JPH09103679A - Exhaust gas-purifying catalyst for diesel engine - Google Patents
Exhaust gas-purifying catalyst for diesel engineInfo
- Publication number
- JPH09103679A JPH09103679A JP7263257A JP26325795A JPH09103679A JP H09103679 A JPH09103679 A JP H09103679A JP 7263257 A JP7263257 A JP 7263257A JP 26325795 A JP26325795 A JP 26325795A JP H09103679 A JPH09103679 A JP H09103679A
- Authority
- JP
- Japan
- Prior art keywords
- exhaust gas
- particle size
- catalyst
- coarse
- supported
- 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
Links
- 239000003054 catalyst Substances 0.000 title claims description 61
- 239000002245 particle Substances 0.000 claims abstract description 44
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 20
- 230000003197 catalytic effect Effects 0.000 claims abstract description 18
- 239000010419 fine particle Substances 0.000 claims abstract description 9
- 239000011362 coarse particle Substances 0.000 claims abstract description 8
- 238000000746 purification Methods 0.000 claims description 28
- 238000011144 upstream manufacturing Methods 0.000 claims description 26
- 239000000463 material Substances 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 abstract description 15
- 230000003647 oxidation Effects 0.000 abstract description 13
- 238000007254 oxidation reaction Methods 0.000 abstract description 13
- 230000001590 oxidative effect Effects 0.000 abstract description 10
- 230000003111 delayed effect Effects 0.000 abstract 1
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 72
- 239000007789 gas Substances 0.000 description 62
- 239000004215 Carbon black (E152) Substances 0.000 description 43
- 229930195733 hydrocarbon Natural products 0.000 description 43
- 150000002430 hydrocarbons Chemical class 0.000 description 43
- 230000000052 comparative effect Effects 0.000 description 13
- 238000010438 heat treatment Methods 0.000 description 12
- 239000010410 layer Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- 238000000354 decomposition reaction Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- 239000000758 substrate Substances 0.000 description 10
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 229910052809 inorganic oxide Inorganic materials 0.000 description 5
- NFOHLBHARAZXFQ-UHFFFAOYSA-L platinum(2+);dihydroxide Chemical compound O[Pt]O NFOHLBHARAZXFQ-UHFFFAOYSA-L 0.000 description 5
- 239000010948 rhodium Substances 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 230000010718 Oxidation Activity Effects 0.000 description 3
- 230000033228 biological regulation Effects 0.000 description 3
- 229910052878 cordierite Inorganic materials 0.000 description 3
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000010485 coping Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
Landscapes
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ディーゼルエンジ
ン用排ガス浄化触媒に関し、詳しくは、ディーゼルエン
ジンからの排ガス中に含まれる有害成分である一酸化炭
素（ＣＯ）、炭化水素（ＨＣ）及び可溶性有機成分（Ｓ
ＯＦ）を浄化するとともに、硫酸塩（サルフェート）の
排出量を低減する排ガス浄化触媒に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying catalyst for a diesel engine, and more specifically, carbon monoxide (CO), hydrocarbon (HC) and soluble organic compounds which are harmful components contained in the exhaust gas from a diesel engine. Ingredient (S
The present invention relates to an exhaust gas purification catalyst that purifies OF and reduces the emission amount of sulfate (sulfate).
【０００２】[0002]
【従来の技術】ガソリンエンジンについては、排ガスの
厳しい規制とそれに対処できる技術の進歩とにより、排
ガス中の有害成分は確実に減少されてきている。しか
し、ディーゼルエンジンについては、有害成分がＰＭ
（炭素微粒子、サルフェート等の硫黄系微粒子、高分子
量炭化水素微粒子等のパティキュレート・マテリアル）
として排出されるという特異な事情から、規制も技術の
進歩もガソリンエンジンに比べて遅れており、確実に排
ガスを浄化できる排ガス浄化装置の開発が望まれてい
る。2. Description of the Related Art With respect to gasoline engines, harmful components in exhaust gas have been steadily reduced due to strict regulations on exhaust gas and advances in technology capable of coping with the regulations. However, for diesel engines, the harmful components are PM
(Particulate materials such as carbon-based particles, sulfur-based particles such as sulfate, and high-molecular-weight hydrocarbon particles)
Due to the peculiar circumstances of being discharged as gas, regulation and technological progress are behind the gasoline engine, and the development of an exhaust gas purifying device that can surely purify exhaust gas is desired.
【０００３】現在までに開発されているディーゼルエン
ジン用排ガス浄化装置としては、大きく分けてトラップ
型の排ガス浄化触媒を用いたトラップ型排ガス浄化装置
と、オープン型の排ガス浄化触媒を用いたオープン型排
ガス浄化装置とが知られている。トラップ型の排ガス浄
化触媒としては、セラミック製の目封じタイプのハニカ
ム体（ディーゼルパティキュレートフィルタ（ＤＰ
Ｆ））等が知られている。この排ガス浄化触媒を用いた
排ガス浄化装置では、ＤＰＦ等で排ガスを濾過してＰＭ
を捕集し、圧損が上昇すればバーナ等で蓄積したＰＭを
燃焼させることによりＤＰＦ等を再生するようになって
いる。また、ＰＭの捕集とともにＣＯ、ＨＣ及びＳＯＦ
を酸化・分解させるべく、ＤＰＦ等の担体基材にアルミ
ナ等により触媒担持層を形成し、この触媒担持層に白金
（Ｐｔ）等を担持させた排ガス浄化触媒も検討されてい
る。[0003] As exhaust gas purifying devices for diesel engines that have been developed to date, trap type exhaust gas purifying devices using trap type exhaust gas purifying catalysts and open type exhaust gas purifying devices using open type exhaust gas purifying catalysts have been roughly classified. A purifying device is known. As a trap-type exhaust gas purifying catalyst, a ceramic plugged honeycomb body (diesel particulate filter (DP
F)) and the like are known. In an exhaust gas purifying apparatus using the exhaust gas purifying catalyst, the exhaust gas is filtered by a DPF or the like and the PM is filtered.
Is collected, and if the pressure loss increases, the PM accumulated by a burner or the like is burned to regenerate the DPF or the like. In addition to collecting PM, CO, HC and SOF
In order to oxidize and decompose the exhaust gas, an exhaust gas purifying catalyst in which a catalyst support layer is formed of alumina or the like on a carrier base material such as DPF and platinum (Pt) or the like is supported on the catalyst support layer is also under study.
