JP2001314763A - CARRIER FOR NOx ABSORBING AND REDUCING CATALYST AND NOx ABSORBING AND REDUCING CATALYST USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for a NOx absorbing and reducing catalyst which is improved in sulfur-poisoning resistance, heat resistance and deteriorating resistance. SOLUTION: This support for the NOx absorbing and reducing catalyst is obtained by incorporating one element, or a mixture of two or more elements, selected from the group consisting of lanthanum, neodymium and praseodymium into the multiple oxide of titanium and zirconium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support for a NOx storage reduction catalyst and a NOx storage reduction catalyst using the same.

[0002] internal combustion engine, in particular, as the exhaust gas purifying catalyst used in an automobile, hydrocarbons, nitrogen oxides, carbon monoxide (H
Three-way catalysts that simultaneously purify C, NOx, and H ₂ ) have been put to practical use. This three-way catalyst converts a reducing component (HC, CO, H ₂ ) and an oxidizing component (NOx, O ₂ ) in the exhaust gas into a harmless component (H ₂ O) by an oxidation-reduction reaction near the stoichiometric air-fuel ratio. , CO ₂ , N ₂ ).

[0003] In the internal combustion engine industry, a lean burn engine has been developed and put into practical use in order to suppress carbon dioxide (CO ₂ ) emission and improve combustion efficiency. In this system, fuel is burned on the lean side of the air-fuel ratio (air A / fuel F), that is, with an excessive oxygen concentration. However, in the lean burn engine, the fuel is burned under the condition of excess oxygen, so that the amount of oxygen in the exhaust gas also becomes excessive. For this reason, when the exhaust gas with excess oxygen is introduced into the three-way catalyst, the reducing components (HC, C
O, H ₂ ) is mainly purified, while oxidizing components (NOx, O ₂ ) in the exhaust gas may not be sufficiently purified.

For this reason, in lean-burn engines, NOx storage reduction catalysts have been developed and used as catalysts for effectively purifying nitrogen oxides. The NOx storage-reduction catalyst stores NOx on the catalyst when the air-fuel ratio is lean, and then switches the air-fuel ratio to the stoichiometric air-fuel ratio or the rich side before the NOx becomes saturated.
It is a catalyst that purifies

On the other hand, the fuel and the lubricating oil for an internal combustion engine contain a trace amount of a sulfur-containing substance, so that the exhaust gas of the internal combustion engine may contain sulfur oxides (SOx). In particular, when the fuel burns under lean conditions, sulfur oxides are mainly generated as SO ₂ and SO ₃ .
These sulfur oxides (SO ₂ , SO ₃ ) are adsorbed on alumina, which is a support material of the NOx storage-reduction type catalyst, because of their acidic properties, and then are basic components (alkali metals, alkaline earths), which are NOx storage components. Metal component) to reduce the original NOx storage capacity. Therefore, there is room for avoiding sulfur poisoning in the NOx storage reduction type catalyst used in the lean burn engine.

On the other hand, JP-A-8-117602 and JP-A-8-192051 propose a NOx occlusion reduction type catalyst which avoids sulfur poisoning.
However, these NOx storage reduction catalysts need to be improved in heat resistance and deterioration resistance.

[0007]

SUMMARY OF THE INVENTION The present inventors have now reported that a support containing titanium-zirconium composite oxide and lanthanum, neodymium and praseodymium has excellent sulfur poisoning resistance, heat resistance and deterioration resistance. Therefore, it has been found that a NOx storage-reduction type catalyst containing the catalyst is excellent in heat resistance and deterioration resistance and can efficiently purify exhaust gas under an excess of oxygen. Accordingly, an object of the present invention is to provide a NOx occlusion reduction type catalyst support material which is excellent in sulfur poisoning resistance, heat resistance and deterioration resistance, and can efficiently purify exhaust gas under an excess of oxygen. I do.

