JPH09253453A - Cleaning of exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning an exhaust gas which enhances a NOx-cleaning performance under a lean atmosphere in which an adequate NOx activity is not displayed as long as a conventional method for cleaning an exhaust gas is employed. SOLUTION: A nitrogen oxide in an exhaust gas which contains an unburnt component coexistent with the nitrogen oxide and changeable in the quantity of oxygen to a case where the unburnt component is equal to a theoretical reaction amount and to a case where the quantity of oxygen is more than that is cleaned using a catalyst for cleaning the exhaust gas. This catalyst is composed of a catalyst 1 containing a composite oxide which contains at least one selected from a group of platinum, palladium and rhodium, and at least one selected from a group of iron, cobalt, nickel and manganese, and barium and lanthanum, carried on a fire-resistant inorganic carrier, and a catalyst 2 containing indium and/or gallium and cobalt, carried on an alumina oxide carrier. In addition, the catalyst 1 is arranged downstream from the exhaust gas while the catalyst 2 is arranged upstream from the exhaust gas. Further, the catalyst 1 is arranged in the lower layer, while the catalyst 2 is arranged in the upper layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification method, and more particularly, to a stoichiometric ratio atmosphere (hereinafter, "stoichi atmosphere").
The present invention relates to an exhaust gas purification method that is excellent in the purification performance of nitrogen oxides (hereinafter, referred to as NOx) under an excess oxygen atmosphere (hereinafter, referred to as “lean”) after passing through.

[0002]

2. Description of the Related Art In recent years, the realization of fuel-efficient automobiles has been increasing in view of the problem of exhaustion of petroleum resources and the problem of global warming, and the development of lean-burn automobiles has attracted attention especially for gasoline automobiles. In a lean-burn vehicle, the exhaust gas atmosphere during lean-burn running becomes an oxygen excess atmosphere (lean) compared to a stoichiometric state (theoretical air-fuel state). When a normal three-way catalyst is used in a lean atmosphere, there is a problem that the NOx purification action becomes insufficient due to the influence of excess oxygen. Therefore, even if oxygen becomes excessive, NOx
There has been a demand for the development of a catalyst for purifying the water.

Conventionally, NOx has been used in a lean atmosphere.
Various exhaust gas purification techniques for improving the purification performance have been proposed. For example, in Japanese Patent Laid-Open No. 168860/1993, lanthanum or the like is supported on platinum (Pt) and NO in a lean atmosphere.
An exhaust gas purifying catalyst that absorbs x and releases and purifies NOx in a stoichiometric state is disclosed.

However, the catalyst disclosed in JP-A-5-168860 has a problem that the NOx absorption capacity is insufficient, and for the purpose of solving such a problem, for example, JP-A-5-261287, JP-A-5-3176
No. 52 and Japanese Unexamined Patent Publication (Kokai) No. 6-31139 propose exhaust gas purification techniques using an alkali metal or an alkaline earth metal. Furthermore, in JP-A-6-142458 and JP-A-6-262040, alkali metal,
An exhaust gas purification technique using an alkaline earth metal, a rare earth metal, and an iron group metal is disclosed.

[0005]

However, the above-mentioned conventional exhaust gas purification technology is not suitable for NOx in a lean atmosphere.
The absorption performance is insufficient, and especially the NOx absorption performance after endurance is insufficient.

Therefore, an object of the present invention is to provide an exhaust gas purification method capable of improving the NOx purification performance in a lean atmosphere where the conventional exhaust gas purification method did not exhibit sufficient NOx activity.

[0007]

Means for Solving the Problems As a result of research for solving the above-mentioned problems, the present inventors have found that by using a catalyst containing a specific composite oxide and a catalyst containing a transition metal, The inventors have found that the NOx absorption performance in an atmosphere is improved and have reached the present invention.

