JP4674264B2 - Exhaust gas purification catalyst - Google Patents
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本発明は、排ガス浄化用触媒に関するもので、自動車などの内燃機関からの排ガス中に含まれる有害成分である一酸化炭素（ＣＯ）、炭化水素（ＨＣ）および窒素酸化物（ＮＯｘ）を同時に除去する排ガス浄化用触媒に係るものである。 The present invention relates to an exhaust gas purification catalyst, which simultaneously removes carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx), which are harmful components contained in exhaust gas from an internal combustion engine such as an automobile. The present invention relates to an exhaust gas purifying catalyst.
従来、排ガス浄化用触媒としては、セラミックスの触媒担体上に耐火性無機酸化物を担持し、該耐火性無機酸化物に触媒となる貴金属元素および貴金属元素を安定化して保持する化合物と共に担持して形成されている。
特許文献１（特開昭６３−１１１６７４１号公報）には、上記の貴金属元素を安定化して保持する化合物として添加されたセリウムが、排ガス浄化条件の高温度下における酸化セリウムの粒成長を抑制し浄化性能を維持するため、ジルコニウム酸化物がセリウム酸化物に一部は複合酸化物ないしは固溶体として存在させた触媒が開示されている。
Conventionally, as a catalyst for exhaust gas purification, a refractory inorganic oxide is supported on a ceramic catalyst carrier, and the refractory inorganic oxide is supported together with a noble metal element serving as a catalyst and a compound that stably holds the noble metal element. Is formed.
In Patent Document 1 (Japanese Patent Laid-open No. Sho 63-1116741), cerium added as a compound that stabilizes and holds the above-mentioned noble metal element suppresses the growth of cerium oxide particles under high temperature exhaust gas purification conditions. In order to maintain purification performance, a catalyst is disclosed in which zirconium oxide is partly present in cerium oxide as a complex oxide or solid solution.
また、特許文献２（特開平２−４３９５１号公報）には、高温酸化雰囲気のような厳しい条件下でも優れた耐久性を有し、低温域でも高い浄化性能を有する排ガス浄化用触媒として、ジルコニア又はジルコニアとイットリアおよびカルシアよりなる群から選ばれた１種によって安定化されたセリウム酸化物と、ロジウム、白金およびパラジウムよりなる触媒金属を担持した耐火性無機酸化物の活性アルミナとをハニカム担体に担持した触媒が開示されている。しかしながら、これらの排ガス浄化用触媒は、高温域で活性であってもエンジン始動直後の低温雰囲気では、必ずしも触媒が活性とならず十分な浄化性能を示さないという不具合を有する。すなわち、ある程度以上の温度に触媒が暖まらないと、排ガスの浄化性能を十分に発揮できない。 Patent Document 2 (Japanese Patent Application Laid-Open No. 2-43951) discloses zirconia as an exhaust gas purifying catalyst having excellent durability even under severe conditions such as a high-temperature oxidizing atmosphere and having high purifying performance even in a low temperature range. Or, a cerium oxide stabilized by one selected from the group consisting of zirconia, yttria and calcia, and activated alumina of a refractory inorganic oxide carrying a catalyst metal made of rhodium, platinum and palladium as a honeycomb carrier A supported catalyst is disclosed. However, these exhaust gas purifying catalysts, at low temperatures the atmosphere immediately after the engine start be active at a high temperature, not necessarily have the disadvantage that the catalyst does not exhibit activity as such regardless sufficient purification performance. That is, the exhaust gas purification performance cannot be fully exhibited unless the catalyst is warmed to a certain temperature or more.
本発明は、上記の事情に鑑みてなされたもので低温域での触媒活性および触媒自体の耐熱性を向上し、エンジン始動後、速やかに触媒を活性化することを課題とする。 The present invention has been made in view of the above circumstances, and it is an object of the present invention to improve the catalyst activity in a low temperature range and the heat resistance of the catalyst itself, and to activate the catalyst promptly after the engine is started.
本発明の排ガス浄化用触媒は、触媒担体と、該触媒担体上に形成された貴金属担持部とを有する排ガス浄化用触媒において、前記貴金属担持部は、担持部成分と、該担持部成分に担持された貴金属触媒とを有し、該貴金属触媒はロジウムのみからなり、該ロジウムのみを担持する前記担持部成分は、少なくともジルコニウムとセリウムとの混合酸化物粉末と、活性アルミナ粉末とで形成されており、前記ジルコニウムとセリウムとの混合酸化物はその総量を１００モル％とするとジルコニウムは７５モル％以上であることを特徴とする。 The exhaust gas purifying catalyst of the present invention is an exhaust gas purifying catalyst having a catalyst carrier and a noble metal supporting part formed on the catalyst carrier, wherein the noble metal supporting part is supported on a supporting part component and the supporting part component. The noble metal catalyst is made of only rhodium, and the supporting part component supporting only the rhodium is formed of at least a mixed oxide powder of zirconium and cerium and an activated alumina powder. The mixed oxide of zirconium and cerium is characterized in that zirconium is 75 mol% or more when the total amount is 100 mol% .
前記触媒担体上には、更に、第２の貴金属担持部が形成されており、該第２の貴金属担持部は、担持部成分と、該担持部成分に担持された貴金属触媒とを有し、該貴金属触媒はロジウム以外の白金、パラジウムなどの貴金属成分から選ばれる少なくとも一種からなることが好ましい。 The front SL on the catalyst support, further, a second of the noble metal loaded portion is formed, the noble metal-supported portion of the second has a carrier part component, a noble metal catalyst supported on said supported portion component The noble metal catalyst preferably comprises at least one selected from noble metal components such as platinum and palladium other than rhodium.
また、本発明の排ガス浄化用触媒は、触媒担体と、該触媒担体上に形成された貴金属担持部とを有する排ガス浄化用触媒において、前記貴金属担持部は、第１の貴金属担持部と、第２の貴金属担持部とからなり、前記第１の貴金属担持部は、担持部成分と、該担持部成分に担持されロジウムのみからなる貴金属触媒とを有し、前記第２の貴金属担持部は、担持部成分と、該担持部成分に担持されロジウム以外の白金、パラジウムなどの貴金属成分から選ばれる少なくとも一種からなる貴金属触媒とを有し、前記ロジウムのみからなる貴金属触媒を担持する前記担持部成分は、ジルコニウム酸化物及びセリウム酸化物からなる酸化物成分と、該酸化物成分を担持する活性アルミナ粉末とからなり、前記活性アルミナ粉末に担持されている前記酸化物成分の中のジルコニウム及びセリウムの総量を１００モル％とすると、前記ジルコニウムの担持量は７５モル％以上であることを特徴とする。 Further, the exhaust gas purifying catalyst of the present invention is an exhaust gas purifying catalyst having a catalyst carrier and a noble metal carrying portion formed on the catalyst carrier, wherein the noble metal carrying portion includes a first noble metal carrying portion and a first noble metal carrying portion. The first noble metal carrying part has a carrying part component and a noble metal catalyst made of only rhodium supported on the carrying part component, and the second noble metal carrying part comprises: The supporting part component having a supporting part component and a noble metal catalyst made of at least one kind selected from noble metal components such as platinum and palladium other than rhodium supported on the supporting part component, and supporting the noble metal catalyst made only of rhodium. It is oxide component consisting of zirconium oxide and cerium oxide and consists of a activated alumina powder carrying the oxide component, wherein said active alumina powder wherein the acid is supported on When 100 mol% zirconium and the total amount of cerium in the object component, the supported amount of the zirconium and wherein the at least 75 mol%.
