JPH05293376A - Catalyst for purifying exhaust gas and method therefor - Google Patents

Catalyst for purifying exhaust gas and method therefor

Info

Publication number
JPH05293376A
JPH05293376A JP4095246A JP9524692A JPH05293376A JP H05293376 A JPH05293376 A JP H05293376A JP 4095246 A JP4095246 A JP 4095246A JP 9524692 A JP9524692 A JP 9524692A JP H05293376 A JPH05293376 A JP H05293376A
Authority
JP
Japan
Prior art keywords
catalyst
layer
catalyst layer
exhaust gas
downstream
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.)
Pending
Application number
JP4095246A
Other languages
Japanese (ja)
Inventor
Toshio Takahata
敏夫 高畑
Hideji Ebara
秀治 江原
Ayanori Yamanashi
文徳 山梨
Katsuhiro Shibata
勝弘 柴田
Fumio Abe
文夫 安部
Tomoharu Kondo
智治 近藤
Junichi Suzuki
純一 鈴木
Naomi Noda
直美 野田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NGK Insulators Ltd
Nissan Motor Co Ltd
Original Assignee
NGK Insulators Ltd
Nissan Motor Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by NGK Insulators Ltd, Nissan Motor Co Ltd filed Critical NGK Insulators Ltd
Priority to JP4095246A priority Critical patent/JPH05293376A/en
Priority to US08/045,083 priority patent/US5376610A/en
Priority to DE69312778T priority patent/DE69312778T2/en
Priority to EP93302918A priority patent/EP0566401B1/en
Publication of JPH05293376A publication Critical patent/JPH05293376A/en
Pending legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B1/00Engines characterised by fuel-air mixture compression
    • F02B1/02Engines characterised by fuel-air mixture compression with positive ignition
    • F02B1/04Engines characterised by fuel-air mixture compression with positive ignition with fuel-air mixture admission into cylinder
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/12Improving ICE efficiencies

Landscapes

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

Abstract

PURPOSE:To remove HC with high efficiency by introducing secondary air at the start of an engine when a large amt. of HC is generated by incorporating at least Pt or Pd into the uppermost surface of the upstream catalyst bed as a catalytically active component and at least Rh into the downstream catalyst bed. CONSTITUTION:The upstream side of a monolithic carrier 14 is coated with the upstream catalyst bed having hydrocarbon purifying activity and contg. at least Pt or Pd in the uppermost surface layer as a catalytically active component, and the downstream side is coated with a downstream catalyst bed having a ternary performance and contg. at least Rh as the catalytically active component. Consequently, secondary air is introduced to form a fuel-lean side to efficiently remove HC at the start of an engine when a large amt. of HC is generated, and the gas warming characteristic is improved by the heat of reaction generated at this time. Further, the ternary performance is appropriately exhibited even in the steady operation after the gas is warmed.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は、排ガス浄化用触媒及び
排ガス浄化方法、特に自動車用内燃機関に好適に用いる
ことができる排ガス浄化用触媒及び排ガス浄化方法に関
し、更に詳しくは、エンジン始動時(コールドスタート
時)に多量に発生する炭化水素(HC)を二次空気とと
もに好適に浄化でき、また暖機後、安定かつ長期間にわ
たり高効率でHC、一酸化炭素(CO)、窒素酸化物
(NOX)を浄化できる排ガス浄化用触媒及び排ガス浄
化方法に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst and an exhaust gas purifying method, and more particularly to an exhaust gas purifying catalyst and an exhaust gas purifying method which can be preferably used for an internal combustion engine of an automobile. Hydrocarbons (HC) generated in large quantities at the cold start) can be suitably purified together with secondary air, and after warming up, HC, carbon monoxide (CO), nitrogen oxides ( The present invention relates to an exhaust gas purifying catalyst that can purify NO x ) and an exhaust gas purifying method.

【0002】[0002]

【従来の技術】排ガス規制強化とともに、エンジンのマ
ニホールド近傍へ触媒を配設し、触媒の暖機特性を向上
させたり、通電発熱型ヒーターを用いて急峻に昇温させ
てヒーターの触媒又は後方側の例えばメイン触媒を加熱
させ、エンジン始動時に多量発生するHCを浄化する技
術が注目されている。更に、燃料がリッチになるエンジ
ン始動時に、触媒の暖機性を向上させる技術に加え、二
次空気を導入し、排ガスを空気過剰率λ=1である理論
空燃比(ストイキオ)付近から燃料リーン側の雰囲気に
して浄化する技術も提案されている。
2. Description of the Related Art Along with the tightening of exhaust gas regulations, a catalyst is installed in the vicinity of the manifold of an engine to improve the warm-up characteristics of the catalyst, or the temperature of the heater or the rear side of the heater is steeply raised by using an electric heating heater. For example, a technique for heating a main catalyst to purify a large amount of HC generated when the engine is started has been attracting attention. Furthermore, in addition to the technology to improve the warm-up of the catalyst at the engine start when the fuel becomes rich, secondary air is introduced and exhaust gas is introduced into the fuel lean range from near the stoichiometric air-fuel ratio (Stoichio) where the excess air ratio λ = 1. Techniques for purifying the atmosphere on the side have also been proposed.

【0003】このような排ガス浄化技術に用いられる触
媒として、例えば特公平3−38892号公報には、触
媒担体上に、白金(Pt)及びロジウム(Rh)のうち
少なくとも一種の触媒成分を含有する触媒層と、該触媒
層上に設けられ、酸素貯蔵能付与剤として作用する酸化
セリウム(CeO2)50〜95%と微量のパラジウム
(Pd)を含有するアルミナの被覆層とを備えた三元触
媒が開示されている。
As a catalyst used in such an exhaust gas purifying technique, for example, Japanese Patent Publication No. 38892/1993 has at least one catalyst component of platinum (Pt) and rhodium (Rh) contained on a catalyst carrier. Ternary provided with a catalyst layer and an alumina coating layer provided on the catalyst layer and containing 50 to 95% of cerium oxide (CeO 2 ) acting as an oxygen storage capacity-imparting agent and a trace amount of palladium (Pd). A catalyst is disclosed.

【0004】また、通電発熱型ヒーターに担持された触
媒として、実開昭63−67609号公報、特表平3−
500911号公報、特開平3−72953号公報記載
の排ガス浄化用触媒がある。更に、コールドスタート時
にストイキオ付近からリッチ側において、特に炭化水素
の浄化活性の高い三元触媒が特開平2−56247号公
報に開示されている。これは、担体上にゼオライトを主
成分とする第1触媒層と、その上にPt、Pd、Rh等
の貴金属をAl23等のコート層に担持した酸化還元能
を備えた第2触媒層を設けてなる排ガス浄化用触媒であ
る。
Further, as a catalyst supported on an electric heating type heater, Japanese Utility Model Publication No. 63-67609 and Japanese Patent Publication No.
There are exhaust gas purifying catalysts described in JP-A-500911 and JP-A-3-72953. Further, Japanese Patent Application Laid-Open No. 2-56247 discloses a three-way catalyst having a particularly high hydrocarbon purification activity on the rich side from the vicinity of stoichio during cold start. This is a second catalyst having a redox ability in which a first catalyst layer containing zeolite as a main component is supported on a carrier, and a precious metal such as Pt, Pd, or Rh is supported on a coat layer of Al 2 O 3 or the like. An exhaust gas-purifying catalyst having a layer.

【0005】更にまた、排ガス流入側と排ガス流出側と
で担持する触媒金属の種類や量を変えた三元触媒とし
て、特開昭63−84635号公報には、例えばコール
ドスタート時の低温時の浄化効率を向上させるために、
モノリス担体のガス流入口側に、触媒担体の全長の1/
10〜2/5の長さの範囲にPdが担持され、ガス流出
口側に触媒担体の全長の3/5〜9/10の長さの範囲
にPtが担持された排気ガス浄化用触媒が開示されてい
る。この場合、NOXの浄化に効果を発揮するRhは、
触媒層全体に担持されてなる。すなわち、この触媒は上
流側にPd、Rh、下流にPt、Rhが担持されてな
る。
Furthermore, Japanese Patent Laid-Open No. 63-84635 discloses a three-way catalyst in which the kind and amount of catalytic metal supported on the exhaust gas inflow side and the exhaust gas outflow side are changed, for example, at low temperature at cold start. In order to improve the purification efficiency,
On the gas inlet side of the monolith carrier, 1 / of the total length of the catalyst carrier
An exhaust gas purifying catalyst in which Pd is carried in the range of 10 to 2/5 and Pt is carried in the range of 3/5 to 9/10 of the total length of the catalyst carrier on the gas outlet side. It is disclosed. In this case, Rh, which is effective in purifying NO x , is
It is supported on the entire catalyst layer. That is, this catalyst has Pd and Rh loaded on the upstream side and Pt and Rh loaded on the downstream side.

【0006】同様に特開昭3−101813号公報に
は、触媒の低温着火性を向上させたる触媒コンバーター
装置として、1つの触媒コンバーター装置内に複数個の
排気ガス浄化用触媒を収納してなる触媒コンバーター装
置において、排気ガス流入側の触媒がPdのみを含有し
てなり、排気ガス流出側の触媒が、Rh及びPt、若し
くはRh、Pt及びPdを含有してなり、かつ排気ガス
流入側の触媒と排気ガス流出側の触媒の体積比が1:8
〜3:1である触媒コンバータ装置が開示されている。
Similarly, in Japanese Patent Laid-Open No. 3-101813, as a catalytic converter device for improving low temperature ignitability of the catalyst, a plurality of exhaust gas purifying catalysts are housed in one catalytic converter device. In the catalytic converter device, the exhaust gas inflow side catalyst contains only Pd, the exhaust gas outflow side catalyst contains Rh and Pt, or Rh, Pt and Pd, and the exhaust gas inflow side The volume ratio of the catalyst to the exhaust gas outflow side catalyst is 1: 8.
Disclosed is a catalytic converter device of ~ 3: 1.

【0007】[0007]

【発明が解決しようとする課題】しかしながら、特公平
3−38892号公報記載の三元触媒は、酸素貯蔵能を
向上させ、理論空燃比(ストイキオ)近傍で有効に作用
させることを目的として考案された触媒であってリーン
側の性能やコールドスタート時の性能について考察され
たものではない。また被覆層の厚さが20〜40μmと
厚く、NOXの還元除去に最も有効なRhを含む触媒層
へのガスの拡散の障害となるため、三元触媒としても完
成されたものではなかった。
However, the three-way catalyst disclosed in Japanese Examined Patent Publication No. 3-38892 is devised for the purpose of improving the oxygen storage capacity and effectively acting near the stoichiometric air-fuel ratio (Stoichio). It is a catalyst that has not been considered for lean side performance or cold start performance. In addition, since the coating layer has a large thickness of 20 to 40 μm, which is an obstacle to the diffusion of gas into the catalyst layer containing Rh, which is most effective in reducing and removing NO x , it was not completed as a three-way catalyst. ..

【0008】また、実開昭63−67609号公報、特
表平3−500911号公報、特開平3−72953号
公報等に示された通電発熱型ヒーターに担持された触媒
は、いずれも例えば貴金属等の触媒成分が、Al23
の耐火性金属酸化物に担持されたいわゆる従来の三元触
媒に関するものであり、通電発熱型に好適な組成、構造
を何ら開示していない。更に、特開平2−56247号
公報に開示されている触媒は、HCを酸化によって最も
効率よく浄化できるリーン側で作用するものではなく、
浄化が不十分なものであった。
Further, the catalysts supported by the electric heating heaters disclosed in Japanese Utility Model Publication No. 63-67609, Japanese Patent Publication No. 3-500911 and Japanese Patent Application Laid-Open No. 3-72953 are all noble metals. The above-mentioned catalyst components are related to so-called conventional three-way catalysts supported on refractory metal oxides such as Al 2 O 3 and do not disclose any composition and structure suitable for electric heating. Further, the catalyst disclosed in Japanese Patent Laid-Open No. 2-56247 does not act on the lean side where HC can be most efficiently purified by oxidation,
The purification was inadequate.

