DE2306785C3 - Catalyst for removing nitrogen oxide from exhaust gases - Google Patents

Description

The invention relates to a catalytic converter for removing nitrogen oxide from exhaust gases.

Known industrial catalysts for cleaning exhaust gases contain agendas that essentially from a carrier material, such as. B. consist of aluminum oxide, which absorbs precious metals such as Pt or Pr or forms a mixture with oxides of Ni, Cu or Cr. If you use precious metals like Pt or Pr, the disadvantage is that they are very expensive and not available in sufficiently large quantities stand that their heat resistance and wear resistance are also insufficient and that each other the processes for their production are not suitable for series production. Various known catalysts, which are formed by alloy systems.

There are also catalysts known by an alloy of copper, the balance nickel and / or Iron are formed (US-PS 35 65 574). However, they are extremely effective at high temperatures small amount.

The object of the invention is to provide a catalyst of the initially; called kind of creating this Does not have disadvantages, can be produced economically and its effectiveness is higher than that of the known Catalysts is. In particular, it should be suitable for extracting nitrogen oxide from the exhaust gases of internal combustion engines to remove.

They are also catalysts made as sintered bodies known (US-PS 32 06 414), in which iron, copper and nickel particles are used as the starting material on the surface of which a copper oxide layer is applied. There are also catalysts known (US-PS 2 75 367), which contain iron and copper in the form of their nitrates as precipitates and certain reduction conditions in a gas atmosphere specially designed for this purpose get abandoned. The US-PS 22 34 264 shows how by intensive mixing of copper oxide and nickel powder a reduction of copper to copper oxide can take place.

The invention makes use of a catalytic converter for removing nitrogen oxide from exhaust gases an alloy consisting of 0.1-40% copper, the balance nickel and / or iron created the characterized in that the surface of the alloy is coated with an oxidation layer enriched with copper of a thickness of more than ΙΟμηι is coated and that this alloy undergoes a reduction treatment for withdrawal after its shaping is subjected to oxygen.

This results, as explained below and in comparison to the known catalysts, a high purification rate with regard to the removal of harmful components from the exhaust gas, in particular the Nitrogen oxide.

An advantageous development of the invention provides that the catalyst additionally contains up to 40% Co or Cr, furthermore contains further elements up to a total of 10% which are soluble in the matrix, none Form an intermetallic compound with copper and no precipitation of copper from the matrix cause.

A method of making such a

The catalyst is characterized in that the final shape of the catalyst is ^{heated in an oxidizing atmosphere of 700-110O 0} C in such a way that an oxidation layer with a thickness of 10 μm forms on the surface of the alloy and then the layer on the surface of the alloy is activated by a reduction treatment in a hydrogen gas atmosphere at a temperature of more than 600 ⁰ C.

Embodiments of the invention are described below with reference to the drawings or photographic representations. It shows:

1 shows a state diagram for illustration the composition of the alloy used for the catalyst,

F i g. 2 shows a graphic representation of the dependence of the NO or CO purification rates and the Bed temperature of the catalyst,

3 to 8 microscopic photographs of alloys and catalysts according to the exemplary embodiments 1 to 6,

9 shows one with the aid of an electronic scanning microscope Created photograph showing the condition of the surface of an alloy without an oxidized layer indicates,

10 photographs of the surface, also made with the aid of an electronic scanning microscope an alloy surface with an oxidized layer more than 10 μ thick.

The catalysts are designed to reduce nitrogen oxide (NO) from the exhaust gas emitted by internal combustion engines and thus remove it from the exhaust gas. With them one obtains considerable effects in the removal of harmful components from exhaust gases in relatively low temperature ranges from 400 to 600 ^° C .; they allow a choice of alloys

and alloy components in a very wide range and can correspond to a large number of Application needs can be deformed as desired. Their composition and manufacture will specified below:

The alloys from which the catalysts are made represent a binary Fe-Cu- or Ni-Cu alloy system or a ternary Fe-Ni-Cu alloy system (hereinafter: alloy system), which is always less than 99.9% Fc and Ni and den The remainder contains Cu (weight percentages are always given here and below).

It is possible to reduce the content of Fe and Ni and instead other elements, that is other than Fe, Ni and Cu to be added at less than 10%.

With regard to the selection of the elements that can be added or added, there is none special restriction. Since, however, the addition of Co and Cr has a very good catalytic effect results, these elements are up to 40% useful. Co has an effect similar to that of Cu. But you can also use the non-metallic elements such as C and Si, which are contained in common alloys are to be attached.

