JP4901440B2 - Exhaust gas purification catalyst, regeneration method thereof, exhaust gas purification apparatus and exhaust gas purification method using the same - Google Patents

Description

  The present invention relates to an exhaust gas purification catalyst, a regeneration method thereof, an exhaust gas purification device using the same, and an exhaust gas purification method.

In order to remove harmful components such as hydrocarbon gas (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ) in exhaust gas from automobile engines, exhaust gas purification catalysts have been used conventionally. As such an exhaust gas purification catalyst, a three-way catalyst that simultaneously purifies HC, CO, and NOx in exhaust gas burned at a stoichiometric air-fuel ratio is known, and is generally made of cordierite, metal foil, etc. A base material (support base material) formed in a shape, a support (catalyst support layer) made of activated alumina powder, silica powder or the like formed on the surface of the base material, and a noble metal such as platinum supported on the support And a catalyst component.

  For example, JP-A-5-317652 (Patent Document 1) discloses an exhaust gas purification catalyst in which an alkaline earth metal oxide and platinum are supported on a porous carrier. In JP-A-6-99069 (Patent Document 2), 1 to 20 g of palladium, 50 to 250 g of alumina, and 10 to 10 of cerium oxide per 1 l of the carrier substrate on the surface of the carrier substrate. An exhaust gas purifying catalyst comprising 150 g and a catalyst component layer supporting each catalyst component of 8 to 50 g of barium oxide is disclosed. Further, in Japanese Patent Application Laid-Open No. 10-174866 (Patent Document 3), a first catalyst layer in which at least palladium is supported on a first porous carrier, and a second porous layer formed on the surface of the first catalyst layer. A second catalyst layer supporting at least rhodium on the support, and the supported mass of palladium per unit mass of the first porous support in the first catalyst layer is the second porous support unit in the second catalyst layer. There is disclosed an exhaust gas purifying catalyst that is larger than the supported mass of rhodium per mass.

  However, in the exhaust gas purifying catalysts as described in Patent Documents 1 to 3, when exposed to high temperature (especially 800 ° C. or higher) exhaust gas for a long time, a catalyst such as platinum, rhodium, or palladium supported on the carrier. Since the noble metal particles having activity are aggregated and sintering occurs, the specific surface area is reduced, so that there is a problem that the catalytic activity is lowered.

  Further, in Japanese Patent Application Laid-Open No. 2004-41866 (Patent Document 4), at least one element selected from rare earth elements that always contain rare earth elements and do not contain rare earth elements that can have a valence smaller than trivalent, cobalt , An exhaust gas purifying catalyst comprising a transition oxide other than palladium and rare earth elements and at least one element selected from Al and palladium, and a composite oxide having a perovskite structure represented by a specific formula Yes. However, in the exhaust gas purifying catalyst as described in Patent Document 4, since the noble metal is dissolved in the perovskite structure and stabilized in the oxidized state, the noble metal contained in the structure is activated by the catalyst. There is a problem that it is difficult to function as a point, and the catalytic activity is not always sufficient.

  Further, JP-A-2003-220336 (Patent Document 5) includes a support containing cerium oxide, and a catalyst metal made of a transition metal and a noble metal and supported on at least the cerium oxide, An exhaust gas purifying catalyst is disclosed in which the relationship between the atomic ratio to the cerium atom and the atomic ratio of the transition metal to the noble metal is in a specific range. However, the exhaust gas purifying catalyst as described in Patent Document 5 is not necessarily sufficient in that the precious metal is redispersed by the regeneration treatment to regenerate the catalyst activity.

In JP-A-2005-270882 (Patent Document 6), the oxide is one or more of ceria, ceria-zirconia, ceria-zirconia-yttria, and ceria-lanthanum-zirconia. A catalyst is disclosed in which catalyst metal particles made of one or two or more transition metals or transition metal oxides having one or two or more atoms of 10 to 50000 are supported on a porous carrier. Furthermore, in Japanese Patent Application Laid-Open No. 2002-79053 (Patent Document 7), a single structure of zirconium oxide containing at least one kind of noble metal, refractory inorganic oxide, cerium and lanthanum and having a tetragonal crystal structure. An exhaust gas purifying catalyst in which a catalytic active component containing a certain zirconium oxide is coated on a fire-resistant three-dimensional structure is disclosed. Further, in Japanese Patent Application Laid-Open No. 2004-141833 (Patent Document 8), a noble metal is supported on metal oxide particles containing ceria and zirconia, and the metal oxide particles contain a zirconia more than ceria. And an exhaust gas purifying catalyst having a surface layer containing more ceria than zirconia. Furthermore, in Japanese Patent Application Laid-Open No. 2004-243177 (Patent Document 9), a noble metal is supported on a composite oxide powder containing at least CeO ₂ and ZrO _{2 in} one particle, and CeO of the composite oxide powder is used. _When the weight percent of ₂ is C _Ce and the weight percent of ZrO ₂ is C _Zr , the relationship 0.5 ≦ C _Zr / C _Ce ≦ 1.5 is satisfied, and the noble metal contains pure water as pure water. An exhaust gas purifying catalyst supported on the composite oxide powder using a noble metal salt aqueous solution exhibiting a pH value lower than the water immersion pH value when suspended in water is disclosed.

  However, in the catalyst as described in Patent Document 6, since the noble metal particles are supported as clusters to achieve thermal stabilization of the noble metal particles, the catalyst activity per unit amount of the noble metal is supposed to withstand higher temperatures. There was a problem that decreased. Further, the exhaust gas purifying catalyst as described in Patent Document 7 has a problem in that the noble metal retention site is insufficient, and thus noble metal grows and the catalytic activity is lowered. Furthermore, the exhaust gas purifying catalysts as described in Patent Documents 8 to 9 have poor heat resistance because the compositions of cerium and zirconium in the support particles are not uniform, and are not necessarily sufficient in terms of suppressing the growth of noble metal grains. It was. In addition, in the exhaust gas purifying catalysts as described in Patent Documents 6 to 9, the catalytic activity per unit amount of the noble metal after long-term use is not always sufficient, and sufficient regeneration of the catalytic activity is achieved by the regeneration treatment. It was not an indication.

  On the other hand, various methods for regenerating an exhaust gas purifying catalyst in which grain growth has occurred in noble metal particles have been developed in response to the problem that the catalytic activity is reduced by the sintering as described above. For example, Japanese Patent Application Laid-Open No. 7-75737 (Patent Document 10) discloses a method for regenerating an exhaust gas purifying catalyst in which a noble metal is supported as an active species on an inorganic porous base material, in which halogen acts on the catalyst. A method is disclosed in which a halide of a noble metal is generated on the base material and then halogen is eliminated from the halide. However, in the method of regenerating the exhaust gas purifying catalyst by acting halogen as in the method described in Patent Document 10, it is very difficult to regenerate the catalyst while it is mounted on the exhaust system of the internal combustion engine. In addition, there is a limit to shortening the time required for the regeneration treatment for redispersing the grain-grown noble metal to regenerate the catalyst activity.

JP 2000-202309 A (Patent Document 11) discloses an exhaust gas purifying catalyst comprising a support containing at least one selected from alkaline earth metal oxides and rare earth oxides and platinum supported on the support. On the other hand, a method of performing an oxidation treatment and then performing a reduction treatment is disclosed. However, even the method described in Patent Document 11 is not necessarily sufficient in terms of shortening the time required for the regeneration treatment for regenerating the catalytic activity by redispersing the grown platinum particles and reducing the temperature. .
JP-A-5-317652 JP-A-6-99069 Japanese Patent Laid-Open No. 10-174866 JP 2004-41866 A JP 2003-220336 A JP-A-2005-270882 JP 2002-79053 A JP 2004-141833 A JP 2004-243177 A JP-A-7-75737 JP 2000-202309 A

  The present invention has been made in view of the above-described problems of the prior art, and even when exposed to high-temperature exhaust gas for a long time, the aggregation of the noble metal particles is sufficiently suppressed and the noble metal particle growth is sufficiently suppressed over a long period of time. It is possible to sufficiently suppress the decrease in the catalyst activity, and when the particles are grown during use, the precious metal particles can be re-dispersed in a short time even in a relatively low temperature range to easily regenerate the catalyst activity. Exhaust gas purification catalyst that can be easily regenerated even when attached to the exhaust system of an internal combustion engine, a method for regenerating the exhaust gas purification catalyst, and exhaust gas purification using the exhaust gas purification catalyst An object is to provide an apparatus and an exhaust gas purification method.

  As a result of intensive research to achieve the above object, the present inventors have been surprised by the specific catalyst having a surface oxide layer in which a noble metal is bonded to a cation of the support through oxygen on the surface of the support. In addition, it is found that the grain growth of the noble metal is sufficiently suppressed over a long period of time, and it is possible to sufficiently suppress the decrease in the catalyst activity. It has been found that the catalyst can be efficiently regenerated by subjecting the exhaust gas purification catalyst to oxidation treatment and reduction treatment, and the present invention has been completed.

The exhaust gas purifying catalyst of the present invention is an exhaust gas purifying catalyst in which a noble metal is supported on an oxide carrier,
The support is a composite oxide of zirconium and at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements and containing cerium, and the amount of the metal element contained in the support Is in the range of 51 to 75 mol% in terms of metal with respect to the support, and the amount of cerium contained in the metal element is in the range of 90 mol% or more in terms of metal with respect to the metal element A carrier of a mold structure ,
Further comprising an additive component containing at least one element selected from the group consisting of magnesium, calcium, neodymium, praseodymium, barium, lanthanum, cerium, yttrium, and scandium supported on the carrier;
The amount of the noble metal supported is in the range of 0.05 to 2% by mass with respect to the mass of the catalyst,
The loading amount of the additive component is an amount such that the molar ratio of the noble metal to the amount of the noble metal (amount of additive component / amount of noble metal) is in the range of 0.5 to 20 in terms of metal,
A surface oxide layer in which the noble metal is present in a highly oxidized state on the surface of the carrier in an oxidizing atmosphere, and the noble metal is bonded to a cation of the carrier via oxygen on the surface of the carrier; And
In a reducing atmosphere, the ratio of the amount of the noble metal that is present on the surface of the carrier in a metallic state and exposed on the surface of the carrier as measured by a CO chemical adsorption method is supported on the carrier. It is an exhaust gas purifying catalyst having an atomic ratio of 10% or more with respect to the total amount.

  In the exhaust gas purifying catalyst of the present invention, the noble metal is preferably at least one element selected from the group consisting of platinum, palladium and rhodium.

  In the exhaust gas purifying catalyst of the present invention, it is preferable that the value of the binding energy of the oxygen 1s orbit in the carrier is 531 eV or less.

  In the exhaust gas purifying catalyst of the present invention, it is preferable that the electronegativity of at least one of the cations in the carrier is lower than the electronegativity of zirconium.

  Furthermore, in the exhaust gas purifying catalyst of the present invention, a molar ratio (cation / noble metal) of the noble metal to a cation exposed on the surface of the carrier and lower than the electronegativity of zirconium is 1.5 or more. Preferably there is.

  The reason why the above object is achieved by the exhaust gas purifying catalyst of the present invention is not necessarily clear, but the present inventors speculate as follows. That is, in the exhaust gas purifying catalyst of the present invention, the electron carrier of the oxide carrier (preferably the cation in the oxide carrier is lower than the electronegativity of zirconium and the oxygen in the oxide carrier is reduced. 1s orbital bond energy value of 531 eV or less) shows a very strong interaction with noble metals. Further, in the exhaust gas purifying catalyst of the present invention having such a carrier, the surface as shown in FIG. 1 in which noble metal is bonded to the cation of the carrier through oxygen on the surface of the carrier in an oxidizing atmosphere. An oxide layer is formed. In the exhaust gas purifying catalyst of the present invention, since such a surface oxide layer is formed, noble metal grain growth can be sufficiently suppressed even when exposed to high temperature exhaust gas for a long time. Furthermore, in the exhaust gas purifying catalyst of the present invention, in a reducing atmosphere, the noble metal is in a metallic state on the surface of the carrier and is exposed on the surface of the carrier measured by a CO chemical adsorption method. Since the ratio of the amount is 10% or more in terms of the atomic ratio with respect to the total amount of the noble metal, the noble metal which is the active point of the catalyst is in a highly dispersed state (a state in which the noble metal is highly dispersed as fine particles). Exist stably on the surface and maintain high catalytic activity.

  Further, even when the exhaust gas-purifying catalyst of the present invention is used for a long period of time to grow grains, the noble metal is mixed with the support by heating in an oxidizing atmosphere containing oxygen (preferably at 500 to 1000 ° C.). A strong oxide is shown at the interface to form a surface oxide layer, which is gradually dispersed in a spread state on the surface of the carrier. As a result, the noble metal on the support is supported in a highly dispersed state in an oxide state (redispersion) by an oxidation treatment for a relatively short time. Next, the present inventors infer that the noble metal in the oxide state is reduced to the metal state by performing the reduction treatment, and the catalytic activity is regenerated.

Catalyzes for purification of exhaust gas of the present invention satisfies the following condition (I).

<Condition (I)>
An additional component containing at least one element selected from the group consisting of an alkaline earth metal element, a rare earth element, and a group 3A element supported on the carrier;
The amount of the noble metal supported is in the range of 0.05 to 2% by mass with respect to the mass of the catalyst, and
The loading amount of the additive component is such that the molar ratio (amount of additive component / amount of noble metal) in the range of 0.5 to 20 in terms of metal with respect to the amount of the noble metal.

  When the exhaust gas purifying catalyst of the present invention satisfies the condition (I), the element contained in the additive component is selected from the group consisting of magnesium, calcium, neodymium, praseodymium, barium, lanthanum, cerium, yttrium, and scandium. It is preferably at least one element selected.

Further, in this case, further comprising iron carried on the carrier,
More preferably, the iron loading is such that the molar ratio of the noble metal to the amount of the noble metal (the amount of iron / the amount of noble metal) is in the range of 0.8 to 12.

  When the exhaust gas purifying catalyst of the present invention satisfies the condition (I), the present inventors have surprisingly been able to suppress the occurrence of noble metal grain growth more sufficiently over a long period of time and reduce the catalytic activity. It has been found that it is possible to suppress more sufficiently, and furthermore, by performing oxidation treatment and reduction treatment on such an exhaust gas purification catalyst, it is possible to shorten the time required for the regeneration treatment and to reduce the temperature. It was found that the activity can be regenerated more efficiently.

In this case, the reason why the above object is achieved is not necessarily clear, but the present inventors infer as follows. That is, in the catalyst for purification of exhaust gas satisfying Condition (I), the composite oxide (preferably, the value of the binding energy of the oxygen 1s orbital indicates the following values 531 eV, the electron density of oxygen is high composite oxide) Shows extremely strong interaction with noble metals. Since the additive containing at least one additive element selected from the group consisting of alkaline earth metal elements, rare earth elements, and Group 3A elements is supported on the carrier, the basicity of the carrier is improved. For this reason, the carrier exhibits a stronger interaction with the noble metal. Therefore, the exhaust gas purifying catalyst that satisfies the condition (I) can sufficiently suppress the grain growth of the noble metal particles even when exposed to the high temperature exhaust gas for a long time, and can more sufficiently suppress the decrease in the catalytic activity.

  Furthermore, when grain growth occurs using an exhaust gas purifying catalyst that satisfies the condition (I) for a long time, a strong interaction occurs at the interface between the noble metal particles supported in the grain grown state and the carrier. Therefore, when heated in an oxidizing atmosphere containing oxygen (preferably heated at 500 to 1000 ° C.), the noble metal forms a composite oxide and a metal oxide with the support and gradually spreads on the support surface. Is done. As a result, the noble metal on the support is supported in a highly dispersed state in an oxide state (redispersion) in a relatively short period of oxidation treatment, and then the noble metal in the oxide state is reduced to the metal state by performing a reduction treatment. The present inventors infer that the catalytic activity is regenerated.

