JP3603328B2 - Exhaust gas purification device - Google Patents

Exhaust gas purification device Download PDF

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Publication number
JP3603328B2
JP3603328B2 JP08791094A JP8791094A JP3603328B2 JP 3603328 B2 JP3603328 B2 JP 3603328B2 JP 08791094 A JP08791094 A JP 08791094A JP 8791094 A JP8791094 A JP 8791094A JP 3603328 B2 JP3603328 B2 JP 3603328B2
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Prior art keywords
way catalyst
exhaust gas
stage
catalyst
adsorbent
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JPH07144119A (en
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敏嗣 上岡
啓司 山田
康人 渡辺
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Mazda Motor Corp
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Mazda Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/18—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an adsorber or absorber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/12—Hydrocarbons
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

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  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)

Description

【０００１】
【産業上の利用分野】
この発明は、例えば、エンジンの排気ポートより排出されるＨＣ（炭化水素）、ＣＯ（一酸化炭素）、ＮＯｘ（窒素酸化物）の有害ガスを浄化するような排気ガス浄化装置に関する。
【０００２】
【従来の技術】
従来、上述例の排気ガス浄化装置としては、例えば特開平２−１３５１２６号公報に記載の装置がある。
すなわち、図６に示すようにエンジンの排気系に介設された排気ガス浄化装置８０であって、排気上流側にはＨＣ吸着剤８１を収納したＨＣトラッパ８２を設けると共に、排気下流側に三元触媒８３を収納した触媒コンバータ８４を配設した排気ガス浄化装置である。
【０００３】
この従来装置においては次のような問題点があった。つまり、上述のＨＣ吸着剤８１は排気ガス中のＨＣ（Hydrocarbon 、炭化水素）を吸着するが、このＨＣ吸着剤８１の特性として約１５０〜２００℃の温度条件下においてＨＣ吸着剤８１で一旦吸着したＨＣが放出される一方、後段の三元触媒８３（three-way catalyst、ＴＷＣ）が活性化温度に達するのは約２５０℃であるため、特にエンジンの冷間時においては良好なＨＣの浄化ができず、排気ガス浄化装置８０からＨＣが放出される問題点があった。
【０００４】
【発明が解決しようとする課題】
この発明は、前段にＰｔとＲｈとを触媒金属として含む三元触媒を、後段にＨＣ吸着剤とＰｄを触媒金属として含む三元触媒との複合触媒をそれぞれ配設し、前段の三元触媒は後段の三元触媒よりも活性化温度が高い一方で、前段の三元触媒は後段の三元触媒よりも熱容量が同じか、または、それ以下にされていることにより、両三元触媒をほぼ同時に活性化するように設定することで、三元触媒を通過して温度低下させた排気ガスをＨＣ吸着剤に導くことによりＨＣ吸着効果の向上を図り（ＨＣ吸着剤は低温時ほど吸着効果が向上する）、さらに三元触媒がライトオフ（活性化）することで未燃ＨＣが燃焼して、三元触媒の温度が上昇し、この温度が後段のＨＣ吸着剤に伝熱することにより、吸着したＨＣの略全部を燃焼させて、ＨＣ浄化率の大幅な向上を図ることができ、かつ車両に対する搭載性（実車搭載性）の向上を図ることができる排気ガス浄化装置の提供を目的とする。
【０００５】
【課題を解決するための手段】
この発明による排気ガス浄化装置は、エンジンの排気系に介設される排気ガス浄化装置であって、１つの触媒コンバータ内において、排気上流側となる前段に
