Method for producing a palladium-based hydrogen gas separating membrane

Abstract

The invention relates to a method for producing a palladium-based hydrogen gas separating membrane having a thickness of 3 to 10 µm, comprising the method steps of: (1) providing (1a) a rectangular strip having a thickness of 40 to 250 µm and made of a palladium-based material A composed of palladium or palladium alloys having a palladium content of 70 to < 100 wt.% with a 0.2% proof stress Rp0.2 in the range from 70 to 250 MPa, (1b) a rectangular strip having a thickness of 250 to 1000 µm and made of a material B composed of metals or metal alloys with a 0.2% proof stress Rp0.2 which differs from the 0.2% proof stress Rp0.2 of the material A by not more than ±20%, and (1c1) an aqueous solution C1 which is capable of dissolving the material B but not the material A, or (1c2) an aqueous solution C2, (2) placing the two strips against one another, (3) connecting the strips by multi-stage cold rolling to form a strip-type composite having a thickness of the material A of 3 to 10 µm, wherein the 0.2% proof stresses Rp0.2 of the materials A and B differ from one another by not more than ±20% after each cold rolling step, and (4a) treating the strip-type composite formed in method step (3) with the aqueous solution C1 until the material B is completely dissolved, or (4b) immersing the strip-type composite formed in method step (3), connected as an anode, in the aqueous solution C2 and keeping said strip-type composite submerged therein without dissolution of the material A and until the material B is completely dissolved.

Description

[0001] 2023PF00173

[0002] 1

[0003] Method for producing a palladium-based hydrogen gas separation membrane

[0004] The invention relates to a method for producing a palladium-based hydrogen gas separation membrane.

[0005] DE 10010387 A 1 discloses a composite membrane for the selective diffusion of at least one predetermined substance, comprising a support layer made of a first material and a permeation layer arranged on the support layer and consisting of a second material that is selectively permeable to the at least one predetermined substance. The support layer has a mechanical support structure with openings through which the at least one predetermined substance can move substantially orthogonally and optionally also laterally to the plane of the permeation layer through the support layer. The support layer leaves surface portions of the permeation layer exposed, which are fluidically connected to the openings. The permeation layer may contain a palladium-silver alloy. The permeation layer may have a thickness of 20 nm to 10 micrometers.The support layer can contain a material selected from stainless steel, copper, copper alloys, aluminum, or a Teflon-like material such as polyfluoroethylene. The predetermined substance can be hydrogen. A permeation layer free of a support layer or mechanical support structure is not disclosed.

[0006] The term "hydrogen gas separation" as used herein refers to the separation of hydrogen gas from a hydrogen-containing gas mixture (i) for the purpose of hydrogen purification, i.e., the removal of gaseous impurities from contaminated hydrogen gas and the recovery of purified hydrogen gas, and / or (ii) for the purpose of purifying a gas mixture containing hydrogen gas as an impurity or trace gas, i.e., the separation of the hydrogen gas from the gas mixture. Prominent examples of scenario (i) include the purification of so-called grey hydrogen (hydrogen obtained by steam reforming of natural gas), the purification of so-called green hydrogen (removal of water and oxygen from hydrogen produced electrolytically using renewably generated electricity), and the removal of nitrogen and / or ammonia from hydrogen formed by the decomposition of the hydrogen derivative ammonia.

[0007] Palladium-based hydrogen gas separation membranes, i.e., membranes in the form of

[0008] Metal foils made of palladium or certain palladium alloys, for example.

[0009] Alloys of palladium with copper and / or silver and the use of such metal foils 2023PF00173

[0010] 2. The methods for hydrogen gas separation are state of the art. Such palladium-based hydrogen gas separation membranes generally have thicknesses in the range of 15 to 100 pm and can be produced by rolling. However, if particularly thin palladium-based hydrogen gas separation membranes are to be produced by rolling, rolling stands with two thin work rolls and a large number of backup rolls are required.

[0011] The present invention aims to enable the efficient production of palladium-based hydrogen gas separation membranes that are as thin as possible and in the simplest and most scalable way possible.