  Further, as the exhaust gas purifying catalyst of the present invention, a catalyst satisfying the following condition (II) is more preferable.

<Condition (II)>
Further comprising iron supported on the carrier;
The amount of the noble metal supported is in the range of 0.05 to 2% by mass with respect to the mass of the catalyst, and
The amount of iron supported is such that the molar ratio (the amount of iron / the amount of noble metal) to the amount of the noble metal in a metal conversion is in the range of 0.8 to 12.

  When the exhaust gas purifying catalyst of the present invention satisfies the condition (II), the inventors surprisingly suppressed the noble metal grain growth more sufficiently over a long period of time, and more sufficiently reduced the activity of the catalyst. It has been found that it is possible to regenerate the catalyst more efficiently by subjecting such an exhaust gas purifying catalyst to oxidation treatment and reduction treatment.

In this case, the reason why the above object is achieved is not necessarily clear, but the present inventors infer as follows. That is, in the catalyst for purification of exhaust gas satisfying Condition (II), the composite oxide (preferably, the value of the binding energy of the oxygen 1s orbital indicates the following values 531 eV, the electron density of oxygen is high composite oxide) Shows extremely strong interaction with noble metals. Further, iron (Fe) is supported on a carrier containing such a complex oxide. Such Fe is alloyed with a noble metal in a reducing atmosphere, and is deposited as an oxide on and around the surface of the noble metal in an oxidizing atmosphere. Therefore, by supporting Fe on the carrier, it is possible to more sufficiently suppress the noble metal grain growth in a fluctuating atmosphere when the catalyst is used, and it is possible to more sufficiently suppress the decrease in the catalyst activity. In such an exhaust gas purifying catalyst, since Fe exists in the vicinity of the noble metal, oxidation and reduction of the noble metal are facilitated, and the activity of the exhaust gas purification reaction can be further improved. In particular, reducing properties are improved by adding Fe. Furthermore, when the catalyst is regenerated by adopting the above regeneration method when the noble metal is grown by using an exhaust gas purifying catalyst that satisfies the condition (II) for a long period of time, the noble metal particles supported on the carrier are used. The present inventors infer that the diameter can be further refined and the catalyst activity can be regenerated more easily and sufficiently.

  Furthermore, the exhaust gas purifying catalyst of the present invention is more preferably one that satisfies the following condition (III).

<Condition (III)>
The support is a support having a fluorite structure containing a composite oxide of zirconium and at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements and containing cerium;
The amount of the metal element contained in the carrier is in the range of 51 to 75 mol% in terms of metal relative to the carrier, and the amount of cerium contained in the metal element is metal equivalent relative to the metal element. And the amount of the noble metal supported per 100 g of the carrier is represented by the formula (1):
X = (σ / 100) × S / s ÷ N × M _nm × 100 (1)
[In the formula (1), X represents a reference value (unit: g) of the amount of the noble metal per 100 g of the support, and σ represents the formula (2):
σ = M−50 (2)
(In the formula (2), M represents a ratio (unit: mol%) of the metal element contained in the carrier.)
Indicates the probability (unit:%) that the metal element is calculated by the metal element, S indicates the specific surface area (unit: m ² / g) of the support, and s indicates the formula (3):

(In formula (3), a represents a lattice constant (unit: Å))
Represents the unit area (unit: 単 位² / piece) per cation calculated by the above formula, N represents the Avogadro number (6.02 × 10 ²³ (unit: piece)), and M _nm is supported on the carrier. The atomic weight of the noble metal formed is shown. ]
Is not more than twice the reference value X calculated by the above and is in the range of 0.01 to 0.8 g.

  When the exhaust gas purifying catalyst of the present invention satisfies the condition (III), the present inventors surprisingly suppress the noble metal grain growth sufficiently even when exposed to high temperature exhaust gas for a long time. The catalyst per unit amount of the supported noble metal can be more sufficiently suppressed, and even when the noble metal grows in use, the noble metal is redispersed to easily regenerate the catalyst activity. It has been found that the activity is sufficiently high and excellent catalytic activity can be exhibited.

  In this case, the reason why the above object is achieved is not necessarily clear, but the present inventors infer as follows. That is, in the exhaust gas purifying catalyst satisfying the condition (III), a complex oxide of zirconium and at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements and containing cerium is added to the noble metal. It shows a very strong interaction. This is because noble metals are bonded to cerium (Ce), rare earth elements and alkaline earth metal elements through oxygen in an oxidizing atmosphere. Therefore, noble metal grain growth is sufficiently suppressed even when exposed to high temperature exhaust gas for a long time, and a decrease in catalytic activity can be sufficiently suppressed.

  Further, in the exhaust gas purifying catalyst that satisfies the condition (III), since the carrier has a fluorite structure and the ratio of cerium in the metal element is in the range as described above, cerium is dissolved in the carrier. Therefore, the decrease in specific surface area is sufficiently suppressed even in a high-temperature atmosphere, and the number of sites capable of holding the noble metal per unit amount of the carrier is sufficient, and the grain growth of the noble metal is sufficiently suppressed. Thus, it is possible to sufficiently suppress the decrease in the catalyst activity. In addition, since the amount of the noble metal is in a range that satisfies the above-described conditions, grain growth caused by excess noble metal is suppressed.

  In addition, when the catalyst for purifying exhaust gas that satisfies the condition (III) is used for a long period of time, the noble metal is heated by heating in an oxidizing atmosphere containing oxygen (preferably heated at 500 to 1000 ° C.). A composite oxide and a metal oxide are formed with the support and are gradually dispersed in a state of spreading on the support surface. As a result, the noble metal on the support is in a state of being highly dispersed and supported in an oxide state (redispersion), and then by performing a reduction treatment, the noble metal in the oxide state is reduced to the metal state, and the catalytic activity is increased. The present inventors speculate that it will be regenerated.

  The regeneration method of the exhaust gas purifying catalyst of the present invention is a method of subjecting the exhaust gas purifying catalyst of the present invention to an oxidation treatment and a reduction treatment in which the exhaust gas purification catalyst is heated in an oxidizing atmosphere containing oxygen.

  In the above method for regenerating an exhaust gas purifying catalyst of the present invention, (i) the temperature in the oxidation treatment is 500 to 1000 ° C. and / or (ii) the oxygen concentration in the oxidizing atmosphere is 1% by volume or more. Preferably there is.

  Moreover, as the regeneration method of the exhaust gas purifying catalyst of the present invention, the oxidation treatment and the reduction treatment can be performed in a state where the exhaust gas purifying catalyst is mounted on an exhaust system of an internal combustion engine.

  Further, as the regeneration method of the exhaust gas purifying catalyst of the present invention, (iii) the exhaust gas purifying catalyst is equipped with a temperature sensor, and the exhaust gas purifying catalyst is based on the operation time and the temperature detected by the temperature sensor. Including a step of determining the degree of catalyst deterioration, and a step of starting the regeneration after it is determined that the catalyst is in a deteriorated state, and / or (iv) a deterioration state of the exhaust gas purifying catalyst. Using a catalyst deterioration diagnosis device for determining whether or not the exhaust gas purifying catalyst is in a deteriorated state, and starting the regeneration process after it is determined that the catalyst is in a deteriorated state. preferable.

The first exhaust gas purification apparatus of the present invention is
An exhaust gas supply pipe;
The exhaust gas purifying catalyst of the present invention disposed inside the exhaust gas supply pipe;
A temperature sensor mounted on the exhaust gas purification catalyst;
The degree of deterioration of the exhaust gas purifying catalyst is determined based on the operation time and the temperature detected by the temperature sensor, and after it is determined that the catalyst is in a deteriorated state, heating is performed in an oxidizing atmosphere containing oxygen. A control means for controlling the oxidation process to be performed and the regeneration process to perform the reduction process to be started,
Is provided.

Moreover, the second exhaust gas purification apparatus of the present invention is
An exhaust gas supply pipe;
The exhaust gas purifying catalyst of the present invention disposed inside the exhaust gas supply pipe;
A catalyst deterioration diagnosis device for determining a deterioration state of the exhaust gas purifying catalyst;
Control for controlling so that the oxidation process for heating in the oxidizing atmosphere containing oxygen and the regeneration process for performing the reduction process are started after the deterioration state of the exhaust gas purifying catalyst is determined by the catalyst deterioration diagnostic device. Means,
Is provided.

  Furthermore, the exhaust gas purification method of the present invention is a method of purifying exhaust gas by bringing the exhaust gas into contact with the exhaust gas purification catalyst of the present invention.

  According to the present invention, noble metal particles can be sufficiently agglomerated over a long period of time even when exposed to high-temperature exhaust gas for a long period of time, thereby sufficiently suppressing a decrease in catalytic activity. When the grains grow in use, the precious metal particles can be re-dispersed in a short time even in a relatively low temperature range, and the catalytic activity can be easily regenerated, and the precious metal particles are attached to the exhaust system of the internal combustion engine. It is possible to provide an exhaust gas purification catalyst that can be easily regenerated, a method for regenerating the exhaust gas purification catalyst, an exhaust gas purification device and an exhaust gas purification method using the exhaust gas purification catalyst.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

First, the exhaust gas purifying catalyst of the present invention will be described. That is, the exhaust gas purifying catalyst of the present invention is a catalyst in which a noble metal is supported on an oxide carrier, the noble metal is present in a highly oxidized state on the surface of the carrier in an oxidizing atmosphere, and the noble metal is Having a surface oxide layer bonded to the cation of the carrier via oxygen on the surface of the carrier; and
In a reducing atmosphere, the ratio of the amount of the noble metal that is present on the surface of the carrier in a metallic state and exposed on the surface of the carrier as measured by a CO chemical adsorption method is supported on the carrier. 10% or more by atomic ratio with respect to the total amount of
It is characterized by.

  The oxide carrier according to the present invention preferably has a bond energy value of oxygen 1s orbital in the oxide carrier of 531 eV or less, particularly preferably 531 to 529 eV. When an oxide having a bond energy value exceeding 531 eV is used, the interaction between the noble metal and the carrier is not sufficiently strong, and the surface oxide layer of the noble metal and the carrier is efficiently formed in an oxidizing atmosphere. There is a tendency not to be. Further, the precious metal on the support does not tend to be sufficiently redispersed even when an oxidation treatment and a reduction treatment described later are performed. On the other hand, when a composite oxide having a binding energy value of less than 529 eV is used, the interaction between the noble metal and the support becomes too strong, and the noble metal on the support is active even when the reduction treatment is performed during the regeneration process. It tends to be difficult to return to a new state.

Examples of the oxide carrier that satisfies such conditions include the following:
_{CeO 2 -ZrO 2 -Y 2 O 3} : 530.04eV
ZrO ₂ -La ₂ O _3: 530.64eV
CeO ₂ —ZrO ₂ : 530 eV
_{CeO 2 -ZrO 2 -La 2 O 3} -Pr 2 O 3: 529.79eV
Is mentioned.

  In the exhaust gas purifying catalyst of the present invention, it is preferable that the electronegativity of at least one of the cations in the oxide carrier is lower than the electronegativity of the cation of zirconium. If the cation electronegativity in such an oxide support is higher than the cation electronegativity of zirconium, the interaction between the noble metal and the support will not be sufficiently strong, and the noble metal and the support will not react in an oxidizing atmosphere. It tends to be difficult to efficiently form the surface oxide layer, and further, the precious metal on the support tends not to be sufficiently redispersed even when the oxidation treatment and the reduction treatment described later are performed.

In addition, such an oxide support is a composite oxide of zirconium and at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements and containing cerium, and is contained in the support. The amount of the metal element is in the range of 51 to 75 mol% in terms of metal with respect to the support, and the amount of cerium contained in the metal element is 90 mol% in terms of metal with respect to the metal element. A fluorite-type structure carrier in the above range is used . Examples of such alkaline earth metal elements include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Among them, interaction with noble metals and oxides thereof. Mg, Ca, and Ba are preferable from the viewpoint of strong and high affinity. Further, as a rare-earth element include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Ga), Examples include terbium (Tb), dysprosium (Dy), ytterbium (Yb), lutetium (Lu), etc. Among them, La, Ce from the viewpoint of strong interaction with noble metals and their oxides and high affinity. , Nd, Pr, Y, and Sc are preferable, and La, Ce, Y, and Nd are more preferable. Such rare earth elements and alkaline earth metal elements having low electronegativity have strong interactions with noble metals, and therefore, they bind to noble metals through oxygen in an oxidizing atmosphere to suppress the evaporation and sintering of noble metals, Deterioration of the noble metal that is a point can be sufficiently suppressed.

In such composite oxide, and zirconia A described above, requires at least one metallic element and selected from the group consisting of rare earth elements and alkaline earth metal elements including cerium form a composite oxide is there. In other words, the zirconia A, a state in which the said metallic element is simply coexist (e.g., a zirconia particle child, the state and the oxide particles are uniformly dispersed in the metal element) in the case subjected to regeneration treatment The precious metal on the support cannot be sufficiently redispersed, and the catalytic activity is not fully restored (regenerated).

The carrier according to the present invention includes a complex oxide of zirconium and at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements and including cerium, and has a fluorite structure Is used . Here, the fluorite structure is one of the crystal structures of the AX type ₂ compound (A is a metal element, X is oxygen) and is represented by fluorite, and is a face-centered cubic lattice in a unit lattice. The structure includes four chemical formula numbers.

In such a carrier, the amount of the metal element contained in the carrier, the area by der of 51～75Mol% in terms of metal relative to the carrier. The amount of such a metal element is preferably in the range of 51.5 to 70 mol%, more preferably in the range of 52 to 65 mol% in terms of metal with respect to the support, and more preferably 52.5 A range of ˜60 mol% is particularly preferred. If the amount of the metal element is less than 51 mol%, the number of sites capable of holding the noble metal of the carrier is reduced, and the noble metal cannot be efficiently held, and the regeneration method of the present invention described later is adopted. particles of the noble metal on the support be subjected to regeneration treatment is not a not sufficiently small Te. On the other hand, if the amount of such a metal element exceeds 75 mol%, the it is difficult to maintain the zirconium ratio is less become specific surface area of the composite oxide, Ru inferior in heat resistance.

Further, the amount of cerium contained in the metal element in such a carrier is in a range of 90 mol% or more in terms of metal with respect to the metal element. In such cerium less than the amount of the 90 mol%, a metal element other than cerium is not completely dissolved in the carrier, a decrease in the specific surface area rather invited.

Further, in such a carrier, zirconium and the metal element are in a solid solution and have a uniform composition in the particles. In general, CeO ₂ in the support significantly reduces the specific surface area at the time of high-temperature reduction. Therefore, if there is a composition distribution between zirconium and cerium in the support, the heat resistance tends to decrease. However, since the composition in the carrier is uniform as described above, a decrease in specific surface area can be suppressed. Therefore, such a carrier is excellent in heat resistance.

  Furthermore, the shape of the oxide support according to the present invention is not particularly limited, but is preferably in the form of a powder because the specific surface area can be improved and higher catalytic activity can be obtained. When the oxide carrier is in powder form, the particle size (secondary particle size) of the carrier is not particularly limited and is preferably 5 to 200 μm. If the particle diameter is less than the lower limit, it is costly to make the carrier finer, and the handling tends to be difficult. On the other hand, if it exceeds the upper limit, the exhaust gas purifying catalyst of the present invention is applied to a substrate as described later. It tends to be difficult to form a stable coat layer.