The composition range of the alloy system for the catalysts is shown in FIG. 1 shown. The square area surrounded by the points ABCD indicates a standard area. Even if other elements are added, any alloy composition within the diagonally hatched area is suitable.

The alloy system in this composition range is made by the conventional methods manufactured and as a plastically deformable and workable semi-finished product, d. H. in the form of Bars, plates, tubes, strands or as alloy powder, cast material, etc., with the desired Composition won. In detail, it depends on the intended type of application.

An essential feature is that on these alloys oxidized layers with a thickness of to apply more than 10 μ. The catalysts already work in a satisfactory manner if they have these oxidized layers. However, an advantageous development of the invention provides propose to improve their properties significantly in that those formed on the alloys oxidized layers are reduced. Several exemplary embodiments are given below.

example 1

A ternary Fe-Ni-Cu alloy with the compositions according to Table 1 is ^{melted down at 1600 °} C. using a Tammann furnace. A cast blank is produced in a mold made of stainless steel with the Japanese standard name SUS 27 with a sufficiently thick graphite layer. After the casting process, pieces (chips or snippets) are machined from the cylindrical rods obtained in this way. These are subjected to an oxidation treatment in a high-temperature atmosphere at 1000 ^{° C. for six hours.} They then represent the catalyst pieces.

Such pieces give a larger apparent surface area per unit weight. Your dimension depends on the material; preferably those with a thickness of 0.1-0.5 mm are used, a lung 2–20 mm and a width of 1-3 mm. The size of the bits of which im The following is in question, is in this size-5 order.

Half of the catalyst obtained in this way (after the oxidation) is subjected to a reduction treatment ^{in hydrogen gas at 800 ° C. for two hours.} The alloy compositions and

ίο the purification rates obtained with this method Catalyst are given in Table 1. The table shows this for the individual samples For example, the alloy composition after casting and the cleaning rates used in tests using 10 ml of the catalyst. These explanations also apply to the further tables, unless otherwise stated.

The apparent surface of a catalyst from

10 ml depends on the composition of the Kata-Jysator, but is mostly in the range of 100 to 1000 cm ² . Unless otherwise stated, this also applies to the other examples.

Example 2

A binary Fe-Cu alloy of Fe and Cu with the compositions according to Table 2 is ^{poured at 1650 °} C. in the same metal mold as in Example 1 after melting into a high-frequency melting furnace. Machine cuts are made from the cylindrical rods obtained in this way. They are exposed to an oxidation treatment in an atmosphere of 1100 ^{° C. for three hours.} This gave the catalysts. Half of the cuts were then subjected to a reduction treatment ^{in hydrogen gas at 800 ° C. for two hours.}

Example 3

A catalyst sheet was obtained by subjecting a sheet with the composition according to Table 3 to atmospheric oxidation at 800, 900, 1000 and 1100 ° C. for 24, 12, 6 and 3 hours, respectively. This catalyst sheet was shaped into a cylindrical shape. It was 0.5 mm thick, 2.5 mm wide and 15 mm long. Half of them were subjected to a reduction treatment in hydrogen gas at 800 ^{° C. for 2 hours.} The apparent surface area of a 10 ml catalyst was approx. 100 cm ² .

Example 4

An Fe-Ni-Cu alloy, which also contained further elements, with the composition according to Table 4, was processed into sections and ^{exposed to an atmospheric high-temperature oxidation at 1000 °} C. for six hours; half of them were subjected to a reduction treatment in hydrogen gas at 800 ^{° C. for two hours.}

Example 5

A binary Fe-Cu alloy, which also received further components, with the composition according to Table 5, was ^{exposed in the form of sections to an atmospheric high-temperature oxidation at 1100 °} C. for three hours; half was then exposed to a reduction treatment in hydrogen gas at 800 ^{° C. for two hours.}

Example 6

A Ni-Cu alloy, which also contained further constituents, with the composition according to Table 6, was formed as a 1.0 mm thick sheet and exposed to atmospheric high-temperature oxidation ^{at 900 ° C. for twelve hours;} the sheet-shaped catalyst was obtained in this way. Half of them were subjected to a reduction treatment in hydrogen gas ^{at 800 ° C. for two hours.} io ^ The sheet with the dimensions 1.0 mm × 2.5 mm × 15 mm (as in Example 3) was shaped cylindrically. The apparent surface area of the 10 ml catalyst was approximately 100 cm ² .

