JP2000310111A - Catalyst device for purifying nox in exhaust gas - Google Patents
Catalyst device for purifying nox in exhaust gasInfo
- Publication number
- JP2000310111A JP2000310111A JP11119962A JP11996299A JP2000310111A JP 2000310111 A JP2000310111 A JP 2000310111A JP 11119962 A JP11119962 A JP 11119962A JP 11996299 A JP11996299 A JP 11996299A JP 2000310111 A JP2000310111 A JP 2000310111A
- Authority
- JP
- Japan
- Prior art keywords
- nox
- exhaust gas
- temperature
- catalyst
- release start
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
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- Exhaust Gas After Treatment (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、内燃機関や燃焼装
置等の排ガスに還元剤を添加して、触媒金属による触媒
作用を利用して排ガス中のＮＯｘを浄化するための触媒
装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic device for purifying NOx in exhaust gas by adding a reducing agent to exhaust gas from an internal combustion engine or a combustion device and utilizing the catalytic action of a catalytic metal. is there.
【０００２】より詳細には、排ガスの低温時にはＮＯｘ
を吸着し排ガスの高温時には吸着したＮＯｘを放出する
ＮＯｘ吸着物質を有する排ガス中のＮＯｘを浄化するた
めの触媒装置に関する。More specifically, when the temperature of exhaust gas is low, NOx
The present invention relates to a catalyst device for purifying NOx in exhaust gas having a NOx adsorbing substance that adsorbs NOx and releases the adsorbed NOx when the temperature of the exhaust gas is high.
【０００３】[0003]
【従来の技術】ディーゼル機関や一部のガソリン機関等
の内燃機関や様々な燃焼装置の排ガス中からＮＯｘを還
元除去するための触媒型の排ガス浄化装置について種々
の研究や提案がなされている。2. Description of the Related Art Various studies and proposals have been made on catalytic exhaust gas purifying devices for reducing and removing NOx from exhaust gas from internal combustion engines such as diesel engines and some gasoline engines and various combustion devices.
【０００４】通常のＮＯｘ触媒は、図３に示すようなモ
ノリス（ハニカム）触媒構造体30として形成されてお
り、このモノリス触媒構造体30では、コージェライト若
しくはステンレスで形成された構造材の担体35に多数の
四角形のセル（ガス流通孔）36を設け、このセル36の内
壁に、触媒活性金属を担持する貴金属担持層31を設けて
いる。An ordinary NOx catalyst is formed as a monolithic (honeycomb) catalyst structure 30 as shown in FIG. 3, and the monolithic catalyst structure 30 includes a carrier 35 made of cordierite or stainless steel. A large number of rectangular cells (gas flow holes) 36 are provided in the cell, and a noble metal supporting layer 31 for supporting a catalytically active metal is provided on the inner wall of the cell 36.
【０００５】そして、図４に示すように、この広い表面
積を持つ貴金属担持層31にアルミナ（Ａｌ2 Ｏ3 ）等の
触媒活性金属32を担持させて、できるだけ排ガス中のＮ
Ｏｘと還元剤に接触させて触媒機能を発揮するように構
成されている。Then, as shown in FIG. 4, a catalytically active metal 32 such as alumina (Al 2 O 3 ) is supported on the noble metal supporting layer 31 having a large surface area, and N
It is configured so as to exhibit a catalytic function by being brought into contact with Ox and a reducing agent.
【０００６】これらのＮＯｘ触媒の中に、希薄燃焼（リ
ーン燃焼）ガソリンエンジンやディーゼルエンジンの排
ガスの浄化に使用されているリーンＮＯｘ触媒やＮＯｘ
吸蔵還元型触媒がある。[0006] Among these NOx catalysts, there are lean NOx catalysts and NOx used for purifying exhaust gas from lean-burn (lean-burning) gasoline engines and diesel engines.
There is an occlusion reduction type catalyst.
【０００７】図５に従来技術のリーンＮＯｘ触媒の構成
と、ＮＯｘの還元浄化のメカニズムを示す。この図５の
リーンＮＯｘ触媒40は、多孔質のゼオライトやアルミナ
等の多孔質コート材で担持体45上に形成された担持層41
に、還元活性能を持つ還元活性金属等の触媒金属42を高
分散に担持している。排ガス中のＮＯｘをこの触媒金属
42の触媒作用により、排ガス中に含まれる炭化水素（Ｈ
Ｃ）等の還元剤で還元して排ガス中のＮＯｘを浄化す
る。このリーンＮＯｘ触媒40は三元触媒と異なり排ガス
中に酸素が存在していてもＮＯｘの浄化を行なうことが
できる。FIG. 5 shows the structure of a conventional lean NOx catalyst and the mechanism of NOx reduction and purification. The lean NOx catalyst 40 shown in FIG. 5 includes a carrier layer 41 formed on a carrier 45 with a porous coating material such as porous zeolite or alumina.
Further, a catalytic metal 42 having a reducing activity, such as a reducing active metal, is supported in a highly dispersed state. NOx in exhaust gas is converted to this catalytic metal
By the catalytic action of 42, the hydrocarbons (H
NOx in exhaust gas is purified by reduction with a reducing agent such as C). Unlike the three-way catalyst, the lean NOx catalyst 40 can purify NOx even if oxygen exists in the exhaust gas.
【０００８】次に、図６に従来技術のＮＯｘ吸蔵還元型
触媒50の構成と、ＮＯｘ浄化のメカニズムを示す。この
図６のＮＯｘ吸蔵還元型触媒50は、ゼオライトやアルミ
ナ等の多孔質コート材で担持体55上に形成された担持層
51に、酸化・還元機能を有する白金（Ｐｔ）等の触媒金
属52とＮＯｘ吸蔵機能を持つバリウム（Ｂａ）等のＮＯ
ｘ吸蔵物質（Ｒ）54を担持している。Next, FIG. 6 shows the structure of a conventional NOx storage reduction catalyst 50 and the mechanism of NOx purification. The NOx storage-reduction catalyst 50 shown in FIG. 6 includes a carrier layer formed on a carrier 55 with a porous coating material such as zeolite or alumina.
51, a catalyst metal 52 such as platinum (Pt) having an oxidation / reduction function and NO such as barium (Ba) having a NOx storage function.
The x-occluding substance (R) 54 is supported.
【０００９】そして、この触媒金属52とＮＯｘ吸蔵物質
54とにより、排ガス温度と排ガス中の酸素濃度によって
ＮＯｘの酸化、吸蔵及びＮＯｘの放出、還元の機能を発
揮して、これらに接触する排ガスを浄化している。The catalyst metal 52 and the NOx storage material
According to 54, the function of oxidizing and occluding NOx, releasing and reducing NOx is exhibited by the exhaust gas temperature and the oxygen concentration in the exhaust gas, and the exhaust gas in contact with these is purified.
【００１０】つまり、図６（ａ）に示すように、ディー
ゼルエンジンや希薄燃焼ガソリンエンジン等の通常の燃
焼におけるように排ガス中に酸素（Ｏ2 ）が含まれる場
合には、この酸素で、酸化・還元機能を持つ白金等の触
媒金属52により、排ガス中の一酸化窒素（ＮＯ）を二酸
化窒素（ＮＯ2 ）に酸化し、更に、この二酸化窒素をバ
リウム等のＮＯｘ吸蔵物質（Ｒ）54と反応させて、例え
ばＢａ（ＮＯ3 ）2 等の硝酸塩54ｂの形にすることによ
り吸蔵して、排ガスを浄化している。しかしながら、こ
のＮＯｘ吸蔵物質54がすべて硝酸塩54ｂになってしまう
と、ＮＯｘを吸蔵できなくなるので、浄化能力が低下し
てしまうことになる。That is, as shown in FIG. 6A, when oxygen (O 2 ) is contained in exhaust gas as in normal combustion of a diesel engine, a lean-burn gasoline engine, etc., the oxygen oxidizes the oxygen. Nitrogen monoxide (NO) in the exhaust gas is oxidized to nitrogen dioxide (NO 2 ) by a catalytic metal 52 such as platinum having a reducing function, and this nitrogen dioxide is further combined with a NOx storage substance (R) 54 such as barium. The exhaust gas is purified by reacting and storing it in the form of a nitrate 54b such as Ba (NO 3 ) 2 , for example. However, if all of the NOx storage substances 54 are converted into nitrates 54b, NOx cannot be stored, so that the purification capacity is reduced.
