EP3474974A1

EP3474974A1 - Membrane arrangement

Info

Publication number: EP3474974A1
Application number: EP17742639.2A
Authority: EP
Inventors: Markus HAYDN
Original assignee: Plansee SE
Current assignee: Plansee SE
Priority date: 2016-06-22
Filing date: 2017-06-14
Publication date: 2019-05-01
Also published as: AT15435U1; CA3029060A1; KR20190020764A; WO2017219053A1; US20190126206A1; CN109414653A; CN109414653B; JP2019525829A

Abstract

The present invention relates to a membrane arrangement for permeative separation of a gas from gas mixtures, comprising: a porous, gas-permeable, metallic support substrate (2); a membrane (8) formed on the support substrate (2) and selectively permeable to the gas to be separated; a ceramic, gas-permeable, porous first intermediate layer (6) which is arranged between the support substrate (2) and the membrane (8) directly on the support substrate; a coupling part (4; 4") integrally connected (3; 3'; 3") to the support substrate, at least the surface of which consists of a gas-tight metallic material. The gas-permeable surface of the support substrate is separated from the gas-tight surface of the coupling part by a boundary line (5). The first intermediate layer (6) extends on the gas-permeable surface of the porous support substrate towards the coupling part (4; 4") at least up to 2 mm from the boundary line (5). The first intermediate layer (6) extends on the gas-tight surface of the coupling part towards the coupling part (4; 4") for a maximum distance of 2 mm beyond the boundary line (5).

Description

REED ARRANGEMENT

The present invention relates to a membrane assembly for permeative

Separation of a gas from gas mixtures. The invention further relates to a method for producing such a membrane arrangement.

Membrane arrangements of this type are generally used for the selective separation of a gas from gas mixtures, in particular for the separation of hydrogen

Hydrogen-containing gas mixtures (eg from steam-reformed natural gas) used. It is known that the property of certain materials, that they are only selectively for certain atoms or molecules (eg H ₂ ) permeable, exploited by being as a thin layer ("membrane"), such as a layer on a support or as intrinsically stable film , For dividing a gas space for the gas mixture from a gas space for the gas to be separated, for example, a gas mixture having a certain partial pressure of the gas to be separated, such as at a certain H2 partial pressure, on one side of the membrane, so are the

Atoms / molecules of the gas to be separated endeavors to pass through the membrane to the other side until the same partial pressure of the gas to be separated exists on both sides. The membrane surface may be a specific gas flow of the gas to be separated, in particular a specific H2 gas flow, as a so-called

Performance parameters are assigned. It regularly applies that the thinner the membrane is and - at least for metallic membranes - the higher the

Operating temperature is, the higher the specific gas flow of the gas to be separated (eg H ₂ ). For this reason, there is a need to use the thinnest possible membranes in order to keep the system as small as possible with a desired gas flow and thus to reduce the system costs. Since thin membranes in the range of several μπι (microns) have a very low dimensional stability and rigidity, they are often as a layer on a porous, gas-permeable, tubular or planar carrier substrate, which ensures gas supply to and / or gas removal from the membrane and a flat surface provides for applying the membrane is formed. Metallic materials for the carrier substrate are distinguished from ceramic materials by low production costs and are relatively easy to connect to a at least superficially gas-tight and metallic coupling part, such as by welding or soldering. So can via the coupling part the Integration of the membrane assembly in a module (with several membrane arrangements of this type) or more generally in a plant within which the gas separation

carried out done. Between the carrier substrate and the membrane, a ceramic, gas-permeable, porous, first intermediate layer is frequently provided which prevents the diffusion effects and, in many cases, also gradually

Reducing the pore size from the metallic carrier substrate to the membrane is used.

The transition from the porous carrier substrate via the cohesive connection (eg weld seam) to the dense, metallic surface of the coupling part presents a high challenge in the application of the above-mentioned layers. In this transition region, a gas-tight separation of the two gas spaces, at least as far as the ensure that other gases are contained in the gas mixture in addition to the gas to be separated. However, due to the different material transitions, this transitional area represents the mechanical weak point and there are always spalling of the layers.

A variant for producing such a dense transition region is described in US Pat. No. 8,753,433 B2. There, the membrane is starting from the

Carrier substrate pulled over the coupling part and runs directly on this. The intermediate layer provided between the carrier substrate and the membrane extends beyond the connection region between the carrier substrate and the coupling part, but extends in the direction of the coupling part in front of the membrane. A

Membrane arrangement in which a dense layer in the transition region on a porous, ceramic support substrate and a gas-tight, ceramic

Ankopplungsteil extends and on which the membrane expires, is in the

JP 2014-046229 A.

The object of the present invention is a membrane assembly of the type specified above and a method for producing such a

To provide membrane arrangement in which the layer structure in the

Transition region between the carrier substrate and the coupling part remains flat over a long Einsatzdauem away with the respective substrate. The object is achieved by a membrane arrangement according to claim 1 and by a method for producing a membrane arrangement according to claim 14. Advantageous developments of the invention are specified in the dependent claims.

According to the present invention, a membrane assembly for the permeative separation of a gas from gas mixtures (eg H ₂ from H ₂ containing

Gas mixtures) (gas separation membrane arrangement). The membrane assembly in this case has a porous, gas-permeable, metallic carrier substrate, a formed on the carrier substrate, selectively for the separated gas-permeable membrane (gas separation membrane), and an at least superficially made of a gas-tight, metallic material coupling part, wherein the carrier substrate along an edge portion of the same cohesively is connected to the coupling part. The gas-permeable surface of the carrier substrate is separated from the gas-tight surface of the coupling part by a boundary line. Between the carrier substrate and the membrane, arranged directly on the carrier substrate, there is a ceramic, gas-permeable, porous, first intermediate layer, which extends on the gas-permeable surface of the porous carrier substrate in the direction of the

Coupling part extends at least to a distance of 2 mm to the boundary line, and in the same direction on the gas-tight surface of the

Coupling part at most over a distance of 2 mm beyond the boundary line extends.

