Other Membranes
The application of polymer membranes is generally limited to temperature below about 200 oC and to the separation of mixtures that are chemically inert. For high temperature operation and/or with chemically active mixtures, membranes made of inorganic materials (e.g. ceramic, metal) can be used. These inorganic membranes can be isotropic or anisotropic.
Inorganic membranes can withstand very high temperatures up to 4,000 oC. The high temperature resistance make these membranes very attractive for gas separation operation, especially in combination with a chemical reaction where the membrane is used as a catalyst as well as a selective barrier to remove one or more of the components which has been formed.
The chemical stability of existing polymeric materials is limited with respect to pH and organic liquids. The chemical stability of inorganic materials is superior and is especially suitable for application in harsh environments. Another important factor is the ease of cleaning for application under high fouling conditions. For inorganic membranes all kinds of cleaning agents can be used, allowing strong acid and alkali treatment.
Lastly, the lifetime of inorganic membranes is generally
greater than that or organic polymeric membranes.