JP2011220123A - Exhaust purification catalyst - Google Patents
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Abstract
Description
本発明は、排気浄化触媒に関し、さらに詳しくは特定の２層構造を有することにより低温でのＣＯ酸化活性を向上させた排気浄化触媒に関する。 The present invention relates to an exhaust purification catalyst, and more particularly to an exhaust purification catalyst that has a specific two-layer structure to improve CO oxidation activity at a low temperature.
近年、大気中に排出される排気の浄化は環境上の重要課題であり、大気汚染防止の観点から規制が強化されている。自動車等の内燃機関その他の燃焼機関から生じる排気中の有害成分を除去するために、排気浄化触媒を用いた処理が行われている。
例えば、エンジンから排出される排気は排気浄化触媒により浄化されて大気中に放出される。しかし、エンジン始動直後は低温のため、排気浄化触媒内の触媒が不活性状態であり、排気が十分浄化されない。
一方、一般に排気浄化に用いられる触媒には担体上にＰｔやＰｄなどの貴金属を担持したものが用いられており、これらの貴金属が高価であって資源的にも問題があることからその使用量を低減することが必要である。
このため、触媒の活性を向上させるために種々の検討がされている。
In recent years, purification of exhaust gas discharged into the atmosphere is an important environmental issue, and regulations have been strengthened from the viewpoint of preventing air pollution. In order to remove harmful components in exhaust gas generated from internal combustion engines such as automobiles and other combustion engines, treatment using an exhaust purification catalyst is performed.
For example, exhaust discharged from the engine is purified by an exhaust purification catalyst and released into the atmosphere. However, since the temperature is low immediately after the engine is started, the catalyst in the exhaust purification catalyst is in an inactive state, and the exhaust is not sufficiently purified.
On the other hand, catalysts that are generally used for exhaust purification are those in which noble metals such as Pt and Pd are supported on a carrier, and these noble metals are expensive and have a problem in terms of resources. Need to be reduced.
For this reason, various studies have been made to improve the activity of the catalyst.
例えば、特許文献１には、触媒層を少なくとも２層設け、白金、パラジウム、ロジウム又はイリジウムである貴金属を貴金属毎に担持したアルミナ又はゼオライトとペロブスカイト型酸化物とを含有し、且つ白金がゼオライトに担持されていて、下層にペロブスカイト型酸化物を含み、上層に白金担持ゼオライトを含有する排気ガス浄化用触媒が記載されている。しかし、特許文献１では触媒活性を７００℃で評価した例が示されており、触媒層の上層の厚みが触媒活性にどのような影響を及ぼすか、特に低温でのＣＯ酸化活性にどのような影響を及ぼすかについては示されていない。
For example,
また、特許文献２には、ハニカム状担体上に、下層、中間層および表層を順次積層して成り、下層が白金、パラジウム又はロジウムとアルカリ金属、アルカリ土類金属又は希土類元素を含有し、中間層がβゼオライトを含有し、表層が銅及び／又はコバルトを含むゼオライトを含有する排気ガス浄化触媒が記載されている。そして、具体例として、３層構造の排気ガス浄化触媒が、中間層を設けない２層構造の排気ガス浄化触媒に比べて１００℃〜５００℃の範囲で高いＮＯＸ浄化率を示すことが示されている。しかし、特許文献２には３層構造および２層構造の排気ガス浄化触媒が１００℃未満の低温域でどのようなＣＯ酸化活性を示すかについては示されていない。
Further,
また、特許文献３には、担体上に浄化触媒金属およびアルカリ又はアルカリ土類金属を含むＮＯＸ吸蔵型触媒層を有し、その上にＳＯＸのＮＯＸ吸蔵材への拡散を抑制するバリヤ層を備え、場合によりさらにバリヤ層の上層に貴金属が担持されたゼオライト層であるＳＯＸ吸放出材層を備えた排気ガス浄化用触媒が記載されている。そして、具体例として、４００℃でのＳ被毒低減効果が示されている。しかし、特許文献３には３層構造および２層構造の排気ガス浄化触媒が１００℃未満の低温域でどのような排気ガス浄化特性、特にＣＯ酸化活性を示すかについては示されていない。
さらに、特許文献４には、担体上に、触媒金属とＮＯＸ吸着材と高表面積耐熱性酸化物粒子とを含有する第一触媒層と、その上に形成されているゼオライトであるＮＨ３吸着材を含有する第二触媒層とからなり、いずれかの触媒層中に酸化鉄微細粒子が分散して含まれるＮＯＸ浄化用の排気ガス浄化用触媒が記載されている。そして、具体例として、排気ガス浄化触媒が、１７０℃又は２４０℃で高いＮＯＸ浄化率を示すことが示されている。しかし、特許文献４には排気ガス浄化触媒が１００℃未満の低温域でどのようなＣＯ酸化活性を示すかについては示されていない。 Furthermore, Patent Document 4, on the carrier, the first catalyst layer containing a catalyst metal and NO X adsorbent and a high surface area refractory oxide particles, NH 3 adsorbing a zeolite formed thereon consists of a second catalyst layer containing wood, either the exhaust gas purifying catalyst for NO X purifying iron oxide fine particles in the catalyst layer are included dispersed is described. As a specific example, it is shown that the exhaust gas purification catalyst exhibits a high NO x purification rate at 170 ° C. or 240 ° C. However, Patent Document 4 does not indicate what CO oxidation activity the exhaust gas purification catalyst exhibits in a low temperature region below 100 ° C.
しかし、これら公知の排気浄化触媒によっても、１００℃未満の低温域で高いＣＯ酸化活性を示す排気浄化触媒を得ることは困難である。
しかるに、近年のＣＯ２排出量低減化の要求により排気温度が大幅に低温化し、この排気温度の低温化に伴って従来は大きな問題となっていなかった、排気浄化触媒の低温でのＣＯ酸化活性が大幅に悪化するという問題が生じている。この排気浄化触媒のＣＯ酸化活性の大幅な悪化はＣＯ排出量の増大をもたらす。
従って、本発明の目的は、１００℃未満の低温域を含む温度範囲で高いＣＯ酸化活性を示す排気浄化触媒を提供することである。
However, even with these known exhaust purification catalysts, it is difficult to obtain an exhaust purification catalyst that exhibits high CO oxidation activity in a low temperature range of less than 100 ° C.
