JP3505739B2 - Exhaust gas purification catalyst - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exhaust gas purification for purifying hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ) in exhaust gas discharged from internal combustion engines such as automobiles. Regarding catalysts.

[0002]

As a conventional exhaust gas purifying catalyst, a platinum group metal component such as platinum (Pt), palladium (Pd) and rhodium (Rh) is supported on alumina, cerium oxide or the like, which is coated on a monolith carrier. The structure of H
A catalyst called a three-way catalyst that removes C, CO and NO _x at a time has been frequently used.

[0003]

However, such a catalyst is effective only when the internal combustion engine is operated under conditions near stoichiometry, and the exhaust gas purifying catalyst treats exhaust gas whose composition varies widely from reducing to oxidizing. In particular, under conditions where the concentration of hydrocarbons is high and the concentration of oxygen is not sufficient, the purification reaction is hindered by the strong adsorption poisoning of hydrocarbons on the catalytically active metal, which lowers the purification rate of harmful components. There was a problem that it would end up.

[0004]

The present invention has been made by paying attention to such conventional problems, and in addition to those conventionally used as catalyst components such as platinum group elements, activated alumina, and cerium oxide. By combining at least one of potassium, cesium, strontium and barium, and at least one of cobalt and manganese, a high purification rate is achieved even for exhaust gas with high hydrocarbon concentration and low oxygen concentration. It is based on finding what can be done.

Therefore, the catalyst for purifying exhaust gas of the present invention is an integrated structure type catalyst having a catalyst component supporting layer, in which at least one of platinum and palladium, activated alumina and cerium oxide are added to the supporting layer as catalyst components. , At least one of potassium, cesium, strontium and barium, and at least one of cobalt and manganese. Amount of catalyst component supported,
That is, the loading amount of platinum and palladium should be 0.1-10 per liter of the finished catalyst, with at least one of platinum and palladium.
g, and the supported amount of potassium, cesium, strontium and barium is 1 to 30 g per 1 liter of the finished catalyst in terms of potassium oxide, cesium oxide, strontium oxide, and barium oxide of at least one of them. In addition, the supported amount of cobalt and manganese is 1 to 50 g per liter of the finished catalyst, when at least one of these is converted into cobalt oxide and manganese oxide.
When the loading amount of each of the above catalyst components is less than the specified range, the effect is not obtained, whereas when the loading amount exceeds the specified range, the effect obtained is not improved.

Next, a method for producing the catalyst of the present invention will be described. First, activated alumina is impregnated with an aqueous solution containing at least one of potassium, cesium, strontium and barium and at least one of cobalt and manganese. Salts used for impregnation are nitrates, chlorides, carbonates,
Any water-soluble substance such as acetate or hydroxide may be used.
After this is dried, it is calcined in the air at, for example, 500 ° C. for 1 hour to obtain a powder (a) containing 1 to 40% by weight of these elements with respect to activated alumina. At the same time, at least one selected from the group consisting of zirconium, cerium, lanthanum and neodymium may be added to the activated alumina.

Next, this powder (a) is impregnated with an aqueous solution containing at least one salt of platinum and palladium, dried and then calcined in the air at 400 ° C. for 1 hour, for example, and the above platinum is added to activated alumina. A powder (b) containing 0.1 to 10% by weight of a group element is obtained. The above powder (b), alumina sol, and cerium oxide, if necessary, are mixed and pulverized to form a slurry, which is attached to a catalyst carrier, for example, a monolith carrier substrate,
For example, it is fired at a temperature of 400 to 650 ° C to obtain an exhaust gas purifying catalyst. It is also possible to prepare several kinds of slurries having different components and attach them in layers to the carrier substrate. Further, in order to further improve the performance, a catalyst layer containing rhodium may be additionally provided.

