JPH02261542A - Production of metallic catalyst supporting platinum family metal - Google Patents

Abstract

PURPOSE:To support several to ten-odd wt.% of a Pt family metal having high catalytic activity on a metallic material with superior adhesion in a single stage by sticking a soln. contg. a compd. of the Pt family metal and at least one of specified glycols to the metallic material and heat-treating this metallic material. CONSTITUTION:A soln. contg. a compd. of a Pt family metal and at least one of glycols represented by formula I (where R is H or CH3, n>=2 when R is H and n>=1 when R is CH3) is stuck to a metallic material and this metallic material is heat-treated to obtain a metallic catalyst supporting the Pt family metal. Several to ten-odd wt.% of the Pt family metal having high catalytic activity can be supported on the metallic material with superior adhesion in a single stage.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a platinum group metal-supported metal in which a platinum group metal is supported on a metal material having a linear, net-like, plate-like, honeycomb-like, or ring-like shape. The present invention relates to a method for producing a catalyst. [Prior Art] Catalysts supporting platinum group metals exhibit excellent catalytic activity at low temperatures for various oxidation properties, and are therefore used to purify various pollutants and bad odors discharged from factories, automobiles, etc. ;. Conventionally, as this platinum group metal supported catalyst,
Ceramic carriers (honeycombs, spheres, granules, pellets, etc.)
A material wash-coated with fine particles of alumina or the like supporting a platinum group metal has been used.

Incidentally, recently, not only the purification of various pollutants and bad odors in a steady state, but also the purification performance when the temperature is raised to reach a steady state has become a problem. Also, attention has been focused on lowering the operating temperature itself.

As a means to solve these problems, it was considered to speed up the warming of the catalyst itself. To this end, switching the carrier, specifically, switching from the traditionally used ceramic material with a large heat capacity to a metal material with a small heat capacity, has started to attract attention.

However, because the metal material was wash-coated with fine particles such as alumina that supported platinum group metals, heat was taken away by the fine particles such as alumina, and the purification characteristics at elevated temperatures and the purification characteristics at low temperatures were not satisfactory. . Another problem was the poor adhesion between metal materials and fine particles such as alumina.

Therefore, it was thought that supporting a platinum group metal directly on a metal material would speed up the warming of the catalyst. As a method for surface coating a platinum group metal on a metal having such a linear, net-like, plate-like, honeycomb-like, ring-like shape, etc., Japanese Patent Application Laid-Open No. 53113292 and Japanese Patent Application Laid-open No. 5311329 are disclosed.
8-159848 discloses an electroplating method.

In addition, ions can be used to precipitate metals by dissolving platinum group metal salts in water, acids, alcohols, etc., depositing them on the target metal, and heating and decomposing them or chemically reducing them. There are two methods: the solid state method, in which platinum group metal powder is deposited on the target metal together with an adhesive, and then fired.

However, each of these methods had advantages and disadvantages. In the electroplating method and the ion method, it is easy to form a catalyst with excellent adhesion to the target metal, but on the other hand, the effective surface area of the platinum group metal tends to decrease, and the catalytic activity tends to be poor. On the other hand, in the solid-state method, it is possible to select powder with a particle size and geometric shape that suit the purpose from the beginning, so it is easier to increase the effective surface area of the platinum group metal compared to electroplating and ion methods. They tended to have poor adhesion.

In order to compensate for these shortcomings, Japanese Patent Application Laid-Open No. 59-123535
In the publication, a mixed solution in which fine powder of a platinum group metal and its ions were made to coexist in an organic solvent such as monoethanolamine or ethylenediamine, and an organic binder such as an aqueous solution of calpitol of ethyl cellulose was added was attached to a ceramic honeycomb carrier, etc. A method for supporting a platinum group metal catalyst is disclosed, which is characterized in that the catalyst is then heated and calcined.

[Problems to be solved by the present invention] First, Japanese Patent Application Laid-Open No. 53-113292 and Japanese Patent Application Laid-open No. 58
The electroplating method disclosed in Publication No. 159848 can coat metal surfaces of any shape with platinum group metal uniformly, and has excellent adhesion to metals, so it is difficult to judge by appearance alone. It had an ideal shape.

