JP2010051886A - Catalyst for cleaning exhaust gas - Google Patents
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- 239000003054 catalyst Substances 0.000 title claims abstract description 93
- 238000004140 cleaning Methods 0.000 title abstract description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims abstract description 214
- 239000002245 particle Substances 0.000 claims abstract description 140
- 238000001179 sorption measurement Methods 0.000 claims abstract description 102
- 239000002131 composite material Substances 0.000 claims description 48
- 238000000746 purification Methods 0.000 claims description 37
- 229910052726 zirconium Inorganic materials 0.000 claims description 9
- 229910052595 hematite Inorganic materials 0.000 claims description 6
- 239000011019 hematite Substances 0.000 claims description 6
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- 229910052598 goethite Inorganic materials 0.000 claims description 4
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 claims description 4
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052748 manganese Inorganic materials 0.000 claims description 4
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 264
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 44
- 239000000463 material Substances 0.000 description 43
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 27
- 239000003463 adsorbent Substances 0.000 description 27
- 239000007789 gas Substances 0.000 description 27
- 239000007864 aqueous solution Substances 0.000 description 22
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 19
- 230000032683 aging Effects 0.000 description 17
- 238000009826 distribution Methods 0.000 description 16
- 238000013507 mapping Methods 0.000 description 14
- 239000000843 powder Substances 0.000 description 14
- 229910052751 metal Inorganic materials 0.000 description 12
- 239000002184 metal Substances 0.000 description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 10
- 238000010304 firing Methods 0.000 description 9
- 239000013078 crystal Substances 0.000 description 8
- 238000000851 scanning transmission electron micrograph Methods 0.000 description 7
- 229910052684 Cerium Inorganic materials 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 229910052763 palladium Inorganic materials 0.000 description 6
- 229910052697 platinum Inorganic materials 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 229910000420 cerium oxide Inorganic materials 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 229910000510 noble metal Inorganic materials 0.000 description 5
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000003860 storage Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 229910052703 rhodium Inorganic materials 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 229910052723 transition metal Inorganic materials 0.000 description 4
- 150000003624 transition metals Chemical class 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 3
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 229910021536 Zeolite Inorganic materials 0.000 description 3
- 230000004913 activation Effects 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
- 230000007423 decrease Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000010457 zeolite Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- -1 at least one of Co Inorganic materials 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical group [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 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 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 238000002336 sorption--desorption measurement Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
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.
エンジンの冷間始動時等、排気ガス温度が低く排気ガス浄化用触媒が十分に活性化していないときは、該触媒上でのＨＣ（炭化水素）やＣＯの酸化反応、並びにＮＯｘ（窒素酸化物）の還元反応が起こりにくい。そのため、例えば、エンジンの排気マニホールドに触媒コンバータを直結して触媒の早期活性化を図ることがなされている。しかし、それでも、エンジン冷間始動から２０秒程度までの間に比較的多く排出されるＨＣを十分に浄化するには至らない。 When the exhaust gas temperature is low and the exhaust gas purification catalyst is not sufficiently activated, such as when the engine is cold started, the oxidation reaction of HC (hydrocarbon) and CO on the catalyst, and NOx (nitrogen oxide) ) Reduction reaction hardly occurs. Therefore, for example, a catalyst converter is directly connected to an exhaust manifold of an engine to achieve early activation of the catalyst. However, it still does not sufficiently purify the HC that is discharged a relatively large amount from the engine cold start to about 20 seconds.
これに対して、エンジン制御によってエンジンのＨＣ排出量を低減する方法は知られている。それは、エンジン始動時から触媒がライトオフするまではエンジン空燃比をリーンにするというものである。しかし、未燃ＨＣの発生を大幅できるというものではなく、かえってＮＯｘ排出量が増大するという問題がある。 On the other hand, a method for reducing engine HC emissions by engine control is known. That is, the engine air-fuel ratio is made lean from when the engine is started until the catalyst is lighted off. However, there is a problem that the generation of unburned HC can not be greatly increased, but rather the amount of NOx emission increases.
そこで、ＨＣ吸着材と、ＰｄやＰｔなど低温でのＨＣ浄化性能に優れた触媒金属とを組み合わせたＨＣトラップ触媒が提案されている。これは、触媒金属が活性化するまでは排気ガス中のＨＣをＨＣ吸着材に吸着させ、触媒温度がある程度上昇してＨＣ吸着材から脱離してくるＨＣを、活性が高くなった触媒金属によって酸化浄化するというものである。例えば、特許文献１には、ＨＣ吸着材からなる第１層と、該第１層の上に設けた、活性セリアおよび／またはアルミナを主成分とした粉末に触媒成分としてＰｔとＰｄの１種以上を含む第２層と、該第２層の上に設けた、触媒成分としてＲｈを含む第３層とを備えてなるＨＣトラップ触媒が開示されている。 Therefore, an HC trap catalyst in which an HC adsorbent and a catalytic metal excellent in HC purification performance at a low temperature such as Pd and Pt are combined has been proposed. This is because the HC in the exhaust gas is adsorbed on the HC adsorbent until the catalytic metal is activated, and the HC adsorbed by the catalyst temperature is increased to some extent by the catalyst metal having increased activity. It is an oxidation purification. For example, Patent Literature 1 discloses a first layer made of an HC adsorbent, and a powder containing active ceria and / or alumina as a main component provided on the first layer as one of Pt and Pd as a catalyst component. An HC trap catalyst comprising the second layer including the above and a third layer including Rh as a catalyst component provided on the second layer is disclosed.
上記ＨＣトラップ触媒では、各々触媒金属を含む第２層及び第３層の触媒層によって排気ガスの浄化がなされるが、触媒金属Ｐｔ、Ｐｄ、Ｒｈ等は希少金属であり、資源保護の観点からそれらの使用量を少なくすることが好ましい。 In the above HC trap catalyst, the exhaust gas is purified by the second and third catalyst layers each containing a catalyst metal, but the catalyst metals Pt, Pd, Rh, etc. are rare metals, from the viewpoint of resource protection. It is preferable to reduce their usage.
この点に関し、特許文献２には、触媒金属量を増大させることなく、酸素吸蔵放出能を向上させることにより、早期活性化を図る三元触媒の例が記載されている。それは、セリウム酸化物を含む担体と、この担体に担持された遷移金属及び貴金属からなる触媒金属とよりなり、セリウム原子及び貴金属各々に対する遷移金属の原子比を所定の範囲にするというものである。遷移金属としては、Ｃｏ、Ｎｉ及びＦｅの少なくとも一種が好ましいとされている。但し、実施例として開示されているのはＣｏ及びＮｉだけであり、Ｆｅについての実施例はない。 In this regard, Patent Document 2 describes an example of a three-way catalyst that achieves early activation by improving the oxygen storage / release capability without increasing the amount of catalytic metal. It consists of a support containing cerium oxide and a catalyst metal comprising a transition metal and a noble metal supported on the support, and the atomic ratio of the transition metal to each of the cerium atom and the noble metal is within a predetermined range. As the transition metal, at least one of Co, Ni and Fe is considered preferable. However, only Co and Ni are disclosed as examples, and there is no example about Fe.
また、特許文献２では、セリアジルコニア固溶体粉末に硝酸Ｎｉ（又は硝酸Ｃｏ）を含浸させ、蒸発乾固、乾燥及び焼成を行ない、得られた粉末にＰｔ溶液を含浸させ、蒸発乾固、乾燥及び焼成を行なうことにより触媒粉末を得るとされている。そして、この触媒粉末とＲｈ／ＺｒＯ２粉末とＡｌ２Ｏ３粉末とアルミナゾルとイオン交換水とを混合してスラリーを調製し、このスラリーをハニカム担体にウォッシュコートして触媒層を形成するとされている。
特許文献１のＨＣトラップ触媒において、その触媒層に特許文献２の三元触媒を採用すれば、触媒金属量を増大させることなく、触媒の早期活性化を図る上で有利になると考えられる。しかし、その三元触媒の担体であるセリウム酸化物は、酸素吸蔵放出能を有する一方、塩基性であることから、酸性であるＮＯｘを吸着する機能も有する。そのため、セリウム酸化物が遷移金属及び貴金属との組み合わせによって酸素吸蔵放出能が高まると、その三元触媒のＮＯｘ吸着能も同時に高まって、ＨＣの浄化に不利になるという問題がある。 In the HC trap catalyst of Patent Document 1, if the three-way catalyst of Patent Document 2 is adopted for the catalyst layer, it is considered advantageous for early activation of the catalyst without increasing the amount of catalyst metal. However, the cerium oxide, which is a carrier of the three-way catalyst, has an oxygen storage / release capability, but also has a function of adsorbing acidic NOx because it is basic. For this reason, if the cerium oxide is combined with a transition metal and a noble metal to increase the oxygen storage / release capacity, the NOx adsorption capacity of the three-way catalyst is also increased, which is disadvantageous for HC purification.
