragments. Therefore, the heat resistance of the catalyst is improved, the primary particles exposed on the surface increase, and the exhaust gas easily passes through the shell wall of the composite oxide, so that it is exposed on the surface of the primary particles. easily Rh there are in contact with the exhaust gas, increasing the exhaust gas purification performance.
また、上記一次粒子の平均結晶子径を１０ｎｍ未満にすると、排気ガス浄化性能の向上に有利になり、また、上記中空の殻を直径が０．０５μｍ以上３．０μｍ以下の略球状とし、その殻壁の厚みを５０ｎｍ以下にすると、一次粒子同士の接触による粒成長の抑制、当該中空殻状複合酸化物のシンタリング防止に有利になるとともに、排気ガスが殻壁を通り易くなり、排気ガスの浄化性能が高まる。 Further, when the average crystallite size of the primary particles less than 10 nm, it is advantageous in improving the exhaust gas purification performance, also the hollow shell diameter and 3.0μm or less substantially spherical or 0.05 .mu.m, the When the thickness of the shell wall is 50 nm or less, it is advantageous for suppressing grain growth due to contact between primary particles and preventing sintering of the hollow shell complex oxide, and the exhaust gas easily passes through the shell wall. increased purification performance of.
また、本発明に係る酸素吸蔵材によれば、Ｃｅ及びＺｒを含有しＲｈが結晶格子又は原子間に配置された複合酸化物の一次粒子が凝集して中空の殻及びその破片の少なくとも一方の形態となったものであるから、耐熱性が高くなり且つ優れた酸素吸蔵特性を示すことに加えて、一次粒子の表面に露出しているＲｈが排気ガスと接触し易くなり、排気ガスの浄化性能を高める上で有利になる。また、上記一次粒子の平均結晶子径を１０ｎｍ未満にすると、排気ガス浄化性能の向上にさらに有利になる。 In addition, according to the oxygen storage material of the present invention, primary particles of a composite oxide containing Ce and Zr and Rh arranged between crystal lattices or atoms aggregate to form at least one of a hollow shell and its fragments. Since it is in a form, in addition to high heat resistance and excellent oxygen storage characteristics, Rh exposed on the surface of the primary particles can easily come into contact with the exhaust gas, thereby purifying the exhaust gas. It becomes advantageous in enhancing the performance. Further, when the average crystallite size of the primary particles less than 10 nm, becomes more advantageous in improving the exhaust gas purification performance.
以下、本発明の実施形態を図面に基づいて詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
本発明の実施形態に係る排気ガス浄化用触媒は、自動車エンジンの排気ガス中のＨＣ、ＣＯ及びＮＯｘを浄化することに適したものであって、そのための触媒層がコージェライト等の無機多孔質によって形成されたハニカム形状等の担体上に形成されている。触媒層は次に説明する酸素吸蔵材として働く複合酸化物及びγ−アルミナをバインダと共に担体にウォッシュコートすることによって形成される。 The exhaust gas purifying catalyst according to the embodiment of the present invention is suitable for purifying HC, CO and NOx in the exhaust gas of an automobile engine, and the catalyst layer therefor is an inorganic porous material such as cordierite. It is formed on a carrier of a honeycomb shape or the like formed by. The catalyst layer is formed by wash-coating a composite oxide and γ-alumina serving as an oxygen storage material, which will be described next, together with a binder.
上記複合酸化物は、Ｃｅ及びＺｒを含有し且つ触媒金属としてのＲｈの少なくとも一部が結晶格子又は原子間に配置されたものであって、この複合酸化物の少なくとも一部は中空の略球状の殻及びその破片のいずれかの形態になっている。なお、上記複合酸化物は、以下の実施例に記載のＮｄ等、Ｃｅ以外の希土類元素を含有してもよい。 The composite oxide is of a type wherein at least a portion of the Rh as and catalyst metal containing Ce and Zr are placed between crystal lattice or atom, generally spherical at least in part hollow composite oxide In the form of a shell and its debris. The composite oxide may contain rare earth elements other than Ce, such as Nd described in the following examples.
