JP2017177095A - Exhaust gas purification catalyst, method for producing the same and exhaust gas purification apparatus using the same - Google Patents
Exhaust gas purification catalyst, method for producing the same and exhaust gas purification apparatus using the same Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 188
- 238000000746 purification Methods 0.000 title claims abstract description 76
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 16
- 239000002245 particle Substances 0.000 claims abstract description 336
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 96
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims abstract description 74
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims abstract description 72
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims abstract description 72
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims abstract description 67
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 47
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 47
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 32
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 30
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 15
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 45
- 150000003839 salts Chemical class 0.000 claims description 22
- 239000000463 material Substances 0.000 claims description 21
- 239000010948 rhodium Substances 0.000 claims description 21
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 19
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 19
- 239000006185 dispersion Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 18
- 229910052703 rhodium Inorganic materials 0.000 claims description 15
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 15
- 239000006104 solid solution Substances 0.000 claims description 14
- 229910052684 Cerium Inorganic materials 0.000 claims description 12
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 12
- 229910052779 Neodymium Inorganic materials 0.000 claims description 10
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 10
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 9
- 229910052746 lanthanum Inorganic materials 0.000 claims description 9
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 9
- 229910052763 palladium Inorganic materials 0.000 claims description 9
- 229910052697 platinum Inorganic materials 0.000 claims description 9
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 9
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- 229910002091 carbon monoxide Inorganic materials 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
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- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 4
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- 238000002485 combustion reaction Methods 0.000 description 1
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- 229910052878 cordierite Inorganic materials 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
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
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- 229910010271 silicon carbide Inorganic materials 0.000 description 1
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Landscapes
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
Description
本発明は、新規な排ガス浄化用触媒及びその製造方法並びにそれを用いた排ガス浄化装置に関する。 The present invention relates to a novel exhaust gas purification catalyst, a production method thereof, and an exhaust gas purification apparatus using the same.
自動車エンジン等の内燃機関からの排ガス中は、窒素酸化物（ＮＯｘ）、一酸化炭素（ＣＯ）、炭化水素（ＨＣ）等を含む。したがって、ＣＯ及びＨＣを酸化し、かつＮＯｘを還元する排ガス浄化用触媒によって浄化した後で、これらの排ガスを大気中に放出している。排ガス浄化用触媒の代表的なものとしては、白金（Ｐｔ）、ロジウム（Ｒｈ）、パラジウム（Ｐｄ）等の貴金属を、γ−アルミナ等の多孔質金属酸化物担体に担持させた三元触媒が知られている。 The exhaust gas from an internal combustion engine such as an automobile engine contains nitrogen oxides (NO x ), carbon monoxide (CO), hydrocarbons (HC) and the like. Therefore, to oxidize CO and HC, and after purification by exhaust gas purifying catalyst for reducing NO x, which emits these exhaust gases to the atmosphere. A typical exhaust gas purification catalyst is a three-way catalyst in which a noble metal such as platinum (Pt), rhodium (Rh), palladium (Pd) is supported on a porous metal oxide carrier such as γ-alumina. Are known.
この金属酸化物担体は、様々な材料で作ることができるが、従来は高表面積を得るためにアルミナ（Ａｌ２Ｏ３）を使用することが一般的であった。しかしながら近年では、担体の化学的性質を利用して排ガスの浄化を促進するために、セリア（ＣｅＯ２）、ジルコニア（ＺｒＯ２）、チタニア（ＴｉＯ２）等の様々な他の材料を、アルミナと組み合わせて又は組み合わせないで、使用することも提案されている。また、このような担体としてセリアジルコニア固溶体を用いることも提案されている。 The metal oxide support can be made of various materials, but conventionally, alumina (Al 2 O 3 ) has been generally used to obtain a high surface area. In recent years, however, various other materials such as ceria (CeO 2 ), zirconia (ZrO 2 ), titania (TiO 2 ), etc. have been combined with alumina in order to promote the purification of exhaust gas by utilizing the chemical properties of the carrier. It has also been proposed to use it in combination or not. It has also been proposed to use ceria zirconia solid solution as such a carrier.
セリアジルコニア固溶体に関して、セリアジルコニア固溶体にアルカリ金属、アルカリ土類金属及び希土類からなる群より選択される元素を加えることによって、セリアジルコニア固溶体の耐熱性を改良できることが知られている（例えば特許文献１）。また特許文献２では、希土類添加ジルコニア担体粒子にロジウムを担持させることによって、良好な排ガス浄化性能が得られることを開示している。 Regarding ceria zirconia solid solution, it is known that the heat resistance of ceria zirconia solid solution can be improved by adding an element selected from the group consisting of alkali metals, alkaline earth metals and rare earths to ceria zirconia solid solution (for example, Patent Document 1). ). Patent Document 2 discloses that good exhaust gas purification performance can be obtained by loading rhodium on rare earth-doped zirconia support particles.
特許文献３及び４は、セリアジルコニア固溶体粒子表面に希土類富化領域を与えた担体粒子を開示している。特許文献３及び４に記載の発明では、希土類酸化物とロジウムとの親和性に着目し、希土類富化領域において、粒子表面におけるロジウムの移動及びシンタリングを抑制し、かつロジウムの酸化を防止することによって、ロジウムの触媒活性を高い状態に維持している。 Patent Documents 3 and 4 disclose carrier particles in which a rare earth-enriched region is provided on the surface of ceria zirconia solid solution particles. The inventions described in Patent Documents 3 and 4 focus on the affinity between rare earth oxides and rhodium, suppress rhodium migration and sintering on the particle surface and prevent rhodium oxidation in the rare earth-enriched region. As a result, the catalytic activity of rhodium is maintained at a high level.
このように金属酸化物担体を、希土類元素と組み合わせることによって、触媒貴金属のシンタリング等を防止することができる。 By combining the metal oxide support with the rare earth element in this way, sintering of the catalyst noble metal can be prevented.
ところで、従来、上記のような金属酸化物担体は、それ自体は排ガス浄化能を持たない基材、例えばコージェライト製のハニカム基材上に形成されていた。しかし近年、金属酸化物担体から構成される基材に、貴金属を担持させた排ガス浄化触媒装置が提案されている（特許文献５）。 By the way, conventionally, the metal oxide support as described above has been formed on a base material that does not itself have an exhaust gas purification ability, for example, a cordierite honeycomb base material. However, in recent years, an exhaust gas purification catalyst device in which a noble metal is supported on a base material composed of a metal oxide support has been proposed (Patent Document 5).
本発明は、従来の排ガス浄化用触媒よりも、さらに貴金属の触媒活性を高い状態に維持できる、新規な排ガス浄化用触媒及びその製造方法並びにそれを用いた排ガス浄化装置を提供することを目的とする。 An object of the present invention is to provide a novel exhaust gas purifying catalyst, a method for producing the same, and an exhaust gas purifying apparatus using the same, which can maintain the catalytic activity of a noble metal at a higher level than conventional exhaust gas purifying catalysts. To do.
本発明の実施態様としては、以下の態様を挙げることができる：
《態様１》
第１の担体粒子、第２の担体粒子、並びに前記第１及び第２の担体粒子に担持されている貴金属触媒粒子を有する排ガス浄化用触媒であって、
前記第１の担体粒子が、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物と、セリア以外の希土類酸化物とを含有し、
前記第２の担体粒子が、セリア以外の希土類酸化物を含有し、そしてシリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物を含有してもよく
前記第１の担体粒子の前記金属酸化物の含有率が、前記第２の担体粒子の前記金属酸化物の含有率よりも高く、
前記第２の担体粒子の前記希土類酸化物の含有率が、前記第１の担体粒子の前記希土類酸化物の含有率よりも高く、かつ
電界放出形走査型電子顕微鏡を用いたエネルギー分散型Ｘ線分析によって得られる特性Ｘ線の強度測定を行ったときに、以下の式で計算される相関係数が８５．０％以上である、排ガス浄化用触媒：
《態様２》
前記第１の担体粒子の前記希土類酸化物の含有率が２０重量％未満であり、前記第２の担体粒子の前記希土類酸化物の含有率が、２０重量％以上である、態様１に記載の排ガス浄化用触媒。
《態様３》
電界放出形走査型電子顕微鏡によって前記第１の担体粒子と前記第２の担体粒子とを観察した場合に、前記第２の担体粒子の投影面積の、前記第１の担体粒子の投影面積に対する比（第２の担体粒子の面積／第１の担体粒子の面積）が、０．０５０以上０．２００以下の範囲である、態様２に記載の排ガス浄化用触媒。
《態様４》
前記第１の担体粒子の前記金属酸化物及び存在する場合の前記第２の担体粒子の前記金属酸化物が、セリアジルコニア固溶体であり、かつ
前記第１の担体粒子の前記希土類酸化物及び前記第２の担体粒子の前記希土類酸化物が、イットリウム、ランタン、プラセオジム、ネオジム及びサマリウムからなる群より少なくとも１種選択される希土類元素の酸化物である、態様１〜３のいずれか一項に記載の排ガス浄化用触媒。
《態様５》
前記第１の担体粒子が、５０〜９５重量％のジルコニア、５．０〜４５重量％のセリア、及び１．０以上２０重量％未満のセリア以外の希土類酸化物を含有し、かつ
前記第２の担体粒子が、０．０〜４０重量％のジルコニア、０．０〜４０重量％のセリア、及び２０〜６０重量％のセリア以外の希土類酸化物を含有している、態様４に記載の排ガス浄化用触媒。
《態様６》
電界放出形走査型電子顕微鏡によって測定される、前記第１の担体粒子及び前記第２の担体粒子平均粒径が、それぞれ０．５０〜１００μｍ及び０．５０〜５μｍである、態様１〜５のいずれか一項に記載の排ガス浄化用触媒。
《態様７》
前記貴金属触媒粒子が、白金粒子、パラジウム粒子、ロジウム粒子又はこれらの組合せを含む、態様１〜６のいずれか一項に記載の排ガス浄化用触媒。
《態様８》
前記相関係数が、８７．０％以上である、態様１〜７のいずれか一項に記載の排ガス浄化用触媒。
《態様９》
態様１〜８のいずれか一項に記載の排ガス浄化用触媒及びそれを含む触媒層が形成されている基材を具備する、排ガス浄化装置。
《態様１０》
態様１〜８のいずれか一項に記載の排ガス浄化用触媒及びそれを含む基材を具備する、排ガス浄化装置。
《態様１１》
以下を含む、排ガス浄化用触媒の製造方法：
シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物と、セリア以外の希土類酸化物とを含有している担体粒子；イットリウム、ネオジム、ランタン、及びプラセオジムから１種以上選択される希土類元素の塩；触媒貴金属の塩；及び有機カルボン酸を水系分散体中で混合して、前記担体粒子に触媒貴金属を担持し、それによって未焼成の排ガス浄化用触媒を含む水系分散体を得る工程；
前記未焼成の排ガス浄化用触媒を含む水系分散体を、乾燥させ、そして焼成する工程。
《態様１２》
前記担体粒子の前記金属酸化物が、セリアジルコニア固溶体であり；前記担体粒子の前記希土類酸化物が、イットリウム、ランタン、プラセオジム、ネオジム及びサマリウムからなる群より少なくとも１種選択される希土類元素の酸化物であり；前記希土類元素の塩が硝酸塩又は硫酸塩であり；かつ前記触媒貴金属の塩が、白金、パラジウム、ロジウム又はこれらの組合せの硝酸塩又は硫酸塩である、態様１０に記載の方法。
《態様１３》
前記有機カルボン酸が、分子量３００以下の有機カルボン酸である、態様１１又は１２に記載の方法。
《態様１４》
前記担体粒子に含有されている希土類元素の総和物質量に対する、前記有機カルボン酸の物質量比［ｍｏｌ／ｍｏｌ−Ｌｎ］が、０．５以上３．５以下である、態様１１〜１３のいずれか一項に記載の方法。
Embodiments of the present invention can include the following aspects:
<< Aspect 1 >>
An exhaust gas purifying catalyst having first carrier particles, second carrier particles, and noble metal catalyst particles carried on the first and second carrier particles,
The first carrier particles contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania, and a rare earth oxide other than ceria,
The second support particles may contain a rare earth oxide other than ceria, and may contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania. The content rate of the metal oxide in the first support particles is higher than the content rate of the metal oxide in the second support particles,
The content rate of the rare earth oxide in the second carrier particles is higher than the content rate of the rare earth oxide in the first carrier particles, and energy dispersive X-ray using a field emission scanning electron microscope When the intensity of characteristic X-rays obtained by analysis is measured, the correlation coefficient calculated by the following formula is 85.0% or more:
<< Aspect 2 >>
The content of the rare earth oxide in the first carrier particles is less than 20% by weight, and the content of the rare earth oxide in the second carrier particles is 20% by weight or more. Exhaust gas purification catalyst.