本願の課題を解決する他の発明の排ガス浄化用触媒は、触媒担体と、該触媒担体上に形成された貴金属担持部とを有する排ガス浄化用触媒において、前記貴金属担持部は、担持部成分と、該担持部成分に担持された貴金属触媒とを有し、該貴金属触媒はロジウムのみからなり、該ロジウムのみを担持する前記担持部成分は、セリウム酸化物を含まずジルコニウム酸化物からなる酸化物成分と、該酸化物成分を担持する活性アルミナ粉末とからなることを特徴とする。An exhaust gas purifying catalyst of another invention that solves the problem of the present application is an exhaust gas purifying catalyst having a catalyst carrier and a noble metal supporting part formed on the catalyst support, wherein the noble metal supporting part includes a supporting part component and A noble metal catalyst supported on the supporting part component, the noble metal catalyst comprising only rhodium, and the supporting part component supporting only the rhodium does not include cerium oxide but an oxide composed of zirconium oxide. It consists of an active alumina powder which carries a component and this oxide component, It is characterized by the above-mentioned.
本発明の排ガス浄化用触媒は、触媒金属であるロジウムがジルコニウム酸化物リッチの担持層上に担持されているため、ロジウムの安定性が高まり従来の触媒に比べて耐熱性が向上する。耐久試験後においても高い浄化性能を有し、かつ比較的低温域で浄化性能を発揮することができる。したがって、エンジン始動後においても速やかに触媒活性を示して、排ガスを浄化することができる。 In the exhaust gas purifying catalyst of the present invention, rhodium, which is a catalyst metal, is supported on a support layer rich in zirconium oxide, so that the stability of rhodium is increased and the heat resistance is improved as compared with conventional catalysts. Even after the endurance test, it has high purification performance and can exhibit purification performance in a relatively low temperature range. Therefore, even after the engine is started, the catalyst activity can be shown quickly and the exhaust gas can be purified.
本発明の第１の排ガス浄化用触媒は、ロジウムと、ロジウム以外の他の貴金属触媒とを担持した担持層がジルコニウムとセリウムとの混合酸化物と活性アルミナとの混合物に担持して形成されている。ロジウムを担持した担持層成分を、ジルコニウムに富むセリウムとの混合酸化物で構成することによりロジウムの安定性を保ち浄化用触媒のクロス浄化率をより高めることができる。 The first exhaust gas purifying catalyst of the present invention is formed by supporting a support layer supporting rhodium and a precious metal catalyst other than rhodium on a mixture of a mixed oxide of zirconium and cerium and activated alumina. Yes. By constituting the support layer component supporting rhodium with a mixed oxide with cerium rich in zirconium, the stability of rhodium can be maintained and the cross purification rate of the purification catalyst can be further increased.
この混合酸化物は、例えばセリウム、ジルコニウムのそれぞれの溶解液を混合してアンモニア水で共沈殿させて生成物を焼成して形成することができる。この際ジルコニウムの量は、混合酸化物中に７５モル％以上存在することが触媒の安定性を高め触媒活性を保持するために好ましい。また、この際ロジウムはジルコニウムとセリウムの混合酸化物に直接担持した後、活性アルミナを混合してスラリー状として担持層を形成してもよい。なお、使用する活性アルミナ粉末はランタンを固溶しなくても安定な担持層の形成が可能となる。 This mixed oxide can be formed, for example, by mixing dissolved solutions of cerium and zirconium, coprecipitating with ammonia water, and firing the product. In this case, the amount of zirconium is preferably 75 mol% or more in the mixed oxide in order to enhance the stability of the catalyst and maintain the catalytic activity. In this case, rhodium may be directly supported on a mixed oxide of zirconium and cerium and then mixed with activated alumina to form a support layer as a slurry. The active alumina powder used can form a stable support layer without dissolving lanthanum in solid solution.
本発明の第１の排ガス浄化用触媒は、後述の他の発明の排ガス浄化用触媒と同様に、貴金属触媒のロジウムに加えて白金を担持した担持層を加えて担持してもよい。白金の担持もロジウムと同様にセリウムとジルコニウムの酸化物に担持して用いることが好ましい。そして、トータルとしてのセリウムとジルコニウムの比率においてもジルコニウムのモル比率が高いもの、すなわちジルコニウムのモル％が７５以上であることが好ましい。 The first exhaust gas purifying catalyst of the present invention may be supported by adding a support layer supporting platinum in addition to the rhodium of the noble metal catalyst, similarly to the exhaust gas purifying catalyst of other invention described later . It is preferable to use platinum supported on an oxide of cerium and zirconium like rhodium. And it is preferable that also in the ratio of cerium and zirconium as a total, the zirconium molar ratio is high, that is, the molar percentage of zirconium is 75 or more.
担持層に担持する酸化物の総量は、触媒容量１リットル当たり、セリウム、ジルコニウム量がそれぞれ０．１〜０．４モル／Ｌ、０．１〜０．６モル／Ｌの範囲であることが望ましい。触媒中でのセリウム量が０．１モル／Ｌ未満の場合、酸素吸蔵量が減少し、触媒活性が低下する。また、０．４モル／Ｌを超えると性能の向上は僅かでコスト面で好ましくない。ジルコニウム量が０．１モル／Ｌ未満の場合、ロジウムの安定性が低下するので好ましくない。また、０．６モル／Ｌを超えて添加しても触媒の安定性の向上は僅かであり高価となるので好ましくない。 The total amount of oxide supported on the support layer is such that the amount of cerium and zirconium is 0.1 to 0.4 mol / L and 0.1 to 0.6 mol / L, respectively, per liter of catalyst capacity. desirable. When the amount of cerium in the catalyst is less than 0.1 mol / L, the oxygen storage amount decreases and the catalytic activity decreases. On the other hand, if it exceeds 0.4 mol / L, the performance is only slightly improved, which is not preferable in terms of cost. When the amount of zirconium is less than 0.1 mol / L, the stability of rhodium decreases, which is not preferable. Moreover, even if it adds exceeding 0.6 mol / L, since the improvement of the stability of a catalyst is slight and it becomes expensive, it is unpreferable.
また、ロジウムの担持量は、触媒容量１リットル当たり０．０１〜５ｇであることが望ましい。ロジウムの担持量が０．０１ｇ／Ｌ未満の場合、十分な触媒活性が得られないので好ましくない。また５ｇ／Ｌを超えると、それ以上ロジウムの担持量を増加させても性能向上は僅かで高価となり好ましくない。白金を担持する場合の担持量は、０．１〜５ｇである。担持量が０．１ｇ／Ｌ未満の場合、十分な触媒活性が得られないおそれがあり好ましくない。また、５ｇ／Ｌを超えると、それ以上白金の担持量を増加させても性能の向上は僅かで高価となるので好ましくない。 The supported amount of rhodium is preferably 0.01 to 5 g per liter of catalyst capacity. A rhodium loading of less than 0.01 g / L is not preferable because sufficient catalytic activity cannot be obtained. On the other hand, if it exceeds 5 g / L, even if the amount of rhodium supported is increased further, the performance improvement is slight and expensive. When platinum is supported, the supported amount is 0.1 to 5 g. When the loading is less than 0.1 g / L, there is a possibility that sufficient catalytic activity may not be obtained, which is not preferable. On the other hand, if the amount exceeds 5 g / L, the improvement in performance is slight and expensive even if the amount of platinum supported is increased.