すなわち、ＨＣ吸着層から脱離するＨＣと、三元触媒のセリウム酸化物上の触媒金属との接触が、該セリウム酸化物に吸着されているＮＯｘによって妨げられ、ＨＣの浄化に不利になるという問題である。 That is, contact between HC desorbed from the HC adsorption layer and the catalyst metal on the cerium oxide of the three-way catalyst is hindered by NOx adsorbed on the cerium oxide, which is disadvantageous for purification of HC. It is a problem.
一般に、触媒のＮＯｘ吸着能が高くなることは、触媒金属が活性化するまでのＮＯｘの大気中への排出を抑えるという観点からは好ましいのであるが、ＨＣトラップ触媒においては、ＨＣ吸着層から脱離するＨＣを浄化すべき触媒層のＮＯｘ吸着能が高くなることは、上述の如く好ましくない。 In general, it is preferable that the NOx adsorption capacity of the catalyst is high from the viewpoint of suppressing the emission of NOx into the atmosphere until the catalytic metal is activated. As described above, it is not preferable that the NOx adsorption ability of the catalyst layer for purifying the separated HC is increased.
以上の点に鑑み、本発明は、ＨＣトラップ触媒において、ＨＣ吸着材から脱離するＨＣの酸化浄化を妨げることなく、ＮＯｘの吸着を図り、触媒が活性化するまでのＨＣ及びＮＯｘの大気中への排出を効果的に抑制することを課題とする。 In view of the above points, the present invention aims to adsorb NOx in the HC trap catalyst without disturbing the oxidation purification of HC desorbed from the HC adsorbent, and in the atmosphere of HC and NOx until the catalyst is activated. It is an issue to effectively control emissions.
本発明は、上記課題を解決するために、ＨＣ吸着層と該ＨＣ吸着層から脱離するＨＣを浄化する触媒層との間に中間層を配置し、該中間層にＮＯｘ吸着能が高い吸着材を含ませるようにした。 In order to solve the above problems, the present invention provides an intermediate layer disposed between an HC adsorption layer and a catalyst layer for purifying HC desorbed from the HC adsorption layer, and the intermediate layer has a high NOx adsorption capability. The material was included.
すなわち、本発明は、担体上に、排気ガス中のＨＣを吸着するＨＣ吸着層と、該ＨＣ吸着層の上側に配置され該ＨＣ吸着層から脱離するＨＣを浄化する触媒層とを備えている排気ガス浄化用触媒であって、
上記ＨＣ吸着層と上記触媒層との間に、Ｃｅ含有酸化物粒子と、該Ｃｅ酸化物粒子に接する酸化鉄粒子とを含有し、上記排気ガス中のＮＯｘを吸着する中間層が設けられていることを特徴とする。
That is, the present invention includes, on a carrier, an HC adsorption layer that adsorbs HC in exhaust gas, and a catalyst layer that is disposed above the HC adsorption layer and purifies HC desorbed from the HC adsorption layer. An exhaust gas purifying catalyst,
An intermediate layer containing Ce-containing oxide particles and iron oxide particles in contact with the Ce oxide particles and adsorbing NOx in the exhaust gas is provided between the HC adsorption layer and the catalyst layer. It is characterized by being.
従って、このような触媒であれば、排気ガス中のＮＯｘは中間層に吸着され、ＨＣ吸着層から脱離するＨＣの触媒層での浄化が、ＮＯｘによって妨げられることは少なくなる。一方、上記中間層はＣｅ含有酸化物粒子と酸化鉄粒子との働きによってＮＯｘが効率良く吸着される。この点は、後述する実験データで明らかになるが、Ｃｅ含有酸化物粒子に接触している酸化鉄粒子が該Ｃｅ含有酸化物粒子の塩基性を強くし、そのことによって、当該中間層のＮＯｘ吸着能が高まると考えられる。 Therefore, with such a catalyst, NOx in the exhaust gas is adsorbed by the intermediate layer, and the purification of the HC catalyst layer desorbed from the HC adsorption layer is less hindered by NOx. On the other hand, the intermediate layer efficiently adsorbs NOx by the action of Ce-containing oxide particles and iron oxide particles. This point will be clarified by experimental data to be described later, and the iron oxide particles in contact with the Ce-containing oxide particles strengthen the basicity of the Ce-containing oxide particles. It is thought that the adsorption capacity increases.
さらに、温度上昇に伴ってＨＣ吸着層から脱離するＨＣと中間層から脱離するＮＯｘとが触媒層で反応することにより、ＨＣ及びＮＯｘの浄化が進み、それらの大気中への排出が効果的に抑制される。 Furthermore, HC and NOx purify by the reaction of HC desorbed from the HC adsorbing layer and NOx desorbed from the intermediate layer as the temperature rises, and their emission into the atmosphere is effective. Is suppressed.
上記中間層に含まれる少なくとも一部の酸化鉄粒子は、粒径が３００ｎｍ以下の微細酸化鉄粒子であり、電子顕微鏡観察において、上記微細酸化鉄粒子の酸化鉄粒子総面積に占める面積比率が３０％以上であることが好ましい。 At least some of the iron oxide particles contained in the intermediate layer are fine iron oxide particles having a particle size of 300 nm or less, and the area ratio of the fine iron oxide particles to the total area of the iron oxide particles is 30 in an electron microscope observation. % Or more is preferable.
上記粒径３００ｎｍ以下の微細酸化鉄粒子の酸化鉄粒子総面積に占める面積比率が３０％以上であるということは、この微細酸化鉄粒子が当該中間層に多数分散して含まれていることを意味する。また、上記Ｃｅ含有酸化物粒子はその二次粒子径が数μｍであることが通常であるから、少なくとも一部のＣｅ含有酸化物粒子には、複数の微細酸化鉄粒子が分散して接触しており、該Ｃｅ含有酸化物粒子に対する微細酸化鉄粒子の付着量が比較的多いことを意味する。 That the area ratio of the fine iron oxide particles having a particle size of 300 nm or less to the total area of the iron oxide particles is 30% or more means that a large number of fine iron oxide particles are contained in the intermediate layer. means. Further, since the Ce-containing oxide particles usually have a secondary particle diameter of several μm, at least some of the Ce-containing oxide particles are dispersed and contacted with a plurality of fine iron oxide particles. This means that the amount of fine iron oxide particles attached to the Ce-containing oxide particles is relatively large.
そのため、Ｃｅ含有酸化物粒子と微細酸化鉄粒子との相互作用を発現し易くなって、当該中間層のＮＯｘ吸着能が高くなり、また、微細酸化鉄粒子がＣｅ含有酸化物粒子と相俟って中間層の酸素吸蔵放出能の向上に有効に働くことになり、排気ガスの浄化に有利になる。 Therefore, the interaction between the Ce-containing oxide particles and the fine iron oxide particles is facilitated, the NOx adsorption capacity of the intermediate layer is increased, and the fine iron oxide particles are combined with the Ce-containing oxide particles. This effectively works to improve the oxygen storage / release capacity of the intermediate layer, which is advantageous for purification of exhaust gas.
上記微細酸化鉄粒子の酸化鉄粒子総面積に占める面積比率は４０％以上であることが好ましい。粒径５０ｎｍ以上３００ｎｍ以下の酸化鉄粒子についてみれば、酸化鉄粒子総面積に占める面積比率が４０％以上９５％以下程度であることが好ましい。 The area ratio of the fine iron oxide particles to the total iron oxide particle area is preferably 40% or more. In view of iron oxide particles having a particle size of 50 nm or more and 300 nm or less, the area ratio in the total area of the iron oxide particles is preferably about 40% or more and 95% or less.
上記微細酸化鉄粒子の少なくとも一部はヘマタイトであることが好ましく、また、上記酸化鉄粒子は、マグヘマイト、ゲータイト及びウスタイトがコロイド粒子として分散したゾルを原料とすることが好ましい。 At least a part of the fine iron oxide particles is preferably hematite, and the iron oxide particles are preferably made from a sol in which maghemite, goethite and wustite are dispersed as colloidal particles.