【００１１】そのため、従来技術のＮＯｘ吸蔵還元型触
媒装置においては、エンジンの運転条件を制御して、空
燃比がリッチな状態の燃焼を行い、リッチスパイクガス
と呼ばれる高温で且つ酸素濃度の低い状態の排ガスを発
生し、このリッチスパイクガスを触媒装置に流す。この
リッチスパイクガスが流れると、図６（ｂ）に示すよう
に、ＮＯｘ吸蔵物質54からはＮＯ2 が放出され、また、
硝酸塩54ｂは元の物質Ｒに戻ることになる。[0011] Therefore, in the conventional NOx storage-reduction type catalytic device, the operating condition of the engine is controlled so that the air-fuel ratio is burned in a rich state, and the state is called a rich spike gas at a high temperature and a low oxygen concentration. The rich spike gas flows through the catalyst device. When this rich spike gas flows, NO 2 is released from the NOx storage substance 54, as shown in FIG.
The nitrate 54b returns to the original substance R.
【００１２】そして、この空燃比がリッチな状態の燃焼
においては、排ガスは酸素濃度が低く、また、未燃のＣ
Ｏ，ＨＣ，Ｈ2 も増大するので、還元雰囲気となり、放
出されたＮＯ2 は、触媒金属52の触媒作用によって、排
ガス中のＣＯ，ＨＣ，Ｈ2 と還元反応して、Ｎ2 ，Ｈ2
Ｏ，ＣＯ2 となり、浄化されて排出される。In the combustion in which the air-fuel ratio is rich, the exhaust gas has a low oxygen concentration and the unburned C
Since O, HC, and H 2 also increase, the atmosphere becomes a reducing atmosphere, and the released NO 2 undergoes a reduction reaction with CO, HC, and H 2 in the exhaust gas by the catalytic action of the catalyst metal 52, and N 2 , H 2
It becomes O and CO 2 and is purified and discharged.
【００１３】[0013]
【発明が解決しようとする課題】しかしながら、これら
の従来技術のリーンＮＯｘ触媒においては、排ガスの温
度が触媒金属の触媒活性が失われる温度より低下すると
ＮＯｘを還元できなくなるので、ＮＯｘが含まれたまま
で排ガスを排出してしまうという問題がある。However, in these lean NOx catalysts of the prior art, NOx cannot be reduced when the temperature of the exhaust gas falls below a temperature at which the catalytic activity of the catalytic metal is lost. There is a problem that exhaust gas is exhausted up to this point.
【００１４】また、ＮＯｘ吸蔵還元型触媒においては、
ＮＯｘを触媒金属により酸化させてＮＯｘ吸蔵物質に吸
蔵するので、酸素を必要とする上に、排ガスの温度が触
媒金属の触媒活性が失われる温度より低下すると吸蔵で
きなくなり、ＮＯｘが含まれたままで排ガスを排出して
しまうという問題がある。In the NOx storage reduction type catalyst,
Since NOx is oxidized by the catalyst metal and stored in the NOx storage material, oxygen is required, and when the temperature of the exhaust gas falls below the temperature at which the catalytic activity of the catalyst metal is lost, storage becomes impossible, and NOx remains contained. There is a problem that exhaust gas is discharged.
【００１５】図７に白金系のリーン触媒Ｃ１の触媒入口
排ガス温度に対するＮＯｘ浄化率を示し、図８にＮＯｘ
吸蔵型還元触媒Ｃ２（Ｃｕ／ＺＳＭ−５）の触媒入口排
ガス温度に対するＮＯｘ浄化率を示すが、いずれの触媒
においても、触媒入口排ガス温度が２５０℃よりも低下
すると、ＮＯｘ浄化率が極端に低下しているのが分か
る。FIG. 7 shows the NOx purification rate with respect to the exhaust gas temperature at the catalyst inlet of the platinum-based lean catalyst C1, and FIG.
The NOx purification rate with respect to the exhaust gas temperature at the catalyst inlet of the storage reduction catalyst C2 (Cu / ZSM-5) is shown. In any of the catalysts, when the exhaust gas temperature at the catalyst inlet falls below 250 ° C., the NOx purification rate drops extremely. You can see that it is doing.
【００１６】この問題は、比較的低温でも触媒活性が高
い白金系の触媒を使用しても、それ以下の温度の排ガス
が排出されるので解決できず、排ガスの低温域では、Ｎ
Ｏｘ浄化が旨くできない。This problem cannot be solved even if a platinum-based catalyst having a high catalytic activity is used even at a relatively low temperature because exhaust gas at a temperature lower than that is discharged.
Ox purification cannot be performed well.
【００１７】図９にＥＣモード運転中の自動車エンジン
の排気管に設けられた触媒装置の触媒入口排ガス温度を
示す。この図８によると、ＥＣモード運転中の触媒装置
の触媒入口排ガス温度は５０℃〜４５０℃の広い温度範
囲で変動しているが、２５０℃以下の触媒の活性が無く
なる低温領域が、運転時間の大半を占めていることが分
かる。FIG. 9 shows a catalyst inlet exhaust gas temperature of a catalyst device provided in an exhaust pipe of an automobile engine during the EC mode operation. According to FIG. 8, the exhaust gas temperature at the catalyst inlet of the catalyst device during the EC mode operation fluctuates in a wide temperature range of 50 ° C. to 450 ° C. You can see that it accounts for most of.
【００１８】従って、ＮＯｘ浄化において、低温時にお
けるＮＯｘ浄化が特に重要であることが分かる。一方、
ＮＯｘ浄化活性が比較的高い、排ガス温度の高温域にお
いても、酸素濃度を低くして、還元雰囲気を作る必要が
あるという問題がある。Therefore, it can be understood that NOx purification at a low temperature is particularly important in NOx purification. on the other hand,
Even in a high temperature range of the exhaust gas temperature where the NOx purification activity is relatively high, there is a problem that it is necessary to lower the oxygen concentration to create a reducing atmosphere.
【００１９】そのために、特開平６−５０１３２号公報
の内燃機関の排気浄化装置では、低温と高温用のＮＯｘ
吸収剤を配設し、広い温度範囲でのリーン燃焼の内燃機
関の排ガス浄化を図っているが、これらのＮＯｘ吸収剤
はいずれ飽和することになるが、飽和した場合について
の記載がなく、ＮＯｘ浄化の対応が不十分となってい
る。Therefore, in the exhaust gas purifying apparatus for an internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 6-50132, low-temperature and high-temperature NOx
Although an absorbent is provided to purify exhaust gas from an internal combustion engine that performs lean combustion in a wide temperature range, these NOx absorbents will eventually be saturated, but there is no description about the case where the NOx absorbent is saturated. Insufficient purification measures.
【００２０】また、特開平８−２４６８４９号公報のエ
ンジンの排ガス浄化装置では、ペロブスカイト化合物か
らなるＮＯｘ吸着剤と、この下流側のＮＯｘ触媒とを配
設して、ＮＯｘの吸着及び放出と還元を行ない、排ガス
浄化を図っている。In the exhaust gas purifying apparatus for an engine disclosed in JP-A-8-246849, a NOx adsorbent composed of a perovskite compound and a NOx catalyst downstream of the NOx adsorbent are disposed to perform NOx adsorption, release and reduction. To purify the exhaust gas.
【００２１】しかしながら、この排ガス浄化装置におい
ては、ＮＯｘ吸着剤とＮＯｘ触媒とが、それぞれ独立し
て別の担持体に担持され、上下流に別れて配置されてい
るために、ＮＯｘ吸着剤が吸着したＮＯｘを放出する場
合に、この放出されたＮＯｘが排ガス全体に分散してし
まうので、排ガス中のＮＯｘ濃度が均一化し低濃度の状
態で、ＮＯｘ触媒に流入することになる。そのため、触
媒表面近傍のＮＯｘ濃度も低くなってしまい、ＮＯｘ浄
化効率が低い状態で還元浄化することになり、充分なＮ
Ｏｘ浄化性能が得られないという問題がある。However, in this exhaust gas purifying apparatus, the NOx adsorbent and the NOx catalyst are independently carried on different carriers, and are separately arranged upstream and downstream. When releasing the released NOx, the released NOx is dispersed throughout the exhaust gas, so that the NOx concentration in the exhaust gas becomes uniform and flows into the NOx catalyst in a low concentration state. Therefore, the NOx concentration in the vicinity of the catalyst surface also decreases, and the reduction and purification are performed in a state where the NOx purification efficiency is low, and a sufficient N
There is a problem that Ox purification performance cannot be obtained.
