JP7425416B2 - catalyst - Google Patents

Description

The present invention relates to a catalyst, and more particularly, to a catalyst that is equipped with a plurality of metal oxide carriers on which different active components are supported and exhibits a plurality of catalytic performances.

Conventionally, for example, exhaust gas purification catalysts installed in automobiles have been used to remove harmful components such as harmful gases (hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx)) contained in exhaust gas. For purification, three-way catalysts, oxidation catalysts, NOx storage reduction catalysts, etc. have been developed. In recent years, as the characteristics required for exhaust gas purifying catalysts have increased, there has been a demand for exhaust gas purifying catalysts having highly excellent catalytic performance that can exhibit two or more different catalytic performances.

As such a catalyst for purifying exhaust gas, JP 2016-175008A (Patent Document 1) discloses a catalyst comprising a first active powder in which rhodium as a first active component is supported on a first metal oxide powder. A first aggregate particle, a second aggregate particle consisting of a second active powder in which a second active ingredient other than rhodium is supported on a second metal oxide powder, and a third metal oxide containing no active ingredient. a matrix made of powder, the first aggregate particles and the second aggregate particles are included in the matrix, and the volume average particle diameter of the first aggregate particles and the A catalyst is disclosed in which the volume average particle diameter of each of the second aggregate particles is within a range of 50 to 600 μm. In this catalyst, even if one active component or the metal oxide powder on which it is supported inhibits the catalytic performance of the other active component, the active components or the metal oxide powder and the other metal oxide powder can be used together. Since the active components are separated by an appropriate distance, the catalytic performance of the other active component is not inhibited, and different catalytic performances are exhibited together.

Japanese Patent Application Publication No. 2016-175008

However, in the catalyst described in Patent Document 1, different catalytic performance is sufficiently exhibited at high temperatures and steady state, but not necessarily sufficiently exhibited at low temperatures or in the early stage of the reaction.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide a catalyst that can sufficiently exhibit different catalytic performances even at low temperatures and in the early stages of reaction.

As a result of extensive research to achieve the above object, the present inventors have discovered that first aggregate particles include a first active powder in which rhodium as a first active ingredient is supported on a first metal oxide powder. , second aggregate particles containing a second active powder in which a second active ingredient other than rhodium is supported on a second metal oxide powder, and a matrix consisting of a third metal oxide powder containing no active ingredient. , the first aggregate particles and the second aggregate particles are included in the matrix, and the volume average particle diameters of the first aggregate particles and the second aggregate particles are respectively The total pore volume of the pores in the first aggregate particle and the second aggregate particle having a pore diameter of 1 to 10 μm is within a specific range. The present inventors have discovered that, by doing so, it is possible to obtain a catalyst that fully exhibits different catalytic performances even at low temperatures and in the early stages of the reaction, and has completed the present invention.

That is, the catalyst of the present invention comprises first aggregate particles containing a first active powder in which rhodium as a first active ingredient is supported on a first metal oxide powder, and a second active ingredient other than rhodium. a second aggregate particle containing a second active powder supported on a second metal oxide powder; and a matrix consisting of a third metal oxide powder containing no active ingredient ; component and the second active ingredient are separately present, the first active ingredient and the second metal oxide powder are separately present, and the second active ingredient and the first active ingredient are separately present. the metal oxide powder exists separately, the first aggregate particles and the second aggregate particles are included in the matrix, and the volume average particle diameter of the first aggregate particles and the The total pore volume of the pores in which the volume average particle diameter of the second aggregate particles is within the range of 50 to 600 μm, and the pore diameter of the first aggregate particles is within the range of 1 to 10 μm. is 0.03 ml/g or more, the total pore volume of the pores in the second aggregate particle having a pore diameter within the range of 1 to 10 μm is 0.03 ml/g or more, and the first aggregate particle has a total pore volume of 0.03 ml/g or more. The total pore volume of pores in the body particle having a pore diameter within the range of 1 to 10 μm; and the total pore volume of the pores in the second aggregate particle having a pore diameter within the range of 1 to 10 μm. 0.05 ml/g or more , and the catalyst is at least one selected from the group consisting of an exhaust gas purification catalyst, a VOC purification catalyst, a reforming catalyst, and an air purifier catalyst. It is something to do.

In the catalyst of the present invention, it is preferable that the second active component is palladium, the second metal oxide powder is ceria-zirconia solid solution powder, and the second aggregate particles further include alumina powder. Preferably, it includes.

Further, in the catalyst of the present invention, it is preferable that the total pore volume of the pores having a pore diameter in the range of 1 to 10 μm in the first aggregate particle is 0.03 to 0.4 ml/g. Further, it is preferable that the total pore volume of the pores having a pore diameter in the range of 1 to 10 μm in the second aggregate particle is 0.06 to 0.4 ml/g.

The reason why the catalyst of the present invention exhibits different catalytic performances sufficiently even at low temperatures and at the initial stage of the reaction is not necessarily clear, but the inventors of the present invention speculate as follows. That is, in the catalyst of the present invention, first aggregate particles containing a first active powder in which rhodium as a first active ingredient is supported on a first metal oxide powder, and a second active ingredient other than rhodium. second aggregate particles containing a second active powder supported on a second metal oxide powder are included in a matrix consisting of a third metal oxide powder containing no active ingredient, and Since the volume average particle diameters of the first aggregate particles and the second aggregate particles are each within a specific range, the first active ingredient and the second active ingredient, the first active ingredient and the a bimetallic oxide powder, and the second active ingredient and the first metal oxide powder are present separated by a suitable distance, and the first active ingredient and the second active ingredient are different from each other. Catalytic performance is not inhibited and both are fully exhibited.

In the catalyst of the present invention, the total pore volume of the pores in the first aggregate particle and the second aggregate particle having a pore diameter within a range of 1 to 10 μm is within a specific range. Therefore, the gas diffusivity in the first aggregate particles and the second aggregate particles is excellent, and the first active ingredient in the first aggregate particles and the second aggregate particle The contact efficiency between the second active component and the gas becomes high, and the different catalytic performances of the first active component and the second active component are fully exhibited even at low temperatures or in the early stage of the reaction. It is inferred.

According to the present invention, it is possible to obtain a catalyst that fully exhibits different catalytic performances even at low temperatures or in the early stages of reaction.

1 is a graph showing the cumulative pore distribution of Rh/alumina-ceria-zirconia pellets (first aggregate particles) obtained in Example 1. 1 is a graph showing the cumulative pore distribution of Pd/ceria-zirconia pellets (second aggregate particles) obtained in Example 1. 3 is a graph showing the cumulative pore distribution of Rh/alumina-ceria-zirconia powder pellets (first aggregate particles) obtained in Comparative Example 3. 3 is a graph showing the cumulative pore distribution of the Pd/ceria-zirconia powder pellets (second aggregate particles) obtained in Comparative Example 3. 1 is a graph showing the cumulative pore distribution of pellet catalysts obtained in Example 1 and Comparative Examples 1 to 3. 1 is a graph showing the 50% purification temperature of CO, C ₃ H ₆ and NOx of pellet catalysts obtained in Example 1 and Comparative Examples 1 to 3.

Hereinafter, the present invention will be explained in detail based on its preferred embodiments.

