JPH05277371A - Catalyst for purification of exhaust gas from engine - Google Patents
Catalyst for purification of exhaust gas from engineInfo
- Publication number
- JPH05277371A JPH05277371A JP4105704A JP10570492A JPH05277371A JP H05277371 A JPH05277371 A JP H05277371A JP 4105704 A JP4105704 A JP 4105704A JP 10570492 A JP10570492 A JP 10570492A JP H05277371 A JPH05277371 A JP H05277371A
- Authority
- JP
- Japan
- Prior art keywords
- catalyst
- palladium
- layer
- exhaust gas
- oxide
- 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.)
- Granted
Links
- 239000003054 catalyst Substances 0.000 title claims abstract description 115
- 238000000746 purification Methods 0.000 title abstract description 6
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims abstract description 48
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 14
- 229910003445 palladium oxide Inorganic materials 0.000 claims abstract description 11
- JQPTYAILLJKUCY-UHFFFAOYSA-N palladium(ii) oxide Chemical compound [O-2].[Pd+2] JQPTYAILLJKUCY-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 7
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000010410 layer Substances 0.000 claims description 60
- 239000002344 surface layer Substances 0.000 claims description 6
- 230000000694 effects Effects 0.000 abstract description 13
- 230000006866 deterioration Effects 0.000 abstract description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 21
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 17
- 229910000510 noble metal Inorganic materials 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 239000002002 slurry Substances 0.000 description 15
- 239000000843 powder Substances 0.000 description 14
- 239000010948 rhodium Substances 0.000 description 11
- 239000007789 gas Substances 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 6
- 229910052697 platinum Inorganic materials 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000010494 dissociation reaction Methods 0.000 description 3
- 230000005593 dissociations Effects 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052703 rhodium Inorganic materials 0.000 description 3
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 239000012760 heat stabilizer Substances 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 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 1
- 239000000446 fuel Substances 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 1
- SONJTKJMTWTJCT-UHFFFAOYSA-K rhodium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Rh+3] SONJTKJMTWTJCT-UHFFFAOYSA-K 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、排気ガス中のＣＯ、Ｈ
Ｃ、ＮＯｘを低減せしめるために用いられるエンジンの
排気ガス浄化用触媒に関する。BACKGROUND OF THE INVENTION The present invention relates to CO, H in exhaust gas.
The present invention relates to an engine exhaust gas purifying catalyst used for reducing C and NOx.
【０００２】[0002]
【従来技術】排気ガス中のＣＯ、ＨＣ、ＮＯｘを浄化す
る排気ガス浄化用触媒としては、特開昭６２−５７６７
１号公報に示すように、触媒担体上に、該触媒担体から
外方側に向けて順に、第１、第２、第３触媒層を設け、
該第１、第２、第３触媒層に、それぞれ異なった貴金属
触媒成分を分離配設したものがある。このものにおいて
は、各貴金属触媒成分同士の合金化による熱劣化を抑圧
して、いままでの触媒層が２つからなるものに比べて浄
化性能が向上することになる。2. Description of the Related Art An exhaust gas purifying catalyst for purifying CO, HC and NOx in exhaust gas is disclosed in Japanese Patent Laid-Open No. 62-5767.
As shown in Japanese Patent Publication No. 1, first, second, and third catalyst layers are provided on a catalyst carrier in this order from the catalyst carrier toward the outside.
There is one in which different noble metal catalyst components are separately disposed in the first, second and third catalyst layers. In this case, the heat deterioration due to the alloying of the noble metal catalyst components is suppressed, and the purification performance is improved as compared with the conventional one having two catalyst layers.
【０００３】[0003]
【発明が解決しようとする課題】しかし、上記排気ガス
浄化用触媒において、各貴金属触媒成分が各触媒層に分
離配設されて熱劣化が抑制されると言っても、最外表面
となる第３触媒層が、直接、排気ガスと接して高温とな
ることは従来と変わりがなく、このため、特に、第３触
媒層の貴金属触媒成分がシンタリング（凝集粗大化）を
起こして熱劣化を生じ易い傾向にある。この結果、触媒
の低温活性の安定化を充分に図ることができないでい
る。本発明は上記実情に鑑みてなされたもので、その目
的は、最外表層の熱劣化を抑制して、触媒の低温活性の
安定化を充分に図ることができるエンジンの排気ガス浄
化用触媒を提供することにある。However, in the above exhaust gas purifying catalyst, even if it is said that each noble metal catalyst component is separately disposed in each catalyst layer and thermal deterioration is suppressed, it becomes the outermost surface. It is no different from the conventional method that the temperature of the 3rd catalyst layer comes into direct contact with the exhaust gas, and therefore the noble metal catalyst component of the 3rd catalyst layer causes sintering (coagulation coarsening) and heat deterioration. It tends to occur. As a result, the low temperature activity of the catalyst cannot be sufficiently stabilized. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas purifying catalyst for an engine that can suppress thermal deterioration of the outermost surface layer and sufficiently stabilize low temperature activity of the catalyst. To provide.