[0012] The invention comprises a method for producing particularly thin palladium-based hydrogen gas separation membranes. More precisely, the invention relates to a method for producing a palladium-based hydrogen gas separation membrane with a thickness in the range of only 3 to 10 pm, preferably 3 to 7 pm. The method comprises the following process steps:

[0013] (1) Provide

[0014] (1a) a first rectangular strip 40 to 250 pm thick made of a palladium-based material A selected from the group consisting of palladium and palladium alloys with a palladium content in the range of 70 to <100 wt.% (weight%), preferably selected from the group consisting of palladium alloys with a palladium content in the range of 70 to <100 wt.%, wherein each of these materials has a 0.2% proof strength R p 0.2 in the range of 70 to 250 MPa,

[0015] (lb) a second rectangular strip 250 to 1000 pm thick made of a material B selected from metals and metal alloys, preferably selected from metal alloys, each with a yield strength R of 0.2% p 0.2 of material A deviating by no more than ± 20 % from the 0.2% proof strength R p 0.2, and

[0016] (1 d) an aqueous solution C1 which is capable of dissolving material B but not material A or (1 c2) an aqueous solution C2,

[0017] (2) Placing the first band next to the second band,

[0018] (3) Joining the first strip to the second strip by multi-stage cold rolling of the adjacent strips to form a continuous strip-shaped composite material with a thickness of material A in the range of 3 to 10 pm, wherein the 0.2% yield strengths R p 0.2 The dimensions of materials A and B do not differ from each other by more than ± 20% after each cold rolling step, and

[0019] (4a) Treating the ribbon-shaped composite material formed in process step (3) with the aqueous solution C1 until the material B or 2023PF00173 is completely dissolved.

[0020] 3

[0021] (4b) Immersion and retention in the submerged state of the ribbon-shaped composite material formed in process step (3) and connected as an anode in the aqueous solution C2 without dissolving material A and until material B is completely dissolved.

[0022] The term “ribbon composite material” used herein is also referred to herein as “ribbon composite” and is synonymous with “ribbon composite”.

[0023] The method according to the invention therefore has two method variants, on the one hand with the process step sequence (1)-(2)-(3)-(4a) or on the other hand with the process step sequence (1)-(2)- (3)-(4b).

[0024] In the method according to the invention, thickness specifications are given with reference to the thickness of the palladium-based hydrogen gas separation membrane, the thickness of the first rectangular strip made of material A, and the thickness of the second rectangular strip made of material B. As is self-evident to those skilled in the art, all three thicknesses mentioned can be determined non-destructively by means of laser triangulation, for example with the VTLG laser measuring device 101 / 1 from Vollmer Feinmesserebau GmbH.

[0025] This section uses the term "0.2% proof stress R", which is familiar to experts. p0 ,2" is used; this refers to the tensile stress below which, after unloading, a plastic strain of exactly 0.2% remains. The respective 0.2% yield strength R p0.2 can be determined in a standard tensile test at 20°C known to those skilled in the art, for example according to DIN EN ISO 6892-1 (December 2009); it is not necessary to explain to those skilled in the art that the respective starting materials A and B (i.e. the rectangular strips provided in steps (1a) and (1b)) and their correspondingly frequently cold-rolled intermediate stages or target materials (i.e. the strips still unjoined) are each subjected to the cold-rolling conditions prevailing in process step (3) in separate tests before the respective tensile tests can be carried out.

[0026] In step (1a) of the inventive method, a first rectangular strip 40 to 250 pm thick made of a palladium-based material A is provided. The material A is selected from the group consisting of palladium and palladium alloys with a palladium content in the range of 70 to <100 wt.%. Preferably, the material A is selected from the group consisting of palladium alloys with a palladium content in the range of 2023PF00173

[0027] 4

[0028] 70 to <100 wt.%. Material A has a 0.2% yield strength R. p 0.2 in the range of 70 to 250 MPa.

[0029] Examples of a 0.2% proof strength R provided in process step (1a). p0.2 Palladium alloys exhibiting in the range of 70 to 250 MPa with a palladium content in the range of 70 to <100 wt.% include palladium-copper alloys (for example PdCu15-30, i.e. alloys of palladium with a copper content in the range of 15 to 30 wt.%), palladium-silver alloys (for example PdAg20-30, i.e. alloys of palladium with a silver content in the range of 20 to 30 wt.%, in particular PdAg23).

[0030] In step (1 b) of the method according to the invention, a second rectangular strip 250 to 1000 pm thick made of a material B is provided. The material B is selected from metals and metal alloys, preferably from metal alloys. The material B has a yield strength R of 0.2%. p 0.2% yield strength R of material A, deviating by no more than ± 20% p 0.2.

[0031] A person skilled in the art can find metal alloys of material type B by studying literature or by producing various binary, ternary to multinary alloys which can be dissolved under the conditions of process steps (4a) and (4b) respectively and which exhibit a yield strength R of 0.2% p 0.2% proof strength of material A, deviating by no more than ± 20% p exhibit 0.2. Examples of materials B include alloys such as CuSn4-10, in particular CuSn6-8 (copper alloys with a tin content in the range of 4 to 10 wt.%, especially 6 to 8 wt.%). Material B, or rather the second strip made of material B, serves as a support material for the first strip made of material A and simplifies the rolling process.

