WO2002092203A1

WO2002092203A1 - Inorganic composite membrane for isolating hydrogen from mixtures containing hydrogen

Info

Publication number: WO2002092203A1
Application number: PCT/EP2002/003568
Authority: WO
Inventors: Christian Hying; Gerhard HÖRPEL
Original assignee: Creavis Gesellschaft Für Technologie Und Innovation Mbh
Priority date: 2001-05-11
Filing date: 2002-03-30
Publication date: 2002-11-21
Also published as: DE10122889C2; DE10122889A1

Abstract

The invention relates to a flexible composite membrane for selectively isolating hydrogen from mixtures containing the same. Said membrane comprises a composite material consisting of a perforated support, preferably a textile and/or nonwoven and also a porous ceramic material and is coated with a metal layer that is suitable for isolating hydrogen. The surface of the ceramic material that is coated with the metal layer has pores and the metal layer is provided with a pattern of alternating concave and convex areas to compensate and/or prevent the stresses arising from changes in volume that are caused by the absorption of hydrogen or a temperature change.

Description

Inorganic composite membrane for the separation of hydrogen from mixtures containing hydrogen

The present invention relates to a nerbund membrane for the selective separation of hydrogen from hydrogen-containing mixtures, a process for producing the nerbund membrane and the use of the nerbund membrane for the selective separation of hydrogen from hydrogen-containing mixtures.

It is known to use membranes for hydrogen separation, which consist of palladium (Pd) or palladium with 25% silver (Ag). These are manufactured in the form of pressure-stable tubes or tubes and used in appropriate equipment. At correspondingly high pressures and temperatures above 300 ° C there is a usable hydrogen permeation through the 20 to 2000 μm thick tube walls. In order to ensure good pressure stability in the thinner layers, the noble metal layers are used in the prior art on ceramic, glass-like or metallic porous supports with the highest possible porosity for a given pore radius.

Porous plates are used less often. With plate-shaped systems it is possible to achieve higher packing densities (more separation area per volume unit), as is required above all in the automotive sector. However, these systems are more susceptible to crack formation than pipe systems, since the volume expansion of the precious metal layer due to hydrogen sorption leads to the destruction of the flat membrane or to problems with the seal after a few cycles. This can be suppressed by a suitable choice of various alloy components such as gold or rhodium, but it cannot be completely avoided. The change in volume leads to a ner change in the surface of the membrane and to stresses which can go so far that cracks form in the membrane and then no separation is possible with this membrane. This problem arises more and more in the Nordergrund the thinner and thus the more sensitive the hydrogen-selective layers become. However, a high hydrogen permeability is only possible in the known metal layers for the selective separation of hydrogen if the metal layer is very thin. This problem also occurs with tubular membranes, although changes in the surface only occur after 10 times more cycles than with plate-shaped systems. However, this does not solve the problem as such. J. Shu provides a summary of the prior art in Catalytic Palladium-based Membrane Reactors; The Canadian Journal of Chemical Engineering, 69, 90/1991; pp. 9036-1060.

The known membranes have further disadvantages. According to the state of the art, they are used in three different forms. On the one hand as pure metal (as a layer or tube with a correspondingly large layer thickness), on the other hand as a thin coating on porous metal membranes or as a very thin layer on known rigid, porous ceramics.

When applied to metal supports, the support and the separating layer have comparable thermal expansion coefficients, but the separating layer cannot be made very thin, since metallic support membranes according to the prior art cannot be produced with pores that are smaller than 0.5 μm. In order to be able to bridge such large pores without defects, the selective separating layers must have a large thickness. In these cases, selective separating layers are therefore always thicker than 5 to 10 μm and a high hydrogen permeability is not possible.

With ceramic substrates, you are able to produce pores with a smallest radius of up to 1 - 5 nm. Correspondingly, the selective separating layers can then be manufactured without defects with a thickness of only 50-500 nm. Ceramic supports, however, have a coefficient of thermal expansion that differs from that of the metallic separating layer, which in practice leads to cracks in the case of relatively small changes in temperature and thus leads to the uselessness of such membranes.

