JP6769862B2 - Three-way catalyst for exhaust gas purification, its manufacturing method, and catalyst converter for exhaust gas purification - Google Patents
Three-way catalyst for exhaust gas purification, its manufacturing method, and catalyst converter for exhaust gas purification Download PDFInfo
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- JP6769862B2 JP6769862B2 JP2016250614A JP2016250614A JP6769862B2 JP 6769862 B2 JP6769862 B2 JP 6769862B2 JP 2016250614 A JP2016250614 A JP 2016250614A JP 2016250614 A JP2016250614 A JP 2016250614A JP 6769862 B2 JP6769862 B2 JP 6769862B2
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- 238000000746 purification Methods 0.000 title claims description 110
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- 239000007789 gas Substances 0.000 claims description 118
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Description
本発明は、Ｐｄ触媒粒子が特定の母材粒子上に担持された排ガス浄化用触媒及びその製造方法、並びに排ガス浄化用触媒コンバータに関する。 The present invention relates to an exhaust gas purification catalyst in which Pd catalyst particles are supported on specific base material particles, a method for producing the same, and an exhaust gas purification catalyst converter.
自動車等の内燃機関から排出される炭化水素（ＨＣ）、一酸化炭素（ＣＯ）、及び窒素酸化物（ＮＯｘ）の浄化において、ルテニウム、ロジウム、パラジウム、オスミウム、イリジウム、プラチナ等の白金族元素（ＰＧＭ：Platinum Group Metal）を触媒活性成分として用いた三元触媒（ＴＷＣ：Three-Way Catalyst）が広く用いられている。従来、三元触媒としては、アルミナ、ジルコニア、セリア等の金属酸化物からなる担体（母材粒子）と、この担体上に担持されたＰｔ等の触媒粒子とを有するものが広く知られている。 Platinum group elements such as ruthenium, rhodium, palladium, osmium, iridium, and platinum (NOx) in the purification of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) emitted from internal combustion engines such as automobiles. A three-way catalyst (TWC: Three-Way Catalyst) using PGM: Platinum Group Metal) as a catalytically active ingredient is widely used. Conventionally, as a three-way catalyst, a catalyst having a carrier (base material particles) made of a metal oxide such as alumina, zirconia, and ceria, and catalyst particles such as Pt supported on the carrier is widely known. ..
この種の排ガス浄化用触媒においては、比較的に高価なＰＧＭの使用量を削減するとともに高い触媒活性を確保するため、微細な粒子の状態で触媒金属を担体上に担持させている。しかしながら、担体上の触媒金属の粒子は、高温環境に曝されると、粒子同士がシンタリングすることで粒成長し、これにより触媒活性サイトが著しく減少してしまうという問題があった。 In this type of exhaust gas purification catalyst, a catalyst metal is supported on a carrier in the form of fine particles in order to reduce the amount of relatively expensive PGM used and to secure high catalytic activity. However, when the catalyst metal particles on the carrier are exposed to a high temperature environment, the particles grow by sintering with each other, which causes a problem that the catalytically active sites are significantly reduced.
かかる触媒金属のシンタリングを抑制する技術として、例えば特許文献１には、Ａｌ2 Ｏ3 粒子と所定の金属酸化物の粒子のそれぞれの一次粒子がナノオーダーで混合された混合物を担体とし、この担体上に白金族元素を担持させた排ガス浄化用触媒が開示されている。この技術によれば、Ａｌ2 Ｏ3 の一次粒子と所定の金属酸化物の一次粒子とが、それぞれの粒子間に介在しているため、単独酸化物の一次粒子の粒成長の進行が抑制され、その結果、表面積及び細孔容積の低下が十分に抑制され、担持させる触媒成分の分散性を十分に保持することができるとされている。 As a technique for suppressing the synterling of such a catalyst metal, for example, in Patent Document 1, a mixture in which primary particles of Al 2 O 3 particles and particles of a predetermined metal oxide are mixed in nano-order is used as a carrier. A catalyst for purifying exhaust gas in which a platinum group element is supported on a carrier is disclosed. According to this technique, since the primary particles of Al 2 O 3 and the primary particles of a predetermined metal oxide are interposed between the respective particles, the progress of grain growth of the primary particles of the single oxide is suppressed. As a result, it is said that the decrease in the surface area and the pore volume is sufficiently suppressed, and the dispersibility of the catalyst component to be supported can be sufficiently maintained.
また、例えば特許文献２には、ＡＺＴ酸化物又はＡＺ酸化物からなる担体と、該担体に担持される一酸化炭素の酸化を触媒する貴金属と、を有する排ガス浄化用酸化触媒が開示されている。この技術によれば、ＡＺＴ酸化物又はＡＺ酸化物からなる担体の表面にある塩基点、すなわち塩基性性質を示す原子若しくは原子団のサイトにおいて、酸素原子を介してパラジウムや白金等の貴金属の原子（イオン）が強固に固定（担持）されるため、シンタリング抑制効果が高く貴金属の粒成長を抑制することができるとされている。 Further, for example, Patent Document 2 discloses an exhaust gas purification oxidation catalyst having a carrier made of AZT oxide or AZ oxide and a noble metal that catalyzes the oxidation of carbon monoxide supported on the carrier. .. According to this technique, at a base point on the surface of a carrier composed of AZT oxide or AZ oxide, that is, at the site of an atom or atomic group exhibiting basic properties, an atom of a noble metal such as palladium or platinum via an oxygen atom. Since (ions) are firmly fixed (supported), it is said that the effect of suppressing syntaring is high and the grain growth of noble metals can be suppressed.
しかしながら、特許文献１及び２の排ガス浄化用触媒は、母材粒子としてＡｌ2 Ｏ3 を用いたディーゼルエンジン用の排ガス浄化用触媒であり、より高温の排ガスを発生するガソリンエンジン等の内燃機関用途においては、耐熱性が不十分で、触媒性能が速やかに低下するという問題がある。 However, the exhaust gas purification catalysts of Patent Documents 1 and 2 are exhaust gas purification catalysts for diesel engines that use Al 2 O 3 as a base material particle, and are used for internal combustion engines such as gasoline engines that generate higher temperature exhaust gas. There is a problem that the heat resistance is insufficient and the catalyst performance is rapidly lowered.
一方、耐熱性を向上させた三元触媒として、特許文献３には、パラジウム含有率が０．０５〜７重量％の範囲であり、Ｐｒ／（Ｚｒ＋Ｐｒ）原子比が０．０５〜０．６の範囲であるＺｒαＰｒβＰｄγＯ2-δ（但し、α＋β＋γ＝１．０００であり、δは電荷中性条件を満たすように定まる値である。）固溶体成分からなる排ガス浄化三元触媒が開示されている。 On the other hand, as a three-way catalyst with improved heat resistance, Patent Document 3 states that the palladium content is in the range of 0.05 to 7% by weight and the Pr / (Zr + Pr) atomic ratio is 0.05 to 0.6. Zr α Pr β Pd γ O 2-δ (where α + β + γ = 1.000, where δ is a value determined to satisfy the charge neutrality condition.) Exhaust gas purification three-way catalyst composed of solid solution components Is disclosed.
他方、特許文献４及び５には、酸素ストレージ能（ＯＳＣ：Oxygen Storage Capacity）を有する助触媒（酸素貯蔵材料）として、イットリウム、ランタン、ネオジム、プラセオジム及びガドリニウム等の希土類元素をドープさせたセリア−ジルコニア系金属酸化物が開示されている。 On the other hand, Patent Documents 4 and 5 describe ceria-doped with rare earth elements such as yttrium, lantern, neodymium, praseodymium and gadolinium as an auxiliary catalyst (oxygen storage material) having an oxygen storage capacity (OSC: Oxygen Storage Capacity). Zirconia-based metal oxides are disclosed.
しかしながら、特許文献３に記載された排ガス浄化三元触媒は、特殊な結晶構造を有する固溶体を得るために空気中８００〜１１００℃で数十時間もの熱処理を必要としており、生産性に劣る。また、特許文献４及び５は、酸素貯蔵材料としてのセリア−ジルコニア系金属酸化物の開示に留まる。 However, the exhaust gas purification three-way catalyst described in Patent Document 3 requires heat treatment in the air at 800 to 1100 ° C. for several tens of hours in order to obtain a solid solution having a special crystal structure, and is inferior in productivity. Further, Patent Documents 4 and 5 are limited to the disclosure of ceria-zirconia-based metal oxide as an oxygen storage material.
本発明は、上記課題に鑑みてなされたものである。すなわち本発明の目的は、パラジウム表面積が大きく、耐熱性及び三元浄化性能に優れ、製造容易で生産性にも優れる、排ガス浄化用三元触媒及びその製造方法、並びに排ガス浄化用触媒コンバータ等を提供することにある。 The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a three-way catalyst for exhaust gas purification, a method for producing the same, a catalyst converter for exhaust gas purification, etc., which have a large palladium surface area, excellent heat resistance and ternary purification performance, and are easy to manufacture and excellent in productivity. To provide.
本発明者らは、上記課題を解決すべく鋭意検討した。その結果、特定の母材粒子上にＰｄ触媒粒子が担持された新規構造を採用することで、上記課題を解決できることを見出し、本発明を完成するに至った。 The present inventors have diligently studied to solve the above problems. As a result, they have found that the above problems can be solved by adopting a new structure in which Pd catalyst particles are supported on specific base material particles, and have completed the present invention.
すなわち、本発明は、以下に示す種々の具体的態様を提供する。
（１）構成金属元素としてＬａ及びＺｒ並びに必要に応じてＮｄを、酸化物換算で以下の質量割合：ＺｒＯ2 ５０〜８０質量％；Ｌａ2 Ｏ3 ２０〜５０質量％；Ｎｄ2 Ｏ3 ０〜２０質量％；Ｌａ2 Ｏ3とＮｄ2 Ｏ3 の合計量が２０〜５０質量％；で含むＬａ固溶ジルコニア系複合酸化物の母材粒子と、前記母材粒子上に担持されたＰｄ触媒粒子と、を少なくとも含有することを特徴とする、排ガス浄化用三元触媒。
（２）前記Ｐｄ触媒粒子が、金属パラジウム換算で０．１〜１０質量％含まれる（１）に記載の排ガス浄化用三元触媒。
（３）前記母材粒子が、１〜１００μｍの平均粒子径Ｄ50を有する（１）又は（２）に記載の排ガス浄化用三元触媒。
（４）一酸化炭素ガスパルス吸着法により算出されるパラジウム表面積が、８〜３０（ｍ2 ／Ｐｄ_ｇ）である（１）〜（３）のいずれか一項に記載の排ガス浄化用三元触媒。
（５）ＢＥＴ比表面積が、１０〜５０（ｍ2 ／ｇ）である（１）〜（４）のいずれか一項に記載の排ガス浄化用三元触媒。
That is, the present invention provides various specific aspects shown below.
