JP2851459B2 - Metal-based catalyst and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a general oxidation catalyst, a redox catalyst, a catalyst for decomposing alcohol, a synthesis catalyst for organic compounds, a catalyst for treating combustion exhaust gas of various fuels, a catalyst for treating organic solvent exhaust gas, etc. The present invention relates to a metal-based catalyst that can be applied to a catalyst and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a catalyst for exhaust gas treatment, platinum, a carrier such as a pellet type, a porous mat and a honeycomb type based on an inorganic material such as alumina, silica / alumina, cordierite, mullite, and zirconia are generally used.
Those supporting a catalytically active component such as palladium, rhodium and ruthenium have been used. Further, those using a heat-resistant silica fiber as a base material and those using a thin metal plate such as a SUS material as a base material have been used.

FIG. 2 is a cross-sectional view of a honeycomb catalyst based on a thin metal plate having a thickness of several tens to several hundreds μm.
2 is formed into a corrugated shape and spirally wound in combination with the flat plate 11. The thin plate surface is wash-coated with, for example, γ-alumina, and the above catalyst component is carried thereon.

[0004]

As shown in FIG. 3, the above-mentioned honeycomb catalyst is wash-coated on the surface of the substrate, so that the catalyst layer 13 is particularly thickly coated on each corner of the honeycomb eyes. (Thickness of several tens to several hundreds of μm), not only the adhesion of the catalyst is non-uniform, but also the opening ratio of the honeycomb is reduced, and the ventilation resistance when exhaust gas flows tends to be increased. In addition, there is also a problem that the cost increases because a large amount of the catalyst is attached.

Therefore, the present inventors have solved the above-mentioned drawbacks and have developed a metal-based catalyst suitable for a honeycomb type catalyst having a small airflow resistance, which can support the catalyst thinly and uniformly on a thin metal plate. Various proposals have been made so far to provide. (Japanese Patent Application Nos. 02-242808, 02-233363 and 02-241197)

However, under actual conditions of use, further heat resistance and durability are strongly required, and at present, there is a demand for a catalyst that can exhibit stable performance over a long period of time. .

The present invention has been made in view of the above technical level, and has as its object to provide a honeycomb-type catalyst having a small airflow resistance, excellent heat resistance and excellent durability, and a method for producing the same.

[0008]

According to the present invention, there is provided (1) a method of forming a thin metal sheet containing aluminum umni in an air atmosphere.
Heat at 0-970 ° C. or in air at 1020-12
Heat at 00 ° C or 870-970 ° C in air
After heating at 1024 to 1200 ° C. in the air, a cerium oxide, aluminum oxide, barium oxide, oxidized One or more cocatalysts selected from the group consisting of strontium, zirconium oxide, lanthanum oxide and samarium oxide are supported, and two or more catalysts selected from the group consisting of platinum, rhodium and palladium are supported thereon Is supported in a layered form.

(2) On the surface of the metal-based catalyst described in (1),
Further, a metal-based catalyst comprising the cocatalyst described in the above item 1 and the layered catalyst described in the above item 1 supported thereon.

(3) The co-catalyst is formed by applying and baking an aqueous solution containing the constituent elements, and the catalyst is formed by electroless plating from the aqueous solution containing the constituent elements. A method for producing the metal-based catalyst according to the above. It is.

[0011]

The production process of the metal-based catalyst of the present invention will be described first with reference to FIG. 1, and then the operation will be described. In FIG. 1, A is a starting material such as platinum, rhodium, or palladium, and the starting material is preferably a chlorine-free water-soluble salt, and specifically, a nitrate, a dinitrodiamine salt, or the like is preferably used. B is a reducing agent that does not contain elements such as sodium, potassium, boron, sulfur, and phosphorus, and specifically, hydrazine, formaldehyde, and the like are preferable. C is a thin metal plate such as stainless steel containing aluminum.

A starting material A such as platinum, rhodium, palladium or the like is dissolved in ion-exchanged water and sent to a raw material reducing agent adjusting tank 1, where a reducing agent B is added to make fine particles of platinum, rhodium, palladium or the like to form fine particles. Send to 2.

The metal sheet C serving as the catalyst carrier is subjected to a heat treatment at 870 to 970 ° C., a heat treatment at 102 to 1200 ° C.
After heating at 0 to 970 ° C, it is further heated to 1020 to 1 in air.
Heat treatment at 200 ° C.