It is therefore an object of the invention to provide a composite membrane for the selective separation of

To provide hydrogen from mixtures containing hydrogen, wherein the membrane has a high hydrogen permeability and selectivity and at the same time a great stability and is thus suitable for stresses due to volume changes due to Compensate and / or avoid absorption of hydrogen or by changing the temperature.

This object is achieved according to the claims. The present invention provides a flexible composite membrane for the selective separation of hydrogen from hydrogen-containing mixtures, the membrane comprising a composite material coated with a metal layer suitable for the removal of hydrogen, comprising a perforated carrier, preferably a woven and / or nonwoven, and a porous ceramic material , wherein the surface of the ceramic material coated with the metal layer has pores and wherein the metal layer has a pattern of alternating concave and convex regions to compensate and / or to avoid stresses due to volume changes due to hydrogen absorption or due to temperature change.

The membranes according to the invention are based on known hydrogen-selective metal layers and the special and new shape of the metallic layer in connection with a special flexible ceramic composite material. The selective layers are preferably palladium layers and layers of various alloys of palladium and other hydrogen-sorbing metals, such as. B. Titanium alloys.

The metallic layers, which have a pattern of alternating concave and convex regions, can better absorb stresses that arise from changes in volume of the selective layers and thereby show a significantly improved long-term stability. These tensions are ensured by the special structure of the metallic layer on the carrier membrane, which has a perforated carrier. In this case, the "corrugated" structure of the surface with "hills" at the uninterrupted areas and "valleys" at the open areas of the openwork substrate lead to this effect. The fact that the entire membrane has a "mountain and valley structure" at irregular or preferably regular intervals, ie a structure with alternating concave and convex areas, can be achieved by the Hydrogen sorption or temperature change induced voltages are reduced by volume changes. An important aspect is that the metallic layer must not be too thick, so that these advantages are canceled out by the disadvantage of an excessively thick layer. Ideally, the metallic layer should be less than 5 μm thick; particularly preferably thinner than 2 μm and very particularly preferably less than 1 μm.

Suitable materials for the metallic layer are all materials which are capable of reversibly depositing hydrogen in their interior with a proportion of 1% by weight to 30% by weight. The metallic layer comprises in particular one or more of the following metals: palladium, silver, gold, copper, cobalt, nickel, ruthenium, rhodium, zinc, aluminum, titanium, zirconium, indium, vanadium, tungsten, rhenium, tungsten, molybdenum and / or rare earth metals.

Palladium is preferred, to which silver or copper is particularly preferably added in order to improve the hydrogen permeability and its mechanical properties when hydrogen is absorbed in a concentration range of 15 to 60% by weight, preferably 20 to 50% by weight. The thickness of the metallic layer is 0.1 μm to 1000 μm, preferably less than 5 μm, particularly preferably less than 2 μm, very particularly preferably less than 1 μm.

The composite membrane according to the invention can in particular comprise a composite material according to DE 19741498 AI or DE 19640461 AI, which is coated with a thin metal layer consisting of a hydrogen-storing material with sufficiently good adhesion, uniformly strong.

In a preferred embodiment of the invention, the coefficient of thermal expansion of the composite and the coefficient of thermal expansion of the metal layer differ by less than 15%, preferably by less than 10%. The thermal expansion coefficient of the composite material and the thermal expansion coefficient of the metal layer are very particularly preferably approximately the same size. This is through ensures the appropriate choice of the openwork carrier, which preferably comprises metal. In this way, cracks in the metallic layer due to temperature changes can be avoided. Due to its special structure (e.g. ceramic-filled fabric), the membrane according to the invention can be produced with pores of up to 5 nm, but the composite material then still has a coefficient of thermal expansion which is close to that of the metallic separating layer.

The perforated carrier preferably comprises a woven and / or nonwoven. The perforated carrier very particularly preferably comprises filaments or fibers made of metal, preferably steel.

