JPH054028A - Exhaust gas purification catalyst manufacturing method - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing an exhaust gas purifying catalyst for purifying NO _x at a high rate in an oxygen excess atmosphere. [Composition] At least one selected from copper and cobalt and zeolite are mixed in ammonia, dried, and then heated at 150 ° C.
Firing is performed at the above temperature, and the fired product is slurried to coat the refractory carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to a method of producing a catalyst for purifying harmful components discharged from an internal combustion engine or the like, in particular, the exhaust gas for purifying NO _X in an oxygen-rich atmosphere at a high rate The present invention relates to a method for producing a purification catalyst.

[0002]

2. Description of the Related Art As a catalyst for purifying exhaust gas of an automobile, a catalyst which simultaneously oxidizes carbon monoxide (CO) and hydrocarbon (HC) and reduces nitrogen oxide (NO _x ) is used. Basically, such a catalyst is obtained by applying a γ-alumina slurry to a refractory carrier such as cordierite and drying it, and then carrying a metal such as platinum (Pt), palladium (Pd) or rhodium (Rh). It was done.

The catalysts that have been used or proposed so far have a great effect on the purification performance depending on the set air-fuel ratio of the engine, and oxygen (O ₂ ) even after combustion on the lean side, that is, on the lean side where the air-fuel ratio is large. Is increased, the oxidative effect becomes active, and the reducing effect becomes inactive. On the contrary, on the rich side where the air-fuel ratio is small, the oxidizing action becomes inactive and the reducing action becomes active. The catalyst works most effectively near the stoichiometric air-fuel ratio (A / F = 14.6) where this oxidation and reduction are balanced.

Therefore, when a catalyst is used, in an automobile equipped with an exhaust gas purifying device, feedback control is performed so that the oxygen concentration in the exhaust system is detected and the air-fuel mixture is maintained near the stoichiometric air-fuel ratio.

As described above, as a catalyst to be used in a lean atmosphere with excess oxygen, nitrogen oxide obtained by containing ammonia and carrying copper or cobalt on zeolite by ion exchange, washing with water and drying. A physical decomposition catalyst is disclosed in Japanese Patent Application Laid-Open No. 1-94946.

[0006]

When a washcoat slurry is prepared using the above-described ammonia-containing copper-zeolite, the copper in the zeolite is [Cu (N
H ₃ ) ₄ ] ²⁺ is eluted into water, and Cu ²⁺ in the zeolite, which is the active site of the NO _x purification reaction, is reduced. Further, Cu eluted in water adheres to the surface of the zeolite as CuO, which adversely affects the destruction of the zeolite and reduces the catalytic performance.

[0007]

The present invention has been made to solve the above problems, and the method for producing an exhaust gas purifying catalyst of the present invention is at least selected from copper and cobalt. It is characterized in that one kind and zeolite are mixed in ammonia, dried, and then calcined at a temperature of 150 ° C. or higher, and the calcined product is slurried to be coated on a refractory carrier.

[0008]

In the method of the present invention, when a washcoat slurry is prepared by mixing at least one selected from copper and cobalt and zeolite in ammonia, drying and firing at a temperature of 150 ° C. or higher. Improvement of initial performance and durability of nitrogen oxide purification performance in the oxygen excess region by preventing elution of copper or cobalt which is an active ingredient in zeolite from water into zeolite and preventing decrease of active ingredient. Can be planned.

[0009]

【Example】

 Example 1

Zeolite powder and an aqueous solution of copper acetate were mixed and stirred at room temperature.
Stir for hours. After solid-liquid separation, it was washed thoroughly with water and then dried to obtain a Cu-exchanged zeolite powder containing ammonia and having CuO / Al ₂ O ₃ = 0.99.

The Cu-exchanged zeolite powder containing ammonia was calcined at a temperature of 500 ° C. for 1 hour and then cooled.
100 parts of this Cu-exchanged zeolite powder and silica sol 40
And 80 parts of pure water were mixed to prepare a washcoat slurry. The slurry has a diameter of 30 mm and a length of 50 m.
m, cordierite honeycomb carrier with 300 cells,
Wash-coating was carried out so that the amount per liter of the honeycomb carrier was 120 g, dried, and calcined at 600 ° C. to obtain a Cu-exchanged zeolite catalyst A. Example 2

