EP2352586A1

EP2352586A1 - Component having a catalytic surface, method for the production thereof, and use of said component

Info

Publication number: EP2352586A1
Application number: EP09763895A
Authority: EP
Inventors: Axel Arndt; Christian Doye; Ursus KRÜGER; Uwe Pyritz; Jens Dahl Jensen; Oliver Stier
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2008-11-24
Filing date: 2009-11-09
Publication date: 2011-08-10
Also published as: RU2011125932A; CN102223950A; WO2010057800A1; DE102008059165A1; BRPI0921870B1; US20110293495A1; RU2490063C2; CN102223950B; BRPI0921870A2; US9029287B2

Abstract

The invention relates to a component comprising a catalyst surface (12). According to the invention, said surface (12) comprises metallic portions (14) and portions of MnO₂ (13) contacting the former, wherein the metallic portions are preferably composed of Ag and/or Ni. Surprisingly, it has been shown that said material combinations achieve a greatly improved catalytic effect compared to the pure metals. Particularly with use of the toxicologically harmless Ni, said surfaces can also be used, for example, in ambient air cleaning to reduce the ozone content. The surface can be applied, for example, through a coating (15) of the component, wherein the metallic portion and the portion of MnO₂ are applied in two layers (19, 20).

Description

description

Component with a catalytic surface, process for its preparation and use of this component

The invention relates to a component with a catalyst surface. In addition, the invention relates to a method for producing a catalyst surface on a component by cold gas spraying. Finally, the invention relates to a use of such a component.

A catalyst surface on a component is known, for example, according to US 2003/0228414 Al. This catalyst surface can be produced by direct deposition of a catalytically active substance on the component.

For this purpose, a cold gas spraying is used, in which the particles of the catalytic layer material are fed into a so-called cold gas jet, a process gas flowing at supersonic velocity. In the cold gas jet, these particles are accelerated toward the surface of the component to be coated and remain adhering to this surface while converting their kinetic energy.

The object of the invention is to specify a component with a catalyst surface, a method for its production or a use of this component, wherein the catalyst surface should have a comparatively high catalytic activity.

This invention is achieved with the aforementioned component or with a cold spraying method in that the catalyst surface consists of metallic portions and the first contacting portions of Mnθ ₂ . To produce such a layer, the invention provides that in the Cold gas spraying the catalyst surface is produced by spraying Mnθ2 particles, wherein the Mnθ2 forms only portions of the catalyst surface and also metallic portions of the catalyst surface are made available, each adjacent to the shares of MnO ₂ . The metallic components can, as will be explained in more detail below, be provided by the metallic surface of the component to be coated or by admixing metallic particles in the cold gas jet.

By using MnO ₂ as a mating with a metal, it is possible according to the invention to achieve a particularly high catalytic activity of the catalyst surface formed. It has surprisingly been found that the catalytic activity of MnO ₂ , which is known per se, can be increased by metallic fractions on the surface, although overall the available catalytic surface of MnO _{2 is} reduced. This contradicts the expected result that a reduction of the real available surface area of MnO ₂ in the event of incomplete coverage of the surface of the component is accompanied by a proportional loss of catalyst activity.

This makes it advantageous to produce components with comparatively efficient catalyst surfaces by using portions of the catalyst surface instead of MnO ₂ with a metal. The surface of the component must therefore not be completely covered with the metallic components and the proportions of the MnO ₂ . A partial coating is already sufficient to achieve the catalytic effect. Depending on the application, this is to be chosen so large that the available catalytic surface is sufficient for the desired effect for the conversion of ozone, for example. The proportion of MnO ₂ in relation to the Both fractions formed total area should be at least 10%, preferably 30 to 70%, in particular 50%.

According to an advantageous embodiment of the invention, it is provided that the MnO _{2 is} at least partially present in the γ-modification. The γ-modification is a structural constitution of the crystal formed by the MnO ₂ , which advantageously exhibits a particularly strong catalytic activity. However, the real structure of MnO ₂ is generally not exclusively in the γ-modification, but partly also in other modifications (eg the β-modification of MnO ₂ ). However, according to a particular embodiment of the invention, the microstructural content of MnO ₂ in the γ-modification should be more than 50% by weight.

