JP6789491B2 - Metal foil catalyst and its manufacturing method, and catalyst converter - Google Patents

Description

The present invention relates to a metal foil catalyst, a method for producing the same, and a catalytic converter.
The present application claims priority based on Japanese Patent Application No. 2015-166264 filed in Japan on August 25, 2015, the contents of which are incorporated herein by reference.

Exhaust gas from gasoline-fueled automobiles (gasoline vehicles) includes hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NO _x ), and the like. For this reason, purification of exhaust gas from gasoline-powered vehicles has become a major social problem in terms of air pollution and the like.

Gasoline vehicles are equipped with a device (catalytic converter) that purifies the components in the exhaust gas by reduction and oxidation.
Conventionally, catalytic converters are mainly manufactured by a wet impregnation method.
For example, the following steps (i) to (v) produce a catalyst converter (so-called honeycomb catalyst) in which a honeycomb-shaped base material is coated with a powder-like catalyst component.
(I) The precious metal of the bullion is crushed into powder.
(Ii) This powder is dissolved in a solvent to prepare a solution of a noble metal salt.
(Iii) A porous powder such as alumina is added to the noble metal salt solution and stirred to prepare a dispersion (slurry) of the porous powder impregnated with the noble metal salt solution.
(Iv) Separately, a honeycomb-shaped base material is prepared, and a wash coat layer is formed in advance on the surface of the base material.
(V) The slurry is applied to a honeycomb-shaped base material on which a wash coat layer is formed and fired.

FIG. 12 shows an embodiment of a conventional honeycomb catalyst.
The honeycomb catalyst 200 shown in FIG. 12 includes a honeycomb-shaped base material 210 (carrier) and a catalyst layer 220 provided on the base material 210. Preferably, the thickness of the base material 210 is 40 μm or more, and the thickness of the catalyst layer 220 is about 10 to 30 μm.
As the base material 210, for example, a metal honeycomb base material (thickness 40 to 50 μm) made of metal and a ceramic honeycomb base material (thickness 100 to 200 μm) made of ceramics are used.
The catalyst layer 220 contains a porous powder such as alumina and a noble metal supported on the porous powder.

According to Patent Document 1, a catalyst layer is formed by applying a slurry obtained by kneading γ-alumina powder, metal component powder and water on the surface of a stainless steel metal honeycomb base material and drying the mixture. The converter is disclosed.

Japanese Unexamined Patent Publication No. 2006-223925

A honeycomb catalyst as proposed in Patent Document 1 and the like is produced by supporting a precious metal on a honeycomb-shaped base material by a wet process. Therefore, when producing a honeycomb catalyst, a base material (carrier) having a predetermined shape is required. In addition, the method for manufacturing a honeycomb catalyst by a wet process has problems in terms of manufacturability, such as an increase in the number of manufacturing steps and a tendency for loss of precious metal to occur in each manufacturing step.
Further, in recent years, with the improvement of automobile engine performance and the tightening of exhaust gas regulations, conventional catalytic converters are required to have improved catalytic activity and further improved durability at high temperatures (for example, 900 ° C. or higher). Will be done.

The present invention has been made in view of the above circumstances, and is a metal leaf catalyst that does not require a base material (carrier) having a predetermined shape, can be molded with a high degree of freedom, and has enhanced catalytic activity. An object of the present invention is to provide a method for producing the metal leaf catalyst having excellent manufacturability, and a catalyst converter.

Conventionally, a honeycomb catalyst is produced by preparing a honeycomb-shaped base material (carrier) and coating the carrier with a powder-like catalyst component in which a noble metal is supported on alumina or the like by a wet process.
On the other hand, in the study, the present inventors adopted a metal foil as a carrier and formed a catalyst layer containing a noble metal thinly with a specific thickness on the metal foil to make it thinner than before. We have found that a metal foil capable of exhibiting a higher catalytic function can be obtained even if the amount of noble metal used is significantly reduced, and have completed the present invention.

That is, the metal foil catalyst of the present invention includes a metal foil, and a catalyst layer provided on the metal foil, the catalyst layer contains a noble metal, the thickness T _{S (nm)} of the metal foil and the thickness T _C of the catalyst layer _(nm) is characterized by satisfying the following formula (1).
_{20 <T S / T C ···} (1)

The noble metal is preferably selected from the group consisting of rhodium, palladium, platinum, silver, iridium, and alloys containing one or more of these.

The metal foil catalyst of the present invention is further provided with an intermediate layer arranged between the metal foil and the catalyst layer and adjacent to both of them, and the catalyst layer is a layer containing rhodium and is the intermediate layer. Is also preferably a layer containing zirconium.

Further, the method for producing a metal foil catalyst of the present invention is the method for producing a metal foil catalyst of the present invention, in which a catalyst layer forming material containing the noble metal is deposited on the metal foil by arc discharge. It is characterized by having a catalyst layer forming step for forming the catalyst layer.

In the catalyst layer forming step, it is preferable to deposit the catalyst layer forming material on the metal foil by continuous arc discharge while transporting the metal foil in a roll-to-roll manner.
As the metal foil, it is preferable to use a metal foil whose surface layer has been oxidized in advance.

Further, the catalyst converter of the present invention is a processed product of the metal foil catalyst of the present invention.

According to the present invention, a metal foil catalyst that does not require a base material (carrier) having a predetermined shape, can be molded with a high degree of freedom, and has enhanced catalytic activity, and its production having excellent manufacturability. Methods, as well as catalytic converters can be provided.