【０００４】一方、オープン型の排ガス浄化触媒として
は、セラミック製のストレートフロータイプのハニカム
体等からなる担体基材と、この担体基材にアルミナ等に
より形成された触媒担持層と、この触媒担持層にガソリ
ンエンジンと同様に担持されたＰｔ等とからなるものが
知られている。このオープン型排ガス浄化装置によれ
ば、Ｐｔ等の触媒作用によりＣＯ等の酸化・分解が可能
である。On the other hand, as an open type exhaust gas purifying catalyst, a carrier base material made of a ceramic straight flow type honeycomb body or the like, a catalyst support layer formed of alumina or the like on the carrier base material, and the catalyst support It is known that the layer is composed of Pt and the like supported in the same manner as a gasoline engine. According to this open type exhaust gas purifying apparatus, CO and the like can be oxidized and decomposed by the catalytic action of Pt and the like.
【０００５】しかし、上記白金等をもつトラップ型又は
オープン型排ガス浄化装置では、触媒担持層が排ガス中
のＳＯ2 を吸着し、高温時にＳＯ2 がＰｔ等の触媒作用
により酸化されてＳＯ3 として排出されてしまう。特
に、ディーゼルエンジンにおいては、排ガス中に酸素ガ
スも充分存在し、この酸素ガスによってＳＯ2 が酸化さ
れてＳＯ3 として排出されやすい。そして、ＳＯ2 はＰ
Ｍとして測定されないが、ＳＯ3 はＰＭとして測定され
る。また、ＳＯ3 は排ガス中に多量に存在する水蒸気と
容易に反応して硫酸ミストを形成し、サルフェートとし
て排出されてしまう。このため、これらの排ガス浄化装
置では、高温時にサルフェートの排出によりＰＭ量が増
大するという問題がある。However, in the above-mentioned trap type or open type exhaust gas purifying device having platinum or the like, the catalyst supporting layer adsorbs SO 2 in the exhaust gas, and at high temperature SO 2 is oxidized by the catalytic action of Pt or the like to be converted into SO 3. It will be discharged. Particularly, in a diesel engine, oxygen gas is sufficiently present in the exhaust gas, and SO 2 is easily oxidized by this oxygen gas and is easily discharged as SO 3 . And SO 2 is P
Not measured as M, but SO 3 is measured as PM. Further, SO 3 easily reacts with a large amount of water vapor present in the exhaust gas to form a sulfuric acid mist and is discharged as a sulfate. Therefore, these exhaust gas purifying devices have a problem that the amount of PM increases due to the discharge of sulfate at a high temperature.
【０００６】かかる実情から、特開昭６２−５６７８３
号公報にはアルミナにＰｔを担持後、７００〜１０００
℃で熱処理することでＰｔをシンタリングさせ、これに
よりＳＯ2 の酸化作用を低下させたディーゼル排気中の
微粒子除去用触媒の製造方法が開示されている。[0006] Under such circumstances, Japanese Patent Application Laid-Open No. 62-56783.
In Japanese Patent Laid-Open Publication No. 700-1000, after supporting Pt on alumina,
A method for producing a catalyst for removing fine particles in diesel exhaust, in which Pt is sintered by heat treatment at ℃, thereby reducing the oxidizing action of SO 2 is disclosed.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら特開昭６
２−５６７８３号公報に開示の触媒では、サルフェート
の生成を抑制する効果は大きいものの、Ｐｔの酸化活性
が低下するため低温域においてＳＯＦやＨＣを酸化浄化
する作用が低いという不具合があった。本発明は、上記
の事情に鑑みてなされたものであり、低温域におけるＳ
ＯＦやＨＣ等の酸化・分解性能を従来と同等以上に維持
するとともに、ＳＯ3 及びサルフェートの生成を抑制す
ることを目的とする。なお、ＳＯＦは比較的高分子量の
炭化水素であるので、以下、低分子量のＨＣとＳＯＦを
まとめてＨＣという。SUMMARY OF THE INVENTION However, Japanese Unexamined Patent Publication No.
The catalyst disclosed in JP-A-2-56783 has a large effect of suppressing the formation of sulfate, but has a problem that the effect of oxidizing and purifying SOF and HC is low in a low temperature range because the oxidation activity of Pt decreases. The present invention has been made in view of the above circumstances, and S in a low temperature range is
The object is to maintain the oxidation / decomposition performance of OF, HC and the like at a level equal to or higher than that of the conventional one, and to suppress the production of SO 3 and sulfate. Since SOF is a relatively high molecular weight hydrocarbon, hereinafter, low molecular weight HC and SOF are collectively referred to as HC.
【０００８】[0008]
【課題を解決するための手段】上記課題を解決する本発
明のディーゼルエンジン用排ガス浄化触媒の特徴は、多
孔質の担体基材と、担体基材に担持された触媒貴金属
と、からなり、触媒貴金属は、排気ガス流の上流側には
平均粒径５ｎｍ以下の微細粒子を含んで担持され、下流
側には平均粒径１０ｎｍ以上の粗大粒子として担持され
ていることにある。The features of the exhaust gas purifying catalyst for a diesel engine of the present invention for solving the above-mentioned problems are characterized by comprising a porous carrier base material and a catalytic noble metal supported on the carrier base material. The noble metal is carried on the upstream side of the exhaust gas flow while containing fine particles having an average particle size of 5 nm or less, and on the downstream side as coarse particles having an average particle size of 10 nm or more.
【０００９】[0009]
【発明の実施の形態】多孔質の担体基材は、アルミナ、
シリカ、チタニア、ゼオライト、シリカ−アルミナ及び
チタニア−アルミナ等の耐火性無機酸化物により形成す
ることができる。耐火性無機酸化物は、平均粒径が２０
μｍ以下、比表面積が１０ｍ2 ／ｇ以上のものであるこ
とが好ましい。耐火性無機酸化物が２０μｍを超える平
均粒径であり、かつ１０ｍ2 ／ｇ未満の比表面積であれ
ば、十分なＨＣの浄化性能が得られない虞れがある。な
おこれらの耐火性無機酸化物からハニカム形状又はペレ
ット形状の担体基材を形成してもよいし、コーディエラ
イト又は金属から形成された基材に上記耐火性無機酸化
物をコーティングして担体基材とすることもできる。BEST MODE FOR CARRYING OUT THE INVENTION A porous carrier substrate is alumina,
It can be formed of a refractory inorganic oxide such as silica, titania, zeolite, silica-alumina and titania-alumina. The refractory inorganic oxide has an average particle size of 20.
It is preferably μm or less and a specific surface area of 10 m 2 / g or more. If the refractory inorganic oxide has an average particle size of more than 20 μm and a specific surface area of less than 10 m 2 / g, sufficient HC purification performance may not be obtained. A honeycomb-shaped or pellet-shaped carrier substrate may be formed from these refractory inorganic oxides, or a carrier substrate formed by coating the above refractory inorganic oxide on a substrate formed of cordierite or metal. It can also be made of wood.