Table 2 (example 2)

Composition and purification rates of an Fe-Cu alloy system

sample
No. Chemical
Settlement Together- Status NO-Rci-
inclination
rate Cu Fe 16 2.5 rest oxidized
activated 6.8
70.0 17th 4.6 rest activated
activated 8.0
71.8

Table 1 (example 1)

Composition and cleaning rates one

Fe-Ni-Cu alloy system

Table 3 (Example 3) Treatment preconditions, composition and

sample Chemical 7! N «ammprKPt7iiniT Ni Fe NO-Reini ^minnc - sample activated .Ult ^ l (111 * 11 VUI 1 I ¹ Il \ ^ U J_ * V * £ 1 Wl UlIgWl CO- No. 2.8 rest rate No. Chemical Status NO- Clean 3.6 rest Status 74.5 Together Clean gearing
ran Cu 8.9 rest oxidized 56.1 18 settlement gearing
rate /O 1 0.5 9.1 rest 30.0 36.2 Cu Ni % 2 0.8 8.7 rest 53.4 64.3 30.0 3 0.9 50.8 rest 28.4 86.2 30 24 66 800 ° C, 14.4 4th 1.8 9.5 rest 56.0 49.9 oxidized 53.3 5 2.6 20.3 rest 19.5 58.1 activated 36.0 52.2 6th 4.4 17.5 rest 51.3 80.0 900 ° C, 76.8 7th 5.2 9.9 rest 30.7 53.2 oxidized 46.0 8th 5.3 35.4 rest 4.0 57.8 35 activated 54.3 9 6.4 15.0 rest 3.3 74.3 0 10 7.4 42.1 rest 4.3 72.1 1000 ⁰ C, 0 11th 8.8 22.3 rest 6.6 70.8 oxidized 58.2 12th 9.5 52.0 rest 4.0 78.5 activated 58.2 1 13th 10.9 0 1100 ° C, 0 14th 18.1 0 oxidized 48.2 15th 26.4 0 activated 62.0

Table 4 (example 4)

Composition and purification rates of an Fe-Ni-Cu alloy system with additives

Sample no. Chemical Composition (%) rest other NO purification ("") activated C-1.0, Status 75.0 Cu Ni St - 2.2, oxidized 19th 8.8 30.4 rest Co - 21.4 germ: C-2.1, Measurement 72.1 rest Sl - 2.3 20th 9.8 18.4 C -1.6, none 80.9 rest Sl - 2.1 Measurement 21 11.6 39.8 C-1.5, none 72.0 rest Si -1.6 Measurement 22nd 17.7 47.6 rest Al - 3.9 none 74.1 C-U, Measurement 72.0 23 17.7 32.0 rest Sl -1.6 3.7 24 18.9 47.4 rest Si - 4.3 none 75.3 rest Cs - 4.1 Meiiau ng no messu 25th 27.9 17.3 rest Al - 2.8 0 77.7 26th 24.3 39.1 Si - 3.1 1.8 70.4 27 29.7 3.7 2.8 28 30.1 8.9 0

Table 5 (example 5)

Composition and cleaning rates one
Fe-Cu alloy system with additives

sample
No. Chemical composition Fe other NO cleaning
rate (%) activated rest Co-36.5 Status 86.2 Cu rest Si-2.9 oxidized 56.5 29 9.4 rest Al -3.0 21.4 84.1 30th 19.0 rest Ti-3.2 28.3 96.3 31 19.3 rest Co-33.0 1.2 76.0 32 20.8 2.4 33 28.9 4.0

Table 6 (example 6)

Composition and cleaning rates one
Ni-Cu alloy systems with additives

Sample chemical

No. Composition (%)

Cu

Ni

other

State NO-clean
delivery rate

O/ /O

4.1 29.0

Cr-20.5
Mon-2.8

oxidizes 50.2
activated 32.2

The following are the reasons for dimensioning the amount of each element in the composition the alloy system shows the effect of these elements.

In order to bring about the catalytic effect, the copper is oxidized and then reduced. CuO * forms on the surface of the alloy; it is assumed that it ^{diffuses into the FcO 1} "and NiO * and is of great importance for the catalytic effect.

In the present context, CuO * denotes oxidized Cu. Us is represented in such a way that because its condition when brrciuhun the optimal cooling effect is unknown and the oxygen content cannot be determined.

