JP2635689B2 - Method for producing exhaust gas purifying catalyst - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas purifying catalyst. More specifically, the present invention simultaneously and efficiently reduces the harmful components of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) contained in exhaust gas from internal combustion engines such as automobiles at low temperatures. The present invention relates to an exhaust gas purifying catalyst to be removed.

[Conventional technology and problems]

Conventionally, a large number of catalysts for purifying exhaust gas discharged from internal combustion engines of automobiles and the like have been proposed. Currently, for automobiles, hydrocarbons (hereinafter referred to as HC), carbon monoxide (hereinafter referred to as CO) are used.
) And nitrogen oxides (hereinafter referred to as NOx) at the same time. Under the situation where the exhaust gas temperature is lowered due to the recent improvement in fuel efficiency of automobiles and the like, there is a strong demand for a three-way catalyst excellent in the purification performance of HC, CO and NOx at low temperatures.

Conventional three-way catalysts include platinum (P
t), palladium (Pd), rhodium (Rh), and other noble metals are mainly used, and a rare earth metal, especially cerium (Ce), is used in combination to promote the catalytic action of these noble metals. there were. However, in such a conventional three-way catalyst, HC at low temperature after endurance running,
It was not always satisfactory in terms of CO and NOx purification performance.

Further, as an exhaust gas purifying catalyst using a noble metal and tin oxide, JP-A-56-141838 discloses an oxidation catalyst using a noble metal and tin oxide, tungsten oxide, titanium oxide or nickel molybdate. However, there is a proposal for a catalyst that is durable against poisoning of lead or the like, and it has not been found at all that tin oxide has an improved purification performance at low temperatures as in the present invention.

JP-A-60-175546 discloses a heat-resistant oxidation catalyst in which Pt is supported on tin oxide calcined at a temperature of 600 ° C. or higher. It is a proposal of a catalyst, and does not mention the NOx purification performance at all, and is different from the three-way catalyst disclosed in the present invention which is excellent in NOx purification performance.

Further, JP-A-62-234547 discloses that HC supported on a honeycomb carrier having an integral structure with a catalytically active substance composed of a noble metal, tin oxide, an inorganic refractory oxide and cerium oxide,
There has been proposed a method for preparing an exhaust gas purifying catalyst that simultaneously purifies and reduces CO and NOx at a low temperature. This method is a catalyst preparation method characterized in that tin oxide is used as a starting material, a refractory inorganic substance carrying a noble metal and cerium oxide are mixed and supported on a honeycomb carrier. HC, CO and NOx at low temperature after driving
However, the three-way catalyst which is required to have high purification performance was not always satisfactory.

Therefore, an object of the present invention is to improve the disadvantages of the conventional three-way catalyst containing tin oxide.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and have found that at least one metal selected from the group consisting of Pt and Pd, and a three-way catalyst containing Rh, cerium oxide, and tin oxide as active components. In manufacturing, after supporting the above-mentioned noble metal and cerium oxide on a honeycomb carrier,
Immerse in an aqueous solution of a water-soluble tin compound, dry and / or
Alternatively, it has been found that the catalyst obtained by calcining has excellent ternary characteristics at low temperatures.

That is, in the present invention, tin oxide is present in a more highly dispersed state in the catalyst supporting layer than when tin oxide is used as a starting material because a water-soluble tin compound is used. For this reason, the interaction between the noble metal and tin oxide is promoted, and even when the amount of tin used is small, the low-temperature purification performance is further improved as compared with the conventional three-way catalyst.

Further, the present inventors, together with the water-soluble tin compound,
Water-soluble chromium (Cr), manganese (Mn), iron (Fe),
By using a solution in which a transition metal compound selected from the group consisting of cobalt (Co) and nickel (Ni) is used,
The present inventors have found a three-way catalyst excellent in HC, CO and NOx purification performance at a better low temperature, and have completed the present invention.

 Thus, the present invention is specified as follows.

(1) A water-soluble tin compound in which at least one noble metal from the group consisting of platinum and palladium and a catalytically active substance containing rhodium, cerium oxide and a refractory inorganic oxide are supported on a honeycomb carrier having an integral structure, A method for producing an exhaust gas purifying catalyst, characterized in that tin oxide is supported on the coating by immersion in an aqueous solution of sintering.