【００１０】触媒貴金属としては、代表的なＰｔ、パラ
ジウム（Ｐｄ）、ロジウム（Ｒｈ）の他、ルテニウム
（Ｒｕ）、オスニウム（Ｏｓ）及びイリジウム（Ｉｒ）
の少なくとも一種を採用することができる。例えば、Ｐ
ｔの担持量は、排ガス浄化触媒の単位容積当り、０．０
１〜１０．０ｇ／Ｌであることが好ましい。Ｐｔの担持
量が０．０１ｇ／Ｌ未満では、十分な酸化・分解性能が
得られない虞れがある。逆に、１０．０ｇ／Ｌを超えて
Ｐｔを担持しても、酸化・分解性能の向上が僅かであ
り、排ガス浄化触媒が高価となる。特に、Ｐｔの担持量
が０．１〜３．０ｇ／Ｌである場合は酸化・分解性能と
コストとの両面で好ましい。Typical catalyst noble metals include Pt, palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir).
At least one of the above can be adopted. For example, P
The carried amount of t is 0.0 per unit volume of the exhaust gas purifying catalyst.
It is preferably from 1 to 10.0 g / L. If the amount of Pt supported is less than 0.01 g / L, sufficient oxidation / decomposition performance may not be obtained. On the contrary, even if Pt is supported in an amount of more than 10.0 g / L, the oxidation / decomposition performance is slightly improved, and the exhaust gas purifying catalyst becomes expensive. Particularly, when the supported amount of Pt is 0.1 to 3.0 g / L, it is preferable in terms of both oxidation / decomposition performance and cost.
【００１１】Ｐｄの担持量は、排ガス浄化触媒の単位容
積当り、０．０１〜２０．０ｇ／Ｌであることが好まし
い。Ｐｄの担持量が０．０１ｇ／Ｌ未満では、十分な酸
化・分解性能が得られない虞れがある。逆に、２０．０
ｇ／Ｌを超えてＰｄを担持しても、酸化・分解性能の向
上が僅かであり、排ガス浄化触媒が高価となる。特に、
Ｐｄの担持量が０．５〜３．０ｇ／Ｌである場合は酸化
・分解性能とコストとの両面で好ましい。The amount of Pd supported is preferably 0.01 to 20.0 g / L per unit volume of the exhaust gas purifying catalyst. If the supported amount of Pd is less than 0.01 g / L, there is a possibility that sufficient oxidation / decomposition performance may not be obtained. Conversely, 20.0
Even if Pd is supported in excess of g / L, the oxidation / decomposition performance is slightly improved, and the exhaust gas purification catalyst becomes expensive. Especially,
When the supported amount of Pd is 0.5 to 3.0 g / L, it is preferable in terms of both oxidation / decomposition performance and cost.
【００１２】Ｒｈの担持量は、排ガス浄化触媒の単位容
積当り、０．０１〜１．０ｇ／Ｌであることが好まし
い。Ｒｈの担持量が０．０１ｇ／Ｌ未満では、十分な酸
化・分解性能が得られない虞れがある。逆に、１．０ｇ
／Ｌを超えてＲｈを担持しても、酸化・分解性能の向上
が僅かであり、排ガス浄化触媒が高価となる。特に、Ｒ
ｈの担持量が０．０５〜０．５ｇ／Ｌである場合は酸化
・分解性能とコストとの両面で好ましい。The supported amount of Rh is preferably 0.01 to 1.0 g / L per unit volume of the exhaust gas purifying catalyst. If the supported amount of Rh is less than 0.01 g / L, there is a possibility that sufficient oxidation / decomposition performance may not be obtained. Conversely, 1.0g
Even if Rh is supported in excess of / L, the oxidation / decomposition performance is slightly improved, and the exhaust gas purification catalyst becomes expensive. In particular, R
When the supported amount of h is 0.05 to 0.5 g / L, it is preferable in terms of both oxidation / decomposition performance and cost.
【００１３】ところで、ＳＯ2 とＨＣとの酸化され易さ
を比較すると、ＳＯ2 はＨＣより酸化され難い特性を有
している。つまり、ＳＯ2 とＨＣとが共存する排ガスに
触媒貴金属を接触させるとＨＣが優先的に酸化される。
したがって、ＨＣが存在していない場合ではＳＯ2 が酸
化され、サルフェートが生成され易くなる。この現象は
特に排ガスが高温になると顕著となる。By the way, comparing the oxidizability of SO 2 and HC, SO 2 has a characteristic that it is harder to oxidize than HC. That is, when the catalytic noble metal is brought into contact with the exhaust gas in which SO 2 and HC coexist, HC is preferentially oxidized.
Therefore, when HC is not present, SO 2 is oxidized and sulfate is easily generated. This phenomenon becomes remarkable especially when the exhaust gas is heated to a high temperature.
【００１４】また触媒貴金属においては、粒径が小さい
ほどＨＣ、ＳＯ2 のいずれの酸化活性も増大する。一
方、粒径が大きくなると、ＨＣの酸化活性は低温時で若
干低下するが高温時では活性低下がほとんど見られない
のに対し、ＳＯ2 の酸化活性は高温時に大きく低下す
る。そこで本発明の排ガス浄化触媒は、排ガス流の上流
側に５ｎｍ以下の粒径からなる貴金属を担持したもの
と、下流側に１０ｎｍ以上の貴金属を担持したものから
なる構成としていることから、低温時においてＨＣを優
先的に酸化分解し、かつ高温時にサルフェートの生成を
防止することが実現可能となったものである。In the catalytic noble metal, the smaller the particle size, the greater the oxidizing activity of both HC and SO 2 . On the other hand, as the particle size increases, the oxidizing activity of HC slightly decreases at low temperature, but the activity hardly decreases at high temperature, whereas the oxidizing activity of SO 2 greatly decreases at high temperature. Therefore, the exhaust gas purifying catalyst of the present invention has a structure in which a noble metal having a particle size of 5 nm or less is carried on the upstream side of the exhaust gas flow and a noble metal having a particle size of 10 nm or more is carried on the downstream side, so that at low temperature It is possible to preferentially oxidize and decompose HC and prevent the formation of sulfate at high temperature.
【００１５】以下に本発明の詳細を説明する。本発明の
排ガス浄化用触媒では、貴金属は排気ガス流の上流側に
５ｎｍ以下の粒径の微細粒子を含んで担持されている。
触媒貴金属は粒径が小さいほど表面積が大きくなり酸化
活性が増大するので、ＳＯ2 とＨＣとが共存する上流側
において触媒貴金属の粒径を５ｎｍ以下とすることによ
りＨＣが優先的に酸化され、高いＨＣの浄化性能が得ら
れる。微細粒子が５ｎｍを超える粒径となると、低温域
における酸化活性が低下するため、ＨＣの浄化性能が低
下する。The details of the present invention will be described below. In the exhaust gas-purifying catalyst of the present invention, the noble metal is supported on the upstream side of the exhaust gas flow, including fine particles having a particle size of 5 nm or less.