It is sectional drawing which shows one Embodiment of a metal foil catalyst. It is sectional drawing which shows the other embodiment of a metal foil catalyst. It is a schematic diagram which shows the schematic structure about one Embodiment of the metal foil catalyst manufacturing apparatus. It is a graph which shows the relationship between the number of times of plasma irradiation (the number of shots) from an arc vapor deposition source, the thickness of a catalyst layer (Rh layer), and the amount of a noble metal (Rh) supported. NO conversion rate, CO conversion rate, C ₃ H with respect to the reaction temperature when the mixed gas is brought into contact with the metal foil catalysts (fresh) of Examples 1 to 4 and the metal foil catalysts (aged) obtained by heat-treating them. ₆ It is a graph which shows each change of conversion rate. 6 is an image showing the surface states of the Rh / heat-resistant SUS foil catalyst before heat treatment (upper stage; fresh) and after heat treatment (lower stage; 900 ° C. aged). It is an image which shows each surface state before and after the heat treatment in a heat-resistant SUS foil. FIG. 8A is a graph showing the change in surface layer composition with respect to the reaction temperature of the heat-resistant SUS foil, and FIG. 8B is a graph showing the measurement result by the X-ray diffraction (XRD) method. NO conversion rate, CO conversion rate, and C ₃ H ₆ conversion rate with respect to the reaction temperature when the mixed gas is brought into contact with the Rh / heat-resistant SUS foil catalyst manufactured using the heat-resistant SUS foil that has been heat-treated in advance. It is a graph which shows each change of. When contacting the mixed gas to the catalyst for each example, NO conversion versus reaction temperature, CO conversion is a graph showing each change of C ₃ H ₆ conversion, FIG. 10 (a) applying the present invention The graph is for the case where the Rh / heat-resistant SUS foil catalyst is used, and FIG. 10 (b) is the graph for the case where the powdery catalyst component (conventional type) is used. When contacting the mixed gas to the catalyst for each example, NO conversion versus reaction temperature, CO conversion is a graph showing each change of C ₃ H ₆ conversion, FIG. 11 (a) of Example 7 The graph when the metal foil catalyst (Rh / heat resistant SUS foil catalyst) is used, FIG. 11B shows the case where the metal foil catalyst (Rh / Zr / heat resistant SUS foil catalyst) of Example 8 is used. It is a graph. It is sectional drawing which shows one Embodiment of the conventional honeycomb catalyst.

(Metal leaf catalyst)
The metal foil catalyst of the present invention includes a metal foil and a catalyst layer provided on the metal foil.

FIG. 1 shows an embodiment of a metal foil catalyst.
The metal foil catalyst 1 of the present embodiment includes a metal foil 10 and a catalyst layer 20 provided on the metal foil 10.
In Figure 1, it has a thickness _{T S} of the metal foil 10, the thickness of the catalyst layer 20 and the _{T C.}
Metal foil catalyst 1 is a thickness _T C of the thickness _T S (nm) and the catalyst layer 20 of the metal foil 10 (nm) satisfies the following formula (1).
_{20 <T S / T C ···} (1)

In the metal foil catalyst _{1, T} S / T _C is greater than 20, preferably lower limit is 50 or more, more and preferably 100 or more, more preferably 500 or more, particularly preferably 1000 or more, and most preferably It is over 2000.
On the other hand, the preferable upper limit value is 20000 or less, and in addition, it is preferably 10000 or less, more preferably 6000 or less, further preferably 5000 or less, particularly preferably 4000 or less, and most preferably 3000 or less.
If T S _/ T _C is the lower limit value greater than the even catalyst layer 20 is provided thinner the metal foil 10, sufficient catalytic function is exhibited, there is a technical significance of the present invention.
If T S _/ T _C is less preferred upper limit of the sufficient strength it is easily maintained as a metal foil catalyst 1.

The thickness of the metal foil catalyst 1 _(T S + T _C) is preferably 5000～70000Nm, more preferably 10000～70000Nm, more preferably 30000～70000Nm, particularly preferably 40000～60000Nm.

<Metal leaf>
The material of the metal foil 10 is appropriately selected in consideration of the heat resistance required according to the application, and examples thereof include stainless steel, aluminum, and titanium. Among these, stainless steel is preferable from the viewpoint of durability and workability.
For example, when the metal foil catalyst 1 is used in a catalyst converter of a gasoline vehicle, it is exposed to high-temperature exhaust gas. Therefore, stainless steel having high heat resistance (heat-resistant stainless steel) may be used as the material of the metal foil 10. preferable. For example, stainless steel having heat resistance to 600 to 1000 ° C. is mentioned, and more preferably stainless steel having heat resistance to 900 to 1000 ° C. is mentioned.
As the preferable heat-resistant stainless steel, for example, iron 75 to 80% by mass, chromium 15 to 20% by mass, and aluminum 5 to 10% by mass with respect to the total amount (100% by mass) of the components constituting the heat-resistant stainless steel. And, those containing.

The thickness of the metal foil 10 _T S (nm) is appropriately determined in accordance with the application etc., for example 5000~70000nm, more preferably 10000～70000Nm, more preferably 30000～70000Nm, particularly preferably at 40000~60000nm is there.

<Catalyst layer>
The catalyst layer 20 contains a noble metal that is a catalyst component.
Preferred such noble metals include, for example, those selected from the group consisting of rhodium, palladium, platinum, silver, iridium, and alloys containing one or more of these. Examples of the alloy include an alloy of rhodium and platinum (for example, a mass ratio of the former: the latter = 1: 6), an alloy of palladium and platinum (for example, a mass ratio of the former: the latter = 1: 1), and the like.
Such a precious metal may be used alone or in combination of two or more.
Among the above, the precious metal is more preferably selected from the group consisting of rhodium, palladium, platinum, and alloys containing one or more of these, because the catalytic activity is further enhanced, and those containing rhodium are more preferable. Especially preferable.

The content of the noble metal in the catalyst layer 20 is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 80% by mass or more, based on the total amount (100% by mass) of the catalyst layer 20. It is 90% by mass or more, and may be 100% by mass.

The catalyst layer 20 may contain components other than the noble metal.
Examples of components other than precious metals include cerium, zirconium and the like.

The thickness _T C (nm) is the catalyst layer 20 is appropriately determined in accordance with the application etc., for example, it is preferably from 1000 nm, more preferably 500nm or less, more preferably 200nm or less, particularly preferably 100nm or less, and most preferably 50nm It is as follows.
On the other hand, the lower limit is preferably 1 nm or more, preferably 2 nm or more, more preferably 5 nm or more, still more preferably 10 nm or more, particularly preferably 15 nm or more, and most preferably 20 nm or more.