(1) La and Zr as constituent metal elements and, if necessary, Nd, in terms of oxide, the following mass ratio: ZrO 2 50 to 80 mass%; La 2 O 3 20 to 50 mass%; Nd 2 O 30 The base material particles of the La solid-soluble zirconia-based composite oxide contained in ~ 20% by mass; the total amount of La 2 O 3 and Nd 2 O 3 is 20 to 50% by mass; and Pd supported on the base material particles. A ternary catalyst for purifying exhaust gas, which comprises at least catalyst particles.
(2) The three-way catalyst for exhaust gas purification according to (1), wherein the Pd catalyst particles are contained in an amount of 0.1 to 10% by mass in terms of metallic palladium.
(3) The three-way catalyst for exhaust gas purification according to (1) or (2), wherein the base metal particles have an average particle diameter D 50 of 1 to 100 μm.
(4) The three-way catalyst for exhaust gas purification according to any one of (1) to (3), wherein the palladium surface area calculated by the carbon monoxide gas pulse adsorption method is 8 to 30 (m 2 / Pd_g).
(5) The three-way catalyst for exhaust gas purification according to any one of (1) to (4), which has a BET specific surface area of 10 to 50 (m 2 / g).
（６）構成金属元素としてＬａ、Ｎｄ及びＺｒを、酸化物換算で以下の質量割合：ＺｒＯ2 ５０〜８０質量％；Ｌａ2 Ｏ3 ２０〜５０質量％；Ｎｄ2 Ｏ3 ０〜２０質量％；Ｌａ2 Ｏ3とＮｄ2 Ｏ3 の合計量が２０〜５０質量％；で含むＬａ固溶ジルコニア系複合酸化物の母材粒子を準備する工程、前記母材粒子の表面に、Ｐｄイオンを少なくとも含有する水溶液を付与する工程、並びに処理後の前記母材粒子を熱処理又は化学処理して、前記母材粒子の表面にＰｄ触媒粒子を担持させる工程、を少なくとも有することを特徴とする、排ガス浄化用三元触媒の製造方法。
（７）触媒担体と、前記触媒担体上に設けられた酸素貯蔵層と、前記酸素貯蔵層上に設けられた触媒層とを少なくとも備え、前記触媒層が、（１）〜（５）のいずれか一項に記載の排ガス浄化用三元触媒を含むことを特徴とする、排ガス浄化用触媒コンバータ。
(6) La, Nd and Zr as constituent metal elements are as follows in terms of oxide mass ratio: ZrO 2 50 to 80% by mass; La 2 O 3 20 to 50% by mass; Nd 2 O 30 to 20% by mass. The step of preparing the base material particles of the La solid-soluble zirconia-based composite oxide containing La 2 O 3 and Nd 2 O 3 in a total amount of 20 to 50% by mass; Pd ions are added to the surface of the base material particles. Exhaust gas having at least a step of applying an aqueous solution containing at least and a step of heat-treating or chemically treating the base material particles after treatment to support Pd catalyst particles on the surface of the base material particles. A method for producing a ternary catalyst for purification.
(7) A catalyst carrier, an oxygen storage layer provided on the catalyst carrier, and a catalyst layer provided on the oxygen storage layer are provided at least, and the catalyst layer is any of (1) to (5). A catalyst converter for exhaust gas purification, which comprises the three-way catalyst for exhaust gas purification according to the above item.
本発明によれば、パラジウム表面積が大きく、耐熱性及び三元浄化性能に優れ、製造容易で生産性にも優れる、排ガス浄化用三元触媒及びその製造方法、並びに排ガス浄化用三元触媒等を実現することができる。本発明の排ガス浄化用触媒は、Ｌａ固溶ジルコニア系複合酸化物の母材粒子上に数多くの微小な活性点（Ｐｄ触媒粒子）が担持された複合構造の触媒粒子であり、その組成及び構造に基づいて、排ガス中のＮＯｘ、ＣＯ、ＨＣ等を削減する三元触媒（TWC：Tree Way Catalyst）として、特に好適に用いることができる。そして、本発明の排ガス浄化用触媒等は、エンジン直下型触媒コンバータやタンデム配置の直下型触媒コンバータ等に搭載することができ、これにより、キャニングコストの削減などを図ることができる。 According to the present invention, a three-way catalyst for exhaust gas purification, a method for producing the same, a three-way catalyst for exhaust gas purification, etc., which have a large palladium surface area, excellent heat resistance and ternary purification performance, are easy to manufacture, and are also excellent in productivity. It can be realized. The exhaust gas purification catalyst of the present invention is a catalyst particle having a composite structure in which a large number of minute active points (Pd catalyst particles) are supported on a base material particle of a La solid-dissolved zirconia-based composite oxide, and the composition and structure thereof. Based on the above, it can be particularly preferably used as a three-way catalyst (TWC: Tree Way Catalyst) that reduces NOx, CO, HC, etc. in the exhaust gas. The exhaust gas purification catalyst or the like of the present invention can be mounted on a catalyst converter directly under the engine, a catalyst converter directly under the engine in a tandem arrangement, or the like, whereby the canning cost can be reduced.
以下、本発明の実施の形態について、詳細に説明する。なお、以下の実施の形態は、本発明を説明するための例示であり、本発明はこれらに限定されるものではない。なお、本明細書において、例えば「１〜１００」との数値範囲の表記は、その上限値「１００」及び下限値「１」の双方を包含するものとする。また、他の数値範囲の表記も同様である。 Hereinafter, embodiments of the present invention will be described in detail. The following embodiments are examples for explaining the present invention, and the present invention is not limited thereto. In the present specification, for example, the notation of the numerical range of " 1 to 100 " includes both the upper limit value " 100 " and the lower limit value " 1 ". The same applies to the notation of other numerical ranges.
本実施形態の排ガス浄化用三元触媒は、特定組成のＬａ固溶ジルコニア系複合酸化物の母材粒子と、この母材粒子上に担持されたＰｄ触媒粒子とを少なくとも含有する。このＬａ固溶ジルコニア系複合酸化物は、構成元素としてランタン（Ｌａ）、ジルコニウム（Ｚｒ）、及び酸素（Ｏ）を少なくとも含有するものであって、Ｌａ及びＺｒ並びに必要に応じてＮｄを、酸化物換算で以下の質量割合で含有するものである。
ＺｒＯ2 ：５０〜８０質量％
Ｌａ2 Ｏ3 ：２０〜５０質量％
Ｎｄ2 Ｏ3 ：０〜２０質量％
Ｌａ2 Ｏ3とＮｄ2 Ｏ3 の合計量：２０〜５０質量％
The three-way catalyst for exhaust gas purification of the present embodiment contains at least the base material particles of the La solid-soluble zirconia-based composite oxide having a specific composition and the Pd catalyst particles supported on the base material particles. This La solid-soluble zirconia-based composite oxide contains at least lanthanum (La), zirconium (Zr), and oxygen (O) as constituent elements, and oxidizes La and Zr and, if necessary, Nd. It is contained in the following mass ratio in terms of material.
ZrO 2 : 50-80% by mass
La 2 O 3 : 20 to 50% by mass
Nd 2 O 3 : 0 to 20% by mass
Total amount of La 2 O 3 and Nd 2 O 3 : 20-50% by mass
このような組成を有するＬａ固溶ジルコニア系複合酸化物の母材粒子を用いることで、母材粒子上に微細なＰｄ触媒粒子が高分散に担持された排ガス浄化用三元触媒を実現することができる。以下、本実施形態の排ガス浄化用三元触媒における推定作用を、説明する。 By using the base material particles of La solid-dissolved zirconia-based composite oxide having such a composition, it is possible to realize a three-way catalyst for exhaust gas purification in which fine Pd catalyst particles are supported on the base material particles in a highly dispersed manner. Can be done. Hereinafter, the estimation action of the three-way catalyst for exhaust gas purification of the present embodiment will be described.
先に述べたとおり、この種の触媒においては、高温環境に曝されると、母材粒子上の触媒粒子同士がシンタリングすることで粒成長し、これにより触媒活性サイトが著しく減少し、触媒性能が低下することが知られている。これに対して、本実施形態の排ガス浄化用三元触媒においては、外部環境が還元性雰囲気から酸化性雰囲気に切り替えられると、母材粒子に含まれるＬａ（及び必要に応じてＮｄ）とＰｄ触媒粒子とが複合酸化物や固溶体を形成し、さらに外部環境が酸化性雰囲気から還元性雰囲気に切り替えられると、その複合酸化物や固溶体から微細なＰｄ触媒粒子が母材粒子上に再分散される。すなわち、本実施形態においてＰｄ触媒粒子は、謂わばＰｄＯ／Ｌａ2 Ｏ3 混合酸化物として用いられており、さらにＮｄを含有する場合にはＰｄＯ／Ｎｄ2 Ｏ3 混合酸化物として用いられており、外部環境の変化に応じて、微細なＰｄ触媒粒子が母材粒子上に高分散に担持されるようになっている。また、母材粒子として、比較的に耐熱性に優れるジルコニア系複合酸化物を用いているため、触媒そのものの耐熱性も高められている。これらが相まった結果、耐熱性及び三元浄化性能に優れる排ガス浄化用三元触媒が実現されたものと推察される。但し、作用はこれらに限定されない。 As mentioned earlier, in this type of catalyst, when exposed to a high temperature environment, the catalyst particles on the base metal particles are sintered to grow, which significantly reduces the catalytically active sites and the catalyst. It is known that performance is reduced. On the other hand, in the three-way catalyst for exhaust gas purification of the present embodiment, when the external environment is switched from the reducing atmosphere to the oxidizing atmosphere, La (and Nd) and Pd contained in the base material particles are contained. When the catalyst particles form a composite oxide or solid solution and the external environment is switched from an oxidizing atmosphere to a reducing atmosphere, fine Pd catalyst particles are redispersed on the base material particles from the composite oxide or solid solution. To. That is, in the present embodiment, the Pd catalyst particles are used as a so-called PdO / La 2 O 3 mixed oxide, and when Nd is further contained, they are used as a Pd O / Nd 2 O 3 mixed oxide. In response to changes in the external environment, fine Pd catalyst particles are supported on the base material particles in a highly dispersed manner. Further, since the zirconia-based composite oxide having relatively excellent heat resistance is used as the base material particles, the heat resistance of the catalyst itself is also enhanced. As a result of these combinations, it is presumed that a three-way catalyst for exhaust gas purification, which has excellent heat resistance and three-way purification performance, has been realized. However, the action is not limited to these.