The smaller the particle size of the catalytic noble metal, the larger the surface area and the higher the oxidation activity. Therefore, by setting the particle size of the catalytic noble metal to 5 nm or less on the upstream side where SO 2 and HC coexist, HC is preferentially oxidized, High HC purification performance can be obtained. When the fine particles have a particle size of more than 5 nm, the oxidizing activity in the low temperature range is lowered, and the purification performance of HC is lowered.
【００１６】なお、上流側には少なくとも粒径５ｎｍ以
下の触媒貴金属の微細粒子が担持されていればよく、５
ｎｍ以上の触媒貴金属粒子の担持を拒むものではない。
そして５ｎｍを超える粒子が担持されていてもコストの
面を除けば特に不具合は生じない。一方、上流側で酸化
されなかったＳＯ2 はそのまま下流側へ流れる。本発明
の排ガス浄化触媒では、触媒貴金属は排ガス流の下流側
に１０ｎｍ以上の粒径の粗大粒子として担持されてい
る。したがって下流側では、高温においても酸化活性が
小さいのでＳＯ2 は酸化されずそのまま排出され、ＳＯ
3 やサルフェートとなるのが防止されている。これによ
りＰＭの排出量が低減される。なお、上流側で酸化され
なかったＨＣが存在しても、ＨＣはＳＯ2 に比べ粗大な
触媒貴金属でも比較的容易に酸化されるので、存在する
ＨＣは酸化浄化され未浄化ＨＣが排出されるのが防止さ
れる。It is sufficient that fine particles of catalytic noble metal having a particle diameter of 5 nm or less are carried on the upstream side.
It does not prevent the loading of catalytic noble metal particles having a size of not less than nm.
Even if particles having a size of more than 5 nm are carried, no particular problem occurs except for cost. On the other hand, SO 2 that has not been oxidized on the upstream side flows to the downstream side as it is. In the exhaust gas purifying catalyst of the present invention, the catalytic noble metal is carried on the downstream side of the exhaust gas stream as coarse particles having a particle size of 10 nm or more. Therefore, on the downstream side, since the oxidizing activity is small even at high temperature, SO 2 is not oxidized and is discharged as it is.
It is prevented from becoming 3 or sulfate. As a result, the emission amount of PM is reduced. Even if there is HC that has not been oxidized on the upstream side, HC is relatively easily oxidized even with a catalytic precious metal that is coarser than SO 2. Therefore, the existing HC is oxidized and purified and unpurified HC is discharged. Is prevented.
【００１７】なお下流側に担持される触媒貴金属の粗大
粒子の粒径が１０ｎｍより小さいと、酸化活性が高くＳ
Ｏ2 が酸化されるようになるため好ましくない。下流側
に担持される粗大粒子の粒径の上限は特に制限されない
が、６０ｎｍ以下とすることが望ましい。６０ｎｍを越
えると下流側におけるＨＣの浄化性能まで低下し、全体
としてＨＣの浄化性能が低下する。If the particle size of the coarse particles of the catalytic noble metal supported on the downstream side is smaller than 10 nm, the oxidation activity is high and S
This is not preferable because O 2 will be oxidized. The upper limit of the particle size of the coarse particles carried on the downstream side is not particularly limited, but is preferably 60 nm or less. If it exceeds 60 nm, the HC purification performance on the downstream side is also deteriorated, and the HC purification performance is deteriorated as a whole.
【００１８】担体基材において、粒径が５ｎｍ以下の微
細粒子が担持される上流側と、１０ｎｍ以上の粗大粒子
が担持される下流側の容積比は、上流側／下流側＝１／
４〜１／１とするのが好ましい。上流側の容積がこれよ
り小さいとＨＣの浄化性能が低下し、上流側の容積がこ
れより大きくなるとＳＯ2 の酸化が生じ易くなるため好
ましくない。なお、上流側と下流側は一の担体基材内で
連続していてもよいし、分離されていてもよい。また担
体基材を分離したタンデム触媒装置とし、５ｎｍ以下の
微細粒子を担持した担体基材を上流側に、１０ｎｍ以上
の粗大粒子を担持した担体基材を下流側に配置して本発
明の排ガス浄化触媒とすることもできる。この場合に
も、上流側の担体基材と下流側の担体基材の容積比を上
記範囲とすることが望ましい。In the carrier substrate, the volume ratio of the upstream side, on which fine particles having a particle size of 5 nm or less are carried, to the downstream side, on which coarse particles having a particle size of 10 nm or more are carried, is upstream / downstream = 1 /
It is preferably 4 to 1/1. If the volume on the upstream side is smaller than this, the purification performance of HC is deteriorated, and if the volume on the upstream side is larger than this, SO 2 is easily oxidized, which is not preferable. The upstream side and the downstream side may be continuous in one carrier base material or may be separated. Further, a tandem catalyst device in which a carrier substrate is separated is used, and a carrier substrate carrying fine particles of 5 nm or less is arranged on the upstream side, and a carrier substrate carrying coarse particles of 10 nm or more is arranged on the downstream side. It can also be used as a purification catalyst. Also in this case, it is desirable to set the volume ratio of the upstream carrier substrate to the downstream carrier substrate within the above range.
【００１９】[0019]
（実施例１）図１及び図２に本実施例の排ガス浄化触媒
の概略構成図を示す。この排ガス浄化触媒は、コーディ
エライト製のハニカム担体（１）と、ハニカム担体
（１）表面に被覆されたコート層（２）と、ハニカム担
体（１）全体に均一に担持された平均粒径１０ｎｍ以上
の粗大Ｐｔ（３）と、ハニカム担体（１）の上流側端面
から容積で４０％の範囲のコート層（２）に担持された
平均粒径５ｎｍ以下の微細Ｐｔ（４）とから構成されて
いる。(Embodiment 1) FIG. 1 and FIG. 2 are schematic configuration diagrams of an exhaust gas purifying catalyst of this embodiment. This exhaust gas purifying catalyst comprises a cordierite honeycomb carrier (1), a coat layer (2) coated on the surface of the honeycomb carrier (1), and an average particle size uniformly supported on the entire honeycomb carrier (1). Coarse Pt (3) having a size of 10 nm or more and fine Pt (4) having an average particle size of 5 nm or less carried by the coat layer (2) in a volume range of 40% from the upstream end surface of the honeycomb carrier (1). Has been done.
