JP2017044202A - Exhaust emission control system for internal combustion engine and exhaust emission control catalyst - Google Patents

Exhaust emission control system for internal combustion engine and exhaust emission control catalyst Download PDF

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JP2017044202A
JP2017044202A JP2015169837A JP2015169837A JP2017044202A JP 2017044202 A JP2017044202 A JP 2017044202A JP 2015169837 A JP2015169837 A JP 2015169837A JP 2015169837 A JP2015169837 A JP 2015169837A JP 2017044202 A JP2017044202 A JP 2017044202A
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岩知道　均一
Kinichi Iwachido
均一 岩知道
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Mitsubishi Motors Corp
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Abstract

PROBLEM TO BE SOLVED: To respond to various types of required exhaust emission control function, improve efficiency of an internal combustion engine by further reducing pressure loss of exhaust gas, and reduce catalyst cost.SOLUTION: In an exhaust emission control system for an internal combustion engine, an exhaust emission control catalyst that comprises a support base material, a catalyst support layer formed on the surface of the support base material and catalyst active components supported by the catalyst support layer is provided in an exhaust passage. The exhaust emission control catalyst comprises the one support base material. The catalyst support layer in the upstream region in the exhaust gas flowing direction of the support base material comprises: a lower layer located near the surface of the support base material; and an upper layer located relatively distant compared to the lower layer. The catalyst active component of the upper layer includes Rh, and the catalyst active component of the lower layer includes Pd. The catalyst active component in the downstream region in the exhaust gas flowing direction of the support base material includes a material that can adsorb HC and NOx and selectively reduce NOx.SELECTED DRAWING: Figure 2

Description

本開示は、簡易な構成で排ガスの浄化を可能にした内燃機関の排ガス浄化システム及び排ガス浄化触媒に関する。   The present disclosure relates to an exhaust gas purification system and an exhaust gas purification catalyst for an internal combustion engine that enable purification of exhaust gas with a simple configuration.

大気のクリーン化が求められる中、ガソリンエンジンでは、触媒を用いた排ガス浄化性能のさらなる向上が求められ、特に、エンジン冷態時の排ガス浄化が重要な課題となっている。エンジン冷態時の排ガス浄化策として、排ガス通路に設けられた触媒が昇温するまでの間に排出されるＨＣの低減を狙って、ＨＣトラップ触媒など、排ガス通路に多種の触媒を直列に配置した浄化システムが検討されている。
しかし、このような浄化システムでは、排ガスの圧力損失が大きくなり、排気圧力の上昇によって、エンジン性能が低下するだけでなく、触媒コストが極めて高価になるという問題がある。特に、触媒担持層を担持する担持基材がハニカム構造体であるとき、排ガスの圧力損失がエンジン性能に及ぼす影響を無視できない。 Amidst demands for clean air, gasoline engines are required to further improve exhaust gas purification performance using a catalyst, and in particular, exhaust gas purification when the engine is cold is an important issue. As an exhaust gas purification measure when the engine is cold, various catalysts are arranged in series in the exhaust gas passage, such as an HC trap catalyst, aiming to reduce the HC discharged until the temperature of the catalyst provided in the exhaust gas passage rises. Purified systems are being considered.
However, in such a purification system, there is a problem that the pressure loss of the exhaust gas becomes large, and not only the engine performance is reduced due to the increase of the exhaust pressure, but the catalyst cost becomes extremely expensive. In particular, when the support base material supporting the catalyst support layer is a honeycomb structure, the influence of exhaust gas pressure loss on engine performance cannot be ignored.

例えば、特許文献１には、排ガス通路に排ガス上流側から第１の触媒コンバータと第２の触媒コンバータとが直列に設けられ、第１の触媒コンバータには、酸化性能を有する高温用ＮＯｘ吸着触媒と触媒温度が低いときＮＯｘを吸着する低温用ＮＯｘ吸着触媒とが内蔵され、第２の触媒コンバータには、第１の触媒コンバータから放出されたＮＯｘを還元浄化するためのＮＯｘ還元触媒と、捕集したＰＭを燃焼し浄化するＰＭ燃焼触媒とが内蔵されている。   For example, in Patent Document 1, a first catalytic converter and a second catalytic converter are provided in series in the exhaust gas passage from the exhaust gas upstream side, and the first catalytic converter includes a high-temperature NOx adsorption catalyst having oxidation performance. And a low-temperature NOx adsorption catalyst that adsorbs NOx when the catalyst temperature is low, and the second catalytic converter includes a NOx reduction catalyst for reducing and purifying NOx released from the first catalytic converter, and a trap. A PM combustion catalyst for burning and purifying the collected PM is incorporated.

特開２０１５−０２５４３３号号公報Japanese Patent Laying-Open No. 2015-025433

特許文献１に開示されたように、別々の担持基材で構成された複数の触媒体を排ガス通路に直列に配置すると、排ガスの圧力損失が増加し、内燃機関の性能が低下するだけでなく、触媒コストが高価になるおそれがある。
この対応策として、触媒コンバータ数を減らし、高い排ガス温度下で高い排ガス浄化効果が見込める内燃機関の近接位置に大容量の触媒担持層を担持した触媒コンバータを設けることが考えられる。
しかし、この対応策のみでは、要求される複雑で多種の浄化機能に対応できない。また、今後、さらなる排気圧力の抑制と触媒コストの削減が求められることが予想される。 As disclosed in Patent Document 1, when a plurality of catalyst bodies composed of different supporting base materials are arranged in series in the exhaust gas passage, not only the pressure loss of the exhaust gas increases and the performance of the internal combustion engine decreases. The catalyst cost may be expensive.
As a countermeasure, it is conceivable to reduce the number of catalytic converters and to provide a catalytic converter carrying a large-capacity catalyst carrying layer at a position close to the internal combustion engine where a high exhaust gas purification effect can be expected at a high exhaust gas temperature.
However, this countermeasure alone cannot cope with the required complex and various purification functions. In the future, further suppression of exhaust pressure and reduction in catalyst costs are expected.

そこで、これら技術的課題に鑑み、本発明の少なくとも一つの実施形態は、求められる多種の排ガス浄化機能に対応でき、排ガスの圧力損失をさらに低減して内燃機関の効率向上を図ると共に、触媒コストの削減を図ることを目的とする。   Therefore, in view of these technical problems, at least one embodiment of the present invention can cope with various types of exhaust gas purification functions that are required, further reduce the pressure loss of exhaust gas, improve the efficiency of the internal combustion engine, and reduce the catalyst cost. The purpose is to reduce this.

（１）本発明の少なくとも一実施形態に係る内燃機関の排ガス浄化システムは、排ガス通路に、担持基材と、該担持基材の表面に形成された触媒担持層と、該触媒担持層に担持された触媒活性成分とで構成され排ガス浄化触媒を備えた内燃機関の排ガス浄化システムであって、前記排ガス浄化触媒は１個の前記担持基材で構成され、前記担持基材の排ガス流れ方向上流側領域の前記触媒担持層は、前記担持基材の表面に近い下層と該下層より相対的に遠い上層とで構成され、前記上層の前記触媒活性成分はＲｈを含むと共に、前記下層の前記触媒活性成分はＰｄを含み、該担持基材の排ガス流れ方向下流側領域の前記触媒活性成分は、ＨＣ及びＮＯｘを吸着可能であり、かつＮＯｘを選択還元する材料を含む。   (1) An exhaust gas purification system for an internal combustion engine according to at least one embodiment of the present invention includes a support base material, a catalyst support layer formed on a surface of the support base material, and a catalyst support layer. An exhaust gas purification system for an internal combustion engine comprising an exhaust gas purification catalyst comprising an active catalyst component, wherein the exhaust gas purification catalyst is composed of one of the supported substrates, and the exhaust gas flow upstream of the supported substrate The catalyst support layer in the side region is composed of a lower layer close to the surface of the support substrate and an upper layer relatively far from the lower layer, and the catalytic active component of the upper layer contains Rh, and the catalyst in the lower layer The active component contains Pd, and the catalytic active component in the downstream region in the exhaust gas flow direction of the supporting substrate contains a material capable of adsorbing HC and NOx and selectively reducing NOx.