In a preferred embodiment of the invention, the perforated carrier of the composite material of the composite membrane according to the invention comprises a metal mesh, preferably a stainless steel mesh and / or stainless steel fleece. The metal mesh can easily be contacted electrically, so that ohmic heat is generated directly in the interior of the composite material by means of an electrical current to be applied. The heat generated in this way can preferably bring about a uniform expansion of the composite material and the metallic layer and thus counteract crack formation in the metallic layer particularly advantageously. This type of energy supply allows the composite material and the composite membrane to be specifically heated. The electrical heating can be regulated.

In a preferred embodiment of the invention, the metallic layer can also be heated. The metallic layer is very particularly preferably indirectly heated by resistance heating.

The membrane according to the invention offers good stability due to the perforated support in the interior, in particular when there is a high pressure difference between the two sides of the membrane.

The flexible, openwork support of the composite membrane according to the invention can also comprise a material selected from glass, quartz glass, ceramics, minerals, plastics, amorphous, non-electrically conductive substances, natural products, composites, composite materials or from at least a combination of these materials, provided that these materials do not impair the usability of the composite membrane according to the invention . As a flexible, openwork support, a support can also be used, which can be obtained by treatment with laser beams, ion beams or an etchant from a previously uninterrupted support, such as a sheet, a foil or a thin sheet.

The openwork carrier preferably comprises fibers and / or filaments with a diameter of 1 to 150 μm, preferably 1 to 20 μm, and / or threads with a diameter of 5 to 150 μm, preferably 20 to 70 μm.

In the event that the openwork carrier is a fabric made of multifilament yarns, then this is preferably a fabric made of 11-Tex yarns with 5-50 warp or weft threads and in particular 20-28 warp and 28-36 weft threads .

The composite membrane according to the invention preferably withstands an increase in temperature to a temperature of more than 300 ° C., particularly preferably more than 400 ° C., very particularly preferably more than 500 ° C., the metallic layer not forming any cracks.

The composite material preferably has a thickness of 10 to 1000 μm, particularly preferably a thickness of 20 to 200 μm.

In a preferred embodiment, the composite membrane is flexible and tolerates a bending radius of less than 100 mm, preferably less than 10 mm.

The composite membrane is preferably asymmetrical.

In a preferred embodiment of the invention, the composite material has pores with an average diameter of less than 500 nm, preferably less than 100 nm. In a very particularly preferred embodiment, the composite material has pores with an average diameter of up to 1 to 5 nm.

The composite membrane according to the invention can have a hydrogen-permeable adhesion-promoting layer between the composite material and the metal layer.

The ceramic material can comprise an oxide of titanium, zirconium, silicon and / or aluminum.

Another aspect of the present invention is a method for producing a flexible composite membrane according to one of claims 1 to 16, comprising the following steps:

(i) Provision of a composite material from an openwork carrier, preferably a woven and / or nonwoven, and a porous ceramic material whose surface has pores, at least one surface of the

Composite a pattern of alternating concave and convex

Areas,

(ii) applying a metal layer to the surface of the composite material provided under (i) by CVD (chemical vapor deposition); PVD (physical vapor deposition), in particular sputtering and plasma coatings; Electroplating or electroless plating.

In a preferred embodiment, the process in step (i) comprises the following steps: (A) hydrolysis of a hydrolyzable metal compound to give a hydrolyzate,

(B) peptizing the hydrolyzate with an acid to form a dispersion,

(C) mixing the dispersion with a nanocrystalline and / or crystalline metal oxide,

(D) applying the mixture obtained under (C) as a thin layer to a fabric and / or nonwoven and

(E) Solidify at a temperature of about 100 ° C to 680 ° C to form a composite (F) to create as well

(G) optionally repeating steps (A) through (E) with the product of step (E) using mixtures containing particles smaller in particle size than in steps (A) through (E) to form a multilayer composite create, wherein the metal oxide for the layer that is applied last preferably has a particle size with an average radius of at most 1000 nm, particularly preferably at most 200 nm, very particularly preferably at most 10 nm. The average diameter of the pore size can be set by selecting the particle size of the metal oxide. A metal oxide with an average radius of particle size of 1000 nm gives pores with an average diameter of 200 nm. A metal oxide with an average diameter of particle size of 200 nm gives pores with an average diameter of 40 nm. A metal oxide with an average radius of Particle size of 10 nm gives pores with an average diameter of 5 nm. A metal oxide with an average radius of the particle size of 2 nm gives pores with an average radius of 1 nm.