【0009】更にまた、特開昭63−84635号公報
記載の排気ガス浄化用触媒は、壁面にアルミナコート層
等をコーティングした触媒担体のガス流入口側を所定長
さまでPd化合物の溶液に浸漬して乾燥・焼成し、次い
で該触媒担体を上下逆にして、ガス流出口側を所定長さ
まで白金化合物の溶液に浸漬して乾燥・焼成し、最後に
Rh化合物の溶液にて触媒層全体にRhを含浸させ、乾
燥・焼成することにより調製されるもので、合金を作り
易いRhとPt、Pdが分離されずに担持されているた
め容易に合金化し、耐熱性に乏しい。
Furthermore, in the exhaust gas purifying catalyst described in Japanese Patent Laid-Open No. 63-84635, the gas inlet side of a catalyst carrier having a wall coated with an alumina coat layer or the like is immersed in a solution of a Pd compound up to a predetermined length. Then, the catalyst carrier is turned upside down, the gas outlet side is immersed in a platinum compound solution up to a predetermined length to dry and calcinate, and finally, the Rh compound solution is applied to the entire catalyst layer for Rh. It is prepared by impregnating and drying and firing. Rh and Pt and Pd, which are easy to make an alloy, are supported without being separated, so they easily alloy and have poor heat resistance.

【0010】特開平3−101813号公報記載の触媒
コンバーター装置においても同様に、RhとPt、Pd
の合金化を防止する対策がなされていない。また、この
触媒コンバーター装置は空燃費リッチ側のHC浄化能向
上を目的とするものであって、二次空気の導入下、HC
を高効率で除去できるリーン側の性能向上を目的に完成
されたものではなく、かつヒーター用触媒として適正な
ものでもない。
Similarly, in the catalytic converter device described in Japanese Patent Application Laid-Open No. 3-101813, Rh, Pt and Pd are also used.
No measures have been taken to prevent alloying. Further, this catalytic converter device is intended to improve the HC purifying ability on the side of rich air-fuel consumption, and is improved by introducing the secondary air into the HC.
It has not been completed for the purpose of improving the performance on the lean side, which is capable of highly efficiently removing carbon dioxide, and is not a proper catalyst for heaters.

【0011】本発明は、このような状況に鑑みてなされ
たものであり、その目的とするところは、HCを効率よ
く除去できるリーン側での浄化作用に優れ、通電発熱型
ヒータに担持された触媒としても好適な組成、構造を有
する排ガス浄化用触媒、及びエンジン始動時に多量に発
生するHCを、二次空気を導入して高効率で浄化できる
排ガス浄化方法を提供することにある。
The present invention has been made in view of such a situation, and an object thereof is to have an excellent purification action on the lean side capable of efficiently removing HC and to be carried by an electric heating heater. An object of the present invention is to provide an exhaust gas purification catalyst having a composition and structure suitable as a catalyst, and an exhaust gas purification method capable of highly efficiently purifying HC generated in large quantities at the time of engine start by introducing secondary air.

【0012】[0012]

【課題を解決するための手段】本発明によれば、少なく
とも1個からなるモノリス担体の上流部に炭化水素浄化
能を有する少なくとも1層からなる上流部触媒層が被覆
され、下流部に三元性能を有する少なくとも1層からな
る下流部触媒層が被覆された排ガス浄化用触媒であっ
て、触媒活性成分として上流部触媒層の最表層が少なく
ともPtかPdの一方を含み、かつ下流部触媒層が少な
くともRhを含むことを特徴とする排ガス浄化用触媒が
提供される。また、本発明によれば、少なくとも1個か
らなるモノリス担体の上流部に炭化水素浄化能を有する
少なくとも1層からなる上流部触媒層が被覆され、下流
部に、三元性能を有する少なくとも1層からなる第1触
媒層と、該第1触媒層の表面に被覆され炭化水素浄化能
を有する第2触媒層とからなる下流部触媒層が設けられ
た排ガス浄化用触媒であって、触媒活性成分として上流
部触媒層の最表層及び下流部触媒層の第2触媒層がPt
かPdの一方を含み、かつ下流部触媒層の第1触媒層が
少なくともRhを含むことを特徴とする排ガス浄化用触
媒が提供される。本発明の排ガス浄化用触媒に用いるモ
ノリス担体としては、耐熱性無機質からなり、ハニカム
構造を有する通電発熱型ヒーター(ハニカムヒーター)
が好ましい。
According to the present invention, the upstream portion of at least one monolithic carrier is coated with the upstream catalyst layer consisting of at least one layer having a hydrocarbon purifying ability, and the downstream portion is ternary. An exhaust gas purifying catalyst coated with a downstream catalyst layer comprising at least one layer having performance, wherein the outermost surface layer of the upstream catalyst layer contains at least one of Pt and Pd as a catalytically active component, and the downstream catalyst layer There is provided an exhaust gas purifying catalyst, characterized in that at least Rh is included. Further, according to the present invention, the upstream portion of at least one monolith carrier is coated with the upstream catalyst layer comprising at least one layer having hydrocarbon purifying ability, and the downstream portion comprises at least one layer having three-way performance. An exhaust gas purifying catalyst comprising a first catalyst layer composed of and a downstream catalyst layer composed of a second catalyst layer coated on the surface of the first catalyst layer and having a hydrocarbon purifying ability. As the outermost surface layer of the upstream catalyst layer and the second catalyst layer of the downstream catalyst layer are Pt
An exhaust gas purifying catalyst is provided, which comprises one of Pd and Pd, and the first catalyst layer of the downstream catalyst layer contains at least Rh. The monolithic carrier used for the exhaust gas purifying catalyst of the present invention is made of a heat-resistant inorganic material and has a honeycomb structure and is an electric heating heater (honeycomb heater).
Is preferred.

【0013】更に、本発明によれば、少なくとも1個か
らなるモノリス担体の上流部に炭化水素浄化能を有する
上流部触媒層が被覆され、下流部に三元性能を有する下
流部触媒層が被覆され、触媒活性成分として上流部触媒
層の最表層が少なくともPtかPdの一方を含み、かつ
下流部触媒層が少なくともRhを含む排ガス浄化用触媒
の前方(排ガス上流側)より、エンジン始動時排ガスに
二次空気を導入することを特徴とする排ガス浄化方法が
提供される。更にまた、本発明によれば、少なくとも1
個からなるモノリス担体の上流部に炭化水素浄化能を有
する少なくとも1層からなる上流部触媒層が被覆され、
下流部に、三元性能を有する少なくとも1層からなる第
1触媒層と、該第1触媒層の表面に被覆され炭化水素浄
化能を有する第2触媒層とからなる下流部触媒層が設け
られ、触媒活性成分として上流部触媒層の最表層及び下
流部触媒層の第2触媒層がPtかPdの一方を含み、か
つ下流部触媒層の第1触媒層が少なくともRhを含む排
ガス浄化用触媒の前方より、エンジン始動時排ガスに二
次空気を導入することを特徴とする排ガス浄化方法が提
供される。本発明の排ガス浄化方法においては、エンジ
ン始動時に二次空気を導入することにより燃料リーン側
の雰囲気にすることが好ましく、また、二次空気導入と
ともに前記ハニカムヒーターを通電加熱することが好ま
しい。
Further, according to the present invention, at least one monolith carrier is coated with an upstream catalyst layer having hydrocarbon purifying ability on the upstream side and a downstream catalyst layer having three-way performance is coated on the downstream side. From the front of the exhaust gas purifying catalyst (exhaust gas upstream side) in which the outermost surface layer of the upstream catalyst layer contains at least one of Pt and Pd as a catalytically active component, and the downstream catalyst layer contains at least Rh. There is provided an exhaust gas purification method characterized by introducing secondary air into the exhaust gas. Furthermore, according to the invention, at least 1
An upstream catalyst layer composed of at least one layer having a hydrocarbon purifying ability is coated on the upstream part of the monolith carrier consisting of
A downstream catalyst layer including a first catalyst layer having at least one layer having three-way performance and a second catalyst layer having a hydrocarbon purifying ability and coated on the surface of the first catalyst layer is provided in the downstream portion. An exhaust gas purifying catalyst in which the outermost surface layer of the upstream catalyst layer and the second catalyst layer of the downstream catalyst layer contain Pt or Pd as the catalytically active component, and the first catalyst layer of the downstream catalyst layer contains at least Rh. There is provided an exhaust gas purification method characterized in that secondary air is introduced into the exhaust gas from the front side of the engine. In the exhaust gas purifying method of the present invention, it is preferable to introduce secondary air at the time of engine startup to create an atmosphere on the fuel lean side, and it is preferable to electrically heat the honeycomb heater together with the introduction of secondary air.

【0014】[0014]

【作用】本発明の排ガス浄化用触媒及び排ガス浄化方法
は上記のように構成され、炭化水素が多量に発生するエ
ンジン始動時(コールドスタート時)においては、主に
炭化水素浄化能を有する上流部触媒層が作用し、触媒の
前方(排ガス上流側)より二次空気を導入して空燃比を
リーン側にすることによって、HCを高効率で浄化でき
るとともに、この時発生する反応熱が下流部触媒層を加
熱して暖気性を向上させ、浄化効率を一層向上させる。
一方、暖機後の定常運転時においては、主に三元性能を
有する下流部触媒層が有効に作用して、好適に三元性能
を発現する。
The exhaust gas purifying catalyst and the exhaust gas purifying method of the present invention are configured as described above, and at the time of engine start (cold start) in which a large amount of hydrocarbons is generated, the upstream portion mainly having hydrocarbon purifying ability is provided. By operating the catalyst layer and introducing secondary air from the front side of the catalyst (exhaust gas upstream side) to make the air-fuel ratio lean, the HC can be purified with high efficiency, and the reaction heat generated at this time is generated in the downstream portion. The catalyst layer is heated to improve warmth and further improve purification efficiency.
On the other hand, in the steady operation after warming up, the downstream catalyst layer having mainly three-way performance effectively acts and preferably three-way performance is exhibited.

【0015】以下、本発明について更に詳細に説明す
る。本発明において、炭化水素浄化能を有する上流部触
媒層は1層又は複数層からなり、その最表層が、触媒活
性成分として、少なくともPtかPdを含有する。Pt
は高温時におけるHC浄化能と不飽和HCの浄化に効果
を発揮するのでPtも好適に使用できるが、Pdは特に
低温におけるHC浄化能が高いので最表層はPdを主成
分とするのが好ましく、必要に応じてPdとPtの両者
を使用できる。
The present invention will be described in more detail below. In the present invention, the upstream catalyst layer having a hydrocarbon purifying ability is composed of one layer or a plurality of layers, and the outermost layer thereof contains at least Pt or Pd as a catalytically active component. Pt
Since Pt has an effect of purifying HC at high temperature and purification of unsaturated HC, Pt can also be preferably used. However, since Pd has particularly high HC purifying ability at low temperature, it is preferable that the outermost layer contains Pd as a main component. If necessary, both Pd and Pt can be used.

【0016】また、上流部触媒層は触媒活性成分として
実質的にPdのみからなる単一層か、又は、最表層がP
dのみからなり、該Pdの最表層の内側に少なくともR
hを含む触媒層が配設された複数層からなる触媒層であ
ってもよい。前者の場合、低温着火特性が向上すること
により、上流部触媒層で発生した反応熱が下流部触媒層
を加熱して触媒の暖気性を向上させ、コールドスタート
時の浄化特性を向上させるので好ましく、また、後者の
場合、前述した最表層のPdの低温活性による触媒暖気
性効果と、内層のRhによる高温時のNOX浄化が好適
に発現し好ましい。更に、最表層にPd、内層にRh、
更に内層にPtを配置することも好適な例の一つであ
る。
The upstream catalyst layer is a single layer consisting essentially of Pd as the catalytically active component, or the outermost layer is Pd.
at least R inside the outermost layer of Pd.
It may be a catalyst layer composed of a plurality of layers in which a catalyst layer containing h is arranged. In the former case, the low-temperature ignition characteristics are improved, so that the reaction heat generated in the upstream catalyst layer heats the downstream catalyst layer to improve the warm-up property of the catalyst, which improves the purification characteristics at the cold start, which is preferable. , in the latter case, the catalyst warm-up effect due to low activity of the outermost layer of Pd as described above, NO X purifying at a high temperature by an inner layer of Rh is preferably expressed preferred. Further, Pd on the outermost layer, Rh on the inner layer,
Further, disposing Pt in the inner layer is also a preferable example.