[0032] Furthermore, the expert is familiar with measures for influencing or adjusting 0.2% yield strengths R. p0.2 of both palladium and palladium alloys of material type A and of materials of type B. Examples of such measures include forming and, in particular, annealing processes.

[0033] Examples of aqueous solutions 01 include aqueous acidic and oxidizing solutions, for example aqueous solutions containing 0.2 to 1.5 mol of sulfuric acid and 0.1 to 0.7 mol of hydrogen peroxide per liter, in particular aqueous solutions without any other components than water, sulfuric acid, hydrogen peroxide, and, if applicable, stabilizers. 2023PF00173

[0034] 5

[0035] Such aqueous solutions can be prepared by mixing dilute sulfuric acid with aqueous hydrogen peroxide solution in the appropriate mixing ratio.

[0036] Examples of aqueous solutions C2 include aqueous acidic solutions, for example aqueous solutions containing 0.2 to 1.5 mol of sulfuric acid per liter. 0.2 to 1 molar aqueous sulfuric acid is preferred.

[0037] In process step (2), the first and second strips are placed next to each other. Prior to this, it may be advantageous to roughen the flat surfaces where the two strips will be placed together, for example using a wire brush with a wire diameter in the range of 80 to 100 pm.

[0038] It is self-evident to a person skilled in the art that the two strips are placed side by side in a manner that constitutes a sensible preparation for the subsequent process step (3), i.e., naturally not with their edges touching, but rather with one of their flat, and preferably also roughened, sides touching. Apart from the generally greater thickness of the second strip made of material B, both rectangular strips, i.e., their flat sides, have the same or substantially the same dimensions and can thus be placed side by side in a congruent or practically congruent manner. For example, said same or substantially the same dimensions can have a width in the range of 50 to 400 mm and a length in the range of several meters up to, in principle, without any length limitation, for example, practically several hundred meters.However, it is also possible that the second band made of material B is applied to the first band made of material A in a manner that completely covers it, but extends beyond it laterally on one or both side edges (practically congruent), i.e. the second band made of material B is then slightly wider than the first band made of material A, for example up to 10 mm wider (for example 5 mm on each side).In other words, to summarize, both strips are to be understood as so-called continuous stock with the same or substantially the same width in the range of 50 to 400 mm, wherein the thickness of the second strip made of material B is generally greater than the thickness of the first strip made of material A, and wherein the width of the second strip made of material B may be slightly greater than the width of the first strip made of material A; in the case of continuous stock, joining typically occurs during the process of unwinding and merging the two continuous strips into the roll gap of the rolling mill. 2023PF00173.

[0039] 6

[0040] In process step (3) of the process according to the invention, the first strip and the second strip are joined together by multi-stage cold rolling of the two adjacent strips. A continuous, strip-shaped composite is formed with a thickness of material A in the range of 3 to 10 pm, preferably 3 to 7 pm; after the thickness of material A has been achieved in the range of 3 to 10 pm, preferably 3 to 7 pm, the thickness of material B can, for example, be in the range of 15 to 100 pm.

[0041] The first cold rolling stage is a roll cladding process, which involves pressure forming with a degree of deformation, for example, in the range of 30 to 60%. The subsequent cold rolling stages are each pressure forming. As already mentioned, those skilled in the art are familiar with measures for influencing or adjusting 0.2% yield strengths R. p0.2 of palladium and palladium alloys of material type A as well as of materials of type B. He can therefore, before carrying out the first cold rolling stage, ensure that the first and / or the second strip does not deviate from the 0.2% yield strength R by means of the aforementioned measures with a maximum of ± 20%. p 0.2 of their materials A and B.

[0042] Multi-stage cold rolling can comprise, for example, a total of 5 to 30 cold rolling stages after the first cold rolling stage, whereby in each of these stages a reduction of both strip thicknesses can take place according to a degree of deformation, for example in the range of 5 to 20%.

[0043] Multi-stage cold rolling can take place in a conventional rolling mill stand, in particular even in a conventional four-roll stand with two work rolls with a diameter, for example, in the range of 30 to 100 mm and only two backup rolls. The method according to the invention makes it possible to dispense with the use of complex rolling mill stands with thin work rolls and a large number of backup rolls.