Accordingly, the present invention provides a support for a NOx storage-reduction catalyst, wherein the composite oxide of titanium and zirconium has one or more selected from the group consisting of lanthanum, neodymium and praseodymium. It comprises a mixture.

According to another aspect of the present invention, there is also provided a NOx storage-reduction catalyst using the support according to the present invention. The NOx storage reduction catalyst includes a noble metal, one or a mixture of two or more selected from the group consisting of an alkali metal, an alkaline earth metal, and a rare earth, and the above-described NOx storage reduction catalyst support material. It becomes.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Support for NOx storage-reduction type catalyst The support for NOx storage-reduction type catalyst in the present invention serves as an active component of the catalyst. Therefore, in the present invention, the “supporting material” is used for stabilizing the active metal, which is the active component of the catalyst, and for exhibiting the catalytic ability, and is one of the active components of the catalyst. Say. In this regard,
It is distinguished from the “carrier” that carries the active ingredient described below. a) Titanium-zirconium composite oxide present invention by the support material, as titanium-zirconium composite oxide _{(Ti x Zr y O z)} . NOx storage-reduction catalysts using a support made of a titanium-zirconium composite oxide are disclosed in JP-A-8-117602 and JP-A-8-117602.
It is disclosed in Japanese Patent Publication No. 192051 and is well known.

[0011] In the present invention, titanium-zirconium composite oxide _(Ti x _Zr y _{O z),} the composite oxide of titanium oxide and zirconium _{(Zr) (Ti x O a} · Z
r _y), a composite oxide of zirconium oxide titanium _{(Ti) (Ti · Zr y} O b), and complex oxides of zirconium oxide and titanium oxide _{(Ti x} O a · Zr
_{y O b),} may be one or a mixture of two or more of the group consisting of. In the above formula, x, y, z, a, and b can be appropriately determined according to the respective valence numbers. Further, as the titanium / zirconium composite oxide, those manufactured by a general manufacturing method or commercially available ones can be used.

In the present invention, the composition of titanium and zirconium in the titanium-zirconium composite oxide is as follows:
1:99 to 99: 1 in atomic ratio of titanium to zirconium
The range is preferably about 5:95 to 95: 5. When the composition of titanium and zirconium is within the above range, a preferable support material can be formed.

B) Lanthanum, neodymium, praseodymium The support according to the invention comprises one or a mixture of two or more selected from the group consisting of lanthanum, neodymium and praseodymium. In particular, among the above, neodymium or a combination of lanthanum and neodymium is preferable.

When the above-mentioned element is added to a titanium-zirconium composite oxide as a support for a NOx storage-reduction catalyst, the heat resistance and the deterioration resistance of the NOx storage-reduction catalyst are remarkably improved. Can be improved.

The amount of addition is 0.05 to 5 with respect to 100 total atoms of titanium and zirconium.
The range is about 0, preferably about 0.5 to 40.

NOx Storage-Reduction Catalyst The NOx storage-reduction catalyst comprises an active component containing an active metal, a NOx storage material, a support material, and, if necessary, a promoter. Note that the support material according to the present invention is used as described above. Accordingly, the support may be similar to that described above. a) Active metal The active metal is responsible for the activation mechanism of the catalyst. As the active metal, a noble metal or a base metal can be used, and a noble metal is preferably used. Specific examples of noble metals include platinum, palladium, rhodium, ruthenium, iridium,
Osmium, gold, or silver can be mentioned, and preferably, platinum, palladium, or rhodium. These noble metals can be used as one kind or as a mixture of two or more kinds. Specific examples of base metals include nickel,
Examples thereof include copper, manganese, iron, cobalt, and zinc, and are preferably nickel, manganese, or iron. Also,
These base metals can be used as one kind or as a mixture of two or more kinds. The amount of the active metal added can be determined as appropriate, but preferably, the NOx storage reduction catalyst 1
The range is about 0.05 to 10 g with respect to 00 g,
Preferably, it is in the range of about 0.1 to 5 g.