  The specific surface area of such an oxide carrier is not particularly limited, but such a specific surface area can be calculated as a BET specific surface area from an adsorption isotherm using a BET isotherm adsorption equation.

Further, the specific surface area of such a carrier is preferably 1 m ² / g or more, more preferably 5 m ² / g or more, further preferably 10 m ² / g or more, and 15 m ² / g. The above is particularly preferable. When the specific surface area is less than the lower limit, it becomes difficult to support an appropriate amount of noble metal in order to exhibit sufficient catalytic activity. In addition, as long as the heat resistance of the support can be ensured, the specific surface area of the support is preferably larger, so the upper limit of the specific surface area is not particularly limited. In addition, since it is one of the important elements for maintaining the catalytic activity that the support does not cause a decrease in specific surface area in a durable atmosphere (high temperature atmosphere), It is also possible to use a material whose specific surface area has been reduced by adding a thermal history. Therefore, as the carrier according to the present invention, a carrier having a specific surface area of less than 80 m ² / g and further less than 60 m ² / g by adding a heat history in advance may be used. Such a specific surface area can be calculated as a BET specific surface area from an adsorption isotherm using a BET isotherm adsorption equation.

  In addition, the manufacturing method in particular of the said carrier concerning this invention is not restrict | limited, For example, it can obtain by the following methods. That is, in the presence of ammonia from an aqueous solution containing a salt of various metals (for example, nitrate) as a raw material of the composite oxide and, if necessary, a surfactant (for example, a nonionic surfactant). Thus, the composite oxide coprecipitate is produced, and the obtained coprecipitate is filtered, washed, dried, and further baked to obtain a support made of the composite oxide.

  In the exhaust gas purifying catalyst of the present invention, a noble metal is supported on the carrier. Examples of such noble metals include platinum, rhodium, palladium, osmium, iridium, and gold. From the viewpoint that the obtained exhaust gas purifying catalyst exhibits higher catalytic activity, platinum, rhodium, and palladium are preferable. From the viewpoint of regeneration, platinum and palladium are preferable.

  In the exhaust gas purifying catalyst of the present invention, the noble metal is present in a highly oxidized state on the surface of the support in an oxidizing atmosphere, and the noble metal is cation of the support via oxygen on the surface of the support. And a surface oxide layer formed by bonding. Therefore, in the exhaust gas purifying catalyst of the present invention, the noble metal that is the active point of the catalyst is present in a highly dispersed state on the surface of the carrier and is supported on the surface of the carrier in a stable state. It is possible to exhibit a sufficiently high catalytic activity and to sufficiently suppress the noble metal grain growth. In the present invention, the “high oxidation state” refers to a state where the noble metal is higher than zero. Further, the “oxidizing atmosphere” referred to here means an atmosphere of gas having an oxygen concentration of 0.5% by volume or more. Furthermore, the oxidation state of the noble metal on the surface of the support and the bonding state with the support can be confirmed by employing TEM (transmission electron microscope) observation or XAFS (X-ray absorption fine structure) spectrum analysis.

  In the exhaust gas purifying catalyst of the present invention, the amount of the noble metal present on the surface of the carrier measured by the CO chemical adsorption method in a reducing atmosphere is the total noble metal supported on the carrier at an atomic ratio. It is 10% (more preferably 15%) or more based on the amount. When the atomic ratio relating to the amount of the noble metal present on the surface of the support is less than 10%, the dispersed state of the noble metal existing on the support surface is insufficient, and the catalytic activity per unit amount of the noble metal is reduced. Regeneration treatment tends to make it difficult to regenerate the catalyst activity. In the present invention, the method described in JP-A-2004-340637 is adopted as such a CO chemical adsorption method. Further, the “reducing atmosphere” referred to here means an atmosphere of gas having a reducing gas concentration of 0.1% by volume or more.

  In the exhaust gas purifying catalyst of the present invention, the molar ratio between the noble metal and a cation having a lower electronegativity than zirconium in the oxide exposed on the surface of the carrier (cation / noble metal). ) Is preferably 1.5 or more. When the molar ratio of the noble metal to the cation (cation / noble metal) is less than the lower limit, a part of the noble metal tends to hardly obtain an interaction with the support.

  In the exhaust gas purifying catalyst of the present invention, the amount of the noble metal supported is in the range of 0.05 to 2% by mass (more preferably 0.1 to 0.5% by mass) with respect to the mass of the catalyst. It is preferable. If the amount of the noble metal supported is less than the lower limit, the catalytic activity obtained from the noble metal tends to be insufficient. On the other hand, if the amount exceeds the upper limit, the cost increases and grain growth tends to occur.

  In the present invention, the amount of the noble metal supported per 100 g of the carrier is not more than twice the reference value X described below and is 0.01 to 0.8 g (more preferably 0.02 to 0.00). 5 g, more preferably 0.05 to 0.3 g). When the amount of the noble metal supported is less than the lower limit, the catalytic activity obtained by the noble metal tends to be insufficient. On the other hand, when the amount exceeds the upper limit, the cost increases and grain growth easily occurs. The catalyst activity per unit amount tends to decrease.

The calculation method of the reference value X is the formula (1):
X = (σ / 100) × S / s ÷ N × M _nm × 100 (1)
[In the formula (1), X represents a reference value (unit: g) of the amount of the noble metal per 100 g of the support, and σ represents the formula (2):
σ = M−50 (2)
(In the formula (2), M represents a ratio (unit: mol%) of the metal element contained in the carrier.)
Indicates the probability (unit:%) that the metal element is calculated by the metal element, S indicates the specific surface area (unit: m ² / g) of the support, and s indicates the formula (3):

(In formula (3), a represents a lattice constant (unit: Å))
Represents the unit area (unit: 単 位² / piece) per cation calculated by the above formula, N represents the Avogadro number (6.02 × 10 ²³ (unit: piece)), and M _nm is supported on the carrier. The atomic weight of the noble metal formed is shown. ]
Indicated by. The amount of the precious metal supported per 100 g of the carrier is preferably 0.01 to 0.8 g and not more than twice the reference value X (more preferably 1.5 times, still more preferably 1 time). In addition, when two or more kinds of noble metals are supported, the atomic weight M _nm of the noble metals is obtained by adding all the values calculated by multiplying the atomic weight of each noble metal by the ratio of each noble metal to the total noble metal amount. To be calculated.

  Such a formula (1) shows the relationship between the amount of sites for stably holding the noble metal on the support, that is, the reference value X of the noble metal, the composition of the support and the specific surface area. If the amount of noble metal supported exceeds twice the reference value X calculated by the above formula (1), the amount of noble metal supported increases with respect to the amount of sites for supporting the noble metal, so that excess noble metal is present. Therefore, grain growth tends to occur, and the catalytic activity per unit amount of the noble metal tends to decrease. However, when the amount of the noble metal supported is twice or less than the reference value X, the noble metal can be redispersed more easily by performing the regeneration treatment of the present invention described later, and the catalyst per unit amount of the noble metal The activity can be regenerated more efficiently. When the loading amount of the noble metal is close to the reference value X, the amount of the noble metal approaches an appropriate amount with respect to the amount of sites for supporting the noble metal of the carrier, and the grain growth is further suppressed and the reproducibility tends to be improved. Furthermore, when the loading amount of the noble metal is equal to or less than the reference value X, it is possible to carry a noble metal amount smaller than the amount of sites for supporting the noble metal of the carrier, and the noble metal is cation on the surface of the carrier via oxygen. The noble metal is stably present on the surface of the support and is maintained in a highly dispersed state, further suppressing grain growth of the noble metal, and having a more sufficient catalytic activity per unit amount of the noble metal. Become.

FIG. 2 is a graph showing the relationship between the reference value X of the amount of noble metal in the above formula (1) and the specific surface area S of the support. FIG. 2 shows an example in which Ce _0.6 Zr _0.4 O ₂ carrier (M = 60 mol%, lattice constant a = 5.304915５) and Pt (atomic mass M _nm : 195.09) are used. It is a graph obtained by calculating.

In particular, even after a long period of use, the amount of noble metal supported per 100 g of the carrier is not more than twice the reference value X calculated by the above formula (1) and is in the range of 0.01 to 0.8 g. It is preferable to satisfy the conditions, for example, rich gas (CO (3.75 vol%) / H ₂ (1.25 vol%) / H ₂ O (3 Volume%) / N ₂ (balance)) and lean gas (O ₂ (5% by volume) / H ₂ O (3% by volume) / N ₂ (balance)) alternately flowed every 5 minutes. Even after an endurance test is performed in an atmosphere under a temperature condition of 1000 ° C. for 5 hours, it is preferable that the amount of noble metal supported per 100 g of the carrier satisfies the above conditions.

  In the exhaust gas purifying catalyst of the present invention, the noble metal is preferably supported on a carrier in the form of finer particles. The particle diameter of such noble metal is more preferably 3 nm or less, and more preferably 2 nm or less. When the particle diameter of the noble metal exceeds the upper limit, it tends to be difficult to obtain high catalytic activity.

  The method for supporting the noble metal on the carrier is not particularly limited except that the amount of the noble metal supported is adjusted so as to satisfy the above-mentioned conditions. For example, the amount of the noble metal supported satisfies the above-mentioned conditions. It is possible to employ a method in which an aqueous solution containing a noble metal salt (for example, dinitrodiamine salt) or a complex (for example, tetraammine complex) prepared as described above is contacted with the carrier, dried, and further calcined.

  In the exhaust gas purifying catalyst of the present invention, the support further carries an additive component containing at least one element selected from the group consisting of an alkaline earth metal element, a rare earth element, and a group 3A element. It is preferable. By supporting such a supporting component on the carrier, the basicity of the carrier can be further improved, and a stronger interaction can be imparted between the carrier and the noble metal supported on the carrier. It becomes possible to sufficiently suppress the grain growth and sufficiently suppress the decrease in the catalytic activity. In addition, by supporting such a supporting component on the carrier, an extremely strong interaction acts between the carrier and the noble metal as described above, and the grain growth of the noble metal tends to be suppressed. Even in this case, by adopting the regeneration method of the exhaust gas purifying catalyst of the present invention, which will be described later, the catalyst activity can be regenerated by redispersing the noble metal more efficiently in a short time.

  Moreover, as an element contained in such an additive component, the basicity of the carrier can be further improved to suppress the grain growth more sufficiently, and the catalytic activity can be revived more easily even when the noble metal grain grows. From the viewpoint that it can be used, at least one element selected from the group consisting of magnesium, calcium, neodymium, praseodymium, barium, lanthanum, cerium, yttrium, and scandium is preferable, and neodymium, barium, yttrium, and scandium are more preferable. Further, the additive component may be any element that contains the above element, for example, the element itself, an oxide of the element, or a salt of the element (carbonate, nitrate, citrate, acetate, sulfate). And mixtures thereof.

  In addition, the supported amount of such an additive component is such that the molar ratio (amount of additive component / amount of noble metal) to the amount of the noble metal in terms of metal is in the range of 0.5 to 20 (more preferably 1 to 10). Amount. If such a molar ratio is less than the lower limit, it is difficult to improve the basicity of the support because the loading amount of the additive component is not sufficient, and the effect of more sufficiently suppressing the noble metal grain growth tends to be reduced, On the other hand, when the above upper limit is exceeded, the specific surface area of the carrier tends to decrease, and the dispersibility of the noble metal tends to decrease.

Furthermore, the loading amount of such an additive component is preferably an amount such that the additive component is 1.28 × 10 ⁻⁶ to 1.28 × 10 ⁻³ mol per 1 g of the carrier. more preferably an amount that a ^{10 -6} ~5.13 × 10 -4 mol, more preferably an amount that the ^{5.13 × 10 -6 ~2.56 × 10 -4} mol, 5. It is particularly preferable that the amount is 13 × 10 ^{−6 to} 1.28 × 10 ⁻⁴ mol.

  In addition, it is preferable to control the amount of the additive component to be supported on the outer surface of the carrier by reducing the amount supported, and further from the viewpoint that the amount supported is preferably small in terms of cost. It is preferable that it is supported at a high density in the vicinity of the outer surface. In such a state, when the carrier is in a powder form, 80% or more of the additive component is 30% from the outer surface of the carrier between the outer surface of the carrier and the center of the carrier. % Is preferably carried in the region.

  Further, the method of supporting the additive component on the carrier is not particularly limited, and for example, an aqueous solution containing a salt of the above element (for example, carbonate, nitrate, acetate, citrate, sulfate) or a complex is used. A method of drying after contact with the carrier and further firing can be employed. In addition, if necessary, the support may be preheated and stabilized, and then the additive may be supported. In addition, when supporting such an additional component, the order in which the additional component and the noble metal are supported on the carrier is not particularly limited.

  In the exhaust gas purifying catalyst of the present invention, it is preferable that iron is further supported on the carrier. By supporting Fe in this way, Fe is alloyed with a noble metal in a reducing atmosphere, and on the other hand, Fe is deposited as an oxide on and around the surface of the noble metal in an oxidizing atmosphere. Can be more sufficiently suppressed, the decrease in catalytic activity tends to be more sufficiently suppressed, and further, when a regeneration process employing the exhaust gas purification catalyst regeneration method of the present invention described later is performed, It tends to be possible to sufficiently regenerate the catalytic activity by making the noble metal particles, which are active points, finer.

  As the amount of iron supported, the molar ratio (the amount of iron / the amount of noble metal) to the amount of the noble metal in terms of metal is 0.5 to 12 (more preferably 0.8 to 12, more preferably 1 to The amount is preferably in the range of 10, particularly preferably 1 to 5). When the molar ratio is less than the lower limit, the amount of iron supported is small and the effect of suppressing the grain growth of the noble metal tends to be insufficient, and when the upper limit is exceeded, excessively supported iron is not supported by the support. The catalytic activity tends to be reduced because the specific evaluation area is reduced or the surface of the noble metal is covered after long-term use. The upper limit of the molar ratio is more preferably 3 and particularly preferably 1.5 from the viewpoints of lowering the specific surface area of the support and coating the surface of the noble metal.

Further, the lower limit of the amount of iron supported is preferably an amount of 1.28 × 10 ⁻⁴ mol per 100 g of the carrier, and an amount of 2.05 × 10 ⁻⁴ mol. More preferably, the amount is 4.10 × 10 ⁻⁴ mol, and even more preferably 5.13 × 10 ⁻⁴ mol. Further, the upper limit of the amount of iron supported is preferably 1.23 × 10 ⁻¹ mol per 100 g of the carrier, and preferably 5.13 × 10 ⁻² mol. More preferably, the amount is 3.10 × 10 ⁻² mol, and particularly preferably 1.28 × 10 ⁻² mol.

  In the exhaust gas purifying catalyst of the present invention, the state of the iron supported on the carrier is not particularly limited, but it is preferable that the iron is supported closer to the noble metal. By supporting the iron in the vicinity of the noble metal, the effect of suppressing grain growth of the noble metal tends to be further improved, and a regeneration treatment employing the regeneration method of the exhaust gas purifying catalyst of the present invention described later was performed. At this time, there is a tendency that the precious metal which is an active point can be refined (redispersed) faster and the catalytic activity can be regenerated.

  Further, the method for supporting such iron is not particularly limited, and for example, an aqueous solution containing an iron salt (for example, carbonate, nitrate, acetate, citrate, sulfate) or a complex is used as the carrier. The method of drying after making it contact and also baking can be employ | adopted. Such iron loading may be carried out simultaneously with the noble metal. For example, a method in which a mixed solution of an aqueous solution of a noble metal salt and an aqueous solution of an iron salt is brought into contact with the carrier and then dried and further fired. Can be adopted. Further, if necessary, the carrier may be supported by heat treatment and then the iron or precious metal may be supported.