As described above, the metal foil catalyst 1 of the present embodiment, on the metal foil 10, in which the catalyst layer 20 containing the noble metal is provided in a specific thickness _{(20 <T S / T C} ) ..
The metal foil catalyst 1 can be manufactured without the need for a base material (carrier) having a predetermined shape, and since it has a foil shape, it can be molded with a high degree of freedom.
In addition, since the metal foil catalyst 1 is provided with a catalyst layer 20 on its surface, it has a catalytic function and its catalytic activity is enhanced. Then, the metal foil catalyst 1 acts as a catalyst in the exhaust gas purification reaction.
Further, according to the metal foil catalyst 1 of the present embodiment, the catalyst layer 20 is provided much thinner than the metal foil 10 as compared with the conventional case, so that the amount of precious metal used can be suppressed.

The metal foil catalyst 1 of the above-described embodiment is a laminate of the metal foil 10 and the catalyst layer 20, but the present invention is not limited to this, and other embodiments may be used.

FIG. 2 shows another embodiment of the metal foil catalyst.
The metal foil catalyst 2 shown in FIG. 2 is a laminate of a metal foil 12, a catalyst layer 22 containing rhodium, and an intermediate layer 60 containing zirconium. The intermediate layer 60 is arranged between the metal foil 12 and the catalyst layer 22 and is adjacent to both of them.
In FIG. 2, the thickness of the metal foil 12 _{T S,} the thickness _{T C} of the catalyst layer 22, the thickness of the intermediate layer 60 as a _{T I.}
Metal foil catalyst 2 is a thickness of the metal foil 12 _T S (nm) and the thickness _T C of the catalyst layer 22 (nm) satisfies the following formula (2).
_{20 <T S / T C ···} (2)
In the metal foil catalyst _2, the preferred range of T S / _{T C} is the same as the above _T S / _{T C.}

_{T S / (T I + T} C) is preferably a lower limit of 20 or more, more preferably 50 or more, further preferably 100 or more. On the other hand, the preferable upper limit value is 1000 or less, more preferably 500 or less, still more preferably 200 or less.
The thickness of the metal foil catalyst _{2 (T S + T I +} T C) is preferably 5000～70000Nm, more preferably 10000～60000Nm.

The description of the metal foil 12 is the same as that of the metal foil 10.

The catalyst layer 22 is a layer containing at least rhodium as a noble metal.
The content of rhodium in the catalyst layer 22 is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass, based on the total amount (100% by mass) of the catalyst layer 22. It is mass% or more, and may be 100 mass%.
The catalyst layer 22 may contain components other than rhodium. Examples of components other than rhodium include palladium, platinum, silver, iridium and the like. The catalyst layer 22 may be a layer containing an alloy of these components other than rhodium and rhodium.
The thickness _{T C} of the catalyst layer 22 is appropriately determined in accordance with the application etc., for example, is preferably from 1000 nm, more preferably 500nm or less, more preferably 200nm or less, particularly preferably 100nm or less, and most preferably is 50nm or less .. On the other hand, the lower limit is preferably 1 nm or more, more preferably 2 nm or more, still more preferably 5 nm or more, and particularly preferably 10 nm or more.

<Middle layer>
The intermediate layer 60 is a layer containing zirconium.
The content of zirconium in the intermediate layer 60 is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass, based on the total amount (100% by mass) of the intermediate layer 60. It is mass% or more, and may be 100 mass%.
The intermediate layer 60 may contain components other than zirconium. Examples of components other than zirconium include cerium and yttrium.
The thickness of the intermediate layer 60 _T I (nm) is appropriately determined in accordance with the application etc.,
For example, it is preferably 50 nm or more, more preferably 100 nm or more, and further preferably 200 nm or more. On the other hand, the upper limit is preferably 1000 nm or less, more preferably 500 nm or less, still more preferably 300 nm or less.

Like the metal foil catalyst 1, the metal foil catalyst 2 shown in FIG. 2 described above can be manufactured without the need for a base material (carrier) having a predetermined shape. In addition, since the metal foil catalyst 2 is provided with a catalyst layer 22 on its surface, it has a catalytic function and its catalytic activity is enhanced. Then, the metal foil catalyst 2 acts as a catalyst in the exhaust gas purification reaction.
Further, in the metal foil catalyst 2, since the metal foil 12 and the catalyst layer 22 are arranged via the intermediate layer 60, the distribution of rhodium contained in the catalyst layer 22 in a uniform and dense state is maintained. , High catalytic action can be stably achieved. This makes it more durable, especially when used at high temperatures.
Further, since the metal foil catalyst 2 has an extremely thin overall thickness and a foil shape even if the intermediate layer 60 is interposed, it can be molded with a high degree of freedom, a surface area, an aperture ratio, and a cell density. is there.

(Manufacturing method of metal foil catalyst)
The method for producing a metal foil catalyst of the present invention is the method for producing a metal foil catalyst described above, wherein a catalyst layer forming material containing the noble metal is vapor-deposited on the metal foil by arc discharge to form the catalyst layer. It has a catalyst layer forming step of forming.

The material for forming the catalyst layer contains a noble metal and, if necessary, a component other than the noble metal. Examples of the noble metal and components other than the noble metal here include the noble metal contained in the catalyst layer 20 and the same components other than the noble metal that the catalyst layer 20 may contain.
The content of the noble metal in the catalyst layer forming material is 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more with respect to the total amount (100% by mass) of the catalyst layer forming material. More preferably, it is 90% by mass or more, and may be 100% by mass.

For example, the metal foil catalyst 1 shown in FIG. 1 can be manufactured by using the manufacturing apparatus shown in FIG.

FIG. 3 shows an embodiment of a metal foil catalyst manufacturing apparatus.
The manufacturing apparatus 100 shown in FIG. 3 is composed of an arc vapor deposition source 30 and a metal foil traveling portion 40. The arc vapor deposition source 30 and the metal foil traveling portion 40 are arranged so that the 10 surfaces of the metal foil on which the catalyst layer is formed face the arc vapor deposition source 30.