＜実施例＞
上記複合酸化物を噴霧熱分解法によって製造した。すなわち、オキシ硝酸ジルコニウム、硝酸セリウム、硝酸ネオジム、硝酸ロジウム及び硫酸マグネシウムの各所定量を水に溶解させることにより、上記複合酸化物の原料溶液を調製した。ここで、硫酸マグネシウムは、中空状複合酸化物を製造する際の結晶子のシンタリングを抑制する、結晶子同士の接触点を減らしつつ中空構造に導く、という作用を有するものとして、各種添加化合物の中から選定されたものであり、その添加量、濃度等は適宜決定することができる。次いで、上記原料溶液を、空気をキャリアガスとして噴霧することにより、液滴化させて加熱炉に供給した。加熱炉の温度は１０００℃に設定した。加熱炉を出た粒子はバグフィルターによって捕集し、これを水洗後、乾燥させることにより、当該複合酸化物を得た。この実施例においては、ＺｒＯ2：ＣｅＯ2：Ｎｄ2Ｏ3＝６８：２２：１０、当該複合酸化物におけるＲｈ量が０．１２５質量％となるようにした。
<Example>
The composite oxide was produced by a spray pyrolysis method. That is, Zirconium oxynitrate, Cerium nitrate, Neodymium nitrate, The predetermined amounts of rhodium nitrate and magnesium sulfate by dissolving in water, A raw material solution of the composite oxide was prepared. here, Magnesium sulfate Suppressing sintering of crystallites in the production of hollow composite oxide, Leading to a hollow structure while reducing the number of contact points between crystallites, As having the action of It has been selected from among the various additives compounds, Its addition amount, The concentration and the like can be determined as appropriate. Then The raw material solution By spraying air as a carrier gas, It was fed to the furnace by dropletized. The temperature of the heating furnace was set to 1000 ° C. Coming out of the heating furnace particles are collected by a bag filter, After washing this with water By drying The composite oxide was obtained. In this example, ZrO 2 : CeO 2 : Nd 2 O Three = 68: 22: 10, the amount of Rh in the composite oxide was 0.125% by mass.
そうして、上記複合酸化物とγ−アルミナ粉末とを２：１の比率で混合してこれにバインダ及び水を加えてスラリーを得、このスラリーをコージェライト製ハニカム担体に担体１Ｌ当たりの担持量が１６７ｇとなるようにウォッシュコートして、乾燥、焼成工程を経て実施例に係る排気ガス浄化用触媒を得た。この触媒の担体に対するＲｈ含有量は０．１２６ｇ／Ｌである。 Then, the composite oxide and γ-alumina powder are mixed at a ratio of 2: 1, and a binder and water are added thereto to obtain a slurry. This slurry is supported on a cordierite honeycomb carrier per 1 L of carrier. Washing was performed so that the amount was 167 g, and the exhaust gas purifying catalyst according to the example was obtained through the drying and firing steps. The Rh content of this catalyst relative to the support is 0.126 g / L.
図１〜図４は上記複合酸化物のＴＥＭ（透過型電子顕微鏡）写真である。図１及び図２の写真に写っている中空球状の殻及び該殻が割れた破片（図２の写真に円弧状ないし直線状に黒く写っているもの）が上記複合酸化物である。球状殻の直径は０．０５μｍ〜３μｍである。図３は図１の写真の一部を拡大したものであり、複合酸化物の殻壁の厚みは５０ｎｍ以下になっている。すなわち、ＴＥＭでは１００ｎｍ程度の厚みのものを観察するとその背部が透過して見えるが、図３によれば大きな中空球状の複合酸化物の裏にやや小さめの中空球状の複合酸化物が見えているところから、殻壁の厚みは５０ｎｍ以下であると特定した。 1 to 4 is a TEM (transmission electron microscope) photograph of the composite oxide. The hollow spherical shells shown in the photographs of FIGS. 1 and 2 and the broken pieces of the shells (those that are black in the shape of an arc or a straight line in the photographs of FIG. 2) are the composite oxide. The diameter of the spherical shell is 0.05 μm to 3 μm. FIG. 3 is an enlarged view of a part of the photograph of FIG. 1, and the thickness of the shell wall of the composite oxide is 50 nm or less. That is, in TEM, when the thickness of about 100 nm is observed, the back part appears to be transmitted, but according to FIG. 3, a slightly smaller hollow spherical composite oxide is seen behind the large hollow spherical complex oxide. Therefore, the thickness of the shell wall was specified to be 50 nm or less.