排ガス中にＣＯ、ＨＣが存在すると、反応式（１）の水性ガス反応と、反応式（２）の水蒸気改質反応が進行してＨ２が生成され、反応式（３）、反応式（４）や反応式（５）に示す反応によりＮＨ３が生成する。これらの反応は、とくに貴金属を担持した触媒上で進行する。
ＣＯ＋Ｈ２Ｏ → ＣＯ２＋Ｈ２ （１）
ＣＨｎ＋２Ｈ２Ｏ → ＣＯ２＋（２＋ｎ/２）Ｈ２ （２）
５/２Ｈ２＋ＮＯ → ＮＨ３＋Ｈ２Ｏ （３）
３/２Ｈ２＋ＮＯ＋ＣＯ → ＮＨ３＋ＣＯ２ （４）
ＮＯ＋ＨＣ＋Ｈ２Ｏ → ＣＯ２＋ＮＨ３ （５）
上記排ガス浄化触媒では、排ガス流れ方向下流側領域（以下「下流側領域」とも言う。）の触媒活性成分により、排ガス中に存在するＮＨ３とＮＯｘとを反応させ、反応式（６）〜（８）の反応によりＮＯｘを選択還元する。
ＮＯ＋ＮＯ２＋２ＮＨ３ → ２Ｎ２＋３Ｈ２Ｏ （６）
４ＮＯ＋４ＮＨ３＋Ｏ２ → ４Ｎ２＋６Ｈ２Ｏ （７）
６ＮＯ２＋８ＮＨ３ → ７Ｎ２＋１２Ｈ２Ｏ （８）
さらに、この触媒活性成分はＨＣ及びＮＯｘの吸着能を有し、排ガス温度の上昇に伴って脱離するＨＣ及びＮＯｘによってＮＨ３の生成が促進され、生成したＮＨ３によってＮＯｘの浄化率を向上できる。 When CO and HC are present in the exhaust gas, the water gas reaction of the reaction formula (1) and the steam reforming reaction of the reaction formula (2) proceed to generate H 2 , and the reaction formula (3), the reaction formula ( NH 3 is produced by the reaction shown in 4) and reaction formula (5). These reactions proceed particularly on a catalyst supporting a noble metal.
CO + H 2 O → CO 2 + H 2 (1)
CH n + 2H 2 O → CO 2 + (2 + n / 2) H 2 (2)
5 / 2H 2 + NO → NH 3 + H 2 O (3)
3 / 2H 2 + NO + CO → NH 3 + CO 2 (4)
NO + HC + H 2 O → CO 2 + NH 3 (5)
In the exhaust gas purifying catalyst, NH 3 and NOx present in the exhaust gas are reacted with the catalytically active component in the downstream region in the exhaust gas flow direction (hereinafter also referred to as “downstream region”), and the reaction formulas (6) to (6) NOx is selectively reduced by the reaction of 8).
NO + NO 2 + 2NH 3 → 2N 2 + 3H 2 O (6)
4NO + 4NH 3 + O 2 → 4N 2 + 6H 2 O (7)
6NO 2 + 8NH 3 → 7N 2 + 12H 2 O (8)
Furthermore, this catalytically active component has the ability to adsorb HC and NOx, and the generation of NH 3 is promoted by HC and NOx that are desorbed as the exhaust gas temperature rises, and the purification rate of NOx is improved by the generated NH 3 . it can.

また、排ガス流れ方向上流側領域（以下「上流側領域」とも言う。）では、触媒活性成分として浄化性能に優れたＲｈを含む上層と、触媒活性成分として低温でのＨＣ吸着性能が高いＰｄを含む下層とで構成され、いわゆる三元触媒としての機能を有する。上流側領域で排ガス中のＨＣ及びＣＯを酸化し、かつＮＯｘを還元して、Ｎ２、ＣＯ２及びＨ２Ｏに変換し低減する。
これによって、上記排ガス浄化触媒は、多種の排ガス浄化機能に対応しつつ１個の担持基材で構成することができ、浄化システム全体の構成を簡素化できる。そのため、触媒コストを削減できると共に、排ガスの圧力損失を低減できるので、内燃機関の性能低下を抑制できる。そのため、担持基材がハニカム構造体であっても、排ガスの圧力損失を抑えることができる。
さらに、排ガス浄化性能が向上することで、触媒担持層の膜厚を低減できるので、排ガスの圧力損失をさらに低減できると共に、触媒担持層のコーティング作業が容易になる。
また、上層に優れた排ガス浄化効果を有するＲｈを含み、下層に比較的安価なＰｄを含むため、高い排ガス浄化能力を維持しつつ触媒コストを抑えることができる。
さらに、ＲｈやＰｄ等の貴金属を担持した触媒担持層を積層させることで、上記反応式（１）〜（５）によりＮＨ３が多く生成され、ここで生成されたＮＨ３がＮＯｘの還元浄化に寄与する。 Further, in the upstream region in the exhaust gas flow direction (hereinafter also referred to as “upstream region”), an upper layer containing Rh having excellent purification performance as a catalytic active component, and Pd having high HC adsorption performance at low temperatures as a catalytic active component. It is comprised by the lower layer containing, and has a function as what is called a three-way catalyst. In the upstream region, HC and CO in the exhaust gas are oxidized and NOx is reduced and converted to N 2 , CO 2 and H 2 O and reduced.
As a result, the exhaust gas purification catalyst can be configured with a single supporting substrate while supporting various exhaust gas purification functions, and the configuration of the entire purification system can be simplified. Therefore, the catalyst cost can be reduced and the pressure loss of the exhaust gas can be reduced, so that the performance deterioration of the internal combustion engine can be suppressed. Therefore, even if the supporting substrate is a honeycomb structure, the pressure loss of the exhaust gas can be suppressed.
Furthermore, since the exhaust gas purification performance is improved, the thickness of the catalyst support layer can be reduced, so that the pressure loss of the exhaust gas can be further reduced and the coating operation of the catalyst support layer is facilitated.
In addition, since the upper layer contains Rh having an excellent exhaust gas purification effect and the lower layer contains relatively inexpensive Pd, the catalyst cost can be suppressed while maintaining a high exhaust gas purification capability.
Further, by laminating a catalyst support layer supporting a noble metal such as Rh or Pd, a large amount of NH 3 is generated by the above reaction formulas (1) to (5), and the generated NH 3 is reduced and purified by NOx. Contribute to.

（２）幾つかの実施形態では、前記構成（１）において、前記排ガス流れ上流側領域と前記排ガス流れ方向下流側領域との間に、前記触媒担持層が前記上層のみで構成された排ガス流れ方向中間領域（以下「中間領域」とも言う。）を有する。
上記構成（２）によれば、高い排ガス温度下で大きな排ガス浄化効果が見込める上流側領域では上記下層を設けて、高い排ガス浄化性能を保持しつつ、上流側領域より排ガス温度が低下し上流側領域ほど排ガス浄化効果が得られない中間領域では上記下層を無くすことで、排ガス浄化性能を維持しつつ触媒コストをさらに節減できる。 (2) In some embodiments, in the configuration (1), the exhaust gas flow in which the catalyst supporting layer is configured only by the upper layer between the exhaust gas flow upstream region and the exhaust gas flow direction downstream region. It has a direction intermediate region (hereinafter also referred to as “intermediate region”).
According to the configuration (2), in the upstream region where a large exhaust gas purification effect can be expected at a high exhaust gas temperature, the lower layer is provided, and the exhaust gas temperature is lowered from the upstream region while maintaining high exhaust gas purification performance. By eliminating the lower layer in the intermediate region where the exhaust gas purification effect cannot be obtained as much as the region, the catalyst cost can be further reduced while maintaining the exhaust gas purification performance.