  Thus, when the exhaust gas purifying catalyst of the present invention comprises the carrier, the noble metal carried on the carrier, and the iron carried on the carrier, the noble metal carried on the carrier and The iron loading state (catalyst structure) is not particularly limited, but it is preferable that the iron is loaded closer to the noble metal. By supporting the iron in the vicinity of the noble metal, the effect of suppressing grain growth of the noble metal tends to be further improved, and when the regeneration treatment described below is performed, the noble metal that is the active site is further refined. Tend to be possible.

  The form of the exhaust gas purifying catalyst of the present invention is not particularly limited, and may be a form of a honeycomb-shaped monolith catalyst, a pellet-shaped pellet catalyst, or the like. The substrate used here is not particularly limited, and is appropriately selected depending on the use of the obtained catalyst, etc., but a DPF substrate, a monolith substrate, a pellet substrate, a plate substrate, etc. are suitably employed. Is done. Also, the material of such a base material is not particularly limited, but a base material made of a ceramic such as cordierite, silicon carbide, mullite, or a base material made of a metal such as stainless steel including chromium and aluminum is suitably employed. Is done. Further, the method for producing such a catalyst is not particularly limited. For example, in the case of producing a monolithic catalyst, the honeycomb-shaped substrate formed of cordierite or metal foil is made of the above carrier powder. A method in which a coat layer is formed and a noble metal is supported thereon is preferably employed. Alternatively, the above-described carrier powder may be preliminarily supported with a noble metal, and then the noble metal-supported powder may be used to form a coating layer on the substrate.

  Further, when the noble metal supported on the support is used for a long time in such an exhaust gas purifying catalyst of the present invention, the noble metal can be obtained by applying the regeneration method of the exhaust gas purifying catalyst of the present invention described later. It is possible to regenerate the particles sufficiently to regenerate the catalyst activity sufficiently. The particle size of the noble metal supported on the carrier after such regeneration treatment is preferably 3 nm or less (more preferably 2 nm or less) from the viewpoint of obtaining high catalytic activity.

  While the exhaust gas purification catalyst of the present invention has been described above, the method for regenerating the exhaust gas purification catalyst of the present invention will be described below.

  The method for regenerating an exhaust gas purifying catalyst of the present invention is a method characterized by subjecting the exhaust gas purifying catalyst of the present invention to an oxidation treatment and a reduction treatment that are heated in an oxidizing atmosphere containing oxygen. .

  As an oxidizing atmosphere in which the oxidation treatment according to the present invention is performed, noble metals corresponding to the number of moles can be oxidized as long as oxygen is contained, but the oxygen concentration is 0.5% by volume or more. It is preferably 1 to 20% by volume. If the oxygen concentration is less than the lower limit, redispersion of the noble metal on the support tends not to proceed sufficiently. On the other hand, the higher the oxygen concentration, the better from the viewpoint of oxidation, but it exceeds the oxygen concentration in the air. In order to exceed 20% by volume, a special device such as an oxygen cylinder is required, and the cost tends to increase. Moreover, as gas other than oxygen in the oxidizing atmosphere concerning this invention, it is preferable not to contain reducing gas, and it is preferable to use nitrogen gas or an inert gas.

  The heating temperature in the oxidation treatment according to the present invention may be a temperature at which the supported noble metal is oxidized, but is preferably a temperature in the range of 500 to 1000 ° C. If the oxidation treatment temperature is less than 500 ° C., the rate of redispersion of the noble metal on the support tends to be extremely slow and does not proceed sufficiently. On the other hand, if the temperature exceeds 1000 ° C., thermal contraction of the support itself tends to occur. The activity tends to decrease.

  Further, the time required for the oxidation treatment according to the present invention is appropriately selected according to the oxidation treatment temperature and the like. If the temperature is low, it takes a long time, and if the temperature is high, it tends to be short. When the oxidation treatment temperature is 500 to 1000 ° C., the time per oxidation treatment step is preferably about 1 second to 1 hour. If the oxidation treatment time is less than 1 second, the redispersion of the noble metal on the support tends not to proceed sufficiently, whereas if it exceeds 1 hour, the redispersion action of the noble metal tends to be saturated.

  The oxidation treatment according to the present invention may be carried out in a predetermined treatment apparatus after the exhaust gas purification catalyst is taken out from the exhaust system, but is preferably carried out in a state where it is mounted on the exhaust system of the internal combustion engine. As a result, the number of man-hours for the oxidation treatment can be greatly reduced, and furthermore, the oxide of the noble metal can be reduced by circulating the exhaust gas after the oxidation treatment. When the oxidation treatment is performed with the exhaust gas purification catalyst attached to the exhaust system in this manner, for example, a large amount of air is introduced from an air valve provided upstream of the catalyst, or the air-fuel ratio (A / F) of the air-fuel mixture It is possible to increase the air-fuel ratio (A / F) of the air-fuel mixture by increasing the fuel flow rate, or conversely, greatly reducing the amount of fuel supplied. Moreover, as a heating means, a catalyst may be heated with a specific heating apparatus, and you may heat using the reaction heat on a catalyst.

  If the oxidation treatment is executed with the exhaust system mounted as described above, the oxidation treatment can be performed in real time in accordance with the degree of deterioration of the catalyst performance. For example, the oxidation treatment may be performed periodically according to the driving time and travel distance of the automobile, or the catalyst performance is detected by providing a NOx sensor or CO sensor downstream of the catalyst, and the value exceeds the reference value. In some cases, oxidation treatment may be performed.

  The reduction treatment according to the present invention can be carried out by heating the catalyst in an atmosphere in which a reducing gas such as hydrogen or carbon monoxide is present. Therefore, since the engine exhaust as a whole contains a reducing gas even in a stoichiometric atmosphere, the noble metal can be sufficiently reduced. Further, in the reduction treatment, it is sufficient that the reducing gas is contained even a little, but the concentration of the reducing gas is preferably 0.1% by volume or more. If the concentration of the reducing gas is less than the lower limit, the noble metal on the support tends to hardly return to an active state. Moreover, as gas other than the reducing gas in the reducing atmosphere concerning this invention, it is preferable not to contain oxidizing gas, and it is preferable to use nitrogen gas or an inert gas.

  The heating temperature in the reduction treatment according to the present invention may be a temperature at which the oxide of the noble metal oxidized by the oxidation treatment is reduced, but is preferably 200 ° C. or higher, and a temperature in the range of 400 to 1000 ° C. It is preferable that When the reduction treatment temperature is less than 200 ° C., the oxide of the noble metal on the support tends not to be sufficiently reduced. On the other hand, when the upper limit is exceeded, thermal contraction of the support itself tends to occur and the catalytic activity tends to decrease. .

  In addition, the time required for the reduction treatment according to the present invention is appropriately selected according to the reduction treatment temperature and the like. If the temperature is low, it takes a long time, and if the temperature is high, it tends to be short. When the reduction treatment temperature is 200 ° C. or higher, the time per one reduction treatment step is preferably about 2 seconds to 5 minutes. When the reduction treatment time is less than the lower limit, the noble metal oxide tends to be not sufficiently reduced, whereas when the upper limit is exceeded, the reduction action of the noble metal oxide tends to be saturated.

  The reduction process according to the present invention may be performed in a predetermined processing apparatus after the exhaust gas purification catalyst is taken out from the exhaust system, but it is preferably performed in a state where it is mounted on the exhaust system of the internal combustion engine. As a result, the number of reduction treatment steps can be greatly reduced, and the oxide of the noble metal can be reduced simply by circulating the exhaust gas after the oxidation treatment. Thus, when the reduction treatment is performed with the exhaust gas purification catalyst mounted on the exhaust system, for example, in the case of an automobile exhaust gas purification catalyst, the stoichiometric atmosphere or oxygen in a stoichiometric equivalence ratio is insufficient. It is preferable that the exhaust gas in a rich atmosphere is brought into contact with the exhaust gas purifying catalyst. As a result, the oxidation treatment and the reduction treatment can be performed with the exhaust gas purification catalyst mounted on the exhaust system, and the regeneration treatment of the present invention can be performed as part of the air-fuel ratio control. Moreover, as a heating means, a catalyst may be heated with a specific heating apparatus, and you may heat using the heat | fever of waste gas.

  When the oxidation treatment and the reduction treatment are each in one step, the reduction treatment is performed after the oxidation treatment. However, in the regeneration method of the present invention, the oxidation treatment and the reduction treatment may be alternately repeated. In that case, the oxidation treatment may be performed first or the reduction treatment may be performed first. Further, when the oxidation treatment and the reduction treatment are alternately repeated, the total time of the former treatment and the total time of the latter treatment are not particularly limited.

Further, in the method for regenerating an exhaust gas purification catalyst of the present invention, a temperature sensor is attached to the exhaust gas purification catalyst, and the exhaust gas purification catalyst is deteriorated based on an operation time and a temperature detected by the temperature sensor. Step (I) of determining the degree;
Step (II) of starting the regeneration process after it is determined that the catalyst is in a deteriorated state;
It is preferable to contain. By including such a step, the regeneration process can be performed while confirming the deterioration state of the exhaust gas purifying catalyst, so that the catalyst can be regenerated more efficiently.

  In such a regeneration method, the exhaust gas supply pipe, the exhaust gas purification catalyst of the present invention disposed inside the exhaust gas supply pipe, the temperature sensor mounted on the exhaust gas purification catalyst, and the operation time And the temperature detected by the temperature sensor, the degree of deterioration of the exhaust gas-purifying catalyst is determined, and after the catalyst is determined to be in a deteriorated state, oxidation is performed in an oxidizing atmosphere containing oxygen. The first exhaust gas purification apparatus of the present invention can be suitably used, comprising a control means for controlling the processing and the regeneration processing for performing the reduction processing to be started.

  Such a temperature sensor is not particularly limited, and a known temperature sensor capable of detecting the temperature state of the exhaust gas purifying catalyst can be appropriately used. Moreover, as said control means, an engine control unit (ECU) is mentioned, for example.

  Further, the method for determining the degree of deterioration is not particularly limited. For example, the degree of grain growth of the noble metal supported on the catalyst (degree of deterioration) is determined in advance depending on the relationship between the operation time and temperature of the exhaust gas purification catalyst. Create a map of the relationship between the operating time and temperature until it becomes a degraded state that requires measurement and regeneration, and use the catalyst for a specific operating time at a specific temperature based on that map It is possible to adopt a method for determining that the material has deteriorated. The degree of deterioration is determined in this way, and the regeneration process is started after determining that the catalyst is in a deteriorated state.

  Further, in the step (II) of starting the regeneration process, it is preferable to perform the regeneration process by controlling so that the regeneration process is started when the temperature of the exhaust gas purification catalyst is in the range of 500 to 1000 ° C. . By performing the reproduction process under such control, it is possible to perform a more efficient reproduction process.

  Furthermore, in the method for regenerating an exhaust gas purification catalyst according to the present invention, the exhaust gas purification catalyst is sufficiently regenerated by performing the regeneration treatment in accordance with the relationship between the degree of deterioration of the exhaust gas purification catalyst and the temperature of the regeneration treatment. Therefore, it is preferable to determine the time required for controlling the time for performing the oxidation treatment and the reduction treatment. By performing the regeneration process in this way, unnecessary heating time and the like can be reduced, and the catalyst can be regenerated more efficiently. In such control, the above-described control means can be used. In addition, the method for determining the time required to sufficiently regenerate the exhaust gas-purifying catalyst by performing the regeneration treatment is not particularly limited, but the time necessary for the regeneration treatment at a specific temperature is measured in advance. There is a method of creating a map of the relationship between the time required for the reproduction process and the temperature at that time, and determining the time necessary for the reproduction process based on the map.

Moreover, in the regeneration method of the exhaust gas purification catalyst of the present invention, using the catalyst deterioration diagnostic device for determining the deterioration state of the exhaust gas purification catalyst, the step of determining the deterioration state of the exhaust gas purification catalyst;
Starting the regeneration process after it is determined that the catalyst is in a deteriorated state;
It is preferable to contain.

  And in the regeneration method of the exhaust gas purifying catalyst of the present invention including such steps, the exhaust gas supply pipe and any one of claims 1 to 7 disposed inside the exhaust gas supply pipe. An exhaust gas purification catalyst, a catalyst deterioration diagnosis device for determining a deterioration state of the exhaust gas purification catalyst, and an oxidation atmosphere containing oxygen after the deterioration state of the exhaust gas purification catalyst is determined by the catalyst deterioration diagnosis device The second exhaust gas purification apparatus of the present invention including an oxidation process for heating inside and a control means for controlling so as to start a regeneration process for performing a reduction process can be suitably used.

  The method for regenerating an exhaust gas purifying catalyst of the present invention including such steps uses a catalyst deterioration diagnosis device for determining the deterioration state of the exhaust gas purifying catalyst instead of the step (I), and The regeneration process can be performed in the same manner as the regeneration method including the above-described process (I) and process (II) except that the process of determining the deterioration state of the catalyst is employed.

  Further, such a catalyst deterioration diagnosis device is not particularly limited as long as it can determine the deterioration state of the exhaust gas purification catalyst. For example, as described in JP-A-2005-180201, And a catalyst deterioration diagnosis device. Moreover, as said control means, an engine control unit (ECU) is mentioned, for example.

  As mentioned above, although the regeneration method of the exhaust gas purifying catalyst of the present invention has been described, in the present invention, the particle size of the noble metal particles grown by performing the regeneration treatment as described above is 3 nm or less (more preferably 2 nm or less). ) Can be refined (redispersed). Then, by performing such a regeneration treatment and refining (redispersing) the noble metal particles to the particle size supported on the carrier, it becomes possible to regenerate the catalyst activity more sufficiently.

  The exhaust gas purification method of the present invention is a method characterized by purifying exhaust gas by bringing the exhaust gas into contact with the exhaust gas purification catalyst of the present invention. Such an exhaust gas purification method is not particularly limited except that the exhaust gas purification catalyst of the present invention is used to contact exhaust gas with the exhaust gas purification catalyst of the present invention. Furthermore, the method of bringing the exhaust gas into contact with the exhaust gas purification catalyst is not particularly limited, and a known method can be adopted as appropriate.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
242.6 g of cerium nitrate aqueous solution (containing 28 wt% as CeO ₂ ), 157.6 g of zirconium oxynitrate aqueous solution (containing 18 wt% as ZrO ₂ ), 12.6 g of yttrium nitrate and nonionic surfactant (product of Lion Corporation, product) Name: Leocon) To 2000 g of a mixed aqueous solution containing 10 g, 142 g of 25 wt% aqueous ammonia was added and stirred at room temperature for 10 minutes to obtain a coprecipitate. Next, the obtained coprecipitate was filtered, washed, dried at 110 ° C., and further calcined in the atmosphere at 1000 ° C. for 5 hours to cerium-zirconium-yttrium composite oxide (CeO ₂ —ZrO ₂ —Y _2). A carrier consisting of O ₃ ) was obtained. The composition ratio of the obtained composite oxide was 55 mol% CeO ₂ , 40 mol% ZrO ₂ , 5 mol% Y ₂ O ₃ . Further, when the value of the bond energy of the oxygen 1s orbit of the composite oxide was determined by XPS (X-ray photoelectron Spectroscopy), it was the value shown in Table 4.

Next, 100 g of the carrier is immersed in a nitric acid aqueous solution of dinitrodiamine platinum (platinum concentration: 4% by weight), filtered and washed, dried at 110 ° C., and further calcined at 500 ° C. for 3 hours in the atmosphere. An exhaust gas purifying catalyst (Pt / CeO ₂ —ZrO ₂ —Y ₂ O ₃ ) of the invention was obtained. The amount of platinum supported on the obtained catalyst was 1% by weight. In addition, a ratio (Ms) of platinum moles (PGM) in the obtained catalyst to cation moles (Ms) having electronegativity lower than that of zirconium in the composite oxide exposed on the surface of the support. / PGM) is shown in Table 1.