図４はさらに倍率を高めた写真であり、黒い粒状のものが見受けられるが、これらが一次粒子である。この写真によれば、該一次粒子の５０％以上は直径が数ｎｍ以下になっていることが確認できる。 FIG. 4 is a photograph in which the magnification is further increased, and black particles can be seen, but these are primary particles. According to this picture, more than 50% of the primary particles can be confirmed that is equal to or less than several nm in diameter.
したがって、実施例に係る複合酸化物は、中空球状の殻と該殻が割れた破片とが混合された形態となっている。また、図４の写真からわかるように、一次粒子である結晶子の一部は互いに接触した状態にあるが、一部の結晶子間には空隙が存在する。つまり、図２や図３に示される中空球状の殻やその破片は、一次粒子が部分的に結晶子間に空隙のある状態で凝集した二次粒子であると云える。そして、このように結晶子間に空隙が存在する、つまり多孔体であるが故に、複合酸化物は後述する比較的大きなＢＥＴ比表面積が確保できているとともに、排気ガスが複合酸化物の殻壁を通り抜けやすく、その通り抜けの過程で一次粒子表面に露出しているＲｈと排気ガスとが接触するため、排気ガス性能が高まる。 Therefore, the composite oxide according to the example is in a form in which a hollow spherical shell and a broken piece of the shell are mixed. Further, as can be seen from the photograph in FIG. 4, some of the crystallites that are primary particles are in contact with each other, but there are voids between some of the crystallites. In other words, hollow spherical shells and fragments thereof, shown in FIGS. 2 and 3, when a secondary particle formed by aggregation of primary particles in the presence of air gaps between the partially crystalline child it can be said. Then, this air gap exists between the crystallites in, that because it is a porous body, along with the composite oxide is secured relatively large BET specific surface area, which will be described later, the shell wall exhaust gas of the complex oxide Exhaust gas performance is enhanced because Rh exposed on the primary particle surface and the exhaust gas come into contact with each other in the process of passing through.
なお、図１及び図２の写真において、複合酸化物の背部に写っている線状のものは写真撮影のために複合酸化物を支持させたＣｕ製ワイヤーメッシュである。 In the photographs of FIGS. 1 and 2, the linear shape that is reflected on the back of the complex oxide is a Cu wire mesh that supports the complex oxide for photography.
図５は上記複合酸化物の平均結晶子径を次に示すシェラーの式から導くために調べたＸＲＤ（Ｘ線回折）パターンである。 FIG. 5 is an XRD (X-ray diffraction) pattern examined in order to derive the average crystallite diameter of the composite oxide from the following Scherrer equation.
結晶子径Ｄ(hkl)＝０．９λ／(β1/2・cosθ)
但し、hklはミラー指数、λは特性Ｘ線の波長（Å)、β1/2は(hkl)面の半価幅（ラジアン）、θはＸ線反射角度である。
Crystallite diameter D (hkl) = 0.9λ / (β 1/2 · cos θ)
Where hkl is the Miller index, λ is the characteristic X-ray wavelength (Å), β 1/2 is the half width (radian) of the (hkl) plane, and θ is the X-ray reflection angle.
このシェラーの式によると、平均結晶子径は５．８ｎｍとなる。 According to this equation for Scherrer, average crystallite diameter becomes 5.8 nm.
＜排気ガス浄化性能について＞
上記実施例の排気ガス浄化性能を比較例との比較において評価した。
<For the exhaust gas purification performance>
The exhaust gas purification performance of the above example was evaluated in comparison with a comparative example.