It is to be assumed that kiitalyllian activity then is given when the O * content in the oxides is almost zero. With FeO * and NiO * is intended with regard to the Iron and nickel oxides are the same as expressed by CuO * with regard to the copper oxides ».

When examining the surface of the at alloys subjected to high temperature oxidation by means of diffraction of X-rays the following compositions were used to ascertain these facts

CuO * - * CuO

FeO * - * FcgO., (Llaemntil)

NiO * - »NiO

When examining the surface of the alloys after the reduction treatment were with the help of diffraction of X-rays determined the following compositions:

CuO * -> Cu (* = 0)
FeO * -> Fe (* = 0)
NiO * -> Ni (* = 0)

CuO * -> Cu (* ^ 0)

FeO * -> Fe ₂ O ₃ (hematite) ^ FeO ₃ z ₂ (** »0) FeO ₃ Z ₂ * - * FeO (* s» 0)
NiO * -> Ni (* «» 0)

After the reduction treatment, the surface of the alloy was examined with With the help of a diffraction of X-rays, the following compositions were found:

CuO * -> Cu (* ^ 0)
FeO * -> Fe (* «* 0)
NiO * -> Ni (* s »0)

ao One cannot conclude from this, however, that all components are present in the specified state was.

The reason for the limitation of the Cu content is as follows: If it exceeds or falls below 40% er 0.1%, then the diffusion of the CuO * into the NiO * and the FeO * becomes dense or poor. Both impairs the catalytic effect. If there is an excess of Cu, separation and deposition takes place in the alloy, provided that no solid solution or intermetallic compound is formed.

This problem arises from the binary Fe-Cu phase diagram according to FIG. 1 from the presence of iron. However, deposited Cu has no catalytic effect.

It is difficult to oxidize intermetallic compounds. Even in the event of oxidation they do not form oxidized layers that show a catalytic effect. Cu results then, though it is contained in the compound, no catalytic effect .. the more the Legicrungssystem a solid Solution of Fc-Ni-Cu or Fe-Cu contains, the more the catalytic effect is greater.

With regard to the Ni and Fc, it is believed that both promote the catalytic effect rather than to have a direct reduction effect with regard to NO. This means that through them the dispersed State of the CuO * becomes more effective and that they have a very strong ability to like Co and II », which contribute to the reduction of NO, to adsorb.

At the same time, the Ni serves to widen the limit for solid solution of the Cu into the Fc. This can be done on the basis of the binary state diagram of Ni-Cu and Fe-Ni according to Fig.

to take. Both coexistence and independent existence of Ni and Fe are acceptable.

If the elements that make up the Fe-Ni-Cu alloy system, be added to the Fe-Cu alloy system or the Ni-Cu alloy system,

meet the following conditions, then the catalytic effect does not suffer:

1. Penetration into the solid solution,

2. no creation of an intermetallic compound with Cu,

3. No deposition of Cu due to the presence of the added elements.

709 626/181

If less than 10% of the added elements meet these conditions, a catalytic effect is obtained. The less these conditions are met, the lower the catalytic effect; however, it remains essentially as long as the quantity of the added elements no longer exists than 10%.

Even a precipitation of graphite in the structure of the alloy as a result of the addition of Carbon or silicon does not impair the catalytic effect. Co behaves similarly to Cu in the sense described; it is not necessary to particularly limit its salary; the upper However, the limit is determined in terms of coexistence with Fe and Ni. Cr lowers the catalytic effect not in any significant way; its salary can be largely restricted. A salary however, Cr of more than 40% is from the standpoint of melting and subsequent working undesirable.

Figures 3 and 8 are microscopic photographs of cast and annealed structures having the compositions of Examples 1 to 6 to explain the effect of each element. Annealed structures that have been annealed for six hours by cooling the furnace after heating at 1000 ⁰ C such.

The following describes the effect of the oxidized and the reduced layers, which are essential for achieving an optimal catalytic effect. The oxidized layers are obtained by oxidation under atmospheric conditions. Since the thickness of the oxidized layers depends on the composition of the alloy, the surface properties, the oxidation temperature and the duration of the oxidation treatment, the treatment conditions cannot be precisely formulated. The desired thickness can be achieved in that the following conditions are observed, however: The oxidation takes place in a temperature range of 700 to HOO ⁰ C for a period of _V2 hour to 24 hours instead.

The oxidized layer must be at least 10 μm thick being. A thickness of more than 10μ: ιη is unlimited up to the extreme case, namely up to the middle range of the alloy.