Insofar as reference is made in this description and the claims to "directly" consecutive layers / components, this becomes so

Presence of intermediate layers / components excluded.

If, on the other hand, the term "direct" is not used, other layers / components may also be provided therebetween, as far as technically expedient.The limits specified are to be included in the range specifications. "Gas-tight" or "gas-permeable" refers to properties with respect to the other, contained in the gas mixture in addition to the gas to be separated gases.

The structure of the claimed membrane assembly is associated with several advantages, which will be described below with reference to the operation of the individual components be explained. The membrane is a thin, selectively for certain types of gas (especially for H ₂ ) permeable layer of a material referred. The membrane (or its material) is selected according to the gas to be separated off (eg H ₂ ). The other gases contained in the respective gas mixture may also have to be included in the design and material selection of the components of the membrane arrangement, for example if a component must be gas-tight for all of these gases of the gas mixture. The membrane may in principle be formed as an intrinsically stable foil as well as (at least) one layer on a carrier substrate. With regard to the highest possible performance parameter is in the membrane assembly according to the invention a flat trained

Carrier substrate used for the membrane to provide the membrane as a thin layer. The carrier substrate must be porous and permeable to gas in order, depending on which side of the membrane, the carrier substrate is used (in tubular design preferably inside the membrane) to ensure the gas supply to or gas removal from the membrane. For the carrier substrate and thus also for the membrane applied thereon, there are two common basic forms, namely a planar and a tubular basic shape, wherein the focus is more and more on the tubular or tubular basic shape. For the carrier substrate, both metallic and ceramic materials are used, wherein the presently claimed, metallic carrier substrate with respect to ceramic

Characterized in that it is cheaper to manufacture, in the transition region to the coupling part easier to seal and relatively easy with the coupling part, such as via a welding process, by soldering or by an adhesive connection, is connectable. The production of such porous, gas-permeable, metallic carrier substrates takes place in particular via a powder-metallurgical production process, which comprises the steps of molding

(For example, pressing) and sintering of metallic starting powders, whereby porous carrier substrates are obtained with a typical for powder metallurgy macrostructure. This microstructure is characterized in that the individual grains of the metal powder are recognizable, these individual grains are interconnected depending on the degree of sintering by more or less pronounced Sinterhälse (recognizable, for example, via an electron micrograph of a micrograph). However, porous, gas-permeable, metallic carrier substrates, in particular such carrier substrates produced by powder metallurgy, have a relatively large size Pore size (sometimes up to 50 μπι), which significantly complicates the sealing with a typically only a few microns thick membrane (thickness in gas separation membranes in particular in the range of 5-15 μπι). Suitable materials for the carrier substrate are in particular iron (Fe) based (ie at least 50 wt.%, In particular at least 70 wt.% Fe-containing), a high chromium content

(Cr: Cr) -containing alloys (e.g., at least 16 weight percent Cr) to which further additives, e.g. Yttrium oxide (Y Oa) (to increase the oxidation resistance), titanium (Ti) and molybdenum (Mo) may be added, wherein the proportion of these additives total preferably less than 3 wt.% Is (see, for example, referred to as ITM material of the company Plansee SE containing 71, 2 wt.% Fe, 26 wt.% Cr and in total less than 3 wt.% Of Ti, Y2O3 and Mo). Furthermore, at high operating temperatures (typically operating temperatures for gas separation in the range of 450-900 ° C), interdiffusion effects occur between the metallic ones

Carrier substrate and the (for the H ₂ separation regularly also metallic) membrane, which would lead over time to a degradation or destruction of the membrane. To avoid these disadvantages, at least one ceramic, gas-permeable, porous is formed between the carrier substrate and the membrane

Interlayer (eg from 8YSZ, ie from a 8 mol% yttria (Y ₂ 0 ₃ ) fully stabilized zirconia) used. It suppresses interdiffusion effects between the carrier substrate and the membrane. Another purpose of

Intermediate layer is that over them, possibly also in stages (in particular on the application of several intermediate layers, i.e., a "graded layer structure"), the pore size to a few μπι, in particular one for the final

Coating through the membrane suitable average pore size in the range of 0.03-0.50 μπι, can be reduced.

The layer structure (carrier substrate with intermediate layer (s) and membrane) is for the gas-tight supply and removal of the process gases with appropriate

Connection lines of the system (eg reactor) to connect. For such a gas-tight coupling of the layer structure to connecting lines, a coupling part which is at least superficially made of a gas-tight, metallic material is provided immediately adjacent to the carrier substrate. The carrier substrate is integrally connected to the coupling part along an edge section thereof (such as, for example, via a welding, soldering or adhesive connection). This connection can be through suitable positive and / or non-positive connections of the coupling part are reinforced with the carrier substrate. The coupling part is preferably a metal component which is metallic in the solid material and which is connected in a material-bonded manner to the carrier substrate. In this case, the carrier substrate and the

Coupling part to originally two separate components. In the present application is to be taken with materially connected components explicitly on an arrangement in which the carrier substrate and the coupling part are integrally formed and thus of two imaginary components that are in material contact, are constructed. In this embodiment, the originally porous carrier substrate can be made gas-tight in an aftertreatment step in the areas required as a coupling part. This can be done, for example, by means of pressing or by superficial superficial melting in the required areas, for example by means of a laser beam, as a result of which the coupling part is rendered gas-tight at least on the surface. The gastight, metallic region of the coupling part is preferably located on the same side as the membrane on the adjacent carrier substrate, in the case of a tubular basic shape, in particular on the outside.