According to another embodiment of the invention, it is provided that the component consists of the metal component making available metal and an only partially covering layer of MnO _{2 is} applied to this component. These are, for example, components made of Ag or Ni, which by virtue of their material composition already make available the one constituent required for the preparation of the catalytic surface. On these components, production of the surface according to the invention is advantageously particularly easily possible by applying a non-covering layer from the other portion of the surface, namely MnO ₂ .

On the other hand, it is also conceivable that the component consists of a ceramic which provides the proportion of MnO ₂ and an only partially covering layer of the metal is applied to this component. For example, the component could be designed as a wear-stressed ceramic component. This does not have to consist exclusively of MnO ₂ . hen. For example, it is conceivable that the ceramic is produced as a sintered ceramic from different types of particles, wherein the Mnθ2 represents a kind of these particles. In this variant, however, it must be considered that the processing temperatures for the component must be below 535 ° C., since the MnO _{2 is} converted into MnO at this temperature and thus loses its outstanding catalytic properties in the material combination according to the invention.

According to another embodiment of the invention it is provided that the component has a coating, which provides the metallic components and the proportions of Mnθ2 the surface. In this variant, components of various materials can be coated, wherein the catalytic properties of the layer according to the invention is advantageously caused solely by the nature of the layer or the catalytic surface formed by them. In this case, a suitable coating method must be selected in each case for the relevant material of the component.

Particularly advantageous, the component may have a lattice-shaped structure. This can be a grid with a two-dimensional orientation, that is to say a component which is essentially flat. However, it is also possible to form three-dimensional lattice structures that can be produced, for example, by means of rapid prototyping technologies. The lattice-shaped structures offer the significant advantage that, on the one hand, the surface available for the application of the catalytic active partner is increased, but on the other hand, the flow resistance generated by the lattice structure is comparatively low. Grid-shaped components can therefore be advantageous in Ventilation ducts are applied. The application is particularly advantageous, for example, in extractor hoods, wherein the lattice-shaped structure forms the outlet grille for cleaned exhaust air. This application is used in so-called recirculation hoods, in which, in contrast to exhaust hoods, the intake air is not discharged from the building but remains in it.

For extractor hoods according to the recirculation principle not only a cleaning of the air of solids, aerosols and

To achieve the smallest particles, such as those contained in the cooking fume, but also to achieve a cleaning of odors, plasma generators are used in the prior art, which have a high-voltage discharge source, with which the air is enriched with atomic oxygen. This causes a decomposition or. Oxidation process that breaks down the carbon compounds responsible for odor generation and eliminates odors in this way. However, this process also produces ozone, which can be catalytically converted into diatomic oxygen by the components according to the invention. As a result, activated carbon filters can advantageously be saved, which disadvantageously oppose the air flow of the extractor hood a relatively high air resistance and also need to be replaced at regular intervals.

As a method for producing the layer on the component, for example, a cold gas spraying can be used, wherein the catalytic surface is produced by spraying MnO ₂ particles. The MnO _{2 forms} only portions of the catalytic surface, the metallic components are formed for example by Ni and / or Ag. The metallic components can, as already described, either by the component itself be made available, or they are added as particles to the cold gas jet, so that the metallic components of the surface are formed by the forming layer.

In particular, it is also possible to use MnO ₂ particles which at least partially exhibit the γ-modification of the MnO ₂ structure. In this case, the cold gas spraying with operating temperatures must be operated in any case below the decomposition temperature of the γ-modification. This temperature is at

535 ° C. In terms of process, when choosing the temperature of the cold gas jet, a certain safety margin to this decomposition temperature can be maintained. On the other hand, it has been shown that a short-term exceeding of this temperature on impact of the MnO.sub.2 particles on the surface does not have any effect on the surface because this temperature increase occurs extremely locally only in the surface region of the processed MnO.sub.2 particles. The particular core of the particles, which remains in an uncritical temperature range, may seem to stabilize the γ-modification of the particle structure sufficiently, so that the γ-modification of the MnO 2 structure is also retained on the catalytically active surface of the particles.

In addition, a heating of Mnθ2 over 450 ⁰ C leads to a

Transformation of Mnθ2 into Mn2θ3. However, this process progresses only slowly, so that a short-term excess of the temperature, as occurs in cold gas spraying, is harmless.