However, the exhaust temperature has been drastically lowered due to the recent demand for reducing CO 2 emissions, and the exhaust purification catalyst has not been a major problem with the lowering of the exhaust temperature. There is a problem that is getting worse. The significant deterioration in the CO oxidation activity of the exhaust purification catalyst results in an increase in CO emissions.
Accordingly, an object of the present invention is to provide an exhaust purification catalyst that exhibits high CO oxidation activity in a temperature range including a low temperature range of less than 100 ° C.
本発明者等は、前記目的を達成することを目的として鋭意検討を行った結果、前記目的を達成するためには低温からＣＯを酸化し得て、共存ガスであるＨＣ被毒の影響を抑制する必要があることを見出しさらに検討を行った結果、本発明を完成した。
本発明は、触媒層が、下層としての担体基材に貴金属を担持した貴金属コート層と、上層としての担体基材に貴金属を担持したＨＣ（炭化水素）吸着材層とからなり、上層のＨＣ吸着材層の厚みが３０〜８０μｍであることを特徴とする排気浄化触媒に関する。
As a result of intensive studies aimed at achieving the above object, the present inventors can oxidize CO from a low temperature in order to achieve the above object, and suppress the influence of HC poisoning, which is a coexisting gas. As a result of further finding out that it is necessary to carry out the present invention, the present invention has been completed.
In the present invention, the catalyst layer is composed of a noble metal coat layer in which a noble metal is supported on a carrier substrate as a lower layer, and an HC (hydrocarbon) adsorbent layer in which a noble metal is supported on a carrier substrate as an upper layer. The present invention relates to an exhaust purification catalyst characterized in that the adsorbent layer has a thickness of 30 to 80 μm.
本発明の排気浄化触媒によれば、１００℃未満の低温域を含む温度範囲で高いＣＯ酸化活性を示す排気浄化触媒を得ることができる。 According to the exhaust purification catalyst of the present invention, it is possible to obtain an exhaust purification catalyst that exhibits high CO oxidation activity in a temperature range including a low temperature range of less than 100 ° C.
本発明の実施態様において、排気浄化触媒は、触媒層が、下層としての担体基材に貴金属、好適にはＰｔおよび／又はＰｄを担持した貴金属コート層と、上層としての担体基材、好適にはゼオライトに貴金属、好適にはＰｔおよび／又はＰｄを担持したＨＣ吸着材層とからなり、上層のＨＣ吸着材層の厚みが３０〜８０μｍである。 In an embodiment of the present invention, the exhaust purification catalyst has a catalyst layer having a noble metal, preferably a Pt and / or Pd supported on a carrier substrate as a lower layer, and a carrier substrate as an upper layer, preferably Consists of an HC adsorbent layer carrying a noble metal, preferably Pt and / or Pd, on the zeolite, and the upper HC adsorbent layer has a thickness of 30 to 80 μm.
本発明の好適な実施態様において、排気浄化触媒は、前記の要件に加えさらに、前記の上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が０．１以上１．５未満である。
さらに本発明の好適な実施態様において、排気浄化触媒は、前記の要件に加えさらに、前記下層がＣｅを含み、上層のＨＣ）吸着材層および下層の貴金属コート層がいずれも貴金属としてＰｔおよびＰｄが担当され、上層におけるＰｔとＰｄとの比率（Ｐｔ／Ｐｄ、質量比）が下層におけるＰｔとＰｄとの比率（Ｐｔ／Ｐｄ、質量比）よりも大である。
In a preferred embodiment of the present invention, in addition to the above-described requirements, the exhaust purification catalyst further includes a ratio (M U ) between the amount of the noble metal supported on the upper layer (M U ) and the amount of the noble metal supported on the lower layer (M D ). / M D , mass ratio) is 0.1 or more and less than 1.5.
Furthermore, in a preferred embodiment of the present invention, in addition to the above-mentioned requirements, the exhaust purification catalyst further includes Ce as the lower layer, and the upper HC) adsorbent layer and the lower noble metal coat layer are both precious metals such as Pt and Pd. The ratio of Pt and Pd in the upper layer (Pt / Pd, mass ratio) is larger than the ratio of Pt and Pd in the lower layer (Pt / Pd, mass ratio).
以下、図面を用いて本発明を説明する。
本発明の実施態様において排気浄化触媒１は、図１に示すように、基材２に設けられた触媒層１０が、下層としての担体基材２１に貴金属２２を担持した貴金属コート層３と、上層としての担体基材３１に貴金属３２を担持したＨＣ（炭化水素）吸着材層４とからなり、上層のＨＣ吸着材層４の厚みが３０〜８０μｍである。
Hereinafter, the present invention will be described with reference to the drawings.
In the embodiment of the present invention, as shown in FIG. 1, the
前記の基材としては、セラミックス材料、例えばコージェライトなどやメタル基材、例えばステンレス鋼などが挙げられる。
前記基材の形状はストレートフロー型、フィルター型、その他の形状が挙げられ、形状に限定されることなく本発明の効果を発揮し得る。
Examples of the substrate include ceramic materials such as cordierite and metal substrates such as stainless steel.
Examples of the shape of the substrate include a straight flow type, a filter type, and other shapes, and the effects of the present invention can be exhibited without being limited to the shape.