The different embodiments of the coupling part and of the carrier substrate have in common that on the carrier substrate provided for the gas separation gas-permeable surface of the carrier substrate is present, while at least the surface of the coupling part is gas-tight. By the meeting of the gas-permeable surface and the gas-tight surface of the arrangement, a boundary line (joint) is defined, wherein surfaces with gas-tight welds or solder joints are assigned to the gas-tight surface.

The coupling part may have other functions, such as the Zusarrmienführung or division of several connecting lines meet. For this purpose, correspondingly functionalized sections can be formed on the coupling part and / or connected to it. In the case of a tubular design, the coupling part is also tubular, at least in the region adjoining the carrier substrate, and the cohesive connection extends around the entire circumference of the adjoining components.

The first intermediate layer (and optionally further intermediate layers) and the membrane extend substantially over the entire, provided for the gas separation gas-permeable surface of the carrier substrate. In the case of a tubular design, this corresponds to the cylindrical outer surface (or possibly the cylindrical inner surface) of the carrier substrate, it being possible for at least one axial edge region (eg for attaching a connection component or a sealing end) to be recessed. In the area of the layer structure, the sealing takes place (apart from the

Permeability to the gas to be separated) through the membrane.

The challenge addressed by the present invention is the gas-tight embodiment of the gas-tight construction, at least with regard to the further gases contained in the gas mixture in addition to the gas to be separated off (hereinafter: "further gases")

Transition region between the coupling part and the carrier substrate

(the area around the borderline). At the core of the present invention is that the first intermediate layer extends substantially over the entire gas-permeable surface of the carrier substrate, but not beyond, i. the first intermediate layer extends (apart from a production-related small gap) to the boundary line in the direction of the coupling part, but not significantly beyond. Quantified, this means that the first intermediate layer moves in the direction of the

Coupling member on the gas-permeable surface of the porous support substrate at least to a distance of 2 mm, in particular up to a distance of 1 mm, more preferably up to a distance of 0.5 mm, extending to the boundary line, while in the same direction at most over a distance of 2 mm, preferably at most over a distance of 1 mm, more preferably at most over a distance of 0.5 mm, extending over the boundary line away.

In other words, the first intermediate layer covers the entire gas-permeable surface of the supporting substrate, except for an area with a maximum distance of 2 mm from the boundary line, and extends except for a maximum distance of 2 mm from the area Borderline removed - not on the gas-tight surface of the assembly. The first intermediate layer is in direct contact with the carrier substrate. Direct contact of the first intermediate layer with the gas-tight surface, which is problematic due to inadequate adhesion, is largely or completely avoided. For sealing in the transition region in particular serves the membrane itself or alternatively also for the other or all gases of the gas mixture gas-tight, adjacent to the membrane or overlapping trained layer, which are pulled out beyond the coupling part, and then directly abut on the coupling part and gas-tight (for the other or all gases of the gas mixture) complete.

The first intermediate layer expediently has a smaller average pore size than the carrier substrate. This reduces the mean pore size towards the membrane and provides a smoother surface for membrane application. The porosity of the first intermediate layer is preferably at least 20%, wherein the determination of the porosity due to the small layer thickness and due to the most angular shape of the individual ceramic particles is associated with a relatively large measurement error. A preferred mean pore size for the first

Intermediate layer is in the range of from 0.20 μπι up to and including 2.00 μπι, in particular in the range of from 0.31 μπι up to and including 1, 2 μιη, more preferably in the range of from 0.31 μπι up to and including 0.8 μιη if the membrane is applied directly to the first intermediate layer and no further intermediate layers are provided for a staggered reduction of the porosity in the direction of the membrane. In this case, if no further intermediate layers are applied, the average pore size is particularly preferably smaller than 0.5 .mu.m inclusive. According to a development, the first intermediate layer has an average particle size in the range from 0.7 to 3.5 μm, in particular in the range from 0.76 to 2.5 μm, more preferably in the range from 0.8 to 1.8 μm. In particular, the particle size distribution of the first intermediate layer is in the range of 0.01 to 100.00 μπι. The other ranges for the mean pore and particle sizes and the corresponding size distributions and in particular the narrower ranges are selected on the one hand to achieve good adhesion of the first intermediate layer on the substrate, on the other hand for producing a good transition to a possible second intermediate layer. The layer thickness of the first intermediate layer is in accordance with a development in the range between 5 - 120 μπι, in particular in the range between 10 - 100 μπι, more preferably in the range between 20 - 80 μπι. The layer thickness data for the first intermediate layer relate to the region of the carrier substrate with a substantially constant layer thickness profile, while in the Transition region to the coupling part out due to unevenness and layer thickness variations may occur. It should be noted that the material of the first intermediate layer may partially seep into the carrier substrate. In a preferred embodiment, at least one further ceramic, gas-permeable, porous, second intermediate layer is arranged between the first intermediate layer and the membrane, which has a smaller mean pore size and preferably a smaller average particle size than the first intermediate layer.

Preferably, this second intermediate layer extends in the direction of

Coupling part beyond the first intermediate layer and runs directly on the coupling part.