<< Aspect 3 >>
When the first carrier particles and the second carrier particles are observed with a field emission scanning electron microscope, the ratio of the projected area of the second carrier particles to the projected area of the first carrier particles The exhaust gas purifying catalyst according to aspect 2, wherein (the area of the second carrier particles / the area of the first carrier particles) is in the range of 0.050 or more and 0.200 or less.
<< Aspect 4 >>
The metal oxide of the first support particles and the metal oxide of the second support particles, if present, are ceria zirconia solid solutions, and the rare earth oxide and the first support particles of the first support particles. The rare earth oxide of the two support particles is an oxide of a rare earth element selected from at least one selected from the group consisting of yttrium, lanthanum, praseodymium, neodymium and samarium. Exhaust gas purification catalyst.
<< Aspect 5 >>
The first carrier particles contain 50 to 95% by weight of zirconia, 5.0 to 45% by weight of ceria, and 1.0 or more and less than 20% by weight of a rare earth oxide other than ceria, and the second The exhaust gas according to aspect 4, wherein the carrier particles contain 0.0 to 40% by weight of zirconia, 0.0 to 40% by weight of ceria, and 20 to 60% by weight of rare earth oxides other than ceria. Purification catalyst.
<< Aspect 6 >>
The average particle diameters of the first carrier particles and the second carrier particles measured by a field emission scanning electron microscope are 0.50 to 100 μm and 0.50 to 5 μm, respectively. The exhaust gas purifying catalyst according to any one of the above.
<< Aspect 7 >>
The exhaust gas purifying catalyst according to any one of aspects 1 to 6, wherein the noble metal catalyst particles include platinum particles, palladium particles, rhodium particles, or a combination thereof.
<< Aspect 8 >>
The exhaust gas purifying catalyst according to any one of aspects 1 to 7, wherein the correlation coefficient is 87.0% or more.
<< Aspect 9 >>
An exhaust gas purifying apparatus comprising the base material on which the exhaust gas purifying catalyst according to any one of aspects 1 to 8 and a catalyst layer including the catalyst are formed.
<< Aspect 10 >>
An exhaust gas purification apparatus comprising the exhaust gas purification catalyst according to any one of aspects 1 to 8 and a base material including the catalyst.
<< Aspect 11 >>
A method for producing an exhaust gas purifying catalyst comprising:
Carrier particles containing at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania and a rare earth oxide other than ceria; from yttrium, neodymium, lanthanum, and praseodymium A salt of a rare earth element selected from one or more kinds; a salt of a catalyst noble metal; and an organic carboxylic acid are mixed in an aqueous dispersion to carry the catalyst noble metal on the carrier particles, thereby forming an unfired exhaust gas purification catalyst. Obtaining an aqueous dispersion comprising:
A step of drying and calcining the aqueous dispersion containing the unfired exhaust gas-purifying catalyst;
<< Aspect 12 >>
The metal oxide of the support particles is a ceria zirconia solid solution; the rare earth oxide of the support particles is selected from at least one selected from the group consisting of yttrium, lanthanum, praseodymium, neodymium, and samarium. The method according to embodiment 10, wherein the rare earth element salt is nitrate or sulfate; and the catalyst noble metal salt is a nitrate or sulfate of platinum, palladium, rhodium, or a combination thereof.
<< Aspect 13 >>
The method according to embodiment 11 or 12, wherein the organic carboxylic acid is an organic carboxylic acid having a molecular weight of 300 or less.
<< Aspect 14 >>
Any of the aspects 11 to 13 wherein the substance amount ratio [mol / mol-Ln] of the organic carboxylic acid to the total amount of rare earth elements contained in the carrier particles is 0.5 or more and 3.5 or less. The method according to claim 1.
本発明によれば、従来の排ガス浄化用触媒よりも、さらに貴金属の触媒活性を高い状態に維持できる、新規な排ガス浄化用触媒及びその製造方法並びにそれを用いた排ガス浄化装置を提供することができる。 According to the present invention, it is possible to provide a novel exhaust gas purifying catalyst, a method for producing the same, and an exhaust gas purifying apparatus using the same, which can maintain the catalytic activity of the noble metal higher than that of the conventional exhaust gas purifying catalyst. it can.
《排ガス浄化用触媒》
本発明の排ガス浄化用触媒は、第１の担体粒子、第２の担体粒子、並びに前記第１及び第２の担体粒子に担持されている貴金属触媒粒子を有する。第１の担体粒子は、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物と、セリア以外の希土類酸化物とを含有し、第２の担体粒子は、セリア以外の希土類酸化物を含有し、そしてシリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物を含有してもよい。第１の担体粒子の金属酸化物の含有率は、第２の担体粒子の金属酸化物の含有率よりも高く、かつ第２の担体粒子の前記希土類酸化物の含有率は、前記第１の担体粒子の前記希土類酸化物の含有率よりも高い。
<Exhaust gas purification catalyst>
The exhaust gas purifying catalyst of the present invention includes first carrier particles, second carrier particles, and noble metal catalyst particles supported on the first and second carrier particles. The first carrier particles contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania, and a rare earth oxide other than ceria, and the second carrier particles are And a rare earth oxide other than ceria, and at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania. The metal oxide content of the first carrier particles is higher than the metal oxide content of the second carrier particles, and the rare earth oxide content of the second carrier particles is the first carrier particles It is higher than the content of the rare earth oxide in the carrier particles.
従来技術においては、金属酸化物担体表面に希土類富化領域を与えて、希土類富化領域において貴金属触媒粒子の移動及びシンタリングを抑制し、かつ貴金属触媒粒子の酸化を防止することによって、触媒活性を高い状態に維持している。それに対して、本発明においては、通常の金属酸化物担体と共に、希土類酸化物の含有率が高い第２の担体を併用することによって、さらに貴金属触媒粒子にさらに高い活性を与えることができた。理論に拘束されないが、本発明では、貴金属触媒粒子が、希土類酸化物の含有率が高い第２の担体に、集中的に担持されることによって、触媒活性をさらに高くすることができたものであると考えられる。 In the prior art, by providing a rare earth-enriched region on the surface of the metal oxide support, the movement and sintering of the noble metal catalyst particles are suppressed in the rare earth enriched region, and the oxidation of the noble metal catalyst particles is prevented. Is maintained at a high level. On the other hand, in the present invention, it was possible to give the noble metal catalyst particles even higher activity by using a second support having a high rare earth oxide content together with a normal metal oxide support. Although not bound by theory, in the present invention, the noble metal catalyst particles can be further enhanced in catalytic activity by being intensively supported on the second support having a high rare earth oxide content. It is believed that there is.
希土類酸化物の含有率が高い第２の担体に貴金属触媒粒子が集中的に担持されるという点に関して、本発明においては、電界放出形走査型電子顕微鏡を用いたエネルギー分散型Ｘ線分析によって得られる特性Ｘ線強度測定を行った場合に、相関係数が８５．０％以上、８６．０％以上、８７．０％以上、８８．０％以上、８９．０％以上、又は９０．０％以上で一致していることが好ましい。相関係数は、９９％未満であってもよい。ここで、相関係数は、次のようにして計算される：
このような測定は、日立ハイテクノロジーズ社製の電界放出形走査型電子顕微鏡Ｓ−４８００及びその装置に付随しているエネルギー分散型Ｘ線分析装置を用いて行うことができる。具体的には、この電界放出形走査型電子顕微鏡で測定した５０００倍の複数の画像中で、貴金属触媒粒子ｉの重心点分析を実施し、その重心点位置での貴金属触媒粒子ｉの貴金属元素のスペクトル強度値と、その重心点位置でのセリウム以外の希土類元素のスペクトル強度値とを測定し、上記の計算を行う。ここで、貴金属元素及びセリウム以外の希土類元素が複数種ある場合には、それらの強度の加算を行う。なお、「スペクトル強度平均値」とは、同一視野、異なる視野で視認可能な貴金属触媒粒子に含まれる貴金属元素又は第２の担体に含まれるセリウム以外の希土類元素の全ての特性Ｘ線強度の平均値をいう。上記の計算を行う場合には、第２の担体及び貴金属触媒粒子をそれぞれ３００個以上用いることが好ましい。 Such a measurement can be performed using a field emission scanning electron microscope S-4800 manufactured by Hitachi High-Technologies Corporation and an energy dispersive X-ray analyzer attached to the apparatus. Specifically, the center-of-gravity point analysis of the noble metal catalyst particle i is carried out in a plurality of images magnified 5000 times measured by this field emission scanning electron microscope, and the noble metal element of the noble metal catalyst particle i at the position of the center of gravity point And the above-mentioned calculation is performed by measuring the spectral intensity value of the rare earth element other than cerium at the position of the center of gravity. Here, when there are a plurality of rare earth elements other than the noble metal element and cerium, their strengths are added. The “spectrum intensity average value” means the average of all characteristic X-ray intensities of the noble metal elements contained in the noble metal catalyst particles visible in the same visual field and different visual fields or the rare earth elements other than cerium contained in the second support. Value. When performing the above calculation, it is preferable to use 300 or more of the second carrier and noble metal catalyst particles.
なお、本明細書中で、「触媒」とは、特記しない限り、貴金属触媒粒子を担持している担体粒子を意味しており、これらは焼成されていてもよく、未焼成のままであってもよい。上記の相関係数は、触媒の焼成前後で実質的に変化しないことが通常であり、好ましくは変化しない。 In the present specification, “catalyst” means carrier particles carrying noble metal catalyst particles unless otherwise specified, and these may be calcined or left unfired. Also good. The correlation coefficient is usually not substantially changed before and after the calcination of the catalyst, and preferably does not change.
図１（ａ）は、従来の排ガス浄化用触媒の概念図であり、図１（ｂ）は、本発明の排ガス浄化用触媒の概念図である。図１（ａ）において、排ガス浄化触媒（１０）は、金属酸化物担体粒子（１）及び貴金属触媒粒子（３）を有し、金属酸化物粒子（１）には、希土類富化領域（１ａ）が存在している。図１（ｂ）において、排ガス浄化触媒（１０）は、金属酸化物の第１の担体粒子（１）、希土類酸化物の含有率が高い第２の担体粒子（２）及び貴金属触媒粒子（３）を有し、貴金属触媒粒子（３）は、その多くが第２の担体粒子（２）に担持されている。 FIG. 1 (a) is a conceptual diagram of a conventional exhaust gas purifying catalyst, and FIG. 1 (b) is a conceptual diagram of an exhaust gas purifying catalyst of the present invention. In FIG. 1 (a), the exhaust gas purification catalyst (10) has metal oxide support particles (1) and noble metal catalyst particles (3). The metal oxide particles (1) include a rare earth enriched region (1a). ) Exists. In FIG. 1 (b), the exhaust gas purifying catalyst (10) includes a first support particle (1) of metal oxide, a second support particle (2) having a high content of rare earth oxide, and a noble metal catalyst particle (3). Most of the noble metal catalyst particles (3) are supported on the second carrier particles (2).
（担体粒子）
本発明の排ガス浄化用触媒には、貴金属触媒粒子の担体として、少なくとも第１の担体粒子と第２の担体粒子とを用いる。第１の担体粒子及び第２の担体粒子以外の第３の担体粒子をさらに用いることもできる。
(Carrier particles)
In the exhaust gas purifying catalyst of the present invention, at least first carrier particles and second carrier particles are used as the carrier for the noble metal catalyst particles. Third carrier particles other than the first carrier particles and the second carrier particles can also be used.