B) NOx occluding material As the NOx occluding material, one or a mixture of two or more selected from the group consisting of alkali metals, alkaline earth metals, and rare earth elements can be used. Specific examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium, and francium. These alkali metals can be used as one kind or as a mixture of two or more kinds. Specific examples of the alkaline earth metal include beryllium, magnesium, calcium, strontium, and barium.
These alkaline earth metals can be used as one kind or as a mixture of two or more kinds. Specific examples of the rare earth element include scandium, yttrium, lanthanum, cerium, praseodymium, and neodymium.
These rare earth elements can be used as one kind or as a mixture of two or more kinds. Preferred among the above are one or a mixture of two or more selected from the group consisting of lithium, sodium, potassium, cerium, strontium, barium, and lanthanum.
The addition amount of the NOx storage material can be determined as appropriate,
Preferably, for 100 g of the NOx storage reduction catalyst,
The range is about 15 to 60 g, preferably 6 to 40 g.
Range.

C) Promoter The NOx storage reduction catalyst according to the present invention may contain a promoter as an optional component. Cerium is mentioned as a promoter. The addition amount of the co-catalyst can be appropriately determined, but is preferably in the range of about 0 to 30 g, preferably 0 to 20 g, per 100 g of the NOx storage reduction catalyst.
g.

D) Carrier The NOx storage-reduction catalyst according to the present invention can be used for purifying exhaust gas by carrying the above-mentioned active component, NOx storage material and, if necessary, a promoter on a carrier. .
Specific examples of the carrier include a pellet-shaped shape (granular shape) made of alumina and a monolith-shaped shape (honeycomb shape) made of metal such as cordierite ceramics or stainless steel. In particular, a monolithic shape excellent in heat resistance, thermal shock resistance, and mechanical strength is preferable.

Method for Producing NOx Storage-Reduction Catalyst The NOx storage-reduction catalyst according to the present invention can be produced by mixing the above-mentioned components by an appropriate method and calcining the mixture. Preferably, first, the titanium-zirconium composite oxide and, if necessary, titanium hydroxide or zirconium hydroxide are mixed, and water is further added and mixed. The mixture is mixed with a suitable dispersing machine (for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ang mill, etc.)
Prepare a slurry. A commercially available cell cordierite honeycomb is immersed in the slurry. After immersion, the cell cordierite honeycomb is pulled up, excess slurry is removed with an air gun, and then dried and fired. The fired cell cordierite honeycomb to which the slurry adhered,
[Pt (NH ₃ ) ₄ ] based on the water absorption of the honeycomb
Immerse in Cl ₂ solution. Thereafter, the excess solution is removed with an air gun, dried and calcined to produce a NOx storage reduction catalyst.

Use of NOx Storage Reduction Catalyst The NOx storage reduction catalyst according to the present invention can be used for an internal combustion engine. In particular, it can be preferably used for a lean-burn engine, a direct-injection engine, and preferably an engine combining them (ie, a direct-injection lean-burn engine). The direct injection engine is an engine that employs a fuel supply system capable of achieving a high compression ratio, improving combustion efficiency, and reducing exhaust gas. Therefore, by combining with a lean burn engine, it is possible to further improve the combustion efficiency and reduce the exhaust gas.

The NOx storage-reduction catalyst according to the present invention can be used, for example, in the case of an exhaust system of an automobile, a start catalyst,
It can be installed as an underfloor or manifold converter. According to a preferred embodiment of the present invention, the NOx storage reduction catalyst according to the present invention is preferably used together with a three-way catalyst. Thus, N
The Ox storage reduction catalyst can provide a method for efficiently eliminating NOx in exhaust gas generated from an internal combustion engine by the above-mentioned application.

Specific examples of the internal combustion engine include, for example, automobiles, buses, trucks, airway cars, motorcycles, motorized bicycles, heavy machinery, etc .; transport vehicles such as airplanes;
Agriculture and forestry industrial machines such as tractors, combiners, chain saws, trolleys, and wood carriers; ships such as ships, fishing boats, and motor boats; civil engineering machines such as cranes, presses, and excavators; and generators. However, it is not limited to these.