なお、以上のとおりであるから、上記の母材粒子及びＰｄ触媒粒子は少なくとも還元性雰囲気において確認されればよく、酸化性雰囲気やストイキ雰囲気におけるＰｄ触媒粒子の性状は特に限定されない。ここで本明細書において、還元性雰囲気とは、水素ガス雰囲気下４００℃で０．５時間以上、静置した状態を意味する。なお、Ｐｄ触媒粒子は、例えば倍率１００万倍の走査透過型電子顕微鏡（ＳＴＥＭ）、日立ハイテクノロジーズ社製ＨＤ−２０００等を用いて確認することができる。以下、各成分について詳述する。 As described above, the base material particles and the Pd catalyst particles may be confirmed at least in a reducing atmosphere, and the properties of the Pd catalyst particles in an oxidizing atmosphere or a stoichiometric atmosphere are not particularly limited. Here, in the present specification, the reducing atmosphere means a state of being allowed to stand at 400 ° C. for 0.5 hours or more in a hydrogen gas atmosphere. The Pd catalyst particles can be confirmed by using, for example, a scanning transmission electron microscope (STEM) having a magnification of 1 million times, HD-2000 manufactured by Hitachi High-Technologies Corporation, or the like. Hereinafter, each component will be described in detail.
Ｌａ固溶ジルコニア系複合酸化物中のＺｒの質量割合は、酸化物（ＺｒＯ2 ）換算で、５２〜７８質量％が好ましく、より好ましくは５５〜７６質量％であり、さらに好ましくは５５〜７５質量％である。ジルコニアは、耐熱性に優れているため、高温環境下で使用する排ガス浄化触媒の母材として適している。また、ジルコニア系複合酸化物は、アルミナに比して、共担持させるＬａ及びＮｄの化合物形成が抑制されるというメリットもある。 The mass ratio of Zr in the La solid-dissolved zirconia-based composite oxide is preferably 52 to 78% by mass, more preferably 55 to 76% by mass, and further preferably 55 to 75% by mass in terms of oxide (ZrO 2 ). It is mass%. Since zirconia has excellent heat resistance, it is suitable as a base material for an exhaust gas purification catalyst used in a high temperature environment. Further, the zirconia-based composite oxide has an advantage that the formation of compounds of La and Nd to be co-supported is suppressed as compared with alumina.
また、Ｌａ固溶ジルコニア系複合酸化物中のＬａの質量割合は、酸化物（Ｌａ2 Ｏ3 ）換算で、２２〜４８質量％が好ましく、より好ましくは２４〜４５質量％であり、さらに好ましくは２５〜４５質量％である。このように希土類元素であるＬａを固溶させたジルコニア系複合酸化物を用いることで、排ガス浄化性能が高められる傾向にある。また、担持されるＰｄ触媒粒子の分散性が高められる傾向にある。 The mass ratio of La in the La solid solution zirconia-based composite oxide is preferably 22 to 48% by mass, more preferably 24 to 45% by mass, and further preferably 24 to 45% by mass in terms of oxide (La 2 O 3 ). Is 25 to 45% by mass. By using the zirconia-based composite oxide in which La, which is a rare earth element, is dissolved in this way, the exhaust gas purification performance tends to be improved. Further, the dispersibility of the supported Pd catalyst particles tends to be improved.
一方、Ｌａ固溶ジルコニア系複合酸化物がＮｄを含む場合（以降において、「ＬａＮｄ固溶ジルコニア系複合酸化物」ともいう。なお、Ｎｄを含む場合／含まない場合の双方を意図する場合には、「Ｌａ固溶ジルコニア系複合酸化物」と総称する。）、ＬａＮｄ固溶ジルコニア系複合酸化物中のＮｄの質量割合は、酸化物（Ｎｄ2 Ｏ3 ）換算で、０〜１９質量％が好ましく、より好ましくは０〜１８質量％である。このように希土類元素であるＮｄを固溶させたジルコニア系複合酸化物を用いることで、ジルコニアの耐熱性が向上し、排ガス浄化性能が高められる傾向にある。また、担持されるＰｄ触媒粒子の分散性が高められる傾向にある。 On the other hand, when the La solid-solved zirconia-based composite oxide contains Nd (hereinafter, also referred to as "LaNd solid-soluble zirconia-based composite oxide". In addition, when both the case where Nd is contained and the case where Nd is not contained are intended. , "La solid solution zirconia-based composite oxide"), LaNd The mass ratio of Nd in the solid solution zirconia-based composite oxide is 0 to 19% by mass in terms of oxide (Nd 2 O 3 ). It is preferable, more preferably 0 to 18% by mass. By using the zirconia-based composite oxide in which Nd, which is a rare earth element, is dissolved in this way, the heat resistance of zirconia tends to be improved and the exhaust gas purification performance tends to be improved. Further, the dispersibility of the supported Pd catalyst particles tends to be improved.
そして、ＬａＮｄ固溶ジルコニア系複合酸化物中のＬａ及びＮｄの合計量は、酸化物（Ｌａ2 Ｏ3 及びＮｄ2 Ｏ3 ）換算で、２２〜４８質量％が好ましく、より好ましくは２５〜４５質量％であり、さらに好ましくは３０〜４５質量％である。このように希土類元素であるＬａ及びＮｄを所定量固溶させたジルコニア系複合酸化物を用いることで、排ガス浄化性能が高められる傾向にある。 The total amount of La and Nd in the LaNd solid solution zirconia-based composite oxide is preferably 22 to 48% by mass, more preferably 25 to 45 in terms of oxides (La 2 O 3 and Nd 2 O 3 ). It is by mass, more preferably 30 to 45% by mass. By using a zirconia-based composite oxide in which a predetermined amount of the rare earth elements La and Nd are dissolved in this way, the exhaust gas purification performance tends to be improved.
ここで、Ｌａ固溶ジルコニア系複合酸化物は、上述した構成元素以外に、他の元素を含んでいてもよい。例えば、本発明の効果を著しく損なわない限り、イットリウム、セリウム、スカンジウム、プラセオジム、プロメチウム、サマリウム、ユウロビウム、ガドリニウム、テルビウム、ジスプロシウム、ホルミウム、エルビウム、ツリウム、イッテルビウム、及びルテチウム等の希土類元素を含んでいてもよい。これらの希土類元素は、１種を単独で、又は２種以上を適宜組み合わせて用いることができる。 Here, the La solid solution zirconia-based composite oxide may contain other elements in addition to the above-mentioned constituent elements. For example, it contains rare earth elements such as ytterbium, cerium, scandium, placeodim, promethium, samarium, urobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, as long as the effects of the present invention are not significantly impaired. May be good. These rare earth elements may be used alone or in combination of two or more.
これらの中でも、イットリウム（Ｙ）、スカンジウム（Ｓｃ）、プラセオジム（Ｐｒ）は、ジルコニア系複合酸化物中にドープされるＬａやＮｄに置き換えて使用可能であり、好ましい。このとき、Ｌａ固溶ジルコニア系複合酸化物は、イットリウム、スカンジウム、及びプラセオジムを、これらの酸化物換算の合計で、０〜１０質量％含んでいることが好ましく、より好ましくは１〜８質量％であり、さらに好ましくは２〜５質量％である。 Among these, yttrium (Y), scandium (Sc), and praseodymium (Pr) can be used in place of La or Nd doped in the zirconia-based composite oxide, and are preferable. At this time, the La solid-dissolved zirconia-based composite oxide preferably contains yttrium, scandium, and praseodymium in a total of 0 to 10% by mass, more preferably 1 to 8% by mass, in terms of these oxides. It is more preferably 2 to 5% by mass.
一方、本発明のより高い効果を維持する観点から、上述した希土類元素のうち、セリウム、プロメチウム、サマリウム、ユウロビウム、ガドリニウム、テルビウム、ジスプロシウム、ホルミウム、エルビウム、ツリウム、イッテルビウム、及びルテチウムは、Ｌａ固溶ジルコニア系複合酸化物中に実質的に含まれないことが好ましい。ここで、実質的に含まないとは、これらの酸化物換算の質量割合が、Ｌａ固溶ジルコニア系複合酸化物に対して０〜５質量％であることを意味し、より好ましくは０〜３質量％であり、さらに好ましくは０〜１質量％である。 On the other hand, from the viewpoint of maintaining the higher effect of the present invention, among the above-mentioned rare earth elements, cerium, promethium, samarium, urobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium are dissolved in La. It is preferable that it is not substantially contained in the zirconia-based composite oxide. Here, substantially not contained means that the mass ratio in terms of these oxides is 0 to 5% by mass with respect to the La solid-soluble zirconia-based composite oxide, and more preferably 0 to 3. It is by mass%, more preferably 0 to 1% by mass.
なお、Ｌａ固溶ジルコニア系複合酸化物は、ジルコニア鉱石中に通常１〜２質量％程度含まれているハフニウム（Ｈｆ）を不可避不純物として含有していても構わない。ここで、ハフニウムを除く不可避不純物の総量は、０．３質量％以下であることが好ましい。また、Ｌａ固溶ジルコニア系複合酸化物は、本発明の効果を著しく損なわない範囲で、ジルコニウムの一部が、アルカリ金属元素やアルカリ土類金属元素等で置換されていてもよい。さらにまた、Ｌａ固溶ジルコニア系複合酸化物は、本発明の効果を著しく損なわない範囲で、鉄（Ｆｅ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、及び銅（Ｃｕ）等の遷移金属元素を含有していてもよい。 The La solid solution zirconia-based composite oxide may contain hafnium (Hf), which is usually contained in about 1 to 2% by mass in the zirconia ore, as an unavoidable impurity. Here, the total amount of unavoidable impurities excluding hafnium is preferably 0.3% by mass or less. Further, in the La solid-dissolved zirconia-based composite oxide, a part of zirconium may be replaced with an alkali metal element, an alkaline earth metal element, or the like as long as the effect of the present invention is not significantly impaired. Furthermore, the La solid-soluble zirconia-based composite oxide contains transition metal elements such as iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) as long as the effects of the present invention are not significantly impaired. It may be contained.
上述した特定組成のＬａ固溶ジルコニア系複合酸化物の母材粒子は、大きな比表面積を保持させる観点から、１〜１００μｍの平均粒子径Ｄ５０を有することが好ましく、より好ましくは１．５〜６０μｍであり、さらに好ましくは２〜３０μｍである。なお、本明細書において、平均粒子径Ｄ５０は、レーザー回折式粒度分布測定装置（例えば、島津製作所社製、レーザー回折式粒度分布測定装置ＳＡＬＤ−３１００等）で測定されるメディアン径を意味する。 The base material particles of the La solid solution zirconia-based composite oxide having the above-mentioned specific composition preferably have an average particle diameter D 50 of 1 to 100 μm, more preferably 1.5 to 100, from the viewpoint of maintaining a large specific surface area. It is 60 μm, more preferably 2 to 30 μm. In the present specification, the average particle size D 50 means a median diameter measured by a laser diffraction type particle size distribution measuring device (for example, a laser diffraction type particle size distribution measuring device SALD-3100 manufactured by Shimadzu Corporation). ..
