JPS6019036A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To enhance CO-purifying capacity as a low temp., by a method wherein upper and lower two activated alumina layers are laminated to the surface of a base material and platinum or Pd is supported by the lower layer while Ph and platinum or Rh and Pd are supported by the upper layer. CONSTITUTION:Upper and lower two activated alumina layers are laminated to the surface of a base material comprising cordierite and platinum or Pd is supported by the lower layer while Rh and platinum or Rh and Pd are supported by the upper layer. With respect to the amount of each catalytic metal, Rh is 0.1- 0.3g/l or Pt or Pd is about 0.5g/l in the upper layer while Pt or Pd is about 0.5g/l in the lower layer. Because this catalyst supports not only Rh having strong poisoning resistance to CO, lead or phosphorus only in the upper layer thereof but also platinum or Pd in a proper amount, platinum or Pd in the lower layer is protected. In addition, because CO-oxidation in the lower layer is facilitated by diffusing CO in the upper layer, the ignition temp. of CO is lowered and this catalyst shows excellent purifying capacity even at a lower temp. as compared with a conventional one.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は、自動車等の内燃機関から排出される排気ガス
の浄化用触媒に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a catalyst for purifying exhaust gas discharged from internal combustion engines such as automobiles.

（従来技術） 内燃機関、特に自動車の排気ガス浄化用触媒には慢めで
高度な浄化性能が要求される。温度的には３００℃付近
から１０００℃近くまでの広い範囲で高い浄化性能が要
求され、特に低温における活性は、最近の省燃費対策と
して抽気ガス温度が低下する頬内にあることから非常に
重要性が増している。(Prior Art) Catalysts for purifying exhaust gas in internal combustion engines, especially automobiles, are required to have relatively high purification performance. High purification performance is required over a wide temperature range from around 300°C to around 1000°C, and activity at low temperatures is especially important because the temperature of the bleed gas drops as a recent fuel saving measure. Sexuality is increasing.

しかしながら従来の排気ガス浄化用触媒は基本的には高
温型であるため、最近の排気ガス温度の低下に対して充
分に対応したものとはいえず、低温における浄化性能の
点ではかならずしも満足できるものではなかった。However, since conventional exhaust gas purification catalysts are basically high-temperature types, they cannot be said to adequately respond to the recent decline in exhaust gas temperature, and are not always satisfactory in terms of purification performance at low temperatures. It wasn't.

（発明の目的） 本発明は上記従来技術における問題点？／、、　Ｗｌ決
するためのものであり、その目的とするところは現在自
動車排気ガス浄化用三元触媒の主流となっている白金族
元素を担持したハニカム形状モノリス触媒についての低
温活性特に−酸化炭素（ＣＯ）に対する浄化特性を向上
させた触媒を提供することにある。(Objective of the Invention) Does the present invention address the problems in the above-mentioned prior art? /,, The purpose is to investigate the low-temperature activity of honeycomb-shaped monolithic catalysts supporting platinum group elements, which are currently the mainstream of three-way catalysts for automobile exhaust gas purification. An object of the present invention is to provide a catalyst with improved purification characteristics for (CO).

（発明の構成） すなわち本発明の抽気ガス浄化用触媒は、コージェライ
ト等からなる基材の表面に活性アルミナ層を上下２層に
積層し、下層には白金捷たはパラジウムを、上層にはロ
ジウムと白金、寸たはロジウムとパラジウムを担持せし
めて低温における一酸化炭素浄化性能全高め／ヒことを
特徴とする。(Structure of the Invention) That is, the bleed gas purification catalyst of the present invention has activated alumina layers laminated in two layers, upper and lower, on the surface of a base material made of cordierite, etc., with platinum or palladium in the lower layer and platinum or palladium in the upper layer. It is characterized by supporting rhodium and platinum, or more specifically rhodium and palladium, to fully enhance carbon monoxide purification performance at low temperatures.

白金、パラジウム、ロジウム等の触媒金１・−５％は通
常活性アルミナ層全体に均一にＪｉ３持するが、光面の
触媒金属は排気ガス中の一酸化炭素（ＣＯ）や鉛（Ｐｂ
）、燐（Ｐ）などにより被毒されやすい。Catalytic gold such as platinum, palladium, or rhodium (1.-5%) usually maintains Ji3 uniformly throughout the activated alumina layer, but the catalyst metal on the light surface absorbs carbon monoxide (CO) and lead (Pb) in the exhaust gas.
), phosphorus (P), etc.

また触媒金属の種類により被毒の程度も異なるため適切
に層別して使用した方が触媒全体としては浄化性能が向
上する。Furthermore, since the degree of poisoning varies depending on the type of catalyst metal, the purification performance of the catalyst as a whole will be improved if the catalyst is used in appropriate stratification.