幾つかの実施形態では、前記構成（１）又は（２）において、前記排ガス流れ方向上流側領域及び前記排ガス流れ方向中間領域の前記上層は、前記触媒活性成分として前記担持基材の容積１リットル当たり０．１乃至２．０ｇのＲｈを含み、前記排ガス流れ方向上流側領域の前記下層は、前記触媒活性成分として前記担持基材の容積１リットル当たり１乃至１５ｇのＰｄを含む。
上記構成によれば、夫々上記含有量の触媒活性成分を含むことで、高い排ガス浄化効果を可能にする。また、排ガス浄化効果の割に触媒活性成分の含有量を少なく抑えることができるため、触媒担持層の膜厚を低減でき、これによって、排ガスの圧力損失を抑制できると共に、触媒担持層のコーティングが容易になる。 In some embodiments, in the configuration (1) or (2), the upper layer of the upstream region in the exhaust gas flow direction and the intermediate region in the exhaust gas flow direction has a volume of 1 liter of the support substrate as the catalytic active component. The lower layer of the upstream region in the exhaust gas flow direction contains 1 to 15 g of Pd per liter of the support substrate as the catalytic active component.
According to the said structure, the high exhaust gas purification effect is enabled by including the catalyst active component of the said content, respectively. In addition, since the content of the catalytically active component can be kept small for the exhaust gas purification effect, the film thickness of the catalyst support layer can be reduced, thereby suppressing the pressure loss of the exhaust gas and the catalyst support layer coating. It becomes easy.

（３）幾つかの実施形態では、前記構成（１）又は（２）において、前記下層はさらに助触媒として触媒用酸素吸蔵材料を含む。
上記構成（３）によれば、上記下層に酸素吸蔵及び放出能を有する触媒用酸素吸蔵材料を含むため、空燃比が変動してもそれに対応して高い排ガス浄化効果を維持できる。 (3) In some embodiments, in the configuration (1) or (2), the lower layer further includes a catalyst oxygen storage material as a promoter.
According to the configuration (3), since the oxygen storage material for catalyst having oxygen storage and release ability is included in the lower layer, even if the air-fuel ratio varies, a high exhaust gas purification effect can be maintained correspondingly.

幾つかの実施形態では、前記構成（３）において、前記下層は、前記担持基材の容積１リットル当たりＣｅＯ２を主成分とする１乃至８０ｇの前記触媒用酸素吸蔵材料を含む。
上記構成によれば、上記含有量の触媒用酸素吸蔵材料を含むことで、高い排ガス浄化効果が可能になる。また、触媒用酸素吸蔵材料の含有量を少なく抑えることができるため、触媒担持層の膜厚を低減でき、これによって、排ガスの圧力損失を抑制できると共に、触媒担持層のコーティングが容易になる。 In some embodiments, in the configuration (3), the lower layer includes 1 to 80 g of the oxygen storage material for the catalyst, the main component being CeO 2 per liter of the support substrate.
According to the said structure, the high exhaust gas purification effect is attained by including the oxygen storage material for catalysts of the said content. In addition, since the content of the oxygen storage material for the catalyst can be suppressed to a low level, the film thickness of the catalyst support layer can be reduced, which can suppress the pressure loss of the exhaust gas and facilitate the coating of the catalyst support layer.

幾つかの実施形態では、前記構成（１）〜（３）の何れかにおいて、前記担持基材の排ガス流れ方向下流側領域の前記触媒活性成分は、前記担持基材の容積１リットル当たり２０乃至３００ｇの前記触媒活性成分を含む。
上記構成によれば、上記含有量の触媒活性成分を含むことで、高い排ガス浄化効果を可能にする。また、排ガス浄化効果の割に触媒活性成分の含有量を少なく抑えることができるため、触媒担持層の膜厚を薄くでき、そのため、排ガスの圧力損失を抑制できると共に、触媒担持層のコーティングが容易になる。 In some embodiments, in any one of the configurations (1) to (3), the catalytically active component in the downstream region in the exhaust gas flow direction of the support base is 20 to 20 per liter of the support base. Contains 300 g of the catalytically active component.
According to the said structure, the high exhaust gas purification effect is enabled by including the catalyst active component of the said content. In addition, since the content of the catalytically active component can be kept small for the exhaust gas purification effect, the thickness of the catalyst support layer can be reduced, so that pressure loss of the exhaust gas can be suppressed and the catalyst support layer can be easily coated. become.

（４）幾つかの実施形態では、前記構成（１）〜（３）の何れかにおいて、前記担持基材の排ガス流れ方向下流側領域に含まれる前記触媒活性成分が吸着したＨＣ及びＮＯｘを脱離させる工程で、内燃機関をリッチ燃焼に制御するための制御装置をさらに備える。
上記構成（４）によれば、上記触媒活性成分が吸着したＨＣ及びＮＯｘを脱離させる工程で、内燃機関をリッチ燃焼に制御することで、排ガス中のＣＯ量やＨＣ量を増やし、これによって、上記反応式（１）〜（５）に示す反応が行われ、排ガス中に含まれるＮＨ３量を増やすことができる。
こうして、増加したＮＨ３によって下層の触媒活性成分から脱離したＨＣ及びＮＯｘを高効率で低減できる。 (4) In some embodiments, in any of the configurations (1) to (3), the HC and NOx adsorbed by the catalytically active components contained in the downstream region in the exhaust gas flow direction of the support substrate are removed. A control device is further provided for controlling the internal combustion engine to rich combustion in the separating step.
According to the configuration (4), in the step of desorbing HC and NOx adsorbed by the catalytic active component, the internal combustion engine is controlled to rich combustion, thereby increasing the amount of CO and HC in the exhaust gas. The reactions shown in the above reaction formulas (1) to (5) are performed, and the amount of NH 3 contained in the exhaust gas can be increased.
In this way, HC and NOx desorbed from the underlying catalytically active component due to the increased NH 3 can be reduced with high efficiency.

（５）幾つかの実施形態では、前記構成（４）において、前記排ガス浄化触媒の温度を検出するための温度センサをさらに備え、前記制御装置は、前記温度センサの検出値が閾値を超えた時、ＨＣ及びＮＯｘの脱離工程が開始されたと判定し、前記内燃機関をリッチ燃焼に制御するものである。
上記構成（５）によれば、排ガス浄化触媒を通る排ガスの温度を検出し、この検出値に基づいてＨＣ及びＮＯｘの脱離工程が開始されたか否かを正確に判定できる。 (5) In some embodiments, the configuration (4) further includes a temperature sensor for detecting the temperature of the exhaust gas purification catalyst, and the control device has a detection value of the temperature sensor exceeding a threshold value. At this time, it is determined that the HC and NOx desorption process has started, and the internal combustion engine is controlled to rich combustion.
According to the configuration (5), the temperature of the exhaust gas passing through the exhaust gas purification catalyst is detected, and it is possible to accurately determine whether or not the HC and NOx desorption process has been started based on the detected value.

（６）本発明の少なくとも一実施形態に係る排ガス浄化触媒は、担持基材と、該担持基材の表面に形成された触媒担持層と、該触媒担持層に担持された触媒活性成分とで構成された排ガス浄化触媒において、前記排ガス浄化触媒は１個の前記担持基材で構成され、該担持基材の排ガス流れ方向上流側領域の前記触媒担持層は、前記担持基材の表面に近い下層と該下層より相対的に遠い上層とで構成され、前記上層の前記触媒活性成分はＲｈを含むと共に、前記下層の前記触媒活性成分はＰｄ及び触媒用酸素吸蔵材料を含み、該担持基材の排ガス流れ方向下流側領域の前記触媒活性成分は、ＨＣ及びＮＯｘを吸着可能であり、かつＮＯｘを選択還元する材料を含む。   (6) An exhaust gas purifying catalyst according to at least one embodiment of the present invention comprises a supporting substrate, a catalyst supporting layer formed on the surface of the supporting substrate, and a catalytically active component supported on the catalyst supporting layer. In the exhaust gas purification catalyst thus configured, the exhaust gas purification catalyst is composed of a single support substrate, and the catalyst support layer in the upstream region in the exhaust gas flow direction of the support substrate is close to the surface of the support substrate. A lower layer and an upper layer relatively far from the lower layer, the catalytically active component of the upper layer containing Rh, and the catalytically active component of the lower layer containing Pd and an oxygen storage material for catalyst, The catalytically active component in the downstream region of the exhaust gas flow direction includes a material capable of adsorbing HC and NOx and selectively reducing NOx.