(2) the sum of the at least one metal and rhodium catalyst per platinum and palladium is 0.1 to 10 g, cerium oxide 1~150g as CeO _2, 0.01 to as tin oxide SnO ₂
The method according to (1), wherein 50 g of the refractory inorganic oxide is supported in a range of 20 to 200 g.

(3) The method according to (1) or (2), wherein the refractory inorganic oxide is activated alumina.

(4) After carrying a catalytically active substance comprising at least one noble metal of platinum and palladium, and rhodium, cerium oxide and a refractory inorganic oxide on a honeycomb carrier having an integral structure, water-soluble groups 6B, 7B and iron Immersed in an aqueous solution of a compound of at least one transition metal (hereinafter sometimes abbreviated as “the transition metal” for simplicity) and a water-soluble tin compound, followed by firing, tin oxide and A method for producing an exhaust gas purifying catalyst, wherein an oxide of at least one transition metal selected from the group consisting of Group 6B, Group 7B and Iron group is supported on the coating.

(5) The total of at least one metal of platinum and palladium and rhodium per catalyst is 0.1 to 10 g, and cerium oxide is ₁ to 150 g as CeO ₂ and at least one selected from the group consisting of the 6B, 7B and iron groups. 0.1-10% by weight of tin oxide as a transition metal oxide, SnO ₂
As 0.01-50g, and refractory inorganic oxide as 20-200g
(4) The method according to (4), wherein

(6) The method according to (4) or (5), wherein the refractory inorganic oxide is activated alumina.

(7) The transition metal used together with the tin compound is chromium,
(4) characterized in that it is at least one selected from the group consisting of manganese, iron, cobalt and nickel.
Or the method according to (5).

As the refractory inorganic oxide powder used in the present invention,
Alumina, silica, titania, zirconia, alumina
Silica, alumina-titania, alumina-zirconia,
Examples thereof include silica-titania, silica-zirconia, titania-zirconia, and alumina-magnesia powder. Among them, use of alumina powder, particularly activated alumina powder, is preferred. As activated alumina, the specific surface area is 50
Activated alumina of 180180 m ² / g is preferred, and as its crystalline form, those in the form of gamma, delta, theta, chi, kappa, and eta can be used. Further, at least one of rare earth elements such as lanthanum, cerium, neodymium and the like or alkaline earth elements such as calcium and barium is 0.1 to 30%.
Activated alumina supported by weight% can also be used.

As the Pt source and the Pd source used in the present invention, chloroplatinic acid, dinitrodiammineplatinum, platinum sulfite complex salt, platinum tetramine chloride, palladium nitrate, palladium chloride, palladium sulfite complex salt, palladium tetramine chloride and the like are preferable. Further, as the Rh source, rhodium nitrate, rhodium chloride, rhodium sulfate, rhodium sulphite complex salt, rhodium ammine complex salt and the like are preferable. The loading amount of these noble metals is P
The total of t, Pd, and Rh is preferably in the range of 0.1 to 10 g.

The starting material for the Ce source used in the present invention is not particularly limited as long as it can exist as CeO _{2 in} the catalyst. For example, commercially available CeO ₂ , cerium carbonate, cerium hydroxide, cerium oxalate and the like can be used. In the case of a cerium salt solution, for example, a cerium nitrate solution may be used by impregnating and supporting the above-mentioned refractory inorganic oxide. The supported amount of cerium oxide is 1 to 15 as CeO ₂ per catalyst.
It is used in the range of 0 g, preferably 10 to 100 g.

The tin compound used in the present invention is not particularly limited as long as it is water-soluble, and tin salts such as commercially available SnCl ₂ , SnCl ₄ , Sn
OCl ₃ , SnSO ₄ , Sn (SO ₄ ) ₂ or the like may be used. The supported amount of the tin compound is used as SnO _{2 in} the range of 0.01 to 50 g per catalyst. The tin compound is present in the catalyst in the form of SnO ₂ after calcination, and promotes the transfer of electrons to the precious metal, which is the main active species, in a reaction atmosphere, and improves the catalytic performance at low temperatures.

