JP2003170047A - Catalyst for cleaning exhaust gas and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the heat resistance or durability of a ternary catalyst 8. <P>SOLUTION: An inside catalyst layer 12 and an outside catalyst layer 13 are formed on the surface of a carrier 11 in a layered state. The inside catalyst layer 12 contains a component wherein Pd is supported on alumina and an oxygen occluding substance such as ceria or the like while the outside catalyst layer 13 contains a component wherein Rh and Ba are supported on a Ce/Zr/Nd compound oxide and a component wherein Pt is supported on alumina. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas purifying catalyst and a method for producing the same.

[0002]

A three-way catalyst is known as a catalyst for purifying exhaust gas of a spark ignition type engine. This is generally because Pt and Rh as active metals, alumina as a support material that stabilizes the active metals and expands the contact area with gas to improve the purification performance, and oxygen storage material (O
It is often composed of ceria (co-catalyst) as SC).

On the other hand, in Patent Document 1, a component prepared by supporting Rh on an Nd-Zr composite oxide and a component prepared by supporting Pt on alumina or ceria are mixed and coated on a carrier. By impregnating the coating layer with a Ba solution, 20 g of BaO was added per 1 L of the carrier.
Loading is described. Moreover, it is described that the heat resistance of Rh improves by that.

[0004]

[Patent Document 1] Japanese Patent Laid-Open No. 09-141098 (paragraphs 0020, 0054, 0060)

[0005]

However, ceria generally has a problem of low heat resistance. For this reason, when the catalyst is exposed to a high temperature due to the high load operation of the engine, the oxygen storage capacity is lowered, and the catalyst performance, particularly the low temperature activity related to purification of HC (hydrocarbon), is largely reduced. Also,
Rh is active in purifying HC, CO, and NOx (nitrogen oxide) three components in a small amount, and particularly has excellent NOx purifying performance. When Rh is supported on ceria, its oxidative deterioration is prevented, That is, it is advantageous to maintain the activity. However, as described above, since ceria has low heat resistance, after the catalyst is exposed to high temperature, Rh becomes unstable, and sintering or the like occurs, so that it cannot be effectively used for purification of exhaust gas. There's a problem.

When the engine oil contains P (phosphorus), this P forms a glassy compound to cover the surface of the catalyst, hinders the diffusion of gas into the inside of the catalyst, and purifies it. There is a problem that it lowers. Further, there is a problem in that P forms a compound with alumina or ceria to deteriorate them, and further, it combines with Pt or the like which is an active component to deteriorate this.

The present invention is intended to solve the above problems of heat resistance of ceria, sintering of Rh, and P poisoning.

[0008]

In order to solve such a problem, the present invention provides a Ce-Zr-Nd composite oxide and Ba.
And are used.

First, the invention according to claim 1 relates to Rh and B.
In the exhaust gas purifying catalyst containing a, C
The above Ce · Zr · Nd containing the e · Zr · Nd composite oxide
The composite oxide is characterized in that the above Rh and Ba are supported.

That is, although Ce / Zr / Nd complex oxide (complex oxide or mixed oxide) acts as an oxygen storage substance like ceria, it has higher heat resistance than ceria and the catalyst is exposed to high temperatures. Even after being treated, the crystals do not coarsen so much.
Therefore, a high oxygen storage capacity is maintained. That is, the window of the air-fuel ratio capable of highly efficiently purifying HC, CO, and NOx in the three-way catalyst is not narrowed, and high purification performance is maintained. At the same time, the activity of Rh supported on this Ce / Zr / Nd complex oxide is also maintained, and HC, CO and N are retained.
It is advantageous for purification of Ox.

Further, in the catalyst according to the present invention, the above Ce.
Since Ba is supported on the Zr.Nd composite oxide together with Rh, the Ba suppresses sintering of Rh. Moreover, this Ba forms a compound with P in the exhaust gas and suppresses performance deterioration due to P poisoning of the catalyst. That is, Ba produces barium phosphate together with P, but since this compound does not hinder the diffusion of gas, it does not deteriorate the catalytic performance. Then, by combining Ba with P, the amount of P poisoning of the catalyst becomes relatively small, which is advantageous for maintaining the activity of the catalyst.