上記構成（６）によれば、上記排ガス浄化触媒は、下流側領域での触媒活性成分により、排ガス中に存在するＮＨ３と、排ガス温度の上昇に伴って脱離するＨＣ及びＮＯｘによって生成されたＮＯｘとによってＮＯｘの浄化率を向上できる。
また、上流側領域は三元触媒としての機能を有し、ＨＣ、ＣＯ及びＮＯｘを低減できる。
これによって、上記排ガス浄化触媒は、多種の排ガス浄化機能に対応しつつ１個の担持基材で構成することができ、浄化システム全体の構成を簡素化できる。そのため、触媒コストを削減できると共に、排ガスの圧力損失を低減できるので、内燃機関の性能低下を抑制できる。
さらに、排ガス浄化性能が向上することで、触媒担持層の膜厚を低減できるので、排ガスの圧力損失をさらに低減できると共に、触媒担持層のコーティング作業が容易になる。
また、上層に優れた排ガス浄化効果を有するＲｈを含み、下層に比較的安価なＰｄを含むため、高い排ガス浄化能力を維持しつつ触媒コストを抑えることができる。 According to the configuration (6), the exhaust gas purifying catalyst is generated by NH 3 present in the exhaust gas and HC and NOx desorbed as the exhaust gas temperature rises due to the catalytically active component in the downstream region. NOx purification rate can be improved by NOx.
Further, the upstream region has a function as a three-way catalyst and can reduce HC, CO, and NOx.
As a result, the exhaust gas purification catalyst can be configured with a single supporting substrate while supporting various exhaust gas purification functions, and the configuration of the entire purification system can be simplified. Therefore, the catalyst cost can be reduced and the pressure loss of the exhaust gas can be reduced, so that the performance deterioration of the internal combustion engine can be suppressed.
Furthermore, since the exhaust gas purification performance is improved, the thickness of the catalyst support layer can be reduced, so that the pressure loss of the exhaust gas can be further reduced and the coating operation of the catalyst support layer is facilitated.
In addition, since the upper layer contains Rh having an excellent exhaust gas purification effect and the lower layer contains relatively inexpensive Pd, the catalyst cost can be suppressed while maintaining a high exhaust gas purification capability.

（７）幾つかの実施形態では、前記構成（６）において、前記排ガス流れ上流側領域と前記排ガス流れ方向下流側領域との間に、前記触媒担持層が前記上層のみで構成された排ガス流れ方向中間領域を有する。
上記構成（７）によれば、高い排ガス温度下で高い排ガス浄化効果が見込める排ガス流れ方向上流側領域では上記下層を設け、排ガス温度が低下し上流側領域ほど排ガス浄化効果が見込めない排ガス流れ方向中間領域では上記下層を無くすことで、排ガス浄化性能を高く維持しつつ触媒コストをさらに節減できる。 (7) In some embodiments, in the configuration (6), the exhaust gas flow in which the catalyst support layer is configured only by the upper layer between the exhaust gas flow upstream region and the exhaust gas flow direction downstream region. It has a direction middle region.
According to the configuration (7), the lower layer is provided in the upstream region in the exhaust gas flow direction in which a high exhaust gas purification effect can be expected under a high exhaust gas temperature, and the exhaust gas flow direction in which the exhaust gas temperature decreases and the exhaust gas purification effect cannot be expected in the upstream region. By eliminating the lower layer in the intermediate region, catalyst costs can be further reduced while maintaining high exhaust gas purification performance.

本発明の少なくとも一実施形態によれば、求められる多種の排ガス浄化機能に対応でき、内燃機関の排ガス通路を流れる排ガスの圧力損失を低減して内燃機関の効率を向上できると共に、排ガス通路に設けられる排ガス浄化触媒のコストを削減できる。   According to at least one embodiment of the present invention, various types of exhaust gas purification functions that are required can be accommodated, the pressure loss of the exhaust gas flowing through the exhaust gas passage of the internal combustion engine can be reduced, the efficiency of the internal combustion engine can be improved, and the exhaust gas passage can be provided. The cost of the exhaust gas purification catalyst to be used can be reduced.

一実施形態に係る内燃機関の排ガス浄化システムを示す概略構成図である。It is a schematic block diagram which shows the exhaust gas purification system of the internal combustion engine which concerns on one Embodiment. 一実施形態に係る触媒コンバータの概略構成図である。It is a schematic block diagram of the catalytic converter which concerns on one Embodiment. （Ａ）は図２中の領域Ａの拡大断面図であり、（Ｂ）は同じく領域Ｂの拡大断面図であり、（Ｃ）は同じく領域Ｃの拡大断面図である。2A is an enlarged sectional view of a region A in FIG. 2, FIG. 2B is an enlarged sectional view of the region B, and FIG. 排ガス浄化プロセスを時系列で示す線図である。It is a diagram which shows an exhaust gas purification process in time series. 触媒内部の排ガス温度分布を示す線図である。It is a diagram which shows the exhaust gas temperature distribution inside a catalyst. 貴金属担持量と総ＨＣの浄化効率との関係を示す線図である。It is a diagram which shows the relationship between the noble metal carrying amount and the purification efficiency of total HC.

以下、添付図面を参照して、本発明の幾つかの実施形態について説明する。ただし、これらの実施形態に記載されている又は図面に示されている構成部品の寸法、材質、形状及びその相対的配置等は、本発明の範囲をこれに限定する趣旨ではなく、単なる説明例にすぎない。
例えば、「ある方向に」、「ある方向に沿って」、「平行」、「直交」、「中心」、「同心」或いは「同軸」等の相対的或いは絶対的な配置を表す表現は、厳密にそのような配置を表すのみならず、公差、若しくは、同じ機能が得られる程度の角度や距離をもって相対的に変位している状態も表すものとする。
例えば、「同一」、「等しい」及び「均質」等の物事が等しい状態であることを表す表現は、厳密に等しい状態を表すのみならず、公差、若しくは、同じ機能が得られる程度の差が存在している状態も表すものとする。
例えば、四角形状や円筒形状等の形状を表す表現は、幾何学的に厳密な意味での四角形状や円筒形状等の形状を表すのみならず、同じ効果が得られる範囲で、凹凸部や面取り部等を含む形状も表すものとする。
一方、一つの構成要素を「備える」、「具える」、「具備する」、「含む」、又は「有する」という表現は、他の構成要素の存在を除外する排他的な表現ではない。 Several embodiments of the present invention will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in these embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Only.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of other constituent elements.

本発明の幾つかの実施形態に係る排ガス浄化システム１０は、図１に示すように、内燃機関（例えばガソリンエンジン）１１の燃焼室（不図示）と連通する排気ポート１２が気筒毎に形成されている。そして、内燃機関１１には夫々の排気ポート１２と連通するように排気マニフォールド１４が接続されている。
排気マニフォールド１４の排ガス流れ方向下流には、排気過給機１６が設けられている。排気過給機１６ではタービンハウジング１６ａと排気管（排ガス通路）１８とが連通し、内燃機関１１から排出される排ガスｅのエネルギを利用して吸入された新気を圧縮し、内燃機関１０の燃焼室に供給する。
排気管１８には、排ガス浄化触媒２０を内蔵した触媒コンバータ２２が設けられている。 As shown in FIG. 1, an exhaust gas purification system 10 according to some embodiments of the present invention has an exhaust port 12 communicating with a combustion chamber (not shown) of an internal combustion engine (for example, a gasoline engine) 11 for each cylinder. ing. An exhaust manifold 14 is connected to the internal combustion engine 11 so as to communicate with the respective exhaust ports 12.
An exhaust supercharger 16 is provided downstream of the exhaust manifold 14 in the exhaust gas flow direction. In the exhaust supercharger 16, a turbine housing 16 a and an exhaust pipe (exhaust gas passage) 18 communicate with each other, compressing fresh air sucked using the energy of the exhaust gas e discharged from the internal combustion engine 11, and Supply to the combustion chamber.
The exhaust pipe 18 is provided with a catalytic converter 22 having a built-in exhaust gas purification catalyst 20.