However, in terms of actual catalytic activity, as will be described later, it was significantly inferior, losing catalytic activity after several ignition tests, and was completely unsuitable for practical use.

Next, a fine powder of a platinum group metal and its ions are made to coexist in an organic solvent such as monoethanolamine or ethylenediamine as disclosed in JP-A-59-123535, and an organic binder such as an aqueous solution of calpitol of ethyl cellulose is added. As mentioned in the examples in the same publication, there is also a method of applying a mixed solution to a carrier and then heating and baking it.
It may have been effective for ceramic honeycombs, which have many macroscopic pores with a diameter of several microns on the surface, but it may be effective for ceramic honeycombs, which have many macroscopic pores with a diameter of several microns on the surface, but it may be effective for metal materials with shapes such as lines, nets, plates, honeycombs, and rings. If the surface has almost no microscopic pores compared to ceramic, there is a risk that the fine powder of platinum group metal coexisting in advance may cause the platinum group metal to peel off after being supported, so the selection of the binder is very difficult. becomes important. In fact, as will be described later, the organic binder of the aqueous solution of ethyl cellulose in calpitol disclosed in the publication was unable to prevent the platinum group metal from peeling off.

Furthermore, in the method disclosed in the same publication, the amount of platinum group metal supported on the ceramic honeycomb is only about 0.2% by weight, and it is possible to carry several to several tens of weight% of platinum group metal without peeling off the platinum group metal. It seemed extremely difficult to carry it. In fact, as will be described later, when platinum group metals are supported on a metal carrier, most of the platinum group metals are peeled off using the method disclosed in the same publication, and the remaining platinum group metals on the metal carrier are removed. The amount was less than a few tenths of a percent.

For this reason, it has excellent adhesion to metal materials with linear, net, plate, honeycomb, and ring shapes, and has high catalytic activity. There has been a need for a method for producing a platinum group metal-supported metal catalyst that can be supported in one step.

[Objective of the present invention] The present invention has excellent adhesion to metal materials having shapes such as linear, net-like, plate-like, honeycomb-like, and ring-like shapes, has high catalytic activity, and has a content of several to several tens of percent by weight. An object of the present invention is to provide a method for producing a platinum group metal-supported metal catalyst that can support a platinum group metal at once.

[Means for Solving the Problems 1] The present inventor has found that among various organic solvents, the following formula % formula %) In the formula, R represents H or CH, and when R is H, n≧ 2, and when R is CH, n≧1, one or more compounds selected from the group consisting of compounds (glycols), such as diethylene glycol, triethylene glycol, tetra Ethylene glycol, polyethylene glycol, propylene glycol, tripropylene glycol has excellent adhesion to metal materials with shapes such as linear, net, plate, honeycomb, and ring shapes, and has high catalytic activity. Moreover, they have discovered that it is an effective substance for producing a platinum group metal-supported metal catalyst that can support several to tens of weight percent of platinum group metal at once, and have completed the present invention. An object of the present invention is to provide a method for producing a platinum group metal-supported metal catalyst in which a platinum group metal is supported on a metal material having a linear, net-like, plate-like, honeycomb-like, or ring-like shape. This is achieved by a method for producing a platinum group metal-supported metal catalyst, which comprises applying a solution containing at least one of the above glycols to a metal material, and then heat-treating the metal or material.

The present invention will be explained in detail below.

Among the above glycols used in the present invention, polyethylene glycol refers to those having an average molecular weight of 200 or more.

Among these, polyethylene glycol having an average molecular weight of 200 to 400 is liquid at room temperature, so it can be used as it is as a solution.

Polyethylene glycol with an average molecular weight of 600 or more is
At room temperature, as the molecular weight increases, the appearance changes from semi-solid (average molecular weight: 600) to white soft wax-like (average molecular weight: 1
000), milky white waxy solid (average molecular weight; 30
00 or more), but since they all dissolve well in water, they can be used as a solution after being dissolved in water. Diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and triethylene glycol are also liquid at room temperature, so they can be used as they are as a solution.