The invention according to claim 2 provides the exhaust gas purifying catalyst according to claim 1, wherein the Rh and Ba are
And Ce / Zr / Nd composite oxide are supported on a carrier, and the amount of supported Ba per 1 L of the carrier is 5 to 30 g.

That is, even if a small amount of Ba is effective in suppressing the sintering of Rh and suppressing P poisoning, if the amount is too small, the effect becomes so low. On the other hand, if the amount of carried Ba is too large, it covers the noble metal component of the catalyst such as Rh and reduces its activity. Also,
In the case of a ceramic carrier, Ba attacks the carrier to make it brittle, and the catalyst coating layer easily peels off from the carrier. Therefore, the amount of Ba supported is preferably about 5 to 30 g / L, and more preferably 10 to 22 g / L or 10 to 15 g / L.

According to a third aspect of the present invention, in the exhaust gas purifying catalyst according to the first or second aspect, Pt and alumina are further contained, and the above Rh and Pt are contained.
The former is the Ce.Zr.Nd composite oxide, the latter is separately supported on the alumina, and the Ce.Zr.Nd composite oxide carrying the Rh is mixed with the alumina carrying the Pt. It is characterized in that it is included in the state.

That is, as described above, Rh and Pt are Ce
By separately supporting Zr.Nd composite oxide and alumina, sintering of both is prevented, and Ce.
It is advantageous for improving the heat resistance of the catalyst by the Zr.Nd complex oxide and Ba and for suppressing P poisoning. Further, since the Ce-Zr-Nd composite oxide supporting Rh and the alumina supporting Pt are in a mixed state, it is advantageous in efficiently purifying HC, CO and NOx.

According to a fourth aspect of the present invention, a plurality of catalyst layers are formed in layers on a carrier, and the inner catalyst layer among the plurality of catalyst layers is a component in which Pd is supported on alumina. And an oxygen storage substance, and the catalyst layer located outside the inner catalyst layer contains a component in which Rh and Ba are supported on a Ce-Zr-Nd composite oxide. It is a gas purification catalyst.

That is, although Pd is advantageous for HC purification at low temperatures, it is known that Pd is easily deteriorated by heat and that it is easily poisoned by lead, sulfur and the like. On the other hand, in the present invention, this Pd is arranged in the inner catalyst layer together with the oxygen storage substance, and is covered with the outer catalyst layer. Therefore, the barrier effect of the outer catalyst layer avoids thermal deterioration and poisoning of Pd. ,
The low temperature activity of the catalyst can be improved. And then
Ce / Zr / Nd composite oxide is used as Rh and Ba for the outer catalyst layer, which has a more severe environment than the inner catalyst layer in terms of heat and poisoning.
As described above (Claim 1), even if the catalyst is exposed to high temperature, the decrease in oxygen storage capacity and sintering of Rh can be suppressed, and P poisoning can be suppressed. It is advantageous in maintaining the catalyst performance for a long period of time.

The invention according to claim 5 is Rh, Ba and C.
A method for producing an exhaust gas purifying catalyst containing an e.Zr.Nd composite oxide, comprising: Ce containing the Rh supported on the Ce.Zr.Nd composite oxide and calcined.
-The above-mentioned Ba is supported on the Zr-Nd composite oxide.

Accordingly, a catalyst comprising Rh and Ba supported on the Ce-Zr-Nd composite oxide can be obtained.
Even when the catalyst is exposed to high temperature, the oxygen storage capacity is reduced and the Rh sintering is reduced, and P poisoning is suppressed, which is advantageous in maintaining the catalyst performance for a long period of time.

[0020]

As described above, according to the invention of claim 1, since Rh and Ba are supported on the Ce-Zr-Nd composite oxide, the oxygen storage capacity is high even when the catalyst is exposed to high temperature. Of P and poisoning of Rh are reduced, and P poisoning is also suppressed, which is advantageous for improving the heat resistance or durability of the catalyst.