前記の担体基材としては、Ａｌ２Ｏ３、ＳｉＯ２、ＴｉＯ２、ＺｒＯ２、ＣｅＯ２のうち少なくとも１種が挙げられる。また、さらに２つ以上からなる複合酸化物を形成することが好適である。また、Ｗ、Ｐｒ、Ｌａ、Ｙ、Ｎｄ、Ｍｇ、Ｆｅ等の添加元素を加えることでさらなる活性向上を図り得る。
そして、上層の担体基材として、ゼオライトをＨＣ吸着材として含有することが好適である。
また、下層の担体基材として、前記の担体基材に加えて、Ｐｄ担体基材としてＣｅを含む酸化物を追加するとが好適である。前記のＣｅを含む酸化物として、セリア（ＣｅＯ２）やセリア複合酸化物、すなわちセリア−ジルコニア（ＣｅＯ２−ＺｒＯ２）複合酸化物（ＣＺ）などのＯＳＣ材が挙げられる。
前記の貴金属としては、Ｐｔ、Ｐｄ、Ｒｈ、Ａｕ、Ａｇからなる群から選ばれる少なくとも１種の元素、好適にはＰｔおよび／又はＰｄが挙げられる。特に、Ｐｔを０．１ｇ／Ｌ-触媒以上、その中でも０．１〜２ｇ／Ｌ-触媒の量を担持したものが好適である。
Examples of the carrier substrate include at least one of Al 2 O 3 , SiO 2 , TiO 2 , ZrO 2 , and CeO 2 . Further, it is preferable to form a composite oxide composed of two or more. Further, the activity can be further improved by adding additional elements such as W, Pr, La, Y, Nd, Mg, and Fe.
Further, it is preferable to contain zeolite as an HC adsorbent as the upper carrier substrate.
Moreover, it is preferable to add an oxide containing Ce as a Pd carrier substrate in addition to the carrier substrate as a lower carrier substrate. Examples of the oxide containing Ce include OSC materials such as ceria (CeO 2 ) and ceria composite oxide, that is, ceria-zirconia (CeO 2 —ZrO 2 ) composite oxide (CZ).
Examples of the noble metal include at least one element selected from the group consisting of Pt, Pd, Rh, Au, and Ag, preferably Pt and / or Pd. In particular, Pt of 0.1 g / L-catalyst or more, preferably 0.1 to 2 g / L-catalyst is supported.
従来の１層構造の排気浄化触媒では、図２に示すように、ＨＣが共存する通常の条件では低温ＣＯ酸化活性が低い。
また、従来の１層構造の排気浄化触媒では、図３に示すように、担体基材としてゼオライトの使用の有無に関らずＣＯ酸化活性が低い。
この従来の１層構造の排気浄化触媒による低いＣＯ酸化活性に関して、図４に示すように、１層のみでは担体基材（ゼオライト）に吸着したＨＣにより触媒貴金属が被毒されていることによると推定される。
In the conventional exhaust purification catalyst having a single layer structure, as shown in FIG. 2, the low temperature CO oxidation activity is low under normal conditions where HC coexists.
Further, in the conventional exhaust purification catalyst having a single layer structure, as shown in FIG. 3, the CO oxidation activity is low regardless of whether or not zeolite is used as the carrier substrate.
Regarding the low CO oxidation activity of the conventional exhaust purification catalyst having a single layer structure, as shown in FIG. 4, the catalyst noble metal is poisoned by HC adsorbed on the support substrate (zeolite) in only one layer. Presumed.
本発明の実施態様の排気浄化触媒によれば、図５に示すように、後述の実施例の欄に詳述する試験条件での試験の結果、従来の１層構造の浄化触媒に比べてＴ５０（℃）／ＣＯが低下することが確認される。
また、２層構造の排気浄化触媒は、図６に示すように、上層担体基材の厚みが３０〜８０μｍであると、後述の実施例の欄に詳述する試験条件での試験の結果、良好な低温ＣＯ酸化活性を示すことが確認される。
According to the exhaust purification catalyst of the embodiment of the present invention, as shown in FIG. 5, as a result of the test under the test conditions detailed in the column of the example described later, the T50 as compared with the conventional purification catalyst having a single layer structure is obtained. It is confirmed that (° C.) / CO decreases.
In addition, as shown in FIG. 6, the exhaust purification catalyst having a two-layer structure has a thickness of the upper carrier substrate of 30 to 80 μm, as a result of the test under the test conditions described in detail in the Examples section below. It is confirmed that it exhibits good low-temperature CO oxidation activity.
２層構造の排気浄化触媒において、前記の上層であるＨＣ吸着材層の厚みが前記下限より薄いとＨＣ吸着能が低下し厚すぎるとガス拡散性が悪化しＣＯ酸化活性が低下するが、前記の上層であるＨＣ吸着材層の厚みが前記の範囲内であることによってＨＣ吸着とＣＯ酸化を両立し得て、低温でのＣＯ酸化が可能となり得ると考えられる。 In the exhaust purification catalyst having a two-layer structure, if the thickness of the HC adsorbent layer as the upper layer is thinner than the lower limit, the HC adsorbing ability is lowered, and if it is too thick, the gas diffusibility is deteriorated and the CO oxidation activity is lowered. It is considered that when the thickness of the HC adsorbent layer, which is the upper layer, is within the above range, HC adsorption and CO oxidation can both be achieved, and CO oxidation at a low temperature can be achieved.
また、本発明の実施態様の排気浄化触媒は、図７に示すように、上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が１．５未満であると、後述の実施例の欄に詳述する試験条件での試験の結果、良好な低温ＣＯ酸化活性を示すことが確認される。
また、本発明の実施態様の排気浄化触媒は、図８に示すように、上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が０．１以上であると、後述の実施例の欄に詳述する試験条件での高ＳＶ時の未燃焼ガス（ＨＣ）のすり抜け量が少ないことが確認される。
In addition, as shown in FIG. 7, the exhaust purification catalyst of the embodiment of the present invention has a ratio (M U / M D ) between the amount of the upper layer noble metal supported (M U ) and the amount of the lower layer noble metal supported (M D ). When the mass ratio is less than 1.5, it is confirmed as a result of the test under the test conditions described in detail in the Examples section below that good low-temperature CO oxidation activity is exhibited.