ＰｔとＲｈとを触媒金属として含む三元触媒を配設し、排気下流側となる後段に排気ガス中のＨＣを吸着するＨＣ吸着剤とＰｄを触媒金属として含む三元触媒とが複合された複合触媒を配設すると共に、上記前段の三元触媒は上記後段の三元触媒よりも活性化温度が高い一方で、上記前段の三元触媒は上記後段の三元触媒よりも熱容量が同じか、または、それ以下にされていることにより、該両三元触媒を略同時に活性化するように設定されているものである。
【０００６】
【発明の効果】
この発明によれば、１つの触媒コンバータ内において、排気上流側となる前段にＰｔとＲｈとを触媒金属として含む三元触媒（いわゆるＴＷＣ）を、後段にＨＣ吸着剤とＰｄを触媒金属として含む三元触媒との複合触媒をそれぞれ配設したので、次のような効果がある。
すなわち、排気ガスはまず前段の三元触媒を通過し、この前段の三元触媒で熱が奪われて冷やされた後に、後段のＨＣ吸着剤に導かれるので、ＨＣ吸着剤によるＨＣ吸着効率が向上する。
また前段の三元触媒がライトオフすることで、未燃ＨＣが燃焼して、この前段の三元触媒の温度が上昇し、この温度が後段のＨＣ吸着剤と三元触媒との複合触媒に伝熱することにより、吸着したＨＣの略全部を後段側において燃焼させるので、ＨＣ浄化率の大幅な向上を図ることができる効果がある。
【０００７】
また上記前段の三元触媒は上記後段の三元触媒よりも活性化温度が高い一方で、上記前段の三元触媒は後段の三元触媒よりも熱容量が同じか、または、それ以下にされていることにより、両三元触媒をほぼ同時に活性化するように設定したので、前後各段の三元触媒を略同時に活性化させて、後段のＨＣ吸着剤で吸着させたＨＣを効率よく燃焼除去して、ＨＣ浄化率の向上を図ることができる効果がある。
【０００８】
さらに、前段の触媒にＰｔとＲｈとを触媒金属として含む三元触媒を用い、後段の触媒にＰｄを触媒金属として含む三元触媒を用いたので、これら各触媒のライトオフ温度の差異により前後両段の触媒を略同時に活性化させることができる。
【０００９】
【実施例】
この発明の一実施例を以下図面に基づいて詳述する。
図面はエンジンの排気系に介設される排気ガス浄化装置を示し、図１において、排気ガス浄化装置としての触媒コンバータ１は、車両のアンダフロア位置に配設されると共に、この触媒コンバータ１は前後両端に接合フランジ部２，３を備え、排気ガス入口４にコーン部５を介してキャタリストケース６の前端側を接続し、このキャタリストケース６の後端側はコーン部７を介して排気ガス出口８に接続している。
【００１０】
上述のキャタリストケース６内の排気上流側となる前段にはＰｔとＲｈとを触媒金属として含む三元触媒９を配設し、排気下流側となる後段にはＨＣ吸着剤とＰｄを触媒金属として含む三元触媒とが複合された複合触媒１０を配設している。
【００１１】
上述の前段の三元触媒９はＭｇ２Ａｌ４Ｓｉ５Ｏ１８（cordierite、コージェライト）製ハニカム担体に、ライトオフ温度約３００℃のＰｔ−Ｒｈ系三元触媒（白金・ロジウム系三元触媒）を、Ｐｔ：Ｒｈ＝５：１、担持量１．６ｇ／リッタの条件下にγーＡｌ２Ｏ３(ガンマ・アルミナ)粉末を介して担持させている。
【００１２】
一方、後段の複合触媒１０のうちのＨＣ吸着剤としては、ケイバン比２００のＭＦＩ（例えばＺＳＭ５ゼオライト）を担持量２００ｇ／リッタとし、三元触媒としては、ライトオフ温度２５０℃のＰｄ系三元触媒（パラジウム系三元触媒）を担持量６ｇ／リッタとして、コージェライト製ハニカム担体にγ−Ａｌ２Ｏ３粉末を介して担持させている。なおコンテナ容量は前段を１リッタ、後段を１．３リッタとし、合計２．３リッタに設定している。また前段容量対後段容量の比率は２：８〜５：５が適当であり、総容量は１リッタ以上が望ましい。なお、上述のケイバン比とはＳｉＯ２/Ａｌ２Ｏ３のことである。
【００１３】
つまり、前段のＰｔ−Ｒｈ系三元触媒９の活性化温度（約３００℃）を後段のＰｄ系三元触媒の活性化温度（約２５０℃）に対して高温に設定している。ここで、上述の前後段の各触媒９，１０は図２に示すように間隔を隔ててキャタリストケース６内に配置してもよい。
【００１４】
このように構成した実施例の触媒コンバータ１と、比較例１〜４の触媒コンバータとを、Ｖ型６気筒２．５リッタエンジンを搭載した車両に取付け、ＦＴＰモード（ＣＶＳ４モードと同意で米国標準走行モードのこと）中のＹ１モードを実車走行テストし、触媒コンバータ前後のＨＣ排出量を測定した後に、ＨＣ浄化率を算出した測定結果を、次の［表１］に示す。
また上記実施例のＹ１モーダルチャートを図３に、比較例１（次表参照）のＹ１モーダルチャートを図４にそれぞれ示す。
【００１５】
【表１】

Figure 0003603328
【００１６】
上述の表１から明らかなように、この実施例の触媒コンバータ１は比較例１〜４と比較して、ＨＣ浄化率が最も優れている。また図３（この実施例のＹ１モーダルチャート）と図４（比較例１のＹ１モーダルチャート）との対比から明らかなように、この実施例の触媒コンバータ１はエンジン冷間時におけるＨＣ浄化率（図３のハッチング部分参照）が大幅に向上している。
【００１７】
特に、比較例１（図４参照）においては時間０〜１００ｓｅｃの間においてＨＣ浄化率が皆無に近いが、この実施例（図３参照）においては時間０〜１００ｓｅｃの間において高いＨＣ浄化率を示した。
