Permeation of wet CO2/CH4 mixed gas through a liquid membrane supported on surface of a hydrophobic microporous membrane

Abstract

A double-layer liquid membrane was proposed where a supported liquid membrane of diglycolamine (DGA) or triethylene glycol (TEG) was supported on the surface of another microporus membrane, a Durapel membrane(Millipore), by its hydrophobicity. This surface supported liquid membrane was used for the separation of CO 2 from a wet CO 2 /CH 4 mixed gas. The liquid membrane of this construction is durable up to a transmembrane pressure of 250 kPa. That is, the liquid membrane is applicable for the vacuum mode permeation and pressurized permeation mode. Permeation experiments through the DGA liquid membrane with a 25 μm thickness shows that the CO 2 permeability was 30–100 Barrer with a CO 2 /CH 4 separation factor of 40–100. The CO 2 permeability was comparable to polymer membranes. The partial pressure dependency of the CO 2 permeability may imply the existence of facilitated transport during the vacuum mode permeation. A comparison of the dry feed and wet feed experiments using the TEG liquid membrane showed that there was no large effect of the water vapor in the feed on the selectivity and permeabilities.