The catalyst of the present invention comprises first aggregate particles containing a first active powder in which rhodium as a first active ingredient is supported on a first metal oxide powder, and a second aggregate particle containing a second active ingredient other than rhodium. The second aggregate particle includes a second active powder supported on a metal oxide powder, and a matrix made of a third metal oxide powder that does not contain an active ingredient. One aggregate particle and the second aggregate particle are included, and the volume average particle diameter of the first aggregate particle and the volume average particle diameter of the second aggregate particle are each within a range of 50 to 600 μm. and the total pore volume of the pores in the first aggregate particle has a pore diameter within the range of 1 to 10 μm and the pore diameter in the second aggregate particle falls within the range of 1 to 10 μm. The total volume of certain pores and the total pore volume is 0.05 ml/g or more.

(first aggregate particle)
It is necessary that the first aggregate particles contain a first active powder in which rhodium as a first active ingredient is supported on a first metal oxide powder. In such first aggregate particles, the first metal oxide powder is not particularly limited as long as it is a metal oxide that can be normally used in the catalyst of the present invention.

In the first metal oxide powder used in the present invention, metals constituting the metal oxide include, for example, base metal elements (Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Mg, Al, K, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ga, Rb, Sr, Zr, Nb, Mo, In, Sn, Cs, Ba, Ta, W, etc.), metalloid elements (Si, Ge, As, Sb, etc.), and among them, Ce, Zr, Al, Ti, Si, Mg, Y, La, and Nd are preferable. These metals may be used alone or in combination of two or more, and when two or more metals are used in combination, they may be used as two or more metal oxides, It may also be used as a composite oxide containing two or more metals, such as ceria-zirconia composite oxide, sepiolite, and zeolite. Moreover, the first metal oxide powder made of such a metal oxide may be used alone or in combination of two or more types.

Among metal oxides containing such metals, zirconium oxide has been developed from the viewpoint of being able to support rhodium (Rh) in a highly active state and with high dispersion, as well as being able to more fully prevent oxidation of the supported Rh. (ZrO ₂ ), cerium oxide (CeO ₂ ), yttrium oxide (Y ₂ O ₃ ), rare earth oxides, aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), and among these Composite oxides and solid solutions containing at least one kind are preferred, such as zirconium oxide, cerium oxide, yttrium oxide, rare earth oxide, aluminum oxide, magnesium oxide, and composite oxides and solid solutions of two or more of these. A solid solution is more preferable, and from the viewpoint of maintaining the heat resistance of rhodium (Rh), at least one of zirconium oxide, cerium oxide, yttrium oxide, rare earth oxide, aluminum oxide, and magnesium oxide. A composite oxide containing seeds is preferred, and a composite oxide of two or more of zirconium oxide, cerium oxide, yttrium oxide, rare earth oxide, aluminum oxide, and magnesium oxide is more preferred.

Furthermore, from the viewpoint of improving the thermal stability of the carrier and the catalytic activity of Rh, the first metal oxide powder may contain additives within a range that does not impair the effects of the present invention. Examples of such additives include lanthanum (La), yttrium (Y), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), Gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), magnesium (Mg), calcium (Ca), Oxides of metals such as rare earths such as strontium (Sr), barium (Ba), scandium (Sc), and vanadium (V), alkali metals, alkaline earth metals, and transition metals; mixtures of oxides of these metals; solid solutions of oxides of metals; composite oxides of these metals. Further, it is preferable that such an additive forms a composite oxide or a solid solution with the metal oxide used in the first metal oxide powder.

The shape of the first metal oxide powder is not particularly limited other than being in powder form, but it is preferably one that has high heat resistance and a high specific surface area. The particle size of such first metal oxide powder is not particularly limited, but is preferably 30 μm or less, more preferably 15 μm or less.

The first active powder used in the present invention is such a first metal oxide powder that supports rhodium (Rh) as the first active ingredient. By supporting Rh on the first metal oxide powder, for example, when the catalyst of the present invention is used as an exhaust gas purification catalyst, the state of Rh is easily maintained in a highly active metal state even in an oxidizing atmosphere, and sufficient A catalyst exhibiting catalytic activity is obtained. Such first active powders may be used alone or in combination of two or more.

The amount of Rh supported in the first active powder is not particularly limited, but it is preferably 0.03 to 1.0 parts by mass, and 0.05 to 0 parts by mass, based on 100 parts by mass of the first metal oxide powder. .3 parts by mass is more preferred. If the supported amount of Rh is less than the above-mentioned lower limit, sufficient catalyst activity cannot be obtained and the emission of harmful components such as NOx and HC tends to be unable to be suppressed.On the other hand, if it exceeds the above-mentioned upper limit, the cost of the catalyst is high. There is a tendency to

There are no particular restrictions on the method for supporting Rh, and any known method may be employed.For example, a method may be employed in which the first metal oxide powder is impregnated with an aqueous solution containing a Rh salt, then dried and fired. Can be mentioned.

The first aggregate particles used in the present invention contain such a first active powder. The content of the first active powder is not particularly limited as long as the effects of the present invention can be sufficiently obtained, but it is preferably 30% by mass or more with respect to the entire first aggregate particles (100% by mass), More preferably 80% by mass or more.

Further, the first aggregate particles may further contain alumina powder from the viewpoint of improving the structural stability of the particles. The particle size of such alumina powder is not particularly limited, but is preferably 30 μm or less, more preferably 15 μm or less. In addition, the content of the alumina powder is determined based on the entire first aggregate particles (100% by mass) from the viewpoint of improving the structural stability of the first aggregate particles without impairing the effects of the present invention. It is preferably 0 to 70% by weight, more preferably 0 to 20% by weight.

The form of such first aggregate particles is not particularly limited, but is preferably an aggregate of the first active powder or an aggregate of the first active powder and the alumina powder. Such an aggregate may be an aggregate of only the first active powder or an aggregate of only the first active powder and the alumina powder, but from the viewpoint of making the aggregate difficult to disintegrate, Preferably, mono-active powder or alumina powder aggregated with a binder interposed therebetween is used. Such a binder is not particularly limited as long as it can firmly bind the first active powder and the alumina powder, and examples thereof include an alumina sol binder. In addition, the content of the binder is 3 to 20% by mass based on the entire aggregate (100% by mass) from the viewpoint of sufficiently suppressing the collapse of the aggregates without impairing the effects of the present invention. is preferable, and 5 to 15% by mass is more preferable.

(Second aggregate particles)
The second aggregate particles need to contain a second active powder in which a second active ingredient other than rhodium is supported on a second metal oxide powder. In such second aggregate particles, the second metal oxide powder is not particularly limited as long as it is a metal oxide that can be normally used in the catalyst of the present invention.

In the second metal oxide powder used in the present invention, metals constituting the metal oxide include, for example, base metal elements (Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Mg, Al, K, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ga, Rb, Sr, Zr, Nb, Mo, In, Sn, Cs, Ba, Ta, W, etc.), metalloid elements (Si, Ge, As, Sb, etc.), and among them, Ce, Zr, Al, Ti, Si, Mg, Y, La, Nd, and Pr are preferable. These metals may be used alone or in combination of two or more, and when two or more metals are used in combination, they may be used as two or more metal oxides, It may also be used as a composite oxide containing two or more metals, such as ceria-zirconia composite oxide, sepiolite, and zeolite. Moreover, the second metal oxide powder made of such a metal oxide may be used alone or in combination of two or more types.