【００１８】
要するに、１つの触媒コンバータ１内において、排気上流側となる前段にＰｔとＲｈを触媒金属として含む三元触媒９（いわゆるＴＷＣ）を、排気下流側となる後段にＨＣ吸着剤とＰｄを触媒金属として含む三元触媒との複合触媒１０をそれぞれ配設したので、次のような効果がある。
すなわち、排気ガスはまず前段の三元触媒９を通過し、三元触媒９で熱が奪われて冷やされた後に、後段のＨＣ吸着剤に導かれるので、ＨＣ吸着剤によるＨＣ吸着効率が向上する。
また前段の三元触媒９がライトオフすることで、未燃ＨＣが燃焼して、この前段の三元触媒９の温度が上昇し、この温度が後段のＨＣ吸着剤と三元触媒との複合触媒１０に伝熱することにより、吸着したＨＣの略全部を後段側において燃焼させるので、ＨＣ浄化率の大幅な向上を図ることができる効果がある。
【００１９】
しかも、前段のＰｔ−Ｒｈ系三元触媒９の活性化温度を後段のＰｄ系三元触媒の活性化温度に対して高温に設定する一方で、前段の三元触媒９は後段の三元触媒よりも熱容量が同じか、または、それ以下に設定したので、次のような効果がある。つまり、排気ガスによる前後各段の温度上昇は前段側が早く、後段側が遅くなるが、上述の如く前段の三元触媒９の活性化温度を後段の三元触媒のそれに対して高く設定したので、前後各段の三元触媒が同時にライトオフして、活性化タイミングを一致させることができ、この結果、後段のＨＣ吸着剤で吸着させたＨＣを効率よく燃焼除去して、ＨＣ浄化率のより一層良好な向上を図ることができる効果がある。加えて、単一のキャタリストケース６内に前後各段の触媒９，１０を配置したので、車両に対する搭載性（実車搭載性）の向上を図ることができる。
【００２０】
因に、上述の比較例で示したように前段および後段共に同じ三元触媒を用いた場合には、前段の活性化温度と後段の活性化温度とが同一になって、排気ガスの流れにより前段の三元触媒が後段の三元触媒より早くライトオフするため、前段側においてＨＣ濃度が急激に低下して、後段側においては吸着ＨＣが何等浄化されることなく、放出されるが、この実施例では上記構成により吸着ＨＣを略全て燃焼除去することができる。
【００２１】
図５は排気ガス浄化装置としての触媒コンバータ１の他の実施例を示し、この実施例ではＰｔ−Ｒｈ系三元触媒９を配設した前段と、ＨＣ吸着剤およびＰｄ系三元触媒の複合触媒１０を配設した後段との間に、ＣｅＯ２（酸化セリウム）を担持させた担体１１を介設し、３段構造と成したものである。
【００２２】
このように構成すると、後段のＨＣ吸着剤に対して吸着ＨＣを燃焼除去するために必要なＯ２（酸素）を効率よく供給することができるので、吸着ＨＣのさらに良好な燃焼除去を達成することができる効果がある。なお、その他の点については図１、図２で示した先の実施例と同様の作用、効果を奏するので、図５において図１、図２と同一の部分には同一符号を付して、その詳しい説明を省略する。
【００２３】
なお、上記各実施例の他に次のような構成を用いてもよい。すなわち後段の担持構造としては上記実施例の構成に代えて、吸着剤粉末（たとえばＭＦＩ）上に貴金属（たとえばＰｄ）を担持させる簡略化構造であってもよい。
【００２４】
さらに上述の各三元触媒に対してＣｅＯ２（酸化セリウム）、ＢａＯ（酸化バリウム）、Ｎｉ（ニッケル）などの添加剤を添加してもよい。
【００２５】
さらに、またＨＣ吸着剤としてはＭＦＩに代えて、ＭＯＲ（モルデナイト）、ＦＡＵ（Ｙ型ゼオライト）、ＦＥＲ（フェリエライト）、ＣＨＡ（シャバサイト）を用いてもよい。
【図面の簡単な説明】
【図１】本発明の排気ガス浄化装置を示す断面図。
【図２】本発明の排気ガス浄化装置の他の実施例を示す断面図。
【図３】図１、図２に示す本発明の排気ガス浄化装置のＹ１モーダルチャート。
【図４】比較例のＹ１モーダルチャート。
【図５】本発明の排気ガス浄化装置のさらに他の実施例を示す断面図。
【図６】従来の排気ガス浄化装置を示す説明図。
【符号の説明】
１…触媒コンバータ
９…三元触媒
１０…複合触媒[0001]
[Industrial applications]
The present invention relates to an exhaust gas purifying apparatus that purifies harmful gases such as HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) discharged from an exhaust port of an engine.
[0002]
[Prior art]
Conventionally, as an exhaust gas purifying apparatus of the above-mentioned example, there is an apparatus described in, for example, Japanese Patent Application Laid-Open No. 2-135126.