【０００４】[0004]
【課題を解決するための手段】かかる目的を達成するた
めに本発明にあっては、触媒担体上に複数の触媒層が設
けられているエンジンの排気ガス浄化用触媒において、
前記複数の触媒層のうち最外表層に、酸化セリウム、パ
ラジウム、酸化パラジウムが添加されてなる、構成とし
てある。In order to achieve the above object, the present invention provides an exhaust gas purifying catalyst for an engine, wherein a plurality of catalyst layers are provided on a catalyst carrier.
Cerium oxide, palladium, and palladium oxide are added to the outermost surface layer of the plurality of catalyst layers.
【０００５】上述の発明の構成により、最外表層となる
第３触媒層に、貴金属触媒成分として、高い耐熱性を有
するパラジウムを配すると共に酸化セリウムをも含有さ
せることから、貴金属触媒成分としてのパラジウムの特
性自体の効果が得られるだけでなく、酸化セリウムの酸
素貯蔵能効果（酸素Ｏ2 濃度が高いときＯ2 を吸着し、
Ｏ2 濃度が低くなったときＯ2 を放出して触媒反応に寄
与する効果）に基づき、第３触媒層のパラジウム酸化物
（焼成等によりパラジウムが酸化物として存在する）が
パラジウムに解離する温度を高めて、第３触媒層におけ
る貴金属触媒成分としてのパラジウムが低い温度でシン
タリングすることを効果的に抑えることができることに
なる。しかも、この場合、第３触媒層に熱安定剤として
酸化パラジウム自体が添付されてなることから、パラジ
ウム酸化物の上記解離温度が一層高められ、パラジウム
のシンタリング抑制は格段に向上することになる。この
ため、触媒の熱劣化が有効に抑制されることになり、触
媒の低温活性の安定化を充分に図ることができることに
なる。According to the structure of the above-mentioned invention, since palladium having high heat resistance is arranged as the noble metal catalyst component and cerium oxide is also contained in the third catalyst layer, which is the outermost surface layer, the noble metal catalyst component is Not only is the effect of the properties of palladium itself obtained, but the effect of oxygen storage capacity of cerium oxide (adsorbing O 2 when the oxygen O 2 concentration is high,
Temperature at which the palladium oxide of the third catalyst layer (palladium exists as an oxide due to firing or the like) dissociates into palladium based on the effect of releasing O 2 when the O 2 concentration becomes low and contributing to the catalytic reaction) Therefore, it is possible to effectively suppress the sintering of palladium as the noble metal catalyst component in the third catalyst layer at a low temperature. Moreover, in this case, since palladium oxide itself is attached to the third catalyst layer as a heat stabilizer, the dissociation temperature of the palladium oxide is further increased, and the sintering inhibition of palladium is significantly improved. . Therefore, the thermal deterioration of the catalyst is effectively suppressed, and the low temperature activity of the catalyst can be sufficiently stabilized.