このような貴触媒金属のロジウムをジルコニウム酸化物が富む担持層に担持した構成とすることで、同じ組成で均一に担持した触媒に比較して、低温域での触媒活性度を高くすることができる。すなわち、本発明の触媒では耐久試験後の触媒の５０％浄化温度を低くでき低温活性の課題が実現できる。 By adopting a structure in which such a noble catalyst metal, rhodium, is supported on a support layer rich in zirconium oxide, the catalyst activity in a low temperature region can be increased compared to a catalyst supported uniformly with the same composition. it can. That is, in the catalyst of the present invention, the 50% purification temperature of the catalyst after the durability test can be lowered, and the problem of low temperature activity can be realized.
排ガス浄化用触媒は、触媒担体と、該触媒担体上に形成された貴金属担持層とからなる排ガス浄化用触媒において、前記貴金属担持層は、担持層成分と、該担持層成分に担持された貴金属触媒とを有し、該貴金属触媒はロジウムを含み、該ロジウムを担持する前記担持層成分は、ジルコニウム酸化物及びセリウム酸化物の中の少なくとも１種からなる酸化物成分と、該酸化物成分を担持する活性アルミナ粉末とからなり、該活性アルミナ粉末に担持されている前記酸化物成分の中のジルコニウムおよびセリウムの総量を１００モル％とすると、前記ジルコニウムの担持量は７５モル％以上である。 The exhaust gas purifying catalyst is an exhaust gas purifying catalyst comprising a catalyst carrier and a noble metal supporting layer formed on the catalyst carrier. The noble metal supporting layer includes a supporting layer component and a noble metal supported on the supporting layer component. The noble metal catalyst contains rhodium, and the support layer component supporting the rhodium includes an oxide component composed of at least one of zirconium oxide and cerium oxide, and the oxide component. It consists of a activated alumina powder carrying, when 100 mol% zirconium and the total amount of cerium in the oxide component carried on the active alumina powder, the supported amount of the zirconium is 75 mol% or more.
なお、ジルコニウム、セリウムの総量１００モル％は、ジルコニウム、セリウム各原子の原子モルを百分率で表すものである。
前記活性アルミナ粉末はランタンが固溶した安定化アルミナ粉末であることが好ましい。
前記担持層成分は予め前記ジルコニウム酸化物が担持された前記活性アルミナをスラリーから形成されたものであることが好ましい。
The total amount of zirconium and cerium of 100 mol% represents the atomic mole of each atom of zirconium and cerium in percentage.
The activated alumina powder is preferably a stabilized alumina powder in which lanthanum is dissolved.
The support layer component is preferably formed from a slurry of the activated alumina on which the zirconium oxide is previously supported.
前記ロジウムを担持する前記担持層成分における前記酸化物成分の中のジルコニウム及びセリウムの総量を１００モル％とすると、前記ジルコニウムの担持量は９０モル％以上であることが好ましい。
本願の課題を解決する他の発明の排ガス浄化用触媒は、触媒担体と該触媒担体上に形成された無機酸化物の担持層と該担持層に担持された貴金属触媒とからなる。本発明の特徴は、貴金属触媒のロジウムがジルコニウム酸化物を担持した活性アルミナ粉末上に担持された担持層を有することにある。貴金属触媒のロジウムがジルコニウム酸化物の近傍に担持されていることでロジウムによる浄化特性を高めると共にロジウムの安定性や耐久性を保持することができる。
ロジウムを活性アルミナ、あるいはセリウム酸化物を含む活性アルミナに担持した場合よりもロジウムの優れた浄化触媒としての効果が発揮できる。さらに、前記ジルコニウムを担持した活性アルミナに対して劣位量セリウム酸化物を配合した担持層成分にロジウムを担持した担持層も同様にロジウムによる浄化特性を高めると共にロジウムの安定性や耐久性を保持することができる。
前記活性アルミナ粉末に担持されているジルコニウム酸化物およびセリウム酸化物の量は、ジルコニウムおよびセリウムの総量を１００モル％とすると、該ジルコニウムの担持量は７５モル％以上とする。セリウムの添加量が２５モル％以上となると触媒の低温活性が失われるので好ましくない。
前記活性アルミナ粉末は、ランタンを固溶すること活性アルミナが安定化され担持している酸化物および貴金属触媒が安定化されて触媒の浄化性能が向上するので好ましい。
触媒担体上に形成される上記の担持層は、ジルコニウム酸化物、必要に応じてセリウム酸化物を混合して担持した活性アルミナ粉末にロジウムを担持した混合物をスラリー状にして触媒担体上にコートして担持することで均一な担持層が形成できる。この活性アルミナ粉末などの酸化物をスラリーで担持する際、貴金属触媒のロジウムを予め前記酸化物粉末に担持したスラリーを用いて担持層を形成することが好ましい。これにより、触媒金属のロジウムがジルコニウム酸化物上に均一に分散し、安定化し触媒の耐熱性を高め触媒活性を有効に発揮させることができる。
前記触媒担体上には、さらに貴金属触媒の白金やパラジウムなどを担持した活性アルミナ粉末およびセリウム酸化物、ジルコニウム酸化物とからなる担持成分を上記のロジウムを担持した担持成分に混合して均一のスラリーとして触媒担体上に担持して触媒を形成することができる。前記触媒担体は、例えばセラミックスや金属製のハニカム構造体のモノリス担体が利用できる。
前記貴金属触媒は、さらに、前記ロジウム以外の貴金属触媒である他貴金属触媒を含み、該他貴金属触媒を担持する前記担持層成分は、ジルコニウム酸化物及びセリウム酸化物の中の少なくとも１種からなる酸化物成分と、該酸化物成分を担持する活性アルミナ粉末とからなることが好ましい。
また、排ガス浄化用触媒は、触媒担体と、該触媒担体上に形成された貴金属担持層とからなる排ガス浄化用触媒において、前記貴金属担持層は、担持層成分と、該担持層成分に担持された貴金属触媒とを有し、該貴金属触媒は、ロジウムと、ロジウム以外の貴金属触媒である他貴金属触媒とからなり、前記担持層成分は、前記ロジウムを担持するロジウム担持部と、ロジウム以外の前記他貴金属触媒を担持する他貴金属担持部とからなり、前記ロジウム担持部は、少なくともジルコニウムとセリウムとの混合酸化物粉末と、活性アルミナ粉末とで形成されており、前記ロジウム担持部における前記混合酸化物粉末の中のジルコニウム及びセリウムの総量を１００モル％とすると前記ジルコニウムの担持量は７５モル％以上１００モル％未満であり、前記他貴金属担持部は、少なくともジルコニウムとセリウムとの混合酸化物粉末と、活性アルミナ粉末とで形成されていてもよい。
When the total amount of zirconium and cerium in the oxide component in the supporting layer component supporting rhodium is 100 mol%, the supported amount of zirconium is preferably 90 mol% or more.