That is, as shown in FIG. 6, an exhaust gas purifying device 80 provided in an exhaust system of an engine, in which an HC trapper 82 containing an HC adsorbent 81 is provided on the upstream side of the exhaust gas, and the HC trapper 82 is provided on the downstream side of the exhaust gas. This is an exhaust gas purification device provided with a catalytic converter 84 containing a main catalyst 83.
[0003]
This conventional apparatus has the following problems. That is, the above-mentioned HC adsorbent 81 adsorbs HC (Hydrocarbon, hydrocarbon) in the exhaust gas. As a characteristic of the HC adsorbent 81, it is once adsorbed by the HC adsorbent 81 under a temperature condition of about 150 to 200 ° C. The released three-way catalyst 83 (TWC) reaches the activation temperature at about 250 ° C. while the exhausted HC is released. Therefore, particularly when the engine is cold, good HC purification is achieved. However, there is a problem that HC is released from the exhaust gas purification device 80.
[0004]
[Problems to be solved by the invention]
According to the present invention, a three-way catalyst containing Pt and Rh as catalyst metals is provided in a first stage, and a composite catalyst of an HC adsorbent and a three-way catalyst containing Pd as a catalyst metal is provided in a second stage. by while activation temperature than the three-way catalyst in the subsequent stage is not high, the front stage of the three-way catalyst which has heat capacity than the subsequent stage of the three-way catalyst is equal to, or below it, both three-way catalyst Is set to be activated almost simultaneously, thereby improving the HC adsorption effect by guiding the exhaust gas, which has passed through the three-way catalyst and whose temperature has been lowered, to the HC adsorbent (the HC adsorbent is adsorbed at lower temperatures. And the three-way catalyst is lighted off (activated), which burns unburned HC and raises the temperature of the three-way catalyst, and this temperature is transferred to the subsequent HC adsorbent. By burning almost all of the adsorbed HC, It is possible to significantly improve, and an object of providing an exhaust gas purification device can be improved mountability (vehicle mountability) relative to the vehicle.