Regarding the platinum group metal used in the present invention, the above-mentioned glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, are all suitable for use with water, alcohol, etc. Since it is well soluble in solvents, the type of platinum group metal is not particularly important, and any compound thereof may be used as long as it is soluble in organic solvents such as water and alcohol.

Alternatively, a solution containing a platinum group metal compound and the above glycols (for example, diethylene glycol, triethylene glycol, tetraethylene glycol), and at least one of polyethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are added. When mixed with a solution containing the metal, fine particles of the platinum group metal and/or its compound may be generated.

The amount of the platinum group metal compound to be dissolved in an organic solvent such as water or alcohol can be added until saturation is achieved depending on the amount of platinum group metal supported on the metal material. Water in which a platinum group metal compound is dissolved, an organic solvent such as alcohol, and at least one of the above glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dibrobylene glycol, and triethylene glycol. The mixing ratio with the solution is not particularly limited, but in order to maintain an appropriate viscosity and to uniformly support the platinum group metal on the metal surface, the weight ratio is l/10 to 50/l, preferably 1/l. 7-30/1, more preferably 115-2
It is desirable that the ratio is 0/l.

Although the quality of the metal material is not particularly limited, it is desirable that it has high heat resistance since it is often exposed to high temperatures due to usage conditions.

Pretreatment of the metal material is not particularly required, but in order to uniformly support the platinum group metal on the metal surface, the metal material may be chemically treated by soaking it in acid, etc., or fine powder such as corundum may be compressed. Roughen the metal surface by physically treating it by blowing with air or
It is preferable to heat the metal surface at a high temperature of 00° C. or higher for several minutes to several hours to generate whiskers and make the metal surface uneven.

At least a platinum group metal compound and the above-mentioned glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, in order to prevent the platinum group metal from peeling off from the metal material. The heat treatment temperature after attaching the mixed solution containing one is 400°C-1100°C1
More preferably, the temperature is 600°C to 900°C. At temperatures below this range, compounds of platinum group metals are difficult to convert into platinum group metals and/or their oxides, and at temperatures above this range, the metal material itself cannot withstand the temperatures. The heat treatment time is 1 minute to 3 hours, preferably 3 minutes to 2 hours.
Time, more preferably 5 minutes to 1 hour.

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

As for the shape of the metal material used, for example, a wire mesh from which the supported platinum group metal is most easily peeled off was selected. Also,
As for the material, Kanthal, which has high thermal durability, was selected.

Example 1 A solution of hydroxyplatinic acid dissolved in monoethanolamine (
Pt concentration: 20% by weight) Ig was collected using a graduated pipette and placed in a 20m12 beaker. 0.5 g of polyethylene glycol (average molecular weight: 400) was collected with a measuring pipette and added to the beaker. After mixing both well with a brush, add 30 mesh, 4 cm square Kanthal wire mesh (1
This mixed solution was applied with a brush to both sides of the substrate (which had been heat treated at 100°C for 3 hours) without any corners. The Kanthal metal coated with the mixed solution was fired in a Matsufuru furnace at 700°C for 130 minutes. The amount of PT supported was 7% by weight (2 mg/cm2).

Example 2 After applying 30 meshes of the mixed solution prepared in the same manner as in Example 1 to a 4 cm square Kanthal wire mesh (spraying of fine powder such as corundum with compressed air has already been done) on both sides with a brush, without any corners. , and baked in a Matsufuru furnace at 700°C for 130 minutes. The amount of Pt supported was 7% by weight (2 mg/am'').

Example 3 A mixed solution prepared in the same manner as in Example 1 was applied to 30 meshes of 4 cm square Kanthal wire mesh (untreated) with a brush on both sides without corners, and then baked in a Matsufuru furnace at 700°C for 130 minutes. The supported amount of pt is 7% by weight (2mg/cm2)
Met.