また、上記Ｃｅ含有酸化物粒子は、Ｚｒ及びＭｎのうちの少なくとも一方とＣｅとを含有する複合酸化物粒子であることが好ましい。すなわち、Ｚｒ又はＭｎの固溶によって、Ｃｅ含有酸化物粒子のＮＯｘ吸着能が高まり、それに伴って、ＨＣ吸着層から脱離するＨＣの浄化も進み易くなる。しかし、ＺｒやＭｎの固溶量を増やしていくとＮＯｘの吸着能が高くなるが、その固溶量が過剰になると、かえってＮＯｘ吸着能が低下することから、当該複合酸化物粒子のＣｅＯ２含有率が６０質量％以上９８質量％以下であることが好ましい。 The Ce-containing oxide particles are preferably composite oxide particles containing Ce and at least one of Zr and Mn. That is, the solid solution of Zr or Mn increases the NOx adsorption ability of the Ce-containing oxide particles, and accordingly, the purification of HC desorbed from the HC adsorption layer is facilitated. However, as the solid solution amount of Zr or Mn increases, the NOx adsorption ability increases. However, when the solid solution amount becomes excessive, the NOx adsorption ability decreases, and thus CeO 2 of the composite oxide particle decreases. The content is preferably 60% by mass or more and 98% by mass or less.
以上のように、本発明によれば、ＨＣ吸着層と、該ＨＣ吸着層から脱離するＨＣを浄化する触媒層との間に、Ｃｅ含有酸化物粒子と酸化鉄粒子とを含有しＮＯｘを吸着する中間層を配置したから、触媒層でのＨＣの浄化がＮＯｘによって妨げられることが少なくなり、しかも、中間層ではＮＯｘが効率良く吸着されるから、触媒層が活性化するまでにＨＣが大気中に排出されることがＨＣ吸着層によって抑制されるだけでなく、ＮＯｘが大気中に排出されることも中間層によって抑制され、さらに、温度上昇に伴ってＨＣ吸着層から脱離するＨＣと中間層から脱離するＮＯｘとが触媒層で反応することにより、ＨＣ及びＮＯｘの浄化が進み、それらの大気中への排出が抑制される。 As described above, according to the present invention, Ce-containing oxide particles and iron oxide particles are contained between the HC adsorption layer and the catalyst layer for purifying HC desorbed from the HC adsorption layer, and NOx is contained. Since the adsorbing intermediate layer is arranged, the purification of HC in the catalyst layer is less likely to be hindered by NOx, and NOx is adsorbed efficiently in the intermediate layer, so that HC is not activated until the catalyst layer is activated. Exhaust into the atmosphere is not only suppressed by the HC adsorption layer, but NOx is also suppressed from being released into the atmosphere by the intermediate layer, and further, HC desorbed from the HC adsorption layer as the temperature rises. And NOx desorbed from the intermediate layer react with each other in the catalyst layer, so that purification of HC and NOx proceeds, and their discharge into the atmosphere is suppressed.
以下、本発明の実施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。 Hereinafter, embodiments of 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.
図１に本発明に係る自動車エンジンの排気ガスの浄化に適した排気ガス浄化用触媒が模式的に示されている。この触媒は、担体１の上に、排気ガス中のＨＣを吸着するＨＣ吸着層２と、該ＨＣ吸着層２の上側に配置され該ＨＣ吸着層２から脱離するＨＣを浄化する触媒層３と、ＨＣ吸着層２と触媒層３との間に配置された中間層としてのＮＯｘ吸着層４とを備えている。担体１としては例えばコージェライト製のハニカム担体を適用することができる。 FIG. 1 schematically shows an exhaust gas purifying catalyst suitable for purifying exhaust gas of an automobile engine according to the present invention. The catalyst includes an HC adsorption layer 2 that adsorbs HC in exhaust gas on a carrier 1, and a catalyst layer 3 that is disposed above the HC adsorption layer 2 and purifies HC desorbed from the HC adsorption layer 2. And a NOx adsorption layer 4 as an intermediate layer disposed between the HC adsorption layer 2 and the catalyst layer 3. As the carrier 1, for example, a cordierite honeycomb carrier can be applied.
ＨＣ吸着層２のＨＣ吸着材には、ゼオライトを採用することが好適であり、なかでもβ−ゼオライトが好ましい。触媒層３の触媒材には、三元触媒を採用することが好適である。その三元触媒は、Ｐｔ、Ｐｄ、Ｒｈ等の触媒貴金属と、該触媒貴金属を担持するサポート材としてのＯＳＣ材及びアルミナとによって構成することができる。ここでいう「ＯＳＣ材」は、ＯＳＣ（酸素吸蔵放出能）を有する材料を意味し、セリア、その他のＣｅ含有酸化物粒子を適用することができる。 As the HC adsorbent of the HC adsorption layer 2, it is preferable to employ zeolite, and β-zeolite is particularly preferred. As the catalyst material of the catalyst layer 3, it is preferable to employ a three-way catalyst. The three-way catalyst can be composed of a catalyst noble metal such as Pt, Pd, and Rh, and an OSC material and alumina as a support material that supports the catalyst noble metal. The “OSC material” here means a material having OSC (oxygen storage and release ability), and ceria and other Ce-containing oxide particles can be applied.
ＮＯｘ吸着層４は、Ｃｅ含有酸化物粒子と、該Ｃｅ酸化物粒子に接する酸化鉄粒子とを含有する層であり、Ｐｔ、Ｐｄ、Ｒｈ等の触媒金属は含まない。このＣｅ含有酸化物粒子と酸化鉄粒子とよりなるＮＯｘ吸着材は、低温時に排気ガス中のＮＯｘを吸着し、高温になるＮＯｘを脱離する一方、高温時にはＯＳＣ材として働く。上記酸化鉄粒子は、後述する酸化鉄ゾルを原料として得ることができ、或いは硝酸鉄水溶液を原料として得ることができる。 The NOx adsorption layer 4 is a layer containing Ce-containing oxide particles and iron oxide particles in contact with the Ce oxide particles, and does not contain catalytic metals such as Pt, Pd, and Rh. The NOx adsorbent composed of Ce-containing oxide particles and iron oxide particles adsorbs NOx in the exhaust gas at a low temperature and desorbs NOx at a high temperature, and functions as an OSC material at a high temperature. The iron oxide particles can be obtained using an iron oxide sol described later as a raw material, or an iron nitrate aqueous solution as a raw material.
＜ＮＯｘ吸着材について＞
[酸化鉄粒子の粒径等]
エタノール１００ｍＬ当たり硝酸第二鉄４０．４ｇを溶かし、９０℃から１００℃の温度で２時間から３時間の還流を行なうことによって、スラリー状の液体、すなわち、酸化鉄ゾル（バインダ）を得た。この酸化鉄ゾルとＣｅ含有酸化物粉末としてのＣｅＺｒＮｄ複合酸化物（ＣｅＯ２：ＺｒＯ２：Ｎｄ２Ｏ３＝２３：６７：１０（質量比））とイオン交換水とを混合することによりスラリーを調製し、このスラリーを基材にコーティングし、乾燥（１５０℃）及び焼成（大気中において５００℃の温度に２時間保持）を行なうことにより、ＮＯｘ吸着材を得た。酸化鉄ゾルとＣｅＺｒＮｄ複合酸化物粉末とは、上記焼成後における質量比で、酸化鉄とＣｅＺｒＮｄ複合酸化物とが２：８となるように混合した。
<About NOx adsorbent>
[Iron oxide particle size, etc.]
By dissolving 40.4 g of ferric nitrate per 100 mL of ethanol and refluxing at a temperature of 90 ° C. to 100 ° C. for 2 to 3 hours, a slurry-like liquid, that is, an iron oxide sol (binder) was obtained. The slurry was prepared by mixing this iron oxide sol and CeZrNd composite oxide (CeO 2 : ZrO 2 : Nd 2 O 3 = 23: 67: 10 (mass ratio)) as Ce-containing oxide powder. The NOx adsorbent was obtained by preparing and coating the slurry on a substrate, followed by drying (150 ° C.) and firing (maintaining at a temperature of 500 ° C. for 2 hours in the air). The iron oxide sol and the CeZrNd composite oxide powder were mixed so that the iron oxide and the CeZrNd composite oxide were in a mass ratio of 2: 8 after firing.