【００２２】本発明は、上述の問題を解決するためにな
されたものであり、その目的は、排ガス中のＮＯｘを浄
化するための触媒装置において、触媒のＮＯｘ浄化活性
が低い排ガスの低温域でＮＯｘを吸着又は吸蔵して排ガ
スを浄化し、また、触媒のＮＯｘ浄化活性が高い排ガス
の高温域では、触媒の近傍でその吸着又は吸蔵したＮＯ
ｘを放出し、触媒表面付近のＮＯｘ濃度を高めることに
より、ＮＯｘ浄化効率を上げて、ＮＯｘを効率良く還元
して、排ガスの全温度域において効率よくＮＯｘを浄化
できる触媒装置を提供することにある。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a catalyst device for purifying NOx in exhaust gas in a low-temperature region of exhaust gas where the catalyst has low NOx purification activity. Exhaust gas is purified by adsorbing or occluding NOx, and in a high temperature region of exhaust gas where the NOx purifying activity of the catalyst is high, the NO adsorbed or occluded in the vicinity of the catalyst.
The present invention provides a catalyst device that releases x, increases NOx concentration near the catalyst surface, thereby increasing NOx purification efficiency, reducing NOx efficiently, and purifying NOx efficiently in all exhaust gas temperature ranges. is there.
【００２３】[0023]
【課題を解決するための手段】以上のような目的を達成
するための排ガス中のＮＯｘを浄化するための触媒装置
は、次のような特徴を有して構成される。 １）排ガス中のＮＯｘを還元剤により還元して浄化する
ための触媒金属と共に、ＮＯｘを吸着及び放出できるＮ
Ｏｘ吸着物質を触媒担体に担持した触媒装置であって、A catalyst device for purifying NOx in exhaust gas to achieve the above object has the following features. 1) N, which can adsorb and release NOx, together with a catalytic metal for purifying NOx in exhaust gas by reducing it with a reducing agent
A catalyst device in which an Ox adsorbing substance is supported on a catalyst carrier,
【００２４】前記ＮＯｘ吸着物質は、排ガス温度が第１
ＮＯｘ放出開始温度より低い時にはＮＯｘを吸着し、排
ガス温度が前記第１ＮＯｘ放出開始温度より高い時には
前記吸着したＮＯｘを放出することを特徴とする。The NOx adsorbent has an exhaust gas temperature of the first
When the temperature is lower than the NOx release start temperature, NOx is adsorbed, and when the exhaust gas temperature is higher than the first NOx release start temperature, the adsorbed NOx is released.
【００２５】このＮＯｘ吸着物質は、低い温度域でＮＯ
ｘを吸着でき、高い温度でＮＯｘを放出できる物質であ
れば良く、ＣｕゼオライトやＹ型ゼオライト、Ｎａ型ゼ
オライト、あるいはアルミナやバナジウム等を採用する
ことができる。Ｃｕゼオライトを採用した場合には、こ
の第１ＮＯｘ放出開始温度は２５０℃付近となる。This NOx adsorbing substance can be used in a low temperature range.
Any substance capable of adsorbing x and releasing NOx at a high temperature may be used, and examples thereof include Cu zeolite, Y-type zeolite, Na-type zeolite, and alumina and vanadium. When the Cu zeolite is employed, the first NOx release start temperature is around 250 ° C.
【００２６】この構成の触媒装置によれば、排ガスがＮ
Ｏｘ吸着物質のＮＯｘ放出開始温度（第１ＮＯｘ放出開
始温度）より低温の時は、ＮＯｘ吸着物質によりＮＯｘ
を吸着して排ガスを浄化し、排ガスが第１ＮＯｘ放出開
始温度より高温の時は、ＮＯｘ吸着物質からＮＯｘを放
出して、触媒表面付近のＮＯｘ濃度を高濃度に維持し
て、触媒金属のＮＯｘ還元機能を高めて、効率よくＮＯ
ｘを浄化する。 ２）又は、ＮＯｘを酸化及び還元する触媒金属と、第１
ＮＯｘ放出開始温度を有するＮＯｘ吸着物質と、前記第
１ＮＯｘ放出開始温度よりも高い第２ＮＯｘ放出開始温
度を有するＮＯｘ吸蔵物質とを触媒担体に担持し、According to the catalyst device having this configuration, the exhaust gas is N
When the temperature is lower than the NOx release start temperature (first NOx release start temperature) of the Ox adsorbent, the NOx adsorbent gives NOx
When the exhaust gas is higher than the first NOx release start temperature, NOx is released from the NOx adsorbing substance, and the NOx concentration near the catalyst surface is maintained at a high concentration, and the NOx of the catalytic metal is reduced. Increase NO reduction efficiency
Purify x. 2) Alternatively, a catalyst metal for oxidizing and reducing NOx,
A NOx adsorbing substance having a NOx release start temperature and a NOx storage substance having a second NOx release start temperature higher than the first NOx release start temperature are supported on a catalyst carrier,
【００２７】前記ＮＯｘ吸着物質は、排ガス温度が前記
第１ＮＯｘ放出開始温度より低い時にはＮＯｘを吸着
し、排ガス温度が前記第１ＮＯｘ放出開始温度より高い
時には前記吸着したＮＯｘを放出し、The NOx adsorbent adsorbs NOx when the exhaust gas temperature is lower than the first NOx release start temperature, and releases the adsorbed NOx when the exhaust gas temperature is higher than the first NOx release start temperature.
【００２８】前記ＮＯｘ吸蔵物質は、排ガス温度が前記
第２ＮＯｘ放出開始温度より低い時にはＮＯｘを前記触
媒金属の触媒作用により酸化させて吸蔵し、排ガス温度
が前記第２ＮＯｘ放出開始温度より高い時には前記吸蔵
したＮＯｘを放出し、かつ、該ＮＯｘを前記触媒金属の
触媒作用により還元する触媒装置であって、排ガス温度
が前記第１ＮＯｘ放出開始温度より低い時には、前記Ｎ
Ｏｘ吸着物質でＮＯｘを吸着し、When the exhaust gas temperature is lower than the second NOx release start temperature, the NOx storage substance oxidizes and stores NOx by the catalytic action of the catalytic metal, and when the exhaust gas temperature is higher than the second NOx release start temperature, the NOx storage substance. A catalytic device for releasing the reduced NOx and reducing the NOx by the catalytic action of the catalytic metal, wherein when the exhaust gas temperature is lower than the first NOx release start temperature,
NOx is adsorbed by the Ox adsorbent,
【００２９】排ガス温度が前記第１ＮＯｘ放出開始温度
より高く、かつ、前記第２ＮＯｘ放出開始温度より低い
時には、前記ＮＯｘ吸着物質が吸着したＮＯｘを放出す
ると共に、該放出されたＮＯｘと排ガス中のＮＯｘを前
記触媒金属の触媒作用により酸化させて前記ＮＯｘ吸蔵
物質で吸蔵し、When the exhaust gas temperature is higher than the first NOx release start temperature and lower than the second NOx release start temperature, NOx adsorbed by the NOx adsorbing substance is released, and the released NOx and NOx in the exhaust gas are released. Is oxidized by the catalytic action of the catalytic metal and occluded by the NOx storage material,
【００３０】排ガス温度が前記第２ＮＯｘ放出開始温度
より高い時には前記ＮＯｘ吸着物質が吸着したＮＯｘを
放出すると共に、前記ＮＯｘ吸蔵物質が吸蔵したＮＯｘ
を放出し、該放出されたＮＯｘと排ガス中のＮＯｘを前
記触媒金属の還元作用により、還元浄化することを特徴
とする。When the exhaust gas temperature is higher than the second NOx release start temperature, the NOx adsorbing substance releases the adsorbed NOx and the NOx adsorbing substance stores the NOx.
And reducing and purifying the released NOx and NOx in the exhaust gas by the reducing action of the catalyst metal.