As in Example 1, containing ammonia, C
Cu-exchanged zeolite powder with uO / Al ₂ O ₃ = 0.99 was calcined at a temperature of 300 ° C. for 1 hour and then cooled. A washcoat slurry was prepared by mixing 100 parts of this Cu-exchanged zeolite powder, 40 parts of silica sol, and 80 parts of pure water. The slurry is 30 mm in diameter, 50 mm in length,
A cordierite honeycomb carrier having 300 cells was wash-coated to give 120 g per liter of the honeycomb carrier, dried and then calcined at 600 ° C. to obtain a Cu-exchanged zeolite catalyst B. Example 3 A catalyst C was obtained in the same manner as in Example 2 except that the calcination temperature of the Cu-exchanged zeolite powder in Example 2 was changed from 300 ° C to 150 ° C. Example 4

Zeolite powder and an aqueous solution of cobalt acetate were mixed and stirred at room temperature. Ammonia water was added thereto and stirred for 12 hours. After solid-liquid separation, washed thoroughly with water and dried to contain ammonia, CoO / Al ₂ O ₃ = 1.08
Co exchanged zeolite powder was obtained.

The Co-exchanged zeolite powder containing ammonia was calcined at a temperature of 300 ° C. for 1 hour and then cooled.
100 parts of this Co-exchanged zeolite powder and silica sol 40
And 80 parts of pure water were mixed to prepare a washcoat slurry. The slurry has a diameter of 30 mm and a length of 50 m.
m, cordierite honeycomb carrier with 300 cells,
A Co-exchanged zeolite catalyst D was obtained by wash-coating so that the weight per liter of the honeycomb carrier was 120 g, drying and firing at 600 ° C. Example 5

CoO / Al ₂ O ₃ = containing ammonia
The Co-Cu exchanged zeolite powder with 0.50 and CuO / Al ₂ O ₃ = 0.55 was calcined at a temperature of 500 ° C. for 1 hour and then cooled. 100 parts of this Co-Cu exchanged zeolite powder, 40 parts of silica sol and 80 parts of pure water were mixed to prepare a washcoat slurry. The slurry was wash-coated on a cordierite honeycomb carrier having a diameter of 30 mm, a length of 50 mm, and a number of cells of 300 so that 120 g was obtained per liter of the honeycomb carrier, dried, and then calcined at 600 ° C. to Co—Cu exchanged zeolite. Catalyst E was obtained. Comparative Example 1

Zeolite powder and an aqueous solution of copper acetate were mixed and stirred at room temperature.
Stir for hours. After solid-liquid separation, it was washed thoroughly with water and then dried to obtain Cu-exchanged zeolite powder containing ammonia and having CuO / Al ₂ O ₃ = 1.0.

The Cu-exchanged zeolite powder containing the ammonia was dried at room temperature (25 ° C.) for 3 hours. 100 parts of this Cu-exchanged zeolite powder, 40 parts of silica sol, and 80 parts of pure water
Parts were mixed to prepare a washcoat slurry.
The slurry was 30 mm in diameter, 50 mm in length, and had 3 cells.
The cordierite type honeycomb carrier of No. 00 was wash-coated so as to be 120 g per liter of the honeycomb carrier, dried and then calcined at 600 ° C. to obtain a Cu-exchanged zeolite catalyst F. Comparative example 2

Including the ammonia obtained in Example 1, CuO
The Cu-exchanged zeolite powder with / Al ₂ O ₃ = 0.99 was dried at 100 ° C. for 3 hours. After cooling, 100 parts of this Cu-exchanged zeolite powder, 40 parts of silica sol, and 80 parts of pure water were mixed to prepare a washcoat slurry. The slurry was wash-coated on a cordierite honeycomb carrier having a diameter of 30 mm, a length of 50 mm, and a number of cells of 300 so that 120 g per 1 liter of the honeycomb carrier was dried and then calcined at 600 ° C. to obtain a Cu-exchanged zeolite catalyst G. Obtained. Comparative Example 3

CoO containing the ammonia obtained in Example 4
Co-exchanged zeolite powder with / Al ₂ O ₃ = 1.08 was dried at room temperature (25 ° C.) for 3 hours. A washcoat slurry was prepared by mixing 100 parts of this Co-exchanged zeolite powder, 40 parts of silica sol, and 80 parts of pure water. This slurry was wash-coated on a cordierite honeycomb carrier having a diameter of 30 mm, a length of 50 mm, and a number of cells of 300 so that 120 g per liter of the honeycomb carrier was dried, and then calcined at 600 ° C. to obtain a Co-exchanged zeolite catalyst H. Got Comparative Example 4