If, however, the thickness of the layer is less than 10 μm, the catalytic effect is noticeably impaired and ultimately unattainable at temperatures of over 700 ° C. This is essentially due to the effect of CuO *, NiO *, FeO * etc. in comparison with that described above An oxidized layer having a thickness of at least 10 µm is also necessary in order to undulate the layer surface and enlarge it, as will be explained below X-ray microanalyser was able to clarify the following: layers enriched with Fe and Cu are formed on the surface; the layer enriched with Cu is closer to the surface than the layer enriched with Fe. This tendency becomes even clearer with a reduction treatment; the layer enriched with Cu The layer then exists entirely on the surface.

Also forms in the area near the surface

a mi). Ni enriched layer; however, it is somewhat lower than that enriched with Fe and Cu Layers and after a reduction treatment in the same position as or slightly closer to the surface than the Fe enriched layer. The gam formed near the surface is enriched with Cu Layer exists regardless of the addition of additional elements. Co shows an enriched state, which is similar to that of Cu.

If the oxidized layer is thinner than 10 μΐη, can one does not form an enriched oxidized layer in the sense described above. If the oxidized layer thicker, then the above-mentioned tendency becomes greater, i. that is, the Cu accumulates in the surface and diffuses into the Ni and Fe. This is advantageous for the catalytic effect. In Examples 1 to 6 was this guaranteed; the thickness of the oxidized layers was in the range between 0.5 and 1.0 mm. When the oxidized layers were observed with the aid of a scanning microscope, it became clear that the oxidized layers were corrugated and porous and that this tendency then became particularly extreme, when its thickness was more than 10 μπα, and further that this tendency became particularly noticeable when the oxidized layer was subsequently subjected to a reduction treatment.

Therefore, an oxidized layer with a thickness of less than 10 μm obviously sets the catalytic effect down. This results from the observation of the surfaces as described. This The tendency is evident from FIGS. 9 and 10 can be seen. F i g. 9 shows the surface when the oxidized layer is deposited insufficiently developed. A corrugation and a porosity cannot be determined. Both are, however

in Fig. 10 is present, which shows a sufficiently oxidized layer.

As explained in connection with the examples, the reduction treatment consists of the oxidized ones Layer in that it is exposed to the influence of hydrogen gas. That happens between Va and 24 hours and depends on the condition of the desired oxidized layer. Partial treatment is also possible.

The following are the test results for individual clnc According to the invention produced Ausführungsbeispiclc the catalysts indicated.

Test example 1

5 "The rate of reduction in terms of NO was measured under the following conditions of the catalysts according to Examples 1 to 7:

Devices used:

NO purification analyzer using a Flow-through mini-reactor for measuring the NO content.

Test gas: CO 1%, NO 1000 ppm, O _t 0.24%, remainder N _a .

Qas flow rate: 2.75 liters / minute.

Amount of catalyst:
10 ml in cuts or curved sheets.

Type of catalyst:
See Examples 1 to 6.

SV (space velocity):
About 16 500 V / Vp-hr- ¹ ,

Vp: apparent volume of the loaded catalyst layer,
V: gas flow rate.

Temperature of the catalyst bed:
Around 400 ⁰ C.

Surface of the catalyst:
Apparent area around 100 to 1000 cm ² (depending on the shapes used).

(2 results

The results are shown in Tables 1 and 6 (Examples 1 to 6). Each result represents a excellent NO purification rate. Certain catalysts achieve with only oxidized Layers, however, still do not have a sufficient cleaning rate; however, it could by reducing treatment be improved. Tests with alloy systems other than those disclosed here under the same conditions Conditions did not show a sufficient rate of NO purification in any case.

The catalysts according to the exemplary embodiments of the invention are also very effective oxidation catalysts for hydrocarbons (HC) and Carbon monoxide (CO) if an oxidizing atmosphere is available.

Test example 2

The test was carried out under the following conditions and using the same analyzers as in Test example 1 carried out.

(1) Eligibility criteria

Use of a CO measuring device

Test gas:
CO 1%,
NO 2000 ppm,
O _a 0.25%,
Remainder N ₀ .

Gas flow rate:
2.5 l / minute.

Amount of catalyst: 5 ml.

Type of catalyst: Ni - 24% Cu catalyst in the form of a curved sheet with an apparent surface of 50 cm.