[0024]

The contents of the present invention will be described in more detail with reference to examples. However, the contents of the present invention are not construed as being limited by the examples.

Preparation of Titanium-Zirconium Composite Oxide Preparation 1 Titanium tetrachloride (TiCl ₄ ) was dissolved in a 1 molar hydrochloric acid solution to prepare a titanium tetrachloride hydrochloric acid solution. Zirconyl chloride (ZrOCl ₂ ) was mixed with this solution such that the atomic ratio of titanium to zirconium was 50:50. While stirring the mixture, aqueous ammonia was added dropwise to adjust the pH to at least 11 or more. Thereafter, the mixture was left for one day while stirring, and washed with deionized water until chloride ions could not be detected by the silver nitrate solution. After the washed material was dried at 110 ° C. for 24 hours, it was baked at 500 ° C. for 3 hours, whereby Preparation 1 was prepared. Preparation 2 Preparation 2 was prepared in the same manner as in Preparation 1, except that titanium and zirconium were mixed such that the atomic ratio was 40:60.

Preparation Example 1 of Support Material for NOx Storage Reduction Catalyst The amount of water adsorbed per 1 g of the composite oxide of Preparation 1 was measured. A lanthanum nitrate solution having the same volume as the measured water adsorption amount was prepared. The lanthanum nitrate solution has an atomic ratio of lanthanum (La) of 100 in total of titanium, zirconium and the number of atoms.
Was prepared to be 6. This lanthanum nitrate solution was uniformly immersed in the composite oxide of Preparation 1. After the immersion was dried at 110 ° C. for 24 hours, it was baked at 500 ° C. for 2 hours to prepare a support material. Example 2 A support material was prepared in the same manner as in Example 1 except that lanthanum was neodymium (Nd) and the lanthanum nitrate solution was neodymium nitrate. Example 3 A support material was prepared in the same manner as in Example 1 except that lanthanum was praseodymium (Pr) and the lanthanum nitrate solution was praseodymium nitrate. Example 4 A support was prepared in the same manner as in Example 1 above, except that Preparation 1 was Preparation 2. Example 5 A support material was prepared in the same manner as in Example 4 except that lanthanum was neodymium (Nd) and the lanthanum nitrate solution was neodymium nitrate. Example 6 A support material was prepared in the same manner as in the above example, except that lanthanum was praseodymium (Pr) and the lanthanum nitrate solution was praseodymium nitrate.

Comparative Example 1 A support for Preparation 1. Comparative Example 2 Support for Preparation 2 Comparative Example 3 A support material was prepared in the same manner as in Example 1 except that lanthanum was yttrium (Y) and the lanthanum nitrate solution was yttrium nitrate. Comparative Example 4 A support material was prepared in the same manner as in Example 4 except that lanthanum was yttrium (Y) and the lanthanum nitrate solution was yttrium nitrate.

Evaluation Test An electric muffle furnace in which a quartz tube through which a high-temperature processing gas can flow was surrounded by an electric heater was used. The support materials of Examples 1 to 6 and Comparative Examples 1 to 4 prepared above were arranged in a quartz tube, and fired in air at 500 ° C., 600 ° C., 700 ° C., 800 ° C., and 900 ° C. for 3 hours, respectively. Thereafter, the surface area was measured by the BET method using nitrogen gas adsorption. The results were as shown in Table 1 below. For the surface area measurement by the BET method, a Gemini type surface area measuring device manufactured by Micromeritics was used.