CoO containing the ammonia obtained in Example 4
The Co-exchanged zeolite powder with / Al ₂ O ₃ = 1.08 was dried at 100 ° C. for 3 hours and then cooled. A washcoat slurry was prepared by mixing 100 parts of this Co-exchanged zeolite powder, 40 parts of silica sol, and 80 parts of pure water. This slurry was wash-coated on a cordierite honeycomb carrier having a diameter of 30 mm, a length of 50 mm, and a number of cells of 300 so as to be 120 g per liter of the honeycomb carrier, dried and then calcined at 600 ° C. to obtain a Co-exchanged zeolite catalyst I. Got Comparative Example 5

CoA / Al ₂ O ₃ = containing ammonia
C of 0.50 and CuO / Al ₂ O ₃ = 0.55
The o-Cu exchanged zeolite powder was dried at room temperature (25 ° C) for 3 hours. 100 parts of this Co-Cu exchanged zeolite powder, 40 parts of silica sol and 80 parts of pure water were mixed to prepare a washcoat slurry. The slurry has a diameter of 30
mm, length 50 mm, cordierite honeycomb carrier with 300 cells, 120 g per liter of honeycomb carrier
Co-Cu exchanged zeolite catalyst J was obtained by applying a wash coat so that When preparing the slurries of Examples 1 to 5 and Comparative Examples 1 to 5, the elution rate of copper and / or cobalt eluted in the slurries was measured, and the results are shown in Table 1 below. Further, the NO _x purification rates of the catalysts A to J obtained in Examples and Comparative Examples were measured under the following conditions, and the results are shown in Table 2 below. <NO _x purification performance evaluation condition> NO _x : 300 to 1,000 ppm Air-fuel ratio (A / F): 16 to 22 Space velocity (SV): 40,000 / Hr Inlet gas temperature: 400 ° C Catalyst capacity: 35 cc Durability condition : Model gas equivalent to A / F = 22 600 ° C., 5 hours

[0022]

[Table 1]

[0023]

[Table 2]

From the results shown in Table 1, the washcoat slurry prepared by calcining copper- and / or cobalt-exchanged zeolite containing ammonia at 150 ° C. or higher remarkably reduces the elution rate of copper and / or cobalt into the slurry. You can see that

Table 2 shows the NO _x purification rate under lean conditions where the oxidizing action is active. Compared to the Cu-exchanged zeolite catalysts of catalysts A to C formed in Examples 1 to 3 of the present invention, catalysts F to G formed in Comparative Examples 1 and 2
It can be seen that the Cu-exchanged zeolite catalyst of No. 1 has a poor purification rate of NO _x . Also, a Co-exchanged zeolite catalyst and Co-C
The u-exchanged zeolite catalyst shows the same result as the above case.

[0026]

According to the method of the present invention, the amount of ammonia-containing copper and / or cobalt exchanged zeolite is 150%.
In the washcoat slurry prepared by firing at a temperature of ℃ or higher, the elution rate of copper and / or cobalt in the slurry is significantly reduced, and as a result, the purification performance of the catalyst can be improved.

Further, according to the method of the present invention, it becomes possible to improve the NO _x removal rate in an oxygen excess atmosphere and to provide an inexpensive exhaust gas purifying catalyst, which can be used for internal combustion engines such as automobiles, boilers and households. It is possible to remove NO _{x in} a wide range of fields such as combustion exhaust gas from stoves and cookware.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Teruhiko Ozawa Inventor Teruhiko Ozawa 7800 Chihama, Daito-cho, Ogasa-gun, Shizuoka Within Kyatterer Industry Co., Ltd. Incorporated (72) Inventor Koichi Yamashita 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Shinichi Matsumoto 1 Toyota Town, Toyota City, Aichi Toyota Motor Co., Ltd. (72) Invention Kazuhiko Sekizawa 4560 Kaisei-cho, Shinnanyo-shi, Yamaguchi Prefecture Tosoh stock company (72) Inventor Izumi Kasahara 4560 Kaisei-cho, Shinnanyo-shi Yamaguchi prefecture Tosoh stock company

Claims (1)

Claim: What is claimed is: 1. At least one selected from copper and cobalt is mixed with zeolite in ammonia, and after drying, 1
A method for producing a catalyst for purifying exhaust gas, which comprises calcination at a temperature of 50 ° C. or higher, slurrying the calcination product, and coating it on a refractory carrier.