Example 4 Using the same amount of diethylene glycol instead of polyethylene glycol (average molecular weight: 400), a mixed solution prepared in the same manner as in Example 1 was brushed onto a 30 mesh, 4 cm square Kanthal wire mesh (heat treated at 110°C for 3 hours). After coating both sides without corners, heat in a Matsufuru furnace at 700°C.
It was baked for 130 minutes.

The supported amount of Pt is 5% by weight (1-5mg/cm2).

Example 5 Using the same amount of propylene glycol instead of polyethylene glycol (average molecular weight: 400), a mixed solution prepared in the same manner as in Example 1 was heat-treated with 30 meshes and a 4 cm square Cantal wire mesh (1100'C!) for 3 hours. After applying it on both sides with a brush without any corners, heat it at 700° in a Matsufuru furnace.
It was fired for C130 minutes.

The amount of Pt supported was 3.3% by weight (1 mg/am2).

Example 6 Using the same amount of dipropylene glycol instead of polyethylene glycol (average molecular weight: 400), a mixed solution prepared in the same manner as in Example 1 was applied to 30 meshes of 4 cm square Kanthal wire mesh (heat treated with llOooc for 3 hours). After applying it on both sides with a brush without any corners, heat it in a Matsufuru oven at 700℃.
, and baked for 30 minutes.

The amount of Pt supported was 1% (4 mg/cm') of 13i.

Example 7 Using the same amount of tripropylene glycol instead of polyethylene glycol (average molecular weight, 400), a mixed solution prepared in the same manner as in Example 1 was heated to 30 mesh, 4 cm square Kanthal wire mesh (11" oooC for 3 hours) completed)
After applying it on both sides with a brush without any corners, heat it in a Matsufuru oven for 70 minutes.
It was baked at 0°C for 130 minutes.

The amount of Pt supported was 13% by weight (4 mg/cm'').

Example 8 Amine solution of hydroxyplatinic acid (Pt concentration: 20% by weight) I
g was collected with a measuring pipette and placed in a 20 m12 beaker. 0.25 g of diethylene glycol was collected with a measuring pipette and added to the beaker. 0.25 g of polyethylene glycol (average molecular weight: 400) was collected with a measuring pipette and added to the beaker. After thoroughly mixing the three types of solutions with a brush, the mixed solution was applied with a brush to both sides of a 30 mesh, 4 crn square Kanthal wire mesh (heat treated at 1100° C. for 3 hours) without any corners. The Kanthal wire mesh coated with the mixed solution was fired in a Matsufuru furnace at 700°C for 30 minutes. The amount of Pt supported was 17% by weight (5 mg/c).

Example 9 Aqueous solution of palladium nitrate (Pd concentration: 20% by weight) Ig
was collected with a graduated pipette and placed in a 20m4 beaker. Polyethylene glycol (average molecular weight; 400) 0
．． 5 g was collected with a measuring pipette and added to the beaker. After mixing both well with a brush, 30 meshes, 4 cm
Corner Kanthal wire mesh (heat treated at 1100°C for 3 hours)
The mixed solution was applied to both sides with a brush without any corners. Kanthal wire mesh coated with the mixed solution is heated to 700°C in a Matsufuru furnace!
, and baked for 30 minutes. The supported amount of Pd was 7% by weight (2mg
/ cm.

Example IO An aqueous solution of rhodium nitrate (Rh concentration: 10% by weight) Ig was collected with a measuring pipette and placed in a 20 mQ beaker.

Polyethylene glycol (average molecular weight: 400) 0.
5 g was collected with a measuring pipette and added to the beaker. After thoroughly mixing both with a brush, the mixed solution was applied to both sides of a 30-mesh, 4 cm square Kanthal wire mesh (heat-treated at 1100° C. for 3 hours) without any corners using a brush. The Kanthal wire mesh coated with the mixed solution was heated in a Matsufuru furnace at 70°C and 30°C.
Bake for a minute. The amount of Rh supported was 3.3% by weight (1mg/
0m2).

Comparative Example 1 30 mesh, 4 cm square Kanthal wire mesh (1100°C
(heat treated for 3 hours) was electroplated with PT. The amount of pt supported was 10% by weight (3 mg/cm'').