例えば、第１の担体粒子を、セリア以外の希土類酸化物の含有率が２０重量％未満である粒子と定義し、第２の担体粒子を、セリア以外の希土類酸化物の含有率が、２０重量％以上である粒子と定義し、そして電界放出形走査型電子顕微鏡によって第１の担体粒子及び第２の担体粒子を観察した場合に、本発明の排ガス浄化用触媒に含まれる第２の担体粒子の投影面積の、第１の担体粒子の投影面積に対する比（第２の担体粒子の面積／第１の担体粒子の面積）は、０．００５以上、０．０１以上、０．０３以上、０．０５以上、又は０．０６以上であってもよく、０．３０以下、０．２５以下、０．２０以下、０．１５以下、０．１０以下、又は０．０８以下であってもよい。このような範囲であれば、貴金属触媒粒子を第２の担体粒子に集中的に担持させ、かつ貴金属触媒粒子のシンタリング等を実質的に防ぐことができ、ＮＯｘ浄化温度の上昇を防げる傾向にある。なお、上記の第１の担体粒子と第２の担体粒子の定義が変更された場合でも、上記の投影面積比は、同じ範囲とすることができる。 For example, the first carrier particle is defined as a particle having a rare earth oxide content other than ceria of less than 20% by weight, and the second carrier particle has a rare earth oxide content other than ceria of 20% by weight. % And the second carrier particles contained in the exhaust gas purifying catalyst of the present invention when the first carrier particles and the second carrier particles are observed by a field emission scanning electron microscope. The ratio of the projected area to the projected area of the first carrier particles (the area of the second carrier particles / the area of the first carrier particles) is 0.005 or more, 0.01 or more, 0.03 or more, 0 .05 or more, or 0.06 or more, or 0.30 or less, 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, or 0.08 or less. . Within such a range, the noble metal catalyst particles can be intensively supported on the second carrier particles, and sintering of the noble metal catalyst particles can be substantially prevented and the NOx purification temperature tends to be prevented from rising. is there. Even when the definitions of the first carrier particles and the second carrier particles are changed, the projected area ratio can be in the same range.
（担体粒子−第１の担体粒子）
本発明の排ガス浄化用触媒で用いられる第１の担体粒子は、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物と、セリア以外の希土類酸化物とを含有する。好ましくは、第１の担体粒子は、セリア及び／又はジルコニアを少なくとも含有する。
(Carrier particles—first carrier particles)
The first carrier particles used in the exhaust gas purifying catalyst of the present invention include at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania, and a rare earth oxide other than ceria. Containing. Preferably, the first carrier particle contains at least ceria and / or zirconia.
例えば、第１の担体粒子を、セリア以外の希土類酸化物の含有率が２０重量％未満である粒子と定義し、第２の担体粒子を、セリア以外の希土類酸化物の含有率が、２０重量％以上である粒子と定義した場合、第１の担体粒子の平均粒径は、０．５０μｍ以上、１．０μｍ以上、３．０μｍ以上、５．０μｍ以上、８．０μｍ以上、又は１０．０μｍ以上であってもよく、１００μｍ以下、８０μｍ以下、５０μｍ以下、３０μｍ以下、又は２０μｍ以下であってもよい。上記の第１の担体粒子と第２の担体粒子の定義が変更された場合でも、第１の担体粒子の平均粒径は、同じ範囲とすることができる。 For example, the first carrier particle is defined as a particle having a rare earth oxide content other than ceria of less than 20% by weight, and the second carrier particle has a rare earth oxide content other than ceria of 20% by weight. %, The average particle size of the first carrier particles is 0.50 μm or more, 1.0 μm or more, 3.0 μm or more, 5.0 μm or more, 8.0 μm or more, or 10.0 μm. It may be 100 μm or less, 80 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less. Even when the definitions of the first carrier particles and the second carrier particles are changed, the average particle diameter of the first carrier particles can be in the same range.
ここで、平均粒径の測定は、日立ハイテクノロジーズ社製の電界放出走査型電子顕微鏡Ｓ−４８００及びその装置に付随しているエネルギー分散型Ｘ線分析装置によって行う。すなわち、この装置で２０，０００倍の測定倍率によって映し出された画面において、等価直径が０．１０μｍ以上である粒子の中から、エネルギー分散型Ｘ線分析によって、第１の担体粒子を見つけ出す。そして、それらの粒子の等価直径を粒子の投影面積から計算する。この作業を任意の２０画面において行い、その全ての平均値を、第１の担体粒子の平均粒径と認定する。ここで、粒子の等価直径とは、粒子の外周長さと等しい外周長さを有する正円の直径をいう。 Here, the average particle diameter is measured by a field emission scanning electron microscope S-4800 manufactured by Hitachi High-Technologies Corporation and an energy dispersive X-ray analyzer attached to the apparatus. That is, the first carrier particles are found by energy dispersive X-ray analysis from particles having an equivalent diameter of 0.10 μm or more on a screen projected with a measurement magnification of 20,000 times with this apparatus. Then, the equivalent diameter of the particles is calculated from the projected area of the particles. This operation is performed on 20 arbitrary screens, and all average values thereof are recognized as the average particle diameter of the first carrier particles. Here, the equivalent diameter of the particles refers to the diameter of a perfect circle having an outer peripheral length equal to the outer peripheral length of the particles.
第１の担体粒子は、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物を含有し、その含有率は、第１の担体粒子の重量に対して、５０重量％以上、５５重量％以上、６０重量％以上、６５重量％以上、又は７０重量％以上であってもよく、９５重量％以下、９０重量％以下、８５重量％以下、又は８０重量％以下であってもよい。 The first carrier particles contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania, and the content thereof is based on the weight of the first carrier particles. 50 wt% or more, 55 wt% or more, 60 wt% or more, 65 wt% or more, or 70 wt% or more, 95 wt% or less, 90 wt% or less, 85 wt% or less, or 80 wt% % Or less.
第１の担体粒子が金属酸化物としてセリアを含む場合、第１の担体粒子のセリア及びセリア以外の希土類酸化物の合計の含有率は、第１の担体粒子の重量に対して、５．０重量％以上、１０重量％以上、１５重量％以上、２０重量％以上、又は２５重量％以上であってもよく、５０重量％以下、４５重量％以下、４０重量％以下、又は３５重量％以下であってもよい。 When the first carrier particles contain ceria as a metal oxide, the total content of ceria and rare earth oxides other than ceria in the first carrier particles is 5.0 with respect to the weight of the first carrier particles. % By weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more, 50% by weight or less, 45% by weight or less, 40% by weight or less, or 35% by weight or less It may be.
第１の担体粒子が金属酸化物としてセリアを含む場合、セリアの含有率は、５．０重量％以上、１０重量％以上、１５重量％以上、又は２０重量％以上であってもよく、４５重量％以下、４０重量％以下、３５重量％以下、又は３０重量％以下であってもよい。さらに、セリア以外の希土類酸化物の含有率は、１．０重量％以上、３．０重量％以上、５．０重量％以上、又は７．０重量％以上であってもよく、３０重量％以下、２５重量％以下、２０重量％以下、２０重量％未満、１５重量％以下、又は１０重量％以下であってもよい。 When the first carrier particles include ceria as a metal oxide, the content of ceria may be 5.0% by weight or more, 10% by weight or more, 15% by weight or more, or 20% by weight or more. It may be not more than wt%, not more than 40 wt%, not more than 35 wt%, or not more than 30 wt%. Furthermore, the content of rare earth oxides other than ceria may be 1.0% by weight or more, 3.0% by weight or more, 5.0% by weight or more, or 7.0% by weight or more, and 30% by weight. Hereinafter, it may be 25% by weight or less, 20% by weight or less, less than 20% by weight, 15% by weight or less, or 10% by weight or less.
第１の担体粒子は、好ましくは上記の金属酸化物の固溶体の形態であり、例えば上記の金属酸化物としてセリアジルコニア固溶体を含有することが好ましい。この場合、第１の担体粒子のジルコニアの含有率は、４０重量％以上、４５重量％以上、５０重量％以上、５５重量％以上、６０重量％以上、６５重量％以上、又は７０重量％以上であってもよく、９５重量％以下、９０重量％以下、８５重量％以下、又は８０重量％以下でもよい。また、この場合、第１の担体粒子のセリアの含有率は、５．０重量％以上、１０重量％以上、１５重量％以上、２０重量％以上、又は２５重量％以上であってもよく、５０重量％以下、４５重量％以下、４０重量％以下、又は３５重量％以下でもよい。ここで、これらの含有率は、元素分析から計算して求めることができる。 The first carrier particles are preferably in the form of a solid solution of the above metal oxide, and preferably contain, for example, a ceria zirconia solid solution as the above metal oxide. In this case, the content of zirconia in the first carrier particles is 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, or 70% by weight or more. It may be 95% by weight or less, 90% by weight or less, 85% by weight or less, or 80% by weight or less. In this case, the content of ceria in the first carrier particles may be 5.0% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more, It may be 50% or less, 45% or less, 40% or less, or 35% or less. Here, these content rates can be obtained by calculation from elemental analysis.
第１の担体粒子の希土類酸化物としては、希土類元素のうちの原子番号が若く、且つ４ｆ電子軌道に空きがある又は空きが多いイオンを形成する元素、例えばイットリウム（Ｙ）、ランタン（Ｌａ）、プラセオジム（Ｐｒ）、ネオジム（Ｎｄ）及びサマリウム（Ｓｍ）からなる群より選択される希土類元素の酸化物を挙げることができる。 As the rare earth oxide of the first carrier particle, an element that has a young atomic number among rare earth elements and has ions in the 4f electron orbit or that has many vacancies, such as yttrium (Y), lanthanum (La), etc. And oxides of rare earth elements selected from the group consisting of praseodymium (Pr), neodymium (Nd) and samarium (Sm).
第１の担体粒子は、上記以外の成分を含有していてもよく、例えば酸化バリウム等を含有していてもよい。 The first carrier particles may contain components other than those described above, and may contain, for example, barium oxide.
第１の担体粒子は、上記の特許文献等に記載された公知の方法によって製造することができる。 The first carrier particles can be produced by a known method described in the above patent documents.
（担体粒子−第２の担体粒子）
本発明の排ガス浄化用触媒で用いられる第２の担体粒子は、セリア以外の希土類酸化物を含有し、そしてシリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物を含有してもよい。ここで、第２の担体粒子の前記金属酸化物の含有率は、第１の担体粒子の前記金属酸化物の含有率よりも低く、かつ第２の担体粒子の希土類酸化物の含有率は、第１の担体粒子の希土類酸化物の含有率よりも高い。これにより、貴金属触媒粒子を第２の担体粒子に集中的に担持させることができる。
(Carrier particles—second carrier particles)
The second carrier particle used in the exhaust gas purifying catalyst of the present invention contains a rare earth oxide other than ceria and at least one metal selected from the group consisting of silica, alumina, ceria, zirconia, and titania. An oxide may be contained. Here, the content rate of the metal oxide in the second support particles is lower than the content rate of the metal oxide in the first support particles, and the content rate of the rare earth oxide in the second support particles is: It is higher than the rare earth oxide content of the first carrier particles. Thereby, the noble metal catalyst particles can be intensively supported on the second carrier particles.
例えば、第１の担体粒子を、セリア以外の希土類酸化物の含有率が２０重量％未満である粒子と定義し、第２の担体粒子を、セリア以外の希土類酸化物の含有率が、２０重量％以上である粒子と定義した場合、第２の担体粒子の平均粒径は、０．５０μｍ以上、１．０μｍ以上、２．０μｍ以上、又は３．０μｍ以上であってもよく、５０μｍ以下、２０μｍ以下、１５μｍ以下、１０μｍ以下、又は５．０μｍ以下であってもよい。このような範囲であれば、貴金属触媒粒子を第２の担体粒子に集中的に担持させ、かつ貴金属触媒粒子のシンタリング等を実質的に防ぐことができ、ＮＯｘ浄化温度の上昇を防げる傾向にある。上記の第１の担体粒子と第２の担体粒子の定義が変更された場合でも、第２の担体粒子の平均粒径は、同じ範囲とすることができる。この平均粒径は、上記の第１の担体粒子の平均粒径と同一の方法によって測定される。 For example, the first carrier particle is defined as a particle having a rare earth oxide content other than ceria of less than 20% by weight, and the second carrier particle has a rare earth oxide content other than ceria of 20% by weight. %, The average particle size of the second carrier particles may be 0.50 μm or more, 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more, 50 μm or less, It may be 20 μm or less, 15 μm or less, 10 μm or less, or 5.0 μm or less. Within such a range, the noble metal catalyst particles can be intensively supported on the second carrier particles, and sintering of the noble metal catalyst particles can be substantially prevented, and an increase in the NOx purification temperature tends to be prevented. is there. Even when the definitions of the first carrier particles and the second carrier particles are changed, the average particle diameter of the second carrier particles can be in the same range. This average particle diameter is measured by the same method as the average particle diameter of the first carrier particles.
