JP2766665B2 - Method for producing exhaust gas purifying catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NO)
_x ) A method for producing an exhaust gas purifying catalyst for purifying harmful gases.

[Prior Art] Conventionally, when an exhaust gas purifying catalyst is produced, it is produced by the following method.

A honeycomb carrier having a large number of channels (cells) is immersed in a slurry composed of activated alumina, alumina sol, nitric acid, water, etc. to form an activated alumina layer on the honeycomb carrier, and the honeycomb carrier is heated to a temperature of 500 ° C. or more. After baking in, cerium, lanthanum, immersed in a rare earth-containing solution such as praseodymium, after supporting a co-catalyst such as cerium, lanthanum, praseodymium, etc., dried at a temperature of 200 ℃ or more, after firing, platinum,
It carries one or more of palladium and rhodium.

[Problems to be Solved by the Invention] However, the conventional method has a problem that the catalyst purification performance is low. The reason is probably that since the honeycomb carrier is dried at a high temperature of 200 ° C. or higher, rare earth elements such as cerium, lanthanum, and praseodymium are supported on the surface of the alumina layer, and the performance of platinum, palladium, and rhodium is degraded. .

Focusing on this, the inventor of the present invention, when carrying the rare earth component in the performance evaluation of the exhaust gas purifying catalyst,
It has been found that the difference in catalyst purification performance significantly occurs due to the difference between the drying temperature of the honeycomb carrier and the ventilation velocity in the cell.

An object of the present invention is to solve the above problems and to provide a method for producing an exhaust gas purifying catalyst having excellent catalyst purifying performance.

[Means for Solving the Problems] The present invention made in order to achieve the above object is to provide a honeycomb carrier having a large number of cells to which an inorganic porous material is attached, after immersing the carrier in a rare earth-containing solution, to a temperature of 100 ° C. or less. At temperature, and
Dry at an air speed of 0.5m / sec to 1.5m / sec inside the cell, then 300 ℃
Baking at the above temperature, one of platinum, palladium, rhodium
The point is to carry more than one species.

The drying temperature is 100 ° C. or lower, but more preferably 50 ° C.
C. to 100C. When the drying temperature exceeds 100 ° C and the air velocity in the cell exceeds 1.5 m / s, the rare earth-containing solution dries rapidly, so the rare earth is supported on the alumina layer surface, and the performance of platinum, palladium, and rhodium decreases. Conceivable.
On the other hand, if the air velocity in the cell is dried at less than 0.5 m / sec, a long time is required and productivity is deteriorated.

[Function] As described above, the present invention supports a honeycomb carrier and supports a rare earth element such as cerium, lanthanum, praseodymium, etc., and then drying at a temperature of 100 ° C. or less at an air velocity in a cell of 0.5 m / sec to 1.5 m / sec. Cerium, lanthanum, praseodymium and the like are uniformly supported on the entire layer, and a decrease in catalytic performance is prevented.

[Example] Example 1 A honeycomb carrier (1.0, 400 cells / in ² ) was immersed in a slurry obtained by mixing and stirring alumina powder containing γ-alumina as a main component, alumina sol, and water, followed by air blowing.
The drying operation was repeated twice, the activated alumina coat layer was adhered to the honeycomb carrier, and baked for 1 hour in an air atmosphere at 650 ° C.

The attached amount of activated alumina was 180 g / piece. The carrier to which the activated alumina was attached was immersed in a cerium nitrate-containing solution (cerium concentration 1.8 mol /) and air blown.
After drying at a temperature of 0 ° C. for 30 minutes at an air velocity in the cell of 1.5 m / sec, baking was performed at 300 ° C. for 2 hours to deposit 35 g of cerium per piece. This carrier was immersed in a dinitrodiaminoplatinum-containing solution and a rhodium chloride-containing solution, respectively.
Drying at ℃ gave Catalyst 1.