図２に示すように、排ガス浄化触媒２０は、担持基材２４と、担持基材２４の表面に形成された触媒担持層２６と、触媒担持層２６に担持される触媒活性成分（不図示）で構成される。
図示した実施形態では、担持基材２４はハニカム構造体を形成し、例えばコーディエライト製や金属箔製のハニカム構造体で構成される。 担持基材２４は１個の担持基材（例えばハニカム構造体）で構成される。担持基材２４の排ガス流れ方向上流側領域２８の触媒担持層２６は、担持基材２４の表面に近い下層３２と、下層３２より相対的に遠い上層３４とで構成される。上層３４の触媒活性主成分はＲｈを含むと共に、下層３２の触媒活性主成分はＰｄを含む。また、上層３４と下層３２は，Ａｌ２Ｏ３、ＺｒＯ２、ＴｉＯ２、ＣｅＯ２のうち少なくとも１つを含む触媒活性主のサポート材料で構成される。
担持基材２４の排ガス流れ方向下流側領域３０の触媒担持層３６が担持する触媒活性成分は、ＨＣ及びＮＯｘを吸着可能であり、かつＮＯｘを選択還元する材料（以下「ＳＣＲ材」とも言う。）、例えば、ゼオライト（結晶性アルミノケイ酸塩）やＶ（バナジウム）を触媒活性の主成分として担持する。ゼオライトとしては、様々な結晶構造を有する材料があるが、ここでは、ＮＨ３によるＮＯｘの選択還元作用を有する材料であればよい。また、Ｆｅ−ゼオライト、Ｃｕ−ゼオライトのように少なくとも１種類の遷移金属元素を含んでもよい。 As shown in FIG. 2, the exhaust gas purification catalyst 20 includes a support base 24, a catalyst support layer 26 formed on the surface of the support base 24, and a catalyst active component (not shown) supported on the catalyst support layer 26. Consists of.
In the illustrated embodiment, the supporting substrate 24 forms a honeycomb structure, and is composed of, for example, a honeycomb structure made of cordierite or metal foil. The supporting substrate 24 is composed of one supporting substrate (for example, a honeycomb structure). The catalyst support layer 26 in the upstream region 28 in the exhaust gas flow direction of the support base 24 is composed of a lower layer 32 close to the surface of the support base 24 and an upper layer 34 relatively far from the lower layer 32. The catalytically active main component of the upper layer 34 includes Rh, and the catalytically active main component of the lower layer 32 includes Pd. Further, the upper layer 34 and lower layer 32, Al 2 O 3, ZrO 2 , TiO 2, composed of a catalytically active main support material containing at least one of CeO 2.
The catalytically active component carried by the catalyst carrying layer 36 in the exhaust gas flow direction downstream region 30 of the carrying substrate 24 is capable of adsorbing HC and NOx, and is also referred to as a material that selectively reduces NOx (hereinafter also referred to as “SCR material”). ), For example, zeolite (crystalline aluminosilicate) or V (vanadium) is supported as a main component of catalytic activity. There are materials having various crystal structures as zeolite, but here, any material may be used as long as it has a selective reduction action of NOx by NH 3 . Moreover, you may contain at least 1 type of transition metal element like Fe-zeolite and Cu-zeolite.

排ガス中にＣＯ、ＨＣが存在すると、前記反応式（１）から（５）に示す反応によって、触媒層３４や触媒層３２でＮＨ３が生成する。
下流側領域３０の触媒担持層３６では、触媒層３４や触媒層３２で生成したＮＨ３と排ガス中に残存するＮＯｘとをＳＣＲ材で反応させ、ＮＯｘを選択還元する。また、ＳＣＲ材に吸着し、排ガス温度の上昇に伴って脱離するＮＯｘも、触媒層３４や触媒層３２で生成したＮＨ３でＮＯｘを選択還元する。
上流側領域２８では、上層３４に含まれるＲｈと下層３２に含まれるＰｄとでいわゆる三元触媒としての機能を有し、排ガス中のＨＣ及びＣＯを酸化し、かつＮＯｘを還元して無害なＮ２、ＣＯ２及びＨ２Ｏに変換する。 When CO and HC are present in the exhaust gas, NH 3 is generated in the catalyst layer 34 and the catalyst layer 32 by the reactions shown in the reaction formulas (1) to (5).
In the catalyst support layer 36 in the downstream region 30, NH 3 produced in the catalyst layer 34 and the catalyst layer 32 reacts with NOx remaining in the exhaust gas with the SCR material, and NOx is selectively reduced. In addition, NOx adsorbed on the SCR material and desorbed as the exhaust gas temperature rises selectively reduces NOx with NH 3 generated in the catalyst layer 34 and the catalyst layer 32.
In the upstream region 28, Rh contained in the upper layer 34 and Pd contained in the lower layer 32 have a function as a so-called three-way catalyst, oxidize HC and CO in the exhaust gas, and reduce NOx to be harmless. Convert to N 2 , CO 2 and H 2 O.

例示的な実施形態では、図２及び図３に示すように、上流側領域２８と下流側領域３０との間に、触媒担持層２６が上層３４のみで構成された排ガス流れ方向中間領域３１を有する。例えば、上流側領域２８、中間領域３１及び下流側領域３０は、排ガス流れ方向へ１／３ずつの領域を形成する。
例示的な実施形態では、上流側領域２８及び中間領域３１に配置される上層３４は、触媒活性成分として担持基材２４の容積１リットル当たり０．１〜２．０ｇのＲｈを含み、上流側領域２８の下層３２は、触媒活性成分として担持基材２４の容積１リットル当たり１〜１５ｇのＰｄを含む。
例示的な実施形態では、下層３２の触媒活性成分はさらに助触媒として酸素吸蔵及び放出能を有する触媒用酸素吸蔵材料（以下「ＯＳＣ材」とも言う。）を含む。ＯＳＣ材は、例えば、ＣｅＯ２やＣｅＯ２−ＺｒＯ２を主成分とする複合酸化物などで構成される。
例示的な実施形態では、下層３２は担持基材２４の容積１リットル当たり１〜８０ｇのＯＳＣ材をさらに含む。
なお、上層３４にはＰｔ、Ｐｄ、ＯＳＣ材を添加してもよく、下層３２にはＲｈ、Ｐｔを添加してもよい。さらに、下層３２にＨＣの吸着量を高めるための材料，例えばゼオライトを添加してもよい。 In the exemplary embodiment, as shown in FIGS. 2 and 3, an exhaust gas flow direction intermediate region 31 in which the catalyst support layer 26 is composed only of the upper layer 34 is provided between the upstream region 28 and the downstream region 30. Have. For example, the upstream region 28, the intermediate region 31, and the downstream region 30 form one-third regions in the exhaust gas flow direction.
In the exemplary embodiment, the upper layer 34 disposed in the upstream region 28 and the intermediate region 31 includes 0.1 to 2.0 g of Rh per liter of the support substrate 24 as a catalytically active component. The lower layer 32 of the region 28 contains 1 to 15 g of Pd per liter of the volume of the support 24 as a catalytic active component.
In the exemplary embodiment, the catalytically active component of the lower layer 32 further includes a catalyst oxygen storage material (hereinafter also referred to as “OSC material”) having oxygen storage and release capability as a co-catalyst. The OSC material is composed of, for example, a composite oxide mainly composed of CeO 2 or CeO 2 —ZrO 2 .
In the exemplary embodiment, lower layer 32 further comprises 1-80 g of OSC material per liter of support substrate 24 volume.
Note that Pt, Pd, and OSC materials may be added to the upper layer 34, and Rh and Pt may be added to the lower layer 32. Further, a material for increasing the adsorption amount of HC, such as zeolite, may be added to the lower layer 32.