【０００６】[0006]
【実施例】以下、本発明の実施例を説明する。図１は、
第１実施例に係る触媒を示す模式拡大図で、この図１に
示すように、触媒１は、触媒担体２上に、該触媒担体２
から外方側（図１中、上側）に向けて順に、第１、第
２、第３触媒層３、４、５が設けられている。上記触媒
担体２は、その材質として、コ−ジライト等の公知のも
のが用いられ、その形状は、ハニカム構造、ペレットタ
イプ等の公知形状とされている。上記第１触媒層３は、
本実施例においては、貴金属触媒成分としてロジウム
（以下、Ｒｈ）を含有するアルミナ層とされており、第
１触媒層３中において、貴金属触媒成分は、Ｒｈだけと
されている。上記第２触媒層４は、本実施例において
は、貴金属触媒成分として白金（以下、Ｐｔ）を含有す
るアルミナ層とされており、この第２触媒層４において
は、貴金属触媒成分は、Ｐｔだけとされている。上記第
３触媒層５は、本実施例においては、主成分が酸化セリ
ウム（以下、ＣｅＯ2 ）とアルミナとされ、その内部に
パラジウム（以下、Ｐｄ）及び酸化パラジウム（以下、
ＰｄＯ）が分散含有されている。EXAMPLES Examples of the present invention will be described below. Figure 1
FIG. 1 is a schematic enlarged view showing the catalyst according to the first embodiment. As shown in FIG. 1, the catalyst 1 is formed on the catalyst carrier 2 by the catalyst carrier 2
To the outer side (upper side in FIG. 1), the first, second, and third catalyst layers 3, 4, and 5 are provided in this order. As the material of the catalyst carrier 2, a known material such as cordierite is used, and the shape thereof is a known shape such as a honeycomb structure or a pellet type. The first catalyst layer 3 is
In the present embodiment, the alumina layer contains rhodium (hereinafter, Rh) as a noble metal catalyst component, and the noble metal catalyst component is only Rh in the first catalyst layer 3. In the present embodiment, the second catalyst layer 4 is an alumina layer containing platinum (hereinafter, Pt) as a noble metal catalyst component, and in the second catalyst layer 4, the noble metal catalyst component is only Pt. It is said that. In the present embodiment, the third catalyst layer 5 is mainly composed of cerium oxide (hereinafter, CeO 2 ) and alumina, and palladium (hereinafter, Pd) and palladium oxide (hereinafter,
PdO) is dispersedly contained.
【０００７】上記のような触媒１は、例えば、次のよう
にして形成される。すなわち、先ず、γ−アルミナ（Ａ
ｌ2 Ｏ3 ）粉末に硝酸ロジウム水溶液を加えて混合撹拌
し、それを、乾燥、焼成し、その後、ボ−ルミルで粉砕
して微粒子状態の粉末とする。そして、上記Ｒｈが固定
化されたγ−Ａｌ2 Ｏ3 ４８０ｇ、ベ−マイト（水和ア
ルミナ）１２０ｇ、水１０００ｃｃ、硝酸１０ｃｃをホ
モミキサにより混合撹拌し、アルミナスラリ−を得、そ
のアルミナスラリ−にハニカム構造の触媒担体２を浸漬
して引き上げた後、余分のスラリ−を高圧エア−ブロ−
で除去し、それを、２５０℃で２時間乾燥してから６０
０℃で２時間焼成し、触媒担体２上に第１触媒層３を形
成する。次に、前記第１触媒層３の形成の場合同様に、
γ−Ａｌ2 Ｏ3 にジントロジアミン白金水溶液を加えて
混合撹拌し、これを、乾燥、焼成した後、ボ−ルミルで
粉砕して微粒子状の粉末とする。そして、上記Ｐｔを固
定したγ−Ａｌ2 Ｏ3 ４８０ｇ、ベ−マイト１２０ｇ、
水１０００ｃｃ、硝酸１０ｃｃをホモミキサにより混合
撹拌し、アルミナスラリ−を得、このアルミナに、第１
触媒層３まで形成した触媒担体を浸漬して引き上げ、余
分のスラリ−を除去した後、それを、２００℃で２時間
乾燥してから６００℃で２時間焼成し、第１触媒層３上
に第２触媒層４を形成する。次に、ＰｄＯ粉末にジント
ロジアミンパラジウム水溶液（若しくは塩化パラジウム
水溶液）を加えて混合撹拌し、それを、乾燥、焼成し、
その後、ボ−ルミルで粉砕して微粒子状態の粉末とす
る。この粉末にＣｅＯ2 粉末を加えて５４０ｇに調整
し、これに、、ベ−マイト６０ｇ、水１０００ｃｃ、硝
酸１０ｃｃを加えて混合撹拌し、スラリ−を得る。そし
て、そのスラリ−に、第１、第２触媒層３、４まで形成
した触媒担体２を浸漬して引き上げ、余分のスラリ−を
除去した後、それを、２００℃で２時間乾燥してから６
００℃で２時間焼成し、第２触媒層４上に第３触媒層５
を形成する。尚、前記各層３、４、５のウォッシュコ−
ト量は、触媒担体２の重量に対して各々１４ｗｔ％にな
るように調整し、貴金属触媒成分としてのＰｔ、Ｒｈ、
Ｐｄ担持量（製品での触媒層全容積に対する貴金属重
量）は、Ｐｔについては１．３３ｇ／ｌ、Ｒｈについて
は０．２７ｇ／ｌ、Ｐｄについては１．０ｇ／ｌになる
ようにする。また、ＰｄＯ、Ｐｄを含む粉末と、ＣｅＯ
2 粉末との混合割合は、１０／９０〜５０／５０とす
る。The catalyst 1 as described above is formed, for example, as follows. That is, first, γ-alumina (A