Another exhaust gas purifying catalyst for solving the problems of the present application comprises a catalyst carrier, an inorganic oxide support layer formed on the catalyst support, and a noble metal catalyst supported on the support layer. A feature of the present invention is that it has a supporting layer in which rhodium as a noble metal catalyst is supported on activated alumina powder supporting zirconium oxide. By supporting rhodium as a noble metal catalyst in the vicinity of zirconium oxide, it is possible to improve the purification characteristics of rhodium and to maintain the stability and durability of rhodium.
The rhodium is more effective as a purification catalyst than the case where rhodium is supported on activated alumina or activated alumina containing cerium oxide. Furthermore, the support layer in which rhodium is supported on the support layer component in which an inferior amount of cerium oxide is mixed with the activated alumina supporting zirconium is also improved in the rhodium purification characteristics and maintains the stability and durability of rhodium. be able to.
With respect to the amounts of zirconium oxide and cerium oxide supported on the activated alumina powder, when the total amount of zirconium and cerium is 100 mol%, the amount of zirconium supported is 75 mol% or more. If the amount of cerium added is 25 mol% or more, the low temperature activity of the catalyst is lost, which is not preferable.
The activated alumina powder is preferable because lanthanum is dissolved to stabilize the activated alumina and the supported oxide and noble metal catalyst are stabilized, thereby improving the purification performance of the catalyst.
The above-mentioned support layer formed on the catalyst support is coated on the catalyst support in the form of a slurry of a mixture of rhodium supported on active alumina powder supported by mixing zirconium oxide and, if necessary, cerium oxide. A uniform support layer can be formed. When the oxide such as activated alumina powder is supported in a slurry, it is preferable to form the support layer using a slurry in which rhodium as a noble metal catalyst is previously supported on the oxide powder. Thereby, the rhodium of the catalyst metal can be uniformly dispersed on the zirconium oxide, can be stabilized, can increase the heat resistance of the catalyst, and can effectively exhibit the catalytic activity.
On the catalyst carrier, an active alumina powder carrying a noble metal catalyst such as platinum or palladium, and a carrying component comprising cerium oxide and zirconium oxide are mixed with the above carrying component carrying rhodium to obtain a uniform slurry. Can be supported on a catalyst carrier to form a catalyst. As the catalyst carrier, for example, a monolith carrier having a honeycomb structure made of ceramics or metal can be used.
The noble metal catalyst further includes another noble metal catalyst which is a noble metal catalyst other than rhodium, and the supporting layer component supporting the other noble metal catalyst is an oxidation comprising at least one of zirconium oxide and cerium oxide. It is preferable to consist of a physical component and the activated alumina powder which carries this oxide component.
The exhaust gas purifying catalyst is an exhaust gas purifying catalyst comprising a catalyst carrier and a noble metal supporting layer formed on the catalyst carrier. The noble metal supporting layer is supported on a supporting layer component and the supporting layer component. The noble metal catalyst comprises rhodium and another noble metal catalyst that is a noble metal catalyst other than rhodium, and the supporting layer component includes a rhodium supporting part for supporting the rhodium, and the non-rhodium other than the rhodium. The rhodium supporting part is formed of at least a mixed oxide powder of zirconium and cerium and an activated alumina powder, and the mixed oxidation in the rhodium supporting part. When the total amount of zirconium and cerium in the product powder is 100 mol%, the supported amount of zirconium is 75 mol% or more and less than 100 mol%. Ri, the other noble metal-supported unit, the mixed oxide powder and at least zirconium and cerium, may be formed by the activated alumina.
前記排ガス浄化用触媒は、触媒金属であるロジウムがジルコニウム酸化物リッチの担持層上に担持されているため、ロジウムの安定性が高まり従来の触媒に比べて耐熱性が向上する。耐久試験後においても高い浄化性能を有し、かつ比較的低温域で浄化性能を発揮することができる。したがって、エンジン始動後においても速やかに触媒活性を示して、排ガスを浄化することができる。 In the exhaust gas-purifying catalyst, rhodium, which is a catalyst metal, is supported on a support layer rich in zirconium oxide, so that the stability of rhodium is increased and heat resistance is improved as compared with conventional catalysts. Even after the endurance test, it has high purification performance and can exhibit purification performance in a relatively low temperature range. Therefore, even after the engine is started, the catalyst activity can be shown quickly and the exhaust gas can be purified.
以下、本発明について、参考例、実施例及び比較例により具体的に説明する。 Hereinafter, the present invention will be specifically described with reference examples, examples and comparative examples .
（参考例１）
３モル％のランタンを含有する活性アルミナ粉末を、硝酸ジルコニウム水溶液中に浸漬し、攪拌後、乾燥、焼成してジルコニウムを担持したランタン含有活性アルミナ粉末を得た。
( Reference Example 1 )
Activated alumina powder containing 3 mol% of lanthanum was immersed in an aqueous zirconium nitrate solution, stirred, dried and fired to obtain lanthanum-containing activated alumina powder supporting zirconium.
このジルコニウム酸化物担持活性アルミナ粉末を硝酸ロジウム水溶液中に浸漬し、乾燥しロジウムを固定した粉末を得た。このロジウムを固定した活性アルミナ粉末と硝酸水溶液、バインダーおよび脱イオン水とでスラリー化しスラリーＡを得た。次に、３モル％のランタンを含有活性アルミナ粉末を、硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でセリウム量が多い溶液）に浸漬し、攪拌後、該溶液中にアンモニア水を添加し、乾燥、焼成してランタン含有活性アルミナに、セリウム酸化物とジルコニウム酸化物を担持した粉末を得た。 This zirconium oxide-supported active alumina powder was immersed in an aqueous rhodium nitrate solution and dried to obtain a powder in which rhodium was fixed. A slurry A was obtained by slurrying the rhodium-fixed activated alumina powder with an aqueous nitric acid solution, a binder and deionized water. Next, the activated alumina powder containing 3 mol% of lanthanum is immersed in a mixed solution of cerium nitrate solution and zirconium nitrate solution (solution having a large amount of cerium in the ratio of cerium and zirconium), and after stirring, in the solution Ammonia water was added thereto, dried and fired to obtain a powder in which cerium oxide and zirconium oxide were supported on lanthanum-containing activated alumina.
更に、この粉末をジニトロジアミン白金溶液中に浸漬し、乾燥し白金を固定したセリウム酸化物とジルコニウム酸化物担持活性アルミナ粉末を得た。この白金を固定したセリウム酸化物とジルコニウム酸化物を担持した活性アルミナ粉末と硝酸水溶液、バインダーおよび脱イオン水でスラリー化しスラリーＢを得た。スラリーＡおよびスラリーＢを１：１の割合で混合し、直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥、焼成して触媒１を得た。 Furthermore, this powder was immersed in a dinitrodiamine platinum solution and dried to obtain a cerium oxide and zirconium oxide-supported activated alumina powder on which platinum was fixed. The activated alumina powder carrying cerium oxide and zirconium oxide with platinum fixed thereon was slurried with an aqueous nitric acid solution, a binder and deionized water to obtain slurry B. Slurry A and slurry B were mixed at a ratio of 1: 1, and coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried and fired to obtain catalyst 1.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．２１ｍｏｌ／Ｌ、Ｚｒ０．２９ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.21 mol / L, Zr 0.29 mol / L, La 0.03 mol / L.