That is, according to the present invention, the nitrogen oxide in the exhaust gas, which contains unburned components coexisting with nitrogen oxides and is switched between the case where the amount of oxygen with respect to the unburned components is equal to the logical reaction amount and the case where it is large, 1) At least one selected from the group consisting of platinum, palladium, and rhodium on a refractory inorganic carrier, and at least one selected from the group consisting of iron, cobalt, nickel, and manganese, and barium and lanthanum. Purification is performed by using an exhaust gas purification catalyst comprising a catalyst 1 containing a complex oxide and (2) a catalyst 2 containing indium and / or gallium and cobalt on an alumina-based oxide carrier. An exhaust gas purification method is disclosed.

The main constituent part of the exhaust gas purifying catalyst of the present invention comprises (1) at least one selected from the group consisting of platinum, palladium and rhodium, and is selected from the group consisting of iron, cobalt, nickel and manganese. Further, there are a catalyst 1 containing a composite oxide composed of at least one kind and barium and lanthanum, and (2) a catalyst 2 composed of indium and / or gallium and cobalt on a carrier of an alumina-based oxide.

By using the catalyst 1 having the above composition, high N
It is possible to obtain the Ox absorption capacity and the released NOx purification capacity. This is because the composite oxide is excellent in the action of absorbing NOx, and platinum, palladium and rhodium are excellent in the ability to purify NOx released from the composite oxide. Note that the NOx absorption efficiency can be increased by combining the composite oxides. Further, it is preferable that all of the components contained in the complex oxide are complexed, but the above effect can be obtained if at least a part of the complex oxide is complexed.

As the carrier component of the catalyst 2, for example, in addition to γ-alumina which is generally used as a carrier, silica-alumina type and porous carriers of alumina type oxides such as β-alumina are used. You can Further, a cocatalyst component effective for stabilizing the alumina-based oxide and a component such as lanthanum oxide can be contained in the alumina-based oxide carrier.

The active components of indium, gallium and cobalt in the catalyst 2 are used in the form of metal and / or oxide. The loading amount of indium and / or gallium is in the range of 0.05 to 30% by weight with respect to the porous carrier. Outside this range, N after the high temperature endurance test
It is not preferable because the Ox removing ability is significantly lowered.

The amount of cobalt supported is in the range of 0.01 to 50% by weight with respect to the porous carrier. If it is out of this range, the NOx removing ability at high temperature is not sufficient, which is not preferable.

When the catalysts 1 and 2 are arranged with respect to the exhaust gas flow, the catalyst 1 is arranged on the exhaust downstream side and the catalyst 2 is arranged on the exhaust upstream side. Alternatively, the above catalyst 1 is in the lower layer,
The catalyst 2 is arranged in the upper layer to purify the exhaust gas. The reason for this arrangement is that when the catalyst 2 reduces NOx to N ₂ in the lean atmosphere and the catalyst 1 absorbs the unreduced NOx, the NOx absorption amount of the catalyst 1 increases. This is because the specific components such as HC in the exhaust gas that interfere with NOx absorption by the catalyst 1 are
It is considered that the NOx absorbing ability of the catalyst 1 is improved because it reacts preferentially with the catalyst 2.

The catalyst carrier can be appropriately selected and used from known catalyst carriers, and examples thereof include a honeycomb carrier having a monolith structure made of a refractory material and a metal carrier. The shape of this catalyst carrier is not particularly limited, but it is usually preferable to use it in a honeycomb shape, and various honeycomb-shaped base materials are coated with catalyst powder for use. As this honeycomb material, generally, a cordierite material such as ceramics is generally used.
It is also possible to use a honeycomb made of a metal material such as ferritic stainless steel. Further, the catalyst powder itself may be formed into a honeycomb shape. The honeycomb shape of the catalyst is extremely advantageous when it is used for an automobile or the like in which the catalyst area of the catalyst and the exhaust gas is increased and the pressure loss is suppressed.