【0017】なお、RhはPt、Pdと合金を作り易く
失活の原因となるため、互いに分離して担持される必要
がある。例えば、予めRhとPtが別々に基体上に担持
された凝集体を触媒層として混相の形で配置するか、又
は、Rhを含む基体とPtを含む基体が層状に配置され
た構成等が好ましい。これらの内、層状に配置する構成
が合金化を実質的に完全に防止できるので好ましい。
Since Rh easily forms an alloy with Pt and Pd and causes deactivation, it is necessary to support Rh separately. For example, it is preferable that an aggregate in which Rh and Pt are separately supported on a substrate in advance is arranged in a mixed phase as a catalyst layer, or a substrate containing Rh and a substrate containing Pt are arranged in layers. .. Of these, the layered structure is preferable because alloying can be substantially completely prevented.

【0018】上流部触媒層の貴金属の総担時量は30〜
130g/ft3の範囲にすることがコスト性能の点で
好ましい。また、Pd、Rh、Pt等を例えば複数層に
して配設する場合は、Pdは5〜60g/ft3、Rh
は1〜15/ft3、Ptは5〜60g/ft3担持する
のが好ましい。なお、Rhは特に高価な貴金属故1.5
〜10g/ft3の範囲にするのが特に好ましい。
The total amount of precious metal in the upstream catalyst layer is 30-
The range of 130 g / ft 3 is preferable in terms of cost performance. When Pd, Rh, Pt, etc. are arranged in multiple layers, for example, Pd is 5 to 60 g / ft 3 , Rh.
1 to 15 / ft 3 and Pt to 5 to 60 g / ft 3 . Rh is 1.5 because it is a particularly expensive precious metal.
It is particularly preferable to set it in the range of 10 to 10 g / ft 3 .

【0019】上流部触媒層は炭化水素浄化能を有するこ
とが必要であり、基体はアルミナ及び/又はゼオライ
ト、更に必要に応じてジルコニアを主成分とする。アル
ミナは通常活性アルミナと呼ばれる比表面積50m2
g以上のものが好適に使用でき、特に100m2/g以
上のものが貴金属の分散性を向上させ、低温着火性能を
向上させるので好ましい。一方、Rhは活性アルミナに
担持しても充分その性能を発揮できるが、活性アルミナ
と比較的強い相互作用を持ち、リーン側で固溶して失活
の原因となるため50m2/g以下のアルミナかジルコ
ニアに担時されることが特に好ましい。ゼオライトはコ
ールドスタート時、HCを選択的に吸着し、暖機ととも
に放出するので、HCの浄化能を向上させる。ゼオライ
トの添加量は活性アルミナに対し、5〜50wt%の範囲
で添加することができ、組成としてはSi/Al比40
以上が耐熱性の点で好ましい。
It is necessary that the upstream catalyst layer has a hydrocarbon purifying ability, and the substrate contains alumina and / or zeolite and, if necessary, zirconia as a main component. Alumina has a specific surface area of 50 m 2 /
Those having a weight of g or more can be preferably used, and those having a weight of 100 m 2 / g or more are preferable because they improve the dispersibility of the noble metal and the low temperature ignition performance. On the other hand, Rh can exhibit its performance sufficiently even when loaded on activated alumina, but has a relatively strong interaction with activated alumina and forms a solid solution on the lean side to cause deactivation, so Rh is 50 m 2 / g or less. It is particularly preferred that the carrier be supported by alumina or zirconia. Zeolite selectively adsorbs HC at the time of cold start and releases it with warming up, thus improving the purification ability of HC. The amount of zeolite added can be in the range of 5 to 50 wt% with respect to activated alumina, and the composition has a Si / Al ratio of 40.
The above is preferable in terms of heat resistance.

【0020】酸素貯蔵能を有するCe02やLa23
の希土類酸化物は特に必要としないが、定常運転時の触
媒性能の点で基体に対し5〜30wt%添加することが好
ましい。更に、必要に応じて、Zr、Ni、Co、F
e、Cu、Re等の遷移金属も助触媒として添加し得
る。
A rare earth oxide such as CeO 2 or La 2 O 3 having an oxygen storage capacity is not particularly required, but it is preferably added in an amount of 5 to 30 wt% with respect to the substrate from the viewpoint of catalytic performance during steady operation. Further, if necessary, Zr, Ni, Co, F
Transition metals such as e, Cu and Re may also be added as co-catalysts.

【0021】上流部触媒層の厚みは、圧損と性能の点で
20〜70μmの範囲にするのが好ましいが、例えば複
数層からなる触媒層であって、その最表層に少なくとも
PdかPtの一方を含み、かつその内側をRhを含む触
媒層から構成される場合、該最表層の厚みは2〜20μ
mの範囲が好ましい。2μm未満の場合、所望HCの浄
化能を示さず、20μmを越えると、内層の高価なRh
のNOX還元除去能が期待できない。
The thickness of the upstream catalyst layer is preferably in the range of 20 to 70 μm in terms of pressure loss and performance. For example, in the case of a catalyst layer composed of a plurality of layers, at least one of Pd and Pt is provided as the outermost layer. And a catalyst layer containing Rh on the inside, the outermost layer has a thickness of 2 to 20 μm.
A range of m is preferred. When it is less than 2 μm, it does not exhibit the desired HC purification ability, and when it exceeds 20 μm, the expensive Rh of the inner layer is high.
The NO x reduction and removal ability of can not be expected.

【0022】上流部触媒層の触媒長は、全体の触媒長の
1/10〜3/5の範囲が好ましい。1/10未満で
は、所望の低温域におけるHC浄化能が期待できず、下
流側の触媒層を反応熱によって加熱する効果が不十分で
あり、触媒長が3/5を越えると、特に高温時、上流側
で三元反応が支配的に反応し始め、上流側触媒層にRh
が含まれない場合は、例えばNOがN2へ還元除去され
ず副生成物であるNH3が発生し始める。上流側触媒層
の触媒長の更に好ましい範囲としては、上流側触媒層に
Rhを含有しない場合は1/10〜3/10であり、R
hを含有する場合には3/10〜3/5の範囲である。
これらの範囲はいずれも副生成物であるNH3の生成量
を低くすることに効果がある。なお、上流部触媒層は1
つのモノリス担体の上流側に配置せしめてもよく、複数
のモノリス担体の上流部のモノリス担体の全体又は上流
側一部に配置せしめてもよい。
The catalyst length of the upstream catalyst layer is preferably in the range of 1/10 to 3/5 of the total catalyst length. If it is less than 1/10, the HC purifying ability in the desired low temperature range cannot be expected, and the effect of heating the downstream catalyst layer by the reaction heat is insufficient. If the catalyst length exceeds 3/5, especially at high temperature. , The three-way reaction begins to react predominantly on the upstream side, and Rh
When is not included, for example, NO is not reduced and removed to N 2 and NH 3 as a by-product starts to be generated. A more preferable range of the catalyst length of the upstream catalyst layer is 1/10 to 3/10 when Rh is not contained in the upstream catalyst layer, and R
When h is contained, the range is 3/10 to 3/5.
All of these ranges are effective in reducing the amount of NH 3 which is a by-product. The upstream catalyst layer is 1
It may be arranged on the upstream side of one monolith carrier, or may be arranged on the whole or a part of the upstream side of the monolith carrier on the upstream side of the plurality of monolith carriers.

【0023】下流部触媒層は、1層又は複数層からなり
触媒活性成分として少なくともRhを含む。上流部触媒
層の反応熱によって加熱された下流部触媒層は三元反応
を支配的に進行し始めるが、特にNOXの還元除去の目
的でRhは不可欠である。Rhは特に下流部触媒層の最
表層に主成分として配置することが、上記目的達成のた
め好ましい。
The downstream catalyst layer is composed of one layer or a plurality of layers and contains at least Rh as a catalytically active component. The downstream catalyst layer, which is heated by the reaction heat of the upstream catalyst layer, starts predominantly proceeding with the three-way reaction, but Rh is indispensable especially for the purpose of reducing and removing NO x . In order to achieve the above purpose, it is preferable to arrange Rh as a main component in the outermost surface layer of the downstream catalyst layer.

【0024】また、必要に応じて、下流部触媒層を、三
元性能を有する少なくとも1層からなる第1触媒層と、
炭化水素浄化能を有する第2触媒層とから構成し、少な
くともRhを含む第1触媒層の上に、PdやPtを含む
第2触媒層(厚み2〜20μmの薄層)を配置すること
も触媒の暖気性向上の点で好ましい。この場合もRhは
第1触媒層の最表層に主成分として配置することがNO
Xの還元除去に好ましく、また、第2触媒層は、Pdを
主成分とするのが暖気性向上に特に有効である。
Further, if necessary, the downstream catalyst layer may include a first catalyst layer composed of at least one layer having three-way performance,
It is also possible to dispose a second catalyst layer (thin layer having a thickness of 2 to 20 μm) containing Pd and Pt on the first catalyst layer containing at least Rh, which is composed of a second catalyst layer having a hydrocarbon purifying ability. It is preferable from the viewpoint of improving the warm air property of the catalyst. Also in this case, Rh should be arranged as the main component in the outermost surface layer of the first catalyst layer.
It is preferable for reducing and removing X , and it is particularly effective for the second catalyst layer to contain Pd as a main component for improving warmth.

【0025】更に、Rhを主成分とする下流部触媒層の
最表層又は第1触媒層の最表層の内側には、PtやPd
を含む層を配置することが、高価なRhを節約しつつ、
所望の触媒性能を発揮する点で好ましい。なお、上流部
触媒層と同様、RhはPt、Pdとの合金化を防止する
ために、分離して担持する必要がある。
Further, Pt or Pd is provided inside the outermost surface layer of the downstream catalyst layer or the first catalyst layer containing Rh as a main component.
Disposing a layer containing a
It is preferable in that it exhibits desired catalyst performance. As with the upstream catalyst layer, Rh must be supported separately in order to prevent alloying with Pt and Pd.

【0026】下流部触媒層の貴金属の総担時量及び各々
の貴金属の好ましい担時量、また触媒層の厚みは、上流
部触媒層と同じくする。ただし、Rhを含む下流部触媒
層の最表層又は第1触媒層の最表層の厚みは、5〜20
μmの範囲が特にNOX浄化能の点で好ましい。
The total amount of noble metals carried by the downstream catalyst layer, the preferred amount of each noble metal carried, and the thickness of the catalyst layer are the same as those of the upstream catalyst layer. However, the outermost surface layer of the downstream catalyst layer containing Rh or the outermost surface layer of the first catalyst layer has a thickness of 5 to 20.
The range of μm is particularly preferable in terms of NO x purification ability.

【0027】下流部触媒層の基体は、アルミナ及び/又
はジルコニアを主成分とする。上流部触媒層と同様、ア
ルミナは比表面積50m2/g以上、特に100m2/g
の活性アルミナが好適に使用でき、Rhは比表面積50
2/g以下のアルミナかジルコニアに担持されること
が特に好ましい。
The substrate of the downstream catalyst layer contains alumina and / or zirconia as a main component. Similar to the upstream catalyst layer, alumina has a specific surface area of 50 m 2 / g or more, especially 100 m 2 / g
Activated alumina can be preferably used, and Rh has a specific surface area of 50
It is particularly preferable that the particles are supported on alumina or zirconia of m 2 / g or less.