According to the invention of claim 2, in the exhaust gas purifying catalyst of claim 1, the carrier 1L is used.
Since the amount of supported Ba is 5 to 30 g per unit, it is possible to suppress the sintering of Rh and prevent P poisoning of the catalyst without hindering the activity of Rh and causing deterioration of the carrier. You can

According to the invention of claim 3, in the exhaust gas purifying catalyst of claim 1 or 2, Rh and Pt are further divided into Ce / Zr / Nd composite oxide and alumina. Ce, which carries this Rh
Since the Zr / Nd composite oxide and Pt-supported alumina were mixed, the heat resistance or durability of the catalyst was improved by the Ce / Zr / Nd composite oxide and Ba while preventing the sintering of Rh and Pt. The property can be improved, and it is also advantageous for purification of HC, CO and NOx.

According to the invention of claim 4, the inner catalyst layer contains a component in which Pd is supported on alumina and an oxygen storage material, and the outer catalyst layer is a Ce / Zr / Nd composite oxide. Since Rh and Ba contain a component loaded with Rh and Ba, it is possible to improve the low temperature activity of the catalyst while avoiding the thermal deterioration and poisoning of Pd, and also to improve the oxygen storage capacity even when the catalyst is exposed to high temperatures. Of Rh and sintering of Rh are suppressed, and P poisoning is also suppressed, which is advantageous in maintaining catalyst performance for a long period of time.

According to the invention of claim 5, Ce.Zr.
The Nd composite oxide was loaded with Rh and fired, and then the Rh-supported Ce / Zr / Nd composite oxide was added with B.
Since a is supported, even if the catalyst is exposed to a high temperature, there is little reduction in oxygen storage capacity and sintering of Rh, and a highly durable catalyst in which P poisoning is suppressed can be obtained.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a spark ignition engine of an automobile, 2 is its cylinder, 4 is its combustion chamber, 5 is a spark plug, 6 is an intake passage, and 7 is an exhaust passage. A three-way catalyst 8 is arranged in this exhaust passage 7.

<Structure of Three-Way Catalyst> As shown in FIG. 2, the three-way catalyst 8 is formed by layering an inner catalyst layer 12 and an outer catalyst layer 13 on the surface of a carrier 11.

The carrier 11 is a cordierite honeycomb carrier. The inner catalyst layer 12 contains a Pd / alumina component in which Pd is supported on alumina, cerium oxide (ceria), a Ce.Zr.Nd composite oxide, and a binder. The outer catalyst layer 13 contains a Pt / alumina component in which Pt is supported on alumina, a Rh / Ce.Zr.Nd component in which Rh is supported on a Ce.Zr.Nd complex oxide, and a binder. .

Further, Ba is supported on the inner catalyst layer 12 and the outer catalyst layer 13 by an impregnation method. Therefore, the Rh / Ce.Zr.Nd component of the outer catalyst layer 13 is a Ce.Zr.Nd composite oxide carrying Rh and Ba. That is, (Rh + Ba) / C
It is an e · Zr · Nd component.

The above cerium oxide and Ce / Zr / Nd composite oxide both function as oxygen storage substances. The above alumina contains a small amount of La (5
%) Is added. As the binder, zirconia is used to improve heat resistance.

<Production Method of Three-Way Catalyst 8> Next, the above three-way catalyst 8
The manufacturing method of is explained.

-Formation of Inner Catalyst Coat Layer- Pd / alumina catalyst powder is obtained by dropping an aqueous palladium nitrate solution onto activated alumina powder obtained by adding 5% by mass of La, and drying and firing at 500 ° C.

The above catalyst powder, cerium oxide, Ce.Zr.N.
The d composite oxide and a binder (zirconyl nitrate) are mixed, water and nitric acid are added thereto, and the mixture is stirred with a disperser to obtain a slurry. By dipping the cordierite honeycomb carrier 11 in this slurry, pulling it up, and removing excess slurry by air blowing, the carrier is coated with a predetermined amount of the slurry. Thereafter, the honeycomb carrier is heated from room temperature to 500 ° C. at a constant temperature rising rate over 1.5 hours and kept at that temperature for 2 hours (drying and firing), whereby the inner catalyst coating layer is formed. To form.

-Formation of Outer Catalyst Coat Layer- Pt / alumina catalyst powder is obtained by adding an aqueous solution of dinitrodiamine platinum nitrate dropwise to activated alumina powder obtained by adding 5% by mass of La and drying and firing at 500 ° C. To get Further, an Rh / Ce.Zr.Nd catalyst powder is obtained by dropping an aqueous rhodium nitrate solution onto the Ce.Zr.Nd composite oxide and drying and firing at 500 ° C.