[0016]

The present invention will be described with reference to the following examples and comparative examples. In the examples and comparative examples, parts and% are parts by weight and% by weight, respectively, unless otherwise specified. Example 1 Activated alumina powder was impregnated with an aqueous rhodium nitrate solution, dried and then calcined at 400 ° C. for 1 hour to obtain Rh-supported activated alumina powder (powder A). The Rh concentration of this powder A was 2.0% by weight. The activated alumina powder was impregnated with an aqueous palladium nitrate solution, dried and then baked at 400 ° C. for 1 hour to obtain a Pd-supported activated alumina powder (powder B). P of this powder B
The d concentration was 2.0% by weight.

The Rh-supported activated alumina powder A was added to 106
g, 530 g of Pd-supporting activated alumina powder B, 264 g of activated alumina powder, and 900 g of water were charged into a magnetic ball, and mixed and pulverized to obtain a slurry liquid. This slurry liquid was attached to a cordierite-based monolith carrier (0.3 L, 400 cells), excess slurry in the cells was removed with an air stream, and the coating was dried at 130 ° C and then baked at 400 ° C for 1 hour to coat. A layer weight of 100 g / L-support material was obtained.

The coating layer weight 100 g / L-The material of the carrier was impregnated with a mixed aqueous solution of barium acetate, manganese acetate and lanthanum acetate, dried at 150 ° C., and then 400
Calcination was performed at 0 ° C. to obtain catalyst 1. The amount of each component contained in the catalyst 1 was 20 g / L of barium, 20 g / L of manganese, and 20 g of lanthanum in terms of oxide.

Next, γ-alumina powder was impregnated and supported with indium and cobalt using an aqueous solution in which indium chloride and cobalt nitrate were dissolved. After that, it was dried at 150 ° C. and then calcined at 850 ° C. to obtain a catalyst composition. This catalyst composition was mixed with nitric acid-acidic boehmite sol to form a slurry, which was coated on a cordierite honeycomb (0.3 L, 400 cells) carrier and dried at 150 ° C., then 60
The catalyst 2 was obtained by firing at 0 ° C. The coating amount of the catalyst 2 thus prepared was 150 g / L for alumina, 4.5 g / L for indium (3% by weight with respect to alumina), and 3 g / L for cobalt (2% by weight with respect to alumina). there were.

The catalyst 2 thus obtained was loaded on the upstream side of the exhaust gas, and the catalyst 1 was loaded on the downstream side of the exhaust gas to obtain a catalytic converter A. The obtained catalyst capacity was 0.6 L in total.

Example 2 In Example 1, the slurry in Catalyst 1 was first adjusted to 0.
6L honeycomb alone is coated, and then catalyst 2 is formed on the upper layer.
A catalytic converter B was obtained in the same manner as in Example 1 except that the slurry in Example 2 was coated.

Example 3 A catalytic converter C was obtained in the same manner as in Example 1 except that gallium nitrate was used instead of indium chloride. Therefore, the coating amount of the catalyst 2 was 150 g / L for alumina, 4.5 g / L for gallium (3% by weight with respect to alumina), and 3 g / L for cobalt (2% by weight with respect to alumina).

Example 4 In Example 3, the slurry in catalyst 1 was first adjusted to 0.
6L honeycomb alone is coated, and then catalyst 2 is formed on the upper layer.
A catalytic converter D was obtained in the same manner as in Example 1 except that the slurry in Example 2 was coated.

Example 5 A catalytic converter was prepared in the same manner as in Example 1 except that gallium nitrate was added when the catalyst 2 was prepared.
I got E. However, the coating amount of the catalyst 2 is 15 for alumina.
0 g / L, gallium 1.5 / L (1% by weight based on alumina), indium 4.5 g / L (3% by weight based on alumina), cobalt 3 g / L (2% by weight based on alumina) Met.

Example 6 In Example 5, the slurry in catalyst 1 was first adjusted to 0.
6L honeycomb alone is coated, and then catalyst 2 is formed on the upper layer.
A catalytic converter F was obtained in the same manner as in Example 1 except that the slurry in Example 1 was coated.