例示的な実施形態では、下流側領域３０の触媒活性成分は、担持基材２４の容積１リットル当たり２０〜３００ｇのＳＣＲ材を含む。
例示的な実施形態では、図１及び図２に示すように、下流側領域３０の触媒担持層２６に担持されたＳＣＲ材に吸着したＨＣ及びＮＯｘが排ガス温度の上昇に伴って脱離する工程で、内燃機関１１をリッチ燃焼に制御するための制御装置４０をさらに備える。
制御装置４０によって、ＳＣＲ材に吸着したＨＣ及びＮＯｘが脱離を開始する工程で、内燃機関１１をリッチ燃焼に制御し、排ガス中のＣＯ量やＨＣ量を増やす。これによって、上記反応式（１）〜（５）に示す反応が行われ、下流側領域３０の排ガス中に含まれるＮＨ３量が増え、ＮＨ３と排ガス中のＮＯｘとの還元反応を促進できる。 In the exemplary embodiment, the catalytically active component in the downstream region 30 comprises 20-300 g SCR material per liter volume of the support substrate 24.
In the exemplary embodiment, as shown in FIGS. 1 and 2, HC and NOx adsorbed on the SCR material supported on the catalyst support layer 26 in the downstream region 30 are desorbed as the exhaust gas temperature increases. The control device 40 for controlling the internal combustion engine 11 to rich combustion is further provided.
In the process in which HC and NOx adsorbed on the SCR material start to be desorbed by the control device 40, the internal combustion engine 11 is controlled to rich combustion, and the amount of CO and HC in the exhaust gas is increased. Thereby, the reactions shown in the above reaction formulas (1) to (5) are performed, the amount of NH 3 contained in the exhaust gas in the downstream region 30 is increased, and the reduction reaction between NH 3 and NOx in the exhaust gas can be promoted. .

例示的な実施形態では、図１及び図２に示すように、排ガス浄化触媒２０の温度を検出するための温度センサ４２をさらに備え、制御装置４０は、温度センサ４２の検出値が閾値を超えた時、ＨＣ及びＮＯｘの脱離工程が開始されたと判定し、内燃機関１１をリッチ燃焼に制御する。
図１に示した実施形態では、触媒コンバータ２２の内部で排ガス浄化触媒２０の入口に温度センサ４２が設けられ、制御装置４０は温度センサ４２の検出値が閾値を超えた時、ＨＣ及びＮＯｘの脱離工程が開始されたと判定し、内燃機関１１をリッチ燃焼に制御する。 In the exemplary embodiment, as shown in FIGS. 1 and 2, a temperature sensor 42 for detecting the temperature of the exhaust gas purification catalyst 20 is further provided, and the control device 40 has a detection value of the temperature sensor 42 exceeding a threshold value. When it is determined that the HC and NOx desorption process has started, the internal combustion engine 11 is controlled to rich combustion.
In the embodiment shown in FIG. 1, a temperature sensor 42 is provided at the inlet of the exhaust gas purification catalyst 20 inside the catalytic converter 22. When the detected value of the temperature sensor 42 exceeds a threshold value, the control device 40 detects HC and NOx. It is determined that the desorption process has started, and the internal combustion engine 11 is controlled to rich combustion.

図４は内燃機関１１の稼動開始からの排ガス浄化プロセスを示し、横軸は稼動開始からの時間を示している。図４において、内燃機関１１の稼動開始と共に下流側領域３０の触媒層３６でＨＣ及びＮＯｘの吸着工程が始まり、その後、排ガス浄化触媒２０が閾値温度Ｔ１（例えば１５０℃）を超えると、ＨＣ及びＮＯｘが触媒層３６から脱離する脱離工程が始まる。この脱離行程中のＨＣ、ＮＯｘが最も多く排出されるタイミングに空燃比をリッチ化することで，上流の触媒層３４と触媒層３２でより多くのＮＨ３が生成されるので，触媒層３６から脱離したＮＯｘの浄化効率が高まる。
図５は、内燃機関１１の稼動開始から数十秒後の触媒内部の温度を示している。図５から、稼動初期には、触媒担体の熱容量の影響で、触媒担体の入口領域と出口領域との間に大きな温度勾配を生じる。したがって、ＨＣ、ＣＯ、ＮＯｘが極めて多く排出される触媒の昇温過程においては、触媒担体の入口領域に触媒活性成分を高密度に担持することが排ガス低減に有効であることがわかる。
図６は、貴金属（ＰＧＭ）、触媒入口温度及び貴金属担持量に対する総ＨＣ量の浄化効率を示し、数値は貴金属担持量を示している。図６から、貴金属担持量が多く、かつ触媒温度が高いほど、触媒活性が優れる。したがって、ＨＣ、ＣＯ、ＮＯｘが極めて多く排出される触媒の昇温過程においては、排ガス浄化効率を高めるには、触媒活性主である貴金属の担持量を増大することが排ガス低減に有効であることがわかる。 FIG. 4 shows the exhaust gas purification process from the start of operation of the internal combustion engine 11, and the horizontal axis shows the time from the start of operation. In FIG. 4, the HC and NOx adsorption process starts in the catalyst layer 36 in the downstream region 30 as the internal combustion engine 11 starts to operate. Thereafter, when the exhaust gas purification catalyst 20 exceeds a threshold temperature T 1 (for example, 150 ° C.), the HC And the desorption process in which NOx desorbs from the catalyst layer 36 starts. By enriching the air-fuel ratio at the timing when the most HC and NOx are discharged during this desorption process, more NH 3 is generated in the upstream catalyst layer 34 and the catalyst layer 32, so the catalyst layer 36 The purification efficiency of NOx desorbed from the catalyst increases.
FIG. 5 shows the temperature inside the catalyst several tens of seconds after the start of operation of the internal combustion engine 11. From FIG. 5, at the initial stage of operation, a large temperature gradient is generated between the inlet region and the outlet region of the catalyst carrier due to the influence of the heat capacity of the catalyst carrier. Therefore, it can be seen that, in the process of raising the temperature of the catalyst from which a large amount of HC, CO, and NOx is discharged, it is effective in reducing exhaust gas to carry the catalyst active component at a high density in the inlet region of the catalyst carrier.
FIG. 6 shows the purification efficiency of the total HC amount with respect to the noble metal (PGM), the catalyst inlet temperature, and the noble metal loading, and the numerical value indicates the noble metal loading. From FIG. 6, the catalytic activity is excellent as the amount of noble metal supported is large and the catalyst temperature is high. Therefore, in the process of raising the temperature of a catalyst that discharges a very large amount of HC, CO, and NOx, increasing the amount of noble metal supported, which is the main catalyst activity, is effective in reducing exhaust gas in order to increase the exhaust gas purification efficiency. I understand.

幾つかの実施形態によれば、図２及び図３に示すように、下流側領域３０の触媒活性成分であるＳＣＲ材により、上流側領域２８と３１で生成したＮＨ３で残存するＮＯｘを選択還元すると共に、ＳＣＲ材から脱離するＮＯｘも、上流側領域２８と３１で生成されたＮＨ３でＮＯｘの選択還元をさらに促進できるため、ＮＯｘの浄化率を向上できる。
また、上流側領域２８では、いわゆる三元触媒としての機能を有し、排ガス中のＨＣ、ＣＯ及びＮＯｘを低減できる。上層３４に貴金属のなかで担持量当たりの触媒活性が最も優れるＲｈを担持し、下層３２に比較的安価なＰｄを担持することで、排ガス浄化性能を高く維持しつつ触媒コストを抑えることができる。
また、ＲｈやＰｄ等の貴金属を担持した上層３４及び下層３２を積層させることで、上記反応式（１）〜（５）によりＮＨ３が多く生成され、ここで生成されたＮＨ３がＮＯｘの還元浄化に寄与すると共に、このＮＨ３生成反応も触媒コストを抑えた上で効率良く進行する。 According to some embodiments, as shown in FIGS. 2 and 3 , the NOx remaining in the NH 3 generated in the upstream regions 28 and 31 is selected by the SCR material that is the catalytically active component in the downstream region 30. In addition to reduction, NOx desorbed from the SCR material can further promote selective reduction of NOx by NH 3 produced in the upstream regions 28 and 31, and therefore the NOx purification rate can be improved.
Further, the upstream region 28 has a function as a so-called three-way catalyst, and can reduce HC, CO and NOx in the exhaust gas. By carrying Rh having the highest catalytic activity per loading amount among the noble metals on the upper layer 34 and carrying relatively inexpensive Pd on the lower layer 32, the catalyst cost can be suppressed while maintaining high exhaust gas purification performance. .
Further, by laminating the upper layer 34 and the lower layer 32 supporting a noble metal such as Rh or Pd, a large amount of NH 3 is generated according to the reaction formulas (1) to (5), and the generated NH 3 is NOx. In addition to contributing to reduction and purification, this NH 3 generation reaction also proceeds efficiently while suppressing catalyst costs.