In addition, as shown in FIG. 8, the exhaust purification catalyst according to the embodiment of the present invention has a ratio (M U / M D ) between the amount of supported noble metal (M U ) in the upper layer and the amount of supported noble metal (M D ) in the lower layer. When the mass ratio is 0.1 or more, it is confirmed that the amount of unburned gas (HC) slipping through at high SV under the test conditions described in detail in Examples below will be small.
以上の低温ＣＯ酸化活性とＰＭ再生時のＨＣすり抜け量とを総合的に考慮すると、図９に示すように、上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が０．１以上１．５以下であることが特に好適であることが理解される。 Considering the above-mentioned low-temperature CO oxidation activity and the amount of HC slipping during PM regeneration comprehensively, as shown in FIG. 9, the upper layer noble metal loading (M U ) and the lower layer noble metal loading (M D ) It is understood that it is particularly preferable that the ratio (M U / M D , mass ratio) is 0.1 or more and 1.5 or less.
本発明の実施態様の２層構造の排気浄化触媒と従来の１層構造の排気浄化触媒とのＣＯ浄化率について比較すると、図１０に示すように、本発明の実施態様の排気浄化触媒のＣＯ浄化率が従来の１層構造の排気浄化触媒のＣＯ浄化率に比べて向上していることが理解される。 When comparing the CO purification rate of the exhaust purification catalyst having the two-layer structure according to the embodiment of the present invention and the exhaust purification catalyst having the conventional one-layer structure, as shown in FIG. 10, the CO of the exhaust purification catalyst according to the embodiment of the present invention is shown. It is understood that the purification rate is improved as compared with the CO purification rate of the conventional exhaust purification catalyst having a single-layer structure.
本発明の実施態様の２層構造の排気浄化触媒において、図１１に示すように、Ｐｔのシンタリング抑制に必要なＰｄ量は、上下層に配置する総Ｐｄ／Ｐｔが１／９以上（貴金属に対してＰｄが１０％以上）で１／２未満、特にＰｄ／Ｐｔが１／５以上（貴金属に対してＰｄが１７％以上）で１／２未満であることが好適であることが理解される。
また、Ｐｄの有効活用の点から、図１２に示すように、本発明の実施態様の下層としての担体基材に貴金属を担持した貴金属コート層と、上層としての担体基材に貴金属を担持したＨＣ（炭化水素）吸着材層との２層構造の排気浄化触媒において、担体基材上の総Ｐｄ／Ｐｔが１／９以上、特に１／５以上で１／２未満にして、排気浄化触媒における担体基材上の触媒層中のＰｄ／Ｐｔ＝１／２との差分のＰｄをＯＳＣ材上に担持して下層に配置することが特に好適であることが理解される。
このＰｄ／ＯＳＣ材系の効果は、図１３に示すように、ＯＳＣ材で被毒したＨＣを酸化除去することによると考えられる。
In the exhaust purification catalyst having a two-layer structure according to the embodiment of the present invention, as shown in FIG. 11, the total amount of Pd / Pt disposed in the upper and lower layers is 1/9 or more (precious metal) It is understood that it is preferable that Pd is 10% or more) and less than 1/2, particularly Pd / Pt is 1/5 or more (Pd is 17% or more with respect to a noble metal) and less than 1/2. Is done.
From the viewpoint of effective use of Pd, as shown in FIG. 12, a noble metal coat layer in which a noble metal is supported on a carrier substrate as a lower layer of an embodiment of the present invention, and a noble metal is supported on a carrier substrate as an upper layer. In an exhaust purification catalyst having a two-layer structure with an HC (hydrocarbon) adsorbent layer, the total Pd / Pt on the carrier substrate is 1/9 or more, particularly 1/5 or more and less than 1/2, and the exhaust purification catalyst It is understood that it is particularly preferable to support Pd of the difference from Pd / Pt = 1/2 in the catalyst layer on the support base material on the OSC material and arrange it in the lower layer.
The effect of this Pd / OSC material system is considered to be due to oxidation removal of HC poisoned by the OSC material, as shown in FIG.
本発明の排気浄化触媒は、図１４に示すように、自動車のエンジン排気浄化にＨＣ酸化触媒として適用し得る。
また、本発明の排気浄化触媒は、図１５に示すように、自動車のエンジン排気浄化にＨＣ酸化触媒としてＤＰＦと組み合わせて適用し得る。
また、本発明の排気浄化触媒は、図１６に示すように、自動車のエンジン排気浄化にＨＣ酸化触媒としてＤＰＦおよびＮＯＸ触媒と組み合わせて適用し得る。
また、本発明の排気浄化触媒は、図１７に示すように、自動車のエンジン排気浄化にＨＣ酸化触媒としてＤＰＦおよびＮＯＸ触媒と配列を変えた組み合わせで適用し得る。
As shown in FIG. 14, the exhaust purification catalyst of the present invention can be applied as an HC oxidation catalyst for automobile engine exhaust purification.
Further, as shown in FIG. 15, the exhaust purification catalyst of the present invention can be applied in combination with DPF as an HC oxidation catalyst for purification of automobile engine exhaust.
The exhaust gas purifying catalyst of the present invention, as shown in FIG. 16 may be applied in combination with DPF and NO X catalyst as HC oxidation catalyst in the engine exhaust gas purification of an automobile.
The exhaust gas purifying catalyst of the present invention, as shown in FIG. 17 may be applied in combination with different sequences and DPF and NO X catalyst as HC oxidation catalyst in the engine exhaust gas purification of an automobile.