【００２０】この排ガス浄化触媒を製造した方法を以下
に詳細に説明することで、本実施例の排ガス浄化触媒の
構成の詳細な説明に代える。コーディエライト製のスト
レートフロータイプのハニカム担体（１）（４００セル
／ｉｎ2 、直径１１７ｍｍ、長さ１２０ｍｍ、容積１．
３リットル）を用意する。次に、シリカとアルミナを重
量比でＳｉＯ2 ：Ａｌ2 Ｏ3 ＝９：１となるように含む
スラリーを調製し、ハニカム担体（１）をこのスラリー
に浸漬し引き上げて余分なスラリーを吹き払った後、１
００℃で１時間乾燥後５００℃で１時間焼成して、ハニ
カム担体（１）１リットル当たり１００ｇのコート層
（２）を形成した。The method for producing the exhaust gas purifying catalyst will be described in detail below, and will replace the detailed description of the structure of the exhaust gas purifying catalyst of this embodiment. Cordierite straight flow type honeycomb carrier (1) (400 cells / in 2 , diameter 117 mm, length 120 mm, volume 1.
3 liters) is prepared. Next, a slurry containing silica and alumina in a weight ratio of SiO 2 : Al 2 O 3 = 9: 1 was prepared, and the honeycomb carrier (1) was immersed in this slurry and pulled up to blow off excess slurry. After 1
After drying at 00 ° C for 1 hour and firing at 500 ° C for 1 hour, 100 g of the coating layer (2) per liter of the honeycomb carrier (1) was formed.
【００２１】次に、コート層（２）が形成されたハニカ
ム担体（１）を所定濃度のテトラアンミンヒドロキシド
白金溶液に１時間浸漬し、引き上げた後余分な水滴を吹
き払い、１００℃で１時間乾燥後３００℃で１時間熱処
理してアンミン等を除去した。Ｐｔの担持量は、ハニカ
ム担体（１）１リットル当たり１．２ｇである。その後
大気中において６００℃で１０時間の熱処理を行い、Ｐ
ｔをシンタリングさせて粗大Ｐｔ（３）とした。顕微鏡
観察の結果、粗大Ｐｔ（３）の平均粒径は１０ｎｍであ
った。Next, the honeycomb carrier (1) having the coat layer (2) formed thereon is dipped in a tetraammine hydroxide platinum solution having a predetermined concentration for 1 hour, pulled up, and then excess water droplets are blown off, followed by 100 ° C. for 1 hour. After drying, heat treatment was performed at 300 ° C. for 1 hour to remove ammine and the like. The amount of Pt carried is 1.2 g per liter of the honeycomb carrier (1). After that, heat treatment is performed at 600 ° C. for 10 hours in the atmosphere, and P
The t was sintered to obtain coarse Pt (3). As a result of microscopic observation, the average particle diameter of coarse Pt (3) was 10 nm.
【００２２】次に、粗大Ｐｔ（３）が担持されたハニカ
ム担体（１）の、排ガスの上流側端面から全容積の４０
％の容積範囲に所定濃度のテトラアンミンヒドロキシド
白金溶液で担持した。担持の方法は、テトラアンミンヒ
ドロキシド白金溶液に担体先端を僅かに浸漬し、ドライ
ヤーで乾燥する方法でＰｔ０．３９ｇを含む溶液全てを
用いて担持した。微細Ｐｔ（４）の担持量は、上流側４
０％の容積部分に０．３９ｇであり、粗大Ｐｔ（３）と
微細Ｐｔ（４）を合わせた全体の平均担持量は、ハニカ
ム担体（１）１リットル当たり１．５ｇである。その時
の微細Ｐｔ粒径を測定したところ３ｎｍであった。 （実施例２）粗大Ｐｔ（３）とするための熱処理温度を
７００℃としたこと以外は実施例１と同様にして実施例
２の排ガス浄化触媒を調製した。粗大Ｐｔ（３）の平均
粒径は２２ｎｍである。 （実施例３）粗大Ｐｔ（３）とするための熱処理温度を
８００℃としたこと以外は実施例１と同様にして実施例
３の排ガス浄化触媒を調製した。粗大Ｐｔ（３）の平均
粒径は３６ｎｍである。 （実施例４）粗大Ｐｔ（３）とするための熱処理温度を
９００℃としたこと以外は実施例１と同様にして実施例
４の排ガス浄化触媒を調製した。粗大Ｐｔ（３）の平均
粒径は６０ｎｍである。 （比較例１）粗大Ｐｔ（３）とするための熱処理温度を
５００℃としたこと以外は実施例１と同様にして比較例
１の排ガス浄化触媒を調製した。粗大Ｐｔ（３）の平均
粒径は３ｎｍである。 （比較例２）粗大Ｐｔ（３）とするための熱処理温度を
１０００℃としたこと以外は実施例１と同様にして比較
例２の排ガス浄化触媒を調製した。粗大Ｐｔ（３）の平
均粒径は９４ｎｍである。 （性能試験）上記のそれぞれの排ガス浄化触媒を２．６
Ｌディーゼルエンジンの排気系に取付け、回転数２００
０ｒｐｍ、入りガス温度５００℃で１時間運転するエー
ジング処理を行った後、入りガス温度を５０℃ずつ降温
させて触媒前後のＰＭを分析するとともに触媒前後のＨ
Ｃ量を測定した。結果をＰＭゼロ％低減温度及びＨＣ５
０％浄化温度に換算して図３に示す。Next, the honeycomb carrier (1) carrying the coarse Pt (3) has a total volume of 40 from the end face on the upstream side of the exhaust gas.
% Of tetraammine hydroxide platinum solution was supported on the volume range. The supporting method was such that the tip of the carrier was slightly dipped in a tetraammine hydroxide platinum solution and dried with a drier to carry all the solution containing 0.39 g of Pt. The amount of fine Pt (4) loaded is 4 on the upstream side.
The volume of 0% is 0.39 g, and the total amount of coarse Pt (3) and fine Pt (4) combined is 1.5 g per liter of the honeycomb carrier (1). The fine Pt particle size at that time was measured and found to be 3 nm. (Example 2) An exhaust gas purifying catalyst of Example 2 was prepared in the same manner as in Example 1 except that the heat treatment temperature for making coarse Pt (3) was 700 ° C. The average particle size of coarse Pt (3) is 22 nm. (Example 3) An exhaust gas purifying catalyst of Example 3 was prepared in the same manner as in Example 1 except that the heat treatment temperature for making coarse Pt (3) was 800 ° C. The average particle size of the coarse Pt (3) is 36 nm. (Example 4) An exhaust gas purifying catalyst of Example 4 was prepared in the same manner as in Example 1 except that the heat treatment temperature for making coarse Pt (3) was 900 ° C. The average particle size of the coarse Pt (3) is 60 nm. (Comparative Example 1) An exhaust gas purifying catalyst of Comparative Example 1 was prepared in the same manner as in Example 1 except that the heat treatment temperature for making coarse Pt (3) was 500 ° C. The average particle size of the coarse Pt (3) is 3 nm. (Comparative Example 2) An exhaust gas purifying catalyst of Comparative Example 2 was prepared in the same manner as in Example 1 except that the heat treatment temperature for forming coarse Pt (3) was 1000 ° C. The average particle size of the coarse Pt (3) is 94 nm. (Performance test) 2.6 each of the above exhaust gas purifying catalysts was used.