これによって、排ガス浄化触媒２０は、多種の排ガス浄化機能に対応しつつ１個の担持基材２４で構成することができ、浄化システム全体の構成を簡素化できる。そのため、触媒コストを削減できると共に、排ガスの圧力損失を低減できるので、内燃機関の性能低下を抑制できる。
さらに、排ガス浄化性能が向上することで、触媒担持層２６の膜厚を低減できるので、排ガスの圧力損失をさらに低減できると共に、触媒担持層２６のコーティング作業が容易になる。特に、担持基材２４がハニカム構造体である場合、触媒担持層２６の膜厚低減は排ガスの圧力損失を大幅に低減すると共に、触媒担持層２６のコーティング作業を飛躍的に制限する。 As a result, the exhaust gas purification catalyst 20 can be composed of a single supporting substrate 24 while supporting various exhaust gas purification functions, and the configuration of the entire purification system can be simplified. Therefore, the catalyst cost can be reduced and the pressure loss of the exhaust gas can be reduced, so that the performance deterioration of the internal combustion engine can be suppressed.
Furthermore, since the exhaust gas purification performance is improved, the film thickness of the catalyst support layer 26 can be reduced, so that the pressure loss of the exhaust gas can be further reduced and the coating operation of the catalyst support layer 26 is facilitated. In particular, when the supporting substrate 24 has a honeycomb structure, the reduction of the film thickness of the catalyst supporting layer 26 greatly reduces the pressure loss of the exhaust gas and drastically limits the coating operation of the catalyst supporting layer 26.

例示的な実施形態によれば、高い排ガス温度下で大きな排ガス浄化効果が見込める上流側領域２８では下層３２を設けて、高い排ガス浄化性能を保持しつつ、上流側領域２８より排ガス温度が低下し上流側領域２８ほど排ガス浄化効果が得られない中間領域３１では下層３２を無くすことで、排ガス浄化性能を維持しつつ触媒コストをさらに節減できる。
また、例示的な実施形態によれば、下層３２の触媒活性成分としてさらにＯＳＣ材を含めることで、空燃比が変動しても空燃比の変動に対応して高い排ガス浄化効果を維持できる。 According to the exemplary embodiment, in the upstream region 28 where a large exhaust gas purification effect can be expected at a high exhaust gas temperature, the lower layer 32 is provided, and the exhaust gas temperature is lower than that in the upstream region 28 while maintaining high exhaust gas purification performance. By eliminating the lower layer 32 in the intermediate region 31 where the exhaust gas purification effect cannot be obtained as much as the upstream region 28, the catalyst cost can be further reduced while maintaining the exhaust gas purification performance.
Further, according to the exemplary embodiment, by including the OSC material as the catalytic active component of the lower layer 32, even if the air-fuel ratio varies, a high exhaust gas purification effect can be maintained corresponding to the variation of the air-fuel ratio.

例示的な実施形態によれば、上層３４に含まれるＲｈを０．１〜２．０ｇ／Ｌ（担持基材２４の容積）とし、下層３２に含まれるＰｄを１〜１５ｇ／Ｌ（担持基材２４の容積）とし、下層３２に含まれるＯＳＣ材を１〜８０ｇ／Ｌ（担持基材２４の容積）としたことで、高い排ガス浄化効果を可能にすると共に、これら触媒活性成分及び助触媒の含有量を少なく抑えることができるので、触媒担持層２６の膜厚を低減できる。これによって、排ガスの圧力損失を抑制できると共に、触媒担持層２６のコーティングを省力化できる。
例示的な実施形態によれば、下流側領域３０の触媒担持層２６に含まれるＳＣＲ材を２０〜３００ｇ／Ｌ（担持基材２４の容積）としたことで、高い排ガス浄化効果を可能にすると共に、これら触媒活性成分及び助触媒の含有量を少なく抑えることができるので、触媒担持層２６の膜厚を低減できる。これによって、排ガスの圧力損失を抑制できると共に、触媒担持層２６のコーティングを省力化できる。 According to the exemplary embodiment, Rh contained in the upper layer 34 is 0.1 to 2.0 g / L (volume of the supporting substrate 24), and Pd contained in the lower layer 32 is 1 to 15 g / L (supporting group). The volume of the material 24) and the OSC material contained in the lower layer 32 are 1 to 80 g / L (volume of the supporting substrate 24), thereby enabling a high exhaust gas purification effect, and these catalytically active components and promoters. Therefore, the film thickness of the catalyst support layer 26 can be reduced. Thereby, the pressure loss of the exhaust gas can be suppressed and the coating of the catalyst support layer 26 can be saved.
According to the exemplary embodiment, the SCR material contained in the catalyst support layer 26 in the downstream region 30 is set to 20 to 300 g / L (volume of the support substrate 24), thereby enabling a high exhaust gas purification effect. At the same time, the contents of the catalytically active component and the cocatalyst can be suppressed to be small, so that the thickness of the catalyst supporting layer 26 can be reduced. Thereby, the pressure loss of the exhaust gas can be suppressed and the coating of the catalyst support layer 26 can be saved.

例示的な実施形態によれば、図１及び図２に示すように、制御装置４０によって、ＳＣＲ材に吸着したＨＣ及びＮＯｘが脱離を開始する工程で、内燃機関１１をリッチ燃焼に制御し、排ガス中のＣＯ量やＨＣ量を増やす。これによって、上記反応式（１）〜（５）に示す反応が行われ、ＮＨ３量が増え、ＮＨ３と排ガス中のＮＯｘとの還元反応を促進できるため、排ガス中のＮＯｘの浄化率を向上できる。
例示的な実施形態によれば、図１及び図２に示すように、制御装置４０によって温度センサ４２の検出値が閾値Ｔ１を超えた時をもって、下流側領域３０でＨＣ及びＮＯｘの脱離工程が開始されたか否かを判定するので、脱離工程の開始時期を正確に判定できる。 According to the exemplary embodiment, as shown in FIGS. 1 and 2, the control device 40 controls the internal combustion engine 11 to rich combustion in the process of starting desorption of HC and NOx adsorbed on the SCR material. Increase the amount of CO and HC in the exhaust gas. As a result, the reactions shown in the above reaction formulas (1) to (5) are performed, the amount of NH 3 increases, and the reduction reaction between NH 3 and NOx in the exhaust gas can be promoted. It can be improved.
According to the exemplary embodiment, as shown in FIGS. 1 and 2, HC and NOx are desorbed in the downstream region 30 when the detected value of the temperature sensor 42 exceeds the threshold value T 1 by the control device 40. Since it is determined whether or not the process has been started, the start time of the desorption process can be accurately determined.

上記実施形態では、触媒層３４や触媒層３２で生成するＮＨ３を用いて、触媒層３４や触媒層３２で浄化できなかったＮＯｘを選択還元浄化しているが、排ガス通路の外部からＮＨ３を供給するようにしてもよい。例えば、排ガス浄化触媒２０の排気管１８に外部から尿素水溶液などを噴霧するようにしてもよい。 In the above-described embodiment, NH 3 generated in the catalyst layer 34 and the catalyst layer 32 is used to selectively reduce and purify NOx that could not be purified by the catalyst layer 34 and the catalyst layer 32, but NH 3 from the outside of the exhaust gas passage. May be supplied. For example, an aqueous urea solution or the like may be sprayed from the outside onto the exhaust pipe 18 of the exhaust gas purification catalyst 20.