前記のＤＰＦ（粒子フィルタ）としては、特に制限はなく例えば多孔質セラミックからなるハニカム構造体を備えたいわゆるウォールフロー型であり得て、ハニカム構造体は、コージェライト、シリカ、アルミナ等のセラミックス材料で形成される。ハニカム構造体にはセルとも称される通路、上流側に詰栓が施された通路と、下流側に詰栓が施された他の通路とが交互に区画形成され、ハニカム状をなしている。排気が上流から下流に向かって流れると、排気は多孔質セラミックの流路壁面を通過して通路に流入し、下流側に流れる。このとき、排気中のＰＭは多孔質のセラミックスによって捕集され、ＰＭの大気への放出が防止される。このように排気が流路壁面を通過し、その際にＰＭを濾過捕集するフィルタ形式がウォールフロー型と称される。 The DPF (particle filter) is not particularly limited, and may be a so-called wall flow type having a honeycomb structure made of, for example, a porous ceramic. The honeycomb structure is made of a ceramic material such as cordierite, silica, and alumina. Formed with. In the honeycomb structure, a passage called a cell, a passage provided with a plug on the upstream side, and another passage provided with a plug on the downstream side are alternately partitioned to form a honeycomb shape. . When the exhaust gas flows from the upstream to the downstream, the exhaust gas passes through the porous ceramic channel wall surface and flows into the channel, and then flows downstream. At this time, the PM in the exhaust gas is collected by the porous ceramics, and the release of the PM into the atmosphere is prevented. A filter type in which exhaust gas passes through the wall surface of the flow path and collects PM at that time is called a wall flow type.
前記のＮＯＸ触媒としては、特に制限はなく例えば吸蔵還元型ＮＯｘ触媒（ＮＳＲ：ＮＯｘ Ｓｔｏｒａｇｅ Ｒｅｄｕｃｔｉｏｎ）又は選択還元型ＮＯｘ触媒（ＳＣＲ：Ｓｅｌｅｃｔｉｖｅ Ｃａｔａｌｙｔｉｃ Ｒｅｄｕｃｔｉｏｎ）が挙げられる。
前記吸蔵還元型ＮＯＸ触媒としては、アルミナＡｌ２Ｏ３等の酸化物からなる基材表面に、触媒成分としての白金Ｐｔのような貴金属と、ＮＯｘ吸収成分とが担持されて構成されている。ＮＯｘ吸収成分は、例えばカリウムＫ、ナトリウムＮａ，リチウムＬｉ、セシウムＣｓのようなアルカリ金属、バリウムＢａ、カルシウムＣａのようなアルカリ土類、ランタンＬａ、イットリウムＹのような希土類が挙げられる。
The NO X catalyst is not particularly limited, and examples thereof include an occlusion reduction type NOx catalyst (NSR: NOx Storage Reduction) or a selective reduction type NOx catalyst (SCR: Selective Catalytic Reduction).
As the storage reduction NO X catalyst, on a substrate surface made of oxide such as alumina Al 2 O 3, and a noble metal such as platinum Pt as a catalyst component, and a NOx absorbing component is composed is carried . Examples of the NOx absorption component include alkali metals such as potassium K, sodium Na, lithium Li and cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y.
そしてＮＯＸ触媒が吸蔵還元型ＮＯｘ触媒の場合、これに流入される排気ガスの空燃比が所定値（典型的には理論空燃比）よりリーンのときにはＮＯｘを吸収し、これに流入される排気ガス中の酸素濃度が低下すると吸収したＮＯｘを放出するという、ＮＯｘの吸放出作用を行う。ディーゼルエンジンが使用される場合、通常時の排気空燃比はリーンであり、ＮＯｘ触媒は排気中のＮＯｘの吸収を行う。また、ＮＯｘ触媒の上流側にて還元剤が供給され、流入排気ガスの空燃比がリッチになると、ＮＯｘ触媒は吸収したＮＯｘの放出を行う。そしてこの放出されたＮＯｘは還元剤と反応して還元浄化される。 And if NO X catalyst of the NOx storage reduction catalyst, the exhaust gas air-fuel ratio of the exhaust gas flowing thereto absorbs predetermined value NOx when the lean side (typically the stoichiometric air-fuel ratio), which is introduced thereto When the oxygen concentration in the gas decreases, the absorbed and released NOx is released by releasing the absorbed NOx. When a diesel engine is used, the exhaust air-fuel ratio at normal times is lean, and the NOx catalyst absorbs NOx in the exhaust. Further, when the reducing agent is supplied on the upstream side of the NOx catalyst and the air-fuel ratio of the inflowing exhaust gas becomes rich, the NOx catalyst releases the absorbed NOx. The released NOx reacts with the reducing agent and is reduced and purified.
また、前記選択還元型ＮＯｘ触媒としては、ゼオライトまたはアルミナ等の基材表面にＰｔなどの貴金属を担持したものや、その基材表面にＣｕ等の遷移金属をイオン交換して担持させたもの、その基材表面にチタニア／バナジウム触媒（Ｖ２Ｏ５／ＷＯ３／ＴｉＯ２）を担持させたもの等が例示できる。
この選択還元型ＮＯｘ触媒においては、流入排気ガスの空燃比がリーンという条件下で、排気ガス中のＨＣ、ＮＯが定常的に且つ同時に反応されてＮ２，ＣＯ２，Ｈ２Ｏといったように浄化される。ただしＮＯｘの浄化にはＨＣの存在が必須である。空燃比がリーンであっても、排気ガス中には未燃ＨＣが必ず含まれているので、これを利用してＮＯｘの還元浄化が可能である。また、前記吸蔵還元型ＮＯｘ触媒のようにリッチスパイクを実施して還元剤を供給してもよい。この場合、還元剤としては前記に例示したもののほか、アンモニアや尿素を使用することもできる。
In addition, as the selective reduction type NOx catalyst, those in which a noble metal such as Pt is supported on the surface of a substrate such as zeolite or alumina, or those in which a transition metal such as Cu is ion-exchanged and supported on the surface of the substrate, Examples thereof include those in which a titania / vanadium catalyst (V 2 O 5 / WO 3 / TiO 2 ) is supported on the surface of the base material.