母在粒子は、各種グレードの市販品を用いることができる。また、上述した組成のＬａ固溶ジルコニア系複合酸化物は、当業界で公知の方法で製造することもできる。Ｌａ固溶ジルコニア系複合酸化物の製造方法は、特に限定されないが、共沈法やアルコキシド法が好ましい。 As the mother particles, various grades of commercially available products can be used. Further, the La solid solution zirconia-based composite oxide having the above-mentioned composition can also be produced by a method known in the art. The method for producing the La solid solution zirconia-based composite oxide is not particularly limited, but the coprecipitation method or the alkoxide method is preferable.
共沈法としては、例えば、ジルコニウム塩、ランタン塩及び必要に応じて配合するネオジム塩や他の希土類金属元素を所定の化学量論比で混合した水溶液に、アルカリ物質を添加して加水分解させ或いは前駆体を共沈させ、その加水分解生成物或いは共沈物を焼成する製法が好ましい。ここで用いる各種塩の種類は、特に限定されない。一般的には、塩酸塩、オキシ塩酸塩、硝酸塩、オキシ硝酸塩、炭酸塩、リン酸塩、酢酸塩、シュウ酸塩、クエン酸塩等が好ましい。また、アルカリ性物質の種類も、特に限定されない。一般的には、アンモニア水溶液が好ましい。アルコキシド法としては、例えば、ジルコニウムアルコキシド、ランタンアルコキシド及び必要に応じて配合するネオジムアルコキシドや希土類金属元素を所定の化学量論比で混合した混合物を加水分解し、その後に焼成する製法が好ましい。ここで用いるアルコキシドの種類は、特に限定されない。一般的には、メトキシド、エトキシド、プロポキシド、イソプロポキシド、ブトキシドや、これらのエチレンオキサイド付加物等が好ましい。また、希土類金属元素は、金属アルコキシドとして配合しても、上述した各種塩として配合してもよい。 As a coprecipitation method, for example, an alkaline substance is added to an aqueous solution prepared by mixing a zirconium salt, a lanthanum salt, a neodymium salt to be blended as necessary, and other rare earth metal elements at a predetermined chemical quantitative ratio, and the mixture is hydrolyzed. Alternatively, a production method in which the precursor is coprecipitated and the hydrolysis product or coprecipitate thereof is calcined is preferable. The types of various salts used here are not particularly limited. In general, hydrochloride, oxy hydrochloride, nitrate, oxynitrate, carbonate, phosphate, acetate, oxalate, citrate and the like are preferable. Further, the type of alkaline substance is not particularly limited. Generally, an aqueous ammonia solution is preferable. As the alkoxide method, for example, a production method in which a mixture of zirconium alkoxide, lanthanum alkoxide, neodymium alkoxide to be blended if necessary, or a rare earth metal element mixed at a predetermined chemical quantitative ratio is hydrolyzed and then fired is preferable. The type of alkoxide used here is not particularly limited. Generally, methoxide, ethoxide, propoxide, isopropoxide, butoxide, and ethylene oxide adducts thereof are preferable. Further, the rare earth metal element may be blended as a metal alkoxide or as various salts described above.
焼成条件は、常法にしたがえばよく、特に限定されない。焼成雰囲気は、酸化性雰囲気、還元性雰囲気、中性雰囲気のいずれの雰囲気でもよい。焼成温度及び処理時間は、所望するＬａ固溶ジルコニア系複合酸化物の組成及びその化学量論比によって変動するが、生産性等の観点からは、一般的には、１５０℃〜１３００℃で１〜１２時間が好ましく、より好ましくは３５０℃〜８００℃で２〜４時間である。なお、高温焼成に先立って、真空乾燥機等を用いて減圧乾燥を行い、約５０℃〜２００℃で約１〜４８時間程度の乾燥処理を行うことが好ましい。 The firing conditions may be according to a conventional method and are not particularly limited. The firing atmosphere may be any of an oxidizing atmosphere, a reducing atmosphere, and a neutral atmosphere. The calcination temperature and treatment time vary depending on the desired composition of the La solid solution zirconia-based composite oxide and its stoichiometric ratio, but from the viewpoint of productivity and the like, generally, 1 at 150 ° C to 1300 ° C. It is preferably ~ 12 hours, more preferably 350 ° C. to 800 ° C. for 2 to 4 hours. Prior to high-temperature firing, it is preferable to perform vacuum drying using a vacuum dryer or the like, and then perform a drying treatment at about 50 ° C. to 200 ° C. for about 1 to 48 hours.
母材粒子上に担持されるＰｄ触媒粒子は、本実施形態の排ガス浄化用三元触媒において主たる触媒活性サイトとして機能する。このＰｄ触媒粒子は、上述したとおり、外部環境に応じてＰｄＯ／Ｌａ2 Ｏ3の複合酸化物や固溶体、場合によってはＰｄＯ／Ｎｄ2 Ｏ3 混合酸化物や固溶体、ＰｄＯ、金属Ｐｄに変化し得るものである。したがって、Ｐｄ触媒粒子の酸化状態は、特に限定されないが、還元性雰囲気下において、ＰｄＯ又は金属Ｐｄの粒子であることが好ましい。 The Pd catalyst particles supported on the base material particles function as the main catalytically active sites in the three-way catalyst for exhaust gas purification of the present embodiment. As described above, the Pd catalyst particles change into a PdO / La 2 O 3 composite oxide or solid solution, and in some cases, a PdO / Nd 2 O 3 mixed oxide or solid solution, PdO, or a metal Pd, depending on the external environment. What you get. Therefore, the oxidation state of the Pd catalyst particles is not particularly limited, but it is preferably PdO or metal Pd particles in a reducing atmosphere.
母材粒子上に担持されるＰｄ触媒粒子の含有量は、所望性能に応じて適宜決定でき、特に限定されないが、リーン環境〜ストイキ環境〜リッチ環境の全域にわたる触媒性能を向上させ、また低温活性を向上させる等の観点から、排ガス浄化用三元触媒の総量に対する金属パラジウム換算量で、０．１〜１０質量％が好ましく、より好ましくは０．２〜８質量％であり、さらに好ましくは０．３〜６質量％である。 The content of the Pd catalyst particles supported on the base metal particles can be appropriately determined according to the desired performance, and is not particularly limited, but improves the catalyst performance over the entire range of lean environment, stoichiometric environment, and rich environment, and also has low temperature activity. From the viewpoint of improving the above, the amount converted into metal-palladium with respect to the total amount of the three-way catalyst for exhaust gas purification is preferably 0.1 to 10% by mass, more preferably 0.2 to 8% by mass, and further preferably 0. .3 to 6% by mass.
母材粒子上に担持されるＰｄ触媒粒子は、触媒活性サイトを多く維持し、高い触媒性能を得る等の観点から、１〜９０ｎｍの平均結晶子径を有することが好ましく、より好ましくは３〜８０ｎｍである。なお、結晶子とは、一般に単結晶とみなせる最大の集まりのことをいい、その結晶子の大きさのことを結晶子径という。また、本明細書において、平均結晶子径は、Ｘ線回折装置を用いて回折パターンを測定し、その測定結果に基づいて下記式（１）で表されるScherrerの式より算出した値を意味する。
結晶子径 Ｄ（Å）＝Ｋ・λ／（β・ｃｏｓθ） ・・・（１）
式（１）中、ＫはScherrer定数であり、ここではＫ＝０．９とする。また、λは使用したＸ線管球の波長、βは半値幅、θは回折角（ｒａｄ）である。
The Pd catalytic particles supported on the base metal particles preferably have an average crystallite diameter of 1 to 90 nm, more preferably 3 to 90 nm, from the viewpoint of maintaining a large number of catalytically active sites and obtaining high catalytic performance. It is 80 nm. The crystallite is the largest group that can be generally regarded as a single crystal, and the size of the crystallite is called the crystallite diameter. Further, in the present specification, the average crystallite diameter means a value calculated from Scherrer's equation represented by the following equation (1) based on the measurement result of the diffraction pattern measured by using an X-ray diffractometer. To do.
Crystallite diameter D (Å) = K · λ / (β · cosθ) ・ ・ ・ (1)
In equation (1), K is a Scherrer constant, where K = 0.9. Further, λ is the wavelength of the X-ray tube used, β is the half width, and θ is the diffraction angle (rad).
なお、本実施形態の排ガス浄化用三元触媒は、Ｐｄ以外の貴金属元素（ＰＭ）及び白金族元素（ＰＧＭ）を含有していてもよいが、高温条件での使用などを考慮すると、Ｐｄ以外の貴金属元素（ＰＭ）及び白金族元素（ＰＧＭ）を実質的に含有しないことが好ましい。ここで、実質的に含有しないとは、Ｐｄ以外の貴金属元素（ＰＭ）及び白金族元素（ＰＧＭ）の総量が、排ガス浄化用三元触媒の全量に対して、０〜１．０質量％の範囲内にあることを意味し、より好ましくは０〜０．５質量％、さらに好ましくは０〜０．３質量％である。 The three-way catalyst for exhaust gas purification of the present embodiment may contain a noble metal element (PM) and a platinum group element (PGM) other than Pd, but in consideration of use under high temperature conditions, other than Pd. It is preferable that the noble metal element (PM) and the platinum group element (PGM) of the above are substantially not contained. Here, "substantially free" means that the total amount of noble metal elements (PM) and platinum group elements (PGM) other than Pd is 0 to 1.0% by mass with respect to the total amount of the three-way catalyst for exhaust gas purification. It means that it is within the range, more preferably 0 to 0.5% by mass, and further preferably 0 to 0.3% by mass.
本実施形態の排ガス浄化用三元触媒の形状は、特に限定されない。例えば、母材粒子上にＰｄ触媒粒子が担持された複合粒子の集合体である触媒粉末のまま用いることができる。また、例えば、触媒粉末を任意の形状に成形して、粒状やペレット状の成形触媒とすることができる。また、この排ガス浄化用三元触媒を触媒担体に担持させることもできる。ここで用いる触媒担体としては、当業界で公知のものを適宜選択することができる。代表的には、コージェライト製、シリコンカーバイド製、窒化珪素製等のセラミックモノリス担体、ステンレス製等のメタルハニカム担体、ステンレス製等のワイヤメッシュ担体等が挙げられるが、これらに特に限定されない。なお、これらは、１種を単独で、又は２種以上を適宜組み合わせて用いることができる。 The shape of the three-way catalyst for exhaust gas purification of the present embodiment is not particularly limited. For example, the catalyst powder, which is an aggregate of composite particles in which Pd catalyst particles are supported on the base material particles, can be used as it is. Further, for example, the catalyst powder can be molded into an arbitrary shape to obtain a granular or pellet-shaped molding catalyst. Further, the three-way catalyst for purifying exhaust gas can be supported on a catalyst carrier. As the catalyst carrier used here, those known in the art can be appropriately selected. Typical examples thereof include ceramic monolith carriers made of cordierite, silicon carbide, silicon nitride and the like, metal honeycomb carriers made of stainless steel and the like, wire mesh carriers made of stainless steel and the like, but are not particularly limited thereto. It should be noted that these can be used alone or in combination of two or more.