Among metal oxides containing such metals, aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), Titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), cerium oxide (CeO ₂ ), composite oxides and solid solutions containing at least one of these, and zeolite are preferred, and also have oxygen storage capacity. From this viewpoint, metal oxides such as cerium (Ce), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), thulium (Tm), and ytterbium (Yb) are preferable, and have higher oxygen content. From the viewpoint of having storage-release performance, cerium oxide (CeO ₂ ), praseodymium oxide (Pr ₂ O ₃ ), and lanthanum oxide (La ₂ O ₃ ) are more preferred, and cerium oxide is particularly preferred. Further, iron-containing composite oxides are also preferred from the viewpoint of improving catalytic performance by using co-catalysts with different characteristics.

In addition, in the second metal oxide powder, the metal oxide having oxygen storage ability and another metal oxide are combined to form a porous metal oxide powder, which has oxygen storage ability and heat resistance. Metal oxide powder with excellent properties can be obtained. Examples of such other metal oxides include known porous metal oxides such as titania, zirconia, lantana, neodia, prasedia, silica, and composite oxides of two or more of these. Specific examples of metal oxide powders having such oxygen storage ability include ceria-zirconia composite oxide powder, alumina-ceria-zirconia composite oxide powder, silica-ceria-zirconia composite oxide powder, and silica-ceria composite oxide powder. Composite oxide powder, ceria-zirconia-lantana composite oxide powder, ceria-zirconia-nedia composite oxide powder, ceria-zirconia-prasedia composite oxide powder, among others, based on the structural stabilization of ceria by zirconia. From the viewpoint of obtaining a higher oxygen storage capacity, ceria-zirconia composite oxide powder, alumina-ceria-zirconia composite oxide powder, ceria-zirconia-prasedia-lantana composite oxide powder are preferable, and ceria-zirconia solid solution Powder is more preferred.

There are no particular limitations on the shape of the second metal oxide powder, other than that it is in powder form, but it is preferably one that has high heat resistance and a high specific surface area. The particle size of such second metal oxide powder is not particularly limited, but is preferably 30 μm or less, more preferably 15 μm or less.

The second active powder used in the present invention is such a second metal oxide powder that supports a second active ingredient other than rhodium (Rh). Here, the "active component" is a component that acts to express or improve catalyst performance. For example, when the catalyst of the present invention is used as an exhaust gas purification catalyst, the "active component" is a component that participates in exhaust gas purification (purifies exhaust gas). Components that act to Such second active powders may be used alone or in combination of two or more.

The second active ingredient is not particularly limited as long as it is an active ingredient other than rhodium (Rh), but includes, for example, Pt, Pd, Ir, Au, Ag, Cu, Co, Ni, V, Fe, Nb, Examples include Mo, W, and the like. These active ingredients may be used alone or in combination of two or more. In addition, among these active ingredients, Pt, Pd, Ir, Au, and Ag can be used to purify exhaust gas by oxidizing hydrocarbons (HC) more efficiently and reducing NOx more efficiently. , Cu are more preferred, Pt and Pd are even more preferred, and Pd is particularly preferred. Furthermore, from the viewpoint of promoter action, Fe is also preferable.

The amount of the second active ingredient supported in the second active powder is not particularly limited, but it is preferably 0.1 to 5.0 parts by mass, and 0.1 to 5.0 parts by mass based on 100 parts by mass of the second metal oxide powder. .3 to 2.0 parts by mass is more preferable. If the supported amount of the second active component is less than the above-mentioned lower limit, sufficient catalytic activity cannot be obtained and the emission of harmful components such as NOx and HC tends to be unable to be suppressed. As the cost of catalyst increases, the activity of the catalyst tends to decrease.

There are no particular restrictions on the method of supporting the second active ingredient, and any known method can be used. For example, an aqueous solution containing a metal salt that is the second active ingredient is applied to the second metal oxide powder. An example is a method of impregnating, drying, and firing.

The second aggregate particles used in the present invention contain such second active powder. The content of the second active powder is not particularly limited as long as the effects of the present invention can be sufficiently obtained, but it is preferably 30% by mass or more based on the entire second aggregate particles (100% by mass), More preferably 45% by mass or more.

Further, the second aggregate particles may further contain alumina powder from the viewpoint of improving the structural stability of the particles. The particle size of such alumina powder is not particularly limited, but is preferably 30 μm or less, more preferably 15 μm or less. In addition, the content of the alumina powder is determined based on the entire second aggregate particles (100% by mass) from the viewpoint of improving the structural stability of the second aggregate particles without impairing the effects of the present invention. It is preferably 0 to 70% by weight, more preferably 0 to 55% by weight.

The form of such second aggregate particles is not particularly limited, but is preferably an aggregate of the second active powder or an aggregate of the second active powder and the alumina powder. Such an aggregate may be an aggregate of only the second active powder or an aggregate of only the second active powder and the alumina powder, but from the viewpoint of making the aggregate difficult to disintegrate, Preferably, the biactivated powder or the alumina powder is aggregated with a binder interposed therebetween. Such a binder is not particularly limited as long as it can firmly bind the second active powder and the alumina powder, and examples thereof include an alumina sol binder. In addition, the content of the binder is 3 to 20% by mass based on the entire aggregate (100% by mass) from the viewpoint of sufficiently suppressing the collapse of the aggregates without impairing the effects of the present invention. is preferable, and 5 to 15% by mass is more preferable.

(matrix)
It is necessary that the matrix consists of a third metal oxide powder containing no active ingredients. In such a matrix, the third metal oxide powder is not particularly limited, except that it is a metal oxide powder that does not contain an active ingredient, and any known metal oxide can be used. Here, the "active component" is a component that acts to express or improve catalyst performance. For example, when the catalyst of the present invention is used as an exhaust gas purification catalyst, the "active component" is a component that participates in exhaust gas purification (purifies exhaust gas). Components that act to In addition, "contains no" means that contamination to the extent of impurities is acceptable. For example, in the process of manufacturing the catalyst of the present invention, rhodium (Rh) supported on the first metal oxide powder, It is acceptable that the second active ingredient supported on the metal oxide powder is transferred to the matrix.

In the third metal oxide powder used in the present invention, metals constituting the metal oxide include, for example, base metal elements (Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Mg, Al, K, Ti, Sr, Zr, Ba, etc.), metalloid elements (Si, Ge, As, Sb, etc.), among them Ce, Zr, Al, Ti, Si and Mg are preferred. These metals may be used alone or in combination of two or more, and when two or more metals are used in combination, they may be used as two or more metal oxides, It may also be used as a composite oxide containing two or more metals, such as ceria-zirconia composite oxide, sepiolite, and zeolite. Further, the third metal oxide powder made of such a metal oxide may be used alone or in combination of two or more types.

Among metal oxides containing such metals, aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), and rare earth oxides are preferred from the viewpoint of heat resistance. Preferably, aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), lanthanum, from the viewpoint of improving the catalytic activity of rhodium (Rh) as the first active component. Preferred are oxide (La ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), praseodymium oxide (Pr ₂ O ₃ ), and yttrium oxide (Y ₂ O ₃ ). The metals constituting these metal oxides are difficult to exchange active oxygen with Rh, and solid phase reactions are also difficult to occur, so they have no or small effect on changing the oxidation state of Rh, further improving the activity of Rh. This makes it possible to maintain the metal state of Rh. In addition, from the viewpoint of high specific surface area and high heat resistance, activated alumina and zirconia are preferable, and from the viewpoint of prevention of peeling of the catalyst coat layer and heat resistance, aluminum oxide (Al ₂ O ₃ ) and zirconium oxide (ZrO ₂ ) are preferable. , and composite oxides in which La, Nd, Pr, Y, etc. are dissolved in solid solution in these metal oxides are preferable.