Commercial sols such as titanium nitrate sol, zirconium nitrate sol or silica sol can be used as dispersions.

However, the dispersions can also be obtained by hydrolysis of a metal compound, semimetal compound or mixed metal compound in a medium such as water, alcohol or an acid. The compound to be hydrolyzed is preferably a metal nitrate, a metal chloride, a metal carbonate, a metal alcoholate compound or a semimetal alcoholate compound, particularly preferably at least one metal alcoholate compound, a metal nitrate, a metal chloride, a metal carbonate or at least one semimetal alcoholate compound selected from the compounds of Elements Ti, Zr, Al, Si, Sn, Ce and Y or the lanthanoids and actinides, such as. B. titanium alcoholates such. B. titanium isopropylate, silicon alcoholates, zirconium alcoholates, or a metal nitrate, such as. B. zirconium nitrate hydrolyzed. It may be advantageous to carry out the hydrolysis with at least half the molar ratio of water, based on the hydrolyzable group of the hydrolyzable Connection to perform.

The hydrolyzed compound can be peptized with an acid, preferably with a 10 to 60% acid, preferably with a mineral acid selected from sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid and nitric acid or a mixture of these acids.

An inorganic component with a grain size of 1 to 10,000 nm can be suspended in the sol. An inorganic component which has a compound selected from metal compounds, semimetal compounds, mixed metal compounds and metal mixed compounds with at least one of the elements of the 3rd to 7th main group, or at least a mixture of these compounds, is preferably suspended. At least one is particularly preferred inorganic component which contains at least one compound from the oxides of the sub-group elements or the elements of the 3rd to 5th main group, preferably oxides, selected from the oxides of the elements Sc, Y, Ti, Zr, Nb, Ce, V, Cr, Mo, W, Mn, Fe, Co, B, AI, In, TI, Si, Ge, Sn, Pb and Bi, such as B. Y ₂ O ₃ , ZrO ₂ , Fe ₂ O ₃ , Fe ₃ O ₄ , SiO ₂ , Al ₂ O ₃ , suspended. The inorganic component can also be aluminosilicates, aluminum phosphates, zeolites or partially exchanged zeolites, such as, for. B. ZSM-5, Na-ZSM-5 or Fe-ZSM-5 or amorphous microporous mixed oxides, which can contain up to 20% non-hydrolyzable organic compounds, such as. B. vanadium oxide, silicon oxide glass or aluminum oxide-silicon oxide-methyl silicon sesquioxide glasses.

The mass fraction of the suspended component is preferably 0.1 to 500 times the hydrolyzed compound used.

Cracks in the composite material can be avoided by a suitable choice of the grain size of the suspended compounds depending on the size of the pores, holes or interstices of the carrier, but also by a suitable choice of the layer thickness of the composite material and the proportionate ratio of sol: solvent: metal oxide. The metal oxide which is mixed with the dispersion in step (C) is preferably selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide and Zirconium oxide or from their mixed oxides and the hydrolyzable metal compound is preferably a compound of titanium, zirconium, silicon or aluminum.

When using a mesh fabric with a mesh size of z. B. 100 microns as an openwork carrier can preferably be used to increase the freedom from cracks, the suspended compound with a grain size of at least

0.7 μm. In general, the ratio of grain size to mesh or

Pore size from 1: 1000 to 100: 1000. The composite material can preferably have a thickness of 5 to 1000 μm, particularly preferably 50 to 150 μm. The mixture of dispersion and compounds to be suspended preferably has one

Ratio of dispersion to suspended compounds from 0.1: 100 to 100: 0.1, preferably from 0.1: 10 to 10: 0.1 parts by weight.