また、本実施形態の排ガス浄化用三元触媒は、高い触媒性能を得る等の観点から、一酸化炭素ガスパルス吸着法により算出されるパラジウム１ｇあたりの金属表面積（ＭＳＡ：Metal Surface Area）、すなわちパラジウム表面積が８〜３０（ｍ2 ／Ｐｄ_ｇ）であることが好ましく、より好ましくは１０〜３０（ｍ2 ／Ｐｄ_ｇ）であり、さらに好ましくは１３〜３０（ｍ2 ／Ｐｄ_ｇ）である。ここで本明細書において、排ガス浄化用三元触媒のパラジウム表面積は、測定対象となる排ガス浄化用三元触媒にエージング処理（高温耐久処理）を施したサンプルを用いて、例えば、金属分散度測定装置（商品名：ＢＥＬ−ＭＥＴＡＬ−３、マイクロベル・トラック株式会社性）等のガス吸着測定装置を用いて測定される触媒単位質量あたりのＣＯ吸着量（ｃｃ／ｇ）から、後述する実施例に記載の換算式で求められる値を意味する。なお、このエージング処理は、三元触媒のランニング性能の安定化を図る目的で行うものである。このエージング処理においては、水分濃度１０％の大気雰囲気下１０５０℃で１２時間の熱処理を施した後、水素ガス雰囲気下４００℃で０．５時間の還元処理を行うものとする。 Further, the three-way catalyst for exhaust gas purification of the present embodiment has a metal surface area (MSA: Metal Surface Area) per gram of palladium calculated by a carbon monoxide gas pulse adsorption method, that is, palladium, from the viewpoint of obtaining high catalytic performance. preferably the surface area is 8~30 (m 2 / Pd_g), more preferably 10~30 (m 2 / Pd_g), more preferably from 13~30 (m 2 / Pd_g). Here, in the present specification, the palladium surface area of the exhaust gas purification three-way catalyst is measured, for example, by using a sample obtained by subjecting the exhaust gas purification three-way catalyst to be measured to an aging treatment (high temperature durability treatment). Examples described later from the CO adsorption amount (cc / g) per catalyst unit mass measured using a gas adsorption measuring device such as an apparatus (trade name: BEL-METAL-3, Microbell Truck Co., Ltd.) It means the value obtained by the conversion formula described in. This aging treatment is performed for the purpose of stabilizing the running performance of the three-way catalyst. In this aging treatment, heat treatment is performed at 1050 ° C. for 12 hours in an air atmosphere having a water concentration of 10%, and then reduction treatment is performed at 400 ° C. for 0.5 hours in a hydrogen gas atmosphere.
さらに、本実施形態の排ガス浄化用三元触媒は、高い触媒性能を得る等の観点から、ＢＥＴ一点法によるＢＥＴ比表面積が、１０〜５０ｍ2 ／ｇであることが好ましく、より好ましくは１２〜５０ｍ2 ／ｇであり、さらに好ましくは１５〜５０ｍ2 ／ｇである。ここで本明細書において、排ガス浄化用三元触媒のＢＥＴ比表面積は、測定対象となる排ガス浄化用三元触媒に上述したエージング処理（高温耐久処理）を施したサンプルを用いて測定される値とする。 Further, the three-way catalyst for exhaust gas purification of the present embodiment preferably has a BET specific surface area of 10 to 50 m 2 / g by the BET one-point method, more preferably 12 to 50 m 2 / g, from the viewpoint of obtaining high catalytic performance. was 50 m 2 / g, more preferably from 15 to 50 m 2 / g. Here, in the present specification, the BET specific surface area of the exhaust gas purification three-way catalyst is a value measured by using a sample obtained by subjecting the exhaust gas purification three-way catalyst to be measured to the above-mentioned aging treatment (high temperature durability treatment). And.
上述した排ガス浄化用三元触媒は、例えば内燃機関の排ガス浄化用触媒、とりわけガソリン自動車の排ガス浄化用触媒として有用である。 The exhaust gas purification three-way catalyst described above is useful, for example, as an exhaust gas purification catalyst for an internal combustion engine, particularly as an exhaust gas purification catalyst for a gasoline vehicle.
排ガス浄化用三元触媒の製造方法は、上述したとおり、Ｌａ固溶ジルコニア系複合酸化物の母材粒子上にＰｄ触媒粒子が担持された構成のものが得られる限り、特に限定されない。排ガス浄化用三元触媒を再現性よく簡易且つ低コストで製造する観点からは、蒸発乾固法（含浸法）等が好ましい。 As described above, the method for producing the three-way catalyst for exhaust gas purification is not particularly limited as long as a structure in which Pd catalyst particles are supported on the base material particles of the La solid-soluble zirconia-based composite oxide can be obtained. From the viewpoint of producing a three-way catalyst for exhaust gas purification with good reproducibility, simple and low cost, the evaporation dry solid method (impregnation method) or the like is preferable.
蒸発乾固法としては、上述した母材粒子に、Ｐｄイオンを少なくとも含有する水溶液を含浸させ、その後に熱処理又は化学処理する製法が好ましい。この含浸処理により、Ｐｄイオンが、母材粒子の表面に高分散状態で吸着（付着）される。なお、Ｐｄイオンは、パラジウムの各種塩として水溶液に配合することができる。ここで用いる各種塩の種類は、特に限定されない。一般的には、塩酸塩、オキシ塩酸塩、硝酸塩、オキシ硝酸塩、炭酸塩、リン酸塩、酢酸塩、シュウ酸塩、クエン酸塩等が好ましい。また、水溶液中のＰｄイオンの含有割合は、得られる排ガス浄化用三元触媒においてＰｄ触媒粒子が所望の含有割合となるように適宜調整することができ、特に限定されない。また、言うまでもないが、ここで用いる水溶液は、上述した任意成分、例えばイットウム、スカンジウム、プラセオジム等の希土類元素や遷移金属元素、さらには不可避不純物を含んでいてもよい。 As the evaporation-drying method, a production method in which the above-mentioned base metal particles are impregnated with an aqueous solution containing at least Pd ions and then heat-treated or chemically treated is preferable. By this impregnation treatment, Pd ions are adsorbed (adhered) to the surface of the base material particles in a highly dispersed state. The Pd ion can be added to the aqueous solution as various salts of palladium. The types of various salts used here are not particularly limited. In general, hydrochloride, oxy hydrochloride, nitrate, oxynitrate, carbonate, phosphate, acetate, oxalate, citrate and the like are preferable. Further, the content ratio of Pd ions in the aqueous solution can be appropriately adjusted so that the Pd catalyst particles have a desired content ratio in the obtained three-way catalyst for exhaust gas purification, and is not particularly limited. Needless to say, the aqueous solution used here may contain the above-mentioned optional components such as rare earth elements such as itum, scandium and praseodymium, transition metal elements, and unavoidable impurities.
熱処理及び化学処理の条件は、常法にしたがえばよく、特に限定されない。例えば、熱処理時の雰囲気は、酸化性雰囲気、大気雰囲気、還元性雰囲気のいずれでもよい。熱処理温度及びその時間は、所望するＬａ固溶ジルコニア系複合酸化物の組成及びその化学量論比によって変動するが、Ｐｄ触媒粒子の生成及び生産性等の観点からは、一般的には、５００〜１１００℃で０．１〜１２時間が好ましく、より好ましくは５５０℃〜８００℃で０．５〜６時間である。なお、熱処理に先立って、真空乾燥機等を用いて減圧乾燥を行い、約５０℃〜２００℃で約１〜４８時間程度の乾燥処理を行ってもよい。また、化学処理としては、上記蒸発乾固法における含浸処理の後に、塩基性成分を用いてＰｄイオンを担体表面にて加水分解させてもよい。ここで用いる塩基性成分は、アンモニア、エタノールアミン等のアミン類、苛性ソーダ、水酸化ストロンチウム等のアルカリ金属水酸化物、水酸化バリウム等のアルカリ土類金属水酸化物が好ましい。これらの熱処理や化学処理により、ナノオーダーサイズに高分散したＰｄ触媒粒子が、母材粒子の表面に生成される。 The conditions of the heat treatment and the chemical treatment may be according to a conventional method and are not particularly limited. For example, the atmosphere at the time of heat treatment may be an oxidizing atmosphere, an atmospheric atmosphere, or a reducing atmosphere. The heat treatment temperature and its time vary depending on the desired composition of the La solid solution zirconia-based composite oxide and its stoichiometric ratio, but from the viewpoint of the formation and productivity of Pd catalyst particles, it is generally 500. It is preferably 0.1 to 12 hours at ~ 1100 ° C., more preferably 0.5 to 6 hours at 550 ° C. to 800 ° C. Prior to the heat treatment, vacuum drying may be performed using a vacuum dryer or the like, and the drying treatment may be performed at about 50 ° C. to 200 ° C. for about 1 to 48 hours. Further, as the chemical treatment, after the impregnation treatment in the evaporation-drying method, Pd ions may be hydrolyzed on the surface of the carrier using a basic component. As the basic component used here, amines such as ammonia and ethanolamine, alkali metal hydroxides such as caustic soda and strontium hydroxide, and alkaline earth metal hydroxides such as barium hydroxide are preferable. By these heat treatments and chemical treatments, Pd catalyst particles highly dispersed in nano-order size are generated on the surface of the base material particles.
なお、成形触媒の作製時には、各種公知の分散装置、混練装置、成形装置を用いることができる。また、触媒担体に排ガス浄化用三元触媒を保持させる際には、各種公知のコーティング法、ウォッシュコート法、ゾーンコート法を適用することができる。 When producing the molding catalyst, various known dispersion devices, kneading devices, and molding devices can be used. Further, when the catalyst carrier holds the three-way catalyst for purifying exhaust gas, various known coating methods, wash coating methods, and zone coating methods can be applied.