Furthermore, using an aqueous solution containing a water-soluble tin compound and at least one transition metal compound selected from the group consisting of a water-soluble group 6B, 7B and iron group, controls the rate of electron transfer of tin oxide after firing. By doing so, the catalyst according to the invention shows better performance. As the transition metal,
Chromium, manganese, iron, cobalt and nickel are preferred, and the transition metal uses a water-soluble salt of each, and the amount of the transition metal supported is 0.
When the content is in the range of 1 to 10% by weight, the above effect is remarkable.

The honeycomb support having an integral structure used in the present invention may be any one usually referred to as a ceramic honeycomb support, and in particular, cordierite, mullite, α-alumina, zirconia, titania, titanium phosphate, aluminum titanate, petalite , Spodumene, Alumino
Honeycomb carriers made of silicate, magnesium silicate, or the like are preferable, and cordierite materials are particularly preferable for internal combustion engines. In addition, a material other than ceramics, for example, an integrated structure using a heat-resistant metal having oxidation resistance such as stainless steel or an Fe-Cr-Al alloy is used. The shape of the gas flow port (cell shape) may be any of a hexagon, a quadrangle, a triangle, or a corrugation type, and the cell density (cell number / unit cross-sectional area) is 150 to 600 cells / Square inches are sufficient and give good results.

The catalyst according to the present invention is a refractory inorganic oxide as described above.
At least one metal selected from the group consisting of Pt and Pd,
Using Rh, Ce and Sn, and if necessary, the transition metal, it is produced, for example, by the following method.

Mixing an aqueous solution of a water-soluble salt of at least one metal selected from the group consisting of Pt and Pd and an aqueous solution of a water-soluble salt of Ph,
After impregnating the activated alumina, it is dried and / or calcined and supported. A slurry is prepared by mixing a predetermined amount of the obtained noble metal-supported alumina and CeO ₂ , adding dilute aqueous nitric acid, and wet-milling with a ball mill. A honeycomb carrier having an integral structure is immersed in the slurry, an excess slurry is blown, and the slurry is dried and / or calcined. After that, a water-soluble tin compound and, if necessary, an aqueous solution of a water-soluble transition metal compound are prepared. Then, a carrier supporting the slurry is immersed, dried and / or calcined to support tin oxide on the coating to obtain a finished catalyst.

However, it goes without saying that the production method of the catalyst according to the present invention is not limited to the above production method.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to only these Examples.

Example 1 A catalyst was prepared using a commercially available cordierite-based monolith carrier (manufactured by Nippon Glass Co., Ltd.). The monolithic carrier used had a cylindrical shape with an outer diameter of 33 mmφ and a length of 76 mmL with a gas flow cell having a cross section of about 400 per square inch.
It had a volume of l.

Dinitro / diammine platinum nitric acid aqueous solution (Pt content: 100
g /) 12.5ml and rhodium nitrate aqueous solution (Rh content: 50g /) 5
An aqueous solution obtained by diluting 150 ml of pure water with 135 g of activated alumina powder having a surface area of 120 m ² / g was sufficiently mixed for 30 minutes.
After drying for an hour, it was calcined in air at 400 ° C. for 2 hours to prepare Pt and Rh-containing alumina powder. The Pt and Rh-containing alumina powder and 75 g of cerium oxide powder were wet-ground with a dilute nitric acid solution in a ball mill for 20 hours to prepare a coating slurry. The monolithic carrier was immersed in the coating slurry for one minute, then taken out of the slurry, and the excess slurry in the cells was blown off with compressed air to remove clogging of all cells. Next, after drying at 150 ° C. for 3 hours, it was calcined in air at 400 ° C. for 2 hours to obtain an integrated product coated with the catalyst substance. Next, the integrated material is immersed in an aqueous solution (SnCl ₄ : 175 g /) of stannic chloride (SnCl ₄ ; Wako Pure Chemical Industries, Ltd.) for 1 minute, and then taken out from the aqueous solution and the excess aqueous solution in the cell is blown off with compressed air. Thus, clogging of all cells was removed. After drying at 150 ° C for 3 hours,
It was calcined at 00 ° C for 2 hours to obtain a completed catalyst.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, Pt 0.83 g and Rh 0.17 g were carried.