Next, after heating to form an aluminum oxide layer, a water-soluble salt such as cerium, aluminum, barium, strontium, zirconium, lanthanum, and samarium is dissolved in ion-exchanged water in an oxide coating step 4, and Accordingly, after immersion in an aqueous solution to which an aluminum hydrosol is added and application, calcination is performed to apply an oxide of the above element to the surface of the metal sheet.

The metal sheet coated with the oxide is plated in a plating tank 2
And a catalyst component is plated by an electroless plating method, and a drying step 5 and a firing step 6 are performed to form a catalyst layer on the metal thin plate.

According to the above steps, the metal-based catalyst of the present invention can be obtained. Further, a water-soluble salt such as cerium, aluminum, barium, strontium, zirconium, lanthanum, samarium, etc. Is dissolved in ion-exchanged water, and if necessary, dipped again in an aqueous solution to which aluminum hydrosol is added, followed by application. Then, the respective elements of platinum, rhodium and palladium are again subjected to a plating operation, drying and baking for each element. Each element may be loaded so as to form a layer.

When forming the catalyst layer, it is preferable that each of platinum, rhodium and palladium be subjected to an electroless plating operation, drying and baking for each element so that at least two kinds of elements are layered. .

In the electroless plating operation, each element is plated independently and each element is supported in a layer. It is effective to form a layer of platinum → rhodium → platin → rhodium (preferably at least 4 layers, and the uppermost layer is preferably a rhodium element), counting from the promoter layer on aluminum oxide.

The metal sheet that has exited the plating tank is finished through a drying step 5 and a firing step 6, but may be activated after firing, if necessary. Drying operation is 105 ° C
0.5 to 1 hour is sufficient, and the firing operation is 500 hours.
It takes 0.5 to 3 hours at ~ 700 ° C. The activation treatment after firing is preferably performed in a hydrogen atmosphere at 400 to 500 ° C. for 5 minutes to 1 hour.

In the electroless plating, the concentration of platinum, rhodium and palladium is preferably in the range of 0.1 to 500 mmol / l, particularly preferably in the range of 10 to 150 mmol / l.

The concentration of the reducing agent in the raw material reducing agent adjusting tank 1 is 0.1.
001 to 10 vol / vol%, particularly 0.002
A range of １1 vol / vol% is preferred. Adjustment tank 1
In the above, the stirring time of the liquid is sufficient for 10 to 20 minutes.
After the adjustment, it is preferable to immediately transfer to the plating tank for use.

The metal sheet C contains 1 to 8% by weight of aluminum.
Ferrite stainless steel containing 25 to 7 thickness
Those having a size of 5 μm are preferred.

Any of the following conditions should be adopted as the conditions for the heat treatment step of the metal sheet C. 1 to 30 in a heating furnace at 870 to 970 ° C. in an air atmosphere
Let stand for a time, preferably 5 to 20 hours. By this heat treatment, an acicular aluminum oxide layer is formed on the surface of the thin metal plate, which effectively functions as a catalyst support surface having a large specific surface area.

It is left still for 1 to 5 hours in a heating furnace in an air atmosphere at 1,200 to 1,200 ° C. By this heat treatment, a spherical aluminum oxide layer is formed on the surface of the thin metal plate, and effectively works as a surface of the catalyst carrier having excellent oxidation resistance.

The needle-shaped aluminum oxide layer is formed on the surface of the thin metal plate by leaving it at 870 to 970 ° C. in a heating furnace in an air atmosphere for 1 to 30 hours, preferably 5 to 20 hours. 0.5-3 in the atmosphere
After standing for 0 hour, preferably 0.5 to 5 hours, a robust aluminum oxide layer is formed under the acicular aluminum oxide layer. By this heat treatment, the heat resistance of a thin metal plate such as stainless steel can be improved, and the acicular aluminum oxide layer can be strongly fixed to the thin metal plate.

One or more oxides selected from the group consisting of cerium oxide, aluminum oxide, barium oxide, strontium oxide, zirconium oxide, lanthanum oxide and samarium oxide, to which aluminum hydrosol is added as a binder if necessary. In the step of applying a water-soluble salt, the concentration of a water-soluble salt not containing a halogen element such as chlorine is adjusted to 0.1.
In the range of 1 to 2000 mmol / l, preferably 0.5
The thin metal plate subjected to the heat treatment step is immersed in a solution adjusted to a range of ~ 1000 mmol / l to apply the solution, and then dried and fired to adhere the oxide.

Each concentration of the electroless plating solution is 0.1 to 500.
mmol / l, preferably 10-150 mmol
Adjust to the range of l / l. The plating time is 1 to 5 minutes, and 3 to 1 minute is sufficient. The plating amount thus obtained is in the range of 0.01 to ² g / m ² (metal surface area).