本実施形態の排ガス浄化用三元触媒は、排ガス浄化用触媒コンバータの触媒層に配合して用いることができる。例えば、上述したセラミックモノリス担体等の触媒担体に、本実施形態の排ガス浄化用三元触媒を含有する触媒層を設けることで実施可能である。また、排ガス浄化用触媒コンバータの触媒エリアは、触媒層が１つのみの単層であっても、２以上の触媒層からなる積層体であっても、１以上の触媒層と当業界で公知の１以上の他の層とを組み合わせた積層体のいずれでもよい。例えば、排ガス浄化用触媒コンバータが触媒担体上に酸素貯蔵層及び触媒層を少なくとも有する多層構成の場合には、少なくとも、触媒層に本実施形態の排ガス浄化用三元触媒を含有させることで、耐熱性及び三元浄化性能に優れる排ガス浄化用触媒コンバータとすることができる。排気ガス規制の強化の趨勢を考慮すると、層構成は、２層以上が好ましい。 The three-way catalyst for exhaust gas purification of the present embodiment can be used by blending it with the catalyst layer of the catalyst converter for exhaust gas purification. For example, it can be carried out by providing a catalyst layer containing the three-way catalyst for exhaust gas purification of the present embodiment on a catalyst carrier such as the ceramic monolith carrier described above. Further, the catalyst area of the exhaust gas purification catalyst converter is known in the art as one or more catalyst layers, regardless of whether the catalyst area is a single layer having only one catalyst layer or a laminate composed of two or more catalyst layers. It may be any of the laminated bodies in combination with one or more other layers of. For example, in the case where the exhaust gas purification catalyst converter has at least an oxygen storage layer and a catalyst layer on the catalyst carrier, the catalyst layer contains at least the three-way catalyst for exhaust gas purification to be heat resistant. It can be a catalytic converter for exhaust gas purification having excellent properties and three-way purification performance. Considering the trend of tightening exhaust gas regulations, the layer structure is preferably two or more layers.
触媒層の形成方法は、常法にしたがって行えばよく、特に限定されない。一例を挙げると、本実施形態の排ガス浄化用三元触媒と、水系媒体と、必要に応じて当業界で公知のバインダー、他の触媒、助触媒粒子、ＯＳＣ材、母材粒子、添加剤等とを所望の配合割合で混合してスラリー状混合物を調製し、得られたスラリー状混合物を触媒担体の表面に付与し、乾燥、焼成することができる。この際、必要に応じてｐＨ調整のために酸や塩基を配合したり、粘性の調整やスラリー分散性向上のための界面活性剤や分散用樹脂等を配合したりすることができる。なお、スラリーの混合方法としては、ボールミル等による粉砕混合が適用可能であるが、他の粉砕、或いは混合方法を適用することもできる。 The method for forming the catalyst layer may be carried out according to a conventional method, and is not particularly limited. As an example, the three-way catalyst for exhaust gas purification of the present embodiment, an aqueous medium, a binder known in the art, other catalysts, cocatalyst particles, OSC material, base material particles, additives, etc., if necessary, etc. And are mixed at a desired blending ratio to prepare a slurry-like mixture, and the obtained slurry-like mixture is applied to the surface of the catalyst carrier, and can be dried and calcined. At this time, if necessary, an acid or a base can be blended for pH adjustment, or a surfactant, a dispersion resin, or the like for adjusting the viscosity or improving the slurry dispersibility can be blended. As a method for mixing the slurry, pulverization and mixing using a ball mill or the like can be applied, but other pulverization or mixing methods can also be applied.
触媒担体へのスラリー状混合物の付与方法は、常法にしたがって行えばよく、特に限定されない。各種公知のコーティング法、ウォッシュコート法、ゾーンコート法を適用することができる。そして、スラリー状混合物の付与後においては、常法にしたがい乾燥や焼成を行うことにより、本実施形態の排ガス浄化用三元触媒を含有する触媒層を備える排ガス浄化用触媒コンバータを得ることができる。 The method for applying the slurry-like mixture to the catalyst carrier may be carried out according to a conventional method, and is not particularly limited. Various known coating methods, wash coating methods, and zone coating methods can be applied. Then, after the slurry-like mixture is added, the exhaust gas purification catalyst converter including the catalyst layer containing the three-way catalyst for exhaust gas purification of the present embodiment can be obtained by drying or firing according to a conventional method. ..
上述した排ガス浄化用触媒コンバータは、各種エンジンの排気系に配置することができる。排ガス浄化用触媒コンバータの設置個数及び設置箇所は、排ガスの規制に応じて適宜設計できる。例えば、排ガスの規制が厳しい場合には、設置箇所を２以上とし、設置箇所は排気系の直下触媒の後方の床下位置に配置することができる。そして、本実施形態の排ガス浄化用三元触媒を含有する触媒組成物や排ガス浄化用触媒コンバータによれば、低温での始動時のみならず、高温での高速走行時を含む種々の走行仕様において、ＣＯ、ＨＣ、ＮＯｘの浄化反応に優れた効果を発揮することができる。 The exhaust gas purification catalytic converter described above can be arranged in the exhaust system of various engines. The number and location of exhaust gas purification catalytic converters can be appropriately designed according to the exhaust gas regulations. For example, when exhaust gas regulations are strict, the number of installation locations may be two or more, and the installation locations may be located under the floor behind the catalyst directly under the exhaust system. Further, according to the catalyst composition containing the three-way catalyst for exhaust gas purification and the catalyst converter for exhaust gas purification of the present embodiment, in various running specifications including not only at the time of starting at a low temperature but also at the time of high-speed running at a high temperature. , CO, HC, NOx can exert an excellent effect on the purification reaction.
以下に試験例、実施例と比較例と参考例を挙げて本発明の特徴をさらに具体的に説明するが、本発明は、これらによりなんら限定されるものではない。すなわち、以下の実施例に示す材料、使用量、割合、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り、適宜変更することができる。 The features of the present invention will be described in more detail below with reference to Test Examples, Examples, Comparative Examples and Reference Examples , but the present invention is not limited thereto. That is, the materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention.
［パラジウム表面積の測定］
パラジウム表面積（ｍ2 ／Ｐｄ_ｇ）は、まず各々の性能評価用サンプル試料のＣＯ吸着量Ｍ（ｃｃ／ｇ）を一酸化炭素ガスパルス吸着法により測定し、単純理想モデルにおけるＣＯ吸着量あたりのＰｄ表面積（３５１７．４８７ｍ2 ／ｍｍｏｌ）を係数Ｗとして用い、これらＣＯ吸着量Ｍ及び係数Ｗ、並びに標準状態の理想気体の体積（２２．４Ｌ／ｍｏｌ）とから、下記式（２）に基づいて算出した。
パラジウム表面積（ｍ2 ／ｇ_Ｐｄ）＝Ｗ＊Ｍ／２２．４ ・・・（２）
なお、このとき用いた係数Ｗは、１質量％のＰｄを担持させたアルミナ粒子（パラジウム平均結晶子径：４５．４ｎｍ、密度：１２．０２３ｇ／ｃｃ、表面積１０．９９２１５ｍ2 ／ｇ）の、一酸化炭素ガスパルス吸着法におけるＣＯ吸着量（０．０７ｃｃ／ｇ）に基づいて算出した。
また、一酸化炭素ガスパルス吸着法によるＣＯ吸着量Ｍの測定では、金属分散度測定装置（商品名：ＢＥＬ−ＭＥＴＡＬ−３、マイクロベル・トラック株式会社性）を用い、４００℃で水素雰囲気下にて還元後、ヘリウムガスによりパージし、２５℃に冷却した条件にて、ＣＯ吸着が見られなくなるまで１分毎に１０％ＣＯガスパルスを注入して、性能評価用サンプル試料のＣＯ吸着量を算出した。なお、排ガス浄化用三元触媒のパラジウム表面積の測定においては、いずれも水分濃度１０％の大気雰囲気下１０５０℃で１２時間の熱処理を施したサンプル１．０ｇを用いた。
[Measurement of palladium surface area]
For the palladium surface area (m 2 / Pd_g), first, the CO adsorption amount M (cc / g) of each performance evaluation sample sample is measured by the carbon monoxide gas pulse adsorption method, and the Pd surface area per CO adsorption amount in the simple ideal model. Using (3517.487 m 2 / mmol) as the coefficient W, it is calculated from the CO adsorption amount M and the coefficient W, and the volume of the ideal gas in the standard state (22.4 L / mol) based on the following formula (2). did.
Palladium surface area (m 2 / g_Pd) = W * M / 22.4 ... (2)
The coefficient W used at this time is the same as that of the alumina particles carrying 1% by mass of Pd (palladium average crystallite diameter: 45.4 nm, density: 12.023 g / cc, surface area of 10.99215 m 2 / g). It was calculated based on the CO adsorption amount (0.07 cc / g) in the carbon monoxide gas pulse adsorption method.
In addition, in the measurement of the CO adsorption amount M by the carbon monoxide gas pulse adsorption method, a metal dispersibility measuring device (trade name: BEL-METAL-3, manufactured by Microbell Truck Co., Ltd.) is used, and the temperature is 400 ° C. under a hydrogen atmosphere. After reduction, purge with helium gas, and under the condition of cooling to 25 ° C., 10% CO gas pulse is injected every minute until CO adsorption disappears, and the CO adsorption amount of the sample for performance evaluation is calculated. did. In the measurement of the palladium surface area of the three-way catalyst for exhaust gas purification, 1.0 g of a sample subjected to heat treatment at 1050 ° C. for 12 hours in an air atmosphere having a water concentration of 10% was used.
［ＢＥＴ比表面積の測定］
ＢＥＴ比表面積は、比表面積／細孔分布測定装置（商品名：BELSORP-mini II、マイクロトラック・ベル株式会社製）及び解析用ソフトウェア（商品名：BEL_Master、マイクロトラック・ベル株式会社製）を用い、ＢＥＴ一点法により求めた。なお、排ガス浄化用三元触媒のＢＥＴ比表面積の測定においては、いずれも水分濃度１０％の大気雰囲気下１０５０℃で１２時間の熱処理を施したサンプル０．１ｇを用いた。
[Measurement of BET specific surface area]
For the BET specific surface area, use a specific surface area / pore distribution measuring device (trade name: BELSORP-mini II, manufactured by Microtrac Bell Co., Ltd.) and analysis software (trade name: BEL_Master, manufactured by Microtrac Bell Co., Ltd.). , BET one-point method. In the measurement of the BET specific surface area of the three-way catalyst for exhaust gas purification, 0.1 g of a sample subjected to heat treatment at 1050 ° C. for 12 hours in an air atmosphere having a water concentration of 10% was used.