Example 2 An aqueous solution obtained by diluting 12.5 ml of an aqueous solution of palladium nitrate (Pd content; 100 g /) and 50 ml of an aqueous solution of rhodium nitrate (Rh content: 50 g /) with 150 ml of pure water, and 135 g of activated alumina powder used in Example 1 were mixed with 30 g of After mixing thoroughly for 150 minutes and drying at 150 ° C. for 3 hours, the mixture was calcined in air at 400 ° C. for 2 hours to prepare Pd and Rh-containing alumina powder. Using this Pd and Rh-containing alumina powder, a completed catalyst was obtained in the same manner as in Example 1 below.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, 0.83 g of Pd and 0.17 g of Rh.

Example 3 Dinitrodiammineplatinum nitric acid aqueous solution (Pt content: 100 g /
) 8.9ml, aqueous solution of palladium nitrate (Pd content: 100g /)
An aqueous solution prepared by diluting 3.6 ml and 5 ml of an aqueous rhodium nitrate solution (Rh content: 50 g /) with 150 ml of pure water and 135 g of the same activated alumina powder as used in Example 1 were thoroughly mixed for 30 minutes.
After drying for 400 hours, calcination in air at 400 ° C for 2 hours, Pt, Pd
And Rh-containing alumina powder were prepared. Using this Pt, Pd and Rh-containing alumina, a completed catalyst was obtained in the same manner as in Example 1 below.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, Pt 0.59 g, Pd 0.24 g, and Rh 0.17 g.

Example 4 In Example 1, an aqueous solution of stannic chloride (SnCl ₄ ; 8
A finished catalyst was obtained in the same manner as in Example 1 except that 7.5 g /) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), and 5 g of tin oxide (as SnO ₂ ) per volume.
g, Pt 0.83 g and Rh 0.17 g were carried.

Example 5 In Example 1, an aqueous solution of stannic chloride (SnCl ₄ : 1.
A finished catalyst was obtained in the same manner as in Example 1 except that 76 g /) was used.

The catalyst contained 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), and 0.1 g of tin oxide (as SnO ₂ ) per volume.
g, Pt 0.83 g and Rh 0.17 g were carried.

Example 6 In Example 1, an aqueous solution (SnSO ₄ : 7) of stannous sulfate (SnSO ₄ : Wako Pure Chemical Industries, Ltd.) was used instead of stannic chloride.
A finished catalyst was obtained in the same manner as in Example 1 except that 2.3 g /) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), and 5 g of tin oxide (as SnO ₂ ) per volume.
g, Pt 0.83 g and Rh 0.17 g were carried.

Example 7 Example 1, stannic nitrate chromium chloride instead of stannic chloride _{(Cr (No 3) 3 ·} 9H 2 O; manufactured by Wako Pure Chemical Industries, Ltd.) mixed aqueous solution of (SnCl _4: 175g / , Cr (NO ₃ ) ₃ : 1
A finished catalyst was obtained in the same manner as in Example 1 except that 5.9 g /) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, chromium oxide (as Cr ₂ O ₃ ) 0.5 g, Pt 0.83 g, Rh 0.1
7 g had been carried.

Example 8 In Example 1, a mixed aqueous solution (SnCl ₄ : 175g /) of stannic chloride and manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O: Wako Pure Chemical Industries, Ltd.) was used instead of stannic chloride. , Mn (NO ₃ ) ₂ : 1
A finished catalyst was obtained in the same manner as in Example 1 except that 0.4 g /) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, manganese oxide (as MnO ₂ ) 0.5 g, Pt 0.83 g, Rh 0.17
g was carried.

Example 9 Example 1, stannic nitrate iron chloride in place of stannic chloride _{(Fe (NO 3) 3 ·} 9H 2 O; manufactured by Wako Pure Chemical Industries, Ltd.) mixed aqueous solution of (SnCl _4: 175g / , Fe (NO ₃ ) ₃ : 15.4g /
) Was obtained in the same manner as in Example 1 except that (1) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, iron oxide (as Fe ₂ O ₃ ) 0.5 g, Pt 0.83 g, and Rh 0.17 g.