Example 2 A method similar to that of Example 1 except that the honeycomb carrier having activated alumina attached thereto was immersed in a cerium nitrate-containing solution, air-blown, and dried at a temperature of 90 ° C. and a cell internal wind speed of 1.0 m / sec for 30 minutes. The catalyst 2 was obtained.

Example 3 A method similar to that of Example 1 except that the honeycomb carrier to which activated alumina was attached was immersed in a cerium nitrate-containing solution, air-blown, and dried at a temperature of 100 ° C. and an air velocity of 0.5 m / sec in a cell for 30 minutes. The catalyst 3 was obtained.

Example 4 A honeycomb carrier to which activated alumina was attached was immersed in a solution containing cerium nitrate and lanthanum nitrate and air blown.
Catalyst 4 was obtained in the same manner as in Example 1 except that 35 g / piece of cerium and 7 g / piece of lanthanum were adhered after drying at a temperature of ° C. and an air velocity in the cell of 1.0 m / sec for 30 minutes.

Example 5 A catalyst 5 was obtained in the same manner as in Example 4 except that lanthanum nitrate in Example 4 was changed to praseodymium nitrate.

Example 6 A catalyst 6 was obtained in the same manner as in Example 4 except that lanthanum nitrate in Example 4 was changed to neodymium nitrate.

Example 7 A catalyst 7 was obtained in the same manner as in Example 1 except that cerium nitrate in Example 1 was changed to lanthanum nitrate.

Example 8 A honeycomb support having activated alumina and cerium attached thereto was immersed in a dinitrodiaminoplatinum-containing solution, a rhodium chloride-containing solution, and a palladium nitrate-containing solution, respectively.
Catalyst 8 was obtained in the same manner as in Example 1, except that the catalyst was supported at 5 g / piece, 0.5 g / piece, and 0.2 g / piece.

Comparative Example 1 A honeycomb carrier (1.0, 400 cells / in ² ) was immersed in a slurry obtained by mixing and stirring alumina powder containing γ-alumina as a main component, alumina sol, and water, followed by air blowing.
The drying operation was repeated twice, the activated alumina coat layer was adhered to the honeycomb carrier, and baked for 1 hour in an air atmosphere at 650 ° C.

The attached amount of activated alumina was 180 g / piece. The carrier to which the activated alumina is attached is immersed in a cerium nitrate-containing solution (cerium concentration: 1.8 mol /), air blown, and then 300 ° C.
At a temperature of 5 ° C., the cells were dried and fired at a wind speed of 5 m / sec in the cell for 2.5 hours to deposit 33 g / cerium. The carrier was immersed in a dinitrodiaminoplatinum-containing solution and a rhodium chloride-containing solution, respectively.
After supporting the catalyst at a rate of g / unit, the catalyst was dried at 250 ° C. to obtain a catalyst A.

Comparative Example 2 A honeycomb carrier having activated alumina attached thereto was immersed in a cerium nitrate-containing solution, air-blown, dried at a temperature of 200 ° C at an air velocity of 1.0 m / sec in a cell for 30 minutes, and baked at 300 ° C for 2 hours. In the same manner as in Comparative Example 1, a catalyst B was obtained.

Comparative Example 3 A honeycomb carrier having activated alumina attached thereto was immersed in a cerium nitrate-containing solution, air-blown, dried at a temperature of 90 ° C. at an air velocity of 0.2 m / sec in a cell for 30 minutes, and baked at 300 ° C. for 2 hours. In the same manner as in Comparative Example 1, a catalyst C was obtained.

Comparative Example 4 A honeycomb carrier having activated alumina attached thereto was immersed in a cerium nitrate-containing solution, air-blown, dried at a temperature of 80 ° C at a flow rate of 5 m / sec in a cell for 30 minutes, and baked at 300 ° C for 2 hours. Catalyst D was obtained in the same manner as in Comparative Example 1.