The above Pt / alumina catalyst powder and Rh / Ce.
Zr.Nd catalyst powder and a binder (zirconyl nitrate) are mixed, water and nitric acid are added thereto, and the mixture is stirred with a disperser to obtain a slurry. The operation of dipping the cordierite honeycomb carrier 11 having the inner catalyst coating layer formed thereon in this slurry and pulling it up to remove excess slurry by air blow is repeated to coat a predetermined amount of the slurry on the carrier. After that, the honeycomb carrier is heated at a constant temperature rising rate from room temperature to 500 ° C. for 1.5 times.
The outer catalyst coat layer is formed by raising the temperature over time and maintaining the temperature for 2 hours (drying and firing).

-Impregnation and Support of Ba- The inner catalyst coat layer and the outer catalyst coat layer formed on the honeycomb carrier 11 are impregnated with an aqueous solution of barium acetate. After that, the honeycomb carrier is heated from room temperature to 200 ° C. at a substantially constant temperature rising rate for 1.5 hours, and is kept at that temperature for 2 hours (drying) until it reaches 200 ° C. to 500 ° C. The temperature is raised at a constant heating rate over 4 hours, and the temperature is maintained for 2 hours (calcination).

<Example> A three-way catalyst having the following constitution was obtained by the above production method.

-Inner catalyst layer- Amount of Pd / alumina component carried; 63.529 g / L (Amount of Pd supported: 4.091 g / L) Cerium oxide supported amount; 4.770 g / L Ce / Zr / Nd complex oxide loading: 4.770 g / L Zirconia binder loading amount; 7.120 g / L -Outer catalyst layer- Amount of Pt / alumina component supported; 25.583 g / L (Amount of Pt carried: 0.136 g / L) Rh / Ce / Zr / Nd component loading: 56.119 g / L (Amount of Rh carried: 0.273 g / L) Zirconia binder loading amount: 9.08 g / L -Ba- Ba supported amount: 11.00 g / L Note that the supported amount is the amount per 1 L of the honeycomb carrier.

<Comparative Example> A comparative catalyst was prepared under the same conditions and methods as those of the above-mentioned Examples except that cerium oxide was used instead of the Ce.Zr.Nd composite oxide.

<Evaluation Test> After the catalysts of the above-mentioned Examples and Comparative Examples were attached to the exhaust pipe of the engine and bench aging was performed, H in the FTP test mode (total) was used.
Emissions of C, CO and NOx were measured. In bench aging, a low load operation in which the exhaust gas temperature at the catalyst inlet is 660 ° C. and a high load operation in which the exhaust gas temperature is 880 ° C. are alternately repeated for 1 minute each for 20 hours, during which P is added. The engine oil is continuously pumped to the intake manifold.
The catalyst was provided with P corresponding to tens of thousands of km travel.

The results are shown in FIG. Ce in the figure
The Zr.Nd composite oxide is related to the example, and the cerium oxide is related to the comparative example. Note that the amount of HC emissions has expanded tenfold. According to the figure, the amount of HC, CO, and NOx of the example is smaller than that of the comparative example. It is recognized that this is due to the effect of the Ce-Zr-Nd composite oxide.

That is, in the case of the embodiment, Ce.Zr.Nd
Since the composite oxide has higher heat resistance than cerium oxide, it maintains a high oxygen storage capacity even after bench aging,
As a result, it is considered that the activity of Rh supported on this Ce / Zr / Nd composite oxide is not significantly reduced. Moreover, Ba suppresses the sintering of Rh and reduces the amount of P poisoning of the catalyst. Therefore, it is considered that the exhaust amount of HC, CO, and NOx after bench aging is smaller in the example than in the comparative example.

<Regarding Ba Carrying Amount> -Test 1-Regarding the above example, the Ba carrying amount was 0.72 g / L,
11.1 g / L, 14.5 g / L, and 19.3 g / L
Each catalyst was prepared, and the same bench aging as described above was applied to each catalyst, and then the emission amounts of HC and NOx in the FTP test mode (total) were measured. The result is shown in Figure 4.
Is shown in.