【0028】また、三元性能を好適に発現するためには
酸素貯蔵能を有するCeO2やLa23等の希土類酸化
物を添加することが好ましく、添加量は基体に対し、5
〜30wt%が三元触媒操作範囲(ウィンドウ)を広げ、
また基体の耐熱性を向上させるため好ましい。この場
合、Rh成分はCeO2等と固溶体を作り易く失活の原
因となるため、RhとCe02は分離した形で触媒層に
含有されることが好ましい。 更に、CeO2等は、Z
rO2と複合酸化物を形成させることが、酸素貯蔵能を
更に向上させより好ましい。また、必要に応じて、N
i、Co、Fe、Cu等の遷移金属も基体に対し1〜1
0wt%添加すると、種々の助触媒作用を発現し好まし
い。
Further, in order to appropriately exhibit the ternary performance, it is preferable to add a rare earth oxide such as CeO 2 or La 2 O 3 having an oxygen storage capacity, and the addition amount is 5 to the substrate.
~ 30wt% widen the operating range (window) of the three-way catalyst,
It is also preferable because it improves the heat resistance of the substrate. In this case, since the Rh component easily forms a solid solution with CeO 2 or the like and causes deactivation, it is preferable that Rh and CeO 2 are contained in the catalyst layer in separate forms. Furthermore, CeO 2 and the like are Z
Forming a composite oxide with rO 2 is more preferable because it further improves the oxygen storage capacity. If necessary, N
Transition metals such as i, Co, Fe, and Cu are 1 to 1 with respect to the substrate.
Addition of 0 wt% is preferable because various cocatalyst effects are exhibited.

【0029】本発明の排ガス浄化用触媒に用いられる触
媒担体は、1つのモノリス担体からなるものであって
も、複数個のモノリス担体からなるものであってもよ
い。1つのモノリス担体からなる場合は、圧力損失が低
くなる点で好ましく、また、複数個のモノリス担体から
なる場合は、モノリス担体とモノリス担体との間でガス
のミキシングが起こり、浄化性能が向上する点で好まし
い。
The catalyst carrier used for the exhaust gas purifying catalyst of the present invention may be composed of one monolith carrier or a plurality of monolith carriers. When it is composed of one monolith carrier, the pressure loss is low, and when it is composed of a plurality of monolith carriers, gas mixing occurs between the monolith carriers to improve the purification performance. It is preferable in terms.

【0030】本発明の排ガス浄化用触媒は、コンバータ
ーや通電発熱型ヒーター等過酷な条件で使用されるの
で、モノリス担体としては、耐熱性無機質からなり、ハ
ニカム構造を有するものが好ましい。また、通電発熱型
ヒーターは、急峻に触媒温度を上昇でき、コールドスタ
ート時の浄化を最大限に活用できるので本触媒を用いる
のに特に好適である。通電発熱型ヒーターとしては、従
来から用いられているフォイル型のヒーターも使用でき
るが、粉末冶金法からなるヒーターの方が、機械的強度
やテレスコープの問題がなく信頼性に富むことから好ま
しい。
Since the exhaust gas purifying catalyst of the present invention is used under severe conditions such as a converter and an electric heating heater, the monolith carrier is preferably made of a heat resistant inorganic material and has a honeycomb structure. In addition, the electric heating heater is particularly suitable for using the present catalyst because it can rapidly raise the catalyst temperature and can maximize the purification at the cold start. As the electric heating heater, a conventionally used foil type heater can be used, but a heater made of a powder metallurgy method is preferable because it has high mechanical reliability and telescope and is highly reliable.

【0031】モノリス担体の構成材料としては、コーデ
ィエライトや通電により発熱する金属質のハニカム構造
体が好適に用いられ、通電により発熱する金属質ハニカ
ム構造体が機械的強度が高いため特に好ましい。金属質
の場合、例えばステンレス鋼やFe−Cr−Al、Fe
−Cr、Fe−Al、Fe−Ni、W−Co、Ni−C
r等の組成を有する材料からなるものが挙げられる。上
記のうち、Fe−Cr−Al、Fe−Cr、Fe−Al
が耐熱性、耐酸化性、耐食性に優れ、かつ安価で好まし
い。ハニカム構造体は、多孔質であっても非多孔質であ
ってもよいが、多孔質のハニカム構造体が触媒層との密
着性が強く熱膨張差による触媒の剥離が生ずることが殆
どないことから好ましい。
As a constituent material of the monolithic carrier, cordierite or a metallic honeycomb structure which generates heat by energization is preferably used, and a metallic honeycomb structure which generates heat by energization is particularly preferable because of its high mechanical strength. In the case of metallic material, for example, stainless steel, Fe-Cr-Al, Fe
-Cr, Fe-Al, Fe-Ni, W-Co, Ni-C
An example is one made of a material having a composition such as r. Of the above, Fe-Cr-Al, Fe-Cr, Fe-Al
Is excellent in heat resistance, oxidation resistance and corrosion resistance, and is inexpensive and preferable. The honeycomb structure may be porous or non-porous, but the porous honeycomb structure has strong adhesion to the catalyst layer, and catalyst peeling due to thermal expansion difference hardly occurs. Is preferred.

【0032】次に、ハニカム構造からなるモノリス担体
のうち金属質ハニカム構造体の製造方法の例を説明す
る。まず、所望の組成となるように、例えばFe粉末、
Al粉末、Cr粉末、又はこれらの合金粉末などにより
金属粉末原料を調製する。次いで、このように調製され
た金属粉末原料と、メチルセルロース、ポリビニルアル
コール等の有機バインダー、水を混合した後、この混合
物を所望のハニカム形状に押出成形する。
Next, an example of a method for manufacturing a metallic honeycomb structure out of a monolith carrier having a honeycomb structure will be described. First, to obtain a desired composition, for example, Fe powder,
A metal powder raw material is prepared from Al powder, Cr powder, or an alloy powder of these. Then, the metal powder raw material thus prepared, an organic binder such as methyl cellulose and polyvinyl alcohol, and water are mixed, and this mixture is extruded into a desired honeycomb shape.

【0033】次に、押出成形されたハニカム成形体を、
非酸化雰囲気下1000〜1450℃で焼成する。ここ
で、水素を含む非酸化雰囲気下において焼成を行うと、
有機バインダーがFe等を触媒にして分解除去し、良好
な焼結体(ハニカム構造体)が得られ好ましい。焼成温
度が1000℃未満の場合、成形体が焼結せず、焼成温
度が1450℃を越えると得られる焼結体が変形するた
め好ましくない。なお、望ましくは、得られた構造体の
隔壁及び機構の表面を耐熱性金属酸化物で被覆する。
Next, the extruded honeycomb molded body is
Baking is performed at 1000 to 1450 ° C. in a non-oxidizing atmosphere. Here, when firing is performed in a non-oxidizing atmosphere containing hydrogen,
It is preferable that the organic binder is decomposed and removed by using Fe or the like as a catalyst to obtain a good sintered body (honeycomb structure). If the firing temperature is lower than 1000 ° C, the molded body will not be sintered, and if the firing temperature exceeds 1450 ° C, the obtained sintered body will be deformed, which is not preferable. Desirably, the partition walls of the obtained structure and the surface of the mechanism are covered with a heat-resistant metal oxide.

【0034】得られたハニカム構造体は、後述する電極
間に、各種の態様により抵抗調節機構を設けることが好
ましい。ハニカム構造体に設ける抵抗調節機構として
は、例えばスリットを種々の方向、位置、長さで設け
ること、貫通軸方向の隔壁長さを変化させること、
ハニカム構造体の隔壁の厚さ(壁厚)を変化させるか、
又は貫通孔のセル密度を変化させること、及びハニカ
ム構造体の隔壁にスリットを設けること、等が好ましい
ものとして挙げられる。このうち、発熱部分を簡易に調
節できる方法として、のスリットの形成が特に好まし
い。
The obtained honeycomb structure is preferably provided with a resistance adjusting mechanism between the electrodes to be described later in various ways. As the resistance adjusting mechanism provided in the honeycomb structure, for example, providing slits in various directions, positions, and lengths, changing the partition wall length in the penetrating axis direction,
Change the thickness of the partition walls (wall thickness) of the honeycomb structure,
Alternatively, changing the cell density of the through holes and providing slits in the partition walls of the honeycomb structure are preferable. Of these, the formation of slits is particularly preferable as a method for easily adjusting the heat generating portion.

【0035】上記のようにして得られた金属質ハニカム
構造体は、通常その外周部の隔壁または内部に、ろう付
け、溶接などの手段によって電極を設けることにより、
ハニカム型のヒーターが作製される。なお、ここでいう
電極とは、当該ヒーターに電圧をかけるための端子の総
称を意味する。ヒーターを複数個のハニカム構造体(モ
ノリス担体)で構成する場合は、それらを電気的に直列
あるいは並列に連結することができる。
The metallic honeycomb structure obtained as described above is usually provided with electrodes by means of brazing, welding or the like on the partition walls or inside of the outer peripheral portion thereof,
A honeycomb heater is manufactured. The term "electrode" used herein means a generic term for terminals for applying a voltage to the heater. When the heater is composed of a plurality of honeycomb structures (monolith carriers), they can be electrically connected in series or in parallel.

【0036】このヒーターは、全体としてその抵抗値が
0.001Ω〜0.5Ωの範囲となるように形成するこ
とが好ましい。ハニカム構造体のハニカム形状としては
特に限定されないが、具体的には、例えば6〜1500
セル/インチ2(cpi2)(0.9〜233セル/cm
2)の範囲のセル密度を有するように形成することが好
ましい。また、隔壁の厚さは50〜2000μmの範囲
が好ましい。
This heater is preferably formed so that the resistance value as a whole is in the range of 0.001Ω to 0.5Ω. The honeycomb shape of the honeycomb structure is not particularly limited, but specifically, for example, 6 to 1500.
Cell / inch 2 (cpi 2 ) (0.9 to 233 cell / cm
It is preferable to form it so as to have a cell density in the range of 2 ). Further, the thickness of the partition wall is preferably in the range of 50 to 2000 μm.

【0037】また、上記したようにハニカム構造体は多
孔質であっても非多孔質でもよくその気孔率は制限され
ないが、0〜50%、好ましくは5〜25%の範囲とす
ることが強度特性、耐酸化性、耐食性、及び触媒層との
密着性の点から好ましい。なお、本発明においてハニカ
ム構造体とは、隔壁により仕切られた多数の貫通孔を有
する一体構造をいい、例えば貫通孔の断面形状(セル形
状)は円形、多角形、コルゲート形等の各種の任意な形
状が使用できる。
As described above, the honeycomb structure may be porous or non-porous and the porosity thereof is not limited, but the strength is preferably in the range of 0 to 50%, preferably 5 to 25%. It is preferable in terms of characteristics, oxidation resistance, corrosion resistance, and adhesion with the catalyst layer. In the present invention, the honeycomb structure refers to an integral structure having a large number of through holes partitioned by partition walls, and for example, the cross-sectional shape (cell shape) of the through holes is circular, polygonal, corrugated, or any other arbitrary shape. Various shapes can be used.

【0038】次に、上流部触媒層の調製法について説明
する。まず、含浸法、共沈法等を利用して活性アルミナ
からなる基体に予めCe等希土類元素の水溶液を酸化物
換算で3〜10wt%添加して、500〜950℃の温度
で焼成し、活性アルミナ−希土類金属酸化物の複合酸化
物を得る。これにより後の工程で担持する貴金属が均一
分散した形で得られる。次いで、酸やアミン等の解膠剤
の共存下で湿式法にて複合酸化物を解砕し、必要に応じ
て希土類金属を酸化物の形態で添加し、更にRh、P
d、Pt等の貴金属の水溶液を添加して所望の担時スラ
リーを得る。これをモノリス担体の上流側(触媒担体が
複数のモノリス担体からなる場合は上流部のモノリス担
体全体又は上流側一部)に被覆し、乾燥工程を経て、5
00〜950℃の温度で焼成して、上流部触媒層を得
る。
Next, a method for preparing the upstream catalyst layer will be described. First, by using an impregnation method, a coprecipitation method, etc., an aqueous solution of a rare earth element such as Ce is added in an amount of 3 to 10 wt% in terms of oxide in advance to a substrate made of activated alumina, and the mixture is fired at a temperature of 500 to 950 ° C. to activate. A composite oxide of alumina-rare earth metal oxide is obtained. As a result, the noble metal supported in the subsequent step is obtained in a uniformly dispersed form. Then, the composite oxide is crushed by a wet method in the coexistence of a deflocculant such as an acid or an amine, and a rare earth metal is added in the form of an oxide, if necessary, and Rh, P
An aqueous solution of a noble metal such as d or Pt is added to obtain a desired supported slurry. This is coated on the upstream side of the monolith carrier (when the catalyst carrier is composed of a plurality of monolith carriers, the entire monolith carrier in the upstream portion or a part of the upstream side), and a drying step is performed to obtain 5
The upstream catalyst layer is obtained by firing at a temperature of 00 to 950 ° C.