第２の担体粒子は、セリア以外の希土類酸化物を含有し、その含有率は、１０重量％以上、１５重量％以上、２０重量％以上、２５重量％以上、又は３０重量％以上であってもよく、６０重量％以下、５５重量％以下、５０重量％以下、４５重量％以下、又は４０重量％以下であってもよい。 The second carrier particles contain a rare earth oxide other than ceria, and the content thereof is 10% by weight, 15% by weight, 20% by weight, 25% by weight, or 30% by weight or more. It may be 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, or 40% by weight or less.
第２の担体粒子は、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物を含有していてもよく、含有していなくてもよい。金属酸化物を含有する場合、その含有率は、第２の担体粒子の重量に対して、１．０重量％以上、２．０重量％以上、３．０重量％以上、５．０重量％以上、１０重量％以上、又は１５重量％以上であってもよく、４０重量％以下、３５重量％以下、３０重量％以下、又は２５重量％以下であってもよい。 The second carrier particles may or may not contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania. When the metal oxide is contained, the content thereof is 1.0% by weight or more, 2.0% by weight or more, 3.0% by weight or more, 5.0% by weight with respect to the weight of the second carrier particles. As described above, it may be 10% by weight or more, or 15% by weight or more, and may be 40% by weight or less, 35% by weight or less, 30% by weight or less, or 25% by weight or less.
第２の担体粒子は、セリア及びセリア以外の希土類酸化物を含有する場合、その合計の含有率は、第２の担体粒子の重量に対して、６０重量％以上、６５重量％以上、７０重量％以上、７５重量％以上、又は８０重量％以上であってもよく、９９重量％以下、９５重量％以下、９３重量％以下、又は９０重量％以下であってもよい。 When the second carrier particles contain ceria and a rare earth oxide other than ceria, the total content is 60% by weight or more, 65% by weight or more, 70% by weight with respect to the weight of the second carrier particles. % Or more, 75% or more, or 80% or more, or 99% or less, 95% or less, 93% or less, or 90% or less.
第２の担体粒子がセリアを含有する場合、その含有率は、２０重量％以上、２５重量％以上、又は３０重量％以上であってもよく、６０重量％以下、５５重量％以下、５０重量％以下、４５重量％以下、又は４０重量％以下であってもよい。 When the second carrier particles contain ceria, the content thereof may be 20% by weight or more, 25% by weight or more, or 30% by weight or more, and may be 60% by weight or less, 55% by weight or less, 50% by weight. % Or less, 45% by weight or less, or 40% by weight or less.
第２の担体粒子の希土類酸化物としては、第１の担体粒子に含有される希土類酸化物と同種のものを用いることができる。 As the rare earth oxide of the second carrier particles, the same kind of rare earth oxide contained in the first carrier particles can be used.
第２の担体粒子は、第１の担体粒子と同様に、ジルコニア及び希土類酸化物以外の第３の成分を含有していてもよく、例えばアルミナ、シリカ、チタニア等を含有していてもよい。 Similar to the first carrier particles, the second carrier particles may contain a third component other than zirconia and rare earth oxide, and may contain, for example, alumina, silica, titania and the like.
第２の担体粒子は、上記の特許文献等に記載された公知の方法によって製造することができる。ただし、第２の担体粒子は、下記に詳細に示すように、担体粒子を、有機カルボン酸溶液に投入し、担体粒子から溶出させて得ることが好ましい。 The second carrier particles can be produced by a known method described in the above patent documents. However, the second carrier particles are preferably obtained by introducing the carrier particles into an organic carboxylic acid solution and eluting from the carrier particles, as will be described in detail below.
（貴金属触媒粒子）
本発明の排ガス浄化用触媒で用いられる貴金属触媒粒子としては、特に白金属粒子を挙げることができ、より好ましくは白金粒子、パラジウム粒子、ロジウム粒子又はこれらの組合せを挙げることができる。
(Precious metal catalyst particles)
Examples of the noble metal catalyst particles used in the exhaust gas purifying catalyst of the present invention include white metal particles, and more preferably platinum particles, palladium particles, rhodium particles, or a combination thereof.
貴金属触媒粒子は、排ガスとの接触面積を高める観点から、十分に小さい粒径の微粒子であることが好ましい。典型的には、触媒粒子の平均粒径は、ＴＥＭ観察によって求められる等価直径の平均値として、１〜２０ｎｍ程度であってもよく、１０ｎｍ以下、７ｎｍ以下又は５ｎｍ以下であってもよい。 The noble metal catalyst particles are preferably fine particles having a sufficiently small particle diameter from the viewpoint of increasing the contact area with the exhaust gas. Typically, the average particle diameter of the catalyst particles may be about 1 to 20 nm as an average value of equivalent diameters obtained by TEM observation, or may be 10 nm or less, 7 nm or less, or 5 nm or less.
貴金属触媒粒子は、第１の担体粒子及び第２の担体粒子の合計１００質量部に対して、合計で０．１質量部以上、０．３質量部以上、０．５質量部以上、又は１．０質量部以上で担持されていてもよく、１０質量部以下、５質量部以下、３．０質量部以下、２．０質量部以下で担持されていてもよい。 The precious metal catalyst particles are 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, or 1 in total with respect to 100 parts by mass in total of the first carrier particles and the second carrier particles. It may be supported at 0.0 parts by mass or more, and may be supported at 10 parts by mass or less, 5 parts by mass or less, 3.0 parts by mass or less, or 2.0 parts by mass or less.
《排ガス浄化装置》
本発明の排ガス浄化装置は、上述の排ガス浄化用触媒及びそれを含む基材を具備する。排ガス浄化用触媒は、基材上の触媒層に含まれていてもよく、基材中に含まれていてもよい。排ガス浄化用触媒は、下記の本発明の排ガス浄化用触媒の製造方法によって得られる排ガス浄化用触媒であってもよい。
<Exhaust gas purification device>
The exhaust gas purification apparatus of the present invention includes the above-described exhaust gas purification catalyst and a base material including the catalyst. The exhaust gas-purifying catalyst may be contained in the catalyst layer on the base material, or may be contained in the base material. The exhaust gas purifying catalyst may be an exhaust gas purifying catalyst obtained by the following method for producing an exhaust gas purifying catalyst of the present invention.
基材としては、排気ガス浄化装置において一般的に使用されているストレートフロー型又はウォールフロー型のハニカム型基材等を挙げることができる。基材の材質も特に限定されず、例えば、セラミック、炭化ケイ素、金属等の基材を挙げることができる。該基材の容量は、例えば１Ｌ程度とすることができる。 Examples of the substrate include a straight flow type or wall flow type honeycomb type substrate generally used in an exhaust gas purification apparatus. The material of the base material is not particularly limited, and examples thereof include base materials such as ceramic, silicon carbide, and metal. The capacity of the substrate can be set to about 1 L, for example.
本発明の排ガス浄化装置における触媒層は、上記の本発明の排ガス浄化触媒のみから形成されていてもよいし、本発明の排ガス浄化用触媒と他の成分との混合物から形成されていてもよい。ここで使用される他の成分としては、例えば、アルミナ、ＣＺ、ゼオライト等、及びこれらの混合物等を挙げることができる。これらに貴金属が担持された公知の排ガス浄化用触媒を、他の成分として用いてもよい。触媒層を、触媒担体粒子を壁面に含む基材、例えば特開２０１５−８５２４１号公報に記載のような基材上に形成してもよい。 The catalyst layer in the exhaust gas purification apparatus of the present invention may be formed only from the above-described exhaust gas purification catalyst of the present invention, or may be formed of a mixture of the exhaust gas purification catalyst of the present invention and other components. . Examples of other components used here include alumina, CZ, zeolite, and the like, and mixtures thereof. A known exhaust gas-purifying catalyst having a noble metal supported thereon may be used as another component. The catalyst layer may be formed on a base material including catalyst carrier particles on the wall surface, for example, a base material described in JP-A-2015-85241.
他の成分の製造、該他の成分と本発明の排ガス浄化用触媒との混合、及び上記基材上への触媒層の形成は、それぞれ、公知の方法により、又はこれに当業者による適宜の変更を加えた方法により、実施することができる。 Production of the other components, mixing of the other components with the exhaust gas purifying catalyst of the present invention, and formation of the catalyst layer on the substrate are each performed by a known method or appropriate by those skilled in the art. It can be carried out by a modified method.
排ガス浄化用触媒が基材中に含まれる場合には、触媒担体粒子を壁面に含む基材、例えば特開２０１５−８５２４１号公報に記載のような基材を用いることができる。この場合、排ガス浄化用触媒を、基材を製造する際に使用する他の無機粒子と混合して用いて排ガス浄化装置を得てもよい。 When the exhaust gas-purifying catalyst is contained in the base material, a base material containing catalyst carrier particles on the wall surface, for example, a base material as described in JP-A-2015-85241 can be used. In this case, the exhaust gas purifying apparatus may be obtained by mixing the exhaust gas purifying catalyst with other inorganic particles used when manufacturing the base material.
以上のようにして製造される本発明の排ガス浄化装置は、貴金属の排ガス浄化活性が高く、かつこれを高い状態のまま維持することができるから、例えば自動車用の排ガス浄化用触媒として、好適に使用することができる。 The exhaust gas purification apparatus of the present invention manufactured as described above has high exhaust gas purification activity of noble metals and can maintain it in a high state, and thus is suitable as an exhaust gas purification catalyst for automobiles, for example. Can be used.
《排ガス浄化用触媒の製造方法》
排ガス浄化用触媒を製造する本発明の方法は、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物とセリア以外の希土類酸化物とを含有している担体粒子；イットリウム、ネオジム、ランタン、及びプラセオジムから１種以上選択される希土類元素の塩；貴金属の塩；及び有機カルボン酸を水系分散体中で混合して、担体粒子に貴金属を担持し、それによって未焼成の排ガス浄化用触媒を含む水系分散体を得る工程；及び未焼成の排ガス浄化用触媒を含む水系分散体を、乾燥させ、そして焼成する工程を含む。
<Method for producing exhaust gas purification catalyst>
The method of the present invention for producing an exhaust gas purifying catalyst contains at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania and a rare earth oxide other than ceria. A carrier particle; a rare earth element salt selected from one or more of yttrium, neodymium, lanthanum, and praseodymium; a salt of a noble metal; and an organic carboxylic acid mixed in an aqueous dispersion to carry the noble metal on the carrier particle; To obtain an aqueous dispersion containing an unfired exhaust gas purification catalyst; and drying and firing the aqueous dispersion containing an unfired exhaust gas purification catalyst.
この方法によれば、有機カルボン酸によって担体粒子から希土類酸化物が溶出して、希土類酸化物が富化した第２の担体粒子と金属酸化物が富化した第１の担体粒子とが得られる。この場合、貴金属は、希土類酸化物が富化した第２の担体粒子に主に担持され、これにより触媒である貴金属のシンタリング及び酸化を防止することができるため、貴金属の触媒活性を高い状態に維持できる好適な排ガス浄化用触媒を得ることができる。出発物質である担体粒子が、金属酸化物の固溶体を含む場合には、固溶していない希土類酸化物が有機カルボン酸によって溶出しやすいため、このような態様は特に好ましい。 According to this method, the rare earth oxide is eluted from the carrier particles by the organic carboxylic acid to obtain the second carrier particles enriched with the rare earth oxide and the first carrier particles enriched with the metal oxide. . In this case, the noble metal is mainly supported on the second support particles enriched with the rare earth oxide, and thereby, sintering and oxidation of the noble metal as a catalyst can be prevented, so that the catalytic activity of the noble metal is high. A suitable exhaust gas purifying catalyst that can be maintained at a high temperature can be obtained. In the case where the carrier particles as the starting material contain a solid solution of a metal oxide, such an embodiment is particularly preferable because the rare earth oxide that is not in solid solution is easily eluted by the organic carboxylic acid.
