Separation of Carbon Dioxide and Hydrocarbons

Separation of the polar gases such as carbon dioxide, hydrogen sulfide and sulfur dioxide behaves in many respects differently from other nonpolar gases. Their transport mechanisms through porous membranes are often different and therefore their separation performances can also be markedly different. This has been observed for separating carbon dioxide from other nonpolar, non-hydrocarbon gases. 

Separation of carbon dioxide and hydrocarbons by inorganic membranes 

Membrane material (pore dia. in nm) Tcmp( TMP Q (bar) S.F. P (barrer) Reference Note 

Note S.F. = Separation factor, KD = Knudsen diffusion P = Permeability (barrer or IQlO X (cm (STP)-cm/s-cm2-cm Hg)) indicates ideal separation factor 

There are, however, evidences that other more effective separating mechanisms such as surface diffusion and capillary condensation can occur in finer pore membranes of some materials under certain temperature and pressure conditions. Carbon dioxide is known to transport through porous media by surface diffusion or capillary condensation. It is likely that some porous inorganic membranes may be effective for preferentially carrying carbon dioxide through them under the limited conditions where either transport mechanism dominates. 

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