METHOD FOR PRODUCING POROUS COMPOSITE BODIES WITH THERMALLY CONDUCTIVE SUPPORT STRUCTURE

Abstract

In a method for producing porous composite bodies, which have a support structure made of a material having good thermal conductivity and which have at least one functional material, a multiplicity of shaped bodies (1) made of the functional material are coated with the material having good thermal conductivity and a solid connection between the coated shaped bodies (1) is established in order to form the support structure made of the material having good thermal conductivity. The coating (2) is generated with a porous structure or is provided with a porous structure, which, after the solid connection has been established, permits access for a liquid or gaseous medium through the coating to the functional material. The method permits cost-effective production of porous composite bodies with very good heat transfer properties.

Claims

1. Method for producing porous composite bodies which have a support structure made of a thermally conductive material and at least one functional material, in particular for producing sorption bodies or catalysts, in which a multiplicity of shaped bodies is prepared from the functional material, the shaped bodies are coated with the thermally conductive material, and a solid connection is established between the coated shaped bodies in order to form the support structure from the thermally conductive material, wherein the coating of the shaped bodies is generated with a porous structure or is furnished with a porous structure which after the solid connection has been established permits access for a liquid or gaseous medium through the coating to the functional material.

2. Method according to claim 1, characterized in that the solid connection between the coated shaped bodies is created by a sintering process.

3. Method according to claim 2, characterized in that the porous structure of the coating is created by the sintering process.

4. Method according to claim 1, characterized in that the coating of the shaped bodies is applied by a deposition process.

5. Method according to claim 4, characterized in that the coating of the shaped bodies is applied by PVD.

6. Method according to claim 4, characterized in that the coating of the shaped bodies is applied by electrochemical deposition of a porous layer of the thermally conductive material.

7. Method according to claim 1, characterized in that in order to coat the shaped bodies with the thermally conductive material the shaped bodies are mixed with a binder and particles or fibres of the thermally conductive material.

8. Method according to claim 7, characterized in that the particles or fibres of the thermally conductive material have sizes that are smaller than the measurements of the shaped bodies by a factor of 10 in at least one dimension.

9. Method according to claim 7, characterized in that the shaped bodies and the particles or fibres of the thermally conductive material are mixed with each other in a mixing ratio at which—with a porosity of the coating between 5 and 25 vol. %—the volume percentage of the functional material is between 40 and 70 vol. % and the volume percentage of the thermally conductive material is between 10 and 30 vol. %.

10. Method according to claim 1, characterized in that the functional material is supplied in the form of a granulate, in the form of rods or in the form of tubes.

11. Method according to claim 1, characterized in that the shaped bodies are prepared from an adsorbent material or a catalyst material as the functional material.

12. Method according to claim 1, characterized in that when the solid connection is established, the coated shaped bodies are also connected with a thermally conductive body, in particular a tube, a housing or a plate.

13. Porous composite body which has a support structure made of a thermally conductive material and a multiplicity of shaped bodies made of at least one functional material, which are covered by a coating of the thermally conductive material and are solidly connected to each other via the coating, wherein the coating has a porous structure which permits access for a liquid or gaseous medium through the coating to the functional medium.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0026] In the following section, the suggested method will be explained again in greater detail with reference to exemplary embodiments in conjunction with the drawing. In the drawing:

[0027] FIG. 1 is a schematic representation of shaped bodies which have been coated and connected solidly to each other according to the suggested method;

[0028] FIG. 2 is a representation of the zeolite as a fraction of the total structure depending on the diameter of a spherical zeolite granulate and the thickness of the coating with porosity of 20 vol. %;

[0029] FIG. 3 is a further representation of the zeolite as a fraction of the total structure depending on the diameter of a spherical zeolite granulate and the thickness of the coating with porosity of 20 vol. %

[0030] FIG. 4 is a photograph of the structure of a composite body produced with the method;

[0031] FIG. 5 is a representation of a spherical shaped body made of zeolite and coated with copper; and

[0032] FIG. 6 is a representation of a tubular shaped body made of zeolite and coated with copper fibres.

WAYS TO IMPLEMENT THE INVENTION

[0033] In the suggested method, a thin layer with high thermal conductivity, of copper for example, is deposited on or applied to the surface of shaped bodies of a functional material such as zeolite. A porous structure of this layer is generated either immediately during the coating or in a subsequent method step. The coated shaped bodies are then connected solidly with each other to form a total structure which forms the porous composite body. This may be done by sintering for example. A connection via a binding agent that may optionally be applied during coating may also be used. The total structure is linked to peripheral elements such as tubes, housings etc., preferably subsequently or also simultaneously with the connection process.

[0034] FIG. 1 shows a highly simplified view of four coated spherical shaped bodies 1 of zeolite, which have been coated with a thin Cu-layer 2 and connected to each other via this thin layer by a sintering process. As a result, the thin Cu-layer has a sufficiently porous structure (not discernible in the figure) to allow liquid or gaseous media to gain access to the zeolite. FIG. 1 with the four shaped bodies shows only a very small detail of the total structure in diagrammatic form.