The invention is based on the finding that in the transition region

Between the first intermediate layer and the gas-tight surface of the coupling part, which has a comparatively low surface roughness and in particular of a solid metal material (such as steel) is formed, exists only a

insufficient liability. This also applies to the area of any cohesive connection (weld seam, solder joint), which also provides a smooth surface locally. Furthermore, different thermal expansion coefficients of the materials used for the coupling part, the carrier substrate and the ceramic intermediate layer lead to stresses within the layer structure,

in particular during the sintering of the layer structure or later in the use of the membrane arrangement. As a result, if cracks develop within the first intermediate layer or if flaking occurs, they settle through the others

Layers of the layer structure continued and led to a failure of the

Membrane assembly. By largely or completely avoiding direct contact of the comparatively coarse-grained ceramic first intermediate layer with the gas-tight surface in the membrane arrangement according to the invention, the adhesion of the further layer (s) in the transition region can be significantly increased. In direct contact with the relatively smooth gas-tight surface of the coupling part come Therefore, only the much denser membrane and in the presence of additional intermediate ceramic layers, these intermediate ceramic layers, but in comparison to the first intermediate layer have a lower porosity and preferably a smaller average particle size. Due to the finer ceramic particles of the second or, if appropriate, further intermediate layer (s), which come into direct contact with the metallic gas-tight surface of the arrangement, sintering forms between the second (and more intermediate layers) and the underlying metallic layer gas-tight surface of the arrangement (in particular the cohesive connection) significantly more sintering necks than would be the case between the metallic gas-tight surface and the first intermediate layer. Since only layers with a lower porosity are in direct contact with the gas-tight, comparatively smooth surface, the adhesion of the layers in the transition region around the boundary line is therefore markedly improved. The risk of the occurrence of flaking, both during a sintem in the context of

Production as well as later use, thereby significantly reduced.

The use of at least one second interlayer, which has a lower porosity than the first interlayer and extends beyond the first interlayer, provides several advantages. By using a second one

Interlayer is the load due to the different thermal expansion coefficients reduced. The second layer further constitutes an additional diffusion barrier between the carrier substrate and the membrane and, in particular, includes a possible small production-related gap region on the gas-permeable surface of the carrier substrate in the transition region in the vicinity of the boundary line. As a further important advantage, the use of a second intermediate layer having a reduced pore size and preferably a reduced particle size starting from the carrier substrate achieves a gradual reduction in the average pore size all the way to the membrane and a sufficiently smooth

Surface provided for the application of the membrane. Since ceramic materials generally adhere well to each other, in particular can be united together well, the application of the second or optionally further intermediate layers as described below is unproblematic in this respect. Particularly advantageous for the second intermediate layer has a middle

Pore size in the range of 0.03 - 0.50 μηι, in particular in the range of

0.03 - 0.30 μπι, more preferably in the range of 0.03 - 0.25 μπι proven. According to a development, the second intermediate layer has an average particle size in the range from 0.01 to 1.00 μm, in particular in the range from 0.01 to 0.75 μm, more preferably in the range from 0.03 to 0.50 μm. In particular, lies the

Particle size distribution of the second intermediate layer in the range of

0.01 to 25.00 μπι. The layer thickness of the second intermediate layer is according to a development in the range between 5 - 75 μπι, in particular in the range between 5 - 50 μπι, more preferably in the range between 10 - 25 μιη.

It should be noted that in particular the layer thickness of the second or further intermediate layers may vary in order to avoid discontinuity, e.g. in the

Transition region, for example, to compensate at the edge of the first intermediate layer or in the region of a cohesive connection and provide a more uniform surface for subsequent layers or the membrane. Thus, for example, the second or a further intermediate layer can become increasingly thinner towards the edge region and leak out or, in the region of a weld seam, e.g. be thicker. This improves the adhesion of the layer structure and reduces the risk of cracking. As a reference for the layer thickness is therefore a position in the range of the first

Intermediate layer chosen with sufficient distance from the transition region. Optionally, an additional layer (cover layer) may be provided in the transition region, wherein this additional layer does not extend over the entire gas-permeable surface of the

Carrier substrate, but only extends over the transition region. This additional layer also serves to compensate for any discontinuity in the transition region.

In general, the second intermediate layer can adjoin the membrane directly. As indicated above, alternatively, one or more further, ceramic, gas-permeable, porous intermediate layer (s) may be provided between the second intermediate layer and the membrane, in which case preferably the mean pore size of this further intermediate layer (s) starting from the second intermediate layer to the Membrane even further decreases. Such a graded layer structure allows an even more uniform adaptation of the

Comparatively coarsely porous structure of the carrier substrate to the finely porous structure, as it is required for the final coating by the membrane. According to a development, the average pore size of the second or further intermediate layer (s) deviates from the first or the immediately underlying intermediate layer by at least 0.10 μπι, in particular by at least 0.15 μηι, preferably even by at least 0.20 μπι, from the average pore size of the first intermediate layer or the immediately underlying intermediate layer. Due to the different porosity and the associated particle size good Hafrungseigenschaften favored possible stresses avoided, and it is ensured that in the manufacturing process when applying the subsequent layer, this does not penetrate too deeply into the previous layer or infiltrated.

In general, in the case of layer thickness information, information relating to the pore size and with regard to the particle size, in each case these parameters are referred to in the ready-to-use state, i. For sintered layers on the sintered state.

The different layers are in an electron micrograph of a cross-section micrograph on the basis of the regularly forming between them interfaces, which are particularly pronounced in the case of layers sintered layers, and the different pore size distinguishable from each other.

The pore size or pore length of a single pore is determined as follows: the area of the respective pore in the micrograph is measured and, subsequently, its equivalent diameter, which would result for a circular shape of the same area size, is determined. Accordingly, the particle size is determined. to

Determining the pore sizes and particle sizes becomes a perpendicular to the

made cross-section through the membrane arrangement and investigated a correspondingly prepared micrograph in the scanning electron microscope (SEM). The analysis is carried out by threshold value of the different gray levels from the respective REM-BSE image (BSE: back-scattered electrons;

backscattered electrons). The brightness and contrast of the

REM BSE image adjusted so that the pores and particles in the image are easily recognizable and distinguishable from each other. With the slider, the

Depending on the grayscale differentiation between pores and particles, a suitable grayscale value is selected as the threshold value. In order to determine the average pore size, the pore size of all the pores of a representative region of the relevant layer previously selected in the micrograph is measured and subsequently becomes whose mean value is formed. Accordingly, the determination of the mean

Particle size. For the individual particles to be measured in each case, its geometric outline is decisive and not the grain boundaries of optionally a plurality of grains connected to a particle, each having a different, crystallographic orientation. Only the pores or particles that are completely within the selected range are included in the evaluation. The porosity of a layer can be determined in the micrograph (SEM-BSE image) by determining the area fraction of the pores within a selected area relative to the total area of that selected area, including the areas of the pores only partially within the selected area be involved. In the present case, the Imagic ImageAccess program (version: 11 Release 12.1) was used with the analysis module "particle analysis".