さらに、驚くべきことに、この方法によって得られた排ガス浄化触媒の貴金属触媒粒子は、有機カルボン酸を添加しない従来の方法と比較して、小径化されることが分かった。理論に拘束されないが、これは、有機カルボン酸添加後に、有機カルボン酸希土が形成され、有機カルボン酸希土に貴金属が選択的に吸着し、焼成後に希土類と貴金属と間の相互作用によって、貴金属が固定化される為であると考えられる。貴金属触媒粒子の粒径が小さいと、単位重量当りの貴金属触媒粒子の表面積が大きくなり、触媒の反応点が増えるため、非常に有利である。 Furthermore, it has been surprisingly found that the noble metal catalyst particles of the exhaust gas purification catalyst obtained by this method have a smaller diameter compared to the conventional method in which no organic carboxylic acid is added. Without being bound by theory, this is because the organic carboxylic acid rare earth is formed after the addition of the organic carboxylic acid, the noble metal is selectively adsorbed on the organic carboxylic acid rare earth, and the interaction between the rare earth and the noble metal after firing, This is thought to be due to the immobilization of precious metals. If the particle diameter of the noble metal catalyst particles is small, the surface area of the noble metal catalyst particles per unit weight is increased, which is very advantageous because the reaction point of the catalyst increases.
排ガス浄化用触媒を製造する本発明の方法によれば、特に本発明の排ガス浄化用触媒を製造することができる。したがって、本発明の方法で用いる担体粒子の粒径、担体粒子のジルコニア、セリア、及びセリア以外の希土類酸化物の添加量、セリア以外の希土類酸化物の種類及び添加量、希土類元素の塩の種類及び添加量、貴金属の種類及び添加量等については、上記の本発明の排ガス浄化用触媒の記載を参照して選択することができる。 According to the method of the present invention for producing an exhaust gas purification catalyst, the exhaust gas purification catalyst of the present invention can be produced in particular. Accordingly, the particle size of the carrier particles used in the method of the present invention, the addition amount of the rare earth oxide other than zirconia, ceria and ceria, the kind and addition amount of the rare earth oxide other than ceria, the kind of the salt of the rare earth element The addition amount, the type and addition amount of the noble metal, etc. can be selected with reference to the description of the exhaust gas purifying catalyst of the present invention.
例えば、未焼成の排ガス浄化用触媒を含む水系分散体を得る工程においては、担体粒子に含まれる固溶していない希土類成分の量に対して、過不足なく反応する量（反応当量点）の有機カルボン酸を水系溶液に溶解させる。そして、有機カルボン酸の水溶液に、貴金属の塩を混合し、そして有機カルボン酸及び貴金属を含有する水溶液を、担体粒子が分散している分散液と混合する。 For example, in the step of obtaining an aqueous dispersion containing an unfired exhaust gas-purifying catalyst, the amount of reaction (reaction equivalent point) that reacts without excess or deficiency with respect to the amount of the rare-earth component not dissolved in the carrier particles. An organic carboxylic acid is dissolved in an aqueous solution. Then, a salt of a noble metal is mixed with an aqueous solution of an organic carboxylic acid, and an aqueous solution containing the organic carboxylic acid and the noble metal is mixed with a dispersion in which carrier particles are dispersed.
本発明の方法において用いられる有機カルボン酸の量は、担体粒子に含有されている希土類元素の総和物質量［ｍｏｌ−Ｌｎ］に対し、添加する有機カルボン酸の物質量比［ｍｏｌ／ｍｏｌ−Ｌｎ］で表わすことができる。好ましい物質量比［ｍｏｌ／ｍｏｌ−Ｌｎ］は、０．５以上、１．０以上、又は１．５以上であり、３．５以下、３．０以下、又は２．５以下であってもよい。このような範囲であれば、担体粒子の金属酸化物が溶解しづらく、かつ希土類酸化物は溶解しやすくなるため、第２の担体粒子を生成しやすい。 The amount of the organic carboxylic acid used in the method of the present invention is the ratio of the amount of the organic carboxylic acid to be added [mol / mol-Ln to the total amount of the rare earth elements contained in the carrier particles [mol-Ln]. ]. A preferable substance amount ratio [mol / mol-Ln] is 0.5 or more, 1.0 or more, or 1.5 or more, and may be 3.5 or less, 3.0 or less, or 2.5 or less. Good. Within such a range, the metal oxide of the carrier particles is difficult to dissolve and the rare earth oxide is easily dissolved, so that the second carrier particles are easily generated.
また、イットリウム、ネオジム、ランタン、及びプラセオジムから１種以上選択される希土類元素の塩を上記の水系分散体に混合することで、カルボン酸によって溶出させた第２の担体粒子に加えて、第２の担体粒子を追加的に生成することができる。希土類元素の塩としては、無機酸塩及び有機酸塩を挙げられることができるが、第２の担体粒子を追加的に生成することができれば、特に限定されない。無機酸塩としては、硫酸塩、塩酸塩、硝酸塩、炭酸塩、リン酸塩、亜硫酸塩、塩素酸塩等を挙げることができ、有機酸塩としては、蟻酸、シュウ酸、酢酸等のカルボン酸塩等を挙げることができる。これらの中でも特に、硝酸塩、酢酸塩等が好ましいことが分かった。これは、その塩が、担体粒子表面に吸着して、担体粒子の分散性を向上させたためと考えられる。このため、好ましくは、希土類元素の塩は、有機カルボン酸を加える前に、水系分散体に添加される。 Further, in addition to the second carrier particles eluted by the carboxylic acid by mixing one or more salts of rare earth elements selected from yttrium, neodymium, lanthanum and praseodymium into the aqueous dispersion, Additional carrier particles can be produced. As the salt of the rare earth element, an inorganic acid salt and an organic acid salt can be mentioned, but there is no particular limitation as long as the second carrier particles can be additionally generated. Examples of inorganic acid salts include sulfate, hydrochloride, nitrate, carbonate, phosphate, sulfite, and chlorate. Examples of organic acid salts include carboxylic acids such as formic acid, oxalic acid, and acetic acid. A salt etc. can be mentioned. Of these, nitrates, acetates and the like were found to be particularly preferable. This is presumably because the salt was adsorbed on the surface of the carrier particles to improve the dispersibility of the carrier particles. For this reason, the salt of rare earth element is preferably added to the aqueous dispersion before adding the organic carboxylic acid.
本発明の方法において用いられる希土類元素の塩の量は、担体粒子の表面積１ｍ２当たりで、０．１μｍｏｌ以上、０．３μｍｏｌ以上、０．５μｍｏｌ以上、１．０μｍｏｌ以上、又は２．０μｍｏｌ以上であってもよく、５０μｍｏｌ以下、３０μｍｏｌ以下、２０μｍｏｌ以下、１０μｍｏｌ以下、８μｍｏｌ以下、又は５μｍｏｌ以下であってもよい。担体粒子１グラム当たりでは、希土類元素の塩の量は、６．６５μｍｏｌ以上、１９．９５μｍｏｌ以上、３３．２５μｍｏｌ以上、６６．５μｍｏｌ以上、１３３μｍｏｌ以上であってもよく、６６５μｍｏｌ以下、５３２μｍｏｌ以下、３３２．５ｍｏｌ以下、又は３３２．５μｍｏｌ以下であってもよい。 The amount of the rare earth element salt used in the method of the present invention is 0.1 μmol or more, 0.3 μmol or more, 0.5 μmol or more, 1.0 μmol or more, or 2.0 μmol or more per 1 m 2 of the surface area of the carrier particles. It may be 50 μmol or less, 30 μmol or less, 20 μmol or less, 10 μmol or less, 8 μmol or less, or 5 μmol or less. The amount of rare earth element salt per gram of carrier particles may be 6.65 μmol or more, 19.95 μmol or more, 33.25 μmol or more, 66.5 μmol or more, 133 μmol or more, 665 μmol or less, 532 μmol or less, 332 It may be 5 mol or less, or 332.5 μmol or less.
ここで、担体粒子としては、上記の本発明の排ガス浄化用触媒で用いられる第１の担体粒子と同じ組成を有していてもよい。 Here, the carrier particles may have the same composition as the first carrier particles used in the exhaust gas purifying catalyst of the present invention.
貴金属の塩としては、貴金属の強酸塩を挙げることができ、特に貴金属の硝酸塩又は硫酸塩を挙げることができる。貴金属としては、白金、パラジウム、及び／又はロジウムを挙げることができる。 Examples of the noble metal salt include strong noble metal acid salts, and particularly noble metal nitrates and sulfates. Examples of noble metals include platinum, palladium, and / or rhodium.
有機カルボン酸としては、好ましくは分子量３００以下の有機カルボン酸を挙げることができ、例えばＣ１〜Ｃ２０の飽和脂肪酸、不飽和脂肪酸、ヒドロキシ酸、芳香族カルボン酸、ジカルボン酸、トリカルボン酸、オキソカルボン酸等を挙げることができる。具体的には、ギ酸、酢酸、プロピオン酸、酪酸、酒石酸、シュウ酸、マロン酸、コハク酸等を挙げることができる。 Examples of the organic carboxylic acid include organic carboxylic acids having a molecular weight of 300 or less. For example, C 1 to C 20 saturated fatty acid, unsaturated fatty acid, hydroxy acid, aromatic carboxylic acid, dicarboxylic acid, tricarboxylic acid, oxo A carboxylic acid etc. can be mentioned. Specific examples include formic acid, acetic acid, propionic acid, butyric acid, tartaric acid, oxalic acid, malonic acid, and succinic acid.
有機カルボン酸の添加量は、担体粒子に含まれる希土類成分、好ましくは固溶していない希土類成分のモル量に対して過不足なく反応するモル量（反応当量点）の０．５０倍以上、１．０倍以上、又は２．０倍以上であってもよく、５．０倍以下、４．５倍以下、４．０倍以下、又は３．５倍以下であってもよい。 The addition amount of the organic carboxylic acid is 0.50 times or more of the molar amount (reaction equivalent point) that reacts without excess or deficiency with respect to the molar amount of the rare earth component contained in the carrier particles, preferably the rare earth component that is not solid solution, It may be 1.0 times or more, or 2.0 times or more, and may be 5.0 times or less, 4.5 times or less, 4.0 times or less, or 3.5 times or less.
未焼成の排ガス浄化用触媒を得た後、これを含む水系分散体を乾燥させ、そして焼成する。乾燥温度は、例えば１５０℃以上、２００℃以上、２５０℃以上であってもよく、３５０℃以下、又は３００℃以下であってもよい。乾燥時間は、１６時間以上、１２時間以上、又は８時間以上であってもよく、２４時間以下又は２０時間以下であってもよい。また、焼成温度は、例えば４００℃以上、５００℃以上、５５０℃以上、又は６００℃以上であってもよく、１０００℃以下、８００℃以下、又は７００℃以下であってもよい。焼成時間は、３０分以上、１時間以上、２時間以上、又は４時間以上であってもよく、１２時間以下、１０時間以下、又は８時間以下であってもよい。 After obtaining an unfired exhaust gas-purifying catalyst, the aqueous dispersion containing the catalyst is dried and fired. The drying temperature may be, for example, 150 ° C. or higher, 200 ° C. or higher, 250 ° C. or higher, 350 ° C. or lower, or 300 ° C. or lower. The drying time may be 16 hours or more, 12 hours or more, or 8 hours or more, and may be 24 hours or less or 20 hours or less. The firing temperature may be, for example, 400 ° C. or higher, 500 ° C. or higher, 550 ° C. or higher, or 600 ° C. or higher, or 1000 ° C. or lower, 800 ° C. or lower, or 700 ° C. or lower. The firing time may be 30 minutes or more, 1 hour or more, 2 hours or more, or 4 hours or more, or 12 hours or less, 10 hours or less, or 8 hours or less.