[0008]

EXAMPLES The present invention will be described with reference to the following examples, reference examples, comparative examples and test examples. In addition, "%" in the examples is "% by weight"
Indicates. Reference Example 1 Activated alumina was impregnated with an aqueous solution of cerium nitrate, an aqueous solution of potassium nitrate and an aqueous solution of cobalt nitrate, dried and calcined at 500 ° C. for 1 hour. The loading concentration of cerium was 7% by weight, the loading concentration of potassium was 5% by weight, and the loading concentration of cobalt was 10% by weight. The powder thus obtained was impregnated with an aqueous palladium nitrate solution, dried and then calcined at 400 ° C. for 1 hour to obtain a palladium-supported activated alumina powder. The supported concentration of palladium is 1.00% by weight. 700 g of this powder, 300 g of cerium oxide powder, and 1000 g of alumina sol were mixed in a ball mill and pulverized to obtain a slurry, which was used as a monolith carrier substrate (1.3
L, 400 cells) and baked (400 ° C. for 1 hour).
The adhesion amount at this time was set to 200 g / L. Thus, the catalyst (A) was obtained. The amount of palladium in the catalyst (A) was 1.8 g / piece.

Example 1 A catalyst (B) was obtained in the same manner as in Reference Example 1 except that potassium nitrate was changed to cesium nitrate and the supported concentration of cesium was changed to 5%.

Example 2 A catalyst (C) was obtained in the same manner as in Reference Example 1 , except that potassium nitrate was changed to strontium acetate and the supported concentration of strontium was changed to 5%.

Example 3 In Reference Example 1 , potassium nitrate was changed to barium acetate,
A catalyst (D) was obtained in the same manner except that the supported concentration of barium was changed to 5%.

Example 4 In Reference Example 1 , potassium nitrate was changed to potassium nitrate, cesium nitrate and barium acetate, and the supported concentration of potassium was set to 1
%, The supported concentration of cesium was 2%, the supported concentration of barium was 2%, cobalt nitrate was changed to cobalt nitrate and manganese nitrate, the supported concentration of cobalt was 8%, and the supported concentration of manganese was 2%. Similarly, a catalyst (E) was obtained.

Example 5 In Reference Example 1 , potassium nitrate was changed to cesium nitrate, strontium nitrate and barium acetate, and the supported concentration of cesium was 1%, the supported concentration of strontium was 2%, the supported concentration of barium was 2%, and cobalt nitrate was used. Was changed to cobalt nitrate and manganese nitrate, and the catalyst (F) was obtained in the same manner except that the cobalt concentration was 9% and the manganese concentration was 2%.

Example 6 In Reference Example 1 , potassium nitrate was changed to cesium nitrate and barium acetate, the cesium loading concentration was changed to 2%, the barium loading concentration was changed to 3%, and cobalt nitrate was changed to cobalt nitrate and manganese nitrate. Catalyst (G) was carried out in the same manner except that the supported concentration was 8% and the supported concentration of manganese was 2%.
Got

Reference Example 2 A catalyst (H) was obtained in the same manner as in Reference Example 1 , except that the platinum nitrate solution was used in place of the dinitrodiammine platinum solution and the supported concentration of platinum was set to 1%. The amount of platinum in the catalyst (H) was 1.8 g / piece.

Example 7 A catalyst (I) was obtained in the same manner as in Reference Example 2 except that potassium nitrate was changed to cesium nitrate and the supported concentration of cesium was changed to 5%.

Reference Example 3 A catalyst (J) was obtained in the same manner as in Reference Example 2 , except that potassium nitrate was changed to strontium acetate and the supported concentration of strontium was changed to 5%.

Reference Example 4 In Reference Example 2 , potassium nitrate was changed to barium acetate,
A catalyst (K) was obtained in the same manner except that the supported concentration of barium was 5%.

Example 8 A catalyst (L) was obtained in the same manner as in Example 4 , except that a dinitrodiammine platinum solution was used instead of the palladium nitrate solution and the platinum concentration was 1%.

Example 9 A catalyst (M) was obtained in the same manner as in Example 5 except that a dinitrodiammine platinum solution was used instead of the palladium nitrate solution and the supported concentration of platinum was set to 1%.

Example 10 A catalyst (N) was obtained in the same manner as in Example 6 except that a dinitrodiammine platinum solution was used instead of the palladium nitrate solution and the supported concentration of platinum was 1%.