【0039】また、前述の担持スラリーを、そのまま乾
燥し、500〜950℃の温度で仮焼して貴金属が基体
に予め固定された複合酸化物を得、これを再び解膠剤と
ともに湿式法にて解砕し、これを担持スラリーとしてモ
ノリス担体に被覆することも可能である。この場合、貴
金属と基体は適切な相互作用を持つので、特に耐久性の
点で好ましい。なお、複層構造にする場合は、前述の2
通りの方法を応用してモノリス担体に被覆するが、この
場合、途中の焼成工程は必ずしも必要ではない。
Further, the above-mentioned supporting slurry is dried as it is, and calcined at a temperature of 500 to 950 ° C. to obtain a composite oxide in which a noble metal is fixed in advance on a substrate, and this is again subjected to a wet method together with a peptizer. It is also possible to disintegrate and coat it on a monolith carrier as a supporting slurry. In this case, the noble metal and the substrate have an appropriate interaction, which is particularly preferable in terms of durability. If a multi-layer structure is used, the above-mentioned 2
The same method is applied to coat the monolithic carrier, but in this case, the intermediate baking step is not always necessary.

【0040】上流部触媒層は、Rhを含む層を配設する
場合も同様に前述の方法を応用してモノリス担体に被覆
することができるが、耐久性の点より、基体として比表
面積50m2/g以下のアルミナ又はジルコニアに担持
されることが好ましく、また、CeO2等の希土類酸化
物との直接的な接触は好ましくないことから、活性アル
ミナ、比表面積50m2/g以下のアルミナ、ジルコニ
ア等を所望の配合比で湿式法にて解砕し、これに、Rh
の金属塩水溶液と必要に応じてCeO2の粉末を添加
し、これを担持スラリーとしてモノリス担体に被覆する
ことができる。また、この場合も前記と同様に、担持ス
ラリーをそのまま乾燥し、500〜950℃の温度で仮
焼してRhが基体に予め固定化された複合酸化物を得、
これを再び湿式法にて解砕し、担持スラリーとすること
ができる。
The upstream catalyst layer can be coated on the monolithic carrier by applying the above-mentioned method in the same manner when a layer containing Rh is provided. However, from the viewpoint of durability, the specific surface area of 50 m 2 as a substrate. / G or less of alumina or zirconia is preferable, and direct contact with a rare earth oxide such as CeO 2 is not preferable. Therefore, activated alumina, alumina or zirconia having a specific surface area of 50 m 2 / g or less are preferable. Etc. were crushed by a wet method at a desired mixing ratio, and Rh
It is possible to coat the monolith carrier with the metal salt aqueous solution ( 2) and CeO 2 powder, if necessary, as a carrying slurry. Also in this case, similarly to the above, the supported slurry is dried as it is, and calcined at a temperature of 500 to 950 ° C. to obtain a composite oxide in which Rh is preliminarily immobilized on the substrate,
This can be crushed again by a wet method to obtain a supported slurry.

【0041】更に、最も好ましい例としては、比表面積
50m2/g以下のアルミナ又はジルコニア、あるいは
これらの複合酸化物にRhをあらかじめ固定担持し、こ
れをモノリス担体に担持するか、あるいはこれに活性ア
ルミナ−希土類複合酸化物(希土類は酸化物で添加して
もよい)を必要量添加して担持スラリーを得ることもで
きる。これによりRhの耐熱性は飛躍的に向上し、Ce
や他のPt、Pdとの接触も実質的に防げるのでRhの
耐熱性が向上して最も好ましい。
Further, as the most preferable example, Rh is previously fixed and supported on alumina or zirconia having a specific surface area of 50 m 2 / g or less, or a composite oxide thereof, and this is supported on a monolith carrier, or active on this. A supported slurry can also be obtained by adding a necessary amount of alumina-rare earth composite oxide (rare earth may be added as an oxide). This dramatically improves the heat resistance of Rh, and Ce
Since it is possible to substantially prevent contact with Pt and other Pd and Pd, the heat resistance of Rh is improved, which is the most preferable.

【0042】下流部触媒層もモノリス担体の下流側(触
媒担体が複数のモノリス担体からなる場合は下流部のモ
ノリス担体全体又は下流側一部)に被覆担持する以外は
上流部触媒層と同様の調製法を用いて調製する。なお、
被覆担持の方法としては、触媒担体が1つのモノリス担
体からなる場合、上流側、下流側を区分するよう、例え
ば反転等しながら担持する。
The downstream catalyst layer is the same as the upstream catalyst layer except that the downstream catalyst layer is also coated and supported on the downstream side of the monolith carrier (when the catalyst carrier is composed of a plurality of monolith carriers, the entire monolith carrier or a part of the downstream side). Prepare using the method of preparation. In addition,
As a method of supporting the coating, when the catalyst carrier is composed of one monolithic carrier, the catalyst carrier is supported by, for example, reversing so that the upstream side and the downstream side are divided.

【0043】次に、上記排ガス浄化用触媒を用いた排ガ
ス浄化方法について説明する。本触媒は、コールドスタ
ート時、HCの浄化能を最大限に発揮するために、エン
ジン始動時に本触媒の前方より二元空気を導入する必要
がある。すなわち、エンジン始動時における過度のリッ
チ側ではHCやCOを浄化できず、またその反応熱によ
る更なる暖機性向上に結びつかないからである。
Next, an exhaust gas purification method using the above exhaust gas purification catalyst will be described. The present catalyst needs to introduce binary air from the front of the present catalyst at the time of engine start in order to maximize the HC purification performance at the cold start. That is, it is because HC and CO cannot be purified on the excessive rich side at the time of starting the engine, and the reaction heat does not lead to further improvement in warm-up.

【0044】二次空気の導入位置は、エンジン排ガス排
気孔から本触媒の間であればどこでもよく特に制限され
ないが、排気孔付近に導入する方が、排気ガスと二次空
気の混合が良くなり特に好ましい。二元空気の導入量
は、エンジンの排気量に依存するが、一般に50〜30
0l/minである。この時の空燃比は、ストイキオ近傍
からリーン側(λ=0.9〜1.5程度)にする。特に
λ=1.0〜1.3程度のリーン側にすることがHC浄
化能を向上させ好ましい。二元空気の導入時期は、エン
ジンクランク後から一般にλセンサーが作動するまでの
時期であり、概ね60秒以内である。
The introduction position of the secondary air may be anywhere between the engine exhaust gas exhaust hole and the main catalyst and is not particularly limited, but the introduction position near the exhaust hole improves the mixing of the exhaust gas and the secondary air. Particularly preferred. The amount of dual air introduced depends on the engine displacement, but is generally 50 to 30.
It is 0 l / min. The air-fuel ratio at this time is from the vicinity of stoichiometry to the lean side (λ = about 0.9 to 1.5). Particularly, it is preferable to set the lean side to about λ = 1.0 to 1.3 because the HC purification performance is improved. The binary air is introduced from the time the engine is cranked to the time when the λ sensor generally operates, and is generally within 60 seconds.

【0045】コールドスタート時の浄化能を最大限に発
揮させるためには、本触媒を通電発熱型ヒーターに用い
ることが最も好ましく、エンジンクランク後に通電と二
次空気の導入を開始し、概ね60秒以内にそれぞれ通
電、供給を停止する。これにより、通常の三元触媒が担
持している場合よりHCやCOの浄化能が高くなり、そ
の反応熱を最大限に利用し得るので、ヒーターへの消費
電力が大幅に低減でき、また、暖機後の定常運転でも好
適に三元性能を示すので、その効果は絶大である。な
お、通電に関しては、エンジンクランク前(例えば30
秒以内)に実施しても好適な浄化性能を得ることができ
る。
In order to maximize the purification performance at cold start, it is most preferable to use the present catalyst in an energizing heat-generating heater, and energization and introduction of secondary air are started after engine cranking for about 60 seconds. Within each, energize and stop the supply. As a result, the ability to purify HC and CO becomes higher than when it is supported by an ordinary three-way catalyst, and the reaction heat can be utilized to the maximum, so that the power consumption to the heater can be greatly reduced, and Even in steady operation after warm-up, the three-way performance is suitably shown, so the effect is great. Regarding energization, before the engine crank (for example, 30
Even if it is carried out within 2 seconds, a suitable purification performance can be obtained.

【0046】[0046]

【実施例】以下、本発明を実施例に基づいて更に詳細に
説明するが、本発明はこれらの実施例に限られるもので
はない。
The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

【0047】[ハニカムヒーターの調製]純Fe粉末、
純Cr粉末、Fe−50wt%Al合金粉末、Fe−20
wt%B粉末、Fe−75wt%Si粉末をFe−20Cr
−5Al−1Si−0.05B(重量%)の組成になる
よう原料を配合し、これに有機バインダー(メチルセル
ロース)と酸化防止剤(オレイン酸)、水を添加して坏
土を調製し、四角セルよりなるハニカムを押出成形し、
乾燥後H2雰囲気下1350℃で焼成し、リブ厚4mil、
貫通孔数400cpi2のハニカム構造体を得た。
[Preparation of Honeycomb Heater] Pure Fe powder,
Pure Cr powder, Fe-50 wt% Al alloy powder, Fe-20
wt% B powder, Fe-75 wt% Si powder to Fe-20Cr
-5Al-1Si-0.05B (wt%) is mixed with the raw materials, and an organic binder (methylcellulose), an antioxidant (oleic acid), and water are added to the mixture to prepare a kneaded clay. Extrude a honeycomb consisting of cells,
After drying, baking at 1350 ° C in H 2 atmosphere, rib thickness 4mil,
A honeycomb structure having a number of through holes of 400 cpi 2 was obtained.

【0048】上記方法により得られた外径90mmφ、
120mmφ2種の体積各々0.2l、0.4lのハニ
カム構造体に、図1に示す如く、特開平3−29518
4号に準じてスリット12を入れて抵抗を調節し、得ら
れたスリット入りハニカム構造体に各種触媒を被覆担持
した。更に、スリット12の外周部13には耐熱性のZ
rO2からなる無機接着剤を充填して絶縁部とし、外側
面10上に電極11をセットし、外径90mmφ、体積
0.2lのハニカム構造体は10mm間隔を経て2個直
列に連結して計0.4lの体積からなるA型のハニカム
ヒーターを、又外径120mmφ、体積0.4lのハニ
カム構造体は1個のみで0.4lの体積からなるB型の
ハニカムヒーターを作製した。なお、A型のハニカムヒ
ーターの場合、上流側の0.2lのハニカム構造体に上
流部触媒層が被覆され、下流側の0.2lのハニカム構
造体に下流部触媒層が被覆される。
An outer diameter of 90 mmφ obtained by the above method,
As shown in FIG. 1, a honeycomb structure having a volume of 0.2 mm and a volume of 0.4 l of 120 mmφ 2 type, as shown in FIG.
According to No. 4, the slit 12 was inserted to adjust the resistance, and various catalysts were coated and carried on the obtained honeycomb structure with slits. Further, the outer peripheral portion 13 of the slit 12 has a heat resistant Z
An inorganic adhesive composed of rO 2 was filled to form an insulating portion, an electrode 11 was set on the outer side surface 10, and two honeycomb structures having an outer diameter of 90 mmφ and a volume of 0.2 l were connected in series at intervals of 10 mm. A type A honeycomb heater having a total volume of 0.4 l and a type B honeycomb heater having an outer diameter of 120 mmφ and a volume 0.4 l of only one honeycomb structure having a volume of 0.4 l were manufactured. In the case of the A-type honeycomb heater, 0.2 l of the honeycomb structure on the upstream side is coated with the upstream catalyst layer, and 0.2 l of the honeycomb structure on the downstream side is coated with the downstream catalyst layer.