なお、記載の本発明の排ガス浄化用触媒の製造方法によらない製造方法で製造された触媒は、上記の相関係数は、６０．０％以上、６５．０％以上又は７０．０％以上で一致している場合があり、典型的には８５％未満又は８０％未満である。 In addition, the catalyst manufactured by the manufacturing method that does not depend on the manufacturing method of the exhaust gas purifying catalyst of the present invention described above has a correlation coefficient of 60.0% or more, 65.0% or more, or 70.0% or more. And typically less than 85% or less than 80%.
このようにして得られた排ガス浄化用触媒をさらに粉砕して、担体粒子の粒径を、本発明の排ガス浄化用触媒の第１の担体粒子の粒径の範囲にすることができる。 The exhaust gas-purifying catalyst thus obtained can be further pulverized so that the particle size of the carrier particles is within the range of the particle size of the first carrier particles of the exhaust gas-purifying catalyst of the present invention.
Ａ．各種の排ガス浄化用触媒の参考的試験
《サンプル調製》
〈参考例１〉
担体粒子に含まれるセリウム以外の希土類の総和に対して、過不足なく反応する物質量の酢酸をイオン交換水に溶解させ、酢酸水溶液を調製した。次いで、酢酸溶液に、ロジウム量が担体粒子の０．５０重量％となるように、硝酸ロジウム溶液を投入し、酢酸及び硝酸ロジウムを含有する水溶液を得た。この水溶液と、担体粒子をイオン交換水に分散させた分散液とを混合した。これを撹拌し、２５０℃で８時間乾燥し、５００℃で１時間焼成し、粉砕することによって、参考例１の排ガス浄化用触媒を得た。
A. Reference test of various exhaust gas purification catalysts << Sample preparation >>
<Reference Example 1>
A total amount of rare earths other than cerium contained in the carrier particles was dissolved in ion exchange water with an amount of a substance that reacted without excess or deficiency to prepare an aqueous acetic acid solution. Next, the rhodium nitrate solution was added to the acetic acid solution so that the amount of rhodium was 0.50% by weight of the carrier particles to obtain an aqueous solution containing acetic acid and rhodium nitrate. This aqueous solution was mixed with a dispersion in which carrier particles were dispersed in ion exchange water. This was stirred, dried at 250 ° C. for 8 hours, calcined at 500 ° C. for 1 hour, and pulverized to obtain an exhaust gas purifying catalyst of Reference Example 1.
〈参考例２〜４及び比較参考例１〜３〉
酢酸の代わりに他の有機カルボン酸を用いたこと以外は参考例１と同様にして、参考例２〜４の排ガス浄化用触媒を得た。また、有機カルボン酸の代わりに他の酸を用いたこと以外は参考例１と同様にして、比較参考例１及び２の排ガス浄化用触媒を得た。さらに、酢酸を使用しなかったこと以外は参考例１と同様にして、比較参考例３の排ガス浄化用触媒を得た。これらの例の組成の詳細を表１に示す。
<Reference Examples 2 to 4 and Comparative Reference Examples 1 to 3>
Exhaust gas purifying catalysts of Reference Examples 2 to 4 were obtained in the same manner as Reference Example 1 except that other organic carboxylic acids were used instead of acetic acid. Further, exhaust gas purification catalysts of Comparative Reference Examples 1 and 2 were obtained in the same manner as Reference Example 1 except that another acid was used instead of the organic carboxylic acid. Further, an exhaust gas purifying catalyst of Comparative Reference Example 3 was obtained in the same manner as Reference Example 1 except that acetic acid was not used. Details of the composition of these examples are shown in Table 1.
〈参考例５〜６及び比較参考例４〜５〉
担体粒子及び貴金属の塩の種類を参考例２から変更して、参考例５〜６の排ガス浄化用触媒を得た。また、有機カルボン酸を使用しなかったこと以外は、参考例５及び６と同様にして、それぞれ比較参考例４及び５の排ガス浄化用触媒を得た。これらの例の組成の詳細を表２に示す。
<Reference Examples 5-6 and Comparative Reference Examples 4-5>
The types of the carrier particles and the noble metal salt were changed from Reference Example 2 to obtain exhaust gas purifying catalysts of Reference Examples 5-6. Exhaust gas purifying catalysts of Comparative Reference Examples 4 and 5 were obtained in the same manner as Reference Examples 5 and 6, respectively, except that no organic carboxylic acid was used. Details of the composition of these examples are shown in Table 2.
〈参考例７〜１５〉
参考例４から担体粒子の組成を変更し、また有機カルボン酸の添加量を変更することによって、参考例７〜１５の排ガス浄化用触媒を得た。これらの例の組成の詳細を表３に示す。
<Reference Examples 7 to 15>
The catalyst for exhaust gas purification of Reference Examples 7 to 15 was obtained by changing the composition of the carrier particles from Reference Example 4 and changing the addition amount of the organic carboxylic acid. Details of the composition of these examples are shown in Table 3.
〈参考例１６〜１９及び比較参考例６〜９〉
参考例１で用いた担体粒子の種類等を変更して、参考例１６〜１９及び比較参考例６〜９の排ガス浄化用触媒を得た。これらの例の組成の詳細を表４に示す。
<Reference Examples 16 to 19 and Comparative Reference Examples 6 to 9>
The types of carrier particles used in Reference Example 1 were changed to obtain exhaust gas purifying catalysts of Reference Examples 16 to 19 and Comparative Reference Examples 6 to 9. Details of the composition of these examples are shown in Table 4.
〈耐久試験後の排ガス浄化用触媒〉
上記のようにして得られた排ガス浄化用触媒を、流通式の耐久試験装置に配置した。そして、試験装置内温度を１０００℃にし、窒素ガスに酸素を１％添加したリーンガスと、窒素ガスに一酸化炭素を２％加えたリッチガスとを、５００ｍＬ／分の流量で、２分周期で交互に１０時間流通させた。その後の排ガス浄化用触媒を、耐久試験後の排ガス浄化用触媒として評価した。
<Exhaust gas purification catalyst after endurance test>
The exhaust gas-purifying catalyst obtained as described above was placed in a flow-type durability test apparatus. Then, the internal temperature of the test apparatus is set to 1000 ° C., and a lean gas in which 1% of oxygen is added to nitrogen gas and a rich gas in which 2% of carbon monoxide is added to nitrogen gas are alternately cycled at a flow rate of 500 mL / min every 2 minutes. For 10 hours. The subsequent exhaust gas purification catalyst was evaluated as an exhaust gas purification catalyst after the durability test.
〈排ガス浄化装置の作製〉
上記のようにして得られた排ガス浄化触媒とアルミナ粉末とを質量混合比１：１で混合し、固形分が３０重量％となるように純水に分散させてスラリーを得た。このスラリーを、モノリスハニカム基材（容積０．３５Ｌ）に、貴金属量が０．２５ｇ／Ｌとなるようにコートした。コートしたモノリスハニカム基材を２５０℃で１０分乾燥し、次に５００℃で２０分焼成することによって、排ガス浄化装置を得た。
<Production of exhaust gas purification device>
The exhaust gas purification catalyst and alumina powder obtained as described above were mixed at a mass mixing ratio of 1: 1 and dispersed in pure water so that the solid content was 30% by weight to obtain a slurry. The slurry was coated on a monolith honeycomb substrate (volume 0.35 L) so that the amount of noble metal was 0.25 g / L. The coated monolith honeycomb substrate was dried at 250 ° C. for 10 minutes and then fired at 500 ° C. for 20 minutes to obtain an exhaust gas purification device.
〈耐久試験後の排ガス浄化装置〉
上記のようにして得られた排ガス浄化装置を、流通式の耐久試験装置に配置した。そして、試験装置内温度を１０００℃にし、窒素ガスに酸素を１％添加したリーンガスと、窒素ガスに一酸化炭素を２％加えたリッチガスとを、５００ｍＬ／分の流量で、２分周期で交互に１０時間流通させた。その後の排ガス浄化装置を、耐久試験後の排ガス浄化装置として評価した。
<Exhaust gas purifier after durability test>
The exhaust gas purification device obtained as described above was placed in a flow-type durability test device. Then, the internal temperature of the test apparatus is set to 1000 ° C., and a lean gas in which 1% of oxygen is added to nitrogen gas and a rich gas in which 2% of carbon monoxide is added to nitrogen gas are alternately cycled at a flow rate of 500 mL / min every 2 minutes. For 10 hours. The subsequent exhaust gas purification apparatus was evaluated as an exhaust gas purification apparatus after the durability test.
《評価方法》
〈第２担体の平均粒径及び存在比〉
排ガス浄化用触媒の担体粒子の平均粒径の測定を、日立ハイテクノロジーズ社製の電界放出形走査型電子顕微鏡Ｓ−４８００及びその装置に付随しているエネルギー分散型Ｘ線分析装置によって行った。
"Evaluation method"
<Average particle diameter and abundance ratio of second carrier>
The average particle size of the carrier particles of the exhaust gas purifying catalyst was measured by a field emission scanning electron microscope S-4800 manufactured by Hitachi High-Technologies Corporation and an energy dispersive X-ray analyzer attached to the apparatus.
具体的には、まずこの装置で２０，０００倍の測定倍率によって映し出された画面において、等価直径が０．１０μｍ以上である粒子の中から、エネルギー分散型Ｘ線分析によって、ジルコニアを５０重量％〜９５重量％で、かつセリア及びセリア以外の希土類酸化物を５．０〜５０重量％で含有する粒子を見つけ出し、これを第１の担体粒子と認定した。そして、それらの粒子の等価直径を粒子の投影面積から計算した。この作業を任意の２０画面において行い、その全ての平均値を、第１の担体粒子の平均粒径とした。 Specifically, first, 50% by weight of zirconia is analyzed by energy dispersive X-ray analysis from particles having an equivalent diameter of 0.10 μm or more on a screen projected at a measurement magnification of 20,000 times with this apparatus. Particles containing ˜95% by weight and 5.0 to 50% by weight of ceria and a rare earth oxide other than ceria were found and identified as first carrier particles. And the equivalent diameter of those particles was calculated from the projected area of the particles. This operation was performed on 20 arbitrary screens, and the average value of all of them was defined as the average particle diameter of the first carrier particles.
さらに、等価直径が０．１０μｍ以上である粒子の中から、ジルコニアを１．０〜４０重量％で、かつセリア及びセリア以外の希土類酸化物を６０重量％〜９９重量％で含有する粒子を見つけ出し、これを第２の担体粒子と認定した。そして、それらの粒子の等価直径を粒子の投影面積から計算した。この作業を任意の２０画面において行い、その全ての平均値を、第２の担体粒子の平均粒径とした。 Further, from particles having an equivalent diameter of 0.10 μm or more, particles containing 1.0 to 40% by weight of zirconia and 60% to 99% by weight of rare earth oxides other than ceria and ceria are found. This was identified as the second carrier particle. And the equivalent diameter of those particles was calculated from the projected area of the particles. This operation was performed on 20 arbitrary screens, and the average value of all of them was defined as the average particle diameter of the second carrier particles.
さらに、各排ガス浄化用触媒について、第２の担体粒子の投影面積の、第１及び第２の担体粒子の投影面積に対する投影面積比（第２の担体粒子の面積／第１及び第２の担体粒子の面積）を計算し、これを第２の担体粒子の存在比とした。 Further, for each exhaust gas purifying catalyst, the ratio of the projected area of the second carrier particles to the projected area of the first and second carrier particles (the area of the second carrier particles / the first and second carriers). The area of the particles) was calculated and used as the abundance ratio of the second carrier particles.
〈触媒位置の相関係数〉
日立ハイテクノロジーズ社製の走査型電子顕微鏡Ｓ−４８００を用いて貴金属粒子の重心点位置にてエネルギー分散型Ｘ線分析を行い、希土類元素と貴金属の特性Ｘ線強度を測定した。担体粒子の希土類元素の特性Ｘ線強度と、貴金属元素の特性Ｘ線強度とを比較し、相関係数が０．６５以上で一致していた場合には、第２の担体上に担持されており、相関係数が０．６５未満であった場合には、担体上に担持されていないと定義した。
<Correlation position correlation coefficient>
Energy dispersive X-ray analysis was performed at the position of the center of gravity of the noble metal particles using a scanning electron microscope S-4800 manufactured by Hitachi High-Technologies, and the characteristic X-ray intensities of the rare earth elements and the noble metal were measured. When the characteristic X-ray intensity of the rare earth element of the carrier particles is compared with the characteristic X-ray intensity of the noble metal element, and the correlation coefficient is equal to or greater than 0.65, it is supported on the second carrier. When the correlation coefficient was less than 0.65, it was defined as not supported on the carrier.