（参考例１）
母材粒子として、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：２３質量％、ＺｒＯ２：７７質量％：Ｄ５０＝２．７μｍ、ＢＥＴ比表面積：７０ｍ２／ｇ）を用いた。次に、硝酸パラジウム（ＩＩ）溶液（ＰｄＯ換算で２０質量％含有）を調製し、上記Ｌａ固溶ジルコニア系複合酸化物に硝酸パラジウム（ＩＩ）溶液を含浸させ、６００℃で３０分間焼成することにより、参考例１のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）を得た。
その後、得られたパウダー触媒を炉内で静置し、水分濃度１０％の大気雰囲気下１０５０℃で１２時間の熱処理を行った後、水素ガス雰囲気下４００℃で０．５時間の還元処理を行うことにより参考例１の性能評価用サンプル（排ガス浄化用三元触媒）を得た。
倍率１００万倍で走査透過型電子顕微鏡（ＳＴＥＭ）を用いて排ガス浄化用三元触媒粉末サンプルを観察したところ、平均粒子径Ｄ50が１〜１００μｍの母材粒子上に、微細なＰｄ触媒粒子が担持されていることが確認された。
( Reference example 1 )
As the base material particles, La solid-dissolved zirconia-based composite oxide (La 2 O 3 : 23% by mass, ZrO 2 : 77% by mass: D 50 = 2.7 μm, BET specific surface area: 70 m 2 / g) was used. Next, a palladium (II) nitrate solution (containing 20% by mass in terms of PdO) is prepared, the La solid-soluble zirconia-based composite oxide is impregnated with the palladium (II) nitrate solution, and calcined at 600 ° C. for 30 minutes. The powder catalyst of Reference Example 1 (three-way catalyst for purifying exhaust gas, supported amount in terms of Pd: 1.0% by mass) was obtained.
Then, the obtained powder catalyst was allowed to stand in a furnace, heat-treated at 1050 ° C. for 12 hours in an air atmosphere having a water concentration of 10%, and then reduced for 0.5 hours at 400 ° C. in a hydrogen gas atmosphere. By doing so, a sample for performance evaluation (three-way catalyst for exhaust gas purification) of Reference Example 1 was obtained.
When a three-way catalyst powder sample for exhaust gas purification was observed using a scanning transmission electron microscope (STEM) at a magnification of 1 million times, fine Pd catalyst particles were observed on a base material particle having an average particle diameter D 50 of 1 to 100 μm. Was confirmed to be supported.
（実施例２）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：３０質量％、ＺｒＯ２：７０質量％：Ｄ５０＝３．１μｍ、ＢＥＴ比表面積：６０ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、実施例２のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Example 2)
Instead of La solid solution of zirconia-based composite oxide used in Example 1, La solid solution of zirconia-based mixed oxide (La 2 O 3: 30 wt%, ZrO 2: 70 wt%: D 50 = 3.1μm, The same operation as in Reference Example 1 was performed except that the BET specific surface area: 60 m 2 / g) was used, and the powder catalyst of Example 2 (three-way catalyst for exhaust gas purification, supported amount in terms of Pd: 1.0% by mass) was performed. ) And a sample for performance evaluation were obtained.
（実施例３）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：４０質量％、ＺｒＯ２：６０質量％：Ｄ５０＝２．７μｍ、ＢＥＴ比表面積：５５ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、実施例３のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Example 3)
Instead of La solid solution of zirconia-based composite oxide used in Example 1, La solid solution of zirconia-based mixed oxide (La 2 O 3: 40 wt%, ZrO 2: 60 wt%: D 50 = 2.7μm, The same operation as in Reference Example 1 was performed except that the BET specific surface area: 55 m 2 / g) was used, and the powder catalyst of Example 3 (three-way catalyst for exhaust gas purification, supported amount in terms of Pd: 1.0% by mass) was performed. ) And a sample for performance evaluation were obtained.
（参考例２）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：５０質量％、ＺｒＯ２：５０質量％：Ｄ５０＝１．８μｍ、ＢＥＴ比表面積：４１ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、参考例２のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
( Reference example 2 )
Instead of La solid solution of zirconia-based composite oxide used in Example 1, La solid solution of zirconia-based mixed oxide (La 2 O 3: 50 wt%, ZrO 2: 50 wt%: D 50 = 1.8μm, The same operation as in Reference Example 1 was performed except that the BET specific surface area: 41 m 2 / g) was used, and the powder catalyst of Reference Example 2 (three-way catalyst for exhaust gas purification, supported amount in terms of Pd: 1.0% by mass). ) And a sample for performance evaluation were obtained.
（実施例５）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、ＬａＮｄ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：２３質量％、Ｎｄ２Ｏ３：１８質量％、ＺｒＯ２：５９質量％：Ｄ５０＝２．５μｍ、ＢＥＴ比表面積：５１ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、実施例５のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Example 5)
Instead of the La solid-soluble zirconia-based composite oxide used in Reference Example 1 , the LaNd solid-soluble zirconia-based composite oxide (La 2 O 3 : 23% by mass, Nd 2 O 3 : 18% by mass, ZrO 2 : 59% by mass) The same operation as in Reference Example 1 was performed except that%: D 50 = 2.5 μm, BET specific surface area: 51 m 2 / g), and the powder catalyst of Example 5 (three-way catalyst for exhaust gas purification, Pd conversion) was performed. Amount carried: 1.0% by mass) and a sample for performance evaluation were obtained.
（実施例６）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、ＬａＮｄ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：３０質量％、Ｎｄ２Ｏ３：９質量％、ＺｒＯ２：６１質量％：Ｄ５０＝２．５μｍ、ＢＥＴ比表面積：５５ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、実施例６のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Example 6)
Instead of the La solid-soluble zirconia-based composite oxide used in Reference Example 1 , the LaNd solid-soluble zirconia-based composite oxide (La 2 O 3 : 30% by mass, Nd 2 O 3 : 9% by mass, ZrO 2 : 61 mass%) The same operation as in Reference Example 1 was performed except that%: D 50 = 2.5 μm, BET specific surface area: 55 m 2 / g), and the powder catalyst of Example 6 (three-way catalyst for exhaust gas purification, Pd conversion) was performed. Amount carried: 1.0% by mass) and a sample for performance evaluation were obtained.
（比較例１）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、ジルコニア系酸化物（ＺｒＯ２：１００質量％：Ｄ５０＝０．１μｍ、ＢＥＴ比表面積：２５ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、比較例１のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Comparative Example 1)
Except for using a zirconia-based oxide (ZrO 2 : 100% by mass: D 50 = 0.1 μm, BET specific surface area: 25 m 2 / g) instead of the La solid-soluble zirconia-based composite oxide used in Reference Example 1. Performed the same operation as in Reference Example 1 to obtain a powder catalyst of Comparative Example 1 (three-way catalyst for exhaust gas purification, supported amount in terms of Pd: 1.0% by mass) and a sample for performance evaluation.
（比較例２）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：３質量％、ＺｒＯ２：９７質量％：Ｄ５０＝１．１μｍ、ＢＥＴ比表面積：５１ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、比較例２のパウダー触媒（排ガス浄化用三元触媒、Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Comparative Example 2)
Instead of the La solid-soluble zirconia-based composite oxide used in Reference Example 1 , the La solid-soluble zirconia-based composite oxide (La 2 O 3 : 3% by mass, ZrO 2 : 97% by mass: D 50 = 1.1 μm, The same operation as in Reference Example 1 was performed except that the BET specific surface area: 51 m 2 / g) was used, and the powder catalyst of Comparative Example 2 (three-way catalyst for exhaust gas purification, supported amount in terms of Pd: 1.0% by mass). ) And a sample for performance evaluation were obtained.
（比較例３）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：８質量％、ＺｒＯ２：９２質量％：Ｄ５０＝２．６μｍ、ＢＥＴ比表面積：７１ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、比較例３の排ガス浄化用三元触媒（Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Comparative Example 3)
Instead of the La solid-soluble zirconia-based composite oxide used in Reference Example 1 , the La solid-soluble zirconia-based composite oxide (La 2 O 3 : 8% by mass, ZrO 2 : 92% by mass: D 50 = 2.6 μm, The same operation as in Reference Example 1 was performed except that the BET specific surface area: 71 m 2 / g) was used, and the ternary catalyst for exhaust gas purification (supported amount in terms of Pd: 1.0% by mass) and performance of Comparative Example 3 were performed. An evaluation sample was obtained.
（比較例４）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：１５質量％、ＺｒＯ２：８５質量％：Ｄ５０＝３．３μｍ、ＢＥＴ比表面積：６７ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、比較例４の排ガス浄化用三元触媒（Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Comparative Example 4)
Instead of La solid solution of zirconia-based composite oxide used in Example 1, La solid solution of zirconia-based mixed oxide (La 2 O 3: 15 wt%, ZrO 2: 85 wt%: D 50 = 3.3μm, The same operation as in Reference Example 1 was performed except that the BET specific surface area: 67 m 2 / g) was used, and the ternary catalyst for exhaust gas purification (supported amount in terms of Pd: 1.0% by mass) and performance of Comparative Example 4 were performed. An evaluation sample was obtained.
（比較例５）
参考例１で用いたＬａ固溶ジルコニア系複合酸化物に代えて、Ｌａ固溶ジルコニア系複合酸化物（Ｌａ２Ｏ３：７５質量％、ＺｒＯ２：２５質量％：Ｄ５０＝３．５μｍ、ＢＥＴ比表面積：２７ｍ２／ｇ）を用いること以外は、参考例１と同様の操作を行い、比較例５の排ガス浄化用三元触媒（Ｐｄ換算の担持量：１．０質量％）及び性能評価用サンプルを得た。
(Comparative Example 5)
Instead of La solid solution of zirconia-based composite oxide used in Example 1, La solid solution of zirconia-based mixed oxide (La 2 O 3: 75 wt%, ZrO 2: 25 wt%: D 50 = 3.5μm, The same operation as in Reference Example 1 was performed except that BET specific surface area (27 m 2 / g) was used, and the ternary catalyst for exhaust gas purification (supported amount in terms of Pd: 1.0% by mass) and performance of Comparative Example 5 were performed. An evaluation sample was obtained.
得られた各性能評価用サンプルについて、パラジウム表面積及びＢＥＴ比表面積の測定をそれぞれ行った。表１に測定結果を示す。また、実施例６の排ガス浄化用三元触媒（性能評価用サンプル）のＳＴＥＭ写真を、図１に示す。
表１から明らかなとおり、本発明に相当する実施例２，３，５及び６の排ガス浄化用三元触媒は、参考例１〜２及び比較例１〜５の排ガス浄化用三元触媒に対して、パラジウム表面積が大きいことが確認された。また、希土類元素の固溶量が大きくなるにつれてＢＥＴ比表面積が低下する傾向にあることも示された。一方、パラジウム表面積とＢＥＴ比表面積との明確な相関関係は確認できなかった。このことから、排ガス浄化用三元触媒の触媒活性サイトの数は、必ずしもＢＥＴ比表面積に比例するものではないことが示されるとともに、ＢＥＴ比表面積が比較的に小さくてもパラジウム表面積が大きく触媒性能に優れる排ガス浄化用三元触媒を実現し得ることが確認された。 As is clear from Table 1, the exhaust gas purification ternary catalysts of Examples 2, 3, 5 and 6 corresponding to the present invention are the exhaust gas purification ternary catalysts of Reference Examples 1 and 2 and Comparative Examples 1 to 5. It was confirmed that the palladium surface area was large. It was also shown that the BET specific surface area tends to decrease as the solid solution amount of the rare earth element increases. On the other hand, no clear correlation between the palladium surface area and the BET specific surface area could be confirmed. From this, it is shown that the number of catalytically active sites of the three-way catalyst for exhaust gas purification is not necessarily proportional to the BET specific surface area, and even if the BET specific surface area is relatively small, the palladium surface area is large and the catalytic performance is large. It was confirmed that a three-way catalyst for purifying exhaust gas can be realized.