図２は得られたＮＯｘ吸着材の透過電子顕微鏡を用いたＳＴＥＭ（走査透過）像、図３乃至図５はＦｅ、Ｚｒ及びＣｅ各原子の相対濃度分布をマッピングしたものである。図２乃至図５から、ＣｅＺｒＮｄ複合酸化物粒子の粒径は１μｍ程度であること、酸化鉄粒子は粒径が３００ｎｍ以下であり、５０ｎｍ以上３００ｎｍ以下の大きさの複数個の酸化鉄粒子がＣｅＺｒＮｄ複合酸化物粒子に接触（粒子上に分布）していることがわかる。この場合、当該顕微鏡観察において、粒径３００ｎｍ以下の微細酸化鉄粒子の酸化鉄粒子総面積に占める面積比率は１００％である（つまり、全ての酸化鉄粒子が粒径３００ｎｍ以下である）ということができる。 FIG. 2 is a STEM (scanning transmission) image of the obtained NOx adsorbent using a transmission electron microscope, and FIGS. 3 to 5 map the relative concentration distribution of each atom of Fe, Zr, and Ce. From FIG. 2 to FIG. 5, the particle size of the CeZrNd composite oxide particles is about 1 μm, the iron oxide particles have a particle size of 300 nm or less, and a plurality of iron oxide particles having a size of 50 nm or more and 300 nm or less are CeZrNd. It can be seen that the composite oxide particles are in contact (distributed on the particles). In this case, in the microscopic observation, the area ratio of fine iron oxide particles having a particle diameter of 300 nm or less to the total area of iron oxide particles is 100% (that is, all iron oxide particles have a particle diameter of 300 nm or less). Can do.
図６乃至図９は上記ＮＯｘ吸着材のエージング（酸素を２％、水蒸気を１０％含む窒素ガス中で９００℃の温度に２４時間保持）後でのＳＴＥＭ像及び各原子の相対濃度分布のマッピングである。ＣｅＺｒＮｄ複合酸化物粒子の粒径は１μｍ程度であり、酸化鉄粒子の粒径は３００ｎｍ以下であり、５０ｎｍ以上３００ｎｍ以下の大きさの酸化鉄粒子がＣｅＺｒＮｄ複合酸化物粒子に複数個接触（粒子上に分布）している。エージング後においても、当該電子顕微鏡観察によれば、全ての酸化鉄粒子の粒径が３００ｎｍ以下になっている。 6 to 9 show mappings of STEM images and relative concentration distribution of each atom after aging of the above NOx adsorbent (held at a temperature of 900 ° C. for 24 hours in nitrogen gas containing 2% oxygen and 10% water vapor). It is. The particle size of the CeZrNd composite oxide particles is about 1 μm, the particle size of the iron oxide particles is 300 nm or less, and a plurality of iron oxide particles having a size of 50 nm to 300 nm are in contact with the CeZrNd composite oxide particles (on the particle Distributed). Even after aging, according to the observation with the electron microscope, the particle diameter of all iron oxide particles is 300 nm or less.
図１０は酸化鉄ゾルを１５０℃で乾燥したもの（乾燥品）、上記エージング前のＮＯｘ吸着材（焼成品）、並びに上記エージング後のＮＯｘ吸着材（焼成・エージング品）各々のＸ線回折チャートである。なお、同図の「ＯＳＣ」は上記ＣｅＺｒＮｄ複合酸化物のことを意味する（この点は他の図面でも同様である。）。酸化鉄ゾルは、マグヘマイト（γ-Ｆｅ２Ｏ３）、ゲータイト（Ｆｅ３＋Ｏ(ＯＨ)）及びウスタイト（ＦｅＯ）がコロイド粒子として分散したものであることがわかる。そして、酸化鉄ゾルのコロイド粒子は焼成によってヘマタイト（α-Ｆｅ２Ｏ３）になっている。 FIG. 10 shows X-ray diffraction charts of the iron oxide sol dried at 150 ° C. (dried product), the NOx adsorbent (baked product) before aging, and the NOx adsorbent (baked / aged product) after aging. It is. In addition, “OSC” in the figure means the CeZrNd composite oxide (this is the same in other drawings). It can be seen that the iron oxide sol is one in which maghemite (γ-Fe 2 O 3 ), goethite (Fe 3+ O (OH)) and wustite (FeO) are dispersed as colloidal particles. The colloidal particles of the iron oxide sol are converted into hematite (α-Fe 2 O 3 ) by firing.
上記エージング前の焼成品におけるヘマタイトの、結晶面（１０４）のピーク強度を１００とする各結晶面の相対ピーク強度は表１に示す通りである。また、上記エージング後のヘマタイトの、結晶面（１０４）のピーク強度を１００とする各結晶面の相対ピーク強度は表２に示す通りである。なお、表中「−」はピーク重複や、ピーク小のために、正確な数値が得られなかったものである。 Table 1 shows the relative peak intensities of the crystal faces of hematite in the fired product before aging, with the peak intensity of the crystal face (104) being 100. Further, the relative peak intensity of each crystal plane with the peak intensity of the crystal plane (104) of the hematite after aging as 100 is shown in Table 2. Note that “−” in the table indicates that an exact numerical value could not be obtained due to peak overlap or small peak.
エージング後において、Ｘ線回折測定によって得られるヘマタイトの各結晶面のピーク強度は、結晶面（１０４）、結晶面（１１０）、結晶面（１１６）の順で小さくなっている。 After aging, the peak intensity of each crystal plane of hematite obtained by X-ray diffraction measurement decreases in the order of crystal plane (104), crystal plane (110), and crystal plane (116).
次に、上記酸化鉄ゾルに代えて、硝酸第二鉄水溶液を上記ＣｅＺｒＮｄ複合酸化物粉末に含浸させ、同様の乾燥及び焼成を行なった。硝酸第二鉄水溶液とＣｅＺｒＮｄ複合酸化物粉末とは、上記焼成後における質量比で、酸化鉄とＣｅＺｒＮｄ複合酸化物とが２：８となるように混合した。 Next, instead of the iron oxide sol, a ferric nitrate aqueous solution was impregnated into the CeZrNd composite oxide powder, and the same drying and firing were performed. The ferric nitrate aqueous solution and the CeZrNd composite oxide powder were mixed so that the iron oxide and the CeZrNd composite oxide were in a mass ratio of 2: 8 after firing.
図１１乃至図１４は得られた上記硝酸第二鉄水溶液によるＮＯｘ吸着材のＳＴＥＭ像及び各原子の相対濃度分布のマッピングである。ＣｅＺｒＮｄ複合酸化物粒子の粒径は１μｍ程度であるが、酸化鉄粒子の粒径は６００〜７００ｎｍ程度になっている。 FIGS. 11 to 14 are STEM images of the obtained NOx adsorbent and the relative concentration distribution of each atom by the obtained ferric nitrate aqueous solution. The particle size of CeZrNd composite oxide particles is about 1 μm, while the particle size of iron oxide particles is about 600 to 700 nm.
図１５乃至図１８は上記硝酸第二鉄水溶液によるＮＯｘ吸着材のエージング（酸化鉄ゾルの場合と同じ条件）後でのＳＴＥＭ像及び各原子の相対濃度分布のマッピングである。ＣｅＺｒＮｄ複合酸化物粒子の粒径は１．５〜２μｍ程度であるが、酸化鉄粒子としては、粒径が６００〜７００ｎｍ程度の粒子が１個と、１００ｎｍ程度の粒子が３個見られる。当該電子顕微鏡観察において、粒径３００ｎｍ以下の酸化鉄粒子の酸化鉄粒子総面積に占める面積比率は１０％未満である。 FIGS. 15 to 18 are STEM images and mapping of the relative concentration distribution of each atom after aging of the NOx adsorbent with the ferric nitrate aqueous solution (the same conditions as in the case of iron oxide sol). The particle size of the CeZrNd composite oxide particles is about 1.5 to 2 μm. As the iron oxide particles, one particle having a particle size of about 600 to 700 nm and three particles of about 100 nm are seen. In the electron microscope observation, the area ratio of the iron oxide particles having a particle diameter of 300 nm or less to the total area of the iron oxide particles is less than 10%.