Note that the value of such a ratio (Ms / PGM) can be obtained as follows. That is, first, in the case of a ceria-based support, it is assumed that 1.54 × 10 ⁻⁵ mol of cation is present on the outermost surface per 1 m ² of the specific surface area of the support. If the proportion of cations having a lower electronegativity than zirconium is X%, 1.54 × 10 ⁻⁵ × X / 100 mol per 1 m ² of the specific surface area of the carrier is present on the outermost surface of the carrier, and zirconium is electronegative. The number of moles of cations (Ms) having an electronegativity lower than the degree. In addition, the number of moles of noble metal per 1 m ² of the specific surface area of the carrier is expressed by the following formula:
Y = W / (100 × S × M)
(In the formula, Y represents the number of moles of the noble metal, W represents the weight ratio of the noble metal to the support (unit: wt%), S represents the specific surface area (unit m ² / g) of the support, and M represents the noble metal. Atomic weight (unit: g / mol)
It can ask for. Therefore, the value of the ratio (Ms / PGM) is given by the following formula:
(Ms / PGM) = 1.54 × 10 ⁻⁵ × X × S × M / W
It can ask for.

(Example 2)
150 g of 25 wt% ammonia water was added to 1500 g of a mixed aqueous solution containing 231 g of zirconium oxynitrate aqueous solution (containing 18 wt% as ZrO ₂ ) and 63 g of lanthanum nitrate, and stirred at room temperature for 10 minutes to obtain a coprecipitate. . Next, the obtained coprecipitate is filtered, washed, dried at 110 ° C., and further calcined in the atmosphere at 1000 ° C. for 5 hours to be composed of zirconium-lanthanum composite oxide (ZrO ₂ —La ₂ O ₃ ). A carrier was obtained. The composition ratio of the obtained composite oxide was 65% by weight ZrO ₂ and 35% by weight La ₂ O ₃ . Further, when the value of the bond energy of the oxygen 1s orbit of the composite oxide was determined by XPS, it was the value shown in Table 4. Then, an exhaust gas purifying catalyst (Pt / ZrO ₂ -La ₂ O ₃ ) of the present invention was obtained in the same manner as in Example 1 except that the carrier thus obtained was used. Further, Table 1 shows Ms / PGM values of the obtained catalyst.

Example 3
Cerium-zirconium-yttrium composite oxide (CeO ₂ —ZrO ₂ —Y ₂ O ₃ , composition ratio: 55 mol% CeO ₂₎ obtained by adopting the same method as the carrier production method employed in Example 1 , 40 mol% ZrO ₂ , 5 mol% Y ₂ O ₃ ) 100 g was stirred in ion-exchanged water, and 3.38 g of barium nitrate was added thereto to obtain a mixed solution. Next, the obtained mixed solution was heated, evaporated to dryness, further dried at 110 ° C., and then calcined at 500 ° C. for 5 hours in the air. Next, 100 g of the carrier is immersed in an aqueous nitric acid solution of dinitrodiamine platinum (Pt concentration: 4% by weight), filtered, washed, dried at 110 ° C., and further calcined at 500 ° C. for 3 hours in the atmosphere. An exhaust gas purifying catalyst (Pt / Ba / CeO ₂ —ZrO ₂ —Y ₂ O ₃ ) of the invention was obtained. The amount of platinum supported in the obtained catalyst was 0.5 wt%, the amount of Ba per 1 g of support was 0.000128 mol, and the molar ratio of Pt to Ba (Ba / Pt) was 5. Moreover, the value of Ms / PGM in the obtained catalyst is shown in Tables 1 and 3.

Example 4
An exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 3 except that 5.62 g of neodymium nitrate hexahydrate was added instead of barium nitrate. In addition, Table 3 shows Ms / PGM values of the obtained catalyst.

(Example 5)
An exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 3, except that an aqueous palladium nitrate solution (Pd concentration: 4 wt%) was used instead of the nitric acid aqueous solution of dinitrodiamine platinum (Pt concentration: 4 wt%). Moreover, the value of Ms / PGM in the obtained catalyst is shown in Tables 1 and 3.

(Example 6)
An exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 4 except that an aqueous palladium nitrate solution (Pd concentration: 4 wt%) was used instead of the nitric acid aqueous solution of dinitrodiamine platinum (Pt concentration: 4 wt%). In addition, Table 3 shows Ms / PGM values of the obtained catalyst.

(Example 7)
An exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 3 except that an aqueous rhodium nitrate solution (Rh concentration: 4% by weight) was used instead of the aqueous nitric acid solution of dinitrodiamine platinum (Pt concentration: 4% by weight). Moreover, the value of Ms / PGM in the obtained catalyst is shown in Tables 1 and 3.

(Example 8)
An exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 4 except that an aqueous rhodium nitrate solution (Rh concentration: 4% by weight) was used instead of an aqueous nitric acid solution of dinitrodiamine platinum (Pt concentration: 4% by weight). In addition, Table 3 shows Ms / PGM values of the obtained catalyst.

(Comparative Example 1)
A comparative catalyst (Pt / Al ₂ O ₃ ) was obtained in the same manner as in Example 1, except that a commercially available γ-Al ₂ O ₃ powder (Grace) was used as the carrier. Moreover, the value of Ms / PGM in the obtained catalyst is shown in Tables 1 and 3.

(Comparative Example 2)
A comparative catalyst (Pt / SiO ₂ ) was obtained in the same manner as in Comparative Example 1 except that commercially available SiO ₂ powder (manufactured by Aerosil) was used as the carrier.

(Comparative Example 3)
A catalyst for exhaust gas purification for comparison was obtained in the same manner as in Comparative Example 1 except that an aqueous palladium nitrate solution (Pd concentration: 4 wt%) was used instead of an aqueous nitric acid solution of dinitrodiamine platinum (Pt concentration: 4 wt%). . In addition, Table 3 shows Ms / PGM values of the obtained catalyst.

(Comparative Example 4)
A catalyst for exhaust gas purification for comparison was obtained in the same manner as in Comparative Example 1 except that an aqueous rhodium nitrate solution (Rh concentration: 4 wt%) was used instead of the nitric acid aqueous solution of dinitrodiamine platinum (Pt concentration: 4 wt%). . In addition, Table 3 shows Ms / PGM values of the obtained catalyst.

[Evaluation of Characteristics of Exhaust Gas Purification Catalysts Obtained in Examples 1-3, 5, 7 and Comparative Example 1]
<TEM observation and XAFS measurement of precious metals>
First, for the catalysts obtained in Examples 1 to 3 and Comparative Example 1, in an oxidizing atmosphere composed of O ₂ (20% by volume) and N ₂ (80% by volume), 800% for each catalyst. Oxidation treatment was performed at 5 ° C. for 5 hours. In addition, for the catalysts obtained in Examples 5 and 7, in an oxidizing atmosphere composed of O ₂ (20% by volume) and N ₂ (80% by volume), each catalyst was treated at 1000 ° C. for 5 hours. Then, oxidation treatment was performed. And TEM (Transmission Electron Microscopy) observation was performed about each catalyst obtained in Example 1 and Comparative Example 1 after performing such oxidation treatment. Moreover, XAFS (X-ray Absorption Fine Structure) of noble metals (Pt, Pd, Rh) for each of the catalysts obtained in Examples 1 to 3, 5, 7 and Comparative Example 1 after such oxidation treatment. Measurements were made to analyze the local structure around the noble metal, and the state of the noble metal on the support was observed. The obtained TEM photographs are shown in FIG. 3 (Example 1) and FIG. 4 (Comparative Example 1), and the results obtained by XAFS measurement are shown in FIG. 5 (Example 1 and Comparative Example 1) and FIG. 6 (Example 2). ), FIG. 7 (Example 3), FIG. 8 (Example 5), and FIG. 9 (Example 7). FIG. 5 shows a spectrum obtained by Fourier transforming the EXAFS spectrum of Pt L ₃ -edge of the catalyst obtained in Example 1 and Comparative Example 1 and the Pt foil and PtO ₂ powder for reference.

<Dispersibility of precious metal after reduction treatment>
With respect to the catalysts obtained in Examples 1-3, 5, 7 and Comparative Example 1 after the oxidation treatment, a gas composed of H ₂ (10% by volume) and N ₂ (90% by volume) at 400 ° C. Reduction treatment was performed in a reducing atmosphere, and the dispersibility of the noble metal was determined by the CO chemical adsorption method described in JP-A-2004-340637. The obtained results are shown in Table 1. In addition, the higher the dispersibility (%) value, the higher the ratio of the noble metal exposed on the surface, indicating a highly dispersed metal state.

  As is clear from the results shown in FIG. 3 and FIG. 4, in the exhaust gas purifying catalyst (Example 1) of the present invention, no Pt particles were observed on the carrier in the TEM measurement. In the exhaust gas purifying catalyst of the present invention (Example 1), the presence of Pt was confirmed by analysis by EDX. Therefore, it was confirmed that Pt was supported in a very highly dispersed state in the exhaust gas purifying catalyst (Example 1) of the present invention. On the other hand, in the exhaust gas purifying catalyst for comparison (Comparative Example 1), 3-150 nm Pt particles were observed, and it was confirmed that Pt was supported in an aggregated state.

  Further, as is clear from the results shown in FIG. 5, in the exhaust gas purifying catalyst of the present invention (Example 1), since a peak due to the Pt—O bond is observed, Pt is in a highly oxidized state. (+2, +4 valence) was present. Further, in the exhaust gas purifying catalyst (Example 1) of the present invention, since a peak due to the Pt—O—Ce bond is observed, Pt is bonded to Ce, which is a cation of the carrier, via oxygen. It was confirmed that Further, the coordination number of the Pt—O—Ce bond was determined to be 3.5. This is a value smaller than the coordination number 12 when Pt is completely dissolved in the support. Therefore, Pt exists on the support surface, and a surface oxide layer of Pt and the support is formed. It was confirmed that Similarly, as is apparent from the results shown in FIGS. 6 to 9, in the exhaust gas purifying catalyst (Examples 2, 3, 5, and 7) of the present invention, the noble metal is bonded with the cation of the support through oxygen. It was confirmed that Further, since the coordination number is smaller than the coordination number when completely dissolved, the surface oxide layer of the noble metal and the support is also obtained in the catalysts obtained in Examples 2, 3, 5, and 7. It was confirmed that was formed. On the other hand, in the exhaust gas purifying catalyst for comparison (Comparative Example 1), only a large peak due to the Pt-Pt bond was observed, so that it was confirmed that Pt was present as large particles in the metal state. . Further, when the coordination number of the Pt—Pt bond was determined, it was 12, and it was confirmed that the Pt—Pt bond was present at a particle size of at least 20 nm.

  Further, as apparent from the results shown in Table 1, the exhaust gas purification catalyst for comparison (Comparative Example 1) has a dispersibility value as low as 2%, whereas the exhaust gas purification catalyst of the present invention is low. In Examples 1 to 3, 5, and 7, it was confirmed that the dispersibility values were all very high, 20% or more, and in the exhaust gas purifying catalyst of the present invention, noble metals were present in high dispersion. confirmed.

  From these results, in the exhaust gas purifying catalysts of the present invention (Examples 1 to 3, 5, and 7), the noble metal exists in a highly oxidized state on the surface of the carrier in an oxidizing atmosphere, and the noble metal is the carrier. The surface oxide layer of the noble metal and the carrier is formed by bonding with the cation of the composite oxide through oxygen exposed on the surface of the metal, and the noble metal is a highly dispersed metal in a reducing atmosphere. It was confirmed to exist in the state.

[Evaluation of characteristics of exhaust gas purifying catalysts obtained in Examples 3 to 8 and Comparative Examples 1 and 3 to 4]
<Measurement of precious metal particle size after durability test>
First, the exhaust gas purifying catalysts obtained in Examples 3 to 8 and Comparative Examples 1 and 3 to 4 were used, respectively, and a cold isotropic pressure pressurization method (CIP method) was adopted, and the pressure was 1 t / cm ^2. After powder molding, it was pulverized to a size of 0.5 to 1 mm to obtain a pellet-shaped catalyst. Next, each pellet-shaped catalyst obtained in this way is charged into a reaction vessel, and the rich gas and the lean gas shown in Table 2 are added so that the flow rate per 3 g of the catalyst is 500 cc / min in the reaction vessel. The precious metal on the support was grain-grown by flowing alternately every 5 minutes and treating at 950 ° C. for 5 hours (endurance test). The average particle diameter of the noble metal particles after such an endurance test was determined, and the results obtained are shown in Table 3. The average particle size of the noble metal particles was determined by a CO chemical adsorption method described in JP-A-2004-340637.

  As is clear from the results shown in Table 3, in the exhaust gas purifying catalyst (Examples 3 to 8) of the present invention, it was confirmed that the noble metal grain growth was more sufficiently suppressed.

[Evaluation of characteristics of exhaust gas purifying catalysts obtained in Examples 1-2 and Comparative Examples 1-2]
<Platinum redispersion test>
(Test Example 1)
Using the catalyst obtained in Example 1, platinum on the support was grown by heat treatment at 1000 ° C. for 5 hours in an atmosphere composed of 3% by volume of CO and 97% by volume of N ₂ . Then, an oxidation treatment (redispersion treatment) is performed for 30 minutes at 800 ° C. in an oxidizing atmosphere composed of 20% by volume of O ₂ and 80% by volume of N ₂ with respect to the catalyst in which platinum is grown in this manner. Attempts were made to redisperse platinum. The average particle diameter of the platinum particles after the durability test and the average particle diameter of the platinum particles after the redispersion treatment were determined, and the obtained results are shown in Table 4. In addition, the average particle diameter of platinum particle | grains was calculated | required by the CO chemical adsorption method described in Unexamined-Japanese-Patent No. 2004-340637. Further, with such redispersion treatment and reduction pretreatment by the CO chemical adsorption method, oxidation treatment and reduction treatment for each exhaust gas purification catalyst were realized, and this was designated as regeneration treatment.

(Test Example 2)
A platinum redispersion test was carried out in the same manner as in Test Example 1 except that the treatment temperature in the redispersion treatment was 500 ° C. Table 4 shows the obtained results.

(Test Example 3)
A platinum redispersion test was carried out in the same manner as in Test Example 1 except that the treatment temperature in the redispersion treatment was set to 1000 ° C. Table 4 shows the obtained results.

(Test Example 4)
A platinum redispersion test was carried out in the same manner as in Test Example 1 except that the treatment temperature in the redispersion treatment was 600 ° C. and the oxygen concentration was 3%. Table 4 shows the obtained results.

(Test Example 5)
A platinum redispersion test was carried out in the same manner as in Test Example 1 except that the catalyst obtained in Example 2 was used. Table 4 shows the obtained results.

(Comparative Test Example 1)
Next, platinum re-dispersion was performed in the same manner as in Test Example 1 except that the catalyst obtained in Comparative Example 1 was used, and the platinum on the carrier was grown by heat treatment at 800 ° C. for 5 hours in an N ₂ atmosphere. The test was conducted. Table 4 shows the obtained results.

(Comparative Test Example 2)
A platinum redispersion test was performed in the same manner as in Comparative Test Example 1 except that the treatment temperature in the redispersion treatment was set to 500 ° C. Table 4 shows the obtained results.

(Comparative Test Example 3)
A platinum redispersion test was carried out in the same manner as in Comparative Test Example 1 except that the catalyst obtained in Comparative Example 2 was used. Table 4 shows the obtained results.