−比較例−
共沈法によって比較例に係る複合酸化物を調製した。すなわち、オキシ硝酸ジルコニウム、硝酸セリウム、硝酸ネオジム及び硝酸ロジウム溶液各々の所定量と水とを混合し、この混合溶液を室温で約１時間撹拌した後、８０℃まで加熱昇温させ、これと２８％アンモニア水５０ｍＬとを素早く混合した。このアンモニア水との混合により白濁した溶液を一昼夜放置し、生成したケーキを遠心分離器にかけ、十分に水洗した。この水洗したケーキを約１５０℃の温度で乾燥させた後、４００℃の温度に５時間保持し、次いで１０００℃の温度に１時間保持するという条件で焼成した。
-Comparative example-
The composite oxide according to Comparative Example by coprecipitation was prepared. That is, a predetermined amount of each of zirconium oxynitrate, cerium nitrate, neodymium nitrate, and rhodium nitrate solution was mixed with water, and this mixed solution was stirred at room temperature for about 1 hour, then heated to 80 ° C. and heated. % and was quickly mixed with ammonia water 50mL. The solution clouded by mixing with the ammonia water was allowed to stand for a whole day and night, and the resulting cake was centrifuged and thoroughly washed with water. The cake washed with water was dried at a temperature of about 150 ° C. and then calcined under the condition that it was kept at a temperature of 400 ° C. for 5 hours and then kept at a temperature of 1000 ° C. for 1 hour.
得られた複合酸化物は、Ｃｅ及びＺｒを含有しＲｈの少なくとも一部が結晶格子又は原子間に配置された中実の粉末であり、組成は実施例と同じく、ＺｒＯ2：ＣｅＯ2：Ｎｄ2Ｏ3＝６８：２２：１０、当該複合酸化物におけるＲｈ量は０．１２５質量％である。また、結晶子径は１０〜２０ｎｍであった。 The obtained composite oxide is a solid powder containing Ce and Zr and having at least a part of Rh arranged between crystal lattices or atoms, and the composition is the same as in the example, ZrO 2 : CeO 2 : Nd. 2 O 3 = 68: 22: 10, and the Rh content in the composite oxide is 0.125% by mass. Further, the crystallite diameter was: 10 to 20 nm.
そうして、上記複合酸化物とγ−アルミナ粉末とを２：１の比率で混合してこれにバインダ及び水を加えてスラリーを得、このスラリーをコージェライト製ハニカム担体に担体１Ｌ当たりの担持量が１６７ｇとなるようにウォッシュコートして、乾燥、焼成工程を経て比較例に係る排気ガス浄化用触媒を得た。従って、比較例触媒の担体に対するＲｈ含有量は実施例と同じく０．１２６ｇ／Ｌである。 Then, the composite oxide and γ-alumina powder are mixed at a ratio of 2: 1, and a binder and water are added thereto to obtain a slurry. This slurry is supported on a cordierite honeycomb carrier per 1 L of carrier. Wash coating was performed so that the amount was 167 g, and an exhaust gas purifying catalyst according to a comparative example was obtained through drying and firing processes. Therefore, Rh content to the carrier of Comparative Example catalyst is also 0.126 g / L Example.
−排気ガス浄化性能の評価試験−
上記実施例及び比較例の各触媒について、Ｏ2を２質量％、Ｈ2Ｏを１０質量％含有するＮ2ガス雰囲気で１０００℃の温度に２４時間加熱するエージング処理を行なった後、モデルガス流通反応装置及び排気ガス分析装置を用いて、空燃比リッチのモデルガス（温度６００℃）を２０分間流した後のＨＣ、ＣＯ及びＮＯｘの浄化に関するライトオフ温度Ｔ５０及び高温浄化率Ｃ４００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。Ｃ４００は触媒入口ガス温度が４００℃のときの浄化率である。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 Test of exhaust gas purification performance -
The catalysts of the above Examples and Comparative Examples, the O 2 2 wt%, after performing the aging treatment of heating for 24 hours of H 2 O to a temperature of 1000 ° C. in N 2 gas atmosphere containing 10% by weight, model gas Using a flow reactor and an exhaust gas analyzer, the light-off temperature T50 and the high-temperature purification rate C400 related to the purification of HC, CO and NOx after flowing an air-fuel ratio rich model gas (temperature 600 ° C.) for 20 minutes were measured. . T50 is the model gas temperature flowing into the catalyst is gradually increased from room temperature, a catalyst inlet gas temperature at which the purification rate reached 50%. C400 is the purification rate when the catalyst inlet gas temperature is 400 ° C. The model gas was A / F = 14.7 ± 0.9. That is, a mainstream gas was allowed to flow A / F = 14.7 constantly, forcing a predetermined amount of gas for changing by adding in pulses at 1 Hz, the A / F amplitude of ± 0.9 It was vibrated on. The space velocity SV is 60000 h −1 , and the heating rate is 30 ° C./min.