In this selective reduction type NOx catalyst, under the condition that the air-fuel ratio of the inflowing exhaust gas is lean, HC and NO in the exhaust gas are reacted steadily and simultaneously so that N 2 , CO 2 , H 2 O, etc. Purified. However, the presence of HC is essential for NOx purification. Even if the air-fuel ratio is lean, unburned HC is always contained in the exhaust gas, and this can be used to reduce and purify NOx. Further, the reducing agent may be supplied by performing rich spike like the NOx storage reduction catalyst. In this case, ammonia or urea can be used as the reducing agent in addition to those exemplified above.
本発明の排気浄化装置は、上記の構成を有することによって１００℃未満の低温域を含む温度範囲で高いＣＯ酸化活性を達成することができる。しかし、前記効果を低減しない限り、内燃機関の排気浄化装置に適用し得る任意の他の手段を加えることも可能である。
本発明の排気浄化装置によれば、ディーゼルエンジンだけでなく１００℃未満の低温でＣＯを発生し得る全ての内燃機関、例えば、直噴の火点火式内燃機関であるリーンバーンガソリンエンジンにも適用し得る。
The exhaust emission control device of the present invention can achieve high CO oxidation activity in a temperature range including a low temperature region of less than 100 ° C. by having the above configuration. However, any other means that can be applied to the exhaust gas purification apparatus for an internal combustion engine can be added as long as the effect is not reduced.
The exhaust emission control device according to the present invention is applicable not only to a diesel engine but also to all internal combustion engines that can generate CO at a low temperature of less than 100 ° C., for example, a lean burn gasoline engine that is a direct injection fire ignition internal combustion engine. Can do.
以下に、実施例に基づいて本発明を説明する。本発明は以下の実施例に限定されない。
以下の実験は、本発明の構成による作用・効果を確認するためのものである。
Hereinafter, the present invention will be described based on examples. The present invention is not limited to the following examples.
The following experiment is for confirming the action and effect of the configuration of the present invention.
以下の各例において、排気浄化触媒の活性を以下の試験条件で評価した。
試験条件１：ＣＯ酸化活性（Ｔ５０＝５０％浄化温度）
モデルガスを用いて、下記の測定法により測定した。
モデルガス：ＣＯ＝１５００ｐｐｍ、Ｃ３Ｈ６＝１０００ｐｐｍ、ＮＯ＝２００ｐｐｍ、Ｏ２＝１０％、Ｈ２Ｏ＝３％、Ｎ２＝バランス、流量＝２０Ｌ／ｍｉｎ
Ｔ５０算出：ＣＯ浄化率が５０％となる温度として求めた。
試験条件２：ＣＯ酸化活性（Ｔ５０）
実機の２．２Ｌディーゼルエンジンを用いて、８０℃からの昇温試験を行った。
試験条件３：ＣＯ酸化活性（ＣＯ浄化率）
実機のＮＥＤＣモード中のＵＤＣ領域を模擬して、２．２Ｌディーゼルエンジンを用い行った。
ＣＯ浄化率算出法：（触媒出ＣＯ量／トータル触媒入りＣＯ量）×１００（％）
In each of the following examples, the activity of the exhaust purification catalyst was evaluated under the following test conditions.
Test condition 1: CO oxidation activity (T50 = 50% purification temperature)
Measurement was performed by the following measurement method using a model gas.
Model gas: CO = 1500 ppm, C 3 H 6 = 1000 ppm, NO = 200 ppm, O 2 = 10%, H 2 O = 3%, N 2 = balance, flow rate = 20 L / min
T50 calculation: It was determined as the temperature at which the CO purification rate was 50%.
Test condition 2: CO oxidation activity (T50)
Using a real 2.2L diesel engine, a temperature rise test from 80 ° C. was performed.
Test condition 3: CO oxidation activity (CO purification rate)
A 2.2 L diesel engine was used to simulate the UDC region in the NEDC mode of the actual machine.
CO purification rate calculation method: (catalyst output CO amount / total catalyst-containing CO amount) × 100 (%)
ＨＣすり抜け量の測定
ＨＣすり抜け量算出法：触媒入りＨＣ量を固定（燃料噴射量を固定）し、２０００ｒｐｍ／１００Ｎｍで昇温。温度が安定したところの触媒出のＨＣ濃度を測定し、算出。
HC slipping amount measurement HC slipping amount calculation method: HC amount with catalyst is fixed (fuel injection amount is fixed), and the temperature is increased at 2000 rpm / 100 Nm. Measure and calculate the HC concentration from the catalyst when the temperature is stable.
比較例１
φ３０ｍｍｘＬ５０ｍｍのテストピースサイズのコージェライト基材に、β−ゼオライト９０ｇ／ＬとＰｔ／Ｐｄ／Ａｌ２Ｏ３７５ｇ／Ｌおよびバインダを塗布し、Ａｌ２Ｏ３担体上の貴金属のＰｔ／Ｐｄ＝２／１（ｇ／Ｌ）である排気浄化触媒を調製した。
この排気浄化触媒を用いて、前記の条件でＣＯ酸化活性を評価した。
Comparative Example 1
β-zeolite 90 g / L, Pt / Pd / Al 2 O 3 75 g / L and a binder were applied to a cordierite base material having a test piece size of 30 mm × L 50 mm, and Pt / Pd = 2 of noble metal on an Al 2 O 3 support An exhaust purification catalyst of 1/1 (g / L) was prepared.
Using this exhaust purification catalyst, CO oxidation activity was evaluated under the above conditions.
比較例２
触媒調製２
触媒担体としてゼオライトをＡｌ２Ｏ３に変えた他は比較例１と同様にして、排気浄化触媒を調製した。
この排気浄化触媒を用いて、前記の条件でＣＯ酸化活性を評価した。
これらの結果をまとめて図２および図３、参考例１の結果とまとめて図５に示す。
Comparative Example 2
An exhaust purification catalyst was prepared in the same manner as in Comparative Example 1 except that the zeolite was changed to Al 2 O 3 as the catalyst carrier.
Using this exhaust purification catalyst, CO oxidation activity was evaluated under the above conditions.
These results are collectively shown in FIGS. 2 and 3, and the results of Reference Example 1 are shown in FIG.