  As apparent from the results shown in Table 4, according to the regeneration method of the present invention (Test Examples 1 to 5), the average particle diameter of the platinum particles that have grown by the durability test becomes very small by the redispersion treatment. Was confirmed. On the other hand, in Comparative Test Examples 1 to 3, the average particle size of the platinum particles is not reduced even when the redispersion treatment is performed. In Comparative Test Example 1 and Comparative Test Example 3, the average particle size is increased by the redispersion treatment. It was confirmed that it had closed. This is because the bond energy value of the oxygen 1s orbital in the carrier is larger than 531 eV, and the interaction between platinum and the carrier is weak, so the effect of redispersion treatment cannot be obtained. The present inventors speculate that this has been done.

<Platinum redispersion rate test>
(Test Example 6)
First, the catalyst (Pt / CeO ₂ —ZrO ₂ —Y ₂ O ₃ ) obtained in Example 1 was heat-treated at 950 ° C. for 5 hours in an atmosphere composed of CO ₃ volume% and N ₂ 97 volume%. The platinum on the carrier was grown until the average particle size became 6.7 nm (endurance test). Next, with respect to the catalyst in which platinum is grown in this manner, a reduction treatment at 700 ° C. for 60 seconds in a reducing atmosphere composed of 3% by volume of H ₂ and 97% by volume of He, and 20% by volume of O ₂ A treatment for alternately repeating an oxidation treatment (redispersion treatment) at 700 ° C. for 10 seconds in an oxidizing atmosphere composed of 80% by volume of He was performed over 100 minutes to attempt redispersion of platinum. And during the process, Pt L3-edge XANES (X-ray Absorption Near Edge Spectra) is measured every second, and the average particle diameter of platinum particles is estimated from the height of the peak called white-line of the XANES spectrum, The change with time of the average particle diameter of the platinum particles during the treatment was examined. The obtained result is shown in FIG.

(Test Example 7)
A platinum redispersion rate test was conducted in the same manner as in Test Example 6 except that the treatment temperature in the treatment of alternately repeating the reduction treatment and the oxidation treatment was 600 ° C. The obtained result is shown in FIG.

  As is apparent from the results shown in FIG. 10, according to the regeneration method of the present invention (Test Examples 6 to 7), the redispersion of platinum proceeds by alternately repeating the reduction treatment and the oxidation treatment, and the test is performed. In Example 6, the average particle size of the platinum particles was reduced to 3.6 nm, and in Example 7 to 2.9 nm. Also, the redispersion rate of platinum was higher when the processing temperature was 700 ° C. than when the processing temperature was 600 ° C.

  As described above, even in the redispersion process as short as 10 seconds, the average particle diameter of the platinum particles is reduced by repeating the redispersion process. Therefore, the regeneration process of the present invention is performed as part of the air-fuel ratio control. Therefore, the catalyst can be efficiently regenerated with the catalyst mounted on the exhaust system of the internal combustion engine. Therefore, according to the regeneration method of the present invention, it was confirmed that high catalytic activity can be maintained for a long time without requiring special maintenance.

Example 9
233 g of cerium nitrate aqueous solution (containing 28% by mass as CeO ₂ ), 152 g of zirconium oxynitrate aqueous solution (containing 18% by mass as ZrO ₂ ), 14 g of yttrium nitrate and 10 g of nonionic surfactant (product name: Leocon, manufactured by Lion Corporation) To 2000 g of the mixed aqueous solution contained, 200 g of 25% by mass ammonia water was added and stirred at room temperature for 10 minutes to obtain a coprecipitate. Next, the obtained coprecipitate was filtered and washed, dried at 110 ° C., and further calcined in the atmosphere at 1000 ° C. for 5 hours to cerium-zirconium-yttrium composite oxide (CeO ₂ —ZrO ₂ —Y _2). A carrier consisting of O ₃ ) was obtained. The composition ratio of the resulting composite oxide (CZY) was 68 wt% _CeO 2, 28 wt% _ZrO 2, 4 _wt% Y 2 _{O 3.} Moreover, when the value of the bond energy of the oxygen 1s orbital of the composite oxide was determined by XPS (X-ray photoelectron Spectroscopy), the values shown in Table 5 were obtained.

  Next, 100 g of the obtained carrier was stirred in ion-exchanged water, and 3.38 g of barium nitrate was added thereto to obtain a mixed solution. Then, the obtained mixed solution is heated and evaporated to dryness, then dried at a temperature condition of 110 ° C., and further calcined in the atmosphere at a temperature condition of 500 ° C. for 5 hours, and an additive component containing barium in the carrier Was added to obtain an additive-supporting carrier.

Subsequently, the obtained additive-supported carrier was immersed in an aqueous nitric acid solution of dinitrodiamine platinum (platinum concentration: 4% by mass), filtered and washed, then dried at a temperature of 110 ° C., and further 500 ° C. in the atmosphere. The catalyst for exhaust gas purification of the present invention in the form of a powder in which an additive component containing Pt and Ba was supported on the carrier was obtained by calcining for 3 hours under the following temperature conditions. The powdery exhaust gas purifying catalyst of the present invention thus obtained is compacted at a pressure of 1 t / cm ^{2 using} a cold isostatic pressing method (CIP method), and then 0.5 to The catalyst was pulverized to a size of 1 mm to obtain a pellet-shaped catalyst. In the obtained exhaust gas purification catalyst, the supported amount of Pt is 0.5 mass%, the supported amount of Ba in the additive component is 0.000128 mol per 1 g of the carrier, and the amount of Pt and the additive component The molar ratio of the amount of Ba (Ba / Pt) was 5.

(Example 10)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 9 except that 5.62 g of neodymium nitrate hexahydrate was added instead of barium nitrate. Table 5 shows the amounts of Pt and Ba supported in the obtained exhaust gas purification catalyst.

(Example 11)
Except that the amount of barium nitrate added was changed to 0.677 g, a pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 9. Table 5 shows the amounts of Pt and Ba supported in the obtained exhaust gas purification catalyst.

(Example 12)
Except that the amount of barium nitrate added was changed to 1.35 g, a pellet-shaped exhaust gas purification catalyst of the present invention was obtained in the same manner as in Example 9. Table 5 shows the amounts of Pt and Ba supported in the obtained exhaust gas purification catalyst.

(Example 13)
Except that the amount of barium nitrate added was changed to 6.77 g, a pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 9. Table 5 shows the amounts of Pt and Ba supported in the obtained exhaust gas purification catalyst.

(Example 14)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 9 except that the amount of barium nitrate added was changed to 0.677 g, and 1.05 g of iron nitrate was further added to the mixed solution. Table 5 shows the amounts of Pt, Ba, and Fe supported on the obtained exhaust gas purification catalyst.

(Example 15)
Exhaust gas purification of the present invention in the form of pellets in the same manner as in Example 14 except that a mixed solution of barium nitrate and iron nitrate was further added with an addition amount of nitric acid aqueous solution of dinitrodiamine platinum to carry Pt, Ba and Fe simultaneously. A catalyst was obtained. Table 5 shows the amounts of Pt, Ba, and Fe supported on the obtained exhaust gas purification catalyst.

(Example 16)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 12 except that the calcination temperature condition for obtaining the support was changed from 1000 ° C to 700 ° C. Table 5 shows the amounts of Pt and Ba supported in the obtained exhaust gas purification catalyst.

(Example 17)
An exhaust gas purification catalyst for comparison was manufactured using the same carrier as that used in Example 9. That is, 100 g of the carrier was immersed in an aqueous nitric acid solution of dinitrodiamine platinum (platinum concentration: 4 mass%), filtered, washed, dried at a temperature of 110 ° C., and further dried in the atmosphere at a temperature of 500 ° C. for 3 hours. An exhaust gas purification catalyst for comparison in the form of a powder having Pt supported on a carrier was obtained. The amount of platinum supported in the obtained catalyst was 0.5% by mass. Further, the exhaust gas purifying catalyst thus obtained is compacted at a pressure of 1 t / cm ^{2 using} a cold isostatic pressing method (CIP method), and then has a size of 0.5 to 1 mm. Then, it was pulverized into a pellet-shaped catalyst. The amount of Pt supported in the obtained exhaust gas purification catalyst is shown in Table 5.

(Comparative Example 5)
A pellet-shaped exhaust gas purification catalyst for comparison was obtained in the same manner as in Example 17 except that a commercially available γ-Al ₂ O ₃ powder (Grace) was used as the carrier. The amount of Pt supported in the obtained exhaust gas purification catalyst is shown in Table 5.

<Durability test>
Durability tests were performed using the pellet-shaped catalysts obtained in Examples 9 to 17 and Comparative Example 5, respectively. That is, the catalyst was charged into the reaction vessel, and the rich gas and the lean gas shown in Table 2 were alternately flowed every 5 minutes so that the flow rate per 3 g of the catalyst was 500 cc / min. The precious metal on the support was grown by treatment for 5 hours (endurance test). The average particle diameter of the noble metal after such an endurance test was determined, and the results obtained are shown in Table 5. In addition, the average particle diameter of the noble metal was determined by a CO chemical adsorption method described in JP-A-2004-340637.

<Platinum redispersion test>
For each exhaust gas purifying catalyst obtained in Examples 9 to 17 and Comparative Example 5 after the durability test, in an oxidizing atmosphere composed of 20% by volume O ₂ and 80% by volume N ₂ at 750 ° C. An oxidation treatment (redispersion treatment) was performed for 30 minutes, and redispersion of the noble metal was attempted. Table 5 shows the average particle diameter of the noble metal particles of each exhaust gas purifying catalyst after such redispersion treatment. In addition, the average particle diameter of the noble metal was determined by a CO chemical adsorption method described in JP-A-2004-340637. With such redispersion treatment and reduction pretreatment by the CO chemical adsorption method, oxidation treatment and reduction treatment for each exhaust gas purification catalyst were realized, and this was designated as regeneration treatment.

  As is clear from the results shown in Table 5, it was confirmed that noble metal grain growth was more sufficiently suppressed in the exhaust gas purifying catalysts of the present invention (Examples 9 to 17, especially Examples 9 to 16). It was done. In addition, it was confirmed by the regeneration method of the present invention that the exhaust gas purifying catalyst of the present invention (Examples 9 to 17, especially Examples 9 to 16) sufficiently refined the noble metal, thereby regenerating the catalyst activity. It was confirmed that it can be easily performed.

(Example 18)
242.6 g of cerium nitrate aqueous solution (including 28% by mass as CeO ₂ ), 157.6 g of zirconium oxynitrate aqueous solution (including 18% by mass as ZrO ₂ ), 12.6 g of yttrium nitrate and nonionic surfactant (product of Lion Corporation, product) Name: Leocon) A mixture of 2000 g containing 10 g of aqueous solution, 142.2 g of 25% strength by weight ammonia water was added and stirred at room temperature for 10 minutes to obtain a coprecipitate. Next, the obtained coprecipitate was filtered and washed, dried at 110 ° C., and further calcined in the atmosphere at 1000 ° C. for 5 hours to cerium-zirconium-yttrium composite oxide (CeO ₂ —ZrO ₂ —Y _2). A carrier consisting of O ₃ ) was obtained. The composition ratio of the resulting composite oxide (CZY) is 67.9 _wt% CeO 2, 28.4 _wt% ZrO 2, it was 3.7 _wt% Y 2 _{O 3.}

  Next, 100 g of the obtained carrier was stirred in ion-exchanged water, and 2.092 g of iron nitrate was added thereto to obtain a mixed solution. Then, the obtained mixed solution is heated and evaporated to dryness, and then dried under a temperature condition of 110 ° C., and further calcined in the atmosphere at a temperature condition of 500 ° C. for 5 hours to load iron on the carrier and add A component-supported carrier was obtained.

Subsequently, the obtained additive-supported carrier was immersed in an aqueous nitric acid solution of dinitrodiamine platinum (platinum concentration: 4% by mass), filtered and washed, then dried at a temperature of 110 ° C., and further 500 ° C. in the atmosphere. The catalyst for exhaust gas purification of the present invention in powder form in which Pt and Fe were supported on the carrier was obtained by calcining for 3 hours under the above temperature conditions. The powdery exhaust gas purifying catalyst of the present invention thus obtained is compacted at a pressure of 1 t / cm ^{2 using} a cold isostatic pressing method (CIP method), and then 0.5 to The catalyst was pulverized to a size of 1 mm to obtain a pellet-shaped catalyst. In the obtained exhaust gas-purifying catalyst, the supported amount of Pt is 1% by mass, the supported amount of Fe is 0.00513 mol per 100 g of the carrier, and the molar ratio of the amount of Pt to the amount of Fe (Fe / Pt ) Was 1 in terms of metal.

(Example 19)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 1 except that the amount of iron nitrate added was changed to 1.046 g and the amount of Pt supported was changed to 0.5% by mass. Table 8 shows the supported amounts of Pt and Fe and the molar ratio of Fe and Pt in the obtained exhaust gas purification catalyst.

(Example 20)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 19 except that the amount of iron nitrate added was changed to 2.092 g. Table 8 shows the supported amounts of Pt and Fe and the molar ratio of Fe and Pt in the obtained exhaust gas purification catalyst.

(Example 21)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 19 except that the amount of iron nitrate added was changed to 5.229 g. Table 8 shows the supported amounts of Pt and Fe and the molar ratio of Fe and Pt in the obtained exhaust gas purification catalyst.

(Example 22)
Exhaust gas purification of the present invention in the form of pellets in which a supported component containing Ba element was further supported in the same manner as in Example 19 except that the addition amount of iron nitrate was changed to 1.046 g and 0.677 g of barium nitrate was further added. A catalyst was obtained. Table 8 shows the amounts of Pt, Fe, and Ba supported on the obtained exhaust gas purification catalyst.

(Example 23)
Exhaust gas purifying catalyst of the present invention in the form of pellets further carrying a supported component containing Ba element was obtained in the same manner as in Example 22 except that a nitric acid solution of dinitrodiamine platinum was added simultaneously with iron nitrate and barium nitrate. It was. Table 8 shows the amounts of Pt, Fe, and Ba supported on the obtained exhaust gas purification catalyst.

(Example 24)
An exhaust gas purifying catalyst for comparison was manufactured using the same carrier as that used in Example 18. That is, 100 g of the carrier was immersed in an aqueous nitric acid solution of dinitrodiamine platinum (platinum concentration: 4 mass%), filtered, washed, dried at a temperature of 110 ° C., and further dried in the atmosphere at a temperature of 500 ° C. for 3 hours. An exhaust gas purification catalyst for comparison in the form of a powder having Pt supported on a carrier was obtained. The amount of Pt supported in the obtained catalyst was 1% by mass. Further, the exhaust gas purifying catalyst for comparison obtained in this way was compacted at a pressure of 1 t / cm ² by adopting a cold isostatic pressing method (CIP method), and then 0.5 The catalyst was pulverized to a size of ˜1 mm to obtain a pellet-shaped catalyst.

(Example 25)
A pellet-shaped exhaust gas purifying catalyst of the present invention was obtained in the same manner as in Example 24 except that the amount of Pt supported was changed to 0.5% by mass. Table 8 shows the amount of Pt supported in the obtained exhaust gas purification catalyst.

(Example 26)
Exhaust gas purification catalysts for comparison in pellet form were obtained in the same manner as in Example 19 except that the amount of iron nitrate added was changed to 0.523 g. Table 8 shows the supported amounts of Pt and Fe and the molar ratio of Fe and Pt in the obtained exhaust gas purification catalyst.

(Example 27)
Exhaust gas purification catalysts for comparison in pellet form were obtained in the same manner as in Example 19 except that the amount of iron nitrate added was changed to 15.69 g. Table 8 shows the supported amounts of Pt and Fe and the molar ratio of Fe and Pt in the obtained exhaust gas purification catalyst.