【００３１】このＮＯｘ吸着物質は、前記の触媒装置と
同様であり、また、ＮＯｘ吸蔵物質としてバリウム（Ｂ
ａ）やカルシウム（Ｃａ）等を採用することができ、こ
のバリウムを採用した場合には、第２ＮＯｘ放出開始温
度は４５０℃付近となる。This NOx adsorbing substance is the same as that of the above-mentioned catalyst device, and barium (B
a), calcium (Ca), or the like can be employed. When barium is employed, the second NOx release start temperature is around 450 ° C.
【００３２】この触媒装置によれば、排ガス温度がＮＯ
ｘ吸着物質のＮＯｘ放出開始温度（第１ＮＯｘ放出開始
温度）より低温の時は、ＮＯｘ吸着物質でＮＯｘを吸着
して排ガスを浄化し、排ガス温度が第１ＮＯｘ放出開始
温度とＮＯｘ吸蔵物質のＮＯｘ放出開始温度（第２ＮＯ
ｘ放出開始温度）の間の時には、ＮＯｘ吸蔵物質により
ＮＯｘを吸蔵して排ガスを浄化し、排ガスが第２ＮＯｘ
放出開始温度より高温の時は、ＮＯｘ吸蔵物質からＮＯ
ｘを放出して、触媒表面付近のＮＯｘ濃度を高濃度に維
持して、触媒金属のＮＯｘ還元機能を高めて、効率よく
ＮＯｘを浄化する。According to this catalyst device, the exhaust gas temperature is NO
When the temperature is lower than the NOx release start temperature (first NOx release start temperature) of the x adsorbent, the NOx adsorbent adsorbs NOx to purify the exhaust gas, and the exhaust gas temperature becomes the first NOx release start temperature and the NOx storage substance NOx release Start temperature (second NO
(x release start temperature), NOx is stored by the NOx storage substance to purify the exhaust gas, and the exhaust gas is converted to the second NOx.
When the temperature is higher than the release start temperature, NOx
By releasing x, the NOx concentration in the vicinity of the catalyst surface is maintained at a high concentration, the NOx reduction function of the catalyst metal is enhanced, and NOx is efficiently purified.
【００３３】３）そして、これらの上記の触媒装置にお
いて、前記ＮＯｘ吸着物質を前記触媒担体に担持させる
代わりに、前記ＮＯｘ吸着物質で前記触媒担体を形成す
ることもできる。3) In these catalyst devices, the catalyst carrier may be formed of the NOx adsorbing material instead of supporting the NOx adsorbing material on the catalyst carrier.
【００３４】従って、以上の構成の排ガス中のＮＯｘを
浄化するための触媒装置によれば、排ガスが低温の時も
高温の時も排ガス中のＮＯｘを吸着若しくは酸化した後
の吸蔵、又は、放出後の還元により、ＮＯｘを浄化す
る。Therefore, according to the catalyst device for purifying NOx in exhaust gas having the above-mentioned structure, storage or release after adsorbing or oxidizing NOx in exhaust gas regardless of whether the exhaust gas is at a low temperature or a high temperature. NOx is purified by the subsequent reduction.
【００３５】つまり、触媒活性が無い排ガス温度の低い
温度域では、排ガス中の酸素濃度に関係なく、ＮＯｘを
吸着し、触媒活性が高い排ガス温度の高い温度域では、
排ガス中の酸素濃度に関係なく、放出されたＮＯｘで触
媒表面付近のＮＯｘ濃度を高めてＮＯｘを効率よく浄化
し、排ガスの温度域全域においてＮＯｘの排出量を低減
する。That is, NOx is adsorbed regardless of the oxygen concentration in the exhaust gas in a low temperature range of the exhaust gas having no catalytic activity, and in a high temperature range of the exhaust gas temperature having a high catalytic activity,
Irrespective of the oxygen concentration in the exhaust gas, the NOx concentration in the vicinity of the catalyst surface is increased by the released NOx to purify the NOx efficiently, and the NOx emission is reduced over the entire temperature range of the exhaust gas.
【００３６】[0036]
【発明の実施の形態】以下、図面を用いて、本発明に係
る排ガス中のＮＯｘを浄化するための触媒装置について
説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A catalyst device for purifying NOx in exhaust gas according to the present invention will be described below with reference to the drawings.
【００３７】この触媒装置は、エンジンの排気管に配設
され、更に、必要に応じて、この触媒装置の上流側に、
ＨＣ等の還元剤を排ガス中に供給するための還元剤供給
装置を設けて構成される。 〔第１の実施の形態〕図１に、本発明の第１の実施の形
態の触媒装置として、リーンＮＯｘ触媒型のＮＯｘを浄
化するための触媒装置の構成とＮＯｘ浄化のメカニズム
を示す。This catalyst device is disposed in the exhaust pipe of the engine, and if necessary, is provided upstream of the catalyst device.
It is provided with a reducing agent supply device for supplying a reducing agent such as HC into exhaust gas. [First Embodiment] FIG. 1 shows a configuration of a lean NOx catalytic type NOx purifying catalytic device and a NOx purifying mechanism as a catalytic device according to a first embodiment of the present invention.
【００３８】この触媒装置は、図３に示すような、触媒
構造体と同じようにモノリス触媒として構成されるが、
その主要部は、図１に示すように、担持体15上にアルミ
ナ等の多孔質コート材で形成した触媒担体の担持層11
に、触媒金属12と共にＮＯｘ（窒素酸化物）を吸着する
ＮＯｘ吸着物質13を担持して形成される。This catalyst device is configured as a monolithic catalyst in the same manner as the catalyst structure as shown in FIG.
As shown in FIG. 1, the main part is a catalyst carrier supporting layer 11 formed of a porous coating material such as alumina on a carrier 15.
And a catalyst metal 12 and a NOx adsorbing substance 13 for adsorbing NOx (nitrogen oxide).
【００３９】この触媒金属12は活性開始温度より高い温
度域で還元活性を持つ白金等で形成されるが、他の触媒
金属を使用することもできる。白金の場合には、この活
性開始温度は約１５０℃〜２００℃の範囲にある。The catalytic metal 12 is formed of platinum or the like having a reducing activity in a temperature range higher than the activation start temperature, but other catalytic metals can be used. In the case of platinum, this activation onset temperature is in the range of about 150 ° C to 200 ° C.
【００４０】このＮＯｘ吸着物質13は、Ｃｕゼオライト
で形成され、約２５０℃の第１ＮＯｘ放出開始温度ＴN1
よりも排ガス温度が低い場合には、ＮＯｘを吸着し、第
１ＮＯｘ放出開始温度ＴN1よりも排ガス温度Ｔｇが高い
場合には、吸着したＮＯｘを放出する特性を有して形成
される。The NOx adsorbing substance 13 is formed of Cu zeolite and has a first NOx release start temperature TN1 of about 250 ° C.
When the exhaust gas temperature is lower than the first NOx release start temperature TN1, NOx is adsorbed, and when the exhaust gas temperature Tg is higher than the first NOx release start temperature TN1, the adsorbed NOx is released.
【００４１】なお、このＮＯｘ吸着物質13は、低い温度
域でＮＯｘを吸着でき、高い温度でＮＯｘを放出できる
物質であれば良く、Ｃｕゼオライトの他にＹ型ゼオライ
ト、Ｎａ型ゼオライト、あるいはアルミナやバナジウム
等を採用することができ、これらの物質や組成に対応し
て第１ＮＯｘ放出開始温度ＴN1が決まる。The NOx adsorbing substance 13 may be any substance that can adsorb NOx in a low temperature range and release NOx at a high temperature. In addition to Cu zeolite, Y-type zeolite, Na-type zeolite, or alumina or Vanadium or the like can be adopted, and the first NOx release start temperature TN1 is determined in accordance with these substances and compositions.
【００４２】また、このＮＯｘ吸着物質13は、図１に示
すように、触媒担体11に担持させることもできるが、代
わりに、このＮＯｘ吸着物質13で触媒担体11を形成する
こともできる。The NOx adsorbing substance 13 can be carried on the catalyst carrier 11 as shown in FIG. 1. Alternatively, the NOx adsorbing substance 13 can be used to form the catalyst carrier 11.