Example 10 In Example 1, a mixed aqueous solution (SnCl ₄ : 175 g / W) of stannic chloride and cobalt nitrate (Co (NO ₃ ) ₂ .6H ₂ O; Wako Pure Chemical Industries, Ltd.) was used instead of stannic chloride. , Co (NO ₃ ) ₂ : 1
A finished catalyst was obtained in the same manner as in Example 1 except that 2.4 g /) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, cobalt oxide (as CoO) 0.5g, Pt0.83g, Rh0.17g
Was carried.

Example 11 In Example 1, a mixed aqueous solution of stannic chloride and nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O; Wako Pure Chemical Industries, Ltd.) (SnCl ₄ ; 175 g / , (Ni (NO ₃ ) ₂ :
A finished catalyst was obtained in the same manner as in Example 1 except that 12.4 g /) was used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, nickel oxide (as NiO) 0.5g, Pt0.83g, Rh0.17g
Was carried.

Comparative Example 1 A completed catalyst was obtained in the same manner as in Example 1 except that stannic chloride was not used.

The catalyst supported 90 g of alumina, 50 g of cerium oxide (CeO ₂ ), 0.83 g of Pt, and 0.17 g of Rh per volume of the catalyst.

Comparative Example 2 A completed catalyst was obtained in the same manner as in Example 2 except that stannic chloride was not used.

The catalyst supported 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 0.83 g of Pd, and 0.17 g of Rh per volume of the catalyst.

Comparative Example 3 A completed catalyst was obtained in the same manner as in Example 3 except that stannic chloride was not used.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 0.59 g of Pt, 0.24 g of Pd, and 0.17 g of Rh per volume.
Was carried.

Comparative Example 4 Dinitro / diammine platinum aqueous nitric acid solution (Pt content: 100
g /) 12.5ml and rhodium nitrate aqueous solution (Rh content: 50g /) 5
An aqueous solution obtained by diluting 150 ml of pure water with 135 g of the same activated alumina powder as used in Example 1 was sufficiently mixed for 30 minutes.
After drying at 400 ° C for 3 hours, baking in air at 400 ° C for 2 hours
Alumina powders containing t and Rh were prepared.

The Pt and Rh-containing alumina powder and commercially available tin oxide (Sn
15 g of O ₂ (manufactured by Kanto Chemical Co., Ltd.) and 75 g of cerium oxide were wet-ground with a dilute nitric acid solution in a ball mill for 20 hours to prepare a coating slurry. The monolith carrier was immersed in the coating slurry for one minute, then taken out of the slurry and the excess slurry in the cells was blown off with compressed air to remove clogging of all cells. Next, after drying at 150 ° C. for 3 hours, it was calcined in air at 400 ° C. for 2 hours to obtain a completed catalyst.

This catalyst contains 90 g of alumina, 50 g of cerium oxide (as CeO ₂ ), 10 g of tin oxide (as SnO ₂ ) per volume of the catalyst.
g, Pt 0.83 g and Rh 0.17 g were carried.

Comparative Example 5 A catalyst was obtained in the same manner as in Comparative Example 4, except that 0.15 g of the commercially available tin oxide (SnO ₂ ; manufactured by Kanto Chemical Co., Ltd.) used in Comparative Example 4 was used.

The catalyst container product per alumina 90 g, cerium oxide (as CeO ₂₎ 50 g, as a tin oxide (SnO ₂₎ 0.1
g, Pt 0.83 g and Rh 0.17 g were carried.

〔The invention's effect〕

The catalyst performances of the catalysts of Example 1 to Example 11 and the catalysts of Comparative Examples 1 to 5 at low temperatures after the engine endurance running were examined.

Endurance running is performed using a commercially available electronically controlled engine (8 cylinders).
Each catalyst was charged into a multi-converter and connected to the exhaust system of the engine. The operating conditions of the engine are a mode operation that combines a steady operation (2800 rpm, -220 mmHg) for 60 seconds and a deceleration (fuel cut) operation for 6 seconds. During steady operation, the converter inlet temperature is 750 ° C and the durability time is 100 hours. Endurance running.