上記酸化鉄ゾルの場合、焼成によって酸化鉄粒子となるコロイド粒子（マグヘマイト、ゲータイト及びウスタイト）が比較的安定なＦｅ化合物であり、そのために、酸化鉄粒子の粒成長を生じ難い。これに対して、上記硝酸第二鉄水溶液の場合は、反応性が高いＦｅイオンから酸化鉄粒子を生ずるから、粒成長し易い。このことが、上記酸化鉄ゾルから得られる酸化鉄粒子と上記硝酸第二鉄水溶液から得られる酸化鉄粒子の粒径の差違となっていると考えられる。 In the case of the iron oxide sol, colloidal particles (maghemite, goethite, and wustite) that become iron oxide particles upon firing are relatively stable Fe compounds, and therefore, iron oxide particle growth hardly occurs. On the other hand, in the case of the ferric nitrate aqueous solution, iron oxide particles are generated from highly reactive Fe ions, so that the grains are easily grown. This is considered to be the difference in particle diameter between the iron oxide particles obtained from the iron oxide sol and the iron oxide particles obtained from the ferric nitrate aqueous solution.
[ＮＯ吸着能]
３種類のＮＯｘ吸着材（材料Ａ，材料Ｂ，材料Ｃ）を調製し、各々のＮＯｘ吸着能を評価した。
[NO adsorption capacity]
Three types of NOx adsorbents (material A, material B, and material C) were prepared, and each NOx adsorbing ability was evaluated.
−材料Ａ−
ＣｅＺｒ複合酸化物粉末（ＣｅＯ２：ＺｒＯ２＝９０：１０（質量比））４０ｇに、上記酸化鉄ゾル及び水を混合し、１５０℃の温度に２時間保持する乾燥、並びに５００℃の温度に２時間保持する焼成を行なうことにより、材料Ａを得た。酸化鉄ゾルの混合量は、焼成によって得られる酸化鉄量が８ｇとなるように調整した。
-Material A-
The iron oxide sol and water are mixed with 40 g of CeZr composite oxide powder (CeO 2 : ZrO 2 = 90: 10 (mass ratio)), dried at a temperature of 150 ° C. for 2 hours, and heated to a temperature of 500 ° C. The material A was obtained by baking for 2 hours. The amount of iron oxide sol mixed was adjusted so that the amount of iron oxide obtained by firing was 8 g.
−材料Ｂ−
酸化鉄ゾルに代えて硝酸第二鉄水溶液を採用する他は材料Ａと同じ条件で材料Ｂを得た。硝酸第二鉄水溶液による酸化鉄量は、材料Ａと同じく、８ｇとなるようにした。
-Material B-
A material B was obtained under the same conditions as the material A except that a ferric nitrate aqueous solution was used instead of the iron oxide sol. The amount of iron oxide by the ferric nitrate aqueous solution was set to 8 g as in the case of the material A.
−材料Ｃ−
酸化鉄ゾルに代えてアルミナゾルを採用する他は材料Ａと同じ条件で材料Ｃを得た。但し、ＣｅＺｒ複合酸化物粉末量は４８ｇとし、アルミナゾルによるアルミナ量は９．６ｇとなるようにした。
-Material C-
A material C was obtained under the same conditions as the material A except that an alumina sol was used instead of the iron oxide sol. However, the CeZr composite oxide powder amount was 48 g, and the alumina amount by alumina sol was 9.6 g.
−ＮＯ吸着量の測定−
上記各材料Ａ，Ｂ，Ｃ各々０．０５ｇを準備し、ガス流通反応装置及びガス分析装置を用いて、プリコンディショニングを行なった後、ＮＯ吸着量を測定した。プリコンディショニングは、試料をＨｅ気流中で６００℃の温度に１０分間保持するというものである。次いで、モデルガス（ＮＯ；５０００ｐｐｍ，Ｏ２；５％，残Ｈｅ）を１００ｍＬ／分の流量で流しながら、ガス温度を室温から６００℃まで上昇させ、その間に吸着されたＮＯ成分量を算出して、ＮＯ吸着量とした。
-Measurement of NO adsorption amount-
0.05 g of each of the above materials A, B, and C was prepared, and after preconditioning using a gas flow reactor and a gas analyzer, the NO adsorption amount was measured. Preconditioning is to hold the sample at a temperature of 600 ° C. for 10 minutes in a He stream. Next, while flowing the model gas (NO; 5000 ppm, O 2 ; 5%, remaining He) at a flow rate of 100 mL / min, the gas temperature is increased from room temperature to 600 ° C., and the amount of NO components adsorbed during that time is calculated. Thus, the NO adsorption amount was used.
−結果−
結果を図１９に示す。酸化鉄ゾルを採用した材料Ａ、並びに硝酸第二鉄水溶液を採用した材料Ｂは、アルミナゾルを採用した材料ＣよりもＮＯ吸着量が多い。このことから、Ｃｅ含有酸化物粒子に酸化鉄粒子を組み合わせると、ＮＯ吸着能が高くなることがわかる。特に酸化鉄ゾルを採用した材料ＡではＮＯ吸着量が１１０×１０−５mol／ｇ以上になっている。材料ＡのＮＯ吸着量が顕著に多いのは、酸化鉄ゾルによる微細酸化鉄粒子がＣｅ含有酸化物の塩基性を強くしたためと考えられる。
-Result-
The results are shown in FIG. The material A employing the iron oxide sol and the material B employing the ferric nitrate aqueous solution have a larger NO adsorption amount than the material C employing the alumina sol. From this, it can be seen that when the iron oxide particles are combined with the Ce-containing oxide particles, the NO adsorption ability is increased. In particular, in the material A employing the iron oxide sol, the NO adsorption amount is 110 × 10 −5 mol / g or more. The reason that the NO adsorption amount of the material A is remarkably large is considered that the fine iron oxide particles by the iron oxide sol strengthen the basicity of the Ce-containing oxide.
＜実施例及び比較例の冷間ＨＣ浄化率及びＮＯ吸着量＞
実施例１〜４及び比較例１，２の各排気ガス浄化用触媒を調製し、各々の冷間ＨＣ浄化率及びＮＯ吸着量を測定した。
<Cold HC purification rate and NO adsorption amount of Examples and Comparative Examples>
The exhaust gas purifying catalysts of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared, and the cold HC purification rate and the NO adsorption amount of each were measured.
[供試サンプルの調製]
−実施例１−
実施例１の排気ガス浄化用触媒は、図１に示すＨＣ吸着層２、触媒層３及びＮＯｘ吸着層４の三層構造において、触媒層３を上三元触媒層と下三元触媒層の２層構造とした。ＮＯｘ吸着層４のＣｅ含有酸化物粒子としてはＣｅＺｒ複合酸化物粒子を採用し、酸化鉄粒子は酸化鉄ゾルを原料として調製した。
[Preparation of test sample]
Example 1
The exhaust gas purifying catalyst of Example 1 has the three-layer structure of the HC adsorption layer 2, the catalyst layer 3 and the NOx adsorption layer 4 shown in FIG. 1, and the catalyst layer 3 is composed of an upper three-way catalyst layer and a lower three-way catalyst layer. A two-layer structure was adopted. CeZr composite oxide particles were employed as the Ce-containing oxide particles of the NOx adsorption layer 4, and the iron oxide particles were prepared using iron oxide sol as a raw material.
この実施例１については、ＣｅＺｒ複合酸化物粒子のＣｅＯ２含有率（ＣｅＯ２／（ＣｅＯ２＋ＺｒＯ２）質量％）が各々５０質量％、６０質量％、７５質量％、９０質量％、１００質量％である５種類のサンプルを準備した。 For Example 1, the CeO 2 content (CeO 2 / (CeO 2 + ZrO 2 ) mass%) of the CeZr composite oxide particles was 50 mass%, 60 mass%, 75 mass%, 90 mass%, and 100 mass, respectively. 5 types of samples were prepared.
５種類のサンプル各々の各層の具体的な構成は次のとおりである。なお、単位（ｇ／Ｌ）はハニカム担体１Ｌ当たりの質量である。
ＨＣ吸着層２；β−ゼオライト １６０ｇ／Ｌ
上三元触媒層；ＣｅＯ２ ５．５ｇ／Ｌ
ＺｒＣｅＮｄ複合酸化物 ５．７ｇ／Ｌ
Ｐｄ／Ｌａ含有アルミナ ４５．４５ｇ／Ｌ
（Ｐｄ ０．４５ｇ／Ｌ）
Ｐｄ／ＣｅＺｒＬａＹアルミナ複合酸化物 ２２．８５ｇ／Ｌ
（Ｐｄ ０．２５ｇ／Ｌ）
下三元触媒層；Ｒｈ／ＺｒＣｅＮｄ複合酸化物 ７０．１ｇ／Ｌ
（Ｒｈ ０．１ｇ／Ｌ）
Ｒｈ／ＺｒＬａ複合酸化物担持アルミナ ３０．０５ｇ／Ｌ
（Ｒｈ ０．０５ｇ／Ｌ）
Ｌａ含有アルミナ １３ｇ／Ｌ
ＮＯｘ吸着層４；ＣｅＺｒ複合酸化物 ４０ｇ／Ｌ
酸化鉄ゾルによる微細酸化鉄 ８ｇ／Ｌ
「Ｐｄ／」、「Ｐｔ／」及び「Ｒｈ／」はＰｄ、Ｐｔ又はＲｈを「／」の次に記載した母材に担持させたことを意味する。
The specific configuration of each layer of each of the five types of samples is as follows. The unit (g / L) is the mass per 1 L of honeycomb carrier.