Example 7 A catalytic converter G was obtained in the same manner as in Example 1 except that iron acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g of barium in terms of oxide.
/ L, iron was 20 g / L, and lanthanum was 20 g / L.

Example 8 A catalytic converter H was obtained in the same manner as in Example 2 except that iron acetate was used in place of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g of barium in terms of oxide.
/ L, iron was 20 g / L, and lanthanum was 20 g / L.

Example 9 A catalytic converter I was obtained in the same manner as in Example 3 except that iron acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g of barium in terms of oxide.
/ L, iron was 20 g / L, and lanthanum was 20 g / L.

Example 10 A catalytic converter J was obtained in the same manner as in Example 4 except that iron acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g of barium in terms of oxide.
/ L, iron was 20 g / L, and lanthanum was 20 g / L.

Example 11 A catalytic converter K was obtained in the same manner as in Example 5 except that iron acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g of barium in terms of oxide.
/ L, iron was 20 g / L, and lanthanum was 20 g / L.

Example 12 A catalytic converter L was obtained in the same manner as in Example 6 except that iron acetate was used instead of manganese acetate used in the production of catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g of barium in terms of oxide.
/ L, iron was 20 g / L, and lanthanum was 20 g / L.

Example 13 A catalytic converter M was obtained in the same manner as in Example 1 except that cobalt acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of cobalt, and 20 g of lanthanum in terms of oxide.
/ L.

Example 14 A catalytic converter N was obtained in the same manner as in Example 2 except that cobalt acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of cobalt, and 20 g of lanthanum in terms of oxide.
/ L.

Example 15 A catalytic converter O was obtained in the same manner as in Example 3 except that cobalt acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of cobalt, and 20 g of lanthanum in terms of oxide.
/ L.

Example 16 A catalytic converter P was obtained in the same manner as in Example 4 except that cobalt acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of cobalt, and 20 g of lanthanum in terms of oxide.
/ L.

Example 17 A catalytic converter Q was obtained in the same manner as in Example 5 except that cobalt acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of cobalt, and 20 g of lanthanum in terms of oxide.
/ L.

Example 18 A catalytic converter R was obtained in the same manner as in Example 6 except that cobalt acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of cobalt, and 20 g of lanthanum in terms of oxide.
/ L.

Example 19 A catalytic converter S was obtained in the same manner as in Example 1 except that nickel acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of nickel, and 20 g of lanthanum in terms of oxide.
/ L.

Example 20 A catalytic converter T was obtained in the same manner as in Example 2 except that nickel acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of nickel, and 20 g of lanthanum in terms of oxide.
/ L.

Example 21 A catalytic converter U was obtained in the same manner as in Example 3 except that nickel acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of nickel, and 20 g of lanthanum in terms of oxide.
/ L.

Example 22 A catalytic converter V was obtained in the same manner as in Example 4 except that nickel acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of nickel, and 20 g of lanthanum in terms of oxide.
/ L.

Example 23 A catalytic converter W was obtained in the same manner as in Example 5, except that nickel acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of nickel, and 20 g of lanthanum in terms of oxide.
/ L.

Example 24 A catalytic converter X was obtained in the same manner as in Example 6 except that nickel acetate was used instead of manganese acetate used in the production of the catalyst 1. At this time, the amount of each component contained in the catalyst 1 is 20 g / L of barium, 20 g / L of nickel, and 20 g of lanthanum in terms of oxide.
/ L.

[0044] The catalyst 1 obtained in Comparative Example 1 Example 1 was loaded on the exhaust upstream side and the downstream side of exhaust gas, to obtain a catalytic converter i. The catalyst capacity at this time was 0.6 L in total.

[0045] The catalyst 2 obtained in Comparative Example 2 Example 1 was loaded on the exhaust upstream side and the downstream side of exhaust gas, to obtain a catalytic converter b. The catalyst capacity at this time was 0.6 L in total.