The arc vapor deposition source 30 is made of a cylindrical porcelain 31 and a material for forming a catalyst layer, and is in contact with a cylindrical cathode 50 arranged so as to be in contact with the inner peripheral surface of the porcelain 31 and an outer peripheral surface of the porcelain 31. It includes an arranged cylindrical trigger electrode 32, an anode 33 concentrically arranged on the outer peripheral side of the trigger electrode 32, and a power supply unit 34.
The power supply unit 34 has an arc power supply 34a, a trigger power supply 34b, and a capacitor 34c.
The arc power supply 34a is connected to the anode 33 via the wiring 35a, is connected to the cathode 50 via the wiring 35c, and is configured so that a voltage can be applied between the anode 33 and the cathode 50.
The trigger power supply 34b is connected to the trigger electrode 32 via the wiring 35b, is connected to the cathode 50 via the wiring 35c, and is configured so that a voltage can be applied between the trigger electrode 32 and the cathode 50.
The capacitor 34c is connected so as to be charged by the arc power supply 34a.

The metal foil traveling portion 40 employs a roll-to-roll system including a pair of transport rolls 41 and 42 arranged parallel to each other.
In FIG. 3, the metal foil 10 is fed from the transport roll 41 side to the transport roll 42 side (in the direction of the arrow), and is wound at the tip.
In FIG. 3, a wavy arrow indicates a state in which the catalyst layer forming material, which has been turned into plasma (Plasma) by arc discharge, is irradiated (pulse discharged) onto the metal foil 10 traveling on the metal foil traveling portion 40. It is expressed.

<Catalyst layer formation process>
In the catalyst layer forming step, for example, using the manufacturing apparatus 100, a catalyst layer forming material is deposited on the metal foil 10 by arc discharge to form a catalyst layer. That is, while the metal foil 10 is conveyed in a roll-to-roll manner, the catalyst layer 20 is formed by continuously depositing a catalyst layer forming material on the metal foil 10 by arc discharge, and the metal foil catalyst 1 is manufactured. Will be done.

The catalyst layer forming step is performed as follows as an example.
First, in a vacuum chamber (not shown), the arc vapor deposition source 30 and the metal foil traveling portion 40 are arranged so that the 10 surfaces of the metal foil on which the catalyst layer 20 is formed face the arc vapor deposition source 30. Further, the metal foil traveling portion 40 is arranged so that the metal foil 10 travels from the transport roll 41 side to the transport roll 42 side.
Next, the inside of the vacuum chamber is adjusted to a predetermined vacuum atmosphere.
Next, the arc power supply 34a applies a voltage between the anode 33 and the cathode 50, while the trigger power supply 34b applies a voltage between the trigger electrode 32 and the cathode 50. As a result, a trigger discharge is generated between the trigger electrode 32 and the cathode 50, and the material for forming the catalyst layer begins to evaporate. After that, an arc discharge is generated between the anode 33 and the cathode 50 by the electric charge charged in the capacitor 34c. By the generation of such an arc discharge, plasma of the evaporated particles of the material for forming the catalyst layer is formed, and the evaporated particles fly to the surface of the metal foil 10 for vapor deposition, and the catalyst layer 20 is formed on the metal foil 10.
The metal foil 10 portion on which the catalyst layer 20 is formed after reaching a predetermined number of plasma irradiations (number of shots) is sequentially sent out to the transport roll 42 side and wound up. At the same time, a new metal foil 10 portion is sent out from the transport roll 41 side to a position facing the arc vapor deposition source 30. Then, the catalyst layer 20 is formed on the new metal foil 10 portion in the same manner as described above.

The voltage (discharge voltage) applied between the anode 33 and the cathode 50 by the arc power supply 34a is preferably 80 to 150V.
The voltage applied between the trigger electrode 32 and the cathode 50 by the trigger power supply 34b is preferably 2 to 5 kV.
The capacitance of the capacitor 34c is preferably 250 to 500 μF.
The frequency of the arc discharge is preferably 1 to 5 Hz.

The number of plasma irradiations (number of shots) from the arc vapor deposition source 30 is appropriately determined in consideration of the heat resistance required according to the application, and is preferably 4000 shots or more, more preferably 6000 shots or more, still more preferably. Is 8000 shots or more, particularly preferably 8000 to 10000 shots.
The amount of the noble metal supported on the metal foil 10 is appropriately determined in consideration of the heat resistance required according to the application, and is preferably 10 to 40 μg · cm- ² , more preferably 15 to 30 μg.・ It is said to be cm- ² .
When the number of shots of plasma irradiation or the amount of the noble metal supported is at least the above-mentioned preferable lower limit value, the catalytic activity of the metal foil catalyst and the durability at high temperature use are further enhanced. Even if the number of shots or the amount of the noble metal supported exceeds the above-mentioned preferable upper limit value, the effect of improving the catalytic activity of the metal foil catalyst and the durability at high temperature use tends to reach a plateau.

Loading of the thickness T _C and the noble metal of the catalyst layer 20 on the metal foil 10 can be controlled by the number of times of the plasma illumination from the arc evaporation source 30 (number of shots).
Regarding the surface condition of the manufactured metal foil catalyst, for example, X-ray diffraction (XRD) method, fluorescent X-ray elemental analysis (XRF) method, X-ray photoelectron spectroscopy (XPS) method, scanning electron microscope / energy dispersive type It can be confirmed by using an X-ray (SEM / EDX) method or the like.

The method for producing a metal foil catalyst described above is a completely dry process, and the metal foil catalyst is wound by depositing a catalyst layer forming material on the metal foil 10 by arc discharge and winding it up. Can be manufactured. That is, in such a manufacturing method, the number of manufacturing steps is significantly smaller than that of the conventional wet manufacturing method of the honeycomb catalyst, and the process can be saved. In addition, such a manufacturing method is excellent in manufacturability because it is less likely to cause loss of precious metals during manufacturing.

The metal foil catalyst produced by such a production method is easy to process because the metal foil has ductility even after the catalyst layer is formed.
According to such a manufacturing method, the noble metal is uniformly and directly deposited on the surface of the metal foil. Therefore, the produced metal foil catalyst has a stronger interaction between the metal foil (carrier) and the noble metal than the conventional wet honeycomb catalyst, and exhibits a high catalytic action in the exhaust gas purification reaction. Further, according to such a manufacturing method, a metal foil having a catalytic function can be easily obtained.