【００４３】この触媒装置では、エンジンの始動時やア
イドリング時などで、排ガス温度Ｔｇが、第１ＮＯｘ放
出開始温度ＴN1である２５０℃程度以下で、触媒金属12
の触媒活性が無い温度域においては、図１（ａ）に示す
ように、排ガス中のＮＯｘを、排ガス中の酸素濃度に関
係なく、ＮＯｘ吸着物質13で吸着するので、排ガスは浄
化されて排出される。In this catalytic converter, when the engine is started or idling, the exhaust gas temperature Tg is not higher than about 250 ° C., which is the first NOx release start temperature TN1, and the catalyst metal 12
In the temperature range where there is no catalytic activity, as shown in FIG. 1A, NOx in the exhaust gas is adsorbed by the NOx adsorbing substance 13 regardless of the oxygen concentration in the exhaust gas, so that the exhaust gas is purified and discharged. Is done.
【００４４】また、加速やロード抵抗等の増加等でエン
ジンの負荷や回転数が上昇して排ガス温度Ｔｇが、第１
ＮＯｘ放出開始温度ＴN1以上に上昇した場合は、図１
（ｂ）に示すように、排ガス中の酸素濃度とは関係なく
ＮＯｘ吸着物質13で吸着したＮＯｘが放出される。Further, the load and the number of revolutions of the engine increase due to acceleration, load resistance and the like, and the exhaust gas temperature Tg becomes the first temperature.
When the temperature rises to the NOx release start temperature TN1 or more, FIG.
As shown in (b), NOx adsorbed by the NOx adsorbent 13 is released regardless of the oxygen concentration in the exhaust gas.
【００４５】しかし、この第１ＮＯｘ放出開始温度ＴN1
の２５０℃以上では、触媒金属12の触媒活性が有る温度
域となるので、放出されたＮＯｘと排ガス中のＮＯｘ
は、触媒金属12の触媒作用により排ガス中のＣＯ，Ｈ
Ｃ，Ｈ2 等の還元剤と化学反応して、Ｈ2 Ｏ，ＣＯ2 ，
Ｎ2 となり、浄化されて排出される。However, the first NOx release start temperature TN1
Above 250 ° C., the temperature is in a temperature range where the catalytic activity of the catalytic metal 12 is present, so the released NOx and the NOx in the exhaust gas
Is the CO, H in the exhaust gas by the catalytic action of the catalytic metal 12.
Chemically reacts with reducing agents such as C and H 2 to form H 2 O, CO 2 ,
It becomes N 2 and is purified and discharged.
【００４６】この時に、排ガス中の還元剤が不足する時
には、ＨＣを噴射するＨＣ添加用噴射弁等の還元剤供給
装置から還元剤を排ガス中に供給する。At this time, when the amount of the reducing agent in the exhaust gas becomes insufficient, the reducing agent is supplied to the exhaust gas from a reducing agent supply device such as an HC addition injection valve for injecting HC.
【００４７】この触媒装置10では、触媒金属12とＮＯｘ
吸着物質13を同じ触媒担体11に担持しているので、この
ＮＯｘ吸着物質13で吸着したＮＯｘが放出される時に
は、触媒金属12の表面のＮＯｘ濃度が高くなるので、触
媒作用による還元が効率よく行なわれることになる。ま
た、ＮＯｘ吸着物質13で、触媒担体11を形成した場合
も、触媒金属12の表面のＮＯｘ濃度が高くなるので、同
様の効果を得られる。In this catalyst device 10, the catalyst metal 12 and NOx
Since the adsorbing substance 13 is carried on the same catalyst carrier 11, when the NOx adsorbed by the NOx adsorbing substance 13 is released, the NOx concentration on the surface of the catalytic metal 12 increases, so that the reduction by the catalytic action is efficiently performed. Will be done. Also, when the catalyst carrier 11 is formed by the NOx adsorbing substance 13, the same effect can be obtained because the NOx concentration on the surface of the catalyst metal 12 is increased.
【００４８】そして、排ガス温度Ｔｇが、第１ＮＯｘ放
出開始温度ＴN1以下となる状態が長時間継続する場合に
は、例えば、定常で長く運転するような場合には、排ガ
スの低温状態の経過時間を計測し、ＮＯｘ吸着物質13に
よるＮＯｘ吸着量が飽和して吸着できなくなる前に、強
制的にエンジンの運転状態を一時的に変更して排ガス温
度Ｔｇを上昇させ、ＮＯｘを放出及び還元浄化する。When the state in which the exhaust gas temperature Tg is equal to or lower than the first NOx release start temperature TN1 continues for a long time, for example, when the operation is steady and long, the elapsed time of the low temperature state of the exhaust gas is determined. Before the measured amount of NOx adsorbed by the NOx adsorbing substance 13 is saturated and cannot be adsorbed, the operating state of the engine is temporarily changed to forcibly raise the exhaust gas temperature Tg to release and purify NOx.
【００４９】この排ガス温度の上昇は、噴射タイミング
をリタード（遅れ) させたり、吸気絞りを行なったり、
還元剤供給装置として使用するＨＣ添加用噴射弁を作動
させて排気管内に燃料を添加して燃焼させたりすること
により実施できる。 〔第２の実施の形態〕図２に、本発明の第２の実施の形
態として、ＮＯｘ吸蔵還元型のＮＯｘを浄化するための
触媒装置の構成とＮＯｘ浄化のメカニズムを示す。The rise in the exhaust gas temperature can be used to retard the injection timing, delay the intake timing, perform intake throttle,
It can be implemented by operating the HC addition injection valve used as the reducing agent supply device to add fuel to the exhaust pipe and burn it. [Second Embodiment] FIG. 2 shows, as a second embodiment of the present invention, the structure of a catalyst device for purifying NOx of the NOx storage reduction type and the mechanism of NOx purification.
【００５０】この触媒装置は、図３に示すような、触媒
構造体と同じようにモノリス触媒として構成されるが、
その主要部は、図２に示すように、担持体25上にアルミ
ナ等の多孔質コート材で形成した触媒担体の担持層21
に、触媒金属22と共にＮＯｘ（窒素酸化物）を吸着する
ＮＯｘ吸着物質23と、更に、ＮＯｘ吸蔵物質24を担持し
て形成される。This catalyst device is configured as a monolithic catalyst in the same manner as the catalyst structure as shown in FIG.
As shown in FIG. 2, the main part is a support layer 21 of a catalyst carrier formed of a porous coating material such as alumina on a support 25.
Further, a NOx adsorbing substance 23 for adsorbing NOx (nitrogen oxide) together with the catalyst metal 22 and a NOx occluding substance 24 are further supported.
【００５１】この触媒金属22は第１の実施の形態の触媒
金属12と同様に、白金等で形成され、また、ＮＯｘ吸着
物質23も、第１の実施の形態のＮＯｘ吸着物質13と同様
に、Ｃｕゼオライト等で形成される。The catalytic metal 22 is made of platinum or the like, similarly to the catalytic metal 12 of the first embodiment. The NOx adsorbing substance 23 is also similar to the NOx adsorbing substance 13 of the first embodiment. , Cu zeolite or the like.
【００５２】また、ＮＯｘ吸蔵物質24は、バリウム（Ｂ
ａ）等で形成され、排ガス温度Ｔｇが約４５０℃の第２
ＮＯｘ放出開始温度ＴN2より低い時にはＮＯｘを触媒金
属23の触媒作用により酸化させて吸蔵し、排ガス温度Ｔ
ｇが第２ＮＯｘ放出開始温度ＴN2より高い時には吸蔵し
たＮＯｘを放出する特性を有して形成される。The NOx storage substance 24 is made of barium (B
a) etc., and the exhaust gas temperature Tg is about 450 ° C.
When the temperature is lower than the NOx release start temperature TN2, NOx is oxidized and stored by the catalytic action of the catalytic metal 23, and the exhaust gas temperature T
When g is higher than the second NOx release start temperature TN2, it is formed so as to release the stored NOx.
【００５３】なお、ＮＯｘ吸着物質23は、図２に示すよ
うに、触媒担体21に担持させることもできるが、代わり
に、このＮＯｘ吸着物質23で触媒担体21を形成すること
こできる。The NOx adsorbing substance 23 can be carried on the catalyst carrier 21 as shown in FIG. 2. Alternatively, the catalyst carrier 21 can be formed by the NOx adsorbing substance 23.
