JPS6025544A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To impart excellent catalytic activity and durability, by supporting a catalyst component by a carrier of which the surface layer is formed of delta-alumina theta-alumina. CONSTITUTION:gamma-alumina is respectively baked at 850 deg.C, 900 deg.C and 1,050 deg.C to obtain delta-alumina, theta-alumina or a mixture thereof. This alumina mixture is mixed with an alumina sol, aluminum nitrate, distilled water and lanthanum carbonate to obtain a slurry. A separation type carrier formed of alumina (e.g., a granular carrier or a pellet like carrier) substrate is immersed in said slurry. Subsequently, impregnated carrier is drawn up and the slurry in the cell of the carrier substrate is blown off by an air stream and, after drying, baking is performed at about 600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas purifying catalyst for purifying automobile exhaust gas.

(Prior Art) Catalysts have been used for a long time to purify exhaust gas emitted from internal combustion engines such as automobiles, and 94 catalysts have already been used. Conventionally, as a catalyst for purifying exhaust gas for automobiles,
A granular carrier made of active or total alumina, etc., or a monolithic carrier made of a honeycomb-shaped base material made of medium cordierite, etc. coated with alumina, supports noble metals having sole catalytic activity, such as platinum, palladium, and rhodium, singly or in combination. In the fusion medium in which the carrier V is used, the carrier V not only plays the role of supporting the catalyst components, but also has a large effect on the catalytic activity and durability of the catalyst. Live alumina (r-alumina) with a large surface area is used.

(Technical Fishing Line, 1) By the way, this type of catalyst can be used at extremely high temperatures (approximately 800
~1000℃)
The catalyst performance must not deteriorate due to heat.

However, when using an exhaust gas purifying catalyst using activated γ alumina as a carrier, there is a problem in that the above-mentioned thermal deterioration occurs to some extent.

(Objective of the Invention) The present invention provides a catalyst for exhaust gas degradation that has little thermal deterioration, fl/2 ity' catalyst activity and durability despite using alumina as a carrier. The inventors of the present invention have conducted various research to solve this technical problem, and as a result, it has been determined that the cause of thermal deterioration of catalyst performance is due to the Tsubame Toguchi situation F. The present invention was completed based on the discovery that the present invention exists in the metamorphosis of alumina.

In other words, Albus's transformation is γ: 300-800℃ δ: 800~900℃ θ:900~1050℃ α: 1050℃ It occurs as follows, but when changing from r → δ → θ.

It was found that the catalytic activity was significantly reduced.

(Structure of the Invention) The exhaust gas purifying catalyst of the present invention has at least the surface (l) of the carrier.
ti)2 was formed from δ-alumina, θ-alumina or a mixture thereof, and the carrier was freed from the solvent component. Let's say 1 and 4 sentences.

In the present invention, the form of the carrier is not particularly limited. Specifically, a separate carrier formed of alumina, such as a granular carrier or a pellet-shaped 2M body, or a monolithic finger formed by coating alumina on a carrier base material such as cordierite, is used. body, nine-thorn honeycomb-like carrier.

As catalyst components, those normally used for this purpose can be used, such as platinum, rhodium! Or a precious metal such as palladium alone or a combination of fc can be mentioned.

(Examples and Comparative Examples) The present invention will be explained in detail below with reference to Examples and Comparative H. Examples 1 to 3 Cordierite monolith carrier base material (diameter 30 mm).

The length is 50 m++t (4 cylindrical) purple, and it will be catalyzed in the following process.
δ-alumina by firing at various temperatures of 0°C.

To obtain θ-alumina or a mixture thereof, Albanazol (-r Lumibou 10 < 57 300 parts,
60 parts of aluminum nitrate, 1 g of steamed water, 300-400 parts,
40 parts of lanthanum carbonate (which becomes about 42% lanthanum oxide upon calcination) and the alumina 53o1flX obtained in step 2 are mixed to form a slurry. The carrier base material marked with # was immersed in this slurry for 2 minutes, then pulled out and the slurry in the carrier base material cells was blown away with an air flow, and the temperature was raised to 150°C.
After drying for 3 hours at a temperature of 600.degree. C. for 3 hours, a catalyst carrier is obtained.

(2) The catalyst carrier obtained in (1) above is exposed to a heptadium nitrate solution, platinum P salt solution B, and rhodium chloride to adsorb cerium, platinum, and rhodium onto the active layer.

Then, by drying and calcining this to catalyze it, the present invention catalysts A (calcined at 850°C) and B (90°C
(fired at 0°C) and C (fired at 1050°C). The supported amount is per carrier 1), CeO2
o, 3 moles, i't L O! and RhO,1,
It is P.

Comparative examples 1 to 3 As alumina, γ-alumina was heated at 700°C.

Comparative catalyst a (70
7), b (fired at 1150°C), and C (fired at 1250°C).

(Test example) Next, the catalysts of Example and Comparison 1 + lJ were subjected to a durability test.
Compare CI) #long test Load each catalyst in a metal container, attach it to the engine exhaust system of a car, and run the J-not gas through it. In this case, the test conditions were set as follows.

Sora ratio (A/F): 16 Exam time (hours): 50 Catalyst bed Q degree (1::): FJso.

Space velocity (1/hour): Approximately 60,000 (2) After the activity evaluation durability test, the Tani catalyst was passed under the following conditions to oxidize l-IC and CO and to ring NOx. The purification rate of HC, CO and NOx is measured.

Heating 11 sacrifice IC) 2 300 Space velocity υt (1/hour): Approximately 80,000 In this case, variable gas 1jco: 0.8%.

Mind JOx: 2200ppm,'C3 as HC
H6: 2200ppm, 02: 0.8%,,
H2: 0.27%, H2O: #10, Co2: 1
0 reward, N2: For remaining model gas.

Excess 02 and C02 are added alternately by 2 and 0.5)12, respectively, and it is removed.

The measurement packing is shown in the figure.

As is clear from the results of Jin), catalyst A according to the practical sequence,
13. C is compared to Comparative Examples a, b, and c.

High quality item 11 inches long and 12 times tall. .

(Effects of the Invention) As shown in I-H, according to the present invention, the problem of swallowing of Albus during use is suppressed, so that the technical issues mentioned above,
It uses the effect of ``Small Screening C Saru''.

It's a waste, because the pore size of Al (compared to that of γ-alumina) is distributed over a large range, so the pore diameters of the pores of the invention are distributed over a large range, so phosphorus, sulfur, etc. The pores are less likely to be clogged, thus reducing the effect of providing water resistance.

[Brief explanation of drawings]

Figure 1 represents a graph showing the catalytic activity of catalysts A, B, and CJ- according to Example 3 and catalysts a, b, and c according to comparative examples. Applicant: Toyota Motor Corporation ((2't or 1 person)

Claims (1)

[Claims] The catalyst components are then impregnated onto a support formed of δ-alumina, θ-alumina, or a mixture thereof, at least on the surface. Catalyst for exhaust gas purification.