Comparative Example 3 The catalyst 2 obtained in Example 3 was loaded on the exhaust upstream side and the exhaust downstream side to obtain a catalytic converter ha . The catalyst capacity at this time was 0.6 L in total.

[0047] The catalyst 2 obtained in Comparative Example 4 Example 5 was loaded into the exhaust upstream side and the downstream side of exhaust gas, to obtain a catalytic converter two. The total catalyst capacity at this time was 0.6 L.

Comparative Example 5 In Example 7, the catalyst 1 was loaded on the exhaust upstream side and the exhaust downstream side to obtain a catalytic converter ho . The total catalyst capacity was 0.6 L.

[0049] In Comparative Example 6 Example 13, the catalyst 1 was charged into the exhaust upstream side and the downstream side of exhaust gas, to obtain a catalytic converter f. The total catalyst capacity was 0.6 L.

[0050] In Comparative Example 7 Example 19, the catalyst 1 was charged into the exhaust upstream side and the downstream side of exhaust gas, to obtain a catalytic converter and. The total catalyst capacity was 0.6 L.

[0051] In Comparative Example 8 Example 1, the catalyst 1 exhaust upstream side, loading the catalyst 2 to the exhaust downstream side, to obtain a catalytic converter switch. The total catalyst capacity was 0.6 L.

[0052] In Comparative Example 9 Example 2, except that the upper layer and the lower layer coat in the reverse order to obtain a catalyst converter Li in the same manner as in Example 2.

[0053] In Comparative Example 10 Example 3, the catalyst 1 exhaust upstream side, loading the catalyst 2 to the exhaust downstream side, to obtain a catalytic converter switch. The total catalyst capacity was 0.6 L.

[0054] In Comparative Example 11 Example 4, except that the upper layer and the lower layer coat in the reverse order to obtain a catalyst converter Le in the same manner as in Example 4.

[0055] In Comparative Example 12 Example 5, the catalyst 1 exhaust upstream side, loading the catalyst 2 to the exhaust downstream side, to obtain a catalytic converter Wo. The total catalyst capacity was 0.6 L.

[0056] In Comparative Example 13 Example 6, except that the upper layer and the lower layer coat in the reverse order to obtain a catalyst converter word in the same manner as in Example 6.

The catalyst compositions of the exhaust gas purifying catalytic converters obtained in Examples 1 to 24 and Comparative Examples 1 to 13 are shown in Table 1.
And 2.

[Test Example] Examples 1 to 24 and Comparative Example
For the catalysts 1 to 13, the catalytic activity was evaluated under the following conditions.
went. For activity evaluation, a model simulating the exhaust gas of an automobile is used.
Propylene and propane with nitrogen gas
Equipped with a chemiluminescent nitrogen oxide analyzer
An automatic evaluation device was used. The L value used here is the acid
Chemical gas (NO, O_Two) And reducing gas (CO, C _ThreeH₆,
C_ThreeH₈) And the stoichiometric ratio is defined by the following formula.

[0059]

[Equation 1]

Activity test conditions Catalyst 0.6 L Honeycomb coat catalyst Total gas flow rate 200 L / min Catalyst inlet gas temperature 450 ° C. Inlet gas composition Model gas composition (L = 10.6) or average air-fuel ratio corresponding to average air-fuel ratio 20.0 Model gas composition equivalent to 14.6 (L = 1.06) When L = 1.06 CO 0.7% HC 1667ppm C (C ₃ H ₆ + C ₃ H ₈ ) NO 500ppm O ₂ 0.62% CO ₂ 10.0% H ₂ O 10.0% N ₂ balance When L = 10.6 CO 0.2% HC 3000ppm C (C ₃ H ₆ + C ₃ H ₈ ) NO 200ppm O ₂ 6.00% CO ₂ 10 0.0% H ₂ O 10.0% N ₂ balance A / F amplitude None

The catalyst activity was evaluated by switching operation at L = 1.06 for 30 seconds and then L = 10.6 for 30 seconds.
The cycle was repeated and the average conversion was measured.
The average conversion rate in the case of 1.06 and the average conversion rate in the case of L = 10.6 were averaged to obtain the total conversion rate, and the catalyst activity evaluation value was determined by the following formula.