(catalyst)
The catalyst of the present invention includes the first aggregate particles, the second aggregate particles, and the matrix, and the first aggregate particles and the second aggregate particles are included in the matrix. It is necessary that the Here, "the first aggregate particles and the second aggregate particles are included" means that the first aggregate particles and the second aggregate particles are contained inside the matrix, preferably dispersed. It means doing. The form in which the first aggregate particles and the second aggregate particles are included is a form similar to a Dalmatian pattern in which islands are floating in the sea, that is, for example, when a cross section of the catalyst of the present invention is observed. Preferably, the first aggregate particles (islands) and the second aggregate particles (islands) are floating in the matrix (sea) like a Dalmatian pattern. Furthermore, in the catalyst of the present invention, the first aggregate particles and the second aggregate particles are preferably uniformly dispersed in the matrix from the viewpoint of exhibiting the effect of the entire catalyst.

In the catalyst of the present invention, it is necessary that the volume average particle diameter of the first aggregate particles and the volume average particle diameter of the second aggregate particles are each in the range of 50 to 600 μm. When the volume average particle diameter of the first aggregate particles and the volume average particle diameter of the second aggregate particles are less than the lower limit, rhodium (Rh) and the second active component are likely to come into contact with each other. On the other hand, if the upper limit is exceeded, the interaction of the second aggregate particles with rhodium (Rh) as a co-catalyst cannot be obtained sufficiently, and different catalyst performance is inhibited. Performance is not fully demonstrated. In addition, from the viewpoint of preventing contact between rhodium (Rh) and the second active component and interaction as the co-catalyst, the volume average particle diameter of the first aggregate particles and the volume average particle size of the second aggregate particles The diameter of each is preferably within the range of 50 to 400 μm, and more preferably within the range of 50 to 200 μm. In the present invention, the "volume average particle diameter" refers to the particle size distribution obtained by measuring the volume-based particle size distribution of the particles by a light scattering method using a suspension prepared by dispersing particles in water. This is the particle diameter (D50) at which the cumulative frequency is 50% in the particle size distribution (volume basis).

Further, in the catalyst of the present invention, the total pore volume of the pores in the first aggregate particle having a pore diameter in the range of 1 to 10 μm and the pore diameter in the second aggregate particle are in the range of 1 to 10 μm. It is necessary that the total pore volume of the pores within the range of 0.05 ml/g or more is 0.05 ml/g or more. The sum of the total pore volume of the first aggregate particle (pore diameter range: 1 to 10 μm) and the total pore volume of the second aggregate particle (pore diameter range: 1 to 10 μm) is less than the lower limit. When this happens, the diffusivity of gas in the first aggregate particles and the second aggregate particles decreases, so rhodium (Rh) in the first aggregate particles and rhodium (Rh) in the second aggregate particles decrease. The contact efficiency between the second active component and the gas decreases, and the different catalytic performances of Rh and the second active component are not fully exhibited at low temperatures or in the early stages of the reaction. In addition, the diffusivity of gas in the first aggregate particles and the second aggregate particles is improved, and the contact efficiency of rhodium (Rh) and the second active ingredient with the gas is improved, so that low temperature The total pore volume (pore diameter range: 1 to 10 μm) of the first aggregate particles is The total pore volume (pore diameter range: 1 to 10 μm) of the second aggregate particles is preferably 0.06 ml/g or more, more preferably 0.08 ml/g or more. Note that the upper limit of the sum of the total pore volume of the first aggregate particle (pore diameter range: 1 to 10 μm) and the total pore volume of the second aggregate particle (pore diameter range: 1 to 10 μm) From the viewpoint of stability in the slurry and catalyst and mechanical strength, the amount is preferably 0.3 ml/g or less, more preferably 0.2 ml/g or less. In addition, in the present invention, "the total pore volume of pores in the aggregate particle with a pore diameter within the range of 1 to 10 μm" (hereinafter referred to as "total pore volume of the aggregate particle (pore diameter range: 1 10 μm) is the sum of the pore volumes of pores with pore diameters within the range of 1 to 10 μm in the pore distribution of aggregate particles measured using a mercury porosimeter. be.

Furthermore, in the catalyst of the present invention, it is preferable that the total pore volume of the pores in the first aggregate particle having a pore diameter within the range of 1 to 10 μm is 0.03 to 0.4 ml/g. , more preferably 0.05 to 0.3 ml/g. When the total pore volume (pore diameter range: 1 to 10 μm) of the first aggregate particles is less than the lower limit, the gas diffusivity in the first aggregate particles decreases. The contact efficiency between the rhodium (Rh) inside and the gas decreases, and the catalytic performance of Rh tends to be insufficient at low temperatures or in the early stages of the reaction.On the other hand, if the upper limit is exceeded, the first aggregate particles Since the strength of the catalyst decreases, the first aggregate particles tend to become fine in the slurry or peel off from the catalyst coat layer, making it difficult to stably hold the catalyst.

Further, in the catalyst of the present invention, it is preferable that the total pore volume of the pores in the second aggregate particle having a pore diameter within the range of 1 to 10 μm is 0.03 to 0.4 ml/g. , more preferably 0.06 to 0.3 ml/g. When the total pore volume (pore diameter range: 1 to 10 μm) of the second aggregate particles is less than the lower limit, the gas diffusivity in the second aggregate particles decreases. The contact efficiency between the second active component and the gas tends to decrease, and the catalytic performance of the second active component tends to be insufficient at low temperatures or in the early stages of the reaction.On the other hand, when the upper limit is exceeded, Since the strength of the second aggregate particles decreases, the second aggregate particles tend to become fine in the slurry or peel off from the catalyst coat layer, making it difficult to stably hold the catalyst.

Further, in the catalyst of the present invention, the total pore volume of the pores in the matrix having a pore diameter within the range of 1 to 10 μm is preferably 0.03 to 0.5 ml/g, and 0.05 ml/g. More preferably, it is 0.4 ml/g. When the total pore volume of the matrix (pore diameter range: 1 to 10 μm) is less than the lower limit, the gas diffusivity in the matrix decreases, so the catalytic performance tends to be insufficient. If the upper limit is exceeded, the strength of the matrix decreases, and the first aggregate particles and the second aggregate particles cannot be stably held, and the first aggregate particles and the second aggregate particles do not form in the catalyst coated layer. It tends to peel off easily.

In the catalyst of the present invention, the content of the first aggregate particles is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, based on the total amount of the catalyst (100% by mass). When the content of the first aggregate particles is less than the lower limit, catalyst performance and heat resistance tend to decrease, while when it exceeds the upper limit, the aggregate particles tend to come into contact with each other. Further, the content of the second aggregate particles is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, based on the total amount of the catalyst (100% by mass). When the content of the second aggregate particles is less than the lower limit, the effect as a promoter for Rh tends to decrease, while when it exceeds the upper limit, the aggregate particles tend to come into contact with each other more easily. .

Further, in the catalyst of the present invention, the content of the matrix is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, based on the total amount of the catalyst (100% by mass). When the content of the matrix is less than the lower limit, the aggregate particles tend to come into contact with each other more easily, while when it exceeds the upper limit, catalyst performance and heat resistance tend to decrease.