【００５４】この触媒装置では、排ガス温度Ｔｇが、第
１ＮＯｘ放出開始温度ＴN1である２５０℃程度以下で、
触媒金属22の触媒活性が無い温度域においては、排ガス
中のＮＯｘを、排ガス中の酸素濃度とは関係なくＮＯｘ
吸着物質23で吸着するので、排ガスは浄化されて排出さ
れる。In this catalyst device, when the exhaust gas temperature Tg is about 250 ° C. or less, which is the first NOx release start temperature TN1,
In a temperature range where the catalytic metal 22 has no catalytic activity, NOx in the exhaust gas is converted into NOx regardless of the oxygen concentration in the exhaust gas.
Since the exhaust gas is adsorbed by the adsorbing substance 23, the exhaust gas is purified and discharged.
【００５５】また、排ガス温度Ｔｇが第１ＮＯｘ放出開
始温度ＴN1より高く、第２ＮＯｘ放出開始温度ＴN2であ
る４５０℃より低い時には、ＮＯｘ吸着物質23が吸着し
たＮＯｘは放出されるが、この放出されたＮＯｘと排ガ
ス中のＮＯｘとは、触媒金属22の触媒作用により酸化さ
れ、ＮＯ2 （二酸化窒素）となり、更に、硝酸塩Ｂａ
（ＮＯ3 ）2 となってＮＯｘ吸蔵物質24で吸蔵されるの
で、排ガスは浄化されて排出される。When the exhaust gas temperature Tg is higher than the first NOx release start temperature TN1 and lower than the second NOx release start temperature TN2 of 450 ° C., the NOx adsorbed by the NOx adsorbing substance 23 is released. NOx and NOx in the exhaust gas are oxidized by the catalytic action of the catalytic metal 22 to become NO 2 (nitrogen dioxide), and further, nitrate Ba
Since it becomes (NO 3 ) 2 and is stored by the NOx storage material 24, the exhaust gas is purified and discharged.
【００５６】つまり、排ガス温度Ｔｇが上昇し、触媒金
属22の酸化活性領域に入ると、触媒金属22の触媒作用に
より、排ガス中に排出されたＮＯ（一酸化窒素）を排ガ
ス中に含まれるＯ2 （酸素）で酸化してＮＯ2 に変化さ
せる。そして、このＮＯ2 をＮＯｘ吸蔵機能を持つバリ
ウムに硝酸塩のかたちで吸蔵させることにより、排ガス
中のＮＯｘを除去して排ガスを浄化する。この間、ＮＯ
ｘ吸着物質22はＮＯｘを徐々に放出すが、このＮＯｘは
ＮＯｘ吸蔵物質24に吸蔵される。That is, when the exhaust gas temperature Tg rises and enters the oxidation active region of the catalytic metal 22, the catalytic action of the catalytic metal 22 causes NO (nitrogen monoxide) discharged into the exhaust gas to be contained in the exhaust gas. Oxidizes with 2 (oxygen) and changes to NO 2 . By occluding the NO 2 in the form of nitrate to barium having NOx storage function, to remove NOx in exhaust gases to purify the exhaust gas. During this time, NO
The x-adsorbing substance 22 gradually releases NOx, and this NOx is stored in the NOx storing substance 24.
【００５７】そして、排ガス温度Ｔｇが第２ＮＯｘ放出
開始温度ＴN2より高い時には、ＮＯｘ吸着物質23が吸着
したＮＯｘを放出すると共に、ＮＯｘ吸蔵物質24が吸蔵
したＮＯ2 を放出する。しかし、これらの放出されたＮ
Ｏｘ（ＮＯ2 を含む）と排ガス中のＮＯｘは、触媒金属
22が還元活性の温度域にあるため、この触媒金属22の還
元作用により、排ガス中のＣＯ，ＨＣ，Ｈ2 等の還元剤
と化学反応して、Ｈ2Ｏ，ＣＯ2 ，Ｎ2 となり、浄化さ
れて排出される。[0057] Then, when the exhaust gas temperature Tg is higher than the 2NOx release initiation temperature TN2, together with NOx adsorbent material 23 emits NOx adsorbed, releasing NO 2 to NOx occluding substance 24 is occluded. However, these released N
Ox (including NO 2 ) and NOx in exhaust gas are catalytic metals
Since the catalyst 22 is in the temperature range of the reduction activity, the reducing action of the catalyst metal 22 causes a chemical reaction with a reducing agent such as CO, HC, H 2 or the like in the exhaust gas to form H 2 O, CO 2 , N 2 , Purified and discharged.
【００５８】この触媒装置20では、触媒金属22とＮＯｘ
吸着物質23を同じ触媒担体21に担持しているので、この
ＮＯｘ吸着物質23で吸着したＮＯｘが放出される時に
は、触媒金属22の表面のＮＯｘ濃度が高くなるので、触
媒作用による還元が効率よく行なわれることになる。ま
た、ＮＯｘ吸着物質23で、触媒担体21を形成した場合
も、触媒金属22の表面のＮＯｘ濃度が同様に高くなるの
で、同じ効果を得ることができる。In this catalyst device 20, the catalyst metal 22 and NOx
Since the adsorbing substance 23 is carried on the same catalyst carrier 21, when the NOx adsorbed by the NOx adsorbing substance 23 is released, the NOx concentration on the surface of the catalytic metal 22 increases, so that the reduction by the catalytic action is efficiently performed. Will be done. Further, when the catalyst carrier 21 is formed by the NOx adsorbing substance 23, the same effect can be obtained because the NOx concentration on the surface of the catalyst metal 22 is similarly increased.
【００５９】また、排ガス温度Ｔｇが、第１ＮＯｘ放出
開始温度ＴN1以下となる状態が長時間継続する場合に
は、排ガスの低温状態の経過時間を計測し、ＮＯｘ吸着
物質23によるＮＯｘ吸着量が飽和して吸着できなくなる
前に、強制的にエンジンの運転状態を一時的に変更して
排ガス温度Ｔｇを上昇させ、高温で且つ低酸素濃度のリ
ッチスパイクガスを作り出して触媒装置20に送る。When the exhaust gas temperature Tg becomes equal to or lower than the first NOx release start temperature TN1 for a long time, the elapsed time of the low temperature state of the exhaust gas is measured, and the NOx adsorption amount by the NOx adsorbing substance 23 is saturated. Before the adsorption becomes impossible, the operating state of the engine is forcibly changed temporarily to increase the exhaust gas temperature Tg, and a rich spike gas having a high temperature and a low oxygen concentration is produced and sent to the catalyst device 20.
【００６０】更に、排ガス温度Ｔｇが、第１ＮＯｘ放出
開始温度ＴN1と第２ＮＯｘ放出開始温度ＴN2との間にあ
る状態が長時間継続する場合にも、この状態の経過時間
を計測し、ＮＯｘ吸蔵物質24によるＮＯｘ吸蔵量が飽和
して吸着できなくなる前に、即ち、ＮＯｘ吸蔵機能を持
つバリウムは全て硝酸塩に変化してＮＯｘ吸蔵機能を失
ってしまう前に、強制的にエンジンの運転状態を一時的
に変更して排ガス温度Ｔｇを上昇させ、リッチスパイク
ガスを作り出して触媒装置20に送る。Further, even when the state in which the exhaust gas temperature Tg is between the first NOx release start temperature TN1 and the second NOx release start temperature TN2 continues for a long time, the elapsed time in this state is measured and the NOx storage substance is measured. The operation state of the engine is forcibly temporarily stopped before the NOx storage amount by the fuel cell 24 becomes saturated and cannot be adsorbed, that is, before all the barium having the NOx storage function changes to nitrate and loses the NOx storage function. And the exhaust gas temperature Tg is increased to generate rich spike gas and send it to the catalyst device 20.
【００６１】排ガス中の酸素が殆ど無くなり排ガス温度
が上昇すると、ＮＯｘを吸蔵したＮＯｘ吸蔵物質24は硝
酸塩から分解してＮＯ２を放出し元のバリウムに戻る。When the oxygen in the exhaust gas almost disappears and the exhaust gas temperature rises, the NOx storage material 24 that has stored NOx decomposes from nitrate, releases NO2 and returns to the original barium.