（実施例１）
３モル％のランタンを含有活性アルミナ粉末を、硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でジルコニウム量が多い溶液）に浸漬し、攪拌後、該溶液中にアンモニア水を添加し、乾燥、焼成してランタン含有活性アルミナにセリウム酸化物とジルコニウム酸化物とを担持した粉末を得た。
( Example 1 )
The activated alumina powder containing 3 mol% of lanthanum is immersed in a mixed solution of cerium nitrate solution and zirconium nitrate solution (solution with a large amount of zirconium in the ratio of cerium and zirconium), and after stirring, ammonia water is added to the solution. Was added, dried and fired to obtain a powder in which cerium oxide and zirconium oxide were supported on lanthanum-containing activated alumina.
上記酸化物担持活性アルミナ粉末を硝酸ロジウム水溶液中に浸漬し、乾燥しロジウムを固定した粉末を得た。このロジウムを固定した酸化物担持活性アルミナ粉末と硝酸水溶液、バインダーおよび脱イオン水とでスラリー化しスラリーＡを得た。次に、３モル％のランタンを含有活性アルミナ粉末を、硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でジルコニウム量が多い溶液）に浸漬し、攪拌後、該溶液中にアンモニア水を添加し、乾燥、焼成してランタン含有活性アルミナにセリウム酸化物とジルコニウム酸化物を担持した粉末を得た。 The oxide-supporting activated alumina powder was immersed in an aqueous rhodium nitrate solution and dried to obtain a powder in which rhodium was fixed. A slurry A was obtained by slurrying this rhodium-fixed oxide-supporting activated alumina powder with an aqueous nitric acid solution, a binder and deionized water. Next, the activated alumina powder containing 3 mol% of lanthanum is immersed in a solution in which a cerium nitrate solution and a zirconium nitrate solution are mixed (a solution having a large amount of zirconium in the ratio of cerium and zirconium), and after stirring, Ammonia water was added thereto, dried and fired to obtain a powder in which cerium oxide and zirconium oxide were supported on lanthanum-containing activated alumina.
更に、上記の酸化物担持粉末をジニトロジアミン白金溶液中に浸漬し、乾燥し白金を固定した活性アルミナ粉末を得た。この白金を固定した上記酸化物を担持した活性アルミナ粉末と硝酸水溶液、バインダーおよび脱イオン水でスラリー化しスラリーＢを得た。スラリーＡおよびスラリーＢを１：１の割合で混合し、直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥、焼成して触媒２を得た。 Further, the above oxide-supported powder was immersed in a dinitrodiamine platinum solution and dried to obtain an activated alumina powder on which platinum was fixed. A slurry B was obtained by slurrying the activated alumina powder carrying the above-mentioned oxide on which platinum was fixed with an aqueous nitric acid solution, a binder and deionized water. Slurry A and slurry B were mixed at a ratio of 1: 1, and coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried and fired to obtain catalyst 2.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．１４ｍｏｌ／Ｌ、Ｚｒ０．３６ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.14 mol / L, Zr 0.36 mol / L, La 0.03 mol / L.
（実施例２）
活性アルミナ粉末にセリウム酸化物とジルコニウム酸化物の担持比率を変えた以外実施例１と同様の操作により触媒３を得た。
( Example 2 )
Catalyst 3 was obtained in the same manner as in Example 1 except that the supported ratio of cerium oxide and zirconium oxide was changed to activated alumina powder.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．１６ｍｏｌ／Ｌ、Ｚｒ０．３４ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.16 mol / L, Zr 0.34 mol / L, La 0.03 mol / L.
（実施例３）
硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でジルコニウム量が多い溶液）にアンモニア水を添加して生成した、セリウム・ジルコニウムの共沈殿物を、乾燥、焼成してセリウム、ジルコニウム混合酸化物を得た。
( Example 3 )
A cerium-zirconium coprecipitate formed by adding ammonia water in a mixed solution of cerium nitrate solution and zirconium nitrate solution (a solution containing a large amount of zirconium in the ratio of cerium to zirconium) is dried and calcined to cerium. A zirconium mixed oxide was obtained.
このセリウム、ジルコニウムの混合酸化物と、活性アルミナ粉末を硝酸ロジウム溶液中に浸漬し、乾燥してロジウムを固定した混合酸化物を含む活性アルミナ粉末を得た。
このロジウムを固定した上記で得た粉末と硝酸水溶液および脱イオン水でスラリー化しスラリーＡを得た。
The mixed oxide of cerium and zirconium and the activated alumina powder were immersed in a rhodium nitrate solution and dried to obtain an activated alumina powder containing the mixed oxide in which rhodium was fixed.
A slurry A was obtained by slurrying this rhodium-fixed powder with an aqueous nitric acid solution and deionized water.
硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でセリウム量が多い溶液）にアンモニア水を添加して生成した、セリウム・ジルコニウムの共沈殿物を、乾燥、焼成してセリウム、ジルコニウム混合酸化物を得た。
このセリウム、ジルコニウムの混合酸化物と、活性アルミナ粉末をジニトロジアミン白金溶液中に浸漬し、乾燥して白金を固定した混合酸化物含有活性アルミナ粉末を得た。
A cerium-zirconium coprecipitate formed by adding aqueous ammonia in a mixed solution of cerium nitrate solution and zirconium nitrate solution (a solution containing a large amount of cerium in the ratio of cerium to zirconium) is dried and calcined to obtain cerium. A zirconium mixed oxide was obtained.
This mixed oxide of cerium and zirconium and activated alumina powder were immersed in a dinitrodiamine platinum solution and dried to obtain a mixed oxide-containing activated alumina powder in which platinum was fixed.
このロジウムを固定した上記の粉末と硝酸水溶液および脱イオン水でスラリー化しスラリーＢを得た。
スラリーＡおよびスラリーＢを１：１の割合で混合し、直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥、焼成して触媒４を得た。
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．１６ｍｏｌ／Ｌ、Ｚｒ０．３４ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。
A slurry B was obtained by slurrying the rhodium-fixed powder with an aqueous nitric acid solution and deionized water.
Slurry A and slurry B were mixed at a ratio of 1: 1, and coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried and fired to obtain catalyst 4.
The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.16 mol / L, Zr 0.34 mol / L, La 0.03 mol / L.
（実施例４）
硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でジルコニウム量が多い溶液）にアンモニア水を添加して生成した、セリウム・ジルコニウムの共沈殿物を、乾燥、焼成してセリウム、ジルコニウム混合酸化物を得た。
( Example 4 )
A cerium-zirconium coprecipitate formed by adding ammonia water in a mixed solution of cerium nitrate solution and zirconium nitrate solution (a solution containing a large amount of zirconium in the ratio of cerium to zirconium) is dried and calcined to cerium. A zirconium mixed oxide was obtained.