【0049】[触媒の調製] (1)方法A 市販のγ−Al23(BET比表面積200m2/g)
に硝酸セリウム水溶液をセリア換算で6wt%になるよう
含浸担持し、600℃で3時間で仮焼して、アルミナ−
セリア複合酸化物を得る。得られたアルミナ−セリア複
合酸化物を湿式法にて解砕し、これにセリア粉末をγ−
Al23に対し24wt%添加し、更に単一の貴金属と適
度な酢酸を添加して担持スラリーを得、これをハニカム
構造体に被覆担持し、乾燥後550℃で3時間焼成し触
媒を得る。更に必要に応じて、同様の方法で準備した異
なる単一の貴金属を含む担持スラリーを被覆担持し、乾
燥後550℃で3時間焼成し触媒を得る。なお、以後の
触媒調製には貴金属は各々ジニトロアミン白金、硝酸パ
ラジウム、硝酸ロジウムを用いる。また、貴金属がRh
の場合、セリウム成分のアルミナへの添加は行わない。
[Preparation of Catalyst] (1) Method A Commercially available γ-Al 2 O 3 (BET specific surface area 200 m 2 / g)
Was impregnated and supported with an aqueous cerium nitrate solution so as to be 6 wt% in terms of ceria, and calcined at 600 ° C. for 3 hours to obtain alumina-
Obtain a ceria composite oxide. The obtained alumina-ceria composite oxide was crushed by a wet method, and ceria powder was γ-
24 wt% of Al 2 O 3 was added, and a single precious metal and an appropriate amount of acetic acid were added to obtain a supporting slurry, which was coated and supported on a honeycomb structure, dried and then calcined at 550 ° C. for 3 hours to obtain a catalyst. obtain. Further, if necessary, supporting slurries containing different single noble metals prepared by the same method are coated and supported, dried and calcined at 550 ° C. for 3 hours to obtain a catalyst. In the subsequent catalyst preparation, dinitroamine platinum, palladium nitrate, and rhodium nitrate are used as noble metals. In addition, the precious metal is Rh
In the case of, the addition of the cerium component to the alumina is not performed.

【0050】(2)方法B 方法Aで得られた担持スラリーを100℃で15時間乾
燥し、550℃で3時間焼成して貴金属が予めアルミナ
−セリア複合酸化物に固定化された貴金属−アルミナ−
セリア複合酸化物を得る。更に適度な酢酸を添加し、湿
式法にて解砕して担持スラリーを得、これをハニカム構
造体に被覆担持し、乾燥後550℃で3時間焼成し触媒
を得る。更に必要に応じて、同様の方法で準備した異な
る単一の貴金属が予めアルミナ−セリア複合酸化物に固
定化された担持スラリーを被覆担持し、乾燥後550℃
で3時間焼成して触媒を得る。なお、貴金属がRhの場
合、セリウム成分のアルミナへの添加は行わない。
(2) Method B The supported slurry obtained in Method A was dried at 100 ° C. for 15 hours and calcined at 550 ° C. for 3 hours to precious metal-alumina in which the precious metal was previously immobilized on the alumina-ceria composite oxide. −
Obtain a ceria composite oxide. Further, an appropriate amount of acetic acid is added, and the mixture is crushed by a wet method to obtain a supporting slurry, which is coated and supported on a honeycomb structure, dried and then calcined at 550 ° C. for 3 hours to obtain a catalyst. Further, if necessary, a different single noble metal prepared by the same method is coated and supported on the carrier slurry in which the alumina-ceria composite oxide is immobilized in advance, and the carrier slurry is dried at 550 ° C.
Calcination for 3 hours to obtain the catalyst. When the noble metal is Rh, the cerium component is not added to alumina.

【0051】(3)方法C 方法Bで得られた貴金属の種類の異なる担持スラリーを
少なくとも2種混ぜて新たなる担持スラリーを得、方法
Bと同様に方法で担持する。
(3) Method C At least two kinds of supporting slurries having different kinds of noble metals obtained in Method B are mixed to obtain a new supporting slurry, which is supported in the same manner as Method B.

【0052】(4)方法D 市販の部分安定化ZrO2粉(Y233mol%含有、BE
T比表面積16m2/g)に硝酸ロジウム水溶液を用い
てZrO2にRhを含浸し、100℃で15時間乾燥
後、550℃で3時間仮焼してRh含有ZrO2粉を得
る。これに適度な酢酸とγ−Al23粉(50部)を添
加し、湿式法にて解砕して担持スラリーを得る。予め、
方法Bで白金−アルミナ−セリア複合酸化物がハニカム
構造体に被覆担持されたハニカムヒーターに、前記Rh
−ZrO2−Al23からなる担持スラリーを被覆担持
し、乾燥後550℃で3時間焼成し触媒を得る。
(4) Method D Commercially available partially stabilized ZrO 2 powder (containing 3 mol% of Y 2 O 3 , BE
Rh was impregnated in ZrO 2 using an aqueous rhodium nitrate solution with a T specific surface area of 16 m 2 / g, dried at 100 ° C. for 15 hours, and then calcined at 550 ° C. for 3 hours to obtain Rh-containing ZrO 2 powder. Proper acetic acid and γ-Al 2 O 3 powder (50 parts) are added to this, and the mixture is crushed by a wet method to obtain a supported slurry. In advance
In Method B, a honeycomb heater in which a platinum-alumina-ceria composite oxide is coated and supported on a honeycomb structure is provided with the above-mentioned Rh.
A supporting slurry composed of —ZrO 2 —Al 2 O 3 is coated and supported, dried and then calcined at 550 ° C. for 3 hours to obtain a catalyst.

【0053】(5)方法E 方法Dで得られた触媒に硝酸パラジウム水溶液を含浸
し、更に乾燥、焼成(550℃で3時間)して触媒表層
にPdが濃縮された触媒を得る。
(5) Method E The catalyst obtained in Method D is impregnated with an aqueous palladium nitrate solution, dried and calcined (550 ° C. for 3 hours) to obtain a catalyst in which Pd is concentrated on the catalyst surface layer.

【0054】(6)方法F 方法Aと同一の方法にてPtとRhを同時に添加した担
持スラリーを得る。得られた触媒はPtとRhが触媒層
内に均一に混在している。
(6) Method F The same method as in Method A was used to obtain a supported slurry to which Pt and Rh were simultaneously added. In the obtained catalyst, Pt and Rh are uniformly mixed in the catalyst layer.

【0055】(7)方法G 方法Bを用い1個のハニカム構造体の上流側に触媒を一
定長担持して乾燥後550℃で3時間焼成し、次いでハ
ニカム構造体を反転し、方法Bを用いて下流側(触媒未
担持部分)に触媒を担持し、同様に乾燥、焼成して触媒
を得る。
(7) Method G Using Method B, a catalyst was carried on the upstream side of one honeycomb structure for a certain length, dried and fired at 550 ° C. for 3 hours, and then the honeycomb structure was inverted to prepare Method B. A catalyst is supported on the downstream side (catalyst unsupported portion) by using the same, and similarly dried and calcined to obtain a catalyst.

【0056】上記、方法A〜Gを単独又は組み合わせ
て、以下の実施例及び比較例の触媒を調製した。
The above-mentioned methods A to G were used alone or in combination to prepare the catalysts of the following Examples and Comparative Examples.

【0057】(実施例1)方法Bにより、上流側に膜厚
40μm、Pd含有量40g/ft3の触媒層が被覆担
持され、下流側に膜厚30μm、Pt含有量35g/f
3の触媒層(内層)及び膜厚10μm、Rh含有量5
g/ft3の触媒層(表層)の2層が被覆担持されたA
型のハニカムヒーターを得た。
(Example 1) According to Method B, a catalyst layer having a film thickness of 40 μm and a Pd content of 40 g / ft 3 is coated and supported on the upstream side, and a film thickness of 30 μm and a Pt content of 35 g / f are provided on the downstream side.
t 3 catalyst layer (inner layer) and film thickness 10 μm, Rh content 5
A in which two layers of a catalyst layer (surface layer) of g / ft 3 were coated and supported
A type honeycomb heater was obtained.

【0058】(実施例2)方法Bにより、上流側に膜厚
40μm、Pt含有量40g/ft3の触媒層が被覆担
持された以外は、実施例1と同じハニカムヒーターを得
た。
Example 2 The same honeycomb heater as in Example 1 was obtained by the method B except that a catalyst layer having a film thickness of 40 μm and a Pt content of 40 g / ft 3 was coated and supported on the upstream side.

【0059】(実施例3)方法Bにより、上流側に膜厚
30μm、Pt含有量35g/ft3の触媒層(内
層)、膜厚10μm、Rh含有量5g/ft3の触媒層
(中間層)及び膜厚10μm、Pd含有量40g/ft
3の触媒層(表層)の3層が被覆担持された以外は実施
例1と同じA型のハニカムヒーターを得た。
(Example 3) According to Method B, a catalyst layer (inner layer) having a film thickness of 30 μm and a Pt content of 35 g / ft 3 on the upstream side, a catalyst layer having a film thickness of 10 μm and an Rh content of 5 g / ft 3 (intermediate layer) ) And film thickness 10 μm, Pd content 40 g / ft
The same type A honeycomb heater as in Example 1 was obtained except that 3 layers of 3 catalyst layers (surface layers) were coated and supported.

【0060】(実施例4)方法Aを用いた以外は、実施
例3と同じA型のハニカムヒーターを得た。
Example 4 The same type A honeycomb heater as in Example 3 was obtained except that the method A was used.

【0061】(実施例5)方法Cにより、上流側に膜厚
40μm、Pd、Rh、Ptの含有量が各々40、5、
35g/ft3の触媒層が被覆担持され、下流側に膜厚
40μm、RhとPtの含有量が各々5、35g/ft
3の触媒層が被覆担持されたA型のハニカムヒーターを
得た。
(Example 5) By the method C, the film thickness of 40 μm and the contents of Pd, Rh and Pt are 40 and 5, respectively on the upstream side.
A catalyst layer of 35 g / ft 3 was coated and supported, the film thickness was 40 μm on the downstream side, and the contents of Rh and Pt were 5 , 35 g / ft, respectively.
An A-type honeycomb heater having the catalyst layer 3 supported thereon was obtained.

【0062】(実施例6)上流側に、方法Dにより、膜
厚30μm、Pt含有量35g/ft3の触媒層(内
層)、膜厚10μm、Rh含有量5g/ft3の触媒層
(中間層)、及び方法Bにより、膜厚10μm、Pd含
有量40g/ft3の触媒層(表層)の3層が被覆担持
され、下流側に、方法Dにより、膜厚30μm、Pt含
有量35g/ft3の触媒層(内層)、膜厚10μm、
Rh含有量5g/ft3の触媒層(表層)の2層が被覆
担持されたA型のハニカムヒーターを得た。
Example 6 On the upstream side, according to Method D, a catalyst layer having a film thickness of 30 μm and a Pt content of 35 g / ft 3 (inner layer), a catalyst layer having a film thickness of 10 μm and a Rh content of 5 g / ft 3 (intermediate layer) was prepared. Layer) and method B, three layers of a catalyst layer (surface layer) having a film thickness of 10 μm and a Pd content of 40 g / ft 3 are coated and supported, and downstream, by method D, a film thickness of 30 μm and a Pt content of 35 g / ft 3 catalyst layer (inner layer), film thickness 10 μm,
An A-type honeycomb heater in which two layers of a catalyst layer (surface layer) having an Rh content of 5 g / ft 3 were coated and supported was obtained.

【0063】(実施例7)上流側に、方法Dにより、膜
厚30μm、Pt含有量35g/ft3の触媒層(内
層)、膜厚10μm、Rh含有量5g/ft3の触媒層
(表層)の2層が被覆担持され、更に、この上流側の触
媒表層に方法EによりPdが含浸担持された以外は実施
例6と同じA型のハニカムヒーターを得た。
Example 7 On the upstream side, according to Method D, a catalyst layer having a film thickness of 30 μm and a Pt content of 35 g / ft 3 (inner layer), a catalyst layer having a film thickness of 10 μm and a Rh content of 5 g / ft 3 (surface layer) The same A-type honeycomb heater as in Example 6 was obtained except that two layers of (1) were coated and supported, and Pd was impregnated and supported by the method E on the upstream catalyst surface layer.

【0064】(実施例8)方法Fを用いた以外は、実施
例5と同じA型のハニカムヒーターを得た。
Example 8 The same type A honeycomb heater as in Example 5 was obtained except that the method F was used.