In the catalyst of the present invention, the combination of the first metal oxide powder, the second metal oxide powder, and the third metal oxide powder is not particularly limited; Combination of powder and alumina powder, combination of zirconia powder, ceria-zirconia composite oxide powder and zirconia powder, combination of zirconia powder and alumina-ceria-zirconia composite oxide powder and zirconia powder, zirconia powder and iron-containing composite Examples include combinations of oxide powder and zirconia-alumina composite oxide powder, and combinations of powders to which La or rare earth elements are added. Among these combinations, from the viewpoint of heat resistance, structural stability, and catalytic activity, combinations of zirconia powder, ceria-zirconia composite oxide powder, and alumina powder, and combinations of zirconia powder, ceria-zirconia composite oxide powder, and zirconia powder are preferred. A combination of zirconia powder, ceria-zirconia composite oxide powder, and alumina powder is more preferred.

Furthermore, in the catalyst of the present invention, "comprising the first aggregate particles, the second aggregate particles, and the matrix" means that the catalyst "comprises the first aggregate particles and the second aggregate particles" and said matrix, or mainly consists of said first aggregate particles, said second aggregate particles, and said matrix, and may contain other components to the extent that the effects of the present invention are not impaired. It means something that is done. Examples of such other components include other metal oxides and additives used as this type of catalyst. In the latter case, the content of "the first aggregate particles, the second aggregate particles, and the matrix" in the catalyst is preferably 50% by mass or more, and 70% by mass based on the total amount of the catalyst (100% by mass). % or more is more preferable. When the content of "the first aggregate particles, the second aggregate particles, and the matrix" is less than the lower limit, the effects of the present invention tend not to be sufficiently obtained.

When the catalyst of the present invention mainly consists of "the first aggregate particles, the second aggregate particles, and the matrix," the other components may be metal oxides that can be normally used in such catalysts. There are no particular limitations, and for example, from the viewpoint of thermal stability and catalytic activity of the catalyst, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Magnesium (Mg), Oxides of metals such as rare earths such as calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), and vanadium (V), alkali metals, alkaline earth metals, and transition metals, and oxidation of these metals. Examples include mixtures of oxides of these metals, solid solutions of oxides of these metals, and composite oxides of these metals.

Specifically, the method for producing the catalyst of the present invention includes first aggregate particles ( or its raw material) (first aggregate particle preparation step); and second aggregate particles containing a second active powder in which a second active ingredient other than rhodium is supported on a second metal oxide powder. (or its raw material) (second aggregate particle preparation step); and a step of preparing a matrix (or its raw material) consisting of a third metal oxide powder containing no active ingredient (matrix preparation step). The present invention is carried out by mixing the prepared first aggregate particles (or its raw material), the prepared second aggregate particles (or its raw material), and the prepared matrix (or its raw material) using a stirrer or the like. The method includes a step of obtaining a catalyst (catalyst production step). There are no particular limitations on the method for preparing such first aggregate particles, the method for preparing second aggregate particles, the method for preparing a matrix, and the method for producing a catalyst, and known methods may be adopted as appropriate. Can be done.

In the first aggregate particle preparation step and the second aggregate particle preparation step, the volume average particle diameter of the obtained first aggregate particles and the volume average particle diameter of the second aggregate particles are each within a predetermined range. It is preferable to adjust so that Such adjustment methods include, for example, a method of agglomerating the active powder (preferably via a binder, etc.) and pulverizing the resulting agglomerates to adjust the particle size, and a method of adjusting the particle size of the slurry containing the active powder. Examples include a method of adjusting the particle size by adding a molecular flocculant and stirring the slurry with a stirrer.

In the first aggregate particle preparation step and the second aggregate particle preparation step, the total pore volume (pore diameter range: 1 to 10 μm) of the obtained first aggregate particles and the second aggregate particle It is preferable to adjust the total pore volume (pore diameter range: 1 to 10 μm) to be within a predetermined range. In such a preparation method, it is necessary to form the first aggregate particles or the second aggregate particles without compacting the first active powder or the second active powder. When powder compacting is performed in the aggregate particle preparation step, the total pore volume (pore diameter range: 1 to 10 μm) of the aggregate particles decreases, and the gas diffusivity in the aggregate particles decreases. The contact efficiency of rhodium (Rh) in the aggregate particles and the second active component in the second aggregate particles with the gas decreases, and the catalytic performance of Rh and the second activity decrease at low temperatures or in the early stage of the reaction. The catalytic performance of the components is not fully demonstrated.

In the catalyst production step, (1) the prepared first aggregate particles (or its raw material), the prepared second aggregate particles (or its raw material), and the prepared matrix (or its raw material) are combined. A method of evaporating the slurry containing the slurry to dryness, drying and calcining the obtained dry matter, and then subjecting it to pulverization treatment as necessary to adjust the particle size. ), the prepared second aggregate particles (or its raw material), and the prepared matrix (or its raw material) as separate slurries, and a method of coagulating these slurries with a polymer flocculant, etc. Can be mentioned. In this way, in the catalyst production step, the first aggregate particles (or the raw material thereof), the second aggregate particles (or the raw material thereof), and the matrix (or the raw material thereof) are formed without powder compaction. , these aggregates need to form. When powder compacting is performed in the catalyst production process, the total pore volume of the first aggregate particles (pore diameter range: 1 to 10 μm) and the total pore volume of the second aggregate particles (pore diameter range: 1 to 10 μm) 10 μm) and the gas diffusivity in the first aggregate particles and the second aggregate particles decreases. The contact efficiency between the second active component in the aggregate particles and the gas decreases, and the different catalytic performances of Rh and the second active component are not fully exhibited at low temperatures or in the early stages of the reaction.

There is no particular restriction on the form of the catalyst of the present invention; for example, it may be formed into a pellet-shaped pellet catalyst, a honeycomb-shaped monolith catalyst, etc., but the powdered catalyst may be placed as it is in a desired location such as a reaction vessel. You may. There are no particular restrictions on the method for producing this type of catalyst, and any known method can be adopted as appropriate.For example, a method of forming a catalyst into pellets to obtain a pellet-shaped catalyst, or A method of obtaining a catalyst coated (fixed) on a catalyst base material by coating the base material can be appropriately employed. In addition, there are no particular restrictions on such catalyst base materials, but they may be selected appropriately depending on the intended use of the resulting catalyst, for example, honeycomb monolith base materials, pellet base materials, plate-like base materials, etc. preferable. Further, the material of the catalyst base material is not particularly limited, but for example, base materials made of ceramics such as cordierite, silicon carbide, and mullite, and base materials made of metals such as stainless steel containing chromium and aluminum are preferable.

The use of the catalyst of the present invention is not particularly limited, and it can be effectively used, for example, as an exhaust gas purification catalyst, a VOC purification catalyst, a reforming catalyst, an air purifier catalyst, and the like. Further, there is no particular restriction on the specific method of using the catalyst of the present invention. For example, when used as an exhaust gas purification catalyst, the catalyst is brought into contact with a gas containing harmful components to be treated in a batch manner or continuously. By doing so, purification of harmful components can be achieved. Harmful components to be treated include NOx, CO, HC, SOx, etc. in exhaust gas.

EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. The methods for preparing each metal oxide powder used in Examples and Comparative Examples are shown below.