According to the figure, although the amount of carried Ba does not affect the HC emission amount so much (it is confirmed that it does not affect the CO emission amount too much), N
It has a great influence on Ox emissions. In particular,
NOx when the amount of carried Ba is about 10 to 15 g / L
The NOx emission amount is large both when the emission amount is the smallest and when the carried amount of Ba is smaller or larger than that.

The reason why the NOx emission amount decreases as the Ba loading amount increases in the range where the Ba loading amount is 15 g / L or less is considered to be due to the effect of improving the P poisoning resistance of the catalyst by Ba. On the other hand, when the supported amount of Ba exceeds 15 g / L and increases, Ba covers the noble metal and other catalyst components and reduces the activity thereof, or the honeycomb carrier 11 becomes brittle and the catalyst layer peels off. Therefore, it is considered that the NOx emission amount is increasing.

Test 2-Regarding the above embodiment, the amount of Ba carried is 0 g / L and 11 g.
/ L, 22 g / L, and 30 g / L of each catalyst were prepared,
After subjecting each to engine aging, T50, C4 regarding purification of HC, CO and NOx by rig test
00 and C500 were measured.

In engine aging, a catalyst is attached to the exhaust pipe of the engine, the engine is operated for 100 hours so that the temperature of the catalyst becomes 900 ° C., and engine oil containing P is supplied to the intake manifold during the operation period. It continues to supply with a pump.

In the rig test, the catalyst aged above was removed from the exhaust pipe and the diameter was 2.54 cm.
It was cut into a cylindrical shape having a length of 5 cm, and this was attached to a fixed-bed flow-type reaction evaluation apparatus to carry out. Simulated exhaust gas is A /
F = 14.7 ± 0.9. That is, A / F = 1
While constantly flowing the mainstream gas of 4.7, the A / F was forcibly oscillated with an amplitude of ± 0.9 by adding a predetermined amount of the fluctuating gas in a pulse shape at 1 Hz.
The composition of the mainstream gas with A / F = 14.7 is as follows. The flow rate of simulated exhaust gas into the catalyst is 25 L /
Minutes (Main stream gas) CO ₂ ; 13.9%, O ₂ ; 0.6%, CO; 0.6%,
H ₂ ; 0.2%, C ₃ H ₆ ; 0.056%, NO; 0.1
%, H ₂ O; 10%, remaining N ₂ As the fluctuation gas, A / F is on the lean side (A / F =
O ₂ is used to swing to 15.6), and H ₂ and CO are used to swing to the rich side (A / F = 13.9).
Was used.

At T50, the temperature of the simulated exhaust gas is gradually raised, and the component (H) of the gas detected downstream of the catalyst is increased.
It is the catalyst inlet gas temperature (light-off temperature) at the time when the concentration of C, CO, or NOx) becomes half the concentration of the component of the gas flowing into the catalyst (at the time when the purification rate reaches 50%).

C400 is the purification rate of each component when the simulated exhaust gas temperature at the catalyst inlet is 400 ° C., and C5
00 is the purification rate of each component when the simulated exhaust gas temperature at the catalyst inlet is 500 ° C.

The T50 results are shown in FIG. Under more severe endurance conditions, for any of HC, CO, and NOx, the B content up to the supported amount of Ba reaches 22 g / L.
The T50 decreases as the amount of a carried increases. That is, the low temperature activity is improved. This is P by Ba
This is considered to be due to the poisoning suppression effect and the Rh sintering suppression effect. When the amount of Ba carried becomes 30 g / L,
A little worse (higher) T50 is B
It is considered that “a” covered the catalytic metals (Pd, Pt, Rh) and slightly reduced their activities.

The results for C400 are shown in FIG.
The results are shown in FIG. Regarding C400 and C500, as in the case of T50, the purification rate increases as the amount of carried Ba increases for all of HC, CO and NOx.
When the carried amount becomes 30 g / L, it is slightly decreased. The reason is considered to be similar to the case of T50.

In the case of test 1, the amount of carried Ba was 19.3 g.
/ L is more N than 11.1 g / L
While the Ox purification performance is lowered, in the case of Test 2, the purification performance of HC, CO and NOx is better when the amount of carried Ba is 22 g / L than when it is 11 g / L. . The reason for this is presumed that the aging condition of Test 2 is more severe than that of Test 1.