1 2 O 3 ) powder, an aqueous rhodium nitrate solution is added, mixed and stirred, dried and fired, and then pulverized with a ball mill to obtain a fine powder. Then, 480 g of γ-Al 2 O 3 having Rh immobilized thereon, 120 g of beehmite (hydrated alumina), 1000 cc of water, and 10 cc of nitric acid were mixed and stirred by a homomixer to obtain an alumina slurry, which was then added to the alumina slurry. After immersing the catalyst carrier 2 having a honeycomb structure and pulling it up, excess slurry is removed by a high pressure air blower.
And dried at 250 ° C. for 2 hours, then 60
The first catalyst layer 3 is formed on the catalyst carrier 2 by firing at 0 ° C. for 2 hours. Next, similarly to the case of forming the first catalyst layer 3,
An aqueous solution of gintrodiamine platinum is added to γ-Al 2 O 3 , mixed and stirred, dried and baked, and then pulverized by a ball mill to obtain fine powder. Then, 480 g of γ-Al 2 O 3 having Pt fixed thereon, 120 g of boehmite,
1000 cc of water and 10 cc of nitric acid were mixed and stirred with a homomixer to obtain an alumina slurry.
After the catalyst carrier formed up to the catalyst layer 3 is dipped and pulled up to remove excess slurry, it is dried at 200 ° C. for 2 hours and then calcined at 600 ° C. for 2 hours to deposit on the first catalyst layer 3. The second catalyst layer 4 is formed. Next, a zinctrodiamine palladium aqueous solution (or a palladium chloride aqueous solution) is added to the PdO powder, and the mixture is stirred, dried, and calcined.
Then, it is pulverized with a ball mill to obtain a fine powder. CeO 2 powder was added to this powder to adjust to 540 g, and 60 g of beammite, 1000 cc of water, and 10 cc of nitric acid were added to this powder and mixed and stirred to obtain a slurry. Then, the catalyst carrier 2 formed up to the first and second catalyst layers 3 and 4 is immersed in the slurry and pulled up to remove excess slurry, and then dried at 200 ° C. for 2 hours, 6
Calcination is performed at 00 ° C. for 2 hours, and the third catalyst layer 5 is formed on the second catalyst layer 4.
To form. In addition, the wash coat of each of the layers 3, 4, and 5 is
The amounts of Pt and Rh as noble metal catalyst components are adjusted so as to be 14 wt% with respect to the weight of the catalyst carrier 2.
The amount of Pd supported (weight of noble metal with respect to the total volume of the catalyst layer in the product) is 1.33 g / l for Pt, 0.27 g / l for Rh, and 1.0 g / l for Pd. Further, PdO, a powder containing Pd, and CeO
The mixing ratio with the two powders is 10/90 to 50/50.
【０００８】このような触媒においては、貴金属触媒成
分として、第１触媒層３にＰｔ、第２触媒層４にＲｈ、
第３触媒層５にＰｄだけを単独にしか設けないようにし
ていることから、合金化を抑えることができ、また、耐
熱性の高いＰｄを第３触媒層５にＣｅＯ2 と共に含有さ
せる一方、そのＣｅＯ2 の酸素貯蔵能効果に基づいて、
Ｐｄの解離（Ｐｄ酸化物→Ｐｄ）温度を高めることがで
きることから、Ｐｄ同士のシンタリングを抑制できるこ
とになる。しかも、第３触媒層５に熱安定剤としてＰｄ
Ｏ自体が添加されてなることから、パラジウム酸化物の
上記解離温度を一層高めて、Ｐｄのシンタリング抑制を
格段に向上させることができることになる。この結果、
最外表層たる第３触媒層５の熱劣化を有効に抑えて、触
媒の低温活性の安定化（耐熱性）を充分に図ることがで
きることになる。In such a catalyst, the noble metal catalyst component is Pt in the first catalyst layer 3 and Rh in the second catalyst layer 4.