In order to obtain the excellent catalytic properties of MnO ₂ , the γ modification of the microstructure must be at least partially contained in the MnO ₂ particles. This can be achieved by mixing the MnO ₂ particles with manganese oxide particles of others Modifications (eg ß-modification of Mnθ2) be realized. Another possibility is that the particles consist of phase mixtures, so that the γ-modification of the Mnθ _{2 is} not the only one present in the particles.

Furthermore, it is advantageous if nanoparticles with a diameter> 100 nm are processed as MnO ₂ particles. For the purposes of this invention, nanoparticles are understood as meaning particles which are <1 μm in diameter. Surprisingly, it has been shown that such small ones

Allow particles of MnO 2 to be deposited on the catalytic surface with a high degree of separation efficiency. Normally, on the other hand, it is assumed that particles of less than 5 μm can not be separated by cold gas spraying, since the low mass of these particles means that the kinetic energy impressed by the cold gas jet is not sufficient for deposition. Why this is not the case for MnO2 particles in particular can not be explained exactly. Apparently, in addition to the effect of kinetic deformation, other adhesion mechanisms are involved in the film formation process.

The processing of nanoparticles of Mnθ2 has the advantage that with comparatively little material, a comparatively high specific surface and thus a strong expression of the catalytic effect can be achieved. Also the

Boundary lines between the proportions of MnO ₂ and metallic proportions of the catalytic surface are advantageously greatly extended in this way, which also has an effect on a high degree of catalytic properties.

It is advantageous if a mixture of MnO ₂ particles and metallic particles is used for the metallic components of the catalytic surface, ie Ni and / or Ag. In particular, then by a suitable choice of temperature and particle velocity in the cold gas jet, the energy input into the particles is controlled to control the specific (or inner) surface of the prepared layer forming the catalytic surface. Because of a higher porosity of the layer produced, namely, the inner surface can be enlarged in order to provide an enlarged catalytic surface. As a result, the germicidal effect can thus be increased. On the other hand, it may also be advantageous if the surface is made possible smoothly, in order to counteract a tendency to fouling.

In addition to the deposition by cold gas spraying, of course, other production methods are conceivable. For example, the catalytic surface can be produced electrochemically. Here, the metallic portion of the catalytic surface is deposited as a layer electrochemically from an electrolyte in which particles of Mnθ2 are suspended. These are then incorporated into the forming layer during the electrochemical deposition process and thus also form a fraction of MnO 2 at the surface of the layer.

Another method can be obtained by making the layer of a ceramic containing at least MnO 2. For this purpose, a mixture of preceramic polymers, which form precursors of the desired ceramic, and metal particles in a solution can be applied to the component to be coated. First, the solvent is evaporated medium, can then by a heat treatment which is advantageously below the decomposition temperature of the γ-modification of the MnO ₂ (535 ° C), are converted to ceramics. Better still, the temperature remains below 450 ⁰ C to prevent the formation of Mn ₂ O ₃ . Among other things, the following embodiments of the component according to the invention can be produced using the methods mentioned. Thus, the coating produced can have a metallic layer on which an only partially covering layer of MnO _{2 is} applied. The metallic layer thus forms the metallic part of the surface that comes to light in the places where the layer of MnO ₂ does not cover. In this component design, only a very small proportion of MnO ₂ is advantageously necessary. It is also conceivable to use the above-mentioned manufacturing methods in combination. For example, the metallic layer can be produced galvanically and the only partially covering layer of MnO ₂ by cold gas spraying.

Another possibility is that the coating has a ceramic layer which provides the proportion of MnO ₂ and on which an only partially covering metallic layer is applied. This design of the component is of importance if the properties of the ceramic layer are structurally advantageous for the component (for example, corrosion protection).

It is also possible for the coating to consist of a ceramic which makes available the proportion of MnO ₂ and in which metallic particles are embedded. This is particularly advantageous if the ceramic layer is subject to wear and, as wear progresses, ie removal of the layer, it should retain its catalytic properties. The latter is ensured by the fact that again and again MnO ₂ particles are exposed during the removal of the ceramic layer, which ensure the proportion of MnO ₂ according to the invention on the surface. Of course, it is also conceivable that the layer has a metallic matrix, in which the particles of Mnθ2 are embedded. For this layer, too, the argument holds that the catalytic properties of a layer removal remain the same.