That is, although the addition of Ba has problems that it covers the catalytic metal to reduce its activity and makes the honeycomb carrier brittle and easily peels off the catalyst layer, if the aging condition becomes strict, it causes P Since the problem of the poisoning and the sintering of Rh becomes large, the larger the amount of Ba carried, the more advantageous in terms of the exhaust gas purification performance.

From the results of tests 1 and 2 above, the amount of Ba carried should be 5 to 3 so as not to be too small or too large.
It can be said that it is preferably about 0 g / L. Moreover, according to the result of the test 1, the amount of carried Ba is 10
It can be said that it is preferable to set the amount to 15 g / L, but if the problems of P poisoning and sintering of Rh are strongly concerned, from the result of Test 2, the Ba loading amount should be 22.
It can be said that it is preferable to increase to about g / L.

[Brief description of drawings]

FIG. 1 is a diagram showing an exhaust gas purifying apparatus for an engine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a catalyst structure according to the same embodiment.

FIG. 3 is a graph showing the exhaust gas purification performance after bench aging of the example of the present invention and the comparative example.

FIG. 4 is a graph showing the relationship between the carried amount of Ba and the respective emission amounts of HC and NOx in the example of the present invention.

FIG. 5: Ba loading amount and HC, C in the example of the present invention
The graph figure which shows the relationship with T50 regarding purification of O and NOx.

FIG. 6 shows the amounts of carried Ba and HC and C in the example of the present invention.
The graph figure which shows the relationship between O and C400 of NOx.

FIG. 7: Ba loading amount and HC, C in the example of the present invention
The graph figure which shows the relationship between C500 of O and NOx.

[Explanation of symbols]

1 engine 7 exhaust passage 8 three-way catalyst 11 Carrier 12 Inner catalyst layer 13 Outer catalyst layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuyuki Fujita             360 Mukohara Town, Takada District, Hiroshima Prefecture             Inside the company (72) Inventor Shuji Iwakuni             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation (72) Inventor Masahiko Shigets             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation (72) Inventor Akihide Takami             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation F-term (reference) 4D048 AA06 AA13 AA18 AB05 BA03X                       BA08X BA15X BA18X BA19X                       BA30X BA31X BA33X BA41X                       BA42X BB02 BB16 EA04                 4G069 AA03 AA08 BA01A BA01B                       BA13B BB06A BB06B BC13A                       BC13B BC43A BC43B BC44A                       BC44B BC51A BC51B BC71A                       BC71B BC72A BC72B BC75A                       BC75B CA03 CA09 EA19                       EC28 EE06 FA02 FB14 FB19                       FC08

Claims (5)

[Claims] 1. An exhaust gas purifying catalyst containing Rh and Ba, further containing a Ce.Zr.Nd composite oxide, wherein the Ce.Zr.Nd composite oxide is loaded with the Rh and Ba. Exhaust gas purification catalyst characterized by 2. The exhaust gas purifying catalyst according to claim 1, wherein the Rh, Ba, and Ce.Zr.Nd composite oxide are supported on a carrier, and the amount of supported Ba per 1 L of the carrier is 5-
An exhaust gas purifying catalyst, which is 30 g. 3. The exhaust gas purifying catalyst according to claim 1 or 2, further comprising Pt and alumina, wherein the Rh and Pt are the former Ce—Zr—Nd composite oxide. In the exhaust gas, the latter is separately supported on the alumina, and the Ce-Zr-Nd composite oxide supporting the Rh and the alumina supporting the Pt are contained in a mixed state. Gas purification catalyst. 4. A plurality of catalyst layers are formed in layers on a carrier, and the inner catalyst layer of the plurality of catalyst layers comprises a component in which Pd is supported on alumina and an oxygen storage material. The catalyst layer that is contained and is located outside the inner catalyst layer is Ce.
An exhaust gas purifying catalyst comprising a Zr.Nd complex oxide containing Rh and Ba supported thereon. 5. A method for producing an exhaust gas purifying catalyst containing Rh, Ba, and a Ce / Zr / Nd composite oxide, wherein the Ce / Zr / Nd composite oxide is supported on the Rh, and then calcined. The above-mentioned Rh-supported Ce / Zr / Nd composite oxide is added to the above B
A method for producing an exhaust gas purifying catalyst, which comprises supporting a.