S.V .:

seen a significant cleaning rate. The term "oxidation" in Fig. 2 indicates that an oxidized splint was formed by treatment in an atmosphere at 900 ° C for 12 hours; the term "reduction nacl · oxidation" indicates that the catalyst was danacr a reduction treatment in hydrogen gas be 800 ⁰ C for a period of two hours exposed

Test example 3

This test shows that the catalyst according to the embodiments Ger invention ir very effective way harmful NO components ent in the exhaust gases of internal combustion engines are able to remove.

The catalyst was made with an alloy composition as shown in Table ' is specified. King cuts were made by machine. After that one was oxidized « Layer made and subjected to a reduction treatment. Thereafter, the catalyst was in air converters used to purify the exhaust gas from combustion machines. It turned out the following test conditions and results:

(1) Test conditions

Combustion engine:
Four-cylinder reciprocating engine with 1900 ecm.

Arrangement of the catalyst converter:
Behind the exhaust pipe of the engine at a distance of about 40 cm from the cylinder head.

Form of the catalyst converter:
Cylindrical with 70 mm diameter and 300 mrr length,
Capacity 1.2 liters.

Type of catalyst:

Composition according to Table 7 compactly packed,

Weight: about 2.0kg,
apparent surface: about 20,000 cm ^a .

Operation mode of the engine:

Endurance test on the test bench:
A 2700 rpm 2.2 mkg,
B 250OUpM 1.2 mkg.

BcUcmpcrutur of the catalyst:
A 66O ⁰ C,
D 63O ⁰ C.

Temperature of the catalyst bed: 300 to 700 ⁰ C.

(2 results

With regard to both NO and CO, it was found in the low temperature range, as from F Ig. 2

SV: A 4 B 27,000 V / Vp-hr ¹ ,

The measurements were carried out with an exhaust gas analyzer.

(2 results

As can be seen from Table 7, the exhaust gas was approximately 40 to 100% with regard to NO and CO or 11% cleaned. With different alloy systems than according to the exemplary embodiments Invention resulted in only a very small cleaning rod.

⁰ I.

Sample no. Composition of
Cu Ni 45.0 Alloy (%)
Fe other Operating
bedin
gungen des
Engine NO cleaning
r »te CO purification
gungsrutc 35 9.4 43.3 rest A.
β 58.3
98.0 10.7
5.0 36 9.0 39.5 rest Cr - 3.7 A.
B. 55.5
94.4 9.9
4.6 37 9.2 41.7 rest Co-1.3 A.
B. 40.5
89.9 8.3
4.7 38 8.9 42.6 rest Co-15.7 Λ
B. 49.7
92.3 9.1
5.0 39 8.8 rest Co - 5.3
Cr - 4.1
Ce - 2.5 A.
B. 45.2
88.3 8.9
4.4

Comment:

Average composition of the exhaust gas under operating conditions A: NO 2400 ppm, CO 2.2% HC 110 ppm. Average exhaust gas composition under operating conditions B: NO 600 ppm, CO 4,;> / ₀ , HC 160 ppm.

The evaluation of the reproduced tests shows that the alloy systems according to the invention as Reduction and oxidation catalysts an excellent Make an impact. The working examples and test examples demonstrate that the alloys can be manufactured at low cost because the composition is relatively broad

Range may vary. The alloys are also very tough and have excellent properties

Deformability, machinability and castability on.

The heat resistance and resilience

against corrosion are also extremely high.

They can advantageously be processed as cuts, sheets or tubes, depending on the area of application.

In addition 5 sheets of drawings

Claims (3)

Patent claims: 1. Catalyst for removing nitrogen oxide from exhaust gases using an alloy consisting of 0.1-40% copper, the remainder nickel and / or iron, characterized that the surface of the alloy with a copper-enriched oxidation layer of a thickness of more than] 0μιτι is coated and that this alloy, after its shaping, undergoes a reduction treatment for the removal of Has been subjected to oxygen. 2. Catalyst according to claim 1, characterized in that it additionally contains up to 40% Co or Cr, furthermore contains further elements up to a total of 10% which are soluble in the matrix, none Form an intermetallic compound with copper and no precipitation of copper from the Effect matrix. 3. A method for producing a catalyst according to claim 1 or 2, characterized in that the brought into the final shape catalyst is ^{heated in an oxidizing atmosphere of 700-HOO 0} C such that an oxidation layer with a thickness is on the surface of the alloy of more than 10 μm, and then the layer on the surface of the alloy is activated by a reduction treatment in a hydrogen gas atmosphere at a temperature of more than 600 ° C.