特に低温においてはＣＯは貴金属に対する吸着力が強い
ため、ＣＯの酸化反応においては反応速度けＣＯ濃城に
ついて負の次数となり、ＣＯａ度が増加するに従って反
応速度が低下し、着火扁庶が高くなる。このため浄化性
能は低下するが、土層にロジウムのような金属捷たは白
金、パラジウムｋｉｄ当墳４す持し、下層に白金、パラ
ジウｌ、　ｙ　４１４持すると、ＣＯの吸着力が強い下
層の白金、パラジウムはＣＯによる被毒から１呆簡され
ると共に、上層のアルミナ層による拡散抵抗により下層
ではＣＯ濃度が低下し、上記の理由により着火温度が低
下する。Particularly at low temperatures, CO has a strong adsorption power for noble metals, so in the CO oxidation reaction, the reaction rate becomes a negative order of CO concentration, and as the COa degree increases, the reaction rate decreases and the ignition angle increases. . For this reason, the purification performance decreases, but if the soil layer contains a metal such as rhodium or platinum or palladium, and the lower layer contains platinum, palladium, or y414, the lower layer has a strong adsorption power for CO. Platinum and palladium are less likely to be poisoned by CO, and the CO concentration in the lower layer decreases due to the diffusion resistance caused by the upper alumina layer, resulting in a decrease in ignition temperature for the above-mentioned reasons.

活性アルミナの種類としてはα−寸たはｒ−アルミナ等
の通常この種の目的に使用するものを用いることができ
る、比表面積や細孔径は活性や被毒による孔の閉塞に関
係するため適当なものを選択する。上層に比表面積の小
さな　（細孔径の大きな）ものを使用すると、被毒に対
して強いものがイ与られる。才だ活性アルミナ層は、通
常は２層で充分であるが３層以上設けてもよい。As for the type of activated alumina, those normally used for this type of purpose, such as α-sized or r-alumina, can be used.The specific surface area and pore diameter are related to activity and pore clogging due to poisoning, so it is appropriate. choose something. If a material with a small specific surface area (large pore size) is used for the upper layer, it will be resistant to poisoning. Two activated alumina layers are usually sufficient, but three or more layers may be provided.

アルミナ層の厚さは、上記のＣＯの吸着や拡散抵抗に関
係するため重要であり、通常は上下２層合せて１００μ
程度とする。各々の層の厚きは任意に選択できる。例え
ば上層ケ６０μ以上の厚みとすればＣＯ濃度が高い場合
でも充分Ｉｔ火温ｍを低下できる。The thickness of the alumina layer is important because it is related to the above-mentioned CO adsorption and diffusion resistance, and the thickness of the upper and lower layers is usually 100 μm in total.
degree. The thickness of each layer can be selected arbitrarily. For example, if the thickness of the upper layer is 60 μm or more, the It fire temperature m can be sufficiently reduced even when the CO concentration is high.

上下両層に担持する触媒金属の量は、上層については触
媒単位容積当り通常Ｊ（ｈ　Ｏ，１〜０．３　ｆ／ｌ　
。The amount of catalyst metal supported on both the upper and lower layers is usually J (h O, 1 to 0.3 f/l) per unit volume of catalyst for the upper layer.
.

ＰｉまたはＰｄ　０．５ｆ／を前後、下層についてはＰ
ｔまたはＰｄ　Ｏ，５９／を前後とするとよい。外にラ
ンタン（Ｌａ）、セリウム（Ｃｅ）、鉄（Ｆｅ　）等の
貴金属触媒成分の活性を向上させるために添加する成分
を適吐用いることもできる。Pi or Pd around 0.5f/, P for the lower layer
It is preferable that t or Pd O,59/ be around. In addition, components added to improve the activity of noble metal catalyst components, such as lanthanum (La), cerium (Ce), and iron (Fe 2 ), can also be appropriately dispensed.

低温活性としては通常３ｏｏ℃以下特に常温〜３００℃
位の間での排気ガス浄化性能が問題となるが、ＣＯに関
しては本発明の触媒を用いることにより実用上充分な性
能を得ることができる。Low-temperature activity is usually below 300°C, especially room temperature to 300°C.
Although the exhaust gas purification performance between the two levels is a problem, the use of the catalyst of the present invention can provide practically sufficient performance regarding CO.

（実施例） 以下の実施例において本発明を更に詳細に説明する。な
お本発明は下記実施例に限定されるものではない。(Example) The present invention will be explained in further detail in the following example. Note that the present invention is not limited to the following examples.