(Preparation example 1)
<Preparation of Rh/alumina-ceria-zirconia powder (Rh/ACZ powder)>
First, as the first metal oxide powder, alumina-ceria-zirconia powder (ACZ powder, Al ₂ O ₃ :CeO ₂ :ZrO ₂ :(La ₂ O ₃ +Nd ₂ O ₃ +Y ₂ O ₃ ) mass ratio=30: After dispersing 850 g of 20:44:6) in 850 ml of distilled water, 700 ml of rhodium nitrate aqueous solution containing 0.85 g of rhodium (Rh) as the first active ingredient in terms of metal was added and thoroughly stirred. The powder was impregnated with an aqueous rhodium nitrate solution. Thereafter, this slurry was evaporated to dryness on a hot stirrer set at a temperature of 150 to 200°C, and the dried product obtained was dried in the air at 150°C for 5 hours, and further dried at 200°C in the air. Heated for 5 hours. The obtained solid content was calcined in the air at 500° C. for 3 hours to obtain Rh-supported alumina-ceria-zirconia coarse powder (Rh/ACZ coarse powder). Note that the amount of Rh supported in the obtained Rh/ACZ powder was 0.1% by mass.

Next, the obtained Rh/ACZ coarse powder was pulverized using a pulverizer (“Wonder Blender” manufactured by As One Co., Ltd.) and sieved to a particle size of 32 μm or less and a volume average particle size D50 = 9.2 μm. Rh/ACZ powder was obtained.

(Preparation example 2)
<Preparation of Pd/ceria-zirconia powder (Pd/CZ powder)>
First, 297 g of ceria-zirconia solid solution powder (CZ powder, mass ratio of CeO ₂ :ZrO ₂ :(La ₂ O ₃ +Pr ₂ O ₃ )=60:30:10) as a second metal oxide powder was added to about 400 ml of distilled water. After dispersing the CZ powder, 50 ml of an aqueous palladium nitrate solution containing 3 g of palladium (Pd) as a second active ingredient in terms of metal was added and thoroughly stirred to impregnate the CZ powder with the aqueous palladium nitrate solution. Thereafter, this slurry was evaporated to dryness on a hot stirrer set at a temperature of 180 to 300°C, and the dried product obtained was dried in the air at 110°C for several hours. The obtained solid content was calcined in the air at 500° C. for 1 hour to obtain Pd-supported ceria-zirconia solid solution coarse powder (Pd/CZ coarse powder). Note that the amount of Rh supported in the obtained Pd/CZ powder was 1% by mass.

Next, the obtained Pd/CZ coarse powder was pulverized using a pulverizer (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain Pd/CZ powder having a particle size of 25 μm or less.

(Preparation example 3)
<Preparation of alumina powder>
A coarse powder of activated alumina (La ₂ O ₃ stabilized Al ₂ O ₃ ) containing 4% by mass of lanthanum (La) was pulverized using a pulverizer (“Wonder Blender” manufactured by As One Corporation) and sieved. , alumina powder having a particle size of 32 μm or less was obtained.

(Preparation example 4)
<Preparation of Rh/alumina-ceria-zirconia pellets (Rh/ACZ pellets)>
200 g of the Rh/ACZ powder (particle size: 32 μm or less) obtained in Preparation Example 1 was charged as the first active powder into a fluidized bed granulation coating device (manufactured by Freund Sangyo Co., Ltd.). While supplying air into the fluidized bed to fluidize the Rh/ACZ powder, an alumina sol binder aqueous solution containing feather-like acicular alumina particles as a binder (solid content concentration: 5.4% by mass, calcined at 500°C for 1 hour) The Rh/ACZ powder was granulated by spraying 185 g (solid content: 10 g) of specific surface area: 300 m ² /g of the subsequent solid content, and then calcined in the air at 500°C for 3 hours to form the Rh Pellets containing Rh/ACZ powder (Rh/ACZ pellets) were obtained. The amount of binder in this Rh/ACZ pellet was 5 parts by mass based on 100 parts by mass of the Rh/ACZ powder.

(Preparation example 5)
<Preparation of Pd/ceria-zirconia pellets (Pd/CZ pellets)>
In a fluidized bed granulation coating device (manufactured by Freund Sangyo Co., Ltd.), 100 g of the Pd/CZ powder (particle size: 25 μm or less) obtained in Preparation Example 2 was added as a second active powder, and Preparation Example was added as a particle structure stabilizer. 100 g of alumina powder (particle size: 32 μm or less) obtained in step 3 was added. While supplying air into the fluidized bed to fluidize the Pd/CZ powder and the alumina powder, an alumina sol containing feather-like acicular alumina particles (average length: 1 μm, average diameter: 0.01 μm) as a binder. 200 g (solid content: 11 g) of a binder aqueous solution (solid content concentration: 5.4% by mass, specific surface area of solid content after drying: 300 to 500 m ² /g) was sprayed to form the Pd/CZ powder and the alumina powder. After granulating the mixed powder, it was fired at 500° C. for 3 hours in the air to obtain pellets (Pd/CZ pellets) containing the Pd/CZ powder and the alumina powder. The amount of binder in this Pd/CZ pellet was 5 parts by mass based on 100 parts by mass of the mixed powder of the Pd/CZ powder and the alumina powder.

(Example 1)
<Sizing of Rh/ACZ pellets>
The Rh/ACZ pellets obtained in Preparation Example 4 were sieved to obtain Rh/ACZ pellets with a particle size within the range of 32 to 100 μm.

<Volume average particle diameter (D50) measurement of Rh/ACZ pellets>
A suspension was prepared by dispersing 0.1 g or less of the sized Rh/ACZ pellets (particle size: 32 to 100 μm) in 200 ml of distilled water. The volume-based particle size distribution of the Rh/ACZ pellets in this suspension was measured by a light scattering method using a laser diffraction/scattering particle size distribution analyzer ("Microtrack MT3300EX" manufactured by Nikkiso Co., Ltd.). The particle diameter (volume average particle diameter D50) at which the cumulative frequency is 50% in the particle size distribution (volume basis) was determined and was found to be D50 = 74 μm.

In addition, after subjecting the suspension after particle size distribution measurement to ultrasonication (frequency: 20 kHz, output: 30 W) for 2 minutes, the volume average particle diameter D50 of the Rh/ACZ pellets was determined in the same manner as above. As a result, D50 was 53 μm. From this result, it was confirmed that the Rh/ACZ pellets were not refined even after ultrasonication and were stably present.

<Pore distribution measurement of Rh/ACZ pellets>
The pore distribution of the sized Rh/ACZ pellets (particle size: 32 to 100 μm) was measured using a mercury porosimeter (“POWERMASTER 60GT” manufactured by Quantachrome). The results are shown in Figure 1. Based on the cumulative pore distribution shown in Figure 1, the total pore volume of the pores in the Rh/ACZ pellet with a pore diameter within the range of 1 to 10 μm was determined to be 0.181 ml/g. Ta.

<Sizing of Pd/CZ pellets>
The Pd/CZ pellets obtained in Preparation Example 5 were sieved to obtain Pd/CZ pellets having a particle size within the range of 32 to 100 μm.