After application to the openwork carrier, the mixture can be solidified by heating the composite of mixture and openwork carrier to 50 to 1000 ° C., preferably about 100 to 680 ° C. In a particular embodiment, the composite is exposed to a temperature of 50 to 100 ° C. for 10 minutes to 5 hours. In a further special embodiment, the composite is exposed to a temperature of 100 to 800 ° C. for 5 seconds to 10 minutes. The composite can be heated with heated air, hot air, infrared radiation, microwave radiation or electrically generated heat. In a further embodiment, the mixture can be solidified by the mixture being applied to a preheated carrier and thus being solidified immediately after the application.

In a further particular embodiment, the perforated carrier is unrolled from a roll at a speed of 1 m / h to 1 m / s, onto an apparatus which contacts the mixture with the carrier and then to another apparatus which solidifies the mixture by heating, and the composite material thus produced is rolled up on a second roll. In this way it is possible to manufacture the composite material continuously. In a further embodiment, a ceramic or inorganic layer is applied to a composite material. This can be done, for example, by laminating a green (unsintered) ceramic layer or an inorganic layer, which is present on an auxiliary film, onto the carrier or by treating the composite material with a further suspension (mixture) as described above. This bond can be solidified by heating. The green ceramic layer used preferably contains a nanocrystalline powder of a semimetal or metal oxide, such as. As aluminum oxide, titanium dioxide or zirconium dioxide. The green layer can contain an organic binder.

By using a green ceramic layer, it is possible in a simple manner to equip the composite material with an additional ceramic layer which, depending on the size of the nanocrystalline powder used, determines the porosity of the composite material produced in this way.

By applying at least one further inorganic layer or ceramic layer, a composite material is obtained which has a pore gradient. In addition, by applying a layer several times, it is also possible to use supports for the production of composite materials with a specific pore size whose pore or mesh size is not suitable for producing a composite material with the required pore size. This can e.g. B. be the case when a composite material with a pore size of 0.25 microns is to be produced using a carrier with a mesh size of over 300 microns. To obtain such a composite material, it may be advantageous to first bring at least one suspension onto the carrier which is suitable for treating carriers with a mesh size of 300 μm, and to solidify this suspension after application. The composite material obtained in this way can now be used as a carrier membrane with a smaller mesh or pore size. A further suspension can be applied to this carrier membrane, which has a compound with a grain size of 0.5 μm. The insensitivity to cracks in composite materials with large mesh or pore widths can also be improved by applying suspensions to the carrier, which have at least two suspended compounds. Compounds to be suspended are preferably used which have a particle size ratio of 1: 1 to 1:20, particularly preferably 1: 1.5 to 1: 2.5. The weight fraction of the grain size fraction with the smaller grain size should not exceed a proportion of at most 50%, preferably 20% and very particularly preferably 10%, of the total weight of the grain size fraction used.

In a preferred embodiment of the invention, a hydrogen-permeable adhesion-promoting layer is provided between the perforated support and the metallic layer.

The composite membrane is preferably elastic and has a minimum bending radius in the range from 1 to 100 mm, without the metallic layer which is subjected to pressure forming cracks.

The composite membrane according to the invention is preferably an asymmetrical composite membrane. For this purpose, it may be advantageous to sputter an electrically conductive metal layer onto one side of the composite material before the galvanic deposition of a palladium layer. This metal layer applied on one side is suitable for the electrodeposition to let the palladium layer grow only on the side of the copper layer.

The metallic layer is applied to the composite material by known means

Coating processes such as CVD (chemical vapor deposition); PVD (physical vapor deposition, in particular sputtering or plasma coating); Galvanic deposition or electroless plating. These processes are suitable for hydrogen-selective layers of good quality and desired thickness on the

Apply composite material.

Another aspect of the present invention is the use of the composite membrane according to the invention for the selective separation of hydrogen from

Mixtures containing hydrogen. The hydrogen-containing mixture is preferably a gas mixture, a liquid mixture in which hydrogen is dissolved or a gaseous or liquid mixture of components, where molecular or atomic hydrogen originates from one of the components alone or from a reaction of two components.