The metal foil catalyst 2 shown in FIG. 2 can also be manufactured by using the manufacturing apparatus shown in FIG.
For example, an intermediate layer forming step of forming an intermediate layer 60 by depositing a material for forming an intermediate layer containing zirconium on a metal foil 12 by an arc discharge, and an intermediate layer 60 formed in the intermediate layer forming step. A production method including a catalyst layer forming step (2) in which a catalyst layer forming material (2) containing rhodium is vapor-deposited to form a catalyst layer 22 by an arc discharge is used.

The material for forming the intermediate layer contains zirconium and, if necessary, components other than zirconium.
The content of zirconium in the material for forming the intermediate layer is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, based on the total amount (100% by mass) of the material for forming the intermediate layer. More preferably, it is 90% by mass or more, and may be 100% by mass.

The catalyst layer forming material (2) contains rhodium and, if necessary, a component other than rhodium. The content of rhodium in the catalyst layer forming material (2) is 50% by mass or more, preferably 70% by mass or more, more preferably 70% by mass or more, based on the total amount (100% by mass) of the catalyst layer forming material (2). Is 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

<Intermediate layer forming process>
In the intermediate layer forming step, the same operation can be performed using the manufacturing apparatus 100 shown in FIG. 3, except that the catalyst layer forming material is changed to the intermediate layer forming material in the above-mentioned <catalyst layer forming step>. Good.

In the intermediate layer forming step, the number of plasma irradiations (number of shots) from the arc vapor deposition source 30 is appropriately determined in consideration of the heat resistance required according to the application, and for example, 5000 shots or more is preferable, and more preferably. It is 10,000 shots or more, more preferably 20,000 shots or more, and particularly preferably 2,000 to 40,000 shots.
The amount of zirconium supported on the metal foil 12 is appropriately determined in consideration of the heat resistance required depending on the application, and is preferably 50 to 300 μg · cm- ² , more preferably 100 to 200 μg, for example.・ It is said to be cm- ² .

Loading of the thickness T _I and zirconium intermediate layer 60 on the metal foil 12 can be controlled by the number of times of the plasma illumination from the arc evaporation source 30 (number of shots).

<Catalyst layer forming step (2)>
In the catalyst layer forming step (2), for example, the catalyst layer 22 is formed by depositing the catalyst layer forming material (2) on the intermediate layer 60 by arc discharge using the manufacturing apparatus 100 shown in FIG. As for the operation of the catalyst layer forming step (2), the operation of the above-mentioned <catalyst layer forming step> may be performed in the same manner.
Loading of the thickness T _C and the noble metal of the catalyst layer 22 in the intermediate layer 60 on is possible to control the number of the plasma illumination from the arc evaporation source 30 (number of shots).

In the method for producing a metal foil catalyst described above, vapor deposition is continuously performed by arc discharge using a manufacturing apparatus 100 provided with a metal foil traveling portion 40 adopting a roll-to-roll method. The method is not limited to this, and the metal foil traveling portion 40 may be replaced with a metal foil holding portion, for example, a metal foil having a certain shape with a new metal foil each time vapor deposition is performed to perform vapor deposition by arc discharge. ..
However, by using the manufacturing apparatus 100, in addition to the process saving, the continuous production line can be realized at the same time.

Further, in the above-mentioned method for producing a metal foil catalyst, it is preferable to use a metal foil whose surface layer has been oxidized in advance as the metal foil. As a result, the durability at high temperature use can be further enhanced, and the amount of precious metal used can be further suppressed.
Such an effect can be obtained in a metal foil catalyst using a metal foil whose surface layer has been oxidized in advance, for example, the metal foil is less likely to be oxidized by heat applied during an exhaust gas purification reaction and is exposed on the surface. This is because the concentration of the noble metal, which is a catalyst component, is easily maintained.
The metal foil whose surface layer is oxidized can be produced, for example, by subjecting it to heat treatment at about 900 to 1000 ° C. for 5 to 30 hours.

(Catalytic converter)
The catalyst converter of the present invention is a processed product of the metal foil catalyst described above. Examples of such a catalyst converter include a metal honeycomb catalyst and the like.
According to such a catalytic converter, exhaust gas (hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NO _x ), etc.) of a gasoline vehicle is sufficiently purified. For example, HC is oxidized or reduced to carbon dioxide and water, CO to carbon dioxide, and NO _x to nitrogen (N ₂ ).
In particular, a catalyst converter, which is a processed product of a metal foil catalyst in which a catalyst layer containing rhodium is provided on a metal foil made of heat-resistant stainless steel, is particularly suitable for gasoline vehicles, and CO- _{NO-C 3} H 6 -O ₂ reaction indicates (stoichiometric air-fuel ratio) relative to the catalytic activity, all of the exhaust gas components at the reaction temperature region of more than 300 ° C. is purified.

Above metal foil catalyst is a thin provided the foil shape in the catalyst layer is specified thickness _{(20 <T S / T C} ) to the metal foil, and one in which the catalytic activity is enhanced. According to the catalyst converter of the present invention using such a metal foil catalyst, miniaturization and high performance can be achieved.
Further, the metal foil catalyst described above can be manufactured by a dry process, and in addition, can be processed into various shapes such as a honeycomb shape, and can be molded with a high degree of freedom. By adopting such a metal foil catalyst, it is possible to realize an innovative production line different from the conventional one in the catalyst converter production without depending on the shape of the final product.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.

<Manufacturing of metal foil catalyst (1)>
(Examples 1 to 4)
A heat-resistant stainless steel foil (heat-resistant SUS foil) was used as the metal foil, and rhodium (Rh) was used as the material for forming the catalyst layer.
The heat-resistant SUS foil, size 30 mm × 30 mm, the thickness _{T S} using 51 [mu] m, what composition consisting of 75 wt% and chromium 20% by mass of aluminum 5 mass% iron.
As the arc vapor deposition source, an arc plasma gun (manufactured by ULVAC-RIKO, Inc.) having the same form as the arc vapor deposition source 30 in FIG. 3 was used.
The characterization of the obtained metal foil catalyst (fresh, aged) is performed by X-ray diffraction (XRD) method, X-ray photoelectron spectroscopy (XPS) method, scanning electron microscope / energy dispersive X-ray (SEM / EDX). The method was used.