Since only the Pd is provided solely in the third catalyst layer 5, alloying can be suppressed, and while Pd having high heat resistance is contained in the third catalyst layer 5 together with CeO 2 , Based on the oxygen storage capacity effect of CeO 2 ,
Since the dissociation temperature of Pd (Pd oxide → Pd) can be increased, sintering of Pd can be suppressed. Moreover, Pd as a heat stabilizer is added to the third catalyst layer 5.
Since O itself is added, the dissociation temperature of the palladium oxide can be further increased, and the suppression of Pd sintering can be significantly improved. As a result,
It is possible to effectively suppress the thermal deterioration of the third catalyst layer 5, which is the outermost surface layer, and sufficiently stabilize the low temperature activity (heat resistance) of the catalyst.
【０００９】次に、上記触媒１の耐熱性能を裏付けるた
めに、各種試験を行った。先ず、下記比較例１（図２参
照）、比較例２（図３参照）を用意し、その両比較例
１、２について、下記試験条件の下、耐熱性試験を行っ
た。Next, various tests were conducted in order to support the heat resistance performance of the catalyst 1. First, the following Comparative Example 1 (see FIG. 2) and Comparative Example 2 (see FIG. 3) were prepared, and a heat resistance test was performed on both Comparative Examples 1 and 2 under the following test conditions.
【００１０】比較例１ ネオジム（Ｎｄ）、ランタン（Ｌａ）、セリウム（Ｃ
ｅ）の各硝酸塩をそれぞれ活性アルミナ粉末に吸水させ
て乾燥した後、７００℃で２時間焼成し、Ｎｄ、Ｌａも
しくはＣｅを０．１ｍｏｌ／ｌ含有するアルミナ粉末を
それぞれ調整する。Ｎｄを含有するアルミナ粉末１００
重量部と、アルミナ含有率１０ｗｔ％のアルミナゾル７
０重量部と水２０重量部とを混合撹拌して、アルミナス
ラリ−を製造する。このスラリ−中に触媒担体を浸漬
し、これをスラリ−から引き上げた後、気流でセル内の
スラリ−を吹き飛ばし、２５０℃で２時間乾燥後６００
℃で２時間焼成し、第１のアルミナコ−ト層を形成し
た。この担体を塩化パラジウム（ＰｄＣｌ2 ）水溶液に
浸漬し、このアルミナコ−ト層にＰｄを担持させる。次
にＬａを含有する活性アルミナ粉末を用い、同様にし
て、アルミナスラリ−を調整し、このスラリ−内に第１
層を形成した担体を浸漬し、上記と同様にして、第２層
を形成する。この後塩化ロジウム（ＲｈＣｌ3 ）水溶液
に浸漬し、第２層にＲｈを担持させる。さらに、Ｃｅを
含有する活性アルミナを用い、上記と同様にして第３層
を形成し、第１層および第２層を形成した担体をジント
ロジアミン白金（Ｐｔ（ＮＨ3）2 （ＮＯ2 ）2 ）水溶
液に浸漬し、この第３層にＰｔを担持させて、図２に示
すようなモノリス触媒を得た。このとき、貴金属触媒成
分担持量（製品での触媒層全容積に対する貴金属重量）
は、Ｐｔについては１．３３ｇ／ｌ、Ｒｈについては
０．２７ｇ／ｌ、Ｐｄについては１ｇ／ｌになるように
調整される。 Comparative Example 1 Neodymium (Nd), Lanthanum (La), Cerium (C
Each nitrate of e) is absorbed in activated alumina powder, dried and then calcined at 700 ° C. for 2 hours to prepare alumina powder containing 0.1 mol / l of Nd, La or Ce, respectively. Alumina powder 100 containing Nd
Parts by weight and alumina sol 7 with an alumina content of 10 wt%
0 parts by weight and 20 parts by weight of water are mixed and stirred to produce an alumina slurry. A catalyst carrier was dipped in this slurry, pulled out from the slurry, blown off the slurry in the cell with an air stream, and dried at 250 ° C. for 2 hours.