Installed in the exhaust system of L diesel engine, the rotation speed is 200
After performing an aging process of operating at 0 rpm and an inlet gas temperature of 500 ° C. for 1 hour, the inlet gas temperature is lowered by 50 ° C. to analyze PM before and after the catalyst, and H before and after the catalyst is analyzed.
The amount of C was measured. The result shows that PM zero% reduction temperature and HC5
It is converted into 0% purification temperature and shown in FIG.
【００２３】なお、ＰＭゼロ％低減温度とは、高温にな
るほど増加するサルフェートの生成量がＳＯＦなど他の
ＰＭ成分の触媒での低減量と同じ値になる温度をいい、
ＳＯＦ等の低減量が同じ場合、ＰＭゼロ％低減温度が高
温側になるほどサルフェートの生成が抑制されているこ
とを意味している。またＨＣ５０％浄化温度とは、触媒
前の排ガス中のＨＣの５０％が浄化される温度をいい、
ＨＣ５０％浄化温度が低いほどＨＣの酸化力が高いこと
を意味している。 （評価）図３より、粗大Ｐｔ（３）の平均粒径が３ｎｍ
の比較例１では、ＰＭゼロ％低減温度が低くＳＯ2 の酸
化が防止できていない。また粗大Ｐｔ（３）の平均粒径
が９４ｎｍの比較例２では、ＨＣの浄化活性が低下して
いる。しかし各実施例の触媒では、ＰＭゼロ％低減温度
が３５０℃以上と高くＳＯ2 の酸化が防止され、かつＨ
Ｃ５０％浄化温度が２５０℃未満と低温で効率良くＨＣ
が酸化浄化されていることが明らかであり、これは粗大
Ｐｔ（３）の平均粒径を１０ｎｍ〜６０ｎｍとしたこと
による作用効果であることが明らかである。 〔試験例２〕 （比較例３）実施例１で用いたコート層（２）を形成し
たハニカム担体（１）に、実施例１と同様にしてＰｔを
担持した。Ｐｔの担持量はハニカム担体（１）１リット
ル当たり１．５ｇとなるようにした。The PM zero% reduction temperature is a temperature at which the amount of sulfate that increases as the temperature rises becomes the same as the amount of reduction of other PM components such as SOF in the catalyst.
When the reduction amount of SOF or the like is the same, it means that the generation of sulfate is suppressed as the PM zero% reduction temperature becomes higher. The 50% HC purification temperature is the temperature at which 50% of the HC in the exhaust gas before the catalyst is purified,
The lower the 50% purification temperature of HC, the higher the oxidizing power of HC. (Evaluation) From FIG. 3, the average particle size of coarse Pt (3) is 3 nm.
In Comparative Example 1, the PM zero% reduction temperature is low and SO 2 oxidation cannot be prevented. Further, in Comparative Example 2 in which the coarse Pt (3) has an average particle size of 94 nm, the HC purification activity is reduced. However, in the catalysts of the respective examples, the PM zero% reduction temperature is as high as 350 ° C. or higher, the SO 2 oxidation is prevented, and the H 2
Efficient HC at low temperature with C50% purification temperature of less than 250 ° C
Is oxidatively purified, and it is clear that this is a function and effect obtained by setting the average particle diameter of the coarse Pt (3) to 10 nm to 60 nm. [Test Example 2] (Comparative Example 3) Pt was loaded on the honeycomb carrier (1) having the coat layer (2) used in Example 1 in the same manner as in Example 1. The loading amount of Pt was set to be 1.5 g per liter of the honeycomb carrier (1).
【００２４】そして実施例１〜４及び比較例１〜２と同
様にして熱処理し、微細Ｐｔ（４）を担持せずにそれぞ
れの触媒を調製した。各触媒の粗大Ｐｔ（３）の粒径は
試験例１の対応する触媒と同様であった。それぞれの触
媒について、試験例１と同様にしてＰＭゼロ％低減温度
とＨＣ５０％浄化温度を測定し、結果を試験例１の結果
と合わせて図４に示す。Then, heat treatment was carried out in the same manner as in Examples 1 to 4 and Comparative Examples 1 and 2 to prepare respective catalysts without supporting fine Pt (4). The coarse Pt (3) particle size of each catalyst was similar to the corresponding catalyst of Test Example 1. For each catalyst, the PM zero% reduction temperature and the HC 50% purification temperature were measured in the same manner as in Test Example 1, and the results are shown in FIG. 4 together with the results of Test Example 1.
【００２５】図４より、比較例３のそれぞれの触媒は、
対応する実施例１〜４及び比較例１〜２の触媒に比べて
ＰＭゼロ％低減温度は高いものの、ＨＣ５０％低減温度
がかなり高くなりＨＣ浄化性能に劣っている。これは微
細Ｐｔ（４）を担持しなかったことに起因していること
が明らかである。 （比較例４）担持されたＰｔの熱処理を行わなかったこ
と、Ｐｔの担持量はハニカム担体（１）１リットル当た
り１．５ｇとなるようにしたこと、及び微細Ｐｔ（４）
を担持しなかったこと以外は実施例１と同様にして比較
例４の触媒を調製した。担持されたＰｔの粒径は０．５
ｎｍときわめて小さい。From FIG. 4, the respective catalysts of Comparative Example 3 were
Although the PM zero% reduction temperature is higher than the corresponding catalysts of Examples 1 to 4 and Comparative Examples 1 and 2, the HC 50% reduction temperature is considerably high and the HC purification performance is poor. It is clear that this is due to the fact that fine Pt (4) was not supported. (Comparative Example 4) The heat treatment of the carried Pt was not carried out, the carried amount of Pt was set to be 1.5 g per liter of the honeycomb carrier (1), and the fine Pt (4)
A catalyst of Comparative Example 4 was prepared in the same manner as in Example 1 except that the catalyst was not supported. The supported Pt particle size is 0.5
nm is extremely small.
【００２６】そして試験例１と同様にしてＰＭゼロ％低
減温度とＨＣ５０％浄化温度を測定し、結果を図４に示
す。図４より、比較例４の触媒はＨＣの浄化性能には極
めて優れているものの、ＰＭゼロ％低減温度が３００℃
と低くＳＯ2 の酸化を防止できていない。これは全体に
微細Ｐｔが担持され、粗大Ｐｔ（３）を担持していない
ことに起因することが明らかである。 〔試験例３〕 （実施例５）実施例１と同様にコート層（２）が形成さ
れたハニカム担体（１）に、同様にしてＰｔをハニカム
担体（１）１リットル当たり１．２ｇとなるように担持
した。その後大気中において８００℃で５時間の熱処理
を行い、Ｐｔをシンタリングさせて粗大Ｐｔ（３）とし
た。顕微鏡観察の結果、粗大Ｐｔ（３）の平均粒径は３
６ｎｍであった。Then, the PM zero% reduction temperature and the HC 50% purification temperature were measured in the same manner as in Test Example 1, and the results are shown in FIG. As shown in FIG. 4, although the catalyst of Comparative Example 4 is extremely excellent in the purification performance of HC, the PM zero% reduction temperature is 300 ° C.