HC adsorption layer 2; β-zeolite 160 g / L
Three-way catalyst layer on; CeO 2 5.5g / L
ZrCeNd composite oxide 5.7 g / L
Pd / La containing alumina 45.45 g / L
(Pd 0.45 g / L)
Pd / CeZrLaY alumina composite oxide 22.85 g / L
(Pd 0.25 g / L)
Lower three-way catalyst layer; Rh / ZrCeNd composite oxide 70.1 g / L
(Rh 0.1g / L)
Rh / ZrLa composite oxide supported alumina 30.05 g / L
(Rh 0.05g / L)
La-containing alumina 13g / L
NOx adsorption layer 4; CeZr composite oxide 40g / L
Fine iron oxide by iron oxide sol 8g / L
“Pd /”, “Pt /” and “Rh /” mean that Pd, Pt or Rh is supported on the base material described next to “/”.
上三元触媒層のＺｒＣｅＮｄ複合酸化物の組成はＺｒＯ２：ＣｅＯ２：Ｎｄ２Ｏ３＝５５：３５：１０（質量比）であり、下三元触媒層のＺｒＣｅＮｄ複合酸化物の組成はＺｒＯ２：ＣｅＯ２：Ｎｄ２Ｏ３＝８０：１０：１０（質量比）である。ＣｅＺｒＬａＹアルミナ複合酸化物の組成はＡｌ２Ｏ３：ＣｅＯ２：ＺｒＯ２：Ｌａ２Ｏ３：Ｙ２Ｏ３＝８０．１：１０．４：７．４：１．７：０．４（質量比）である。Ｌａ含有アルミナのＬａ２Ｏ３含有量はいずれも４質量％である。ＺｒＬａ複合酸化物担持アルミナの組成はＺｒＯ２：Ｌａ２Ｏ３：Ａｌ２Ｏ３＝３８：２：６０（質量比）である。 The composition of ZrCeNd composite oxide of the upper three-way catalyst layer ZrO 2: CeO 2: Nd 2 O 3 = 55: 35: 10 (mass ratio), the composition of ZrCeNd composite oxide under the three-way catalyst layer is ZrO 2 : CeO 2 : Nd 2 O 3 = 80: 10: 10 (mass ratio). The composition of the CeZrLaY alumina composite oxide was Al 2 O 3 : CeO 2 : ZrO 2 : La 2 O 3 : Y 2 O 3 = 80.1: 10.4: 7.4: 1.7: 0.4 (mass Ratio). The La 2 O 3 content of the La-containing alumina is 4% by mass. The composition of the ZrLa composite oxide-supported alumina is ZrO 2 : La 2 O 3 : Al 2 O 3 = 38: 2: 60 (mass ratio).
ＮＯｘ吸着層４のＮＯｘ吸着材は、ＣｅＺｒ複合酸化物粉末に、上記酸化鉄ゾル及び水を混合し、１５０℃の温度に２時間保持する乾燥、並びに５００℃の温度に２時間保持する焼成を行なうことにより調製した。 The NOx adsorbent of the NOx adsorption layer 4 is obtained by mixing the above-mentioned iron oxide sol and water with CeZr composite oxide powder, drying for 2 hours at a temperature of 150 ° C., and firing for 2 hours at a temperature of 500 ° C. Prepared by performing.
ＨＣ吸着材のハニカム担体への担持にはバインダとしてアルミナゾルを用い、ＮＯ吸着材及び三元触媒のハニカム担体への担持にはバインダとして硝酸ジルコニルを用いた。 Alumina sol was used as the binder for supporting the HC adsorbent on the honeycomb carrier, and zirconyl nitrate was used as the binder for supporting the NO adsorbent and the three-way catalyst on the honeycomb carrier.
−実施例２−
ＮＯｘ吸着層４のＮＯｘ吸着材の調製において酸化鉄ゾルに代えて硝酸第二鉄水溶液を採用する他は、実施例１と同じ構成とした５種類のサンプル（ＣｅＺｒ複合酸化物粒子のＣｅＯ２含有率（ＣｅＯ２／（ＣｅＯ２＋ＺｒＯ２）質量％）が各々５０質量％、６０質量％、７５質量％、９０質量％、１００質量％である５種類のサンプル）を準備した。上記硝酸第二鉄水溶液による酸化鉄担持量は、実施例１の酸化鉄ゾルを原料とする場合と同じく８ｇ／Ｌである。
-Example 2-
Five types of samples (containing CeO 2 of CeZr composite oxide particles) having the same configuration as in Example 1 except that a ferric nitrate aqueous solution was employed instead of the iron oxide sol in the preparation of the NOx adsorbent for the NOx adsorption layer 4 rate (CeO 2 / (CeO 2 + ZrO 2) mass%) is respectively 50 wt%, 60 wt%, 75 wt%, 90 wt%, were prepared from 5 types of samples) 100% by weight. The amount of iron oxide supported by the ferric nitrate aqueous solution is 8 g / L as in the case of using the iron oxide sol of Example 1 as a raw material.
−比較例１−
ＮＯｘ吸着層４のＮＯｘ吸着材の調製において酸化鉄ゾルに代えてアルミナゾルを採用する他は、実施例１と同じ構成とした５種類のサンプル（ＣｅＺｒ複合酸化物粒子のＣｅＯ２含有率（ＣｅＯ２／（ＣｅＯ２＋ＺｒＯ２）質量％）が各々５０質量％、６０質量％、７５質量％、９０質量％、１００質量％である５種類のサンプル）を準備した。但し、上記ＮＯｘ吸着材を構成するＣｅＺｒ複合酸化物担持量は４８ｇ／Ｌであり、上記アルミナゾルによるアルミナ担持量は９．６ｇ／Ｌである。
-Comparative Example 1-
Five types of samples (CeO 2 content of CeZr composite oxide particles (CeO 2 )) having the same configuration as in Example 1 except that alumina sol was used instead of iron oxide sol in the preparation of the NOx adsorbent for the NOx adsorption layer 4. / (CeO 2 + ZrO 2 ) mass%) was prepared in each of 5 types of samples (50 mass%, 60 mass%, 75 mass%, 90 mass%, and 100 mass%). However, the amount of CeZr composite oxide supported by the NOx adsorbent is 48 g / L, and the amount of alumina supported by the alumina sol is 9.6 g / L.
−実施例３−
ＮＯｘ吸着層４のＮＯｘ吸着材を構成するＣｅ含有酸化物粒子として、ＣｅＺｒ複合酸化物粒子に代えて、ＣｅＭｎ複合酸化物粒子を採用する他は、実施例１と同じ構成とした５種類のサンプル（ＣｅＭｎ複合酸化物粒子のＣｅＯ２含有率（ＣｅＯ２／（ＣｅＯ２＋ＭｎＯ２）質量％）が各々５０質量％、６０質量％、７５質量％、９０質量％、１００質量％である５種類のサンプル）を準備した。酸化鉄ゾルによる酸化鉄担持量は８ｇ／Ｌである。
-Example 3-
Five types of samples having the same configuration as in Example 1 except that CeMr composite oxide particles are used instead of CeZr composite oxide particles as Ce-containing oxide particles constituting the NOx adsorbent of NOx adsorption layer 4 (CeO 2 content of CeMn composite oxide particles (CeO 2 / (CeO 2 + MnO 2 )% by mass)) are 50% by mass, 60% by mass, 75% by mass, 90% by mass, and 100% by mass, respectively. Sample) was prepared. The amount of iron oxide supported by the iron oxide sol is 8 g / L.