[0035] Exemplary volume ratios for the functional material in the total structure, i.e. the composite body, may be deduced from FIGS. 2 and 3, each of which shows, using the example of zeolite as the functional material, the percent of zeolite in the total structure depending on the diameter of the zeolite granulate used in this example and on the thickness of the coating. In this context, FIG. 2 shows granulate diameters between 50 and 250 μm with coating thicknesses of 1, 3 and 5 μm Cu, FIG. 3 shows granulate diameters between 1000 and 3000 μm with coating thickness of 50, 100 and 150 μm. The volume percentages of the zeolite are preferably each in the range between 0.5 and 0.75. Volume percentages of the zeolite of about 70 vol. % are particularly advantageous.

[0036] In the following section, various examples of the production of porous composite bodies with the suggested method are described. In a first example, Y-zeolite granulate with a fraction of 63-125 μm is stirred together with water and an organic binder (e.g., ExOne®). Then, Cu-UF10 powder (<10 μm) is added. The mass is stirred, introduced into a form, for example a cylinder form, and dried. This is followed by heat treatment at 420° C. for 1 h in air to burn out the binder, and a sintering in hydrogen atmosphere at 600° C. for 3 h. The result is a cylinder which is stable enough for simple handling. The zeolite still exhibits good water uptake even after sintering. The sintering conditions have not caused a degradation of the zeolite. FIG. 4 shows an photo of a structure of the cylinder for exemplary purposes. It is evident from this figure that only the surface of the zeolite granulate is covered with a porous layer of Cu particles. The stability of the overall body is established by the sintered contacts among the Cu layers.

[0037] In this example, it is also possible to economise on the heat treatment at 420° C./1 h in air, and to effect the burnoff of the binder by maintaining a temperature ramp during the sintering treatment.

[0038] If the first example is performed with round Y-zeolite granulate (granulate diameter approx. 2 to 3 mm), coarser structures are created, wherein the porous copper layer on the zeolite particles is still porous even after sintering and also exhibits shrinkage cracks which improve access to the zeolite.

[0039] In a second example, Y-zeolite granulate (fraction 63-125 μm) is mixed with water and a suitable binder. Cu-UF10 powder is added and the mass is stirred. A coppered polyamide fabric is laid out flat and the mass is painted onto the textile. This is followed by drying in air, burning out the binder and polyamide, and oxidising at 420° C. for 1 h. Finally, the structure is sintered for 3 h at 600° C. in H.sub.2. The thin layers of copper powder ensure that Y-zeolite holds together well and connects to the fabric during the sintering. The fabric serves both to stabilise the total structure mechanically and functions as a directed, heat conducting structure (strongly directed thermal conductivity). Textiles coated in this way are very well suited for connection with cooling pipes. The coated fabric may by connected to a copper flat tube for example during sintering. The fabric is aligned towards the flat tube and accordingly transports heat away from the tube very effectively.

[0040] In a third example, Y-zeolite granulate (fraction 63-125 μm) is stirred together with water and silicone based binder (e.g., P8OX). Then, Cu-UF10 powder is added. The mass is stirred again and then dried. This is followed by an oxidation treatment at 420° C. for 1 h in air and sintering at 600° C. for 2 h in hydrogen atmosphere. Since the thermally resistant binder still has good strength even after the sintering, the mechanical resistance of the total structure is not based solely on the strength of the sinter contacts within and among the copper layers. The copper content may therefore be reduced to a level which is just sufficient to meet the thermal requirements (thermal conductivity). This in turn serves to reduce costs further.

[0041] In a fourth example, Y-zeolite granulate (fraction >400 μm) is stirred together with water and a suitable binder. In this case, the water and binder are added in small enough quantities to ensure that a cohesive slurry does not form, but instead the granulate beads are coated individually, and so remain flowable. The coated beads are then dried and can be stored for longer. Later, the coated granulate can be poured into hollow structures that are to be filled. A sintering treatment such as was described in the first example then cause the granules to bind to each other and the surrounding coating structure.

[0042] A further option for producing the porous composite body exploits material displacements during sintering processes. It is known that homogenous copper layers can be deposited on ceramic granulates, e.g., cenospheres (aluminium silicates) by using fluid bed PVD processes. With the aid of layers of this kind, the granulates can be sintered together to form solid structures. A known but hitherto neglected effect is that under certain sintering conditions the compact cupper layers are transformed into porous, flat meshes. This phenomenon is used in the present example to create the porous structure.

[0043] Finally, FIG. 5 shows another example of spherical shaped bodies of zeolite coated with copper particles, FIG. 6 shows an example of zeolite tubes which have been coated with copper fibres. With the suggested method, many such coated shaped bodies are produced and connected with each other to form the porous composite body. When metallic material us used as the material having good thermal conductivity, the method by means of a sintering process enables a connection to be created which is materially bonded, metallic and electrically conductive in each case to form a metal structure as a thermally conductive support structure.