According to a development, the first intermediate layer and, if appropriate, further, provided intermediate layers are / are in each case a sintered ceramic layer (s). A ceramic, sintered layer is characterized by a typical microstructure, in which the individual ceramic grains are recognizable, these being interconnected by more or less pronounced sintering necks, depending on the degree of sintering (in the present, ceramic, sintered layers, the sintering necks can only be very weak). The typical microstructure is e.g. over a

Electron micrograph of a micrograph recognizable. Preferably, the individual, ceramic layers are each a wet-chemical

Process (eg screen printing, wet powder coating, dip coating, etc.), in particular via dip coating in tubular basic form, applied and sintered in layers. A layered sintering is for example in an electron micrograph of a micrograph of the sintered layer structure recognizable that the interfaces between the individual layers are more pronounced than in a common sintering of all, originally present in the green state layers, since in the latter production route, the interfaces between the layers due of diffusion effects become more blurred. According to a development, the materials of the at least one intermediate layer are selected from the group of the following materials:

a. yttria (Y2O3) stabilized zirconia (Zr0 ₂ )

b. zirconia stabilized with calcium oxide (CaO) (ZrO ₂ ),

c. magnesia (MgO) stabilized zirconia (Zr0 ₂ ), and

d. Alumina (A Os).

Preference is given to a yttria-stabilized zirconium oxide (abbreviated to YSZ), in particular a zirconium oxide (in short 8YSZ) fully stabilized with 8 mol% yttrium oxide (Y 2 O 3). Preferably, for the second intermediate layer and optionally further

Intermediate layers the same starting material and the same sintering process as used for the first intermediate layer, the ceramic intermediate layers are therefore in a preferred embodiment of the same material (or material).

Composition). As a result, comparable, thermal

Coefficient of expansion achieved and allows a cost-effective production. Preferably, these are YSZ, in particular 8YSZ. However, the individual layers may differ in their milieu structure, for example in the average pore size, the average particle size and the porosity. Instead of fully stabilized zirconium oxide (eg addition of typically 8 mol% yttrium oxide with Y 2 O 3 as stabilizer) it is also possible to use a partially stabilized zirconium oxide (eg addition of typically 3 mol% yttrium oxide with Y 2 O 3 as stabilizer). Further stabilizers of zirconium oxide furthermore include cerium oxide (CeO ₂ ), scandium oxide (SCO 3) or ytterbium oxide (YbO ₃ ). According to a development, the carrier substrate and the coupling part are each tubular or tubular. Its cross-section is preferably circular with a constant diameter along the axial direction. Alternatively, however, it is also possible to provide an otherwise closed cross section, such as an oval cross section, as well as a cross section widening along the axial direction. A cohesive connection can, for example, by an integral design of the

Coupling and the carrier substrate, be formed by a solder joint, by an adhesive bond or by a welded joint. According to a further development, the cohesive connection is formed by a welded connection, which in the case of a tubular basic shape is preferably around the entire Extending circumference of the respective tubular edge portion. A

Welded connection is inexpensive and process reliable to produce. Due to the porosity of the carrier substrate is typically formed in the

Welded joint a recess. In a further advantageous embodiment, the cohesive connection is designed as a solder joint, which extends analogous to the welded joint in a tubular basic shape preferably around the entire circumference of the respective tubular edge portion. The solder joint is also inexpensive and reliable, it has the advantage over a welded joint that the parts to be joined are not melted and thus no distortion or no shrinkage occurs. An adhesive bond is also very inexpensive and has opposite to the aforementioned cohesive

Connection forms also have the advantage that they can be carried out at room temperature or at comparatively low temperatures. For hydrogen separation, the materials used for the membrane are basically pure metals which have a certain permeability to hydrogen but which are a barrier to other atoms / molecules. With a view to avoiding formation of an oxide layer which would impair this selective permeability, for hydrogen separation (H 2) it is preferable to use noble metals, in particular palladium, palladium-containing alloys (in particular more than 50% by weight of palladium), e.g. Palladium-vanadium, palladium-gold,

Palladium-silver, palladium-copper, palladium-ruthenium or else

Palladium-containing composite membranes, such as with the layer sequence palladium, vanadium, palladium, used. According to a development, the membrane is accordingly formed of palladium or a palladium-based, metallic material (eg alloy, composite, etc.). The Pd content of such membranes is in particular at least 50% by weight, preferably at least 80% by weight. Furthermore, it is preferred that the at least one intermediate layer is formed from yttrium oxide (Y ₂ Os) stabilized zirconium oxide (ZrO ₂ ), in particular from 8YSZ. Furthermore, it is preferred that the carrier substrate and the coupling part are each formed from iron-based materials. These features of the various components are advantageous per se, in particular, they show advantageous effects in combination. The present invention further relates to a method for producing a

Membrane arrangement for the permeative separation of a gas from gas mixtures, especially for the separation of H ₂ from H ₂ -containing gas mixtures comprising a porous, gas-permeable, metallic carrier substrate and an at least superficially made of a gas-tight, metallic coupling part, wherein the carrier substrate along an edge portion the same cohesively connected to the coupling part. The method has the following steps: a. Applying a ceramic first intermediate layer directly on the

gas-permeable surface of the porous carrier substrate, wherein the first intermediate layer in the direction of the coupling part on the gas-permeable

Surface of the porous support substrate extends at least to a distance of 2 mm to the boundary line, and the first intermediate layer in the direction of the coupling part on the gas-tight surface of the

Coupling part at most over a distance of 2 mm beyond the boundary line extends

b. Application of a selectively permeable to the gas to be separated membrane on the ceramic first intermediate layer, wherein the membrane extends in the direction of the coupling part beyond the first intermediate layer and immediately runs out on the coupling part.