〈触媒粒子の粒径変化〉
上記の耐久試験後の排ガス浄化用触媒を、Ｘ線回折装置によって分析し、貴金属触媒粒子の粒径を解析した。ロジウムは２θ＝４１．１°；パラジウムは２θ＝４０．１°；そして白金は２θ＝３９．８°の回折ピークの半値幅を用いて、シェラーの式から粒径を算出した。この結果から、参考例１〜４及び７〜１９並びに比較参考例１〜２及び６〜９については、有機カルボン酸を添加していない比較参考例３を基準として、有機カルボン酸の添加によって貴金属粒径が何％変化したかを算出した。参考例５及び６については、それぞれ比較参考例４及び５を基準として、貴金属粒径が何％変化したかを算出した。ただし、ここでは、表１中で「−」は粒径の微細化を意味し、「＋」は粒径の肥大を意味している。
<Changes in catalyst particle size>
The exhaust gas-purifying catalyst after the durability test was analyzed by an X-ray diffractometer to analyze the particle diameter of the noble metal catalyst particles. The particle size was calculated from Scherrer's equation using the half-width of the diffraction peak of rhodium 2θ = 41.1 °; palladium 2θ = 40.1 °; and platinum 2θ = 39.8 °. From these results, for Reference Examples 1 to 4 and 7 to 19 and Comparative Reference Examples 1 to 2 and 6 to 9, noble metals were added by adding an organic carboxylic acid based on Comparative Reference Example 3 to which no organic carboxylic acid was added. The percentage of particle size change was calculated. For Reference Examples 5 and 6, the percentage of change in the noble metal particle size was calculated based on Comparative Reference Examples 4 and 5, respectively. However, in Table 1, “−” means that the particle size is refined, and “+” means that the particle size is enlarged.
〈５０％ＮＯｘ浄化温度〉
耐久試験後の排ガス浄化装置を、常圧固定床式流通反応装置に配置し、ストイキ相当のモデルガスを流通させながら１００℃〜５００℃まで１２℃／分の速度で消音し、その間のＮＯｘ浄化率を連続的に測定した。排ガスが５０％浄化された時の温度を、各サンプルについて調べた。
<50% NO x purification temperature>
The exhaust gas purification device after the endurance test is placed in an atmospheric pressure fixed bed type flow reaction device, and silenced at a rate of 12 ° C./min from 100 ° C. to 500 ° C. while flowing a model gas equivalent to stoichiometric, NO x during that time The purification rate was measured continuously. The temperature at which the exhaust gas was purified by 50% was examined for each sample.
〈ＳＥＭ−ＥＤＸ画像〉
参考例３及び比較参考例３について、走査型電子顕微鏡を用いたエネルギー分散型Ｘ線分析による元素マッピングを撮影した。
<SEM-EDX image>
Regarding Reference Example 3 and Comparative Reference Example 3, elemental mapping by energy dispersive X-ray analysis using a scanning electron microscope was taken.
《結果》
上記のようにして評価した結果を表１〜表４に示す。また、参考例３及び比較参考例３のＳＥＭ−ＥＤＸ画像を図２に示す。さらに、参考例５の排ガス浄化用触媒について行った、電界放出形走査型電子顕微鏡の５０００倍の観察像を図３に示す。
The results of evaluation as described above are shown in Tables 1 to 4. In addition, SEM-EDX images of Reference Example 3 and Comparative Reference Example 3 are shown in FIG. Further, FIG. 3 shows an observation image of the field emission scanning electron microscope, which was performed on the exhaust gas purifying catalyst of Reference Example 5, at a magnification of 5000 times.
表１から理解できるように、有機カルボン酸を用いた場合（参考例１〜４）に、適切な平均粒径を有する第２の担体が容易に得られた。比較参考例１及び２を見ると、第２の担体粒子自体は生成していることが分かるが非常に粒径が小さく、この場合には相関係数から判断できるように、触媒粒子が第２の担体粒子に実質的に担持されていなかった。これは、第２の担体粒子が小さすぎるために、第１の担体粒子にも貴金属触媒粒子が担持されて、そこで貴金属触媒粒子がシンタリングを起こしたためと考えられる。 As can be understood from Table 1, when an organic carboxylic acid was used (Reference Examples 1 to 4), a second carrier having an appropriate average particle diameter was easily obtained. In Comparative Reference Examples 1 and 2, it can be seen that the second carrier particles themselves are formed, but the particle size is very small. In this case, the catalyst particles are the second particles so that the correlation coefficient can be judged. The carrier particles were not substantially supported. This is probably because the noble metal catalyst particles were supported on the first carrier particles because the second carrier particles were too small, and the noble metal catalyst particles were sintered there.
また、有機カルボン酸を用いた場合（参考例１〜４）には、耐久後に貴金属触媒粒子が小径化したことが分かる。有機カルボン酸の代わりにベンゼンスルホン酸及び硝酸を用いた場合（比較参考例１及び２）には、酸を用いていない場合（比較参考例３）に比べて、貴金属触媒粒子が肥大化していた、さらに、参考例１〜４の場合には、５０％ＮＯｘ浄化温度が非常に低い温度となった。 Moreover, when organic carboxylic acid is used (Reference Examples 1-4), it turns out that the diameter of the noble metal catalyst particles was reduced after durability. When benzenesulfonic acid and nitric acid were used in place of the organic carboxylic acid (Comparative Reference Examples 1 and 2), the noble metal catalyst particles were enlarged compared to the case where no acid was used (Comparative Reference Example 3). Furthermore, in the case of Reference Examples 1 to 4, the 50% NO x purification temperature was very low.
表２及び表４から理解できるように、このような傾向は、出発担体粒子の組成及び貴金属の種類を変更した場合であっても、同様であった。 As can be understood from Tables 2 and 4, such a tendency was the same even when the composition of the starting support particles and the type of the noble metal were changed.
表３を見ると、有機カルボン酸の添加量を増やすと、第２担体の粒径が大きくなることが分かる。ただし、貴金属触媒粒子については、有機カルボン酸の量を増やしていくと、小径化しなくなることが分かる。それに対応して、５０％ＮＯｘ浄化温度も変化した。 From Table 3, it can be seen that as the amount of organic carboxylic acid added increases, the particle size of the second carrier increases. However, it can be seen that noble metal catalyst particles are not reduced in diameter as the amount of organic carboxylic acid is increased. Correspondingly, the 50% NO x purification temperature also changed.
図２の比較参考例３の排ガス浄化触媒の元素マッピングを見ると、各元素の存在率の分布は、一様であることが分かる。それに対して、参考例３の元素マッピングを見ると、ジルコニウム（Ｚｒ）の存在率が低くなっている場所で、セリウム（Ｃｅ）及びネオジム（Ｎｄ）の存在率が非常に高くなっており、その場所が第２の担体粒子であることが分かる。また、第２の担体粒子の位置において、ロジウム（Ｒｈ）の存在率が高くなっており、貴金属触媒粒子が第２の担体粒子に集中的に担持されていることが分かる。 When the element mapping of the exhaust gas purification catalyst of Comparative Reference Example 3 in FIG. 2 is seen, it can be seen that the distribution of the abundance of each element is uniform. On the other hand, when the elemental mapping of Reference Example 3 is seen, the abundance of cerium (Ce) and neodymium (Nd) is very high at a place where the abundance of zirconium (Zr) is low, It can be seen that the location is the second carrier particle. In addition, the abundance of rhodium (Rh) is high at the position of the second support particles, and it can be seen that the noble metal catalyst particles are concentratedly supported on the second support particles.
Ｂ．本発明の排ガス浄化用触媒の試験
《サンプル調製》
〈比較例１〉
１．触媒の調製
Ｒｈ金属換算量が担体粒子に対して０．５質量％となる量の硝酸ロジウムを水に溶解して貴金属溶液を調製した。酸化物換算の組成がＺｒ：Ｃｅ：Ｌａ：Ｎｄ＝７０：２０：５：５の質量比である担体粒子（粒径１０μｍ、表面積７０ｍ２／ｇ）をイオン交換水中に分散して、担体粒子分散液を調製した。この担体粒子分散液に、上記貴金属溶液を加えて撹拌した。固体を回収し、１１０℃において８時間加熱乾燥し、更に５００℃において１時間焼成した後、粉砕及び分級することによって、比較例１の触媒を得た。
B. Test of exhaust gas purifying catalyst of the present invention << Sample preparation >>
<Comparative example 1>
1. Preparation of catalyst A noble metal solution was prepared by dissolving rhodium nitrate in water such that the amount of Rh metal equivalent was 0.5% by mass with respect to the support particles. Carrier particles in which the composition in terms of oxide is a mass ratio of Zr: Ce: La: Nd = 70: 20: 5: 5 (particle size 10 μm, surface area 70 m 2 / g) are dispersed in ion-exchanged water, and carrier particles A dispersion was prepared. The noble metal solution was added to the carrier particle dispersion and stirred. The solid was recovered, dried by heating at 110 ° C. for 8 hours, and further calcined at 500 ° C. for 1 hour, and then pulverized and classified to obtain the catalyst of Comparative Example 1.
〈実施例１〉
担体粒子中のセリウムを除く希土類元素と過不足なく反応する量（反応当量点）に対して２．５倍量（倍−ｅｑ）のプロピオン酸をイオン交換水に溶解して酸水溶液を調製した。この酸水溶液に、Ｒｈ金属換算量が担体粒子に対して０．５質量％となる量の硝酸ロジウムを加えて溶解させることにより、貴金属溶液を調製した。
<Example 1>
An aqueous acid solution was prepared by dissolving 2.5 times (times-eq) propionic acid in ion-exchanged water with respect to the amount (reaction equivalent point) that reacts with the rare earth element excluding cerium in the carrier particles without excess or deficiency. . A noble metal solution was prepared by adding and dissolving rhodium nitrate in an amount such that the Rh metal equivalent amount was 0.5% by mass with respect to the carrier particles.
上記比較例１と同様にして調製した担体粒子分散液に、該担体粒子の表面積１ｍ２当たり０．５μｍｍｏｌの硝酸ランタンを含有する水溶液を添加した後に、上記の貴金属溶液と混合した。その後の操作を比較例１と同様にして行い、実施例１の触媒を得た。 An aqueous solution containing 0.5 μmmol of lanthanum nitrate per 1 m 2 of the surface area of the carrier particles was added to the carrier particle dispersion prepared in the same manner as in Comparative Example 1, and then mixed with the noble metal solution. Subsequent operations were performed in the same manner as in Comparative Example 1, and the catalyst of Example 1 was obtained.
[実施例２〜１６、並びに比較例２及び３]
プロピオン酸の代わりに表５に示した種類及び量（倍−ｅｑ）の酸を用い、硝酸ランタンの代わりに表５に示した種類及び量（μｍｏｌ／ｍ２）の希土類化合物を用いた他は上記実施例１と同様にして、排ガス浄化用触媒を調製し、評価した。評価結果は表５に示した。表５に示した貴金属粒径は、比較例１の測定値を基準とする相対値（％）である。
[Examples 2 to 16 and Comparative Examples 2 and 3]
The types and amounts (times-eq) of acids shown in Table 5 were used instead of propionic acid, and the rare earth compounds of the types and amounts (μmol / m 2 ) shown in Table 5 were used instead of lanthanum nitrate. In the same manner as in Example 1, an exhaust gas purification catalyst was prepared and evaluated. The evaluation results are shown in Table 5. The noble metal particle size shown in Table 5 is a relative value (%) based on the measured value of Comparative Example 1.
《評価方法》
評価方法は、上記の実験Ａと同様にした。
"Evaluation method"
The evaluation method was the same as in Experiment A above.