[0005]
[Means for Solving the Problems]
An exhaust gas purifying apparatus according to the present invention is an exhaust gas purifying apparatus interposed in an exhaust system of an engine, and is provided at a stage upstream of an exhaust gas upstream side in one catalytic converter.
A three-way catalyst containing Pt and Rh as catalyst metals was provided, and a HC adsorbent for adsorbing HC in exhaust gas and a three-way catalyst containing Pd as a catalyst metal were combined at a downstream stage downstream of exhaust gas. with disposing the composite catalyst, the front stage of the three-way catalyst whereas the activation temperature is not higher than the three-way catalyst of the subsequent stage, the previous stage of the three-way catalyst heat capacity equal than the three-way catalyst of the subsequent stage By setting it to be less than or equal to, the two-way catalysts are set to be activated substantially simultaneously.
[0006]
【The invention's effect】
According to the present invention, in one catalytic converter, a three-way catalyst (so-called TWC) containing Pt and Rh as catalytic metals is included in a preceding stage on the exhaust upstream side, and an HC adsorbent and Pd are included as catalytic metals in a subsequent stage. Since the composite catalyst with the three-way catalyst is provided, the following effects are obtained.
That is, the exhaust gas first passes through the former three-way catalyst, and after the heat is removed by the former three-way catalyst and cooled, the exhaust gas is guided to the latter HC adsorbent, so that the HC adsorption efficiency of the HC adsorbent is reduced. improves.
In addition, when the three-way catalyst in the first stage is turned off, unburned HC is burned, and the temperature of the three-way catalyst in the first stage rises, and this temperature becomes a combined catalyst of the HC adsorbent and the three-way catalyst in the second stage. By transferring the heat, substantially all of the adsorbed HC is burned in the subsequent stage, so that there is an effect that the HC purification rate can be significantly improved.
[0007]
The preceding-stage three-way catalyst whereas the activation temperature is not higher than the three-way catalyst of the subsequent stage, the previous stage of the three-way catalyst or heat capacity than the subsequent stage of the three-way catalyst is the same, or are in less As a result, both three-way catalysts are set to be activated almost at the same time.Thus, the three-way catalysts at the front and rear stages are activated almost at the same time, and the HC adsorbed by the HC adsorbent at the subsequent stage is efficiently burned. Removal has the effect of improving the HC purification rate.
[0008]
Further, a three-way catalyst containing Pt and Rh as catalyst metals was used for the first-stage catalyst, and a three-way catalyst containing Pd as the catalyst metal was used for the second-stage catalyst. The catalysts in both stages can be activated almost simultaneously.
[0009]
【Example】
An embodiment of the present invention will be described below in detail with reference to the drawings.
The drawing shows an exhaust gas purifying device provided in an exhaust system of an engine. In FIG. 1, a catalytic converter 1 as an exhaust gas purifying device is disposed at an underfloor position of a vehicle. The front and rear ends of the catalyst case 6 are connected to the exhaust gas inlet 4 via a cone portion 5, and the rear end side of the catalyst case 6 is connected to the exhaust gas inlet 4 via a cone portion 7. It is connected to the exhaust gas outlet 8.
[0010]
Three-way catalyst 9 is disposed, a stage subsequent to the exhaust downstream side HC adsorbent and Pd catalytic metal comprising Pt and Rh is in front as the exhaust upstream side of the catalytic converter casing 6 above as a catalyst metal And a three-way catalyst including the catalyst.
[0011]
The above-mentioned three-way catalyst 9 in the former stage is a Pt-Rh-based three-way catalyst (platinum-rhodium-based three-way catalyst) having a light-off temperature of about 300 ° C. on a honeycomb carrier made of Mg 2 Al 4 Si 5 O 18 (cordierite). ) Is supported via γ-Al 2 O 3 (gamma-alumina) powder under the conditions of Pt: Rh = 5: 1 and a supported amount of 1.6 g / liter.