このセリウム、ジルコニウムの酸化物を硝酸ロジウム溶液中に浸漬し、乾燥してロジウムを固定した混合酸化物粉末を得た。
このロジウムを固定したセリウム、ジルコニウムの混合酸化物粉末と活性アルミナと、硝酸水溶液および脱イオン水でスラリー化しスラリーＡを得た。
硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でセリウム量が多い溶液）にアンモニア水を添加して生成した、セリウム・ジルコニウムの共沈殿物を、乾燥、焼成してセリウム、ジルコニウム混合酸化物を得た。
The cerium and zirconium oxides were immersed in a rhodium nitrate solution and dried to obtain a mixed oxide powder in which rhodium was fixed.
A slurry A was obtained by slurrying the mixed oxide powder of cerium and zirconium with fixed rhodium, activated alumina, nitric acid aqueous solution and deionized water.
A cerium-zirconium coprecipitate formed by adding aqueous ammonia in a mixed solution of cerium nitrate solution and zirconium nitrate solution (a solution containing a large amount of cerium in the ratio of cerium to zirconium) is dried and calcined to obtain cerium. A zirconium mixed oxide was obtained.
このセリウム、ジルコニウムの混合酸化物粉末をジニトロジアミン白金溶液中に浸漬し、乾燥して白金を固定した粉末を得た。
このロジウムを固定したセリウム、ジルコニウム混合酸化物粉末と、活性アルミナ粉末と硝酸水溶液および脱イオン水でスラリー化しスラリーＢを得た。
スラリーＡおよびスラリーＢを１：１の割合で混合し、直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥、焼成して触媒５を得た。
This mixed oxide powder of cerium and zirconium was immersed in a dinitrodiamine platinum solution and dried to obtain a powder on which platinum was fixed.
A slurry B was obtained by slurrying this rhodium-fixed cerium and zirconium mixed oxide powder, activated alumina powder, nitric acid aqueous solution and deionized water.
Slurry A and slurry B were mixed at a ratio of 1: 1, and coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried and fired to obtain catalyst 5.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．１６ｍｏｌ／Ｌ、Ｚｒ０．３４ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.16 mol / L, Zr 0.34 mol / L, La 0.03 mol / L.
（比較例１）
３モル％のランタンを含有する活性アルミナを、硝酸ロジウム水溶液中に浸漬し、乾燥してロジウムを固定した粉末を得た。
(Comparative Example 1)
Activated alumina containing 3 mol% lanthanum was immersed in an aqueous rhodium nitrate solution and dried to obtain a powder in which rhodium was fixed.
このロジウムを固定した粉末と硝酸水溶液および脱イオン水でスリラー化しスラリーＡを得た。次に３モル％のランタンを含有する活性アルミナをジニトロジアミン白金溶液中に浸漬し、乾燥して白金を固定した粉末を得た。この白金を固定した粉末と硝酸水溶液および脱イオン水でスリラー化しスラリーＢを得た。 Slurry was obtained by thrilling the rhodium-fixed powder with an aqueous nitric acid solution and deionized water. Next, activated alumina containing 3 mol% lanthanum was immersed in a dinitrodiamine platinum solution and dried to obtain a powder on which platinum was fixed. Slurry B was obtained by thrilling the platinum-fixed powder with an aqueous nitric acid solution and deionized water.
スラリーＡおよびスラリーＢを１：１の割合で混合し、直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥、焼成して触媒２を得た。触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 Slurry A and slurry B were mixed at a ratio of 1: 1, and coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried and fired to obtain catalyst 2. The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, and La 0.03 mol / L.
（比較例２）
活性アルミナ粉末を硝酸セリウム溶液中に浸漬し、乾燥、焼成してセリウム含有アルミナ粉末を得た。セリウム担持活性アルミナ粉末を硝酸ロジウム溶液中に浸漬し、乾燥してロジウムを固定した粉末を得た。このロジウムを固定した粉末と硝酸水溶液および脱イオン水でスラリー化しスラリーＡを得た。
(Comparative Example 2)
The activated alumina powder was immersed in a cerium nitrate solution, dried and fired to obtain a cerium-containing alumina powder. The cerium-supporting activated alumina powder was immersed in a rhodium nitrate solution and dried to obtain a powder in which rhodium was fixed. A slurry A was obtained by slurrying the rhodium-fixed powder with an aqueous nitric acid solution and deionized water.
活性アルミナ粉末を硝酸セリウム溶液中に浸漬し、乾燥、焼成してセリウム含有アルミナ粉末を得た。セリウム担持活性アルミナ粉末をジニトロジアミン白金溶液中に浸漬し、乾燥して白金を固定した粉末を得た。この白金を固定した粉末と硝酸水溶液および脱イオン水でスラリー化しスラリーＢを得た。スラリーＡおよびスラリーＢを１：１の割合で混合し、直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥、焼成して触媒２を得た。 The activated alumina powder was immersed in a cerium nitrate solution, dried and fired to obtain a cerium-containing alumina powder. The cerium-supporting activated alumina powder was immersed in a dinitrodiamine platinum solution and dried to obtain a powder on which platinum was fixed. A slurry B was obtained by slurrying the platinum-fixed powder with an aqueous nitric acid solution and deionized water. Slurry A and slurry B were mixed at a ratio of 1: 1, and coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried and fired to obtain catalyst 2.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, and La 0.03 mol / L.
（比較例３）
ロジウムの担持部のセリウムとジルコニウムの比率を表１に示したように３０：７０に変え、白金担持部をジルコニウムのみとした以外は実施例１と同様の方法で触媒を調製した。
(Comparative Example 3)
A catalyst was prepared in the same manner as in Example 1 except that the ratio of cerium and zirconium in the rhodium support was changed to 30:70 as shown in Table 1 and the platinum support was only zirconium.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．７５ｍｏｌ／Ｌ、Ｚｒ０．４２５ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.75 mol / L, Zr 0.425 mol / L, La 0.03 mol / L.
（比較例４）
ロジウム担持部および白金担持部のセリウムとジルコニウムの比率を表１に示したように変えた以外は実施例１と同様の方法で触媒を調製した。
(Comparative Example 4)
A catalyst was prepared in the same manner as in Example 1 except that the ratio of cerium and zirconium in the rhodium-carrying part and the platinum-carrying part was changed as shown in Table 1.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．３ｍｏｌ／Ｌ、Ｚｒ０．２ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.3 mol / L, Zr 0.2 mol / L, La 0.03 mol / L.
（比較例５）
ロジウム担持部および白金担持部のセリウムとジルコニウムの比率を表１に示したように変えた以外は実施例１と同様の方法で触媒を調製した。
(Comparative Example 5)
A catalyst was prepared in the same manner as in Example 1 except that the ratio of cerium and zirconium in the rhodium-carrying part and the platinum-carrying part was changed as shown in Table 1.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．１６ｍｏｌ／Ｌ、Ｚｒ０．３４ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.16 mol / L, Zr 0.34 mol / L, La 0.03 mol / L.