本発明所定の構成を有する実施例１〜１６の触媒は、従来技術の典型的な例である比較例１と比較して、５０％ＮＯｘ浄化温度が低く、ＮＯｘ浄化性能に優れることが検証された。このような触媒は、有機カルボン酸と希土類化合物とを使用する本発明所定の製造方法により、容易に製造することができる。 The catalysts of Examples 1 to 16 having a predetermined configuration of the present invention have a 50% NO x purification temperature lower than that of Comparative Example 1 which is a typical example of the prior art, and are excellent in NO x purification performance. Verified. Such a catalyst can be easily produced by the predetermined production method of the present invention using an organic carboxylic acid and a rare earth compound.
有機カルボン酸に代えてスルホン酸化合物又は無機酸を使用した比較例２及び３では、いずれも、希土類酸化物粒子の粒径が小さく、５０％ＮＯｘ浄化温度の低下は見られず、かえって上昇する結果となった。これは、該粒子の粒径が過度に小さいため、貴金属がセリアジルコニア担体上にも担持されることとなり、このセリアジルコニア上の貴金属が耐久によって粒成長して粒径が大きくなったことによってＮＯｘ浄化性能が損なわれたものと考えられる。 In Comparative Examples 2 and 3 in which a sulfonic acid compound or an inorganic acid is used instead of the organic carboxylic acid, the particle size of the rare earth oxide particles is small and no decrease in the 50% NO x purification temperature is seen, but the increase. As a result. This is because the particle diameter of the particles is excessively small, so that the noble metal is also supported on the ceria zirconia support. x It is considered that the purification performance was impaired.
［比較例４及び５、並びに実施例１７及び１８］
硝酸Ｒｈの代わりに硝酸Ｐｔ（比較例４及び実施例１７）又は硝酸Ｐｄ（比較例５及び実施例１８）を、それぞれ、担体粒子に対して０．５質量％となる量用いた他は、比較例４及び５は上記比較例１と同様にして、実施例１７及び１８は上記実施例１と同様にして、それぞれ排ガス浄化触媒を調製し、評価した。評価結果は表６に示した。なお、表６に示した実施例１７の貴金属粒径は比較例４の測定値を基準とする相対値（％）であり、実施例１８の貴金属粒径は比較例５の測定値を基準とする相対値（％）である。
[Comparative Examples 4 and 5 and Examples 17 and 18]
Aside from using Pt nitrate (Comparative Example 4 and Example 17) or Pd nitrate (Comparative Example 5 and Example 18) in place of nitrate Rh in an amount of 0.5% by mass with respect to the carrier particles, Comparative Examples 4 and 5 were prepared in the same manner as in Comparative Example 1, and Examples 17 and 18 were prepared and evaluated in the same manner as in Example 1 above. The evaluation results are shown in Table 6. The noble metal particle size of Example 17 shown in Table 6 is a relative value (%) based on the measurement value of Comparative Example 4, and the noble metal particle size of Example 18 is based on the measurement value of Comparative Example 5. Relative value (%).
貴金属として、Ｒｈの代わりにＰｔ又はＰｄを用いた場合であっても、本発明所定の構成を有する実施例１７及び１８の触媒が、所期の効果を発現することが検証された。 Even when Pt or Pd was used as the noble metal instead of Rh, it was verified that the catalysts of Examples 17 and 18 having the predetermined configuration of the present invention exhibited the desired effect.
［参考例２０〜２７］
プロピオン酸の使用量を表７に示した量（倍−ｅｑ）に変更し、かつ硝酸ランタン水溶液を使用しなかった以外は、上記実施例１と同様にして、排ガス浄化触媒を調製し、評価した。評価結果は、比較例１の結果とともに表７に示した。表７に示した参考例の貴金属粒径は、比較例１の測定値を基準とする相対値（％）である。
[Reference Examples 20 to 27]
Exhaust gas purification catalyst was prepared and evaluated in the same manner as in Example 1 except that the amount of propionic acid used was changed to the amount shown in Table 7 (times-eq) and no lanthanum nitrate aqueous solution was used. did. The evaluation results are shown in Table 7 together with the results of Comparative Example 1. The noble metal particle size of the reference example shown in Table 7 is a relative value (%) based on the measured value of Comparative Example 1.
希土類酸化物粒子の粒径が０．５μｍ超５μｍ以下である参考例２１〜２５の場合に、従来技術の典型的な例である参考例２０と比較して、５０％ＮＯｘ浄化温度が有意に低く、ＮＯｘ浄化性能に優れることが検証された。このような触媒は、有機カルボン酸を使用する特定の製造方法により、容易に製造することができる。 In the case of Reference Examples 21 to 25 in which the particle size of the rare earth oxide particles is more than 0.5 μm and not more than 5 μm, the 50% NO x purification temperature is significant compared to Reference Example 20 which is a typical example of the prior art the low, to be excellent in the NO x purification performance was verified. Such a catalyst can be easily produced by a specific production method using an organic carboxylic acid.
１ 第１の担体粒子
１ａ 希土類富化領域
２ 第２の担体粒子
３ 触媒粒子
１０ 排ガス浄化用触媒
DESCRIPTION OF SYMBOLS 1 1st support particle 1a Rare earth rich area 2 2nd support particle 3 Catalyst particle 10 Exhaust gas purification catalyst
Claims (14)
前記第１の担体粒子が、シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物と、セリア以外の希土類酸化物とを含有し、
前記第２の担体粒子が、セリア以外の希土類酸化物を含有し、そしてシリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物を含有してもよく
前記第１の担体粒子の前記金属酸化物の含有率が、前記第２の担体粒子の前記金属酸化物の含有率よりも高く、
前記第２の担体粒子の前記希土類酸化物の含有率が、前記第１の担体粒子の前記希土類酸化物の含有率よりも高く、かつ
電界放出形走査型電子顕微鏡を用いたエネルギー分散型Ｘ線分析によって得られる特性Ｘ線の強度測定を行ったときに、以下の式で計算される相関係数が８５．０％以上である、排ガス浄化用触媒：
The first carrier particles contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania, and a rare earth oxide other than ceria,
The second support particles may contain a rare earth oxide other than ceria, and may contain at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania. The content rate of the metal oxide in the first support particles is higher than the content rate of the metal oxide in the second support particles,
The content rate of the rare earth oxide in the second carrier particles is higher than the content rate of the rare earth oxide in the first carrier particles, and energy dispersive X-ray using a field emission scanning electron microscope When the intensity of characteristic X-rays obtained by analysis is measured, the correlation coefficient calculated by the following formula is 85.0% or more:
前記第１の担体粒子の前記希土類酸化物及び前記第２の担体粒子の前記希土類酸化物が、イットリウム、ランタン、プラセオジム、ネオジム及びサマリウムからなる群より少なくとも１種選択される希土類元素の酸化物である、請求項１〜３のいずれか一項に記載の排ガス浄化用触媒。 The metal oxide of the first support particles and the metal oxide of the second support particles, if present, are ceria zirconia solid solutions, and the rare earth oxide and the first support particles of the first support particles. 4. The rare earth oxide of the support particles of 2 is an oxide of a rare earth element selected from at least one selected from the group consisting of yttrium, lanthanum, praseodymium, neodymium and samarium. Exhaust gas purification catalyst.
前記第２の担体粒子が、０．０〜４０重量％のジルコニア、０．０〜４０重量％のセリア、及び２０〜６０重量％のセリア以外の希土類酸化物を含有している、請求項４に記載の排ガス浄化用触媒。 The first carrier particles contain 50 to 95% by weight of zirconia, 5.0 to 45% by weight of ceria, and 1.0 or more and less than 20% by weight of a rare earth oxide other than ceria, and the second 5. The carrier particles of claim 4 containing 0.0 to 40 wt% zirconia, 0.0 to 40 wt% ceria, and 20 to 60 wt% rare earth oxides other than ceria. Exhaust gas purification catalyst.
シリカ、アルミナ、セリア、ジルコニア、及びチタニアからなる群より選択される少なくとも１種の金属酸化物と、セリア以外の希土類酸化物とを含有している担体粒子；イットリウム、ネオジム、ランタン、及びプラセオジムから１種以上選択される希土類元素の塩；触媒貴金属の塩；及び有機カルボン酸を水系分散体中で混合して、前記担体粒子に触媒貴金属を担持し、それによって未焼成の排ガス浄化用触媒を含む水系分散体を得る工程；
前記未焼成の排ガス浄化用触媒を含む水系分散体を、乾燥させ、そして焼成する工程。 A method for producing an exhaust gas purifying catalyst comprising:
Carrier particles containing at least one metal oxide selected from the group consisting of silica, alumina, ceria, zirconia, and titania and a rare earth oxide other than ceria; from yttrium, neodymium, lanthanum, and praseodymium A salt of a rare earth element selected from one or more kinds; a salt of a catalyst noble metal; and an organic carboxylic acid are mixed in an aqueous dispersion to carry the catalyst noble metal on the carrier particles, thereby forming an unfired exhaust gas purification catalyst. Obtaining an aqueous dispersion comprising:
A step of drying and calcining the aqueous dispersion containing the unfired exhaust gas-purifying catalyst;
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2021507804A (en) * | 2017-09-26 | 2021-02-25 | ジョンソン、マッセイ、パブリック、リミテッド、カンパニーＪｏｈｎｓｏｎ Ｍａｔｔｈｅｙ Ｐｕｂｌｉｃ Ｌｉｍｉｔｅｄ Ｃｏｍｐａｎｙ | Exhaust gas purification catalyst |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04219140A (en) * | 1990-02-22 | 1992-08-10 | Engelhard Corp | Catalyst composition containing separated platinum and rhodium |
| WO2010119904A1 (en) * | 2009-04-14 | 2010-10-21 | 株式会社 キャタラー | Exhaust gas purifying catalyst and method for producing same |
| JP2011183317A (en) * | 2010-03-09 | 2011-09-22 | Mazda Motor Corp | Exhaust gas cleaning catalyst |
| JP2013117190A (en) * | 2011-12-02 | 2013-06-13 | Mazda Motor Corp | Particulate filter with catalyst |
| JP2014509241A (en) * | 2010-11-22 | 2014-04-17 | ユミコア・アクチエンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフト | Three way catalyst system with upstream single layer catalyst |
| WO2017163916A1 (en) * | 2016-03-25 | 2017-09-28 | 株式会社キャタラー | Exhaust gas purifying catalyst and production method therefor, and exhaust gas purification device using same |
| JP6516862B2 (en) * | 2015-10-27 | 2019-05-22 | 株式会社キャタラー | EXHAUST GAS PURIFICATION CATALYST, METHOD FOR MANUFACTURING THE SAME, AND EXHAUST GAS PURIFICATION DEVICE USING THE SAME |
-
2017
- 2017-03-06 JP JP2017041884A patent/JP6851225B2/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04219140A (en) * | 1990-02-22 | 1992-08-10 | Engelhard Corp | Catalyst composition containing separated platinum and rhodium |
| WO2010119904A1 (en) * | 2009-04-14 | 2010-10-21 | 株式会社 キャタラー | Exhaust gas purifying catalyst and method for producing same |
| JP2011183317A (en) * | 2010-03-09 | 2011-09-22 | Mazda Motor Corp | Exhaust gas cleaning catalyst |
| JP2014509241A (en) * | 2010-11-22 | 2014-04-17 | ユミコア・アクチエンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフト | Three way catalyst system with upstream single layer catalyst |
| JP2013117190A (en) * | 2011-12-02 | 2013-06-13 | Mazda Motor Corp | Particulate filter with catalyst |
| JP6516862B2 (en) * | 2015-10-27 | 2019-05-22 | 株式会社キャタラー | EXHAUST GAS PURIFICATION CATALYST, METHOD FOR MANUFACTURING THE SAME, AND EXHAUST GAS PURIFICATION DEVICE USING THE SAME |
| WO2017163916A1 (en) * | 2016-03-25 | 2017-09-28 | 株式会社キャタラー | Exhaust gas purifying catalyst and production method therefor, and exhaust gas purification device using same |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2021507804A (en) * | 2017-09-26 | 2021-02-25 | ジョンソン、マッセイ、パブリック、リミテッド、カンパニーＪｏｈｎｓｏｎ Ｍａｔｔｈｅｙ Ｐｕｂｌｉｃ Ｌｉｍｉｔｅｄ Ｃｏｍｐａｎｙ | Exhaust gas purification catalyst |
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