<Durability test (I)>
Durability test (I) was carried out using the pellet-shaped catalysts obtained in Examples 18 and 24, respectively. That is, Pt on the carrier was grown by treatment for 10 hours at a temperature of 950 ° C. in a gas atmosphere composed of H ₂ (3% by volume) and N ₂ (97% by volume) (endurance test (I )). The average particle diameter of Pt after such an endurance test was determined, and the obtained results are shown in Tables 6 and 7. In addition, the average particle diameter of Pt was calculated | required by the CO chemical adsorption method described in the X-ray-diffraction method (XRD) and Unexamined-Japanese-Patent No. 2004-340637. Table 6 shows the average particle size determined by XRD, and Table 7 shows the average particle size determined by the CO chemical adsorption method.

  As is clear from the results shown in Table 6, it was confirmed that even in a simple rich atmosphere, the presence of Fe in the vicinity of Pt suppresses the grain growth of Pt. Furthermore, in the catalyst obtained in Example 18, the Pt (1, 1, 1) diffraction line was shifted to the wide-angle side, and Fe was dissolved in Pt and alloyed.

<Regeneration test (I)>
For each exhaust gas purifying catalyst of Examples 18 and 24 after the endurance test (I), first, an oxidation treatment was performed at 800 ° C. for 1 minute in an oxidizing atmosphere composed of 20 vol% O ₂ and 80 vol% He. (Redispersion treatment) was performed, and redispersion of Pt was attempted. Table 7 shows the average particle diameter of Pt of each exhaust gas purifying catalyst after such redispersion treatment. In addition, the average particle diameter of Pt was calculated | required by the CO chemical adsorption method described in Unexamined-Japanese-Patent No. 2004-340637. With such redispersion treatment and reduction pretreatment by the CO chemical adsorption method, oxidation treatment and reduction treatment for each exhaust gas purification catalyst were realized, and this was designated as regeneration treatment.

  As shown in Table 7, after the durability test in a rich atmosphere, the Pt particle size of the exhaust gas purifying catalyst obtained in Example 18 was estimated to be larger than the Pt particle size of the catalyst obtained in Example 24. As is clear from these results, the Pt particle size shown in Table 6 was single-order, so that Fe cannot be adsorbed on the outermost surface of the active site by forming a solid solution and alloying with Pt. This is influenced by the measurement method (CO chemisorption method). Therefore, the Pt particle size shown in Table 7 does not indicate the true Pt particle size. In addition, after the regeneration treatment, the Pt particle diameter of the catalyst of Example 18 was smaller than that of the catalyst of Example 24. This was because iron oxide precipitated from the alloyed active sites and the Pt surface appeared. This is because the amount of adsorption of CO increased. From these results, it was confirmed that in the catalyst obtained in Example 18, the growth of Pt grains was suppressed in a rich atmosphere, and the active sites were regenerated by performing regeneration treatment.

<Durability test (II)>
Durability tests were performed using the pellet-shaped catalysts obtained in Examples 19 to 23 and 25 to 27, respectively. That is, a catalyst is charged in a reaction vessel, and a rich gas and a lean gas shown in Table 2 are alternately introduced every 5 minutes so that the flow rate per 3 g of the catalyst is 500 cc / min, and the treatment is performed at a temperature condition of 950 ° C. for 5 hours. By doing so, Pt on the carrier was grown (endurance test (II)). The average particle diameter of Pt after such an endurance test was determined by the CO chemical adsorption method described in JP-A No. 2004-340637, and the obtained results are shown in Table 8.

<Regeneration test (II)>
Each of the exhaust gas purifying catalysts 19 to 23 and 25 to 27 after the durability test (II) was oxidized at 750 ° C. for 30 minutes in an oxidizing atmosphere composed of 20 vol% O ₂ and 80 vol% N _2. Processing (redispersion processing) was performed, and redispersion of Pt was attempted. Table 8 shows the average particle diameter of Pt of each exhaust gas purifying catalyst after such redispersion treatment. In addition, the average particle diameter of Pt was calculated | required by the CO chemical adsorption method described in Unexamined-Japanese-Patent No. 2004-340637. With such redispersion treatment and reduction pretreatment by the CO chemical adsorption method, oxidation treatment and reduction treatment for each exhaust gas purification catalyst were realized, and this was designated as regeneration treatment.

  As is clear from the results shown in Table 8, the exhaust gas purifying catalyst of the present invention obtained in Examples 19 to 23 in which the molar ratio of Fe to Pt (Fe / Pt) is in the range of 0.8 to 12 is The exhaust gas purification catalyst obtained in Example 25 in which the value of Fe / Pt is 0 and in Examples 26 to 27 in which the value of Fe / Pt is outside the range of 0.8 to 12 is rich / lean. It was confirmed that the Pt grain growth after the durability test was suppressed. Furthermore, in the exhaust gas purifying catalyst of the present invention (Examples 19 to 23), it was confirmed that the catalyst activity can be sufficiently regenerated and high catalyst activity can be obtained because the Pt particle diameter after regeneration treatment is fine. Further, when the amount of Fe supported is small like the catalyst obtained in Example 26, the effect of suppressing the grain growth of Pt and the refinement of the particles during the regeneration process tends to be insufficient. On the other hand, it was confirmed that when the amount of Fe supported was large as in the catalyst obtained in Example 27, the specific surface area of the support tends to decrease. Further, from the results of the exhaust gas purifying catalysts obtained in Examples 22 to 23, Ba (additive component) is equally effective whether it is supported before or simultaneously with Pt. confirmed.

  From the results as described above (Tables 6 to 7 and Table 8), in the exhaust gas purifying catalyst of the present invention (Examples 18 to 27, especially Examples 18 to 23), noble metal grain growth is more sufficiently suppressed. It was confirmed that Further, it was confirmed by the regeneration method of the present invention that the exhaust gas purifying catalyst of the present invention (Examples 18 to 27, especially Examples 18 to 23) sufficiently refined the noble metal, thereby regenerating the catalyst activity. It was confirmed that it can be easily performed.

(Example 28)
First, cerium as a carrier - zirconium - praseodymium - produced lanthanum composite oxide _{(CeO 2 -ZrO 2 -Pr 2 O} 3 -La 2 O 3). That is, first, 217.3 g of a 28 wt% cerium nitrate aqueous solution, 205.4 g of an 18 wt% zirconium oxynitrate aqueous solution, 2.18 g of praseodymium nitrate, 2.89 g of lanthanum nitrate, a nonionic surfactant (product name: Lion Corporation) (Leocon) 10 g was dissolved in 2 L of ion exchanged water, 25 wt% ammonia water was added in an amount of 1.2 times the cation, and the resulting coprecipitate was filtered and washed to obtain a carrier precursor. Next, the obtained carrier precursor was dried at 110 ° C. and then calcined in the atmosphere at 1000 ° C. for 5 hours to form a fluorite-type carrier composed of a cerium-zirconium-praseodymium-lanthanum composite oxide (composition ratio). : 53 mol% CeO ₂ , 45 mol% ZrO ₂ , 0.5 mol% Pr ₂ O ₃ , 0.5 mol% La ₂ O ₃ , the amount M of metal element relative to the support (metal conversion): 55 mol%). The obtained carrier had a lattice constant of 5.304５.

Next, an exhaust gas purification catalyst of the present invention was produced by loading a noble metal on the carrier. That is, after impregnating and supporting 25 g of the carrier obtained as described above in a mixed solution obtained by mixing 0.625 g of a nitric acid aqueous solution (platinum concentration: 4% by weight) of dinitrodiamine platinum in 200 ml of ion-exchanged water, to obtain a 500 ° C. for 3 hours calcined to exhaust gas purifying catalyst of the present invention _{(Pt (0.1g) / CeO 2} -ZrO 2 -Pr 2 O 3 -La 2 O 3 (100g)) in the atmosphere.

(Example 29)
First, cerium as a carrier - zirconium - praseodymium - produced yttrium composite oxide _{(CeO 2 -ZrO 2 -Pr 2 O} 3 -Y 2 O 3). Specifically, 218.1 g of a 28 wt% cerium nitrate aqueous solution, 201.7 g of an 18 wt% zirconium oxynitrate aqueous solution, 2.19 g of praseodymium nitrate, 5.13 g of yttrium nitrate, a nonionic surfactant (trade name: manufactured by Lion Corporation) (Leocon) 10 g was dissolved in 2 L of ion exchanged water, 25 wt% ammonia water was added in an amount of 1.2 times the cation, and the resulting coprecipitate was filtered and washed to obtain a carrier precursor. Next, the obtained carrier precursor was dried at 110 ° C. and then calcined in the atmosphere at 1000 ° C. for 5 hours to form a fluorite-type carrier composed of a cerium-zirconium-praseodymium-yttrium composite oxide (composition ratio). : 53 mol% CeO ₂ , 44 mol% ZrO ₂ , 0.5 mol% Pr ₂ O ₃ , 1 mol% Y ₂ O ₃ , the amount M of metal element relative to the support (metal conversion): 56 mol%. The obtained carrier had a lattice constant of 5.304５.

Next, an exhaust gas purification catalyst of the present invention was produced by loading a noble metal on the carrier. That is, after impregnating and supporting 25 g of the carrier obtained as described above in a mixed solution obtained by mixing 1.563 g of a nitric acid aqueous solution (platinum concentration: 4% by weight) of dinitrodiamine platinum with 200 ml of ion-exchanged water, to obtain a 500 ° C. for 3 hours calcined to exhaust gas purifying catalyst of the present invention _{(Pt (0.25g) / CeO 2} -ZrO 2 -Pr 2 O 3 -Y 2 O 3 (100g)) in the atmosphere.

(Example 30)
First, a cerium-zirconium composite oxide (CeO ₂ —ZrO ₂ ) was produced as a support. Specifically, first, 273.3 g of a 28 wt% cerium nitrate aqueous solution, 130.4 g of an 18 wt% zirconium oxynitrate aqueous solution, and 10 g of a nonionic surfactant (product name: Leocon, manufactured by Lion Corporation) were dissolved in 2 L of ion-exchanged water. 25 wt% aqueous ammonia was added in an amount equivalent to 1.2 times the cation, and the resulting coprecipitate was filtered and washed to obtain a carrier precursor. Next, the obtained carrier precursor was dried at 110 ° C. and then calcined in the atmosphere at 1000 ° C. for 5 hours to form a fluorite-type carrier composed of a cerium-zirconium composite oxide (composition ratio: 70 mol% CeO ₂ , 30 mol% ZrO ₂ , and the amount M of metal element relative to the carrier (metal conversion): 70 mol%). The obtained carrier had a lattice constant of 5.334５.

Next, an exhaust gas purification catalyst of the present invention was produced by loading a noble metal on the carrier. That is, after impregnating and supporting 25 g of the carrier obtained as described above in a mixed solution obtained by mixing 1.563 g of a nitric acid aqueous solution (platinum concentration: 4% by weight) of dinitrodiamine platinum with 200 ml of ion-exchanged water, The exhaust gas-purifying catalyst (Pt (0.25 g) / CeO ₂ —ZrO ₂ (100 g)) of the present invention was obtained by calcination at 500 ° C. for 3 hours in the air.

(Example 31)
First, a cerium-zirconium-yttrium composite oxide (CeO ₂ —ZrO ₂ —Y ₂ O ₃ ) was produced as a carrier. That is, first, ion exchange of 242.6 g of 28 wt% cerium nitrate aqueous solution, 157.6 g of 18 wt% zirconium oxynitrate aqueous solution, 12.6 g of yttrium nitrate, and 10 g of nonionic surfactant (product name: Leocon, manufactured by Lion Corporation) It melt | dissolved in 2L of water, 25 wt% ammonia water was added 1.2 times equivalent with respect to the cation, and the obtained coprecipitate was filtered and wash | cleaned, and the support | carrier precursor was obtained. Next, the obtained carrier precursor was dried at 110 ° C., and then calcined at 1000 ° C. for 5 hours in the air to form a fluorite-type carrier composed of a cerium-zirconium-yttrium composite oxide (composition ratio: 60 mol). % CeO ₂ , 35 mol% ZrO ₂ , 2.5 mol% Y ₂ O ₃ , the amount M of metal element relative to the support (metal conversion): 65 mol%). The obtained carrier had a lattice constant of 5.305.

Next, an exhaust gas purification catalyst of the present invention was produced by loading a noble metal on the carrier. That is, first, 25 g of the carrier obtained as described above was added to a mixed solution obtained by mixing 0.169 g of barium nitrate in 200 ml of ion-exchanged water, impregnated and supported, and then fired at 500 ° C. for 5 hours in the atmosphere. Thus, a catalyst precursor was obtained. Next, 25 g of the catalyst precursor was added to a mixed solution obtained by mixing 1.563 g of a nitric acid aqueous solution (platinum concentration: 4% by weight) of dinitrodiamine platinum in 200 ml of ion-exchanged water, and then impregnated and supported at 500 ° C. in the atmosphere. And the exhaust gas-purifying catalyst (Pt (0.5 g) / CeO ₂ —ZrO ₂ —Y ₂ O ₃ —BaO (100 g)) of the present invention was obtained.

(Example 32)
Exhaust gas purifying catalyst of the present invention (Pt (0.5 g) / CeO ₂ —ZrO ₂ —Y ₂ O) in the same manner as in Example 31 except that the amount of barium nitrate mixed in the mixed solution was changed to 0.338 g. _3- BaO (100 g)) was obtained.

(Example 33)
Exhaust gas purifying catalyst (Pt (0)) of the present invention was prepared in the same manner as in Example 28 except that the amount of nitric acid aqueous solution (platinum concentration: 4% by weight) of dinitrodiamine platinum mixed in the mixed solution was changed to 3.125 g. _{.5g) / CeO 2 -ZrO 2 -Pr} 2 O 3 -La 2 O 3 (100g)) was obtained.

(Example 34)
Exhaust gas purifying catalyst (Pt (Pt ()) for comparison in the same manner as in Example 28 except that the amount of nitric acid aqueous solution (platinum concentration: 4% by weight) of dinitrodiamine platinum mixed in the mixed solution was changed to 6.25 g. _{1g) / CeO 2 -ZrO 2 -Pr} 2 O 3 -La 2 O 3 (100g)) was obtained.

(Example 35)
Exhaust gas purification catalyst (Pt (0.25 g) / CeO ₂ —ZrO ₂ (100 g)) for comparison was obtained in the same manner as in Example 30, except that the nonionic surfactant was not mixed.

<Durability test A (1000 ° C.)>
Using the exhaust gas purifying catalysts obtained in Examples 28 to 30 and 34 to 35, rich / lean durability tests simulating the durability mode of the three-way catalyst were performed. That is, first, each catalyst was pulverized to a size of 0.5 to 1 mm in diameter at a pressure of 1 t / cm ² using a cold isostatic pressing method (CIP method) to obtain a pellet-shaped catalyst. Next, a rich gas (CO (3.75 vol%) / H ₂ (1.25 vol%) / H ₂ O (3 Volume%) / N ₂ (balance)) and lean gas (O ₂ (5 volume%) / H ₂ O (3 volume%) / N ₂ (balance)) are alternately flowed every 5 minutes (model gas) The atmosphere was maintained at 1000 ° C. for 5 hours (endurance test A). The specific surface area of each catalyst after such an endurance test and the average particle diameter of the noble metal were determined, and the results obtained are shown in Table 10. In addition, the average particle diameter of the noble metal was determined by a CO chemical adsorption method described in JP-A-2004-340637.

