Ceramic membranes

Patent metadata

Field	Value
Publication number	US-9512041-B2
Application number	US-97210510-A
Country	US
Kind code	B2
Filing date	Dec 17, 2010
Priority date	Dec 17, 2010
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

Processes for fabricating ceramic membranes include providing a porous substrate having at least one inner channel extending therethrough and having surfaces defined by porous walls, depositing a coating slurry on surfaces of the inner channel(s), and sintering. Sintering temperatures for the processes range from about 400° C. to 800° C. Coating slurries for use in the processes include a boehmite sol and a colloidal suspension of porous alumina particles.

First claim

The invention claimed is:

1. A process for fabricating a defect-free ceramic membrane comprised of a ceramic membrane comprised of a porous support, at least one intermediate layer disposed on the porous support, and an outermost filtration layer comprised of alumina particles having a multi-modal size distribution disposed on the intermediate layer, said process comprising
providing a ceramic membrane base having at least one open channel therewithin, wherein the ceramic membrane base is comprised of a porous support and at least one intermediate layer on the porous support,
preparing a boehmite sol by hydrolyzing an aluminum alkoxide to form a hydrolysis product, and combining the hydrolysis product with a peptizing agent;
preparing a colloidal suspension of porous alumina particles;
preparing a coating slurry by combining the boehmite sol with the colloidal suspension;
depositing the coating slurry onto the intermediate layer to form a coating thereon; and
sintering the ceramic membrane base having the coating thereon at a temperature of about 400° C. to 800° C., thereby forming the outermost filtration layer comprised of alumina particles having a multi-modal size distribution,
wherein the multi-modal size distribution of alumina particles comprises a first population of porous alumina particles and a second population of alumina particles disposed within interstices between the particles of the first population; the second population of alumina particles having a median particle size ranging from about 5 to about 500 nm; and the first population of alumina particles having a median particle size of less than about 100 times the median particle size of the second population of particles.

2. A process according to claim 1 , wherein the depositing the coating slurry comprises pumping the coating slurry through channels of the membrane.

3. A process according to claim 1 , wherein the coating slurry is pumped through the at least one channel at a rate ranging from 50 to 500 ml/min.

4. A process according to claim 1 , wherein the coating slurry is pumped through the at least one channel at a pressure ranging from about 5 to about 50 psi.

5. A process according to claim 1 , wherein the coating slurry is pumped through the at least one channel for a time ranging from about 2 to about 30 minutes.

6. A process according to claim 1 , wherein the temperature ranges from about 450° C. to about 600° C.

7. A process according to claim 1 , wherein the filtration layer comprises a continuous porous alumina layer having a maximum nominal pore size ranging from about 100 nm to about 800 nm.

8. A process according to claim 7 , wherein the porous alumina layer has a minimum pore size ranging from about 2 nm to about 10 nm.

9. A process according to claim 7 , wherein thickness of the porous alumina layer ranges from about 3 μm to about 21 μm.

10. A process according to claim 1 , wherein volume percent of the first population of particles is less than about 30 percent of the total volume of the first and second populations of particles.

11. A process according to claim 1 , wherein median particle size of the second population of particles ranges from about 50 nm to about 300 nm.

12. A process according to claim 1 , wherein median particle size of the first population of particles is less than about ten times the median particle size of the second population of particles.

13. A process according to claim 1 , wherein median particle size of the first population of particles ranges from about 300 nm to about 2000 nm.

14. A process according to claim 1 , wherein the alumina particles of the second population comprise gamma-alumina.

15. The process of claim 1 wherein the porous support has a nominal pore size of less than about 1 μm.

16. A process for fabricating a ceramic membrane comprised of a porous support and a coating on the outermost surface of the ceramic membrane wherein the coating is comprised of alumina particles having a multi-modal size distribution, said process comprising
providing a porous support having at least one inner channel extending therethrough and having surfaces defined by porous walls;
preparing a boehmite sol by hydrolyzing an aluminum alkoxide to form a hydrolysis product, and combining the hydrolysis product with a peptizing agent;
preparing a colloidal suspension of porous alumina particles;
preparing a coating slurry by combining the boehmite sol with the colloidal suspension;
depositing the coating slurry on surfaces of the porous support and the at least one inner channel to form coated surfaces thereon; and
sintering the coated surfaces at a temperature ranging from about 400° C. to 800° C. to form the outermost surface of the ceramic membrane comprised of alumina particles having a multi-modal size distribution,
wherein the multi-modal size distribution of alumina particles comprises a first population of porous alumina particles and a second population of alumina particles disposed within interstices between the particles of the first population; the second population of alumina particles having a median particle size ranging from about 5 to about 500 nm; and the first population of alumina particles having a median particle size of less than about 100 times the median particle size of the second population of particles.

17. A process according to claim 16 , wherein the coating slurry additionally comprises a polymeric binder.

18. A process according to claim 17 , wherein the polymeric binder is polyvinyl alcohol.

19. A process according to claim 16 , wherein the peptizing agent is nitric acid.

20. A process according to claim 16 , wherein particle size of the boehmite sol ranges from about 50 nm to about 500 nm.

21. A process according to claim 16 , wherein particle size of the boehmite sol ranges from about 200 nm to about 300 nm.

22. A process according to claim 16 , wherein the porous alumina particles are prepared by calcining a porous alumina powder at a temperature ranging from about 800° C. to about 1400° C. to yield a calcined powder.

23. A process according to claim 22 , additionally comprising milling the calcined powder with water at a pH of less than about 8.

Assignees

• Mcevoy Kevin Paul
• Ku Anthony Yu-Chung
• Hagerdon Randall Scott
• Antolino Nicholas Edward
• Gen Electric

Inventors

• Mcevoy Kevin Paul
• Ku Anthony Yu-Chung
• Hagerdon Randall Scott
• Antolino Nicholas Edward

Classifications

• C04B38/0096 Primary

  Pores with coated inner walls · CPC title

• C04B35/00

  Shaped ceramic products characterised by their composition {(porous ceramic products C04B38/00; ceramic articles characterised by particular shape, see the relevant classes, e.g. linings for casting ladles, tundishes, cups or the like B22D41/02; ceramic substrates for microelectronic semi-conductors H10W70/692)}; Ceramics compositions ({shaping of ceramics B28B;} containing free metal bonded to carbides, diamond, oxides, borides, nitrides, silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides or sulfides other than as macroscopic reinforcing agents C22C); Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products {(infiltration of sintered ceramic preforms with molten metal C04B41/51; chemical preparation of powders of inorganic compounds C01)} · CPC title

• B01D2323/283

  Reducing the pores · CPC title

• B01D71/025

  Aluminium oxide · CPC title

• C04B2111/00801

  Membranes; Diaphragms · CPC title