In the method according to the invention is thus with the first intermediate layer in

Essentially covered the entire gas-permeable surface of the carrier substrate. In a preferred embodiment, at least one ceramic, porous gas-permeable second intermediate layer, which has a smaller average pore size and preferably a smaller average particle size than the first intermediate layer, is applied to the first intermediate layer prior to application of the membrane. By the method according to the invention substantially the same advantages as in the membrane arrangement according to the invention described above are achieved. The further developments and variants described above can also be realized correspondingly in the method according to the invention while achieving corresponding advantages. In the case of the at least one ceramic intermediate layer, the application is applied

in particular in that the intermediate layer containing an organic binder and ceramic particles is applied by means of a wet-chemical process and then sintered, and the subsequent layer (if appropriate in a corresponding manner) is applied only subsequently. Preference is given to the suspension of the second intermediate layer selected a lower viscosity than that of the first intermediate layer. The suspension used for the first intermediate layer has a high viscosity, whereby penetration (infiltration) of the material of the first

Intermediate layer is largely prevented in the relatively coarsely porous carrier substrate. The suspension of the second intermediate layer has a low viscosity, so that the sintered layer adheres well to a dense surface or to unsteady transitions.

Further advantages and expediencies of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures.

From the figures show:

Fig. 1: a schematic cross-sectional view of an inventive

Membrane arrangement in the axial direction according to a first embodiment of the invention;

Fig. 2: a schematic cross-sectional view of an inventive

Membrane arrangement in the axial direction according to a second

Embodiment of the invention;

Fig. 2a: an enlarged, marked with x section of the

Membrane arrangement in Fig. 2;

3 shows a schematic cross-sectional view of a device according to the invention

Membrane arrangement in the axial direction according to a third

Embodiment of the invention;

4 shows a schematic cross-sectional view of a device according to the invention

Membrane arrangement in the axial direction according to a fourth

Embodiment of the invention;

5: pore size distribution of the first intermediate layer according to a

Embodiment of the invention;

FIG. 6: Particle size distribution of the first intermediate layer according to FIG

Embodiment of the invention;

Fig. 7: pore size distribution of the second intermediate layer according to a

Embodiment of the invention; and

8: particle size distribution of the second intermediate layer according to a

Embodiment of the invention. 1-4 are different, differing in construction embodiments of a membrane assembly for the permeative separation of a gas to be separated (eg H ₂ ) from a gas mixture (eg steam-reformed natural gas containing CH ₄ , H ₂ 0, C0 ₂ , CO, H ₂ , etc.), with only the

Transition region is shown by the carrier substrate to the coupling part. In Fig. 1, a tubular, porous, gas-permeable, metallic support substrate 2 (e.g., ITM) is integrally bonded along its (circular) edge portion to a tubular coupling member 4 formed in solid metal (e.g., steel). The gas-permeable surface of the carrier substrate 2a is separated from the gas-tight surface of the coupling part 2b by a boundary line 5. Immediately on the support substrate is disposed a ceramic, gas-permeable, porous, first intermediate layer 6 (e.g., sintered 8YSZ) extending over the entire gas-permeable surface of the support substrate. This first intermediate layer has a smaller average pore size than the carrier substrate 2. Over this first intermediate layer 6 is disposed a second ceramic, gas-permeable, porous intermediate layer 7 (for example made of sintered 8YSZ). This second intermediate layer 7 has a smaller mean pore size than the first one

Intermediate layer on; it extends beyond the first intermediate layer 6 and runs directly on the coupling part 4. Due to their reduced compared to the first intermediate layer 6 average pore length, it can be a sufficiently smooth surface for the subsequent selectively permeable to the gas to be separated

Provide membrane 8 (e.g., Pd). The second intermediate layer is in

Transition region formed slightly thicker to compensate for the discontinuity at the edge of the first intermediate layer and a more uniform surface for the

subsequent membrane 8 to provide. Optionally, as in

4, an additional layer 7 'may be provided in the transition area, which serves the same purpose, an adjustment of any discontinuities. The membrane 8 immediately adjacent to the second intermediate layer extends in the direction of the coupling part (a) over the two

Intermediate layers 6 and 7 and runs directly on the coupling part 4, to which it produces a gas-tight connection for the gas to be separated (eg H ₂ ). In the following description of the second, third and fourth embodiments shown in FIGS. 2, 3 and 4, the same reference numerals are used for the same components. In the present case, only the differences compared to the first Ausruhrungsform will be discussed. In the second embodiment (FIG. 2 and the enlarged detail in FIG. 2 a), the integral connection is realized by a solder connection 3 '. The gas-permeable surface 2a of the carrier substrate passes continuously into the gas-tight surface 4a of the coupling part, wherein the solder joint 3 'forms part of the gas-tight surface 4a. As shown in the enlarged illustration in FIG. 2a, the first intermediate layer 6 extends on the gas-permeable surface of the carrier substrate as far as the limit line 5, but not beyond. Due to the manufacturing process, only a very small area around the boundary line 5 is not covered by the first intermediate layer 6 on the gas-permeable surface of the carrier substance. According to the invention, the maximum distance d on the gas-permeable surface of the carrier substrate, which is not through the first

Intermediate layer 6 is covered, smaller than 2 mm. All embodiments also have in common that the first intermediate layer 6 extends in the direction of the coupling part a on the gas-tight surface at most over a distance d 'of 2 mm beyond the boundary line 5 addition. The connection to the coupling part 4 is made by the second intermediate layer 7, which has a lower porosity, thereby better

Has adhesive properties as the first intermediate layer 6 and provides a sufficiently smooth surface for the application of the membrane.