As a result, SO 2 cannot be prevented from being oxidized. It is clear that this is because fine Pt is supported on the entire surface and coarse Pt (3) is not supported. [Test Example 3] (Example 5) In the same manner as in Example 1, the honeycomb carrier (1) on which the coat layer (2) was formed had Pt in an amount of 1.2 g per liter of the honeycomb carrier (1). So that it was carried. After that, heat treatment was performed in the air at 800 ° C. for 5 hours to sinter Pt to obtain coarse Pt (3). As a result of microscopic observation, the average particle size of coarse Pt (3) was 3
6 nm.
【００２７】次に、粗大Ｐｔ（３）が担持されたハニカ
ム担体（１）の、排ガスの上流側端面から容積の２０％
の範囲を所定濃度のテトラアンミンヒドロキシド白金溶
液で担持した。担持方法は、テトラアンミンヒドロキシ
ド白金溶液に担体先端を僅かに浸漬しドライヤーで乾燥
する方法で、Ｐｔ０．３９ｇを含む溶液全てを用いて担
持した。乾燥後３００℃で１時間熱処理してアンミン等
を除去して、平均粒径０．６ｎｍの微細Ｐｔ（４）を担
持した。微細Ｐｔ（４）の担持量は、上流側２０％の容
積部分に０．３９ｇであり、粗大Ｐｔ（３）と微細Ｐｔ
（４）を合わせた全体の平均担持量は、ハニカム担体
（１）１リットル当たり１．５ｇである。 （実施例６）微細Ｐｔ（４）を担持する部分を上流側４
０％の容積部分としたこと以外は実施例５と同様にし
て、実施例６の排ガス浄化触媒を調製した。 （実施例７）微細Ｐｔ（４）を担持する部分を上流側５
０％の容積部分としたこと以外は実施例５と同様にし
て、実施例７の排ガス浄化触媒を調製した。 （実施例８）微細Ｐｔ（４）を担持する部分を上流側６
０％の容積部分としたこと以外は実施例５と同様にし
て、実施例８の排ガス浄化触媒を調製した。 （性能試験及び評価）上記の実施例５〜８の触媒につい
て、試験例１と同様にしてＰＭゼロ％低減温度とＨＣ５
０％浄化温度を測定し、結果を図５に示す。Next, 20% of the volume of the honeycomb carrier (1) carrying the coarse Pt (3) from the end face on the upstream side of the exhaust gas.
The above range was supported by a tetraammine hydroxide platinum solution having a predetermined concentration. The loading method was a method in which the tip of the carrier was slightly dipped in a tetraammine hydroxide platinum solution and dried with a dryer, and all the solutions containing 0.39 g of Pt were loaded. After drying, heat treatment was performed at 300 ° C. for 1 hour to remove ammine and the like, and fine Pt (4) having an average particle size of 0.6 nm was supported. The amount of fine Pt (4) loaded was 0.39 g in the volume portion of the upstream 20%, and the amount of coarse Pt (3) and fine Pt (3)
The total average carrying amount of (4) is 1.5 g per liter of the honeycomb carrier (1). (Example 6) A portion supporting fine Pt (4) is provided on the upstream side 4.
An exhaust gas purification catalyst of Example 6 was prepared in the same manner as in Example 5 except that the volume portion was 0%. (Embodiment 7) The portion supporting the fine Pt (4) is located on the upstream side 5.
An exhaust gas purification catalyst of Example 7 was prepared in the same manner as in Example 5 except that the volume portion was 0%. (Embodiment 8) The portion carrying the fine Pt (4) is placed on the upstream side 6
An exhaust gas purification catalyst of Example 8 was prepared in the same manner as Example 5 except that the volume portion was 0%. (Performance test and evaluation) For the catalysts of Examples 5 to 8 described above, in the same manner as in Test Example 1, the PM zero% reduction temperature and HC5
The 0% purification temperature was measured, and the results are shown in FIG.
【００２８】図５より、微細Ｐｔ（４）の担持部分の容
積が大きくなるにつれてＰＭゼロ％低減温度が低下する
傾向がみられ、実施例８ではＰＭゼロ％低減温度が３５
０℃未満となってＳＯ2 の酸化が生じ易くなっている。
したがって微細Ｐｔ（４）の担持部分は、上流側端面か
ら５０％の容積の部分までに止めることが望ましいこと
がわかる。From FIG. 5, it can be seen that the PM zero% reduction temperature tends to decrease as the volume of the fine Pt (4) supporting portion increases, and in Example 8, the PM zero% reduction temperature is 35%.
When the temperature is below 0 ° C., SO 2 is likely to be oxidized.
Therefore, it is understood that it is desirable to stop the portion carrying the fine Pt (4) from the upstream end surface to the portion having a volume of 50%.
【００２９】なお、上記実施例では、微細Ｐｔの担持量
を０．３９ｇ一定としたが、本発明はこれに限られるも
のではなく、この担持量は目的及び効果に応じて種々変
化させることができることはいうまでもない。また上記
実施例では、上流側に微細Ｐｔとともに粗大Ｐｔも担持
しているが、上流側の粗大Ｐｔが担持されていなくても
ほぼ同様の結果を示すことがわかっている。また上記実
施例では触媒貴金属としてＰｔのみを用いているが、本
発明はこれに制限されるものではなく他に種々の触媒貴
金属を用いてもそれなりの効果が得られることは自明で
ある。In the above embodiment, the amount of fine Pt carried was fixed at 0.39 g. However, the present invention is not limited to this, and the amount carried can be variously changed according to the purpose and effect. It goes without saying that you can do it. Further, in the above-mentioned embodiment, the coarse Pt is also supported on the upstream side together with the fine Pt, but it is known that the same result is obtained even if the coarse Pt on the upstream side is not supported. Further, although only Pt is used as the catalytic noble metal in the above-mentioned examples, the present invention is not limited to this, and it is obvious that the various catalytic noble metals can be used to obtain some effect.
【００３０】[0030]
【発明の効果】すなわち本発明のディーゼルエンジン用
排ガス浄化触媒によれば、低温域におけるＨＣの酸化浄
化活性に優れるとともに、高温域におけるＳＯ2 の酸化
が防止されサルフェートの排出を防止することができ
る。したがってＨＣの浄化活性を高く維持しつつ、広い
温度範囲にわたってＰＭの排出量を低減することができ
る。[Effects of the Invention] According to the exhaust gas purifying catalyst for a diesel engine of the present invention, it has excellent oxidative purifying activity for HC in a low temperature range, and can prevent SO 2 from being oxidized in a high temperature range to prevent sulfate emission. . Therefore, it is possible to reduce the emission amount of PM over a wide temperature range while maintaining a high HC purification activity.