【0065】(実施例9)方法Bにより、上流側に膜厚
40μm、Pd含有量40g/ft3の触媒層が被覆担
持され、下流側に膜厚30μm、Pt含有量35g/f
3の触媒層(内層)、膜厚10μm、Rh含有量5g
/ft3の触媒層(中間層)、膜厚10μm、Pd含有
量40g/ft3の触媒層(表層)の3層が被覆担持さ
れたA型のハニカムヒーターを得た。
(Example 9) According to Method B, a catalyst layer having a film thickness of 40 μm and a Pd content of 40 g / ft 3 is coated and supported on the upstream side, and a film thickness of 30 μm and a Pt content of 35 g / f are provided on the downstream side.
t 3 catalyst layer (inner layer), film thickness 10 μm, Rh content 5 g
An A-type honeycomb heater was obtained in which three layers of a catalyst layer (intermediate layer) of / ft 3 , a film thickness of 10 μm, and a catalyst layer (surface layer) having a Pd content of 40 g / ft 3 were coated and supported.

【0066】(実施例10)方法Gにより、上流側より
触媒長1/2の範囲内に膜厚40μm、Pd含有量40
g/ft3の触媒層が被覆担持され、下流部側残部に膜
厚30μm、Pt含有量35g/ft3の触媒層(内
層)、膜厚10μm、Rh含有量5g/ft3の触媒層
(表層)の2層が被覆担持されたB型のハニカムヒータ
ーを得た。
(Example 10) By Method G, the film thickness was 40 μm and the Pd content was 40 within the range of the catalyst length 1/2 from the upstream side.
A catalyst layer of g / ft 3 is coated and supported, and a film thickness of 30 μm, a Pt content of 35 g / ft 3 of a catalyst layer (inner layer), a film thickness of 10 μm, and a Rh content of 5 g / ft 3 of the catalyst layer ( A B-type honeycomb heater in which two layers (surface layer) were coated and supported was obtained.

【0067】(比較例1)方法Bにより、上流側に膜厚
40μm、Rh含有量5g/ft3の触媒層が被覆担持
され、下流側に膜厚30μm、Pt含有量35g/ft
3の触媒層(内層)、膜厚10μm、Pd含有量5g/
ft3の触媒層(表層)の2層が被覆担持されたA型の
ハニカムヒーターを得た。
(Comparative Example 1) According to Method B, a catalyst layer having a film thickness of 40 μm and a Rh content of 5 g / ft 3 is coated and supported on the upstream side, and a film thickness of 30 μm and a Pt content of 35 g / ft 3 are provided on the downstream side.
3 catalyst layer (inner layer), film thickness 10 μm, Pd content 5 g /
An A-type honeycomb heater in which two catalyst layers (surface layers) of ft 3 were coated and supported was obtained.

【0068】(比較例2)方法Bにより、上流側に膜厚
40μm、Rh含有量5g/ft3の触媒層が被覆担持
され、下流側に膜厚30μm、Pt含有量35g/ft
3の触媒層(内層)、膜厚10μm、Rh含有量5g/
ft3の触媒層(表層)の2層が被覆担持されたA型の
ハニカムヒーターを得た。
(Comparative Example 2) According to Method B, a catalyst layer having a film thickness of 40 μm and an Rh content of 5 g / ft 3 is coated and supported on the upstream side, and a film thickness of 30 μm and a Pt content of 35 g / ft 3 are provided on the downstream side.
3 catalyst layer (inner layer), film thickness 10 μm, Rh content 5 g /
An A-type honeycomb heater in which two catalyst layers (surface layers) of ft 3 were coated and supported was obtained.

【0069】[評価方法] (1)触媒の耐久試験 実エンジンの排ガスを用いて、上記実施例及び比較例か
ら得られた触媒の長期寿命を推定するために、触媒温度
が750℃になるようにセットし、燃料カットモードを
取り入れて合計100時間エージングした。
[Evaluation Method] (1) Catalyst Endurance Test In order to estimate the long-term life of the catalysts obtained from the above Examples and Comparative Examples by using the exhaust gas of an actual engine, the catalyst temperature was set to 750 ° C. And the fuel cut mode was incorporated and aged for a total of 100 hours.

【0070】(2)触媒のコールドスタート時の特性評価 上記耐久試験後のサンプルを用い、エンジン始動時の排
ガス浄化特性を評価した(FTPにおけるBag1Aテ
スト)。サンプルはエンジン排気孔から200mmの位
置にセットし、通電中のヒーター温度が450℃になる
ようにオン−オフ制御で60秒間通電した。また、二次
空気はエンジン排気孔から100mmの位置でエンジン
始動後40秒間、200l/minで導入し、λ=1.0
〜1.3の雰囲気を保持するようにした。なお、ヒータ
ーを通電加熱しない場合における排ガス浄化特性も合わ
せて評価した。得られた結果を表1に示す。
(2) Evaluation of characteristics of catalyst at cold start Using the sample after the above durability test, exhaust gas purification characteristics at engine start were evaluated (Bag 1A test in FTP). The sample was set at a position 200 mm from the engine exhaust hole, and energized for 60 seconds by on-off control so that the heater temperature during energization was 450 ° C. Further, the secondary air is introduced at a position of 100 mm from the engine exhaust hole at 200 l / min for 40 seconds after the engine is started, and λ = 1.0.
The atmosphere of ~ 1.3 was maintained. The exhaust gas purification characteristics when the heater was not electrically heated were also evaluated. The results obtained are shown in Table 1.

【0071】[0071]

【表1】 [Table 1]

【0072】表1より、本実施例のサンプルは、比較例
のものよりCO、HCのエミッション値が低く、排ガス
の浄化能に優れることがわかる。特に通電加熱ありの場
合、実施例のサンプルは炭化水素浄化能を有する上流部
触媒層を配置しているのでHCの浄化能が高い。また、
二次空気を導入した場合(ヒーターは通電加熱せず)の
性能より、マニホールド用コンバーター(マニバータ
ー)としての性能が推定できるが、実施例のものがいず
れも浄化効率が高い。二次空気を導入しない場合のエミ
ッション値は、実施例、比較例ともにHC1.8g、CO 25
g、NOX 1.4gであり、二次空気が導入されたこと
によって、はじめて実施例の如く効果が発現する。な
お、耐久後のサンプルを同一の構成になるように切り出
して、合成ガスからなるエンジン模擬ガスを用い、触媒
の着火性能(リーン側とストイキオの2点)と定常特性
を評価したところ、実施例のサンプルが比較例のサンプ
ルに比し優れた三元性能(低温活性、400℃における
高浄化率)を示すことが確認でき、暖気後の定常運転に
も好適に作用することが確認できた。
It can be seen from Table 1 that the sample of this example has lower emission values of CO and HC than the sample of the comparative example and is superior in exhaust gas purification ability. In particular, in the case of heating with energization, the sample of the example has a high HC purification performance because the upstream catalyst layer having hydrocarbon purification performance is arranged. Also,
The performance as the manifold converter (maniverter) can be estimated from the performance when the secondary air is introduced (the heater is not electrically heated), but all of the examples have high purification efficiency. The emission values when secondary air is not introduced are 1.8 g of HC and 25
g, NO x 1.4 g, and the effect is exhibited as in the embodiment only after the secondary air is introduced. In addition, when the samples after the endurance were cut out so as to have the same configuration and the ignition performance (two points of lean side and stoichio) and the steady-state characteristics of the catalyst were evaluated using an engine simulation gas composed of synthetic gas, an example was obtained. It was confirmed that the sample of No. 3 showed excellent ternary performance (low temperature activity, high purification rate at 400 ° C.) as compared with the sample of Comparative Example, and it was also confirmed that the sample of No. 3 also suitably operates in steady operation after warming.

【0073】[0073]

【発明の効果】以上説明したように、本発明の排ガス浄
化用触媒及び排ガス浄化方法によれば、炭化水素(H
C)が多量に発生するエンジン始動時(コールドスター
ト時)には、主に炭化水素浄化能を有する上流部触媒層
が作用し、二次空気を導入してHCを最も効率よく浄化
できる燃料リーン側にすることにより、HCを高効率で
浄化できる。また、この時発生する反応熱により暖機特
性が向上し、特に通電発熱型ヒーターに用いる場合は、
その反応熱を最大限に利用し得るので、ヒーターへの消
費電力が大幅に低減できる。更に、暖機後の定常運転に
おいては、三元性能を有する下流部触媒層が有効に作用
して、好適に三元性能を発現する。
As described above, according to the exhaust gas purifying catalyst and the exhaust gas purifying method of the present invention, the hydrocarbon (H
At the time of engine start (cold start) in which a large amount of C) is generated (upstream), the upstream catalyst layer mainly having hydrocarbon purifying ability acts to introduce secondary air to most efficiently purify HC. By setting it to the side, HC can be purified with high efficiency. In addition, the reaction heat generated at this time improves the warm-up characteristics, and especially when used for an electric heating heater,
Since the reaction heat can be used to the maximum extent, the power consumption to the heater can be greatly reduced. Further, in the steady operation after the warm-up, the downstream catalyst layer having the three-way performance effectively acts, and the three-way performance is preferably expressed.

【図面の簡単な説明】[Brief description of drawings]

【図1】ハニカムヒーターの一例を示す説明図である。FIG. 1 is an explanatory diagram showing an example of a honeycomb heater.

【符号の説明】[Explanation of symbols]

10 外側面 11 電極 12 スリット 13 スリットの外周部 14 ハニカムヒーター 10 Outer Side Surface 11 Electrode 12 Slit 13 Outer Part of Slit 14 Honeycomb Heater

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 FI 技術表示箇所 F01N 3/22 321 P 3/28 301 P (72)発明者 山梨 文徳 神奈川県横浜市神奈川区宝町2番地 日産 自動車株式会社内 (72)発明者 柴田 勝弘 神奈川県横浜市神奈川区宝町2番地 日産 自動車株式会社内 (72)発明者 安部 文夫 愛知県半田市相賀町1番地の29 (72)発明者 近藤 智治 岐阜県土岐市泉西窯町4丁目43番地 (72)発明者 鈴木 純一 三重県桑名市大字小貝須字柳原351番地の 13 (72)発明者 野田 直美 愛知県一宮市大和町馬引字郷裏13番地─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 5 Identification number Reference number within the agency FI Technical indication location F01N 3/22 321 P 3/28 301 P (72) Inventor Fuminori Yamanashi Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa No. 2 in Nissan Motor Co., Ltd. (72) Inventor Katsuhiro Shibata No. 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Fumio Abe 29 (72) Inventor, No. 1 Aga-cho, Handa-shi, Aichi Tomoji Kondo 4-43, Izuminishi-machi, Toki City, Gifu Prefecture (72) Inventor Jun-ichi Suzuki, Kuwana City, Mie Prefecture 13 (72) Yanagihara, Kogaisu, Mie Prefecture (72) Inventor Naomi Noda, Yamato-machi, Ichinomiya-shi, Aichi Prefecture 13 back

Claims (25)