In the third embodiment (Figure 3), the integral connection is formed by a welded joint 3 ", the welding process causing a circumferential depression due to the porosity Similar to the second embodiment, direct contact of the first intermediate layer 6 with the smooth surface of the weld is avoided ,

In the fourth embodiment (Figure 4), the coupling part 4 "is formed of a porous, gas-permeable base material, in particular of the same material as the carrier substrate 2 (for example 1TM) and has only on the outside thereof

Surface on a gas-tight surface area 4a. The gas-tight

Surface area 4a can be, for example, by applying a coating or a sealant or by superficial melting of the porous

In this case as well (except for an extremely small area around the boundary line), the first one extends Intermediate layer 6 does not have the gas-tight surface 4a of the coupling part.

Preferably, the carrier substrate and the coupling part are integrally formed.

In the following, an example for the production of an inventive

Membrane arrangement described. A carrier substrate in the form of a porous tube made of ITM with an outer diameter of 5-10 mm, a length of 100-300 mm, a porosity of about 40% and an average pore size of <50 μπι is at an axial end of the same with a in the Solid material made of steel,

rohrfbrmigen coupling part with the same outer diameter welded by laser welding. In order to ensure a homogenization of the weld transition, the resulting component is annealed under a hydrogen atmosphere at a temperature of 1200 ° C. Subsequently, the surface in the area of the welded joint is sandblasted to obtain a more uniform surface. Next, the coupling part is covered with the weld. In a further step, for the first intermediate layer of an 8YSZ powder, in particular a powder having a d80 value of about 2 μm (and having a d 50 value of about 1 μm), a suspension suitable for a wet-chemical coating method,

for example, with addition of dispersant, solvent

(e.g., BCA [2- (2-butoxyethoxy) ethyl] acetate, available from Merck KGaA Darmstadt) and Binder. The first intermediate layer is formed by dip-coating, i. by immersing the rohrfbrmigen component in the suspension, to the beginning of

Weld applied. After drying, the cover of the gas-tight surface of the coupling part is removed and the resulting component is then sintered under a hydrogen atmosphere at a temperature of 1300 ⁰ C, whereby the organic constituents are burned out, a sintering of the ceramic

Layer takes place and the porous, sintered, ceramic first intermediate layer is obtained. A typical pore size distribution and particle size distribution of a first intermediate layer produced in this way is shown in FIGS. 5 and 6. In particular, the pore size distribution is in the range of 0.08 to 12.87 μηι (with an average pore size of 0.55 μπι), as shown in FIG. 5 can be seen (with a few pores are not shown with a larger diameter), and the

Particle size distribution is in the range of 0.08 - 61.37 μπι (with an average particle size of 1.27 μπι), as shown in FIG. 6 can be seen (with a few particles are no longer shown with a larger diameter). In the next step For example, a suspension of 8YSZ powder for the second intermediate layer is prepared, with the statements made above on the first intermediate layer applying mutatis mutandis, except that an overall finer 8YSZ powder is used and a slightly lower viscosity of the suspension is set than in the first intermediate layer. In particular, as a ceramic powder, a mixture of two 8YSZ powders of different particle size, in particular a powder having a d80 value of about 2 μπι (and with a d50 value of about 1 μπι) and a very fine powder having a particle size ( crystallite size) of about 25 nm (nanometers). The second intermediate layer is also applied by dip coating. The second

Intermediate layer completely covers the first intermediate layer and runs out directly on the coupling part. Any discontinuities in the transition area at the edge of the first intermediate layer are compensated by applying (brushing) of additional material. Subsequently, the obtained component is sintered under a hydrogen atmosphere at a temperature of 1,200 ° C, whereby the organic components are burned out, takes place sintering of the ceramic layer and the porous, sintered, ceramic second intermediate layer is obtained. The micrograph of the second intermediate layer shows in cross-section a homogeneous course, even if the material of the second intermediate layer in several

Process steps (dip-coating with subsequent brushing) has been applied. A typical pore size distribution and particle size distribution of a second intermediate layer produced in this way is shown in FIGS. 7 and 8. In particular, the pore size distribution is in the range of 0.03 to 5.72 μπι (with an average pore size of 0.13 μπι), as can be seen from FIG. 7 (with a few pores having a larger diameter are no longer shown), and the

Particle size distribution is in the range of 0.03 to 18.87 μπι (with an average particle size of 0.24 μπι), as with reference to FIG. 8 can be seen (with a few particles with a larger diameter are no longer shown).

Subsequently, a Pd membrane is applied via a sputtering process. It completely covers the second intermediate layer as well as the underlying first intermediate layer. Finally, a further Pd layer is applied to the Pd sputter layer via a galvanic process in order to seal the latter and to achieve the required gas tightness.