Further, using the specific surface area value after such an endurance test, for each catalyst, the following formula (4):
X = (σ / 100) × S / s ÷ N × M _nm × 100 (4)
(Σ, S, s, N and M _nm in the formula are the same as those in the formula (1).)
The ratio (V / X) of the supported amount V of Pt with respect to the reference value X obtained by calculating. Table 10 shows the obtained results. The ratio (V / X) of the supported amount V of Pt with respect to the reference value X obtained by calculating the above equation (4) of the exhaust gas purifying catalyst of the present invention (Examples 28 to 30) is about 0.00. 59 (Example 28), about 1.23 (Example 29), and about 0.51 (Example 30). On the other hand, in the exhaust gas purifying catalysts obtained in Examples 34 to 35, they were about 5.58 (Example 34) and about 7.50 times (Example 35), respectively.

<Evaluation of three-way catalyst activity>
Table 9 shows the exhaust gas purification catalyst (initial) obtained in Examples 28, 30, 34, and 35, and the exhaust gas purification catalyst of Examples 28, 30, 34, and 35 after the durability test A, respectively. In the stoichiometric model gas shown, a variable atmosphere gas in which λ = 1 ± 0.02 (2 sec) by CO (75% by volume) / H ₂ (25% by volume) or O ₂ (100% by volume) is added to 1 g of the catalyst. After flowing at a flow rate of 3.5 L / min and treating at 550 ° C. for 10 minutes, the temperature was raised from 100 ° C. to 550 ° C. at a temperature rising rate of 12 ° C./min, and the 50% purification temperature of each component was measured. Table 10 shows the 50% purification temperature of propylene (C ₃ H ₆ ). In addition, the 50% purification temperature of propylene shown in Table 10 is a measure of the performance of the three-way catalyst, and the lower this temperature, the higher the activity of the catalyst.

  Further, the CO adsorption amount per unit amount of Pt after the durability test A was compared using the exhaust gas purifying catalyst (initial stage) obtained in Example 28 as a reference (measurement of specific activity). The results are shown in Table 10. It should be noted that the specific activity value obtained in this manner indicates that the larger the value is, the higher the activity than the catalyst (initial) obtained in Example 28, and the closer the value is to 1, the higher the value obtained in Example 28. It shows that the activity per unit amount of Pt is close to the catalyst obtained (initial), and the activity per unit amount of Pt is lower than the catalyst (initial) obtained in Example 28 as the value is smaller than 1. Indicates.

  From the results of the three-way catalyst performance (50% purification temperature of propylene) after the endurance test of the exhaust gas purification catalysts obtained in Examples 28 and 34 shown in Table 10, the amount of Pt supported was obtained in Example 28. It can be seen that the catalyst obtained in Example 34, which is 10 times the catalyst, shows higher activity. However, the value of the specific activity of the catalyst obtained in Example 34 decreased to 0.04 after the durability test, whereas the catalyst obtained in Example 28 had a specific activity even after the durability test. The value was as high as 0.85. From these results, it was confirmed that the exhaust gas purifying catalyst of the present invention (Example 28) can sufficiently suppress the deterioration of the catalyst performance. This is because, in the exhaust gas purifying catalyst obtained in Example 28, there is a sufficient holding site for the amount of noble metal on the surface of the carrier, so that the Pt grain growth is suppressed and the performance difference before and after the durability test is small. On the other hand, in the exhaust gas purifying catalyst obtained in Example 34, it is surmised that excess Pt grows after the durability test and the catalytic activity is remarkably reduced with respect to the initial performance.

  In addition, when comparing the three-way catalyst performance after the durability test of the exhaust gas purification catalysts obtained in Examples 30 and 35 (propylene 50% purification temperature), despite the same Pt amount and the same carrier composition, It can be seen that there is a difference close to 100 ° C. in the 50% purification temperature of propylene. As a result, even if the exhaust gas purification catalyst obtained in Example 29 and the carrier used have the same composition, the carrier used in the exhaust gas purification catalyst obtained in Example 35 has a specific surface area. Since it is not sufficient, it is surmised that there is not a sufficient holding site for the amount of the noble metal on the surface of the carrier, and the noble metal cannot be held in a highly dispersed state.

<Durability test B (950 ° C.)>
Using the exhaust gas purifying catalyst obtained in Examples 28, 29 and 31 to 34, a rich / lean durability test simulating the durability mode of the three-way catalyst was performed. That is, first, each catalyst was pulverized to a size of 0.5 to 1 mm in diameter at a pressure of 1 t / cm ² using a cold isostatic pressing method (CIP method) to obtain a pellet-shaped catalyst. Next, the rich gas (CO (5 vol%) / CO ₂ (10 vol%) / H ₂ O (3 vol%) / N ₂ is adjusted to 500 cc / min with respect to 3 g of the obtained pellet-shaped catalyst. (Balance)) and lean gas (O ₂ (5 vol%) / CO ₂ (10 vol%) / H ₂ O (3 vol%) / N ₂ (balance)) are alternately flowed every 5 minutes ( Under a model gas atmosphere), the temperature was maintained at 950 ° C. for 5 hours (endurance test).

  The specific surface area of each catalyst after such an endurance test and the average particle diameter of the noble metal were determined, and the results obtained are shown in Table 11. In addition, the average particle diameter of the noble metal particles was determined by a CO chemical adsorption method described in JP-A-2004-340637.

<Reproduction processing conditions>
Using 0.7 g of each of the exhaust gas purifying catalysts of Examples 28, 29 and 31 to 34 after the durability test B, O ₂ (20 vol%) / He (80 vol.) So as to be 150 ml / min per 0.7 g of the catalyst. %) In an oxidizing atmosphere in which a gas comprising 80% was introduced, an oxidation treatment (redispersion treatment) was performed at 800 ° C. for 15 minutes, and redispersion of the noble metal was attempted. Table 11 shows the average particle diameter of the noble metal of each exhaust gas purifying catalyst after such redispersion treatment. In addition, the average particle diameter of the noble metal was determined by a CO chemical adsorption method described in JP-A-2004-340637. With such redispersion treatment and reduction pretreatment by the CO chemical adsorption method, oxidation treatment and reduction treatment for each exhaust gas purification catalyst were realized, and this was designated as regeneration treatment.

  As is clear from the results shown in Table 11, it was confirmed that the exhaust gas purifying catalysts obtained in Examples 28, 29, and 31 to 33 were suppressed in Pt grain growth after the durability test. Further, in the exhaust gas purifying catalysts obtained in Examples 28, 29 and 31 to 33, the activity (specific activity) per unit amount of Pt was as high as 0.17 or more after the durability test, and further, the regeneration treatment. As a result, it was confirmed that the Pt particle diameter was reduced and the specific activity was regenerated to near 0.4. On the other hand, in the exhaust gas purifying catalyst obtained in Example 34, it was confirmed that the noble metal was grown and the specific activity was reduced to 0.1 or less. Further, it was confirmed that the specific activity was not regenerated so much even when the regeneration treatment was performed.

  Further, the exhaust gas purifying catalysts obtained in Examples 31 and 32 were obtained by supporting noble metal after supporting barium, which is an alkaline earth metal, on the support surface. It was confirmed that it was suppressed. Such a result is presumed to be due to the improvement of the basicity of the support by addition of barium. Further, the ratio (V / X) of the supported amount V of Pt with respect to the reference value X obtained by calculating the expression (4) in Table 11 is a value calculated by assuming that the amount of barium supported on the carrier is uniform throughout the bulk. For this reason, it can be inferred that it is smaller than the actual size. Also in the exhaust gas purifying catalyst obtained in Example 33, it was confirmed that the Pt grain growth was suppressed, and the specific activity was regenerated by refining Pt by regeneration treatment. In addition, it was confirmed that these effects were more remarkable in the exhaust gas purifying catalyst.

  As described above, according to the present invention, it is possible to sufficiently suppress the noble metal particle growth over a long period of time by sufficiently suppressing the aggregation of the noble metal particles even when exposed to a high temperature exhaust gas for a long time, thereby reducing the catalytic activity. In addition, when the grains grow during use, the precious metal particles can be redispersed in a short time even in a relatively low temperature range, and the catalyst activity can be easily regenerated. Provided are an exhaust gas purifying catalyst that can be easily regenerated even when mounted in a system, a method for regenerating the exhaust gas purifying catalyst, an exhaust gas purifying device using the exhaust gas purifying catalyst, and an exhaust gas purifying method. It becomes possible.

  Therefore, the present invention is a technique for using an exhaust gas purifying catalyst for removing harmful components such as HC, CO, NOx, etc., in exhaust gas discharged from an automobile engine for a long time without causing deterioration of catalytic activity. As very useful.

FIG. 1 is a schematic diagram showing a state of a surface oxide layer in which a noble metal is bonded to a cation of a carrier via oxygen on the surface of the carrier. FIG. 2 shows the case where Ce _0.6 Zr _0.4 O ₂ (M = 60 mol%, lattice constant a = 5.304915Å) as a support and Pt (M _nm = 195.09) as a noble metal. It is a graph which shows the relationship between the specific surface area S and the reference value X of the quantity of noble metal calculated by Formula (1). 2 indicates a range of 0.01 to 0.8 g, which is not more than twice the reference value X. FIG. 3 is a transmission electron microscope (TEM) photograph of the exhaust gas purifying catalyst obtained in Example 1. 4 is a transmission electron microscope (TEM) photograph of the exhaust gas-purifying catalyst obtained in Comparative Example 1. FIG. FIG. 5 is a graph showing a spectrum obtained by Fourier transforming the EXAFS spectrum of the Pt L ₃ -edge of the exhaust gas purifying catalyst obtained in Example 1 and Comparative Example 1 and the Pt foil and PtO ₂ powder for reference. FIG. 6 is a graph showing a spectrum obtained by Fourier transforming the EXAFS spectrum of the exhaust gas purifying catalyst obtained in Example 2. FIG. 7 is a graph showing a spectrum obtained by Fourier transforming the EXAFS spectrum of the exhaust gas purifying catalyst obtained in Example 3. FIG. 8 is a graph showing a spectrum obtained by Fourier transforming the EXAFS spectrum of the exhaust gas purifying catalyst obtained in Example 5. FIG. 9 is a graph showing a spectrum obtained by Fourier transforming the EXAFS spectrum of the exhaust gas purifying catalyst obtained in Example 7. FIG. 10 is a graph showing the results of a platinum redispersion rate test.

Claims (15)

An exhaust gas purifying catalyst in which a noble metal is supported on an oxide carrier,
The support is a composite oxide of zirconium and at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements and containing cerium, and the amount of the metal element contained in the support Is in the range of 51 to 75 mol% in terms of metal with respect to the support, and the amount of cerium contained in the metal element is in the range of 90 mol% or more in terms of metal with respect to the metal element A carrier of a mold structure ,
Further comprising an additive component containing at least one element selected from the group consisting of magnesium, calcium, neodymium, praseodymium, barium, lanthanum, cerium, yttrium, and scandium supported on the carrier;
The amount of the noble metal supported is in the range of 0.05 to 2% by mass with respect to the mass of the catalyst,
The loading amount of the additive component is an amount such that the molar ratio of the noble metal to the amount of the noble metal (amount of additive component / amount of noble metal) is in the range of 0.5 to 20 in terms of metal,
A surface oxide layer in which the noble metal is present in a highly oxidized state on the surface of the carrier in an oxidizing atmosphere, and the noble metal is bonded to a cation of the carrier via oxygen on the surface of the carrier; And
In a reducing atmosphere, the ratio of the amount of the noble metal that is present on the surface of the carrier in a metallic state and exposed on the surface of the carrier as measured by a CO chemical adsorption method is supported on the carrier. An exhaust gas purifying catalyst having an atomic ratio of 10% or more with respect to the total amount of.   The exhaust gas-purifying catalyst according to claim 1, wherein the noble metal is at least one element selected from the group consisting of platinum, palladium, and rhodium.   The exhaust gas purifying catalyst according to claim 1 or 2, wherein a value of binding energy of 1s orbital of oxygen in the carrier is 531 eV or less.   The exhaust gas-purifying catalyst according to any one of claims 1 to 3, wherein an electronegativity of at least one of the cations in the carrier is lower than an electronegativity of zirconium.   The molar ratio (cation / noble metal) between the noble metal and a cation exposed on the surface of the support and lower than the electronegativity of zirconium is 1.5 or more. The exhaust gas-purifying catalyst according to Item. Before SL loading amount of the noble metal per carrier 100g has the formula (1):
X = (σ / 100) × S / s ÷ N × M _nm × 100 (1)
[In the formula (1), X represents a reference value (unit: g) of the amount of the noble metal per 100 g of the support, and σ represents the formula (2):
σ = M−50 (2)
(In the formula (2), M represents a ratio (unit: mol%) of the metal element contained in the carrier.)
Indicates the probability (unit:%) that the metal element is calculated by the metal element, S indicates the specific surface area (unit: m ² / g) of the support, and s indicates the formula (3):
(In formula (3), a represents a lattice constant (unit: Å))
Represents the unit area (unit: 単 位² / piece) per cation calculated by the above formula, N represents the Avogadro number (6.02 × 10 ²³ (unit: piece)), and M _nm is supported on the carrier. The atomic weight of the noble metal formed is shown. ]
The exhaust gas-purifying catalyst according to any one of claims 1 to 5 , which is not more than twice the reference value X calculated by the formula (1) and is in the range of 0.01 to 0.8 g. A method for regenerating an exhaust gas purifying catalyst, comprising subjecting the exhaust gas purifying catalyst according to any one of claims 1 to 6 to an oxidation treatment and a reduction treatment in an oxidizing atmosphere containing oxygen. The regeneration method according to claim 7 , wherein a temperature in the oxidation treatment is 500 to 1000 ° C. The regeneration method according to claim 7 or 8 , wherein an oxygen concentration in the oxidizing atmosphere is 1% by volume or more. The regeneration method according to any one of claims 7 to 9 , wherein the oxidation treatment and the reduction treatment are performed in a state where the exhaust gas-purifying catalyst is attached to an exhaust system of an internal combustion engine. Attaching a temperature sensor to the exhaust gas purification catalyst, and determining a degree of deterioration of the exhaust gas purification catalyst based on an operation time and a temperature detected by the temperature sensor;
Starting the regeneration process after it is determined that the catalyst is in a deteriorated state;
Including The reproducing method according to any one of claims 7-10. Using a catalyst deterioration diagnosis device for determining a deterioration state of the exhaust gas purification catalyst, and determining a deterioration state of the exhaust gas purification catalyst;
Starting the regeneration process after it is determined that the catalyst is in a deteriorated state;
Including The reproducing method according to any one of claims 7-10. An exhaust gas supply pipe;
The exhaust gas purifying catalyst according to any one of claims 1 to 6 disposed inside the exhaust gas supply pipe,
A temperature sensor mounted on the exhaust gas purification catalyst;
The degree of deterioration of the exhaust gas purifying catalyst is determined based on the operation time and the temperature detected by the temperature sensor, and after it is determined that the catalyst is in a deteriorated state, heating is performed in an oxidizing atmosphere containing oxygen. A control means for controlling the oxidation process to be performed and the regeneration process to perform the reduction process to be started,
An exhaust gas purification apparatus comprising: An exhaust gas supply pipe;
The exhaust gas purifying catalyst according to any one of claims 1 to 6 disposed inside the exhaust gas supply pipe,
A catalyst deterioration diagnosis device for determining a deterioration state of the exhaust gas purifying catalyst;
Control for controlling so that the oxidation process for heating in the oxidizing atmosphere containing oxygen and the regeneration process for performing the reduction process are started after the deterioration state of the exhaust gas purifying catalyst is determined by the catalyst deterioration diagnostic device. Means,
An exhaust gas purification apparatus comprising: An exhaust gas purification method for purifying exhaust gas by bringing the exhaust gas into contact with the exhaust gas purification catalyst according to any one of claims 1 to 6 .