本発明の少なくとも一実施形態によれば、内燃機関の排ガス通路を流れる排ガスの圧力損失を低減して内燃機関の効率を向上できると共に、触媒コストを削減できる。   According to at least one embodiment of the present invention, the pressure loss of the exhaust gas flowing through the exhaust gas passage of the internal combustion engine can be reduced to improve the efficiency of the internal combustion engine, and the catalyst cost can be reduced.

１０ 排ガス浄化システム
１１ 内燃機関
１２ 排気ポート
１４ 排気マニフォールド
１６ 排気過給機
１６ａ タービンハウジング
１８ 排気管
２０ 排ガス浄化触媒
２２ 触媒コンバータ
２４ 担持基材
２６、３６ 触媒担持層
２８ 排ガス流れ方向上流側領域
３０ 排ガス流れ方向下流側領域
３１ 排ガス流れ方向中間領域
３２ 下層
３４ 上層
４０ 制御装置
４２ 温度センサ
ｅ 排ガス DESCRIPTION OF SYMBOLS 10 Exhaust gas purification system 11 Internal combustion engine 12 Exhaust port 14 Exhaust manifold 16 Exhaust supercharger 16a Turbine housing 18 Exhaust pipe 20 Exhaust gas purification catalyst 22 Catalytic converter 24 Support base material 26, 36 Catalyst support layer 28 Exhaust gas flow direction upstream area 30 Exhaust gas Flow direction downstream side 31 Exhaust gas flow direction intermediate region 32 Lower layer 34 Upper layer 40 Control device 42 Temperature sensor e Exhaust gas

Claims (7)

排ガス通路に、担持基材と、該担持基材の表面に形成された触媒担持層と、該触媒担持層に担持された触媒活性成分とで構成され排ガス浄化触媒を備えた内燃機関の排ガス浄化システムであって、
前記排ガス浄化触媒は１個の前記担持基材で構成され、
前記担持基材の排ガス流れ方向上流側領域の前記触媒担持層は、前記担持基材の表面に近い下層と該下層より相対的に遠い上層とで構成され、
前記上層の前記触媒活性成分はＲｈを含むと共に、前記下層の前記触媒活性成分はＰｄを含み、
該担持基材の排ガス流れ方向下流側領域の前記触媒活性成分は、ＨＣ及びＮＯｘを吸着可能であり、かつＮＯｘを選択還元する材料を含むことを特徴とする内燃機関の排ガス浄化システム。 Exhaust gas purification of an internal combustion engine provided with an exhaust gas purification catalyst, which is composed of a supporting substrate, a catalyst supporting layer formed on the surface of the supporting substrate, and a catalytically active component supported on the catalyst supporting layer in an exhaust gas passage A system,
The exhaust gas purification catalyst is composed of one supporting substrate,
The catalyst support layer in the upstream region in the exhaust gas flow direction of the support substrate is composed of a lower layer close to the surface of the support substrate and an upper layer relatively far from the lower layer,
The catalytically active component of the upper layer contains Rh, and the catalytically active component of the lower layer contains Pd,
The exhaust gas purification system for an internal combustion engine, wherein the catalytically active component in the downstream region in the exhaust gas flow direction of the supporting base material includes a material capable of adsorbing HC and NOx and selectively reducing NOx. 前記排ガス流れ上流側領域と前記排ガス流れ方向下流側領域との間に、前記触媒担持層が前記上層のみで構成された排ガス流れ方向中間領域を有することを特徴とする請求項１に記載の内燃機関の排ガス浄化システム。   2. The internal combustion engine according to claim 1, wherein the catalyst support layer has an intermediate region in the exhaust gas flow direction constituted by only the upper layer between the exhaust gas flow upstream region and the exhaust gas flow direction downstream region. Engine exhaust gas purification system. 前記下層はさらに助触媒として触媒用酸素吸蔵材料を含むことを特徴とする請求項１又は２に記載の内燃機関の排ガス浄化システム。   The exhaust gas purification system for an internal combustion engine according to claim 1 or 2, wherein the lower layer further includes a catalyst oxygen storage material as a promoter. 前記担持基材の排ガス流れ方向下流側領域に含まれる前記触媒活性成分が吸着したＨＣ及びＮＯｘを脱離させる工程で、内燃機関をリッチ燃焼に制御するための制御装置をさらに備えることを特徴とする請求項１乃至３の何れか１項に記載の内燃機関の排ガス浄化システム。   A control device for controlling the internal combustion engine to rich combustion in the step of desorbing HC and NOx adsorbed by the catalytically active component contained in the downstream region of the support base material in the exhaust gas flow direction; The exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 3. 前記排ガス浄化触媒の温度を検出するための温度センサをさらに備え、
前記制御装置は、前記温度センサの検出値が閾値を超えた時、ＨＣ及びＮＯｘの脱離工程が開始されたと判定し、前記内燃機関をリッチ燃焼に制御することを特徴とする請求項４に記載の内燃機関の排ガス浄化システム。 A temperature sensor for detecting the temperature of the exhaust gas purification catalyst;
5. The control device according to claim 4, wherein when the detected value of the temperature sensor exceeds a threshold value, the control device determines that the HC and NOx desorption process has started and controls the internal combustion engine to rich combustion. An exhaust gas purification system for an internal combustion engine as described. 担持基材と、該担持基材の表面に形成された触媒担持層と、該触媒担持層に担持された触媒活性成分とで構成された排ガス浄化触媒において、
前記排ガス浄化触媒は１個の前記担持基材で構成され、
該担持基材の排ガス流れ方向上流側領域の前記触媒担持層は、前記担持基材の表面に近い下層と該下層より相対的に遠い上層とで構成され、
前記上層の前記触媒活性成分はＲｈを含むと共に、前記下層の前記触媒活性成分はＰｄ及び触媒用酸素吸蔵材料を含み、
該担持基材の排ガス流れ方向下流側領域の前記触媒活性成分は、ＨＣ及びＮＯｘを吸着可能であり、かつＮＯｘを選択還元する材料を含むことを特徴とする排ガス浄化触媒。 In an exhaust gas purification catalyst comprising a supporting substrate, a catalyst supporting layer formed on the surface of the supporting substrate, and a catalytically active component supported on the catalyst supporting layer,
The exhaust gas purification catalyst is composed of one supporting substrate,
The catalyst-carrying layer in the upstream region in the exhaust gas flow direction of the carrying substrate is composed of a lower layer close to the surface of the carrying substrate and an upper layer relatively far from the lower layer,
The catalytically active component of the upper layer contains Rh, and the catalytically active component of the lower layer contains Pd and a catalyst oxygen storage material,
An exhaust gas purifying catalyst characterized in that the catalytically active component in the downstream region in the exhaust gas flow direction of the supporting substrate contains a material capable of adsorbing HC and NOx and selectively reducing NOx. 前記排ガス流れ上流側領域と前記排ガス流れ方向下流側領域との間に、前記触媒担持層が前記上層のみで構成された排ガス流れ方向中間領域を有することを特徴とする請求項６に記載の排ガス浄化触媒。   The exhaust gas according to claim 6, wherein the catalyst supporting layer has an intermediate region in the exhaust gas flow direction constituted by only the upper layer between the exhaust gas flow upstream region and the exhaust gas flow direction downstream region. Purification catalyst.
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CN111495063A (en) * 2019-01-31 2020-08-07 广州汽车集团股份有限公司 Air filter

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111495063A (en) * 2019-01-31 2020-08-07 广州汽车集团股份有限公司 Air filter
CN111495063B (en) * 2019-01-31 2021-08-31 广州汽车集团股份有限公司 Fuel cell power system air filter

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