【特許請求の範囲】[Claims] 【請求項1】 少なくとも1個からなるモノリス担体の
上流部に炭化水素浄化能を有する少なくとも1層からな
る上流部触媒層が被覆され、下流部に三元性能を有する
少なくとも1層からなる下流部触媒層が被覆された排ガ
ス浄化用触媒であって、触媒活性成分として上流部触媒
層の最表層が少なくともPtかPdの一方を含み、かつ
下流部触媒層が少なくともRhを含むことを特徴とする
排ガス浄化用触媒。
1. A downstream portion comprising at least one upstream layer of a monolithic carrier, which is coated with an upstream catalyst layer comprising at least one layer having hydrocarbon purifying ability, and a downstream portion comprising at least one layer having three-way performance. An exhaust gas purifying catalyst coated with a catalyst layer, characterized in that the outermost surface layer of the upstream catalyst layer contains at least one of Pt and Pd as a catalytically active component, and the downstream catalyst layer contains at least Rh. Exhaust gas purification catalyst.
【請求項2】 上流部触媒層の最表層がPdを主成分と
する請求項1記載の排ガス浄化用触媒。
2. The exhaust gas purifying catalyst according to claim 1, wherein the outermost surface layer of the upstream catalyst layer contains Pd as a main component.
【請求項3】 上流部触媒層が、Pdのみからなる単一
層か、又は、最表層がPdからなり、該最表層の内側に
少なくともRhを含む層が設けられた複数層からなる請
求項1又は2記載の排ガス浄化用触媒。
3. The upstream catalyst layer is a single layer composed of only Pd or a plurality of layers in which the outermost surface layer is composed of Pd and a layer containing at least Rh is provided inside the outermost surface layer. Alternatively, the exhaust gas-purifying catalyst according to item 2.
【請求項4】 下流部触媒層の最表層がRhを主成分と
する請求項1ないし3のいずれかに記載の排ガス浄化用
触媒。
4. The exhaust gas-purifying catalyst according to claim 1, wherein the outermost surface layer of the downstream catalyst layer contains Rh as a main component.
【請求項5】 下流部触媒層が、最表層がRhからな
り、該最表層の内側に少なくともPtかPdのどちらか
一方を含む層が設けられた複数層からなる請求項1ない
し4のいずれかに記載の排ガス浄化用触媒。
5. The downstream catalyst layer according to claim 1, wherein the outermost surface layer is composed of Rh, and the outermost surface layer is formed of a plurality of layers in which a layer containing at least one of Pt and Pd is provided. The exhaust gas-purifying catalyst according to Crab.
【請求項6】 上流部触媒層及び/又は下流部触媒層に
含まれるRhが、Pt及びPdと接触しないよう分離さ
れている請求項1ないし5のいずれかに記載の排ガス浄
化用触媒。
6. The exhaust gas purifying catalyst according to claim 1, wherein Rh contained in the upstream catalyst layer and / or the downstream catalyst layer is separated so as not to come into contact with Pt and Pd.
【請求項7】 上流部触媒層がアルミナ及び/又はゼオ
ライト、必要に応じてジルコニアを主成分とする基体と
必要に応じて希土類酸化物とからなる請求項1ないし6
のいずれかに記載の排ガス浄化用触媒。
7. The upstream catalyst layer comprises alumina and / or zeolite, optionally a base material containing zirconia as a main component, and optionally a rare earth oxide.
The exhaust gas-purifying catalyst according to any one of 1.
【請求項8】 下流部触媒層がアルミナ及び/又はジル
コニアを主成分とする基体と必要に応じて希土類酸化物
とからなる請求項1ないし7のいずれかに記載の排ガス
浄化用触媒。
8. The exhaust gas-purifying catalyst according to claim 1, wherein the downstream catalyst layer comprises a substrate containing alumina and / or zirconia as a main component and, if necessary, a rare earth oxide.
【請求項9】 少なくとも1個からなるモノリス担体の
上流部に炭化水素浄化能を有する少なくとも1層からな
る上流部触媒層が被覆され、下流部に、三元性能を有す
る少なくとも1層からなる第1触媒層と、該第1触媒層
の表面に被覆され炭化水素浄化能を有する第2触媒層と
からなる下流部触媒層が設けられた排ガス浄化用触媒で
あって、触媒活性成分として上流部触媒層の最表層及び
下流部触媒層の第2触媒層がPtかPdの一方を含み、
かつ下流部触媒層の第1触媒層が少なくともRhを含む
ことを特徴とする排ガス浄化用触媒。
9. A first catalyst comprising at least one monolithic carrier coated with an upstream catalyst layer consisting of at least one layer having hydrocarbon purifying ability, and a downstream part comprising at least one layer having three-way performance. An exhaust gas purifying catalyst comprising a downstream catalyst layer comprising one catalyst layer and a second catalyst layer which is coated on the surface of the first catalyst layer and has a hydrocarbon purifying ability, the upstream portion serving as a catalytically active component. The outermost surface layer of the catalyst layer and the second catalyst layer of the downstream catalyst layer include one of Pt and Pd,
An exhaust gas-purifying catalyst, characterized in that the first catalyst layer of the downstream catalyst layer contains at least Rh.
【請求項10】 上流部触媒層の最表層がPdを主成分
とする請求項9記載の排ガス浄化用触媒。
10. The exhaust gas-purifying catalyst according to claim 9, wherein the outermost surface layer of the upstream catalyst layer contains Pd as a main component.
【請求項11】 上流部触媒層がPdのみからなる単一
層か、又は、最表層がPdからなり該最表層の内側に少
なくともRhを含む層が設けられた複数層からなる請求
項9又は10記載の排ガス浄化用触媒。
11. The upstream catalyst layer comprises a single layer consisting of Pd alone, or a plurality of layers in which the outermost layer is composed of Pd and a layer containing at least Rh is provided inside the outermost layer. Exhaust gas purification catalyst described.
【請求項12】 下流部触媒層の第2触媒層がPdを主
成分とする請求項9ないし11のいずれかに記載の排ガ
ス浄化用触媒。
12. The exhaust gas-purifying catalyst according to claim 9, wherein the second catalyst layer of the downstream catalyst layer contains Pd as a main component.
【請求項13】 下流部触媒層の第1触媒層の最表層が
Rhを主成分とし、該最表層の内側に少なくともPtか
Pdの一方を含む層が設けられている請求項9ないし1
2のいずれかに記載の排ガス浄化用触媒。
13. The outermost layer of the first catalyst layer of the downstream catalyst layer contains Rh as a main component, and a layer containing at least one of Pt and Pd is provided inside the outermost layer.
2. The exhaust gas purifying catalyst according to any one of 2 above.
【請求項14】 上流部触媒層及び/又は下流部触媒層
に含まれるRhが、Pt及びPdと接触しないよう分離
されている請求項9〜13のいずれかに記載の排ガス浄
化用触媒。
14. The exhaust gas purifying catalyst according to claim 9, wherein Rh contained in the upstream catalyst layer and / or the downstream catalyst layer is separated so as not to come into contact with Pt and Pd.
【請求項15】 上流部触媒層がアルミナ及び/又はゼ
オライト、必要に応じてジルコニアを主成分とする基体
と必要に応じて希土類酸化物とからなる請求項9ないし
14のいずれかに記載の排ガス浄化用触媒。
15. The exhaust gas according to claim 9, wherein the upstream catalyst layer is composed of alumina and / or zeolite, optionally a substrate containing zirconia as a main component, and optionally a rare earth oxide. Purification catalyst.
【請求項16】 下流部触媒層がアルミナ及び/又はジ
ルコニアを主成分とする基体と必要に応じて希土類酸化
物とからなる請求項9ないし15のいずれかに記載の排
ガス浄化用触媒。
16. The exhaust gas-purifying catalyst according to claim 9, wherein the downstream catalyst layer comprises a substrate containing alumina and / or zirconia as a main component and, if necessary, a rare earth oxide.
【請求項17】 モノリス担体が耐熱性無機質からな
り、ハニカム構造を有する請求項1ないし16のいずれ
かに記載の排ガス浄化用触媒。
17. The exhaust gas-purifying catalyst according to claim 1, wherein the monolith carrier is made of a heat resistant inorganic material and has a honeycomb structure.
【請求項18】 モノリス担体がハニカム構造からな
り、少なくとも1個の電極を有し、必要に応じてモノリ
ス担体を連結し、通電により発熱する請求項1ないし1
7のいずれかに記載の排ガス浄化用触媒。
18. The monolithic carrier has a honeycomb structure, has at least one electrode, and the monolithic carrier is connected as necessary to generate heat by energization.
7. The exhaust gas purifying catalyst according to any one of 7.
【請求項19】 ハニカム構造からなるモノリス担体の
電極間に抵抗調節機構を設けた請求項18記載の排ガス
浄化用触媒。
19. The exhaust gas purifying catalyst according to claim 18, wherein a resistance adjusting mechanism is provided between the electrodes of the monolith carrier having a honeycomb structure.
【請求項20】 少なくとも1個からなるモノリス担体
の上流部に炭化水素浄化能を有する上流部触媒層が被覆
され、下流部に三元性能を有する下流部触媒層が被覆さ
れ、触媒活性成分として上流部触媒層の最表層が少なく
ともPtかPdの一方を含み、かつ下流部触媒層が少な
くともRhを含む排ガス浄化用触媒の前方より、エンジ
ン始動時排ガスに二次空気を導入することを特徴とする
排ガス浄化方法。
20. An upstream catalyst layer having hydrocarbon purifying ability is coated on the upstream portion of at least one monolithic carrier, and a downstream catalyst layer having three-way performance is coated on the downstream portion, and as a catalytically active component. Secondary air is introduced into the exhaust gas at engine startup from the front of the exhaust gas purifying catalyst in which the outermost surface layer of the upstream catalyst layer contains at least one of Pt and Pd and the downstream catalyst layer contains at least Rh. Exhaust gas purification method.
【請求項21】 少なくとも1個からなるモノリス担体
の上流部に炭化水素浄化能を有する少なくとも1層から
なる上流部触媒層が被覆され、下流部に、三元性能を有
する少なくとも1層からなる第1触媒層と、該第1触媒
層の表面に被覆され炭化水素浄化能を有する第2触媒層
とからなる下流部触媒層が設けられ、触媒活性成分とし
て上流部触媒層の最表層及び下流部触媒層の第2触媒層
がPtかPdの一方を含み、かつ下流部触媒層の第1触
媒層が少なくともRhを含む排ガス浄化用触媒の前方よ
り、エンジン始動時排ガスに二次空気を導入することを
特徴とする排ガス浄化方法。
21. A first catalyst comprising at least one monolithic carrier coated with an upstream catalyst layer consisting of at least one layer having hydrocarbon purifying ability, and a downstream part comprising at least one layer having three-way performance. A downstream catalyst layer consisting of one catalyst layer and a second catalyst layer having a hydrocarbon purifying ability that is coated on the surface of the first catalyst layer is provided, and the outermost surface layer and the downstream portion of the upstream catalyst layer serve as catalytically active components. The second catalyst layer of the catalyst layer contains either Pt or Pd, and the first catalyst layer of the downstream catalyst layer contains at least Rh. From the front of the exhaust gas purifying catalyst, secondary air is introduced into the exhaust gas at engine start. An exhaust gas purification method characterized by the above.
【請求項22】 エンジン始動時に二次空気を導入する
ことにより、排ガスをリーン側にする請求項20又は2
1記載の排ガス浄化方法。
22. The exhaust gas is made leaner by introducing secondary air when the engine is started.
The exhaust gas purification method described in 1.
【請求項23】 モノリス担体が耐熱性無機質からな
り、ハニカム構造を有する請求項20ないし22のいず
れかに記載の排ガス浄化方法。
23. The exhaust gas purification method according to claim 20, wherein the monolith carrier is made of a heat resistant inorganic material and has a honeycomb structure.
【請求項24】 モノリス担体がハニカム構造からな
り、少なくとも1個の電極を有し、エンジン始動時に二
次空気を導入するとともに通電により発熱する請求項2
0ないし22のいずれかに記載の排ガス浄化方法。
24. The monolith carrier has a honeycomb structure, has at least one electrode, and introduces secondary air at the time of engine start and generates heat by energization.
23. The exhaust gas purification method according to any one of 0 to 22.
【請求項25】 ハニカム構造からなるモノリス担体の
電極間に抵抗調節機構を設けた請求項24記載の排ガス
浄化方法。
25. The exhaust gas purification method according to claim 24, wherein a resistance adjusting mechanism is provided between the electrodes of the monolith carrier having a honeycomb structure.
JP4095246A 1992-04-15 1992-04-15 Catalyst for purifying exhaust gas and method therefor Pending JPH05293376A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
JP4095246A JPH05293376A (en) 1992-04-15 1992-04-15 Catalyst for purifying exhaust gas and method therefor
US08/045,083 US5376610A (en) 1992-04-15 1993-04-12 Catalyst for exhaust gas purification and method for exhaust gas purification
DE69312778T DE69312778T2 (en) 1992-04-15 1993-04-15 Exhaust gas purification catalyst and exhaust gas purification method
EP93302918A EP0566401B1 (en) 1992-04-15 1993-04-15 Catalyst for exhaust gas purification and method for exhaust gas purification

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4095246A JPH05293376A (en) 1992-04-15 1992-04-15 Catalyst for purifying exhaust gas and method therefor

Publications (1)

Publication Number Publication Date
JPH05293376A true JPH05293376A (en) 1993-11-09

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ID=14132402

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Country Link
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