Methods of making inorganic membranes

1. A method comprising:

providing a monolith comprising a first end, a second end, and a plurality of inner channels having surfaces defined by porous walls and extending through the monolith from the first end to the second end, wherein the inner channels each have a hydraulic inside diameter of 3 mm or less;

providing a first mixture comprising boehmite particles;

adjusting the particle size of the boehmite particles in the first mixture; and

flow-coating the first mixture to the inner channel surfaces of the monolith to form an inorganic membrane after adjusting the particle size.

2. The method according to claim 1 , wherein adjusting the particle size comprises adjusting the median particle size.

3. The method according to claim 1 , wherein applying the first mixture comprises drying and firing the boehmite particles to form gamma-alumina.

4. The method according to claim 3 , further comprising:

providing a second mixture comprising boehmite particles;

adjusting the particle size of the boehmite particles in the second mixture; and

applying the second mixture to the inorganic membrane after the drying and firing of the boehmite particles of the first mixture and after adjusting the particle size of the boehmite particles in the second mixture.

5. The method according to claim 4 , wherein adjusting the particle size comprises adjusting the median particle size.

6. The method according to claim 4 , wherein the adjusted median particle size of the boehmite particles in the second mixture is smaller than the adjusted median particle size in the first mixture.

7. The method according to claim 4 , wherein applying the second mixture comprises drying and firing the boehmite particles to form gamma-alumina.

8. The method according to claim 4 , wherein adjusting the particle size of the boehmite particles in the second mixture comprises controlling the pH value of the second mixture.

9. The method according to claim 1 , wherein providing the first mixture comprising boehmite particles comprises preparing a sol.

10. The method according to claim 9 , wherein preparing the sol comprises hydrolysis and condensation.

11. The method according to claim 1 , wherein adjusting the particle size of the boehmite particles in the first mixture comprises controlling the pH value of the first mixture.

12. The method according to claim 1 , wherein adjusting the particle size of the boehmite particles in the first mixture comprises combining the first mixture with a polymer binder, a solution comprising a polymer binder, an acid, acetic acid, nitric acid, or a combination thereof.

13. The method according to claim 12 , wherein the polymer binder is selected from polyethylene glycol, polyvinyl alcohol, and combinations thereof.

14. The method according to claim 12 , wherein the solution comprising the polymer binder comprises water, distilled water or a combination thereof.

15. The method according to claim 1 , wherein the adjusted particle size of the boehmite particles in the first mixture is larger than the pore size of monolith.

16. The method according to claim 1 , wherein the inorganic porous support is a honeycomb monolith.

17. The method according to claim 1 , wherein the monolith comprises a material selected from alumina, alpha-alumina, gamma-alumina, zirconia, ceria, titania, mullite, cordierite, perovskite, stainless steel, and combinations thereof.

18. The method according to claim 1 , wherein monolith comprises at least one inorganic porous intermediate layer on the inner channel surfaces.

19. The method according to claim 18 , wherein the adjusted median particle size of the boehmite particles in the first mixture is larger than the median pore size of the at least one inorganic porous intermediate layer.

20. The method according to claim 18 , wherein the at least one inorganic porous intermediate layer comprises alpha-alumina, zirconia, titania, ceria, mullite, cordierite, perovskite, or combinations thereof.