Firing was carried out for 2 hours at a temperature of ℃ to form a first alumina coat layer. This carrier is immersed in an aqueous solution of palladium chloride (PdCl 2 ) to support Pd on the alumina coat layer. Next, an activated alumina powder containing La was used to prepare an alumina slurry in the same manner, and the first slurry was prepared in this slurry.
The carrier on which the layer is formed is immersed, and the second layer is formed in the same manner as above. After that, it is immersed in a rhodium chloride (RhCl 3 ) aqueous solution to support Rh on the second layer. Furthermore, using activated alumina containing Ce, the third layer was formed in the same manner as above, and the carrier on which the first layer and the second layer were formed was treated with gintrodiamine platinum (Pt (NH 3 ) 2 (NO 2 ). 2 ) Immersed in an aqueous solution, Pt was supported on this third layer to obtain a monolith catalyst as shown in FIG. At this time, the amount of noble metal catalyst component supported (weight of noble metal to the total volume of the catalyst layer in the product)
Is adjusted to 1.33 g / l for Pt, 0.27 g / l for Rh, and 1 g / l for Pd.
【００１１】比較例２ 触媒担体上に、該触媒担体から外方側に向けて順に、第
１、第２触媒層が設けられ、第１触媒層においてはアル
ミナ内にＰｔとＲｈとが分散され、第２触媒層において
は、主成分のＣｅＯ2 及びアルミナの内部にＰｄが分散
含有されている。この場合、各層のウォッシュコ−ト層
は、触媒担体の重量に対して各々１４ｗｔ％になるよう
に調整され、第１触媒層における触媒担持量は１．６ｇ
／ｌ（Ｐｔ／Ｒｈ＝５／１）、第２触媒層におけるＰｄ
担持量は、１．０ｇ／ｌとされる。 Comparative Example 2 On a catalyst carrier, first and second catalyst layers were provided in order from the catalyst carrier to the outside, and Pt and Rh were dispersed in alumina in the first catalyst layer. In the second catalyst layer, Pd is dispersedly contained in the main component CeO 2 and alumina. In this case, the washcoat layer of each layer is adjusted to 14 wt% with respect to the weight of the catalyst carrier, and the catalyst loading amount in the first catalyst layer is 1.6 g.
/ L (Pt / Rh = 5/1), Pd in the second catalyst layer
The supported amount is 1.0 g / l.
【００１２】試験条件 （１）触媒容量：２４ｍｌ （２）エ−ジング条件：触媒を、１０００℃の温度で５
０時間加熱する。 （３）空燃比１４．５の下、空間速度を６０００００Ｈ
-1とする。 Test conditions (1) Catalyst capacity: 24 ml (2) Aging conditions: The catalyst was heated at a temperature of 1000 ° C. for 5 hours.
Heat for 0 hours. (3) Space velocity of 600,000H under an air-fuel ratio of 14.5
-1 .
【００１３】上記耐熱性試験の結果、図４に示す内容を
得た。この図４によれば、実施例２が、比較例１に対し
て低い温度から高いＨＣ浄化率を示し、該比較例２は比
較例１よりも高い耐熱性を示した。この結果から、比較
例１では、期待している耐熱性に対して、得る耐熱性が
低過ぎることから、以後、この比較例１に係る触媒を比
較対象から省くこととした。As a result of the heat resistance test, the contents shown in FIG. 4 were obtained. According to FIG. 4, Example 2 showed a higher HC purification rate from a lower temperature than Comparative Example 1, and Comparative Example 2 showed higher heat resistance than Comparative Example 1. From these results, in Comparative Example 1, the heat resistance obtained was too low with respect to the expected heat resistance, and hence the catalyst according to Comparative Example 1 was omitted from the comparison targets.
【００１４】次に、第３触媒層５のＰｄＯとＰｄとの重
量比率が耐熱性（低温活性の安定性）に及ぼす影響につ
いて調べるために、前記比較例２との比較の上で、触媒
１のＰｄＯとＰｄとの比率を変化させ、ＨＣ５０％浄化
率となる浄化温度を測定した。試験条件は、前記耐熱性
試験の試験条件と同じである。Next, in order to examine the influence of the weight ratio of PdO and Pd in the third catalyst layer 5 on the heat resistance (stability of low temperature activity), the catalyst 1 was compared with the above Comparative Example 2. By changing the ratio of PdO and Pd in Example 1, the purification temperature at which the HC50% purification rate was obtained was measured. The test conditions are the same as those of the heat resistance test.