Reference Example 5 A catalyst (O) was obtained in the same manner as in Reference Example 1 , except that cobalt nitrate was changed to manganese nitrate and the supported concentration of manganese was changed to 5%.

Example 11 A catalyst (P) was obtained in the same manner as in Reference Example 5 , except that potassium nitrate was changed to cesium nitrate and the supported concentration of cesium was changed to 5%.

Reference Example 6 A catalyst (Q) was obtained in the same manner as in Reference Example 5 , except that potassium nitrate was changed to strontium acetate and the supported concentration of strontium was changed to 5%.

Reference Example 7 In Reference Example 5 , potassium nitrate was changed to barium acetate,
A catalyst (R) was obtained in the same manner except that the supported concentration of barium was changed to 5%.

Reference Example 8 A catalyst (S) was obtained in the same manner as in Reference Example 5 except that a dinitrodiammine platinum solution was used in place of the palladium nitrate solution and the supported concentration of platinum was set to 1%. The amount of platinum in the catalyst (S) was 1.8 g / piece.

Example 12 A catalyst (T) was obtained in the same manner as in Reference Example 5 except that potassium nitrate was changed to cesium nitrate and the supported concentration of cesium was changed to 5%.

Reference Example 9 A catalyst (U) was obtained in the same manner as in Reference Example 5 , except that potassium nitrate was changed to strontium acetate and the supported concentration of strontium was changed to 5%.

Reference Example 10 In Reference Example 5 , potassium nitrate was changed to barium acetate,
A catalyst (V) was obtained in the same manner except that the supported concentration of barium was changed to 5%.

Comparative Example 1 A catalyst (W) was obtained in the same manner as in Reference Example 1 except that potassium nitrate was not used.

Comparative Example 2 A catalyst (X) was obtained in the same manner as in Reference Example 1 , except that potassium nitrate was not used, the palladium nitrate solution was changed to a dinitrodiammine platinum solution, and the platinum supported concentration was set to 1%.
The amount of platinum in the catalyst (X) was 1.8 g / piece.

Comparative Example 3 A catalyst (Y) was obtained in the same manner as in Reference Example 1 , except that cobalt nitrate was not used.

Test Examples The above Examples 1 to 12 , the Reference Examples 1 to 10 and the Comparative Examples 1 to 1
For the catalyst of No. 3, activity evaluation after durability was performed under the following conditions.

Test Example Regarding the catalysts of Examples 1 to 22 and Comparative Examples 1 to 3,
The activity evaluation after endurance was performed under the following conditions.

[0035]

[Table 1]

[0036]

[Table 1]

[0037]

As described above, the catalyst of the present invention contains at least one of potassium, cesium, strontium and barium in a catalyst composition having a catalytically active component-supporting layer containing at least one of platinum and palladium.
The catalyst contains at least one of cobalt and manganese, so that even in a gas atmosphere where conventional catalysts are adsorbed and poisoned and the purification performance deteriorates, the adsorbed poisoning effect is mitigated and the oxidation activity is improved. And maintain high performance. Therefore, it exhibits higher activity than the conventional catalyst for purification of engine exhaust gas whose composition fluctuates greatly, so that it is possible to improve catalyst performance or reduce catalyst cost.

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Claims (3)

(57) [Claims] 1. A monolithic structure type catalyst having a catalyst component carrying layer, and at least one kind of platinum and palladium as the catalyst component, and activated alumina and cerium oxide, Se
At least one of sium, cobalt and manganese
When, the exhaust gas purifying catalyst, which comprises a. 2. Further, potassium, strontium and
And at least one of barium and barium.
Exhaust gas purification catalyst. 3. At least one of platinum and palladium as a catalyst component is 0.1 to 10 per liter of the finished catalyst.
g, at least one of potassium, cesium, strontium, and barium is 1 to 30 g per liter of the finished catalyst in terms of potassium oxide, cesium oxide, strontium oxide, and barium oxide, respectively, and among cobalt and manganese. At least 1 type is converted into cobalt oxide and manganese oxide, and 1-50g is included per 1 liter of a completed catalyst, The 1 or 2 characterized by the above-mentioned.
2 wherein the exhaust gas purifying catalyst.