【００６２】そして、この放出されたＮＯｘは、排ガス
中に酸素が殆ど存在しないため、排ガス中のＣＯ，Ｈ
Ｃ，Ｈ2 を還元剤として還元機能を持つ白金等の触媒金
属上で、Ｈ２Ｏ，ＣＯ２，Ｎ２に変換され、排ガスは浄
化される。Since the released NOx contains almost no oxygen in the exhaust gas, the released NOx contains CO, H in the exhaust gas.
H 2 O, CO 2 and N 2 are converted to H 2 O, CO 2 and N 2 on a catalytic metal such as platinum having a reducing function using C and H 2 as a reducing agent, and the exhaust gas is purified.
【００６３】なお、ＮＯｘ吸蔵物質24からのＮＯｘの放
出は通常は１秒程度以下の時間であるので、排ガス温度
上昇の継続時間は、温度上昇に要する時間と放出及び還
元浄化に要する時間を考慮して、通常は１秒〜５秒の間
に設定される。Since the release of NOx from the NOx storage substance 24 is usually about 1 second or less, the duration of the temperature rise of the exhaust gas takes into account the time required for the temperature rise and the time required for release and reduction and purification. Then, it is usually set between 1 second and 5 seconds.
【００６４】〔効果〕以上の構成の排ガス中のＮＯｘを
浄化するための触媒装置によれば、ＮＯｘ吸着物質13，
23を担持させているので、このＮＯｘ吸着物質13，23に
より、触媒の活性が低い排ガスの低温域でＮＯｘを吸着
して排ガスを浄化でき、また、触媒のＮＯｘ浄化活性が
高い排ガスの高温域では、その吸着したＮＯｘを放出
し、この放出したＮＯｘを触媒金属12，22の触媒作用に
より還元して排ガスを浄化できる。[Effects] According to the catalyst device for purifying NOx in exhaust gas having the above configuration, the NOx adsorbing substance
Since the NOx adsorbing substances 13 and 23 carry NOx, the NOx adsorbing substances 13 and 23 can adsorb NOx in a low temperature region of the exhaust gas with low activity of the catalyst and purify the exhaust gas, and also have a high temperature region of the exhaust gas where the NOx purification activity of the catalyst is high. Then, the adsorbed NOx is released, and the released NOx is reduced by the catalytic action of the catalytic metals 12 and 22, thereby purifying the exhaust gas.
【００６５】特に、ＮＯｘ吸着物質13，23を、触媒金属
12，22を有する触媒担持体11，21に担持するので、担持
体11，21の同一表面上の極近傍に、ＮＯｘ還元用の触媒
金属12，22とＮＯｘ吸着物質13，23が存在することにな
る。そのため、排ガス温度が高い時に、ＮＯｘ吸着物質
13，23から放出されたＮＯｘにより、触媒金属12，22の
表面付近のＮＯｘ濃度が高くなるのでＮＯｘの浄化効率
を著しく向上できる。In particular, the NOx adsorbing substances 13 and 23 are
Since they are supported on the catalyst carriers 11 and 21 having the catalysts 12 and 22, the catalyst metals 12 and 22 for NOx reduction and the NOx adsorbing substances 13 and 23 exist in the vicinity of the same surface of the carriers 11 and 21 in the very close vicinity. become. Therefore, when the exhaust gas temperature is high, the NOx adsorbent
The NOx released from 13 and 23 increases the NOx concentration near the surfaces of the catalytic metals 12 and 22, so that the NOx purification efficiency can be significantly improved.
【００６６】従って、排ガスの全温度域において効率よ
くＮＯｘを浄化でき、エンジン運転状態の全般に対して
ＮＯｘ浄化率を向上することができる。Accordingly, NOx can be efficiently purified in the entire exhaust gas temperature range, and the NOx purification rate can be improved over the entire operating state of the engine.
【００６７】[0067]
【発明の効果】以上の説明したように、本発明に係る排
ガス中のＮＯｘを浄化するための触媒装置によれば、次
のような効果を奏することができる。As described above, according to the catalyst device for purifying NOx in exhaust gas according to the present invention, the following effects can be obtained.
【００６８】触媒の活性が低い排ガスの低温域では、Ｎ
Ｏｘ吸着物質によりＮＯｘを吸着して排ガスを浄化で
き、また、触媒のＮＯｘ浄化活性が高い排ガスの高温域
では、その吸着したＮＯｘを放出し、この放出されたＮ
Ｏｘを触媒金属の触媒作用により還元して排ガスを浄化
できる。In the low temperature region of the exhaust gas where the activity of the catalyst is low, N
Exhaust gas can be purified by adsorbing NOx by the Ox adsorbing substance. In a high temperature range of exhaust gas where the NOx purification activity of the catalyst is high, the adsorbed NOx is released, and the released Nx is released.
Ox can be reduced by the catalytic action of the catalytic metal to purify the exhaust gas.
【００６９】特に、ＮＯｘ吸着物質を担持する触媒担持
体に、又はＮＯｘ吸着物質で形成した触媒担持体に、触
媒金属を担持して、ＮＯｘ還元用の触媒金属と同一表面
上の極近傍にＮＯｘ吸着物質を存在させているので、排
ガス温度が高い時に、ＮＯｘ吸着物質から放出されるＮ
Ｏｘで触媒金属の表面付近のＮＯｘ濃度を高めることが
できる。そのため、効率よくＮＯｘを浄化できる。従っ
て、排ガスの全温度域において効率よくＮＯｘを浄化で
きることになり、エンジン運転状態の全般に対してＮＯ
ｘ浄化率を向上することができる。In particular, a catalyst metal is carried on a catalyst carrier carrying a NOx adsorbing substance or a catalyst carrier formed of a NOx adsorbing substance, and the NOx is brought into close proximity on the same surface as the catalyst metal for NOx reduction. Due to the presence of the adsorbent, when the exhaust gas temperature is high, the N
Ox can increase the NOx concentration near the surface of the catalyst metal. Therefore, NOx can be efficiently purified. Therefore, NOx can be efficiently purified over the entire temperature range of the exhaust gas, and NOx can be reduced over the entire engine operating state.
x The purification rate can be improved.
【図１】本発明に係る第１の実施の形態の排ガス中のＮ
Ｏｘを浄化するための触媒装置のメカニズムを示す模式
図であり、（ａ）は排ガスが低温時の場合を、（ｂ）は
排ガスが高温時の場合を示す。FIG. 1 shows N in exhaust gas according to a first embodiment of the present invention.
It is a schematic diagram which shows the mechanism of the catalyst apparatus for purifying Ox, (a) shows the case where exhaust gas is low temperature, (b) shows the case where exhaust gas is high temperature.
【図２】本発明に係る第２の実施の形態の排ガス中のＮ
Ｏｘを浄化するための触媒装置のメカニズムを示す模式
図でであり、（ａ）は排ガスが低温時の場合を、（ｂ）
は排ガスが中温時の場合を、（ｃ）は排ガスが高温時の
場合を示す。FIG. 2 shows N in exhaust gas according to a second embodiment of the present invention.
It is a schematic diagram which shows the mechanism of the catalyst apparatus for purifying Ox, (a) is a case where exhaust gas is at low temperature, (b)
Shows the case where the exhaust gas is at a medium temperature, and FIG. 3C shows the case where the exhaust gas is at a high temperature.
【図３】触媒構造体を示す図である。FIG. 3 is a view showing a catalyst structure.
【図４】従来技術の触媒構造体の構成を示す、図３のＡ
部分の拡大模式図である。FIG. 4A shows the configuration of a prior art catalyst structure, FIG.
It is an expansion schematic diagram of a part.
【図５】従来技術のリーンＮＯｘ触媒型触媒装置のメカ
ニズムを示す模式図である。FIG. 5 is a schematic view showing a mechanism of a conventional lean NOx catalyst type catalytic device.
【図６】従来技術のＮＯｘ吸蔵還元型触媒装置のメカニ
ズムを示す模式図で、（ａ）はＮＯｘの吸蔵状態を、
（ｂ）はＮＯｘの還元状態を示す。FIG. 6 is a schematic view showing a mechanism of a conventional NOx storage reduction type catalyst device, wherein (a) shows a NOx storage state;
(B) shows the reduction state of NOx.
【図７】各種触媒の触媒入口排ガス温度に対するＮＯｘ
浄化率を示す図である。FIG. 7: NOx with respect to catalyst exhaust gas temperature of various catalysts
It is a figure showing a purification rate.