Ｔ５０の結果を図６に示す。ＨＣ、ＣＯ及びＮＯｘいずれの浄化に関しても実施例触媒の方が比較例触媒よりも５０℃前後低いＴ５０になっている。Ｃ４００の結果を図７に示す。ＨＣ、ＣＯ及びＮＯｘいずれの浄化率に関しても、実施例触媒は比較例触媒よりも５％前後高くなっている。 The results of the T50 shown in FIG. Regarding purification of HC, CO, and NOx, the catalyst of the example has a T50 lower by about 50 ° C. than the catalyst of the comparative example. The results of the C400 shown in FIG. With respect to the purification rates of HC, CO, and NOx, the example catalyst is about 5% higher than the comparative example catalyst.
即ち、実施例触媒は比較例触媒に比べて、より低温でも高い触媒活性を発揮するとともに、高温域においても高い触媒活性が維持されるものであって、耐熱性に優れ、排気ガス浄化性能が高い。従って、本発明の如く、Ｃｅ及びＺｒを含有しＲｈの少なくとも一部が結晶格子又は原子間に配置された複合酸化物が中空略球状の殻及びその破片のいずれかの形態になると、耐熱性の向上、排気ガス浄化性能の向上に有利であることがわかる。 That is, example catalyst as compared with the comparative example catalyst, as well as exhibits a high catalytic activity even at lower temperatures, there is the high catalytic activity even at high temperature region is maintained, excellent heat resistance, the exhaust gas purifying performance high. Therefore, as in the present invention, when a complex oxide containing Ce and Zr and at least a part of Rh is arranged between crystal lattices or atoms is in the form of a hollow substantially spherical shell and its fragments, It can be seen that this is advantageous for improving the exhaust gas purification performance.
これは、本発明の場合、複合酸化物が中空略球状の殻又はその破片の形態であるから、排気ガスが当該複合酸化物の殻壁を通り抜けやすくなるとともに、凝集によって内部に埋もれる一次粒子が可及的に少なくなるため、排気ガスとＲｈなどの触媒金属及び酸素吸蔵材との接触効率が向上したこと、しかも、高温に暴露した場合でも、複合酸化物の粒成長が抑制され粒子内部に埋没するＲｈが少ないため、Ｒｈのほぼ全量、つまり一次粒子内部における結晶格子又は原子間に配置されたＲｈと、当該一次粒子内部から表面に露出したＲｈとが、それぞれの機能を発揮して排気ガスの浄化に寄与したことによるものであり、少量でも高い浄化性能を維持できるものである。 This is because, in the case of the present invention, since the composite oxide is in the form of a hollow substantially spherical shell or a fragment thereof, the exhaust gas can easily pass through the shell wall of the composite oxide, and the primary particles buried inside by aggregation are formed. Because it reduces as much as possible, the contact efficiency between exhaust gas and catalytic metals such as Rh and oxygen storage materials has been improved, and even when exposed to high temperatures, the growth of complex oxide particles is suppressed and the inside of the particles is reduced. Since the buried Rh is small, almost the entire amount of Rh, that is, Rh arranged between crystal lattices or atoms inside the primary particle and Rh exposed on the surface from the inside of the primary particle exert their respective functions and exhaust. are those due to the contribution to the purification of gases, as it can maintain the high purification performance even in a small amount.