[0044] In process step (4a) of the inventive process with the process step sequence (1)- (2)-(3)-(4a), the ribbon-shaped composite material formed in process step (3) is treated with the aqueous solution C1 until the complete dissolution of material B. In other words, the material B is etched away. Preferably, the treatment can be carried out by introducing the ribbon-shaped composite material formed in process step (3) into the aqueous solution C1 until the complete dissolution of material B, i.e., generally by immersion in the aqueous solution C1 and keeping it submerged until the 2023PF00173

[0045] 7

[0046] Material B is dissolved. Material A, which has a more noble character than material B, remains undamaged; it may undergo passivation.

[0047] Process step (4a) can be carried out discontinuously, i.e., in batches. In another and preferred embodiment, process step (4a) is carried out as a continuous flow process, wherein the ribbon-shaped composite material is guided through the aqueous solution C1, for example, a vat filled with it, while submerged. The flow rate can be adjusted so that the material B is completely dissolved before or upon emergence from and exiting the aqueous solution C1.

[0048] It may be advantageous if the temperature of the aqueous solution C1 during process step (4a) is in the range of 30 to 60 °C.

[0049] Process step (4a) can be carried out without current. However, it is possible to carry out or assist the dissolution process of material B in the aqueous solution C1 by connecting the ribbon-shaped composite material as an anode while submerged. A person skilled in the art will select the applied voltage level such that material A is not attacked.

[0050] After completion of process step (4a), the strip, now free of material B and consisting only of material A, is removed and can be washed with water to remove any adhering residues of aqueous solution C1. Generally, the resulting 3 to 10 pm, preferably 3 to 7 pm, thin strip of material A is then dried. This means that the resulting 3 to 10 pm, preferably 3 to 7 pm, palladium-based hydrogen gas separation membrane can, for example, be wound into a continuous roll after drying. In other words, after completion of process step (4a), a palladium-based film free of any support structure or material is obtained.

[0051] In process step (4b) of the inventive process with the process sequence (1)- (2)-(3)-(4b), the ribbon-shaped composite material formed in process step (3) and connected as the anode is immersed in the aqueous solution C2 and kept submerged therein without dissolving material A and until material B is completely dissolved. Material A, which has a more noble character than material B removed in this way, remains undamaged; optionally, it undergoes passivation. 2023PF00173

[0052] 8

[0053] Process step (4b) can be carried out discontinuously, i.e., in batches. In another and preferred embodiment, process step (4b) is carried out as a continuous flow process, wherein the ribbon-shaped composite material is guided in a submerged state through the aqueous solution C2, for example, a vat filled with it. The flow rate can be adjusted so that the material B is completely dissolved before or upon emergence and exiting the aqueous solution C2.

[0054] It may be advantageous if the temperature of the aqueous solution C2 during process step (4b) is in the range of 30 to 60 °C.

[0055] Process step (4b) comprises connecting the ribbon-shaped composite material as the anode. The person skilled in the art will select the magnitude of the applied voltage such that material A is not attacked.

[0056] After completion of process step (4b), the strip, now free of material B and consisting only of material A, is removed and can be washed with water to remove any adhering residues of aqueous solution C2. Generally, the resulting 3 to 10 pm, preferably 3 to 7 pm, thin strip of material A is then dried. This means that the resulting 3 to 10 pm, preferably 3 to 7 pm, thin palladium-based hydrogen gas separation membrane can, for example, be wound into a continuous roll after drying. In other words, after completion of process step (4b), a palladium-based film free of any support structure or material is obtained.

[0057] The palladium-based hydrogen gas separation membrane, produced by the inventive method and only 3 to 10 pm, preferably only 3 to 7 pm, thin, can be used for hydrogen gas separation. It surpasses thicker palladium-based hydrogen gas separation membranes in terms of separation efficiency due to the faster passage of hydrogen gas through the thin membrane and also has the advantage of requiring less palladium or palladium alloy.

[0058] Example of implementation

[0059] A 5 mm thick and 60 mm wide rectangular sheet of PdAg23 was rolled into a strip with a thickness of 500 pm and then annealed at an oven temperature of 830°C in a 2.5 m long continuous furnace at a throughput speed of 0.5 m / min. The annealed 2023PF00173

[0060] 9

[0061] The strip was further rolled in several process steps to a thickness of 50 pm and annealed again in a continuous furnace at 830°C and a throughput speed of 1 m / min. The 0.2% proof strength R p The density of 0.2 of the annealed 50 pm thin and 60 mm wide PdAg23 strip was 180 MPa.