【図８】各種触媒の触媒入口排ガス温度に対するＮＯｘ
浄化率を示す図である。FIG. 8: NOx against catalyst inlet exhaust gas temperature of various catalysts
It is a figure showing a purification rate.
【図９】ＥＣモード運転における触媒入口排ガス温度を
示す図である。FIG. 9 is a diagram showing a catalyst inlet exhaust gas temperature in EC mode operation.
【符号の説明】 10，20 触媒装置 11，21 触媒担体（Ｃ） 12，22 触媒金属（ＰＭ，Ｐｔ） 13，23 ＮＯｘ吸着物質（Ｔ1 ） 24 ＮＯｘ吸蔵物質（Ｒ） Ｔｇ 排ガス温度 ＴN1 第１ＮＯｘ放出開始温度 ＴN2 第２ＮＯｘ放出開始温度[Description of Signs] 10, 20 Catalyst device 11, 21 Catalyst carrier (C) 12, 22 Catalyst metal (PM, Pt) 13, 23 NOx adsorbing substance (T1) 24 NOx occluding substance (R) Tg Exhaust gas temperature TN1 First NOx Release start temperature TN2 Second NOx release start temperature
フロントページの続き Ｆターム(参考） 3G091 AA02 AA12 AA13 AB02 AB04 AB05 AB06 AB09 BA04 BA14 BA33 BA39 CA18 CA26 CB02 CB03 CB07 DA01 DA02 DA03 DA04 DA07 DB10 EA17 EA30 FA01 FA08 FA09 FA12 FA13 FA14 FA17 FA18 FB02 FB03 FB10 FB12 FC07 FC08 GA06 GA16 GB01X GB01Y GB03Y GB06W GB09Y GB10X GB10Y GB16Y HA18 Continued on the front page F-term (reference) GA16 GB01X GB01Y GB03Y GB06W GB09Y GB10X GB10Y GB16Y HA18
Claims (3)
て浄化するための触媒金属と共に、ＮＯｘを吸着及び放
出できるＮＯｘ吸着物質を触媒担体に担持した触媒装置
であって、 前記ＮＯｘ吸着物質は、排ガス温度が第１ＮＯｘ放出開
始温度より低い時にはＮＯｘを吸着し、排ガス温度が前
記第１ＮＯｘ放出開始温度より高い時には前記吸着した
ＮＯｘを放出することを特徴とする排ガス中のＮＯｘを
浄化するための触媒装置。1. A catalyst device comprising a catalyst carrier carrying a NOx adsorbing substance capable of adsorbing and releasing NOx together with a catalyst metal for reducing and purifying NOx in exhaust gas by a reducing agent, wherein the NOx adsorbing substance is For purifying NOx in exhaust gas, characterized in that NOx is adsorbed when the exhaust gas temperature is lower than the first NOx release start temperature, and the adsorbed NOx is released when the exhaust gas temperature is higher than the first NOx release start temperature. Catalyst device.
第１ＮＯｘ放出開始温度を有するＮＯｘ吸着物質と、前
記第１ＮＯｘ放出開始温度よりも高い第２ＮＯｘ放出開
始温度を有するＮＯｘ吸蔵物質とを触媒担体に担持し、 前記ＮＯｘ吸着物質は、排ガス温度が前記第１ＮＯｘ放
出開始温度より低い時にはＮＯｘを吸着し、排ガス温度
が前記第１ＮＯｘ放出開始温度より高い時には前記吸着
したＮＯｘを放出し、 前記ＮＯｘ吸蔵物質は、排ガス温度が前記第２ＮＯｘ放
出開始温度より低い時にはＮＯｘを前記触媒金属の触媒
作用により酸化させて吸蔵し、排ガス温度が前記第２Ｎ
Ｏｘ放出開始温度より高い時には前記吸蔵したＮＯｘを
放出し、かつ、該ＮＯｘを前記触媒金属の触媒作用によ
り還元する触媒装置であって、 排ガス温度が前記第１ＮＯｘ放出開始温度より低い時に
は、前記ＮＯｘ吸着物質でＮＯｘを吸着し、 排ガス温度が前記第１ＮＯｘ放出開始温度より高く、か
つ、前記第２ＮＯｘ放出開始温度より低い時には、前記
ＮＯｘ吸着物質が吸着したＮＯｘを放出すると共に、該
放出されたＮＯｘと排ガス中のＮＯｘを前記触媒金属の
触媒作用により酸化させて前記ＮＯｘ吸蔵物質で吸蔵
し、 排ガス温度が前記第２ＮＯｘ放出開始温度より高い時に
は前記ＮＯｘ吸着物質が吸着したＮＯｘを放出すると共
に、前記ＮＯｘ吸蔵物質が吸蔵したＮＯｘを放出し、該
放出されたＮＯｘと排ガス中のＮＯｘを前記触媒金属の
還元作用により、還元浄化することを特徴とする排ガス
中のＮＯｘを浄化するための触媒装置。2. A catalyst metal for oxidizing and reducing NOx,
A NOx adsorbing material having a first NOx release start temperature and a NOx storage material having a second NOx release start temperature higher than the first NOx release start temperature are supported on a catalyst carrier. When the temperature is lower than 1 NOx release start temperature, NOx is adsorbed, and when the exhaust gas temperature is higher than the first NOx release start temperature, the adsorbed NOx is released. When the exhaust gas temperature is lower than the second NOx release start temperature, NOx is oxidized and occluded by the catalytic action of the catalytic metal, and the exhaust gas temperature is reduced to the second N
A catalyst device that releases the stored NOx when the temperature is higher than the Ox release start temperature and reduces the NOx by the catalytic action of the catalyst metal; and when the exhaust gas temperature is lower than the first NOx release start temperature, the NOx NOx is adsorbed by the adsorbent, and when the exhaust gas temperature is higher than the first NOx release start temperature and lower than the second NOx release start temperature, the NOx adsorbent releases the adsorbed NOx and the released NOx And the NOx in the exhaust gas is oxidized by the catalytic action of the catalytic metal and occluded by the NOx storage material. When the exhaust gas temperature is higher than the second NOx release start temperature, the NOx adsorbed material releases NOx adsorbed, The NOx storage substance releases the stored NOx, and converts the released NOx and NOx in the exhaust gas into the catalyst. The reducing action of the genus, the catalytic device for purifying NOx in the exhaust gas, characterized in that the reduction and purification.
持させる代わりに、前記ＮＯｘ吸着物質で前記触媒担体
を形成したことを特徴とする請求項１又は２に記載の排
ガス中のＮＯｘを浄化するための触媒装置。3. The purification of NOx in exhaust gas according to claim 1, wherein the catalyst carrier is formed of the NOx adsorbing material instead of supporting the NOx adsorbing material on the catalyst carrier. For catalytic devices.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11996299A JP3835057B2 (en) | 1999-04-27 | 1999-04-27 | Catalyst device for purifying NOx in exhaust gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11996299A JP3835057B2 (en) | 1999-04-27 | 1999-04-27 | Catalyst device for purifying NOx in exhaust gas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000310111A true JP2000310111A (en) | 2000-11-07 |
| JP3835057B2 JP3835057B2 (en) | 2006-10-18 |
Family
ID=14774519
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11996299A Expired - Fee Related JP3835057B2 (en) | 1999-04-27 | 1999-04-27 | Catalyst device for purifying NOx in exhaust gas |
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| Country | Link |
|---|---|
| JP (1) | JP3835057B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005023855A (en) * | 2003-07-03 | 2005-01-27 | Nissan Motor Co Ltd | Exhaust emission control device for internal combustion engine |
| WO2010106695A1 (en) * | 2009-03-19 | 2010-09-23 | トヨタ自動車株式会社 | Exhaust purifying device for internal combustion engine |
-
1999
- 1999-04-27 JP JP11996299A patent/JP3835057B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005023855A (en) * | 2003-07-03 | 2005-01-27 | Nissan Motor Co Ltd | Exhaust emission control device for internal combustion engine |
| WO2010106695A1 (en) * | 2009-03-19 | 2010-09-23 | トヨタ自動車株式会社 | Exhaust purifying device for internal combustion engine |
| JP5163808B2 (en) * | 2009-03-19 | 2013-03-13 | トヨタ自動車株式会社 | Exhaust gas purification device for internal combustion engine |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3835057B2 (en) | 2006-10-18 |
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