参考例１
担体基材として触媒調製１と同様のものを用い、上層としてβ−ゼオライト６０ｇ／ＬとＰｔ０．６７ｇ／Ｐｄ０．３３ｇ／Ａｌ２Ｏ３２５ｇ／Ｌおよびバインダを、下層としてβ−ゼオライト３０ｇ／ＬとＰｔ１．３３ｇ／Ｐｄ０．３３ｇ／Ｌおよびバインダに塗布した他は触媒調製１と同様にして、２層構造の排気浄化触媒を調製した。
この排気浄化触媒を用いて、前記の条件でＣＯ酸化活性を評価した。
結果を他の結果とまとめて図５に示す。
Reference example 1
The same carrier as
Using this exhaust purification catalyst, CO oxidation activity was evaluated under the above conditions.
The results are shown together with other results in FIG.
実施例１および比較例３〜４
上層厚さを１０〜１００μｍの間で変えた他は参考例１と同様にして、２層構造の排気浄化触媒を調製した。
この排気浄化触媒を用いて、前記の条件でＣＯ酸化活性を評価した。
得られた結果を、他の結果とまとめて図６に示す。
Example 1 and Comparative Examples 3-4
An exhaust purification catalyst having a two-layer structure was prepared in the same manner as in Reference Example 1 except that the upper layer thickness was changed between 10 and 100 μm.
Using this exhaust purification catalyst, CO oxidation activity was evaluated under the above conditions.
The obtained results are shown together with other results in FIG.
実施例２〜４
上層と下層との貴金属担持量の割合を０．１〜３の間で変え、但し担持密度は変えないで調製した他は実施例１と同様にして、２層構造の排気浄化触媒を調製した。
この排気浄化触媒を用いて、前記の条件でＣＯ酸化活性およびＨＣすり抜け量を評価した。
得られた結果を、他の結果とまとめて図７、図８および図９に示す。
Examples 2-4
Exhaust purification catalyst having a two-layer structure was prepared in the same manner as in Example 1 except that the ratio of the amount of the noble metal supported between the upper layer and the lower layer was changed between 0.1 and 3 except that the supported density was not changed. .
Using this exhaust purification catalyst, CO oxidation activity and HC slipping amount were evaluated under the above-mentioned conditions.
The obtained results are shown together with other results in FIG. 7, FIG. 8, and FIG.
以上の図２〜図９の結果から、従来の１層構造の排気浄化触媒では低温でのＣＯ酸化活性が低く、２層構造の排気浄化触媒によりＣＯ酸化活性が高くなり、特に上層担体基材の厚みが３０〜８０μｍであると良好な低温ＣＯ酸化活性が達成され、上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が１．５未満であると良好な低温ＣＯ酸化活性を示し、上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が０．１以上であると、高ＳＶ時の未燃焼ガス（ＨＣ）のすり抜け量が少ないこと、
そして、上層の貴金属の担持量（ＭＵ）と下層の貴金属の担持量（ＭＤ）との割合（ＭＵ／ＭＤ、質量比）が０．１以上１．５未満であることが特に好適であるという結果が得られた。
From the results shown in FIGS. 2 to 9, the conventional one-layer exhaust purification catalyst has low CO oxidation activity at a low temperature, and the two-layer exhaust purification catalyst has high CO oxidation activity. When the thickness of the material is 30 to 80 μm, good low-temperature CO oxidation activity is achieved, and the ratio (M U / M D ) between the amount of the upper layer noble metal supported (M U ) and the amount of the lower layer noble metal supported (M D ), When the mass ratio is less than 1.5, good low-temperature CO oxidation activity is exhibited, and the ratio (M U / M D ) between the amount of the noble metal supported on the upper layer (M U ) and the amount of the noble metal supported on the lower layer (M D ) The mass ratio) is 0.1 or more, the amount of unburned gas (HC) slipping through at high SV is small;
The ratio (M U / M D , mass ratio) between the loading amount (M U ) of the upper layer noble metal and the loading amount (M D ) of the lower layer noble metal is particularly preferably 0.1 or more and less than 1.5. The result was preferred.
実施例５および比較例５
試験条件４
１）Ｆｒｅｓｈサンプル
Ａｌ２Ｏ３上にＰｔに対してＰｄを０〜３３％と変えた比で含浸法で含浸後、１２０℃で一晩乾燥し、５００℃で２時間焼成した。
２）Ａｇｅｄサンプル
Ｆｒｅｓｈサンプルを７５０℃で５時間、電気炉にて耐久を行った。
算出法：ＣＯ吸着量からＰｔ粒径を算出
Example 5 and Comparative Example 5
Test condition 4
1) Fresh sample After impregnating the Al 2 O 3 with Pd in a ratio of 0 to 33% with respect to Pt by an impregnation method, it was dried at 120 ° C. overnight and calcined at 500 ° C. for 2 hours.
2) Aged Sample A Fresh sample was subjected to durability in an electric furnace at 750 ° C. for 5 hours.
Calculation method: Calculate Pt particle size from CO adsorption amount
触媒１
Ｐｔ／Ｐｄ＝２／１ｇ／Ｌの割合で同一担体基材に担持した。基材として壁厚３ｍｉｌ、６００ｃｐｓｉの１．１Ｌコージェライト基材を使用した。上層にβ−ゼオライト６０ｇ／ＬとＰｔ／Ｐｄ／Ａｌ２Ｏ３が０．６７／０．３３ｇ／２５ｇ／Ｌとバインダ、下層にβ−ゼオライト３０ｇ／ＬとＰｔ／Ｐｄ／Ａｌ２Ｏ３が１．３３／０．３３ｇ／５０ｇ／Ｌとバインダを塗布し、担体上の貴金属のＰｔ／Ｐｄ＝２／１（ｇ／Ｌ）である排気浄化触媒を調製した。
It was supported on the same carrier substrate at a ratio of Pt / Pd = 2/1 g / L. A 1.1 L cordierite substrate with a wall thickness of 3 mil and 600 cpsi was used as the substrate. Β-zeolite 60 g / L and Pt / Pd / Al 2 O 3 are 0.67 / 0.33 g / 25 g / L and binder in the upper layer, and β-zeolite 30 g / L and Pt / Pd / Al 2 O 3 are in the lower layer. 1.33 / 0.33 g / 50 g / L and a binder were applied to prepare an exhaust purification catalyst having Pt / Pd = 2/1 (g / L) of the noble metal on the support.