In a preferred embodiment, high purity hydrogen with impurities of at most 50 ppm, preferably 10 ppm, can be generated after the use according to the invention.

The use according to the invention can take place in a membrane reactor, a hydrogen detector, a cleaning plant for hydrogen, an electrolysis cell, a hydrogenation apparatus or dehydrogenation apparatus.

The invention is described below with reference to figures and preferred embodiments. 1 shows the surface of a composite material of a composite membrane according to the invention; Fig. 2 is a schematic representation of a cross section through the composite according to

1 shows a cross section through the composite material according to FIG. 1 (in area C of the schematic illustration of FIG. 2); 4 shows a cross section through a composite membrane according to the invention;

Fig. 5 is a schematic representation of a cross section through an inventive

Composite membrane.

1 shows the surface of a composite material made of a metal mesh as an openwork support and a porous ceramic material, this surface having a pattern of alternating concave and convex areas on the basis of a photograph. These concave and convex areas are described in more detail in FIGS. 2 and 3. The mesh size is approximately 100 μm as can be seen at the bottom right in FIG. 1.

FIG. 2 shows three metal fibers 10 of a metal mesh, which form an openwork support, and the porous ceramic material 18. The convex regions 12 ("hills") of the The surface (s) of the composite material are located at the non-perforated points of the perforated carrier, ie in the present case around the metal fibers 10. The concave regions 14 ("valleys") of the surface (s) are located at the perforated points of the perforated carrier, ie in the present case between the metal fibers 10.

FIG. 3 shows the area C according to FIG. 2 in enlarged form as a photograph.

FIG. 4 shows a cross section through a composite membrane according to the invention made of a metal mesh with metal fibers 10, porous ceramic material 18 and the metallic layer 16. This metallic layer 16 consists of a Pd / Ag alloy which contains 80% Pd and 20% Ag.

FIG. 5 shows a schematic illustration of FIG. 4 with the metal fibers 10, the porous ceramic material 18, the metallic layer 16, the convex regions 22 and the concave regions 24 of the metallic layer 16.

The invention will now be explained in more detail using specific examples.

Production of dispersions

Production example 1.1

70 g of fully deionized (VE) water are cooled to 4 ° C. in a beaker and 50 g of ethanol are added. 40 g of titanium isopropylate (Aldrich) are added to this mixture and the resulting precipitate is peptized with 30 g of conc. Nitric acid. 200 g of aluminum oxide (et 3000 SG from Alcoa, Ludwigshafen) are added to the dispersion obtained in this way and everything is completely dispersed in order to create a dispersion.

Production example 1.2

300 g of demineralized water with 37.5 g of ethanol are placed in a beaker. You acidify with conc. Nitric acid and then adds 375 g (et 1200 SG from Alcoa, Ludwigshafen). After the aluminum oxide has been dispersed, 75 g of zirconium nitrate sol (from Goldmann, Bielefeld) added to create a dispersion.

Production example 1.3

100 g of zirconium oxide (VP 25; Degussa) are dispersed in 200 g of demineralized water. For this purpose, 50 g of a 10% by weight polyvinyl alcohol solution (MW 72,000 g / mol; from Aldrich) are added with stirring. After adding a further 50 g of water and 25 g of zirconium nitrate sol (from Goldmann, Bielefeld) and complete dispersion, a dispersion is created which can be used as such.

Production example 1.4

100 g of silicon dioxide (Ox 50; Degussa) are dispersed in 200 g of demineralized water. For this purpose, 50 g of a 10% by weight polyvinyl alcohol solution (MW 72000 g / mol;

Aldrich). After adding a further 50 g of water and 25 g of silica sol (Levasil; Fa.

Bayer, Leverkusen) and complete dispersion, a dispersion is created that can be used as such.

Production example 1.5

100 g of titanium dioxide (P 25; Degussa) are dispersed in 200 g of demineralized water. For this purpose, 50 g of a 10% by weight polyvinyl alcohol solution (MW 72000 g / mol; Aldrich) are added with stirring. After adding a further 50 g of water and 10 g of titanium tetraisopropylate (from Aldrich) and complete dispersion, a dispersion is created which can be used as such.