<Volume average particle diameter (D50) measurement of Pd/CZ pellets>
The volume average particle diameter D50 of the sized Pd/CZ pellets (particle size: 32 to 100 μm) was measured in the same manner as in the case of the Rh/ACZ pellets, and was found to be D50 = 74 μm. Further, as in the case of the Rh/ACZ pellets, the volume average particle diameter D50 of the Pd/CZ pellets after 2 minutes of ultrasonic treatment was measured and found to be D50 = 61 μm. From this result, it was confirmed that the Pd/CZ pellets were not refined even by ultrasonication and existed stably.

<Pore distribution measurement of Pd/CZ pellets>
The pore distribution of the sized Pd/CZ pellets (particle size: 32 to 100 μm) was measured in the same manner as the Rh/ACZ pellets. The results are shown in FIG. Based on the cumulative pore distribution shown in Figure 2, the total pore volume of the pores in the Pd/CZ pellet with a pore diameter within the range of 1 to 10 μm was determined to be 0.091 ml/g. Ta.

<Catalyst preparation>
First, in 15 g of distilled water, 1.5 g of a 20 mass % citric acid aqueous solution, 0.3 g of a 50 mass % acetic acid aqueous solution, and an alumina sol binder aqueous solution (solid content concentration: 6.75) containing feather-like acicular alumina particles as a binder. Mass %, specific surface area of solid content after firing at 500°C for 1 hour: ^22.2 g (solid content: 1.5 g) was added and stirred.

To the obtained aqueous solution, 7.5 g of alumina powder (particle size: 32 μm or less) obtained in Preparation Example 3 was added as a matrix and stirred, and the above-mentioned alumina powder, which was sized as a first aggregate particle, was added and stirred. 2.5 g of Rh/ACZ pellets (particle size: 32 to 100 μm, D50 = 74 μm, total pore volume (pore diameter range: 1 to 10 μm): 0.181 ml/g) were sized as second aggregate particles. 5 g of the Pd/CZ pellets (particle size: 32 to 100 μm, D50 = 74 μm, total pore volume (pore diameter range: 1 to 10 μm): 0.091 ml/g) were added and stirred.

The obtained slurry was evaporated to dryness at 200° C. for 1 hour, the obtained dried product was dried at 300° C. for 1 hour, and further calcined at 500° C. for 1 hour in the air. The obtained calcined product was pulverized and sieved to obtain pellet catalysts having a particle size of 0.5 to 1 mm.

In the obtained pellet catalyst, the total pore volume of the Rh/ACZ pellet (pore diameter range: 1 to 10 μm) and the total pore volume of the Pd/CZ pellet (pore diameter range: 1 to 10 μm) After calculating the total,
(0.181ml/g×2.5g+0.091ml/g×5g)/(2.5g+5g)
=0.121ml/g
Met.

(Comparative example 1)
<Crushing and sizing of Rh/ACZ pellets>
The Rh/ACZ pellets obtained in Preparation Example 4 were pulverized using a pulverizer (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain Rh/ACZ pellets with a particle size of 32 μm or less.

<Crushing and sizing of Pd/CZ pellets>
The Pd/CZ pellets obtained in Preparation Example 5 were pulverized using a pulverizer (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain Pd/CZ pellets with a particle size of 32 μm or less.

<Catalyst preparation>
2.5 g of the sized Rh/ACZ pellets (particle size: 32 μm or less) were used as the first aggregate particles, and 5 g of the sized Pd/CZ pellets (particle size: 32 μm or less) were used as the second aggregate particles. Pellet catalysts having a particle size of 0.5 to 1 mm were obtained in the same manner as in Example 1, except that the catalyst was used.

(Comparative example 2)
<Powder compacting, crushing and sizing of pellet catalyst>
In Comparative Example 1, the pellet catalyst with a particle size of 0.5 mm or less, which was removed by sieving after crushing, was pressed at 3000 kgf/cm using a hydrostatic press device ("CL4-22-60" manufactured by Nikkiso Co., Ltd.). Cold isostatic pressing (CIP) was performed at a pressure of ² (molding pressure) for 2 minutes, and the resulting green compact was pulverized using a pulverizer (“Wonder Blender” manufactured by As One Co., Ltd.) and sieved. By dividing, powder pellet catalysts having a particle size of 0.5 to 1 mm were obtained.

(Comparative example 3)
<Crushing and sizing of Rh/ACZ pellets>
The Rh/ACZ pellets obtained in Preparation Example 4 were pulverized using a pulverizer (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain Rh/ACZ pellets with a particle size of 32 μm or less.

<Powder compaction, crushing and sizing of Rh/ACZ pellets>
The sized Rh/ACZ pellets (particle size: 32 μm or less) are cold pressed at a pressure of 2000 kgf/cm ² (molding pressure) using an isostatic press device (“CL4-22-60” manufactured by Nikkiso Co., Ltd.). Isostatic pressing (CIP) is performed for 2 minutes, and the resulting compacted powder is crushed using a crusher (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain particles with a particle size of 32 to 100 μm. Rh/ACZ compacted powder pellets within the range were obtained.

<Volume average particle diameter (D50) measurement of Rh/ACZ powder pellets>
The volume average particle diameter D50 of the sized Rh/ACZ compacted powder pellets (particle size: 32 to 100 μm) was measured in the same manner as in Example 1, and was found to be D50 = 84 μm.

<Pore distribution measurement of Rh/ACZ powder pellets>
The pore distribution of the sized Rh/ACZ powder pellets (particle size: 32 to 100 μm) was measured in the same manner as in Example 1. The results are shown in FIG. Based on the cumulative pore distribution shown in FIG. 3, the total pore volume (pore diameter range: 1 to 10 μm) of the Rh/ACZ powder pellet was determined to be 0.029 ml/g.

<Crushing and sizing of Pd/CZ pellets>
The Pd/CZ pellets obtained in Preparation Example 5 were pulverized using a pulverizer (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain Pd/CZ pellets with a particle size of 32 μm or less.

<Powder compaction, crushing and sizing of Pd/CZ pellets>
The sized Pd/CZ pellets (particle size: 32 μm or less) were cold pressed at a pressure of 2000 kgf/cm ² (molding pressure) using an isostatic press device (“CL4-22-60” manufactured by Nikkiso Co., Ltd.). Isostatic pressing (CIP) is performed for 2 minutes, and the resulting compacted powder is crushed using a crusher (“Wonder Blender” manufactured by As One Corporation) and sieved to obtain particles with a particle size of 32 to 100 μm. Pd/CZ compacted powder pellets within the range were obtained.

<Volume average particle diameter (D50) measurement of Pd/CZ powder pellets>
The volume average particle diameter D50 of the sized Pd/CZ powder pellets (particle size: 32 to 100 μm) was measured in the same manner as in Example 1, and was found to be D50 = 81 μm.

<Pore distribution measurement of Pd/CZ powder pellets>
The pore distribution of the sized Pd/CZ powder pellets (particle size: 32 to 100 μm) was measured in the same manner as in Example 1. The results are shown in FIG. Based on the cumulative pore distribution shown in FIG. 4, the total pore volume (pore diameter range: 1 to 10 μm) of the Pd/CZ powder pellet was determined to be 0.055 ml/g.