The component can also be designed such that this layer or a layer applied to it consists of a material which is different from the metallic component and from MnO ₂ and is present in this material (in the case of wear, see above) and / or on this particle each provide the metallic components and the proportions of MnO ₂ on their surface (meaning the surface of the particles). These are advantageously tailor-made particles with catalytic properties which can be applied universally to any surface or matrix. In each case, the method suitable for introduction or application must be selected. With this measure, for example, components made of plastic with catalytic properties can be produced. The particles introduced into the layer or the component are either exposed to wear or, in the case of a porous structure of the component, can also be involved in the catalytic effect if they form the walls of the pores.

Finally, the invention relates to a use of the already described component for reducing the ozone content of a gas sweeping over the catalyst surface. This gas can be provided primarily by the earth's atmosphere. Under certain conditions, the air is enriched with ozone, z. B. on hot summer days in the inner city area or in higher atmospheres, which are used by air traffic. Since ozone is harmful to the human organism, the respiratory air released from the atmosphere in the interior of the car or is pumped into the passenger cabin of an aircraft, are largely freed by the inventive catalyst surface of ozone. Of course, applications in chemical engineering are also conceivable.

The catalyst surface can be configured, for example, as an inner lining of air-carrying pipe systems. This has the advantage that by providing the catalyst surface no additional flow obstruction must be installed in the air-conducting channels. In order to increase the available catalyst surface, the air duct system can also be provided with an air-permeable insert, which must be flowed around by the sucked air.

Further details of the invention are described below with reference to the drawing. Identical or corresponding drawing elements are provided in the individual figures with the same reference numerals and are explained only to the extent that there are differences between the individual figures. Show it

Figures 1 to 5 different embodiments of the component according to the invention with different catalytic surfaces and

Figure 6 curves of the catalytic effect of an embodiment of the catalyst surface according to the invention in comparison to reference surfaces.

FIGS. 1 to 5 each show a component 11 with a surface 12 which has catalytic properties. These properties are generated by the surface each having a portion 13 consisting of MnO ₂ and further a metallic portion 14 of Ag or Ni is provided. The component could be, for example, an air duct whose inner walls form the said surface.

The structure of the components 11, which is shown in section, however, has differences. The component according to FIG. 1 itself consists of Ni or Ag, so that its surface 12 automatically provides the metallic component 14. On the surface 12 further island-like areas of Mnθ2 are formed, which make the share 13 available. These can be applied, for example, as non-opaque coating by cold gas spraying.

According to FIG. 2, a component 11 is shown which consists of a material which is unsuitable for producing the catalytic properties of the surface. Therefore, a metallic layer 15 of Ni or Ag is applied to this component 11. On this layer, which makes the portion 14 available, Mnθ2 is applied in the manner described for Figure 1, so that shares 13 arise.

FIG. 3 shows that the metallic layer can also be doped with particles 16 of MnO 2, ie. h., That these particles are in the metallic matrix 17 of the metallic layer 15. In this respect, they also form that part of the surface 12 which makes the share 13 available. The rest of the surface forms the portion 14.

In Figure 4, the coating 15 by a ceramic

Matrix 21 is formed, which has pores 22 which increase the inner surface compared to the outer surface 12 of the component and thus also enhance a catalytic effect. In the ceramic matrix 21 are metallic Particles 23 are provided which provide the portion 13 both on the surface 12 and can also be catalytically active in the pores. As in the case of FIG. 2 and FIG. 3, the component 11 according to FIG. 4 can consist of any desired material, wherein only the adhesion of the coating 15 to the component 11 has to be ensured.

The component 11 according to Figure 5 has a matrix of any material 24, for. B. plastic. In this particle 25 are introduced, whose respective surface both metallic components of Ni or Ag as well as shares of Mnθ2 have. In the embodiment according to FIG. 5, the particles themselves consist of the metal and the ceramic components are formed on the surface of the particles. Of course, the reverse case is also conceivable. The particles are partially exposed on the surface 12 of the component 11, whereby the metallic portions 14 and the portions 13 of Mnθ2 13 are formed. Furthermore, there are portions 26 of the surface 26 made of plastic, which are not catalytically effective. The ratio of the stated proportions can be influenced directly by the degree of filling of particles 25 in the material 24.

FIG. 6 shows the measurements on a component with different catalytic surfaces. Here, the concentration of ozone in stationary flowing air is plotted on the Y-axis (unit ppb). The duration of the stationary flow is shown on the X-axis.