実施例１： アルミナ含有量１０チの市販のアルミナシルア００　ｙ
、　４０重量係の硝酸アルミニウム水溶液１５（１、イ
オン交換水２００　ｆより成る混合混濁液にアルミナ粉
末１０００ｆｉ加えスラリーとした。Example 1: Commercially available alumina silua 00y with alumina content of 10y
A slurry was prepared by adding 1000 fi of alumina powder to a mixed turbid solution consisting of 40% by weight aqueous aluminum nitrate solution 15 (1) and 200 f of ion-exchanged water.

この中にコージェライト質モノリス担体基材（直径９３
ｍ長さ７６ｍ）ｋ　２分間浸漬し、引き上げてセル内の
スラＩＪ　ｉ空気流で吹き飛ばして除いた。２００℃で
２時間乾燥した後、７００　Ｕで２時間焼成してアルミ
ナ／脅Ａ　′ｆｒ：形成した。次に、０．２６５’／ｚ
　（Ｐｔｍり）濃１＆　（ｒ）　シ＝　）　ｏ　ジアミ
ノ白金水溶液１ｔに１時間浸漬した後２０ｏ℃で１時間
乾燥してＰｔヲアルミナ層に担持した。次に再び上記の
アルミナスラリーに２分間浸漬した後同様な操作を行い
、第２のアルミナＩｆ／ｆ１３を形成した。この後ｏ、
ｚ６ｙ７ｔの濃麻のジニトロシフ　ミ／　白金水溶液１
ｔ、　次イ？　０．０５２１ｉ’／／、　ノ濃ＩＩＩの
塩化ロジウム溶液１ｔに浸漬し、２００’Ｃで１時間乾
燥して本発明のＰ　ｔ　／ｌｔ　ｈ剛；媒ａを曲た。Inside this is a cordierite monolith carrier base material (diameter 93 mm).
m Length 76 m) k It was immersed for 2 minutes, then pulled up and removed by blowing it away with the air stream inside the cell. After drying at 200°C for 2 hours, it was calcined at 700 U for 2 hours to form alumina/metal A'fr:. Next, 0.265'/z
It was immersed in 1 t of diaminoplatinum aqueous solution for 1 hour and then dried at 20° C. for 1 hour to support the Pt on the alumina layer. Next, the sample was immersed in the alumina slurry for 2 minutes again and the same operation was performed to form a second alumina If/f13. After this o,
z6y7t thick hemp dinitrosifumi/platinum aqueous solution 1
t, next a? It was immersed in 1 t of rhodium chloride solution of 0.0521 i'//, concentration III, and dried at 200'C for 1 hour to bend the P t /lt h stiffness medium a of the present invention.

実施例２ニ ジニトロジアミノ白金のがわりに塩化パラジウム全周い
て実施例１と全く同様な方法により本発明のｐｄ／ｌｔ
ｈ触媒すを得た。Example 2 The pd/lt of the present invention was prepared in exactly the same manner as in Example 1 except that palladium chloride was used instead of dinitrodiaminoplatinum.
A catalyst was obtained.

第１図に本発明の排気ガス浄化用触媒１の斜視図を示す
。また第２図は第１図の触媒の一部拡大断面図であり、
図中２ｅすコージェライト質担体基材、３はアルミナ層
Ａ、４はアルミナ層１３を表わす。FIG. 1 shows a perspective view of an exhaust gas purifying catalyst 1 of the present invention. FIG. 2 is a partially enlarged sectional view of the catalyst in FIG.
In the figure, 2e represents the cordierite carrier base material, 3 represents the alumina layer A, and 4 represents the alumina layer 13.

比較例１： 実施例１と同様の方法でアルミナ層を形成した。この時
実例１とアルミナコート量全同−にするため、アルミナ
コートの操作を２回繰り返した。この後ジニトロジアミ
ノ白金水溶液（０，５２９／ｌ　）　１ｔ、次いで０．
０５２　’／／ｌの塩化ロジウム溶液に浸漬して比較例
のＰ　Ｌ／　）ｔｈ触媒Ｃを得た。Comparative Example 1: An alumina layer was formed in the same manner as in Example 1. At this time, in order to achieve the same amount of alumina coating as in Example 1, the alumina coating operation was repeated twice. After this, add 1 t of dinitrodiaminoplatinum aqueous solution (0,529/l), then 0.
A comparative example of P L/ )th catalyst C was obtained by immersing it in a rhodium chloride solution of 052'//l.

比較例２ニ ジニトロアミノ白金のかわりに塩化ノ（ラジウムを用い
て実施例１と同様の方法により比較例のＰｄ／ｌ（ｈ触
媒ｄを得た。Comparative Example 2 A Pd/l (h catalyst d) of Comparative Example was obtained in the same manner as in Example 1 using radium chloride instead of dinitroaminoplatinum.