−実施例４−
ＮＯｘ吸着層４のＮＯｘ吸着材の調製において酸化鉄ゾルに代えて硝酸第二鉄水溶液を採用する他は、実施例３と同じ構成とした５種類のサンプル（ＣｅＭｎ複合酸化物粒子のＣｅＯ２含有率（ＣｅＯ２／（ＣｅＯ２＋ＭｎＯ２）質量％）が各々５０質量％、６０質量％、７５質量％、９０質量％、１００質量％である５種類のサンプル）を準備した。上記硝酸第二鉄水溶液による酸化鉄担持量は、実施例３の酸化鉄ゾルを原料とする場合と同じく８ｇ／Ｌである。
Example 4
Five samples (containing CeO 2 of CeMn composite oxide particles) having the same structure as in Example 3 except that a ferric nitrate aqueous solution was used instead of the iron oxide sol in the preparation of the NOx adsorbent for the NOx adsorption layer 4 5 types of samples having a ratio (CeO 2 / (CeO 2 + MnO 2 ) mass%) of 50 mass%, 60 mass%, 75 mass%, 90 mass%, and 100 mass%, respectively, were prepared. The amount of iron oxide supported by the ferric nitrate aqueous solution is 8 g / L as in the case of using the iron oxide sol of Example 3 as a raw material.
−比較例２−
ＮＯｘ吸着層４のＮＯｘ吸着材の調製において酸化鉄ゾルに代えてアルミナゾルを採用する他は、実施例３と同じ構成とした５種類のサンプル（ＣｅＭｎ複合酸化物粒子のＣｅＯ２含有率（ＣｅＯ２／（ＣｅＯ２＋ＭｎＯ２）質量％）が各々５０質量％、６０質量％、７５質量％、９０質量％、１００質量％である５種類のサンプル）を準備した。但し、上記ＮＯｘ吸着材を構成するＣｅＭｎ複合酸化物担持量は４８ｇ／Ｌであり、上記アルミナゾルによるアルミナ担持量は９．６ｇ／Ｌである。
-Comparative Example 2-
Five samples (CeO 2 content of CeMn composite oxide particles (CeO 2 )) having the same configuration as in Example 3 except that alumina sol was used instead of iron oxide sol in the preparation of the NOx adsorbent for the NOx adsorption layer 4 / (CeO 2 + MnO 2 )% by mass) was prepared in each of 5 types of samples (50% by mass, 60% by mass, 75% by mass, 90% by mass, and 100% by mass). However, the supported amount of CeMn composite oxide constituting the NOx adsorbent is 48 g / L, and the supported amount of alumina by the alumina sol is 9.6 g / L.
[冷間ＨＣ浄化率及びＮＯ吸着量の測定]
−冷間ＨＣ浄化率−
上記実施例１〜４及び比較例１，２の各触媒に対して、図２０に示すようにトルエン含有ガス（トルエン ２５００ｐｐｍＣ，ＮＯ １０００ｐｐｍ，Ｏ２ ０．６％，残Ｎ２）を５０℃の温度で９００秒間流してトルエンを吸着させた（ＨＣ吸着）。そのときの９００秒間で流したトルエン量をＡ、触媒（ＨＣ吸着層）に吸着されたトルエン量をＢとする。トルエン吸着量Ｂは、触媒を素通りしたトルエン量より求めた。次にトルエンの流通のみを止めたガス（ＮＯ １０００ｐｐｍ，Ｏ２ ０．６％，残Ｎ２）を触媒に流しながら、そのガス温度を３０℃／分の速度で上昇させていき、触媒から流出するトルエン量Ｃを測定した（ＨＣ脱離、浄化）。そうして、［（Ｂ−Ｃ）×１００／Ａ］を各触媒の冷間ＨＣ浄化率として求めた。
[Measurement of cold HC purification rate and NO adsorption amount]
-Cold HC purification rate-
As shown in FIG. 20, toluene-containing gas (toluene 2500 ppmC, NO 1000 ppm, O 2 0.6%, residual N 2 ) was added to each catalyst of Examples 1 to 4 and Comparative Examples 1 and 2 at 50 ° C. The toluene was adsorbed by flowing at a temperature for 900 seconds (HC adsorption). The amount of toluene flowed in 900 seconds at that time is A, and the amount of toluene adsorbed on the catalyst (HC adsorption layer) is B. The toluene adsorption amount B was determined from the amount of toluene passed through the catalyst. Then it stopped and gas flow only toluene (NO 1000ppm, O 2 0.6% , remainder N 2) while flowing into the catalyst, will the gas temperature was raised at 30 ° C. / min, flow out from the catalyst The amount of toluene C to be measured was measured (HC desorption, purification). Then, [(BC) × 100 / A] was obtained as the cold HC purification rate of each catalyst.
−ＮＯ吸着量−
上記実施例１〜４及び比較例１，２の各触媒に、室温（２５℃）にて、ＮＯ含有ガス（ＮＯ １０００ｐｐｍ，残Ｎ２）９００秒間流してＮＯを触媒に吸着させた。次にＮＯの流通を止め、Ｎ２ガスを触媒に流しながら、そのガス温度を３０℃／分の速度で上昇させていくことにより、触媒からＮＯを脱離させた。脱離したＮＯに相当する質量数３０の信号強度を質量分析計により検出した。得られた上記信号強度に基いて、検量線（予め標準試料を用いて作成した濃度と信号強度の関係を示す特性線）を参照し、各触媒のＮＯ吸着量を求めた。
-NO adsorption amount-
NO-containing gas (NO 1000 ppm, remaining N 2 ) was allowed to flow through the catalysts of Examples 1 to 4 and Comparative Examples 1 and 2 at room temperature (25 ° C.) for 900 seconds to adsorb NO to the catalyst. Next, the flow of NO was stopped, and the NO 2 was desorbed from the catalyst by increasing the gas temperature at a rate of 30 ° C./min while flowing N 2 gas through the catalyst. A signal intensity of mass number 30 corresponding to the desorbed NO was detected by a mass spectrometer. Based on the obtained signal intensity, a calibration curve (characteristic line indicating the relationship between concentration and signal intensity prepared in advance using a standard sample) was referred to determine the NO adsorption amount of each catalyst.
ＮＯｘ吸着層のＣｅ含有酸化物粒子としてＣｅＺｒ複合酸化物粒子を用いた実施例１，２及び比較例１の各ＮＯｘ吸着量については、比較例１のＣｅＯ２含有率５０質量％のサンプルの値を１００とする相対値で表すようにした。ＣｅＭｎ複合酸化物粒子を用いた実施例３，４及び比較例２の各ＮＯｘ吸着量についても、比較例２のＣｅＯ２含有率５０質量％のサンプルの値を１００とする相対値で表すようにした。 About each NOx adsorption amount of Examples 1, 2 and Comparative Example 1 using CeZr composite oxide particles as Ce-containing oxide particles of the NOx adsorption layer, the value of the sample of Comparative Example 1 with a CeO 2 content of 50 mass% Is expressed as a relative value of 100. As for each NOx adsorption amount of Examples 3 and 4 and Comparative Example 2 using CeMn composite oxide particles, the value of the sample of CeO 2 content 50 mass% of Comparative Example 2 is expressed as a relative value with 100 as the value. did.
[測定結果]
実施例１，２及び比較例１の冷間ＨＣ浄化率及びＮＯ吸着量の測定結果を図２１に示し、実施例３，４及び比較例２の冷間ＨＣ浄化率及びＮＯ吸着量の測定結果を図２２に示す。
[Measurement result]
The measurement results of the cold HC purification rates and NO adsorption amounts of Examples 1 and 2 and Comparative Example 1 are shown in FIG. 21, and the measurement results of the cold HC purification rates and NO adsorption amounts of Examples 3 and 4 and Comparative Example 2 are shown. Is shown in FIG.
図２１（ＮＯｘ吸着層のＣｅ含有酸化物粒子；ＣｅＺｒ複合酸化物粒子）によれば、冷間ＨＣ浄化率及びＮＯ吸着量のいずれに関しても、ＮＯｘ吸着層に酸化鉄粒子が含まれる実施例１，２は、酸化鉄粒子を含まない比較例１より良い結果を示している。実施例１，２では、酸化鉄粒子の働きによってＮＯｘ吸着層のＮＯ吸着能が高くなり、このＮＯ吸着層に吸着されて脱離するＮＯが触媒層でのＨＣの浄化に利用されて、冷間ＨＣ浄化率が高くなっているものと認められる。また、実施例１は実施例２よりも冷間ＨＣ浄化率及びＮＯ吸着量が良くなっており、酸化鉄ゾルによる微細酸化鉄粒子がＮＯ吸着能の向上に顕著な効果を示すことがわかる。 According to FIG. 21 (Ce-containing oxide particles of NOx adsorption layer; CeZr composite oxide particles), Example 1 in which iron oxide particles are contained in the NOx adsorption layer with respect to both the cold HC purification rate and the NO adsorption amount. , 2 show better results than Comparative Example 1 which does not contain iron oxide particles. In Examples 1 and 2, the NO adsorption capacity of the NOx adsorption layer is increased by the action of the iron oxide particles, and the NO adsorbed and desorbed by the NO adsorption layer is used for the purification of HC in the catalyst layer and is cooled. It is recognized that the HC purification rate has increased. Further, Example 1 has a better cold HC purification rate and NO adsorption amount than Example 2, and it can be seen that fine iron oxide particles by iron oxide sol show a remarkable effect in improving NO adsorption ability.