【図１】本発明の一実施例の排ガス浄化触媒の構成を説
明する模式図である。FIG. 1 is a schematic diagram illustrating a configuration of an exhaust gas purifying catalyst according to an embodiment of the present invention.
【図２】本発明の一実施例の排ガス浄化触媒の構成を説
明する図１の要部拡大断面図である。FIG. 2 is an enlarged cross-sectional view of a main part of FIG. 1 for explaining the structure of an exhaust gas purifying catalyst according to an embodiment of the present invention.
【図３】試験例１における粗大Ｐｔの粒径とＰＭゼロ％
低減温度及びＨＣ５０％浄化温度の関係を示すグラフで
ある。FIG. 3 shows the coarse Pt particle size and PM zero% in Test Example 1.
It is a graph which shows the relationship between reduction temperature and HC50% purification temperature.
【図４】試験例１と試験例２における粗大Ｐｔの粒径と
ＰＭゼロ％低減温度及びＨＣ５０％浄化温度の関係を示
すグラフである。FIG. 4 is a graph showing the relationship between the coarse Pt particle size, PM zero% reduction temperature, and HC 50% purification temperature in Test Examples 1 and 2.
【図５】試験例３における微細Ｐｔの担持容積とＰＭゼ
ロ％低減温度及びＨＣ５０％浄化温度の関係を示すグラ
フである。FIG. 5 is a graph showing the relationship between the loading volume of fine Pt, the PM zero% reduction temperature, and the HC50% purification temperature in Test Example 3.
１：ハニカム担体 ２：コート
層 ３：粗大Ｐｔ ４：微細Ｐ
ｔ1: Honeycomb carrier 2: Coat layer 3: Coarse Pt 4: Fine P
t
───────────────────────────────────────────────────── フロントページの続き (72)発明者 田口 教夫 愛知県豊田市トヨタ町１番地 トヨタ自動 車株式会社内 (72)発明者 坂野 幸次 愛知県愛知郡長久手町大字長湫字横道41番 地の１ 株式会社豊田中央研究所内 (72)発明者 渡邊 佳英 愛知県愛知郡長久手町大字長湫字横道41番 地の１ 株式会社豊田中央研究所内 (72)発明者 笠原 光一 静岡県小笠郡大東町千浜7800番地 キャタ ラー工業株式会社内 (72)発明者 青野 紀彦 静岡県小笠郡大東町千浜7800番地 キャタ ラー工業株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Taguchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd. (72) Inventor Koji Sakano 1 41, Nagakute, Nagakute Town, Aichi County, Aichi Prefecture Toyota Central Research Institute Co., Ltd. (72) Inventor, Kaei Watanabe, Aichi Prefecture, Nagakute Town, Aichi Prefecture 1 41, Yokosuka, Yokouchi Central Research Co., Ltd. (72) Inventor, Koichi Kasahara Chihama, Daito Town, Ogasa County, Shizuoka Prefecture 7800 At Cataler Industry Co., Ltd. (72) Inventor Norihiko Aono Chihama, Daito Town, Ogasa County, Shizuoka Prefecture 7800 At Cataler Industry Co., Ltd.
Claims (1)
された触媒貴金属と、からなり、 該触媒貴金属は、排気ガス流の上流側には平均粒径５ｎ
ｍ以下の微細粒子を含んで担持され、下流側には平均粒
径１０ｎｍ以上の粗大粒子として担持されていることを
特徴とするディーゼルエンジン用排ガス浄化触媒。1. A porous carrier base material and a catalytic noble metal supported on the carrier base material, wherein the catalytic noble metal has an average particle diameter of 5 n on the upstream side of the exhaust gas flow.
An exhaust gas purification catalyst for a diesel engine, characterized in that it is carried by containing fine particles of m or less, and is carried on the downstream side as coarse particles having an average particle size of 10 nm or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7263257A JPH09103679A (en) | 1995-10-11 | 1995-10-11 | Exhaust gas-purifying catalyst for diesel engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7263257A JPH09103679A (en) | 1995-10-11 | 1995-10-11 | Exhaust gas-purifying catalyst for diesel engine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09103679A true JPH09103679A (en) | 1997-04-22 |
Family
ID=17386963
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7263257A Pending JPH09103679A (en) | 1995-10-11 | 1995-10-11 | Exhaust gas-purifying catalyst for diesel engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09103679A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998006492A1 (en) * | 1996-08-13 | 1998-02-19 | Toyota Jidosha Kabushiki Kaisha | Exhaust emission control catalyst for diesel engines |
| US6147027A (en) * | 1997-09-24 | 2000-11-14 | Toyota Jidosha Kabushiki Kaisha | Alloy catalyst and process for producing the same |
| JP2002089240A (en) * | 2000-09-08 | 2002-03-27 | Nissan Motor Co Ltd | Exhaust emission control device and exhaust emission control method using this |
| JP2002177788A (en) * | 2000-12-06 | 2002-06-25 | Nissan Motor Co Ltd | Exhaust gas cleaning catalyst and its manufacturing method |
| JP2007111625A (en) * | 2005-10-20 | 2007-05-10 | Ne Chemcat Corp | Oxidation catalyst for exhaust gas purification, integral-type oxidation catalyst using the same, and exhaust gas purifying method |
-
1995
- 1995-10-11 JP JP7263257A patent/JPH09103679A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998006492A1 (en) * | 1996-08-13 | 1998-02-19 | Toyota Jidosha Kabushiki Kaisha | Exhaust emission control catalyst for diesel engines |
| US6426316B2 (en) | 1996-08-13 | 2002-07-30 | Toyota Jidosha Kabushiki Kaisha | Exhaust emission control catalyst for diesel engines |
| US6147027A (en) * | 1997-09-24 | 2000-11-14 | Toyota Jidosha Kabushiki Kaisha | Alloy catalyst and process for producing the same |
| JP2002089240A (en) * | 2000-09-08 | 2002-03-27 | Nissan Motor Co Ltd | Exhaust emission control device and exhaust emission control method using this |
| JP2002177788A (en) * | 2000-12-06 | 2002-06-25 | Nissan Motor Co Ltd | Exhaust gas cleaning catalyst and its manufacturing method |
| JP4600710B2 (en) * | 2000-12-06 | 2010-12-15 | 日産自動車株式会社 | Exhaust gas purification catalyst |
| JP2007111625A (en) * | 2005-10-20 | 2007-05-10 | Ne Chemcat Corp | Oxidation catalyst for exhaust gas purification, integral-type oxidation catalyst using the same, and exhaust gas purifying method |
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