≪Making of metal foil catalyst (fresh)≫
An arc deposition source with a Rh cathode target is installed in the vacuum chamber, and Rh is vapor-deposited on one side of the heat-resistant SUS foil by arc discharge (capacitor capacity 360 μF, discharge voltage 125 V, frequency 1 Hz) to form a catalyst layer. Then, metal foil catalysts (Rh / heat-resistant SUS foil catalyst) having different numbers of shots of plasma irradiation were obtained.

4, in the manufacture described above, is a graph showing the number of shots plasma irradiation, and the supported amount of the catalyst layer (Rh layer) having a thickness of T _C and noble metal (Rh), the relationship between the arc evaporation source.
It can be confirmed that the relationship between the number of shots and the thickness of the Rh layer and the relationship between the number of shots and the amount of Rh supported are substantially proportional to each other (dotted line: approximate straight line).

For the Rh / heat resistant SUS foil catalyst of each example, the thickness T of the Rh layer_C, Rh loading amount, T_S/ T _CAre shown in Table 1, respectively.

≪Manufacturing of metal foil catalyst (aged)≫
The metal foil catalyst (fresh) of each example was deteriorated by being heat-treated at 900 ° C. for 25 hours in an atmosphere in which 10% H ₂ O / air flows at 25 mL · min ^-1. A catalyst (aged) was obtained.

<Evaluation of catalytic activity of metal foil catalyst (1)>
As a sample for evaluation, a strip-shaped metal foil catalyst having a size of 2 mm × 30 mm was cut out and prepared.
Using a fixed-bed flow type reactor, the mixed gas is passed through the reactor in which the evaluation sample (metal foil catalyst) is arranged while raising the temperature so as to come into contact with the metal foil catalyst. Was purified.
The composition of the mixed gas, the flow rate of the mixed gas, the reaction temperature, the rate of temperature rise, and the gas analysis method were set as follows.

Composition of mixed gas: 0.050% NO, 0.51% CO, 0.039% C ₃ H ₆ , 0.40% O ₂ , He balance
Flow rate of mixed gas: 100 mL ・ min ^-1
Reaction temperature: Range from room temperature (25 ° C) to 600 ° C Temperature rise rate: 10 ° C. min ^-1
Gas analysis method: Non-dispersed infrared absorption method (NDIR)

When the gas was purified, the NO conversion rate, the CO conversion rate, and the C ₃ H ₆ conversion rate were determined by NDIR, respectively.

FIG. 5 shows NO for the reaction temperature when the mixed gas is brought into contact with the metal foil catalysts (fresh) of Examples 1 to 4 having different shot numbers and the metal foil catalysts (aged) obtained by heat-treating them. conversion, CO conversion _is a graph showing each change of C 3 _{H 6} conversion.

About metal foil catalyst (fresh):
In all the metal foil catalysts, all the gases react at 400 to 500 ° C., showing a high conversion rate.

About metal foil catalyst (aged):
In the metal foil catalyst (aged) in Example 1 (2000 shots), a significant decrease in catalytic activity due to heat treatment is observed.
As the number of shots increases (that is, the amount of Rh supported increases), the catalytic activity increases, and if the number of shots is 8000 shots, all the gas is purified at about 500 ° C. at almost 100%. You can check it.

≪Evaluation of surface condition of metal foil catalyst≫
In FIG. 6, the upper image shows the surface state of the metal foil catalyst (fresh) of Example 4, and the lower image shows the metal foil catalyst (aged) obtained by heat-treating the metal foil catalyst (fresh) of Example 4. Shows the surface condition of. The surface state of each metal foil catalyst was analyzed using the SEM / EDX method.

In both the metal foil catalyst (fresh) and the metal foil catalyst (aged), Rh is uniformly and densely distributed on the surface layer, and the state is almost maintained even after heat treatment at 900 ° C. for 25 hours. You can confirm that it is.
Further, in the metal foil catalyst (aged), Al, Fe and Cr are non-uniformly distributed (Al raised by heat treatment covers a part of Fe and Cr); also by heat treatment. , It can be confirmed that Rh exists on the surface layer.

The upper image of FIG. 7 is an SEM image showing the surface state of the heat-resistant SUS foil used as the metal foil.
The lower image of FIG. 7 is an SEM image showing the surface state of the heat-resistant SUS foil after being heat-treated at 1000 ° C. for 25 hours in an air atmosphere.

FIG. 8A shows the surface composition (analysis result by the XPS method) of the heat-resistant SUS foil after heat-treating the heat-resistant SUS foil in an air atmosphere at each reaction temperature for 25 hours. There is. When the heat-resistant SUS foil is heated at 1000 ° C., it can be confirmed that almost 100% of the elements detected as constituents of the surface layer are aluminum.

FIG. 8B is a graph showing the measurement results by the X-ray diffraction (XRD) method, in which the horizontal axis represents the incident angle and the vertical axis represents the diffraction intensity.
In FIG. 8 (b), (X1) shows the results of the heat-resistant SUS foil subjected to the heat treatment at 1000 ° C. for 25 hours in an air atmosphere. (X2) shows the result for α-Al ₂ O ₃ . (X3) shows the result for γ-Al ₂ O ₃ .
It can be confirmed that the position of the peak observed in (X1) and the position of the peak observed in (X2) are almost the same.

From FIGS. 7 and 8, it can be seen that in the heat-resistant SUS foil, oxidation is generated by heat treatment at 1000 ° C., and an aluminum oxide film (α-Al ₂ O ₃ film) is formed on the surface.