Table 1 Composition: Atomic ratio Additive (ratio) BET value at each temperature (° C) Supporting material Ti: Zr 500 600 700 800 900 Example 1 50:50 La 6 115 94 58 35 14 Example 2 50:50 Nd 6 123 101 64 37 12 Example 3 50:50 Pr 6 118 94 56 32 11 Comparative Example 1 50:50 None 0 123 96 58 32 11 Comparative Example 3 50:50 Y 6 116 89 48 23 11 Example 4 40:60 La 6 165 124 86 44 20 Example 5 40:60 Nd 6 168 118 84 46 23 Example 6 40:60 Pr 6 162 117 87 46 21 Comparative Example 2 40:60 None 0 173 98 72 36 14 Comparative Example 4 40:60 Y 6 170 108 80 38 20

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 32/00 F01N 3/10 A F01N 3/08 3/28 301C 3/10 301P 3/28 301 B01D 53 / 36 102H 102B B01J 23/56 301A (72) Inventor Geng Zhang, Kitsuregawa-cho, Kitsuregawa-cho, Shioya-gun, Tochigi Prefecture Johnson Matthey Japan Co., Ltd., Kitsuregawa Technical Center (72) Inventor Hideaki Muraki, Shioya-gun, Tochigi Inside the Kitsuregawa Industrial Park in Kitsuregawa-cho Johnson Massey Japan Co., Ltd.In the Kitsuregawa Technical Center (72) Inventor Yasunori Kurashima In Kitsuregawa-cho, Kitayagawa-cho, Shioya-gun, Tochigi Prefecture Johnson Matthey Japan Co., Ltd. three Consideration) 3G091 AA12 AA24 AB06 BA07 BA11 BA14 GA01 GA06 GB02Y GB03Y GB04Y GB05W GB06W GB07W GB10W GB17X 4D048 AA06 AB02 AB07 BA01Y BA02Y BA07X BA08X BA14Y BA15Y BA18X BA19Y BA30Y BA31A BA04 BA03 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA04 BA05 BA BC02A BC03A BC04A BC05A BC06A BC07A BC08A BC09A BC10A BC11A BC12A BC13A BC32A BC33A BC38A BC39A BC40A BC41A BC42A BC42B BC43A BC44A BC50A BC50B BC51A BC51B BC69A BC70A BC71A BC72A BC73A CA74EA

Claims (10)

[Claims] 1. A composition comprising a titanium-zirconium composite oxide and one or a mixture of two or more selected from the group consisting of lanthanum, neodymium, and praseodymium.
Support material for NOx storage reduction type catalyst. 2. A NOx storage reduction comprising a noble metal, one or a mixture of two or more selected from the group consisting of an alkali metal, an alkaline earth metal and a rare earth, and the support material according to claim 1. Type catalyst. 3. The method according to claim 2, wherein the noble metal is one or a mixture of two or more selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold, and silver. , Potassium, rubidium, cesium, and a mixture of one or more selected from the group consisting of francium, the alkaline earth metal, beryllium, magnesium,
One or a mixture of two or more selected from the group consisting of calcium, strontium, and barium, wherein the rare earth element is one or two selected from the group consisting of scandium, yttrium, lanthanum, cerium, praseodymium, and neodymium. 3. The catalyst according to claim 2, which is a mixture of at least one species. 4. The catalyst according to claim 2, wherein the catalyst is used by being supported on a carrier having a pellet shape or a monolith shape. 5. The catalyst according to claim 1, which is used for purifying NOx in exhaust gas generated from an internal combustion engine. 6. The catalyst according to claim 5, wherein the internal combustion engine is a lean burn engine, a direct injection type engine, or an engine combining these. 7. The catalyst according to claim 6, wherein said lean-burn engine, direct-injection engine, or an engine combining them is used for an automobile. 8. The NO according to any one of claims 2 to 4,
A method for purifying NOx in exhaust gas generated from an internal combustion engine, using an x storage reduction catalyst. 9. The method according to claim 8, wherein said internal combustion engine is a lean burn engine, a direct injection engine, or an engine combining them. 10. The method according to claim 9, wherein said lean-burn engine, direct-injection engine, or an engine combining them is used in an automobile.