Comparative Example 5 A honeycomb carrier to which activated alumina was attached was immersed in a solution containing cerium nitrate and lanthanum nitrate and air blown.
After drying at a temperature of 3 ° C for 30 minutes at a wind speed of 3 m / sec in the cell, cerium 3
Catalyst E was obtained in the same manner as in Comparative Example 1 except that 5 g / unit and 7 g / unit of lanthanum were adhered.

Comparative Example 6 Catalyst F was obtained in the same manner as in Comparative Example 5, except that lanthanum nitrate in Comparative Example 5 was changed to praseodymium nitrate.

Comparative Example 7 A catalyst G was obtained in the same manner as in Comparative Example 5 except that lanthanum nitrate in Comparative Example 5 was changed to Neodymium Nitrate.

Comparative Example 8 Catalyst H was obtained in the same manner as in Comparative Example 1 except that cerium nitrate in Comparative Example 1 was changed to lanthanum nitrate.

Comparative Example 9 A honeycomb carrier to which activated alumina and cerium were attached was immersed in a dinitrodiaminoplatinum-containing solution, a rhodium chloride-containing solution, and a palladium nitrate-containing solution, respectively.
Catalyst I was obtained in the same manner as in Comparative Example 1 except that the catalyst was carried so as to be 5 g / piece, 0.5 g / piece, and 0.2 g / piece.

Catalyst 1 obtained in Examples 1 to 8 and Comparative Rows 1 to 9
In order to investigate the catalytic performance of the catalysts A to I and the catalysts A to I, the following durability test was conducted, and the catalyst purification performance after the durability was shown in Table 1.

<Endurance conditions> 2000cc, 4-cylinder engine, gas temperature 900 ° C, endurance atmosphere 0.1 lean [A / F (air-fuel ratio) = 14.7… A / F = 14.
6 (theoretical air-fuel ratio)], and the endurance time is 50 hours.

<Evaluation conditions> 2000 cc, 4-cylinder engine used for endurance, evaluation atmosphere: A / F = 14.6 (Stoich ... stoichiometric air-fuel ratio), SV (space velocity) 60,000Hr ^-1 And HC,
CO, purification rate of the NO _x showed temperatures reached 50%, respectively in Table 1.

From Table 1, it can be seen that the honeycomb carrier having the activated alumina layer attached thereto is immersed in a rare earth-containing solution and air blown, and then dried at a temperature of 100 ° C. or less and at an air velocity in the cell of 0.5 m / sec to 1.5 m / sec. After baking at 300 ° C., catalysts 1 to 8 supporting platinum, palladium, and rhodium have improved purification performances of HC, CO, and NO by about 20 ° C., respectively, as compared with comparative catalysts A to G. This indicates that Examples 1 to 8 have higher catalyst purification rates at the same temperature than Comparative Catalysts A to G.

In Comparative Examples A to G, cerium, lanthanum, praseodymium, and neodymium were used for rapid drying or insufficient drying.
It is considered that the catalyst is supported on the surface of activated alumina and reduces the purification performance of platinum, palladium and rhodium.

[Effects of the Invention] As described above, after immersing a honeycomb carrier having a large number of cells to which an inorganic porous substance is attached in a rare earth-containing solution, at a temperature of 100 ° C or less, and 0.5 m / sec to 1.5m /
Secondly, the cell is dried at an air velocity of 2 seconds and then baked at a temperature of 300 ° C. or more. Then, at least one of platinum, palladium, and rhodium is supported, so that cerium, lanthanum, praseodymium, etc. Is uniformly supported,
Platinum, palladium and rhodium can be prevented from deteriorating in performance and have an effect of improving catalyst purification performance.

Claims (1)

(57) [Claims] 1. A honeycomb carrier having a large number of cells to which an inorganic porous substance is attached is immersed in a rare earth-containing solution and then heated at 100 ° C.
It is characterized by being dried at the following temperature and at an air velocity of 0.5 m / sec to 1.5 m / sec in the cell, then baked at a temperature of 300 ° C. or more, and carrying at least one of platinum, palladium and rhodium. A method for producing an exhaust gas purifying catalyst.