[0062] The support material used was a soft-annealed CuSn6 strip, 800 pm thick and 70 mm wide, with a 0.2% yield strength R. p 0.2 of 160 MPa used.

[0063] Both strips were roughened using wire brushes with a wire diameter of 80 pm, placed one on top of the other with a 5 mm overhang of the CuSn6 strip on each side, inserted into the roll gap of a four-roll stand (work roll diameter 60 mm), and rolled to a thickness of 450 pm for the strip composite, thus cold-welding them together. The strip composite was then cold-rolled in 15 passes to a final thickness of 85 pm; the thickness of the PdAg23 layer in the strip composite was 5 pm. The strip composite was then immersed in an aqueous solution containing

[0064] One mole of sulfuric acid and 0.5 moles of hydrogen peroxide per liter were immersed at 50°C and kept submerged until the CuSn6 was dissolved. The remaining 5 pm thick PdAg23 film was then removed, rinsed with water, and dried.

Claims

2023PF00173 10 Patent claims 1. Method for producing a palladium-based hydrogen gas separation membrane with a thickness in the range of 3 to 10 pm, comprising the process steps: (1) Provide (1a) a first rectangular strip 40 to 250 pm thick made of a palladium-based material A selected from the group consisting of palladium and palladium alloys with a palladium content in the range of 70 to <100 wt.%, each of these materials having a 0.2% proof strength R p 0.2 in the range of 70 to 250 MPa, (lb) of a second rectangular strip 250 to 1000 pm thick made of a material B selected from metals and metal alloys, each with a yield strength R of 0.2% p 0.2 of material A deviating by no more than ± 20% 0.2% Yield limit R p 0.2, and (1 d) an aqueous solution 01 which is capable of dissolving material B but not material A or (1 c2) an aqueous solution C2, (2) Placing the first band next to the second band, (3) Joining the first strip to the second strip by multi-stage cold rolling of the adjacent strips to form a continuous strip-shaped composite material with a thickness of material A in the range of 3 to 10 pm, wherein the 0.2% yield strengths R p 0.2 The dimensions of materials A and B do not differ from each other by more than ± 20% after each cold rolling step, and (4a) Treating the ribbon-shaped composite material formed in process step (3) with aqueous solution 01 until material B is completely dissolved or (4b) Immersion and retention in the submerged state of the ribbon-shaped composite material formed in process step (3) and connected as an anode in the aqueous solution O2 without dissolving material A and until material B is completely dissolved.

2. Method according to claim 1, wherein the palladium alloys are PdCu15-30 or PdAg20-30.

3. Method according to claim 1 or 2, wherein the metal alloys of material type B are CuSn4-10.

4. Method according to any of the preceding claims, wherein the aqueous solution 01 is an aqueous acidic and oxidizing solution. 2023PF00173 11 5. The method according to claim 4, wherein the aqueous acidic and oxidizing solution C1 is an aqueous solution containing 0.2 to 1.5 mol of sulfuric acid and 0.1 to 0.7 mol of hydrogen peroxide per liter.

6. Method according to any one of claims 1 to 3, wherein the aqueous solution C2 is an aqueous acidic solution.

7. The method of claim 6, wherein the aqueous acidic solution C2 is an aqueous solution containing 0.2 to 1.5 mol of sulfuric acid per liter.

8. Method according to any of the preceding claims, wherein the multi-stage cold rolling comprises 5 to 30 cold rolling stages after the first cold rolling stage.

9. Method according to one of the preceding claims, wherein the multi-stage cold rolling takes place in a quarto stand with two work rolls having a diameter in the range of 30 to 100 mm and two backup rolls.

10. Method according to any one of claims 1 to 5, 8 or 9, wherein the treatment in process step (4a) is carried out by introducing the ribbon-shaped composite material formed in process step (3) into the aqueous solution C1 by immersion in the aqueous solution C1 and keeping it in the submerged state.

11. Method according to claim 10, wherein the ribbon-shaped composite material is connected as an anode in the submerged state during process step (4a).

12. Method according to one of claims 1 to 5 or 8 to 11, wherein process step (4a) is carried out in batches or as a continuous process.

13. Method according to one of claims 1 to 5 or 8 to 12, wherein the temperature of the aqueous solution C1 during process step (4a) is in the range of 30 to 60 °C.

14. Method according to one of claims 1 to 3 or 6 to 9, wherein process step (4b) is carried out in batches or as a continuous process. 2023PF00173 12 15. Method according to any one of claims 1 to 3, 6 to 9 or 14, wherein the temperature of the aqueous solution C2 during process step (4b) is in the range of 30 to 60 °C.