The content of ozone in the stationary air was between 980 and 1000 ppb, as can be seen from curve 30. If a surface with proportions of Ag and Pd is used as the catalyst surface, curve 31 results. It can be seen that for a longer service life, about 90% of the in the stationary flowing air containing ozone could be reduced.

Furthermore, a surface-identical sample of silver was used, which was completely covered with MnO (Ag was not the surface-forming part, but only the material of the component). With this sample, the curve 32 could be measured, it can be seen that the sample has settled at a reduction of 97% of the stationary air in the flowing ozone.

With the catalyst surface of the invention, each half of the surface of Ag and half of MnO, can be compared to achieve a further improvement in the catalytic properties. Measurement curve 33 shows that with this catalyst surface permanently more than 99% of the ozone contained in the stationarily flowing air could be degraded.

Claims

claims

1. component with a catalyst surface (12), characterized in that the catalyst surface (12) of metallic portions (14) and the first contacting portions (13) to Mnθ ₂ consists.

2. Component according to claim 1, characterized in that the manganese oxide is present at least partially in the γ-modification of Mnθ2.

3. Component according to claim 2, characterized in that the present in the γ-modification structure content of manganese oxide is greater than 50 wt .-%.

4. Component according to one of the preceding claims, characterized in that the surface portion of the portions (13) of Mnθ2 in relation to the sum of the metallic portions (13) and the proportions (13) of Mnθ2 at least 10%, preferably between 30 and 60 % and especially at 50%.

5. Component according to one of the preceding claims, characterized in that the metallic portion (13) consists of Ag and / or Ni.

6. Component according to one of the preceding claims, characterized in that this consists of the metallic portion (13) made available metal and an only partially covering layer of MnO _{2 is} applied to this component.

7. Component according to one of claims 1 to 5, characterized in that this consists of a proportion (13) of Mnθ _2- making available ceramic and an only partially covering layer of the metal is applied to this component.

8. Component according to one of claims 1 to 5, characterized in that this has a coating (15) which provides the metallic portions (14) and the proportions (13) of Mnθ2 the catalyst surface (12).

9. Component according to claim 8, characterized in that the coating (15) has a metallic layer (19) on which an only partially covering layer (20) of Mnθ2 is applied.

10. The component according to claim 8, characterized in that the coating (15) has a share (13) of Mnθ2-making available ceramic layer on which an only partially covering metallic layer is applied.

11. The component according to claim 8, characterized in that the coating (15) consists of the portion (13) of Mnθ2 available ceramic, in which metallic particles (23) are embedded.

12. Component according to claim 8, characterized in that the coating (15) consists of a metallic matrix (17) in which particles (16) of MnO 2 are embedded.

13. Component according to one of claims 1 to 5, characterized in that this or a layer applied to this consists of one of the metallic portion (14) and the MnO ₂ different material (24) and in this and / or on this particle (25) are provided, which each provide the metallic portions (14) and the proportions (13) of MnO ₂ on their surface.

14. Component according to one of the preceding claims, characterized in that the component has a lattice-shaped structure.

15. Component according to claim 14, characterized in that the component is designed as a ventilation grille, in particular as an outlet grille of a fume hood or a flow-through plasma generator.

16. A method for producing a catalyst surface (12) on a component by cold gas spraying, characterized in that the catalyst surface (12) is produced by spraying MnO ₂ - particles, wherein the MnO ₂ only portions (13) of the catalyst Surface (12) and also a metallic portions (14) of the catalyst surface are made available, each adjacent to the portions (13) of the MnO ₂ .

17. The method according to claim 16, characterized in that MnO 2 particles are used which at least partially exhibit the γ modification of the MnO 2 structure and the cold gas spraying is operated at operating temperatures below the decomposition temperature of manganese oxide.

18. The method according to any one of claims 16 or 17, characterized in that are processed as Mnθ ₂ ~ particles nanoparticles with a diameter> 100 nm.

19. The method according to any one of claims 16 to 18, characterized in that a mixture of Mnθ ₂ particles and metallic particles for the metallic portions (14) of the catalyst surface is used.

20. The method according to any one of claims 16 to 19, characterized in that the catalyst surface forming the specific surface of the layer produced by the energy input is controlled in the cold gas jet.

21. Use of a component according to one of claims 1 to 13 for reducing the ozone content of a catalyst surface sweeping gas.