[0012]
On the other hand, as the HC adsorbent of the latter composite catalyst 10, MFI (for example, ZSM5 zeolite) having a Caban ratio of 200 was used at a loading amount of 200 g / liter, and as the three-way catalyst, a Pd-based three-way A catalyst (palladium-based three-way catalyst) is supported on a cordierite honeycomb carrier at a supporting amount of 6 g / liter via γ-Al 2 O 3 powder. The container capacity is set to 1 liter in the former stage and 1.3 liters in the latter stage, and is set to a total of 2.3 liters. The ratio of the front-stage capacity to the rear-stage capacity is appropriately 2: 8 to 5: 5, and the total capacity is desirably 1 liter or more. Note that the silica-alumina ratio above is that the SiO 2 / Al 2 O 3.
[0013]
That is, the activation temperature (about 300 ° C.) of the former Pt-Rh three-way catalyst 9 is set to be higher than the activation temperature (about 250 ° C.) of the latter Pd-based three-way catalyst. Here, the catalysts 9 and 10 in the preceding and following stages may be arranged in the catalyst case 6 at an interval as shown in FIG.
[0014]
The catalytic converter 1 of the embodiment configured as described above and the catalytic converters of Comparative Examples 1 to 4 are mounted on a vehicle equipped with a V-type 6-cylinder 2.5-liter engine, and are mounted in an FTP mode (US standard in agreement with the CVS4 mode). The driving results are shown in Table 1 below, after the actual vehicle running test in the Y1 mode during the running mode) was performed, the HC emission before and after the catalytic converter was measured, and the HC purification rate was calculated.
FIG. 3 shows the Y1 modal chart of the above embodiment, and FIG. 4 shows the Y1 modal chart of Comparative Example 1 (see the following table).
[0015]
[Table 1]
Figure 0003603328
[0016]
As is clear from Table 1 above, the catalytic converter 1 of this embodiment has the highest HC purification rate as compared with Comparative Examples 1 to 4. As is clear from a comparison between FIG. 3 (Y1 modal chart of this embodiment) and FIG. 4 (Y1 modal chart of Comparative Example 1), the catalytic converter 1 of this embodiment has an HC purification rate (C) when the engine is cold. (Refer to the hatched portion in FIG. 3).
[0017]
In particular, in Comparative Example 1 (see FIG. 4), the HC purification rate is almost nil between time 0 and 100 sec, but in this embodiment (see FIG. 3), the HC purification rate is high between time 0 and 100 sec. Indicated.
[0018]
In short, in one catalytic converter 1, a three-way catalyst 9 (so-called TWC) containing Pt and Rh as a catalyst metal is provided upstream of the exhaust gas upstream of the catalyst , and an HC adsorbent and Pd are provided downstream of the exhaust gas downstream of the catalyst metal. Since the composite catalyst 10 with the three-way catalyst is disposed, the following effects are obtained.
That is, the exhaust gas first passes through the three-way catalyst 9 in the former stage, and is cooled by the heat taken off by the three-way catalyst 9, and then guided to the latter HC adsorbent, so that the HC adsorption efficiency by the HC adsorbent is improved. I do.
In addition, when the three-way catalyst 9 in the first stage is lighted off, unburned HC burns, and the temperature of the three-way catalyst 9 in the first stage rises. By transferring heat to the catalyst 10, substantially all of the adsorbed HC is burned in the subsequent stage, and there is an effect that the HC purification rate can be significantly improved.
[0019]
In addition, the activation temperature of the former Pt-Rh three-way catalyst 9 is set higher than the activation temperature of the latter Pd three-way catalyst, while the former three-way catalyst 9 is replaced with the latter three-way catalyst. Since the heat capacity is set equal to or less than the heat capacity, the following effects are obtained. In other words, the temperature rise of each stage before and after due to the exhaust gas is earlier in the former stage and later in the latter stage, but as described above, the activation temperature of the former three-way catalyst 9 is set higher than that of the latter three-way catalyst, The three-way catalysts at the front and rear stages are simultaneously turned off, so that the activation timings can be matched. As a result, the HC adsorbed by the subsequent HC adsorbent is efficiently burned and removed, and the HC purification rate is improved. There is an effect that a more favorable improvement can be achieved. In addition, since the catalysts 9 and 10 at the front and rear stages are arranged in the single catalyst case 6, the mountability to a vehicle (real vehicle mountability) can be improved.