The metal-based catalyst of the present invention can provide a catalyst support surface having a large specific surface area by the aluminum oxide layer deposited on the metal sheet, and the cerium oxide coated on the acicular aluminum oxide layer Oxides such as aluminum oxide, barium oxide, strontium oxide, zirconium oxide and lanthanum oxide remarkably improve the heat resistance and durability of the catalyst, and also remarkably improve the catalytic function of platinum, rhodium, palladium and the like. Further, since a reducing agent is added to an aqueous solution of a catalytic element such as platinum, rhodium, palladium or the like, and ultrafine particles of the catalytic element are plated on the surface of the metal sheet, a strong bond can be secured. Furthermore, since catalytic elements such as platinum, rhodium, and palladium are supported in a layer, the frequency of contact between the same elements is reduced, and the sintering (semi-fusing) phenomenon can be prevented, so that the heat resistance is improved and the layer is formed. By interposing a co-catalyst layer between the supported catalyst elements, the activity, heat resistance and durability can be increased, and the incorporation of a substance that reduces the catalytic activity into the electroless plating solution can be prevented. Therefore, a decrease in the catalytic function can be avoided.

[0029]

【Example】

(Example 1) 50 μm thickness containing 5 wt% aluminum
Of stainless steel sheet into a corrugated shape by gear processing,
It was corrugated together with the flat plate to form a honeycomb shape of 60 cells / cm ² . This was thoroughly washed with an organic solvent and degreased, and then heat-treated at 960 ° C. for 16 hours in the air.
After a heat treatment at 1050 ° C. for 1 hour, the mixture was cooled.

Next, 1 mol / l of cerium nitrate, 0.1 mol / l of aluminum hydroxide (including those derived from aluminum hydrosol), and 0.005 mol / l of barium nitrate, using aluminum hydrosol as a binder.
The metal sheet after the heat treatment is immersed for 2 minutes in an aqueous solution containing
Further, the oxide was applied by heating at 700 ° C. for 1 hour in the air.

The metal sheet coated with this oxide was treated with 0.025 mol / l of dinitrodiamine platinum and 0.025 mol / l of hydrazine.
After being immersed in a liquid containing 2 vol / vol% for 3 minutes, this was taken out, dried at 105 ° C. for 30 minutes, and dried at 600 ° C. for 30 minutes.
Bake for a minute.

Next, rhodium nitrate 0.005 mol /
l, immersed in a solution containing 0.02 vol / vol% hydrazine for 3 minutes, taken out, and then taken out at 105 ° C. for 3 minutes.
Dried for 0 minutes and baked at 600 ° C. for 30 minutes. next,
After being immersed again in the above-mentioned platinum solution, dried and baked in the same manner, it was immersed again in the above-mentioned rhodium solution, dried and baked in the same manner.

Further, an activation treatment was performed at 450 ° C. for 15 minutes in a 2% hydrogen atmosphere (nitrogen base) to obtain a thin catalyst layer having a thickness of 2 to 3 μm or less in which platinum and rhodium were alternately laminated. The porosity of the obtained catalyst cross section was 90% or more.

Using this catalyst, SV = 50,000 / h
Under the conditions of r, CO: 2000 ppm, propane: 50
When a combustion exhaust gas containing 00 ppm, NO: 1000 ppm, and O ₂ : 2.6% was passed at 350 ° C., the purification rates of CO, propane, and NO were all 95% or more.

Example 2 A 50 μm-thick stainless steel sheet containing 5 wt% aluminum was formed into a corrugated shape by gear processing, and formed into a corrugated shape together with a flat plate to form 60 cells / sheet.
cm ² honeycomb shape. This was thoroughly washed with an organic solvent and degreased, and then heat-treated at 1050 ° C. for 1 hour in air to cool.

Next, using aluminum hydrosol as a binder, 1 mol / l of cerium nitrate, 0.1 mol / l of aluminum hydroxide (including those derived from aluminum hydrosol) and 0.005 mol / l of barium nitrate
The metal sheet after the heat treatment is immersed for 2 minutes in an aqueous solution containing
Further, heating was performed in air at 700 ° C. for 1 hour to form an oxide.