【００１５】この結果、図５の内容を得た。この内容に
よれば、ＰｄＯ／Ｐｄ＝５／９５〜５０／５０の範囲
で、比較例２よりも低い値を示し、低温活性の安定化
（耐熱性）に関し、好結果を示した。As a result, the contents shown in FIG. 5 were obtained. According to this content, in the range of PdO / Pd = 5/95 to 50/50, the value was lower than that of Comparative Example 2, and good results were shown regarding stabilization of low temperature activity (heat resistance).
【００１６】[0016]
【発明の効果】本発明は以上述べたように、最外表層の
熱劣化を抑制して触媒の低温活性の安定化を充分に図る
ことができる。INDUSTRIAL APPLICABILITY As described above, the present invention can suppress the thermal deterioration of the outermost surface layer and sufficiently stabilize the low temperature activity of the catalyst.
【図１】実施例に係る触媒を概念的に示す図。FIG. 1 is a diagram conceptually showing a catalyst according to an example.
【図２】比較例１に係る触媒を概念的に示す図。FIG. 2 is a view conceptually showing a catalyst according to Comparative Example 1.
【図３】比較例２に係る触媒を概念的に示す図。FIG. 3 is a diagram conceptually showing a catalyst according to Comparative Example 2.
【図４】比較例１と２に係る触媒の耐熱性試験の結果を
示す特性線図。FIG. 4 is a characteristic diagram showing the results of heat resistance tests of catalysts according to Comparative Examples 1 and 2.
【図５】第３触媒層のＰｄＯとＰｄとの重量比率が耐熱
性に及ぼす影響を示す図。FIG. 5 is a diagram showing the effect of the weight ratio of PdO and Pd in the third catalyst layer on heat resistance.
１ 触媒 ２ 触媒担体 ３ 第１触媒層 ４ 第２触媒層 ５ 第３触媒層 1 catalyst 2 catalyst carrier 3 first catalyst layer 4 second catalyst layer 5 third catalyst layer
Claims (3)
いるエンジンの排気ガス浄化用触媒において、 前記複数の触媒層のうち最外表層に、酸化セリウム、パ
ラジウム、酸化パラジウムが添加されてなる、ことを特
徴とするエンジンの排気ガス浄化用触媒。1. An engine exhaust gas purifying catalyst having a plurality of catalyst layers provided on a catalyst carrier, wherein cerium oxide, palladium, and palladium oxide are added to the outermost surface layer of the plurality of catalyst layers. A catalyst for purifying engine exhaust gas, which is characterized by:
ウムに担持されている、ことを特徴とするエンジンの排
気ガス浄化用触媒。2. The engine exhaust gas purifying catalyst according to claim 1, wherein the palladium and the palladium oxide are supported on the cerium oxide.
５：９５〜５０：５０である、ことを特徴とするエンジ
ンの排気ガス浄化用触媒。3. The exhaust gas purifying catalyst for an engine according to claim 1, wherein the weight ratio of the palladium oxide to the palladium is 5:95 to 50:50.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10570492A JP3272395B2 (en) | 1992-03-31 | 1992-03-31 | Engine exhaust gas purification catalyst |
| KR1019920011525A KR0132560B1 (en) | 1991-07-01 | 1992-06-30 | Dynamic semiconductor memory device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10570492A JP3272395B2 (en) | 1992-03-31 | 1992-03-31 | Engine exhaust gas purification catalyst |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05277371A true JPH05277371A (en) | 1993-10-26 |
| JP3272395B2 JP3272395B2 (en) | 2002-04-08 |
Family
ID=14414751
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10570492A Expired - Fee Related JP3272395B2 (en) | 1991-07-01 | 1992-03-31 | Engine exhaust gas purification catalyst |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3272395B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001070791A (en) * | 1999-09-03 | 2001-03-21 | Daihatsu Motor Co Ltd | Exhaust gas cleaning catalyst |
-
1992
- 1992-03-31 JP JP10570492A patent/JP3272395B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001070791A (en) * | 1999-09-03 | 2001-03-21 | Daihatsu Motor Co Ltd | Exhaust gas cleaning catalyst |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3272395B2 (en) | 2002-04-08 |
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