[0020]
However, when the same three-way catalyst is used in both the front and rear stages as shown in the above comparative example, the activation temperature in the front stage and the activation temperature in the rear stage become the same, and the flow of exhaust gas causes Since the former three-way catalyst light-offs faster than the latter three-way catalyst, the concentration of HC drops sharply in the former stage, and the adsorbed HC is released without any purification in the latter stage. In the embodiment, substantially all of the adsorbed HC can be burned and removed by the above configuration.
[0021]
FIG. 5 shows another embodiment of the catalytic converter 1 as an exhaust gas purifying apparatus. In this embodiment, the former stage in which a Pt-Rh three-way catalyst 9 is provided, and a composite of an HC adsorbent and a Pd-based three-way catalyst. A carrier 11 supporting CeO 2 (cerium oxide) is interposed between the catalyst 10 and the subsequent stage, and has a three-stage structure.
[0022]
With such a configuration, O 2 (oxygen) necessary for burning and removing the adsorbed HC can be efficiently supplied to the subsequent HC adsorbent, so that even better combustion and removal of the adsorbed HC can be achieved. There is an effect that can be. In other respects, the same operation and effect as those of the previous embodiment shown in FIGS. 1 and 2 are obtained. Therefore, in FIG. 5, the same parts as those in FIGS. The detailed description is omitted .
[0023]
Na us, may be used in addition to the following configuration of the above embodiments. That is, instead of the configuration of the above-described embodiment, a simplified structure in which a noble metal (for example, Pd) is supported on an adsorbent powder (for example, MFI) may be used as the subsequent supporting structure.
[0024]
Further, additives such as CeO 2 (cerium oxide), BaO (barium oxide), and Ni (nickel) may be added to each of the above three-way catalysts.
[0025]
Further, as the HC adsorbent, MOR (mordenite), FAU (Y-type zeolite), FER (ferrierite), or CHA (shabasite) may be used instead of MFI.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an exhaust gas purifying apparatus of the present invention.
FIG. 2 is a sectional view showing another embodiment of the exhaust gas purifying apparatus of the present invention.
FIG. 3 is a Y1 modal chart of the exhaust gas purifying apparatus of the present invention shown in FIGS. 1 and 2;
FIG. 4 is a Y1 modal chart of a comparative example.
FIG. 5 is a sectional view showing still another embodiment of the exhaust gas purifying apparatus of the present invention.
FIG. 6 is an explanatory view showing a conventional exhaust gas purification device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Catalytic converter 9 ... Three-way catalyst 10 ... Composite catalyst

Claims (1)

エンジンの排気系に介設される排気ガス浄化装置であって、１つの触媒コンバータ内において、
排気上流側となる前段にＰｔとＲｈとを触媒金属として含む三元触媒を配設し、
排気下流側となる後段に排気ガス中のＨＣを吸着するＨＣ吸着剤とＰｄを触媒金属として含む三元触媒とが複合された複合触媒を配設すると共に、
上記前段の三元触媒は上記後段の三元触媒よりも活性化温度が高い一方で、上記前段の三元触媒は上記後段の三元触媒よりも熱容量が同じか、または、それ以下にされていることにより、該両三元触媒を略同時に活性化するように設定されている
排気ガス浄化装置。An exhaust gas purifying device provided in an exhaust system of an engine, wherein one catalytic converter includes:
A three-way catalyst including Pt and Rh as catalyst metals is disposed at a stage upstream of the exhaust gas,
A composite catalyst in which an HC adsorbent for adsorbing HC in the exhaust gas and a three-way catalyst containing Pd as a catalytic metal are disposed in a downstream stage on the downstream side of the exhaust gas,
The front stage of the three-way catalyst whereas the activation temperature is not higher than the three-way catalyst of the subsequent stage, the previous stage of the three-way catalyst or heat capacity than the three-way catalyst of the subsequent stage are the same, or are in less The exhaust gas purifying apparatus is set so that the two-way catalysts are activated at substantially the same time.
JP08791094A 1993-10-01 1994-03-31 Exhaust gas purification device Expired - Fee Related JP3603328B2 (en)

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