複合酸化物の粒成長を抑制できたのは、一次粒子同士の接触面積を限りなく小さくしたことにより、接触面での相互拡散による焼結を抑制できたこと、並びにＲｈは結晶格子又は原子間に配置されているのでＲｈ同士の接触が抑制されたことによるものと考えられる。更に、結晶子サイズが小さいことによって、一次粒子表面に露出するＲｈが多くなり、反応効率が向上したものと推定される。 Was possible to suppress the grain growth of the composite oxide is made smaller as possible the contact area between the primary particles that could inhibit sintering due to mutual diffusion at the interface, and Rh is between crystal lattice or atom because it is arranged to be considered to be due to the contact of Rh each other is suppressed. Furthermore, it is presumed that the reaction efficiency is improved because the Rh exposed on the surface of the primary particles is increased due to the small crystallite size.
すなわち、上記実施例及び比較例の複合酸化物について、そのフレッシュ時及びエージング後のＢＥＴ比表面積を測定したところ、表１の結果が得られた。このエージングは複合酸化物を大気雰囲気で１０００℃の温度に２４時間加熱するというものである。 That is, for the composite oxides of the above Examples and Comparative Examples, the BET specific surface area at the time of freshness and after aging was measured, and the results shown in Table 1 were obtained. This aging is that the composite oxide is heated for 24 hours to a temperature of 1000 ° C. in an air atmosphere.
この比表面積の測定結果によれば、実施例の複合酸化物は比較例に比べてフレッシュ時の比表面積が十数倍大きく、エージング後も５倍程度大きい。これは、実施例の複合酸化物が中空略球状の殻又はその破片の形態となっているからであり、このように比表面積が大きいということは、複合酸化物表面に露出しているＲｈ量も多いということであり、触媒中のＲｈが排気ガス浄化に効率良く働いているということができる。 According to the measurement result of the specific surface area, the complex oxide of the example has a specific surface area of 10 times larger than that of the comparative example and about 5 times larger after aging. This is because the complex oxide of Example has a shell or form of the pieces of the hollow substantially spherical, thus that a large specific surface area, the amount of Rh exposed on the composite oxide surface it means that often, it can be said that Rh in the catalyst is working efficiently exhaust gas purification.
−複合酸化物の酸素吸蔵能について−
上述のＣｅ及びＺｒを含有し且つＲｈが結晶格子又は原子間に配置された複合酸化物は、雰囲気が酸素過剰になると、速やかに酸素を吸蔵するとともに、酸素吸蔵量も多くなるが、その酸素吸蔵のメカニズムは以下のように推定される。
- The oxygen storage capacity of the composite oxide -
The composite oxide containing Ce and Zr and having Rh arranged between crystal lattices or atoms quickly absorbs oxygen and increases the amount of oxygen stored when the atmosphere is excessive in oxygen. mechanism of storage is estimated as follows.
すなわち、図８（ａ）は実施例の複合酸化物（以下、Ｒｈドープ複合酸化物という。）の、図８（ｂ）はＣｅ及びＺｒを含有する複合酸化物にＲｈを後から担持させた従来例のＲｈ後担持複合酸化物の、各々推定される酸素吸蔵メカニズムを模式的に表したものである。なお、図８ではＺｒ原子の図示は省略している。 That is, FIG. 8A shows a composite oxide of the example (hereinafter referred to as Rh-doped composite oxide), and FIG. 8B shows a composite oxide containing Ce and Zr, with Rh supported later. FIG. 3 schematically shows an estimated oxygen storage mechanism of a post-Rh-supported composite oxide of a conventional example. In FIG. 8, illustration of Zr atoms is omitted.
まず、図８（ｂ）のＲｈ後担持複合酸化物では、酸素（Ｏ2）は、複合酸化物内部の表面近傍に存する酸素欠損部（Ｏ空孔）には酸素イオンとなって吸蔵されるが、複合酸化物内部の比較的深い部位に存する酸素欠損部には到達することができず、この酸素欠損部は酸素吸蔵にはあまり利用されていないと考えられる。 First, in the post-Rh-supported composite oxide in FIG. 8B, oxygen (O 2 ) is occluded as oxygen ions in oxygen deficient portions (O vacancies) existing near the surface inside the composite oxide. However, it is considered that the oxygen deficient part existing in a relatively deep part inside the complex oxide cannot be reached, and this oxygen deficient part is not often used for oxygen storage.
