Carbon membrane, process for the manufacture of carbon membranes and use thereof
The invention relates to a permselective membrane ( 1 ) for removal of water from water-containing gas mixtures, said permselective membrane ( 1 ) being a carbon membrane of a material whose structure is graphite similar and formed by at least one sequence of layers of the material, the layers being arranged in planes, adjacent layers having an average distance between the layers of less than 0.45 nm (4.5 Å), and the sequence of layers being turbostratically disordered. The invention further relates to processes for preparing membrane ( 1 ) and to uses of membrane ( 1 ) for exchanging water between two gas streams and also for removing water from chemical equilibrium reactions. Assemblies comprising membrane ( 1 ) on porous ceramic carriers ( 2 ) and apparatuses for separating water from a water-containing gas mixture are also described.
1. A method for removing water from a gas mixture which contains water and at least one other gas, wherein the at least one other gas has a smaller kinetic gas diameter than water and wherein the method comprises selectively separating water by a carbon membrane of a material whose structure is similar to that of graphite and formed by at least one sequence of layers of the material, the layers being arranged in planes, adjacent layers having an average distance between the layers of less than 0.45 nm (4.5 Å), and the sequence of layers being turbostratically disordered.
2. The method of claim 1 , wherein the material of the membrane is hydrophobic at least on its free surfaces.
3. The method of claim 1 , wherein the membrane has been produced by pyrolysis of a polymeric precursor.
4. The method of claim 3 , wherein the membrane has been produced by pyrolysis of an ethylenically unsaturated polyester.
5. The method of claim 1 , wherein the at least one other gas comprises helium.
6. The method of claim 1 , wherein the at least one other gas comprises ammonia.
7. The method of claim 1 , wherein the membrane is present as a layer on a porous ceramic carrier.
8. The method of claim 7 , wherein the porous ceramic carrier comprises a mesoporous ceramic-type oxide layer of TiO 2 , ZrO 2 , Al 2 O 3 , SiO 2 , or mixtures thereof.
9. The method of claim 8 , wherein the mesoporous ceramic-type oxide layer is made of γ-Al 2 O 3 .
10. The method of claim 1 , wherein water is selectively removed from a chemical equilibrium reaction, the equilibrium reaction taking place in the presence of a gas mixture which contains water and at least one other gas which has a smaller kinetic gas diameter than water.
11. The method of claim 1 , wherein water is exchanged between two gas streams.
12. The method of claim 1 , wherein heating gases flowing into a PEM fuel cell are moistened and heated with water removed from moist and hot off-gases of the PEM fuel cell.