Comparative Example 2 Amine solution of hydroxyplatinic acid (Pt concentration: 2o wt%) I
g was collected with a measuring pipette and placed in a 20 mff beaker. Calpitol aqueous solution of ethylcellulose 0.5g
was collected with a measuring pipette and added to the beaker. Mix both well with a brush, and after confirming that a large number of P particles have been generated, apply the mixed solution on both sides of a 3° mesh, 4 cm square Kanthal wire mesh (heat treated with lloO'c! for 3 hours) using a brush. I painted it without any problem. The Kanthal wire mesh coated with the mixed solution was fired in a Matsufuru furnace at 700'C for 130 minutes.

As a result of gently lifting the wire mesh and weighing it, the amount of Pt supported was 3.3% by weight (1 mg/am'').

Comparative Example 3 Amine solution of hydroxyplatinic acid (Pt concentration: 20% by weight) I
g was collected with a measuring pipette and placed in a 2o-beaker. 0.5 g of ethylene glycol was collected with a measuring pipette and added to the beaker.

After mixing the two well with a brush, the above solution was applied to both sides of a 30-mesh, 4 cm square Kanthal wire mesh (heat-treated at 1100° C. for 3 hours) without any corners using a brush.

The Kanthal wire mesh coated with the mixed solution was heated in a Matsufuru furnace.
It was baked at 00°C for 130 minutes. As a result of weighing the wire mesh, there was almost no increase in weight.

Comparative Example 4 Amine solution of hydroxyplatinic acid (Pt concentration: 20% by weight) 1
．． 5 g was collected with a graduated pipette and placed in a 20++i2 beaker. 30 mesh, 4cm square Kanthal wire mesh (
Heat-treated at 1100°C for 3 hours), apply the above solution to both sides with a brush without any corners, then heat at 700°C in a Matsufuru furnace.
It was baked for 30 minutes. As a result of weighing the wire mesh, there was almost no increase in weight.

Weight measurement The catalyst obtained in Comparative Example 3.4 was weighed after supporting Pt, and it was found that almost no PL was attached.

Although the catalysts obtained in 5ME German Examples 1 to 1O and Comparative Example 1 supported platinum group metals in an amount of several to ten-odd percent by weight, they did not react well even when beaten or rubbed with a brush. Almost no peeling of the platinum group metal occurred. On the other hand, when the catalyst obtained in Comparative Example 2 was struck or rubbed, most of the Pt was peeled off from the wire gauze, and when the weight was measured, the weight returned to almost the same as before supporting Pt.

JP-A-59-123535 discloses a method for supporting a platinum group metal catalyst characterized by the coexistence of a fine powder of a platinum group metal and its ions, but from a peel test of the catalyst obtained in Comparative Example 2, As is clear, the organic binder (carpitol aqueous solution of ethyl cellulose) disclosed in the same publication
It was found that the peeling of platinum group metals could not be suppressed with this method.

On the other hand, as is clear from the peeling tests of the catalysts obtained in Examples 1 to IO, when the various organic substances disclosed in the present invention are used, platinum group metals are hardly peeled off from metal materials. lko.

The catalysts obtained in Examples 1 to 10 and Comparative Example 1 were each observed using an optical microscope with a magnification of 20 to 80 times.

In the catalysts obtained in Examples 1.2.4 to 10 and Comparative Example 1, the platinum group metal was almost uniformly distributed on the surface of the Canthal wire. The state of adhesion of the platinum group metal was as shown in Example 1 using an ethylene glycol-based organic substance and a propylene glycol-based organic substance.
The catalysts obtained in , 2.4 to 10 adhered to the surface of the Kanthal wire rather roughly, whereas the catalyst obtained in Comparative Example I using the electroplating method adhered smoothly to the surface of the Kanthal wire. Ta. In addition, Example 3 in which the same polyethylene glycol was used but the Kanthal wire mesh was not pretreated.
In the catalyst obtained in the above, PL was distributed slightly thickly in the corners of the Kanthal wire gauze and slightly thinly distributed in the straight parts. Similar to the catalysts obtained in Examples 1 and 2.4 to 1O, Pt was adhered quite roughly to the surface of the Kanthal wire.