The catalyst performance at low temperature was evaluated under the following conditions by connecting the multi-converter filled with the catalyst after the above-mentioned endurance running to the exhaust system of a commercially available electronically controlled engine (4-cylinder 1800 cc).

The engine was operated at a constant air-fuel ratio of 14.6 (2200 rpm,
The engine was operated at -350 mmHg). At this time, a sine wave type signal of 1 Hz was introduced from an external oscillator into the engine control unit, and the air-fuel ratio was oscillated at ± 0.5 A / F, 1 Hz. Under these constant operating conditions, the temperature of the exhaust gas at the catalyst inlet was continuously changed from 200 ° C to 450 ° C by a heat exchanger attached in front of the catalytic converter in the exhaust system. Analyze the composition for each catalyst
The purification rates of HC, CO and NOx were determined. The obtained purification rates of HC, CO and NOx versus the catalyst inlet temperature are plotted on a graph, and the catalyst inlet temperatures at which the purification rates show 50% and 80% (each,
T ₅₀ and T ₈₀ ) were obtained and used as criteria for evaluating the purification performance of the catalyst at low temperatures.

Next, Table 1 shows the results obtained by the above evaluation methods.

As is evident from Table 1, the catalysts of Examples 1 to 6 according to the present invention have higher HC,
Approx. 45 ° C at 50% and 80% of CO and NOx, purification rate temperature
It turns out that it shows activity from low temperature. It can also be seen that the catalysts according to the invention have a remarkably high tin usage in at least high performance. In addition, the catalysts of Examples 7 to 11 containing tin oxide and the transition metal exhibited low temperatures of HC, CO and
NOx purification performance was even better. From these results, it is clear that the catalyst according to the present invention dramatically improves the catalytic performance at low temperatures after endurance running.

Claims (7)

(57) [Claims] 1. A honeycomb carrier having an integral structure coated and supported on at least one metal selected from the group consisting of platinum and palladium, and a catalytically active substance containing rhodium, cerium oxide and a refractory inorganic oxide, A method for producing an exhaust gas purifying catalyst, comprising immersing in a water-soluble aqueous solution of a tin compound, drying and / or calcining to carry tin oxide on the coating. 2. A total of 0.1 to 10 g of rhodium and at least one metal selected from the group consisting of platinum and palladium per catalyst, and 1 to 150 g of cerium oxide as CeO ₂ ;
The method of claim 1, wherein tin oxide is 0.01~50g and refractory inorganic oxide as SnO _2, characterized in that the formed by carrying a range of 20 to 200 g. 3. The method according to claim 1, wherein the refractory inorganic oxide is activated alumina. 4. A honeycomb carrier having an integral structure, wherein at least one metal selected from the group consisting of platinum and palladium, and a catalytically active substance containing rhodium, cerium oxide and a refractory inorganic oxide are coated and supported on a honeycomb carrier having an integral structure. Then, immersed in an aqueous solution of at least one transition metal compound selected from the group consisting of water-soluble 6B, 7B and iron groups and a water-soluble tin compound, dried and / or calcined,
A method for producing an exhaust gas purifying catalyst, wherein tin oxide and at least one oxide of a transition metal selected from the group consisting of Group 6B, Group 7B and Group iron are supported on the coating. 5. A catalyst, wherein the total of at least one metal selected from the group consisting of platinum and palladium and rhodium is 0.1 to 10 g, and cerium oxide is 1 to 150 g as CeO ₂ .
g, at least one transition metal selected from the group consisting of the 6B group, the 7B group and the iron group as an oxide to tin oxide
0.1 to 10 wt%, claim (4) The method according tin oxide 0.01~50g and refractory inorganic oxide as SnO ₂ is characterized by comprising loaded in a loading in the range of 20 to 200 g. 6. The method according to claim 4, wherein the refractory inorganic oxide is activated alumina. 7. The method according to claim 4, wherein the transition metal used together with the tin compound is at least one selected from the group consisting of chromium, manganese, iron, cobalt and nickel.