（比較例６）
３モル％のランタンを含有活性アルミナを、硝酸セリウム溶液と硝酸ジルコニウム溶液を混合した溶液中（セリウムとジルコニウムの比でジルコニウム量が多い溶液）に浸漬し、攪拌後、該溶液中にアンモニア水を添加し、乾燥、焼成してランタン含有活性アルミナと、セリウム、ジルコニウム酸化物含有粉末を得た。この混合粉末に硝酸水溶液、バインダーおよび脱イオン水でスラリー化しスラリーＡを得た。
(Comparative Example 6)
The activated alumina containing 3 mol% of lanthanum is immersed in a mixed solution of cerium nitrate solution and zirconium nitrate solution (a solution containing a large amount of zirconium in the ratio of cerium and zirconium). After stirring, aqueous ammonia is added to the solution. The lanthanum-containing activated alumina, cerium and zirconium oxide-containing powders were obtained by adding, drying and firing. This mixed powder was slurried with an aqueous nitric acid solution, a binder and deionized water to obtain slurry A.
このスラリーＡを直径８０ｍｍ、長さ１００ｍｍのハニカム担体にコート、乾燥後、硝酸セリウム溶液および硝酸ジルコニウム溶液に浸漬後、乾燥、焼成してコート層を形成した。次に上記のコート層をジニトロジアミン白金溶液、および硝酸ロジウム溶液に浸漬し触媒を調製した。 The slurry A was coated on a honeycomb carrier having a diameter of 80 mm and a length of 100 mm, dried, dipped in a cerium nitrate solution and a zirconium nitrate solution, dried and fired to form a coat layer. Next, the coating layer was immersed in a dinitrodiamine platinum solution and a rhodium nitrate solution to prepare a catalyst.
触媒組成は、Ｐｔ１．５ｇ／Ｌ、Ｒｈ０．３ｇ／Ｌ、Ｃｅ０．１２５ｍｏｌ／Ｌ、Ｚｒ０．３７５ｍｏｌ／Ｌ、Ｌａ０．０３ｍｏｌ／Ｌであった。上記の各触媒の構成と組成およびトータルのＣｅおよびＺｒの担持量を表１に示した。 The catalyst composition was Pt 1.5 g / L, Rh 0.3 g / L, Ce 0.125 mol / L, Zr 0.375 mol / L, La 0.03 mol / L. Table 1 shows the composition and composition of each of the above catalysts and the total supported amounts of Ce and Zr.
（試験例）
参考例１、実施例１〜４および比較例１〜６で得られた触媒を２個ずつ別々に排気量４０００ＣＣのガソリンエンジンに取り付け、第１図に示すエージング条件で、平均のエンジン回転数３５００ｒｐｍ、触媒入り口排気ガス温度８００℃、触媒中央部の排気ガス温度１０５０℃で２０時間の耐久試験を行った。
(Test example)
Two catalysts obtained in Reference Example 1, Examples 1 to 4 and Comparative Examples 1 to 6 were separately attached to a gasoline engine having a displacement of 4000 CC, and the average engine speed was 3500 rpm under the aging conditions shown in FIG. The endurance test was conducted for 20 hours at an exhaust gas temperature of 800 ° C. at the catalyst inlet and an exhaust gas temperature of 1050 ° C. at the center of the catalyst.
エージング条件は第１図に示すように、１サイクルを３０秒とするサイクルで、１サイクル中の初めの１０秒は理論空燃費Ａ／Ｆ＝１４．６で制御し、その後、燃料を２６秒目まで増大させ１０秒目から１６秒目までＡ／Ｆ＝１３前後の状態を保つ。また、１６秒目から３０秒目まで２次空気を導入することにより、１６秒目から２５秒目までＡ／Ｆ＝１４．８に制御し、そのまま３０秒目まで続ける制御をするものである。１サイクルの１６秒目から触媒中央部の温度が上昇し、１０５０℃に達し、２６秒目からは酸素過剰下で１０５０℃から温度が降下する耐久試験となる。 As shown in FIG. 1, the aging condition is a cycle in which one cycle is 30 seconds. The first 10 seconds in one cycle is controlled by the theoretical air fuel consumption A / F = 14.6, and then the fuel is 26 seconds. Increase to the eye and maintain the state of A / F = 13 from the 10th to the 16th. In addition, by introducing secondary air from the 16th to the 30th, A / F = 14.8 is controlled from the 16th to the 25th, and the control is continued until the 30th. . From the 16th second of the cycle, the temperature in the center of the catalyst increases and reaches 1050 ° C., and from the 26th second, the durability test starts from 1050 ° C. under excess oxygen.
前記した耐久試験を行った各触媒は、次に排気量２０００ＣＣのガソリンエンジンに取り付け、触媒性能を評価した。評価条件はエンジン回転数を１４００ｒｐｍ、理論空燃費Ａ／Ｆ＝１４．６で制御し、触媒入口の温度を変化させてＨＣ、ＣＯおよびＮＯｘの５０％浄化温度を求めた。また、ＨＣ−ＮＯｘとＣＯ−ＮＯｘのクロス浄化率と、その評価結果を表２に示す。なお、表１中の貴金属触媒の量は全て同じ量であり担持部の組成および担持状態の差異によることを示している。 Each of the catalysts subjected to the above durability test was then attached to a gasoline engine having a displacement of 2000 CC, and the catalyst performance was evaluated. The evaluation conditions were such that the engine speed was controlled at 1400 rpm and the theoretical air-fuel consumption A / F = 14.6, and the temperature at the catalyst inlet was varied to obtain 50% purification temperatures for HC, CO, and NOx. Table 2 shows the cross purification rate of HC-NOx and CO-NOx and the evaluation results. The amounts of the noble metal catalysts in Table 1 are all the same amount, which indicates that they are due to differences in the composition of the supporting part and the supporting state.
表２に示すように参考例１及び本実施例１から４の各触媒は、比較例１から６の各触媒と比較してＨＣ、ＣＯ、ＮＯｘの各５０％浄化温度が耐久試験後においても低くなっている。すなわち、低温域においても活性を示し触媒が耐熱性を保持していることが判る。さらにクロス浄化率の値も高くなっている。
比較例６はアルミナにセリウムとジルコニウムを同時に担持したコート層を形成した後に、触媒金属を担持した触媒で、５０％浄化温度が高く、クロス浄化率が最も低い。比較例１はアルミナの単独のコート層の場合でクロス浄化率および５０％浄化温度は比較例６よりは向上するが５０％浄化温度は、各実施例に比べても低い。比較例２は、ジルコニウムを全く含まない場合でクロス浄化率および５０％浄化温度も充分でない。比較例３は、セリウムがロジウム担持部で多く、白金担持部では存在しない例で比較例２と同様に充分な浄化性能を示さない。比較例４は、ロジウム、白金担持部共セリウム量が多い場合でこの場合も実施例に比べて充分な浄化性能を示していない。比較例５は、ロジウム担持部のセリウム量が多い場合でありトータルとして同じセリウムとジルコニウム量の実施例２に比べて浄化性能が充分でない。
As shown in Table 2, the catalysts of Reference Example 1 and Examples 1 to 4 had 50% purification temperatures of HC, CO, and NOx even after the endurance test as compared with the catalysts of Comparative Examples 1 to 6. It is low. That is, it can be seen that the catalyst is active even in a low temperature range and the catalyst maintains heat resistance. Furthermore, the value of the cross purification rate is also high.