［ＨＣ及びＮＯ浄化性能のラボ測定］
次に、上記の性能評価用サンプルについて、ＨＣ及びＮＯ浄化性能をそれぞれ評価した。ここでは、炉内で空気雰囲気下、８００℃、２０時間の熱処理をした性能評価用サンプルを、５０ｍｇ秤量ずつしてサンプルホルダーに入れ、ＴＰＤリアクター（昇温脱離ガス分析装置、商品名：ＢＥＬ Ｍａｓｓ、マイクロトラック・ベル株式会社製）を用いて、モデルガスの定常気流中３００℃で浄化性能試験を行った。
[Lab measurement of HC and NO purification performance]
Next, the HC and NO purification performances of the above performance evaluation samples were evaluated, respectively. Here, a sample for performance evaluation that has been heat-treated at 800 ° C. for 20 hours in an air atmosphere in a furnace is placed in a sample holder by weighing 50 mg each, and is placed in a TPD reactor (heated desorption gas analyzer, trade name: BEL). A purification performance test was conducted at 300 ° C. in a steady air flow of the model gas using Mass, manufactured by Microtrac Bell Co., Ltd.
ここで用いたモデルガス組成を、表２に示す。
なお、ＨＣ浄化率及びＮＯ浄化率は、下記式（３）及び（４）に基づいて算出した。
ＨＣ浄化率（％）＝１００−（ＨＣ−ＭＡＳＳピーク強度（測定時）／ＨＣ−ＭＡＳＳピーク強度（Ｂｌａｎｋ））×１００ ・・・（３）
ＮＯ浄化率（％）＝１００−（ＮＯ−ＭＡＳＳピーク強度（測定時）／ＮＯ−ＭＡＳＳピーク強度（Ｂｌａｎｋ））×１００ ・・・（４）
The HC purification rate and the NO purification rate were calculated based on the following formulas (3) and (4).
HC purification rate (%) = 100- (HC-MASS peak intensity (at the time of measurement) / HC-MASS peak intensity (Blank)) x 100 ... (3)
NO purification rate (%) = 100- (NO-MASS peak intensity (at the time of measurement) / NO-MASS peak intensity (Blank)) x 100 ... (4)
ＨＣ及びＮＯ浄化性能の測定結果を、表３に示す。
表３から明らかなとおり、本発明に相当する実施例の排ガス浄化用三元触媒は、ＨＣ浄化率５０％以上及びＮＯ浄化率４０％以上をいずれも達成しており、比較例の排ガス浄化用三元触媒に比して、触媒性能に優れることが確認された。 As is clear from Table 3, the three-way catalyst for exhaust gas purification of the examples corresponding to the present invention has achieved both an HC purification rate of 50% or more and a NO purification rate of 40% or more, and is used for exhaust gas purification of a comparative example. It was confirmed that the catalyst performance was superior to that of the three-way catalyst.
本発明の排ガス浄化用三元触媒及び排ガス浄化用触媒コンバータは、排ガス中のＮＯｘ、ＣＯ、ＨＣ等を削減する三元触媒として、広く且つ有効に利用することができ、ディーゼルエンジンよりも耐熱性が要求されるガソリンエンジン用途において殊に有効に利用可能である。また、本発明の排ガス浄化用三元触媒は、エンジン直下型触媒コンバータやタンデム配置の直下型触媒コンバータ等のＴＷＣとして有効に利用することができる。 The three-way catalyst for exhaust gas purification and the catalyst converter for exhaust gas purification of the present invention can be widely and effectively used as a three-way catalyst for reducing NOx, CO, HC, etc. in exhaust gas, and have higher heat resistance than a diesel engine. It can be used particularly effectively in gasoline engine applications where Further, the three-way catalyst for exhaust gas purification of the present invention can be effectively used as a TWC for a catalyst converter directly under an engine, a catalyst converter directly under a tandem arrangement, or the like.
Claims (6)
ＺｒＯ2 ５０〜８０質量％；
Ｌａ2 Ｏ3 ３０〜４８質量％；
Ｎｄ2 Ｏ3 ０〜２０質量％；
Ｌａ2 Ｏ3とＮｄ2 Ｏ3 の合計量が３０〜５０質量％；
で含むＬａ固溶ジルコニア系複合酸化物の母材粒子と、
前記母材粒子上に担持されたＰｄ触媒粒子と、
を少なくとも含有し、
一酸化炭素ガスパルス吸着法により算出されるパラジウム表面積が１０〜３０（ｍ 2 ／Ｐｄ＿ｇ）であることを特徴とする、
排ガス浄化用三元触媒。 La and Zr as constituent metal elements and Nd if necessary, the following mass ratio in terms of oxide:
ZrO 2 50-80% by mass;
La 2 O 3 30 to 48 % by mass;
Nd 2 O 30 to 20% by mass;
The total amount of La 2 O 3 and Nd 2 O 3 is 30 to 50% by mass;
La solid solution zirconia-based composite oxide base material particles contained in
Pd catalyst particles supported on the base material particles and
At least it contains,
The palladium surface area calculated by the carbon monoxide gas pulse adsorption method is 10 to 30 (m 2 / Pd_g) .
Three-way catalyst for exhaust gas purification.
請求項１に記載の排ガス浄化用三元触媒。 The three-way catalyst for exhaust gas purification according to claim 1, wherein the Pd catalyst particles are contained in an amount of 0.1 to 10% by mass in terms of metallic palladium.
請求項１又は２に記載の排ガス浄化用三元触媒。 The three-way catalyst for exhaust gas purification according to claim 1 or 2, wherein the base material particles have an average particle diameter D 50 of 1 to 100 μm.
請求項１〜３のいずれか一項に記載の排ガス浄化用三元触媒。 The BET specific surface area is 10 to 50 (m 2 / g).
The three-way catalyst for exhaust gas purification according to any one of claims 1 to 3 .
ＺｒＯ2 ５０〜８０質量％；
Ｌａ2 Ｏ3 ３０〜４８質量％；
Ｎｄ2 Ｏ3 ０〜２０質量％；
Ｌａ2 Ｏ3とＮｄ2 Ｏ3 の合計量が３０〜５０質量％；
で含むＬａ固溶ジルコニア系複合酸化物の母材粒子を準備する工程、
前記母材粒子の表面に、Ｐｄイオンを少なくとも含有する水溶液を付与する工程、並びに
処理後の前記母材粒子を熱処理又は化学処理して、前記母材粒子の表面にＰｄ触媒粒子を担持させる工程、を少なくとも有することを特徴とする、
一酸化炭素ガスパルス吸着法により算出されるパラジウム表面積が１０〜３０（ｍ 2 ／Ｐｄ＿ｇ）である排ガス浄化用三元触媒の製造方法。 La and Zr as constituent metal elements and Nd if necessary, the following mass ratio in terms of oxide:
ZrO 2 50-80% by mass;
La 2 O 3 30 to 48 % by mass;
Nd 2 O 30 to 20% by mass;
The total amount of La 2 O 3 and Nd 2 O 3 is 30 to 50% by mass;
Step of preparing base particle of La solid solution zirconia-based composite oxide contained in
A step of applying an aqueous solution containing at least Pd ions to the surface of the base material particles, and a step of heat-treating or chemically treating the base material particles after treatment to support the Pd catalyst particles on the surface of the base material particles. , Characterized by having at least
A method for producing a three-way catalyst for exhaust gas purification , which has a palladium surface area of 10 to 30 (m 2 / Pd_g) calculated by a carbon monoxide gas pulse adsorption method.
前記触媒層が、請求項１〜４のいずれか一項に記載の排ガス浄化用三元触媒を含むことを特徴とする、
排ガス浄化用触媒コンバータ。 At least a catalyst carrier, an oxygen storage layer provided on the catalyst carrier, and a catalyst layer provided on the oxygen storage layer are provided.
The catalyst layer contains the three-way catalyst for exhaust gas purification according to any one of claims 1 to 4 .
Catalytic converter for exhaust gas purification.
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| JP2016250614A JP6769862B2 (en) | 2016-12-26 | 2016-12-26 | Three-way catalyst for exhaust gas purification, its manufacturing method, and catalyst converter for exhaust gas purification |
| CN201780058549.8A CN109715289B (en) | 2016-11-11 | 2017-10-24 | Exhaust gas purifying three-way catalyst, method for producing same, and exhaust gas purifying catalytic converter |
| PCT/JP2017/038372 WO2018088201A1 (en) | 2016-11-11 | 2017-10-24 | Exhaust gas purifying three-way catalyst, method for manufacturing same, and exhaust gas purifying catalyst converter |
| EP17869302.4A EP3539648A4 (en) | 2016-11-11 | 2017-10-24 | Exhaust gas purifying three-way catalyst, method for manufacturing same, and exhaust gas purifying catalyst converter |
| US16/347,274 US10857520B2 (en) | 2016-11-11 | 2017-10-24 | Exhaust gas-purifying three-way catalyst and method for producing the same, and exhaust gas-purifying catalytic converter |
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| JP2698302B2 (en) * | 1992-11-24 | 1998-01-19 | 株式会社日本触媒 | Exhaust gas purification catalyst |
| JPH09313938A (en) * | 1996-06-03 | 1997-12-09 | Nissan Motor Co Ltd | Catalyst for cleaning exhaust gas |
| JP3799466B2 (en) * | 1999-01-14 | 2006-07-19 | 株式会社豊田中央研究所 | Exhaust gas purification catalyst |
| JP4325648B2 (en) * | 2005-10-24 | 2009-09-02 | トヨタ自動車株式会社 | Catalyst carrier and exhaust gas purification catalyst |
| JP2008100152A (en) * | 2006-10-18 | 2008-05-01 | Cataler Corp | Catalyst for cleaning exhaust gas |
| CN102089076A (en) * | 2008-07-17 | 2011-06-08 | 株式会社科特拉 | Exhaust gas purification catalyst |
| 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 |
| US9011784B2 (en) * | 2011-08-10 | 2015-04-21 | Clean Diesel Technologies, Inc. | Catalyst with lanthanide-doped zirconia and methods of making |
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