実施例１，２及び比較例１各々では、ＣｅＯ２含有率９０質量％位置に冷間ＨＣ浄化率及びＮＯ吸着量のピークが現れている。比較例１の冷間ＨＣ浄化率のピーク値を基準に検討すると、酸化鉄ゾルを採用した実施例１では、ＣｅＯ２含有率が５０質量％から１００質量％の全範囲において、また、硝酸第二鉄水溶液を採用した実施例２では、ＣｅＯ２含有率が６０質量％から９８質量％の範囲において、比較例１のピーク値よりも冷間ＨＣ浄化率が高くなっている。このことから、ＣｅＺｒ複合酸化物粒子のＣｅＯ２含有率は６０質量％以上９８質量％以下にすることが好ましいということができる。 In Examples 1 and 2 and Comparative Example 1 each peak of cold HC purification rate and NO adsorption amount appears in the CeO 2 content of 90 wt% position. Examining the peak value of the cold HC purification rate of Comparative Example 1 as a reference, in Example 1 employing the iron oxide sol, the CeO 2 content was in the entire range from 50% by mass to 100% by mass, and the nitric acid first in example 2 employing the Nitetsu solution, CeO 2 content in the range of 60 wt% to 98 wt%, the cold HC purification rate is higher than the peak value of Comparative example 1. From this, it can be said that the CeO 2 content of the CeZr composite oxide particles is preferably 60% by mass or more and 98% by mass or less.
図２２に示すように、ＮＯｘ吸着層のＣｅ含有酸化物粒子としてＣｅＭｎ複合酸化物粒子を用いたケースにおいても、実施例１，２は、冷間ＨＣ浄化率及びＮＯ吸着量のいずれも、比較例１より良い結果を示しており、また、ＣｅＺｒ複合酸化物粒子の場合と同じく、実施例１は実施例２よりも冷間ＨＣ浄化率及びＮＯ吸着量が良くなっている。 As shown in FIG. 22, even in the case where CeMn composite oxide particles were used as the Ce-containing oxide particles in the NOx adsorption layer, Examples 1 and 2 were compared for both the cold HC purification rate and the NO adsorption amount. The results are better than those of Example 1 and, like the case of CeZr composite oxide particles, Example 1 has a better cold HC purification rate and NO adsorption amount than Example 2.
ＣｅＭｎ複合酸化物粒子の場合は、実施例１，２及び比較例１各々の冷間ＨＣ浄化率及びＮＯ吸着量のピークは、ＣｅＯ２含有率７５質量％位置に現れている。比較例２の冷間ＨＣ浄化率のピーク値を基準に検討すると、実施例１，２では、ＣｅＯ２含有率が６０質量％から９８質量％の範囲において、比較例２のピーク値よりも冷間ＨＣ浄化率が高くなっている。このことから、ＣｅＭｎ複合酸化物粒子の場合も、ＣｅＯ２含有率は６０質量％以上９８質量％以下にすることが好ましいということができる。 In the case of CeMn composite oxide particles, the peak of the cold HC purification rate and the NO adsorption amount in each of Examples 1 and 2 and Comparative Example 1 appear at a CeO 2 content of 75% by mass. Considering the basis of the peak value of the cold HC purification rate of Comparative Example 2, carried out in Examples 1 and 2, in the range of 98 wt% CeO 2 content is from 60% by mass, the cold than the peak value of Comparative Example 2 The HC purification rate is high. From this, also in the case of CeMn composite oxide particles, it can be said that the CeO 2 content is preferably 60% by mass or more and 98% by mass or less.
１ 担体
２ ＨＣ吸着層
３ 触媒層
４ ＮＯｘ吸着層
1 Support 2 HC adsorption layer 3 Catalyst layer 4 NOx adsorption layer
Claims (5)
上記ＨＣ吸着層と上記触媒層との間に、Ｃｅ含有酸化物粒子と、該Ｃｅ酸化物粒子に接する酸化鉄粒子とを含有し、上記排気ガス中のＮＯｘを吸着する中間層が設けら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 comprising an HC adsorbing layer that adsorbs HC in exhaust gas and a catalyst layer that is disposed above the HC adsorbing layer and purifies HC desorbed from the HC adsorbing layer. Because
An intermediate layer containing Ce-containing oxide particles and iron oxide particles in contact with the Ce oxide particles and adsorbing NOx in the exhaust gas is provided between the HC adsorption layer and the catalyst layer. An exhaust gas purification catalyst characterized by comprising:
上記中間層に含まれる少なくとも一部の酸化鉄粒子は、粒径が３００ｎｍ以下の微細酸化鉄粒子であり、電子顕微鏡観察において、上記微細酸化鉄粒子の酸化鉄粒子総面積に占める面積比率が３０％以上であることを特徴とする排気ガス浄化用触媒。 In claim 1,
At least some of the iron oxide particles contained in the intermediate layer are fine iron oxide particles having a particle size of 300 nm or less, and the area ratio of the fine iron oxide particles to the total area of the iron oxide particles is 30 in an electron microscope observation. Exhaust gas purification catalyst characterized by being at least%.
上記Ｃｅ含有酸化物粒子は、Ｚｒ及びＭｎのうちの少なくとも一方とＣｅとを含有する複合酸化物粒子であり、該複合酸化物粒子のＣｅＯ２含有率が６０質量％以上９８質量％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 Ce-containing oxide particles is a composite oxide particles containing at least one and Ce of Zr and Mn, CeO 2 content of the composite oxide particles is 60 wt% or more 98 wt% or less An exhaust gas purifying catalyst characterized by that.
上記微細酸化鉄粒子の少なくとも一部はヘマタイト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,
An exhaust gas purifying catalyst, wherein at least a part of the fine iron oxide particles is hematite.
上記微細酸化鉄粒子は、マグヘマイト、ゲータイト及びウスタイトがコロイド粒子として分散したゾルを原料とすることを特徴とする排気ガス浄化用触媒。 In any one of Claims 1 thru | or 4,
The fine iron oxide particles are made from a sol in which maghemite, goethite, and wustite are dispersed as colloidal particles as a raw material.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014083492A (en) * | 2012-10-23 | 2014-05-12 | Toyota Motor Corp | Exhaust gas cleaning catalyst |
| WO2015173881A1 (en) * | 2014-05-13 | 2015-11-19 | 日産自動車株式会社 | Hydrogen-generating catalyst, and exhaust gas purification catalyst |
| WO2015174102A1 (en) * | 2014-05-13 | 2015-11-19 | 日産自動車株式会社 | Exhaust gas purification catalyst |
| US20210299641A1 (en) * | 2020-03-27 | 2021-09-30 | Ngk Insulators, Ltd. | Porous ceramic structure and method of producing porous ceramic structure |
-
2008
- 2008-08-27 JP JP2008218689A patent/JP2010051886A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014083492A (en) * | 2012-10-23 | 2014-05-12 | Toyota Motor Corp | Exhaust gas cleaning catalyst |
| WO2015173881A1 (en) * | 2014-05-13 | 2015-11-19 | 日産自動車株式会社 | Hydrogen-generating catalyst, and exhaust gas purification catalyst |
| WO2015174102A1 (en) * | 2014-05-13 | 2015-11-19 | 日産自動車株式会社 | Exhaust gas purification catalyst |
| JPWO2015174102A1 (en) * | 2014-05-13 | 2017-04-20 | 日産自動車株式会社 | Exhaust gas purification catalyst |
| US20210299641A1 (en) * | 2020-03-27 | 2021-09-30 | Ngk Insulators, Ltd. | Porous ceramic structure and method of producing porous ceramic structure |
| US11731111B2 (en) * | 2020-03-27 | 2023-08-22 | Ngk Insulators, Ltd. | Porous ceramic structure and method of producing porous ceramic structure |
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