[Equation 2]

Tables 1 and 2 show the results of the catalytic activity evaluation obtained as the total conversion.

[0063]

[Table 1]

[0064]

[Table 2]

From the above results, for example, in the exhaust gas purifying catalytic converters A and B of Examples 1 and 2, In and C were added to the catalyst 2.
2% Rh-2% Pd-BaO-
This is a case where Mn-Zr / alumina (NOx absorption catalyst) is arranged in the lower layer and the downstream side, and both are Comparative Examples 1 and 2.
HC and C rather than catalytic converters I and B for exhaust gas purification
O, NOx conversion rate is high.

In the exhaust gas purifying catalytic converters C and D of Examples 3 and 4, the catalyst 2 contained Ga and Co, respectively, and each contained 2% Rh-2% Pd-BaO-Mn-Zr.
/ When alumina is placed in the lower layer and the downstream side,
Both are catalytic converters for exhaust gas purification of Comparative Examples 1 and 3.
Than) and (c HC, CO, high NOx conversion.

Further, the exhaust gas-purifying catalytic converters E and F of Examples 5 and 6 were those containing In, Ga, and Co, and each contained 2% Rh-2% Pd-BaO-Mn-Zr.
/ When alumina is placed in the lower layer and the downstream side,
Both are catalytic converters for exhaust gas purification of Comparative Examples 1 and 4.
Lee and HC than two, CO, high NOx conversion.

[0068]

As described above, according to the present invention, NOx can be effectively absorbed in the lean atmosphere, and the NOx purification performance in the lean atmosphere, which is not sufficiently activated by the conventional catalyst, can be obtained. By improving and using a specific catalyst, the NOx oxidation reaction required for NOx absorption is enhanced, and a significant effect that an excellent NOx absorption action can be obtained is obtained.

Further, according to the present invention, since the arrangement of the exhaust gas purifying catalyst is specified, in addition to the above effects, the reaction of the NOx absorption inhibiting component by the catalyst 1 is prioritized, and the N 2 in the catalyst 2 is prioritized.
Ox absorption performance can be improved.

Claims (6)

[Claims] 1. A nitrogen oxide in exhaust gas, which contains unburned components coexisting with nitrogen oxides and is switched between when the amount of oxygen relative to the unburned components is the same as the theoretical reaction amount and when it is large,
(1) contains at least one selected from the group consisting of platinum, palladium and rhodium on a refractory inorganic carrier, and
A catalyst 1 containing at least one selected from the group consisting of iron, cobalt, nickel and manganese, and a complex oxide consisting of barium and lanthanum, and (2) indium and / or gallium on an alumina-based oxide carrier. And an exhaust gas purification catalyst comprising a catalyst 2 containing cobalt. 2. The exhaust gas purification method according to claim 1, wherein the catalyst 1 is arranged on the exhaust gas downstream side and the catalyst 2 is arranged on the exhaust gas upstream side. 3. The exhaust gas purification method according to claim 1, wherein the catalyst 1 is arranged in a lower layer and the catalyst 2 is arranged in an upper layer. 4. The exhaust gas purification method according to any one of claims 1 to 3, wherein the amount of indium and / or gallium supported on the catalyst 2 is 0.
The exhaust gas purification method is characterized in that it is in the range of 05 to 30% by weight, and the supported amount of cobalt is in the range of 0.01 to 50% by weight. 5. The exhaust gas purification method according to claim 1, wherein the catalysts 1 and 2 are provided as a coat layer on a catalyst carrier. 6. The exhaust gas purification method according to claim 5, wherein the catalyst carrier is a honeycomb monolith carrier substrate.