Comparative Example 6 is a catalyst in which a coating layer in which cerium and zirconium are simultaneously supported on alumina is formed, and then a catalyst metal is supported. The 50% purification temperature is high and the cross purification rate is the lowest. Comparative Example 1 is a single coating layer of alumina. The cross purification rate and the 50% purification temperature are improved as compared with Comparative Example 6, but the 50% purification temperature is lower than in each Example. In Comparative Example 2, when no zirconium is contained, the cross purification rate and the 50% purification temperature are not sufficient. Comparative Example 3 is an example in which cerium is abundant in the rhodium-carrying part and does not exist in the platinum-carrying part, and does not exhibit sufficient purification performance as in Comparative Example 2. Comparative Example 4 is a case where the amount of rhodium and platinum carrying part co-cerium is large, and in this case as well, it does not show sufficient purification performance compared to the examples. Comparative Example 5 is a case where the rhodium carrying part has a large amount of cerium, and the purification performance is not sufficient as compared with Example 2 having the same amount of cerium and zirconium.
実施例１，２が請求項３に相当する触媒組成であり、実施例３と４が請求項１、２に相当する触媒組成を用いている。上記のように本発明の触媒はいずれも優れた排ガス浄化性能を有していることを示している。
また、実施例２と比較例１についての耐久試験後の触媒の５０％浄化温度およびクロス浄化率を図２、３に示した。
Examples 1 and 2 are catalyst compositions corresponding to claim 3, and Examples 3 and 4 use catalyst compositions corresponding to claims 1 and 2 . As described above, all the catalysts of the present invention have excellent exhaust gas purification performance.
Further, the 50% purification temperature and the cross purification rate of the catalyst after the durability test for Example 2 and Comparative Example 1 are shown in FIGS.
表２および図２，図３に示したように、本発明の触媒は耐久試験後においても浄化性能が優れ低温域でも高い排ガス浄化性能を有することを示している。 As shown in Table 2 and FIGS. 2 and 3, the catalyst of the present invention has excellent purification performance even after the durability test, and has high exhaust gas purification performance even in a low temperature range.
Claims (3)
前記貴金属担持部は、担持部成分と、該担持部成分に担持された貴金属触媒とを有し、
該貴金属触媒はロジウムのみからなり、
該ロジウムのみを担持する前記担持部成分は、少なくともジルコニウムとセリウムとの混合酸化物粉末と、活性アルミナ粉末とで形成されており、
前記ジルコニウムとセリウムとの混合酸化物はその総量を１００モル％とするとジルコニウムは７５モル％以上であることを特徴とする排ガス浄化用触媒。 In an exhaust gas purifying catalyst having a catalyst carrier and a noble metal support formed on the catalyst carrier,
The noble metal supporting part has a supporting part component and a noble metal catalyst supported on the supporting part component,
The noble metal catalyst consists only of rhodium,
The supporting part component supporting only the rhodium is formed of at least a mixed oxide powder of zirconium and cerium, and an activated alumina powder ,
An exhaust gas purifying catalyst, wherein the mixed oxide of zirconium and cerium is 75 mol% or more when the total amount is 100 mol% .
該第２の貴金属担持部は、担持部成分と、該担持部成分に担持された貴金属触媒とを有し、
該貴金属触媒はロジウム以外の白金、パラジウムなどの貴金属成分から選ばれる少なくとも一種からなることを特徴とする請求項１に記載の排ガス浄化用触媒。 A second noble metal support is further formed on the catalyst carrier,
The second noble metal support has a support component and a noble metal catalyst supported on the support component,
2. The exhaust gas purifying catalyst according to claim 1, wherein the noble metal catalyst is composed of at least one selected from noble metal components such as platinum and palladium other than rhodium.
前記貴金属担持部は、第１の貴金属担持部と、第２の貴金属担持部とからなり、
前記第１の貴金属担持部は、担持部成分と、該担持部成分に担持されロジウムのみからなる貴金属触媒とを有し、
前記第２の貴金属担持部は、担持部成分と、該担持部成分に担持されロジウム以外の白金、パラジウムなどの貴金属成分から選ばれる少なくとも一種からなる貴金属触媒とを有し、
前記ロジウムのみからなる貴金属触媒を担持する前記担持部成分は、ジルコニウム酸化物及びセリウム酸化物からなる酸化物成分と、該酸化物成分を担持する活性アルミナ粉末とからなり、
前記活性アルミナ粉末に担持されている前記酸化物成分の中のジルコニウム及びセリウムの総量を１００モル％とすると、前記ジルコニウムの担持量は７５モル％以上であることを特徴とする排ガス浄化用触媒。 In an exhaust gas purifying catalyst having a catalyst carrier and a noble metal support formed on the catalyst carrier,
The noble metal carrying portion includes a first noble metal carrying portion and a second noble metal carrying portion,
The first noble metal supporting part has a supporting part component, and a noble metal catalyst made of only rhodium supported on the supporting part component,
The second noble metal support has a support component and a noble metal catalyst made of at least one selected from precious metal components such as platinum and palladium other than rhodium supported on the support component.
The supporting part component supporting the noble metal catalyst consisting only of rhodium consists of an oxide component consisting of zirconium oxide and cerium oxide, and an activated alumina powder supporting the oxide component ,
The active when zirconium and total amount of cerium in the oxide components which are carried on alumina powder to 100 mol%, the supported amount of the zirconium catalyst for exhaust gas purification, characterized in der Rukoto least 75 mol% .
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| JPS63156545A (en) * | 1986-12-18 | 1988-06-29 | Nippon Shokubai Kagaku Kogyo Co Ltd | Catalyst for purifying exhaust gas |
| JPS6439824U (en) * | 1987-09-03 | 1989-03-09 | ||
| WO1990014888A1 (en) * | 1989-06-09 | 1990-12-13 | N.E. Chemcat Corporation | Exhaust gas purifying catalyst excellent in thermal resistance and method of production thereof |
| JPH03131343A (en) * | 1989-10-18 | 1991-06-04 | Nissan Motor Co Ltd | Preparation of catalyst for purifying exhaust gas |
| JPH08229394A (en) * | 1994-12-28 | 1996-09-10 | Toyota Central Res & Dev Lab Inc | Production of oxide-deposited catalyst carrier |
| JPH08290063A (en) * | 1995-02-24 | 1996-11-05 | Mazda Motor Corp | Catalyst for waste gas purification and manufacture thereof |
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| JPS63156545A (en) * | 1986-12-18 | 1988-06-29 | Nippon Shokubai Kagaku Kogyo Co Ltd | Catalyst for purifying exhaust gas |
| JPS6439824U (en) * | 1987-09-03 | 1989-03-09 | ||
| WO1990014888A1 (en) * | 1989-06-09 | 1990-12-13 | N.E. Chemcat Corporation | Exhaust gas purifying catalyst excellent in thermal resistance and method of production thereof |
| JPH03131343A (en) * | 1989-10-18 | 1991-06-04 | Nissan Motor Co Ltd | Preparation of catalyst for purifying exhaust gas |
| JPH08229394A (en) * | 1994-12-28 | 1996-09-10 | Toyota Central Res & Dev Lab Inc | Production of oxide-deposited catalyst carrier |
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