High permeance sulfur tolerant Pd/Cu alloy membranes
A method of making a membrane permeable to hydrogen gas (H 2 ↑) is disclosed. The membrane is made by forming a palladium layer, depositing a layer of copper on the palladium layer, and galvanically displacing a portion of the copper with palladium. The membrane has improved resistance to poisoning by H 2 S compared to a palladium membrane. The membrane also has increased permeance of hydrogen gas compared to palladium-copper alloys. The membrane can be annealed at a lower temperature for a shorter amount of time.
1. A method of making a membrane, comprising the steps of:
a) forming a palladium layer;
b) depositing a layer of copper on the palladium layer;
c) galvanically displacing a portion of the copper with palladium; and
d) annealing the layers of palladium and copper to form the membrane.
2. The method of claim 1 , wherein the palladium layer is formed on porous stainless steel.
3. The method of claim 1 , wherein the dense palladium layer is formed on a tubular support.
4. The method of claim 3 , further including the step of cleaning the support with an alkaline solution prior to forming the palladium layer.
5. The method of claim 3 , further including the step of oxidizing the support prior to forming the palladium layer.
6. The method of claim 5 , wherein the support is oxidized at about 700° C.
7. The method of claim 6 , wherein the support is oxidized for about 12 hours.
8. The method of claim 3 , further including the step of grading the support.
9. The method of claim 8 , wherein the support is graded with Al 2 O 3 .
10. The method of claim 8 , further including the step of plating the support with a porous barrier.
11. The method of claim 10 , wherein the porous barrier is a Pd/Ag barrier.
12. The method of claim 1 , wherein the copper layer is deposited on the palladium layer by electroless deposition in a copper plating bath.
13. The method of claim 12 , wherein the copper plating bath includes CuSO 4 .5H 2 O, Na 2 EDTA.2H 2 O, HCHO (37%), EDA, K 4 Fe(CN) 6 .3H 2 O, and (C 2 H 5 ) 2 NCS 2 Na.3H 2 O.
14. The method of claim 13 , wherein the CuSO 4 .5H 2 O is present in an amount of between about 2.5 g/l to about 25 g/l.
15. The method of claim 13 , wherein the Na 2 EDTA.2H 2 O is present in an amount of between about 4.75 g/l to about 47.5 g/l.
16. The method of claim 13 , wherein the HCHO (37%) is present in an amount of between about 2.5 ml/l to about 25 ml/l.
17. The method of claim 13 , wherein the EDA is present in an amount of between about 11.2 ppm to about 112 ppm.
18. The method of claim 13 , wherein the K 4 Fe(CN) 6 .3H 2 O is present in an amount of between about 3.5 ppm to about 35 ppm.
19. The method of claim 13 , wherein the (C 2 H 5 ) 2 NCS 2 Na.3H 2 O is present in an amount of between about 0.5 ppm to about 5 ppm.
20. The method of claim 13 , wherein the pH of the copper plating bath is between about 12 to about 12.7.
21. The method of claim 13 , wherein the temperature of the copper plating bath is between about 20° to about 25° C.
22. The method of claim 13 , wherein the copper plating bath has a composition of about 25 g/l of CuSO 4 .5H 2 O, 47.5 g/l of Na 2 EDTA.2H 2 O, 25 ml/l HCHO (37%), 112 ppm of EDA, 35 ppm of K 4 Fe(CN) 6 .3H 2 O, and 5 ppm of (C 2 H 5 ) 2 NCS 2 Na.3H 2 O.
23. The method of claim 14 , wherein the pH of the copper plating bath is about 12.
24. The method of claim 14 , wherein the temperature of the copper plating bath is between about 20° to about 25° C.
25. The method of claim 13 , wherein the copper plating bath has a composition of about 2.5 g/l of CuSO 4 .5H 2 O, 4.75 g/l of Na 2 EDTA.2H 2 O, 2.5 ml/l HCHO (37%), 11.2 ppm of EDA, 3.5 ppm of K 4 Fe(CN) 6 .3H 2 O, and 0.5 ppm of (C 2 H 5 ) 2 NCS 2 Na.3H 2 O.
26. The method of claim 25 , wherein the copper plating bath has a pH of approximately 12.7.
27. The method of claim 25 , wherein the temperature of the copper plating bath is between about 20° to about 25° C.
28. The method of claim 12 , wherein the copper plating bath is agitated.
29. The method of claim 28 , wherein the copper plating bath is agitated at about 400 rpm.
30. The method of claim 1 , wherein the galvanic displacement bath is agitated.
31. The method of claim 30 , wherein the galvanic displacement bath is agitated at about 400 rpm.
32. The method of claim 1 , wherein the galvanic displacement bath includes PdCl 2 .
33. The method of claim 32 , wherein the galvanic displacement bath has a composition of about 1.0 g/l of PdCl 2 .
34. The method of claim 1 , wherein the membrane is annealed in the presence of H 2 .
35. The method of claim 34 , wherein the membrane is annealed for between 24 hours to 144 hours.
36. The method of claim 35 , wherein the membrane is annealed at about 450° C.
37. The method of claim 36 , wherein the membrane is annealed for between 24 to 36 hours.
38. A membrane having a tri-layer of palladium/copper/palladium, wherein the membrane is made by:
a) forming a palladium layer;
b) depositing a layer of copper on the palladium layer;
c) galvanically displacing a portion of the copper with palladium; and
d) annealing the layers of palladium and copper to form the membrane.
39. The membrane of claim 38 , wherein the membrane has a permeance of at least 90% of the theoretical permeance of a Pd membrane.
40. The membrane of claim 39 , wherein the membrane has a permeance of about 93% of the theoretical permeance of a Pd membrane.
41. The membrane of claim 38 , wherein the palladium layer is between about 5 μm and about 11 μm.
42. The membrane of claim 38 , wherein the gravimetric thickness of the copper layer prior to the galvanic displacement step is between about 0.9 μm and about 1.7 μm.
43. The membrane of claim 38 , wherein the thickness of the surface palladium layer resulting from the galvanic displacement step is about 0.15 μm.
44. The membrane of claim 38 , wherein x-ray diffraction indicates the presence of a Pd/Cu fcc alloy.