<Catalyst preparation>
The Rh/ACZ powder pellets sized as first aggregate particles (particle size: 32-100 μm, D50 = 84 μm, total pore volume (pore diameter range: 1-10 μm): 0.029 ml/g)2 The above-mentioned Pd/CZ compacted powder pellets (particle size: 32 to 100 μm, D50 = 81 μm, total pore volume (pore diameter range: 1 to 10 μm): 0.5 g were used and sized as second aggregate particles). A pressed powder pellet catalyst having a particle size of 0.5 to 1 mm was obtained in the same manner as in Example 1 except that 5 g of 0.055 ml/g) was used.

In the obtained powder pellet catalyst, the total pore volume of the Rh/ACZ pellet (pore diameter range: 1 to 10 μm) and the total pore volume of the Pd/CZ pellet (pore diameter range: 1 to 10 μm) When calculating the sum of
(0.029ml/g×2.5g+0.055ml/g×5g)/(2.5g+5g)
=0.046ml/g
Met.

[Pore distribution measurement of pellet catalyst]
The pore distribution of the pellet catalysts obtained in Example 1 and Comparative Examples 1 to 3 was measured using a mercury porosimeter (“POWERMASTER 60GT” manufactured by Quantachrome). The results are shown in FIG. Based on the cumulative pore distribution shown in FIG. 5, the total pore volume (pore diameter range: 1 to 10 μm) of the entire pellet catalyst was determined for each pellet catalyst. The results are shown in Table 1.

In addition, regarding the pellet catalysts obtained in Example 1 and Comparative Example 3, the total pore volume of the entire pellet catalyst (pore diameter range: 1 to 10 μm) and the difference between the Rh/ACZ pellet and the Pd/CZ pellet The total pore volume of the matrix (pore diameter range: 1 to 10 μm) was determined from the sum of the total pore volume (pore diameter range: 1 to 10 μm), and for Example 1,
(0.239ml/g×16.5g-0.121ml/g×7.5g)/9.0g
=0.337ml/g
And for Comparative Example 3,
(0.193ml/g×16.5g-0.046ml/g×7.5g)/9.0g
=0.316ml/g
Met.

[50% purification temperature measurement]
The 50% purification temperatures of CO, C ₃ H ₆ and NOx of the pellet catalysts obtained in Example 1 and Comparative Examples 1 to 3 were measured. That is, first, 0.3 g of pellet catalyst was placed in an atmospheric pressure fixed bed flow reactor, and rich model gas and lean model gas having the gas compositions shown in Table 2 were mixed under the conditions of a temperature of 500°C and a gas flow rate of 20 L/min. The pellet catalyst was pretreated by flowing it for 5 minutes while changing it every 5 seconds, and then the pellet catalyst was cooled to 100°C. Next, a steady stoichiometric model gas (corresponding to A/F = 14.2) shown in Table 2 was applied to the pretreated pellet catalyst while heating it from 100°C to 500°C at a temperature increase rate of 36°C/min. , at a rate of 20 L/min, the concentrations of CO, C ₃ H ₆ and NOx in the catalyst inlet gas and catalyst outlet gas were measured at each catalyst inlet gas _temperature , and their purification rates were calculated. The catalyst temperature (50% purification temperature) at the time when the purification rate of _NOx and NOx reached 50% was determined. The results are shown in Table 1 and FIG. 6.

As shown in Table 1 and FIG. 6, Rh/ACZ pellets and Pd/CZ pellets having a volume average particle diameter within a predetermined range were prepared without powder compaction, and using these pellets, The pellet catalyst (Example 1) prepared without compaction had a total pore volume (pore diameter range: 1 to 10 μm) of the Rh/ACZ pellets and the Pd/CZ pellets within a predetermined range. It was found that the 50% purification temperature of CO, C ₃ H ₆ and NOx was within the range, and that the purification activity at low temperatures was excellent.

On the other hand, the pellet catalysts (Comparative Examples 1 and 2) prepared using Rh/ACZ pellets and Pd/CZ pellets whose volume average particle diameter is smaller than a predetermined range are different from Rh whose volume average particle diameter is within a predetermined range. Compared to the pellet catalyst prepared using /ACZ pellets and Pd/CZ pellets (Example 1), it was found that the 50% purification temperature of CO, C ₃ H ₆ and NOx was higher, and the purification activity at low temperatures was inferior. Ta. In particular, when compacting was performed during the preparation of pellet catalysts (Comparative Example 2), the total pore volume of the entire pellet catalyst (pore diameter range: 1 ~10 μm) became extremely small, the 50% purification temperature of CO, C ₃ H ₆ and NOx was extremely high, and the purification activity at low temperatures was found to be very poor.

In addition, when powder compaction was performed when preparing Rh/ACZ pellets and Pd/CZ pellets having a volume average particle diameter within a predetermined range (Comparative Example 3), the Rh/ACZ pellets and the Pd/CZ pellets were The total pore volume (pore diameter range: 1 to 10 μm) of /CZ pellets is small, the sum of these is smaller than the predetermined range, and the 50% purification temperature of CO, C ₃ H ₆ , and NOx is high. It was found that the purification activity at low temperatures was inferior.

As explained above, according to the present invention, it is possible to obtain a catalyst that can sufficiently exhibit different catalytic performances even at low temperatures and in the early stages of reaction. Therefore, the catalyst of the present invention is useful as a catalyst used when it is necessary to exhibit different catalytic performances, such as an exhaust gas purification catalyst, a VOC purification catalyst, a reforming catalyst, and an air purifier catalyst. be. In particular, when purifying exhaust gas from internal combustion engines such as automobiles, it is useful as a catalyst etc. that can be used in place of multiple catalysts that individually exhibit different catalytic performances, and that can exhibit different catalytic performances together. .

Claims (5)

first aggregate particles containing a first active powder in which rhodium as a first active ingredient is supported on a first metal oxide powder;
second aggregate particles containing a second active powder in which a second active ingredient other than rhodium is supported on a second metal oxide powder;
a matrix consisting of a third metal oxide powder containing no active ingredient;
It is equipped with
the first active ingredient and the second active ingredient are present separately,
the first active ingredient and the second metal oxide powder are present separately;
the second active ingredient and the first metal oxide powder are present separately;
The first aggregate particles and the second aggregate particles are included in the matrix,
The volume average particle diameter of the first aggregate particles and the volume average particle diameter of the second aggregate particles are each within a range of 50 to 600 μm, and
The total pore volume of the pores in the first aggregate particle having a pore diameter within the range of 1 to 10 μm is 0.03 ml/g or more,
The total pore volume of the pores in the second aggregate particle having a pore diameter within the range of 1 to 10 μm is 0.03 ml/g or more,
The total pore volume of the pores having a pore diameter within the range of 1 to 10 μm in the first aggregate particle and the total pore volume of the pores having the pore diameter within the range of 1 to 10 μm in the second aggregate particle. The total sum with the pore volume is 0.05 ml/g or more,
At least one type selected from the group consisting of an exhaust gas purification catalyst, a VOC purification catalyst, a reforming catalyst, and an air purifier catalyst,
A catalyst characterized by: The catalyst of claim 1, wherein the second active component is palladium and the second metal oxide powder is a ceria-zirconia solid solution powder. The catalyst according to claim 1 or 2, wherein the second aggregate particles further contain alumina powder. The total pore volume of the pores within the range of 1 to 10 μm in the pore diameter of the first aggregate particle is 0.03 to 0.4 ml/g. Catalyst according to any one of the above. The total pore volume of the pores within the range of 1 to 10 μm in the pore diameter of the second aggregate particle is 0.06 to 0.4 ml/g. Catalyst according to any one of the above.