Further, from the analysis by the XPS method, between the metal foil catalyst (fresh) and metal foil catalyst (aged), NO conversion versus reaction temperature, CO _conversion, C 3 _{H 6} conversion behavior differs greatly in the , Rh oxidation state (Rh ⁰ , Rh ³⁺ , Rh ^4+, etc.) is different, or Rh distribution state is different.
About the distribution of Rh:
In the metal foil catalyst (fresh), Rh is distributed on the heat-resistant SUS foil to form a Rh layer (FIG. 6). On the other hand, in the metal foil catalyst (aged), Rh diffuses inside the heat-resistant SUS foil as the aluminum oxide film is formed on the surface layer, and Rh oxide (Rh ₂ O ₃ ) is formed on the surface layer. Etc.) were confirmed to exist (XPS depth analysis).

<Manufacturing of metal foil catalyst (2)>
(Example 5)
As the metal foil, to heat-resistant SUS foil used in Example 1-4, under air atmosphere was used that has been subjected to heat treatment for 25 hours at 1000 ° C. (thickness _T S _52000nm).
Using the heat-resistant SUS foil that has been heat-treated in advance and Rh as a material for forming the catalyst layer, the metal foil catalyst of Example 5 is used in the same manner as in the above-mentioned << Production of metal foil catalyst (fresh) >>. Fresh) was obtained.
The number of shots of plasma irradiation from the arc deposition source was set to 2000 shots.
For the metal foil catalyst of Example 5, the thickness _{T C} of the Rh layer 5.07Nm, the loading amount of Rh is 6.2μg ^· cm _-2, a _T S / _T C = 10256.

Further, the metal foil catalyst (fresh) of Example 5 was deteriorated by being heat-treated at 900 ° C. for 25 hours in an atmosphere in which 10% H ₂ O / air flows at 25 mL · min ^-1. A metal foil catalyst (aged) was obtained.

<Evaluation of catalytic activity of metal foil catalyst (2)>
In the same manner as evaluation of the above-described (1), the purification of gas by NDIR, determined NO conversion, CO _conversion, the C 3 _{H 6} conversion, respectively.

FIG. 9 shows the NO conversion rate, the CO conversion rate, and C with respect to the reaction temperature when the mixed gas is brought into contact with the metal foil catalyst (fresh) of Example 5 and the metal foil catalyst (aged) which has been heat-treated. it is a graph showing each change in ₃ H ₆ conversion.

In the metal foil catalyst (aged) in Example 1 (2000 shots), a significant decrease in catalytic activity was observed due to the heat treatment, but in the metal foil catalyst (aged) in Example 5 (2000 shots), the decrease in catalytic activity was observed. It was not observed, and it can be confirmed that all the gas was purified at about 100% at about 500 ° C.
The metal foil catalyst (fresh, aged) in Example 5 (2000 shots) is the same as the metal foil catalyst (fresh, aged) in Example 4 (8000 shots), and the NO conversion rate, CO conversion rate, and C ₃ H ₆ conversion with respect to the reaction temperature. The rate behavior is similar. That is, by using a heat-resistant SUS foil (a metal foil whose surface layer is oxidized in advance) that has been heat-treated in advance as the metal foil, the metal foil catalyst has improved durability in high-temperature use. , The amount of precious metal used is suppressed.

<Manufacturing of metal foil catalyst (3)>
(Example 6)
As the metal foil, to heat-resistant SUS foil used in Example 1-4, under air atmosphere was used that has been subjected to heat treatment for 25 hours at 1000 ° C. (thickness _T S _52000nm).
Using the heat-resistant SUS foil that has been heat-treated in advance and Rh as a material for forming the catalyst layer, the metal foil catalyst of Example 6 is used in the same manner as in the above-mentioned << Production of metal foil catalyst (fresh) >>. Rh / heat resistant SUS foil catalyst) was obtained.
The number of shots of plasma irradiation from the arc deposition source was set to 2000 shots.
For the metal foil catalyst of Example 6, the thickness _{T C} of the Rh layer 5.07Nm, the loading amount of Rh is 6.2μg ^· cm _-2, was _T S / _T C = 10256.

(Comparative Example 1)
Rh was vapor-deposited on Al ₂ O ₃ of the porous powder by arc discharge to obtain a powdery catalyst component. At that time, the ratio of Rh to the total (100% by mass) of Al ₂ O ₃ and Rh of the porous powder was set to 0.7% by mass.
With respect to the powdery catalyst component (0.7 wt% Rh / Al ₂ O ₃ ) of Comparative Example 1, the amount of Rh supported on Al ₂ O ₃ was 350 μg · cm- ² .

<Evaluation of catalytic activity of metal foil catalyst (3)>
In the same manner as evaluation of the above-described (1), the purification of gas by NDIR, determined NO conversion, CO _conversion, the C 3 _{H 6} conversion, respectively.

10, when contacting the mixed gas to the catalyst for each example, NO conversion versus reaction temperature, CO conversion is a graph showing each change of C ₃ H ₆ conversion.
FIG. 10A shows the results when the metal foil catalyst (Rh / heat resistant SUS foil catalyst) of Example 6 to which the present invention was applied was used.
FIG. 10B shows the results when the catalyst of Comparative Example 1 (powder-like catalyst component (conventional type)) was used.
From the comparison between Example 6 and Comparative Example 1, the metal foil catalyst to which the present invention is applied can reduce the amount of noble metal used as compared with the conventional type catalyst (reduced to about 1/100). In addition, it can be confirmed that it exerts a higher catalytic action in the exhaust gas purification reaction.

<Manufacturing of metal foil catalyst (4)>
(Example 7)
Using the heat-resistant SUS foil used in Examples 1 to 4 as the metal foil and Rh as the material for forming the catalyst layer, Example 7 was carried out in the same manner as in << Preparation of metal foil catalyst (fresh) >> described above. The metal foil catalyst (fresh) of the above was obtained.
The number of shots of plasma irradiation from the arc deposition source was set to 2000 shots.
For the metal foil catalyst of Example 7 (Rh / heat-resistant SUS foil catalyst), the catalyst layer thickness _{T C} is 5.07Nm, the loading amount of Rh is ^{_{6.2μg · cm -2, T S /}} T C = It is 10059.