これに対して、図８（ａ）のＲｈドープ複合酸化物では、酸素（Ｏ2）が酸素イオンとなって複合酸化物内部に存するＲｈに引き寄せられ、このＲｈを介して複合酸化物内部の酸素欠損部に瞬時に移動すると考えられる。また、複合酸化物内部にはＲｈが分散して存在するから、酸素イオンは複合酸化物表面から複数のＲｈを介してホッピング移動し、複合酸化物内部の深いところの酸素欠損部に入ると考えられる。このため、Ｒｈドープ複合酸化物の場合は、酸素過剰雰囲気になったときの酸素吸蔵速度が速やかに高くなるとともに、この酸素吸蔵速度の最高値も高くなり、また、酸素吸蔵材内部の比較的深いところの酸素欠損部も酸素吸蔵に利用されるから、酸素吸蔵量が多くなると考えられる。 On the other hand, in the Rh-doped composite oxide of FIG. 8A, oxygen (O 2 ) becomes oxygen ions and is attracted to Rh existing in the composite oxide, and through this Rh, It believed moves instantaneously to the oxygen defect. Further, since Rh is dispersed inside the complex oxide, oxygen ions are considered to hop through the complex oxide surface through a plurality of Rhs and enter oxygen deficient portions deep inside the complex oxide. It is done. For this reason, in the case of the Rh-doped composite oxide, the oxygen storage rate when an oxygen-excess atmosphere is rapidly increased, the maximum value of this oxygen storage rate is also increased, It is considered that the oxygen storage amount increases because the oxygen deficient portion in the deep part is also used for oxygen storage.
なし None
Claims (5)
上記一種類の触媒金属はＲｈであり、
上記複合酸化物の少なくとも一部は、中空の殻及びその破片の少なくとも一方の形態となって上記触媒層に存在し、
上記中空の殻又はその破片を構成する一次粒子の結晶格子又は原子間に上記Ｒｈの少なくとも一部が配置されていることを特徴とする排気ガス浄化用触媒。 An exhaust gas purifying catalyst in which a catalyst layer formed on a catalyst carrier contains a composite oxide containing Ce and Zr, Al 2 O 3 , and at least one kind of catalyst metal,
The one type of catalytic metal is Rh,
At least a part of the composite oxide is present in the catalyst layer in the form of at least one of a hollow shell and fragments thereof,
An exhaust gas purifying catalyst, wherein at least a part of the Rh is disposed between crystal lattices or atoms of primary particles constituting the hollow shell or fragments thereof.
Ｒｈが結晶格子又は原子間に配置された上記一次粒子の平均結晶子径が１０ｎｍ未満であることを特徴とする排気ガス浄化用触媒。 In claim 1,
An exhaust gas purifying catalyst, wherein Rh is a crystal lattice or an average crystallite diameter of the primary particles arranged between atoms is less than 10 nm.
上記中空の殻は、その直径が０．０５μｍ以上３．０μｍ以下の略球状であり、その殻壁の厚みが５０ｎｍ以下であ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 exhaust gas purifying catalyst, wherein the hollow shell has a substantially spherical shape with a diameter of 0.05 μm or more and 3.0 μm or less, and a thickness of the shell wall is 50 nm or less.
Ｃｅ及びＺｒを含有し且つ結晶格子又は原子間にＲｈが配置されている複合酸化物の一次粒子から構成されていて、
上記一次粒子が凝集して中空の殻及びその破片の少なくとも一方の形態となっていることを特徴とする酸素吸蔵材。 An oxygen storage material contained in the exhaust gas purifying catalyst,
It is composed of primary particles of a composite oxide containing Ce and Zr and having Rh arranged between crystal lattices or atoms,
An oxygen storage material, wherein the primary particles are aggregated to form at least one of a hollow shell and fragments thereof.
上記一次粒子の平均結晶子径が１０ｎｍ未満であることを特徴とする酸素吸蔵材。 In claim 4,
An oxygen storage material, wherein an average crystallite diameter of the primary particles is less than 10 nm.
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