上記実施例１．２および比較例１．２の触媒の貴　１金
属担持量を第１表に示す。Table 1 shows the amount of noble metal supported on the catalysts of Example 1.2 and Comparative Example 1.2.

／／ ／／″′ ７−／ 、／′ 〕／ ２／／ 、、′ｚ ／ 第１表：触媒１ｔあたりの貴金属担持量（ｆ／ｌ）耐久
試験： 実施例と比較例で得られた計４種の触媒全触媒コンバー
タに装填してこれを排気量２０００ＣＣのエンジンの排
気系に連設し通常走行で３００時間運転して耐久試験を
行った後排気ガスの浄化性能を評価した。結果を第３図
に示す。// //″' 7-/ , /' ]/ 2// ,,'z / Table 1: Amount of precious metal supported per 1 ton of catalyst (f/l) Durability test: Obtained in Examples and Comparative Examples A total of four types of catalytic converters were loaded and connected to the exhaust system of an engine with a displacement of 2,000 cc, and the exhaust gas purification performance was evaluated after a durability test of 300 hours of normal driving.Results. is shown in Figure 3.

図より明らかなように本発明の触媒ａと比較例の触媒Ｃ
１および本発明の触媒すと比較例の触媒ｄｉ比べると総
ての温度範囲にわたって一酸化炭素浄化率が向上してお
り、また人ガス温度が２５０℃以下の場合でも本発明の
触媒は充分な浄化率金示す。As is clear from the figure, catalyst a of the present invention and catalyst C of the comparative example.
1 and the catalyst of the present invention compared to the catalyst di of the comparative example, the carbon monoxide purification rate is improved over the entire temperature range, and even when the human gas temperature is 250°C or less, the catalyst of the present invention has a sufficient Shows purification rate.

（発明の効果） 上述のように本発明の排気ガス浄化用触媒は、−酸化炭
素や鉛、燐に対する被審に強いロジウムを上層にのみ担
持し、また白金やノくラジウムを適数担持したものであ
る几め下層の白金やノくラジウムを保膿するものとなり
、また−酸化炭素を上層で拡散させる。ことによって下
層での酸化を容易ならしめるため一酸化炭素の着火温度
が低下し、従来よりも低温においても優れた浄化性能を
示すものとなり、近年の省燃費により１ノド気ガス温度
が低トする状況下においても浄化性能を低下させること
なく、またますます厳しくなる環境保全の硬水にも適合
し７た優れた効果を奏する。(Effects of the Invention) As described above, the exhaust gas purifying catalyst of the present invention supports rhodium, which is resistant to carbon oxide, lead, and phosphorus, only in the upper layer, and also supports an appropriate amount of platinum and radium. It serves to retain platinum and radium in the lower layer, and also diffuses carbon oxide in the upper layer. This makes it easier to oxidize in the lower layer, lowering the ignition temperature of carbon monoxide, resulting in superior purification performance at lower temperatures than before, and fuel efficiency in recent years has lowered the gas temperature by 1 nod. It does not reduce purification performance even under various conditions, and is compatible with hard water, which is an increasingly strict environmental protection requirement, and has excellent effects.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の排気ガス浄化用触媒の斜視図、 第２図は第１図の触媒の一部拡大断面図、第３図は本発
明の触媒と比較例の触媒の各人ガス温度における一酸化
炭素浄化率＋Ｓわすグラフである。 図中、 １・・・排気ガス浄化用触媒 ２・・・コージェライト質担体 ３・・・アルミナ層Ａ ４・・・アルミナ層Ｂ 特許出願人　トヨタ自動車株式会社Fig. 1 is a perspective view of the exhaust gas purifying catalyst of the present invention, Fig. 2 is a partially enlarged sectional view of the catalyst of Fig. 1, and Fig. 3 is the individual gas temperature of the catalyst of the present invention and the catalyst of the comparative example. It is a graph of carbon monoxide purification rate +S. In the figure, 1... Exhaust gas purification catalyst 2... Cordierite support 3... Alumina layer A 4... Alumina layer B Patent applicant Toyota Motor Corporation

Claims (1)

【特許請求の範囲】[Claims] コージェライト等からなる基拐の表面に活性アルミナ層
を上下２層に積層し、下層には白金またはパラジウムを
、上層にはロジウムと白金、−！、りはロジウムと７４
ラジウムを担持せしめて低温における一酸化炭素浄化性
能を高めたことを特徴とする排気ガス浄化用触媒。Activated alumina layers are laminated in two layers, upper and lower, on the surface of a substrate made of cordierite, etc., with platinum or palladium in the lower layer and rhodium and platinum in the upper layer. , Ri is rhodium and 74
An exhaust gas purification catalyst characterized by supporting radium to improve carbon monoxide purification performance at low temperatures.