Further, the metal foil catalyst (fresh) of Example 7 was deteriorated by being heat-treated at 900 ° C. for 25 hours in an atmosphere in which 10% H ₂ O / air flows at 25 mL · min ^-1. A metal foil catalyst (aged) was obtained.

(Example 8)
As the metal foil, the heat-resistant SUS foil used in Examples 1 to 4, zirconium (Zr) as the material for forming the intermediate layer, and Rh as the material for forming the catalyst layer were used.
Intermediate layer forming process:
An arc vapor deposition source with a Zr cathode target is installed in the vacuum chamber, and the number of shots of plasma irradiation from the arc vapor deposition source is 20000 shots on one side of the heat-resistant SUS foil, and arc discharge (capacitor capacity 360 μF, discharge voltage 125 V, Zr was vapor-deposited at a frequency of 1 Hz) to form an intermediate layer.
Catalyst layer formation step:
Next, an arc vapor deposition source having a Rh cathode target is installed, and the number of shots of plasma irradiation from the arc vapor deposition source is set to 2000 shots on the intermediate layer, and Rh is generated by arc discharge (capacitor capacity 360 μF, discharge voltage 125 V, frequency 1 Hz). Was vapor-deposited to form a catalyst layer to obtain a metal foil catalyst (voltage) of Example 8.
Regarding the metal foil catalyst (Rh / Zr / heat resistant SUS foil catalyst) of Example 8, the thickness T of the intermediate layer_IIs 259 nm, and the thickness of the catalyst layer is T._CIs 5.07 nm; the amount of Zr supported is 168 μg · cm. ^-2, Rh supported amount is 6.2 μg · cm^-2, T_S/ T_C= 10059, T_S/ (T_I+ T_C) = 193.

Further, the metal foil catalyst (fresh) of Example 8 was deteriorated by being heat-treated at 900 ° C. for 25 hours in an atmosphere in which 10% H ₂ O / air flows at 25 mL · min ^-1. A metal foil catalyst (aged) was obtained.

For the metal foil catalyst in each example, the thickness _T C of the catalyst layer, the amount of supported Rh, thickness _T I of the intermediate layer, the supported amount of _{Zr, T S / T C,} T S / a _(T I + _{T C)} Each is shown in Table 2.

<Evaluation of catalytic activity of metal foil catalyst (4)>
In the same manner as evaluation of the above-described (1), the purification of gas by NDIR, determined NO conversion, CO _conversion, the C 3 _{H 6} conversion, respectively.

11, when contacting the mixed gas to the catalyst for each example, NO conversion versus reaction temperature, CO conversion is a graph showing each change of C ₃ H ₆ conversion.
FIG. 11A shows the results when the metal foil catalyst (Rh / heat resistant SUS foil catalyst) of Example 7, which is the same embodiment as that of FIG. 1, is used.
FIG. 11B shows the results when the metal foil catalyst (Rh / Zr / heat resistant SUS foil catalyst) of Example 8 which is the same embodiment as that of FIG. 2 is used.
In the metal foil catalyst (aged) in Example 7 (without intermediate layer), a significant decrease in catalytic activity was observed due to the heat treatment, but in the metal foil catalyst (aged) in Example 8 (with intermediate layer), the catalyst was observed. No decrease in activity was observed, and it can be confirmed that all the gas was purified at about 100% at about 500 ° C. That is, by providing the intermediate layer of Zr between the metal foil and the catalyst layer of Rh, the durability of the metal foil catalyst in high temperature use is enhanced.

The metal foil catalyst according to the present invention is useful as a material for a catalytic converter mounted on a two-wheeled or four-wheeled gasoline vehicle. Since such a metal foil catalyst has a high degree of freedom in molding, it can be used for a wide range of vehicle types.
Further, by selecting a noble metal, such a metal foil catalyst can be expected to further improve the catalyst performance and be used as a catalyst converter for diesel vehicles.

1 metal foil catalyst, 2 metal foil catalyst, 10 metal foil, 12 metal foil, 20 catalyst layer, 22 catalyst layer, 30 arc deposition source, 31 porcelain, 32 trigger electrode, 33 anode, 34 power supply unit, 34a arc power supply, 34b Trigger power supply, 34c capacitor, 40 metal foil running part, 41 transfer roll, 42 transfer roll, 50 cathode, 60 intermediate layer, 100 manufacturing equipment, 200 honeycomb catalyst, 210 base material, 220 catalyst layer.

Claims (6)

A metal foil, a catalyst layer, and an intermediate layer arranged between the metal foil and the catalyst layer and adjacent to both of them are provided.
The catalyst layer is a layer containing rhodium.
The intermediate layer is a layer containing zirconium.
The thickness _T S of the metal foil (nm), the thickness _T C of the catalyst layer (nm) and the thickness _T I (nm) of the intermediate layer, the following equation (1), the following equation (3) and lower A metal foil catalyst for exhaust gas purification that simultaneously satisfies the formula (4).
_{1000 ≦ T S / T C ≦} 20000 ··· (1)
T _C ≦ 50 ··· (3)
T _I ≦ 1000 ··· (4) The sum of the thickness _T S (nm) and the thickness _T the thickness of the C (nm) of the catalyst layer of the metal foil _(T S + _{T C)} is a 5,000 to 70000 (nm), in claim 1 The metal foil catalyst described. The method for producing a metal foil catalyst according to claim 1 or 2 .
An intermediate layer forming step of forming the intermediate layer by depositing a material for forming an intermediate layer containing zirconium on the metal foil by arc discharge.
A catalyst layer forming step of forming the catalyst layer by depositing a catalyst layer forming material containing rhodium on the intermediate layer formed in the intermediate layer forming step by arc discharge.
A method for producing a metal foil catalyst. In the catalyst layer forming step, the while the metal foil intermediate layer is formed is conveyed by a roll-to-roll method, thereby depositing said catalyst layer forming material by continuously arcing on the intermediate layer, according to claim 3 The method for producing a metal foil catalyst according to. The method for producing a metal foil catalyst according to claim 3 or 4 , wherein a metal foil whose surface layer has been oxidized in advance is used as the metal foil. A catalytic converter which is a processed product of the metal foil catalyst according to claim 1 or 2 .