Production of composite materials Production example 2.1

The dispersion from preparation example 1.1 is applied in a thin layer by brushing onto a square mesh fabric made of stainless steel (180 mesh; 90 μm mesh size; 50 μm wire thickness) and then cured at 550 ° C. within 2 minutes to form a composite material with an average pore radius of approx To create 100 nm.

Production example 2.2 The dispersion from preparation example 1.2 is applied in a thin layer by brushing onto a square mesh fabric (made of stainless steel; 180 mesh; 90 μm mesh size; 50 μm wire thickness) and then cured at 650 ° C. within 1 minute to form a composite material with an average pore radius of approx To create 200 mn.

Production example 2.3

An approximately 50 μm thick layer of the dispersion from preparation example 1.3 is applied to the composite material from preparation example 2.1 by knife coating. This is dried and solidified at 450 ° C with an IR radiator to create a composite material with pores with an average pore radius of 20 to 50 nm.

Production example 2.4

An approximately 50 μm thick layer of the dispersion from preparation example 1.4 is applied to the composite material from preparation example 2.2 by knife coating. This is dried and solidified at 500 ° C. using an IR radiator to create a composite material with pores with an average pore radius of 30 to 40 nm.

Production example 2.5

An approximately 50 μm thick layer of the dispersion from preparation example 1.5 is applied to the composite material from preparation example 2.1 by knife coating. This is dried and solidified at 550 ° C. using an IR radiator in order to create a composite material with pores with an average pore radius of 25 to 35 nm.

Production of the composite membrane

example 1

A copper layer is applied on one side to the composite material obtained according to production example 2.3 by sputtering, by means of which the average pore radius is reduced to 5 nm. In a second step, a Pd layer is galvanically deposited. The layer thickness of the palladium layer is limited to a thickness of 500 nm by controlling the current strength and time in order to form a composite membrane of the present invention create. The composite membrane produced in this way shows a hydrogen flow of more than 1900 L / m ² h at 200 ° C., the hydrogen permeating more than 30 times faster than nitrogen.

Example 2

An approximately 2 μm thick palladium layer is applied to the composite material produced according to production example 2.4 by plasma coating in order to create a composite membrane of the present invention. The composite membrane thus produced shows a hydrogen flow of 40,000 L / m ² h at a temperature of 400 ° C and a pressure of 20 bar. Tests with nitrogen show that no hydrogen permeation takes place.

Claims

Claims:

1. Flexible composite membrane for the selective separation of hydrogen from hydrogen-containing mixtures, the membrane comprising a composite material coated with a metal layer suitable for the removal of hydrogen, comprising a perforated carrier, preferably a fabric and / or nonwoven, and a porous ceramic material, the with the Metal layer coated surface of the ceramic material has pores and the metal layer has a pattern of alternating concave and convex areas to compensate and / or to avoid stresses due to volume changes due to hydrogen absorption or temperature change.

2. The composite membrane according to claim 1, wherein the thermal expansion coefficient of the composite and the thermal expansion coefficient of the metal layer differ by less than 15%, preferably less than 10%.

3. The composite membrane according to claim 2, wherein the thermal expansion coefficient of the composite material and the thermal expansion coefficient of the metal layer are approximately the same size.

4. Composite membrane according to one of claims 1 to 3, wherein the ceramic material comprises an oxide of titanium, zirconium, silicon and / or aluminum.

5. A composite membrane according to any one of claims 1 to 4, wherein the perforated support comprises metal, glass or ceramic.

6. The composite membrane according to claim 5, wherein the perforated support comprises metal, preferably steel.

7. Composite membrane according to one of claims 1 to 6, wherein the perforated support has a mesh size of 5 to 500 microns and a fiber or filament thickness of 20 to 70 μm.

8. Composite membrane according to one of claims 1 to 7, wherein the composite material has a thickness of 10 to 1000 microns, preferably 20 to 200 microns.