The present invention is not limited to those shown in the figures

Limited embodiments. In particular, the cohesive connection is not mandatory to realize as a welded joint. For example, it can also be executed as a solder joint or adhesive bond. Furthermore, the

Coupling member and the support substrate also be formed integrally or monolithically and the cohesive connection forms the transition between the

gas-permeable carrier substrate and the at least superficially gas-tight

Coupling part. For example, in the fourth embodiment (FIG. 4), a monolithic design of the carrier substrate and of the coupling part would also be possible. Furthermore, the structure described is suitable not only for the H2 separation, but also for the separation of other gases (eg C0 ₂ , 0 ₂ , etc.). Furthermore, alternative membranes can be used, such as microporous, ceramic membranes (A1 ₂ 0 ₃ , Zr0 ₂ , Si0 ₂ , Ti0 ₂ , zeolites, etc.) or dense, proton-conducting ceramics (SrCe0 _3-5 , BaCe0 ₃ -5, etc. ).

Claims

claims

1. membrane assembly (1) for the permeative separation of a gas

Gas mixtures, comprising

a porous, gas-permeable, metallic carrier substrate (2),

a membrane (8) permeable to the gas to be separated and formed on the carrier substrate (2),

a ceramic, gas-permeable, porous, first intermediate layer (6) arranged between the carrier substrate (2) and the membrane (8), directly on the carrier substrate,

a bonded to the carrier substrate cohesively (3; 3 '; 3 "), at least superficially consisting of a gas-tight, metallic material

Coupling part (4, 4 "), wherein the gas-permeable surface of the

Carrier substrate is separated from the gas-tight surface of the coupling part by a boundary line (5),

characterized in that the first intermediate layer (6) in the direction of the coupling part (4, 4 ") on the gas-permeable surface of the porous support substrate at least up to a distance of 2 mm to the

Border line (5) extends, and the first intermediate layer (6) in the direction of the coupling part (4, 4 ") on the gas-tight surface of the

Coupling part at most over a distance of 2 mm over the

Border line (5) extends beyond.

2. Membrane arrangement according to claim 1, characterized in that the first

Intermediate layer (6) has a smaller average pore size than the carrier substrate (2).

3. Membrane arrangement according to claim 1 or 2, characterized in that the first intermediate layer (6) has a mean pore size in the range of

including 0.20 μπι up to and including 2.00 μπι.

4. Membrane arrangement according to one of the preceding claims, characterized in that extending between the first intermediate layer (6) and the membrane (8) at least one further ceramic, gas-permeable, porous, second intermediate layer (7) having a smaller average pore size than the first intermediate layer (6).

5. Membrane arrangement according to one of the preceding claims, characterized in that the second intermediate layer (7) has a mean pore size in the range of 0.03 μπι inclusive of up to and including 0.5 μπι.

6. Membrane arrangement according to one of the preceding claims, characterized in that the second intermediate layer (7) extends in the direction of the coupling part (4, 4 ") beyond the first intermediate layer (6) and directly on the coupling part (4; 4"). expires.

7. Membrane arrangement according to one of claims 1 to 5, characterized

in that the first and / or second intermediate layer (6, 7) is / are a sintered, ceramic layer.

8. Membrane arrangement according to one of the preceding claims, characterized

in that the material of the at least one intermediate layer (6, 7) is selected from the group of the following materials:

a. zirconia stabilized with yttria (Y ₂ O ₃ ) (ZrO ₂ ),

b. zirconia stabilized with calcium oxide (CaO) (ZrO ₂ ),

c. magnesia (MgO) stabilized zirconia (Zr0 ₂ ), and d. Alumina (Al 2 O 3).

9. Membrane arrangement according to one of the preceding claims, characterized

characterized in that the first and at least one second

Intermediate layer (6,7) are formed from one and the same material.

10. Membrane arrangement according to one of the preceding claims, characterized in that the carrier substrate (2) and the coupling part (4, 4 ") are each rohrf formed.

1 1. Membrane arrangement according to one of the preceding claims, characterized in that the cohesive connection (3, 3 ', 3 ") by a welded joint, a solder joint or an adhesive bond is formed.

12. Membrane arrangement according to one of the preceding claims, characterized in that the membrane (8) in the direction of

Coupling part (4, 4 ") over the at least one intermediate layer (6, 7) extends out and immediately on the coupling part (4, 4") expires.

13. Membrane arrangement according to one of the preceding claims, characterized in that the membrane (8) made of palladium or a

Palladium-based, metallic material is formed,

in that the at least one intermediate layer (6, 7) is / are formed from yttrium oxide (Y ₂ O ₃ ) stabilized zirconium oxide (ZrO ₂ ) and

the carrier substrate (2) and the coupling part (4; 4 ") are each formed from iron-based materials.

14. A process for producing a membrane assembly (1) for permeative

Separation of a gas from gas mixtures, the

a porous, gas-permeable, metallic carrier substrate (2) and

has a coupling part (4, 4 ") consisting at least superficially of a gas-tight, metallic material,

wherein the carrier substrate (2) along an edge portion of the same is materially connected to the coupling part (4; 4 ") and the gas-permeable surface of the carrier substrate from the gas-tight surface of the coupling part is separated by a boundary line (5),

characterized by the following steps:

a. Applying a ceramic first intermediate layer (6) directly to the gas-permeable surface of the porous carrier substrate, wherein the first intermediate layer (6) in the direction of

Coupling part (4; 4 ") extends on the gas-permeable surface of the porous carrier substrate at least to a distance of 2 mm to the boundary line, and the first intermediate layer (6) in Direction of the coupling part (4, 4 ") extends on the gas-tight surface of the coupling part at most over a distance of 2 mm beyond the boundary line addition

b. Applying a selectively permeable to the gas to be separated

Membrane (8) on the ceramic first intermediate layer (6), wherein the membrane extends in the direction of the coupling part beyond the first intermediate layer (6) and immediately on the coupling part (4; 4 ") expires.

15. The method according to claim 14, characterized in that prior to the application of the membrane at least one ceramic, porous gas-permeable second intermediate layer (7) having a smaller average pore size than the first

Intermediate layer (6), is applied to the first intermediate layer (6).