The metal sheet coated with this oxide was treated with 0.025 mol / l of dinitrodiamine platinum and 0.025 mol / l of hydrazine.
After being immersed in a liquid containing 2 vol / vol% for 3 minutes, this was taken out, dried at 105 ° C. for 30 minutes, and dried at 600 ° C. for 30 minutes.
Bake for a minute. Next, rhodium nitrate 0.005mol
/ L, immersed in a solution containing 0.02 vol / vol% hydrazine for 3 minutes, taken out, dried at 105 ° C for 30 minutes, and baked at 600 ° C for 30 minutes. Next, it was immersed again in the above-mentioned platinum solution, dried and baked in the same manner, then immersed again in the above-mentioned rhodium solution, dried and baked in the same manner.

Further, an activation treatment was performed at 450 ° C. for 15 minutes in a 2% hydrogen atmosphere (nitrogen base) to complete a thin catalyst layer having a thickness of 2 to 3 μm or less in which platinum and rhodium were alternately laminated. The porosity of the obtained catalyst cross section was 90% or more.

Using this catalyst, SV = 50,000 / h
Under the conditions of r, CO: 2000 ppm, propane: 50
When a combustion exhaust gas containing 00 ppm, NO: 1000 ppm, and O ₂ : 2.6% was passed at 350 ° C., the purification rates of CO, propane, and NO were all 95% or more.

Example 3 A 50 μm-thick stainless steel thin plate containing 5 wt% aluminum was formed into a corrugated shape by gear processing, and formed into a corrugated shape together with a flat plate to form 60 cells / sheet.
cm ² honeycomb shape. This was thoroughly washed with an organic solvent and degreased, and then heated in air at 960 ° C. for 16 hours and cooled.

Then, using aluminum hydrosol as a binder, cerium nitrate 1 mol / l, aluminum hydroxide 0.1 mol / l (including those derived from aluminum hydrosol) and barium nitrate 0.005 mol / l
The metal sheet after the heat treatment is immersed for 2 minutes in an aqueous solution containing
Further, heating was performed in air at 700 ° C. for 1 hour to form an oxide.

A metal sheet coated with this oxide was treated with 0.025 mol / l of dinitrodiamine platinum and 0.025 mol / l of hydrazine.
After being immersed in a liquid containing 2 vol / vol% for 3 minutes, this was taken out, dried at 105 ° C. for 30 minutes, and dried at 600 ° C. for 30 minutes.
Bake for a minute. Next, rhodium nitrate 0.005mol
/ L, immersed in a solution containing 0.02 vol / vol% hydrazine for 3 minutes, taken out, dried at 105 ° C for 30 minutes, and baked at 600 ° C for 30 minutes. Next, it was immersed again in the above-mentioned platinum solution, dried and baked in the same manner, then immersed again in the above-mentioned rhodium solution, dried and baked in the same manner.

Further, an activation treatment was performed at 450 ° C. for 15 minutes in a 2% hydrogen atmosphere (nitrogen base) to complete a thin catalyst layer having a thickness of 2 to 3 μm or less in which platinum and rhodium were alternately laminated. The porosity of the obtained catalyst cross section was 90% or more.

Using this catalyst, SV = 50,000 / h
Under the conditions of r, CO: 2000 ppm, propane: 50
When a combustion exhaust gas containing 00 ppm, NO: 1000 ppm, and O ₂ : 2.6% was passed at 350 ° C., the purification rates of CO, propane, and NO were all 95% or more.

Example 4 A 50 μm-thick stainless steel sheet containing 5 wt% aluminum was formed into a corrugated shape by gear processing and corrugated together with the flat plate to form a corrugated sheet of 60 cells / cell.
cm ² honeycomb shape. This was thoroughly washed with an organic solvent and degreased, and then heat-treated at 960 ° C. for 16 hours in air, then heat-treated at 1050 ° C. for 1 hour, and then cooled.

Next, 1 mol / l of cerium nitrate, 0.1 mol / l of aluminum hydroxide (including those derived from aluminum hydrosol), and 0.005 mol / l of barium nitrate, using aluminum hydrosol as a binder.
The metal sheet after the heat treatment is immersed for 2 minutes in an aqueous solution containing
Further, the oxide was applied by heating at 700 ° C. for 1 hour in the air.

The metal sheet coated with this oxide was treated with 0.025 mol / l of dinitrodiamine platinum and 0.025 mol / l of hydrazine.
After being immersed in a liquid containing 2 vol / vol% for 3 minutes, this was taken out, dried at 105 ° C. for 30 minutes, and dried at 600 ° C. for 30 minutes.
Bake for a minute. Next, rhodium nitrate 0.005mol
/ L, immersed in a solution containing 0.02 vol / vol% hydrazine for 3 minutes, taken out, dried at 105 ° C for 30 minutes, and baked at 600 ° C for 30 minutes.