触媒２
基材として壁厚３ｍｉｌ、６００ｃｐｓｉの１．１Ｌコージェライト基材を使用した。上層にβ−ゼオライト６０ｇ／ＬとＰｔ／Ｐｄ／Ａｌ２Ｏ３が０．６７／０．１３４ｇ／２５ｇ／Ｌとバインダ、下層にβ−ゼオライト３０ｇ／ＬとＰｔ／Ｐｄ／Ａｌ２Ｏ３が１．３３／０．２６６ｇ／３５ｇ／ＬとＰｄ／Ａｌ２Ｏ３が０．６／１５ｇ／Ｌとバインダを塗布し、排気浄化触媒を調製した。
A 1.1 L cordierite substrate with a wall thickness of 3 mil and 600 cpsi was used as the substrate. Β-zeolite 60 g / L and Pt / Pd / Al 2 O 3 are 0.67 / 0.134 g / 25 g / L and binder in the upper layer, and β-zeolite 30 g / L and Pt / Pd / Al 2 O 3 are in the lower layer. An exhaust purification catalyst was prepared by applying 1.33 / 0.266 g / 35 g / L, Pd / Al 2 O 3 0.6 / 15 g / L, and a binder.
触媒３
下層のＰｄ／Ａｌ２ＩＯ３をＰｄ／ＣＺ（ＣｅＯ２−ＺｒＯ２複合酸化物）に変えた他は触媒２と同様にして、排気浄化触媒を調製した。
An exhaust purification catalyst was prepared in the same manner as in
上記の各排気浄化触媒を用いて、下記の条件で触媒性能を評価した。
Ｐｔ粒径測定
ＣＯ吸着量より、Ｐｄへの吸着分を引き、Ｐｔのみの粒径に換算して求めた。
ＣＯ酸化活性（ＣＯ浄化率）測定
ＮＥＤＣモード中のＵＤＣ領域を模擬して、２．２Ｌディーゼルエンジンを使用して測定した。
Using each of the above exhaust purification catalysts, the catalyst performance was evaluated under the following conditions.
Pt particle size measurement The amount adsorbed on Pd was subtracted from the amount of CO adsorption, and converted to the particle size of only Pt.
CO oxidation activity (CO purification rate) measurement A 2.2 L diesel engine was used to simulate the UDC region during NEDC mode.
上記の排気浄化触媒および従来の触媒を用いて評価を行った。
得られた結果を他の触媒を用いて得られた結果とまとめて図１０および図１２にまとめて示す。
図１０および図１２から、本発明の実施態様の下層としての担体基材に貴金属を担持した貴金属コート層と、上層としての担体基材に貴金属を担持したＨＣ（炭化水素）吸着材層との２層構造の排気浄化触媒において、担体基材上の総Ｐｄ／Ｐｔ＝１／５として、従来の排気浄化触媒におけるＰｄ／Ｐｔ＝１／２との差分のＰｄ（合計貴金属量は同量とする）をＯＳＣ材に担持した排気浄化触媒は、従来の排気浄化触媒に比べて排気浄化触媒のＣＯ浄化率の向上に効果が得られる。
Evaluation was performed using the exhaust purification catalyst and the conventional catalyst.
The obtained results are shown together with the results obtained using other catalysts in FIGS. 10 and 12.
From FIG. 10 and FIG. 12, a noble metal coat layer in which a noble metal is supported on a carrier substrate as a lower layer of an embodiment of the present invention, and an HC (hydrocarbon) adsorbent layer in which a noble metal is supported on a carrier substrate as an upper layer. In the exhaust purification catalyst having a two-layer structure, the total Pd / Pt = 1/5 on the carrier base material is set to be different from Pd / Pt = 1/2 in the conventional exhaust purification catalyst (the total amount of precious metals is the same amount). The exhaust purification catalyst in which the OSC material is carried is effective in improving the CO purification rate of the exhaust purification catalyst as compared with the conventional exhaust purification catalyst.
本発明の排気浄化触媒は、１００℃未満の低温域を含む温度範囲で高いＣＯ酸化活性を示すので、自動車などの内燃機関の低ＣＯ２化時の排気浄化触媒として、高い触媒性能を実現し得る。 Since the exhaust purification catalyst of the present invention exhibits high CO oxidation activity in a temperature range including a low temperature range of less than 100 ° C., it achieves high catalytic performance as an exhaust purification catalyst when reducing internal combustion engines such as automobiles with low CO 2 . obtain.
１ 排気浄化触媒
２ 基材
３ 貴金属コート層
４ ＨＣ吸着層
１０ 触媒層
２１ 下層の担体基材
２２ 貴金属
３１ 上層の担体基材
３２ 貴金属
DESCRIPTION OF
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| JP2015500134A (en) * | 2011-12-12 | 2015-01-05 | 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 Ｐｕｂｌｉｃｌｉｍｉｔｅｄ Ｃｏｍｐａｎｙ | Oxidation catalyst for exhaust gas treatment of internal combustion engines |
| WO2015029853A1 (en) * | 2013-08-30 | 2015-03-05 | 大塚化学株式会社 | Exhaust gas purification filter and exhaust gas purification apparatus |
| JP2016504182A (en) * | 2012-11-29 | 2016-02-12 | ビーエーエスエフ ソシエタス・ヨーロピアＢａｓｆ Ｓｅ | Diesel oxidation catalyst containing palladium, gold and ceria |
| EP2992955A4 (en) * | 2013-04-19 | 2017-01-18 | Cataler Corporation | Exhaust-gas purification catalyst |
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