Comparing the results of optical microscopic observation of the catalysts obtained in Examples 1 and 2.4 to IO with the catalyst obtained in Comparative Example I, it was found that diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, diethylene glycol If at least one of tripropylene glycol is used, the platinum group metal can be almost uniformly coated on the surface of the Kanthal wire, but it is considerably rougher (larger effective surface area) than the electroplating method (Comparative Example 1).
It was found that it was carried.

Furthermore, as is clear from the optical microscopic observation of the catalysts obtained in Examples 1 to 3, it is better to roughen the metal surface by subjecting the Kanthal wire gauze to heat treatment, chemical or physical treatment, etc. was found to be more uniformly distributed on the surface.

After roasting the catalysts obtained in Examples 1 to 10 and Comparative Example 1 with the flame of a gas burner, the catalysts obtained in Examples 1 to 10 and Comparative Example 1 were heated to red hot, and then the flame of the gas burner was extinguished by blowing forcefully with air, and the flame of the gas burner was extinguished using only the gas from the gas burner. A test was conducted to see if it would catalytically burn (become red hot). Example 1
The catalysts obtained in Comparative Example 1 and Comparative Example 1 all underwent catalytic combustion at first.

However, only the electroplated catalyst of Comparative Example 1 did not become red hot after several combustion tests and lost its catalytic activity. From these results, it can be said that the electroplated platinum group metal-supported metal catalyst has significantly inferior catalytic activity.

On the other hand, all the catalysts obtained in Examples 1 to 10 continued to perform catalytic combustion, and in particular, the catalysts obtained in Examples 1 and 4 to 8 carrying PT were subjected to 8000 blowout tests. Even after that, the appearance of red heat caused by catalytic combustion did not change at all.

Example 11 of loading platinum group metal onto a metal plate A mixed solution prepared in the same manner as in Example 1 was applied to a 4 cm square stainless metal thin plate (heat treated at 1100°C for 3 hours) on both sides without corners using a brush. After that, 700 in the Matsufuru furnace
Baked for 130 minutes. The amount of Pt supported was 3% by weight (2
0mg/cm"). Even if stainless metal carrying Pt is struck or rubbed with a brush, almost no Pt is removed.
No peeling occurred.

Comparative Example 5 A mixed solution prepared in the same manner as Comparative Example 2 was applied to a 4 cm square stainless metal thin plate (heat treated at 1100°C for 3 hours) on both sides with a brush, and then heated in a Matsufuru furnace for 7 hours.
It was baked at 00°C for 130 minutes.

When the stainless steel metal supporting PL was struck or rubbed with a brush, most of the Pt was peeled off from the metal plate, and when the weight was measured, the weight returned to almost the same as before supporting Pt.

As is clear from the results of the weight measurement of the catalyst obtained in Comparative Example 5, even if a metal plate from which the platinum group metal is relatively difficult to peel off is used as a carrier, the same method as disclosed in JP-A-59-123535 can be used. As long as an aqueous solution of ethyl cellulose in calpitol was used as an organic binder, it was not possible to suppress the peeling of platinum group metals.

[Effects] As is clear from the above, the method of the present invention has excellent adhesion to metal materials, high catalytic activity, and can support several to tens of weight percent of platinum group metals at once. Platinum group metal supported metal catalysts can be produced.

Claims (1)

[Scope of Claims] When producing a platinum group metal-supported metal catalyst in which a platinum group metal is supported on a metal material having a linear, net-like, plate-like, honeycomb-like, or ring-like shape, (1) platinum group metal Compound and (2) The following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ In the formula, R represents H or CH_3, When R is H, n≧2, When R is CH_3, A platinum group metal, characterized in that a solution containing one or more compounds selected from the group consisting of compounds represented by n≧1 is applied to a metal material, and then the metal material is heat-treated. A method for producing a metal-supported metal catalyst.