Next, using the aluminum hydrosol as a binder, the above-mentioned cerium nitrate 1 mol / l, aluminum hydroxide 0.1 mol / l (including those derived from aluminum hydrosol) and barium nitrate 0.005 mol
2 minutes in an aqueous solution containing
The coating was dried at 5 ° C. for 30 minutes and heated in air at 700 ° C. for 1 hour to apply the oxide. Then, it was immersed in a platinum solution again, dried and baked in the same manner as above, and then immersed again in the rhodium solution, dried and fired.

Further, an activation treatment was performed at 450 ° C. for 15 minutes in a 2% hydrogen atmosphere (nitrogen base) to complete a thin catalyst layer having a thickness of 2 to 5 μm or less in which platinum and rhodium were alternately laminated. The porosity of the obtained catalyst cross section was 90% or more.

Using this catalyst, SV = 50,000 / h
Under the conditions of r, CO: 2000 ppm, propane: 50
When a combustion exhaust gas containing 00 ppm, NO: 1000 ppm, and O ₂ : 2.6% was passed at 350 ° C., the purification rates of CO, propane, and NO were all 95% or more.

(Example 5) As in Example 4, a stainless steel sheet containing 5% aluminum, which was corrugated and formed into a honeycomb shape, was heated at 1,200 to 1,200 ° C in air and at 870 to 970 ° C in air. After heating, the same catalyst activity was exhibited by the same catalyst preparation as in Example 4 in the case of further heating in the air to 1024 to 1200 ° C.

The metal-based catalyst of the present invention and the method for producing the same have been described in detail with reference to specific examples. However, strontium oxide, zirconium oxide, lanthanum oxide other than cerium oxide, aluminum oxide and barium oxide are used as promoters. Even when samarium oxide was used, or when palladium other than platinum and rhodium was used as a catalyst, almost the same effect was obtained.

[0053]

According to the present invention, by employing the above structure, an extremely thin catalyst layer having a thickness of 2 to 3 μm or less as compared with a thickness of 50 to 100 μm of the catalyst layer formed by the conventional wash coat method is formed. Therefore, it is suitable for forming a honeycomb-shaped catalyst or the like having a small airflow resistance, and is particularly suitable for a vehicle exhaust gas treatment catalyst or the like which is required to suppress an increase in pressure loss from the viewpoint of improving engine output. .
In addition, the plating solution when carrying the catalytically active component does not contain any poisoning component that inhibits the catalytic activity,
The combination of the acicular aluminum oxide and / or spherical aluminum oxide oxide film on the substrate thin plate, the co-catalyst, and the catalyst component, and further, the catalyst active component is supported in a layered form, so that high catalytic activity and excellent heat resistance and durability are achieved. It has become possible to obtain a sheet metal catalyst.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a production process of a metal-based catalyst of the present invention.

FIG. 2 is a cross-sectional view of a general honeycomb catalyst based on a thin metal plate.

FIG. 3 is an explanatory view of a drawback of a conventional sheet metal honeycomb catalyst.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code FI B01J 23/63 B01J 23/56 301A (72) Inventor Sakae Kanou 12 Nishikicho, Naka-ku, Yokohama-shi Yokohama Heavy Industries Ltd. 72) Inventor Yasuo Inoue 12 Nishiki-cho, Naka-ku, Yokohama-shi Honichi Engineering Co., Ltd. Honmoku Office (56) References JP-A-63-7839 (JP, A) JP-A-4-114743 (JP, A) Kaihei 4-122440 (JP, A) JP-A 4-122442 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 21/00-38/74

Claims (3)

(57) [Claims] 1. A sheet metal containing aluminum is heated in air at 870-970 ° C. or in air.
Heat at 0-1200 ° C or 870 in air
After heating at ９970 ° C., it was further heated in air to
First, cerium oxide, aluminum oxide, barium oxide, strontium oxide, zirconium oxide, lanthanum oxide, and samarium oxide are formed on the surface of a thin metal sheet containing aluminum obtained by depositing acicular or spherical aluminum oxide on the surface by heating at 200 ° C. One or more co-catalysts selected from the group consisting of platinum, rhodium and palladium, and two or more catalysts selected from the group consisting of palladium supported thereon in a layered manner. Metal-based catalyst. 2. A metal-based catalyst comprising a metal-based catalyst according to claim 1 and a co-catalyst according to claim 1 and then a layered catalyst according to claim 1. 3. The cocatalyst is formed by applying and baking an aqueous solution containing a constituent element, and the catalyst is formed by electroless plating from an aqueous solution containing a constituent element. A method for producing the metal-based catalyst according to the above.