9. Composite membrane according to one of claims 1 to 8, wherein the metal layer palladium, silver, gold, copper, cobalt, nickel, ruthenium, rhodium, zinc, aluminum, titanium, zirconium, indium, vanadium, tungsten, rhenium, tungsten, molybdenum and / or includes rare earth metals and is permeable to hydrogen.

10. The composite membrane of claim 9, wherein the metal layer comprises palladium or alloys thereof.

11. The composite membrane according to claim 10, wherein the metal layer is an alloy of palladium and silver or copper, preferably with a composition of 40 to

85% by weight of palladium and 15 to 60% by weight of silver or copper.

12. Composite membrane according to one of claims 1 to 11, wherein the metal layer has a thickness of less than 5 μm, preferably less than 2 μm, very particularly preferably less than 1 μm.

13. Composite membrane according to one of claims 1 to 12, wherein the composite membrane is flexible and tolerates a bending radius of less than 100 mm, preferably less than 10 mm

14. Composite membrane according to one of claims 1 to 13, characterized in that the composite membrane is asymmetrical.

15. Composite membrane according to one of claims 1 to 14, characterized in that the pores of the composite material have an average diameter of less than 500 nm, preferably less than 100 nm.

16. Composite membrane according to one of claims 1 to 15, characterized in that the pores have an average diameter of up to 5 nm, preferably up to 1 nm.

17. A composite membrane according to any one of claims 1 to 16, wherein a hydrogen-permeable adhesion promoter between the composite material and the metal layer

Layer is provided.

18. A method for producing a flexible composite membrane according to one of claims 1 to 16, comprising the following steps:

(i) providing a composite material from an openwork carrier, preferably a woven and / or nonwoven, and a porous ceramic material whose surface has pores, at least one surface of the composite material having a pattern of alternating concave and convex regions,

19. The method of claim 18, wherein step (i) comprises the following steps:

(A) hydrolysis of a hydrolyzable metal compound to a hydrolyzate,

(B) peptizing the hydrolyzate with an acid to form a dispersion,

(D) Applying the mixture obtained under (C) as a thin layer to a fabric and / or fleece and

(E) Solidify at a temperature of about 100 ° C to 680 ° C to create a composite as well

(F) optionally repeating steps (A) through (E) with the product of step (E) using mixtures containing particles smaller in particle size than in steps (A) through (E) to form a multilayer composite create, wherein the metal oxide for the layer which is applied last preferably has a particle size with an average radius of at most 1000 nm, particularly preferably at most 200 nm, very particularly preferably of at most 10 nm.

20. The method according to claim 19, characterized in that the metal oxide is selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide and zirconium oxide or from their mixed oxides and the hydrolyzable metal compound is a nitrate, oxynitrate, chloride, oxychloride, carbonate, alcoholate, acetate or acetylacetonate of titanium, zirconium, silicon or aluminum.

21. The method according to any one of claims 18 to 20, wherein a hydrogen-permeable, adhesion-promoting layer is applied to the composite material before the application of the metal layer.

22. The method according to any one of claims 19 to 21, wherein the application of the mixture obtained under (C) as a thin layer according to step (D) or the application of the adhesion-promoting layer by printing, pressing, pressing, rolling, knife coating, spreading, dipping , Spraying or pouring.

23. Use of the composite membrane according to one of claims 1 to 17 for the selective separation of hydrogen from hydrogen-containing mixtures.

24. Use according to claim 23, characterized in that that the hydrogen-containing mixture is a gas mixture, a liquid mixture in which hydrogen is dissolved or is a gaseous or liquid mixture of components, molecular or atomic hydrogen originating from one of the components alone or from a reaction of two components.

25. Use according to one of claims 23 or 24 for the production of high-purity hydrogen with impurities of at most 50 ppm, preferably 10 ppm.

26. Use according to one of claims 23 to 25 in a membrane reactor, a hydrogen detector, a purification system for hydrogen, an electrolysis cell, a hydrogenation apparatus or dehydrogenation apparatus.